阅读说明：本技术 用于罐内固化的系统及方法 (System and method for in-tank curing ) 是由 D·W·科克伦 B·D·约翰逊 J·M·卡茨 于 2020-04-20 设计创作，主要内容包括：本发明提供一种经改进罐内固化技术。一种实施方案使用窄带半导体产生的红外能量,其经聚焦到罐的内部以影响非常高速的固化结果。所述实施方案使用所聚焦高功率辐射能量,其将直接影响覆盖所述罐的内壁的涂层以使所述涂层快速固化。所述固化如此快速完成使得没有时间发生铝罐体的去回火及退火,从而使罐更坚固。(The present invention provides an improved in-can curing technique. One embodiment uses infrared energy generated by a narrow band semiconductor that is focused into the interior of the can to affect a very high speed cure result. The embodiments use focused high power radiant energy that will directly affect the coating covering the inner wall of the can to cause the coating to cure rapidly. The solidification is done so rapidly that no time for de-tempering and annealing of the aluminum can body occurs, making the can stronger.)

1. A method for use in a can manufacturing interior coating and curing process wherein a coating has been sprayed onto the interior surface of a can, the method comprising:

continuously transporting the cans towards at least one curing station; and a process for the preparation of a coating,

radiant infrared energy generated using a narrowband semiconductor and optical elements positioned outside the cans in the at least one curing station individually and electrically heats the cans such that the coating on the interior surface of each successive can in a series of single row production cans is brought to a critical temperature to complete a bond curing process in the coating in less than 20 seconds to prevent de-tempering or annealing from occurring in the cans.

2. The method of claim 1 wherein each can is formed from a manufacturing tool reconfigured to reduce the diameter of a cut edge of a blank from which a starting cup of the can is drawn, whereby the thickness of the coil aluminum is substantially the same as before tool reconfiguration but making the coil narrower, reducing the weight of aluminum required to manufacture each can by more than 3%.

3. The method of any preceding claim wherein each can is formed using a can design and tooling modified to manufacture the can from a thinner web material to reduce the weight of the aluminum used to manufacture the can, whereby the heating to complete the joint curing process in less than 20 seconds eliminates a reduction in the strength of the can such that the can will have similar sidewall axial strength, bottom reversal strength and overall strength, the longer time weakening the metal compared to a thicker can that requires longer time to cure.

4. The method of any preceding claim, wherein a semiconductor-based system that generates the narrow band radiant energy is capable of being turned on or off in a few microseconds and capable of heating the coating and/or the canister to the critical temperature in less than 10 seconds.

5. A method according to any preceding claim, wherein a conveyor transports the cans during the curing process and utilizes continuous rotary motion, whereby the at least one irradiation curing station is in continuous rotary motion in synchronism with the cans being cured thereby and at least one of electrical power, coolant and control signals is connected to the at least one curing station by a rotary joint.

6. The method of any preceding claim, wherein at least one of a DC power supply, a cooling heat exchanger, a cooling chiller, a cooling recirculation pump, and a control system serving the at least one curing station moves in a rotational motion and in synchronization with the tank, thereby providing a continuous rotational motion curing system, wherein the continuous motion of the system facilitates a cooling function.

7. A method according to any preceding claim wherein a conveyor transports the cans during the curing process and utilises an indexed rotary motion whereby a plurality of irradiation curing stations are located around the periphery of a turntable but not on the turntable so that a group of cans are successively loaded into a selected number of empty stations around the turntable as the turntable is indexed rotationally so that the cans are each under their respective narrow band curing stations, the curing stations being actuated to cure the cans and then the turntable is indexed rotationally again, this withdrawing the cured cans whilst a new group of cans are indexed into their positions under the curing stations for curing and the process continues to repeat.

8. The method of any preceding claim, wherein each can is cured individually in less than 5 seconds.

9. The method of any preceding claim, wherein a narrowband semiconductor device emits the narrowband radiant infrared energy at a wavelength that matches an absorption characteristic of the coating on the interior surface of each successive can.

10. The method of any preceding claim, wherein the wavelength of the narrowband radiant infrared energy for heating is in a range of one of 800nm to 1200nm, 1400nm to 1600nm, and 1850nm to 2000 nm.

11. The method of any preceding claim, wherein the narrowband infrared radiant energy for heating is generated using at least one of a semiconductor-based illumination device, a Light Emitting Diode (LED), and a laser diode.

12. The method of any preceding claim, wherein the semiconductor devices that produce the illumination are configured as a multi-device array that combines optical output power of more than 10 individual semiconductor devices to produce a total optical output power of 100 watts or more.

13. A method according to any preceding claim, wherein the semiconductor device is a laser diode and the full width/half maximum output bandwidth is made narrower than 20 nanometers.

14. A method according to any preceding claim, wherein the semiconductor device is a surface emitting laser diode having a full width/half maximum output bandwidth narrower than 2 nanometers.

15. A method according to any preceding claim, wherein the energy source comprises a surface emitting laser diode array producing a photonic energy output thereof between 825 and 1075 nanometers.

16. The method of any preceding claim, wherein can handling facilitates individual curing of a row of cans at production speeds in excess of 300 cans per minute.

17. A method according to any preceding claim, wherein a plurality of parallel curing stations are arranged to cure individually at a total throughput speed in excess of 1,800 cans per minute whilst running all but one row which can be used for any maintenance which may be required, or if required, to provide additional production, enabling a higher level of total run time.

18. The method of any preceding claim, wherein the method eliminates hydrocarbon based fuel usage and saves more than 3% aluminum in a can manufacturing process due to higher speed within 20 seconds of solidification, which eliminates annealing and weakening of the aluminum of the can body.

19. The method of any preceding claim, wherein specific additives are explicitly added to the coating to interact with the wavelength of narrow band infrared light for improving the performance of the cured coating or promoting new functionality of the cured coating.

20. The method of any preceding claim, wherein the method facilitates reworking of the coating to eliminate BPA or other undesirable components in the coating formulation.

21. A method according to any preceding claim, wherein the plant configuration of the method is capable of being easily started and stopped without detrimental effect on the tank or downstream part of the production process.

22. A method according to any preceding claim, wherein an embodiment provides the ability to respond to modulation of the method both instantaneously and in motion as a result of sensory information obtained from an inspection system.

23. A system for use in a can manufacturing interior coating and curing process wherein a coating has been sprayed onto the interior surface of a can, the system comprising:

a tank handling system configured to continuously move production tanks into at least one curing zone;

an array of semiconductor-based narrowband irradiation devices positioned to individually and electrically heat interior surfaces of each can moving into a curing zone using optical elements positioned outside of an open end of the can such that the coating on the interior surface of each successive can in a series of production cans is brought to a critical temperature to create a bond curing process in the coating within less than 20 seconds to prevent de-tempering or annealing from occurring in the can.

24. The system of claim 23, wherein the array of semiconductor-based narrowband irradiation devices and the optical element are positioned just outside a top plane of a cut edge of the can and aim more than 90% of narrowband infrared photon energy generated by the array of semiconductor-based narrowband irradiation devices into an interior of a cured can, with a majority of the energy focused on an upper half of a sidewall such that internal reflection exposes a lower portion of the can.

25. The system of any of claims 23-24, wherein the optical element comprises: at least one microlens array aligned with respective devices of the array of semiconductor-based narrowband irradiation devices to form columnar energies; a condenser lens configured to focus the column of energy toward and through a pinhole or aperture element and into the interior of the tank being cured, and the pinhole or aperture provides an opening through the apex of the reflective engineered surface, the effect of which is to redirect the narrow band of energy that would otherwise escape the tank back into the tank.

26. The system of any one of claims 23-25, wherein the reflective engineered surface is equipped with ventilation slots or openings to facilitate vapor removal from a curing canister.

27. The system of any one of claims 23 to 26, wherein the reflective engineered surface is substantially conical and is made of one of copper, aluminum, gold-plated metal, silver-plated material, and highly reflective nanostructures.

28. The system of any one of claims 23-27, wherein the optical element and the array of semiconductor-based narrowband irradiation devices are mounted in a housing configured to prevent stray infrared energy from escaping the housing except through the pin-hole or hole element, and configured with a recirculating water cooling arrangement to maintain the array and optical element at an acceptable operating temperature in a production curing environment.

29. The system of any one of claims 23-28, wherein the array of semiconductor-based narrowband irradiation devices includes at least one array of laser diodes positioned outside the cans, and the corresponding optical elements are looped to the interior of each can during at least a portion of a curing operation.

30. The system of any one of claims 23-29, wherein the optical element comprises an objective lens configured to receive energy from the semiconductor-based narrowband irradiation device array via optics and a mirror assembly, and the system further comprises an insertion and retrieval mechanism to translate the optical element into the canister by a reflection containment plate configured to be positioned over each canister such that optical energy transfer is aligned when the insertion mechanism positions portions of the optical assembly within the canister so irradiation can be activated to achieve the curing when optical system is properly positioned inside container.

31. A system for tank or container manufacturing to cure a coating that has been sprayed onto an interior sidewall of the container, the system comprising:

an entry track or conveyor configured to organize or facilitate movement of individual containers in a single row sequence toward a second conveyor;

the second conveyor is configured to rotate a turntable to move the individual containers into and away from at least one curing station;

the at least one curing station comprises an optical configuration in which photon energy from at least one surface emitting laser diode array passes through a cylindrical optic and is then focused by at least one condenser lens element through a pinhole or aperture at which the photon energy diverges to illuminate the interior of a sidewall of a coated container, this pinhole or aperture being positioned at the apex of a reflection cone used to reflect photon energy back into the container to enable further curing work;

wherein the coating cures in less than 20 seconds sufficiently fast to prevent weakening or annealing in the aluminum comprising the container;

the second conveyor delivers the containers and is directed to a third conveyor configured to carry the containers out and away from the second conveyor so empty pockets can be used to load waiting uncured cans to continue curing continuously while cured containers are transferred on the third conveyor toward a subsequent container manufacturing operation.

32. The system of any one of claims 23 to 31, wherein the subsequent manufacturing operations include an inspection station positioned on the third conveyor, the function of the inspection station being to verify the authenticity of coating and curing at least by imaging and searching for bare metal areas inside each container, and to the extent that the imaged quality level of the cured coating is insufficient, rejecting the container with a faulty coating at a rejection station configured as a third party after the inspection station, and then sending a signal to at least one of a coating system control system and a curing control system to correct the respective process.

33. A system for can or open top container manufacturing to cure a coating that has been sprayed onto an interior surface of the container, the system comprising:

an entry track or conveyor configured to move a single row of individual containers toward a second conveyor;

the second conveyor is configured to use a rotary motion stage to move the containers into and away from at least one curing station;

the at least one curing station incorporates one of the engineered reflectors to be used to redirect photonic energy from the array through the open top of the container and directly onto the sprayed coating on the interior surface of the container to perform a curing process;

wherein the coating cures in less than 20 seconds sufficiently fast to prevent weakening or annealing in the aluminum comprising the container;

wherein the second conveyor is configured to rotate to provide a third conveyor with an outlet for already cured containers while new uncured cans are continuously loaded to an vacation location;

wherein the third conveyor is configured to receive the already cured containers on an outlet and convey the already cured containers all the way toward a subsequent container manufacturing operation.

34. The system of any of claims 23-33, wherein the second conveyor is a rotary configuration having a plurality of curing stations positioned around a periphery, each of the plurality of curing stations being simultaneously usable to cure an interior of a container with infrared energy generated by at least one laser diode array.

35. The system of any one of claims 23-34, wherein the plurality of curing stations comprises more than 8 curing stations.

36. The system of any one of claims 23-35, wherein the second conveyor is a rotary configuration having a plurality of curing stations that rotate synchronously with the containers so curing can continue without table rotation starting or stopping, and wherein at least one of electrical power, cooling, and control signals is connected to the curing stations through at least one rotary joint.

37. The system of any one of claims 23-36, wherein the entry track or conveyor is configured to advance the containers that are single-row using gravity and apply gravitational pressure to feed each individual can into the second conveyor.

38. A system for use in a can manufacturing interior coating and curing process wherein a coating has been sprayed onto the interior surface of a can, the system comprising:

a tank handling system configured to continuously move production tanks into at least one curing zone;

a broadband infrared source positioned to individually and electrically heat an interior surface of each can moved into a curing zone using an optical element positioned to direct illumination toward an upper sidewall of the interior surface of the can such that the coating on the interior surface of each successive can in a series of production cans is brought to a critical temperature to create a bond cure process in the coating in less than 20 seconds to prevent de-tempering or annealing from occurring in the can body; and a process for the preparation of a coating,

a control system configured to modulate the output of the broadband infrared source using sensor information to maintain consistent curing temperature and results.

Background

In the process of manufacturing cans, for example two-piece aluminium or steel beverage cans, it is necessary to apply a coating so that the raw aluminium or steel from which the can is produced never directly contacts the product with which the can will ultimately be filled. Some of the liquid to be placed in the tank may be damaged by contact with the aluminum material. Other liquids may react adversely with the aluminum, such that the integrity of the container may be compromised. For example, beer is damaged even with the slightest contact with raw aluminum. Soft drinks, on the other hand, are generally sufficiently acidic that they chemically etch into an already thin aluminum surface, thereby weakening its strength and integrity. Other products may be adversely affected by taste changes. Some processes for coating aluminum materials are in use, the aluminum material still exists in a flat cut length or coil before the aluminum material is formed into the final can shape. However, most cans are coated after they have been subjected to a forming process in which they are formed from a starting flat web. There are two main processes for the manufacture of modern food or beverage cans. They are subjected to a drawing and redrawing process (D & R) or, even more typically, to a stretching and ironing process (D & I). The D & I process is sometimes referred to as a drawn wall ironing process or DWI. In both processes, the drawn cup is made from a flat (usually) web. That cup is then further processed by drawing an even deeper but final size cup. The second step of the D & I process involves continuously "ironing" the walls of the cups until they reach the correct and desired thickness and dimensions. A lot of engineering and experimentation was done in the process and finally the shape developed finally was formed at the bottom and finally the neck of the can was formed in a later process. The precise geometry is critical so that the finished can withstand the pressure exerted by the gas from the canned liquid food or beverage. This structural form is intended to maintain pressure along the side walls, but ultimately must prevent actual failure of the dome-shaped bottom, known as bottom inversion failure.

For a more detailed explanation, reference is made to fig. 6, taking as an example a typical drawing and ironing process (D & I or DWI). In fig. 6, an example process 600 for forming a can using D & I is illustrated. As shown, cans are formed using an uncoiler (602), a lubricator (604), a cup-aspirator (606), a bodymaker (608), and an edger (610). The form and function of these elements in a typical D & I process will be understood by those skilled in the art.

After the can is in the shape of a straight-walled, neck-less can, it is cleaned using a cleaner (612) and dried at about 400 ° f using, for example, a gas dryer oven (614) before being put into a coating process including an internal coating process.

The coating process is initiated by applying an ink base coat to the exterior of the can, optionally using a primer (616), and then drying any applied base coat using an optional primer oven (618) operating at about 400 ° f. The can is then passed through a decorator (620) to apply an ink pattern to the exterior surface of the can and through a bottom applicator (622) to apply a layer of protective coating to the bottom of the can. The cans were then sent to a kiln (624) (also operating at about 400 ° f) to dry the applied exterior coating.

Then, the internal coating process is initiated to coat the internal surfaces of the can. The internal coating process typically involves a row of single cans passing through an internal applicator (626), indexing star wheel or continuously running star wheel, with the spray guns inside the coating cans being actuated. The spray gun is highly developed and can atomize very fine wet coatings into a tank so that all surfaces are covered. The tank is rotated under the lance during operation to provide about 360 degrees of furnace coverage within the perimeter of the tank. Generally, the can is aimed to rotate two to five revolutions when sprayed internally. When wet, the coating looks like a thin white paint that adheres to the entire interior surface of the can. The cans are rotated at high speed during the process to use centripetal force to even out the coating. It is important that the spraying is performed with the correct thickness so that it provides sufficient coverage of the aluminium or steel can stock. It cannot be too thin or too thick to perform properly. If too thick, flow marks and thick areas may result, which may not cure properly and the coating will be wasted. Immediately after the spray process is complete, the cans must be thermally cured in an internal oven called IBO (628).

A row of single row cans exiting the applicator are routed to the mass transport. Mass conveyor material handling groups cans together as close as possible because they can nest tens of widths on wide conveyors ranging from 30 to 80 "in width. The conveyor belt on which the cans are transported by the IBO (628) is designed to handle the repeated harsh high temperatures so that the belt material can be safely passed through the oven to transport the cans to the curing oven. The travel through the curing oven typically requires two to four minutes. The furnace will typically have multiple hot sections through which the cans pass gradually. A typical IBO furnace configuration would introduce the cans into the first section of the furnace, which would subject the cans to preheating at 200 to 270 degrees fahrenheit for about 60 seconds. Zone two or zone two will raise the temperature to 270 to 400 deg. for about 60 seconds. The last zone or zone 3 typically maintains a temperature of 380 to 450 degrees fahrenheit for a final cure of about 60 seconds. The tank takes a total of about 180 seconds in the furnace, which may vary, but this represents a conventional situation.

When the mass transfer tank leaves the IBO, the interior epoxy coating should appear almost transparent if properly cured. Transparency is an indicator, but does not guarantee complete curing of the coating. Must be tested in the laboratory to be determined. The concept of IBO is to gradually bring the temperature of the mass transfer tank to the full cure temperature and then determine that it has been held at 380 to 450 Fahrenheit for at least a minimum number of seconds. This is the time required for the epoxy coating to begin the bonding or joining process required for proper, complete curing. Once the bonding process is initiated at this "temperature time", the bonding process will continue until fully cured if it has in fact been held above the 375 ° temperature for a specified time. As mentioned, "transparent" compound does not mean that it has been properly cured. If the temperature provided at the time is slightly lower, it will become transparent even if the correct bonding temperature is never activated. If the temperature is too high or if the holding time is too long, excessive curing may also occur, which may cause the coating to yellow or to blister. For example, if the coated can is held at an elevated temperature for 15 minutes, it will result in variable yellowing or even blistering, which is clearly an unacceptable cure result. This will typically occur if the furnace conveyor is shut down for any reason and there are still a large number of cans in the furnace. Beverage cans typically contain a total internal coating weight of 80 to 150 milligrams, which must be properly cured.

After the cans leave the IBO (628), they are sent to a waxing machine (630) for further processing. Those skilled in the art will appreciate that after the waxing machine function is completed, the can forming process is completed using a necking machine (632) and a flanging machine (634). A light tester (636) may also be used. Finally, the formed cans are sent to a palletizer (638).

This process is used worldwide and is widely accepted as a standard for two-piece can safe food and beverage packaging. The same or very similar processes are also often used for other types of tanks.

It is worth noting, however, that current IBO furnaces use incredible energy. Most furnaces are fired with natural gas, but some are also electrically powered. Either type uses a very large amount of energy and occupies a large amount of floor space. The furnace requires a significant amount of maintenance because the belt carrying the can mass transport must pass through the furnace and be cycled hot/cold on a continuous basis of 24/7. The bearings, drive train, guides and belt material itself are subject to constant thermal and mechanical wear. Furthermore, given that furnaces typically capture energy on the basis of fossil fuels, there are sustainability and air pollution issues around IBO furnaces. In addition, five large motors, about 95HP in total, are typically required to run the belt and continue to ventilate, vent, and scrub the air associated with the oven.

It is well known in the can manufacturing industry that the aluminum from which the cans are produced actually loses strength because of the time spent in the IBO. It is widely recognized that cans require two to three minutes at high temperatures and that a de-tempering/annealing effect can occur, thereby weakening the 3004 aluminum alloy. While the time required for normal annealing is much longer than these times, it is believed that annealing is performed in the can body because the aluminum is thin, full heat penetration can occur and almost immediately begins to affect the grain structure.

Due to this de-tempering/annealing effect, the can must be made practically stronger than the final gauge. As the IBO furnaces trip, they lose about 8 to 10% of their bottom reversal strength, which is required for their normal performance. Before carbonated soft drinks "bottom invert" they must maintain a pressure containment strength of 92 to 95PSI, while beer must maintain 105 to 110 PSI. This high-speed softening, de-strengthening, or annealing has the effect of reducing the tensile strength and yield strength of the aluminum alloy, so that the aluminum must be thicker to have the desired strength as compared to the unannealed can.

Disclosure of Invention

In one aspect of the presently described embodiments, a method for a can manufacturing interior coating and curing process, wherein a coating has been sprayed onto an interior surface of a can, the method generally comprising: transporting the cans towards at least one curing station; and individually and electrically heating the cans in the at least one curing station using narrow band radiant infrared energy and optical elements positioned outside the cans such that the coating on the interior surface of each successive can in a series of production cans is brought to a critical temperature to initiate a cure bond process in the coating in less than 20 seconds to prevent de-tempering or annealing from occurring in the cans.

In another aspect of the presently described embodiments, each can is formed from a manufacturing tool reconfigured to reduce the diameter of the cut edge of the blank from which the starting cup of the can was drawn, whereby the thickness of the coil aluminum is substantially the same as before the tool reconfiguration but the coil is made narrower, reducing the weight of aluminum required to manufacture each can by more than 3%.

In another aspect of the embodiments described herein, each can is formed using can designs and tools modified to manufacture the can from thinner web materials to reduce the aluminum from which the can is manufactured, whereby the heating to complete the bond curing process in less than 20 seconds eliminates a reduction in the strength of the can, such that the can will have similar sidewall axial strength, bottom reversal strength, and overall strength, which longer time weakens the metal, as compared to a thicker can that requires longer time to cure.

In another aspect of the described embodiments of the invention, the electro-curing of the coating is performed by a narrow band semiconductor-based radiant heating system.

In another aspect of the presently described embodiments, the semiconductor-based system that generates the narrow band radiant energy may be turned on or off in a few microseconds, and the coating and/or the canister may be heated to a curing temperature in less than 10 seconds.

In another aspect of the embodiments described herein, a conveyor transports the cans and utilizes continuous rotary motion during the curing process, whereby the at least one irradiation curing station is in continuous rotary motion in synchronization with the cans being cured thereby and at least one of electrical power, coolant, and control signals is connected to the at least one curing station by a rotary joint.

In another aspect of the presently described embodiments, at least one of a DC power supply, a cooling heat exchanger, a cooling chiller, a cooling recirculation pump, and a control system serving the at least one curing station moves in a rotational motion and in synchronization with the tank, thereby providing a continuous rotational motion curing system, wherein the continuous motion of the system facilitates a cooling function.

In another aspect of the presently described embodiments, a conveyor transports the cans during the curing process and utilizes an indexing rotary motion whereby a plurality of irradiating curing stations are positioned around the periphery of a turntable but not on the turntable so that a group of cans are successively loaded into a selected number of empty stations around the turntable as the turntable is rotationally indexed so that the cans are each under their respective narrow band curing stations, the curing stations are actuated to cure the cans and then the turntable is rotationally indexed again which withdraws cured cans while a new group of cans are indexed into their positions under the curing stations for curing and the process continues to repeat.

In another aspect of the described embodiment of the invention, the cans are individually cured in less than 5 seconds.

In another aspect of the presently described embodiments, a narrowband semiconductor device emits the narrowband radiant infrared energy at a wavelength that matches an absorption characteristic of the coating on the interior surface of each successive can.

In another aspect of the presently described embodiments, the wavelength of the narrowband radiant infrared energy for heating is in a range of one of 800nm to 1200nm, 1400nm to 1600nm, and 1850nm to 2000 nm.

In another aspect of the presently described embodiments, the narrow band infrared radiant energy for heating is generated using at least one of a semiconductor-based illumination device, a Light Emitting Diode (LED), and a laser diode.

In another aspect of the presently described embodiments, the semiconductor devices that produce the illumination are configured as a multi-device array that combines the optical output power of more than 10 individual semiconductor devices to produce a total optical output power of 100 watts or more.

In another aspect of the embodiments described herein, the semiconductor device is a laser diode and has a full width/half maximum output bandwidth narrower than 20 nanometers.

In another aspect of the described embodiments of the present invention, the semiconductor device is a surface emitting laser diode whose full width/half maximum output bandwidth is narrower than 2 nanometers.

In another aspect of the described embodiment of the present invention, the energy source comprises an array of surface emitting laser diodes producing a photonic energy output thereof between 825 and 1075 nanometers.

In another aspect of the described embodiments of the invention, the material/can processing facilitates individual curing of a row of cans at production speeds in excess of 300 cans per minute.

In another aspect of the presently described embodiments, a plurality of parallel curing stations are arranged to individually cure all but one row running simultaneously at a total throughput speed in excess of 1,800 cans per minute, which row may be used for any maintenance that may be required, or if required, to provide additional production so that a higher level of total run time can be achieved.

In another aspect of the embodiments described herein, the method eliminates hydrocarbon-based fuel usage and saves more than 3% aluminum in a can manufacturing process within 20 seconds of solidification due to the higher speed, which eliminates annealing and weakening of the aluminum of the can body.

In another aspect of the presently described embodiments, specific additives are explicitly added to the coating to interact with the narrow band infrared light to improve the performance or functionality of the cured coating.

In another aspect of the embodiments described herein, the method facilitates reworking of the coating to eliminate BPA or other undesirable components in the coating formulation.

In another aspect of the described embodiments of the invention, the equipment configuration of the curing process can be easily started and stopped without detrimental effects on the tank or production process.

In another aspect of the presently described embodiments, implementations provide the ability to respond to modulation of the method both instantaneously and in motion as a result of sensory information obtained from the inspection system.

In another aspect of the described embodiments of the invention, a system for use in a can manufacturing interior coating and curing process, wherein a coating has been sprayed onto the interior surface of a can, the system comprising: a tank handling system configured to continuously move production tanks into at least one curing zone; an array of semiconductor-based narrowband irradiation devices positioned to individually and electrically heat interior surfaces of each can moving into a curing zone using optical elements positioned outside of an open end of the can such that the coating on the interior surface of each successive can in a series of production cans is brought to a critical temperature to create a link curing process in less than 20 seconds to prevent de-tempering or annealing from occurring in the cans.

In another aspect of the presently described embodiments, the array of semiconductor-based narrowband irradiation devices and the optical element are positioned just outside of the top plane of the cut edge of the can and aim more than 90% of the narrowband infrared photon energy generated by the semiconductor-based narrowband irradiation devices into the interior of the cured can, with a majority of the energy focused on the upper half of the sidewall such that internal reflection exposes the lower portion of the can.

In another aspect of the described embodiments of the present invention, the optical element comprises: at least one microlens array aligned with respective devices of the array of semiconductor-based narrowband irradiation devices to form columnar energies; a condenser lens configured to focus the column of energy toward and through a pinhole or aperture element and into the interior of the tank being cured, and the pinhole or aperture provides an opening for vortices that pass through the reflective engineered shape surface, the effect of which is to redirect narrow band energy that would otherwise escape the tank back into the tank.

In another aspect of the embodiments described herein, the reflective engineered surface is equipped with ventilation slots or openings to facilitate vapor removal from the curing canister.

In another aspect of the presently described embodiments, the reflective engineered surface is substantially conical and is made of one of copper, aluminum, gold plated metal, silver plated material, and highly reflective nanostructures.

In another aspect of the embodiments described herein, the optical element and the array of semiconductor-based narrowband irradiation devices are mounted in a housing configured to prevent stray infrared energy from escaping the housing except through the pin-hole or aperture element, and configured with a recirculating water cooling arrangement to maintain the array and optical elements at an acceptable operating temperature in a production curing environment.

In another aspect of the presently described embodiments, the array of semiconductor-based narrowband irradiation devices includes at least one array of laser diodes positioned outside of the cans, and the corresponding optical elements are looped to the interior of each can during at least a portion of curing.

In another aspect of the presently described embodiments, the optical element comprises an objective lens configured to receive energy from the array of semiconductor-based narrowband illumination devices via an optics and lens assembly, and the system further comprises an insertion and retrieval mechanism to translate the optical element into the canister by a reflection containment plate configured to be positioned over each canister such that optical energy transfer is aligned when the insertion mechanism positions portions of the optical assembly within the canister so illumination can be activated to effect the curing when optical system is properly positioned inside container.

In another aspect of the embodiments described herein, a system for curing a coating that has been sprayed onto the interior walls of the containers in can or container manufacturing includes an entry track or conveyor configured to organize or facilitate movement of individual containers in a single-file sequence toward a second conveyor configured to rotate a turntable to move individual containers to and away from at least one curing station, the at least one curing station including an optical configuration in which photon energy from at least one surface emitting laser diode array is passed through cylindrical optics and then focused by at least one condenser lens element through a pinhole or aperture at which the photon energy diverges to illuminate the interior side walls of the coated containers, such pinhole or aperture being positioned at the apex of a reflection cone that reflects for reflecting the photon energy back into the containers to perform further curing work, wherein the coating cures in less than 20 seconds sufficiently fast to prevent weakening or annealing from occurring in the aluminum comprising the containers, the second conveyor meaning the delivery containers and being directed to a third conveyor configured to show the containers out and away from the second conveyor so empty pockets can be used to load waiting uncured cans to continue continuous curing while the cured containers are conveyed on the third conveyor towards a subsequent container manufacturing operation.

In another aspect of the presently described embodiments, the subsequent manufacturing operations include an inspection station positioned on the third conveyor, the function of the inspection station being to verify the authenticity of coating and curing at least by imaging and searching for bare metal areas inside each container, and to the extent that the imaged quality level of the cured coating is insufficient, rejecting containers with a faulty coating at a rejection station configured as a third conveyor after the inspection station, and then sending a signal to at least one of a coating system control system and a curing control system to correct the respective process.

In another aspect of the described embodiments of the invention, a system for can or open top container manufacturing to cure a coating that has been sprayed onto an interior surface of the container, comprises: an entry track or conveyor configured to move a single row of individual containers toward a second conveyor configured to use a rotating motion stage to move the containers into and away from at least one curing station incorporating one of the engineered reflectors that will be used to redirect photonic energy from the array through the open top of the containers and directly onto the sprayed coating on the interior surface of the containers to perform a curing process, wherein the coating cures in less than 20 seconds sufficiently fast to prevent weakening or annealing from occurring in the aluminum comprising the containers, the second conveyor configured to rotate to provide a third conveyor with an outlet for already cured containers while new uncured cans are continuously loaded to an empty location, the third conveyor is configured to receive the already solidified containers on the outlet and convey the already solidified containers all the way toward a subsequent container manufacturing operation.

In another aspect of the embodiments described herein, the second conveyor is a rotary configuration having a plurality of curing stations positioned around the periphery, each of the plurality of curing stations being simultaneously operable to cure the interior of the container with infrared energy generated by at least one laser diode array.

In another aspect of the described embodiments of the present invention, the plurality of curing stations comprises more than 8 curing stations.

In another aspect of the embodiments described herein, the second conveyor is a rotary configuration having a plurality of curing stations that rotate synchronously with the containers so curing can continue without the stations starting or stopping rotation, and wherein at least one of electrical power, cooling, and control signals is connected to the curing stations through at least one rotary joint.

In another aspect of the presently described embodiments, the entry track or conveyor is configured to advance the containers that are single-row using gravity and apply gravity pressure to feed each individual can into the second conveyor.

In another aspect of the described embodiments of the invention, a system for use in a can manufacturing interior coating and curing process, wherein a coating has been sprayed onto the interior surface of a can, the system comprising: a tank handling system configured to continuously move production tanks into at least one curing zone; and a broadband infrared source positioned to individually and electrically heat an interior surface of each can moved into a curing zone using an optical element positioned to direct illumination toward an upper sidewall of the interior surface of the can such that the coating on the interior surface of each successive can in a series of production cans is brought to a critical temperature to create a bond cure process in the coating in less than 20 seconds to prevent de-tempering or annealing from occurring in the can body; and a control system configured to modulate the output of the broadband infrared source using sensor information to maintain consistent curing temperature and results.

Drawings

FIG. 1 shows an exemplary can cured using the embodiments described herein;

FIG. 2 shows a system according to a described embodiment of the invention;

FIG. 3 shows another system according to a described embodiment of the invention;

FIG. 4 shows another system in accordance with the described embodiments of the invention;

FIG. 5 shows another system according to a described embodiment of the invention;

FIG. 6 shows a flow chart illustrating an exemplary previous method for forming a can;

FIG. 7 shows another system in accordance with a described embodiment of the invention; and a process for the preparation of a coating,

FIG. 8 shows another system in accordance with the described embodiments of the invention.

Detailed Description

The embodiments described herein teach an entirely new concept for curing coatings on the interior of food, beverage, and other types of cans. Many embodiments are suitable for replacing the conventional internal oven (IBO) described above in connection with known techniques of forming cans, according to the examples described herein.

One preferred embodiment contemplates the use of narrow band semiconductor generated infrared energy that is focused into the interior of the can to affect a very high speed cure result. It is contemplated to use focused high power radiant energy that will directly affect the coating and the sidewall of the can interior to quickly transmit energy to both the coating material and the wall of the can, which then both reflects and re-radiates back to the coating material. This high power radiating narrow band energy will be introduced directly into each individual can and will bounce inside the can at the speed of light until virtually all of its energy is absorbed into the coating and the aluminum substrate.

While it is possible to affect the same amount of direct radiant energy reaching the tank with a broadband source, a narrow band source is the preferred and perhaps most desirable solution for many reasons. A broadband source such as a quartz lamp may be used, but many advantages are not achieved and implementations are not as beneficial. However, it is possible to implement and practice the embodiments described herein with a broadband source. For example, quartz lamps, high density discharge or arc lamps may be utilized. They tend to have wavelength output bands that fall within a sufficiently short wavelength range for focusing with common glass optics. However, conventional optical glasses begin to be ineffective at wavelengths in excess of about 2.7 microns, even though the upper ends of most broadband light sources and resistive heating sources will not pass through the focusing optics without heating the optics to sometimes excessive temperatures. Instead of focusing the thermal photon energy with refractive optics, a reflective optical configuration may be used. For example, a generally cone-shaped reflector or an elliptical, circularly symmetric mirror may be used to focus infrared energy inside the upper sidewall of the tank or container. That is the optimal zone with energy hitting the interior of the tank, since internal reflection from there will distribute it from that preferred starting zone. At such production speeds for can coating curing processes, it is almost certainly necessary to continuously switch on the various broadband sources, as they cannot be switched off and on at the speeds required for such applications. While this can be done, it is also expensive to equip the system with switching electronics to, for example, handle the 2,000 to 3,000 watt quartz bulbs required at each curing station. More care is needed to ensure that the can is heated to a temperature required to achieve the joint solidification action but not yet to anneal the aluminum body of the can. Close monitoring of tank temperature and the ability to modulate the broadband device output in the electronic controls would be highly desirable. One of the essential advantages of the present invention is the elimination of the weakening effect on aluminum in order to facilitate the use of less weight aluminum to manufacture cans of the same strength as can result from conventional processes that are currently almost universally used in the worldwide can industry. An additional consideration of broadband sources is that they have an inherent service life that is shorter than semiconductor devices used for narrowband sources. For example, quartz lamps have a short lifetime, but continue to have less photon output as they deplete themselves. The electronics must be able to modulate the power until the reduced output continues to be accounted for. A monitoring sensor may be employed just as it may provide feedback on the canister temperature and thus cure integrity with a narrow band device.

There are many narrow-band sources that can be implemented, including high power lasers, various semiconductor-based illumination devices, laser diodes, edge emitter laser diodes, VCSEL laser diodes, surface emitting laser diodes including SE-DFB laser diodes, laser arrays, and even Light Emitting Diodes (LEDs), such as high power LED arrays. Multiple arrays of devices (e.g., more than 10 devices per array) may be used to generate output power (e.g., more than 100 watts). Although the embodiments described herein may be performed with other modal high power laser diode arrays, this is because it is easy to implement and efficacy would be the preferred embodiment. Also, various examples and implementations of narrowband sources or arrays, including semiconductor narrowband infrared sources or arrays, such as laser diode arrays, are described in, for example, U.S. application No. 11/003,679, filed on 3/12/2004 (now U.S. patent No. 7,425,296), U.S. application No. 12/718,899, filed on 5/3/2010 (now U.S. publication No. 2011/0002677a 1), and U.S. application No. 12/718,919, filed on 5/3/2010 (now U.S. patent No. 9,282,851), all of which are hereby incorporated by reference herein.

The narrow band energy also promotes better optical accuracy because the wavelengths are similar enough to be nearly identically focused, which is not the case with broadband radiation sources. In some embodiments, a coating, such as an anti-reflective coating, on the optical device may be optimized to be very effective at the particular wavelength or narrow range of wavelengths employed.

Because the laser diode array is digitally switched, turned on immediately, and turned off immediately, it will facilitate a wide variety of possible implementations of the embodiments described herein. It can also be configured so that it can be optically treated in several conventional ways to facilitate bringing the direct energy directed into the tank to the precise areas of an effective implementation where it is needed for high speed curing. The precise application and preferences of the embodiments described in this disclosure depending on the disclosure will teach several optical implementations and several can handling mechanical implementations that are possible examples.

If the described embodiment of the invention is practiced effectively, then there should be a system that could affect the fastest one second that will cure the coating on the interior of the can. With sufficient power from the radiation source, it is even possible to cure in less than one second if the coating is so formulated as to start the joining process fast enough. It will be appreciated that any reduction in cure time as compared to conventional methods will result in overall efficiency, benefits and improved results. Significantly, as the cure time is reduced to less than one minute, for example, the improvement substantially increases. As a further example, cure times of less than 30 seconds, less than 20 seconds, less than 10 seconds, less than 5 seconds, and (as noted above) less than 1 second show even greater improvement. If the curing time is fast enough, for example, less than 20 seconds in at least one embodiment, or as another example, less than 30 seconds in at least another embodiment, the can is prevented from annealing. Shorter curing times (e.g., less than 10 seconds, less than 5 seconds, or less than 1 second) also result in avoiding annealing. If the annealing effect can be prevented, it will prevent the need for over-strengthening the can to maintain sufficient holding strength after the curing process. This can be a great advantage to the can manufacturer, since about 70% of the bill of materials and the average can manufacturing cost is the cost of the aluminum material used to produce the can. There is a huge potential for material savings and therefore a significant cost savings if 8% to 10% over-reinforcement of the tank is not required. Until this time, there has been no way to perform high speed curing at production speeds that prevent the need to over-build the cans. This is a completely novel idea, as manufacturers typically have to over-build tanks to maintain adequate strength, as previous ideas were not possible to cure at these rapid rates. Cans have historically solidified during mass transport. The embodiments described herein introduce a high speed narrow band cure of each individual can.

It is useful to summarize many of the advantages that will result from suitable implementation of the described embodiments of the invention. Reducing the amount of material is a major advantage in can manufacture. An alternative savings may be a slightly lower alloy content of aluminum, which may be less costly than the current higher alloy content aluminum. Another advantage of the described embodiments of the invention is that the width of the aluminum coil can be reduced due to the shorter cutting edge length and therefore the smaller diameter on the drawn cup. The reduced width, in turn, means lower cost, and higher reliability in the feeding equipment and the roll handling equipment. It also means that narrower bed double action presses can be purchased and implemented, as well as smaller lighter and higher speed press dies. A narrower press bed also means greater machine stiffness and lower moving mass resulting in longer press life and longer tool life. The cupper tool that makes the smaller diameter cup will initially be less expensive and the replacement tooling assembly will also be less expensive because there is a smaller diameter involved and there is less tool steel involved. Another advantage is that the embodiments described herein use, for example, a digital narrowband curing system that facilitates changing and fine tuning of curing parameters to improve or optimize the grade and overall curing process. Another advantage is that this tuning can be done dynamically to preferably correspond to any selected production speed and improvement or optimal energy savings. A closed loop process may also be developed that will verify the authenticity of the cure and correct any under-cure or over-cure that may be occurring. Furthermore, the amount of curing energy can be optimized by verifying curing with machine vision inspection, laser scanning, or otherwise in a real-time manner. This can be used to further save energy by not injecting more joule energy into the tank that is really needed for proper curing. Another advantage is that the embodiments described herein, in some embodiments, facilitate the placement of additives into coatings that will readily absorb more and be better at selected wavelengths, thereby paving roads for even lower energy curing and potentially higher throughput speeds. The described embodiments of the invention have the further advantage of facilitating a huge energy saving. Yet another advantage is the elimination or near elimination of any hydrocarbons or fossil fuels in the curing process. Other additional advantages result from the uniformity with which the can will solidify within itself and compared to other surrounding cans. Another advantage is that the system will provide the ability to stop and start the production line immediately with minimal detrimental results. A similar advantage is the elimination of the need for preheating before the line starts, whether from the cold line or the hot line after shutdown. Another related advantage is avoiding the necessity of cleaning the furnace and scrapped cans due to unplanned shutdowns, power outages, and the like. Other quality advantages arise from the ability to stop the line more randomly without deleterious results, practice being avoided by users of current technology due to fear of such deleterious results. A further advantage is created by eliminating the undesirable additional plant heating that occurs around the IBO furnace, which in many climatic zones will reduce the need for additional plant cooling or air conditioning. Additional advantages include the reduction or elimination of hydrocarbon-based fuel usage. Yet another advantage of the described embodiments of the invention is the ability to switch from one type of tank to another quickly and completely under programmable control. Yet another advantage arises from the ability to service portions of the curing section of the line, while the balance of the line continues to extend as individual single row curing lanes can be serviced independently. This brings the further advantage of being able to extend more continuously and eliminate the need for periodic shutdowns for furnace maintenance. Ultimately, this should result in more production throughput and less downtime.

The high-speed in-can curing techniques described in connection with the embodiments described herein can now be practiced in several different ways with reference to the drawings. The different ways of practicing the exemplary embodiments described herein mainly pertain to two general fields. Firstly how the system is arranged so that the tank is introduced to and taken from the narrowband irradiation source, and secondly how the narrowband irradiation is generated and directed specifically into the area where it is required inside the tank.

According to the described embodiments of the invention, a two-piece beverage can with an internal coating to be cured generally comprises the sections described hereinafter, as it is generally known in the industry and as shown in fig. 1. While other shapes and configurations may be cured, such as a can with tapered walls, most two-piece cans still have configurations that will be detailed herein for practicing the teachings of the embodiments described in the present disclosure. In this regard, the tank (22) includes a straight vertical wall (23) extending from the moat (26) and heel region (25) to the top of the tank. The topmost part of a straight walled can (22) without a neck is commonly referred to as the cut or trim edge (21). The internal coating and subsequent curing operations typically occur on straight walled, neck-less cans (22). Which in necking/flanging machine operation narrows and flanges in a later operation in the region near the trim edge. At the bottom of the tank (22), a zone starting with the bottom section of the wall (23) is formed and called heel (25), which transforms into a moat zone (26) and then finally into an arched dome zone (24) at the central bottom of the tank (22). These various sections of the can (22) have been designed to be manufactured and thoroughly tested to hold at the pressures required for soft drink or beer containers, with the pressure typically ranging from 90 to 110 PSI. The base metal (28) from which the entire body of the can (22) is made is most commonly made from aluminum alloy #3,004. This alloy has been selected and standardized by most industries because it combines strength, formability, and elasticity in can manufacturing processes and applications. It is certain that this alloy is more expensive than straight aluminum materials and anything that can be done to facilitate the manufacture of a complete enough to be competent tank from lower alloy materials will save money for the manufacturer.

The exterior surface of the can (22) is typically coated or printed with a coating or ink layer (29), as shown. The entire interior surface of the can (22) of current industrial practice is coated with a layer of epoxy-based material, such as layer (27), baked thereon to properly cure it. The practice of industry specifications for properly cured coatings is well known within the industry and is part of the manufacturer's specifications. Of course, it is simply not acceptable to have any areas on the interior of the can that have not been completely coated or properly cured. The can manufacturing industry is continually concerned with ensuring that the coating is all properly cured and that there are no void areas in the finished product where uncured epoxy is present. Coatings other than epoxy have been tested but have not been widely spread. The embodiments described in this invention would be well suited to other types of coatings or partial coatings if those types or portions of coatings require heat or thermal curing. The same is true for newer coatings that reduce or eliminate BPA in coatings that are thermally cured.

Although there are two main areas that require design attention, the first challenge encountered in practicing the described embodiments of the present invention is how to generate powerful narrow-band illumination. The first impulse of the designer is to try to configure something that can be inserted into the tank, which would shine in multiple directions if there were no 360 ° pattern. While this is possible, most techniques available for generating high power narrow band energy are significantly larger than something that can be inserted into a can through the neck-free top of the beverage can. It is of course possible that this will become more practical as technology shrinks and narrow band energy devices are more efficient and produce more power in smaller packages. The problem with the "plug-in-tank" technique is that it involves many more moving parts and mechanisms, regardless of the size of the energy generating device. The insertion/retraction movement will have to occur between 200 and 400 strokes or insertions per minute and the speed will likely increase in the future. This assumes that the entire production flow through the can manufacturing line is divided into six to eight curing lanes, each running at a throughput rate of 200 to 400 cans per minute. In this regard, for example, a typical production rate may be about 300 cans per minute or more. Nevertheless, the concept of inserting and retrieving a radiation source from a tank is a viable implementation technique, but would require more mechanisms in order to insert and retrieve the radiation delivery arrangement at this rapid rate. It would be expected that it would be more complex and therefore require more maintenance than a non-looping arrangement that does not enter through the opening plane of the can body.

Instead of inserting and retrieving the actual source of the narrowband irradiation, the portion that can be inserted and retrieved can just be the optics or some form of light guide that guides the narrowband irradiation generated outside the tank into the appropriate position on the inside of the tank. This may take the form of a fiber optic light guide configured to collect energy from one or more narrow band sources and deliver it into the tank. For example, if a single very high power laser is used to provide narrow band radiant energy, a fiber optic light guide may be coupled to the laser in a location that will locate the laser safely away from the rigors, vibrations, or contaminants of the actual curing station. It is necessary to design the correct lens or diffuser at the exit end of the fiber optic light guide to produce an output pattern that will be sufficient to illuminate the coating on the interior of the tank.

The light guide may also take the form of a lens configuration (see fig. 3) arranged to collect narrow band energy near the source (32) and then project the narrow band energy through a final objective lens configuration (38) and lens assembly (34) at the full correct focal length when the articulating mechanism (33) fully inserts it into its illuminated position inside the tank (22). Photon energy (30) may be directed down a tube (35) to the output of an objective lens (38) inside the tank (22), possibly in conjunction with an additional diffuser (37), which may then directly irradiate the coating (27) on the tank interior. Many different arrangements of lens and light guide type approaches may be configured by those skilled in the art of high energy lenses and optical design. The vertical insertion and retrieval mechanism (33) would ideally have a containment baffle arrangement (36) to maintain photonic energy in the tank by reflecting the energy back into the tank. It is also possible to ensure a safer arrangement by ensuring that the irradiation is all delivered to the interior of the tank. All components and mechanisms will have to be designed so that they can handle the rigors of moving to and retrieving from the tank at high speed to meet the requirements of high volume manufacturing. This method can prove to be an excellent way of irradiating the interior of the tank with a uniform irradiation pattern, but would require much in the mechanism of articulation and engineering design and therefore be more costly to implement. It has the distinct advantage of providing a very straightforward way of projecting narrow-band illumination onto a coated surface to achieve excellent results. It has the following disadvantages: an obstacle (35) is placed into the tank, the obstacle (35) will block some of the reflected energy (39) that needs to continue to hit the coated surface until its energy is depleted. It will itself become a reflector (35), but this will waste some of the energy (30) lost during reflection on the uncoated surface. Considerable heat that must be handled and removed is also given to the optical assembly (35) & (34).

Another technique for providing irradiation energy to the interior of the tank (22) is shown in fig. 2. It includes a design concept whereby no components would damage the plane of the cut edge (21) by protruding into the can interior. It is assumed that the irradiation mechanism does not have to circumscribe into and out of the tank, but rather can be fixed in some way just slightly above the tank and still provide sufficient and properly dispersed irradiation into the tank. In this regard, the optical system may be incorporated into and/or used in conjunction with the illumination system. A well designed optical illumination system will in at least some embodiments be able to focus a relatively high percentage (e.g. 95% or more or 90% or more) of the optical energy emerging from the optical arrangement directly and evenly to the interior of the tank for curing purposes. Since aluminum is highly reflective at these infrared wavelengths and since the can is cylindrical, a large amount of internal reflection can be reliably predicted with low confidence. For most embodiments, care should be taken in the design to ensure that energy randomly reflected through the open top of the tank is reflected back into the tank to continue the internal reflection process until the energy is depleted. Because infrared light energy travels at the speed of light, a large amount of reflection can occur over an exposure time of several seconds long for high speed curing.

This configuration relies on aluminum being highly reflective not only in the visible and near infrared but also in the shortwave infrared band. If the plane of the bottom of the narrowband irradiation assembly is located, for example, about 0.030 "to 0.045" from the top cut edge of the tank (21), it is close enough without excessive energy loss through the gap, but close enough that sufficient energy transfer will occur at the necessary angle to effectively cure the coating by bouncing energy inside the tank. It needs to be close enough so that the cone or cone surface (64) can interface with the tank internal geometry to return most of the energy reflected out of the open top of the tank back into the tank. The conical surface may be formed from a variety of different materials including copper, aluminum, gold-plated metal, silver-plated metal, and/or highly reflective nanostructured materials.

The embodiment shown in fig. 2 may also be modified. In this respect, with reference to fig. 7, the reflection cone (64), or whatever geometry it is chosen, should in most embodiments also provide optimal ventilation of the water vapour in the tank by positioning the shutters accordingly. The shutters (74) must be shaped so that they are reflectors facing the inside of the tank but with spaces between the shutters to provide vacuum airflow through the vacuum ports (72). A well designed airflow system actually both pushes air into the canister and draws vapor-laden air out of the canister through a shroud (74) or vent in the reflex cone.

If the 90 ° angle (69) is designed, for example, as the internal geometry of the cone (64), it will act as an excellent polygonal reflector to reflect narrow band energy back or into the tank for further curing. The energy may bounce inside the can hundreds or even thousands of times depending on the selected wavelength until all of the energy is absorbed into the coating (27) or substrate aluminum (28).

The primary purpose of the optical arrangement shown in fig. 2 (or fig. 7) is to inject photonic energy into the interior of the tank (22), as shown. In one example, the narrow band photon radiant energy is generated in an array (51) at the top of the graph in fig. 2. An array or arrays (51) may have any number of laser diodes connected to the appropriate power supply. The designer of the array may use a combination of series and/or parallel connections of laser diode devices to obtain their desired current and voltage input preferences to meet the system he is designing. This will determine the current capacity and voltage required from the power supply. Selecting the correct combination will allow optimization of the power supply specifications. The laser diode may have an edge emitter design or a surface emitting type design. Surface emission designs have practical robustness advantages because the effective aperture is much larger and therefore less vulnerable to contamination. Conventional edge emitters are most commonly coupled to fiber optic light guides to provide a better way to deliver narrow band energy to the optical system without exposing its rather fragile aperture to difficult environments and contaminants that could lead to catastrophic aperture failure. The additional cost and assembly complexity associated with fiber coupling to the device make conventional edge-emitting laser diodes a viable solution to practicing the embodiments described in this disclosure, but are less desirable and cost much higher than other solutions. On the other hand, surface-emitting type laser diodes generally do not require fiber coupling. It can generally be configured to shine directly into the optical configuration that will direct the narrowband output directly into the tank. This arrangement may make it more fragile in some cases because it is closer to the curing location, but the elimination of fiber coupling may save significant costs and provide more reliability in the overall configuration. Whichever type of device may be selected for the application, it must be mounted in a housing (55) in such a way that its optical output is directed towards a condenser lens (56). In at least one embodiment, the housing is configured to prevent stray infrared energy from escaping the housing, except through a pinhole element or a suitably sized aperture element (described below), although various configurations of the housing can be implemented. The output of the laser diode will diverge in two directions-the fast and slow axes, or in a single direction. In the case of SE-DFB, the output is columnar in one direction and has a slow divergence in the other direction. With respect to SE-DFB, the slow axis will be considered to be the columnar direction and the fast axis will typically diverge at 7 to 10. A VCSEL has a conical output mode if it is used as a narrow-band photonic energy generating device. Whichever type of laser diode is selected, it must be packaged and configured in multiple device arrays so that its total output power is sufficient. With regard to SE-DFB, VCEL, and any other surface emitting device, it may be packaged onto a cooling circuit board in an X by Y or some other pattern, but such that energy is directed primarily orthogonal to the mounting circuit board.

The arrays are of course of different sizes to perform the embodiments described in this disclosure. In at least some embodiments, the array can be built and used for internal curing of the cans with a total output ranging from 250 watts to over 500 watts. For example, a 500 watt array may include 50 surface emitting laser diodes, each of which may generate 10 watts of optical narrowband near infrared power. This optical power may not be sufficient to perform in-coating curing in a specified time, so that multiple identical arrays may be the best configuration for the designer. One experiment shows that a 300 watt laser diode array can properly cure ultra-thick internal coatings in 10 to 15 seconds without careful attention to the optimized optical arrangement. An example of a suitable optical configuration, such as the one shown in fig. 2, can accurately distribute photon energy where improved uniformity and much faster curing are desired. This optical configuration will ensure that less photon energy is wasted and a much faster cure time will be achieved. By combining the correct number and design of arrays, it is reasonably reasonable in improved (e.g., up to optimal) and production engineering configurations to cure the epoxy coating inside each individual can within one second. It should be appreciated that the optical configuration can be designed or tuned in at least some embodiments to deposit a desired amount of energy in a desired location on the interior of the tank. For example, an optical configuration may be implemented that deposits more energy at the top of the interior sidewall surface of the can and smoothes the reduction of energy along the sidewall of the can. Various optical elements (e.g., refractive, reflective, non-linear, aspheric, or other elements) may be used to achieve these and other goals to meet the requirements of a particular configuration.

In this improved or optimized configuration, with continued reference to fig. 2 (and fig. 7), the optics or microlens array (52) may be selected such that it produces a columnar energy (54) directed parallel to the central optical axis of the system. Once the column of energy has been generated and directed towards the condenser lens (56), the output energy (57) will converge towards a focal point in the pinhole (65), then the light energy will cross in the pinhole (65) and become a diverging ray (58) as it is then directed towards the coating on the interior of the can (22). Once the photon energy has reached the wall of the interior of the tank that has passed through the first layer of coating (27), it will reflect from the inner side wall of the tank () so that the energy passes back through the coating (27) again. The photon energy will continue to advance through the coating (27) and bounce off the wall (28) and back through the coating (27), as shown, for example, at (59), until it imparts all of its energy to the coating and the can wall. Some of those bounces will also affect the reflective cone surface (64) and then will bounce back to the tank and continue the process. The tapered surface (64) should be made of or coated with a highly reflective material. It may be copper, silver, gold or other specific infrared wavelength that makes it as highly reflective as possible as utilized. The needle hole (65) & (71) is in a plate (62) designed to be replaceable to provide easy maintenance to maintain a clean sharp needle hole area. The pinhole size (which may be 3mm, but as just one example) and sidewall shape should be the smallest that the optical configuration can accommodate, so that virtually all focused photon energy passes through the aperture without depositing energy on the pinhole plate (62), but not through the unnecessarily large openings in the plate (62) and cone (64). However, it should be appreciated that a suitably sized hole may be used as the pinhole (65) or in place of the pinhole (65). In this regard, a pinhole such as pinhole (65) may be well implemented for the system as described embodiments of the present invention that more accurately focus the illumination to the tank interior as desired. However, such an arrangement (which may generate more heat or have higher implementation costs) may be necessary for all configurations. Thus, any suitably sized hole, such as a hole having a diameter smaller than the opening of the top of the can, may be implemented to achieve the desired result. In this regard, this aperture (but as just one example) may be less than 2 inches or another size depending on the size of the can. A reflective structure (64), which may be formed into any geometry for optimal reflection of energy back into the tank, is also manufactured so that it can be replaced to be easily renewed and provide a clean reflective surface. It can be replaced quickly and easily on a periodic basis when necessary, and should be designed so that it can be done with minimal tools. Given the particular shape of the geometry of the tank, the angle of the reflective cone insert (64) should be carefully modeled so that the maximum amount of energy is reflected back into the tank. The housing (55) should be made of a material that allows the disposer to reflect the scattering of the contained infrared radiation. It should preferably be designed with a machined hole (61) through it so that water or coolant can be circulated through the housing to remain cold at all times. It is necessary to maintain it at a comfortable operating temperature so that the array of semiconductor devices (51) does not attempt to operate in an excessively warm environment. The laser diode array (51) should also have some form of cooling. It may be cooled by a refrigeration cycle through the actual array or it may be deionized water. In the most desirable embodiment, it may be a fresh water circuit through the array. If the device is highly efficient, as in future situations, no gaseous or liquid coolant may be required, and air cooling with a heat sink and fan may be sufficient to maintain the device within a comfortable operating temperature range. The housing (55) may also have cooling facilities so that any components mounted thereon, including the optics and laser diode array, do not experience excessive heat. Again, the cooling of the housing (66) may be a recirculating water jacket or may be a forced air cooling arrangement. It should also be appreciated that the bottom surface (67) is configured in at least one form to control the reflection of any energy escaping from the interior of the tank (22). While various configurations and/or techniques may be implemented to achieve this goal, as shown, surface (67) is provided with grooves, such as deep grooves, to provide such control over any leakage energy. Regardless of the configuration of the bottom surface (67), the flush mating surfaces before and after the housing (55) should be engineered and assembled so that the entrance face (73) is at the same level as the furthest extent of the bottom surface (67) of the housing (55). The exit face (72) must also be at the same level or slightly above the furthest extent of the bottom surface (67) of the housing (55) so that the trimmed edge surface of the top of the can (22) does not encounter a bump.

With these various technologies, it is possible to use a broadband infrared illumination source such as quartz lamps or high-energy discharge lamps and the like. However, it is more difficult to accurately focus the energy. It is less energy efficient at producing the most efficient wavelengths to match the coating for optimal and fastest curing. It will inherently operate much more thermally due to the way it fundamentally generates its output energy. This would require many additional engineering designs to keep everything cold and not allow the tank to completely overheat. If the can is overheated, it is annealed or de-tempered, even for a short duration. These broadband infrared sources will have less control over the heat given to the tank and will need to modulate its output depending on the throughput speed. Although they cannot be turned on and off quickly and in a precise manner as semiconductor-based illumination, they can be modulated with careful engineering design. For example, as noted above, a broadband electrical infrared component such as a quartz lamp, a high-density discharge lamp, or an arc lamp may be utilized. Again, instead of focusing the thermal photon energy with refractive optics, a reflective optical configuration may be used. For example, a suitably engineered reflector arrangement, a generally cone-shaped reflector, or an elliptical circularly symmetric mirror may be used to focus infrared energy inside the upper sidewall of the tank or container. That is the optimal zone with energy hitting the interior of the tank, since internal reflection from there will distribute it from that preferred starting zone. In this regard, the configuration shown in fig. 3 (as well as the configuration shown in fig. 2) may be suitably modified to implement a broadband embodiment, wherein the radiation source is implemented with a broadband source and the optical elements are implemented using reflective (rather than refractive) elements and arranged to aim or direct radiation at the upper sidewall of the inner surface of the tank.

Also, referring now to fig. 8, a broadband infrared system 200 is representatively illustrated. The system 200 for use in a can manufacturing internal coating and curing process in which a coating has been sprayed onto the internal surfaces of the cans includes a can handling system 205 (not shown in detail) that is configured to continuously move the production cans into at least one curing zone. In addition, the system 200 includes a broadband infrared source, such as a broadband infrared source 230 including quartz lamps 220, positioned to individually and electrically heat the interior surface of each can 22 (shown in cross-section) moved into the curing zone using optical elements 240, the optical elements 240 positioned to direct illumination (shown representatively at 260, for example) toward the upper sidewall of the interior surface of the can such that the coating on the interior surface of each successive can in a series of production cans is brought to a critical temperature to create a bond curing process in the coating in less than 20 seconds to prevent de-tempering or annealing from occurring in the cans. The system is also provided with a control system 210 (connected using link 250-which may take various forms and is only representatively shown) configured to use sensor information (not shown) to modulate the output of the broadband infrared source to maintain consistent curing temperature and results. Although the form of this system 200 may vary, as shown, the optical elements may take the form of an appropriately engineered reflector arrangement, such as described above, a generally conical reflector or an elliptical circularly symmetric mirror for focusing infrared energy on the interior of the upper sidewall of the tank or container 22. In at least one form, such optical elements may have a size at least slightly smaller than the diameter of a container, such as container 22, or the opening of the container, to allow for proper transmission of energy into the tank and proper maintenance of those energy in the tank for curing purposes.

However, as noted herein, precise digital control and precise energy control are advantageous for semiconductor solutions. A semiconductor-based illumination configuration should have a much longer lifetime and more consistent output over the useful lifetime. While a broadband source may have a useful lifetime of thousands of hours, its output will continue to drop over that time, so it must be carefully modulated to ensure consistent curing results. It will not wear at the same rate, so it will be an engineering challenge as well as a long-term maintenance issue to ensure that the irradiance output of each lamp is sufficient to ensure proper curing.

Referring now to fig. 4 and 5, the embodiments of the embodiments described herein should also address the preferred configuration of mechanical tank processing in most forms. These configurations can take at least four different forms. Also, it should be understood that the description of fig. 4 and 5 includes reference to examples of narrowband illumination sources; however, the broadband infrared source correspondence system may also be used in these embodiments with suitable modifications as necessary.

Further, although an example implementation is illustrated in fig. 4 and 5, the implementation may take various forms. In such a way, methods and/or systems in accordance with embodiments described herein may be implemented in can manufacturing interior coating and curing processes, where the coating has been sprayed onto can interior surfaces. A can handling system (including, for example, a conveyor that may take various forms) transports cans continuously toward at least one curing station. The cans are then individually and electrically heated in at least one curing station using, for example, radiant infrared energy generated by a narrow-band semiconductor (generated by, for example, an array of semiconductor-based narrow-band illumination devices) and optical elements positioned outside the cans, such that the coating on the interior surface of each successive can in a series of single-row production cans is brought to a critical temperature to complete a bond curing process in the coating in less than 20 seconds to prevent de-tempering or annealing from occurring in the cans. Thus, using this technique, the amount of aluminum can be reduced, for example, by 3% or more, and will have similar sidewall axial strength, bottom reversal strength, and overall strength compared to thicker, heavier cans that cure over a longer period of time, as the thicker cans weaken during a longer cure, as compared to the prior art. Also, example embodiments include an entry track or conveyor configured to organize or facilitate movement of individual containers in a single row sequence toward a second conveyor configured to rotate a turntable to move individual containers to and away from at least one curing station, the at least one curing station comprising an optical configuration in which photon energy from at least one surface emitting laser diode array is passed through a cylindrical optic and then focused by at least one condenser lens element through a pinhole or aperture at which the photon energy diverges to illuminate an interior sidewall of a coated container, the pinhole or aperture positioned at an apex of a reflection cone for reflecting the photon energy back into the container to perform further curing work, wherein the coating cures in less than 20 seconds sufficiently fast to prevent weakening or annealing from occurring in the aluminum comprising the container, and the second conveyor delivers containers and is directed to a third conveyor configured to display containers out and away from the second conveyor so empty pockets can be used to load waiting uncured cans to continue curing continuously while cured containers are transferred on the third conveyor toward a subsequent container manufacturing operation. In addition, example embodiments include an entry track or conveyor configured to organize or facilitate movement of individual containers in a single row sequence toward a second conveyor configured to rotate a turntable to move individual containers to and away from at least one curing station, the at least one curing station comprising an optical configuration in which photon energy from at least one surface emitting laser diode array is passed through a cylindrical optic and then focused by at least one condenser lens element through a pinhole or aperture at which the photon energy diverges to illuminate an interior sidewall of a coated container, such pinhole or aperture positioned at an apex of a reflection cone for reflecting the photon energy back into the container to perform further curing work, wherein the coating cures in less than 20 seconds sufficiently fast to prevent weakening or annealing from occurring in the aluminum comprising the container, and the second conveyor delivers containers and is directed to a third conveyor configured to display containers out and away from the second conveyor so empty pockets can be used to load waiting uncured cans to continue curing continuously while cured containers are transferred on the third conveyor toward a subsequent container manufacturing operation.

More particularly, referring back to the drawings, one example configuration that will be outlined in connection with FIG. 5 is one that involves continuous rotational motion. In this arrangement, the narrow band illumination source (and possibly a controller), optics, cooling (such as a heat exchange, cooler, and/or recirculation pump), and power supply (such as a DC power supply) rotate with the star wheel which organizes the cans into the correct spacing, provides propulsion to move the cans, and delivers them to the appropriate location for illumination. The rotary joints would be designed into the system to provide delivery of whatever electrical power, control signals, compressed air, vacuum, and/or cooling is required on the continuously rotating turntable or turntable. It is assumed at this point that it is configured such that the narrowband irradiation array or source can continuously irradiate the interior of the tank through its optical configuration for the period of time necessary to impart sufficient joule energy to effect a complete cure. The entire illumination system will rotate with the canister in a synchronous motion. The irradiation energy will be switched on when the tank is rotated by the initial irradiation station and then switched off before the tank leaves the planet. As an example, if a particular narrowband irradiation system is capable of generating 500 joules, and a particular canister requires 850 joules for proper curing, the irradiation must be turned on during the 1.7 second portion of the arc of the planet. The start time and duration of the on-time may be fixed or, more desirably, programmable parameters. The density or pulse width modulation on-time (duty cycle) should be programmable in at least some form. The user interface may be configured to meet the requirements of the end customer. It may be as simple as a screen entry on the display of a programmable controller or as complex as a PC driven user interface with user friendly graphics showing on/off timing, duration and density. It may also facilitate programmability or graphical setting of the density profile in terms of time or turret position. The controller of the system may also communicate with a portable device, whether a tablet computer, smart phone, smart watch, or otherwise, to facilitate monitoring of the curing system settings, speed, and functionality. The diameter and RPM of the planets must be configured so as to provide sufficient dwell period for the irradiation to perform proper curing. This configuration of the described embodiments of the invention will be described in more detail below.

Since this narrow-band radiation-curing system is so programmable and flexible, it can also be connected in other ways. A downstream inspection system (97) may inspect the transfer-out can (89) to ensure that the coating has covered the entire interior of the can and that it is fully and properly cured. This inspection system may utilize a visible light grayscale or color camera or it may use an infrared camera on the way out of the curing system, or it may use both types. The inspection system may ultimately attempt to determine if there is any bare, uncoated metal or uncured coating. If the inspection system (97) has not verified that the coating is not properly cured, the system can close the loop and develop joule energy, which is applied to the various cans from the respective stations to ensure that they are properly cured. The system will be able to correlate the content that it will know which can is cured by which curing system (91). To the extent that cans from individual curing stations are under-cured, the system will be able to correct and increase the curing energy from any particular curing station. Similar process corrections by closing the loop from the inspection station back to a particular curing station can be done on any configuration in which the embodiments described herein can be practiced.

The system in fig. 5 may operate as follows. The ejected but uncured cans (82) will be reached by a conveyor, track, or similar mechanism or system configured to organize or facilitate movement of the individual containers in a single row sequence toward, for example, another conveyor or device. This conveyor may be any form of conveyor, including a vacuum conveyor, or it may mean a track that simply guides the cans while air or gravity pushes them forward. A vacuum belt type conveyor (80) is shown schematically, also having guide tracks (81) along both sides of a row of cans. A row of canisters (82) is pushed so that a slight pressure is exerted on the support plate (87) as the next canister to be loaded is on the fixed plate (96). As the turntable or turntable (84) rotates, the cans continue to press against the support plate (87) until the next empty pocket (86) is reached and the can be pushed into the pocket. As the canister is pushed into the pocket (86), it may be assisted by a vacuum drawn from a rear section of the cavity support plate (87) that is closest to the center of the carousel. The shape of the support/nest plate must be carefully derived so that the can slides smoothly when the pocket is open and available and so that it does not dent or deform the can. It must also create a consistent position for the canister and hold it securely and in a consistent position during the time the canister is cured. As the turntable (84) continues to rotate, it will transport the cans in the nest locations (86) and will give a signal to turn on the irradiation energy once it clears the loading station. The control system will switch on the energy at a rate that is not harmful, but not so slow that the time available for curing is wasted, which can be handled by the irradiation device. As the array of illumination devices (85) is actuated, they are powered by the control system and power supply (95) corresponding to each illumination station. They should be centrally located under the illumination optics (91) throughout the time the cans are rotated by the turntable. The optics (91), array (85) and power supply and control system (95) rotate with the turntable (84) and maintain their relative positions to each other throughout the course of rotation. The encoder (93) continuously feeds the rotational position and speed information back to the central control system (99) through a cable (98). The central control system (99) feeds back the relevant information that each station has to have its own local controls (95) in order to correctly actuate each irradiation station (91) with its proper timing and power level. Each of the control systems (95) will monitor the cooling of each of its respective stations and will feed the content back to the central control (99) through the interconnect (98) in order to facilitate full supervisory control of all stations.

As the cured can (89) approaches the unloaded station, it will gradually come into contact with the stripper arm (90), which will gradually and slowly push it out of the station onto the already moving vacuum conveyor belt (88). The cured canister (89) will continue to travel along the vacuum conveyor (88) and will be transferred on its way from the curing system under the inspection station (97). Instead of a vacuum conveyor, a rail system uses gravity or high volume low pressure air to move it on to exit the curing system.

Another possible configuration of the described embodiment of the invention is somewhat similar in that it employs continuous rotational or linear motion, but it uses a fixed position irradiation system that is gated to impart energy as the tank passes the correct position. This configuration would require a very powerful and very short pulse of illumination energy that must be properly timed. The duration of this high speed strobe pulse will vary with respect to the precise implementation details and throughput speed of material processing but will likely require a pulse of less than 500 milliseconds, but may be as short as 300 microseconds for some higher speed applications. An over-pulse array of narrow band infrared semiconductors is likely to achieve very high outputs in a very short period of time. The concept at this point is that if the nominal normal electrical supply current on the array could be x, then for a very short duration, perhaps 10, 15 or 20x is possible to obtain a much higher peak output. If, for example, 1700 joules are required for correct illumination, a group of illumination arrays typically produces 1700 joules in 1.7 seconds with a current input of 15 amps, may be gated at ten times their normal current to produce 1700 joules in 170 milliseconds, in which case the normal current may be 150 amps. This overall configuration requires fewer mechanisms and the illumination array need not be mechanically moved or dynamically looped, but more electrical and electronic work is required to pulse such high current power and the array needs to be able to withstand the pulsed power and produce proportionally high output. They need to be tested to verify that they are in fact over-pulsed to this extent and still have a usable service life for the particular implementation.

The gated or over-pulsed configuration may be implemented in a system of a rotational motion configuration or a system of a continuous linear motion configuration. Either arrangement will facilitate allowing the canister to deliver a single row under a gated narrowband irradiation array for curing exposure. Practitioners of the described embodiments of the present invention will continue to discuss the relative advantages of material processing throughput speed versus power and configuration of illumination systems. A more powerful illumination system will illuminate internally over a shorter period of time proportional to the power it incorporates. For example, for practical purposes, a 2,000 watt array will illuminate approximately twice as fast as a1,000 watt array, but a1,000 watt array requires more material handling equipment to run at slower speeds because the system must be designed with more parallel or series mechanisms to achieve a particular throughput speed. If the material handling system is running at double speed, twice as many cans can be handled in a given period of time, whether it be a star wheel, conveyor, or otherwise. However, to cure at double speed, approximately twice the power output is required in narrow-band illumination arrays and larger power supplies, and the like. Higher power illumination systems typically require much more cooling and the various items in the system, including the optics, must be able to handle much higher power levels. Similarly, high speed material processing equipment presents its own challenges. Since the kinetic energy in the motion term increases as the square of its velocity, a material handling system running at twice the velocity must handle four times the inertia or kinetic energy within the overall system (contained in the tank being handled). Because of all these factors, designers and implementers of the described embodiments of the present invention must determine how many individual lanes the system will be divided into to get a specified throughput and then determine how much power is needed in the illumination system in order to cure at the speed required by the material handling system.

A typical can line divides the production flow into seven passes to run inside the can coating. Assume that one of the lanes is available for maintenance at any time while the other six runs continue to produce. According to the described embodiment of the invention, each curing lane may cure individual cans (converted to six lanes of 1800 cans per minute), for example, at a production rate of 300 cans per minute. The complete outputs of those six active traces are then brought together into mass transfer before passing through the IBO. With respect to the embodiments described herein, the lanes will continue through the corresponding curing lanes while still being separated. Thus, since the cure lanes are parallel independent lanes, they can be started and stopped separately. They maintain independence from control, service and speed optimization. The independent curing lanes of this configuration allow starting or stopping for any reason without shutting down the plant or the entire production line. It facilitates scheduled maintenance while maintaining production, as well as spontaneous maintenance or plug clearance without stopping production. If any electronic troubleshooting or component replacement is required, it can be done seamlessly while normal production continues. The individual cure lanes may then be merged again into one high speed single row lane for the next production step, which is typically a neck flanger.

Another arrangement, which can be implemented in accordance with embodiments described in this disclosure, incorporates high speed indexed rotary motion. This configuration would involve a dial or star wheel arrangement incorporating a rotationally indexed configuration that would repeatedly move a specified arc. The indexing technique may be one of several mechanical or electromechanical considerations. The periodic indexing may be one of several techniques including electrical servos, cams, ratchets or clutches, mechanical, pneumatic or any number of other indexing mechanisms. Although it is employed here in a unique way, all these mechanical mechanisms are detailed in the literature and patent databases and will not be explained in detail here. Commercial products can meet this requirement of the base establishment well, but then they must be processed very well and the cans are therefore handled by the high-speed irradiation curing station.

A properly indexed star wheel or turntable facilitates moving the cans under the irradiation source and will provide a dwell during which the irradiation source can be turned on and then finally turned off before indexing the cans out from under the narrowband irradiation source and bringing new cans to a position that allows them to be irradiated. This repeated indexing cycle has the following advantages: the application needs to provide a dwell duration of any length. It must provide any number of joules of energy required for proper curing, but the speed and throughput will require that the specific radiant power be matched to the correct speed of the indexer to meet the overall production requirements of the system.

The indexing arrangement may provide for moving a single can to the narrowband irradiation source away from the narrowband irradiation source. Alternatively, with respect to each index, it may move multiple cans to positions under multiple irradiation sources. It is therefore possible to design the system such that it is optimized by having a perfect number of irradiation sources to process the curing cycle, while the indexing carousel can be run at speeds within the high reliability range of its mechanism.

It is important to design a servo driven indexing system to have the correct indexing dwell and indexing time to indexing arc length ratio. This will facilitate configuring the narrowband illumination sources such that they can fully utilize the maximum irradiation time while minimizing the actual dividing time. It is also possible to have multiple irradiation stations so that all of the irradiation does not have to occur at a single station. This technique will facilitate gradual irradiation so that the coating in the can be heated by a series of irradiation stops. This can lead to a large waste of heat as the aluminium cans cool down quickly, which may require more heat to be injected at a subsequent station. However, it may be a viable configuration if the coating is kept at an elevated temperature for a more extended duration to meet a particular type of coating. It will also facilitate multiple repeated exposures if a longer illumination period is required than can be facilitated by other mechanisms. This may also facilitate higher throughput speeds if carefully configured. In some cases, a longer effective duration may be required to drive off water or for other curing reasons.

Embodiments of the rotational motion arrangements of the described embodiments of the invention may utilize gravity to assist the movement of the cans through their respective tracks. The cans can substantially touch each other as they move on a path through the track or from the narrow band high speed radiation curing station. The steeply inclined or vertical track filling the cans is very helpful in order to provide slight pressure to push their next can into their respective carousel-transporting nest. For example, in fig. 5, if the track (81), whether supported by a vacuum conveyor (80) or not, may be configured such that it is vertical or at a steep angle such that the cans (82) push each other. Gravity nudge, which can be increased or decreased by increasing the verticality or stack length of the shipping nest (86) before the peel guide (87) lightly guides the next can to the shipping nest (86).

Another way of implementing the embodiments described in the present invention is by means of a linear escapement configuration, as illustrated for example in fig. 4. This involves having two parallel conveyors: an input conveyor and an output conveyor. They are positioned parallel and side by side to each other, but with space between them for the escape track and the station. A programmable escapement pusher is arranged along the input conveyor that is configured to provide appropriately timed advancement into the escapement track between the two conveyors. A narrow band illumination system is provided above the workstation on each escapement rail at the escapement workstation so that when the canister is pushed away and remains at the workstation, illumination can continue as long as necessary for proper curing. Once the curing duration is complete, the cans are pushed out of the workstation and to the exit conveyor in the correct timing so that they fit into the gaps between other cans that have been processed on the high speed exit conveyor. This type of arrangement allows a large amount of parallelism over long latencies but has high programmability. It can typically be implemented at a lower cost point and can provide higher reliability and more modularity than most other configurations. However, it requires more sensing, more programming and more ringing of the canister. The linear escapement configuration in fig. 4 will be explained in more detail herein.

The linear escapement configuration will work as follows. Referring to fig. 4, the infeed conveyor (111) brings a row of single-row upright cans. The open top faces away from the vacuum conveyor that transports it. The input speed of the conveyor (111) will depend on the throughput speed and processing speed of the overall balance of the system. The actual speed and belt position are continuously monitored by an encoder (109), the encoder (109) being linked directly to the drives of the conveyors (118) and (119). The encoder is connected to a computer, control system or programmable controller which continuously records the position of the belt and monitors the position of each can entering the material handling system by input from a photocell (100). As uncured cans (112) are fed onto the input belt, the control system determines which irradiation station will be available for the can to enter. Seven completely independent radiation curing stations (106) are shown in fig. 4. If the programmable controller determines that it will send cans to station three, it will alert the station three diverter (114) to extend its fingers in very precise timing to provide the necessary vector force to tip the cans to the third irradiation station. As the cans hit the fingers of the diverter (114) as they approach station three, there will be a propulsive sliding motion produced by a combination of dynamic actions provided by the moving belt. As the can is pushed off onto the station three-sided rail conveyor, it will first slide over the dead plate (113) before being picked up by the station diverter conveyor (105). The diverter conveyors will continue to transport the uncured cans to their respective curing stations (106) until the center point (110) is above the center point of the uncured cans below the curing stations (106). The diverter (105) will continue to convey the can to the curing station (106) until the photocell (120) verifies its arrival. At this point, the diverter conveyor (105) will stop moving the conveyor and the irradiation station (106) will be activated and will irradiate the interior of the tank. The electro-optical system is very similar to that shown in figure 2. When the on-time indicates that the correct number of joules of energy has been imparted to the interior of the canister, the narrow band curing system (106) will be turned off and the control system will know that the cured canister is now ready to exit. A control system that tracks the position of all cans in the system will know how long it will take for the divert conveyor to transport the cans to the exit conveyor (108). When the timing is correct and the gap between cans (107) is as shown in fig. 4, it will be ready to reactivate the diverter conveyor to transport the cured cans into the correct gap between cans traveling along the exit conveyor (108). It knows the speed of the diverter conveyor (105) and, if so equipped, can modulate its speed to facilitate positioning cans on the exit conveyor (108) at reasonably even intervals. The diverter conveyor (105) may be equipped with a perforated belt through which vacuum is drawn so that the cans are tightly adhered and thus they can be accelerated quickly. The exit conveyor (108) may also be equipped with vacuum holes (104) through which vacuum may be drawn to hold the cans in detail tightly on the belt for good acceleration and control. The inlet conveyor (111) will be driven by a motor (119) and gear drive (118), and the outlet conveyor (108) will similarly be driven by a motor (101) and gear drive (102), and both may be variable speed motors that can be adjusted by the control system according to the supported production speeds to achieve the smoothest can engagement. The diverter (114) must be designed so that the fingers are fast enough to divert the cans, but it must do so smoothly so that the cans do not tip over or deform. But the fingers must also retract quickly enough to make way before the next can comes in the near future. The control system must know the retraction time to extend and retract the fingers and must be able to coordinate the timing of all can transports, turns, and then exits the system on the conveyor (108).

It should be understood that most of the functionality of the embodiments described herein, such as functionality to generate narrow band infrared energy (or broadband energy), functionality to produce cans, functionality to inspect cans/coatings and/or feedback information, and functionality to perform can processing, in at least some forms, will be controlled by a suitable controller or control system. Such a controller or control system may take various forms depending on the particular implementation, but will be implemented in at least one form with suitable hardware configurations and/or software routines to achieve the form and function of the described embodiments of the invention. Further, such a controller or control system may be, for example, a stand-alone system, a distributed system, or incorporated into another puppet more complex system.

The different form factors detailed above by which the described embodiments of the present invention can be performed are primarily direct narrow-band illumination portions that facilitate curing. Depending on various factors, it may be necessary to expand the above configuration for a complete cure. One form of expansion may involve having a pre-warm section before the narrowband irradiation section through which the tank may pass immediately. This can facilitate pre-warming the tank so that less joule energy is required from the narrowband irradiation section.

Another form of expansion may involve a post-blow section following the narrow band illumination. Since most of the wet coating is liquid water, it is necessary to drive off the moisture at some point in the curing process. Once the water evaporates, which should occur before the curing and crosslinking temperatures are reached, the vapor must be removed from the can. It may require warm air or it may only require blowing air over the canister to remove vapor from the canister. This may be configured as a warmback section having a circular or linear arrangement of tracks that guide the cans through the respective section.

The pre-warm section may be warm air or it may be radiant and equipped with, for example, a quartz lamp bank to provide a gentle radiant pre-heat. The expansion sections can vary widely and will depend on the precise environment in which the system is to be installed, the plant configuration, and the geographical climate. Those skilled in the art will appreciate that not only can the narrow band curing system be configured in many different ways beyond the scope of the specific examples taught herein, but the extensions can also take many forms both before and after.

One important difference between the described embodiments of the present invention and the conventional manner of curing the interior of a beverage can is that the described embodiments of the present invention are cured by direct radiant energy. Conventional IBO curing ovens heat the interior of the can by hot gas convection. An IBO heats air by burning natural gas in some form or by withstanding electrical heating. Both of which heat the air and the hot gas heats the tank. Because the belt on which the cans are located is hot, a small amount of heating occurs by conduction from the conveyor belt to the base of the metal can. This is also a drawback and inefficiency of IBO, in that heat is removed from the oven by continuously heating the belt as it passes repeatedly through the oven. Of course, the current older IBO aims to accomplish most tank heating by direct thermal convection air.

Convection heating is generally an inefficient heat transfer process. It is a multi-stage process and inherently has losses between each stage. The air must initially be heated and then the air must be in contact with the can to transfer its heat into the can and its coating. A similar amount of hot gas hits the outside of the tank as it hits the inside of the tank. Of course, the hot gas hitting the inside of the can hits the coating first before it conductively penetrates to heat the metal. However, hot gas hitting the outside of the can must heat the metal and then the metal must heat the coating. In the perfect world, it is more desirable to heat the coating to just its cross-linking cure temperature. However, this is not practically possible, since the coating is in close contact with the aluminium substrate comprising the body of the can, and because it is thin, it will transfer heat directly into the metal substrate. Due to this heating method, the metal substrate is heated as well as the coating. Moreover, the hot gases in the furnace are not completely uniform. Hot spots are inherently present in the oven and air movement varies from location to location, so they have a tendency to overheat some cans and the others under-heat. The trend is to use more furnace heat than is truly optimal to prevent uncured cans.

With particular regard to aluminium cans, maintaining aluminium at these temperatures for a significant period of time has the result that it weakens. It is well known in the industry that the can must be made heavier and stronger than the final gauge so that it can withstand the weakening effects that occur in the BIO at high temperatures after two to three minutes of waste.

Whether this weakening effect is a de-tempering or an annealing effect is not completely clear. Metallurgists do not agree on how to name the effects. It is clear and well known that aluminium is certainly weakened during passage through an IBO. It is generally believed that 8% to 10% of the bottom reversal strength is lost as a direct result of passing through the furnace.

Conventional annealing typically requires higher temperatures and longer high temperature durations than the time the can spends in the IBO furnace. This is confirmed by a literature search for 3004 alloy and other similar alloy families. Extensive research and at least one study have shown that this annealing and de-tempering process can be performed so rapidly in cans because of the extreme thinness of aluminum. Aluminum is an excellent thermal conductor and hot dipping occurs almost immediately at typical three or four thousandths of an inch wall thickness. It is in seconds rather than minutes or hours, as is the case with most annealing candidates.

The 3004 alloy aluminum, also known as UNS a93004, has the following chemical composition in addition to the base aluminum. It has up to 0.3% of silicone, up to 0.7% of iron, up to 0.25% of copper, between 1% and 1.5% of manganese, between 0.8 and 1.3% of magnesium, up to 0.25% of zinc and then other elements, which are less than or equal to 0.05%, each up to 0.15% in total. Several temper variations can be used for this alloy. Standard tempers including 0 (anneal), H32, H34, H36, and H38 may be used. H indicates strain hardening, and there is strain hardened and stabilized H3X. A particular temper value commonly used for aluminum beverage cans is H19, which has a strain hardening lower than H32, but is harder than the annealed condition. H19 temper seems to be the ideal choice for handling the important cold work that occurs in the D & I (drawing and ironing) process. The specifications regarding tensile strength vary from 26KPSI to 41 KPSI. The yield strength varies from 10KPSI for 0 temper or annealed product to 36KPSI for H38 temper.

The 8% to 10% reduction in can strength does reduce the buckling strength or bottom reversal strength that the can withstand under pressure. It should be noted that the pinch strength has no direct relationship to the yield or tensile strength, as the exact geometry and thickness of the can shape are important factors affecting can strength. However, since these are the same as those measured before and after curing, it is clear that the change in tensile strength and yield strength is responsible for the loss of buckling or bottom reversal strength. This annealing/de-tempering effect is obviously a factor that the can industry must deal with.

The embodiments described herein may actually eliminate this annealing/de-tempering effect that occurs in IBOs. The described embodiments of the present invention eliminate IBO and replace it with a high speed narrow band infrared radiation curing technique. The tanks are single-row and the irradiation is directed individually to each tank. They cure continuously one at a time, rather than collectively as a group. Due to the controllability and relative efficiency of narrow band irradiation heating, the coating can reach full cure and crosslinking temperatures in just a few seconds. Since the tank has little residence time at high temperatures, there is no time for the weakening effect to occur. Details and techniques for implementing such high speed radiation curing techniques are taught in more detail throughout this document.

Based on the results of the absorption spectroscopy analysis, the penetration depth of the spray coating sample can be calculated. In this application, low penetration is actually advantageous, since it corresponds to faster absorption of IR radiation.

The expression for penetration depth (95% absorption) is: β ═ 3 × l)/a, where β is the depth in millimeters, l is the path length of the experimental sample and a is the absorbance at a given wavelength. As an example, a wavelength of 1930nm (where the absorption is 1.526) results in a penetration depth β of 3.93 mm. This means that the infrared light will have to pass through a 3.93mm coating before 95% of the incident energy is absorbed. This is clearly not possible when considering coating thicknesses on can side walls as low as 0.00254 mm. Fortunately, aluminum is a very good reflector for IR radiation. The infrared light is slightly absorbed on the first pass through the spray coating, but then reflects off the aluminum substrate below the coating, and then returns through the coating in the process of starting to reflect around the interior of the can. It will contact the spray coating and the aluminum wall as each reflection passes. Even a small amount of energy absorbed by the aluminum during the slightly imperfect reflection may facilitate the curing process as it may generate thermal energy on the aluminum surface that holds the sprayed compound, thereby further heating the compound. Also, it should be appreciated that if the aluminum is sufficiently heated, the exterior trim on the can may also cure. This is desirable for some embodiments, so the system can be designed, configured, or tuned to accommodate this heating and curing goal.

For the thinnest standard coating thickness, each reflection within the canister would result in a 0.00508mm travel through the spray coating, as each reflection would pass through the double coating. To achieve the 95% absorption figure identified above, 774 passes through the body of the canister are required before interacting with the 3.93mm spray coating. In a 65mm wide tank (which would not be practical given the perfect orthogonal reflection wall to wall), this means that the light must pass around 50m to be fully absorbed. This seems to be a long process, but the speed of light (c 3x 10)⁸m/s) is actually too fast. The timing calculations for the thinnest and thickest coating thicknesses are: the 0.1 mil thickness is 0.17 nanoseconds and the 0.5 mil thickness is 0.03 nanoseconds. The results show that emitting energy from the laser diode will actually require much more time than the coating absorbs energy.

As discussed, current conventional methods for can coating curing utilize large furnaces with mass conveyors. Three consecutive sections heat the tank. The furnace is fed with natural gas, with the temperature of the last section maintained between 375 and 450 degrees Fahrenheit. The curing time of the cans through this hottest section of the oven by using a mass conveyor belt is approximately one (1) minute. Due to the high cost associated with the initial oven heating program, these ovens remain as on as possible, which is wasteful during production line down time or during a jam that may be in front of or backed up in the oven.

Table 1 shows the cost accumulation based on reasonable assumptions and the current natural gas costs in the united states. As table 1 shows, a considerable amount of heat must be continuously supplied to keep the interior of the furnace at a high temperature at all times. Natural gas costs are also a significant component of the total annual operating costs.

Table 1: operating costs of conventional natural gas fired furnaces

Fractional rate	2,400cpm
		BTU per hour	3,000,000
BTU/MCF natural gas	1,026,000
		Conversion efficiency	90％
Consumption of	3.25MCF per hour
		Cost of	$11.00/MCF
Cost per hour	$35.74
		Cost per 24 hours	$857.70
Furnace uptime (% of 24/7)	95％
		Annual cost	$297,407

The above high coating thickness results are used to represent the worst case. Additional differences between this analysis and conventional variables include the difference in conversion efficiency between natural gas to heat and electricity to radiant heat, the difference between $/MCF for natural gas and $/kWh for electricity, and the difference between furnace uptime and diode array uptime.

Although not directly comparable, the difference does favor narrow band radiant electrical heating. Assuming a common line uptime (time for actually producing the cans) of 89% of all available time in the year, the furnace is assumed to actually remain active for a longer period of time due to the costs and time associated with cold starts. Thus, while the production line may only be 89% of the time in producing the cans, the furnace will actually maintain the temperature for 95% of the available time of the year. On the other hand, the narrow band radiant heating element is designed to be pulsed and therefore uses electrical power only when the canister is present and actually cures. This not only improves efficiency during operation, but also the diodes do not operate when the line is shut down for maintenance or line plugging. The result is that the uptime of the diode array is comparable to the actual line uptime.

From a purely environmental perspective, in a contemplated example, the 3,000,000BTU/hr required to cure the canister and maintain the oven within the correct temperature range can be converted to joules, making 3,165,167,700 joules for 3,000,000 BTU. Comparing this with the hourly plug power of the radiant heating system, table 2 shows the significant savings that are available when the heat is properly "aimed". The energy required to heat only a conventional oven is more than 12 times the theoretical energy requirement for a narrow band radiant heating system to cure the coating. In other words, with current IBO technology, about 92% of the energy consumption is actually wasted.

Table 2: operating costs of narrow band radiation curing

Fractional rate	2,400cpm
		Joule per pot for curing	700
Conversion efficiency	40％
		Joule amount, wall insertion per can	1786
Joule per minute, wall socket	4,285,714
		Joule per hour, wall plug	257,142,857
kW	71.4
		Cost per kWh	$0.107
Cost per hour	$7.64
		Cost per 24 hours	$183.43
Diode uptime (% of 24/7)	89％
		Annual cost	$59,587

Comparing the results of the conventional current standard curing process with the results of the examples described herein shows that a significant savings of about $240,000 per year can be achieved based on current cost estimates.

This technique is of great benefit to can manufacturers. Not only is energy significantly saved as discussed in the above prophetic example, but air pollution is also greatly reduced. The energy and cost savings are actually greater than in the above example, as it does not account for the energy savings that eliminate the high maintenance aspects of the typical 95HP motor and large conveyor furnace. Perhaps the most significant benefit to can manufacturers is the complete or almost complete elimination of the annealing/de-tempering effect if the described embodiments of the invention are implemented correctly. Thus, the can manufacturer can produce cans with less aluminum. Some production cans weigh about 0.34 to 0.39 ounces, but it should be understood that the weight/mass of the can may vary depending on, for example, the precise geometry and material thickness. Also, can manufacturers periodically redesign the cans, can tooling, and manufacturing processes to change weight/mass (e.g., make the cans lighter in weight). Furthermore, some tanks, such as specialty tanks, may even be designed with increased weight/mass. Smart embodiments can save as much as 9% to 14% of the aluminum usage. However, any reduction in the amount of aluminum, for example, a reduction in the weight of aluminum by 3%, 5%, 8% or more, would be beneficial. Since about 70% of the cost of a beverage can is the cost of aluminum material, this represents a tremendous savings to the can manufacturer or can user. This is an environmental benefit in other respects as well, since less aluminium needs to be mined, refined, manufactured and transported.

The elimination of the weakening effect by the oven would be beneficial in one or more combinations of three ways. The can be made with current aluminum and tooling, but it is much stronger than current cans due to the elimination of aluminum weakening. Alternatively, less aluminum is required to produce the tank. A third possibility is that cheaper, lower alloy or lower temper aluminium may be used instead of the currently more expensive aluminium products. It may be a combination of these depending on how the manufacturer chooses to implement the described embodiments of this technology.

When employing the described embodiments of the present invention, there are a number of novel ways to reduce the amount of aluminum used to produce cans. Manufacturers and suppliers of aluminum coils typically charge a premium for rolling aluminum to a particular precision and thickness. Aluminum is priced and sold in pounds, but rolling thickness and finishing processes also require a significant process cost. While less weight of aluminum is required, manufacturers of aluminum coil stock may need to roll it to thinner, yet still precise specifications. To maintain their profit margins, they may charge a higher roll premium than heavier, thicker aluminum. In this case, if the steel mill employs this business method, there may be no cost savings. A more recent way of implementing the described embodiments of the invention is to reduce the diameter of the cutting edge of the blank, thereby reducing the diameter of the resulting cup. A typical 12 ounce two piece can has a starting cup diameter of 5.100 ". This technique will reduce weight by scaling down the cup size, but maintain the same coil thickness and therefore the same rolling premium. The first step of the D & I process is to deep draw the "starting cup". Again, this means that the width of the roll will be smaller, but the same as the current thickness, so it should meet industry standard pricing and only need to be cut to a narrower width. By starting with a smaller diameter cup, the can body end product will reach the desired thinner gauge in the finished can, but without paying additional fees for rolling the aluminum to the thinner gauge. The skilled tool manufacturer should understand the modification or reconfiguration of the tool. In order to finally obtain a cup of proportionally smaller diameter, the deep drawn cup of the first step in the D & I process, the tooling must be made or modified so that each part thereof fits and correctly specifies the new diameter. The cups are made in a double acting cup suction press and the tool has many cups depending on the design and year of cup suction press setup. The diameter of the blank must be smaller, thereby reducing the so-called "cutting edge". Those blanks are closely nested across the width of the roll at a 60 angle to the curled edge to reduce the amount of scrap between the blanks and leave a minimum of aluminum web between the tangential edges of the blanks. To achieve this, the overall width of the web can be reduced and the same number of cup blanks can be produced across its width as conventional size blanks of larger diameter. An alternative method is to rework in such a way that a wider roll width is maintained but more cup blanks and cups are manufactured across its width. In any case, the composite deep drawing tools of each processing station in the press mold will have to be remanufactured to the correct new diameter, clearance and depth. A new punch, tab, collet and all associated tooling components will have to be matched to the new diameter. It would be necessary to adjust the geometric relationship of each processing station to maintain a close nesting arrangement and minimal scrap relationship between the respective blanks. The diameter of the tool assembly will be smaller and will therefore require less tool steel and less machining, so that they should be relatively cheaper than the current larger versions. Although modifications to the cupper press tooling would be required to produce smaller diameter cups, the return on making such changes may be considerable. The balance of the cupper press, the feed equipment and the overall system should be reconfigured to be modified with new tools or tools.

In order to properly implement this technology, it is important to understand how the described embodiments of the present invention work in more detail. The preferred simplified practice of the described embodiments of the invention teaches the injection of intense infrared narrowband energy as directly as possible into the interior of the tank and the coating itself. This means that infrared energy is aimed and projected directly into the interior of each individual tank and no energy is wasted by bouncing around the plant or trying to heat groups or large numbers of tanks. While it is possible to implement the embodiments described herein by irradiating the exterior of the tank or both the exterior of the tank and the interior of the tank, a more efficient implementation would be to target the energy directly to the interior of the tank. This is much more efficient because photons from the narrow band energy will actually penetrate the coating in its liquid, pre-cured form and be partially absorbed by it. It will actually pass all the way through the coating while some energy will be directly absorbed and will then be reflected back from the aluminium substrate to the coating for a second pass and corresponding further absorption. When a photon passes through the coating on the return path, additional energy will be absorbed and, on each subsequent reflection, will pass through the coating twice. The coating is so thin that it will not absorb all of the photon energy very quickly and the photons will continue along their reflected path until they strike the next coated surface. Imagine that one cue ball bounces off the inner surface of the can and the inbound and outbound pass through the coating before additional reflections of each bounce. The reason why the cue ball eventually decelerates and stops as we continue to analogize with cue ball is because it has consumed all of the energy on the bumper and the amount of rolling friction is small. Also, a photon loses its energy in two main ways. Energy is absorbed each time it passes through the coating, and aluminum loses a small amount of energy in the influence of imperfect reflection. Depending on the wavelength of the narrow band infrared radiant energy used, there will be several hundred to about 1,500 reflections before the full energy of the photon is absorbed by the coating and heats the aluminum. Of course, the thicker the coating, the more energy is absorbed per pass through the coating. Longer paths through the coating mean more absorption from photon strikes that occur as photons pass through the coating. As an example, a steep angle into and through the coating will provide more path length, and thus more absorption.

There are a number of ways to generate and efficiently direct powerful narrow band illumination energy into the tank. While it is possible to use broadband irradiation energy, it is much more cumbersome to implement efficiently and effectively. For example, broadband energy generated from quartz lamps cannot be turned on and off at the various speeds required for a true cleaning implementation. The turn-on slew rate and full preheat time of a quartz lamp are measured in seconds, and for many configurations the overall optimum turn-on time may be only one or two seconds or even a fraction of a second. It is also more difficult to accurately focus the energy where needed due to its inherent shape and filament configuration. They do not easily facilitate the precise transfer of the correct number of joules, but tend to work better in a flood arrangement where the joule energy is transferred to a larger specific area but is difficult to control. The broadband source may not promote ultra-fast curing due to its inherent properties, and thus may still cause some or all of the annealing effect by rapidly overheating the can. Both narrow band illumination and semiconductor-based narrow band energy generation have many advantages. First, they can be turned off and on at a rate of microseconds. They produce photon energy only when they actually receive a DC voltage input (typically between 1.2 and 3.3 volts), and they have no hysteresis or high blackbody equivalence, resulting in a large output after the input current stops flowing, as do quartz or gas discharge lamps. Broadband sources typically operate at very high temperatures, which can present a complete set of implementation problems. Their presence can cause the entire curing environment to be very hot, reducing the reliability of the assembly and requiring optics capable of withstanding higher temperatures. Their service life is inherently much shorter and must be replaced often, thereby increasing maintenance and downtime. Furthermore, the narrow-band arrangement also contributes to its excellent implementation of the antireflection coating. This is so because the coating can be designed and optimized for the exact narrow wavelength band being used. It need not be a less than ideal broadband antireflection coating. Similarly, optics and optical coatings (e.g., cold mirror coatings) can be more easily designed for a particular narrow wavelength range. The lenses are focused at different distances for different wavelengths, so that a higher accuracy is an advantage when designing the optical system for a narrow band system. It should be understood that narrow bands can have different interpretations, but we refer to the generation of optical or photonic energy, whose full width half maximum bandwidth is typically less than 100 nanometers. This is typically the case if the narrow band energy source is a solid state or semiconductor source, unless broadband fluorescence is added to the device configuration. The raw output of an LED is typically a narrow band inherent in the range, but for some types, laser diodes are narrower, e.g., less than 20 nanometers (nm), typically less than ± 10 nanometers (full width/half maximum), or even as narrow as ± 1 nanometer (full width/half maximum). For example, the bandwidths of VCELS and SE-DFB devices are typically less than + -2 nm (full width/half maximum). The exact bandwidth is not as important as the center wavelength of the output. The wavelength may determine the rate at which the coating itself absorbs energy. The transmittance of the coating can be measured at different wavelengths and the wavelength can be selected to achieve the best absorption results. For example, in at least some embodiments, the narrow band infrared energy used for curing (which, as detailed above, may be as narrow as ± 1nm (full width/half maximum), depending on the embodiment) will match at least one absorption characteristic of the coating. Thus, for the example of a water-based epoxy coating typically applied to the interior surface of a can, a narrow band of wavelengths may fall within the range of 800 to 1200nm, for example about 972 nm. As discussed herein, 972nm represents the deep penetration wavelength of a water-based epoxy coating. In the 1400nm to 1600nm range (e.g., about 1,454nm or 1456nm), the absorption rate of the coating may be significantly faster, but the wall plug efficiency is not as high, so the trade-off is the decision that the system designer must make. Similar wall plug efficiency challenges exist in the 1850nm to 2000nm range (e.g., at 1935 nm).

As with many high power industrial processes, this process must be performed safely in the mind of system designers. Regardless of how the described embodiment of the invention is reduced to practice in its final design, it must have adequate safety precautions to prevent physical or optical exposure to the hazardous aspects of the technology. Intense infrared energy can cause eye damage or blindness and must therefore be prevented by safety design. The actual material handling portion of the system has many moving parts that can be dangerous when moving or suddenly actuated to perform a function. Safeguards, whether physical or electronic, must be implemented to safely stop motion when a person is present. When designing a system, OSHA, CSA or CE security standards should be adhered to ensure all aspects of system security.

The narrow band illumination aspect of the system should pay very strict attention to the security aspect of the system. Powerful infrared energy, which is very effective for fast curing coatings, is very dangerous to the naked eye. It is stealthy and powerful enough to cause rapid blindness before blinking in humans or animals. Even sunglasses or electro-spectacles are not sufficient to prevent strong photon energy from causing damage to the eye because their filters are weak and may filter wrong wavelengths. Some of the longer infrared wavelengths that may be used to reduce practice do not penetrate to the retina of the eye, but still damage the cornea, sclera, iris and/or lens of the eye. Typically, such wavelengths are mistakenly referred to as "eye-safe", but this applies only to potential damage to the retina of the eye. The system should be designed such that it should eliminate the possibility of exposure of any human eye to outside the minimum safe threshold of narrowband photon energy produced by the laser diode or array. Fail-safe, such as a dual backup interlock system, may be designed as a control panel or safety guard. They should be designed so as to ensure that the guard cannot be removed when powering the narrowband device, and the design should not allow the device to be powered across or by the operator when any safety guard is removed. Furthermore, all housings and shields should be designed so that they are light-tight when power can be supplied to the narrowband device. It is also strongly recommended that arrays be designed so that they cannot be connected to a power supply at will when they are not in the system, so that service personnel or curious seekers will not attempt to power the device and therefore be harmed. Since the powerful narrow band infrared energy is completely invisible to the human eye, the eye cannot actuate the blink reflex until the injury is complete. While exposure to other parts of the body may be unpleasant or even result in serious burns, it is not as severe as the eye is momentarily exposed to such energy. Accordingly, all applicable institutional safety standards should be adhered to, and substantial design knowledge applied to ensure that the narrow band high speed curing system is safe. It will provide excellent utility, but security must be an integral part of all aspects of using a system constructed in accordance with the described embodiments of the invention.

Furthermore, an effective way to further improve the performance of the described embodiments of the invention includes the placement of special additives into the coating. This will significantly increase the absorption at a given wavelength. This can help to transfer more heat into the coating and less heat into the aluminum or steel can stock if carefully selected and matched to the wavelength used for curing. In other words, the additive or dew point will cause the coating to absorb more ore at the wavelength used, and therefore more heat goes directly into the coating itself, rather than being conducted from the metal. It can improve the efficiency of the system with less bounce-back and thus reduce the energy wasted on the non-curing function to reach the desired curing or crosslinking temperature.

It is also possible to incorporate the use of narrow band infrared energy of this curing system to further optimize the coating used. The manufacturer of the coating may use an IR-actuated chemical reaction actuator or accelerator suitable for in-can coating purposes. In addition, functional dyes are available that can absorb a specific narrow band infrared wavelength band. For example, such dyes are manufactured by Yamada Chemical Co. Chemical coating manufacturers can inventively use narrow band IR irradiation to improve their coatings, reduce or eliminate BPA-based coatings, or improve performance in various ways. Some reflections within the tank will inherently direct energy outwardly through the open top of the tank. A properly designed system would place the reflective surfaces appropriately to at least partially direct any exiting energy back into the tank to perform further curing until it is exhausted. However, even the most reflective surfaces will release a few percent of the impact energy into the reflective material. They are commonly referred to as Fresnel (Fresnel) reflections. Furthermore, some of the energy may be mistakenly scattered or reflected and may never return into the tank. An appropriately designed reflective shape or cone (64) may better place the returned energy so that more energy will be absorbed when additionally passing through the coating and reflecting from the base material.

The concepts taught herein of the described embodiments of the invention as to how to implement narrow band infrared radiation curing are intended to aid those who wish to configure the described embodiments of the invention for their particular application and production needs. Examples will show how there are many different ways to implement the described embodiments of the invention, far beyond the specific examples given. Those skilled in the respective arts or teams will be able to expand the new concepts accordingly to meet their unique application needs.