阅读说明：本技术 一种多光束水导激光加工装置与加工系统 (Multi-beam water-guided laser processing device and system ) 是由 张广义 张文武 王吉 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种多光束水导激光加工装置与加工系统,属于激光加工技术领域,本发明通过将多路激光束导入水柱,提高了激光束在水柱的耦合功率；多路激光束依次经过聚焦扩束模块、光束旋转调节模块及聚焦透镜进行处理,实现多路激光束的空间位置、角度调控及旋转,从而提高聚合后的激光束的光斑均匀性,最终实现对工件的高功率、零锥度及大深度加工。(The invention discloses a multi-beam water-guided laser processing device and a processing system, belonging to the technical field of laser processing.A plurality of paths of laser beams are guided into a water column, so that the coupling power of the laser beams in the water column is improved; the multi-path laser beams are sequentially processed by the focusing beam expanding module, the light beam rotation adjusting module and the focusing lens, and spatial position, angle regulation and rotation of the multi-path laser beams are realized, so that the spot uniformity of the polymerized laser beams is improved, and high-power, zero-cone and large-depth processing of workpieces is finally realized.)

1. A multi-beam water-guide laser processing device is characterized by comprising a beam rotation adjusting module, a liquid chamber and a plurality of focusing beam expanding modules;

each focusing beam expanding module is used for focusing the laser beam which is correspondingly input;

the light beam rotation adjusting module and the liquid chamber are coaxially arranged along the transmission direction of the laser beam;

the light beam rotation adjusting module is used for carrying out eccentric processing on the focused multipath laser beams and enabling the laser beams subjected to the eccentric processing to be incident into the liquid chamber;

the liquid chamber is used for transmitting the laser beam after eccentric processing along the water column emitted by the liquid chamber and cutting a workpiece by utilizing the laser in the water column,

after the eccentric processing, one path of laser beam is focused and coupled at the central shaft of the water column, and the rest one path or multiple paths of laser beam are focused and coupled in the water column and are positioned at the periphery of the central shaft.

2. The processing apparatus according to claim 1, wherein the beam rotation adjustment module includes an upper lens and a lower lens disposed along the transmission direction of the laser beam;

adjusting an eccentric distance of the laser beam by adjusting a distance and an angle between the upper lens and the lower lens.

3. The processing apparatus as claimed in claim 2, further comprising a frame structure, wherein the focused beam expanding module, the beam rotation conditioning module and the liquid chamber are disposed within the frame structure;

the light beam rotation adjusting module is in rolling connection with the frame structure and is used for controlling the laser beam processed by the focusing and beam expanding module to do revolving body movement along the axis of the light beam rotation adjusting module and the axis of the liquid chamber.

4. The processing apparatus of claim 1, further comprising a focusing lens disposed coaxially between the beam rotation adjustment module and the liquid chamber;

the focusing lens is used for focusing the laser beam subjected to eccentric processing and then enabling the laser beam to enter the liquid chamber.

5. The processing device of claim 4, wherein the liquid chamber comprises a first cavity, a window lens, and a liquid outlet;

the window lens is coaxially and fixedly arranged on the top wall of the first cavity and used for transmitting the laser beam focused by the focusing lens;

the window lens is also used for keeping the first cavity in a high-pressure environment;

the liquid outlet is arranged on the bottom wall of the first cavity and is used for ejecting a water column of high-pressure laminar flow;

the focus of the focusing lens is located at the liquid outlet.

6. The processing device as claimed in claim 5, wherein the side wall of the first cavity is uniformly provided with a plurality of liquid inlets, and a porous filtering unit is annularly arranged inside the first cavity close to the liquid inlets.

7. The processing apparatus as claimed in claim 4, further comprising a gas chamber coaxially disposed on a side of the liquid chamber adjacent to the liquid outlet;

the gas chamber is used for carrying out gas protection on the water column which is emitted from the liquid chamber.

8. The processing device according to claim 7, wherein the gas chamber comprises a second cavity and a gas-liquid outlet, and the gas-liquid outlet is coaxially arranged with the liquid outlet;

the focus of the laser beam focused by the focusing beam expanding module is positioned between the liquid outlet and the gas-liquid outlet.

9. The processing apparatus as claimed in claim 8, wherein the sidewall of the second chamber has a plurality of gas inlets uniformly formed therein, and the interior of the second chamber is annularly provided with a gas filter element adjacent to the gas inlets.

10. A multi-beam water-guided laser processing system, comprising an electronic control module, a laser generator, an optical element, a gas transmission module, a fluid transmission module and the laser processing device of any one of claims 1 to 9;

the electric control module is used for controlling the opening and closing of the laser generator, the fluid transmission module and the gas transmission module;

the laser generator is used for generating a laser beam, and the generated laser beam is transmitted into the laser processing device through the optical element;

the fluid transmission module is used for providing high-pressure fluid, and the generated high-pressure fluid is input into a liquid chamber of the laser processing device;

the gas transmission module is used for providing high-pressure gas, and the generated high-pressure gas is input into a gas chamber of the laser processing device;

the laser processing device is used for cutting a workpiece by utilizing the laser generated by the laser generator.

Technical Field

The invention relates to a multi-beam water-guide laser processing device and a processing system, and belongs to the technical field of laser processing.

Background

At present, the efficiency and quality of conventional laser processing are rapidly reduced along with the increase of depth, because of the processing taper effect of focused laser processing, the method has a depth limit; the constant accumulation of heat severely thermally affects the material. Therefore, achieving low thermal influence and large depth of intervention processing is a significant problem in the laser processing community.

The known short pulse dry laser processing is mainly advantageous in terms of instantaneous removal efficiency and thermal influence control of shallow materials, but still has a significant problem: hole machining has a taper and lack of depth capability, and short pulse advantage is lost in large depth (>5 mm) machining.

In order to solve the heat influence of materials in the laser processing process and expand the processing depth, SYNOVA company develops a micro-jet type water-assisted laser processing technology. The micro-jet water-assisted laser processing technology represented by SYNOVA company has excellent processing performance on penetrating cutting of various materials, and has a series of advantages of obviously reduced processing taper, small processing heat influence, clean surface and the like compared with dry laser processing, but the technology is difficult to maintain the high efficiency of large-depth processing, and the depth capability meets the limit about 10 mm; in addition, in order to ensure reliability, the laser transmission intensity is not too high, the improvement of coupling power is limited, and the processing speed is influenced.

The GE global research and development center invented the liquid-core fiber laser processing technology, which uses special micro-tube to pass water and light, and the photoconductive coefficient of the tube wall material is lower than that of pure water, so that the total reflection transmission of light can be realized. Laminar water columns can be emitted in the air, which is equivalent to a SYNOVA technology; but at the same time, the fixed tube wall allows the optical fiber to be bent, and can be processed deep into narrow space or underwater. Because of the scattering effect of the end-effectors on the light and the vulnerability of the fiber to the head being too close to the machining area, interventional machining has not been achieved to date, and preferably records about 3 mm of drilled material.

The patent of 'a laser processing head and application thereof, a laser processing system and method' developed by Ningbo material technology and engineering research institute of Chinese academy of sciences solves the contradiction between high energy density coupling of laser and system reliability; the patent of 'a rotary water-guide laser processing system and method' can carry out large-depth laser processing; the patent of 'a high-power coupling laser processing device and a laser processing system' uses a method of total reflection coating and rotating water-guided laser to improve the laser coupling power and further expand the depth capability of laser processing; the patent of 'a rotary laser processing device and application thereof, a laser processing system and a method' utilizes a rotary laser processing mode to improve the processing depth.

In the existing water-jet guided laser processing process, the high-power coupling, the water column energy distribution and the uniformity thereof directly influence the processing efficiency and the depth capability of the water-jet guided laser.

Disclosure of Invention

The invention provides a multi-beam water-guided laser processing device and a processing system, which can solve the problem that the processing efficiency and depth capability of water-guided laser are influenced by high-power coupling, water column energy distribution and uniformity of the water column energy distribution.

In one aspect, the invention provides a multi-beam water-guided laser processing device, which comprises a beam rotation adjusting module, a liquid chamber and a plurality of focusing and beam expanding modules;

each focusing beam expanding module is used for focusing the laser beam which is correspondingly input;

the light beam rotation adjusting module and the liquid chamber are coaxially arranged along the transmission direction of the laser beam;

the light beam rotation adjusting module is used for carrying out eccentric processing on the focused multipath laser beams and enabling the laser beams subjected to the eccentric processing to be incident into the liquid chamber;

the liquid chamber is used for transmitting the laser beam subjected to eccentric processing along a water column emitted by the liquid chamber, and cutting a workpiece by using the laser in the water column;

after the eccentric processing, one path of laser beam is focused and coupled at the central shaft of the water column, and the rest one path or multiple paths of laser beam are focused and coupled in the water column and are positioned at the periphery of the central shaft.

Optionally, the beam rotation adjusting module includes an upper lens and a lower lens arranged along the transmission direction of the laser beam;

adjusting an eccentric distance of the laser beam by adjusting a distance and an angle between the upper lens and the lower lens.

Optionally, the processing apparatus further includes a frame structure, and the focusing and beam expanding module, the light beam rotation adjusting module and the liquid chamber are all disposed in the frame structure;

the light beam rotation adjusting module is in rolling connection with the frame structure and is used for controlling the laser beam processed by the focusing and beam expanding module to do revolving body movement along the axis of the light beam rotation adjusting module and the axis of the liquid chamber.

Optionally, the processing apparatus further includes a focusing lens coaxially disposed between the beam rotation adjusting module and the liquid chamber;

the focusing lens is used for focusing the laser beam subjected to eccentric processing and then enabling the laser beam to enter the liquid chamber.

Optionally, the liquid chamber comprises a first cavity, a window lens and a liquid outlet;

the window lens is coaxially and fixedly arranged on the top wall of the first cavity and used for transmitting the laser beam focused by the focusing lens;

the window lens is also used for keeping the first cavity in a high-pressure environment;

the liquid outlet is arranged on the bottom wall of the first cavity and is used for ejecting a water column of high-pressure laminar flow;

the focus of the focusing lens is located at the liquid outlet.

Optionally, evenly be provided with a plurality of inlets on the first cavity lateral wall, first cavity is inside to be close to inlet department is cyclic annular and is provided with porous filtration unit.

Optionally, the processing apparatus further includes a gas chamber, and the gas chamber is coaxially disposed on one side of the liquid chamber close to the liquid outlet;

the gas chamber is used for carrying out gas protection on the water column which is emitted from the liquid chamber.

Optionally, the gas chamber includes a second cavity and a gas-liquid outlet, and the gas-liquid outlet and the liquid outlet are coaxially arranged;

the focus of the laser beam focused by the focusing beam expanding module is positioned between the liquid outlet and the gas-liquid outlet.

Optionally, a plurality of air inlets are uniformly formed in the side wall of the second cavity, and an air filtering element is annularly arranged inside the second cavity and close to the air inlets.

In another aspect, the present invention provides a multi-beam water-guided laser processing system, comprising an electronic control module, a laser generator, an optical element, a gas transmission module, a fluid transmission module, and any one of the above laser processing devices;

the electric control module is used for controlling the opening and closing of the laser generator, the fluid transmission module and the gas transmission module;

the laser generator is used for generating a laser beam, and the generated laser beam is transmitted into the laser processing device through the optical element;

the fluid transmission module is used for providing high-pressure fluid, and the generated high-pressure fluid is input into a liquid chamber of the laser processing device;

the gas transmission module is used for providing high-pressure gas, and the generated high-pressure gas is input into a gas chamber of the laser processing device;

the laser processing device is used for cutting a workpiece by utilizing the laser generated by the laser generator.

The invention can produce the beneficial effects that:

the invention improves the coupling power of the laser beam in the water column by leading the multi-path laser beam into the water column; the multi-path laser beams are sequentially processed by the focusing beam expanding module, the light beam rotation adjusting module and the focusing lens, and spatial position, angle regulation and rotation of the multi-path laser beams are realized, so that the spot uniformity of the polymerized laser beams is improved, and high-power, zero-cone and large-depth processing of workpieces is finally realized.

According to the invention, the laser cutting efficiency and the cutting quality are improved by adjusting the laser energy distribution in the water column; the invention has large-depth intervention type processing capability and breaks through the depth limit of the traditional laser processing; the invention has low technical cost and small technical difficulty, and has important significance for processing materials with larger thickness (more than 10mm) in the aviation and civil fields.

Drawings

FIG. 1 is a schematic diagram of an overall structure of a multi-beam water-guided laser processing apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of water-guided laser beam propagation of a multi-beam water-guided laser processing apparatus according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the distribution of light spots in a water column of the multi-beam water-guided laser processing apparatus according to the embodiment of the present invention;

FIG. 4 is a schematic diagram of a rotating beam coupling processing structure of the multi-beam water-guided laser processing apparatus according to the embodiment of the present invention;

fig. 5 is a system block diagram of a multi-beam water-guided laser processing system according to an embodiment of the present invention.

List of parts and reference numerals:

1. a light beam A; 2. a focusing beam expanding module A; 3. a light beam B; 4. a focusing beam expanding module B; 5. a liquid chamber; 51. a first cavity; 52. a window lens; 53. a liquid outlet; 54. a liquid inlet; 55. a porous filtration unit; 6. a light beam rotation adjusting module; 61. an upper lens; 62. a lower lens; 7. a gas chamber; 71. a second cavity; 72. a gas-liquid outlet; 73. an air inlet; 74. a gas filter element; 8. a frame structure; 9. a focusing lens; 10. an electronic control module; 11. a laser generator; 12. an optical element; 13. a gas delivery module; 14. a fluid transfer module; 15. a workpiece; 16. a laser processing device; 17. an energy storage device.

Detailed Description

The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

As shown in fig. 1 and fig. 2, in one aspect, an embodiment of the present invention provides a multi-beam water-guided laser processing apparatus 16, which includes a beam rotation adjusting module 6, a liquid chamber 5, a focusing lens 9, and a plurality of focusing beam expanding modules.

Each focusing beam expanding module is used for focusing the corresponding input laser beam.

The beam rotation regulating module 6 and the liquid chamber 5 are coaxially arranged along the direction of laser beam transmission.

The light beam rotation adjusting module 6 is used for performing eccentric processing on the focused multipath laser beams and enabling the laser beams subjected to the eccentric processing to be incident into the liquid chamber 5.

One path of the laser beam after eccentric processing is focused and coupled at the central shaft of the water column, and the other one or more paths of the laser beam are focused and coupled in the water column and are positioned at the periphery of the central shaft.

The focusing lens 9 is coaxially arranged between the light beam rotation adjusting module 6 and the liquid chamber 5; the focusing lens 9 is used for focusing the laser beam subjected to the eccentric processing and then irradiating the laser beam into the liquid chamber 5.

And the liquid chamber 5 is used for transmitting the laser beam processed by the focusing lens 9 along a water column emitted by the liquid chamber 5, and the workpiece 15 is cut by the laser in the water column.

In one embodiment of the present application, when multiple laser beams are arranged, a laser beam passing through one of the focusing beam expanding modules is coaxially disposed with the liquid chamber 5, and laser beams passing through the remaining multiple focusing beam expanding modules are obliquely disposed toward the coaxially disposed laser beams.

In another embodiment of the present application, there is no laser beam coaxially disposed with the liquid chamber 5, and the laser beams passing through the multi-path focusing beam expanding module are all obliquely disposed toward the axis where the beam rotation adjusting module 6 and the focusing lens 9 are located.

As shown in fig. 1 and 4, the beam rotation adjustment module 6 includes an upper lens 61 and a lower lens 62 disposed along the transmission direction of the laser beam. The eccentric distance of the laser beam is adjusted by adjusting the distance and angle between the upper lens 61 and the lower lens 62, i.e., the laser beam is shifted by a distance in the radial cross section as required.

The processing device further comprises a frame structure 8, and the focusing beam expanding module, the light beam rotation adjusting module 6, the focusing lens 9 and the liquid chamber 5 are all arranged in the frame structure 8.

The beam rotation adjustment module 6 may be fixedly connected to the frame structure 8, and the focusing lens 9 is fixedly connected to the frame structure 8.

The light beam rotation adjusting module 6 can also be in rolling connection with the frame structure 8 and is used for controlling the laser beam processed by the focusing and beam expanding module to do revolving body motion along the axis of the light beam rotation adjusting module 6 and the liquid chamber 5.

The liquid chamber 5 comprises a first cavity 51, a window lens 52 and a liquid outlet 53; the window lens 52 is coaxially and fixedly disposed on the top wall of the first chamber 51, and is used for transmitting the laser beam focused by the focusing lens 9, and the window lens 52 is also used for maintaining the high-pressure environment in the first chamber 51.

A liquid outlet 53 is provided on the bottom wall of the first chamber 51 for ejecting a high-pressure laminar water column, and the focal point of the focusing lens 9 is located at the liquid outlet 53. The liquid outlet 53 in this embodiment is a precision thin-walled circular hole.

A plurality of liquid inlets 54 are uniformly arranged on the side wall of the first cavity 51, and a porous filtering unit 55 is annularly arranged in the first cavity 51 near the liquid inlets 54. In this embodiment, the liquid introduced into the liquid chamber 5 is water.

The processing device also comprises a gas chamber 7, and the gas chamber 7 is coaxially arranged on one side of the liquid chamber 5 close to the liquid outlet 53; the gas chamber 7 is used for gas protection of the water column exiting from the liquid chamber 5.

The gas chamber 7 comprises a second cavity 71 and a gas-liquid outlet 72, and the gas-liquid outlet 72 and the liquid outlet 53 are coaxially arranged; the focus of the laser beam focused by the focusing and beam expanding module is located between the liquid outlet 53 and the gas-liquid outlet 72. A plurality of air inlets 73 are uniformly formed on the side wall of the second cavity 71, and an air filter element 74 is annularly arranged in the second cavity 71 and close to the air inlets 73.

As shown in fig. 1 and 2, the laser beam is totally reflected and transmitted on the surface of the water column, and finally, the laser beam and the water column reach the surface of the workpiece 15 together, so that the workpiece 15 is machined.

In order to ensure the total reflection effect of the laser beam on the water-vapor interface of the water column, the emergent laser beam meets the following conditions:

wherein, θ 1 is the incident angle of the laser beam and the water-vapor laminar interface of the water column, θ 2 is the refraction angle, n1 is the refractive index of the laser beam and the water, and n2 is the refractive index of the laser beam and the gas.

When theta 2 is 90 degrees, namely the critical angle of total reflection of the laser beam at the water-vapor laminar flow interface of the water column, the calculated theta 1 is the minimum incident angle of the total reflection of the laser beam and the water-vapor laminar flow interface, and the incident angle of the laser beam and the water-vapor laminar flow interface is not less than theta 1, so that the laser can be totally reflected at the water-vapor laminar flow interface.

As shown in fig. 3, the multi-beam water-guided laser processing apparatus 16 of the present invention can effectively increase the power density of the laser beam in the water column by processing the incident laser beam, and convert the energy originally in the gaussian-like distribution in the water column into an annular uniform spot or a quasi-uniform spot. The energy distribution of the laser beam in the water column can form annular distribution or quasi-uniform distribution.

The invention improves the coupling power of the laser beam in the water column by leading the multi-path laser beam into the water column; the multi-path laser beams are sequentially processed by the focusing beam expanding module, the light beam rotation adjusting module 6 and the focusing lens 9, and spatial position, angle regulation and rotation of the multi-path laser beams are realized, so that the spot uniformity of the polymerized laser beams is improved, and finally high-power, zero-taper and large-depth processing of the workpiece 15 is realized.

As shown in fig. 5, another embodiment of the present invention provides a multi-beam water-guided laser processing system, which includes an electronic control module 10, a laser generator 11, an optical element 12, a gas transmission module 13, a fluid transmission module 14, and the laser processing apparatus 16.

The electronic control module 10 is used for controlling the opening and closing of the laser generator 11, the fluid transmission module 14 and the gas transmission module 13.

The laser generator 11 is used to generate a laser beam which is conducted through an optical element 12 into a laser machining device 16.

The fluid delivery module 14 is used to provide a high pressure fluid that is input into the liquid chamber 5 of the laser machining apparatus 16.

The gas delivery module 13 is used to provide high-pressure gas, which is fed into the gas chamber 7 of the laser processing device 16.

The laser processing device 16 is used to cut the workpiece 15 by the laser light generated by the laser generator 11.

The laser machining device 16 further comprises an energy storage device 17 for storing energy for the water column.

In an embodiment of the present application, as shown in fig. 1, fig. 2, fig. 3, and fig. 5, the electronic control module 10 opens the switch of the fluid transmission module 14 and the switch of the gas transmission module 13, so that the energy storage device 17 and the liquid chamber 5 are filled with the fluid substance at a certain pressure, and a protected high-speed laminar water column is formed under the assistance of gas, and the high-speed laminar water column is ejected from the gas-liquid outlet 72, in this embodiment, the fluid substance is water.

The electronic control module 10 turns on the switch of the laser generator 11 to emit multiple laser beams, and the optical element 12 reflects the laser beams to guide the multiple laser beams into the laser processing device 16. The laser beam is focused in the laser processing device 16 sequentially through the focusing beam expanding module, the beam rotation adjusting module 6 and the focusing lens 9, then is processed through the window lens 52, the energy storage effect of the liquid chamber 5, the protection of the gas chamber 7 and the total reflection effect of the water column water-gas laminar flow interface, and then is transmitted to the surface of the workpiece 15 for material removal processing.

In this embodiment, the multi-path laser beam includes a light beam a1 and a light beam B3, when the multi-path laser beam enters the laser processing device 16, the light beam a1 is parallel to the light beam B3 and is parallel to the axis where the light beam rotation adjustment module 6 and the focusing lens 9 are located, the focusing beam expansion module includes a focusing beam expansion module a2 and a focusing beam expansion module B4, the light beam a1 correspondingly enters the focusing beam expansion module a2, and the light beam B3 correspondingly enters the focusing beam expansion module B4 and then enters the light beam rotation adjustment module 6.

Along with the processing of the workpiece 15 by the laser beam, the water column ejected by the laser processing device 16 can reach the inside of the workpiece 15, so that the high-efficiency, stable, heat-influence-free and deep removal processing of the workpiece 15 is realized.

In another embodiment of the present application, as shown in fig. 2, fig. 3, fig. 4 and fig. 5, the electronic control module 10 opens the switch of the fluid transmission module 14 and the switch of the gas transmission module 13, so that the energy storage device 17 and the liquid chamber 5 are filled with the fluid substance at a certain pressure, and a protected high-speed laminar water column is formed under the assistance of gas, and the high-speed laminar water column is ejected from the gas-liquid outlet 72, in this embodiment, the fluid substance is water.

The electronic control module 10 turns on the switch of the laser generator 11 to emit one or more laser beams, and the optical element 12 reflects the laser beams to guide the laser beams into the laser processing device 16. One or more paths of laser beams pass through one or more paths of focusing beam expanding modules, so that part of one path of laser beams with larger diameter or one path of laser beams with smaller diameter are coaxially arranged with the axis where the beam rotation adjusting module 6 and the focusing lens 9 are located, and the coaxially arranged laser beams are transmitted along the axis through the beam rotation adjusting module 6; a part of the laser beam remaining the larger diameter laser beam or a plurality of smaller laser beams uniformly distributed around the axis deviate the laser beam to a position away from the axis by the refraction action of the upper lens 61 and the lower lens 62 of the beam rotation adjustment module 6.

In this embodiment, the laser beam emitted by the laser generator 11 is a path of laser beam a1, the focusing and beam expanding module is a focusing and beam expanding module a2, and the laser beam a1 is processed by the beam rotation adjusting module 6 into a path of laser beam coaxial with the axis of the beam rotation adjusting module 6 and the focusing lens 9 and a path of laser beam deviated away from the coaxial laser beam.

The processed laser beam is sequentially focused by a focusing lens 9, processed by a window lens 52, subjected to an energy storage effect of a liquid chamber 5, protected by a gas chamber 7 and a water column water-gas laminar flow interface total reflection effect, and then transmitted to the surface of a workpiece 15 for material removal processing.

Along with the processing of the workpiece 15 by the laser beam, the water column ejected by the laser processing device 16 can reach the inside of the workpiece 15, so that the high-efficiency, stable, heat-influence-free and deep removal processing of the workpiece 15 is realized.

The invention can adjust the laser energy distribution in the water column, and improve the laser cutting efficiency and the cutting quality; the invention has large-depth intervention type processing capability and breaks through the depth limit of the traditional laser processing; the invention has low technical cost and small technical difficulty, and has important significance for processing materials with larger thickness (more than 10mm) in the aviation and civil fields.

Although the present application has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application.