阅读说明：本技术 用于液体电子照相印刷的载体蒸发器 (Carrier vaporizer for liquid electrophotographic printing ) 是由 M·桑德勒 P·奈德林 于 2017-05-04 设计创作，主要内容包括：本文提出的方面针对用于液体电子照相印刷(LEP)的印刷系统的载体蒸发器。在一个示例中,所述载体蒸发器提供：用于吸收蒸发的载液的热空气供应,从而产生包括载体蒸气的第一空气流；用于排出所述载体蒸气中的至少一部分载体蒸气的排出装置；用于降低剩余载体蒸气的温度的热交换装置,从而将第一空气流转换为包含载体粒子的第二空气流；以及从第二空气流中去除载体粒子的过滤装置。(Aspects presented herein are directed to a carrier vaporizer for a printing system for Liquid Electrophotographic Printing (LEP). In one example, the carrier vaporizer provides: a supply of hot air for absorbing the evaporated carrier liquid, thereby generating a first air stream comprising carrier vapor; a venting means for venting at least a portion of the carrier vapor; heat exchange means for reducing the temperature of the remaining carrier vapour, thereby converting the first air stream into a second air stream containing carrier particles; and a filter device for removing carrier particles from the second air stream.)

1. A carrier vaporizer for a printing system for Liquid Electrophotographic Printing (LEP), the carrier vaporizer comprising:

a heating device providing a supply of hot air for absorbing the evaporated carrier liquid, thereby generating a first air stream containing carrier vapour;

a vent for venting at least a portion of the carrier vapor;

heat exchange means for reducing the temperature of the remaining carrier vapour, thereby converting said first air stream into a second air stream containing carrier particles; and

a filter device for removing the carrier particles from the second air stream.

2. The carrier evaporator of claim 1 wherein said supply of hot air, said first air stream comprising said carrier vapor and said second air stream comprising said carrier particles are at a predetermined flow rate comprising a rate of at most 8L/s at a print productivity level of 0.6 square meters per second.

3. The carrier evaporator according to claim 1, wherein the heating device provides the hot air supply with a temperature above room temperature.

4. The carrier vaporizer of claim 1, wherein the heating device provides the supply of hot air with a temperature of at least 120 ℃.

5. The carrier vaporizer of claim 1, wherein the heating device provides the supply of hot air having a temperature in the range of 160 ℃ to 165 ℃.

6. The carrier evaporator of claim 1, wherein the filtering device is an electrostatic demister.

7. The carrier evaporator of claim 6, wherein the electrostatic mist eliminator comprises:

at least two parallel ionization plates defining a first path for an air flow containing the carrier particles, the at least two parallel ionization plates supplying an electrostatic charge to the carrier particles traveling through the first path;

at least two parallel collection plates defining a second path for the air stream comprising electrostatically charged carrier particles, the at least two parallel collection plates creating an electric field in the second path such that when the air stream enters the second path, the electrostatically charged carrier particles are attracted to the parallel collection plates and neutralized; and

a carrier discharge part that collects the neutralized carrier particles.

8. The carrier evaporator according to claim 1, wherein the suction and heat exchange means is for reducing the temperature of the carrier vapor to 5-10 ℃.

9. The carrier vaporizer of claim 1, wherein the heating device is a ceramic, tungsten wire, or injection heating device.

10. The carrier evaporator according to claim 1, wherein the heating device is adapted to heat at 0.6m²s receives less than 1kW of power at the print productivity level.

11. The carrier evaporator of claim 1, wherein the carrier fluid is an isoparaffinic hydrocarbon.

12. A filter device in the form of an electrostatic mist eliminator of a printing system for Liquid Electrophotographic Printing (LEP), wherein the filter device comprises:

at least two parallel ionization plates defining a first path for an air flow containing carrier particles, the at least two parallel ionization plates providing an electrostatic charge to the carrier particles;

at least two parallel collection plates defining a second path for an air stream containing electrostatically charged carrier particles, the at least two parallel collection plates creating an electric field in the second path such that when the air stream enters the second path, the electrostatically charged carrier particles are attracted to the parallel collection plates and neutralized; and

a carrier discharge part that collects the neutralized carrier particles.

13. A Liquid Electrophotographic Printing (LEP) system, the liquid electrophotographic printing system comprising a carrier vaporizer, the vaporizer comprising:

a heating device providing a supply of hot air for absorbing the evaporated carrier liquid, thereby generating a first air stream containing carrier vapour;

a vent for venting at least a portion of the carrier vapor;

heat exchange means for reducing the temperature of the remaining carrier vapour, thereby converting said first air stream into a second air stream containing carrier particles; and

a filter device for removing the carrier particles from the second air stream.

14. The liquid electrophotographic printing system of claim 13, wherein the filtering device is an electrostatic mist eliminator.

15. The liquid electrophotographic printing system of claim 14, wherein the electrostatic mist eliminator further comprises:

at least two parallel ionization plates defining a first path for the air flow, the at least two parallel ionization plates for supplying an electrostatic charge to carrier particles in the air flow traveling through the first path;

at least two parallel collection plates defining a second path for an air stream containing electrostatically charged carrier particles, the at least two parallel collection plates for creating an electric field in the second path such that when the air stream enters the second path, the carrier particles are attracted to the parallel collection plates and neutralized; and

a carrier discharge part that collects the neutralized carrier particles.

Background

Liquid Electrophotographic Printing (LEP) is a printing process in which a suspension of a printing dye and a carrier liquid is transferred or printed onto an intermediate printing object, sometimes referred to as a blanket. Thereafter, the carrier liquid is evaporated so that the printing dye substantially free of the carrier liquid is transferred to the printing object.

Drawings

The foregoing will be apparent from the following more particular description of examples provided herein, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the examples provided herein:

fig. 1 is an illustrative example of a Liquid Electrophotographic Printing (LEP) system, according to some examples presented herein;

FIG. 2 is a graphical illustration of vapor evaporation versus temperature of an air stream used in evaporating a carrier liquid isoparaffin (Isopar L) in accordance with some examples presented herein;

FIG. 3 is a graphical illustration of the amount of vapor evaporation versus the amount of heat applied to a hot air stream used in evaporating carrier liquid isoparaffins, in accordance with some examples presented herein;

FIG. 4 is an example of hardware for a carrier evaporator (carrier evaporator) according to some examples presented herein;

FIG. 5 is an example of a filtration device in the form of a non-effective demister (vain demister);

FIG. 6 is an example of a filtration device in the form of an electrostatic mist eliminator, according to some examples presented herein;

FIG. 7 is another example of hardware for a carrier vaporizer, according to some examples presented herein; and

fig. 8 is a flow chart illustrating example operations that may be employed by a carrier vaporizer in accordance with some examples presented herein.

Detailed Description

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular components, elements, techniques, etc. in order to provide a thorough understanding of the examples provided herein. However, examples may be practiced in other ways than these specific details. In other instances, detailed descriptions of well-known methods and elements are omitted so as not to obscure the description of the examples provided herein.

Example aspects presented herein are directed to an efficient and effective means of evaporating a carrier liquid in a Liquid Electrophotographic Printing (LEP) system. In particular, some aspects described herein utilize elevated temperatures during evaporation. The use of a flow of hot air allows the use of a smaller amount of air during the evaporation, for example at a lower flow rate, and thus less energy in maintaining the temperature of the carrier used for absorption of the evaporation.

FIG. 1 illustrates an example of a liquid electrophotographic printing system. A printing system for liquid electrophotographic printing includes a first drum 10 in which a suspension of a carrier liquid (e.g., an isoparaffin) and a printing dye 12 of various colors is supplied in the first drum 10. The printing dye may initially be in powder form. The printing dye will be mixed with the carrier liquid and supplied to the first drum by using an electric charge. The first drum will comprise an electrical potential in those parts where the dye is intentionally transferred to form the printed pattern. While the use of a drum is discussed, other elements, such as belts or other transfer members, may also be utilized.

The first drum 10 is adjacent an electrically biasable Intermediate Transfer (ITM) drum 14. The electrically biasable intermediate transfer drum 14 receives a carrier liquid and a suspension of printing dye in a print pattern from the first drum 10. The carrier liquid is then evaporated and the printing dye in the printing pattern is transferred to the printing object.

Evaporation of the carrier liquid is provided via the heating system 20. Once the electrically biasable intermediate transfer drum 14 including the suspension is rotated toward the heating system 20, the carrier liquid is evaporated 22 such that printing dye substantially free of carrier liquid is transferred to the transfer drum 16 and subsequently to the print object 18.

During evaporation of the carrier liquid, the suspension of carrier liquid and printing dye is heated, typically via a flow of air at room temperature. Once the suspension is heated, the carrier liquid vapor 22 passes through a filtration device (not shown) whereby carrier liquid particles (e.g., condensed liquid vapor droplets) can be collected and recycled for subsequent printing cycles.

According to some example aspects presented herein, there is provided a carrier vaporizer for a liquid electrophotographic printing system. In particular, some aspects described herein provide a heating system 20 for providing a flow of air above Room Temperature (RT)21, thereby providing a supply of heated air. With the hot air supply, the carrier vaporizer provides an efficient and cost-effective way of vaporizing the carrier liquid from the suspension of carrier liquid and printing fuel.

Fig. 2 shows a graph representing the relationship between concentration and temperature of carrier vapor (e.g., isoparaffin) vaporization. As the temperature of the air stream heating the suspension increases, the concentration of the evaporated vapor also increases, as shown in the graph. As shown in this graph, the relationship between the concentration of vaporized carrier liquid and the temperature of the applied hot air stream is an exponentially increasing logarithmic function. The data contained in figure 2 were obtained experimentally using isoparaffins as carrier fluids.

Fig. 3 shows a graph representing the relationship between the concentration of evaporated carrier vapor and the amount of heat applied to the air stream utilized in the evaporation of the carrier vapor. As shown in this graph, the relationship between the concentration of the vaporized carrier liquid and the temperature applied to the hot air stream used in the vaporization is a linearly increasing function. The data contained in figure 3 were obtained experimentally using isoparaffin as the carrier liquid.

As can be seen in fig. 3, a greater concentration of carrier liquid will utilize more heat applied to the hot air stream used in evaporation. More heat applied to the hot air stream is generally associated with increased operating costs, as more energy will be used to provide a higher level of temperature to the air stream. Therefore, to maintain low production costs, the suspension of carrier liquid and printing dye is typically heated using an air stream maintained at room temperature.

However, as shown in FIG. 2, since the relationship between the concentration of the vaporized carrier liquid and the temperature of the air stream used in the vaporization is an exponential logarithmic function, a large amount of additional heat need not be utilized in order to significantly increase the concentration of the vaporized carrier vapor. And thus the amount of air that needs to be heated.

According to some aspects, it has been recognized that an increase in heating temperature results in a greater amount of carrier liquid being evaporated. Points 3 and 7 of fig. 2 and 3, respectively, illustrate the operating points of a liquid electrophotographic printing vaporizer that uses air flow at room temperature to vaporize the carrier liquid. Points 5 and 9 of fig. 2 and 3, respectively, illustrate a liquid electrophotographic printing vaporizer using a flow of hot air to vaporize a carrier liquid, according to some aspects described herein.

While increased heating is generally believed to result in increased power and operating costs, the aspects presented herein have recognized that as the heating temperature increases, lower flow rates may be employed due to the ability to vaporize greater amounts of carrier liquid. Thus, a reduced amount of power may be used to provide the air flow at an elevated temperature (thereby causing an increase in the concentration of the vaporized carrier liquid).

Fig. 4 shows a detailed view of the carrier vaporizer 20 within a printing system for liquid electrophotographic printing. As discussed with respect to fig. 1, the electrically biasable intermediate transfer drum 14 includes a carrier liquid and a suspension of printing dye in a print pattern. As the surface of the electrically biasable intermediate transfer drum 14 passes through the carrier evaporator 20, the suspension will be heated and the carrier liquid will be evaporated.

The carrier evaporator 20 provides a low flow rate supply of hot air. According to some aspects, the hot air supply is at a temperature above room temperature. According to some aspects, the hot air supply is at a temperature of at least 120 ℃. According to some aspects, the temperature of the hot air supply is in the range of 160 ℃ to 165 ℃. According to some aspects, the supply of hot air is provided at a low flow rate. In particular, it may be at 0.6m²The printing productivity level of/s provides a supply of hot air at a flow rate of at most 8L/s. According to some aspects, the flow rate may be at most 5L/m of the print target area²The flow rate of (c).

According to some aspects, the carrier vaporizer 20 provides an air supply via a blower/pump 36. The air supply is then heated using the air heating device 34, thereby providing a hot air supply 30. According to some aspects, the heating device may be a ceramic, tungsten wire, or injection heating device. According to some aspects, the enclosed heating device 38(blanket heater) may also assist in regulating the temperature of the hot air supply.

The carrier evaporator 20 applies a supply of hot air to the electrically biasable intermediate transfer drum 14 surface via an air knife 32. The application of the hot air supply results in the absorption of the evaporated carrier liquid, and thus in the flow rate of the air containing the carrier vapour. When a lower flow rate is used in the hot air supply, a reduced power level can be achieved. According to some aspects, the evaporator may be at 0.6m²The hot air supply is supplied at a print productivity level of/s receiving less than 1kW of power. According to some aspects, the power level may be less than 0.6J/m of the print target area²。

The carrier vapor then enters the exhaust and heat exchange unit 40. The exhaust section of the exhaust and heat exchange unit 40 exhausts at least a portion of the carrier vapor. The heat exchange means of the exhaust and heat exchange unit 40 reduces the temperature of the remaining carrier vapor. The reduction in temperature causes the air stream containing the carrier vapor to change to an air stream containing the carrier particles. According to some aspects, the heat exchange means of the discharge and heat exchange unit 40 may reduce the temperature of the carrier vapor to 5-10 ℃.

Thereafter, the air stream comprising the carrier particles passes through the filter device 42. According to some aspects, the filter device 42 removes carrier particles from the air stream. Fig. 5 shows a filtering device in the form of an inactive demister 52. As shown in fig. 5, the velocity of the air passes through the mist eliminator 52. The mist eliminator 52 separates the carrier particles from the air stream. Thereafter, the separated carrier particles may pass through a fine filter device 54, in which fine filter device 54 the carrier particles are bound. The weight of the bound carrier particles increases, and therefore drops into the carrier discharge portion due to gravity. The remaining air flow present in the mist eliminator is clean air. The dropped carrier particles are then recycled for future printing.

According to some aspects, it is understood herein that the air stream containing the carrier particles may pass through the filtration device (e.g., the inactive mist eliminator of fig. 5) at a lower flow rate such that the inactive mist eliminator does not provide effective filtration. FIG. 6 illustrates an electrostatic mist eliminator 60 that may be used as the filtration device 42 of FIG. 4.

According to some aspects, the electrostatic mist eliminator 60 comprises at least two parallel ionization plates. Fig. 6 shows three ionization plates 61 to 63. Any number (two or more) of ionization plates may be used. The parallel ionization plates define a first path P1 for the air flow. According to some aspects, the ionizing plate is charged such that, when the airflow enters the first path P1, the carrier particles within the airflow are electrostatically charged. A positive or negative electrostatic charge may be applied to the carrier particles.

The air stream containing the charged carrier particles may then enter a second path P2 defined by at least two parallel collection plates. Fig. 6 shows the use of five parallel collection plates 64 to 68. Any number (two or more) of collection plates may be used. According to some aspects, the collection plates create an electric field within the second path P2. When the low flow rate air stream enters the second path P2, the electrostatically charged carrier particles are attracted to the collection plate and then neutralized. In particular, the carrier particles will be neutralized by getting their missing electrons or protons.

According to some aspects, the electrostatic mist eliminator 60 further comprises a carrier discharge 70 positioned to collect the neutralized carrier particles as they fall from the collection plate due to gravity. Thereafter, the neutralized carrier particles can be recovered and used for future printing. The electrostatic mist eliminator 60 of FIG. 6 provides an efficient and effective way of filtering carrier particles that are traveling in a low velocity air stream.

Fig. 7 shows the control unit 73. According to some aspects, a control unit 73 may be used to control the operation of the carrier vaporizer, including the operation of the various components of the carrier vaporizer. The control unit 73 may include any number of network interfaces 75, and the network interfaces 75 may be configured to receive and transmit any form of heating, evaporation, or sensing related information and/or instructions. According to some aspects, the network interface may also include a single transceiver interface or any number of receive and/or transmit interfaces.

The control unit 73 may also include at least one memory 77 that may communicate with the network interface. Memory 77 may store received or transmitted data and/or executable program instructions. The memory may also store information related to evaporation or heating of the carrier liquid as described herein. The memory may be any suitable type of machine-readable medium and may be of a volatile and/or nonvolatile type.

The control unit 73 may also include at least one processing unit 79, which processing unit 79 may be configured to process received information relating to the evaporation or heating provided by the evaporator for the printing system of liquid electrophotographic printing. The processing unit may be any suitable computational logic, for example, a microprocessor, Digital Signal Processor (DSP), Field Programmable Gate Array (FPGA), or Application Specific Integrated Circuit (ASIC), or any other form of circuitry.

Fig. 8 shows a flowchart depicting exemplary operations that may be undertaken by an evaporator (e.g., including the control unit of fig. 7) in a printing system for liquid electrophotographic printing as described herein.

FIG. 8 includes some operations shown as solid line boxes and some operations shown as dashed line boxes. The operations included in the solid lines are the operations included in the broadest aspects. The operations included in the dashed outline are example aspects that may be included in or as part of the operations of the broader example aspects, or other operations that may be taken. The operations of fig. 8 need not be performed in sequential order. Furthermore, not all operations need be performed. The example operations may be performed in any order and in any combination.

Operation 80

The evaporator is configured to apply a supply of hot air. The heating device (e.g., at least any one of the components 30-38) may be configured to supply or maintain the temperature of the hot air supply. The processing unit may be configured to provide computer readable instructions for supplying such a hot air supply.

According to some aspects, the use of a hot air stream allows for the use of less air than systems relying on air at room temperature. In addition, the temperature of the air stream is maintained above room temperature with less energy and system resources. According to some aspects, the hot air supply and the generated air flow have a low flow rate.

Example operation 81

According to some aspects, the applying 80 further comprises applying a supply of hot air 81 at a temperature above room temperature. The heating device (e.g., at least any one of the components 30-38) may be configured to supply or maintain the temperature of the hot air supply at a temperature above room temperature. The processing unit may be configured to provide computer readable instructions for supplying such a hot air supply at a temperature above room temperature.

Example operation 82

According to some aspects, the applying 80 further comprises applying a supply of hot air 82 at a temperature above 120 ℃. The heating device (e.g., at least any one of the components 30-38) may be configured to supply or maintain a temperature of the hot air supply at a temperature above 120 ℃. The processing unit may be configured to provide computer readable instructions for supplying such a hot air supply at a temperature above 120 ℃.

Example operation 83

According to some aspects, the applying 80 further comprises applying a hot air supply 83 at a temperature between 160 ℃ and 165 ℃. The heating device (e.g., at least any one of the components 30-38) may be configured to supply or maintain the temperature of the hot air supply at a temperature between 160 ℃ and 165 ℃. The processing unit may be configured to provide computer readable instructions for supplying such hot air at a temperature between 160 ℃ and 165 ℃.

Example operation 84

According to some aspects, the applying 80 further comprises applying at 0.6m²The print productivity level of/s applies the hot air supply 84 at a flow rate of up to 8L/s. The heating device (e.g., blower/pump 36) may be configured at 0.6m²The hot air supply is supplied at a rate of at most 8L/s at a printing productivity level of/s. The processing unit may be configured to provide for at 0.6m²A print productivity level of/s supplies computer readable instructions of such a hot air supply at a rate of at most 8L/s.

Operation 85

The evaporator is further configured to supply an absorption carrier liquid 85 with the hot air, wherein the absorption results in a first air flow comprising the carrier vapor. The suction of the unit 40 is configured to absorb the carrier liquid with the hot air supply. The processing unit is configured to provide computer readable instructions for controlling the absorption.

As described above, the absorption of the carrier liquid may be provided by a blanket on an electrically biasable intermediate transfer drum of a printing system that includes applying heat to liquid electrophotographic printing. According to some aspects, the carrier liquid may be a dielectric volatile liquid, such as mineral oil. Examples of such mineral oils are isoparaffins, such as isoparaffins.

Operation 86

The evaporator is further configured to convert the first air stream containing the carrier vapor into a second air stream containing the carrier particles by reducing the temperature of the carrier vapor. The heat exchange device of unit 40 is configured to convert the first air stream containing the carrier vapor into a second air stream containing the carrier particles by reducing the temperature of the carrier vapor. The processing unit is configured to provide computer readable instructions for facilitating the reduction in temperature. According to some aspects, a vent device may also be used to vent a portion of the carrier vapor prior to the temperature reduction.

Example operation 87

According to some aspects, the converting 86 may further include reducing the temperature of the first air stream including the carrier vapor by 87 to 5 ℃ -10 ℃. The heat exchange means of unit 40 may reduce the temperature of the first air stream comprising the carrier vapor to 5 ℃ to 10 ℃. The processing unit may be configured to provide computer readable instructions for facilitating reducing the temperature to 5 ℃ to 10 ℃.

Operation 88

The evaporator is also configured to filter the carrier particles 88 from the second air stream. The filter device 42 is configured to filter the carrier particles from the second air stream. The processing unit may be configured to provide computer readable instructions for facilitating filtration of the carrier particles.

Example operation 89

According to some aspects, the filtering 88 may further include supplying an electrostatic charge 89 between at least two parallel ionization plates defining the first path. The ionization plates (e.g., plates 61-63) of the electrostatic mist eliminator 60 may be configured to supply an electrostatic charge. The processing unit may be configured to provide computer readable instructions for providing an electrostatic charge between at least two parallel ionization plates defining a first path. This example operation is further described at least in fig. 6.

Example operation 90

According to some aspects, the filtering 88 and supplying 89 may further include electrostatically charging 90 the carrier particles in the second air stream once the second air stream passes through the first path. The at least two parallel ionization plates (e.g., plates 61-63) of the electrostatic mist eliminator 60 may be configured to electrostatically charge carrier particles in the second air stream. The processing unit may be configured to provide computer readable instructions for electrostatically charging the carrier particles.

Example operation 91

According to some aspects, the filtering 88, supplying 89, and electrostatically charging 90 may further comprise supplying an electric field 91 between at least two parallel collection plates defining the second path. At least two collector plates (e.g., collector plates 64-68) can provide an electric field. The processing unit may be configured to provide instructions for supplying an electric field between the at least two parallel collector plates.

Example operation 92

According to some aspects, the filtering 88, the power supply 89, the electrostatic charging 90, and the power supply 91 may further include: as the second air stream passes through the second path, the electrostatically charged carrier particles 92 are neutralized and the electrostatically charged particles are attracted to one of the parallel collection plates. The at least two collection plates of the electrostatic mist eliminator can neutralize the electrostatically charged carrier particles. The processing unit may provide computer readable instructions for controlling the electric field in order to neutralize the electrostatically charged carrier particles and attract said electrostatically charged particles to one of said parallel plates when the air flow passes the second path.

Example operation 93

According to some aspects, the filtering 88, the supplying 89, the electrostatically charging 90, the supplying 91, and the neutralizing 92 may further include collecting the neutralized carrier particles 93 via a carrier discharge. The processing unit may provide computer readable instructions for facilitating collection of neutralized carrier particles.

Throughout the description and claims of this specification, the words "comprise" and "comprise," and variations thereof, mean "including but not limited to," and are not intended to (and do not) exclude other moieties, additions, components, integers or examples. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise indicates a similar singular use. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context indicates otherwise the use of the similar singular.

Features, integers, characteristics, groups described in conjunction with a particular aspect or example are to be understood to be applicable to any other aspect or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the operations of any method or process so disclosed, may be combined in any combination, but with at least some of such features and/or operations being mutually exclusive. The examples presented herein are not limited to the details of any of the foregoing aspects. These examples extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the operations of any method or process so disclosed.