Reduced flow processing system for flexographic printing plates

Abstract

A processing system for processing flexographic printing plates may include a processing path for processing flexographic printing plates. A hollow tube may be positioned to extend across the processing path. A pressurized processing liquid supply system is provided. A plurality of pressure compensation emitters are coupled to the hollow tube. Each pressure compensation emitter may include a casing having a fluid flow path fluidly coupled to the hollow tube and having an outlet. Each emitter may also include a resilient planar member positioned within the casing to form at least one resilient surface of the fluid flow path. Each pressure compensation emitter is configured to control a flow rate of pressurized processing liquid to generate droplets of processing liquid from the outlet. The resilient planar member may be positioned to provide a variable outlet cross-sectional shape at the outlet in response to pressure within the casing.

Description

[Technical Field]

[0001] U.S. Government Rights This invention was made with government support under CA191785 awarded by the National Institutes of Health. The government has certain rights in this invention.

[0002] Field The present invention relates to the field of flexographic printing, and more particularly to a pressure compensated emitter and method of using a pressure compensated emitter to reduce water usage in the manufacture of flexographic printing plates. [Background technology]

[0003] 2. Description of Related Art Letterpress printing plates, such as flexographic printing plates, fall into two main categories: (1) those that are processed using aqueous solutions to remove unexposed photopolymer, and (2) those that require processing using other chemical solvents. In recent years, flexographic printing plates using aqueous-processable photopolymers have gained market interest due to their environmentally friendly properties. These plates also have the added benefit of reducing workplace exposure to organic solvents. Aqueous-processable printing plates are sometimes called aqueous-washable printing plates because their processing typically involves washing away the unexposed photopolymer. There are also two main types of aqueous-processable flexographic printing plates: (1) those that can be processed by dissolving the photopolymer using a strong alkaline solution (i.e., pH > 11) and (2) those that can be processed by dispersing the photopolymer using a processing solution containing a dispersant (usually pH < 11).

[0004] Aqueous-processable flexographic printing plates can be processed (i.e., "washed") in a number of ways. For example, U.S. Patent No. 5,124,736 (Yamamoto et al.), entitled "Process and Apparatus for Developing Photopolymer Plate," describes a system in which a processing solution (i.e., a "wash-out solution") is sprayed onto the printing plate under pressure to form a relief, and a system in which a brush is rubbed against the printing plate in the presence of the processing solution, thereby dissolving the unexposed portions with the processing solution to form a relief. Yamamoto et al. describe a system in which the processing solution is filtered and recycled back through the printing plate processor after an entire batch of platemaking is complete.

[0005] As noted in U.S. Patent No. 6,247,856 (Shibano et al.) entitled "Developing system of photosensitive resin plates and apparatus used therein," photopolymer (i.e., resin) can accumulate in used processing solutions after processing a large number of printing plates. This can cause various problems, including reduced development speed and dispersed resin residue that adheres to printing plates and brushes. This can necessitate frequent disposal of used processing solutions and preparation of new ones. Shibano et al. discloses removing a portion of the resin-containing processing solution while adding new processing solution to the processing unit to maintain a substantially constant resin content in the processing solution.

[0006] A rinse station can be employed after the main plate processing step to remove debris adhering to the surface of the printing plate. U.S. Patent Application Publication No. 2009 / 0013888 (Danon), entitled "Methods and means relating to photopolymer printing plates," discloses treating the printing plate with a processing solution and then rinsing it with water in a rinse station. The used processing solution is recycled back to the processor after filtration. Wastewater from the rinse station may also be recycled back to the processor after filtration.

[0007] U.S. Patent No. 5,828,923 (Harabin et al.), entitled "Apparatus and method for processing water wash photopolymer solution," discloses sending spent processing solution to a holding tank where a coagulant is added to coagulate the solids for disposal.

[0008] European Patent Specification No. 0586470B1 (Danon), entitled "Preparation of photopolymerized elastomeric printing plates," discloses a processing system including (a) a wash-off section that removes unexposed areas of the printing plate, (b) a rinsing section, (c) a section that removes excess water, (d) a light finishing section in which the printing plate is exposed to ultraviolet light to reduce tackiness of the surface of the printing plate, and (e) a drying section.

[0009] European Patent Specification No. 0586483B1 (Danon), entitled "Method and Apparatus for Washing-Out Printing Plates," discloses a printing plate processing system in which processing solution is directed through a spray bar along downwardly directed bristles of a scrubbing brush.

[0010] Even when utilizing printing plate processing equipment that includes a rinsing process, such as that disclosed in the aforementioned U.S. Patent Application Publication No. 2009 / 0013888, it has been found that significant problems with printing plate defects can occur after only a few plates have been produced. The occurrence of printing plate defects is particularly problematic with increasingly popular photopolymer plates that contain microstructures on their raised printing plate surface (i.e., printing surface). As discussed in U.S. Patent No. 8,399,177 (Stolt et al.) entitled "Enhanced printing plate," this microstructure is beneficial for increasing print density and uniformity. In such cases, debris particles tend to accumulate on the microstructured surface of the printing plate, resulting in unacceptable printing defects after processing even a small number of printing plates.

[0011] It is desirable to minimize the amount of processing solution required to process a printing plate, thereby reducing costs and the amount of used processing solution that must be disposed of. However, it has been found that prior art processing systems require relatively high processing solution flow rates to maintain high quality levels. A need remains for an improved processing system for processing flexographic printing plates that requires lower processing solution flow rates. Summary of the Invention [Means for solving the problem]

[0012] In some embodiments, a processing system for processing flexographic printing plates is provided. The processing system can include a processing path configured to process flexographic printing plates. A hollow tube having a length can be positioned to extend across the processing path, and the processing path can be at an angle, such as perpendicular. A pressurized processing liquid supply system (e.g., including at least one pump) is provided for supplying pressurized processing liquid to the interior of the hollow tube. A plurality of pressure compensation emitters are coupled to the hollow tube and distributed along the length of the hollow tube. For example, there can be approximately 33 pressure compensation emitters, or ±10, 8, 5, 2, 1, or any other integer number. Each pressure compensation emitter can include a casing having a fluid path fluidly coupled to the hollow tube and having an outlet. Each emitter can also include a resilient planar member within the casing positioned to form at least one resilient surface of the fluid flow path. In some embodiments, each pressure compensation emitter is configured to control the flow rate of pressurized processing liquid to generate droplets of processing liquid from the outlet. In some embodiments, the resilient planar member is positioned to impart a variable outlet cross-sectional shape to the outlet in response to pressure within the casing.

[0013] In some embodiments, the casing and the resilient planar member define a fluid flow path (e.g., a channel, conduit, tunnel, etc.) that is a serpentine flow path configured to create a pressure drop in a pressurized process liquid. In some aspects, the serpentine flow path is created by one or more flow redirection members that create changes in direction within the serpentine flow path. In some aspects, the one or more flow redirection members include a plurality of first members that protrude partially into the fluid flow path from at least one side along the length of the serpentine flow path so that liquid flowing through the fluid flow path repeatedly undergoes a first change in direction. In some aspects, the one or more flow redirection members include a plurality of second members that protrude partially into the fluid flow path and at an angle relative to the first members, the plurality of second members positioned along the length of the serpentine flow path so that liquid flowing through the fluid flow path repeatedly undergoes a second change in direction at an angle relative to the first change in direction.

[0014] In some embodiments, the resilient planar member is an elastomer, rubber, or other resilient material, such as a membrane, configured and positioned to regulate the flow of pressurized treatment liquid through the outlet at a predetermined substantially constant flow rate over a range of water pressures at the inlet.

[0015] In some embodiments, the outlet includes an upwardly opening discharge adjustment groove through which process fluid flows from the fluid flow path to the outlet, and the resilient planar member is positioned to overlap and engage the groove to form a pressure compensation means for adjusting fluid flow from the fluid flow path to the outlet. In some aspects, the resilient planar member is a resilient valve member disposed within the casing in a position that overlaps the flow path pattern to form a flow path channel. The resilient valve member can be positioned to cooperate with the flow path pattern to define an elongated pressure reduction flow path having an upstream end in flow communication with the hollow tube and a downstream end in flow communication with the outlet.

[0016] In some embodiments, the system can include one or more brushes extending across the processing path with the hollow tube, and the plurality of pressure-compensating emitters positioned and configured to deliver the processing liquid as droplets onto the one or more brushes.

[0017] In some embodiments, a method for processing a flexographic printing plate having a relief image is provided. The method can include providing the relief image to a processing unit that processes the flexographic printing plate with a processing liquid. The processing unit can be configured with a processing path that includes a hollow tube and a pressure-compensated emitter according to embodiments described herein. The method can include emitting processing liquid as droplets from a plurality of pressure-compensated emitters. The droplets from the emitters can be used to wash the relief image with processing liquid from the processing liquid droplets.

[0018] In some embodiments, the method can include applying the treatment liquid as droplets to one or more brushes that move relative to the surface of the flexographic printing plate. The one or more brushes can be positioned and configured to apply the treatment liquid to the relief image.

[0019] In some embodiments, the pressure compensation emitters can adjust the fluid flow so that the flow rates of processing liquid droplets from each pressure compensation emitter are equal to within 30% of each other. In some embodiments, the flow rate of processing liquid droplets from each of the pressure compensation emitters is less than 0.1 liters / minute. In some embodiments, the volume of processing liquid droplets is about 0.076 liters / minute, or about 0.0023 liters / minute, for 33 pressure compensation emitters. The volume of processing liquid droplets can be about 0.0010 liters / minute to about 0.0035 liters / minute, or about 0.002 liters / minute to about 0.003 liters / minute. The number of pressure compensation elements is an integer, but can range from 10 to 50 emitters, 15 to 45 emitters, 20 to 40 emitters, or 25 to 35 emitters.

[0020] In some embodiments, the processing liquid is an aqueous processing solution that includes a dispersant. In some aspects, the processing liquid includes a solvent. In some aspects, the processing liquid is water. In some aspects, the pressurized processing liquid supply system pressurizes the processing liquid to about 30-60 psi (0.2 MPa-0.41 MPa).

[0021] In some embodiments, the resilient planar member is a resilient valve member disposed within the casing in a position that overlies the flow path pattern. The resilient valve member is positioned and configured to cooperate with the flow path pattern to define an elongated reduced pressure flow path having an upstream end in flow communication with the hollow tube and a downstream end in flow communication with the outlet. In some aspects, the outlet includes an upwardly opening discharge adjustment groove through which process fluid flows from the fluid flow path to the outlet, and the resilient planar member overlies and engages the groove to form a pressure compensation means for regulating fluid flow from the fluid flow path to the outlet.

[0022] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the exemplary aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

[0023] The foregoing and following information, as well as other features of the present disclosure, will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings, in which: The present disclosure will be described with additional specificity and detail using the accompanying drawings, with the understanding that these drawings illustrate only some embodiments in accordance with the present disclosure and therefore should not be considered limiting of its scope. [Brief explanation of the drawings]

[0024] [Figures 1A-1D] 1 illustrates the steps involved in forming a flexographic printing plate according to an exemplary process. [Figure 2] 1 shows a schematic diagram of a system for processing photosensitive flexographic printing plates. [Figure 3]1 shows a conventional processing unit incorporating a trough-based liquid distribution system. [Figure 4] 4 shows additional details of the trough of FIG. 3. [Figure 5] 1 illustrates an improved processing unit incorporating multiple pressure compensated emitters according to an exemplary embodiment; [Figure 6] 6 illustrates additional details of the processing unit of FIG. 5. [Figure 7] 10 shows an alternative embodiment incorporating laterally moving brushes. [Figure 8A] 1 shows a cross-sectional view of an embodiment of a pressure compensated emitter. [Figure 8B] 8B shows an exploded view of the pressure-compensated emitter of FIG. 8A. [Figure 8C] 8B shows a perspective view of the housing base of the pressure compensated emitter of FIG. 8A showing the serpentine flow channels formed from the fluid path pattern. DETAILED DESCRIPTION OF THE INVENTION

[0025] It should be understood that the accompanying drawings are for purposes of illustrating the concepts of the invention and may not be drawn to scale. Where possible, the same reference numerals have been used to designate the same features common to the figures.

[0026] The elements and components in the figures may be arranged in accordance with at least one of the embodiments described herein, but the arrangement may be modified by one skilled in the art in accordance with the disclosure provided herein.

[0027] Detailed Description In the following detailed description, reference is made to the accompanying drawings, which form a part of this specification. In the drawings, like symbols generally identify like elements unless the context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit and scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure as outlined herein and illustrated in the figures may be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are expressly contemplated herein.

[0028] The present invention describes a processing system for treating flexographic printing plates moving along a processing path in an orbital direction, the processing unit including: a hollow tube having a length extending across the cross-dimension of the orbit of the flexographic printing plate; a processing solution supply system for supplying pressurized processing solution to the interior of the hollow tube; and a plurality of pressure-compensating emitters distributed along the length of the tube for delivering processing solution to the surface of the flexographic printing plate, the processing solution flowing at a controlled flow rate from the interior of the hollow tube through the pressure-compensating emitters. An advantage of this invention is that it allows for a uniform flow of processing solution across the entire width of the printing plate with a reduced total flow rate. Another advantage is that it allows for the processing of printing plates while using less processing solution, thereby reducing processing solution costs and processing solution disposal costs.

[0029] In accordance with the present invention, a flexographic printing plate is formed by applying an aqueous processing solution to a photosensitive flexographic printing plate precursor having a latent image formed in an aqueous-processable photopolymer. In an exemplary embodiment, the photosensitive flexographic printing plate is similar to that described in U.S. Pat. No. 8,492,449 (Inoue et al.), entitled "Photosensitive resin composition, printing plate precursor and flexographic printing plate." However, the processing systems and methods described are also applicable to other types of aqueous-processable printing plates, including other types of aqueous-processable relief printing plates (e.g., letterpress printing plates).

[0030] Prior to processing, a latent image is formed on the photosensitive flexographic printing plate using any suitable method known in the art. In an exemplary embodiment, the latent image is formed using a mask image as described in commonly assigned U.S. Pat. No. 9,250,527 (Kidnie), entitled "Mask forming imageable material and use," which is incorporated herein by reference. This method is illustrated in Figures 1A-1D.

[0031] FIG. 1A shows a mask material 10 including a mask layer 12 on a substrate 14. In an exemplary embodiment, the mask material 10 is commercially available Kodak Flexcel NX Thermal Imaging Layer material. Further information regarding such mask materials 10 can be found in the aforementioned U.S. Pat. No. 9,250,527. The mask layer 12 is opaque to the radiation (e.g., ultraviolet radiation) used to expose photosensitive flexographic printing plates. The mask material 10 is imagewise exposed to radiation 16 to form a mask image 18 in the mask layer 12. The mask image 18 typically includes a pattern of halftone dots, lines, text, and solid areas (with or without microsurface patterning) according to the image content to be printed. In an exemplary embodiment, the radiation 16 is provided by a commercially available Kodak Trendsetter NX imager, which uses an infrared laser to ablate portions of the mask layer 12 where it is desired to create raised features on the flexographic printing plate.

[0032] 1B, mask material 10 is laminated to photosensitive printing plate 20. Photosensitive printing plate 20 includes a photosensitive photopolymer layer 22 on a substrate 24. Mask material 10 is laminated so that mask layer 12, bearing mask image 18, faces photopolymer layer 22. In an exemplary embodiment, photosensitive printing plate 20 is of a type similar to that described in the aforementioned U.S. Pat. No. 8,492,449 (Inoue et al.) (except that it does not include an anti-adhesion layer on the photopolymer layer), and lamination is performed using a commercially available Kodak Flexcel NX laminator so that mask material 10 is in intimate contact with photopolymer layer 22 of photosensitive printing plate 20 (after removing the cover film from photosensitive printing plate 20).

[0033] In FIG. 1C, the laminated photosensitive printing plate 20 is exposed to radiation 26 to form a latent image 28 in the photopolymer layer 22. Various commercially available ultraviolet exposure devices can be used to accomplish this. In an exemplary embodiment, the radiation 26 is ultraviolet radiation provided by a commercially available Concept 302 EDLF system available from Mekrom Engineering. When the mask image 18 is ablated, the radiation 26 passes through the mask layer 12 and exposes the photopolymer layer 22, thereby crosslinking and hardening the photopolymer to provide a developable latent image 28 including crosslinked polymer regions 29. The ultraviolet exposure 26 can be carried out over a wide temperature range, from approximately room temperature to 60° C. However, it has been found that ultraviolet radiation exposure at elevated temperatures, in the range of 42° C. to 52° C., results in better final printing plate quality (e.g., improved minimum dot retention and enhanced resolution of surface topography).

[0034] After the latent image 28 is formed, the mask material 10 is removed, and the photosensitive printing plate 20 is processed to produce a developed relief image 30, as shown in FIG. 1D. This processing operation (sometimes referred to as "plate development") removes the unexposed portions of the photopolymer layer that were not hardened by the radiation 26 (FIG. 1C), leaving behind crosslinked polymer regions 29. In accordance with the present invention, the photopolymer layer 22 is made from an aqueous-processable photopolymer, such that the processing operation employs an aqueous processing solution (i.e., a water-based processing solution) that typically contains an active ingredient such as a dispersant. Aqueous processing solutions are generally preferred over processing solutions that use other solvents (e.g., organic solvents) due to their environmentally friendly characteristics.

[0035] 2 shows a schematic diagram of an exemplary processing system 100 for processing an aqueous-processable photosensitive printing plate 20 according to the present invention. In the exemplary embodiment, the photosensitive printing plate 20 is of a type similar to that described in the aforementioned U.S. Pat. No. 8,492,449 (Inoue et al.) (except that it does not include an anti-adhesion layer on the photopolymer layer). However, other types of aqueous-processable printing plates can also be used.

[0036] 2, printing plate processing is performed as an "in-line process," where photosensitive printing plate 20 advances through processing system 100 along processing path 101, where a series of processing operations are applied. In an alternative embodiment, printing plate processing can also be performed as a "batch process," where, after the main printing plate processing, the printing plate moves in the reverse direction and secondary processing is performed similar to an in-line process.

[0037] In an exemplary arrangement, photosensitive printing plate 20 is mounted on platen 110 as it moves along processing path 101. The input to processing system 100 is photosensitive printing plate 20 having a latent image 28 formed by exposing photopolymer layer 22 to light. Latent image 28 includes exposed portions 124 where photopolymer layer 22 has hardened upon exposure to appropriate actinic radiation, and unexposed portions 126 where photopolymer layer 22 remains soft and is removed from substrate 24 during processing.

[0038] The main processing unit 102 is used to develop the latent image 28 into a relief image 30 by removing the unexposed portions 126 of the photopolymer layer 22 from the photosensitive printing plate 20. The main processing unit 102 is also referred to as a processing station or a developing unit / station. The main processing unit 102 includes a pump 112 for drawing an aqueous processing solution 142 from a processing solution tank 140 and directing it through a series of pipes 113 to contact the aqueous processing solution 142 with the photosensitive printing plate 20.

[0039] The aqueous processing solution 142 includes a dispersant (i.e., "soap") to aid in the removal of unexposed photopolymer. Any suitable dispersant known in the art can be used in accordance with the present invention. Some examples of suitable dispersants are described in U.S. Pat. No. 9,005,884 (Yawata et al.), entitled "Developer composition for printing plates, developer, and method for manufacturing printing plates," which is incorporated herein by reference. In one example, the dispersant is a salt of a fatty acid, preferably having an average carbon number in the range of 10 to 20. In another example, the dispersant is a sulfonate, such as an alkylbenzene sulfonate having an average carbon number in the range of 8 to 16, or an α-olefin sulfonate having an average carbon number in the range of 10 to 20. In a preferred embodiment, the aqueous processing solution 142 is heated to a predetermined value between 40°C and 60°C.

[0040] In a preferred configuration, the main processing unit 102 includes a mechanical cleaning system 160 that assists in removing unexposed photopolymer from the photosensitive printing plate 20. The mechanical cleaning system 160 typically includes one or more brushes that contact the photopolymer layer 22 of the photosensitive printing plate 20 while the photosensitive printing plate 20 is in contact with the aqueous processing solution 142. The brushes are preferably moved relative to the photosensitive printing plate 20, for example, in a side-to-side motion or a circular orbital motion.

[0041] Various brush configurations can be used in accordance with the present invention. For example, the brushes can be downward-facing, as shown in FIG. 2. Examples of downward-facing brush configurations are shown in EP 0586483 B1, EP 0586470 B1, and U.S. Pat. No. 8,444,333 (Suzuki et al.), each of which is incorporated herein by reference. Alternatively, the brushes can be upward-facing, such as the configurations described in U.S. Pat. No. 5,124,736 (Yamamoto et al.) and U.S. Pat. No. 6,247,856 (Shibano et al.), each of which is incorporated herein by reference.

[0042] A collection system 144 is used to collect the used aqueous processing solution 143 and return it to the processing solution tank 140 through a conduit 146. The used aqueous processing solution 143 contains the photopolymer removed from the unexposed portions 126 of the photopolymer layer 22. The used aqueous processing solution 143 is preferably passed through a filter 148 to remove larger particles of the removed photopolymer. In an exemplary embodiment, the filter 148 is a coarse woven-type filter material having a pore size of approximately 100 μm, similar to that described in International Publication No. WO 2014 / 114900 A2 (Danon), entitled "Processing waste washout liquid." In some configurations, the filter 148 is supplied in roll form, and the filter material is advanced to provide new filter material during operation of the processing system 100. The used filter material containing the photopolymer particles is collected on a take-up roll.

[0043] The main processing unit 102 removes most of the unexposed photopolymer from the photosensitive printing plate 20 to provide the relief image 30. However, it has been observed that debris 128 is typically present on the surface of the relief image 30. The debris 128 is primarily composed of residual particles of photopolymer that have not been washed off the surface of the photosensitive printing plate 20.

[0044] The secondary processing unit 104 is used to wash the developed relief image 30 with a secondary aqueous processing solution 152 supplied from a supply tank 150 to remove any remaining debris 128. The secondary processing unit 104 may also be referred to as a secondary processing station, a secondary development unit / station, or a washing unit / station. Preferably, a pump 114 is used to direct the secondary aqueous processing solution 152 under pressure onto the photosensitive printing plate 20 and into contact with the developed relief image 30. The pump 114 can be positioned anywhere to apply pressure to the secondary aqueous processing solution 152 or any fluid in the supply tank 150.

[0045] In a preferred embodiment, an optional mechanical cleaning system 162, such as a rotating brush, is used to improve the performance of the secondary treatment unit 104, supplementing the cleaning action of the secondary aqueous treatment solution 152 with mechanical cleaning.

[0046] Some prior art systems utilize a water rinse step to clean the surface of the developed relief image 30. However, rather than a simple water rinse, the secondary aqueous processing solution 152 used in the secondary processing unit 104 of the present invention contains an active ingredient (i.e., a dispersant) to aid in the removal of debris 128. The secondary aqueous processing solution 152 is virgin, i.e., has never been used to process a photosensitive printing plate 20, and therefore does not contain photopolymers. This has been found to significantly improve the removal of debris 128. In a preferred embodiment, the temperature of the secondary aqueous processing solution is between 40°C and 55°C.

[0047] Any suitable dispersant may be used in the secondary aqueous treatment solution 152, such as those described above with respect to the aqueous treatment solution 142. In an exemplary configuration, the dispersant in the secondary aqueous treatment solution 152 is the same as the dispersant used in the aqueous treatment solution 142 used in the main treatment unit 102. In other configurations, the dispersant in the secondary aqueous treatment solution 152 may be different from the dispersant used in the aqueous treatment solution 142.

[0048] In an exemplary configuration, the concentration of dispersant in the secondary aqueous treatment solution 152 is the same as the initial concentration of dispersant in the aqueous treatment solution 142 used in the main treatment unit 102. In other configurations, the concentration of dispersant in the secondary aqueous treatment solution 152 can be higher (or lower) than the concentration of dispersant in the aqueous treatment solution 142.

[0049] A collection system 154 collects the used secondary aqueous processing solution 153 from the secondary treatment unit 104 and directs it to the processing solution tank 140 via a conduit 156. This has the advantage that the used aqueous processing solution 143, which may contain large amounts of photopolymer, can be replenished with fresher used secondary aqueous processing solution 153 from the secondary treatment unit 104 that contains only small amounts of photopolymer (i.e., removed debris 128).

[0050] The processing solution removal system 105 is used to remove aqueous processing solution 142 from the processing solution tank 140 and direct it to the holding tank 180. This maintains the volume of aqueous processing solution 142 in the processing solution tank 140 below a predetermined maximum volume as used secondary aqueous processing solution 153 is added to the processing solution tank 140. In an exemplary configuration, the processing solution removal system 105 uses a pump 116 to pump the processing solution 142 from the processing solution tank 140 to the holding tank 180. Preferably, the amount of aqueous processing solution 142 removed from the processing solution tank 140 is equal to the amount of used secondary aqueous processing solution 153 added to the processing solution tank 140, thereby maintaining the total amount of aqueous processing solution 142 in the processing solution tank 140 approximately constant. In some embodiments, the pump 116 operates on a predetermined schedule (e.g., after processing each photosensitive printing plate 20). In another embodiment, the pump 116 may be operated when the volume of aqueous processing solution 142 in the processing solution tank 140 is detected to exceed a predetermined threshold.

[0051] The combination of removal of aqueous processing solution 142 by processing solution removal system 105 and addition of used secondary aqueous processing solution 153 from secondary processing unit 104 maintains the concentration of photopolymer in the aqueous processing solution 142 in processing solution tank 140 below a predetermined maximum photopolymer concentration. Without this replenishment process, it has been found that the concentration of photopolymer in the aqueous processing solution 142 in processing solution tank 140 would rapidly increase to an unacceptable level after processing only a few (e.g., five or fewer) photosensitive printing plates 20, adversely affecting the performance of processing system 100. However, it has been found that by using the above-described replenishment process, acceptable performance can be maintained even after processing a large number (e.g., more than 50) of photosensitive printing plates 20.

[0052] Aqueous processing solution 142 functions optimally within a defined pH range. The presence of photopolymers in used aqueous processing solution 143 can alter the pH of the solution, thereby reducing its effectiveness. The above-described process, combined with the removal of aqueous processing solution 142 by processing solution removal system 105 and the addition of used secondary aqueous processing solution 153 from secondary processing unit 104, enables the pH of aqueous processing solution 142 in processing solution tank 140 to be maintained within a predefined, acceptable pH range for processing a large number of photosensitive printing plates 20.

[0053] In the exemplary processing system 100, after the photosensitive printing plate 20 has been processed by the secondary processing unit 104, it is rinsed using a rinsing unit 106 that directs a stream of water 170 at the surface of the developed relief image 30. This water rinse is used to remove residual processing solution from the surface of the photosensitive printing plate 20. The photosensitive printing plate 20 is then dried using a drying unit 108. In the exemplary configuration, the drying unit 108 uses an air knife 172 to direct a stream of air at the surface of the developed relief image 30.

[0054] At some point, the waste treatment solution 181 collected in the holding tank 180 will need to be disposed of. In an exemplary configuration, a coagulant supply system 182 can be used to add a suitable coagulant 184 to the waste treatment solution 181 to coagulate the polymer in the waste treatment solution 181. The resulting solid coagulated polymer 186 can then be removed from the solution and disposed of in an appropriate manner. The remaining waste treatment solution 181 can be disposed of in most locations without significant environmental concerns. Examples of coagulants 184 that can be used to produce the coagulated polymer 186 include bentonite clay (e.g., commercially available RM-10 from Cetco), alum (potassium aluminum sulfate), aluminum sulfate, strong acids (such as hydrochloric acid), ferric chloride, and many other chemicals commonly used in wastewater treatment. Bentonite clay RM-10 is particularly preferred.

[0055] In some prior art processing systems, the secondary processing unit 104 includes a fluid distribution trough 200 that distributes the processing solution 152 across the width of the printing plate 20, as shown in FIG. 3 . Distribution of the processing solution 152 can be accomplished by releasing the processing solution 152 into the trough 200 from a supply tank, which can be at or above atmospheric pressure. In another configuration, instead of using a supply tank, a metering pump (such as a Dosatron D14MZ10 available from Dosatron International, Clearwater, Fla.) can be used to mix processing agents directly into a pressurized water supply to provide the processing solution 152. The total flow rate (i.e., the flow rate per unit time) is limited by an orifice, such as a valve 215 (e.g., a flow control valve or needle valve). The trough 200 includes a small hole 205 at its bottom. The processing solution 152 drips through the hole 205 by gravity and flows onto the printing plate 20. In an exemplary configuration, a mechanical cleaning system 162, such as a rotating brush, is used to assist in removing debris 128 from the printing plate 20. Although not shown, a pump (e.g., 114) may be used to pressurize the supply tank 15 and the processing solution 152 therein.

[0056] FIG. 4 shows additional details of the trough 200. Multiple holes 205 are distributed along the length of the trough 200 to supply processing solution 152 across the cross-track width of the printing plate 20 (FIG. 3). Processing solution 152 flows into the trough 200 through an inlet 210 and is distributed along the length of the trough 200 by gravity at atmospheric pressure, dripping from the holes 205. A drawback of this design is that when the total flow rate is reduced to reduce waste, the difference in drip rate of processing solution 152 from the holes 205 becomes significant. This results in uneven liquid discharge across the printing plate 20, to the point where defects are created. In some cases, the holes 205 furthest from the inlet 210 may not drip at all. Furthermore, when the total flow rate is reduced, any lack of uniformity in the distribution trough 200 adversely affects the uniformity of the drip rate through the holes 205. In some processing systems, a pipe with a series of holes is used instead of a trough 200. Because this pipe is supplied with processing solution at atmospheric pressure, such an arrangement suffers from the same drawbacks as discussed above.

[0057] Examples of treatment systems that utilize liquid distribution systems similar to those shown in Figures 3-4 include water wash systems such as the Dantex DigiWash models DW2735, DW4835, and DW4260, and solvent treatment systems such as the Vianord EVO 5BP and Glunz & Jensen Concept 505 DW.

[0058] FIG. 5 illustrates an improved processing unit 104 that overcomes the drawbacks of the prior art configuration described in connection with FIGS. 3-4. In this improved configuration, the trough 200 containing the processing solution 152 at atmospheric pressure in FIG. 3 is replaced with a hollow tube 300 supplied with a pressurized processing solution 320. The pressurized processing solution 320 is supplied to the interior of the hollow tube 300 by a processing solution supply system 310. In an exemplary embodiment, the processing solution supply system 310 includes a pump 315. The pump 315 can be used to pressurize the processing solution 152; however, this pump 315 or another pump can be located in connection with the supply tank 150 or the hollow tube 300. In some cases, the pump 315 can be a metering pump, such as a Dosatron D14MZ10, that adds processing agent to a pressurized water supply. Typically, the pressurized water supply provides water at a pressure of 30-60 psi. Multiple pressure-compensating emitters 305 are distributed along the length of the hollow tube 300. Pressurized processing solution 320 flows at a controlled rate from the interior of the hollow tube through a pressure-compensated emitter 305, generating processing solution droplets 325 that flow onto the printing plate 20. The pressure-compensated emitter 305 is fabricated to provide a predetermined drop rate over a wide range of pressures within the hollow tube 320.

[0059] Pressure-compensating emitters are well known in the field of drip irrigation systems, and such components can be adapted for use in the present invention. Examples of pressure-compensating emitters are described in U.S. Pat. No. 4,281,798 to Lemelstrich, entitled "Drip or trickle emitter," U.S. Pat. No. 4,971,253 to Lazarus, entitled "Pressure compensating emitters for drip irrigation systems," U.S. Pat. No. 5,820,029 to Marans, entitled "Drip irrigation emitter," and U.S. Pat. No. 9,307,705 to Akritanakis, entitled "Pressure compensating drip irrigation emitter." Pressure-compensating emitters 305 that accommodate a wide range of drip rates are commercially available from various suppliers, including Rain Bird Corporation (Azusa, Calif.). These patent documents describing pressure-compensating emitters are incorporated herein by specific reference in their entirety.

[0060] 2, after the processing unit 104 completes the processing operation, the rinsing unit 106 can be used to rinse the printing plate 20 with water 170, and an air knife 172 (i.e., a pressurized air system) can be used to blow any remaining liquid off the surface of the printing plate 20. In some embodiments, the rinsing unit 106 can also include a liquid supply system having multiple pressure-compensating emitters 305 distributed along the length of the hollow tube 300, similar to the processing unit 104.

[0061] Additional details of the processing unit 104 of Figure 5 are shown in Figure 6. The hollow tube 300 has a length L that extends across the cross-track width W of the printing plate 20. A plurality of pressure compensation emitters 305 are distributed along the length of the hollow tube 300. The total flow rate of processing solution through the processing unit 104 is controlled by the drop rates associated with the pressure compensation emitters 305 and the total number of pressure compensation emitters 305. The total flow rate is substantially independent of the internal pressure within the hollow tube 300 over a wide range of operating pressures.

[0062] In the configuration of Figure 6, the processing solution droplets 325 impact a rotating brush 330 that rotates about an axis of rotation 335 parallel to the surface of the printing plate 20. The rotating brush 330 carries the processing solution to the printing plate 20 and helps remove debris 128 from the relief image 30. Figure 7 shows an alternative configuration that uses a brush 340 that translates laterally relative to the surface of the printing plate 20 using an oscillating motion.

[0063] An advantage of the present invention is that the flow rates through each of the pressure-compensating emitters 305 are substantially equal (e.g., within 30%), so that processing solution is applied uniformly across the cross-track width of the processing plate 20. Furthermore, the flow rate uniformity is independent of the flatness of the hollow tube 300.

[0064] 8A-8C show an example of a pressure compensated emitter 805 according to the examples incorporated herein.

[0065] The pressure-compensated emitter 805 comprises a compact emitter casing 802 that can be formed from assembled plastic-molded emitter casing components. The emitter casing 802 includes a cup-shaped bottom body 820 adapted to be assembled with an upper body 822 to form a substantially enclosed emitter casing cavity. The fluid path 814 is defined by a fluid path pattern 826 ( FIG. 8C ) formed in the bottom body 820 in cooperative relationship with a resilient, flexible elastomeric planar body 828 (e.g., a pressure-deformable member, a pressure-activated valve, a non-controlled valve, a passive valve, etc.). Water (e.g., or pressurized process fluid) or other aqueous solution is supplied to the fluid path 814 via an inlet 830 formed by the upper body 822, and the solution is discharged from the flow channel via a discharge outlet 816 formed in the bottom body 820. The shape of the fluid pathway pattern 826 cooperates with the deformable elastic planar body 828 to define a three-dimensional fluid pathway 814 for improving the pressure drop between the inlet 830 and the outlet 816 .

[0066] The emitter casing bottom body 820 has an upwardly open, cup-like structure with a circular bottom or base 832 joined around its periphery to a cylindrical, upstanding outer wall 834. A fluid path pattern 826 is formed on the base 832 in a circular or spiral configuration disposed around the outlet 816, which may include a short, downwardly projecting hollow stem 836. The downwardly projecting hollow stem 836 may be omitted or replaced with an opening or tube to allow droplets to drain in a controlled manner. A plurality of support members 838 are also formed on the bottom body 820 and project upwardly from the base 832 around the periphery, terminating at their upper ends above the fluid path pattern 826 but below the upper edge of the outer wall.

[0067] The deformable elastic plane 828 comprises a resilient disk sized and shaped to fit within the emitter casing bottom body 820, with the outer periphery of the deformable elastic plane 828 fitting within the support member 838. The emitter casing top body 822 is then assembled with the bottom body 820 by press-fitting the disk-shaped top body 822 into the open end of the base so that the top body 822 seats on the top end of the support member 838. The top body 822 can be securely and sealingly connected to the bottom body 820 by the use of a suitable adhesive, ultrasonic welding, or the like. Once assembled, the emitter casing bottom body 820 and top body 822 define an inlet chamber 840 ( FIG. 8A ) within which the deformable elastic plane 828 is held in an aligned position over the fluid path pattern 826 with at least some floating movement. Inlet 830 is formed in upper body 822 and is generally associated with inlet stem 842, which may include barb structure for a press-through type attachment to tube 812 (eg, tube 320).

[0068] As best shown in FIG. 8C , the fluid pathway pattern 826 is defined by a pair of relatively short, upright, laterally spaced sidewalls 844. To fit within the desired compact package, the sidewalls 844 extend at substantially uniform lateral intervals through a generally curved shape between an outer inlet or upstream end disposed about the periphery of the base 832 between a pair of support members 838 and a generally centrally located downstream end in flow communication with an outlet chamber 850 leading to the outlet 816. The base 832 extends from the bottom or lower wall of the fluid pathway 814 between laterally spaced opposing portions of the sidewalls 844. The deformable, resilient planar body 828 is forced into the inlet chamber 840 by the pressure of the water in the supply tube 812 and is positioned to seat against the upper edges of the two sidewalls 844. Thus, during normal operation, the deformable resilient plane 828 engages the side walls 844 of the fluid pathway pattern 826 , thereby cooperating to form the upper wall boundary of the fluid pathway 814 .

[0069] In accordance with the present invention, fluid pathway 814 includes surface structures formed as part of fluid pathway pattern 826 to define a three-dimensional, serpentine flow path. More specifically, a plurality of flow diverting arms or teeth 846 are formed extending partially into fluid pathway 814 from both sidewalls 844, with these arms 846 being staggered or alternatingly arranged. In a preferred form, each diverting arm 846 has a length that extends generally laterally to the centerline of the flow channel, thereby obstructing the direct through-flow path of the solution. Arms 846 force the solution to flow in a back-and-forth lateral direction, resulting in reduced velocity, turbulence, and significant pressure drop.

[0070] In accordance with a primary aspect of the present invention, the fluid path pattern 826 further includes a plurality of flow diverting surfaces, which are upwardly protruding ridges 848 formed in the lower wall or floor 832 of the emitter casing bottom body 820, that protrude into the fluid path 814 and deflect water flowing through the channel vertically, thereby providing an up-and-down directional change in the flow. The ridges 848 are evenly spaced along the length of the channel and extend laterally, projecting into the flow path in a generally perpendicular orientation to the arms 846. The ridges 848 are preferably provided in a number generally corresponding to the number of flow diverting arms 846, and the ridges 848 are shown aligned with the individual arms 846. Preferably, the height of the ridges 848 is sufficient to extend from about one-third to about one-half of the height of the fluid path 814. The ridges 848 function to diverge the solution flow up and down, again resulting in reduced velocity and associated turbulence and achieving significant additional pressure loss.

[0071] From the fluid path 814, in a preferred form of the invention, the solution enters a centrally located outlet chamber 850 bounded by the deformable resilient flat body 828 and the inner wall surface of the side 844 of the underlying fluid path pattern 826. The outlet chamber 850 includes a raised circular ridge 852 projecting upwardly from the floor 832 of the emitter casing bottom body 820 for engagement with the deformable resilient flat body 828. The ridge 852 defines an upwardly opening discharge accommodation groove 854 for allowing discharge flow of the solution from the outlet chamber 850 to the emitter outlet 816. Importantly, the effective cross-sectional size of the discharge accommodation groove 854 changes in response to the solution pressure in the inlet chamber 840, as the deformable resilient flat body 828 is partially pressed into the groove 854 as a result of the processing solution pressure acting on its upper surface. In this manner, the emitter provides pressure compensation by varying the effective size of the discharge grooves 854 as a function of inlet pressure, maintaining a substantially constant discharge outlet flow over a range of typical supply water pressures. Furthermore, due to the increased pressure drop created by the three-dimensional flow fluid path pattern 826, the discharge modulation grooves 854 can be relatively large in size and still provide the desired pressure modulation function for dripping.

[0072] In use, the droplet pressure compensation emitters 805 (e.g., 305) of the present invention are typically mounted at selected points along the length of a supply tube 812 (e.g., tube 320), and processing solution is supplied to and passes through the supply hose at an appropriate boosted supply pressure. Each emitter 805 draws a portion of water from the supply tube. When water is initially released, the deformable elastic planar body 828 typically shifts slightly from the underlying fluid path pattern 826, briefly directing the water to the outlet 816. However, as processing solution begins to flow under pressure, the pressure in the inlet chamber 840 rapidly increases, seating the deformable elastic planar body 828 in the fluid path pattern 826 and providing appropriate pressure compensation for the drain grooves 854. Thereafter, the flow of processing solution through the emitter between the inlet 830 and the outlet 816 is confined within the three-dimensional redirected fluid path 814, providing a trickle or droplet discharge flow rate that may be less than that provided by previous emitters of comparable size due to significant flow turbulence and pressure drop. The deformable elastic plane can function as a pressure-sensitive valve that partially restricts flow. As such, the deformable elastic plane can function as a valve that is not controlled, opened, or required, either manually or under a valve control. Instead, fluid pressure causes the deformable elastic plane to reposition and / or deform, restricting flow through and out of the pressure compensating emitter 805.

[0073] In some embodiments, a droplet irrigation emitter can include an emitter casing having an inlet suitable for connection to a pressurized treatment solution supply conduit, an outlet, and a flow path structure forming an elongated, reduced-pressure flow channel defined by vertically spaced upper and lower walls interconnected by laterally spaced side walls extending between the inlet and the outlet. The flow path structure can include a plurality of flow diverting arms projecting partially into the flow channel from opposite sides thereof and arranged in an alternating array along the length of the channel, such that treatment solution flowing within the flow channel undergoes repeated back-and-forth lateral changes between the sides. The flow path structure further includes a plurality of flow diverting ridges positioned along the length of the channel and projecting partially into the flow channel from at least one of the walls, such that treatment solution flowing through the flow channel undergoes repeated up-and-down direction changes between the walls.

[0074] Thus, the drip pressure compensated emitter includes a housing (e.g., an emitter casing in the form of a container with a cavity therein, including first and second housing components assembled to form a hollow housing interior. An inlet can be formed in the first housing component and an outlet can be formed in the second housing component. Laterally spaced side and bottom walls of a flow path structure can be formed in the second housing component within the housing interior and can define a fluid path pattern. A resilient valve member can be positioned within the housing interior to overlap and engage the fluid path pattern. The valve member can also define an upper wall of the flow channel. The second housing component can include an upwardly opening drain adjustment groove through which processing solution flows from the flow path structure to the water outlet, the resilient valve member overlapping and engaging the groove to form pressure compensation means for regulating the flow of water from the fluid path pattern to the emitter outlet.

[0075] The valve member can be an elastic diaphragm. For example, the membrane can be rubber or elastomer or other material. When a relatively high fluid pressure is present in the supply tube, a pressure differential is created across the elastic planar member (e.g., diaphragm, resiliently flexible planar valve member), causing the diaphragm to deform into a second, high-pressure diaphragm configuration. Specifically, this pressure differential is created by fluid flow through the fluid path portion. Because the fluid path is configured as a tortuous path or labyrinth, fluid flowing through the flow path experiences a pressure drop. This creates a pressure differential across the elastic valve member (e.g., diaphragm) between the inlet (high pressure) and the outlet (low pressure).

[0076] In the configuration of a second high-pressure elastic planar member (e.g., a diaphragm, elastic planar valve member), the deformed diaphragm covers the inner portion of the fluid path, eliminating bypass and forcing the fluid to flow through the entire fluid path. In this way, uniform flow is achieved across a range of line pressures. At low pressures, the fluid bypasses the inner fluid path portion, but at high pressures, the fluid is forced through the inner fluid path portion where the pressure and flow rate are reduced. This results in the formation of droplets as described herein.

[0077] Another advantage of the present invention is that it allows for the use of a lower flow rate of processing solution 152 compared to the prior art configuration of FIG. 3 without compromising printing plate quality. This is desirable because it reduces the amount of processing solution 152 that needs to be used and discarded for each processed plate. For comparison, a Dantex DigiWash DW4835 system was fitted with a trough-based liquid distribution system similar to that shown in FIG. 3. In this case, the trough 200 was provided with 43 drip holes 205. The minimum flow rate that could achieve a uniform drip rate along the length of the trough 200 was 7.5 liters / minute, corresponding to a drip rate of 0.175 liters / minute through each of the holes 205. The processing system was then re-fitted with the pressure-compensated emitter-based system of FIG. 5, in this case using a total of 33 pressure-compensated emitters 305. It was found that the total flow rate could be reduced to 2.5 liters / minute while maintaining uniform flow across the width of the printing plate 20. This corresponds to a drip rate of 0.076 liters / minute through each of the pressure compensated emitters 305, representing a 66% reduction in the total amount of processing solution 152 required without compromising plate quality. Prior art configurations are unable to operate at high quality levels at such low flow rates (e.g., less than 0.1 liters / minute per hole).

[0078] While the exemplary embodiment is described in connection with a processing unit 104 used to process printing plates 20 using an aqueous processing solution 152 containing a dispersant, it will be apparent to those skilled in the art that the present invention can be used in other types of processing systems as well. For example, the present invention can be used in processing systems that use solvent-based processing solutions. The present invention can also be used in a rinse system 106 that rinses printing plates 20 with water, as described above. In one such embodiment, it was found that an improved rinse system 106 using a pressure-compensated emitter-based water delivery system can achieve good results with a flow rate of 4.0 liters / minute, compared to the 10.0 liters / minute required in prior art systems.

[0079] The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

[0080] In some embodiments, a method for processing a flexographic printing plate having a relief image is provided. The method may include providing the relief image to a processing unit that treats the flexographic printing plate with a processing liquid. The processing unit may be configured with a processing path including a hollow tube and a pressure compensation emitter according to embodiments described herein. The method may include emitting processing liquid as droplets from a plurality of pressure compensation emitters. The droplets from the emitters may be used to wash the relief image with processing liquid from the processing droplets.

[0081] In some embodiments, the method can include applying the treatment liquid as droplets to one or more brushes that move relative to the surface of the flexographic printing plate. The one or more brushes can be positioned and configured to apply the treatment liquid to the relief image.

[0082] In some embodiments, the pressure compensation emitters can adjust the fluid flow so that the flow rates of the processing liquid dripping from each pressure compensation emitter are equal to within 30% of each other. In some embodiments, the flow rate of the processing liquid droplets from each of the pressure compensation emitters is less than 0.1 liters / minute. In some embodiments, the processing liquid drip rate is about 0.076 liters / minute, or about 0.0023 liters / minute, for 33 pressure compensation emitters. The liquid drip rate can be about 0.0010 liters / minute to about 0.0035 liters / minute, or about 0.002 liters / minute to about 0.003 liters / minute. The number of pressure compensation elements is an integer, but can range from 10 to 50 emitters, 15 to 45 emitters, 20 to 40 emitters, or 25 to 35 emitters.

[0083] In some embodiments, the processing liquid is an aqueous processing solution that includes a dispersant. In some aspects, the processing liquid includes a solvent. In some aspects, the processing liquid is water. In some aspects, the pressurized processing liquid supply system pressurizes the processing liquid to about 30-60 psi (0.2 MPa-0.41 MPa).

[0084] In some embodiments, the resilient planar member is a resilient valve member disposed within the casing in a position overlying the flow path pattern. The resilient valve member is positioned and configured to cooperate with the flow path pattern to define an elongated reduced pressure flow path having an upstream end in flow communication with the hollow tube and a downstream end in flow communication with the outlet. In some aspects, the outlet includes an upwardly opening discharge adjustment groove through which process fluid flows from the fluid flow path to the outlet, and the resilient planar member covers and engages the groove to form a pressure compensation means for adjusting fluid flow from the fluid flow path to the outlet.

[0085] Those skilled in the art will understand that for the processes and methods disclosed herein, the functions performed in the processes and methods may be performed in differing orders. Furthermore, the outlined steps and operations are provided by way of example only, and some of the steps and operations are optional and may be combined into fewer steps and operations or expanded into additional steps and operations without detracting from the essence of the disclosed embodiments.

[0086] With respect to the use of substantially any plural and / or singular terms herein, those skilled in the art can convert from plural to singular and / or from singular to plural as appropriate to the context and / or application. For clarity, the specification may expressly provide for various singular / plural permutations.

[0087] Those skilled in the art will generally understand that the terms used herein, and particularly in the appended claims (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "including" should be interpreted as "including, but not limited to," etc.). Furthermore, those skilled in the art will understand that where a specific numerical value is intended in the introduced claim recitation, such intention will be expressly recited in the claim, and that, in the absence of such recitation, no such intention exists. For example, to aid in understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce the claim recitation. However, the use of such phrases should not be construed as meaning that introducing a claim recitation with the indefinite article "a" or "an" limits a particular claim that includes such an introduced claim recitation to embodiments that include only such recitations, even when the same claim includes the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should be construed to mean "at least one" or "one or more"); the same applies to the use of definite articles used to introduce claim recitations. Moreover, even if a specific number of introduced claim recitations is explicitly recited, those skilled in the art will recognize that such recitation should be construed to mean at least the recited number (e.g., the mere recitation of "two recitations" means at least two recitations, or more than two recitations, in the absence of other modifiers).Furthermore, when a convention similar to "at least one of A, B, and C, etc." is used, such a structure is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" includes, but is not limited to, systems having A only, B only, C only, A and B together, A and C together, B and C together, and / or A, B, and C together). When a convention similar to "at least one of A, B, or C, etc." is used, such a structure is generally intended in the sense that one of ordinary skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" includes, but is not limited to, systems having A only, B only, C only, A and B together, A and C together, B and C together, and / or A, B, and C together). Those skilled in the art will further appreciate that virtually any alternative word and / or phrase in the description, claims, or drawings that presents two or more alternative terms should be understood to contemplate the inclusion of one of the terms, either of the terms, or both terms. For example, the phrase "A or B" is understood to include the possibilities of "A" or "B" or "A and B."

[0088] Furthermore, where features or aspects of the disclosure are described in terms of a Markush group, those skilled in the art will recognize that the disclosure is also described in terms of individual members or subgroup members of the Markush group.

[0089] As will be understood by those skilled in the art, for any and all purposes, e.g., in terms of providing a written description, all ranges disclosed herein encompass any and all possible subranges and combinations of subranges thereof. It can be readily recognized that all described ranges fully describe and allow for the same range to be divided into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily divided into a lower third, middle third, upper third, etc. As will also be understood by those skilled in the art, phrases such as "up to," "at least," and the like, refer to ranges that are inclusive of the recited numerical values ​​and that can subsequently be further divided into subranges, as described above. Finally, as will be understood by those skilled in the art, a range includes each individual member. Thus, for example, a group having 1 to 3 cells refers to groups having 1, 2, or 3 cells. Similarly, a group having 1 to 5 cells refers to groups having 1, 2, 3, 4, or 5 cells, etc.

[0090] From the foregoing, it will be recognized that various embodiments of the present disclosure have been described herein for purposes of illustration and that various modifications can be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

[0091] All documents mentioned herein are specifically incorporated herein by reference in their entirety.

[0092] Additionally, cross-reference is made to commonly assigned, co-pending U.S. Pat. No. 10,324,378 to D. Swihart et al., entitled "Aqueous processing method for flexographic printing plates"; and commonly assigned, co-pending U.S. Patent Application Publication No. 2018 / 0004090 to D. Swihart et al., entitled "Aqueous processing system for flexographic printing plates," each of which is incorporated herein by reference.

Claims

1. 1. A processing system for processing flexographic printing plates, comprising: a processing path configured to process the flexographic printing plate; a hollow tube having a length extending across the processing path; a pressurized processing liquid supply system for supplying a pressurized processing liquid to the inside of the hollow tube; a plurality of pressure compensation emitters coupled to the hollow tube and distributed along the length of the hollow tube; each pressure compensation emitter comprising: a casing having a fluid flow passage fluidly coupled to the hollow tube and having an outlet; a resilient planar member positioned within the casing to form at least one resilient surface of the fluid flow path, each pressure compensating emitter configured to control a flow rate of the pressurized treatment liquid to generate droplets of treatment liquid from the outlet. Processing system.

2. 10. The treatment system of claim 1, wherein said resilient planar member is positioned to provide said outlet with a variable outlet cross-sectional shape in response to pressure within said casing.

3. 10. The processing system of claim 1, wherein the fluid flow path is a serpentine flow path configured to create a pressure drop in the pressurized processing liquid.

4. 4. The treatment system of claim 3, wherein the serpentine flow path is formed by one or more flow direction change members that create a change of direction within the serpentine flow path.

5. 5. The treatment system of claim 4, wherein the one or more flow direction change members include a plurality of first members protruding partially into the fluid flow path from at least one side thereof along the length of the serpentine flow path so that liquid flowing through the fluid flow path undergoes repeated first direction changes.

6. 5. The treatment system of claim 4, wherein the one or more flow direction change members include a plurality of second members that protrude partially into the fluid flow path and at an angle to the first members, the second members positioned along the length of the serpentine flow path such that liquid flowing through the fluid flow path undergoes repeated second direction changes at an angle to the first direction changes.

7. 3. The treatment system of claim 2, wherein the resilient planar member is an elastomer, rubber, or other elastic material configured and positioned to regulate the flow of the pressurized treatment liquid through the outlet at a predetermined substantially constant flow rate over a range of water pressures at the inlet.

8. 8. The treatment system of claim 7, wherein said outlet includes an upwardly opening discharge adjustment groove through which treatment fluid flows from said fluid flow path to said outlet, and said resilient planar member overlaps and engages said groove to form a pressure compensation means for adjusting fluid flow from said fluid flow path to said outlet.

9. 2. The treatment system of claim 1, wherein the resilient planar member is a resilient valve member positioned within the casing in a position that overlaps the flow path pattern, the resilient valve member cooperating with the flow path pattern to define an elongated reduced pressure flow path having an upstream end in flow communication with the hollow tube and a downstream end in flow communication with the outlet.

10. 10. The processing system of claim 1, further comprising one or more brushes extending across the processing path with the hollow tube, wherein the plurality of pressure-compensating emitters deliver the processing liquid as droplets onto the one or more brushes.

11. 1. A method for treating a flexographic printing plate having a relief image thereon, comprising: providing a relief image to a processing unit that processes the flexographic printing plate with a processing solution, the processing unit comprising: a processing path configured to process the flexographic printing plate; a hollow tube having a length extending across the processing path; a pressurized processing liquid supply system for supplying a pressurized processing liquid to the inside of the hollow tube; a plurality of pressure compensation emitters coupled to the hollow tube and distributed along the length of the hollow tube; each pressure compensation emitter comprising: a casing having a fluid flow passage fluidly coupled to the hollow tube and having an outlet; a resilient planar member positioned within the casing to form at least one resilient surface of the fluid flow path, wherein each pressure compensating emitter is configured to control a flow rate of the pressurized treatment liquid to generate droplets of treatment liquid; emitting the treatment liquid as droplets from the plurality of pressure compensated emitters; washing the relief image with the processing liquid from the processing liquid droplets; A method comprising:

12. 12. The method of claim 11, further comprising applying the treatment liquid as droplets to one or more brushes moving relative to the surface of the flexographic printing plate, the one or more brushes applying the treatment liquid to the relief image.

13. 12. The method of claim 11, wherein the flow rates of the treatment liquid droplets from each pressure compensated emitter are equal to within 30% of each other.

14. The method of claim 11 , wherein the flow rate of the treatment liquid droplets from each of the pressure-compensated emitters is less than 0.1 liters per minute.

15. The method of claim 11 , wherein the treatment liquid is an aqueous treatment solution that includes a dispersant.

16. The method of claim 11 , wherein the processing liquid comprises a solvent.

17. The method of claim 11 wherein the treatment liquid is water.

18. The method of claim 11, wherein the pressurized processing fluid supply system pressurizes the processing fluid to about 30 to 60 psi.

19. 12. The method of claim 11, wherein the resilient planar member is a resilient valve member disposed within the casing in a position overlying a flow path pattern, the resilient valve member cooperating with the flow path pattern to define an elongated reduced pressure flow path having an upstream end in flow communication with the hollow tube and a downstream end in flow communication with the outlet.

20. 12. The method of claim 11, wherein the outlet includes an upwardly opening discharge adjustment groove through which process fluid flows from the fluid flow path to the outlet, and the resilient planar member overlaps and engages the groove to form a pressure compensation means for adjusting fluid flow from the fluid flow path to the outlet.

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