Apparatus and method for filtering process fluid

Abstract

A method of filtering process fluid and apparatus for receiving and filtering process fluid from a printing plate manufacturing process. The apparatus is configured to receive the process fluid and re

Description

[0002] Printing plates are manufactured using a process in which an image is set onto the printing plates. The process of image setting causes a printing surface of the printing plate in question to be modified in a way such that selected areas of the printing surface pick up and hold onto ink for the purpose of printing, whereas other areas of the printing surface do not pick up ink.

[0003] As an example, a printing plate may be composed of a polymer material. In some examples, the areas of the printing surface intended to pick up ink are hardened, e.g., by crosslinking the polymer in those areas, whereas other parts of the printing surface are not hardened. For example, a UV light source and / or one or more lasers may be used in this process to trigger a selective hardening of the printing surface. There is then a washing process using water, or another suitable solution or suspension. In the washing process, material is carried away into the water (or such other solution / suspension as may be used), hereinafter referred to as the process fluid, from the areas of the printing surface which were not hardened. In this way, the parts of the printing surface not intended to carry ink are seemingly depressed down by the described etching process, whereas the hardened parts defining the image to be printed come into relief.

[0004] The process fluid circulates within the printing plate processing apparatus. However, eventually and after a given number of process cycles, the process fluid is contaminated with material from the printing plates enough to have to be replaced. Replacing the process fluid means that large quantities of process fluid may be used, which comes at a financial and environmental cost (for example, the process fluid may be water). In addition, there is also a time and labour cost when the process fluid is replaced. Furthermore, the printing plate processing apparatus may not be usable when the process fluid replacement is taking place. A high frequency of process fluid replacement may thus significantly limit the throughput of a plate manufacturing process.

[0005] The present disclosure seeks to provide solutions to at least some of these problems, among other advantages, as will become apparent from the following description. Summary

[0006] According to a first aspect of the present disclosure, there is provided an apparatus for receiving and filtering process fluid from a printing plate manufacturing process. The apparatus is configured to receive the process fluid and return the process fluid after subjecting it to a filtering process. The apparatus comprises a filtration bath configured to receive a fluid. The apparatus further comprises a single vacuum cavity filtration drum comprising a single vacuum cavity therein and a circumferential wall comprising a fluid permeable mesh. The single vacuum cavity filtration drum is configured to rotate about a rotation axis, wherein the rotation axis is configured to remain within an operational zone of the filtration bath. The apparatus further comprises a vacuum pump fluidically connected to the single vacuum cavity of the single vacuum cavity filtration drum. The apparatus further comprises a first fluid junction positioned in a fluid flow path between the single vacuum cavity and the vacuum pump, the first fluid junction comprising a fluid outlet leading to a fluid output flow path.

[0007] Optionally, the first fluid junction comprises a cyclone separator configured to separate from one another a liquid and air received from the single vacuum cavity.

[0008] Optionally, the first fluid junction is configured to supply the air separated by the cyclone separator to the fluid flow path onward to the vacuum pump; and the first fluid junction is configured to supply the liquid separated by the cyclone separator to the fluid outlet.

[0009] Optionally, the apparatus comprises a filtration suspension reservoir fluidically connected to the filtration bath.

[0010] Optionally, the filtration suspension reservoir is fluidically connected to the single vacuum cavity via the fluid output flow path.

[0011] Optionally, the fluid output flow path comprises a second fluid junction and a second fluid junction valve; and, depending on the state of the second fluid junction valve, fluid in the fluid output flow path is directed to the filtration suspension reservoir or to a filtered process fluid outlet for returning process fluid to a printing plate manufacturing process.

[0012] Optionally, the filtrate suspension reservoir is configured to contain a perlite suspension reservoir.

[0013] Optionally, the filtration bath comprises a flushing inlet configured to provide flushing fluid to the filtration bath; and a flushing outlet configured to remove the flushing fluid from the filtration bath. The filtration bath is configured such that the flushing fluid flows through the filtration bath so as to remove residual matter from the filtration bath. The flushing inlet and flushing outlet may be suitably spaced apart from one another for this purpose.

[0014] Optionally, the vacuum pump is a liquid ring vacuum pump.

[0015] Optionally, the filtration drum has an internal diameter of between 50 millimetres and 1000 millimetres.

[0016] Optionally, the rotation axis is translationally fixed relative to the filtration bath.

[0017] Optionally, the filtration bath comprises a reception inlet and a drainage outlet, the reception inlet being spaced apart from the drainage outlet such that when both the reception inlet and the drainage outlet are in use, a flow is provided over substantially the whole of a base surface of the filtration bath.

[0018] Optionally, the filtration bath comprises one or more sluice gate valves for controlling the flow of fluid through the reception inlet and / or the drainage outlet.

[0019] Optionally, the apparatus comprises a controller configured to control the operation of the apparatus. The controller is configured to cause the filtration bath to receive a filtration suspension comprising filtration particles to a level such that the filtration suspension makes contact with the single vacuum cavity filtration drum. The controller is configured to evacuate the single vacuum cavity filtration drum and cause the single vacuum cavity filtration drum to rotate so as to cause a cake of filtration particles from the filtration suspension to be built up on the fluid permeable mesh, while filtration suspension fluid from the filtration solution is drawn into the single vacuum cavity. The controller is further configured to remove the filtration suspension from the filtration bath and flush the filtration bath with a flushing fluid. The controller is further configured to cause the filtration bath to receive the process fluid to a level such that the cake of filtration particles contacts the process fluid. The controller is furtherconfigured to evacuate the single vacuum cavity filtration drum and cause the single vacuum cavity filtration drum to rotate so as to filter the process fluid through the cake of filtration particles and into the single vacuum cavity filtration drum.

[0020] Optionally, the filtration bath comprises a blade, the blade arranged at a tangent to the single vacuum cavity filtration drum and configured to remove a layer of material from the filtration drum.

[0021] Optionally, a position and / or angle of the blade within the filtration bath is adjustable.

[0022] Optionally, the vacuum pump has a variable speed and / or variable pressure.

[0023] In a further aspect of the present disclosure, there is provided a method of filtering process fluid from a printing plate manufacturing process. The method comprises deploying an apparatus configured to receive the process fluid and return the process fluid after subjecting it to a filtering process. The apparatus comprises a filtration bath configured to receive a fluid and a single vacuum cavity filtration drum comprising a single vacuum cavity therein and a circumferential wall comprising a fluid permeable mesh, wherein the single vacuum cavity filtration drum is configured to rotate about a rotation axis, wherein the rotation axis is configured to remain within an operational zone of the filtration bath. The apparatus further comprises a vacuum pump fluidically connected to the single vacuum cavity of the single vacuum cavity filtration drum. The apparatus further comprises a first fluid junction positioned in a fluid flow path between the single vacuum cavity and the vacuum pump, the first fluid junction comprising a fluid outlet leading to a fluid output flow path. The method comprises building a filtration particle cake on the fluid permeable mesh using filtration suspension received in the filtration bath; and filtering the process fluid received subsequently in the filtration bath through the filtration particle cake.

[0024] Optionally, the method further comprises flushing the filtration bath so as to remove residual matter from the filtration bath after building the filtration particle cake and before filtering the process fluid through the filtration particle cake.

[0025] Optionally, the method further comprises operating a cyclone separator in the first fluid junction to separate the filtered process fluid and air received from the single vacuum cavity.

[0026] A person skilled in the art recognises that technical features and advantages that have been disclosed in relation to the apparatus described herein, equally apply to the method disclosed herein, and vice versa. Brief Description of the Drawings Examples of the present disclosure will now be described with reference to the accompanying drawings, in which: Figure 1 is a simplified schematic sketch of an apparatus for receiving and filtering process fluid from a printing plate manufacturing process according to examples; Figure 2 is a first simplified schematic front cross-sectional view of a single vacuum cavity filtration drum, according to examples; Figure 3 is a simplified schematic plan cross-sectional view of the filtration drum, according to examples; Figure 4 is a second simplified schematic front cross-sectional view of a single vacuum cavity filtration drum, according to examples; and Figure 5 is a simplified schematic front cross-sectional view of the filtration drum and the filtration bath, according to examples. Detailed Description

[0027] According to examples, there is provided an apparatus for receiving and filtering process fluid from a printing plate manufacturing process. The process fluid may be received from a printing plate processing apparatus. In this manner, by filtering the process fluid, the same process fluid may be used for a greater number of process cycles in the printing plate manufacturing process.

[0028] The apparatus according to the present disclosure is configured to receive the process fluid and return the process fluid after subjecting it to a filtering process. The apparatus comprises a filtration bath configured to receive a fluid. The apparatus also comprises a single vacuum cavity filtration drum comprising a single vacuum cavity therein and a circumferential wall comprising a fluid permeable mesh. The single vacuum cavity filtration drum is configured to rotate about a rotation axis. The rotation axis is configured to remain within an operational zone of the filtration bath. For example, the single vacuum cavity filtration drum may be translationally fixed relative to the filtration bath, or only be movable so as to remain within the operational zone of the filtration bath. For example, the single vacuum cavity filtration drum remains functionally coupled to the filtration bath and does not move away to another component of the apparatus.

[0029] The apparatus also comprises a vacuum pump fluidically connected to the single vacuum cavity of the single vacuum cavity filtration drum. The apparatus also comprises a first fluid junction comprising a fluid outlet leading to a fluid output flow path.

[0030] Figure 1 is a simplified schematic sketch of the apparatus 100, according to examples. Atop view of the apparatus 100 is provided, showing its features in anx-y plane, thex-y plane as referred to herein being parallel to the ground. In these examples, there is indicated the filtration bath 102 and the single vacuum cavity filtration drum 104. The filtration bath 102 is configured to receive a fluid. In these examples, the filtration bath 102 comprises a reception inlet 106 configured to deliver said fluid to the filtration bath 102. In these examples, there is also provided a drainage outlet 108 configured to drain away fluid which is in the filtration bath 102. Those skilled in the art will appreciate that there may be various configurations for adding to and taking away fluid from the filtration bath 102.

[0031] In some examples, the filtration bath 102 comprises a reception inlet 106 and a drainage outlet 108, the reception inlet 106 being spaced apart from the drainage outlet 108 such that when both the reception inlet 106 and the drainage outlet 108 are in use, a flow is provided over substantially the whole of a base surface of the filtration bath 102. This advantageously inhibits suspended particles from settling or becoming trapped in dead spaces of the filtration bath 102, in particular by means of maintaining a flow, in particular a turbulent flow, throughout the filtration bath 102. This improves contact between the suspended particles and the single vacuum cavity filtration drum 104, improving the efficiency of cake formation and / or filtration.

[0032] In some examples, the filtration bath 102 comprises one or more sluice gate valves for controlling the flow of fluid through the reception inlet 106 and / or the drainage outlet 108.

[0033] In some examples, the reception inlet 106 and the drainage outlet 108 are interchangeable in use, such that the drainage outlet 108 may become the reception inlet 106 when a direction of flow is reversed and vice versa.

[0034] In some examples, the filtration suspension is fed through the reception inlet 106, the filtration bath 102 and the drainage outlet 108 in a first flow direction. Preferably, the process fluid is fed through the reception inlet 106, the filtration bath 102 and the drainage outlet 108 in a second flow direction.

[0035] In some examples, the filtration bath 102 comprises a first reception inlet and a first drainage outlet for the filtration suspension. In some examples, the filtration bath 102 comprises a second reception inlet and a second drainage outlet for the process fluid. Preferably, each of the first reception inlet, second reception inlet, first drainage outlet and second drainage outlet is provided with a sluice gate valve.

[0036] In some examples, one or more of the sluice gate valves is pneumatically operated.

[0037] Figure 2 is a simplified schematic front cross-sectional view of the single vacuum cavity filtration drum 104 (hereinafter referred simply to as filtration drum 104), showing its features in a z-y plane, according to examples. As referred to herein with reference to Figure 2, the z-y plane is perpendicular to the ground and perpendicular to the rotation axis which points into / out of the page with respect to Figure 2. In these examples, the circumferential wall of the filtration drum 104 comprises the fluid permeable mesh 202. The fluid permeable mesh 202 surrounds the single vacuum cavity 204. As referred to herein, the vacuum cavity 204 is the cavity which can exchange fluid through the entirety of the fluid permeable mesh 202. In other words, there is the vacuum cavity 204 which is single in the sense that there is no other cavity which may exchange fluid via the fluid permeable mesh 202. In other words, the fluid permeable mesh 202 directly communicates fluid with a single unified space within the filtration drum 104. In other words, the space immediately inside of the fluid permeable mesh 202 is not split into sections. The filtration drum 104 is not sectional, for example. A consequence of this arrangement and structure is that when the single vacuum cavity 204 is evacuated, fluid may be drawn into the filtration drum 104 with substantially equal strength at all regions of the fluid permeable mesh 202, assuming that the same fluid is present all about the fluid permeable mesh 202 at substantially the same pressure. In practicality, in use, the filtration drum 104 may be partly in contact with a liquid and partly in contact with air. For example, there are no sections about the filtration drum 104, moving in the circumferential direction, where there is a vacuum draw substantially different to any other section. In particular, the interior of the filtration drum 104 is free of partitions extending radially from a central region of the filtration drum 104 to the fluid permeable mesh. The single vacuum cavity 204 may thus have a substantially equal vacuum pressure therein, in particular, substantially equal about a circumferential direction. For example, this leads to a similar or an approximately equal pressure magnitude throughout the single vacuum cavity 204.

[0038] For example, the fluid permeable mesh 202 exchanges fluid with a single space which is the single vacuum cavity 204, undivided at the radius where it meets the fluid permeable mesh 202. Figure 3 is a simplified schematic plan cross-sectional view of the filtration drum 104, according to examples. The cross-section is viewed from above, e.g., from a z-axis extending into and out of the page and shows certain example features of the filtration drum 104 in an x-y plane. In these examples, there is indicated the rotation axis 302 about which the filtration drum 104 rotates. For example, the filtration drum 104 is rotatably mounted at opposing ends, which ends are coincident with the rotation axis 302. In some examples, there may be a central shaft (not shown) concentric with the rotation axis 302.

[0039] Referring again to Figure 1, the apparatus 100 comprises the vacuum pump 110. There is also provided the first fluid junction 112. There is the fluid flow path 126, as indicated in Figure 1 by connections between the filtration drum 104 and the first fluid junction 112, and between the first fluid junction 112 and the vacuum pump 110. As shown, the vacuum pump 110 is fluidically connected to the single vacuum cavity 204. For example, the fluidic connection to the single vacuum cavity 204 may be provided atone of the ends at which the filtration drum 104 is rotatably mounted. For example, the fluidic connections are formed by use of appropriate pipework.

[0040] In some examples, there may be a central shaft in the filtration drum 104. For example, the filtration drum 104 may rotate about the central shaft. In some such examples, there may be orifices in the central shaft through which the vacuum can be created and fluid can be drawn out from the filtration drum 104 at one of the ends of the central shaft where the filtration drum 104 ends. However, it should be noted that the single vacuum cavity, as referred to herein is the cavity which is immediately adjacent to and in direct fluid communication with the fluid permeable mesh 202, as described above.

[0041] In these examples, the first fluid junction 112 comprises the fluid outlet 114 which leads to the fluid output flow path 116. For example, fluid pulled away from the filtration drum 104 by action of the vacuum pump 110 and not drawn into the vacuum pump 110 itself is directed into the fluid output flow path. The fluid pulled away from filtration drum 104 by action of the vacuum pump 110 and not drawn into the vacuum pump 110 itself is preferably a liquid and may contain any residual solid particles.

[0042] As previously described, the rotation axis is configured to remain within the operational zone of the filtration bath 102. For example, the rotation axis does not come away from the filtration bath 102 to some other component of the apparatus 100. Instead, the rotation axis (and therefore the filtration drum 104) remains in a position such that it operates together with the filtration bath 102. Those skilled in the art will appreciate that, in some examples, different filtration baths may be used for different stages of relevant processes. However, because in this case, the filtration drum 104 is positioned and remains positioned to operate in conjunction with the filtration bath 102, it need not move away from the filtration bath 102. Accordingly, the apparatus 100 does not need to have another region (e.g., another filtration bath) to which the filtration drum 104 must move. In this way, there is advantageously greater space efficiency within the apparatus 100. In addition, advantageously, the complications of providing the filtration drum 104 movement means is avoided.

[0043] For example, the apparatus 100 is configured such that all the aspects of the filtration process to be performed can be performed using only the one filtration bath 102. Various aspects of example filtration processes which may be performed are described further below.

[0044] In some examples, the first fluid junction 112 comprises a cyclone separator 118 configured to separate from one another, a liquid and air, received from the single vacuum cavity 204. The inclusion of the cyclone separator 118 is particularly advantageous for the apparatus 100. That is because it provides for the liquid phase portion of the fluid in question to be separated and drawn away to a different place compared to the gas phase portion (e.g., air). The liquid phase portion may also comprise any residual solid particulates retained therein, in particular as these will have a higher inertia than the gas phase portion.

[0045] In some examples, the first fluid junction 112 is configured to supply air separated by the cyclone separator 118 to the fluid flow path onward to the vacuum pump 110, and the first fluid junction 112 is configured to supply the liquid separated by the cyclone separator 118 to the fluid outlet 114. For example, the first fluid junction 112 is configured with the cyclone separator 118 such that the gas portion (e.g., air) is drawn away towards the vacuum pump 110, whereas the liquid phase portion is drawn away to the fluid outlet 114.

[0046] The reason this configuration is advantageous is because liquid is not fed to the vacuum pump 110, and the vacuum pump 110 can therefore continue to operate in the intended manner and its operation is not hindered. For example, if any / too much liquid to drawn into the vacuum pump 110, the pulling power of the vacuum pump may be reduced. In some examples, the vacuum pump 110 is a liquid ring vacuum pump. Those skilled in the art will appreciate that although in certain examples a liquid ring vacuum pump may tolerate a limited amount of liquid being drawn into it, too much liquid being drawn in inhibits the operation of the pump. For example, the vacuum created in the single vacuum cavity 204 may become weaker so that the pressure differential between the single vacuum cavity 204 and an exterior of the filtration drum 104 may come closer to zero. As a result, liquid, e.g., form the filtration bath 102 may be drawn in at a rate slower than desired. Other advantages of maintaining adequate function of the vacuum pump 110, as provided for by the inclusion of the cyclone separator 118 are discussed further below.

[0047] In some examples, the apparatus comprises a filtration suspension reservoir 120 fluidically connected to the filtration bath 102. For example, the filtration suspension is received in the filtration bath 102 from the filtration suspension reservoir 120 via the reception inlet 106. However, in some examples, the filtration suspension may not be provided from a reservoir within the apparatus 100 itself, and may instead be delivered into the apparatus 100 from elsewhere. However, the apparatus 100 having its own filtration suspension reservoir 120 allows the apparatus to be a more self-contained unit.

[0048] For example, in order to filter a fluid, said fluid is to be passed through a cake of filtration particles. The filtration particles are provided in the filtration suspension that is received from the filtration suspension reservoir 120. For example, when the apparatus is operated (as described later) such that the filtration drum 104 rotates while in contact with the filtration suspension received in the filtration bath 102, and the single vacuum cavity 204 is being evacuated, the filtration suspension is drawn into the cavity 204 through the fluid permeable mesh 202. The filtration particles are too large to pass through the mesh 202 and build up on the mesh 202 circumferentially around the wall of the filtration drum 104. The cake of filtration particles can filter other fluids for example. Accordingly, provision of the filtration suspension is for building the cake to be used in the filtering process.

[0049] In some examples, the filtration suspension reservoir 120 is fluidically connected to the single vacuum cavity 202 via the fluid output flow path 116. In this way, as the cake is being built, the vacuum draws fluid from the filtration suspension out of the single vacuum cavity 202, which may then be returned to the filtration suspension reservoir 120 via the fluid output flow path 116. For example, where the cyclone separator 118 is included, the air pulled out of the single vacuum cavity 202 is transferred to the vacuum pump 110 and the liquid is returned to the filtration suspension reservoir 120.

[0050] For example, the vacuum drawn in the single vacuum cavity 204 holds the cake onto the outer surface of the fluid permeable mesh 202. In these examples, the inclusion of the cyclone separator 118 is particularly advantageous. As previously discussed, the cyclone separator 118 provides for better operation of the vacuum pump 110 and a stronger vacuum to be drawn in the single vacuum cavity 204. The cake of the filtration particles is held onto the outer circumferential surface (defined by the fluid permeable mesh 202) by virtue of the vacuum inside. Therefore, the better / stronger the vacuum created, the more robustly the cake can be held on.

[0051] In some examples, the fluid output flow path 116 comprises a second fluid junction 122 and a second fluid junction valve 124. In these examples, depending on the state of the second fluid junction valve 124, fluid in the fluid output flow path 116 is directed to the filtration suspension reservoir 120, or to a filtered process fluid outlet (not shown) for returning the process fluid to a printing plate manufacturing process. For example, during the building of the cake, liquid from the filtration suspension is returned to the filtration suspension reservoir 120.

[0052] In some examples, the filtration suspension is a perlite suspension. Those skilled in the art will appreciate that perlite may be used in water filtration applications. In some examples, the filtration suspension reservoir 120 contains the perlite suspension.

[0053] For example, once the cake has been built up on the circumferential surface of the filtration drum 104 and is held by the vacuum, the filtration suspension may be removed, or cleared out from the filtration bath 102 and the filtration drum 104. For example, no further filtration suspension may be added via the reception inlet 106, while what is left in the filtration bath 102 is allowed to drain away via the drainage outlet 108. In addition, for example, time is allowed for the liquid from the filtration suspension to leave the filtration drum 104, and the fluid flow path leading away from the filtration drum 104. In addition, time may be allowed for the liquid of the filtration suspension to clear the fluid outlet flow path 116 as much as possible.

[0054] In some examples, it may be desired that contamination between the filtration suspension and a fluid to be filtered (which is to be added after the cake has been built) is further diminished. Therefore, in some examples, the filtration bath 102 comprises a flushing inlet configured to provide flushing fluid to the filtration bath 102. In some examples, the reception inlet 106 may itself act as the flushing inlet. In other examples, there may be provided one or more dedicated flushing inlets. For example, there may be provided an array of flushing inlets which are positioned to enhance the area of the filtration bath 102 where the flushing fluid can be let in. For example, the flushing outlets ofthe array may be distributed about the filtration bath 102 to reach various areas of the filtration bath 102. For example, the flushing fluid may be delivered at pressure such that the flushing fluid moves at greater velocity than, e.g., gravity and the like may provide. The flushing fluid may simply be water, for example. In other examples, the flushing fluid may comprise (either wholly or partly) a solvent other than water.

[0055] In some such examples, the filtration bath 102 comprises a flushing outlet configured to remove the flushing fluid from the filtration bath 102. In some examples, the drainage outlet 108 may act as the flushing outlet. In other examples, one or more dedicated flushing outlets may be provided. In some examples, differently to the flushing inlets, the flushing outlets may not be distributed about the filtration bath 102, and instead may be positioned where fluid collects for example. For example, the filtration bath 102 may define a gentle slope such that fluid collects at a particular part of the filtration bath. This may be the case even in examples which do not provide the described flushing inlets and outlets, e.g., the drainage outlet 108 may be positioned where the fluid is configured to collect.

[0056] In examples comprising the flushing inlet and flushing outlet, the filtration bath 102 is configured such that the flushing fluid flows through the filtration bath so as to remove residual matter from the filtration bath 102. In this manner, matter which may otherwise contaminate a fluid to be filtered can be removed as much as is practical by operation of this described flushing arrangement. For example, as described above, a plurality of flushing inlets may be distributed about the filtration bath 102, and there may be a gentle slope and the like towards one or more flushing outlet. So, the flushing fluid may flow into the filtration bath 102, contacting various parts of the filtration bath 102 and drain away via the filtration outlet, taking contaminant particles with it. In this manner, the filtration fluid may flow through the filtration bath 102 so as to remove residual matter. In some examples, the flushing may be further enhanced by delivering the flushing fluid via the flushing inlet(s) at pressure.

[0057] In examples, either or both of the flushing inlet and the flushing outlet is provided with a flushing valve, preferably a sluice gate valve. The flushing valve may be operable to control the flow of flushing fluid through the filtration bath.

[0058] In some examples, a translatable sluice may be provided for a pair of inlets or outlets, preferably selected from the flushing fluid inlet, the flushing fluid outlet, the first reception inlet, the second reception inlet, the first drainage outlet and the second drainage outlet, whereby the translatable sluice may be configured to be translated between a first position corresponding to one inlet or outlet and a second position corresponding to a different inlet or outlet. The translatable sluice is preferably pneumatically actuated.

[0059] In some examples, a set of translatable sluices are provided. Preferably, the set of translatable sluices are controlled to move between two or more positions such as to selectively cause filtration suspension, process fluid or flushing fluid to flowthrough the filtration bath 102.

[0060] Whether or not examples comprising configurations for flushing, after the filtration suspension has been removed from the filtration bath 102, the process fluid to be filtered may be introduced. During this process and until the cake of the filtration particle is no longer required to be held onto the outer surface of the mesh 202, the operation of the vacuum pump 110 is maintained.

[0061] In examples, the filtration bath 102 and the filtration drum 104 are sized so as to be appropriate for filtering part of the process fluid from the printing plate manufacturing process. For example, not the entirety, but some of the process fluid from the printing plate manufacturing process may come away to the apparatus 100 to be filtered, while the remainder of the process fluid stays within the printing plate manufacturing apparatus. For example, the filtration drum 104 is sized accordingly. In some examples, the filtration drum has an internal diameter of between 50 millimetres and 1000 millimetres.

[0062] In some examples, the single vacuum cavity filtration drum has an internal diameter not greaterthan 1000 mm, preferably not greater than 700 mm, more preferably not greater than 500 mm, even more preferably not greaterthan 350 mm.

[0063] In some examples, the single vacuum cavity filtration drum has an internal diameter of at least 50 mm, preferably at least 100 mm, more preferably at least 120 mm, even more preferably at least 150 mm.

[0064] In some examples, the single vacuum cavity filtration drum has an internal diameter of between 50 mm - 1000 mm, preferably between 100 mm - 700 mm, even more preferably between 120 mm - 500 mm, especially preferably between 150 mm - 350 mm.

[0065] For example, once the cake is ready, and in examples where relevant, a flushing process has occurred, the process fluid may be introduced to the filtration bath 102. At least a part of the cake contacts the process fluid in the filtration bath 102, while the filtration drum 104 rotates about the rotation axis 302. By action of the vacuum generated in the single vacuum cavity 204, the process fluid is drawn through the cake of filtration particles and into the single vacuum cavity 204. The cake acts to filter the process fluid. Thereby, contaminants in the process fluid desired to be removed mostly do not pass through the cake of filtration particles and remain and layer mostly on the outer circumferential surface which is defined by the cake of filtration particles.

[0066] The filtered process fluid is drawn, by the vacuum, into the fluid flow path leading away from the single vacuum cavity 204. In examples where there is provided the cyclone separator 118, the gaseous contents of what is drawn away from the single vacuum cavity 204 is directed to the vacuum pump 110, whereas the liquid content is direction towards the fluid outlet 114 and into the fluid output flow path 116. In relevant examples, during this filtration process, the second fluid junction valve 124 is configured to function as the above-described filtered process fluid outlet. From the filtered process fluid outlet, the filtered process fluid is thus returned to the apparatus which performs the printing plate manufacturing process.

[0067] Advantageously, there is provided the apparatus 100 which can be more compact, and with less complication / moving mechanisms, as compared to a filtration apparatus requiring a filtration drum to be moved between different baths (e.g., one for the building of the cake of filtration particles, and another for the filtration of the process fluid). Furthermore, of notable advantage is the addition of the cyclone separator 118 in some examples, which, surprisingly greatly enhances the operation of the apparatus 100 by maintaining a vacuum in the single vacuum cavity 204 such that the cake of filtration particles can be securely held.

[0068] Figure 4 shows a simplified schematic cross-sectional view of a filtration drum 104 according to further examples. The cross-sectional view is a top view taken from a z-axis extending into and out of the page and shows the extension of the filtration drum 104 in an x-y plane. The filtration drum 104 is analogous to the filtration drum shown in Figures 2 and 4 and is additionally provided with sealed ends 206. The filtration drum 104 according to examples is preferably configured as a replaceable cartridge. For example, the filtration drum 104 may be rotatably coupled to the filtration bath 102 by a bolt at each end 206. The filtration drum 104 may thus be removed and replaced by simply unbolting and re-bolting the filtration drum 104.f

[0069] During operation, when the filtration drum 104 is rotating and liquid is to be drawn into the cavity 204, the filtration drum 104 is in contact with liquid on the filtration bath 102 such that it is partly submerged in said liquid. In some examples, the filtration drum 104 is mounted in a translationally moveable manner within the operational zone of the filtration bath 102, for example such as to adjust the level of submersion of the filtration drum 104 within a fluid in the filtration bath 102. However, the filtration drum 104 even if translated to come away from liquid in the filtration bath 102 remains within the operational zone of the filtration bath 102. For example, the filtration drum 104 is not configured to translate so much that it can operate with a disparate filtration bath and the like. In some examples, the rotation axis 302 is translationally fixed relative to the filtration bath. In such examples, the level of submersion is controlled simply by controlling the amount of liquid content in the filtration bath 102.

[0070] Figure 5 is a simplified schematic front cross-sectional view of the filtration drum 104 and the filtration bath 102, according to examples. In these examples, there is depicted a stage at which the cake has previously been built and filtration of the process fluid is taking place. There is shown the cake 402 of the filtration particles. There is built up atop the cake 402 a layer 404 of contaminant particles 414. In these examples, there is also provided a blade 406 which is configured to be movable towards and away from the filtration drum 104. The blade 406 is configured to peel, as the filtration drum 104 rotates, an outer layer of material on the circumferential surface of the filtration drum 104. In some examples, the blade 406 may be operated to peel away the layer of contaminant particles 404, and optionally, a part of the cake 402. For example, this may be advantageous where contaminant particles have penetrated partly into the cake 402.

[0071] In some examples, the blade 406 is arranged at a tangent to the single vacuum cavity filtration drum 104. Preferably, an angle formed between the blade 406 and a radius of the single vacuum cavity filtration drum 104 is configured such that the blade 406 may remove a layer of material (e.g., particles to be filtered and / or the cake) having an optimally low thickness, from the vacuum cavity filtration drum 104. For example, the blade 406 may be arranged to remove a layer of material having a thickness of less than 2 mm, preferably less than 1 mm, more preferably less than 0.5 mm. In some examples, the blade 406 is configured and operated to remove a given thickness, such as the values just described, of the cake (e.g., this may be irrespective of how much of the contaminant particles from filtering have been deposited atop the cake). The remainder of the cake may be left intact by the blade 406. This advantageously allows precise removal of the layer 404 of contaminant particles 414 whilst retaining the cake 402 of filtration particles. The cake 402 may thus only need to be replaced at a low frequency.

[0072] In some examples, the apparatus 100 comprises a controller configured to control the operation of the apparatus 100. For example, the controller may comprise one or more processors configured to communicate with the operational components of the apparatus 100. The one or more processors may be in data communication with one or more computer readable memories. There may be stored instructions in the memories, which when executed by the processors, cause the apparatus 100 to be operated in a manner defined by the instructions. In some examples, the controller is configured to perform any combination of the described operations.

[0073] In some examples, the controller is configured to cause the filtration bath to receive a filtration suspension comprising filtration particles, preferably perlite, to a level such that the filtration suspension makes contact with the single vacuum cavity filtration drum. The controller is further configured to evacuate the single vacuum cavity filtration drum and cause the single vacuum cavity filtration drum to rotate so as to cause a cake of filtration particles from the filtration suspension to be built up on the fluid permeable mesh, while filtration suspension fluid from the filtration solution is drawn into the single vacuum cavity. Th controller is also configured to remove the filtration suspension from the filtration bath and flush the filtration bath with a flushing fluid. In addition, the controller is configured to cause the filtration bath to receive the process fluid to a level such that the cake of filtration particles contacts the process fluid. Furthermore, the controller is configured to evacuate the single vacuum cavity filtration drum and cause the single vacuum cavity filtration drum to rotate so as to filter the process fluid through the cake of filtration particles and into the single vacuum cavity filtration drum.

[0074] In some examples, the blade 406 is arranged to be adjustable in its position within the filtration bath 102 and / or adjustable in its angle to the radius of the filtration drum 104. This allows the thickness at which the layer 404 of contaminant particles 414 is removed from the filtration drum 104 to be adjusted. The adjustment of the blade 406 may be automated, e.g., by a controller and an actuator in communication with the controller.

[0075] In some examples, the speed at which the filtration drum 104 rotates relative to the blade 406 is also adjustable, preferably automatically adjustable. This further allows the build-up and removal of cake on the filtration drum 104 to be adjusted. For example, an actuator for rotating the filtration drum 104 within the filtration bath 102 may be controlled by a controller (such as the described controller) which is in communication with the actuator.

[0076] In some examples, the blade 406 may be configured (by means of its actuation system) to gradually move closer to the filtration drum 104 as the filtration drum rotates. This movement may also be controlled to control the manner in which layers of material are removed from the filtration drum 104.

[0077] In some examples, the vacuum pump has a variable speed and / or variable pressure. The speed and / or pressure of the vacuum pump may be varied by a controller, e.g., in response to a signal from the controller.

[0078] In some examples, the controller is configured to adjust the speed and / or pressure of the vacuum pump in order to provide an optimal cake 402 and / or to collect a particular amount of contamination particles 404. For example, one or more cake parameters such as the density or thickness may be brought closer to an optimal value by adjusting the operation of the vacuum pump. As referred to herein, the “optimal” value may be a value which achieves a desired result. For example, if it is advantageous to have a cake of a given thickness (for example, due to characteristics of the contamination particles to be filtered), then the vacuum pump may be operated in a manner (in combination with other relevant parameters such as time allowed for the cake to build, immersion depth of the filtration drum 104 in the filtration suspension in the filtration bath 102, rotation speed, etc.) so as to achieve that given thickness of cake.

[0079] In some examples, the controller is configured to adjust a composition of the filtration suspension, in particular by adjusting the concentration of filtration particles in the suspension particles. This may be for example by controlling a flow of the components of the filtration suspension upstream of the filtration bath 102. As an example, additional water may be added to the filtration suspension at the filtration suspension reservoir 120, or thereafter but before the filtration bath 102. In some examples, there may be provided controllable feed systems for adding water and perlite to the filtration suspension reservoir 120. The feed systems may be controlled to adjust the relative quantities of the water and the perlite so as to control the composition of the filtration suspension. The composition of the filtration suspension may be optimised for the production of an optimal filtration cake 402. For example, one or more cake parameters such as the density, thickness, and the like, may be brought closer to a desired value by adjusting the composition of the filtration suspension.

[0080] In some examples, there is provided a method of filtering process fluid from a printing plate manufacturing process, the method comprising deploying an apparatus configured to receive the process fluid and return the process fluid after subjecting it to a filtering process. The apparatus of the method may be the apparatus 100 according to any of the examples described herein. For example, the method comprises building a filtration particle cake on the fluid permeable mesh using filtration suspension received in the filtration bath, and filtering the process fluid received subsequently in the filtration bath through the filtration particle cake. In some examples, the method comprises flushing the filtration bath so as to remove residual matter from the filtration bath after building the filtration particle cake and before filtering the process fluid through the filtration particle cake. In some examples, the method comprises operating a cyclone separator in the first fluid junction to separate the filtered process fluid and air received from the single vacuum cavity.

[0081] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0082] In the above description, various specific examples are described. The invention is not restricted to the details of the foregoing example(s). The invention extends 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 steps of any method or process so disclosed.

Claims

1. An apparatus for receiving and filtering process fluid from a printing plate manufacturing process, the apparatus configured to receive the process fluid and return the process fluid after subjecting it to a filtering process, the apparatus comprising:a filtration bath configured to receive a fluid;a single vacuum cavity filtration drum comprising a single vacuum cavity therein and a circumferential wall comprising a fluid permeable mesh, wherein the single vacuum cavity filtration drum is configured to rotate about a rotation axis, wherein the rotation axis is configured to remain within an operational zone of the filtration bath;a vacuum pump fluidically connected to the single vacuum cavity of the single vacuum cavity filtration drum; anda first fluid junction positioned in a fluid flow path between the single vacuum cavity and the vacuum pump, the first fluid junction comprising a fluid outlet leading to a fluid output flow path.

2. The apparatus according to claim 1, wherein:the first fluid junction comprises a cyclone separator configured to separate from one another a liquid and air received from the single vacuum cavity.

3. The apparatus according to claim 2, wherein:the first fluid junction is configured to supply the air separated by the cyclone separator to the fluid flow path onward to the vacuum pump; andthe first fluid junction is configured to supply the liquid separated by the cyclone separator to the fluid outlet.

4. The apparatus according to any one of the preceding claims, comprising:a filtration suspension reservoir fluidically connected to the filtration bath.

5. The apparatus according to claim 4, wherein:the filtration suspension reservoir is fluidically connected to the single vacuum cavity via the fluid output flow path.

6. The apparatus according to claim 5, wherein:the fluid output flow path comprises a second fluid junction and a second fluid junction valve; anddepending on the state of the second fluid junction valve, fluid in the fluid output flow path is directed to the filtration suspension reservoir, or to a filtered process fluid outlet for returning the process fluid to a printing plate manufacturing process.

7. The apparatus according to claim 5 or claim 6, wherein:the filtration suspension reservoir contains a perlite suspension.

8. The apparatus according to any one of the preceding claims, wherein the filtration bath comprises:a flushing inlet configured to provide flushing fluid to the filtration bath; anda flushing outlet configured to remove the flushing fluid from the filtration bath,wherein:the filtration bath is configured such that the flushing fluid flows through the filtration bath so as to remove residual matter from the filtration bath.

9. The apparatus according to any one of the preceding claims, wherein:the vacuum pump is a liquid ring vacuum pump.

10. The apparatus according to any one of the preceding claims, wherein:the filtration drum has an internal diameter of between 50 millimetres and 1000 millimetres.

11. The apparatus according to any one of the preceding claims, wherein:the rotation axis is translationally fixed relative to the filtration bath.

12. The apparatus according to any of the preceding claims, wherein:the filtration bath comprises a reception inlet (106) and a drainage outlet (108), the reception inlet (106) being spaced apart from the drainage outlet (108) such that when both the reception inlet (106) and the drainage outlet (108) are in use, a flow is provided over substantially the whole of a base surface of the filtration bath.

13. The apparatus according to the preceding claim, wherein:the filtration bath comprises one or more sluice gate valves for controlling the flow of fluid through the reception inlet (106) and / orthe drainage outlet (108).

14. The apparatus according to any one of the preceding claims comprising a controller configured to control the operation of the apparatus, wherein the controller is configured to:cause the filtration bath to receive a filtration suspension comprising filtration particles to a level such that the filtration suspension makes contact with the single vacuum cavity filtration drum;evacuate the single vacuum cavity filtration drum and cause the single vacuum cavity filtration drum to rotate so as to cause a cake of filtration particles from the filtration suspension to be built up on the fluid permeable mesh, while filtration suspension fluid from the filtration solution is drawn into the single vacuum cavity;remove the filtration suspension from the filtration bath and flush the filtration bath with a flushing fluid;cause the filtration bath to receive the process fluid to a level such that the cake of filtration particles contacts the process fluid; andevacuate the single vacuum cavity filtration drum and cause the single vacuum cavity filtration drum to rotate so as to filter the process fluid through the cake of filtration particles and into the single vacuum cavity filtration drum.

15. The apparatus according to any one of the preceding claims, wherein:the filtration bath comprises a blade, the blade arranged at a tangent to the single vacuum cavity filtration drum and configured to remove a layer of material from the filtration drum.

16. The apparatus according to the preceding claim, wherein:a position and / or angle of the blade within the filtration bath is adjustable.

17. The apparatus according to any one of the preceding claims, wherein:the vacuum pump has a variable speed and / or variable pressure.

18. A method of filtering process fluid from a printing plate manufacturing process, the method comprising deploying an apparatus configured to receive the process fluid and return the process fluid after subjecting it to a filtering process, the apparatus comprising:a filtration bath configured to receive a fluid;a single vacuum cavity filtration drum comprising a single vacuum cavity therein and a circumferential wall comprising a fluid permeable mesh, wherein the single vacuum cavity filtration drum is configured to rotate about a rotation axis, wherein the rotation axis is configured to remain within an operational zone of the filtration bath;a vacuum pump fluidically connected to the single vacuum cavity of the single vacuum cavity filtration drum; anda first fluid junction positioned in a fluid flow path between the single vacuum cavity and the vacuum pump, the first fluid junction comprising a fluid outlet leading to a fluid output flow path,the method comprising:building a filtration particle cake on the fluid permeable mesh using filtration suspension received in the filtration bath; andfiltering the process fluid received subsequently in the filtration bath through the filtration particle cake.

19. The method according to claim 18, further comprising:flushing the filtration bath so as to remove residual matter from the filtration bath after building the filtration particle cake and before filtering the process fluid through the filtration particle cake.

20. The method according to claim 18 or claim 19, further comprising:operating a cyclone separator in the first fluid junction to separate the filtered process fluid and air received from the single vacuum cavity.21

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