Method and device for determining the condition of the filter unit of an ink supply system

Abstract

A device (101) for determining the state of a filter unit (214) of an ink supply system (200) of a printing bar (102) of an inkjet printing device (100) is described, wherein the filter unit (214) is arranged on a supply line (213) to the printing bar (102) in series with a supply valve (215). The device (101) is configured to determine a degree of opening (320) of the supply valve (215) that arises while ink (212) is being conveyed through the supply line (213) at a specific target volume flow (310). Furthermore, the device (101) is configured to determine state information relating to the state of the filter unit (214) based on the determined degree of opening (320) of the supply valve (215).

Description

[0001] The invention relates to a method and a corresponding device designed to determine the state of the filter unit for filtering the ink in an ink supply system of an inkjet printing device.

[0002] An inkjet printing device for printing on a recording medium can comprise a printing bar with one or more print heads, each with one or more nozzles. The nozzles are each configured to eject ink droplets to print pixels of a print image onto the recording medium. The individual print heads of a printing bar are supplied with ink by an ink supply system, which typically includes a filter unit configured to filter the ink for the printing bar. With increasing operating time, the filter unit may contain an increasingly high amount of contaminants and thus an increasingly high degree of clogging, which can ultimately lead to clogging of the filter unit.

[0003] This document addresses the technical problem of efficiently and precisely determining the condition, in particular the occupancy status, of the filter unit of the ink supply system of a print bar of an inkjet printing device, in particular to enable optimized replacement of the filter unit. This problem is solved by the features of independent device claim 1 and by the features of independent method claim 10, respectively.

[0004] According to one aspect, a device for determining the state of the filter unit of the ink supply system of a printing bar of an inkjet printing device is described, wherein the filter unit is arranged on a supply line to the printing bar in series with a supply valve, and wherein the filter unit is configured to receive contaminants from ink conveyed through the supply line. The device is configured to determine a degree of opening of the supply valve that arises while ink is being conveyed through the supply line at a specific target volume flow. The device is further configured to determine state information relating to the state of the filter unit based on the determined degree of opening of the supply valve, wherein the state information indicates, in particular, the occupancy state of the filter unit due to received contaminants.

[0005] According to a further aspect, a method for determining the state of the filter unit of the ink supply system of a printing bar of an inkjet printing device is described, wherein the filter unit is arranged on a supply line to the printing bar in series with a supply valve, and wherein the filter unit is configured to collect contaminants from ink conveyed through the supply line. The method comprises determining, while ink is being conveyed through the supply line at a specific target volume flow, a degree of opening of the supply valve that is thereby established. Furthermore, the method comprises determining status information relating to the state of the filter unit based on the determined degree of opening of the supply valve.

[0006] In the following, exemplary embodiments of the invention are described in more detail with reference to the schematic drawings. In the drawings: Fig. 1 is a block diagram of an exemplary inkjet printing apparatus; Fig. 2 shows an exemplary ink supply system for one or more print heads of a print bar of an inkjet printing device; Fig. 3 an exemplary temporal progression of the degree of opening of the supply valve of the ink supply system; and Fig. 4 a flowchart of an exemplary method for determining status information relating to the status, in particular the occupancy status, of the filter unit of an ink supply system.

[0007] The Fig. The printing device 100 shown in Figure 1 is designed for printing on a sheet-, sheet-, plate-, or web-shaped recording medium 120. The recording medium 120 can be made of paper, cardboard, carton, metal, plastic, textiles, a combination thereof, and / or other suitable and printable materials. The marking medium 120 is guided along the transport direction 1, represented by an arrow, through the printing unit 140 of the printing device 100.

[0008] The printing unit 140 of the printing device 100 comprises, in the illustrated example, two printing bars 102, wherein each printing bar 102 can be used for printing with ink of a specific color, e.g., black, cyan, magenta, and / or yellow, and possibly MICR ink. Different printing bars 102 can be used for printing with different inks. Furthermore, the printing device 100 typically comprises at least one fixing or drying unit, which is not included in Fig. 1 and which is configured to fix a print image printed on the recording medium 120.

[0009] A printing bar 102 may comprise one or more print heads 103, which may be arranged in several rows next to one another, in order to print the pixels of different columns 31, 32 of a print image onto the recording medium 120. In the Fig. In the example shown in Figure 1, a printing bar 102 comprises five print heads 103, each print head 103 printing the pixels of a group of columns 31, 32 of a print image onto the recording medium 120. The number of print heads 103 of a printing bar 102 can be, for example, 5, 10, or more.

[0010] Each print head 103 of the printing unit 140 comprises in the Fig. 1, a plurality of nozzles 21, 22, each nozzle 21, 22 being configured to fire or impinge ink droplets onto the recording medium 120. A print head 103 of the printing unit 140 can, for example, comprise several thousand effectively used nozzles 21, 22 arranged along several rows transversely to the transport direction 1 of the recording medium 120. By means of the nozzles 21, 22 of a print head 103 of the printing unit 140, pixels of a line of a print image can be printed onto the recording medium 120 transversely to the transport direction 1, i.e., along the width of the recording medium 120.

[0011] The printing device 100 further comprises a control device 101, e.g. a control hardware and / or a controller, which is configured to control the actuators of the individual nozzles 21, 22 of the individual print heads 103 of the printing unit 140 in order to apply the print image to the recording medium 120 as a function of print data.

[0012] The printing unit 140 of the printing device 100 thus comprises at least one printing bar 102 with K nozzles 21, 22, which can be arranged in one or more print heads 103 and which can be controlled with a specific line clock in order to print one line each, which runs transversely to the transport direction 1 of the recording medium 120, with K pixels or K columns 31, 32 of a print image on the recording medium 120, e.g. with K>1000. In the example shown, the nozzles 21, 22 are immovably or permanently installed in the printing device 100, and the recording medium 120 is guided past the stationary nozzles 21, 22 at a specific transport speed.

[0013] Fig. 2 shows an exemplary ink supply system 200 configured to supply the one or more print heads 103 of a print bar 102 with ink 212. One or more print heads 103 can be combined to form a print head group 203, wherein the one or more print heads 103 of a print head group 203 are supplied with ink 212 via a common ink path, in particular via a common print head supply line 205 and / or via a common print head discharge line 206.

[0014] The ink supply system 200 comprises an ink container 211 for ink 212. Using a pump 210, ink 212 can be pumped from an ink reservoir (not shown) into the ink container 211. Ink 212 from the ink container 211 can be guided via a supply line 213 to an inlet-side distribution unit 221. A filter unit 214 for filtering, in particular for cleaning, the ink 212 can be arranged on the supply line 213. Furthermore, a supply valve 215 can be arranged on the supply line 213, which can be opened and closed to change the volume flow of ink 212 through the supply line 213. The supply valve 215 can be designed such that the degree of opening of the supply valve 215 can be changed smoothly, for example, between 0% and 100%. The supply valve 215 can be a proportional valve.

[0015] The ink supply system 200 includes an input-side pressure sensor 223 configured to detect pressure measurements related to the physical pressure of the ink 212 in and / or at the input-side distribution unit 221.

[0016] Starting from the input-side distribution unit 221, the ink 212 can be directed to the individual printhead groups 203. A printhead supply line 205 can lead from the input-side distribution unit 221 to each individual printhead group 203 to supply ink 212 from the input-side distribution unit 221 to the respective printhead group 203. The individual printhead supply lines 205 can each be opened or closed by a supply valve 201.

[0017] Furthermore, a printhead drain line 206 can lead from each of the individual printhead groups 203 to an output-side distribution unit 223, in which the ink 212 from the individual printhead groups 203 is collected. The individual printhead drain lines 206 can each be opened or closed by a drain valve 202.

[0018] In Fig. 2 shows, by way of example, the printhead supply lines 205, the supply valves 201, the printhead drain lines 206, and the drain valves 202 for two printhead groups 203. Typically, the ink supply system 200 has a printhead supply line 205, a supply valve 201, a printhead drain line 206, and a drain valve 202 for each printhead group 203 of the print bar 102.

[0019] The ink supply system 200 may include an output pressure sensor 224 configured to detect pressure measurements related to the physical pressure of the ink 212 in and / or at the output manifold 222.

[0020] By means of an output-side (vacuum) pump 225, which is designed, for example, as a gear pump, ink 212 can be conveyed from the output-side distribution unit 222 via a discharge line 226 into the ink container 211.

[0021] The ink supply system 200 may further include a bypass line 231, via which ink 212 can be routed directly from the input-side distribution unit 221 and past the one or more printhead groups 203 to the output-side distribution unit 222. The bypass line 231 can be opened or closed via a bypass valve 230. The bypass valve 230 and the bypass line 231 are typically closed during the printing operation of the print bar 102. On the other hand, the bypass valve 230 and the bypass line 231 can be opened in the standby mode of the printing bar 102 and / or the ink supply system 200 to allow circulation of the ink 212 and thereby in particular to prevent the ink 212 from drying out in the ink supply system 200 and / or to thereby prepare the printing bar 102 for subsequent printing operation.

[0022] As already explained, during operation of the ink supply system 200, the filter unit 214 on the supply line 213 collects contaminants from the ink 212 supplied to the inlet-side distribution unit 221. As a result, the occupancy or degree of occupancy of the filter unit 231 typically increases with increasing operating time of the ink supply system 200, which typically leads to an increase in the resistance of the filter unit 231 for ink 212 flowing through the filter unit 214. If the quantity of contaminants collected by the filter unit 231 reaches a certain quantity threshold and / or if the degree of occupancy of the filter unit 214 reaches a certain occupancy threshold, the filter unit 214 may become clogged, interrupting the ink supply to the printing bar 102 and thus the printing operation of the printing bar 102.This document describes measures by which the condition, in particular the occupancy condition, such as the degree of occupancy, of the filter unit 214 can be determined in an efficient and precise manner, in particular to enable a time-optimized replacement of the filter unit 214, by which the service life of the filter unit 214 is maximized without impairing the availability of the printing device 100.

[0023] During the standby mode of the pressure bar 102 and / or the ink supply system 200, the bypass valve 230 and the bypass line 231 can be open. Furthermore, the output-side pump 225 can be operated to pump ink 212 from the output-side distribution unit 222 into the ink container 211. Furthermore, the device 101 can be configured to set the pressure of the ink 212 in the input-side distribution unit 221 and / or in the output-side distribution unit 222 to a specific target pressure. Alternatively or additionally, the device 101 can be configured to effect a specific target volume flow of the ink 212 through the supply line 213. This can be achieved in particular by adjusting the degree of opening of the supply valve 215 as a function of pressure measurement values ​​of the inlet-side and / or outlet-side pressure sensor 223, 224 and, if necessary, using a control system.

[0024] As exemplified in Fig. 3, the output-side pump 225 can be operated during the standby mode of the ink supply system 200 to effect a specific volume flow 310 of ink 212 from the output-side distribution unit 222 to the ink container 211 and / or through the supply line 213, i.e., from the ink container 211 to the input-side distribution unit 221. Furthermore, the resulting degree of opening 320 of the supply valve 215 can be determined.

[0025] During the service life of the filter unit 214, the pressure bar 102 repeatedly has operating phases that are interrupted by standby phases. In each of the individual standby phases, the aforementioned standby operation of the ink supply system 200 can be effected, and the opening degree 320 of the supply valve 215 can be determined. As a result, a temporal progression 325 of the opening degree 320 of the supply valve 215 results as a function of time 300. As can be seen from Fig. As can be seen from Figure 3, the degree of opening 320 typically increases over time 300 to compensate for the increasing occupancy of the filter unit 214 and thus the increasing resistance of the filter unit 214. Consequently, the degree of opening 320 of the supply valve 315 is a reliable indicator of the occupancy state of the filter unit 214.

[0026] In the Fig. In the example shown in Figure 3, the supply valve 215 initially has an initial degree of opening 321 in order to set the target pressure and / or to effect the target volume flow 310. As the service life of the filter unit 214 increases, the degree of opening 320 increases until, at a first point in time 301, a first degree of opening 323 is reached, which is preferably below a threshold value 322 at which the filter unit 214 should or must be replaced. At the first point in time 301, based on the time profile 325 of the degree of opening 320, the expected point in time 302 at which the threshold value 322 for replacing the filter unit 214 will be reached can be predicted. The estimated time 302 can be output via a user interface of the printing device 100 to inform the user of the printing device 100 that and, if applicable, when the filter unit 214 should or must be replaced.This allows the availability of the printing device 100 to be increased in a convenient and reliable manner. Furthermore, this allows the maximum possible service life of the filter unit 214 to be achieved.

[0027] The state of the filter unit 214 can thus be determined based on the degree of opening 320 of the supply valve 215 during standby operation for circulating ink 212, if necessary in combination with the operating state of the output-side pump 225 in the return circuit of the ink supply system 200. During standby operation, a specific target volume flow 310 of ink 212 is effected, e.g., to prepare the printing device 100 for the subsequent printing operation. The ink 212 flows from the ink container 211, through the filter unit 214, through the supply valve 215, through the inlet-side distribution unit 221, via the bypass line 231 to the outlet-side distribution unit 222, before the ink 212 is pumped back into the ink container 211 by the outlet-side pump 225, in particular by a gear pump.As the service life and / or occupancy of the filter unit 214 increases, the degree of opening 320 of the supply valve 215 increases in order to achieve a specific target volume flow 310, e.g., 50 ml / min., of ink 212. Based on the temporal profile 325 of the degree of opening 320, a trend can be identified. In particular, the time 302 can be predicted at which the supply valve 215 can no longer be opened sufficiently wide due to the clogged filter unit 214 in order to supply the print bar 102 with a sufficiently high quantity of ink 212 for printing operation. By predicting this time 302, it is possible to utilize the entire service life of the filter unit 214 and still avoid downtimes of the printing device 100.

[0028] Fig.4 shows a flowchart of an exemplary, possibly computer-implemented, method 400 for determining the state of the filter unit 214 of the ink supply system 200 of a printing bar 102 of an inkjet printing device 100. The method 400 can be executed by a control device 101 of the printing device 100. The filter unit 214 is arranged on a supply line 213 to the printing bar 102 in series with a supply valve 215. The supply valve 215 can be arranged downstream of the filter unit 214 in the flow direction of the ink 212 through the supply line 213. The filter unit 214 can be configured to collect contaminants from the ink 212 conveyed through the supply line 213. As a result, the filter unit 214 can contain an increasingly large amount of contaminants and / or become increasingly heavily clogged over time.The status information may indicate the occupancy status of the filter unit 214 due to captured contaminants. Alternatively or additionally, the status information may indicate the degree of occupancy and / or the degree of clogging of the filter unit 214.

[0029] The method 400 comprises determining 401, while ink 212 is being conveyed at a specific target volume flow 310, in particular through the supply line 213, the degree of opening 320 of the supply valve 215 that is thereby established. For example, during the standby operation of the ink supply system 200, it can be caused that ink 212 flows at the specific target volume flow 310 through the supply line 213, in particular in order to effect circulation of the ink 212 in the ink supply system 200, for example in order to prevent the ink 212 from drying out and / or in order to prepare the printing bar 102 for printing operation.

[0030] The target volume flow 310 of the ink 212 can be achieved by adjusting one or more operating parameters, e.g., the rotational speed of a pump 225 of the ink supply system 200 and / or by adjusting the opening degree 320 of the supply valve 215. The adjustment can be achieved using a control loop. The resulting opening degree 320 of the supply valve 215 can be used as an indicator of the condition, in particular the resistance, of the filter unit 214. Typically, a relatively high degree of opening 320 of the supply valve 215 indicates a relatively high resistance and / or a relatively high degree of occupancy and / or clogging of the filter unit 214. On the other hand, a relatively low degree of opening 320 of the supply valve 215 indicates a relatively low resistance and / or a relatively low degree of occupancy and / or clogging of the filter unit 214.

[0031] The method 400 further includes determining 402 status information relating to the status of the filter unit 214 based on the determined degree of opening 320 of the supply valve 215. Thus, the status of the filter unit 214 can be determined in an efficient and precise manner, which in turn can increase the availability of the pressure bar 102.

[0032] If necessary, characteristic data determined in advance, in particular experimentally, can be provided, which indicate a value of the degree of occupancy and / or clogging of the filter unit 214 for a plurality of different values ​​of the opening degree 320 of the supply valve 215. The value of the degree of occupancy and / or clogging of the filter unit 214 can then be determined as status information based on the determined opening degree 320, i.e., the determined value of the opening degree 320, using the characteristic data.

[0033] Thus, a device 101 for determining the status of the filter unit 214 of the ink supply system 200 of a print bar 102 of an inkjet printing device 100 is described. The status information can indicate the occupancy state and / or the resistance of the filter unit 214 due to captured contaminants.

[0034] The ink supply system 200 can be configured to provide ink 212 for the N printhead groups 203 or printheads 103 of the printing bar 102, where N≥1, in particular N≥2. The ink supply system 200 can have an input-side distribution unit 221 configured to provide ink 212 at the input of the one or more ink supply channels of the N different printhead groups 203 or printheads 103 of the printing bar 102. Alternatively or additionally, the ink supply system 200 can have an output-side distribution unit 222 configured to receive ink 212 from the output of the one or more ink supply channels of the N different printhead groups 203 or printheads 103 of the printing bar 102.

[0035] The print bar 102 can have a supply valve 201 for each of the N different print head groups 203 or print heads 103, which is designed to open or close a print head supply line 205 from the input-side distribution unit 221 to the respective print head group 203 or to the respective print head 103. Furthermore, the print bar 102 can have a discharge valve 202 for each of the N different print head groups 203 or print heads 103, which is designed to open or close a print head discharge line 206 from the respective print head group 203 or from the respective print head 103 to the output-side distribution unit 222. The supply valves 201 and / or the discharge valves 202 of the N print head groups 203 or print heads 103 thus enable a selective provision of ink 212 in the individual print head groups 203 or print heads 103.

[0036] The ink supply system 200 may include an input-side pressure sensor 223 configured to detect one or more pressure measurement values ​​related to the pressure of the ink 212 in the input-side distribution unit 221. Alternatively or additionally, the ink supply system 200 may include an output-side pressure sensor 224 configured to detect one or more pressure measurement values ​​related to the pressure of the ink 212 in the output-side distribution unit 222.

[0037] The supply valve 215 of the ink supply system 200 can be configured to change the volume flow of ink 212 into the inlet-side distribution unit 221 and / or through the supply line 213 to the inlet-side distribution unit 221 by changing the degree of opening 320 of the supply valve 215. The supply valve 215 is preferably configured such that the degree of opening can be adjusted, in particular substantially continuously, between 0%, i.e., completely closed, and 100%, i.e., completely open.

[0038] The ink supply system 100 may include an input-side pump 210 configured to convey ink 212, in particular via and / or from an ink container 211 and / or via the supply valve 215 and / or via the filter unit 214, into the input-side distribution unit 221. Thus, ink 212 can be reliably provided to the N printhead groups 203.

[0039] The ink supply system 100 may include an output-side pump 225 configured to pump ink 212 out of the output-side distribution unit 222, and in particular into the ink reservoir 211. This allows for a reliable flow of ink 212 through the N printhead groups 203.

[0040] The filter unit 214 of the ink supply system 200 is arranged on the supply line 213 to the pressure bar 102, in particular to the inlet-side distribution unit 221, in series with the supply valve 215. The filter unit 214 can be configured to capture contaminants from ink 212 conveyed through the supply line 213.

[0041] The ink supply system 200 can include a bypass line 231 that can be opened or closed via a bypass valve 230. The bypass line 231 can be configured to direct ink 212 from the supply line 213 past the one or more printheads 103 or the one or more printhead groups 203 of the printing bar 102. The bypass line 231 can, in particular, be configured to direct ink 212 directly from the input-side distribution unit 221 to the output-side distribution unit 222, in particular without the ink 212 being guided through the N printhead groups 203 or printheads 103 of the printing bar 102. The bypass line 231 can be used for circulating ink 212 within the ink supply system 200.

[0042] The device 101 is configured to determine a degree of opening 320 of the supply valve 215 that is set while ink 212 is being conveyed through the supply line 213 at a specific desired volume flow 310.

[0043] The device 101 can be configured to operate the ink supply system 200 in a standby mode, in which ink 212 is circulated at the specific volume flow 310 past the one or more print heads 103 or print head groups 203 of the print bar 102. For this purpose, the device 101 can be configured to open the bypass valve 230. The standby mode can occur, in particular, when the print bar 102 is in a standby state in which no pixels are printed by the print bar 102. The standby mode of the ink supply system 200 can be initiated in preparation for the printing operation of the print bar 102.

[0044] The device 101 can be configured to determine the degree of opening 320 of the supply valve 215 in a particularly reliable manner while the ink supply system 200 is operated in the standby mode.

[0045] As already explained, the ink supply system 200 can comprise a pump 225, in particular on the output side, which is designed to convey ink 212 through the ink supply system 200. The pump 225 can in particular be designed to convey ink 212 from the supply line 213 downstream of the filter unit 214 and the supply valve 215 back into the ink container 211.

[0046] The device 101 can further be configured to operate the pump 225 and / or the supply valve 215 such that the specific target volume flow 310 of ink 212 is delivered via the supply line 213. For this purpose, pressure measurement values ​​of the pressure of the ink 212 in the ink supply system 200, in particular in the supply line 213, can be determined, e.g., using one or more pressure sensors 223, 224 of the ink supply system 200. The pump 225 and / or the supply valve 215 can be operated as a function of the pressure measurement values ​​to cause the specific target volume flow 310 of ink 212 to be delivered through the supply line 213.

[0047] By adjusting the target volume flow 310 of ink 212 through the supply line 213, a specific degree of opening 320 of the supply valve 215 can be achieved. The device 101 is configured to determine status information regarding the status of the filter unit 214 based on the degree of opening 320 of the supply valve 215. Thus, the status of the filter unit 214 can be determined in a particularly efficient and precise manner.

[0048] The device 101 can be configured to output the status information via a user interface, in particular via a user interface of the printing device 100. Thus, the user of the printing device 100 can be informed precisely when the filter unit 214 needs to be replaced. Thus, the service life of the filter unit 214 can be maximized without compromising the availability of the printing device 100.

[0049] The device 101 can be configured to determine, at a sequence of consecutive times 300 at which ink 212 is conveyed through the supply line 213 at the determined target volume flow 310, a degree of opening 320 of the supply valve 215 that is thereby established, in order to determine a temporal profile 325 of the degree of opening 320 of the supply valve 215 for the sequence of times 300. The ink supply system 200 can be operated in standby mode at each of the individual times 300.

[0050] The status information relating to the status of the filter unit 214 can be determined in a particularly precise manner on the basis of the determined temporal profile 325 of the degree of opening 320 of the supply valve 215.

[0051] The device 101 can be configured to predict, based on the temporal profile 325 of the degree of opening 320 of the supply valve 215, in particular based on the temporal gradient of the temporal profile 325 of the degree of opening 320 of the supply valve 215, as status information, a future point in time 302 at which the filter unit 214 will be clogged and / or needs to be replaced due to impurities absorbed from the ink 212. For this purpose, for example, the temporal profile 325 of the degree of opening 320 can be extrapolated into the future. By predicting the replacement point in time 302, the operation of the ink supply system 200 and the pressure bar 102 can be further optimized.

[0052] Furthermore, this document describes an ink supply system 200 that includes the device 101 described in this document. Furthermore, this document describes a printing device 100 that includes the ink supply system 200 described in this document. List of reference symbols 1 Transport direction (of the recording medium) 21, 22 nozzle 31, 32 columns (of the print image) 100 printing device 101 (Control) Device 102 pressure bars 103 Printhead 120 recording media 140 printing units 200 ink supply system 201 Supply valve 202 Drain valve 203 Printhead Group 205 Print head supply line 206 Printhead Derivation 210 inlet pump 211 ink tanks 212 ink 213 supply line 214 filter unit 215 Supply valve 221 input-side distribution unit 222 output-side distribution unit 223 input-side pressure sensor 224 output pressure sensor 225 output-side (vacuum) pump 226 Derivation 230 bypass valve 231 Bypass line 300 time 301, 302 Time 310 Target volume flow of ink 320 degree opening 321 Initial opening degree 322 Opening degree threshold 323 first degree of opening 400 Methods for detecting a printhead with air inclusion 401-402 Procedural steps

Claims

[1] Device (101) for determining the condition of a filter unit (214) of an ink supply system (200) of a print bar (102) of an inkjet printing device (100); wherein the filter unit (214) is arranged on a supply line (213) to the print bar (102) in series with a supply valve (215); wherein the filter unit (214) is configured to capture impurities from ink (212) conveyed through the supply line (213); wherein the device (101) is configured - while ink (212) is conveyed through the supply line (213) at a specific target volume flow rate (310), to determine the resulting degree of opening (320) of the supply valve (215); and - To determine status information regarding the state of the filter unit (214) based on the determined opening degree (320) of the supply valve (215); wherein the status information indicates in particular a contamination state of the filter unit (214) due to absorbed impurities. [2] Device (101) according to claim 1, wherein the device (101) is configured, - at a sequence of successive time points (300), at each of which ink (212) is conveyed through the supply line (213) at the specified target volume flow rate (310), to determine the resulting degree of opening (320) of the supply valve (215) in order to determine a time course (325) of the degree of opening (320) of the supply valve (215) for the sequence of time points (300); and - To determine status information regarding the state of the filter unit (214) based on the determined time course (325) of the opening degree (320) of the supply valve (215). [3] Device (101) according to claim 2, wherein the device (101) is configured to predict, based on the temporal profile (325) of the degree of opening (320) of the supply valve (215), in particular based on a temporal gradient of the temporal profile (325) of the degree of opening (320) of the supply valve (215), as state information an upcoming time (302) at which the filter unit (214) will be clogged and / or need to be replaced due to impurities absorbed from the ink (212). [4] Device (101) according to one of the preceding claims, wherein the device (101) is configured, - to operate the ink supply system (200) in a standby mode in which ink (212) circulates past one or more printheads (103, 203) of the print bar (102) at the specified volumetric flow rate (310) when the print bar (102) is in a standby state in which no pixels are printed by the print bar (102); and - to determine the degree of opening (320) of the supply valve (215) while the ink supply system (200) is operating in standby mode. [5] Device (101) according to claim 4, wherein - the ink supply system (200) includes a bypass line (231) which can be opened or closed via a bypass valve (230); - the bypass line (231) is designed to divert ink (212) from the supply line (213) past the one or more printheads (103, 203) of the print bar (102); and - the device (101) is set up to open the bypass valve (230) in order to operate the ink supply system (200) in standby mode [6] Device (101) according to any of the preceding claims, wherein - the ink supply system (200) comprises a pump (225) configured to deliver ink (212) through the ink supply system (200); and - the device (101) is set up to operate the pump (225) and / or the supply valve (215) in such a way that the specified target volume flow (310) of ink (212) is conveyed via the supply line (213). [7] Device (101) according to claim 6, wherein - the ink supply system (200) includes an ink reservoir (211) for ink (212); and - the pump (225) is designed to pump ink (212) from the supply line (213) downstream of the filter unit (214) and the supply valve (215) back into the ink reservoir (211). [8] Device (101) according to one of claims 6 to 7, wherein the device (101) is configured, - To determine pressure measurements of the ink pressure (212) in the ink supply system (200), in particular in the supply line (213); and - to operate the pump (225) and / or the supply valve (215) depending on the pressure measurements in order to ensure that the specified target volume flow (310) of ink (212) is conveyed through the supply line (213). [9] Device (101) according to one of the preceding claims, wherein the device (101) is configured to output the status information via a user interface, in particular a user interface of the printing device (100). [10] Method (400) for determining the condition of a filter unit (214) of an ink supply system (200) of a print bar (102) of an inkjet printing device (100); wherein the filter unit (214) is arranged on a supply line (213) to the print bar (102) in series with a supply valve (215); wherein the filter unit (214) is configured to capture impurities from ink (212) conveyed through the supply line (213); wherein the method (400) comprises, - Determine (401) the degree of opening (320) of the supply valve (215) that results while ink (212) is conveyed through the supply line (213) at a specific target volume flow rate (310); and - Determining (402) status information regarding the state of the filter unit (214) based on the determined opening degree (320) of the supply valve (215); wherein the status information specifically indicates a contamination state of the filter unit (214) due to absorbed contaminants.

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