How to clean the print head of a CIJ printer, and CIJ printer

Abstract

A method for cleaning the print head (40) of a CIJ printer (1) is provided, wherein at least one fluid required during cleaning is actively supplied into the print head (40) and passively collected into a collection container (51), and a CIJ printer (1) that implements this method is also provided.

Description

Technical Field

[0001] The present invention relates to a method for cleaning a print head of a CIJ printer and a CIJ printer for implementing this method.

Background Art

[0002] Inkjet printers are a widely used classification of printers. So-called continuous inkjet printers (CIJ printers) are part of this classification family, are particularly suitable for industrial applications, and have thus achieved a high level of market penetration.

[0003] Continuous inkjet printers generally print using ink that is mixed with a variable ratio of solvent within the printer, thereby enabling control of, in particular, viscosity and jet speed. The ink mixed with the solvent is supplied under pressure to the nozzles of the print head, where the droplets required for the actual printing process are generated from the inkjet according to the basic principle of Rayleigh breakup of a laminar fluid jet, which is hereinafter referred to as the ink outlet nozzle. Droplet formation, particularly droplet size, is controlled, for example, by modulation applied to the inkjet by a suitably excited piezoelectric element.

[0004] The droplets thus generated are charged in a suitable manner and guided along a desired trajectory by a deflection electrode, which is also part of the print head, and this trajectory either guides the droplets to the desired position on the substrate to be printed or, if the printing process is not being carried out, guides the droplets to a collection device, such as a collection tube, for returning the ink for reuse.

[0005] As can be seen from the above, different fluids are transported and used within an inkjet printer. The components required for this, particularly lines, valves, pumps, compressors and reservoirs, together with the control electronics for these components, form the hydraulic system of the CIJ printer. It should be noted that the hydraulic system of a CIJ printer can also have several completely separate hydraulic circuits.

[0006] In each case, the elements to be printed, such as letters or numbers, are thus realized by a matrix or bitmap of ink droplets, with one dimension, namely the rows or columns of the matrix or bitmap, typically realized by the deflection of the ink droplets, and the other dimension realized by the supply of the material to be printed.

[0007] When a CIJ printer is operated for a long period of time, ink accumulates in the print head, not only in the ink outlet nozzles but also in the electrodes, deflection plates, and collection area, impairing the proper function of the CIJ printer. Therefore, it is common practice to perform cleaning processes on these components, especially the nozzles, as needed.

[0008] From the prior art, for example from U.S. Patent No. 8,628,169, it is known that a printhead is suspended in a cleaning station having liquid access for this purpose, in which cleaning fluid flows in through an inlet contained in the cleaning station until it comes into contact with the printhead or its components to be cleaned, thereby this inflow can also be achieved, under certain circumstances, by a jet directed at the components of the printhead to be cleaned. After a specified cleaning time, the cleaning fluid, which may be formed by a solvent, particularly for the ink, is discharged again. In this solution, the cleaning fluid is therefore supplied from outside the printhead for essentially passive cleaning, and the cleaning process takes place mainly within the tank.

[0009] While this method can achieve good cleaning results, it has several significant drawbacks. In particular, the solvent must be present in or supplied to the cleaning station, which requires an additional supply line and, in some cases, an additional pump. The cleaning process also takes a relatively long time.

[0010] An alternative approach to this is known, in particular from Japanese Patent Publication No. 2015-134435, in which an attempt is made to perform the entire cleaning process in each case by spraying a solvent from one or more additional nozzles in the print head onto the print head components to be cleaned while the printer is switched off and fully inside the print head, and attempting to remove the soiled solvent actively rather than passively by suction with a collection tube. However, the problem here is that the efficiency of the suction process is not optimal, and although the actual cleaning can be done faster than in the tank, the suction by the collection tube is not as efficient as expected, so it takes longer for the cleaned components to dry again.

[0011] Therefore, the object of the present invention is to provide a method for cleaning the printhead of a CIJ printer, which enables a high-speed cleaning and drying process using as few additional components as possible and yields good cleaning results, and to provide a CIJ printer capable of carrying out this method. These objections are achieved by a method for cleaning the printhead of a CIJ printer having the features of claim 1, and a CIJ printer having the features of claim 11. Advantageous further embodiments of the method and / or CIJ printer are the subject of their respective dependent claims. [Overview of the project]

[0012] The invention relates to a method for cleaning the print head of a CIJ printer, characterized in that at least one fluid required during the cleaning is supplied into the print head by being actively driven, particularly by the application of pressure (i.e., not through a nozzle outside the print head, for example, in a cleaning station), and is passively discharged into a collection container (i.e., without assistance from a suction mechanism or the like).

[0013] On the other hand, this approach allows for the extensive use of components already present in the CIJ printer, such as lines and / or pumps, to enable active solvent supply and solvent cleaning, particularly under pressure and with solvent jets, and significantly contributes to the rapid and complete cleaning of soiled areas of the printhead. This eliminates the need to provide such additional components in the cleaning station or collection container.

[0014] However, at the same time, such cleaning stations, essentially formed by collection containers, still exist. After interaction with the parts of the printhead to be cleaned, the fluid used for cleaning, especially the solvent, can simply flow passively into the collection container under the influence of gravity, thereby facilitating a rapid drying process without the need to actively aspirate the fluid used for cleaning in a complex manner, sometimes with incomplete success. This also makes implementing the cleaning station very easy and cost-effective.

[0015] In a particularly preferred embodiment of this method, the clean solvent required for cleaning is preferably supplied entirely through the collection tube of the print head and sprayed onto the components of the print head to be cleaned. This eliminates the need to provide a separate cleaning nozzle inside the print head.

[0016] In addition, the collection tube is positioned at a single point on the printhead, and from this point, the solvent jet can be directed very directly and with favorable geometric parameters towards the printhead components to be cleaned, particularly the ink outlet nozzle. This allows for rapid and effective removal of deposits.

[0017] Therefore, in this washing mode, the collection tube is not configured to have negative pressure for suction, but is pressurized with excess pressure and connected to the solvent reservoir. To return the CIJ printer to a usable state as quickly as possible, it is advantageous that the method includes a drying step, and that the air required for drying is supplied as an additional fluid through the printhead collection tube and blown onto the printhead components to be dried. In this case, it is particularly advantageous that the drying air jet is directed directly to the area that has been primarily moistened beforehand by the solvent jet, since it comes from the same opening, i.e., the opening of the collection tube. Thus, in this configuration, the collection tube is connected to a compressor and / or a compressed air reservoir.

[0018] The efficiency of both the actual cleaning and drying is further improved if the location where the fluid required during cleaning (i.e., cleaning fluid in the form of a solvent and / or air) is actively supplied into the print head (40), particularly under overpressure, is changed during cleaning. This can be achieved by changing the position of the collection tube within the print head, preferably by moving the collection tube, and most preferably by doing so substantially parallel to the jet axis of an unbiased inkjet.

[0019] In principle, discontinuous supply of the fluid required during cleaning is possible, for example, by impacting individual components with droplets of solvent. However, it has been shown that actively supplying the fluid required during cleaning with a jet results in better cleaning outcomes, which may be due to the fact that redeposition of previously separated dirt particles is more reliably avoided in this case.

[0020] It is desirable that this jet travels substantially parallel to the axial direction with respect to the direction in which the unbiased inkjet propagates during the printing operation of the CIJ printer. In practice, this choice of direction has proven to be particularly efficient in removing deposits from the components to be cleaned.

[0021] Preferably, the characteristics of the jet are modified during the active supply of the fluid required for the cleaning. For example, by changing the pressure at which the solvent is discharged from the collection tube, the impact point can be changed, taking into account the position of the collection tube, and / or affecting the jet profile. This can also allow the current jet parameters to be adapted to each component to be cleaned, and efficiently suppress undesirable behavior of the fluid used for cleaning at specific locations, such as droplet scattering when the jet hits a component to be cleaned at a point on the printhead where it is difficult to dry again.

[0022] It may also be advantageous that the modifications to the characteristics of the jet are adapted to the ink used in each case. If at least one pulsed discharge of at least one fluid, i.e., a pressure pulse, is performed, the probability of successfully removing even very stubborn deposits or residues during cleaning can be further increased.

[0023] In a preferred embodiment of this method, it is further provided that the success of the cleaning is verified by electrical verification before the process is completed. In principle, this can be done using additional components, but it can also be verified by the proper operation and monitoring of electrodes already present in the print head. A CIJ printer according to the present invention for carrying out the method according to the present invention comprises, in particular, a print head having at least one solvent tank, at least one ink tank, a nozzle for ejecting ink, a deflection electrode, and a collection tube for returning ink ejected from the nozzle and not used for printing. It also comprises a hydraulic system. The hydraulic system comprises components necessary for transporting and using the fluids used in the CIJ printer, in particular solvent, concentrated ink, ink, and, where applicable, compressed air, in particular lines, valves, pumps, compressors, and reservoirs, and also includes control electronics for these components, and can also form separate hydraulic circuits that are isolated from each other. In particular, the ink tank and the solvent tank are also components of the hydraulic system.

[0024] For the purposes of this disclosure, the ink tank should also be understood as an ink cartridge or another replaceable storage container into which ink is supplied. The term “solvent tank” should be understood similarly.

[0025] It is essential for the present invention that the hydraulic system (100) is configured to have means for actively supplying at least one fluid required for the cleaning into the print head (40), and that the CIJ printer (1) has a collection container for passively collecting the fluid after it has been used for cleaning.

[0026] Particularly preferably, the hydraulic system is designed to draw fluid from the collection tube in a first operating mode and to supply fluid to the collection tube under pressure in a second operating mode.

[0027] For example, when the collection tube is connected to a supply line that can be designed, for example, as a hose, the supply line is in fluid communication with a suction pump via a two-way valve in a first operating mode and the ink droplets sucked from the collection tube are supplied to a reservoir that can be formed, for example, by a mixing tank, while in a second operating mode, fluid communication of the supply line with a tank for a cleaning fluid, which can be formed particularly by a solvent tank, is established and there is a pressure pump to pressurize the solvent conveyed from this tank. In this example, the switching between operating modes can be done simply by switching the two-way valve.

[0028] In a preferred embodiment of the CIJ printer, the hydraulic system is designed to supply a different fluid under pressure to the collection tube in a third operating mode. Also in this case, an exemplary configuration that can achieve this and is based on the above exemplary configuration is shown here. For this purpose, the two-way valve is replaced by a two-way valve and in the third operating mode, fluid communication can be established between the supply line and a connection line to a compressor and / or a compressed air reservoir via the two-way valve, whereby compressed air can be blown out from the collection tube.

[0029] It has also been proven advantageous when the hydraulic system is designed such that the pressure at which the fluid is supplied to the collection tube is variable. This is particularly the case when it is constructed using a pump or compressor with controllable pressure, but it can also be achieved by appropriate means for influencing the line cross-section or by a controllable pressure reducing valve. One advantage of such a hydraulic system design is that it can change the impact point of the jet and / or influence the jet profile of the jet by changing the pressure. When the hydraulic system is designed to allow the introduction of a first fluid and a second fluid into the collection tube for ejection from the collection tube in addition to the normal suction function of the collection tube, a design that allows variable pressure for each of the two fluids can have specific advantages.

[0030] In advantageous variations of the CIJ printer, the hydraulic system is designed to have an intermediate reservoir for pressurized fluid, the contents of which can be supplied into the collection tube through other components of the hydraulic system, particularly lines. Such an intermediate reservoir, which may also be designed as an additional reservoir, can be used to enable pulsed discharge of fluid in the form of pressure pulses, which offers advantages in the cleaning process.

[0031] Another further development of the CIJ printer is that the collection tube is movable within the print head. It is particularly preferable that the directions in which the collection tube can move include directions parallel to the propagation direction. This opens up further parameters for changing the collision point of the fluid discharged from the collection tube and can be highly beneficial for both solvent-based cleaning processes and compressed air-based drying processes. [Brief explanation of the drawing]

[0032] The present invention will be described in more detail below with reference to the drawings illustrating exemplary embodiments. [Figure 1] This is a schematic diagram of the CIJ printer from the outside. [Figure 2] Figure 1 shows a schematic diagram of the essential components of the hydraulic system of the CIJ printer, and also a schematic diagram of the printhead configuration of the CIJ printer. [Figure 3] This is a flowchart of an exemplary embodiment of the method. [Modes for carrying out the invention]

[0033] The CIJ printer 1, schematically shown from the outside in Figure 1, has a base unit 10 with an HMI display 20, which is connected to a print head 40 via a headline 30 shown in a very shortened form. Furthermore, a cleaning station 50 having a collection container 51 is provided, into which the print head 40 can be inserted completely, or at least with its components to be cleaned (e.g., without its outer housing) for cleaning. In this exemplary embodiment, the cleaning station 50 is located on the side of the housing wall of the base unit 10, but it can also be implemented as a separate cleaning station.

[0034] Figure 2 schematically shows the essential components of the hydraulic system 100 of the CIJ printer 1 located inside the base unit 10, and the internal configuration of the print head 40 of the CIJ printer 1.

[0035] The hydraulic system 100 includes an ink tank 101 and a solvent tank 102. A pump 103 can deliver ink from the ink tank 101 to the mixing tank 110 via a line 104 equipped with a controllable valve 105. In addition, the pump 103 can deliver solvent from the solvent tank 102 via a line 106 equipped with a controllable valve 107, so that viscosity or jet speed can be controlled by adjusting the ratio of ink to solvent in the mixing tank 110.

[0036] From the mixing tank 110, the ink mixed with the solvent may be supplied from the base unit 10 through line 111 to the ink supply line that passes through the inside of the head line 30, where the ink is carried by pump 112 and flows through the pressure tank 113 while still inside the base unit. In this example, one side of the pressure tank 113, separated from the ink / hydraulic system by a membrane, is pressurized with compressed air from the compressor 150. Thus, the wet side deforms the membrane under operating pressure, and the compressed air forms back pressure.

[0037] Inside the print head 40, ink mixed with solvent enters tube 42 via a portion 41 of the ink supply line that runs through the inside of the print head 40. At the ink outlet nozzle formed by the nozzle 43 at the exit of tube 42, droplets necessary for the actual printing process are generated from the inkjet according to the basic principle of Rayleigh splitting of laminar fluid jets.

[0038] The droplets to be printed are charged in a defined manner at the charging electrode 44 and deflected by the deflection electrode 45. Their trajectories are shown as curved dashed lines in the schematic diagram of the printhead 40 configuration in Figure 2. Droplets that are not to be printed are not charged at the charging electrode 44 and therefore not deflected by the deflection electrode 45, and their trajectories are shown as straight dashed lines in the schematic diagram of the printhead configuration in Figure 2, ending in a collection device. The collection device is designed here as a collection tube 46. The collection tube 46 can be moved within the printhead 40 substantially parallel to the trajectories of the undefended ink droplets via a drive unit 47 formed by a motor and a spindle to which the collection tube 46 is attached.

[0039] The collection tube 46 is connected to line 48, which is a return suction line shown by a dashed line in Figure 2, and the return suction line is returned to the base unit 10 through the head line 30.

[0040] The return suction line is connected to the hydraulic system 100 via a valve block 120 having three two-way valves 121, 122, and 123. Depending on the positions of the two-way valves 121, 122, and 123, the collection tube 46 and the return suction line connected to the collection tube 46 may be used in different ways.

[0041] In the first position of the two-way valve 121, line 48, shown as a dashed line, actually operates as a return suction line. In this position, which is set particularly during normal printing operation, the suction pump 131 draws fluid, especially unprinted ink droplets, from the collection tube 46. In this example, the collection tube 46 is in fluid communication with the mixing tank 110 via line 132, which has the return suction line and the suction pump 131, so that unused ink droplets are returned to the supply in this mode of operation, and the material used to form them can be reused for printing.

[0042] The second position of the two-way valve 121 is selected when the fluid is transported in the opposite direction through line 48, which forms a return suction line, and as a result the fluid exits the collection tube 46. In particular, depending on the position of the two-way valve 122, the fluid transported through line 48 and exiting the collection tube 46 is either the solvent transported from the solvent tank 102 through line 142 by the pump 141, or compressed air generated by the compressor 150 and supplied through the two-way valve 123 and line 151, which are set accordingly. A pressure tank (not shown) may also be provided, through which compressed air can be supplied instead of or in addition to the compressor 150. The strength at which the solvent exits the collection tube can be set, for example, by appropriate control of the pump 141.

[0043] During normal printing operation of the CIJ printer 1, compressed air generated by the compressor 150 is supplied to the pressure tank 113 through a two-way valve 123 in the other switching position, where it is used to form a back pressure against the operating pressure that spreads across the wet side of the membrane of the pressure tank 113.

[0044] An exemplary embodiment of the cleaning method may be initiated using a wizard after the print head 40 has been fully or at least fully inserted into the cleaning station 50 along with its components to be cleaned, as can be seen from the flowchart in Figure 3.

[0045] In step S1, the collection tube 46 and the return suction line connected to the collection tube 46 are emptied by suction using a suction pump to remove any ink residue still contained in the collection tube 46.

[0046] Preferably in step S2, which may be performed entirely or partially in parallel with step S1, the collection tube 46 is moved as far away as possible from the ink outlet nozzle and the charging electrode 44 or deflection electrode 45, which is hereafter referred to as the “open” position. This is to prevent the solvent that exits the collection tube 46 in the next step and may still be contaminated with ink residue from accumulating on the components to be cleaned and having a counterproductive effect.

[0047] In step S3, the solvent is supplied to the return suction line and the collection tube 46 and passes through them. This cleanses the return suction line and the collection tube 46. Therefore, at the start of step S3, the solvent coming out of the collection tube 46 is contaminated with the in-house ink residue. This contamination continues to decrease over time. During this step, the solvent coming out of the collection tube 46 flows into the collection container 51, and in particular, the solvent simply seeps out of the collection tube 46, i.e., the solvent is not sprayed from its opening under high pressure, as long as the outgoing solvent can still be contaminated.

[0048] In step S4, the electrode block and nozzle 43 are cleaned. For this purpose, the collection tube 46 moves to the electrode block, and the solvent supplied through the collection tube 46 is pressurized by the pump 141, so that clean solvent is sprayed from the collection tube 46 and cleans the nozzle 43 and the charging electrode 44. This part of the cleaning process is very efficient because the opening of the collection tube is close to the components to be cleaned, and a sharp jet is generated by the pressurization by the pump 141. The efficiency of this process is also enhanced by the fact that the collection tube 46, and therefore the solvent jet coming out of the collection tube 46, are positioned essentially parallel or collinear with the trajectory of the undefended ink droplets, which is particularly advantageous for cleaning the ink outlet nozzle, i.e., the nozzle 43.

[0049] Next, in step 5, the deflection electrode 45 is cleaned. To do this, the collection tube 46 is returned to the "open" position. The solvent supplied through the collection tube 46 is pressurized again by the pump 141 so that clean solvent is sprayed from the collection tube 46 to clean the deflection electrode 46. Again, a few seconds is sufficient. It may be useful to use different pressures in this case, in particular, as this can compensate for different distances of the opening of the collection tube 46 from the surface to be cleaned, and the jet profile can be adjusted by the parameters of the distance of the opening from the surface to be cleaned and the pressure of the pump 141.

[0050] Furthermore, in steps S4 and S5, the contaminated solvent (generated during the washing process) passively flows into the collection container 51 located at the bottom, under the influence of gravity. It should be noted that the optimal pressure applied to the trajectory and solvent jet may also depend on the geometric shape of the printhead 40 to be cleaned and the ink used in each case. If stubborn localized stains are anticipated, it may be useful to induce a pulsed release of the cleaning fluid, for example, by short pressure spikes.

[0051] In step S6, after the solvent cleaning is complete, the collection tube 46 is moved slightly toward the ink outlet nozzle, i.e., nozzle 43. Here, line 48, which forms the return suction line in print mode, is disconnected from the solvent supply unit of the CIJ printer by the switching valve 122 and connected to its compressed air supply unit, which is usually a compressor 150, and / or a compressed air tank, and the liquid column of solvent still in the return suction line and collection tube is first blown out through the collection tube 46 by compressed air.

[0052] After a few seconds, the collection tube 46 returns completely to the "open" position in step S7 and remains in that position for a few seconds with the compressor 150 operating or the compressed air tank open, so that the fluid flowing out through the collection tube 46 is air, drying the deflection electrode 45 in this position.

[0053] In step S8, the collection tube 46 in this exemplary embodiment moves to just before the charged electrode 44 and nozzle 43, and then returns completely to its original "open" position, while compressed air from a compressor or compressed air tank flows continuously through the collection tube 46 to further dry the cleaned components. However, depending on the design of the print head 40, the drying results can be improved if the pressure of the compressed air fluctuates and is pulsed, in particular by pressure spikes that may occur at specific points along the path of movement.

[0054] At the end of the cleaning process in step S9, the collection tube 46 remains in the "open" position for several seconds, and then is moved by the compressor or compressed air tank to just before the ink outlet nozzle while compressed air is still being supplied. The supply of compressed air is then cut off, and the valve 121 is switched to reactivate the original function of line 48 and collection tube 46, namely the return of unused ink, and the normal printer controls for the printing process are also reactivated.

[0055] In this case, it is useful to place the printhead 40, or at least a portion of the printhead having components to be cleaned, in a cleaning station 50, which may be located in the CIJ printer 1 or may be designed as a separate device, during the cleaning procedure. In particular, if at least the components of the printhead 40 to be cleaned are introduced inside the cleaning station 50, this can be useful to effectively prevent contaminated solvent from leaking into the surroundings, for example, when the spray of solvent onto the surface to be cleaned causes the formation of droplets that propagate uncontrollably in different spatial directions. In this case, it is advantageous if the collection container 51 is a component of the cleaning station 50 or is detachably connected to the cleaning station 50. [Explanation of Symbols]

[0056] 1 CIJPRO 10 Base Units 20 HMI displays 30 Headlines 40 printheads 41 part 42 tubes 43 nozzles 44 charged electrodes 45 Deflection electrode 46 Collection tube 47 Drive unit Lines 48, 104, 106, and 111 50 Washing Stations 51 Collection container 100 Hydraulic Systems 101 Ink Tank 102 Solvent Tank 103 Pump 105, 107 valves 110 Mixing Tank 113 Pressure Tank 120 valve block 121, 122, 123 Two-way valve 131 Suction pump Lines 132, 142, and 151 141 Pump 150 Compressor Steps of the method from S1 to S9

Claims

1. A method for cleaning the print head (40) of a CIJ printer (1), characterized in that at least one fluid required during the cleaning is actively supplied into the print head (40) and passively discharged into a collection container (51).

2. The method according to claim 1, characterized in that the clean solvent required for the cleaning is preferably supplied completely through the collection tube (46) of the print head (40) and sprayed onto the components of the print head (40) to be cleaned.

3. The method according to claim 1 or 2, comprising a drying step, wherein air required for drying is supplied through the collection tube (46) of the print head (40) and blown onto the components of the print head (40) to be dried.

4. The method according to any one of claims 1 to 3, characterized in that the position at which the fluid required during cleaning is actively supplied into the print head (40) is changed during cleaning.

5. The method according to any one of claims 1 to 4, characterized in that the active supply of the fluid required for the cleaning is performed as a jet.

6. The method according to claim 5, characterized in that the jet extends substantially parallel to the axis in the direction in which the unbiased inkjet propagates during the printing operation of the CIJ printer (1).

7. The method according to claim 5 or 6, characterized in that the characteristics of the jet are changed during the active supply of the fluid required for cleaning.

8. The method according to claim 7, characterized in that the modification of the characteristics of the jet is adapted to the ink used in each case.

9. The method according to any one of claims 1 to 8, characterized in that at least one pulsed discharge of at least one fluid is performed.

10. The method according to any one of claims 1 to 9, characterized in that the results of the cleaning are verified by electrical verification before the completion of the method.

11. A CIJ printer (1) for performing the method described in any one of claims 1 to 10, At least one solvent tank (102) and At least one ink tank (101) and A print head (40) having a nozzle (43) for ejecting ink, a deflection electrode (45), and a collection tube (46) for returning ink ejected from the nozzle (43) but not used for printing, Hydraulic system (100) and Equipped with, The hydraulic system (100) is configured to have means for actively supplying at least one fluid required for cleaning into the print head (40), and the CIJ printer (1) is characterized by having a collection container for passively collecting the fluid used for cleaning after it has been used for cleaning.

12. The CIJ printer according to claim 11, characterized in that the hydraulic system (100) is designed to draw fluid from the collection tube (46) in a first operating mode and to supply fluid to the collection tube (46) under pressure in a second operating mode.

13. The CIJ printer according to claim 12, characterized in that the hydraulic system (100) is designed to supply a fluid other than the fluid supplied in the second operating mode to the collection tube (46) under pressure in the third operating mode.

14. The CIJ printer according to claim 12 or 13, characterized in that the hydraulic system (100) is designed such that the pressure at which the fluid is supplied to the collection tube (46) is variable.

15. The CIJ printer according to any one of claims 11 to 14, characterized in that the hydraulic system (100) is configured to have an intermediate reservoir for pressurized fluid, the contents of which can be introduced into the collection tube (46).

16. The CIJ printer according to any one of claims 1 to 15, characterized in that the collection tube (46) is displaceable within the print head (40) by a drive unit (47).

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