DEVICE AND METHOD FOR RINSE AND / OR OPERATION OF AN INK OR INK JET PRINTING HEAD EQUIPPED WITH A PRE-CONNECTED PRESSURE DAMPER

Description

[0001] The invention relates to a device and a method for flushing and / or operating an inkjet or inkjet print head equipped with an upstream pressure damper, wherein the pressure damper is provided with a closed damper chamber bordered at least partially by a damper foil, comprising a refill valve arranged in the damper chamber for refilling the damper chamber with ink in response to a bulging of the damper foil into the damper chamber, wherein an external pressure is exerted on at least one region of the damper foil bordering the damper chamber by means of a controllable device arranged outside the damper chamber in order to open the refill valve arranged in the damper chamber and thereby create a continuously open channel through the pressure damper for flushing the inkjet or inkjet print head,and / or to apply an adjustable preload to the refill valve located in the damper chamber.

[0002] The problem of ensuring the most consistent ink supply possible was recognized early on in the development of ink-based writing or printing devices. For example, DE 2 224 590 A describes vibrations in the ink supply tube, which can temporarily interrupt the ink supply. It is therefore proposed to arrange a small auxiliary reservoir, fed from the actual ink container, on a carriage supporting the writing device. From there, the ink is to be guided in a short, thin tube to the actual writing needle with as little vibration as possible. However, it is described as a disadvantage that vibrations are also generated on a carriage, which, for example, result in the increased formation of air bubbles.The ink carried on the carriage also represents an additional mass that must be accelerated with each change in carriage speed, and this in turn causes pressure surges in the ink system.

[0003] In order to reduce pressure fluctuations in an auxiliary ink reservoir carried on the carriage side as much as possible, DE 31 37 970 A1 proposes arranging a flexible bladder within such an auxiliary reservoir, the interior of which is connected to the atmosphere, so that the ink pressure within the auxiliary reservoir always remains approximately constant, namely at approximately the level of atmospheric pressure. However, the construction of such a system is very complex.

[0004] DE 35 25 810 A1 discloses a dampening and filtering element for the ink supply to an inkjet print head, comprising a trough-shaped, meandering depression in a base portion, which is closed off at the top by a flexible wall and thus separated from the atmospheric pressure above the flexible wall. In the event of pressure fluctuations, the flexible wall can temporarily bulge inwards or outwards, thereby dampening such pressure fluctuations. Here, the space in the trough-shaped depression is closed off from the atmosphere, but not from a supply hose, from which, due to the lack of a valve, pressure fluctuations can constantly occur. The base portion is provided with a mounting wall that serves as a cover plate, to which the actual inkjet print head can be secured using screws.An extraction channel leads from the meandering recess in a base section to a gap between the cover plate and the inkjet print head, directing the air-free ink fluid to a cavity containing the inkjet print head's piezoceramic pressure generators. Presumably for flushing purposes, a second channel is provided in the mounting wall serving as the cover plate for mounting the inkjet print head. This second channel terminates blindly at an external connection—presumably for a flushing hose. For flushing purposes, a flushing hose would have to be manually connected to this connection. Such a flushing hose cannot remain permanently connected because it would reintroduce pressure fluctuations into the printing system. However, manually connecting and disconnecting a flushing hose prevents automated flushing.

[0005] DE 690 06 521 T2 describes a plate-shaped pressure damper for an inkjet printer, which has one or more damper chambers, each bordered by a flexible film in the area of ​​the plate base(s). These flexible films can compensate for pressure fluctuations by means of appropriate curvature. Furthermore, a filter is provided to remove air bubbles and other contaminants from the ink. If irregular ink ejection occurs from the inkjet print head, cleaning is performed to subject the ink in the ink line to a pressure or tensile force, thereby expelling the foreign matter from the clogged nozzles.However, in this device, the pressure damper is provided with a continuous channel from its inlet to its outlet, which on the one hand impairs its damping capacity and on the other hand makes it difficult to generate the negative pressure required for modern piezo inkjet print heads, because ink is immediately sucked in whenever there is a negative pressure.

[0006] US 2017 / 0 151 805 A1 discloses a liquid ejection device with a pressure regulating mechanism provided in a liquid supply path for supplying liquid to a liquid ejection unit. The pressure regulating mechanism comprises a chamber for receiving a liquid, which is bordered in one region by a diaphragm wall, which is surrounded at the edge by a bead with a wave-shaped cross-section and is fixed to the housing of the chamber beyond this bead. Beyond this diaphragm wall, a second chamber acts as a control chamber, opposite the liquid-filled chamber. Either a filled balloon is arranged in the control chamber to exert pressure on the diaphragm wall, or one or more limiting bodies are arranged in the liquid-filled chamber to limit movement of the diaphragm wall into this liquid chamber.When the pressure conditions at the diaphragm wall change, it can shift perpendicular to its surface to a limited extent, deforming its bead, and the volume within the chamber changes accordingly. However, due to its dimensional stability, the diaphragm wall can only deform in the area of ​​the bead and thus deforms nonlinearly, so that any deflection of the diaphragm wall is not proportional to the differential pressure.

[0007] US 2016 / 0 257 126 A1 discloses a liquid ejection device having a plurality of pressure chambers, each generating a pressure for ejecting liquid from a nozzle. Furthermore, this prior art arrangement includes a common liquid chamber for storing a liquid that can be supplied to the multiple pressure chambers. A flexible film forms part of the wall surface of the common liquid chamber. In this document, one embodiment includes a "damper chamber" opposite the liquid-filled chamber beyond the flexible film. However, neither of the two chambers adjacent to the flexible film is connected to a print head. Instead, there are other pressure chambers that are connected to the nozzles of the print heads but are not in contact with the film. Furthermore, a refill valve is not disclosed anywhere.A valve covered with a foil is connected upstream of a peripheral pressure generation unit, so that the valve position depends on the ambient air pressure. However, this ambient air pressure cannot be influenced.

[0008] The disadvantages of the described prior art give rise to the problem initiating the invention, namely to develop a device for flushing a print head together with an upstream pressure damper that is as simple as possible, wherein the pressure damper should have good damping properties and should also be able to generate and maintain the negative pressure required for piezo inkjet print heads.

[0009] This problem is solved by a generic device having a valve arranged in the chamber for refilling this chamber with ink from an ink reservoir or intermediate container in response to a bulging of the film into the chamber by a controllable device arranged outside the chamber for exerting an external pressure on at least one area of ​​the film bordering the chamber, in order to open the valve arranged in the chamber and thereby create a continuously open channel through the pressure damper for flushing the ink or inkjet print head, wherein the device for exerting an adjustable preload on the refill valve has a control chamber hermetically sealed from the environment, a) with a connection for a control line arranged on the housing of the control chamber to allow a control fluid to flow into or out of the control chamber and to influence the filling pressure within the control chamber, and b) with an opening which faces the damper foil so that the damper chamber and the control chamber are only separated from each other by the damper foil, c) wherein the damper foil is designed as a flexurally elastic foil and is subject to the pressure difference between the pressures in the damper chamber and in the control chamber and bulges into the chamber where the lower pressure prevails, d) wherein the opening in the control chamber has a circular circumference so that the damper foil can bulge uniformly over its entire surface without local overloading of individual surface areas.

[0010] The refill valve within the damper chamber of the pressure damper closes the inlet side of the channel, which is open on both sides, as per DE 690 06 521 T2, as long as the refill valve is closed. This completely isolates the pressure within the damper chamber from pressure fluctuations on the inlet side and only briefly connects it to the ink supply system during short refill phases. Furthermore, the refill valve can be set to open at a negative pressure threshold below the vacuum typical for piezo inkjet print heads; it can even be set to close again at a still negative pressure value (i.e., below atmospheric pressure), meaning that the pressure in the damper chamber never reaches atmospheric pressure.This refill valve can react to the bulging of the damper foil due to the pressure difference between the internal ink pressure and the external atmospheric pressure. However, since it is located entirely within the damper chamber, it cannot be opened from the outside, making flushing through the pressure damper impossible. Therefore, an external flushing connection must be provided, similar to that in DE 35 25 810 A1. However, as in that case, automatic flushing is not possible here either, because the flushing hose must be manually removed after each flushing process to avoid pressure fluctuations. Therefore, an externally controllable device is provided outside the chamber to exert external pressure on at least one area of ​​the foil surrounding the chamber.This creates a pressure difference on the damper foil that is greater than the ink pressure in the damper chamber, simulating an internal negative pressure, which causes the internal refill valve to open. This creates a continuous channel for flushing the print head. After the flushing process is complete, a suitable control signal removes the external pressure from the damper foil. Only atmospheric pressure remains, and therefore the refill valve only responds to an internal negative pressure, above which it closes.

[0011] Because the control chamber has at least one opening facing the area of ​​the damper foil bordering the damper chamber, the damper chamber and the control chamber lie directly opposite each other and are only separated by the damper foil. The damper foil is then subjected to the pressure difference between the pressures in the damper chamber and in the control chamber and bulges into the chamber where the lower pressure prevails. While the pressure in the damper chamber will usually be close to atmospheric pressure, possibly slightly below, because a print head typically requires a small negative pressure, the pressure in the control chamber can be varied within wide limits, with both negative pressure compared to atmospheric pressure and positive pressure compared to atmospheric pressure being conceivable.However, unlike the pressure in the damper chamber, this pressure within the control chamber can be actively influenced from the outside. This allows the curvature of the damper foil to be specifically influenced at any time and thus adjusted to open the refill valve in the damper chamber. Once this refill valve is opened, the print head can be flushed with ink by simply applying pressure from the ink reservoir, for example, using a pump.

[0012] To specifically influence the pressure within the control chamber, it must be hermetically sealed or closable from the environment, i.e., the atmosphere. The control chamber typically has only one opening, which faces the damper foil, and possibly a connection from which the fill pressure or fill volume can be adjusted. If two or more print heads are to be flushed simultaneously, the control chamber could also have multiple openings, each facing one of the damper foils of the various pressure dampers.

[0013] A flow of a control fluid into or out of the control chamber is made possible by the fact that a connection for a control line is arranged on the housing of the control chamber.

[0014] An optimal effect is achieved when the opening in the control chamber is approximately the same size as the opening in the damper chamber covered by the damper foil, so that the damper foil can move freely over its entire flexible area between the two chambers.

[0015] The position of the damper foil can thus vary in response to a varying filling pressure within the control chamber and / or in response to a varying mass or quantity of a fluid within the control chamber. Both effects influence the pressure and the actual volume of the control chamber and, accordingly, the deflection of the damper foil between the control chamber and the damper chamber. The control chamber could therefore be filled with a different fluid than the damper chamber, in particular even with a liquid, e.g., ink or water.However, filling the control chamber with air offers the advantage that it behaves exactly like atmospheric air without a control chamber. This means that the control chamber, in a depressurized state—i.e., without overpressure or underpressure relative to atmospheric pressure—is imperceptible to the damper foil. Thus, the original switching behavior—namely, the pressure-dependent opening of the refill valve when there is negative pressure in the damper chamber, and its closing, for example, after pressure equalization—is not affected. This depressurized state can be achieved at any time by opening a valve between the control chamber and the atmosphere.

[0016] The invention can be further developed in such a way that the opening in the control chamber facing the damper foil is covered by a control foil. Such a thin control foil has the advantage of pronounced flexural elasticity or even tensile elasticity and can therefore react sensitively to a change in the filling mass and / or filling pressure within the control chamber. Such a control foil can then form a flat contact with the actual damper foil, so that both together behave more or less like a single foil. However, the use of a separate control foil is recommended, especially if air is not used as the control fluid. The control device can then be disassembled from the pressure damper without the control fluid escaping. Naturally, such a control foil should be impermeable to air and / or liquids.Such a control foil should be flexible and / or elastic so that its deflection can be easily controlled, and it should be tightly fixed all around the edge of the opening in the control chamber for its anchoring and at the same time for sealing the control chamber.

[0017] Furthermore, it has proven effective to have the opening in the control chamber approximately the same dimensions as the edge area of ​​the damper chamber formed by the damper foil. This ensures that the pressure difference between the two chambers has a maximum influence on the damper foil and leads to its optimal deflection.

[0018] The opening in the control chamber should have a circular circumference so that the damper foil can bulge uniformly over its entire surface without local overloading of individual surface areas.

[0019] Because the control chamber housing is fixed or can be fixed to the pressure damper, abutment forces caused by the pressure in the control chamber, which, in the event of excess pressure, tend to push the control device away from the pressure damper, can be directly diverted to the pressure damper. Adhesive bonding, for example, is a simple method for securing the control device; other fastening methods, such as screwing, are removable and therefore allow for replacement of the control device according to the invention, independent of the pressure damper itself.

[0020] The invention is further characterized by the use of air as the control fluid. This is always present in sufficient quantities in the atmosphere and therefore does not need to be stored. A compressor can compress the air to fill the control chamber; to empty it, an outlet valve can simply be opened, allowing pressure equalization with the atmosphere.

[0021] It is within the scope of the invention that a pressure sensor is arranged on the control chamber and / or on the control line in order to detect and / or regulate the control pressure. This allows a control loop to be implemented, for example, to ensure reliable operation and / or to prevent a film from tearing due to excess pressure.

[0022] A pressure sensor can also be installed on the pressure damper or downstream of it to detect the opening of the refill valve in the damper chamber. This is because such a refill valve is usually opened as a result of the damper foil bulging, especially if this bulging is due to a negative pressure within the damper chamber. When the refill valve opens, this pressure rises again.

[0023] The refill valve in the damper chamber can be preloaded into a closed position by a spring element. At the same time, this spring element can act directly or indirectly on the damper foil, preloading or bulging it outward. This creates a counterforce to external air pressure, which is normally unable to open the refill valve. Only when the pressure within the damper chamber decreases due to consumption of the ink contained therein does the external pressure gain the upper hand after a certain hysteresis and can open the refill valve, thus implementing a simple two-point control.

[0024] This coupling can be realized in such a way that the spring element presses a movable element of the refill valve in a pre-tensioned state from the inside against the damper foil, and if necessary together with it in an outward direction.

[0025] Finally, it is in accordance with the teaching of the invention that the control pressure of the control fluid required to open the refill valve is greater than the force of the spring element required to close the refill valve, divided by the area of ​​the damper foil. In this case, pressure can be exchanged via the damper foil, i.e., in a state of equilibrium, the total forces acting on both sides of the damper foil - i.e., within the control chamber on the one hand, and within the damper chamber on the other - are approximately equal. On the control chamber side, only the control pressure contained therein acts, while on the damper chamber side, the pressure there and, if applicable, the preload of a spring element are effective. Assuming that the pressure in the damper chamber is approximately equal to atmospheric pressure, this is compensated for without additional control pressure, i.e., even when atmospheric pressure prevails in the control chamber.A control pressure within the control chamber - i.e. an overpressure compared to atmospheric pressure - must therefore essentially apply or overcome the preload force of a spring element within the damper chamber.

[0026] A device according to the invention can also be used to operate an inkjet or inkjet print head equipped with an upstream pressure damper, wherein the pressure damper is provided with a closed damper chamber bordered at least partially by a damper foil, in which a refill valve is arranged for refilling the damper chamber with ink in response to a bulging of the damper foil into the damper chamber, provided that a controllable device is provided outside the damper chamber for exerting a preferably variable and / or predetermined external pressure on at least one region of the damper foil bordering the damper chamber in order to exert an adjustable preload on the refill valve arranged in the damper chamber. Without such a device, the preload depends only on the atmospheric pressure, which is subject to weather-related fluctuations.However, the altitude above sea level also has a noticeable influence on atmospheric pressure. Since the switching threshold is only a few millibars of differential pressure, such fluctuations or deviations can have a negative impact on the pressure result. However, with a device according to the invention, a switching threshold for an internal refill valve can be set to a specific value. For this purpose, an externally acting (counter) pressure can be kept exactly constant beyond the diaphragm of a damper chamber, i.e., outside it, and / or controlled to specific pressure values ​​as required.

[0027] Accordingly, the invention can also be described as a device for operating and / or flushing an inkjet or inkjet print head equipped with an upstream pressure damper, wherein the pressure damper is provided with a closed damper chamber bordered at least partially by a damper foil, comprising a refill valve arranged in the damper chamber for refilling the damper chamber with ink in response to a bulging of the damper foil into the damper chamber, and a controllable device arranged outside the damper chamber for exerting external pressure on at least one area of ​​the damper foil bordering the damper chamber in order to open the refill valve arranged in the damper chamber and thereby create a continuously open channel through the pressure damper for flushing the inkjet or inkjet print head,and / or to apply an adjustable preload to the refill valve located in the damper chamber.

[0028] Further features, details, advantages, and effects based on the invention will become apparent from the following description of a preferred embodiment of the invention and from the drawings. Herein: Fig. 1 is a perspective view of a device according to the invention for flushing an ink or inkjet print head, mounted on a pressure damper arranged upstream of the ink or inkjet print head; Fig. 2 is the pressure damper of the arrangement according to Fig. 1 in a front view, with the flushing device removed; Fig. 3 a rear view of the pressure damper from Fig. 2 ; Fig. 4 a longitudinal section through the arrangement according to Fig. 2 in normal pressure condition; Fig. 5one of the Fig. 4 corresponding longitudinal section through the Fig. 2during flushing; Fig. 6 a pressure damper according to the invention according to another embodiment of the invention, in a front view similar to Fig. 2 ; Fig. 7 a rear view of the pressure damper from Fig. 6 ; and Fig. 8 a section through the pressure damper from Fig. 6 along a central cutting plane parallel to the front.

[0029] The Fig. 1 The device 1 shown in the drawing serves the purpose of flushing an ink or inkjet print head (not shown) with ink through an upstream pressure damper 2.

[0030] The internal structure of the pressure damper 2 is shown in the Figures 2 to 5to recognize: The pressure damper 2 is provided with a closed damper chamber 4, which is at least partially bordered by a damper foil 3, in which a refill valve 5 is provided, which controls the refilling of the damper chamber 4 with ink in response to a bulging of the damper foil 3 into the damper chamber 4.

[0031] While the entire pressure damper module 2 has a cuboid shape, the actual damper chamber 4 contained therein is approximately circular. However, the housing 7 of the pressure damper 2 has the shape of a frame 8 open on both flat sides with four interconnected walls, namely a top side 9, a bottom side 10, and two longitudinal sides 11 connecting these.

[0032] On the top side 9 there is a first hose connection piece 12 for a first hose, which leads, for example, to an ink reservoir.

[0033] On the underside 10 is a second hose connection 13 for a second hose, which directs the ink to the actual print head. Of course, this connection could also be made without a hose if the pressure damper is located in the immediate vicinity of the print head.

[0034] The two flat sides of the housing 7, which is preferably manufactured as an injection-molded part, are open; however, the top side 9, bottom side 10 and the two long sides 11 are connected to each other by an inner partition wall 14, which preferably corresponds to the Fig. 3 shown back 15 of the frame 8 is closer than the one shown in Fig. 2 shown front 16.

[0035] Due to the vertical arrangement with an inlet at the top and an outlet at the bottom, the ink can flow inside the pressure damper under the influence of gravity alone.

[0036] The internal structure of the pressure damper 2 is divided into an upper section 17 and a lower section 18. The space in the lower section 18 in front of the intermediate wall 14 is almost completely occupied by the damper chamber 4, which is surrounded by a cylindrical outer surface 19, which is arranged concentrically to a horizontal axis in the center of the lower section 18. The damper chamber 4 does not extend completely over the entire thickness of the pressure damper 2, but only from the open front side 15 of the frame-shaped housing 7 to its intermediate wall 14. The cylindrical outer surface 19 is connected in sections to the underside 10 and the two longitudinal sides 11, as in Fig. 2 shown.

[0037] In the upper section 17 of the pressure damper, behind the partition wall 14, there is an approximately rectangular filter chamber 20, which borders the upper side 9 on the one hand and one of the two long sides 11 on the other. A fine-mesh ink filter 21 is arranged in this filter chamber 20, with a base plane parallel to the partition wall 14. The ink filter 21 is spaced from both the partition wall 14 and the rear side 15 of the housing 7.

[0038] The entire open front side 16 of the housing 7 is covered by a flexible, elastic film 22 glued to the front end edges of the upper, lower and longitudinal walls 9, 10, 11, which forms the damper film 3 in the area of ​​the damper chamber 4.

[0039] On the other hand, the entire open rear side 15 of the housing 7 is covered by a preferably slightly flexible film 23 glued to the rear end edges of the upper, lower and longitudinal walls 9, 10, 11.

[0040] From the upper hose connection piece 12 as ink inlet, a first flow channel 24 integrated in the housing 7 leads to the rear part of the filter chamber 20, behind the ink filter 21.

[0041] In the lower region of the filter chamber 20, a second flow channel 25 branches off laterally from its front part between the ink filter 21 and the intermediate wall 14 and extends in front of the intermediate wall 14 approximately horizontally from the filter chamber 20 to the opposite longitudinal side 11 of the housing 7.

[0042] There is an opening through the intermediate wall 14, and this is followed by a third flow channel 26, which in turn runs behind the intermediate wall 14 and extends radially inwards with respect to the damper chamber 4 to behind its center 27.

[0043] There, namely behind the center 27, the damper chamber 4, there is again an opening towards the damper chamber 4, and there is then the refill valve 5, which finally opens with its downstream opening into the damper chamber 4.

[0044] Thus, when the refill valve 5 is open, ink can flow from the inlet-side hose connection piece 12 via the first flow channel 24, the rear filter chamber section, through the ink filter 21 to the front filter chamber section, and from there further via the second flow channel 25 and the third flow channel 26, as well as through the refill valve 5 into the damper chamber 4.

[0045] As soon as the damper chamber 4 is refilled, the refill valve 5 closes again, and from there the ink can then be sucked in and printed by the print head as needed, while the refill valve 5 remains closed and thus keeps upstream pressure surges away from the damper chamber 4 and thus from the actual printing system.

[0046] The refill valve 5 is opened and closed only depending on the pressure conditions in the damper chamber 4. For this purpose, the opening from the third flow channel 26 into the damper chamber 4 is covered at its mouth facing the flow channel 26 by an internal film or membrane, which is normally pressed firmly against the mouth of the opening by the pressure upstream of the damper chamber 4, thus closing it.

[0047] This inner foil or membrane cannot be opened from the outside, but can only be pushed outwards by a central tappet 28 located within the damper chamber 4, i.e., in the direction of the rear side 15 of the housing 7, whereby the inner foil or membrane is then lifted from the upstream opening of the opening between the third flow channel 26 and the damper chamber 4, thus opening the refill valve 5.

[0048] The plunger 28 is located on the rear side of a plate 29, which rests flat against the inside of the damper foil 3. The plate 29 can have a circular disk-shaped geometry and be integrated with the plunger 28 as a single part, for example, manufactured with the latter as a single injection-molded part.

[0049] The tappet 28 is loosely guided within the opening between the third flow channel 26 and the damper chamber 4, wherein this opening can be surrounded by a cylindrical edge or apron projecting into the damper chamber 4 to improve the guidance.

[0050] The plunger 28 then communicates its position to the plate 29, which therefore always remains concentric with the center 27 of the damping chamber 4.

[0051] In addition, the plunger 28 also serves as a guiding core for a spring element, in particular a spiral spring 30, which loosely winds around the plunger in the form of a helical line. This spiral spring 30 is supported on the one hand on the intermediate wall 14 in the vicinity of the opening between the third flow channel 26 and the damper chamber 4, and on the other hand on the back of the plate 29. The spiral spring 30 is preformed in such a way that, in the force-free state, it is slightly longer than the thickness of the damper chamber 4 between the intermediate wall 14 and the damper foil 3 and therefore strives to press the plate 29 firmly against the damper foil 3 from the inside and can even push the flexurally elastic damper foil 3 slightly outwards.

[0052] If the print head gradually sucks more and more ink out of the damper chamber 4, a negative pressure is created there, and the atmospheric pressure pressing on the outside of the damper foil 3 gradually compresses the outwardly pre-tensioned spring 30, whereby the plunger 28 is pressed ever deeper into the opening between the third flow channel 26 and the damper chamber 4 and finally the foil or membrane can lift off from the opening on the other side of the opening, thereby opening the refill valve 5. The incoming ink now refills the damper chamber 4, and the damper foil 3 consequently bends outwards again, whereby the plunger 28 gradually moves out of its opening due to the compression spring 30 and can then close the inner foil or membrane again.

[0053] This arrangement has the advantage that not only are particles and air bubbles retained in the ink filter 21, but also pressure surges and fluctuations are kept away from the actual print head by the membrane of the closed refill valve 5, so that it is optimally supplied with pure, evenly flowing ink for the printing process.

[0054] However, this arrangement has another disadvantage, which is related to the fact that the refill valve 5 is located entirely within the damper chamber 4, completely inaccessible from the outside. External overpressure upstream of the refill valve 5 cannot open it, but only presses the diaphragm even more strongly against the edge of the opening between the damper chamber 4 and the flow channel 26 located immediately upstream of it.

[0055] Therefore, the pressure damper 2 would be more likely to break than the ink or inkjet print head could be flushed with ink through the pressure damper 2 if it is not possible to open the refill valve 5 within the damper chamber 4 before flushing.

[0056] For this purpose, the invention provides a controllable device 6 arranged outside the damper chamber 4 for exerting an external pressure on at least one area of ​​the damper foil 3 bordering the damper chamber 4 in order to open the refill valve 5 arranged in the damper chamber 4 and thereby create a continuously open channel through the pressure damper 2 for flushing the ink or inkjet print head.

[0057] The externally controllable device 6 comprises a cuboid-shaped, preferably plate-shaped housing 31 with two opposing flat sides 32 and four end faces connecting them, namely an upper side 33, a lower side 34 and two longitudinal sides 35. As with the housing 7 of the pressure damper 2, the upper and lower sides 33, 34 of the housing 31 can be of equal size to one another, but are shorter than the two longitudinal sides 35, which are also equal to one another.

[0058] Preferably, the base area of ​​the housing 31 of the controllable device 6 is approximately equal to the base area of ​​the housing 7 of the pressure damper 2. Thus, the housing 31 can be placed flat and approximately congruently on the front side 16 of the housing 7 and can even be fixed there in this position, for example by means of adhesive.

[0059] The housing 31 encloses a control chamber 36, which has approximately the same geometry and base area as the damper chamber 4, and is also positioned in the housing 31 according to the position of the damper chamber 4 in the housing 7, so that when the pressure damper 2 and the controllable device 6 are joined together in a congruent manner, the control chamber 36 can also be brought into alignment with the damper chamber 4.

[0060] The control chamber 36 can have an opening 37 on one or both flat sides 32 of the controllable device 6. Normally, i.e., for controlling a single damper foil 3, only a single opening 37 should be present, and the flat side 32 with the single opening 37 can be referred to below as the front side. Only if two pressure dampers 2 are to be controlled simultaneously can a second opening 37 be provided, which would then be located on the other flat side 32.

[0061] It is conceivable to cover the opening 37 of the control chamber 36 with a foil facing the pressure damper 2. Such a control foil should be flexibly elastic, at least as flexible as the damper foil 3. However, such a control foil represents additional expense and is therefore justified primarily if air is not used as the filling medium within the control chamber 36; in this case, such a control foil would allow the control device to be disassembled without the filling medium escaping.

[0062] The controllable device 6 is positioned with its flat side 32 having the opening 37 on the front side 16 of the pressure damper 2 in such a way that the control chamber 26 and the damper chamber 4 are approximately concentric to one another and are separated from one another there only by the damper foil 3.

[0063] The control chamber 36 is tightly closed by the housing 31 on the one hand and by the damper foil 4 covering the opening 37 in its flat side 32; however, in the edge of the control chamber 36 there is a control opening 38 passing through the respective end face, i.e. preferably a longitudinal side 35 or the underside 34 of the controllable device 6, which can be provided with an internal thread for screwing in a hose connection piece. In the embodiment according to Fig. 1 For example, an angle piece 39 is screwed into it, to which a control hose can then be attached.

[0064] A control medium can then be conveyed into the control chamber or discharged from there via such a control hose. The control medium is preferably compressed air or compressed atmospheric air, although a liquid is also conceivable.

[0065] If a control medium is conveyed or pressed into the control chamber 36, the damper foil 4 bulges out of the control chamber 36 and into the damper chamber 4 under the resulting internal overpressure. Due to the plate 29, it presses the plunger 28 against the internal foil or membrane of the refill valve 5, opening it even when there is no negative pressure in the damper chamber 4. The refill valve 5 is now open, and the print head can be flushed with ink.

[0066] Once the flushing process is complete, the excess pressure can be released from the control chamber 36, and the spring 30 pushes the plate 29, including the plunger 28 and the damper foil 3 adjacent to it, outward again, i.e., in the direction from the damper chamber 4 to the control chamber 36, thereby closing the refill valve 5. Once the control chamber 36 is completely vented or depressurized, atmospheric pressure again takes over the counterpart of the compression spring 30, and the refill valve 5 is automatically opened and closed again to regulate the pressure within the damper chamber within narrow limits as part of a two-point control.

[0067] Within the scope of the present invention, the operating point of the spring 30 can also be adjusted by applying a variable pressure to the outer side of the damper foil 3 facing away from the damper chamber 4. This means that if the spring 30 loses its tension over time, for example, increasing the pressure beyond the damper foil 3 can cause a greater deflection of the spring 30, so that it is adjusted to an operating point where it again generates a stronger spring force, which must then be overcome to open the refill valve 5.

[0068] In the Figures 6 to 8 The device 1' shown for flushing a not-shown ink or inkjet print head with ink through an upstream pressure damper 2' is an integrated embodiment where the flushing device 1' is integrated with the pressure damper 2'.

[0069] Since the basic structure and functionality is the same as in the embodiment according to the Figures 1 to 5 , corresponding parts in the drawing are provided with corresponding reference symbols.

[0070] The Fig. 8 most likely the Fig. 2 , because in both cases - in one case by removing the device 1 at Fig. 2 , in the other case by a section through the device 1' integrated with the pressure damper 2' - substantially only the pressure damper 2, 2' can be seen, namely from the damper foil 3, 3' covering the damper chamber 4, 4'.

[0071] The housing 7' surrounding the pressure damper 2' is visible in the form of a frame 8' with a top side 9', a bottom side 10', and two connecting longitudinal sides 11'. On the top side 9' there is an inlet-side hose connection 12', and on the bottom side 10' there is an outlet-side hose connection 13'.

[0072] In contrast to the device 1 with the pressure damper 2, in the second embodiment the depth extension of the frame 8' - i.e. the distance between its rear side 15' and its front side 16' - does not correspond to the depth extension of the damper chamber 4' or of the pressure damper 2' receiving it, but is greater than that and corresponds to the sum of the depth extensions of the pressure damper 2' on the one hand and of the device 1' according to the invention for controlling the refill valve 5' within the damper chamber 4'.

[0073] The pressure damper 2' itself is divided into an upper section 17' and a lower section 18'. While the actual damper chamber 4' is located in the lower section 18' - surrounded by a preferably cylindrical outer surface 19' - an optional filter chamber 20' with an ink filter 21' is arranged in the upper section 17'. The filter chamber 20' is connected upstream of the ink filter 21' by a first flow channel 24' to the inlet-side hose connection piece 12', while a second flow channel 25' connects the part of the filter chamber 20' located downstream of the ink filter 21' to the refill valve 5' in the center 27' of the damper chamber 4'.

[0074] A third flow channel 26' then leads from the periphery of the damper chamber 4' to the drain-side hose connection piece 13'.

[0075] The internal structure of the refill valve 5' can be identical to the refill valve 5 according to the Figures 4 and 5or have a similar or equivalent structure.

[0076] As in the first embodiment, the actual pressure damper 2' can be covered on its two flat sides by at least one film each, namely by a front film 22' and by a rear film 23'.

[0077] In the illustrated embodiment, however, the front film 22' is divided into a first film section 40 covering the upper section 17' of the pressure damper 2' and a second film section 41 covering the lower section 18' of the pressure damper 2'.

[0078] These two film sections 40, 41 do not lie in the same plane, but in mutually parallel planes. In particular, the first film section 40 is spaced from the rear film 23' by a distance corresponding to the entire depth of the housing-side frame 8', while the second film section 41 is spaced at a reduced distance, corresponding only to the depth of the damper chamber 4'.

[0079] As a result, the frame 8' can be additionally closed in its lower section 18', namely at its front side 16', by a preferably rigid cover 42. This cover 42 can be aligned with the first film section 40 in the upper section 17' of the housing 7'.

[0080] Thus, between this cover 42, the second film section 41 located behind it, the underside 10' of the frame 8' and its longitudinal sides 11', and an intermediate wall 43 separating the two sections 17', 18', a control chamber 36' is formed, which is largely hermetically sealed to the outside. It communicates with the exterior of the assembly consisting of the pressure damper 2' and the control device 1' only through a channel 44, which leads from the control chamber 36' to the frame 8', preferably to its upper side 9', and opens into a hose connection piece 45 there, to which a control hose (not shown) can be connected.

[0081] If excess pressure is introduced into the control chamber 36' via the hose connection nozzle 45, the second, lower foil section 41 bulges into the damper chamber 4', thereby opening the refill valve 5'. If, however, the control chamber 36' is depressurized, the lower foil section 41 expands, and the refill valve 5' closes. List of reference symbols

[0082] 1 device 26 third flow channel 2 pressure damper 27 center 3 Damper foil 28 pestle 4 Damper chamber 29 plate 5 Refill valve 30 spiral spring 6 Furnishings 31 Housing 7 Housing 32 Flat side 8 Frame 33 Top 9 Top 34 bottom 10 bottom 35 long side 11 long side 36 Tax Chamber 12 Hose connection piece 37 opening 13 Hose connection piece 38 Control opening 14 partition wall 39 Angle piece 15 back 40 first slide section 16 front 41 second slide section 17 upper section 42 cover 18 lower section 43 partition wall 19 lateral surface 44 channel 20 filter chamber 45 Hose connection piece 21 ink filter 22 front foil 23 rear film 24 first flow channel 25 second flow channel

Claims

1. Device (1) for cleaning an ink or ink-jet print head equipped with an upstream pressure absorber (2), wherein the pressure absorber (2) is provided with a closed damper chamber (4) that is at least partially limited by a damper film (3), comprising a refill valve (5) arranged in the damper chamber (4) for refilling the damper chamber (4) with ink in response to a curvature of the damper film (3) into the damper chamber (4), and a controllable device (6) arranged outside the damper chamber (4) for exerting an external pressure on an area of the damper film (3) limiting the damper chamber (4) in order to open the refill valve (5) arranged in the damper chamber (4) and thereby create a continuously open channel through the pressure absorber for cleaning the ink or ink-jet print head, wherein the device (6) for opening the refill valve (5) comprises a control chamber (36) which is hermetically sealed from the surroundings, a) with a connector for a control line which is arranged on the housing of the control chamber (36) in order to allow a control fluid to flow into the control chamber (36) or out of the control chamber (36) and to influence the filling pressure inside the control chamber (36), and b) with an opening (37) facing to the damper film (3) so that the damper chamber (4) and the control chamber (36) are separated from each other only by the damper film (3), c) wherein the damper film (3) is designed as a flexurally elastic film (22) and is subjected to the pressure difference between the pressures in the damper chamber and in the control chamber and bulges into the chamber where the lower pressure prevails, characterized in that d) the opening (37) in the control chamber (36) has a circular periphery, so that the damper film (3) can bulge uniformly over its entire surface without local overloading of individual surface areas.

2. Device (1) according to claim 1, characterized in that the opening (37) of the control chamber (36) has substantially the same dimensions as the peripheral area of the damper chamber (4) formed by the damper film (3).

3. Device (1) according to one of the claims 1 or 2, characterized in that the opening (37) of the control chamber (36) has a circular periphery.

4. Device (1) according to one of claims 1 to 3, characterized in that the housing (31) of the control chamber (36) is secured or securable on the pressure absorber (2).

5. Device (1) according to one of the preceding claims, characterized by air as the control fluid.

6. Device (1) according to one of the preceding claims, characterized in that a pressure sensor is arranged on the control chamber (36) and / or on the control line in order to facilitate a recording and / or regulation of the control pressure.

7. Device (1) according to one of the preceding claims, characterized in that a pressure sensor is arranged on the pressure absorber (2) or downstream of it in order to facilitate a detection of an opening of the refill valve (5) in the damper chamber (4).

8. Device (1) according to one of the preceding claims, characterized in that the refill valve (5) in the damper chamber (4) is pretensioned by a spring element (30) into a closed position.

9. Device (1) according to claim 8, characterized in that the spring element (30) presses a movable element or a movable plate (29) of the refill valve (5) in pretensioned condition from the inside against the damper film (3).

10. Device (1) according to claim 9, characterized in that the control pressure of the control fluid necessary for opening the refill valve (5) is greater than the force of the spring element (30) necessary for closing the refill valve (5), divided by the surface area of the damper film (3) directly limiting the damper chamber (4).

11. Device (1) for operating an ink or ink-jet print head equipped with an upstream pressure absorber (2), wherein the pressure absorber (2) is provided with a closed damper chamber (4) that is at least partially limited by a damper film (3) in which a refill valve (5) is arranged for refilling the damper chamber (4) with ink in response to a curvature of the damper film (3) into the damper chamber (4), comprising a controllable device (6) arranged outside the damper chamber (4) for exerting an external pressure on an area of the damper film (3) limiting the damper chamber (4) in order to exert an adjustable pretensioning on the refill valve (5) arranged in the damper chamber (4), wherein the device (6) for exerting a controllable external pressure on the refill valve (5) comprises a control chamber (36) which is hermetically sealed from the surroundings, a) with a connector for a control line which is arranged on the housing of the control chamber (36) in order to allow a control fluid to flow into the control chamber (36) or out of the control chamber (36) and to influence the filling pressure inside the control chamber (36), and b) with an opening (37) facing to the damper film (3) so that the damper chamber (4) and the control chamber (36) are separated from each other only by the damper film (3), c) wherein the damper film (3) is designed as a flexurally elastic film (22) and is subjected to the pressure difference between the pressures in the damper chamber and in the control chamber and bulges into the chamber where the lower pressure prevails, characterized in that d) the opening (37) in the control chamber (36) has a circular periphery, so that the damper film (3) can bulge uniformly over its entire surface without local overloading of individual surface areas.

12. Device (1) according to claim 11, characterized in that is formed according to one of claims 1 to 10.

13. Process for operating and / or cleaning an ink or ink-jet print head equipped with an upstream pressure absorber (2), wherein the pressure absorber (2) is provided with a closed damper chamber (4) that is at least partially limited by a damper film (3), comprising a refill valve (5) arranged in the damper chamber (4) for refilling the damper chamber (4) with ink in response to a curvature of the damper film (3) into the damper chamber (4), wherein an external pressure on an area of the damper film (3) limiting the damper chamber (4) is applied by a controllable device (6) arranged outside the damper chamber (4) in order to open the refill valve (5) arranged in the damper chamber (4) and also to create a continuously open channel through the pressure absorber for cleaning the ink or ink-jet print head, and / or in order to exert an adjustable pretensioning on the refill valve (5) arranged in the damper chamber (4), wherein the device (6) comprises a control chamber (36) which is hermetically sealed from the surrounding for opening the refill valve (5) and / or for exertion of an adjustable pretensioning on the refill valve (5), a) with a connector for a control line which is arranged on the housing of the control chamber (36) in order to allow a control fluid to flow into the control chamber (36) or out of the control chamber (36) and to influence the filling pressure inside the control chamber (36), and b) with an opening (37) facing to the damper film (3) so that the damper chamber (4) and the control chamber (36) are separated from each other only by the damper film (3), c) wherein the damper film (3) is designed as a flexurally elastic film (22) and is subjected to the pressure difference between the pressures in the damper chamber and in the control chamber and bulges into the chamber where the lower pressure prevails, characterized in that d) the opening (37) in the control chamber (36) has a circular periphery, so that the damper film (3) can bulge uniformly over its entire surface without local overloading of individual surface areas.