Fluid ejection device

Abstract

A compact fluid ejection device for a printhead assembly is provided that allows for efficient removal of gas from the device during operation and purging. The device includes a fluid chamber with a fluid-permeable filter that forms a partition within the fluid chamber such that an inlet is located on a first side of the filter and an outlet is located on a second side of the filter. The filter is tilted relative to a first direction parallel to the vertical during operation. A first volume within the fluid chamber between the filter and a first sidewall opposite the filter tapers in a direction away from the inlet. FIG.

Description

Technical Field

[0001] The present invention relates to a fluid ejection device for an inkjet printhead assembly.

[0002] Background of the Invention 1. Field of the Invention The present invention relates to a fluid distribution device for an inkjet printhead assembly.

[0003] 2. Description of the Related Art A printhead assembly generally includes a fluid distribution device that distributes fluid or ink to individual droplet forming units of one or more printhead units, as known, for example, from U.S. Patent Application Publication No. 2012 / 062659. Each droplet forming unit includes a pressure chamber in which or adjacent to which an actuator applies a pressure pulse to the pressure chamber so that droplets of fluid can be ejected. The fluid distribution device may include a filter for filtering the fluid and / or a damper element for absorbing pressure pulses transmitted through the fluid so as to avoid the pulses affecting the pressure within the pressure chamber. The fluid distribution device may further be provided with a return channel that allows fluid to continuously recirculate between the device and a central reservoir. This results in a manifold with various bends and corners, and gas bubbles can be trapped within the fluid distribution device. The gas bubbles accumulate into larger gas pockets and can affect the performance of the fluid distribution device, such as the throughflow and / or the filter capacity. Although some gas actually remains in the device after purging, it is known that the gas bubbles can be removed, for example, by a so-called purge flow, via the return channel and / or via the nozzles.

[0004] Summary of the Invention It is an object of the invention to provide an improved fluid dispensing device, particularly with regard to overall size, footprint, cost and / or performance.

[0005] According to the present invention, there is provided a fluid ejection device for a printhead assembly according to claim 1, comprising: a fluid chamber with an inlet and a print head supply outlet, each configured for fluid connection with a supply channel and at least one drop formation unit, and a fluid permeable filter forming a dividing wall in the fluid chamber, the inlet being located on a first side of the filter and the print head supply outlet being located on a second side of the filter opposite the first side, the filter being inclined with respect to a first direction, the first direction being parallel to a vertical direction in operation, and when viewed in the first direction, a first volume in the fluid chamber between the filter and a first side wall facing the filter tapers in a direction away from the inlet.

[0006] The filter is positioned slanted with respect to a first direction. As a result of the distortion or tilt of the filter, a first volume between the filter and one of the opposing side walls of the fluid chamber narrows in the first direction. The cross section of the first volume perpendicular to the first direction at the inlet decreases moving away from the inlet in the first direction. This allows a relatively larger effective area of ​​the filter without increasing the footprint of the fluid chamber. The larger effective area of ​​the filter contributes to improving fluid through-flow and increasing the life of the filter. Thereby, the object of the invention is achieved.

[0007] Further specific and attendant features of the invention are set out in the dependent claims.

[0008] In one embodiment, the inlet is located in the top wall of the fluid chamber and the printhead supply outlet is located in the bottom wall opposite the top wall. The top and bottom are here defined with respect to a first direction parallel to the vertical, as during operation of the device. Both the top wall and the bottom wall are provided with at least one opening, and fluid preferably flows into and out of the fluid chamber along or against the first direction respectively. During operation, the fluid enters the fluid chamber substantially vertically and exits the fluid chamber in the same direction. Looking from above, this reduces the effective footprint of the fluid dispensing device since the inlet and the printhead supply outlet overlap the fluid chamber.

[0009] In one embodiment, the filter extends from the bottom wall to the top wall. Preferably, the filter contacts the bottom wall and the top wall. This allows for a relatively large filter area, which is advantageous for the operation and lifespan of the filter. Preferably, the filter is inclined with respect to the first direction, so that the filter has a total effective area larger than the effective cross-sectional area of the vertical cross-section of the fluid chamber passing through the filter.

[0010] In one embodiment, the bottom wall is longitudinal in a second direction perpendicular to the first direction, and the filter extends parallel to the second direction. The print head unit is generally elongated for one or more rows of a number of nozzles. The perpendicular footprint of the fluid dispensing device is kept small by following the longitudinal shape of the print head unit to which it is connected. The second direction is preferably parallel to the direction of one or more nozzle rows. As a result, the length of the bottom wall of the fluid chamber in the second direction is greater than the width in a third direction perpendicular to both the first and second directions. A large filter area is achieved by extending the filter substantially parallel to the second direction. The first volume tapers when viewed from the second direction, but preferably does not taper (or is at least significantly suppressed) when viewed from the third direction.

[0011] In one embodiment, the filter extends parallel to the second direction. The edge of the filter is located at the bottom edge, which is also parallel to the second direction. From said edge, the filter slopes in the third direction towards the opposite edge of the bottom wall. Preferably, the other end of the filter contacts the upper wall, whereas the other end of the filter contacts the side wall of the fluid chamber in the second direction. Preferably, the fluid chamber is dimensioned such that the side wall has a small area of all the walls defining the fluid chamber.

[0012] In one embodiment, the filter further extends from and / or contacts both side walls of the fluid chamber in the second direction. When viewed in the third direction, the entire area of the fluid chamber is filled by the filter. When viewed in the third direction, the filter extends and / or contacts the full circumference of the fluid chamber. The filter extends along the upper wall, the bottom wall and the side walls in the second direction. Due to the inclination, the total and / or effective area of the filter is larger than the cross-sectional area of the fluid chamber for the cross-sections in the first and second directions.

[0013] In one embodiment, the print head supply outlet comprises at least two outlet openings in the bottom wall, the outlet openings being spaced apart from each other in a second direction. Due to the inclination of the filter, a relatively large area for the print head supply outlet in the bottom wall is available so that the total open area can be relatively large. Having two or more spaced-apart outlet openings further contributes to a more uniform supply of fluid to the print head unit since sufficient fluid supply to each nozzle is required for optimal performance. Preferably, the two outlet openings are also at different positions in a third direction.

[0014] In one embodiment, when viewed in a first direction, the filter at least partially overlaps the print head supply outlet. This allows for a relatively large filter without reducing the cross-section of the print head supply outlet and / or without adjusting its position. The filter extends at least partially above the print head supply outlet. The filter is positioned between the inlet and the print head supply outlet. Preferably, the inlet is positioned on a wall opposite the wall comprising the print head supply outlet. For example, the upper wall of the fluid chamber comprises the inlet, whereas the print head supply outlet is provided in or in the bottom wall during operation. Similarly, in other embodiments, when viewed in a first direction, the filter at least partially overlaps the inlet. Such a relatively large filter is applicable without compromising the position and / or size of the inlet. Preferably, when viewed in a first direction, the filter at least partially overlaps the inlet as well as the print head supply outlet. Preferably, the filter is inclined at an angle of at least 10° with respect to the first direction.

[0015] In one embodiment, the fluid ejection device further comprises a return channel for returning fluid, bypassing a fluid chamber and a first vent channel connecting the fluid chamber to the return channel such that a first vent channel inlet is located on a second side of the filter. The return channel runs parallel to the fluid chamber, preferably parallel to a supply channel connected to the inlet. The fluid effectively flows through the return channel in a direction opposite to the average or main flow direction through the inlet and / or within the fluid chamber. The first vent channel is configured for removing air bubbles from the fluid chamber to the return channel, specifically from a second volume of the fluid chamber downstream of the filter, herein the second side which is downstream of the filter. The cross-section of the first vent channel may be narrower compared to the inlet and / or the return channel thereto in order to reduce the loss of fluid flowing through the first vent channel. The first vent channel is preferably provided at the highest point of the second volume measured upward with respect to the first direction. The first vent channel provides means for removing the gas accumulating at the top of the second volume. Air bubbles or pockets that partially obstruct the filter can be removed and / or prevented by the means of the first vent channel. The first vent channel allows, during purging, substantially the entire second volume to be filled with fluid by removing the gas through the first vent channel.

[0016] In one embodiment, when viewed in the first direction, a second volume between the filter and a second side wall opposite the first side wall tapers towards the first vent channel opposite to the first direction. The first vent channel inlet is preferably located on an upper wall of the fluid chamber above the second volume. The upper end of the filter is measured perpendicular to the first direction and is located closer to the first vent channel inlet than its bottom edge. This results in the second volume tapering towards the first vent channel inlet so as to direct air bubbles into the relatively narrow first vent channel. Since the first vent channel inlet is relatively small, this arrangement is space-efficient.

[0017] In one embodiment, the first ventilation channel inlet and the print head supply outlet are located on opposite sides of the fluid chamber in the first direction, whereas in other embodiments, the inlet and the print head supply outlet are located on opposite sides of the fluid chamber in the first direction. The inlet, and preferably the first ventilation channel inlet, may be provided in or on the upper wall, and the first ventilation channel inlet is separated from the inlet by a filter. The print head supply outlet is preferably located, for example, on the bottom wall of the fluid chamber, opposite the upper wall having the inlet and / or the first ventilation channel inlet.

[0018] Preferably, the first ventilation channel is inclined with respect to the first direction such that during operation the first ventilation channel inlet is below the connection between the first ventilation channel and the return channel. The first ventilation channel outlet is located higher than the first ventilation channel inlet during operation. The upward inclination in the desired flow direction of the first ventilation channel results in a more effective removal of bubbles due to the effect of gravity on the bubbles.

[0019] In one embodiment, the cross-section of the first ventilation channel is substantially smaller than that of the inlet and / or the print head supply outlet. The effective area of the first ventilation channel is preferably less than 30%, very preferably less than 20%, and even more preferably less than 10% of the average inlet or return channel area.

[0020] In one embodiment, the fluid dispensing device further comprises a damper element having a deformable membrane located on a second side of the filter within the fluid chamber. When viewed in a first direction, the damper element, the filter, the inlet, and the printhead supply outlet overlap the bottom wall. Also, the filter overlaps the inlet and the printhead supply outlet. The overlap may be partial. The deformable membrane is part of the damper element located within the second volume. The deformable membrane is deformable to absorb pressure pulses passing through the fluid, which may be generated from the imaging unit and / or a fluid supply upstream of the inlet. Elimination of the pressure fluctuations improves the performance of the printhead unit. The damper element is conveniently positioned such that a single damper element is sufficient to absorb pressure pulses generated from either upstream or downstream of the damper element. When viewed from above during use, all of the above components are positioned to overlap the footprint of the bottom wall, creating a compact device.

[0021] In one embodiment, the deformable membrane extends along a second sidewall of the fluid chamber, the second sidewall extending substantially in a first direction during operation. The second sidewall is substantially perpendicular during operation, on which the membrane is mounted, and an expansion volume is formed between the membrane and the second sidewall. The membrane is allowed to deform into the expansion volume to reduce and / or remove pressure fluctuations or pulses in the fluid. Preferably, the deformable membrane extends along the entire length of the second sidewall between the upper and bottom walls of the fluid chamber, thereby fluidically sealing a portion of the fluid chamber between the second sidewall and the membrane. This allows for a relatively large area of the membrane and improves its absorption characteristics. The sealed portion forms the expansion volume, and the second sidewall may be provided with an opening for connecting the expansion volume to the ambient. This results in an efficient and low-cost damper element.

[0022] In one embodiment, the end of the filter, preferably the bottom edge, is located at a corner between the bottom wall comprising the printhead supply outlet and the first sidewall on the inlet side of the filter. The lower end of the filter is attached on the outside to the bottom corner outside the first volume in the fluid chamber. From there, the filter extends obliquely upward towards the upper corner outside the second volume.

[0023] In one embodiment, the upper wall is formed by two upper wall portions located at different heights in the first direction, the upper wall portions being connected by an intermediate wall portion extending in the first direction, and the end of the filter being attached to the intermediate wall portion. The intermediate wall portion allows fixing the end of the filter without bending the filter and thereby damaging it. The bottom end of the filter can be locally fixed to the first side wall. The remaining side edges of the fluid chamber can be configured to extend the intermediate wall portion towards the bottom wall. This provides a convenient holder for arranging and fixing the filter, which facilitates the manufacture of the fluid distribution device.

[0024] In one embodiment, the fluid dispensing device further comprises a fluid distribution manifold for dispensing fluid towards at least one image forming unit, the fluid distribution manifold being fluidly connected to a printhead supply outlet for receiving fluid and a return channel for removing fluid from the fluid distribution manifold, at least one second ventilation channel extending between the return channel and the supply channel and / or the fluid chamber moving air bubbles into the return channel, the return channel comprising a first narrowed portion in the ventilation channel to establish a local decrease in static pressure for drawing in air bubbles. The first channel may be provided to a second volume of the fluid chamber and / or the second ventilation channel may be provided between the supply channel and the return channel to remove air bubbles rising through the supply channel. This allows gas accumulation to be removed from the first volume. The efficiency of removing air bubbles can be increased by locally reducing the cross-sectional area of the return channel in the first and / or second ventilation channels. This results in a local increase in fluid velocity along the exit of the first and / or second ventilation channels, resulting in a decrease in static pressure. As a result, the static pressure difference across the first and / or second ventilation channels is increased, providing an increased driving force for pushing air bubbles out of each ventilation channel.

[0025] In one embodiment, the first narrowed portion has a cross-sectional area of less than half of the cross-sectional area of the return channel, preferably less than 40% of the cross-sectional area of the return channel, and very preferably less than 30% of the cross-sectional area of the return channel. The cross-sectional area is inversely proportional to the fluid velocity and, as a result, inversely proportional to the static pressure. Since the static pressure varies roughly quadratically, for example, depending on the flow rate, reducing the cross-sectional area is an efficient way to reduce the static pressure and thereby reduce the driving force for pushing air bubbles into the return channel.

[0026] In one embodiment, the supply channel and the return channel are substantially parallel lines that approximate each other. This creates an efficient configuration of space. Preferably, both the supply channel and the return channel extend in a first direction such that bubbles can efficiently rise through the channels during operation. The supply channel and the return channel are preferably positioned close to each other. By positioning the channels close to each other, the return channel extends at least partially along and in the vicinity of the supply channel, which allows for a relatively small or short second ventilation channel. Preferably, the length of the second ventilation channel and / or the distance between the return channel and the supply channel is less than half, preferably less than a quarter, of the length and / or width of the fluid chamber in a direction perpendicular to the first direction, and is preferably parallel to the filter and / or the membrane. The relatively short second ventilation channel allows for effective bubble removal. Advantageously, the supply channel and the return channel can be positioned on the side of the fluid chamber with the first ventilation channel outlet so as to allow the lengths of both ventilation channels to be relatively short.

[0027] In one embodiment, the return channel bypasses the fluid chamber and is attached to the fluid distribution manifold. The fluid distribution manifold is fluidly positioned between the fluid chamber and the return channel, and similarly, between the fluid chamber and the imaging unit of at least one print head unit. While the return channel allows for a certain circulation of fluid through the fluid distribution manifold regardless of the operation of the imaging unit, a portion of the fluid is supplied to the imaging unit. The return channel preferably has a length in the first direction that is at least as long as the combined length of the supply channel and the fluid chamber.

[0028] In one embodiment, the return channel extends along and adjacent to the fluid chamber, a first ventilation channel is formed between the upper part of the fluid chamber and the return channel, and a second ventilation channel is formed between the supply channel and the return channel away from the fluid chamber. Two ventilation channels are provided to remove gas accumulation from the first and second volumes on the opposite side of the filter in the fluid chamber. The first ventilation channel connects the upper or uppermost part of the second volume to the return channel to remove gas accumulation from the second volume of the fluid chamber. The second ventilation channel is provided in the supply channel, and the supply channel is connected to the upper wall portion above the first volume of the fluid chamber. Bubbles in the first volume are thereby allowed to escape through the supply channel. As a result, gas accumulation on both sides of the filter in the fluid chamber can be prevented and / or removed. The ventilation channels also contribute to gas removal during both normal operation and purge operations in which fluid is pushed into the fluid chamber at an increased pressure. During purging, substantially all gas accumulation is forced out of the first and second volumes, allowing the fluid chamber to be completely filled with fluid covering both sides of the filter. This extends the throughflow capacity and / or lifespan of the filter.

[0029] In one embodiment, the supply channel includes a second constriction located in a vent line, and the second constriction extends above at least one ventilation channel in the direction of gravity during operation. The supply channel narrows at and / or above the second ventilation channel during operation. This effectively results in a reduction in the cross-sectional area of the supply channel in the upward direction of the bubbles. The reduction in cross-sectional area is preferably sudden, such as an obstacle or step along the inner wall of the supply channel. This narrowing disrupts the trajectory of the bubbles and makes it easier for them to enter the second ventilation channel. Thereby, the efficiency of gas removal is improved. The narrowing preferably relates to a reduction in cross-sectional area of at least 50%, preferably at least 40%, very preferably at least 30%, and even more preferably at least 20%.

[0030] In one embodiment, the supply channel, return channel, and fluid chamber are formed from injection molded plastic, and preferably at least a portion of the fluid chamber is integrally formed with the supply channel and / or the return channel. To reduce costs, the fluid dispensing device is formed in part by injection molding. There, one or more components, such as for example a first portion of the supply channel and the fluid chamber, can be integrally formed in the same mold.

[0031] In one embodiment, the printhead supply outlet and inlet are located on opposite sides of the fluid chamber in a first direction in which the supply channel and return channel extend during operation. The inlet is located on an upper wall facing a bottom wall that holds the printhead supply outlet. This allows the supply channel to be at least partially located above the fluid chamber when viewed in the first direction. Similarly, the printhead supply port overlaps the bottom wall when viewed from the first direction. This maintains a relatively small footprint of the fluid dispensing device while allowing a relatively large filter area. Preferably, the inlet is located on a first sidewall facing the inlet side of the filter or on the side of the upper wall in the vicinity thereof.

[0032] The present invention further relates to an inkjet printhead assembly comprising a fluid dispensing device according to the present invention fluidly connected to at least one printhead unit.

[0033] The present invention further relates to an inkjet printer comprising a printhead assembly comprising a fluid dispensing device according to the present invention fluidly connected to at least one printhead unit.

[0034] The further scope of the application of the present invention will become apparent from the following detailed description. However, it is to be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are provided by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art who are familiar with this detailed description.

Brief Description of the Drawings

[0035] Brief Description of the Drawings The invention can be more fully understood from the accompanying drawings, which are given by way of illustration only and not limitation, in the following detailed description: FIG. 1 is a schematic cross-sectional view of a fluid dispensing device known in the prior art; FIG. 2 is a schematic front view of a fluid dispensing device according to the present invention; FIG. 3 is a schematic side view of the fluid dispensing of FIG. 2; and FIG. 4 is a schematic front view depicting the trajectories of air bubbles in the fluid in the fluid dispensing device of FIG. 2.

Modes for Carrying Out the Invention

[0036] Detailed Description of the Embodiments Referenced The present invention will now be described with reference to the accompanying drawings, and the same reference numerals are used to identify the same or similar elements throughout several of the figures.

[0037] Figure 1 discloses a print head assembly known in the prior art. The print head assembly comprises a plurality of print head units 10 attached to the bottom surface of the fluid dispensing device 1. Each print head unit 10 comprises a plurality of image forming units each having a nozzle 12 connected to a pressure chamber (not shown) to which a pressure pulse can be applied to eject fluid droplets from the nozzle 12. A suitable actuator for generating the pressure pulse can be, for example, a piezoelectric actuator, a thermal actuator, or a so-called bubble jet actuator. The fluid is supplied to the print head units 10 via a fluid distribution manifold 20. The fluid distribution chamber 20 is provided with a damper element 21 to prevent a pressure pulse from one image forming unit from affecting the pressure in the pressure chambers of other image forming units. The damper element 21 comprises a deformable elastic membrane 22 that can absorb the pressure pulse by bending into an enclosed expansion volume 23 from the chamber 20. The fluid is supplied to the fluid distribution chamber 20 via a filter unit 30 formed by a fluid chamber 31 divided by a porous membrane 32. The openings of the membrane are suitably narrow to prevent larger dirt particles or air bubbles from reaching the print head units 10. On its inlet side, the fluid chamber is connected to a supply channel 33 for receiving the fluid, and on the opposite side of the membrane 32, the fluid chamber 31 is provided with a return channel 34 for recirculating the fluid to a central reservoir. A drawback of the known print head assembly is the gas entrapment in any of its components. Small air bubbles are transported or formed in the liquid during the process of passing through the print head assembly and are trapped in the corners or other dead spaces of the device 1. The air bubbles interact to form larger air pockets, preventing the liquid from accessing all areas of the print head assembly.Such air pockets are known to be removed by so-called purging, which uses a relatively high-pressure flow or counterflow to drive out the air pockets. However, in practice, some residual gas remains trapped within the apparatus 1 even after purging. Further, known printhead assemblies are relatively complex or large in terms of components and / or volume.

[0038] A compact and highly productive printhead assembly 100 according to the present invention is shown in FIGS. 2, 3, and 4. The fluid distribution device 130 is fluid-connected and mounted on the fluid distribution manifold 120, and the fluid distribution manifold 120 holds the image forming unit of the printhead unit 110 and supplies fluid. The fluid distribution device 130 is connected to one or more fluid supply reservoirs (not shown) via its fluid interface elements 138, 139. Supply channel 133 and return channel 134 are provided together with their respective fluid interface elements 138, 139. The supply channel 133 extends perpendicularly in a first direction D1 parallel to the direction of gravity during operation. The supply channel 133 forms an inlet 137 in the upper wall portion 128 of the fluid chamber 131. The fluid chamber 131 includes a filter 132 formed of a fluid permeable membrane, which divides the fluid chamber 131 into a first upstream volume V1 and a second upstream volume V2. The filter 132 forms a barrier between the first and second volumes V1, V2, which prevents particles larger than a certain size threshold from passing through. The second volume V2 of the fluid chamber 131 holds a damper element 121 formed of a deformable membrane 122 that extends along the second side wall 124 of the fluid chamber 131. The second side wall 124 may be provided with an opening to improve the function of the damper element 121. The membrane 122 is attached above or on the second side wall 124 and seals a part of the second side wall 124 with the opening. Preferably, the deformable membrane 122 extends along the entire length of the second side wall 124 between the respective upper wall portion 127 and the bottom wall 126 of the fluid chamber 131.

[0039] The upper wall portion 127 is inclined upward or is inclined toward the first ventilation channel 140 that connects the second volume V2 to the return channel 134. The first ventilation channel 141 is a relatively narrow channel compared to the channels 133 and 134 in order to reduce the amount of liquid flowing back into the return channel 134. This allows gas or bubbles to be removed from the fluid in the second volume V2 without substantial loss of fluid flow in the main fluid transport direction.

[0040] The bottom wall 126 of the fluid chamber 131 is provided with at least one print head supply outlet 135 opened into one or more print head supply channels 136 through which fluid is transported from the second volume V2 to the fluid distribution manifold 120. The fluid distribution manifold includes a plurality of channels that not only supply fluid to the print head unit 110 but also supply fluid to a return channel 134 for returning and recirculating the fluid to one or more central reservoirs. The return channel 134 bypasses the fluid chamber 131 and extends parallel to the supply channel 133. The supply channel 133 and the return channel 134 are positioned adjacent to the same side of the fluid chamber 131, allowing connection from the supply channel 133 to the return channel 134 via the second ventilation channel 141. The second ventilation channel 141 removes air bubbles from the supply channel 133 and the first volume V1 and prevents the air bubbles from flowing back toward the fluid chamber 131. Due to the adjacent positions of the supply channel 133 and the return channel 134 above the second volume V2 of the fluid chamber 131, both the ventilation channels 140 and 141 may be relatively short, allowing for efficient removal of air bubbles.

[0041] Figure 4 shows the trajectory of the bubble B within the print head assembly 100 shown in Figure 2. The bubble B flows towards the print head unit 110 and circulates through the fluid distribution manifold 120. From the fluid distribution manifold 120, the gas moves upward through the return channel 134 in the return flow direction D3. Similarly, the bubble B can move upward through the supply channel 133 against the fluid supply direction D2. The bubble B can be generated from and / or accumulate within the fluid chamber 131. The accumulation A1 of the bubble B gathers at the upper part of the first volume V1, not only preventing proper inflow of the fluid, but also partially blocking the filter 132 and reducing the through-flow of the fluid towards the print head unit 110. The bubble B can further accumulate in the second volume V2, forming an accumulation A2. This accumulation A2 can reduce the through-flow through the fluid chamber 131. The fluid distribution device 130 according to the present invention provides several means for reducing and / or removing the accumulation of the bubble B, and the means can be described as follows.

[0042] To reduce such accumulation and / or remove the bubbles, the ventilation channels 140, 141 are provided to guide the bubbles into the return channel 134. The first ventilation channel 140 is provided on the upper wall portion 127 of the second volume V2 to remove gas from the accumulation A2. The first ventilation channel 140 is preferably provided at the highest point of the second volume V2. To reduce or prevent gas accumulation in the first volume V1 (similarly for the second volume V2), the supply channel 133 is connected to the return channel 134 via the second ventilation channel 141. The second ventilation channel 141 removes at least partially the bubbles from the supply channel 133 towards the return channel 134. Preferably, the inlet 137 of the supply channel 133 is provided at the highest point of the first volume V1. The ventilation channels 140, 141 are preferably relatively narrow to reduce the loss of fluid through the ventilation channels 140, 141, for example, with a diameter or cross-sectional area not exceeding 40%, preferably 30%, very preferably 20%, and even more preferably 10% of the supply channel 133 and / or the return channel 134.

[0043] Return channel 134 has a constriction 142 at the height position of the second ventilation channel 141. The constriction 142 results in a local reduction in the cross-sectional area of the return channel 134, for example, a reduction of at least 40%, preferably at least 30% of the area. This reduction can be achieved by locally reducing the diameter of the return channel when it is formed and / or by providing an insertable obstruction with a through-hole as shown in FIG. 2. By locally reducing the cross-sectional area of the return channel 134, the fluid velocity in the return channel 142 along the second ventilation channel 141 locally increases. This results in a local reduction in static pressure, improving the entrainment of bubbles through the second ventilation channel 141. As a result of Bernoulli's law, the constriction increases the static pressure difference across the second ventilation channel 141 between the supply channel 133 and the return channel 134. The increased pressure difference provides a driving force for pushing bubbles through the second ventilation channel 141 into the return channel 134. The narrow portion can further be applied to the return channel 134 at the first ventilation channel 140.

[0044] A further improvement for delivering bubbles through the second ventilation channel 141 can be achieved by locally reducing the cross-sectional area of the supply channel 133 in the second ventilation channel 141. Further, as shown in FIG. 2, the supply interface element 138 is provided with an effective diameter smaller than the lower part of the supply channel 133. This reduction in diameter can be achieved by an insertable obstruction with a through-hole and / or by the reduced effective diameter of the supply interface element 138 compared to the supply channel 133. It has been found that a local reduction in the cross-sectional area in the supply channel 133 forms an obstruction in the path of the bubbles rising through the supply channel 133. This obstruction disrupts the trajectory of the bubbles and makes them more likely to enter the second ventilation channel 141. Preferably, the narrowing is abrupt due to a step or protrusion in the supply channel 133.

[0045] To reduce the entrapment of bubbles B in the first volume V1, the inlet 137 of the supply channel 133 is preferably provided at the highest part of the upper wall portion 128 during operation. Preferably, the upper wall portion 128 is inclined upwardly towards the inlet 137. Under the influence of gravity, the bubbles B are thereby guided into the supply channel 133 towards the inlet 137. This configuration is advantageous during operation and during the purge operation, allowing the first volume V1 to be filled with fluid and substantially filled.

[0046] The upper wall portion 127 of the second volume V2 may be inclined upwardly towards the first ventilation channel 140 to assist the bubbles B in heading towards the first ventilation channel 140. Since the diameter of the first ventilation channel 140 is relatively small compared to the cross-section of the second volume V2, the second volume V2 may further taper towards the first ventilation channel 140, directing the bubbles B into the first ventilation channel 140. The small first ventilation channel 140 leaves room, for example, to curve and / or incline the upper wall so that the first ventilation channel is located at the highest point. The upper wall comprises upper wall portions 127, 128 located above the second and first volumes V2, V1 respectively. The upper wall portion 127 of the second volume V2 is located at a different height from the upper wall portion 128 of the first volume V1 such that a vertically extending intermediate top wall portion 129 is formed between the upper wall portions 127, 128. The upper end of the filter 132 is attached to the intermediate upper wall portion 129. This allows for the placement of the inlet 137 and the upper wall of the second ventilation channel 140 while allowing for a secure attachment to the upper wall without bending and potentially damaging the filter 132. The intermediate upper wall portion 129 may extend circumferentially around the filter 132, forming an attachment ridge along a partial or entire length of the filter 132. The intermediate upper wall portion 129 allows for the inclined arrangement of the filter 132 by positioning its stop end closer to the first ventilation channel 140 than its lower end, measured in a direction perpendicular to the first direction.

[0047] The fluid distribution device 130 further allows for a compact structure with a relatively small number of components. This reduces both cost and the footprint of the printhead assembly, allowing for a compact structure. Here, the filter 132 is positioned at an angle inclined with respect to the first direction D1. The bottom end of the filter 132 is positioned in or at a corner of the bottom wall 126 and the first side wall 125. The first side wall 125 faces and / or is opposite to the second side wall 124 against which the membrane 122 of the damper element 121 is disposed. The filter 132 extends further and further upwardly away from the first side wall 125 in a direction opposite to the first direction D1. This results in a roughly triangular cross-section of the first volume V1 formed between the filter 132 and the first side wall 125. The length and / or area of the upper wall portion 128 of the first volume V1 is substantially smaller than those of the filter 132 and the first side wall 125. The angle between the filter 132 and the first side wall 125 is acute, preferably less than 20°, and very preferably less than 10°. The inlet 137 is positioned in the upper wall portion 128 facing the acute angle between the filter 132 and the first side wall 125. Since the inlet 137 is positioned above the filter 132 when viewed in the first direction D1, the inlet 137 at least partially overlaps the filter 132. The upper wall portions 127, 128 are positioned at different heights and form an intermediate wall portion 129 that extends vertically and against which the upper end of the filter 132 is fixed. This allows for the positioning of the first ventilation channel 140 at the top of the second volume while positioning the upper end of the filter 132 closer to the first ventilation channel 140 than its bottom end. The filter 132 extends from the bottom wall 126 to the upper wall, resulting in a relatively large filter area. When viewed in the second direction D2, the first volume V1 tapers continuously because the filter 132 is inclined in the first direction D1 over its entire height. When viewed in the third direction D3, the filter 132 does not substantially taper and has a constant length over most of its height. The length of the filter 132 in the second direction D2 is greater than the width of the bottom wall 126 in the third direction D3.Also, the height of the filter 132 in the first direction is greater than the width of the bottom wall 126 in the third direction D3. Due to the inclination, the distance or length measured between the bottom wall 126 and the upper wall above the filter 132 is greater than the height of the fluid chamber 131 in the first direction D1 between the said walls. The area of the filter 132 through which fluid can pass is greater than the cross-sectional area of the fluid chamber 131 in the first and second directions D1, D2. The filter 132 contacts the peripheral wall of the fluid chamber 131 when viewed in the third direction D3. The edges of the filter 132 contact the upper wall, the bottom wall 126, and the third and fourth side walls 117, 119.

[0048] The inclination of the filter 132 results in a skewed wall of the second volume V2, tapering the second volume V2 towards the first ventilation channel 140. This inclination allows for a larger area of the filter 132. On the opposite side of the filter 132, the membrane 122 of the damper element 121 is positioned. The damper element 121 extends completely along the second side wall 124, resulting in a relatively large and thus effective damper. The membrane 122 is formed of a corrugated foil as described in US20200376843A. The damper element 121 is positioned such that it can absorb not only the pressure pulses generated from the print head unit 110 but also the pressure pulses or variations generated from the liquid supply moving in the first direction D1 through the supply channel 133. When viewed in the first direction D1, the filter 132 overlaps with the upper wall portion 128 of the first volume V1 but does not overlap with the upper wall portion 127 of the second volume V2. From the same top-bottom perspective, the upper end of the filter 132 is positioned closer to the first ventilation channel 140 than its bottom end. Similarly, the upper end is preferably farther from the inlet 137 than the bottom end. To minimize the footprint, the first and first side walls 124, 125 are preferably parallel to each other and to the first direction D1. Similarly, the membrane 122 extends from its upper surface to its bottom surface, or between the upper wall portion 127 and the bottom wall 126, parallel to the second side wall 124.

[0049] The bottom wall 126 is longitudinal in shape. The length of the bottom wall 126 measured in the second direction D2 is significantly greater than its width in the third direction D3. The second and third directions D2, D3 are preferably both horizontal during use. By positioning the filter 132 at the end of the bottom wall 126 on the inlet 137 side, substantially the entire area of the bottom wall 126 is available for the print head supply outlet 135. The print head supply outlet 135 comprises two outlet openings, each defining a print head supply channel 136 and being spaced apart from each other along the second direction D2. As a result, the filter 132, the damper element 121, the inlet 137 and the print head supply outlet 135 all overlap the bottom wall 126 when viewed from above in the first direction D1. This ensures a small footprint and allows for dense stacking of print heads. The height of the fluid chamber 131 in the first direction D1 is also greater than its width in the direction D3, as well as the length in the second direction D2. As a result, the third and fourth side walls 117, 119 in the second direction are smaller than the other walls, which are the upper wall, the bottom wall 126, the first side wall 124 and the second side wall 125.

[0050] The filter 132 further overlaps with one of the print head supply outlets 135 when viewed in the first direction. The second volume V2 tapers towards the first ventilation channel 140. The upper surface of the filter 132 is located closer to the first ventilation channel 140 than the bottom surface of the filter 132 in a direction perpendicular to the first direction.

[0051] Preferably, the fluid dispensing device 130 is formed at least in part from injection molded plastic. Specifically, the fluid chamber 131 can be formed of a plastic component to which the filter 132 and the membrane 122 are attached.

[0052] While specific embodiments of the invention have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that various alternative and / or equivalent implementations exist. It should be understood that the singular or plural exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description provide a convenient roadmap for those of ordinary skill in the art to implement at least one exemplary embodiment, and various changes can be made in the functions and arrangements of the elements described in the exemplary embodiments without departing from the scope as set forth in the appended claims and their legal equivalents. In general, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

[0053] In this document, the terms "comprises," "comprising," "includes," "including," "contains," "containing," "has," "having" and their variations are intended to be inclusive (i.e., non-exclusive) in meaning such that a process, method, device, apparatus, or system described herein is not limited to the recited features, parts, elements, or steps thereof, but may include other elements, features, parts, or steps not expressly listed or particular to such a process, method, article, or device. Further, the term "a" and "an" as used herein is intended to mean "one or more" unless specifically stated otherwise. Additionally, the terms "first," "second," "third," etc. are used merely as labels and are not intended to impose numerical requirements on, or establish a particular order of importance for, their objects.

[0054] Having thus described the invention, it will be apparent that it may be modified in many ways. Such modifications should not be regarded as departing from the spirit and scope of the invention, and all such modifications that are obvious to those of ordinary skill in the art are intended to be included within the scope of the following claims.

Claims

1. A fluid ejection device (130) for a print head assembly (100), A fluid chamber (131) with an inlet (137) and a print head supply outlet (135), the fluid chamber (131) being configured for fluid connection to a supply channel (133) and at least one droplet formation unit respectively, A fluid permeable filter (132) forming a partition wall within the fluid chamber (131), the inlet (137) being located on a first side of the filter (132) and the print head supply outlet (135) being located on a second side of the filter (132) opposite to the first side, The filter (132) is inclined with respect to a first direction (D1), The first direction (D1) is parallel to the vertical direction during operation, When viewed in the first direction, a first space within the fluid chamber (131) between the filter (132) and a first side wall (125) facing the filter (132) tapers in a direction away from the inlet (137), The inlet (137) is located on an upper wall of the fluid chamber (131), and the print head supply outlet (135) is located on a bottom wall (126) opposite to the upper wall, The fluid ejection device (130) further comprises a damper element (121) having a deformable membrane (122) located on the second side of the filter (132) within the fluid chamber (131), When viewed in the first direction (D1), the damper element (121), the filter (132), the inlet (137) and the print head supply outlet (135) overlap the bottom wall (126), and the filter (132) overlaps the inlet (137) and the print head supply outlet (135), the deformable membrane (122) extends along a second side wall (124) of the fluid chamber (131), and the second side wall (124) extends in the first direction (D1) during operation, The upper wall is formed of two upper wall portions (127, 128) positioned at different heights in the first direction (D1), and the upper wall portions (127, 128) are connected by an intermediate wall portion (129) extending in the first direction (D1), and an end of the filter (132) is attached to the intermediate wall portion (129). The fluid ejection device (130) is characterized by this.

2. The filter (132) extends from the bottom wall (126) to the upper wall. The fluid ejection device (130) according to claim 1, characterized by this.

3. The filter (132) contacts the bottom wall (126) and the upper wall. The fluid ejection device (130) according to claim 2, characterized by this.

4. The bottom wall (126) is longitudinal in a second direction (D2) perpendicular to the first direction (D1), and the filter (132) extends parallel to the second direction (D2). The fluid ejection device (130) according to claim 2, characterized by this.

5. The print head supply outlet (135) has at least two outlet openings in the bottom wall (126), and the at least two outlet openings are spaced apart from each other in the second direction (D2). The fluid ejection device (130) according to claim 4, characterized by this.

6. When viewed in the first direction (D1), the filter (132) at least partially overlaps the print head supply outlet (135). The fluid ejection device (130) according to claim 1, characterized by this.

7. When viewed in the first direction (D1), the filter (132) at least partially overlaps the inlet (137). The fluid ejection device (130) according to claim 1, characterized by this.

8. A return channel (134) for returning the fluid, bypassing the fluid chamber (131) and a first ventilation channel (140) connecting the fluid chamber (131) to the return channel (134) such that the ventilation channel inlet (131) is located on the second side of the filter (132). The fluid discharge device (130) further comprises a return channel (134). The fluid discharge device (130) according to claim 1, characterized in that.

9. The second space between the filter (132) and the second side wall (124) opposite the first side wall (125) tapers towards the first ventilation channel (140) facing in the first direction (D1). The fluid discharge device (130) according to claim 8, characterized in that.

10. The ventilation channel inlet and the print head supply outlet are located on the opposite side of the fluid chamber (131) in the first direction (D1). The fluid discharge device (130) according to claim 8, characterized in that.

11. The first ventilation channel (140) is inclined with respect to the first direction (D1) such that during operation the ventilation channel inlet is below the connection between the first ventilation channel (140) and the return channel (134). The fluid discharge device (130) according to claim 8, characterized in that.

12. The edge of the filter (132) is located at the corner between the bottom wall (126) having the print head supply outlet (135) and the first side wall (125) opposite the second side wall (124). The fluid discharge device (130) according to claim 1, characterized in that.

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