Fluid distribution device for inkjet printhead assembly

Abstract

A compact fluid distribution device (130) for a printhead assembly (100) is provided that allows for efficient removal of gas from the device during operation and purging. The device includes a fluid chamber (131) having a fluid permeable filter (132) forming a partition wall in the fluid chamber such that an inlet (137) is located on a first side of the filter and an outlet (135) is located on a second side of the filter. The filter is tilted with respect to a first direction parallel to a vertical direction during operation such that a first volume in the fluid chamber between the filter and a first side wall facing the filter gradually decreases in a direction away from the inlet.

Description

TECHNICAL FIELD

[0001] The present invention relates to a fluid distribution device for a printhead assembly. BACKGROUND

[0002] Printhead assemblies, such as the printhead assembly known from US 2012062659A, generally comprise a fluid distribution device for distributing fluid or ink to individual drop forming units of one or more printhead units. Each drop forming unit comprises a pressure chamber from which a drop of fluid can be ejected by means of applying a pressure pulse to the pressure chamber by means of an actuator positioned in or near the pressure chamber. The fluid distribution device can comprise a filter for filtering the fluid and / or a damper element to absorb pressure pulses travelling through the fluid, so as to prevent the pulses from influencing the pressure in the pressure chamber. The fluid distribution device can further be provided with a return channel allowing the fluid to continuously recirculate between the device and a central reservoir. This results in a manifold comprising various bends and corners in which air bubbles can become trapped inside the fluid distribution device. The air bubbles can accumulate into larger air pockets and affect the performance of the fluid distribution device, such as its throughflow and / or filtering capacity. It is known that air bubbles can be removed, for example by means of a so-called purge flow, through, for example, the return channel and / or through the nozzles, but in practice there is often some gas left inside the device after purging. SUMMARY

[0003] It is an object of the present invention to provide an improved fluid distribution device, in particular with regard to its overall size, footprint, cost and / or performance.

[0004] According to the invention, there is provided a fluid distribution device for a printhead assembly. The fluid distribution device comprises:

[0005] - a fluid chamber provided with an inlet and a printhead supply outlet, the inlet and the printhead supply outlet being configured for fluid connection to a supply channel and at least one drop forming unit, respectively;

[0006] - a fluid permeable filter forming a partition wall in the fluid chamber, such that the inlet is positioned at a first side of the filter and the printhead supply outlet is positioned at a second side of the filter opposite the first side, wherein the filter is inclined with respect to a first direction, the first direction being parallel to a vertical direction during operation, such that a first volume between the filter and a first side wall facing the first side of the filter gradually decreases in a direction away from the inlet when viewed in the first direction.

[0007] The filter is positioned obliquely with respect to the first direction. Due to the oblique or slanted position of the filter, the first volume between the filter and one of the opposite 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 as one moves away from the inlet in the first direction. This allows a relatively large effective area of the filter without increasing the footprint of the fluid chamber. The larger effective area of the filter improves the flow-through of the fluid and can also contribute to a longer lifetime of the filter. The object of the invention is thus achieved.

[0008] In some embodiments more specific optional features of the invention are indicated.

[0009] In an embodiment, the inlet is located at a top wall of the fluid chamber and the printhead supply outlet is located at a bottom wall opposite the top wall. Top and bottom are here defined with respect to a first direction parallel to the vertical direction, as during operation of the device. Both the top wall and the bottom wall comprise at least one opening through which fluid flows into and out of the fluid chamber, respectively, preferably along or against the first direction. During operation, fluid enters the fluid chamber substantially in the vertical direction and leaves the fluid chamber in the same direction. This further reduces the effective footprint of the fluid dispensing device, as the inlet and the printhead supply outlet overlap with the fluid chamber as seen from above.

[0010] In an 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 a relatively large filter area, which is beneficial for the operation and lifetime of the filter. Due to the oblique position of the filter with respect to the first direction, the total effective area of the filter is preferably larger than the area of the vertical cross-section of the fluid chamber through the filter.

[0011] In an embodiment, the bottom wall is longitudinal in a second direction perpendicular to the first direction, and wherein the filter extends parallel to the second direction. Printhead units are often longitudinal due to their one or more columns of a large number of nozzles. By following the longitudinal shape of the printhead unit to which the fluid dispensing device is connected, the vertical footprint of the fluid dispensing device remains small. The second direction is preferably parallel to the direction of the one or more nozzle columns. Thus, the length of the bottom wall of the fluid chamber in the second direction is larger than its width in a third direction perpendicular to the first and second directions. By extending the filter substantially parallel to the second direction, a large filter area can be obtained. The first volume gradually decreases when viewed in the second direction, but preferably not (or at least not significantly) when viewed in the third direction.

[0012] In an embodiment, the filter extends parallel to the second direction. An edge of the filter is located at an edge of the bottom, which edge is also parallel to the second direction. From said edge, the filter is inclined in a third direction towards an opposite edge of the bottom wall. Preferably, another edge of the filter contacts the top wall, while another edge of the filter contacts a side wall of the fluid chamber in the second direction. Preferably, the fluid chamber is dimensioned such that said side wall has the smallest area of all walls defining the fluid chamber.

[0013] In an 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 total area of the fluid chamber is filled by the filter. When viewed in the third direction, the filter extends to and / or contacts the entire perimeter of the fluid chamber. The filter extends along the top wall, the bottom wall and the side walls in the second direction. Due to the inclination, for cross sections in the first and second directions, the total area and / or the effective area of the filter is larger than the cross sectional area of the fluid chamber.

[0014] In an embodiment, the printhead supply outlet comprises at least two outlet openings in the bottom wall, which outlet openings are spaced apart from each other in the second direction. Due to the inclination of the filter, the printhead supply outlet in the bottom wall can obtain a relatively large area, such that its total opening area can be relatively large. Having two or more spaced apart outlet openings further contributes to a more uniform supply of fluid to the printhead unit, since for optimal performance, it is required that each nozzle is supplied with sufficient fluid. Preferably, the two outlet openings are also located at different positions in the third direction.

[0015] In an embodiment, the filter at least partially overlaps the printhead supply outlet when viewed in the first direction. This allows for a relatively large filter without reducing the cross section of the printhead supply outlet and / or adjusting its position. The filter extends at least partially above the printhead supply outlet. The filter is positioned between the inlet and the printhead supply outlet. Preferably, the inlet is positioned in a wall opposite to the wall comprising the printhead supply outlet. The top wall of the fluid chamber can for example comprise said inlet, while the printhead supply outlet is provided in or at the bottom wall during operation. Similarly, in another embodiment, the filter at least partially overlaps the inlet when viewed in the first direction. This way, a relatively large filter can be applied without having to compromise on the position and / or size of the inlet. Preferably, the filter at least partially overlaps the inlet as well as the printhead supply outlet when viewed in the first direction. Preferably, the filter is inclined at an angle of at least 10° to the first direction.

[0016] In an embodiment, the fluid dispensing device further comprises a return channel for returning fluid, the return channel bypassing the fluid chamber, and a first vent channel connecting the fluid chamber to the return channel, such that the first vent channel inlet of the fluid chamber is positioned at the second side of the filter. The return channel extends parallel to the fluid chamber, and preferably parallel to the supply channel connected to the inlet. Fluid effectively flows through the return channel in a direction opposite to the average or main flow direction through the inlet and / or in the fluid chamber. The first vent channel is configured for removing gas bubbles from the fluid chamber into the return channel, in particular from the second volume of the fluid chamber downstream of the filter, where the second side of the filter is the downstream side. The cross section of the first vent channel can be narrow compared to the cross section of the inlet and / or the return channel, to reduce fluid loss through the first vent channel. The first vent channel is preferably provided at the highest point of the second volume, measured upwards against the first direction. The first vent channel provides a measure for removing gas accumulated at the top of the second volume. Gas bubbles or cavities that partially obstruct the filter can be removed and / or prevented by means of the first vent channel. During purging by removing gas via the first vent channel, the first vent channel allows to fill substantially the entire second volume with fluid.

[0017] In an embodiment, the second volume between the filter and the second side wall opposite the first side wall gradually decreases towards the first vent channel in the first direction when viewed in the first direction. The first vent channel inlet is preferably positioned in a top wall of the fluid chamber above the second volume. The top edge of the filter is positioned closer to the first vent channel inlet than its bottom edge when measured perpendicular to the first direction. This results in the second volume gradually decreasing towards the first vent channel inlet to direct gas bubbles into the relatively narrow first vent channel. This arrangement saves space as the first vent channel inlet is relatively small.

[0018] In an embodiment, the first vent channel inlet and the printhead supply outlet are positioned on opposite sides of the fluid chamber in the first direction, while in another embodiment the inlet and the printhead supply outlet are positioned on opposite sides of the fluid chamber in the first direction. The inlet, and preferably the first vent channel inlet, can be provided in or at the top wall, with the first vent channel inlet separated from the inlet by the filter. The printhead supply outlet is preferably positioned facing the top wall with the inlet and / or the first vent channel inlet, e.g. in a bottom wall of the fluid chamber.

[0019] Preferably, the first gas vent channel is inclined with respect to the first direction such that during operation the first gas vent channel inlet is below the connection between the first gas vent channel and the return channel. During operation, the first gas vent channel outlet is positioned higher than the first gas vent channel inlet. The upward inclination of the first gas vent channel in the direction of the desired flow makes it more efficient to remove the gas bubbles due to the influence of gravity on the gas bubbles.

[0020] In an embodiment, the first gas vent channel has a cross section that is substantially smaller than the cross section of the inlet and / or the printhead supply outlet. The effective area of the first gas vent channel is preferably less than 30% of the average area of the inlet or the return channel, very preferably less than 20% thereof, even more preferably less than 10% thereof.

[0021] In an embodiment, the fluid dispensing device further comprises a damper element comprising a deformable membrane positioned in the fluid chamber at the second side of the filter. The damper element, the filter, the inlet and the printhead supply outlet overlap with the bottom wall when viewed in the first direction. Furthermore, the filter overlaps with the inlet and the printhead supply outlet. The overlap can be partial. The deformable membrane is a part of the damper element that is positioned in the second volume. The deformable membrane is deformable to absorb pressure pulses travelling through the fluid that can originate from the imaging unit and / or the fluid supply upstream of the inlet. By eliminating pressure fluctuations, the performance of the printhead unit is improved. The damper element is conveniently positioned such that a single damper element is sufficient to absorb pressure pulses originating upstream or downstream of the damper element. When viewed from above during use, all of the above components are positioned to overlap with the footprint of the bottom wall, thereby forming a compact device.

[0022] In an embodiment, the deformable membrane extends along a second side wall of the fluid chamber, the second side wall extending substantially in the first direction during operation. The second side wall is substantially vertical during operation and the membrane is mounted on the second side wall such that an augmented volume is formed between the membrane and the second side wall. The membrane is allowed to deform into the augmented volume to reduce and / or eliminate pressure fluctuations or pulses in the fluid. Preferably, the deformable membrane extends along the entire length of the second side wall between the top wall and the bottom wall of the fluid chamber, thereby fluidically sealing the part of the fluid chamber between the second side wall and the membrane. This allows the membrane to have a relatively large area, improving its absorbency. The sealed part forms the augmented volume and the second side wall can be provided with an opening to connect the augmented volume to the ambient environment. This results in an efficient and low-cost damper element.

[0023] In an embodiment, an edge of the filter, preferably the bottom edge, is positioned in a corner between a bottom wall comprising the printhead supply outlet and a first side wall located at the inlet side of the filter. The bottom edge of the filter is attached at the outer side bottom corner of the first volume in the fluid chamber. From there, the filter extends upwards in an inclined manner towards the outer side top corner of the second volume.

[0024] In an embodiment, the top wall is formed by two top wall portions located at different heights in the first direction, which are connected by an intermediate wall portion extending in the first direction, and wherein an edge of the filter is attached to the intermediate wall portion. The intermediate wall portion allows fixing the edge of the filter without bending the filter and thereby damaging the filter. The bottom edge 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 placing and fixing the filter, making the fluid dispensing device easy to manufacture.

[0025] In an embodiment, the fluid dispensing device further comprises a fluid dispensing manifold for dispensing fluid towards at least one imaging unit, which is fluidly connected with the printhead supply outlet for receiving fluid and with a return channel for removing fluid from the fluid dispensing manifold, and at least one second gas vent channel extending between the return channel and the supply channel and / or the fluid chamber for moving gas bubbles into the return channel, wherein the return channel comprises a first constricted portion at the gas vent channel to establish a local decrease of static pressure for sucking in gas bubbles. The first channel can be provided at the second volume of the fluid chamber, and / or the second gas vent channel can be provided between the supply channel and the return channel to remove gas bubbles rising through the supply channel. This allows removing an accumulation of gas from the first volume. The efficiency of removing gas bubbles can be increased by locally decreasing the cross section of the return channel at the first and / or second gas vent channel. This results in a local increase of the fluid velocity along the outlet of the first and / or second gas vent channel, such that the static pressure decreases. Therefore, the static pressure difference across the first and / or second gas vent channel increases, providing an increased driving force for forcing gas bubbles through the respective gas vent channel.

[0026] In an embodiment, the first constricted portion has a cross sectional area which is 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, very preferably less than 30% of the cross sectional area of the return channel. The cross section is inversely proportional to the fluid velocity, and therefore to the static pressure. The static pressure is for example proportional to the fluid velocity to the power of for example approximately two, so that reducing the cross section is an effective way of reducing the static pressure and thereby the driving force for pushing gas bubbles into the return channel.

[0027] In an embodiment, the supply channel and the return channel are substantially parallel lines next to each other. This forms a space saving configuration. Preferably, both the supply channel and the return channel extend in the first direction, so that gas bubbles can efficiently rise through the channels during operation. The supply channel and the return channel are preferably positioned next to each other. By positioning the channels next to each other, the return channel extends at least partly along the supply channel, next to the supply channel, which allows the second gas removal channel to be relatively small or short. Preferably, the length of the second gas removal 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, preferably parallel to the filter and / or membrane. The relatively short second gas removal channel allows efficient removal of gas bubbles. Advantageously, the supply channel and the return channel can be positioned on a side of the fluid chamber comprising the first gas removal channel outlet, to allow both gas removal channels to have a relatively short length.

[0028] In an embodiment, the return channel is mounted on the fluid distribution manifold around the fluid chamber. The fluid distribution manifold is fluidically positioned between the fluid chamber and the return channel and between the fluid chamber and the imaging unit of the at least one printhead unit. A portion of the fluid is supplied to the imaging unit, while the return channel allows continuous circulation of the fluid through the fluid distribution manifold, independent of the activity of the imaging unit. The length of the return channel in the first direction is preferably at least the length of the supply channel and the fluid chamber added together.

[0029] In an embodiment, the return channel extends along and next to the fluid chamber, wherein the first gas removal channel is formed between the top of the fluid chamber and the return channel, and wherein the second gas removal channel is formed between the supply channel and the return channel, away from the fluid chamber. To remove accumulations of gas from both the first and second volumes on opposite sides of the filter located in the fluid chamber, two gas removal channels are provided. The first gas removal channel connects the top or highest portion of the second volume to the return channel to remove accumulations of gas from the second volume of the fluid chamber. The second gas removal channel is provided at the supply channel, which is connected to the top wall portion above the first volume of the fluid chamber. Thereby, gas bubbles in the first volume are allowed to escape through the supply channel. Thus, accumulations of gas on both sides of the filter in the fluid chamber are prevented and / or can be removed. Both during normal operation and during a purging action, in which fluid is forced into the fluid chamber at an increased pressure, the gas removal channels contribute to the removal of gas. During purging, substantially all of the gas accumulations can be pushed from the first volume and the second volume, allowing the fluid chamber to be completely filled with fluid on both sides of the filter. This extends the throughflow capacity and / or prolongs the service life of the filter.

[0030] In one embodiment, the supply channel includes a second narrowing portion located at the exhaust line, which extends over at least one exhaust channel in the direction of gravity during operation. During operation, the supply channel narrows at and / or above the second exhaust channel. This effectively results in a reduction in the cross-section of the supply channel in the direction of bubble ascent. The reduction in cross-section is preferably abrupt, such as an obstacle or step along the inner wall of the supply channel. This narrowing interferes with the trajectory of the bubbles, making them easier to enter the second exhaust channel. Therefore, the efficiency of gas removal is improved. The narrowing preferably involves a reduction of at least 50%, preferably at least 40%, very preferably at least 30%, and even more preferably at least 20% of the cross-section.

[0031] In one embodiment, the supply channel, return channel, and fluid chamber are formed of injection-molded plastic, and preferably, at least a portion of the fluid chamber is integrally formed with the supply channel and / or return channel. To reduce costs, the fluid dispensing device is partially formed by injection molding. One or more components, such as a first portion of the fluid chamber and the supply channel, can be integrally formed in the same mold.

[0032] In one embodiment, the printhead supply outlet and inlet are positioned on opposite sides of the fluid chamber in a first direction, and the supply channel and return channel extend along the first direction during operation. The inlet is located at the top wall, which faces the bottom wall that holds the printhead supply outlet. This allows the supply channel to be positioned at least partially above the fluid chamber when viewed along the first direction. Similarly, the printhead supply outlet overlaps with the bottom wall when viewed along the first direction. This keeps the fluid dispensing device relatively compact while allowing for a relatively large filtration area. Preferably, the inlet is located on or near the first sidewall of the top wall, which faces the inlet side of the filter.

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

[0034] The present invention also relates to an inkjet printer including a printhead assembly, the printhead assembly including a fluid dispensing device according to the invention fluidly connected to at least one printhead unit.

[0035] Further applications of the invention will become apparent from the following detailed description. However, it should be understood that while the detailed description and specific examples indicate preferred embodiments of the invention, they are given by way of illustration only, as various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art based on this detailed description. Attached Figure Description

[0036] The invention will be more fully understood from the following detailed description and accompanying drawings, which are given by way of illustration only and are not intended to limit the invention. In the drawings:

[0037] Figure 1 This is a schematic cross-sectional view of a fluid distribution device known in the prior art;

[0038] Figure 2 This is a schematic front view of the fluid distribution device according to the present invention;

[0039] Figure 3 yes Figure 2 A schematic side view of fluid distribution in the middle; and

[0040] Figure 4 It shows that by Figure 2 A schematic front view of the bubble trajectory of fluid in a fluid distribution device. Detailed Implementation

[0041] The invention will now be described with reference to the accompanying drawings, in which the same reference numerals are used in all the views to identify the same or similar elements.

[0042] Figure 1A printhead assembly known in the prior art is disclosed. This printhead assembly includes a plurality of printhead units 10 mounted on the underside of a fluid distribution device 1. Each printhead unit 10 includes a plurality of imaging units, each including a nozzle 12 connected to a pressure chamber (not shown), in which a pressure pulse can be applied to eject droplets of fluid from the nozzle 12. Suitable actuators for generating the pressure pulses can be, for example, piezoelectric actuators, thermal actuators, or so-called bubble jet actuators. Fluid is supplied to the printhead units 10 via a fluid distribution manifold 20. The fluid distribution chamber 20 is provided with a damper element 21 to prevent pressure pulses from one imaging unit from affecting the pressure in the pressure chamber of another imaging unit. The damper element 21 includes a deformable elastic membrane 22 capable of absorbing pressure pulses by bending into an expanded volume 23, which is sealed relative to the chamber 20. Fluid is supplied to the fluid distribution chamber 20 via a filter unit 30 formed by fluid chambers 31 separated by a porous membrane 32. The membrane opening is appropriately narrow to prevent larger dirt particles or air bubbles from reaching the printhead unit 10. On its inlet side, a fluid chamber is connected to a supply channel 33 for receiving fluid, while on the opposite side of the membrane 32, the fluid chamber 31 is provided with a return channel 34 for recirculating the fluid back to the central container. A disadvantage of the known printhead assemblies is gas trapping in any of their components. As fluid passes through the printhead assembly, small air bubbles are transported or formed in the fluid and become trapped in the corners and other dead zones of the device 1. These bubbles interact to form larger cavitations that prevent fluid from entering from all areas of the printhead assembly. Such cavitations are known to be removed by so-called purging, which uses a relatively high-pressure flow or countercurrent to expel the cavitations; however, in practice, some residual gas remains trapped inside the device 1 even after purging. Furthermore, known printhead assemblies are relatively complex or large in terms of components and / or volume.

[0043] Figure 2 , Figure 3 and Figure 4A compact and productive printhead assembly 100 according to the present invention is shown. A fluid distribution device 130 is fluidly connected to a fluid distribution manifold 120, which holds and supplies fluid to the imaging unit of the printhead unit 110. The fluid distribution device 130 is connected to one or more fluid supply containers (not shown) via its fluid interface elements 138, 139. Both the supply channel 133 and the return channel 134 are provided with their respective fluid interface elements 138, 139. The supply channel 133 extends vertically along a first direction D1 parallel to the direction of gravity during operation. The supply channel 133 forms an inlet 137 in the top 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 downstream volume V2. The filter 132 forms a barrier between the first volume V1 and the second volume V2 that prevents particles exceeding a certain size threshold from passing through. The second volume V2 of the fluid chamber 131 holds a damper element 121, which is formed of a deformable membrane 122 extending along a second sidewall 124 of the fluid chamber 131. The second sidewall 124 may be provided with openings to improve the function of the damper element 121. The membrane 122 is mounted on or above the second sidewall 124 to seal the portion of the second sidewall 124 including the openings. Preferably, the deformable membrane 122 extends along the entire length of the second sidewall 124 between a corresponding top wall portion 127 and a bottom wall 126 of the fluid chamber 131.

[0044] The top wall portion 127 is tilted or inclined upward toward the first exhaust passage 140, which connects the second volume V2 to the return passage 134. The first exhaust passage 141 is a relatively narrow passage compared to passages 133 and 134 to reduce the amount of fluid flowing back into the return passage 134. This allows for the removal of gas or bubbles from the fluid in the second volume V2 without significant fluid flow loss in the main fluid delivery direction.

[0045] The bottom wall 126 of the fluid chamber 131 is provided with at least one printhead supply outlet 135, which leads to one or more printhead supply channels 136 through which fluid is delivered from the second volume V2 to the fluid distribution manifold 120. The fluid distribution manifold includes multiple channels supplying fluid to the printhead unit 110 and to a return channel 134 for recirculating the fluid back to one or more central containers. 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 very close to each other on the same side of the fluid chamber 131 to allow the supply channel 133 to be connected to the return channel 134 via a second vent channel 141. The second vent channel 141 removes air bubbles from the supply channel 133 and the first volume V1, thereby preventing the air bubbles from traveling back toward the fluid chamber 131. Since the supply channel 133 and the return channel 134 are located adjacent to each other on the higher side of the second volume V2 of the fluid chamber 131, both exhaust channels 140, 141 can be relatively short, thereby allowing for efficient removal of air bubbles.

[0046] Figure 4 It shows Figure 2 The trajectory of bubble B in the printhead assembly 100 is shown. Bubble B flows to the printhead unit 110 and circulates through the fluid distribution manifold 120. The bubble travels upward from the fluid distribution manifold 120 in the return direction D3 through the return channel 134. Similarly, bubble B can travel upward against the fluid supply direction D2 through the supply channel 133. Bubble B may originate from and / or accumulate in the fluid chamber 131. Accumulation A1 of bubble B gathers at the top of the first volume V1, which may obstruct proper fluid inflow and partially block the filter 132, reducing fluid flow toward the printhead unit 110. Bubble B may further accumulate in the second volume V2, forming accumulation A2. This accumulation A2 may reduce flow through the fluid chamber 131. The fluid distribution device 130 according to the invention provides several measures to reduce and / or remove the accumulation of bubble B, which will be described below.

[0047] To reduce this buildup and / or remove bubbles, exhaust channels 140 and 141 are provided to guide the bubbles into the return channel 134. The first exhaust channel 140 is located at the top wall portion 127 of the second volume V2 to remove gas from the buildup A2. The first exhaust channel 140 is preferably located at the highest point of the first volume V2. To reduce or prevent gas buildup in the first volume V1 (and in the second volume V2), the supply channel 133 is connected to the return channel 134 via the second exhaust channel 141. The second exhaust channel 141 at least partially removes the bubbles rising through the supply channel 133 into the return channel 134. Preferably, the inlet 137 of the supply channel 133 is located at the highest point of the first volume V1. The exhaust passages 140 and 141 are preferably relatively narrow to reduce fluid loss through the exhaust passages 140 and 141, for example, the diameter or cross-section does not exceed 40%, preferably 30%, very preferably 20%, or even more preferably 10% of the diameter or cross-section of the supply passage 133 and / or the return passage 134.

[0048] The return channel 134 includes a narrowing portion 142 at a height position of the second exhaust channel 141. The narrowing portion 142 provides 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%. 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, such as... Figure 2 As shown. By locally reducing the cross-sectional area of ​​the return channel 134, the fluid velocity along the second exhaust channel 141 in the return channel 142 is locally increased. This results in a localized reduction in static pressure, improving the intake of bubbles through the second exhaust channel 141. Due to Bernoulli's law, the narrowing increases the static pressure difference across the second exhaust channel 141 between the supply channel 133 and the return channel 134. The increased pressure difference provides the driving force for propelling bubbles through the second exhaust channel 141 into the return channel 134. The narrowing can also be applied to the return channel 134 at the first exhaust channel 140.

[0049] Further improvements to the method of driving bubbles through the second exhaust channel 141 can be achieved by locally reducing the cross-sectional area of ​​the supply channel 133 at the second exhaust channel 141. Additionally, as... Figure 2As shown, the supply interface element 138 has an effective diameter smaller than the lower portion of the supply channel 133. This reduced diameter can be achieved by an insertable obstruction with a through-hole and / or by reducing the effective diameter of the supply interface element 138 compared to the effective diameter of the supply channel 133. It has been found that the local reduction in the cross-sectional area in the supply channel 133 creates an obstruction in the path of the rising bubbles through the supply channel 133. This obstruction interferes with the bubble trajectory, making them easier to enter the second exhaust channel 141. Preferably, the supply channel 133 is abruptly narrowed by steps or protrusions.

[0050] To reduce the retention of bubble B in the first volume V1, the inlet 137 of the supply channel 133 is preferably located at the highest point of the top wall portion 128 during operation. Preferably, the top wall portion 128 slopes upward toward the inlet 137. Under gravity, bubble B is thus guided to the inlet 137 and into the supply channel 133. This configuration is advantageous during operation and during purging, allowing substantially the entire first volume V1 to be filled with fluid.

[0051] The top wall portion 127 of the second volume V2 can also be inclined upward toward the first exhaust channel 140 to help guide bubble B toward the first exhaust channel 140. Since the diameter of the first exhaust channel 140 is relatively small compared to the cross-section of the second volume V2, the second volume V2 can further taper toward the first exhaust channel 140 to guide bubble B into the first exhaust channel 140. The smaller first exhaust channel 140 allows space for, for example, to bend and / or tilt the top wall, such that the first exhaust channel is located at its highest point. The top wall includes top wall portions 127 and 128 respectively positioned above the second volume V2 and the first volume V1. The top wall portion 127 of the second volume V2 is positioned at a different height than the top wall portion 128 of the first volume V1, such that a vertically extending intermediate top wall portion 129 is formed between the top wall portions 127 and 128. The top edge of the filter 132 is attached to said intermediate top wall portion 129. This allows for secure attachment to the top wall without folding and potentially damaging the filter 132, while also allowing the inlet 137 and the second exhaust passage 140 to be positioned at the top wall. The intermediate top wall portion 129 may extend circumferentially around the filter 132 to form an attachment ridge along a portion or the entire length of the filter 132. The intermediate top wall portion 129 allows the filter 132 to be tilted by positioning its top edge closer to the first exhaust passage 140 (measured in a direction perpendicular to the first direction) than its bottom edge.

[0052] The fluid distribution device 130 also allows for a compact structure with a relatively small number of components. This reduces costs and the space occupied by the printhead assembly, thus allowing for a compact construction. Additionally, the filter 132 is positioned at an angle relative to the first direction D1. The bottom edge of the filter 132 is positioned at or at the corner of the bottom wall 126 and the first sidewall 125. The first sidewall 125 faces and / or is opposite to the second sidewall 124, and the membrane 122 of the damper element 121 is positioned against the second sidewall. The filter 132 extends upward against the first direction D1, moving further away from the first sidewall 125. This results in a generally triangular cross-section of the first volume V1 formed between the filter 132 and the first sidewall 125. The length and / or area of ​​the top wall portion 128 of the first volume V1 is significantly smaller than the length and / or area of ​​the filter 132 and the first sidewall 125. The angle between the filter 132 and the first sidewall 125 is an acute angle, preferably less than 20°, and very preferably less than 10°. Inlet 137 is located in top wall portion 128, facing the acute angle between filter 132 and first side wall 125. When viewed along the first direction D1, inlet 137 at least partially overlaps with filter 132 because inlet 137 is positioned above filter 132. Top wall portions 127, 128 are positioned at different heights to form a vertically extending intermediate wall portion 129 against which the top edge of filter 132 is fixed. This allows the first exhaust passage 140 to be positioned at the top of the second volume, while positioning the top edge of filter 132 closer to the first exhaust passage 140 than its bottom edge. Filter 132 extends from bottom wall 126 to top wall, resulting in a large filtration area. When viewed along the second direction D2, the first volume V1 continuously decreases in size because filter 132 is inclined along the first direction D1 throughout its height. When viewed along the third direction D3, filter 132 does not decrease significantly in size and has a constant length for most of its height. The length of filter 132 in the second direction D2 is greater than the width of bottom wall 126 in the third direction D3. Furthermore, the height of filter 132 in the first direction is greater than the width of bottom wall 126 in the third direction D3. Due to the inclination, the distance or length between bottom wall 126 and top wall measured on filter 132 is greater than the height of fluid chamber 131 between the walls in the first direction D1. The area of ​​filter 132 through which fluid can flow is greater than the cross-sectional area of ​​fluid chamber 131 in the first direction D1 and the second direction D2. When viewed along the third direction D3, filter 132 contacts the peripheral wall of fluid chamber 131. The edges of filter 132 contact the top wall, bottom wall 126, and third and fourth side walls 117 and 119.

[0053] The tilt of filter 132 results in a sloping wall for the second volume V2, which causes the second volume V2 to gradually decrease towards the first exhaust passage 140. This tilt also allows filter 132 to have a larger surface area. The membrane 122 of damper element 121 is positioned relative to filter 132. Damper element 121 extends entirely along the second sidewall 124, thereby forming a relatively large and therefore effective damper. Membrane 122 is formed of corrugated foil as described in US 20200376843A. Damper element 121 is positioned such that it can absorb not only pressure pulses from printhead unit 110, but also pressure pulses or changes from the fluid supply traveling along the first direction D1 through supply passage 133. When viewed along the first direction D1, filter 132 overlaps with the top wall portion 128 of the first volume V1, but not with the top wall portion 127 of the second volume V2. In the same top view, the top edge of filter 132 is positioned closer to the first exhaust passage 140 than its bottom edge. Similarly, the top edge is preferably further away from the inlet 137 than the bottom edge. To minimize space occupation, the second sidewall 124 and the first sidewall 125 are preferably parallel to each other and parallel to the first direction D1. Similarly, membrane 122 extends parallel to the second sidewall 124 from its top side to its bottom side, or extends between the top wall portion 127 and the bottom wall 126.

[0054] The bottom wall 126 is longitudinal. The length of the bottom wall 126, measured along the second direction D2, is significantly greater than its width along the third direction D3. In use, both the second direction D2 and the third direction D3 are preferably horizontal. By positioning the filter 132 at the edge of the bottom wall 126 on the side of the inlet 137, essentially the entire area of ​​the bottom wall 126 is available for the printhead supply outlet 135. The printhead supply outlet 135 includes two outlet openings, each defining a printhead supply channel 136 spaced apart from each other along the second direction D2. As a result, when viewed from above along the first direction D1, the filter 132, damper element 121, inlet 137, and printhead supply outlet 135 all overlap with the bottom wall 126. This ensures a smaller footprint, allowing for tighter stacking of printheads. The height of the fluid chamber 131 in the first direction D1 and its length in the second direction D2 are greater than its width in the direction D3. As a result, the third sidewall 117 and the fourth sidewall 119 in the second direction are smaller than the other walls, namely the top wall, the bottom wall 126, the first sidewall 124 and the second sidewall 125.

[0055] When viewed along the first direction, filter 132 also overlaps with one of the printhead supply outlets 135. The second volume V2 gradually decreases toward the first exhaust channel 140. The top side of filter 132 is positioned closer to the first exhaust channel 140 in a direction perpendicular to the first direction than the bottom side of filter 132.

[0056] Preferably, the fluid distribution device 130 is at least partially formed of injection-molded plastic. Specifically, the fluid chamber 131 may be formed of a plastic component in which a filter 132 and a membrane 122 are already installed.

[0057] Although specific embodiments of the invention have been shown and described herein, those skilled in the art will understand that various alternatives and / or equivalent implementations exist. It should be understood that one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or construction in any way. Rather, the foregoing overview and detailed description will provide a convenient guide for those skilled in the art to implement at least one exemplary embodiment, and it should be understood that various changes may be made to the function and arrangement of the elements described in the exemplary embodiments without departing from the scope set forth in the appended claims and their legal equivalents. In general, this application is intended to cover any modifications or variations to the specific embodiments discussed herein.

[0058] It should also be understood that, in this document, the terms “comprising,” “including,” “containing,” “having,” and any variations thereof are intended to be understood in an inclusive (i.e., non-exclusive) sense, such that the process, method, apparatus, device, or system described herein is not limited to those features, components, elements, or steps described herein, but may include other elements, features, components, or steps not expressly listed or inherent to such a process, method, article, or apparatus. Furthermore, unless otherwise expressly stated, the terms “a” and “an” as used herein are intended to be understood as meaning one or more. Moreover, the terms “first,” “second,” “third,” etc., are used merely as designations and are not intended to impose numerical requirements on the importance of their objects or to establish a specific order of importance.

[0059] As the invention has been described thus, it will be apparent that the invention can be modified in many ways. Such modifications should not be considered a departure from the spirit and scope of the invention, and all such modifications that are obvious to those skilled in the art are to be included within the scope of the appended claims.

Claims

1. A fluid dispensing device (130) for a printhead assembly (100), comprising: A fluid chamber (131) is provided with an inlet (137) and a printhead supply outlet (135), the inlet and the printhead supply outlet being configured for fluid connection to a supply channel (133) and at least one droplet forming unit, respectively; A fluid-permeable filter (132) forms a partition wall in the fluid chamber (131) such that the inlet (137) is located on a first side of the filter (132), and the printhead supply outlet (135) is located on a second side of the filter (132) opposite to the first side. The filter (132) is inclined relative to a first direction (D1), which is parallel to the vertical direction during operation, such that when viewed along the first direction, the first volume (V1) in the fluid chamber (131) between the filter (132) and the first sidewall (125) facing the filter (132) gradually decreases in the direction away from the inlet (137). The inlet (137) is located on the top wall of the fluid chamber (131), and the printhead supply outlet (135) is located on the bottom wall (126) opposite to the top wall. The fluid distribution device (130) further includes a damper element (121) comprising a deformable membrane (122) positioned in the fluid chamber (131) on a second side of the filter (132). When viewed along a first direction (D1), the damper element (121), filter (132), inlet (137), and printhead supply outlet (135) overlap with the bottom wall (126), and the filter (132) overlaps with the inlet (137) and printhead supply outlet (135). The deformable membrane (122) extends along a second sidewall (124) of the fluid chamber (131), which extends substantially along the first direction (D1) during operation. The top wall is formed by two top wall portions (127, 128) positioned at different heights in the first direction (D1), the two top wall portions (127, 128) being connected by an intermediate wall portion (129) extending along the first direction (D1), and wherein the edge of the filter (132) is attached to the intermediate wall portion (129).

2. The fluid distribution device (130) according to claim 1, wherein, The filter (132) extends from the bottom wall (126) to the top wall.

3. The fluid distribution device (130) according to claim 2, wherein the filter (132) contacts the bottom wall (126) and the top wall.

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

5. The fluid distribution device (130) according to claim 4, wherein, The printhead supply outlet (135) includes at least two outlet openings in the bottom wall (126), the outlet openings being spaced apart from each other in the second direction (D2).

6. The fluid distribution device (130) according to claim 1, wherein, When viewed along the first direction (D1), the filter (132) at least partially overlaps with the printhead supply outlet (135).

7. The fluid distribution device (130) according to claim 1, wherein, When viewed along the first direction (D1), the filter (132) at least partially overlaps with the inlet (137).

8. The fluid distribution device (130) according to claim 1, further comprising: A return channel (134) for returning fluid, the return channel (134) bypassing the fluid chamber (131); And a first exhaust passage (140) that connects the fluid chamber (131) to the return passage (134) such that the inlet of the first exhaust passage is located on the second side of the filter (132).

9. The fluid distribution device (130) according to claim 8, wherein, The second volume (V2) located between the filter (132) and the second sidewall (124) opposite to the first sidewall (125) gradually decreases toward the first exhaust passage (140) in the opposite direction (D1).

10. The fluid distribution device (130) according to claim 8, wherein, The first exhaust channel inlet and the printhead supply outlet are positioned on opposite sides of the fluid chamber (131) in the first direction (D1).

11. The fluid distribution device (130) according to claim 8, wherein, The first exhaust passage (140) is inclined relative to the first direction (D1) such that during operation, the first exhaust passage inlet is below the connection between the first exhaust passage (140) and the return passage (134).

12. The fluid distribution device (130) according to claim 1, wherein, The edge of the filter (132) is positioned in a corner between the bottom wall (126) including the printhead supply outlet (135) and the first sidewall (125) opposite to the second sidewall (124).

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