Droplet ejection head and operation method thereof

Abstract

A droplet ejection head and a method for operating the same. The droplet ejection head includes one or more actuator components, an inlet path for supplying fluid to the one or more actuator components, and an outlet path for discharging fluid from the one or more actuator components. The one or more actuator components include multiple fluid chambers, each with at least one nozzle, operable to eject one or more droplets through the at least one nozzle in response to an ejection command. The multiple fluid chambers are fluidly connected at a first end to the inlet path and at a second end to the outlet path. The outlet path includes one or more heat exchangers arranged in series downstream of the one or more actuator components, with one or more actuator drive electronics disposed adjacent to each heat exchanger. The one or more heat exchangers include one or more heat exchanger flow paths, and during use, heat is transferred from the actuator drive electronics to the one or more heat exchangers and removed via a return fluid. The area bounded by the actuator drive electronics is substantially contained within a coplanar area bounded by the one or more heat exchanger flow paths. A method for cooling actuator drive electronics of a droplet ejection head. A droplet ejection device including such a droplet ejection head, a method of operating the droplet ejection device to cool an actuator driving electronic component, and a method of operating the droplet ejection device to heat a fluid using the actuator driving electronic component.

Description

[Technical Field]

[0001] The present disclosure relates to a droplet ejection head. The droplet ejection head may be a drop-on-demand inkjet printhead. The droplet ejection head may include one or more actuator components, a supply path for supplying fluid to the one or more actuator components, and a return path for removing fluid from the one or more actuator components. The actuator components may include actuators operable to expel droplets from nozzles in a jetting direction in response to electrical signals provided by actuator drive electronics. In applications requiring high jetting frequencies and / or high jetting duties, the actuator drive electronics may generate significant amounts of heat at levels that may adversely affect the reliability and / or lifespan of the droplet ejection head. The present disclosure relates to a droplet ejection head with improved thermal management capabilities. [Background technology]

[0002] Droplet ejection heads are now widely used in both traditional applications such as inkjet printing and in 3D printing and other rapid prototyping technologies. Droplet ejection heads have been developed for industrial applications, such as printing directly onto substrates like ceramic tiles and textiles, and for forming elements like color filters in LCD and OLED displays for flat-screen televisions. These industrial printing techniques using droplet ejection heads have enabled short-run production runs, product customization, and even the printing of custom designs. It is therefore understandable that droplet ejection heads continue to evolve and specialize to suit new and / or increasingly challenging applications. However, despite the significant developments in the droplet ejection head field, there is still room for improvement.

[0003] In recent years, there has been growing interest in operating at higher frequencies, for example, to increase printing speeds. Increasing operating frequencies tends to increase the amount of heat generated by the actuator drive electronics, which can result in undesirable increases in internal temperatures. This effect is exacerbated when operating at high or maximum ejection duty (i.e., when most to most of the droplet-ejecting nozzles are ejecting droplets simultaneously). Consequently, thermal management of the actuator drive electronics under these operating conditions has become an increasing concern. Lowering the temperature of the actuator drive electronics improves operating temperatures, extends product life, increases reliability, and reduces thermal stress on the actuator components, resulting in improved droplet uniformity, for example, by allowing fluid viscosity to be maintained within a narrower operating window. Furthermore, removing most of the heat generated by the actuator drive electronics may reduce thermally induced structural variations in the droplet ejection heads and improve printing performance by limiting variations in the alignment position, shape and size of the droplet ejection heads and limiting or eliminating alignment variations between a particular droplet ejection head and other components (such as other droplet ejection heads) within the droplet ejection device.

[0004] The present invention has been made in view of the above problems. Summary of the Invention

[0005] Aspects of the invention are set out in the accompanying independent claims, and details of particular embodiments of the invention are set out in the accompanying dependent claims.

[0006] According to a first aspect of the present invention, there is provided a droplet ejection head comprising one or more actuator components, an inlet pathway for supplying fluid to the one or more actuator components, and an outlet pathway for discharging fluid from the one or more actuator components. wherein the one or more actuator components comprise a plurality of fluid chambers, the plurality of fluid chambers comprising at least one nozzle, the plurality of fluid chambers operable to eject one or more droplets through the at least one nozzle in response to an ejection command. The plurality of fluid chambers are fluidly connected at respective first ends to the inlet pathway and at respective second ends to the outlet pathway. The outlet path includes one or more heat exchangers arranged in series downstream of one or more actuator components. One or more actuator drive electronics are located adjacent to each heat exchanger. Here, the one or more heat exchangers comprise one or more heat exchanger flow paths, and in use, heat from the actuator drive electronics is transferred to the one or more heat exchangers and removed via a return fluid. The area defined by the actuator drive electronics is substantially contained within the coplanar area defined by the one or more heat exchanger flow paths.

[0007] According to a second aspect of the present invention, there is provided a droplet ejection device comprising one or more droplet ejection heads according to the first aspect of the present invention, and a droplet ejection fluid source fluidly connected to the one or more droplet ejection heads via a fluid inlet path for supplying fluid to the one or more droplet ejection heads and a fluid return path for exhausting fluid from the one or more droplet ejection heads.

[0008] According to a third aspect of the present invention, there is provided a method of cooling one or more actuator drive electronics for a droplet ejection head according to the first aspect of the present invention, the method comprising: - supplying fluid to the one or more actuator components via the inlet passage; - discharging fluid from the one or more actuator components via the outlet path and introducing the fluid into a heat exchanger flow path to pass through the one or more heat exchangers and remove heat transferred from the actuator drive electronics to the heat exchangers via fluid flowing through the one or more heat exchangers.

[0009] According to a fourth aspect of the present invention there is provided a method of operating a droplet ejection device according to the second aspect of the present invention, the method comprising: - supplying fluid to the one or more droplet ejection heads via the fluid inlet pathway; - supplying fluid to the one or more actuator components via the inlet passage; - ejecting a portion of said fluid from one or more nozzles in said actuator component in response to an ejection command; - draining undischarged fluid from the one or more actuator components via the outlet path; and - transferring thermal energy from the one or more actuator drive electronics to the heat exchanger; and - a part or all of the thermal energy, - transferring thermal energy to the undischarged fluid in the outlet path; - draining the unejected fluid from the one or more droplet ejection heads via the fluid return path; and removing the heat from the heat exchanger by

[0010] According to a fifth aspect of the present invention there is provided a method of operating a droplet ejection device according to the second aspect of the present invention to heat fluid in one or more droplet ejection heads according to the first aspect of the present invention, the method comprising: - supplying fluid to one or more droplet ejection devices via the fluid return path; - using an appropriate waveform or function to generate heat within said one or more actuator drive electronics; - transferring the thermal energy from the one or more actuator drive electronics to the heat exchanger; - transferring some or all of the thermal energy from the heat exchanger to a fluid in the heat exchanger flow path; - supplying fluid from the heat exchanger to the one or more actuator components; - exhausting fluid from the one or more actuator components via the inlet passage; Includes: [Brief explanation of the drawings]

[0011] [Figure 1] Figure 1A shows a droplet ejection device including a droplet ejection head according to an embodiment including a fluid supply, a fluid flow path including a fluid inlet path and a fluid return path, and a heat exchanger disposed adjacent to actuator drive electronics. Figure 1B shows an end view of the droplet ejection head of Figure 1A. Figure 1C shows a cross section of the droplet ejection head of Figures 1A and 1B, as shown in Figure 1B, showing that the heat exchanger includes a return loop within the flow path of the heat exchanger, with the straight legs of the return loop separated by a peninsula wall aligned with the array direction. [Figure 2] FIG. 2A illustrates a droplet ejection device similar to FIG. 1A , but with a droplet ejection head according to another embodiment including a heat exchanger, the heat exchanger including a protrusion with a heat exchange boundary surface adjacent to the actuator drive electronics, and the heat exchanger flow paths including multiple channels separated by walls, as shown in FIG. 2C. FIG. 2B illustrates an end view of the droplet ejection head of FIG. 2A. FIG. 2C illustrates a cross-section BB of the droplet ejection head of FIGS. 2A and 2B, as shown in FIG. 2B, showing the heat exchanger flow paths including multiple channels separated by walls, the walls aligned with the alignment direction within the heat exchanger flow paths. FIG. 2D illustrates a cross-section CC of the heat exchanger of FIGS. 2A-2C, as shown in FIG. 2C, showing horizontal walls within the heat exchanger flow paths. [Figure 3]Figure 3A shows an end view of another embodiment of a heat exchanger similar to Figure 2D. Figure 3B shows a DD cross section of the embodiment shown in Figure 3A, where the walls within the flow channels of the heat exchanger are replaced with ridges that leave openings or gaps in the central flow space of the heat exchanger. Figure 3C shows an EE cross section of the embodiment of Figures 3A and 3B shown in Figure 3B, showing the ridges from another perspective. [Figure 4] Figure 4A shows an end view of a heat exchanger suitable for use in an alternative embodiment comprising multiple pillars within the flow paths of the heat exchanger, and Figure 4B shows a cross section F-F of the embodiment shown in Figure 4A, showing multiple pillars within the flow paths of the heat exchanger. [Figure 5] Figure 5A shows an end view of a heat exchanger suitable for use in an alternative embodiment with a serpentine flow path. Figure 5B shows a cross section GG of the embodiment shown in Figure 5A, illustrating a serpentine path including multiple return loops in the heat exchanger flow path separated by peninsula walls, with the legs of the straight portions of the peninsula walls and return loops aligned with the discharge direction. [Figure 6] FIG. 6A shows an end view of a heat exchanger suitable for use in an alternative embodiment with a heat exchanger flow path having a serpentine path similar to that shown in FIG. 5B, with protruding heat exchange boundary surfaces angled relative to the discharge direction and fluid connection spigots located at the inlet and outlet of the heat exchanger. FIG. 6B shows an H-H cross section of the embodiment shown in FIG. 6A, illustrating a serpentine-shaped flow path with a return loop with rounded corners and straight legs aligned and parallel to the discharge direction, and a loop with straight legs perpendicular to the discharge direction and a fluid connection spigot before the heat exchanger outlet. FIG. 6C shows detail C of the H-H cross section shown in FIG. 6B, illustrating the outlet path, specifically the spigot located to connect a first portion of the outlet path to the heat exchanger inlet. FIG. 6D shows a side view of the heat exchanger and spigot of FIGS. 6A-6C, further illustrating a portion of the outlet path and a fluid diverter for connection to an actuator component. FIG. 6E shows the fluid diverter of FIG. 6D. FIG. 6F shows the underside of the fluid diverter of FIGS. 6E and 6D. [Figure 7]Figure 7A shows an end view of a PCB (printed circuit board) suitable for use in embodiments of the present invention. Figure 7B shows cross section II of the PCB of Figure 7A, illustrating the internal structure. Figure 7C shows an end view of the PCB of Figure 7A, with actuator drive electronics positioned adjacent to and attached to the second heat transfer area. Figure 7D shows the actuator drive electronics of Figure 7C from the interface side (i.e., the side adjacent to the second heat transfer area), illustrating that the actuator drive electronics includes multiple actuator drive electronics. [Figure 8] Figure 8A shows another embodiment of a droplet ejection head, similar to Figures 7A and 7B, with a thermally conductive adhesive layer between the protrusion heat exchange interface surface on the heat exchanger and the first thermally conductive region of each PCB. The second thermally conductive region of each PCB is located adjacent to the actuator drive electronics. Figure 8B shows an end view of the droplet ejection head of Figure 8A, showing the presence of an air gap between the PCB and the heat exchanger, except in the protrusion region. [Figure 9] FIG. 9 shows another embodiment of a droplet ejection head comprising two actuator components, a nozzle plate, and two heat exchangers positioned adjacent to the actuator drive electronics, each heat exchanger being in series with a respective actuator component. [Figure 10] Figure 10A shows an end view of a heat exchanger suitable for use in an alternative embodiment with a serpentine-shaped heat exchanger flow path similar to Figure 6B and further including a sleeve, and Figure 10B shows a JJ cross section of the embodiment shown in Figure 10A, showing the heat exchanger flow path and sleeve. [Figure 11]Figure 11A shows an end view of a heat exchanger suitable for use in an alternative embodiment with a serpentine-shaped heat exchanger flow path similar to Figures 10A and 10B, further including a sleeve and interface material. Figure 11B shows a KK cross section of the embodiment shown in Figure 11A, showing the heat exchanger flow path, sleeve, and interface material. Note that the drawings are not to scale and certain features may be exaggerated in size for greater clarity. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE INVENTION The present invention and various embodiments thereof will now be described with reference to the drawings, in which like reference numerals are used where appropriate to refer to like elements throughout the following description.

[0013] FIG. 1A illustrates a droplet ejection device 1 including a fluid supply 140, a fluid flow path 143 including a fluid inlet path 141 and a fluid return path 142, and a droplet ejection head 100 according to an embodiment. The droplet ejection head 100 includes a heat exchanger 150 disposed adjacent to actuator drive electronics 60. It can be seen that pairs of actuator drive electronics 60i, 60ii are mounted on PCBs 70i, 70ii, respectively, and are disposed adjacent to either side of the heat exchanger 150 (i.e., each PCB 70i, 70ii is interposed between the heat exchanger 150 and one of the respective actuator drive electronics 60i, 60ii). This can be seen more clearly in FIG. 1B, which illustrates an end view of the droplet ejection head 100 of FIG. 1A. It should be understood that this arrangement is not required, and that in other arrangements, each actuator drive electronics 60i, 60ii may be interposed between the heat exchanger 150 and its respective PCB 70i, 70ii.

[0014] FIG. 1C shows a cross section of the droplet ejection head 100 of FIG. 1A taken along the dashed line AA in FIG. 1B, illustrating flow paths 144 and 145 within the droplet ejection head 100. The droplet ejection head 100 includes an actuator component 90, an inlet path 144 for supplying fluid to the actuator component 90, and an outlet path 145 for discharging fluid from the actuator component 90. Although not shown in FIGS. 1A-1C, the actuator component 90 includes multiple fluid chambers, each of which includes at least one nozzle. The multiple fluid chambers are operable to eject one or more fluid droplets through at least one nozzle in response to an ejection command. It is generally understood that the multiple fluid chambers are fluidly connected at their respective first ends to the inlet path 144 and at their respective second ends to the outlet path 145. The outlet path 145 includes a heat exchanger 150 arranged in series downstream of the actuator component 90.

[0015] 1B, it can be seen that there are two actuator drive electronics 60 (in this case 60i, 60ii) positioned adjacent to the heat exchanger 150, one on each side of the heat exchanger 150. The present invention is therefore directed to cooling the actuator drive electronics 60 using a heat exchanger 150 positioned downstream of and adjacent the actuator drive electronics 60, with return (non-discharged) fluid from the actuator component 90 passing through the heat exchanger 150 to remove heat therefrom.

[0016] The fluid inlet path 141 can be connected to a first end of the plurality of fluid chambers via one or more inlet manifold chambers. Fluid passes through the plurality of fluid chambers, a portion of which is ejected through one or more nozzles in response to an ejection command. The remainder of the fluid, i.e., return fluid, can pass through the plurality of fluid chambers. The plurality of fluid chambers are connected at their second ends to one or more return manifold chambers, through which they are fluidly connected to the outlet path 145.

[0017] It is generally understood that the nozzles are arranged in an array, extend in an array direction 10 (e.g., the x direction), eject droplets from the nozzles towards the medium in an ejection direction 16 (e.g., the z direction), and that the nozzle outlets are provided in the medium-facing surface 80 of the droplet ejection head 100. The fluid chamber extends from a first end to a second end thereof in a fluid chamber extension direction 5 (e.g., the y direction). It is generally understood that during operation, the medium-facing surface 80 is appropriately aligned with the medium so that droplets ejected in the ejection direction 16 land at desired locations on the medium.

[0018] 1A-1C, the outlet path 145 includes a heat exchanger 150 disposed in series downstream of the actuator component 90. In this embodiment, the outlet path 145 includes three main portions: a first portion 146 fluidly connecting the actuator component 90 to the heat exchanger 150; a second portion of the heat exchanger 150 including a heat exchanger flow path 151; and a third portion 147 connecting the heat exchanger 150 to the fluid return path 142. The heat exchanger flow path 151 can be seen to include two legs 151_a, 151_b, or straight flow path sections, with a return loop disposed perpendicular to the discharge direction 16. The heat exchanger flow path 151 has a depth 158 (not shown in FIGS. 1A-1C) in a depth direction 5 (y-direction).

[0019] It can further be seen that the two legs 151_a, 151_b are separated by a wall 153, which is perpendicular to the discharge direction 16. It can also be seen that the wall 153 is peninsular in cross section, i.e., it is contained almost entirely within the flow path and has one end attached to the outer wall of the heat exchanger 150, so that in this arrangement it has a base or root 153_r near the inlet 151in of the heat exchanger 150 in the arrangement direction 10.

[0020] First portion 146 and third portion 147 of outlet path 145 may be, for example, a tube or a pipe, similar to inlet path 144. It may generally be understood that inlet path 144 and outlet path 145 may be provided with appropriate connectors to enable fluid-tight connection with external flow paths 143 within droplet ejection head 100.

[0021] 1A and 1B, it can be seen that the actuator drive electronics 60i, 60ii are disposed adjacent to the heat exchanger 150, in this case, one on each side of the heat exchanger 150. The heat exchanger 150 has a flow path 151 through which, in use, heat is transferred from the actuator drive electronics 60 to the one or more heat exchangers 150 and removed from the droplet ejection head via return fluid in the outlet path 145. In this arrangement, it is generally understood that printed circuit boards 70i, 70ii are interposed between the heat exchanger 150 and the actuator drive electronics 60i, 60ii, respectively, and that the printed circuit boards 70i, 70ii are designed to transfer heat to the heat exchanger 150 via the printed circuit boards 70i, 70ii; i.e., the actuator drive electronics 60i, 60ii are thermally connected to the heat exchanger 150 via heat conduction paths 70_v that pass through the printed circuit boards 70i, 70ii. The heat exchanger 150 may include one or more highly thermally conductive materials, for example, a thermally conductive polymer, or a suitable metal or metal alloy having high thermal conductivity, such as aluminum or an aluminum alloy.

[0022] 1A (and FIG. 2A ), it can be seen that the area defined by actuator drive electronics 60 is substantially contained within the coplanar area defined by heat exchanger 150, and preferably contained within the coplanar area defined by flow channel 151. It can further be seen that flow channel 151 is serpentine-shaped, in this case including one return loop having outward leg 151_a (i.e., away from first portion 146 of outlet path 145 in negative alignment direction 10) and inward leg 151_b (back from first portion 146 of outlet path 145 in positive alignment direction 10). This arrangement, in which actuator drive electronics 60i, 60ii are aligned with heat exchanger 150, may be preferred to maximize heat transfer from actuator drive electronics 60i, 60ii to heat exchanger 150 when droplet ejection head 100 is operated.

[0023] FIG. 2A shows a droplet ejection device 2 similar to FIG. 1A, including a fluid supply 140, an external flow path 143 including a fluid inlet path 141 and a fluid return path 142, and a droplet ejection head 200 according to another embodiment of the present invention. The droplet ejection head 200 includes a heat exchanger 250 having two protrusions, one on each side, adjacent to the actuator drive electronics 60, with the heat exchange interface surfaces 252i, 252ii aligned with the actuator drive electronics 60. These protrusions can be seen more clearly in FIG. 2B, which shows an end view of the droplet ejection head 200 of FIG. 2A. It can also be seen that each actuator drive electronics 60i, 60ii is positioned on a respective PCB 70i, 70ii such that the PCB 70i, 70ii is interposed between the protrusion heat exchange interface surfaces 252i, 252ii and the actuator drive electronics 60i, 60ii. The protrusion heat exchange boundary surfaces 252i, 252ii allow contact between the PCBs 70i, 70ii and the heat exchanger 250 within a predetermined area, such that the area defined by each actuator drive electronic component 60i, 60ii is substantially contained within the area defined by each heat exchange boundary surface 252i, 252ii. This ensures that the majority of heat from the actuator drive electronic components 60i, 60ii is transferred to the heat exchanger 250 through a limited cross-sectional area (the cross-sectional area of ​​the heat exchange boundary surfaces 252i, 252ii adjacent to them). To further facilitate control of this heat transfer, the protrusions also mean that the remainder of the PCBs 70i, 70ii are separated from the heat exchanger 250 by air gaps 259i, 259ii, as shown in FIG. 2B. This arrangement ensures that the majority of heat transfer from the actuator drive electronic components 60i, 60ii to the heat exchanger 250 occurs through a defined area. In other words, the protrusions provide an air gap 259 , 859 between the PCB 70 and the heat exchanger 250 , except in the area of ​​alignment with the actuator drive electronics 60 .

[0024] FIG. 2C shows a cross section BB of the droplet ejection head 200 of FIG. 2A, indicated by line BB in FIG. 2B. This cross section shows that the heat exchanger 250 includes a plurality of horizontal channels 251i-251iv separated by walls 254i-254iii within the heat exchanger channel 251. The walls 254i-254iii are parallel to the depth direction 5 and perpendicular to the ejection direction 16, and in the ZX cross section, they appear as island-like shapes surrounded or contained within the channel 251 (comparable to the peninsula wall 153 of FIG. 1C, which is not completely contained within the channel 151 in the ZX cross section). The area 60_a bounded by the actuator drive electronics 60 is indicated by a dashed line in FIG. 2C. It can be seen that in the same plane (in this case the plane of the discharge direction 16 and the array direction 10), the area defined by the flow path 251 in the plane is substantially larger than the area 60_a defined by the actuator drive electronics 60 in the same plane, and the area of ​​the heat exchanger 250 in the plane is substantially larger than the area 60_a defined by the actuator drive electronics 60.

[0025] Figure 2D is a cross-sectional view of heat exchanger 250 as indicated by line CC in Figure 2C. It can be seen that heat exchanger flow path 251 has a depth 158 in the depth direction 5. Furthermore, it can be seen that island wall 254 extends throughout heat exchanger flow path 251 in the depth direction 5. In the embodiment of Figures 2A-2D, three walls 254i-254iii are present, but this is not limited, and it can be understood that there may be one or more walls 254, for example, multiple walls 254i-254n, where n is any integer.

[0026] 3A-3C show another embodiment similar to those shown in FIGS. 2A-2D. Only a heat exchanger 350 is shown in FIGS. 3A-3C, which has raised portions 355ai-355biii separated by gaps 355_g in the center of heat exchanger flow passages 351 in the depth direction 5. This is clearly seen in cross section EE of FIG. 3C, indicated by section line EE in FIG. 3B (compared to cross section CC of heat exchanger 250 in FIG. 2D, where wall 254 extends completely across heat exchanger flow passages 251 in the depth direction 5). It can be seen that gap 355_g is less than depth 158 in the depth direction 5; it is generally understood that in a gapped configuration, gap 355_g is greater than zero and less than the depth in the depth direction (158 > 355_g > 0).

[0027] In this embodiment, the protrusions 355 are aligned symmetrically in the E-E cross section (Z-Y plane), but this is not essential, and other arrangements are also possible. For example, in other arrangements, the protrusions 355 located on both sides of the flow path 351 in the Z-Y plane may be arranged alternately on both sides of the gap 355_g in the Z direction.

[0028] 4A-4B, an end view of a heat exchanger 450 and a cross section FF indicated by dashed line FF in the end view of FIG. 4A are shown, respectively. The heat exchanger 450 is suitable for an alternative embodiment of a droplet ejection head and includes a plurality of pillars 456 distributed in both the ejection direction 16 and the array direction 10 in a heat exchanger channel 451. As previously described, the heat exchanger channel 451 has a depth 158 in a depth direction 5 (not shown), with the pillars extending completely across the heat exchanger channel 451 in the depth direction 5. It will be appreciated that in the alternative embodiment, the pillars 456 extend completely across the heat exchanger channel 451 in the depth direction 5, similar to the embodiment of FIGS. 3A-4B. As shown in FIG. 3C, the pillars 456 may be replaced with towers that do not span the entire width of the channel 451 in the depth direction 5. Such towers may extend partially across the flow path 451 such that there is a gap similar to gap 355_g of FIG. 3C separating the tops of the towers on opposite sides of the flow path 451 in the depth direction 5.

[0029] 5A-5B, which respectively show an end view of a heat exchanger 550 and a cross section GG indicated by dashed line GG in the end view of FIG. 5A. The heat exchanger 550 is suitable for an alternative embodiment of a droplet ejection head and includes multiple return loops in a heat exchanger flow path 551. The return loops are formed by staggered (in the array direction 10) peninsula walls 553i-553vi that are alternately positioned in the discharge direction 16 on opposite sides of the heat exchanger flow path 551. The legs 551_a-551_g of the straight portions of the return loops are aligned and parallel to the discharge direction 16. Adjacent peninsula walls 553i-552vi are staggered in the array direction 10 by a distance 553_g, and each peninsula wall 553i-552vi has a width 553_w in the array direction 10, where 553_g>553_w, thereby forming a serpentine shape. The peninsula walls 553i-553vi define a serpentine flow path 551. The peninsula walls 553i-553vi have an overlap distance 553_o in the discharge direction 16, where the overlap distance 553_o is greater than zero. While the embodiment of Figures 5A-5B shows six peninsula walls 553i-553vi, this is not required and more than one peninsula wall 553 may be provided.

[0030] 6A shows an end view of a heat exchanger 650 suitable for an alternative embodiment, with a heat exchanger flow path 651 having a serpentine path similar to that of FIG. 5B, with protruding heat exchange boundary surfaces 652i, 652ii at an angle 652an relative to the ejection direction 16, such that when PCBs 70i, 70ii are positioned adjacent their respective protruding heat exchange boundary surfaces 652i, 652ii, the PCBs 70i, 70ii are also at an angle 652an relative to the ejection direction 16. It should be appreciated that this is not required, but such an arrangement may be suitable where there are large components that need to be mounted on the PCBs 70i, 70ii within the limited footprint available for the droplet ejection head.

[0031] FIG. 6B shows an H-H cross section of the embodiment shown in FIG. 6A, depicting a serpentine-shaped flow path 651 with rounded return loop corners, straight legs 651_a-651_f aligned and parallel to the discharge direction 16, and a loop before the heat exchanger outlet 651o with straight leg 651_g perpendicular to the discharge direction 16. The main difference compared to FIG. 5B is that in this embodiment, the heat exchanger 650 includes a rounded return loop, which may be preferable for use with particle-laden fluids to prevent deposit buildup in bends and improve fluid flow smoothness within the heat exchanger 650. Other key differences are that the straight legs 651_a-651_f are not all the same length, are not all oriented in the same direction, and 651_g is approximately perpendicular to the other legs 651_a-651_f. Such an arrangement can be used to maximize the length and / or wetted surface area of ​​the flow channels 651 in the heat exchanger 650 when not all of the flow channel legs 651_a-651_g are the same length and / or have the same orientation, thereby maximizing the heat transferred to the fluid in the fluid return path 142. In general, the design principle is to maximize the heat transfer from the heat exchanger to the return fluid, which can be done by increasing the surface area (i.e., wetted surface area) of the flow channels and / or by increasing the residence time of the return fluid in the heat exchanger (i.e., by increasing the length of the heat exchanger flow channels 651).

[0032] The length of the heat exchanger flow passages 651 within the heat exchanger 650 may be limited by the proximity of adjacent legs and the potential for heat exchange between fluids within the legs, and the routing of the flow passages 651 may be selected to maximize the cooling effect on the actuator drive electronics 60 by providing the most efficient balance between the length and / or wetted surface area of ​​the flow passages 651 and the proximity of adjacent sections of the flow passages 651. Additionally, it may be necessary to balance the cooling effect with the fluid pressure loss within the heat exchanger flow passages 651 by maximizing the wetted surface area of ​​the flow passages within the heat exchanger 650 while minimizing fluid pressure loss within the heat exchanger, i.e., minimizing fluid pressure loss within the heat exchanger flow passages 651. For example, this balance may be achieved by controlling the cross-sectional area of ​​the heat exchanger flow passages 651, the length of the flow passages, and / or the smoothness of the routing (i.e., designing the heat exchanger flow passages 651 with rounded corners and providing chamfers or blends at sharp angles to smooth out changes in direction of the heat exchanger flow passages 651). The serpentine heat exchanger flow path 651 may improve fluid mixing, thereby improving heat transfer from the wetted area of ​​the heat exchanger flow path 651 to the return fluid.

[0033] FIG. 6C shows detail C of cross section HH shown in FIG. 6B, illustrating a spigot 660 positioned to connect the outlet passage 145, specifically the first section 146 of the outlet passage 145, to the heat exchanger inlet 651 in. The heat exchanger outlet 651 also has a spigot 660 positioned therein for connecting to the third section 147 of the outlet passage 145 (not shown). The spigot 660 may have an outer spherical feature 661 for receiving a flexible pipe or tube, for example, for connecting the first stage 146 of the outlet passage 145 to the heat exchanger inlet 651 in (see, e.g., FIG. 6D) and the third stage 147 of the outlet passage 145 to the heat exchanger outlet 651 in (not shown). For example, a flexible tube or pipe having a diameter smaller than the spherical feature 661 can be used, the diameter being smaller than the outer diameter of the plug to which the first section 146 of the outlet passage 145 is connected. The flexible tube or pipe may be deformed when forced through the spherical feature 661. These spherical features 661 allow for greater alignment tolerance between fluidly connected components, thereby increasing the positioning flexibility of the droplet ejection head. For example, this allows for greater alignment tolerance between the heat exchanger 650 and the actuator component 90 (not shown) while maintaining a fluid-tight connection. Additionally, the spigot 660 is seen to include a spherical recess 663 that aligns with a portion of the cylindrical feature of the heat exchanger inlet 651 in (and outlet 651 o). This spherical recess 663 may provide a location for a fluid-sealing component, such as an O-ring, or may be partially or fully filled with an adhesive / sealant 664 to ensure a fluid-tight and permanent internal connection, preferably. Additionally, an adhesive or sealant 664 or a fluid-sealing component may also be disposed between the collar 662 of the spigot 660 and the heat exchanger 650. Thus, the droplet ejection heads described herein may have a channel 651 with cylindrical features at the inlet 651 in and outlet 651 o to receive a portion of the spigot 660 .Additionally, the interface between the spigot 660 and the inlet 651 in and outlet 651 o includes an adhesive and / or sealant and / or fluid sealing component. Similarly, it will be appreciated that the first portion 146 of the outlet path 145 can be connected to the actuator component 90 using such a spigot 660, optionally with one or more such sealant features 664. Furthermore, the inlet path 144 can be connected to the actuator component 90 using such a spigot 660. Alternatively, a diverter 670 (see FIG. 6D ) comprising a spherical feature 671 similar to the spigot 660 can be utilized. FIG. 6D illustrates a side view of the heat exchanger 650 and spigot 660 of FIGS. 6A-6C . FIG. 6C further illustrates a portion of the outlet path 145 and a diverter 670 connecting the first portion 146 of the outlet path 145 to the actuator component 90 (not shown). FIG. 6E shows the fluid diverter of FIG. 6D in more detail, and FIG. 6F shows the underside of the fluid diverter of FIGS. 6E and 6D.

[0034] 6D , the first portion 146 of the outlet path 145 may be comprised of, for example, a flexible tube or pipe, which is pressed onto the spherical feature 661 of the spigot 660 and the spherical feature 671 of the outlet path 146 a of the diverter 670. For example, the diameter of the flexible tube or pipe may be smaller than the spherical feature 661 and smaller than the outer diameter of the portion of the outlet path 146 a of the diverter 670 to which the first portion 146 of the outlet path 145 is connected. The flexible tube or pipe may deform when pressed onto the spherical feature 661. Similarly (not shown), the diverter 670 may connect the inlet path 144 to the actuator component 90; for example, the inlet path 144 may be comprised of a flexible tube or pipe similar to that described above with respect to the outlet path 145, which may be pressed onto the spherical feature 671 of the inlet path 144 a of the diverter 670. The diameter of the flexible tubing can be smaller than the diverter's spherical feature 671 and smaller than the outer diameter of the inlet passage 144a of the diverter 670 to which the inlet passage 144 is connected, as described above. As described above, the use of such spherical feature 671 and flexible tubing facilitates aligning components within the droplet ejection head, such as the actuator component 90, the inlet to the droplet ejection head (not shown), and the heat exchanger 650, such that their relative positions do not need to be so strictly defined, thereby maintaining a fluid-tight connection and allowing for variations in relative positions by design.

[0035] The inlet passage 144a and the outlet passage 146a of the diverter 670 further include a collar 672, and an adhesive and / or sealant and / or fluid sealing compound may be disposed between the collar 672 and the first portion 146 of each of the inlet passage 144 and the outlet passage 145. The diverter 670 may be fluidly connected to first ends of a plurality of fluid chambers via the inlet passage 144a of the diverter 670. The inlet passage 144a may be connected to the plurality of fluid chambers via an inlet manifold chamber, as described above. Similarly, second ends of the plurality of fluid chambers may be connected to the outlet passage 146a of the diverter 670 via an outlet manifold chamber, as described above. The diverter provides a compact configuration for supplying fluid from the inlet passage 144 to the actuator component 90 and discharging fluid from the actuator component 90 to the outlet passage 145, and the spherical feature 761 provides a fluid-tight connection, enabling reduced positional tolerance requirements between the heat exchanger 650 and the actuator component 90. Thus, in general, the diverter 670 fluidly connects the inlet passage 144 and the outlet passage 145 to the actuator component 90 and includes a spherical feature 671 that provides a fluid-tight connection to the inlet passage 144 and the outlet passage 145, respectively.

[0036] The fluid connection between the inlet and outlet paths 144a and 146a is shown in FIG. 6F for the underside of the fluid diverter of FIGS. 6E and 6D. It is understood that in some configurations, there are two fluid chamber arrays extending in the array direction 10, each with a first end connected to an inlet manifold chamber. The second end of each of the first arrays is connected to one of two outlet manifold chambers, and the second end of each of the second arrays is connected to the other of two outlet manifold chambers (in other words, there is one inlet manifold chamber supplying fluid to the two fluid chamber arrays, and one outlet manifold chamber for each fluid chamber array). This configuration can increase nozzle density while limiting the number of manifold chambers required. In such configurations, the flow paths discharging fluid from the two outlet manifold chambers can be connected to each other, for example, within or adjacent to the diverter 670. 6D-6F, two sub-outlet paths 146a_1, 146a_2 discharge fluid from two outlet manifold chambers within the actuator component 90 (not shown). The sub-outlet paths 146a_1, 146a_2 connect to the outlet path 146a within the diverter 670, thereby disposing multiple heat exchangers 650 in series downstream of the two outlet manifold chambers. In general, the diverter 670 can fluidly connect one or more secondary manifold chambers to their respective heat exchangers, as described herein. It will be understood that one or more inlet manifold chambers and appropriate path splitters may be disposed to deliver fluid from the inlet path 144 to the inlet manifold chamber(s), if multiple.

[0037] It is generally understood that such spigot 660 and diverter components 670, and various connection point geometries at the inlets and outlets, can be incorporated into any droplet ejection head described herein and used to connect to the inlets 651 in and outlets 651 o of any heat exchanger described herein. It is further understood that the relative positions of the inner and outer spherical features of the spigot 660 can be positioned at the inlets 651 in and outlets 651 o to the diverter 670 and / or heat exchanger flow passages 651, and the flow passage 144, 146 tubes can be provided with appropriate spherical recesses 663 or outer spherical features 661, and the spigot 660 and / or diverter 670 can be designed to fit accordingly.

[0038] When the heat exchanger 650 forms part of a droplet ejection head, it is generally understood that the plurality of fluid chambers are fluidly connected at a first end to one or more inlet manifold chambers, which are fluidly connected to the inlet pathways 144, and the plurality of fluid chambers are connected at a second end to one or more outlet manifold chambers, which are fluidly connected to the outlet pathways 145, which are fluidly connected in series to a respective heat exchanger 650. To enable a fluid-tight connection between the components, the outlet pathways 145 include one or more spigots 660, each spigot 660 including one or more outer spherical features 661, each arranged to provide a fluid-tight connection with a portion of the outlet pathway 145. For example, a fluid pipe or tube (see FIG. 6D ) can be mounted on each spherical feature 661 such that there is a pipe or tube for each spherical feature 661.

[0039] FIG. 7A illustrates an end view of a PCB 70 suitable for use in embodiments of the invention described herein. From FIG. 7A, it can be seen that the PCB 70 includes first and second thermally conductive areas 70_c1 and 70_c2 disposed on opposite sides of the PCB 70. The thermally conductive areas 70_c1 and 70_c2 can be constructed of a thermally conductive material, such as copper, gold, or other metal or thermally conductive material. The first and second thermally conductive areas 70_c1 and 70_c2 can be thermally connected to each other by one or more thermally conductive paths 70_v. The location of the first thermally conductive area 70_c1 aligns with the heat exchange boundary surface of a protrusion found in various embodiments described herein, and the second thermally conductive area 70_c2 can correspond to an area defined by the actuator drive electronics 60 when the actuator drive electronics 60 is mounted on the printed circuit board 70, or the second thermally conductive area 70_c2 can include an area on the printed circuit board surrounding the area defined by the actuator drive electronics 60. Thus, as described herein, when the printed circuit board 70 is mounted on a droplet ejection head, the first thermally conductive area 70_c1 may be aligned with and adjacent to the heat exchanging boundary surfaces 252-852 of one or more protrusions, and the second thermally conductive area 70_c2 may be aligned with and adjacent to the area defined by the actuator drive electronics 60. The thermally conductive areas 70_c1, 70_c2 may serve to concentrate or focus heat transfer from the actuator drive electronics 60 located within the defined area to the heat exchangers 250-650, thereby reducing or preventing heat transfer to other components, such as other electrical components, on the PCB 70.

[0040] Referring now to FIG. 7B, cross section II of the PCB 70 shown in FIG. 7A is shown, illustrating the internal structure of the PCB 70 and the thermal conduction regions 70_c1 and 70_c2 thermally connected to one another by one or more thermal conduction paths 70_v. Here, the thermal conduction paths 70_v can include multiple vias 70_vi, which are formed by drilling (e.g., laser drilling) multiple holes in the PCB 70 and lining or filling the multiple holes with a thermally conductive material, such as copper, gold, or other metal or thermally conductive material, such that the thermal conduction regions and thermal conduction paths 70_v are comprised of metal. It is further understood that the PCB 70 includes one or more layers 70_b made of a material such as fiberglass, with the vias 70_vi penetrating one or more layers 70_b. In one possible arrangement, the PCB 70 includes multiple layers 70_b_1 through 70_b_n, each having a via 70_vi formed therein. The vias 70_vi of each layer 70_b_i do not have to be aligned with the vias of the previous layer 70_b_(i-1). Instead, an interface thermal conduction region 70_ci is disposed between adjacent material layers 70_b, thermally connecting the vias 70_vi of one layer to the vias 70_vi of the adjacent layer, the arrangement thus formed providing a thermal conduction path 70_v through the PCB connecting the first and second thermal conduction regions 70_c1, 70_c2. The interface thermal conduction region 70_ci can define an area substantially the same as the area defined by the first thermal conduction region 70_c1 and / or the second thermal conduction region 70_c2, respectively.

[0041] 7C shows an end view of the PCB 70 of FIG. 7A, in which the actuator drive electronic component 60 is disposed adjacent to and attached to the second thermal conduction area 70_c2. FIG. 7D shows the actuator drive electronic component 60 of FIG. 7C as seen from the interface side (i.e., the surface disposed adjacent to and facing the second thermal conduction area 70_c2 in FIG. 7C). The actuator drive electronic component 60 includes multiple actuator drive electronic components 60_1 to 60_7 (it should be understood that the number of actuator drive electronic components 60 is not limited and may be one or more). When multiple actuator drive electronic components 60 are present, it can be seen that the area defined by the actuator drive electronic components 60 is surrounded by a dotted line 60_d passing through the outermost edges of the multiple actuator drive electronic components 60_1 to 60_7. In other words, the actuator driving electronic components 60 each include one or more coexisting components 60_1 to 60_n (n is an integer), and these components coexist in an area adjacent to the heat exchanger 150. For example, one or more components coexist in a sub-area of ​​each PCB 70i, 70ii, and the sub-area is generally understood to be located at the center of the PCB 70i, 70ii in the discharge direction 16. When heat transfer areas 70_c1, 70_c2 are present, the coexisting sub-area may be such that the actuator driving electronic components 60 are substantially contained within the area of ​​the second and / or first heat transfer areas 70_c2, 70_c1. Whether there is one or more actuator driving electronic components 60, it is understood that the area defined by them is substantially contained within the area of ​​the second heat transfer area 70_c2 in the same plane. Furthermore, it is understood that one or more actuator driving electronic components 60 may be potted or encapsulated within a cover 60_p, as shown in FIG. 7D . The area defined by the cover 60_p also falls substantially within the area of ​​the coplanar second heat conduction area 70_c2.

[0042] FIG. 8A illustrates another embodiment of a droplet ejection head 800 including a PCB similar to those shown in FIGS. 7A and 7B, but with thermally conductive adhesive layers 871i and 871ii disposed between the respective protruding heat exchange interface surfaces 852i and 852ii on the heat exchanger 850 and the respective first thermally conductive regions 70_c1i and 70_c1ii of the PCBs 70i and 70ii. The thermally conductive adhesive layers 871i and 871ii may include a thermally conductive resin and / or a thermally conductive adhesive. The thermally conductive adhesive layers 871i and 871ii may include a thermosetting material. The thermally conductive adhesive layers 871i and 871ii may include a polymer resin containing a filler to improve thermal conductivity, and the filler may be, for example, ceramic or metal. Alternatively, the thermally conductive adhesive layers 871i and 871ii may be liquid metal. Liquid metal is a flowable alloy that can be used to fill small gaps between the PCB and the heat exchanger, thereby forming a thermal path. Other alternatives include thermally conductive paste or semi-solid, deformable thermally conductive pads. Generally, a thermally conductive adhesive layer 871i, 871ii bonds each PCB 70i, 70ii to each heat exchanging interface surface 852i, 852ii of each protrusion.

[0043] The second thermally conductive areas 70_c2i, 70_c2ii of each PCB 70i, 70ii in Figure 8A can be positioned adjacent to the actuator drive electronics 60i, 60ii, similar to that shown in Figure 7C. The actuator drive electronics 60 can be attached to the second thermally conductive areas 70_c2i, 70_c2ii using wire bonding or other thermally conductive bonding methods (which may include the use of thermally conductive adhesives or resins). The area defined by the actuator drive electronics 60 can be substantially contained within the area defined by the first and second thermally conductive areas 70_c1i, 70c1ii, 70_c2i, 70_c2ii.

[0044] FIG. 8B shows an end view of the droplet ejection head of FIG. 8A, excluding the protrusions, illustrating the presence of air gaps 859i, 859ii between each PCB 70i, 70ii and the heat exchanger 850. In the embodiment of FIGS. 8A-8B, it can be seen that the droplet ejection head 800 includes two actuator drive electronics 60i, 60ii for each heat exchanger 850, one on each side of the heat exchanger 850. It will be appreciated that each actuator drive electronics 60i, 60ii may include multiple actuator drive electronics 60_1 through 60_n (n is an integer), as shown in FIG. 7D. In use, fluid is supplied to the actuator component 90 via the inlet path 144. The multiple heat exchangers 850 are arranged in series downstream of the actuator component 90 and are fluidly connected to the actuator component 90 via a first portion 146 of the outlet path 145. The fluid exits the heat exchanger 850 via the third portion 147 of the outlet path 145. Each PCB 70i, 70ii includes a first and second thermally conductive area 70_c1i, 70_c1ii, 70_c2i, 70_c2ii. Each first thermally conductive area 70_c1i, 70_c1ii is aligned with and adjacent to a respective heat exchanging boundary surface 852i, 852ii of one or more protrusions. A thermally conductive adhesive layer 871i, 871ii bonds each PCB 70i, 70ii to the respective heat exchanging boundary surface 852i, 852ii of the respective protrusions. Each second thermally conductive area 70_c2i, 70_c2ii is aligned with and adjacent to an area bounded by a respective actuator drive electronics component 60i, 60ii.

[0045] 9 illustrates another embodiment of a droplet ejection head 900, including two actuator components 90a, 90b, a nozzle plate 80, and two heat exchangers 950a, 950b positioned adjacent to actuator drive electronics 60ai (not shown), 60aii, 60bi, and 60bii. While it can be seen that inlet path 144 branches into two subpaths 144a, 144b to supply fluid to each of actuator components 90a, 90b that share nozzle plate 80, it will be understood that this is not required and that in other configurations, each actuator component 90a, 90b may have its own nozzle plate 80a, 80b. It can also be seen that third portion 147 of outlet path 145 is connected to each of heat exchangers 950a, 950b by two subpaths 147a, 147b.

[0046] Similar to the conventional droplet ejection heads described herein, the heat exchangers 950a, 950b are arranged in series downstream of their respective actuator components 90a, 90b. Generally, a droplet ejection head, as described herein, may include two or more actuator components 90 and two or more respective heat exchangers, each arranged in series downstream of the two or more actuator components. In other words, in some arrangements, there may be a one-to-one relationship between each heat exchanger 950 and each actuator component 90. Furthermore, FIG. 9 shows that two or more actuator drive electronics components 60ai, 60aii, 60bi, 60bii are arranged for each heat exchanger 950a, 950b. These are arranged so that there are two actuator drive electronics components 60i, 60ii for each heat exchanger 950, one adjacent to each side of each heat exchanger 950. It will be appreciated that such an arrangement is not required and that in other arrangements there is only one actuator drive electronics 60 and PCB, with the heat exchanger described herein located adjacent to one actuator drive electronics 60.

[0047] Figure 10A shows an end view of a heat exchanger 1050 suitable for an alternative embodiment with a serpentine-shaped heat exchanger flow path 1051 similar to Figure 6B, further comprising a sleeve 1082, which is comprised of one or more thin-walled pieces having a continuous cross section, such as a pipe or tube. Figure 10B shows a JJ cross section of the embodiment shown in Figure 10A, showing the heat exchanger flow path 1051 and the sleeve 1082.

[0048] The sleeve 1082 can be formed into a serpentine or other shape. The length of the sleeve 1082, coupled with its cross-sectional shape and area, wall thickness, thermal conductivity, and other related properties, can be sufficient for adequate heat transfer from the one or more actuator drive electronics 60 to the fluid in the heat exchanger flow path 1051. The sleeve 1082 can be made of any suitable material and any suitable surface finish (e.g., chemical / mechanical, modified / coated) to provide chemical resistance to the fluids used for fluid delivery. The sleeve 1082 can be substantially surrounded and thermally connected to the heat exchanger 1050 by direct contact of the sleeve 1082 with one or more interior surfaces of the heat exchanger 1050 that define the shape of the heat exchanger flow path 1051, as shown in FIG. 10B . For example, the heat exchanger 1050 can be composed of two or more parts that, when assembled, form a void that defines the heat exchanger flow path profile into which a substantial portion (length) of the sleeve 1082 fits. The tightness of the fit between the heat exchanger flow path profile and the sleeve 1082, and the extent and shape of the flow paths enclosed by the heat distributor, can be determined according to functional and manufacturing requirements. For example, the heat exchanger flow path profile may fit more closely in straight sections of the sleeve 1082 than in curved sections, or may not fit at all in curved sections (e.g., the sleeve 1082 passes through larger gaps in such areas).

[0049] Alternatively, the heat exchanger 1050 may be formed around the sleeve 1082, for example, by pouring a curable material having suitable thermal properties for the heat exchanger 1050 into a mold in which the sleeve 1082 is placed. It will be appreciated that the sleeve 1082 may extend beyond the mold and protrude from the heat exchanger 1050, as shown in Figures 10A and 10B, to allow fluid connection with the remainder of the flow path. Once the material has cured, the heat exchanger 1050, encapsulating the sleeve 1082, can be removed from the mold and the inlet 1051in and outlet 1051o of the flow path 1051 can be connected as needed.

[0050] FIG. 11A shows an end view of a heat exchanger 1150 suitable for use in an alternative embodiment. Similar to FIGS. 10A and 10B, this heat exchanger 1150 includes a serpentine-shaped heat exchanger flow path 1151, which further includes a sleeve 1182 and an interface material 1183. FIG. 11B shows a KK cross section of the embodiment of FIG. 11A, showing the heat exchanger flow path 1151, sleeve 1182, and interface material 1183, as shown in FIG. 11A. As can be seen in FIG. 11B, the interface material 1183 provides a connection between the sleeve 1182 and the body of the heat exchanger 1150. This could be, for example, an adhesive, gel, or putty. It could also be a material that hardens into a hard or rigid shape, or a paste or other material that maintains softness and / or flexibility.

[0051] It is generally understood that using separate components for the flow paths 1051, 1151 and the heat exchangers 1050, 1150 increases the possibility of optimizing individual materials for their respective performance and other requirements. Notable performance requirements include chemical resistance and heat transfer, respectively. For example, considering manufacturing requirements (e.g., d) below), a material may be selected for the body of the heat exchangers 1050, 1150 that is easy to cast (e.g., a very low melting point alloy) or otherwise process (perhaps 3D printing). However, that material may not be chemically robust enough or easily coated / plated, making it unsuitable for fluid contact. The use of sleeves 1082, 1182 for the flow paths 1051, 1151 allows for the selection of different materials with properties suitable for handling fluids within the flow paths, such as corrosion resistance, chemical resistance, electrical resistance, and / or insulating properties. The interface material 1183, if present, may be selected based, for example, on its heat transfer and / or bonding properties.

[0052] [How to operate] The droplet ejection heads 100-900 described herein can be used to cool the actuator drive electronics 60. For example, the droplet ejection heads 100-900 include one or more actuator drive electronics 60 for the droplet ejection head 100-900, and the droplet ejection head 100-900 includes one or more actuator components 90, an inlet path 144 for supplying fluid to the one or more actuator components 90, and an outlet path 145 for discharging fluid from the one or more actuator components 90. The one or more actuator components 90 can include multiple fluid chambers, each of which can include at least one nozzle. The multiple fluid chambers can be actuated (or include an actuator) to eject one or more droplets through the at least one nozzle in response to an ejection command. The multiple fluid chambers can be fluidly connected to the inlet path 144 at a first end and fluidly connected to the outlet path 145 at a second end. The outlet path 145 may comprise one or more heat exchangers 150-950 arranged in series downstream of one or more actuator components 90. One or more actuator drive electronics 60 may be arranged adjacent to each of the heat exchangers 150-950. One or more heat exchangers 150-950 may comprise one or more flow paths 151-951. Thereby, in use, heat is transferred from the actuator drive electronics 60 to the one or more heat exchangers 150-950 and is discharged via a return fluid (wherein the return fluid is the fluid that has passed through the actuator component 90 and not ejected from the nozzle). The area defined by the actuator drive electronics 60 may be substantially contained within the area defined by the one or more flow paths 151-951. Cooling methods may include the following: - supplying fluid to the one or more actuator components 90 via the inlet passage 144; - Discharge return fluid from the one or more actuator components 90 via the outlet path 145 and introduce the return fluid into a heat exchanger flow path 151-951 so that it passes through one or more heat exchangers 150-950 and removes heat transferred from the actuator drive electronic components 60 to the heat exchangers 150-950 via the return fluid flowing through the one or more heat exchangers 150-950.

[0053] The droplet ejection devices 1 and 2 described in this specification include one or more droplet ejection heads 100 to 900 described in this specification, and can have the following operation method. - supplying fluid to one or more droplet ejection heads 100-900 via fluid inlet pathway 141; - supplying fluid to one or more actuator components 90 in each droplet ejection head 100-900 via one or more inlet passages 144 in each droplet ejection head 100-900; - ejecting a portion of fluid from one or more nozzles in said actuator component 90 in response to a ejection command; - ejecting un-ejected fluid from one or more actuator components 90 via one or more outlet paths 145 within each droplet ejection head 100-900; - transferring thermal energy from the one or more actuator drive electronic components 60 to the heat exchanger 150-950; and removing some or all of the thermal energy from the heat exchangers 150-950 by: transferring thermal energy to the undischarged fluid in the outlet path 145; Discharging the undischarged fluid from the one or more droplet discharging heads 100-900 via the fluid return path 142.

[0054] [General Considerations] As previously mentioned, the droplet ejection heads 100-900 described herein may include one or more actuator components 90, an inlet path 144 for supplying fluid to the one or more actuator components 90, and an outlet path 145 for discharging fluid from the one or more actuator components 90. The one or more actuator components 90 may include multiple fluid chambers, each of which includes at least one nozzle, operable to eject one or more droplets through the at least one nozzle in response to an ejection command. The multiple fluid chambers are fluidly connected at their respective first ends to the inlet path 144 and at their respective second ends to the outlet path 145. The outlet path 145 may include one or more heat exchangers 150-950 arranged in series downstream of the one or more actuator components 90. One or more actuator drive electronics 60 may be arranged adjacent to each of the heat exchangers 150-950. One or more heat exchangers 150-950 may include one or more flow paths 151-951 such that, in use, heat is transferred from the actuator drive electronics 60 to the one or more heat exchangers 150-950 and discharged via a return fluid (it should be understood that the return fluid is fluid that has not been discharged from the actuator component 90). As noted above, an area defined in a plane (e.g., the ZX plane) by the actuator drive electronics 60 may be substantially contained within an area defined by one or more flow paths 151-951 in the same plane, which may be referred to as a defined area. When components such as the heat exchangers and actuator drive electronics are physically separated, for example in the Y direction, it should be understood that the plane referred to here is a common plane (e.g., the ZX plane) onto which the defined areas can be projected.

[0055] The actuator component 90 described herein may include a plurality of fluid chambers with associated actuators operable to eject droplets through one or more nozzles associated with each of the plurality of fluid chambers. For example, one or more walls of the plurality of fluid chambers may be operable to eject droplets through one or more nozzles. For example, one or more sidewalls of each fluid chamber may comprise a material exhibiting piezoelectric properties and a suitable drive electrode arrangement, or the fluid chambers may comprise a roof-mode actuator arrangement. However, it will be appreciated that other forms of actuators may be used as long as they are suitable for ejecting fluid from the respective fluid chambers through their respective nozzles in response to an ejection command.

[0056] The heat exchangers 150-950 described herein can be manufactured using any suitable method, such as, for example, 3D printing, casting, molding, machining, etc. Additionally, the heat exchangers 150-950 can be constructed from one or more parts. It will be appreciated that if the heat exchanger is constructed from two or more parts, appropriate additional parts and / or joining methods may be used to prevent fluid leakage.

[0057] Additionally, it is generally understood that the heat exchanger 150-950 may include one or more highly thermally conductive materials. For example, the heat exchanger 150-950 may include a thermally conductive polymer. Alternatively, the heat exchanger 150-950 may include aluminum and / or an aluminum alloy 150-950. This allows the heat exchanger 150-950 body to heat to a substantially uniform temperature as heat is transferred from one or more actuator components 60 to the heat exchanger 150-950 body. This temperature uniformity within the heat exchanger body means that the heat exchanger flow path 151-551 is not limited to the area defined by one or more actuator components 60, but instead can be optimized to utilize a wider area of ​​the flow path by providing a heat exchanger 150-950 that is larger, preferably significantly larger, than the area defined by one or more actuator components 60.

[0058] It is understood that the heat exchanger 150-950 may include one or more surface treatments and / or coatings on the wetted surfaces of the heat exchanger flow paths 151-951 to protect against erosion, corrosion, and other deleterious effects of the return fluid passing through the heat exchanger flow paths 151-951. Such surface treatments include methods that alter the structural or chemical behavior of the surface of a bulk material, such as surface treatments such as shot peening and / or anodizing. The coatings consist of one or more layers applied to the wetted surfaces to provide corrosion protection, such as improved electrochemical compatibility with the fluid, and also provide electrical insulation between the fluid and the heat exchanger 150-950.

[0059] As discussed above, it is generally understood that the heat exchanger 1050, 1150, including the sleeve 1082, 1182 and (if present) the interface material 1183, may be manufactured using any suitable method and assembled in any suitable order. For example, as discussed above, the sleeve 1082, 1182 may be molded first, and the remainder of the heat exchanger 1050, 1150 may be assembled around it. For example, the sleeve 1082, 1182 may be molded from a metal tube, such as stainless steel or titanium, and formed into the intended longitudinal and cross-sectional shape, for example, by a tube former. The heat exchanger 1050, 1150 may then be molded and / or assembled around the sleeve, for example, by placing the sleeve 1082, 1182 as an insert in a mold and casting the heat exchanger 1050, 1150 around it. Alternatively, the heat exchanger 1050, 1150 may first have flow-channel-shaped cavities formed therearound. The sleeve 1082, 1182 may be constructed from a flexible material, such as a flexible polymer sleeve, that is inserted into a preformed passage in the heat exchanger 1050, 1150 using any suitable method. Alternatively, the heat exchanger 1050, 1150 may be formed in two or more parts, for example, by machining, casting, or extrusion, with appropriate voids in each part, so that when the parts are joined, the sleeve 1082, 1182 and, if present, the interface material 1183 are contained within the heat exchanger 1050, 1150. These parts may be fabricated from, for example, metal (aluminum, zinc, or a suitable alloy). The thermal connection between the sleeve 1082, 1182 and the body of the heat exchanger 1050, 1150 may be achieved by one or more of adhesives, pastes, mechanical methods (such as hydroforming, pultrusion, etc.), overmolding, and / or casting. Additionally, it is generally understood that the sleeve 1082, 1182 can have a more complex shape than a simple pipe or tube, for example, the sleeve can be formed into one or more connecting pieces to achieve complex flow path configurations as described with respect to other embodiments herein.Such complex sleeves 1082, 1182 may be formed by casting, molding, or 3D printing, for example.

[0060] It will be understood that any of the heat exchangers 150-1150 described herein are suitable for use in droplet ejection devices, and that any of the heat exchangers 150-1150 may include one or more flow control devices in the heat exchanger flow paths 151-1151. The flow control devices may act to increase the internal wetted area of ​​the heat exchanger flow paths 151-1151, thereby improving heat transfer from the heat exchanger body 150-1150 to the heat exchanger flow paths 151-1151. Additionally, the flow control devices may include wall and / or surface undulations and / or protrusions (e.g., multiple ridges and / or ridges and / or grooves and / or rifling). The heat exchanger flow paths 151-1151 may be serpentine, without any straight sections. The wetted volume of the heat exchanger flow path 151-1151 may be configured as a chamber (rather than a long path) as shown in FIG. 4B, with one or more towers (like stalactites or stalagmites in a cave) protruding from opposing sides, or may have a series of columns or pillars 456 spanning the entire chamber. The towers on opposing sides may be aligned in a row, or may be arranged such that a tower on one side is positioned between towers on a second opposing side. In general, the heat exchanger flow path 151-951 may include one or more flow control devices, which may include one or more walls (such as peninsula walls 153, 553 or island walls 254) and / or ridges 355 and / or pillars 456 and / or columns and / or vanes and / or grooves and / or towers. The purpose of using such flow control devices is to maximize contact between the wetted surface area of ​​the heat exchanger flow paths 151-951 and the return fluid, and this contact may need to be balanced with the flow of fluid within the flow paths so that the fluid does not experience large pressure drops across the heat exchanger 150-950 or experience dead spots of near-static or stationary fluid that could cause hot spots in the heat exchanger 150-950.

[0061] When the flow paths 151-951 of the heat exchanger are comprised of one or more pipes or tubes (e.g., serpentine paths), the bends and straight sections can be oriented in any direction. Furthermore, the flow paths 151-951 can include one or more return loops. The return loops can be separated by peninsula walls 153, 553. For example, the return loop can be comprised of one or more straight sections oriented parallel to the discharge direction 16, such as legs 551_a-551_g in FIG. 5B, with the respective peninsula walls 553 also parallel to the discharge direction 16. Alternatively, the return loop can be comprised of one or more straight sections oriented perpendicular to the discharge direction 16, such as legs 151_a, 151_b in FIG. 1C, with the respective peninsula walls 153 also perpendicular to the discharge direction 16. Alternatively, it can be understood that the return loops, and thus the peninsula walls 153, 553, can be oriented at any suitable angle or angles relative to the discharge direction 16. Additionally, while the peninsula wall 153, 553 is shown herein as being generally straight, it may be configured with any suitable shape, for example, it may follow a non-linear path or have a non-linear shape, or it may have a shape (e.g., serpentine, spiral, or serpentine). In some arrangements, the return loop has substantially the same shape as the outer loops of the flow path and / or is configured to fit into the gaps between the outer loops, thereby efficiently utilizing the available space within the heat exchanger 150-1150.

[0062] It is generally understood that the heat exchanger flow path 151-1151 may be comprised of two or more subpaths. For example, as shown in FIG. 2C, it may branch into multiple subpaths 251i-251n (where n is any integer greater than 1), and the subpaths 251i-251n may be comprised of any suitable shape. The subpaths may branch at one or more points; similarly, the subpaths may merge downstream at a single point, or groups of two or more subpaths 251i-251n may merge at different points.

[0063] While the flow control devices illustrated and described herein, such as ridge 355 in FIGS. 3A-3C, wall 254 in FIGS. 2A-2D, and peninsula walls 153, 553 in FIGS. 1A-1C and 5A-5B, are shown as having straight edges and generally rectangular cross sections, this is not required; other configurations may use flow control devices with curved profiles, zigzag or other nonlinear paths, or any other suitable shape. Similarly, while post 456 in FIG. 4A is illustrated as a small rectangle, it may have any suitable cross-sectional shape, such as a circular, vaned, or oval cross-section. Furthermore, any of the flow control devices described herein may provide a smooth surface for fluid passing through their respective flow passages 151-951 by appropriate rounding of corners, chamfering of edges, and smoothing of junctions between the flow control devices and the heat exchanger walls to which they are attached. This may be desirable to prevent viscous losses in the flow path and to prevent settling when using colored fluids.

[0064] It is generally understood that the flow channels described herein may include flow control devices arranged in one or more planes within the flow channel. For example, the flow control devices may be quasi-two-dimensional, such as the heat exchangers 150-950 shown in Figures 1A-5B. In this case, the flow control devices have a substantially constant cross-sectional profile in the depth direction 5 and are arranged in a pattern or shape in the xy plane. Alternatively, the structure may have a substantially constant cross-sectional profile in the array direction 10, with the shape, position, and shape of the fluidic devices varying primarily in the yy plane. Furthermore, some arrangements may have varying shapes, configurations, and positions in all three directions. Such more complex cross-sectional shapes may be more easily formed using techniques such as 3D printing.

[0065] In general, it is understood that the paths of the flow channels 151-1151, regardless of their shape, such as serpentine, serpentine, or spiral paths with curved and / or straight portions, and / or paths including the flow control devices described herein, can be selected to maximize the cooling effect on the actuator drive electronics 60 by providing the most efficient balance between the length and / or wetted surface area of ​​the flow channels 151-1151 and the proximity of adjacent portions of the serpentine flow channels. This may be within the area bounded by the electronics 60 and / or within the area defined by the heat exchangers 150-1150. The wetted surface area includes the area in contact with the fluid carried by the flow channels 151-1151. It is further understood that the cooling effect can be balanced against the fluid pressure loss within the flow channels 151-1151 by maximizing the wetted surface area of ​​the flow channels within the heat exchangers 150-1150 while simultaneously minimizing the fluid pressure loss within the heat exchangers.

[0066] Minimizing fluid pressure loss within the heat exchangers 150-1150 can be achieved by smoothing corners and joints, for example, using chamfers, and by avoiding sharp bends and abrupt changes in cross-sectional area, for example. It will be appreciated that the heat exchangers can have a fluid impedance that is substantially matched to the fluid inlet path 141. It is also advantageous to have the fluid impedance of the heat exchangers 150-1150 lower than that of the actuator component 90, so that the pressure loss within the heat exchangers 150-1150 is lower than that within the actuator component 90. In general, the heat exchangers 150-1150 can be designed to minimize their impact on the overall flow path impedance within the droplet ejection head. Among the many factors that affect the flow path and its impedance, the flow path can be designed to accommodate various recirculation flow ratios (e.g., the percentage of ink ejected from the droplet ejection nozzles of the actuator component 90 versus the percentage discharged as return fluid). For example, a worst-case (most severe) fluid recirculation flow ratio is such that 1 / 3 of the fluid supplied to the actuator component 90 is dispensed from the nozzles and 2 / 3 is returned from the actuator component 90. The flow paths can also be designed to cover the full range of possible fluid dispensing duties, from zero fluid dispensing duty (all fluid enters the return path) to 100% fluid dispensing duty (i.e., all nozzles dispense fluid simultaneously; note, however, that this does not mean that 100% of the fluid supplied to the actuator component 90 is dispensed from the nozzles).

[0067] While the embodiments described herein generally include at least two actuator drive electronics 60i, 60ii per heat exchanger 150-1150, one on each side of the respective heat exchanger 150-1150, this is not required, and in other arrangements, actuator drive electronics 60 may be provided on only one side of the heat exchanger 150-1150. Generally, more than one actuator drive electronics 60 may be provided per heat exchanger 150-1150. Furthermore, each actuator drive electronics 60 may include one or more parts or components 60_1 through 60_n (n is an integer) that may be positioned adjacent to one another. Furthermore, it may be understood that these parts or components, individually or as a group, may be potted or encapsulated such that faces not aligned with the heat exchanger 150-1150 are sealed.

[0068] The actuator drive electronics 60 are generally understood to be comprised of components sometimes referred to as ASICs (Application Specific Integrated Circuits). These are one or more electronic components designed to provide drive signals to the actuator components 90, and thus the actuators in the plurality of fluid chambers, to drive the plurality of fluid chambers to eject fluid droplets as needed. Because the ASIC is a large heat-generating component on the PCB 70, it is preferable to co-locate it in a sub-area of ​​the PCB 70, i.e., the area defined by the actuator drive electronics 60. This area is preferably located in the central area of ​​the PCB 70 in the ejection direction 16.

[0069] It is further understood that other electronic components may be mounted at various locations on the PCB 70, but may be located outside the area defined by the actuator drive electronics 60, and / or outside the area defined by the protruding heat exchanging boundary surfaces 252i, 252ii, and / or outside the area defined by the first and second thermal conduction regions 70_c1, 70_c2, and / or outside the area defined by the thermally conductive adhesive layers 871i, 871ii. It is further understood that these other electronic components may generate levels of heat that are orders of magnitude less than the heat generated by the actuator drive electronics 60, and therefore these other electronic components do not need to be cooled via a thermal connection with the heat exchangers 150-1150.

[0070] PCB may be commonly understood to be an abbreviation for printed circuit board, but it is sometimes simply called a circuit board.

[0071] It will be appreciated that in some configurations, the droplet ejection head may be operated in reverse, with the fluid passing through the heat exchanger 150-1150, being heated by heat transferred from the actuator drive electronics 60 to the heat exchanger 150-1150, and then passing through the actuator component 90. This may be done, for example, to warm the fluid in the actuator component 90 prior to droplet ejection to change its viscosity or to enable effective priming. Such methods may include using an appropriate waveform or electronic signal, or performing an appropriate function, to generate heat in the actuator drive electronics 60. Such methods may include operating the droplet ejection device 1, 2 described herein, including any of the heat exchangers 150-1150 described herein, in which case the method may include the following steps: - supplying fluid to one or more droplet ejection devices 1, 2 via a fluid return path 142; - generating heat in one or more actuator drive electronics 60 using a suitable waveform or function; - transferring thermal energy from another actuator drive electronics 60 to a heat exchanger 150-1150; transferring some or all of the thermal energy from the heat exchanger 150-1150 to a fluid in the heat exchanger flow path 151-1151; - supplying fluid from the heat exchanger 150-1150 to one or more actuator components 90; - Exhausting fluid from one or more actuator components via inlet passage 142.

[0072] If the devices 1, 2 are operating in reverse as part of the droplet ejection process, the method may further include: Discharging a portion of the fluid from one or more nozzles in the actuator component 90 in response to a dispensing command, and then expelling any undischarged fluid from the actuator component 90 via the inlet path 140.

[0073] It will be generally understood that the diverter 670 and spigot 660 described herein can be used with any of the heat exchangers and droplet ejection devices described herein, and they can also be combined with suitable flexible tubing to form part of the inlet and outlet paths 144 and 145, respectively.

[0074] It is generally understood that the droplet ejection heads 100-900 described herein further include a mount and / or top cover, and that the one or more heat exchangers 150-1150 are thermally insulated from the mount and / or top cover. For example, the top cover can be positioned to enclose and house most of the internal structure of the droplet ejection head, leaving some or all of the medium-facing surface exposed so that, for example, the nozzles can be aimed at and eject droplets from a medium, such as a print medium like a tile, paper, card, ceramic, or an article like a bottle, container, or other 3D part.

[0075] The mounts are used to attach the droplet ejection heads to the printbar, which may include one or more droplet ejection heads. The mounts are thermally isolated from the heat exchangers 150-1150 using appropriate components and materials to form a thermal barrier. For example, a low-conductivity polymer material can be disposed between the mount and the heat exchanger 150-1150. Thermally isolating the mounts from one or more heat exchangers 150-1150 can reduce structural variations in the droplet ejection heads 100-900 and improve alignment to the printbar in droplet ejection devices 1, 2 that include one or more droplet ejection heads 100-900. Furthermore, it can prevent heat transfer from the droplet ejection heads 100-900 to the printbar. This may be desirable because heating the printbar can cause thermal expansion within the printbar, which can affect alignment between components in the droplet ejection device (e.g., alignment between droplet ejection heads when multiple droplet ejection heads are mounted on a printbar in the droplet ejection device 1, 2).

[0076] Similarly, it will generally be appreciated that the actuator components 90 can be thermally isolated from the heat exchangers 150-1150 by using appropriate components and materials to provide a thermal barrier.

[0077] The outer surface of the top cover may be provided with one or more inlets and one or more outlets, for example, fluidly connected through the top cover and fluidly connected to inlet paths 144 and outlet paths 145 within the droplet ejection heads 100-900. The one or more inlets and one or more outlets may be arranged such that when the droplet ejection heads 100-900 are mounted on the droplet ejection device 1, 2, the fluid inlet paths 141 are fluidly connected to the one or more inlets and the fluid return paths 142 are fluidly connected to the one or more outlets. The droplet ejection device 1, 2 may include one or more droplet ejection heads 100-900 as described herein, a droplet ejection fluid source 140 fluidly connected to the one or more droplet ejection heads 100-900 via the fluid inlet paths 141 to supply fluid to the one or more droplet ejection heads 100-900, and a fluid return path 142 to exhaust fluid from the one or more droplet ejection heads 100-900.

[0078] It will be generally understood that the features and components of the droplet ejection heads 100-900 described herein may be suitably combined with the features and components of the other droplet ejection heads 100-900 described herein, and with any of the heat exchangers 150-1150 described herein. It will further be understood that any of the droplet ejection heads 100-900 described herein may be used in the droplet ejection devices 1 and 2 described herein.

Claims

1. 1. A droplet ejection head comprising: one or more actuator components; an inlet path for supplying fluid to the one or more actuator components; and an outlet path for exhausting fluid from the one or more actuator components, the one or more actuator components comprising a plurality of fluid chambers, the plurality of fluid chambers comprising at least one nozzle, the plurality of fluid chambers operable to eject one or more droplets through the at least one nozzle in response to an ejection command; the plurality of fluid chambers are fluidly connected at respective first ends to the inlet pathway and at respective second ends to the outlet pathway; the outlet path comprises one or more heat exchangers arranged in series downstream of the one or more actuator components; one or more actuator drive electronics components disposed adjacent each of the heat exchangers; the one or more heat exchangers comprise one or more heat exchanger flow paths such that, in use, heat is transferred from the actuator drive electronics to the one or more heat exchangers and removed by a return fluid; an area defined by the actuator drive electronics is substantially contained within an area defined by the one or more heat exchanger flow paths in the same plane; Droplet ejection head.

2. The drop ejection head of claim 1 , wherein an area defined by the heat exchanger flow path is substantially larger than an area defined by the actuator drive electronics.

3. A drop ejection head according to claim 1 or claim 2, wherein the area of ​​the heat exchanger is substantially larger than the area defined by the actuator drive electronics.

4. The droplet ejection head according to claim 1 , wherein the heat exchanger flow path is a serpentine flow path.

5. A droplet ejection head according to claim 1 , wherein the heat exchanger flow path comprises two or more sub-paths.

6. A droplet ejection head according to claim 1 , wherein the heat exchanger flow path comprises one or more flow control devices.

7. The droplet ejection head of claim 6 , wherein the flow control devices comprise one or more of walls, and / or ridges, and / or pillars, and / or struts, and / or vanes, and / or grooves.

8. A droplet ejection head described in any one of claims 1 to 7, wherein the route of the heat exchanger flow path is selected to maximize the cooling effect on the actuator driving electronic components by maximizing the length and / or wetted surface area of ​​the heat exchanger flow path.

9. A droplet ejection head as described in any one of claims 1 to 8, wherein the cooling effect is balanced with fluid pressure loss in the heat exchanger flow paths by maximizing the wetted surface area of ​​the flow paths in the heat exchanger while minimizing fluid pressure loss in the heat exchanger.

10. A droplet ejection head according to claim 1 , wherein the heat exchanger has a fluid impedance that is substantially matched to the inlet path.

11. A droplet ejection head according to claim 1 , wherein the heat exchanger comprises one or more high thermal conductivity materials.

12. A droplet ejection head according to any preceding claim, wherein the heat exchanger comprises a thermally conductive polymer.

13. The droplet ejection head of claim 1 , wherein the heat exchanger comprises aluminum or an aluminum alloy.

14. A drop ejection head according to claim 1 , wherein the heat exchanger flow path comprises one or more return loops.

15. The drop ejection head of claim 14 , wherein the return loop comprises one or more straight leg portions arranged parallel to the ejection direction.

16. A droplet ejection head according to claim 1 , wherein the one or more actuator drive electronics are aligned with the heat exchanger to maximise heat transfer in use.

17. A droplet ejection head according to claim 1 , wherein the heat exchanger comprises one or more protrusions having a heat exchanging interface surface aligned with the actuator drive electronics.

18. 18. The droplet ejection head of claim 17, wherein the actuator drive electronics are disposed on the one or more PCBs such that the one or more PCBs are sandwiched between the one or more heat exchange boundary surfaces and the actuator drive electronics.

19. 20. The droplet ejection head of claim 18, wherein the actuator drive electronics are located in a central area of ​​the one or more PCBs in the ejection direction.

20. 20. A droplet ejection head according to any one of claims 17 to 19, wherein the protrusion provides an air gap between the PCB and the heat exchanger except in areas aligned with the actuator drive electronics.

21. each of the one or more PCBs comprising first and second thermal conduction areas disposed on opposite sides of each of the PCBs; the first and second thermal conduction regions are thermally connected to one another by one or more thermal conduction paths; A droplet ejection head described in any one of claims 18 to 20, wherein the first heat conduction area is aligned with and adjacent to the heat exchange boundary surface of the one or more protrusions, and the second heat conduction area is aligned with and adjacent to an area defined by the actuator drive electronic components.

22. 22. The drop ejection head of claim 21, wherein an area defined by the actuator drive electronics is substantially contained within an area defined by the first and second thermally conductive regions.

23. 23. A drop ejection head according to claim 21 or claim 22, wherein the one or more thermally conductive paths comprise a plurality of vias, the vias being lined or filled with a thermally conductive material.

24. 24. A droplet ejection head according to any one of claims 21 to 23, wherein the heat conducting region and the heat conducting path comprise a metal.

25. 25. A droplet ejection head according to any one of claims 18 to 24, wherein a thermally conductive bonding layer bonds each PCB to a respective heat exchanging boundary surface of the one or more protrusions.

26. A droplet ejection head according to any preceding claim, comprising two or more actuator drive electronics per heat exchanger.

27. 27. A droplet ejection head according to any preceding claim, comprising two or more actuator components and a respective heat exchanger arranged in series downstream of each of the two or more actuator components.

28. the plurality of fluid chambers are fluidly connected at the first end to one or more first manifold chambers and at the second end to one or more second manifold chambers; the one or more first manifold chambers are fluidly connected to the inlet pathway; the one or more second manifold chambers are fluidly connected to the outlet pathway; the one or more second manifold chambers are fluidly connected in series to each heat exchanger of the one or more heat exchangers; The droplet ejection head according to any one of claims 1 to 27.

29. the outlet path comprises one or more spigots for connecting to a connecting portion of the outlet path; each of the spigots and / or the respective connecting portions comprises one or more outer spherical features; each respective outer spherical feature is positioned to provide a fluid-tight connection between the spigot and the respective connecting portion of the outlet path; The droplet ejection head according to any one of claims 1 to 28.

30. a diverter fluidly connects the inlet and outlet paths to the actuator component while maintaining fluid separation between the inlet and outlet paths; the diverter comprising spherical features that provide a fluid-tight connection to the inlet and outlet paths, respectively; The droplet ejection head according to any one of claims 1 to 29.

31. 30. The drop ejection head of claim 28, wherein a diverter fluidly connects the one or more second manifold chambers to the respective heat exchanger.

32. 30. The drop ejection head of claim 29, wherein the flow path of the drop ejection head comprises cylindrical features at the inlet and outlet for receiving a portion of the spigot.

33. 33. A droplet ejection head according to claim 32, wherein an interface between each spigot and the inlet and / or the outlet comprises an adhesive and / or sealant and / or sealing component.

34. the droplet ejection head further comprises a mount and / or a top cover, and the one or more heat exchangers are thermally insulated from the mount and / or the top cover; The droplet ejection head according to any one of claims 1 to 33.

35. A droplet ejection device comprising one or more droplet ejection heads as described in any one of claims 1 to 34, a droplet ejection fluid source fluidly connected to the one or more droplet ejection heads via a fluid inlet path to supply fluid to the one or more droplet ejection heads, and a fluid return path for discharging fluid from the one or more droplet ejection heads.

36. 1. A method of cooling one or more actuator drive electronics for a droplet ejection head comprising one or more actuator components, an inlet pathway for supplying fluid to the one or more actuator components, and an outlet pathway for removing fluid from the one or more actuator components, the method comprising: the one or more actuator components comprising a plurality of fluid chambers, the fluid chambers comprising at least one nozzle, the fluid chambers operable to eject one or more droplets through the at least one nozzle in response to an ejection command; the plurality of fluid chambers are fluidly connected at respective first ends to the inlet pathway and at respective second ends to the outlet pathway; the outlet path comprises one or more heat exchangers arranged in series downstream of the one or more actuator components; one or more actuator drive electronics components disposed adjacent each of the heat exchangers; the one or more heat exchangers comprise one or more heat exchanger flow paths such that, in use, heat is transferred from the actuator drive electronics to the one or more heat exchangers and removed by a return fluid; an area defined by the actuator drive electronics is substantially contained within an area defined by the one or more heat exchanger flow paths, and the method comprises: supplying fluid to the one or more actuator components via the inlet passage; Discharging fluid from the one or more actuator components through the outlet path and introducing fluid into the heat exchanger flow path, whereby the fluid flows through the one or more heat exchangers, removing heat transferred from the actuator drive electronics to the heat exchangers by the fluid flowing through the one or more heat exchangers; A method comprising:

37. 36. A method of operating a droplet ejection device according to claim 35, said method comprising: supplying fluid to the one or more droplet ejection heads via the inlet passage; supplying fluid to the one or more actuator components via the inlet passage; ejecting a percentage of the fluid from one or more nozzles in the actuator component in response to a ejection command; exhausting un-ejected fluid from the one or more actuator components via the outlet path; transferring thermal energy from the one or more actuator drive electronics components to the heat exchanger; A part or all of the thermal energy transferring thermal energy to the undischarged fluid in the outlet path; Discharging the unejected fluid from the one or more droplet ejection heads via the fluid return path. removing the heat exchanger by A method comprising:

38. 36. A method of operating a drop ejection device according to claim 35 to heat fluid in the one or more drop ejection heads, the method comprising: supplying fluid to the one or more droplet ejection devices via the fluid return path; using an appropriate waveform or function to generate heat within said one or more actuator drive electronics; transferring thermal energy from the one or more actuator drive electronics components to the heat exchanger; transferring some or all of the thermal energy from the heat exchanger to a fluid in the heat exchanger flow path; supplying fluid from the heat exchanger to the one or more actuator components; venting fluid from the one or more actuator components via the inlet passage; A method comprising:

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