print head

Abstract

A method for operating an actuator unit for a print head, wherein the actuator unit comprises: a first piezoelectric element connected to a first potential and a third potential; a second piezoelectric element connected to a second potential and the third potential; and wherein the actuator unit is configured to deflect when the first potential and the second potential have the same polarity with respect to the third potential; wherein the method comprises: applying a first variable high voltage Vt between the first potential and the third potential; applying a second variable high voltage Vb between the second potential and the third potential; and applying a switchable ground connection to the third potential.

Description

Technical Field

[0001] This invention relates to a printhead, preferably a printhead for a 3D printer or a 2D printer. More specifically, this invention relates to an actuator for said printhead, a fluid system for said printhead, and a method for driving said actuator. Background Technology

[0002] An example of a 3D printing head is disclosed in, for example, patent applications EP 3 825 100 A1; EP 21 215 072.6; and EP 21 212 024.0, all of which are incorporated herein by reference. In particular, where possible, the same names and definitions as in the foregoing applications are used. However, the same printing head can be deployed in a 2D printer. Summary of the Invention

[0003] The main principle of a printhead is that the material is initially stored in a reservoir, preferably in a liquid phase. The material (also called a fluid or liquid) is then transported to and / or enters the printhead via conduit elements (e.g., pipes, tubes, or connector elements).

[0004] Within the printhead, the fluid is further delivered to the pressurized zone. A portion of the fluid is then ejected from the pressurized zone through nozzle openings in the nozzle plate. This ejection is caused by the movement of the actuator and the displacement of the liquid in the pressurized zone by the moving actuator (preferably via an extension attached to the actuator).

[0005] The displacement of material caused by the extension member results in localized and instantaneous positive pressurization of the liquid material within the injection zone. The shaped region located between one or more lower surfaces (which are displaced by the displacement of the extension member) and its orthogonal projection onto the upper surface of the nozzle plate and / or spacer plate can be referred to as the injection zone, and can additionally be referred to as a virtual chamber when the injection zone experiences a portion of the positive pressurization present in the larger pressurized region.

[0006] To improve overall performance and allow for higher native resolution printing of high-viscosity inks, the mechanical and electrical actuator design and / or fluid design of the printhead can be optimized.

[0007] In detail, the improved design of material transport in the printhead enhances printing efficiency and capability, such as printing settled and / or pooled ink, or printing with a printhead at an angle relative to gravity.

[0008] Furthermore, the simplified structural design of the printhead components reduces the structural complexity of the printhead, particularly the material circulation system, thereby reducing assembly complexity. Consequently, one or more of printing efficiency, capability, and cost efficiency are improved.

[0009] Furthermore, improved electrical and / or electrical signal design allows for more efficient movement and new movement patterns. Therefore, printing efficiency is improved.

[0010] The present invention is set forth in the appended claims. Any references in the following text to embodiments, objects, aspects and / or examples not included within the scope of the appended claims are not considered part of this invention.

[0011] According to one aspect of the invention, a printhead for a printer is provided, comprising: a first housing element including at least two first channel structures, wherein the first channel structures extend along a first direction and are configured to convey a liquid material; a second housing element disposed below the first housing element and including a plurality of second channel structures, wherein the second channel structures extend along a second direction substantially perpendicular to the first direction and are configured to convey a liquid material; wherein each second channel structure overlaps a portion of one of the first channel structures and a portion of at least another of the first channel structures to allow liquid communication of the liquid material between two portions of the two or more first channel structures.

[0012] The first housing element is also referred to below as the main fluid plate. The second housing element is referred to below as the spacer plate.

[0013] In one embodiment of the invention, the printhead further includes a plurality of extension members, each extension member projecting from the actuator through a corresponding opening in the first housing element in a direction substantially perpendicular to a plane defined by a first direction and a second direction; and wherein the extension members are arranged substantially parallel to each other and substantially form a line in the first direction.

[0014] In one embodiment of the invention, each second channel structure is configured to form a spray area below the corresponding end portion of the extension member.

[0015] In one embodiment of the invention, the printhead further includes a nozzle plate having nozzle openings for spraying liquid material and disposed below the second housing element, wherein the nozzle openings are preferably disposed at positions corresponding to the spraying areas, and wherein the printhead is preferably configured to spray liquid from the respective spraying areas through the respective nozzle openings based on actuation of the respective extension members.

[0016] In one embodiment of the invention, the printhead further includes a membrane element disposed below a first housing element and above a second housing element, wherein the membrane element is configured to seal the first housing element relative to the second housing element at least in a region of the end portion of the extension member and to form a pressurized region within a second channel in said region.

[0017] In one embodiment of the invention, the printhead further includes a heating element, wherein the heating element is disposed in: a) Inside the first housing element, b) Below the first housing element and above the membrane element, or c) Below the first housing element and below the membrane element.

[0018] In one embodiment of the invention, the membrane element includes a forming portion at the end portion of the extension member, wherein the forming portion is configured to match the shape of the end portion of the extension member or the shape of an intermediate element attached to the end portion of the extension member.

[0019] In one embodiment of the invention, one or more additional reference elements are provided on the end portion of the free actuator to define the position from which the extension member protrudes.

[0020] In one embodiment of the invention, at least one of the first channel structures is configured as an inflow channel and preferably connected to an inflow connector; and wherein at least another of the first channel structures is configured as an outflow channel and preferably connected to an outflow connector.

[0021] In one embodiment of the invention, the cross-section of the inflow channel decreases continuously from one end to the other along the material conveying direction; and / or the cross-section of the outflow channel increases continuously from one end to the other along the material conveying direction.

[0022] In one embodiment of the invention, a top clamping element and / or a bottom clamping element are provided at the center of the actuator, the top clamping element and / or the bottom clamping element being configured to restrict the movement of the actuator.

[0023] In one embodiment of the present invention, the first channel structure and / or the second channel structure are formed by at least one of the following methods: etching, laser ablation, injection molding or milling.

[0024] In one embodiment of the invention, one or more junction portions are formed in at least one of the first channel structures to connect the respective channel structure to the connector element.

[0025] In one embodiment of the invention, at least one bypass channel is formed to connect at least two of the first channel structures.

[0026] According to one aspect of the invention, a method for assembling a printhead is provided, comprising: providing a first housing element including at least two first channel structures, wherein the first channel structures extend along a first direction and are configured to convey a liquid material; disposing a second housing element below the first housing element, wherein the second housing element includes a plurality of second channel structures, wherein the second channel structures extend along a second direction substantially perpendicular to the first direction and are configured to convey the liquid material; wherein the second housing element is arranged such that each second channel structure overlaps a portion of one of the first channel structures and a portion of at least another of the first channel structures for liquid communication of the liquid material between two portions of the two or more first channel structures.

[0027] According to one aspect of the invention, an actuator unit for a printhead is provided, comprising: a first piezoelectric element and a second piezoelectric element disposed on opposite surfaces of a spacer element, wherein the non-spacer-facing surfaces of each of the first and second piezoelectric elements are respectively connected to a first potential and a second potential, preferably high voltage signals, wherein the spacer-facing surfaces of the first and second piezoelectric elements are connected to a third potential, preferably switchable ground potential, and wherein the first and second piezoelectric elements are configured such that when the first and second potentials have the same polarity relative to the third potential, one contracts while the other expands in a direction substantially parallel to the spacer-facing surface.

[0028] The spacer element is also referred to below as a reinforcing element. The first piezoelectric element is preferably a top piezoelectric element; the second piezoelectric element is preferably a bottom piezoelectric element.

[0029] In one embodiment of the present invention, the first piezoelectric element and the second piezoelectric element have the same polarity axis direction.

[0030] In one embodiment of the invention, the actuator unit has a thickness direction, a width direction, and a length direction longer than the width direction, wherein a first piezoelectric element and a second piezoelectric element are disposed on a spacer element along the thickness direction, wherein the polarity axes of the first piezoelectric element and the second piezoelectric element are configured such that the corresponding d31 mode is deformed in the length direction of the actuator.

[0031] In one embodiment of the present invention, the first potential and the second potential originate from the same high-voltage signal.

[0032] In one embodiment of the invention, an electrode is disposed on at least one of the surfaces of the first piezoelectric element (302) and the second piezoelectric element (303), wherein the electrode is preferably a thin film electrode.

[0033] In one embodiment of the invention, one end portion of the actuator is fixed to the print head in the length direction and the other end portion is a free end.

[0034] In one embodiment of the invention, at the free end of the actuator, an extension member protrudes from a surface of the first piezoelectric element or the second piezoelectric element.

[0035] In one embodiment of the invention, the spacer element is a reinforcing element and is configured to increase the stiffness of the actuator.

[0036] In one embodiment of the invention, the spacer element is made of a non-conductive material, preferably one or more of the following materials: glass fiber material, carbon fiber material, metal oxide material, composite material or ceramic material.

[0037] In one embodiment of the invention, the first piezoelectric element (302) and the second piezoelectric element (303) are made of one or more variants of lead zirconate titanate (PZT).

[0038] According to one aspect of the present invention, an actuator block for a printhead is provided, comprising: a plurality of actuator units according to any of the foregoing embodiments, the plurality of actuator units being arranged substantially parallel in the width direction of the actuator units, wherein a corresponding first potential, a second potential and a third potential of each actuator unit are controlled by a controller, the controller providing a separate output for each actuator unit.

[0039] In one embodiment of the present invention, each actuator unit is arranged in a sawtooth configuration along the length of the actuator unit.

[0040] According to one aspect of the invention, an actuator assembly for a printhead is provided, comprising: a plurality of actuator blocks as described in the foregoing aspect, wherein the plurality of actuator blocks are arranged substantially parallel in the width direction of the actuator unit.

[0041] According to one aspect of the present invention, a method is provided for an actuator unit according to any of the foregoing embodiments, the method comprising the steps of: applying a first variable high voltage Vt between a first potential and a third potential, applying a second variable high voltage Vb between a second potential and a third potential, and applying a switchable ground connection to the third potential, wherein the first variable high voltage Vt and the second variable high voltage Vb are the same variable high voltage, and preferably are positive or negative voltages.

[0042] In one embodiment of the invention, a first voltage and a second voltage, as well as a ground connection state, are selected such that the displacement of the actuator is lower than the speed of sound of the liquid material ejected from the printhead.

[0043] According to one aspect of the invention, a method for operating an actuator unit for a printhead, wherein the actuator unit includes: a first piezoelectric element connected to a first potential and a third potential; a second piezoelectric element connected to a second potential and a third potential; and wherein the actuator unit is configured to deflect when the first potential and the second potential have the same polarity relative to the third potential; wherein the method includes: applying a first variable high voltage Vt between the first potential and the third potential; applying a second variable high voltage Vb between the second potential and the third potential; and applying a switchable ground connection to the third potential.

[0044] In one embodiment of the present invention, the first variable high voltage Vt and the second variable high voltage Vb are the same variable high voltage, and preferably are positive or negative voltages.

[0045] In one embodiment of the present invention, the first variable high voltage Vt and the second variable high voltage Vb can be discretely switched between n states.

[0046] In one embodiment of the invention, n is between 2 and 200, more preferably between 3 and 150.

[0047] In one embodiment of the invention, the switchable grounding connection has two states: a) First state, wherein the ground connection is in the connected state to allow current to flow from the corresponding first and second potentials, thereby generating an electric field on the corresponding piezoelectric elements, causing them to deform, preferably in mode d31. b) Second state, wherein the grounding connection is in the open state so as not to allow current to flow from the corresponding first potential and second potential, thereby preventing the generation of an electric field on the corresponding piezoelectric element and thus not causing deformation.

[0048] In one embodiment of the invention, the maximum upward deflection AD n This corresponds to the ground connection being in the connected state and Vb and Vt being at their maximum positive voltages; where the maximum downward deflection AD -n This corresponds to the ground connection being in the connected state and Vb and Vt being at their maximum negative voltage.

[0049] In one embodiment of the invention, the average deflection speed v n By AD n and AD -n The position difference between them is divided by the rise time t required to reach the corresponding maximum deflection state, where the rise time t is calculated from the moment the corresponding voltage is applied; and preferably v nIt is between 0.025 μm / μs and 100 μm / μs, more preferably between 0.2 μm / μs and 37.5 μm / μs.

[0050] In one embodiment of the invention, the maximum voltages Vb-n and Vt-n are between 20 and 250 volts, more preferably between 40 and 200 volts.

[0051] In one embodiment of the invention, ET is defined as an ejection threshold for downward deflection, at which material is ejected from the printhead; and Preferably, ET is between 0.3 μm and 40 μm, and more preferably between 1 μm and 30 μm.

[0052] In one embodiment of the invention, PT is defined as the refill threshold when the printhead is deflected upward, at which point the ejection area is filled with the material to be ejected; and wherein, preferably, PT is between 0.3 μm and 40 μm, more preferably between 1 μm and 30 μm.

[0053] In one embodiment of the invention, a first voltage and a second voltage, as well as a ground connection state, are selected such that the actuator unit is maintained in a deflection state above ET for a duration between 0.2 and 75 microseconds.

[0054] In one embodiment of the invention, a first voltage and a second voltage, as well as a ground connection state, are selected such that the actuator unit is maintained in a deflection state above PT for a duration between 0.2 and 70 microseconds.

[0055] In one embodiment of the invention, a first voltage and a second voltage, as well as a ground connection state, are selected such that the actuator unit deflects at an average deflection rate between 0.025 μm / μs and 100 μm / μs.

[0056] In one embodiment of the invention, a first voltage and a second voltage, as well as a ground connection state, are selected such that the displacement of the actuator is lower than the speed of sound of the liquid material ejected from the printhead.

[0057] Printhead structure When referring to the printhead, the following directional definitions apply. The motion of the actuator is typically defined in upward and downward directions, with jetting associated with downward motion.

[0058] The vertical direction defines the length of the printhead, which is also the smaller dimension of the actuator and the larger dimension of the printhead. Therefore, the remaining direction is called the width direction of the actuator, which is the larger dimension of the actuator and the smaller dimension of the printhead.

[0059] It should be noted that the directions described above are defined only to improve the comprehensibility of this description, and any other coordinate system suitable for describing 3D space may be used to identify directions and / or dimensions, especially in the accompanying drawings.

[0060] In one embodiment of the invention, the printhead includes a plurality of material ejection units. Each material ejection unit includes at least one actuator unit. The material ejection units are preferably arranged in a side-by-side manner, i.e., the respective actuator units are arranged parallel to each other in the length direction of the printhead. Preferably, the material ejection units are formed in a common housing, i.e., the printhead housing.

[0061] In one embodiment of the invention, the printhead housing further includes, or partially includes, electromechanical components and / or fluid components of one or more material ejection units.

[0062] In one embodiment of the invention, two or more actuator units form an actuator block. Preferably, one or more actuator blocks form an actuator assembly. The actuator assembly, the corresponding fluid structure in the printhead housing, and the corresponding electrical and fluid connection means form a printhead.

[0063] A general embodiment of the actuator unit according to the invention, for example Figure 6 As shown. A plurality of said actuator units, preferably 32 said units, are arranged as follows: Figure 8 The actuator block shown. Multiple actuator blocks connected in series form a configuration as shown. Figure 9 The actuator assembly is shown. A generally linear arrangement of the actuator units and / or actuator blocks is preferred, but other arrangements such as zipper-type arrangements, double-row (column) or multi-row (column) patterns are equally applicable, and may even form preferred specific embodiments depending on the application.

[0064] In the following description, basic features will be described with reference to general embodiments, and specific features will be described with reference to particular embodiments. Unless otherwise stated or obvious to those skilled in the art, all features may be included in all embodiments.

[0065] In a preferred embodiment of the invention, an actuator block includes 4 to 256 actuator units, more preferably 32 actuator units. In a preferred embodiment of the invention, an actuator assembly includes 1 to 16 actuator blocks, more preferably 3 actuator blocks. In one embodiment of the invention, the printhead housing includes a space for receiving the actuator assembly. The printhead housing may also include a fluid structure corresponding to the actuator assembly.

[0066] In one embodiment of the invention, the fluid structure includes a material jetting structure having a jetting region for each actuator unit, adapted to jet material based on the instantaneous pressurization of material within the jetting region by the respective actuator unit.

[0067] The fluid structure also includes a material transport structure for conveying the sprayed material to and from the corresponding material spraying area.

[0068] In one embodiment of the invention, the material delivery structure includes one or more material inflow channels for delivering material from an inflow connector to one or more material spraying areas.

[0069] In one embodiment of the invention, the material inflow channel includes at least one junction portion that connects at least one inflow channel and an outflow channel to a corresponding one of one or more inflow and / or outflow connectors at one or more locations in the width direction.

[0070] In addition, the junction is a fluid conduit section that is located at a point where one or more material inflow connectors are connected to the material inflow channel, other than the endpoint of the material inflow channel, thereby causing the material flow direction to bifurcate from the junction toward the inflow channel.

[0071] Furthermore, the junction is a fluid conduit section located at a point other than the endpoint of the material outflow channel where one or more material outflow connectors are connected, thereby causing the convergence of multiple material flow directions from the outflow channel toward the junction.

[0072] In one embodiment of the invention, the material delivery structure includes one or more material outflow channels for delivering material from one or more material spraying areas to an outflow connector.

[0073] In an alternative embodiment of the invention, a plurality of material inflow connectors may be connected to an inflow channel, wherein the inflow channel includes one or more junction portions, preferably in the case of two or more junction portions, spaced at equal distances along the length of the material inflow channel, and the inflow channel is connected to a corresponding inflow connector.

[0074] In an alternative embodiment of the invention, a plurality of material outflow connectors may be connected to an outflow channel, wherein the outflow channel includes one or more junction portions, preferably in the case of two or more junction portions, spaced at equal distances along the length of the material outflow channel, and the outflow channel is connected to a corresponding outflow connector.

[0075] In an alternative embodiment of the invention, a plurality of material outflow connectors are connected to an inflow channel, wherein the outflow channel includes connected outflow connectors, preferably spaced at equal distances along the length of the material inflow channel.

[0076] In an alternative embodiment of the invention, the flow direction of the liquid material in the conduit structure between the inflow connector and the outflow connector can be reversed.

[0077] In one embodiment of the invention, a material spraying region is formed in a material spraying channel.

[0078] In one embodiment of the invention, a material delivery structure is located below the actuator assembly and above the nozzle plate. The material delivery structure has openings for corresponding extension members of the actuator assembly to extend into the fluid structure and communicate with the corresponding material injection area.

[0079] In a preferred embodiment of the invention, the printhead housing is formed by stacking two or more plate-like elements on top of each other, thereby defining the aforementioned spatial and / or fluid structure. When attached to corresponding other plates, the plate-like elements may have one or more recessed and / or slit portions to define the aforementioned spatial and fluid structure.

[0080] In other words, the central shell component can be formed by two or more adjacent plate-like structures with complex shapes that define the cross-section of the main shell structure.

[0081] The stacking of the plate-like elements allows for a simplified manufacturing process for the printhead components using one or more of the following methods: etching, laser ablation, disc cutting, injection molding, or milling. This simplified manufacturing process enables the production of multi-layered conduit networks to achieve appropriate fluid distribution.

[0082] Furthermore, alignment can be enhanced during the joining or bonding of the components by adhesives or welding by allowing each component of the fluid plate to be referenced along the xy plane during the manufacturing process.

[0083] To improve the comprehensibility of this description, in the following text, the injection unit is considered to include an actuator unit and a portion of the lower plate stack, which corresponds to the width of the material injection channel and the two halves of the separating sidewalls of the channel formed in the fluid plate, as shown below. Figure 3a and Figure 3b As shown.

[0084] Specifically, the injection unit may include a section of the entire channel width, two half sidewall widths of the elements present in the spacer element, a section of the nozzle plate, a section of the membrane element, a section of the lower intermediate plate, a section of the main fluid plate, a section of the heating plate, and a corresponding actuator unit.

[0085] However, since the jetting unit may not be a physically separate component of the printhead, it can be defined in any other way as long as the same printhead structure is obtained by connecting the jetting units in series.

[0086] Electromechanical actuator design To improve the efficiency and / or quality of the printing process, a scalable printhead design is required. That is, it allows a large number of material ejection units to be arranged relatively close to each other within the printhead and / or within a printhead housing.

[0087] The preferred spacing between the nozzle openings 201 of the material ejection unit is 2 mm to 0.2 mm, more preferably 1.5 mm to 0.5 mm. The preferred number of material ejection units in the printhead is 32 to 256, more preferably 96.

[0088] The first core concept of this invention is to provide a simplified mechanical and electrical actuator design. This allows actuator units to be efficiently connected in series in the printhead, thereby reducing spacing and providing a high native resolution printhead.

[0089] The second core concept of this invention is to provide a simplified fluid design for the material circulation system. This allows actuator units to be efficiently connected in series in the printhead, thereby reducing spacing and providing a higher native resolution printhead.

[0090] The third core concept of this invention is to provide a simplified printhead driving method. This allows for efficient droplet ejection, thereby reducing pitch and providing a higher native resolution printhead.

[0091] In the foregoing, the term "higher native resolution" is relative to other systems capable of handling high viscosity. High DPI is generally considered to be above 800 DPI. The present invention has achieved 20 DPI, which is an improvement over the 10 DPI typically obtained from the other systems capable of handling high viscosity.

[0092] In embodiments of the invention, the actuator is configured as a cantilever actuator with reinforcing elements (also referred to as spacers).

[0093] A reinforcing element is attached to the upper or lower surface of the piezoelectric element. This connection provides an elastic mechanism for the piezoelectric element, transforming the d31 deformation into a substantially orthogonal deformation through differential expansion of the piezoelectric element and the reinforcing element at the connection boundary.

[0094] The reinforcing elements further provide spacing between two or more piezoelectric elements adhesively bonded to the upper and lower surfaces, and increase the width of the stack of reinforcing elements rigidly bonded to the stack, thereby increasing stiffness. In a preferred embodiment, the reinforcing elements are non-conductive and may be composed of one or more of the following materials: glass fiber, carbon fiber, metal oxide, composite material, or ceramic material.

[0095] The actuator's electrical connection is configured to easily adjust the actuator's displacement by switching a switch that connects the reinforcing element to ground via a grounding wire, thereby displacing the actuator through the elongation and contraction of the piezoelectric element, wherein a voltage potential generates an electric field from the piezoelectric electrode to the reinforcing element.

[0096] The electrodes to be formed on the piezoelectric element discussed in this disclosure preferably cover the top and / or bottom surfaces of the piezoelectric element and are preferably formed of a conductive thin film.

[0097] The displacement of the actuator is driven by positive and negative voltages (preferably simultaneously) applied to the top and bottom piezoelectric electrodes. By selecting the respective polarization directions of the top and bottom piezoelectric elements (hereinafter also referred to as the lower piezoelectric element), a difference in the displacement direction of the piezoelectric elements in response to the same voltage value applied to the top and bottom piezoelectric electrodes can be achieved.

[0098] The polarization directions are chosen to be the same, preferably downward, so that the direction of the electric field applied to one piezoelectric element is substantially parallel to its polarization direction, while the direction of the electric field applied to another piezoelectric element is substantially antiparallel to its polarization direction.

[0099] By switching the values ​​of one or more high-voltage signals between multiple states, while independently switching the grounding switch between open and closed states, time-dependent actuation speed shaping, also known as time-dependent shaping, can be achieved.

[0100] This time-dependent formation leads to improved adaptability to high-viscosity materials with complex rheological properties. Furthermore, this allows for compensation of individual nozzle performance without the need for complex drive electronics such as FPGAs. In particular, the invention allows for multi-pulse-based control, eliminating the need for highly complex drive electronics and instead utilizing a fast-switching grounding gate.

[0101] Time-dependent shaping of actuator displacement, preferably with a large displacement amplitude, is a key element in achieving high-viscosity injection.

[0102] In the printhead according to the invention, the pumping displacement lasts longer than the normal displacement in some other printheads due to the longer time-dependent vertical displacement (following the variable speed), thereby allowing for a longer period of pressure maintenance relative to the normal pressurization time in other printheads.

[0103] Furthermore, the prolonged pressurization of the liquid material, primarily in the subsonic range, leads to differences in droplet formation and the release of the liquid material below the nozzle.

[0104] This results in a short pressure front, which in turn transfers a portion of its energy (preferably its physical portion) to the liquid-gas interface of the meniscus, causing the meniscus to expand and leading to the formation and expulsion of droplets.

[0105] This allows material to flow from the nozzle and form droplets, while the size and release point of the droplets can be controlled by waveform modulation and / or multiple actuations.

[0106] The cantilever configuration according to the invention allows for large displacements similar to previous actuator designs, but with a much smaller footprint, for example, 4 mm to 6 mm by 1 mm, compared to 8 mm to 10 mm by 2 mm for previous designs. Furthermore, comparable results can be obtained at much lower voltages, for example ±150 volts, instead of the previous ±200 volts.

[0107] Furthermore, according to the present invention, a significantly reduced harmonic resonance is achieved.

[0108] In embodiments of the invention, the displacement of the actuator remains primarily vertical. However, due to the geometry of the actuator, radial displacement may be introduced, thus introducing substantially lateral displacement of the lower surface of the extension member.

[0109] Regarding the multi-actuator unit, according to the present invention, a very simplified production and adhesion process is allowed, which is fully modular and can be infinitely expanded.

[0110] Fluid Design As described above, the actuator unit according to the invention preferably comprises a piezoelectric system with precision electrical and / or mechanical components. Furthermore, a high voltage is used to actuate one or more piezoelectric elements of the piezoelectric system. Therefore, it is desirable that the liquid in the printhead does not come into contact with the actuator assembly.

[0111] Furthermore, since the liquid is preferably heated to maintain a certain viscosity, excessive heat transfer from the liquid to the actuator should be prevented, and vice versa. However, effective impulse transfer should also be maintained at the same time, which requires direct contact between the actuator assembly and the liquid.

[0112] A core concept of this invention is to provide a membrane within the printhead to separate the liquid from the actuator. Embodiments of the invention relate to different variations and placements of the membrane.

[0113] In embodiments of the invention, the membrane prevents liquid materials from contacting the actuator, thereby reducing heat transfer and the need to coat actuator components to prevent short circuits.

[0114] Furthermore, the membrane according to the invention allows for more efficient pressurization of the pressurized area (i.e., the jetting area) and better refilling or refilling, i.e., removal of trapped gas from the pressurized area.

[0115] It should be noted that the term infusion generally refers to eliminating any two-phase gas-liquid flow from a geometry by introducing material into the geometry. More specifically, in the context of this invention, the geometry may be a jetting region, also referred to as a virtual chamber during positive pressurization, where positive pressurization refers to pressurizing the pressurized region relative to ambient pressure or the back pressure of the printhead when the actuator has not deflected from its neutral state.

[0116] The injected area needs to contain liquid material in order to be prepared to be pressurized for material injection, while during the pressurization, only the movement of the gas-liquid interface at or near the corresponding nozzle opening is affected, also known as the formation of a meniscus.

[0117] In other words, the geometry must be completely wetted or filled with the liquid material, leaving no enclosed gas or vacuum pockets within the infused geometry. If gas trapping occurs within the internal geometry, for example through undervoltage and gas intake, infusion is necessary to ensure that performance does not degrade during the injection process.

[0118] Refilling refers to the repeated supply of material to a region in a specific context of alternating states, where material has been ejected from the region and needs to be reintroduced, without forming any closed two-phase flow within the refilling region to prevent material shortage in the ejection region.

[0119] In the context of this invention, refilling typically occurs, at least in part, during a period of negative pressurization, which is the opposite of the pressurization performed for spraying liquid material.

[0120] In embodiments of the invention, multiple spraying units are connected in series, and corresponding channels are connected and formed into a material circulation system together with optional membranes and other auxiliary components (such as connectors). The material circulation system is configured to deliver liquid material to and from the respective spraying areas.

[0121] Regarding the inflow and outflow channels, there are corresponding positive and negative pressures. Pressurization creates a pressure difference, which in turn generates a material flow. Its relative pressure is lower than the ambient pressure, but not so low as to draw in air bubbles through the nozzle opening, nor so high as to cause material to leak from the nozzle opening.

[0122] In embodiments of the invention, pressure can be continuously measured at or near the highest and lowest pressurization zones within the material circulation system. Specifically, measurements are taken within the material conduit section between the pump generating positive pressure and the printhead, and / or within the material conduit section between the pump generating negative pressure and the printhead. This allows for electrical regulation of the pressurization pump to adjust its relative pressure based on a reference material and its characteristics at a corresponding temperature. The corresponding temperature can also be measured and adjusted via a heating plate inside the printhead or additional heating elements formed within the material supply system.

[0123] This results in a minimum material flow rate that remains stable in the material circulation system according to the aforementioned criteria.

[0124] In a first embodiment of the invention, the corresponding fluid channels are formed with a constant cross-section and a bypass structure with a reduced cross-section, in order to provide equalization of the flow rate and pressure of the material present in the jet channels during material recirculation. In this configuration, balanced refilling of all existing jet regions is possible.

[0125] In a second embodiment of the invention, the corresponding fluid channel is formed such that the volume of the inflow channel gradually decreases as the distance from the material inflow connector increases, and correspondingly, the volume of the outflow channel gradually increases as the distance from the material inflow connector increases.

[0126] In other words, the cross-section of the corresponding channel changes gradually, preferably along its length. This allows for improved uniform pressurization and flow rate of the liquid material present in the channel manifold between the inflow and outflow channels.

[0127] Nozzle plate displacement In embodiments of the invention, the nozzle plate is configured to displace during material ejection. This displacement may occur due to pressurization in the liquid material near the nozzle plate caused by actuator displacement, resulting in a displacement of the portion around the nozzle opening substantially parallel to the ejection direction, and transferring displacement energy to the material present below the nozzle plate during ejection.

[0128] This could lead to improved jetting performance, as it may help release or break the fluid filaments of the jetted material in the case of very high viscosity or very viscoelastic materials. Attached Figure Description

[0129] In the attached diagram: Figure 1A printhead according to an embodiment of the present invention is shown in an isometric apex view; Figure 2 The printhead according to an embodiment of the present invention is shown in an isometric bottom-angle view; Figure 3a A cross-sectional view of the printhead, cut along the direction of the actuator according to an embodiment of the present invention, is shown; Figure 3b A cross-sectional view of the printhead, cut along the direction of the actuator, is shown according to an alternative embodiment of the invention. Figure 4 The bottom side of a printhead according to an embodiment of the present invention is shown, wherein the fluid plate is open; Figure 5a The bottom side of a printhead according to an embodiment of the present invention is shown, wherein spacer elements are present; Figure 5b The bottom side of a printhead according to an embodiment of the present invention is shown, wherein spacer elements are present and the recessed channel structure of the fluid plate is shown in dashed lines; Figure 6 A diagonal isometric view of a printhead cross-section cut along the length of the actuator according to an embodiment of the present invention is shown; Figure 7 A cross-sectional view of an actuator unit according to an embodiment of the present invention is shown; Figure 7a The layered structure of the actuator unit according to an embodiment of the present invention is shown; Figure 7b A graph showing the driving signal applied to the actuator unit according to an embodiment of the present invention and the corresponding actuator displacement as a function of time is shown. Figure 8 An actuator block according to an embodiment of the present invention is shown in an isometric apex view; Figure 9 An actuator block assembly according to an embodiment of the present invention is shown in an isometric apex view; Figure 10a A schematic side view of a printhead having an extension member in a neutral position according to a first embodiment of the present invention is shown; Figure 10b A schematic side view of a printhead having an extension member in a deflected position is shown according to a first embodiment of the present invention; Figure 11a A schematic side view of a printhead according to a second embodiment of the present invention is shown; Figure 11b A printhead according to a second embodiment of the present invention is shown in an isometric apex view; Figure 12aA schematic side view of a printhead having an extension member in a deflected position is shown according to a first embodiment of the present invention; Figure 12b A schematic side view of a printhead having an extension member in a deflected position is shown according to a first embodiment of the present invention; Figure 13a A printhead according to a third embodiment of the present invention is shown in an isometric apex view; Figure 13b A schematic side view of a printhead according to a third embodiment of the present invention is shown; Figure 14 A printhead according to a fourth embodiment of the present invention is shown in cross-sectional view; Figure 15 A printhead according to a sixth embodiment of the present invention is shown in cross-sectional view; Figure 16a A printhead according to a seventh embodiment of the present invention is shown in an isometric apex view; and Figure 16b A cross-sectional view of a printhead according to a seventh embodiment of the present invention is shown. Detailed Implementation

[0130] Embodiments of the invention will be described below. It should be noted that, unless otherwise stated or obvious to those skilled in the art, certain aspects of each described embodiment may also be found in some other embodiments. However, for the sake of understanding, each aspect is described in detail only upon its first mention, and any repeated descriptions of the same aspect are omitted.

[0131] Figure 1 A printhead according to an embodiment of the present invention is shown in an isometric apex view. The printhead includes a housing, a fluid connector for inputting and removing liquid material, a vacuum connector, and an electrical connector for supplying electrical signals to an actuator unit within the housing actuator assembly.

[0132] As detailed above, in a preferred embodiment of the invention, the printhead is formed of different plate-like elements stacked in the vertical direction (i.e., along the jetting direction of the printhead). This design allows for an improved assembly process because each plate-like element can be independently referenced and positioned.

[0133] exist Figure 1 In this design, the printhead includes a main fluid plate 107 and a housing element 106. Furthermore, the printhead includes an electrical connector 102, a material inflow connector 103, a material outflow connector 104, a first vacuum connector 111, and a second vacuum connector 112.

[0134] Electrical connector 102, material inlet connector 103, and material outlet connector 104 can be disposed protruding upward from the top surface of housing element 106. The structural and functional relationships of these components will be discussed below.

[0135] Figure 2 A printhead according to an embodiment of the invention is shown from an isometric perspective. The main fluid plate 107 (see...) Figure 1 Below the nozzle plate 102, there is a spacer element 202. Below the spacer element 202, there is a nozzle plate 109.

[0136] like Figure 2 The enlarged section is shown in detail, showing that one or more nozzle openings or injection openings 201 are provided in the nozzle plate 109.

[0137] Figure 3a and Figure 3b Each figure shows a cross-sectional view of the printhead cut along the actuator direction according to an embodiment of the invention.

[0138] refer to Figure 1 and Figure 2 The printhead includes an electrical connector 102, a main housing 106, a top PCB (printed circuit board) board 502, a middle PCB board 503, a lower PCB board 504, a second vacuum connector 112, a heating plate 207, a main fluid plate 107, an actuator 301, an inflow channel 601, an outflow channel 602, a material jetting channel 603, a membrane 203, a spacer element 202, a nozzle plate 109, and an actuator 401.

[0139] It should be noted that the first vacuum connector 111, the material inflow connector 103, and the material outflow connector 104, and their respective conduits are connected in... Figure 3a Not shown in the image.

[0140] Inside the printhead, preferably within the space defined by the main fluid plate 107 and the housing element 106, an actuator 301 with an extension member 401 is provided. The extension member 401 extends from the actuator 301 to or into the material present in the main fluid plate 107. The actuator has a fixed end portion in the longitudinal direction, which is fixed relative to the housing. Furthermore, the actuator has a free end portion in the longitudinal direction, which is capable of vertical deflection, thereby actuating the extension member.

[0141] As described above, additionally or alternatively, a top PCB board 502 may be provided to enclose the actuator 301 in conjunction with the intermediate PCB board 503, the lower PCB board 504, and the main fluid board 107.

[0142] The top PCB board 502, the middle PCB board 503, and the lower PCB board 504 preferably include conductive connection elements, thereby allowing electrical signals to be transmitted from the electrical connector 102 to the actuator 301, to the heating plate connection element 501, and / or to other components inside the printhead.

[0143] The main fluid plate 107 may also include one or more fluid connector elements for supplying liquid material to the printhead and removing liquid material from the printhead, respectively.

[0144] The main fluid plate 107 is provided with a plurality of spaces for liquid, preferably defined by recesses in the main fluid plate 107.

[0145] In detail, the main fluid plate 107 includes a fluid inflow channel 601, a fluid outflow channel 602, and one or more material jetting channels 603. Each inflow / outflow channel extends along the lower surface of the main fluid plate 107 in a direction perpendicular to the jetting direction and substantially parallel to the actuator tandem direction, i.e., in the length direction of the printhead.

[0146] In one embodiment of the invention, the extension member 401 is located on the free end portion of the lower surface of the actuator to achieve maximum deflection.

[0147] In alternative embodiments of the invention, such as Figure 3b and Figure 6 As shown, the extension member 401 is formed at a predetermined distance from the free end of the actuator, and an additional reference element 403 is positioned between the extension member 401 and the free end.

[0148] More generally, at least one additional reference element 403 is provided to define the position of the extension member relative to the end portion of the actuator. The reference element is configured to allow for simplified manufacturing.

[0149] Below the main fluid plate 107, a spacer element 202 is provided. Above the spacer element 202, i.e., between the spacer element 202 and the main fluid plate 107, a membrane 203 is provided, and the membrane 203 is configured to be connected to the center surface of the main fluid plate 107.

[0150] The main fluid plate 107 preferably includes corresponding through portions that form spaces in which corresponding extension members are located to extend from or into the injection channel 603 from the corresponding actuator 301.

[0151] The membrane 203 is also connected to the lower surface of the extension member 401 and the main fluid plate surface that defines the upper surface of the injection channel 203.

[0152] The membrane 203 is configured to separate the through portion of the fluid plate from the channel formed by the spacer element, thereby preventing liquid material present in the jet channel 603 from entering the through portion.

[0153] Figure 3b A cross-sectional view of a printhead with reference element 403, cut along the actuator direction according to an embodiment of the invention, is shown. Specifically, the figure shows the inflow connector 103, the outflow connector 104, the inflow channel 601, and the outflow channel 602. As described above, the printhead also includes a top reference element 505, a middle reference element 506, and a lower reference element 507.

[0154] The inflow channel 601 passes through the heating plate 207 ( Figure 3b (Not shown) is in fluid communication with the injection channel 603, preferably through one or more holes in the heating plate.

[0155] The outflow channel 602 is in fluid communication with the injection channel 603 through the heating plate 207, preferably through one or more through holes or openings in the heating plate.

[0156] In one embodiment of the invention, the channel structure (also referred to as a conduit) and / or other elements of the fluid structure are preferably manufactured in a thermoplastic polyimide material or similar material by injection molding or laser ablation to form the plate elements of the printhead. Alternatively, the structure can be etched into a metal substrate to form the plate elements of the printhead.

[0157] In other words, according to the general concept of the invention, two separate first channels are provided in the fluid plate 107 along the length of the printhead. A membrane and a heating plate are optionally provided below the main fluid plate. Below the main fluid plate and the heating plate, a spacer element having multiple second channels (also referred to as material jet channels) is provided.

[0158] The second channel is preferably formed through a through-hole and / or recess in the spacer element 202. The second channel is substantially perpendicular to the first channel. The second channel is positioned corresponding to the extension members of the actuator unit of the printhead, which pass through the through portion of the main fluid plate.

[0159] A nozzle plate is provided below the spacer element, and the nozzle plate includes multiple nozzle openings 201 with positions corresponding to the second channel.

[0160] One of the first channels is for material inflow. That is, it is connected to the inflow connector and / or configured for material delivery in the inflow direction.

[0161] Another first channel is for material outflow. That is, it is connected to an outflow connector and / or configured for material transport in the outflow direction. A second channel is suitable for connecting the two first channels. The first and second channels are in fluid communication, preferably through an optional heating plate. Fluid communication is preferably achieved through corresponding holes in the heating plate.

[0162] In other words, a pressurized area is formed due to the arrangement of the first and second channels. In addition, a spray area is formed below the lower surface of the extension member and above the nozzle opening 201.

[0163] Due to the plate-like structure, channels can be formed as cutouts and / or recesses, or combinations thereof, in the corresponding plate-like elements. During assembly, each plate-like element can be referenced individually. Therefore, the assembly of the material delivery structure is more efficient and precise.

[0164] In one embodiment of the invention, the preferred dimensions of the first channel (i.e., the inflow channel) are a width between 0.4 mm and 10 mm and a height between 0.4 mm and 4.2 mm, more preferably a width between 0.8 mm and 7 mm and a height between 0.5 mm and 3.8 mm, and the length of the first channel is at least longer than the length of the tandem channel injection manifold.

[0165] In an alternative embodiment, the cross-sectional dimensions of the first channel are varied, meaning the channel is convex and orthogonal to the overall flow direction and length of the first channel.

[0166] The ratio of the major axis to the corresponding minor axis of the cross-sectional area is between 1 and 5, and the area is 0.16 mm². 2 up to 42 mm 2 More preferably, between 0.4 mm 2 up to 26.6 mm 2 Between. The length of the first channel is at least longer than the length of the 96-channel injection manifold, i.e., at least 130 mm plus an additional 20 mm of space for accommodating one or more bypass structures surrounding the channel injection manifold.

[0167] In one embodiment of the invention, the preferred dimensions of the first channel (i.e. the outflow channel) are a width between 0.4 mm and 10 mm and a height between 0.4 mm and 4.2 mm, more preferably a width between 0.8 mm and 7 mm and a height between 0.5 mm and 3.8 mm, and the length of the first channel is at least longer than the length of the series channel injection manifold.

[0168] In other words, for a manifold with 96 nozzles, the length must be at least 130 mm plus an additional 20 mm of space to accommodate one or more bypass structures surrounding the channel jet manifold.

[0169] In a preferred embodiment of the invention, the size of the second channel is determined by its cross-sectional area, which is orthogonal to the overall flow direction and length of the second channel.

[0170] The ratio of the major axis to the corresponding minor axis of the cross-sectional area is between 1 and 10, and the cross-sectional area is less than 0.01 mm. 2 up to 0.45mm 2 More preferably, between 0.08 mm 2 up to 0.3 mm 2 Between. The length of the first channel is at least longer than the length of the series channel injection manifold.

[0171] In one embodiment of the invention, the preferred dimensions of the second channel (i.e., manifold channel or injection channel) are a width between 0.7 mm and 1.2 mm and a height between 0.1 mm and 0.35 mm, more preferably a width between 0.8 mm and 1.3 mm and a height between 0.14 mm and 0.25 mm, and the length of the second channel is at least 3.4 mm.

[0172] In an alternative embodiment of the invention, the second channel includes a substantially parallel and narrower third channel, which is recessed and / or cut off at the center portion of the second channel. The third channel is narrower than the second channel, with a width between 0.1 mm and 1 mm and a height between 0.01 mm and 0.09 mm, more preferably between 0.2 mm and 0.8 mm and between 0.02 mm and 0.07 mm. The channel width may vary within these values ​​along the length of the third channel.

[0173] As described above, in one embodiment of the present invention, the corresponding fluid channel is formed such that the volume of the inflow channel gradually decreases as the distance from the material inflow connector increases, and correspondingly, the volume of the outflow channel gradually increases as the distance from the material inflow connector increases.

[0174] In other words, the cross-section of the corresponding channel changes gradually. This allows for the uniform pressurization of the liquid material present in the manifold between the inflow and outflow channels.

[0175] In a preferred embodiment of the invention, the inflow channel has a height of 1.9 mm and a width of 6 mm along its length.

[0176] In an alternative embodiment of the invention, the size of the first channel is determined by its cross-sectional area, which is convex and orthogonal to the overall flow direction and length of the first channel. The ratio of the major axis to the corresponding minor axis along the length of the inflow channel is between 1 and 5, and the area is approximately 10 mm². 2 Up to 16 mm 2 between.

[0177] In an alternative embodiment of the invention, the inflow channel has a height of 1.9 mm and a width of 6 mm at the inflow connector of the printhead, the dimensions of which decrease to a height of 0.19 mm and a width of 1 mm at the opposite end.

[0178] Alternatively, in an alternative embodiment of the invention, the size of the first channel is determined by its cross-sectional area, which is convex and orthogonal to the overall flow direction and length of the first channel. The ratio of the major axis to the corresponding minor axis of the cross-sectional area at the inflow end of the printhead is between 1 and 5, and the area is approximately 10 mm². 2 Up to 16 mm 2 Between, and decreases to 0.1 mm at the opposite end. 2 up to 0.2 mm 2 The area between.

[0179] Correspondingly, the dimensions of the outflow channel, which are 0.18 mm in height and 0.8 mm in width at the inflow end of the printhead, increase to 3.7 mm in height and 3.7 mm in width at the opposite end.

[0180] Alternatively, the dimensions of the second channel are determined by its cross-sectional area, which is convex and orthogonal to the overall flow direction and length of the second channel. The ratio of the major axis to the corresponding minor axis of this cross-sectional area at the inflow end of the printhead is between 1 and 5, and the area is approximately 0.1 mm². 2 up to 0.2 mm 2 Between, and increase to 10 mm at the opposite end. 2 Up to 16 mm 2 The area between.

[0181] The above example applies to rectangular cross-sections. However, other cross-sectional shapes are possible in other embodiments of the invention.

[0182] That is, in a preferred embodiment of the invention, the cross-sectional dimension of the inflow channel decreases to about 1% from the first end to the second end. The cross-sectional dimension of the outflow end increases accordingly.

[0183] Alternatively, in a preferred embodiment of the invention, the cross-sectional dimension of the inflow channel decreases to approximately 1 / x from the first end to the second end, where x is the number of channels present in the channel manifold along its length. The cross-sectional dimension of the outflow end increases accordingly.

[0184] In a preferred embodiment of the invention, the reduction in cross-sectional area is non-uniform relative to the main and secondary axes along the overall flow direction axis. That is, the height is reduced to about 4.8%, and the width is reduced to about 21%.

[0185] The decrease / increase is preferably carried out in a substantially linear manner.

[0186] In one embodiment of the invention, the heating plate 207 may be disposed below the fluid plate 107 and above the spacer element 202. Alternatively, the membrane element 203 may also include a heating portion embedded therein.

[0187] The heating plate is connected to the top plate or top PCB via a heating plate connecting element 501. Thermal emission is regulated by pulse width modulation of the voltage. In an alternative embodiment of the invention, thermal emission is regulated by a variable voltage. The heating plate is configured to transfer heat to a liquid material primarily present in the conduits of the fluid plate 107 and the spacer element 202.

[0188] Actuator 301 includes one or more piezoelectric elements. The piezoelectric elements are connected to electrical connector 102 via flexible printed circuit board 501 (flexible PCB).

[0189] This configuration allows for improved scalability by placing actuators close to each other. This allows for the formation of prefabricated actuator blocks and, further, allows for the cascading of these blocks to obtain variable-sized actuator assemblies with variable printhead widths.

[0190] Furthermore, this configuration allows the actuator unit to be simply fixed to the fluid plate and / or (in an alternative embodiment of the invention) to the retaining element, essentially fixing the actuator at a specific point so that the unfixed actuator portion can have precise deformation.

[0191] This effectively leads to an improvement in the uniform displacement range of the extended member when the same electrical signal is applied.

[0192] Figure 4 The bottom side of the printhead according to an embodiment of the present invention is shown, wherein the fluid plate 107 is visible. That is, the bottom side of the fluid plate 107 is shown.

[0193] The fluid plate 107 includes a fluid inflow channel 601 and a fluid outflow channel 602. The inflow and outflow channels are respectively connected to one of the inflow connection point 604 and the outflow connection point 605. The inflow and outflow channels are preferably formed as recesses in the fluid plate 107.

[0194] The inflow and outflow channels are preferably configured to allow liquid material to flow through openings in the heating plate, spacer element, and / or nozzle plate, or through openings in another element fixed below the main fluid plate 107 (not shown). The geometry of the inflow and outflow channels can be optimized as described below.

[0195] In a preferred embodiment of the invention, a membrane 203 is disposed below approximately the center portion of the fluid plate 107, and a spacer element 202 is disposed below the membrane to define a portion of the printhead fluid delivery structure including the pressurized area. A nozzle plate having corresponding nozzle openings is disposed below the spacer element.

[0196] In a preferred embodiment, the thickness of the membrane is between 7 μm and 100 μm, preferably between 10 μm and 50 μm, and is made of one or more of the following materials: polyimide, PTFE, PFA, FEP or ETFE polymer materials.

[0197] In a preferred embodiment of the invention, the inflow and outflow channels are connected by a jet channel and one or more bypass portions 612 and 611, which allow material to flow directly from the inflow channel into the outflow channel. The cross-sectional area of ​​the bypass portion is preferably equal to or smaller than the cross-sectional area of ​​the inflow and outflow channels.

[0198] In addition, the fluid plate 107 includes extension members through openings 206, which are configured to receive at least one end portion 606 of the extension member or an extension member of a corresponding actuator unit disposed above the fluid plate 107.

[0199] Figure 5a The bottom side of a printhead according to an embodiment of the present invention is shown, wherein a spacer element 202 is present, and the lower surface in contact with the film and the through portion in contact with the film are shown in dashed lines.

[0200] In one embodiment of the invention, a membrane is bonded to the region surrounding the through portion where the extension member is located on the main fluid plate 107 and to the lower surface of the extension member. The membrane is elastic, and therefore undergoes partial displacement in the region covering the through portion during actuator actuation of the extension member.

[0201] In one embodiment of the invention, the lower surface of the membrane is bonded to a lower intermediate plate 613, which is directly attached to the lower surface of the extension member and may have a different diameter or shape than the lower surface of the extension member. Displacement of the lower intermediate plate 613 by the extension member causes membrane deformation.

[0202] Alternatively, a lower intermediate plate 613 can be used because the manufacturing method of the film or formed film is more efficient and can be precisely bonded to the actuator unit, see [link to relevant documentation]. Figure 11a .

[0203] In one embodiment of the invention, a spacer element 202 is disposed below the fluid plate 107. The spacer element 202 also includes a recess and / or a through-hole defining a material injection channel having a non-rectangular cross-sectional area.

[0204] In an alternative embodiment of the invention, the spacer element 202 includes a through-hole defining a material injection channel 603 below the membrane 203, wherein the defined material injection channel has a rectangular cross-sectional area.

[0205] As detailed above, the material injection channel 603 of each injection unit is in fluid communication with each inflow and outflow channel, preferably through holes in the heating plate 207. The shape of the membrane can be optimized as described below.

[0206] Figure 5b The lower side of the printhead according to an embodiment of the present invention is shown, wherein the spacer element 202 is present, the recessed channel structure of the fluid plate 107 is shown in dashed lines, and the recessed channel structure and through holes are present in the spacer element 202.

[0207] As detailed above, a spacer element 202, a membrane 203, and a fluid plate 107 above the membrane 203 are provided. In the fluid plate 107, an inflow channel 601 and an outflow channel 602 are formed along the length direction of the printhead (i.e., the series direction of the actuator assembly).

[0208] The applicant has recognized that the flow velocity in the injection channel 603 is related to the back pressure at the nozzle opening. Therefore, a trade-off needs to be made between the ideal flow velocity and pressure variations.

[0209] To address the aforementioned issues, one or more bypass sections are incorporated between the inflow and outflow channels. These bypass sections allow for independent control of flow rate and back pressure. In other words, uniform back pressure can be achieved for all nozzle openings, while simultaneously increasing the flow rate.

[0210] In a preferred embodiment, the height of the bypass portion is between 0.18 mm and 2 mm, the width is between 0.8 mm and 6 mm, and the length is between 6 mm and 20.3 mm.

[0211] A first bypass section 611 is shown, which bypasses the injection channel manifold and connects the inflow and outflow channels. A second bypass section (not shown) is preferably arranged symmetrically about the first bypass section.

[0212] In the spacer element 202 disposed below the membrane 203, a plurality of injection channels 603 corresponding to each injection unit are provided. The injection channels 603 are disposed in a direction perpendicular to the channel of the fluid plate 107.

[0213] In other words, each injection channel 603 connects the inflow channel 601 and the outflow channel 602 at the location of the corresponding injection unit. That is, the injection channel 603 is located at a position corresponding to the lower part of the extension member 606 passing through the fluid plate, or at the opening 207 of the extension member of the fluid plate 107, in contact with the membrane 203.

[0214] As detailed above, at the corresponding intersection of the inflow and outflow channels with the injection channel 603, the channels are connected to the liquid. Preferably, a heating plate through hole is provided for liquid communication between the corresponding channel and the injection channel 603.

[0215] Figure 6 A diagonal isometric view of a cross-section of a printhead section cut along the length of the actuator according to an embodiment of the present invention is shown.

[0216] In other words, it shows the segmented cross-section of the printhead, which is essentially a three-dimensional interpretation of Figure 3, and illustrates the three-dimensional structure formed by stacking different plates of the printhead.

[0217] As detailed above, Figure 6 The segments shown can be chained together any number of times to scale the size of the printhead, i.e., the number of jetting units.

[0218] In a preferred embodiment of the invention, the plate element has one or more of the following thicknesses: - The general thickness of the plate-shaped portion of the main fluid plate 107 is between 1 mm and 6 mm, preferably between 1.5 mm and 5 mm, and most preferably between 2.5 mm and 4 mm.

[0219] - Membrane 203: between 0.005 mm and 0.07 mm, preferably between 0.008 mm and 0.05 mm, and most preferably between 0.01 mm and 0.025 mm.

[0220] - Spacer element 202: between 0.1 mm and 0.25 mm, preferably between 0.12 mm and 0.22 mm, and most preferably between 0.15 mm and 0.21 mm.

[0221] - Nozzle plate 109: between 0.01 mm and 0.3 mm, preferably between 0.025 mm and 0.1 mm, and most preferably between 0.04 mm and 0.08 mm.

[0222] The width of the fluid channel is between 2 mm and 8.2 mm, more preferably between 0.8 mm and 7.1 mm, and most preferably between 3.8 mm and 6.5 mm.

[0223] Figure 6 It further illustrates how the injection channel 603 is formed beneath the membrane 203, and how the nozzle opening 201 and the extension member are aligned.

[0224] Figure 7 A cross-sectional view of an actuator unit according to an embodiment of the present invention is shown, along with electrical signals in the actuator design according to an embodiment of the present invention. Each actuator unit includes a reinforcing element 304, a top piezoelectric element 302, and a bottom piezoelectric element 303, which are sandwiched together to form a piezoelectric stack, also referred to as a three-mode actuator 301.

[0225] In a preferred embodiment of the invention, the top and bottom piezoelectric elements are bonded to the reinforcing element using one or more different adhesives (preferably epoxy resin adhesives). Alternatively, the piezoelectric elements can be bonded to the reinforcing element by direct thermal welding or ultrasonic welding.

[0226] Each piezoelectric element is electrically connected to a high-voltage line 514 and a ground line 516 for transmitting electrical signals into and out of the piezoelectric element.

[0227] Figure 7a The layered structure of an actuator according to an embodiment of the present invention is shown. In detail, Figure 7a The various surfaces in the actuator structure are shown.

[0228] In a preferred embodiment of the invention, the top surface J of each top piezoelectric element is connected to a high-voltage drive signal via a conductive structure on or within the intermediate PCB board 503, and preferably further connected to an electrical connector 102 via a conductive structure on or within the top PCB board 502, which in turn allows connection of a drive signal source to provide a high voltage to the top surface of the top piezoelectric element.

[0229] The conductive structure or electrode is preferably a thin metal film, preferably having one or more of the following components: copper-nickel alloy, copper, gold, silver, nickel, rhodium, or copper-zinc alloy. The thin film is applied and / or patterned by one of sputtering, physical vapor deposition, atomic layer deposition, spin coating, etching, or inkjet printing.

[0230] In a preferred embodiment of the invention, the lower surface (K) of each bottom piezoelectric element is connected to a high-voltage drive signal via a conductive structure on or within the lower PCB board 504, and preferably further connected to an electrical connector 102 via conductive structures on or within the lower reference element 507, the intermediate reference element 506, the top reference element 505, the intermediate PCB board 503, and the top PCB board 502. The electrical connector 102 then allows connection of a drive signal source to provide a high voltage to the lower surface of the bottom piezoelectric element.

[0231] In one embodiment of the invention, the top surface J of the top piezoelectric element is connected to a common high-voltage drive signal. The bottom surface C of the top piezoelectric element is connected to ground.

[0232] In one embodiment of the invention, the bottom surface K of the lower piezoelectric element is connected to a common high-voltage drive signal. The top surface A of the bottom piezoelectric element is connected to ground.

[0233] The length of the piezoelectric element, i.e., its longest dimension, is preferably between 5 mm and 13 mm, more preferably between 6 mm and 12 mm, and most preferably between 9 mm and 11 mm. The width is preferably between 0.5 mm and 2 mm, more preferably between 0.8 mm and 1.2 mm, and most preferably 1 mm.

[0234] In a preferred embodiment of the invention, the thickness is preferably between 0.05 mm and 0.5 mm, more preferably between 0.1 mm and 0.3 mm, and most preferably between 0.13 mm and 0.25 mm.

[0235] The preferred length and width dimensions of the reinforcing element are substantially the same, but the length on one side is at least 0.1 mm shorter than that of the piezoelectric element.

[0236] In a preferred embodiment of the invention, the thickness of the reinforcing element is preferably between 0.1 mm and 0.7 mm, more preferably between 0.2 mm and 0.6 mm, and most preferably between 0.3 mm and 0.5 mm.

[0237] The piezoelectric elements have directional residual polarization along the stacking direction, and are typically polarized in such a way that when a positive voltage is applied through a high-voltage line, the difference in lateral deformation between the top and bottom piezoelectric elements causes the actuator to deflect downward.

[0238] Two common modes are used in piezoelectric actuation. In the d33 mode, the applied stress and the applied voltage are in the same direction, while in the d31 mode, the stress is applied axially, but the voltage is applied vertically.

[0239] In a preferred embodiment of the invention, the deflection of the actuator is caused by differential lateral d31 deformation of the piezoelectric elements present in the actuator, so as to produce a deflection substantially orthogonal to the length direction of the actuator by differential compliant deformation of the reinforcing elements caused by the lateral deformation of the separately coupled piezoelectric elements. When a negative voltage is applied through the high-voltage line, a reverse actuator deflection is caused.

[0240] In a preferred embodiment of the invention, the voltages provided by the first high-voltage line and the second high-voltage line have the same value.

[0241] In an alternative embodiment of the invention, the piezoelectric elements have oriented residual polarization along the stacking direction, and are typically polarized in such a way that when a negative voltage is applied through a high-voltage line, the difference in lateral deformation generated by the top and bottom piezoelectric elements causes the actuator to deflect downward.

[0242] In an alternative embodiment of the invention, different voltages are applied to the first high-voltage line and the second high-voltage line to create a controlled difference in the deflection of the piezoelectric element.

[0243] In an alternative embodiment of the invention, the residual polarization directions of the piezoelectric elements are opposite or different, and voltages can be applied independently to produce controlled actuator deflection.

[0244] In a preferred embodiment of the invention, the instantaneous polarization of the piezoelectric element (i.e., polarization generated by the applied voltage) is generated by electrical connections at the upper and lower surfaces of the top and bottom piezoelectric elements. The upper side of the top piezoelectric element... Figure 7a The surface in the middle is called the J surface.

[0245] The surface is preferably coated with a thin conductive metal film, in other words, an electrode. The film is applied completely or selectively by one of sputtering, physical vapor deposition, atomic layer deposition, spin coating, etching, or inkjet printing. The surface preferably has one or more of the following components: copper-nickel alloy, copper, gold, silver, nickel, rhodium, or copper-zinc alloy.

[0246] Preferably, the same film is applied to the upper and / or lower surfaces of the top and / or bottom piezoelectric elements.

[0247] The drive signal can be provided by a suitable signal source, which is not detailed in this manual.

[0248] In a preferred embodiment of the invention, the lower surface (M) of the top piezoelectric element is connected to a conductive structure present in the intermediate reference element 506, which is further electrically connected to an electrical connector 102 providing a ground connection via conductive structures on or within the top reference element 505, the intermediate PCB board 503, and the top PCB board 502.

[0249] In a preferred embodiment of the invention, the top surface (L) of the lower piezoelectric element is connected to a conductive structure present in the intermediate reference element 506, which is further electrically connected to an electrical connector 102 providing a ground connection via conductive structures on or within the top reference element 505, the intermediate PCB board 503, and the top PCB board 502.

[0250] In a preferred embodiment of the invention, each ground connection corresponds to a separate piezoelectric element, and each separate ground connection can be switched from a ground connection to a state that forms an electrically disconnected conductive element.

[0251] In a preferred embodiment of the invention, the connecting element may consist of pads, conductive lines, contact pads, or through-holes, allowing connection to conductive elements via soldering and / or conductive bonding.

[0252] In an alternative embodiment of the invention, the top reference element 505, the middle reference element 506, and the lower reference element 507 may be replaced by a single element having a conductive structure and size configured to allow the same function as the single reference element.

[0253] As detailed above, the piezoelectric stack includes a reinforcing element 304, a top piezoelectric element 302, and a bottom piezoelectric element 303. An extension member 401, also known as a free end portion, may be provided at one end of the piezoelectric stack.

[0254] At the other end, electrical connections are provided via pads, contact pads, conductive lines, or through-holes through a central reference plate 506 to allow soldering or bonding through conductive elements.

[0255] A top clamping element 305 and a bottom clamping element 306 are provided at a central location. These elements restrict the movement of the actuator at the central location such that only the end extending beyond the last contact point with either clamping element towards the direction of the extending member defines a free end portion of the piezoelectric stack and / or a free end portion of the actuator. The top clamping element 305 is further preferably fixed to the top PCB element 502, and the bottom clamping element 306 is further preferably fixed to the main fluid plate 107.

[0256] The actuator stack is spatially referenced and positioned using a top reference element 505, a middle reference element 506, and a bottom reference element 507, thereby forming surfaces (G and K) on the underside of the bottom piezoelectric element and the bottom reference element to enable precise bonding and positioning of the piezoelectric stack to the bottom PCB board 504. The bottom PCB board is further bonded to the main fluid board 107 to enable precise positioning of the actuator.

[0257] Additional surfaces (F and J) are formed on top of the top piezoelectric element and the top reference element to enable precise bonding of the piezoelectric stack and electrical connection of the piezoelectric stack to the top PCB board 505.

[0258] In a preferred embodiment of the invention, the top reference element and the bottom reference element have substantially the same thickness as the corresponding top and bottom piezoelectric elements, and the intermediate reference element has the same thickness as the reinforcing element.

[0259] The reinforcing element preferably extends onto the intermediate reference element, which is a separate element and has a constant width corresponding to the width of the piezoelectric element, and preferably has a combined length at least 1 mm longer than the length of the longest piezoelectric element.

[0260] In a preferred embodiment of the invention, the top and bottom piezoelectric elements are of similar length.

[0261] In an alternative embodiment of the invention, the length of the lower piezoelectric element is between 100% and 134% of the length of the upper piezoelectric element, wherein the length of the corresponding reference element is changed such that the total combined length of the reference element and the corresponding piezoelectric element corresponds to a length approximately equal to the combined length of the reinforcing element and the intermediate reference element.

[0262] The reinforcing element can be made of non-conductive materials, such as glass fiber, carbon fiber, metal oxide, composite material, or ceramic material.

[0263] In an alternative embodiment of the invention, the connection of the piezoelectric element can be switched from a high-voltage connection to a ground connection and vice versa, and conductive reinforcing elements can be used, which can be composed of conductive carbon fiber material, metal material or any non-conductive material, and have a conductive coating or film applied to the surface in contact with the piezoelectric element and the intermediate reference element.

[0264] The lower surface of the top piezoelectric element and the top surface of the lower piezoelectric element are connected to a common ground wire 516, which can be switched to ground or disconnected from ground, and through... Figure 7a The surfaces L and M formed in the middle are connected to the corresponding piezoelectric elements.

[0265] In an alternative embodiment of the invention, the conductive structure on or within the intermediate PCB board 503 is in complete contact with the surface (J) and is bonded to the top piezoelectric element 302 by a conductive adhesive or solder joint.

[0266] Surface A is the corresponding interface between the bottom piezoelectric element 303 and the reinforcing element 304. This interface is also preferably bonded non-conductively by an epoxy resin adhesive or another non-conductive binder.

[0267] In an alternative embodiment of the invention, the electrical signal connection directions of the top and bottom surfaces of the piezoelectric element are opposite, and a conductive adhesive is used to bond the conductive reinforcing element to the piezoelectric element.

[0268] Surface B is the interface between the intermediate reference element 506 and the reinforcing element 304. That is, B non-conductively bonds the reinforcing element to the intermediate reference element. There are no conductive structures on this surface of the intermediate reference element.

[0269] Surfaces D, E, F, G, H, and I are bonded by a non-conductive epoxy resin adhesive or another non-conductive binder, so that portions of one or more surfaces are free of adhesive, so as to electrically connect or bond to different conductive structures on or within elements that are in contact with the aforementioned surfaces.

[0270] Surfaces J and M are bonded by a non-conductive epoxy resin adhesive or another non-conductive binder, leaving certain areas of these surfaces adhesive-free so that they can be electrically connected or bonded to different conductive structures on or within elements that are in contact with the aforementioned surfaces.

[0271] In an alternative embodiment of the invention, surfaces J and K are bonded by a conductive epoxy resin adhesive or another conductive binder or by welding. Surfaces L and M are bonded by a conductive epoxy resin adhesive or another conductive binder or by welding.

[0272] In an alternative embodiment of the invention, surfaces J and M are bonded by a non-conductive epoxy resin adhesive or another non-conductive binder, such that portions of these surfaces are adhesive-free, so as to electrically connect or bond to different conductive structures on or within the elements that are in contact with the aforementioned surfaces.

[0273] In a preferred embodiment of the invention, one or more of the top, middle and bottom reference elements are composed of non-conductive glass fiber, polyimide, pps (polyphenylene sulfide) or pe (polyethylene).

[0274] In a preferred embodiment of the invention, the extension member is positioned between 0 and 500 μm from the longitudinal end portion of the lower piezoelectric element, located on the central axis along the width of the piezoelectric element, and is bonded to the element via an epoxy resin adhesive film.

[0275] In this disclosure, the thickness of all epoxy resin adhesives or binder films is preferably between 0.5 and 60 μm. Furthermore, the term binder may refer to cyanoacrylate, acrylic, epoxy, polyurethane, or polyimide-based adhesives.

[0276] Figure 7bA graph illustrating the drive signals applied to the actuator over time according to an embodiment of the present invention is shown. That is, different voltages, deflections, and switching states are shown on the vertical axis, and time is shown on the horizontal axis. The individual values ​​and scales are exemplary and do not represent any scale.

[0277] In the following text, the common input voltage is defined as V, and corresponds to the variable high voltage value provided by the first high voltage line to the top surface of the top piezoelectric element in one embodiment of the invention.

[0278] Vt represents an input signal corresponding to a variable high voltage value provided by a first high voltage line to the top surface of the top piezoelectric element in one embodiment of the invention.

[0279] Vb represents the input signal corresponding to the variable high voltage value provided by the second high voltage line to the bottom surface of the bottom piezoelectric element in one embodiment of the invention.

[0280] In a preferred embodiment of the invention, the input voltage is provided by a high-voltage signal generating unit, and the common value of Vt and Vb can be discretely switched between n states, where V0 corresponds to no voltage applied, and v n Indicates the maximum positive voltage that can be applied, V -n This indicates the maximum negative voltage that can be applied. Note that at V... -n and v n There can be any number of intermediate voltages n. Figure 7b Simplified for clarity.

[0281] In an alternative embodiment of the invention, the values ​​of Vt and Vb are individually addressable.

[0282] In an alternative embodiment of the invention, the values ​​of Vt and Vb are individually addressable for each piezoelectric element.

[0283] The minimum variation between the most recent discrete addressable values ​​of V is preferably between 0.5 and 10 volts, more preferably between 1 and 7 volts, and most preferably between 1.5 and 5.5 volts.

[0284] The preferred maximum voltage is between ±20 and ±150 volts, more preferably between ±45 and ±105 volts. The number of discrete voltage steps can vary freely according to the most recent discrete addressable value of V.

[0285] TPD corresponds to the lateral d31 mode deflection of the top piezoelectric element.

[0286] BPD corresponds to the lateral d31 mode deflection of the bottom piezoelectric element.

[0287] SG1 corresponds to the grounding wire of the switch in the connected state, allowing current to flow to the grounding electrode of the corresponding piezoelectric element, thereby allowing an electromagnetic field to be generated between the electrode elements of the piezoelectric element, which essentially causes a deflection caused by the corresponding positive or negative value of the generated high voltage signal.

[0288] SG0 corresponds to the grounding wire of the switch in the open state, which does not allow current to flow to the grounding electrode of the corresponding piezoelectric element, thereby preventing the generation of an electromagnetic field between the electrode elements of the piezoelectric element and essentially preventing deflection caused by any positive or negative value of the generated high voltage signal.

[0289] In this document, the deflection of the actuator refers to the deflection of a reference point at the free end of the actuator. That is, the free end of the actuator deflects, and the extension member according to the invention is disposed on this free end.

[0290] AD corresponds to the deflection of a basically orthogonal actuator, and roughly corresponds to the deflection of the reinforcing element. It should be noted that... Figure 7b The deflection is shown in simplified form based on the instantaneous actuator dynamics; the actual deflection may vary and may have a shape that is more sinusoidal.

[0291] PDT defines a positive deflection threshold, which is the distance of downward deflection over a period of time, relative to the highest deflection position of the actuator required to eject liquid by generating pressure in the pressurized region. PDT depends on the rheological properties of the material to be ejected and requires a certain positive deflection over a period of time for successful material ejection.

[0292] NDT defines a negative deflection threshold, which is the amount of upward deflection over a period of time, relative to the lowest position of the actuator required to ensure that the spray area is filled or refilled with liquid material. NDT depends on the rheological properties of the material to be sprayed and requires a certain negative deflection over a period of time for successful material filling or refilling.

[0293] Depending on the time scale, the deflection of the actuator can roughly correspond to Figure 7b The displacement diagram presented in the image. Figure 7b It only describes the displacement modes that can be achieved by different electrical signal configurations that can be provided to one or more piezoelectric elements at a given time, but it is not exhaustive.

[0294] At higher frequencies, as the actuator approaches the resonant frequency of the actuator system, the deflection of the actuator over time may have a more sinusoidal shape.

[0295] Compared to low voltage and single piezoelectric actuation, using higher voltage or multiple piezoelectric elements generally results in faster acceleration and greater displacement.

[0296] This allows for a wider range of controllable displacement acceleration, velocity, and deceleration over a longer time period. Therefore, the ejection threshold for a given material depends on the total displacement and the acceleration and deceleration at which the displacement occurs.

[0297] The preferred maximum deflection of the free end of the actuator relative to its rest position (i.e., when no voltage is applied through any high-voltage line) is between ±0.4 μm and ±25 μm, more preferably between ±0.9 μm and ±17.5 μm.

[0298] The preferred values ​​for PDT and NDT are between 0.8 μm and 40 μm, and more preferably between 1 μm and 30 μm.

[0299] The rise and fall times are represented by t on the horizontal axis, which is the amount of time required for deflection to be completed under the applied voltage and the corresponding deformation of any piezoelectric ceramic element.

[0300] The preferred rise time t is between 0.5 μs and 120 μs, and more preferably between 0.8 μs and 85 μs.

[0301] Position Status AD n and AD -n The difference between them, i.e., ΔAD n AD -n Dividing by time Tn, the average deflection velocity v is defined. n Average deflection velocity v n This can typically be controlled by the difference (delta) between the deflections of the corresponding piezoelectric ceramic elements during displacement voltage switching, where v is higher when the difference between the deformations is higher. n The value is usually high.

[0302] When the voltage is positive or negative for both elements, the voltage applied to one piezoelectric element is always opposite to the polarization direction of the other piezoelectric element, thus causing the maximum deflection of the piezoelectric ceramic element when the maximum positive or negative voltage is applied.

[0303] Preferred v n The value is between 0.025 μm / μs and 100 μm / μs, more preferably between 0.1 μm / μs and 37.5 μm / μs, and most preferably between 0.21 μm / μs and 8 μm / μs.

[0304] The rise time t associated with actuation (during which the maximum voltage is applied to the two piezoelectric ceramic elements) causes the maximum difference between the displacements applied to the two piezoelectric ceramic elements when the input signal switches, further leading to the realization of v. n The maximum value.

[0305] Furthermore, the deflection acceleration, velocity, and deceleration—in other words, the time-dependent shaping of the actuator deflection—can be controlled by the shaped electronic input signal (i.e., waveform), so that the voltage experienced by one or more piezoelectric elements can be gradually increased or decreased, or can be increased or decreased sharply, and thus affect the deflection speed accordingly.

[0306] like Figure 7b As shown, applying a differential voltage to the top and bottom piezoelectric elements allows for more precise control of actuator deflection, which in turn controls the pressure application.

[0307] Allowing the voltage to vary freely (rather than being discrete) allows for more precise shaping of the actuator deflection.

[0308] In an alternative embodiment of the invention, pulse width modulation is used on one or more input signals to the top and bottom piezoelectric elements to more accurately shape the actuator deflection.

[0309] Figure 8 An isometric top-angle view shows an actuator block 701 according to an embodiment of the present invention. The actuator block 701 includes a plurality of actuator units, preferably 32 to 96 units. A conductive structure 511 on or within a top PCB element 503 is also shown.

[0310] In one embodiment of the invention, 32 units are preferred because the production and quality characteristics are easy to control when a small number of piezoelectric elements are present in a block; in addition, high-voltage drive electronics (e.g., high-voltage shift registers) can address 8 or 32 channels, so corresponding drive electronics can be equipped outside the printhead to facilitate the construction of a variable-length printhead.

[0311] The core concept of this invention is that actuator blocks can be prefabricated, and any number of actuator blocks can be connected in series to form an actuator assembly with a scalable number of actuator units.

[0312] In an alternative embodiment of the invention, the printhead consists of a single actuator block.

[0313] Figure 9 An actuator assembly according to an embodiment of the present invention is shown in an isometric top-angle view. The actuator assembly 702 includes a plurality of actuator stacks 701, preferably three stacks.

[0314] Pumping Actuation Figure 10a A schematic side view of a printhead having an extension member in a neutral position according to a first embodiment of the present invention is shown; Figure 10b A schematic side view of a printhead having an extension member in a deflected position is shown according to a first embodiment of the present invention.

[0315] In other words, the extension member 401 is also in a neutral position and has no compression injection channel. Figure 10a and Figure 10b The spray area 607 in the spray channel 603 and the nozzle opening 201 below the end of the extension member 401 are also shown. A membrane 203 is provided between the end of the extension member 401 and the spray area 607.

[0316] Figure 10b A schematic side view of a printhead with a piezoelectric element in a deflected position, according to an embodiment of the invention, is shown. That is, the extension member 401 moves downward, compressing the jet channel 603 and pressurizing the liquid material present in the pressurized region 608.

[0317] In other words, the downward displacement of the actuator unit is shown, which causes the membrane element 203 to elastically deform and apply positive pressure to the injection region 607, thereby creating a virtual chamber 609 (not shown) within the pressurized region 608 surrounding the injection channel 603.

[0318] The pressurization is crucial for the jetting of high-viscosity materials and enables the jetting of liquid materials with rheological properties that are not suitable for traditional inkjet systems.

[0319] The material is injected by directional pressurizing the liquid material present in the aforementioned pressurized region 608 within the injection channel. Pressurization requires the creation of a pressure differential between the ambient pressure on the opposite side of the virtual chamber 609 and the nozzle plate.

[0320] The applicant has recognized that, in the system according to the invention, the pressure differential must be maintained for about 0.5 microseconds or longer to allow droplet formation and sufficient material flow so that the material ejection exceeds an Oh value of 2.3 (Oh is the Oh number).

[0321] In previous systems, it was impossible to eject materials with Oh values ​​far exceeding 2.3 without using an ejector valve and with relatively low ambient back pressure differential. In existing technologies of conventional inkjet systems, the highest Oh value that materials can be ejected is achieved using a multi-pulse ejection method.

[0322] The multi-pulse jetting method requires much more complex waveforms and is limited by the rheological properties of the jetted liquid material, especially since the material has a strong viscoelastic response at high frequencies.

[0323] For materials exceeding this Oh value, the key to achieving the desired spraying effect is through prolonged pressurization, which is caused by the displacement of an actuator, wherein most of the actuator's displacement typically occurs at a speed lower than the speed of sound of the sprayed liquid medium.

[0324] This type of actuation can be called non-acoustic or pumping actuation, and using the system according to the invention, a value of approximately 8 or 9 Oh can be achieved.

[0325] Formed film Figure 11a A schematic side view of a printhead according to a second embodiment of the present invention is shown; Figure 11b A printhead according to a second embodiment of the present invention is shown in an isometric apex view.

[0326] Figure 11a An embodiment of the invention is illustrated, depicting a formed film element 204. The element is preferably attached to an extension member 401 or, more preferably, to a lower intermediate plate 613 at the lower end of the extension member. Preferably, the formed film is attached by an adhesive.

[0327] In one related embodiment, the extension member may have a reduced or partially reduced diameter at its lower end to accommodate a shaped membrane within the through portion. Preferably, the shaped membrane is attached by an adhesive. The reduced diameter results in a lower surface of the extension member with a reduced diameter that is in direct contact with the shaped portion of the membrane, which forms a new lower surface of the actuator that interacts with the fluid beneath it.

[0328] Therefore, the displacement of the extension member 401 results in an equal displacement of the central forming portion of the forming membrane, thereby more effectively transferring displacement energy and pressure to the central pressurizing region 608, which closely surrounds the virtual chamber, without losing energy due to the portion of the displacement membrane surrounding the lower membrane surface, thus preventing pressurization of liquid materials not present near the virtual chamber.

[0329] Figure 11b It shows Figure 11a Different perspectives of the formed membrane. The membrane is formed to make it substantially cylindrical at the end portion surrounding the extension member and a lower intermediate plate set in a circular shape.

[0330] In a preferred embodiment of the invention, the film is formed by thermal deformation of the material sheet or by ablation of the material sheet.

[0331] The diameter of the reduced-diameter extension member or lower intermediate plate that is in direct contact with the forming film is preferably between 300 and 700 μm, more preferably 400 μm, on the lower part of the reduced-diameter extension member, compared to the original diameter which is preferably between 700 and 1000 μm, more preferably 800 μm.

[0332] In an alternative embodiment of the invention, the diameter reduction may occur only in a portion of the extension member to facilitate a simpler adhesion method to the upper end of the extension member. The amount of diameter reduction is the same as the amount of total diameter reduction mentioned above.

[0333] That is, in the preferred embodiment of the present invention, the diameter of all or part of the extension member 401 is reduced by 50% to 75% compared with the diameter of the upper end portion of the extension member 401 in other embodiments, more preferably by about 63%.

[0334] Nozzle plate displacement Figure 12a A schematic side view of a printhead having an extension member in a deflected position is shown according to a first embodiment of the present invention; Figure 12b A schematic side view of a printhead having an extension member in a deflected position is shown according to a first embodiment of the present invention.

[0335] In other words, Figure 12a and Figure 12b A closer side view of the printhead is shown, in which a section along the piezoelectric actuator direction shows the actuator unit displaced downwards, and further displacement of the nozzle plate.

[0336] In addition, Figure 12a The displaced nozzle plate 610 is shown in the figure. This displacement occurs as a secondary effect of pressurization in the region below the lower surface of the extension member. The displacement of the nozzle plate is much smaller than the displacement of the actuator and is exaggerated for visibility in the figure. The applicant has recognized that the deformation of the nozzle plate affects the material present on the underside of the nozzle plate (i.e., the jetting side). The displacement of the nozzle plate helps to release droplets that are still in contact with the nozzle plate. This displacement is closely related to the fluid communication between the underside of the extension member and the nozzle plate, as well as the distance between them.

[0337] The nozzle plate elastically follows the downward and upward displacements, with the downward displacement based on the pressure buildup above the plate relative to the ambient pressure below the plate, and the upward displacement based on the pressure generally reduced relative to the previous internal pressurized state or the general ambient pressure.

[0338] This displacement is directly related to the pressurization and the distance from the nozzle plate to the lower surface of the actuator in its neutral position. This secondary displacement affects droplet ejection by inducing surface disturbances in the droplet filaments, which generally helps to release the droplet from the ejection orifice.

[0339] In one embodiment of the invention, the maximum nozzle plate displacement is between approximately 0.1 and 4 μm, relative to an actuator displacement between approximately 2 and 60 μm.

[0340] exist Figure 12b The image shows an elongated filament 614 of the jetting material. For some materials, this filament may make droplet jetting impossible. Filaments are generally associated with higher viscosity or higher viscoelastic response of the liquid material under dynamic jetting conditions.

[0341] When these filaments form, they can break in different states. These filamentary breakage states are commonly referred to as atomization state, first and second wind-induced states, Rayleigh state, or dripping state.

[0342] Since the material lacks acceleration when ejected from the nozzle, the droplet state is not applicable, and the most relevant state is usually the Rayleigh state for producing a single droplet for precise droplet deposition.

[0343] The Rayleigh breakage is achieved by surface perturbation of the fluid filament surface, resulting in droplet separation or breakage from the fluid filament. This leads to Rayleigh-Platau instability and causes the perturbation to increase with the length of the fluid filament. At a certain point, the fluid filament becomes very thin, thus causing it to break into one or more droplets.

[0344] If there is insufficient kinetic energy in the jet material, preventing the fluid filament from reaching the length where it might break, or if the rheological properties of the material make breaking difficult, then such fluid filament breakage may become impossible. This is more likely to occur in highly viscous or viscoelastic materials or in materials jetted under conditions characterized by high Weber numbers.

[0345] like Figure 12b As shown, the secondary effect of nozzle plate displacement during injection causes surface disturbance of the fluid filaments during injection, leading to stable droplet release through auxiliary droplet pinch-off. This further facilitates pinch-off at predetermined time intervals associated with the initial material injection, thereby enabling the injection of individual droplets of high-viscosity material with high regularity.

[0346] The time interval is typically determined by the pressure of the material in the pressurized area between the lower surface of the actuator and the nozzle plate, which in turn is related to the distance between the lower side of the actuator element and the upper side of the nozzle plate.

[0347] It has been found that a certain distance from the surface 606 of the lower extension member or the surface of the alternative underground membrane to the upper side of the nozzle plate can achieve stable spraying for most materials below a certain viscosity limit, specifically when the distance between the elements is 80 to 90 μm and 180 to 200 μm.

[0348] The energy transfer resulting from the displacement of the main actuator is the primary effect, which is more critical when spraying high-viscosity materials, but the secondary effect is more critical when releasing materials with other rheological properties that would normally prevent material spraying.

[0349] Currently, for materials with rheological properties that are more conducive to pinch-off, the upper limit of energy injection is about 380 mPa×s at the injection point, while for materials with less favorable properties it is about 350 mPa×s.

[0350] Liquid material properties that are generally not conducive to pinch-off are: high material viscosity, high viscoelastic response under low-frequency material pressure, low surface tension under certain conditions at high viscosity, and low material density under certain conditions at high viscosity.

[0351] Furthermore, when materials are primarily actuated acoustically, lower nozzle diameters and lower injection speeds are generally unfavorable for spraying high-viscosity materials.

[0352] In this invention, the main pressurization of the actuator typically occurs at a speed lower than the speed of sound in the liquid material present in the pressurized region, and therefore is not acoustic actuation but pumping actuation.

[0353] A portion of the actuator's displacement may occur at a speed higher than the material's sound velocity in the early stages of actuation, or it may not occur at that speed, and thus can be considered an acoustic interaction.

[0354] The extended pressurization caused by the large displacement of the actuator over a longer period of time allows material to be transported primarily through the nozzle opening by pressurization, rather than as a result of the interaction of sound waves with the outer surface of the meniscus or with suspended droplets present on the nozzle duct or under the nozzle plate.

[0355] The pressurization directly controls the size and velocity of the droplets, and further controls the filament breakage and droplet release through secondary effects, and is generally affected by the actuator displacement velocity and actuator displacement range.

[0356] According to the present invention, the speed and range can be achieved by using a variable voltage and a switchable grounding wire to shape the acceleration and distance of the actuator's displacement.

[0357] Alternative actuator geometry Figure 13a A printhead according to a third embodiment of the present invention is shown in an isometric apex view; Figure 13b A schematic side view of a printhead according to a third embodiment of the present invention is shown.

[0358] Specifically, the printhead has two rows of actuator assemblies, as discussed in the embodiments above. The actuator assemblies are mirror images of each other and arranged in parallel. This results in two rows of parallel extensions that interact with two corresponding jet manifolds. In this embodiment, each jet manifold has an inflow and an outflow channel.

[0359] Figure 14 A printhead according to a fourth embodiment of the present invention is shown in cross-sectional view.

[0360] exist Figure 14 In the embodiments (and its) Figure 13a and Figure 13b (Related to the embodiments), the central channel is a shared channel, which can be an inflow channel or an outflow channel depending on the desired flow direction of the material.

[0361] Figure 15 A printhead according to a sixth embodiment of the present invention is shown in cross-sectional view.

[0362] exist Figure 15 In one embodiment, the row of actuator assemblies shares a single injection manifold, which effectively connects each pair of corresponding extension members through corresponding injection channels.

[0363] Figure 16a A printhead according to a seventh embodiment of the present invention is shown in an isometric apex view; Figure 16b A cross-sectional view of a printhead according to a seventh embodiment of the present invention is shown.

[0364] exist Figure 16a and 16b In one embodiment, a shaped three-morph bending actuator is provided. The shaped three-morph bending actuator includes horizontally tapered top and bottom piezoelectric element stacks, and reinforcing elements as described above.

[0365] The element typically tapers from the end connected to the reference element toward the end where the extension member is located, allowing two opposing actuator assemblies to interlock in a zipper-like arrangement to form a single row of extension members. According to this embodiment, double the density of injection members can be obtained along a single injection manifold. Each extension member preferably has a corresponding injection channel associated with it. The associated injection channel preferably has a reduced width.

[0366] The embodiments and variations of the present invention have been described and illustrated above. The terminology, descriptions, and drawings used herein are for illustrative purposes only and are not intended to be limiting. Those skilled in the art will recognize that many modifications can be made within the spirit and scope of the invention, which is intended to be defined by the following claims and their equivalents, wherein, unless otherwise stated, all terms are intended to take the broadest reasonable meaning.

[0367] List of reference numerals Printhead assembly 102 Electrical Connectors 103 Material flowing into the connector 104 Material Outflow Connector 106 Housing Components 107 Main Fluid Plate 109 Nozzle Plate 110 Membrane fastening element 111 First Vacuum Connector 112 Second Vacuum Connector Jet side 201 Nozzle opening 202 Spacer element 203 Membrane element 204 Formed Film Element 205 Extension member through opening 206 Membrane Penetration Opening 207 heating plate Actuator assembly 301 Actuator 302 Top Piezoelectric Element 303 Bottom piezoelectric element 304 reinforcing element 305 Top clamping element 306 Bottom clamping element 401 Extension Member 403 Extension Component Reference Element Actuator accessories 501 Heating Plate Connecting Components 502 Top PCB Board 503 Intermediate PCB Board 504 bottom / front PCB board 505 Top Reference Component 506 Intermediate Reference Element 507 Lower Reference Element 508 First High Voltage Line 509 Second High Voltage Line 510 Grounding wire 511 Conductive Structure fluid elements 601 Fluid Inflow Channel 602 Fluid Outflow Channel 603 Material Injection Channel 604 Inflow Connection Point 605 Outflow Connection Point 606 Lower surface of extension member 607 Spray Area 608 Pressurized Area 609 Virtual Chamber 610 Displaced Nozzle Plate 611 First Bypass Structure 612 Second Bypass Structure 613 Lower Middle Plate 614 Elongated droplet filaments Stack of actuator units 701 Actuator Block 702 Actuator Assembly

Claims

1. A method for operating an actuator unit for a printhead, in, The actuator unit includes: A first piezoelectric element is connected to a first potential and a third potential; A second piezoelectric element is connected to both a second potential and a third potential; and The actuator unit is configured to deflect when the first potential and the second potential have the same polarity relative to the third potential; The method includes: A first variable high voltage Vt is applied between the first potential and the third potential; A second variable high voltage Vb is applied between the second and third potentials; and Apply a switchable ground connection to the third potential.

2. The method according to claim 1, wherein, The first variable high voltage Vt and the second variable high voltage Vb are the same variable high voltage, and are preferably positive or negative voltages.

3. The method according to claim 1 or 2, in, The first variable high voltage Vt and the second variable high voltage Vb can be discretely switched between n states.

4. The method according to claim 3, in, n is between 2 and 200, preferably between 3 and 150.

5. The method according to any one of claims 1 to 4, in, The switchable grounding connection has two states: a) First state, in which the ground connection is in the connected state to allow current to flow from the corresponding first potential and second potential, thereby generating an electric field on the corresponding piezoelectric elements, thus causing them to deform, preferably in mode d31. b) Second state, in which the grounding connection is in the open state so as not to allow current to flow from the corresponding first potential and second potential, thereby preventing the generation of an electric field on the corresponding piezoelectric element and thus not causing deformation.

6. The method according to claim 5, in, Maximum upward deflection AD n This corresponds to the ground connection being in the connected state and Vb and Vt being at their maximum positive voltage; Among them, the maximum downward deflection AD -n This corresponds to the ground connection being in the connected state and Vb and Vt being at their maximum negative voltage.

7. The method according to claim 6, in, Average deflection speed v n By AD n and AD -n The position difference between them is divided by the rise time t required to reach the corresponding maximum deflection state from the moment the corresponding voltage is applied; and Wherein, preferably v n It is between 0.025 μm / μs and 100 μm / μs, more preferably between 0.2 μm / μs and 37.5 μm / μs.

8. The method according to any one of claims 1 to 7, wherein, Maximum second voltage Vb n The first voltage Vtn is between 20 and 250 volts, preferably between 40 and 200 volts.

9. The method according to any one of claims 1 to 8, in, ET is defined as the ejection threshold for downward deflection, at which material is ejected from the printhead; and Preferably, ET is between 0.3 μm and 40 μm, and more preferably between 1 μm and 30 μm.

10. The method according to any one of claims 1 to 9, in, PT is defined as the refill threshold when the printhead is deflected upwards, at which the ejection area is filled with the material to be ejected. and Preferably, PT is between 0.3 μm and 40 μm, and more preferably between 1 μm and 30 μm.

11. The method according to any one of claims 9 or 10, wherein, By selecting the first voltage and the second voltage, as well as the ground connection state, the actuator unit is maintained at a deflection state above ET for a duration between 0.2 and 75 microseconds.

12. The method according to any one of claims 10 to 11, wherein, By selecting the first voltage and the second voltage, as well as the ground connection state, the actuator unit is maintained in a deflection state above PT for a duration between 0.2 and 70 microseconds.

13. The method according to any one of claims 1 to 12, wherein, By selecting the first voltage and the second voltage, as well as the ground connection state, the actuator unit deflects at an average deflection speed between 0.025 μm / μs and 100 μm / μs.

14. The method according to any one of claims 1 to 13, wherein, By selecting the first voltage and the second voltage, as well as the ground connection state, the displacement of the actuator is made lower than the speed of sound of the liquid material ejected from the printhead.

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