HK1147229B - A print head and a method of aligning laminates - Google Patents

Description

Printhead and method of aligning a stack

The present application is a divisional application of a chinese patent application with application number 200780015481.1 entitled "print head module" filed by fuji film dimustris gmbh on 26.4.2007 by the chinese patent office.

Technical Field

The present invention relates to a stack assembly and a method of aligning a stack.

Background

An ink jet printer is a droplet ejection device. Ink jet printers typically include a supply of ink to a nozzle path. The nozzle passage terminates at a nozzle opening through which ink droplets are ejected. Ink drop ejection is controlled by squeezing ink in the ink path with an actuator, which may be, for example, a piezoelectric deflector, a thermal bubble jet generator, or an electrostatically deflected element. A typical printhead has an array of ink paths corresponding to the nozzle openings and associated actuators so that drop ejection from each nozzle opening can be individually controlled. In a drop on demand printhead, each actuator is turned on as the printhead and a printing substrate are moved relative to each other to selectively eject a drop at a particular pixel location of an image. In high performance printheads, the nozzle openings typically have a diameter of 50 microns or less, for example about 35 microns, are separated at a pitch of 100 and 300 nozzles/inch, have a resolution of 100 to 3000dpi or more, and provide drop sizes of about 1 to 70 picoliters or less. The droplet ejection frequency is 10kHz or more.

Printing accuracy is affected by a number of factors, including the size and velocity uniformity of the droplets ejected by the print head and the nozzles between the multiple print heads in the printer. The drop size and drop velocity, in turn, are affected by factors such as the dimensional uniformity of the ink vias, acoustic interference effects, contaminants in the ink vias, and the braking uniformity of the actuators.

Disclosure of Invention

In general, in one aspect, a printhead includes a body; an actuator adhered to the body, an enclosed space between the actuator and the body forming a chamber; an opening defined by the body for releasing pressure in the chamber; and a sealing body adhered to the opening, sealing the chamber while ensuring pressure relief.

This aspect can include one or more of the following features. The actuator comprises a piezoelectric material and the seal is formed of a plastic, such as polyimide. The printhead includes a stack assembly. The actuator is adhered to the stack assembly, which includes a flexible printed circuit, a cavity plate, a descender plate, a sound suppressor, a spacer plate, and an orifice plate. An opening is formed in the acoustic wave suppressor, and a channel is formed in the falling plate. The printhead includes an ink manifold defined by the body. The seal body is adhered to the opening using a detachable adhesive.

In another aspect, a flexible circuit includes a body formed of a flexible material; an electrical trace formed on the body; and an opening defined by the body for the flow of liquid therethrough.

This aspect can include one or more of the following features. The body is formed of polyimide or comprises two layers of flexible material (e.g. polyimide) bonded together (e.g. with an adhesive comprising polyimide). The body includes a base layer (e.g., a polyimide material), electrical traces formed on the base layer, and a cover layer (e.g., a printable polyimide) covering the traces.

In another aspect, a stack assembly includes a plurality of stacks including an actuator, a cavity plate, a descender plate, and an orifice plate, each stack having an opening, the openings in each stack being aligned with the openings of the other stacks, the openings being inspected to ensure alignment and placement of the stacks.

This aspect can include one or more of the following features. The stack assembly further comprises a fiducial mark on the actuator such that the fiducial mark is visible when the stacks are aligned. The plurality of stacks further includes an acoustic wave suppressor, a flexible circuit, and a spacer.

In one aspect, a method of aligning a stack includes providing a plurality of stacks having an opening, including an actuator, a cavity plate, a descender plate, and an orifice plate, one of the stacks including a fiducial mark; aligning the stack of layers using the opening in the stack of layers and the fiducial mark on one of the stack of layers; adhering the laminates together; and inspecting the opening to determine an alignment stack. Inspecting the opening includes viewing the opening in the laminate with a camera to verify that the fiducial mark is aligned with the opening.

Furthermore, other aspects, features, and advantages will become apparent from the following detailed description, the accompanying drawings, and the claims.

Drawings

FIG. 1A is a perspective view of a printhead;

FIG. 1B is an exploded view of a printhead;

FIG. 2A is a perspective view of a body and stack assembly of a printhead;

FIG. 2B is a cross-sectional view of the printhead;

FIG. 2C is a perspective view of the underside of the body

FIG. 3 is an exploded view of the stack assembly;

FIG. 4A is a perspective view of a flexible printed circuit;

fig. 4B is a cross-sectional view of the flexible printed circuit.

Detailed Description

Referring to fig. 1A and 1B, a printhead 10 includes a body 12 bonded to a stack assembly 14. The parts are bonded together with an adhesive such as an epoxy. Ink is first introduced into the printhead 10 through the filter 16 and the tube 18 and enters the body 12 through ink barbs (barb)20 formed in the body 12. An opening 22 is formed in the body 12 for releasing air pressure between the body 12 and the component 14; a seal 24 is placed over the opening 22. The lid 26 is adhered to the top of the body 12.

Fig. 2A and 2B show the body 12 and assembly 14 of the printhead 10. The first layer in the assembly 14 is a piezoelectric element 28 bonded to a flexible printed circuit 30. When the body 12 is bonded to the assembly 14, a chamber 32 is formed that protects the piezoelectric element 28 from the external environment and seals with the ink passages.

Referring to fig. 3, the assembly 14 includes the following components bonded together: piezoelectric element 28, flexible printed circuit 30, cavity plate 34, descender plate 36, acoustic wave suppressor 38, diaphragm 40, and orifice plate 42. The parts are bonded together with an adhesive such as an epoxy.

Referring to fig. 2A, from the ink barb 20, flows down the underside of the body 12 and into a manifold 44 formed in the body 12 as shown in fig. 2C. The ink fills the manifold 44 and then flows through the opening 46 in the flexible printed circuit 30 and into the pump chamber 48 formed in the cavity plate 34 as shown in fig. 3.

Referring to FIG. 3, when the piezoelectric element 28 is activated, ink in the pump chambers is drawn through openings 50 in the pump chambers, through openings 52 in the descender plate 36, through openings (not shown) in the acoustic dampener 38, through the diaphragm openings 54, and out of orifices 56 in the orifice plate 42.

Fig. 2B shows a cross-sectional view of the chamber 32 formed when the body 12 is bonded to the assembly 14 with the piezoelectric element 28 as the first layer in the assembly 14. The chamber 32 protects the piezoelectric element 28 from the external environment. An opening 22 is formed in the body 12 to release air pressure in the chamber 32, and the seal 24 is bonded to the opening 22 with an adhesive (e.g., epoxy). The seal 24 is formed of a compliant material that changes shape under pressure, such as polyimide.

When the air pressure within the chamber 32 increases, pressure is applied near the perimeter of the opening 22 where the seal 24 contacts the opening 22. The amount of pressure applied to the seal 24 is a function of the radius of the opening 22. At a certain pressure, the adhesive bonding the sealing body 24 to the opening 22 is separated from the surface of the opening 22, thereby releasing the air pressure, and then is re-adhered. The radius of the opening 22 and the strength of the adhesive are designed for a specific air pressure so that the adhesive separates and re-adheres at the specific air pressure.

Fig. 2A shows the opening 22 in the body 12 raised above the surface of the body 12. By raising the opening 22, the piezoelectric element 28 is protected from ink leakage, and the seal 24 further protects the piezoelectric element 28 from ink or other environmental factors.

Referring to fig. 3, the openings in the flexible printed circuit 30 provide ink flow paths from the manifold 44 to the pumping chambers. Fig. 4A shows a flexible printed circuit 30 having electrical traces 58 extending through the spaces between the openings to avoid contacting the liquid as it flows through the openings 46. Electrical traces 58 extend from electrodes near the middle of the flexible printed circuit 30 (near the piezoelectric element) to connectors 60 at the ends of the flexible printed circuit 30. A tab 62 extends on each side of the connector 60 that snaps into the cover 26 as shown in fig. 1A.

Fig. 4B shows the flexible printed circuit 30 having a first layer 64 and a second layer 66 bonded together with an adhesive. Over time, the ink may separate the adhesive from the two layers, leaking into the flexible printed circuit 30 and contacting the electrical traces 58. In one aspect, the two layers of the flexible printed circuit 30 are formed of polyimide, and the adhesive also includes polyimide. When the layers of the flexible printed circuit 30 and the adhesive are formed of the same material, it is impossible for the ink to separate the adhesive from the two layers. The openings may be cut in the flexible printed circuit 30 using a die, laser, or other similar method. A coating or other material may be used to protect the edges of the opening in the flexible printed circuit 30 from damage due to liquid flow through the opening.

Referring to figure 3, although the openings in the flexible printed circuit 30 provide ink flow paths to the pump chambers, only some of the openings are actually aligned with the pump chambers in the cavity plate 34. The remaining pump chambers are blocked by spaces between the openings. For ink to reach the blocked pumping chambers, the ink flows through the unblocked pumping chambers through the openings in the flexible printed circuit 30 and into the channels 68 in the descender plate 36. The ink in these channels 68 then flows back into the cavity plate 34 to enter the unobstructed pump chambers.

Referring to FIG. 3, if the acoustic wave suppressor 38 is made of a material such asA plastic material such as polyimide, the material is not uniformly bonded, which may leave regions of material unbonded. For better bonding, openings 70 may be cut out of the acoustic dampener 38.

The body 12 may be formed of a plastic material such as polyphenylene sulfide (PPS), or a metal such as aluminum. The cover 26 may be made of a material such asAcetal, or other such plastic material. The flexible printed circuit 30 and the acoustic wave suppressor 38 may be composed ofThe drop plate 36 and cavity plate 34 may be formed of, for example, polyimideA metal alloy. The separator 40 may be formed of a material having a low modulus, such as carbon (about 7MFa) or polyimide (about 3 MPa). The orifice plate 42 may be formed of stainless steel.

The spacer 40 is used to bond the orifice plate 42 and acoustic dampener 38 within the stack 14. Instead of directly applying the adhesive to the orifice plate 42 or the acoustic wave suppressor 38, the adhesive may be directly applied on both sides of the separator, and then the orifice plate 42 and the acoustic wave suppressor 38 are bonded to the separator. The spacers may also distribute stresses between the stacks due to different coefficients of thermal expansion. For example, laminates having different coefficients of thermal expansion that are bonded together at a bonding temperature of about 150 ℃ may bend when the laminate is cooled to room temperature (about 22 ℃). The spacer may reduce bending of the stack by distributing the bonding stress. The thickness of the spacer and its modulus can affect its ability to distribute stresses within the assembly. The percent stress of the separator is a function of the stress divided by the thickness of the separator.

Fig. 2C depicts the body 12 having three holes 72, two holes on one side of the body 12 and one hole on the other side for receiving three eccentric screws for fastening the printhead 10 to the rack assembly.

Referring to fig. 3, the missing parts and alignment of the parts are checked using openings 74 on the end of each part. An inspection camera views the opening 74 to visually inspect the alignment of the components. A reference mark is provided on the piezoelectric element 28 which can be seen when all components are correctly aligned. In addition, after manufacture or during maintenance of the printhead 10, visual inspection through the openings 74 can ensure that all components are present and that the components are in the correct order.

In other aspects, the body and laminate assembly may be connected by other fastening means such as adhesives, screws, and clasps. The parts of the assembly may be secured by other materials or adhesives. The seal body 24 may be bonded to the opening in the body by other adhesives. Referring to fig. 2A and 2B, the piezoelectric element may be protected by a coating layer, in addition to forming a cavity between the assembly and the body to protect the piezoelectric element. Although fig. 1A shows the tab 62 snapped into the cover 26 of the printhead 10, the tab may be secured to the printhead by screws, snap rings, adhesives, or other securing means. The flexible printed circuit 30 in fig. 3 shows several openings on both sides of the flexible printed circuit 30, however the flexible printed circuit 30 may have only one opening for ink access or only one opening on one side. Similarly, the cavity plate in fig. 3 shows several pump chambers on both sides of the cavity plate, but the cavity plate may have only one pump chamber or only one side.

The connector 60 in fig. 1A may be secured directly to the cover 26 without the use of the tabs 62. For example, the connector 60 may be adhered to the cover 26 using an adhesive.

Referring to fig. 4A, the electrical traces 58 on the flexible printed circuit 30 are sealed to prevent liquid flowing through the opening 46 from contacting the traces. For example, the first layer 64 in FIG. 4B may be a polyimide material (e.g., polyimide material)Polyimide), the electrical traces are formed on a first layer 64, and a second layer 66 is a cladding that covers the electrical traces. The coating may be, for example, available from Nippon Steel Chemical, JapanSPI screen printed polyimide overlay such printable polyimide. The polyimide is deposited using a screen printing process or other deposition process.

Referring to FIG. 1A, the dimensions of printhead l0 include a height of about 29.15mm, a length of about 115.9mm, and a width of about 30.6 mm. Referring to fig. 3, the stack assembly 14 may further include a ground plate 41 including bumps 43. When the laminations are stacked together, as shown in fig. 2A, the tab 43 extends from the assembly 14 and folds over the frame 12. The ground line 13 in fig. 1 is connected to the bump 43 of the ground plate 4 l.

Referring to fig. 3, the stack assembly 14 may further include a ground plate 41 including bumps 43. When the laminations are stacked together, as shown in fig. 2A, the tab 43 extends from the assembly 14 and folds over the frame 12. The ground line 13 in fig. 1 is connected to the bump 43 of the ground plate 41.

Referring again to fig. 3, liquid flowing through the stack 14 passes through the openings 54 in the ground plate 41 and out the apertures 56 in the aperture plate 42. The ground plate 41 may also have openings 74 that align with the openings 74 of the other stacks in the assembly 14.

Other versions are within the scope of the following claims.

Claims (4)

1. A printhead, comprising:

a stack assembly having a plurality of stacks including an actuator, a flexible circuit, a cavity plate including a plurality of pumping chambers, a drop plate, and an orifice plate, one of the stacks including a fiducial mark, the other stacks having an opening, the plurality of stacks being stacked together such that the opening in each stack is aligned with the opening of the other stack and the fiducial mark upon inspection of the openings,

wherein the reference mark is on the actuator.

2. The printhead of claim 1, wherein the plurality of stacks further comprise an acoustic dampener and a diaphragm, both having openings aligned with the openings on the fiducial mark and the other stacks.

3. A method of aligning a stack, comprising:

providing a plurality of stacks having openings, including an actuator, a flexible circuit, a cavity plate including a plurality of pumping chambers, a drop plate, and an orifice plate, one of the stacks including a fiducial mark, the other stack including an opening;

stacking the stacks such that each stack is aligned with an opening in the fiducial mark and the other stacks;

adhering the laminates together; and

inspecting the opening to determine an alignment stack,

wherein the reference mark is on the actuator.

4. The method of claim 3, wherein the step of inspecting comprises viewing an opening in the laminate using a camera to verify that the fiducial mark is aligned with the opening.