Patent Application
20060227182
The present invention relates generally to printheads, and more specifically to printhead filter systems and methods of manufacturing the same.
An ink jet printer typically includes a printhead and a carrier. The ink jet printhead can comprise a printhead body, nozzles, and corresponding ink ejection actuators, such as heaters on a printhead chip. The actuators cause ink to be ejected from the nozzles onto a print medium at selected ink dot locations within an image area. The carrier moves the printhead relative to the medium, while the ink dots are jetted onto selected pixel locations, such as by heating the ink at the nozzles.
In some such systems, the ink reservoir comprises a removable or separable tank, such that the tank can be separated from the printhead, and replaced or refilled, when the ink is low. The printhead components can then be re-used. In such ink tank systems, a separable fluid connection between the tank and the printhead body is needed, in contrast to systems where the printhead body is integral with the ink reservoir. The connection permits ink to flow to the nozzles from the tank, but is separable such that the ink tank can be removed when empty.
The printhead assembly can also include a filter within an ink passageway leading from the ink reservoir to the nozzles, for isolating any contaminants or debris from the ejectors and nozzles. The filter is typically swaged onto a tower or passage leading to the nozzles. However, when the tank is installed in this manner, the filter edges can rub against the tank entrance, thereby abrading the raw filter edges and creating the possibility that the filter becomes damaged, and allowing loose particles to reach the nozzles and create clogging issues.
In some manufacturing techniques, the sides of the filter are swaged onto the tower, and the filter edges are encapsulated in plastic. However, such a process can require tight tolerances for precise placement of the filter that are difficult to achieve and require significant manufacturing time. Swaging also can place cut edges of the filter inside a pocket during the swage operation, and in a position for any particles that shed from the filter edge to be pushed under the filter. Particles from the edges can then travel to the chip and clog the nozzles on the chip.
In addition, some designs do not protect the filter when the tank is removed, such that ink on the filter can dry out, or the filter can otherwise be damaged, prior to the installation of the replacement tank. The dried ink can permanently clog the filter and ruin the printhead.
Accordingly, improved ink tank connections, printhead filter systems and methods of manufacturing the same are desired.
According to one embodiment, an ink delivery system for an ink jet printer is provided comprising a printhead body, a filter, a retainer, a wick, and ink ejectors. The ejectors are associated with the printhead body. A tower portion of the printhead body defines an ink entrance passage that receives ink from an ink tank, and the ink ejectors are in fluid communication with the entrance passage. The retainer includes a printhead end and a tank end. The retainer is engaged with the tower portion of the printhead body at the printhead end, and is configured to engage an exit structure on an ink tank at the tank end. The filter is disposed between the ink tank and the entrance passage. Moreover, the wick is disposed adjacent the filter.
According to another embodiment, an ink delivery system for an ink jet printer is provided comprising an ink tank, a printhead body, a retainer, a filter, and a filter cover. The ink tank is configured to hold ink and includes an exit port configured to provide ink to a printhead. The printhead includes a printhead body having a tower portion defining an ink entrance passage that receives ink from the ink tank. The printhead body and ink tank are separable from one another. The printhead also includes ink ejectors, the ink ejectors receiving ink from the entrance passage. The retainer has a printhead end portion and a tank end portion, the retainer being engaged with the tower portion of the printhead body at the printhead end portion and with the exit port of the ink tank at the tank end portion. The retainer includes an inner passage extending from the tank end portion to the printhead end portion. A filter is attached to at least one of the tower portion and the retainer, and a filter cover member is disposed between the tank end portion and the filter. The filter cover member can comprise a wick or a septum for example.
According to another embodiment, a method of manufacturing a printhead assembly is provided. The method comprises placing a filter over a printhead opening to a printhead body such that an edge of the filter extends past an edge of the printhead opening, the printhead opening being in fluid communication with at least one printhead nozzle. The method further comprises placing a retainer having an inner passage on the printhead opening such that the inner passage is in fluid communication with the printhead opening, fusing the filter to at least one of the printhead opening and the retainer, and placing a cover in the retainer and adjacent the filter, such that the cover extends at least partially within the inner passage of the retaining member. The fusing operation can be conducted, for example, without swaging, and by using heat, such as by heat staking or insert molding. The cover can comprise a wick or a septum for example.
According to another embodiment, a method of manufacturing a printhead assembly is provided. The method comprises attaching a filter to at least one of the retaining member and the tower portion. The method further comprises placing the retainer on the printhead body, the body defining an ink flow passage to a printhead chip. Moreover, the method comprises engaging the retainer with a removable ink tank, the ink tank being separable from the printhead body, and the retainer providing a substantially sealed fluid passage between the ink tank and the printhead body.
While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed the same will be better understood from the following description taken in conjunction with the accompanying drawings in which:
a is a perspective view of yet another example embodiment of an ink delivery system having a filter and cover assembly, which is made and operates in accordance with principles of the present invention;
b is a cross-sectional view of the retainer shown in
a is a perspective view of another example embodiment of an ink delivery system having a filter and cover assembly, which is made and operates in accordance with principles of the present invention; and
b is a cross-sectional view of the retainer and tank shown in
With reference now to the figures,
Attached to the printhead body 12 is a print head chip 16 including a plurality of nozzles 11 for delivery of the ink to the print medium. In other embodiments, the nozzles are provided on a structure separate from the chip 16. The ink flows from the exit ports 17/19 of the ink tanks 13/15 through channels in the lower portion of the body 12. The ink then flows within the body 12 to a manifold in the print head chip 16, from which it is drawn to nozzles 11 for ejection onto the print medium, such as by using heater elements or piezoelectric elements formed in the chip 16. The system 10 is moved relative to the print medium, such that the nozzles 11 drop ink at one or more desired locations on the medium.
In this example, the lower portion of the printhead body 12 includes towers 20 for each ink tank. The towers 20 can comprise any appropriate extension, structure, port, or interface for receiving ink for printing. The towers 20 of this example comprise raised tubular extensions, or standpipes, having one or more openings 21 through which the ink may flow. But other tower configurations are also possible as will be readily apparent to one of ordinary skill in the art.
Retainers 30 are also provided in this example, each engaging one of the tower portions 20. Each retainer 30 can comprise a conduit or guide component for providing a passage between the printhead body 12 and the ink tank 13/15. In this example, each retainer 30 includes an inner passage 37 for providing ink therethrough, the passage being defined by a smaller diameter upper pipe portion 31 on the tank end and a larger diameter lower pipe portion 33 on the printhead end. Near the middle of each retainer 30 is a ledge portion 35, which can comprise a lip, extension, or other surface.
The upper pipe portion 31 of each retainer 30 engages a corresponding exit port 17/19 of the tanks 13/15 allow ink to flow from the tanks to the passage 37 of the retainer. A sealing member 34 is disposed adjacent each retainer 30 and assists in sealing between the retainer and its corresponding ink tank 13/15. In this example, the sealing member comprises a gasket 34 that resides on the ledge 35 and includes an aperture that engages the upper pipe portion 31, so as to create a seal to control evaporative losses from the system. The gasket 34 can comprise a suitable elastomer material, or other material with good sealing properties.
In this example, each lower pipe portion 33 of each retainer 30 engages the corresponding towers 20 of the printhead body 12, to allow the ink to be provided to the towers. In some embodiments the lower pipe portion 33 and/or the towers 20 can be tapered to allow for a tightening fit as the pipe portion slides onto the tower. Each retainer 30 can comprise polypropylene or polyethylene, or other suitable material that can provide a fluid resistant seal against the tower 20, printhead body 12, and/or ink tanks 13/15.
Within each retainer 30 of this embodiment is provided a filter 39 for filtering contaminants in the ink from reaching the printhead chip 16. The filter 39 can also provide capillary functions to allow ink to pass upon demand to the printhead chip 16 and to prevent air passage into the printhead chip. The filter 39 can be made of a metal weave, a polymer weave, or other mesh, screen, or weave materials. For instance, a stainless steel dutch twill or a stainless steel random weave material could be utilized. In this embodiment, the filter 39 is molded within the material of the retainer 30. For example, an insert injection molding process may be utilized to form the retainer and internal filter 39. In particular, the retainer 30 can be formed by an injection molding machine which injects molten plastic into a mold cavity having the shape of the retainer. Prior to the molding process, the filter 39 is loaded into the mold robotically or manually at the desired position, the mold is closed, and the molten plastic injected into the mold cavity. Upon cooling, the mold is opened and the retainer 30 with internal filter 39 is removed. In other embodiments, the filter 39 can be insert injection molded in the printhead tower 20, or otherwise disposed in the printhead body 12. Such a molding process can reduce manufacturing time with respect to the filter and reduce the likelihood that portions of the filter 39 will break free and cause damage or clogging of the printhead. For example, encapsulating the edges 41 of the filter 39 in the retainer 30, such as by insert molding for instance, can reduce the risk that particles of the filter will break free. This process does not require swaging, crimping, rolling, or bending the filter edges 41 about the tower 20, and can be carried out without the need for a welding or staking tool.
A cover for the filter can also be provided, to protect the filter, to keep the filter moist, and to protect it from air and/or otherwise impede access to the filter from the tank side of the retainer 30, when the ink tank has been removed. In the example of
To assemble the system of this embodiment of
Other embodiments and configurations are also possible without departing from the principles of the inventions. For example,
To fuse the filter 39 to the tower 20, a heat staking process can be utilized. This process uses heat and pressure to reform the filter 39 into the tower 20 and thereby attach it thereto, without the need to swage, crimp, bend, or roll the edges of the filter about the tower. In other embodiments, the filter 39 is fused to the retainer 30 by heat staking. Other fusing methods may also be utilized, such as ultrasonic welding and heat sealing or attachment methods that do not require the filter edges to be swaged, bent, crimped or rolled. In an example heat staking process, a thermal tool or probe can transfer heat to the filter 39 and/or tower 20, to reset the memory of the plastic material that makes up the filter 39 and/or the tower 20. The temperature is high enough to soften the plastic. Force is provided by the tool to stake the filter 39 to the tower 20, by deflecting the material without damaging the plastic. Post cooling steps can also be utilized to cool the plastic. For example, cooling can be applied to the tip of the thermal tool at the end of the staking process.
As shown in the example of
a is a perspective view of yet another example embodiment of an ink delivery system 10 with a filter assembly, which is made and operates in accordance with a principle of the present invention. In this example embodiment, the retainer and gasket configuration is slightly different than the previous example embodiment. In particular, the upper portion 31 and lower portion 33 of the retainer 30 adjoin to form a ledge 35, upon which the gasket 34 rests. The gasket 34 in this example comprises an elastomer material bonded to the upper portion 31 of the retainer 30, and provided for sealing between the upper portion and a tower 49 extending from the ink tank 13. In addition, an additional gasket material is provided in this example, such as gasket 45 bonded within an exterior notch of the retainer 30 and gasket 47 bonded within the inner diameter of the lower portion 33. Gaskets 34, 45, and 47 can be overmolded or co-injected onto the retainer 30. Interior gasket 47 can provide a seal against the tower 20 when the retainer engages the printhead body 12, and exterior gasket 45 can provide an additional seal against the printhead body.
In this example, a filter 39 is encapsulated within the retainer 30, as best shown in
To assemble the system, the retainer 30 and its encapsulated filter 39 is placed on the tower 20. The wick 38 is disposed in the top entrance of the retainer 30 and against the filter. And the replaceable ink tank 13 is disposed about the upper portion 31 of the retainer, such that the wick 38 extends in through the exit port 17 on the tank. In operation, ink from the tank 13 flows through the exit port 17 and wicks through the wicking material 38 to the filter 39, where contaminants are filtered out. The ink then proceeds to the passage 21 of the printhead tower 20, through the printhead body 12, and to the printhead chip 16 for ejection to the medium.
a and
The tank 13 of this example includes a tower 49 in which resides a needle 53 having small ink flow passages formed therein. When the tank 13 engages the retainer 30, the tower 49 surrounds the outside of the retainer 30, and the interface between the needle 53 and the septum 50 provides a seal between the tank 13 and the retainer 30. In particular, the tower 49 of the tank 13 surrounds the upper pipe portion 31 of the retainer 30 and the needle 53 is inserted through the entry 51 in the septum 50. The size of the needle 53 and the septum entry 51 provide an interference fit, and the septum is made of a flexible material, such as an elastomer, such that a sealing engagement is achieved between the needle 52 and septum 50. The needle 53 enters the entry 51 in the septum 50 and thereby is able to provide ink to the filter 39 through the openings in the needle. In this embodiment, the diameter of the holes in the needle 53 are chosen to be small enough such that backpressure on the ink in the tank 13 is maintained when the tank 13 is disengaged from the printhead body 12, and to resist air infusion into the tank 13. Accordingly, a covering is not needed to protect the needle 53 when it is disengaged from the septum 50. When the ink tank 13 and retainer 30 are engaged, the ink is provided through the needle 53 to the filter 39, and the ink is then filtered by the filter 39 and provided to the tower 20 for supplying to the printhead chip 16. When the ink is expired from the tank 13, the tank can be removed by disengaging the tower 49 from the retainer 30 (causing the needle 53 to disengage the septum 50). The tank 13 can then be refilled or replaced by another tank having ink.
The foregoing description of various embodiments and principles of the inventions has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the inventions to the precise form disclosed. Many alternatives, modifications and variations will be apparent to those skilled in the art. For example, some principles of the invention may be used in different printhead configurations and types of printers. Moreover, although multiple inventive aspects have been presented, such aspects need not be utilized in combination, and various combinations of inventive aspects are possible in light of the various embodiments provided above. Accordingly, the above description is intended to embrace all possible alternatives, modifications, combinations, and variations that have been discussed or suggested herein, as well as all others that fall within the principles, spirit and broad scope of the inventions as defined by the claims.
