Ink jet device with filter element

Abstract: Ink jet device comprising an ink reservoir (10) and a filter element (24) made of a sheet-like material having a curved shape and sealingly disposed in a port (18) of the ink reservoir, characterized in that the filter element (24) is inserted in the port (18) in an elastically deformed state and is held in engagement with the walls (14) of this port by its elastic restoration forces.

Description: The invention relates to an ink jet device comprising an ink reservoir and a filter element made of a sheet-like material having a curved shape and sealingly disposed in a port of the ink reservoir. In an ink jet device, such as an ink jet printer, an ink reservoir is incorporated in the printhead or in a separate cartridge and serves to accommodate a certain amount of liquid ink which is to be supplied to a nozzle system of the printhead. In order to avoid that the nozzle system becomes clogged with particulate matter, a filter element is disposed either in an inlet port or an outlet port of the ink reservoir, so that the ink is filtered before it is supplied to the nozzle system. The port should be sealed by the filter element so that the ink may not leak around the filter element. US-A-5 537 136 discloses an ink jet device of the type indicated above wherein the filter element is a stainless steel wire mesh which has a spherically curved shape. US-A-5 502 479 and EP-A-0 603 902 disclose similar ink jet devices in which the filter element is bent into a cylindrical shape so that it forms a slitted tubular member. In these known devices the filter element is secured in the port of the ink reservoir by means of an adhesive, by welding or by injection molding techniques. For example, as is disclosed in US-A-5 537 136, the edge of the dome-shaped filter element is imbedded in an elastomeric material by injection molding, so that a self-sealing cap is formed which is placed over the port of the ink reservoir. It is an object of the present invention to provide an ink jet device of the type indicated above which can be manufactured more efficiently. This object is achieved with the features indicated in claim 1. According to the invention, the filter element is inserted in the port of the ink reservoir in an elastically deformed state and is held in engagement with the walls of this port by its elastic restoration forces. Thus, the filter element can simply be mounted by inserting it into the port in a slightly compressed state, and elastic restoration forces of the filter element will cause the same to expand again and to sealingly engage the walls of the port. As a result, neither the use of an adhesive, nor welding or molding techniques are required for securely mounting filter element. More specific optional features of the invention are indicated in the dependent claims. In a preferred embodiment the filter element, which may be woven or non-woven fabric of stainless steel fibres, has a tubular shape and is inserted into a channel defined between opposing walls of the port of the ink reservoir. Preferably, the walls of this channel are matched to the tubular shape of the filter element, so that the filter element will sealingly engage the walls of the channel in a larger surface area. In a particularly preferred embodiment, the port of the ink reservoir has a rectangular cross-section, and the channel extends in parallel with the longer sides of this rectangular cross-section. Both ends of the channel are prolonged by recesses or holes formed in the shorter side walls of the port, so that both ends of the tubular filter element can be accommodated in these recesses or holes. At least one end of the channel is formed as a through-hole in the side wall of the port, so that the filter element can be inserted into the channel through this through-hole which may then be closed with a plug or the like. A preferred embodiment of the invention will now be described in conjunction with the accompanying drawings, in which: Fig. 1 is a cross-sectional view of an ink reservoir and a filter element of an ink jet device; and Fig. 2 is a longitudinal section of the ink reservoir with the filter element fitted therein. An ink reservoir 10 in an ink cartidge or a printhead of an ink jet printer is formed by a casing having a bottom wall 12, two parallel longer side walls 14 and two parallel shorter side walls 16. In the top part of the ink reservoir, the side walls 14, 16 define an inlet port 18 which has an elongated rectangular cross-section when viewed from above. Liquid ink can be filled into the ink reservoir 10 through the inlet port 18. Outlet ports 20, through which the ink is supplied to a nozzle system (not shown) of the printhead, are formed as elongate slots in the side walls 14 close to the bottom wall 12. In a portion of the inlet port 18 the internal surfaces of the longer side walls 14 are formed with elongate recesses which have the cross-sectional shape of a segment of a circle and are mutually opposed to each other so that they define a cylindrical channel 22 which extends in parallel with the side walls 14. This channel 22 accommodates a filter element 24. The filter element 24 is formed by a rectangular sheet of stainless steel mesh or fabric which has been rolled or bent into a tubular shape, so that it has the configuration of a circular cylinder with a longitudinal slit 26. As is shown in Fig. 2, the channel accommodating the filter element 24 is slightly inclined and is extended into the shorter side walls 16 of the ink reservoir. The lower end of the channel 22 terminates in a blind hole or recess 28 in one of the side walls 16, whereas the other end of the channel is formed as a through-hole 30 penetrating the other side wall 16. The opposite ends of the tubular filter element 24 are accommodated in the recess 28 and the through-hole 30, respectively, so that the total cross-section of the port 18 is completely blocked by the filter element, and the mesh of the filter element is in surface-to-surface engagement with the internal surfaces of the recess 28, the through-hole 30 and the portions of the side walls 14 defining the channel 22. Thus, the ink liquid filled-in through the port 18 is forced to pass through the filter element 24 and is prevented from leaking around the filter element. The through-hole 30 is closed by a plug 32. In the shown embodiment a rod-like sensor element 34 is imbedded in the plug 32 and extends coaxially in the tubular filter element 24. This sensor element 34 may for example serve as a level detector for detecting the level of the ink liquid in the ink reservoir or the port 18 thereof or, in case of a hot-melt ink jet device, as a temperature sensor for monitoring the temperature of the hot-melt ink. The metal mesh forming the filter element 24 has a certain elasticity, and the tubular filter element, in its natural state, has a radius of curvature which is slightly larger than the one shown in Fig. 1. When the filter element is mounted in the ink reservoir 10, it is slightly compressed in lateral direction in Fig. 1, so that the slit 26 becomes narrower and the filter element can be inserted into the channel 22 through the through-hole 30. Then, due to its own elasticity, the filter element 24 tends to flex back into its natural state, until its outer surface firmly engages the internal surfaces of the channel 22. The filter element 24 is then held in the channel 22 in a slightly compressed state. In this way, the filter element can be firmly secured in the ink reservoir 10 without the aid of any adhesive and without employing any other bonding techniques. The assembly is completed by inserting the plug 32 with the sensor element 34. Under normal conditions the elasticity is large enough to ensure an ink-tight contact between the filter element and the ink reservoir. It is however possible to enhance this pressure by inserting a pressurizing element into the filter element 24 such as a spiral spring or long leaf spring.

Claims: Ink jet device comprising an ink reservoir (10) and a filter element (24) made of a sheet-like material having a curved shape and sealingly disposed in a port (18) of the ink reservoir, characterized in that the filter element (24) is inserted in the port (18) in an elastically deformed state and is held in engagement with the walls (14) of this port by its elastic restoration forces. Ink jet device according to claim 1, wherein the filter element (24) has a tubular shape. Ink jet device according to claim 2, wherein the tubular filter element (24) has a longitudinal slit (26). Ink jet device according to claim 2 or 3, wherein the port (18) has an elongated rectangular shape and the filter element (24) extends in parallel with the longer watts (14) of the port. Ink jet device according to claim 4, wherein the internal surfaces of the longer walls (14) of the port (18) are formed with mutually opposing recesses defining a channel (22) in which the filter element (24) is accommodated. Ink jet device according to claim 4 or 5, wherein recesses (28) and/or holes (30) are formed in the shorter side walls (16) of the port (18), and the opposite ends of the filter element (24) are accommodated in these recesses (28) or holes (30): Ink jet device according to claim 6, wherein one of the holes (30) is formed as a through-hole penetrating the side wall (16) of the port (18) and the outer end of this through-hole (30) is closed by a plug (32). Ink jet device according to claim 7, wherein a sensor element (34) is incorporated in the plug (32) and extends into the tubular filter element (24). Ink jet device according to any of the preceding claims, wherein the filter element (24) is made of metal mesh or a fabric of metal fibres. Ink jet device according to any of the preceding claims, adapted for use with hot-melt ink.

Inventors: HOLLANDS PETER JOSEPH, HOLLANDS, PETER JOSEPH
Applicants: OCE TECH BV, OCE-TECHNOLOGIES B.V.
Application year: 1999
Main classification: B41J2
IPC codes: B41J2