WO1996040524A1

WO1996040524A1 - Inkjet cartridge with ink expiry detection means

Info

Publication number: WO1996040524A1
Application number: PCT/US1996/008993
Authority: WO
Inventors: Michael A. Baezner; Anthony Campbell; Charles N. Schwarz, Iii; Miller Sheu; James D. Story
Original assignee: Jetfill, Inc.
Priority date: 1995-06-07
Filing date: 1996-06-06
Publication date: 1996-12-19

Abstract

An inkjet cartridge (10) is formed out of a conducting material wherein a single electrode (18a) is inserted into an ink reservoir formed by the cartridge (10), allowing the ink level to be measured by checking for a closed circuit between the electrode (18a) and any point on the cartridge (10).

Description

Inkjet cartridge with ink expiry detection means

(JF-CS02) Field of the Invention The present invention relates to a recording apparatus and, more specifically, to an iπkjet cartridge equipped with a means for determining when ink within the cartridge has been depleted.

Background of-the Invention

Iπkjet cartridges such as those used in iπkjet printers, facsimiles, postal meters and other recording devices are generally well known in the art. Such cartridges comprise an ink reservoir for supplying ink. The ink is supplied to a priπthead through a series σf microchaππels, where the ink is heated or charged, causing it to be expelled through the priπthead onto a recording sheet. To prevent the microchaππels from overheating or drawing air into the priπthead, which can cause a deterioration σf print quality or ruin the priπthead, it is desirable to know when the ink supply in an ink reservoir has been depleted. Nσf using an ink expiry means creates user frustration, as a printout may need to be restarted after blank pages were printed without wamiπg. Description of Related Art

There are several known iπkjet cartridge configurations with various ink level detecting systems, all of which have limitations.

One type of ink level detection system known in the art is the use σf a transparent reservoir. This allows a user to readily discern the level σf ink upon cartridge examination. However, Inkjet cartridges are usually hidden from view when used in recording devices. Therefore, in order to check the ink level in a transparent cartridge, a user most stop the printer, open its cartridge access lid and remove the cartridge. Depending upon the cartridge- printer coupling system, a cartridge containing ink may spill ink if it r_r removed from a printer. If the cartridge has a circuit panel, the circuit panel may be damaged by excessive removal and installation. In general, a transparent cartridge is not effective as an ink level detecting means because iπkjet printer cartridges are not visible when in use. Another type of cartridge ink level detection system uses a pair σf electrical sensors

The sensors allow ink level to be determined by detecting a change in electrical resistance between the sensors. Such a change is usually detected by an ink detection circuit, which is electrically connected to the sensors via a pair σf metal plates. Such an ink detection circuit and its associated connecting plates are included in at least two printers known in the art.

The plates are positioned so as to connect to a cartridge inserted into the printer. One known embodiment of an ink level detection system uses two wires which are inserted through the cartridge into an ink-containing sponge within the cartridge reservoir. Another embodiment of the system uses two electrodes, a first electrode inserted through the cartridge into the ink reservoir, and a second electrode inserted through the cartridge into the cartridge-printer coupling area. This system has several deficiencies. Inserting two electrical sensors into a cartridge is labor intensive, and each sensor throughhole creates a potential for ink leakage.

A further limitation of this system is the reliability of sensor contact: each sensor must properly align with a plate used to connect the sensors to an ink detection circuit. If proper contact is not made, ink level cannot be detected.

Summary of the Invention

To address the above discussed deficiencies of the prior art, an improved system of ink level detection has been developed. The present invention uses a single electrode in conjunction with a conductive container. In a preferred embodiment of the invention, this is accomplished by using a single electrode which is isolated from the container by an insulating sheath and inserted through the cartridge with one end exposed on the cartridge exterior and an opposite end exposed to the ink egress port located at the printercartridge interface. In this embodiment, the container is molded out of a plastic containing carbon fiber, a conductive material.

One object of this invention is to provide a means of detecting ink level by measuring the electrical resistance between the electrode and any point on the container surface. The placement of the electrode determines when the electrical resistance will cause an open circuit, so any given level of ink may be detected by controlling the placement of the electrode.

Another advantage of the invention is the fact that the container contact may be made at any point. This reduces the probability of improper ink detection circuit plate contact, as only one plate must be aligned with an electrode, while the second plate merely needs to touch the container at any point. As the plates often bend after repeated use, this improvement provides increased printer reliability.

Another object of the invention is to alleviate the risk of leakage by reducing the number of holes required in the container, while still providing an ink detection means. In order to insert a sensor through the cartridge, there must be a hole in the cartridge. While the hole may be plugged by a gasket, a potential for leakage still exists. The present invention reduces the risk of potential leakage by halving the number of holes required by the known art. A further object of the invention is to reduce assembly time and cost by reducing the number of parts required to complete a cartridge. Assembly time is reduced by making the cartridge a virtual electrode. The usual injection molding process of creating a cartridge also creates part of an ink detecting means, so it is only necessary to insert one, rather than two, electrical sensors. The foregoing has outlined rather broadly the features and technical advantages of the present invention so that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. Brief Description of the Drawings Fig. 1 is an exterior perspective view of an inkjet cartridge.

Fig. 2 is a front exterior view of a cartridge. A contact nipple and an exposed portion of an electrode are shown.

Fig. 3 is a top view of the interior of an inkjet cartridge with the lid removed. Fig. 4 is a cross-sectional view of an inkjet cartridge. An electrode insulated by a insulating sheath and frictionally locked into place by a gasket and inserted into a cartridge throughhole is shown. A cross-section of an ink egress port is also shown. Detailed Description of the Invention

Reference is now directed to Fig. 1, where there is shown, in a preferred embodiment thereof, an exterior view of an inkjet cartridge 10. The particular cartridge shown is suitable for use in an Epson Stylus 800 printer. The top lid 12, side wall 14 and front wall 16 of the cartridge are shown. Along the front wall, a protruding portion 18a of an electrode 18 is shown. The protruding portion 18a is placed so as to contact a first ink detection circuit contact plate (not shown) in a printer (not shown) which accommodates the cartridge. A integrally molded contact nipple 22 extending from the cartridge 10 is also displayed. This nipple 22 is placed so as to contact a second ink detection circuit contact plate in a printer which accommodates a cartridge 10. Together, the electrode protrusion 20 and cartridge contact nipple 22 connect to an ink detection circuit (not shown) with a printer (not shown) in which the cartridge 10 is used. When the cartridge 10 contains ink, which functions as an electrical conductor, the printer ink detection circuit is closed, allowing the printer to sense the presence of ink. When the cartridge 10 has voided its ink supply, the circuit cannot be completed, and the open circuit indicates to the printer ink detection circuit that the cartridge is empty. In the preferred embodiment of the invention, the cartridge is molded out of an ABS plastic containing 20% carbon fiber, such as Stat-Kon® AC- 1004 by LNP Engineering Plastics, Inc. The carbon fiber allows the cartridge 10 to be highly conductive, while the material allows the cartridge 10 to be made via a standard injection molding process. Fig. 2 is a front view of a cartridge exterior. A contact nipple 22 is shown, as is the electrode protrusion 18a and a sealing gasket 24. The sealing gasket 24 is placed in an enlarged portion of a cartridge throughhole 26, frictionally securing the electrode 18 to the cartridge 10 and sealing the cartridge 10 from ink leakage.

Fig. 3 is a top view of the interior of an inkjet cartridge with the lid removed. An ink egress port 30 located at a cartridge bottom 35 is shown. When the cartridge 10 is inserted in a printer, the ink egress port 30 couples to a channel on the printer to supply ink to a printhead. An interior end 18b of an electrode 18 may be seen in the ink egress port 32. An electrode throughhole duct 32 is also shown. The electrode throughhole duct 32 is molded as part of the cartridge 10, and allows the electrode 18 to be inserted through the cartridge 10 and into the ink egress port 30. Alternatively, the electrode 18 could be mounted higher on the cartridge to trip a circuit when the ink is depleted to a level below the electrode 18. It is a further advantage of the present invention to allow any preselected level of ink to be determined merely by the placement of a single electrode.

Fig. 4 illustrates a cross-section of the inkjet cartridge 10. A cross-section of the ink egress port 30 and the electrode throughhole duct 32, along with an electrode 18 and its associated gasket 24 and insulating sheath 40, are also shown. When the electrode 18 is inserted into the cartridge 10, the insulating sheath 40 prevents the electrode 18 from contacting the conductive material of the cartridge 10, which would cause the ink detection circuit to short. The gasket 24 is located at a wider portion of the electrode throughhole duct 26 at the cartridge exterior. The gasket 24 serves to both frictionally hold the electrode 18 in place and to seal the throughhole 26 to prevent ink leakage. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

We claim:

1. An inkjet cartridge, comprising: an ink container made of a conductive material, said ink container having an interior chamber to receive ink; an electrical sensor electrically insulated from said container; mount means mounting said electrical sensor within said ink container such that said cartridge form an electrically connective circuit with said sensor being immersed in ink; said electrical sensor including means for relaying an electrical signal from said sensor to a point exterior to said container.

2. The inkjet cartridge of claim 1 wherein said conductive material is a plastic containing at least 12% carbon fiber.

3. The inkjet cartridge of claim 1 wherein said sensor is an electrode attached through said container and exposed in said interior chamber and an exterior portion of said cartridge to transmit said electrical signal.

4. The inkjet cartridge of claim 3 wherein said mount means is a throughhole in said container leading to an ink egress port.

5. The inkjet cartridge of claim 1 wherein said container is filled with ink contained within a sponge.

6. An inkjet cartridge comprising: an ink container formed of a bottom, top and side wall which provide an interior chamber, said container formed out of a conductive plastic; an electrode mounted to said container and electrically exposed to an interior of said container and to an exterior of said container.