US 4992802

Patent Overview — US 4,992,802 A

Title: Method and apparatus for extending the environmental operating range of an ink jet print cartridge

Source: https://patents.google.com/patent/US4992802/en

Bibliographic data (from excerpt): Application US07/289,876; inventors John H. Dion and Thomas H. Winslow; original assignee Hewlett-Packard Company (current assignee listed as HP Inc); priority/filing date 1988-12-22; publication/grant date 1991-02-12; status listed as expired — lifetime. Foreign counterparts noted in the excerpt include EP0375383B1, CA1323243C, JP2957617B2, and KR0141518B1.

Purpose: The invention addresses the problem of maintaining proper "underpressure" (sub-ambient reservoir pressure) in drop-on-demand ink jet print heads. If underpressure is too small or positive, ink escapes through the drop generators; if too large, air can be drawn in through them. The stated aim is to extend the environmental operating range of an ink jet print cartridge while permitting a volumetrically efficient package.

Plain-language scope: An ink jet print cartridge has an ink reservoir plus two pressure-control mechanisms that cooperate to hold reservoir underpressure at a desired value. The first mechanism limits underpressure by controllably introducing replacement fluid (air or ink) — e.g., a "bubble generator orifice" sized to admit air at a chosen underpressure (five inches of water in the illustrated embodiment). The second limits underpressure by changing reservoir volume — e.g., a collapsible flexible bladder in a wall of a rigid, fixed-volume chamber. The orifice is made larger than the print nozzle orifices (0.0078 in. vs. 0.0020 in.) so ink preferentially exits the orifice under overpressure. A catchbasin receiving the orifice is vented to atmosphere.

Not established by this excerpt: The full claim set, dependent-claim scope, the complete description and drawings (only partially quoted), and the specific figures referenced (e.g., FIG. 6). The prosecution history, any prior-art rejections, and the excerpt's note of an International Trade Commission proceeding are not described. No assessment of validity, enforceability, or claim coverage is offered or supported by the supplied text.