Patent ID: 6139137
Filing Date: 2000-10-31
Classification: B41J

Abstract:
An inkjet cartridge, comprisinga case defining an internal reservoir for storing ink, wherein during operation back pressure accumulates within the reservoir;a printhead in communication with the reservoir and having a plurality of nozzles through which ink is ejected;a bubble generator in communication with the reservoir and an external environment of the inkjet cartridge for maintaining back pressure within the reservoir, the bubble generator having a passageway in communication with air from the external environment; anda cover attached to the case over the bubble generator, the cover defining a vent opening for the passageway of the bubble generator;wherein the bubble generator comprises:a first surface and second surface which together define the passageway, the first surface defining a first opening to the reservoir, the first surface having a tapered portion along a circumference of the first opening, the second surface defining a channel leading to the first opening, the first opening and the channel forming the passageway, the channel communicating air from an environment outside the case to the first opening;means positioned within the first opening for defining an area within the first opening of generally consistent size in the presence of either one of expansive forces or contractive forces resulting from either one of variations in temperature or pressure of the external environment, said defining means allowing an air bubble to pass from the external environment through the passageway to regulate back pressure within the reservoir, said defining means comprising:(i) a movable object positioned in the first opening; and(ii) a plurality of ribs extending longitudinally within the first opening along the tapered portion of the first surface, said plurality of ribs supporting the movable object;wherein said area occurs in the first opening between the object and the first surface, and wherein in the presence of said either one of expansive forces or contractive forces a variation in a perimeter length of the first opening occurs which is offset by a variation in a perimeter length of the object to maintain said area at the generally consistent size.