Abstract: An ink-jet pen for storing at below-ambient pressure has an orifice formed therein for providing air bubbles to prevent the back pressure from rising above a level that would cause malfunction of the pen. The amount of air drawn into the reservoir is restricted by the reservoir ink that covers the orifice whenever the pen is in an upright position. The valve operates to occlude the orifice whenever the pen is moved into a position, such as inverted, where the reservoir ink no longer covers the orifice. The occlusion of the orifice prevents the unrestricted flow of ambient air into the reservoir that would otherwise eliminate the required back pressure in the reservoir. The valve includes a sealing liquid selected so that the liquid occludes a passage between the orifice and ambient air without flowing through that passage.

Abstract: An ink jet pen has two modes of operation, a normal speed mode and a high speed mode. In the normal speed mode, the pen's ink reservoir is maintained at a desired below-atmospheric pressure by a bubble generator orifice that introduces air from an atmospherically vented chamber into the reservoir to relieve the partial vacuum caused by ejection of ink. In the high speed mode, a heater heats air trapped in the ink reservoir. As the air tries to expand, it pressurizes the ink and causes it more quickly to refill the pen's ink-ejecting nozzle after firing. The pen can thus be fired at a faster rate. The bubble generator orifice is blocked during the high speed mode by the first droplet of ink expelled through the orifice, which acts to wet and seal a vent tube.

Abstract: Underpressure changes in an ink-jet pen (20, 120) reservoir (22, 122) are compensated for by volumetric changes in the reservoir (22, 122) effected by movement of a piston (56, 156) within a sleeve (50, 150) that is connected to the reservoir (22, 122). The piston (56, 156) and sleeve (50, 150) are sized to provide capillarity for holding ink (72, 172) therebetween. The ink (72, 172) between the piston (56, 156) and sleeve (50, 150) acts as a low-friction seal for preventing fluid communication between ambient air and the interior of the resevoir (22, 122). In one embodiment (120), the volumetric efficiency of the pen is enhanced with an auxiliary ink reservoir carried on the piston (156).

Abstract: An ink jet pen has two modes of operation, a normal speed mode and a high speed mode. In the normal speed mode, the pen's ink reservoir is maintained at a desired below-atmospheric pressure by a bubble generator orifice that introduces air from an atmospherically vented chamber into the reservoir to relieve the partial vacuum caused by ejection of ink. In the high speed mode, a heater heats air trapped in the ink reservoir. As the air tries to expand, it pressurizes the ink and causes it more quickly to refill the pen's ink-ejecting nozzle after firing. The pen can thus be fired at a faster rate. The bubble generator orifice is blocked during the high speed mode by the first droplet of ink expelled through the orifice, which acts to wet and seal a vent tube.

Abstract: An ink jet print cartridge includes an ink reservoir, a print head for ejecting ink from the reservoir and first and second pressure control mechanisms for limiting the reservoir underpressure. The first pressure control mechanism limits reservoir underpressure by controllably introducing replacement fluid (i.e. air or ink) thereto. The second pressure control mechanism limits reservoir underpressure by changing the volume thereof. The two pressure control mechanisms cooperate to regulate the underpressure in the reservoir at a desired value over a broad range of environmental excursions and permit use of a volumetrically efficient package.