Hewlett-packard Company

Bruce A Anderson

Thomas H Winslow

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).

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Corvallis, OR, United States of America

Bruce A Anderson