Balanced capillary ink jet pen for ink jet printing systems

An ink jet comprising:

• a. an ink supply housing having a primary ink reservoir and a secondary ink reservoir therein,
• b. a balancing capillary member positioned adjacent to or within said ink supply housing and including an open ink flow path extending between said primary ink reservoir and said secondary ink reservoir and operative to draw ink from said primary ink reservoir and into or towards said secondary ink reservoir by capillary action with changes in pressure above the ink within said primary ink reservoir, and
• c. means interconnecting said primary ink reservoir to an ink jet printhead for supplying ink to said printhead during an ink jet printing operation.

In an ink jet pen having a pen body housing with a primary ink reservoir therein for storing ink and a printhead with ink ejection means mounted on or in said housing and operative to receive ink from said primary ink reservoir during an ink jet printing operation, the improvement characterized in that said housing further includes a secondary reservoir and means including an open capillary path for flowing ink back and forth between said primary reservoir and said secondary reservoir as a function of changes in pressure above the surface of ink stored in said primary reservoir.

A device for maintaining a substantially constant backpressure in an ink jet pen which comprises:

• a. primary and secondary ink reservoirs in a pen body housing and an ink ejection printhead mounted on or in said housing, and
• b. means interconnecting said primary and secondary reservoirs for drawing ink by capillary action into or toward said secondary reservoir from said primary reservoir when the pressure above the liquid surface in said primary reservoir is increasing and further for returning ink into or towards said primary reservoir from said secondary reservoir when the pressure above the liquid surface in said primary reservoir is decreasing, whereby the backpressure at the ink ejection printhead of said device is maintained substantially constant over a given temperature range.