Variable pressure control for ink replenishment of on-carriage print

Abstract

A variable height reservoir system that allows for reliable ink replenishment to an on-carriage pen reservoir from an off-carriage ink reservoir on an as needed basis. The off-carriage reservoirs are mounted on a platform that is actively moved up and down in a vertical motion. A pen cartridge with an internal spring to provide vacuum pressure is intermittently connected to an off-carriage reservoir, by movement of the pen carriage to a refill station for ink replenishment. In the refill station, a valve is engaged into the pen, thus connecting the ink reservoir to the pen cartridge. Using only the vacuum pressure present in the pen cartridge, ink is pulled into the pen from the reservoir. The ink replenishment occurs in a first stage with the reservoir placed very close to the pen cartridge elevation, with only a small offset between the top of the ink reservoir and the pen nozzles. This small offset distance ensures flow of ink into the pen cartridge, and results in acceleration of ink into the pen, decreasing the fill time. The pen can be overfilled, decreasing the pen vacuum pressure such that high print quality will be sacrificed. The reservoir is then lowered which results in a small amount of ink moving back into the reservoir, raising the vacuum pressure into the appropriate range.