PRESSURE CONTROL DEVICE FOR AN INK JET PRINTER

摘要

A tower chamber (20) of a thermal ink jet cartridge (10) has an ink reservoir (14) communicate therewith through a first passage (22), which is controlled by a spring biased valve (23). Ink exits from the tower chamber to nozzles (34) in a printhead chip (37) through a second passage (33). The valve has a pressure compliant bladder (30) attached to its bottom surface (27) in sealing relation therewith. A passage (31) extends through the valve to provide continuous communication between the interior of the bladder and the reservoir. The bladder is formed of a material to continuously urge it to its relaxed state. When the back pressure in the tower chamber increases, ink flows into the bladder to expand it to fill the volume of the tower chamber. If an air bubble is trapped within the tower chamber, it will expand or shrink when subjected to pressure variation and/or a temperature variation. The bladder will expand to fill the volume in the tower chamber when the air bubble shrinks and will contract when the air bubble expands so that the tower chamber accommodates the increased volume of the air bubble. The valve does not open to allow ink to flow into the tower chamber from the reservoir until after the bladder is fully expanded.