The illustrated embodiment teaches a three-way valve system for an ink jet printer. The system has an inlet, Needle & Gauge Valvesa main outlet, a vent, and two needle valves (a shut-off valve and a vent valve) which sit in respective valve guides. The passageways are arranged so that for ink to reach the outlet or vent, it travels through the shut-off valve seat and guide. Similarly, Plug Valvesto reach the vent, fluid must pass through the vent valve seat and guide. The shut-off valve and vent valves are arranged to reciprocate through the action of a lever with a fulcrum between the two needle valves. The lever is connected to an actuator solenoid and an opposing bias spring. BALL VALVES For opening of the valve system, the solenoid pulls the lever to shut the vent valve, thereby permitting the pressurized ink to lift the shut-off valve off its seat. When the shut-off valve is seated, a smaller area is exposed to pressure than when it is not seated. Therefore, the ink exerts a greater force on the opened shut-off valve. This greater force is communicated by the lever to seat the vent valve even more firmly. This is called self-energization. Decisive closing of the system occurs due to the vent arrangement permitting fluid in the passageways after the shut-off valve is seated to open the vent valve and exit through the vent.

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