Abstract: A fluid-jet writing system in which writing fluid is pumped from a fluid container or reservoir to one or more fluid-jet writing nozzles. A valve is located in the hydraulic circuitry which connects the pump to the nozzles for controlling the flow of writing fluid to the nozzle. A comparator is also located in the hydraulic circuitry for maintaining a predetermined fluid pressure between the pump and the valve by controlling the operation of the pump.

Abstract: A pump mechanism for pumping ink or similar writing fluid from a fluid reservoir to a writing device. A piston is moved in a cylinder in one direction to draw ink into the cylinder from a reservoir through a capillary tube, and is moved in an opposite direction to discharge the ink to a writing device while at the same time, in cooperation with a flexible membrane located in the cylinder and connected to the piston, to discharge any air in the capillary tube back into the reservoir.

Abstract: A pump mechanism for delivering ink or the like writing fluid from a reservoir to a point of utilization such as a writing device. The mechanism includes a piston slidable in a cylinder for drawing ink into the cylinder during a suction stroke and discharging the ink during a pumping stroke. The cylinder is formed by a cylinder wall which includes a frusto-conical portion tapered inwardly in a direction away from the piston. The piston comprises a single plastic member having a forward end portion which faces and cooperates with the tapered portion of the cylinder wall and which has an outside diameter which is greater than the smallest diameter of the tapered cylinder wall portion, whereby the forward end portion of the piston engages the tapered cylinder wall portion as the piston moves forward during a pumping stroke.