Patent ID: 7793804

Claim:
A pump for developing pressure for spraying liquid material via said pump, said pump comprising a pressure chamber with respect to which a piston reciprocates in compression and suction strokes, a pressurizable reservoir for said liquid, one way valves communicating said chamber and a supply of said liquid material on the suction stroke, and said reservoir and said chamber on said compression stroke, said reservoir receiving from said chamber and retaining said liquid material under pressure for spraying from an outlet from said reservoir, and a passage for venting said chamber from outside air via another one-way valve on an end of said piston at said chamber exclusively on said suction stroke and closing said passage during said compression stroke, wherein the air and liquid material in the chamber maintains the pressure developed in said chamber on successive compression strokes and also maintains pressure in said reservoir as said reservoir fills with air and liquid material from the pressure chamber on successive compression strokes.