Patent ID: 6899530

Claim:
A diaphragm pump for receiving drive power from a motor, said pump comprising: a housing having a pumping chamber adapted to contain fluid to be pumped, a transfer chamber adapted to contain hydraulic fluid, and a hydraulic fluid reservoir; a diaphragm having a transfer chamber side and a pumping chamber side, said diaphragm being disposed between said pumping chamber and said transfer chamber and adapted for reciprocation toward and away from said pumping chamber; a piston in a cylinder in said housing adapted for reciprocation between a power stroke and a suction stroke, said cylinder forming a portion of said transfer chamber, said piston moving longitudinally in said cylinder with said cylinder having a surface with an upper portion when said pump is oriented so that said cylinder is generally horizontal; a fluid communication path for the hydraulic fluid between said hydraulic fluid reservoir and said transfer chamber and a valve in said path for selectively allowing flow of hydraulic fluid from said hydraulic fluid reservoir to said transfer chamber when said valve is open; and a vent between said transfer chamber and said hydraulic fluid reservoir formed in the upper portion of the surface of said cylinder, said vent include a longitudinal notch in the upper portion of the surface of the said cylinder, said vent being without access external to said housing; wherein air in said transfer chamber is forced therefrom through said vein in said cylinder to enhance the quality of the fluid in the transfer chamber and to sell prime said pump.