Patent ID: 7665974

Claim:
A diaphragm pump, comprising: a diaphragm movable between first and second positions along a first axis; a pumping chamber on one side of the diaphragm, the pumping chamber adapted to carry a fluid to be pumped; a transfer chamber on the other side of the diaphragm, the transfer chamber being filled with a hydraulic fluid; first and second one-way valves; a fluid reservoir in fluid communication with the transfer chamber via the first valve and a first conduit leading directly to the fluid reservoir, and the second valve and a second conduit extending directly from the fluid reservoir to the transfer chamber; and a valve spool positioned in the transfer chamber to control fluid flow through the first and second valves, the valve spool moveable along a second axis that is different from the first axis between a plurality of positions relative to openings to the first and second valves.