Patent ID: 7025578

Claim:
A pump comprising: a spool slidably positioned within a housing, the spool having an exterior surface and the housing having an interior surface, the exterior surface of the spool having a first spool port in fluid communication with a first diaphragm chamber and a second spool port in fluid communication with a second diaphragm chamber, the interior surface of the housing having a supply inlet port, a first exhaust port and a second exhaust port, and wherein the spool is slidable between a first position wherein the supply inlet port is in fluid communication with the first spool port and the second spool port is in fluid communication with the second exhaust port and a second position wherein the supply inlet port is in fluid communication with the second spool port and the first spool port is in fluid communication with the first exhaust port; and wherein with the spool in both the first and second positions, the supply inlet port is in fluid communication with a supply face of the spool, the supply face being substantially perpendicular to an axis of motion along which the spool slides and having a surface area less than a surface area of a first end face of the spool that is substantially parallel to the supply face.