Automatic double acting differential pump

Claim 1

An automatic, double acting fluid operated differential pump comprising a body having an inner cavity, a reciprocating piston located in said cavity, said piston having a pair of radially enlarged ends dividing said cavity into an inner first functional pressure space and a pair of second functional pressure spaces straddling said first functional pressure space, valve means operable for alternatively distributing a pressurized fluid medium to said second functional pressure spaces, inlet and outlet means communicating with said valve means for delivering and discharging said pressurized fluid medium to and from said second functional pressure spaces, sealing means located between the inner wall of said body and about said piston, said sealing means dividing said first functional pressure space into a first and second portion in which the ends of said piston are located and inlet and outlet means communicating with each of said first and second portions for delivering and discharging a second fluid medium to and from each of said first and second portions, each end of said piston being provided with two spaced circumferential seals defining a groove located between them, a discharge duct extending through said piston from each of said grooves to an outlet port located adjacent the end of the piston opposite to said groove to communicate with the outlet means in the respective first and second portion of the first functional pressure space, and a uni-directional valve located in each duct to permit fluid to flow from said groove only when said piston is selectively caused to move towards the opposite one of the pair of second functional pressure spaces.