Patent 4492537 Issued on January 8, 1985. Estimated Expiration Date: December 10, 2002. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
A fluid operated pump for use in a vertical orientation includes an outer casing with a closure member disposed at one end thereof. A piston is operatively mounted for reciprocation within the outer casing and defines a first fluid chamber between the closure member, the outer housing and a first face of the piston. A first casing is provided at a point spaced from the closure of the housing. A second fluid chamber is formed between the outer housing, the first casing and a second face of the piston. A rod member is operatively disposed for reciprocation within the outer housing. The first piston member is affixed to one end of the rod member. A second casing is provided which is spaced at a predetermined distance from the first casing. A chamber is defined between the outer housing and the first and second casings. A plurality of tubes having inner and outer surfaces are disposed within the chamber and define a plurality of fluid passages between the inner and outer surfaces and the first and second casings. A third and fourth casing are operatively positioned at a predetermined distance with respect to each other within an inner tube disposed within said chamber. A working pump chamber is defined between the third and fourth casings and the inner tube. A second piston member is affixed to the rod and is operatively disposed within the working pump chamber. An inlet conduit is in communication with one of said plurality of fluid passages for supplying fluid to said working pump chamber. An outlet conduit is in communication with one of said fluid passages for discharging fluid from the working pump chamber. Pressurized fluid is in communication with at least one of said plurality of fluid passages for selectively supplying fluid to said first and second fluid chambers to impart movement to said first piston member. Imparting movement to said first piston member imparts movement to the rod to reciprocate the second piston member. Reciprocating the second piston member within the working pump chamber supplies fluid to a first working chamber while discharging fluid from a second working chamber.