Abstract: A downhole bladder pump for pumping ligher-than-water liquids. The pump includes an outer tube closed at its bottom and top, but having slots adjacent its upper end to admit the liquid to be pumped. Positioned concentrically within the outer tube is a cylindrical bladder chamber. A cylindrical bladder is mounted within the bladder chamber and registers with the internal surface of such chamber. A cyclically-operated pneumatic control system periodically delivers pressurized air to the space between the bladder and the bladder chamber to collapse the bladder and pump liquid which has flowed into the bladder. At other times during the cycle, the control system draws the bladder outwardly against the internal surface of the bladder housing by the application of vacuum. The liquid to be pumped is then forced into the bladder through a check valve subassembly positioned in the lower end of the bladder housing.

Abstract: A reciprocating device comprising a housing having a chamber and a reciprocable member reciprocable in the chamber. First and second pressure valves are connectible to a source of fluid under pressure to drive the reciprocable member and first and second passages lead from the first and second pressure valves to the chamber on opposite sides of the reciprocable member, respectively. First and second exhaust valves are coupled, respectively, to the first and second passages at locations intermediate the associated pressure valve and the chamber and communicating with the first and second vents, respectively. Actuators are drivable by the piston for switching the valves between first and second positions, and the fluid under pressure retains the valves in whichever of the positions they are placed.