A hydraulically operated downhole pump that is connected to or disposed in a string of tubing, and when operated by pressurized oil from the ground surface, is capable of discharging production fluid, gas, and pressurized oil from the well either separately or in desired combinations thereof. The pump...http://www.google.es/patents/US4386654?utm_source=gb-gplus-sharePatente US4386654 - Hydraulically operated downhole oil well pump
