A downhole reciprocating piston pump is driven pneumatically from a surface facility for producing formation fluid from a well bore. The pump is cycled automatically without the use of electrical controls or components. A piston is received within a pump chamber thereby defining a power chamber and a...http://www.google.fr/patents/US4515532?utm_source=gb-gplus-shareBrevet US4515532 - Single action pneumatic powered spring retractable pump
Single action pneumatic powered spring retractable pump
