Abstract: The invention is concerned with an improvement in a gas pressure driven pump which comprises a vessel, means for introducing a liquid into the vessel, means for preventing reverse flow of the liquid into the liquid introducing means, means for introducing a pressurized gas to the vessel, and means responsive to a gas pressure increase in the vessel for flowing the liquid out of the vessel. The invention is an improved system for controlling the flow of pressurized gas into the vessel responsive to the liquid level therein, which system is substantially independent of the density of the liquid. More specifically the improved system comprises a valve having a first, a second and a third port, the valve providing a first mode in which the first port is in communication with the second port and a second mode in which the first port is in communication with the third port. The second port communicates in both modes with the surrounding outside atmosphere.

Abstract: The present invention is a secondary recovery system normally used for retrieving oil from the producing zone after the bottom hole pressure has decreased so that artificial lift is required for production. An accumulator is positioned in the lower portion of the casing where oil will accumulate from the producing zone. A standing valve is located in the bottom of the accumulator to prevent oil collected therein from leaving the accumulator. Above the accumulator is located a free floating piston having passageways therethrough. By proper control of the pressure line from the surface, oil is gradually moved through the free floating piston into a production tubing thereabove. Next, again in response to surface control, the free floating piston and oil collected thereabove is moved to the surface of the well by a rapid pressurization of the accumulator. Thereafter, pressure is exhausted from the accumulator allowing the piston to drop back to its lowermost position immediately above the accumulator.

Abstract: A slurry pump including a pressure tank with an inlet and a lower outlet and having a pneumatically operated, inwardly opening closure at the inlet and a hinged, outwardly opening door at the outlet swingable between opened and closed positions. An external source of air under pressure hydraulically shuts the closure and pressurizes the tank, forcing a semi-liquid slurry such as liquid manure contained within the tank through the outlet and into a duct leading to a lagoon or the like. A slurry level sensor shuts off the supply of air to the tank when the slurry reaches a given level in the tank.