Abstract: An air-operated pump includes a pair of poppet valves affixed to a vertical valve shaft and arranged so that the upper valve is closed when the lower valve is open, and vice versa. When a connected displacer is immersed in tank fluid, its buoyancy in combination with a bias spring translates the valve shaft to operate the poppet valves. An upper poppet valve chamber is connected [1 ] via a restrictance to an auxiliary air supply, and also [2] to an air operator that triggers a three-way pneumatic valve, an inlet port of which controls a main air supply while a second port is vented to atmosphere. A third port transmits an air supply to the tank through the intermediation of a quick exhaust valve, which rapidly vents the tank at the end of each pump cycle and also serves to isolate the three-way valve from any tank-fluid contamination.

Abstract: A hybrid gate-controlled three-way valving device that because of its regenerative-feedback-induced bistable action is a fluid-logic analogue of the electronic thyristor. The device is more particularly analogous to a common electronic thyristor known as the silicon controlled rectifier (SCR) because each is a switching device that in its normal state blocks forward conduction of the control-agent fluid, but which upon receipt at a control gate of an appropriate signal will trigger full forward conduction of the control-agent fluid. Each is moreover a device wherein such full forward conduction, once triggered by a brief signal, will continue even after the signal has been removed, until the control-agent supply flow has been cut off, reduced or reversed.

Abstract: A latching liquid-level sensor including a vertically mounted free-floating float member which carries a magnet. A second magnet or ferromagnetic member separated from the first magnet by a liquid- and gas-impervious barrier is selectively actuated by the first magnet. The second magnet or ferromagnetic member is connected to a control logic system which is isolated from the float member which may be hermetically contained in a highly corrosive or explosive environment.

Abstract: An elongated thin walled elastic member arcuately shaped and connected on the inside wall of a pipe section having a portion deformable under fluid pressure permitting fluid flow in one direction only.