Pneumatic reciprocating pump

Abstract

A pneumatically-actuated reciprocating fluid pump and shuttle valve combination operates in an “air-assist” mode and a “non-air-assist” mode. In the non-air-assist mode, the shuttle valve is shifted by a blast of pressurized supply air from the pneumatic chamber in its pumping stroke as the flexible diaphragms and drive shaft reach the end of their pumping stroke. This blast of pressurized air used to shift the shuttle valve has the effect of reducing the air pressure in the pneumatic chamber immediately prior to the point in time that the drive shaft reaches the end of its stroke in order to provide a cushioning effect at the end of each pumping strokes cycle, in order to lessen the effect of the drive shaft and diaphragms abruptly reversing direction at full air pressure. In the air-assist mode, a secondary source of compressed air is utilized to shift the shuttle valve, rather than drawing pressurized air from the pneumatic chamber during its pumping stroke. In the air-assist mode, the full effect of the pressurized air to the pump is directed to pump fluid through the pump, and is not lessened by tapping a minute amount compressed air at the end of each pumping stroke cycle for shifting the shuttle valve.