Abstract

A pneumatically powerable single action fluid pump has a housing, an improved diaphragm assembly dividing the housing into fluidly discrete propellant and pumping chambers, a fluid inlet and outlet in the pumping chamber, a fluid port to the propellant chamber and a spring motor biasing the diaphragm assembly in a direction away from the pumping chamber side of the housing; the diaphragm assembly includes a perforate rigid diaphragm plate, an elongate motor stem connected to the plate, a contiguous elastomeric diaphragm having an imperforate front layer covering a front side of the plate and stem, a rear layer on a rear side of the plate, pins in the plate perforations and between and adjoining the diaphragm layers, and a bellows section to the outside of the plate. The spring motor biases the diaphragm to a position in close proximity to the fluid port of the propellant chamber in the absence of propellant therein against a plurality of spacer ribs. The spacer ribs permit an even and rapid distribution of propellant into the propellant chamber to drive the diaphragm assembly against the biasing action of the spring motor toward the pumping chamber.