A novel changeover mechanism for a compressed air driven double diaphragm pump comprises a shaft slidably mounted through aligned apertures in opposing surfaces of the twin diaphragm chambers. At the center of the shaft between the two diaphragm chambers is provided an annular notch in to which is located an arm extending from a U shaped frame. The U shaped frame is pivotally mounted atop a valve plate which includes multiple ports. Positioned against a surface of the valve plate is a valve closure component which is configured to slide across the surface selectively obstructing the multiple ports. The valve closure component is held in place by a metal peg hingedly mounted in slots provided in parallel extension of the U shaped frame. Linear tension springs connect the hinged wire pusher with U shaped frame adjacent the pivot point. The springs bias the position of the valve closure component against the valve plate in an off center position.

Provided is a fuel pump comprising: a pump body; a plunger reciprocatably displaceable with respect to the pump body; and a plurality of valve elements inclusive of a suction valve to allow the fuel to be sucked into the fuel pressurizing chamber and a discharge valve to allow the fuel to be discharged out of the fuel pressurizing chamber, in which the pump body comprises a tubular valve retention member to retain the plurality of valve elements, a cylinder member to slidably retain the plunger, and an outer shell member having an inner wall surface facing an outer surface of the valve retention member, the inner wall surface and the outer surface of the valve retention member collectively forming a suction gallery chamber.

Pump subsystem for fluid delivery (e.g., in a wearable patch pump) comprises a fluid chamber with pumping motion and a valve shaft assembly with valving motion, both being driven by the same drive mechanism. Fluid chamber has variable volume chamber provided by a piston driven by the drive mechanism and translated relative to a plug in the pump housing. Piston extends the fluid chamber during an intake stroke and retracts the fluid chamber during a discharge stroke. Valve assembly has at least one valve shaft controllably translated by the drive mechanism to selectively align a first throughway with an opening in the pump chamber and a fluid intake port for an intake stroke to draw fluid into the fluid chamber, and align a second throughway with the opening in the pump chamber and a fluid discharge port for an discharge stroke to discharge fluid from the fluid chamber.