OVER-CENTER LINKAGE

摘要

A novel changeover mechanism for a compressed air driven double diaphragm pump comprises a shaft (21) slidably mounted through aligned apertures (22) in opposing surfaces of the twin diaphragm chambers (23). At the centre of the shaft (21) between the two diaphragm chambers (23) is provided an annular notch (24) in to which is located an arm (25) extending from a U shaped frame (26). The U shaped frame (26) is pivotally mounted atop a valve plate (27) which includes multiple ports (28). Positioned against a surface of the valve plate (27) is a valve closure component (29) which is configured to slide across the surface selectively obstructing the multiple ports (28). The valve closure component (29) is held in place by a metal peg (30) hingedly mounted in slots (31) provided in parallel extension of the U shaped frame (26). Linear tension springs (32) connect the hinged wire pusher (30) with U shaped frame (26) adjacent the pivot point. The springs (32) bias the position of the valve closure component (29) against the valve plate (27) in an off centre position.