Abstract: A double diaphragm pump comprises a center body 10 and two end-caps 11, 12, the outer peripheries of two diaphragms 20, 21 being clamped between the center body and the two end-caps respectively. The diaphragms are interconnected by a hollow push-rod 26 slidably and sealingly mounted in a bush 17 in the center body. A shaft 30 extends centrally through the push-rod, diaphragm and end-cap and has a radial flange at one end and a nut engaged on a screw-thread at its other end whereby the end-caps, diaphragm and center body are clamped axially together. Air under pressure is supplied to the two axially outer chamber 23, 24 formed between the diaphragms and the end-caps under the control of a change-over spool valve 45, change-over operation of which is initiated by the approach of the push-rod 26 to either end of its reciprocating movement.

Abstract: A device for interconverting linear and rotatory motions, and particularly a pressure fluid operated actuator for rotary plug valves and the like. A piston axially slideable and rotatable in a cylinder is supported by first and second sets of connecting elements which are spaced from and inclined to the axis of the cylinder. Each element of one set is pivotally connected at one end with a fixed member and at the other with the piston. Each element of the other set is pivotally connected at one end with the piston and at the other with a rotary output element, for example, a shaft. Axial movement of the piston is translated into rotatory movement of the output element by pivotal action of the connecting elements. The connecting elements of the first and second sets extend from the fixed member to the piston and from the piston to the output element in opposite circumferential directions.