Fluid-operated valve for pumps and the like

A fluid flow machine comprising a housing defining a chamber;

• a piston movable relative to said housing to alternatively perform first and second strokes at a selected frequency and to thereby respectively draw fluid into and expel fluid from said chamber;
• a fluid-operated first valve arrived by said housing to admit fluid into said chamber when said piston performs a first stroke;
• and a fluid-operated second valve carried by said housing to discharge fluid from said chamber when said piston performs a second stroke, at least one of said valves comprising a substantially disc-shaped resilient valving element having a predetermined thickness and a predetermined diameter, a central portion and a marginal portion, a seat for said margin portion at one side of said valving element and a support for said central portion at the other side of said valving element, said marginal portion being moved away from said seat by the fluid whenever said piston performs one of said first and second strokes and said at least one valving having a compartment surrounding said support to receive said marginal portion when the marginal portion moves away from said seat, said support having a substantially circular first surface which contacts said central portion and having a radius such that said selected frequency of said piston induces a resonant frequency in said valving element.