Valve assembly

A flow control valve for providing liquid flow at different flow rates in two alternative flow directions through the valve under the control of the inflow pressure to the valve, said valve comprising a body having a fluid passageway therethrough, first and second ports provided respectively at opposite ends of said fluid passageway, first and second valve elements mounted for linear movement in said fluid passageway between said ports being capable of engagement along mutually abutting surfaces, said first and second valve elements additionally including facing spaced surfaces between which a volumetric space between the valve elements is defined, first biasing means mounted in said body for yieldably biasing said first valve element toward said second valve element and said second port, second biasing means mounted in said body for yieldably biasing said second valve element toward said first valve element and said first port so that said first and second valve elements are normally engaged at their mutually abutting surfaces, movement limiting means disposed in said body for limiting the extent of movement of said first and second valve elements respectively toward said second and first ports under the influence of said biasing means, said first valve element having a main fluid passageway therethrough providing communication between said first port and said second valve element so that fluid pressure in said main fluid passage urges said second valve element toward said second port against the action of said biasing means, said main fluid passageway and said volumetric space being blocked from communication with each other when said valve elements are disposed in engagement with each other, said second valve element including a primary fluid passageway therethrough providing communication between said main fluid passageway and said second port when said valve elements are disposed in engagement with each other, flow between said ports in either direction being limited to a relatively low rate of flow through said main fluid passageway and said primary fluid passageway when said valve elements are engaged and the fluid input pressure is below a predetermined value, said second valve element including secondary fluid passageway means providing communication between the volumetric space between said valve elements and said second port, said second biasing means exerting a predetermined force so that fluid pressure in said first port above a predetermined value is effective to overcome said second biasing means to move said second valve element from contact with said first valve element to permit flow from said first port to said second port at a relatively high flow rate through said main fluid passageway, said volumetric space, said primary fluid passageway and said secondary fluid passageway to said second port, said first biasing means exerting a predetermined force so that pressure in said second port above a predetermined pressure is effective through said secondary fluid passageway means to said volumetric space to overcome said first biasing means to move said first valve element from contact with said second valve element to permit flow at a relatively high rate from said second port through said primary fluid passageway, said second fluid passageway means, said volumetric space between said valve element and said main fluid passageway to said first port.