Four-way control valve

Claim 1

A pilot operated supply and waste control valve of the type comprising two main valves associated with at least one load port for alternately supplying and exhausting a supply fluid to and from each load port and control means for applying fluid control pressure to open and close a main supply valve associated with each load port while conversely closing and opening a main waste valve associated with each load port, wherein: each main valve comprises a diaphragm which presses against a valve seat with a high pressure applied to a control surface of the diaphragm opposite to the valve seat; and the control means is a four way pilot valve comprising: first and second output pressure chambers, each having a high pressure inlet port in communication with a source of said supply fluid, a low pressure inlet port and an output control conduit for applying opposite high and low pressures to the control surfaces of the diaphragms of said main supply and waste valves associated with each load port; a valve member associated with each output pressure chamber, each valve member comprising an arm having a first end thereof positioned between the high and low pressure inlet ports, a second end, and a fluid sealed pivot between the first and second ends, the arm being pivoted about the pivot to move said first end alternately against the high and low pressure inlet ports to alternately close the ports; and one actuator for simultaneously driving the second ends of the pivotal arms of the respective valve members such that the high pressure port to one output pressure chamber is closed by one valve member arm as the opposite, low pressure port to the other output pressure chamber is closed by the other valve member arm such that one of the main supply and waste valves of each load port is opened due to the resultant pressure in one of the chambers and the other of the main supply and waste valves of each load port is closed due to the resultant pressure in the other chamber.