Automatic pressure valve

An automatic valve for a pressure enclosure submersible in a liquid medium, said valve comprising a valve body, an inlet port in said body having an actuable valve member to admit pressurized gas in a valve chamber in communication with an enclosure to which said valve is secured, an adjustable cover member displaceably secured to said body and having at least one exhaust orifice, an outlet port in said body communicating with said valve chamber and having an automatic pressure regulating valve mechanism therein preventing liquid ingress to said chamber, said valve mechanism being adjustable by a pressure biasing member controlled by a first displacement of said adjustable cover member to control the pressure of said gas in said enclosure by automatically exhausting some of said gas through said outlet port when said pressure exceeds a preset pressure of said mechanism, a displaceable valve member associated with said valve mechanism and displaceable by a second displacement of said cover member to exhaust gas from said enclosure through said outlet port while preventing ingress of liquid to said chamber.