Combined pressurizing and relief valve for fire extinguishers

Claim 1

A combined pressurizing and relief valve for a pressurized container, said valve including a body mounted to said pressurized container, said body formed with a chamber, means forming an inlet passage to said body in fluid flow communication with said chamber through which said container is to be pressurized from a source of pressurized fluid, said body also being formed with a first passage in fluid flow communication between the interior of said container and said chamber, and a vent passage in fluid flow communication between said chamber and the atmosphere surrounding said body, a valve member located in said chamber movable between a closed position blocking fluid flow communication between said inlet passage and said first passage and an open position for permitting fluid flow between said inlet and said first passages, spring means biasing said valve member into said closed position, said valve member having a first piston area in fluid flow communication with said inlet passage to move said valve member against the biasing force of said spring to said open position upon application of the pressurizing fluid from the source to said inlet passage, said valve member also having a second piston area in fluid flow communication with the interior of said container to move said valve member to said open position in response to excessive pressure within said container in the absence of the pressurizing fluid being applied to the inlet passage, said first and second piston areas also moving said valve to a position to provide fluid flow communication between the inlet passage and the vent passage in response to a combined excess pressure in the container on said second piston area and the pressure on said first piston area from the pressurizing fluid.