Relief valve

Claim 1

A high pressure relief valve comprising a cylindrical housing with a reduced cylindrical end portion, said end portion being externally threaded, an annular flange threadedly connected to said end portion for attachment to an inflatable raft and communicating with a chamber therein, a stepped bore extending through said housing, said bore having a first upper bore portion and a second lower bore portion, said second bore portion being of smaller diameter than said first bore portion and located in said cylindrical end portion, an annular shoulder formed between said first and second bore portions defining an annular valve seat, a piston slidably received by said first bore portion, said piston having an outer wall length that is greater than one-half of the depth of first bore portion, said piston is cup-shaped, the lowermost portion of said piston having a circumferentially extending O-ring for engaging said valve seat, said O-ring exposes a portion of said annular valve seat to pressurized medium from said second bore portion, spring means extending into said cup-shaped piston and is guided by and seated therein, said spring means biasing said piston into engagement with said valve seat, said cylindrical housing having a plurality of circumferentially spaced and evenly spaced passageways communicating the exterior of said cylindrical housing with the interior of said first bore portion, said passageways located closely adjacent to said valve seat, an annular washer located in said first bore for retaining said piston in said first bore, said annular washer having a central bore for venting gases to atmosphere along with said passageways defining exhaust means, and wherein the area of said exhaust means is less that the area of said second bore which communicates with the bottom of said piston to initiate the venting of said relief valve.