Line control

Claim 1

A control device adapted to be positioned intermediate a source of fluid under pressure and a valve actuator, said control device including: a housing having an axial bore extending centrally thereof, said housing including fluid inlet means communicating with said axial bore, and fluid outlet means also communicating with said axial bore; slide valve means movable within said axial bore from a first position allowing relatively unrestricted fluid communication between said inlet means and said outlet means to a second position blocking such communication between said inlet means and said outlet means; first spring means, internal of said axial bore for biasing said slide valve means toward said second position; said slide valve means including first force transmitting means, extending at least partially outward of said housing, for causing movement of said slide valve means from said second position to said first position; said slide valve means further including means for preventing said fluid under pressure from causing movement of said slide valve from said second position to said first position, and means for retaining said slide valve means in said first position against the biasing force of said first spring means, said retaining means including a piston portion having a fluid pressure receiving surface, for receiving said fluid under pressure thereagainst, said piston being sealingly engageable with the wall of said axial bore when said slide valve means is in said first position; and check valve means, carried within an axial bore through a reduced diameter portion of said slide valve means, yieldably obstructing communication between said fluid inlet means and said fluid outlet means.