Fire resistant pressure switch

Claim 1

A fire resistant switch device responsive to the pressure of a fluid medium, said device comprising: a housing having a tubular end for connection with the fluid medium; a pressure responsive piston in said housing supported for movement therein between first and second positions; a switch element; actuating means for effecting a first condition of said element when said piston is in said first position and a second condition of the switch element when said piston is in said second position; yieldable means for urging said piston toward said first position; a metal fitting insertable in the said end of said housing, said fitting located on the opposite side of said piston from said switch, said fitting including (a) a pressure port therethrough for communication with the fluid medium, said port having opposite ends including an inlet end for the fluid medium, (b) a flexible metal diaphragm overlying the end of said port opposite the inlet end and having its periphery generally coincident with the periphery of the fitting, (c) a metal ring member overlying said diaphragm and having its periphery generally coincident with the periphery of said diaphragm, (d) the adjoining peripheries of said fitting, diaphragm and ring member all being joined together by a continuous weld seam providing a pressure tight connection sealing off the housing from the fluid medium which will remain effective in the event of high temperature destruction of other components of the device, (e) a movable disk assembly within said ring member and disposed to respond to movement of said diaphragm caused by pressure changes in the medium and operable to move said piston in response to movement of said diaphragm thereby to actuate said piston between said first and second positions.