Warning device for breathing apparatus having a pressure gas supply

Claim 1

A warning device for a protective breathing gas apparatus of the type having a high pressure gas supply and a pressure reducer connected to the high pressure gas supply for providing a low pressure gas supply comprising a conduit defining a respiratory gas flowpath, a housing having a first chamber, first diaphragm valve means mounted in said first chamber and dividing said first chamber into a high pressure space connected to the high pressure gas supply and a low pressure space connected to the low pressure gas supply, said first diaphragm valve means being movable responsive to the differential pressure between said pressure spaces, a second chamber, second diphragm valve means movably mounted in said second chamber dividing said second chamber into a vestibule space and a rear space and including a bore connecting said vestibule space and said rear space, wall means defining an orifice for connecting said low pressure space and said vestibule space and including a first valve seat adjacent said low pressure space for sealingly receiving said first diaphragm valve means and a second valve seat adjacent said vestibule space for sealingly receiving said second diaphragm valve means, a third chamber having a piston compartment in fluid communication with the gas flowpath, a piston slidably mounted in said piston compartment and dividing said piston compartment into a first piston space communicating with said flowpath and a second space, said piston having a signal portion movable with said piston between a first portion into the flowpath and a second position out of the flowpath, said signal portion being responsive to fluid flow in said flowpath for actuating a warning signal, a first passage connecting said low pressure space and said first piston space, a second passage connecting said vestibule space and said second piston space, a third passage connecting said second piston space and said flowpath, means for throttling said third passage, said first diaphragm valve means being operative to sealingly engage said first valve seat when the differential pressure is above a predetermined level and to sealingly disengage from said first valve seat when the differential pressure is below the predetermined level, said second valve means being operative to sealingly engage said second valve seat when the pressure in said vestibule space and said rear space is equal, and said piston being operative to move the signal portion into the flowpath when said first diaphragm valve means and said second diaphragm valve means are respectively disengaged from said first valve seat and said second valve seat.