Breathing apparatus demand valve

Claim 1

A BREATHING APPARATUS DEMAND VALVE COMPRISING A HOUSING HAVING A BACK WALL PROVIDED WITH A CENTRAL OUTLET PORT, A FLEXIBLE DIAPHRAGM IN THE HOUSING, MEANS SEALING THE EDGE OF THE DIAPHRAGM TO THE HOUSING NEAR ITS FRONT TO FORM A CHAMBER BETWEEN THE DIAPHRAGM AND THE BACK WALL OF THE HOUSING COMMUNICATING WITH SAID PORT, THE DIAPHRAGM BEING RESPONSIVE TO VARIATIONS IN PRESSURE IN SAID CHAMBER AND HAVING A STIFF CENTRAL PORTION MOVABLE TOWARD THE OUTLET PORT DURING INHALATION AT SAID OUTLET PORT, THE SIDE OF THE HOUSING IN SAID CHAMBER BEING PORVIDED WITH AN INLET PASSAGE ENCIRCLED AT ITS OUTER END BY A VALVE SEAT, A TILTABLE VALVE HEAD FOR SAID SEAT, A SPRING NORMALLY HOLDING SAID HEAD ON THE SEAT, A STEM FASTENED TO THE CENTER OF THE VALVE HEAD AND EXTENDING THROUGH THE INLET PASSAGE TO A POINT ADJACENT SAID STIFF CENTRAL PORTION OF THE DIAPHRAGM, A HEAD ON THE INNER END OF THE STEM FOR ENGAGEMENT BY THE REARWARDLY MOVING DIAPHRAGM TO TILT THE STEM AND VALVE HEAD, AND A STOP RIGIDLY MOUNTED BETWEEN THE STEM AND DIAPHRAGM IN THE PATH OF THE PART OF SAID STIFF PORTION BETWEEN SAID INLET PASSAGE AND THE PORTION OF THE DIAPHRAGM ENGAGING SAID STEM HEAD, WHEREBY WHEN THE DIAPHRAGM IS DRAWN BACKWARD IN THE HOUSING DURING INHALATION AND STIFF PORTION OF THE DIAPHRAGM WILL ENGAGE SAID STOP AND WILL TILT ON IT BACK INTO ENGAGEMENT WITH THE BACK WALL OF THE HOUSING AT THE SIDE OF SAID OUTLET PORT OPPOSITE TO SAID INLET PASSAGE.