Means for preventing flashback in powder melting torches

Claim 1

IN A POWDER MELTING TORCH, A TORCH BODY HAVING A CHAMBER THEREIN INTO WHICH A COMBUSTIBLE GAS MIXTURE FLOWS, SAID TORCH BODY HAVING AN OPENING FOR ADMITTING POWDER INTO SAID CHAMBER, A POWDER HOPPER, A PASSAGENWAY FROM SAID HOPPER TO SAID OPENING IN SAID TORCH BODY FOR FLOWING POWDER BY GRAVITY INTO SAID CHAMBER, A NOZZLE SECURED TO THE FORWARD END OF SAID TORCH BODY AND THROUGH WHICH SAID COMBUSTIBLE GAS MIXTURE FLOWS FROM SAID CHAMBER TO PROVIDE A POWDER MELTING FLAME AT THE TIP OF THE NOZZLE, THE IMPROVEMENT WHICH COMPRISES: MEANS FOR PREVENTING FLASHBACK IN SAID HOPPER AND SAID PASSAGEWAY, SAID MEANS COMPRISING A VALVE DISPOSED IN SAID TORCH BODY AT THAT END OF SAID PASSAGEWAY WHICH OPENS INTO SAID CHAMBER, SAID VALVE BEING INHERENTLY SELFCLOSING, BUT OPENABLE DURING FLOW OF SAID COMBUSTIBLE GAS MIXTURE THROUGH SAID TORCH IN A FORWARD DIRECTION AND REMAINING OPEN DURING PASSAGE OF THE COMBUSTIBLE GAS MIXTURE THROUGH SAID TORCH AND BEING SELF-CLOSABLE ON CESSATION OF SAID GAS FLOW THROUGH SAID TORCH AND CLOSING IN RESPONSE TO REVERSAL OF THE DIRECTION OF FLOW OF THE GAS MIXTURE THROUGH THE TORCH ON FLASHBACK.