Gas backing blocks for welded joints

Claim 1

TUBE WELDING APPARATUS COMPRISING A PAIR OF AXIALLY SPACED INFLATABLE SEALING TUBES, GAS SUPPLY TUBE MEANS EXTENDING COAXIALLY THROUGH SAID SEALING TUBES AND HAVING A CENTRAL PASSAGE WITH AT LEAST ONE INFLATE PORT IN RESPECTIVE COMMUNICATION WITH EACH SEALING TUBE, SAID SUPPLY TUBE MEANS BEING ADAPTED FOR CONNECTION AT ONE END OF ITS CENTRAL PASSAGE TO A GAS SOURCE AND BEING CLOSED AT THE OTHER END OF SAID CENTRAL PASSAGE, SAID SUPPLY TUBE MEANS HAVING RADIALLY EXTENDING INLET PORTS AXIALLY INTERMEDIATE SAID SEALING TUBES IN COMMUNICATION WITH SAID CENTRAL PASSAGE, SAID SUPPLY TUBE MEANS DEFINING AN OUTLET PASSSAGE EXTENDING FROM A POSITION INTERMEDIATE SAID SEALING TUBES TO A POSITION DISPOSED OUTWARDLY OF ONE OF SAID SEALING TUBES, A PLURALITY OF RADIALLY EXTENDING GAS ESCAPE TUBVES SECURD TO SAID SUPPLY TUBE MEANS IN COMUNICATIOIN WITH SAID OUTLET PASSAGE, SAID ESCAPE TUBES EACH HAVING AN END OPENING DISPOSED INTERMEDIATE SAID SEALING TUBES IN LONGITUDINALLY SPACED RELATION WITH SAID INLET PORTS AND SPACED RADIALLY FROM THE AXIS OF SAID SUPPLY TUBE MEANS, FIRST VALVE MEANS FOR CONTROLLING THE RATE OF FLOW OF GAS THROUGH SAID INLET PORTS, AND SECOND VALVE MEANS FOR CONTROLLING THE RATE OF FLOW OF GAS THROUGH SAID OUTLET PASSAGE.