Method and apparatus of fusing a coating to a metal surface

Claim 1

IN THE METHOD OF MAKING A GLASS COATED TUBULAR MEMBER, THE IMPROVEMENT COMPRISING RESISTANCE PREHEATING THE TUBULAR MEMBER WITH GLASS TUBE DISPOSED THEREIN BY PASSING AN ELECTRIC CURRENT THROUGH THE TUBULAR MEMBER, MAINTAINING THE TEMPERATURE OF SAID GLASS TUBE AT A TEMPERATURE APPROACHING BUT BELOW ITS FUSING TEMPERATURE, SIMULTANEOUSLY PROVIDING SUPPLEMENTAL HEAT TO SUCCESSIVE LOCALIZED PORTIONS OF SAID TUBULAR MEMBER BY INDUCING HEAT IN THE TUBULAR MEMBER BY BRINGING THE TUBULAR MEMBER INTO A HIGH FREQUENCY MAGNETIC FIELD THEREBY INCREASING THE TEMPERATURE OF THE TUBULAR MEMBER PROGRESSIVELY TO THE FUSION TEMPERATURE OF THE GLASS TUBE, APPLYING A VACCUUM BETWEEN THE GLASS TUBE AND THE TUBULAR MEMBER TO MOVE THE GLASS TUBE PROGRESSIVELY OUTWARDLY INTO FIRM ENGAGEMENT WITH THE TUBULAR MEMBER AS THE TUBE IS HEATED TO A PLASTIC CONDITION BY THE SUPPLEMENTAL HEAT INDUCED THEREIN TO BOND THE GLASS TUBE TO SAID TUBULAR MEMBER AND REMOVE ALL AIR AND GASES FROM THE BONDING AREA, AND POST HEATING SAID GLASS COATED TUBULAR MEMBER BY PASSING AN ELECTRIC CURRENT THERETHROUGH FOR A PREDETERMINED TIME TO SLOWLY COOL THE GLASS COATED METAL MEMBER WHEREBY CRACKING OF THE GLASS FROM THE TUBULAR MEMBER IS ELIMINATED.