Film-surface welding backup tape

Claim 1

IN A WELDING BACKUP TAPE OF THE TYPE IN WHICH AN ELONGATED HEAT-RESISTANT FLEXIBLE TAPE BACKING OF GLASS CLOTH, METAL FOIL OR THE LIKE IS COATED WITH A PRESSURE-SENSITIVE ADHESIVE AND PROVIDED WITH, MEDIALLY ADHERED AONG THE LENGTH THEREOF, A STRIP OF FLEXIBLE REFRACTORY MATERIAL COMPRISING REFRACTORY PARTICLES HELD TOGETHER BY A FLEXIBLE BINDER, THE IMPROVEMENT WHICH COMPRISES, DISPOSED ON THE SURFACE OF SAID REFRACTORY STRIP OPPOSITE SAID BACKING, A THIN TACKY LAYER OF FILM-FORMING ADHESIVE WHICH US CURABLE WHEN HEATED TO ABOUT 150*C. OR MORE FOR EXTENDED PERIDOS, AND A MONOLAYER OF INORGANIC PARTICLES PROTECTIVELY COVERING THE EXPOSED SURFACE OF THE TACKY ADHESIVE LAYER TO PERMIT EASY ROLLING AND UNROLLING OF THE TAPE, WHEREBY WHEN SAID TAPE IS APPLIED OVER ONE SIDE OF A JOINT TO BE WELDED AND PREHEATED TO TEMPERATURE ABOVE ABOUT 150*C. THE HEAT HARDENABLE FILM WILL RETAIN SAID REFRACTORY PARTICLES IN POSITION, AND SAID INORGANIC PARTICLES WILL FORM A SMOOTH GLAZE DURING WELDING, INSURING A SMOOTH, SOUND WELD.