Method for forming joints in tubes

Claim 1

IN A METHOD OF FORMING A PLURALITY OF FLUID TIGHT JOINTS SIMULTANEOUSLY BETWEEN A PLURALITY OF U-SHAPED TUBULAR RETURN BENDS AND A PLURALITY OF GENERALLY STRAIGHT TUBE SECTIONS EXTENDING FROM THE ENDS OF THE RETURN BEND SECTIONS WHEREIN THE ENDS OF ONE OF SAID TUBE SECTIONS IS CUP-SHAPED TO RECEIVE THE ENDS OF THE OTHER OF SAID TUBE SECTIONS SNUGLY WHILE PROVIDING CLEARANCE THEREBETWEEN AT THE OUTER ENDS OF THE CUP SECTIONS THEREON WITH RESPECT TO THE TUBE SECTIONS RECEIVED THEREIN, THE STEPS OF, PROVIDING A FLUIDIZED BED OF SEALING AGENT PARTICLES, IMMERSING THE ASSEMBLY OF THE U-SHAPED TUBULAR SECTIONS AND THE STRAIGHT TUBULAR SECTION WITHIN SAID BED WITH THE CUPPED ENDS EXTREMELY UPWARDLY, HOLDING THE ASSEMBLIES IN SAID FLUIDIZED BED FOR A PREDETERMINED PERIOD OF TIME UNTIL THE CLEARANCE PORTIONS OF SAID CUP ENDS ARE FILLED WITH SAID PARTICLES REMOVING THE ASSEMBLY FROM SAID BED, HEATING THE ASSEMBLY TO MELT SAID PARTICLES AND COOLING SAID PARTICLES TO PRODUCE A FLUID TIGHT SEAL AT THE JOINTS BETWEEN THE TUBE SECTIONS.