Method and apparatus for making thermoplastic film seams

Claim 1

APPARATUS FOR THERMALLY SEALING FILLED BAGS OF THERMOPLASTIC MATERIAL COMPRISING AN ENDLESS CONVEYOR BELT FOR CONVEYING FILLED BAGS ALONG A PREDETERMINED PATH; MEANS TO OPERATE SAID CONVEYOR BELT; A PAIR OF ENDLESS BELTS POSITIONED SO AS TO GRIP THE OPEN TOPS OF BAGS TRAVELING ON SAID CONVEYOR BELT AND PRESS THE SIDES OF THE OPEN TOPS OF THE BAGS TOGETHER WITH THE EDGE PORTIONS TO BE SEALED EXTENDING BEYOND THE BELTS; A RADIANT HEATING ELEMENT COMPRISING A CONTINUOUS LENGTH OF FLAT RIBBON OF UNINSULATED RESISTENCE METAL FOLDED IN A SERIES OF REVERSE TURNS AND ELONGATED PORTIONS, SAID ELONGATED PORTIONS BEING CURVED TO FORM A CONFIGURATION DEFINED AS A SECTOR OF A HOLLOW RIGHT CIRCULAR CYLINDER HAVING AN ARC OF ABOUT 130* TO 180* WHEREIN SAID ELONGATED PORTIONS OF SAID HEATING ELEMENT ARE SUBSTANTIALLY PERPENDICULAR TO THE LONGITUDINAL AXIS OF SAID SECTOR OF SAID CYLINDER; MEANS TO POSITION SAID HEATING ELEMENT SO THAT THE EDGE PORTIONS OF THE OPEN ENDS OF THE BAGS PASS WITHIN THE ARC OF SAID HEATING ELEMENT AND SPACED FROM SAID HEATING ELEMENT, MEANS TO SUPPLY ELECTRICAL ENERGY TO SAID HEATING ELEMENT; MEANS DIRECTLY BELOW SAID HEATING ELEMENT TO COOL THE SIDES OF THE BAGS WHICH ARE CONFINED BY THE PAIR OF ENDLESS BELTS; AND MEANS TO COOL THE HEAD FORMED BY FUSING THE EDGE PORTIONS OF THE BAG SIDES SPACED FROM SAID HEATING ELEMENT ALONG SAID PREDETERMINED PATH.