Roll-fed thermoforming machine

Claim 1

AN INDEXING ATTACHMENT FOR ADVANCING SECTION-BYSECTION A THERMOPLASTIC WEB FROM A SUPPLY ROLL THROUGH THE FORMING STATION OF A THERMOFORMING MACHINE HAVING A CLAMPING FRAME TO HOLD THE WEB AT SAID FORMING STATION, SAID ATTACHMENT COMPRISING MEANS ATTACHABLE TO ONE END OF THE MACHINE FOR SUPPORTING THE SUPPLY ROLL AND GUIDING THE WEB THEREFROM TO THE FORMING STATION AND SAID CLAMPING FRAME; A FRAME ATTACHABLE TO THE DELIVERY END OF THE MACHINE; A DELIVERY TABLE ON THE FRAME TO RECEIVE THE FORMED LEADING END OF THE WEB; A GRIPPER CARRIAGE MOUNTED ON THE FRAME TO TRAVEL ALONG THE LATTER; WEB-GRIPPING MEANS MOUNTED ON THE CARRIAGE AND MOVABLE TO ENGAGE AND DISENGAGE THE WEB BETWEEN FORMED SECTIONS THEREOF; MEANS FOR RECIPROCATING THE CARRIAGE THROUGH A SECTIONLENGTH DISTANCE; MEANS CAUSING THE GRIPPING MEANS TO ENGAGE THE WEB BETWEEN SAID SECTION-LENGTHS WHEN THE CARRIAGE IS IN RETRACTED POSITION WHILE THE CLAMPING FRAME ENGAGES AND HOLDS THE WEB AT THE FORMING STATION; MEANS FOR CAUSING THE CARRIAGE TO ADVANCE ONE SECTION-LENGTH WHEN THE FORMING OPERATION HAS BEEN COMPLETED AND THE CLAMPING FRAME DISENGAGES THE WEB TO BRING A FRESH PORTION OF THE WEB TO THE FORMING STATION, SAID MEANS FOR SUPPORTING THE SUPPLY ROLL AND GUIDING THE WEB TO THE FORMING STATION COMPRISING MEANS FOR MAINTAINING AS UNIFORM DRAG ON THE PORTION OF THE WEB BETWEEN SAID SUPPLY ROLL AND THE WEB-GRIPPING MEANS ON SAID CARRIAGE AS THE WEB IS ADVANCED A SECTION-LENGTH BY THE ADVANCING MOVEMENT OF THE CARRIAGE AND THEREBY CONTROL THE TAUTNESS OF THE SECTION OF THE WEB BETWEEN THE SUPPLY ROLL AND THE GRIPPING MEANS ON THE CARRIAGE; MEANS FOR CAUSING THE CLAMPING FRAME TO REENGAGE THE WEB; AND MEANS FOR CAUSING THE GRIPPING MEANS ON THE CARRIAGE TO DISENGAGE THE WEB AND THE CARRIAGE TO BE RETRACTED ONE SECTIONLENGTH.