Process and device for the production of a multiply tube and bag manufactured from such tube

Claim 1

A PROCESS FOR THE CONTINUOUS PRODUCTION OF A MULTIPLY TUBE OF PAPER OR THE LIKE, WITH AN INNER PLY HAVING A GREATER ABSOLUTE LENGTH THAN ITS APPARENT LENGTH AND ONE OR MORE OUTER PLIES HAVING A LENGTH CORRESPONDING TO THE APPARENT LENGTH OF THE INNER PLY, COMPRISING THE STEPS OF USING A PREFORMED FLAT TUBE TO CONSTITUTE THE INNER PLY, IMPARTING A SPEED OF FORWARD MOVEMENT TO SAID FLAT TUBE, PRODUCING PERMANENT TRANSVERSE UNDULATIONS TO SAID FLAT TUBE, THEREBY TO GIVE IT A SMALLER APPARENT LENGTH THAN ITS ABSOLUTE LENGTH, SURROUNDING THE THUS OBTAINED UNDULATED TUBE WITH OUTER PLIES AND LONGITUDINALLY CLOSING SAID OUTER PLIES AND LONGITUDINALLY CLOSING SAID AND SIMULTANEOUSLY MOVING FORWARD THE ASSEMBLY OF INNER AND OUTER PLIES OF THE SO OBTAINED MULTIPLY TUBE AT A SPEED SUCH THAT THE RATION BETWEEN THE LATTER SPEED AND SAID SPEED IMPARTED TO SAID FLAT TUBE SUBSTANTIALLY CORRESPONDS TO THE RATION BETWEEN SAID APPARENT LENGTH AND SAID ABSOLUTE LENGTH.