Apparatus for making double walled tube

Claim 1

A MECHANISM FOR EXTRUDING A MULTI-WALL SHEET HAVING FASTENER ELEMENTS AT ITS EDGES AND ADAPTED TO BE ROLLED INTO A TUBE, THE MECHANISM COMPRISING MEANS DEFINING AN EXTRUSION CHAMBER, A CENTRAL DIE MEMBER HAVING A DIE WALL WITH AN ELONGATED DIE OPENING THEREIN RECEIVING EXTRUDATE FROM THE CHAMBER AND PROVIDE WITH UPPER AND LOWER EDGES DEFINING OUTER WALL SURFACES OF THE SHEET AND SIDE EDGES, EDGE DIE MEMBERS BESIDE THE CENTRAL DIE MEMBER HAVING OPENING DEFINING THE OUTER SURFACES OF LINKING PORTIONS JOINED TO THE SHEET FORMED BY THE CENTRAL DIE MEMBER FOR JOINING THE WALLS OF THE SHEET, A PLATE MEMBER SUPPORTED IN SAID DIE OPENING OF THE CENTRAL DIE MEMBER AND CONSTITUTING A MANDREL HAVING OUTER SURFACES FOR DEFINING THE INNER SURFACES OF THE SHEET WALLS, MEANS FOR ADJUSTABLY SUPPORTING SAID PLATE MEMBER FOR ADJUSTING ITS POSITION RELATIVE TO SAID OPENING OF THE CENTRAL DIE MEMBER SO THAT THE THICKNESS OF SAID WALLS CAN BE SIMULTANEOUSLY CHANGED, AND MEANS FOR FORCING PLASTIC MATERIAL INTO SAID CHAMBER AND THROUGH THE DIE OPENINGS.