Patent GB-817020-A (GB)
Title: Method and apparatus for the production of gusseted tubing
IPC: B29C48/10
Filed: 1957-03-28
Abstract: 817,020. Making tubes. UNION CARBIDE CORPORATION. March 28, 1957 [April 18, 1956], No. 10149/57. Class 99(2). [Also in Group VIII] A method of producing tubing from thermoplastic materials comprises the steps of forming flattened tubing having gusseted sides and an overlapping seam, and forming a number of continuous heat seals between the overlapping seam portions, the seals being disposed parallel to the longitudinal axis of the tubing. As shown, the annular die 14 of an extruder 12 forms a seamless tube 16 which is inflated by air and withdrawn in a vertical direction from the die by rotatable squeeze rolls 18, 20 either or both of which are driven, the two-ply ribbon 32 resulting from the collapsing action of the rolls then being conveyed over a roller 34 to a number of blades 38 which slit the ribbon into two-ply strips of predetermined width ; the blades are secured in holders 36 mounted on a shaft 40 and are adjustable transversely of the path of travel of the ribbon. The individual strips 42, 44 are separated by a guide roll 50 and the series of strips 44 travel downwardly while the series of strips 42 move laterally to engage a roll 52; each strip then passes to tube-forming means 54 comprising a former plate 56 and cooperating gusset-forming blades 60. Following the formation of each strip into a gusseted tube, the overlapping seam portions 58 of each strip are engaged by heat-sealing units 64 whereby the overlapping edges of the strips are sealed. The heat-sealing units 64, of brass, aluminium or stainless steel, have a longitudinal aperture 66 for reception of a heating element 68 whereby the temperature of the unit is regulated, and at least two integral, projecting members 70 of arcuate configuration coated with a tetrafluoroethylene resin to reduce friction between the members and the strips. Each unit is secured by bolts 77 to a mounting 69 attached to a support channel 65 by a bolt 67 screwed into the mounting and passing through a traversing slot in the channel; tension between the unit and the channel is assured by a spring 63, and adjusting means in the form of a turn-buckle 85 enables the distance between the members 70 and the former plate 56 and the resulting arc of contact between the members and the thermoplastic strips to be regulated. An aperture 72 is provided in the tube-forming plate 56 at the location of the unit 64, or the surface 71 of the plate is relieved. Upon emergence from the tube-forming means 54, the gusseted tubes pass between rollers 86, 88 and in the collapsed state thereof are wound upon reels 94, 96. The thermoplastic materials of which the tubes are made may be polyethylene, cellulose acetate, cellulose acetate butyrate, ethyl cellulose, methyl methacrylate polymer, nylon, polystyrene, polyvinyl formal-acetate butyral, copolymers of vinyl chloride and vinyl acetate such as Vinylite (Registered Trade Mark), polyvinyl chloride such as Geon (Registered Trade Mark) or copolymers of vinyl chloride and vinylidene chloride such as Saran (Registered Trade Mark). The properties of these materials may be modified by the incorporation therein of plasticizers, fillers, colouring agents, heat stabilizers or anti-oxidants.