| 摘要 |
1,006,046. Producing tubular films. CANADIAN INDUSTRIES Ltd. Aug. 4, 1964 [Aug. 17, 1963], No. 31607/64. Drawings to Specification. Heading B5B. In the production of tubular film which when flattened by passage through the nip of a pair of squeeze rolls forms a doubled ribbon or " layflat " tubular film of predetermined width by melt-extruding a thermoplastic material such as polyethylene through the annular extrusion orifice of a die to form a seamless tubing continuously withdrawing and flattening the tubing at a predetermined distance from the extrusion orifice and maintaining a constant continuous bubble of a gas in the section of the tubing extending between the extrusion orifice and the line of flattening, the quantity of gas constituting the bubble being such as to inflate the tubing while it is in the formative plastic state, the inflated tubing is passed in the unset condition through a sizing means coaxial with the extrusion orifice and being either an annulus or of annular cross-section, located on or beyond the front-line from the extrusion orifice, said sizing means contacting the tubing so as to simultaneously chill it to the set condition and control its diameter to give tubular film of said predetermined width when converted to a layflat form. The tubing may be cooled to an extent insufficient to bring it to the set condition before it is passed through the sizing means by an external air flow directed on to and around the tubing in the vicinity of the extrusion orifice. The rate of air flow may be adjusted to position the frontline of the tubing so that the sizing means lies on or slightly beyond it in the direction of travel of the tubing. The sizing means may consist of at least one turn of tubing in the form of a helix or a jacketed cylinder through the jacket of which a cooling medium is circulated. When the sizing means consists of one turn of tubing (through which a liquid cooling medium is circulated), the tubing may be circumferentially adjustable in contact with the outer surface of the inflated tubing, the distance between two plates or lugs mounted on the two arms of the helix being adjustable by means of a turn screw. |
