| 摘要 |
862,967. Apparatus for making films. DOW CHEMICAL CO. June 28, 1957 [July 11, 1956], No. 3438/60. Divided out of 862,966. Class 2(2). A guide ring for use in the trapped bubble process for making thermoplastic film, in association with a tube-forming plastics extruder 10 and a pair of pinch rolls 11 disposed with their nip centred transversely on the extrusion centre-line, comprises a hollow metal ring of internal diameter greater than that of the orifice of the tube-forming extruder but smaller than that of an inflated film tube 14 to be produced in the apparatus, said ring having a smooth surface where the inflated film tube is contacted, e.g. bead 19, and being provided with means 17, 18 for internally cooling the ring, the ring being mounted coaxially with the tube-forming extrusion die and spaced a short distance therefrom. Preferably, the ring has a circumferential strip 21 of absorptive material disposed adjacent to the smooth contacting surface. |
