| 摘要 |
895,704. Extruding thermoplastic tubes. METAL BOX CO. Ltd. Sept. 5, 1960 [Nov. 6, 1959], No. 37739/59. Class 87(2). An extruded tube of molten thermoplastic material, e.g. polyethylene, is chilled by directing cooling air towards its external surface and causing oscillation of the air about the axis of the tube. For this purpose an annular element 4 is supported in close relation with an extrusion head 3 by means of a fixed annular support 5 on which are mounted rollers 6. The annular element 4 is hollow and connected by flexible couplings 7 with a source of cooling air, e.g. refrigerated air, an annular jet-forming channel 8 extending from the interior of the element to its inner face at such an inclination as to direct the cooling air towards the extruded tube 1 in the direction of its movement. A reversible electric motor (not shown) drives a pinion which meshes with the gear teeth 9 around the periphery of the annular element 4 and operation of the motor to cause oscillation of the element 4 is controlled by a trip means comprising a cam 12 projecting from the element 4 to effect operation of one or other of two switches 13. The distance between the switches 13 determines the angle of oscillation of the element 4. With good air flow conditions, an oscillation through 30 degrees may be sufficient but, in some circumstances, this may have to be increased to 180 degrees in order to produce optimum results. The optimum results are obtained when the direction of movement is reversed every 15 to 90 seconds. |
