| 摘要 |
1,214,631. Extruding convoluted strip material. DUNLOP CO. Ltd. 8 May, 1968 [10 May, 1967], No. 21727/67. Heading B5A. [Also in Division B8] An extruded strip having a convoluted portion as at 40, Fig. 12, is made by extruding material, e.g. rubber, through a die orifice having a first part with bevelled leading edges and a second part which is obturated, the rate of flow through the first part thereby being greater than that through the second and the convolutions being formed by the restraining effect of material passing through the second part on that passing through the first part. The die plate of Fig. 4 has an essentially L-shaped orifice with the upstream edges of limb 19 being bevelled and an obturator 22, upstream of limb 20, being adjustable towards and away from limb 20 by rotation of bolts 23. The obturator may be angled to the die plate by rotating one of these bolts more than the other. In a modification, Figs. 8-11 (not shown), for producing the extrudate of Fig. 12, both limbs (31, 32) are bevelled, the former more so than the latter. At the junction of the limbs is an enlarged portion (35), Fig. 10 (not shown), which is masked on its upstream side by a throttle (37) attached to an obturator (36), Figs. 8, 9 (not shown). Throttle (37) is adjusted to produce an unconvoluted step portion 39, Fig. 12, which buttresses both unconvoluted limb 38, produced by material passing through die limb (32), and convoluted limb 40, produced by material passing through die limb (31). Preferred materials are vulcanizable elastomers such as natural rubber and styrene-butadiene copolymers or blends thereof. In the apparatus of Fig. 1, vulcanization takes place in a bath 7, which may contain a mixture of sodium nitrate and sodium nitrite, and the vulcanized product is washed with warm water in a bath 11. Other methods of vulcanization or curing mentioned are heating by use of heated liquids such as glycol, heated gases such as air, infra-red and micro-wave heaters and fluid bed techniques. Other materials mentioned are P.V.C., ethylene vinyl acetate copolymers and polystyrene-polyisoprene block copolymers in the use of all of which bath 7 may be dispensed with. The apparatus is particularly intended for the production of conveyer-belt edging. |
