| 摘要 |
1,229,218. Sheet forming. BRITISH PETROLEUM CO. Ltd. 29 Oct., 1968 [13 Nov., 1967], No. 51491/67. Heading B5A. Containers such as egg-boxes are made from, for example, foamed polystyrene sheet material by co-operating male and female mould halves, one of which carries retractable projections adapted to engage in recesses carried by the outer half to form undercuts in the finished article. As shown in the Figure, part 2 of the female mould 1, 2 is provided with four projections 6 (only one of which is shown) each of which is carried by the vertical arm of an L- shaped lever 7, the horizontal arm of which is attached to a common rod 8 rotatably mounted at either end 9 in the end wall of the mould. The horizontal arms of the levers 7 engage a vertically slidable striker plate 10 the upper edge of which projects beyond the upper surface of the mould. The striker plate is biased upwardly by a compression spring so that the levers are normally pivoted clockwise and the projections are in their withdrawn inoperative positions. The parts of the male half of the mould which co-operate with the projections each consist of a correspondingly shaped recess 24 the lower surface of which is defined by a swingable tongue 23 biased by counterweight 25 to its horizontal operative position. In operation the male half of the mould is forwarded into the female half and at the appropriate point in its stroke the plate 10 is depressed to cause the levers 7 to pivot anti-clockwise to bring the projections to their forward operative position within the recesses of the male mould half. After forming, as the male half is withdrawn, the striker plate rises under the action of the spring and the projections are again withdrawn. Also, the part of the article which is retained by the female half engaging the tongue 23 causes the tongue to pivot downwardly to the position shown in Fig. 5 thereby releasing the male half from the article to allow continued upward movement of the male half. |
