| 摘要 |
1,213,200. Sheet forming BORG-WARNER CORP. 27 March, 1968 [10 April, 1967], No. 14681/68. Heading B5A. In a process for cold drawing hollow articles from plastics sheet material, the sheet is initially peripherally clamped under a first pressure and, during the drawing operation, the pressure is reduced to a lower value. This prevents wrinkling and fraying of the lip of the article and increases its dimensional stability. In the described embodiment, the sheet is drawn between co-operating male and female dies 16 and 32 and is initially applied by the female die against an annular draw pad 26 having an outer peripheral ridge 40. In operation, the sheet is initially clamped against the ridge by forward movement of the female mould, further movement of the mould causing the sheet to be drawn over the male mould. At a predetermined instance during the drawing stroke, the sheet is completely drawn off the ridge into the larger gap adjacent thereto thus causing the desired decrease in clamping pressure on the sheet. |
