| 摘要 |
806,687. Cupping. FAWCETT, PRESTON & CO. Ltd., and FINNEY PRESSES Ltd. April 5, 1957 [April 5, 1956], No. 10473/56. Class 83 (4). [Also in Group XXIX] A cushioning device for die cushion plates on draw presses is characterized in that downward movement of a cushion plate is resisted by substantially constant forces exerted through primary pistons or plungers in a plurality of cylinders by liquid under pressure and the liquid is maintained under a predetermined pressure by connections from the cylinders to one or more hydro-pneumatic accumulators each having a movable or elastic separating element by which the liquid is separated from nitrogen or other gas at the same pressure. The press frame comprises two upright members 1 connected by a base 2 and a head 3. A bolster 5 bears against the upper part of the base 2 and supports the lower die 24. Below the head 3 is located a pressure applying member 6 operated by hydraulic pistons 9 in cylinders 8. Stop members 7 determine the lower limit of the member 6 and rams 12 return the member to its uppermost position after the cupping operation. Six pressure-resisting control cylinders 14 are located below the bolster 5 opposite to the cylinders 8. The plungers 15 in the three front cylinders are connected to a die cushion plate 16 (Fig. 2), slidable on guides 18 and the rear plungers are connected to a similar die cushion plate 17. The die cushion plates 16, 17 may each, independently of the other, raise a blank holder through the medium of pins 19 passing through the bolster 5. In operation, the blank holding pressure between the blank holder 27 and the upper die 23 is controlled by the movement of the die cushion plate 16 downwardly against hydro-pneumatic resistance Group XXIX). |
