GB928260A - Improvements in or relating to deep drawing presses - Google Patents

Abstract

928,260. Cupping. SZERSZAMGEPFEJLESZTO INTEZET. April 6, 1962, No. 13370/62. Class 83 (4). An hydraulic deep drawing press has pistons which exert a rim gripping force on a workpiece, said pistons being operatively associated with a deep drawing piston for movement in a common hydraulic chamber, the arrangement being such that in operation the hydraulic pressure generated in said chamber acts upon said deepdrawing piston and at the same time upon the said first mentioned pistons in order to develop a rim gripping force to act on the workpiece. The deep drawing tool 1 is carried by a piston 9 operating in an hydraulic chamber 8 of the press. Pistons 12 mounted in the chamber 8 and passing through the piston 9 operate a rim gripping disc 2 to press a gripping ring 16 against the rim of a workpiece 15. Oil pressure in chamber 8 acts on all the pistons and oil pressure in a chamber 10 surrounding the pistons 12 acts on a portion of the under-surface of the piston 9 and also on rings 11 accommodated on the pistons 12. Thus the pressure on pistons 12 is increased by the pressure in chamber 10. The oil can leave the chamber 10 via a valve 7 into an oil reservoir 4 via a reversing valve 5. On the return movement of the press the oil fed by a pump 3 flows through the reversed valve 5 and a check valve 6, the chamber 8 being connected to the reservoir via the valve 5. In a modification instead of the valve 7 the oil flow is divided into two branches, one branch having a restricted bore for delivering only high pressure oil and the other branch having means for adjusting its internal cross-section so that the oil pressure can be regulated. When the tool engages the workpiece the adjustable branch is closed so that the pressure in chamber 10 increases strongly as the deep drawing commences and provides a given initial rim gripping force. As the pressure in chamber 8 rises the adjustable means are opened automatically by the increased pressure to allow the oil to flow out of the chamber 10 via the larger adjustable branch to the oil reservoir.