Patent GB-771001-A (GB)
Title: Hydraulic press
IPC: B21D22/12
Filed: 1954-05-05
Abstract: 771,001. Stamping. YATES, G. May 5, 1954 [May 25, 1953], No. 13102/54, Class 83 (4). [Also in Group XXIX] A stamping press comprises a frame, a bed member supporting a forming die, a reciprocable forming head having a cavity across which is disposed a flexible diaphragm, means for applying fluid pressure to said cavity to force said diaphragm toward said bed member and means for releasably holding said head against said bed member while fluid pressure is applied to said cavity. A press bed 12 and cross-beam 13 are mounted on vertical support-members 10 and 11. Intermediate the bed and cross-beam a forming head 20 is reciprocable on-guide rails 21 and 24. Keys 26 on the head 20 ride in the guideways 28 (Fig. 6) to maintain alignment of the head 20. Flexible chains 30 engaging and attached to lifting sprockets 34 on two pairs of shafts 36 support and reciprocate the head 20. Slack is provided in the chains to ensure that the head rests upon the bed 12 when fully lowered. The stub shafts 36 are uniformly rotated to raise or lower the head by drive gears 40, each pair of which mesh with a double-faced rack 41 reciprocated by pistons 46 in hydraulic cylinders 47 pivotally mounted on the members 10 and 11. Hold-down means for the head 20 includes a pair of parallel shafts 50, one mounted between each pair of stub shafts 36 and secured thereto by a conical press jib (Fig. 4). The shafts 50 are supported in bearing hangers 53 depending from the beam 13. Hold-down arms 56 are secured to the shafts 50 and arranged so that they are raised and lowered with the head 20 by means of the chains 30. The angular disposition of the arms on the shafts is such that they do not engage the head until it is seated by weight on the bed 12 and the chains begin to slacken. The curved outer ends of the arms engage curved blocks 59 on the head. The bed 12 is surmounted by a fixed platen 60 on which rests the forming die 61. The head 20 has a pressure chamber 63 which can be supplied with pressure fluid from a conduit 64. A tapered bead 67 on the head co-operates with a complementary groove 68 in the bed to ensure accurate registration of the head in its lowered position. The side wall of the cavity terminates in a peripheral lip 71. The cupped diaphragm 80 has a sealing flange 84 and a marginal flange 86 which receives the lip 71 in a recess 87 to retain and seal the diaphragm to the chamber mouth. A frame 88 bolted to the head clamps the flange 86 to the head. To prevent cold flow of the diaphragm between the head 20 platen 60 or around the frame 88 a floating angle frame 90 (Fig. 13) is vertically adjustably secured within the fixed frame 88. The press is actuated by an electro-hydraulic system comprising a motor 100 driving a high fluid-pressure pump 101, a low-pressure pump 102 and an intermediate pressure pump 103, the motor being controlled by a switch S (Fig. 15). Fluid from a reservoir 104 is discharged from the pumps to regulator valves 111, 112 and 113. The low-pressure valve 112 supplies fluid to the cylinder control valve housing 118 via a check-valve 120 and also to the chamber C in the head 20, via a relief valve 121, a check-valve 121<SP>1</SP> and a valve chamber 123. High pressure for the forming operation may also be supplied to the valve chamber 123 from regulator valve 111. From the valve housing 118 conduits lead to the top and bottom of the cylinders 47 and also to the valve chamber 123 and the reservoir. The electrical system includes a second control switch 140 for energizing a secondary circuit when the motor has been switched on. This secondary switch controls four solenoid-operated safety detents 142 which extend beneath the head 20 and also a solenoid 150 which locks the cylinder control valve 200 in the head lowering position. The secondary circuit also includes solenoid-operated safety devices for releasably locking the valve 123 and also the control valve 200 in the head raising position to ensure that the operations occur in their proper sequence.