Patent GB-545495-A (GB)
Title: Improvements in metal bending machines
IPC: B21D5/02
Filed: 1940-04-01
Abstract: 545,495. Mechanism for starting and stopping machinery. BLISS CO., E. W. April 1, 1940. No. 5830. Convention date, March 31, 1839. [Class 80 (ii)] [Also in Groups XXII and XXVI] In a metal bending machine having a frame carrying a ram, provide with a movable tool holder and operated by power through a clutch, power operated means are provided 'to engage the clutch and manual means auxiliary to the power means are also provided to engage the clutch independently of the power means. The frame consists of end plates 20, 21 bolted to a support and connected by an angle iron 32. The plates have outwardly extending shoulders 24 to receive the recessed ends of the bed 25 and shock absorbing steel strips 26. The bed is fixed to the plates by bolts 28 and also by triangular bracing pieces 30. The movable die is carried by a ram 35 reciprocated on guides 34, Fig. 3, carried by the plates 20, 21, the ram being operated by eccentrics 50 and pitmans 49, Fig. 7, which are positioned so as to transmit the thrust in the plane of the plates so as to avoid deformation of the plates. The eccentrics shafts 55 are mounted in bifurcated supports 52 secured in recesses in the plates 20, 21. The shafts 55 are each provided with gears 57 driven from a shaft 65, which is geared to a shaft 70, Figs. 3 and 6, that may be clutched to a pulley 77 driven by a belt from a motor 80. The limits of the strokes of the ram may be varied by using pitman rods in two parts, the lower part 40, Fig. 7, having a ball end and being screw adjusted in the upper part 45 by worm gear 63 from a shaft 62 driven by a motor 60 carried by the ram. The shaft 70 is mounted at one end in a bearing 105, which is removable from the shaft 70 and frame 20 so that a new belt may be inserted through the frame when necessary, the pulley 77 resting on an adjustable stud 107 after removal of the bearing The clutch consists of a hub 82, Fig. 6, keyed to the shaft 70 and carrying a flange 118 and a spring retracted disc 84 between which an axially movable friction disc 110 mounted on the pulley may be held by pins 94 engaging pistons 90 operated by oil supplied by a pump 125, Figs. 3 and 10, through a fixed pipe 102 and axial passage 95. When the oil pressure is released the springs 87 retract the disc 84 so that the disc 84 together with an adjustable disc 115 engage a brake disc 114 axially movable on the clutch housing 112. The pump piston 135, Fig. 10, which is normally held upward by a spring 137 is pushed down by a cam 140 on a shaft 130 driven by a motor 127 which becomes stalled when it has turned the cam far enough to apply a fluid measure equal to the power of the motor. The pump housing communicates by a port 183 with the pipe 150 when the piston is raised and also communicates with the pipe 150 direct via check valve 184, and through pipes 187 and 177 via check valves 188 and 175. The pipe 177 is in communication with a high pressure pump to increase the operating pressure on the clutch immediately after the drive has been established. The pump consists of a two-part piston 162, 164 connected together by an adjustable bolt 167 and operated by a cam 158 on one of the shafts 55. A safety mechanism is provided to prevent application of an unsafe pressure to the fluid system. This consists of separating the parts 162, 164 by a spring 165 of predetermined strength to be compressed when the highest desired operating pressure is attained. The operation is started by a pedal lever 190, Fig. 3, which operates an adjustable plunger to close a switch 200, Fig. 9, which thus energizes a solenoid to close a switch 207 and thus operate the combined clutch motor 127a and magnetic brake 127b. The clutch mechanism is thus engaged through the cam 140 and piston. When the pedal is released the switch 200 opens and a spring operates the brake 127b to hold the cam in position with the clutch in operation. If the clutch is to be disengaged after one cycle a limit switch 212 is closed by a lug 214 on the pitman to energize a solenoid to close the switch 208 and thus reverse the motor 127. The inertia of the parts causes the ram and pitman to position the electric circuit again for operation through a second cycle, the switches 212, 208 being opened again. A limit switch 213 is also opened by an adjustable arm on the shaft 130 so as to release the reversing switch 208 if the switch 212 does not open. For continuous working a hand switch 215 in the circuit of the reversing solenoid is left permanently open. A manual emergency switch 217 is also provided which may be pressed down to engage the lower contacts to reverse the motor 127 and release the clutch at will. To prevent undue stressing of the end plates 20, 21 the plates have pinned at 226, Fig. 3, to their lower portions straps 225 passing through guides 228 and carrying brackets provided with sensitive limit switches 220 and 222, which are closed by engagement with adjustable stops 232, Fig. 12, to reverse the motor and so release the clutch if either end plate is unduly strained. The ram may be inched by connecting the clutch by an independent hand lever 247 operating a piston 244 conected by a pipe 245 with the fluid system.