Patent GB-671547-A (GB)
Title: Improvements relating to presses
IPC: B30B15/24
Filed: 1949-12-13
Abstract: 671,547. Angular bending. TRIGGS, W. W. (Pacific Industrial Manufacturing Co.). Dec. 13, 1949, No. 31943/49. Class 83 (iv). [Also in Groups XXIX and XXXV] In a machine wherein a pair of co-operating members of substantial width are brought toward each other to perform an operation of said machine, one of said members having a piston at each end to drive the same, a hydraulic system comprising a pump, a cylinder enclosing one of said pistons, a liquid circuit between said pump and cylinder, and a pump driving motor in drive connection to the pump of each hydraulic system is provided with equalizing means responsive to the relative advance of any one of said pistons during movement of said member for effectively disconnecting operating pressure from the associated cylinder, said means including a low-resistance passageway by-passing said cylinder, and a normally closed valve blocking said passageway and adapted for instantaneous opening upon occurrence of the relative advance of such piston. Side-plates 1, 3 are connected to a fixed blade 7 and have a movable blade 13 slidably mounted above the blade 7. A double-acting hydraulic cylinder 15 is secured to each plate 1, 3 and each piston-rod 19 is connected to the blade 13 by links 23 pivoted on arms 21 pivoted to the side-plates 1, 3. Each cylinder 15 is independently supplied with liquid from pumps 25 driven by a common motor 59, through reversing valves 33 operated by solenoids 57, 55, Fig. 3. By-pass valves 63 operated by solenoids 65 are connected between the outlets of the pump and tanks 27. A switch mechanism 79 comprising two microswitches 69, 70 is connected at one end by a spring 81 to the blade 7 and at the other end by a wire 83 to one end of the blade 13. A switch actuator 89 having an actuating arm 87 between the switches 69, 70 is connected to the blade 7 by a spring 91 and at the other end by a wire 93 to the opposite end of the blade 13. Relative movement of the switch mechanism 79 and the actuator 89 operates one or other of the switches 69, 70 each of which is connected through reversing means 99 with one of the solenoids 65 which opens one of the valves 63 to by-pass pressure liquid from that cylinder which has caused greater movement of the blade 13. Reversing valves 33 controlled by up solenoids 55 and down solenoids 57 are normally positioned to by-pass the outputs of the pumps to the tanks. The solenoids 55 are controlled by a solenoid switch 127, Fig. 4, in circuit with one switch 109 of a pair of limit switches 107, 109 mounted on one of the side-plates 1, 3 and actuated by stops 117 mounted on the blade 13. When the blade reaches the upper limit the switch 109 is opened and the solenoid 55 deenergized. Downward movement is controlled by a pedal 101 which energizes the solenoids 57 and disconnects the solenoid 127. The blade descends until switch 107 is closed to energize a solenoid switch 153 one side of which energizes solenoid 55 for upward movement again through switch 109, the other side provides a holding circuit for solenoid 153 since switch 107 opens when the blade commences to rise. Switch 109 again opens the circuit to solenoid 55 when the blade reaches the upper limit.