Patent GB-763153-A (GB)
Title: Improvements in or relating to precision grinding machines
IPC: B24B47/20
Filed: 1954-11-10
Abstract: 763,153. Grinding machines. CINCINNATI MILLING MACHINE CO. Nov. 10, 1954 [Nov. 13, 1953], No. 32524/54. Class 60 [Also in Group XXIX] A grinding machine includes a bed 15, Fig. 1, a grinding wheel slide 22, Fig. 2, movable on the bed, a wheel driving motor carried by the slide, a hydraulic motor 47 for effecting feeding movement of the slide and actuating means electrically responsive to load fluctuation of the wheel driving motor to determine the rate of operation of the hydraulic 'motor 47. The hydraulic circuit is fed by a pump 41 from a reservoir 39 and is provided with a pressure relief valve 43 and a low pressure valve 46 in a return conduit 45. When a start-stop valve 55<SP>1</SP> is moved by a handle T to the left pressure fluid from the supply conduit 42 closes the switch 58 which energizes the solenoids A, B, C and D to operate spring loaded valves 69, 70, 71 and 72. The valve 72 couples the pressure conduit 42 through a valve 76 to a piston 29 which moves the wheel head 22 to the left. At the same time, the left-hand end of a piston 25 is connected to the exhaust conduit 45 by the valve 72 and conduit 77. As the piston 29 moves to the left a dog 80 shifts the valve 76 which then throttles the supply to the piston 29 so that the latter is supplied through a choke coil 84 to reduce the rate of infeed of the head 22. After the movement of the piston 29 has been arrested by the cylinder head, pressure builds up in the conduit 74 to open check valve 86<SP>1</SP> and thereby allow fluid to flow through valve 89 and conduits 87, 89 to the intake of the motor 47, the exhaust from the motor taking place through conduits 90 and 45 and fast and fine feed valves 61, 97 the setting of which determines the feed rate. The motor 47 drives the wheel head 22 through toothed and worm gearing and a feed screw 31. Conduit 90 is also connected to the exhaust conduit 45 through a valve 102, the valve 121 actuated by a solenoid 123 energized by a switch 128, and a variable throttle valve 108 which is controlled by fluctuations in the power required by the grinding wheel motor 110. With the head 22 retracted the switch 128 is open whilst switch 126, Fig. 5. to the solenoid 123 is closed. As the head advances the switch 128 is closed and the solenoid 123 energized. A transformer 115 inductively coupled with one of the supply leads to the grinding wheel driving motor energizes the relay 127 as the load on motor builds up and opens the switch 126 which de-energizes the solenoid 123 so that the valve 102 is moved by a spring 105 to prevent flow through the throttle 108. The rate of infeed is thus reduced since the wheel head is controlled by throttles 61 and 97 only. The electrical circuit may be arranged to prevent recurrence of the fast approach feed once the latter has been interrupted or to isolate the solenoid 123 from the relay 127 once it has been energized. A by-pass valve 62 is automatically operated to permit the motor 47 to speedup during reversal. Alternatively, the valve 102 may be modified and operated automatically from the electric circuit to permit rapid reverse movement of the motor 47. The work-piece 21 is supported between a tail stock 18 and a driven headstock 17 mounted on a traversable table 16.