GB485323A - Improvements relating to precision grinding machines - Google Patents

Abstract

485,323. Grinding-machines. CHURCHILL MACHINE TOOL CO., Ltd., and JONES, J. C. April 14, 1937, No. 10584. [Class 60] In a grinding-machine having automatic infeed mechanism for the grinding-wheel, whereby the wheel is fed to a predetermined position for finishing the work and in which position it is maintained for a predetermined interval during which an electric circuit is closed, after which it is withdrawn from the work, the interval is controlled by means of a condenser, across which a voltage is built up at a controllable rate. The wheel slide a is fed through gearing d, e, f, by movement of a piston c in a cylinder to which fluid is fed through a reversing-valve b ; when the piston rod engages a plunger g in a cylinder h connected by piping h<1> to a calibrated leak-off valve i, the feed is slowed down, and as the slide reaches its final position the plunger closes the contacts k, m. These contacts are in series, across direct current mains p, q, with a condenser s, a fixed resistance t, which determines the minimum time for charging the condenser, and a variable resistance u to determine the actual time for charging the condenser. Across the condenser is placed a gas-filled impulse valve, of the neon or other type, v in series with a relay w, which is operated when the voltage across the condenser rises sufficiently to make the valve conductive. The relay closes a contact w<1> to energize a relay coil x, closing the contact x<1> to maintain the circuit of the relay coil x. The coil x also closes a contact x<2> energizing a solenoid n and thereby reversing the valve b to withdraw the grinding-wheel from the work. The relay coil x also closes a contact x<3> so as to discharge the condenser through the relay coil w ready for the next cycle of operations. The dwell of the grinding- wheel in the finishing position is determined by adjustment of the variable resistance u by a knob y which may be calibrated ; a pilot lamp z remains lit until the dwell period is completed. Specification 465,210 is referred to.