Patent GB-431535-A (GB)
Title: Grinding machines
IPC: B24B47/20
Filed: 1934-03-10
Abstract: 431,535. Grinding-machines; valves. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Landis Tool Co. ; Waynesboro, Pennsylvania, U.S.A.) March 10, 1934, No. 7709. [Class 60] [See also Group XXIX] A grinding-machine is provided with driving means for rapidly moving the grinding wheel support to or from the work support, or vice versa, together with means for intermittently changing the speed of the movement comprising mechanism which applies a force opposing the driving means and is automatically controlled by means responsive to the size of the work. In the grinding machine shown the work 43, such as a crank-shaft, is held between centres on a transversely-adjustable table 40, and is operated on by a wheel the base 38 of which is adjustable on a slide 16 by a hand-wheel 39. The slide 16 is moved by an hydraulic cylinder 12 to feed the wheel to and from the work, the feed being rapid until checked by the engagement of an arm depending from the slide 16 with the piston 18 of a dash-pot 17 connected to an oil reservoir 19. The oil displaced from the dash-pot passes through a valve port 28 and also past a hand-operated valve 29 into the reservoir 19, the latter valve being closed for rough grinding. The resistance produced by the passage of the oil through the port 28 causes the slide to move at a slower speed, which is maintained until the work is approximately to size. A gauging device 71 controlling the height of a mercury column then causes the mercury to close contacts to energize a solenoid which operates a rock-arm to rotate the screwed stem 30 of a needle valve 107 which thus closes the port 28, the feed of the grinding wheel then practically ceasing. The slight further reduction in diameter of the work causes the mercury column controlled by the gauge to rise further and close contacts which energize a solenoid 59 which releases a latch 57 and allows the reversing lever 54 to be moved over by a spring, thus causing withdrawal of the grinding wheel. At the same time the lever 54 closes a switch 66 which energizes a solenoid 68 to operate a valve 69 which cuts off the supply of lubricant. The oil in the reservoir 19 flows back past a valve 26 to the dash-pot cylinder 17. To compensate for change in viscosity of the oil with change of temperature, the needle valve 107 controlling the port 28 is caused to move towards the port as the temperature rises by slidably mounting it in a bore in the stem 30 and pivoting to it links 110, the other ends of which are carried by pivots 113 adjustably mounted in slots in a transverse bar 109 carried by the stem 30. The bar 109 is of material having a coefficient of expansion different from that of the links 110, so that by suitable adjustment of the pivots 113 the movements of the valve produced by temperature changes may be caused to produce the desired compensation. In a modification, the valve 29 is operated by a solenoid controlled by a switch operated through a cam by the slide 16. When the dash-pot regulator 17 first comes into action the valve 29 is open, allowing a comparatively rapid in-feed of the grinding wheel between the edges of the shoulders on the crank-pin being ground. Just before contact of the wheel with the crank-pin the cam-operated switch is operated and the valve 29 is partially or entirely closed, the wheel then being fed at rough grinding speed until the valve 107 is closed as in the previous case.