Patent GB-981608-A (GB)
Title: Improvements in or relating to supporting mechanism for machine tool feed members
IPC: B24B5/18
Filed: 1961-04-07
Abstract: 981,608. Change-speed and clutch control. EARL A. THOMPSON MANUFACTURING CO. April 7, 1961 [April 18, 1960], No. 12598/61. Headings F2D and F2L. [Also in Division B3] The drive unit of a grinding machine includes a motor 246 driving, through belt 250, a shaft 248 which drives, through grass 252, 256, 260, a gear 262. The shaft 248 and gear 262 drive the input members of hydraulically engaged, spring released clutches 254, 264 the output members of which are secured to a shaft having a worm 268 and a brake drum 270, a spring-biased hydraulic motor 272 being provided for engaging the brake. The worm 268 drives a worm-wheel 274 on a cam-shaft 275. The gear 262 drives a pump 276 delivering oil to a combined accumulator and relief valve comprising a spring-loaded piston 278 and also supplying control valves 280, 282, 284. Valve 280 is shifted by the solenoid 286 and valves 282, 284 are shifted by adjustable cams 288, 290 on the camshaft 275. An hydraulic cylinder 292 holds the valve 282 in its shifted position until it is released by the shifting of valve 284. Energization of solenoid 286 disengages the brake and engages the clutch 264 to start slow speed rotation of the camshaft; thereafter the cam 288 shifts the valve 282 to disengage the clutch 264 and engage the clutch 254 so that the cam-shaft rotates at fast speed; still later, the cam 290 shifts the valve 284 to release the valve 282 which disengages the clutch 254 and engages the clutch 264 so that the camshaft rotates at slow speed. As long as the solenoid 286 remains energized, the cam-shaft rotates alternately at slow and fast speeds. The motor 246 and the solenoid 286 are controlled by an electric circuit including a master relay 294, with start switch 296 and stop switch 298, controlling the motor 246 and a cycle control relay 300, with start switch 302 and stop switch 304. The normally open contacts of relay 300, which are of the make-beforebreak type, control energization of the solenoid 286 directly; the normally closed contacts of relay 300 also control the solenoid 286 but are in series with a switch 306 opened once during each revolution of the cam-shaft, so that when the stop switch 304 is operated at any point in the rotation of the cam-shaft, relay 300 is de-energized but solenoid 286 remains energized until the switch 306 opens at a predetermined stopping point. Operation of stop switch 298 de-energizes solenoid 286 immediately regardless of the point in the cycle and also deenergizes motor 246. The cam-shaft 275 drives hydraulic pulsator devices a-g each comprising a cam 308 on the cam-shaft actuating a single acting pistoncylinder unit 312, 310 communicating by a conduit 318 with one of the hydraulic motors of the machine. The device b actuates a motor 320 for axially reciprocating the grinding wheel, the device d actuates the motor for rapidly advancing a carrier, and the device f actuates the motor for slowly feeding the carrier. The return strokes of the motors are effected by pressure fluid from a source RO, e.g. a gas, spring or weight-loaded accumulator, a variable displacement pump with pressure compensation or a fixed displacement pump with relief valve, this pressure fluid also acting on the piston 122 which biases the carrier away from the grinding wheel. The devices a, c, e, g actuate various other automatic fluid motor actuated mechanisms, such as loading mechanism for automatically feeding workpieces sequentially to their work position prior to grinding and removing them after grinding. The rapid portion of each rotation of the camshaft 275 is used for the non-work performing functions of the grinding cycle and the slower portion when work is being performed by the grinding wheel. Specification 981,609 is referred to.