Patent GB-583810-A (GB)
Title: Improvements in or relating to grinding or abrading machines
IPC: B24B47/06
Filed: 1943-09-23
Abstract: 583,810. Grinding - machines. CINCINNATI MILLING MACHINE CO. Sept. 23, 1943, No. 15613. Convention date, Dec. 19, 1942. [Class 60] A grinding or abrading machine is fitted with power means for advancing the grinding wheel support and power means for reciprocating the work support during grinding, a single control lever effecting sequential actuation of each power means. The machine comprises a bed upon which is slidable a work table traversed relatively to a grinding-wheel carried by a cross slide. The table carries a rack 19, Fig. 12, driven by a pinion 20 on a shaft carrying a worm 22 driven through a worm 23, bevel gearing 25, clutch 28 and gearing 30 by a hydraulic motor 31 to which fluid is supplied in a closed circuit by a variable displacement pump 32. The pump and motor are connected by a delivery line 33 and return 34 with an interposed reversing valve 34<1> and a start- and-stop valve 39, the operation of the reversing valve being controlled by a pilot valve 53. The plunger 55 of the pilot valve is trip controlled from the table by reversing dogs which engage a lever 58 thereby rotating a sleeve 59 geared at 60 to a pinion 61 on a plunger 62 which is rotatable and axially movable. The rotation of the plunger 62 through a crank 63 thereon, a lever, and a bell-crank 68, shifts the plunger 53, complete shifting being ensured by an enlarged spool 72 on the valve acted upon by the pressure fluid. The return line 34 is connected through the pilot valve for deceleration of the table at the ends of its stroke, a double tapered spool 73 on the valve operating with a port 74 gradually to restrict the return from the motor ; just as the plunger is given the complete movement, tarry valves 77, 90 are brought into line circuit to limit variably the tarry at table reversals. The lines 33, 34 are interconnected by a differential valve 83 to maintain a prescribed pressure difference between them and the line 34 is supercharged by a pump 84 to replace losses due to leakage. The starting and stopping of the motor 31 is controlled by the plunger 40 of the valve 39 which is moved by fluid pressure under control of a manually operable pilot valve 92; the valve is connected to a channel 70 which is the pressure line of a pump 94 driven, with pumps 32 and 84, by a motor 112; the exhaust goes to a reservoir 102. The valve 92 is operated by a lever 107 acting on a bell-crank which moves the valve up for start and down for stop. The pump 32 has a variable output controlled by a pintle 116 connected by a rod 117 to a piston 118 movable in a cylinder 119 thereby to vary the speed of the motor 31; the cylinder 119 itself is slidable in a fixed sleeve 120 but is normally held stationary by two pistons 130, 131 moving in cylinders 134, 135 which when under pressure clamp the end 120 of a lever 127, the other end of which is connected to the cylinder. With the cylinder held stationary the piston is movable under control of a manually-operated rate control valve 140, and the table speed is indicated by a speedometer driven from the shaft 24. In order to true the grinding-wheel the grinding operation is interrupted intermittently, the table then being moved at fast speed for setting up and slowly for trueing. These operations are carried out, without disturbing the feed rate mechanism, by the use of separate control means comprising a trueing control valve 154 to which the cylinders 134, 135 are connected and which sets the pump 32 for maximum displacement for high speed and minimum displacement for low speed ; these operations take place with the start and stop valve in stop position. The valve 154 is interconnected to the start stop valve 30, and also to ports in a valve sleeve 178 in which the plunger 62 moves. The actual speed changes are brought about by up and down movement of the plunger 62 by means of a lever 177 actuated by up and down movements of the trip lever 58, operating by means of a control valve 158 to byepass the start-stop valve and supply fluid to the cylinders 134, 135 thereby moving the cylinder 119; during operation of the table for trueing, the tarry mechanism is rendered inoperative. The table may be traversed manually by the wheel 18 through a gear train 222, worm gear 223, and a clutch 225 which is actuated by a piston 227 in the cylinder 236 normally held by a spring 228 to engage the clutch. The clutch member 28 also is actuated through a lever 234 by a piston 231 in a cylinder 235 and normally held by a spring 230 with the clutch open ; when the line 159 is connected to pressure either by the start-stop valve or raid traverse valve, the pistons 227, 231 are moved to disengage the clutch 225 and engage the clutch 28 so that manual operation during power drive is prevented. The wheel is fed during grinding by a pick-feed operated by the table-reversing mechanism, the wheel-head being moved by a screw 254, Fig. 13, engaging a nut 256 on the head and driven through gearing 252, 253, clutch 249, gearing 246, 247 and a wheel 244 ; the wheel 244 is keyed to a sleeve 245 and actuated by pawls moved by a pinion 240 which is driven by a rack pinion 239 in a cylinder 238. The feed is under control of a selector valve 259 having a rotatable plunger 260 whereby feed may occur at either end only of the table stroke, or at both ends of each stroke. The movements of the piston 239 are produced by the movements of the table reversing pilot valve 53 from which channels 89, 206 lead to the valve 259, and a pick-feed reversing valve 267. Included in the circuits are accumulators 262, 272, throttle valves 279, 300 for controlling the speed of operation, and a pick-feed stop valve 288, which causes the feed to cease at a predetermined position and is actuated by a button 326 on a gear 325 driven by a gear 319 on the sleeve 245 through gearing 321 connected to a hand-wheel 322; the hand-wheel is connected to a gear 323 driving a gear 324 in mesh with the gear .325. The plunger 334 of the valve 288 is reset by a valve 329 with a plunger 330 operated by a knob 331. In order to reduce the force necessary to rotate the feed screw 254, a booster motor 338 is provided geared to the screw and providing a torque insufficient to turn the screw, but reducing the force necessary therefor ; the motor is reversed with reversal of the direction of rotation of the screw by a valve 340, the plunger 348 of which is moved by a lever 349 frictionally mounted on the sleeve- 245. In the operation of the machine the start and stop lever serves to bring the wheel to the work and also to start the table traverse ; the cycle is then automatic until cessation of feed when the table is allowed to reciprocate a few times to finish off the grinding. The grinding cycle is started by means of the lever 107 which is supported for universal movement to engage a bell-crank which moves the plunger 361 thereby admitting fluid through a reversing valve 374 to a cylinder 382 on the machine bed to move a piston 383 and with it the screw 254 towards the work as limited by a stop 254<1>. The lever 107 is then moved to actuate the plunger 92 causing the valve 40 to move to start the table traverse. When the manual control wheel is rotated on completion of grinding, it operates the valve 340 which controls the booster pump and also acts as a pilot valve for an interlock valve 392 ; the valve 392 admits fluid below the plungers 92 and 361 which move upwards, causing the table to stop, the wheel slide to be withdrawn from the work and the resetting of the parts ready for the next grinding operation.