Patent GB-831927-A (GB)
Title: Grinding machine having an incremental feed mechanism
IPC: B24B47/20
Filed: 1958-05-29
Abstract: 831,927. Grinding. CINCINNATI MILLING MACHINE CO. May 29, 1958 [June 10, 1957], No. 17147/58. Class 60. A grinding machine comprises a grinding wheel 14, Fig. 1, carried by a cross-slide 15 on a base 10, a feed-screw 23, Fig. 2, having a threaded connection with the cross-slide, means 29 journalled on the feed-screw for translating the screw axially to provide a rapid traverse movement of the wheel, and a plunger 70 which has a limited stroke of reciprocation and is connected to the screw by a unidirectional drive transmission 66 whereby, when selectively-operable means are actuated for effecting a single reciprocation of the plunger, the feed-screw is given an increment of rotation in one direction only to move the wheel an incremental distance relative to the translating means 29. The cross-slide 15, Fig. 1, is carried on a lower slide 16 which, in turn, is slidable on the base 10, clamps 18, 19 being operable to clamp the slides in selected positions. A handwheel 20 is connected to a nut which is carried by the slide 15 and engages the feedscrew 23, and by selectively operating the clamps 18, 19, the lower slide 17 carrying a work-rest 13 can be adjusted relative to a grinding wheel 11 on an axis fixed with respect to the base, and the cross-slide 15 can be adjusted, relative to the work-rest 13 to adjust the position of the grinding wheel 14 which runs at a slower speed than the wheel 11 and serves to regulate the speed of rotation of a workpiece 12 ; when the slides have been adjusted a clamp 21 is tightened to prevent rotation of the nut. The feed-screw 23 is axially moved to provide a rapid infeed of the cross-slide by movement of a beam 29, Fig. 2, which is connected by pivot pins 30, 31 to a sleeve 34 carried by bearings 35, 36 between a shoulder 37 and a nut 38 on the screw ; during setting up, when the handwheel 20 is operated to rotate the nut, the feed-screw is prevented from rotating by a clamp 39 disposed in the pivot pin 30. An extension of the feed-screw carries a gear 51 meshing with a gear 53 on a shaft 54 connected by a cam-clutch 66 to a hub 61 journalled on the shaft 54 and having gears 62, 63 engaging racks on plungers 70, 68, respectively. The cam-clutch consists of a series of circumferentially arranged sprags or cams which bear against the shaft 54 so that only movement in one direction during the reciprocatory movement of the plungers is transmitted by the gears and hub to the shaft 54 and hence the feed-screw and cross-slide. The plunger 70 is moved back and forth once when it is desired to advance the cross-slide a very small amount to compensate for wear of the grinding wheel by manual operation of a switch 125, Fig. 6, which energises a solenoid 123 to actuate a valve 115 and supply fluid pressure from a pump P to the right-hand end of the plunger 70 which thus moved to the left a distance determined by abutment against a piston 93, the other side of which abuts a micrometer screw 105 adjustable, by a graduated drum 97, in a piston 102 fitted with seals 103 and urged to the right by fluid pressure supplied to a chamber 107 ; release of the switch 125 causes return of the plunger to the right. When it is desired to adjust the cross-slide a larger amount to compensate for the reduction in size of the wheel following a trueing operation, a switch 140 is manually operated to energize solenoid 123 to actuate valve 115 as before, and also to energize a solenoid 137 to actuate a valve 116. The latter valve causes the chamber 107 to be connected to exhaust so that fluid to the right hand end of the plunger 70 from the valve 115 moves the plunger, piston 93, and piston 102 carrying the screw 105 to the left. The movement of the cross-slide is then limited by the movement of the plunger 68, which is driven from the gear 62 on the hub 61, abutting a micrometer screw adjustable to a predetermined position by a graduated drum. A nut 48, Fig. 2, is secured to the feedscrew and serves to limit the maximum movement of the screw by abutment against the base 10. The mechanism is suitable for application to through and infeed types of centreless grinders and to centre-type grinders, and may be operated before, after or during a machining operation.