Patent GB-529610-A (GB)
Title: Improvements in or relating to the grinding of ball races
IPC: B24B19/06
Filed: 1939-06-05
Abstract: 529,610. Grinding. LANDIS TOOL CO. June 5, 1939, No. 16412. Convention date, June 17, 1938. [Class 60] In a method of grinding, a ball-race is oscillated and subjected to the action of a grinding-wheel until a pre-determined size is reached, whereupon oscillation is stopped and grinding is continued until a final pre-determined size is reached. Transverse feed of the grinding-wheel may be stopped or reduced to a very small amount during the final grinding. The method enables the final grinding, with consequent elimination of zig-zag marks, to be performed in the same machine as the rough grinding. In the machine shown in Fig. 1, a headstock 53 is mounted on an oscillating column 54 which is supported in a sleeve 55 on the bed 50 and carries a motor 11 for driving the headstock. To reduce inertia, the centre of gravity of the motor is arranged in the axis of the column. A connecting-rod 61 for oscillating the column is operated by a crank-pin which is adjustably mounted in a slot 218 formed in a cam 217 driven by a motor through reducing- gear 62. The spindle 80 of the'grinding-wheel 52 is mounted in a tapered sleeve secured in a ram 83, Fig. 5, of octagonal section fitting in a housing 85 on a slide 51. The spindle is beltdriven, by a motor 14. The slide 51 is operated by means of a fluid-pressure motor 107, Figs. 4 and 5, mounted thereon and comprising a rotor 108. A crank 129 on the rotor-shaft 109 operates a connecting-rod 130 which is in yielding engagement, through a spring 142, with a member 139 mounted on a pin 140. A sleeve 137 carrying the pin is mounted in a sleeve 138 on the slide and is provided with a nut 134 which co-operates with a feed-screw 133. The grinding-wheel is moved axially by means of a bell-crank 103 having a yoke co-operating with a flanged sleeve 98 which is yieldingly mounted on an extension of the ram 83. The bell-crank is connected by a link 104 to another bell-crank 105 co-operating with a roller 113 mounted on an arm 112 on the rotor-shaft 109. A latch 116 normally co-operates with a shoulder 118 on the bell-crank 105 to prevent accidental movement of the grinding-wheel. The latch is released by means of a lug 111 on the shaft 109. The feed-screw 133 is provided with a ratchetwheel 185 co-operating with a feed-pawl carried by a piston 189, Fig. 13. During rough-grinding a screw 196, Fig. 1, on the head of the piston co-operates with the bed 50 to limit the feed. At the end of the rough-grinding, a solenoid moves a stop into the path of another screw 198 on the piston to stop or reduce the feed. The sleeve 137 is returned by co-operation of another ratchet-wheel 186 on the feed-screw with a pawl 205 on a rock-arm 206 connected to a piston 210. The fluid-pressure system of the machine includes valves 230, 235, 240, Fig. 13, operated by the cam 216 and solenoids 41, 34 respectively. The valve 235, when operated, cooperates with the valve 230 to direct fluid intermittently to the cylinder 192 containing the piston 189. The valve 240 directs fluid to one side or other of the rotor 108, and also to the cylinder 211 containing the piston 210. The work is mounted in a chuck 115 of the kind described in U.S.A. Specification 2,026,639 and co-operates with the gauging-device described in Specifications 405,817 and 409,129 and U.S.A. Specifications 2,064,427, 2,088,682, and 2,105,841. The gauging-device comprises a feeler carried by a spring-urged shaft having an arm for controlling the flow of air through a nozzle in connection with a manometer tube containing mercury and provided with contacts for controlling the series of operations described below. On depression of push-buttons 19, 22, Fig. 1, the motor 14, and a pump-motor are started, the solenoid 34 is energized, and the rotor 108 turns counter-clockwise. The connecting-rod 130 abuts on the stationary pin 140 and in co-operation with the crank 129 moves the slide 51 and thereby causes the grinding- wheel to move from position A to position B, Fig. 5. Thereupon, the roller 113 engages the right-hand part of the bell-crank 105, and the ram 83 is displaced to carry the grinding-wheel from position B to position C. The ram is arrested by co-operation of a bevelled block thereon with an adjustable stop-screw 88, the arrangement causing the ram to be forced into firm contact with the base of the housing 85. A lug 165 on the connecting-rod 104, actuates a switch 23 and thereby closes relays for starting the motors 11, and energizing a coil for releasing a brake from the motor. During further movement of the crank 129, the slide 51 is retracted slightly and the grinding-wheel is moved from position C to position D, in which the grinding- wheel is active. The movement from position C to D is limited adjustably by co-operation of a stop 128 with a stop-pin 124 which is lifted and dropped by means of a lever 121 operated by a cam 119 on the bell-crank 105. The stop-pin is eccentrically mounted in a revoluble block 125 which is secured adjustably by a screw 127 passing through an arcuate slot 126. On energization of the solenoid 41 by the timing- contacts, the valve 235 is operated, fluid passes intermittently to the cylinder 192, a pawl operates the feed-screw 133, and rough-feed is effected. When rough-grinding is complete, the stop for the stop-screw 198 is positioned by its solenoid under control of the timing-contacts, and fine-feed is effected. On de-energization of the solenoid 41, the feed pawl is stopped, the motor 13 is cut off, and the brake-coil thereof is de-energized to stop oscillation of the work. A tappet-switch arranged in holding-circuits ensures application of the brake at the moment the motor is cut off. Final forming of the work occurs for a pre-determined time without oscillation thereof or feed of the grinding-wheel. The solenoid 34 is then de-energized, and the rotor 108 turns clockwise, thereby causing the grinding-wheel to move successively to the positions C, B, A. Moreover, fluid is directed to the cylinder 211 to rotate the feed-screw backwards into the starting position. Cooling-fluid, under control of a valve 25, Fig. 1, passes to the work through a tube 256 in the column 54. Lubricant is supplied to the sleeve 138, Fig. 13, through a fine tube. The grinding-wheel can be trued by means of diamonds adjustably mounted in a dummy race supported by the chuck 115, Fig. 5. During truing, the chuck is prevented from rotating by co-operation of a push-pin with a slot in the chuck.