Patent GB-894221-A (GB)
Title: Improvements in or relating to lapping and polishing machines
IPC: B24B5/42
Filed: 1960-09-14
Abstract: 894,221. Lapping crankshafts &c. NORTON CO. Sept. 14, 1960 [Sept. 14, 1959], No. 31636/60. Class 60. Different portions of a crankshaft 40, Figs. 1 and 2, are simultaneously lapped or polished by rotating and reciprocating it against an abrasive medium held against the portions to be lapped by individually-positioned jaws 79, the crankshaft being rotated and reciprocated when clamped between a headstock 30 and tailstock 35 which are swingable between an outer loading and inner lapping position. The headstock 30 and tailstock 35 are respectively carried by brackets 45, 46, Figs. 3 and 4, arranged to be rocked with a shaft 50 under the action of an hydraulic piston-and-cylinder device 250 to swing the crankshaft between its two positions. The headstock spindle 100 is driven through a belt-drive from a motor 90 and can ies a driving head 112 and pin 114 for clamping and driving engagement with a flange 113 at one end of the crankshaft. Both the headstock and tailstock are axially reciprocated on rods 125, 183 on their respective brackets 45, 46 by a drive from the spindle 100 which includes a belt-drive; eccentric 138 driven by worm gearing in the bracket 45 and a link 140 connecting the headstock and eccentric; a tie rod 150 connects the headstock and tailstock for joint reciprocation. The tailstock is fitted with an axially-movable member 195 carrying a freely-rotatable spindle 196 mounting a tapered centre pin 200 and this pin is movable to and from clamping position as the shaft 50 swings the crankshaft to and from lapping position by providing the member 195 with an arm 210 having a cam follower 211 co-operating during the swinging movement with a fixed cam surface 205; a cam 215 pivotally mounted at 216 is urged by a spring 217 against the follower as controlled by a fixed stop 214. A positive lock of the centre pin in clamping position is provided by a pin 220 on the member 195 then being engaged by a cam-operated arm 221. Initially, a crankshaft to be lapped is supported between the headstock and tailstock (with these swung to the outer position) on a V-block 266, Figs. 1 and 4, fixed to the tailstock and a V-block 265, Figs. 1 and 2, which is pivoted on a bell-crank 272 carried by the shaft 50 and, at the start, is held in supporting position by a fixed cam surface 274. The crankshaft is first lifted slightly away from the block 266 as the centre pin enters a tapered recess in the end of the crankshaft and then, as it swings with the shaft 50 (and becomes clamped in position), is no longer supported by the block 265 since this member passes beyond the supporting cam surface 274. The above mechanism acts in reverse to unclamp the crankshaft on its return swing and deposit it on the V-blocks, a rod 231, Fig. 1, also being operated by the cam-actuated arm 210 at this time to engage the crankshaft and withdraw it axially from the headstock. In its lapping position, the crankshaft is swung into engagement with a number of transverselydisposed abrasive tapes 69a, Figs. 1 and 2, at the position where each tape passes over a pair of pivoted jaws 79 (72, Fig. 10) at the end of an arm 280. Each arm embodies an hydraulic piston-and-cylinder device 281 for operating a linkage 287, 288, Fig. 10, whereby the two jaws may be moved between one position in which they can receive one of the main bearings or crank pins of the crankshaft and a closed one in which they bring the tape into close contact with such parts. While all the arms are carried between a series of vertical plates, those operating upon the main bearings of the crankshaft and therefore requiring no vertical or pivotal motion are mounted on transverse pins 305 and supported on fixed pins 310. On the other hand, those arms which operate upon the crank pins and must therefore have a reciprocating and pivotal motion are-carried pivotally at one end by the pins 305 engaging slots 311 in the arm at the other end by the jaws 79 embracing the crank pins; at those periods when these jaws do not embrace the crank pins, the corresponding arms are supported by stops 322 on arms on a shaft 320 which is actuated by an hydraulic piston-and-cylinder device 325 to move the stops to and from supporting position. The tapes are led from rolls 340 over the jaws 79 and rod 346 and then between spring-biased feed rolls 350, 351 to a waste receptacle 353. The roll 350 is intermittently rotated, between polishing cycles, to advance new portions of the tapes to operative position over the jaws by an hydraulic piston-and-cylinder device 360 acting through an arm 365 and overrunning clutch upon the roll. In order to provide some slackness in the tapes, which is particularly necessary for those having a reciprocating and pivotal jaw action, a transverse rod 372 carried by arms 371 is so actuated by linkage from the piston-and-cylinder device 325 that it is swung down across the tapes when the stops 322 are moved to supporting position and raised to release the slack during the polishing operation. When the drive motor 90 is stopped at the end of an automatic cycle, a solenoid S5, Fig. 8, is de-energized and so allows a brake 380 to close on to the motor shaft 91. If, however, the angular position of the crank shaft is not then in the desired position as set by the closure of a switch 2LS, Fig. 3, by a cam 165 driven by the spindle 100, the solenoid S5 is energized to release the brake and energize an inching motor 390 which acts through gearing 391 and belt drive 393 to rotato the crankshaft slowly until the switch 2LS is closed. All the piston-and-cylinder devices are arranged for control by a circuit which includes valves, limit switches and relays and is arranged to be operative only when, with a crankshaft in correct angular position on the blocks 265, 266, one of the crank pins is in position to close a control switch; at this stage, the headstock 30 is in correct angular position with its drive pin 114, Fig. 3, aligned with a recess 115 in the crankshaft flange 113. At the start of the operation, the control circuit ensures that hydraulic pressure is applied to maintain the jaws 79 fully open and the stops 322 properly operative beneath the arms 280, prior to release of pressure from the piston-and-cylinder device 250 to permit the inward swing of the crankshaft. This inward swing then occurs either automatically or as the result of the closure of switches and is accompanied by the clamping action of the centre pin 200. With the crankshaft in lapping position, a switch is automatically actuated to cause closure of the jaws, release of the slack previously imposed by the rod 372 on the tapes, movement of the stops 322 away from supporting position, and preparation of the tape feed drive for subsequent operation. At this stage, the drive motor 90 is energized to cause rotation and reciprocation of the crankshaft, a time delay relay is actuated to over-rule the control effected by the limit switch 2LS, and a timer motor is also energized. After the prescribed lapping time has elapsed, the timer motor stops, the motor 90 is de-energized and brake 380 applied, and, with the crankshaft in correct angular position to cause closure of the limit switch 2LS (which would be preceded by the automatic operaticn of the inching motor 390 if the motor 90 had not stopped the crankshaft in correct position), the hydraulic circuit is set to cause the stops 322 to move into jaw-supporting position and the rod 372 to produce slack in the tapes. The crankshaft is then swung back to its initial position, being finally deposited in unclamped position on the blocks 265, 266. The actuation of the tape-feed mechanism to advance new portions of the tapes through the machine is timed to occur after the crankshaft has been swung from the jaws. A flow of coolant over the crankshaft while it is being lapped is provided from nozzles 495, Fig. 2. Specification 531,128 is referred to.