Patent GB-1075649-A (GB)
Title: A bevelling machine
IPC: B24B9/14
Filed: 1965-11-15
Abstract: 1,075,649. Grinding. AUTOFLOW ENGINEERING Ltd. Nov. 15, 1965 [Nov. 16, 1964], No. 48355/65. Heading B3D. A forming and sizing machine for finishing articles, such as eyeglass lens to a predetermined edge formation comprises a first frame 312 reciprocable along a first axis, a second frame 314 reciprocable along a second axis transverse to the first axis, work-holder means 312 on the first frame for holding the median plane of a workpiece generally parallel to the first axis, a plurality ,of finishing means 318 mounted generally in side-by-side relation to one another on the second frame with the finishing surfaces 412, 414 intersected by respective planes parallel to the first axis, and means for reciprocating the frames along their respective axes in timed relation to one another to bring a workpiece into engagement selectively with each of the finishing means. The first frame 312 is provided with sleeves 326, Figs. 2 and 4 (not shown), engaging.guide rods 322 in a base 310 and with a plate 332 supporting the work-holding means 316 which consists of a member 334 mounted on rods 336 slidable in bearings 335 in the member for free movement transverse to the direction of movement of the first frame 312. The member 334 rotatably supports chuck shafts 360, 342 between which the workpiece, such as a lens, is gripped by pads 356, 374. Shaft 360 carries an extension 341 which carries a template 352, corresponding to the desired finished shape of the lens, and a sprocket 348 connected by a toothed belt 360 to an electric motor 360 to effect rotation of the workpiece and template. The chuck shaft 342, which is connected by a belt drive 376 to a shaft 378 in turn connected by a second belt drive 376 to the shaft 340 for rotation therewith, has an enlarged head 370 in a piston 380 acted on by an adjustable spring 388 to urge the shaft 342 against the workpiece. The piston has an extension passing through a slot in a tube 384 receiving the piston, the extension having a roller 391, Fig. 1, which engages one side of a cam portion 393 on a collar 392 on the tube, the other side of the cam portion engaging a roller 389 on the tube whereby when the collar is rotated about the tube by a handle 394, the piston is moved to cause separation of the shafts 340, 342 to release the workpiece gripped therebetween. The first frame 312 is urged towards the second frame by spring 438, the second frame, which supports a motor 406 driving the finishing means 318 which may consist of a rough grinding wheel 412 adjacent a finish grinding wheel 414, being slidable on guide rods 396 carried by the base 310, a spring 482, Fig. 5 (not shown), urging the frame in one direction. The second frame carries an extension 431, Fig. 1, on which a slide 430 is adjustable by a micrometer. The slide carries a switch which controls the operation of the motor 360 for rotating the work-holder and is actuated by engagement of the template 352 with one or other of pads 424, 426 which are carried by a hinge plate movable against spring pressure to operate the switch. The pad 426, which is used when the finishing wheel is engaging the workpiece, is fixed to the plate while the pad 424, used during the rough grinding, is adjustably mounted on the plate to determine the difference between the rough and finish ground sizes. The arrangement is such that motor 360 is only operated when the switch is closed so that the grinding is effected to finish a portion of the workpiece, the switch then actuating the motor to turn the workpiece a small increment so that the next portion is finished, and so on. The micrometer adjusts the slide relative to the template 352 to compensate for wear or change of size of the grinding wheels. The pad 424 used during rough grinding may be adjusted to determined amount by insertion or removal of a shim between the pad and plate for grinding of thick or thin lenses, respectively. The movements of the frames 312, 314 are controlled by the means 320 comprising three cams 440, 470 and 570 mounted on a shaft 352 driven by gearing 460, 462 from the motor 360. The cam 440 has a pair of holes 442, 440 which co-operate with a follower 446 adjustably mounted on the frame 314 to move the frame carrying the work-holder against the action of the springs to a forward position to permit removal and replacement of a workpiece in the work-holder and effect operation of a switch 468 and, as the follower leaves the lobes, to permit the springs to move the frame 312 to a position determined by the template 352 engaging one of the pads. The cam 4 also has cut-outs 542, 544 permitting a switch 540 to assume its normal " off" position, the switch being in series with the switch 468 and motor 360. The cam 470 has a pair of surfaces 472, 474 interconnected by ramps 478 and acting on a follower 480 on a bell-crank lever, the other end of which engages a roller 481 which is mounted on the second frame carrying the grinding wheels and urged by the spring 482 against the lever. The third cam 570 rooks a bell-crank lever 580 to cause an end thereof to engage a notch 581 in the work-holding means to prevent free reciprocation thereof when the workpiece is being rough ground, the second frame then being slowly traversed by engagement of the follower 480 with the surface 474 of the cam 470 which is slightly inclined, the movement ensuring uniform wear of the rough grinding wheel which has a straight configuration. During finish grinding, the workholder is free to reciprocate so that the finish grinding wheel, which has a V-configuration, forms a bevel on the lens central to its thickness. The work-holder may be guided in one direction during finish grinding so that the bevel is not central by a roller 593, Fig. 1, engaging a pivotably adjustable cam 591 having a surface conforming to the curvature of the major planar axis of the lens. In operation, a lens blank is placed between the chuck shafts 340, 342 by operation of the lever 394, and a knob 469 is depressed to close switch 468 and energize motor 360, the grinding wheel motor 406, and a motor for supplying grinding lubricant. Motor 360 causes rotation of the cam-shaft and follower 480 rides down ramp 476 to engage cam surface 470 thereby moving the second frame so that the rough grinding wheel 412 and rough pad 424 are opposite the lens blank and template 352 respectively. Cam 570 moves lens 580 to engage notch 581 and stop free reciprocation of the work-holder and as lobe 442 of cam leaves the follower 446, the springs urge the grinding wheel against the workpiece which is then ground portion by portion under the control of the template moving the hinge plate to actuate switch 434 each time a portion of the blank is ground to size, the switch 540 at this time being open so that the motor 360 is controlled only by the hinge-operated switch. During rough grinding, the wheel is traversed under the control of the inclined cam 474 to ensure even wear of the grinding wheel. When rough grinding is completed, lobe 444 on cam 440 moves the frame 312 away from the grinding wheel and switch 540 is closed to operate motor 360 and rotate the cam-shaft so that cam 470 moves follower 480 and hence the second frame 314 to position the finish grinding wheel 414 and finish pad 426 adjacent the lens blank and template respectively. Thereafter, switch 540 is again opened and the lobe 444 is moved away from the follower for the finish grinding operation, the cam 520 withdrawing lever 500 from notch 581 to permit the lens blank to centre itself relative to the groove of the finish grinding wheel. The grinding operation continues until the lobe 442 moves the frame 312 to actuate switch 468; the latter may be so arranged that it stops the machine after the finish grinding operation. Grinding dust may be prevented from dispersing by an enclosure 484 which has a hinged upper portion and is connected by flexible seals 487 to the member 334. Hoses 488 facilitate the use of coolants and liquid grinding compounds. A device is provided to permit accurate positioning of the lens in the work-holder and consists of an aligning member 602, Fig. 1, which is mounted on the base 310 and has a pair of flats 606 conforming with a pair of flats 600 on the chuck shaft 340. The centre of the member 602 has a bore 608 illuminated by a light source and the lens blank, the optical centre of which is marked by cross-hairs OA, is placed centrally on the member. A manuallyoperable clamp, Figs. 13 and 14 (not shown), has parts 612, 614 hinged together, the part 612 having a portion which embraces the member 602 for supporting the lower annex surface of the lens and the upper part has a pair of hinges 620 which are placed on marks TA indicating the major transverse axis of the blank. The blank is then removed by the clamp from the aligning member 602 and placed on the chuck shaft 340. After shaft 342 is released to grip the lens, the clamp is removed.