Patent GB-1135957-A (GB)
Title: Grinding machine
IPC: B24B49/16
Filed: 1966-03-23
Abstract: 1,135,957. Grinding. HEALD MACHINE CO. 23 March, 1966 [28 April, 1965], No. 12873/66. Heading B3D. A grinding machine comprises a base 11 on which is mounted a workhead 12 for supporting a workpiece 23 and a wheelhead 13 for supporting an abrasive wheel 22, mechanism 18 for bringing about relative movement between the workhead and wheelhead to contact the wheel with the workpiece with a predetermined force during a roughing grind, and a retractable stop 34 regulating the rate of relative movement between the workhead and wheelhead during a finish grind. The workpiece 23, such as the rear of a ball-bearing, is gripped externally by the workhead which is mounted on a table 14 reciprocatable along guideways 15 on the base 11 by an hydraulic cylinder 19. The inner surface of the workpiece is ground by the wheel 22 of the wheelhead 13 on a table 16 movable transversely to the axis of the workpiece along guideways 17 by a feed cylinder 18. A pneumatic gauge 24 is provided for sensing the size of the workpiece and a dressing tool 29 is carried by table 14. A horn 32 extends .downwardly from the table 16 into a slot 31 in a block 26 which is slidable along base 11 in movements by rotation of a screw 27 driven by a motor 28, the movement being used to compensate for dressing of the grinding wheel. An insert 33 in the front of the block co-operates with the contact rod 35 of the retractable stop 34 which is mounted on the wheelhead table 16. The contact rod 35 of the retractable stop 34 is secured to a shaft (64, Figs. 2 and 3) fixed to a sleeve (65) in screw-threaded engagement with a nut (67) attached to a gear (36) which is engageable by opposed pawls (47, 48) connected to pistons (42, 45) in cylinders (38, 39), the pistons being operated if the spark-out time is too long or too short to adjust the contact rod. The nut (67) is also in screw-threaded engagement with the housing (51) of the stop, and the sleeve 65 is supported by balls (69) in a further sleeve (68), pressure oil being supplied to the space between the sleeves to takeup backlash in the screw threads. The sleeve (65) is connected by a crank (59) and pin (58) to a piston (53) in a cylinder (52), rocking of the crank rotating the sleeve to effect axial movement of the contact rod (35) for controlling the movement of the wheolhead during finish grinding, the rate of movement of the piston being controlled by an adjustable throttle valve (56, 37). A finger (72) extends from the crank (59) and has a button (73) engaging an adjust. able stop (74). The machine is operated according to a grinding cycle (Fig. 5). The wheel is initially advanced through a distance a to b at a low force and at a rapid speed by the cylinder 18, and at the same time motor 28 is operated to compensate for a previous retraction movement and dressing operation by a distance x + y. The grinding wheel contacts the workpiece when it reaches point d and grinding is effected at a low force to point e to effect rounding up of the workpiece for a predetermined time, after which high pressure fluid is supplied to cylinder 18 to effect grinding at a high force from point e to point f. At point f, the contact rod 35 abuts the block 33 and fluid pressure is supplied to cylinder 52 to move the contact rod 35 which thus controls the advance of the wheelhead until the gauge 24 stops further advance at a first gauge size and operates a spark-out timer until the wheel has advanced to point g. The wheelhead is then retracted to point h wherein an abutment (62, Fig. 3) on the horn 32 abuts a stop (61) on the block 26 and the workhead is retracted by cylinder 19 to traverse the dressing tool 29 across the grinding wheel and returned so that the wheel is within the bore of the workpiece. Upon advance of the wheelhead from point k to point I the contact rod 35 again abuts the block 33, no grinding taking place until the cylinder (52) is again supplied with fluid pressure to rock the crank (59) so that the wheelhead is advanced by the high pressure in cylinder 18 under the control of the retracting contact rod 35 to the point m close to the finish size. The final feed m to n is produced by spark-out and if the time of spark-out is too long or too short, the gear 36 is rotated in one direction or the other by the pawls (47, 48, Fig. 2) to compensate for the error.