Patent GB-1018007-A (GB)
Title: Grinding machine
IPC: B24B49/00
Filed: 1962-12-14
Abstract: 1,018,007. Grinding. NORTON CO. Dec. 14, 1962 [Jan. 3, 1962], No. 47236/62. Heading B3D. The surface of a driven grinding means is dressed during a grinding operation by increasing the rate of grinding attrition of the work beyond that normally employed for grinding to effect simultaneous grinding and breakdown of the grinding means surface, the normal grinding condition then being restored. Preferably a signal emitted by a detector when the performance of a grinding machine having a grinding wheel deteriorates due to loading and dulling of the grinding wheel initiates a remedial change in the grinding conditions resulting in breakdown and renewal of the grinding wheel surface. The remedial change may take place immediately or after completion of part of the grinding cycle. The remedial change may continue for a predetermined part of the grinding cycle or may continue until the performance has returned to normal. The emission of the signal may be the result of (a) an increase in the power taken by a motor driving a grinding wheel, (b) a deterioration in the surface finish of the workpiece, or (c) a change in the grinding ratio. In a surface grinder, the remedial change may be (a) an increase in traverse speed, (b) an increase in infeed speed, (c) an increase in crossfeed speed, or (d) a decrease in the grinding wheel rotational speed. In a cylindrical grinder the remedial change may be an increase in the speed of the work drive motor. In a centreless grinder the remedial change may be (a) an increase in the speed of the work drive motor, or (b) an increase in the speed of the regulating wheel. The invention may be applied to a surface grinder comprising a grinding wheel, driven by a D.C. motor M, carried by a slide 12 vertically movable on a base 10 by a feed screw 24a engaging a nut 26 on the base 10. The screw 24a is connected through bevel gears 30, 32 to a shaft 34 having a hand wheel 36. An extension of the shaft is connected by a one-way clutch 122, Fig. 5 (not shown), to a pinion 124 meshing with a rack 126 on the rod of a piston 132 in a cylinder 130. The piston is urged in one direction by a spring 140 and in the other direction by pressure fluid. A collar 134 adjustably fixed to the piston rod is normally movable between the end of the cylinder and a stop 138 held in operative position by a relay 200; if the latter is de-energized, the stop 138 is moved to inoperative position by a spring 201, and the collar 134 makes an extended stroke limited by a fixed stop 136. The work W is supported by a table 48 longitudinally reciprocated on a carriage 40 by a cylinder 54 mounted on the carriage and containing a piston 56, both ends of the piston rod being secured to the table 48. The cross-feed carriage 40 is mounted on the base 10 for transverse movement. A nut 61 on the base 10 is engaged by a feed screw 60 supported on the carriage 40 and has a hand wheel 62. Gears 68, 69 are mounted on a sleeve 70 slidably keyed to the screw 60 and movable axially by a reversing lever 72. In one end position of the sleeve, gear 69 meshes with an idler gear 74 meshing with a gear 76 to cause cross-feed towards the wheel slide 12. In the other end position of the sleeve, gear 60 meshes with the gear 76 to move the carriage away from the wheel slide; in the central position of the sleeve, both gears 68, 69 are disengaged to allow rotation of the screw 60 by the hand wheel 62. The gear 76 is connected to a ratchet wheel 92 engageable by a pawl 90 carried by a lever 88 connected to a pinion 86 meshing with a rack 84 on the rod of a piston in a cylinder 80 on the carriage 40. In one control arrangement, Fig. 2 (not shown), when the power taken by the grinding wheel motor M, as detected by a resistor 100, increases a relay CR1 is energized. This prepares relay CR3 so that on actuation of switch S1 or S1<SP>1</SP> at the end of a traverse stroke relay CR3 is energized so that a solenoid 118 is energized to increase the rate of traverse. After a predetermined number of cycles, counted by a rotary switch S, relay L is energized to open contacts SL and the solenoid 118 is de-energized so that the traverse rate returns to normal. In a modification, Fig. 3 (not shown), the rate of traverse is increased, by energization of solenoid 118-X, when the power taken by the grinding wheel reaches an upper limit determined by a potentiometer 116a-116x. Simultaneously the potentiometer 116a-116x is taken out of circuit and a potentiometer 116b- 116x, set to give a lower limit, is put in circuit. The increased traverse rate is maintained so long as the power taken is above the lower limit. The solenoid 118-X of Fig. 3 (not shown) may be replaced by an arrangement, Fig. 4 (not shown), for decreasing the grinding wheel speed. The solenoid 118-X of Fig. 3 (not shown) may be replaced by an arrangement, Fig. 5 (not shown) for increasing the infeed or the cross feed. The resistor 100-X of Fig. 3 (not shown) may be replaced by a transducer sensing surface finish. In one arrangement, Fig. 6 (not shown), the rate of traverse is increased; in another arrangement, Fig. 7 (not shown), the grinding wheel speed is reduced; in a further arrangement, Fig. 8, not shown, the infeed or cross feed are increased. An arrangement, Fig. 10 (not shown), for sensing the grinding ratio comprises a servo F1 for continuously measuring the radius of the grinding wheel by means of a magnetic or capacitance pick-up 153 and a servo F2 for continuously measuring the position of the grinding wheel axis. The outputs of the servos are fed to a circuit, Fig. 11 (not shown), giving an output signal equivalent to the grinding, this signal being used to initiate wheel breakdown. A similar arrangement, Fig. 13 (not shown), may be used to shut down the machine when the workpiece is of the desired size.