GB1105972A - Grinding machine - Google Patents

Abstract

1,105,972. Grinding. HEALD MACHINE CO. 10 June, 1965 [11 June, 1964], No. 24572/65. Heading B3D. A grinding machine comprises a workhead 11 which has workpiece holding means 24 and is mounted on a base 10, a wheelhead 13 having a rotatable abrasive wheel mounted on the base, a dresser 31 for the wheel, means 29, 34 for effecting relative movement longitudinally and transversely between the wheelhead and the workhead, means for determining a deterioration of wheel quality, and means bringing about a dressing operation when the deterioration reaches a predetermined amount. The workpiece holding means 24 is rotated in the workhead 11 by a belt-drive from a motor 25, and the workhead, together with the motor, is mounted on a table 22 movable along ways 23 on the base by an hydraulic actuator 29. A gauge 26, which may be pneumatic or, as shown, of the plug type, is movable by an actuator 28 to enter and determine the finished size of the workpiece 12 which may be the race of a ball bearing and is supported on shoes forming part of the workhead. When the gauge enters the workpieoe upon its reaching the finished size, a switch 32 is operated. The abrasive wheel 14 is driven by a motor 13 mounted on a table 16 which is movable along ways 18 on an intermediate table 17 by an hydraulic actuator 34 to effect feed of the wheel into the workpiece, the feed being effected at a constant force or feed rate, the initial position of the wheelhead being determined by a stop 35 adjustable by means of an electric motor 36. The wheelhead carries a finger 37 which cooperates with switches 38, 39 during operation of the machine. The intermediate table 17 is movable along ways 21 on the base 10 to compensate for wear of the wheel by a screw 41 incrementally rotated by a rack-and-pinion mechanism driven from an actuator 44. In operation, the switch 38 is set so that it is struck by the finger 37 when the workpiece is to finished size or 0À001 inch undersize, and the switch 39 set so that it is closed by the finger 37 when the workpiece has been ground 0À001 inch further. If, during grinding, the gauge 26 enters the bore and the switch 32 is operated before the switch 37 is reached by the finger, the wheel is larger than ideal and a relay 52 of the circuit of the machine actuates the motor 36 to adjust the stop 35 and actuates a coil 69 to effect a dressing operation. The wheel may have been larger because the diamond of the dressing device is chipped. When the gauge 26 enters the bore of the workpiece to actuate the switch 32 after the finger 37 has actuated switch 38, the operation of the machine continues normally. If, however, the gauge enters the bore of the workpiece and operates switch 32, a coil 63 is energized to operate a servo valve 47 controlling the actuator 44 to advance the intermediate table an amount to compensate for the wear of the wheel. At the same time, a coil 64 is energized to operate a counter 66 which records when a compensation action has taken place. After a predetermined number of compensation actions, a switch 67 is closed to cause current to pass through the coil 69 and effect a dressing operation.