Patent GB-658306-A (GB)
Title: Improvements in and relating to grinding machines and method of shaping grinding wheels
Inventor: WILSON JOHN CLIFFORD
IPC: B24B53/07
Filed: 1949-02-17
Abstract: 658,306. Surface grinders; crush dressing. THOMPSON GRINDER CO. Feb. 17, 1949, No. 4346. [Class 60] A method of dressing a grinding wheel 26, Fig. 1, by a crushing roll 24 includes the steps of pressing the wheel and roll against each other, driving the wheel and roll at the same peripheral speed, and intermittently feeding the wheel and roll relatively towards each other during continued rotation of the wheel and roll and for a complete dressing cycle. The grinding wheel and the crushing roll may rotate in opposite directions The crush-dressing mechanism 22 is mounted on a table 12 adapted to be reciprocated, preferably by fluid-pressure means, under the grinding wheel 26 of a surface grinder. The wheel head 18 is horizontally adjustable, also preferably by fluid-pressure means, on a saddle 16 which can be vertically adjusted by a screw and nut mechanism connected to a shaft 34, Fig. 2. This shaft can be engaged by a manually-operated clutch 36 with a sleeve 32 fixedly carrying, a hand wheel 28 and two ratchet wheels 52, 68. The pawls for the latter act in opposite directions and are mounted on gear sectors 46, 64, the gear sector 46 being in direct engagement with a plunger 42, while the sector,64 is engaged with a plunger 44 through a gear train 62 60, 48. The wheel head is lowered by increments during crush dressing by reciprocating the plunger 42 with pressure fluid under the control of a solenoidoperated valve, the solenoid being intermittently energized by a cam-operated switch driven from a variable-speed motor. The increments of feed are determined by an adjustable stop which limits the movement of the sector 46. Movement of the plunger 44, also by pressure fluid, raises the wheel head. The latter is also under the control of the handwheel 28 which is graduated and provided with a fine-feed device in the form of a reduction gear 72 connected to a hand control 70. The depth of feed is predetermined by a cam member 76 adjustable around the periphery of the hand wheel 28 by a toothed shoe and pinion rotated by a lever 86 which is locked in the adjusted position. This cam member engages a plunger 78 when dressing is complete to open a limit switch LS1 which stops the drive for the cam-operated switch. The wheel head motor is stopped when the grinding wheel is positioned over the crushing roll by a cam 153, Fig. 1, mounted on the table 12 to operate a switch which open circuits the motor and brakes it dynamically. The crushing roll is mounted on a bed 108, Fig. 7, pivotally supported at 106 on a base 100 which is adjustably mounted on the table 12 and is driven by a motor 110 also under the control of the switch LS1. The free end of the bed 108 is supported by two eccentrics on a shaft which can be rotated by a hand-operated worm drive 128 to vary the height of the crushing roller. A bolt 132 is provided to lock the bed at the required height and locking means are also provided for the worm drive. In a modification, feed is imparted to the crushing roller instead of the grinding wheel by connecting the worm drive 128 to a pawl and ratchet substituted for the valve controlling the plunger 44. The bed 108 carries an adjustable stop to operate the switch LS1. A second modification employs a freely-journalled crushing roll and a slowspeed motor connected to the grinding wheel motor through an over-run clutch.