Patent GB-982868-A (GB)
Title: Improvements in or relating to balancing of a rotary tool in a machine tool
IPC: B24B41/04
Filed: 1964-01-29
Abstract: 982,868. Balancing grinding wheels; machine tool details. A. A. JONES & SHIPMAN Ltd., and J. HOULDSWORTH. Jan. 29, 1964, No. 3746/64. Headings B3B and B3D. A unit for balancing a rotary grinding wheel G or the like in its plane of rotation comprises a pair of balancing masses 2, 3 located eccentrically with respect to the axis a-a of rotation of the grinding wheel and rotatable coaxial therewith, the masses being such as to produce identical moments about the axis, and means for adjusting the angular positions of the masses about the axis both independently relative to one another and also in unison relatively to the grinding wheel. The grinding wheel is mounted on one end of a hollow spindle S, the other end of which carries a pulley 1 for driving the wheel. A sleeve 4 and shaft 7 are coaxially disposed within the spindle and each carries, respectively, a balance weight 2, 3 of semicircular shape and of identical mass, the centres of gravity of the weights being the same distance from the axis a-a of the grinding wheel. The sleeve 5 is supported by a bearing 6 in the spindle S and the shaft 7 is supported by a bearing 9 in a gear plate 10 secured to the pulley 1. The sleeve and shaft respectively carry gears 11,13 which respectively engage gears 12, 14 supported on shafts passing through the gear plate 10, the shaft of gear 14 carrying a worm-wheel 16, and the shaft of gear 12, carrying a worm-wheel 33. Worm-wheel 16 meshes with a worm 17 on a shaft to which is keyed a worm-wheel 18 engaging a worm 19 on the shaft of an electric motor 19 secured to the gear plate 10. The worm 19 also engages a worm-wheel 36 freely rotatable on a shaft 34 carrying a clutch 35 which is movable between a position in which the wheel 36 is clutched to the shaft to rotate the shaft in one direction and a position in which a gear 45 engaging an intermediate gear 46 driven by the wheel 18 is clutched to the shaft to rotate the shaft in the opposite direction, the shaft having a worm engaging the worm-wheel 33 on the shaft of the gear 12. The clutch 35 is movable by a fork 44 which is turnable on a rod 41 and has teeth engaging a lever 40 also turnable on the rod. A spring 43 acts to urge the fork to a position in which the clutch 35 engages the gear 45. The lever 40 is movable by a further lever 48 which is in turn movable by axial displacement of rods 38, 39, effected by a cam 37 and lever L. An electric supply is connected to the motor from a line 25, brushes 28, 29, slip rings in a plate 30 and brushes 31, 32. A further line is connected by a brush 50 and a slip ring to a line, shown dotted, joined to a pin 51 which extends through an insulated bush in the gear plate and is connected to a slip ring 52 also insulated from the plate. An insulated brass sleeve 53 is carried by gear 13 and has outwardly urged balls 54, 55 engaging the slip ring 52 and an insulated ring 56 in the gear 11. A pin 57 extends into earthing contact with the gear 11. When the weights 2, 3 are in the position of maximum unbalance, the ball 55 contacts pin 57 to cause an indicator to be operated. In operation, when it is desired to balance the rotating grinding wheel, the lever L is moved to cause the cam 37 to rock the lever 40 and move the clutch 35 to engage gear 36 so that rotation of worm 19 by the motor 22 causes the balance weights to rotate in opposite directions until the weights are at a position of maximum unbalance with their centres of mass coincident as shown by the pin 57 being contacted by the ball 55 to operate the indicator. Lever L is thus operated to disengage clutch 35 from worm-wheel 36 and engage it with gear 45 so that rotation of worm 19 by the motor then moves both weights in the same direction. When the weights have been moved to a position in which they are diametrally opposite the unbalanced force generated by the wheel, the clutch is again moved to engage the worm-wheel 36 so that rotation of the worm 19 moves the weights in opposite directions to reduce their unbalance until it is at a value equal to the unbalance of the grinding wheel. When the balanced position is reached, the motor 22 is stopped and the lever L moved to a position allowing teeth on the lever 48 to engage teeth on the end of the shaft of the motor to prevent rotation of the motor. A vibration detector may be incorporated with the unit and have control means for automatically operating the unit upon detection of unbalance of the wheel.