Patent GB-880048-A (GB)
Title: Improvements relating to an edge grinding machine for lenses
Inventor: WALTON JOHN ROBERT
IPC: B24B9/14
Filed: 1959-09-14
Abstract: 880,048. Grinding the edges of lenses. TEXTRON Inc. Sept. 14, 1959, No. 31314/59. Class 60. A machine for grinding flat or bevelled edges on lenses comprises an annular grinding wheel W, Fig. 7, a rotary work support disposed with its axes at right-angles to the axis of the grinding wheel for holding the lens in edgewise engagement with an end face of the wheel, means for intermittently rotating the work support, and means for determining the periods of rotation of the work support consisting of a template 182, Fig. 6, which is arranged to rotate with the work support and engages with its periphery the plane active surface 186 of a follower 187. The grinding wheel W, Fig. 7, is of cup shape and clamped to a spindle 22 which is rotated inside a tubular support 21 from a motor 50 acting through a pulley drive 57; a vertically-adjustable guard 40 surrounds the wheel. The end of the grinding wheel may be shaped to provide flat or bevelled edges on the lens. The lens to be ground is clamped between two opposed carriers 125, 126, Fig. 4, carried by spindles 127, 128 journalled in the spaced legs of an H-shaped work-supporting carriage 120 which, by means of pins 117, Figs. 1, 4 and 6, swings about a horizontal axis on a bracket 112, Fig. I, journalled on vertical pins 110 in a bracket 95 adjustable vertically on a pillar 60; the pillar 60 is adjustable laterally on a base 20 by a rack-andgear device and clamped in adjusted position by an eccentric 76, Fig. 7, acting between the underside of the base and a strap 78 connected to the pillar. The carrier 126, Fig. 4, is pressed towards clamping position by a spring 132, but can be retracted manually when desired, and the spindles 127, 128 of both carriers are driven through gearing by a motor 150 disposed at the opposite end of the carriage 120. The template 182 is arranged to be pushed over a ring of spring detents 184 on a block 180 on the spindle 127 and engages the plane control face 186, Fig. 6, of the follower shoe 187 which is mounted by a screw stud 188 in the forked end of an arm 190 pivoted at 200 on an arm 113 projecting from the pivoted bracket 112; the follower 187 is adjustable vertically by a nut 191 on the stud with the aid of scale graduations. The follower 187 is constantly pressed towards engagement with the template by a spring plunger 201 at the opposite end of the arm 190 contacting a block 202 mounted in a second arm 114 projecting from the bracket 112; a screw 203 in the arm 190 adjacent the plunger 201 co-operates with a limit switch carried by the block 202 and controlling the operation of the lens-driving motor 150. When the carriage 120 is lowered to bring the lens blank (which is not then rotating) into contact with the rotating grinding wheel; the template 182 at first only lightly engages the follower 187 (because the blank is then oversize) and so the plunger 201 prevents the screw 203 actuating the switch 202. As, however, the blank becomes worn down in this position to proper size, the template is lowered far enough to bear heavily on the follower and so rocks the arm 190 against the resistance of the plunger 201 to the extent necessary to actuate the switch and start the motor 150. The blank is thus indexed to a point where it lifts the template and results in the opening of the switch and stopping of the motor. Grinding to size (as provided by the adjustment of the follower 187) then occurs at this point, followed by further indexing and so on. When the lens blank is being indexed for the last time, say to complete three full revolutions of the blank, a cam 175 driven through gearing from the motor 150 disengages a catch 225, Fig. 6, so that a weight 221 then slides down an inclined rod 220 on the carriage 120 and tilts the latter about its pivot axis 117 to raise the lens clear of the work; a spring bumper 227 cushions the downward slide of the weight. A modified means for stopping the machine consists of a spring catch 290, Fig. 17, not shown, which, after a predetermined number of revolutions of the lens blank, is released by a trip driven from the motor 150 and acts through toggle linkage and a plunger 276, Fig. 16, to rock the arm 1190 (190, Fig. 6) in a direction to raise the follower 187 and therefore the template 182. The resultant upward movement of the carriage 120 is only sufficient for the lens to clear the grinding wheel. The carriage can then be raised manually to its uppermost position for removal of the lens and in this position is locked by a spring catch 310 engaging a pin 253 and prevented from swinging about its vertical axis (i.e. the pins 110) by a keeper 320 which depends adjustably from a guard 326 and engages by a slot 325 with a pin 250. The pressure of the work on the grinding wheel is, in this construction, adjustable by means of a weight 330 slidable along a rod 331. The operative end of the grinding wheel may be either flat or provided with a V-groove according to whether the lens is to have a flat or bevelled edge; in the former case, the lens may be reciprocated axially during the operation to prevent wear of the wheel in one place. Trueing of the grinding wheel is effected by a diamond 235, Fig. 1, carried by an arm 247 provided with a follower arm 237. With the carriage 120 swung downwardly about its pivots 117, pressure is applied to the arm 247 through a knob 245 and the diamond moved swung the rotating grinding wheel about the axes of the pins 110 while the follower arm 237 contacts a template 102. After the trueing operation, the bracket 95, with the carriage 120, is adjusted vertically on the pillar 60 to make the necessary compensation for trueing.