Patent GB-663419-A (GB)
Title: Improvements in or relating to surfacing-machines, more particularly for surfacing lens-blanks and similar articles
IPC: B24B13/04
Filed: 1949-05-13
Abstract: 663,419. Grinding lenses &c. ABBEY, A. (American Optical Co.). May 13, 1949, No. 12862/49. Class 60 A surfacing-machine has a work-supporting member and a tool-supporting member, the latter being adjustable about an axis substantially perpendicular to the axis of a rotating cup tool and intersecting the effective abrading portion of the latter, means for yieldably feeding one of the supporting members in an arcuate path about a second axis parallel to the first-mentioned axis, and means for displacing the second axis to vary the curvature produced on the work. The machine base 15 supports a bed 16, Fig. 1, on which is slidably mounted a supporting plate 19 rotatably carrying a post 32, Fig, 3, in roller bearings 36 and 45. This post is keyed to a turntable 33 fixedly secured to a table 77 on which is slidably mounted a carriage 85 connected by a pivot 95 with a quadrant plate 94 carrying, by means of a transverse slide 120 and a longitudinal slide 130, an electric motor 137 for driving a cup-type abrasive tool 140 with a curved edge 141. The lens blank 183, Fig. 9, is stuck by pitch to a block 184 secured to an adaptor 186 which forms a tapered fit on a plug 173, Fig. 6, secured to the end of a spindle 153 and provided with a nut 175 for the purpose of dislodging the adaptor. The spindle contains a spring 181 bearing against one end of a displaceable rod 178 which may be secured with respect to the spindle by a screw 182 and abuts the screwed member 162 of a micrometer adjustment 157 supported on a head 143 attached to the bed 16. The spindle rests in a V-grooved chuck 145, which is preferably magnetic, and may be displaced longitudinally with respect to the chuck by turning the adjustment 157 which thereby controls the depth of feed. During the cut, the tool is swung through an arc about the post 32 by the descent of a weight (not shown) which is attached to the turntable 33 by a cord 49, the turntable being locked or released by a cam device 72 and the rate of rotation being adjustably governed by a valve-controlled dashpot the piston of which is engaged with the post 32 by a rack 59 and a gear 60. The radius of this arc corresponds to the curvature to be imparted to the blank in the horizontal meridian and is determined by the adjustment of the carriage 85 which is effected by a screw 76 provided with a handle 81, the extent of the adjustment being indicated by two scales 92, 93 calibrated in diopters and millimetres. The curvature of the lens in the vertical meridian is determined by the tilt of the tool about the pivot 95 and the quadrant plate 94 co-operates with an arcuate scale on the carriage 85 to show the extent of this adjustment. A clamp 113 holds the plate 94 in the position to which it has been approximately adjusted and, after the clamp has been tightened a fine-screw adjustment between the clamp and the plate is used to obtain the precise setting. Wear of the tool is allowed for and its correct positioning in relation to the axis of the pivot 95 is ensured by inserting a gauge 195 in a bore in the pivot and adjusting the slide 130 by means of a screw 132 until the rod makes contact with the face of the gauge, and then adjusting the slide 120 by means of a screw 122 until the centre of the curved edge is aligned with the edge of the gauge 195 when the latter has been rotated through a right angle about the pivot axis from the illustrated position. The gauge is provided with one or more locating pins to fit holes in the pivot which is covered by a cap 101 when the gauge is not in use. A jig 188 provided with two V-grooved members 189 and an axiallyadjustable pin 192 is used to adjust the rod 178 so that the distance from the end of the rod to the face of the lens blank exactly corresponds to the distance between the tip of the screwed member 162 and the abrading surface of the tool. To enable a zero setting of the micrometer to be made and to allow for wear of contacting parts, a bush 161 in engagement with the member 162 is adapted to be axially displaced with respect to the head 143 and locked in adjusted position. Since the work, and hence the position of the rod, is more or less fixed in relation to the bed 16, the adjustment of the carriage 85 has to be compensated by an equal and opposite adjustment of the supporting plate 19 which is similarly provided with scales 30, 31, the adjustment being affected by a screw 26 connected by gears with a handle 21. During operation the tool is enclosed in a casing provided with splash guards and a hinged cover and is fed with coolant or lubricant from a tank in the base 15 by means of a pump, the fluid being returned to the tank by gravity. A vacuum system may be used to draw the mist formed by the fluid upon engaging the tool from the casing and expel it into the tank.