Patent GB-1226090-A (GB)
IPC: B24B9/14
Filed: 1969-12-02
Abstract: 1,226,090. Grinding. TEXTRON Inc. 2 Dec., 1969, No. 58840/69. Heading B3D. A cribber for grinding the edges of blocked lens blanks comprises a grinding wheel 39 rotatable about a first axis on a base 20, a member 66 mounted to swing about a second axis 64 parallel to the first, a carrier 110 mounted for pivotal movement on the member about a third axis 108 transverse to the second, a spindle 153 mounted in the carrier for rotation about a fourth axis parallel to the third, means for mounting a blocked lens L on the spindle, operating means 184 for moving the carrier about the third axis, and drive means for rotating the spindle when the carrier is in its operative position to intermittently incline the blank about the fourth axis to bring successive portions of the blank into engagement with the wheel, the lens blank mounting means including a chuck 210 secured to the spindle 153 and having an axial bore into which projects a locating element 214 for locating the lens block in a predetermined position. The base 20 is formed with an aperture 26 in which is secured a motor 32 having a head to which a ring 37 is mounted carrying an annular grinding wheel 39 having a plane upper face. A trough 29 surrounds the wheel and a pair of nozzles 42, 44 supply coolant to the wheel and trough, a guard 50 being releasably held by clamps 52 to the base to prevent splashing. A post 64, which constitutes the second axis, is secured to the rear of the base and pivotally supports a bearing 66 formed with arms 65, 68 and pins 108, 109, constituting the third axis, on which the carrier 110 is mounted. A pneumatic piston-andcylinder device 184 is normally operative to hold the carrier in an upper, inoperative, position as shown in Fig. 1 and is connected between arm 65 and the carrier. Arm 66 has a screw-and-nut connection 72, 74 with the base whereby the arm, and hence the carrier, can be adjusted about the post to vary the position of engagement of the lens blank with the grinding wheel to equalize wear of the latter. A cover 130 extends along one side of the carrier and the spindle 153 is mounted in bearings 148, 149 in the cover and well 113 of the carrier, a pulley 146 on the spindle being connected by a belt 144 to a pulley mounted on the shafts of a motor 124 on the carrier. A cam 138 on the shaft is formed with a notch 139 and co-operates with a follower 140 on a microswitch 135. One end of the spindle 153 mounts the chuck 210 which has a bore for receiving the block 216 carrying the lens L, the block having a flat 218 engaged by the locating element 214 so that the horizontal axis of the lens is aligned with the spindle. The block is retained in the chuck by a piston 174 of a cylinder 170 mounted in the other wall 114 of the carrier. The other end of the spindle has a chuck 222 for a template 100 corresponding to the desired finished shape of the lens, a key 232 aligning the template with the lens block and lens L. The template co-operates with a shoe 101 which, when engaged by the template, moves against a spring 96 to close a microswitch 90 on a block 88 which is carried by the arm 68 and vertically adjustable by a screw 82 to compensate for wear of the grinding wheel. In operation, with a template mounted on chuck 222 and a lens block 216 held in chuck 210 by piston 174, device 184 is actuated to lower the carrier by gravity until the lens engages the grinding wheel. A flat is ground on the lens until the follower 100 engages shoe 101 to close switch 90 which energizes the motor 124 to index the lens and template, the template disengaging the shoe to stop the motor until a a further flat is ground on the lens. The intermittent rotation of the lens and template continues until the complete periphery is ground to the shape of the template and the follower 140 on switch 135 engages the notch 135 on cam 138, the switch preventing further operation of the motors 124. An angled guard 182 on the carrier co-operates with guard 50 to prevent splashing of coolant. A transparent cover 164 permits observation of the grinding process.