Patent GB-656690-A (GB)
Title: Improvements in apparatus for grinding the bevel edge of spectacle and other lenses
IPC: B24B9/14
Filed: 1948-10-25
Abstract: 656,690. Grinding lenses. TAIG, W. A. Oct. 25, 1948, No. 27653. [Class 60] Apparatus for grinding a double bevel edge on spectacle and other lenses comprises in combination means for forming simutaneously the bevel surfaces on the peripheral edge of the lens, lens-supporting means for holding the lens in contact with the grinding means and for imparting rotary movement to the lens during the grinding, means for displacing the lenssupporting means to cause the lens to advance inwards and recede from the grinding means in accordance with the peripheral shape of the lens to produce the finished shape and means operable as a result of the displacement of the lens-supporting means to impart axial movement to the lens-supporting means to maintain the peripheral edge of the lens in predetermined positioned relationship with the grinding means. Grinding wheels 2, 3, belt-driven in opposite directions are supported by pedestal-bearing brackets 6 secured by clamping nuts 7 to the machine bed. Two spindles 8, 9 are mounted coaxially in bearing sleeves 10, 11 forming part of a bracket 12, the spindle 8 being non-rotatable but capable of sliding longitudinally, and the spindle 9 being rotatable. The opposed ends of the spindles carry ferrules 13 having rubber pads 15 between which the lens 1 is gripped. The ferrule 13 on the spindle 9 is pinned thereto by a transverse pin; the ferrule 13 on the spindle 8 is rotatably mounted; ball thrust bearings 14 are provided. The spindle 8 is slidable in its bearing sleeve and is urged towards the spindle 9 by a spring 16 bearing at one end on a flange 17 on the spindle 8 and at the other end on a bush 18 mounted on the end of the spindle 8 and within a sleeve 19, the bush and sleeve being pinned together and jointly rotated by a hand-wheel 20 secured on the sleeve 19. An internal flange 22 on the inner end of the sleeve 19 engages with the flange 17 on the spindle 8 to limit the inward axial movement of the swindle 8 under the influence of the spring 16. The sleeve 19 has an external thread 23 engaging an internal thread 24 in a bush 25 secured in the bore of a housing 26 forming an extension of the bearing sleeve. Rotation of the handwheel 20 in one direction effects inward movement of the sleeve 19 to permit the spring 16 to urge the spindle 8 axially towards the spindle 9, and rotation of the hand wheel 20 in the opposite direction causes the sleeve 19 to move outwardly and through the flanges 17, 22 to move the spindle 8 axially away from the spindle 9. The spindle 9 has a pulley 27 by which it is driven. The bracket 12 is mounted on a shaft 28 by two pairs of arms 29, 30, secured at their upper ends to the bracket by headless conical point screws 31 with lock nuts 32, the lower end of each pair of arms being similarly secured by headless conical point screws 33 with lock nuts 34 to bearing blocks 35, 36 carried by and keyed to shaft 28 which is mounted in spaced bearings 37 on the machine bed. The shaft 28 is urged axially in one direction by a spring 38 interposed between one bearing 37 and a collar 39 secured to the shaft 28; the shaft is movable against the spring action by a handwheel 40 having a threaded spindle 41 mounted in the threaded bore of a block 42, the end of the spindle abutting against a thrust ball 43 in a bore of the shaft 28. Rocking of the bracket 12 is effected by a rotary cam 44 detachably mounted on a spigot 45 projecting from one end of the spindle 9; the bracket 12 is biassed towards the grinding wheels by a spring 44a attached at one end to the sleeve 10 and at the other end to a fixed stud 44b. The cam is connected in driving engagement with the spindle 9 by two driving pins 46 projecting outwardly from a bush 47 mounted on the spigot 45, the pins passing through holes in the cam. The cam is maintained axially in position on the spigot 45 by a headed plunger the head 48 of which is pressed against the face of the cam by a spring 49, one end of which engages the stem 50 of the plunger, the other end engaging the inner end of a bore 51 in a sleeve 52 in which the stem 50 slides, the sleeve 52 being mounted in a bearing 53 carried by the bracket 12. The plunger is forced back against the action of spring 49 when it is desired to remove the cam 44 for replacement by a different cam. The cam periphery bears against an abutment surface 54 formed on a vertical bracket 55 carried by one end of a spindle 56 mounted in a bore in a housing 57 secured to the bed plate. For adjusting the position of the abutment surface 54 to permit different sizes of cams to be fitted the end of the spindle 56 has a micrometer screw thread 57a carrying a micrometer adjusting nut 58, backlash being taken up by a compression spring 59. The micrometer screw may be adjusted as grinding proceeds to effect gradual grinding of the lens to finished size or the lens may be plunge ground by adjusting the micrometer screw to the finished size of the lens before grinding commences. Axial movement of the lens between the grinding surfaces of the grinding wheels is effected by a cam 60 which, as a result of the rocking motion of the bracket 12, causes the latter to swing in one direction axially on the pivot pins 31, the arms 29, 30 moving similarly about the pivot pins 33, the cam operating against the action of a spring 61 stretched between two posts, one 61a being carried by one of the arms 30, the other 61b being fixed to the machine bed. The cam 60 is detachably mounted on a spindle 60a carried on the upper end of an arm 62, the lower end of which has a boss 63 pinned to the shaft 28. The cam 60 has a cam surface 64, the shape of which corresponds to the sectional curvature of the lens, and as the cam is rocked lateral movement is imparted to the lens-supporting means through a cam follower roller 65 interposed between the cam and a pressure plate 66 mounted on the end of sleeve 52, the pressure plate forming part of a boss 67 bearing against one end of the bearing 53. The roller 65 is carried on a pivot pin 68 mounted on the upper end of an arm 69, the lower end of which is mounted on a pivot pin 70 supported in spaced lugs 71 on a bracket 72 carried by the shaft 28. In a modification the roller 65 can be replaced by two separate rollers carried by the upper end of the arm 69, one of said rollers bearing against the surface of the cam 60 and the other bearing against the face of the thrust plate 66. The shaft 28 is freely rotatable in the bracket 72 which is held against movement by a stud 73 engaging in a support 74 projecting vertically upwards from the machine bed. The cam 60 is removable so that it can be replaced by a different cam or, if desired, the cam surface can be divided radially, each division corresponding to a different shaped lens, and the cam being indexed around on its spindle to bring the desired section into line with the cam follower. The arm 69 is so mounted that it can be moved transversly of the spindles 8, 9 to permit the roller 65 to be brought into correct registration with the surface of cam 60; to this end the pivot pin 70 has a threaded portion engaging a thread in one of the lugs 71, the pivot pin having a knob 75 whereby it can be rotated. When it is desired to remove the cam 60 the lens-supporting assembly is. moved axially away from the cam; this is effected by a cam disc 76 mounted eccentrically on a rotatable pivot 77 carried on a bracket arm 78 projecting from the bracket 72. The edge of the cam disc 76 bears. against a surface 79 forming part of the arm 30.