GB1450710A - Machine for producing aspherical surfaces - Google Patents

Abstract

1450710 Grinding aspherical surfaces ESSILOR INTERNATIONAL SA COMPAGNIE GENERALE D OPTTQUE 28 Dec 1973 [29 Dec 1972] 60101/73 Heading B3D A machine for producing concave or convex aspherical surfaces comprises a blank carrier spindle 46 mounted for rotation about a first axis X-X, a cutting tool 254 mounted for travelling movement in the direction of a second axis and pivotable about a third axis Y-Y perpendicular to the first and second axes, a control cam 16 and means controlled by the cam for displacing the tool along the second axis. The machine may be used for forming aspheric surfaces on the two parts M, M 1 , Fig. 14, of a mould for producing corneal lens, and has a frame 10 supporting a base 11 carrying the support 12 for the spindle 46. A turret 14 carrying the tool in the form of a diamond wheel 254 is pivotable about the axis Y-Y of a pivot 15. The frame 10 is rigid and supports the base 11 at three points 20, 21, 22 by means of brackets 26 having screws 27 engaging ground washers resting on rubber on the frame. The base is of welded construction and damping of the structure is effected by concrete 30 poured into compartments in the base which has lower and upper portions 11A, 11B. The upper portion 11B carries the spindle support 12 formed in two halves 40, 41 which together form a bore for a hydrodynamic spindle carrier 45 in which the spindle 46 is rotatable by a belt drive 51 and is axially movable. One end of the spindle carries a chuck 47 for a holder E for the blank, the holder being held against a radial orientation pressure screw 59 by two pairs of support points 55 ... 58. The other end of the spindle having the pulley 50 for the belt drive 51 is formed with a notch 90 engaged by the ball 91 of damping means 13. The ball is adjustable by a graduated disc 95 on a body 93, and magnets 48 act to urge the ball against the notch. The body is slidable on a ground plate 32 on the upper part 11B between a pair of pillars 100, 101. The end of the body has lateral extensions 103, 104. A spring 107 and damping jack 105 extend between pillar 100 and extension 103, and a micrometer screw 114 is adjustable in pillar 101 and engages extension 104 to axially position the spindle. The support 12 is located on the ground plate 32 and is located by a spring 64 in a pillar 60 pressing the support so that a curved segment 73 engages a recess 75 in a post 61 and, to adjust the orientation of the axis X-X, is pivoted about the axis of the segment to a position determined by an abutment 80 on a lever 81 adjustable about a post 82 by a screw 83. The tool carrier turret 14 is carried by the pivot 15 which is rotatable by a motor and transmission 153. The pivot carries a base 160 on which a shoe 161 is movable by means of a slide (not shown), the shoe being coupled to the tool carrier 164. The base has bearings for shafts 173 engaging lugs in a lever arm 177, the lower end of which supports a follower 181 urged against the cam 16 by a spring 190. Movement of the lever is imparted to the shoe by a micrometer mechanism 200 which can be mounted in the lever so that a shoe thereon engages an eccentric point 204 in one or other of screws 202, 203 in the shoe. The movement imparted to the shoe is varied according to the axial adjustment of the operative screw and the rotational position of its point. The cam 16 is mounted on a plate 216 located in the machine by points 250... 253, Fig. 3, but is removable from the machine for adjustment of its profile, the plate then being located by points 240, Fig. 12, on a further plate 225. The cam consists of a strip 218 adjustable on the plate 216 by a plurality of screws 220 to a shape indicated by a gauge 229 which has a pointer 228 engaging the cam and is carried by a frame 227 adjustable about a pivot 226.