Patent GB-1032049-A (GB)
Title: Lens generating method and apparatus
IPC: B24B13/00
Filed: 1963-08-07
Abstract: 1,032,049. Grinding. D. VOLK. Aug. 7, 1963 [Aug. 22, 1962], No. 31119/63. Heading B3D. [Also in Division G2] A method of generating a surface of revolution for a lens, mirror or member for forming a lens or mirror, or a template for use in generating a surface of revolution, comprises mounting a work blank in a fixed position or for rotation about a work axis, mounting a tool having a generally planar and circular material-removing edge with the plane of the edge at an angle to its direction of movement, and moving the tool towards and across the work blank whilst rotating the tool about an axis perpendicular to the plane of its edge and, if desired, the work blank about a work axis. The work blank may be of glass, plastic or metal to form a lens, mirror, mould for a lens, cam for generating a lens, or a tool to the surface of which diamond dust is applied, or may be of sheet metal which has its edge shaped to form a template for use in a machine for generating optical surfaces. In apparatus for carrying out the method, the work blank 72, shown in Fig. 52 as a circular blank, is mounted on a work-holder 71 carried by a shaft 70 rotatably mounted in a tubular housing 67 adjustably clamped to the top of a post 63 which is vertically adjustable by a rack- and-pinion mechanism 64, 65 in a support 61 mounted on a base 60. A motor 76 is carried by the housing and has a shaft 75 connected by gearing 73, 74 to the shaft 20 to rotate the work blank 72. The housing is rotatably adjustable in the post 63 to position the axis " p " of the work blank at a desired angle in a vertical plane normal to the axis of the housing, and is vertical adjustable by the rack-and-pinion 64, 65 to adjust the vertical height of the work blank. The base 60 is formed with a longitudinal slot along which a slide 81 is adjustable by a screw 84 and hand wheel 85. A cross-slide 86 is adjustable on the slide 81 transversely of the direction of movement of the slide 81 by a screw 89 and handwheel 90 and carries a pivot 92 for an arm 93. An upper part 93a, Fig. 54 (not shown), of the arm is slidable in a recess 93b in the lower part of the arm and retainable in adjusted position by a pin 94a selectively engageable with one of a plurality of holes 95 in the part 93a. The upper part 93a carries a vertical pivot 99 supporting an arm 98 which, in turn, has a horizontal pivot 103 to which is secured an electric motor 105 driving a tool 94 which, as shown in Fig. 52, has an internal annular grinding edge 111. The centre m of the plane of the grinding edge lies at the intersection of the pivots 99, 103 and the grinding-wheel can be adjusted about the pivots so that, when the pivot 92 is moved into the vertical plane containing the work axis " p " and the arm 93 is moved about the pivot by power means or a screw mechanism 113, an optical surface is produced on the work blank. The surface may be formed by maintaining the arm 93 vertical and advancing the grinding-wheel by means of the screw 84; with the workpiece stationary, a surface having a curvature in one direction only may be formed while if the workpiece is maintained stationary and the arm 93 is swung about the pivot 92, a surface having a different curvature in two directions, i.e. a toric surface. will be formed. Alternatively, the arm 93 may be fixed in the vertical position and the plane of the grinding edge adjusted so that it is parallel to the position shown in Fig. 54 with the point m in the plane of the axis " p," the grinding edge then being moved in its plane by the screw 89 to engage the work blank. By adjusting the grinding-wheel about the pivots 99 and 103 and the point m transversely by the screw 89, movement of the grinding edge by movement about the pivot 92 or by movement of the slides 81 or 86 permits optical surfaces of revolution such as parts of spheres, prolate or oblate ellipsoids, paraboloids and hyperboloids with or without apical umbilical points or cusps, ellystical toroids, one principal meridian being non-circular and having a prolate or oblate elliptical profile, saddle-shaped elliptical toroids with and without apical cusps, right circular cones and elliptical cylinders. When a template is to be produced, a sheet of metal, such as brass, is mounted on the work-holder which is held against rotation and the grinding-wheel adjusted as referred to above and advanced into the plane of the workpiece. The template may be non-symmetrical and the grinding edge moved in one pass over the workpiece, or symmetrical in which case the grinding-wheel is advanced into the workpiece until the apical point of the grinding-wheel engages the workpiece and is then retracted, the workpiece then being rotated through 180 degrees and the process repeated. The edge 111 of the grinding-wheel may be sharp or of toric shape and the wheel may be cup-shaped, as shown, or in the form of a disc. If the workpiece 72 is of metal, diamond dust may be applied to its surface so that it may serve as a grinding tool. The workpiece may be inverted so that concave surfaces are formed, or two workpieces may be mounted at opposite ends of the workholder shaft 70 for simultaneous grinding; if the grinding-wheel is advanced by movement of the slide 81, similarly-shaped workpieces will be produced whereas, if the arm 93 is moved about the pivot 92, dissimilar surfaces will be produced. In another embodiment, the tubular housing carrying the motor 76<SP>1</SP>, Fig. 57 (not shown), and work-holder is as described for the previous embodiment and mounted in a post 63<SP>1</SP> vertically adjustable in a support 60<SP>1</SP> by a rack-and-pinion mechanism 64<SP>1</SP>, 65<SP>1</SP>. A second support 60<SP>11</SP> is secured to the support 60<SP>1</SP> and carries the longitudinal and transverse slides 81<SP>1</SP>, 86<SP>1</SP> movable by screws 84<SP>1</SP>, 891. The slide 861 carries a pivot 96<SP>1</SP> which is rotatable by a bevel gearing 128, 129 and has a block 125 slidably receiving the arm 93<SP>1</SP>. The latter is vertically adjustable by rack-and-pinion mechanism 123, 124 and has the vertical pivot 99<SP>1</SP> for the arm 98<SP>1</SP> which, in turn, has the pivot 103<SP>1</SP> for the arm supporting the motor 105<SP>1</SP> and grinding-wheel. In this embodiment, the grinding-wheel is adjustable through a greater vertical distance and is also adjustable through 360 degrees about both pivots 99<SP>1</SP> and 103<SP>1</SP>.