Patent GB-947174-A (GB)
Title: Improvements in or relating to the generation of shaped surfaces
Inventor: RAWSTRON GEORGE ORMEROD
IPC: B24D9/00
Filed: 1959-02-18
Abstract: 947,174. Working of metal; copying machines; grinding. RANK PRECISION INDUSTRIES Ltd., [trading as TAYLOR, TAYLOR & HOBSON]. Feb. 15, 1960 [Feb. 18, 1959], No. 5566/59. Headings B3B, B3D and B3T. Apparatus for producing on a workpiece a surface of revolution which deviates from a basic surface by relatively small amounts at different radial distances from the axis of symmetry comprises a rotating workholder and a toolholder moved relatively thereto by transmission means and a cam device. The basic surface may be plane or spherical and the invention is suitable for producing aspheric lenses. The workpiece C, Figs. 1 and 2, which in the first embodiment is a flat glass disc, is mounted in a holder A on the end of a spindle A<SP>1</SP> rotatable in a fixed headstook A<SP>2</SP> by an electric motor A<SP>4</SP>. A toolholder D is carried by a transverse " slide " E moving on three bearings E<SP>1</SP> in guide tracks F<SP>1</SP>. The slide E is supported on a longitudinally-movable carriage F, similarly supported by bearings F<SP>2</SP> on a fixed base slab B. The tool D<SP>1</SP>, which may be a sharply pointed diamond or a diamond wheel, is moved transversely across the face of the work by a crank and connecting rod device H<SP>4</SP>, J driven by a motor and worm gear H<SP>3</SP>, H<SP>2</SP> respectively. The rod J is connected through a micrometric adjuster J<SP>1</SP> to one end of a beam J<SP>2</SP>, the other end of which is guided transversely in a slot B<SP>3</SP> in the base. Transverse movements of the beam are transmitted to the tool slide E by two pairs of rollers E<SP>2</SP> between which the beam is located. The incremental movements required to be put on the tool are obtained from an adjustable strip cam K mounted on a disc H which rotates with the crank H<SP>4</SP>. The cam operates through a reducing lever G having an adjustable pivot G<SP>3</SP> which moves a push rod G<SP>1</SP> and an adjuster F<SP>4</SP> connected to the longitudinal carriage F. The cam K is set to the desired profile at the start of an operation by adjusters K<SP>1</SP>, K<SP>2</SP> and the setting is effected from a microscope L and a pair of glass scales L<SP>1</SP>, L<SP>2</SP>. The latter move at right angles along the edges of a glass reference plate L<SP>5</SP> according to the movement of the tool-slide E and the point of intersection of the scales is sighted through the microscope. When the basic surface is spherical, Fig. 11, the tool is guided to follow this by a former R attached to the tool slide and a follower roller R<SP>3</SP> connected to a rod R<SP>1</SP>, which is guided between rollers in the base-plate. This rod is in turn connected through an adjuster to the rod G<SP>1</SP> giving the incremental movements from the cam device. An optical cam following device described in Specifications 936,951 and 936,952 [Group XX], may be used in lieu of the strip K. The traversing and/or correcting movements may be given to the workpiece holder instead of to the toolholder. Chucks. The glass workpiece C, Fig. 3, is normally secured by wax in recesses C<SP>5</SP> in a holder C<SP>1</SP> which is loosely threaded to the driving spindle A<SP>1</SP> but which is precisely aligned by surfaces A<SP>5</SP> and C<SP>2</SP>. Specification 716,719 also is referred to.