Patent GB-538726-A (GB)
Title: Improvements in or relating to milling, engraving and like copying machines
IPC: B23Q17/24
Filed: 1940-02-13
Abstract: 538,726. Engraving machines KAPELLA, Ltd., and WARMISHAM, A. Feb. 13, 1940, No. 2753. [Class 100 (ii)] [Also in Groups XXII and XXIII] A copying machine for milling or grinding work from a copy such as a drawing or templet, comprises work and tool supports; a drawing or other flat copy, an optical system for projecting a primary image of an illuminated part of the copy on a graticule, means whereby relative movement between the graticule and the primary image causes similar movement on an appropriate scale between the tool and work supports and a second optical system for projecting on a screen superposed images of the graticule and primary image. In one form, Figs. 1 and 2, the machine comprises a fixed base A carrying a carriage B which may be moved on perpendicular'slideways B<SP>1</SP>, B<SP>2</SP> by hand wheels B<SP>3</SP>, B<SP>4</SP>. The carriage B carries a work table C and the frame D on which the copy such as a large scale drawing, is mounted, the parts C and D being synchronously rotated from a hand wheel C' by gearing C<SP>2</SP>. Alternatively the table C and frame D may be fixed to the carriage B. The tool E shown is a grinding wheel which may have both rotary movement about an axis parallel to the plane of the table C and also a reciprocating movement perpendicular to said plane to. shape the work throughout its thickness. The direction of reciprocation may be varied to enable the work to be ground to a rake angle. An objective F throws an image of the drawing on to a graticule G mounted on the fixed base A and having markings corresponding to a section of the edge of the grinding wheel. The image is of the same size as that to be produced on the work so that the graticule and image constitute a replica of the tool and finished work. A ring of lamps mounted on gimbals is arranged to illuminate part of the drawing, each lamp having a reflector which directs the light on to a part of the drawing lying in the axis of the ring. The axis of the ring passes through a datum point on the graticule, preferably a datum corresponding with the working point of the grinding wheel. The gimbal rings HH' have forked arms engaging perpendicular fixed rods G' , G<SP>2</SP> carrying the graticule in order to tilt the lamp ring as the carriage B is moved to maintain the coincidence of the centre of the illuminated area of the drawing with the datum point of the graticule. A field lens J and second objective L on a fixed bracket A<SP>1</SP> direct rays through reflecting prisms K<SP>1</SP>, K<SP>2</SP> on to an inspection screen K, forming superposed images of the graticule and primary image. During the movement the images of copy and graticule move relatively to each other on the screen, such movement corresponding to the movement of the tool on the work. In a modification Fig. 3, the work N and copy frame O are both supported on the fixed base M. The sliding carriage P carries the tool Q and also the graticule R and field lens S. The first objective T, lamp gimbals, screen V and reffecting prisms V<SP>2</SP> are mounted on fixed parts while the second objective W is mounted on a pantograph pivoted at a fixed point W<SP>2</SP> and connected at W<SP>1</SP> to the movable carriage, the objective movements being thus proportional to the graticule movements with a ratio which maintains the datum point on the graticule always at the same point on the screen. In a further modification the copy is transparent and the illuminating device shown in Fig. 1 is replaced by a single lamp arranged on a pantograph pivoted at a fixed point and connected also to the bearing of the work table. The Provisional Specification refers to Specifications 481,591 and 499,751.