Patent GB-614321-A (GB)
Title: Improvements in or relating to motion translating devices or tracers
IPC: B23Q35/32
Filed: 1945-08-03
Abstract: 614,321. Copying by milling. MILLER, T. Aug. 3, 1945, No. 20067. Convention date, July 28, 1944. [Class 83 (iii)] [Also in Group XXXVIII] In a tracer machine-tool lateral movements of the stylus with respect to its longitudinal axis do not cause longitudinal movements of the stylus and vice versa. As shown, the outer frame O is secured rigidly to a suitable support of a machine tool to be controlled, and supports the intermediate frame I in which is mounted the drum D which carries the tracer stem S. Supporting brackets 11 at the top plate 10 of the frame O receive the bolts 14. In each of the four sides of the frame I is an elongated aperture 31 covered by a flexible metal plate 32, of spring steel, secured to the frame I along its edge by bolts 34 and clamping rings 33. Two holes 35 are drilled in each plate. The drum D comprises a hollow cylinder 52 provided with the rectangular member 53, at two opposite sides of which are the bolts 51 with the spacers 51a, 51b, held thereon. The flexible spring steel discs 55 are clamped by rings 56 and screws 57 to close the ends of the cylinder 52 and are centrally drilled to receive a rod (not shown) which is rigidly secured to both discs by a nut at the upper end, intermediate spacers and the holding bracket 61 at the lower end. The tracer stem S, which may receive tracing fingers of varying sizes, has an upper disc which fits within and is held to a complementary formed disc in the holding bracket 61 by spring clips 91. When assembled, the four bolts 14, pass through the holes 35 in two opposite plates 32 secured to frame I, thereby gripping the plates between the bolt heads and spacers 14a when the nuts at the outer ends of the bolts are tightened against the supporting brackets 11. The flexibility of the plates 32 permits a limited displacement of the frame I along the line V, relative to the frame O, which is detected by switch members 72, 70 positioned on opposite sides of the frame I and at the two brackets 11 respectively. The remaining two oppositely disposed plates 32 on frame I carry the inner drum D by means of the screws 51. The plates 32 are gripped between the large spacer 51a on one side, and the small spacer 51b and bar 54 on the other. A relative displacement between the drum D and frame I may take place along the line H and is detected by the two switches, each comprising members 72, 70 respectively mounted on the bars 54 and the bridges 36 secured to frame I. The flexibility of the steel discs 55 permits of a relative displacement between the stem S and drum D in the direction L, detected by two switches comprising further members 72 (not shown) and 70. The latter are mounted on a bracket 65 supported on member 53 which extends through notch 38 in frame I, and the former on a contact arm (not shown) secured to the upper end of the rod passing through and movable with the discs 55, and extending through the notch 37 in frame I. The sensing devices may take a form other than a switch, e.g. pressure bellows, valves, carbon piles, and variable condensers. In the present embodiment, the ground element of each switch is mounted upon a spring member 72 and the second elements on a micrometer 70 which is adjusted to allow of operating gaps, in the normal or neutral position of between 0.0005 inches and 0.002 inches. Each micrometer comprises a screw (not shown) carrying a contact point at one end, adjusted by a graduated head and supported in a bushing insulated from earth. Frictional contact between the screw and bushing is ensured by means of a bakelite plug constrained to grip the screw under pressure from a small set screw. Only one switch of each associated pair may make at once.