Patent GB-878636-A (GB)
Title: Improvements in copying mechanisms
Inventor: WOSTBROCK WERNER
IPC: B23Q35/123
Filed: 1958-02-03
Abstract: 878,636. Electric copying machines. HURXTHAL, C. A., [trading as FRITZ HURXTHAL [Firm of]]. Feb. 3, 1958, No. 3515/58. Class 38 (6). A copy-milling machine utilizing a pattern and a tracer has two feeds for each dimensional direction, the main feed being constant and the auxiliary feed being controlled by signals derived from the tracer mechanically linked to differential transformers responsive to movement in each of three mutually perpendicular directions As shown (Fig. 2), a motor 17 attached to the frame 1 of a copy-milling machine drives a spindle 2 through an electromagnetic clutch via gears 10 and a bushing 4 keyed to spindle 2, but axially movable thereon. Spindle 2 carries a sleeve nut 3 which produces longitudinal movement of the milling table 5 when spindle 2 is rotated. An auxiliary drive for the sleeve nut 3 by motor 17 is effected through, another electromagnetic clutch via gears 21, 21a and infinitely variable (within certain limits) gearing 24, coupled to gear 29 which is rigidly fixed to sleeve nut 3. Gearing 24 is adjusted by a member 31, driven by a motor 32, energized by signals from transducers associated with a disc tracer 51 and a template 50. The tracer is attached to an arm 52, supported by a ball and socket joint 54, 55 at one end, and a ball 57 in a conical recess 58 at the other end, a spring force being applied at this end to maintain the tracer 51 in contact with the edge of the template 50. Between the ends of the arm 52 is a square block 56 on which rests the armature of a differential transformer 63, so that movement of the tracer in the appropriate direction produces corresponding signals from the transformer 63. A similar differential transformer 62 (Fig. 5), is associated with a perpendicular face of block 56 to measure movement in the perpendicular directions, and a third transformer 64 is located on the arm 52 to measure movement in the third initially perpendicular direction. Each of the transformers feeds through an amplifier 71 to its motor 32 to adjust the member 31 associated with the variable gearing 24 of the auxiliary drive, simultaneously adjusting a feedback device consisting of a wedge 77 and a differential transformer 79 also feeding into amplifier 71. The feedback voltage may alternatively be derived from a tacho-generator 84 on the output shaft 25 of variable gearing 24. A mechanical link may be introduced between the square block 56 and the armatures of the differential transformers to obtain mechanical amplification of the movement of the tracer 51. For three-dimensional copying the tracer 51 may be a ball instead of a disc, the diameters being appropriate to the diameter of the cutting tool. Additional differential transformers are associated with the tracer arm 52, which feed into a resolver energizing an additional motor which rotates the shaft 59 in which is eccentrically located the conical recess 58, thus ensuring that the tracer 51 is always biased against the pattern 50 at a predetermined angle, and correspondingly ensuring that the tool presents the same predetermined angle to the workpiece at the point of cutting.