Patent GB-770645-A (GB)
Title: Improvements in or relating to movement controlling apparatus for copying machines
IPC: B23Q35/123
Filed: 1952-11-21
Abstract: 770,645. Electric copying machines. LANCASHIRE DYNAMO ELECTRONIC PRODUCTS, Ltd., and ROBINSON, K. A. Feb. 22, 1954 [Nov. 21, 1952], No. 26417/52. Class 40 (1). [Also in Group XXXV] In a copying machine wherein the feeler head produces an A.C. signal of magnitude and phase angle corresponding to the magnitude and direction of the feeler deflection, and this signal controls the usual x, y co-ordinate follower motors through respective phase-andamplitude detectors responsive to the x, y components of the signal, an additional control of the motors is provided by a phase shifter which acts on the usual reference signal according to the magnitude of the resultant feeler deflection. Feeler head, construction, Fig. 1. The feeler 4a is secured to the lower end of a ferromagnetic rod 4 capable of limited universal movement about its upper end 4b. The rod is biased by means, not shown, normally to assume a symmetrical position within the cores of four magnets 3a . . . 3d disposed in coplanar pairs at right angles to one another and energized by quadrature voltages so that a pick-off coil 5 mounted on the rod 2 develops a voltage whose magnitude and phase correspond to the magnitude and direction of the deviation of the rod 2 from normal. Operation, Figs. 2, 6, 7. The feeler had is mounted on a cross slide D1, Fig. 6, movable in the co-ordinate direction X-X on a slide D2 movable in the direction Y-Y. The magnets 3a-3c are aligned with the axis X-X and magnets 3b-3d with the axis Y-Y. The feeler axis 4a is perpendicular to both of these axes, and, being deflected normal to the contour of the template 20 generates a resultant voltage F, Fig. 7, in the direction of this normal relative to the energizing voltages a . . . d of the magnets 3a . . . 3d. The magnets are energized from a source 1, Fig. 2, through a phase splitter 2, and the pick-off voltage F of coil 5 is amplified at 6 and fed in parallel to two phase-and-amplitude detectors 7, 8 which receive quadrature reference signals from the source 1 through a phase shifter 11 and a phase splitter 9. The D.C. outputs at 12 of the detectors control the speed and direction of rotation of the respective X-X, Y-Y co-ordinate drive motors. These motors are initially controlled by hand to bring the feeler into engagement with the template when a relay controlled by a detector sensitive to the pick-off signal switches in the automatic control. The motors continue to move in directions to move the feeler head further in towards the template thereby increasing the amplitude of the pick-off signal. A portion of this signal is rectified at 10 and applied to the phase shifter 11 to produce a sudden phase shift of approximately 90 degrees of the reference signal applied to the phase detectors 7, 8 when the pick-off output reaches a predetermined value. This results in a variation of the phase detector outputs and hence of the speeds of the co-ordinate drive motors whereby the feeler moves tangentially of the template at a speed regulated by the pick-off signal amplitude required to produce the sudden phase shift of the reference signal. Detailed circuitry, Figs. 4, 5. The output of the pick-off coil 5 is amplified at V4A. V4B and applied over a transformer T5 (secondary 24) to one phase detector T4-V7A-V7B, the output of which is applied at m1 to a double triode V2 controlling through triodes V10, V11 the differential fields 21 of a Ward-Leonard generator G1 driving one of the co-ordinate drive motors M1. The other motor M2 is similarly controlled through a phase detector fed from the secondary 25 of the signal output transformer T5. The quadrature reference signals for the phase detectors are derived from a phase splitter 26-27, T3 in the output of an amplifier V3A, V3B fed at 14 from the phase shifter 11. A portion of the amplified pick-off signal output is rectified at 28 and fed at 15 to control the impedance of a tube V2, Fig. 4, of the phase shifter. The reference A.C. from source 1 is applied at 13, the phase of the output taken off at 14 depending on the impedance of the tube V2. Modifications. The slides D1, D2 may be driven pneumatically or hydraulically. More than two pairs of magnets may be used in the feeler head.