Patent GB-779525-A (GB)
Title: Continuous electrical contact feeler control
IPC: B23Q35/122
Filed: 1953-12-21
Abstract: 779,525. Electric copying machines. SCHMID, W. K. Dec. 21, 1953 [Dec. 20, 1952], No. 35511/53. Class 40 (1). In an electric copying machine a templatesensing feeler selectively actuates a group of relays in accordance with its deflection, either by means of a brush moving over insulated contact segments, or by means of a spindle with projections selectively operating leaf-spring switches, the relays controlling gears and/or clutches associated with feed motors to produce the correct rectangular components of movement of the template and workpiece, or feeler and tool. In one embodiment the feeler spindle 1 (Fig. 1) is mounted for limited universal movement in a seating 2, itself movable axially in a frame 3. Movements of the feeler 4 are applied through a cone 6 and magnifying lever 7 to a contact brush 10 which is moved vertically from contact I (Fig. 3) over a series of contact segments I . . . IX according to the magnitude of the feeler deflection from neutral. In the case of a copying lathe, the feeler and the cutter are carried by the cross-slide (not shown), the drive screw 62 of which is driven by the main lathe drive through a reversible electromagnetic coupling and four variable speed gears 12 controlled by electromagnetic clutches 18, 41, 47, 53. The longitudinal slide is similarly driven by a screw 64, also driven from the main drive, through a reversible coupling 88 and four variable speed gear clutches 81-84. The connections of the couplings and speed gear clutches are effected selectively by relays R1 . . . R7. As the feeler 4 is deflected so that brush 10 moves from segment I to segment V, relays R1-R5 operate successively, selectively energizing the electromagnetic clutches and gears 12, 61 in accordance with the position of brush 10 to reduce the longitudinal speed in steps from maximum at segment I to zero at segment V, whilst increasing the cross-speed in steps from zero at segment I to maximum at segment V. When the brush 10 contacts segment VI relays R6, R7 are energized, R7 closing a holding circuit whereby it remains energized as the brush moves from segment VI to segment IX. Through contacts R7r, R7a2 the reversing clutch 88 is changed over so that the longitudinal movement is in the opposite direction. Relay R7 is released when the brush 10 moves down on to segment V, energizing relay R5 and releasing R7 at contact R5a1. Thus the movement of the feeler and tool varies as shown in Fig. 4, in accordance with the segment in contact with brush 10. In a second embodiment (Fig. 5) wherein the relays R1 . . . R7 are again actuated selectively in accordance with feeler deflection, the cross and longitudinal feed screws 62, 64 are driven by three-phase motors 109, 110 with D.C.-fed rotors, the rotor current being interrupted at selected rates by cylindrical interrupter devices 99, 100 driven at constant speed. The surface of each interrupter has wedgeshaped conducting portions such as 101, 102 which are engaged by longitudinally spaced brushes 111 . . . 120 selectively energized by relays R1 . . . R6, and the speed of the motors 109, 110 is reduced by the selected interruption in the D.C. supply to the rotor. Reversal of motor 110 is effected by relay R7 and switch 121 which produce a reversal of two of the phase fed to the motor stator. Relay R7 is energized as before when the brush 10 is on contact segments VI . . . IX. The number of contact segments may be increased to thirteen and an additional relay provided to cater for reversal of the cross-feed drive as well as the longitudinal drive. By using a brush 10 wider than the insulating strips between contact segments I . . . XIII the number of control steps may be increased to 25, so that the apparatus is substantially continuous. In a further embodiment (Fig. 8), deflection of the feeler 4 from the neutral position raises a block 131 with projections 132 . . . 135 which operate switch leaf springs 136 . . . 139 to actuate contacts energizing the relays R1 . . . R5 singly or in combination to effect speed control of the drive screws 62, 64 by means of constantly driven interrupters 99, 100 and electromagnetically reversible clutch drives 147a, 148 substantially as before. In modifications, speed control may be effected by driving each motor through a Ward-Leonard system, using relays R1 . . . R6 to control the generator fields. The speed steps may be graded according to a sine or cosine law to give a constant speed of feed in each direction. The invention may be applied to copying machines in which a rotary and longitudinal movement are controlled. Specification 740,603, [Group XXXV], is referred to.