GB907387A - Electrical lead screw - Google Patents

Abstract

907,387. Electric correspondence control systems. SPERRY GYROSCOPE CO. Ltd. Dec. 4, 1959 [Dec. 5, 1958], No. 39230/58. Class 40 (1). [Also in Groups IX and XXII] An electrical lead screw for cutting screwthreads on a lathe comprises a pick-off device having one member 6a (Fig. 1) attached to the lathe saddle 2 and the other member 6b moved linearly by rotation of the headstock 7, the error signal in the pick-off being used to adjust the position of the saddle so that accurate proportionality is maintained between the linear movement of the saddle 2 and rotational movement of the headstock 7. The pick-off member 6b is carried by a thin metal tape 8 paid off from a drum 9 geared to the headstock 7, the free end of the tape 8 being attached to a spring 12 to keep it taut. The pick-off signal is fed through amplifiers 14, 17, a phase-sensitive rectifier 15 and a low-pass filter 16, to an actuator 18 controlling the hydraulic motor 1 driving the saddle 2. In one embodiment (Fig. 4), the spring 12 is replaced by a torque motor 67 coupled via clutches 64, 65 and gear-boxes 63, 66 to the headstock driving spindle 62, and the drum 20 is arranged to travel along a bar as the tape 8 is paid off to ensure that its position is maintained constant. The support 69 to which the tape is secured is associated with a locking device 71 to allow manual control of the lathe saddle, and is also supplied with microswitches 73, 74 operated by the support 69 to stop the lathe if the tape tension does not remain constant. The extent of travel of the saddle is determined by limit switches 90-93. The hydraulic motor 75 driving the saddle is fed from amplifier 77 whose input is the positional error signal from the pick-off 68, a headstock speed signal from tachogenerator 79, and an antihunting signal from tachogenerator 78. Specifications 816,714, 842,376 and 880,763 are referred to.