Patent GB-777021-A (GB)
Title: Improvements in and relating to gyroscopes
IPC: G01C19/30
Filed: 1955-10-28
Abstract: 777,021. Gyroscopic apparatus. GENERAL ELECTRIC CO. Oct. 28, 1955 [Oct. 29, 1954, Nov. 26, 1954], No. 30939/55. Class 97(3) In gyroscopic apparatus having a rotor suspended in a gimbal for angular displacement about two axes at right angles, stops are arranged to limit the displacement of the rotor and to remove the gyroscopic major axis rigidity, at least one torque producing device being connectible to the gimbal for applying torque in a given direction about the major axis for setting purposes, a torque producing device being also connectible to the gimbal to apply a reverse torque upon the removal of torque in the first direction, thus to restore gyroscopic rigidity. As shown in Fig. 1, the gimbal 2 is supported for rotation about a major axis 3-3 in a casing 1. The rotor, which consists of two similar parts 6, 7, is rotatable about an axis 8-8 and is pivoted for rotation in the gimbal 2 about an axis 5-5. A card 10 carried by the gimbal 2 is viewed through a window 11 in the casing to give the heading of the instrument. Whenever the axis 8 of the rotor is not horizontal, electric signals are induced in the windings 16 of a pickoff in the manner described in Specification 751,018. These signals are applied to a torque motor 14, 15, which applies a torque about the axis 3-3 in order to precess the gyroscopic rotor in to the horizontal plane about the axis 5-5. A torque motor 17, 18 may be provided in order to apply torque about the minor axis 5-5 in order to bring the instrument heading into agreement with the indications of a magnetic compass or earth's field detector in known manner. The movement of the rotor in the gimbal 2 is restricted by means of fixed stops 23 (Fig. 2, not shown) and a pin 22 projecting from the rotor. An electric motor 24 is connected to a pinion 25 through gears 26, 27, 28, 29. Pinion 25 is mounted on a shaft 30 slidable axially but keyed to the gear 29. When motor 24 is energized, gear 29 drives a further gear 31 which is coupled to a clutch disc 32. A spring 34 urges clutch disc 32 against a second clutch disc 33 which is fixed to an externally grooved cam 35. The cam groove engages a tongue 37 on a sleeve 38 fixed to shaft 30, and when the cam is in its rest position, the pinion 25 is out of engagement with a gear 19 fast with the gimbal 2. When the cam 35 has rotated through half a revolution, it is prevented from moving further by a spring 36, the clutch members 32, 33 slipping. In this position, the pinion 25 is in engagement with gear 19. Motor 24 then applies torque to the gyroscope rotor, which is thereby caused to process until stops 22, 23 engage. Gyroscopic rigidity about the axis 3-3 is then destroyed, and the rotor is free to turn. As soon as a desired heading has been attained, the direction of motor 24 is reversed. This causes cam 35 to return to its original position, disengaging pinion 25 from gear 19, and then to turn half a revolution in the opposite direction, reengaging the pinion 25 with the gear 19. The motor 24 then exerts torque on the gimbal 2 in the opposite direction, with the result that the rotor axis precesses away from the stop towards its normal horizontal position. Motor 24 is then de-energized, cam 35 returns to its original position, and pinion 25 is disengaged from gear 19. Several arrangements are described whereby the above-described course of events can be caused to occur automatically. As shown in Fig. 7, a rotor 39 is supported in a gimbal 40 and provided with limit stops 41, 42. A gear 43 fast with the gimbal 40 engages a cup gear 50 connected to an azimuth dial. Small correcting torques may be applied about the major and minor axes respectively by torque motors 52, 57. When the rotor spin axis deviates from the horizontal, a signal is generated in a pick-up 62, amplified by an amplifier 70 stop when the amplifier signal is applied to the torque motor 52 to precess the rotor spin axis back to the horizontal. Additional excitation for the torque motor 57 is provided by a potentiometer 66 connected across a voltage source 67 to provide adjustable precession about the major axis to compensate for small azimuth errors and to introduce latitude correction from those known purposes. Re-setting of the gyroscope is effected by an axially movable knob 68. In the position shown, knob 68 is in its outermost position and the gyroscope operates normally. When the gyroscope is to be re-set, knob 68 is pushed inwards, and switch contacts are altered so that the polarity of the signals from the output of amplifier 70 to the torque motor 52 is reversed. At the same time, the winding 80 of a torque motor 48, corresponding to the torque motor 24 in Fig. 1, is energized. This results in the rotation of a cam 45 and the engagement of a pinion 44 with the gear 43, so that torque is applied to the gimbal 40. This causes the spin axis of rotor 39 to precess away from the horizontal, and the effect is now reinforced by torque motor 52, the connection of which to the amplifier 70 has now been reversed. When the gyroscope spin axis has reached its desired position in azimuth, the operator pulls out the knob 68, whereupon the winding 80 of the torque motor 48 is de-energized, pinion 44 is withdrawn from engagement with gear 43, and torque motor 50 in co-operation with pick-up 62 restores the spin axis of the rotor to the horizontal position. In another arrangement, rotation of the resetting knob causes the rotor to precess into engagement with its stops, and rotates the gimbal to the desired position. In a further construction, the torque motor on the major axis is used, not only for providing levelling torque, but also to provide the torques for setting the rotor spin axis to a desired direction as described above. A gyro vertical which may be oriented according to the principles set out above is also described. Specification 740,796 also is referred to.