Patent GB-663437-A (GB)
Title: Improvements in or relating to gyroscopic apparatus for defining a vertical reference line
IPC: G01C19/38
Filed: 1949-08-18
Abstract: 663,437. Gyroscopic apparatus. SPERRY CORPORATION. Aug. 18, 1949 [Sept. 8, 1948], No. 21510/49. Class 97 (iii). Gyroscopic apparatus comprises a platform adapted for mounting in a craft about two mutually perpendicular axes, a first gyro compass having a rotor with a horizontal spin axis which is rendered northseeking by virtue of the interaction of gravity control and the Earth's rotation, a second gyro compass having a rotor with a horizontal spin axis which is rendered east-seeking by virtue of the interaction of gravity control and orthogonalizing azimuth control from the first compass, pick-off devices associated one with each compass providing measures of the relative tilt of the platform and a plane generally defined by the spin axes of the rotors of the compasses and servomotors connected to position the platform about its axes in response to such measures. As shown, the apparatus is carried by a framework 1, Fig. 1, gimballed at 2, 2 in a horizontal gimbal-ring 3 supported by pivots 2<SP>1</SP> in a binnacle. A conventional north-seeking gyro compass is supported in a vertical ring 6 and phantom ring 8 from a stem 9 journalled by bearings 17 in the frame 1. The compass is rendered northseeking by the pendulous bail 12 with the usual eccentric connection to the casing 4 for damping purposes. The phantom ring 8 is maintained coplanar with the vertical ring 6 by an azimuth motor 24 controlled by the amplified output of transformer pick-off 25, 27. The pendulous moment of the bail 12 is varied according to the secant of the latitude, for correct ballistic deflection, by means of a nut 70 adjustable on an extension 71 of the bail 12 by means of a motor 72 controlled by a Selsyn system from a handoperated nut 70<SP>1</SP> movable over a scale 76, calibrated in latitudes. A second conventional gyro compass 104 is mounted in the framework 1 by means of a vertical ring 106, phantom ring 108 and stem 109 so that its spin axis is at right angles to that of the north-seeking compass. This gyro is also provided with a pendulous bail 112 connected eccentrically to the rotor casing and with a transformer pick-off 125, 127 and azimuth motor 64 for maintaining its phantom ring 108 coplanar with the vertical ring 106. This second gyro-compass is constrained to settle in the E.-W. direction by means of a torque applied about its vertical axis by a spring 60, one end of which is attached to a rod 61 projecting upwardly from the vertical ring 106 and the other end of which is connected to a gear-wheel 58 which is driven through gearing 55, 57 from a gear 36 positioned in azimuth by the north-seeking gyro. The spring 60 thereby applies a torque to the vertical ring 106 of the east-west compass which is dependent on the difference of azimuth between the two gyro axles and this torque taking the place of the earth's rotation is causing a tilt of the east-west gyro axle. The relative positions of the two gear-wheels 55, 57 are variable in order that the spring 60 may be given an initial stress appropriate to the latitude, the operating knob 781 for this adjustment having a pointer 77 movable over a latitude scale engraved on a flange 791 of the wheel 55. In order that the torque applied by the spring 60 may be proportional to the true differences in azimuth the position of the gear 36 is corrected for speed error by means of a corrector of the kind described in Specification 433,494 and comprising gearing 37, 38 for adjusting the position of the azimuth gear 36, this corrector being adjusted by a toothed sector 38 positioned according to speed, course and latitude by means of an inclinable flat ring 41. The ring 41 is positioned for speed and latitude by means of a threaded rod 44 adjustable by a knob 48 and, being fixed to the frame 1, its inclination relative to the sector 38 varies appropriately with the cosine of the course. The true angle of the ship's course, corrected for speed error, is applied to the compass transmitter 54 by gears 36, 55, 79<SP>1</SP> and 53. Both the north-south and east-west gyros are precessed at a rate corresponding to the vertical component of the earth's rotation by means of light spiral springs 80, Fig. 4, coupled between the gyro casing and the phantom ring. One end of the spring is pinned to a pinion 82 engaging with a dial 83 calibrated in terms of latitude and mounted on the phantom ring 8 (108) and the other end of the spring is clamped in a bracket 84 projecting from the gyro casing 4 (104). The ball-bearing 18, Fig. 3, carrying the bail pivot 14 is carried by the intersection of a horizontal slot 32 in the phantom ring with a sloping slot 33 in a plate 31 sliding vertically in guides 34 on the phantom ring. A rod 30 secured to plate 31 is hinged at pivot 29 to a lever 28 hinged in turn to lever 39. As lever 39 moves with varying speed error the plate 31 moves vertically, thus shifting the bail pivots 14 horizontally relatively to the bearings 5. Although the gyro casing will have a resultant tilt after a ballistic deflection due to change of speed and course, the bail will, by reason of its pivot, return to the vertical, thus eliminating the damping acceleration error. A similar mechanism, controlled from an inclined ring 141 of a speed corrector, is provided on the east-west gyro compass. The frame 1 is stabilized about the horizontal spin axes of the north-south gyro and of the east-west gyros by means of transformer pick-offs 67, 69, resolver 65 and torque motor 66, and by means of transformer pick-offs 167,169, resolver 65 and torque motor 150, respectively. Specifications 15679/11, 154,618, [both in Class 97 (iii)], and 360,428 are referred to.