Patent GB-558276-A (GB)
Title: Improvements in and relating to gyro verticals and gyro stabilised artificial horizons
IPC: G01C19/44
Filed: 1942-08-20
Abstract: 558,276. Automatic control systems. HOLMES, E. L., HUGHES, A. J., and HUGHES & SON, Ltd., H. Aug. 20, 1942. No. 11743. [Class 38 (iv)] [Also in Groups XX and XXXVII] A gyro vertical or artificial horizon suitable for navigational observations from aircraft comprises a neutrally balanced gyro system mounted freely on inner and outer gimbal rings, means by which the system can be oriented relatively to calibrations, means for constinuously applying a' torque to the axle of the outer gimbal ring to process the spin axis steadily towards the vertical and pendulum means for controlling the application of torque to the axles of the inner and outer gimbal rings to precess the spin axis towards the dynamic vertical. The gyro system is mounted in gimbal rings e, f, pivoted on horizontal axes arranged at right angles and may be oriented as a whole relatively to a pointer i. The rotor, with spin axis vertical, is driven bv three phase current supplied to its stator windings 1, 2, 3, Fig. 4, from a generator c. Latitude error and velocity error are compensated for by a spring b, Fig. 2, which applies a torque to the axle f<SP>1</SP> of the outer gimbal ring f and therebv steadily processes the axis of the rotor towards the vertical. The influence of the spring mav be adjusted by a finger knob b<SP>2</SP> and a scale b<SP>3</SP>. Alternatively, the torque may be produced by an induction motor. A polished plate h for observational purposes is carried bv the inner gimbal ring. "Flight error" caused by transient accelerations, and instrument error caused by the moments of unbalanced masses are compensated for by torque-applying motors p, q operating on the axes of the two gimbal rings. The current to one stator winding of each motor is controlled by means of a pendulum k. k<SP>3</SP> carried by the inner gimbal ring e and immersed in an electrolyte. Four electrodes m, m' and n, n' (arranged at right angles) are grouped around the central electrode k and are fed with twophase currents in quadrature supplied from a static transformer r through transformers u, v. The stator coils 7 and 9 of the torque motors p, q are energized by the currents across the electrodes m, m<SP>1</SP>, k and n, n', k after amplification by a thermionic valve s, the coils 6, 8 of the motors being energized respectively by the separate phases of the alternating current supply. A torque meter w and adjustable resistance x are included in the output circuit of the valve. In operation, any migration of the pendulum k, k<SP>3</SP> is resolved by the electrodes m, m' and n, n' into two alternating circuits which modify the torques of the two motors p, q so as to maintain the vertical position of the spin axis of the gyro. " Instrument error " due to the varying and unbalanced moments arising from the migrations of the pendulum k, k<SP>3</SP> is compensated by auxiliary stator coils 6a, 8a. In a modification, this error is avoided by the use of two pendulums k, k<SP>3</SP> one at each side of the inner gimbal ring e and both arranged on the axis a<SP>1</SP>... a<SP>1</SP>. One pendulum operates in connection with the contacts m, m' and the other in connection with the contacts n, n'. In order to minimize " friction error" the electric transmissions are effected through lightly loaded axial contacts. As shown in Fig. 9, the outer gimbal ring f carries a number of rigid conductors 40 terminating in spherical contacts 41 which are respectively held between pairs of stationary elastically supported contacts arranged along the axis of the gimbal ring.