Patent GB-603430-A (GB)
Title: Improvements relating to gyro-compasses
IPC: G01C19/38
Filed: 1944-10-06
Abstract: 603,430. Automatic control systems for gyroscopes. SPERRY GYROSCOPE CO., Inc. Oct. 6, 1944, No. 19206. Convention date, April 29, 1943. [Class 38 (iv)] [Also in Group XX] In a gyro compass having a normal period of the order of a few minutes which is changed, when the craft accelerates, to a period of the order of one and a half hours the outer casing 10 is pendulously mounted in a gimbal ring 11 carried by a yoke 12. A phantom ring 14 is carried by upper and lower bearings 15, 16 and actuates the rotor 37, Fig. 2, of a " Selsyn " transmitter 17. The phantom ring carries a permeable core with three poles' 25, 26, 27, Fig. 3, co-operating with an armature-24 on the bottom of the vertical ring 18 of the gyro. The central polepiece has a winding 28, Fig. 4, energized from an A.C. source 30 and the outer poles have opposed windings 31, 32. When the armature covers equal portions of the outer polepieces no signal is,derived from the pick-off but departure of the rings 14, 18 in either direction produces a phase-sensitive signal amplified at 33, Fig. 4, and fed to the reversible motor 23 which actuates the phantom ring through gearing 35, 36 to restore the oriented relationship. The " Selsyn " receiver 38, Fig. 2, has a rotor 39 which positions a compass card 40 and corrections for speed, heading and latitude are introduced by a corrector 43 controlling the phase relation between the voltages induced in the stator windings 41 of the transmitter 17. The rotor case 44 is mounted on trunnions in the ring 18 and carries, on brackets 52, the rotor 51 of a squirrel-cage inductive gravity-torque motor 48, the wound stator 50 of which is mounted on the ring 18. A similar damping-torque motor 49 operates about the vertical axis of the ring. These give the compass a relatively short period of, say, 5 to 10 minutes. The stators are two-phase wound and are supplied from a source 48<SP>1</SP>, Fig. 5; splitphase control windings 57, 57<SP>1</SP> and 58, 58<SP>1</SP> are energized from a pick-off 60 having its armature 61 on one of the horizontal trunnions of the rotor case and a three-pole core 62 pendulously mounted on a weighted plate 76. The arrangement is similar to that on the phantom ring and the gyro spin axis is maintained In a N-S plane and free from tilt. Included in the control circuit is an amplifier 63 and a resistor 64 normally shunted by switches 65, 55 which open when acceleration occurs and diminish the gravity and damping torques, the compass then having a period of about 85 minutes. A rate of turn gyro 71 in the base of the case 10 is used tc operate the switch 65 and the switch 6 consists of a delayed-action relay energized by another three-pole pick-off 75 also actuated by the pendulous plate 76 and responsive to accelerations having a component in the N-S plane, the switch 66 responding only when the accelerations are of sufficient magnitude and duration. A further normally closed switch 77, Fig. 5, consists of a liquid-level device 78 mounted on the gyro case and responsive to tilt of the trunnion axis to minimize intercardinal rolling error. In a modified control circuit acceleration causes the signal to the damping torque motor to be completely cut out and that to the gravity torque motor to be weakened.