Patent GB-623356-A (GB)
Abstract: 623,356. Gyroscopic apparatus. SPERRY GYROSCOPE CO., Inc. Sept. 13, 1943, No. 15030. Convention date, Sept. 12, 1942. [Class 97 (iii)] [Also in Group XXXV] An erecting means for a gyro instrument, wherein the rotor is spun by alternating current, comprises an alternating current torque motor having one of its windings permanently energized from the alternating current supplied to the rotor and its other winding or windings energized from a control circuit including a tilt-respon sive switching device the control circuit be ing supplied with energy from the first circuit in such a manner that the latter winding is provided with less energy than if it were directly energized from the first circuit. In Fig. 1 is shown a gyro instrument of the directional type wherein the gyro rotor spins about an horizontal axis within a case 34 supported in horizontal bearings 35, 36 in a ring 33 pivotally mounted in vertical bearings 31, 32. The gyro rotor is spun by a three-phase motor with windings 37, 38, 39, Fig. 5, supplied from lines 1, 2, 3. If the rotor case tilts relative to the ring 33, it is re-erected by a turning moment applied in the appropriate direction to the vertical ring by a two-phase torque motor 53 of the squirrel cage induction type. The stator 50 of the two-phase motor comprises windings 54, 55, fixed to the vertical ring. The squirrel cage 51 is attached to the instrument casing 30. The winding 54 is in series with the phase line 3 of the gyro rotor circuit so as to be continuously energized, the other winding 55 being energized through a reversing switch 58 of the commutator and brush type, the commutator being fixed upon the trunnion of the rotor case 34. When the rotor case tilts, energy at a reduced level is supplied to the commutator by leads 65, 67, connected respectively to the phase line 2 of the gyro rotor supply and to an autotransformer 66 arranged in parallel with the phase lines 1, 2. The arrangement results in the current vectors for the windings of the torque motor being substantially 90 degrees out of phase. In a modification, the continulously-energized winding 54 of the torque motor is arranged across the lines 1, 2 whilst in a further modification, the winding 55 is supplied by a secondary transformer winding on the stator of the rotor-spinning motor. In other modifications, the auto-transformer is replaced by a transformer, the circuit being appropriately modified. In a further modification, the energy for the torque motor winding 55 is obtained by a shunt circuit arranged about a resistance in one of the phase lines. As adapted to a gyro vertical; two torque motors 101, 104, Fig. 19, are applied, one to each horizontal axis of the gyro in order to precess the spin axis to the vertical if departure occurs. The torque motors are selectively energized by electric contacts 110 ... 113, in a liquid level switch 116 attached to the base of the gyro rotor. Energy is supplied to the switch by a bleeder lead 117 tapped to one of the windings of the rotor spinning motor. The torque motors, have continuously energized field windings 118, 119 connected across the line 1, 2 and centre-tapped field windings 120, 124, supplied from the switch contacts and connected to the return line 3. The rate of erection of the gyro may be increased by operating a switch 130 to reverse the leads 41, 42 and consequently reverse the gyro rotor and torque motors. During the reversal, the torque motors become more effective to erect the gyro. In a modification, the accelerated erection is obtained by increasing the energy flow through the torque motor circuits, a switch being provided for this purpose to shunt a resistance incorporated in the circuits. Specification 601,656 is referred to.