Patent GB-638972-A (GB)
Title: Improvements in or relating to gyroscopic systems
IPC: G01C19/00
Filed: 1942-10-12
Abstract: 638,972. Gyroscopic apparatus. SPERRY GYROSCOPE CO., Inc. Oct. 12, 1942, No. 14309. Convention date, Oct. 10, 1941. [Class 97 (iii)] [Also in Groups XXXVI, XXXVIII and XL (c)] A gyroscope is precessed about its outer axis by the application to precessing coils, co-operating with permanent magnets on the rotor case, of a direct current whose polarity is reversed in accordance with the reversing phase of an alternating current signal which is compared with a reference A.C. voltage. Two flux-valves 1, 2, Fig. 1, are mounted one on each wing of an aircraft and have their primary energizing coils 3, 4 energized in parallel from an A.C. source 5. The outputs from the fluxvalves obtained from triple secondary windings 6, 7, 8 and 9, 10, 11 are connected to a rotary selector switch 12 adapted to transmit the output from either or both flux-valves to a signal transformer 13. The switch 12 has contacts 14, 16, 18 connected to the output of the flux-valve 2 and contact 15, 17, 19 connected to the output of the flux-valve 1. The rotor 20 of the switch 12 has contacts 21, 22, 23 by which the windings of the polyphase stator 35 of the signal transformer 13 are connected selectively to flux-valve 1, flux-valve 2, both flux-valves, or neither flux-valve, according to the setting of the switch. The singlephase rotor 27 of the transformer 13 is carried by the vertical ring 28 of a directional gyro 29. The output of the rotor 27 is fed to a control amplifier 31 energized from the source 5. The output of the amplifier 31 controls the precessing coils 32, 33 which co-operate with permanent magnets 34 fixed to the rotor bearing housing 36, pivoted in the vertical ring 28 about horizontal pivots 37, to precess the gyro 29 until its spin axis corresponds to the direction of the earth's field so that the gyro is controlled in azimuth from the flux-valves and gives an integrated average indication of the direction of the external magnetic field acting on the flux-valves. One of the coils 32, 33 and its corresponding pair of magnets 34 may be dispensed with. Instead of using a centre-tapped coil, a single coil may be used at the top and one at the bottom, each cooperating with two magnets and energized oppositely. Attached to the vertical ring 28, Fig. 2, is a horizontal ring gear 141 which meshes with a vertical gear 142 and actuates a shaft 143 through a friction clutch 140. Mounted on the shaft 143 is the rotor of the signal transformer 13, the casing of which is fastened to the instrument casing 30. The shaft 143 extends through the signal transformer 13 and carries a compass card 144 and a gear 146 driving a transmitter .148 for a repeater compass. Associated with the card 144 is an indicator 149 and a masking shield 150. The friction clutch 140 permits, by means of the knob 160, relative adjustment between the vertical ring 28 and the rotor of the transformer 13 together with the card 144. The control amplifier is shown in Fig. 3. The input to the amplifier derived from the output of the signal transformer 13, is of twice the frequency of the source 5 and is fed to a two-stage amplifier comprising valves 151, 152 coupled by a combined coupling transformer and band-pass filter 153 tuned to pass twice the frequency of the source 5. The output of the valve 152 is coupled through a tuned transformer 154 to a phase-sensitive rectifier comprising two valves 156, 157 connected in push-pull. These valves are energized antiphasally from the output of the valve 152 and co-phasally from the source 5 through a frequency doubler comprising a rectifier bridge 158 and transformer 159. The load circuits of the valves 156, 157 contain the coils 161, 162 of a double-throw balanced relay. According to the phase of the input signal relative to the voltage of the transformer 159 the armature 166 of the relay engages contacts connected through wires 167, 169 to the precessing coils 32, 33 so that the current in these coils is controlled according to the relative deviation between the signal transformer 13, or the gyro 29, and the flux valve. Precessing torques are thereby produced by which the gyro is turned into correspondence with the flux valve indication and so maintained oriented in accordance with the earth's magnetic field. The parts to the right of the line A-A, Fig. 11, may be replaced by the arrangement shown in Fig. 4. The output of the valves 156, 157 is amplified in a D.C. energized D.C. amplifier 171 comprising valves 172, 173 connected in push-pull. The centretapped precessing coil 32 forms the load impedance of this amplifier, the coil 33 being connected in parallel with the coil 32 and the centre taps being connected together. Across the sections of the coil 32 are neon indicators 174 adjusted to glow when current in the corresponding section of the coil 32 exceeds the normal current by a predetermined amount, thus indicating when manual resetting by means of the knob 160 is required. The valves 172, 173 may be gas-filled. Specifications 599,605, 638,971, 638,982 and 638,983 are referred to.