Patent GB-805038-A (GB)
Title: Gyroscopic apparatus
Inventor: BLIZARD ROBERT B
IPC: G01C19/38
Filed: 1955-06-30
Abstract: 805,038. Gyro-compasses. SPERRY RAND CORPORATION. June 30,1955, No. 18952/55. Class 40 (1). A gyro-compass with facilities for correcting the direction of the spin axis in accordance with the tilt, speed of travel, beading and latitude of the craft on which it is mounted is provided with means for feeding the azimuth and levelling torque motors with selected signal combinations in a predetermined sequence to bring the gyro rapidly to rest on the meridian. The gyrocompass comprises a rotor 1 (Fig. 1), with a horizontal spin axis 2, in a case 3 mounted for rotation about a perpendicular horizontal axis 3<SP>1</SP>, in a vertical ring 4, rotatable about a vertical axis 5 in a follow-up ring 6. Movement between the rings 4, 6 is sensed by an electric pick-up 8 which feeds a motor 7 to restore the relationship between the vertical rings 4, 6 and transmits the movement via coarse and fine selsyns 9, 9<SP>1</SP> to remote compass indicators. The tilt signal obtained from an inclinometer 12 described below is amplified at 32 to energize a motor 34 which drives a selsyn transmitter 38 whose output signal, plus a rate signal from tacho-generator 36, opposes the tilt signal input to amplifier 32. Hence the resultant signal from selsyn 38 represents the average tilt of the gyro. To correct the reading of the gyro a levelling torque motor 11 is fed with the tilt signal modified by the addition, in a resolver 35, of a further signal depending on the north component of the speed of craft obtained from a tacho-generator 54 modified by the beading angle determined from ring 6 of the gyro, and an azimuth torque motor 10 is fed with the tilt signal modified in a latitude computer 37, where it is multiplied by a factor representing the secant of the angle of latitude and also modified by an earth rate resolver 76 adjusted in accordance with the latitude, the latitude adjustments being made mechanically by knob 68. To bring the gyro rapidly to rest on the meridian, switches are operated to direct the tilt signal from inclinometer 12 direct to the torque motor 11, a push-button switch 13 being released when tilt meter 86 reads zero. The control selsyn receivers 40, 42 are then brought to a standard zero position by momentarily operating switch 29, with switch 23 in the C.T. position, relay 31 holding until the zero position is reached and the relay falls, indicated by meter 110 and lamp 51. The tilt signal is now again fed into the latitude compute 37, where it is weighted by a sine wave voltage of one complete cycle in four minutes obtained from timer 92 operating on sine resolver 58 and is then fed into the averaging circuit 30 to shift the selsyn receivers 40, 42 by the computed error. At the end of the four minutes relay 21 is energized via timer 92 and the computed error output of selsyns 40, 42 is fed to the azimuth torque motor 10 to bring the gyro quickly to the meridian. The inclinometer (Fig. 6) comprises two parallel metal plates 18, 20 suspended in a viscous electrolyte in a tube 16, with a pendulum bob 12 of insulating material suspended between them on a wire 14. The plates 18, 20 and the wire 14 form two arms of an A.C. bridge, whose amplified unbalance current is therefore indicative of the magnitude and direction of the tilt. Specifications 625,661, 668,462; 763,750, 791,556 and 804,372, [all in Group XXXV], are referred to.