GB654658A - Improvements in or relating to gyroscopic apparatus for use in steering a great-circle track - Google Patents

Abstract

654,658. Course indicators. SPERRY GYROSCOPE CO., Inc. July 25, 1947, No. 20098. Convention date, Jan. 6, 1944. [Class 40 (i)] [Also in Group XX] In a great-circle courseindicator, to compensate for the local vertical component of the earth's spin, a correction proportional to the sine of the latitude is added to the indication of a gyro. The initial position on the great circle, and the speed of the craft are set on a device comprising two series-connected Selsyns, and the correction signal obtained therefrom is (a) fed to a torquemotor tending to precess a levelled directional gyro, or (b) as in the Specification as open to inspection under Sect. 91, it is caused to drive one element of a Selsyn, forming an electrical differential, and having its other element driven by a slaved-directional-gyro, said differential output being connected to a Selsyn indicator. The rotor of the first Selsyn 23, Fig. 4, is set at an angle corresponding to the inclination X of the great-circle-course to the equator, Fig. 3. The rotor of the second Selsyn 27 is set to correspond to the angular distance Yo of the origin of the course along the great-circle, and is rotated during the passage according to the ground-speed of the craft by means such as a constant speed motor 33 and variable speed drive 31, 32, 34. This control may be effected automatically by a ground-speed measuring instrument, and may alternatively comprise a variable frequency-oscillator feeding a clock motor. The Selsyn output in the first embodiment supplies a torque motor 19, tending to precess the horizontally spinning gyro 18 about the vertical axis. The gyro is maintained horizontal in the conventional way by a levelling switch 43 mounted thereon and controlling a torque motor 42 which causes the gyro to precess vertically. The "heading" of the gyro which will be the great-circle-course, is indicated on a card 12 driven through bevel gears 15, 16 or may be fed to an automatic pilot from the Selsyn 38. In the Specification as open to inspection under Sect. 91 the course indicator may be a Selsyn receiver 50 fed from a Selsyn transmitter 54 having the position of its rotor controlled by a directional gyro, slaved to a magnetic or gyro compass, Fig. 5 (Cancelled), and the position of its "stator" controlled through a servomotor system by the correction signal. The servomotor system comprises a differential 56 having two input shafts driven in opposite directions by repulsion motors 57, 58 energized from the supply, through transformer 59, symmetrically with respect to the correction signal, which is obtained as before from Selsyns 23, 29, whereby the differential output shaft 55 and hence the "stator" of Selsyn 54 moves in accordance with the correction signal. This subject-matter does not appear in the Specification as accepted.