Patent GB-179918-A (GB)
Title: Improvements in and relating to gyroscopic compasses
IPC: G01C19/38
Filed: 1922-04-21
Abstract: 179,918. Ford Instrument Co., Inc., (Assignees of Tanner, H. L.). May 13, 1921, [Convention date], Gyroscopic compasses.-The axis of rotation of the gyroscope is inclined to the horizontal and the gyroscope is mounted so that it can precess around an inclined axis, the precession, which is set up when the gyro-axis deviates from the meridian plane, being adapted to control the circuit of a servo-motor arranged to turn the gyrocasing in azimuth to restore the axis to the meridian plane. The casing 3 is mounted on trunnions 4 in an inclined ring 5 pendulously mounted on horizontal trunnions 6 in projections 43 formed on a ring 7 which is pivoted on the trunnion axis 8-S, at right-angles to the axis 6-6, in an annular member 9 capable cf being rotated in azimuth. The member 9 is mounted in ball-bearings within a member 10 which is mounted in gimbal rings 23, 25, the ring 25 being attached by springs 26 to the binnacle 27. The ring 7 is provided with two depending brackets 16 in the N-S plane, between the lower ends of which is mounted on trunnions 57 a ring 17 in which is pivoted a gyroscope 18 having a vertical axis, and serving to stabilize the ring 7 against disturbances caused by rolling &c. of the craft. The compass-card 28 is disposed on the upper surface of the member 9, the member 10 being provided with a lubber mark 29. The member 9 carries an externally-toothed ring 70 adapted to be driven, through the gear train shown in Fig. 10, by a reversible servomotor 13 carried by the member 10. The circuit of the motor includes a switch device comprising a roller 79 carried by the casing 3 and a pair of contacts 15 carried by the ring 5. Precession of the casing 3 about the axis 4-4 causes the roller to move on to one of the contacts 15 to complete the circuit of the motor and thereby rotate the member 9 in the appropriate direction. The gear train between the motor 13 and ring 70 includes a member 72 for controlling the circuits of one or more repeaters. The precession resulting from changes s in speed, course, or latitude of the craft is prevented from actuating the motor 13 by imparting to the contacts 15, by means of a correction device, a movement equal to the movement of the roller 79 consequent upon such precession. The correction device comprises a ring 86 mounted between brackets 87 secured to the member 10. The brackets carry rollers 88 bearing on the periphery of the ring which has two diametrically opposite depressed portions 89, the arrangement being such that, as shown in Fig. 10, when the innermost part of one depression engages the corresponding roller 88, the outermost part of the other depression engages the opposite roller. The ring 86 can be turned in accordance with the speed by a lever 90 pivoted at 91 to the member 10 and secured at its lower end to the ring, the upper end of the lever being formed as a pointer which can be moved over a speed scale 93 attached to the member 10. The member 9 carries at its south side an arm 95 the free end 96 of which bears against the ring 86, and a plunger 97 passing through the trunnion 8 bears at one end against the arm. The other end of the plunger bears on one arm of a bell-crank lever 98 pivoted to the bracket 16 and the other arm of the lever bears on one end of an arm 100, Fig. 13, attached at its other end to a rod 101 passing through the ring 7 and capable of vertical adjustment by means of a nut 103 marked with a latitude scale. The arm 100 is connected by a link 105 with the ring 17 and the parts of the correction device are retained in engagement by a tension spring 106. Movement of the upper end of the link 105 produces a tilt of the ring 7 and axis 6-6, and a consequent movement of the contacts 15. This movement depends on the settings of the speed and latitude pointers and also on the orientation of the ring 86 in relation to the member 9, i.e. on the course. The oscillations of the compass are damped by an annular mass 21 carried by arms 22 which are pivoted to the casing on an axis inclined to the meridian plane. Alternatively damping may be effected by two liquidcontaining vessels secured to opposite sides of the casing in the meridian plane and connected by a capillary tube. With this form of damping- means the latitude correction-device is not required. The rotors of the gyroscopes are electrically driven, preferably by a three phase current which also operates the motor 13, the current being introduced through the several trunnions. Fig. 10 shows a pair of trunnions 30, 31 for the ring 17, one being used for two of the conductors and the other for a single conductor of a three phase system. The trunnion 30 consists of a sleeve 32 passing through and insulated from the ring. 17 and threaded to receive a trunnion 34 extending into a ball bearing 35 seated in and insulated from the gyro-casing 18. The trunnion is bored to receive an insulating bush 37 containing a pin 38 the inner end of which is held against a plate 39 within the insulated member of the bearing by a spring 40 attached to, but insulated from, the ring 17. One conductor is connected to the spring 40 and the other to the member 32. The earthed bearing 31 comprises a threaded trunnion 41 extending into a ball-bearing seated. in the casing 18. The other trunnions are similarly constructed as required for the conduction of current. In the upper trunnion 4 the member 34 is eccentrically mounted so that a fine adjustment may be obtained by turning the member 32. To provide an earth connection between the rings 5, 7 the former carries a spring bracket 44 carrying a contact-point 45 co-operating with a bracket 46 attached to the ring 7. The current is introduced through slip rings 47-50, Fig. 9, carried by the member 9. The rotor 1 rotates in the direction shown by the arrows in Fig. 8 when the gyro-casing 3 is pendulous about the trunnions 6. A movable mass 85 is provided for balancing the casing about the axis 4-4