Patent GB-175292-A (GB)
Title: Improvements in and relating to gyroscopic compasses
IPC: G01C19/38
Filed: 1922-02-13
Abstract: 175,292. Ford Instrument Co., Inc., (Assignees of Ford, H. C.). Feb. 12, 1921, [Convention date]. Gyroscopic compasses.-Deviations of a compass due to the meridional component of the ship's speed are prevented by applying a torque about the vertical axis of suspension so as to set up around the horizontal axis a precession having an angular velocity equal to the meridional component of the ship's angular velocity over the earth's surface. Ballistic deviations due to changes in course or speed are compensated by a displaceable mass which is automatically moved when such changes occur so as to vary the torque which it exerts around the horizontal axis. The gyro-casing] 10 is pendulously mounted on pivots 12 in a ring 14 pivoted in the vertical ring 16 which is supported by pivots 17 within the followup ring 19. The ring 19 is secured to the cylindrical member 20 and the follow-up member 21 bearing the compass-card, the member 21 being rotatable within the frame 23 which bears the lubber-line and is mounted in gimbals in brackets 27 secured to the ship. The gyroscope is suspended by a wire 38 secured to the upper pivot 17 and to a member 39 which is rotatable within the member 21. The part 39 is carried by an arm 40 having a radially-adjustable block 42 to which is secured a forked arm 46 engaging the horizontal extension 47 of an arm 48 which is pivoted in a bracket 51 carried by the member 21. Secured to the arm 48 is one end of a semicircular member 59 bearing a pin 60 engaging in a groove in a cam-ring 61 which is pivoted at 62 in brackets 63 carried by the frame 23. The ring 61 can be tilted by a. motor 66 controlled by the propeller 70, so as to have an inclination depending on the ship's speed, the inclination of the member 59 consequently depending on the meridional component of this speed.. Movement of the member 59 causes rotation of the arm 40 and hence the application of torque to the wire 38, the parts being so proportioned that the angular velocity of the resulting precession around the pivots 12 has the desired value. The ballistic deviation is compensated as follows. The casing 53 of a fluidbrake device is carried by a pivot 52 in a bracket 51 carried by the member 21 and is also secured to the other end of the member 59. The vane 55 is attached to one end of a curved arm 56, the other end of which forms a bearing 50 for the arm 48; the arm 56 is centralized by springs 57, 58. Secured to the arm 56 are two curved arms 71. 72 concentric with the gyro-casing and terminating respectively above and belnw the pivot axis 12, 12. Pivoted in the extremities of these, arms is an arm 73 having a cylindrical part 74 on which is mounted a mass 75 having a groove 76 which normally bears on the edge of a flat pivoted arm 77 connected by springs 79 to lugs 80 on the casing. Movement of the arm 59 conse,- quent upon change of course or speed produces movement of the casing 53 and consequent rotation of the vane 55. arm 56. and arms 71, 72, the mass 75 being thereby moved to vary its moment about the axis 12, 12. When the change ceases, the arm 56 is centralized by the springs 57, 58. The precessional oscillations of the gyro-casing about the axis 12, 12 are damped by the resulting motion of the arm 73 and mass 75 which displaces the arm 77 and strains the springs 79. Oscillations about the axis 15, 15 are prevented by an auxiliary stabilizing gyroscope 83 having an horizontal axis at right-angles to that of the main gyroscope, and pivoted in a ring 82 which is pivoted in brackets 81 on the casing. The gyroscope 83 also serves to eliminate devia. tions due to intercardinal swinging. The motor 30 operating the follow-up element also directly operates a transmitter 31 controlling the repeaters.