Patent GB-255745-A (GB)
Title: Improvements relating to gyroscopic compasses
IPC: G01C19/38
Filed: 1926-02-04
Abstract: 255,745. Jackson, P. R., (Sperry Gyroscope Co.). Feb. 4, 1926. Gyroscopic compasses. - In a compass in which disturbances due to changes in course or speed are avoided by eliminating the damping action during such changes, means are provided for maintaining the oscillation period of the compass at the standard value of 85 minutes when the damping-means are inoperative, in order to prevent the occurrence of secondary oscillations. This standardization may be effected either by arranging for the compass to have a longer period when it is damped or by varying the gravity control when the damping is removed so that the compass, whether damped or undamped, has a constant period. Means are also provided for displacing the centre of gravity of the gyroscope when the damping is eliminated, so as to avoid the errors which would otherwise be introduced at such times by the ordinary means for correcting for latitude errors. The gyro-casing, 4 is mounted in the vertical ring 3 which is pivoted in the followup support 2 carried by the spider 1. The gravitational control means comprises two liquidcontaining vessels 5 connected together by a tube 26 and connected to the casing 4 by an arm 6, the point of connection with the casing being normally to one side of the vertical axis so that a damping torque about the vertical is set up in addition to the orienting torque. In order to eliminate the damping -when the ship turns or accelerates, the arm 6 is pivoted at 8 and is connected by a link 12<1> and lever 11 to the core 10 of a solenoid 9. Automatic energization of the solenoid is effected when a change of course occurs, by a device 20<1> comprising a pinion 21<1> engaging the follow-up gear-ring 221 and geared to a pinion 25<1> secured to the casing 26' of a liquid-drag device containing vanes 35 on a spindle 32 carrying a contact arm 36 adapted to dose together either the contacts 37, 38 or the contacts 37<1>, 38<1>; either movement results in the solenoid 9 being energized, sufficient lost motion being allowed to prevent the circuit from being closed by the hunting of the follower or the yawing of the ship. To preserve the standard period of oscillation when the damping is eliminated, each of the containers 5 is divided by a partition 16 into two compartments 21, 23 both normally communicating with the pipe 26 by apertures 20, 22. The flow through these apertures is controlled by a slide valve 17 connected to the lever 11, so that when the solenoid 9 is energized the valve is moved to cut off the outlet from the smaller compartment 21 and so reduce the gravity control. The means for adjusting the centre of gravity comprises a weight 40 on each side of the casing, secured to the core 42 of a solenoid 43. A switch 45 can be set to obtain movement of one of the weights in North latitudes and of the other in South latitudes, neither being moved when the ship is on the equator. The circuits of the solenoids are also under the control of the arm 36 so as only to be completed when the damping is. inoperative. To adjust the movement of the weight according to the degree of latitude, an adjustable stop 46, which may carry a pointer P moving over a latitude scale, passes through it. In a modification the core 42 is formed with a number of slots of varying lengths, and the weight can be turned so that any one of the slots can be brought into engagement with a fixed pin. A switch, manually or automatically controlled, is provided to perform the function of the switch 36 when a change of speed occurs. Specification 215,594 is referred to.