Gyro compass and directional gyro arrangement

Claim 1

In a gyro arranged to be mounted in a vehicle and operable selectively as a directional gyro or as a gyro compass, which gyro includes: a gyro rotor rotatable about a horizontal spin axis; an inner gimbal supporting the gyro rotor via its spin axis and pivotal about an axis which is maintained vertical when the gyro is operating as a gyro compass; means defining a yieldable restraint tending to maintain the inner gimbal in a selected position and opposing pivoting of the inner gimbal about its axis away from the selected position; a first position sensor disposed for providing a signal in dependence on such pivoting of the inner gimbal; a second gimbal supporting the inner gimbal via its axis and pivotal about an axis parallel to the rotor spin axis when the inner gimbal is in its selected position; an outer gimbal supporting the second gimbal and pivotal about an axis oriented approximately parallel to the vertical axis of the vehicle when the vehicle is upright; follow-up means connected between the position sensor and the outer gimbal axis for pivoting the outer gimbal about its axis in response to pivoting of the inner gimbal relative to the second gimbal; and drive means selectively connected for placing the second gimbal into a position where the axis of the inner gimbal is vertical when the gyro is to operate as a gyro compass, and for placing the second gimbal into a position where the axis of the inner gimbal is substantially inclined to the vertical when the gyro is to operate as a directional gyro, the improvement wherein said gyro further comprises: an intermediate gimbal disposed between said second gimbal and said outer gimbal, supporting said second gimbal via its axis, and having a pivot axis which is supported by said outer gimbal and which extends orthogonally to the axes of said second gimbal and said outer gimbal, said second gimbal and intermediate gimbal being so arranged that the axis of said inner gimbal is vertical when said gyro is operating as a gyro compass; and control means includng a verticality sensor associated with said intermediate gimbal and arranged for maintaining the axis of said second gimbal horizontal when said gyro is operating as a directional gyro, and wherein said drive means are arranged for placing the axis of said inner gimbal parallel to the axis of said intermediate gimbal when said gyro is operating as a directional gyro.