Patent GB-172029-A (GB)
Title: Improvements in gyroscopic compasses
IPC: G01C19/38
Filed: 1921-11-28
Abstract: 172,029. Paxton Gyroscope Corporation, (Assignees of Paxton, C. M.). Nov. 26, 1920, [Convention date]. Gyroscopic compasses. - The rotor casing is mounted so as to have three degrees of freedom and the gyro-axis is oriented into the meridian plane by the application of alternating torque around the E-W axis, the torque being applied for limited periods only with a frequency of about 20 to 75 per minute and its magnitude being considerably greater than that due to the earth's rotation. The gyro-axis is also rotated in the meridian plane until it is parallel to the earth's axis, by the application of similar alternating torque around the vertical axis, the application of the torques being so controlled by a timing device that their periods of operation occur alternately. The rotor 11 is mounted in neutral equilibrium on the trunnions 13, 14 in a vertical ring 15, which may 'be suspended by gimbals as shown in Fig. 1 The means shown in Figs. 1, 6, and 7 for applying the alternating torque around the axis 13, 14 comprise a clutch of which the member 40 is resiliently connected to an extension 13' of the trunnion 13 by a spring 42 secured to the member 40 and to a collar 43<1> on the extension, while the member 41 is mounted on a stub axle 45 carried in a frame 46 secured to the ring 15. The member 41 is secured to the armature 52 of an electromagnet 54 so that when the circuit is completed the member 41 is moved into engagement with the member 40 against, the action of a spring 48. Oscillation of the member 41 during its engagement with the member 40, which results in the application of the required alternating torque to the axis 13, is produced by pivoting it at 61 to a link 62 pivotad on a crank-pin 63 secured to a wheel 64 which is adapted to be rotated by a motor 69. A stop 55 on a spring member 56 is adapted to engage with the armature 52 when the magnet 54 is de-energized to prevent rotation of the clutch. The circuit of the motor 69 is completed through contact strips 34, 35 which are brought into engagement when the armature 52 is moved to engage the clutch. The means for exerting alternating torque around the vertical trunnion 16 are exactly similar to those described above. The circuit of the magnets 54, 54a are completed alternately by the timing-device shown in Fig. 8 comprising a rotating disc 70 of insulating material with a conducting portion 71. A wire a is ccnnected to the spindle 72 and brushes 74, 75, in the circuits of the magnets 54, 54<a> respectively, hear on the circumference of thedisc. To ensure that any rotation of the frame- 1. due to change of course of the ship &c., whilst the magnet 54a is in operation, shall not result in the application of torque around the vertical, means are provided for breaking the circuit of magnet 54<a> when such change of course occurs. These means comprise a contact arm secured to the trunnion 16 and adapted, when a change of course occurs, to come into engagement with one of two contacts 83 carried by the clutch member 40a, to complete the circuit of an electromagnetic switch device which opens the circuit of the magnet 54a and closes that of the magnet 54. The separation of the points 83 is such that the normal oscillations of the member 40<a> do not produce a contact. In consequence of the sudden and resilient application of large torques as above described, each lasting for a very short time, the resulting movements of the gyro-axis are almost wholly precessional, the yields in the directions of the torques being negligible. The ring 15 carries a compass card 25 reading against a lubber ring 26 carried by the frame 1, and the trunnion 14 carries an index 20 co-operating with a graduated ring 23 secured to the ring 15 to indicate latitude. Specification 170,864 is referred to.