Patent GB-218358-A (GB)
Title: Improvements in gyro compasses
IPC: G01C19/38
Filed: 1923-03-07
Abstract: 218,358. Henderson, Sir J. B. March 7, 1923. Gyroscopic compasses.-A compass having a gravity control of the order of magnitude usually employed in periodic compasses is arranged to be subject to a deviation to the virtual meridian due to changes in speed or course of the ship &c. but to have no subsequent oscillation about the said meridian. To attain this result, ballistic deviation due to such changes is eliminated but a subsequent slow precession to the virtual meridian takes place. The means for operating the follow-up element and the repeaters are so arranged that the deviation of the sensitive element is not communicated to these members. The gyrocasing 1 is mounted in a vertical ring 2 supported in pivots 4 in the follow-up ring 5, which is mounted on pivots 6, 7 in a frame 8 suspended in the binnacle, the follow-up element being operated by a motor 9 geared to the ring 12 on the member 5. The gravity control is of the kind described in Specification 166,570 consisting of mercury vessels 14, 15 joined by a tube 16 and connected by springs 24, 25 to a pin 26 on the casing 1, the pin being displaced from the vertical centre line of the casing. The vessels 14, 15 are connected by glass tubes 17, 18 to vessels 19, 20 and are half filled with mercury, a light fluid filling the remainder of the vessel 14 and part of the tube 17. The whole of the tube 18 and part of the vessel 20 are also filled with light fluid, a valve 22 being provided in the vessel 20 for adjusting the rate of flow of the mercury. The vessels 19, 20 are carried by a frame 21 pivoted on trunnions 23 on the ring 5, these trunnions being normally coaxial with these supporting the gyroscope in the ring 2 but one or both of them being adjustable parallel to the gyro-axis by being mounted on a lever 27 pivoted on an eccentric 28 attached to the ring 5. Mounted on pivots 31, 32 in the frame 8 is the cosine ring 30, the pivot 32 being secured to a slotted arm 33, Fig. 2, connected by a link 34 to a bell-crank 35 provided with a gear sector 37 engaged by a pinion 38 on the frame 8. The pinion 38 carries a speed scale 40 which is set to indicate the ship's speed against an index 41. The arm 33 carries a latitude scale 43 along which the end of the link 34 is adjusted in accordance with the latitude, the arrangement being such that the tilt of the ring 30 is proportional to V/Cos #. The ring engages with a roller 45 carried by the arm 47 of a bell-crank mounted on the follow-up ring 5, this arm 47 being connected by a link 50 to the lever 27. A tension spring 51 maintains the roller 45 in engagement with the ring 30. The arm 48 of the bell-crank passes through a holle in the ring 12 and is connected by springs 58, 59 to a toothed wheel 55 carrying the compass card 53. The wheel 55 is geared to a pinion 56 driving the rotor of a viscous brake 57 carried by the ring 12. The displacement of the belicrank is proportional to the meridional component of the speed and inversely proportional to Cos #. By the action of the brake 57 this displacement is not immediately imparted to the card 53, which, however, is moved by the springs 58, 59 to follow the crank according to a logarithmic law. The rate of flow of the liquid in the level control device is so adjusted that the displacement of the liquid due to a change in speed is proportional to the meridional component of the said change so that the compass is not subject to ballistic deviation but moves subsequently to the virtual meridian according to a logarithmic law. For operating the motor 9 and the transmitter 65 for the repeaters a contact 68 mounted on the ring 2 co-operates with reversing contacts 70 carried by the ring 55. Since the sensitive element and the ring 55 deviate together to the virtual meridian, the member 5 and the repeaters ar,e not affected by such deviations. Specifications 159,604 and 188,390 also are referred to.