Patent GB-191516098-A (GB)
Title: Improvements in Gyro-compasses.
Inventor: HENDERSON JAMES BLACKLOCK
IPC: G01C19/38
Filed: 1915-11-15
Abstract: 16,098. Henderson, J. B. Nov. 15. [Cognate Applications 17,593/15 and 1307/16.] Gyroscopic compasses.-A gyroscopic compass is constructed with two gyroscopes, the rotors of which revolve in opposite directions, one of the gyroscopes being gravitationally in stable equilibrium and the other in unstable equilibrium, so that both of them are meridian seeking; the gyroscopes are interconnected so that their mutual reactions damp the oscillations about the meridian and also prevent deviation due to periodic angular movement of the ship. As described, the compass is of the known type comprising a " sensitive element " and a " following element," and the stability and instability are produced by weights, springs or pendulums. As shown in Fig. 1, the rotor casings 11, 12 are mounted on horizontal trunnions 13, 14 respectively in rings 15, 16, and are rendered stable and unstable respectively by weights 24, 25. The weights, or the speeds or moments of inertia of the rotors, are such that the period of oscillation of the sensitive element when the stable gyroscope is running alone is less than when the unstable gyroscope is running alone, the oscillations of the sensitive element being thus damped. The rings 15, 16 are connected by an elastic torsional element 17 and also by means for damping their relative oscillations, comprising plates 18, 19 separated by a viscous fluid. The damping of the sensitive element may be improved by mounting the casings 11, 12 on trunnions which are inclined so as to be farther apart on the east side of the compass than on the west side. Alternatively, the casings may be separately mounted side by side on horizontal trunnions, and be connected by an horizontal spring, each casing being carried by a vertical ring mounted on vertical trunnions in a surrounding frame, or one on such a ring and the other directly on the frame. Viscous dampers are provided between the rings and the frames. Damping of the sensitive element may be effected by a modification of the method described in Specification 26,068/13, in which a torque is applied through the suspending-wire or otherwise and is proportional to the tilt of the axes to the horizontal; the viscous damper may then be omitted. As shown in Fig. 5, the sensitive element is carried by a sub-frame 33, which is rigidly connected to the torsional element 17 and is suspended by the wire 21. By means of mechanism involving linked cranks 34, 35, 36 on the trunnion axes, a contact roller 38 is moved over a two-part commutator 42 on the frame 6 of the following element a distance proportional to the difference of tilt of the gyroscopes, and operates a motor to put a twist in the wire 21. The use of two gyroscopes enables the gravitational control system to be designed so that, as a whole, it is practically in neutral equilibrium, rolling or pitching of the ship then having no effect on the compass. This may be effected, as shown in Fig. 8, by providing pendulums 42, 43, which are pivoted on the trunnion axes, have holes loosely engaging pins on the casings 11, 12, and are connected together by T-heads 46, 47 and pivoted rods 48 sliding in pivoted tubes 49 carrying a viscous fluid. As a modification, the casings 11, 12 may themselves form the pendulums and be connected by the rods, tubes, and fluid. In both cases, the viscosity of the fluid causes the connexions to act as if they were rigid for stresses due to wave motion, but does not interfere with the slow precessional motion of the compass as a whole. The pendulums may be connected as shown in Fig. 11, so as to obtain a gravitational system in which the pendulums do not deviate from the true vertical when the compass swings. The axes 52, 53 are connected to the casings 11, 12 respectively, and are co-axial with, or parallel to, the rotor axes. According to the Provisional Specification 1307/16, the period of the pendulums may be rendered long by means of gyroscopes. Frictional forces may be overcome by making the pendulum 50 heavier than the pendulum 51, or by connecting it by a very light spring to the centre of the casing 11. As friction on the trunnion axis of the unstable gyroscope tends to increase oscillations of this gyroscope, the direction of the friction may be reversed. A construction is described in which this is effected by a loose sleeve bearing for the unstable gyrotrunnions, the sleeve carrying a pulley connected by a belt to a pulley on a trunnion of the stable gyroscope. According to the Provisional Specification 17,593/15, the sleeve may be turned by a separate motor. Fig. 14 shows a construction in which the frictional couple arising when the rotor axis contacts with some part outside the gyroscope damp out oscillations about the meridian. A ring 65 is mounted on trunnions 66 and is connected by linked cranks to one trunnion of the casing 11 so that it tilts and turns in azimuth in phase with the stable gyroscope. The ring has square holes into which the ends of the rotor axis 69 project, the sides of the holes being slightly greater than the diameter of the axis 69. The holes may alternatively engage non-rotating spindles secured to the rotor casing 12; or they may be made rectangular, two sides then engaging the rotor axis and the other two sides engaging projections from the casing 12. The sides of the holes may be made springy. The Provisional Specification 16,098/15 states that any of the features described in Specifications 26,068/13 and 26,160/13 may be utilized in the design of the compass. Reference has been directed by the Comptroller to Specification 137,059.