Patent GB-188390-A (GB)
Title: Improvements in gyro navigational apparatus
IPC: G01C19/38
Filed: 1921-08-08
Abstract: 188,390. Henderson, Sir J. B. Aug. 8, 1921. Gyroscopic apparatus for navigational purposes is provided with means to prevent dynamical deviations due to (1) acceleration of the ship &c. and (2) the swinging of the apparatus in its binnacle. The invention is described with reference to a compass in which the gravitational control is obtained by a pivoted level, as described in Specification 166,570. The level is so arranged that the quantity of fluid displaced as a result of acceleration of the ship &c. is proportional to the change of speed, and the point of attachment of the level is moved by an amount proportional to the said change so that a resultant torque is produced of sufficient magnitude to set up a precession at an angular velocity equal to that represented by the change of speed of the ship &c. over the earth; the gyroscope thus retains a - constant bearing relatively to the earth. Deviations due to swinging in the binnacle are avoided by arranging the gimbal supports so that there shall be dynamical symmetry when swinging in any plane, this being effected by fixing the horizontal gimbal ring supporting the gyroscope to a vertical ring in the plane of the rotor axis. The gyro-casing 1 is mounted on trunnions 2, 3 in a vertical ring 4 which is mounted on trunnions 7, 8, coaxial with the trunnions 2, 3, in an horizontal ring 9 to which is secured, in the plane of the rotor axis, a vertical ring 10 mounted on trunnions 11, 12 in a ring 13 which is mounted on trunnions 25, 26 in a frame 27 mounted in gimbal rings 29, 30 attached to the binnacle. The ring 4 carries a shoot 6, as described in Specification 149,727, on which air from a nozzle 5 impinges to make the ring follow the gyroscope in altitude, and a similar shoot 15 on the ring 13 causes this ring to follow the gyroscope in azimuth. The suspension for the sensitive element comprises a torsion head 21 carried by the ring 13 and carrying a wire 18 secured to a tube 19 which is fastened to the ring 10. Arms 22 carried by the tube 19 support the card 23. The level controlling the gyroscope comprises two liquid containers 32, 33, connected by a tube 35 and' carried by a frame 34 pivoted on trunnions 37 to the casing. The rate of flow of liquid can be adjusfed by valves 36. The level is constrained relatively to the casing by an air jet from a nozzle 38 impinging on a shoot 39 carried by a ring 40 secured to the frame 34 and carrying, on a level with the trunnion 3, two pins 41 attached by springs 42 to a ring 43 pivoted on a pin 44 which is capable of a small adjustment in a N-S direction. The ring 43 is attached by a spring 45 to a pin 46 on the casing. Pivoted within the frame 27 is a channel ring 50 which can be tilted, for example by the step-by-step motor 51, to an inclination proportional to the speed of the ship &c. The outer end 56 of a lever 55, pivoted between brackets 54 on the South side of the ring 13, engages in the ring 50 and the inner end 57 of the lever passes between collars 58 on a pin 59 housed within the trunnion of the ring 13. Bearing on the pin 59 is one arm of a lever 61 pivoted to a bracket 60 on the East side of the ring 10. The tail 63 of the lever engages in a plate 64, Fig. 1<a>, slidably mounted in a disc 65 carried bv an arm 67 mounted on a crankpin to which is secured an arm 68 carrying the pin 44; the crankpin is mounted in a bracket 69 secured to the trunnion 8. The ring 43 is thus displaced in the meridian plane proportionally to the rate of change of latitude of the ship &c. Torsional stiffness in the suspension is reduced by springs 70, 71 mounted between the rings 10, 13. The point of attachment of the spring 71 to the ring 13 is automatically moved so as to produce a torque around the vertical proportional to the rate of change of latitude, by attaching the spring to an arm 81 carried by a nut 79 mounted on a screw 78, Fig. 1<b>, which carries a pinion 77 gearing with a segment 76 forming one arm of a lever 75, the other arm. of which passes between the collars 58. This torque is so adjusted that, in conjunction with the torque about the vertical set up by the reaction on the shoot 39 due to the tilt of the level, a torque is produced of sufficient value to set up a precession equal to the rate of change of latitude and so to maintain the gyroscope on a constant bearing relatively to the earth. Alternatively the torque around the vertical axis may be produced by introducing a torque into the suspension by a displacement of the ring 13, this being effected by mounting the shoot 15 on a linkage similar to that which carries the pin 44. The gyro-axis is retained horizontal by a weight 84 mounted on a screw 85 so that it can be adjusted in accordance with the latitude, indicated on a dial 88. The follower 91 is operated by a motor 94 controlled by a trolley 95 on the ring 13 which engages contacts 96 on the follower. In aircraft compasses the nozzles 14, 38 may be omitted, the damping being then effected bv twisting the suspension, as in Specification 26068/13. In this case the toothed ring 91 is secured to the ring 13 and the trolley 95 is carried by arms secured to the level. The rotor of the gyroscope is driven counterearthwise by three-phase current introduced through The hollow trunnions of the suspension. The level is in neutral equilibrium on the pivots 37 when the liquid is equally distributed between the vessels 32, 33 and the whole sensitive system is in neutral equilibrium on the trunnions 2, 3 when the rotor axis and level are horizontal and the weight 84 is set to zero latitude. Specification 159,604 is also referred to.