Patent GB-166906-A (GB)
Title: Improvements in gyroscopic instruments and apparatus
IPC: G01C19/44
Filed: 1917-07-26
Abstract: 166,906. Henderson, Sir J. B. July 26, 1917. Adapted for sighting from aircraft; courses, indicating; latitude, instruments.-In apparatus as described in Specifications 166,570 and 166,571, [both in Class 97(iii), Thermometers &c.,] and in which the gyro is normally in neutral equilibrium, but when tilted out of its normal position is controlled by means of a level, the angular velocities of precession necessary to maintain the gyro in a steady state relatively to the earth or to the vessel carrying it are brought about by couples produced by displacement of the controlling level; according to the invention the displacement of the level is indicated or measured so that the gyro can be used as a navigational instrument for : (a) indicating the true vertical for position finding or bomb dropping, (b) indicating the course, (c) measuring the latitude. An instrument for (a) is shown by elevations at right-angles to each other in Figs. 1 and 2. A pivoted level 4. 5, 7 connected by springs 11, 12 to the gyro casing 1 controls air-jets issuing from nozzles 13, 14 in the casing and passing into tubes 15, 16 which have oppositely-directed horizontal upper ends and are carried by the levels. Light from a diaphragm 18 carrying a cross-wire 19 passes from a collimating lens 17 to a right-angle reflecting system 21, 20, the mirror 21 being half-silvered to enable the ground below to be seen through it, light from a similar arrangement of level collimator, &c. at right-angles to the first with a cross-wire 19<1> being thrown upwards by the semi-transparent mirror 22 so as to produce an image of cross-wire 19<1> to intersect the image of cross-wire 19 and so indicate the vertical; the spring control is adjusted so that the various angles of tilt are adjusted as the gyro tilts. Fig. 3 is a side elevation of a course indicator comprising a gyro in the casing, with an approximately vertical axis. There is a control system consisting of an airnozzle 31 co-operating with a shoot 32 carried by a level 4, 7, 5, and a similar system at rightangles to the first. The gyro axis tilts to the west by an amount proportional to the cosine of the .latitude and the tilt is measured by an opticalprojection device throwing a spot of light upon a compass-card 44 adjustable about a pin 45; the distance of the spot from the pin is proportional to the cosine of the latitude, the card being turned so that the spot is in line with the west mark. The projection device consists of an illuminated diaphragm 36 carried by the level 4, a projecting lens 38 carried by the level 4', and a doublereflecting prism 40, the prism and card 44 being carried by the gyro casing 1. The instrument can be used to steer a course by setting the card 44 to bring the lubber-line to the point corresponding to the course and then steering so as to keep the spot of light on the west point. Fig. 6 shows a gyro similar to that of Fig. 3, but embodying a sighting-telescope. A short-focus objective 50 carried by the gyro casing 1 throws an image of the ground after double reflection in a prism 52 carried by the level 4, 5 on to a graticule 53, the image being then transmitted by prism 54 and collimating lens 56 mounted in a separate tube 55 to the entrance prism of telescope 58. Fig. 8 shows a course-indicator employing only one level 4, 5 which is revolubly mounted on a hollow vertical spindle 66 which is connected to the gyro-casing and serves to carry an airjet co-operating with a shoot carried by the gyro, and an air-control device 70, 71 carried by the level for producing restoring couples about the vertical. Owing to the westward tilt of the gyro, the level sets E. and' W. Fig. 10 shows optical means for measuring the tilt of the controlling level relatively to the gyro of a compass. A collimator 77 with a scale in the focal plane is arranged to throw an image into the telescope 78 after double reflection by mirrors 74, 75 carried by the level and gyro respectively, and the tilt is read off on the scale by the telescope crosswire.