Patent GB-167503-A (GB)
Title: Improvements in speed indicators for aircraft, ships and like bodies
IPC: G01C19/02
Filed: 1921-08-08
Abstract: 167,503. Chessin, A. Aug. 6, 1920, [Convention date]. Gyroscopic speed indicators.-Apparatus for measuring the ground speed, the drift, and the direction of travel of aircraft and ships comprises two pendulously-mounted gyroscopic devices with their axes at right angles, the speed being measured in two directions in terms of the tension of springs restraining precession of the gyroscope. A correction is made by means of a compass needle and scale for the speed of the earth at the latitude in which the vessel is travelling. Several forms of gyroscopic devices are described. In the first form, Figs. 1 and 7, two gyroscopes 4', 4<11> rotating about a vertical axis are mounted in frames 2<1>, 2" having plain sectors 3<1>, 3<11> in rolling contact. Floats 5<1>, 5<11> relieve the pressure on the bearings. A single pointer 6 is employed and the movements of the frames 2<1>, 2<11> in opposite directions are opposed by springs 7<1>, 7", which may be adjusted by screws. The scale 9 may be adjusted circumferentially. In the second form, Fig. 2, two gyroscopes rotating about horizontal axes have their frames connected by bevel gearing 3a. Separate pointers 6<a> and adjustable volute springs 7a, Fig. 5, are employed. In a third form only a single gyroscope mounted similarly to the upper one in Fig. 2 is used. A table 11 bearing a chart 15 for compounding the readings of two instruments 12, 13 is shown in Fig. 8. The instrument 12 is set in the N.-S. direction as shown by a compass 14, and the other is set in the E.-W. direction. A cursor 18 on a pivoted radial arm 16 is set along the horizontal and vertical scales to the readings of the two scales 9 of the instruments. The true course is then given by the direction of the radial arm and the ground speed by the distance of the cursor along the arm. A further form of instrument is described, similar to that shown in Fig. 2, in which a magnetic needle is mounted coaxially with the gyroscope pointer. Two such instruments with their axes at right angles are mounted separately or together in gimbals, under the influence of gravity, or they may be placed on stabilized tables. The magnetic needle 25 of one, Fig. 12, indicates over a scale 30 proportional to the cosine of the bearing angle, while the scale 29, Fig. 13, of the other instrument is proportional to the sine of the bearing angle. The outer scales 31, 32 are proportional to the torques exerted on the gyroscopes in the two directions, and readings thereon by the gyroscope pointers 26 give the absolute speeds. The ground speeds in the two directions are obtained by the differences of the inner and outer readings, and are compounded to give the ground speed and course,. A series of concentric scales for various latitudes may be arranged on the dials. The pointer of the gyroscopic member may be mounted on a separate axis and receive movement through multiplying levers. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the following subject-matter :-The scales may be modified to adapt the instrument for use as a clinometer for aircraft. The casing of the first form of instrument described may be mounted about a knife edge and be supported resiliently by springs at the bottom; in the second form of instrument the gyro-wheel may be mounted in resilient bearings in the frame. This subject-matter does not appear in the Specification as accepted.