GB187969A - Improvements in and relating to compass and magnetic dip indicators - Google Patents

Abstract

187,969. British Thomson - Houston Co., Ltd., (Assignees of Abbot, C. G.). Oct. 27, 1921, [Convention date]. Magnetic compasses. - In a compass and magnetic dip indicator of the kind in which the magnetic needle is supported in liquid, the liquid is contained in a closed transparent gimbal-mounted vessel 10, the needle 22 is mounted on horizontal pivots on a frame which is mounted to turn about pivots in line with the vertical axis of the vessel, and the mean densities of the needle and of the frame are made equal to that of the liquid. In one construction, Fig. 1, an electromagnetic needle 22 is pivoted horizontally at its centre of gravity within a frame 29 free to turn about a vertical axis within the vessel 10. The upper part of the vessel 10 is hemispherical and the lower part is cylindrical and is closed by a base 16 with a packing ring 19, the parts being held together by bolts 17 connecting rings 18, 18<1> bearing on flanges on the vessel and the base respectively. The needle 22 carrying at one end a pointer 23 is provided with bearings 24, 25 formed on a metal band 26 which is secured to the needle so that the pivotal axis passes through the centre of gravity. The bearings 24, 25 are mounted on pivot needles 27, 28 carried by the frame 29 which comprises two hollow forked members 32, 33 of glass connected by metallic tubes 34, 35, and is mounted between upper and lower pivot bearings carried by the vessel 10. A pointer 44, secured to the frame 29 and disposed at right angles to the needle 22, indicates the compass bearing on a scale 21<1> on the vessel 10, which is also marked with concentric circles 21 co-operating with the pointer 23 to indicate the dip. The needle 22 is in the form of an electromagnetic winding 49, Fig. 3, on an iron core 50 within an insulating closed casing 51, the terminals 52, 53 of the winding passing through the wall of the casing near the pivotal axis. Two pairs of weighted clamping rings 54, 55 are adjustable on the casing 51 for balancing the needle. The terminals 52, 53 are connected to conductors enclosed within the frame 29 and supplied with current through the upper and lower pivots of this frame. In a modification, Fig. 5, the needle 22 is secured diametrically within a metallic sphere 60 formed in two halves insulated from each other and secured together by insulated bolts 61. At the ends of a horizontal diameter perpendicular to the needle, the sphere is connected by silk threads to a tubular ring 64 which is connected by other silk threads 65, 66 to the top and bottom of the vessel 10. The needle 23 indicates in this case both the compass bearing and the dip.