GB1149167A - Compass - Google Patents

Abstract

1,149,167. Compasses. PATRICK HARRISON & CO. Ltd. July 22, 1966 [May 13, 1966], No.33120/66. Heading G1F. A magnetic compass comprises an azimuth indicating ring 40 carried by an inner gimbal ring 34 which is pivotally mounted in an intermediate gimbal ring 28 for rotation about an axis which is maintained vertical by weighting the ring 34, a magnetic element 45 being pivotally mounted in the inner ring 34 about an axis normal to the plane of Figure 3 so that the magnet or magnets 46 carried by the element can align themselves with the direction of the earths magnetic field. The magnet or magnets 46 may be a press fit in the element 45 or they may be adjustable by being screw-threaded. Metal screw plugs may also be provided in tapped apertures as shown to enable the balance of the element 45 to be adjusted. The intermediate gimbal ring is preferably transparent and is marked with a datum line for co-operation with the azimuth markings on the ring 40. The ring 28 is mounted in an outer gimbal ring 18 about a pivotal axis as shown, and the ring 18 is pivotally mounted in a spherical housing 12. The gimbal rings and housing 45 may be of hollow metal or plastics material, and their density is arranged to be the same as that of a liquid which fills the housing 12 so that the gimbal bearings support no weight. The liquid is a mixture of two liquids, one having a density higher than that of the moving components and the other a lower density. An expandible pouch 24 in a cylindrical member 22 is provided to allow for the effects of thermal expansion on the liquid.