GB168495A - Improvements in or relating to course finders - Google Patents

Abstract

168,495. Westwood, C. N. July 21, 1920. Protractors. -. A course-finder for use with a chart comprises a blade 1, a hub 9 at one end of the blade, a compass card 11 rotatably mounted on. the hub, a ring 12 with four pointers 13 at right-angles to each other mounted on the hub above, the card, and an additional pointer 15 mounted above the ring. The pointer 15 may be clamped to the hub by a screw 17, and the ring and compass card may be clamped together and to the pointer 15 by means of a screw 18 engaging an arcuate slot 19 in the ring. A washer 20, Fig. 4, between the head of the screw 18 and the ring is provided with a projection 21 adapted to engage a flange on the collar carrying the pointer 15 in order to clamp the pointer to the ring. The blade is provided with a fixed indicator 28 and with a pair of adjustable indicators 27 carried by a slide 26 mounted in a guide 23 secured to the blade. The blade also carries a slide 4, which may be secured in any position on the blade by a set-screw 6, and can be used in conjunction with a gauge line 3 for measuring distances. The slide caries a perforated lug 8 for engagement by a pencil, marker, or the like, and a spring 7 adapted to engage a hole 2 at the end of the blade to prevent accidental displacement of the slide from the blade. One of the pointers 13 is marked with the letter N and is set at a distance from the north point of the compass card corresponding to the magnetic variation. A transparent plate 10 with a centering dot is provided within the hub 9 at the level of the blade. The adjustable indicators 27 are used to correct for compass deviation and the pointer 15 may be used in finding the true courses from the magnetic courses or for indicating the direction of tides, currents or wind. In a modification, the perforated lug 8 on the slide is replaced by a spring-controlled pin which serves as a pivot for the blade.