GB741389A - Improvements in navigational and the like computing devices - Google Patents

Abstract

741,389. Calculating-apparatus. SO, C., and WANG, L. J. Aug. 27, 1954 [May 29, 1953], No. 14999/53. Class 106 (1). A calculating device, particularly for use in connection with astro-navigation, comprises at least two relatively rotatable discs, and a rotatable cursor, a pair of similar but radiallyseparated logarithmic haversine scales of angles marked on two of the discs respectively and a pair of similar but radially-separated haversine scales of angles marked on two of the discs respectively. In one arrangement, Fig. 3, the first scales C, C<SP>1</SP> are marked on a base disc 10 and an upper transparent disc 11 and each is divided into several radially-separated sections or is drawn as several turns of a spiral. The scales W, W<SP>1</SP> of the second pair are also divided into sections and are drawn in an opposite sense to the C scales, on the same discs. A crescent-shaped transparent cursor 12 with a radial line is arranged between the discs and a further cursor 14 having a diametrically arranged edge is pivoted above the disc 11. The discs also bear logarithmic sine scales A a, A<SP>1</SP> a<SP>1</SP> and logarithmic secant scales B b, Bl bl. The cursors are marked as shown in accordance with the several scales and the individual sections thereof. In a modification, one scale of each pair is mounted on an independently rotatable disc, while in another arrangement, the scales of each pair are mounted on adjacent ones of a set of five discs. In a further modification, Fig. 5, two opaque discs 19, 20 are separated by a transparent cursor 21, and a further cursor 23 is mounted above the disc 20 on the common pivot. The logarithmic sine and secant scales are omitted but a normal logarithmic scale is marked on each disc. Various examples are given of the use of the device.