GB190822620A - A Logarithmic Disc Calculating Machine. - Google Patents

Abstract

22,620. Leder, E. Oct. 24. Calculating apparatus.-In logarithmic disk calculating-apparatus, the logarithmic scale is spread over a number of radii enclosed between two concentric circles. The number of radii is preferably one hundred, and the length enclosed between the two circles ten centimetres. The total length of the scale is taken to represent log. 10, and the first division on each part radius is repeated on a prolongation of the preceding radius. The first two figures of the mantissae are shown on the inner circle opposite to the radius and on the disk rim at a tangential opening in the casing, the remaining digits being given by the length of the partial radius as measured by a scale carried on the casing. The numbers corresponding to the logarithms are marked along the scale as shown in Fig. 5. The disk a is mounted, as shown in Fig. 2, to rotate in the casing d, which is provided with a slot e, Fig. 1, formed so that only one radial portion of the scale is visible. Mounted on the casing is a slide carrier f on the edge of which is formed a scale i equal in length to the one-hundredth part of the whole scale. Mounted in a groove g in the carrier is a movable slide h graduated in lengths equal to the scale i and marked with graduations +2, +1, 0, -1 as shown in Fig. 1. Attached to the slide is a runner k consisting of a frame l provided with a glass plate having an etched line o<1> arranged in the same plane as a pointer carried by the plate k. A stop-pin on the carrier f limits the movement of the runner to the left. Mounted on the casing so as to be revolved by a milled head s is a disk q carrying numbers 00-99. An opening r in the casing allows one of these numbers to be seen, and an opening y shows one of the numbers on the edge of the disk a. Mounted on the axis of the disk q is a pinion u engaging a toothed wheel v mounted on the axis of a disk x, the gearing being in the ratio of 20 to 1, and the rotation of the wheel v being indicated by a frictionally mounted pointer w on a scale x divided as shown into two parts showing + and - figures. An auxiliary scale z is provided, and is graduated as shown in Fig. 1 to facilitate simple multiplication and division.