GB589711A - Improvements in calculating apparatus - Google Patents

Abstract

589,711. Calculating-apparatus. DUCE, R. G. (Duce, H. J.). March 27, 1945, No. 7758. [Class 106 (i)] A logarithmic calculator for evaluating problems such as axb/c comprises two similar assemblies A, B, each having a drum 5 on the left-hand. half of which is marked a table of five-figure antilogs. 8, Fig. 3, arranged in one hundred lines, each containing ten antilogs. One line only is at any time adjacent a viewing slot 14. The first two figures of a log. corresponding to a given antilog. are read through the slot from a graduation 10 on the drum and the third figure is indicated by a set of marking " 0 " ... " 9 " (not shown) along the slot adjacent the antilogs. 8. One antilog. 8 only is exposed to any time through the slot 14, since the drum is surrounded by a screen 6 having ten sets of helically arranged slots 11. The screen is adjusted by a knurled flange 16 and after each tenth of a rotation it advances the drum 5 through transfer gearing 36 to bring the next line of antilogs. beneath the viewing stot. The right-hand side of the drum is provided with a set of difference scales 9, one for each line of antilogs. and all the same length. The scales are obtained by determining the mean difference between the figures in an antilog. row (including the first figure in the next row) and dividing the corresponding scale into this number of equal divisions. The part of the drum 5 carrying the difference scales 9 is surrounded by a transparent screen 7, marked with a helix of dots 12 and with a scale 15 marked " 00 " ... " 99 ". The screen 7 is adjusted by a knurled flange 17. The assembly A is coupled to the similar assembly B by a coupler 20, slidable into three positions. In the first position, as shown, there is no coupling. When the coupler is slid one step to the right, the two left-hand screens 6 are connected by gearing 24, 25, 26. When moved two steps to the right, the difference screens 7 are connected by gearing 27, 28, 39 and also each difference screen 7 is connected to the corresponding left-hand screen 6 by transfer gearing, comprising a single tooth 33 engaging a transfer pinion 39, such that the left-hand screen is moved one-hundredth of a rotation for each rotation of the difference screen. Additional assemblies, graduated with trigonometrical functions, may be provided.