GB914617A - Improvements in or relating to slide rules - Google Patents

Abstract

914,617. Slide rules. LICENCIA TALALMANYOKAT ERTEKISITO VALLALAT. Sept. 9, 1960 [Feb. 9, 1960], No. 31187/60. Class 106 (1). A slide rule comprises a scale-bearing base member which may be a rectangular plate 1, as shown, or of disc, cylindrical or other suitable form, a relatively movable cover-plate 2 of substantially the same shape and size as the scale-bearing surface or surfaces of the base member and carrying index marks and a cursor 4 movable over the cover-plate. The base member carries logarithmic and reciprocal logarithmic scales 9, 10 and linearly graduated date scales 6, 7 one of wnich is graduated according to the days and months of a year, and the other from 0 to 365. Index lines 8 and 11 on the cover-plate co-operate with the scales 7 and 10 respectively. The scales 6, 7 may be used to determine the number of days between dates for use in making calculations of interest. Also for use in such calculations are index marks 12, 13 suitably positioned on the coverplate to take account of the number of days in a year which may be taken as either 360 or 365. Index lines 16 co-operate with the scale 9 and are so positioned as to take account of various currency conversion factors. A further pair of scales 14, 15 are so graduated as to relate percentage increases on net prices with the corresponding increases expressed as percentages of the increased price. Further scales (not shown) may be provided for compound interest and similar calculations, i.e. for solving equations of the form S N = (S(1+0.01p)<SP>N</SP>; these include scales drawn to base e. Some scales may be marked on the reverse side of the base member and in this case, the cover-plate and cursor extend round both sides of it. In addition to the marking of the main graduations, sub-divisions may be marked as shown in Fig. 5.