Patent GB-189518-A (GB)
Title: Improvements in or relating to logarithmic calculating devices
IPC: G06G1/10
Filed: 1921-08-29
Abstract: 189,518. Beauvais, G. Aug. 29, 1921. Slide-rules; adding and subtracting apparatus.- A circular slide-rule in which the scale is traced on curves of the form r = a# + m, a, m being parameters, has an " angle totalizer " corresponding to the characteristic and further a numerical scale is provided by means of which addition and subtraction may be performed. In the form shown in Fig. 1, the logarithmic scale a is traced on a series of equidistant concentric semi-circles, and the angle totalizer is constituted by a plate b on the central axis o and an alidade c bearing a reference line r and mounted on the same axis, which alidade may drive the plate through frictional engagement therewith, or may be turned independently thereof, transfer being effected by means of two teeth m gearing with the teeth of a wheel n. The line totalizer comprises an endless ribbon k wound on rollers mounted on the alidade, and graduated to correspond with successive semi-circles of the scale. The plate b is turned clockwise by rotation of the alidade in frictional engagement therewith successively from each number registered to zero, and the result is obtained after reverse rotation of both until the plate b is returned to zero from the alidade reading. Meanwhile the ribbon k of the line totalizer is moved by the finger according to the semi-circle upon which each number lies, and the number indicated on the transfer wheel n at the end of the angle registration is also added on the line totalizer. In another form of line totalizer, Figs. 5 and 6, a second wheel n<1> is mounted above the wheel n and has apertures through which the graduations of the latter are viewed, a stationary plate h separating the wheels also having apertures graduated in the direction opposite to those of the wheel n. A transfer tooth q on the wheel n gears with integral wheels n', n<2>. The plate h takes the place of the ribbon in the previous form, the reading of the wheel n being automatically registered by the movement of the zero graduation thereon, and the additional wheel n<3> enables numbers of a greater denomination to be dealt with. In another form of line totalizer, the automatic transfer is effected by the actuation of the ribbon by a rider carrying a crank, which may also drive the plate b when the ribbon is moved in one direction. For addition and subtraction, a scale p, p<1> divided into 10,000 equal parts is provided, and the wheels n', n<2> are used for higher denominations, the operation by means of the alidade being substantially the same as for multiplication and division. Scales of square roots, sines and tangents may also be provided, and common logarithms may be obtained by comparison between the logarithmic and numerical scales. Instead of semi-circles, arcs of angle 2#/N may be employed, N being any whole number, and the plate b then having N transfer teeth. The semicircles may be replaced by convolutions of an archimedes' spiral, or of two such spirals as shown in Fig. 10. The angle totalizer is then constituted by two transparent discs b<2>, b<3>, each with a diametral reference line, and the line totalizer by the same two discs and two additional discs c<2>, c<3> bearing reference spiral arcs of the equation r = 10 a# + m. The' discs are mounted so that the pair b<2>, c<2> turn together, and may drive both the discs b<3>, c<3>, or only the disc c<3>. The mathematical theory is given, and the operation is substantially the same as in the alidade form, the result being obtained from the final readings of the discs b<3>, c<3>.