GB598167A - Improvements in or relating to computing instruments - Google Patents

Abstract

598,167. Computing-apparatus. NEWTON, E. P. (Reece, F. A.). Sept. 7, 1943, No. 14672. [Classes 106 (i), 106 (ii) and 106 (iv)] A computing instrument, for use with maps, comprises a traction element movable over a map 'surface in contact therewith, a time scale graduated in units of time, a movable indicator, means connecting said traction element and indicator to cause said indicator to move relatively to said time scale distances proportional to the distances traversed by said element, said time scale being adjustable to cause said indicator to indicate on said time scale variable times with respect to the distances traversed by said element, and a speed scale for indicating the adjustment of said time scale. As shown in Figs. 1, 2, 3 and 8, the instrument has front and rear face plates 20 and 21 secured together to form a casing. Projecting from the bottom of this casing is a pointer 25 and a traction wheel 24 for traversing distances on a map. The wheel 24 is geared to a disc 30 on the rear of which is a circular distance scale 33 visible through an opening 34 in the plate 21 and graduated in miles. The wheel 24, the gearing and the scale 33 are so co-ordinated that when the wheel 24 traverses a certain distance on the map, the corresponding distance in miles will be indicated on the scale 33 by an index mark 35. On its front face the disc 30 is inscribed with a spiral line 36 which acts as an indicator and intersects a radial slot 37, Figs. 1 and 8, in the front plate 20. The slot 37 is also intersected by a series of spiral lines 38 inscribed in a transparent disc 32 above the disc 30. The slot 37 has a transparent cover 370 with a reference line 371 on it constituting a time scale, the graduations of which comprise the portions of the lines 38 visible through the slot 37. The disc 32 is provided with a circular speed scale 41 outside the spiral lines 38 and part of which is visible through an opening 39, Figs. 1 and 8, on the plate 20. The user of the instrument can vary the graduations of the time scale 371, 38 by turning the disc 32 by means of its serrated edge.