GB882415A - An improved calculator for fractions - Google Patents

Abstract

882,415. Mechanical calculating-apparatus. GOULTER, V. H. July 4, 1960 [July 2, 1959]. No. 23242/60. Class 106 (1). [Also in Group XX] A proportionating device, more especially for use by dressmakers and tailors, comprises a pair of arms 10, 11 pivoted together at one end of each and each bearing markings of fractions (see Fig. 3), at distances from the pivot corresponding to those fractions of the total length of the arm. Markings for fractions having the same denominator are preferably in a line and of the same colour. The inner edges of the arms are radial to the pivot and have notches 41 to correspond with the fraction graduations. The distance between corresponding notches on the two arms is the marked fraction of the distance between points 43 at the ends of the arms. The outer edges of the arms bear measuring scales and the arm 11 has a further measuring scale separated from the edge scale by a groove 37 in which runs a slide 38 carrying opposed pointers 39. Other measuring scales are marked on the underside of the arms, including a double-length scale for use when the arms are fully opened. A detent 36 may be set to co-operate with notches in the end 12 of the arm 10 so as to hold the arms at various angles to one another, the angles being fractions of 360 degrees as indicated by the markings adjacent to the notches. A scale of angles 49 is marked round the end 13 of the arm 11. A flexible strip 46, Fig. 12, may be detachably secured between the ends of the arms to facilitate the drawing of curves. The ends 12, 13 of the arms are formed with mating annular ridges 16, Fig. 4, and are accurately located by a flanged cylinder 17 also carrying a quadrant 19 to define the axis of rotation. A locking ring 25 engages in the cylinder 17 by means of a bayonet joint and has lugs 27, 28 by which a downward and turning force may be applied against the action of a spring (not shown) frictionally to lock the arm in position.