GB718479A - Improvements in drawing equipment - Google Patents

Abstract

718,479. Mathematical drawing instruments. KROSLAK, H. Feb. 6, 1950, No. 24478/52. Divided out of 702,594. Class 97(3) A draughtman's set square is provided on a transparent portion thereof on a straight-line perpendicular to the hypotenuse edge 58, Fig. 1, with a single scale 56-or double scale c-c graduated e.g. in millimetres, centimetres, inches, ounces, or logarithms so arranged that the first graduation measured from the hypotenuse is shortened by a distance " x which compensates for the normal distance between the actual edge 58 of the set square and an imaginary base line 60 such as would be traced by the point of a drawing pen or pencil moving along that edge. There is further provided on one side or as shown on both sides including the right angle a scale of angles so applied that the graduation marks converge towards a vertex 62 located on the base line 60. Alternatively the angular scale lines on the edges may radiate from a point on the set square where a base line F, Fig. 3, and the perpendicular line G from. the right angle on to the hypotenuse intersect and a second inner angular scale H provided on 'the set square having its origin at the point 62. [n another alternative for convenience in drawing parallel lines at unit distance apart the 60 degrees set square 53, Fig. 3, may be provided with a scale 61<SP>1</SP> on the side subtending the 30 degrees angle representing the scale units multiplied by 2/#3. The amplified scale 61<SP>1</SP> is used in conjunction with a reference mark r on the set square 55, e.g. the base line F, for drawing parallel lines as indicated. In the case of a 45 degrees set square the sides containing the right angle may be provided with a scale representing the units multiplied by #2. The set square is bevelled at the corners as shown at 63. When the scale 56, Fig. 3, is a double millimetre scale. the half units are marked by points 56<SP>1</SP> or by short strokes. The set square may have a skeleton frame 53, 66, Fig. 5, of opaque synthetic material or hard wood with a transparent insertion 65 upon which the scale 56 is marked.