New or improved drawing instrument combining the features of an isometric protractor, ellipse proportion meter and radial scale

摘要

595,537. Drawing -instruments. LOWE, C. B. July 6, 1945, No. 17275. [Class 97 (iii)] The markings on a device for use in the production of isometric drawings indicate (1) angles, (2) the proportions of ellipses representing tilted circles and (3) linear measurements, taken in any of the three isometric planes. The area a is graduated in apparent degrees. The lines h give the ellipse proportions of the ellipses representing circles at those angles in any plane. Measurements of lines at any angle are taken from a family of ellipses l, each of which represents one dimension. Base lines e and f are provided whereby the protractor may be correctly disposed for the setting out of angles on any isometric plane. The three isometric planes are shown by the cube d.