Geometrical instruments – Straightedge type – Plural straightedges nonadjustably fixed at right angles
Patent
1982-09-13
1985-01-01
Martin, Jr., William D.
Geometrical instruments
Straightedge type
Plural straightedges nonadjustably fixed at right angles
33 1N, 33 27C, 33494, B43L 900
Patent
active
044909217
ABSTRACT:
A drafting tool for use in drafting or work layout is made of a pocket-sized piece of flat, transparent, rectangular material. The opposite edges are marked with full-scale and half-scale rulers and a center line is marked connecting the mid points of these rulers. This center line is perpendicular to both reference edges, and at least one of the rulers is marked with units in increasing dimension toward both ends of the reference edge starting with zero at the center line. The base line of a protractor is spaced inwardly from one of the reference edges and is parallel to that reference edge. The protractor itself is layed out in the form of a trapezoid, the top of which is parallel to the base line and the two sides of which slope inwardly from the base line toward the top at forty-five degree angles. The connections of these sides with the top is at an angle of sixty degrees with the base line measured at the origin on opposite sides of the center line. A small hole is formed through the tool at the origin of the protractor, and a number of spaced holes are formed through the base line in alignment with the markings of the ruler nearest the base line for use in striking circles of various diameters.
REFERENCES:
patent: 239691 (1881-04-01), Appleton
patent: 647339 (1900-04-01), Thompson
patent: 1043789 (1912-11-01), Whalen
patent: 1182638 (1916-05-01), Carnahan
patent: 2003172 (1935-05-01), Burt
patent: 2016489 (1935-10-01), Escalante
patent: 3795053 (1974-03-01), Burke
Pigman John H.
Woods William D.
International Design Corporation
Martin, Jr. William D.
Ptak LaValle D.
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