Geometrical instruments – Straightedge type – Plural straightedges nonadjustably fixed at right angles
Patent
1991-09-03
1993-04-13
Will, Thomas B.
Geometrical instruments
Straightedge type
Plural straightedges nonadjustably fixed at right angles
33482, B43L 7027, B43L 7033
Patent
active
052017834
ABSTRACT:
The drafting instrument of the invention (10) disclosed herein generally compromises a planar body in a quadrilateral, symmetrical form, having four perimeter sides (22,24,26 and 28), interconnected end to end to form a quadrilateral configuration and show an open space (40) in the interior of the body, and of which two pairs of sides are right angles to each other and positioned opposite and symmetrical to each other on the planar body. The instrument is provided in two primary embodiments, the first, adapted from a 45 degree triangular instrument, where side intersections of the present invention comprises a 135 degree, a 90 degree, a 45 degree and a 90 degree interior angle, respectively and the second adapted from a 30/60 degree triangular instrument, where side intersections of the present invention comprise a 150 degree, a 90 degree, a 30 degree and a 90 degree interior angle, respectively. The instrument is provided with a handle (18) that is integrally formed near the intersection of two of the perimeter sides on the planar body and extends perpendicular from the planar body, and in the preferred embodiment of the invention, the handle (18) is provided with a groove or rigid structure at its outer most edge for permitting easy indexing and pivoting with handle (18) to aid in reversing the instrument from side to side. The instrument includes a plurality of support points (38) extending outwardly from one face (16) of the instrument only, to permit pivoting and to support the instrument slightly above the surface upon which it is used.
REFERENCES:
patent: 827989 (1906-08-01), Noble
patent: 2401265 (1946-05-01), Nash
patent: 3375589 (1968-04-01), Dolgorukov
patent: 4974330 (1990-12-01), Covert
patent: 4999922 (1991-03-01), Loggins
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