Geometrical instruments – Straightedge type
Patent
1980-05-14
1983-12-27
Haroian, Harry N.
Geometrical instruments
Straightedge type
33 42, B43L 1302
Patent
active
044222459
ABSTRACT:
In a preferred embodiment, there is provided a drafting board having x and y axes and of a predetermined size for a specifically desirable paper size, the drafting board having indicia in juxtaposition to and following each edge of the x and y axes and the bottom edge of the drafting board being of a width sufficient to support two spaced-apart roller surfaces of a T-square to be positioned on the drafting board, the bottom edge's width extending laterally across the board's bottom as a planar surface, and a T-square having a straight edge along a first longitudinal axis that extends from bottom to top of the board when placed thereon, and the T-square having a helve head unitary with a proximal end of the blade, and the helve head having a second longitudinal axis extending substantially at a right angle to the straight edge and extending substantially parallel to the board's bottom edge and to the planar surface of the board's bottom edge, and structure of the helve head along the second longitudinal axis carrying three separate and spaced-apart roller surfaces arranged in tri-pod triangular arrangement positioned to each roll laterally along the planar surface of the board's bottom edge such that when the T-square is mounted on the drafting board and concurrently the roller surface positioned against the planar surface, the straight edge is held stably against vertical and lateral shifting relative to the board's upper face, and an indexed open-throat of the T-square provides for accurate reading of position with regard to positioning of the straight edge laterally to and from left and right.
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Haroian Harry N.
Hough William T.
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