Geometrical instruments – Straightedge type – Combined with level
Patent
1987-02-17
1988-04-12
Haroian, Harry N.
Geometrical instruments
Straightedge type
Combined with level
33353, 33469, 33418, G01C 912
Patent
active
047365242
ABSTRACT:
There is disclosed a framing T-Square and protractor wherein the head of the T-Square and the elongated rule thereof are connected by means of a ballbearing allowing the rule portion to be free-swinging with respect to the head, which is in the form of a rectangular plate having a protractor scale thereon marked in degrees and auxiliary scales marked with inches of rise per 12 inches of run for common rafters and for hip and valley rafters. A rectangular panel is hingedly attached to the plate on a hinged line normally at right angles to the elongated rule; a friction locking mechanism permits the rule to be locked at any desired angle relative to the plate and panel. The rule, plate, and panel are marked on the back with rafter tables and other data including run lengths and protractor angle settings useful in roof framing and other construction or carpentry work. A vernier scale on the front of the panel facilitates setting of angle measurements to an accuracy of one-tenth of a degree.
REFERENCES:
patent: 591964 (1897-10-01), Gilcrest
patent: 981867 (1911-01-01), McCormick
patent: 1381808 (1921-06-01), Davis
patent: 2423786 (1947-07-01), Morris
patent: 2768448 (1956-10-01), Rineer
patent: 2918962 (1959-12-01), Jones
patent: 3828436 (1974-08-01), King
Haroian Harry N.
Keegan Robert R.
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