Geometrical instruments – Straightedge type – Base attached
Patent
1989-02-17
1990-11-13
Will, Thomas B.
Geometrical instruments
Straightedge type
Base attached
33471, 33 1SD, B43L 1300
Patent
active
049692712
ABSTRACT:
The map reading and plotting instrument comprises two transparent discs coaxially held together by a hollow fastener for rotary motion relative to each other and two transparent arms disposed between and extending radially of the discs and secured by the hollow fastener for pivotal movement relative to each other and the discs. The top disc has a sight-slide subassembly consisting of a plurality of first scales of linear measure and a sight-slide moveable relative to the first scales. The bottom disc has adjacent its periphery a plurality of scales of angular measure while each of the arms has a plurality of scales of linear measure extending from the hollow fastener longitudinally to the distal end thereof. The top disc has a north-south diametral line which coacts with a declination scale of the bottom disc to effect orientation of the instrument with the magnetic north as shown on a map having grid azimuths and/or a declination diagram.
REFERENCES:
patent: 905249 (1908-12-01), Townsend
patent: 2003172 (1935-05-01), Burt
patent: 2039333 (1936-05-01), Musham
patent: 2477556 (1949-07-01), Shaw
patent: 2545935 (1951-03-01), Warner
patent: 2996242 (1961-08-01), Bannister
patent: 3059339 (1962-10-01), Danforth
patent: 3432927 (1969-03-01), Springer
patent: 3855706 (1974-12-01), Price
patent: 4359628 (1982-11-01), Lambert
patent: 4625409 (1986-12-01), Arakawa
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