Geometrical instruments – Straightedge type – Base attached
Patent
1994-06-01
1995-02-07
Wirthlin, Alvin
Geometrical instruments
Straightedge type
Base attached
33430, B43L 1302
Patent
active
053866401
ABSTRACT:
A drafting device includes a pair of magnetic boards securely mounted to upper and lower surfaces of a base frame respectively, a ruler movably engaged on the magnetic board, a pair of cavities defined in each of the four corners of the lower surface of the base frame, and a protrusion being formed between the pair of cavities. A guiding member is securely mounted to each of the four corners of the base frame and includes a locking block having a first wall member and a second wall member mounted on the upper and lower surfaces of the base frame respectively, a slot being defined in the second wall member through which the protrusion is received, a recess defined in an underside of the locking block between the first and second wall members and having a width equal to the distance between a bottom face of the cavity and the upper surface of the base frame. A guiding line loops around each of the guiding members and passes through two ends of the ruler.
REFERENCES:
patent: 1482606 (1924-02-01), Goldrick
patent: 3283410 (1966-11-01), Truhon
patent: 4934061 (1990-06-01), Knight et al.
Chen Chiang-Ming
Chen Kun-Mao
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