Title: Standard parallel rule with perspective drawing device

Abstract: A standard draftsman's parallel bar or rule is adapted to draw perspective lines by an auxiliary cable and differential pulley system which when detached allows conventional parallel operation.

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Inventors: Harvey, Douglas P. (Houston, TX, US)

Application Number: 829952
Filing Date: 1977-09-01
Publication_date: 1979-02-06
Assignee:
Primary Class(es): 33/432
Other Classes:
US Patent Ref:

1964198	Jun, 1934	Edison	33/77.
2184718	Dec, 1939	Lopez	33/77.
2590252	Mar, 1952	Horst et al.	33/77.
3783519	Jan, 1974	Sartori	33/77.

Other Refs: 426987162666

Apr, 1935	GB
May, 1964	SU

Primary Examiner: Phillips, Charles E.
Assistant Examiner:
Attorney: Lee & Smith