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Патент USA US2411529

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NOV- 26,1946-
Filed July 12, 1944
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Patented Nov. 26, 1946 _ '
John F. Dohrwardt and Dorothy M.
Dohrwardt, Detroit, Mich.
Application July 142, 1944, Serial No. 544,532
2 Claims. (Cl. 334-407)
This invention relates to straight edges used in
drafting and particularly to attachments for
straight edges.
In moving an ordinary straight edge up and,‘
down on a penciled drawing, friction tends to
detract from the sharpness of the lines and lead
is to some extent transferred over the entire sur
face of the drawing, detracting from its appear
ance. If a drawing is being inked the draftsman
must exercise great caution in moving the straight‘
edge or wet lines will be blurred.
An object of the invention is to provide a simple '
and inexpensive attachment for a straight edge
that will predeterminedly space it from a draw
ing in a manner to almost completely eliminate
detriment to the drawing.
over the end of a straight edge, whereby the de
- vice acquires a slight ‘yielding grip-on the straight
edge to resist its accidental shifting. ' It is pre
ferred' to form the attachment at its margins with
, slight rounded beads 5 coextensive with said mar
gins, said beads minimizing the areas of contact
with a drawing. Because of their small areas and
their very smooth faces, said beads permit of prac
tically no adhesion of lead as the attachment is
shifted on a penciled drawing.
The number of the attachments used on any
straight edge depends on its length, the requisite
being to avoid unsupported lengths of the straight
edge adequate to sag into engagement with a
drawing. The strip from which the attachment is
fashioned may be formed in any desired length
by an extrustion or other suitable process, and
may be sheared to shorter lengths suitable for
Further objects are to adapt such an attach
ment to be readily shifted along the straight edge
to the point where it is most needed; to shape
the attachment so as to minimize its area of con
tact with a drawing; and to form the attachment
of a material that will give rise to a minimum
friction in engaging a drawing.
These and various other objects are attained by
the construction hereinafter described and illus
trated in the accompanying drawing, wherein:
Fig. 1 is a perspective view of a drawing board,
showing several of our attachments applied to a
_ our purpose. The thickness of the beaded portions
20 of the strip is preferably about three sixty-fourths
of an inch, this being sufficiently less than the
standard thickness of drafting triangles and
‘curves that these will not tend to slip beneath
the‘ straight edge.
The term “straight edge” as used in the follow
ing claims is inclusive of the blade ‘of a T-square
whereon our attachment may be used just as on a
straight edged member guided atboth ends.
What we claim is:
straight edge associated with said board.
1. An attachment for a straight edge compris
Fig. 2 is a fragmentary top plan view of the 30 ing an elongated strip of material bent to provide
straight edge and one of our attachments applied
a mid portion for underlying the straight edge
and end portions projecting toward each other
Fig. 3 is an end View of the same.
overlying the straight edge, said attachment
In these views, the reference character I desig
proportioned to slide freely along the
nates an ordinary drafting board and 2 the usual
straight edge, said strip being formed on its draw
straight edge movable up and down on such board.
-Mechanisms for restraining a straight edge from
any angular shifting are well‘ known and require
ing-engaging face‘ with at least one rib trans
versely rounded and extending substantially from I
endto end of said face to minimize contact of
Our, attachment consists of an elongated strip 40 the attachment with adrawing.
2. An attachment for a straight edge compris—
of light and very smooth plastic material having
ing‘an elongated strip of material bent to provide
its mid portion 3 disposed transversely to and
a mid portion for underlying the straight edge
beneath the straight edge and having end por
and end portions projecting toward each other
tions 4 return-bent to project toward each other
for overlying the straight edge, said attachment
above the straight edge, terminally contacting its
being proportioned to slide freely along the
top face. To facilitate shifting of the attach
straight edge, said strip being formed on its
ment and permit of accurately predetermining
drawingeengaging face with ‘spaced marginal
a pressure exerted on the straight edge \by the
transversely rounded ribs substantially cbexten
' end portions 4, it is preferred to slightly arch
such portions as clearly appears in Fig. 3. Thus 50 sive with said face and affording reduced areas
of contact with a drawing.
the attachment may be manufactured with the
ends of its portions 4 spaced above the portions 3
a distance slightly less than is required in use,
so that there will be a slight upward springing
. no illustration in this connection.
of the end portions in slipping the attachment
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