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Патент USA US2124051

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July 19, 1938.
_ 1__ v_ CANTRELL
Filed Feb. 24, 1937
Lorraine l/ Cantrell
q’, 427%
Patented July 19, 1938
Lorraine V. Cantrell, Berkeley, Calif.
Application February 24, 1937, Serial No. 127,449
2 Claims.
My invention relates to draftsmen’s rules, and
more particularly to an architect’s and engineer’s
rule which may be read in interchangeable units
and fractions of units.
Among the objects of my invention are: To
provide a rule having interchangeable unit mark
ings and interchangeable vernier movements; to
provide a self-reading rule for architects and
engineers wherein the vernier movements may be
read upon an enlarged scale; to provide a rule in
units and fractions of units which may be easily
read with great accuracy; and to provide a rule
having removable and interchangeable combina
tions of units and fractions thereof which is
15 adaptable for use where units of different char
acter are involved.
Other objects of my invention will be apparent
or will be speci?cally pointed out in the descrip
tion forming a part of this speci?cation, but I do
20 not limit myself to the embodiment of the inven
(Cl. 33-—107)
end of the scale, and drives through worm gear
I4 a longitudinal threaded rod I5. The end of
the rod I5 is ?rmly attached to a spline block I6
mounted in a bearing II. The spline block is provided with a diametrical slot I9 into which is in U!
serted a vernier screw block 20, the head of which
fits the spline block recess in such a manner that
the vernier block will rotate with the screw block
I6 and will also be prevented from coming out of
the block. Vernier screw block 20 has an axial 10
threaded bore therein into which is ?tted a
vernier screw 2| terminating in a square ?anged
head 22, dropping into a square slot in a vernier
positioning block 24 which is ?rmly attached to
the vernier extension III.
Thus it will be seen that when the thumb screw
I2 is rotated the vernier extension will be moved
outwardly or inwardly in accordance with the
pitch of the screw 2|. Inasmuch as the pitch of
the screw ZI must necessarily be different for 20
tion herein described, as various forms may be di?erent scales, I have provided on the upper side
of the scale frame I a hinged window 26, which
adopted within the scope of the claims.
In the drawing illustrating a preferred embodi- ~ may be opened, and when the vernier screw block
and screw are in their maximum engagement the
ment of my invention, Figure 1 is a top view of
entire assembly of vernier block and screw may
one form of my invention.
Figure 2 is a sectional view taken by the line be removed from the scale by sliding the assem
bly upward out of the respective engagements
2-2 in Figure 1.
Figure 3 is a sectional View taken as indicated ‘ with the terminal block, and a new block and
screw inserted. The cover when closed prevents
by the line 3—3 in Figure 1.
Figure 4 is a sectional view taken as indicated the vernier screw and block from moving out of 30
by the line 4—4 in Figure 1; and
Figure 5 is an enlarged view of a removable
vernier movement.
My invention may be more fully understood by
35 direct reference to- the preferred embodiment
shown herein.
A rule frame I is provided with a unit scale 2
graduated in one particular type of units, as for
example, in feet, as the illustrations herein show
40 a foot scale. The foot scale 2 ?ts over the bot
tom of the frame I and is held thereto by an in
turned front edge 3 and an inturned back edge II.
The scale, therefore, may he slid onto the frame
from one end, and is pushed on until the zero end
45 abuts a scale stop 5. Once in that position it is
locked to the frame by a locking screw 6. The
engagement with their terminal blocks.
At the
same time, the vernier block 20 can be seen
through the transparent cover 26, and I may pre
fer to- mark upon the vernier screw block 20 the
ratio of vernier extension with respect to the 35
units used.
The indication of the amount of extension of
the vernier portion of the scale is given by an
enlarged vernier scale 21 positioned under ver
nier scale window 28, and the indication of the
position of the vernier extension III with respect
to this scale is given by an indicator block 29,
traveling on screw thread I5 and carrying an in
dex pointer 30 projecting over the scale 21. Inas
50 an end stop II in the same line as that projected
much, however, as several different vernier scales 45
are to be used, as determined by the vernier
block, I prefer to mark the enlarged vernier scale
2‘! on the periphery of a rotatable cylinder 3|
rotated by a scale wheel 32 projecting through the
frame. I have found that at least three, and
from the main scale 2, the entire edge of this
stop thus providing a convenient locating point
for initiating the measurement.
The vernier extension I0 is operated by a
55 thumb screw I2, preferably located at the right
riphery of this cylinder.
In operation, the proper unit scale desired is
slipped onto the frame and ?xed. The scale
Wheel 32 is then rotated until the proper frac 55
scale is preferably provided at each unit mark
with marking recesses ‘I. Telescoping into the
frame I is a vernier extension II) having thereon
possibly more, scales can be inscribed on the pe
tions appear beneath the vernier scale window.
For example, I have shown feet on the scale 2,
and therefore a 12-inch scale‘ on the vernier cyl
thereon and abutting a stop on said frame, a
vernier extension telescoping into one end of
said frame and having an index point thereon
Under these circumstances, then, the
lining up with said scale, an enlarged scale
proper vernier block and screw 20 and 2| are
inserted to move the vernier so that the index
pointer 30 will move the full scale range, while
the vernier extension I 0 is moving the distance
representing one foot as determined by scale 2.
10 If, however, the measurements are to be taken in
some other units and the vernier read in tenths,
then the thumb screw 32 may be rotated to bring
an enlarged tenths scale under the vernier win
mounted on said frame, a rotatable screw hav
ing a pointer actuated by rotation of said screw
dow 28, the corresponding vernier block and
15 screw inserted, and, if desired, a new main unit
scale 2 substituted for the one shown. .Under
these circumstances it can be seen that this scale
may be equipped With accessory vernier screws
and main scales together with a proper enlarged
20 scale that will give measurements of practically
all the units and fractions of units utilized in
draftsmanship. Furthermore, the scale can be
adapted to any reduction ratios desired.
The use of the rule has been found to increase
the speed of scaling for architects and engineers,
it produces greater accuracy, and makes the work
of scaling much easier for the operator.
I claim:
and moving along said enlarged scale, and means
for extending said vernier extension by rotation
of said screw by an amount reduced in distance
but in proportion to the divisions of said enlarged 10
2. A draftsman’s rule comprising a frame, a
removable and interchangeable scale mounted
thereon and abutting a stop on said frame, a
vernier extension telescoping into one end of
said frame andhaving an index point thereon
lining up» with said scale, an enlarged scale
mounted on said frame and calibrated in fractions
of the units of said removable scale, a rotatable
screw having a pointer actuated by rotation of 20
said screw and moving along said-enlarged scale,
a reduction screw and thread linking said ro
tatable screw and said extension whereby said
extension will be moved by rotation of said screw
by an amount reduced in distance but propor
tional to the calibrations of said enlarged scale
and in fractions of the units of said removable
1. A draftsman’s rule comprising a frame, a
30 removable and interchangeable scale mounted
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