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Патент USA US2107670

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Feb. 8, 1938.
5.o, KARLsoN
Fiìled Feb. 1 8.
‘Patented Feb. 8, 1938
Erik 0. Karlsen, Elmont, N. Y.
Application February 18, 1937, Serial No. 126,348
3 Claims.
This invention has relation to carpenters’ im
plements and comprehends an improved device
for facilitating the computation or determination
of the lengths and angles of rafter cuts.
The invention broadly aims to provide a device
vaverage carpenter may expeditiously compute
I9 are also inscribed on the upper surface I3 and 5
said lines are parallel to each other and to the
line I4. The line I8 has associated therewith
and with the aid of the usual steel square mark
the lumber for the various cuts to be made in
indicia 2E) which is here designated “common
rafter”, while the line I9 has associated there~
of the indicated character by means of which the
10 Aiashioning common rafters, hip and valley raft
ers, and jack rafters.
More particularly the invention resides in a
device of the character set forth and for the
purpose specified which includes a base having
graduations, lines and indicia on one surface
thereof and cooperative graduated sliding and
swinging members adjustable to positions coin
transverse line I5. The line I4 is subdivided by
longitudinally spaced graduations I6 having as
sociated indicia Il beginning at the line I5.
A pair of longitudinally extending lines I8 and
ciding with the building and roof measurements
to compute and determine the lengths of the
various rafters and the heel, plumb and angle
cuts to» be made.
Other objects of the invention reside in the
provision of a device of this character which is
comparatively simple in its construction and
mode of use, inexpensive to produce, highly ef ficient in its purpose and which is small and
compact whereby it may be readily carried in the
carpenter’s kit or pocket.
With the above enumerated and other objects
>in view, reference is now made to the following
3 specification and accompanying drawing in
which there is disclosed a preferred embodiment
of the invention, while the appended claims cover
variations and modifications thereof which fall
3 Cl . within the scope of the invention.
In the drawing:
Fig. 1 is a face view of the device constructed
in accordance with the invention, illustrating the
slide member and pivoted arm in adjusted set
Fig. 2 is an end edge view thereof as viewed
from the left hand edge of the device.
Fig. 3 is a face view illustrating the slide mem
ber and pivoted arm in folded inactive compact
45 position for storage of the device.
Fig. 4 is` a vertical sectional view taken ap
proximately on. the line 4--4 of Fig. 3.
Referring to the drawing by characters of ref~
erence, Ill designates the base of the devicel which
50 is preferably of rectangular configuration hav
ing parallel opposite longitudinal side edges Il
and I2 and a plane upper surface I3 which is
provided with a longitudinally extending line I4
adjacent to and parallel with the side edge I2
56 and adjacent one end edge with a perpendicular
with indicia 2l, here designated “hip or valley mi
rafter”. The line I4 together with its gradua
tions I5 and indicia I'lhas further indicia 22 as
sociated therewith designated the “rise”,
A slide member designated generally by the
reference character 23 is mounted for guided 1P
sliding movement with reference to the base I0
and said member 23 is preferably of T-shaped
construction having a longitudinally extending
head 24 which is formed with a groove 25 in its
inner edge to slidably fit over the side edge I2
of the base. The slide member 23 further in w i
cludes a slotted arm 26 disposed at an angle to
the head 2li and extending transversely of the
base I0 with the base received by the slotted por
tion so that the arm 26 straddles the same, and
the upper surface of the portion of the arm 26
which overlies the base is provided with a series
of graduations 2l which start at the line III and
extend throughout its length to the free end
thereof. Indicia 28 is associated with the graduations and the arm 26 is also provided with in
dicia 29 designated the “run”. In order to lock
the slide member 23 in adjusted relation to the
base, a set screw 30 having a knurled manipulat
ing head 3l is threaded through the outer end
edge of the slide arm 26 and is designed to be 35
impinged against the side edge'l I of the base.
The device further includes a swinging arm 32
which is mounted to swing on a pivot 33 having
a vertical axis located at the intersection of the
lines i4 and I5 adjacent one corner of the base,
the edge 34 of the swinging arm intersecting the
axis of the pivotal connection of the arm and said
edge being provided with a line of graduations 35
and associated indicia 3S starting at the pivotal
point of the arm.
The arm is disposed between the resilient fur
cations of a bracket 3l and the arm is secured
in adjusted angular position by means of a thumb
nut 38 which threadedly engages the pivot 33 for 50
frictionally clamping the arm between the furca
tions. In order to limit the swinging of the arm
32 to a position parallel with the head 24 of the
slide member, a clip 39 is provided on the head 24
of the slide member.
The upper plane surface I3 of the base is pro
eighths” inches which combined with the base
vided with curved lines 4D and 4I which extend
graduation at the intersection of the slide arm
from the axis of the pivot 33, diverge with refer
26, is “eleven and one-quarter” inches.
ence to each other and terminate at the oppositeY
end edge of the base. These curved lines are re
spectively designated by the indicia 42 and 43 as
“bevel for hip or valley rafter” and “bevel for jack
In use and operation, when it is desired to de
10 termine the length of a common rafter and the
angle ofthe heel and plumb cuts thereof, the
slide is first moved so that the graduated edge of
the slide arm coincides with the graduation I6
and indicia Il corresponding to the rise of the
rafter is obtained by reading the base graduation
which shows “eleven and one-quarter” inches and
the slide graduation at the intersection of the
curved line marked “bevel for jack rafter” which
15 roof. Y The set screw 30 is then tightened to re
is found to be “eight and one-quarter” inches. .
The plumb cuts at the opposite endsV of the jack
rafters are the same as thaplumb cuts for the
common rafter and the bevel of the lower plumb
cut which is to rest against the side of the valley
tain the adjustment and the swinging arm 32 is
In order to determine the length of the valley
then swung to a position where its graduated edge
coincides with the graduation 2l and indicia 28
which corresponds to the “run” which is half the
width of the building. The graduation 35 and
rafter, adjust the swinging arm 32 to the point
of intersection of the graduated edge of the slide
indicia 35 on the swinging arm 32 at the point
of intersection of the graduated edges of the arms
26 and 32 will give the length of the rafter.
use of the usual carpenter’s steel square, the an
gles of the heel and plumb cuts and the bevel
cuts for roofs of equal pitch are obtained as fol
lows: Assuming that the run is “fifteen” feet and
the rise “fourteen” feet, first set the slide mem
ber at the base graduation I6 indicated by the
indicia il as “fourteen”, then tighten the set
screw 3l?. The swinging arm 32 is then adjusted
steel square is then laid on the edge of the lum
ber and marked along the tongue of the steel
arm with the line i9 designated “hip or valley
rafter” and tighten the clamping nut 38. Then 20
move the slide to the base graduation I6 which
corresponds to the rise of “fourteen” feet and
read the graduation 35 on the swinging arm 32
at the point of intersection of the graduated edge
of the slide arm 26 with the swinging arm 32. 25
This, in the example being given, will show “twen
ty-ñve feet, six inches”.
To determine the difference in length between
the common rafter and the ñrst jack rafter, move
at an angle where its-edge 34 intersects the grad
uated edge of the arm portion 26 of the slide
the slide arm 26 to the base graduation “eleven 30
and one-half”, set therrswinging arm 32 yto the
point of intersection of the line 4|, designated
“bevel for jack rafter”, tighten the swinging arm
member 23 at the graduation 21 which corre
spends to the run, namely “fifteen” feet. The
in this position and then move the slide arm, 26
to the point where it intersects the edge 34 of
graduation 35 indicated by the indicia 36 on the
swinging arm 32Will indicate the length of the
common rafters, namely “twenty feet, six and
ione-half” inches. For the purpose of obtaining
the heel and plumb cuts so that the graduation
the swinging arm 32 at the graduation 2l on the
slide arm which corresponds to the spacing of
the jack rafters, which spacing has been pre~
determined, say for example, as “sixteen” inches
apart. By then reading the graduation I6 and
marked twelve on the blade of the steel square
may be used as one measurement, tighten the
clamping nut 38 to retain the swinging arm in
indicia il on the base at the intersection of the
set position and move the slide until the grad
45 uated edge thereof coincides with the intersec
tion of the graduated edge 34 with the common
rafter line i8 and tighten the set screw 30. ‘The
swinging arm^32 is now released and» swung to the
out-of-the-way position illustrated in Fig. 3 of the
50 drawing and the base graduation where the slide
member arm 26 is now adjusted will givethe other
reading as “eleven and one-quarter” inches for
the steel square tongue. When the steel square
is placedv on vthe lumber with the “twelve” inch
55 blade graduation at one edge of the lumber and
the “eleven and one-quarter” inch tongue grad
uation> at the edge of the lumber, the marking of
the lumber along the edge of the blade will give
the heel out while the marking of the lumber
60 along the edge of the tongue will give the plumb
To'determine the heel vand plumb cuts for the
valley rafter, read the graduation at the point
of intersection of the hip or Valley rafter line des
65 ignated i9, with the slide arm 26, and the read
ing for the steel square will then be “eleven and
one-quarter” inches on the tongue and “seven
teen” inches on the blade, thelatter being the
reading shown at the hip and valley rafter line.
To determine the setting of the steel square
for the bevel cut of a hip or valley rafter, read
the graduation on the slide arm 26 at the in
tersectíon with the curved line designated “bevel
for hip or valley rafter” which, in the example
given, will be found to be “nine and ' three~
graduated edge of the slide arm, the difference
in length between the common rafter and the
first jack rafter, as well as between each of the
succeeding jack rafters, will be obtained in inches
and Will in the example given be “twenty-one
and seven-eighths” inches.
What is claimed is:
l. In a device for computing rafter cuts, a base
having a plane upper surface, a slide member 50
overlying and extending across the upper sur-`
face of the base, vmeans mounting the slide mem
ber for guided sliding movement lengthwise of
the base, an arm pivoted adjacent one corner of
the base, means for locking the slide member and 55
arm respectively in adjusted relation to each
other, and curved lines on the surface of the base
extending from the pivotal point of the arm for
obtaining readings to determine the angle of the
bevel cuts for the hip or valley and jack rafters.
2. In a device for computing rafter cuts, a rec
tangular base having a surface inscribed with
lines and indicia, a T-shaped slide member hav
ing a slotted arm portion straddling and extend~
ing across opposite surfaces of said base, gradu 65
ations and indicia on the surface of the arm por
tion overlying the inscribed surface of the base,
a slotted head portion of said slide member en~
gaging over one edge of the base for mounting
the slide member for guided sliding movement 70
lengthwise of the base, an arm pivoted adjacent
one corner of the` base having graduations and
indicia thereon, and means for locking the slide
member and arm respectively in adjusted relation
to each other, the lines on the surface of the base 75
being so arranged as to be- intersected by the slide
member and the pivoted arm for designating the
points of reading of the graduations to determine
the length of common, hip and valle-y rafters and
5 the angles of the cuts to be made.
3. A device for computing rafter cuts including
a base having a plane surface bearing a length
Wise line having graduations for indicating the
rise, a pair of parallel lines spaced therefrom and
10 from each other for use in computing the cuts
of common rafters and hip or valley rafters re
spectively, and divergent curved lines ,for use in
computing the bevel cuts of the jack rafters and
hip or Valley rafters respectively, a slide member
overlying the surface of said base extending
thereacross perpendicular to the parallel lines,
mounted for guided sliding movement length
wise thereof and having graduations indicating
the run and cooperating With said parallel and 5
curved lines to compute said rafter cuts, a grad
uated arm pivoted to said base at the intersec
tion of the curved lines with each other and with
the graduated line indicating the rise for the pur
pose of computing the length of the rafters, and 10
means for locking the slide member and arm re
spectively in adjusted positions.
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