U.S. patent number 3,863,409 [Application Number 05/313,944] was granted by the patent office on 1975-02-04 for log cabin structure.
Invention is credited to Charles Raymond Fell.
United States Patent |
3,863,409 |
Fell |
February 4, 1975 |
LOG CABIN STRUCTURE
Abstract
Log cabin wall element having generally cylindrical surface and
a longitudinally extending groove. Groove has spaced side walls
extending from groove face to cylindrical outer surface to form
groove corners. Radial slot extends inwards from groove face to
reduce splitting of log. Initially groove corners of upper element
contact upper surface of lower element, groove face being clear of
lower element. Weight of element deforms groove corners and brings
groove face to contact uppermost portion of lower element, so that
weight of upper element is divided between groove corners and
groove face. Groove corners and groove face produce pair of space
parallel cavities between the first and second elements. Corner
deformation can vary along wall element to accommodate differences
in fit and improve sealing between adjacent elements.
Inventors: |
Fell; Charles Raymond (Hudson
Hope, British Columbia, CA) |
Family
ID: |
23217859 |
Appl.
No.: |
05/313,944 |
Filed: |
December 11, 1972 |
Current U.S.
Class: |
52/233;
446/106 |
Current CPC
Class: |
E04B
2/702 (20130101) |
Current International
Class: |
E04B
2/70 (20060101); E04b 001/10 () |
Field of
Search: |
;52/233 ;46/20,28 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
783,292 |
|
Apr 1968 |
|
CA |
|
129,688 |
|
Apr 1946 |
|
SW |
|
41,122 |
|
Mar 1924 |
|
NO |
|
Primary Examiner: Purser; Ernest R.
Assistant Examiner: Raduazo; Henry
Attorney, Agent or Firm: Carver and Company
Claims
I claim:
1. A portion of a log cabin wall structure, comprising:
a. an elongated first wall element having a substantially
cylindrical cross section,
b. an elongated second wall element having a substantially
cylindrical cross section and disposed immediately below and in
alignment with the first wall element,
c. locking means disposed along the lowermost surface of the first
wall element for firmly engaging and holding the first wall element
in superposed relation with the second wall element,
d. the locking means including a recessed horizontal planar
supporting surface for directly supporting the first wall element
which has two spaced substantially perpendicular side walls, the
planar supporting surface directly engaging and supported on the
uppermost peripheral section of the cylindrical surface of the
second wall element,
e. the locking means also including laterally spaced groove corners
formed at the intersection of the spaced side walls with the
cylindrical surface of the first wall element, said groove corners
disposed below the horizontal planar supporting surface and which
are resiliently urged into sinking engagement with the cylindrical
surface of the second wall element,
f. a longitudinally extending radial slot disposed perpendicular to
the horizontal planar supporting surface and having a length
approximately one-third the radius of the wall element so as to
permit resilient lateral spreading of the groove corners,
g. the distance between the groove corners before engagement with
the cylindrical surface of the second wall element being slightly
less than the cordal distance between the two opposed points of
engagement with the laterally spread groove corners after the
horizontal planar supporting surface comes into engagement with the
cylindrical surface of the second wall element.
2. The portion of a log cabin wall structure as set forth in claim
1, wherein:
a. there is a clearance of approximately one-sixteenth to
one-eighth of an inch between the horizontal planar supporting
surface of the first wall element and the upper periphery of the
cylindrical surface of the second wall element on initial
engagement and before full seating of the horizontal planar
supporting surface on the cylindrical surface of the second wall
element.
3. The portion of a log cabin wall structure as set forth in claim
1, wherein:
a. the depth of the groove formed by the planar horizontal surface
decreases with increase in the diameter of the first and second
wall elements so as to attain sufficient corner compression to
permit the planar supporting surface to absorb most of the weight
transmitted through the first wall element.
4. The portion of a log cabin wall structure as set forth in claim
3, wherein:
a. the groove has a virtual depth defined by a radial distance
between a midpoint of the groove face and the cylindrical surface
of the wall member produced as a virtual arc extending across the
groove, the virtual arc being concentric with the cylindrical
surface of the wall element and having a radius equal to the radius
of a cylindrical surface,
b. the initial groove depth being the perpendicular distance from
the groove corner to the horizontal planar supporting surface and
having a value one half that of the virtual depth.
5. The portion of a log cabin wall structure as set forth in claim
3, wherein:
a. the first and second wall elements have a diameter of
approximately twelve inches,
b. the groove depth is approximately five-sixteenths of an
inch,
c. the groove width is approximately 2 1/2 inches.
6. The portion of a log cabin wall structure as set forth in claim
3, wherein:
a. the diameter of the first and second wall elements is
approximately 6 inches,
b. the groove depth is approximately eleven-sixteenths of an
inch,
c. the groove width is approximately 2 1/2 inches.
7. The portion of a log cabin wall structure as set forth in claim
3, wherein:
a. the diameter of the first and second wall elements is
approximately 4 inches,
b. the groove depth is approximately 1 1/2 inches,
c. the groove width is approximately 3 inches.
8. The portion of a log cabin wall structure as set forth in claim
3, wherein:
a. the diameter of the first and second wall elements is
approximately 16 inches,
b. the groove depth is approximately three-sixteenths of an
inch,
c. the groove width is approximately 2 inches.
9. The portion of a log cabin wall structure as set forth in claim
1, wherein:
a. the two cavities formed between the horizontal planar surface
and the cylindrical surface of the second wall element are filled
with insulation.
10. The portion of a log cabin wall structure as set forth in claim
1, wherein:
a. the first wall element includes a first saddle having a concave,
partially cylindrical first saddle face concentric with the first
saddle axis, which axis is inclined at a saddle angle to the
longitudinal axis of the wall element,
b. the second wall element has an essentially similar saddle to the
first wall element, the first and second wall elements being a
portion of a first wall, and further including a portion of a
second wall intersecting and inclined at a corner angle to the
first wall,
c. the second wall having an essentially similar third wall element
having a similar saddle and saddle face, the third wall element
disposed between and intersecting the first and second wall
elements at the corner angle, so that the saddle face of the third
wall element engages the upper surface of the second element and
the saddle face of the first wall element engages the upper surface
of the third element, the saddle angles being complementary to the
corner angle.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a wall element for use in log cabin and
similar buildings.
2. Prior Art
Traditionally log cabins were made of logs cut to length, the logs
having a saddle cut near each end so that, when assembled,
longitudinal peripheral contact between adjacent logs is
approached. In practice, irregularities between the logs and taper
cause gaps between adjacent logs and produce ill-fitting
corners.
Commonly modern log cabins are constructed of logs cut to suitable
length and turned to cylindrical form so that they have zero taper.
Sometimes such turned logs have axial grooves extending lengthwise,
the grooves accepting location members to locate and seal one log
relative to an adjacent log. Such grooving requires accurate
machining and close tolerances are required to obtain a
satisfactory fit. Swelling and checking often cause difficulties.
Radial splitting as the log dries is reduced by providing narrow
radial slots extending into the log.
SUMMARY OF THE INVENTION
The present invention reduces difficulties of the prior art by
providing a wall element for use in log cabins in which
satisfactory seal between adjacent wall elements is attained
without requiring accurate machining of location members. Radial
splitting is also reduced.
A wall element according to the present invention has a central
longitudinal axis and a generally cylindrical surface concentric
with the axis. The cylindrical surface has a longitudinally
extending groove having a groove face, the groove having spaced
groove side walls extending from the groove face to the cylindrical
surface to form groove corners, the face and side walls being
within planes parallel to the central longitudinal axis. When a
similar second wall element is disposed beneath a first wall
element, the groove face of the first wall element lies on an upper
surface of the second element, the groove corners being forced
against the lower element and deformed to lock the wall elements
together to produce two longitudinally extending cavities between
the first and second wall elements. The corners produce effective
sealing between the elements, and deformation of the groove corners
varies along the wall elements and accommodates variations in fit
between elements.
A detailed disclosure following related to the drawings describes
one embodiment of the invention, which however is capable of
expression in structure other than that particularly described and
illustrated.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is fragmented perspective of a corner of a log cabin using
wall elements according to the invention,
FIG. 2 is a simplified fragmented vertical section through a
portion of a wall of the cabin remote from a corner,
FIG. 3 is a simplified fragmented detail vertical section of
adjacent wall elements, crosshatching being omitted,
FIG. 4 is a fragmented central section of portions of wall elements
adjacent a corner,
FIG. 5 is a simplified section on 5--5 of FIG. 4,
FIG. 6 is simplified bottom plan view of an element of FIG. 4,
FIG. 7 is a diagram showing dimensional characteristics of the wall
element .
DETAILED DISCLOSURE
Figs. 1 and 2
A portion 10 of a log cabin has a corner 11 formed at an
intersection of walls made of wall elements according to the
invention. A lower portion of one wall has a wall element 12 cut
essentially along a horizontal diameter so as to lie as shown on
foundations of the building (not shown), as is common practice with
log cabins of this construction. With reference to FIG. 2 a log
cabin wall element 13 according to the invention has a central
longitudinal axis 14 and is disposed upon a similar second wall
element 16. The element 13 has a generally cylindrical surface 15
having a radius, the surface being concentric with the longitudinal
axis. A lower portion of the cylindrical surface of the element 13
has a longitudinal groove 17, the groove extending along the
element. A radial slot 18 extends from the groove to an end edge
20, radial length of the slot being approximately one-third of the
radius of the element 13, the slot similarly extending along the
element.
Fig. 3
the groove 17 has a generally plane groove face 22 having spaced
parallel generally plane groove side walls 24 and 25, the side
walls extending from the groove face to the cylindrical surface to
form groove corners 26 and 27. The groove has a groove width 28
defined as space between the groove corners 26 and 27. The groove
face and side walls are within planes parallel to the axis 14, the
sidewalls being normal to the groove face 22.
The radial slot 18 is disposed symmetrically about a central plane
or centreline 32 passing through the axis 14, not shown, the slot
having a width 36 equal to kerf of a saw used to cut the slot,
about one-quarter of an inch. The slot is provided to reduce
splitting of the element as the wood dries and for the following
discussion effects of the slot or splitting are ignored. The
longitudinally extending groove 17 is thus defined by the groove
face 22 disposed generally normally to the longitudinal plane 32
and two spaced groove sidewalls 24 and 25 extending normally to the
groove face 22 and generally parallel to the longitudinal plane 32
to define a generally rectangular cross-sectioned groove. Due to
the slot above the groove, the groove corners have the capacity to
resiliently spread laterally.
The cylindrical surface 15 of the element is produced as a virtual
arc shown as a broken line 29, the arc being concentric with the
cylindrical surface 15 and having a radius equal to the radius of
the cylindrical surface. A virtual depth 30 of the groove is
defined by a radial distance between a mid point 31 of the groove
face 22 and the virtual arc 29, thus is depth of the groove
measured on the centre line 32. The virtual depth represents a
maximum depth of cut a cutter or planer would make to cut the
groove 17 in a cylindrical wall element having a surface continuing
as the virtual arc 29. The groove 17 has an initial true depth 34
defined as perpendicular distance from the corner 27 to the face
22, and by geometry is one half of the virtual depth 30.
An upper cylindrical surface 38 of the second wall element 16 is
shown as a broken line 38.1 in a first position in contact with the
corners 26 and 27, and in full outline in a second position in
contact with the groove face 22. Initial true depth of the groove
is such that, in the first position the surface 38 clears the face
22 by a clearance 39. Weight of the wall element 13 and structure
above the element compresses and deforms the corners 26 and 27 and
portions of the surface 38 contacted by the corners so that the
corners engage the surface. The deformation permits the upper
surface 38 to approach the groove face 22 until an equilibrium
condition is attained in which weight of the element 13 and
structure above is distributed about the two corners 26 and 27 and
a central portion of the face 22 adjacent the centreline 32.
Compression of the corners 26 and 27 reduces the initial true depth
of the groove to a final true depth 40, difference between the
depths 34 and 40 being approximately equal to the clearance 39. The
final true depth is generally between one-sixteenth and one-eighth
of an inch less than the initial true depth and is dependent on
physical characteristics and diameter of the wall elements. With
respect to FIG. 3, the distance between the horizontal planar
supporting surface or groove face 22 of the groove 17 and the
uppermost cylindrical portion of the cylindrical surface 38 has an
initial clearance of one-sixteenth to one-eighth of an inch prior
to seating of the groove corners and the horizontal planar
supporting surface with the cylindrical surface of th lower or
second wall element. It would appear that more weight from upper
wall elements is transferred through the groove face than through
the groove corners. The corners 26 and 27 sink into the surface 38
and tend to locate the corner relative to the lower element thus
reducing a tendency of groove 17 and the slot 18 to open, and thus
serve as a locking means. A substantially constant groove width
along the elements is maintained. The sidewalls 24 and 25 are
parallel to each other, seen in FIG. 3, and extend normally from
the groove face 22. The sidewalls can be inclined at an angle to
the groove face 22 somewhat greater than a right angle, but this
tends to reduce sinking of the corner into the surface 38 and tends
to open the groove 17.
Variations in loading between adjacent wall elements and
dimensional variations between elements results in some positions
of corner deformation being in excess of one-eighth of an inch,
whereas in other positions on the same wall element corner
deformation may be negligible. Such fluctuations in corner
deformation provide a convenient means of accommodating the
variations to reduce chances of gaps occuring between adjacent
elements, thus producing an essentially weather-proof seal between
the groove corners and the lower wall element. Also, as the groove
corners are below and straddle an uppermost portion of a lower
element, horizontal lateral movement between adjacent elements is
essentially eliminated without using locating members as in prior
art construction. This is of particular advantage with small
diameter elements, which are less stiff than larger diameter
elements. If desired to compensate for deformation of the corners
26 and 27, the groove width 28 can be adjusted to be somewhat less
than that required with no corner deformation. Alternately the
groove depth can be similarly compensated.
As can be seen, a portion of the groove face 22, the groove
sidewall 24 and the portion of the upper surface 38 of the second
element between the groove corner and the groove face define a
cavity 42 extending longitudinally between the first and second
wall elements. A similar cavity 43 is also defined by a portion of
the groove face 22, the sidewall 25 and a portion of the upper
surface 38 and thus two essentially similar cavities extend in
spaced parallel relationship between the first and second elements.
Before the element 13 is positioned on the element 16, a strip of
compressible insulation (not shown) can be fitted in the groove 17,
which insulation, when the element 13 rests on the element 16 is
compressed and fills the cavities 42 and 43, and also provides
resilient mounting between the wall elements.
As seen, overall thickness of the wall at a join between adjacent
elements is determined by groove width and depth, and wall element
size. Particularly for small diameter wall elements with relatively
wide grooves, overall wall thickness at a join is reduced a
relatively small amount from wall thickness remote from the join,
which thickness is maximum at a diameter of the wall element. Thus
heat losses by conduction through the join are only slightly more
than heat losses through the element remote from the join. Heat
losses through the join are reduced further by the compressible
thermal insulation.
Figs. 4, 5 and 6
An end face 49 of the element 13 of one wall is adjacent the
right-angled corner 11 of the cabin (FIG. 1), and has a saddle cut
50 to accommodate a lower element (not shown) in an adjacent wall,
the second wall, the walls being inclined at a corner angle. The
second wall has an element 51 disposed directly above and supported
in part by the lower element.
The saddle cut 50 has a concave, partially cylindrical saddle face
52 concentric with a saddle axis 54, which axis is inclined at a
saddle angle 55 to the axis 14 of the element 13, the saddle angle
being complementary to the corner angle, i.e., 90.degree.. For
walls intersecting at a corner angle other than 90.degree., the
saddle angles of the elements are equal to each other and
complementary to the corner angle, an alternative saddle angle 62
on an element having a longitudinal axis 64 being shown in FIG. 6
only. The saddle face 52 has a radius 56 approximately equal to the
radius of the cylindrical surface of the log to be accommodated in
the saddle cut, and thus is approximately equal to the radius of
the cylindrical surface 15. The saddle has a thickness 57 defined
as a radial distance between a midpoint 59 of the saddle face and
an uppermost point 61, hereinafter termed outermost point, on the
cylindrical surface of the wall element, the saddle thickness being
measured within the plane 32.
In common log cabin construction the saddle thickness as defined
above is approximately equal to the radius of the logs at the
corner, assuming a cylindrical log. In the present invention the
saddle thickness is reduced by an amount proportional to the depth
of the groove 17, as will be described with reference to FIG.
7.
At a corner using staggered wall elements the wall element 13 is
disposed beneath the wall element 51, the wall element 51 having a
similar saddle face 63, FIG. 5 only, which lies on the upper
surface of the wall element 13. Thus the saddle face of a first
wall element engages an upper surface of a second wall element of
an adjacent wall, the second element staggered below the first
element, the first element being engaged by a saddle face of a
third wall element of the adjacent wall staggered above the first
wall element.
Fig. 7
as previously stated, for a common saddle cut the saddle thickness
is approximately equal to the radius of the cylindrical wall
element, that is half the diameter. In the present invention the
groove 17 (FIG. 3) modifies saddle thickness by an amount dependent
of groove depth as is described below. In the following idealised
analysis, the groove face 22 (FIG. 3) is considered as a datum face
as this face contacts a lower element. As deformation of groove
corners tends to vary considerably in distance from the groove
face, groove corners are considered to be unpractical for use as a
datum.
Consider first and second wall elements A and B of a first wall,
and a third wall element C of a second wall which intersects the
first wall at right angles.
Let diameter of the cylindrical surfaces
of the wall elements = D
and virtual depth 30 of groove = d
Therefore effective depth of wall
member i.e., vertical distance
between uppermost surface and
groove face = D - d
An effective central plane Ec of wall member C is midway between
uppermost surface Uc of C and groove face Gc of C. For staggered
wall members of adjacent walls, as shown in FIGS. 4 and 5, Ec is
coplanar with a join between adjacent wall elements A and B, i.e.,
Ec is coplanar with groove surface Ga of A.
Thus Ec is spaced equally from
both Uc and Gc, a distance = D - d/2
Geometric true centre Ta of the cylindrical surface of wall member
A is on the central longitudinal axis (14, FIG. 2).
Distance between Ta and Ga = D/2 - d
Because all wall elements are equal,
Distance between Ea and Ga =D - d/2
Therefore spacing Sa between
effective centre Ea and true
centre Ta = (D - d)/2 - (D/2 - d) = d/2
Thus effective centre Ea is one-half virtual groove depth d spaced
above true centre Ta. Thus saddle thickness is one-half of groove
virtual depth less than the radius of the surface 15, in contrast
to a saddle depth of the radius in prior art construction.
The above is an idealised consideration and in practice is used as
a starting point for a trial and error cutting of the saddle cut,
depth of which may be compensated somewhat.
Wall Element Dimensions
A suitable wall element can be made from grooved and slotted
cylindrically turned log having a diameter of between 6 and 12
inches, a particular wall usually having logs of the same diameter.
A lower limit is about four inches diameter, an upper limit for
practical handling and economics being about 16 inches diameter. As
larger wall elements have a shallower curved upper surface, for a
constant groove width, groove depths of larger elements are
generally smaller than groove depths of smaller elements, so as to
maintain contact of groove face with an uppermost surface of a
lower element. A simple geometrical construction provides a
starting point to determine groove virtual depth, simple trial and
error methods determining actual depth of cut to be made. Virtual
depth i.e., depth of cut is considered in the following.
For a 12 inch diameter log, a five-sixteenths groove depth has been
found convenient with a groove having a width of 21/2 inches. That
is, groove depth is 5 percent of the radius, and groove width is 42
percent of the radius. For a 6 inch diameter log with a 21/2 inch
groove width, a groove depth of eleven-sixteenths of an inch has
been found suitable. That is groove depth is 23 percent of the
radius and groove width is 84 percent of the radius.
Outer practical limits of groove depth might be about a 11/2 inch
groove depth on a 4 inch diameter log, that is 75 percent of the
radius, and a three-sixteenths groove depth on a 16 inch diameter
log, that is 2 percent of the radius. Outer practical limits of
groove width might be a 3 inch groove width on a 4 inch diameter
log, that is 150 percent of the radius, and a 2 inch groove width
on a 16 inch diameter log, that is 25 percent of the radius. As can
be seen groove width and depth are interdependent for a fixed log
diameter, and a suitable combination is found by the graphical
construction or trial and error. Simple measurement of the initial
true depth of cut 34 FIG. 3, before corner compression, is half the
virtual depth. A generalized relationship is that the depth of the
groove decreases with increase in diameter of the wall elements so
as to attain sufficient corner compression to permit the planar
supporting surface to absorb most of the weight transmitted through
the first wall element.
It is usual to select and fix two variables, namely log diameter
and groove width, the groove width being determined by a cutter
used to produce the groove. The groove depth is adjusted
accordingly to attain sufficient corner compression so that most of
the weight of the log is transferred through the groove face to an
upper surface of the lower log.
The groove, slot and saddle cut above can be produced in a
cylindrical log by a variety of apparatus. Particular apparatus for
turning, grooving and slotting a log is described in a patent
application of the present inventor entitled "Apparatus for
Machining Logs." Apparatus for cutting a saddle cut in a log is
described in a patent application of the present inventor entitled
"Apparatus for Grooving Logs," both applications above and the
present application being filed concurrently.
* * * * *