Note: Descriptions are shown in the official language in which they were submitted.
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1
i Title: JOINTING SYSTEM FOR WALL-BUILDING PIECES
2
3
4 This invention is applicable for use in joining wood-pieces in
s building construction, for example in buildings of the log-cabin
s type, for joining logs end-to-end.
a
9 BACKGROUND TO THE INVENTION
io
m It is the common practice in the construction of modern log
i2 cabins, to manufacture the logs to the final size and shape in-
i3 factory, and to ship the finished logs for assembly on site. It
i4 is conventional to provide a means for securing the rows or
is courses of logs to the courses of logs above and below. This is
is done by means, for example, of a spline and groove engagement.
i~ It is also conventional to clamp the logs together vertically by
ie means of long through-bolts that pass through holes pre-drilled
i9 in the logs.
Zi Given that the walls of buildings are longer than the logs, the
zz logs need to be joined end to end, in butt-joints. One of the
i3 difficulties of conventional factory-made log cabin construction
z4 is that it has been difficult to keep the end-faces of the logs
together at the joints, and to stop the logs from separating, and
zs gaps from opening, at the joints. As the joints open, the joints
z~ become no longer weather-tight.
28
z9 It might be considered that the way to keep the butt-joints held
3o tightly together, and to resist separation at the joints, would
3i be to use dovetails. While dovetail joints possible might hold
32 the logs together, they would be hopelessly uneconomical because
33 dovetail joints are far too difficult to assemble, and the
34 dovetail shape cannot be formed in one pass of a saw-blade type
Of cutter. Dovetail joints would require several passes of a
3s saw-blade (each cut requiring the log and the saws to be re-set)
3~ or would require the use of a routing process, which would be far
3e too slow to be contemplated on a mass-production basis.
39
4o The invention aims to provide a butt-joint that compares as to
4i physical security with a dovetail joint, but which is far easier
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1 (and less costly) to manufacture and assemble.
2
s The invention also aims to provide a butt-joint that offers
4 excellent weather protection.
s The invention aims to be applicable to walls made of pieces of
7 wood, in the form of logs as in a log cabin; in the form of
a siding; and in the form of large-area sheets. It is an aim that
s the shapes provided at the joints are easy to cut, using simple
to machinery.
11
lz
is THE PRIOR ART
14
Splines and grooves in the upper and lower surfaces are shown in
is (for example) US-5,638,649 (Hovland, June 1997). A system for
17 butt-jointing logs, in which shaped slots are cut in the logs,
is and complementarily-shaped pegs are driven through the slots, is
19 shown in US-5,020,289 (Wrightman, June 1991).
21
22 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
23
24 By way of further explanation of the invention, exemplary
z5 embodiments of the invention will now be described with reference
zs to the accompanying drawings, in which:
27
ze Fig 1 is a plan view of a portion of a wall of a log cabin, which
zs embodies the invention;
3o Fig 2 is a pictorial view of the portion of the wall of Fig 1;
31 Fig 3 is a diagram illustrating a saw-cutting operation during
3z the manufacture of the logs shown in Fig 1;
33 Fig 4 is a pictorial view of a portion of another wall;
34 Fig 5 is a pictorial view of two courses (shown separated) of
3s logs, showing a corner in another wall;
3s Fig 6 is a close-up of a joint between two logs;
37 Fig 6a shows the joint of Fig 6 with the logs separated;
3e Fig 7 is the same view as Fig 5 of an alternative construction;
39 Fig 8a is a side elevation of a wall, shown to illustrate the
4o terminology used;
41 Fig 8b is a plan view of some pieces of the same wall;
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i Fig 8c is a pictorial view of one of the pieces of the wall;
z Fig 9 is a plan view of a prior art system.
3
a The apparatuses shown in the accompanying drawings and described
s below are examples which embody the invention. It should be
6 noted that the scope of the invention is defined by the
accompanying claims, and not necessarily by specific features of
s exemplary embodiments.
9
io Fig 1 is a plan view of a wall which comprises several rows or
m courses of logs. The portion of the course 20 of the wall shown
iz in Fig 1 comprises a log 20a, having a left end-face 23a and a
i3 right end-face 24a. The log 20b to the left has a corresponding
i4 right end-face 24b, and the log 20c to the right has a
is corresponding left end-face 23c. The end faces are shaped as
i6 shown, and are in end-to-end interlocking configuration.
m
ie Each log has splines 25 on its upper surface 26, and
is corresponding grooves 27 on its lower surface 28. The splines
zo and grooves engage with corresponding grooves and splines in the
zi logs of the respective courses above and below. Since the
az courses of logs are resting on each other under gravity in a
z3 vertical stack, the engagement of the grooves and splines keeps
z4 the logs from moving laterally relative to the logs above and
zs below.
26
z~ Log 20a is prevented from separating lengthwise, or
ze longitudinally, with respect to adjacent log 20b by virtue of the
zs shapes of the end faces 23a and 24b. It will be understood that,
3o because of the interlocking shapes of the end-faces 23a and 24b,
3i the logs 20a,20b,20c, in order to separate longitudinally, would
s2 have to move laterally; but the logs cannot move laterally. Logs
33 20a,20b,20c cannot move laterally relative to each other because
34 of their splines-to-grooves engagement with the logs in the
3s courses above and below. The designer should ensure that the
36 breaks between the logs in the courses above and below do not
3~ coincide with the breaks in the course 20.
38
3s Fig 2 shows the manner of assembling the wall. The log 20a is
4o already in place, resting in spline-to-groove engagement on the
4i logs in the course below. To assemble the next or junior log 20c
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1 in the course, the end-face 23c of the log 20c is placed to
z engage with the end-face 23a of the already-placed or senior log
3 20a. Preferably, the junior log should be carefully engaged face
4 to face, but with the junior log at first held vertically clear
s of splines-to-grooves engagement with the logs below. After
s checking that the junior log is aligned correctly, the junior log
is lowered to its assembled final position.
a
9 The nature of the engagement of the logs, in fact, is such that
to the junior log cannot be assembled partially; either the junior
11 log 20c is fully and properly engaged with the senior log 20a in
12 the same course, and with the logs in the course below, or the
13 junior log is so far out of engagement that its out-of-engagement
14 status is unmistakably clear.
is As shown in Fig 2, the end-face 23c comprises four block-surfaces
1~ 29, and three re-entrant platforms 30. The four block-surfaces
le are all flat planes, which are parallel. Similarly, the three
19 re-entrant platforms 30 are all flat planes, which are parallel,
zo and the platforms 30 lie at right angles to the block-surfaces
21 29. It is the engagement of the re-entrant platforms 29 on end-
zz face 23c with the corresponding re-entrant platforms on the end-
z3 face 24a that locks the logs 20a and 20c together against
z4 possible separation in the longitudinal sense.
zs It may be noted that this engagement locks the logs together very
z~ securely, and also locks them together right at the very ends.
2e Thus, any tendency of the logs to shrink, and therefore to
z9 separate at the end-faces, is well resisted by the design as
3o shown. The more the logs shrink, the harder the re-entrant
31 platforms will press themselves together.
32
33 The splines 25 and grooves 27 may be given a slight draft or
34 taper, as shown. Thus, the logs are easy to assemble together,
and the engagement between the splines and grooves only becomes
3s tight at the very last. The designer can even choose to have the
3~ fit of the splines to the grooves so tight that the logs have to
38 be finally hammered together.
39
4o Of course, the designer must see to it that the logs are cut to
al shape accurately enough that the logs fit and engage properly
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1 together. It is recognised that the accuracy required in the
z cutting of the shapes of the logs is readily achieved using
3 conventional industrial methods. The grooves and splines, when
4 straight, can be cut with ordinary plain saw blades, and the
s surfaces of the logs are cut each in a single pass by running the
s logs lengthwise under the rotating blades. When tapered, the
grooves and splines are cut with respective specially-shaped saw
a blade cutters, but again the surfaces are cut each in a single
9 lengthwise pass.
to
ii Fig 3 shows the saw-blade arrangement for cutting the end-faces
lz of the logs. Here, as shown, four blades 32 are ganged on a
13 single spindle 34. The cut is made by passing the saw-blades
14 through the log (or the log through the saw blades) in the
is direction into the drawing. This system of shaping the end-face
is is very accurate as regards the relationship between the
l successive re-entrant platforms 30 on the end-face. The depth
le setting of the saw-gang need only be set once, i.e the depth does
1g not need to be individually set, once for each platform.
zo
zl As shown, the end-faces of the logs are symmetrical about a plane
zz of symmetry that is defined as the vertical plane passing through
z3 the longitudinal axis of the log. This symmetry ensures that the
z4 logs can be placed with either side surface of the log serving as
zs the outside of the wall. Thus, the builder can select and
zs assemble the logs so that their good sides all face outwards. On
z~ the other hand, the end-faces might be made non-symmetrical,
za deliberately so that the good side can be selected in-factory and
Zs that selection enforced on the builder. (The splines and grooves
3o can be arranged non-symmetrically also, if desired.) However,
31 the logs from which houses are built are generally good both
3z sides; therefore, the designer can make assembly a little less
33 restrictive by specifying symmetry of the end-faces, and symmetry
34 of the splines and grooves.
3s It may be noted that the re-entrant platforms 30 and block-
3~ surfaces 29 that make up the end-faces are all vertical. When a
3e junior end-face is properly assembled to an adjoining senior end-
3s face, the junior end-face does not rest upon, and is not
4o supported by, the senior end-face.
41
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1 The platform 30 is re-entrant in that a line parallel to the
z longitudinal axis of the log, and emerging from any point on the
3 re-entrant platform, is directed towards (i.e not away from) the
4 main bulk of that log.
s Other shapes are contemplated for the end-faces, besides the
four-block-three-platform end-face as shown in Figs 1 and 2. In
a Fig 4, for example, the end-face has three block surfaces and two
9 re-entrant platforms. This is more suitable when the logs are
to much narrower in width than in height (in which case, the pieces
11 of wood now have the dimensions of siding or cladding, rather
lz than logs).
13
14 Fig 5 also illustrates the manner in which corners of the log
is cabin building can be arranged. Two courses of logs are shown in
is Fig 5. Corners require the provision of a special-log 36. The
1~ special-log 36 is cut with a complementary three-block-two-
le platform side-end-face 37, which fits the end-face 38 of log 39.
19 All the logs on the same course of logs have a common design of
2o end-face 38, both ends, apart from the special-log 36, of which
21 only one of its end-faces 40 is to the common design.
zz
z3 Gaskets 42 are provided for sealing the corners. Recesses 43,44
z4 are cut in the logs 36,39, which combine to create an
z5 accommodation for the gasket 42. The grooves 27 cut in the
zs undersurface of the special-corner-log 39 are ramped out, so as
2~ not to leave in the outside surface thereof.
ze
zs At the corners, a vertical hole 45 is provided right through all
3o the logs. A metal rod can be passed through the holes in all the
3i courses, for tightening the courses together vertically.
32
33 It may be noted that the log 39 which abuts the special-log 36 at
34 the corners is (apart from the simple-to-cut recess 43) not
35 itself special. The log 39 is provided simply with the common
3s end-face on both ends, just like the logs that make up the rest
s~ of the length of the wall. In other words, all the specialness
3a needed at the corners is provided in and by the special log
3s itself .
41 Fig 5 shows the end-faces in the lower course being angled in the
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i opposite sense to the end-faces in the upper course. (Of course,
z the wall comprises many more courses, which are arranged
3 alternatingly.) By contrast, Fig 2 shows the end-faces angled
9 all in the same sense in successive courses. The problem with
s the end-faces in all the courses being angled in the same sense,
s as in Fig 2, is that, at the corners, the side-end-faces would
z all be in vertical alignment, which is not good.
a
9 When the courses shown in Fig 5 are brought together, very
io effective protection against water ingress is achieved. The
ii spline 25 serves as a watershed, which deflects any water that
iz might collect on the outside land 46 of the upper surface of the
i3 log. The first re-entrant platform 47 of the end-face 40 lies to
i4 the outside of the watershed formed by the spline 25.
is
is The vicinity of the first re-entrant platform 47 is shown in
i~ close-up in Fig 6. Fig 6a shows the two logs separated. The
ie manner of cutting the re-entrant platforms (as was described with
i9 reference to Fig 3) in fact leaves a slight undercut at 48,
za because of the set of the saw-teeth. Also, wood is a material
zi that basically will not support a sharp edge, and so the point 49
zz is slightly rounded or chamfered. As a result, there are
z3 inevitably two small channels 50 formed when the logs are
z~ assembled together, at the vicinity of the first re-entrant
z5 platform ( and any other re-entrant platforms). These channels
zs serve to receive and collect any water that might enter the gap
z~ 52. Under driving rain conditions, water might penetrate
zs forcefully into the gap 52, but once the water reaches the
z9 channels 50 its energy is spent, and the water now simply seeps
3a down the channels. If desired, the channels can be purposely cut
3i larger, by modifying the saw blades in Fig 3. However, it is
3z recognised that the kind of channels 50 that arise naturally,
33 with standard saw-blades, are adequate in most cases.
34
35 The bottom mouth of the channels 50 opens right onto the outside
3s land 46 on the upper surface of the log below. The watershed
37 prevents the water penetrating to the inside, and the water
3e harmlessly emerges outwards from the land 46, and outside.
39
4a This system of placing the first re-entrant platform outside the
4i watershed provides a very effective protection against water-
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1 penetration. The labyrinth of surfaces and facets between the
z logs also provides excellent protection against air penetration,
3 whereby any air that might leak through the wall has so little
4 energy that it can hardly give rise to a draft. The gaskets 42
provide extra draft and water protection at the corners.
6
7 Fig 7 shows how the system of placing the first re-entrant
a platform outside the watershed can be put into effect even when
s using large sheets of wood. The upper and lower surfaces of the
to sheets are tented, as at 54, which serves as the watershed. The
l end-edges 56 of the sheets have the complementary re-entrant
lz platforms, as previously described.
13
la one of the problems with systems of interlocking edges of sheets
is together can be that the sheets have to be slid into engagement
16 lengthwise, which can be very inconvenient. In the design as
i7 shown, the sheets do not have to be assembled. In fact, the
is sheets only interlock tightly upon final assembly into position,
lg and yet the joints are physically robust and secure, and weather
zo protection is excellent.
zl As to weather-proof sealing, in the configurations as shown the
zz logs can be expected to hold themselves together so tightly that
z3 light caulking between the joints during assembly is all that is
za needed to keep the joints weather-tight for many years.
zs Alternatively, gasket-retaining seal-grooves can be provided in
zs the logs at appropriate locations. Although more labour-
z7 intensive during assembly, caulking is generally preferred over
za gaskets, in that caulking can be inspected from outside the
zs finished wall, and caulking can be replaced, at least to some
so extent, from outside the finished wall (which a gasket cannot).
31 The problem with caulking as a method of sealing the logs in
3z conventional log cabin construction has been that caulking cannot
33 cope with distortions that tend, over the years, to cause
34 separation of the logs, especially at the corners; but that
35 tendency is reduced to a minimum in the present design, whereby
3s caulking is more likely to be acceptable.
37
se The scope of the invention is defined in the accompanying claims.
3s Figs 8a,8b,8c illustrate how the terminology used in the claims
4a applies to the depicted embodiment.
41
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i Fig 9 shows a prior art system for joining pieces of wood siding.
z It will be noted that of course this system provides little
3 protection against water penetration.
