Note: Descriptions are shown in the official language in which they were submitted.
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
Constructional element and method for its manufacture
The present invention concerns a constructional element intended for building
with logs
with cogged joints, hereinafter generally referred to as notching, as well as
a method for the
manufacture of such element.
The invention further concerns a method for the manufacture of a structural
element
intended to be part of a constructional element according to the first aspect
of the invention,
or in other constructional elements. The structural element may also be used
as an
independent product.
Background
1o It is an old tradition to raise buildings with timber logs. In recent years
this tradition has
mainly been upheld with respect to building of cabins/ leisure buildings.
Cabins with
cogged joints are generally seen to be particularly beautiful. Building with
this tradition is,
however, not free of problems.
A disadvantage with notching of cabins/ buildings in real timber is the high
requirement of
premium quality timber. Such timber is today a scarce resource and the
buildings therefore
become expensive. Another disadvantage is the specific thermal insulation.
Compared to
well insulated buildings of modern construction, the thermal insulation is
significantly
poorer. In a Nordic climate, notched buildings that are not provided with an
internal
insulation is not suited for use all year, and is quite uneconomical also for
cabin use.
A third disadvantage is related to the fact that buildings in timber logs
sinks several per
cents (cm per meter height) the first years, which leads to severe problems
with respect to
maintaining tight doors, doors that do not get jammed and to maintain lealcage
free roof
openings for pipes and ventilation.
On this basis and on the basis of a need for a more extensive use of recycle
material in
building production, attempts have been made with respect to male a
constructional
element that loolcs life real timber but consists of an internal, insulated
core and a wooden
or wood-lilce "shell".
Norwegian patent No. 311 583 describes timber-life elements for notching where
each side
of the elements is comprised by several (e.g. 3) joined panel elements that
are profiled in a
manner so that their outer sides subsequent to the joining appear as
substantially
continuous, convex surfaces. Between these joined panel elements spacer
elements are
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
arranged that serve to hold the panels in a steady, unchanged mutual distance
from each
other. The same spacer elements serve to give the entire building its required
strength. The
void between the outer parts is intended to be filled with a thermally
insulating material,
e.g. polyurethane. Near the ends the elements are provided with recesses for
notching. The
construction has the disadvantage that preparing and assembling of each timber-
like
element from individual panels and spacers is a comparatively complex process.
Swedish laid-open publication No. 457 456 describes a "timber-element" with
outer tree
panels provided with longitudinal groves, where the spacers are arranged in
the groves. The
void between the panels and the 'spacers are also in this construction
intended to be filled
to with a thermally insulating material like foamed polyurethane. Holes are
arranged in
certain positions of the spacers so that rods 8 may be positioned (vertically)
through the
holes in each element of a completed wall, whereby said rods may constitute
the weight
carrying elements of the wall. Like for the construction discussed above, this
construction
comprises a lot of components that need to be adapted to each other. It is
quite a "puzzle"
work to put together one single timber element from its separate components.
LTS patent No. 4,433,519 describes a hollow, cylindrical prefabricated
constructional
element intended for the same use as the above mentioned publication. Here it
is assumed
that the convex outer surfaces are comprised either by glass fibre, metal,
plastic or moulded
wooden products with the required structural integrity. The outer panels are
thus not made
2o in a natural wooden material. Flanges at the upper and lower side of the
constructional
elements are arranged to overlap when the elements are placed on top of each
other, and
they are provided with holes so that bolts or the like may be inserted through
the elements
to lock the elements together. Like the previously discussed constructions
this one also
comprises spacer elements that are arranged at certain intervals along the
elements, but here
the prefabricated elements themselves are designed to carry most of the weight
load. The
void between the elements is preferably filled with a thermally insulating
material. This
construction has the advantage over the previous ones that it is assembled
from fewer
components but on the other hand the side panels are not in "whole wood".
Swedish laid-open publication No. 440 250 describes still another product
intended for
notching, and it constitutes outer wooden panels with inner spacers that are
attached to the
side panels by means of longitudinal grooves in the latter. A wooden panel
according to
this publication does not comprise a convex outer surface. It is mentioned,
however, that
the edges may be chamfered to give a visual impression of such a convex
surface.
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
Objectives
It is an object of the present invention to provide a constructional element
and a method for
the manufacture of such an element, which visually and in assembled state
gives an optimal
impression of notched timber logs.
It is thus an obj ect of the present invention to provide a constructional
element with convex
outer surfaces in "whole wood", which may be manufactured in a quick and
rational
process.
It is furthermore an object to provide a constructional element of said type
with the required
volume for all thermal insulation in an inner void, and which is simple to
insulate with
to conventional fibrous or foamed insulation materials before or after
assembly to a building.
The invention
Said objects are achieved by a constructional element and the method according
to the
invention as further elaborated below.
According to a first aspect the invention concerns a constructional element as
defined by
15 claim 1 and a method for the manufacture of such an element as defined by
claim 12.
According to another aspect the invention concerns a structural element that
constitutes a
side wall of the constructional element according to the first aspect of the
invention as
defined by claim 18 and a method for the manufacture of such an element as
defined by
claim 22.
2o Preferred embodiments of the invention are disclosed by the dependent
claims.
A central aspect of the present invention is the fact that the components
constituting a
constructional element are assembled in a simple and rational process that may
be largely
automatized. It is a further important aspect that said objects are achieved
without
compromising the aesthetical aspects of the product which has sides in whole
wood. The
25 process of making grooves on one side (the inside) of the boards removes
tension in the
boards and in addition the grooves provide a mechanical grip for the plastic
material. By
the option to "lock" the side edges of the boards when they are bent to a
curved shape, a
controllable degree of cracks are formed, thus making the boards look even
more like real
timber logs. It is an alternative to use a thermosetting plastic material
instead of a
3o thermoplastic material, requiring an alternative technique for application
that is also
described in detail.
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
Furthermore it is preferred that the side walls are based on panels of real
(whole) wood,
even though materials like fibreboard panels and other tree-like materials may
also be used.
It is also possible to use one material for the outside wall and a different
material for the
inside wall. It is even feasible to use an even simpler type of panel for the
inner wall, e.g.
one that is not convex and if it is not desired to give the impression of real
timber logs
inside, the panels for the inside walls may have a flat surface that
subsequently may be
covered with wall paper or the like. In this latter case a structural element
manufactured as
defined by claim 12 is used for the inside panel of the constructional element
and a
structural element manufactured as defined by claim 11 is used for the outside
panel of the
to constructional element.
Concrete embodiments of the invention
The invention will now be described in further detail with reference to the
enclosed
drawings, wherein,
Fig. 1-6 show vital steps of the manufacture process for a constructional
element.
Fig. 7 is a schematic illustration of the process comprising the steps shown
in Figs 1-6.
Fig. 7b is an enlarged partial view of a variant of the process shown in Fig.
7.
Figs. 8 and 9 are two different side sectional views of a completed
constructional element
according to the present invention.
Fig. 10 is a sectional side view of a wall comprised by constructional
elements according to
2o the invention.
Figure 11 is a cross sectional view of two constructional elements of the
invention, one
placed on top of the other.
Figure 12 and 13 show steps of manufacture for parts of a constructional
element according
to the invention in a case where a thermosetting plastic material is used
instead of a
thermoplastic material.
Figure 1 shows an end view of a board 1 for forming a structural element that
constitutes a
side surface (wall) of a constructional element according to the invention.
The side that is
faced down will form an outside of the constructional element while the side
that is faced
up and provided with a number of longitudinal grooves 2, will form an inside
of the
constructional element.
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
Figure 2 shows the board of Fig. 1 at a stage where rolls (not all shown) on
all sides of the
board have begun to force the board into a curved shape in a direction cross
the board's
longitudinal direction.
Figure 3 shows the board in the final curved shape, in the manner it is fed
into an extruder.
Figure 4 shows the board as emerging from the extruder. A thermoplastic
material fills the
grooves 2 in the board's inner (concave) side and forms a coating a few nun
thick on this
side. Close to the side edges of the board the same thermoplastic material
forms two
longitudinal flanges 4a and 4b whose function are explained below.
Polypropylene and
polyethylene are preferred thermoplastic materials and preferably high density
polyethylene.
1o PVC is also a well suited plastic material.
Figure 5 shows the board subsequent to having been furnished with a rib 5 in
the still soft
thermoplastic material on the concave side of the board 1. The rib 5 is
sideways delimited
by the flanges 4a and 4b. Such ribs 5 are arranged at even intervals in the
longitudinal
direction of the board. The term "rib" is used instead of "spacer" to
emphasize that the
function of the rib is to hold the board stable and curved, not merely to
hold/ define the
distance between the boards of a completed constructional element. A similar
function is
not included in any one of the previously known constructional elements, which
is why
these previous elements do not provide such a close resemblance to real timber
logs. When
using ribs that is cut from a single plate or board, it will be understood
that the orientation
of the rib on the board will be substantially perpendicular to the
longitudinal direction (axis)
of the board. When later refernng to the "ends" of the ribs, the parts of the
ribs close to the
flanges 4a and 4b in Fig. 5 is what is meant.
As shown by Fig. 5 and 6 the ribs may have recesses 6 intended to be filled
with additional
thermoplastic material in a subsequent step (Fig. 6). Alternatively the ribs 5
are fully
covered by a thin layer of thermoplastic material. Each rib is preferably
furnished with two
holes for reception of pegs corresponding to the pegs used in the furniture
industry for
assembly of furniture. The holes are preferably localized near each end of the
ribs (near the
longitudinal flanges 4a, 4b), and at a right angle with the longitudinal
direction of the
structural element, such that one and the same peg may be received by a hole
in a rib
3o attached to a structural element that forms part of an exterior wall
surface and by a hole in a
corresponding rib attached to a structural element that forms part of an
internal wall surface,
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
thereby contributing in binding together the inner and the outer structural
element of a
constructional element.
Figure 7 shows the entire process schematically. Boards are fed from left in
the Figure
between pairs of rolls A. With reference to Figure 7 the entire process is
described in
relation to the treatment of a single board. Grooves 2 in the board 1 may be
formed at an
earlier stage but may conveniently be made at this stage of the process. The
grooves may
be solely longitudinal, as such grooves are the simplest to make, or they can
have other
shapes or patterns, such as a diamond-shaped pattern. Alternatively the
grooves may be
omitted. The rolls B causes an initial curving (bending) of the board as shown
in Figure 2,
l0 while the board at the point of entering the extruder C has been given its
final curved shape
as shown in Figure 3. Prior to covering the board's concave side with plastics
in the
extruder, it is preferred to treat this side with an adhesive agent or a
compatibilizer that
makes the plastic material bind better to the wood. Such an adhesive agent may
be malefic
anhydride. As an alternative to the shown pair of rolls A and B the board may
be fed by
means of an articulated belt.
An endless belt 19 is furnished with fixtures 18 to which the ribs are
temporarily attached.
At point D the ribs are forced against the side of the board 1 that has been
covered with a
layer of thermoplastic material in the extruder. If the ribs are provided with
holes the holes
may be used for an exact positioning of the ribs relative to the board on
which they are to be
attached. Irmnediately thereafter, at the point E in Figure 7, each rib 5
receives
thermoplastic material in through openings of the rib, fed to it in by
injection moulding so
that the thermoplastic material sticks to an inner surface of the rib as well
as to the still soft
thermoplastic material 3 on the board 1. Alternatively, as shown in Fig. 7b,
each rib is
forced against the board in an enveloping die 18' that follows the endless
belt 19, and at
point E a thermoplastic material is injected through a conduit 20 to cover the
entire rib S
completely with thermoplastic material. Figure 7b also shows how a layer of an
adhesive
agent 21 is fed to the board 1 immediately prior to the addition of
thermoplastic material 3
in the extruder C.
Coolant air is blown over the thermoplastic material 3 and the ribs 5 at the
point F so that
the thermoplastic material sets and ensures a permanent attachment of the ribs
to the board,
thereby safeguarding a permanent curved shape of the latter. Alternatively
water may be
used as a coolant, by filling the voids between the ribs with water
immediately subsequent
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
to the injection moulding. The water is sucked up again at the point where the
product
element (structural element) is about to leave the belt/ production station.
It is convenient to use wooden ribs as wood is quite dimensionally stable in
the direction of
the fibres, and maintains its shape even when exposed to severe temperature
variations over
a long time. It is most important that the ribs are dimensionally stable
across the
longitudinal direction of the constructional element, which will mean in the
vertical
direction for the common use if the elements. It is otherwise not required
with any kind of
refinement of the wood used for ribs, non-planed wooden boards may be used and
it does
not matter if there are knots or holes from lcnots in the boards. Also other
materials may be
l0 used for the ribs, like steel, synthetic materials and composite materials,
but it is hard to
find materials with the positive properties of wood without adding costs to
the production.
When using steel ribs they may be provided with spikes that penetrate the
board to which
the rib is attached. When using a synthetic material or a composite material,
the ribs may
be dimensioned with a larger extension in the longitudinal direction of the
board compared
to when using steel or wooden ribs, without increasing the weight of
structural element/
constructional element, as such ribs may be designed as non-compact structure.
When it is stated that a number of ribs are arranged with defined intervals,
this usually
means one fixed interval between each rib, even though from a productional
point of view
also other solutions may work equally well.
2o It will be recognized that with the method described above, which may be
automatized and
controlled by a CAD/ CAM system, completed side surfaces or panels for
constructional
elements may be fabricated in tailor-made dimensions that are limited only by
the length of
the boards fed to the process. With "completed side surfaces" is understood
that the boards
have received their final curved shape, the ribs provide the structure with
strength and
integrity and the thermoplastic material provide the structure a moisture
barrier. The
integral intermediate product thus formed constitutes what is also referred to
as a structural
element for the constructional element.
Figure 8 is a sectional view that illustrates how two side surfaces
manufactured in
accordance with the process of Figures 1-6 and 7 are assembled to make up a
complete
3o constructional element according to the invention. Attachment means 8 are
mounted at
upper and lower end of each rib or some of the ribs with screws or the like,
and also to a
pipe element 7. Each constructional element in one and the same wall will have
such pipe
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
elements positioned straight above each other so that continuous rods may be
inserted from
the uppermost to the lowermost element of the wall in selected positions. This
feature is
more fully explained with reference to Figure 10.
It is preferred to use identical attachment means 8 in one and the same
building or in one
and the same wall. It should be noted, however, that by simply replacing the
attachment
means with some of another and larger horizontal dimension, a thicker
constructional
element is obtained which allows room for more thermally insulating material.
It is thus
not required to change the shape or dimension of the ribs to obtain a thicker
constructional
element. This is a feature of importance when comparing the present invention
with
to constructional elements according to the prior art.
Figure 9 is a sectional view of a constructional element between to sets of
ribs. Sealing
tape or foil 9 up and down running the entire length of the constructional
element, delimits
the internal void of the constructional element, such that a preferably
injected thermally
insulating material 10, like mineral wool, is kept steady within the element.
Figure 10 is a sectional view of a wall 11 notched from constructional
elements according
to the invention. At even intervals along the length of the constructional
elements pipe
elements 7 suited to accommodate bolts or rods 14 are arranged as mentioned.
Such bolts
or rods typically extend through the entire height of the wall. Each bolt 14
preferably is
provided with threads at both ends for simple attachment to an anchoring
element 15 in the
2o cement base 16 and (at upper end) e.g. a nut 17, possibly in combination
with a washer (not
shown).
In practice it is convenient that e.g. the lower end of each pipe element 7
has a conical
tapered shape that fits into the upper end of a similar pipe element that
protrudes somewhat
from the constructional elements, such that the pipe elements during assembly
of a wall are
pushed into and slightly overlaps each other. In this way the pipe elements
lock each
constructional element to the adjacent element above and below with respect to
any
sideways movement. By tightening the nuts 17 with an appropriate torque a
strong and
reliable binding of each wall is achieved while the risk of a gradual sinking
of the wall is as
good as completely eliminated. Furthermore, as the constructional elements are
very
lightweight, they normally need to be secured to the base wall to avoid the
risk of being
blown away during very heavy winds.
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
It should be emphasized that it is also an alternative to replace the above
mentioned pipe
element by an element that on one hand is able to function as a connective
element for the
two structural elements constituting the side walls of the constructional
element and on the
other hand is able to work as a guide for vertical bolts through an assembled
wall. Such
alternative elements will be equivalent to the pipe elements described above
even if they do
not have the shape of a whole pipe.
The wall shov~m in Fig. 10 has a lower log or half log 12 in solid wood and a
corresponding
upper log 13 in solid wood. It is not required with such solid wood logs, but
it represents a
preferred embodiment.
Figure 11 is a sectional view of two adjacent constructional elements which
constitute part
of a wall. The nethermost 2/3 of the sectional vies is within the body of rib
5 which is
provided with holes into which pegs 22 are inserted to position the ribs 5
relative to each
other in the pairs of oppositely arranged structural elements that form
respective sides of a
constructional element. It should be noted that in contradiction to Figure 8
no pipe element
7 or attachment means 8 is shown. Some of the pairs of ribs require a type of
pipe element
or the like that extends in the full height of the wall while other pairs of
ribs 5 may be just
' as shown in Figure 11. The uppermost 1/3 of the sectional view is placed
between the ribs
and shows the insulating material 10 in the constructional element.
Figures 12 and 13 show process steps for the manufacture of structural
elements of the
2o invention where the plastic layer coated to the inside of the boards 1, is
a layer of
thermosetting plastics rather than thermoplastics. The choice of material
requires that the
manufacture talces place in a press shape mould instead of in an extruder (as
shown in
Figures 7 and 7b).
Figure 12 shows an open mould 23 with a lower part 23a and an upper part 23b,
hinged
about an axis 24. The upper part comprises a frame structure 24 that holds a
hinged, three-
part pressing profile 25a-c with a shape adapted to the shape of the
structural elements to be
manufactured. Between the frame 24 and the pressing profile 25 a-c are
arranged hoses 26
for pressurized air. A board 1 is positioned I upper part 23b while ribs 5 and
epoxy with
reinforcement 3' are positioned in lower part 23a of the mould.
Figure 13 shows the forming of a structural element as the mould 23 has been
closed and
locked with hatch 27. The hoses 26 have been filled with pressurized air
causing the
hinged, three-part pressing profile, preferably made in aluminium, to apply a
significant
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
downwards force to the entire board. The side of the board that was faced up
in Figure 12
is now faced down and is pressed to an intimate contact with and thus binds to
the epoxy
resin 3' which is preferably reinforced with glass fibres. As most clearly
seen from Figure
13 only the central part 25b of the three-part pressing profile 25 is rigidly
connected to the
frame structure 24, while the outer parts 25a, 25c of the pressing profile are
hinged to the
central part 25b with a certain degree of rotational freedom, such that the
outermost edges
of the outer parts 25a, 25c under influence of the hoses filled with
pressurised air, in the
closed condition of the mould are moved downwards until the curvature of the
pressing
profile 25 a-c corresponds to the curvature of the rib s 5.
to With respect to the cogged joints, these are preferably not made as an
integral part of the
constructional element according to the invention. Rather the constructional
elements are
terminated with an open recess intended to receive separate cogging elements
of the type
described in Norwegian patent application No. 1996 3642.
When using separate cogging elements each constructional element is terminated
as
mentioned with an open end towards the joint. At the open end a pre-fabricated
transition-
element (not shown) will preferably be attached to the constructional element
by means of
"speilsveising" or the like. The outer profile of such a transition-element
will have a profile
corresponding to the internal profile of the constructional element while the
inner profile of
said transition-piece is a rectangular opening with a shape that corresponds
to the outer
2o profile of a cogging or splicing element. After attachment (welding) of the
transition-
element to the thermoplastic material inside the constructional element, the
transition-
element forms part of a sealed barner that prevents moisture from entering the
constructional element from an end of same.
When in this description there is made a distinction between a cogging element
and a
splicing element, this has to do with the fact that long (outer) walls are
divided where an
inner wall cross such outer walls. The separating inner wall will include a
cogging element
(also denoted end element) at the outside of and at a right angle to the outer
wall, while a
splicing element that is completely hidden by the constructional elements and
the cogging
joint, ties together two principally equal constructional elements of the
outer wall that meet
3o at the cogging joint. These cogging elements and splicing elements are
described in
Norwegian patent application No. 1996 3642 and do therefore not constitute
part of the
present invention. The splicing and cogging elements are preferably made in
whole wood,
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
11
but particularly the splicing elements that after assembly are invisible, may
also be made in
other materials.
At terminations of walls towards windows and doors, the constructional element
is
terminated in an end-piece that in contradiction to the transition-element
does not have any
opening. The end-piece may, like the transition-element, be made as a
prefabricated
thermoplastic element. The manner for attachment to the rest of constructional
element
may be as for the transition-element, i.e. it may be welded to the
thermoplastic material at
the inside of the boards by means of "speilsveising" or the like. While
otherwise visible
parts of the transition elements are hidden by the cogging joints, the
otherwise visible parts
to of the end-pieces are hidden behind a door frame, window frame or the like.
It is worth noticing that at delivery from a factory to a constructional site
the constructional
elements according to the invention will already be famished with end-pieces
and
transition-elements as well as separate cogging elements where appropriate. It
is also worth
noticing that the constructional element according to the present invention
does not
comprise the cogging element.
Extrusion of the plastic material to the board represents a rate determining
step of the
manufacture process and a realistic speed for this process is about lm per
minute, which for
a relevant log thickness corresponds to a production of 10 m2 wall per hour or
a normal
sized cabin per day.
The list of advantages with the present invention is long.
Firstly the method of manufacture is simple and may readily be automated and
is therefore
inexpensive. A normal cabin may be drawn in A CAD system within an hour's
time, be
manufactured in 1-2 days and normally be delivered in less than 2 weeks.
Secondly the applied plastic material constitutes a diffusion proof barrier
that prevents any
moisture form entering the void of the thermally insulating material.
A third advantage is the design of the element's walls - with a curved shape
that is
mistakenly similar to solid logs.
A forth advantage is the weight. The constructional elements has a 1/3 weight
of solid logs
and still makes a strong wall construction when assembled. Only 1/3 of the
wood needed
for a timber cabin is consumed and the quality of the wood is less critical.
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
12
A fifth advantage is the thermal insulation, as the walls are easy to insulate
and an entire
wall may be insulated in one single operation with fibre or foam. Pre-
fabricated
constructional elements has three times the insulating ability of whole timber
logs, and is
thus at level with buildings in framework and mats of mineral wool. The sound
insulation
ability is also very good.
As a sixth advantage may be mentioned that supply of electrical power if
desired may be
hidden in the walls.
The production is easy to adapt/ change (tailor-made), whereby an architect-
designed cabin
or the like is read into a CAD/ CAM software that automatically calculates and
initiates
l0 production of the correct number and size of numbered constructional
elements. Such
elements may be delivered as a ready to raise building-kit with an instruction-
CD that
contains a step-by step explanation of how to best raise the kit.
The properties may be associated with the individual components of a preferred
constructional element according to the invention, as follows:
15 - The side walls are wooden or of a wood-like material that provides the
desired look and
provides stability in the longitudinal direction of the constructional element
while at the
same time allowing sufficient hold for nails, screws and the like.
- The plastic material makes the elements diffusion proof, stabilizes the side
walls (the
boards) in the cross direction and binds the ribs to the boards.
20 - The ribs provide dimension stability (constant height and curvature) and
provides
attachment for the attachment means.
- The attachment means decide the thickness of a constructional element and
hold together
- aided by the pipe elements - pairs of structural elements (side walls) thus
forming a
constructional element.
25 - The pipe elements bind together two and two of said structural elements
to one
constructional element, provide the latter a weight carrying ability and
stable height and
contribute to guide the constructional elements when assembled to a.wall.
Subsequent to
such assembly the pipe elements form guides for bolts or rods that hold the
constructional
elements of a wall tightly together.
30 - Tape or foil strips over and under each element in their longitudinal
direction provide a
diffusion barrier at these sides of the constructional element.
- Insulating material in the constructional element insulates against
temperature and sound.
CA 02512014 2005-06-27
WO 2004/059101 PCT/N02003/000430
13
While the structural elements comprising the visible parts of a constructional
element
according to the invention are mainly intended for assembly in pairs to such
constructional
elements as discussed in this description, such structural elements may also
be used as for
panelling or cleading. For such a purpose it is convenient but not required to
provide the
side edges with some kind of tongue and groove or the like to ensure a nice
and even
transition between each of the elements.
