Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
P1229 PCTe ca o22942io 1999-i2-22 December 15, 1999
SNOW SLIDING BOARD
The invention relates to a snow sliding board and a method for its manufacture
according to the generic terms of the independent claims.
Distinctions are made between different kinds of snow sliding boards such as
e.g.
alpine-, cross-county- or ski jumping skies, "Big Foot"s, snowboards ete.
Snowboards differ from most other snow sliding boards in their design and
application. They are wider than the other snow slidi:~g boards. Most skies
must be
made available in pairs as one is strapped to each leg of the skier for use.
With a
snowboard only one snow sliding board is required, which, in contrast to other
snow
sliding boards comprises two areas for the application of bindings. These
areas, again
in contrast to most other snow sliding boards, comprise integrated receptacles
for the
binding, so-called inserts.
Most snow sliding boards comprise a well-tried and constant structure. This
consists
of sandwich designs, whereby a core is furnished with bearing covering layers
or
flanges consisting of fiber reinforced plastic laminates, plastic coating and
cheeks
consisting of plastic or steel elements.
A disadvantage of known snow sliding boards is their relatively high density
of more
than 900 kg/m3 and thus their considerable intrinsic weight. Thus snowboards
with
the typical dimensions of 1500 mm length and 290 mm maximal width have an
CA 02294210 1999-12-22
P 1229 PCTe December 15, 1999
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intrinsic weight of more than 2.3 kg. These heavy boards are toilsome to
carry, their
use requires considerable force and they are inert when changing direction.
For these
reasons lightweight snow sliding boards, so called lightweight boards are
sought
after.
A solution for the design of a lightweight board is disclosed in Swiss patent
CH-686
028. Using a lightweight core with a density of no more than 400 kg/m3 results
in
lightweight snowboards with average densities of maximally 850 kg/m3.
Honeycomb
materials or fiber reinforced high-resistance foam is suggested as lightweight
core
material.
A first disadvantage of this kind of lightweight snow sliding boards relates
to the
absorbing of shear stresses between the covering layers as well as a low shear
strength and the comparatively poor damping of vibrations and impacts. Shear
stresses are e.g. created by the bending of the snow sliding board due to
axial load
and affect its deformation or breaking strength respectively and the
properties when
in use. Vibrations and impact are caused by outer disturbances such as
unevenness of
the path followed as well as hunches and reduce the ride smoothness and the
grip of
the edges. Lightweight core materials have a low shear strength as well as a
low
modulus of elasticity in shearing such that there is an imminent danger of
breaking or
cracking.
A second disadvantage of lightweight snow sliding boards concerns compression
resistance. Lightweight core materials have a low compression resistance, they
are
compressible. Especially the compression resistance of honeycomb structures is
considerably reduced when the component is bent. The result is that the
distance
between the layers is changed which again has a negative effect on the
stiffness, the
firmness and the resistance to bending.
1'12291'C~l'e CA 02294210 1999-i2-22 December I5, 1999
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A third disadvantage of lightweight snow sliding boards concerns the force
transmission to the snow. A high force transmission from the feet via the
shoes,
bindings and layers makes precise steering and fast maneuvering possible. For
this
reason snowboards with high force resistance are sought after.
As a solution to these problems publication WO 97/06864 discloses a ski, in
which
the carrier of the binding surrounds the core laterally in form of monocoque
design
such that the thus mechanically de-coupled binding earner withstands torsion
as well
as forces in longitudinal and transverse directions of the snow sliding board.
In the
upper layer elasticoviscous damping layers are provided in order to absorb
vibrations
and impact rapidly. This mechanically de-coupled binding carrier further
allows a
high force transmission into the riding surface.
The solution with a mechanically de-coupled binding carrier, which surrounds
the
core laterally, is only applicable to relatively narrow skis. Snowboards,
however, are
considerably wider than skis, typically at least double as wide. The
laminates, which
take up the shearing forces, are too small for snowboards; they would have to
be
reinforced which would lead to problems concerning thickness and weight.
Publication FR-2 667 discloses a snow sliding board designed as a layer-
construction
with a core which contains a zone with honeycomb structure which reaches over
its
complete thickness and the rest of which is formed by a polymer mixture. This
snow
sliding board also has the disadvantages described further above, especially
the low
absorption of shear stresses, low shear strength and low compression
resistance. The
core is manufactured separately by means of placing the honeycomb structure in
a
mold and injecting the polymer mixture around it. After manufacture of the
core the
snow gliding board must be assembled from the core and other components. The
production in several steps is complicated and costly.
P1229 PCTe ca 02294210 1999-12-22 December 15, 1999
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It is the object of the invention to remedy the mentioned disadvantages by
means of a
simple design. The object is especially to show a snowboard design, which is
at the
same time lightweight, of high resistance to shear stress and high resistance
to
compression. Furthermore a high steering force transmission is to be achieved.
A
S further object of the invention is to disclose a method for manufacture of
snow
sliding boards. The invention concerns snow sliding boards such as skis, "Big
Foot"s, snowboards etc., especially, however, snowboards.
This object is achieved by means of the invention defined in the claims.
The inventive idea is the development of lightweight componeri~s for static
and
dynamic kinds of stress such as particularly occur in snow sliding boards.
Between
the upper and then lower layer a core matrix consisting of very lightweight
materials
as well as reinforcing materials of greater strength, preferably high-strength
materials, is arranged. This sandwich composite lightweight design withstands
high
dynamic bending and compressing stress. The reinforcing materials of greater
strength are let in in regions of very lightweight core materials. The forming
of a
core matrix in which mainly very lightweight materials have bearing functions
and
are stabilized against bending, compression and shear stress by means of
locally
attached reinforcing materials of greater strength is advantageous.
The resulting very lightweight snow sliding board has a very high shear and
compression strength because the reinforcing materials of greater strength are
let into
clearances in the very lightweight core materials in correspondence to the
direction
of main loading in order to increase the core modulus of elasticity in
shearing, the
P1229 PCTe CA 02294210 1999-i2-22 December 15, 1999
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core shear strength, the core compression strength, the component stii~'ness
and the
component strength. A combination of very lightweight core materials such as
e.g.
honeycomb-materials such as aramide paper drenched with phenolic resin
(Nomex),
polytherimide (PEI) tubular honeycomb or foamed plastics, e.g. polyamide,
polyimide or polystyrene or fiber reinforced plastics, e.g. fiberglass
reinforced
- plastics (GFK) or carbon fiber reinforced plastics (CFK), acrylonitrile-
butadiene
styrene (ABS) or also wood or metals. The following table indicates typical
values of
resistance of some of the materials mentioned above. Considering the table it
becomes evident that the used reinforcing materials have strikingly higher
resistances
than the used lightweight materials; thus it makes sense to call them
materials of
higher resistance.
Use as Material Com- Shear Modules Density
pression strength of (kg/m3)
re-
sistance (MPa) elasticity
(MPa) in shearing
(MPa)
LightweightNomex- 3.9 2.0 63 64
Material honeycomb
ReinforcingWood (average140 40 1200 650
Material value in
fiber
direction
)
ReinforcingGFK-laminate500 200 15000 1850
Material in fiber
direction
With the inventive method for manufacture of a snow sliding board regions
consisting of reinforcing materials are connected to regions of lightweight
materials
1'1229 1'C~1'e CA 02294210 1999-i2-22 December 15, 1999
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by means of bonding. The individual components of the core are advantageously
brought into a mold together with all the other components of the snow sliding
board
and bonded to form the finished product in one single step. This means that
the
operative core is not prefabricated with an individual method but that the
components must only be prefabricated correspondingly. It has proven to be
especially suitable to bond the individual regions together mutually as well
as the
regions with ends and with covering layers together by means of the known
prepreg-
method.
The invention is explained in detail in connection with the following figures.
Figure 1 diagrammatically shows forces and pressures to which a snow sliding
board (seen from the side) is exposed when stressed.
Figures 2 to 7 show longitudinal sections of exemplified embodiments of the
inventive snow sliding board.
Figure 8 shows a cross section of the embodiment in Figure 2.
Figure 9 shows a cross section of a further exemplified embodiment of the
invention.
Figure 10 shows a honeycomb material between two covering layers partially
opened for view of the inside.
Y1229 I'CTe CA 02294210 1999-i2-22 December 15, 1999
_7_
For the more general representation of the problem Figure 1 shows a snow
sliding board, e.g. a snowboard, viewed from the side, exposed to typical
stress.
A snowboarder (not shown) exerts forces F l and F2 onto the snowboard with two
feet. A bending of the snowboard results in a pressure sl on an upper side 2
and a
tension s2 on a lower side 3 of the snowboard. A shearing force s3 can also
act.
Figures 2 to 7 show longitudinal sections in parallel to the base 3 of the
snow
sliding board through parts of the exemplified embodiments of the present
invention. All these embodiments have in common that they concern a snow
sliding board, which is a snowboard. The invention is also applicable to other
snow sliding boards such as skis, "Big Foot"s etc., even when this is not
explicitly stated. Figures Z to 7 all show longitudinal sections through the
snow
sliding board and through its core 1, which consists of several regions of
differing
materials.
According to Figure 2 the core 1 e.g. contains regions 11, 12.1, 12.21, 12.22,
12.31, 13.32, 13, 14, 15, whereby the regions 11, 13 consist of very
lightweight
core materials and the regions 12.1, 12.21, 12.22, 12.31, 13.32, 14, 15
consist of
reinforcing materials of higher strength. The snow sliding board further
contains a
front end 45 and a rear end 54 which advantageously also consist of
reinforcing
materials. The design of the core matrix can e.g. be of alternating manner,
such
that the reinforcing materials are positioned in bounding outer regions 14, 15
and
in at least one inner region 12.1, 12.21, 12.22, 12.31, 12.32 and that the
lightweight materials are positioned in at least one intermediate region 11,
13.
Naturally more or less regions of material can be arranged to form a core
matrix;
thus e.g. a design without the reinforcing materials 12.21, 12.22, 12.31,
12.32
would be possible. Furthermore an alternating arrangement is not compulsory.
P1229 PCTe ca o22942io 1999-i2-22 December 15, 1999
_g_
Figure 8 shows a cross section through the embodiment of Figure 2 along line
VII-VII, whereby, for reasons of symmetry, only half of the cross section is
shown. Apart from the components previously described in connection with
S Figure 2 a pressure layer 20 and a tension layer 30 and a steel edge 40 are
to be
seen in Figure 8. The pressure layer 20 can be covered with a surface material
on
the surface 2 on which graphic design can be applied. The tension layer 30 is
advantageously covered with a riding surface 31.
Figures 3 to 7 show, in the same representation as Figure 2, further
embodiments
of a core matrix containing regions 11,13 consisting of lightweight material
and a
plurality of more or less systematically arranged, larger or smaller as well
as more
or less mosaic-like inner regions 12.1, 12.2 ... and bounding outer regions
14, 1S
consisting of reinforcing material. They can be larger or smaller, they can
be,
must, however, not be, mutually connected and can have any form. The expert
has, with knowledge of the present invention, nearly unlimited possibilities
for
the design of a core matrix. In general regions consisting of reinforcing
material
are applied purposefully concerning their size and orientation such that they
coincide with the directions of main loading in the snow sliding board.
The dimensioning, i.e. the relative size of the individual regions 11, 12.1,
12.2,
..., 13, 14, 15 as well as the front ends 45 and rear ends 54 is freely
adjustable.
Figures 2, 3, 6 and 7 show relatively narrow outer regions 14, 15 and
relatively
short front and rear ends 45, 54 while the intermediate regions 11, 13 cover
relatively large areas or volumes respectively. The inner region 12.1
according to
Figure 3 is designed to be narrower than that according to Figures 2, 4 and 5.
In
P1229 PCTe ca 02294210 1999-12-22 December 15, 1999
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Figures 6 and 7 the inner region is practically reduced to bonding bases 12.1,
12.2. Figure 5 shows a relatively large front end 45 and rear end 54. These
variations in dimensioning take preferred specifications of users into
consideration and result in snow sliding boards, which are of different
stiffness,
S more or less lightweight and different to maneuver. Furthermore these
variations
in dimensioning take the used lightweight and reinforcing materials into
consideration. Especially high-strength materials require smaller areas or
volumes
respectively than normal high-strength materials. Depending on the ratio of
lightweight and high-strength materials a weight reduction of ca. 20-40% can
be
achieved compared to standard-design-snowboards with conventional core
material such as e.g. wood with an average density of ca. 600 kg/m3.
The high-strength materials must not necessarily, as described so far, be laid
into
clearances in the very lightweight core materials in two-dimensional manner
but
they can also be looped through slotted core materials as shackles in three-
dimensional manner. An exemplified embodiment for this is shown in Figure 9
in the same manner as in Figure 8. The material of layer 20, 30 can be high-
strength reinforcing material. Shackles 20.1, 20.2 consisting of high-strength
layer material allow a direct connection of tension layer 30 with pressure
layer
20.
The reinforcing materials are for absorbing forces acting between tension
layer 30
and pressure layer 20. Especially regions 12.i, 12.2, ..., 14, 15 consisting
of
reinforcing materials make a high, bending stressing of the snow sliding board
possible. The regions 12.1, 12.2, ...14, 15 consisting of reinforcing material
further serve local reinforcement for purposes specific to application, e.g.
to form
bonding bases 12.1, 12.2 and to support steel edges 40. Naturally other
Y12291'C;~1'e CA 02294210 1999-i2-22 December 15, 1999
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possibilities of application of locally reinforcing materials which are not
listed
here are possible. The regions consisting of reinforcing materials stabilize
the
regions the regions consisting of lightweight materials when the snow sliding
board is subjected to dynamic bending stress. The shearing and compression
strength of the lightweight materials such as e.g. honeycomb materials is, as
is
known, drastically reduced under bending stress, e.g. because, with bending
and
transverse misalignment the cell walls in the honeycomb are no longer vertical
in
relation to the loaded plane. By means of local integration of reinforcing
material
which is transversally resistant under bending stress this low value of the
bearing
lightweight materials is impeded; the honeycombs are thus also stabilized when
bending stress is high. This core matrix which is reinforced and stabilized
according to the directions of main loading in the snow sliding board actually
makes the successful use of lightweight materials with low values of stiffness
possible.
According to Figures 2 to 7 the regions 12.1, 12.2, ... , 14, 15 consisting of
reinforcing materials are connected via front and rear ends consisting of
reinforcing materials in a high-strength manner. This makes it possible to
purposefully reinforce the most stressed edge region of the snow sliding board
in
high-strength manner. Regions 12.1, 12.2, ..., 14, 15, 45, 54 consisting of
high
strength reinforcing materials can be connected in a closed manner. This,
however, is not a condition. In general this sandwich-composite-structure has
a
high modulus of elasticity in shearing in longitudinal direction, it is very
resistant
against pressure and bending. The snow sliding board especially has a high
resistance against torsion and a high absorbing behavior. The stiffness and
resistance of its components are increased. It is advantageous to use plastics
reinforced with fiberglass (GFK), with carbon fiber (CFK), acrylic-nitirle
butadiene-styrene (ABS), wood etc. This listing is not complete. The expert
with
CA 02294210 1999-12-22
P 1229 PCTe December 15, 1999
knowledge of the present invention can also use other reinforcing materials
such
as metals, e.g, steel and/or aluminum.
The lightweight core materials have the purpose of keeping the weight of the
snow sliding board low. It is advantageous to use materials with cavities such
as
honeycomb materials with typical cell diameters of 3 to 10 mm or closed cells
with a density of no more than 400 kg/m3 as lightweight materials. A snow
sliding
board of the inventive design is embodied as a snowboard with typical
dimensions such as 1500 mm length, 290 mm maximal width and a maximal
thickness of 10 mm, has a weight of ca. 2.3 kg which means a weight reduction
of
20-40% compared to a standard design snowboard. This variation of weight
reduction is the consequence of the share of high-strength reinforcing
materials
(of minor weight) in the snowboard.
Figure 10 shows a lightweight honeycomb core material 6 between a tension
layer 30 and a pressure layer 20, the layers are partially left away in the
drawing
for a view of the inside. The honeycomb material 6 consists of advantageously
prismatic cells 6.1, 6.2, ...with e.g. hexagonal or circular cross section the
axes a
of which are advantageously directed vertically in relation to the
longitudinal axis
A of the snow sliding board. The most various honeycomb materials 6 consisting
of metallic materials such as aluminum or consisting of non-metallic materials
such as plastics such as e.g. polypropylene (PP), polycarbonate (PC),
polytherimide (PEI), aramide paper drenched in phenolic resin (Nomex) etc. are
available on the market. Honeycomb materials 6 are not only preferred for
their
low density but also for their extraordinary weight specific pressure
resistance.
P1229 PCTe ca o22942io 1999-i2-22 December 15, 1999
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The honeycomb materials are hardly compressible in the direction of cell axes
a,
which means that they are extremely pressure resistant but, compared to
conventional core materials they have a relatively low modulus of elasticity
in
shearing or a low shearing strength respectively. This is also valid for
alternative
lightweight materials such as e.g. foamed, not reinforced plastics.
The precise machining of honeycomb materials 6 and also of other lightweight
materials such as plastics, plastic fibers, prepregs etc. is e.g. carried out
by means
of ultrasonic cutting. Other processing methods for honeycomb materials and
lightweight materials as well as other ultrasonic cutting methods can
naturally
also be used. CNC-controlled ultrasonic cutting with CA.D-interface is
advantageous because it allows fast and economical cutting as well as swift
changes for variants of cutting. The precision of the cutting in serial
manufacture
is e.g. at ca. +/- 0.2 mm. Furthermore it is advantageous for there to be no
heat
1 S and media effect during the cutting; this is disadvantageous when using
other
cutting methods such as laser or water jet cutting because the edges can be
warped, damaged and contaminated.
The lightweight and reinforcing materials named in the present invention
cannot
be listed exhaustively, they are too many. The expert with knowledge of the
present invention can add further materials and combinations. Honeycomb
materials of higher density or honeycomb materials with larger or smaller cell
diameters can e.g. also be used.
The cavities of the lightweight materials such as e.g. honeycomb materials can
also be filled with reinforcing materials in order to act locally as
reinforcing
Y1229 YCTe CA 02294210 1999-i2-22 December 15, 1999
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materials in the sense of the invention. Foams and plastic pastes such as
polyurethane (PUR) or GFK, ABS or also metal, wood etc. are possible materials
in this context. Finally the cavities of the lightweight materials 6 can be
filled
with elasticoviscous materials in order to be elasticoviscous and to absorb
vibrations and impact quickly.
The durable stable connection of the individual regions 1, 12.1, 12.2, ... ,
13, 14,
as well as with front an back edges 45, 54 and with covering layers 20, 30 is
advantageously carried out by means of bonding, e.g. by means of the known
10 prepreg method. prepregs are reinforcing materials, which are drenched pre-
reacted duroplastics or thermoplastics. For a prepreg-matrix e.g.
thermosetting
duroplastic epoxy resin is used. Planar sandwich components can be
manufactured relatively economically by means of compression. Sandwich
components consist of relatively thin covering layers and a relatively thick
but
15 lightweight core. The covering layers are mostly high-strength layer
materials,
which are bonded to the core materials with high compression resistance and
low
weight. The viscoplastic prepreg-matrix and the use of a formable bedding
matrix
make various possibilities of component design possible.
For manufacture of the inventive very lightweight shear and pressure resistant
snow sliding boards for dynamic bending stress it is advantageous to use the
known prepreg method. The prepreg method is characterized by low cost and is
economical as all materials and parts are bonded with epoxy resin contained in
the prepreg in a fully automatic manner without additional bonding agent being
required. E.g. epoxy resin in B-condition is used for the viscoplastic prepreg-
matrix. If heat is supplied the viscosity of the resin is reduced and the
components
may be wetted by the flow of the resin. The variant of the prepreg method used
P1229 PCTe ca o22942io 1999-i2-22 December 15, 1999
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here uses massive tools machined to the contour of the workpiece which tools
are
spatially designed to correspond to the requirements. Walls which are oblique
in
relation to the pressing plane can, hereby, be pressurized in a frictional
connection. The polyaddition of resin and hardener depends largely on the
temperature, the pressing pressure and the time of action. The use of prepreg
guarantees a constant content of resin in the sandwich composite and a high
reproducibility of the connection.
In the prepreg method used here finished components emerge directly after the
hardening; the method is characterized by small required manufacturing effort
concerning the preparation of the parts and secondary treatment such as
debarring, smoothing, lacquering etc. In particular surfaces with graphic
designs
can be co-bonded simultaneously without additional effort. The prepreg method
used here is not restricted to the connecting of differing lightweight
materials to
form planar (two-dimensional) sandwich components but also makes possible an
economical sandwich-lightweight-construction consisting of three-dimensional
parts. E.g. a combination with a pressure bag method is possible in a manner
that
a pressure bag is either integrated into the machined part or locally into the
tool
and a constant pressure transmission into three dimensions (in all planes)
takes
place.
The expert with knowledge of the present invention can naturally also use
other
known techniques for connection and other connecting means. Wet laminating,
Reaction Injection Molding (RIM)-technology, Resin Transfer Molding (RTM)-
method or a bonding by means of adhesive foil, adhesive film, glue-coated
laminates consisting of plastic or fiber reinforced plastic such as GFK, CFK,
ABS, PFK or metals such as aluminum etc. are examples of such other
I'1229 I'C~1'c CA 02294210 1999-i2-22 December 15, 1999
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techniques. When a combination with an injection method is used an expanded
system is injected into the machined part, whereby the activating of the
foaming
system can then be carried out, during the pressing process, by means of heat.
By
means of such methods of connection lightweight materials and reinforcing
materials as well as covering layers can be connected to form break-proof,
flexible snow sliding boards.
