Process for making a snow board and snow board thus obtained

This invention relates to a snow board especially provided for high speed performance in competition. It is slit, longitudinally and axially, at least in its front at rear parts. Furthermore, its simple flexural strength in the front and rear parts is increased by at least 20% with respect to the greatest stiffness existing at those spots for a conventional one-piece snow board, while its stiffness in the binding mounting area is rendered at least equal to the greatest stiffness existing at that spot for such a traditional snow board, and may even be greater by about 10%.

FIELD OF THE INVENTION 
The present invention relates to a process for manufacturing a snow board. 
It also concerns a snow board obtained by this process. 
BACKGROUND OF THE INVENTION 
Unlike a ski or a monoski, the board for gliding over snow constituting the 
snow board is used asymmetrically, the user having neither his body nor 
his feet directed along the longitudinal axis of the board, but placed at 
an angle with respect thereto. The surfer's body is placed crosswise with 
respect to his board with either the right foot at the rear and the left 
foot in front, for persons with "regular foot", or the left foot at the 
rear and the right foot in front, for persons with "goofy foot". The 
distance between the feet depends on the user's morphology and essentially 
on his size. The toes are more or less turned towards the front of the 
snow board, this orientation being indicated by an angle measured from the 
perpendicular to the longitudinal axis of the snow board. This orientation 
may generally vary, for the rear foot, between 0 and 40 degrees about and, 
for the front foot, between 10 and 45 degrees, the position most in favour 
with numerous high-level surfers at the present time being the so-called 
intermediate position: 
rear foot: angle of orientation included between 10 and 15 degrees, 
front foot: angle of orientation included between 30 and 45 degrees. 
Be that as it may, the surfer's body is crosswise with respect to the board 
and to the 20 direction of his displacement. Bends are taken either by 
leaning forwards, towards the toes (or more simply expressed 
"front-side"), or by leaning backwards towards the heels (or "back-side"). 
The surfer's centre of gravity then moves along an axis whose orientation 
is substantially the bisectrix of the angle formed by his two feet. 
Snow surfing is exceedingly popular at the present time, particularly among 
young people, with the result that snow surf competitions are now being 
organized, like ski competitions, and the "speed" factor is becoming 
essential for snow surfboards intended for competitions, and, of course, 
the capacity of these boards to take bends with maximum precision. 
Generally speaking, a board for gliding over snow must be sufficiently 
rigid in order to penetrate in the snow as little as possible and 
therefore to slide flat at a maximum speed. On the other hand, in order to 
inscribe the edge line in a curve when taking a bend, this board must, on 
the contrary, be as flexible as possible. 
These two conditions are contradictory and the whole science of snow board 
manufacturers consists in finding a good compromise between stiffness and 
flexibility which will make it possible both to move rapidly flat, while 
having optimum facility and precision when taking a bend. 
It is an object of the present invention to overcome this difficulty and 
therefore to obtain a snow board which has excellent performances in speed 
when gliding flat and likewise excellent performances for easy and precise 
execution of bends. 
SUMMARY OF THE INVENTION 
To that end, it relates to a process for manufacturing a snow board, whose 
structure comprises at least: 
a sole for gliding bordered, on each of its sides and over at least the 
whole of its supporting length, by metal edges, 
one or more reinforcing elements, 
one or more filling elements, 
one or more decorating elements, 
this snow board having a width at the level of its central part or "binding 
mounting area" which is included between 150 and 300 millimeters, 
and it being specified that the qualities of gliding and of manoeuvrability 
of a snow board are principally associated with characteristics of simple 
flexural strength of each of the areas: 
of binding mounting (stiffness of binding mounting) 
of front end (stiffness of tip) 
of rear end (stiffness of heel) 
characterized in that it consists in making this snow board with a 
stiffness which is, in said tip and heel ends, at least 20% greater than 
the greatest stiffness known at the present time for a snow board, then in 
slitting this snow board, in the substantially longitudinal direction, at 
least over its front part and over its rear part and so as to pass 
entirely through the thickness of the board. 
This at least partially slit snow board is advantageously provided in the 
binding mounting area with a stiffness which is at least 10% greater than 
the greatest stiffness at that spot for the range of snow boards known at 
the present time. 
The invention also relates to a snow board, characterized in that: 
it is slit, in the substantially longitudinal direction and over the whole 
of its thickness, at least in its front part and in its rear part, 
and its stiffness in the front and rear parts, obtained by measuring the 
deflection "f" obtained by pressing on the board, with a force of 40 Kgf, 
applied in the middle distance between two supports supporting the board 
flat and placed, the first on the line of contact, front or rear 
respectively depending on whether it is question of the stiffness in the 
front part or of the stiffness in the rear part, and the other at a 
distance from the first, towards the rear or towards the front 
respectively, which is equal to: 
EQU (Lp/2).times.0.55 
(Lp being the distance, the so-called "supporting length", between the 
front line of contact and the rear line of contact), 
is given by a deflection value f less than 16 millimeters. 
Advantageously, its stiffness in the binding mounting area, determined by 
measuring the deflection "fo" obtained by pressing, with a force of 40 
Kgf, in the middle distance d between two supports supporting the board 
flat on either side of the middle of the supporting length Lp, and 
longitudinally distant from the value: 
EQU (Lp).times.0.45 
is given by a deflection value less than or equal to 35 millimeters. 
Advantageously, said stiffnesses in the front and rear parts are 
advantageously given, under said conditions of measurement, by a 
deflection "f" of the order of 15 millimeters, while the corresponding 
stiffness in its binding mounting zone is given, under said conditions of 
measurement, by a deflection "fo" of the order of 35 millimeters. 
For information, the stiffnesses in the binding mounting zone of 
conventional snow boards of the prior art are of the order of 40 to 60 mm 
in deflection "fo", while the stiffnesses of these snow boards at the tip 
and at the heel are of the order of 20 to 50 mm in deflection "f". 
It should be noted that certain inventors have already proposed slitting a 
snow board in the longitudinal direction into two equal, removable parts, 
in order thus to obtain a pair of skis, enabling a T-bar to be easily 
taken, for example. This solution does not make it possible to solve the 
problem raised here, as it does not really improve the speed performances 
of this snow board, and, moreover, is in no way envisaged to that end.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to the drawings, and firstly to FIG. 1, a conventional snow 
board, of so-called "shell" type, is shown in cross section. 
This snow board comprises: 
a lower sole 1 for gliding, which is bordered by metal side edges 2, 
a lower reinforcement 3 which is constituted by one or more layers of a 
fibrous fabric, more or less loaded with warp yarns and with weft yarns; 
this lower reinforcement 3 is, in the present case, placed on the sole 1 
between the upper parts of the metal edges 2, 
a central core 4 which is made in the present case by injecting the 
compounds of a polyurethane foam but which might also be made of wood, 
"honeycomb", or other light material, 
an upper plastic shell 5 which is conventionally internally lined with one 
or more layers of fibrous fabric, these layers forming the upper 
reinforcement 6 of the structure of this snow board. 
The width of such a snow board at the level of its central part or "binding 
mounting area" is in any case included between 150 and 300 millimeters. 
The flexural strength of a snow board of this type, or of a similar snow 
board of "sandwich" structure of still more conventional type, is in 
practice adjusted by the manufacturer by playing on the or each inner 
reinforcement, such as reinforcements 3 and 6. In order to obtain more or 
less flexural strength, different parameters may consequently come into 
play: distribution in quantity of the warp yarns and weft yams in the 
fibrous fabrics of which these reinforcements are constituted, more or 
less spaced apart relationship of these reinforceing layers with respect 
to the neutral axis of the board, number of layers of fabric in each 
reinforcement, materials constituting these fabrics, total number of 
fibers per layer of fabric, etc . . . 
It is therefore principally the reinforcing layers of fibrous material 
which characterize the flexural strength of a snow board and which allow 
it to be adjusted. This flexural strength in the direction orthogonal to 
the surface of glide of the board, or "simple deflection" will be referred 
to as "stiffness" in the present specification as well as in the claims. 
Another important notion is that of the "supporting length" of a board for 
gliding over snow. This notion will be recalled with reference to FIG. 2. 
In FIG. 2, a board for gliding over snow, such as a snow board 7, is shown 
applied on a strictly flat plate 8. 
Under these conditions, the limits of the plane zone of contact of the sole 
with the plate 8 determine two transverse lines: 
a line 9 at the front of the board, where its tip 11 originates, called 
"front line of contact", 
a line 10 at the rear of the board, where its heel 12 originates, called 
"rear line of contact". 
The "supporting length" of the board 7 is then defined as being the 
distance Lp between its front line of contact 9 and its rear line of 
contact 10. 
FIG. 3 shows how the stiffness of this snow board 7 in its binding mounting 
area, i.e. in its median zone, is measured. 
This stiffness is measured by applying a force F in a zone Po which is 
located in the middle of the supporting length Lp, and which is 
consequently considered as being located in the middle of the binding 
mounting area. 
The snow board 7 is then placed on two supports, for example two transverse 
bars 13, 14 which are disposed symmetrically and on either side of the 
transverse line of positioning of the force F, the distance d between 
these two supports being adjusted to a value: 
EQU d=Lp.times.0.45 
In order to measure this "stiffness of the binding mounting area", a 
downward force F equal to 40 Kgf is then exerted on the board 7 at 
P.sub.0. The board 7 then bends at that spot, between the two supports 13, 
14, adopting a shape as indicated in broken lines, thus defining a 
deflection "fo" whose value in millimeters defines said stiffness at that 
spot. 
FIGS. 4A and 4B respectively show how the stiffness is measured in the 
front part of the board 7, called "front-side stiffness", then its 
stiffness in the rear part, called "back-side stiffness". 
The board is slid over the supports 13 and 14, with the result that support 
13 is at the location of its front line of contact 9, and the support 14 
is displaced to obtain a distance between the two supports 13, 14 of: 
##EQU1## 
In order to measure the stiffness of the front part of the board, a force F 
of 40 Kgf is then exerted in the middle P.sub.1 of the distance between 
these two front supports 13 and 14, and the value in millimeters of the 
deflection "f" then obtained for the deformation of the board 
characterizes the stiffness of the snow board in this front part. 
According to FIG. 4B, the stiffness of the rear part of the snow board is 
measured in the same way, by exerting a force F of 40 Kgf in the middle 
P.sub.2 of the distance between the two supports 13 and 14, the rear 
support 14 having been positioned on the rear line of contact 10 and the 
front support 13 being spaced apart from support 14 by the same distance 
as for the measurement of the stiffness in the front part, and the value 
in millimeters of the deflection "f" then obtained for the deformation of 
the board characterizes the stiffness of the snow board in this rear part. 
Each of the three measurements mentioned above is, of course, effected by 
pressing each time on one spot only, viz. P.sub.0, P.sub.1 or P.sub.2. 
Reference will now be made to FIGS. 5 and 6 which show in plan view and in 
substantially median cross section, a snow board 7 which is produced in 
accordance with the present invention. 
This snow board 7 is not constituted by a board in one piece, but is 
constituted by two halves 17, 18 which are symmetrical with respect to its 
median longitudinal plane 19 and which are separated by a gap "i", of the 
order of 2 millimeters to give an idea, this gap defining for this snow 
board 7 a median longitudinal slit which in the present case extends from 
one end of the board to the other. 
This gap is an air gap, except on the binding mounting area where it is 
filled with a supple bonding material 20, for example constituted by 
rubber or elastomer which is added by adhesion. 
In a variant embodiment, this supple bonding material may also, or 
exclusively, be added in the front part and/or in the rear part of the 
snow board. 
This axial strip 20 creates an advantageously non-removable connection 
between the two halves 17 and 18 and useful for avoiding infiltrations of 
snow. 
The two halves 17 and 18 of the board 7 are further maintained fast by 
fixed plates 24 and 25, which constitute either the very base of the 
bindings of the surfer's boots, or shims for raising these bindings. 
As shown in FIG. 6, the structure of this snowboard 7 comprises: 
a sole for gliding, composed here of two parts 1a and 1b, 
lateral metal edges 2, 
a lower reinforcing element, composed here of two parts 3a, 3b, 
a filling element constituted by an injected core 4, composed here of two 
parts 4a, 4b which are each internally bordered by a respective inner 
half-longitudinal element, or longeron, 21a, 21b, 
an upper reinforcing element, composed here of two parts 6a, 6b, 
a plastic shell for protection and decoration composed here of two parts 
5a, 5b. 
At manufacture, a longeron 21 is positioned in the axial zone of the snow 
board, before the core 4 is made, so that, after the slit i is 
subsequently cut out, the remaining core 4a, 4b is protected as shown by 
the two remaining half-longerons 21a and 21b. 
According to the invention, the simple flexural strength of the front part 
and of the rear part of this snow board is rendered, at manufacture, 
greater by at least 20% than the corresponding greatest stiffness of a 
conventional snow board, taken from the whole range existing for these 
snow boards, i.e. constituted by a one-piece board such as the one shown 
in FIG. 1, while the simple flexural strength in the binding mounting area 
is rendered at least equal at that spot to the greatest stiffness in the 
binding mounting area of this same traditional snow board. 
In fact, in the example in question, the stiffness in the binding mounting 
area of the snow board according to FIGS. 5 and 6 is provided, at 
manufacture, to be of the order of 10% greater than the greatest stiffness 
measured for the range of conventional snow boards. 
Of course, as mentioned hereinabove, the different stiffnesses are adjusted 
by playing on the respective constitutions of the fibrous reinforcing 
layers 3a, 3b and 6a, 6b, and the stiffnesses are measured by the 
deflections fo and f mentioned above, obtained under the conditions of 
measurement described hereinbefore with reference to FIGS. 3 and 4. 
It should be noted that the fact of slitting the snow board along "i" does 
not significantly modify the characteristics of stiffnesses defined 
hereinabove, after these stiffnesses according to the invention have been 
given to this board. 
More precisely, by way of non-limiting numerical example: 
the stiffnesses in the front part and in the rear part of the snow board 
according to FIGS. 5 and 6 both correspond to a deflection f of the order 
of 15 millimeters, while the greated stiffness measured at these two spots 
for the traditional snow boards sold at the present time corresponds to a 
deflection of the order of 20 millimeters. 
the stiffness in the binding mounting area of this same snow board of the 
invention corresponds to a deflection fo of the order of 35 millimeters, 
while the greatest stiffness measured at that spot for the same range of 
traditional snow boards corresponds to a deflection fo of the order of 40 
millimeters. 
When a surfer takes a bend, he leans his body either forwardly, for a 
"front side" edge grip or rearwardly for a "back-side" edge grip. 
Thanks to the invention, in an edge grip, only the corresponding board half 
17 or 18 is stressed in simple bending, which considerably reduces the 
effective stiffness and allows a better flexion and therefore a better 
inscription in a bend. At the tip as at the heel, the respective spacing 
between the two halves 17 and 18 can then attain about ten centimeters. 
The manufacturer can take advantage of the fact that only one half of the 
board is then stressed in simple bending, to increase the different 
stiffnesses as specified hereinabove, without penalizing flexion of the 
board in bends. Such increases advantageously lead to a clear improvement 
in speed performances when gliding flat, in particularly in a straight 
line. 
In position of pure gliding, with the snow board flat, the weight of the 
surfer is distributed over the two parts 17 and 18 of the board. This 
board being in that case very rigid, the load is distributed virtually 
uniformly over the whole supporting surface with minimum deformation, 
which gives a very rapid snow board. 
It goes without saying that the invention is not limited to the embodiment 
which has just been described. 
It is not necessary that the snowboard be slit in the binding mounting 
area, since this area bends little when a bend is taken, unlike the front 
and rear parts. In this respect, FIG. 7 shows a snow board produced like 
the one of FIG. 5, but which is slit along i only in its front part and in 
its rear part, the binding mounting area in that case being in one piece. 
In order to lighten the snow board to a maximum, it is also possible, 
according to FIG. 8, to increase the width of the slits, within said 
slits, in the front and/or rear part of the snow board, by transforming 
these slits into wide openings 27 and 27, over a determined inner length. 
In that case, these inner widenings 26, 27 will preferably be made in front 
of and behind the front and rear contact lines 9 and 10 respectively, in 
order to avoid the snow accumulating on the top of the board by passing 
through these openings. 
In the same spirit, the slit at the rear of the board might present a 
rearwardly flaring triangular shape, the rear part of the snow board in 
that case being in the form of a "dove-tail", as shown in FIG. 9. 
Neither is it really indispensable that the longitudinal slit i of the snow 
board be strictly axial, strictly rectilinear, or even strictly 
longitudinal. On the contrary, as shown in FIGS. 10 to 12, it is possible, 
by no longer being subjected to one or the other of these three strict 
characteristics, to create for this snow board 7 a "half right/half left" 
asymmetry which may prove beneficial. 
In fact, surfing necessarily creates, in bends, an asymmetry of efforts 
between the tip and the heel of each of the surfer's boots. An asymmetry 
of the load distribution is then created, which consequently creates an 
asymmetrical need for stiffness which is satisfied by the asymmetrical 
embodiments in accordance with one or the other of FIGS. 10 to 12. 
According to FIG. 10, the snow board 7 presents a slit i which is 
substantially longitudinal, but curved and not rectilinear, with concavity 
on the "back" side of the snow board. Part 17 of the board, on the front 
side, therefore contains more matter than part 18, on the back side. 
According to FIG. 11, the slit i is rectilinear and strictly longitudinal, 
but it is not axial: it is offset on the front side, with the result that 
part 17 contains less matter than part 18 and this snow board consequently 
presents asymmetrical reactions other than the preceding one. 
According to FIG. 12, the slit i is rectilinear, but it is no longer 
strictly axial and longitudinal; it is slightly slanting with respect to 
the median longitudinal axis of the snow board 7. 
The invention is, of course, in no way limited to a snow board of the 
"shell" type according to FIG. 6 and it is equally well applicable to a 
much more conventional snow board of "sandwich" structure.