Patent Application
20060064904
The invention relates to a sports boot subassembly and also to the sports boot itself, and is particularly suited to the field of boots for boards for gliding, such as skiing or snowboarding, or skating boots, which are subjected to significant stresses during use and for which a particularly robust structure is required. For example, the invention relates to subassemblies of the shell or collar type for a ski boot. The invention also relates to a manufacturing process.
A ski boot is a good example of a boot subjected to numerous stresses that has to be very stiff. However, it also has to be sufficiently flexible to guarantee the skier's comfort and to enable him to open the boot in order to put it on and to take it off and to enable him to flex his knees forward.
A process for manufacturing a ski boot was described in patent EP 1295540, allowing the production of a ski boot with the aid of several carbon-fiber fabrics connected by a resin by means of a technique of polymerization of the resin on molds in order to form two half-shells, prior to the joining of the two half-shells in order, finally, to form the boot. This process makes it possible to obtain a very stiff boot but has a first disadvantage of being complex and costly compared to currently used injection-molding techniques, such an injection-molding operation not being applicable in the case of a reinforced material, a second disadvantage of not meeting the requirements of flexibility of such boots, and a third disadvantage of allowing only a basic design for the outer surface of the boot. For these reasons it was quickly abandoned.
In response to the disadvantages mentioned above, the processes for manufacturing ski boots that are most in use nowadays are based on processes of injection-molding of plastics materials of polyurethane, polypropylene, polyethylene or polyamide type. Such a solution is described in patent application EP 0903087, which discloses a boot shell composed of a first layer in a relatively stiff plastics material of polyurethane type partially covered by a second layer in a more flexible plastics material, the relatively stiff layer including thicker zones in order to form reinforcements on certain carefully selected surfaces. A first disadvantage of this solution is that it greatly increases the overall weight of the boot on account of the weight of the materials used and their considerable total thickness. A second disadvantage stems from the fact that the performance levels obtained in terms of stiffness are mediocre, despite the various increased thicknesses used. A third disadvantage stems from the fact that such boots are ill-suited to the production of adornments on their outer surfaces. Indeed, the adornment of the outer surface may either be achieved with the aid of specific shapes given to the plastics material placed on the outer surface of the boot, which gives rise to increased thicknesses of plastics for the production of designs, these increased thicknesses generating excess weight and an increase in the boot's stiffness, and thus, ultimately, having a negative impact on the essential characteristics of the boot, or be produced with the aid of marks on the outer surface of the boot, such marks generally lasting only a short time given the numerous aggressive influences to which they are subjected.
An object of the present invention consists in proposing a sports boot subassembly and a process for manufacturing it that does not present the disadvantages of the prior art.
More precisely, a first object of the present invention consists in proposing a sports boot subassembly that makes it possible to achieve satisfactory stiffness while conserving zones of flexibility.
A second object of the present invention consists in proposing a sports boot subassembly that is light in weight.
A third object of the present invention consists in proposing a sports boot subassembly that has an attractive esthetic appearance.
A fourth object of the present invention consists in proposing a process for manufacturing a sports boot subassembly that is relatively simple.
According to the concept of the invention, the wall of a sports boot subassembly astutely combines the use of a very stiff material and a flexible plastics material in such a way as to achieve a good stiffness/flexibility compromise for minimum weight. This combination of materials is, furthermore, defined in order to allow implementation of a simple manufacturing process.
More precisely, the invention relates to a sports boot subassembly of the shell or collar type, which comprises at least two parts, each comprising a flexible plastics material and a very stiff material partially embedded in the flexible plastics material, and wherein the at least two parts comprise an assembly surface for joining them together.
Advantageously, the very stiff material occupies at least half the total surface area of the wall of the subassembly.
The invention also relates specifically to a ski boot shell and to a ski boot.
It also relates to a process for manufacturing a sports boot subassembly of the shell or collar type, wherein it is obtained by the assembly of several parts, at least two of these parts being obtained by means of the following steps:
The blank in very stiff material may be obtained from a composite sheet composed of a fiber-reinforced thermoplastic or thermosetting matrix or by means of drawing a metal sheet.
These objects, characteristics and advantages of the present invention will be set forth in detail in the following description of a non-limiting particular embodiment with reference to the appended figures, in which:
FIGS. 1 to 4 illustrate an embodiment of the invention for manufacturing a ski boot shell.
FIGS. 1 to 3 illustrate a first part 1 of a ski boot shell according to the invention.
This part 1 has a wall composed of a very stiff material 2 and a flexible plastics material 3. In this embodiment, the very stiff material is a reinforced material composed of a carbon-fiber-reinforced polyurethane thermoplastic matrix and the flexible plastics material is a polyurethane of 55 Shore D hardness.
As shown in
As illustrated in
Lastly, the shell obtained includes a reinforced material 2 that is present over more than half the total surface area of its wall. Furthermore, except for the zones of the periphery of the blanks in reinforced material 2 and the reinforcement zones 8, the wall of the shell comprising the reinforced material is very thin as it comprises the thickness of the reinforced material, optionally covered by a thin layer of plastics material. The shell is composed of two distinguishable parts 1, 21 connected by a fixing means that leaves an assembly line visible on the assembly surfaces 12 and 22.
The invention also relates to the process for manufacturing such a ski boot shell, which thus comprises the following steps:
The reinforced material may consist of a polyurethane matrix comprising carbon or glass fibers, and the plastics material may be polyurethane. According to another solution, allowing optimum recycling of the boot, the reinforced material may consist of polypropylene fibers embedded in a polypropylene matrix, the plastics material also being polypropylene. The fibers may, according to the applications and characteristics sought, be glass, carbon, Kevlar or polypropylene fibers.
As variant embodiments, the blank may be produced by last-molding a fiber-reinforced thermosetting matrix or by drawing a metal sheet. This blank may also include reinforcement ribs on its surface.
The injection-overmolding step may make it possible to form the top part of a shell comprising a flap 9 and a part 10 designed to bear on the shin and also reinforcements and/or front and rear curbs 8, the assembly surface 12 with the rib 13 and, possibly, shapes of an esthetic nature.
As a variant embodiment, the injection-overmolding step may comprise two successive steps of injection-molding a different plastics material, for example, allowing the injection-molding of a polyurethane of 65 Shore D hardness in order to form the front and rear curbs of the interface with the ski binding, and the injection-molding of a more flexible polyurethane of 45 Shore D hardness in order to form the flaps. The second injection-molding operation may also consist in the injection-molding of a cellular plastics material over the inner surface of the boot in order to exploit the comfort and thermal insulation properties thereof. Assembly may be achieved by any other solution—welding, bonding or mechanical fixing.
The invention has been described in the case of a ski boot shell, but it could be applied to the collar of a ski boot or to a subassembly of another sports boot.
In the embodiment described previously, the two parts of the shell correspond to two parts obtained by cutting the shell on a vertical plane passing through the center of the front and rear curbs. However, any other cutting plane could be imagined. The two complementary parts could also be designed in accordance with a non-planar cut, the assembly surfaces not being planar. Lastly, the concept of the invention could also be applied to the assembly of more than two parts of a boot subassembly.
The concept of the invention thus consists of the association of a very stiff material with a much more flexible injection-overmolded plastics material, which we will therefore call a flexible plastics material, the term flexible being understood to include any plastics material of which the flexibility is equivalent to that of a polyurethane customarily used for boots, whose hardness is between 30 and 70 Shore D, the expression “very stiff” being understood to be a material of markedly greater stiffness than the flexible plastics materials defined previously. The very stiff material may be any fiber-reinforced thermoplastic or thermosetting matrix or any metallic material, such as stainless steel, aluminum or magnesium. Its function is to ensure the stiffness of the boot by its very nature and to guarantee a light weight since it is, by nature, light and a thin layer suffices. The injection-overmolded plastics material has the function of providing flexibility in predetermined zones and forming the more complex decorative and functional parts of the boot, while fixing the two materials.
The embodiment described previously demonstrates an advantageous combination of a very rigid material with a flexible plastics material to form a wall of a sports boot. This combination could, however, be different without departing from the scope of the invention.
The flexible plastics material could also totally cover the very stiff material on the outer face, for example, with the aim of protecting a decoration arranged on the surface of the very stiff material and visible from the outside by using a transparent plastics material. The blank in very stiff material could also be arranged in the front and/or rear curbs of the shell. Lastly, the invention relates to any other combination of the very stiff material and the flexible plastics material in accordance with the concept explained above allowing the following objectives to be achieved.
Finally, the advantages of the solution are thus as follows:
| Number | Date | Country | Kind |
|---|---|---|---|
| 04425729.3 | Sep 2004 | EP | regional |
