FR2630894A1 - Ski boot and method for manufacturing it - Google Patents

Abstract

The invention relates to a ski boot produced in a manner making it possible to improve its adaptation to the skier's foot and its behaviour under certain forces. The boot includes an outer shell 1, an inner bootee 2 and a soft and deformable intermediate layer between these. This layer is produced by injecting a fluid material 41 which is then hardened while a foot or foot model 10 is in the bootee 2. Thus, the outer shell can withstand irregular forces without undergoing irregular deformations. Consequently, the boot remains better adapted to the foot during its use.

Description

SKI SHOE AND MANUFACTURING METHOD THEREOF
The present invention relates to a ski boot and a method of manufacturing such a boot, and it relates more particularly to the improvement of the holding and adaptation properties at the foot of the skier, in a ski boot made of synthetic resin hard with an inner boot.

It is known to use, in a ski boot having a shell of hard synthetic resin, an inner boot made of a soft material, such as a spongy material, and inserted on a skier's foot so that it is better wedged in the shoe. In such a ski boot with an inner boot, local clearance tends to appear between the outer shell and the inner boot. If an irregular force is applied to the shoe during its use, for example due to a tilting of the skier's body forward, areas of the shoe in the vicinity of these local games will undergo irregular deformations. These deformations interfere with the proper adaptation of the boot to the foot, that is to say that the boot cannot fulfill its normal function. Consequently, the classic ski boots made of hard synthetic resin have deficiencies from the point of view of their functioning and their adaptation to the skier's foot.

The present invention therefore aims to manufacture a ski boot shell hard synthetic resin, so as to overcome the aforementioned drawbacks.

To this end, a first aspect of the invention relates to a ski boot comprising an outer shell of hard synthetic material, - an inner boot inserted in the outer shell, and a soft and deformable intermediate layer, placed in a gap between the inner surface of the outer shell and the outer surface of the inner liner.

A second aspect of the invention relates to a method of manufacturing a ski boot, comprising the steps consisting in - inserting an inner boot into an outer shell of the
ski boot while holding in place said boot slipped on a
skier's foot, - introduce a fluid material in a gap between the surface
inside of the outer shell and the outer surface of the liner
inside, and - hardening said fluid material.

Preferably, said fluid material is soft and deformable. It can also be incompressible.

The present invention will be better understood on reading the following description of exemplary embodiments, with reference to the appended drawings, in which FIG. 1 is a view in longitudinal section of an embodiment of a ski boot according to the invention, and FIGS. 2 and 3 are views similar to FIG. 1 and illustrate an embodiment of the method according to the invention.

In the embodiment illustrated in FIG. 1, an outer shell 1 of the ski boot is made of hard synthetic resin and it is arranged to receive an inner boot 2 inserted on a foot L of a skier. In an interval 3 between the inner surface 1a of the outer shell 1 and the outer surface 2a of the inner boot 2, there is a soft and deformable intermediate layer 4 made of an incompressible material.

Figs. 2 and 3 show successive stages of a process for manufacturing such a ski boot. First, the inner liner 2 is inserted on a relatively hard foot model 10 and it is placed in the outer shell I as shown in fig. 2. Next, a fluid material 41 is injected in the gap 3 between the inner surface 1a of the outer shell 1 and the outer surface 2a of the inner liner 2, as shown in FIG. 3, for example through an opening 11 formed in the part of the instep of the outer shell 1. The injected fluid material 41 is then hardened in a suitable manner.

For the outer shell 1 of the ski boot, the following synthetic materials are preferably used: nylon 12, nylon 6, nylon 66, nylon 11, polyurethane, polyethylene, polyvinyl chloride, polypropylene and polyester elastomer.

For the fluid material 41 of the intermediate layer 4, a reversible hardening thermoplastic synthetic resin or an irreversible thermosetting synthetic resin is used. Often the reversible synthetic resin is preferred because it allows subsequent correction of the forming. The reversible synthetic resin can be chosen from a group formed by copolymers of ethylene and vinyl acetate, synthetic resins of the ethylene and acrylate type, such as ethylene resins, vinyl acetate and methyl methacrylate, or ethylene and methacrylates, or ethylene and ethyl acrylate, as well as waxes. The irreversible synthetic resin can be chosen from a group formed by resins epoxies and expandable synthetic resins to form a foam, especially an expandable polyester or an expandable silicone.

A user's foot can be inserted into the inner boot in place of the foot model 10. In this case, the injection of a molten material requires that the following conditions are met, for reasons of quality and safety a) a low calorific intake must be necessary to pass from the
ambient temperature at melting; b) the melting point must be higher than room temperature,
but bearable by the skier's foot; c) there should be no sudden change in bass hardness
temperatures; d) the material must not exhibit excessive fluidity on melting, so
to prevent it from flowing completely in the interval at the bottom of the
shoe; e) the hardness must remain moderate during use.

A thermoplastic resin such as ethylene methacrylate-vinyl acetate-methyl is considered to meet these conditions.

Thanks to the presence of the intermediate layer in the gap between the outer shell and the inner boot, an irregular force applied to the ski boot during use does not create an irregular deformation of the boot and, consequently, the boot fills its normal functions even under severe conditions. In addition, the skier's foot is better protected and changes in position of the foot are better transmitted to the boot, to better control the ski. In addition,
The injection of the fluid material when a model of the foot or the foot of the user is in the liner improves the adaptation of the shoe to the skier's foot.

Claims (8)

Claims 1. Ski boot comprising an outer shell (1) of hard synthetic material, an inner boot (2) inserted in the outer shell, and a soft and deformable intermediate layer (4), placed in a gap (3) between the surface inside of the outer shell and the outer surface of the inner boot. 2. A method of manufacturing a ski boot, comprising the steps of - inserting an inner boot (2) into an outer shell (1) of the  ski boot while holding in place said boot slipped on a  skier's foot, - introduce a fluid material (41) into a gap (3) between the  inner surface of the outer shell and the outer surface of the  inner liner, and - hardening said fluid material. 3. Method according to claim 2, characterized in that said fluid material (41) is soft and deformable. 4. Method according to claim 2, characterized in that said fluid material (41) is incompressible. 5. Method according to claim 3 or 4, characterized in that said fluid material (41) comprises a reversible synthetic resin. 6. Method according to claim 5, characterized in that said reversible synthetic resin is chosen from a group formed by copolymers of ethlylene and vinyl acetate, synthetic resins of the type based on ethylene and acrylates, and waxes 7. Method according to claim 3 or 4, characterized in that said fluid material comprises an irreversible synthetic resin. 8. Method according to claim 7, characterized in that said irreversible synthetic resin is chosen from a group formed by epoxy resins and expandable synthetic resins to form a foam.