Method and devices for adapting a sports shoe and a sports shoe suitable for modification by such a method

Abstract

Shell or portion of a shell for a sports shoe (1) or portion of a shell of a sports shoe made at least partially from a thermoplastic material and further comprising metallic particles embedded in said thermoplastic material. The metallic particles constitute a proportion of between 0.1% and 25% of the mass of said shell or portion of the shell. The size of the metallic particles is characterized by an average diameter D50 of between 10 μm and 500 μm, preferably between 10 μm and 100 μm. The method for adapting said shell or portion of the shell using an induction heating device (2, 3) capable of producing an alternating magnetic field with a frequency of between 150 and 300 kHz. Figure for the abstract: Figure 1

Description

Title of the invention: Method and devices for adapting a sports shoe and sports shoe capable of being modified by such a method

[0001] The invention relates to shoes which comprise a rigid shell or only a portion of a rigid shell. In particular, but not exclusively, the invention relates to a sports shoe such as that used for practicing sliding sports, for example skiing, snowboarding, roller skating or ice skating. It may also relate to other types of shoe having a rigid shell such as walking shoes, or even shoes of which a part of the upper is a rigid element (counterfort, collar, etc.). It also relates to a pair of shoes and a device for shaping said shoe or the position of the shoe.

[0002] As is known, a ski boot comprises a rigid shell made of plastic and a comfort inner liner formed from an assembly of different flexible components. As a general rule, the shell is composed of a lower shell that envelops the foot, and an upper that goes up along the user's ankle.

[0003] The shell, with its rigidity properties, transmits the forces between the foot and the board. The liner envelops the user's foot, ensuring the comfort of the foot inside the shell. It also transmits the stresses to which the shell is subjected to the different areas of the foot or ankle.

[0004] In order to ensure good transmission of forces between the foot and the sliding device, the shell and the liner must fit the shape of the skier's foot. However, feet have complex shapes which vary from one individual to another.

[0005] To allow the volume of the foot to be adapted to a shoe, the shell is equipped with hook mechanisms or other equivalent devices which allow its internal volume to be modified.

[0006] But it is also necessary to avoid the shoe exerting local excess pressure on the foot. Such excess pressure disrupts the perception of stresses for an experienced skier.

[0007] For an occasional skier, it produces a feeling of discomfort which in the long run turns into pain.

[0008] Conversely, it is also necessary to avoid the foot floating in the liner due to an empty space between the foot and the liner or between the shell and the liner. Such floating makes ski handling imprecise.

[0009] Thus, to precisely adapt the shoe to the volume of the foot, it is known to work on the shape of the liner. For example, patent application FR2788410 describes a method of producing a liner in which inserts are cut into the wall of the liner to locally reduce its thickness or, on the contrary, to add shims. Other techniques for adapting the inner liner are also known. These techniques give good results, however their scope of application is limited because the deformation of the liner is limited by the wall thickness of the liner and the internal volume of the shell.

[0010] Also, in some cases, we resort to deformation of the shell itself. However, deforming a shell requires locally heating the wall to a high temperature and requires heavy tools, such as a 500°C hot air blower, a caliper and a hydraulic piston, which are introduced into the shell to exert a thrust on its walls. This results in a certain imprecision regarding the location and amplitude of the deformation because we are working on the bare shell. This is specialist work. We can also observe a deterioration in the external appearance of the shoe in the areas that have been heated. However, deformation of the shell by heating with hot air has the major disadvantage of the difficulty of targeting the area that will be heated.

[0011] To partially solve this problem, it is proposed in document FR 29029081 to add an additive to the thermoplastic material which allows its melting and softening temperature to be lowered. This additive can be added only in the areas which will be deformed so that it is possible to place the entire shoe in a convection oven whose temperature is lower than the softening temperature of the material without additive. This solution improves the possibilities of adapting sports shoes, it does however have limitations. In particular, with this solution, all the elements of the shell are heated at the same time, even the non-targeted areas, at the risk of causing involuntary and negative deformations. This can for example lead to a change in the angle of inclination of the shoe.On the other hand, conventional heating devices based on convention do not heat the material to the core and there is a risk that there will be a gradual return of the applied deformations over time.

[0012] In view of this state of the art, there is a need for a shoe of which at least one portion is rigid and for which the adaptation to the specific needs of the user is improved. At the same time, there is a need for a new heating device and for a new method for adapting the shape and the internal volume of a shoe of which at least one portion is rigid.

[0013] The objective of the invention is to propose a sports shoe, a device and a method which makes it possible to adapt said sports shoe to the foot of a user of a much more advantageous way than is currently possible.

[0014] The object of the invention is achieved by providing a shell or a portion of a shell for a sports shoe made at least partially from a thermoplastic material and which further comprises metal particles embedded in said thermoplastic material.

[0015] Preferably, all of the metal particles represent a proportion greater than 0.1% of the mass of said shell or of said portion of shell.

[0016] In a preferred embodiment of the invention, all of the metal particles represent a proportion of less than 25% of the mass of said shell or said portion of shell.

[0017] Preferably, the size of the metal particles is characterized by an average diameter, D50, of between 10 qm and 500 qm. Good results are obtained with particles of average diameter of between 10 qm and 100 qm.

[0018] The objective of the invention is also achieved by implementing a method for adapting a shell or a portion of a shell of a sports shoe using an induction heating device to locally heat and soften said shell or portion of shell until it becomes malleable in order to be able to conform it to the wishes of the user.

[0019] Finally, the objective of the invention is achieved by providing a device for heating a sports shoe comprising a shell or a portion of a shell made of a thermoplastic material, which device comprises at least one inductor capable of producing a magnetic field.

[0020] Preferably, said inductor produces an alternating magnetic field with a frequency between 150 and 300 kHz.

[0021] The invention will be better understood in light of the following description. The drawing attached thereto comprises 3 figures:

[0022] [Fig.l] [Fig.l] is a view showing a sports shoe according to the invention as well as a portable heating device allowing the adaptation of a sports shoe according to the invention.

[0023] [Fig.2] [Fig.2] is a view of an oven equipped with several heating devices.

[0024] [Fig.3] [Fig.3] is a horizontal sectional view of the furnace of [Fig.2].

[0025] [Fig.l] shows a ski boot 1 according to the invention. The boot comprises an outer shell topped with a collar designed to surround the lower leg of a user. The shell and the collar are made by injection of a thermoplastic material which may be, for example, polyurethane, polyethylene, polypropylene or any other equivalent material. A comfort liner is inserted inside the shell.

[0026] When manufacturing the shell and the collar, the basic raw material is prepared in the form of granules and it is mixed with one or more colorants chosen according to the desired shade. In the context of the invention, metallic particles are added to the mixture. The metallic particles can be made of different metals or metal alloys. It is possible to use particles of iron, cobalt, aluminum, or an alloy based on iron, cobalt or aluminum. The particles must be very small so as not to interfere too much with the mechanical resistance of the shell. In practice, particles are used whose distribution is such that the mass average diameter, D50, is between 0.1 qm and 1000 qm. In certain configurations, particles whose distribution is such that the mass average diameter, D50, is preferably between 10 qm and 500 qm.

[0027] It is possible to use particles in the form of flakes, such as those used as additives in certain paints, particularly in metallic paints. Particles having a spherical shape can also be used. In practice, it may be advisable to incorporate the particles into the colorant before mixing the latter with the thermoplastic material. The mixture thus obtained, which comprises the granules of thermoplastic material, the colorant(s) and the metallic particles, then feeds the injection press for the manufacture of the shell or shell portion of the sports shoe.

[0028] In the final mixture, the metal particles represent a proportion of between 0.1% and 25% of the total mass. Tests have shown that proportions of between 0.5 and 10% give satisfactory results when the base material is polyurethane or polyamide. Of course, the invention can be implemented with any type of thermoplastic, in particular with Polypropylene, PEBA or ABS.

[0029] Once the shell or shell portion of the sports shoe is obtained by injection of the aforementioned mixture, the latter is subsequently assembled with the other components and a ski shoe is obtained as shown in [Fig.l].

[0030] Let us now see how a ski boot according to the invention can be adapted to the morphology of a user. When the latter, after putting on the boot, notices a lack of comfort. For example, he may feel strong pain localized in an area of ​​his foot. This pain may be due to the fact that the portion of the shell located opposite the painful area exerts too much pressure there.

[0031] The user is then asked to remove the shoe so that the store technician or the bootfitting specialist (a specialty which consists of adapting shoes to a user's foot) can soften by heating the portion of the shell which needs to be adapted. According to the invention, heating the shell or the portion of The shell is made by an induction heating device that uses the principle of electromagnetic induction. Figures 1 to 3 show such heating devices.

[0032] [Fig.l] shows a portable induction heating device. The device comprises a copper-type inductor, powered by a generator in parallel circuit. The power of the device is approximately 6 kW and it operates at a frequency between 150 and 300 kHz.

[0033] The technician positions the heating device near the area of ​​the hull or the portion of the hull whose shape he wishes to modify. A few seconds are enough for a sufficient temperature of the hull portion to be reached and can be deformed (between 40°C and 120°C). The desired deformation is obtained using bootfitting tools or simply by the user's foot. Once cooled, the hull, which is again rigid, will retain the modified shape and the pain felt by the user will have disappeared.

[0034] [Fig. 2] shows a second induction heating device. This is a furnace 3 which comprises several inductors, each with a power of approximately 6 kW and operating at a frequency of 150 to 500 kHz. The furnace 3 comprises a cavity open at the rear and on the top so as to allow the shoe to be placed there. The latter can be placed there alone or when it is already worn by the user. The technician will then start the inductor(s) which are placed opposite the area(s) to be deformed. It will be noted that the different inductors are placed at the locations which are most likely to undergo adaptations. In practice, two front inductors 31, 31' are positioned at the forefoot, on each side of the shoe, two rear inductors 32, 32' are positioned opposite the ankle area and an upper inductor 33 faces the instep area of ​​the shoe and the upper area thereof.The position of the different inductors is visible in figures 2 and 3.

[0035] When the inductor(s) are in operation, eddy currents are generated in the metal particles present inside the shell. The resulting Joule effect raises their temperature. However, the temperature rise is also due, to a large extent, to the magnetic hysteresis effect which is the consequence of the variation in the magnetic field of the inductor. Indeed, this polarizes and depolarizes the particles and this alternation is accompanied by a loss of energy in the form of heat. The rise in temperature of the particles has the consequence of heating and softening the thermoplastic material surrounding them.

[0036] The invention is described here for a ski boot, but the invention can be implemented for any sports boot which has a shell or a portion of a shell which is made from a thermoplastic material. Or it could for example use it for the manufacture and adaptation of ice skating or roller skating shoes, but also for snowboard or cross-country ski boots.

Claims

Claims

1. Shell or portion of shell for a sports shoe (1) comprising a thermoplastic material characterized in that it further comprises metal particles embedded in said thermoplastic material.

2. Shell or portion of shell according to the preceding claim, characterized in that all of the metal particles represent a proportion greater than 0.1% of the mass of said shell or said portion of shell.

3. Shell or portion of shell according to one of the preceding claims, characterized in that all of the metal particles represent a proportion of less than 25% of the mass of said shell or said portion of shell.

4. Shell or portion of shell according to one of the preceding claims, characterized in that the size of the metal particles is characterized by an average diameter D50 of between 10 qm and 500 qm, preferably of between 10 qm and 100 qm.

5. Method for adapting a shell or a portion of a shell of a sports shoe according to one of claims 1 to 4, characterized in that it uses an induction heating device to locally heat and soften said shell or portion of shell until it becomes malleable in order to be able to conform it to the wishes of the user.

6. Heating device (2, 3) for a shell or a portion of a shell of a sports shoe according to one of claims 1 to 4, characterized in that it comprises at least one inductor (31, 31', 32, 32', 33) capable of producing a magnetic field

7. Heating device according to the preceding claim, characterized in that it comprises a cavity capable of receiving, at least partially, said sports shoe.

8. Heating device according to one of claims 6 or 7 characterized in that said inductor produces an alternating magnetic field with a frequency between 150 and 300 kHz.

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