US20190142111A1

US20190142111A1 - Liner for sports shoes

Info

Publication number: US20190142111A1
Application number: US16/181,934
Authority: US
Inventors: Francesca MARCHETTI; Stefano NOAL; Vanio Tessaro
Original assignee: Head Technology GmbH
Current assignee: Head Technology GmbH
Priority date: 2017-11-10
Filing date: 2018-11-06
Publication date: 2019-05-16
Also published as: EP3482648B1; EP3482648A1; CN109757823A

Abstract

A liner for sports shoes includes a sole, an upper to which is associable at least one deformable hollow insert, adapted to custom fit the liner to a user's foot. Specifically, in the deformable hollow insert a plastically deformable filler material is injectable at room temperature in a reversible manner by applying an injection pressure of a device. Moreover, the plastically deformable filling material is suitable to be suctioned, at room temperature, with the device from the deformable hollow insert applying a suction pressure.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention refers to liners for sports shoes, preferably ski boots or the like. Specifically, the invention refers to a device and a method for adapting the liner to the morphology of a user's foot and lower leg, based on the user's needs. In other words, it is possible to customize the liner by adapting it to the preferences of the user and to the sport, according to the use to which the shoe is to be subjected.

STATE OF THE PRIOR ART

Liners, worn by a user, are inserted inside of sports shoes, such as, for example, ski boots. These liners provide thermal insulation, cushioning and comfort during use and are generally made of a plurality of portions, glued or sewn together, of different shapes and materials.
The liners are generally produced in different sizes, each of which has a predetermined size; however, users of the same size may have a different foot shape. Moreover, the feet of a same user may have asymmetries between them.
For this reason, the liner, although correctly selected on the basis of size, requires a specific fit to the morphology of the user's foot and to the sports shoe in which it is used.
In addition, the fit of the shoe also depends on the type of sport, and, for example, for skiing, a same user requires liners with a more or less tight fit depending on the discipline one wishes to practice.
Thus, the shape of the shoe influences both the user's comfort and performance. Specifically, custom fitting the shoe to the user's foot is particularly important for sports shoes which provide for portions made of rigid materials, such as ski boots, which generally comprise a rigid shell.
In the practice of skiing, a constant transmission of the impulses of the skier's movement to the skis via the ski boots is required. Therefore, the task of the boot, and of the liner contained therein, is to transmit said impulses of movement ensuring the user can constant maneuver the skis and offering, in addition, adequate comfort.
The morphological variety of the skier's foot is such that it is usually necessary to apply some padding in the liner which contains the foot and the lower portion of the leg, ensuring that the heel and the instep are maintained in a firm position without, however, creating painful pressure points in critical regions, such as the malleolus, which would make practicing the sport uncomfortable.
In the sports footwear sector, technical solutions are now available that make it possible to adapt the liner to the shape of the user's foot, but the solutions currently offered have some disadvantages as indicated below.
A first solution is to insert, in portions of the liner, a foam, usually polyurethane, which makes it possible to properly custom fit the liner to the shape of the user's foot. However, for the production of this type of material, chemicals are used, for which a careful preparation is required in order to control the chemical reactions on which the final result depends. Moreover, the chemical reactions involved are exothermic, producing heat during the foam-forming stage, and require a relatively long wait time to ensure complete crosslinking and expansion of the resin, during which any foot movements may lead to an incorrect fit. Finally, the polyurethane foam produced cannot be further transformed and, therefore, this process is irreversible and does not allow a subsequent custom fit or optimization of the shape of the liner to the user's foot.
A similar solution to the preceding one provides for forming inserts in the liner into which a silicone compound is injected, which, when mixed with a catalyst through special injection devices, crosslinks by polyaddition or polycondensation. The compound, occupying the free space around the user's foot, after the crosslinking of the resin, forms a liner corresponding to the user's anatomy. This solution has the advantage of not producing heat during crosslinking; however, it has the disadvantage, as in the preceding case, of requiring a relatively long wait time to ensure the complete crosslinking of the compound, and therefore, if the foot moves during the process, it is possible to get an incorrect fit. Finally, the silicone compound produced may not be further transformed, and thus this process is irreversible.
Another solution is to insert appropriate air-filled cushions inside the liner. This solution makes it possible to adapt or optimize the fit at a later stage. However, these cushions do not guarantee a stable custom fit of the liner to the foot because, during operation, uneven pressures are applied thereon that instantly modify the shape of the cushion and, since the air is compressible, the impulse of the user's movement is not transmitted correctly, thus compromising the maneuverability of the sports equipment, such as skis.
A further solution is to use self-molding inserts with a shape predetermined according to the region of the foot to which the liner must conform. These inserts, comprising at least one portion made of thermoplastic material, once inserted into the liner, may be thermoformed and custom fitted to the shape of the foot by heating the portion of the corresponding liner. The advantage of such solution is that the insert may be molded appropriately and in a reversible manner. However, since this is a predetermined shape and cannot expand or compress, as in the case of polyurethane foams, it is not possible to properly occupy the free space around the user's foot, thus creating an insert which is only partially customized.
These solutions, therefore, involve the use of chemicals, possibly dangerous ones, and procedures that are difficult to control and require complex equipment that is not easily purchased by small shops or individual users, thus discouraging the shops of the sector from offering their customers custom fitting services for sports shoes.
It is apparent that the processes of custom fitting these liners are extremely delicate and require the assistance of qualified personnel to ensure they are done properly. An error at this stage is in fact very easy and causes damage without remedy as the processes are generally irreversible.
Moreover, the customization is usually carried out in different environmental conditions from those in which the sports shoe and the liner contained therein are used, therefore entailing the risk that the result obtained at the time of the custom fit procedure will not meet the user's requirements while practicing the sport.
Finally, it is not possible to carry out a subsequent custom fit or optimization of the liner following, for example, the change over time of the morphology of the foot or subsequent adjustments of the sports shoe, possibly forcing a complete replacement of the padding or the liner.

SUMMARY OF THE INVENTION

The task of the present invention is to create a liner comprising appropriate inserts to ensure the customization of the liner in a reversible way, and a simple method of customization that does not provide for the use of special equipment and that, therefore, may be achieved by non-specialized personnel.
In the scope of the task outlined above, a first object of the present invention concerns the creation of a liner comprising inserts capable of expanding and adapting to the morphology of the user's foot in the regions of greatest criticality such as the malleolus and the instep.
A second object concerns a method for filling such inserts with a material that makes a reversible-type process of custom fitting the liner to the user's foot possible, as well as any ongoing customization of the liner.
A third object concerns the creation of a liner comprising said inserts capable of providing a custom fit to the morphology of the user's foot while maintaining, at the same time, a consistency adapted to transmit correctly the impulse of the movement from the foot to the rigid shell of the sports shoe, through the liner.
A fourth object of the present invention concerns a method for customizing the liner that reduces production times, avoiding the stages of waiting for a complete crosslinking of the materials used so as to considerably reduce possible errors in customization due to foot movements.
A further object of the present invention concerns a method for the customization of the liner that is simple, safe and that may therefore be applied preferably in shops of the sector or by individual users, making the use of such solution possible for mass consumption.
The task and the objects indicated above, and others which will be better explained in the following description, are achieved by a liner as defined in claim 1.

BRIEF DESCRIPTION OF THE FIGURES

Further features and advantages of the liner and the inserts of this invention will become more evident in the following description relating to an embodiment given purely by way of non-limiting example, with reference to the following figures, wherein:

FIG. 1 is a side view in cross-section of a liner for sports shoes comprising the inserts according to the present invention.

FIG. 2 is a side view of a liner for sports shoes according to the present invention.

FIG. 3 is a side view of an insert and a device according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention refers to the use thereof in liners for ski boots. This embodiment may in no way be understood as a limitation of the field of application of the invention and this may be applied to any sports shoe for which it is necessary or advantageous to customize the shoe to fit the specific morphology of the foot of a user.
With reference to FIG. 1, a liner 10 is shown, which comprises two deformable hollow inserts 18 inserted or applied on the liner 10 in the regions corresponding to the critical points of a foot, such as malleoli and ankles, or points where the spaces between the foot and the shoe must be minimal or zero for an immediate transmission of force to the sports equipment for the proper use thereof. For simplicity, in FIG. 1 only one of the two deformable hollow inserts 18 is represented, which are arranged symmetrically at the two malleoli of the foot.
With reference to FIGS. 1 and 2, the liner 10 is shown for a sports shoe of conventional shape and produced with standard dimensions for the size type of the shoe. The outer surfaces of the liner 10 act on the inner surfaces of the shell, made of a rigid material, of a sports shoe (not shown) and transmit the impulses of movement from the foot to the skis while practicing the sport.
The liner 10 comprises a sole 11 and an upper 12 consisting of a first lower portion 13 and a second upper portion 14 to accommodate, respectively, the foot and the lower part of the user's leg, connected together at the height of the ankle. The portion accommodating the lower part of the leg 14 has an upper opening and a front and/or rear opening to facilitate the fit of the foot.
In addition, the portion accommodating the foot 13 provides for two connected seats, whereby respectively the first seat 15 extends in the region of the malleolus and the second seat 16 in the anterior region of the ankle. Finally, the portion accommodating the lower leg 14 provides for a third seat 17 connecting the first seat 15, corresponding to the malleolus region, to the upper edge of the lower part of the leg 14.
Said first 15, second 16 and third 17 seats, define a pocket, consisting of the upper 12, preferably facing the foot of the user, adapted to accommodate the deformable hollow insert 18 and having a shape complementary thereto. Alternatively, said pocket faces the shell of the sports shoe.
Referring to FIG. 3, the diagram of a deformable hollow insert 18 is shown, having substantially the same orientation as the insert installed in the liner 10, as in FIG.1.
The deformable hollow insert 18 comprises a first inlet portion 19, a first chamber in the shape of a sac 20 and a second chamber 21. The portion 19 has a substantially tubular shape and acts as a sleeve extending vertically from the upper edge of the second portion accommodating the ankle 14, from which it protrudes, to the region of the malleolus 15 of the upper 12 of the liner 10.
The top end of the tubular portion 19 provides an access portion to the deformable hollow insert 18 for a device 23, as described below, while the lower end is connected to the first chamber 20 of the deformable hollow insert 18 through an inlet or outlet valve 22 for a filler material of the deformable hollow insert 18, as described below.
Said valve 22 is preferably a valve the shutter element of which consists of two films, that is, layers, with mutual electrostatic adhesion, each consisting of portions over the inner walls of the first chamber 20 facing each other and located at the lower end of the tubular portion 19. The two films with mutual electrostatic adhesion, thus arranged, couple with each other as a result of electrostatic attraction, sealing the first chamber 20 of the deformable hollow insert 18, thus preventing a loss of said filling material through the tubular portion 19 while practicing sports.
The two films with mutual electrostatic adhesion extend over the inner surfaces of the first chamber 20 in a region of which the extension is adapted to ensure a seal if pressure is exerted from the inside of the first chamber 20 of the deformable hollow insert 18 outwards, but are separable from each other with a mechanical effort exerted from the outside by means of a tapered element. In other words, the two films with mutual electrostatic adhesion allow for a reversible seal of the valve 22.
Advantageously, this type of valve permits a simple design of the shape of the deformable hollow insert 18, without being bound to a specific shape of a traditional valve, and, moreover, being essentially flat with relatively small thickness, it does not interfere with the functionality and comfort of the liner 10 when used in practicing sports.
Said first chamber 20 has a substantially lung-like shape that extends to the region of the malleolus 15 of the upper 12 of the liner 10.
Moreover, the first chamber 20, near the anterior region of the ankle 16 of the upper 12, provides for a protrusion 21 forming the second chamber of the deformable hollow insert 18 that extends from the region of the malleolus 15 towards the anterior region of the ankle 16 of the upper 12, which, in operation, i.e. when the liner 10 is inserted in the sports shoe, acts on the region of the instep of said sports shoe.
The material with which the hollow insert 18 is made is an elastomer such as to allow, following the injection of said filling material through the tubular portion 19 and the valve 22, the elastic deformation, i.e. non-permanent, of the walls of the first chamber 20 and the second chamber 21, producing, in a reversible way, an increase in the volume of the deformable hollow insert 18, i.e. the expansion thereof.
In a preferred embodiment, the deformable hollow insert 18 is made of a thermoplastic elastomer such as thermoplastic polyurethane (TPU), but it is possible to use resins of a different chemical nature such as olefinic thermoplastic elastomers (TPE-O), styrenic block copolymers (TPE-S), polyvinyl chloride (PVC) or the like.
Moreover, preferably also the films with mutual electrostatic adhesion of the valve 22 are made of a material based on thermoplastic elastomer, such as thermoplastic polyurethane (TPU).
As mentioned, within the deformable hollow insert 18 is injected a filling material of the first 20 and second 21 chambers adapted to expand the volume of the deformable hollow insert 18, making it assume, at the same time, a shape that conforms to the morphology of the foot and fills the gaps between the foot, the walls of the liner 10 which is worn on it, and the shell of the sports shoe. Specifically, the expansion takes place in the most critical anatomical regions, i.e. at the region of the malleolus 15 and in the anterior region of the ankle 16 of the upper 12, so as to keep the heel and the instep firm without creating painful pressure points.
The procedure for custom fitting the liner 10 to the foot, comprising the deformable hollow inserts 18, is carried out in room temperature conditions, preferably defined between 15° C. and 23° C. Moreover, while performing the sports activity, pressures are applied to the sole 11 and to the upper 12 of the liner 10, which will be defined in the following as “operating pressures”, due to the closure of the sports shoe with conventional devices and to the pressure of the foot that ensure the maneuverability of the sports equipment, such as skis.
The filling material is a viscous material that is malleable at room temperature, i.e. it is plastically deformable at room temperature by applying an operating pressure thereto. At the end of the application of said operating pressure, the filling material remembers and preserves the new shape assumed, in other words, the filling material maintains over time the deformation obtained until a possible application of an additional operating pressure.
Moreover, while practicing the sport, the filling material is chemically stable, has a consistency suitable to transmit the impulses of the movement from the foot to the sports shoe by means of the liner 10, and is not compressible, thus ensuring the degree of filling of the deformable hollow insert 18, or the degree of expansion thereof, when operating pressures are applied while practicing the sport.
Finally, such filling material may be transferred operationally by means of a suitable device 23, exerting alternately at room temperature appropriate pressures which will be defined below as “injection pressure” or “suction pressure”. Given the ability to be plastically deformed at room temperature through the application of pressure, the material is able to flow inside the deformable hollow insert 18 and may then be injected or suctioned out with said device 23. The filling material, during its deformation and flow induced by the injection or suction pressures, dissipates part of the energy exchanged through the compression or expansion work performed by the device 23 into heat, thus increasing the temperature and lowering the viscosity of the material, facilitating the injection or suction process.
Following several experimental tests, it was discovered that a material capable of meeting the aforementioned requirements is, preferably, a suitable mixture of mineral oil and wax and, even more preferably, a suitable mixture of mineral oil and microcrystalline wax.
Naturally, materials of a different chemical nature may be used, provided they meet the requirements described above. For example, systems based on amino or montan waxes may be used instead of hydrocarbon waxes and, in addition, these materials may be combined with plasticizers, thickeners or the like to obtain the features of the filling material described above.
As mentioned above, the filling material has characteristics such that it may be injected or suctioned from the deformable hollow insert 18 by means of a device 23 in the quantity desired by the user. Devices of this type are known per se and, as visible in FIG. 3, generally include a cylindrical container 24, containing the filling material, a piston 25 being provided at one end of the container 24 and on the other end a nozzle 26, which in turn is connected to a flexible cannula 27. Said cannula 27 is adapted to be inserted into the hollow insert 18, through the tubular portion 19 and the valve 22, until it reaches the chamber 20. As is known, by applying a mechanical force in opposite directions on the piston 25, it is possible to inject or suction material from or into the cylindrical container 24 by exerting an injection pressure or a suction pressure, respectively.
Preferably, when purchasing the liner 10, the deformable hollow insert 18 is empty and contains no filler material. Therefore, the customization stage, preferably performed by shops or individual users, provides for the injection of the filling material into the deformable hollow insert 18 and any adjustment of the quantity thereof by using said device 23.
Moreover, the thickness of the walls of the first 20 and second 21 cavities of the hollow insert 18 is such as to guarantee their integrity both during the stage of injecting with said filling material, during which an injection pressure is applied by means of the device 23, and in the operating conditions, i.e., during the execution of the sporting activity during which operating pressures are applied to the liner 10.
The method of custom fitting the liner to the foot and to the shell of the sports shoe therefore comprises the following steps:
The user inserts his/her foot, at room temperature, into the sports shoe containing the liner 10 and closes the sports shoe by tightening it with conventional devices, such as levers or ratcheting buckles.
Subsequently the shopkeeper, or the user him/herself, inserts in the deformable hollow insert 18, through the tubular portion 19 and the valve 22, the cannula 27 of the device 23 until it reaches the first chamber 20, and applies an injection pressure to the device 23, by means of the piston 25, adapted to inject a desired quantity of filling material, contained in the chamber 24.
In this injection stage, the filling material, plastically deforming, begins to fill the first 20 and second 21 chambers of the deformable hollow insert 18, which then expands, reducing the gaps between the foot, the liner 10 and the shell of the sports shoe.
Continuing with the injection of the filling material, the operating pressure, applied by the walls of the shell of the sports shoe on the portions of the region of the malleolus 15 and the anterior region of the ankle 16 of the upper 12 of the liner 10, plastically deforms the filling material contained in the respective first 20 and second 21 chambers of the deformable hollow insert 18.
Then, until the desired amount of filling material is fully injected, the deformable hollow insert 18 continues to expand and, at the same time, conforms to the profile of the foot according to the morphology thereof to cancel out the gaps between the foot, the liner 10 and the shell of the sports shoe.
Once the injection of the filling material in the desired quantity has been completed, the cannula 27 of the device 23 is removed from the deformable hollow insert 18, maintaining the operating pressure applied by the walls of the shell of the sports shoe on the foot through the liner 10, and the user, depending on the pressure he/she perceives on the foot in the malleolus area 15 and on the anterior part of the ankle 16 of the upper 12, may decide if this is an optimal pressure for the execution of the sport, or may decide if it is suitable to keep the heel and the instep in a firm position, or if the pressure is lower or higher than said optimal pressure.
In case the pressure perceived on the foot is not optimal, the shopkeeper, or the user him/herself, may adjust the amount of filling material by inserting the cannula 27 in the deformable hollow insert 18, through the tubular portion 19 and the valve 22, until it reaches the first chamber 20, and by applying an injection or suction pressure to the device 23, through the piston 25, suitable for injecting or suctioning the filling material, respectively, to increase or decrease the pressure exerted by the deformable hollow insert 18 of the liner 10 on the foot.
Once the quantity of filling material has been adjusted, the cannula 27 of the device 23 is removed from the deformable hollow insert 18, maintaining the operating pressure applied by the walls of the shell of the sports shoe on the liner 10, and the user may check if the new pressure perceived on the foot is the optimal pressure for practicing the sport.
It should be noted that, as the filling material is malleable at room temperature, i.e. plastically deformable at room temperature, it is possible to correct the procedure for fitting the liner 10 to the user's foot by repeating the step of adjusting the quantity of filling material using the device 23 just described, until the optimum pressure perceived on the foot is reached.
Furthermore, the reversibility of the entire process is ensured in that it is possible to repeat the entire procedure described above for fitting the liner 10 to the user's foot, as it is possible to completely remove, at room temperature, the filling material from the deformable hollow insert 18 of the liner 10, which again assumes its original shape, i.e. that prior to expansion, by means of the elastic properties of the material of which it is made.
During a possible stage of using the device 23 to suction the filling material from the deformable hollow insert 18, it is possible to provide for a mild heating of the liner 10 in the area of the first chamber 20 to facilitate the insertion of the cannula 27 inside the filling material and to facilitate the suction thereof. Preferably, one may use a hair dryer or heat gun, keeping the temperature below 80° C.
Moreover, it should be noted that the malleable nature of the filling material, although less at temperatures lower than room temperature, may advantageously make it possible to continuously fit the deformable hollow insert 18 of the liner 10 to the foot even in the conditions of practicing the sport, while still maintaining a consistency adapted to transmit the impulse of the movement of the foot to the sports shoe by means of the liner 10. In effect, it is known that while practicing a sport, a foot may swell or the thicknesses of the portions of the upper 12 of the liner 10 may undergo permanent deformations, linked to the viscoelastic characteristics of the materials of which they are made, leading to a change in fit.
Naturally, numerous modifications or variations of the present invention are possible, without thereby departing from the protective scope as defined in the claims 1 and 5.
For example, the deformable hollow insert 18 is integrated in the liner 10, fixed by sewing or gluing to the inside of the pocket defined by the seats 15, 16 and 17; however, it is possible to provide a removable deformable hollow insert 18, making it possible to open said pocket with appropriate opening elements. The possibility of removing the deformable hollow insert 18 makes it possible to easily perform any additional processes on the liner 10 such as, for example, cleaning. The possible repositioning of the deformable hollow insert 18 in a region not corresponding exactly to the one before removal, due to possible play inside said pocket, may still be adjusted to the foot with an additional custom fitting procedure.
Moreover, at the purchase of the liner 10, the deformable hollow insert 18 is supplied without a quantity of filling material, but it is possible to provide for a partial filling thereof during the production of the article.
The first 20 and second 21 chambers of the deformable hollow insert 18 inside the first housing portion of the foot 13 may have different shapes and extensions from those described in the preferred embodiment and may be optimized as a function of the different types of sports shoes in which the liners 10 are used.
Moreover, the deformable hollow insert 18 may be equipped with additional valves and tubular portions, in addition to the valve 22 and the tubular portion 19 described above, possibly arranged in different portions of the deformable hollow insert 18 to facilitate the injection or suction of the filling material.
In addition, the liner 10 of this invention provides for two deformable hollow inserts 18, however, it is possible to provide only one, larger extension, or a plurality of inserts properly arranged to ensure adequate comfort for the user while practicing the sport.
Furthermore, the valve 22, which in the present description comprises a shutter element consisting of two films with mutual electrostatic adhesion, may comprise only one that closes the valve 22 by coupling to the inner surface of the deformable hollow insert 18, or may be replaced by a traditional check valve element.
Moreover, the description of the invention executed on a preferred embodiment is related to liners with front entry, but solutions that provide for a rear or side entry may also be applied.
Finally, the device 23 may advantageously provide for heating elements comprised in the container 24 and in the cannula 27 to facilitate the injection or suction process by means of a small increase in temperature with respect to the ambient temperature and, therefore, a decrease in the viscosity of the filling material.
From what has been described so far, it is clear that significant results have been achieved, overcoming the drawbacks of the state of the art, making it possible to create a liner 10 comprising appropriate deformable hollow inserts 18, applied to the upper 12, adapted to achieve the reversible customization of the fit. This makes it possible, for example, to fit the liner 10 in the case of changes in the morphology of the foot.
Furthermore, the customization method does not provide for the use of special equipment and may be conducted in room temperature conditions and, therefore, it is achievable by non-specialized personnel, as it is safe, avoiding the use and mixing of hazardous chemicals, and simple, as it makes it possible to repeat the fitting procedure in case of errors.
Moreover, the customization method is substantially conducted at room temperature, avoiding heating stages at too high of temperatures, which could damage the various portions that make up the liner 10.
A further result is to have reduced the time required for the method of custom fitting the inner liner 10, as there is no crosslinking reaction of the materials, which requires relatively long times, making possible the substantially immediate use the inner liner 10, considerably reducing possible errors due to foot movements during the customization procedure of the liner 10.
Finally, the features of the filling material of the deformable hollow insert 18 allow, while practicing the sport, a continuous fit to the morphology of the user's foot while at the same time maintaining a consistency that correctly transmits the impulse of the movement, necessary for the maneuverability of the sports equipment, from the user's foot to the sports shoe by means, therefore, of the liner 10.
Naturally, the materials and equipment used for the production of the present invention, as well as the shape and sizes of the individual components, may be those most suitable according to the specific requirements.

Claims

1. A liner comprising a sole, an upper to which is associable at least one deformable hollow insert, adapted to custom fit the liner to a user's foot

wherein

a plastically deformable filling material is reversibly injectable into the at least one deformable hollow insert, the plastically deformable filling material being injectable at room temperature by applying an injection pressure by means of a device, the plastically deformable filling material being also adapted to be suctioned at room temperature by means of the device from the at least one deformable hollow insert by applying a suction pressure.

2. A liner according to claim 1,

wherein the deformable hollow insert is adapted to reversibly increase its volume when the plastically deformable filling material is therein injected.

3. A liner according to claim 1, wherein the deformable hollow insert is made of elastomer.

4. A liner according to claim 1, wherein the plastically deformable filling material is made of a mixture of mineral oil and wax.

5. A liner according to claim 1, wherein the at least one deformable hollow insert comprises a valve, and the valve comprises a shutter element, the shutter element tightly closing the valve by means of electrostatic adhesion.

6. A liner according to claim 5, wherein the shutter element comprises at least one layer made of an electrostatic elastomer.

7. A method for custom fitting a liner to a user's foot according to claim 1, comprising the steps of:

a. inserting the foot in a sports shoe containing the liner and closing the sports shoe at an operating pressure,

b. injecting a plastically deformable filling material inside the at least one deformable hollow insert of the liner by means of a device,

c. maintaining the operating pressure of the sport shoe for custom fitting the at least one deformable hollow insert to the foot by means of the plastic deformation of the filling material until reaching an optimum pressure,

d. if the pressure on the foot at the end of step c) is greater than the optimum pressure, suctioning a portion of the plastically deformable filling material from the at least one deformable hollow insert by means of the device until the optimum pressure is reached,

e. if pressure on the foot at the end of step c) is lower than the optimum pressure, injecting an additional quantity of the plastically deformable filling material into the at least one deformable hollow insert by means of the device until optimum pressure is reached.

8. A sports shoe comprising a liner according to claim 1.