FR3135383A1 - METHOD FOR MANUFACTURING A SPORTS SHOE - Google Patents

Abstract

METHOD FOR MANUFACTURING A SPORTS SHOE A midsole (1) of a sports shoe comprises a body (1) and a shock-absorbing element (3). The body (2) made of polymer material has an upper face and a lower face. The body (2) defines at least one through hole (4) with a side wall connecting the upper face and the lower face. The section of the through hole (4) in the lower face is larger than the section of the through hole (4) in the upper face. The damping element (3) is mounted removable relative to the body (2). The damping element (3) fills the through hole (4) and rests continuously on the side wall. The shock absorber element (3) is arranged in a heel area or in a metatarsal area.

Description

METHOD FOR MANUFACTURING A SPORTS SHOE

The invention relates to a sports shoe midsole, a sports shoe, a method of adapting a sports shoe and to a method of manufacturing a sports shoe sole and a sports shoe. sport.

To practice a sport, it is recognized that it is preferable to use suitable equipment, in particular to reduce the risk of injury. For running, on the track, on the road or on the path, there are many configurations of sports shoes which all have a midsole, an outsole and an insole. The soles are adapted to meet the specific needs of the different sports addressed. The many shoes on the market make it possible to cover the needs of athletes who have different body shapes and in particular feet that are very different from each other.

It is obvious to adapt the length of the sole to the length of the foot. It is also known to make shoes more or less wide so as to better adapt to different widths of feet. Finally, it is known to modify the mechanical performance of the soles so as to distinguish training shoes and competition shoes, shoes for short distances and shoes for longer distances. There have also appeared shoes adapted to more or less heavy people. Finally, manufacturers provide shoes with different drops, that is to say with different inclinations between the heel and the toes. Depending on the type of shoe sought, the sole is modified in its dimensions, in its shape or in its mechanical performance, in particular to provide the most suitable cushioning.

Despite a large offer, it is not always possible to find the most suitable pair of shoes because retailers cannot have all models in stock. There is therefore a compromise to be made between the different parameters when choosing a sports shoe. If the shoe does not fit well, it increases the risk of injury and/or leads to premature wear of at least one of the shoes.

To better adapt a shoe to the needs of its user, it is known to replace the internal sole with a sole whose mechanical performance is different. In particular, insoles are known whose volume differs from the insoles supplied with the shoes so as to better adapt to the shape of the arch of the foot.

Object of the invention

An object of the invention consists of providing a method of adapting a sports shoe to the needs of the user and in particular by allowing better adaptation of the shoe to the characteristics of the user's gait/stride.

According to one aspect of the invention, a method of manufacturing a shoe is proposed comprising the following steps:
- provide a shoe provided with an intermediate sole and an external sole, the intermediate sole having a lower face and an upper face, the external sole being fixed in a non-removable manner to the lower face;
- engrave part of the intermediate sole so as to form a blind hole which extends from the upper face to the outer sole, the hole having a variable section between the lower face and the upper face, the section being measured according to a cutting plane parallel to the upper face, the hole presenting on at least a first part of the thickness of the intermediate sole a reduction in the value of the section in a direction perpendicular to the cutting plane and directed from the lower face towards the upper face, the thickness being measured in said direction perpendicular to the cutting plane;
- insert a damping element into the hole, the damping element having a stiffness different from a stiffness of the engraved part of the intermediate sole, the damping element filling the hole and bearing continuously on the side wall of the hole at least on the first part of the thickness of the midsole.

Advantageously, the method includes acquiring data relating to the walking/stride of a user. The mechanical characteristics of the shock-absorbing element are chosen based on data relating to the user's gait/stride.

In a particular configuration, the data relating to the user's gait/stride comprises at least one of the following data: the user's weight, the determination of a pronator, supinator or neutral stride.

In an advantageous development, data is acquired before etching the midsole.

Preferably, the damping element is formed by 3D printing in the form of a deformable lattice. The characteristics of the deformable mesh are defined using data relating to the user's gait/stride.

According to one embodiment, the hole and the damping element together form an anti-rotation device. The damping element has a different stiffness between a first lateral portion and a second lateral portion, the stiffness being measured in a first direction which connects the lower face and the upper face, a second direction connecting the first lateral portion and the second lateral portion , the second direction being perpendicular to the first direction and perpendicular to the longitudinal axis of the body.

In an advantageous development, the hole presents over at least a second part of the thickness of the intermediate sole an increase in the value of the section in the direction perpendicular to the cutting plane and directed from the lower face towards the upper face, the midsole successively comprising at least the lower face, the first part, the second part and the upper face.

Preferably, the damping element has a shape complementary to the hole.

Summary description of the drawings

Other advantages and characteristics will emerge more clearly from the following description of particular embodiments and implementation of the invention given by way of non-limiting examples and represented in the appended drawings, in which:

: there schematically illustrates a longitudinal sectional view of a first embodiment of an intermediate sole according to the invention;

: there schematically illustrates a longitudinal sectional view of a second embodiment of an intermediate sole according to the invention;

: there schematically illustrates a top view of a first embodiment of a midsole without damping element according to the invention;

: there , schematically illustrates a top view of a first embodiment of an intermediate sole with two shock-absorbing elements according to the invention;

: there , illustrates schematically, in sectional view of a damping element in the form of a spring;

: there , illustrates schematically, in sectional view of a damping element made in two parts;

: there , illustrates schematically, in sectional view of another embodiment of a damping element.

As illustrated in Figures 1 and 2, the midsole 1 of a sports shoe has a body 2 and at least one shock-absorbing element 3. Conventionally, the body 2 is made of a flexible material whose stiffness is adapted to the sought-after practicality of sports shoes. The body 2 of the sole is preferably made of a polymer material and even more preferably in the form of a foam. It is possible to use thermoplastic polyurethane (TPU) foam or expanded thermoplastic polyurethane, EVA foam, a combination of these or another material capable of forming a midsole of a sports shoe.

The midsole 1 is called “midsole” in English. The midsole 1 has an upper face which is intended to be in contact with the internal sole of the shoe or “insole”. The insole is intended to be in direct contact with the user's foot. The insole preferably has insulation and comfort functions. The midsole 1 has a lower face which is intended to be fixed to the outsole also called outsole or “outsole”. The outsole is the sole that is in contact with the ground, it is made of a material that resists aggression from the ground. The outsole is immovably fixed to the midsole 1 and it provides mechanical strength in the directions perpendicular to the direction of thickness, that is to say in the direction of length and in the direction of width. . For example, the outsole is made of rubber, polyurethane, or polyvinyl chloride (PVC). The outsole is made of a material different from the material forming the midsole, preferably in a material which is less compressible than the material forming the midsole, preferably in a solid material, that is to say which is not not a foam. The outsole has greater resistance to abrasion, for example by means of a higher hardness than that of the material forming the midsole 1. The outsole may have greater stiffness than the midsole in the first direction. In a particular embodiment, the midsole 1 and the outer sole are formed monolithicly. The same element forms the outsole and the midsole, for example the sole comes from a single molding step. The outer part of the sole has mechanical properties of the upper part, so as to dissociate the parts forming the outer sole and the midsole.

The body of the intermediate sole 1 defines at least one hole 4 which is intended to receive a shock-absorbing element 3. The body 2 of the intermediate sole 1 defines a hole 4 which may be a blind hole but which is preferably a through hole. The hole 4 extends in a first direction which corresponds to the thickness of the intermediate sole 1, that is to say in a direction which passes through an upper face and a lower face of the sole . The hole 4 preferably extends over at least 50% of the thickness of the intermediate sole 1, preferably over at least 75% of the thickness of the intermediate sole 1 and even more preferably over the entire thickness of the sole. intermediate 1, hole 4 is then a through hole. The greater the thickness of the intermediate sole 1, the greater the modulation of the mechanical characteristics of the intermediate sole 1 will be, and in particular the modulation of the stiffness in a first direction which connects the upper face and the lower face. Body 2 defines a ring which is continuous around hole 4, in an observation along the direction of thickness. The ring formed by the body 2 makes it possible to maintain mechanical continuity which ensures a certain rigidity of the intermediate sole 1. The body 2 can define one or more holes 4, for example under the heel and/or under the metatarsal area. It is also possible to provide that the midsole 1 defines two holes or more than two holes in order to provide greater adaptability of the mechanical performance of the midsole. Advantageously, the hole 4 which is located under the user's heel is a through hole. However, it is also possible that the hole 4 which is located under the metatarsal area is also a through hole so as to be able to install a shock absorber element 3 which offers cushioning better suited to the user. Preferably, the damping element(s) 3 provide cushioning better adapted to the needs of the user under the calcaneus and the metatarsals by allowing shock absorption. The flared shape of the damping elements 3 facilitates the maximum distribution of the shock wave and its transmission to the body 2. The body 2 is preferentially configured to provide dynamic and support properties for the arch of the foot. For example, body 2 may include reinforcements, preferably thermoplastic plates.

The body 2 of the midsole 1 defines a hole 4 which is delimited by a side wall which extends from the upper face to the opposite end, preferably to the lower face. In order to increase the effectiveness of the modulation of the cushioning, it is advantageous to have a shock-absorbing element 3 with a large surface area under the zone(s) of force transmission from the foot. It is therefore advantageous to have a hole 4 which extends as far as possible according to the width of the intermediate sole 1. The width is measured in a direction which connects the internal face and the external face of the intermediate sole 1.

By producing a sole which comprises a body 2 and a shock-absorbing element 3 which are made of different materials, the body 2 and the shock-absorbing element deform differently during walking phases and especially when running. The difference in behavior can cause an unpleasant feeling. It is therefore interesting to control the differential deformation between the body and the damping element 3. It is appropriate to avoid the formation of a side wall which extends substantially perpendicular to the upper face of the intermediate sole because this causes the creation a step between the body and the shock-absorbing element, which is unpleasant, especially during running phases.

To have good mechanical connection between the body 2 and the damping element 3, it is advantageous for the through hole 4 to have a variable section between the lower face and the upper face. The section is measured along a cutting plane parallel to the upper face. More preferably, the through hole presenting on at least a first part of the thickness of the body 2 a reduction in the value of the section in a direction perpendicular to the cutting plane and directed from the lower face towards the upper face. The thickness being measured in the direction perpendicular to the cutting plane. Thus, as we move away from the lower face, the section of hole 4 decreases, in the first part, that is to say there is a narrowing. In the embodiment illustrated in , the first part extends over the entire thickness of the body 2.

The damping element 3 fills the through hole 4 and it bears continuously on the side wall of the hole 4 at least on the first part of the thickness of the body 2. This continuous support between the side wall of the body 2 and the side wall of the damping element 3 allows good transfer of lateral forces between the damping element 3 and the body 2.

Advantageously, the hole 4 has a section in the upper face which is less important than the section in the thickness of the body 2 and less important than the section of the hole 4 at the opposite end preferably when the latter opens into the lower side. The reduced section in the upper face makes it possible to avoid degrading the mechanical properties around the attachment points between the upper and the midsole 1. The large section in the lower face allows for good transfer of energy with the outsole which is more rigid.

Preferably, the damping element 3 has a shape complementary or substantially complementary to that of the hole 4 so as to achieve an effective transfer of forces between the body 2 and the damping element 3 during running phases, jumps and more generally shocks between the foot and the ground. The use of a damping element 3 which has a side wall inclined relative to the upper face of the body of the intermediate sole makes it possible to maintain the damping element 3 in the hole 4 during impacts without forming an annoying zone at the interface between the damping element 3 and the body 2. The use of inclined side walls also makes it possible to modulate the stiffness in the first direction as one moves away from the damping element 3. Such configuration helps avoid a feeling of hardness under the foot. The overlap between the body 2 and the damping element 3 with preferably complementary lateral faces allows a modulation of the stiffness which improves the mechanical interaction between the body 2 and the damping element 3.

Advantageously, the through hole 4 presents over at least a second part of the thickness of the body 2 an increase in the value of the section in the direction perpendicular to the cutting plane and directed from the lower face towards the upper face, c that is to say an enlargement. The body 2 successively comprises at least the lower face, the first part, the second part and the upper face. In other words, the section of the through hole increases as it approaches the upper face. By approaching the upper face, the damping element 3 occupies a more important place which makes it possible to move the interface between the damping element 3 and the body 2 on the lateral edges of the sole, that is to say say in less sensitive places. The side wall of the body can define a convex surface while the side wall of the damping element 3 can define a concave surface. Preferably, the two surfaces are complementary. In an embodiment illustrated in , in section in the transverse direction, the damping element 3 is in the form of an hourglass, that is to say with two trapezoids substantially opposed by their small bases. This embodiment is more advantageous than the configuration illustrated in because this makes it possible to better manage the differences in stiffness between the damping element 3 and the body 2 and particularly when body 2 is made of a more rigid material than the damping element 3. The damping element 3 has a restriction zone where its section is reduced which makes it possible to form a complementary zone where the body 2 has a larger section which allows better mechanical strength.

The side wall may be planar or substantially planar. The inclination of the side wall allows an increasing increase in the hole section from the upper face to the opposite end. In another embodiment, the side faces are textured, they can define hollows and bumps. It is preferable that the side walls of the hole 4 and the damping element 3 are complementary to fix the damping element in the body in the length direction, in the width direction as well as in the thickness direction and better distribute the forces between the damping element 3 and the body 2.

It is advantageous to have continuous contact between the side wall of the absorber element 3 and the side wall of the body 2 over the entire height of the hole 4 and over the entire perimeter of the hole 4 so as to have an absorber element 3 maintained fixedly in body 2 and which effectively transfers the forces with body 2.

The body 2 and the absorber element 3 are formed by elastically deformable materials and which have different stiffnesses depending on the direction of thickness. When walking or running, the body 2 and the absorber element 3 deform differently. The body 2 and the absorber element 3 are made of compressible materials, for example foams. The absorber element 3 can be formed from a single material, but it is also possible to use a composite material, a combination of several foams and possibly a foam and gel combination.

By installing a shock absorber element 3 better adapted to the biomechanical specificities of the user, this makes it possible to adapt the performance of the midsole 1 of a shoe to the needs of its user. There is an interest in adapting a running shoe, but it is also possible to adapt the mechanical performance of a walking shoe, a racket sports shoe or an indoor sports shoe. In all these configurations, there is an interest in better adapting the mechanical performance of the midsole 1 to the specificities of the user. It is advantageous to use a damping element 3 which has a greater viscoelastic character than that of the material forming the body 2.

It is preferable that the hole 4 extends as much as possible in the direction of width in order to receive the forces provided by the foot and mainly from the heel or the metatarsal area without disturbing the fixing zone between the body 2 and the upper . To facilitate energy dissipation, it is preferable that the damping element 3 extends as much as possible in the direction of width inside the body 2, it is advantageous that the damping element 3 extends under the attachment zones between the body 2 and the upper, for example under the seams (in the first direction).

In a preferred embodiment, the ratio between the width of the hole 4 in the upper face and the width of the hole 4 at the opposite end is greater than 0.5, preferably greater than 0.7 and advantageously less than 0.9 . The width is measured in a second direction which is perpendicular to the first direction and which is also perpendicular to the longitudinal direction of the midsole 1. The longitudinal direction of the midsole 1 corresponds to the direction of the largest dimension of the sole which corresponds to the direction that connects the heel to the toes. The dimension ratio between the top of the hole (the upper face) and the bottom of the hole (the opposite end) can have another value along the longitudinal axis. The damping element 3 has a ratio between the dimension of the top of the hole and the dimension of the bottom of the hole along the longitudinal axis which is different from the ratio along the transverse axis.

In a particular embodiment illustrated in Figures 1 and 2, the hole 4 is in the form of a truncated cone, that is to say it defines an axis of symmetry which is parallel to the first direction . In a sectional view according to the thickness of the midsole 1, the hole 4 is in the form of a trapezoid. The angle of inclination of the side wall relative to the first direction is constant. Alternatively, the side wall can define a curve or stairs or other shapes.

It is possible to have side walls with more complex shapes, for example with notches so as to better fix the damping element 3 in the hole 4.

In a preferred embodiment, the angle of inclination of the side wall relative to the first direction is different depending on whether a section is observed in the longitudinal direction or in the second direction. It is preferable that the angle of inclination in the cut in the second direction is greater in the longitudinal direction.

The damping element 3 is elastically deformable under the effect of stress in the first direction. The damping element 3 can be in the form of a foam, for example an EVA foam, a thermoplastic polyurethane foam. The damping element 3 can also be a polymer spring obtained by 3D printing or a gel. It is also possible to combine these materials in order to modulate the characteristics of the shock-absorbing element 3 with respect to the cushioning and reactivity of the sole or the recovery of the sole. It is advantageous to form a damping element in the form of a lattice and whose side wall is continuous, that is to say without holes. By 3D printing, we mean an additive method in which material is added in successive layers to form a predefined three-dimensional model as well as a subtractive method in which a block of material is engraved to define the predefined three-dimensional model.

The damping element 3 fills the hole 4 and rests continuously on the side wall. Preferably, the damping element 3 is mounted removable relative to the body 2. The damping element 3 is mounted removable which allows it to be replaced by another damping element 3 which is more adapted to the needs of the user in order to better adapt the performance of the sole to the specificities of the user. This also makes it possible to replace the damping element 3 when the latter is worn, for example when the Young's modulus of the damping element 3 or the stiffness in the first direction has decreased by 10%.

As it is used, the shoe deteriorates. However, the degradation of multiple components of the shoe is not uniform. The area of the midsole 1 located under the heel supports the vast majority of shocks, which leads to preferential wear of this part of the shoe compared to the other components. By allowing the dismantling of a shock-absorbing element 3 which is located in the midsole under the heel, it becomes easier to replace the shock-absorbing element 3 when the latter is worn. It can be the same under the metatarsal area.

The shock absorber element 3 can then be replaced, which allows the shoe to be used for a new cycle of use. The replacement of the shock-absorbing element 3 makes it possible to form a shoe suitable for its original use. Replacing the shock-absorbing element 3 reduces the ecological footprint of the shoe by only replacing the element considered worn.

The use of an intermediate sole 1 provided with a shock absorber element 3 removable relative to the body 2 makes it possible to replace the shock absorber element 3 with another which has a stiffness better suited to the needs of the user. During its manufacture, the midsole 1 is configured for a user of a predefined weight (reference weight). The stiffness of the midsole 1 and more particularly the area under the heel is dimensioned in order to withstand the shocks resulting from the running phases for a user having the predefined weight. However, when the user is heavier, the cushioning provided by the sole may be insufficient, which can lead to injuries. Conversely, when the user is lighter, the sole does not respond as expected because it becomes too rigid. It is therefore interesting to be able to quickly and easily modulate the mechanical performance of the sole and preferably the area under the heel or the metatarsal area.

In one embodiment, the damping element 3 has a difference in stiffness between a first lateral portion and a second lateral portion. The two side portions are adjacent in width. The use of a damping element 3 which has a difference in stiffness between a first lateral portion and a second lateral portion is particularly advantageous in order to regulate the phenomena of walking/stride in pronation or supination. By using the adapted damping element 3, it is possible to increase the stiffness of the internal portion of the midsole relative to the external portion or to reduce the stiffness of the internal portion of the midsole relative to the external portion. . The use of an intermediate sole 1 having a hole 4 which allows the dismantling of the shock-absorbing element 3 is particularly interesting for better adapting the mechanical characteristics of the shoe to a pronating stride or a supinating stride. Furthermore, each shoe can be modified independently of the other, it is possible to adapt one shoe to a type of stride chosen from a pronator, supinator or neutral stride and to independently adapt the other shoe to a type of stride chosen from a pronator, supinator or neutral stride.

In a particular embodiment, the hole 4 and the damping element 3 together form an anti-rotation device configured to prevent the rotation of the damping element 3 in the hole 4 around an axis substantially parallel to the first direction. The use of an anti-rotation device is particularly advantageous when the damping element 3 has a difference in stiffness between a first lateral portion and a second lateral portion. The difference in stiffness is measured according to the width, that is to say according to the second direction which is perpendicular to the direction which connects the lower face and the upper face of the sole 1. During repeated shocks linked to the running phases or when walking, the damping element 3 deforms. The anti-rotation means prevent the forces applied to the damping element 3 from rotating the damping element 3 in the hole 4.

Preferably, the damping element 3 which has a difference in stiffness between a first lateral portion and a second lateral portion can be installed in the hole 4 in a first position or in a second position. The first position can be adapted to a pronator walk/stride while the second position can be adapted to a supinator walk/stride. The anti-rotation means prevent the rotation of the damping element 3 when the latter is in the hole.

In a particular embodiment, the damping element 3 is a foam. In another embodiment, the damping element 3 is a deformable lattice. It is advantageous to have a deformable lattice which defines a first stiffness in the first direction different from a second stiffness in the second direction. The first direction connects the lower face and the upper face, the second direction is perpendicular to the first direction and perpendicular to the longitudinal axis of body 2.

The use of a deformable lattice is particularly advantageous because it is possible to form an anisotropic damping element 3 and preferably a strongly anisotropic damping element 3. It is particularly advantageous to form a lattice whose Young's modulus in the second direction is lower than the Young's modulus in the first direction. It is then easy to deform the damping element 3 in the second direction in order to facilitate its installation in the hole 4. Once in place, the damping element 3 is mainly stressed in the first direction. For example, the Young's modulus or the stiffness in the second direction is less than the Young's modulus or the stiffness in the first direction by at least 30%.

Particularly advantageously, the damping element 3 in lattice is formed by 3D printing, preferably using an additive method which makes it possible to adapt the mechanical characteristics of the lattice to the needs of the user, in particular its stiffness in the first direction. It is also possible to adapt the chemical composition of the material to the needs of the user, in particular to obtain the desired stiffness in the first direction. The trellis is tailor-made to adapt to the user's specifications as closely as possible.

In another embodiment, the damping element 3 is formed by an isotropic element, for example in the form of a gel or a foam. It is possible to combine the use of a deformable mesh and a foam or gel in order to more finely adapt the mechanical characteristics of the damping element 3.

In a preferred embodiment, the damping element 3 is formed by at least first and second parts, the first part 3a being inseparable from the body 2 when the second part 3b is installed in the hole 4. When the damping element 3 has a significant stiffness and in particular a significant stiffness in the second direction and/or the longitudinal direction, it is advantageous to divide the damping element 3 into several distinct parts 3a/3b. The first part 3a is installed in the hole, then the second part 3b is installed in the hole 4 so as to block the first part 3a in the hole 4. It is also possible to provide for the damping element 3 to be formed by a plurality of foam and/or gel elements which have different mechanical properties and some of these elements are removable from others. Once the mechanical characteristics of the damping element 3 have been defined according to the first direction, it is possible to choose the correct set of elements to form the damping element 3.

In a particular embodiment illustrated in , the first part 3a and the second part 3b have different stiffnesses in the first direction which makes it possible to form a shock-absorbing element 3 with different stiffnesses between the first lateral portion and the second lateral portion, for example to manage pronating strides or supinators.

It is particularly advantageous to form a sports shoe which has an intermediate sole 1 according to one of the configurations presented above. In the case where the body 2 of the intermediate sole 1 defines a through hole 4, the external sole closes the through hole 4 so that the association of the intermediate sole 1 and the external sole defines a blind hole. The shock absorber element 3 rests on the external sole. It is particularly advantageous to have a through hole because the forces are better managed between the damping element 3 and the body 2.

In order to more precisely adapt the mechanical performance of the midsole 1 to the specific characteristics of the user, it is advantageous to determine one or more characteristics relating to the use of the shoe.

In order to better adapt the mechanical performance of the sole and therefore of the shoe to the needs of the user, it is advantageous to determine the weight of the user. Once the user's weight is known, it is possible to compare the value obtained with a reference value, that is to say the current value of the midsole 1.

When the user's weight does not correspond to the reference weight or the reference weight range, the damping element 3 must be replaced by another damping element 3 whose stiffness is better suited, i.e. say a damping element 3 whose reference weight corresponds to or includes the weight of the user.

As an alternative or in addition, it is advantageous to determine the user's experience which can condition their running technique and therefore the need for cushioning. The mechanical characteristics of the damping element 3 depend on the user's experience. The lower the experience, the more advantageous it is to have cushioning. The stiffness of the damping element is at least a function of a parameter representative of the user's experience.

As an alternative or in addition, it is advantageous to determine whether the shoe is intended to cover short distances, for example less than 10 km, or if, on the contrary, the shoe is intended for greater distances, for example more than 20 km. It is also beneficial to know your weekly mileage. It is advantageous to provide more cushioning for long distances compared to short distances. Once the average distance of the stroke is known, it is possible to replace the damping element 3 with another damping element 3 whose stiffness is better suited. It is advantageous to combine this information with the weight of the user in order to provide an even more suitable damping element 3. The mechanical characteristics of the shock absorber element 3 depend on the mileage per outing and the weekly mileage. The greater the mileage, the more beneficial it is to have cushioning. The stiffness of the damping element is at least a function of a parameter representative of the average or weekly distance intended to be covered by the user.

As an alternative or in addition, it is advantageous to determine whether the shoe is intended for training or competition, that is to say whether the shoe must have high reactivity or low reactivity. Once the use of the shoe has been determined, it is advantageous to determine the most suitable mechanical characteristics for the shock-absorbing element. It is also possible to determine the type of terrain (flat or textured) as well as the elevation.

Depending on the information provided by the user, it is then possible to modify the mechanical performance of the damping element so as to adapt more finely to the user's needs.

Since the adaptation is carried out independently for each shoe, it is possible to make different modifications between the two shoes.

Modifying the midsole 1 to better adapt its mechanical performance to the needs of the user is more advantageous than modifying the insole because the available thickness is greater. It also appears that the modification of the midsole is compatible with the use of a tailor-made insole to adapt to the morphology of the foot. The modification of the midsole 1 makes it possible not to modify the internal volume of the shoe.

As an alternative or in addition, to better adapt the technical characteristics of the sole, it is advantageous to define the characteristics of the stride. It is beneficial to determine the user's gait/stride characteristics. If the analysis of the stride determines that the gait/stride is pronator or supinator, it is advantageous to modify the characteristics of the damping element 3 in order to adapt the mechanical characteristics in the second direction to the characteristics of the gait/stride. Depending on whether the attack of the walk/stride is carried out by the heel or by the middle of the foot, the characteristics of the shock-absorbing element 3 are modified so as to define the value of the stiffness and therefore the necessary cushioning. There is therefore an interest in taking images of the gait/stride to analyze the gait/stride and determine the characteristics which define the damping element 3.

To adapt a sports shoe, it is useful to have an adaptation process which includes the following steps:
- provide a shoe according to any of the preceding configurations;
- acquire data relating to a user's walk/stride;
- determine the mechanical characteristics of a shock-absorbing element to adapt to the user's gait/stride
- remove the shock absorber element 3 from the shoe;
- introduce a new damping element 3 according to the data acquired, the new damping element 3 being better adapted to the user's walking/stride.

Preferably, the data relating to the user's gait/stride comprises at least one of the following data: the user's weight, the determination of a pronator, supinator or neutral gait/stride. It is also advantageous if the data includes the determination of the expected distance to be covered (average or weekly) and the determination of the attack of the foot during the user's walk/stride.

Once the gait/stride analysis has been carried out, this information is transmitted to a processing circuit which proposes to install one or more damping elements 3 in the midsole 1. The processing circuit indicates which type of damping element 3 must be installed.

Preferably, the new damping element 3 is formed by 3D printing in the form of a deformable lattice. The characteristics of the deformable mesh are defined using the user's gait/stride data. The processing circuit can provide the plans of the lattice to the 3D printing device which will form the damping element 3 according to the information collected.

As there are a multitude of shoe models, it is particularly interesting to use 3D printing in order to form the shock-absorbing element 3 so as to adapt the mechanical performance of the shock-absorbing element 3 to the space available in the hole. 4 of body 2. The volume of hole 4 can change from one model to another, from one size to another. It is therefore advantageous to identify the type of shoe so as to identify the dimensions of the hole as well as the mechanical characteristics of the body 2 of the sole. The mechanical characteristics of the shock-absorbing element 3 will be defined according to these data to best integrate the shock-absorbing element 3 into the sole as well as to adapt the sole to the needs of the user.

In one case, the shape of the hole 4 is defined during the manufacture of the midsole 1, preferably before its attachment to the upper and/or its attachment to the outsole. Hole 4 has a height (the dimension in the first direction) and transverse dimensions which are predefined and correspond to a shape imposed for this sole model. It is then possible to form one or more damping elements 3 with different stiffnesses to quickly adapt the performance of the sole and to choose the most suitable damping element 3 based on the information obtained from the user.

In a first embodiment, the damping element 3 or a pad representing the damping element 3 is installed in a mold. The polymer material(s) intended to form the body 2 are introduced into the mold and form the body 2 around the damping element 3. The damping element 3 opens at least onto the upper face of the intermediate sole 1. The element shock absorber 3 or a stud representing the shock absorber element 3 defines the hole 4. It is advantageous to manufacture the shoe with the shock absorber element 3 rather than the stud so that the shoe can be used immediately. The midsole 1 is substantially identical to a sole of the prior art, which avoids significantly modifying the shoe manufacturing processes.

The midsole 1 is fixed to the lower sole in a conventional manner, for example by gluing. It is advantageous to add a separation layer between the shock-absorbing element 3 and the layer of glue which is intended to fix the intermediate sole 1 with the lower sole. The separation layer makes it easier to remove the damping element 3 by preventing the damping element 3 from sticking with the lower sole. Alternatively, it is always possible to remove the damping element 3 by etching before installing a new damping element 3.

This embodiment is simple to implement and it makes it possible to have a process for manufacturing midsole 1 which is close to those of the prior art.

The midsole 1 is attached to the upper as well as to the other elements of the sports shoe as is done in the manufacturing processes of the prior art. To access the shock absorber element 3, simply remove the insole. We remove the damping element 3 and replace it with a more suitable damping element 3. We can then reinstall the insole.

In another embodiment, the midsole 1 was initially manufactured without defining a hole 4. It is then possible to define a hole 4 and preferably a through hole 4 by eliminating a part of the body 2 of the midsole 1. In one embodiment, the hole 4 is formed before fixing the midsole 1 with the outsole and/or the upper. In another embodiment, the shoe is finished or the shoe has already been worn or even used, it includes the lower sole and the upper.

The hole 4 in the intermediate sole 1 is formed by any means suitable for engraving the body 2, for example by means of a drill or a milling cutter. It is particularly advantageous to use a template which will make it possible to define the precise position of hole 4, as well as its depth and its shape. The combination of a predefined drill bit with a predefined template makes it possible to control the depth of hole 4 so as not to weaken the outsole. This also makes it possible to form the hole 4 most suited to the configuration of the shoe, that is to say a hole 4 which makes it possible to install a shock-absorbing element 3, that is to say whose dimensions according to the first direction and perpendicular to the first direction ensure to have a notable effect on the modification of the stiffness in the first direction without degrading the mechanical performance of the intermediate sole 1 in the second direction and in the longitudinal direction.

In a particular embodiment, the dimensions of the hole are unknown, for example the hole was engraved in the intermediate sole 1 from its upper face. It is advantageous to make a three-dimensional optical impression of the hole in order to know its exact shape. Once the shape is known and the data relating to the user's stride known, it is possible to define which type of damping element 3 is most suitable. Preferably, a determination of the stiffness of the body of the sole is carried out in order to form a shock-absorbing element which takes into account the mechanical performance of the body which surrounds it. When the sole is known, this information can be present in the memory of the processing device and taken into account in the definition of the technical characteristics of the damping element 3.

In one embodiment, hole 4 is formed by engraving after having acquired the data relating to the user (weight, stride, mileage, etc.). It is possible to use this data to adapt the shape of hole 4. It is then advantageous to use a damping element formed by 3D printing.

The damping element 3 is inserted into the hole 4 to modify the mechanical behavior of the midsole 1. The damping element 3 has a stiffness different from the stiffness of the engraved part of the midsole 1.

Conventionally, the midsoles 1 of running shoes are made of EVA foam for ethylene vinyl acetate. This material provides a very good compromise between mass and cushioning, i.e. good shock absorption. However, the manufacturing process of an EVA sole is quite difficult to master and it generates a significant environmental impact. There is therefore an interest in limiting the use of such a material as much as possible. There are also shoes whose midsole 1 is made of thermoplastic polyurethane, but the performance is less good.

The use of an intermediate sole 1 such as that which was presented above makes it possible to differentiate the mechanical performances of the sole, according to the first direction, for different portions of the sole. It is possible to differentiate the mechanical performances of the midsole 1 between the heel zone and the arch zone and/or between the metatarsal zone and the arch zone.

In order to provide a sports shoe sole that is pleasant to use, it is particularly advantageous to have significant cushioning under the heel and/or under the metatarsal area. On the other hand, the cushioning requirements are less important under the arch of the foot, under the toes and all around the sole. It is therefore particularly advantageous to form a body 2 in a material other than EVA foam and to add to it a damping element 3 made from EVA foam. For example, the body 2 of the midsole 1 is made of thermoplastic polyurethane foam or of another material which is different from EVA and the shock-absorbing element 3 is made of EVA foam. Such an association makes it possible to form a running shoe sole made mainly of polyurethane foam with the same level of cushioning as a foam sole formed exclusively or almost exclusively in EVA. In a particular embodiment, the body 2 is made of a polymer material other than EVA and thermoplastic polyurethane foam. The damping element 3 is made of EVA and/or thermoplastic polyurethane or deformable mesh. Body 2 is made of a material which has less damping than the material forming the damping element 3. Body 2 is made of a material which provides greater mechanical rigidity so as to better withstand lateral forces. It is advantageous for the body to be free of EVA and even more preferably free of EVA and expanded thermoplastic polyurethane.

In a particular embodiment, the EVA foam damping element is not removable relative to the body 2 of the midsole 1. The EVA foam element can be replaced by a damping element 3 made of three-dimensional printing with a lattice (lattice) which defines a porous network. The lattice makes it possible to form a damping element 3 which has a Young's modulus or a stiffness greater in the direction of the thickness of the sole than the Young's modules or a stiffness in the direction of the length and in the direction of the width.

The EVA foam damping element 3 is installed in a mold and the body 2 is formed around the EVA foam damping element 3. The damping element 3 extends from one end to the other of the body 2 in the direction of the thickness. The damping element 3 and the body 2 have complementary shapes which facilitates the transfer of forces between the damping element 3 and the body 2. As indicated above, the side walls are inclined which allows better transfer of forces between the damping element 3 and the body 2. If a stud representative of the damping element 3 is used, the stud is removed after forming the body to be replaced by the damping element in EVA, in expanded thermoplastic polyurethane or in the form of a deformable lattice.

Claims (8)

Process for manufacturing a shoe comprising the following steps:
- provide a shoe provided with an intermediate sole (1) and an external sole, the intermediate sole (1) having a lower face and an upper face, the external sole being fixed in an unremovable manner to the lower face;
- engrave part of the intermediate sole (1) so as to form a blind hole (4) which extends from the upper face to the outer sole, the hole (4) having a variable section between the lower face and the upper face, the section being measured along a cutting plane parallel to the upper face, the hole (4) presenting on at least a first part of the thickness of the intermediate sole (1) a reduction in the value of the section in a direction perpendicular to the cutting plane and directed from the lower face towards the upper face, the thickness being measured in said direction perpendicular to the cutting plane;
- insert a damping element (3) into the hole (4), the damping element (3) having a stiffness different from a stiffness of the engraved part of the midsole (1), the damping element (3) filling the hole (4) and bearing continuously on the side wall of the hole (4) at least on the first part of the thickness of the intermediate sole (1). Method of manufacturing a shoe according to the preceding claim comprising acquiring data relating to the gait/stride of a user and in which the mechanical characteristics of the damping element (3) are chosen as a function of the data relating to the gait/stride user's stride. Method of manufacturing a shoe according to the preceding claim in which the data relating to the user's gait/stride comprises at least one of the following data: the user's weight, the determination of a pronating stride, supinator or neutral. Method of manufacturing a shoe according to one of claims 2 and 3 in which the data is acquired before engraving the midsole. Method of manufacturing a shoe according to any one of the preceding claims in which the damping element (3) is formed by 3D printing in the form of a deformable lattice and in which the characteristics of the deformable lattice are defined by means of data relating to the user's gait/stride. Method of manufacturing a shoe according to any one of the preceding claims in which the hole (4) and the damping element (3) together form an anti-rotation device and in which the damping element (3) has a stiffness different between a first lateral portion and a second lateral portion, the stiffness being measured in a first direction which connects the lower face and the upper face, a second direction connecting the first lateral portion and the second lateral portion, the second direction being perpendicular to the first direction and perpendicular to the longitudinal axis of the body (2). Method of manufacturing a shoe according to any one of the preceding claims in which the hole (4) presents over at least a second part of the thickness of the body (2) an increase in the value of the section in the perpendicular direction to the cutting plane and directed from the lower face towards the upper face, the body (2) successively comprising at least the lower face, the first part, the second part and the upper face. Method of manufacturing a shoe according to any one of the preceding claims in which the shock-absorbing element (3) has a shape complementary to the hole (4).