SOLE STRUCTURE AND SHOES USING SAME

Abstract

An outsole includes: a first stud projecting downwards in a stationary manner in a vertical direction from a reference surface and having a first projection surface; and a second stud having a second projection surface. The second stud moves in the vertical direction so that, when an external force acts on the second projection surface, the outsole hollow is compressively transformed and the second projection surface comes close to the reference surface.

Claims

1. A sole structure for a shoe, the sole structure comprising a midsole made of an elastic material, and an outsole overlaid on a lower side of the midsole, the outsole including: a reference surface provided on a lower side of the outsole; a first stud projecting downwards and in a stationary manner in a vertical direction from the reference surface, and having a first projection surface positioned below the reference surface; and a second stud being provided adjacent to the first stud and projecting downwards from the reference surface, the second stud having a second projection surface positioned below the first projection surface, the second stud being provided with an outsole hollow positioned on an upper side of the second stud and defined between an outsole recess set back into an upper face of the outsole and a lower portion of the midsole, and the second stud being configured to be movable in a vertical direction so that, when an external force acts on the second projection surface, the outsole hollow is compressively transformed and the second projection surface comes close to the reference surface.

2. The sole structure of claim 1, wherein the second stud is formed so that a thickness of the second stud from the second projection surface to a bottom of the outsole recess is greater than a depth of the outsole recess.

3. The sole structure of claim 1, wherein the second stud is formed so that a surface area of the second projection surface is smaller than an opening area of the outsole recess.

4. The sole structure of claim 1, wherein the outsole recess curves to be substantially concave over a region from an opening to a bottom of the outsole recess.

5. The sole structure of claim 1, wherein the outsole hollow includes an outsole rib extending upwards from the bottom of the outsole recess toward the midsole, the outsole rib being transformable when the external force acts on the second projection surface.

6. The sole structure of claim 1, further comprising a plurality of reinforcements arranged on an outer periphery of the second stud, spaced apart from each other in a circumferential direction of the second stud, and formed integrally with the second stud and the reference surface.

7. A sole structure for a shoe, the sole structure comprising a midsole made of an elastic material, and an outsole overlaid on a lower side of the midsole, the outsole including: a reference surface provided on a lower side of the outsole; a first stud projecting downwards in a stationary manner in a vertical direction from the reference surface, and having a first projection surface positioned below the reference surface; and a second stud being provided adjacent to the first stud and projecting downwards from the reference surface, the second stud having a second projection surface positioned below the first projection surface, the midsole being provided with a midsole hollow positioned on a lower side of the midsole and defined, in a position facing an upper side of the second stud, between a midsole recess set back into a lower surface of the midsole and an upper portion of the outsole, the second stud being configured to be movable in a vertical direction so that, when an external force acts on the second projection surface, the second projection surface comes close to the reference surface.

8. The sole structure of claim 7, wherein the second stud is formed so that a surface area of the second projection surface is smaller than an opening area of the midsole recess.

9. The sole structure of claim 7, wherein the second stud being provided with an outsole hollow positioned on an upper side of the second stud and defined between an outsole recess set back into an upper face of the outsole and a lower portion of the midsole, and the second stud being configured to be movable in a vertical direction so that, when an external force acts on the second projection surface, the outsole hollow is compressively transformed and the second projection surface comes close to the reference surface.

10. The sole structure of claim 9, wherein the midsole hollow is provided with a midsole rib extending downwards from a bottom of the midsole recess toward the outsole, and the outsole hollow is provided with an outsole rib extending upwards from a bottom of the outsole recess toward the midsole, and making contact with a lower end of the midsole rib.

11. The sole structure of claim 7 wherein the midsole hollow is provided with an elastic soft member.

12. A shoe comprising the sole structure of claim 1.

13. A shoe comprising the sole structure of claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a bottom plan view of a sole structure according to a first embodiment of the present invention.

[0036] FIG. 2 is a partially enlarged plan view illustrating an X part of FIG. 1 on an enlarged scale.

[0037] FIG. 3 is a cross-sectional view taken along line III-III shown in FIG. 2.

[0038] FIG. 4 corresponds to FIG. 3 and shows a sole structure according to a second embodiment of the present invention.

[0039] FIG. 5 corresponds to FIG. 2 and shows a sole structure according to a third embodiment of the present invention.

[0040] FIG. 6 corresponds to FIG. 3 and shows a sole structure according to the third embodiment of the present invention.

[0041] FIG. 7A is a bottom plan view and a cross-sectional view schematically illustrating a variation in the shape of a second stud.

[0042] FIG. 7B is a bottom plan view and a cross-sectional view schematically illustrating a variation in the shape of the second stud.

[0043] FIG. 8A is a bottom plan view and a cross-sectional view schematically illustrating another variation in the shape of the second stud.

[0044] FIG. 8B is a bottom plan view and a cross-sectional view schematically illustrating another variation in the shape of the second stud.

[0045] FIG. 8C is a bottom plan view and a cross-sectional view schematically illustrating another variation in the shape of the second stud.

[0046] FIG. 9 is a bottom plan view of a sole structure according to a fourth embodiment of the present invention.

[0047] FIG. 10 is a lateral view of a sole structure seen from a medial side according to the fourth embodiment of the present invention.

[0048] FIG. 11 is a cross-sectional view taken along line XI-XI in FIG. 9.

[0049] FIG. 12 is a partial cross-sectional view illustrating the portion XII in FIG. 11 on an enlarged scale.

[0050] FIG. 13 corresponds to FIG. 12 and illustrates a state where an external force acts on a projection surface of a second stud illustrated in FIG. 12.

[0051] FIG. 14 is a partial bottom view schematically illustrating, on an enlarged scale, the second stud of a sole structure according to a fifth embodiment of the present invention.

[0052] FIG. 15 is a cross-sectional view taken along line XV-XV in FIG. 14.

[0053] FIG. 16 corresponds to FIG. 15 and illustrates a cross-sectional structure around the second stud as a sole structure according to a sixth second embodiment of the present invention.

[0054] FIG. 17 is a partially-enlarged cross-sectional view illustrating a cross-sectional structure around the second stud in a variation of the sole structure according to the fourth embodiment of the present invention.

[0055] FIG. 18 is a partially-enlarged cross-sectional view illustrating a cross-sectional structure around the second stud in a variation of the sole structure according to the fifth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0056] Embodiments of the present invention will now be described in detail with reference to the drawings. Note that the following description of the embodiments is a mere example in nature, and is not intended to limit the scope, application, or uses of the present invention.

First Embodiment

[0057] FIGS. 1 to 3 illustrate an overall configuration of a sole structure 1 according to a first embodiment of the present invention. The sole structure 1 is configured to support a plantar surface of a wearer. A pair of shoes including this sole structure 1 provided with a shoe upper (not shown) may be used, for example, as shoes to be used for various ground surfaces in various sports such as trail running on uneven grounds or ball games on the dirt or on the grass. Note that the road surface is not limited to leveled grounds such as general roads paved with asphalt, and includes uneven grounds such as a sand pool, a grassy area, a rocky area, and a wet area.

[0058] The drawings show the sole structure 1 for a left shoe only. A sole structure for a right shoe is symmetrical to the sole structure 1 for the left shoe. In the following description, only the sole structure 1 for the left shoe will be described and the description of the sole structure for the right shoe will be omitted.

[0059] In the following description, the expressions above, upwards, on a/the top of, below, under, and downwards, represent the vertical positional relationship between components of the sole structure 1. The expressions front, fore, forward, rear, back, hind, behind, and backward represent the positional relationship in the longitudinal direction between components of the sole structure 1.

[0060] As illustrated in FIG. 1, the sole structure 1 includes a midsole 2 which supports the entire plantar surface of the foot from the forefoot to the hind foot. The midsole 2 is made from a soft elastic material. Non-limiting suitable examples of the material for the midsole include thermoplastic resins such as ethylene-vinyl acetate copolymer (EVA) and foams of the thermoplastic resins, thermosetting resins such as polyurethane (PU) and foams of the thermosetting resins, and rubber materials such as butadiene rubber and chloroprene rubber and foams of the rubber materials. Note that a shoe upper (not shown) for covering the wearer's foot is attached to a peripheral portion of the midsole 2.

[0061] The sole structure 1 includes an outsole 3 overlaid on the lower side of a midsole 2. The outsole 3 is arranged over an area corresponding to a region extending from the forefoot to the hindfoot of the wearer's foot. The outsole 3 is made of a hard elastic material which is harder than the material for the midsole 2. Examples of materials suitable for the outsole 3 include, but are not limited to, thermoplastic resins such as ethylene-vinyl acetate copolymer (EVA), thermosetting resins such as polyurethane (PU), and rubber materials such as butadiene rubber and chloroprene rubber.

[0062] Referring to FIGS. 1 to 3, the outsole 3 illustrated therein has a reference surface 4 formed on a lower side of the outsole 3. The reference surface 4 functions as a main ground surface at a moment when the sole structure 1 makes contact with the ground surface during wearer's running or walking.

[0063] First studs 11 and second studs 12, which are different in projection height, are provided on the reference surface 4 of the outsole 3. According to the first embodiment, a plurality of groups of studs (a stud group 10) are spaced apart from each other and provided on the reference surface 4 of the outsole 3. Each of the stud groups 10 is a combination of the first studs 11, 11, . . . with a second stud 12. These stud groups 10 are appropriately positioned in relation to the wearer's foot As shown in FIG. 1, the first studs 11, 11, . . . are not necessarily included in the stud groups 10. Alternatively, the first studs 11, 11, . . . may be arranged alone and provided in different locations from those of the stud groups on the reference surface 4 of the outsole 3.

[0064] As shown in FIG. 2 and FIG. 3, in one of the stud groups 10, the first studs 11 described above project downwards from the reference surface 4. The first studs 11, 11, . . . are arranged around each of second studs 12 described later, and spaced apart from each other in a circumferential direction of the second stud 12. For example, each of the first studs 11 is made of the same material as that of the outsole 3, and formed integrally with the outsole 3 so that the first studs 11 are stationary in a vertical direction with respect to the reference surface 4. Each of the first studs 11 is formed in a substantially triangular shape (a substantially isosceles triangle) tapering toward the radial outside of the second stud 12 in bottom view. Note that the statement stationary in a vertical direction also means, for example, a configuration in which the first studs 11 slightly move in a vertical direction with respect to the reference surface 4 through elastic transformation of at least one of the midsole 2 and the outsole 3. In other words, the first studs 11 may be substantially stationary in a vertical direction with respect to the reference surface 4.

[0065] Each stud 11 has, on a lower portion thereof, a substantially flat projection surface 11a. Specifically, the first projection surface 11a has an outline shaped into a substantially isosceles triangle in bottom view, and is located (a position H1 of FIG. 3) below the reference surface 4 (a position H0 of FIG. 3). In other words, the first stud 11 is formed to have a projection height of a dimension h1 (see FIG. 3).

[0066] As shown in FIGS. 2 and 3, the reference surface 4 has a base 5 projecting downwards and shaped into a substantial circle. In bottom view, the base 5 is formed integrally with each of the first studs 11 so that the outer periphery of the base 5 is continuously formed with an end side 11b of each first stud 11 (a portion corresponding to a bottom side of the isosceles triangle).

[0067] In one of the stud groups 10, the above second stud 12 in bottom view is positioned in the center of the base 5. The second stud 12 is shaped into a substantial cylinder, and projects downwards from the base 5. For example, the second stud 12 is made of the same material as that of the outsole 3, and formed integrally with the base 5 so that the second stud 12 is movable in a vertical direction with respect to the reference surface 4. Each of the second studs 12 is tapered downwards from the base 5, in cross section.

[0068] The second stud 12 has, on a lower portion thereof, a substantially flat second projection surface 12a. The second projection surface 12a has an outline shaped into a substantial circle in bottom view (see FIG. 2). The second projection surface 12a is positioned (a position H2 of FIG. 3) below the first projection surface 11a (a position H1 of FIG. 3) of each of the first studs 11. In other words, the second stud 12 is formed to have a projection height of a dimension h2 (see FIG. 3).

[0069] As illustrated in FIG. 3, the second stud 12 is provided with an outsole recess 13 positioned on an upper side of the second stud 12, and set back into an upper face of the outsole 3. Specifically, the outsole recess 13 is provided directly above the second projection surface 12a, and curves to be substantially concave over a region from an opening 13a toward a bottom 13b of the outsole recess 13. The second stud 12 is provided with an outsole hollow 14 positioned on an upper side of (directly above) the second stud 12 and defined between the outsole recess 13 and a lower portion of the midsole 2.

[0070] The second stud 12 is formed so that a thickness of the second stud 12 from the second projection surface 12a to the bottom 13b of the outsole hollow 13 (a dimension A of FIG. 3) is greater than a depth of the outsole recess 13 (a dimension B of FIG. 3). Furthermore, the second stud 12 is formed such that a surface area of the second projection surface 12a (an area of a circle having a dimension C as a diameter in FIG. 3) is smaller than an opening area of the outsole recess 13 (a surface area of a circle having a dimension D as a diameter in FIG. 3).

[0071] The second stud 12 is configured to be movable in a vertical direction so that the second projection surface 12a comes close to the reference surface 4 when the wearer wearing a pair of shoes including the sole structure 1 is running on, for example, leveled or uneven grounds.

[0072] As shown in FIG. 3, when an external force F such as repulsion force, which the sole structure 1 receives from a road surface when making contact with the road surface, acts on the second projection surface 12a of the second stud 12, the outsole recess 14 compressively transformed so that the bottom 13b of the outsole hollow 13 comes close to the midsole 2. When the outsole hollow 14 is compressively transformed, the second projection surface 12a of the second stud 12 rises from the position prior to the compressive transformation of the outsole hollow 14 (a position H2 of FIG. 3) to the position substantially coplanar with, for example, the first projection surface 11a (the position H1 of FIG. 3). (See imaginary lines in FIG. 3). Although not shown, the second stud 12 is configured so that the second projection surface 12a rises above the first projection surface 11a (specifically, the position near the reference surface 4). In this way, when the second projection surface 12a makes contacts with the road surface, the second stud 12 moves upwards so that the second projection surface 12a comes close to the reference surface 4. On the other hand, when the second projection surface 12a moves away from the road surface, the external force F does not act on the second projection surface 12a so that the outsole hollow 14 returns to the original state from the compressively transformed state. As a result, the second stud 12 moves downwards to a position prior to the transformation (the position H2 of FIG. 3) so that the projection surface 12a moves away from the reference surface 4.

Advantageous Effects of First Embodiment

[0073] As to the sole structure 1 according to the first embodiment of the present invention, when the wearer wearing shoes with this structure is running on a road surface of a leveled ground, the compressive transformation of the outsole hollow 14 brings the second projection surface 12a close to the reference surface 4 so that the first stud 11 and the second stud 12 become the same in projection height. As a result, the sole structure 1 ensures to maintain a constant ground contact area between the first and second studs 11 and 12 and the road surface of a leveled ground. Such a feature makes it possible to obtain predetermined grip characteristics for the road surface of a leveled ground while keeping the posture of the wearer stable. On the other hand, when the wearer is running on an uneven road surface found in, for example, a trail running course, the reference surface 4 and the first projection surface 11a make contact with the uneven road surface at their respective predetermined positions (i.e., the positions H0 and H1 of FIG. 3). The second stud 12 vertically moves, in conformity with irregularities of the uneven road surface, between the position of the second projection surface 12a prior to transformation (the position H2 of FIG. 3) and the position of the reference surface 4 (the position H0 of FIG. 3). In other words, the second stud 12 is formed so that the position of the second projection surface 12a conforms to irregularities peculiar to uneven grounds such as sandy areas or rocky areas. The second projection surface 12a prior to the transformation of the outsole hollow 14 is positioned below the first projection surface 11a. Therefore, the second projection surface 12a can be made contact with an uneven road surface at any given position spaced apart upwards or downwards with respect to the first projection surface 11a. In this way, the sole structure 1 ensures a sufficient ground contact area between (i) the reference surface 4 and the first and second projection surfaces 11a and 12a and (ii) an uneven road surface, contributing to exhibiting reliable grip characteristics for the uneven road surface while keeping the posture of the wearer stable. Hence, the sole structure 1 makes it possible to exhibit appropriate grip characteristics in conformity with various road surfaces while keeping the posture of the wearer wearing the shoes stable.

[0074] The second stud 12 is formed so that the thickness between the second projection surface 12a and the bottom 13b of the outsole recess 13 is greater than the depth of the outsole recess 13. That is, the thickness of the second stud 12 between the second projection surface 12a and the bottom 13b of the outsole recess 13 is kept constant. Such features can ensure the wear resistance of the second studs 12. In addition, when the external force F acts on the second stud 12a, the features can reduce a transformation of the second stud 12 to keep the second stud 12 from excessively transforming.

[0075] The second stud 12 is formed so that the surface area of the second projection surface 12a is smaller than the opening area of the outsole recess 13. That is, the opening 13a of the outsole recess 13 is formed relatively large. Hence, when the external force F acts on the second projection surface 12a, the large opening 13a facilitates the retraction of a lower end, including the second projection surface 12a, of the second stud 12 into the outsole hollow 14. Such features encourage the compressive transformation of the outsole hollow 14 accompanying the vertical movement of the second stud 12.

[0076] The outsole recess 13 curves to be substantially concave over a region from the opening 13a toward the bottom 13b. Accordingly, no corners appear between the side walls or between a side wall and the bottom 13b in the outsole recess 13, and neither does an area where stress concentrates. As a result, even after the repeated use of the sole structure 1, the inside of the outsole recess 13 is less likely to be damaged due to compressive transformation of the outsole hollow 14, making it possible to reduce aged deterioration of the outsole recess 13.

Second Embodiment

[0077] FIG. 4 illustrates the sole structure 1 according to a second embodiment of the present invention. The second embodiment differs from the first embodiment in some of the structure of the outsole hollow 14. Note that other than the above difference, the sole structure 1 of this embodiment is the same in configuration as the sole structure 1 of the first embodiment. Therefore, elements that are the same as those shown in FIGS. 1 to 3 are denoted by the corresponding reference characters, and detailed descriptions thereof are omitted herein.

[0078] As shown in FIG. 4, provided inside the outsole hollow 14 is an outsole rib 21 to be transformable when the external force F acts on the second projection surface 12a. Specifically, the outsole rib 21 is formed integrally with the bottom 13b of the outsole recess 13, and extends upwards from the bottom 13b of the outsole recess 13 toward the midsole 2.

[0079] As to this sole structure 1 of this embodiment, the outsole rib 21 is provided inside the outsole hollow 14. Thus, during the compression-bonding of the outsole 3 and the midsole 2 together in producing the sole structure 1, the outsole rib 21 can keep the outsole hollow 14 from being crushed unintentionally, thereby maintaining the interior space of the outsole hollow 14. In the produced sole structure 1, the outsole rib 21 can be transformed when the external force F acts on the second projection surface 12a. As a result, the outsole rib 21 allows the outsole hollow 14 to be still compressively transformed.

[0080] Furthermore, in the sole structure 1 of this embodiment, a restrictor 22 is formed into a step-like shape toward the bottom 13b, and provided to an interior wall of the outsole recess 13. The restrictor 22 is configured such that the upper face of the restrictor 22 abuts onto the lower face of the midsole 2 when the outsole hollow 14 is compressively transformed. The restrictor 22 provided inside the outsole hollow 14 can keep the second projection surface 12a from coming excessively close to the reference surface 4.

Third Embodiment

[0081] FIGS. 5 and 6 illustrate a sole structure 1 according to a third embodiment of the present invention. The third embodiment differs from the first embodiment in some of the structure of the second stud 12. Note that other than the above difference, the sole structure 1 of this embodiment is the same in configuration as the sole structure 1 of the first embodiment. Therefore, elements that are the same as those shown in FIGS. 1 to 3 are denoted by the corresponding reference characters, and detailed descriptions thereof are omitted herein.

[0082] As illustrated in FIGS. 5 and 6, the second stud 12 is provided with a plurality of reinforcements 23, 23, . . . . The reinforcements 23, 23, . . . are arranged on an outer periphery of the second stud 12. The reinforcements 23, 23, . . . are spaced apart from each other in a circumferential direction of the second stud 12, and formed integrally with the second stud 12 and the reference surface 4. Specifically, each of the reinforcements 23 is made of the same material as that of the outsole 3, for example, and shaped into a substantial plate in bottom view. Each of the reinforcements 23 is formed to be inclined toward the radial outside, of the second surface 12a in cross section, from the second projection surface 12a to the reference surface 4. Note that, in FIG. 6, the cross section of the reinforcement 23 is dot-hatched to be emphasized.

[0083] In this sole structure 1 of this embodiment, when the external force F acts on the second projection surface 12a, the reinforcements 23, 23, . . . can reinforce the second stud 12 to keep the second stud 12 from being transformed in a direction orthogonal to the vertical direction and substantially parallel to the reference surface 4; that is, a lateral movement.

Other Embodiments as to First to Third Embodiments

[0084] In the sole structure 1 of each of the embodiments described above, the second stud 12 has the second projection surface 12a shaped into, but not limited to, a substantial circle. For example, as can be seen from FIG. 7A, the second projection surface 12a can be shaped into a triangle in bottom view. Furthermore, as can be seen in FIG. 7B and FIG. 8A, the second projection surface 12a can be shaped into a quadrangle in bottom view. Moreover, as can be seen in FIG. 8B, the second projection surface 12a can be shaped into a substantially V-shape in bottom view. In addition, as can be seen in FIG. 8C, the second projection surface 12a may include a plurality of polyhedrons each shaped into a substantial rectangle in bottom view. The polyhedrons may extend toward the radial outside from the center of the second projection surface 12a, and are arranged in a circumferential direction at equal intervals.

[0085] In the sole structure 1 of each of the embodiments described above, the outsole recess 13 curves to be substantially concave over a region from the opening 13a toward the bottom 13b. However, this is merely a non-limiting example. For example, as can be seen in FIGS. 8A to 8C, a corner may be formed between a side wall and the bottom 13b.

[0086] In the sole structure 1 of each of the above embodiments described above, in one of the stud groups 10, the first studs 11, 11, . . . are arranged around each of the second studs 12, and spaced apart from each other in the circumferential direction of the second stud 12. However, this is merely a non-limiting example. For example, the first studs 11, 11, . . . are arranged around a group of the second studs 12, 12, . . . , and spaced apart from each other around the group.

Fourth Embodiment

[0087] FIGS. 9 to 13 illustrate the sole structure 1 according to a fourth embodiment of the present invention. The fourth embodiment differs from the first embodiment particularly in the structure of the midsole and in the mechanism of the vertical movement of the second studs 12. Note that other than the above difference, the sole structure 1 of this embodiment is the same in configuration as the sole structure 1 of the first embodiment. Therefore, elements that are the same as those shown in FIGS. 1 to 3 are denoted by the corresponding reference characters, and detailed descriptions thereof are omitted herein.

[0088] As can be seen in FIGS. 9 to 11, the midsole 2 is comprised of two parts stacked together in a vertical direction. Specifically, the midsole 2 is a multilayer including an upper midsole 2a and a lower midsole 2b overlaid on the lower side of the upper midsole 2a.

[0089] In an upper portion of the upper midsole 2a, a planta support surface 2c configured to support a plantar surface extends in the longitudinal direction. A shoe upper (not shown) for covering the wearer's foot is attached to a peripheral portion of the upper midsole 2a.

[0090] The lower midsole 2b has midsole recesses 2d, 2d, . . . set back into a lower surface of the lower midsole 2b. Each midsole recess 2d is formed at a position facing the upper side of an associated one of second studs 12, which will be described later. Each midsole recess 2d is tapered upwards from the lower surface of the lower midsole 2b in cross section. The lower midsole 2b is provided with midsole hollows 6, 6, . . . positioned on a lower side of the lower midsole 2b. Each of the midsole hollows 6, 6, . . . is defined between an associated one of the midsole recesses 2d, 2d, . . . and an upper portion of the outsole 3.

[0091] A reinforcing plate 7 is disposed between the upper and lower midsoles 2a and 2b so as to correspond to the hindfoot of the wearer's foot. The reinforcing plate 7 is comprised of a thin layer which is harder than the upper and lower midsoles 2a and 2b and has a corrugated shape having projections and depressions alternating with each other in the longitudinal direction. Note that the reinforcing plate 7 is not limited to the corrugated shape, and may have a flat plate shape, for example.

[0092] Next, as shown in FIG. 9, the first studs 11, 11, . . . and the second studs 12, 12, . . . are arranged at the position on the outsole 3 corresponding to the wearer's forefoot. The first studs 11, 11, . . . and the second studs 12, 12, . . . are arranged alternately in the longitudinal direction and in a foot width direction in a checkered pattern. The first and second studs 11 and 12 are spaced apart from each other.

[0093] The first studs 11 and the second studs 12 project downwards from the reference surface 4, and are shaped into a substantial quadratic prism. The first studs 11 and the second studs 12 are made of the same material as that of the outsole 3, for example, and formed integrally with the outsole 3. Note that, in this embodiment, the base 5 described in the first embodiment is not provided.

[0094] For example, as can be seen in FIGS. 9 and 11, the first projection surface 11a of each of the first studs 11 is shaped into a substantial rectangle in bottom view. As illustrated in FIGS. 12 and 13, each of the second studs 12 is tapered downwards from the reference surface 4 in cross section. The second projection surface 12a has a substantially rectangular shape in bottom view. Note that the positional relationship in a vertical direction among the reference surface 4, the first projection surface 11a and the second projection surface 12a is similar to that of the first embodiment. Therefore, detailed descriptions thereof are omitted here.

[0095] The second stud 12 is configured to be movable in a vertical direction so that the second projection surface 12a comes close to the reference surface 4 when the wearer wearing a pair of shoes including the sole structure 1 is running on, for example, leveled or uneven grounds.

[0096] Specifically, as illustrated in FIG. 12, when the external force F such as repulsion force, which the sole structure 1 receives from a road surface when making contact with the road surface, acts on the second projection surface 12a of the second stud 12, root portions 3a, 3a, of the outsole 3 continuous with an upper portion of the second stud 12 are elastically transformed to enter the inside of the midsole hollow 6. The elastic transformation of the root portions 3a, 3a causes the second stud 12 to come close to the midsole hollow 6. That is, the second stud 12 enters the inside of the midsole hollow 6.

[0097] As the second stud 12 comes close to the midsole hollow 6, the second projection surface 12a rises from the position prior to vertical movement of the second stud 12 (a position H2 of FIG. 12) to the position coplanar with the first projection surface 11a, for example (a position H1 of FIG. 12) (see the imaginary outline in FIG. 12). As shown in FIG. 13, if the external force F keeps acting on the second projection surface 12a, the entire stud 12 is retracted into the midsole hollow 6, while maintaining its shape. When the second stud 12 is retracted, the second projection surface 12a is substantially coplanar with the reference surface 4 of the outsole 3 except the root portions 3a, 3a.

[0098] As can be seen, the midsole hollow 6 is provided directly above the second studs 12. When the external force F such as repulsion force, which the sole structure 1 receives from a road surface when making contact with the road surface, acts on the second projection surface 12a of the second stud 12, the second stud 12 moves in a vertical direction toward the midsole hollow 6. As a result, the sole structure 1 can exhibit cushioning properties.

[0099] When the sole structure 1 comes out of contact with the road surface, the second projection surface 12a is released from the action of the external force F, so that the root portions 3a, 3a of the outsole 3 recover to the original state. The second stud 12 retracted inside the midsole hollow 6 is brought out of the midsole hollow 6 and moves downwards out of the midsole hollow 6 to return to the original position (i.e., the position H2 illustrated in FIG. 12) while the second projection surface 12a moves away from the reference surface 4 of the outsole 3 except the root portions 3a, 3a.

Advantageous Effects of Fourth Embodiment

[0100] As described above, the midsole hollow 6 is disposed directly above the second stud 12. As a result, the second stud 12 is configured to move, when the external force F acts on the second projection surface 12a, in a vertical direction such that the second projection surface 12a comes close to the reference surface 4. Hence, with the sole structure 1 of this embodiment, the first and the second studs 11, 12 make it possible to obtain appropriate grip characteristics for various types of road surfaces while keeping a stable posture of the wearer wearing the shoes with this sole structure 1, as can be seen in the above first embodiment. Unlike the first embodiment, in the sole structure 1 of this embodiment, it is unnecessary to form the outsole recess 13, as an element causing the second studs 12 to move in a vertical direction. The thickness of each of the second studs 12 is therefore not particularly restricted. The second studs 12 can be formed to have a relatively large thickness, making it possible to reduce aged deterioration due to, for example, the influence of abrasion of the second studs 12.

[0101] As shown in FIGS. 11 to 13, each of the second studs 12 is formed so that a surface area of the second projection surface 12a is smaller than an opening area of the associated one of the midsole recesses 2d. Thus, the second projection surface 12a comes close to the reference surface 4 when the external force F acts on the second projection surface 12a, and the entire second stud 12 including the second projection surface 12a easily enters the associated midsole hollow 6. As can be seen, the vertical movement of the second studs 12 is facilitated, resulting in further improvement in the cushioning properties of the sole structure 1.

Fifth Embodiment

[0102] FIGS. 14 and 15 illustrate the sole structure 1 according to a fifth embodiment of the present invention. The fifth embodiment differs from the fourth embodiment in some of the structure of the second stud 12. Note that other than the above difference, the sole structure 1 of this embodiment is the same in configuration as the sole structure 1 of the fourth embodiment. Therefore, elements that are the same as those shown in FIGS. 9 to 13 are denoted by the corresponding reference characters, and a detailed description thereof is omitted herein.

[0103] As illustrated in FIG. 14, in the sole structure 1 of this embodiment, each of the second studs 12 has a second projection surface 12a shaped into a substantial trapezoid in bottom view. As illustrated in FIG. 15, an outsole recess 13 is provided in an upper portion of the second stud 12. The outsole recess 13 is set back into an upper surface of the outsole 3. Specifically, the outsole recess 13 is disposed directly above the second projection surface 12a, and is tapered in a direction from the opening toward the bottom 13b of the outsole recess 13. The second stud 12 is formed such that the thickness between the second projection surface 12a and the bottom 13b of the outsole recess 13 is greater than the depth of the outsole recess 13.

[0104] The outsole hollow 14 is defined between the outsole recess 13 and the lower midsole 2b, and disposed in the upper portion of the second stud 12 (i.e., directly above the projection surface 12a). The second stud 12 is formed so that the surface area of the second projection surface 12a is smaller than the opening area of the outsole recess 13.

[0105] The second stud 12 of this embodiment is configured to move, when the external force acts on the second projection surface 12a, in a vertical direction while the outsole hollow 14 is compressively transformed and the second projection surface 12a comes close to the reference surface 4. As can be seen, the vertical movement of each second stud 12 of the fifth embodiment is further facilitated by the compressive transformation of the outsole hollow 14, as compared to the fourth embodiment. As a result, the cushioning properties of the sole structure 1 are further improved.

Sixth Embodiment

[0106] FIG. 16 illustrates the sole structure 1 according to a sixth embodiment of the present invention. The sixth embodiment differs from the fifth embodiment in some of the structures of the midsole hollow 6 and the outsole hollow 14. Note that other than the above difference, the sole structure 1 of this embodiment is the same in configuration as the sole structure 1 of the fifth embodiment. Therefore, elements that are the same as those shown in FIGS. 14 and 15 are denoted by the corresponding reference characters, and a detailed description thereof is omitted herein.

[0107] As shown in FIG. 16, in this embodiment, the midsole rib 24 and the outsole rib 21 are respectively provided inside the midsole hollow 6 and the outsole hollow 14.

[0108] The outsole rib 21 is formed integrally with the bottom 13b of the outsole recess 13 and extends upwards from the bottom 13b toward the lower midsole 2b. The outsole rib 21 is disposed such that its upper end is in contact with the lower end of the midsole rib 24.

[0109] The midsole rib 24 is formed integrally with the bottom of the midsole recess 2d, and extends downwards from the bottom toward the outsole 3.

[0110] As to a variation of the sole structure 1 of the fifth embodiment, the outsole rib 21 and the midsole rib 24 are provided. Thus, during the compression-bonding of the outsole 3 and the lower midsole 2 (the midsole 2) together in producing the sole structure 1, the outsole rib 21 and the midsole rib 24 can keep the outsole hollow 14 and the midsole hollow 6 from being crushed unintentionally, thereby maintaining the interior spaces of the outsole hollow 14 and midsole hollow 6.

[0111] In the produced sole structure 1, the outsole rib 21 and the midsole rib 24 can be deformed when an external force F acts on the second projection surface 12a. The ribs 21, 24 therefore allow the outsole hollow 14 to be still compressively transformed.

Other Embodiments Regarding Fourth to Sixth Embodiments

[0112] FIGS. 17 and 18 illustrate a variation of the sole structure 1 of the fourth and the fifth embodiments. As can be seen, an elastic soft member 30 may be provided in the midsole hollow 6. Specifically, the soft member 30 is made of a material softer than that of the midsole 2, for example, and overlaid on the bottom of the midsole recess 2d. In this variation, an impact acting on the second stud 12 is alleviated when the sole structure 1 makes contact with the ground, further enhancing the cushioning properties of the sole structure 1. Note that the cross section of the soft member 30 in FIGS. 17 and 18 is dot-hatched to be emphasized.

[0113] In the sole structure 1 of the fourth to sixth embodiments described above, the second stud 12 has the second projection surface 12a formed into a substantial rectangle in bottom view. However, this is merely a non-limiting example. For example, the second projection surface 12a may have a circular or triangular shape in bottom view.

[0114] In the sole structure 1 of the fourth to sixth embodiments described above, each midsole recess 2d is tapered in the direction from the opening to the bottom. However, this is merely a non-limiting example. For example, the midsole recess 2d may curve to be substantially concave over a region from the opening to the bottom. This applies also in the case of the outsole recess 13 described in the fifth embodiment.

[0115] Note that the present invention is not limited to the embodiment described above, and various changes and modifications may be made without departing from the scope of the present invention.

INDUSTRIAL APPLICABILITY

[0116] The present invention may be used, for example, as shoes to be used for various ground surfaces for trail running on uneven grounds or for ball games on the dirt or on the grass.

DESCRIPTION OF REFERENCE CHARACTERS

[0117] 1 Sole Structure [0118] 2 Midsole [0119] 2d Midsole Recess [0120] 3 Outsole [0121] 4 Reference Surface [0122] 5 Base Portion [0123] 6 Midsole Hollow [0124] 10 Stud Group [0125] 11 First Stud [0126] 11a First Projection Surface [0127] 12 Second Stud [0128] 12a Second Projection Surface [0129] 13 Outsole Recess [0130] 14 Outsole Hollow [0131] 21 Outsole Rib [0132] 22 Restrictor [0133] 23 Reinforcement [0134] 24 Midsole Rib