Shoe sole having outsole and midsole

Abstract

A shoe sole including an outsole 2 and a midsole 1, wherein: the midsole 1 includes a lower midsole 4 of a lower layer formed by a foamed body of a resin, and an upper midsole 3 of an upper layer formed by a foamed body of a resin and arranged on the lower midsole 4; a lateral roll-up portion 42 for supporting a lateral side of a foot from a side of the foot is formed integrally with the lower midsole 4; a hardness of a lateral portion 40 of the lower midsole 4 including the lateral roll-up portion 42 is a first hardness; a hardness of a medial portion 41 of the lower midsole 4 is a second hardness lower than the first hardness; a hardness of a lateral portion 30 of the upper midsole 3 is a third hardness lower than the first hardness; and a part or a whole of the high-hardness lateral roll-up portion 42 is protruding in an upward direction past the upper midsole 3 on a lateral side of the upper midsole 3 so that the lateral side of the foot is supported by the lateral roll-up portion 42 from the side of the foot without being supported by the upper midsole 3 from the side of the foot.

Claims

1. A shoe sole comprising an outsole having a tread surface to be in contact with a road surface, and a midsole arranged on the outsole, wherein: the midsole includes a lower midsole of a lower layer formed by a foam body of a resin, and an upper midsole of an upper layer formed by a second foam body of a resin and arranged on the lower midsole; a lateral roll-up portion configured to support a lateral side of a foot from a side of the foot is formed integrally with the lower midsole; the lower midsole includes a lateral portion and a medial portion; the lateral portion of the lower midsole including the lateral roll-up portion has a first hardness; the medial portion of the lower midsole has a second hardness that is lower than the first hardness; a lateral portion of the upper midsole has a third hardness that is lower than the first hardness; and a part or a whole of the lateral roll-up portion is configured to protrude in an upward direction past the upper midsole on a lateral side of the upper midsole so that the lateral side of the foot is supported by the lateral roll-up portion from the side of the foot without being supported by the upper midsole from the side of the foot, wherein the lateral portion of the upper midsole has a hollowed out and narrowed portion in an area adapted to a metatarsophalangeal joint of a fifth toe, hollowed out and narrowed portion defined by a line that is curved so as to protrude toward a medial side; an outer edge line of the lateral portion of the upper midsole is curved so as to protrude toward a lateral side in an area anterior to a most narrowed portion of the hollowed out and narrowed portion, the outer edge line of the lateral portion of the upper midsole is curved so as to protrude toward the lateral side in an area posterior to the most narrowed portion of the hollowed out and narrowed portion; the lateral portion of the lower midsole forms a base portion that is configured to cover from below at least a part of the metatarsophalangeal joint of the fifth toe; the base portion of the lower midsole fills the hollowed out and narrowed portion; and the lateral roll-up portion of the lower midsole rolls up in the upward direction in a lateral edge of the base portion.

2. The shoe sole according to claim 1, wherein: the lateral portion of the upper midsole is configured to support a lower surface of a lateral side of a fore foot section of the foot; and the lateral roll-up portion of the lower midsole is configured to cover a lateral side surface of a head of a metatarsal bone of the fifth toe so as to support a lateral side of the head in the fore foot section.

3. The shoe sole according to claim 2, wherein: the lateral portion of the lower midsole is configured to cover a lower surface of the metatarsal bone of the fifth toe from the head to a bottom thereof; and the medial portion of the lower midsole is configured to cover a lower surface of a metatarsal bone of a first toe from a head to a bottom thereof and a lower surface of a proximal phalanx.

4. The shoe sole according to claim 3, wherein a hardness of a medial portion of the upper midsole is a fourth hardness lower than the second hardness and the third hardness.

5. The shoe sole according to claim 3, wherein: the lateral portion of the upper midsole is configured to cover the lower surface of the metatarsal bone of the fifth toe from the head to the bottom thereof; and the medial portion of the upper midsole is configured to cover the lower surface of the metatarsal bone of the first toe from the head to the bottom thereof and a lower surface of the proximal phalanx.

6. The shoe sole according to claim 1, wherein the hollowed out and narrowed portion of the lateral portion of the upper midsole is configured so that at least one portion of the metatarsophalangeal joint of the fifth toe protrudes over the hollowed out and narrowed portion, and the base portion of the lateral portion of the lower midsole is configured to cover the at least one portion of the metatarsophalangeal joint of the fifth toe.

7. The shoe sole according to claim 1, further comprising a stabilizer arranged along a lateral side surface of the lateral roll-up portion further on a lateral side of the lateral roll-up portion, wherein the lateral roll-up portion protrudes in the upward direction past the stabilizer.

8. The shoe sole according to claim 1, wherein the outsole is formed by a foam body or a non-foam body of a rubber and is rolled up in the upward direction further on a lateral side of the lateral roll-up portion, and the lateral roll-up portion protrudes in the upward direction past a rolled-up portion of the outsole.

9. The shoe sole according to claim 1, wherein the lower midsole includes a part on which a whole of the upper midsole is downwardly projected, and the whole of the upper midsole is arranged above the part of the lower midsole.

10. The shoe sole according to claim 1, wherein a whole of the upper midsole is made of the second foam body.

11. The shoe sole according to claim 1, wherein the lower midsole includes a part on which a whole of the upper midsole is downwardly projected, the whole of the upper midsole is arranged above the part of the lower midsole, and a whole of the upper midsole is made of the second foam body.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an exploded perspective view showing a midsole according to Embodiment 1 of the present invention.

(2) FIG. 2 is a perspective view of a midsole showing an upper midsole placed on a lower midsole.

(3) FIG. 3A is a longitudinal cross-sectional view of a shoe sole, and FIG. 3B is a lateral side view of the shoe sole.

(4) FIG. 4 is a plan view of the midsole.

(5) FIG. 5 is a plan view showing the relationship between the midsole and the foot bone structure.

(6) FIGS. 6A, 6B, 6C, and 6D are cross-sectional views taken along lines VIA-VIA, VIB-VIB, VIC-VIC and VID-VID of FIG. 4, respectively.

(7) FIGS. 7A, 7B, 7C, and 7D are schematic front views each showing an action of a subject, and FIGS. 7E and 7F are graphs showing the test results.

(8) FIGS. 8A, 8B, and 8C are cross-sectional views taken along line VIB-VIB of FIG. 4, each showing a variation of the midsole.

DESCRIPTION OF EMBODIMENTS

(9) In the first invention, in a preferred example, the lateral portion 30 of the upper midsole 3 supports a lower surface of a lateral side of a fore foot section of the foot; and

(10) the high-hardness lateral roll-up portion 42 of the lower midsole 4 covers a lateral side surface of a head 05 of a metatarsal bone of a fifth toe so as to support a lateral side of the head 05 in the fore foot section.

(11) Although a large force, which may cause a lateral shake, occurs at the head 05 of the metatarsal bone of the fifth toe when making a turn, or the like, the lateral side of the head 05 of the metatarsal bone of the fifth toe is supported by the high-hardness lateral roll-up portion 42 in the present embodiment. This will prevent the lateral shake of the head 05 of the metatarsal bone of the fifth toe, i.e., the ball of the little toe.

(12) More preferably, the high-hardness lateral portion 40 of the lower midsole 4 covers a lower surface of the metatarsal bone of the fifth toe from the head 05 to a bottom 051 thereof; and

(13) the low-hardness medial portion 41 of the lower midsole 4 covers a lower surface of a metatarsal bone of a first toe from a head 01 to a bottom 011 thereof and a lower surface of a proximal phalanx B3.sub.1.

(14) In such a case, the hardness of the medial portion 41 of the lower midsole 4 is lower than the hardness of the lateral portion 40, and therefore the bendability of the sole may be less likely to be detracted from. Moreover, the impact-absorbing property is less likely to be detracted from.

(15) Note that a bottom refers to a portion of each bone that is close to the posterior joint and that is slightly expanding to a greater thickness and it is referred to also as a proximal head. On the other hand, a head refers to a portion of each bone that is close to the anterior joint and that is slightly expanding to a greater thickness and it is referred to also as a distal head. A shaft refers to a portion between the bottom and the head, and the thickness thereof typically changes smoothly.

(16) More preferably, the lateral portion 30 of the upper midsole 3 is narrowed in an area of the metatarsal bone of the fifth toe; and

(17) the lateral roll-up portion 42 of the lower midsole 4 is rolled up in an upward direction in the area of the narrowed upper midsole 3.

(18) In such a case, as the lateral portion 30 of the upper midsole 3 is narrowed in the area of the metatarsal bone of the fifth toe, the lateral roll-up portion 42 rises from the lower midsole 4 without the volume of the lateral roll-up portion 42 of the lower midsole 4 decreasing and without the volume of the area extending from the lateral portion 40 of the lower midsole 4 to the lateral roll-up portion 42 decreasing. Therefore, with the hard lateral roll-up portion 42, it is possible to prevent the lateral shake of the head 05 of the metatarsal bone of the fifth toe.

(19) In another preferred embodiment, a hardness of a medial portion 31 of the upper midsole 3 is a fourth hardness lower than the second hardness and the third hardness.

(20) In such a case, since the medial portion 31 of the upper midsole 3 is soft, the upper surface of the midsole will be tilted in a diagonally downward direction from the lateral side toward the medial side upon landing on one foot. Therefore, with tennis shoes for women, or the like, a moment which would be a burden on the knee is unlikely to occur upon landing on one foot.

(21) More preferably, the lateral portion 30 of the upper midsole 3 covers a lower surface of the metatarsal bone of the fifth toe from the head 05 to the bottom 051 thereof; and

(22) the medial portion 31 of the upper midsole 3 covers a lower surface of the metatarsal bone of the first toe from the head 01 to the bottom 011 thereof and a lower surface of the proximal phalanx B3.sub.1.

(23) In such a case, it will be easy to prevent the occurrence of a moment which would be a burden on the knee.

(24) Preferably, the shoe sole further includes a stabilizer 5, made of a non-foamed body of a resin, for example, arranged along a lateral side surface of the lateral roll-up portion 42 further on a lateral side of the lateral roll-up portion 42.

(25) The stabilizer 5 formed by a non-foamed body of a resin further enhances the lateral shake preventing function.

(26) Preferably, the outsole 2 is formed by a foamed body or a non-foamed body of a rubber and is rolled up in an upward direction further on a lateral side of the lateral roll-up portion 42.

(27) The roll-up of the outsole 2 will further enhance the lateral shake preventing function.

(28) Prior to the detailed description of the second invention, a test conducted by the inventors of the second invention will be described.

(29) Using shoes of the same structure, male and female subjects performed a one-foot-landing action as seen when landing after a jump serve or when volleying, as shown in FIGS. 7A to 7D, and the moments M (torques) occurring about the knee were measured. As a result, it was found that the moment M was greater for females than for males.

(30) The moment M about the knee is calculated as the outer product between the ground reaction force vector F1, extending from the center of load indicated by a solid line in the figures, and the lower limb vector F2 indicated by a one-dot-chain line. FIGS. 7E and 7F are bar graphs showing the magnitudes of the moments M for males and females, indicating that females have a greater moment M than males.

(31) If a low-hardness midsole layer is inserted in the medial portion of the fore foot portion, the low-hardness midsole is compressed significantly, thereby tilting the sole toward the medial side, upon stepping in during the one-foot-landing action. When the sole is tilted toward the medial side, the ground reaction force vector F1 shown in FIGS. 7A and 7C is similarly tilted, but the lower limb vector F2 hardly changes. Therefore, the ground reaction force vector F1 and the lower limb vector F2 will be of the same direction, and the moment M around the knee, which is calculated from the outer product therebetween, will be small.

(32) Thus, the second invention in one aspect is a shoe sole including an outsole 2 having a tread surface to be in contact with a ground upon landing, and a midsole 1 arranged on the outsole 2, wherein:

(33) the midsole 1 includes a lower midsole 4 of a lower layer formed by a foamed body of a resin for supporting a fore foot section of a foot, and an upper midsole 3 of an upper layer formed by a foamed body of a resin and arranged on the lower midsole 4 in the fore foot section; and

(34) a hardness of a medial portion 31 of a fore foot section of the upper midsole 3 is lower than a hardness of a fore foot section of the lower midsole 4, and the hardness of the medial portion 31 of the fore foot section of the upper midsole 3 is lower than a hardness of a lateral portion 30 of the fore foot section of the upper midsole 3.

(35) Now, as a shoe sole for correcting bowlegs, a shoe is known (JP 2005-224335 A) in which an easily-compressed layer is provided in a medial side layer below an elastic intermediate layer. However, with this shoe sole in which an easily-compressed layer is inserted below the elastic intermediate layer, the deformation of the easily-compressed layer is likely to delay when an impact load on the foot sole is imparted upon the sole due to the viscosity present in the elastic body of a resin such as EVA.

(36) Therefore, although this conventional technique may be helpful for correcting bowlegs through static deformation, one cannot expect an advantageous effect against the impact load such as those from landing on one foot in tennis, etc.

(37) In contrast, according to the second invention, the medial portion 31 of the fore foot section of the upper midsole 3 has a low hardness, and the medial portion 31 of the upper midsole 3 is therefore compressed instantaneously by an impact load, thereby bringing the direction of the ground reaction force vector F1 and the direction of the lower limb vector F2 shown in FIGS. 7A and 7B closer to each other. Therefore, when the invention is applied to tennis shoes for women, the moment M occurring at the knee will be small.

(38) On the other hand, if the hardness of the medial side of the fore foot section of the midsole is lowered without using an upper-lower two-layer structure, the amount of compression on the medial side of the fore foot section will be excessive, and a difference is therefore likely to occur between the direction of the ground reaction force vector F1 and the direction of the lower limb vector F2.

(39) Preferably, a low-hardness area of the upper midsole 3 where the hardness is low is provided over an area extending from a shaft of a metatarsal bone of a first toe to a head of a proximal phalanx of the first toe.

(40) By employing such an extent for the low-hardness area, the foot is likely to be tilted in the medial-side fore foot portion.

(41) Preferably, the medial portion 31 of the upper midsole 3 is set to 40 degrees to 55 degrees in JIS-C hardness, and the lateral portion 30 of the upper midsole 3 is set to 50 degrees to 65 degrees in JIS-C hardness.

(42) Note that the hardness difference between the medial portion 31 of the upper midsole 3 and the lateral portion 30 of the upper midsole 3 is preferably about 5° to about 15° in JIS-C hardness.

(43) With such a hardness difference therebetween, the tilt angle of the foot will be of an appropriate value.

(44) If the hardness is lower than such hardness settings, the entire sole is typically likely to sink, whereas if the hardness is higher than the hardness settings, it is typically difficult to achieve a level of flexibility that is needed for the sole.

(45) Preferably, the hardness of the medial portion 31 of the upper midsole 3 is lower than a hardness of a central portion 34, 44 of the upper midsole 3 or the lower midsole 4 in a medial and lateral direction;

(46) a hardness of a lateral portion 30, 40 of the upper midsole 3 or lower midsole 4 is higher than the hardness of the central portions 34, 44 of the upper midsole 3 or the lower midsole 4 in the medial and lateral direction.

(47) If the central portions 34, 44 have such an intermediate hardness between the hardness of the medial portion and the lateral portion, it will be easy to achieve a smooth slope of the midsole.

(48) Thus, the second invention in another aspect is a shoe sole including an outsole 2 having a tread surface to be in contact with a ground upon landing, and a midsole 1 arranged on the outsole 2 and formed by a foamed body of a resin, the midsole 1 including:

(49) a lateral portion 30, 40 covering a lower surface of a metatarsal bone of a fifth toe from a head to a bottom thereof;

(50) a medial portion 31, 41 covering a lower surface of a metatarsal bone of a first toe from a head to a bottom thereof and a lower surface of a first proximal phalanx; and

(51) a central portion 34, 44 between the lateral portion 30, 40 and the medial portion 31, 41, wherein:

(52) the lateral portion 30, 40 has a layer of a first hardness;

(53) the central portion 34, 44 has a layer of a second hardness lower than the first hardness; and

(54) the medial portion 31, 41 has a layer of a third hardness lower than the second hardness.

(55) In the second invention, the midsole 1 includes a layer of a lower midsole 4 and a layer of an upper midsole 3 arranged on the lower midsole 4;

(56) the layer of the first hardness is provided in one of the upper midsole 3 and the lower midsole 4 in the lateral portions 30, 40; and

(57) the layer of the third hardness is provided in one of the upper midsole 3 and the lower midsole 4 in the medial portions 31, 41.

(58) Embodiment

(59) The present invention will be understood more clearly from the following description of preferred embodiments taken in conjunction with the accompanying drawings. Note however that the embodiments and the drawings are merely illustrative, and should not be relied upon in defining the scope of the present invention. The scope of the present invention shall be defined only by the appended claims. In the accompanying drawings, like reference numerals denote like components throughout the plurality of figures.

(60) One embodiment of the present invention will now be described with reference to FIGS. 1 to 6D.

(61) As shown in FIGS. 1 to 3A, the shoe sole is suitable for tennis shoes for women, for example, including an outsole 2 having a tread surface to be in contact with the road surface, and a midsole 1 arranged on the outsole 2.

(62) The midsole 1 is formed by, for example, a material suitable for impact absorption such as a foamed body of a resin such as EVA (ethylene-vinyl acetate copolymer). On the other hand, the outsole 2 is formed by, for example, a material having a good abrasion resistance such as a foamed body or a non-foamed body of a rubber.

(63) As shown in FIG. 1, the midsole 1 includes a lower midsole 4 of the lower layer, and an upper midsole 3 of the upper layer arranged on the lower midsole 4 and supporting the fore foot section of the foot. A lateral roll-up portion 42 for supporting a lateral side of the foot from the side of the foot is formed integrally with the lower midsole 4. The lower midsole 4 is provided over the entire length of the foot, whereas the upper midsole 3 is provided over a front-half area of the foot.

(64) The hardness of a lateral portion 40 of the lower midsole 4 including the lateral roll-up portion 42 is a first hardness. The hardness of a medial portion 41 of the lower midsole 4 is a second hardness lower than the first hardness. The hardness of a lateral portion 30 of the upper midsole 3 is a third hardness lower than the first hardness. The hardness of a medial portion 31 of the upper midsole 3 is a fourth hardness lower than the second hardness and the third hardness.

(65) More specifically, the lateral portion 30 of the upper midsole 3 and the medial portion 41 of the lower midsole 4 are set to an intermediate hardness, e.g., about 50 degrees to about 65 degrees, and more preferably about 54 degrees to about 62 degrees, in JIS-C hardness. Note that the hardness of the lateral portion 30 of the upper midsole 3 and the hardness of the medial portion 41 of the lower midsole 4 may be about the same or may be slightly different from each other.

(66) On the other hand, the lateral portion 40 of the lower midsole 4 is set to a high hardness and is thick (coarsely) dotted in FIGS. 1 and 4. For example, the hardness is set to about 55 degrees to about 75 degrees, and more preferably about 61 degrees to about 69 degrees, in JIS-C hardness.

(67) The medial portion 31 of the upper midsole 3 is set to a low hardness and is densely dotted in FIGS. 1 and 4. For example, the hardness is set to about 40 degrees to about 55 degrees, and more preferably about 44 degrees to about 52 degrees, in JIS-C hardness.

(68) Note that in FIG. 4, a portion of the area of the lower midsole 4 set to a high hardness over which the upper midsole 3 is arranged is dotted with an intermediate density between the coarse dotting and the dense dotting.

(69) As shown in FIGS. 1 and 2, a part or a whole of the high-hardness lateral roll-up portion 42 is protruding in an upward direction past the upper midsole 3 on a lateral side of the upper midsole 3 so that the lateral side of the foot is supported by the lateral roll-up portion 42 from the side of the foot without being supported by the upper midsole 3 from the side of the foot.

(70) As shown in FIG. 3B, when the shoe sole is viewed from the lateral side surface, the lateral roll-up portion 42 is protruding in the upward direction past the upper midsole 3, and there is a portion of the lateral portion 30 of the upper midsole 3 that is hidden by the lateral roll-up portion 42 and cannot be seen from the lateral side surface. That is, as seen from the lateral side surface, the lateral roll-up portion 42 of the lower midsole 4 supporting the side of the foot is located between the lateral portions 30, 30 of the upper midsole 3, and in other words, the lateral portions 30, 30 of the upper midsole 3 are exposed anterior and posterior of the lateral roll-up portion 42.

(71) Note that the lateral portion 30 of the upper midsole 3 may be rolled up slightly in the upward direction.

(72) In the case of the present embodiment, the lateral portion 30 of the upper midsole 3 of FIG. 5 is hollowed out and narrowed in the area of the head 05 of the metatarsal bone of the fifth toe. That is, in this area, the outer edge line of the lateral portion 40 of the lower midsole 4 is curved so as to protrude toward the lateral side, whereas the outer edge line of the lateral portion 30 of the upper midsole 3 is curved so as to protrude toward the medial side.

(73) Specifically, the lateral portion 30 of the upper midsole 3 is not covering at least one portion of an MP joint MP.sub.5 of the fifth toe, and the lateral portion 40 of the lower midsole 4 covers at least one portion of the MP joint MP.sub.5 of the fifth toe.

(74) As shown in FIGS. 1 and 2, the lateral roll-up portion 42 of the lower midsole 4 is rolled up in the upward direction in the narrowed area of the upper midsole 3. As the lateral portion 30 of the upper midsole 3 is narrowed as described above, a base portion 43 of the lateral roll-up portion 42 of the lower midsole 4 has a large thickness, as shown in FIG. 6B, thereby enhancing the lateral shake preventing effect by the lateral roll-up portion 42.

(75) Specifically, as the lateral portion 30 of the upper midsole 3 is narrowed, the lateral portion 30 does not extend to the base portion 43, and the thickness of the base portion 43 capable of supporting the load from above is larger than other areas of the lateral portion 40 of the lower midsole 4, thereby making it less likely that the lateral roll-up portion 42 collapses due to the force which laterally shakes the foot toward the lateral side.

(76) The lateral roll-up portion 42 protruding in the upward direction past the upper midsole 3 has an anterior end 42f and a posterior end 42b in the longitudinal direction Y. The anterior end 42f is located anterior to the MP joint MP.sub.5 of the fifth toe and posterior to the tip of the fifth distal phalanx B1.sub.5, whereas the posterior end 42b is located posterior to the MP joint MP.sub.5 of the fifth toe and anterior to the bottom 051 of the metatarsal bone B4.sub.5 of the fifth toe.

(77) The lateral portion 30 of the upper midsole 3 supports the lower surface of the lateral side of the fore foot section of the foot. As shown in FIGS. 5 and 6B, the high-hardness lateral roll-up portion 42 of the lower midsole 4 covers the lateral side surface of the head 05 of the metatarsal bone of the fifth toe so as to support the lateral side of the head in the fore foot section.

(78) At least a portion of the proximal phalanx B3.sub.5 of the fifth toe and at least a portion of the metatarsal bone B4.sub.5 of the fifth toe may be covered by the lateral portion 40 of the lower midsole 4 from below.

(79) Specifically, as shown in FIG. 5, the lateral portion 30 of the upper midsole 3 is not covering at least one portion of the head 05 of the metatarsal bone and/or at least one portion of the MP joint MP.sub.5 of the fifth toe, and these areas are covered from below by the lateral portion 40 of the lower midsole 4.

(80) The lateral portion 30 of the upper midsole 3 is at least covering a portion of the distal phalanx B1.sub.5 of the fifth toe and a portion of the metatarsal bone B4.sub.5 of the fifth toe. That is, in the vicinity of the MP joint MP.sub.5 of the fifth toe or the head 05 of the metatarsal bone of the fifth toe, the lateral portion 40 of the lower midsole 4 is exposed, and at least the distal phalanx B1.sub.5 of the fifth toe and a portion of the metatarsal bone B4.sub.5 of the fifth toe are covered from below by the lateral portion 30 of the upper midsole 3 and the lateral portion 40 of the lower midsole 4.

(81) As shown in FIG. 5, the high-hardness lateral portion 40 of the lower midsole 4 may be provided to extend along the lateral side of the midsole 1 to the posterior end of the midsole 1, covering an area posterior to the forth and fifth proximal phalanges B3.sub.4 and B3.sub.5. The high-hardness area may be arranged so as to bulge toward the central portion in the fore foot portion.

(82) That is, the lateral line Ll, defining the high-hardness area, is curved so as to protrude toward the medial side in the fore foot portion, and is extending on the medial side of the MP joint MP.sub.5 of the fifth toe.

(83) On the other hand, the low-hardness medial portion 31 of the upper midsole 3 may be arranged over an extent that covers the first and second metatarsal bones B4.sub.1 and B4.sub.2, the first and second proximal phalanges B3.sub.1 and B3.sub.2, the first distal phalanx B1.sub.1 and the medial cuneiform bone, and may be covering the second middle phalanx B2.sub.2. The low-hardness area may be arranged so as to bulge toward the central portion in the fore foot portion.

(84) That is, the medial line Lm, defining the low-hardness area, is curved so as to protrude toward the lateral side in the fore foot portion, and is extending on the lateral side of the head 01 of the metatarsal bone of the first toe.

(85) Note that the lateral line Ll and the medial line Lm may come closest to each other in the vicinity of the MP joint MP.sub.3 of the third toe.

(86) In FIG. 5, the high-hardness lateral portion 40 of the lower midsole 4 covers the lower surface of the head 05 to the bottom 051 of the metatarsal bone of the fifth toe. The medial portion 41 of the lower midsole 4 set to the intermediate hardness covers the lower surface of the head 01 to the bottom 011 of the metatarsal bone of the first toe and the proximal phalanx B3.sub.1.

(87) In FIG. 5, the lateral portion 30 of the upper midsole 3 set to the intermediate hardness covers the lower surface of the head 05 to the bottom 051 of the metatarsal bone of the fifth toe. The medial portion 31 of the upper midsole 3 set to the lower hardness covers the lower surface of the head 01 to the bottom 011 of the metatarsal bone of the first toe and the proximal phalanx B3.sub.1, and this low-hardness area is preferably provided at least over an area from the shaft of the first metatarsal bone B4.sub.1 to the head of the first proximal phalanx B3.sub.1.

(88) As the areas are set as described above, the hardness of the medial portion 31 of the upper midsole 3 is lower than the hardness of a central portion 34, 44 of the upper midsole 3 or the lower midsole 4 in the medial-lateral direction, and the hardness of the lateral portion 30, 40 of the upper midsole 3 or the lower midsole 4 is higher than the hardness of the central portion 34, 44 of the upper midsole 3 or the lower midsole 4 in the medial-lateral direction.

(89) That is, as shown in FIG. 4, in the fore foot portion, the lateral portion 30, 40 has a layer of the first hardness, the central portion 34, 44 has a layer of the second hardness lower than the first hardness, and the medial portion 31, 41 has a layer of the third hardness lower than the second hardness.

(90) Specifically, as shown in FIG. 4, for example, in the area between the front line Lf and the back line Lb in the fore foot portion, the coarsely-dotted area on the lateral side of the lateral line Ll is the layer of the first hardness including the high-hardness lower midsole 4 and the intermediate-hardness upper midsole 3, whereas the densely-dotted area on the medial side of the medial line Lm is the layer of the third hardness including the intermediate-hardness lower midsole 4 and the low-hardness upper midsole 3. The undotted area between the first layer and the third layer is the layer of the second hardness including the intermediate-hardness lower midsole 4 and the intermediate-hardness upper midsole 3.

(91) As shown in FIGS. 4 and 5, the medial line Lm and the lateral line Ll are each bulging toward the center in the width direction X, and come closest to each other in the vicinity of the MP joint MP.sub.3 of the third toe. That is, in the fore foot portion, the width of the layer of the second hardness is smaller in the central portion thereof, and larger in the area anterior to the central portion and in the area posterior to the central portion, like an hourglass.

(92) Note that the layer of the first hardness may be provided in either the upper midsole 3 or the lower midsole 4 in the lateral portion 30, 40, and the layer of the third hardness may be provided in either the upper midsole 3 or the lower midsole 4 in the medial portion 31, 41.

(93) In FIG. 1, a through hole 33 is formed in the medial portion 31 of the upper midsole 3. The through hole 33 is provided at the position of the ball 01 of the big toe as shown in FIG. 5. As shown in FIG. 6B, the through hole 33 is filled with a low-resilience part 35 of a foamed resin. The hardness of the low-resilience part 35 is even lower than the hardness of the medial portion 31 of the upper midsole 3, and is set to about 22 degrees to about 28 degrees in JIS-C hardness.

(94) As shown in FIG. 6B, the lower midsole 4 may be slightly bulging in the area where the through hole 33 is provided, so that the thickness of the low-resilience part 35 is smaller than the thickness of the upper midsole 3. Then, it is possible to prevent the foot sole from sinking excessively in the area of the low-resilience part 35.

(95) Note that the through hole 33 and the low-resilience part 35 do not always need to be provided.

(96) As shown in FIGS. 3B, 6B and 6D, the stabilizer 5 for preventing a lateral shake may be provided. The stabilizer 5 is made of a non-foamed body of a resin, and the like, and is arranged along the lateral side surface of the lateral roll-up portion 42 further on the lateral side of the lateral roll-up portion 42. The height of the stabilizer 5 is less than the height of the lateral roll-up portion 42.

(97) As shown in FIGS. 3B and 6B, in the area of the lateral roll-up portion 42, a roll-up portion 22 of the outsole 2 is provided further on the lateral side of the stabilizer 5. The roll-up portion 22 is rolled up in the upward direction further on the lateral side of the lateral roll-up portion 42, serving to prevent a lateral shake of the ball 05 of the little toe. The height of the roll-up portion 22 is less than the height of the lateral roll-up portion 42.

(98) That is, as shown in FIG. 3B, when the shoe sole of the present invention is seen from the lateral side surface, in the area of the lateral roll-up portion 42 of the lower midsole 4, the stabilizer 5 is located at a level above the roll-up portion 22 of the outsole 2, and the lateral roll-up portion 42 of the lower midsole 4 is located at a level above the stabilizer 5.

(99) In the present shoe sole, the lateral roll-up portion 42 is formed by the lower midsole 4 made of a foamed body of a resin, the height (level) of the rubber outsole and the height of the stabilizer made of a non-foamed body of a resin, and the like, are set to be lower than the lateral roll-up portion 42 in the area of the lateral roll-up portion 42. This realizes an appropriate hardness and a light weight of the shoe sole, and it will unlikely lead to a decrease in the bendability of the foot at the MP joint or a decrease in the athletic functionality.

(100) The upper midsole 3 and the lower midsole 4 of the midsole 1 may be separately molded in primary molding, and may then be bonded together or molded together in secondary molding. Alternatively, only the intermediate-hardness area 41, 30 of FIG. 6B may be molded in primary molding, and the low-hardness and high-hardness areas may be molded with the intermediate-hardness areas, which have been molded in primary molding, inserted in the mold.

(101) As shown in FIGS. 3A and 5, the front line Lf and the back line Lb may define an area of the lower midsole 4 where the upper midsole 3 is arranged, and the lower midsole 4 may have steps along the front line Lf and the back line Lb so that the lower midsole 4 is dented down across the area. That is, the lower midsole 4 may be formed so as to have a depressed cross section.

(102) Specifically, as shown in FIG. 3A, in the vicinity of the back line Lb, the area posterior to the back line Lb may have an abruptly-increased thickness from the area anterior to the back line Lb. On the other hand, in the vicinity of the front line Lf, the area anterior to the front line Lf may have an abruptly-increased thickness from the area posterior to the front line Lf.

(103) The upper midsole 3 is fitted into the depressed portion of the lower midsole 4. That is, the upper midsole 3 does not extend to the anterior end 4e of the lower midsole 4, and the anterior end 4e of the lower midsole 4 is located anterior to the anterior end 3e of the upper midsole 3.

(104) FIGS. 8A to 8C each show a variation of the midsole of the embodiment.

(105) As shown in FIG. 8A, the lower midsole 4 may only include the lateral portion 40 so that the midsole is formed by two layers of the lower midsole 4 and the upper midsole 3 on the lateral side OUT of the shoe. On the medial side IN of the shoe, the midsole may be formed by a single upper midsole 3 whose thickness is equal to the two layers.

(106) For other than tennis shoes for women, e.g., for tennis shoes for men or shoes for other court sports, the upper midsole 3 with no hardness difference between the lateral side and the medial side may be arranged on the lower midsole 4 as shown in FIG. 8B.

(107) As shown in FIG. 8C, a high-hardness layer (the layer of the first hardness) may be provided on the lateral side OUT of the shoe, an intermediate-hardness layer (the layer of the second hardness) in the central portion, and a low-hardness layer (the layer of the third hardness) on the medial side IN.

(108) While preferred embodiments have been described above with reference to the drawings, various obvious changes and modifications will readily occur to those skilled in the art upon reading the present specification.

(109) For example, the hardness of the lateral portion 30 of the upper midsole 3 and the hardness of the medial portion 41 of the lower midsole 4 may be generally equal to each other or may be different from each other.

(110) For tennis shoes for men, the medial portion 31 of the upper midsole 3 may be set to a hardness generally equal to the hardness of the lateral portion 30 or that of the medial portion 41 of the lower midsole 4. That is, for example, the hardness of the medial portion and that of the lateral portion of the upper midsole 3 may be set to a certain hardness (a generally equal hardness).

(111) For tennis shoes for women, the lateral portion 40 of the lower midsole 4 may be set to a hardness generally equal to the hardness of the medial portion 41 of the lower midsole 4 or that of the lateral portion 30 of the upper midsole 3.

(112) Thus, such changes and modifications are deemed to fall within the scope of the present invention, which is defined by the appended claims.

INDUSTRIAL APPLICABILITY

(113) The present invention is applicable to a shoe sole for court sports such as tennis and basketball.

REFERENCE SIGNS LIST

(114) 1: Midsole 2: Outsole 22: Roll-up portion 3: Upper midsole 30: Lateral portion 31: Medial portion 32: Roll-up portion 33: Through hole 34: Central portion 35: Part 3e: Anterior end 4: Lower midsole 40: Lateral portion 41: Medial portion 42: Lateral roll-up portion 43: Base portion 44: Central portion 4e: Anterior end 5: Stabilizer CL: Central axis F1: Ground reaction force vector F2: Lower limb vector Lf: Front line Lb: Back line Ll: Lateral line Lm: Medial line M: Moment IN: Medial side OUT: Lateral side Y: Longitudinal direction X: Width direction