Shoes

BACKGROUND

The present invention relates to a shoe. Shoes have been known which are configured to absorb or cushion an impact applied in vertical direction when the wearer of the shoes steps on the ground during his/her running or walking. Specifically, such a shoe includes a midsole structure for absorbing and cushioning an impact applied in the vertical direction when the weight of a human body is put on the planta support surface of the shoe, in particular, to the heel support surface which supports the heel of a foot.

For example, Patent Document 1 discloses a shoe including a sole comprised of an outer sole of a synthetic resin and a midsole of a soft elastic member bonded to the upper surface of the outer sole. The midsole has a recess formed in a portion, of its upper surface, corresponding to the wearer's heel. A cushioning member which is softer than the midsole is received in the recess without leaving any gap between the cushioning member and the recess.

Patent Document 2 discloses a sport shoe including a shoe body and a shoe sole. A receiving recess having a predetermined depth is formed in the bottom surface of the shoe sole. A buffering element is received in the receiving recess. In plan view, the receiving recess has a shape similar to that of the buffering element. The receiving recess has a deformation allowance space for allowing the buffering element to become deformed freely in the radial direction when the buffering element bulges in the radial direction due to a vertical load applied thereonto.

CITATION LIST
Patent Documents

Patent Document 1: Japanese Unexamined Patent Publication No. 2008-18167

Patent Document 2: Japanese Unexamined Patent Publication No. H08-38211

SUMMARY
Technical Problem

Meanwhile, in general, main functions required for shoes such as running shoes and walking shoes include, for example, impact cushioning ability, heel stabilizing ability, fitting ability, gripping ability, and torsional rigidity. Various improvements have been made to enhance these functions. Among them, enhancement of the impact cushioning ability has been needed to provide shoes which can improve the wearer's performance. It has been found that when a wearer of shoes steps on the ground during his/her walking and running, a planta support surface (in particular, a heel support surface) provided at a midsole is subjected to not only an impact applied in a vertical direction, but also impacts applied in non-vertical directions (e.g., in the longitudinal and width directions of the shoes). This means that in order to give sufficiently enhanced comfortable feeling to wearer's feet when he/she steps on the ground, and to allow the wearer to walk and run with sufficiently increased comfort, it is important to appropriately absorb and cushion not only an impact applied in the vertical direction to a heel support surface, but also impacts applied in non-vertical directions to the heel support surface.

However, in the shoes of Patent Documents 1 and 2, although the buffering member having cushioning ability absorbs only an impact applied in the vertical direction to the heel support surface, the buffering member is immovably received in the receiving recess without any gap, and consequently, is not capable of cushioning impacts applied in non-vertical directions. In other words, the midsole structures of the shoes of Patent Documents 1 and 2 have insufficient impact cushioning ability, and thus, allow the wearer to step on the ground, run and walk with insufficiently-increased comfort.

In view of the foregoing background, it is therefore an object of the present invention to achieve improvement of a midsole structure so as to enable a wearer to step on the ground, walk and run with increased comfort.

Solution to the Problem

To achieve the object, with attention to the fact that when the weight of a human body is put on the heel support surface of a shoe, strong impacts are applied not only in the vertical direction but also in a non-vertical direction, the present invention is configured to permit a buffering member to relatively move within a receiving portion when a ground surface of an outsole contacts the ground.

Specifically, a first aspect relates to a shoe including a midsole which is arranged above an outsole having a ground surface configured to contact the ground, and which is configured to support a planta of a human body. The midsole include a longitudinally-extending midsole body which is made of an elastic material and has, on an upper surface, a planta support surface configured to support a plantar surface of the foot of the human body from the tiptoe to the back of the heel, a receiving portion which is provided in a back region in the planta support surface of the midsole body and which is a recess recessed toward the outsole, and a buffering member which is received in the receiving portion in an unfixed manner, includes, on an upper surface, a heel support surface configured to support the heel of the foot of the human body, and is configured to absorb an impact applied in a vertical direction to the heel support surface. A front clearance is provided between a front wall surface facing an inside of the receiving portion and a front end of the buffering body received in the receiving portion, and a back clearance is provided between a back wall surface facing the inside of the receiving portion and a back end of the buffering body received in the receiving portion.

The first aspect has a configuration in which the front clearance provided between the front wall surface of the receiving portion and the front end of the buffering body received in the receiving portion and the back clearance provided between the back wall surface of the receiving portion and the back end of the buffering body received in the receiving portion permit the buffering body to relatively move in the longitudinal direction of the shoe when the ground surface of the outsole contacts the ground and the human body weight is put on the heel support surface. As a result, an impact applied in the vertical direction to the heel support surface is absorbed by the buffering member having cushioning ability, and in addition, an impact applied in the longitudinal direction to the heel support surface is relieved in the midsole by the movement of the buffering member in the longitudinal direction within the receiving portion. That is, the buffering member having cushioning ability and movability cushions the impacts which are applied in the vertical and longitudinal directions to the heel support surface when the ground surface of the outsole contacts the ground. As a result, the foot of a wearer of the shoes of the first aspect can be given sufficiently enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and the wearer can run and walk with sufficiently increased comfort.

A second aspect of the present invention is an embodiment of the first aspect. According to the second aspect, each of the front and back clearances ranges from 0.5 mm to 5.0 mm.

Further, according to the second aspect, the buffering member is not allowed to relatively move in the longitudinal direction more than necessary. Consequently, the wearer of the shoes of the second aspect can be given sufficiently enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with sufficiently increased comfort.

A third aspect is an embodiment of the first or second aspect. In the third aspect, the buffering member has a width, in a width direction, which is substantially equal to a distance between left and right wall surfaces facing the inside of the receiving portion.

According to the third aspect, the buffering member is received in the receiving portion without leaving any gap between the left wall surface of the receiving portion and the left end of the second buffering member and between the right wall surface of the receiving portion and the right end of the buffering member. Consequently, the buffering member is permitted to move in the longitudinal direction within the receiving portion. In other words, the buffering member is restrained so as to resist relative movement in the width direction within the receiving portion. This makes it possible to relieve, with in the midsole, an impact applied in the longitudinal direction to the heel support surface. As a result, a wearer of the shoes of the third aspect can be given further enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with further increased comfort.

A fourth aspect is an embodiment of the first or second aspect. In the fourth aspect, a left clearance is provided between a left wall surface facing the inside of the receiving portion and a left end of the buffering body received in the receiving portion, and a right clearance is provided between a right wall surface facing the inside of the receiving portion and a right end of the buffering body received in the receiving portion, and the left and right clearances enable the buffering member to move relatively in a width direction in the receiving portion when the ground surface of the outsole contacts the ground and a weight of the human body is put on the heel support surface.

The fourth aspect has a configuration in which the left clearance provided between the left wall surface of the receiving portion and the left end of the buffering body received in the receiving portion and the right clearance provided between the right wall surface of the receiving portion and the right end of the buffering body received in the receiving portion permit the buffering body made of the elastic material to relatively move also in the width direction when the ground surface of the outsole contacts the ground and the human body weight is put on the heel support surface. As a result, an impact applied in the vertical direction to the heel support surface is absorbed by the buffering member having cushioning ability, and in addition, an impacts applied in the longitudinal and width direction to the heel support surface is relieved in the midsole by the movement of the buffering member in the width direction within the receiving portion. That is, impacts that are applied in the vertical, longitudinal, and width directions to the heel support surface when the ground surface of the outsole contacts the ground are cushioned by the buffering member having cushioning ability and movability and permitted to move within the receiving portion toward the four wall surfaces of the receiving portion. As a result, a wearer of the shoes of the fourth aspect can be given further enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with further increased comfort.

A fifth aspect of the present invention is an embodiment of the fourth aspect. According to the fourth aspect, each of the left and right clearances ranges from 0.5 mm to 5.0 mm.

According to the fifth aspect, the buffering member is not allowed to relatively move in the width direction more than necessary. Consequently, the wearer of the shoes of the fifth aspect can be given sufficiently enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with sufficiently increased comfort.

A sixth aspect is an embodiment of any one of the first to fifth aspects. In the sixth aspect, the buffering body has a stack structure in which a plurality of thin plates each made of an elastic material are stacked one above the other, and the thin plates are movable independently and relatively within the receiving portion.

According to the sixth aspect, since the buffering member has the stack structure comprised of the thin plates each made of an elastic material, relative movement of the thin plates causes a relative increase in the movement of the buffering member within the receiving portion. This contributes to further improvement of the cushioning ability for an impact applied to the heel support surface.

A seventh aspect is an embodiment of any one of the first to sixth aspects. In the sixth aspect, the buffering member is made of the same material as that forming the midsole body.

According to the seventh aspect, the buffering member has a cushioning capability equivalent to that of the midsole body. This configuration allows the entire midsole to evenly absorb impacts applied in the vertical direction to the planta support surface and the heel support surface, and enables a wearer to walk and run with increased comfort without making the wearer feel unpleasantness.

An eighth aspect is an embodiment of any one of the first to sixth aspect. In the eighth aspect, the buffering body is made of an elastic material which has a lower specific gravity or lower hardness than the midsole body.

According to the eighth aspect, the buffering member that has a greater cushioning ability than the midsole body can more concentratedly absorb an impact applied in the vertical direction to the planta support surface, in particular to the heel support surface.

Advantages of the Invention

As can be seen from the foregoing, according to the present invention, the buffering member provided with cushioning ability and movability increases the impact cushioning ability of the shoes. The wearer of the shoes of the present invention can be given further enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with further increased comfort.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a sole structure of a shoe according to a first embodiment of the present invention.

FIG. 2 corresponds to FIG. 1, and shows a sole structure of a shoe and a skeleton of a human foot in an overlapping fashion.

FIG. 3 is a cross-sectional view taken along line in FIG. 1.

FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1.

FIG. 5 corresponds to FIG. 1, and shows a sole structure of a shoe according to a second embodiment.

FIG. 6 corresponds to FIG. 4, and shows the sole structure of the shoe according to the second embodiment.

FIG. 7 corresponds to FIG. 4, and shows a variation of the second embodiment.

FIG. 8 corresponds to FIG. 4, and shows another variation of the second embodiment.

FIG. 9 corresponds to FIG. 3, and shows a sole structure of a shoe according to another embodiment.

FIG. 10 corresponds to FIG. 4, and shows a sole structure of a shoe according to another embodiment.

FIG. 11 is a graph showing relation between time and acceleration waveforms in the longitudinal direction in Example 1.

FIG. 12 is a graph showing accelerations in the longitudinal direction in Example 2 and samples.

DESCRIPTION OF EMBODIMENTS
First Embodiment

A first embodiment 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.

FIGS. 1 to 4 show a shoe S according to a first embodiment of the present invention. In the drawings, only the left shoe of a pair of shoes S is shown as an example. Since the right shoe is symmetrical to the left shoe S, only the left shoe S will be described in the following description, and the description of the right shoe will be omitted herein. In the following description, the expressions “above,” “upward,” “on a/the top of,” “below,” “under,” and “downward,” represent the vertical positional relationship between respective parts of the shoe S, and “front,” “fore,” “back,” and “hind” represent the longitudinal positional relationship between respective parts of the shoe S.

As shown in FIGS. 1 to 4, the shoe S includes an outsole 1 which includes ground surface 2 configured to contact the ground. The outsole 1 is made from a hard elastic material which is harder than a midsole body 4, which will be described later. Examples of suitable materials for the outsole 1 include 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. The outsole 1 is designed to have a thickness within the range, for example, from 2 mm to 7 mm. A more preferable proper range of the thickness is from 3 mm to 5 mm. Note that for the sake of convenience, hatching of the outsole 1 is omitted from the cross sections shown in FIGS. 3 and 4.

A midsole 3 configured to support a planta of a human body is provided above the outsole 1. A lower portion of the midsole 3 is bonded to an upper portion of the outsole 1 with an adhesive, for example. An upper (not shown) configured to cover a foot of a wearer is provided above the midsole 3.

The midsole 3 includes a midsole body 4 configured to support a plantar surface of the wearer. As shown in FIGS. 1 and 2, the midsole body 4 has, on its upper surface, a planta support surface 5 which is configured to support the plantar surface of a human body from the tiptoe to the back of the heel, and which extends in the longitudinal direction of the shoe. The midsole body 4 is made of a soft elastic material. Examples of suitable materials for the midsole body 4 include thermoplastic synthetic resins such as ethylene-vinyl acetate copolymer (EVA) and foams of the thermoplastic synthetic 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. The midsole body 4 is designed to have a hardness ranging from 30 C to 80 C (more preferably ranging from 45 C to 70 C, and specifically of 55 C) on the Asker C scale. The midsole body 4 is also designed to have a thickness of, for example, about 12 mm at a substantially middle portion in the longitudinal direction.

As shown in FIGS. 1 and 2, a first receiving portion 6 and a second receiving portion 7 are respectively formed in a front region and a back region in the planta support surface 5 of the midsole body 4. The first and second receiving portions 6, 7 are configured to receive a first buffering member 8 and a second buffering member 10, respectively, which will be described later. As shown in FIG. 3, each of the first and second receiving portions 6 and 7 is a recess which is formed in the planta support surface 5 of the midsole body 4 and recessed downward toward the outsole 1.

The first receiving portion 6 is formed at a location corresponding to a tread portion of a human foot (i.e., a front portion of a foot). Specifically, as shown in FIG. 2, the first receiving portion 6 is formed at a location corresponding to a region around the boundary between the foot phalanx part F and the metatarsal part M of the foot of the wearer wearing the shoe S.

As shown in FIGS. 1 and 2, a front wall surface 6a and a back wall surface 6b facing the inside of the first receiving portion 6 both extend linearly in the substantially width direction of the shoe. A left wall surface 6c facing the inside of the first receiving portion 6 (i.e., the wall surface close to the lateral side of the left foot shown in FIG. 2) extends along a curved portion of an outer edge 4a of the midsole body 4 which is adjacent to the left wall surface 6c. A right wall surface 6d facing the inside of the first receiving portion 6 (i.e., the wall surface close to the medial side of the left foot shown in FIG. 2) extends along a curved portion of an inner edge 4b of the midsole body 4 which is adjacent to the right wall surface 6d.

The second receiving portion 7 is formed at a location corresponding to the heel of a foot of a human body, (i.e., a back portion of a foot). Specifically, as shown in FIG. 2, the second receiving portion 7 is formed in a region which is in contact mainly with the heel bone H of the foot of the wearer wearing the shoe S.

As shown in FIGS. 1 and 2, a front wall surface 7a facing the inside of the second receiving portion 7 extends linearly in the substantially width direction, while a back wall surface 7b facing the inside of the second receiving portion 7 extends along a curved portion of a back edge 4c of the midsole body 4 which is adjacent to the back wall surface 7b. A left wall surface 7c facing the inside of the second receiving portion 7 (i.e., the wall surface close to the lateral side of the left foot shown in FIG. 2) extends linearly along the outer edge 4a of the midsole body 4 which is adjacent to the left wall surface 7c. On the other hand, a right wall surface 7d (i.e., the wall surface close to the medial side of the left foot shown in FIG. 2) extends along a curved portion of the inner edge 4b of the midsole body 4 which is adjacent to the right wall surface 7d.

As shown in FIGS. 3 and 4, each of the front and back wall surfaces 7a, 7b and the left and right wall surfaces 7c and 7d is flat in the vertical direction, so that the second receiving portion 7 has a cross-sectional structure in which its opening portion (upper portion) and bottom portion (lower portion) have the same shape. The second receiving portion 7 has a bottom 7e at a depth corresponding to a third or a half of the thickness of a back portion of the midsole body 4.

[As shown in FIGS. 1 and 2, the first receiving portion 6 receives therein the first buffering member 8 that is configured to support the treading portion of a human foot. The first buffering member 8 has, on its upper surface, a tread portion support surface 9 configured to support the tread portion of a human foot. The first buffering member 8 is made of an elastic material capable of absorbing an impact applied in the vertical direction to the tread portion step support surface 9. The shape formed by the outer peripheral surface of the first buffering member 8 corresponds to the shape formed by the inner peripheral surface of the first receiving portion 6. As a result, the first buffering member 8 is received in the first receiving portion 6 without any gap therebetween. In addition, the first buffering member 8 is received, without being fixed to the wall surfaces 6a to 6d and the bottom 6e of the first receiving portion 6, i.e., in an unfixed manner. The first buffering member 8 is preferably made of the same material as the material for thin plates 11, 11 forming the second buffering member 10. The thin plates 11, 11 will be described later.

As shown in FIGS. 1 and 2, the second receiving portion 7 receives therein the second buffering member 10 that is configured to support the heel of a foot (i.e., a portion including the heel bone H shown in FIG. 2). As shown in FIGS. 3 and 4, the second buffering member 10 has a stack structure comprised of the two thin plates 11, 11 made of an elastic material and stacked one above the other. A heel support surface 12 configured to support the heel of a human foot is formed on the upper surface of the upper thin plate 11. The thin plates 11, 11 forming the second buffering member 10 are made of the same material as that forming the midsole body 4.

As shown in FIG. 4, the heel support surface 12 is downwardly recessed and curved to cover the heel of the human foot. The heel support surface 12 has left and right ends which smoothly continue to the planta support surface 5 of the midsole body 4, except the second receiving portion 7. In other words, the second buffering member 10 is configured to absorb an impact which is applied in the vertical direction to the heel support surface 12 when the ground surface 2 of the outsole 1 contacts the ground and the weight of a human body is put on the heel support surface 12. In addition, just like the first buffering member 8, the second buffering member 10 is received, without being fixed to the wall surfaces 7a to 7d and the bottom 7e of the second receiving portion 7, i.e., in an unfixed manner.

As shown in FIG. 1, the present invention a feature in which the front end 10a of the second buffering member 10 extends linearly, in the width direction of the shoe, along the linear front wall surface 7a of the second receiving portion 7 with a predetermined clearance interposed between the front end 10a and the front wall surface 7a of the second receiving portion 7. On the other hand, the back end 10b of the second buffering member 10 is curved along the curved back wall surface 7b of the second receiving portion 7 with a predetermined clearance interposed between the back end 10b and the back wall surface 7b of the second receiving portion 7. In other words, in a state where the second receiving portion 7 has the second buffering member 10 received therein, the front clearance 21 is provided between the front wall surface 7a facing the inside of the second receiving portion 7 and the front end 10a of the second buffering member 10, and the back clearance 22 is provided between the back wall surface 7b facing the inside of the second receiving portion 7 and the back end 10b of the second buffering member 10. Each of the front and back clearances 21, 22 is preferably within the range from 0.5 mm to 5.0 mm, and more preferably is about 2.0 mm.

The front and back clearances 21, 22 enable the second buffering member 10 to move relatively in the longitudinal direction within the second receiving portion 7 when the ground surface 2 of the outsole 1 contacts the ground and the weight of a human body is put on the heel support surface 12. The thin plates 11, 11 forming the second buffering member 10 are unfixed to each other and can move independently and relatively in the longitudinal direction within the second receiving portion 7. To make the thin plates 11, 11 further movable with respect to each other, portions of the thin plates 11, 11 which are in contact with each other may be provided with a surface treatment (e.g., a treatment to attach a film), a treatment to apply lubricant, or a treatment to add powder such as baby powder.

As shown in FIG. 1, the left end 10c of the second buffering member 10 extends linearly along the left wall surface 7c facing the inside of the second receiving portion 7, while the right end 10d of the second buffering member 10 is curved along the right wall surface 7d facing the inside of the second receiving portion 7. The second buffering member 10 has a width, in the width direction, which is equal to the distance between the left and right wall surfaces 7c, 7d of the second receiving portion 7. In other words, in a state where the second receiving portion 7 has the second buffering member 10 received therein, no clearance is provided between the left wall surface 7c of the second receiving portion 7 and the left end 10c of the second buffering member 10, and between the right wall surface 7d of the second receiving portion 7 and the right end 10d of the second buffering member 10. As a result, while being permitted to move relatively in the longitudinal direction within the second receiving portion 7, the second buffering member 10 is restrained so as to resist relative movement in the width direction within the second receiving portion 7.

As can be seen from the foregoing, the shoe S of the first embodiment has the front and back clearances 21, 22 respectively provided between the front wall surface 7a of the second receiving portion 7 and the front end 10a of the second buffering member 10 received in the second receiving portion 7 and between the back wall surface 7b of the second receiving portion 7 and the back end 10b of the second buffering member 10 received in the second receiving portion 7. The front and back clearances 21, 22 permit the second buffering member 10 made of an elastic material to move relatively in the longitudinal direction within the second receiving portion 7 when the ground surface 2 of the outsole 1 contacts the ground and weight of a human body is put on the heel support surface 12. As a result, an impact applied in the vertical direction to the heel support surface 12 is absorbed by the second buffering member 10 having cushioning ability, and in addition, an impact applied in the longitudinal direction to the heel support surface 12 is relieved in the midsole 3 by the movement of the second buffering member 10 in the longitudinal direction within the second receiving portion 7. That is, the second buffering member 10 having cushioning ability and movability cushions the impacts which are applied in the vertical and longitudinal directions to the heel support surface 12 when the ground surface 2 of the outsole 1 contacts the ground. As a result, a wearer of the shoes S can be given enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with sufficiently increased comfort.

Further, since each of the front and back clearances 21, 22 is within the range from 0.5 mm to 5.0 mm, the second buffering member 10 is not allowed to move more than necessary in the longitudinal direction. Consequently, the wearer of shoes S can be given enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with sufficiently increased comfort.

Furthermore, since the width in the width direction of the second buffering member 10 is substantially equal to the distance between the left and right wall surfaces 7c, 7d of the second receiving portion 7, the second buffering member 10 is received in the second receiving portion 7 without leaving any gap between the left wall surface 7c of the second receiving portion 7 and the left end 10c of the second buffering member 10, and between the right wall surface 7d of the second receiving portion 7 and the right end 10d of the second buffering member 10. Consequently, the second buffering member 10 is permitted to move in the longitudinal direction within the second receiving portion 7. Thus, the second buffering member 10 is restrained so as to resist relative movement in the width direction within the second receiving portion 7. This makes it possible to concentratedly reduce an impact applied in the longitudinal direction to the heel support surface 12. As a result, a wearer of the shoes S can be given further enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with further increased comfort.

The second buffering member 10 has a stack structure in which two or more thin plates 11, 11 each made of an elastic material are stacked one above the other and in which the thin plates 11, 11 can move independently and relatively in the longitudinal direction within the second receiving portion 7. Therefore, the relative movement of the thin plates 11, 11 in the longitudinal direction causes a relative increase in the movement of the second buffering member 10 in the longitudinal direction within the second receiving portion 7. This contributes to further improvement of the cushioning ability for an impact applied in the longitudinal direction to the heel support surface 12.

In addition, since the second buffering member 10 and the midsole body 4 are made of the same material, the second buffering member 10 has a cushioning ability equivalent to that of the midsole body 4. This configuration allows the entire midsole to evenly absorb an impact applied in the vertical direction to the planta support surface 5 and the heel support surface 12, and enables a wearer to walk and run with increased comfort without making the wearer feel unpleasantness.

Second Embodiment

FIGS. 5 and 6 show a shoe S according to a second embodiment of the present invention. This embodiment differs from the first embodiment in that the second buffering member 10 of this embodiment can move also in the width direction of the shoe with in the second receiving portion 7. Note that except the second receiving portion 10, the components and configurations of the shoe S of this embodiment are the same as those of the shoe S of the first embodiment. Therefore, components that are the same as those shown in FIGS. 1 to 4 are denoted by the corresponding reference characters, and a detailed description thereof is omitted herein.

Specifically, as shown in FIGS. 5 and 6, the left end 10c of the second buffering member 10 linearly extends along the linear left wall surface 7c facing the inside of the second receiving portion 7 with a predetermined clearance interposed between the left end 10c and the left wall surface 7c of the second receiving portion 7. On the other hand, the right end 10d of the second buffering member 10 is curved along the curved right wall surface 7d facing the inside of the second receiving portion 7 with a predetermined clearance interposed between the right end 10d and the right wall surface 7d of the second receiving portion 7. In a state where the second receiving portion 7 has the second buffering member 10 received therein, the left clearance 23 is provided between the left wall surface 7c facing the inside of the second receiving portion 7 and the left end 10c of the second buffering member 10, and the right clearance 24 is provided between the right wall surface 7b facing the inside of the second receiving portion 7 and the right end 10d of the second buffering member 10. That is, in the second receiving portion 7, the clearances 21 to 24 are provided between the second buffering member 10 and the all wall surfaces of the second receiving portion 7 including the front, back, left, and side walls. Each of the left and right clearances 23, 24 is preferably within the range from 0.5 mm to 5.0 mm, and more preferably is about 2.0 mm.

The left and right clearances 23, 24 enable the second buffering member 10 to move relatively in the width direction within the second receiving portion 7 when the ground surface 2 of the outsole 1 contacts the ground and the weight of a human body is put on the heel support surface 12. The thin plates 11, 11 forming the second buffering member 10 are unfixed to each other and can move independently and relatively in the width direction within the second receiving portion 7.

As can be seen from the foregoing, the shoe S of the second embodiment has the left and right clearances 23, 24 respectively provided between the left wall surface 7c of the second receiving portion 7 and the left end 10c of the second buffering member 10 received in the second receiving portion 7 and between the right wall surface 7d of the second receiving portion 7 and the right end 10d of the second buffering member 10 received in the second receiving portion 7. The left and right clearances 23, 24 permit the second buffering member 10 made of an elastic material to move relatively also in the width direction within the second receiving portion 7 when the ground surface 2 of the outsole 1 contacts the ground and the weight of a human body is put on the heel support surface 12. As a result, an impact applied in the vertical direction to the heel support surface 12 is absorbed by the second buffering member 10 having cushioning ability, and in addition, impacts applied to the heel support surface 12 in the longitudinal and width directions of the shoe are relieved in the midsole 3 by the movements of the second buffering member 10 in the longitudinal and width directions within the second receiving portion 7. That is, when the ground surface 2 of the outsole 1 contacts the ground, impacts applied in the vertical direction and the longitudinal and width directions to the heel support surface 12 are cushioned by the second buffering member 10 that has cushioning ability and movability toward the four wall surfaces 7a to 7d surrounding the second receiving portion 10. As a result, a wearer of the shoes S can be given further enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with further increased comfort.

Moreover, since each of the left and right clearances 23, 24 is within the range from 0.5 mm to 5.0 mm, the second buffering member 10 is not allowed to move more than necessary in the width direction. Consequently, a wearer of the shoes S can be given sufficiently enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and can run and walk with sufficiently increased comfort.

Furthermore, the second buffering member 10 has a stack structure in which two thin plates 11, 11 each made of an elastic material are stacked one above the other. The thin plates 11, 11 can move independently in the width direction within the second receiving portion 7. Therefore, the relative movement of the thin plates 11, 11 in the width direction causes a relative increase in the movement of the second buffering member 10 in the width direction within the second receiving portion 7. This contributes to further improvement of the cushioning ability for an impact applied in the width direction to the heel support surface 12.

Variation of Second Embodiment

In this embodiment, the second receiving portion 7 provided in the midsole 3 of the shoe S has the flat wall surfaces so as to have a cross-sectional structure in which its opening portion (upper portion) and bottom portion (lower portion) have the same shape. However, this is a mere example.

For example, as shown in FIG. 7, each of the left and right wall surfaces 7c and 7d facing inside of the second receiving portion 7 may have a step such that its cross section is stepped in the vertical direction. In this case, it is suitable that the lower portions of the left and right wall surfaces 7c, 7d are less distant in the width direction from each other than the upper portions of the left and right wall surfaces 7c, 7d, and that the lower thin plate 11 forming part of the second buffering member 10 is narrower in the width direction than the upper thin plate 11. In this variation, the thin plates 11, 11 placed one above the other can move independently in the width direction within the second receiving portion 7.

Alternatively, as shown in FIG. 8, the second receiving portion 7 may have a V-shaped cross section. Specifically, the distance in the width direction between left and right portions of the bottom 7e (the left and right side walls 7c, 7d) may decrease downwardly. In this case, it is suitable that the second buffering member 10 includes the lower thin place 11 which is bended to have a V-shaped cross section and the upper thin plate 11 having a cross-section in a substantially inverted triangle shape. Also in this variation, the thin plates 11, 11 placed one above the other can move relatively and independently in the width direction within the second receiving portion 7.

Specifically, in each of the variations shown in FIGS. 7 and 8, the second receiving portion 7 is formed to have a width in the width direction decreasing downward. This configuration easily concentrates an impact applied in the vertical direction to the heel support surface 12 to a central portion of the second buffering member 10, and contributes to an increase in the impact absorbability of the second buffering member 10. In each of the variations, the thin plates 11, 11 placed one above the other can move independently in the width direction within the second receiving portion 7. As described previously, this configuration causes a relative increase in the movement of the second buffering member 10 in the width direction within the second receiving portion 7, and consequently, contributes to improvement of the cushioning ability for an impact applied in the width direction to the heel support surface 12.

Moreover, in the variation shown in FIG. 8, the second buffering member 10 having a cross section in a substantially inverted triangle shape is fitted in the second receiving portion 7 having a V-shaped cross section. This configuration limits relative movement in the width direction, as compared to the configuration of the variation shown in FIG. 7, while facilitating relative movement in the longitudinal direction. Even if an impact applied in the width direction to the heel support surface 12 causes relative movement of the thin plates 11, 11 in the width direction, the central portion of the lower thin plate 11 (i.e., a vertex of the inverted triangle) is easily returned to the central portion in the width direction of the second receiving portion 7 (i.e., the valley of the bottom 7e shown in FIG. 8), and the central portion of the upper thin plate 11 (i.e., a vertex of the inverted triangle) is easily returned to the valley on the upper surface of the lower thin plate 11. As can be seen, in the variation shown in FIG. 8, the second buffering member 10 is permitted to move relatively also in the width direction within the second receiving portion 7, while being easy to stably hold at its home position (i.e., its initial position) within the second receiving portion 7.

Other Embodiments

As shown in FIGS. 9 and 10, the shoes S of the embodiments described above may include an additional corrugated plate 30 between the outsole 1 and the midsole 3. The corrugated plate 30 extends from a portion corresponding to the plantar arch to the back of the heel of a human foot, and is corrugated in the vertical direction as viewed from a side. The provision of the corrugated plate 30 substantially prevents the midsole 3 from being deformed locally and significantly even if an impact is applied in the vertical direction to the heel support surface 12 and the planta support surface 5. Consequently, when the wearer is walking and running, the wearer's ankle is substantially prevented from excessively leaning inward or outward, thereby enabling increased stability to be ensured.

In the midsole 3 of the shoe S of each embodiment described above, the first buffering member 8 is received, without being fixed to the wall surfaces 6a to 6d and the bottom 6e of the first receiving portion 6, i.e., in an unfixed manner. However, this is a mere example. Specifically, the first buffering member 8 may be received in and fixed to the first receiving portion 6.

In the midsole 3 of the shoe S of each embodiment described above, the thin plates 11, 11 forming the second buffering member 10 are made of the same material as that forming the midsole body 4. However, this is a mere example. The thin plates 11, 11 forming the second buffering member 10 may be made of an elastic material which has a lower specific gravity or a lower hardness than the midsole body 4. With this configuration, the second buffering member 10 that has a greater cushioning ability than the midsole body 4 can concentratedly absorb an impact applied in the vertical direction to the planta support surface 5, in particular, to the heel support surface 12.

In the midsole 3 of the shoe S of each embodiment described above, the second buffering member 10 is comprised of the thin plates 11, 11 stacked one above the other. However, this is a mere example.

Specifically, the second buffering member 10 may be comprised of three or more thin plates 11, 11, . . . made of an elastic material and stacked one above the other.

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

Examples

Next, examples which were actually implemented will be described.

[Acceleration Characteristic Evaluation Test 1]

In this evaluation test, force acting on the foot of a running test subject was studied from a kinematic view point. Specifically, an accelerometer was attached to an area, of the test subject, corresponding to a tibia and located above an ankle joint (at a point about 4 cm directly above an inner malleolus). Time-varying changes in the acceleration acting in the longitudinal direction on the foot of the running test subject were measured.

The results are shown in the graph of FIG. 11. Changes in the state in which the test subject's foot contacted the ground are represented by the peaks and valleys of each waveform. The horizontal axis represents time (msec). The vertical axis represents the acceleration waveform in the longitudinal direction (Unit). Backward acceleration and the forward acceleration in the running direction are shown above and below the origin, respectively. Note that the values (each of which is an acceleration value at a point of time) constituting each waveform shown in FIG. 11 are actual values measured with the accelerometer described above.

The waveforms shown in FIG. 11 correspond to two types of shoes, i.e., the shoes of Example 1 and shoes of Comparative Example 1. The waveform of Comparative Example 1 represents the result of shoes of the known art not provided with the clearances, which constitute a feature of the present invention. The waveform of Example 1 represents the result of the shoes of the present invention provided with the front, back, left, and right clearances (each having a dimension of 2.0 mm).

FIG. 11 shows that, in a continuous cycle from the contacting the ground to the separation from the ground, backward acceleration and forward acceleration alternately act on the foot of the running test subject. It has been found that in the time range from 10 msec to 30 msec, the differences between the peaks and the valleys of the waveform of Example 1 is smaller than those of the waveform of Comparative Example 1. In particular, at the point of time at about 17 msec (i.e., at which the first deep valley of each waveform appears), the valley of the waveform of Comparative Example 1 indicates an acceleration value of about −4000, whereas the valley of the waveform of Example 1 indicates a limited acceleration value of about −2000. Thus, with respect to the forward acceleration, the waveform of Example 1 indicates a value limited to about a half of the value indicated by the waveform of Comparative Example 1. On the other hand, at the point of time at about 19 msec (i.e., at which the first high peak of each waveform appears), the peak of the waveform of Comparative Example 1 indicates an acceleration value of about 7000, whereas the peak of the waveform of Example 1 indicates a limited acceleration value of about 5000. Thus, also with respect to the backward acceleration, the waveform of Example 1 indicates a limited value which is smaller than the value indicated by the waveform of Comparative Example 1. It has been confirmed, from these results, that the shoes of the present invention reduced the impact applied in the longitudinal direction when the test subject stepped on the ground, to a greater extent than the shoes of the known art.

[Acceleration Characteristic Evaluation Test 2]

In this evaluation test, a test subject wore shoes of Examples 2 to 7 and shoes of Comparative Examples 2 and 3 described in Table 1, and the accelerations in the longitudinal direction were measured for each pair of shoes.

TABLE 1

Second Buffering Member
Clearances

(Number of layers of
Front and Back Clearances
Left and Right Clearances
Corrugated

thin plates)
(Clearance Dimension)
(Clearance Dimension)
Plate

Comparative
Absent
Absent
Absent
Absent

Example 2

Example 2
Present
Present
Present
Absent

(Two Layers)
(0.5 mm each)
(0.5 mm each)

Example 3
Present
Present
Present
Absent

(One Layer)
(0.5 mm each)
(0.5 mm each)

Example 4
Present
Present
Present
Absent

(Two Layers)
(2.0 mm each)
(2.0 mm each)

Example 5
Present
Present
Present
Absent

(Two Layers)
(0.5 mm each)
(0.5 mm each)

Example 6
Present
Present
Absent
Absent

(Two Layers)
(2.0 mm each)

Comparative
Absent
Absent
Absent
Present

Example 3

Example 7
Present
Present
Present
Present

(Two Layers)
(2.0 mm each)
(2.0 mm each)

Just like the evaluation test 1, the forward and backward accelerations were measured with an accelerometer attached to an area, of the test subject, corresponding to a tibia and located above an ankle joint (at a point about 4 cm directly above an inner malleolus). Time-varying changes in the acceleration acting in the longitudinal direction on the foot of the running test subject were measured. The results of this evaluation test are shown in FIG. 12. The values represented in the bar graph of FIG. 12 were derived by integrating the absolute values of actual values measured with the accelerometer described above within the range from 0 ms to 100 ms.

FIG. 12 shows that the acceleration values in the longitudinal direction of the shoes of Examples 2 to 6 and 7 provided with the clearances that constitute the feature of the present invention, i.e. the front and back clearances within the range from 0.5 mm to 5.0 mm are generally lower than those of the shoes of Comparative Examples 2 and 3 not provided with the clearances that constitute the feature of the present invention. It has also been found that among the shoes of Examples 2 to 6, the acceleration values in the longitudinal direction of the shoes of Examples 2 and 4 to 6 including the second buffering member comprised thin plates stacked in two layers are lower than those of the shoes of Example 3 including the buffering member comprised of only one layer of a buffering member.

The results also show that the acceleration values in the longitudinal direction of the shoes of Example 6 provided with the front and back clearances are yet lower than those of the shoes of Examples 2 to 5 provided with the front, back, left, and right clearances. The reason for this is as follows: In the shoes of Example 6, while being permitted to move relatively in the longitudinal direction within the second receiving portion, the second buffering member is restrained so as to resist relative movement in the width direction within the second receiving portion. Therefore, the impact applied in the longitudinal direction to the heel support surface is reduced concentratedly, resulting in limitation of the acceleration values in the longitudinal direction to lower values. As to the dimension of each of the front and back clearances, it has been found that the clearance of, in particular, 2.0 mm, which is included in the range from 0.5 mm to 5.0 mm, limits the acceleration values in the longitudinal direction to particularly low values.

In addition, it has been found that the acceleration values in the longitudinal direction of the shoes of Example 7 provided with the corrugated plate are lower than those of the shoes of Examples 2 to 6.

It has been confirmed, from the foregoing results, that the shoes of the present invention reduce the impact applied in the longitudinal direction when the test subject stepped on the ground to a greater extent than the shoes of the known art. Thus, it has been found that the shoes of the present invention can give a wearer enhanced comfortable feeling when he/she steps on the ground during his/her walking and running, and allows the wearer to run and walk with increased comfort.

INDUSTRIAL APPLICABILITY

The present invention is industrially applicable as shoes such as walking shoes and running shoes.

DESCRIPTION OF REFERENCE CHARACTERS

- S Shoe
- 1 Outsole
- 2 Ground Surface
- 3 Midsole
- 4 Midsole Body
- 5 Planta Support Surface
- 7 Second Receiving Portion (Receiving Portion)
- 7
  a Front Wall Surface
- 7
  b Back Wall Surface
- 7
  c Left Wall Surface
- 7
  d Right Wall Surface
- 7
  e Bottom
- 10 Second Buffering Member (Buffering Member)
- 10
  a Front End
- 10
  b Back End
- 10
  d Left End
- 10
  e Right End
- 11, 11 Thin Plate
- 12 Heel Support Surface
- 21 Front Clearance
- 22 Back Clearance
- 23 Left Clearance
- 24 Right Clearance
- 30 Corrugated Plate

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