Sole Structure for a Shoe

TECHNICAL FIELD

The present invention relates generally to a sole structure for a shoe, and more particularly, to an improved sole structure that can prevent deterioration of cushioning performance to improve cushioning properties and that can enhance flexibility.

BACKGROUND ART

As a sole structure for a shoe that can prevent deterioration of athletic ability while securing cushioning properties at the time of striking the ground, the applicant of the present invention has proposed such a sole structure as shown in Japanese Patent No. 3308482. Japanese Patent No. 3308482 describes a sole structure in which the wavy corrugated sheet is interposed between the soft elastic upper midsole and the soft elastic lower midsole at least at the heel region of the shoe (see FIG. 1 of JP Pat. No. 3308482).

On the other hand, Japanese Patent No. 4656543 describes a sole structure in which a number of deep indentations are formed on the bottom surface of the midsole at the region extending from the heel region to the forefoot region of the sole structure of the shoe (see FIG. 1 of JP Pat. No. 4656543).

In the above-mentioned structure described in JP Pat. No. 3308482, the wavy corrugated sheet is interposed between the upper and lower midsoles and the amplitude and/or wavelength of the wave shape of the wavy corrugated sheet are changed appropriately according to a part where the wavy corrugated sheet is disposed, thereby adjusting the cushioning properties and preventing a foot from leaning sideways to restrain deterioration of athletic ability. Also, in the above-mentioned structure described in JP Pat. No. 4656543, a number of deep indentations facilitates bending deformation of the midsole, thus improving sole flexibility during running (see FIG. 7 of JP Pat. No. 4656543).

However, in the structure of JP Pat. No. 3308482, interposition of the wavy corrugated sheet between the upper and lower midsoles can prevent deterioration of the cushioning properties of the sole structure compared with a sole structure without a wavy corrugated sheet, while longitudinal deformation of the wavy corrugated sheet is restrained by the upper and lower midsoles having the wavy corrugated sheet embedded therein thus cushioning properties based on a vertical deformation of the wavy corrugated sheet is restrained. Also, in the structure of JP Pat. No. 4656543, a number of midsole elements, which are separated by a number of deep indentations formed on the bottom surface of the midsole along the approximately entire length of the midsole from the heel part to the forefoot part of the midsole, are easy to deform excessively and each of the midsole elements is easy to be exposed to external environment. As a result, there is a risk that cushioning properties of the midsole easily become deteriorated.

The present invention has been made in view of these circumstances and its object is to provide a sole structure for a shoe that can not only prevent deterioration of cushioning performance and improve cushioning properties but also enhance flexibility.

DISCLOSURE OF INVENTION

A sole structure for a shoe according to a first aspect of the present invention includes a rear foot sole disposed at a rear foot region of the sole structure, a forefoot sole disposed at a forefoot region of the sole structure, and a plate disposed at the rear foot region of the sole structure and having an upwardly convexly curved shape along a heel part to a midfoot part of the sole structure. A front end portion of the plate is disposed at a front end portion of the rear foot sole and there is formed a gap in front of the front end port ion of the plate between the front end portion of the rear foot sole and a rear end portion of the forefoot sole.

According to the first aspect of the present invention, since the plate having the upwardly convexly curved shape is provided at the rear foot region of the sole structure, deterioration of cushioning performance of the rear foot region of the sole structure can be prevented. Also, since the front end of the plate is disposed at the front end of the rear foot sole and the gap is formed in front of the front end of the plate between the front end of the rear foot sole and the rear end of the forefoot sole, a forward movement of the front end of the plate at the time of deformation of the plate is not hindered by the sole thereby allowing for a smooth deformation of the plate to improve cushioning properties. Moreover, the gap formed in front of the front end of the plate facilitates bending deformation of the rear foot sole relative to the forefoot sole thus enhancing flexibility.

The rear foot sole and the forefoot sole may be respectively formed of a midsole of a soft elastic material, and the rear end portion of the forefoot sole may be provided separately from the front end portion of the rear foot sole through the gap.

Since the forefoot sole is separated from the rear foot sole through the gap, the rear foot sole is easier to bending-deform relative to the forefoot sole, thus further improving flexibility. Also, cushioning properties can be further improved by employing the midsole of soft elastic material.

The rear foot sole and the forefoot sole may have a first ground-contact outsole and a second ground-contact outsole respectively attached on a bottom surface of each of the rear foot sole and the forefoot sole. The first outsole and the second outsole may be interconnected with each other via a connection in the gap between the front end portion of the rear foot sole and the rear end portion of the forefoot sole.

The connection can prevent pebbles, sand and the like from entering the gap from outside. Also, since the first outsole and the second outsole are connected through the connection, the rear foot sole and the forefoot sole are connected to each other through the first and second outsoles and the connection and the entire sole structure is thus integrated.

The connection may have a path length that is longer than a longitudinal length of the gap between the front end portion of the rear foot sole and the rear end portion of the forefoot sole.

Since the connection has an elongation allowance as the rear foot sole bending-deforms relative to the forefoot sole, the connection does not hinder bending-deformation of the rear foot sole thus allowing for a smooth bending-deformation of the rear foot sole to improve flexibility of the sole structure.

The connection may have a bending portion of an inverted V-shape or an inverted U-shape viewed from a side face of the connection in the gap. Such a bending portion of an inverted V-shape or U-shape of the connection can secure adequate amount of elongation allowance.

The rear foot sole may include a heel sole that protrudes downwardly at the heel region of the sole structure and a midfoot sole that that protrudes downwardly at the midfoot region of the sole structure. There may be provided a region in which the rear foot sole is not provided or the rear foot sole recedes upwardly between the heel sole and the midfoot sole.

Since the rear end portion of the plate is supported by the heel sole and the front end portion of the plate is supported by the midfoot sole at the time of impacting the ground, thus allowing for a stable support of the entire plate. Also, since there is provided the region where the rear foot sole is not provided or the rear foot sole recedes upwardly between the heel sole and the midfoot sole and a thickness of the sole structure at the region is thus made relatively small, thereby improving flexibility and cushioning properties of the sole structure at the region.

The rear foot sole may be formed of an upper midsole disposed on an upper side of the rear foot sole and a lower midsole disposed on a lower side of the rear foot sole. The plate may be interposed between the upper midsole and the lower midsole.

The upper midsole of a soft elastic material provided above the plate can improve wearer's touch on the foot and the lower midsole of a soft elastic material provided under the plate can attenuate shock transmitted from the ground at the time of impacting the ground thus further improving cushioning properties.

The plate may be formed of a hard elastic material. Since the plate is relatively hard to lose elasticity compared to the case in which the plate is formed of a soft elastic material, deterioration of cushioning performance of the sole structure can be more securely prevented.

The rear foot sole and the forefoot sole may be respectively formed of a midsole of soft elastic material. The rear foot sole and the forefoot sole may be connected to each other through a connection that extends from the midsole and that is disposed in the gap between the front end of the rear foot sole and the rear end of the forefoot sole.

The connection can prevent pebbles, sand and the like from entering the gap from outside. Also, since the rear foot sole and the forefoot sole are connected to each other through the connection and the entire sole structure is thus integrated.

The connection may be formed of a thin part of the midsole. Since the connection is easy to deform elastically, the connection does not hinder bending-deformation of the rear foot sole relative to the forefoot sole, thereby allowing for a smooth bending-deformation of the rear foot sole to improve flexibility of the sole structure.

The connection may have a path length that is longer than a longitudinal length of the gap between the front end portion of the rear foot sole and the rear end portion of the forefoot sole.

The connection may have a bending portion of an inverted V-shape or U-shape viewed from a side face of the connection in the gap. Such a bending portion of an inverted V-shape or U-shape of the connection can secure adequate amount of elongation allowance.

The rear foot sole and the forefoot sole may have a first ground-contact outsole and a second ground-contact outsole respectively attached on a bottom surface of each of the rear foot sole and the forefoot sole. The first outsole and the second outsole may be separated through the gap between the front end portion of the rear foot sole and the rear end portion of the forefoot sole.

Since the first outsole and the second outsole are separated through the gap, as the rear foot sole bending-deforms relative to the forefoot sole the outsole does not hinder bending-deformation of the rear foot sole, thereby allowing for ease of smooth bending-deformation of the rear foot sole and thus improving flexibility of the sole structure.

A sole structure for a shoe according to a second aspect of the present invention includes a forefoot sole disposed at a forefoot region of the sole structure, a rear foot sole disposed on a rear side of the forefoot region of the sole structure, and a plate disposed along the rear foot sole. There is formed a gap without the rear foot sole in front of the front end of the plate.

According to the second aspect of the present invention, the plate provided at the rear foot sole of the sole structure can prevent deterioration of cushioning performance of the rear foot sole. Also, since there is formed a gap without the rear foot sole in front of the front end of the plate, a forward movement of the front end of the plate at the time of deformation of the plate is not hindered by the sole thereby allowing for a smooth deformation of the plate to improve cushioning properties. Moreover, the gap formed in front of the front end of the plate facilitates bending deformation of the rear foot sole relative to the forefoot sole thus enhancing flexibility.

The plate may be provided at a heel part or a midfoot part of the sole structure.

The plate may have an upwardly convexly curved shape.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a bottom view of a sole structure for a shoe according to an embodiment of the present invention;

FIG. 2 is a medial side view of the sole structure of FIG. 1;

FIG. 3 is a lateral side view of the sole structure of FIG. 1;

FIG. 4 is a top plan view of the sole structure of FIG. 1;

FIG. 5 is a longitudinal sectional view of FIGS. 1 and 4 taken along line V-V;

FIG. 6 is a cross sectional view of FIGS. 1 to 5 taken along line VI-VI;

FIG. 7 is a cross sectional view of FIGS. 1 to 5 taken along line VII-VII;

FIG. 8 is a cross sectional view of FIGS. 1 to 5 taken along line VIII-VIII;

FIG. 9 is a cross sectional view of FIGS. 1 to 5 taken along line IX-IX;

FIG. 10 illustrates a position of a gap between a rear foot sole and a forefoot sole in the sole structure of FIG. 1 along with a bone structure of a foot;

FIG. 11 is a perspective view of an entire plate composing the sole structure of FIG. 1;

FIG. 12 is a bottom view of the plate of FIG. 11;

FIG. 13 is a medial side view of the plate of FIG. 11;

FIG. 14 is a lateral side view of the plate of FIG. 11;

FIG. 15 is a longitudinal sectional view of the plate of FIG. 11;

FIG. 16 illustrates a longitudinal position and a vertical protrusion height of a maximum protruding part of the plate of FIG. 11 along with a bone structure of a foot;

FIG. 17A corresponds to FIG. 5, illustrating a state of the sole structure of FIG. 1 before impacting the ground;

FIG. 17B illustrates a foot-flat state of the sole structure of FIG. 1 after impacting the ground;

FIG. 18 is a longitudinal sectional view of a sole structure for a shoe according to another embodiment of the present invention, corresponding to FIG. 5; and

FIG. 19 is a longitudinal sectional view of a sole structure for a shoe according to a still another embodiment of the present invention, corresponding to FIG. 5.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be hereinafter described in accordance with the appended drawings.

FIGS. 1 to 17B show a sole structure for a shoe according to an embodiment of the present invention. In the illustrated example, a running shoe is taken as an example.

In the following explanations, upward direction (upper side), downward direction (lower side), forward direction (front side), and rearward direction (rear side) of the sole structure designate upward direction (upper side), downward direction (lower side), forward direction (front side), and rearward direction (rear side) of the shoe, respectively. That is, taking FIG. 2 as an example, an upward direction and a downward direction of the sole structure indicate a left side and a right side of FIG. 2 respectively, and a forward direction and a rearward direction of the sole structure indicate an upward direction and a downward direction of FIG. 2 respectively. Also, in FIGS. 1 to 5, H designates a heel part of the sole structure, M for a midfoot part, and F for a forefoot part respectively.

As shown in FIGS. 1 to 5, Sole structure 1 for a shoe includes a rear foot sole 2 (2A, 2B) disposed at a rear foot region that extends from the heel part H to the midfoot part M of the sole structure 1, a forefoot sole 3 disposed at the forefoot part F of the sole structure 1, and a plate 4 disposed at the rear foot region of the sole structure 1. The rear foot sole 2 is formed of an upper sole 2A disposed on an upper side of the sole structure 1 and a lower sole 2B disposed below the upper sole 2A. The plate 4 is interposed between the upper sole 2A and the lower sole 2B.

The plate 4 extends from a heel rear end of the sole structure 1 to a border or in the vicinity of the border between the midfoot part M and the forefoot pat F. A front end 4f of the plate 4 is located at a front end portion of the rear foot sole 2, that is, a front end portion 2Af of an upper sole 2A and a front end portion 2Bf of a lower sole 2B. There is formed a gap S in front of the front end 4f of the plate 4 between the front end portion of the rear foot sole 2 and a rear end portion 3r of the forefoot sole 3. In other words, in front of the front end portion 4f of the plate 4 is formed a space area in which the rear foot sole 2 as well as the forefoot sole 3 does not exist. A longitudinal clearance of the gap S depends on the size of the shoe but is set to 1-10 mm. Because the gap S of at least 1 mm enables a forward movement of the plate 4 (the details of the grounds are described hereinafter) and when the gap S exceeds 10 mm a sensory evaluation test by a wearer who actually wore the shoe proved that wearer's touch on the foot worsened due to an excessive clearance under a foot sole of the wearer. The rear end portion 3r of the forefoot sole 3 is separated from the front end portion of the rear foot sole 2 through the gap S.

In this embodiment, the rear foot sole 2 (i.e. the upper and lower soles 2A, 2B) and the forefoot sole 3 are preferably formed of a midsole of a soft elastic material, more specifically, thermoplastic resin such as ethylene-vinyl acetate copolymer (EVA) and the like, foamed thermoplastic resin, thermosetting resin such as polyurethane (PU) and the like, foamed thermosetting resin, rubber materials such as butadiene rubber, chloroprene rubber and the like, or foamed rubber materials.

The plate 4 is preferably formed of a hard elastic material, more specifically, thermoplastic resin such as thermo plastic polyurethane (TPU), polyamide elastomer (PAE), acrylonitrile-butadiene-styrene (ABS) resin and the like, or thermosetting resin such as epoxy resin, unsaturated polyester resin and the like. In addition, the plate 4 may be formed of fiber reinforcedprastics (FRP) formed of reinforcing fibers such as carbon fibers, aramid fibers, glass fibers or the like and matrix resin such as thermosetting resin or thermoplastic resin.

On bottom surfaces of the lower sole 2B and the forefoot sole 3, outsoles 5A, 5B and 5C each having ground contact surface that contacts the ground are attached. The outsole 5A is disposed at a heel rear end portion of the lower sole 2B, the outsole 5B at a midfoot portion of the lower sole 2B, and the outsole 5C at the forefoot sole 3.

The outsoles 5B and 5C are connected to each other through a connection 50 that extends from the outsoles 5B, 5C in the gap S between the front end portion of the rear foot sole 2 and the rear end portion 3r of the forefoot sole 3. The connection 50 extends not only in a longitudinal direction but also in a sole width direction in the gap S. Also, the connection 50 has a bending portion of an inverted V-shape or an inverted U-shape viewed from a side face of the connection 50 in the gap S. The connection 50 thus has a path length that is longer than a longitudinal length of the gap S between the front end portion of the rear foot sole 2 and the rear end portion 3r of the forefoot sole 3.

In this embodiment, the outsole 5C has a groove 51 extending substantially in the longitudinal direction. The outsole 5C is separated in the longitudinal direction by a clearance 52 extending in the width direction and also separated in the width direction by a clearance 53 extending in the longitudinal direction. The clearances 52, 53 may be a groove, and the outsole 5C is not necessarily separated in the longitudinal/width direction. On the other hand, the outsole 5B is separated in the width direction by a clearance 54 that extends in the longitudinal direction along the clearance 53. The clearance 54 may be a groove, and the outsole 5B is not necessarily separated in the width direction. In either case, in the event that the outsole is separated by the clearance, respective parts separated by the clearance are easier to deform independently from other parts, which contributes to improvement of sole flexibility (in the longitudinal direction as well as the width direction) at the time of impacting the ground.

As shown in cross sectional views of FIGS. 7-9, the upper sole 2A of the rear foot sole 2 has a foot sole contact portion 2A₀that a wearer's foot sole contacts via an upper bottom portion, insole board, insole or the like (not shown). On opposite sides of the foot sole contact portion 2A₀, an upraised portion 2A₁extending upwardly is provided. Similarly, as shown in a cross sectional view of FIG. 6, the forefoot sole 3 has a foot sole contact portion 30 that the wearer's foot sole contacts via the upper bottom portion, insole board, insole or the like (not shown). On opposite sides of the foot sole contact portion 30, an upraised portion 31 extending upwardly is provided. A thickness of the foot sole contact portion 30 is determined such that an unnatural difference in surface level is not generated at the front and the rear of the gap S between a surface of the foot sole contact portion 30 and a surface of the foot sole contact portion 2A₀of the upper sole 2A (see FIG. 5). In addition, at the time of assembly of the shoe, the upper bottom portion or the insole board is fixedly attached through bonding and the like to the foot sole contact portion 2A₀of the upper sole 2A and the upraised portion 2A₁, and the foot sole contact portion 30 of the forefoot sole 3 and the upraised portion 31 (not shown).

Turning back to FIGS. 1-5, the lower sole 2B of the rear foot sole 2 has a vertically extending through hole 21 formed at a heel central portion thereof (see FIG. 9). A bottom surface of the lower sole 2B is located above the ground contact surfaces of the outsoles 5A, 5B at a region extending from the heel central portion to a midfoot central portion and the lower sole 2B thus has a concave portion 20 at the region. A heel rear end portion and the heel central portion of the lower sole 2B protrude downwardly at the rear of the concave portion 20. The midfoot central portion of the lower sole 2B protrudes downwardly in front of the concave portion 20.

The midfoot central portion of the lower sole 2B has a laterally extending groove 20. The outsole 5B attached on a bottom surface of the midfoot portion of the lower sole 2B has a thin part that extends in a groove 22 of the midfoot portion in a bent shape like a flat inverted V-shape or U-shape and a front portion and a rear portion of the outsole 5B are connected through the thin part.

The outsole 5B has respective contact surfaces 5B₁across the groove 22, which are attached to the respective lower surfaces of the midfoot portion of the lower sole 2B and have arc-shaped surfaces or curved surfaces that extend upwardly in a curved shape. At the rear of the groove 22, the contact surface 5B₁is located at an uppermost position immediately adjacent the groove 22, and in front of the groove 22, the contact surface 5B₁is located at an uppermost position farthest from the groove 22. That is, the outsole 5B has a thickness that gradually becomes thin toward the groove 22 at the rear of the groove 22 and that gradually becomes thin away from the groove 22 in front of the groove 22. The respective contact surfaces 5B₁act in such a way as to conduct a smooth forward load transfer at the time of impacting the ground and to promote deformation of the lower sole 2B and the plate 4 along with the lower sole 2B. Also, the midfoot portion of the lower sole 2B is separated in the width direction by a longitudinally extending clearance 23 (see FIG. 7). Respective separated regions improve sole flexibility in the width direction.

Then, we will explain the longitudinal position of the gap S formed between the front end portion of the rear foot sole 2 and the rear end portion 3r of the forefoot sole 3, using the schematic of the bone structure of a wearer's foot shown in FIG. 10.

The position of the gap S is shown by a double dotted line in FIG. 10. As shown in FIG. 10, the gap S preferably extends from a generally central portion of the first metatarsus MB₁of the foot to a generally central portion of the fifth metatarsus MB₅. In other words, the gap S is disposed at the rear of distal end portions of the first to fifth metatarsi MB₁to MB₅. This is intended so that the gap S does not exist at the ball of the foot for avoiding the stat that the wearer feels uncomfortable around the foot sole when wearing the shoe. In FIG. 10, the solid line MJ designates the position of the metatarsophalangeal joints.

Next, the shape of the plate 4 will be explained using FIGS. 11 to 16.

As shown in FIG. 11, the plate 4 has a body portion 40 extending in the longitudinal direction (i.e. up-and-down direction of FIG. 11) as well as in the width direction and an upraised portion 41 provided at an outer circumferential edge portion of the body portion 40 and extending upwardly. On the bottom surface of the plate 4, as shown in FIG. 12, a plurality of longitudinally extending ribs 4r are provided (see FIGS. 1, 7-9). The body portion 40 of the plate 4, as shown in FIGS. 13-15, has an upwardly convexly curved shape at a rear portion (corresponding to the heel part H) to a longitudinally central portion (corresponding to the midfoot part M). The body portion 40 is disposed below the foot sole of the wearer (see FIGS. 5, 7-9). The upraised portion 41 of the plate 4 is disposed at the heel rear end of the foot to the medial and lateral sides of the heel part.

With regard to the upwardly convexly curved shape of the body portion 40 of the plate 4, in this embodiment, the position of the highest point of a medial longitudinal arch in the body portion 40 of the plate 4 is set at a higher position than the position of the highest point of a lateral longitudinal arch. In this case, since respective arch shapes on the medial and lateral sides of the plate 4 correspond to the shape of a human's foot, wearer's touch on the foot is made favorable, whereas a pronation angle is made greater. To the contrary, the position of the highest point of the medial longitudinal arch in the body portion 40 of the plate 4 may be set at a lower position than the position of the highest point of the lateral longitudinal arch. In this case, since the arch drops lower on the lateral side than on the medial side, supination is thus easy to occur and also arch shapes do not correspond to the shape of the human's foot and wearer's touch on the foot is thus made worse, whereas a pronation angle is made smaller.

The position of the highest point disposed at the uppermost position in the upwardly convexly curved shape of the body portion 40 of the plate 4 is designated by the mark ▾ in FIG. 13 and the mark ∇ in FIG. 14. The positions of these marks do not coincide with each other and are spaced apart at a small distance in the longitudinal direction on the lateral side and the medial side of the foot. The position of the highest point on the media side is shown in the bone structure schematic of FIG. 16. As shown by the mark ▾ of FIG. 16, the longitudinal position of the highest point of the upwardly convexly curved shape of the plate 4 is located at the position corresponding to the longitudinal arch of the foot and corresponds to the position directly under the navicular bone NA and the cuneiform bone CN of the foot. This is for making the plate 4 follow the shape of the foot and for securing a movable range of the plate 4. In FIG. 16, reference character CA shows calcaneus of the foot.

Also, the position of the highest point of the upwardly convexly curved shape of the plate 4 on the medial side is preferably located at the position of the line L₁that is spaced upwardly away from the line L₀by at least height h ((foot length)×2%) as shown in FIG. 16, wherein the line L₀is drawn to connect a skin surface directly under the distal end portion of the first metatarsus MB₁to a skin surface directly under the calcaneus CA. The height h is approximately 5 mm in the case of the foot length of 26 cm. This is for preventing the plate 4 from bottoming. In this case, the amount (calculated value) of forward movement of the front end portion 4f of the plate 4 is 1 mm.

Then, the action and effect of the present invention will be explained using FIGS. 17A and 17B.

Here, FIG. 17A shows the state before the shoe impacts the ground and FIG. 17B shows the state at the time of foot flat (i.e. the entire sole surface is in contact with the ground) after the shoe has impacted the ground.

When impacting the ground, the sole structure 1 deforms from the state of FIG. 17A to the state of FIG. 17B. At this juncture, the upwardly convexly curved shape elastically compression-deforms downwardly, so that the body portion 40 of the plate 4 changes into a flat shape. Accordingly, the foot sole contact portion 2A₀of the rear foot sole 2 also changes into a flat shape. Also, the midfoot portion of the lower sole 2B of the rear foot sole 2 deforms so as to be fallen forwardly. Further, the gap S between the forefoot sole 3 and the upper and lower soles 2A, 2B of the rear foot sole 2 is narrowed, and the connection 50 between the outsoles 5B and 5C compression-deforms longitudinally.

In this case, the upwardly convexly curved shape of the body portion 40 of the plate 4 elastically deforms downwardly, such that thereby the cushioning properties can be maintained and deterioration of the cushioning performance can be prevented. Moreover, in this case, the gap S is formed in front of the front end portion 4f of the plate 4, such that thereby at the time of elastic deformation of the plate 4 the forward movement of the front end portion 4f of the plate 4 can be conducted smoothly without being obstructed by the rear foot sole 2 (the upper and lower soles 2A, 2B) and the forefoot sole 3. Thereby, the plate 4 can deform smoothly thus improving the cushioning properties. Furthermore, in this case, since the gap S formed in front of the front end portion 4f of the plate 4 facilitates bending-deformation of the rear foot sole 2 relative to the forefoot sole 3, flexibility of the rear foot sole 2 relative to the forefoot sole 3 can be enhanced especially after transition from the foot-flat moment to the heel-off moment. Also, since the plate 4 can be smoothly deformed forwardly, shock in the longitudinal direction as well can be mitigated at the time of impacting the ground.

In addition, the front end portion 4f of the plate 4 faces the connection 50 disposed in front of the front end portion 4f (see FIGS. 3, 5). However, since the connection 50 is a thin member and is extensible and contractable in the forward direction in the gap S, the forward movement of the front end portion 4f of the plate 4 is not hindered by the connection 50.

Alternative Embodiment 1

In the above-mentioned embodiment, an example was explained in which the heel part of the plate 4 is formed in a heel-cup shape by providing the upraised portion 41 at the region extending from the heel rear end of the body portion 40 of the plate 4 to the heel medial and lateral sides, but the application of the present invention is not limited to such an embodiment. Of the entire upraised portion 41 of the body portion 40, the upraised portion 41 provided at the heel rear end may be omitted.

In the event that the upraised portion 41 is provided at the heel rear end of the plate 4, when impact load in the forward direction is applied to the plate 4 at the time of impacting the ground the upraised portion 41 at the heel rear end may interfere with the heel rear end surface of the upper sole 2A and the forward movement of the plate 4 may be restricted. However, by removing the upraised portion at the heel rear end of the plate 4, the forward movement of the plate 4 is conducted in a smooth manner without being restricted by the upraised portion at the heel rear end. Thereby, the impact load to the plate 4 in the forward direction can be effectively decreased.

Alternative Embodiment 2

In the above-mentioned embodiment, as a preferred embodiment, an example was shown where the plate 4 extends along the rear foot region from the heel part H to the midfoot part M of the sole structure 1. However, at the heel part H, the plate 4 has only to be placed to cover the position directly under at least the calcaneus CA, and at the midfoot part M, the plate 4 has only to be placed at the position to cover at least the proximal portions of the first to fifth metatarsus MB₁to MB₅. This is for receiving the shock load securely at the time of heel contact and midfoot contact during running. The present invention also has application to the structure where the plate 4 is provided either at the heel part H only or at the midfoot part M only.

In the event that the plate 4 is provided only at the heel part H, for example, the plate 4 is provided along the heel portion of the rear foot sole 2B (to cover the position directly under at least the calcaneus CA) and the front end portion 4f of the plate 4 faces outwardly from the front end surface of the heel portion of the rear foot sole 2B, there is formed a gap without the rear foot sole in front of the front end portion 4f of the plate 4 as with the above-mentioned embodiment. Also, in the event that the plate 4 is provided only at the midfoot part M, for example, the plate 4 is provided along the midfoot portion of the rear foot sole 2B and the front end portion 4f of the plate 4 faces outwardly from the front end surface of the midfoot portion of the rear foot sole 2B, there is formed a gap without the rear foot sole in front of the front end portion 4f of the plate 4 as with the above-mentioned embodiment. In this case, the plate 4 preferably has an upwardly convexly curved shape similar to the above-mentioned embodiment.

Alternative Embodiment 3

In the above-mentioned embodiment, an example was shown where the connection 50 has a single bent portion of an inverted V-shape or U-shape (see FIGS. 2, 3, 5), but the present invention also has application to the case in which the connection 50 has a plurality of bent portions of inverted V-shapes or U-shapes. In this case, the connection 50 is bent in a bellows-shape as viewed from the side thereof.

Alternative Embodiment 4

In the above-mentioned embodiment, an example was shown where the rear foot sole 2 and the forefoot sole 3 are interconnected through the connection 50 in the gap S extending from the outsoles 5B, 5C, but the application of the present invention is not limited to such an example. FIGS. 18 and 19 illustrate a sole structure according to another embodiment of the present invention. In these drawings, the same reference numbers as those in the above-mentioned embodiment indicate identical or functionally similar elements.

This embodiment differs from the above-mentioned embodiment in that the upper midsole 2A of the rear foot sole 2 and the forefoot sole 3 are interconnected through a connection 20 or 20′ in the gap S extending from the upper sole 2A and the forefoot sole 3. That is, in this embodiment, the rear foot sole 2 and the forefoot sole 3 are interconnected through an extension of the midsole of a soft elastic material. The outsoles 5B, 5C are separated via the gap S. In this case as well, the gap S is disposed in front of the front end portion of the plate 4.

In the structure shown in FIG. 18, the connection 20 includes a thin bending portion of a V-shape or a U-shape as viewed from the side of the structure. The connection 20 has a path length that is longer than a longitudinal length of the gap S between the front end of the rear foot sole 2 and the rear end portion 3r of the forefoot sole 3. Also, the connection 20 extends in the gap S in the sole width direction as well as in the longitudinal direction. The connection 20 is not limited to such one as includes a single V-shaped or U-shaped bending portion. The connection 20 may include a plurality of V-shaped or U-shaped bending portions. In this case, the connection 20 is bent in a bellows-shape as viewed from the side of the structure.

In the structure shown in FIG. 19, the connection 20′ is formed of a thin extending portion that extends linearly in the longitudinal direction. The connection 20′ extends in the gap S in the sole width direction as well as in the longitudinal direction. The connection 20′ has a path length that is substantially the same as a longitudinal length of the gap S between the front end of the rear foot sole 2 and the rear end portion 3r of the forefoot sole 3. The reason why the path length of the connection 20′ is not made longer than the longitudinal length of the gap S is as follows:

When the rear foot sole 2 bending-deforms relative to the forefoot sole 3 at the gap S, the bending center is located at the position immediately adjacent the connection 20′. Accordingly, elongation of the connection 20′ is small at the time of bending deformation and the connection 20′ can absorb such elongation through its own elastic deformation. As a result, there is no need to secure extension allowance in the connection 20′ in advance.

In either of the sole structures shown in FIGS. 18 and 19, when the shoe strikes onto the ground, the upwardly convexly curved shape of the body portion 40 of the plate 4 elastically deforms downwardly, such that thereby the cushioning properties can be maintained and deterioration of the cushioning performance can be prevented. At this juncture, since the gap S is formed in front of the front end portion 4f of the plate 4, such that thereby at the time of elastic deformation of the plate 4 the forward movement of the front end portion 4f of the plate 4 can be performed smoothly without being obstructed by the rear foot sole 2 (the upper and lower soles 2A, 2B) and the forefoot sole 3. Thereby, the plate 4 can deform smoothly thus improving the cushioning properties. Furthermore, in this case, since the gap S formed in front of the front end portion 4f of the plate 4 facilitates bending-deformation of the rear foot sole 2 relative to the forefoot sole 3, flexibility of the rear foot sole 2 relative to the forefoot sole 3 can be enhanced.

Additionally, in the structure shown in FIG. 18, the connection 20 disposed in front of the plate 4 faces the front end portion 4f of the plate 4. Since this connection 20 is a thin soft elastic member and extensible in the gap S in the longitudinal direction, the forward movement of the front end portion 4f of the plate 4 is not hindered by the connection 20.

Other Applicable Example

In the above examples, the sole structure of the present invention was applied to a running shoe, but the application of the present invention is not limited to such an example. The present invention also has application to other various sports shoes including walking shoes.

INDUSTRIAL APPLICABILITY

As mentioned above, the present invention is of use to a sole structure for a shoe, and it is especially suitable for a sole structure for a sports shoe that requires a superb sole deformability.

Sole Structure for a Shoe

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