U.S. patent application number 17/255391 was filed with the patent office on 2021-10-14 for shoe.
The applicant listed for this patent is ASICS Corporation. Invention is credited to Mizuho IRIE, Shigeyuki MITSUI, Sho TAKAMASU.
Application Number | 20210315320 17/255391 |
Document ID | / |
Family ID | 1000005682607 |
Filed Date | 2021-10-14 |
United States Patent
Application |
20210315320 |
Kind Code |
A1 |
TAKAMASU; Sho ; et
al. |
October 14, 2021 |
SHOE
Abstract
A shoe having a structure with excellent acceleration
performance is provided. A shoe includes: a sole made of a soft
material, which includes a ground contact surface and also includes
a foot contact surface facing a side opposite to the ground contact
surface; and an upper combined with the foot contact surface side
of the sole. A thickness of the sole at a position corresponding to
an MP joint of a wearer is different from a thickness of the sole
at a position corresponding to the center of the heel such that an
angle between the foot contact surface and the ground contact
surface falls within the range of 8 to 16 degrees. Accordingly, a
shoe having a structure that provides excellent feeling of
acceleration is provided.
Inventors: |
TAKAMASU; Sho; (Kobe-shi,
Hyogo, JP) ; IRIE; Mizuho; (Kobe-shi, Hyogo, JP)
; MITSUI; Shigeyuki; (Kobe-shi, Hyogo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASICS Corporation |
Hyogo |
|
JP |
|
|
Family ID: |
1000005682607 |
Appl. No.: |
17/255391 |
Filed: |
October 18, 2019 |
PCT Filed: |
October 18, 2019 |
PCT NO: |
PCT/JP2019/041127 |
371 Date: |
December 22, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A43B 13/18 20130101;
A43B 13/02 20130101 |
International
Class: |
A43B 13/18 20060101
A43B013/18; A43B 13/02 20060101 A43B013/02 |
Claims
1-9. (canceled)
10. A shoe, comprising: a sole made of a soft material, the sole
including a ground contact surface and also including a foot
contact surface facing a side opposite to the ground contact
surface; and an upper combined with the foot contact surface side
of the sole, wherein a thickness of the sole at a position
corresponding to an MP joint of a wearer is different from a
thickness of the sole at a position corresponding to the center of
the heel such that an angle between the foot contact surface and
the ground contact surface falls within the range of 8 to 16
degrees.
11. The shoe of claim 10, wherein the foot contact surface is flat
at the forefoot portion of the sole corresponding to the toe side
of a virtual line connecting the wearer's MP joint and the heel
side of the virtual line connecting the wearer's MP joint is tilted
forward from the midfoot portion to the rearfoot portion.
12. The shoe of claim 10, wherein the sole includes an arch portion
recessed upward in a midfoot portion.
13. The shoe of claim 10, further comprising a reinforcement member
that reinforces the midfoot portion of the sole and a rearfoot
portion of the sole.
14. The shoe of claim 13, wherein the reinforcement member extends
continuously from the rearfoot portion to a position corresponding
to an MP joint.
15. The shoe of claim 13, wherein the reinforcement member includes
a curled-up part that extends upward along a heel part.
16. The shoe of claim 15, wherein the sole includes a curled-up
part that extends upward along a heel part, and a height of the
curled-up part of the reinforcement member is 1.0 to 2 times the
height of the curled-up part of the sole.
17. The shoe of claim 10, wherein a rear end part of the rearfoot
portion of the sole has a curved shape, the lowest point being
immediately below the center of the heel, the radius of curvature
is 100 to 200 mm in a side view.
18. The shoe of claim 10, wherein the maximum thickness of the
rearfoot portion of the sole is 3 to 5 times the maximum thickness
of a forefoot portion of the sole.
19. The shoe of claim 10, wherein the sole includes a hollow part
formed in the rearfoot portion.
Description
TECHNICAL FIELD
[0001] The present invention relates to shoes, and particularly to
sports shoes.
BACKGROUND ART
[0002] For shoes used for sports, such as middle-distance or
long-distance running, various technologies have been
conventionally proposed to improve the functionality including
comfort in running, and stability. Such functionality of shoes
includes acceleration performance. For example, Patent Literature 1
describes improving the restitution function of shoe soles to
improve acceleration performance of the shoes.
PRIOR ART REFERENCE
Patent Literature
[0003] Patent Literature 1: Japanese Patent No. 4704429
SUMMARY OF INVENTION
Technical Problem
[0004] A purpose the present invention is to provide a shoe having
a structure with excellent acceleration performance using a
technical means completely different from that in Patent Literature
1.
Solution to Problem
[0005] In response to the above issue, the present invention
includes: [0006] a sole made of a soft material, which includes a
ground contact surface and also includes a foot contact surface
facing a side opposite to the ground contact surface; and [0007] an
upper combined with the foot contact surface side of the sole, in
which [0008] a thickness of the sole at a position corresponding to
an MP joint of a wearer is different from a thickness of the sole
at a position corresponding to the center of the heel such that an
angle between the foot contact surface and the ground contact
surface falls within the range of 8 to 16 degrees.
[0009] With such a configuration, the bottom of a wearer's foot can
be tilted forward when the ground contact surface of the shoe comes
into contact with the ground. Accordingly, the wearer's force to
push off the ground can be efficiently converted into the force to
advance.
Advantageous Effects of Invention
[0010] The present invention provides a shoe having a new structure
with excellent acceleration performance.
BRIEF DESCRIPTION OF DRAWINGS
[0011] Embodiments will now be described, by way of example only,
with reference to the accompanying drawings which are meant to be
exemplary, not limiting, and wherein like elements are numbered
alike in several Figures, in which:
[0012] FIG. 1 is a top view of a foot skeleton;
[0013] FIG. 2 is a side view of a shoe according to an
embodiment;
[0014] FIG. 3 is another side view of the shoe;
[0015] FIG. 4 is a sectional view of the shoe;
[0016] FIG. 5 is a top view of the shoe;
[0017] FIG. 6 is a top view of a shoe according to a
modification;
[0018] FIGS. 7 are schematic side views of the shoe;
[0019] FIG. 8 is a side view of a shoe according to another
modification;
[0020] FIG. 9 is a side view of a shoe according to yet another
modification; and
[0021] FIG. 10 is a graph that shows experimental results of the
shoe according to the embodiment.
DESCRIPTION OF EMBODIMENTS
[0022] Definitions of terms used in this specification will be
described. In this specification, front and back directions, width
directions, and vertical directions may be used as terms indicating
directions. These terms indicate directions viewed from a viewpoint
of a wearer wearing a shoe placed on a flat surface. Accordingly,
the front direction means a direction toward the toe side, and the
back direction means a direction toward the heel side. Also, a
medial side and a lateral side of a foot may be used as terms
indicating directions. The medial side of a foot means the inner
side of the foot in a width direction, i.e., the big toe (first
toe) side of the foot, and the lateral side of the foot means the
side opposite to the medial side along a width direction.
[0023] Also, in the following description, a sole of a shoe may be
referred to. The sole means a midsole only, or both an outsole and
a midsole. Further, in some examples, directions may be described
using a three-dimensional Cartesian coordinate system. In this
case, the X-axis extends from the lateral side toward the medial
side of the foot, the Y-axis extends from the heel side toward the
toe side, and the Z-axis extends from the bottom surface side
toward the upper side.
[0024] Before a shoe according to an embodiment is described, a
foot skeleton relevant to the shoe according to the embodiment will
be described with reference to FIG. 1.
[0025] FIG. 1 is a top view of a foot skeleton. A human foot is
mainly constituted by cuneiform bones Ba, a cuboid bone Bb, a
navicular bone Bc, a talus Bd, a calcaneus Be, metatarsal bones Bf,
and phalanges Bg. Joints of a foot include MP joints Ja, Lisfranc
joints Jb, and a Chopart's joint Jc. The Chopart's joint Jc
includes a calcaneocuboid joint Jc1 formed by the cuboid bone Bb
and the calcaneus Be, and a talocalcaneonavicular joint Jc2 formed
by the navicular bone Bc and the talus Bd. In this specification, a
"forefoot portion" of a wearer means a portion positioned forward
of the MP joints Ja; when it is restated with shoe length ratio,
the forefoot portion means a portion of about 0-30% of the entire
shoe length measured from the toe side. Also, a "midfoot portion"
means a portion from the MP joints Ja to the Chopart's joint Jc
and, similarly, also means a portion of about 30-80% of the entire
shoe length measured from the toe side. Also, a "rearfoot portion"
means a portion positioned rearward of the Chopart's joint Jc and,
similarly, also means a portion of about 80-100% of the entire shoe
length measured from the toe side. In FIG. 1, a center line S
indicates a center line of a shoe and extends along a middle part
in a foot width direction. The center line S is assumed to be a
region positioned on a straight line passing through a third
metatarsal bone Bf3 and a medial process Be1 of calcaneal
tuberosity of the calcaneus Be in a human body. FIG. 1 shows an
area in which the medial process Be1 of calcaneal tuberosity is
assumed to be positioned. The ratios in the entire shoe length are
indications and do not limit the ranges of the forefoot portion,
midfoot portion, and rearfoot portion.
[0026] FIGS. 2 and 3 are side views of the shoe. More specifically,
FIG. 2 is a side view of the shoe viewed from the medial side of
the foot (from the negative X side), and FIG. 3 is a side view of
the shoe viewed from the lateral side of the foot (from the
positive X side). Also, FIG. 4 is a sectional view of the shoe, and
more specifically a sectional side view along the center line S.
For the sake of convenience, the upper is omitted in FIG. 4.
[0027] As illustrated in FIGS. 2 through 4, a shoe 10 includes a
sole 12 having a ground contact surface to be in contact with the
ground, and an upper 14 that covers the sole 12.
[0028] The upper 14 has a shape that covers an upper side of an
instep. The upper 14 includes an upper body 16, a tightening means
(tightening structure) 18 for the upper, and a slit 20 that extends
along the front and back directions of the upper 14 around the
middle in a width direction of the upper 14. Also, to the upper 14,
a shoe tongue 22 is attached. In the present embodiment, as the
tightening means 18 for adjusting the degree of tightening the
upper 14, a structure constituted by a combination of grommets and
a shoelace is employed. As the tightening means 18, a hook-and-loop
fastener or the like may also be used. Also, the upper may be a
monosock upper having no slit.
[0029] The upper body 16 may be made of a mesh material obtained by
knitting synthetic fiber, such as polyester and polyurethane, or
made of synthetic leather or natural leather, for example, and has
a shape covering an instep. The slit 20 is a buffer portion for
adjusting the width of the upper body by adjusting the degree of
tightening the shoelace. On each side in a width direction of the
slit 20, multiple grommets are provided. The shoe tongue 22 is
exposed through the slit 20, and, when a shoelace is tied, the
shoelace has no contact with the wearer's instep.
[0030] The sole 12 is a sheet member having a foot shape as a whole
in top view. On one surface (the bottom surface) of the sole 12, a
ground contact surface 24 is formed, and, on the other surface (the
upper surface) thereof, a foot contact surface 26 is formed. At
least part of the sole 12 is formed of a soft material. Along the
front and back directions (the directions along the Y-axis), the
sole 12 is continuously provided from the front end to the rear end
of the shoe 10, in which the forefoot portion, midfoot portion, and
rearfoot portion are integrally formed. The thickness of the sole
12 is largely different along the front and back directions. The
forefoot portion is thinner, and the rearfoot portion is thicker.
In this case, the maximum thickness of the rearfoot portion of the
sole 12 may suitably be three to five times the maximum thickness
of the forefoot portion of the sole 12. When the thickness of the
forefoot portion of the sole 12 is 10 mm, for example, the
thickness of the rearfoot portion of the sole 12 may be 30-50 mm.
By setting the maximum thickness of the rearfoot portion of the
sole 12 to five times the maximum thickness of the forefoot portion
of the sole 12 or less, the stability in wearing the shoes can be
maintained. Also, by setting the maximum thickness of the rearfoot
portion of the sole 12 to three times the maximum thickness of the
forefoot portion of the sole 12 or greater, the feeling of
acceleration in wearing the shoes 10 can be obtained. With the
structure of the sole 12 having thickness different along the front
and back directions, an angle between the foot contact surface 26
and the ground contact surface 24 (hereinafter may be referred to
as a "forward tilt angle") falls within the range of 8 to 16
degrees. The method for measuring the angle between the foot
contact surface 26 and the ground contact surface 24 will be
described later.
[0031] As particularly illustrated in FIG. 4, the sole 12 includes
an outsole 28 formed on the bottom surface, and a midsole 30
disposed on the outsole 28 and having certain elasticity. Also, on
the midsole 30, an insole 32 may be disposed. In the sole 12, the
outsole 28, midsole 30, and insole 32 are laminated in this order
from the bottom. The thickness of the sole 12 is substantially
equal to the total thickness of the outsole 28 and the midsole 30.
Accordingly, to make the thickness of the sole 12 different along
the front and back directions as described previously, the
thickness of each of the outsole 28 and the midsole 30 constituting
the sole 12 is appropriately adjusted. Meanwhile, when the
thickness of the outsole 28 is uniform overall, the thickness of
the outsole 28 does not affect the forward tilt angle between the
foot contact surface 26 and the ground contact surface 24.
Accordingly, the thickness of the outsole 28 sometimes need not be
considered when the angle is adjusted.
[0032] The outsole 28 may be formed by shaping rubber into a
predetermined shape, for example. The outsole 28 is pasted over the
bottom surface of the midsole 30 such as to cover at least part of
the bottom surface of the midsole 30. Accordingly, when viewed from
a side, the shape of the outsole 28 substantially follows the shape
of the bottom surface of the midsole 30. The outsole 28 has the
ground contact surface 24 to be in contact with the ground G. The
ground contact surface 24 has a rugged pattern, which improves
grip.
[0033] The outsole 28 is formed such that multiple insular portions
thereof are pasted onto predetermined positions of the bottom
surface of a predetermined midsole. The ground contact surface 24
need not necessarily be a continuous surface, and may be separated
into multiple portions on an X-Y plane. Even though the ground
contact surface 24 is separated, when the shoe 10 is placed on a
horizontal flat surface, one ground contact surface can be defined
between the shoe 10 and the horizontal surface.
[0034] The midsole 30 absorbs impact, and part of or the entirety
of the midsole 30 is formed of a soft material for absorbing
impact, which may be a foam material, such as expanded EVA or
urethane foam, GEL, or cork, for example. The material of the
midsole 30 may suitably have the Young's modulus of 10 MPa or less
(when the strain is 10%) or a value measured using the ASKER
Durometer Type C of 70 or less. Also, as will be described in a
modification, when the midsole 30 has a predetermined elastic
structure, instead of a solid structure, the midsole 30 may be
formed of a hard material. In this case, rigid urethane, nylon,
FRP, or the like may be used as the hard material. The midsole 30
is tilted forward such that the upper surface thereof faces the
front side (toward the positive Y direction). More specifically, in
the upper surface of the midsole 30, the range from the midfoot
portion to the rearfoot portion is tilted forward, and the forefoot
portion is flat along a substantial X-Y plane. The boundary between
the forward tilt portion and the flat portion in the midsole 30
substantially corresponds to a virtual line that connects the MP
joints Ja. Accordingly, it may be simply said that, in the upper
surface of the midsole 30, the toe side from the virtual line
connecting the MP joints Ja is flat, and the heel side from the
virtual line is tilted forward.
[0035] The outer edge of the midsole 30 has a planar shape
approximated to a projected shape of a foot in top view. The upper
surface of the midsole 30 has an uneven shape that corresponds to
the uneven shape of the bottom of a foot. The upper 14 is combined
with the upper surface of the midsole 30. More specifically, the
upper 14 is combined along the outer edge of the midsole 30, or
along a line slightly inside the outer edge of the midsole 30. To
combine the upper 14 with the midsole 30, the edge of the upper 14
may be sewed onto the midsole 30, or a bonding means, such as an
adhesive, may be used for the combination, for example.
[0036] In the midfoot portion of the bottom surface of the midsole
30, an arch portion 34 is formed to be recessed toward the positive
Z direction. The arch portion 34 is formed by providing a groove
extending along the Y-axis such as to space a portion between the
rearfoot portion and the forefoot portion of the midsole 30 from
the ground in the positive Z direction. With the arch portion 34
provided, when the midsole 30 is compressed from the above while
the shoe 10 is in contact with the ground G, a space for
deformation of the midsole 30 can be ensured. The shape of the arch
portion 34 in side view is not particularly limited. As
illustrated, the shape may be an inverted V shape in which the toe
side surface and the heel side surface of the groove are tilted
such that the vertex points to the positive Z side. Also, the heel
side surface may be a vertical surface extending along a Z-axis
direction, for example. With the groove of an inverted V shape, the
amount of the midsole 30 on the heel side of the arch portion 34
can be increased, so that the rearfoot portion of the midsole 30
cannot be easily deformed. In the arch portion 34, the outsole 28
need not necessarily be provided.
[0037] A heel part 36 of the bottom surface of the midsole 30 has a
curved shape when viewed from a side. More specifically, when
viewed from a side, the heel part 36 has an arc shape that is
concave in the negative Y direction and the negative Z direction.
With such a shape of the heel part 36, when the wearer's heel lands
on the ground, the foot is rolled in the positive Y direction along
the curved shape, leading to smooth landing. For smoother landing,
the curved shape may desirably be formed such that the lowest point
is positioned immediately below the center of the calcaneus, and
the radius of curvature R is about 100 to 200 mm. At the time, to
ensure a sufficient contact area, a section of about 10 mm from the
lowest point in the positive and negative Y directions may be a
flat surface. Even if a step or an inverted curve is provided
outside the section of 10 mm from the lowest point in the positive
and negative Y directions such that the corresponding part is not
in contact with the ground, a similar rolling effect can be
obtained.
[0038] The shoe 10 includes a reinforcement member 38 that
reinforces the midsole.
[0039] FIG. 5 is a top view of the shoe. More specifically, FIG. 5
is a top view of the shoe without the upper. As illustrated in
FIGS. 4 and 5, the reinforcement member 38 is disposed on the upper
surface of the midsole 30 and continuously extends from the
rearfoot portion to the vicinity of the boundary between the
midfoot portion and the forefoot portion of the midsole 30. In FIG.
4, the cross section of the reinforcement member 38 is indicated by
hatching in the interest of clarity. The reinforcement member 38
may be formed of a polyurethane resin, such as thermoplastic
polyurethane, or a plastic material, such as a fiber reinforced
plastic, for example. The reinforcement member 38 as a whole has an
outer shape similar to that of the midsole 30 when viewed from the
top. As illustrated in FIG. 5, when viewed from the top, a middle
part of the reinforcement member 38 may be hollow. Such a middle
hollow is not essential. In the rearfoot portion, the reinforcement
member 38 specifically extends along an outer edge of the rearfoot
portion. In the midfoot portion, the reinforcement member 38
extends along the medial side and the lateral side. The
reinforcement member 38 also extends along the boundary between the
midfoot portion and the forefoot portion, and the front side of the
reinforcement member 38 is terminated at the boundary. Such a
reinforcement member 38 can improve the strength of the midsole 30
from the rearfoot portion to the boundary between the midfoot
portion and the forefoot portion and also improve the integrity.
Also, with the reinforcement member 38, force can be appropriately
transmitted to the ground G. Further, with the reinforcement member
38 provided, twist of the shoe 10 around the center line S can be
restrained.
[0040] The forward tilt angle of the reinforcement member 38 is
approximate to the forward tilt angle of the upper surface of the
midsole 30, and may suitably fall within the range of 8 to 20
degrees. Also, the reinforcement member 38 may be regarded as part
of the sole 12 and an insole may be provided on the reinforcement
member 38, and the forward tilt angle may be determined based on
the upper surface of the insole 32 as the foot contact surface.
While the forward tilt angle of the reinforcement member 38 falls
within the range of 8 to 20 degrees, the forward tilt angle of the
upper surface of the midsole 30 falls within the range of 8 to 16
degrees, so that the upper limit of the forward tilt angle of the
reinforcement member 38 is larger. This is because, when the
reinforcement member 38 is provided, the rearfoot portion is
thicker by the thickness of the reinforcement member 38, so that
the forward tilt angle becomes larger. The forward tilt angle of
the reinforcement member 38 may be made substantially identical
with the forward tilt angle of the upper surface of the midsole 30
by adjusting the thickness of the reinforcement member 38.
[0041] As illustrated in FIG. 6, which is a top view of a shoe
according to a modification, a reinforcement member 40 may be
formed only by two elongate plate members 42. Each plate member 42
on the medial side or the lateral side of the foot extends from the
rearfoot portion to the vicinity of the boundary between the
midfoot portion and the forefoot portion. The reinforcement member
40 provided at such a position can also improve the strength of the
midsole 30 from the rearfoot portion to the boundary between the
midfoot portion and the forefoot portion.
[0042] Referring back to FIG. 4, the reinforcement member 38 may
suitably have a cup shape extending in the positive Z direction
along an outer edge in the rearfoot portion. In this case, the
reinforcement member 38 has a first curled-up part 44 that extends
upward along a predetermined height from the bottom surface of the
reinforcement member having a cup shape. The first curled-up part
44 surrounds at least part of the heel. More specifically, the
first curled-up part 44 surrounds the both side surfaces and the
rear surface of the heel. The height of the first curled-up part 44
may suitably fall within the range of 10 to 60 mm. With the first
curled-up part 44 provided, the stability around the heel can be
improved. To further improve the stability around the heel, a
curled-up part may be provided on each of the medial heel and the
lateral heel such as to restrain pronation at the time of landing.
In this case, the height of the curled-up part on the medial heel
may suitably fall within the range of 10 to 55 mm, and the height
of the curled-up part on the lateral heel may suitably fall within
the range of 5 to 50 mm. In terms of restraining pronation, the
height of the curled-up part on the medial heel may suitably be
about 5 millimeters higher than the height of the curled-up part on
the lateral heel.
[0043] Also, the midsole 30 may suitably have a cup shape extending
in the positive Z direction in the rearfoot portion along the
reinforcement member 38 having a cup shape. In this case, the
midsole 30 has a second curled-up part 46 that extends upward along
a predetermined height from the bottom surface of the midsole 30
having a cup shape. The second curled-up part 46 surrounds at least
part of the reinforcement member 38. More specifically, the second
curled-up part 46 surrounds the both side surfaces and the rear
surface of the reinforcement member 38. The second curled-up part
46 is lower in height than the first curled-up part 44. The height
of the second curled-up part 46 may be 1.0 to 2.0 times the height
of the first curled-up part 44. With the second curled-up part 46
provided, the stability around the heel can be further
improved.
[0044] There will now be described a method for measuring the angle
between the foot contact surface 26 and the ground contact surface
24. The angle between the foot contact surface 26 and the ground
contact surface 24 is measured when the shoe 10 is placed on a flat
horizontal surface in a no-load state, i.e., a state where the sole
12 is not deformed. When the foot contact surface 26 and the ground
contact surface 24 are not uniform planes, the angle between the
foot contact surface 26 and the ground contact surface 24 is
determined in the following way. First, as illustrated in FIGS. 4
and 5, the intersection of the center line S and a virtual line L1,
which corresponds to the MP joints Ja, is connected with the point
P1 of the medial process of calcaneal tuberosity. Each of the
intersection of the center line S and the virtual line L1 and the
point P1 is set at the height of the foot contact surface 26. When
the line connecting the intersection of the center line S and the
virtual line L1 with the point P1 is viewed from a side, a tilted
virtual line L2 can be drawn. FIG. 4 illustrates a cross section
along the center line S, in which the symbol L1 indicates the
position of the virtual line L1 on the cross section, i.e., the
position corresponding to the MP joints Ja, and the symbol P1
indicates the position of the medial process of calcaneal
tuberosity. Since the position of the virtual line L1 corresponding
to the MP joints Ja may be slightly different (shifted along the
Y-axis) according to the foot size of the wearer, the position need
not necessarily be fixed to one position in the same way. In this
case, the positions of the MP joints Ja may be obtained in the
state where the wearer's heel is in close contact with the heel
side of the shoe upper, and, subsequently, the positions of the MP
joints Ja may be obtained again in the state where the wearer's toe
is in close contact with the tip end of the shoe upper, for
example. The position of the virtual line used to measure the angle
between the foot contact surface 26 and the ground contact surface
24 may be located between the two sets of the positions of the MP
joints Ja thus obtained. When multiple sets of the positions of the
MP joints Ja are considered, the forward tilt angle may fall within
a predetermined angle range with respect to at least one set of the
positions.
[0045] The tilted virtual line L2 may be regarded as a line
representing a tilt that indicates an angle between the foot
contact surface 26 and a horizontal surface. When a shoe is placed
on a flat surface, the ground contact surface 24 is substantially
horizontal. Accordingly, the angle between the foot contact surface
26 and the ground contact surface 24 corresponds to an angle
between the tilted virtual line L2 and a horizontal line H. In FIG.
5, the horizontal line H is provided at the height (the position
along a Z direction) of the virtual line L1. However, since the
virtual line L2 is a straight line, the angle between the virtual
line L2 and the horizontal line H is unchanged at any height. With
the angle between the foot contact surface 26 and the ground
contact surface 24 falling within the aforementioned angle range,
the bottom of the wearer's foot can be tilted forward when the
ground contact surface 24 of the shoe 10 comes into contact with
the ground G. Accordingly, the wearer's force to push off the
ground G can be efficiently converted into the force to
advance.
[0046] FIGS. 7 are schematic side views that illustrate the
operation of the shoe when the wearer is running.
[0047] As illustrated in FIG. 7A, when the wearer's heel lands on
the ground G, the heel part 36 having a curved shape comes into
contact with the ground G first. When the heel part 36 having a
curved shape comes into contact with the ground G first, forward
rolling as indicated by an arrow A1 is prompted. FIG. 7B
illustrates a state where, as a result of rolling, the shoe 10 is
entirely in contact with the ground G at an angle such that the
ground contact surface 24 of the shoe 10 becomes parallel to the
ground G. In this state, the bottom of the wearer's foot is tilted
forward. When the wearer steps in the negative Z direction in this
state, repulsion from the ground G has a positive Y component in
addition to a positive Z component. This is similar to the case of
stepping on a surface tilted forward, such as a starting block used
in sprints, for example. Although a general running shoe may also
have a tilt angle of about 4 degrees, the shoe 10 according to the
embodiment has a tilt angle of 8 to 16 degrees. Accordingly, with
the shoe 10 according to the embodiment, far greater acceleration
can be obtained in stepping on a forward-tilted surface. Therefore,
forward acceleration force can be obtained, as illustrated in FIG.
7C. In FIG. 7C, dotted lines indicate the shoe in the state of FIG.
7B.
[0048] As described above, with the shoe 10 of the embodiment, the
bottom of the wearer's foot can be tilted forward when the ground
contact surface 24 of the shoe 10 comes into contact with the
ground G. Accordingly, the wearer's force to push off the ground G
can be efficiently converted into the force to advance, so that the
wearer can obtain the feeling of acceleration.
[0049] FIG. 8 is a side view of a shoe according to another
modification. A shoe 50 according to the modification includes a
hollow part 54 provided in the rearfoot portion of a midsole 52.
The hollow part 54 is provided between the upper surface and the
bottom surface of the midsole 52 in a Z-axis direction. In the
illustrated example, the hollow part 54 pierces the midsole 52
along the Y-axis, but need not necessarily pierce the midsole 52.
With the hollow part 54 provided, acceleration provided by elastic
deformation along the Z-axis of the midsole 52 can be obtained.
When the hollow part 54 is provided, the midsole may suitably be
made harder compared to the case of the solid midsole such as to
improve the rigidity. When the hollow part 54 is provided, the
thickness of the midsole 52 is measured without regard for the
presence of the hollow part 54 and defined as the distance from the
ground contact surface to the upper surface (uppermost surface) of
the midsole 52, as described previously. With the hollow part 54
provided in the midsole 52, in addition to the feeling of
acceleration provided by the conversion of force as described
previously, the feeling of acceleration provided by the repulsion
from the midsole 52 can also be obtained.
[0050] FIG. 9 is a side view of a shoe according to yet another
modification. As with the shoe 50, a shoe 60 according to the
modification includes a hollow part 64 provided in the rearfoot
portion of a midsole 62. The midsole 62 surrounding the hollow part
64 has an unclosed shape when viewed from a side, and is separated
in a vertical direction near the midfoot portion. Near the midfoot
portion of the midsole 62, a soft material 66 is disposed such as
to connect the separated portions of the midsole 62. The soft
material 66 is made of a highly elastic material, such as foam or
GEL. The soft material 66 is fixed to a surface of the midsole 62,
which constitutes an inner surface of the hollow part 64, at two
positions one on each of the upper side and the lower side. Thus,
by using the soft material 66 to form part of the structure that
defines the hollow part 64, the effect of the aforementioned
modification can be obtained and, in addition, impact absorption
can be improved.
[0051] FIG. 10 is a graph that shows experimental results of the
shoe according to the embodiment. Eight subjects ran 350 meters
wearing the shoes according to the embodiment, and also ran 350
meters wearing conventional shoes (comparative example). FIG. 10
shows variations of the running time. The shoes according to the
embodiment have a tilt angle of 12 degrees. Meanwhile, the shoes of
the comparative example have a tilt angle of 3 degrees. The
vertical axis in FIG. 9 represents a variation of the running time
of a subject wearing the shoes according to the embodiment, with
respect to the running time of the subject wearing the shoes of the
comparative example. As shown in FIG. 10, it is found that the
running time of most of the wearers reduced. The speed ratio of
part of the wearers increased by nearly 10%.
[0052] The present invention is not limited to the aforementioned
embodiment, and modifications may be appropriately made to each
configuration without departing from the scope of ideas of the
present invention. When the embodiment set forth above is
generalized, the following aspects are derived.
Aspect 1
[0053] A shoe, comprising: [0054] a sole made of a soft material,
the sole including a ground contact surface and also including a
foot contact surface facing a side opposite to the ground contact
surface; and [0055] an upper combined with the foot contact surface
side of the sole, wherein [0056] a thickness of the sole at a
position corresponding to an MP joint of a wearer is different from
a thickness of the sole at a position corresponding to the center
of the heel such that an angle between the foot contact surface and
the ground contact surface falls within the range of 8 to 16
degrees.
Aspect 2
[0057] The shoe of Aspect 1, wherein the sole includes an arch
portion recessed upward in a midfoot portion.
[0058] With this configuration in which the arch portion is
provided, when the midsole is compressed from the above while the
shoe is in contact with the ground, a space for deformation of the
midsole can be ensured.
Aspect 3
[0059] The shoe of Aspect 1 or 2, further comprising a
reinforcement member that reinforces the midfoot portion of the
sole and a rearfoot portion of the sole.
[0060] This configuration can improve the strength of the sole, and
also improve the integrity of the midsole.
Aspect 4
[0061] The shoe of Aspect 3, wherein the reinforcement member
extends continuously from the rearfoot portion to a position
corresponding to an MP joint.
[0062] With this configuration, force can be appropriately
transmitted to the ground.
Aspect 5
[0063] The shoe of Aspect 3 or 4, wherein the reinforcement member
includes a curled-up part that extends upward along a heel
part.
[0064] This configuration can stabilize the heel part.
Aspect 6
[0065] The shoe of Aspect 5, wherein the sole includes a curled-up
part that extends upward along a heel part, and a height of the
curled-up part of the reinforcement member is 1.0 to 2 times the
height of the curled-up part of the sole.
[0066] This configuration can further stabilize the heel part.
Aspect 7
[0067] The shoe of any one of Aspects 1 through 6, wherein a rear
end part of the rearfoot portion of the sole has a curved shape in
a side view.
[0068] With this configuration, when the wearer's heel lands on the
ground, forward rolling can be prompted.
Aspect 8
[0069] The shoe of any one of Aspects 1 through 7, wherein the
maximum thickness of the rearfoot portion of the sole is 3 to 5
times the maximum thickness of a forefoot portion of the sole.
[0070] This configuration can ensure the stability and also provide
the feeling of acceleration.
Aspect 9
[0071] The shoe of any one of Aspects 1 through 8, wherein the sole
includes a hollow part formed in the rearfoot portion.
[0072] With this configuration, repulsion provided by the sole
structure can be obtained.
INDUSTRIAL APPLICABILITY
[0073] The present invention is applicable to the technical field
of shoes.
REFERENCE SIGNS LIST
[0074] 10 shoe
[0075] 12 sole
[0076] 14 upper
[0077] 24 ground contact surface
[0078] 26 foot contact surface
[0079] 36 heel part
[0080] 38, 50 shoe
[0081] 60 shoe
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