U.S. patent application number 14/226422 was filed with the patent office on 2015-10-01 for sole construction with stretch flex zone.
The applicant listed for this patent is Newton Running Company, Inc.. Invention is credited to Danny Abshire.
Application Number | 20150272268 14/226422 |
Document ID | / |
Family ID | 54188586 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150272268 |
Kind Code |
A1 |
Abshire; Danny |
October 1, 2015 |
SOLE CONSTRUCTION WITH STRETCH FLEX ZONE
Abstract
In accordance with one implementation, a sole construction
includes a flexible membrane in a forefoot region of the sole
construction. The flexible membrane interconnects a first rigid
plate to a second rigid plate along a longitudinal axis of the sole
construction. The flexible membrane is adapted to flex in the
forefoot region responsive to a contact force, causing the first
rigid plate to move relative to the second rigid plate.
Inventors: |
Abshire; Danny; (Boulder,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Newton Running Company, Inc. |
Boulder |
CO |
US |
|
|
Family ID: |
54188586 |
Appl. No.: |
14/226422 |
Filed: |
March 26, 2014 |
Current U.S.
Class: |
36/25R |
Current CPC
Class: |
A43B 13/223 20130101;
A43B 13/141 20130101; A43B 13/122 20130101 |
International
Class: |
A43B 13/14 20060101
A43B013/14 |
Claims
1. A sole construction for a shoe comprising: a substantially
flexible membrane in a forefoot region of the sole construction
interconnecting a first substantially rigid plate to a second
substantially rigid plate, the first substantially rigid plate
axially aligned with the second substantially rigid plate along a
longitudinal axis of the sole construction.
2. The sole construction of claim 1, wherein the flexible membrane
is adapted to flex in the forefoot region to allow movement of the
first substantially rigid plate relative to the second
substantially rigid plate.
3. The sole construction of claim 1, wherein the first rigid plate
is positioned in a toe region and the second rigid plate is
positioned in the forefoot region.
4. The sole construction of claim 1, wherein the first
substantially rigid plate and the second substantially rigid plate
are substantially planar and lie within a common plane in the
absence of applied force.
5. The sole construction of claim 1, wherein the flexible membrane
forms part of a ground-facing outer surface of the sole
construction.
6. The sole construction of claim 1, wherein the second
substantially rigid plate extends into a midfoot region on a
lateral side of the sole construction.
7. The sole construction of claim 1, wherein the first
substantially rigid plate includes a number of articulated regions
adapted to move relative to one another.
8. The sole construction of claim 1, wherein the first
substantially rigid plate includes five articulated regions adapted
to move relative to one another.
9. The sole construction of claim 1, further comprising a plurality
of fastening means for attaching spikes to a ground-facing outer
surface of the sole construction.
10. The sole construction of claim 1, wherein the flexible membrane
allows for movement of a portion of the first substantially rigid
plate about both a torsional axis and a lateral axis, the torsional
axis substantially perpendicular to the lateral axis.
11. A method comprising: flexing a membrane in a forefoot region of
a sole construction, the membrane connecting a first substantially
rigid plate to a second substantially rigid plate, the first
substantially rigid plate axially aligned with the second
substantially rigid plate along a longitudinal axis of the sole
construction.
12. The method of claim 11, wherein the flexing operation moves the
first substantially rigid plate relative to the second
substantially rigid plate.
13. The method of claim 11, wherein the first substantially rigid
plate is positioned in a toe region and the second substantially
rigid plate is positioned in the forefoot region.
14. The method of claim 11, wherein the second substantially rigid
plate extends into a midfoot region on a lateral side of the sole
construction.
15. The method of claim 11, wherein the first substantially rigid
plate includes a number of articulated regions adapted to move
relative to one another.
16. The method of claim 11, wherein the first substantially rigid
plate includes five articulated regions adapted to move relative to
one another.
17. The method of claim 11, wherein the membrane allows for
movement of a portion of the first substantially rigid plate about
both a torsional axis and a lateral axis, wherein the torsional
axis is substantially perpendicular to the lateral axis.
18. A sole construction comprising: a substantially rigid forefoot
plate and a substantially rigid toe plate separated from one
another and interconnected by a flexible membrane, the flexible
membrane adapted to flex between the substantially rigid forefoot
plate and the substantially rigid toe plate responsive to a contact
force.
19. The sole construction of claim 18, wherein the rigid forefoot
plate includes a number of articulated regions adapted to move
relative to one another.
20. The sole construction of claim 19, wherein each articulated
region is sized and shaped to underlie a corresponding metatarsal
of a user's foot.
Description
BACKGROUND
[0001] During a typical running gait of a runner not wearing
footwear, a foot lands first on a lateral side of the foot on a
region of the foot underlying the fifth metatarsal bone. The
runner's weight then settles on the middle and medial side of the
foot, putting weight on one metatarsal at a time. As the foot
lands, the joints and bones of the foot extend laterally, and the
toes dorsiflex upward, toward the runner's body.
[0002] Some traditional shoes do not allow for this natural motion
of the foot. For example, traditional track shoes are generally
formed of a uniform, stiff sole. Rather than allow the metatarsals
to land on the ground individually, these shoes can instead
restrict and constrain the foot's motion. As a result, a runner's
toes may move largely as a single unit, rather than as individual
bones and joints. Restricting the movement of the bones and joints
of the foot reduces efficiency and may be a factor contributing to
injury.
SUMMARY
[0003] Implementations described herein may be utilized to address
at least one of the foregoing problems by providing a shoe sole
construction including a stretch flex zone in a forefoot region
that makes it easier for the toes to bend away from the rest of the
foot (i.e., to dorsiflex). In some implementations, the forefoot
stretch flex zone is shaped to provide for independent movement of
the metatarsal bones, joints, and toes of a user's foot.
[0004] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter. These and various other features and advantages
will be apparent from a reading of the following Detailed
Description.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0005] A further understanding of the nature and advantages of the
present technology may be realized by reference to the figures,
which are described in the remaining portion of the
specification.
[0006] FIG. 1 illustrates a bottom plan view of an example sole
construction with a stretch flex zone.
[0007] FIG. 2 illustrates a bottom plan view of an example sole
construction including a stretch flex zone that interlinks a rigid
forefoot plate and a rigid toe plate.
[0008] FIG. 3 illustrates a bottom plan view of another example
sole construction including a stretch flex zone that interlinks a
rigid forefoot plate and a rigid toe plate.
[0009] FIG. 4A illustrates an exploded elevation view of a sole
construction with a stretch flex zone.
[0010] FIG. 4B illustrates an exploded plan view of a sole
construction with a stretch flex zone.
[0011] FIG. 5 illustrates another elevation view construction
during a mid-stance stage of the gait cycle.
[0012] FIG. 6 illustrates another elevation view of a sole
construction during a toe-off stage of the gait cycle.
[0013] FIG. 7 illustrates example operations for energy
conservation in a sole construction.
DETAILED DESCRIPTIONS OF THE DRAWINGS
[0014] Recent studies have shown that a "natural running" form can
help to reduce the frequency and severity of some common running
injuries. "Natural running" refers to a form of running that a
runner adopts to reduce loading rates and protect the foot from
excessive impact while moving quickly and efficiently. A runner
practicing natural running form strikes the ground close to a point
under the body's center of gravity with a relaxed foot rather than
over striding (e.g., landing with the foot in front of the runner's
center of gravity) with an aggressively dorsiflexed ankle.
[0015] In an efficient gait cycle, the runner lands lightly with a
relaxed foot and avoids exaggerated joint positions and excessive
use of muscular force. When pushing off from the ground during a
"toe-off" phase of the gait cycle, the toes dorsiflex upward away
from the metatarsals of the foot. This dorsiflexion of the toes
applies a flexing force to the runner's shoe sole in a region
underlying the forefoot, where the toes meet the metatarsals. When
a hard material, such as a plastic or carbon plate, is included in
this "flex zone" the runner expends energy bending the hard
material. Much of the energy expended in bending the hard material
is not returned to the runner and is instead lost to damping forces
of the shoe sole, heat dissipation, etc. By decreasing the amount
of energy utilized in bending material of a forefoot region, the
amount of energy retained by the runner is increased, allowing a
proportional increase in the runner's efficiency and speed.
[0016] Implementations disclosed herein provide a sole construction
including a stretch flex zone in a forefoot region underlying the
metatarsophalangeal joints of the foot. The stretch flex zone is
formed by a stretchable membrane that interconnects a first rigid
plate, substantially underlying the toes, to a second rigid plate,
substantially underlying the metatarsals. The disclosed technology
may be of particular benefit in shoes designed for speed, such as
sprinting shoes including track spikes. However, the technology is
also contemplated for use in a variety of other types of footwear
including athletic shoes of many types (e.g., cross-training,
walking, running, etc.), as well as shoes designed for biking,
hiking, driving, and any garment where increased flexibility is
desired between two or more rigid areas.
[0017] FIG. 1 illustrates a bottom plan view of an example shoe
sole construction 100 with a stretch flex zone 120. The sole
construction 100 includes a hindfoot or heel region 106, a midfoot
region 104, a forefoot region 102, and a toe region 112. The heel
region 106 underlies or substantially underlies the length and
width of a heel of a runner's foot. The midfoot region 104 is
positioned forward or anterior to the heel region 106, and
underlies or substantially underlies the arch or "middle" region of
the foot, which typically includes the region underlying the
navicular, cuboid, and cuneiform bones of the foot. The forefoot
region 102 is positioned forward or anterior to the midfoot region
104, and underlies or substantially underlies the ball of the foot.
In particular, the forefoot region 102 underlies the metatarsal
bones and metatarsophalangeal joints. The toe region 112 is
anterior to the forefoot region 102, and underlies or substantially
underlies the phalanges (i.e., toes). The terms "heel region,"
"midfoot region," "forefoot region," and "toe region" are used
throughout the application, as defined above.
[0018] The sole construction 100 includes a forefoot plate 108 in
the forefoot region 102 and a toe plate 110 in the toe region 112.
The forefoot plate 108 and the toe plate 110 are substantially
rigid, planar components separated from one another and
interconnected by a substantially flexible, stretchable material.
As used herein, "substantially rigid" refers to a hardness in a
range between about shore 40 D and shore 90 D. In one
implementation, "substantially rigid" refers to a hardness of about
shore 70 D. In contrast, the term "substantially flexible" refers
to a hardness in a range between about shore 20 D and shore 60 D.
In one implementation, "substantially flexible" refers to narrower
range between shore 30 D and shore 45 D. Within any single
implementation, a "substantially rigid" material has a hardness
that is greater than a "substantially flexible" material.
[0019] The stretch flex zone 120 includes the flexible, stretchable
material in the region between the forefoot plate 108 and the toe
plate 110. The stretch flex zone 120 extends through the forefoot
region 102 between lateral (outside) and medial (inside) sides of
the sole construction 100, permitting the toe plate 110 to move
relative to the forefoot plate 108. When the sole construction 100
is implemented in a shoe, the stretch flex zone 120 provides a zone
of increased flexibility in a region substantially underlying a
runner's metatarsophalangeal joints.
[0020] In FIG. 1, the forefoot plate 108 and the toe plate 110 are
affixed to a ground-facing surface of the sole construction 100,
providing a rigid, outer surface for contacting the ground and/or
for affixing one or more "track spikes" or other friction-providing
elements. In the implementation shown, track spikes (not shown) can
be attached to each of a number of receiving divots (e.g., a
receiving divot 116) on the toe plate 110 and the forefoot plate
108. In at least one implementation, a user can selectively attach
and remove track spikes to the receiving divots 116. Other
implementations may not include receiving divots or features for
track spike attachment. For example, the forefoot plate 108, toe
plate 110, and stretch flex zone 120 may be included in a walking
or general-purpose athletic shoe that is not specially designed for
speed or increased traction provided by track spikes.
[0021] The forefoot plate 108 and the toe plate 110 may form a
portion of a ground-facing outer surface of the sole construction
100, as shown. However, in other implementations, the forefoot
plate 108 and/or the toe plate 110 do not form part of the
ground-facing outer surface. For example, the forefoot plate 108
and/or toe plate 110 may be coated with a protective or
friction-providing material, such as a soft or hard rubber.
Alternatively, the forefoot plate 108 and/or toe plate 110 may be
embedded within the sole construction 100.
[0022] FIG. 2 illustrates a bottom plan view of an example sole
construction 200 including a stretch flex zone 220. The stretch
flex zone 220 includes a flexible, stretchable material (i.e., a
flex-stretch material) that interlinks a rigid forefoot plate 208
and a rigid toe plate 210. Elongated slots (e.g., an elongated slot
214) in the rigid forefoot plate 208 and the rigid toe plate 210
separate each of the plates into different, articulated regions
(e.g., an articulated region 218). In various implementations, the
number, length, and positioning of such slots may vary. The slots
are filled with the flex-stretch material and form a portion of the
stretch flex zone 220. The articulated regions of FIG. 2 may each
move independently of one another responsive to movement of an
overlying metatarsal of a user's foot. Movement of each of the
articulated regions may be in multiple cardinal directions. For
example, the articulated region 218 may be able to twist about a
torsional axis (e.g., an example torsional axis "Y") and
simultaneously about a lateral axis (e.g., a lateral axis X).
Movement about such lateral axis may be bidirectional. For example,
if a user lands with a forefoot plate first with the toe plate
vertically higher due to dorsiflexion, the sole may rotate about
the lateral axis toward the ground, as well as away from the ground
during a toe-off phase.
[0023] Although other implementations are contemplated, the sole
construction 200 includes four elongated slots (e.g., an example
slot 214) extending into the forefoot plate 208. Each slot in the
rigid forefoot plate 208 is substantially aligned with a
corresponding slot formed in the rigid toe plate 210. Each of the
articulated regions in the rigid forefoot plate 208 substantially
underlies and provides support for one of the five metatarsals of
the foot, while each of the articulated regions in the rigid toe
plate 210 underlies and provide support for one of the toes of the
foot. In another implementation, the articulated regions are formed
in one rather than both of the rigid toe plate 210 and the rigid
forefoot plate 208.
[0024] The articulated regions of the rigid forefoot plate 208 and
the rigid toe plate 210 allow for independent movement of different
metatarsals of the foot. For example, a runner may strike the
ground on the lateral (i.e., outside) region of the foot, putting
weight on the fifth (outermost) metatarsal. The metatarsals then
contact the ground one at a time, from the outside in. As the
remaining metatarsals contact the ground, the runner's weight
settles onto the middle and then onto the medial (i.e., inner) side
of the foot. A shoe including the technology illustrated in FIG. 2
may allow the metatarsals and/or toes of the user's foot to each
"move" an associated articulated region in the forefoot plate 208
and/or toe plate 210 as the weight settles over that region. This
allows for more natural movement of the foot, increasing running
efficiency and reducing injury.
[0025] FIG. 3 illustrates a bottom plan view of another example
sole construction 300 including a stretch flex zone 320. The
stretch flex zone 320 includes a flexible, stretchable (i.e.,
"flex-stretch") material that interlinks a rigid forefoot plate 308
and a rigid toe plate 310. Elongated slots (e.g., an elongated slot
314) in the rigid forefoot plate 308 and the rigid toe plate 310
separate each of the plates into different, articulated regions
(e.g., an articulated region 318). The slots are vertically aligned
with the flex-stretch material and form a portion of the stretch
flex zone 320. The articulated regions of FIG. 3 may each move
independently of one another responsive to movement of an overlying
metatarsal of a user's foot.
[0026] In FIG. 3, the forefoot plate 308 and the toe plate 310 are
affixed to a ground-facing surface of the sole construction 300,
providing a rigid, outer surface for contacting the ground and/or
for affixing one or more "track spikes" or other friction-providing
elements. In the implementation shown, track spikes (not shown) can
be attached to each of a number of receiving divots (e.g., a
receiving divot 316) on the toe plate 310 and the forefoot plate
308. In addition, a number of friction providing elements (e.g., a
friction providing element 330, 331) are formed on each of the
forefoot plate 308 and the toe plate 310 to provide increased
friction with between the sole construction 300 and the ground.
[0027] FIG. 4A illustrates an exploded elevation view of an example
sole construction 400 with a forefoot stretch flex zone 420. FIG.
4B illustrates an exploded plan view of the sole construction 400
of FIG. 4A. Dashed lines indicate corresponding components of FIG.
4A and FIG. 4B.
[0028] The example sole construction 400 includes an upper 430, a
midsole layer 418, a flex-stretch layer 422, a rigid toe plate 410,
and a rigid forefoot plate 408. The upper 430 (shown in FIG. 4A)
includes fabric forming a top of a shoe construction. Other
implementations may not include either the upper 430 and/or the
midsole layer 418. The upper 430 attaches to the midsole layer 418,
which is sized and shaped to receive and substantially underlie and
provide support for a user's foot. One or more cut-outs or
depressions (not shown) may be formed in a ground-facing surface of
the midsole layer 418 to receive one or more of the flex-stretch
layer 422, the rigid toe plate 410, or the rigid forefoot plate
408. The midsole layer 418 can be formed of a variety of materials
such as ethylene-vinyl acetate (e.g., EVA foam), or other foam or
soft, pliable material. In one implementation, the midsole layer
418 is substantially more pliable (e.g., softer) than the
flex-stretch layer 422.
[0029] The ground-facing surface of the midsole layer 418 is bonded
to the flex-stretch layer 422. The flex-stretch layer 422 is
positioned in a forefoot region of the sole construction 400, so as
to underlie a user's metatarsals and metatarsophalangeal joints. A
portion of the flex-stretch layer 422 extends into a toe region of
the sole construction so that it is vertically aligned with the
rigid toe plate 410. As used herein, "vertical alignment" refers to
alignment about an axis (e.g., the z-axis) that is substantially
perpendicular to both a lateral (e.g., the x-axis) and torsional
axis (e.g., the y-axis) of the sole construction 400. Another
portion of the flex-stretch layer 422 extends toward a midfoot
region of the sole construction 400 so that it is vertically
aligned with the rigid forefoot plate 408.
[0030] The flex-stretch layer 422 is substantially planar and may
have either a fixed or variable thickness. In one example
implementation, the flex-stretch layer 422 has a fixed thickness of
between about 1-2 mm. In the same or another implementation, the
flex-stretch layer 422 is a variable thickness layer with a region
of an increased thickness forming a perimeter (e.g., an "outline")
around the stretch flex zone 420. For example, a boundary
separating the stretch flex zone 420 from either the rigid forefoot
plate 408 or the rigid toe plate 410 may be raised by an additional
1 mm from the remainder (e.g., interior) of the flex-stretch layer
422. This design allows the stretch-flex layer 420 to be fitted
precisely to the rigid forefoot plate 408 and/or the rigid toe
plate 410, and may also allow for greater independent plate
articulation.
[0031] A variety of materials are suitable for use in the
flex-stretch layer 422 including without limitation elastic,
DuPont.TM. Hytrel.RTM., natural or synthetic gum rubber, and
various thermoplastic elastomers such as polyether block amides
(e.g., Pebax.RTM.). The hardness of the flex-stretch layer 422 may
vary depending upon design criteria. In one implementation, the
flex-stretch layer 422 has a hardness of about Shore 30D and is 1.2
mm thick. In some shoe constructions designed for running on track
surfaces, the flex-stretch layer 422 is softer than Shore 30D. In
other implementations, the flex-stretch layer 422 is harder than
Shore 30D.
[0032] The rigid forefoot plate 408, and rigid toe plate 410 are
made of a harder material than the flex-stretch layer 422. Suitable
materials for one or more of the rigid plates include without
limitation plastics, carbon-fiber, metal, rubber, synthetic rubber,
Nylon (e.g., Nylon-12) and Pebax.RTM.. In various implementations,
the hardness of the rigid plates ranges from Shore 40D to Shore
90D. The thickness of the rigid forefoot plate 408 and the rigid
toe plate 410 may vary depending on material type and desired
design criteria. However, in one implementation, the hardness of
the plates is approximately Shore 70D. In another implementation,
forefoot plate 408 and the toe plate 410 are about 1.5 mm
thick.
[0033] The rigid toe plate 410 and the rigid forefoot plate 408 are
separated from one another by a gap (e.g., in the y-direction, as
shown in FIG. 4A) that spans a few millimeters (e.g., between about
3 mm and about 10 mm) or enough to allow for relative movement
between the forefoot plate 408 and the toe plate 410 responsive to
an applied force. The gap may of constant or variable thickness. In
on implementation, the gap is 7 mm when measured on a medial
(inside) of the sole construction 400 and 10 mm on a lateral
(outside) edge of the sole construction 400.
[0034] The rigid forefoot plate 408 and the rigid toe plate 410 can
be of a variety of different shapes and sizes. In one
implementation, the forefoot plate 408 extends longitudinally
toward the heel of the sole construction 400 and into a midfoot
(i.e., arch) region and/or a heel region of the sole construction
400.
[0035] In FIG. 4, the forefoot plate 408 includes a flange portion
436 that extends from a forefoot region and into a midfoot region
on a lateral side of the sole construction 400. One purpose of the
flange portion 436 is to provide support for the bones in the fifth
metatarsal of the user's foot. When running with proper form, the
fifth metatarsal is the first part of the user's foot to contact
the ground. Thus, injuries to the fifth metatarsal are common. The
flange portion 436 of the rigid forefoot plate 402 may help to
reduce the incidence of such injuries. In some implementations, the
forefoot plate 408 does not include the flange portion 436.
[0036] A number of elongated slots (e.g., an elongated slot 414)
are formed in the forefoot plate 408 and the toe plate 410,
separating the forefoot plate 408 and the toe plate 410 into
different, articulated regions. In various implementations, the
number, length, and positioning of such slots may vary. In
operation, the slots provide for independent movement of each of
the articulated regions under force applied by associated regions a
user's foot.
[0037] Track spikes (e.g., a track spike 434) are shown positioned
in each of the rigid toe plate 410 and the rigid forefoot plate
408. In at least one implementation, these spikes can be
selectively attached and/or detached by the user. For example, a
track spike may include a grooved screw that twists and locks into
a receiving slot. Functionally, the forefoot plate 408 and/or the
toe plate 410 help to distribute a user's weight across evenly
across the sole construction.
[0038] FIG. 5 illustrates an elevation view of another example shoe
sole construction 500 during a mid-stance (e.g., contact) stage of
a gait cycle. The shoe sole construction 500 includes a forefoot
stretch flex zone 520 between a rigid forefoot plate 508 and a
rigid toe plate 510. Material included in the stretch flex zone 520
between the rigid forefoot plate 508 and the rigid toe plate 510 is
substantially more pliable than either of the rigid forefoot plate
508 or the rigid toe plate 510.
[0039] When in use, the rigid toe plate 510 underlies or
substantially underlies a user's phalanges (i.e., toes), the rigid
forefoot plate 508 underlies the user's metatarsal bones, and the
stretch flex zone 520 substantially underlies the user's
metatarsophalangeal joints. A midsole layer 518 receives and
cradles the user's foot and separates the foot from the underlying
rigid forefoot plate 508, rigid toe plate 510, and forefoot stretch
flex zone 520. In at least one implementation, the midsole layer
518 is a softer (e.g., more pliable) material than the material of
the stretch flex zone 520. Receiving divots (e.g., a receiving
divot 516) may be formed on or attached to the toe plate 510 and/or
the forefoot plate 508 to allow for attachment of one or more track
spikes or other friction-providing elements.
[0040] A first axis "Y" indicates a torsional axis extending
through toe and heel regions of the sole construction 500. A second
axis "X" indicates a lateral axis extending through a forefoot
region, between lateral and medial sides of the sole construction
500. When a runner's foot first strikes the ground, the runner's
phalanges, metatarsals, and metatarsophalangeal joints may lie
substantially flat within a common plane (e.g., within the X-Y
plane as shown in FIG. 5). Then, as the runner pushes off of the
ground during a "toe-off" phase of the gait cycle, the toes
dorsiflex away from the rest of the foot, bending material of the
shoe construction 500. An example flexure of the sole construction
500 responsive to dorsiflexion of the toes is shown in FIG. 6.
[0041] FIG. 6 illustrates another elevation view of a shoe sole
construction 600 during a toe-off stage of a gait cycle. The shoe
sole construction 600 includes a forefoot stretch flex zone 620
between a rigid forefoot plate 608 and a rigid toe plate 610.
Material included in the stretch flex zone 620 between the rigid
forefoot plate 608 and the rigid toe plate 610 is substantially
more pliable than either of the rigid forefoot plate 608 or the
rigid toe plate 610.
[0042] A first axis "Y" indicates a torsional axis that extends
longitudinally through toe and heel regions of the sole
construction 600. A second axis "X" indicates a lateral axis that
extends through a forefoot region between lateral and medial sides
of the sole construction 600. As a runner pushes off of the ground
during a "toe-off" phase of the gait cycle, the toes dorsiflex away
from the rest of the foot, bending material in the stretch flex
zone 620 out of the x-y plane (e.g., in a z-direction).
[0043] In the same or another implementation, the stretch flex zone
620 is shaped to provide for additional rotation in another
direction. For example, articulated regions in the forefoot plates
(e.g., as shown in FIG. 2) may allow for torsional rotation of
different regions of the sole construction 600 about Y or other
axes substantially parallel to Y. In other implementations, the
stretch flex zone 620 provides for rotational movement of the sole
construction 600 about one or more axes non-parallel to the X or Y.
For example, one or more articulated regions of the sole
construction 600 may have freedom to move in more than two cardinal
directions. In one implementation, the articulated regions in the
forefoot plate 608 allow a user's metatarsals to strike the ground
individually (e.g., one at a time) rather than all at once.
[0044] Receiving divots (e.g., a receiving divot 616) may be formed
on or attached to the toe plate 610 and/or the forefoot plate 608
to allow for attachment of one or more track spikes or other
friction-providing elements.
[0045] FIG. 7 illustrates example operations 700 for energy
conservation in a sole construction. A providing operation 705
provides a sole construction with a flexible, stretchable material
(i.e., a flex-stretch layer) in a forefoot region. The flex-stretch
layer interconnects a first rigid plate to a second rigid plate
across a gap between spanning a distance along a longitudinal axis
of the sole construction. In one implementation, the flex-stretch
layer is visible through the gap and forms a part of the
ground-facing outer surface of the sole construction. In another
implementation, one or more additional layers are formed between
the flex-stretch layer and the ground-facing outer surface of the
sole construction.
[0046] The first rigid plate is positioned so as to be vertically
aligned or in contact with a portion of the flex-stretch layer
extending into a toe region. The second rigid plate is positioned
so as to be vertically aligned or in contact with another portion
of the flex-stretch layer in the forefoot region. The first rigid
plate and the second ridged plate may include a number of slots or
gaps forming articulated regions.
[0047] In one implementation, the flex-stretch layer and the rigid
plates are each positioned within a corresponding cut or depression
in an overlying soft (e.g., foam) midsole layer. The flex-stretch
layer is attached to the first rigid plate, second rigid plate, and
the foam midsole layer through an adhesion process. In another
implementation, the midsole layer is attached to the flex-stretch
layer and the rigid plates via a co-injection process through which
the elements are cohesively bonded through a molding process, or
via a high-frequency welding process.
[0048] A force application operation 710 applies a contact force to
a forefoot region of a sole construction. The force may be, for
example, the weight of a runner applied to forefoot region of the
sole when the runner's foot first strikes the ground. If the runner
strikes the ground with a lateral edge of the foot so as to
establish contact between the ground and the fifth (outermost
metatarsal), the foot may have the tendency to rotate inward.
[0049] A torsional flex operation 715 flexes the flex-stretch layer
in the region between the first rigid plate and the second rigid
plate about a torsional axis, permitting two or more articulated
regions of the first rigid plate and/or the second rigid plate to
move independently of one another. In one implementation, a
separate articulated region of the forefoot plate underlies each
metatarsal of a user's foot. The user strikes the ground with one
metatarsal at a time, from the outside in, until all five
metatarsals are in contact with the ground.
[0050] A lateral flex operation 720 flexes the flex-stretch layer
in the region between the first rigid plate and the second rigid
plate about a lateral axis, permitting the first rigid plate to
move relative to the second rigid plate. For example, the lateral
flex operation may flex the sole construction about an axis below a
user's metatarsophalangeal joints responsive to dorsiflexion of the
user's toes. In other implementations, lateral and/or torsional
rotation may occur in directions other than those described
herein.
[0051] The above specification, examples, and drawings provide a
complete description of the structure and use of exemplary
implementations of the invention. Since many implementations of the
invention can be made without departing from the spirit and scope
of the invention, the invention resides in the claims hereinafter
appended. Furthermore, structural features of the different
implementations may be combined in yet another implementation
without departing from the recited claims.
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