U.S. patent application number 09/526862 was filed with the patent office on 2002-05-09 for article of footwear with a motion control device.
Invention is credited to Swigart, John F..
Application Number | 20020053146 09/526862 |
Document ID | / |
Family ID | 24099114 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020053146 |
Kind Code |
A1 |
Swigart, John F. |
May 9, 2002 |
Article of footwear with a motion control device
Abstract
An article of footwear with a bladder system providing
cushioning and dynamic motion control in a multi-bladder system.
The bladder system gives the needed amount of motion control by
stiffening a portion of the footwear in response to the individual
user's side-to-side motion. When used in the heel, the bladder
system takes into consideration a center-of-pressure pathway of the
foot to increase medial stiffness in response to lateral-to-medial
rotation of the foot, so the more a user pronates, the stiffer the
medial portion of the footwear is made. The bladder system provides
comfort and control without the extra weight and bulk of prior art
support structures. The bladder system dynamically changes the
stiffness of a portion of the footwear when pressure is applied
thereto, and returns to equilibrium when the pressure is
removed.
Inventors: |
Swigart, John F.; (Portland,
OR) |
Correspondence
Address: |
BANNER & WITCOFF
1001 G STREET N W
SUITE 1100
WASHINGTON
DC
20001
US
|
Family ID: |
24099114 |
Appl. No.: |
09/526862 |
Filed: |
March 16, 2000 |
Current U.S.
Class: |
36/29 ; 36/28;
36/35B |
Current CPC
Class: |
A43B 13/206 20130101;
A43B 13/203 20130101 |
Class at
Publication: |
36/29 ; 36/28;
36/35.00B |
International
Class: |
A43B 013/18 |
Claims
I claim:
1. An article of footwear for controlling side-to-side motion of a
foot of a wearer comprising: an upper for covering at least a
portion of a wearer's foot; a sole attached to said upper; a
bladder system positioned within said sole and including at least
first and second bladder chambers in fluid communication with one
another, said first and second bladders being positioned
side-by-side of one another in a medial to lateral direction of
said sole; a first valve positioned between said first bladder
chamber and said second bladder chamber; said first valve including
a first pressure regulator that prevents fluid flow from said first
bladder chamber to said second bladder chamber when the pressure in
said first bladder chamber is below a first predetermined pressure
and allows fluid flow from said first bladder chamber to said
second bladder chamber when the pressure in said first bladder
chamber is at or above said first predetermined pressure to
increase the pressure in said second bladder chamber and
dynamically increase the support provided by said second bladder
chamber on the side it is disposed.
2. The footwear of claim 1 wherein said first valve is a one-way
check valve.
3. The footwear of claim 2 wherein said one-way check valve has a
regulator which allows fluid to return to said first bladder
chamber after it has been forced into said second bladder
chamber.
4. The footwear of claim 1 wherein said valve regulator allows said
bladder chambers to return to an initial rest pressures in between
strides.
5. The footwear of claim 1 wherein said second bladder chamber
extends along a medial side to control pronation.
6. The footwear of claim 1 wherein said second bladder chamber
extends along a lateral side of the forefoot region to control
supination.
7. The footwear of claim 1 further including a second valve located
between said first bladder chamber and said second bladder chamber,
wherein said second valve allows return flow into said first
bladder chamber.
8. The article of footwear of claim 1 wherein: said bladder system
positioned is within a heel region of said sole and said first
bladder chamber is disposed adjacent one side of said heel region,
a third bladder chamber is disposed adjacent the other side of said
heel region and said second bladder chamber is disposed between
said first and third bladder chambers in fluid communication
therewith; a second valve positioned between said third bladder
chamber and said second bladder chamber; said second valve
including a second pressure regulator that prevents fluid flow from
said second bladder to said third bladder chamber when the pressure
in said second bladder chamber is below a second predetermined
pressure and allows fluid flow from said second bladder chamber to
said third bladder chamber when the pressure in said second bladder
chamber is at or above said second predetermined pressure to
increase the pressure in said third bladder chamber and dynamically
increase the support provided by said third bladder chamber.
9. The footwear of claim 8 wherein said valves are one-way check
valves which allow fluid flow between said chambers when said heel
region is compressed for increasing pressure within said third
bladder chamber to thereby stiffen an area of said heel region in
which said third bladder chamber is located and control motion of
the foot.
10. The footwear of claim 9 wherein each said one-way check valve
has a regulator which allows fluid to return to said first and
second bladder chambers after it has been forced into said third
bladder chamber.
11. The footwear of claim 8 wherein said valve regulators allow
said bladder chambers to return to an initial rest pressure in
between strides by the user.
12. The footwear of claim 8 wherein said third bladder chamber
extends along a medial side of said heel region to control
pronation.
13. The footwear of claim 8 further including a third valve located
between said first bladder chamber and said second bladder chamber,
and a fourth valve located between said third bladder chamber and
said second bladder chamber, wherein said third and fourth valves
allow return flow into the first and second bladder chambers,
respectively.
14. A dynamic bladder system for use within footwear to control
motion of a foot of a wearer, said bladder system comprising: at
least first and second bladder chambers in fluid communication with
one another, said first and second bladders being positioned
side-by-side of one another in a medial to lateral direction of
said sole; a first valve positioned between said first bladder
chamber and said second bladder chamber; said first valve including
a first pressure regulator that prevents fluid flow from said first
bladder chamber to said second bladder chamber when the pressure in
said first bladder chamber is below a first predetermined pressure
and allows fluid flow from said first bladder chamber to said
second bladder chamber when the pressure in said first bladder
chamber is at or above said first predetermined pressure to
increase the pressure in said second bladder chamber and
dynamically increase the support provided by said second bladder
chamber on the side it is disposed.
15. The bladder system of claim 14 wherein said first valve is a
one-way check valve.
16. The bladder system of claim 15 wherein said one-way check valve
has a regulator which allows fluid to return to said first bladder
chamber after it has been forced into said second bladder
chamber.
17. The bladder system of claim 14 wherein said valve regulator
allows said bladder chambers to return to an initial rest pressures
in between strides.
18. The bladder system of claim 14 further including a second valve
located between said first bladder chamber and said second bladder
chamber, wherein said second valve allows return flow into said
first bladder chamber.
19. The bladder system of claim 14 including: a third bladder
chamber, wherein said second bladder chamber is disposed between
said first and third bladder chambers in fluid communication
therewith; a second valve positioned between said third bladder
chamber and said second bladder chamber; said second valve
including a second pressure regulator that prevents fluid flow from
said second bladder to said third bladder chamber when the pressure
in said second bladder chamber is below a second predetermined
pressure and allows fluid flow from said second bladder chamber to
said third bladder chamber when the pressure in said second bladder
chamber is at or above said second predetermined pressure to
increase the pressure in said third bladder chamber and dynamically
increase the support provided by said third bladder chamber.
20. The bladder system of claim 19 wherein said valves are one-way
check valves which allow fluid flow between said chambers when said
bladder system is compressed for increasing pressure within said
third bladder chamber to thereby stiffen an area in which said
third bladder chamber is located and control motion of the
foot.
21. The bladder system of claim 20 wherein each said one-way check
valve has a regulator which allows fluid to return to said first
and second bladder chambers after it has been forced into said
third bladder chamber.
22. The bladder system of claim 19 wherein said valve regulators
allow said bladder chambers to return to an initial rest pressure
in between strides by the user.
23. The article of claim 19 further including a third valve located
between said first bladder chamber and said second bladder chamber,
and a fourth valve located between said third bladder chamber and
said second bladder chamber, wherein said third and fourth valves
allow return flow into the first and second bladder chambers,
respectively.
24. A bladder system for use in footwear to dynamically control the
side-to-side support provided by the bladder system comprising: a
plurality of fluid containing bladder chambers arranged in a
side-by-side relationship; conduits fluidly connecting adjacent
chambers; and flow control devices to direct the flow of fluid from
one of said bladder chambers undergoing impact from a wearer's foot
when the pressure in said one of said bladder chambers exceeds a
predetermined level to at least one of said other bladder chambers
to increase the pressure in, and the support provided by, the at
least one of said other bladder chambers.
25. The bladder system of claim 24 wherein said plurality of
bladder chambers includes at least three bladder chambers,
including two outer bladder chambers and a central bladder chamber,
and said flow control devices being arranged to serially direct
fluid flow from one of said outer bladder chambers to said central
bladder chamber and thereafter to the other one of said outer
bladder chamber as the impact of a wearer's foot increases the
pressure in said one of said outer bladder chambers above a first
predetermined level and thereafter increases the pressure in said
central bladder chamber above a second predetermined level to
increase the pressure in, and the support provided by, said other
one of said outer bladder chambers.
26. The bladder system of claim 25 wherein said flow control
devices allow fluid to return from said other one of said outer
bladder chamber to said central bladder chamber and said one of
said outer bladder chambers after footstrike by the wearer has been
completed.
Description
FIELD OF THE INVENTION
[0001] The invention relates to an article of footwear which has a
dynamically changing motion control and cushioning bladder system.
The bladder system provides varying amounts of resistance to
side-to-side motion depending on the severity of such motion while
walking, running, or participating in other athletic
activities.
BACKGROUND OF THE INVENTION
[0002] The typical running stride involves the runner landing on
the lateral, posterior edge of the footwear in the heel region
followed by pronation toward the medial side as the foot continues
through its stride. As footstrike continues, the foot stops
pronating and begins to supinate as the foot rocks forward so that
the foot reaches a neutral position at midstance. From midstance,
the foot rocks forward to the forefoot region where toe-off occurs
at the ball and front of the foot. Toe-off typically involves the
toes on the medial side of the foot pushing off the running surface
as the foot leaves the ground to begin a new cycle.
[0003] Pronation involves the rolling of the foot from its lateral,
posterior side to its inner, medial side. Although pronation is
normal and necessary to achieve proper foot positioning, it can be
a source of foot and leg injuries for runners who over pronate. The
typical runner who over pronates lands on the outer, lateral side
of the heel in a supinated position and then rolls medially across
the heel toward the inner side of the footwear beyond a point which
may be considered normal. While some amount of pronation is helpful
in decreasing pressure and stress experienced by the leg, excessive
pronation can cause stress on various joints, bones and soft
tissue. Supinating, which involves rolling of the foot from the
medial to the lateral side, while not as common as over pronating,
can also cause foot and leg injuries if it is excessive.
[0004] Modern running and walking footwear are a combination of
many elements each having a specific function which aids in the
overall ability of the footwear to withstand many miles of running
or walking, while providing cushioning and support for the foot and
leg. Articles of athletic footwear are divided into two general
parts, an upper and a sole. The upper is designed to snugly and
comfortably enclose the foot, while the sole must provide traction,
protection and a durable wear surface. It is often desirable to
provide the footwear with a midsole having a layer of resilient,
cushioning materials for enhanced protection and shock absorption
when the heel strikes the ground during the stride of the wearer.
This is particularly true for training or jogging footwear designed
to be used over long distances or over a long period of time. These
cushioning materials, must be soft enough to absorb the shock
created by the foot strike and firm enough not to "bottom out"
before the impact of the heel strike is totally absorbed.
[0005] Attempts have also been made to provide support and comfort
in an article footwear by incorporating bladders in fluid
communication with each other within a sole. Examples of these
devices include U.S. Pat. No. 4,183,156 to Rudy (which is hereby
incorporated by reference); U.S. Pat. No. 4,446,634 to Johnson et
al.; U.S. Pat. No. 4,999,932 to Grim; Austrian Patent No. 200,963
to Schutz et al.; and HYDROFLOW.RTM.ST, by BROOKS.RTM. Sports,
Inc.
[0006] Conventional running and walking footwear designed to
provide the user with the maximum amount of available cushioning
tend to sacrifice footwear stability by using a midsole cushioning
system that is too soft and has too much lateral flexibility for a
person who over pronates or requires some form of motion control.
The lateral flexibility and deformation of traditional cushioning
materials contribute to the instability of the subtalar joint of
the ankle and increase the runner's tendency to over pronate. This
instability has been cited as one of the causes of "runners knee"
and other such athletic injuries. As a result, over-pronators
generally do not use contemporary shoes specifically designed for
maximum cushioning, but instead use heavier, firmer footwear, or
footwear having motion control devices specifically designed to
correct physical problems such as excessive pronation. Motion
control devices limit the amount and/or rate of subtalar joint
pronation immediately following foot strike.
[0007] Various ways of resisting excessive pronation or instability
of the subtalar joint have been proposed and incorporated into
running footwear as motion control devices. In general, these
devices have been fashioned by modifying conventional footwear
components, such as the heel counter, and/or the midsole cushioning
materials. Unlike the present invention, current motion control
devices do not repeatedly adjust their level of support to match
the varying degree of side-to-side motion accompanying each foot
strike. Instead, when used to control pronation, devices such as
firm medial posts limit over pronation by providing a substantially
rigid structure with a constant stiffness and level of support that
presses against the medial side of the foot, limiting internal
rotation of the ankle. Examples of motion control devices include:
U.S. Pat. No. 5,046,267, to Kilgore et al.; U.S. Pat. No.
5,155,927, to Bates et al.; and U.S. Pat. No. 5,367,791, to Gross
et al.
SUMMARY OF THE INVENTION
[0008] Two of the most common reasons for foot and knee injuries
sustained by runners and walkers are insufficient shock absorption
and a lack of proper lateral motion control. Both reasons must be
considered when designing footwear so the wearer receives the
proper amount of cushioning and motion control without
significantly increasing the overall weight of the footwear. Many
runners who require a moderate amount of motion control may have to
use heavy, bulky footwear, which is weighted down by support
features, and designed for the severe over pronator.
[0009] The present invention introduces cushioning and dynamic
motion control in a single, multi-bladder system providing optimum
cushioning, while simultaneously providing the needed amount of
motion control by stiffening a portion of the footwear in response
to the individual user's lateral motion, most frequently pronatory
motion. The bladder system of the present invention takes into
consideration the center-of-pressure pathway of the foot during
typical footstrike to increase medial stiffness in response to
lateral-to-medial rotation of the foot, so the more a user
pronates, the stiffer the medial portion of the footwear is made.
The bladder system provides comfort and control without the extra
weight and bulk of prior art support structures because the support
is provided by the flow of fluid in the cushioning system. The
bladder system also provides a dynamically changing cushioning
system that functions when pressure is applied to its region of the
footwear and returns to equilibrium when the pressure is
removed.
[0010] The present invention utilizes lightweight bladders for the
dual purposes of cushioning and motion control. As a result, motion
control footwear incorporating the present invention can be made
lighter than its contemporary counterparts and provides a level of
support commensurate with the degree of lateral motion, such as
over-pronation, in each stride of the user.
[0011] An article of footwear for controlling side-to-side motion
of a foot of a wearer according to the present invention comprises
an upper, a sole attached to the upper, and a bladder system
positioned within the sole of the footwear. The system includes at
least first and second bladder chambers positioned side-by-side of
one another and in fluid communication. A first valve is positioned
between the first bladder chamber and the second bladder chamber.
The first valve opens at a first predetermined level of pressure so
that a fluid contained within the first outer bladder chamber is
forced into the second bladder chamber when pressure within the
first bladder chamber reaches the predetermined level to increase
the pressure in the second bladder chamber and dynamically increase
the support provided by the second bladder chamber on the side it
is disposed.
[0012] In one preferred embodiment, the bladder system positioned
is within a heel region of the sole and the first bladder chamber
is disposed adjacent one side of the heel region, a third bladder
chamber is disposed adjacent the other side of the heel region and
the second bladder chamber is disposed between the first and third
bladder chambers in fluid communication therewith. A second valve
is positioned between the third bladder chamber and the second
bladder chamber. The second valve includes a second pressure
regulator that prevents fluid flow from the second bladder to the
third bladder chamber when the pressure in the second bladder
chamber is below a second predetermined pressure and allows fluid
flow from the second bladder chamber to the third bladder chamber
when the pressure in the second bladder chamber is at or above the
second predetermined pressure to increase the pressure in the third
bladder chamber and dynamically increase the support provided by
the third bladder chamber.
[0013] The present invention also includes an embodiment which
forces fluid from a central chamber into two outer chambers which
surround it to stabilize the foot and prevent medial and lateral
turning of the foot. In this embodiment, valves positioned within
conduits connecting the chambers allow the contained fluid to
immediately flow from the central chamber into the outer chambers
when pressure is applied to the central chamber. In this
embodiment, the direction of immediate fluid flow between the
central chamber and the first outer chamber is opposite to that
discussed above with respect to the other embodiments of the
present invention. In this embodiment, fluid immediately flows from
the central bladder to the two outer bladders when pressure is
applied. Fluid only flows from the first outer bladder to the
central bladder when it slowly bleeds back into it during the rest
phase of the running or walking stride.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is an exploded view of an article of footwear
incorporating a bladder system according to the present
invention;
[0015] FIG. 2A is a top view of the bladder system according to the
present invention having a single conduit housing between the
bladder chambers;
[0016] FIG. 2B is a perspective view of the bladder system
according to the present invention;
[0017] FIG. 3A is a top view of the bladder system according to the
present invention having a single housing with two conduit lines
extending between the bladder chambers;
[0018] FIG. 3B is a top view of the bladder system according to the
present invention having two conduit lines extending between the
bladder chambers;
[0019] FIG. 4 illustrates a typical path of the center of pressure
of the foot during a stride.
[0020] FIGS. 5A and 5B are cross-sectional views, with valves
removed, taken generally along lines 5A-5A and 5B-5B of FIGS. 3A
and 3B to illustrate different embodiments of the conduits
according to the present invention; and
[0021] FIG. 6 is a top view of another embodiment of the bladder
system according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] An article of athletic footwear 80 including a dynamic,
cushioning and motion control bladder system 10 according to the
present invention is shown in FIG. 1. Footwear 80 is comprised of
an upper 75 for covering a wearer's foot and a sole assembly 85.
Bladder system 10 is incorporated into a midsole layer 60. An
outsole layer 65, for engaging the ground, is secured to at least a
portion of midsole layer 60 to form sole assembly 85. A sock liner
70 is preferably placed in shoe upper 75. Depending upon the
midsole material and performance demands of the shoe, midsole layer
60 can also form part or all of the ground engaging surface so that
part or all of outsole layer 65 can be omitted. Bladder system 10
is located in the heel region 81 of footwear 80 and is incorporated
therein by any conventional technique such as foam encapsulation or
placement in a cut-out portion of a foam midsole. A suitable foam
encapsulation technique is disclosed in U.S. Pat. No. 4,219,945 to
Rudy, hereby incorporated by reference.
[0023] As illustrated in FIGS. 1 and 2A, bladder 12 includes outer,
lateral bladder chamber 12 and outer, medial bladder chamber 14. A
central bladder chamber 16 is positioned between and in fluid
communication with lateral and medial bladder chambers 12, 14 so
that bladders 12, 14, and 16 are arranged in a side-by-side
relationship. Lateral bladder chamber 12 and central bladder
chamber 16 are fluidly connected by a first conduit 20. A second
conduit 30 fluidly connects central bladder chamber 16 and medial
bladder chamber 14. In the embodiment illustrated in FIG. 2A,
chambers 12, 14, and 16 are fluidly connected by conduits 27.
[0024] Bladder chambers 12, 14, 16 and conduits 27 of FIG. 2A, or
conduits 20, 30 of FIGS. 3A and 3B, are formed of a thermoplastic
elastomeric barrier film, such as polyester polyurethane, polyether
polyurethane, such as a cast or extruded ester based polyurethane
film having a shore "A" hardness of 80-95, e.g., Tetra Plastics
TPW-250. Other suitable materials can be used such as those
disclosed in the `156 patent to Rudy. Among the numerous
thermoplastic urethanes which are particularly useful in forming
the film layers are urethanes such as Pellethane.TM., (a
trademarked product of the Dow Chemical Company of Midland, Mich.),
Elastollan.RTM. (a registered trademark of the BASF Corporation)
and ESTANE.RTM. (a registered trademark of the B.F. Goodrich Co.),
all of which are either ester or ether based and have proven to be
particularly useful. Thermoplastic urethanes based on polyesters,
polyethers, polycaprolactone and polycarbonate macrogels can also
be employed. Further suitable materials could include thermoplastic
films containing crystalline material, such as disclosed in U.S.
Pat. Nos. 4,936,029 and 5,042,176 to Rudy, which are incorporated
by reference; polyurethane including a polyester polyol, such as
disclosed in U.S. Pat. No. 6,013,340 to Bonk et al., which is
incorporated by reference; or multi-layer film formed of at least
one elastomeric thermoplastic material layer and a barrier material
layer formed of a copolymer of ethylene and vinyl alcohol, such as
disclosed in U.S. Pat. No. 5,952,065 to Mitchell et al., which is
incorporated by reference.
[0025] In a preferred embodiment of the present invention, bladder
chambers 12, 14, 16 and conduits 27, 20, 30 are integrally formed
of first and second sheets 40, 45 of elastomeric barrier film. In a
preferred embodiment of the present invention, bladders 12, 14, 16
are formed from generally transparent or translucent elastomeric
film to enable visibility through the bladders.
[0026] U.S. Pat. Nos. 4,183,156 (`156) and 4,219,945 (`945) to
Marion F. Rudy, the contents of which are hereby expressly
incorporated by reference, describe conventional welding techniques
which can be used to form the shapes of the bladder chambers 12,
14, 16 and conduits 20, 30. As disclosed in the `156 and `945
patents, sheet 40 and 45 can be welded to one another to define the
side walls of bladder chambers 12, 14, 16 and conduits 20, 30, as
well as interior welds (not shown in the drawings) within the
bladder chambers to maintain the bladder chambers in a generally
flat configuration.
[0027] In an alternative embodiment of the present invention
bladder chambers 12, 14, 16 and conduits 27, 20, 30 are formed
using conventional blow-molding techniques.
[0028] Bladder chambers 12, 14, 16 can be sealed to hold air or
other fluid at ambient pressure, or can be pressurized with an
appropriate fluid, for example, hexafluorethane, sulfur
hexafluoroide, nitrogen, air, or other gases such as those
disclosed in the aforementioned `156, `945, `029, or `176 patents
to Rudy, or the `065 patent to Mitchell et al. If pressurized, the
fluid or gas can be placed in the bladder through an inflation tube
(not shown) in a conventional manner by means of a needle or hollow
welding tool. After inflation, the bladder can be sealed at the
juncture of the bladder and inflation tube, or by the hollow
welding tool around the inflation point on the inflation tube.
[0029] FIG. 4 diagrammatically illustrates the path C.sub.p of the
center of pressure that a foot applies during typical running. As
seen therein, the center of pressure is initially applied at the
rear lateral edge of the foot at footstrike and moves diagonally
medially and forward. The medial motion of the center of pressure
is indicative of the natural pronation motion that the foot
undergoes immediately after footstrike. As the foot rolls forward
past the heel area, the pronation motion stops and the foot begins
a degree of supination motion in the opposite direction, i.e., from
the medial side to the lateral side.
[0030] As the center of pressure of the foot during a foot strike
moves medially across footwear 80, the pressure within the bladders
serially increases in the direction of the pronatory motion until
the medial chamber fills and stiffens the medial side of the
footwear to prevent excessive pronation, pronation beyond the point
which may be considered normal. A pressure gradient created in the
bladders during a foot strike, works in conjunction with the
pronatory motion of the foot to provide a dynamic level of motion
control commensurate with the degree of over-pronation.
[0031] In order to accomplish this dynamic control, as shown in
FIG. 3A, the pressure between the bladder chambers is controlled by
first and second flow valves 22, 32 located within first and second
conduits 20, 30, respectively. Valves 22, 32 include one-way valves
such as Vernay duck-bill valves or flapper valves. Valves 22, 32
can also include those discussed in U.S. Pat. No. 5,253,435 to
Auger et al. and U.S. Pat. No. 5,257,470 to Auger et al., both
hereby expressly incorporated by reference. One way or check valves
which limit fluid flow to only one direction and which are commonly
found in medical devices such as syringes and bulb pumps can also
be used. Conduit 20 and valve 22 freely deliver fluid in the
direction of the foot stride. Conduit 30 and valve 32 allow the
displaced fluid to slowly return to its original chamber. Valves
22, 32 are positioned at the forward end of bladder system 10 in
order to protect them from impact during a foot strike. Conduits
20, 30 can either be two separate members each having its own fluid
line as shown in FIG. 5B, or as shown in Figure 5A, one member
including two fluid lines.
[0032] As shown in FIG. 2A, a single, one-way valve 28 with a slow
return bleed can be substituted for valves 22 and 32. A single
valve 28 is located within a single conduit 27 extending between
two adjacent bladders. As with valves 22 and 32, each single valve
and each single conduit would be in fluid communication with the
forward end of a pair of adjacent bladders.
[0033] Valves 22 or single, one-way valve 28 can open
instantaneously when pressure rises within chamber 12 or 16 as a
result of a foot strike to allow fluid to pass into chamber 16 or
14, respectively. The time the regulating members within these
valves may remain open is between 1 and 5 milliseconds. One
preferred opening time is about 5 milliseconds. The regulating
members included, for example, the flaps on a flapper valve. These
valves may also be set to open for fluid flow in the direction of
the stride when the differential pressure between the bladders
reaches a predetermined level, for example, from any minimal
differential up to a 10 psi or greater differential. Other well
known pressures levels may also be used to trigger these valves.
The triggering pressure levels will vary depending upon the initial
cushioning pressures established in the bladders when they are
inflated. Setting the valves to open at a preset pressure
differential allows the bladder chambers and fluid flow to be
customized for severe pronators, larger runners or other users who
require specific or additional amounts of cushioning from a
bladder.
[0034] Prior to the heel of a user touching down, the predetermined
pressure in the bladder chambers preferably is equal:
P.sub.L=P.sub.C=P.sub.M. The range of pressure within the bladders
is preferably between 15 and 30 psi, with the preferred pressure
being 20 psi. Initial striking of the heel increases the pressure
P.sub.L within lateral bladder chamber 12 by deforming it. As the
foot strike continues and P.sub.L exceeds P.sub.C or the value for
which flow valve 22 is calibrated, valve 22 opens and fluid flows
through conduit 20 from lateral bladder chamber 12 to central
chamber 16 causing a pressure rise in central chamber 16 which
results in P.sub.C>P.sub.M. The pressure in central bladder
chamber 16 rises even further with the pronating motion because the
center-of-pressure moves medially to compress center bladder
chamber 16. As P.sub.C exceeds P.sub.M or the calibrated
differential limit for valve 22, between chambers 14 and 16, valve
22 opens and fluid from central bladder chamber 16 flows into
medial bladder chamber 14. The resulting increased pressure in
chamber 14 stiffens the medial side of heel region 81 to prevent
any further medial rolling of the foot i.e., limit pronation. The
increased pressure in medial bladder chamber 14 and stiffness of
the medial side of footwear 80 is dependent on the location and
force of the heel strike.
[0035] Bladder system 10 adapts to the amount of pronation during a
stride and stiffens the medial side of footwear 80 accordingly. The
serial increase of pressure from lateral bladder chamber 12 to
central bladder chamber 16 to medial bladder chamber 14 can be
referred to as pressure ramping. The degree of lateral to medial
motion and the location of the foot strike dictate the resulting
pressure in medial bladder chamber 14 and the resulting degree of
stiffness along the medial side of footwear 80. Pressure ramping
within system 10 is greatest when the user lands on the outer,
lateral edge of the footwear and the resulting foot motion is
largely in the lateral to medial direction. As previously
discussed, this type of pronatory foot motion initially applies
pressure to lateral bladder chamber 12, forcing its fluid into
central bladder chamber 16. As the foot stride continues, pressure
is applied to central bladder chamber 16 and a volume of fluid in
the central chamber is forced into medial bladder chamber 14,
thereby stiffening the medial side of footwear 80.
[0036] A user who does not over pronate generally will put less
initial pressure on the lateral side of the footwear and will force
less fluid, if any, into bladders 16 and 14 during a typical stride
when compared to an over pronator having the same striking force.
When a person who does not pronate uses footwear 80, the resulting
stiffness along the medial side differs from that discussed above,
assuming that both heel strikes are equal in force. For example, if
the heel strike of a user first compresses only central bladder
chamber 16 and the pressure in lateral chamber 12 remains below the
release limit of valve 22 in conduit 20, only fluid from central
bladder 16 will be available to transfer to medial bladder chamber
14. The resulting pressure in chamber 14 will therefore be only the
sum of the fluid pressure in chamber 14 and the amount transferred
from chamber 16. Flow valve 22 positioned between chambers 12 and
16 will prevent fluid from leaving lateral bladder chamber 12 until
the pressure in chamber 12 is greater than the pressure at which
valve 22 opens. Valve 32 maintains the pressure in chamber 12 at
its initial level, either by preventing fluid from flowing into
chamber 12 or by working in conjunction with valve 22 so that the
amount of fluid that enters chamber 12 through valve 32 will exit
through valve 22 into chamber 16. Hence, the pressure in medial
bladder 14 will not rise to the aggregate pressure achieved during
a more pronatory heel strike, i.e. one that begins by striking the
lateral portion of the footwear, because the available fluid in
bladder 16 will not be an aggregate of that from bladders 12, 14
and 16. Instead, it will only effectively include fluid from
chambers 14 and 16. Accordingly, the less a runner pronates, the
less the medial side of the shoe stiffens.
[0037] After the landing phase of running is over, equilibrium or
initial pressure between the bladders is re-established before the
next heel strike, either by a slow leak through the single two-way
valve 28, or through valve 32, which allows fluid to pass back into
the central and lateral bladder chambers. The typical recovery time
for returning these bladder chambers to rest pressure is between
0.1 and 2 seconds with the most preferred time being approximately
1 second. As discussed above, the recovery time will depend on the
amount of the fluid forced from each bladder chamber. The smaller
the chambers or the less fluid transferred, the shorter the
recovery time for the system.
[0038] As seen in FIG. 6, a cushioning system 100, can extend along
the length of footwear 80, i.e., with bladder chambers in the heel
region and the forefoot region. Cushioning system 100 includes a
bladder system 110. Bladder system 110 is constructed the same as
bladder system 10, with similar components in FIG. 6 labeled with
like numbers as bladder system 10, but in the 100 series of
numbers. Bladder chambers 112, 114 and 116 function in the same way
as bladder chambers 12, 14 and 16, respectively, to stiffen the
medial side of footwear 80 behind the instep in the heel region
135.
[0039] Cushioning system 100 also includes a bladder system 148
formed of bladder chambers 152 and 156 in the forefoot region 150
to provide lateral stability and increased performance when running
or jumping. Bladder chambers 152 and 156 extend along the forefoot
region of footwear 80 and are formed of the same material as
bladder chambers 12, 14 and 16. Bladder chambers 152 and 156
include a supportive, cushioning fluid which can be the same as
that used in the rear bladder chambers 112, 114 and 116 or a
different fluid, as discussed above. Bladder chambers 152 and 156
are in fluid communication with each other by a pair of conduits
158, each having a valve 160, 162. Valves 160, 162 are the same as
valves 122, 132, respectively, except that they may be designed to
function at different pressure levels or differentials than bladder
122, 132. In contrast to valve 122, discussed above, valve 160
allows fluid flow in the medial to lateral direction in order to
stiffen the lateral side of the forefoot of footwear 80 during a
foot stride. As the foot strike moves through the forefoot of
footwear 80, fluid flows out of medial chamber 152 into lateral
chamber 156 to stiffen the lateral side of footwear 80. The
pressure ramping in the forefoot follows the same principles as
that in the heel region, except that fluid flows in the opposite
direction. Pressure ramping in the forefoot stiffens the lateral
side of footwear 80 to support to the foot when cutting or turning
for increased performance, or to support the forefoot during the
propulsion phase of running or walking. As bladder chamber 156
fills with the fluid from chamber 152, it creates a wedge effect
within the forefoot that the user can push against when turning,
jumping, or running. Valve 162 allows for the return of fluid from
chamber 152 to chamber 156.
[0040] The pressure ramping system can be divided into any number
of chambers. Its effectiveness is determined by relative volumes,
locations and the number of chambers used to provide the pressure
ramping function. The number of chambers used is at least in part
based on the pressure in the plantar region as a function of time
for any give defined movement. The positioning and size of the
bladders depends on the type of footwear they are incorporated into
and the activity in which they will be used. For example, a system
located within an article of footwear intended to be used for
basketball may be have a different size, a different at rest
pressure and different valve triggering pressures than footwear
used for running. Also, the basketball footwear may incorporate the
forefoot portion of cushioning system 100 where as such a system
may not be needed within running footwear.
[0041] Numerous characteristics, advantages and embodiments of the
invention have been described in detail in the foregoing
description with reference to the accompanying drawings. However,
the disclosure is illustrative only and the invention is not
limited to the illustrated embodiments. Various changes and
modifications may be effected therein by one skilled in the art
without departing from the scope or spirit of the invention.
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