Note: Descriptions are shown in the official language in which they were submitted.
TITLE OF THE INVENTION
INSERT MEMBER FOR USE IN AN ATHLETIC SHOE
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to athletic shoes, and
more particularly to an apparatus and method for providing
increased durability and rebound in athletic shoes.
2. Description of Related Art
A recent surge to provide footwear which is both
comfortable and anatomically beneficial has resulted in a
plethora of ideas having varying degrees of effectiveness.
Most of these ideas are merely variations of ideas which have
been around for years. Historically, there have been a number
of attempts to increase the cushioning and control of an
athletic shoe by making modifications to the midsole, which is
that material which generally lies above the outsole. The
development of the midsole has led to shoes which take into
account the physiology of the foot. The numerous attempts to
provide superior cushioning in athletic shoes have led to
three broad categories of developments, two of which involve
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the midsole directly and the third involves modification of
the outsole.
The first broad category utilizes different materials and
configurations of the midsole to improve cushioning as we-ll as
provide effective foot control. For example, materials of
different hardnesses may be used to provide cushioning and
foot control, or a variety of devices may be encapsulated in a
midsole to increase cushioning. This type of shoe has the
disadvantage of a short life due to breakdown of the materials
used to form the midsole. Since many shoes use only ethyl
vinyl acetate (EVA) or polyurethane (PU) for cushioning, the
cells of these foams have a tendency to break down and thus
virtually eliminating the usefulness of the midsole. This in
turn can cause serious ;njuries.
The second category of device utilizes pneumatic devices
within the midsole. An example of this is taught in U.S.
Patent No. 545,705, issued to McDonald. The McDonald device
is an elastic air filled cushioning device which is incor-
porated into the heel of a shoe to provide cushioning. A
similar device is taught in U.S. Patent No. 1,498,838 to
Harrison Jr. which uses a number of tubes which lie within the
midsole. These tubes are inflated by a valve to maintain a
pressure above ambient. The tubes in the Harrison Jr. device
are made of a flexible inelastic material.
The disadvantages of encapsulating gas within the midsole
of a shoe are numerous. It is exceedingly difficult and
costly to encapsulate gas in a material. It is much easier,
for example, to cut a piece of conventional midsole material
such as ethyl vinyl acetate (EVA) to a desired specification
than to make a container which retains pressurized air or
other gas.
Material puncture is also a problem with pressurized gas
midsoles. Even careful material selection does not fully
alleviate the problem; the problem of puncture nevertheless
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exists and the solution to such a problem can add additional
manufacturing expense. Yet another serious drawback with this
type of shoe is that the pressure of the gas within the
encapsulating container is temperature dependent. As such,
the stiffness of the shoe varies as the shoe warms up.
Similarly, the shoe may respond differently in cold and warm
temperatures. Along these same lines5 the midsoles are
altitude dependent, which means that the shoe will have
different support characteristics depending on what altitude
it is used at.
Stability is another problem with shoes which encapsulate
gas within the midsole. In simple terms, encapsulated gas
midsoles are oftentimes too soft to give proper support.
In light of the multitude of problems associated with
gas-encapsulated midsoles, it is of great importance to find
alternatives which provide both adequate cushioning, stability
and support. Such alternatives must be economical and must
eliminate the problems of encapsulated tube technology without
sacrificing cushioning.
The third broad category of devices which are intended to
increase the cushioning of a shoe include outsole configura-
tions. An outsole is typically made of material such as
rubber, polyurethane (PU), thermoplastic rubber (e.g., EVA)
and the like. These materials are chosen for outsoles because
they are wear resistant. Typically, these materials have
fairly good memory characteristics. That is, if the outsole
material is deformed either by compression or bending forces,
it tends to return to its original shape. The best example of
a shoe which falls into this third broad category is U.S.
Patent No. 4,372,058 to Stubblefield, which teaches an outsole
in which the periphery of the heel of the outsole maintains
the remaining portion of the heel of the outsole in a spaced
apart relationship to the ground. This configuration is known
as a cantilever outsole. The cantilever configuration helps
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to redirect vertical forces while increasing energy return to
the midsole.
In the Stubblefield patent referred to above, an outsole
is provided which has a plurality of lugs or levers which
extend from the periphery of the bottom of the outsole. These
lugs are designed to redirect vertical forces on the outsole
so that the forces have at least a horizontal component
thereby reducing the stresses on a runner. The Stubblefield
patent provides a shoe which provides both cushioning and
stability.
Many of the devices described above are directed
primarily for cushioning of the heel portion of the midsole,
and are not entirely suitable or desirable for use in the
forefoot area of an athletic shoe. The present invention,
while usable in the heel area of an athletic shoe, has
particular advantages when used in the forefoot of an athletic
shoe and may in fact be utilized in conjunction with other
cushioning devices such as the cantilever orientation of the
above-referenced Stubblefield patent.
It is one object of the invention to provide an insert
for use in a midsole which provides cushioning and durability.
It is a further object of the invention to provide an
insert for use in an athletic shoe which is easily adaptable
for use in conjunction with other cushioning or rear foot
control devices.
It is yet a further object of the invention to provide an
insert which is easily incorporated into an athletic shoe
design.
SUMMARY OF THE INVENTION
In accordance with the purposes of the present invention
as embodied and described herein, the present invention is an
insert member for use in an athletic shoe. The insert member
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is made of a sheet of material which tends to return to its
original shape when bent and is substantially of uniform
thickness, having undulations which form a plurality of
parallel rows of peaks and valleys. Each row of peaks and
valleys is out of phase from an adjacent row of peaks and
valleys. In another aspect of the invention, each row of
"valleys" is 180 out of phase from the adjacent row of peaks
and valleys. In yet another aspect of the invention, the
sheet forming the insert member is made of a material such as
a thermoplastic polymer.
In yet another aspect of the invention, the insert member
comprises a plurality of substantially circular peaks and
valleys.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate the embodiments
of the present invention and, together with the description,
serve to explain the principles of the invention. In the
drawings:
Figure 1 is a bottom plan view of an athletic shoe which
has the invention incorporated therein;
Figure 2 is a left elevational view of the sole of an
athletic shoe which incorporates the invention;
Figure 3 is a cross-sectional view of Figure 1 cut along
line III-III;
Figure 4 is a cross-sectional view of Figure 1 cut along
line IV-IV;
Figure 5 is an exploded view of the components of one
embodiment of the invention; and
Figure 6 is a perspective view of a piece of material
from which the insert member of the invention is made.
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Figure 7 is a schematic view of one embodiment of the
invention showing the component elements superimposed.
DETAILED DESCRIPTION OF THE - --
PREFER~ED EMBODIMENTS OF THE INVENTION
Referring to the accompanying drawings, the present
invention is a device and system which improves an athletic
shoe by increasing its useful life and by improving the memory
characteristics thereof. To assist in the understanding of
the invention as it is incorporated into the sole of an
athletic shoe, the environment of the invention will first be
described. Figure 1 depicts a sole for an athletic shoe,
designated generally as lO, which includes a number of
component parts. In the embodiment of the invention shown in
Figures 1 and 2, the sole 10 includes a midsole 12, which,
like most athletic shoes, provides cushioning to the foot of a
wearer. The midsole 12 may be made of a material such as
ethyl vinyl acetate (EVAJ or polyurethane (PU) and may be
formed from materials of differing densities. For example, it
is sometimes desirable for the medial side of an athletic
shoe to be formed of a material having a higher density than
that of the lateral side of the shoe. This is done in order
to correct for certain biomechanical problems such as
pronation. Similarly, many other midsole configurations may
be used in conjunction with the invention.
As shown in Figure 2, also provided on the sole 10 is an
outsole 14 for contacting the ground. The outsole 14 may be
made of an abrasive resistant material such as rubber and
includes a heel portion 16 which has a central heel portion 18
of the outsole 14 which may be in spaced relationship with the
ground. This relationship of the central heel portion 18 and
peripheral portion of the outsole 14 is known generally as a
cantilever outsole, an outsole orientation which is described
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in detail in U.S. Patent No. 4,372,058 to Stubblefield. The
heel portion 16 has a plurality of lugs 20 around the
periphery thereof. These lugs 20 deflect outward upon the
application of pressure onto the sole 10 and help to reduce
shock to a wearer's foot upon impact with the ground.
In the sole shown in Figure 1 the weight of the outsole
14 has been reduced by providing a central opening 22 which
exposes midsole 12; wedge-shaped openings 24 which also help
to separate the lugs 20 thereby making lugs 20 move indepen-
dently of each other; and circular openings 26. In the
embodiment of the invention shown in Figures 1 and 2 a PU wrap
member 28 is provided which is attached adhesively to the
remaining portions of the outsole 14. The PU wrap member 28
has a lateral extension 30 which helps to provide stability to
the wearer's foot. Also provided on the PU wrap member 28 may
be a med;al extension 32 which is best seen in Figures 4 and
5. This m;dsole wrap helps provide stability by providing
surfaces which tend to prevent excessive pronation or
supination. If a conventional toe bumper 33 is used in
conjunction with the wrap member 28, the medial extension 32
and lateral extension 30 may wrap over the bumper 33. In the
embodiment of the invention shown in Figure 1, flexure grooves
34 are provided in the PU wrap member 28 in the metatarsal
area. These help to provide bending of the sole in the area
of the shoe where such bending is necessary in many athletic
sports.
In a preferred embodiment of the invention, midsole 12 is
provided with a heel component 36 which is made of a cushion-
ing material such as polyurethane (PU). Also provided in the
midsole 12 is a forefoot component 38. The forefoot component
38 may include a forefoot foam 40 such as Ethyl Vinyl Acetate
(EVA) or PU and may have a Shore C durometer hardness of
approximately 50 or 60. Forefoot foam 40 provides cushioning
to the forefoot of a wearer.
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The invention is the use of a insert member 42 in
conjunction with other component parts of an athletic shoe.
Referring to Figures 3-6, the insert member 42 used to
practice the invention is illustrated; Figures 3-4 show the
insert member 42 in cross-section in conjunction with other
components of an athletic shoe; Figure 5 illustrates an
exploded view of an athletic shoe embodying the invention; and
Figure 6 depicts a sheet of material from which an insert
mPmber 42 may be formed. Even though Figure 6 is a sheet of
material from which an insert member 42 is formed, it will be
described below as if it were an insert member 42 since the
only difference between the material shown in Figure 6 and an
insert member is that Figure 6 shows material of arbitrary
dimensions.
The geometric configuration of the insert member 42 gives
the midsole of an athletic shoe increase life because much of
the input energy is absorbed by the insert member rather than
by midsole material. In addition, the midsole may be lighter
because less midsole material is necessary. Further, the
midsole will return quickly to its relaxed configuration.
The insert member 42 is an undulating sheet of material
which has a uniform local thickness. This thickness (t) is
typically about 1/32" but may be tailored to a particular use.
Naturally, the thickness may be greater or less than 1/32"
when used in the forefoot. For example, if the invention were
to be used in a location other than the forefoot, it may need
to have a greater or lesser thickness. Similarly, a non-
uniform thickness may be used if different responses are
desired for different portions of the insert member. The
overall shape of the insert member 42 may, but need not, be
substantially rectangular in shape. In the embodiment of the
invention shown in Figure 5, insert member 42 approximates a
rectangle with two rounded and two hard corners. The precise
overall shape of insert member 42 is not critical and it
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should be understood that the shape of insert member 42 can be
tailored as desired. The material forming the insert member
has undulations which form a plurality of rows of substan-
tially circular peaks and valleys. A first row, designated as
44 in Figure 6, has a cross-section which is substantially
sinusoidal. In this configuration, the magnitude of the
amplitude of the peaks 46 and valleys 48 is the same and the
wavelength of the sinusoidal cross-section is constant. These
two geometric characteristics (constant amplitude and constant
wavelength) are not critical to the invention and it is
anticipated that a number of geometries could be used to
practice the invention. Again, referring to Figure 6, the
spacing between peaks 46 in row 44 is approximately 11/16 inch
and the magnitude of the amplitude of each peak and valley is
approximately 3/32 inch. In other words the thickness of the
insert member measured from the maximum peak to the minimum
valley is 3/16 inch. Naturally, these values can vary
depending on whether the insert 42 is to be used in, for
example, the heel of an athletic shoe instead of in the
forefoot.
A second row, designated as 50 in Figure 6, is positioned
so that the first row 44 and the second row 50 are juxtaposed
at a distance of one-half the distance between adjacent peaks
46 of the first row 44. The second row 50 similarly has peaks
52 and valleys 54. In cross-section, the second row is
identical to the first row 44 except that the second row 50 is
180 out of phase from the first row 44. Every second row
forming the insert member is in phase and all rows are 180
out of phase with its adjacent row.
Another way of describing the geometry of the insert
member is to say that it is formed from a continuous quincunx
arrangement. That is, the circular peaks of the insert member
are arranged in a quincunx, the four sides of which are the
sides of the adjacent quincunx arrangements. There are
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circular valleys formed between each of the circular peaks
forming the corners of each quincunx arrangement.
Figures 3 and 5. A frame is provided for the insert
member 42 by the forefoot foam 40. In one embodiment of the
invention, a cutout is provided in which the insert 42 is
positioned. The insert member 42 can be made of many
different materials as long as the material or combination of
materials forming the insert 42 has good memory characteris-
tics, is durable, and provides cushioning. By good memory
characteristics it is meant that the material forming the
insert, when deflected tends to return to its original
configuration. This return to its original configuration
should take place in a time frame which is less than the
average period between deflections. For example, in a running
shoe, the insert member 42 will deflect each time the foot
contacts the ground in the region of the insert member 42.
Therefore, it is important that when pressure on the insert
member 42 is no longer exerted, the insert return to its
original configuration prior to the next time the foot
contacts the ground in the region of the insert member 42.
In addition to having good memory characteristics the
insert member 42 must be durable. It must be able to
constantly withstand the cycling from a mode in which a force
is exerted on the insert to a mode in which the insert is
relaxed. In addition, the insert 42 must be made of a
material which resists cracking due to either impact forces or
due to fatigue; and must not have varying properties as a
function of change of ambient conditions such as temperature
and pressure. One commercially available material which had
these characteristics is Hytrel which is the registered
trademark of a material which is manufactured by E.I. DuPont
de Nemours. Hytrel is a chemically stable, semi-crystalline,
fully polymerized, high molecular weight, thermoplastic poly-
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ester elastomer having alternate amorphous and crystalline
chains.
Hytrel is selected as a material because of its ability
to store energy upon impact and return that energy to the
source. Hytrel 4056, having a Shore 0 durometer hardness of
40; Hytrel 4074, also having a Shore C durometer hardness of
40; and Hytrel 8236, having a Shore C durometer hardness of
82, are three materials (all DuPont) which may be used to
practice the invention. It should be noted however that many
other materials may be used to practice the invention.
The insert member 42 is generally positioned in the
forefoot of an athletic shoe to improve the cushioning
characteristics of the midsole by providing good memory
characteristics and by returning energy to the midsole. The
insert member 42, when used in conjunction with forefoot foam
40, is generally positioned within forefoot cavity 56 (Figure
5). This forefoot cavity 56 may extend completely through
the forefoot foam 40 or may only be an indentation in the
forefoot foam 40. A cover 57 may be placed above insert 42.
Typically, the insert member 42 is cemented in place with a
thin film of cement which attaches the crests of the peaks to
the other midsole components such as the forefoot foam 40 (see
point A, Figure 3) or the outsole 14 (see point B, Figure 3).
Figure 5 is an exploded view of an athletic shoe
embodying the present invention. The sole 10 has an outsole
14. Above outsole 14 is a midsole having a heel component 36
and a forefoot component 38. The forefoot component is made
up of a forefoot foam 40 having a forefoot cavity 56 in which
an insert member 42 as previously described is inserted.
Figure 7 shows a superimposition of some of the component
parts of an athletic shoe embodying ihe invention. Line 62
shows the interface between heel component 36 and forefoot
component 38 (in a preferred embodiment, the interface between
the PU and EVA which makes up the midsole); lines 64a and 64b
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show the outline of the PU wrap member 28; line 66 is the
perimeter of insert member 42; and line 68 shows the rearmost
boundary of cover 57.
In another embodiment of the invention, the insert member
may be completely encapsulated within the midsole so that
there are no air spaces between the insert and the midsole.
In yet another embodiment of the invention, the insert member
may be partially encapsulated. For example, one side of the
insert member may have midsole material filling the valleys in
that side.
The foregoing description of the preferred embodiments of
the invention has been presented for purposes of illustration
and description. It is not intended to be exhaustive or to
limit it to the precise form disclosed. Obviously, many
i5 modifications and variations may be made in light of the above
teachings. For example, although the drawings depict
undulations which in cross-section are sinusoidal in shape,
configuratîons in which the undulations have varying periods
or amplitudes are also possible. Also, the positioning of the
insert member need not necessarily be placed in the forefoot
of an athletic shoe.
The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
application to thereby enable others skilled in the art to
best utilize the invention in various embodiments and with
various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention
be defined by the claims appended hereto.
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