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Description  |
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This invention relates to internally pressurizable multi-layered envelopes,
and more particularly, to a multi-layered envelope which is particularly
adapted for use as an insole in a shoe.
Previously considerable difficulty had been experienced in providing
internally pressurizable multi-layered envelopes wherein the envelope is
thin and of a substantially uniform thickness with the capacity of being
pressurized to a level such that more than 40% of the energy of impact on
the structure is returned in a beneficial, efficient and comfortable
manner rather than being absorbed and dissipated in heat. Previous
difficulty had been experienced in producing lightweight structures which
possess a high degree of springiness. Previously considerable difficulty
had been experienced in preventing aneurysms from occurring in lightweight
pressurized multi-layer envelopes. Previously substantial difficulty had
been encountered in providing large flat chambers which are substantially
uniformly compressible over the load bearing areas while maintaining a
substantially uniform thickness and avoiding the propensity for the
formation of aneurysms.
These and other difficulties of the prior art have been overcome according
to the present invention. The present invention provides a structure which
comprises a hermetically sealed outer covering barrier layer which is
bonded, at least partially through mechanical means, substantially all
over the outer sides of a double walled fabric structure. The double
walled fabric structure comprises first and second fabric layers which are
normally spaced from one another for predetermined distance. Filaments,
preferably in the form of yarn, extend internally between the proximal
surfaces of the respective fabric layers. The transversely extending
restraining means are anchored to the respective fabric layers. The
restraining means function to maintain the general plainer form of the
structure and the mechanical bonding of the outer covering to the distal
sides of the respective fabric layer prevents the outer covering from
peeling away from the distal surfaces and forming an aneurysm. The
transversely extending yarns or filaments which function as the preferred
restraining means are present in quantities sufficient to hold the
structure in the desired plainer form without offering substantial
resistance to the compression of the two-fabric layer towards one another.
That is, the restraining means have very little compressive strength and
very substantial tensile strength. The region between the proximal
surfaces of the fabric layers is of sufficient openness to allow movement
of the pressurizing gas throughout the pressurized chamber.
The hermetically sealed outer barrier layers is composed of an elastic
semi-permeable material which is substantially impervious to those gases
which are essentially inert and that have very large molecular sizes and
is slightly permeable to oxygen. With this material, an inward diffusion
of oxygen occurs from the ambient air which, by reason of partial
pressures, tends to increase the total pressure within the enclosure. This
is described in some detail in for example, Rudy, U.S. Pat. No. 4,340,626
patented Jul. 20, 1982; Rudy et al, U.S. Pat. No. 4,183,156 patented Jul.
15, 1980; Rudy et al, U.S. Pat. No. 4,271,606 patented Jun. 9, 1981; and
Rudy et al, U.S. Pat. No. 4,219,945 patented Sept. 2, 1980. Attention is
respectfully invited to these patents, which are hereby incorporated
herein by reference, for a description as to the barrier film, the
pressuring gas and the physical phenomenon which are involved in the
diffusion of gas through the semi-permeable barrier layer.
The structures according to the present invention are particularly suited
for use where they are required to cushion an impact and then return as
much as possible of the energy of that impact. The unique ability of the
device to return a substantial part of the otherwise wasted energy which
is cushioned at impact, is greatly improved by designing the structure to
have the absolute minimum mass, and the constraining walls to have a low
hysterisis loss when flexed. Gas pressurized to at least 2 and preferably
more than 15 psi, functions well to provide excellent cushioning and then
returns the stored energy in a comfortable, resilient, life-like manner.
When the structure of the present invention is pressurized to a level in
excess of 40 to 50 psi the structures gives back as much as 90% of the
energy of an impact. Thus, if a weight such as a steel ball is dropped on
a structure of the present invention which is pressurized to a level of
approximately 55 psi the ball will rebound to a height which is
approximately 90% of the distance from which it was dropped.
The present invention is uniquely suited to footwear and other similar
applications where high style and/or maximum cushion comfort, support and
protection must be achieved in the very minimum thickness and space.
Thicker devices as disclosed in Rudy U.S. Pat. No. 4,183,156, were, in
large measure, poorly suited for this type of application. The hills can
valleys of the earlier product, coupled with the need for some type of
moderator to provide a smooth, comfortable support surface created a
product that was too thick and clumsy for this very difficult type of
application.
The flat plainer load bearing surfaces of the present invention achieve a
completely new and unique degree of 100% "floating on air" cushioned,
resilient support, comfort and protection never before possible. This
invention eliminates the need for foam encapsulation. However, in certain
circumstances it may be desirable to use foam in order to achieve the
optimum benefits of both techniques.
In the present invention the formation of one or more aneurysms constitutes
failure. Aneurysms can develop when there is delamination of the barrier
material from the distal surfaces of the double-walled fabric, or by
cutting; abrasion or tensile failure of the drop threads. The present
invention solves these problems for the life of the product.
The use of drop threads in a double walled structure acting in tension to
constrain and shape the barrier surfaces has been proposed previously. An
example of the aneurysm which can develop when the drop threads are of
insufficient strength or are deliberately severed, is illustrated for
example in Cross, U.S. Pat. No. 3,205,106 patented Sept. 7, 1965. The use
of drop threads and filaments as cushioning or stiffening members in
double walled structures has been proposed, for example, by Tungseth, U.S.
Pat. No. 3,616,126 patented Oct. 26, 1971 and Giese et al, U.S. Pat. No.
4,005,532 patented Feb. 1, 1977. These prior structures are comprised of a
single heavy (i.e., large 0.003 to 0.025 inch diameter) plastic
mono-filament thread woven into s stiff three-dimensional, compression
load supportive mat. The Tungseth '126 patent describes a product of this
type that relies completely on the buckling characteristics of select
diameter plastic mono-filaments in the woven structure in order to absorb
compression shock loads. No support is provided here by the ambient
atmosphere surrounding said structure.
The Giese patent '532 likewise is a stiff compression load supporting mat
woven from a 0.010" diameter mono-filament thread in order to form a
thermal insulation insert for articles of footwear; wherein it is stated
"The separating material" (i.e., threads) "is of such a strength as to
prevent deformation of the mesh-like fabrics towards each other when
subjected to the weight of the wearer of the shoes." The embodiment calls
for the mat to be covered with a barrier material and closed to form a
hermetically sealed chamber. In one form air may be left within the
chamber, while in other forms, the air may be evacuated from the chamber
or, replaced with a gas such as CO2 in order to achieve a thermal
coefficient of heat transfer that is lower than the ambient air. These
structures are very poor shock absorbing devices returning little if any
of the impact energy to the user and throwing said energy away as internal
frictional heat.
In the present invention the drop threads consist of many separate
filaments (not a single mono-filament as in the above inventions) each
having a high tensile strength and being of a very small cross-section
diameter in comparison with the prior art such that they are completely
incapable of supporting any significant compression load by themselves.
Thus the load supporting mechanism of the present invention is completely
different from and greatly superior in load carrying capability, shock
absorption, fatigue life, resiliency and beneficial life-like energy
storage and return characteristics that are not even remotely possible
with the above stated prior art.
Various gas containing foam materials have previously been sealed in
flexible air-tight compartments, see for example, Rosenberg, U.S. Pat. No.
4,590,689 patented May 27, 1986 and Striegel, U.S. Pat. No. 3,914,881
patented Oct. 28, 1975. Foam products of this type pressurized even with
"supergas" (Rudy U.S. Pat. No. 4,183,156 have not been successful because
of several problems; (1) the tensile strength of even the best foam
materials is not sufficiently strong and reliable to support the necessary
inflation pressures over the life of a product to be used in footwear; (2)
under heavy cyclic compression typical of the foot strike when walking or
running, the walls individual cells constituting the foam structure abrade
and tear as they move against one another and thus rapidly fail, resulting
in an aneurysm and subsequent loss of pressure.
It is known that the highest possible quality foam, when used as a
cushioning load supportive, compression member (i.e., mid-sole or insole)
in athletic footwear such as running shoes, loses a substantial percent of
its original cushioning properties within just a few miles of running, and
at about 150 miles approximately 75% of the initial cushioning properties
have been lost. The loss of cushioning is the result of internal break
down of the cell walls of the foam. In this usage, the footwear does not
become unusable because of said breakdown of the foam. The user simply is
exposed to much greater shock forces. However, with a pressurized
structure, breakdown of the foam structure results in formation of a high
aneurysm or bump under the foot. Even the smallest failure of this type
(i.e., 1/4 to 1/2" diameter) makes the product painful to use and
therefore unusable.
The relatively high pressures which are required to provide the desired
degree of springiness present very substantial problems with the peeling
of the outer barrier film away from the distal surfaces of the
double-walled fabric. It has been found that a fiber interface
reinforcement and mechanical interlocking of the barrier film and the
distal surfaces of the double-walled fabric is necessary to provide the
required to provide the necessary peel strength at this location. It has
been found that if the yarn which is used to form the double-walled fabric
is in some way texturized or flannellized or made from at least 20%
discontinuous filaments, so that there are numerous loops tendrils and
projections of filamentary material projecting slightly from the distal
surfaces of the fabric layers, that greatly improved the mechanical
bonding that can be achieved. The texturizing can be provided for example,
by abrading the distal surfaces of the double-walled fabric, by crimping
the individual filaments which go to make up the yarn, by using a false
twist in manufacturing the yarn, and the like. It is also desirable to use
a yarn wherein the filaments are "dull" or "semi-bright". In a preferred
embodiment the yarn from which the double-walled fabric is constructed is
treated so that in the final product, the distal sides of the respective
fabric layers present a great many tiny loops of outwardly projecting
filamentary material. The individual filaments may be continuous in nature
in the preferred embodiment so that the loops are anchored at both ends.
Crimped filaments when combined into a yarn are also suitable for use
according to the present invention.
The cloth or fabric structure which forms the tensile load bearing portion
of the envelope may be constructed according to any known procedures
including knitting and weaving. The double needle bar Raschel knit
material is particularly satisfactory for use according to the present
invention. Also material which is woven with a locking stitch is suitable
for use.
The yarn from which the drop thread linked double-walled fabrics are
constructed must be made of a high tensile strength material which is
stable under the intended conditions of usage. A wide variety of synthetic
yarn materials, may be used, however, filaments composed of nylon 66 have
been found to have superior strength and durability characteristics.
Where the mechanical coupling or bonding sites on the distal sides of the
fabric layers are provided by the use of discontinuous filaments in the
yarn, those discontinuous filaments should preferably comprise at least
approximately 20% of the filaments in the yarn.
In general the filaments utilized in the yarn according to the present
invention have a denier per filament of from about 1-20 with a preferred
range of from about 2-5. The individual filaments in general exhibit
tensile strengths of from 2-10 grams per denier with a preferred range of
from approximately 4-6 grams per denier. In general the number of
filaments per yarn ranges from about 1-100 with the preferred range being
from about 40-60. In general there are from approximately 1-8 yarns per
tuft or strand with the preferred range being from about 3-5 yarns per
strand. The preferred fabric is knitted with from about 200-1000 strands
or tufts pounds per square inch of fabric and preferably from about
400-500 strands per square inch. The bulk density of the fabric is
therefore in general in the range of from about 20,000-300,000 fibers per
square inch - denier.
It has been found that if the filaments are heat set prior to being woven
into the double-walled fabric the drop threads will tend to stand up so
that a given point on one fabric layer will tend to remain axially aligned
with the same given point on the opposed fabric layer. This is
advantageous in construction. It is undesirable to have the individual
fabric layers move, slip or lie-down in their own plaines relative to each
other.
The construction of the internally pressurizable multi-layer envelope
according to the present invention begins with the selection of an
appropriate double-walled fabric which incorporates drop threads extending
between the proximal surfaces of the respective fabric layers. The distal
sides of the respective fabric layers are impregnated with a carefully
metered quantity of bonding agent. In general the bonding agent is a
material which will melt and in flow when heated so as to melt and bond
with the outer semi-permeable barrier layer. The bonding or coupling agent
may be applied using conventional application procedures including, for
example, extrusion procedures, or calendaring and doctor blading. In
general, however, the preferred method application is to provide the
bonding agent in a sheet form and to melt and press the sheet into the
distal sides of the fabric layers. The application of the bonding agent in
a viscous molten sheet form by extrusion permits a very accurate control
of the amount of bonding agent which is applied to any particular
location. Accurate control is essential so as to avoid driving the bonding
agent all the way through the fabric which would impair the flexibility of
the drop threads or at worst, bond the opposite fabric layers together so
the product could not be inflated and pressurized. In general the bonding
agent should penetrate the fabric layer sufficient to securely bond to it,
however not deep enough to pass entirely therethrough. In the preferred
embodiment the quantity of bonding agent available to penetrate the fabric
is controlled by controlling the thickness of the sheet of bonding agent
which is applied to the fabric. Also, the heat is regulated so that hot
spots do not occur and the depth of penetration does not vary from one
area of the fabric to another due to changes in the fluidity of the
bonding agent. A superior and preferred procedure presently used repeats
this bonding agent application step.
The bonding agent impregnated fabric is then placed between two layers of
semi-permeable membrane, and the semi-permeable membrane is bonded to the
bonding agent and fabric layers, preferably by radio frequency heating.
The temperature of the dies which are used to effect these laminations are
preferably adjusted so that melting occurs at the interface between the
bonding agent and the outer barrier membranes and not otherwise. The radio
frequency power setting, pre-seal, seal, and cooling cycle and die
temperatures (heat sinks) are preferably selected so as to minimize the
amount of heating to the fabric and the barrier film. The part which
results from the bonding of the semi-permeable membrane to the distal
sides of the fabric is uniformly attached to a multiplicity of tiny
connection sites so that the attachment of the semi-permeable membrane to
the fabric is substantially continuous throughout the structure and
completely free from pin-holes. The peel strength exhibited by this
structure must be very high; i.e., in excess of 20 pounds per linear inch.
In the preferred method, the viscous or molten coupling or bonding material
is extruded in sheet form onto the distal surfaces of the double-walled
fabric or cloth, followed by squeeze rollers heated to the correct
temperature so that they simultaneously chill and also drive the molten
material into the distal fabric layers so as to penetrate and bond to the
fabric, however only penetrating said fabric to a carefully controlled
depth not to exceed the thickness of the fabric layers.
The perimeter of the structure is sealed by bringing the sheets of
semi-permeable membrane together at the edge of the double-walled fabric
and sealing the edges together around the entire perimeter. Sealing is
conveniently accomplished by conventional techniques such as radio
frequency welding, thermal impulse sealing, cementing, ultrasonic welding,
magnetic particle sealing and the like. As a final step, the chamber,
which is now defined between the walls of the double-walled fabric, is
pressurized with a suitable large molecule gas. The gas is conveniently
injected through the use of a needle with the injection port being sealed
after the pressurization is completed is complete. The physical phenomenon
which occur with inflation and diffusion are described for example in Rudy
U.S. Pat. No. 4,340,626 patented Jul. 20, 1982 and attention is
respectfully invited to this patent disclosure.
The pressurized structures according to the present invention enjoy wide
utility in all sorts and varieties of footwear including boots, athletic
shoes, everyday casual and leisure shoes, dress shoes, prosthetic shoes as
well as in other devices including prosthetic devices, helmets and
protective gear for recreational military industrial and aerospace
applications, equipment controls such as bicycles handle grips, jack
hammer handles, chain saws, hammers, bats, saddles and seats for bicycles,
motorcycle and equestrian purposes, playing surfaces, athletic mats,
flooring, work station pads, and the like.
BRIEF DESCRIPTION OF THE DRAWING
Referring particularly to the drawings for the purpose of illustration only
and not limitation there is illustrated:
FIG. 1, a plan view of an insole according to the present invention;
FIG. 2, is an exploded cross-sectional view taken along line 2--2 in FIG.
1;
FIG. 3, a view similar to FIG. 2 showing the device in the assembled
configuration.
Referring particularly to the drawings there is illustrated generally at 10
an insole according to the present invention. Insole 10 is composed of a
composite structure in which an outer semi-permeable barrier layer 12
defines an pressure tight sealed chamber in which a tensile load-bearing
structure which comprises a double-walled thread linked fabric indicated
generally at 14 is positioned. The double-walled thread linked fabric
structure 14 is composed of a first fabric layer 16, a second fabric layer
18 and drop threads 20. As indicated particularly in FIG. 2 the distal
sides of fabric layers 16 and 18 are impregnated with a bonding agent to a
depth which is slightly less than the total thickness of the fabric
layers.
The distal sides 22 and 24, respectively, of the fabric layers are
populated with a multiplicity of tiny mechanical attachment sites or
points FIGS. 2, 29 and 30. These are shown as extending outwardly from the
distal surfaces in FIG. 2 for the purpose of illustration, it being
understood that they are in fact bound with the bonding agent. These
attachment sites are provided by the filaments from which the fabric is
constructed.
In the completed structure indicated for example in FIG. 3 the portion of
the outer semi-permeable barrier layer 12 which is rendered molten for
purposes of bonding with the bonding agent is indicated by molten zone 26.
The application of heat to the envelope during manufacturing is preferably
controlled so that molten zone 26 and the corresponding region of the
bonding agent within the respective fabric layers are the only parts of
the structure which become molten. The barrier layer 12 is hermetically
sealed by means of a weld 28 which extends entirely around the periphery
of the structure to achieve a pressure tight enclosure. The weld 28 is
made as close as possible to the edge of the double-walled fabric 14
without trapping any of that fabric material in the weld itself. Any
filaments trapped in the weld will probably cause the device to leak.
If desired, the distal sides of the fabric may be treated with chemical
coupling agents such as silanes (DOW X16106) to improve adhesion. It has
been found, however, that chemical coupling agents are not adequate alone
to provide the necessary peel strength. A fiber interface reinforcement
and mechanical interlock with the substance of the fabric is necessary. In
general a peel strength of 20 pounds per linear inch is the absolute
minimum necessary to accomplish the desired function. Peel strengths in
excess of 23 pounds per linear inch are preferred. At peel strengths in
excess of approximately 35 pounds per linear inch the tensile fibers or
drop threads fail first.
In a less preferred procedure the distal sides of the fabric 14 are flame
treated to oxidize the surface so as to oxidize the surface and provide a
multiplicity of mechanical attachment sites. It has been found, however,
that flame treatment reduces the strength of the fabric beyond a
satisfactory level.
Structures according to the present invention having thicknesses in the
range of 0.100" to 0.500" have been successfully inflated to over 180 psi
and have retained those pressures for several weeks without failure.
In general the preferred barrier film material is polyurethane as described
in the above identified prior Rudy U.S. patents the other elastomeric
barrier films as identified in said patent are also applicable. The
bonding agent is conveniently the same urethane material which is used as
the outer barrier layer. The coupling agent is preferably provided in the
form of a freshly extruded sheet which is immediately hot pressed in the
molten state, into the distal sides of the fabric. The fabric is composed
of heat set filaments so that the fabric layers remain in accurate
registry with respect to one another during handling and formation. Very
satisfactory results have been achieved using filaments having a denier of
3, a tensile strength of 3 grams per denier, approximately 40 filaments
per yarn and 3 yarns per tuft or strand with the fabric being composed of
approximately 440 strands or tufts per square inch. It has been found that
using less than 3 yarns per tuft tends to impair the wear-life of the
resulting structure. When radio frequency heating has been utilized to
bond the semi-permeable layer to the distal sides of the double-walled
fabric it has been found that heating the dies to between approximately
100 and 150 degrees Fahrenheit and utilizing a radio frequency of 27.12
megahertz, achieves the desired bonding without impairing the rest of the
structure. Using filaments composed of nylon 66 material have been found
to produce the preferred tensile strength, wear and durability
characteristics. Very satisfactory results have been achieved using a
continuous filament yarn which has been texturized with a false twist.
What has been described are preferred embodiments and modifications in
which changes may be made without departing from the spirit and scope of
the accompanying claims.
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