Note: Descriptions are shown in the official language in which they were submitted.
1 33631 6
IMPACT ABSORBING COMPOSITES AND THEIR PRODUCTION
Descriction
Technical Field
This invention relates to improved impact absorbing
compressible composites. These composites can be shaped into smooth
compound curves and find application wherever high efficiency impact
10 absorption is called for such as in athletic wear, in seating systems, in
vehicle interior padding materials and the like. More particularly, the
present invention relates to improvements in the production of these
composites.
15 Background Art
There is a well recognized need for high performance
materials for spreading or absorbing impacts. In recent years, athletes,
athletic equipment manufacturers and sports medicine professionals have
recognized the need for improved impact absorbing materials in athletic
20 equipment. These materials find application as heel pads and foot sole
pads in shoes to absorb the shock of foot strike and as cushioning points
under football or hockey pads such as shoulder pads, thigh pads, hip
pads and the
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like to name but a few typical applications. Similar
needs may be found in seating systems and in vehicle
interiors, to name but a few representative fields in
which impact absorption is a major interest.
One common approach to impact absorption in the
past has involved using felts or blocks of a soft padding
material. Padding materials known heretofore include cot-
ton padding, horsehair padding, foam rubber, foamed
plastics, sponge rubber and the like. In these designs,
the inherent resilience of the padding material is
employed to absorb and disperse the applied impact. These
designs have the disadvantage that they often "bottom out"
or fully compress on severe impacts of the type regularly
encountered during use such as in athletic equipment or in
lS vehicle interiors and thus provide minimal protection.
When made thicker to avoid this problem, they become
cumbersome and can interfere with the design of the
article being padded, and in the case of athletic equip-
ment can interfere with the wearer's freedom and perform-
ance.
Impact absorbers have also been proposed whichemploy fluid-filled bladders such as cushioning air sacks
These devices rely upon the compressibility of the
enclosed fluid to provide the desired shock-absorbing. In
some embodiments of these devices, the fluid is fully
enclosed and can not escape. In others, the fluid is
gradually and controllably forced out of the bladder dur-
ing the impact with the rate of release being selected to
prevent exhaustion of the fluid during the impact event.
While effective as shock-absorbers, these devices can have
the failing of ballooning or otherwise expanding in one
region when another region is being compressed. This can
lead to discomfort or at minimum give an unnatural or
unstable feel to the user. In the case of footwear, this
problem can lead to an unstable foot plant with increased
3 1 33631 6
opportunity for injury. Another issue with this~type of
pad has related to problems in forming shapes based on
compound curve and to retaining structural integrity with
the above-described ballooning.
Representative patents in the field of shock-
absorbing or impact absorbing devices include United
States Patent No. 4,513,449, SHOCK ABSORBING ATHLETIC
EQUIPMENT; United States Patent No. 4,370,754, VARIABLE
PRESSURE PAD; United States Patent No. 4,453,271, PROTEC-
TIVE GARMENT; United States Patent No. 4,217,705, SELF-
CONTAINED FLUID PRESSURE FOOT SUPPORT DEVICE, all issued
to Donzis, United States Patent No. 4,446,634 for FOOTWEAR
HAVING IMPROVED SHOCK ABSORPTION; United States Patent No.
4,397,104 for INFLATABLE SOLE-SHOE; United States Patent
15 No. 2,863,230 for CUSHIONED SOLE AND HEEL FOR SHOES;
United States Patent No. 4,229,889 for PRESSURIZED POROUS
MATERIAL CUSHION SHOE BASE; United States Patent No.
4,637,716 for METHOD FOR MAKING ELASTOMERIC SHOE SOLES;
United States Patent No. 4,635,384 for FOOTWEAR SOLE;
20 United States Patent No. 4,610,099 for SHOCK-ABSORBING
SHOE CONSTRUCTION; and United States Patent No. 4,571,853
for SHOE INSERT.
It is an object of the present invention to
provide an improved impact absorbing composite. It is
25 desired that this composite provide superior shock-absorb-
ing performance and also be capable of being formed into
complex compound curve shapes, be durable and hygienic.
1 3363 1 6
5 Summary of the Invention
According to a first aspect of the invention there is
provided a method for producing a shock-absorbing composite for
absorbing and dispersing impacting forces comprising forming a
10 flexible foam core having an outer surface shaped and sized as
required for said shock-absorbing composite, applying to the outer
surface of said core a layer of prepolymer solution/suspension,
curing the layer of prepolymer solution/suspension to yield a
flexible plastic layer thereby forming a flexible enclosure surround
15 and adhered on all sides to said core, said flexible enclosure
being capable of having its internal pressure changed.
According to a second aspect of the invention there is
provided a method of producing a shock absorbing composite and
dispersing impacting forces comprising forming a plastic enclosure
20 having a shock absorbing configuration and defining an internal
cavity therein having an internal surface, placing with said
enclosure a foam core filling said cavity and having an external
surface, retaining said core within said cavity such that the
- 5 _ l 3363 1 6
5 composite is generally impermeable to air but includes means for
adding and removing pressurizing fluid from the internal cavity and
such that the enclosure and the core are prestressed by one
another, the core adhered on substantially all of its external
surface with a heat activated adhesive to the internal surface of
10 the enclosure, and pressurizing the core through said means for
adding and removing pressurizing fluid from the internal cavity to
a value between 0 and 20 psig effective to provide efficient
impact absorption.
According to a third aspect of the invention there is
15 provided a method for producing a shock absorbing composite for
absorbing and dispersing impacting forces comprising forming a
flexible plastic enclosure which is impermeable to air having a
shock absorbing configuration and defining an internal cavity
therein having an internal surface, placing within said enclosure a
20 preshaped foam core partially filling said cavity and having an
external surface, forming in situ between said enclosure and said
preshaped foam core a further foam core filling said cavity and
joining substantially all of the core's external surface to the
internal surface of the enclosure, etaining said cores within said
25 cavity such that the composite is generally impermeable to air and
capable of having its internal pressure changed and the enclosure
and the core are prestressed by one another, and pressurizing the
core to a value between 0 and 20 psig effective to provide
- 6 - 1336316
5 efficient impact absorption.
According to a fourth aspect of the invention t here is
provide a method for producing a shock absorbing composite for
absorbing and dispersing impacting forces comprising forming a
flexible form core having an outer surface shaped and sized as
10 required for said shock absorbing composite, applying to the outer
surface of said core a flexible plastic layer thereby forming a
flexible enclosure surrounding and adhered on all sides to said
core, said flexible enclosure and said core being prestressed
by one another, said enclosure being generally impermeable
15 to air and capable of having it internal pressure changed,
and pressurizing the core to a value between 0 and 20
psig effective to provide efficient impact absorption.
Brief Description of the Drawings
The present invention will be described herein with
reference being made to the accompanying drawings. Where
practical in the drawings, a common reference numeral is
used for the same part when it appears in more than one
25 Figure. In the drawings:
Figure 1 is an exploded perspective view of the
~ .
_ 7 _ 1 3363 ~ 6
5 components of an impact absorber of this invention;
Figure 2 is an cut away cross-sectional view of
a shock-absorber of this invention;
1 3363 1 6
Figure 3 is a partially schematic cross
sectional view of an impact absorbing heel pad not
embodying this invention. This heel pad has a wall defin-
ing a pressure-tight cavity but does not have a foam core
adhered to and filling its inner surface. This figure
illustrates the flaw in this design that an impact can be
absorbed but at the same time ballooning occurs;
Figure 4 is similar to Figure 3 but illustrates
that with the present invention ballooning is prevented;
Figure 5 is a perspective view of an alternative
foam core for use in this invention. This core has a
plurality of differing compression strength foams arranged
parallel to the impact force;
Figure 6 is a cut away cross-sectional view of
another alternative embodiment of the impact absorber of
this invention in which the wall material defining the
cavity is further shaped to provide a supportive column;
Figure 7 is another cross sectional view of the
absorber shown in Figure 6 taken along line 7-7';
Figure 8 is an exploded perspective view of the
components of the absorber of Figures 6 and 7;
Figure 9 is a perspective view of an alternative
embodiment of the impact absorber of this invention. This
embodiment employs a core which has a plurality of differ-
ing compression strength foams arranged perpendicular to
the impact force;
Figure 10 is a phantom top view of a core
configuration for use with closed cell foam materials;
Figure 11 is a cross sectional view of the core
shown in Figure 10 taken along line 11-11';
Figure 12 is a phantom top view of another core
configuration for use with closed cell foam materials;
Figure 13 is a cross sectional view of the core
shown in Figure 12 taken along line 13-13';
1336316
g
Figure 14 is a cut away cross sectional view of
a shoe containing a shock-absorber of the present inven-
tion and additionally having a pump for pressurizing the
core of the absorber;
Figure 15 is a cross sectional view of an auto-
motive dash board incorporating an impact absorber of this
invention;
Figures 16 and 17 are two views of an additional
representative application for the shock-absorbers of this
invention as a foot pad;
Figure 18 is a perspective view of a shoulder
pad under pad application for the shock-absorbers of this
invention;
Figures 1~ and 20 are graphs illustrating the
effectiveness of the impact absorbers of this invention
and their adaption to various body weights and to various
impacts;
Figure 21 is a partially cross-sectional view of
a shock-absorber of this invention employing an
alternative pressurization modality and an alternative
wall-forming technique; and
Figures 22A and 22B are partially cross-
sectional views of two stages of pressurization of a
shock-absorber of this invention employing a diffusional
pressurization modality.
Modes for Carrying Out the Invention
Referring to Figures 1 and 2 in more detail,
these figures illustrate an impact absorber 10. Impact
absorber 10 includes a foam core 11 and top and bottom
wall sections 12 and 14 which when joined define a cavity
15. A layer of adhesive 16 is present between essentially
all of the inner surface of cavity 15 and the outer
surface of foam core 11. This layer is shown on core 11
but could as well be on the inside surface of the wall or
133631 b
1o--
on both the core and the wall as desired. When wall sec-
tions 12 and 14 are joined, the cavity which they define
is pressure tight. It is possible to equip the impact
absorber with a valve or fitting such as valve 16. Valve
S 16 is a ~Halkey-Roberts~ type urethane valve which is
shown in Figure 1 in its pre-assembly form. After in-
corporation, the top end of valve 16 is cut off flush with
the surface of the shock-absorber as shown in Figure 2.
Any equivalent form of valve, pressure control aperture or
other means to increase the pressure within the cavity can
be used, if desired. This valve allows the pressure in
the interior (cavity 15) of the impact absorber to be
adjusted, as desired, by adding or removing fluid from the
cavity.
The outer wall of the impact absorber is formed
of flexible plastic. The materials used to form the wall
can be selected from the film-forming flexible plastics.
Virtually any plastic can be used so long as it is resist-
ant to bacterial attack, flexible and shapable into the
forms and configurations desired. Useful film-forming
plastics include poly(urethane)s both of the poly(ether)
and the poly(ester) form, poly(ester)s such as
poly(ethylene terphthalate), flexible poly(vinyl)s,
elastomeric poly(olefin)s such as poly(isoprene),
poly(isobutylene), and neoprene, low density
poly(ethylene)s and the like.
In the embodiment shown in Figures 1 and 2, the
outer wall is preshaped into the desired configuration and
then the foam core is adhered to it. In another
embodiment, the outer wall can be formed around the foam
core. One way to accomplish this is to use a liquid
polymer precure solution or suspension which is applied to
the outer surface of the core and then cured. It has been
found that this method has advantages when the solution or
suspension is sprayed onto the foam. Since the foam
-11- 1 3363 1 6
employed herein is preferably of open-cell construction,
it has been found that the use of spraying allows a
coherent outer film to be achieved without soaking the
foam with excess solution or suspension. Another way to
S accomplish this is to use plastic sheet stock and laminate
it to the core or shrink it around the core. In any of
these alternative modes of construction, it is essential
that there be a strong adherent bond between the wall and
essentially the entire outer surface of the core.
Of the plastics useful in forming the films,
preference is given to the flexible poly(urethane)s
because of their ready availability. These materials are
available from J.P. Stevens Company and Deerfield
Urethane,Inc., to name but two regular suppliers.
Representative useful plastic films include the Deerfield
"Dureflex'*poly(urethane) films. These materials can be
preformed, as in Figures 1 and 2 or they can be used as
stock goods. When a liquid is used to apply the outer
wall, it is typically a solution of a prepolymer or resole
resin. Vinyl films can be used in this application. A
typical vinyl film is the vinyl adhesive sealant produced
by W.R. Grace and marketed by Eclectic Products as
Eclectic 6000 adhesive sealant. These materials are
solvented in halocarbons such as perchloroethylene and the
like. A preferred liquid coating is based on the
polyurethanes. Again, the nonrigid urethane polymers are
preferred. The solutions known in the art for forming
flexible urethane films are very suitable for this ap-
plication. Typical urethane polymer solutions include the
reaction product of a diisocyanate such as toluene
diisocyanate or hexamethylene diisocyanate with a polyol
such as a poly(ether polyol). These reaction products are
commonly produced in a mixed solvent system such as a
polar solvent (for example, 2-butoxyethanol, 2-ethoxyethyl
acetate, 2-(2-butoxyethoxy)ethanol, or diacetone alcohol
(*) Trademark
-12- l 3363 1 6
or the like) in combination with an aromatic solvent such
as toluene, benzene, or hydrocarbon distillate fractions
heavy in aromatics and having a boiling range in the range
of from about 140 to 240C. In preferred applications,
the fluid film-forming material is sprayed onto the foam
so as to minimize soak in and build up. In this case, it
is preferable to use a relatively viscous, high solid
content suspension/solution. Typical viscosities are
100cps or greater such as us to about 1,000 cps. Typical
solids contents are from about 25% to about 60%.
Materials outside of these ranges can be used but the
above ranges are preferred.
In one preferred application, the liquid film
forming material is applied to the foam by dipping. In
this case it is preferable to use a high solid content
suspension/solution. Preferably, the suspension/solution
shall contain at least about 50% by weight solids and more
preferably from abot 50 to about 75% by weight solids.
Such solution/suspension has the advantage of not soaking
into the foam core even when the foam core is open celled
construction.
This outer wall, when applied as a liquid can be
dried (solvent removed) and cured by the application of
heat and/or the application of a curing catalyst such as
an amine. Other curing modalities such as photocuring can
be employed as well, if appropriate. The liquid wall-
forming compositions can contain plasticizers and builders
and the like, if desired. The particular conditions used
for forming the outer wall are conventional for processing
polymers such as the urethanes which are preferred and are
known to those of skill in the polymer arts.
In those applications where the outer wall is
applied as a liquid, either by dipping or by spraying, it
can be of advantage to preheat the foam core. This
preheating raises the temperature of the foam core to
-13- 1 3363 1 6
above ambient, that is preferably above 80 and more
preferably above 90 and up to the highest temperature at
which the foam core remains thermally stable. Such high
temperatues include 250F or higher if possible.
Preferred temperatures are from about 90-250F and
especially from about 100-150F. This preheating of the
core appears to assist the formation of a film when the
liquid wall-forming material is applied. These elevated
temperatures can be achieved by autoclaving the core prior
to applying the outer material.
The outer wall, whether supplied as a preformed
structure, a cured liquid overcoat or a shrunk or adhered
layer of stock goods is commonly from about 1 to 200 mils
in thickness with thicknesses in the range of from about 2
to 50 mils being preferred and excellent results being
attained with thicknesses of from about 3 to about 35
mils.
The core of the impact absorber is a foam. This
foam is preferably an open-celled foam, that is a foam in
which the various cells are in communication with each
other and with the outer surface of the foam. Similar
properties are achieved with a reticulated foam, that is a
foam which has been treated to break down membranes which
separated various cells. Foam rubber, foamed latex, vinyl
foams and the like can be used. The preferred foam
material for use in the core is poly(urethane) foam.
Representative foams include the ~Ensolite~*poly(urethane)
foams sold by Uniroyal Plastics Co., Inc. and the flexible
urethane foams sold by the E.R. Carpenter Company.
Typical densities for the foam core range from
between about 0.5 to about 15 pounds per cubic foot.
Preferred foam densities are from about 2 to 10 pounds per
cubic foot.
It will be appreciated that because the foam
core is adhered to the outer wall it is in effect a
(*) Trademark
,~Y,"
-14- l 3363 1 6
structural member. The adhered foam serves to prevent the
ballooning of the device as previously described. This
duty puts strain upon the foam of the core. If the foam
separates under this strain it can result in a loss of
S integrity of the device. With this potential problem in
mind, it is possible to reinforce the foam by including
filaments or fibers or fabrics in it. Typical reinforce-
ments can be inorganic materials such as fiberglass or
carbon fiber; natural organic fibers such as silk, cotton,
wool or the like or synthetic organic fibers such as
urethane fibers, nylon filaments, nylon fabrics, aramid
filaments and fabrics, and the like. This reinforcement
can be laminated into the foam, incorporated into the foam
or otherwise compounded into the foam as is known by those
skilled in the art.
In the embodiment shown in Figures 1 and 2, the
internal foam core is preshaped to fit tightly within the
outer wall of the impact absorber.
This intimate fit may be accomplished in other
20 ways as well. For one, the core can be foamed in place
within the wall structure using injectable flexible foam
forming materials known in the art. With the preferred
urethane foams, a typical foaming mixture can include a
polyether polyol, a diisocyanate such as toluene
diisocyanate, water, and amine and organotin catalysts.
This mixture generally contains polymeric fillers and
flexibilizers (plasticizers) as well. The added water
reacts with the isocyanates to produce an amine plus
carbon dioxide gas which foams the liquid. Other foaming
agents such as gases including carbon dioxide, nitrogen,
air or the like as well as low boiling liquids, (commonly
low-boiling fluorocarbons and the like) can also be added.
By controlling the amount of foaming material added and
the cure conditions, the core so formed can, if desired,
prestress the outer wall as is preferred. The in situ
1 3363 1 6
-15-
cores can be closed-cell foams, open-celled foams or
reticulated foams as desired.
In a hybrid form of construction, the foam core
can be a composite of a preshaped foam body which does not
completely fill the cavity created by the outer wall and
an added foam-in-place layer between the wall and the
preshaped body. This form of fabrication has the
advantage that the desired intimate fit is achieved with a
minimum of preshaping and fitting while at the same time
the preshaped core provides a measure of dimensional
stabilty and integrity to the composite during fabrica-
tion.
The third component of the impact absorbers of
this invention is an adhesive for affixing the foam core
to the wall. This adhesive is most conveniently an
activated adhesive such as a light activated adhesive, UV
activated adhesive or heat activated adhesive so as to
permit the parts to be fitted together and then bonded. A
typical heat-activated adhesive is the Royal Adhesive DC-
11324 material sold by Uniroyal. This adhesive is a twopart poly(urethane)/isocyanate adhesive which has the
added advantage of being water-based. When applied to the
foam and/or wall it dries to a non-tacky surface which
permits easy assembly. This material heat-activates at
300-325F to form a tough adherent bond. Other useful
adhesives can include epoxy adhesives, contact cement type
poly(urethane) adhesives such as the Uniroyal
"Silaprene~', the 3M ~'Scothgrip~ adhesives and the
isoprene contact cements. In general, one can employ as
adhesive any material which will bond the foam to the
outer wall with a strength which will not be exceeded by
the forces of impact applied to the impact absorber or by
the forces applied by the pressure applied to the impact
absorber.
(*) Trademark
f~
-16- 1336316
In the fabrication methods in which a liquid
solution of prepolymer is applied to the core to create
the outer layer or in which the core is foamed in place,
it is often the case that the required intimate bond
between the core and the outer wall is formed directly
without the need for added adhesive.
The outer wall portions of the impact absorber
are joined together such as by the use of adhesive or by
heat sealing or the like to give a fluid impermeable wall
to which the inner core is bonded. After the fusing
together of the wall components, the impact absorber can
be trimmed and, if desired, further shaped to conform to
the environment of use.
The core of the present impact absorbers contain
a fluid. Gases and in particular air are very suitable
fluids. Liquids and gells could be used as well, if
desired. One interesting class of fluids for use in
inflating the present shock-absorbers are the gases
denominated the "supergases" by Marion Rudy in his United
States Patent No. 4,219,945 FOOTWEAR. These gases are
large molecule gases such as the heavily substituted
halocarbons, for example hexafluoroethane,
perfluoropropane, perfluorobutane, perfluorohexane,
perfluoroheptane, octafluorocyclobutane,
hexafluoropropylene, tetrafluormethane, 1,2-
dichlorotetrafluorethane, l,1,2-trichloro-1,2,2-
trifluorethane, bromotrifluoromethane and the like. These
gases have the property of being preferentially retained
within elastomeric membranes through which air, nitrogen,
oxygen and other "smaller" molecules can diffuse. This
leads to the interesting phenomenum that these smaller
molecules of gas can, with the passage of time, diffuse
into the cavity created by the polymeric wall and filled
with the supergases and thus increase the observed
pressure within the cavity.
-17- 1 3363 1 6
Turning to Figures 3 and 4, the advantages of
the impact absorber of this invention are graphically il-
lustrated. In each of these figures a shoe 30 is shown
together with foot 31 impacting downward into a heel pad
shown as 32 (in Figure 3 - not according to the invention)
and as 10 (in Figure 4 - in accord with this invention).
In the case of heel pad 32, the downward pressure of the
heel causes the center of the pad 34 to be severely
depressed while permitting the edges 35 and 36 to balloon
up. This can be uncomfortable and unstable. With pad 10
the center 33 depresses somewhat but there is minimal bal-
looning.
Turning now to Figure 5, a variation of the core
11 is shown. This core (core 50) is fabricated from a
plurality of foams of differing properties, for example
density. As shown, the core includes a series of plugs
51A, SlB, etc of firm density foam inserted into the body
of core 11. This can result in a light weight core having
the firmness of the plugs. This is merely a
representative configuration and one could as well have
one entire section of the core with one density foam and
another section with another density. One could also vary
the core based on other properties, such as the ability of
a region of the foam to take a set or the like. The
various core sections are adhered to the outer wall of the
impact absorber as is shown in Figures 1 and 2. One could
form a core of this type by placing preshaped pieces of
one foam in the cavity and then foaming in place the other
material, if desired.
The plastic wall of the impact absorber can have
structural properties and contribute to the rigidity and
shock-absorbing properties of the device. Figures 6, 7
and 8 illustrate an embodiment 60 of the impact absorber
which includes a depression or "column" 61 in its
structure so as to provide additional wall surface and
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structure in that region of the absorber. In this
embodiment as shown in Figure 8, the valve 16 is il-
lustrated being laminated into the composite as the top 12
is joined to the bottom 14.
Figure 9 illustrates other variations which may
be employed without departing from the spirit of this
invention. Figure 9 shows impact absorber 80. The foam
core of absorber 80 is fabricated from several different
foams including foam section 81, section 82, section 83
and section 84. These sections are all adhered to the
wall 12/14. Valve 16 is again provided to permit the
pressure of the core to be altered and controlled. The
various core sections can be adhered to one another, if
desired. If they are adhered to one another, it must be
borne in mind that the glue layers or the like between the
various sections can serve as barriers for the transport
of fluid between the various sections. If such fluid com-
munication is desired, gaps must be left in the glue lay-
ers or glues which are fluid-permeable must be used.
Absorber 80 includes several other features
which can be incorporated into the present absorbers. An
exterior pad 85 is provided. This can provide additional
shock-absorbancy. A top layer 86 is also present. This
can be a cosmetic over layer or can be provided as a
replaceable hygienic layer.
In the absorbers shown in Figures 1, 6 and 9,
the means for adjusting the pressure (valve 16) has been
in communication with the foam core itself and has relied
upon the open-cell foam structure of the core to
distribute the applied pressure throughout the core and
thus provide a uniform level of support throughout the
absorber. While this structure is very suitable, one can
also employ closed-cell foams, if desired. Figures 10 and
11, and Figures 12 and 13 respectively illustrate two
representative configurations for a closed-cell foam core.
-19- 1 33631 6
In the configuration shown in Figures 10 and 11, the core
87 contains an aperture 88 into which the pressure adjust-
ing valve 16 can fit. This aperture 88 communicates with
a network of channels 89 spaced throughout the core so as
to transmit and distribute the pressure applied to
aperture 88. In this embodiment, the network of channels
is contained by and enclosed by the closed-cell foam core.
This means that the core itself can contribute to the
containment of the pressure applied to the channels. This
offers the advantage that localized stress on the outer
wall is avoided or minimized and possible failures due to
rupture at localized stress points are minimized.
The configuration shown in Figures 12 and 13 is
substantially the same as that shown in Figures 10 and 11
with the exception that aperture 97 communicates with a
network of passages 98 which are not fully contained
within the core. This configuration does not offer the
localized stress relief of the configuration of Figures 10
and 11 but would be less expensive and simpler to produce.
Turning to Figure 14 an additional embodiment of
the impact absorber is shown as foot pad 90 housed within
the sole portion of shoe 95. Foot pad 90 includes the
foam core 11 and adherent outer wall 12/14 described
herein. Pad 90 is equipped with a built in pump to alter
the pressure within its core. This pump includes a one
way check valve 16 which admits air into pump cavity 91.
Pump cavity 91 is compressed and released to give a region
of low pressure so that air can enter through valve 16.
When the cavity 91 is depressed again, this forces the
newly admitted air through passage 92 into the core 11,
thus increasing its pressure. This process is repeated
until the proper pressure is attained. Shoe 95 also
includes a collar 93. This can be formed with the same
structure as pad 90 with an internal core adhered to the
walls. Such a collar would be very effective at absorbing
-20- l 33631 6
the shock which would occur as the wearer's foot comes up
in the shoe and impacts it or would be effective as a
protection to the wearer's ankle and achilles tendon
region.
Figure 15 illustrates that the present invention
finds application in many areas beyond athletic equipment.
It illustrates an automotive dashboard structure 101 hav-
ing an impact pad 100 on its face as well as phantom
steering wheel 102. Impact pad 101 includes core 11, wall
12/14 and valve 16. Such a pad can provide efficient
dashboard impact protection for the occupants of the auto-
mobile in the event of a crash.
Figures 16 and 17 illustrate in two views a
ventilated footpad 110 for use in shoes. Pad 110 has a
complex shape which requires numerous compound curves. In
-its application as a shoe footpad, pad 110 will be
subjected to a wide variation in impacts depending upon
the weight of the runner using it and the runner's light-
ness of footstrike. It is of substantial advantage to
adjust the pressure within the pad with valve 16 to accom-
modate these variations.
Figure 18 illustrates another embodiment of the
present invention, an underpad 180 for use in conjunction
with contact sports shoulder pads. Underpad 180 has a
structure which includes numerous compound curves and a
plurality of "Swiss-cheese~' holes through its structure.
The compound curve-forming ability and the plurality of
holes permit the pad to conform to and bend over the
wearer's shoulder with comfort and breathability. It is a
special advantage that the present invention makes these
complex curves possible and provides superior shock and
impact absorption in such settings.
Figure 21 illustrates another embodiment of the
present invention. It shows pad 210 in which the foam
core 11 is surrounded by a wall 211 which has been formed
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around and in intimate adhesion to the core by applying a
liquid polymer suspension to the outer surface of the core
and then curing the polymer to produce the wall.
In one preferred embodiment, the outer surface
is created by spraying several layers of a curable polymer
suspension onto the open-cell foam of core 11. Typical
polymer suspensions are the urethane suspensions such as
the two part sprayable system marketed by Technical
Urethanes, Inc, Clearbrook, Virginia as Techthane*9OSS.
This representative material is a mixture of an aliphatic
poly(ether urethane) and a curing agent. These two
materials are mixed in about equal volume ratio and ap-
plied typically with an airless sprayer at a viscosity of
100-200 cps. This suspension has a solids content of
about 45-50% by weight which, when coupled with the
viscosity just recited, gives rise to minimal soak-in into
the open-cell foam. The material cures to a tightly
adhered layer around the core at room temperature or can
be quick-cured by the application of heat. Additional
layers of the suspension can be applied to produce the
desired strength and thickness of coating.
As noted above, the coating can be applied by
dipping, as well, when the solids content of the suspen-
sion is above about 50% by weight. This coating can be
carried out with improved efficiency when the core is
preheated and this preheat condition is maintained during
the coating, or at least the initial stages of the coat-
ing.
Under atmospheric conditions, this process will
give rise to a shock-absorber having an atmospheric pres-
sure within the core. This pressure can be increased by
adding additional pressurization fluid to the core. This
can be carried out using a valve as has been previously
described or alternatively can be carried out as depicted
in Figure 21 by injecting fluid such as a gas directly
(*) Trademark
-22- 1 33 63 1 6
through the wall 211 by means of a needle 213. In the
figure, this gas is supplied through line 212. Wall 211
can be self-sealing, or a sealant can be applied over the
hole created by needle 213 so as to assure the retention
of the pressure applied from line 212.
As previously noted, in some embodiments, the
core or the shock-absorber can be pressurized using the
process of diffusion pumping as disclosed in United States
Patents Nos. 4,219,945 and 4,271,606, both of which il-
lustrate typical materials for forming walls suitable forthis process. Figures 22A and 22B illustrate this process
in schematic view.
In these figures, Figure 22A illustrates a shock-
absorber 220 having a spray-on outer wall 211 and a ~-e~izable
open-celled foam core 11. Large molecule gas is present
within the voids or cells of core 11. These large
molecules are fancifully shown as 221, even though, of
course they can not in fact be seen. These molecules are
held and enclosed by wall 211 and can not escape as shown
representationally by their bouncing off of the wall.
Absorber 220 is at a low pressure mode as shown by its
flat to concave section. Wall 211 is fabricated of a
material which is permeable to small gas molecules and in
particular nitrogen and oxygen molecules from air, shown
as 222. These small molecules permeate the wall and cause
the internal pressure of core 11 to increase. This effect
is shown in Figure 21B where the diffused "small"
molecules have entered the core and caused it to press
against the affixed wall 211 and expand the body. This
pressurization by diffusion can lead to enhanced life for
the shock-absorbers and to increased performance.
The effectiveness of the present invention can
be demonstrated by comparative tests. A series of impact
tests were run on a standard state-of-the-art basketball
shoe. The same tests were then performed on the same
~- .
, . . .
-23- 1 3363 1 6
model shoe which had been modified by replacing a portion
of its sole structure (the heel pad region) with an impact
absorber of this invention. The impact absorber was
fabricated from 35 mil flexible poly(urethane). The core
was about 1/2 inch thick open-cell poly(urethane) foam of
5 lbs per cubic foot density. The foam core slightly pre-
stressed the outer wall by being somewhat oversized and
was adhered to the walls using a heat activated water-
based urethane adhesive. Tests were run with the core
sealed at atmospheric pressure and with the core pres-
surized to 5 and 10 psig. Figures 19 and 20 present the
results of these tests. In each figure line A is the
results observed with the prior art shoe. It can be seen
that for a given application of energy to the shoe, i.e. a
given impact, the shoe transmits a certain peak force and
a certain acceleration, (in G's) to the wearer. Lines B
show the results achieved when the atmospheric bladder is
used. They show that the force and acceleration transmit-
ted to the wearer is significantly reduced. Importantly,
this reduction occurs over the entire range of applied
energies. Thus the effectiveness of the present absorbers
is substantially universal and will be observed with hard
impacts such as may result with heavy athletes and also
with lighter impacts such as may result with lighter
weight athletes, etc.
Lines C show that even better shock-absorbancy
is achieved when a positive pressure is applied to the
bladders. Similar results were obtained with the 5 and 10
pound pressures which suggest that in practical terms
these pressures may be quite adequate. On the basis of
these tests, it is believed that pressures in the range of
0 to about 20 psig are preferred.
The present invention has been described herein
in detail with respect to a number of preferred
embodiments and configurations. It will be appreciated,
-24- 1 3363 1 6
however, that modifications and changes to various aspects
of these embodiments may be made while still coming with
in the spirit and scope of this invention which is as
defined by the following claims.
