Shoe with dual cushioning component

A shoe of the present invention comprises a sole, a flexible bladder, and a cushioning material. The sole has a recess configured to receive the flexible bladder. The flexible bladder has interior surface portions defining at least one chamber. The chamber includes a first region and a second region. A cushioning material occupies the first region and a compressible fluid occupies the second region. The compressible fluid provides a primary elastic response to an external pressure applied to an external surface of the bladder through compression of the compressible fluid. The cushioning material, elastically deformable but generally incompressible, provides a secondary elastic response to the external pressure applied to the external surface of the bladder through elastic deformation of the cushioning material. A method of the present invention comprises forming a shoe sole having a recess therein, providing a flexible bladder having interior surface portions defining an interior volume, placing an amount of fluid which is curable to an elastomeric solid condition into the interior volume of the bladder, and allowing the fluid to cure to said elastomeric solid condition.

BACKGROUND OF THE INVENTION 
This invention relates to shoes and methods for making shoes having 
cushions in their soles. The shoe construction of the invention is 
preferably employed in athletic shoes, but may be employed in various 
other types of shoes as well. 
A typical athletic shoe includes an outsole, a midsole overlying the 
outsole, and an upper secured to the midsole. The midsole is generally 
made of a resilient foam material, such as ethylene vinyl acetate (EVA) or 
polyurethane (PU), which provides at least some cushioning and support to 
the athlete's foot. Some midsoles have recesses formed therein for 
containing resilient pads or fluid filled bladders. Fluid filled bladders 
are frequently positioned in the heel areas of shoe soles since, in a 
normal walking or running gait, the heel area of the foot usually strikes 
the ground first at each footfall. However, fluid filled bladders or 
cushioning pads may be positioned in other areas of the shoe and shoe sole 
that accept significant external forces during use. 
Many prior art fluid filled bladders have been filled with a gas, such as 
air, while others have been filled with liquids or viscous gels. Air 
filled bladders provide good shock absorption of relatively light external 
loads through compression of the air. As the air compresses, the 
resistance of the bladder increases. However, one disadvantage of prior 
art air filled bladders is that they fail to provide adequate shock 
absorption in response to extreme external forces. Under extreme loads, 
the walls of air filled bladders have a tendency to "bottom out" against 
one another. Thus, there is a need for a cushioning component that 
provides good shock absorption in response to light external loads, and 
which is capable of accepting extreme external loads without "bottoming 
out." 
Another disadvantage of prior art air filled bladders is that they have a 
tendency to lose air. The typical plastic bladder allows some permeation 
of air. When a higher air pressure exists on the inside of the bladder, 
which is usually the case during normal loading of the shoe sole, the air 
contained within the bladder tends to leak through the bladder walls over 
time. Also, any rupture of the bladder due to fatigue or puncture results 
in a total loss of cushioning through compression of the air. In an effort 
to prevent the leakage of air, liquid or gel, some prior art fluid filled 
bladders have been made with thickened plastic bladders. However, this 
tends to make the bladder undesirably stiff and heavy, thereby increasing 
the stiffness and weight of the shoe. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a shoe and a method for 
making a shoe having an improved cushion in a recess of the shoe's 
midsole. Another object is to provide a shoe and a method for making a 
shoe in which the cushion provides excellent cushioning, shock absorption, 
and energy return in response to light external loads as well as extreme 
external loads. Yet another object is to provide a cushion having the 
shock absorption of an air-filled bladder but which does not "bottom out" 
when subjected to extreme external loads. A further object is to provide a 
fluid-filled bladder configured to resist leakage of fluid therefrom even 
if the bladder is punctured. Another object is to provide a cushion which 
does not appreciably degrade in effectiveness over time. Still another 
object is to provide a shoe and a method for making a shoe in which the 
cushion is configured to provide two forms of shock absorption in response 
to external forces resulting from footstep impact. Yet another object is 
to provide a shoe which is an improvement over conventional shoe 
constructions. 
In general, a shoe of the present invention comprises a sole, a flexible 
bladder, and a cushioning material. The sole has a recess configured to 
receive the flexible bladder. The flexible bladder has interior surface 
portions defining at least one chamber. The chamber includes a first 
region and a second region. The cushioning material is formed from a 
curable fluid which has cured to an elastomeric solid condition, and 
occupies at least the first region of the chamber. Preferably, the chamber 
is a closed chamber and the second region is occupied by a compressible 
fluid. 
In another aspect of the shoe of the present invention, a liner of 
cushioning material lines interior surface portions of a flexible bladder. 
The liner of cushioning material completely defines at least one cavity 
within the bladder which is occupied by a compressible fluid. 
In still another aspect of the shoe of the present invention, a flexible 
bladder has interior surface portions defining at least one chamber. The 
chamber includes a first region and a second region. A cushioning material 
occupies the first region and a compressible fluid occupies the second 
region. The compressible fluid provides a primary elastic response to an 
external pressure applied to an external surface of the bladder through 
compression of the compressible fluid. The cushioning material provides a 
secondary elastic response to the external pressure applied to the 
external surface of the bladder through elastic deformation of the 
cushioning material. The compressible fluid provides a first degree of 
elastic response to a first degree of external pressure applied to the 
external surface of the bladder and, if the external pressure is high 
enough, the cushioning material provides a second degree of elastic 
response. 
Generally, a method of the present invention is for making a shoe having a 
sole, a flexible bladder for the sole, and a cushioning material within 
the flexible bladder. The method comprises forming a shoe sole having a 
recess therein; placing a flexible bladder into the recess of the shoe 
sole, the bladder having interior surface portions defining an interior 
volume; placing an amount of fluid which is curable to an elastomeric 
solid condition into the interior volume of the bladder; and allowing the 
fluid to cure to said elastomeric solid condition. 
Other objects and features will be in part apparent and in part pointed out 
hereinafter.

Reference characters in the written specification indicate corresponding 
parts throughout the several views of the drawings. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A shoe of the present invention is represented in its entirety by the 
reference numeral 20 (see FIG. 5). The shoe 20 includes an outsole 22, a 
midsole 24 overlying the outsole 22, an upper 26 secured to the midsole, 
and a cushioning component 30 adjacent to the midsole 24. As shown in FIG. 
1, the midsole 24 includes a recess 32 sized to receive the cushioning 
component 30. In FIG. 1, the recess 32 is shown in the heel area of the 
midsole 24. However, it is to be understood that a cushioning component 
may have other configurations and may be positioned in other areas of the 
midsole or shoe without departing from the scope of the present invention 
as defined by the claims. 
As best shown in FIG. 4, the cushioning component 30 comprises a flexible 
bladder 34, a cushioning material 36, and a compressible fluid 38. 
Preferably, the bladder 34 is formed from blow molded or thermo-formed 
polymeric material. Preferred polymeric materials include thermoplastic 
urethane (TPU), polyvinyl chloride (PVC), and ethyl vinyl acetate (EVA). 
However, the bladder 34 could be formed from other materials without 
departing from the scope of this invention. Generally, the configuration 
of the bladder 34 will match the anatomy of a portion of a human foot (not 
shown). The specific configuration will vary depending on the area of a 
shoe in which the bladder is to be placed. 
The flexible bladder 34 is generally fluid impervious and has interior 
surface portions 40 defining at least one chamber. The cushioning material 
36 occupies a first region of the chamber and the compressible fluid 38 
occupies a second region of the chamber. In FIG. 4, the cushioning 
material 36 is shown in the form of a liner 44 which lines the interior 
surface portions 40 of the flexible bladder 34. FIGS. 6-8 show other 
configurations of the cushioning material. The liner 44 shown in FIG. 4 
and the configurations of the cushioning material shown in FIGS. 6-8 will 
be discussed in more detail below. 
The cushioning component 30 provides shock absorption through compression 
of the compressible fluid 38. As the compressible fluid 38 compresses, the 
fluid pressure within the flexible bladder 34 increases and the resistance 
of the cushioning component 30 to external forces applied to an external 
surface 46 of the bladder 34 increases correspondingly. Preferably, the 
compressible fluid 38 is air. However, other compressible liquid or 
gaseous fluids could be used without departing from the scope of the 
invention. 
The cushioning material 36 is formed from a curable fluid which has cured 
to an elastomeric solid condition. Preferably, the cushioning material 36 
is formed of a solid material which is elastically deformable, but 
generally incompressible. Although the shape of the cushioning material 36 
is deformable under load, its volume does not substantially change. 
Therefore, the cushioning component 30 will not "bottom out," (i.e., 
opposing bladder walls will not come into contact with one another) even 
under extreme loading conditions. This protects the shoe wearer from high 
pressure impacts. Although it is preferable to use a material which is 
generally incompressible, closed or open cell foam materials could 
comprise the solid cushioning material even though they may not be 
incompressible. 
In the preferred embodiment, the cushioning material 36 is formed of a 
curable liquid polyurethane which has cured to an elastomeric solid 
condition. The elastomeric solid material provides cushioning and shock 
absorption due to its softness. In forming the cushioning component 30, 
the curable fluid preferably starts as a mixture of two fluids: a polymer 
and a catalyst. As the two fluids are mixed together, a chemical reaction 
occurs and, after a short period of time elapses, an elastomeric solid 
forms. The actual time necessary for the curable fluid to cure will vary 
depending on the mixing ratio of the polymer and catalyst. Typically, the 
reaction occurs in between about 5 and 20 minutes. This relatively slow 
reaction time allows the curable fluid to be molded and shaped to various 
configurations as it cures to a solid form. Once cured, the elastomeric 
solid will preferably have a durometer hardness of between about 45 Shore 
000 and 55 Shore 000. More preferably, the elastomeric solid will have a 
durometer hardness of about 50 Shore 000. However, depending on the 
particular needs of the shoe wearer, a curable fluid can be developed 
which results in a cured solid having other hardness characteristics. 
Preferably, the liner 44 of cushioning material 36 lines the interior 
surface portions 40 of the flexible bladder 34 and has an inner surface 48 
which envelopes the second region. In the embodiment shown in FIG. 4, the 
liner 44 of cushioning material 36 completely closes and defines the 
second region. Because the soft, elastomeric cushioning material 36 
completely closes the second region, it serves as a plug to prevent 
leakage in the event the bladder is punctured. The cushioning material 36 
also decreases the diffusion rate of air across the bladder wall, thus 
maintaining the internal bladder pressure. Preferably, the liner 44 has a 
thickness of between about 0.5 to about 1.5 millimeters. More preferably, 
the liner 44 has a thickness of about 1.0 millimeters. However, the 
thickness can be varied depending on the particular needs of the shoe 
wearer without departing from the scope of the invention. In some 
instances, it may be preferable to vary the thickness of the liner even 
within the same chamber. 
The flexible bladder 34 includes a top wall 50 and a bottom wall 52 and, as 
shown in FIGS. 2, 4-6 and 8, preferably has a plurality of chambers 
defined by welds 54 connecting the top wall 50 to the bottom wall 52. 
In use, the cushioning component 30 provides two stages of cushioning and 
shock absorption. The compressible fluid 38 provides a primary elastic 
response to an external pressure applied to the external surface 46 of the 
flexible bladder 34 through compression of the compressible fluid 38. The 
cushioning material 36 provides a secondary elastic response to the 
external pressure. Under relatively light external loading conditions the 
primary elastic response provided by the compressible fluid 38 may be 
sufficient. However, under more extreme loading conditions, compression of 
the compressible fluid 38 alone may not provide sufficient cushioning and 
shock absorption. Accordingly, under more extreme loading conditions, the 
cushioning material 36 will provide a secondary elastic response to the 
external pressure. 
As discussed above, a liner 44 of the cushioning material 36 lines the 
interior surface portions 40 of the flexible bladder 34 and envelops the 
compressible fluid 38. The liner 44 includes opposed top and bottom 
portions 56 and 58 which line the top and bottom walls 50 and 52 of the 
bladder 34. Therefore, in the embodiments shown in FIGS. 4, 5 and 7, the 
liner 44 provides the secondary elastic response when the opposed top and 
bottom portions 56 and 58 of the liner 44 come into contact with one 
another. 
FIG. 6 shows an alternative embodiment of a cushioning component 60 of the 
present invention wherein an amount of cushioning material 62 occupies 
bottom portions of a flexible bladder 64, rather than lining substantially 
all of the interior surface portions of the bladder. However, the 
cushioning component 60 of this embodiment functions similarly to the 
embodiments shown in FIGS. 4, 5 and 7. As the flexible bladder 64 flexes 
in response to external loading conditions, a compressible fluid 66 
provides a primary elastic response through compression of the 
compressible fluid 66. Under higher external loading conditions, the 
cushioning material 62 occupying the bottom portions of the bladder 64 
provide a secondary elastic response when the unlined top wall 68 of the 
bladder 64 comes into contact with the cushioning material 62 occupying 
the bottom portions of the bladder 64. This embodiment is similar to the 
embodiment shown in FIGS. 4 and 5 in all other respects. 
FIG. 7 shows another alternative embodiment of a cushioning component 70 
having an undivided chamber. Similar to the embodiment of FIG. 4, this 
embodiment includes a flexible bladder 72, a cushioning material 74, and a 
compressible fluid 76. The cushioning material 74 forms a liner lining 
interior surface portions 78 of the flexible bladder 72. 
FIG. 8 shows yet another alternative embodiment of a cushioning component 
80 having a central chamber 82 and an annular peripheral chamber 84. The 
annular peripheral chamber 84 is substantially filled with a cushioning 
material 86. The central chamber 82 has a liner 88 of the cushioning 
material 86 which is structurally and functionally similar to that shown 
in FIGS. 4 and 5. In this embodiment, the annular peripheral chamber 84 
provides cushioning and shock absorption solely through elastic 
deformation of the cushioning material 86 since no compressible fluids are 
present. This embodiment is similar to the embodiment shown in FIGS. 4 and 
5 in all other respects. 
To make a shoe of the present invention, a midsole is formed having a 
recess therein, a flexible bladder is placed in the recess, an amount of 
fluid which is curable to an elastomeric solid condition is placed into an 
interior volume of the bladder, and the fluid is allowed to cure to the 
elastomeric solid condition. 
Preferably, a predetermined amount of curable fluid is placed into the 
bladder interior volume through a fill port, such as by injecting, so that 
the interior volume is partially filled with the curable fluid. For the 
embodiments shown in FIGS. 4-7, the interior volume of the bladder is 
filled with an amount of curable fluid sufficient to form a liner of the 
cured elastomeric solid lining the interior surface portions of the 
bladder. For these embodiments, the bladder interior volume is only 
partially filled so as to leave room for the compressible fluid. 
As discussed above, the embodiment shown in FIG. 8 includes a central 
chamber 82 and an annular peripheral chamber 84. For this embodiment, the 
annular peripheral chamber 84 is substantially filled with the curable 
fluid so that the cured elastomeric solid 86 occupies substantially the 
entire interior volume annular peripheral chamber 84. Similar to the 
embodiments of FIGS. 4-7, the central chamber 82 of this embodiment is 
filled with an amount of curable fluid sufficient to form a liner 88 of 
the cured elastomeric solid. 
Once the curable fluid has been injected into the interior volume of the 
bladder, it will tend to settle to the bottom portions of the bladder 
interior volume due to gravity. After the curable fluid has been injected, 
the fill port is sealed. Then, the bladder is moved to allow the curable 
fluid to flow along the interior surface portions of the bladder. 
Preferably, the viscosity of the curable fluid is sufficiently high so 
that, even before curing, the fluid will tend to coat the interior surface 
portions of the bladder due to surface tension. Movement of the bladder 
may be accomplished by mounting the bladder to a device which slowly but 
continuously rotates the bladder about at least one axis of rotation. This 
slow but continuous rotation of the bladder is maintained for a time 
sufficient to allow the curable fluid to cure, thereby forming a liner 88 
of cured elastomeric solid cushioning material along the interior surface 
portions of the bladder. 
In an alterative method, the bladder is turned at predetermined time 
intervals, rather than being turned continuously. After the curable fluid 
has been settled in the bottom portions of the bladder interior volume for 
a predetermined amount of time, a portion of the curable fluid will have 
cured along the bottom portions of the bladder. Then, the bladder may be 
turned to allow the remainder of the uncured fluid to flow, by gravity, in 
order to coat other portions of the bladder. This process is repeated at 
predetermined time intervals until substantially all of the curable fluid 
has cured to an elastomeric solid condition in the form of a liner 88 
which lines the interior surface portions of the bladder. The time 
intervals will vary depending on, among other things, the mixing ratio of 
the polymer and catalyst used to develop the curable fluid. 
In another alternative method, the bladder is formed by rotational molding. 
In other words, the partially filled bladder placed in a three-dimensional 
centrifuge that rotates the bladder and its contents at high speeds in 
three dimensions. The high speed rotating, or "spinning" of the bladder in 
the centrifuge forces the curable fluid against the interior surface 
portions of the bladder and lines the interior surface portions with the 
curable fluid. The spinning continues for a time sufficient to allow the 
curable fluid to cure to a solid elastomeric condition lining the internal 
surface portions of the bladder. 
In view of the above, it will be seen that the several objects of the 
invention are achieved and other advantageous results attained. 
As various changes could be made in the above constructions and methods 
without departing from the scope of the invention, it is intended that all 
matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense.