Shoe with shock absorbing and stabiizing means

A shoe having a shock absorber therein. In one embodiment, the shock absorber includes an inflatable member having a hole placing the interior of the inflatable member in fluid communication with the atmosphere. The shock absorber is restrained by a stabilizing structure against lateral instability. The stabilizing structure is in the form of a box of any one of several configurations. During foot strike, air is forced out of the inflatable member to cushion the heel while the stabilizing structure keeps it stable in the shoe. During toe-off of the shoe and swing-through to the foot strike, atmospheric air enters the inflatable member and inflates the same so that the member is ready to cushion the foot during the next foot strike. Several embodiments of the shock absorber are disclosed.

BACKGROUND OF THE INVENTION 
In a sport shoe, shock absorption upon foot strike is a vital consideration 
in protecting the lower extremity from injury. Distance runners usually 
impact the ground at the heel and with a force as high as three times the 
body weight. Most running shoes have been made with resilient elastomer 
(EVA) soles to at least partially cushion such impact. Other shoes have 
been constructed with shock absorption systems that include open or closed 
gas or liquid filled bladders. As these various soles are made thicker or 
contain more or larger air cells, bladders or tubes to improve shock 
absorption characteristics, the shoes become increasingly unstable. This 
instability is not particularly critical in a longitudinal direction. 
However, instability in a lateral direction adversely effects the function 
of the foot and leg in distance running and other sports and significantly 
increases the probability of acute and chronic lower extremity injury. 
In distance running, from toe off until foot strike, the lower extremity is 
internally rotated, placed toward the midline of the body, and the foot is 
in a raised arch or supinated position. Most runners contact the ground 
with the outside edge of their shoes and for approximately ten to twenty 
percent of the total time the foot is on the ground, the foot continues to 
internally rotate. The foot longitudinal arch also lowers or pronates. 
This pronation, which occurs in the subtalar joint, allows the foot to act 
as a shock absorber and to become a mobile adapter to varying types of 
surfaces. The ground contact usually occurs with between two to four 
degrees of supination. The heel then angulates inwardly as the foot 
flattens about six degrees to a pronated position. 
Many runners have a tendency to overpronate which makes subsequent raising 
of the longitudinal arch (supination) and external rotation of the foot to 
form a rigid lever for effective toe off more difficult. This "rolling" 
movement of the rear foot toward the inside (pronation) during midstance 
is exaggerated if the sole is particularly thick and soft or if the heel 
counter is unstable. This overpronation can lead to imbalance and overuse 
injuries which are common disabilities among runners. The subtalar joint 
functions as a mitered hinge with a diagonal or oblique axis. Thus, when 
the foot pronates excessively, the leg is forced to rotate inwardly to an 
excessive degree causing abnormal stress on the cartilage and 
musculotendinous components of the foot, leg and knee. 
Repeated and continuous stress can cause numerous disorders. The additional 
load on the plantar fascia of the foot because of excessive pronation can 
result in plantar fascutes. "Shin splints" caused by traction on the 
posterior tibialis muscle and tendon which raises the longitudinal arch or 
tarsal tunnel syndrome caused by excessive friction on the posterior 
tibialis tendon under the medial malleolus, are pronation related 
disabilities. Torque on the achilles tendon initiates and aggravates 
achilles tendonitis. The abnormal internal rotation of the leg causes a 
stress on the structures of the medial aspect of the knee with pes 
anserinus bursitis being a common ailment. Misalignment of the quadraceps 
tendon can cause patellar compression syndrome due to the increased and 
abnormal pressure on the patellar cartilage. 
Since foot impact is approximately two times body weight on level terrain 
and three times body weight in downhill running, a shoe sole that will 
deform to absorb the considerable energy of impact with minimal lateral 
instability is necessary to prevent injury. Several sport shoe 
manufacturers have attempted to solve this problem of lateral instability 
by various means including use of a stabilizing bar that traverses the 
midsole and heel counter (Converse), a stabilizing pillar in the midsole 
(Asics), a semirigid external heel counter that traverses the midsole (New 
Balance), and a stabilizing varus wedge in the midsole (Brooks). In all of 
these attempts to control lateral instability, the shock absorption 
qualities of the midsole are significantly compromised. This is because 
the stabilizer decreases the potential vertical compression or deformation 
of the midsole available for energy absorption. Also, these rigid or 
semirigid stabilizers cause the sole to "bottom out". Although most 
distance runners contact the ground with the outside edge of their shoes, 
this contact force is small. By the time the force reaches twice the body 
weight the distribution is centered approximately twenty five percent 
forward of the shoe length from the heel and near the midline of the shoe. 
It is, therefore, essential that the shoe sole provide maximum vertical 
shock absorption toward the center of the heel while minimizing lateral 
instability. 
Disclosures relating to shock absorption systems for shoes include the 
following U.S. Pat. Nos.: 
______________________________________ 
663,270 3,716,930 
2,474,815 3,754,339 
3,029,530 3,785,069 
3,120,712 3,791,051 
3,180,039 4,183,156 
3,335,505 4,215,492 
3,475,836 4,219,945 
3,589,037 4,224,746 
4,237,625 
______________________________________ 
SUMMARY OF THE INVENTION 
The present invention provides an improved shoe having a shock absorption 
system in which the absorption of shock and other impact loads and the 
lateral stability of the shoe are increased over those achieved with 
conventional shock absorption systems for shoes while reducing sole wear. 
The present invention provides a shoe with a shock absorption system which 
has either a closed cell elastomer or bladder construction, or a chamber 
or tube construction that is open to the atmosphere. In the later 
embodiments, air can flow out of the system to the atmosphere during heel 
strike and air can flow into the system from the atmosphere during toe off 
and swing-through when the shoe is off the support surface therebelow 
during walking and running. In each of these constructions, members 
shiftable relative to the shoe are included to minimize lateral 
instability. 
In one embodiment, the present invention includes a shoe having means 
defining an air chamber with an unobstructed air hole which allows the air 
chamber to communicate directly with the atmosphere at all times. In 
another embodiment, the invention has an air chamber defined by a flexible 
bladder which has a relatively large air hole and an internal flapper 
valve which can move across the hole during foot strike. The valve has a 
relatively small hole therethrough to allow limited flow of air out of the 
air chamber during foot strike yet air can easily enter the bladder when 
the shoe is being lifted during toe off and swing-through because the 
valve is unseated and opens the relatively large hole. Thus, a bellows 
effect is created with the use of the bladder. Because the bladder can 
collapse to a minimal height during foot strike and the shock absorption 
system includes members shiftable relative to the shoe, stability and 
cushioning of the foot are significantly increased for the distance 
between the heel and the ground during midstance compared to that achieved 
with shoes having conventional shock absorbing systems therein. 
The present invention includes shiftable stabilizing plates located in the 
sole and heel counter of the shoe. These stabilizing plates can shift 
vertically in the sole and heel counter to permit maximum vertical 
displacement of the sole or deformation of the elastomer shock absorber or 
bladder of the shoe and yet permit only minimum lateral displacement of 
the sole or lateral deformation of the cellular material in the midsole. 
Lateral displacement can result in angulation of the sole and heel counter 
with consequent overpronation of the foot. Longitudinal instability of the 
sole is not critical in preventing overpronation and formation of the 
rigid lever for toe off. This design provides for displacement and 
cellular material elastic deformation in vertical and longitudinal 
directions to maximize shock absorption, elastic rebound and lateral 
stability of the shoe. 
The stabilizing structure of the present invention is based on the 
observation that the rigid lower portion of the shoe heel counter can be 
utilized to form a rigid box in which stabilizing plates are nested. These 
plates extend from the lower portion of the box into the midsole and can 
telescope further into the heel counter box or cavity upon foot strike. 
Nesting of the plates in the rigid box prevents rotary or angular movement 
of the plates. These plates can be made of metal or plastic or other 
materials and can be rigid or semirigid. As the thickness of the elastomer 
midsole is increased to improve cushioning, lateral instability increases. 
As the size of the elastomer air cells or included bladder or tubes 
increase lateral instability increases. This is particularly apparent in a 
closed gas or liquid filled bladder which also provides less reliability, 
longevity and greater cost of manufacture than an open bladder. A 
relatively large bladder or chamber which is open to the atmosphere 
provides the greatest potential cushioning or shock absorption while 
retaining reliability, longevity and lower cost of manufacture. However, a 
large open bladder presents a formidable problem in preventing undesirable 
lateral instability. Lateral, vertically shiftable stabilizing plates in a 
shoe sole and heel counter allow the greater potential shock absorption 
qualities of an open bladder to become a practical and efficient means for 
absorbing foot strike energy in a shoe. 
If a shock absorber insert is used in the shoe or a dynamically movable 
footbed insert is utilized with or without stabilizing plates in the sole, 
lateral stability is increased by the use of meshing plates or telescoping 
pillars on the sides or rear of the shoe inserts to prevent the upper and 
lower surfaces from tilting or angulating to the side. 
The primary object of the present invention is to provide an improved shoe 
having a shock absorption system in which the system is open to the 
atmosphere to allow air to flow into an air chamber of the system during 
raising of the foot off the support surface therebelow yet air will be 
forced out of the air chamber during heel strike on the support surface so 
that the shoe can provide improved shock absorption capabilities for the 
foot yet the lateral stability of the shoe remains high so as to provide 
comfort for the wearer of the shoe and support for the foot regardless of 
the impact forces exerted on the shoe by the foot during walking or 
running.

A first embodiment of the shoe of the present invention is broadly denoted 
by the numeral 10 and includes an upper shell 12 attached to a lower sole 
14. The upper shell and lower sole are conventional in construction and 
can be formed of any suitable materials. Also, the shoe can be a dress 
shoe, a casual shoe or a sport shoe, such as a running shoe; thus, the 
teachings of the present invention are not limited to use with any 
particular type of shoes. 
Shoe 10 includes an insole or footbed 16 which, for purposes of 
illustration, extends from the arch of the upper shell to the rear end 
thereof. Insole 16 has a shock absorber insert 18 attached thereto or 
imbedded therein near the rear end thereof. Insert 18 includes an upper, 
flat plate 20 and a lower flat plate 22 which are pivotally interconnected 
with each other at their front ends by a hinge 24. The bottom plate 22 has 
opposed, stabilizing side plates 26 which are secured to and extend 
upwardly from the side margins of plate 22. Side plates 26 can extend only 
partially forwardly from the rear end of plate 22 as shown in FIG. 1, or 
plates 26 can extend almost to hinge 24, whichever if desired. In the 
latter case, the plates 26 are generally triangular in configuration and 
extend along the side margins of plates 20 and 22. 
Plate 20 has a pair of flat side flanges 27 which are adjacent to the inner 
surfaces of respective side plates 26. Flanges 27 shift relative to side 
plates 26 and are guided thereby as plate 20 moves toward and away from 
plate 22. Also, flanges 27 are held against lateral movement by side 
plates 26. 
Insert 18 further includes an inflatable bladder 28 which is provided with 
a relatively large opening 30 and a flapper valve 32 for closing opening 
30 when the bladder is compressed. Valve 32 has a relatively small opening 
33 therein. The bladder is placed between plates 20 and 22 as shown in 
FIGS. 1 and 1A, and the opening is near the upper rear end of the bladder 
to cushion the downward movement of upper plate 20 as the heel of the foot 
in shoe 10 moves downwardly when the shoe strikes the ground. 
The bladder 28 is of any suitable shape. For purposes of illustration, the 
bladder is rectangular; however, it can be circular or any other shape as 
well. Its thickness is less than its width so that the bladder can 
conveniently underlie the major portion of the heel of the foot for 
maximum cushioning of the heel during downward movement of the heel. The 
bladder, for instance, could be loosely received in the space between 
plates 20 and 22 or it could be adhesively bonded to either or both of 
such plates. The bladder is of a resilient material, such as rubber. 
In use, assuming that bladder 28 has air in it and that the wearer of shoe 
10 is striding such that shoe 10 is moving downwardly, the heel of the 
wearer presses down on insert 18, forcing plate 20 downwardly toward plate 
22. This causes bladder 28 to be compressed to force air from the bladder 
out of the small opening 33, thereby allowing air to escape from the 
bladder to the atmosphere through opening 33 because flapper valve 32 will 
close the larger opening 30. This air, therefore, escapes with difficulty 
and passes out of the shoe along the inner, rear surface of the shoe. As 
the air slowly leaves the bladder, a bellows effect is created, and 
because the bladder can collapse to a minimal height during heel strike, 
and because shifting of the stabilizing side plates provides lateral 
stability, stability and cushioning are significantly increased for the 
distance between the heel and support surface therebelow during mid-stance 
compared to that achieved with conventional walking or running shoes. 
As the foot is lifted during toe off and swing-through of the foot, the 
bladder 28 expands to allow air to rush into the bladder through the 
relatively large opening 30 past the flapper valve 32, since the flapper 
valve is now opened. This action allows the bladder to inflate rapidly and 
the bladder is then in condition for use as a shock absorber during the 
next heel strike. 
The shock absorber insert 18 in shoe 10 provides a footbed which permits 
reduction in sole wear and prolongs the shock absorbing qualities of the 
shoe. Insert 18, therefore, minimizes injury to the foot yet provides much 
greater comfort and stability to the wearer of the shoe than can be 
achieved with the shoe without insert 18. 
Plates 20 and 22 permit maximum vertical displacement of bladder 28 yet 
side plates 26 and flanges 27 permit only minimal lateral displacement of 
the foot during heel strike. Lateral displacement can result in angulation 
of the sole and heel with consequent overpronation of the foot. 
Longitudinal instability of the sole is not critical in preventing 
overpronation and formation of the rigid lever for toe off. Plates 20, 22, 
and 26 and flanges 27 form a heel counter box or cavity for providing 
maximum lateral stability for the foot. These plates and flanges can be 
made of metal, plastic or other materials, and can be rigid or semi-rigid. 
FIG. 1D is an enlarged, rear elevational view of a shock absorber insert 
18a which is a modified version of the insert shown in FIGS. 1 and 1A. In 
insert 18a, upper plate 20a is pivotally connected by a hinge (not shown) 
to the front end of a bottom plate 22a. A bladder 28a is disposed between 
plates 20a and 22a much in the same manner as insert 28 is disposed 
between plates 20 and 22 (FIG. 1). 
Instead of using side plates 26, the insert of FIG. 1D has a pair of 
crossed struts 26a and 26b which are pivotally interconnected by pin 26c 
at the midpoints of the struts. Each strut has slotted members at the 
outer ends thereof for receiving adjacent pins 26d secured to the rear 
flat faces of respective plates 20a and 22a. Thus, struts 26a and 26b 
allow upper plate 20a to move upwardly and downwardly with respect to 
plate 22a without permitting any substantial lateral movement of plate 20a 
relative to plate 22a. 
FIG. 1E shows a particular embodiment of the hinge 24 interconnecting the 
front ends of plates 20 and 22 (FIG. 1). Plate 24 is constructed in the 
same manner as a door hinge, with a hinge pin 25 and adjacent, tubular 
knuckles 29 on plates 20 and 22 for receiving pin 25. 
Another embodiment of the shoe of the present invention is broadly denoted 
by the numeral 40 and includes an upper shell 42 attached to a lower sole 
44. The shoe has an insole 46 provided with a shock absorber insert 48 
which includes an air filled, closed bladder 50 which is imbedded in the 
insole 46 or below the insole and resting on the upper surface of sole 44. 
Insert 48 further includes stabilizing means comprised of a pair of 
stabilizing pillars or pins 52 which are spaced apart and extend upwardly 
from the upper surface of sole 44 adjacent to the inner surface 56 at the 
rear portion 58 of shoe 40. 
A footbed upright member 60 is secured to and extends upwardly from the 
rear end of insole 46. Member 60 is substantially rigid and is between and 
in engagement with pillars 52 so that the pillars serve to guide member 60 
as the rear part of insole 46 moves up and down. Thus, the pillars provide 
lateral stability for insole 46 during heel strike and prevent lateral 
movement of insole 46 relative to sole 44. 
Bladder 50 can be of the type shown in FIGS. 1 and 1A, if desired. However, 
insert 48 illustrates the fact that the bladder can be opened or closed to 
the atmosphere, as desired. 
Shoe 40 further includes a strap 62 provided with a buckle or other 
fastening means (not shown) which can be used to further stabilize the 
foot. The strap is typically forward of an upper, rear part 64 of the 
tongue of shoe 40 so that the strap is across the leg of the wearer. The 
purpose of strap 62 is to cause a lifting of the rear part of insole 46 as 
the wearer flexes the leg during walking or running and just prior to 
lifting of the foot off the support surface therebelow for follow through 
of the foot in making the next step. 
While pillars 52 can be mounted in any suitable manner, typically, they are 
imbedded in sole 44. They can be made of any suitable material, such as 
metal or plastic and can be rigid or semirigid. Similarly, the rear end 
portion of insole 46 and member 60 are generally rigid or semirigid and 
can be made of a metal, plastic or other suitable material. 
In the use of shoe 40, a foot strike will cause bladder 50 to flatten as 
the rear portion of insole 46 descends due to impact by the heel of the 
foot. During this time, member 60 is guided downwardly and retained 
against side movement by pillars 52 so as to avoid lateral instability of 
the rear portion of insole 46. In this way, the foot is cushioned, yet the 
foot does not become subjected to lateral forces which would occur in the 
absence of pillars 52 and member 60. 
Another embodiment of the shoe of the present invention is broadly denoted 
by the number 70 and includes an upper shell 72 mounted on a lower sole 
74. An insole 76 above sole 74 is provided with a shock absorber insert 78 
near the rear end thereof. Insert 78 includes an inflatable bladder 80 
below the rear portion of insole 76 and supported on sole 74. Bladder 80 
is adapted to contain air, and the bottom part of the bladder has an 
opening 82 communicating with an L-shaped fluid passage 84 extending 
downwardly from opening 82 into sole 74 and then through sole 74 
rearwardly thereof to an opening at the rear end 86 of the sole 74. 
The front and rear walls 88 and 90 of bladder 80 are spring-like to provide 
a bellows effect to cause expansion of the bladder into the full line 
position thereof as shown in FIG. 4 when no downward force is exerted on 
the bladder. A flapper valve 92 is used to close opening 82 when a 
downward force is exerted on the upper wall of the bladder, allowing air 
to flow through a relatively small opening 94 in the flapper valve, the 
air flowing outwardly of the bladder through passage 84. 
A compressible plug 96 on the inner surface of the upper wall of bladder 80 
(FIGS. 4 and 5) is formed by a suitable compressible material, such as 
rubber. The plug has a cross-shaped groove 98 (FIGS. 5C and 5D) in its 
lower surface. The central part of groove 98 vertically overlies the small 
hole 94 in flapper valve 92 so that, when a downward force is applied to 
the rear part of insole 76, plug 96 is moved downwardly against the bias 
forces of the front and rear sides 88 and 90 of bladder 80 to cause 
flapper valve 92 to close the relatively large opening 82 yet allow air to 
flow out of the interior of the bladder through groove 98, small hole 94 
and passage 84 to the atmosphere. As plug 96 is progressively compressed 
with downward movement of the insole, the groove 98 in plug 96 is 
substantially closed. Thus, the pneumatic spring rate of the shock 
absorber is increased and controlled. 
An adjustable valve 100 is provided at the rear end of passage 84 to meter 
the flow of air into and out of the tube. Valve 100 includes an inner wall 
102 provided with a crescent-shaped hole 108 alignable with a 
crescent-shaped hole 110 in the outer wall 104. Wall 104 has a knurled 
flange 112 surrounding the outer periphery of wall 102, and wall 104 is 
rotatable by a pin 106 relative to wall 102 to vary the size of the air 
passage formed by the combined effect of openings 108 and 110. This air 
passage can be fully or partially opened or can be fully closed by proper 
adjustment of outer wall 104 relative to inner wall 102. 
To provide lateral stability for shoe 70, insert 78 has a pair of 
stabilizing plates 116 imbedded in sole 74 as shown in FIGS. 5 and 6 and 
extending upwardly from the sole. The upper margins of plates 116 are 
shiftably received in hollow boxes 118 which are carried by the heel 
counter sides 120 of shoe 70. Insole 76 has a pair of side flanges 122 
(FIG. 5) which are guided by the upper margins of plates 116 as the rear 
portion of insole 76 moves downwardly and upwardly relative to sole 74. 
Thus, plates 116 and flanges 122 form a box structure which provides 
lateral stability for the foot during walking and running. Boxes 118 
permit vertical movement of plates 116 during compression of sole 74. 
In use, assuming bladder 80 is filled with air as shoe 70 moves downwardly, 
a foot strike forces the rear part of insole 76 downwardly to compress 
bladder 80. This causes air to flow out of the bladder through large hole 
82 and passage 84 to the atmosphere. Eventually, plug 96 will engage 
flapper valve 92, closing opening 82 and allowing air in the bladder to 
pass through groove 98 into and through relatively small hole 94, into 
passage 84 and out of the tube past valve 100. The amount of difficulty of 
the air leaving the bladder will be determined by the setting of valve 100 
as well as the spring constant defined by front and rear sides 88 and 90 
of bladder 80. This spring constant will determine the rate at which plug 
96 moves into a position closing flapper valve 92 to thereby enclose 
opening 82. 
As the shoe is lifted during toe off and follow-through movement of the 
foot, the resilience of sides 88 and 90 will cause the bladder to increase 
in volume, creating a vacuum which opens valve 92, allowing air to rush 
into the bladder through valve 100, passage 84 and into the bladder 
through opening 82. This action occurs at a relatively short time because 
of the relatively large size of opening 82 and because of the vacuum 
created by the lifting of the upper wall of the bladder under the bias 
force of sides 88 and 90. Eventually, the bladder will expand sufficiently 
so that it will be ready to cushion the shock of the next foot strike as 
the shoe is lowered into engagement with a surface below the shoe. Thus, 
the shock absorber insert 78 of shoe 70 provides a cushioning effect to 
cushion the shock of downward movement of the heel in the shoe yet the 
insert provides lateral stability by way of plates 116 and flanges 122. 
FIG. 7 shows a fourth embodiment of a shoe of the present invention, the 
shoe being denoted by the numeral 130 and having an upper shell 132 and an 
outer lower sole 134. The outer sole 134 is formed from an elastomer 
material, such as rubber, neoprene, or the like, and the outer sole 134 
has an air chamber 136 therein near the rear end thereof. Chamber 136 is 
formed by an upper wall 138 and a lower wall 139, wall 138 having a hole 
140 (FIG. 7) therethrough which communicates with the atmosphere. An 
insole 142 is mounted in the shoe and the rear end of the insole is 
slightly forwardly of hole 140 as shown in FIG. 7. 
The resilience of the material of outer sole 134 provides an inherent bias 
which tends to expand chamber 136 into the full line position of FIG. 8 
when no downward force is exerted on upper wall 138. Thus, during a heel 
strike, the heel forces wall 138 downwardly against wall 139 (FIG. 9) 
causing chamber 136 to decrease in volume and causing air to be forced out 
of chamber 136 through opening 140 to the atmosphere. This causes a 
bellows effect which cushions the shock of the downward movement of the 
heel yet chamber 136 is sufficiently low with reference to the lower 
surface of outer sole 134 so that the foot has maximum stability in the 
shoe. 
A pair of stabilizing plates 143 are provided at the sides of sole 134 near 
chamber 136 as shown in FIGS. 7-9. Each plate 143 has a flange 141 at its 
lower end to anchor the plate in sole 134. The upper margins of plates 143 
extend upwardly from sole 134 and are received in boxes 144 imbedded in 
the sides 146 of shoe 130. Each box 144 may contain a leaf spring 245 to 
engage and bias the corresponding plate 143 downwardly. FIG. 7 shows the 
side plates 143 before the deformation of upper wall 138 relative to lower 
portion 139, and FIG. 9 shows the deformation of the sole upon foot strike 
with plates 143 deeper in boxes 144. Thus, the box like construction 
defined by plates 143 and boxes 144 provide lateral stability for the shoe 
along with the cushioning action afforded by top wall 138. 
During toe off and follow-through of the shoe, the shoe is lifted off the 
ground and when this occurs, the inherent resilience of sole 134 causes 
chamber 136 to expand, creating a partial vacuum in the chamber and 
drawing air suction into the chamber 136 through hole 140. The movement of 
the air into chamber 136 is sufficiently rapid so that the chamber is 
effectively filled with air before the next heel strike. Thus, the lower 
extremity of the wearer of the shoe is protected against damage, yet the 
shoe is simple and rugged in construction and provides lateral stability 
and cushioning over long periods of time. 
The embodiments of the present invention shown in FIGS. 1-6 can be provided 
with springs for the same purpose as spring 147 (FIGS. 7-9), namely, to 
bias the lateral stabilizing plates into initial positions.