Abstract:
An article of footwear with a bladder system providing cushioning and dynamic motion control in a multi-bladder system. The bladder system gives the needed amount of motion control by stiffening a portion of the footwear in response to the individual user&#39;s side-to-side motion. When used in the heel, the bladder system takes into consideration a center-of-pressure pathway of the foot to increase medial stiffness in response to lateral-to-medial rotation of the foot, so the more a user pronates, the stiffer the medial portion of the footwear is made. The bladder system provides comfort and control without the extra weight and bulk of prior art support structures. The bladder system dynamically changes the stiffness of a portion of the footwear when pressure is applied thereto, and returns to equilibrium when the pressure is removed.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to an article of footwear which has a dynamically changing motion control and cushioning bladder system. The bladder system provides varying amounts of resistance to side-to-side motion depending on the severity of such motion while walking, running, or participating in other athletic activities.  
         BACKGROUND OF THE INVENTION  
         [0002]    The typical running stride involves the runner landing on the lateral, posterior edge of the footwear in the heel region followed by pronation toward the medial side as the foot continues through its stride. As footstrike continues, the foot stops pronating and begins to supinate as the foot rocks forward so that the foot reaches a neutral position at midstance. From midstance, the foot rocks forward to the forefoot region where toe-off occurs at the ball and front of the foot. Toe-off typically involves the toes on the medial side of the foot pushing off the running surface as the foot leaves the ground to begin a new cycle.  
           [0003]    Pronation involves the rolling of the foot from its lateral, posterior side to its inner, medial side. Although pronation is normal and necessary to achieve proper foot positioning, it can be a source of foot and leg injuries for runners who over pronate. The typical runner who over pronates lands on the outer, lateral side of the heel in a supinated position and then rolls medially across the heel toward the inner side of the footwear beyond a point which may be considered normal. While some amount of pronation is helpful in decreasing pressure and stress experienced by the leg, excessive pronation can cause stress on various joints, bones and soft tissue. Supinating, which involves rolling of the foot from the medial to the lateral side, while not as common as over pronating, can also cause foot and leg injuries if it is excessive.  
           [0004]    Modern running and walking footwear are a combination of many elements each having a specific function which aids in the overall ability of the footwear to withstand many miles of running or walking, while providing cushioning and support for the foot and leg. Articles of athletic footwear are divided into two general parts, an upper and a sole. The upper is designed to snugly and comfortably enclose the foot, while the sole must provide traction, protection and a durable wear surface. It is often desirable to provide the footwear with a midsole having a layer of resilient, cushioning materials for enhanced protection and shock absorption when the heel strikes the ground during the stride of the wearer. This is particularly true for training or jogging footwear designed to be used over long distances or over a long period of time. These cushioning materials, must be soft enough to absorb the shock created by the foot strike and firm enough not to “bottom out” before the impact of the heel strike is totally absorbed.  
           [0005]    Attempts have also been made to provide support and comfort in an article footwear by incorporating bladders in fluid communication with each other within a sole. Examples of these devices include U.S. Pat. No. 4,183,156 to Rudy (which is hereby incorporated by reference); U.S. Pat. No. 4,446,634 to Johnson et al.; U.S. Pat. No. 4,999,932 to Grim; Austrian Patent No. 200,963 to Schutz et al.; and  HYDROFLOW ®ST, by BROOKS® Sports, Inc.  
           [0006]    Conventional running and walking footwear designed to provide the user with the maximum amount of available cushioning tend to sacrifice footwear stability by using a midsole cushioning system that is too soft and has too much lateral flexibility for a person who over pronates or requires some form of motion control. The lateral flexibility and deformation of traditional cushioning materials contribute to the instability of the subtalar joint of the ankle and increase the runner&#39;s tendency to over pronate. This instability has been cited as one of the causes of “runners knee” and other such athletic injuries. As a result, over-pronators generally do not use contemporary shoes specifically designed for maximum cushioning, but instead use heavier, firmer footwear, or footwear having motion control devices specifically designed to correct physical problems such as excessive pronation. Motion control devices limit the amount and/or rate of subtalar joint pronation immediately following foot strike.  
           [0007]    Various ways of resisting excessive pronation or instability of the subtalar joint have been proposed and incorporated into running footwear as motion control devices. In general, these devices have been fashioned by modifying conventional footwear components, such as the heel counter, and/or the midsole cushioning materials. Unlike the present invention, current motion control devices do not repeatedly adjust their level of support to match the varying degree of side-to-side motion accompanying each foot strike. Instead, when used to control pronation, devices such as firm medial posts limit over pronation by providing a substantially rigid structure with a constant stiffness and level of support that presses against the medial side of the foot, limiting internal rotation of the ankle. Examples of motion control devices include: U.S. Pat. No. 5,046,267, to Kilgore et al.; U.S. Pat. No. 5,155,927, to Bates et al.; and U.S. Pat. No. 5,367,791, to Gross et al.  
         SUMMARY OF THE INVENTION  
         [0008]    Two of the most common reasons for foot and knee injuries sustained by runners and walkers are insufficient shock absorption and a lack of proper lateral motion control. Both reasons must be considered when designing footwear so the wearer receives the proper amount of cushioning and motion control without significantly increasing the overall weight of the footwear. Many runners who require a moderate amount of motion control may have to use heavy, bulky footwear, which is weighted down by support features, and designed for the severe over pronator.  
           [0009]    The present invention introduces cushioning and dynamic motion control in a single, multi-bladder system providing optimum cushioning, while simultaneously providing the needed amount of motion control by stiffening a portion of the footwear in response to the individual user&#39;s lateral motion, most frequently pronatory motion. The bladder system of the present invention takes into consideration the center-of-pressure pathway of the foot during typical footstrike to increase medial stiffness in response to lateral-to-medial rotation of the foot, so the more a user pronates, the stiffer the medial portion of the footwear is made. The bladder system provides comfort and control without the extra weight and bulk of prior art support structures because the support is provided by the flow of fluid in the cushioning system. The bladder system also provides a dynamically changing cushioning system that functions when pressure is applied to its region of the footwear and returns to equilibrium when the pressure is removed.  
           [0010]    The present invention utilizes lightweight bladders for the dual purposes of cushioning and motion control. As a result, motion control footwear incorporating the present invention can be made lighter than its contemporary counterparts and provides a level of support commensurate with the degree of lateral motion, such as over-pronation, in each stride of the user.  
           [0011]    An article of footwear for controlling side-to-side motion of a foot of a wearer according to the present invention comprises an upper, a sole attached to the upper, and a bladder system positioned within the sole of the footwear. The system includes at least first and second bladder chambers positioned side-by-side of one another and in fluid communication. A first valve is positioned between the first bladder chamber and the second bladder chamber. The first valve opens at a first predetermined level of pressure so that a fluid contained within the first outer bladder chamber is forced into the second bladder chamber when pressure within the first bladder chamber reaches the predetermined level to increase the pressure in the second bladder chamber and dynamically increase the support provided by the second bladder chamber on the side it is disposed.  
           [0012]    In one preferred embodiment, the bladder system positioned is within a heel region of the sole and the first bladder chamber is disposed adjacent one side of the heel region, a third bladder chamber is disposed adjacent the other side of the heel region and the second bladder chamber is disposed between the first and third bladder chambers in fluid communication therewith. A second valve is positioned between the third bladder chamber and the second bladder chamber. The second valve includes a second pressure regulator that prevents fluid flow from the second bladder to the third bladder chamber when the pressure in the second bladder chamber is below a second predetermined pressure and allows fluid flow from the second bladder chamber to the third bladder chamber when the pressure in the second bladder chamber is at or above the second predetermined pressure to increase the pressure in the third bladder chamber and dynamically increase the support provided by the third bladder chamber.  
           [0013]    The present invention also includes an embodiment which forces fluid from a central chamber into two outer chambers which surround it to stabilize the foot and prevent medial and lateral turning of the foot. In this embodiment, valves positioned within conduits connecting the chambers allow the contained fluid to immediately flow from the central chamber into the outer chambers when pressure is applied to the central chamber. In this embodiment, the direction of immediate fluid flow between the central chamber and the first outer chamber is opposite to that discussed above with respect to the other embodiments of the present invention. In this embodiment, fluid immediately flows from the central bladder to the two outer bladders when pressure is applied. Fluid only flows from the first outer bladder to the central bladder when it slowly bleeds back into it during the rest phase of the running or walking stride. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is an exploded view of an article of footwear incorporating a bladder system according to the present invention;  
         [0015]    [0015]FIG. 2A is a top view of the bladder system according to the present invention having a single conduit housing between the bladder chambers;  
         [0016]    [0016]FIG. 2B is a perspective view of the bladder system according to the present invention;  
         [0017]    [0017]FIG. 3A is a top view of the bladder system according to the present invention having a single housing with two conduit lines extending between the bladder chambers;  
         [0018]    [0018]FIG. 3B is a top view of the bladder system according to the present invention having two conduit lines extending between the bladder chambers;  
         [0019]    [0019]FIG. 4 illustrates a typical path of the center of pressure of the foot during a stride.  
         [0020]    [0020]FIGS. 5A and 5B are cross-sectional views, with valves removed, taken generally along lines  5 A- 5 A and  5 B- 5 B of FIGS. 3A and 3B to illustrate different embodiments of the conduits according to the present invention; and  
         [0021]    [0021]FIG. 6 is a top view of another embodiment of the bladder system according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    An article of athletic footwear  80  including a dynamic, cushioning and motion control bladder system  10  according to the present invention is shown in FIG. 1. Footwear  80  is comprised of an upper  75  for covering a wearer&#39;s foot and a sole assembly  85 . Bladder system  10  is incorporated into a midsole layer  60 . An outsole layer  65 , for engaging the ground, is secured to at least a portion of midsole layer  60  to form sole assembly  85 . A sock liner  70  is preferably placed in shoe upper  75 . Depending upon the midsole material and performance demands of the shoe, midsole layer  60  can also form part or all of the ground engaging surface so that part or all of outsole layer  65  can be omitted. Bladder system  10  is located in the heel region  81  of footwear  80  and is incorporated therein by any conventional technique such as foam encapsulation or placement in a cut-out portion of a foam midsole. A suitable foam encapsulation technique is disclosed in U.S. Pat. No. 4,219,945 to Rudy, hereby incorporated by reference.  
         [0023]    As illustrated in FIGS. 1 and 2A, bladder  12  includes outer, lateral bladder chamber  12  and outer, medial bladder chamber  14 . A central bladder chamber  16  is positioned between and in fluid communication with lateral and medial bladder chambers  12 ,  14  so that bladders  12 ,  14 , and  16  are arranged in a side-by-side relationship. Lateral bladder chamber  12  and central bladder chamber  16  are fluidly connected by a first conduit  20 . A second conduit  30  fluidly connects central bladder chamber  16  and medial bladder chamber  14 . In the embodiment illustrated in FIG. 2A, chambers  12 ,  14 , and  16  are fluidly connected by conduits  27 .  
         [0024]    Bladder chambers  12 ,  14 ,  16  and conduits  27  of FIG. 2A, or conduits  20 ,  30  of FIGS. 3A and 3B, are formed of a thermoplastic elastomeric barrier film, such as polyester polyurethane, polyether polyurethane, such as a cast or extruded ester based polyurethane film having a shore “A” hardness of 80-95, e.g., Tetra Plastics TPW-250. Other suitable materials can be used such as those disclosed in the ‘156 patent to Rudy. Among the numerous thermoplastic urethanes which are particularly useful in forming the film layers are urethanes such as Pellethane™, (a trademarked product of the Dow Chemical Company of Midland, Mich.), Elastollan® (a registered trademark of the BASF Corporation) and ESTANE® (a registered trademark of the B.F. Goodrich Co.), all of which are either ester or ether based and have proven to be particularly useful. Thermoplastic urethanes based on polyesters, polyethers, polycaprolactone and polycarbonate macrogels can also be employed. Further suitable materials could include thermoplastic films containing crystalline material, such as disclosed in U.S. Pat. Nos. 4,936,029 and 5,042,176 to Rudy, which are incorporated by reference; polyurethane including a polyester polyol, such as disclosed in U.S. Pat. No. 6,013,340 to Bonk et al., which is incorporated by reference; or multi-layer film formed of at least one elastomeric thermoplastic material layer and a barrier material layer formed of a copolymer of ethylene and vinyl alcohol, such as disclosed in U.S. Pat. No. 5,952,065 to Mitchell et al., which is incorporated by reference.  
         [0025]    In a preferred embodiment of the present invention, bladder chambers  12 ,  14 ,  16  and conduits  27 ,  20 ,  30  are integrally formed of first and second sheets  40 ,  45  of elastomeric barrier film. In a preferred embodiment of the present invention, bladders  12 ,  14 ,  16  are formed from generally transparent or translucent elastomeric film to enable visibility through the bladders.  
         [0026]    U.S. Pat. Nos. 4,183,156 (‘156) and 4,219,945 (‘945) to Marion F. Rudy, the contents of which are hereby expressly incorporated by reference, describe conventional welding techniques which can be used to form the shapes of the bladder chambers  12 ,  14 ,  16  and conduits  20 ,  30 . As disclosed in the ‘156 and ‘945 patents, sheet  40  and  45  can be welded to one another to define the side walls of bladder chambers  12 ,  14 ,  16  and conduits  20 ,  30 , as well as interior welds (not shown in the drawings) within the bladder chambers to maintain the bladder chambers in a generally flat configuration.  
         [0027]    In an alternative embodiment of the present invention bladder chambers  12 ,  14 ,  16  and conduits  27 ,  20 ,  30  are formed using conventional blow-molding techniques.  
         [0028]    Bladder chambers  12 ,  14 ,  16  can be sealed to hold air or other fluid at ambient pressure, or can be pressurized with an appropriate fluid, for example, hexafluorethane, sulfur hexafluoroide, nitrogen, air, or other gases such as those disclosed in the aforementioned ‘156, ‘945, ‘029, or ‘176 patents to Rudy, or the ‘065 patent to Mitchell et al. If pressurized, the fluid or gas can be placed in the bladder through an inflation tube (not shown) in a conventional manner by means of a needle or hollow welding tool. After inflation, the bladder can be sealed at the juncture of the bladder and inflation tube, or by the hollow welding tool around the inflation point on the inflation tube.  
         [0029]    [0029]FIG. 4 diagrammatically illustrates the path C p  of the center of pressure that a foot applies during typical running. As seen therein, the center of pressure is initially applied at the rear lateral edge of the foot at footstrike and moves diagonally medially and forward. The medial motion of the center of pressure is indicative of the natural pronation motion that the foot undergoes immediately after footstrike. As the foot rolls forward past the heel area, the pronation motion stops and the foot begins a degree of supination motion in the opposite direction, i.e., from the medial side to the lateral side.  
         [0030]    As the center of pressure of the foot during a foot strike moves medially across footwear  80 , the pressure within the bladders serially increases in the direction of the pronatory motion until the medial chamber fills and stiffens the medial side of the footwear to prevent excessive pronation, pronation beyond the point which may be considered normal. A pressure gradient created in the bladders during a foot strike, works in conjunction with the pronatory motion of the foot to provide a dynamic level of motion control commensurate with the degree of over-pronation.  
         [0031]    In order to accomplish this dynamic control, as shown in FIG. 3A, the pressure between the bladder chambers is controlled by first and second flow valves  22 ,  32  located within first and second conduits  20 ,  30 , respectively. Valves  22 ,  32  include one-way valves such as Vernay duck-bill valves or flapper valves. Valves  22 ,  32  can also include those discussed in U.S. Pat. No. 5,253,435 to Auger et al. and U.S. Pat. No. 5,257,470 to Auger et al., both hereby expressly incorporated by reference. One way or check valves which limit fluid flow to only one direction and which are commonly found in medical devices such as syringes and bulb pumps can also be used. Conduit  20  and valve  22  freely deliver fluid in the direction of the foot stride. Conduit  30  and valve  32  allow the displaced fluid to slowly return to its original chamber. Valves  22 ,  32  are positioned at the forward end of bladder system  10  in order to protect them from impact during a foot strike. Conduits  20 ,  30  can either be two separate members each having its own fluid line as shown in FIG. 5B, or as shown in Figure  5 A, one member including two fluid lines.  
         [0032]    As shown in FIG. 2A, a single, one-way valve  28  with a slow return bleed can be substituted for valves  22  and  32 . A single valve  28  is located within a single conduit  27  extending between two adjacent bladders. As with valves  22  and  32 , each single valve and each single conduit would be in fluid communication with the forward end of a pair of adjacent bladders.  
         [0033]    Valves  22  or single, one-way valve  28  can open instantaneously when pressure rises within chamber  12  or  16  as a result of a foot strike to allow fluid to pass into chamber  16  or  14 , respectively. The time the regulating members within these valves may remain open is between 1 and 5 milliseconds. One preferred opening time is about 5 milliseconds. The regulating members included, for example, the flaps on a flapper valve. These valves may also be set to open for fluid flow in the direction of the stride when the differential pressure between the bladders reaches a predetermined level, for example, from any minimal differential up to a 10 psi or greater differential. Other well known pressures levels may also be used to trigger these valves. The triggering pressure levels will vary depending upon the initial cushioning pressures established in the bladders when they are inflated. Setting the valves to open at a preset pressure differential allows the bladder chambers and fluid flow to be customized for severe pronators, larger runners or other users who require specific or additional amounts of cushioning from a bladder.  
         [0034]    Prior to the heel of a user touching down, the predetermined pressure in the bladder chambers preferably is equal: P L =P C =P M . The range of pressure within the bladders is preferably between 15 and 30 psi, with the preferred pressure being 20 psi. Initial striking of the heel increases the pressure P L  within lateral bladder chamber  12  by deforming it. As the foot strike continues and P L  exceeds P C  or the value for which flow valve  22  is calibrated, valve  22  opens and fluid flows through conduit  20  from lateral bladder chamber  12  to central chamber  16  causing a pressure rise in central chamber  16  which results in P C &gt;P M . The pressure in central bladder chamber  16  rises even further with the pronating motion because the center-of-pressure moves medially to compress center bladder chamber  16 . As P C  exceeds P M  or the calibrated differential limit for valve  22 , between chambers  14  and  16 , valve  22  opens and fluid from central bladder chamber  16  flows into medial bladder chamber  14 . The resulting increased pressure in chamber  14  stiffens the medial side of heel region  81  to prevent any further medial rolling of the foot i.e., limit pronation. The increased pressure in medial bladder chamber  14  and stiffness of the medial side of footwear  80  is dependent on the location and force of the heel strike.  
         [0035]    Bladder system  10  adapts to the amount of pronation during a stride and stiffens the medial side of footwear  80  accordingly. The serial increase of pressure from lateral bladder chamber  12  to central bladder chamber  16  to medial bladder chamber  14  can be referred to as pressure ramping. The degree of lateral to medial motion and the location of the foot strike dictate the resulting pressure in medial bladder chamber  14  and the resulting degree of stiffness along the medial side of footwear  80 . Pressure ramping within system  10  is greatest when the user lands on the outer, lateral edge of the footwear and the resulting foot motion is largely in the lateral to medial direction. As previously discussed, this type of pronatory foot motion initially applies pressure to lateral bladder chamber  12 , forcing its fluid into central bladder chamber  16 . As the foot stride continues, pressure is applied to central bladder chamber  16  and a volume of fluid in the central chamber is forced into medial bladder chamber  14 , thereby stiffening the medial side of footwear  80 .  
         [0036]    A user who does not over pronate generally will put less initial pressure on the lateral side of the footwear and will force less fluid, if any, into bladders  16  and  14  during a typical stride when compared to an over pronator having the same striking force. When a person who does not pronate uses footwear  80 , the resulting stiffness along the medial side differs from that discussed above, assuming that both heel strikes are equal in force. For example, if the heel strike of a user first compresses only central bladder chamber  16  and the pressure in lateral chamber  12  remains below the release limit of valve  22  in conduit  20 , only fluid from central bladder  16  will be available to transfer to medial bladder chamber  14 . The resulting pressure in chamber  14  will therefore be only the sum of the fluid pressure in chamber  14  and the amount transferred from chamber  16 . Flow valve  22  positioned between chambers  12  and  16  will prevent fluid from leaving lateral bladder chamber  12  until the pressure in chamber  12  is greater than the pressure at which valve  22  opens. Valve  32  maintains the pressure in chamber  12  at its initial level, either by preventing fluid from flowing into chamber  12  or by working in conjunction with valve  22  so that the amount of fluid that enters chamber  12  through valve  32  will exit through valve  22  into chamber  16 . Hence, the pressure in medial bladder  14  will not rise to the aggregate pressure achieved during a more pronatory heel strike, i.e. one that begins by striking the lateral portion of the footwear, because the available fluid in bladder  16  will not be an aggregate of that from bladders  12 ,  14  and  16 . Instead, it will only effectively include fluid from chambers  14  and  16 . Accordingly, the less a runner pronates, the less the medial side of the shoe stiffens.  
         [0037]    After the landing phase of running is over, equilibrium or initial pressure between the bladders is re-established before the next heel strike, either by a slow leak through the single two-way valve  28 , or through valve  32 , which allows fluid to pass back into the central and lateral bladder chambers. The typical recovery time for returning these bladder chambers to rest pressure is between 0.1 and 2 seconds with the most preferred time being approximately 1 second. As discussed above, the recovery time will depend on the amount of the fluid forced from each bladder chamber. The smaller the chambers or the less fluid transferred, the shorter the recovery time for the system.  
         [0038]    As seen in FIG. 6, a cushioning system  100 , can extend along the length of footwear  80 , i.e., with bladder chambers in the heel region and the forefoot region. Cushioning system  100  includes a bladder system  110 . Bladder system  110  is constructed the same as bladder system  10 , with similar components in FIG. 6 labeled with like numbers as bladder system  10 , but in the  100  series of numbers. Bladder chambers  112 ,  114  and  116  function in the same way as bladder chambers  12 ,  14  and  16 , respectively, to stiffen the medial side of footwear  80  behind the instep in the heel region  135 .  
         [0039]    Cushioning system  100  also includes a bladder system  148  formed of bladder chambers  152  and  156  in the forefoot region  150  to provide lateral stability and increased performance when running or jumping. Bladder chambers  152  and  156  extend along the forefoot region of footwear  80  and are formed of the same material as bladder chambers  12 ,  14  and  16 . Bladder chambers  152  and  156  include a supportive, cushioning fluid which can be the same as that used in the rear bladder chambers  112 ,  114  and  116  or a different fluid, as discussed above. Bladder chambers  152  and  156  are in fluid communication with each other by a pair of conduits  158 , each having a valve  160 ,  162 . Valves  160 ,  162  are the same as valves  122 ,  132 , respectively, except that they may be designed to function at different pressure levels or differentials than bladder  122 ,  132 . In contrast to valve  122 , discussed above, valve  160  allows fluid flow in the medial to lateral direction in order to stiffen the lateral side of the forefoot of footwear  80  during a foot stride. As the foot strike moves through the forefoot of footwear  80 , fluid flows out of medial chamber  152  into lateral chamber  156  to stiffen the lateral side of footwear  80 . The pressure ramping in the forefoot follows the same principles as that in the heel region, except that fluid flows in the opposite direction. Pressure ramping in the forefoot stiffens the lateral side of footwear  80  to support to the foot when cutting or turning for increased performance, or to support the forefoot during the propulsion phase of running or walking. As bladder chamber  156  fills with the fluid from chamber  152 , it creates a wedge effect within the forefoot that the user can push against when turning, jumping, or running. Valve  162  allows for the return of fluid from chamber  152  to chamber  156 .  
         [0040]    The pressure ramping system can be divided into any number of chambers. Its effectiveness is determined by relative volumes, locations and the number of chambers used to provide the pressure ramping function. The number of chambers used is at least in part based on the pressure in the plantar region as a function of time for any give defined movement. The positioning and size of the bladders depends on the type of footwear they are incorporated into and the activity in which they will be used. For example, a system located within an article of footwear intended to be used for basketball may be have a different size, a different at rest pressure and different valve triggering pressures than footwear used for running. Also, the basketball footwear may incorporate the forefoot portion of cushioning system  100  where as such a system may not be needed within running footwear.  
         [0041]    Numerous characteristics, advantages and embodiments of the invention have been described in detail in the foregoing description with reference to the accompanying drawings. However, the disclosure is illustrative only and the invention is not limited to the illustrated embodiments. Various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.