Patent Publication Number: US-2022211144-A1

Title: Method of manufacturing a fluid-filled chamber with a reinforcing element

Description:
CROSS-REFERENCE To RELATED APPLICATIONS 
     This non-provisional U.S. Patent Application is a divisional application and claims priority to U.S. patent application Ser. No. 12/014,974, which was filed in the U.S. Patent and Trademark Office on Jan. 16, 2008 and entitled “Fluid-Filled Chamber With A Reinforcing Element,” such prior U.S. Patent Application being entirely incorporated herein by reference. 
    
    
     BACKGROUND 
     A conventional article of athletic footwear includes two primary elements, an upper and a sole structure. The upper may be formed from a plurality of material elements (e.g., textiles, leather, and foam materials) defining a void that securely receives and positions the foot with respect to the sole structure. The sole structure is secured to a lower surface of the upper and is generally positioned to extend between the foot and the ground. In addition to attenuating ground reaction forces, the sole structure may provide traction and control various foot motions, such as pronation. Accordingly, the upper and the sole structure operate cooperatively to provide a comfortable structure that is suited for a wide variety of ambulatory activities, such as walking and running. 
     The sole structure of an article of athletic footwear generally exhibits a layered configuration that includes a comfort-enhancing insole, a resilient midsole formed from polymer foam, and a ground-contacting outsole that provides both abrasion-resistance and traction. Suitable polymer foam materials for the midsole include ethylvinylacetate or polyurethane that compress resiliently under an applied load to attenuate ground reaction forces. Conventional polymer foam materials compress resiliently, in part, due to the inclusion of a plurality of open or closed cells that define an inner volume substantially displaced by gas. Following repeated compressions, the cell structure of the polymer foam may deteriorate, thereby resulting in an decreased compressibility and decreased force attenuation characteristics of the sole structure. 
     One manner of reducing the mass of a polymer foam midsole and decreasing the effects of deterioration following repeated compressions is disclosed in U.S. Pat. No. 4,183,156 to Rudy, in which cushioning is provided by a fluid-filled chamber formed of an elastomeric material. The chamber includes a plurality of subchambers that are in fluid communication and jointly extend along a length and across a width of the footwear. The chamber may be encapsulated in a polymer foam material, as disclosed in U.S. Pat No. 4,219,945 to Rudy. The combination of the chamber and the encapsulating polymer foam material functions as a midsole. Accordingly, the upper is attached to the upper surface of the polymer foam material and an outsole is affixed to the lower surface. 
     Fluid-filled chambers suitable for footwear applications may be manufactured by a two-film technique, in which two separate sheets of elastomeric film are formed to exhibit the overall peripheral shape of the chamber. The sheets are then bonded together along their respective peripheries to form a sealed structure, and the sheets are also bonded together at predetermined interior areas to give the chamber a desired configuration. That is, interior bonds (i.e., bonds spaced inward from the periphery) provide the chamber with a predetermined shape and size upon pressurization. In order to pressurize the chamber, a nozzle or needle connected to a fluid pressure source is inserted into a fill inlet formed in the chamber. Following pressurization of the chamber, the fill inlet is sealed and the nozzle is removed. A similar procedure, referred to as thermoforming, may also be utilized, in which a heated mold forms or otherwise shapes the sheets of elastomeric film during the manufacturing process. 
     Chambers may also be manufactured by a blow-molding technique, wherein a molten or otherwise softened elastomeric material in the shape of a tube is placed in a mold having the desired overall shape and configuration of the chamber. The mold has an opening at one location through which pressurized air is provided. The pressurized air induces the liquefied elastomeric material to conform to the shape of the inner surfaces of the mold. The elastomeric material then cools, thereby forming a chamber with the desired shape and configuration. As with the two-film technique, a nozzle or needle connected to a fluid pressure source is inserted into a fill inlet formed in the chamber in order to pressurize the chamber. Following pressurization of the chamber, the fill inlet is sealed and the nozzle is removed. 
     SUMMARY 
     An article of footwear having an upper and a sole structure is disclosed. The sole structure includes a chamber and a reinforcing element. The chamber encloses a fluid, and at least a portion of an exterior surface of the chamber may be formed from a first polymer material. The reinforcing element has a first surface and an opposite second surface. The first surface may be at least partially formed from the first polymer material and bonded to the exterior surface of the chamber. The second surface is at least partially formed from a second polymer material, the first polymer material being different than the second polymer material. 
     A method of manufacturing a sole structure for an article of footwear is also disclosed. The method includes die-cutting a reinforcing element from a planar sheet of polymer material, the reinforcing element having a first surface and an opposite second surface. The reinforcing element is located within a mold such that the second surface contacts a surface of the mold. The chamber may also be shaped by drawing a polymer material against the surface of the mold and against the first surface of the reinforcing element. 
     The advantages and features of novelty characterizing aspects of the invention are pointed out with particularity in the appended claims. To gain an improved understanding of the advantages and features of novelty, however, reference may be made to the following descriptive matter and accompanying drawings that describe and illustrate various configurations and concepts related to the invention. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing Summary and the following Detailed Description will be better understood when read in conjunction with the accompanying drawings. 
         FIG. 1  is a lateral side elevational view of the article of footwear incorporating a sole component. 
         FIG. 2  is a perspective view of the sole component. 
         FIG. 3  is an exploded perspective view of the sole component. 
         FIG. 4  is a top plan view of the sole component. 
         FIG. 5  is a lateral side elevational view of the sole component. 
         FIG. 6  is a medial side elevational view of the sole component. 
         FIGS. 7A-7C  are cross-sectional views of the sole component, as defined by section lines  7 A- 7 C in  FIG. 4 . 
         FIGS. 8A-8C  are schematic perspective views depicting a method of forming a reinforcing element of the sole component. 
         FIGS. 9A and 9B  are plan views of portions of a mold for manufacturing the sole component. 
         FIGS. 10A-10D  are side elevational views depicting a method of manufacturing the sole component with the mold. 
         FIG. 11  is a perspective view of the sole component following removal from the mold. 
         FIGS. 12A-12F  are cross-sectional views corresponding with  FIG. 7A  and depicting additional configurations of the sole component. 
         FIGS. 13A-13J  are perspective views depicting additional configurations of the sole component. 
         FIG. 14  is a cross-sectional view corresponding with  FIG. 7A  and depicting an additional configuration of the sole component. 
     
    
    
     DETAILED DESCRIPTION 
     The following discussion and accompanying figures disclose various sole component configurations suitable for footwear applications. In addition, methods of manufacturing the sole components are disclosed. Concepts related to the sole components and manufacturing methods are disclosed with reference to an article of footwear having a configuration that is suitable for running. The sole components are not limited solely to footwear designed for running, and may be applied to a wide range of athletic footwear styles, including basketball shoes, cross-training shoes, walking shoes, tennis shoes, soccer shoes, and hiking boots, for example. The sole component may also be applied to footwear styles that are generally considered to be non-athletic, including dress shoes, loafers, sandals, and work boots. The concepts disclosed herein apply, therefore, to a wide variety of footwear styles. 
     An article of footwear  10  is depicted in  FIG. 1  as including an upper  11  and a sole structure  12 . Upper  11  may incorporate a plurality of material elements (e.g., textiles, foam, and leather) that are stitched or adhesively bonded together to form an interior void for securely and comfortably receiving a foot. The material elements may be selected and located with respect to upper  11  in order to selectively impart properties of durability, air-permeability, wear-resistance, flexibility, and comfort, for example. In addition, upper  11  may include a lace that is utilized in a conventional manner to modify the dimensions of the interior void, thereby securing the foot within the interior void and facilitating entry and removal of the foot from the interior void. The lace may extend through apertures in upper  11 , and a tongue portion of upper  11  may extend between the interior void and the lace. Accordingly, upper  11  may have a substantially conventional configuration. 
     Sole structure  12  is secured to upper  11  and includes a midsole  13  and an outsole  14 . A conventional midsole may be primarily formed of a polymer foam material, such as polyurethane or ethylvinylacetate, as discussed in the Background section. In contrast with the structure of the conventional midsole, midsole  13  incorporates a sole component  20 , as depicted in  FIGS. 2-7C , that includes a fluid-filled bladder  30  and an external reinforcing element  40 . Sole component  20  provides ground reaction force attenuation (i.e., cushioning) as footwear  10  impacts the ground during running, walking, or other ambulatory activities. In addition, sole component  20  may impart stability or otherwise control foot motions, such as the degree of pronation. Outsole  14  is secured to a lower surface of midsole  13  and is formed of a durable, wear-resistant material suitable for engaging the ground. Sole structure  12  may also include an insole with the configuration of a thin cushioning member that is positioned within the interior void formed by upper  11  and located to contact a plantar surface of the foot, thereby enhancing the overall comfort of footwear  10 . 
     The following discussion references various general regions of footwear  110 , upper  11 , and sole structure  12  based upon their relative locations. For reference purposes, footwear  10  may be divided into three general regions: a forefoot region  15 , a midfoot region  16 , and a heel region  17 , as depicted in  FIG. 1 . Forefoot region  15  generally includes portions of footwear  10  corresponding with the toes and the joints connecting the metatarsals with the phalanges. Midfoot region  16  generally includes portions of footwear  10  corresponding with the arch area of the foot, and heel region  17  corresponds with rear portions of the foot, including the calcaneus bone. Regions  15 - 17  are not intended to demarcate precise areas of footwear  10 . Rather, regions  15 - 17  are intended to represent general areas of footwear  10  to aid in the following discussion. In addition to footwear  10 , regions  15 - 17  may also be applied to upper  11 , sole structure  12 , and individual elements thereof. 
     Sole Component Structure 
     Sole component  20  includes an upper surface  21  and an opposite lower surface  22 . Upper surface  21  is secured to upper  11  in a conventional manner, such as adhesive bonding, and may be contoured to conform to the shape of the plantar surface of the foot. Accordingly, upper surface  21  may exhibit an elevation in heel region  17  that is greater than an elevation in forefoot region  15 , with midfoot region  16  forming a transition between the elevations. Differences in the overall thickness of sole component  20  may account for the elevation in heel region  17  that is greater than the elevation in forefoot region  15 . The overall shape of sole component  20 , as depicted in the plan view of  FIG. 4 , corresponds with a shape of a foot. Accordingly, a width of heel region  17  may be less than a width of forefoot region  15  to accommodate the varying width dimensions of the foot. Outsole  14  is also secured to lower surface  22  in a conventional manner, such as adhesive bonding. In addition to upper surface  21  and lower surface  22 , sole component  20  includes a lateral side surface  23  and an opposite medial side surface  24 . Both side surfaces  23  and  24  are exposed portions of midsole  13  and have a tapered configuration from heel region  17  to forefoot region  15  that facilitates the difference in elevation between heel region  17  and forefoot region  15 . 
     The primary elements of sole component  20  are a fluid-filled bladder  30  and an external reinforcing element  40 . Bladder  30  is formed from an upper barrier layer  31  and a lower barrier layer  32  that are substantially impermeable to a pressurized fluid contained by bladder  30 . Upper barrier layer  31  and lower barrier layer  32  are bonded together around their respective peripheries to form a peripheral bond  33  and cooperatively form a sealed chamber, in which the pressurized fluid is located. The pressurized fluid contained by bladder  30  induces an outward force upon barrier layers  31  and  32  that tends press outward upon barrier layers  31  and  32 , thereby distending barrier layers  31  and  32 . In order to restrict the degree of outwardly-directed swelling (i.e., distension) of barrier layers  31  and  32  due to the outward force of the pressurized fluid, a plurality of interior bonds  34  are formed between barrier layers  31  and  32 . Interior bonds  34  are spaced inward from side surfaces  23  and  24 , and interior bonds  34  are distributed throughout sole component  20 . In the absence of interior bonds  34 , the outward force induced by the pressurized fluid would impart a rounded or otherwise bulging configuration to bladder  30 , particularly in areas corresponding with upper surface  21  and lower surface  22 . Interior bonds  34 , however, restrict the degree of the outwardly-directed swelling or distension of barrier layers  31  and  32  and retain the intended contours of upper surface  21  and lower surface  22 . 
     Interior bonds  34  may exhibit a variety of configurations. In heel region  17 , the indentations formed by interior bonds  34  have a greater depth than in forefoot region  15  due to the increased overall thickness of sole component  20  in heel region  17 . In addition, the area of each interior bond  34  in heel region  17  is generally greater than the area of each interior bond  34  in forefoot region  15 . The position of interior bonds  34  with respect to upper surface  21  and lower surface  22  may also vary. For example, interior bonds  34  may be positioned so as to be closer to upper surface  21 , midway between surfaces  21  and  22 , or at a position that is closer to lower surface  22 . Although interior bonds  34  are depicted as being generally horizontal in  FIGS. 7A-7C , interior bonds  34  may also be inclined in some configurations of sole component  20 . 
     During running or walking, sole component  20  generally flexes or otherwise bends to accommodate the natural flexing of the foot, particularly in forefoot region  15 . In order to facilitate the flexing of sole component  20 , a pair of flexion indentations  35  are formed in bladder  30 . Each flexion indentation  35  extends laterally across a lower portion of bladder  30 . That is, flexion indentations  35  extend between side surfaces  23  and  24 , and flexion indentations  35  are formed in lower surface  22 . The location of flexion indentations  35  is also selected based upon the average location of the joints between the metatarsals and the proximal phalanges of the foot. More particularly, flexion indentations  35  are spaced such that one flexion indentation  35  is located forward of the joints between the metatarsals and the proximal phalanges and the other flexion indentation  35  is located behind the joints between the metatarsals and the proximal phalanges. The specific locations of flexion indentations  35  may be selected, for example, to be three standard deviations away from the average position of the joints between the metatarsals and the proximal phalanges, as determined through statistical anatomical data. Depending upon the specific configuration and intended use of sole component  20 , however, the location of flexion indentations  35  may vary significantly from the positions discussed above. 
     Flexion indentations  35  extend laterally (i.e., between side surfaces  23  and  24 ) across lower surface  22 . Although this configuration is suitable for footwear structured for running and a variety of other athletic activities, flexion indentations  35  may extend in a generally longitudinal direction (i.e., between forefoot region  15  and heel region  17 ) in footwear structured for athletic activities such as basketball, tennis, or cross-training. Accordingly, flexion indentations  35  may extend in a variety of directions in order to provide a defined line of flexion in sole component  20 . The figures also depict flexion indentations  35  as extending entirely across bladder  30 . In some configurations, however, flexion indentations  35  may extend only partially across bladder  30 . 
     Flexion indentations  35  define portions of sole component  20  that have a reduced thickness. Given that the degree of force necessary to bend an object is at least partially dependent upon the thickness of the object, the reduced thickness of sole component  20  in the areas of flexion indentations  35  facilitates flexing. In addition, portions of outsole  14  may extend into flexion indentations  35 , thereby forming stiffer, less compressible areas of sole structure  12  that also facilitate flexing about flexion indentations  35 . 
     Flexion indentations  35  form an indentation in lower surface  22  that corresponds with the locations of various interior bonds  34 . Referring to  FIG. 7C , a cross-section through one of flexion indentations  35  is depicted. With respect to this area, interior bonds  34  extend downward to bond upper barrier layer  31  with the portion of lower barrier layer  32  that defines the flexion indentation  35 . Some prior art bladders incorporate bonds that form flexion points, and the flexion points may form relatively hard areas due to the lack of a fluid cushion in the area of the flexion points. That is, the flexion points generally form non-cushioning areas of the prior art bladders. In contrast with the prior art flexion points, a space is formed between flexion indentations  35  and upper barrier layer  31  that includes the fluid such that flexion indentations  35  provide an advantage of simultaneously accommodating flexing and providing ground reaction force attenuation. As an alternative, no interior bonds  34  may be formed in areas that define flexion indentations  35 . 
     A variety of thermoplastic polymer materials may be utilized for bladder  30 , and particularly barrier layers  31  and  32 , including polyurethane, polyester, polyester polyurethane, and polyether polyurethane. Another suitable material for bladder  30  is a film formed from alternating layers of thermoplastic polyurethane and ethylene-vinyl alcohol copolymer, as disclosed in U.S. Pat. Nos. 5,713,141 and 5,952,065 to Mitchell et al, incorporated herein by reference. A variation upon this material wherein the center layer is formed of ethylene-vinyl alcohol copolymer; the two layers adjacent to the center layer are formed of thermoplastic polyurethane; and the outer layers are formed of a regrind material of thermoplastic polyurethane and ethylene-vinyl alcohol copolymer may also be utilized. Bladder  30  may also be formed from a flexible microlayer membrane that includes alternating layers of a gas barrier material and an elastomeric material, as disclosed in U.S. Pat. Nos. 6,082,025 and 6,127,026 to Bonk et al., both incorporated herein by reference. In addition, numerous thermoplastic urethanes may be utilized, such as PELLETHANE, a product of the Dow Chemical Company; ELASTOLLAN, a product of the BASF Corporation; and ESTANE, a product of the B.F. Goodrich Company, all of which are either ester or ether based. Still other thermoplastic urethanes based on polyesters, polyethers, polycaprolactone, and polycarbonate macrogels may be employed, and various nitrogen blocking materials may also be utilized. Additional suitable materials are disclosed in U.S. Pat. Nos. 4,183,156 and 4,219,945 to Rudy, incorporated herein by reference. Further suitable materials include thermoplastic films containing a crystalline material, as disclosed in U.S. Pat. Nos. 4,936,029 and 5,042,176 to Rudy, incorporated herein by reference, and polyurethane including a polyester polyol, as disclosed in U.S. Pat. Nos. 6,013,340; 6,203,868; and 6,321,465 to Bonk et al., also incorporated herein by reference. 
     The fluid within bladder  30  may be any of the gasses disclosed in U.S. Pat. No. 4,340,626 to Rudy, incorporated herein by reference, such as hexafluoroethane and sulfur hexafluoride, for example. The fluid may also include gasses such as pressurized octafluorapropane, nitrogen, or air. In addition to gasses, various gels or liquids may be sealed within bladder  30 . Accordingly, a variety of fluids are suitable for bladder  30 . With regard to pressure, a suitable fluid pressure is fifteen pounds per square inch, but may range from zero to thirty pounds per square inch. Accordingly, the fluid pressure within bladder  30  may be relatively high, or the fluid pressure may be at ambient pressure or at a pressure that is slightly elevated from ambient in some configurations. 
     Interior bonds  34 , as discussed above, are spaced inward from side surfaces  23  and  24  to restrict the degree of outwardly-directed swelling (i.e., distension) of barrier layers  31  and  32 , particularly in areas corresponding with upper surface  21  and lower surface  22 . Interior bonds  34  may not, however, significantly restrict the outwardly-directed swelling of side surfaces  23  and  24 . One purpose of reinforcing element  40  is, therefore, to restrict the degree of outwardly-directed swelling in side surfaces  23  and  24 , thereby retaining the intended overall shape of sole component  20 . 
     Reinforcing element  40  includes an upper portion  41 , a lower portion  42 , and a plurality of connecting portions  43 . When incorporated into sole component  20 , reinforcing element  40  exhibits a generally U-shaped configuration. Upper portion  41  is positioned at the interface of upper surface  21  and side surfaces  23  and  24 . Accordingly, upper portion  41  extends along lateral side  23  from midfoot region  16  to heel region  17 , extends around heel region  17 , and also extends along medial side  24  from midfoot region  16  to heel region  17 . Lower portion  42  is positioned at the interface of lower surface  22  and side surfaces  23  and  24 . Lower portion  42  extends through heel region  17  and may extend into rearward portions of midfoot region  16 . Connecting portions  43  extend along side surfaces  23  and  24  and also extend in a diagonal direction between upper portion  41  and lower portion  42 . More particularly, connecting portions  43  exhibit a forwardly-inclined configuration, but may also be substantially vertical or rearwardly-inclined. 
     Upper portion  41 , lower portion  42 , and connecting portions  43  collectively form a plurality of apertures that expose portions of bladder  30 . The apertures extend along side surfaces  23  and  24  in at least heel region  17 , and the shape of the apertures generally depends upon the orientations of connecting portions  43  and the configurations of upper portion  41  and lower portion  42 . The apertures formed through reinforcing element  40  are depicted as having the shape of a parallelogram, but may have a variety of shapes that include, for example, oval, hexagon, triangle, circle, or various non-geometric shapes. The shape of the apertures may affect the compression characteristics of reinforcing element  40  and may be selected, therefore, to provide particular properties to reinforcing element  40 . 
     Reinforcing element  40  restricts the degree of outwardly-directed swelling in side surfaces  23  and  24 , thereby retaining the intended overall shape of sole component  20 . That is, the pressurized fluid within bladder  30  presses outward upon barrier layers  31  and  32 , and reinforcing element  40  restrains the distension in side surfaces  23  and  24  due to the pressure of the fluid. Portions of reinforcing element  40  may, therefore, placed in tension by the pressurized fluid. Although upper portion  41  and lower portion  42  may experience such tension, connecting portions  43 , which extend along side surfaces  23  and  24 , may generally experience greater degrees of tension. Accordingly, connecting portions  43  may be placed in tension by the fluid pressure and operate to restrict the degree of outwardly-directed swelling or distension in side surfaces  23  and  24 . As shown in  FIG. 3  bladder  230  may have recessed portions in side surfaces  23  and  24  to receive reinforcing element  40  and allow closer contact between the bladder  30  and reinforcing element  40 . 
     The specific configuration of reinforcing element  40  discussed above is intended to provide an understanding of reinforcing element  40  according to one configuration, and as depicted in  FIGS. 2-7C . In further configurations, however, the configuration of reinforcing element  40  may be significantly modified. For example, upper portion  41  may extend into forefoot region  15 , may extend over portions upper surface  21 , or may extend be absent from portions of regions  16  and  17 . Similarly, lower portion  42  may extend through each of regions  15 - 17 , or lower portion  42  may extend over portions of lower surface  22 . The numbers and dimensions of connecting portions  43  may also vary significantly. Accordingly, reinforcing element  40  may have a variety of configurations. 
     Reinforcing element  40  is recessed into bladder  30  such that an outward-facing surface of reinforcing element  40  is generally flush with surfaces  21 - 24  of bladder  30 . Referring to  FIGS. 7A-7C , the outward-facing surfaces of connecting portion  43  are generally flush with side surfaces  23  and  24 . Accordingly, side surfaces  23  and  24  form recesses that receive connecting portions  43 . While the figures show squared edges where contact is made with bladder  30 , reinforcing element  40  have beveled edges. Forming the various outward-facing surfaces of reinforcing element  40  to be generally flush with surfaces  21 - 24  of bladder  30  has an advantage of providing a smooth exterior configuration to sole component  20 . In some configurations, however, the outward-facing surfaces of reinforcing element  40  may be inset or recessed into bladder  30  or may protrude outward beyond bladder  30 . 
     A die-cutting process or molding process, for example, may be utilized to form reinforcing element  40  from a diverse range of materials. Suitable materials for reinforcing element  40  include polyester, thermoset urethane, thermoplastic urethane, thermoplastic polyurethane, various nylon formulations, blends of these materials, or blends that include glass fibers. In addition, reinforcing element  40  may be formed from a high flex modulus polyether block amide, such as PEBAX, which is manufactured by the Atofina Company. Polyether block amide provides a variety of characteristics that benefit reinforcing element  40 , including high impact resistance at low temperatures, few property variations in the temperature range of minus 40 degrees Celsius to positive 80 degrees Celsius, resistance to degradation by a variety of chemicals, and low hysteresis during alternative flexure. Another suitable material for reinforcing element  40  is a polybutylene terephthalate, such as HYTREL, which is manufactured by E.I. duPont de Nemours and Company. Composite materials may also be formed by incorporating glass fibers or carbon fibers into the polymer materials discussed above in order to enhance the strength of reinforcing element  40 . 
     Although reinforcing element  40  may be formed from a single material, two or more materials may be incorporated into reinforcing element  40  in some configurations. One possibility is to make a laminate material where there are different material layers. This would allow the inside portion of reinforcing element  40  (i.e., the portion adjacent to bladder  30 ) to have one set of properties, and the outside portion of reinforcing element  40  (i.e., the portion facing outward from footwear  10 ) to have a different set of properties, depending on the materials chosen. For example, the inside portion of reinforcing element  40  could have a layer that facilitates bonding to bladder  30 , and the outside portion may be formed from a durable and wear-resistant material. More particularly, the portion of reinforcing element  40  that contacts and bonds with bladder  30  may be formed from the same material as bladder  30  to facilitate bonding, and the portion of reinforcing element  40  that faces away from bladder  30  may be formed from a different material. 
     The material forming reinforcing element  40  may exhibit a greater modulus of elasticity than the material forming bladder  30 . Whereas the material forming bladder  30  is generally flexible, the material forming reinforcing element  40  may exhibit semi-rigid or rigid properties. Comparisons between bladder  30  and reinforcing element  40  may also relate to the melting point and recrystalization temperatures. As discussed in greater detail below, materials forming bladder  30  and reinforcing element  40  are joined through a molding process. Although the melting point and recrystalization temperatures of bladder  30  and reinforcing element  40  may vary significantly, a difference in melting points that is less than 35 degrees Celsius and a difference in recrystalization temperatures that is at least 5 degrees Celsius may be beneficial to the manufacturing process. In some configurations, the ultimate tensile strength of the material forming bladder  30  may be less than the ultimate tensile strength of the material forming reinforcing element  40 . 
     Sole component  20 , as described above, provides ground reaction force attenuation as footwear  10  impacts the ground during running, walking, or other ambulatory activities. In addition, sole component  20  may impart stability or otherwise control foot motions, such as the degree of pronation. The degree of ground reaction force attenuation provided by sole component  20 , and the manner in which sole component  20  controls foot motions, are primarily determined by the configuration of both bladder  30  and reinforcing element  40  and the properties of the materials forming bladder  30  and reinforcing element  40 . Accordingly, variations in the configuration of both bladder  30  and reinforcing element  40 , and the materials utilized therein, may be employed to tune or otherwise control the ground reaction force attenuation and motion control properties of sole structure  12 . 
     As an additional matter, lower surface  22  forms an upwardly-beveled area  25  in a rear-lateral portion of sole component  20  in order to permit the footwear to smoothly roll both forward and to the medial side following heel strike. As depicted in  FIGS. 1 and 5 , the vertical thicknesses of the portions of bladder  30  and reinforcing element  40  forming lateral side surface  23  decrease in rear portions of heel region  17 . The rationale for the decreased thickness, which forms beveled area  25 , corresponds with the typical motion of the foot during running, which proceeds as follows: Initially, the heel strikes the ground, followed by the ball of the foot. As the heel leaves the ground, the foot rolls forward so that the toes make contact, and finally the entire foot leaves the ground to begin another cycle. During the time that the foot is in contact with the ground and rolling forward, it also rolls from the outside or lateral side to the inside or medial side, a process called pronation. While the foot is air-borne and preparing for another cycle, the opposite process, called supination, occurs. An advantage of beveled area  25  is to permit footwear  10  to smoothly transition from the position at heel strike, wherein only the rear-lateral portion of sole structure  12  is in contact with the ground, to the position where a substantial portion of outsole  14  is in contact with the ground. That is, beveled area  25  permits footwear  10  to smoothly roll both forward and to the medial side following heel strike. Furthermore, the positions of connecting portions  43  are selected such that a space is formed between two adjacent connecting portions  43  at the location of beveled area  25 . The space between adjacent connecting portions  43  further facilitates a smooth transition from the position at heel strike by providing greater compressibility to sole component  20  at the position of beveled area  25 . 
     Manufacturing Process for the Sole Component 
     One suitable manufacturing process for sole component  20  begins with the formation of the reinforcing element  40 . Although a variety of techniques may be utilized, reinforcing element  40  may be die-cut from sheet stock, which enhances the efficiency of manufacturing footwear  10  by eliminating the need for separate molds and molding operations. More particularly, a sheet  51  that forms reinforcing element  40  may be placed between opposing portions of a die-cutting apparatus  50 , as depicted in  FIG. 8A . As apparatus  50  compresses sheet  51 , as depicted in  FIG. 8B , edges on a cutting surface  52  of apparatus  50  having the shape of reinforcing element  40  may extend though and cut sheet  51 . Following the opening of apparatus  50 , as depicted in  FIG. 8C , reinforcing element  40  may be removed. Additional milling may be required to add beveled edges or other modifications to the basic shape. Reinforcing element  40  may then be cleansed with a detergent or alcohol, for example, in order to remove surface impurities, such as dust or fingerprints. The surface of reinforcing element  40  may also be plasma treated to enhance bonding with bladder  30 . 
     Following the formation of reinforcing element  40 , a mold is utilized to form bladder  30  and bond reinforcing element  40  to bladder  30 . The mold includes an upper mold portion  60  and a corresponding lower mold portion  70 , which are respectively depicted in  FIGS. 9A and 9B . When joined together, mold portions  60  and  70  form a cavity having dimensions substantially equal to the exterior dimensions of sole component  20 . The mold may be utilized for thermoforming bladder  30  and simultaneously bonding or otherwise securing reinforcing element  40  to the exterior of bladder  30 . In general, reinforcing element  40  is placed within upper mold portion  60  and two thermoplastic polymer sheets are placed between mold portions  60  and  70 . The thermoplastic sheets are then drawn into the contours of the mold such that at least one of the thermoplastic sheets contacts and is bonded to reinforcing element  40 . In addition, mold portions  60  and  70  compress the thermoplastic sheets together to form peripheral bond  33 . Once the thermoplastic sheets have conformed to the shape of bladder  30 , reinforcing element  40  is bonded to the thermoplastic sheets, peripheral bond  33  is formed, and bladder  30  may be pressurized with a fluid and sealed, thereby forming sole component  20 . 
     Upper mold portion  60  is depicted individually in  FIG. 9A  and includes a cavity  61  that forms the portions of sole component  20  corresponding with upper surface  21  and side surfaces  23  and  24 . A ridge  62  extends around cavity  61  and is partially responsible for forming peripheral bond  33 . In addition, a plurality of protrusions  63  extend from a surface of cavity  61  and are partially responsible for forming interior bonds  34 . Accordingly, the area of upper mold portion  60  located within the area bounded by ridge  62  forms upper surface  21  and side surfaces  23  and  24 . An extension of ridge  62  extends outward from cavity  61  and forms an L-shaped channel  64 . As discussed in greater detail below, channel  64  is utilized to form a conduit through which a fluid may be injected into sole component  20 . Another feature of upper mold portion  60  is a plurality of slot vents  65  distributed throughout cavity  61 . Vents  65  provide outlets for air as a thermoplastic sheet of polymer material is drawn into the contours of upper mold portion  60  during the formation of sole component  20 . 
     Lower mold portion  70  is depicted individually in  FIG. 9B  and includes a surface  71  that forms the portion of sole component  20  corresponding with lower surface  22 . A ridge  72  extends around surface  71  and, in combination with ridge  62 , is responsible for forming peripheral bond  33 . In addition, a plurality of protrusions  73  extend from surface  71  and join with protrusions  63  to form interior bonds  34 . Accordingly, the area of lower mold portion  70  located within the area bounded by ridge  72  forms lower surface  22 . An extension of ridge  72  extends outward from surface  71  and forms an L-shaped channel  74 . Channel  74  joins with channel  64  to form the conduit through which the fluid may be injected into sole component  20 . Another feature of lower mold portion  70  is a plurality of slot vents  75  distributed throughout surface  71 . Vents  75  provide outlets for air as a thermoplastic sheet of polymer material is drawn into the contours of lower mold portion  70  during the formation of sole component  20 . 
     The manner in which the mold is utilized to form sole component  20  from reinforcing element  40  and barrier layers  31  and  32  will now be discussed. Initially, reinforcing element  40  is bent into a U-shape, placed between mold portions  60  and  70  and then positioned within upper mold portion  60 , as depicted in  FIGS. 10A and 10B , respectively. Upper mold portion  60  forms the portions of sole component  20  corresponding with upper surface  21  and side surfaces  23  and  24 . In the configuration of sole component  20  discussed above, reinforcing element  40  is generally bonded to side surfaces  23  and  24 . Accordingly, positioning reinforcing element  40  within upper mold portion  60 , as depicted in  FIG. 10B , properly positions reinforcing element  40  with respect to the mold for the process of forming sole component  20 . A variety of techniques may be utilized to secure reinforcing element  40  within upper mold portion  60 , including a vacuum system, various seals, or non-permanent adhesive elements, for example. 
     Reinforcing element  40  may conduct heat from the mold, thereby raising the temperature of reinforcing element  40 . In some configurations, reinforcing element  40  may be heated prior to placement within the mold in order to decrease manufacturing times. Radiant heaters may also be utilized to heat surfaces of reinforcing element  40  while located within the mold. Following placement of reinforcing element  40  within upper mold portion  60 , a pair of thermoplastic polymer sheets that form barrier layers  31  and  32  are heated and then positioned between mold portions  60  and  70 , as depicted in  FIG. 10C . The temperatures to which reinforcing element  40  and barrier layers  31  and  32  are heated depends upon the specific material used. 
     Once barrier layers  31  and  32  are positioned, mold portions  60  and  70  are then located such that ridge  62  aligns with ridge  72  and the various protrusions  63  are aligned with protrusions  73 . In this position, the areas of mold portions  60  and  70  that form corresponding portions of sole component  20  are positioned on opposite sides of barrier layers  31  and  32  and are also aligned. Mold portions  60  and  70  then translate toward each other such that the mold contacts and compresses barrier layers  31  and  32 , as depicted in  FIG. 10D . 
     As the mold contacts and compresses portions of barrier layers  31  and  32 , a fluid, such as air, having a positive pressure in comparison with ambient air may be injected between barrier layers  31  and  32  to induce barrier layers  31  and  32  to respectively contact and conform to the contours of mold portions  60  and  70 . A variety of methods may be employed to pressurize the area between barrier layers  31  and  32 . For example, the fluid may be directed through the conduit formed by channels  64  and  74 . Air may also be removed from the area between barrier layers  31  and  32  and mold portions  60  and  70  through vents  65  and  75 , thereby drawing barrier layers  31  and  32  onto the surfaces of mold portions  60  and  70 . In addition, drawing barrier layers  31  and  32  onto the surfaces of mold portions  60  and  70  also draws barrier layers  31  and  32  into contact with reinforcing element  40 . Accordingly, barrier layers  31  and  32  contact and are bonded to reinforcing element  40  during this portion of the manufacturing process. 
     As the area between barrier layers  31  and  32  is pressurized and air is removed from the area between barrier layers  31  and  32  and mold portions  60  and  70 , barrier layers  31  and  32  conform to the shape of the mold and are bonded together. More specifically, barrier layers  31  and  32  stretch, bend, or otherwise conform to extend along the surfaces of cavity  61  and surface  71  and form the general shape of bladder  30 . Ridge  62  and ridge  72  also compress a linear area of barrier layers  31  and  32  to form peripheral bond  33 . In addition, barrier layers  31  and  32  conform to the shapes of protrusions  63  and  73  and are bonded together by being compressed between protrusions  63  and  73 , thereby forming interior bonds  34 . 
     Although barrier layers  31  and  32  conform to extend along the contours of cavity  81  and surface  71 , upper barrier layer  31  generally does not contact the portions of cavity  61  that are covered by reinforcing element  40 . Rather, upper barrier layer  31  contacts and is compressed against the inward-facing surface of reinforcing element  40 , thereby bonding upper barrier layer  31  to reinforcing element  40 . As barrier layers  31  and  32  conform to the shape of the mold and are bonded together, upper barrier layer  31  bends at the location of upper portion  41  to form side surfaces  23  and  24 . That is, upper barrier layer  31  extends in a generally horizontal direction to form upper surface  21 , and upper barrier layer  31  bends at the location of upper portion  41  to extend in a generally vertical direction and form side surfaces  23  and  24 . Accordingly, upper barrier layer  31  bends during the process of molding bladder  30  in order to form upper surface  21  and side surfaces  23  and  24 . 
     The thickness of upper barrier layer  31  prior to molding may be greater than the thickness of lower barrier layer  32 . Although barrier layers  31  and  32  may exhibit different thicknesses prior to molding, each of barrier layers  31  and  32  may have a substantially uniform thickness following molding. Whereas lower barrier layer  32  only forms lower surface  22 , upper barrier layer  31  forms both upper surface  21  and side surfaces  23  and  24 . The rationale for the difference in thickness is that upper barrier layer  31  may stretch to a greater degree in order to form both upper surface  21  and side surfaces  23  and  24 . Accordingly, differences between the original, pre-stretched thicknesses of barrier layers  31  and  32  compensate for thinning in upper barrier layer  31  that may occur when upper barrier layer  31  is stretched or otherwise distorted during the formation of upper surface  21  and side surfaces  23  and  24 . 
     The various outward-facing surfaces of reinforcing element  40  are generally flush with some portion of surfaces  21 - 24  of bladder  30 . As air pressurizes the area between barrier layers  31  and  32  and air is drawn out of the mold through vents  65  and  75 , both upper barrier layer  31  and reinforcing element  40  are compressed against the surface of cavity  61 . Upper barrier layer  31  contacts the inward-facing surface of reinforcing element  40 , conforms to the shape of reinforcing element  40 , extends around reinforcing element  40 , and contacts the surface of cavity  61 . In this manner, the surfaces of reinforcing element  40  are formed to be generally flush with surfaces  21 - 24  of bladder  30 . 
     Once sole component  20  is formed within the mold, mold portions  60  and  70  separate such that reinforcing element  40  and barrier layers  31  and  32  may be removed from the mold, as depicted in  FIG. 11 . The polymer materials forming reinforcing element  40  and barrier layers  31  and  32  are then permitted to cool and a pressurized fluid may be injected through the conduit formed by channels  64  and  74 . The conduit is then sealed to enclose the fluid within bladder  30 . In addition, excess portions of barrier layers  31  and  32  may be trimmed or otherwise removed from sole component  20 . The excess portions may them be recycled or reutilized to form additional thermoplastic sheets. 
     Following the formation of sole component  20 , upper  11  may be secured to upper surface  21  and outsole  14  may be secured to lower surface  22 , thereby substantially completing the manufacture of footwear  10 . The process of bonding outsole  14  to lower surface  22  may be performed following the formation of sole component  20 , as discussed above. Alternately, one or more traction elements may be located within the mold in order to form a bond between the traction elements and lower surface  22  during the thermoforming process. That is, the traction elements may be bonded to bladder  30  through a process that is similar to the process of bonding reinforcing element  40  to bladder  30 . The traction elements may be one or more elements of rubber material, for example, that are similar in configuration to a conventional outsole. The traction elements may also be additional elements of thermoplastic material that reinforce those areas of sole component  20  that contact the ground. Accordingly, the traction elements may have a variety of configurations. 
     Although thermoforming is a suitable manner of forming sole component  20 , a blow-molding process may also be utilized. In general, a suitable blow-molding process involves positioning reinforcing element  40  within at least one of two mold portions and then positioning a parison between the mold portions. The parison is a generally hollow and tubular structure of molten polymer material. In forming the parison, the molten polymer material is extruded from a die. The wall thickness of the parison may be substantially constant, or may vary around the perimeter of the parison. Accordingly, a cross-sectional view of the parison may exhibit areas of differing wall thickness. Suitable materials for the parison include the materials discussed above with respect to bladder  30 . Following placement of the parison between the mold portions, the mold portions close upon the parison and pressurized air within the parison induces the liquefied elastomeric material to contact the surfaces of the mold. In addition, closing of the mold portions and the introduction of pressurized air induces the liquefied elastomeric material to contact the surfaces of reinforcing element  40 . Air may also be evacuated from the area between the parison and the mold to further facilitate molding and bonding. Accordingly, sole component  20  may also be formed through a blow molding process wherein reinforcing element  40  is placed within the mold prior to the introduction of the molten polymer material. 
     A variety of other manufacturing techniques may also be utilized to form sole component  20 , in addition to thermoforming and blow-molding. For example, bladder  30  may be formed separate from reinforcing element  40 , and both components may be subsequently bonded together. A dual-injection technique may also be utilized to simultaneously form bladder  30  and reinforcing element  40  from separate materials. In some configurations, a first element corresponding with upper surface  21  and side surfaces  23  and  24  may be formed, a second element corresponding with lower surface  22  may be joined thereto, and a third element corresponding with reinforcing element  40  may then be secured to the exterior. Accordingly, structures having the general shape and features of sole component  20  may be formed from a variety of processes. 
     Additional Configurations of the Sole Component 
     The specific configuration of sole component  20  disclosed above is intended to provide an example of a suitable structure for a sole component. In further configurations, either of bladder  30  or reinforcing element  40  may exhibit various alternate configurations. As an example, bladder  30  may be structured to have two or more subchambers. Whereas bladder  30  is disclosed above as being a single chamber that extends along the entire length of footwear  10 , bladder  30  may have various subchambers that are pressurized differently and isolated from fluid communication with each other. Another configuration is possible wherein bladder  30  includes various indentions or depressions that receive side portions of outsole  14  and permit the side portions of outsole  14  to wrap upward and onto one or both of side surfaces  23  and  24 . An advantage of having outsole  14  wrap upward and onto one or both of side surfaces  23  and  24  is that outsole  14  protects side surfaces  23  and  24  from contacting the ground and incurring damage. Outsole  14  may not be flush in all configurations of sole component  20 . 
     Reinforcing element  40  may also exhibit various alternate configurations. As an example, reinforcing element  40  may form bridges that extend across upper surface  21  and between medial and lateral sides of upper portion  41  to enhance the stability of sole component  20 . As with other portions of reinforcing element  40 , the bridges may be recessed within indentations in bladder  30  and may be bonded to bladder  30  during the thermoforming process. Bridges may also extend across lower surface  22  or across both of surfaces  21  and  22  in any of regions  15 - 17 . Reinforcing element  40  may also form extensions that extend upward from sole component  20  to interface with areas of upper  11 . More particularly, the extensions may extend upward from reinforcing element  40  to join with upper  11 . In further configurations, a portion of reinforcing element  40  may extend upward to form a heel counter, or portions of reinforcing element  40  may extend upward to form lacing members. Another configuration is that reinforcing element  40  may be formed from two or more materials. For example, upper portion  41  may be formed from a first material, while lower portion  42  and connecting portions  43  may be formed from a second material. The first material may exhibit lesser stiffness than the second material. This configuration provides a softer material adjacent to upper  11 , which may enhance the comfort of footwear  10  and promote bonding between sole structure  12  and upper  11 . Also, the dimensions of reinforcing element  40  may be modified to change the compressibility, stability, flexibility, reaction force attenuation properties, and the torsional resistance of sole component  20 . 
     Sole component  20  may also include a supplemental layer that extends over lower surface  22 . Modifying the thickness and placement of the supplemental layer may impart specific properties as regards stability, compression, and puncture resistance to sole component  20  and allow different configurations of sole component  20  for different needs or activities. As an alternative to the supplemental layer or in addition to the supplemental layer, outsole  14  may be structured to control the degree to which surfaces of sole component  20  compress or otherwise deform. 
     The stability and compressibility properties of sole component  20  may be modified by altering the configuration of interior bonds  34 . In contrast with the generally horizontal configuration of interior bonds  34  depicted in  FIGS. 7A-7C , alternate configurations of the bonds could be inclined or otherwise sloped. For example, interior bonds  34  can be oriented to form a downward incline extending away from each of side surfaces  23  and  24 . In this configuration, the stretch in upper barrier layer  31  during the thermoforming process is lessened adjacent to side surfaces  23  and  24 . Another example involves decreasing an elevation of interior bonds  34  in a central area of sole component  20 . In this form, the stretch in upper barrier layer  31  is increased in the central area due to the configuration of interior bonds  34 . The increased stretch in this area provides upper barrier layer  31  with lesser thickness, thereby increasing the compressibility of upper barrier layer  31  in the central area. 
     The configuration of reinforcing element  40  depicted in  FIGS. 7A and 7B  is formed from a single layer of material. As discussed above, however, reinforcing element  40  may be formed from multiple layers, including various laminate materials. As an example, which is depicted in  FIG. 12A , reinforcing element  40  may be a laminate formed from two layers of equal thickness. Different thickness ratios may also be used. For example,  FIG. 12B  depicts a layered configuration wherein each of the layers have a different thickness. More particularly, a thickness of the interior layer is approximately one-half a thickness of the exterior layer. Other thickness ratios or even additional layers within the laminate are also possible. 
     An advantage to forming reinforcing element  40  with a layered configuration may be to impart different properties to the inside and outside of reinforcing element  40 . For example, the interior layer may be formed from a material that readily bonds to bladder  30 , and the exterior layer may be formed from a material that resists wear or imparts greater stability to sole component  20 . In some configurations, the interior layer may be formed from the same material as bladder  30 . When, for example, the interior layer of reinforcing element  40  and bladder  30  are both formed from the same thermoplastic polymer material, then the bonding affinity between reinforcing element  40  and bladder  30  may be increased. As another example, the exterior layer may be formed from a material (e.g., a metal or a textured or colored polymer) that imparts a particular aesthetic aspect to footwear  10 , whereas the interior layer may be a material that bonds with bladder  30 . Accordingly, forming reinforcing element  40  to have a layered configuration may be utilized to impart the properties of two different materials to sole component  20 . 
     Additionally, other portions of reinforcing element  40  may be made from differing materials. For example, as shown in  FIG. 12C , upper portion  41  may be formed from a material that exhibits lesser stiffness than a material forming lower portion  42 . This configuration provides a softer material adjacent to upper  11 , which may enhance the comfort of footwear  10  and promote bonding between sole structure  12  and upper  11 . In addition, some configurations may vary the materials throughout reinforcing element  40  in order to provide specific compression, stability, and flexibility properties to particular portions of reinforcing element  40 . An example is shown in  FIG. 12D , wherein a medial side of reinforcing element  40  is formed from a different material than a lateral side of reinforcing element  40 . An advantage to structuring sole component  20  to exhibit lesser medial compressibility may be to reduce the degree of pronation in the foot. Accordingly, forming reinforcing element  40  from different materials in various areas may be utilized to impart different properties to the various areas. 
     The compressibility of peripheral areas of sole component  20  may be selected through modifications in the overall thickness of reinforcing element  40 . As depicted in  FIG. 12E , the thickness of reinforcing element  40  may be tapered between upper portion  41  and lower portion  42  in order to control the compressibility of reinforcing element  40  or limit the degree to which reinforcing element  40  creases or buckles during compression. In addition, a central area of reinforcing element  40  may exhibit a greater thickness than portions  41  and  42  in order to impart a specific compressibility, as shown in  FIG. 12F . 
     In the configuration discussed above, reinforcing element  40  extends from heel region  17  to approximately midfoot region  16  on both the lateral and medial sides of sole structure  20 . However, reinforcing element  40  may extend through all of regions  15 - 17  or may be restricted to one or more of the regions  15 - 17 .  FIG. 13A  depicts a configuration of reinforcing element  40  that is limited only to the heel region  17 . Alternately,  FIG. 13B  depicts a configuration of reinforcing element  40  that extends through each of regions  15 - 17 . 
     Reinforcing element  40  is depicted above as having relatively large apertures with an approximate parallelogram shape. However, the size and shape of the apertures is not limited to this configuration and may be round, oval or other geometric or non-geometric shapes.  FIGS. 13C-13H  depict several possible aperture shapes, including triangular as in  FIG. 13C , hexagonal as in  FIG. 13D , circular as in  FIG. 13E , or slit-shaped as in  FIG. 13F . However, possible shapes are not limited to these and may be other geometric or non-geometric shapes. Additionally, the apertures themselves may be of any size from relatively large, as depicted in  FIGS. 1-6 , to relatively small, as in  FIG. 13G . Reinforcing element  40  may also have a mixture of aperture sizes, as shown in  FIG. 13H . In other configurations, a mixture of aperture sizes and shapes may be used, as in  FIG. 13I . In some configurations, apertures may be absent from reinforcing element  40 , as depicted in  FIG. 13J . 
     The edges of reinforcing element  40 , as depicted in  FIGS. 7A and 7B , exhibit a squared cross section. In order to facilitate closer contact between reinforcing element  40  and bladder  30 , some or all of the edges of reinforcing element  40  may be beveled, as depicted in  FIG. 14 . This may minimize stretch and potential thinning in areas where upper barrier layer  31  contacts reinforcing element  40  during the manufacturing process. 
     Conclusion 
     The preceding discussion disclosed various sole component configurations and a methods of manufacturing the sole components. In general, the sole components include a fluid-filled bladder and a reinforcing element extending around the bladder. The reinforcing element is bonded to the exterior of the bladder, and may be recessed into the bladder. In some configurations, the reinforcing element extends along the side surfaces of the bladder and between upper and lower surfaces of bladder. In manufacturing the sole component, the reinforcing element may be located within a mold, and the polymer material forming the bladder may be bonded to the reinforcing element during the molding process. 
     The present invention is disclosed above and in the accompanying drawings with reference to a variety of configurations. The purpose served by the disclosure, however, is to provide an example of the various features and concepts related to the invention, not to limit the scope of the invention. One skilled in the relevant art will recognize that numerous variations and modifications may be made to the configurations described above without departing from the scope of the present invention, as defined by the appended claims.