Patent Publication Number: US-9402441-B2

Title: Sole and article of footwear

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 14/203,133, filed Mar. 10, 2014, titled “Sole and Article of Footwear,” which is a continuation of U.S. patent application Ser. No. 12/980,961, filed Dec. 29, 2010, titled “Sole and Article of Footwear.” Each of these applications is incorporated herein in its entirety by reference thereto. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to an article of footwear having a sole. 
     2. Background Art 
     Individuals are often concerned with the amount of cushioning an article of footwear provides, as well as the aesthetic appeal of the article of footwear. This is true for articles of footwear worn for non-performance activities, such as a leisurely stroll, and for performance activities, such as running, because throughout the course of an average day, the feet and legs of an individual are subjected to substantial impact forces. When an article of footwear contacts a surface, considerable forces may act on the article of footwear and, correspondingly, the wearer&#39;s foot. The sole functions, in part, to provide cushioning to the wearer&#39;s foot and to protect it from these forces. To achieve adequate cushioning, many footwear soles are relatively thick and heavy. When sole size and/or weight are reduced to achieve other performance goals, protection of the wearer&#39;s foot is often compromised. 
     The human foot is a complex and remarkable piece of machinery, capable of withstanding and dissipating many impact forces. The natural padding of fat at the heel and forefoot, as well as the flexibility of the arch, help to cushion the foot. Although the human foot possesses natural cushioning and rebounding characteristics, the foot alone is incapable of effectively overcoming many of the forces encountered during every day activity. Unless an individual is wearing shoes which provide proper cushioning and support, the soreness and fatigue associated with every day activity is more acute, and its onset accelerated. The discomfort for the wearer that results may diminish the incentive for further activity. Equally important, inadequately cushioned footwear can lead to injuries such as blisters; muscle, tendon and ligament damage; and bone stress fractures. Improper footwear can also lead to other ailments, including back pain. 
     Proper footwear should complement the natural functionality of the foot, in part, by incorporating a sole which absorbs shocks. Therefore, a continuing need exists for innovations in providing cushioning and support to articles of footwear. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of the present invention relate to a sole and an article of footwear having a sole. In one embodiment, the article of footwear may comprise: an upper; an outer midsole having a base coupled to the upper, and a rim portion extending from the periphery of the base, wherein the rim portion defines a plurality of spaced apart gaps; and an inner midsole disposed interiorly to the rim portion, wherein a portion of the inner midsole is disposed in at least one gap. The inner midsole may be discrete from the outer midsole. 
     In one embodiment, a sole for an article of footwear comprises: a base having a medial side, a lateral side, and a periphery; a rim portion extending from the periphery of the base, the rim portion having a top surface and a bottom surface, and wherein the rim portion undulates to define a plurality of spaced apart gaps in the top surface and a plurality of spaced apart gaps in the bottom surface; and a core member disposed interiorly to the rim portion, the core member having a top surface and a bottom surface, and wherein the core member undulates to define a plurality of spaced apart gaps in the top surface and a plurality of spaced apart gaps in the bottom surface. 
     In yet another embodiment, a sole for an article of footwear comprises: a foam midsole having a base and an undulating rim portion extending from a periphery of the base along a medial side and a lateral side; and a core member disposed interiorly to the undulating rim portion, wherein the midsole material has at least one different characteristic than the core member material. The different material characteristic may include at least one of hardness, density, and modulus. 
     In another embodiment, an article of footwear may comprise: an upper; an outer midsole having a base coupled to the upper, a forefoot pod, a heel pod, and a plurality of outer protrusions extending from the periphery of the base between the forefoot pod and the heel pod; and an inner midsole disposed interiorly to the outer protrusions, the inner midsole having a plurality of bars each extending a portion of the width of the base between the outer protrusions. 
     In one embodiment, a sole for an article of footwear comprises: a base having a periphery; a plurality of outer protrusions extending from the periphery of the base; and a core member disposed interiorly to the outer protrusions and having a plurality of horizontally elongated protrusions extending horizontally across a portion of the width of the base between the outer protrusions. 
     In still another embodiment, a sole for an article of footwear comprises: a base having a periphery, a heel end, and a forefoot end; a plurality of outer protrusions extending from the medial and lateral periphery of the base at an angle toward the heel end, wherein a gap is disposed between adjacent outer protrusions; and a core member disposed between the medially and laterally disposed outer protrusions and having a plurality of substantially rectangular protrusions extending across a portion of the width of the base between the outer protrusions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. 
         FIG. 1  is a medial side perspective view of a sole according to an embodiment of the present invention. 
         FIG. 2  is a lateral side view of an article of footwear having the sole of  FIG. 1  according to an embodiment of the present invention. 
         FIG. 3  is a bottom view of an outer midsole according to an embodiment of the present invention. 
         FIG. 4  is a medial side perspective view of an inner midsole according to an embodiment of the present invention. 
         FIG. 5  is a bottom view of an article of footwear having the sole of  FIG. 1  according to an embodiment of the present invention. 
         FIG. 6  is a medial side view of an article of footwear having the sole of  FIG. 1  according to an embodiment of the present invention. 
         FIG. 7  is a bottom view of an article of footwear according to an embodiment of the present invention. 
         FIG. 8  is a partial close-up medial side view of the article of footwear of  FIG. 7  according to an embodiment of the present invention. 
         FIG. 9  is a partial close-up medial side view of an article of footwear according to an embodiment of the present invention. 
         FIG. 10  is a side view of a plate and sole according to an embodiment of the present invention. 
         FIG. 11  is a perspective view of a sole according to an embodiment of the present invention. 
         FIG. 12  is a exploded bottom perspective view of the sole of  FIG. 11  according to an embodiment of the present invention. 
         FIG. 13  is a side view of an article of footwear according to an embodiment of the present invention. 
         FIG. 14  is a bottom view of the article of footwear of  FIG. 13  according to an embodiment of the present invention. 
         FIG. 15  is a partial close-up view of the article of footwear of  FIG. 13  according to an embodiment of the present invention. 
         FIG. 16  is a bottom view of a sole according to an embodiment of the present invention. 
         FIG. 17  is a bottom view of an outer midsole of the sole of  FIG. 16  according to an embodiment of the present invention. 
         FIG. 18  is a bottom view of an inner midsole of the sole of  FIG. 16  according to an embodiment of the present invention. 
         FIG. 19  is a bottom view of a sole according to an embodiment of the present invention. 
         FIG. 20  is a bottom view of an outer midsole of the sole of  FIG. 19  according to an embodiment of the present invention. 
         FIG. 21  is a bottom view of an inner midsole of the sole of  FIG. 19  according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described in detail with reference to embodiments thereof as illustrated in the accompanying drawings, in which like reference numerals are used to indicate identical or functionally similar elements. References to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
     The following examples are illustrative, but not limiting, of the present invention. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the field, and which would be apparent to those skilled in the art, are within the spirit and scope of the invention. 
     Embodiments of the present invention include an article of footwear  10  having an upper  20  and a sole  30  attached to the upper  20 . With reference to  FIGS. 1 and 2 , the sole  30  includes an outer midsole  100  and an inner midsole  200 , and generally includes a heel region  32 , a midfoot region  34 , and a forefoot region  36 , and a medial side  31  and a lateral side  33 . The outer midsole  100  and the inner midsole  200  may be shaped and sized to provide a desired combination of cushioning, stability, and ride characteristics to the article of footwear. The term “ride” may be used herein in describing some embodiments as an indication of the sense of smoothness or flow occurring during a gait cycle including heel strike, midfoot stance, toe off, and the transitions between these stages. Some embodiments of the present invention may provide particular ride features including, but not limited to, appropriate control of pronation and supination, support of natural movement, support of unconstrained or less constrained movement, appropriate management of rates of change and transition, and combinations thereof. 
     In one embodiment, the outer midsole  100  includes a base  110  and a rim portion  120  extending from the base  110 . The base  110  may be attached to the upper  20  by adhesive bonding, welding, or other suitable technique, and may include a top surface  111  generally shaped to accommodate the contours of the foot. The rim portion  120  defines a plurality of spaced apart gaps  122 . In one embodiment, the rim portion  120  may include a top surface  121  and a bottom surface  123 , and the rim portion  120  may undulate such that one or more of the plurality of gaps  122  may be formed in the top surface  121  and/or one or more of the gaps  122  may be formed in the bottom surface  123 . In this manner, the rim portion  120  may be substantially sinusoidal. In one embodiment, the area between adjacent gaps  122  formed in the top surface  121  may be described as a peak, and the area between adjacent gaps  122  formed in the bottom surface  123  may be described as a trough. The rim portion  120  may include an outer sidewall  124  and, as shown in  FIG. 3 , an inner sidewall  125 , and all or a portion of the outer sidewall  124  and/or the inner sidewall  125  may be substantially sinusoidal. In some embodiments, as shown, for example, in  FIG. 5 , portions of the outer sidewall  124  may angle inwardly and/or outwardly from the sole  30 . 
     In one embodiment, at least a portion of the rim portion  120  may extend from all or a portion of the perimeter  112  of the base  110 . In one embodiment, the rim portion  120  extends from the perimeter  112  of the base  110  from the forefoot region  36  to the heel region  32 , as shown, for example, in  FIG. 1 . In other embodiments, the rim portion  120  extends from the midfoot region  34  to the heel region  32 , or from the forefoot region  36  to the midfoot region  34 . In one embodiment, the rim portion  120  may extend from the base  110  along the entire length of the base. In one embodiment, the rim portion  120  extends from the perimeter  112  of the base  110  on the medial side  31  and the lateral  33  side of the sole  30 . In other embodiments, the rim portion  120  may only extend along the medial side  31  or the lateral side  33 . 
     With reference to  FIG. 3 , a plurality of voids  114  may be formed in the base  110 . The outer midsole  100  may also include larger areas, such as, for example, a toe pod  117 , a midfoot pod  116 , and a heel pod  115 , and a plurality of voids  114  may be disposed therebetween. In one embodiment, one or more of the voids  114  may be disposed interiorly to the rim portion  120 . The voids  114  may be varied in size and shape, or, in one embodiment, may be uniform. In one embodiment, the voids  114  may have a generally quadrilateral (e.g., rectangular) shape. The voids  114  may be formed at an angle relative to the longitudinal axis of the base  110 . For example, as shown in  FIG. 3 , one or more forward most voids  114  may be disposed at an angle with the medial side closer to the forefoot region  36 , and one or more rear most voids  114  may be disposed at an angle with the lateral side closer to the forefoot region  36 . The angle of the voids  114  may vary depending on the orientation of the inner midsole  200  which may be disposed in the voids  114 , as discussed below. In another embodiment, one or more voids  114  may be formed substantially perpendicular relative to the longitudinal axis of the base  110 . 
     One or more of the voids  114  may be disposed adjacent to a gap  122 , and, in one embodiment, may bleed into an adjacent gap  122 . For example, as shown in  FIG. 3 , a void  114  may bleed into an adjacent gap  122  formed in the top surface  121  of the rim portion  120 . In one embodiment, at least a portion of the outer sidewall  124  of the rim portion  120  may be formed along an outer edge  35  of the base. In one embodiment, at least a portion of the outer sidewall  124  may be flush with the outer edge  35  of the base  110 . In other embodiments, the outer sidewall  124  may be disposed inwardly from the outer edge  35 , or may extend outwardly beyond the outer edge  35 . 
     With reference to  FIGS. 1 and 4 , all or a portion of the inner midsole  200  is disposed interiorly to the rim portion  120 . The inner midsole  200  may include a top surface  221  and a bottom surface  223 . All or a portion of the top surface  221  may be generally shaped to conform with the contours of the top surface  111  of the base  110  and/or shaped to accommodate the foot. 
     The size and shape of the inner midsole  200  may be varied depending on the desired characteristics of the sole. In one embodiment, as shown in  FIG. 4 , the inner midsole  200  defines a plurality of spaced apart gaps  222 . In one embodiment, the inner midsole  200  may include a top surface  221  and a bottom surface  223 . In one embodiment, the inner midsole  200  may undulate such that one or more of the plurality of gaps  222  may be formed in the top surface  221  and/or one or more of the gaps  222  may be formed in the bottom surface  223 . In this manner, the inner midsole  200  may be substantially sinusoidal. In one embodiment, the area between adjacent gaps  222  formed in the top surface  221  may be described as a peak, and the area between adjacent gaps  222  formed in the bottom surface  223  may be described as a trough. In one embodiment, the inner midsole  200  may include an outer sidewall  224  and all or a portion of the sidewall  224  may be substantially sinusoidal. 
     In one embodiment, the top surface  221  between adjacent gaps  222  (i.e., peaks) may have a generally quadrilateral (e.g., rectangular) shape, as shown, for example, in  FIG. 4 . The peaks may be formed at an angle relative to the longitudinal axis of the inner midsole  200 . For example, as shown in  FIG. 4 , one or more forward most peaks may be disposed at an angle with the medial side closer to the forefoot region  36 , and one or more rear most peaks may be disposed at an angle with the lateral side closer to the forefoot region  36 . The angle of the inner midsole generally may vary. In another embodiment, the peaks may be formed substantially perpendicular relative to the longitudinal axis of the inner midsole  200 . 
     The inner midsole  200  and the outer midsole  100  comprise material for providing the desired cushioning, ride, and stability of the sole  30 . Suitable material for the inner midsole  200  and the outer midsole  100  may include, but is not limited to, foam and thermoplastic polyurethane. When the inner midsole  200  and/or the outer midsole  100  are a foam, the foam may comprise, for example, ethyl vinyl acetate (EVA) based foam or polyurethane (PU) based foam and the foam may be an open-cell foam or a closed-cell foam. In other embodiments, the inner midsole  200  and/or the outer midsole  100  may comprise elastomers, thermoplastic elastomers (TPE), foam-like plastic, and gel-like plastics. Suitable materials for inner midsole  200  and/or outer midsole  100  may be obtained from, for example, Eclipse Polymers Co., Sung Shin Co., and Korea Fine Chemical Co. 
     In one embodiment, the inner midsole  200  and the outer midsole  100  may comprise different materials to provide different characteristics to different portions of the sole  30 . In one embodiment, the inner midsole  200  and the outer midsole  100  may have different hardness characteristics. For example, in one embodiment it may be desirable for the sole  30  to be stiffer near the periphery of the sole to provide required lateral and/or medial stability. In this manner, all or a portion of the rim portion  120  may comprise a harder material than inner midsole  200 . 
     In some embodiments, the material hardness of the outer midsole  100  (e.g., the base  110  and/or the rim portion  120 ) may range from about 50 Asker C to about 70 Shore D, for example, about 60C to about 75C or about 65C to about 70C. In some embodiments, the material hardness of the inner midsole  200  may range from about 20C to about 70C, for example, about 40C to about 60C or about 50C to about 55C. In some embodiments, the material hardness of the outer midsole  100  may range from about 50 Asker C to about 70 Shore D and the material hardness of the inner midsole  200  may range from about 20C to about 70C, for example, the material hardness of the outer midsole  100  may range from about 60C to about 75C and the material hardness of the inner midsole  200  may range from about 40C to about 60C. 
     In some embodiments, the material density of the outer midsole  100  may be about 0.3 to about 0.5 grams/cubic centimeter (g/cm 3 ), for example, such as about 0.35 to about 0.4 g/cm 3 . In some embodiments, the material density of the inner midsole  200  may be about 0.25 to about 0.5 g/cm 3 , for example, such as about 0.25 to about 0.3 g/cm 3 . In some embodiments, the material density of the outer midsole  100  is higher than the material density of the inner midsole  200 . For example, in one embodiment, the material density of the outer midsole  100  is about 0.35 to about 0.4 g/cm 3  and the material density of the inner midsole  200  is about 0.25 to about 0.3 g/cm 3 . In other embodiments, the material density of the outer midsole  100  is lower than, or even equal to, the material density of the inner midsole  200 . 
     In some embodiments, the outer midsole  100  material has a higher modulus than that of the inner midsole  200  material. In other embodiments, the outer midsole  100  material has a modulus that is lower, or even equal to, that of the inner midsole  200  material. 
     The inner midsole  200  and the outer midsole  100  may be formed using suitable techniques, including, but not limited to, injection molding, blow molding, compression molding, and rotational molding. The inner midsole  200  and the outer midsole  100  may be discrete components that are formed separately and attached. In one embodiment, the inner midsole  200  may be attached to the outer midsole  100  by adhesive bonding, welding, or other suitable technique. For example, the inner midsole  200  may be attached to the base  110  and/or the rim portion  120 . In another embodiment, the inner midsole  200  and the outer midsole  100  may be monolithic and may be integrally formed as a unitary structure. For example, the inner midsole  200  and the outer midsole  100  may be co-molded and thereby formed together simultaneously. In one embodiment, as shown in  FIG. 3 , the base  110  and the rim portion  120  may define a cavity  127  for receiving the inner midsole  200 . 
     The physical connection, interrelation or “overlap” between the outer midsole  100  and the inner midsole  200  may be varied to provide the desired characteristics for the sole  30 . In one embodiment, a portion of the inner midsole  200  may be disposed in one or more voids  114  in the base  110 . With reference to  FIGS. 1 and 4 , a portion of the inner midsole  200  between adjacent gaps  222  in the top surface  221  (i.e., a peak) may be disposed in one or more voids  114  in the base  110 . In this manner, portions of the base  110  in between voids  114  may be disposed in gaps  222  in the top surface  221  and the inner midsole  200  may be referred to as being bottom loaded. In another embodiment, as shown, for example, in  FIGS. 11 and 12 , a portion of the inner midsole  200  between adjacent gaps  222  in the bottom surface  223  (i.e., a trough) may extend through one or more voids  114  in the base  110 . In some embodiments, these portions of the inner midsole  200  may contact the ground during use. The portion of the inner midsole  200  between adjacent gaps  222  in the top surface  221  (i.e., one or more peaks) may be disposed above the base  110 . In this manner, portions of the base  110  in between voids  114  may be disposed in gaps  222  in the bottom surface  223  and the inner midsole  200  may be referred to as being top loaded. In one embodiment, the inner midsole  200  may fit snugly within the one or more voids  114  such that adhesive is not required. In other embodiments, the inner midsole  200  may be directly attached to the upper  20 . 
     In one embodiment, a portion of the inner midsole  200  is disposed in one or more of the gaps  122  formed in the rim portion  120 . The inner midsole  200  may be disposed in a gap  122  defined by the top surface  111  and/or a gap  122  defined by the bottom surface  123 . For example, with reference to  FIGS. 1, 2, and 4 , an extension  225  of the inner midsole may be disposed in the rearmost gap  122  in the rim portion  120 . In this manner, the inner midsole may provide increased stability to the rim portion  120  at a particular location of the outer midsole and/or may provide better overall ride of the footwear. In one embodiment, the extension  225  may be disposed in a gap  122  on the medial side  31  or the lateral side  33  of the sole. In one embodiment, as shown in  FIGS. 1 and 5 , the extension  225  may be disposed in a gap  122  on both the medial side  31  and the lateral side  33  of the sole. In some embodiments, the inner midsole  200  may be disposed in more than one gap  122 . In one embodiment, the inner midsole  200  may be disposed in the two rearmost gaps  122 . In another embodiment, as shown, for example, in  FIGS. 7 and 8 , the inner midsole  200  may include multiple extensions  225  such that the inner midsole may be disposed in the three rearmost gaps  122 . Other variations may be provided, including, but not limited to, the inner midsole  200  disposed in one or more gaps  122  in the heel region  32 , midfoot region  34 , and the forefoot portion  36 . In other embodiments, a portion of the outer midsole  100  may be disposed in one or more of the gaps  222  formed in the inner midsole  200 . In this manner, the outer midsole  100  may provide increased stability to a particular inner portion of the sole  30  and/or may provide better overall ride of the footwear. 
     The amount that the inner midsole  200  extends into the gap  122  may be varied depending on the desired characteristics of the sole. In one embodiment, the inner midsole may be disposed in the gap  122  such that the inner midsole is substantially flush with the outer sidewall  124  of the outer midsole  100 , as shown, for example, in  FIG. 2 . In other embodiments, the inner midsole may be disposed in the gap  122  such that the inner midsole extends only partially within the gap  122 . 
     The size and shape of the gaps  122  in the rim portion  120  and the gaps  222  in the inner midsole  200  may be varied to provide the desired characteristics for the sole  30 . In one embodiment, as shown for example in  FIG. 1 , the width and depth of gaps  122  may vary along the length of the rim portion  120 . For example, gaps  122  may be wider and deeper in the heel region  32 , and generally become more narrow and shallow toward the forefoot region  36 . In this manner, the rim portion  120  may deform more, and, thereby, provide increased cushioning in the heel region  32 , where greater impact forces may be experienced during the gait cycle, and/or may provide better overall ride of the footwear. In one embodiment, as shown in  FIGS. 1 and 6 , a larger midfoot gap  128  may be provided in the midfoot region  34  on the medial side  31  of the rim portion  120 . The midfoot gap  128  may be formed in the bottom surface  123 , and, in some embodiments, may allow for better deformation of the outer midsole  100  during gait cycle transitions and/or may provide weight saving to the article of footwear  10  because this area of the sole may not be subject to the higher forces to which the heel and toe areas may be subject. In one embodiment, as shown in  FIG. 4 , the inner midsole  200  may include a corresponding larger midfoot gap  228  defined by the top surface  221 . 
     In one embodiment, gaps  122  and  222  may be substantially U-shaped such that each gap is more narrow and rounded at the closed end and wider at the open end. The embodiments described above are merely exemplary and gaps  122  and gaps  222  may have any combination of shapes as would be apparent to one of ordinary skill in the art. For example, in one embodiment rim portion  120  and/or inner midsole  200  may include a combination of v-shaped and omega-shaped gaps. 
     In some embodiments, the material used for the outer midsole  200  and the inner midsole  100  may be varied and may determine the desired shape, width and spacing of the gaps  122  and gaps  222 . For example, in one embodiment if a harder material is used for the rim portion  120 , the gaps  122  may be spaced further apart. Other geometries of the outer midsole  100  and the inner midsole  200  may be altered depending on the hardness, the density, or the modulus of the materials used. For example, the height of the undulations in the sole  30  (e.g., peaks and troughs); the height of projections extending from the sole  30 ; whether and how the projections/undulations are connected or joined; the width or cross-sectional areas of projections/undulations (e.g., at the point of attachment to the base or at the ground contacting surface); and the number of projections/undulations. In some embodiments, the thickness (or cross sectional area) of the rim portion  120  and/or the inner midsole  200  may vary. For example, the undulations in the outer midsole  100  and the inner midsole  200  may be thicker on the medial side to influence stability or ride, as shown, for example, in  FIGS. 5 and 6 . 
     As best shown in  FIG. 5 , in one embodiment a space  126  is disposed between the inner midsole  200  and the outer midsole  100 . For example, the space  126  may be disposed between the sidewall  224  of the inner midsole  200  and the inner sidewall  125  of the rim portion  120 . In one embodiment, the space  126  may be narrower proximate the base  110  and wider at the ground contacting end such that the space resembles an upside-down V-shaped notch. In other embodiments, the space  126  may have a uniform width at a particular location in the sole  30 . The space  126  may allow movement of the rim portion  120  relative to the inner midsole  200 , which may provide for the desired cushioning and feel of the sole  30  to the user during a gait cycle. For example, the space  126  may allow the rim portion  120  at the location of the space to splay in multiple directions—outwardly from and inwardly toward the sole—when under a compressive load during use, and thereby allow for a tailored cushioning effect (e.g., allow for increased cushioning) and/or provide better overall ride of the footwear. In one embodiment, the space  126  may be disposed along all or a portion of the length of the sidewall  224  of the inner midsole  200  on one or both of the medial side  31  and the lateral side  33  of the sole depending on the desired characteristics. In one embodiment, the width of the space  126  may vary along the sidewall for desired characteristics. For example, along the medial side  31  of the sole where less movement of the rim portion  120  relative to the inner midsole  200  may be desired to provide increased stability or improved ride, the width of the space may be narrower than at other locations of the sole  30 . In other embodiments, portions of the sidewall  224  of the inner midsole  200  and portions of the inner sidewall  125  of the rim portion  120  may be made to directly abut each other. 
     In one embodiment, a portion of one or more gaps  122  may be filled or partially filled with the outer midsole  100 . For example, as shown in  FIG. 9 , one or more gaps  122  on the medial side  31  in the heel region  32  may be filled to provide the desired cushioning and stability. The gaps  122  may be filled from the upper closed portion of the gap downward or may be filled from the lower open end upward. Similarly, in one embodiment, one or more gaps  222  may be filled or partially filled with the inner midsole  200 . 
     In one embodiment, as shown in  FIG. 10 , the article of footwear  10  may further include a plate  140  disposed between the outer midsole  100  and the upper  20 . The plate  140  may include an upper surface  142  generally shaped to accommodate the foot and a lower surface  144 . The lower surface  144  may be shaped to receive the base  110  and/or the top surface  221  of the inner midsole  200 . The plate  140  may comprise any suitable thermoplastic material or composite material and, in some embodiments, may be manufactured through molding or lay-up. In other embodiments, plate  140  may be a molded foam, such as a compression molded foam, TPU, or Pebax®. In one embodiment, the plate  140  may be made of a stiffer material than the sole  30 . In one embodiment, the plate  140  may be formed separately from outer midsole  100  and/or inner midsole  200  and then attached to the sole  30  through adhesive bonding, welding, or other suitable techniques as would be apparent to one of ordinary skill in the art. For example, the plate  140  may be attached to the base  110 , the rim portion  120 , and/or the inner midsole  200 . In another embodiment, the plate  140  and one or both of the outer midsole  100  and the inner midsole  200  may be co-molded and thereby formed together simultaneously. In one embodiment, the plate  140  may be a full foot plate such that it substantially covers the top surface of the sole  30 . In other embodiments, the plate  140  may be a partial foot plate accommodating portions of the heel region  32 , the midfoot region  34 , and the forefoot region  36 , and combinations thereof For example, the plate  140  may accommodate the heel region  32  and the midfoot region  34 , or the heel region  32  only. In some embodiments, the plate  140  may include hinges (e.g., natural hinges), scoring, grooves, or cuts (e.g., cuts that extend (lateral-to-medial or medial-to-lateral) partially across the plate) to allow for movement of the plate  140 . 
     All or a portion of one or both of the inner midsole  200  and the outer midsole  100  may contact the ground during use of the article of footwear  10 . In one embodiment, a portion of the bottom surface  123  of the rim portion  120  in between adjacent gaps  122  may contact the ground, and a portion of the bottom surface  223  of the inner midsole  200  between adjacent gaps  222  may contact the ground. The ground contacting portions of the outer midsole  100  and the inner midsole  200  may be substantially flat, or may be slightly rounded or crowned. In embodiments of the present invention, as shown in  FIGS. 5 and 7 , an outsole  130  may be disposed on all or a portion of the outer midsole  100  and/or the inner midsole  200 . In some embodiments, outsole  130  may be disposed on areas of the sole  30  subjected to heavy wear, including but not limited to, a toe area, a midfoot area corresponding to the ball of the foot, and a heel portion. The outsole  130  may comprise a wear resistant material, including, but not limited to, synthetic or natural rubber, polyurethane (e.g., thermoplastic polyurethane (TPU)), foam (e.g., a wear-resistant foam), or a combination thereof, or any suitable material typically utilized for an outsole to provide additional traction and wear resistance. In one embodiment, the outsole  130  may comprise a high abrasion rubber compound, such as, for example, Shin Ho KA2BF. In some embodiments, the sole  30  and the outsole  130  may be formed of the same or different material. In one embodiment, the outsole  130  may be formed separately from the inner midsole  200  and/or the outer midsole  100  and attached, or they may be molded together to form a unitary structure. 
     In embodiments of the present invention, a portion of the inner midsole  200  may be visible from the exterior of the article of footwear  10  through a gap  122 . For example, as shown in  FIG. 2 , a portion of the sidewall  224  may be visible through one or more gaps  122 . In one embodiment of the present invention in which the outer midsole  100  and the inner midsole  200  are substantially sinusoidal, the outer and inner midsoles may be substantially out of phase such that a gap  122  defined by the upper surface  121  of the rim portion  120  aligns with a gap  222  defined by the bottom surface  223  of the inner midsole  200 . In this manner, a peak defined by the outer midsole  100  may align with a trough defined by the inner midsole  200 . 
     Embodiments of the present invention will now be described with reference to  FIGS. 13-21 , in which like reference numerals refer to like elements. The embodiments of  FIGS. 13-21  may include some or all of the features of other embodiments of the present invention described herein. With reference to  FIGS. 13-15 , the sole  30  includes an outer midsole  300  and an inner midsole  400 , and generally includes a heel region  32 , a midfoot region  34 , and a forefoot region  36 , and a medial side  31  and a lateral side  33 . The outer midsole  300  and the inner midsole  400  may be shaped and sized to provide a desired combination of cushioning, stability, and ride characteristics to the article of footwear. 
     In one embodiment, the outer midsole  300  includes a base  310  and a rim portion defined by a plurality of outer protrusions  320  extending from the base  310 . The base  310  may be attached to the upper by adhesive bonding, welding, or other suitable technique. Some or all of the outer protrusions  320  may be disposed about all or a portion of the perimeter  311  of the base  310 . In this manner, the outer protrusions  320  may be formed along the outer edge  35  of the base  310 . For example, as shown best in  FIG. 14 , a plurality of outer protrusions  320  may be formed about the perimeter  311  of the base  310  on the medial side  31  of sole  30  and the lateral side  33  of the sole. In one embodiment, the outer sidewall  323  of one or more outer protrusions  320  may be flush with the outer edge  35  of the base  310 . In other embodiments, the outer sidewall  323  may be disposed inwardly from the outer edge  35 , or may extend outwardly beyond the outer edge  35 . 
     In one embodiment, one or more outer protrusions  320  are columnar in shape. For example, the protrusions generally may have four sides, which may include outer sidewall  323 , that extend downwardly from the base  310 , and may have a generally square or quadrilateral cross-section, as shown, for example, in  FIG. 14 . As such, in one embodiment the bottom surface  321  of a protrusion  320  may be generally square or quadrilateral in shape. In other embodiments, the outer protrusions  320  may have other cross-sectional shapes, including, but not limited to, round, circular, oval, triangular, elliptical, hexagonal, and polygonal. In one embodiment, one or more outer protrusions  320  may have different shapes. The outer protrusions  320  may also be differently sized. For example, as shown in  FIG. 13 , the outer midsole  300  may include longer outer protrusions  320  toward the heel region  32  of the sole, and shorter outer protrusions  320  toward the forefoot region  36 . In other embodiments, one or more outer protrusions  320  may be wider at a portion of the sole  30  to provide desired cushioning and stability. For example, outer protrusions  320  in the heel region  32  and the forefoot region  36  may be wider than protrusions in the midfoot region  34 . In another embodiment, outer protrusions  320  may be wider on the medial side  31  or lateral side  33  of the sole to provide desired stability and/or better overall ride. 
     The outer midsole  300  may define a plurality of spaced apart gaps  322  such that one or more adjacent outer protrusions  320  may be spaced apart by gaps  322 . In one embodiment, the gaps  322  are each of the same size such that the perimeter protrusions  320  are evenly spaced. In alternative embodiments, the width of some or all of the gaps  322  may be different. For example, in embodiments in which one or more outer protrusions  320  may be wider at a portion of the sole  30  to provide desired cushioning and stability, gaps  322  may correspondingly be narrower. In one embodiment, gaps  322  may generally have the same width as an adjacent outer protrusion  320 . In other embodiments, gaps  322  may be wider or narrower than the protrusions. For example, in some embodiments, gaps  322  are at least about one-quarter of the width of one or both of adjacent protrusions. In other specific embodiments, gaps  322  are at least about one-half of the width of one or both of adjacent protrusions. In yet other embodiments, gaps  322  are at least about the same as, at least about 1.25 times, or at least about 1.5 times the width of one or both of adjacent protrusions. 
     In one embodiment, the gaps  322  may extend in between adjacent protrusions from the bottom surface  321  of the protrusions  320  to the base  310 . In other embodiments, a portion of the gap  322  may be filled. For example, material may be disposed between adjacent protrusions such that the gap  322  between them extends only partially up from the bottom surface  321 . In some embodiments, the depths of a majority of the gaps  322  (e.g., substantially all of the gaps) are at least as deep (from ground contact surface to base) as each of those gaps are wide between adjacent projections. In other embodiments, the majority of the gaps  322  located in a heel region (e.g., substantially all of the gaps in a heel region) are at least as deep as those gaps are wide. For example, in one embodiment, the majority of the gaps  322  located in a heel region (e.g., substantially all of the gaps in a heel region) are at least about 1.5 to about 2 times as deep as those gaps are wide. In some embodiments, the depth of the gaps increases progressively from the toe region to the heel region. For example, in one specific embodiment, at least one gap in a toe region is at least as deep as that gap is wide; at least one gap located in the heel region is at least about 1.5 to about 2 times as deep as that gap is wide; and a plurality of gaps between the at least one gap in the toe region and the at least one gap located in the heel region are at least about 1 to about 2 times as deep as those gaps are wide. 
     In one embodiment, outer midsole  300  may include a toe pod  312  disposed at the forward end of the forefoot region  36  of the sole and/or a heel pod  314  disposed at the rear end of the heel region  32 . The toe pod  312  may include a generally curved front edge  313  that may conform to the contour of the front or toe of the sole  30 . Similarly, the heel pod  314  may include a generally curved rear edge  315  that may conform to the contour of the rear or heel of the sole  30 . During the gait cycle, the heel pod  314  may provide cushioning to the wearer during a heel strike event with the ground, and the toe pod  312  may provide cushioning during a toe-off event. In one embodiment, a plurality of outer protrusions  320  may be disposed between the heel pod  314  and the toe pod  312  on the medial  31  and/or lateral side  33  of the sole  30 . As shown in  FIG. 14 , in one embodiment the heel pod  314  may be integrally formed with one or more protrusions  320 . In one embodiment, as shown in  FIGS. 16 and 18 , the heel pod  314  may be formed as part of the inner midsole  400 . 
     The inner midsole  400  includes a centrally disposed midfoot pod  410 , a plurality of heel bars  420  that extend generally across a portion of the width of the sole  30  in the heel region  32 , and a plurality of forefoot bars  421  that extend generally across a portion of the width of the sole  30  in the forefoot region  36 . In one embodiment, the inner midsole  400  extends from the base  310  of the outer midsole  300 . In this manner, the outer midsole  300  may be disposed above the inner midsole  400  and may also be referred to as the upper midsole and the inner midsole  400  may also be referred to as the lower midsole. The inner midsole  400  may thus be bottom loaded. In another embodiment, a portion of the inner midsole  400  may be disposed above the base  310 , and a portion of the inner midsole, for example, one or more heel bars  420  and/or forefoot bars  421  may extend below the base  310 . For example, one or more heel bars  420  and/or forefoot bars  421  may extend through voids formed in the base  310 . In this manner, the inner midsole may be top loaded in some embodiments. 
     The heel bars  420  and forefoot bars  421  may be substantially parallel to each other, and may be connected by connecting members  412  that extend longitudinally along the length of the sole  30 . The connecting members  412  may be disposed in the center portion of the sole  30 , and may connect protrusions  420  and  421  generally at a center portion. In other embodiments, one or more connecting members  412  may connect other portions (e.g., an end portion) of a protrusion. In one embodiment, the inner midsole  400  may comprise three heel bars  420  and three forefoot bars  421 ; however, any suitable combination of heel and forefoot bars to provide the desired cushioning and stability may be used. For example, in one embodiment, the inner midsole  400  may comprise two heel bars  420  and four forefoot bars  421 . 
     In one embodiment, the heel bars  420  and forefoot bars  421  are generally rectangular in shape. The heel bars  420  and forefoot bars  421  may have four sides and may have a generally rectangular or quadrilateral cross-section, as shown in  FIG. 14 . As such, the bottom surface  423  of a heel bar  420  and/or a forefoot bar  421  may be generally rectangular or quadrilateral in shape. In one embodiment, one or more heel bars  420  and forefoot bars  421  may have curved sides such that the bars are wavy in shape, as shown, for example, in  FIG. 14 . In alternative embodiments, the heel bars  420  and forefoot bars  421  may include substantially straight sides. In some embodiments, a heel bar  420  may have a different shape than another heel bar and/or another forefoot bar  421 , and vice versa. The heel bars  420  and/or forefoot bars  421  may also be differently sized. For example, as shown in  FIG. 13 , the forefoot bars  421  may be longer than heel bars  420 . In other embodiments, one or more heel bars  420  and/or a forefoot bars  421  may be longer or wider at a portion of the sole  30  to provide desired cushioning, ride characteristics, and/or stability. 
     As shown in  FIG. 14 , the midfoot pod  410  may be disposed between the forward most heel bar  420  and the rear most forefoot bar  421 . In one embodiment, the midfoot pod  410  may widen from its lateral side  411  to its medial side  413  so as to be generally triangular in shape. The medial side  413  of the midfoot pod  410  may be forked. In other embodiments, the midfoot pod  410  may be wider on the lateral side  411 . Other shapes for the midfoot pod  410  suitable for providing the desired cushioning, ride, and/or stability, including, but not limited to, a generally quadrilateral shape may be used. 
     One or more adjacent heel bars  420  and/or forefoot bars  421  may be spaced apart by gaps  422 . In one embodiment, the gaps  422  are each of the same size such that the heel bars  420  and/or forefoot bars  421  are evenly spaced. In alternative embodiments, the width of some or all of the gaps  422  may be different. For example, in embodiments in which one or more heel bars  420  and/or forefoot bars  421  may be wider at a portion of the sole  30  to provide desired cushioning and stability, gaps  422  may correspondingly be narrower. In one embodiment, gaps  422  may generally have the same width as an adjacent heel bar  420  and/or forefoot bar  421 . In other embodiments, gaps  422  may be wider or narrower than the bars. In embodiments where the inner midsole  400  is top loaded and one or more heel bars  420  and/or forefoot bars  421  extend through the base  310 , portions of the base  310  may be disposed in the gaps  422 . 
     As discussed above, heel bars  420  and/or forefoot bars  421  extend across all or a portion of the width of the sole  30 . In one embodiment, as shown, for example in  FIG. 14 , a heel bar  420  and a forefoot bar  421  may not extend the entire width between two outer protrusions  320 . As such, a space  326  may be provided between ends of the heel bar  420  or the forefoot bar  421  and the adjacent protrusion. The space  326  may allow movement of the outer midsole  300  rim portion or protrusions  320  relative to the inner midsole  400 , which may provide for the desired cushioning and feel of the sole  30  to the user during a gait cycle. For example, the space  326  may allow an outer protrusion  320  at the location of the space to splay in multiple directions—outwardly from and inwardly toward the sole—when under a compressive load during use, and thereby allow for a tailored cushioning effect (e.g., allow for increased cushioning) or provide better overall ride of the footwear. In one embodiment, the space  326  may be disposed along all or a portion of the length of the sole on one or both of the medial side  31  and the lateral side  33  depending on the desired characteristics. In one embodiment, the width of the space  326  may vary along the sidewall for desired characteristics. For example, along the medial side  31  of the sole where less movement of the outer midsole  300  relative to the inner midsole  400  may be desired to provide increased stability, the width of the space may be narrower than at other locations of the sole  30 . 
     In other embodiments, the heel bar  420  and/or the forefoot bar  421  may extend the entire width between two outer protrusions  320 . As such, no space may be provided between ends of the heel bar  420  or the forefoot bar  421  and the adjacent protrusion, and the heel bar or forefoot bar may be contacting or attached to the protrusion. In one embodiment, one or more heel bars  420  and/or forefoot bars  421  may extend to the outer edge  35  of the base  310 , thereby eliminating outer protrusion(s)  420  along the periphery of the base at that location. For example, as shown in  FIGS. 16 and 19 , the forefoot bars  421  may extend to the outer edge  35  of the base on the medial side  31  of the sole. In this embodiment, the sole  30  may be without any outer protrusions  320  on the medial side in the forefoot region; however, the forefoot bars  421  may provide the desired cushioning and stability in the area. 
     In one embodiment, with reference to  FIGS. 13 and 15 , portions of the outer midsole  300  and the inner midsole  400  may be angled to provide the desired cushioning and/or stability of the sole  30 . In one embodiment, the outer protrusions  320  may be angled toward the rear of the footwear  10  from the base  310  to the bottom surface  321 . In one embodiment, the heel bars  420  and the forefoot bars  421  may be angled toward the front of the footwear  10 . In alternative embodiments, one or more of the outer protrusions  320 , the heel bars  420  and the forefoot bars  421  may be straight while others are angled. As best shown in  FIG. 15 , in one embodiment, a portion of the inner midsole  400  may be visible through a gap  322 . In embodiments in which both elements of the inner midsole  400  and the outer midsole  300  are angled, the visibility of the inner midsole  300  may create a cross-hatched or latticed appearance of the side of the sole  30 . 
     The inner midsole  400  and the outer midsole  300  comprise material for providing the desired cushioning, ride, and stability of the sole  30 . Suitable material for the inner midsole  400  and the outer midsole  300  may include, but is not limited to, foam and thermoplastic polyurethane. When the inner midsole  400  and/or the outer midsole  300  are a foam, the foam may comprise, for example, ethyl vinyl acetate (EVA) based foam or polyurethane (PU) based foam and the foam may be an open-cell foam or a closed-cell foam. In other embodiments, the inner midsole  400  and/or the outer midsole  300  may comprise elastomers, thermoplastic elastomers (TPE), foam-like plastic, and gel-like plastics. Suitable materials for inner midsole  400  and/or outer midsole  300  may be obtained from, for example, Eclipse Polymers Co., Sung Shin Co., and Korea Fine Chemical Co. 
     In one embodiment, the inner midsole  400  and the outer midsole  300  may comprise different materials. In one embodiment, the inner midsole  400  and the outer midsole  300  may have different hardness characteristics. For example, in one embodiment it may be desirable for the sole  30  to be stiffer near the periphery of the sole to provide required lateral and/or medial stability. In this manner, outer midsole  300  including one or more outer protrusions  320  may comprise a harder material than inner midsole  400 . 
     In some embodiments, the material hardness of the outer midsole  300  (e.g., the base  310  and/or the protrusions  320 ) may range from about 50 Asker C to about 70 Shore D, for example, about 60C to about 75C or about 65C to about 70C. In some embodiments, the material hardness of the inner midsole  400  may range from about 20C to about 70C, for example, about 40C to about 60C or about 50C to about 55C. In some embodiments, the material hardness of the outer midsole  300  may range from about 50 Asker C to about 70 Shore D and the material hardness of the inner midsole  400  may range from about 20C to about 70C, for example, the material hardness of the outer midsole  300  may range from about 60C to about 75C and the material hardness of the inner midsole  400  may range from about 40C to about 60C. 
     In some embodiments, the material density of the outer midsole  300  may be about 0.3 to about 0.5 grams/cubic centimeter (g/cm 3 ), for example, such as about 0.35 to about 0.4 g/cm 3 . In some embodiments, the material density of the inner midsole  400  may be about 0.25 to about 0.5 g/cm 3 , for example, such as about 0.25 to about 0.3 g/cm 3 . In some embodiments, the material density of the outer midsole  300  is higher than the material density of the inner midsole  400 . For example, in one embodiment, the material density of the outer midsole  300  is about 0.35 to about 0.4 g/cm 3  and the material density of the inner midsole  400  is about 0.25 to about 0.3 g/cm 3 . In other embodiments, the material density of the outer midsole  300  is lower than, or even equal to, the material density of the inner midsole  400 . 
     In some embodiments, the outer midsole  300  material has a higher modulus than that of the inner midsole  400  material. In other embodiments, the outer midsole  300  material has a modulus that is lower, or even equal to, that of the inner midsole  300  material. 
     The inner midsole  400  and the outer midsole  300  may be formed using suitable techniques, including, but not limited to, injection molding, blow molding, compression molding, and rotational molding. The inner midsole  400  and the outer midsole  300  may be formed separately and attached. In one embodiment, the inner midsole  400  may be attached to the base  310  by adhesive bonding, welding or other suitable attachment techniques. In some embodiments, as shown, for example, in  FIGS. 17 and 20 , a cavity  327  may be formed in the base  310  for receiving the inner midsole  400 . One or more indentions  328  formed in the base  310  may further facilitate attachment or securing of the inner midsole  400  to the outsole  300 . In another embodiment, the inner midsole  400  and the outer midsole  300  may be monolithic and may be integrally formed as a unitary structure. For example, the inner midsole  400  and the outer midsole  300  may be co-molded and thereby formed together simultaneously. 
     All or a portion of the outer midsole  300  and/or the inner midsole  400  may contact the ground during a gait cycle. The bottom surface  321  of the outer protrusions  320  and may be substantially flat, or may be slightly rounded or crowned. Similarly, the bottom surface  423  of the inner midsole  400 , including the heel bars  420 , the forefoot bars  421 , and the midfoot pod  410 , may be substantially flat, or may be slightly rounded or crowned. In one embodiment, the sole  30  may include an outsole  330  disposed on the outer midsole  300  and/or the inner midsole  400  to provide increased traction and durability to the sole  30 . For example, as shown in  FIG. 14 , outsole  330  may be disposed on the toe pod  312  and the heel pod  314 . In some embodiments, outsole  330  may be disposed on all or some of the bottom surface  321  of the outer protrusions  320 , and/or all or some of the bottom surface  423  of the heel bars  420  and/or the forefoot bars  421 . The outsole  130  may comprise a rubber compound, such as, for example, Shin Ho KA2BF high abrasion rubber compound, or other suitable material. The outsole  330  may be formed separately from the inner midsole  400  and/or the outer midsole  300  and attached, or formed integrally to form a unitary structure. 
     As discussed herein, in embodiments of the present invention the geometry, interrelation, and material properties of the outer midsole  100  and inner midsole  200 , and the outer midsole  300  and inner midsole  400  may be varied to provide the desired characteristics of the sole. For example, when harder or denser materials are used, generally, one or a combination of more gaps, larger gaps, smaller cross-section undulating portions (e.g., peaks and/or troughs) or protrusions, fewer undulating portions (e.g., peaks and/or troughs) or protrusions, and larger splay angles may be needed to obtain similar cushioning, stability, and/or ride characteristics. When softer or less dense materials are used, generally, one or a combination of fewer gaps, smaller gaps, larger cross-section undulating portions (e.g., peaks and/or troughs) or protrusions, more undulating portions (e.g., peaks and/or troughs) or protrusions, and smaller splay angles may be needed to obtain similar cushioning, stability, and/or ride characteristics. 
     The article of footwear  10  for various embodiments described herein may comprise an athletic shoe suited for a particular activity, such as, for example, a walking shoe, a running shoe, a basketball shoe, a court shoe, a tennis shoe, a training shoe, a boot, and the like. It is contemplated that the article of footwear may not include an upper  20 . For example, in one embodiment, the sole  30  may be used in conjunction with a sandal or other footwear not including an upper. 
     The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. For example, embodiments of the outer midsole  100  may be used in conjunction with the inner midsole  400 , and embodiments of the inner midsole  200  may be used in conjunction with the outer midsole  300 . Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. 
     The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.