Abstract:
An article of footwear is disclosed that includes an upper, an outsole, and a midsole. The upper is configured to receive a foot, and the outsole is secured to the upper. The outsole defines a plurality of apertures extending entirely through the outsole. In addition, the outsole has a ground-engaging surface positioned at a first elevation. The midsole is separate from the upper and the outsole. The midsole is also positionable within the upper such that a lower surface of the midsole extends into the apertures of the outsole and is exposed by the apertures. The lower surface is at a second elevation, the first elevation being less than the second elevation.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to footwear. The invention concerns, more particularly, an article of footwear with a removable and replaceable midsole element.  
         [0003]     2. Description of Background Art  
         [0004]     Conventional articles of footwear generally include two primary elements, an upper and a sole structure. The upper is secured to the sole structure and forms a void on the interior of the footwear for securely and comfortably receiving a foot. The upper is generally formed from multiple elements that are stitched and adhesively bonded together to form a comfortable structure for receiving the foot. More particularly, conventional footwear may include, for example, an exterior formed of leather and textile materials that are resistant to abrasion and provide the footwear with a particular aesthetic. Foam materials may be located on the interior of the upper to enhance the comfort of the upper, and moisture-wicking textiles may be positioned adjacent the foot to limit the quantity of perspiration within the upper.  
         [0005]     The sole structure attenuates ground reaction forces and absorbs energy as the footwear contacts the ground, and often incorporates at least two discrete layers that are conventionally referred to as a midsole and an outsole. The midsole forms the middle layer of the sole and serves a variety of purposes that include controlling foot motions, such as pronation, and shielding the foot from substantial ground reaction forces. The outsole forms the ground-contacting element of footwear and is usually fashioned from a durable, wear resistant material that includes texturing to improve traction. The sole structure may also include an insole, which is a thin, cushioning member located within the upper and adjacent to a sole of the foot to enhance footwear comfort.  
         [0006]     The upper and sole structure of most conventional articles of footwear are permanently secured together through adhesive bonding or stitching, for example. Accordingly, wear or damage occurring to either the upper or sole structure may require that the entire article of footwear be discarded. In addition, sole structures are generally configured for use during specific activities, particularly with athletic footwear. For example, a sole structure may incorporate pronation control elements that are beneficial for running, stability elements for court-style activities, or relatively soft cushioning for walking. A sole structure that is configured for one athletic activity, such as long-distance running, may not be suitable for use during another athletic activity, such as tennis. Each different type of sole structure, therefore, requires a distinct upper in footwear where the upper and sole structure are permanently secured together.  
         [0007]     In contrast with the conventional article of footwear that includes a permanently secured upper and sole structure, footwear configurations embodying an upper and detachable sole structure have been proposed. U.S. Pat. No. 6,023,857 to Vizy et al. discloses footwear with a permanently attached upper and outsole that includes a separate midsole and heel counter structure, which is removable from the upper. U.S. Pat. No. 5,083,385 to Halford and U.S. Pat. No. 4,974,344 to Ching both disclose an outsole structure that is detachable from the remainder of the footwear. Finally, U.S. Pat. Nos. 6,023,859 and 5,799,417 to Burke et al. disclose an article of footwear with removable and exchangeable inserts that are positioned between the upper and a lower portion of the sole structure. The inserts protrude through the lower portion of the sole structure to provide a ground-contacting surface.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention is an article of footwear having an upper, an outsole, and a midsole. The upper is configured to extend around at least a portion of a foot, and the outsole is secured to the upper. The outsole defines a plurality of apertures extending entirely through the outsole. In addition, the outsole has a ground-engaging surface positioned at a first elevation. The midsole is separate from the upper and the outsole. The midsole is also positionable within the upper such that a lower surface of the midsole extends into the apertures of the outsole and is exposed by the apertures. The lower surface is positioned at a second elevation, the first elevation being less than the second elevation.  
         [0009]     The outsole form a web that extends between opposite sides of the upper, and the web defines the apertures. The outsole may also include a rim section that extends around a periphery of the footwear. In order to secure the midsole to the outsole, the midsole may include at least one flange that extends under the rim section. In some embodiments, the midsole includes a foot-supporting portion and a plurality of projections that extend downward from the foot-supporting portion. The projections have a configuration that extends into the apertures of the outsole and is exposed by the apertures. A lower surface of the foot-supporting portion may contact an upper surface of the outsole. An upper surface of the foot-supporting portion may also be contoured to include a raised periphery, and an insole may be positioned adjacent the upper surface of the midsole.  
         [0010]     Another aspect of the invention pertains to a method of assembling an article of footwear. The method includes a step of providing a combination of an upper and an outsole that are secured together. A separate midsole is inserted into the upper such that a portion of the midsole extends through apertures formed by the outsole and are exposed by the apertures. The midsole is then positioned such that a lower surface of the midsole is at a greater elevation than a lower surface of the outsole.  
         [0011]     The advantages and features of novelty characterizing the present 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 embodiments and concepts related to the invention. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0012]     The foregoing Summary of the Invention, as well as the following Detailed Description of the Invention, will be better understood when read in conjunction with the accompanying drawings.  
         [0013]      FIG. 1  is a side elevational view of an article of footwear in accordance with the present invention.  
         [0014]      FIG. 2  is a bottom plan view of the article of footwear.  
         [0015]      FIG. 3  is a perspective view of the article of footwear.  
         [0016]      FIG. 4  is an exploded perspective view of the article of footwear.  
         [0017]      FIG. 5  is a first cross-sectional view of the article of footwear, as defined by section line  5 - 5  in  FIG. 2 .  
         [0018]      FIG. 6  is a second cross-sectional view of the article of footwear, as defined by section line  6 - 6  in  FIG. 2 .  
         [0019]      FIG. 7  is an exploded perspective view of another embodiment of the article of footwear.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     The following discussion and accompanying  FIGS. 1-6  disclose an article of footwear  10  having an upper  20 , an outsole  30 , a midsole  40  in accordance with the present invention. Upper  20  is secured to outsole  30  to form a single element. Midsole  40 , however, is separable from the combination of upper  20  and outsole  30 . This structure provides a plurality of advantages over the conventional, non-separable articles of footwear. For example, either midsole  40  or the combination of upper  20  and outsole  30  may be separately cleansed in a manner that best suits the respective materials forming each component. If one of midsole  40  or the combination of upper  20  and outsole  30  becomes worn or otherwise damaged, the damaged component may be replaced without the necessity of replacing the undamaged component, and the damaged component may be more easily recycled. Furthermore, midsole  40  or the combination of upper  20  and outsole  30  may be interchanged with alternate components to suit a particular activity or a preference of an individual.  
         [0021]     Upper  20  exhibits a generally conventional structure incorporating a plurality of elements that are stitched or otherwise connected to form a comfortable structure for receiving the foot. Suitable materials for upper  20  include various textiles, foam, leather, and polymer materials that are stitched or adhesively bonded together. The textile materials, for example may include a mesh cloth that provides enhanced air-permeability and moisture-wicking properties. The foam materials may be a lightweight thermoset foam that conforms to the shape of the foot and enhances the comfort of footwear  10 . Finally, the leather and polymer materials may be positioned in high-wear portions of upper  20 , or in portions of upper  20  that require additional stretch-resistance or support. In some embodiments, and as depicted in the figures, upper  20  may be primarily formed from a synthetic leather material that is supplemented with woven structures that stretch and conform with the shape of the foot. Accordingly, upper  20  may be manufactured from generally conventional materials.  
         [0022]     The various elements forming upper  20  define a lateral side  21   a , an opposite medial side  21   b , and an ankle opening  22 . Lateral side  21   a  and medial side  21   b  generally cover the sides, heel, and instep portion of the foot, and may include laces or another adjustment system for tightening upper  20  around the foot and securing the foot within footwear  10 . Lateral side  21   a  and medial side  21   b  define ankle opening  22  and extend downward from ankle opening  22  to join with outsole  30 . Ankle opening  22  provides access to a void within upper  20  that accommodates both midsole  40  and the foot. Lateral side  21   a , medial side  21   b , and ankle opening  22  have, therefore, a generally conventional configuration. As discussed above, midsole  40  is separable from the combination of upper  20  and outsole  30 . Ankle opening  22  provides, therefore, access to the void within upper  20  and also an area for removing and inserting midsole  40 .  
         [0023]     Outsole  30  is permanently secured to a lower portion of upper  20  to form a lower, ground-engaging surface of footwear  10 . A variety of attachment techniques may be utilized for permanently securing outsole  30  to lateral side  21   a  and medial side  21   b , including stitching, adhesive bonding, thermobonding, or a combination of stitching and bonding, for example. Outsole  30  may be a single element or a plurality of elements that are joined together. Suitable materials for outsole  30  include any of the various abrasion-resistant rubber materials that are conventionally utilized in footwear outsoles, including blown rubber, carbon rubber or a combination of blown and carbon rubbers. As utilized in the present document, the term “permanently secured” encompasses various securing techniques (e.g. stitching, adhesives, and thermobonding) that a consumer is not intended to modify.  
         [0024]     Outsole  30  includes a rim section  31  and a plurality of elements  32  that define multiple apertures  33 . Rim section  31  extends around the periphery of outsole  30  and is joined with upper  20 , thereby permanently joining upper  20  and outsole  30  together. Elements  32  are relatively thin members that extend across a lower surface of footwear  10  to provide portions of outsole  30  that engage the ground. More particularly, elements  32  extend generally from lateral side  21   a  to medial side  21   b , for example, and are spaced to define the various apertures  33  and expose a lower surface of midsole  40 . That is, elements  32  generally form a web structure in outsole  30 . Apertures  33 , as depicted in the figures, exhibit generally rectangular, triangular, and diamond-shaped configurations. In further embodiments of the invention, however, apertures  33  may exhibit a variety of other shapes or combinations of shapes, including circular, oval, hexagonal, octagonal, square, or other geometrical or non-geometrical shapes, for example. Accordingly, the specific shape of apertures  33  may vary considerably within the scope of the present invention.  
         [0025]     Midsole  40  is separable from the combination of upper  20  and outsole  30  by disengaging midsole  40  from outsole  30  and drawing midsole  40  through ankle opening  22 , thereby removing midsole  40  from the void formed within upper  20 . The primary elements of midsole  40  are a foot-supporting portion  41  and a plurality of projections  42 . Foot-supporting portion  41  extends from a heel portion to a forefoot portion of footwear  10  and provides an upper surface for contacting and supporting the foot. The upper surface of foot-supporting portion  41  may be contoured to conform with a natural shape of the foot. Peripheral areas of foot-supporting portion  41  may also be raised to form a general depression in the upper surface of midsole  40 , thereby providing an area for securely receiving the foot. In order to enhance the comfort of midsole  40 , a generally conventional insole  50  may extend over the upper surface of foot-supporting portion  41 , as depicted in  FIG. 7 . That is, insole  50  may be positioned to extend between midsole  40  and the foot, and insole  50  may also be removable in the same general manner as midsole  40 .  
         [0026]     A lower surface of foot-supporting portion  41  contacts the various elements  32  when midsole  40  is received by the combination of upper  20  and outsole  30 . In addition, projections  42  extend downward and into apertures  33 . Projections  42  exhibit the general shape of apertures  33 . Those projections  42  that are located in peripheral areas of midsole  40 , however, may include a flange  43  that extends under rim section  31  to secure midsole  40  in position relative to outsole  30 . In addition to extending downward, those projections  42  that are located in peripheral areas of midsole  40  also extend laterally to form flanges  43 . In combination with outsole  30 , flanges  43  extend under rim section  31  to secure the position of midsole  40 .  
         [0027]     Midsole  40  is formed of a polymer foam material that provides cushioning as footwear  10  contacts the ground. More specifically, midsole  40  operates to attenuate ground reaction forces and absorb energy as midsole  40  is compressed between the foot and the ground. This may occur, for example, during various ambulatory activities that involve either walking or running. Suitable materials for midsole  40  are, therefore, any of the conventional polymer foams that are utilized in the midsoles of athletic footwear, such as ethylvinylacetate and polyurethane foam. Midsole  40  may also incorporate a fluid-filled bladder in the heel portion or along the entire length of foot-supporting portion  41  in order to provide additional cushioning, as disclosed in U.S. Pat. Nos. 4,183,156; 4,219,945; 4,906,502; and 5,083,361 to Marion F. Rudy and U.S. Pat. Nos. 5,993,585 and 6,119,371 to David A. Goodwin et al., for example.  
         [0028]     When midsole  40  is properly positioned within upper  20  and joined with outsole  30 , projections  42  extend downward and into apertures  33 . The shapes of projections  42  generally correspond with the shapes of apertures  33  to provide a secure connection between outsole  30  and midsole  40 . The secure connection ensures, for example, that midsole  40  remains properly positioned relative to upper  20  during walking, running, or other ambulatory activities. The secure connection also ensures that debris (e.g., dirt, stones, twigs) do not enter upper  20  through apertures  33 . In order to enhance the secure connection, flanges  43  extend under rim section  31 , as discussed above. The combination of flanges  43  and rim section  31  discussed above provides an example of a mechanical locking system that is suitable for footwear  10 . In some embodiments, a locking system may not be necessary to form a secure connection between sole structure  30  and upper  20 . In other embodiments, a friction fit between outsole  30  and midsole  40 , various pins that extend through outsole  30  and into midsole  40 , or a temporary adhesive may be utilized. Accordingly, the use of an aperture edge and flange (i.e., rim section  31  and flanges  43 ) is not the only type of mechanical locking system that may be utilized to form a secure connection between sole structure  30  and upper  20 .  
         [0029]     Projections  42  extend downward and into apertures  33 , and projections  42  are exposed by apertures  33 . Although projections  42  extend downward and into apertures  33  and are exposed, a lower surface of the various projections  42  remains at a higher elevation than a lower surface of elements  32 . This configuration ensures that outsole  30  is the primary element of footwear  10  that contacts or otherwise engages the ground. If, for example, the lower surface of the various projections  42  was at a lower elevation than the lower surface of elements  32 , then midsole  40  would provide the primary ground-engaging element of footwear  10  and would be subject to considerable abrasive forces. As discussed above, however, outsole  30  is formed from an abrasion-resistant rubber material, whereas midsole  40  is formed from a polymer foam. Outsole  30  is, therefore, formed from a material that is more capable of withstanding the abrasive forces associated with walking, running, or other ambulatory activities. In some embodiments of the invention, however, the lower surface of projections  42  may be covered by an abrasion-resistant material to enhance the durability of midsole  40 .  
         [0030]     Although the lower surface of the various projections  42  remains at a higher elevation than a lower surface of elements  32 , the lower surface of the various projections  42  may still contact the ground as outsole  30  and midsole  40  are compressed between the foot and the ground. A majority of the abrasive forces associated with walking, running, or other ambulatory activities, however, may still be absorbed by outsole  30 . Accordingly, the difference in elevations between outsole  30  and the lower surface of the various projections  42  is not intended to prevent midsole  40  from contacting the ground. Rather, the difference in elevations operates to limit the degree to which the abrasive forces wear or otherwise degrade midsole  40 .  
         [0031]     The structure of footwear  10  described above provides a variety of advantages over conventional footwear, wherein the sole is permanently attached to the upper. During running, for example, some individuals may prefer a sole structure that limits the degree to which the foot pronates upon contact with the ground. The same individual, however, may prefer a sole structure that exhibits a high degree of stability during court-style activities, such as basketball or tennis. Rather than purchase multiple pairs of upper-sole structure combinations that are permanently secured together, the individual may acquire the combination of upper  20  and outsole  30 , and the individual may acquire multiple midsoles  40 , each midsole  40  being suitable for different activities. The individual may then select one of the multiple midsoles  40  for use with the combination of upper  20  and outsole  30 . Similarly, the individual may acquire multiple combinations of upper  20  and outsole  30  for use with a single midsole  40 .  
         [0032]     The combination of upper  20  and outsole  30  includes different materials than midsole  40 . Whereas midsole  40  is formed primarily from a polymer foam material, the combination of upper  20  and outsole  30  are formed from different materials. The respective portions of footwear  10  may benefit, therefore, from cleansing techniques that are specifically suited to their respective materials. Accordingly, the combination of upper  20  and outsole  30  may be separated from midsole  40  and each may be cleansed in an appropriate manner.  
         [0033]     Midsole  40  is formed from a polymer foam material. Following significant use, the various cells within the polymer foam material may experience compression set or otherwise degrade, or midsole  40  may become significantly worn. Rather than dispose of footwear  10 , midsole  40  may be properly recycled and replaced with an alternate midsole  40 , thus extending the lifespan of footwear  10 . Similar considerations apply to the combination of upper  20  and outsole  30 .  
         [0034]     With regard to recycling, a significant portion of footwear  10  and many conventional articles of footwear is the midsole. As discussed above, the midsole of conventional articles of footwear is permanently secured to the upper and outsole. This configuration increases the difficulty of recycling the midsole or other footwear components. In footwear  10 , however, midsole  40  is separable from the combination of upper  20  and outsole  30 . In comparison with the conventional footwear, therefore, midsole  40  may be recycled with significantly greater efficiency.  
         [0035]     From an aesthetic viewpoint, the interchangeability of midsole  40  and the combination of upper  20  and outsole  30  also provides the individual with the ability to customize the appearance of footwear  10 . For example, footwear  10  may be purchased with a first color combination. By interchanging midsole  40  with an alternate midsole  40 , for example, the color combination of footwear  10  may be customized to the preferences of the individual. Support for a particular athletic team, for example, may also be demonstrated by selecting midsole  40  and the combination of upper  20  and outsole  30  to reflect the colors of the athletic team.  
         [0036]     The present invention is disclosed above and in the accompanying drawings with reference to a variety of embodiments. 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 embodiments described above without departing from the scope of the present invention, as defined by the appended claims.