Abstract:
A shoe including an upper; a bottom located below the upper and facing the ground; and a flexible plate having an upper surface, a lower surface, and an interior portion and peripheral portions is disclosed. The flexible plate is positioned between at least a portion of the bottom and at least a portion of the upper. The peripheral portions are restrained from movement in a substantially vertical direction relative to the interior portion, so that the interior portion is capable of being deflected relative to the peripheral portions in a substantially vertical direction. The flexible plate has a width that is greater than one-half the width of the upper. At least one opening is in the bottom of the shoe. The lower surface of the flexible plate is in air communication with the outside of the shoe through the at least one opening in the bottom of the shoe.

Description:
This application is a continuation of application Ser. No. 10/882,729, filed Jun. 30, 2004 now U.S. Pat. No. 7,540,099; which is a continuation of application Ser. No. 10/447,003, filed May 28, 2003, now U.S. Pat. No. 7,114,269; which is a continuation of application Ser. No. 10/007,535, filed Dec. 4, 2001, now U.S. Pat. No. 6,604,300; which is a continuation of application Ser. No. 09/641,148, filed Aug. 17, 2000, now U.S. Pat. No. 6,324,772; which is a continuation of application Ser. No. 09/512,433, filed Feb. 25, 2000, now U.S. Pat. No. 6,195,916; which is a continuation of application Ser. No. 09/313,667, filed May 18,1999, now U.S. Pat. No. 6,050,002; which is a continuation of application Ser. No. 08/723,857, filed Sep. 30, 1996, now U.S. Pat. No. 5,918,384; which is a CIP of 08/291,945, filed Aug. 17, 1994, now U.S. Pat. No. 5,560,126; all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to an improved rear sole for footwear and, more particularly, to a rear sole for an athletic shoe with an extended and more versatile life and better performance in terms of cushioning and spring. 
     2. Discussion of the Related Art 
     Athletic shoes, such as those designed for running, tennis, basketball, cross-training, hiking, walking, and other forms of exercise, typically-include a laminated sole attached to a soft and pliable upper. The laminated sole generally includes a resilient rubber outsole attached to a more resilient midsole usually made of polyurethane, ethylene vinyl acetate (EVA), or a rubber compound. When laminated, the sole is attached to the upper as a one-piece structure, with the rear sole being integral with the forward sole. 
     One of the principal problems associated with athletic shoes is outsole wear. A user rarely has a choice of running surfaces, and asphalt and other abrasive surfaces take a tremendous toll on the outsole. This problem is exacerbated by the fact that most pronounced outsole wear, on running shoes in particular, occurs principally in two places: the outer periphery of the heel and the ball of the foot, with heel wear being, by far, a more acute problem. In fact, the heel typically wears out much faster than the rest of the athletic shoe, thus requiring replacement of the entire shoe even though the bulk of the shoe is still in satisfactory condition. 
     Another problem associated with outsole wear is midsole compression. As previously noted, the midsole is generally made of a resilient material to provide cushioning for the user. However, after repeated use, the midsole is compressed due to the large forces exerted on it during use, thereby causing it to lose its cushioning effect. Midsole compression is the worst in the heel area, particularly the outer periphery of the heel and the area directly under the user&#39;s heel bone. 
     Despite technological advancements in recent years in midsole and outsole design and construction, the benefits of such advancements can still be largely negated, particularly in the heel area, by two months of regular use. The problems become costly for the user since athletic shoes are becoming more expensive each year, with some top-of-the-line models priced at over $150.00 a pair. By contrast with dress shoes, whose heels can be replaced at nominal cost over and over again, the heel area (midsole and outsole) of an athletic shoe cannot be. To date, there is nothing in the art to address the combined problems of midsole compression and outsole wear in athletic shoes, and these problems remain especially severe in the heel area of such shoes. 
     Designs are known that specify the replacement of the entire outsole of a shoe. Examples include those disclosed in U.S. Pat. Nos. 4,745,693, 4,377,042 and 4,267,650. These concepts are impractical for most applications, especially athletic shoes, for several reasons. First, tight adherence between the sole and the shoe is difficult to achieve, particularly around the periphery of the sole. Second, replacement of the entire sole is unnecessary based upon typical wear patterns in athletic shoes. Third, replacing an entire sole is or would be more expensive than replacing simply the worn elements, a factor which is compounded if a replaceable, full-length sole for every men&#39;s and women&#39;s shoe size is to be produced. Finally, it would appear that the heel section, in particular, has entirely different needs and requirements from the rest of the shoe sole and deteriorates at a much faster rate. 
     Other designs, which are principally directed to shoes having a relatively hard heel and outsole (e.g., dress shoes), disclose rear soles that are detachable and which can be rotated when a portion of the rear sole becomes worn. For example, U.S. Pat. No. 1,439,758 to Redman discloses a detachable rear sole that is secured to a heel of the shoe with a center screw that penetrates the bottom of the rear sole and which is screwed into the bottom of the heel of the shoe. Such a design cannot be used in athletic shoes because the resilient midsole and the soft, pliable upper are not rigid enough to retain the center screw. In addition, the center screw would detrimentally affect the cushioning properties of the resilient midsole and may possibly be forced into the heel of the user when the midsole is pressed during use. 
     Shoes with detachable rear soles that incorporate a center screw or other related securing means to attach the rear sole to the shoe also may experience gapping problems. Gapping refers to the gap that may appear, either initially or over time with extended use, between any detachable and non-detachable elements of a shoe. Any gapping will eventually attract debris or cause flapping and is otherwise aesthetically unpleasing. Such a problem would be particularly severe in a shoe that includes a rear sole made of resilient material that is likely to sag or move away from other surfaces with extended use. Similarly, rear soles dependent on center screws are likely to be pried away at the periphery when resilient materials are used. While related art discloses vertical heel support sidewalls, they do not solve either the gapping or the peripheral pry-away problem in the case of a resilient rear sole. For example, debris is still likely to lodge between a heel support vertical sidewall and a vertical rear sole sidewall; and the rear sole may still be pried away at the periphery if caught in a pavement crack or abrasion, if there is only a vertical wall to retain it. The latter problem is compounded by the fact that a vertical heel support sidewall would grip a resilient rear sole about its midsole where resiliency, by design, is the greatest and least able to resist displacement. 
     Rotating a rear sole will not, of course, counteract or alleviate midsole compression occurring at the heel center. While replacement of the entire rear sole is always an option, it may be that the full benefit of rotation will not have been realized when heel-center compression makes that necessary or desirable. That is to say that there may be good peripheral outsole and midsole remaining. 
     Although never in combination with a rotating or removable rear sole, there have been attempts to deal with heel-center midsole compression and/or to add spring to the users gait by introducing various mechanical components into heel construction. One approach has been to insert horizontally in the heel area a thin layer of hard, flexible material that bends under the user&#39;s weight and then returns to its original position when the weight of the user is shifted to the other foot. Such attempts have met with only minimal success, however, for several reasons. Such insert may have lacked enough inherent resiliency from the outset. In other cases, it may have deteriorated with use. In all cases, it has rested on a resilient foundation around its periphery, limiting its ability to flex in the center. 
     Another problem is that athletic shoe purchasers cannot customize the cushioning or spring in the heel of a shoe to their own body weight, personal preference, or need. They are “stuck” with whatever a manufacturer happens to provide in their shoe size. 
     Finally, there appears to be relatively few, if any, footwear options available to those persons suffering from foot or leg irregularities, foot or leg injuries, and legs of different lengths, among other things, where there is a need for the left and right rear soles to be of a different height and/or different cushioning or spring properties. Presently, such options appear to include only custom-made shoes that are rendered useless if the person&#39;s condition improves or deteriorates. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a shoe that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the system particularly pointed out in the written description and claims, as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the shoe includes an upper, a forward sole attached to the upper, a heel support attached to the upper, and a rear sole detachably secured or rotatably mounted to the heel support and including at least one ground-engaging layer and a midsole attached to the ground-engaging layer, the midsole made of an elastomeric material that is more resilient than the ground-engaging layer. 
     In another aspect, the shoe includes an upper, a forward sole attached to the upper, a heel support attached to the upper and having at least one wall extending downwardly from the upper, the wall at least partially defining a recess, a rear sole receivable in the recess of the heel support and having at least one ground-engaging surface, and a graphite insert either supported within the recess of the heel support or by the wall of the heel support between the rear sole and a heel portion of the upper. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are exploded isometric views of an embodiment of the shoe of the present invention. 
         FIG. 2  is a plan view of the shoe of  FIG. 1A . 
         FIG. 3  is a side elevation view of the shoe of  FIG. 1A . 
         FIG. 4  is a rear elevation view of the shoe of  FIG. 1A . 
         FIG. 5  is an expanded view of a securing band for the shoe of  FIG. 1A . 
         FIG. 6  is a rear elevation view of another embodiment of the shoe of the present invention. 
         FIG. 7  is a plan view of the shoe of  FIG. 6 . 
         FIGS. 8A and 8B  are views depicting another embodiment of the shoe of the present invention. 
         FIG. 9  is an isometric view of another embodiment of the shoe of the present invention. 
         FIG. 10  is an exploded isometric view of a heel support and rear sole for the shoe of  FIG. 9 . 
         FIG. 11  is another exploded isometric view of the heel support and rear sole of  FIG. 10 . 
         FIG. 12  is a side elevation view of the rear sole of  FIG. 11 . 
         FIG. 13  is a side elevation view of another rear sole that can be used in the embodiment shown in  FIG. 11 . 
         FIG. 14  is an isometric view of another embodiment of the shoe of the present invention. 
         FIG. 15  is an isometric view of a heel support for the shoe of  FIG. 14 . 
         FIG. 16  is another isometric view of the heel support of  FIG. 15 . 
         FIG. 17  is isometric view of another embodiment of the shoe of the present invention. 
         FIG. 18  is an isometric view of a heel support for the shoe of  FIG. 17 . 
         FIG. 19  is another isometric view of the heel support of  FIG. 18 . 
         FIGS. 20A and 20B  are side elevation and plan views, respectively, of another embodiment of the heel support for the shoe of the present invention. 
         FIG. 21  is an exploded isometric view of a rear sole and wafer for the shoe of the present invention. 
         FIG. 22  is an exploded isometric view of a heel support, rear sole, and graphite insert for use in the shoe of the present invention. 
         FIG. 23  is a side elevation view of the rear sole of  FIG. 22 . 
         FIG. 24  is an exploded isometric view of a heel support, graphite insert, and rear sole for use in the shoe of the present invention. 
         FIG. 25  is an exploded isometric view of another embodiment of a heel support, graphite insert, and rear sole for use in the shoe of the present invention. 
         FIG. 26  is an exploded isometric view of another embodiment of the heel support, graphite insert, and rear sole for use in the shoe of the present invention. 
         FIG. 27  is an exploded isometric view of another embodiment of the heel support, graphite insert, and rear sole for use in the shoe of the present invention. 
         FIG. 28  is an isometric view of a graphite insert for use in the shoe of the present invention. 
         FIG. 29  is an exploded isometric view of a rear sole and elastic band for use in the shoe of the present invention. 
         FIG. 30  is a side elevation view of the rear sole and elastic band of  FIG. 29 . 
         FIGS. 31-33  are views of a rear sole for use in the shoe of the present invention. 
         FIG. 34  is an exploded isometric view of another embodiment of the heel support, graphite insert, and rear sole for use in the shoe of the present invention. 
         FIG. 35  is an isometric view of the rear sole of  FIG. 34 . 
         FIG. 36  is a side elevation view of the heel support of  FIG. 34 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference characters will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1A  illustrates a first embodiment of the shoe of the present invention. The shoe, designated generally as  20 , has a shoe upper  22 , a forward sole  24 , a heel support  26 , and a rear sole  28 . The forward sole and heel support are attached to the shoe upper in a conventional manner, typically by injection molding, stitching or gluing. 
     As shown in  FIG. 3 , the forward sole  24  includes a forward midsole  50  and an outsole  54 . The forward midsole  50  is attached to the upper, in conventional fashion, e.g., injection molding or gluing, etc., and the outsole  54  is attached to the forward midsole  50 , in similar conventional fashion known to those skilled in the art. 
     As shown in  FIG. 1A , the heel support  26  preferably includes a heel counter  27  for stabilizing a heel portion of the upper  22  above the heel support and a side wall  38  that extends downwardly from the upper and defines a recess  40  sized to receive the rear sole. The heel support may also include a substantially horizontal top wall  38 ′ for supporting the heel portion of the upper. Otherwise, the top of the rear sole or an insert, as will be discussed in more detail later, will support the heel portion of the upper. The components of the heel support, including heel counter  27  and the side wall  38 , are preferably made integral through injection molding or other conventional techniques and are preferably composed of plastic, such as a durable plastic manufactured under the name PEBAX. 
     The rear sole  28  is preferably made from two different materials: a rubber compound for a first ground-engaging surface  30 ; and a softer, elastomeric material such as polyurethane or ethylene vinyl acetate (EVA) for the midsole  32  of the heel. Optionally, a notched section  46  of the midsole  32  can be made of a hard plastic material. However, the rear sole could be comprised of a single homogenous material, or two materials (e.g., EVA enveloped by hard rubber), or any number of layers or combinations of materials, including a material comprising the air encapsulating tubes, for example, disclosed in U.S. Pat. No. 5,005,300. 
     The rear sole  28  is detachable from the heel support  26 . This allows the user the ability to change rear soles entirely when either the sole is worn to a significant degree, or the user desires a different sole for desired performance characteristics for specific athletic endeavors or playing surfaces. 
     The rear sole  28  can also be rotatably mounted on the heel support  26 . The rear sole can be rotated to a plurality of positions (although only four positions are possible in the  FIG. 1A  embodiment), with a means provided to allow the user to secure the rear sole at each desired position. After a period of use, the periphery of the ground-engaging surface  30  will exhibit a wear pattern at the point in which the heel first contacts the ground, when the user is running, for example. Excessive wear occurs at this point, and at the midsole, degrading the performance of the rear sole. When the user determines that the wear is significant enough, the user detaches the rear sole  28  from the heel support  26 , and rotates the rear sole so that the worn portion will no longer be in the location of the user&#39;s first heel strike. Rotation can occur in an axis aligned with the major axis of the shoe, so that the heel is in effect “flipped” or inverted. Rotation can also occur about an axis normal to the major axis of the shoe, or any combination of the above. The user then re-engages and secures the rear sole to its new position so that the rear sole will not become dislodged during use. The number of positions into which the rear sole can be rotated is not limited; however, the embodiment depicted in  FIG. 1A  permits on both axes a total of only four such positions due to the elliptical shape of the rear sole. 
     Rotating the rear sole about an axis normal to the shoe&#39;s major axis to a position of, for example, of 180 degrees beyond its starting point, will locate the worn portion of the rear sole at or near the instep portion of the shoe. The instep portion is an area of less importance for tractioning, stability, cushioning and shock absorbing purposes. It is important to note, however, that in embodiments other than that depicted in  FIG. 1A , the rear sole need not be rotated a full 180 degrees to achieve the benefit of extended use. As long as the worn portion of the rear sole is rotated beyond the area of the initial heel strike, prolonged use of the rear sole is possible. The user can continue periodically to rotate the rear sole so that an unworn portion of the rear sole is located in the area of the first heel strike. 
     The shape of the rear sole  28  can be circular, polygonal, elliptical, “sand-dollar,” elongated “sand-dollar,” or otherwise. Preferably, the rear sole is shaped so that the rear edge of the ground-engaging surface  30  has a substantially identical profile at each rotated position. To allow for a plurality of rotatable positions, the shape of the ground-engaging surface  30  preferably should be symmetrical about at least one axis. The ground-engaging surface  30  can be planar or non-planar. Preferably, the ground-engaging surface, particularly on running shoe models, includes one or more tapered or beveled edges  48 , as shown in  FIG. 1A , to soften heel strike during use. 
     A plurality of compression slits  39  which run generally vertically around the periphery of the side wall  38  may be included and are shown in  FIG. 1A . The slits may create a void completely through the side wall  38 , or they may merely be a weakened area of the side wall, so that the side wall thickness in the area of the slit is less than the side wall thickness elsewhere. The compression slits allow the side wall to expand enough so that the rear sole can be press-fitted into the recess, as shown in  FIG. 4 , and then press against the peripheral surface of the rear sole to retain it in the recess. Optionally, a securing band  44  sized to fit around the side wall can be used to further secure the rear sole in the recess, as shown in  FIGS. 1A and 3 . The securing band may be a separate component, as shown in  FIG. 1A , or made integral with the side wall  38  of the heel support, as is securing band  44 ′ shown in  FIG. 1B , thereby reducing the number of loose parts associated with the shoe. 
     When rotation of the rear sole  28  is desired, the user releases the band  44  (if provided), “rotates” the rear sole, and resecures the band. The rear sole is sized to allow rotation about two axes of the shoe. In addition to being rotatable about a first axis, which is normal to the major axis of the shoe, the rear sole is invertible, meaning that the sole can be rotated about a second axis that is aligned with the major axis of the shoe. In order to be invertible, the rear sole must have a first ground-engaging surface  30  located opposite a second ground-engaging surface  130 . When the user desires to change the ground-engaging surface entirely, instead of merely rotating the worn spot about an axis normal to the shoe&#39;s major axis, the user detaches the rear sole and inverts it, and the first ground-engaging surface  30  assumes the relative position of the second ground-engaging surface  130 , and vice-versa. Of course, the user could rotate the rear sole about both axes at the same time, if desired, when the rear sole is disengaged and re-engaged. 
     The side wall  38  preferably contains a first notched section  42  that extends generally horizontally along the entire periphery of the side wall  38 . The securing band  44 , if used, fits around the side wall  38  of the heel support and within the first notched section. Both ground-engaging surfaces of the rear sole  28  are sized to fit within and mate with the recess  40  of the heel support  26  when assembled. The horizontal mid-section of the rear sole  28  has a second notched section  46  along its periphery, and is sized to fit within and mate with the first notched section  42 . After the rear sole is positioned up within the recess of the heel support, the securing band  44  fits within the first notch  42  and, upon tightening, securely holds the rear sole  28  in place during use. The compression slits  39  allow the side wall  38  of the heel support  26  to be compressed when the securing band  44  is tightened, ensuring a snug and secure fit. 
     As shown in  FIGS. 1A and 4 , located on the interior surface of the first notched section  42  is a plurality of alignment dimples  43 . A plurality of alignment nipples  41  are located at corresponding positions on the exterior of the second notched section  46  of the rear sole  28 . The alignment dimples  43  are sized to fit within and mate with the nipples  41  when the two sections are assembled, to help align the two sections, to help provide structural stability generally, and specifically to prevent a twisting of the rear sole in a horizontal plane within the recess  40  when the user pivots on the heel of the shoe. 
     When the rear sole is attached to the heel support, the beveled edges  48  are preferably aligned as shown in  FIG. 2 .  FIG. 3  depicts a side view of an improved athletic shoe  20 , where the beveled edges  48  of the ground-engaging surface, as per a running shoe model, again are depicted. Although two beveled edges are shown, the ground-engaging surface can include one or more beveled edges as desired, and they can be aligned (at an infinite number for circular rear soles) relative to the heel support as desired by the user. 
       FIG. 5  shows an expanded view of the securing band  44 . The clamping assembly is similar to the conventional latch and clasp system used on most ski boots and similar equipment. The latch pivots from a first position, where the clasp is engaged, to a second and locking position, which forces the two ends of the assembly together. Similar clamping assemblies are well-known in the industry, e.g., radiator hose clamps, etc. could be used and still achieve the benefits of this invention. 
     The means for locking or securing the rear sole to the heel support is not limited. A secure and tight fit is required, but also the means must be easily accomplished so the user will not be required to return the shoe to the manufacturer or a shoe repair store in order to replace or remove the rear sole. 
     The ability to remove the rear sole serves several purposes. The user can rotate and/or invert the rear sole to relocate a worn section to a less critical area of the sole, and eventually replace the rear sole altogether when the sole is excessively worn. Additional longevity in wear may also be achieved by interchanging removable rear soles as between the right and left shoes, which typically exhibit opposite wear patterns. However, some users will prefer to change the rear soles not because of adverse wear patterns, but because of a desire for different performance characteristics. For example, it is contemplated that a person using this invention in a shoe marketed as a “cross-trainer” may desire one type of rear sole for one sport, such as basketball, and another type of rear sole for another, such as running. A basketball player might require a harder and firmer rear sole for stability where quick, lateral movement is essential, whereas a runner or jogger might tend to favor increased shock absorption features achievable from a softer, more a cushioned heel. Similarly, a jogger planning a run outside on rough asphalt or cement might prefer a more resilient rear sole than the type that would be suitable to run on an already resilient indoor wooden track. Rear sole performance may also depend on the weight of the user or the cushioning desired. 
     Further embodiments are disclosed that show the various ways of attaching the rear sole to the heel support in accordance with the invention. The general features of the first embodiment, such as the shape of the rear sole and the material composition of the shoe elements, will apply to all embodiments unless otherwise noted. 
     In a second embodiment shown in  FIGS. 6 and 7 , a rear sole  29  has a plurality of spaced-apart protrusions  86  located along the periphery of a mating surface  88  of the rear sole  29 . The protrusions  86  are sized to mate with a plurality of inverted “L”-shaped slots  90  located in a recess  41  of a heel support  26 ′. The slots are sized to receive the protrusions such that the rear sole is mated to the heel support by inserting the rear sole and protrusions up within the heel support recess, and rotating the rear sole about an axis normal to the major axis of the shoe to lock the protrusions into a horizontal segment of the inverted “L”-shaped slots. To further lock the rear sole into place and also to then prevent undesired rotation of the rear sole  29  within the recess  41  when the user pivots on the heel, resilient snaps  94  such as those shown in  FIG. 6  may be employed. More particularly, such snaps are formed on the heel support as shown in  FIG. 6  and engage apertures  92  in the wall and rear sole  29 . 
     While the above discussion is directed towards a rear sole that rotates or separates in its entirety, it is specifically contemplated that the same benefits of this invention can be achieved if only a portion of the rear sole is rotatable or removable. In this respect, “at least one rotatable ground-engaging surface” means that at least one surface of the rear sole, that contacts the ground during use, rotates or is removable. For example, this invention includes the embodiment whereby a portion of the rear sole, e.g., the center area, remains stationary while the periphery of the ground-engaging surface rotates and/or is detachable. 
     A third embodiment of the shoe of the present invention is shown in  FIGS. 8A and 8B . A rear sole  98  has a transverse edge  100  and a peripheral edge  102 . A tongue  110  and groove  112  mechanism secures the transverse edge  100  of the rear sole  98  to allow the rear sole to first engage the heel support  106 . The tongue  110  in the embodiment shown in  FIG. 8A  extends the entire distance of the transverse edge  100 . To assemble, the user slides the rear sole  98  in transversely to the major axis of the shoe. (Alternatively, the tongue  110  may be designed to “snap” into the groove  112  by inserting the rear sole from the rear of the shoe and directly into the groove  112 .) The user then swings the rear sole  98  up to the heel support  106 , using a means for securing the rear sole to the heel support so that the rear sole is securely attached. To disassemble, the process is reversed. The means for securing the rear sole is not limited; alternatives can include any of the securing means described herein, or as used conventionally in analogous applications. Alternatives can, of course, include integral locking mechanisms all around the outer periphery of the heel, such as a plurality of resilient protrusions  108  on the rear sole which engage a corresponding number of receiving apertures  116  on an overhanging portion  114  of the heel support  106 . The existence of an overhanging portion  114  may require the tongue  110  to be made of a resilient material so that the rear sole  98  can bend downwards and clear the overhanging portion  114  during assembly or disassembly. 
     It is important to note that the rear sole of the improved athletic shoe sole of  FIGS. 8A and 8B  can be oriented in several different manners and still be an embodiment of this invention. The transverse edge  100  and tongue  110  may be angled in the plane of the outsole of the shoe so that they are nonperpendicular to the major axis of the shoe. This orientation will allow for a greater amount of surface contact between the tongue  110  and groove  112  than achievable if the transverse edge  100  and tongue  110  are oriented, within the plane of the outer sole, perpendicularly to the major axis of the shoe as shown in  FIGS. 8A and 8B . Such orientation will also permit the isolation of the wear spot which typically occurs on the outer periphery of the heel of most runners within a smaller, removable rear sole element. A transverse edge with a different angle would achieve the same purpose for runners who tend to pronate. Also, although  FIG. 8A  depicts the tongue  110  extending out from the rear sole along an axis which is parallel to the major axis of the shoe, the tongue could instead extend upwards or downwards at an angle to the major axis of the shoe, and still fall within the invention described herein. In addition, the rear sole  98  need not extend, from the rear of shoe forward, the full horizontal distance of the portion of the shoe commonly referred to as the “heel portion”; rather, the benefits of this invention are achieved if, as shown in  FIGS. 8A and 8B , the rear sole includes only a segment of such “heel portion”. Finally, the rear sole  98  of  FIGS. 8A and 8B  could be rotatable about an axis aligned with the shoe&#39;s major axis, just as in the other embodiments discussed above. This feature allows the user to disengage the rear sole, “invert” or flip the rear sole about the shoe&#39;s major axis, and then re-engage the rear sole to the shoe. Consequently, the “heel strike” portion of the rear sole could be changed in this fashion. 
     Another embodiment of the present invention is shown in  FIGS. 9-12 . The shoe includes an upper  22 , a heel support  140 , a rear sole  150 , and a forward sole  160 . As shown in  FIG. 10 , the heel support  140  includes a heel counter  142 , a downwardly extending wall  144  that defines a recess  146  sized to receive the rear sole, and a rim  148  formed around the lower portion of the wall and extending inwardly into the recess. Anchors  152  may be formed on the bottom surface of the rim  148  and extend downwardly toward the rear sole  150 . 
     The rear sole  150  includes a rubber ground-engaging surface  154  containing, in this embodiment, three beveled segments or edges  156 . As shown in  FIG. 12 , the rear sole  150  also includes a midsole  158  laminated to the ground-engaging surface  154  that includes a substantially cylindrical lower portion  162  and a substantially cylindrical upper portion  164  that is smaller in diameter than the lower portion. A groove  166  is formed between these upper and lower portions and receives the rim  148  of the heel support to retain the rear sole in the heel support recess. 
     The upper midsole portion  164  includes a spiral groove  168 , as shown in  FIGS. 10-12 , that allows the rear sole to be screwed into the heel support. As shown in  FIG. 10 , a portion of the rim of the heel support is cut away at  170 . The rear sole is screwed into the heel support by aligning the top of the spiral groove with an edge  172  of the rim adjacent the cut-away portion. A sharp instrument (such as a slender screwdriver), inserted through the window  174  and into the top of the spiral groove  168  may aid in the start-up process. The rear sole is then simply rotated, and the rim engages the spiral groove of the rear sole to screw the upper midsole of the rear sole into the recess. Once fully inserted, the rear sole may be rotated freely within the recess by hand, albeit with desired resistance. When the rear sole is attached to the heel support, the optional anchors sink into the lower midsole portion of the rear sole due to the weight of the user to prevent rotation of the rear sole during use. 
     It should be noted that the configuration of the midsole  158 , i.e., the upper midsole portion having a diameter equal to or slightly larger than that of the recess defined by the rim and a lower midsole portion having a diameter substantially equal to the diameter defined by the circular wall  144 , further eliminates any vertical gapping problems from occurring between the wall of the heel support and the peripheral surface of the rear sole. 
     To assist in removing the rear sole from the heel support, the two windows  174 ,  176  ( FIG. 10 ) are formed in the wall of the heel support, a first window  174  above the cut-away portion of the rim and a second window  176  positioned 180.degree. around the wall of the heel support from the first window. In addition, a small indention  178  is formed on the peripheral surface of the upper midsole portion  164  at a position 180.degree. from the point at which the spiral groove  168  intersects the bottom of the upper midsole portion  164 , as shown in  FIG. 12 . To remove the rear sole from the heel support, the rear sole is rotated in the heel support until the small indention appears in the second window  176 . At this point, the bottom of the spiral groove is aligned with the center of the cut-away portion. The user, again using a screwdriver or similar instrument inserted through the window  174  into the spiral groove  168 , can then simply rotate the rear sole so that the rim of the heel support engages the spiral groove. The rear sole is then simply rotated to screw the rear sole out of the heel support. 
     It is not necessary to include a spiral groove in the rear sole for attaching and removing the rear sole from the heel support. As shown in  FIG. 13 , a rear sole  250  is similar to that shown in  FIG. 12 , but includes no spiral groove and no small indention. Because the upper portion  264  and lower portion  262  of the midsole  258  are made of a soft material, it can be press-fitted into the recess of the heel support until the rim  148  engages the groove  266 . In this instance, the rim of the heel support need not include the cut-away portion or the windows, as shown in  FIG. 10 , and can be a continuous rim, as shown in  FIGS. 14-19 . In this instance, the heel support may be made of a plastic or other material that is flexible enough to allow a slight expansion of the recess so that the rear sole can be press-fitted into position. Alternatively, the wall or rim may include compression slits similar to those shown in  FIG. 1A . Still another alternative is for the rim to be slightly narrower (shown), to accommodate the press-fit. 
     As shown in  FIGS. 10 and 11 , the heel counter  142  extends upwardly from the heel support and is attached to the heel portion of the upper by gluing or other conventional methods. The heel counter is preferably made of the same material as the heel support and is preferably molded to be integral with the heel support. The heel counter serves to stabilize lateral movement of the heel during use. 
     As shown in  FIGS. 9-11 , the shoe of the present invention also preferably includes an arch bridge  180  attached to, and integral with, the heel support  140  to provide an even firmer support for the arch of the foot and for alleviating potential gapping problems where the wall of the heel support is adjacent the forward sole. The arch bridge  180  generally extends from the rear of the recess  146  (where it attaches to the heel counter  142  and side wall  144 ) to the ball of the foot and is attached to the upper  22  and forward sole  160  by gluing or other conventional methods. The arch bridge  180  also is preferably composed of the same material as the heel support and is made integral with the heel support  140  by molding. Such one-piece construction of the arch bridge together with the heel support solves another major problem, and that is the tendency of an athletic shoe of conventional “full body” arch construction to curl at the juncture of the hard heel support with the resilient forward sole. 
     As shown in  FIGS. 14-16 , another embodiment of a heel support  240  includes a heel counter  242 , a vertically extending side wall  244  that defines a recess  246 , and a generally horizontal, continuous rim  248  extending inwardly into the recess. Anchors  252  may be formed on the bottom of the rim and engage the lower midsole portion  262  of the rear sole  250  shown in  FIG. 13  to prevent rotation of the rear sole during use. 
     In this embodiment, the heel support  240  may include a generally horizontal top wall  245  positioned above the side wall  244  to support the heel portion of the upper  22 . The top wall  245  is preferably composed of plastic and is made integral with the heel support. A gap  249  is preferably formed between the top wall  245  and a portion of the side wall  244  to enable the user not to feel the front side wall  244  beneath his or her foot. An optional hole (not shown) may be cut in the top wall  245  as in  FIG. 10  to allow the user&#39;s foot to have direct contact with the center of the midsole. 
     As an alternative to using the arch bridge  180 , the heel support  240  includes a thickened tongue  247  that extends toward the ball of the foot. The thickened tongue  247  provides additional gluing surface for attaching the heel support to the forward sole  260  and additional stiffness to the heel portion of the shoe and the arch area, thus minimizing the chances of separation of the forward sole from the heel support, and at the same time minimizing the tendency of the shoe to curl at the juncture of the hard heel support with the soft forward sole. 
     Another embodiment of the heel support is shown in  FIGS. 17-19 . In this embodiment, a heel support  340  includes a heel counter  342 , wall  344 , rim  348 , top wall  345 , gap  349 , and anchors  352  similar to those shown in  FIGS. 14-16 . The tongue  347  is thinner and slightly smaller than the tongue  247  shown in  FIGS. 14-16 . However, the heel support, as shown in  FIGS. 17 and 18 , includes a curved wall  341  that has a pocket formed on its forward side for receiving a mating rear edge of the forward sole  360  adjacent the heel support. The curved wall  341  provides a firm, smoothly contoured transition from hard-to-align resilient materials of the forward and rear soles and thereby minimizes gapping. It also provides a desirable brace or bumper for the lower portion of the rear sole when the user is running. 
     Although several of the embodiments show a heel support having a continuous wall that defines a recess, a continuous wall is not required. As shown in  FIGS. 20A and 20B , a heel support  200  may include two or more spaced-apart wall portions  202  that extend downwardly to at least partially define a recess. These wall portions each include a rim  204  that extends into the recess in a manner similar to the previous embodiments. The rear sole shown in  FIG. 13  can be slid and press-fitted into the recess, and the rims formed on the downwardly extending walls of the heel support engage the groove  266  to retain the rear sole in the recess, with anchors  206  preventing rotation of the rear sole during use. The spacing between the wall portions preferably occurs where wear spots are typically formed on the rear sole to provide extra cushioning at the wear spots. 
     Another manner of attaching the rear sole to the heel support is shown in  FIGS. 22 and 23 . In this embodiment, the upper midsole portion  364  includes a plurality of resilient knobs  365  extending from its peripheral surface. The knobs may be cylindrical as shown or any geometrical shape that will prevent rotation of the rear sole, including those knobs shown in  FIG. 35 . In addition, the heel support  440  includes a side wall  444  that has a plurality of openings  445  that receive the knobs  365 . 
     As previously discussed, in addition to being rotatable, the rear sole may also be invertible. In this instance, the rear sole would have two ground-engaging surfaces composed of rubber compound. If each ground-engaging surface also includes one or more beveled surfaces, the heel support of the upper must be molded to account for the beveled surfaces of the ground-engaging surface that is not in use. Alternatively, as shown in  FIG. 21 , a wafer  210  may be positioned between the ground-engaging surface that is not in use and either the top of the heel support or the bottom of the upper. As shown in  FIG. 21 , the wafer includes inserts  212 , the number of which corresponds to the number of beveled edges  156 ′, joined by bars  214 . Each insert has a flat top surface  216  and a bottom surface  218  that conforms to the shape of the beveled surfaces to effectively provide a rear sole that has a flat top surface. As a result, the rear sole is effectively stabilized when the heel of the shoe strikes the ground during use, and the rear sole can be rotatably positioned in an infinite number of positions, which cannot occur if the top horizontal wall of the recess is simply molded to mate with the surface of the invertible rear sole that is not in use, as contemplated by  FIGS. 1A and 1B . 
     As also shown in  FIGS. 22 and 23 , an insert  400  made of graphite or other stiff, but flexible, material is supported by the heel support side walls  444  and positioned between the rear sole and the heel portion of the upper (not shown) of the shoe, among other things, to reduce heel-center midsole compression. As shown in  FIG. 22 , the circular graphite insert  400  has a diameter that is slightly larger than the diameter of the recess  446  defined by the downwardly extending wall  444  of the heel support  440 . A lip  448  is formed between the inner surface of the heel counter  442  and the recess  446  to support the periphery of the insert. 
     The graphite insert can either be permanently attached to the top of the heel support or removable through a pocket formed in the canvas-type material typically located on top of the heel support (not shown) or it can be simply removed after removing the sock liner where no such canvas material is employed. The removability of the graphite insert allows the use of several different types of graphite inserts of varying stiffness or composition and, therefore, can be adapted according to the weight of the runner, the ability of the runner, the type of exercise involved, or the amount of spring desired in the heel of the shoe. 
     As shown in  FIGS. 22 and 23 , the rear sole  350  preferably has a concave top surface  367 . Therefore, when the rear sole is attached to the heel support, the top surface of the rear sole does not come into contact with the graphite insert. As a result, the middle of the graphite insert can flex under the weight of the runner, and thus acts like a trampoline to provide extra spring in the user&#39;s gait in addition to preventing midsole compression. 
     Another embodiment for attaching the graphite insert is shown in  FIG. 24 . In this embodiment, the graphite insert  400  is inserted through the bottom of the heel support  540  so that the periphery of the graphite insert presses against the lower surface of an upper rim  549  of the heel support. A plastic ring  410  is also inserted in the recess between the graphite insert and the rim  548 . Such ring  410  is flexible enough to allow it to be inserted into the heel support. The ring supports the periphery of the lower surface of the graphite insert. The rear sole  450  is a screw-in type identical to the rear sole  150  shown in  FIG. 12  except that it has a concave top surface (like the top surfaces shown in  FIGS. 30 and 33 ) to allow the graphite insert to flex during use. 
     As shown in  FIG. 24 , the rim  548  of the heel support includes two cut-away portions at  570  and windows  574 ,  576  to allow the graphite insert and the ring to be inserted into the recess of the heel support, in addition to allowing the rear sole to be screwed onto the heel support in the same manner as contemplated by  FIGS. 10 ,  11  and  12 . The ring  410  also has windows  412 ,  414  that are aligned with the windows  574 ,  576  when the ring is inserted into the recess. 
     Alternatively, the rim  648  and  748  of the heel support and the graphite insert  500  and  600  can be “gear-shaped”, as shown in  FIGS. 25 and 26 , to allow the graphite insert  500  and  600  to be inserted into the heel support. Again, the ring  510  is flexible enough to allow it to be inserted into the heel support. 
     A further embodiment is shown in  FIG. 27 . In this embodiment, a rear sole  550  is identical to the rear sole  250  shown in  FIG. 13  except that it has a concave top surface as in  FIGS. 30 and 33 . A heel support  840  includes a downwardly extending wall  844  that has a serrated bottom edge  846  and a threaded inner surface  848 . The heel support  840  also includes an upper rim  849 . 
     A threaded ring  610  includes a threaded outer surface  612  that mates with the threaded inner surface  848  of the heel support  840 . The ring also includes an outwardly and inwardly extending flange  617  that presses against the serrated bottom edge  846  when the ring is screwed into the heel support. The bottom surface of the flange  617  includes anchors  618 , and may also be serrated to further grip the rear sole to prevent rotation. The ring also has two ends  614  and  616 , with end  614  having a male member and end  616  shaped to receive the male member to lock the two ends together. 
     The rear sole  550  is attached to the heel support by unlocking the ends of the ring and positioning the ring around the upper midsole portion  564  of the rear sole such that the flange  617  engages groove  566  of the rear sole. The ring  610  is then firmly locked onto the rear sole by mating end  614  with end  616 . The graphite insert  400  is inserted into the heel support so that it presses against the upper rim  849 . The ring  610 , with the rear sole  550  attached, is then screwed into the heel support by engaging the threaded surface  612  of the ring with the threaded surface  848  of the wall  844 . The ring is then screwed into the heel support until the serrated edge  846  of the wall  844  engages the flange  617  of the ring  610 . The serrated edge  846  serves to prevent rotation of the ring during use. 
     The graphite insert is not limited to a circular graphite insert and can be adapted to conform to the shape of the rear sole. In addition, the graphite insert may be concave or convex in shape and may include cut-out portions such as those in the graphite insert  700  shown in  FIG. 28 , to provide additional spring. The graphite insert also need not be used only in conjunction with a detachable rear sole, but can be used with permanently attached rear soles as well. 
     Another approach to providing additional spring and/or increasing heel cushioning is shown in  FIGS. 29 and 30 . In this embodiment, a highly resilient band  900 , stretched to fit over the upper portion of the rear sole, rests on the top surface of the lower midsole portion  362 . A hard plastic or graphite O-ring  902  may be provided between the band  900  and the top surface to enhance the spring effect. The top of the band, when the rear sole is attached to a heel support, such as heel support  440  shown in  FIG. 22 , is positioned against the lower edge of the wall  444 . Thus, when the heel of the shoe strikes the ground during use, the force exerted by the wall of the heel support is directly applied to the resilient band rather than the cushiony midsole, thereby providing additional spring. Alternatively, the band  990  may be air-filled, gas-filled, or gel-filled and still achieve the same effect. 
     If additional cushioning is desired, the rear sole can be modified as shown in  FIGS. 31-33 . In this embodiment, a “doughnut-shaped” void  652  is created in the middle of a rear sole  650  to support an air-filled cushion  670  similar in shape to an inner tube for a tire. In addition, several voids  654  are formed around the periphery of the rear sole to reduce the weight of the rear sole and better exploit the cushioning properties of the air-filled cushion  670  when the shoe strikes the ground during use. The voids are preferably positioned directly below the knobs  656  to cushion the force transmitted from the heel support to the knobs. The air cushion  670  may include a valve  672  for inflating and deflating the cushion. 
     Another embodiment is shown in  FIGS. 34-36  and includes a heel support  940 , a graphite insert  800 , a ring  710 , and a rear sole  750 . As shown in  FIG. 35 , the rear sole  750  includes a substantially planar ground-engaging surface  752 , a lower midsole portion  754 , and an upper midsole portion  756 . A plurality of knobs  758  having bulbous end portions are formed around the periphery of the upper midsole portion  756 . In addition, three voids  759  are formed in the upper midsole portion  756  and a portion of the lower midsole portion  754 . 
     As shown in  FIG. 36 , the heel support  940  includes a downwardly extending wall  944  that contains a plurality of openings  946  for receiving the knobs  758 . The heel support  940  also includes a rim  948  having a rearward bent portion  949 . Given this configuration, the ring  710 , which also has a plurality of openings  712  that are aligned with the openings  946  of the heel support, and the graphite insert  800  are shaped accordingly to fit within the recess of the heel support. 
     The graphite insert  800  and the ring  710  are inserted into the recess of the heel support and the rear sole  750  is press-fitted into the recess so that the knobs  758  of the rear sole engage the openings  946  formed in the wall  944  of the heel support. Since the rim of the heel support is bent, the portion of the rear sole adjacent the bent rim will also be bent upwardly to effectively create a beveled edge on the ground-engaging surface. The voids  759  created in the rear sole allow the rear sole easily to be bent to conform to the shape of the bent rim. Wedges  760  may be inserted into the voids of the rear sole that are not adjacent to the bent rim to provide lateral support. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the system of the present invention without departing from the scope or spirit of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the claims and their equivalents.