Abstract:
A heel support for an athletic shoe that in one embodiment includes a recumbent-U shaped member to assist in shock absorption. The member may include a tent-shaped wall with an upper perimeter in contact with a non-ground-engaging member.

Description:
[0001]     The present application is a continuation of application Ser. No. 10/735,343, filed Dec. 11, 2003; which is a continuation of application Ser. No. 09/419,641, filed Oct. 18, 1999, now U.S. Pat. No. 6,662,471; which is a continuation of application Ser. No. 09/149,142, filed Sep. 8, 1998, now U.S. Pat. No. 5,970,628; which is a continuation of application Ser. No. 08/542,251, filed Oct. 12, 1995, now U.S. Pat. No. 5,806,210; all of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to multi-purpose athletic shoes and, more particularly, to athletic shoes with interchangeable/detachable rear soles that provide extended and more versatile life and better performance in terms of cushioning and spring.  
         [0004]     2. Description of the Prior Art  
         [0005]     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 sole usually includes an abrasion-resistant, rubber outsole attached to a cushioning midsole usually made of polyurethane, ethylene vinyl acetate (EVA), or a rubber compound.  
         [0006]     One of the principal problems associated with athletic shoes is wear to both the outsole and midsole. A user rarely has a choice of running or playing surfaces, and asphalt and other abrasive surfaces take a tremendous toll on the outsole. This problem is exacerbated by the fact that, with the exception of the tennis shoe, the most pronounced outsole wear for most users, 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 because of the great force placed on the heel during the gait cycle. 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.  
         [0007]     Midsole wear, on the other hand, results not from abrasive forces, but from repeated compression of the resilient material forming the midsole due to the large force exerted on it during use, thereby causing it to lose its cushioning effect. Midsole compression is also the worst in the heel area, particularly the outer periphery of the heel directly above the outsole wear spot and the area directly under the user&#39;s calcaneus or heel bone.  
         [0008]     Despite higher prices and increased specialization, no one has yet addressed heel wear problems in an effective way. 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.  
         [0009]     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, however, 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 which derive in substantial part from its rate of deterioration.  
         [0010]     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. Such designs, however, have never caught on in the marketplace because it is simply too easy and relatively inexpensive to have the entire heel on such footwear replaced at a commercial shoe repair shop.  
         [0011]     It is difficult to adapt such “dress shoe” designs to athletic shoes for various reasons. One reason is that the soft, resilient materials utilized in athletic shoe soles make it extremely difficult to devise a mechanism for detachably securing heel elements to each other without adversely affecting the cushioning and other desired properties of the shoe. On the other hand, utilization of hard materials in athletic shoes tends to increase weight and decrease comfort and performance.  
         [0012]     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 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 compressed during use. Furthermore, a center screw does little for peripheral adherence of the sole to the shoe heel in the case of resilient materials.  
         [0013]     Another truism in the athletic shoe industry is that, while cushioning has received a lot of attention, spring has received very little, despite the fact that materials like graphite and various forms of graphite composite possess the proper characteristics for spring enhancement without increasing weight. One reason may be the perceived tendency of graphite or graphite composite to crack under stress. Yet another reason may be the increased cost associated with such materials. Yet another reason may be that the tremendous variation in body weight and spring preference of would-be users makes it commercially unfeasible to mass-market athletic shoes with graphite spring enhancement, given the countless options that would have to be offered with each shoe size. Since heel spring is largely ignored, it goes without saying that spring options are also non-existent.  
         [0014]     Also absent from the marketplace are truly multi-purpose athletic shoes. Notwithstanding a few “run-walk,” “aerobic-run,” and all-court models, the unmistakable commercial trend appears to be increased specialization, with no apparent industry awareness of the fact that the use and function of an athletic shoe can be changed dramatically if it is simply given interchangeable rear soles. Similarly, no athletic shoe manufacturer has yet to offer varying heel cushioning firmness in each shoe size, despite the fact that consumer body weight for each shoe size spans a huge spectrum. While a few manufacturers offer width options in shoe sizes, varying firmness of cushioning in a single model or shoe size is nonexistent in the marketplace.  
       SUMMARY OF THE INVENTION  
       [0015]     The present invention is directed to a shoe that substantially obviates one or more of the needs or problems due to limitations and disadvantages of the related art.  
         [0016]     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.  
         [0017]     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the shoe in one embodiment includes an upper having a heel region and rear sole support attached to the heel region of the upper. The rear sole support includes a base, a first wall extending downwardly from the base and having a first groove, and a second downwardly extending wall opposite the first wall and having a second groove facing the first groove. A rear sole is detachably secured to the rear sole support with a mounting member attached to the rear sole and including at least one rim for engaging the first and second grooves. A locking member engages the rear sole support and one of the rear sole and mounting member to prevent rotation of the rear sole relative to the rear sole support during use.  
         [0018]     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.  
         [0019]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a Respective view of one embodiment of a shoe of the present invention.  
         [0021]      FIG. 2  is an Exploded perspective view of the heel structure for the shoe own in  FIG. 1 .  
         [0022]      FIG. 3  is a perspective view of a rear sole support for the heel structure shown in  FIG. 2 .  
         [0023]      FIG. 4  is a perspective view showing the underside of the rear sole support shown in  FIG. 3 .  
         [0024]      FIG. 5  is a perspective view of another embodiment of the shoe of the present invention.  
         [0025]      FIG. 6  is a perspective view of a rear sole support for the shoe shown in  FIG. 5 .  
         [0026]      FIG. 7  is a perspective view showing the underside of the rear sole support shown in  FIG. 6 .  
         [0027]      FIG. 8  is a side view of a rear sole for the heel structure shown in  FIG. 2 .  
         [0028]      FIG. 9  is a perspective view showing the underside of the rear sole show  FIG. 8 .  
         [0029]     FIGS.  10 A-C are bottom views showing alternative ground-engaging surfaces-for the rear sole shown in  FIG. 8 .  
         [0030]      FIG. 11  is a side view of a mounting member for the heel structure shown in  FIG. 2 .  
         [0031]      FIG. 12  is a perspective view of a locking member for the heel structure shown in  FIG. 2 .  
         [0032]      FIG. 13  is a perspective view showing the opposite side of the locking member shown in  FIG. 12 .,  
         [0033]     FIGS.  14 A-C are top, perspective, and side views, respectively, of a flexible plate for the heel structure shown in  FIG. 2 .  
         [0034]     FIGS.  15 A-C are top, perspective, and side views, respectively, of another embodiment of a flexible plate for use in the heel structure shown in  FIG. 2 .  
         [0035]      FIGS. 16A and 16B  are top and side views, respectively, of another embodiment of the flexible plate for use in the heel structure shown in  FIG. 2 .  
         [0036]      FIG. 17  is an exploded perspective view of another embodiment of the heel structure of the present invention.  
         [0037]      FIG. 18  is a perspective view of a mounting member for the heel structure shown in  FIG. 17 .  
         [0038]      FIGS. 19A and 19B  are perspective views of a locking member for the heel structure shown in  FIG. 17 .  
         [0039]      FIG. 20  is an exploded perspective view of another embodiment of the heel structure of the present invention.  
         [0040]      FIG. 21  is an exploded perspective view of another embodiment of the heel structure of the present invention.  
         [0041]      FIG. 22  is a perspective view of several of the heel components shown in  FIG. 21 .  
         [0042]     FIGS.  23 A-C are top, side, and bottom views, respectively, of outsole segment for the heel structure shown in  FIG. 21 .  
         [0043]      FIG. 24  is an exploded perspective view of another embodiment of the heel structure of the present invention.  
         [0044]      FIG. 25  is a perspective view of another embodiment of a rear sole for use with the shoe of the present invention.  
         [0045]      FIG. 26  is an exploded perspective view of another embodiment of a heel structure of the present invention.  
         [0046]      FIGS. 27A and 27B  are side and front views, respectively, of a wafer for use in the heel structure shown in  FIG. 26 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0047]     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.  
         [0048]      FIG. 1  illustrates an embodiment of the shoe of the present invention. The shoe, designated generally as  20 , is an athletic shoe principally designed for running, walking, basketball, tennis, and other forms of exercise.  
         [0049]     As shown in  FIG. 1 , shoe  20  includes an upper  22 , which is that portion of the shoe that covers the upper portion of the user&#39;s foot. The upper may be made of leather, a synthetic material, or any combination of materials well known in the art.  
         [0050]     A forward sole  24  is attached to the forefoot region of the upper. The forward sole is a lightweight structure that provides cushioning to the forefoot region, and may include an abrasion-resistant rubber outsole laminated to a softer, elastomeric midsole layer. The forward sole is attached to the upper in a conventional manner, typically by injection molding, stitching or gluing.  
         [0051]     In some conventional shoes, the forward sole (simply referred to in the industry as a “sole”) would extend from the forefoot region to the rear edge of the heel. In other conventional models, portions of the outsole and/or midsole are reduced or eliminated in certain non-stress areas, such as the arch area, to reduce weight. However, in a radical departure from conventional shoes, the shoe in an embodiment of the present invention incorporates a heel structure, including a detachable rear sole, that significantly alleviates heel wear problems associated with conventional soles and provides enhanced cushioning and/or spring.  
         [0052]     An embodiment of the heel structure is shown in  FIGS. 1 and 2  and includes a rear sole support  26  attached to the heel region of the upper  22 , a rear sole  28  detachably secured to the rear sole support  26 , a mounting member  60  for detachably securing the rear sole  28  to the rear sole support  26 , and locking members  90  for preventing rotation of the rear sole  28  relative to the rear sole support  26  during use. In addition, the heel structure may include a flexible plate  80  for providing spring to the heel of the user and reducing wear caused by midsole compression.  
         [0053]     As shown in  FIGS. 3 and 4 , the rear sole support  26  includes a substantially oval or elliptically-shaped base  30 , with somewhat flattened, medial and lateral sides, having a top surface that is attached to the upper by stitching, gluing, or other conventional means. The shape of such base is not limited, and could be circular, polygonal, or any variation of the foregoing. A front wall  32  extends downwardly from a front edge of the base  30 , and a rear wall  38  extends downwardly from a rear edge of the base  30 . Together, the front and rear walls define a recess that, as later described, receives means for detachably securing the rear sole to the rear sole support.  
         [0054]     The front wall  32  includes a lip  34  turned toward the recess, with lip  34  and the recess side of wall  32  defining an arc-shaped front groove. The rear wall  38  includes a lip  40  turned toward the recess, with lip  40  and the recess side of wall  38  defining an arc-shaped rear groove otherwise substantially identical to and facing the front groove. The front and rear grooves have the same radius of curvature and together may constitute arcs of a common circle. At least one, and preferably both, of the front and rear grooves disclosed in  FIG. 4  (and all drawings that disclose front and rear grooves), define a circular arc that is less than 180°. As shown in all of such drawings, both of such circular arcs also may substantially traverse the rear sole support  26  from its lateral to its medial side. The front and rear grooves may also be shaped to define arcs of a common circle having a diameter greater than the width of the rear sole support  26  or mounting member  60  or rear sole  28  or even the heel region of the upper  22 . The front and rear walls may be flush with the outer edge of base  30  and are spaced from each other on the medial and lateral sides of the base by a distance X, as shown in  FIG. 4 , which may be slightly greater than the width of the rear sole support  26  or mounting member  60  or rear sole  28 .  
         [0055]     The rear sole support also has a central opening  36  directly below the heel region of the upper. This central opening, which may be circular, oval, or virtually any polygonal shape, allows the heel of the user to be cushioned by the rear sole attached to the rear sole support or by the flexible plate  80 , instead of the firm material comprising the rear sole support.  
         [0056]     The rear sole support may be composed of hard plastic, such as a durable plastic manufactured under the name PEBAX.™, graphite, a graphite composite, or other material having sufficient rigidity and strength to securely engage the rear solve attaching mechanism (discussed below). Injection molding or other conventional techniques may be used to form the rear sole support.  
         [0057]     The rear sole support  26  may also include a heel counter  44 , as shown in  FIG. 3 , for providing lateral stabilization to the user&#39;s heel. The heel counter extends upwardly from the edge of the base  30  in a contoured fashion and is preferably made of the same material as, and integral with, the rear sole support through injection molding or other conventional techniques.  
         [0058]     As shown in  FIGS. 1-4 , an arch bridge  46  may generally extend from the base  30  of the rear sole support to the forward sole for supporting the arch region of the foot. The arch bridge  46  is an optional feature composed of a firm, lightweight material. The arch bridge  46  is attached to the upper  22  and forward sole  24  by gluing or other conventional methods. The arch bridge  46  also may be composed of the same material as the rear sole support or a more flexible material and may be made integral with the rear sole support. Such one-piece construction of the arch bridge together with the rear sole support solves a major problem, and that is the tendency of an athletic shoe of conventional “full body” arch construction to curl or twist at the juncture of the hard rear sole support and the resilient forward sole. It also reduces the weight of the shoe by reducing or eliminating the midsole material, e.g., polyurethane or EVA, that would normally occupy the arch area of the shoe.  
         [0059]     The rear sole support, heel counter, and arch bridge need not be made of a solid material. Holes or spaces may be created, at the time of manufacture, throughout the structure to decrease weight without diminishing strength.  
         [0060]     As an alternative to the arch bridge  46 , the rear sole support  26  in all of the embodiments may include upper and lower horizontal walls  144  and  145 , as shown in  FIGS. 5-7 , extending from, and preferably integrated with, front wall  32 . In this embodiment, the forward sole  24  extends into the arch region and is sandwiched between upper and lower walls  144  and  145  and against front wall  32 . It may then be further secured by gluing. As a further alternative, the rear portion of the forward sole may simply extend to the rear sole support, without upper and lower walls  144  and  145 , and be glued to the front wall  32 . Alternatively, the rear sole support  26  could have one wall like either  144  or  145  extending from and preferably integrated with it, but not both walls; or posts, rods, or other members, substantially parallel to the ground, could be substituted for walls and may extend from and be integrated with front Wall  32  into or along the surface of the midsole or outsole material in the forward sole and then secured by gluing. Other means may be employed as an alternative to the arch bridge  46 . An advantage to combining the rear sole support with walls  144  and/or  145 , or eliminating both of such walls entirely, and all other alternatives to the integral arch bridge, is that such options, unlike the integral arch bridge, permit manufacture of only one rear sole support suitable for either the left or right shoe, thus decreasing manufacturing costs.  
         [0061]     The heel structure shown in  FIG. 2  also includes a rear sole  28  detachably secured to the rear sole support. As shown in  FIGS. 8 and 9 , rear sole  28  may include a ground-engaging outsole  48  laminated to a midsole  50 , which may be more resilient than the outsole, with both the outsole and midsole being more resilient than the rear sole support. The outsole, which may be composed of a rubber compound, provides abrasion resistance and some cushioning, while the midsole, which may be composed of a more resilient, elastomeric material such as polyurethane, ethylene vinyl acetate (EVA), HYTREL.™ (made by E.I. DuPont de Nemours &amp; Co.), or other materials well known in the art, primarily provides cushioning to the heel during heel strike. Optionally, the rear sole could be comprised of a single homogenous material, or any number of layers or combinations of materials, including a material comprising air encapsulating tubes disclosed, for example, in U.S. Pat. No. 5,005,300.  
         [0062]     The outsole  48  may be planar or non-planar. Preferably, the outsole, particularly on running shoe models, includes one or more tapered or beveled segments  52 , as shown in  FIG. 8 , which when located at the rear of the shoe will soften and/or align heel strike during the gait cycle. The beveled segments  52  may be located at the front and rear portions of the rear sole, as shown in  FIG. 10A , slightly offset from the front and rear portions, as shown in  FIGS. 10B and 10C , or at any other location, depending on the preference of the user or any heel strike or wear pattern. The beveled segments  52  may also be aligned on a “special order” basis to deal with particular pronation or supination characteristics of the user.  
         [0063]     As shown in  FIG. 9 , rear sole  28  is elliptical or oval in shape, with somewhat flattened medial and lateral sides, with its length along the major axis of the shoe (when attached to the rear sole support and ready for use) being greater than its lateral width. As a result, the rear sole has a greater ground-engaging surface than if it were circular or equilaterally polygonal. Such increased ground-engaging surface provides greater stability, particularly if multiple or large beveled segments are used. However, the shape of the rear sole  28  may also be circular, polygonal, or otherwise. Regardless of the shape of the rear sole  28 , outsole  48  has an aggregate area having a substantially planar surface and multiple beveled surfaces non-planar with the planar surface. An aggregate area of the beveled surfaces is less than the remaining aggregate area of outsole  48 , as shown in  FIGS. 2, 5 ,  8 ,  9 ,  10 A-C,  17 ,  20 , and  26 , to provide a stable ground-engaging surface for the wearer of the shoe. Rear sole  28  may or may not feature a hole in its center as shown in  FIG. 9 , and preferably should not exist if flexible plate  80  (later discussed) is not used.  
         [0064]     Rear sole  28  is detachably secured to the rear sole support  26  with a mounting member  60 . As shown in  FIGS. 2 and 11 , mounting member  60  has a base layer  62  that is affixed to the top surface of the rear sole  28  with adhesive or other conventional means that will not degrade the cushioning/spring properties of the rear sole. There is an engaging layer  64  above base layer  62  and notch layer  74 A. Lateral sides  66  each contain protrusions  68  with bulbous ends. Front and rear ends  70  of the engaging layer  64  include circular arc-shaped rims  72  having substantially the same radius of curvature as the front and rear grooves of the rear sole support and engage the front and rear grooves of the rear sole support.  
         [0065]     For the embodiments of the present invention relating to detachable rear soles, to attach the rear sole to the rear sole support, the rear sole, with the mounting member  60  attached (and, optionally, with a flexible plate  80 , discussed later, supported on the mounting member  60 ), is positioned relative to the rear sole support so that the front and rear rims of the mounting member are rotated in a circular manner no more than about 90°, about axis Y from their positions shown in  FIG. 2 . The mounting member is centered between the front and rear grooves, then pressed against the bottom of the base  30  and rotated less than 180°, and generally no more than about 90° (clockwise or counterclockwise), so that rims  72  fully engage the front and rear grooves of the rear sole support defined by lips  34  and  40  seen in  FIG. 4 . When the rear portion of the rear sole becomes worn, the rear sole can be rotated in a circular manner 180° so that the worn rear portion now faces toward the front of the shoe and occupies an area somewhat forward of the calcaneus where little or no weight of the user is applied. When the rotated rear portion of the rear sole also becomes worn, the rear sole may be detached and exchanged with the rear sole of the other shoe, since wear patterns of left and right heels are typically opposite. The rear sole may also be discarded and replaced with a new one with or without any rotation or exchange between left and right shoe.  
         [0066]     The mounting member  60  may be made of any number of hard, lightweight materials that provide sufficient strength and rigidity to firmly engage the rear sole support, and support the flexible plate  80  if used. Examples of such materials include: hard plastic; PEBAX.™; HYTREL.™ in its hard format; graphite; and graphite, graphite/fiberglass, and fiberglass composites. Hardness of the mounting member may in fact be especially important if flexible plate  80  is used, because the peripheral edges of such plate need to press against a firm foundation if the central portion of such plate is to properly deflect under the weight of the user&#39;s foot and impart spring to the user&#39;s gait cycle. In any event, the mounting plate material is generally stiffer than the materials used for the rear sole midsole and outsole.  
         [0067]     Base layer  62  may be entirely eliminated from the mounting member  60  shown in  FIG. 2 , in which case the periphery of the top surface of rear sole  28  presses tightly against lips  34  and  40  of the rear sole support when engaged.  
         [0068]     To prevent the rear sole from rotating relative to the rear sole support once engaged with each other, locking members  90  lock the mounting member to the rear sole support at the appropriate orientation. As shown in  FIGS. 12 and 13 , locking member  90  includes a base  92  with a substantially planar inner surface  94  and an outer surface  96  contoured according to the sides of the rear sole support when attached thereto. A pair of L-shaped arms  98  extend from the base  92  (preferably from its top, e.g., from the external surface of the heel counter) and engage opposed openings  42  ( FIG. 2 ) in the rear sole support to pivotally attach the locking member  90  to the rear sole support. Openings  42  may also be formed in the heel region of the upper. When attached to the rear sole support, the locking members occupy the spaces (having a length X as shown in  FIG. 4 ) between the front and rear walls of the rear sole support, as shown in  FIG. 1 .  
         [0069]     Apertures  100  are formed in the base  92  for receiving the protrusions  68  of mounting member  60 . The apertures have a small opening adjacent surface  94 , then expand in diameter within the base to a larger opening near surface  96  to accommodate the bulbous ends of the protrusions  68 . As a result, the protrusions “snap” into the apertures  100  to lock the locking members in position. In addition, projections  102  extend inwardly from opposite ends of base  92  and engage notches  74  in the mounting member between the front and rear ends and the lateral sides ( FIGS. 2 and 11 ) to prevent rotation of the rear sole when the locking members are in the position shown in  FIG. 1 .  
         [0070]     For the embodiment of the present invention relating to flexible plates, and as shown in  FIG. 2 , mounting member  60  includes slots  76  for supporting a flexible plate  80  between the rear sole and the heel portion of the upper so that a portion of plate  80  is exposed through central opening  36 . The flexible plate, which may be made of a graphite composite or other stiff, but flexible, material, reduces heel-center midsole compression and provides spring to the user. The flexible plate is, of course, stiffer than the materials used for the outsole or midsole, but must be sufficiently flexible so as to not detrimentally affect cushioning of the user&#39;s heel. A graphite or graphite/fiberglass composite, including carbon or carbon and graphite fibers woven in an acrylic or resin base, such as those manufactured by Biomechanical Composites Co. of Camarillo, Calif., may be used.  
         [0071]     As shown in FIGS.  14 A-C, flexible plate  80  includes front and rear edges  82  and  84  that are supported by slots  76  (see  FIG. 2 ) in the mounting member. The flexible plate may have a substantially convex upper surface that curves upwardly between the front and rear edges to an apex  86 , which is preferably located below the calcaneus of the user when the rear sole is attached to the rear sole support. An aperture  88  may be provided at the apex  86  to increase spring.  
         [0072]     The plate may also be flat or concave, and may be substantially hour glass-shaped, as shown in FIGS.  14 A-C, or H-shaped, as is the plate  180  shown in FIGS.  15 A-C. Other shapes are also contemplated as long as such shapes provide spring and reduce midsole compression of the rear sole. For example,  FIGS. 16A  and B show another hour glass-shaped flexible plate  280  with discrete upper and lower sections  282  and  284 .  
         [0073]     When the flexible plate is used, the rear sole may be devoid of material in its center, as shown in  FIG. 2 , to reduce the weight of the rear sole. If the center is devoid of material, a thin horizontal membrane (not shown), with or without a flanged edge, composed of plastic or other suitable material may be inserted into the void and attached to the walls of the void, by compression fit or otherwise, to seal the void and prevent moisture or debris from entering or collecting therein.  
         [0074]     Apex  86  is located, in  FIGS. 14C and 15C , slightly to the rear of the center of the major axis of plate  80 , so as to be positioned more directly beneath the center of the calcaneus. Thus, it will be necessary to remove and rotate plate  80  by 180° on an axis perpendicular to the major axis of the shoe when the rear sole is rotated, in order to keep the apex positioned directly beneath the calcaneus. However, plate  80  may be formed with the apex in any position to suit a user&#39;s preference. It may even be placed in the exact center of plate  80  so as to obviate the need for plate rotation when the rear sole is rotated.  
         [0075]     Flexible plate  80  provides spring to the user&#39;s gait cycle in the following manner. During heel strike in the gait cycle, the user&#39;s heel provides a downward force against the plate. Since the peripheral edges of the plate are firmly supported by the mounting member, the interior portion of the plate deflects downwardly relative to the peripheral edges. As the force is lessened (with the user&#39;s weight being transferred to the other foot) the deflected portion of the plate, due to its elastic characteristics, will return to its original shape, thereby providing an upward spring force to the user&#39;s heel. Such spring effect will also occur whenever a force is otherwise applied to and then removed from the flexible plate (e.g., jumping off one foot, or jumping from both feet simultaneously).  
         [0076]     The removability of the flexible plate allows the use of several different types of flexible plates of varying stiffness or composition. Thus, flexible plate designs and characteristics can be adapted according to the weight of the user, the ability of the user, the type of exercise or use involved, or the amount of spring desired in the heel of the shoe. Removability also permits easy replacement of the plate should deterioration occur, a concern in the case of virtually any truly spring-enhancing plate material.  
         [0077]     The heel structure embodiment shown in  FIG. 2  is but one of many embodiments contemplated by the present invention. While further embodiments are discussed below, additional embodiments are possible and within the scope of the invention. Unless otherwise noted, the structure, material composition, and characteristics of the heel components shown in  FIGS. 1 and 2  apply to all of the embodiments.  
         [0078]     One such embodiment is shown in  FIGS. 17-19B . In this embodiment, rear sole support  126  is substantially identical to rear sole support  26  shown in  FIG. 2  except that it has horizontal grooves  128  on the exterior surfaces of each of the downwardly extending walls and no holes  42 . The mounting member  160  shown in  FIG. 17  is also identical to mounting member  60  shown in  FIG. 2  except that protrusions  168  do not have bulbous ends.  
         [0079]     Locking members  190  differ from those shown in  FIG. 2  in that the hinges are eliminated. Instead, the exterior surfaces of each of the locking members  190  have a horizontal groove  192  that aligns with the exterior grooves  128  formed on the rear sole support. In addition, apertures  194  ( FIG. 19A ) are cylindrical in shape and need not have expanded interior portions since the protrusions  168  have no bulbous ends.  
         [0080]     To lock the locking members in place, an elastic band  110  is stretched and fitted within the grooves  128  on the rear sole support and grooves  192  on the locking members. The elastic band  110  may be a separate component completely removable from the rear sole support, as shown in  FIG. 17 , or permanently secured to the rear sole support by, for example, enclosing one of the grooves  128  after the elastic band has been inserted therein. Also, the band may be pushed or rolled upward above grooves  128  on the rear sole support prior to detaching locking members  190 , and then simply rolled downward to return to an in-groove position following reattachment. As a further option, the elastic band may be a removable or permanently attached strap fitted within the grooves and having opposing ends that may be latched together like a belt or ski boot latch.  
         [0081]     As a further alternative (not shown), a U-shaped connector having opposite ends permanently attached to one end of both locking members  90  may be removably or permanently secured to the outer surface of either the front or rear wall of the rear sole support, as a substitute for the system involving hinges  98  on locking members  90 . The elastic band and other alternatives to the hinged locking member can be used in all of the embodiments of the invention.  
         [0082]     If a flexible plate is not desired, the embodiment shown in  FIG. 20  may be used to supply tore conventional midsole cushioning. In this embodiment, the mounting member  260  is identical to the mounting member  60  shown in  FIG. 2  except that the base layer and slots  76  are eliminated. It should again be noted that the base layer  62  is an optional feature in all of the mounting member embodiments. In place of the rear sole  28  shown in  FIG. 2 , a rear sole  200  has an abrasion-resistant outsole  202  laminated to a midsole layer  204 . On top of this midsole layer  204  are two additional midsole layers  206  and  208 , each layer being smaller than the layer upon which it rests, with midsole layer  208  sized to fit within the central opening  36  in the rear sole support  26 . Midsole layers  206  and  208  may comprise two separate pieces laminated together or a single piece molded or otherwise shaped to have two regions as shown.  
         [0083]     In this embodiment, the mounting member  260  is adhered by gluing or other means to the top of the midsole layer  204  such that it surrounds and abuts against the sides of midsole layer  206 . It may be further secured to the sides of midsole layer  206  by gluing or other means. The manner of attaching the rear sole and mounting member to the rear sole support is identical to that describe with respect to the embodiment shown in  FIG. 2 . In addition, the top midsole layer  208  may, but need not be, made circular to facilitate rotation of the rear sole when the midsole layer  208  is pressed into the central opening  36 . Alternatively, this layer may be severed from layer  206  and placed in opening  36  with the shoe in an inverted position. This may make installation easier if layer  208  is oval in shape, like opening  36 . It also permits replacement of layer  208 , should its cushioning properties deteriorate at a faster rate than the rest of the rear sole. Of course, this step would be accomplished before engagement of mounting member  260  with rear sole support  26 , which similarly could be accomplished while the shoe is in an inverted position in order that layer  208  does not fall out or dislodge during installation.  
         [0084]     It should be noted that layers  204 ,  206 , and  208  may be made of different cushioning materials, including without limitation air-filled chambers, gell-filled chambers, EVA or polyurethane, or any combinations thereof.  
         [0085]     The rear sole support is designed to accommodate a variety of rear sole configurations, which vary according to the activity involved, the weight of the user, and the cushioning and/or spring desired by the user. Although additional rear sole configurations are discussed below, many other rear sole configurations may be used in conjunction with the rear sole support  26 .  
         [0086]     One such example is shown in  FIGS. 21 and 22 . In this embodiment, a rear sole  300  is a U-shaped member having substantially parallel walls  302  and  304  joined by a bend  305 . The member is composed of a stiff, but flexible, material that will provide spring to the heel of the user without sacrificing comfort. Materials such as those disclosed with respect to the flexible plate  80  may be used for the rear sole  300 .  
         [0087]     Two layers of resilient midsole material  206  and  208 , which may be more resilient than the U-shaped member, are secured to the top of wall  302  by gluing or other means to provide cushioning to the heel of the user, and mounting member  260  is glued or otherwise attached to the top surface of top wall  302  to surround and abut against the sidewall of midsole layer  206 . It may also be attached to the side wall of layer  206  by gluing or other means. The mounting member may also be molded to the rear sole  300  as a one-piece structure. The midsole layers  206  and  208 , the mounting member  260 , and the rear sole support  26  (as well as optional features) are identical to those shown in  FIG. 20 , and the manner and options for attaching the rear sole and mounting member to the rear sole support is the same, including without limitation the option of severing and separately installing layer  208 .  
         [0088]     To protect the bottom ground-engaging surface of the U-shaped member and to provide cushioning, the rear sole may include an abrasion-resistant outsole which may be more resilient than the U-shaped member. As shown in  FIG. 21 , the bottom wall  304  of the rear sole  300  includes holes  306  through which removable outsole segments  308  are inserted. The outsole segments  308 , which may be made of a rubber compound or other material typically used for outsole material, provide an abrasion-resistant layer for protecting the bottom surface of wall  304 . As shown in FIGS.  23 A-C, the outsole segments have a substantially conically-shaped top portion  316 , a cylindrical middle portion  318 , and a rounded ground-engaging portion  320 . The conically-shaped portion  316  snaps into openings  306 , and the bottom of the conically-shaped portion acts to retain the outsole segments in the openings. Alternatively, a one-piece outsole layer may be attached to the bottom surface of wall  304 , utilizing openings  306  and segments  308 , or eliminating both and utilizing gluing or some other means instead. Such outsole layer may then be permanent or removable.  
         [0089]     The rear sole  300  provides spring to the heel of the user in the following manner. When the heel of the user strikes the ground, wall  304  will deflect toward wall  302 . Since the material is elastic, energy stored in bend  305  and wall  304  during deflection will spring bend  305  and wall  304  back to their original position as weight is shifted, thereby providing a spring effect to the user&#39;s heel. Stiffening members  312  or  312 A are optional elements that may be used to increase the spring generated by the rear sole  300 . The stiffening members include protrusions  314  that engage apertures  310  in the bend of the rear sole  300 . Alternatively, bottom wall  304  (shown with large hole in middle) may be solid to increase spring or may be tent-shaped as shown in  FIG. 25  to further increase spring, with or without a stiffening member  412 .  
         [0090]     Flexible plate  80  may also be used in conjunction with a rear sole very similar to that shown in  FIG. 21 . As shown in  FIG. 24 , rear sole  400  is identical to rear sole  300  shown in  FIG. 21  except that it has an optional opening in the top wall to reduce the weight of the rear sole and allow additional space within which flexible plate  80  may flex. Alternatively, the bottom wall may be solid to increase spring or may be tent-shaped as shown in  FIG. 25  to further increase spring, with or without a stiffening member  412 . Mounting member  360  is similar to that shown in  FIG. 2  except that the base  62  is deleted. Again, flexible plate  80  rests in slots  376  formed in the mounting member and is exposed to the heel region of the upper via the central opening  36  in the rear sole support  26 .  
         [0091]     Another rear sole option is shown in  FIG. 25 . In this embodiment, rear sole  500  is identical to rear sole  400  shown in  FIG. 24  except that it has a “tent-like” wall  506  extending from the bottom wall  504  toward top wall  502 . Wall  506  may have a top surface  508 , or may be devoid of material at this location. Wall  506  has the effect of increasing stiffness and, therefore, provides more spring than that of the rear sole  400  as shown. A stiffening member  412  may also be used to further increase spring. Stiffening member  412  is identical to member  312  shown in FIGS.  24  except that it has a slanted wall  413  to complement and press against the front sloped surface of wall  506 . Top wall  502  may have a central opening, as shown in  FIG. 25 , or may be solid, such as wall  302  shown in  FIG. 21 . Wall  506  may be used in any of the U-shaped rear sole embodiments.  
         [0092]     Finally, an optional wafer  600 , usable in combination with any of the above embodiments incorporating a flexible plate, is disclosed in  FIGS. 26-27B . As shown in  FIG. 26 , wafer  600  is disclosed in conjunction with the heel structure shown in  FIG. 2 . Wafer  600  is placed on the top surface of flexible plate  380  so that it is exposed to the heel region of the upper (not shown) via central opening  36  of rear sole support  26 . Wafer  600  is made of any suitable materials, such as those materials disclosed for the midsole layer or outsole layer of rear sole  28 , that provide cushioning to the heel of the user and which are more resilient than the flexible plate.  
         [0093]     As shown in  FIGS. 27A and 27B , wafer  600  includes knobs  602  and  604  that snap engage with corresponding openings  382  and  384  (see  FIG. 26 ) in flexible plate  380 . Although two knobs are shown in this embodiment, any number of knobs may be used; in fact, the knobs may be eliminated entirely.  
         [0094]     As shown in  FIG. 26 , wafer  600  is oval in shape, although any shape is contemplated so long as it provides the desired cushioning to the heel of the user. If desired, the bottom surface  0 . 608  of wafer  600  may be concave in order to conform with the curved top surface of flexible plate  380 . The top surface  606  of wafer  600  may also be concave in order to conform with the contours of the heel region of the upper or the user&#39;s heel.  
         [0095]     The wafer need not be attached to the flexible plate  380 . Instead, the wafer may, for example, be permanently attached to the bottom of the upper, secured within or made integral with a shoe sock liner (not shown), secured to the rear sole support, or attached at any other location that would be capable of cushioning the user&#39;s heel.  
         [0096]     It will be apparent to those skilled in the art that various modifications and variations can be made in the shoe of the present invention without departing from the scope or spirit of the invention and that certain features of one embodiment may be used interchangeably in other embodiments. By way of example only, the rear sole support/locking member combinations shown in  FIGS. 2 and 17  can be used in conjunction with any of the above-described rear sole configurations, and can be used with or without the flexible plate. Similarly, the arch bridge shown in  FIGS. 1-4 , upper and lower horizontal walls shown in  FIGS. 5-7  and other alternatives to the arch bridge discussed herein may be employed with any embodiment shown. Thus, it is intended that the present invention cover all possible combinations of the features shown in the different embodiments, as well as modifications and variations of this invention, provided they come within the scope of the claims and their equivalents.