Patent Publication Number: US-2023148707-A1

Title: Footwear and sole structure assemblies with adhesive-free mechanical attachments between insoles and midsoles

Description:
CLAIM OF PRIORITY AND CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/104,484, which was filed on Nov. 25, 2020, is now allowed, and is a continuation of U.S. patent application Ser. No. 16/288,871, which was filed on Feb. 28, 2019, and is now U.S. Pat. No. 10,874,169 B2. All of the foregoing patent matters are incorporated herein by reference in their respective entireties and for all purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to articles of footwear. More specifically, aspects of this disclosure relate to footwear with multilayered sole structures having impact-attenuating midsoles, wear-reducing outsoles, and foot-cushioning insoles. 
     BACKGROUND 
     Articles of footwear, such as shoes, boots, slippers, sandals, and the like, are generally composed of two primary elements: an upper for securing the footwear to a user&#39;s foot; and a sole for providing subjacent support to the foot. Uppers may be fabricated from a variety of materials, including textiles, foams, polymers, natural and synthetic leathers, etc., that are stitched or bonded together to form a shell or harness for securely receiving a foot. Many sandals and slippers have an upper with an open toe or heel construction, with some designs incorporating an upper that is limited to a series of straps extending over the instep and, optionally, around the ankle. Conversely, boot and shoe designs employ a full upper with a closed toe and heel construction that encases the foot. An ankle opening through a rear quarter portion of the footwear provides access to the footwear&#39;s interior, facilitating entry and removal of the foot into and from the upper. A shoelace or strap may be utilized to secure the foot within the upper. 
     A sole structure is generally attached to the underside of the upper, positioned between the user&#39;s foot and the ground. In many articles of footwear, including athletic shoes and boots, the sole structure is a layered construction that generally incorporates a comfort-enhancing insole, an impact-mitigating midsole, and a surface-contacting outsole. The insole, which may be located partially or entirely within the upper, is a thin and compressible member that provides a contact surface for the underside “plantar” region of the user&#39;s foot. By comparison, the midsole is mounted underneath the insole, forming a middle layer of the sole structure. In addition to attenuating ground reaction forces, the midsole may help to control foot motion and impart enhanced stability. Secured underneath the midsole is an outsole that forms the ground-contacting portion of the footwear. The outsole is usually fashioned from a durable, waterproof material that includes tread patterns engineered to improve traction. 
     SUMMARY 
     Presented herein are footwear sole structures with foot-cushioning insoles movably mounted onto impact-attenuating midsoles, methods for making and methods for using such sole structures, and articles of footwear fabricated with such sole structures. By way of example, and not limitation, an athletic shoe is disclosed that includes a multilayered sole structure assembly having a compressible polymer foam insole (“core”) with an adhesive-free mechanical attachment to a polymer-foam based midsole (“carrier”). A multi-piece, synthetic-rubber outsole may be inlaid at discrete locations along a downward facing, ground-contacting surface of the midsole. In this representative assembly, the insole and midsole are independently molded as distinct, single-piece structures with the insole movably mounted inside the midsole. The midsole and insole nest together via complementary “egg-crate” geometries, with prolate-spheroid-shaped protrusions projecting from an upward facing surface of the midsole and interleaving with prolate-spheroid-shaped protrusions projecting from a downward facing surface of the insole. Distal ends of the prolate-spheroid-shaped protrusions nest flush within complementary pockets recessed into the facing structure of the opposing sole structure element. The respective heights and widths of these protrusions may be distinct from one another, varying in both fore-aft and medio-lateral directions of the footwear. 
     Nubs projecting upward from distal tips of the midsole&#39;s protrusions extend through complementary holes in the insole. In addition to maintaining proper longitudinal and lateral alignment of the insole within the midsole, these nubs cooperate with the egg-crate interface to allow the insole to “float” on top of the midsole. Moreover, the nubs may have rounded tips and may be arranged in an engineered pattern that gives a “foot massaging” proprioceptive response for the user. The aforementioned mechanical engagement eliminates the need for adhesives and fasteners to join together the insole and midsole. However, the sole structure assembly may be attached to the upper via adhesives and/or fasteners, e.g., along an inner perimeter of an upwardly extending sidewall of the midsole. For at least some designs, an outer periphery of the insole is sandwiched between the midsole and upper, helping to retain the insert in place while not obstructing the footbed portion of the insole against which the user&#39;s foot rests. The midsole foam composition may absorb about 30% or less of compression forces imparted by the user to provide a softer feel with 15-20% more energy return compared to comparable foam sole structures. 
     Aspects of this disclosure are directed to multilayered footwear sole structures with foot-cushioning insoles coupled to impact-attenuating midsoles via complementary, intermeshing convoluted surfaces. In an example, a sole structure for an article of footwear includes an insole that is movably mounted—or “floats”—on a subjacent midsole. The midsole is formed, in whole or in part, from a compressible (first) material having an engineered (first) hardness. The midsole has a ground-facing lower surface opposite a foot-facing upper surface. Multiple (first) protrusions project upwardly from the midsole&#39;s upper surface, and multiple (first) pockets are recessed into the midsole&#39;s upper surface and interleaved with the midsole&#39;s protrusions. The insole is formed, in whole or in part, from a compressible (second) material having an engineered (second) hardness that is less than the hardness of the midsole. The insole has opposing upper and lower surfaces with multiple (second) protrusions projecting downwardly from the insole&#39;s lower surface and interleaved with the midsole&#39;s protrusions. Multiple (second) pockets are recessed into the insole&#39;s lower surface and interleaved with the insole&#39;s protrusions. Each midsole protrusion nests within one of the insole&#39;s pockets, while each insole protrusion nests within one of the midsole&#39;s pockets. 
     Other aspects of this disclosure are directed to footwear fabricated with any of the disclosed multilayered sole structure assemblies. As an example, an article of footwear includes an upper that receives and attaches to a foot of a user, and a sole structure that is attached to the upper to support thereon the user&#39;s foot. The sole structure includes a midsole, an insole movably mounted on the midsole, and an optional outsole rigidly mounted along the underside of the midsole. The midsole, which is formed with a compressible polymeric material, includes a ground-facing lower midsole surface opposite an upper midsole surface. Multiple protrusions project from the upper midsole surface, and multiple pockets are recessed into the upper midsole surface and interleaved with the first protrusions. The insole is formed with a distinct compressible polymeric material having a hardness that is less than the hardness of the midsole material. The insole has an upper insole surface opposite a lower insole surface, multiple protrusions projecting from the lower insole surface and interleaved with the midsole&#39;s protrusions, and multiple pockets recessed into the lower insole surface and interleaved with the insole&#39;s protrusions. Each midsole protrusion nests within a respective one of the insole&#39;s pockets, whereas each insole protrusion nests within a respective one of the midsole&#39;s pockets. 
     Additional aspects of this disclosure are directed to methods for manufacturing and methods for using any of the disclosed footwear and/or sole structures. In an example, a method is presented for manufacturing a sole structure for an article of footwear. This representative method includes, in any order and in any combination with any of the above or below disclosed features and options: forming, using a first material having a first hardness, a midsole having opposing upper and lower midsole surfaces, multiple first protrusions projecting from the upper midsole surface, and multiple first pockets recessed into the upper midsole surface and interleaved with the first protrusions; forming, using a second material having a second hardness less than the first hardness, an insole having opposing upper and lower insole surfaces, multiple second protrusions projecting from the lower insole surface and interleaved with the first protrusions, and multiple second pockets recessed into the lower insole surface and interleaved with the second protrusions; and mounting the insole onto the midsole such that each of the first protrusions is nested within a respective one of the second pockets, and each of the second protrusions is nested within a respective one of the first pockets. 
     For any of the disclosed sole structures, footwear, and manufacturing methods, each midsole protrusion may sit substantially flush against its respective insole pocket, whereas each insole protrusion may sits substantially flush against its respective midsole pocket. While innumerable shapes, sizes and orientations are envisioned, each protrusion may have a prolate-spheroid shape with a rectangular base. Moreover, a plurality of the midsole protrusions may each have a distinct height, and a plurality of the insole protrusions may each have a distinct height. In the same vein, a plurality of the midsole protrusions may each have a distinct width, and a plurality of the insole protrusions may each have a distinct width. Optionally, the midsole&#39;s protrusions and pockets may be arranged in a series of mediolateral rows that extend transversely across the midsole. Likewise, the insole protrusions and pockets may be arranged in a series of mediolateral rows that extend transversely across the insole. 
     For any of the disclosed sole structures, footwear, and manufacturing methods, a subset of the midsole&#39;s protrusions may each include a respective nub that projects upwardly from a distal tip thereof. A corresponding subset of the insole&#39;s pockets may each include a respective hole that receives therein one of these nubs. In at least some configurations, the holes in the insole have a first width, and the nubs of the midsole protrusions have a second width greater than the first width. In so doing, press fitting the nubs into the holes creates an interference fit coupling between the insole and midsole. As a further option each nub may extend all the way through its respective hole from the lower insole surface to the upper insole surface. While innumerable shapes, sizes and orientations are envisioned, each nub may have a cylindrical body with a rounded tip that protrudes from the insole&#39;s upper surface. 
     For any of the disclosed sole structures, footwear, and manufacturing methods, the midsole may be fabricated with a stepped shelf that extends substantially continuously around and circumscribes the midsole&#39;s upper surface. The insole may be fabricated with a flange that extends substantially continuously around and circumscribes the insole&#39;s lower surface. When the insole is properly mounted on the midsole, the insole&#39;s flange is buttressed on the midsole&#39;s stepped shelf. While not per se required, any of the disclosed sole structure assemblies may include an outsole that is formed, in whole or in part, from a third material that is harder than the insole and midsole materials. The outsole may be mounted to the ground-facing lower surface of the midsole. The outsole may be molded as a bipartite structure from a synthetic rubber. Optionally, the midsole may be molded as a distinct, single-piece structure from one polymer foam material, and the insole may be molded as a distinct, single-piece structure from another polymer foam material. An optional toe shield formed from a wear-resistant polymeric material may be mounted on a front end of the midsole. It is envisioned that any suitable manufacturing technique may be used to fabricate a disclosed sole structure assembly or a constituent part thereof, including injection, compression and/or multi-shot molding. 
     The above summary is not intended to represent every embodiment or every aspect of the present disclosure. Rather, the foregoing summary merely provides an exemplification of some of the novel concepts and features set forth herein. The above features and advantages, and other features and attendant advantages of this disclosure, will be readily apparent from the following detailed description of illustrated examples and representative modes for carrying out the present disclosure when taken in connection with the accompanying drawings and the appended claims. Moreover, this disclosure expressly includes any and all combinations and subcombinations of the elements and features presented above and below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a lateral side-view illustration of a representative article of footwear with a multilayered sole structure assembly in accordance with aspects of the present disclosure. 
         FIG.  2    is a bottom-view illustration of the representative article of footwear and multilayered sole structure assembly of  FIG.  1   . 
         FIG.  3    is an elevated, perspective-view illustration of the sole structure assembly of  FIG.  2    with the footwear upper removed. 
         FIG.  4    is an exploded, perspective-view illustration of the sole structure assembly of  FIG.  3    with the insole partially inverted to show the insole&#39;s lower surface. 
         FIG.  5    is a longitudinal cross-sectional illustration of the representative insole and midsole of the sole structure assembly of  FIG.  1    taken along line  5 - 5  of  FIG.  3   . 
         FIG.  6    is a transverse cross-sectional illustration of the representative insole and midsole of the sole structure assembly of  FIG.  1    taken along line  6 - 6  of  FIG.  3   . 
     
    
    
     The present disclosure is amenable to various modifications and alternative forms, and some representative embodiments are shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the novel aspects of this disclosure are not limited to the particular forms illustrated in the above-enumerated drawings. Rather, the disclosure is to cover all modifications, equivalents, combinations, subcombinations, permutations, groupings, and alternatives falling within the scope of this disclosure as encompassed by the appended claims. 
     DETAILED DESCRIPTION 
     This disclosure is susceptible of embodiment in many different forms. Representative examples of the disclosure are shown in the drawings and will be described in detail herein with the understanding that these representative examples are provided as an exemplification of the disclosed principles, not limitations of the broad aspects of the disclosure. To that extent, elements and limitations that are described in the Abstract, Technical Field, Background, Summary, and Detailed Description sections, but not explicitly set forth in the claims, should not be incorporated into the claims, singly or collectively, by implication, inference or otherwise. 
     For purposes of the present detailed description, unless specifically disclaimed: the singular includes the plural and vice versa; the words “and” and “or” shall be both conjunctive and disjunctive; the words “any” and “all” shall both mean “any and all”; and the words “including,” “comprising,” “having,” “containing,” and the like shall each mean “including without limitation.” Moreover, words of approximation, such as “about,” “almost,” “substantially,” “approximately,” and the like, may be used herein in the sense of “at, near, or nearly at,” or “within  0 - 5 % of,” or “within acceptable manufacturing tolerances,” or any logical combination thereof, for example. Lastly, directional adjectives and adverbs, such as fore, aft, medial, lateral, proximal, distal, vertical, horizontal, front, back, left, right, etc., may be with respect to an article of footwear when worn on a user&#39;s foot and operatively oriented with a ground-engaging portion of the sole structure seated on a flat surface, for example. 
     Referring now to the drawings, wherein like reference numbers refer to like features throughout the several views, there is shown in  FIG.  1    a representative article of footwear, which is designated generally at  10  and portrayed herein for purposes of discussion as an athletic shoe or “sneaker.” The illustrated article of footwear  10 —also referred to herein as “footwear” or “shoe” for brevity—is an exemplary application with which novel aspects and features of this disclosure may be practiced. In the same vein, implementation of the present concepts for a trilayer, polymer sole structure assembly should also be appreciated as a representative implementation of the disclosed concepts. It will therefore be understood that aspects and features of this disclosure may be utilized for sole structures with alternative chemical makeups and/or sole structures with different layer compositions, and may be incorporated into any logically relevant type of footwear. As used herein, the terms “shoe” and “footwear,” including permutations thereof, may be used interchangeably and synonymously to reference any suitable type of garment worn on a human foot. Lastly, features presented in the drawings are not necessarily to scale and are provided purely for instructional purposes. Thus, the specific and relative dimensions shown in the drawings are not to be construed as limiting. 
     The representative article of footwear  10  is generally depicted in  FIGS.  1  and  2    as a bipartite construction that is primarily composed of a foot-receiving upper  12  mounted on top of a subjacent sole structure  14 . For ease of reference, footwear  10  may be divided into three anatomical regions: a forefoot region R FF , a midfoot region R MF , and a hindfoot (heel) region R HF , as shown in  FIG.  2   . Footwear  10  may also be divided along a vertical plane into a lateral segment S LA —a distal half of the shoe  10  farthest from the sagittal plane of the human body—and a medial segment S ME —a proximal half of the shoe  10  closest to the sagittal plane of the human body. In accordance with recognized anatomical classification, the forefoot region R FF  is located at the front of the footwear  10  and generally corresponds with the phalanges (toes), metatarsals, and any interconnecting joints thereof. Interposed between the forefoot and hindfoot regions R FF  and R HF  is the midfoot region R MF , which generally corresponds with the cuneiform, navicular and cuboid bones (i.e., the arch area of the foot). Hindfoot region R HF , in contrast, is located at the rear of the footwear  10  and generally corresponds with the talus (ankle) and calcaneus (heel) bones. Both lateral and medial segments S LA  and S ME  of the footwear  10  extend through all three anatomical regions R FF , R MF , R HF , and each corresponds to a respective transverse side of the footwear  10 . While only a single shoe  10  for a right foot of a user is shown in  FIGS.  1  and  2   , a mirrored, substantially identical counterpart for a left foot of a user may be provided. Recognizably, the shape, size, material composition, and method of manufacture of the shoe  10  may be varied, singly or collectively, to accommodate practically any conventional or nonconventional footwear application. 
     With reference again to  FIG.  1   , the upper  12  is depicted as having a shell-like closed toe and heel configuration for encasing a human foot. Upper  12  of  FIG.  1    is generally defined by three adjoining sections, namely a toe box  12 A, a vamp  12 B and a rear quarter  12 C. The toe box  12 A is shown as a rounded forward tip of the upper  12  that extends from distal to proximal phalanges to cover and protect the user&#39;s toes. By comparison, the vamp  12 B is an arched midsection of the upper  12  that is located aft of the toe box  12 A and extends from the metatarsals to the cuboid. As shown, the vamp  12 B also provides a series of lace eyelets  16  and a shoe tongue  18 . Positioned aft of the vamp  12 B is a rear quarter  12 C that extends from the transverse tarsal joint to wrap around the calcaneus bone, and includes the rear end and rear sides of the upper  12 . While portrayed in the drawings as comprising three primary segments, the upper  12  may be fabricated as a single-piece construction or may be composed of any number of segments, including a toe shield  28 , heel cap, ankle cuff, interior liner, etc. For sandal and slipper applications, the upper  12  may take on an open toe or open heel configuration, or may be replaced with a single strap or multiple interconnected straps. 
     The upper  12  portion of the footwear  10  may be fabricated from any one or combination of a variety of materials, such as textiles, engineered foams, polymers, natural and synthetic leathers, etc. Individual segments of the upper  12 , once cut to shape and size, may be stitched, adhesively bonded, fastened, welded or otherwise joined together to form an interior void for comfortably receiving a foot. The individual material elements of the upper  12  may be selected and located with respect to the footwear  10  in order to impart desired properties of durability, air-permeability, wear-resistance, flexibility, appearance, and comfort, for example. An ankle opening  15  in the rear quarter  12 C of the upper  12  provides access to the interior of the shoe  10 . A shoelace  20 , strap, buckle, or other commercially available mechanism may be utilized to modify the girth of the upper  12  to more securely retain the foot within the interior of the shoe  10  as well as to facilitate entry and removal of the foot from the upper  12 . Shoelace  20  may be threaded through a series of eyelets  16  in or attached to the upper  12 ; the tongue  18  may extend between the lace  20  and the interior void of the upper  12 . 
     Sole structure  14  is rigidly secured to the upper  12  such that the sole structure  14  extends between the upper  12  and a support surface upon which a user stands. In effect, the sole structure  14  functions as an intermediate support platform that separates and protects the user&#39;s foot from the ground. In addition to attenuating ground reaction forces and providing cushioning for the foot, sole structure  14  of  FIGS.  1  and  2    may provide traction, impart stability, and help to limit various foot motions, such as inadvertent foot inversion and eversion. It is envisioned that the sole structure  14  may be attached to the upper  12  in any presently available or hereinafter developed suitable means. For at least some applications, the upper  12  may be coupled directly to the midsole  24  and, thus, lack a direct coupling to either the insole  22  or the outsole  26 . By way of non-limiting example, the upper  12  may be adhesively attached to only an inside periphery of a midsole sidewall  21 , e.g., secured with a  10 mm bonding allowance via priming, cementing, and pressing. 
     In accordance with the illustrated example, the sole structure  14  is fabricated as a sandwich structure with a foot-contacting insole  22  ( FIG.  3   ), an intermediate midsole  24 , and a bottom-most outsole  26 . Alternative sole structure configurations may be fabricated with greater or fewer than three layers. Insole  22  is shown located within an interior void of the footwear  10 , operatively located at a lower portion of the upper  12 , such that the insole  22  abuts a plantar surface of the foot. Underneath the insole  22  is a midsole  24  that incorporates one or more materials or embedded elements that enhance the comfort, performance, and/or ground-reaction-force attenuation properties of footwear  10 . These elements and materials may include, individually or in any combination, a polymer foam material, such as polyurethane or ethyl vinyl acetate (EVA), filler materials, moderators, air-filled bladders, plates, lasting elements, or motion control members. Outsole  26  is located underneath the midsole  24 , defining only some or all of the bottom-most, ground-engaging portion of the footwear  10 . The outsole  26  may be formed from a natural or synthetic rubber material that provides a durable and wear-resistant surface for contacting the ground. In addition, the outsole  26  may be contoured and textured to enhance the traction (i.e., friction) properties between footwear  10  and the underlying support surface. 
     With collective reference to  FIGS.  1 - 3   , the sole structure  14  is fabricated with the foot-cushioning insole  22  movably attached to the impact-force-attenuating midsole  24 , which is formed with a pressure-mapped, outboard-facing topography and inlaid with the wear-mitigating, multipart outsole  26 . In accord with the illustrated example, the midsole  24  is formed, in whole or in part, from a compressible (first) material having a relatively moderate (first) hardness, e.g., as measured according to a suitable one of the Shore Hardness Scales or other universally-recognized methodology for gauging material rigidity. The detachable insole  22 , which floats on a top surface of the midsole  24 , is formed, in whole or in part, from a distinct, compressible (second) material having a relatively low (second) hardness that is measurably less than that of the midsole  24 . In this regard, the sole structure  14  may be characterized by a lack of an adhesive bond between the insole  22  and the midsole  24  (or any other structure, for that matter). By comparison, first and second outsole segments  26 A and  26 B, respectively, are rigidly mounted to the midsole  24 , e.g., priming, cement adhesive, stock-fitting and pressing, and is formed, in whole or in part, from an elastic (third) material with a relatively high (third) hardness that is greater than the hardnesses of the midsole&#39;s and insole&#39;s materials. 
     It may be desirable, for at least some applications, that the Shore A hardness of the outsole material be larger than the Shore A hardness of the midsole material, e.g., by at least about 20% and larger than the Shore A hardness of the insole material by at least about 50%. As a non-limiting example, the midsole material may include a polymer foam material, such as thermoplastic polyurethane (TPU) foam, Phylon, Phylite, or EVA, having a material hardness in the range of about 40 to about 60 Shore A (e.g., about 65 to about 80 Asker C). Conversely, the outsole material may include an elastic polymer material, such as polyvinylchloride (PVC), hard-compound polyurethane (PU), or a polycaprolactone (PCL) or polyester-based TPU, having a material hardness of about 75 to about 90 Shore A. The insole, on the other hand, may include a softer polymer foam material, such as a lightweight polyurethane foam, having a material hardness of about 20 to about 35 Shore A. In a specific implementation, the midsole  24  is formed via compression molding as a one-piece, unitary structure from a polymer foam, such as a proprietary REACT® TPU elastomer, having a density of about 0.15 to about 0.25 g/cm 3 . In this example, the outsole  26  is formed via blowing and cutting as a bipartite structure from a synthetic rubber, such as ethylene propylene rubber (EPR), styrene isoprene styrene (SIS) copolymer rubber, styrene butadiene rubber. Insole  22  may be formed via compression molding as a one-piece, unitary structure from a polymer foam, such as a PU foam having a specific gravity of about 0.15-0.25 and a density of less than about 0.25 g/cm 3 . 
     To enhance underfoot cushioning during use of the footwear  10 , while concomitantly enhancing attenuation or ground reaction forces, increasing energy return, and minimizing gross shoe weight, the midsole&#39;s outboard topography is provided with an engineered pattern of projections and cavities, the shapes, sizes, locations, and orientations of which are designed to coincide with pressure zones identified through sensor-generated pressure map data. A normative population of individuals were provided with athletic shoes retrofit with a distributed array of sensors in the sock liner. These individuals underwent pressure-map testing throughout a full day of use to chart the points along the plantar region of the foot that experiences the largest and smallest magnitudes of pressure from walking, running, frequent lateral maneuvers, and the like. The aforementioned topology parameters of the midsole were then derived through algebraic tiles applied to the resultant pressure map data to create a patterned midsole that allocates polymer foam density according to pressure magnitude distribution. 
     The largest concentrations of midsole  24  and outsole  26  mass may be allocated at regions of the sole structure  14  that have been determined to coincide with increased-magnitude pressure zones of the plantar region. At the same time, respective concentrations of midsole  24  and outsole  26  mass may be minimized or completely eliminated at regions of the sole structure  14  that coincide with decreased-magnitude pressure zones of the plantar region. Outwardly facing surfaces of the midsole  24 , including rearward and lateral-facing surface segments of a midsole sidewall  21  and ground-facing surface segments of a midsole base  23 , are formed with an assortment of recessed cavities  32  interleaved with an assortment of outwardly protruding projections  34 . Each of the cavities  32  is delineated by coterminous, ground-contacting projections  34  of varying shapes, sizes and orientations. Empty cavities  32 —those not occupied by a segment  26 A,  26 B of the outsole  26 —are concentrated by volume at predetermined sections of sole structure  14  that coincide with reduced-magnitude pressure zones of the user&#39;s plantar region. To do so, however, may require each cavity  32  have a distinct shape, depth and/or width from every other cavity  32 . Conversely, filled cavities  32 —those occupied by a section of the outsole  26 —are mapped to predetermined sections of sole structure  14  that coincide with increased-magnitude pressure zones of the plantar region. As a result of the distinctly shaped cavities  32 , each projection  34  may have a distinct shape, height and/or orientation from every other projection  34 . According to the illustrated example, the outsole  26  fills multiple sections of the midsole channels  34 ; in so doing, segments of the outsole  26  will share the shape and dimensions of the corresponding midsole channel(s)  34  in which they occupy. 
     By way of contrast to the outsole  26 , which is rigidly mounted on and, thus, fixedly attached to the midsole  24 , the insole  22  is movably mounted on and detachable from the midsole  24 . That is not to say that the insole  22  is loosely laid on top of the midsole  24 ; rather, an adhesive-free mechanical attachment couples the insole  22  to the midsole  24  while allowing for a predetermined amount of fore-aft and medio-lateral play between the two elements. As best seen in the exploded perspective-view illustration of  FIG.  4   , an array of midsole protrusions  40  (also referred to herein as “first protrusions”) projects upwardly from a foot-facing upper surface  25  of the midsole  24 , which is opposite a ground-facing lower midsole surface  27  ( FIG.  1   ). While it is envisioned that the protrusions  40  may take on assorted combinations of shapes, sizes, and orientations, each protrusion  40  of  FIG.  4    has a prolate-spheroid shaped body  41  with a rectangular base  43  (see lower inset view of  FIG.  4   ). A prolate-spheroid shape may provide added underfoot comfort, e.g., as compared to blunt ended or sharp pointed protrusions. The midsole protrusions  40  may be approximately 1.0-4.0 mm high, as measured from the base  43 , and may project generally perpendicular from the upper midsole surface  25 . It may be desirable, for at least some applications, that the midsole  24  includes at least about fifty protrusions  40  or, for at least some applications, at least about seventy protrusions  40  depending, for example, on the shoe size of the footwear  10 . 
     Interleaved with the midsole&#39;s protrusions  40  is an array of midsole pockets  42  (also referred to herein as “first pockets”) recessed into the upper midsole surface  25 . Like the midsole protrusions  40 , the pockets  42  may take on assorted combinations of shapes, sizes, and orientations; pockets  42  of  FIG.  4    are portrayed as having a prolate-spheroid shaped cavity  45  with a rectangular window  47 . These midsole pockets  42  may be approximately 1.0-3.0 mm deep, as measured from the window  47 . In accord with the illustrated architecture, each of the pockets  42  may neighbor and be delineated by multiple coterminous protrusions  40 . As shown, the midsole protrusions  40  and pockets  42  are arranged in a series of mediolateral rows—represented herein by first, second and third rectilinear rows R 1 -R 3  of  FIG.  4   —extending transversely across the midsole  24  and, thus the sole structure  14 . Optionally, the midsole protrusions  40  and pockets  42  may also be arranged in a series of fore-aft columns—represented herein by first, second and third curvilinear columns C 1 -C 3  of  FIG.  4   —extending longitudinally across the midsole  24  and, thus the sole structure  14 . It may be desirable, for at least some applications, that the midsole  24  includes at least about fifty pockets  42  or, for at least some applications, at least about seventy pockets  42 . The protrusions  40  and pockets  42  may cooperatively cover at least about 60-70% of the midsole&#39;s  24  upper surface  25 . 
     To provide a complementary interface for mechanically attaching to the midsole  24 , the insole  22  has a ground-facing lower surface  29 , opposite a foot-facing upper insole surface  31  ( FIG.  3   ), with multiple insole protrusions  44  (also referred to herein as “second protrusions”) projecting downwardly therefrom. Similar to the midsole protrusions  40 , insole protrusions  44  may take on various combinations of shapes, sizes, and orientations; each protrusion  44 , for example, has a prolate-spheroid shaped body  49  with a rectangular base  51  (see upper inset view of  FIG.  4   ). The insole protrusions  44  may be approximately 1.0-3.0 mm high, as measured from the base  51 , and may project generally perpendicular from the lower insole surface  27 . It may be desirable, for at least some applications, that the insole  24  includes at least about fifty protrusions  44  or, for at least some applications, at least about seventy protrusions  44 , e.g., to coincide with the number of midsole pockets  42 . 
     Multiple insole pockets  46  (also referred to herein as “second pockets”) are recessed into the lower insole surface  29 , interleaved with the insole protrusions  44 . Similar to the midsole pockets  42 , the insole pockets  46  may take on assorted combinations of shapes, sizes, and orientations; pockets  46  of  FIG.  4    are portrayed as having a prolate-spheroid shaped cavity  53  with a rectangular window  55 . Generally speaking, the inner periphery of each midsole/insole pocket  42 ,  46  coincides with the outer periphery of a respective insole/midsole protrusion  44 ,  40  of the opposing shoe structure element. For instance, the insole pockets  46  may be approximately 1.0-4.0 mm deep, as measured from the window  47 , to match the heights of the midsole protrusions  40 . With this arrangement, each insole pocket  46  may neighbor and be delineated by multiple coterminous insole protrusions  44 . It may be desirable, for at least some applications, that the insole  24  includes at least about fifty pockets  46  or, for at least some applications, at least about seventy pockets  46 , e.g., to coincide with the number of midsole protrusions  40 . The protrusions  44  and pockets  46  may cooperatively cover at least about 80-90% of the insole&#39;s  22  lower surface  29 . 
     As shown, the insole protrusions  44  and pockets  46  are arranged in a series of mediolateral rows—represented herein by fourth, fifth and sixth rectilinear rows R 4 -R 6  of  FIG.  4   —extending transversely across the insole  22  and, thus, the sole structure  14 . The illustrated mediolateral rows of the insole  22  (e.g., rows R 4 -R 6 ) are parallel to one another and, for at least the illustrated embodiment, parallel with the mediolateral rows of the midsole  24  (e.g., rows R 1 -R 3 ). As a further option, the insole protrusions  44  and pockets  46  may also be arranged in a series of fore-aft columns—represented herein by fourth, fifth and sixth curvilinear columns C 4 -C 6  of  FIG.  4   —that extend longitudinally across the insole  22 . Each fore-aft insole column (e.g., columns C 4 -C 6 ) may be aligned with a respective one of the fore-aft midsole columns (e.g., columns C 1 -C 3 ). 
     When properly mated, the insole  22  and midsole  24  intermesh via complementary “egg-crate” geometries with the midsole protrusions  40  inserted alternatively between the insole protrusions  44 . Concomitantly, each midsole protrusion  40  seats inside and is surrounded by a respective insole pocket  46 , while each insole protrusion  44  seats inside and is surrounded by a respective midsole pocket  42 . With this configuration, most of the midsole protrusions  40  will be neighbored on three or four sides thereof by insole protrusions  44 , while most of the insole protrusions  44  will be neighbored on three or four sides thereof by midsole protrusions  40 , as best seen in FIGS.  5  and  6 . According to the illustrated example, each midsole protrusion  40  sits substantially flush against its corresponding insole pocket  46 , and each insole protrusion  44  sits substantially flush against its corresponding midsole pocket  42 . Additional subjacent support for the insole  22  may be provided by a stepped shelf  48  that is integrally formed into the midsole  24  and extends substantially continuously around the portion of the upper midsole surface  25  against which the insole  22  abuts. A flange  50  is integrally formed into and projects transversely from the insole  22 , extending substantially continuously around the lower insole surface  29 . Once properly aligned, the flange  50  of the insole  22  is buttressed on the stepped shelf  48  of the midsole  24 . 
     With reference again to  FIGS.  5  and  6   , a plurality of the midsole protrusions  40  may have distinct heights and widths. In  FIG.  5   , for example, a large midsole protrusion  40 A is shown to be wider and taller than a medium midsole protrusion  40 B, which is shown to be taller yet thinner than a small midsole protrusion  40 C. The heights of the midsole protrusions  40  may progressively increase in a fore-aft direction from the front of the shoe  10  (e.g., forefoot region R FF  of  FIG.  2   ) to the middle of the shoe  10  (e.g., midfoot region R MF ), and thereafter progressively decrease from the middle to the rear of the shoe (e.g., midfoot to hindfoot region R MF , R HF ). The heights of the midsole protrusions  40  may also progressively increase and decrease in a mediolateral direction from side-to-side of the shoe  10  (e.g., traversing across the lateral and medial segments S LA  and S ME  from top-to-bottom and bottom-to-top in  FIG.  2   ). The foregoing description may be similarly applicable to the midsole pockets  42 , as represented by the large, medium and small pockets  42 A,  42 B and  42 C, respectively, in  FIG.  5   . 
     Similar to the midsole protrusions  40 , many of the insole protrusions  44  may have distinct heights and widths from one another. In  FIG.  5   , for example, a large insole protrusion  44 A is shown to be taller yet thinner than a medium insole protrusion  44 B; medium insole protrusion  44 B, in turn, is taller yet thinner than a small insole protrusion  44 C. In the same vein, the heights of the insole protrusions  44  may progressively increase in a fore-aft direction from the front of the shoe  10  (e.g., forefoot region R FF ) to the middle of the shoe  10  (e.g., midfoot region R MF ), and thereafter progressively decrease from the middle to the rear of the shoe (e.g., midfoot region R MF  to hindfoot region R HF ). Further coinciding with the midsole protrusions  40 , the heights of the insole protrusions  44  may also progressively increase and decrease in a mediolateral direction from side-to-side of the shoe  10 . The foregoing description may be similarly applicable to the insole pockets  46 , as represented by the large, medium and small insole pockets  46 A,  46 B and  46 C, respectively, in  FIG.  5   . 
     A subset of the midsole protrusions  40  each includes an integrally formed nub  52  that projects upwardly from a distal tip thereof. These midsole protrusion nubs  52  may be fabricated in a variety of shapes in sizes; as best seen in the lower inset view of  FIG.  4   , each nub  52  may be formed with a cylindrical body with a rounded tip at a distal end of the cylindrical body. Likewise, a corresponding subset of the insole pockets  46  each includes a respective through hole  54  that extends through the insole  22  and receives therein a respective one of the midsole protrusion nubs  52 . As shown, each nub  52  extends through a corresponding insole pocket hole  54 , from the lower insole surface  29  to the upper insole surface  31 . The nubs are arranged in an engineered pattern that gives a “foot massaging” proprioceptive response for a user of the footwear  10 . While not per se required, the insole pocket holes  54  may be narrower than the width/diameter of the midsole protrusion nubs  52  such that press fitting the nubs  52  into the holes  54  creates an interference fit coupling between the insole  22  and midsole  24 . 
     Aspects of the present disclosure have been described in detail with reference to the illustrated embodiments; those skilled in the art will recognize, however, that many modifications may be made thereto without departing from the scope of the present disclosure. The present disclosure is not limited to the precise construction and compositions disclosed herein; any and all modifications, changes, and variations apparent from the foregoing descriptions are within the scope of the disclosure as defined by the appended claims. Moreover, the present concepts expressly include any and all combinations and subcombinations of the preceding elements and features.