Patent Publication Number: US-11653714-B2

Title: Footwear sole plate with non-parallel waves of varying thickness

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Nonprovisional application Ser. No. 16/395,589, filed Apr. 26, 2019, which claims the benefit of priority to U.S. Provisional Application No. 62/678,503, filed May 31, 2018, and both of which are incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present teachings generally include a sole plate for an article of footwear. 
     BACKGROUND 
     Footwear typically includes a sole structure configured to be located under a wearer&#39;s foot to space the foot away from the ground. Sole structures may typically be configured to provide one or more of cushioning, motion control, and resiliency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic illustration in plan view of a foot-facing surface of a sole plate. 
         FIG.  2    is a schematic illustration in plan view of a ground-facing surface of the sole plate of  FIG.  1   . 
         FIG.  3    is a schematic illustration in lateral side view of the sole plate of  FIG.  1   . 
         FIG.  4    is a schematic illustration in medial side view of the sole plate of  FIG.  1   . 
         FIG.  5    is a schematic illustration in front view of the sole plate of  FIG.  1   . 
         FIG.  6    is a schematic illustration in rear view of the sole plate of  FIG.  1   . 
         FIG.  7    is a schematic cross-sectional illustration of the sole plate of  FIG.  1    taken at lines  7 - 7  in  FIG.  1   . 
         FIG.  8    is a schematic cross-sectional illustration of the sole plate of  FIG.  1    taken at lines  8 - 8  in  FIG.  1   . 
         FIG.  9    is a schematic cross-sectional illustration of the sole plate of  FIG.  1    taken at lines  9 - 9  in  FIG.  1   . 
         FIG.  10    is a schematic cross-sectional illustration of the sole plate of  FIG.  1    taken at lines  10 - 10  in  FIG.  1   . 
         FIG.  11    is a schematic cross-sectional illustration of the sole plate of  FIG.  1    taken at lines  11 - 11  in  FIG.  1   . 
         FIG.  12    is a schematic illustration in medial side view of an article of footwear having a sole structure that includes the sole plate of  FIG.  1   , with the sole plate shown in hidden lines. 
         FIG.  13    is a schematic illustration in medial side view of the article of footwear of  FIG.  12   , in a first stage of motion. 
         FIG.  14    is a schematic illustration in medial side view of the article of footwear of  FIG.  12   , in a second stage of motion. 
         FIG.  15    is a schematic illustration in medial side view of the article of footwear of  FIG.  12   , in a third stage of motion. 
         FIG.  16    is a schematic illustration in cross-sectional view of the article of footwear of  FIG.  12    taken at lines  16 - 16  in  FIG.  12   . 
         FIG.  17    is a schematic fragmentary cross-sectional illustration of a forefoot portion of the article of footwear of  FIG.  16    when in the second stage of motion of  FIG.  14   . 
         FIG.  18    is a schematic illustration in cross-sectional view of an alternative embodiment of an article of footwear with an alternative midsole system. 
     
    
    
     DESCRIPTION 
     A sole plate is provided that is tuned for stiffness, energy absorption, and direction of energy return with any or all of a varying thickness, non-parallel, longitudinally-extending ridges, and a generally spoon-shaped forefoot portion. More particularly, a sole structure for an article of footwear comprises a sole plate that may include a midfoot region, and at least one of a forefoot region or a heel region. The sole plate may have a foot-facing surface with ridges extending longitudinally in the midfoot region and in the at least one of a forefoot region or a heel region. The sole plate may have a ground-facing surface with grooves extending longitudinally in correspondence with the ridges. The ridges and the grooves may be configured such that a thickness of the sole plate from the foot-facing surface to the ground-facing surface varies at a transverse cross-section of the sole plate through the ridges, or varies along a length of at least one of the ridges, or varies at both the transverse cross-section and along the length of the at least one of the ridges. The ridges, grooves, and a varied thickness as described may tune the stiffness and energy absorption of the sole plate for different zones while permitting a unitary, one-piece component of uniform material. The plate may function as a stiffness modifier within the sole structure. 
     In one or more embodiments, the ridges may have crests, and at least some of the crests may extend non-parallel with one another in a longitudinal direction of the sole plate. The grooves may also have crests, and at least some of the crests of the grooves may extend non-parallel with one another in the longitudinal direction. 
     In one or more embodiments, the sole plate may include both the forefoot region and the heel region. The ridges and the grooves may extend only in the midfoot region and the forefoot region, and the sole plate may have an undulating profile at any transverse cross-section of the sole plate through the ridges. In one or more of such embodiments, the transverse cross-section may be a first transverse cross-section of the sole plate in the midfoot region, and the undulating profile of the sole plate at the first transverse cross-section may include a first set of multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges. The undulating profile of the sole plate at a second transverse cross-section in the forefoot region may include a second set of multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges. Waves of the first set may each have a first wavelength, and waves of the second set may each have a second wavelength greater than the first wavelength. 
     In one or more embodiments, a lateral-most one of the ridges may curve in the longitudinal direction to follow a curved lateral edge of the sole plate, and a medial-most one of the ridges may curve in the longitudinal direction to follow a curved medial edge of the sole plate. Because the ridges may be non-parallel, the wavelengths can be different at the different transverse cross-sections. Generally, ridges with shorter wavelengths are stiffer in compression than ridges with longer wavelengths. 
     In one or more embodiments, the amplitude of the crests of the ridges may be greater in a zone of the sole plate configured for relatively high compressive loads than in a zone of the sole plate configured for relatively low compressive loads. For example, at least some of the crests may have an amplitude in a rearward portion of the forefoot region that is greater than in a forward portion of the forefoot region and than in the midfoot region. The rearward portion may be configured to underlie the metatarsal-phalangeal joints of a wearer, thus increasing stiffness and energy-absorbing capability where loading is greatest. 
     In one or more embodiments, the sole plate may be a resilient material such that the crests of the ridges may decrease in elevation from a steady state elevation to a loaded elevation under a dynamic compressive load and may return to the steady state elevation upon removal of the dynamic compressive load. For example, the sole plate may be one of a fiber strand-lain composite, a carbon-fiber composite, a thermoplastic elastomer, a glass-reinforced nylon, wood, or steel. The sole plate may resiliently deform to absorb and return energy. The areas of greater amplitude can absorb more energy than those of less amplitude. When sandwiched between foam layers of less compressive stiffness, such as a resilient foam midsole layer overlying and underlying the sole plate, the foam layers may react against the sole plate when resiliently deforming, so that the sole plate acts as a moderator both of bending stiffness and compressive stiffness of the sole structure. 
     In one or more embodiments, the foot-facing surface may be concave in a longitudinal direction of the sole plate in a forefoot region of the sole plate, and the ground-facing surface may be convex in the longitudinal direction of the sole plate in the forefoot region, creating a spoon-shaped forefoot region. In one or more embodiments, the sole plate may also have a heel region, and the sole plate may slope in the longitudinal direction in the midfoot region from the heel region to the forefoot region. The sole plate may be biased to this spoon shape in the forefoot region. Bending of the sole plate in the longitudinal direction during dorsiflexion may store energy that is released after toe-off, with the sole plate unbending to its original biased, spoon shape at least partially in the direction of forward motion. 
     In one or more embodiments, the foot-facing surface may have an undulating profile at the transverse cross-section that may include multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges. The crests at the ridges may be aligned with crests of the grooves. The thickness of the sole plate at the transverse cross-section may be less at the crests of the ridges than between the crests of the ridges and the troughs. 
     In one or more embodiments, the ground-facing surface may be flat between the grooves at the transverse cross-section. 
     In one or more embodiments, the sole plate may include both the forefoot region and the heel region, and may be a unitary, one-piece component. 
     In an aspect of the disclosure, a sole structure for an article of footwear may comprise a sole plate including a midfoot region, a forefoot region, and a heel region. The sole plate may have a foot-facing surface with ridges extending longitudinally such that the foot-facing surface may have an undulating profile at a transverse cross-section of the sole plate through the ridges. The sole plate may have a ground-facing surface with grooves extending longitudinally. At least some of the ridges of the foot-facing surface may extend non-parallel with one another, and at least some of the grooves of the ground-facing surface may extend non-parallel with one another in correspondence with the ridges. The ridges and the grooves may be configured such that a thickness of the sole plate from the foot-facing surface to the ground-facing surface varies at the transverse cross-section, or varies along a length of at least one of the ridges, or varies at both the transverse cross-section and along the length of the at least one of the ridges. At least some of the ridges may vary in amplitude in a longitudinal direction of the sole plate. 
     In one or more embodiments, the amplitude of at least some of the ridges may be greater in a rearward portion of the forefoot region than in a forward portion of the forefoot region, and greater in the rearward portion of the forefoot region than in the midfoot region. 
     In one or more embodiments, the ridges may have crests, and the sole plate may be a resilient material such that the crests of the ridges may decrease in elevation from a steady state elevation to a loaded elevation under a dynamic compressive load and may return to the steady state elevation upon removal of the dynamic compressive load. 
     In one or more embodiments, the transverse cross-section may be a first transverse cross-section of the sole plate in the midfoot region, and the undulating profile of the sole plate at the first transverse cross-section may include a first set of multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges. The undulating profile of the sole plate at a second transverse cross-section in the forefoot region may include a second set of multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges. Waves of the first set may each have a first wavelength. Waves of the second set may each have a second wavelength greater than the first wavelength. A lateral-most one of the ridges may curve in the longitudinal direction to follow a curved lateral edge of the sole plate. A medial-most one of the ridges may curve in the longitudinal direction to follow a curved medial edge of the sole plate. 
     In one or more embodiments, the foot-facing surface may be concave in the longitudinal direction in the forefoot region. The ground-facing surface may be convex in the longitudinal direction in the forefoot region. The sole plate may slope in the longitudinal direction in the midfoot region from the heel region to the forefoot region, and the ground-facing surface may be flat between the grooves at the transverse cross-section. 
     The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the modes for carrying out the present teachings when taken in connection with the accompanying drawings. 
     Referring to the drawings, wherein like reference numbers refer to like components throughout the views,  FIG.  1    shows an embodiment of a sole plate  10  for an article of footwear  12 , such as the article of footwear  12  of  FIG.  10   . More specifically, the sole plate  10  is included in a sole structure  14  of the article of footwear  12 . The sole plate  10  described herein is configured to moderate bending stiffness during dorsiflexion, and direct return energy to the foot at least partially in a forward direction when dynamic compressive loading is removed following dorsiflexion during a stride. More specifically, the sole plate  10  has varying, non-parallel ridges and grooves, and a general spoon shape, and resiliently deforms when under a dynamic load, storing elastic energy, and resiliently returns to an unloaded state when the dynamic load is removed, releasing the stored elastic energy. 
     As used herein, the term “plate”, such as in sole plate  10 , refers to a member of a sole structure that has a width greater than its thickness and is generally horizontally disposed when assembled in an article of footwear that is resting on the sole structure on a level ground surface, so that its thickness is generally in the vertical direction and its width is generally in the horizontal direction. A plate need not be a single component but instead can be multiple interconnected components. Portions of a plate can be flat, and portions can have some amount of curvature and variations in thickness when molded or otherwise formed in order to provide a shaped footbed and/or increased thickness for reinforcement in desired areas. 
     With reference to  FIG.  1   , the sole plate  10  has a forefoot region  16 , a midfoot region  18 , and a heel region  20 , and as such is referred to as a full-length sole plate  10  and is a unitary, one-piece component. Alternatively, in other embodiments within the scope of the present teachings, the sole plate  10  could include only a forefoot region  16  and midfoot region  18 , or only a midfoot region  18  and heel region  20 . 
     When a human foot  26  of a size corresponding with the sole structure  14  (see  FIG.  13   ) is supported on the sole structure, the forefoot region  16  generally includes portions of the sole plate  10  corresponding with the toes and the joints connecting the metatarsals with the phalanges of the foot  26  (interchangeably referred to herein as the “metatarsal-phalangeal joints” or “MPJ” joints). The midfoot region  18  generally includes portions of the sole plate  10  corresponding with an arch area of the human foot, including the navicular joint. The heel region  20  generally includes portions of a sole plate corresponding with rear portions of the foot  26 , including the calcaneus bone. The forefoot region  16 , the midfoot region  18 , and the heel region  20  may also be referred to as a forefoot portion, a midfoot portion, and a heel portion, respectively, and may also be used to refer to corresponding regions of an upper  23  shown in  FIG.  12    and other components of the article of footwear  12 . The midfoot region  18  is disposed between the forefoot region  16  and the heel region  20  such that the forefoot region  16  is forward of (i.e., anterior to) the midfoot region  18  and the heel region is rearward of (i.e., posterior to) the midfoot region  18 . 
     The sole plate  10  has a first side  22  shown in  FIG.  1   , also referred to as a foot-facing side  22  that includes a foot-facing surface  24 . As shown in  FIG.  2   , the sole plate  10  also has a second side  28  referred to as a ground-facing side  28  that includes a ground-facing surface  30 . The foot-facing side  22  is closer to the foot  26  (shown in phantom in  FIG.  16   ) than is the ground-facing side  28  when the sole plate  10  is assembled in the article of footwear  12  and worn on a foot  26 . The foot-facing side  22  is above the ground-facing side  28  when the sole plate  10  is assembled in the article of footwear  12  and worn on the foot  26 . The sole plate  10  also has a curved lateral edge  34  and a curved medial edge  32 . The sole plate  10  is a sole plate for a right foot. It should be understood that a sole plate for a left foot is a mirror image of the sole plate  10 . 
     Referring to  FIG.  1   , the foot-facing surface  24  has ridges  40  extending longitudinally in the midfoot region  18  and in the forefoot region  16 . The ridges  40  do not extend to the heel region  20 . The foot-facing surface  24  is generally flat in the heel region  20  as best shown in  FIGS.  10  and  11   . The ground-facing surface  30  has grooves  42  extending longitudinally in correspondence with the ridges  40 . In the embodiment shown, there are four ridges  40  and four grooves  42 . More specifically, as best shown in  FIGS.  7 - 9   , there are four ridges  40 A,  40 B,  40 C,  40 D in order between the medial edge  32  and the lateral edge  34 . The ridges  40 A,  40 B,  40 C,  40 D have crests  44 A,  44 B,  44 C,  44 D, respectively, that extend along the lengths of the respective ridges. A lateral-most one of the ridges  40 D curves in the longitudinal direction to follow the curved lateral edge  34 , and the medial-most one of the ridges  40 A curves in the longitudinal direction to follow the curved medial edge  32 . Stated differently, the ridge  40 D curves relative to a longitudinal midline LM to generally follow the lateral edge  34 , and the ridge  40 A curves relative to the longitudinal midline LM to generally follow the medial edge  32 . The longitudinal direction is generally a direction along a longitudinal midline LM of the sole plate  10 , and may be either a forward direction (i.e., from the midfoot region  18  toward the forefoot region  16 ), or a rearward direction (i.e., from the forefoot region  16  toward the midfoot region  18 ). 
     With reference to  FIGS.  3  and  4   , the foot-facing surface  24  is concave in a longitudinal direction of the sole plate  10  in the forefoot region  16 , and the ground-facing surface  30  is convex in the longitudinal direction of the sole plate  10  in the forefoot region  16 . The concavity of the foot-facing surface  24  and the convexity of the ground-facing surface  30  extend into the midfoot region  18  so that the midfoot region  18  and the forefoot region  16  together establish a spoon shape. Additionally, the sole plate  10  slopes in the longitudinal direction in the midfoot region  18  from the heel region  20  to the forefoot region  16 . More specifically, the midfoot region  18  slopes downward from the heel region  20  to the forefoot region  16  when the sole plate  10  is assembled in the sole structure  14  and the sole structure  14  rests on a level ground surface G as shown in  FIG.  12   .  FIGS.  5  and  6    also illustrate the concavity of the foot-facing surface  24  and the convexity of the ground-facing surface  30  in the forefoot region  16 . In  FIGS.  5  and  6   , the sole plate  10  is shown with the lowest point resting on a level ground surface G (i.e., prior to installation in the sole structure  14 ). The sole plate  10  slopes downward in the forefoot region  16  from a front edge  36 . The sole plate  10  slopes down in the midfoot region  18  relative to the heel region  20  which is level with a rear edge  38 . The front edge  36  is higher than the rear edge  38  when in this position. 
     As used herein, a transverse cross-section of the sole plate  10  through the ridges  40  is a cross-section perpendicular to the longitudinal midline LM, and includes the cross-sections of  FIGS.  7 - 11   . As best shown in  FIGS.  7 - 9   , at any particular transverse cross-section of the sole plate  10  through the ridges  40 A,  40 B,  40 C,  40 D, the crests  44 A,  44 B,  44 C,  44 D are equally spaced apart from one another. Stated differently, all adjacent crests  44 A,  44 B,  44 C,  44 D are equally-spaced. However, because the distance between the lateral edge  34  and the medial edge  32  varies along the length of the sole plate  10  (i.e., the sole plate  10  has different widths at different transverse cross-sections), the crests  44 A,  44 B,  44 C,  44 D extend non-parallel with one another in the longitudinal direction of the sole plate  10 . 
     With reference to  FIG.  2   , there are four grooves  42 A,  42 B,  42 C,  42 D on the ground-facing surface  30 , in order, between the medial edge  32  and the lateral edge  34 . As is apparent in  FIG.  2   , the grooves  42 A,  42 B,  42 C,  42 D do not extend to the heel region  20 , and the ground-facing surface  30  is generally flat in the heel region  20 . The ridges  40  and the grooves  42  extend only in the midfoot region  18  and the forefoot region  16 . The grooves  42 A,  42 B,  42 C,  42 D have crests  46 A,  46 B,  46 C,  46 D, respectively, that extend along the lengths of the respective grooves. A lateral-most one of the groove  42 D curves in the longitudinal direction to follow the curved lateral edge  34 , and the medial-most one of the grooves  42 A curves in the longitudinal direction to follow the curved medial edge  32 . Stated differently, the groove  42 D curves relative to the longitudinal midline LM to generally follow the lateral edge  34 , and the groove  42 A curves relative to the longitudinal midline LM to follow the medial edge  32 . Like crests  44 A,  44 B,  44 C,  44 D, at any transverse cross-section of the sole plate  10  through the ridges  40 A,  40 B,  40 C,  40 D, the crests  46 A,  46 B,  46 C,  46 D are equally spaced apart from one another (i.e., all adjacent crests  46 A,  46 B,  46 C,  46 D are equally-spaced) and the crests  46 A,  46 B,  46 C,  46 D extend non-parallel with one another in the longitudinal direction of the sole plate  10 . 
     The crests  46 A,  46 B,  46 C,  46 D of the grooves  42 A,  42 B,  42 C,  42 D are aligned with crests  44 A,  44 B,  44 C,  44 D of the ridges  40 A,  40 B,  40 C,  40 D. As used herein, the crests  44 A,  44 B,  44 C,  44 D are aligned with the crests  46 A,  46 B,  46 C,  46 D because the crests directly underlie the crests  44 A,  44 B,  44 C,  44 D along the length of the ridge  40 A,  40 B,  40 C,  40 D so that a line connecting crests of a corresponding ridge and groove (e.g., a line connecting crest  44 A and crest  46 A) is perpendicular to a line along the flat portions of the ground-facing surface  30  at the transverse cross-section. As is apparent in  FIGS.  1 - 2 , and  5 - 9   , the ground-facing surface  30  of the sole plate  10  is flat between the grooves  42  at any transverse cross-section. 
     Due to the ridges  40  and the grooves  42 , the sole plate  10  has an undulating profile at any transverse cross-section of the sole plate  10  through the ridges  40 . For example, the transverse cross-section of  FIG.  9    is a first transverse cross-section of the sole plate  10  in the midfoot region  18 . The foot-facing surface  24  has an undulating profile P 1  of the sole plate at the first transverse cross-section. The undulating profile P 1  includes a first set of multiple waves W 1 , W 2 , W 3 , W 4  having crests  44 A,  44 B,  44 C,  44 D at the ridges  40 A,  40 B,  40 C,  40 D, and having troughs  50 A,  50 B,  50 C between respective adjacent ones of the ridges. Each of the waves W 1 , W 2 , W 3 , W 4  is of an equal wavelength first L 1 . 
     The transverse cross-section at  FIG.  7    is a second transverse cross-section of the sole plate  10  through the ridge  40  in the forefoot region  16 . The undulating profile P 2  of the sole plate  10  at the second transverse cross-section includes a second set of multiple waves W 1 A, W 2 A, W 3 A, W 4 A having crests  44 A,  44 B,  44 C,  44 D at the ridges  40 A,  40 B,  40 C,  40 D, and having the troughs  50 A,  50 B,  50 C between respective adjacent ones of the ridges. Each of the waves W 1 A, W 2 A, W 3 A, W 4 A is of an equal second wavelength L 2 . The second wavelength L 2  is greater than the first wavelength L 1  due to the greater width of the sole plate  10  (from the medial edge  32  to the lateral edge  34 ) at the second transverse cross-section. 
     A third transverse cross-section of the sole plate  10  across the ridges  40  is shown in  FIG.  8    and is positioned longitudinally between the first and second cross-sections of  FIGS.  9  and  7   . The undulating profile P 3  of the sole plate  10  at the third transverse cross-section includes a third set of multiple waves W 1 B, W 2 B, W 3 B, W 4 B having the crests  44 A,  44 B,  44 C,  44 D at the ridges  40 A,  40 B,  40 C,  40 D, and having the troughs  50 A,  50 B,  50 C between respective adjacent ones of the ridges. Each of the waves W 1 B, W 2 B, W 3 B, W 4 B is of an equal third wavelength L 3 . The third wavelength L 3  is greater than the first wavelength L 1  and the second wavelength L 2  due to the width of the sole plate  10  at the third transverse cross-section being greater than that at the first transverse cross-section and greater than that at the second transverse cross-section. Generally, increasing the number of ridges  40  over a given width (i.e., decreasing the wavelength) increases the bending stiffness in the longitudinal direction of the sole plate  10 . The sole plate  10  is wider in the forefoot region  16  at the third transverse cross-section of  FIG.  8    than in the midfoot region  18  at the first transverse cross-section of  FIG.  9   . Because the ridges  40  are nonparallel and the wavelengths of the waves at a given transverse cross-section are equal, the sole plate  10  has the same number of ridges (four) over the forefoot region  16  and midfoot region  18 . 
     In addition to the number of ridges  40 , the thickness of the sole plate  10  and the amplitude of the crests  44 A,  44 B,  44 C,  44 D affect the bending stiffness as well as the energy return of the sole plate  10 . When the crests  44 A,  44 B,  44 C,  44 D are referred to generally herein, the reference numeral  44  may be used. The ridges  40  and the grooves  42  are configured such that a thickness of the sole plate  10  from the foot-facing surface  24  to the ground-facing surface  30  varies at a transverse cross-section of the sole plate  10  through the ridges  40  and varies along a length of at least one of the ridges  40 . For example, as shown at the transverse cross-section in  FIG.  8   , the thickness T 1  of the sole plate  10  at the crests  44  of the ridges  40  (as shown at crest  44 D) is less than the thickness T 2  of the sole plate  10  at a location between the crests of the ridges and the troughs. The sole plate  10  will thus tend to elastically deform under a dynamic compressive load applied to the foot-facing surface  24  beginning at the crests  44 . For example, the sole plate  10  may be a resilient material such that the foot-facing surface  24  including the crests  44  of the ridges  40  decreases in elevation under a dynamic compressive load from the steady state elevation shown with solid lines in  FIG.  8    to a loaded elevation  24 A shown in phantom in  FIG.  8   , and returns to the steady state elevation upon removal of the dynamic compressive load. At the crest  44 C, for example, the elevation decreases from elevation E 1  to elevation E 2 . For example, the sole plate  10  may be a fiber strand-lain composite, a carbon-fiber composite, a thermoplastic elastomer, a glass-reinforced nylon, wood, steel, or combinations thereof. 
     The ability of and the degree to which the sole plate  10  elastically deforms is also tuned by varying the thickness of the sole plate  10  along the length of the ridges  40 , and by varying the amplitude of the crests  44  along the length of the ridges  40 . A comparison of the transverse cross-sections of  FIGS.  7 - 11    shows that the sole plate  10  is thinnest (i.e., has the least thickness) at the ridges  40  where the amplitude of the crests  44  is the highest (e.g., in  FIG.  8   ), and the thickens gradually at the crests  44  as the amplitude decreases, as can be seen in  FIGS.  7  and  9   . 
     The ability of and the degree to which the sole plate  10  elastically deforms is tuned by varying the thickness of the sole plate  10  along the length of the ridges  40 , and by varying the amplitude of the crests  44  along the length of the ridges  40 . When the crests  46 A,  46 B,  46 C,  46 D are referred to generally herein, the reference numeral  46  may be used. The amplitude of the crests  46  is greater in zones of the sole plate  10  configured for relatively high compressive loads than in zones of the sole plate  10  configured for relatively low compressive loads. For example, referring to  FIG.  1   , at least some of the crests  46  may have an amplitude that is greater in a rearward portion  16 A of the forefoot region  16  (e.g., including at the transverse cross-section of  FIG.  8   ) than in a forward portion  16 B of the forefoot region (e.g., including at the transverse cross-section of  FIG.  7   ), and greater in the rearward portion  16 A of the forefoot region  16  than in the midfoot region  18  (e.g., including at the transverse cross-section of  FIG.  9   ). The greater amplitude of the crests  46  enables greater energy absorption under sufficient dynamic loading as more elastic deformation can occur with a greater possible change in height of the crests  46  between a steady state elevation and a loaded elevation. In the embodiment of the sole plate  10 , the amplitude of the crests  44  at any given transverse cross-section is uniform. Stated differently, each of the crests  44 A,  44 B,  44 C,  44 D has the same amplitude at the cross-section of  FIG.  7   , and has the same amplitude at the cross-section of  FIG.  8    (although different from that at  FIG.  7   ), and has the same amplitude at the cross-section of  FIG.  9    (although different from that at  FIGS.  7  and  8   ). 
     Referring to  FIG.  12   , the sole structure  14  includes a resilient foam midsole  60 . The sole structure  14  also includes discrete outsole elements  62 , or alternatively, could include a unitary outsole. The midsole  60  includes a first foam layer  60 A secured to the foot-facing surface  24 , and a second foam layer  60 B secured to the ground-facing surface  30 . The first and second foam layers  60 A,  60 B are separate components having different compressive stiffnesses. The first foam layer  60 A may be more or less stiff than the second foam layer  60 B. The first foam layer  60 A and the second foam layer  60 B may be the same material composition, with different densities to provide the different compressive stiffnesses, or may be different materials. 
     Alternatively, as shown in  FIG.  18   , an alternative article of footwear  112  has a midsole  160  that includes first and second foam layers  160 A,  160 B that are portions of a single component (i.e., a single, unitary, one-piece resilient foam midsole  160 ). The first and second resilient foam midsole layers  160 A,  160 B are an upper portion and a lower portion of a single resilient foam midsole  160  surrounding the sole plate  10 , and in one embodiment, may be formed by injecting foam around the sole plate. The first and second foam layers  160 A,  160 B are the same material and have the same compressive stiffness. 
     As indicated in  FIG.  17   , the foam midsole  60  compresses between the foot  26  and the ground G under a dynamic compressive load and reacts against both the foot-facing surface  24  and the ground-facing surface  30  of the stiffer sole plate  10 . The first foam layer  60 A and the second foam layer  60 B resiliently deform under the dynamic compressive load. The dynamic compressive load is illustrated by distributed loads F 1 , F 2 , F 3 , F 4 , F 5  having various magnitudes represented by the length of the arrows. The first and second foam layers  60 A,  60 B return energy upon removal of the dynamic compressive load. Under dynamic loading, the first foam layer  60 A is compressed against the foot-facing surface  24 , and the second foam layer is compressed against the ground-facing surface  30 . 
       FIG.  12    shows the article of footwear in a resting position, under steady state loading by the foot  26 .  FIG.  12    may also represent an interim position of the article of footwear  12  during a stride in which the sole structure  14  is flat on the ground G.  FIGS.  13 - 15    show the article of footwear  12  in progressive first, second, and third stages of motion during the stride. The first stage of motion show in  FIG.  13    is the beginning of the stride, with the heel portion  20  of the sole structure  14  and at least part of the midfoot portion  18  lifted from the ground G and the forefoot portion  16  in contact with the ground G. The second stage of motion in  FIG.  14    shows further lifting of the midfoot portion  18  of the sole structure  14  away from the ground surface G and the forefoot portion  16  in contact with the ground G. Finally,  FIG.  15    shows the article of footwear  12  completely lifted away from the ground G, as may occur during running. During the stride, the sole plate  10  bends along its length (e.g., along its longitudinal midline LM shown in  FIG.  1   ). Progressive bending occurs in the forefoot region  16 , generally under the metatarsal-phalangeal joints of the foot  26 , when the foot  26  is dorsiflexed and increased loading is placed in the forefoot region  16  as the wearer&#39;s weight shifts to the forefoot. 
     The spoon shape of the sole plate  10 , best shown in  FIG.  16   , including the concave foot-facing surface  24  and convex ground-facing surface  30  in the forefoot region  16  helps to encourage forward rolling of the foot  26 . When the foot  26  lifts the sole structure  14  away from the ground Gin  FIG.  15   , the compressive forces in the sole plate  10  above a neutral axis of the sole plate  10  to the foot-facing surface  24 , and tensile forces below the neutral axis to the ground-facing surface  30  are relieved, returning the sole plate  10  to its unloaded orientation shown in  FIG.  15   , which is the same as in  FIG.  12    except lifted from the ground. The internal compressive and tensile forces in the sole plate  10  due to the wearer bending the sole plate  10  are released as the sole plate  10  unbends creates a net force F at least partially in the forward direction. 
     Accordingly, as discussed herein the sole plate  10  is tuned by varying its thickness, the amplitude of crests of ridges, and by the spoon shape, all of which contribute to the energy absorption during dynamic compression and longitudinal bending, and subsequent energy return during forward strides. 
     The following Clauses provide example configurations of a sole structure for an article of footwear disclosed herein. 
     Clause 1: A sole structure for an article of footwear comprising: a sole plate including a midfoot region, and the sole plate further including at least one of a forefoot region or a heel region; wherein the sole plate has a foot-facing surface with ridges extending longitudinally in the midfoot region and in the at least one of a forefoot region or a heel region; wherein the sole plate has a ground-facing surface with grooves extending longitudinally in correspondence with the ridges; and wherein the ridges and the grooves are configured such that a thickness of the sole plate from the foot-facing surface to the ground-facing surface varies at a transverse cross-section of the sole plate through the ridges, or varies along a length of at least one of the ridges, or varies at both the transverse cross-section and along the length of the at least one of the ridges. 
     Clause 2: The sole structure of Clause 1, wherein: the ridges have crests at least some of which extend non-parallel with one another in a longitudinal direction of the sole plate; and the grooves have crests at least some of which extend non-parallel with one another in the longitudinal direction. 
     Clause 3: The sole structure of any of Clauses 1-2, wherein the ridges have crests at least some of which vary in amplitude in a longitudinal direction of the sole plate such that the amplitude is greater in a zone of the sole plate configured for relatively high compressive loads than in a zone of the sole plate configured for relatively low compressive loads. 
     Clause 4: The sole structure of Clause 3, wherein: The sole plate includes the forefoot region; and at least some of the crests have an amplitude that is greater in a rearward portion of the forefoot region than in a forward portion of the forefoot region and, greater in the rearward portion of the forefoot region than in the midfoot region. 
     Clause 5: The sole structure of any of Clauses 1-4, wherein the ridges have crests, and the sole plate is a resilient material such that the crests of the ridges decrease in elevation from a steady state elevation to a loaded elevation under a dynamic compressive load and return to the steady state elevation upon removal of the dynamic compressive load. 
     Clause 6: The sole structure of Clause 5, wherein the sole plate is one of a fiber strand-lain composite, a carbon-fiber composite, a thermoplastic elastomer, a glass-reinforced nylon, wood, or steel. 
     Clause 7: The sole structure of any of Clauses 1-6, wherein: the sole plate includes the forefoot region; the foot-facing surface is concave in a longitudinal direction of the sole plate in the forefoot region; and the ground-facing surface is convex in the longitudinal direction of the sole plate in the forefoot region. 
     Clause 8: The sole structure of Clause 7, wherein: the sole plate includes the heel region; and the sole plate slopes in the longitudinal direction in the midfoot region from the heel region to the forefoot region. 
     Clause 9: The sole structure of any of Clauses 1-8, wherein: the foot-facing surface has an undulating profile at the transverse cross-section that includes multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges; and the crests at the ridges are aligned with crests of the grooves. 
     Clause 10: The sole structure of Clause 9, wherein the thickness of the sole plate at the transverse cross-section is less at the crests of the ridges than between the crests of the ridges and the troughs. 
     Clause 11: The sole structure of any of Clauses 1-10, wherein: the sole plate includes both the forefoot region and the heel region; the ridges and the grooves extend only in the midfoot region and the forefoot region; and the sole plate has an undulating profile at any transverse cross-section of the sole plate through the ridges. 
     Clause 12: The sole structure of Clause 11, wherein: the transverse cross-section is a first transverse cross-section of the sole plate in the midfoot region; the undulating profile of the sole plate at the first transverse cross-section includes a first set of multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges; the undulating profile of the sole plate at a second transverse cross-section in the forefoot region includes a second set of multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges; waves of the first set each have a first wavelength; and waves of the second set each have a second wavelength greater than the first wavelength. 
     Clause 13: The sole structure of any of Clauses 1-12, wherein: a lateral-most one of the ridges curves in the longitudinal direction to follow a curved lateral edge of the sole plate; and a medial-most one of the ridges curves in the longitudinal direction to follow a curved medial edge of the sole plate. 
     Clause 14: The sole structure of Clause 1, wherein the ground-facing surface is flat between the grooves at the transverse cross-section. 
     Clause 15: The sole structure of any of Clauses 1-14, wherein the sole plate includes both the forefoot region and the heel region and is a unitary, one-piece component. 
     Clause 16: A sole structure for an article of footwear comprising: a sole plate including a midfoot region, a forefoot region, and a heel region; wherein the sole plate has a foot-facing surface with ridges extending longitudinally such that the foot-facing surface has an undulating profile at a transverse cross-section of the sole plate through the ridges; wherein the sole plate has a ground-facing surface with grooves extending longitudinally; wherein at least some of the ridges of the foot-facing surface extend non-parallel with one another, and at least some of the grooves of the ground-facing surface extend non-parallel with one another in correspondence with the ridges; wherein the ridges and the grooves are configured such that a thickness of the sole plate from the foot-facing surface to the ground-facing surface varies at the transverse cross-section, or varies along a length of at least one of the ridges, or varies at both the transverse cross-section and along the length of the at least one of the ridges; and at least some of the ridges vary in amplitude in a longitudinal direction of the sole plate. 
     Clause 17: The sole structure of Clause 16, wherein the amplitude of at least some of the ridges is greater in a rearward portion of the forefoot region than in a forward portion of the forefoot region, and greater in the rearward portion of the forefoot region than in the midfoot region. 
     Clause 18: The sole structure of any of Clauses 16-17, wherein the ridges have crests, and the sole plate is a resilient material such that the crests of the ridges decrease in elevation from a steady state elevation to a loaded elevation under a dynamic compressive load and return to the steady state elevation upon removal of the dynamic compressive load. 
     Clause 19: The sole structure of any of Clauses 17-18, wherein: the transverse cross-section is a first transverse cross-section of the sole plate in the midfoot region; the undulating profile of the sole plate at the first transverse cross-section includes a first set of multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges; the undulating profile of the sole plate at a second transverse cross-section in the forefoot region includes a second set of multiple waves having crests at the ridges and having troughs between respective adjacent ones of the ridges; waves of the first set each have a first wavelength; waves of the second set each have a second wavelength greater than the first wavelength; a lateral-most one of the ridges curves in the longitudinal direction to follow a curved lateral edge of the sole plate; and a medial-most one of the ridges curves in the longitudinal direction to follow a curved medial edge of the sole plate. 
     Clause 20: The sole structure of any of Clauses 16-19, wherein: the foot-facing surface is concave in the longitudinal direction in the forefoot region; the ground-facing surface is convex in the longitudinal direction in the forefoot region; the sole plate slopes in the longitudinal direction in the midfoot region from the heel region to the forefoot region; and the ground-facing surface is flat between the grooves at the transverse cross-section. 
     To assist and clarify the subsequent description of various embodiments, various terms are defined herein. Unless otherwise indicated, the following definitions apply throughout this specification (including the claims). 
     “A”, “an”, “the”, “at least one”, and “one or more” are used interchangeably to indicate that at least one of the items is present. A plurality of such items may be present unless the context clearly indicates otherwise. As used herein, “at least some” of an item means at least two of the items. All numerical values of parameters (e.g., of quantities or conditions) in this specification, unless otherwise indicated expressly or clearly in view of the context, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. In addition, a disclosure of a range is to be understood as specifically disclosing all values and further divided ranges within the range. All references referred to are incorporated herein in their entirety. 
     The terms “comprising”, “including”, and “having” are inclusive and therefore specify the presence of stated features, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, or components. Orders of steps, processes, and operations may be altered when possible, and additional or alternative steps may be employed. As used in this specification, the term “or” includes any one and all combinations of the associated listed items. The term “any of” is understood to include any possible combination of referenced items, including “any one of” the referenced items. The term “any of” is understood to include any possible combination of referenced claims of the appended claims, including “any one of” the referenced claims. 
     For consistency and convenience, directional adjectives are employed throughout this detailed description corresponding to the illustrated embodiments. Those having ordinary skill in the art will recognize that terms such as “above”, “below”, “upward”, “downward”, “top”, “bottom”, etc., may be used descriptively relative to the figures, without representing limitations on the scope of the invention, as defined by the claims. 
     The term “longitudinal”, as used throughout this detailed description and in the claims, refers to a direction extending a length of a component. For example, a longitudinal direction of a shoe extends between a forefoot region and a heel region of the shoe. The term “forward” is used to refer to the general direction from a heel region toward a forefoot region, and the term “rearward” is used to refer to the opposite direction, i.e., the direction from the forefoot region toward the heel region. In some cases, a component may be identified with a longitudinal axis as well as a forward and rearward longitudinal direction along that axis. 
     The term “vertical”, as used throughout this detailed description and in the claims, refers to a direction generally perpendicular to both the lateral and longitudinal directions. For example, in cases where a sole structure is planted flat on a ground surface, the vertical direction may extend from the ground surface upward. It will be understood that each of these directional adjectives may be applied to individual components of a sole structure. The term “upward” or “upwards” refers to the vertical direction pointing towards a top of the component, which may include an instep, a fastening region and/or a throat of an upper. The term “downward” or “downwards” refers to the vertical direction pointing opposite the upwards direction, and may generally point towards the sole structure, or towards the outermost components of the sole structure. 
     The “interior” of an article of footwear, such as a shoe, refers to portions at the space that is occupied by a wearer&#39;s foot when the shoe is worn. The “inner side” of a component refers to the side or surface of the component that is (or will be) oriented toward the interior of the shoe in an assembled shoe. The “outer side” or “exterior” of a component refers to the side or surface of the component that is (or will be) oriented away from the interior of the shoe in an assembled shoe. In some cases, the inner side of a component may have other components between that inner side and the interior in the assembled shoe. Similarly, an outer side of a component may have other components between that outer side and the space external to the assembled shoe. Further, the terms “inward” and “inwardly” shall refer to the direction toward the interior of the component or article of footwear, such as a shoe, and the terms “outward” and “outwardly” shall refer to the direction toward the exterior of the component or article of footwear, such as the shoe. In addition, the term “proximal” refers to a direction that is nearer a center of a footwear component, or is closer toward a foot when the foot is inserted in the article as it is worn by a user. Likewise, the term “distal” refers to a relative position that is further away from a center of the footwear component or is further from a foot when the foot is inserted in the article as it is worn by a user. Thus, the terms proximal and distal may be understood to provide generally opposing terms to describe the relative spatial position of a footwear layer. 
     While various embodiments have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the embodiments. Any feature of any embodiment may be used in combination with or substituted for any other feature or element in any other embodiment unless specifically restricted. Accordingly, the embodiments are not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims. 
     While several modes for carrying out the many aspects of the present teachings have been described in detail, those familiar with the art to which these teachings relate will recognize various alternative aspects for practicing the present teachings that are within the scope of the appended claims. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and exemplary of the entire range of alternative embodiments that an ordinarily skilled artisan would recognize as implied by, structurally and/or functionally equivalent to, or otherwise rendered obvious based upon the included content, and not as limited solely to those explicitly depicted and/or described embodiments.