Patent Publication Number: US-8984773-B2

Title: Footwear outsole

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This U.S. patent application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application 61/432,317, filed on Jan. 13, 2011, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to outsoles for articles of footwear. 
     BACKGROUND 
     Articles of footwear, such as shoes, are generally worn while exercising to protect and provide stability of a user&#39;s feet. In general, shoes include an upper portion and a sole. When the upper portion is secured to the sole, the upper portion and the sole together define a void that is configured to securely and comfortably hold a human foot. Often, the upper portion and/or sole are/is formed from multiple layers that can be stitched or adhesively bonded together. For example, the upper portion can be made of a combination of leather and fabric, or foam and fabric, and the sole can be formed from at least one layer of natural rubber. Often materials are chosen for functional reasons, e.g., water-resistance, durability, abrasion-resistance, and breathability, while shape, texture, and color are used to promote the aesthetic qualities of the shoe. The sole generally provides support for a user&#39;s foot and acts as an interface between the user&#39;s foot and the ground. 
     SUMMARY 
     One aspect of the disclosure provides an outsole for an article of footwear. The outsole includes an outsole body having a ground contact surface and defining grooves having a sinusoidal path along the ground contact surface. The grooves are arranged to provide an edge density of between about 40 mm/cm 2  and about 200 mm/cm 2  and a surface contact ratio of between about 40% and about 95%. 
     Implementations of the disclosure may include one or more of the following features. In some implementations, at least some of the sinusoidal grooves are arranged substantially parallel to each other to provide an edge density of about 59 mm/cm 2  and a surface contact ratio of about 67%. In additional implementations, at least some of the sinusoidal grooves are arranged substantially parallel to each other to provide an edge density of about 106 mm/cm 2  and a surface contact ratio of about 91%. In yet additional implementations, at least some of the sinusoidal grooves are arranged substantially parallel to each other to provide an edge density of about 80 mm/cm 2  and a surface contact ratio of about 84%. At least some of the sinusoidal grooves, in some implementations, are arranged substantially parallel to each other to provide an edge density of about 77 mm/cm 2  and a surface contact ratio of about 90%. 
     At least one sinusoidal groove path along the ground contact surface may have an amplitude of between about 3 mm and about 25 mm and/or a frequency of between about 4 mm and about 50 mm. For example, at least one sinusoidal groove path along the ground contact surface may have an amplitude of between about 5 mm and a frequency of about 6.3 mm. Moreover, the corresponding groove may have a width of between about 0.1 mm and about 5 mm and/or a depth of between about 25% a thickness of the outsole and about 75% the thickness of the outsole. For example, the corresponding groove may have a width of about 0.4 mm and/or a depth of about 1.2 mm. 
     In some implementations, each groove has a sinusoidal groove path along the ground contact surface having an amplitude of about 5 mm and a frequency of about 6.3 mm. Adjacent grooves are offset from each other along the ground contact surface in a common direction by an offset distance of about 3.15 mm. At least one channel may connect two adjacent grooves. The at least one channel can have a depth of about half a depth of the grooves and/or a width substantially equal to a width of the grooves. 
     In additional implementations, at least one sinusoidal groove path along the ground contact surface has an amplitude of about 17.6 mm and a frequency of about 40 mm. The corresponding groove may have a width of about 1 mm and/or a depth of about 1.5 mm. 
     Each groove may have a sinusoidal groove path along the ground contact surface having an amplitude of about 17.6 mm and a frequency of about 40 mm, where adjacent grooves are offset from each other along the ground contact surface in a common direction by an offset distance of between about 3 mm and about 3.75 mm. For three consecutive grooves along the ground contact surface, a first groove may be offset from a second groove by an offset distance of about 3 mm and the second groove may be offset from a third groove by an offset distance of about 3.75 mm. 
     Each groove may have at least one shoulder edge with the ground contact surface. The at least one shoulder edge may define a right angle with a substantially non-radiused corner. Other shoulder edge configurations are possible as well, such as rounded, chamfered, etc. 
     The outsole body may comprise at least one of rubber having a durometer of between about 45 Shore A and about 65 Shore A, a rubber having a minimum coefficient of friction of about 0.9 and a durometer of between about 50 Shore A and about 65 Shore A, and a rubber having a minimum coefficient of friction of about 1.1 and a durometer of between about 50 Shore A and about 65 Shore A. 
     Another aspect of the disclosure provides an outsole for an article of footwear that includes an outsole body having a ground contact surface and defining grooves having a sinusoidal path along the ground contact surface. The grooves define a sinusoidal groove path along the ground contact surface having an amplitude of about 5 mm and a frequency of about 6.3 mm. 
     In some implementations, the grooves have a width of about 0.4 mm and/or a depth of about 1.2 mm. Adjacent grooves may be offset from each other along the ground contact surface in a common direction by an offset distance (e.g., about 3.15 mm). In some examples, the outsole includes at least one channel connecting the adjacent grooves. The at least one channel may have a depth of about half a depth of the grooves and/or a width substantially equal to a width of the grooves. Moreover, the grooves may be arranged substantially parallel to each other to provide an edge density of about 106 mm/cm 2  and a surface contact ratio of about 91%. 
     In another aspect, an outsole for an article of footwear includes an outsole body having a ground contact surface and defining grooves having a sinusoidal path along the ground contact surface. The grooves define a sinusoidal groove path along the ground contact surface having an amplitude of about 17.6 mm and a frequency of about 40 mm. 
     In some implementations, the grooves have a width of about 1 mm and/or a depth of about 1.5 mm. Adjacent grooves may be offset from each other along the ground contact surface in a common direction by an offset distance (e.g., between about 3 mm and about 3.75 mm). For example, for three consecutive grooves along the ground contact surface, a first groove may be offset from a second groove by an offset distance of about 3 mm and the second groove is offset from the third groove by an offset distance of about 3.75 mm. 
     Each groove may have at least one shoulder edge with the ground contact surface. The at least one shoulder edge may define a right angle with a substantially non-radiused corner. Moreover, at least some adjacent grooves may intersect each other periodically along their respective sinusoidal paths. The grooves can be arranged substantially parallel to each other to provide an edge density of about 59 mm/cm 2  and a surface contact ratio of about 67%. 
     In yet another aspect, an outsole for an article of footwear includes an outsole body having lateral and medial portions and a ground contact surface. The outsole defining a longitudinal axis along a walking direction and perpendicular transverse axis. The ground contact surface has a first tread region disposed on the lateral outsole body portion near a lateral periphery of the outsole, a second tread region disposed on the medial outsole body portion near a medial periphery of the outsole, and a third tread region disposed between the first and second tread regions in at least a ground striking portion of the outsole. The first and second tread regions define grooves having a sinusoidal path along the ground contact surface with an axis of propagation substantially parallel to the longitudinal axis of the outsole. Adjacent grooves are offset from each other along the transverse axis by a first offset distance. The third tread region defines grooves having a sinusoidal path along the ground contact surface with an axis of propagation substantially parallel to the transverse axis of the outsole. Adjacent grooves are offset from each other along the longitudinal axis by a second offset distance. 
     In some implementations, the grooves of the first and second tread regions define a sinusoidal groove path along the ground contact surface having an amplitude of about 17.6 mm and a frequency of about 40 mm. The grooves of the first and second tread regions may have a width of about 1 mm and/or a depth of about 1.5 mm. The first offset distance may be between about 3 mm and about 3.75 mm. For example, for three consecutive grooves along the ground contact surface of the first and second tread regions, a first groove is offset from a second groove by an offset distance of about 3 mm and the second groove is offset from a third groove by an offset distance of about 3.75 mm. At least some adjacent grooves of the first and second tread regions may intersect each other periodically along their respective sinusoidal paths. Moreover, the grooves of the first and second tread regions may be arranged to provide an edge density of about 59 mm/cm 2  and a surface contact ratio of about 67%. 
     The grooves of the third tread region may define a sinusoidal groove path along the ground contact surface having an amplitude of about 5 mm and a frequency of about 6.3 mm. In some examples, the grooves of the third tread region have a width of about 0.4 mm and/or a depth of about 1.2 mm. The second offset distance may be about 3.15 mm. The third tread region sometimes includes at least one channel connecting adjacent grooves. The at least one channel has a depth of about half a depth of the grooves of the third tread region and/or a width substantially equal to a width of the grooves the third tread region. The grooves of the third tread region can be arranged to provide an edge density of about 106 mm/cm 2  and a surface contact ratio of about 91%. 
     Each groove may have at least one shoulder edge with the ground contact surface. The at least one shoulder edge defines a right angle with a substantially non-radiused corner. 
     For each of the aspects discussed, the outsole body may comprise at least one of rubber having a durometer of between about 45 Shore A and about 65 Shore A, a rubber having a minimum coefficient of friction of about 0.9 and a durometer of between about 50 Shore A and about 65 Shore A, and a rubber having a minimum coefficient of friction of about 1.1 and a durometer of between about 50 Shore A and about 65 Shore A. 
     The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a bottom view of an exemplary sole assembly. 
         FIG. 2  is a top view of the sole assembly shown in  FIG. 1 . 
         FIG. 3  is a lateral side view of the sole assembly shown in  FIG. 1 . 
         FIG. 4  is a medial side view of the sole assembly shown in  FIG. 1 . 
         FIG. 5  is a front view of the sole assembly shown in  FIG. 1 . 
         FIG. 6  is a rear view of the sole assembly shown in  FIG. 1 . 
         FIG. 7  is a section view of the sole assembly shown in  FIG. 1  along line  7 - 7 . 
         FIG. 8  is a section view of the sole assembly shown in  FIG. 1  along line  8 - 8 . 
         FIG. 9  is a section view of the sole assembly shown in  FIG. 1  along line  9 - 9 . 
         FIG. 10  is a section view of the sole assembly shown in  FIG. 1  along line  10 - 10 . 
         FIG. 11  is a section view of the sole assembly shown in  FIG. 1  along line  11 - 11 . 
         FIG. 12  is a section view of the sole assembly shown in  FIG. 1  along line  12 - 12 . 
         FIG. 13  is a bottom view of a portion of an exemplary outsole having sinusoidal grooves. 
         FIG. 14  is a section view of the outsole shown in  FIG. 13  along line  14 - 14 . 
         FIG. 15  is a bottom view of a portion of an exemplary outsole having sinusoidal grooves. 
         FIG. 16  is a section view of the outsole shown in  FIG. 15  along line  16 - 16 . 
         FIG. 17  is a section view of the outsole shown in  FIG. 15  along line  17 - 17 . 
         FIG. 18A  is a bottom view of a portion of an exemplary outsole having sinusoidal grooves. 
         FIG. 18B  is a section view of the outsole shown in  FIG. 18A  along line  18 B- 18 B. 
         FIG. 19A  is a bottom view of a portion of an exemplary outsole having sinusoidal grooves. 
         FIG. 19B  is a section view of the outsole shown in  FIG. 19A  along line  19 B- 19 B. 
         FIG. 20A  is a bottom view of a portion of an exemplary outsole having sinusoidal grooves. 
         FIG. 20B  is a section view of the outsole shown in  FIG. 20A  along line  20 B- 20 B. 
         FIG. 21A  is a bottom view of a portion of an exemplary outsole having sinusoidal grooves. 
         FIG. 21B  is a section view of the outsole shown in  FIG. 21A  along line  21 B- 21 B. 
         FIG. 22A  is a bottom view of a portion of an exemplary outsole having sinusoidal or zig-zag style grooves. 
         FIG. 22B  is a section view of the outsole shown in  FIG. 22A  along line  22 B- 22 B. 
         FIG. 23A  is a chart of slip test resistance results under wet and dry conditions for various tread configurations of an outsole comprising a rubber having a coefficient of friction of 0.9 and a durometer of 50-55 Shore A. 
         FIG. 23B  is a chart of slip test resistance results under wet and dry conditions for various tread configurations of an outsole comprising latex having a durometer of 50-55 Shore A. 
         FIG. 23C  is a chart of slip test resistance results under wet and dry conditions for various tread configurations of an outsole comprising latex having a durometer of 60-65 Shore A. 
         FIG. 24A  is a chart of slip test resistance results under wet and dry conditions for various tread configurations of an outsole comprising a rubber having a coefficient of friction of 0.9 and a durometer of 50-55 Shore A. 
         FIG. 24B  is a chart of slip test resistance results under wet and dry conditions for various tread configurations of an outsole comprising latex having a durometer of 50-55 Shore A. 
         FIG. 24C  is a chart of slip test resistance results under wet and dry conditions for various tread configurations of an outsole comprising latex having a durometer of 60-65 Shore A. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. By way of example only, all of the drawings are directed to an outsole for an article of footwear (e.g., a shoe) suitable to be worn on a user&#39;s right foot. The invention includes also the mirror images of the drawings, i.e. an outsole for an article of footwear suitable to be worn on the user&#39;s left foot. 
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-7 , in some implementations, a sole assembly  50  includes an outsole  100  supporting a midsole  200 . The outsole  100  has a forefoot portion  102 , a heel portion  104  as well as a lateral portion  106  and a medial portion  108 . The outsole  100  also defines a ground contact surface  110  for contacting the ground. The midsole  200  can be made of ethylene vinyl acetate (EVA), foam, or any suitable material for providing cushioning in an article of footwear. 
     The outsole  100  may have a tread configuration designed for slip resistance. For example, the ground contact surface  110  of the outsole  100  may define a plurality of grooves or channels  112 , such as siped grooves or slits, that receive water escaping from between the ground contact surface  110  and the ground as the outsole  100  is pressed against the ground (e.g., when the sole assembly  50  bears the weight of a user). Liquid can flow in the grooves or channels  112  toward a perimeter of the outsole  100  (i.e., away from weight-bearing and contact surfaces). The grooves or channels  112  may also be configured to provide flex regions of the outsole  100 , such as in the forefoot portion  102  to accommodate toe lifting of a user or flexing during walking or running. The grooves or channels  112  may be adequately sized for liquid movement there-through, while deterring the accumulation of small objects therein. Moreover, the grooves or channels  112  may flex open (e.g., during walking or running), providing traction and water escapement from the ground contact surface  110 . In some implementations, the grooves or channels  112  are cut into the outsole  100 , while in other implementations, the grooves or channels  112  are molded with the outsole  100 . The grooves or channels  112  can have a width W G  of between about 0.1 mm to about 5 mm (e.g., 1.2 mm) and/or a depth D G  of between about 25% to about 75% of a thickness T of the outsole  100 . For example, for an outsole  100  having a thickness of 3.5 mm, the grooves  112  can have a depth D of between about 0.8 mm and about 2.6 mm (e.g., a depth D of 1 mm, 2 mm, or 2.5 mm). Siped grooves  112  may have a relatively thin width W G  as compared to other types of grooves  112 . Siped grooves  112  may be formed by razor cutting the groove  112  into the outsole  100  or molding the groove  112  with a relatively narrow width W G . 
     In the examples shown, the outsole  100  defines first and second tread regions  120 ,  130 ; however, the outsole  100  may define one contiguous tread region or many tread regions arranged randomly or in specific locations on the ground contact surface  130 . Each tread region  120 ,  130  includes a corresponding configuration grooves or channels  122 ,  132  that provides traction on wet or slippery surfaces. The groove or channel configuration can be arranged to have a certain edge density and a certain surface contact ratio to provide a certain level of traction performance (or resistance to slip). Edge density can be defined as a length of surface edges of the ground contact surface  110  (e.g., the cumulative length (millimeters) of edges on the ground contact surface  110  from the grooves or channels  122 ,  132 ) within a square centimeter. In general, the greater the edge density, the greater the traction; however, manufacturability, aesthetics, resistance to wear and other factors may limit the edge density. The surface contact ratio can be defined as an overall area of the ground contact surface  110  minus a groove area of the ground contact surface  110  (i.e. an area of the ground contact surface removed for the grooves or channels  122 ,  132 ) divided by the overall area of the ground contact surface  110 . In dry conditions, a surface contact ratio of 100% can provide the best traction; however, a ground contact surface  110  with no grooves or channels  122 ,  132  provides very poor traction or slip resistance in wet conditions. Therefore, a relationship or balance between the edge density and the surface contact ratio of the ground contact surface  110  can provide certain traction and performance characteristics of the outsole  100  in various environmental conditions. 
     The grooves or channels  112 ,  122 ,  132  of the outsole  100  can be arranged to provide an edge density of between about 40 mm/cm 2  and about 200 mm/cm 2  and/or a surface contact ratio of between about 40% and about 95%. In some implementations, the grooves or channels  112 ,  122 ,  132  of the outsole  100  are arranged to provide an edge density of between about 100 mm/cm 2  and about 110 mm/cm 2  and/or a surface contact ratio of between about 50% and about 95%. Moreover, the grooves or channels  122 ,  132  can define a sinusoidal path along the ground contact surface  110 . For example, the sinusoidal path of the grooves or channels  122 ,  132  may be defined by the following equation:
 
 y ( t )= A ·sine(ω t +φ)  (1)
 
     where t is time, A is amplitude, ω is angular frequency and φ is phase at a time of t=0. Referring to  FIGS. 1-7  and  15 - 17 , a tread pattern for the outsole  100  may include grooves  112 ,  122 ,  132  having one or more of the parameters provided in Table 1. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Parameter 
                 Value 
               
               
                   
               
             
            
               
                 Edge Density 
                 40-200 mm/cm 2   
               
               
                 Surface Contact Ratio 
                 40%-90%  
               
               
                 Amplitude (A) of Sinusoidal Path 
                 3 mm-25 mm 
               
               
                 Frequency (ω) of Sinusoidal Path 
                 4 mm-50 mm 
               
               
                 Groove Offset (O G ) 
                 2 mm-5 mm  
               
               
                 Groove Width (W G ) 
                 0.1 mm-5 mm   
               
               
                 Groove Depth (D G ) 
                 25-75% of outsole thickness 
               
               
                 Groove Edge Angle (α) 
                 75°-150° 
               
               
                 Outsole Compound Durometer 
                 45-65 Shore A 
               
               
                   
               
            
           
         
       
     
     Referring to  FIGS. 13-17 , in some examples, the sinusoidal path of a groove  122 ,  132  has an amplitude and frequency that provides a substantially symmetric shape (e.g., a one-to-one ratio). Adjacent wave grooves or channels  122 ,  132  can be arranged as close as possible, providing a relatively high edge density. Moreover, a width W T , W Q  of the grooves or channels  122 ,  132  can be maintained as small as possible (e.g., via razor siping) to provide a relatively large surface contact ratio of the ground contact surface  110 . In some examples, the grooves or channels  122  can each have a width W T , W Q  of between about 0.1 mm and about 1 mm (e.g., 0.5 mm) and a depth D T , D Q  of between about 25% and about 75% of a thickness T of the outsole  100 . For example, for an outsole  100  having a thickness of 3.5 mm, the grooves or channels  122 ,  132  can have a depth D T , D Q  of between about 0.8 mm and about 2.6 mm (e.g., a depth D of 1 mm, 1.5 mm, 2 mm, or 2.5 mm). 
     Referring to  FIGS. 1-17 , in some implementations, the first and second tread regions  120 ,  132  define grooves or channels  122 ,  132  in wave configurations (e.g., sine waves). In the example shown in  FIGS. 8-12 , the grooves or channels  122 ,  132  can each define a corresponding shoulder  123 ,  133  ( FIGS. 13-17 ) that defines a right angle or substantially at right angle (e.g., a non-radiused, non-chamfered corner or a minimally radiused corner for mold release). Other shoulder configurations are possible as well. The right angle edge style shoulder  123 ,  133  provides a traction edge for slip resistance. A sharp corner edge provides relatively better traction over a rounded corner, since the sharp edge can catch on surface features of the ground. As the outsole  100  flexes, each shoulder or edge  123 ,  133  can grab the ground for traction. Each shoulder or edge  123 ,  133  within a square centimeter can be counted for determining the edge density of that corresponding region of the outsole  100 . 
     Referring to  FIGS. 1 ,  13  and  14 , in some implementations, the first tread region  120  defines grooves or channels  122  propagating in a wave pattern with an axis of propagation  125  ( FIG. 13 ) substantially parallel to a longitudinal axis  101  of the outsole  100 . The first tread region  120  provides traction for lateral movements of the outsole  100  against the ground, such as side-to-side movements by a user. The groove or channel arrangement places a relatively longer leading edge  123  of each groove or channel  122  perpendicular to a direction of slip, thus providing slip resistance against forces substantially parallel to a transverse axis  103  of the outsole  100 . In the example shown, the outsole  100  includes a lateral first tread region  120   a  and a medial first tread region  120   b  disposed on corresponding lateral and medial portions  106 ,  108  of the outsole  100 . The lateral first tread region  120   a  can be arranged near a lateral perimeter  106   a  of the outsole  100  and the medial first tread region  120   b  can be arranged near a medial perimeter  108   a  of the outsole  100 . The second tread region  130  can be arranged between the lateral first tread region  120   a  and the medial first tread region  120   b  in at least a ground striking portion  107  of the outsole  100  (e.g., substantially under the heel and metatarsal of a user&#39;s foot). As a user moves side-to-side, weight can be placed on the respective lateral and medial portions  106 ,  108  of the outsole  100 . The respective lateral and medial first tread regions  120   a ,  120   b  can provide traction or slip resistance against forces incurred by the ground contact surface  130  along the transverse axis  103  of the outsole  100 . 
     In some examples, each grooves or channels  122  follows a sinusoidal path with an amplitude of about 8.8 mm (or 8.8 mm+/−1 or 2 mm) and an angular frequency of about 20 mm (or 20 mm+/−3 mm). Each grove or channel  122  can have a width W T  of about 0.5 mm and/or a depth D T  of about 1.5 mm. The outsole  100  can have thickness T of about 3.5 mm in the first tread region  120 . In some implementations, the axis of propagation  125  of each grove or channel  122  is offset from the axis of propagation  125  of an adjacent grove or channel  122  by an offset distance O T  of between about 1 mm and about 2 mm. Adjacent grooves or channels  122  can be arranged such that their corresponding groove paths merge at various or periodic groove intersections  127 . The first tread region  120  may have an edge density of groove edges  123  of about 124 mm/cm 2  and a surface contact ratio of about 65%. 
     Referring to FIGS.  1  and  15 - 17 , in some implementations, the second tread region  130  defines grooves  132  propagating in a wave pattern with an axis of propagation  135  ( FIG. 15 ) substantially parallel to the transverse axis  103  of the outsole  100 . The second tread region  130  provides traction for forward and rearward movements of the outsole  100  against the ground along a walking direction of the user. The groove arrangement places a relatively longer leading edge  123  of each groove  122  perpendicular to a direction of slip, thus providing slip resistance against forces on the ground contact surface  130  substantially parallel to the longitudinal axis  101  of the outsole  100  (as during walking or running along a normal walking direction (forward or reverse)). 
     In some examples, each grooves  132  follows a sinusoidal path with an amplitude of 5 mm (or 5 mm+/−1 or 2 mm) and an angular frequency of 6.3 mm (or 6.3 mm+/−1 or 2 mm). Each grove  132  can have a width W Q  of about 0.4 mm, a depth D Q  of about 1.2 mm. The outsole  100  can have thickness T of about 4 mm in the second tread region  130 . In some implementations, the axis of propagation  135  of each grove  132  is offset from the axis of propagation  135  of an adjacent grove  132  by an offset distance O Q  of between about 1.5 mm and about 3.5 mm (e.g., about 2.75 mm). Moreover, branch or cross-linking grooves  134  can interconnect adjacent grooves  132  (e.g., every quarter or half a wavelength of the sinusoidal grooves  132 ). In some examples, the branch grooves  134  extend in a direction substantially parallel to or at a relatively small angle (e.g., between about 1° and about 45°) with respect to the longitudinal axis  101 . The branch grooves  134  may have a width W Q  of about 0.4 mm, a depth D Q  of about 0.6 mm (or about half the depth D Q  of the other grooves and siping  132 ). The second tread region  130  may have an edge density of siping edges  133  of about 106 mm/cm 2  and a surface contact ratio of about 91%. 
       FIGS. 18A-22B  depict a number of outsole tread patterns.  FIGS. 18A and 18B  illustrate a first tread pattern  1800  for the outsole  100  that includes grooves  1810  having a sinusoidal path along the ground contact surface  130  and equally spaced parallel to each other in a common direction. Each groove  1810  may have an amplitude A of about 5 mm, a frequency ω of about 6.3 mm, a width W O  of about 0.4 mm, and/or a depth D O  of about 1.2 mm. Moreover, the groove  1810  can have a wavelength λ of about 6.3 mm. Each groove  1810  can be formed or cut to have a shoulder  1813  that defines right angle or substantially a right angle (e.g., a non-radiused, non-chamfered corner or a minimally radiused corner for mold release). The right angle edge style shoulder  1812  provides a traction edge for slip resistance. A sharp corner edge provides relatively better traction over a rounded corner. An axis of propagation  1815  of each groove  1810  can be offset from the axis of propagation  1815  of an adjacent groove  1810  by an offset distance O O  of about 3.15 mm. The outsole  100  may have a thickness T of about 4 mm. The first tread pattern  1800  may have an edge density (e.g., of shoulder edges  1812 ) of about 79.5 mm/cm 2  and a surface contact ratio of about 84%. 
       FIGS. 19A and 19B  illustrate a second tread pattern  1900  for the outsole  100  that includes grooves  1910  having a sinusoidal path along the ground contact surface  130  and equally spaced parallel to each other in a common direction. Each groove  1910  may have an amplitude A of about 5.25 mm, a frequency ω of about 6.3 mm, a width W P  of about 0.25 mm, and/or a depth D P  of about 1.2 mm. Moreover, the groove  1910  can have a wavelength λ of about 6.3 mm. Each groove  1910  can be formed or cut to have a shoulder  1912  that defines right angle or substantially a right angle (e.g., a non-radiused, non-chamfered corner or a minimally radiused corner for mold release). An axis of propagation  1915  of each groove  1910  can be offset from the axis of propagation  1915  of an adjacent groove  1910  by an offset distance O P  of about 3 mm. The outsole  100  may have a thickness T of about 4 mm. The second tread pattern  1900  may have an edge density (e.g., of shoulder edges  1912 ) of about 77 mm/cm 2  and a surface contact ratio of about 90.5%. 
       FIGS. 20A and 20B  illustrate a third tread pattern  2000  for the outsole  100  that includes grooves  2010  having a sinusoidal path along the ground contact surface  130  and equally spaced parallel to each other in a common direction. Each groove  2010  may have an amplitude A of about 5 mm, a frequency ω of about 6.3 mm, a width W Q  of about 0.4 mm, and/or a depth D Q  of about 1.2 mm. Moreover, the groove  2010  can have a wavelength λ of about 6.3 mm. Each groove  2010  can be formed or cut to have a shoulder  2012  that defines right angle or substantially a right angle (e.g., a non-radiused, non-chamfered corner or a minimally radiused corner for mold release). An axis of propagation  2015  of each groove  1910  can be offset from the axis of propagation  2015  of an adjacent groove  2010  by an offset distance O Q  of about 3.15 mm. The outsole  100  may have a thickness T of about 4 mm. Cross-linking grooves  1014  connecting adjacent grooves  1812  may have a width W Q  of about 0.4 mm, and a depth D Q  of about 0.6 mm. The third tread pattern  2000  may have an edge density (e.g., of shoulder edges  2012 ) of about 106 mm/cm 2  and a surface contact ratio of about 91%. 
       FIGS. 21A and 21B  illustrate a fourth tread pattern  2100  for the outsole  100  that includes grooves  2110  having a sinusoidal path along the ground contact surface  130  and equally spaced parallel to each other in a common direction. Each groove  2110  may have an amplitude A of about 17.6 mm, a frequency ω of about 40 mm, a width W T  of about 1 mm, and/or a depth D T  of about 1.5 mm. Moreover, the groove  2110  can have a wavelength λ of about 20 mm. Each groove  2110  can be formed or cut to have a shoulder  2112  that defines right angle or substantially a right angle (e.g., a non-radiused, non-chamfered corner or a minimally radiused corner for mold release). An axis of propagation  2115  of each groove  2110  can be offset from the axis of propagation  2115  of an adjacent groove  2110  by an offset distance O T  of between about 3 mm and about 3.75 mm. In the example, for three consecutive grooves  2110 , a first groove  2110  is offset from a second groove  2110  by an offset distance O T  of about 3 mm, and the second groove  2110  is offset from a third groove  2110  by an offset distance O T  of about 3.75 mm. The outsole  100  may have a thickness T of about 3.5 mm. The fourth tread pattern  2100  may have an edge density (e.g., of shoulder edges  2112 ) of about 59 mm/cm 2  and a surface contact ratio of about 67%. 
       FIGS. 22A and 22B  illustrate a fifth tread pattern  2200  for the outsole  100  that includes razor siping or grooves  2210  having a sinusoidal or zig-zag path along the ground contact surface  130  and equally spaced parallel to each other in a common direction. Each groove  2210  may have an amplitude A of about 5.12 mm, a frequency ω of about 6.5 mm, a width W W  of about between 0 mm and about 0.25 mm, and/or a depth D W  of about 1.2 mm. Moreover, each groove  2210  can be cut to have a shoulder  2212  that defines right angle or substantially a right angle (e.g., a non-radiused, non-chamfered corner). An axis of propagation  2215  of each groove  2210  can be offset from the axis of propagation  2215  of an adjacent groove  2210  by an offset distance O P  of about 5.12 mm. The outsole  100  may have a thickness T of about 5 mm. The fifth tread pattern  2200  may have an edge density (e.g., of shoulder edges  2212 ) of about 98 mm/cm 2  and a surface contact ratio of about 98%. 
     Anti-slip characteristics of the outsole  100  may depend on the ground contact surface configuration (e.g., tread pattern, edge density, and/or surface contact ratio) as well as the material of the outsole  100 . The outsole  100  may be comprised of one or more materials. In some examples, the outsole comprises at least one of natural rubber, rubber, 0.9 anti-slip rubber (rubber having a minimum coefficient of friction of 0.9 for a durometer of 50-55 Shore A), and 1.1 anti-slip rubber (rubber having a minimum coefficient of friction of 1.1 for a durometer of 50-55 Shore A), and latex, each having a durometer of between about 50 Shore A and about 65 Shore A. 
     A slip resistance test can be performed to determine a slip index or slip angle for different combinations of tread configurations and outsole materials to select a tread configuration and outsole material appropriate for a particular application, such as boating, fishing, or activities on wet surfaces. The slip resistance test can be performed using a tribometer (also known as a slipmeter), which is an instrument that measures a degree of friction between two rubbing surfaces. The English XL Variable Incidence Tribometer (VIT) (available from Excel Tribometers, LLC, 160 Tymberbrook Drive, Lyman, S.C. 29365) is an exemplary Tribometer for determining slip resistance for various outsole configurations. The VIT instrument mimics biomechanical parameters of the human walking gait and replicates a heel strike of a human walking (e.g., using a leg and ankle device). A leg of the VIT instrument is free to accelerate once a slip occurs, as with a real-world human slip event. For example, some testing instruments that drag across the floor at a constant rate do not account for what happens when humans slip and fall. Moreover, the phenomenon of “sticktion” may produce misleading results when a walking surface is wet and the testing instrument has residence time before slip dynamics are applied. Testing instruments that drag across a wet test surface generally experience a micro-time jumping motion that is a series of “sticktion-release-sticktion-release” cycles. The dynamics of the VIT instrument permits measurement of slip resistance in wet conditions because there is no residence time. ASTM F1679-04 provides a test method for using a Variable Incidence Tribometer (VIT). ANSI A1264.2 provides a provision of slip resistance in the workplace. 
     Table 2 provides results of slip resistance tests conducted on a number of materials having the same surface configuration in wet and dry conditions in accordance with ASTM D1894 measuring a coefficient of friction between a smooth sample material (i.e., flat without treads) and a metal surface. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Durometer 
                 Slip Index 
                 Slip Index 
               
               
                   
                 Material 
                 (Shore A) 
                 Dry 
                 Wet 
               
               
                   
                   
               
             
            
               
                   
                 First Rubber 
                 50-55 
                 1.06 
                 1.08 
               
               
                   
                 Second Rubber 
                 60-65 
                 0.96 
                 0.85 
               
               
                   
                 0.9 Anti-Slip Rubber 
                 50-55 
                 1.16 
                 1.03 
               
               
                   
                 0.9 Anti-Slip Rubber 
                 60-65 
                 0.74 
                 0.70 
               
               
                   
                 1.1 Anti-Slip Rubber 
                 50-55 
                 1.57 
                 1.52 
               
               
                   
                 Third Rubber 
                 60-65 
                 0.93 
                 0.68 
               
               
                   
                 Latex 
                 60-65 
                 1.37 
                 1.27 
               
               
                   
                   
               
            
           
         
       
     
     Table 3 provides results of slip resistance tests conducted on a number of materials having the same surface configuration in wet and dry conditions in accordance with ASTM F1679-04 using a Variable Incidence Tribometer (VIT). A slip angle is the determined between a sample material and a test surface (e.g., a textured surface, Teak wood, Polyester-fiberglass, or metal). The sample material defined grooves having the third tread pattern (Q)  2000  described herein with reference to  FIGS. 20A and 20B . Textured polyester fiberglass was used as the test surface for the results shown in Table 3. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Durometer 
                 Dry Slip 
                 Wet Slip 
               
               
                 Material 
                 (Shore A) 
                 Angle (Deg.) 
                 Angle (Deg.) 
               
               
                   
               
             
            
               
                 First Rubber 
                 50-55 
                 46 
                 46 
               
               
                 Second Rubber 
                 60-65 
                 39 
                 — 
               
               
                 0.9 Anti-Slip Rubber 
                 50-55 
                 54 
                 53 
               
               
                 0.9 Anti-Slip Rubber 
                 60-65 
                 43 
                 42 
               
               
                 1.1 Anti-Slip Rubber 
                 50-55 
                 56 
                 57 
               
               
                 1.1 Anti-Slip Rubber 
                 60-65 
                 46 
                 47 
               
               
                 Third Rubber 
                 60-65 
                 45 
                 42 
               
               
                 Latex 
                 50-55 
                 47 
                 47 
               
               
                 Latex 
                 60-65 
                 55 
                 38 
               
               
                   
               
            
           
         
       
     
     Table 4 provides results of slip resistance tests conducted on a number of materials having the same surface configuration in wet and dry conditions in accordance with ASTM F1679-04 using a Variable Incidence Tribometer (VIT). The sample material defined grooves having the fourth tread pattern (T)  2100  described herein with reference to  FIGS. 21A and 21B . Textured polyester fiberglass was used as the test surface for the results shown in Table 4. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                 Durometer 
                 Dry Slip 
                 Wet Slip 
               
               
                 Material 
                 (Shore A) 
                 Angle (Deg.) 
                 Angle (Deg.) 
               
               
                   
               
             
            
               
                 First Rubber 
                 50-55 
                 47 
                 42 
               
               
                 Second Rubber 
                 60-65 
                 37 
                 — 
               
               
                 0.9 Anti-Slip Rubber 
                 50-55 
                 54 
                 52 
               
               
                 0.9 Anti-Slip Rubber 
                 60-65 
                 48 
                 46 
               
               
                 1.1 Anti-Slip Rubber 
                 50-55 
                 55 
                 56 
               
               
                 1.1 Anti-Slip Rubber 
                 60-65 
                 46 
                 48 
               
               
                 Third Rubber 
                 60-65 
                 38 
                 35 
               
               
                 Latex 
                 50-55 
                 45 
                 46 
               
               
                 Latex 
                 60-65 
                 58 
                 40 
               
               
                   
               
            
           
         
       
     
     The slip resistance test results shown in Tables 2-4 reveal that the 1.1 Anti-Slip Rubber having a durometer of 50-55 Shore A out-performed the other samples, while latex having a durometer of 60-65 Shore A and the 0.9 Anti-Slip Rubber having a durometer of 50-55 Shore A performed relatively well in comparison to the remaining samples as well. The selection of an outsole material for an outsole  100  may depend on the combined performance of the material type and a tread configuration of the outsole  100 . 
     Table 5 provides results of slip resistance tests for different combinations of tread designs and outsole materials on Teak wood under 20 psi of pressure. A sixth sample is smooth with no treads as a control sample. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 5 
               
             
            
               
                   
                   
               
               
                   
                   
                 VIT Slip 
                   
               
               
                   
                 Durometer 
                 Test Angle (°) 
               
            
           
           
               
               
               
               
               
            
               
                 Tread Pattern 
                 Material 
                 (Shore A) 
                 Dry 
                 Wet 
               
               
                   
               
               
                 First tread 
                 0.9 Anti- 
                 50-55 
                 44 
                 42 
               
               
                 pattern 1800 
                 Slip Rubber 
               
               
                 (O) 
                 Latex 
                 50-55 
                 40 
                 39 
               
               
                   
                 Latex 
                 60-65 
                 40 
                 40 
               
               
                 Second tread 
                 0.9 Anti- 
                 50-55 
                 45 
                 68 
               
               
                 pattern 1900 
                 Slip Rubber 
               
               
                 (P) 
                 Latex 
                 50-55 
                 37 
                 33 
               
               
                   
                 Latex 
                 60-65 
                 — 
                 — 
               
               
                 Third tread 
                 0.9 Anti- 
                 50-55 
                 41 
                 43 
               
               
                 pattern 2000 
                 Slip Rubber 
               
               
                 (Q) 
                 Latex 
                 50-55 
                 42 
                 41 
               
               
                   
                 Latex 
                 60-65 
                 — 
                 — 
               
               
                 Fourth tread 
                 0.9 Anti- 
                 50-55 
                 43 
                 42 
               
               
                 pattern 2100 
                 Slip Rubber 
               
               
                 (T) 
                 Latex 
                 50-55 
                 40 
                 40 
               
               
                   
                 Latex 
                 60-65 
                 43 
                 41 
               
               
                 Fifth tread 
                 0.9 Anti- 
                 50-55 
                 44 
                 14 
               
               
                 pattern 2200 
                 Slip Rubber 
               
               
                 (W) 
                 Latex 
                 50-55 
                 40 
                 37 
               
               
                   
                 Latex 
                 60-65 
                 — 
                 — 
               
               
                 Smooth 
                 0.9 Anti- 
                 50-55 
                 47 
                 43 
               
               
                 (no treads) 
                 Slip Rubber 
               
               
                 (AA) 
                 Latex 
                 50-55 
                 43 
                  7 
               
               
                   
                 Latex 
                 60-65 
                 50 
                 25 
               
               
                   
               
            
           
         
       
     
       FIGS. 23A-23C  provide three graphs of the results shown in Table 5 separated by material type. The third and fourth tread patterns (Q, T)  2000 ,  2100  each perform substantially equally between wet and dry conditions, in addition to providing relatively high slip resistance. 
     Table 6 provides results of slip resistance tests for different combinations of tread designs and outsole materials on Teak wood under 25 psi of pressure. A sixth sample is smooth with no treads as a control sample. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 6 
               
             
            
               
                   
                   
               
               
                   
                   
                 VIT Slip 
                   
               
               
                   
                 Durometer 
                 Test Angle (°) 
               
            
           
           
               
               
               
               
               
            
               
                 Tread Pattern 
                 Material 
                 (Shore A) 
                 Dry 
                 Wet 
               
               
                   
               
               
                 First tread 
                 0.9 Anti- 
                 50-55 
                 47 
                 43 
               
               
                 pattern 1800 
                 Slip Rubber 
               
               
                 (O) 
                 Latex 
                 50-55 
                 40 
                 39 
               
               
                   
                 Latex 
                 60-65 
                 40 
                 40 
               
               
                 Second tread 
                 0.9 Anti- 
                 50-55 
                 45 
                 36 
               
               
                 pattern 1900 
                 Slip Rubber 
               
               
                 (P) 
                 Latex 
                 50-55 
                 37 
                 33 
               
               
                   
                 Latex 
                 60-65 
                 — 
                 — 
               
               
                 Third tread 
                 0.9 Anti- 
                 50-55 
                 47 
                 45 
               
               
                 pattern 2000 
                 Slip Rubber 
               
               
                 (Q) 
                 Latex 
                 50-55 
                 42 
                 41 
               
               
                   
                 Latex 
                 60-65 
                 — 
                 — 
               
               
                 Fourth tread 
                 0.9 Anti- 
                 50-55 
                 44 
                 43 
               
               
                 pattern 2100 
                 Slip Rubber 
               
               
                 (T) 
                 Latex 
                 50-55 
                 40 
                 40 
               
               
                   
                 Latex 
                 60-65 
                 43 
                 41 
               
               
                 Fifth tread 
                 0.9 Anti- 
                 50-55 
                 48 
                 29 
               
               
                 pattern 2200 
                 Slip Rubber 
               
               
                 (W) 
                 Latex 
                 50-55 
                 40 
                 37 
               
               
                   
                 Latex 
                 60-65 
                 — 
                 — 
               
               
                 Smooth 
                 0.9 Anti- 
                 50-55 
                 53 
                 15 
               
               
                 (no treads) 
                 Slip Rubber 
               
               
                 (AA) 
                 Latex 
                 50-55 
                 43 
                  7 
               
               
                   
                 Latex 
                 60-65 
                 50 
                 25 
               
               
                   
               
            
           
         
       
     
       FIGS. 24A-24C  provide three graphs of the results shown in Table 6 separated by material type. The third and fourth tread patterns (Q, T)  2000 ,  2100  each perform substantially equally between wet and dry conditions, in addition to providing relatively high slip resistance. 
     Table 7 provides results of slip resistance tests for different tread designs made of the 0.9 anti-slip rubber having durometer of 50-55 Shore A on Teak wood under 25 psi of pressure with a VIT instrument angle of 15°. A sixth sample is smooth with no treads as a control sample. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 7 
               
             
            
               
                   
                   
               
               
                   
                 VIT Slip 
                   
               
               
                   
                 Test Angle (°) 
               
            
           
           
               
               
               
               
            
               
                   
                 Tread Pattern 
                 Dry 
                 Wet 
               
               
                   
                   
               
               
                   
                 First tread pattern 1800 (O) 
                 47 
                 43 
               
               
                   
                 Second tread pattern 1900 (P) 
                 45 
                 36 
               
               
                   
                 Third tread pattern 2000 (Q) 
                 47 
                 45 
               
               
                   
                 Fourth tread pattern 2100 (T) 
                 44 
                 43 
               
               
                   
                 Fifth tread pattern 2200 (W) 
                 48 
                 29 
               
               
                   
                 Smooth (no treads) (AA) 
                 53 
                 15 
               
               
                   
                   
               
            
           
         
       
     
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.