Patent Publication Number: US-6705027-B1

Title: Traction elements for an article of footwear

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 10/093,362, filed Mar. 5, 2002, which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to footwear. The invention concerns, more particularly, elements that protrude from a footwear sole to provide dynamic traction. 
     2. Description of Background Art 
     The game of golf is one of the oldest international sports and has its formal origins in the 16 th  century at The Royal and Ancient Golf Club at St. Andrews, located in Scotland. During the ensuing centuries, the game of golf has gained and maintained a populous following due to inherent challenges of the game, a prestigious reputation, and its suitability for relaxation. 
     Growth in the number of individuals playing the game of golf provides an incentive for manufacturers of golf equipment, which includes golf clubs, golf balls, and golf shoes, to improve upon the various features and characteristics of golf equipment. In general, golf equipment has evolved over time to provide enhanced performance and suitability for a wide range of playing abilities and styles. Golf club shafts, for example, were originally fashioned from wood and are commonly formed of metal or graphite materials today. Golf balls originally included a wound, twine core and a balata rubber cover. Modern golf balls, however, may incorporate a solid core formed of polybutadiene, titanium, nickel, or cobalt, and a cover formed of ionomeric resin, surlyn, or polyurethane. Similarly, advances in golf shoe outsoles are of particular interest to sporting goods manufacturers, especially with respect to enhancing performance by insuring controlled contact with the ground while permitting the body to correctly pivot for purposes of swinging a golf club. 
     A proper golf club swing involves a side-to-side twisting motion that coordinates movement of the arms, torso, hips, legs, and feet of the golfer. Initially, the weight of the golfer is uniformly distributed over each foot. As the golfer begins the back swing, the driving foot, which is positioned furthest from the flag, tends to experience an increased vertical force and tends to rotate laterally outward in the forefoot region and medially inward in the heel region. During the back swing, the driving foot acts as a brace and counters rotation of the torso, hips, and legs. Accordingly, a majority of the weight of the golfer shifts to the driving foot during the back swing such that the stabilizing foot, which is positioned closest to the flag, supports only a small portion of the weight of the golfer. During the down swing, the golfer&#39;s weight is shifted from the driving foot to the stabilizing foot, which has a tendency to rotate in a manner that is similar to the driving foot during the back swing. That is, the stabilizing foot tends to rotate laterally outward in the forefoot region and medially inward in the heel region. 
     Traditional golf shoes include a generally smooth outsole having a plurality of fixed or removable spikes that engage the ground and prevent each foot from slipping during the golf club swing. Although metal spikes are effective for preventing the feet from slipping, the spikes may damage putting greens, walkways, floors, and other surfaces that the golfer walks upon. Metal spikes may also pose a hazard to the golfer or other individuals. Many modern golf shoes, however, continue to incorporate metal spikes. 
     A modified golf shoe is disclosed in U.S. Pat. No. 4,885,851 to Peterson and includes an outsole with a flat, ground engaging surface and spikes positioned in the forefoot and heel regions. In addition, the outsole includes a plurality of supplementary protrusions distributed along a medial side of the right shoe and along the lateral side of the left shoe to aid a right-handed golfer. An opposite configuration is disclosed for a left-handed golfer. One purpose of the supplementary protrusions is to inhibit the shoes from slipping as the golfer shifts weight from the driving foot to the stabilizing foot during the golf swing. 
     Golf shoes may also be structured in a manner that considers the rotational motion of the feet during the various stages of the golf swing, as discussed above, in addition to the tendency for slipping throughout the golf swing. U.S. Pat. No. 6,016,613 to Campbell et al. discloses a golf shoe outsole with a plurality of polymer projections. The various projections are configured to extend outward in a radial geometry from a pivot point in the forefoot region and another pivot point in the heel region, thereby controlling the rotational motion of the feet during the various portions of the golf swing. In addition, the outsole may incorporate traditional metal spikes or modern polymer spikes. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is an article of footwear having an upper for receiving a foot and a sole structure attached to the upper. The sole structure includes an outsole with an exposed surface and a plurality of traction elements projecting from the exposed surface. The traction elements have an end portion located opposite the exposed surface and an undercut surface that extends between the exposed surface and the end portion to form an acute angle with the exposed surface. A forefoot portion of the traction elements are located in a forefoot area of the sole structure, and a heel portion of the traction elements are located in a heel area of the sole structure. The undercut surfaces of the forefoot portion are oriented to generally face a lateral side of the footwear, and the undercut surfaces of the heel portion are oriented to generally face a medial side of the footwear. 
     The undercut surfaces of the traction elements engage the ground and resist rotation of the footwear. When an individual stands on a compliant surface, such as turf, the traction elements will protrude into the ground such that the undercut surfaces contact the ground. As the foot rotates, the ground presses against the undercut surfaces and deforms the traction elements, thereby increasing the angle that the undercut surfaces form with the ground. The angle, however, generally remains acute such that the traction elements continue to remain securely engaged with the ground. 
     During the back swing portion of a golf swing, the driving foot tends to rotate laterally outward in the forefoot area and medially inward in the heel area. Similarly, the stabilizing foot tends to rotate laterally outward in the forefoot area and medially inward in the heel area during the down swing. By orienting the traction elements such that the undercut surfaces face the lateral side in the forefoot area and the medial side in the heel area, rotation of the feet during the various portions of the golf swing may be effectively controlled. 
     The traction elements may also be utilized to provide the individual with additional cushioning. As the individual walks, the traction elements deform such that the angle between the undercut surface and the exposed surface decreases. The deformation in the traction elements effectively attenuates impact forces and absorbs energy, thereby providing the individual with cushioning. 
    
    
     The advantages and features of novelty that characterize the present invention are pointed out with particularity in the appended claims. To gain an improved understanding of the advantages and features of novelty that characterize the present invention, however, reference may be made to the descriptive matter and accompanying drawings that describe and illustrate various embodiments of the invention. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a lateral side elevational view of an article of footwear that incorporates traction elements in accordance with the present invention. 
     FIG. 2A is a perspective view of an individual traction element. 
     FIG. 2B is a first elevational view of the traction element. 
     FIG. 2C is a second elevational view of the traction element. 
     FIG. 2D is a third elevational view of the traction element. 
     FIG. 2E is a top plan view of the traction element. 
     FIG. 3 is an elevational view of a traction element in a compressed configuration. 
     FIG. 4A is a side elevational view of a traction element protruding into the ground. 
     FIG. 4B is a side elevational view of a traction element in a deformed configuration. 
     FIG. 5 is a first bottom plan view of the article of footwear depicted in FIG.  1 . 
     FIG. 6 is a second bottom plan view of the footwear depicted in FIG. 1 showing traction element orientation. 
     FIG. 7A is bottom plan view of an article of footwear that includes traction elements and secondary traction elements. 
     FIG. 7B is a perspective view of an individual secondary traction element of the footwear depicted in FIG.  7 A. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following discussion and accompanying figures disclose an article of footwear  10  in accordance with the present invention. Footwear  10  is discussed and depicted as a golf shoe. The concepts disclosed with reference to footwear  10 , however, may be applied to other styles of athletic footwear, including shoes for the sports of track and field and football. In addition, the present invention may be applied to non-athletic footwear, such as sandals, boots, and dress shoes, for example. The present invention, therefore, is not limited to footwear designed solely for golf, but may also be applied to a wide range of other footwear styles. 
     Footwear  10  is depicted in FIG.  1  and includes an upper  12  that is structured to form a foot cavity (not depicted) for receiving a foot and comfortably securing the foot to footwear  10 . Upper  12  may have a generally conventional structure that is formed of a durable and comfortable leather or synthetic material, for example. Footwear  10  also includes a sole structure  14  that is attached to upper  12  and generally located between the foot cavity and the ground. Sole structure  14  is, therefore, located to provide support for the foot and may include materials such as foam that attenuate shock and absorb energy as footwear  10  makes contact with the ground. Sole structure  14  includes an outsole  16  with an exposed surface  18 , and a plurality of traction elements  20  that project downward from exposed surface  18 . 
     An individual traction element  20  is depicted in FIGS. 2A and 2B. Traction element  20  may be formed integral with outsole  16 , or may be formed separate from outsole  16  and subsequently attached. Traction element  20  includes an undercut surface  22 , a back surface  24 , and a pair of side surfaces  26   a  and  26   b  that form an end portion  28  located opposite exposed surface  18 . Each traction element  20  forms, therefore, a generally pointed structure that projects downward from outsole  16 . 
     Undercut surface  22  may be planar or curved, and forms an acute angle  30  with exposed surface  18 . As depicted in the figures, angle  30  is approximately 20 degrees, but may range from 10-40 degrees when traction element  20  is in a non-deformed configuration. Traction element  20  is, therefore, inclined toward undercut surface  22  such that end portion  28  is located directly below exposed surface  18 . 
     Back surface  24  is located opposite undercut surface  22  and forms a back portion of traction element  20 . Back surface  24  is depicted as being curved, but may also be planar within the scope of the present invention. A portion of back surface  24  may be bifurcated by a slit  38  to alter the deformation characteristics of each traction element  20 . Side surface  26  extend between undercut surface  22  and back surface  24 . Bottom portions of side surfaces  26  may flare outward adjacent to exposed surface  18  to provide a secure base for traction element  20 . 
     Traction element  20  may be formed of a single material, including thermoplastic urethane having a Shore A hardness of approximately 75 or rubber, through a single step injection molding process. In addition, traction element  20  may be formed of a combination of materials. For example, the portion of traction element  20  adjacent to end portion  28  may be formed of a relatively durable material that resists wear, and the portion of traction element  20  adjacent to exposed surface  18  may be formed of a relatively stiff material. Although a variety of materials are suitable for traction element  20 , the material selected should exhibit a deformable property, as discussed in greater detail below. 
     Traction elements  20  provide footwear  10  with a variety of benefits. While walking over various surfaces, traction elements  20  engage the ground to provide an individual with traction. During the game of golf, an individual may encounter terrain that includes turf, dirt, concrete, sand, and mud, for example. Traction elements  20  are configured to protrude into terrain such as turf or dirt and limit the degree that footwear  10  moves relative to the terrain. In general, end portion  28  is sufficiently pointed to penetrate a variety of surfaces such that undercut surface  22 , back surface  24 , and side surfaces  26  engage the ground. Friction between the ground and these surfaces will generally inhibit slipping or sliding. 
     Traction elements  20  also provide the individual with cushioning by attenuating impact forces and absorbing energy as the individual walks. This provides the individual with greater comfort when traversing the long distances that comprise modem golf courses. As noted above, traction elements  20  are formed of a deformable material and, therefore, deflect in the present of compressive forces. When traction elements  20  contact and are compressed against the ground, a force directed toward outsole  16  tends to compress traction elements  20 . Referring to FIG. 3, a force  32  is depicted as being incident upon the portion of back surface  24  that is adjacent to end portion  28 . In general, the ground will contact traction elements  20  in this area and traction elements  20  will deflect toward exposed surface  18 , thereby decreasing angle  30 . FIG. 3 depicts traction element  20  in the compressed configuration, with the non-compressed, non-deformed configuration shown in dashed lines. 
     The compression of traction elements  20  is most pronounced on less penetrable surfaces, such as concrete or hard dirt. Accordingly, the cushioning properties of traction elements  20  have their greatest effect on relatively non-compliant surfaces. On more penetrable surfaces, however, traction elements  20  protrude into the ground, thereby significantly decreasing the compression of traction elements  20 . Although traction elements  20  do not provide a significant amount of additional cushioning on more penetrable surfaces, such surfaces are generally compliant and little additional cushioning is required. 
     An additional benefit of traction elements  20  relates to the manner in which the rotation of the foot during the various stages of the golf swing is controlled. As discussed in the Description of Background Art section, the feet have a tendency to rotate during portions of the golf swing. More specifically, the driving foot, which is positioned furthest from the flag, tends to rotate laterally outward in the forefoot area and medially inward in the heel area during the back swing. Similarly, the stabilizing foot, which is positioned closest to the flag, tends to rotate laterally outward in the forefoot area and medially inward in the heel area during the down swing. Traction elements  20  are structured to resist rotation of footwear  10  in the direction that each undercut surface  22  faces. That is, traction elements  20  may be oriented with undercut surfaces  22  facing in the direction of unwanted rotation to effectively limit the degree of rotation. Combined with a proper orientation, as discussed in greater detail below, a plurality of traction elements  20  may be utilized to effectively limit the degree of rotation in the driving foot and the stabilizing foot during the back swing and down swing. 
     Referring to FIG. 4A, an individual traction element  20  is depicted as protruding into the ground, which is represented by reference numeral  34 , such that exposed surface  18  is located adjacent the ground. When an individual is preparing to swing a golf club, each traction element  20  may be engaged with the ground as depicted in FIG.  4 A. In general, forces incident traction element  20  during preparation for the swing will be minimal and, therefore, traction element  20  will be in an undeformed configuration. During the swing, however, each foot tends to rotate. Assuming, for example, that the traction element  20  depicted in FIG. 4A is located in a forefoot area of footwear  10  and is oriented toward a lateral side of footwear  10 , then the ground will induce a substantially horizontal force on undercut surface  22  during the back swing, as represented by force  36  in FIG.  4 B. Force  36  will deform traction element  20 , thereby increasing angle  30 . The forces typically generated by an individual during portions of the golf swing, however, will generally not be sufficient to increase angle  30  to 90 degrees or more. Accordingly, angle  30  will remain acute throughout the golf swing. 
     Prior to the golf swing, and throughout the golf swing, undercut surface  22  faces the direction of rotation. The undercut formed by undercut surface  22  engages the ground in a manner that is similar to the teeth on a saw. Accordingly, the undercut tends to remain engaged with the ground, particularly when a force is developed between undercut surface  22  and the ground. Like the teeth of a saw, therefore, traction element  20  tends to become more securely Pa engaged when a force is incident upon undercut surface  22  The force, however, will generally not be sufficient to deform traction element  20  to the degree that angle  30  becomes non-acute. The deformation in traction element  20  will not, therefore, affect the propensity of traction element  20  to remain engaged with the ground. 
     Following the golf swing, the rotational forces in the feet will subside and traction element  20  will return to the undeformed configuration. Traction elements  20  are not configured to remain engaged with the ground following the golf swing and will slide out of the ground with the application of an upward force by the feet. The curved shape to back surface  24  also promotes disengagement between traction elements  20  and the ground. Whereas, the undercut formed by undercut surface  22  tends to securely engage traction elements  20  and the ground, the curved geometry of back surface  24  has the opposite effect. Accordingly, the configuration of back surface  24  promotes release between traction element  20  and the ground following the golf swing. 
     In order for traction elements  20  to effectively limit the rotational forces in the feet during the back swing and down swing, a plurality of traction elements  20  should be properly oriented on exposed surface  18  of a pair of footwear  10 . FIG. 5 depicts a bottom plan view of footwear  10 . To aid in the following discussion concerning the orientation of traction elements  20 , footwear  10  includes a lateral side  40 , a opposite medial side  42 , a forefoot area  44  generally located in a forefoot portion of footwear  10 , and a heel area  46  generally located in a heel area of footwear  10 . 
     During the back swing, the driving foot tends to rotate laterally outward in forefoot area  44  and medially inward in heel area  46 . With reference to forefoot area  44 , undercut surfaces  22  generally face toward lateral side  40 . Accordingly, traction elements  20  in forefoot area  44  will inhibit the movement of footwear  10  toward lateral side  40 . Similarly, undercut surfaces  22  located in heel area  46  generally face toward medial side  36 . Accordingly, traction elements  20  in heel area  46  will inhibit the movement of footwear  10  toward medial side  42 . The configuration of traction elements  20  depicted in FIG. 5 will, therefore, effectively limit rotation of the foot during the back swing. During the down swing, the stabilizing foot tends to rotate laterally outward in forefoot area  44  and medially inward in heel area  46 . An article of footwear that is a mirror image of footwear  10 , as depicted in FIG. 5, may be utilized, therefore, to limit rotation in the stabilizing foot during the down swing. Unlike many prior art articles of footwear that have a different configuration depending upon whether the right foot or the left foot is the driving foot, footwear  10  may be utilized by an individual regardless of the foot that is selected as the driving foot. 
     As discussed above, traction elements  20  located in forefoot area  44  generally have undercut surfaces  22  that face lateral side  40 , and traction elements  20  located in heel area  46  generally have undercut surfaces that face medial side  42 . Although traction elements  20  may be randomly distributed on exposed surface  18 , the portion of traction elements  20  located in forefoot area  44 , as depicted in FIG. 6, are aligned along a plurality of radial lines  50  that emanate from a localized region  52 . This configuration orients undercut surfaces  22  in different directions that all generally face lateral side  40 . Every individual has a golf swing with different characteristics and will, therefore, have a different point of rotation in the feet. Differences in the precise direction in which undercut surfaces  22  face will generally ensure that at least a portion of the traction elements  20  located within forefoot area  44  have undercut surfaces  22  that are oriented directly into the direction of rotation. 
     The above discussion discloses footwear  10  and the many considerations relevant to the structure and function of traction elements  20 . Footwear  10  may also include other elements, such as spike receptacles  48 , as depicted in FIG. 6, that receive either metal spikes or supplemental polymer spikes  49 , as depicted in FIG.  1 . Although traction elements  20  are effective in preventing rotation of the feet, particularly on the short grass surfaces that characterize the area for initially hitting a golf ball, spikes  49  may be utilized to prevent the foot from slipping on other surfaces, such as longer grass or rocky terrain, for example. In addition, traction elements may weaken due to continued compressions against surfaces such as concrete. FIG. 7A depicts an article of footwear  10 A with a configuration wherein a plurality of secondary traction elements  54  are distributed among traction elements  20 . Secondary traction elements  54  contact surfaces such as concrete and effectively form a gap between exposed surface  18  and the surface, thereby limiting the degree to which traction elements  20  compress. 
     Secondary traction elements  54  may have a configuration that promotes the rotation-resisting properties of traction elements  20 , and, therefore, function as secondary traction elements. As depicted in FIGS. 7A and 7B, secondary traction elements  54  each have a gripping surface  56 , an opposite back surface  58 , and a pair of side surfaces  60 a and  60 b. In general, gripping surfaces  56  are perpendicular to exposed surface  18  and are oriented to face the same direction as undercut surfaces  22 . When compressed into a compliant surface, such as turf, gripping surfaces  56  will also engage the ground to resist rotation of footwear  10 A. Accordingly, secondary traction elements  54  may be utilized in combination with traction elements  20  to limit the degree of compression in traction elements  20  and assist in inhibiting rotation of footwear  10 A. In an alternate embodiment of the present invention, gripping surfaces  56  of secondary traction elements  54  may also have an undercut that is similar to undercut surfaces  22 . 
     The present invention is disclosed above and in the accompanying drawings with reference to a variety of embodiments. The purpose served by disclosure of the embodiments, however, is to provide an example of the various aspects embodied in the invention, not to limit the scope of the invention. One skilled in the relevant art will recognize that numerous variations and modifications may be made to the embodiments without departing from the scope of the present invention, as defined by the appended claims.