Abstract:
A footwear cleat of flexible plastic includes a central hub portion and a series of resilient protrusions cantilevered from and extending radially outward and downwardly beyond the central hub portion. The protrusions are capable of horizontally engaging turf under the footwear for providing secure footing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 09/208,334, filed Dec. 9, 1998 now U.S. Pat. No. 6,094,843, which is a continuation of U.S. patent application Ser. No. 08/806,580, filed Feb. 18, 1997, now U.S. Pat. No. 5,887,371, each of which is hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Athletic shoes for use in sporting activities often employ spikes protruding from the soles of the shoes for better traction. Referring to FIG. 1, golf shoes such as shoe  60  traditionally have a series of individual spikes  62  protruding from the sole  60   a  which extend downwardly about 8 mm from respective base flanges  64  mounted to the sole  60   a . Spikes  62  are long enough to penetrate into the soil  36  to provide traction. Recently, golf courses have begun to prohibit the use of these traditional golf spikes due to the damage they cause to the turf, particularly to golf course greens. 
     The response of golf spike manufacturers to the prohibition of traditional spikes is to position a series of small protrusions  66  approximately 2 mm high in a circular pattern on a traditional spike base flange  64  as seen in FIG. 2. A drawback of this approach is that little ground engaging ability is provided particularly on wet surfaces resulting in sub-standard support and protection for the golfer. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to cleats for footwear such as golf shoes which provide support similar to traditional spikes while at the same time do not damage turf such as golf course greens. The present invention footwear cleat includes a central hub portion and a series of protrusions or projections cantilevered from and extending radially outward from the hub portion for engaging turf. 
     In preferred embodiments, the protrusions also extend slightly downwardly beyond the hub portion. When the cleat is secured to a footwear sole, the protrusions are spaced away from the footwear sole. The cleat is formed from flexible plastic so that the protrusions are resilient and are capable of deflecting upwardly. The protrusions are curved with a first convex edge and a second concave edge and the second edge is preferably shorter than the first edge. A threaded portion extends from the central hub portion for securing the cleat to footwear. 
     While traditional spikes are designed to penetrate turf, the cleat of the present invention is not adapted to provide traction between the footwear and the turf by penetrating the turf. Should a user of the present cleat invention cleat start to slip in any direction on a fairway or in a rough area with a hilly surface, the protrusions snare strands of turf above the soil, trapping some grass in the area between the protrusions and the sole of the footwear. However, when walking on a relatively flat, firm surface such as golf greens, the weight of the user causes the protrusions to deflect or fold upwardly retracting the protrusions from engagement with the turf. This renders the cleats dormant and prevents damage to surfaces such as golf greens. Most golf greens are relatively flat surfaces so that traction is generally not needed and there is little chance of slipping while walking without traction. An additional benefit of the present cleat invention is that footwear including the cleats can be worn indoors without damaging the flooring due to the soft plastic material of the cleats and the fact that the cleat protrusions become inactivated or detented when pressed upon the flooring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a traditional prior art metal spike in a section of dense short turf such as a golf green. 
     FIG. 2 is a side view of a prior art spike consisting of a series of small protrusions in a section of dense short turf. 
     FIG. 3 is a bottom view of a golf shoe including the present invention cleats. 
     FIG. 4 is a bottom view of the present invention cleat. 
     FIG. 5 is a side view of the present invention cleat. 
     FIG. 6 is a side sectional view of the present invention cleat. 
     FIG. 7 is a side view of the present invention cleat on the bottom of a shoe positioned over a section of turf. 
     FIG. 8 is a side view of the cleat within the section of turf. 
     FIG. 9 is a side view of the cleat with the turf engaging protrusions engaging the section of turf. 
     FIG. 10 is a side view of the cleat with the turf engaging protrusions in the compressed position on a section of dense short turf such as a golf green. 
     FIG. 11 is a bottom view of another preferred cleat. 
     FIG. 12 is a bottom view of still another preferred cleat. 
     FIG. 13 is a bottom view of yet another preferred cleat. 
     FIG. 14 is a bottom view of still another preferred cleat. 
     FIG. 15 is a side sectional view of the cleat shown in FIG.  14 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIGS. 3,  4 ,  5  and  6  golf shoe  30  includes a series of the present invention cleats  10  mounted to the sole  30   a  of golf shoe  30 . Each cleat  10  includes a plurality of turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  extending radially outwardly and curving downwardly beyond a central hub portion  20 . Each turf engaging element  12   a ,  12   b ,  12   c  and  12   d  has a respective first curved convex edge  16   a ,  16   b ,  16   c  and  16   d  as well as a respective second curved concave edge  14   a ,  14   b ,  14   c  and  14   d . The curved convex edges  16   a ,  16   b ,  16   c  and  16   d  are longer than the curved concave edges  14   a ,  14   b ,  14   c  and  14   d . This results in tips  18   a ,  18   b ,  18   c , and  18   d  spiraling outward from and beyond central hub portion  20 . Preferably, the curved convex edges  16   a ,  16   b ,  16   c  and  16   d  are more than 3 times longer than the curved concave edges  14   a ,  14   b ,  14   c  and  14   d . The turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  are cantilevered from central hub portion  20 . The downward curve of turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  begins to curve outwardly near tips  18   a ,  18   b ,  18   c  and  18   d  such that the tips are substantially horizontal and parallel to sole  30   a . A circular gap  34  is formed around the circumference of central hub portion  20  between sole  30   a  and turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  (FIG. 7) due to the radially outward and downward extension of the turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  from central hub portion  20 . 
     Cleat  10  is preferably molded from a pliable soft plastic material such as  40  durometer thermal plastic urethane so that turf engaging protrusions  12   a ,  12   b ,  12   c , and  12   d  are flexible. For example, as seen in FIG. 4, turf engaging protrusions  12   a  and  12   c  are flexible along arcs  19 ′ and  19  respectively. This allows turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  to fold or deflect upwardly or downwardly. The turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  fold upwardly when sufficient weight is applied onto cleats  10  as the user is walking on a relatively flat firm surface such as a golf green. The flexibility of the turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  can be controlled by material selection. For example, softer materials resulting in more flexible protrusions  12   a ,  12   b ,  12   c  and  12   d  can be employed for cleats  10  for users that are light in weight such as children. 
     The central hub portion  20  of each cleat  10  has a threaded portion  24  for attaching cleat  10  to a corresponding mating threaded hole in sole  30   a . A cross-shaped hole  22  is formed in central hub portion  20  and extends upwardly into the core of threaded portion  24 . The cross-shaped hole  22  accepts a phillips head screwdriver for tightening cleat  10  to sole  30   a.    
     FIGS. 7,  8  and  9  depict the operation of a single cleat  10  when a user wearing golf shoes  30  walks over a turf region  32  such as a fairway. In FIG. 7, at the beginning of a step, golf shoe  30  and cleat  10  are suspended over turf  32  and soil  36 . Turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  of cleat  10  are oriented as originally molded. 
     In FIG. 8, golf shoe  30  is set down on turf  32  and soil  36 . An area of turf  38  is compacted underneath cleat  10 . On a typical fairway, the turf  32  has a high loft and turf engaging protrusions  12   a ,  12   b ,  12   c , and  12   d  remain in their molded position. The circular gap  34  remains open as the pressure against the compacted turf  38  is not sufficient to fold or deflect the turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  upwardly. 
     Referring to FIG. 9, when golf shoe  30  and cleat  10  slip along the turf in the direction of arrow  27  (FIG.  4 ), turf engaging protrusions  12   a  and  12   b  become tangled in turf  32  and fold downwardly causing golf shoe  30  to stop slipping in the direction of arrow  27 . Circular gap- 34  fills with turf further forcing turf engaging protrusions  12   a  and  12   b  downwardly. Turf engaging protrusion  12   d  (not visible), tends not to tangle within the turf because the attacking edge is the convex edge  16   d  against which the turf slides. As a result, turf engaging protrusion  12   d  tends to fold upwardly into circular gap  34 . Turf engaging element  12   c  also tends to fold upwardly into circular gap  34 . 
     The longer convex edges  16   a ,  16   b ,  16   c  and  16   d  in combination with the shorter concave edges  14   a ,  14   b ,  14   c  and  14   d  facilitates self tightening of cleat  10  during use. Arrow  26  (FIG. 4) designates the direction in which cleat  10  is screwed into sole  30   a . Should cleat  10  slip in the direction of arrow  27 , resistance by the turf would be applied equally from a direction indicated by arrows  28 ,  28 ′ and  28 ″. The turf grabs the short concave surface of edge  14   a  on turf engaging protrusion  12   a . At the same time the turf slides around the long convex edge  16   c  of turf engaging protrusion  12   c  such that turf engaging protrusion  12   c  is not grabbed with as much force as turf engaging protrusion  12   a . This means that the net result of the applied forces tightens cleat  10  in the direction of arrow  26  rather than loosening the cleat  10 . 
     FIG. 10 depicts the operation of cleat  10  when walking on a section of dense short turf  40  such as a golf green. A region of turf  42  under cleat  10  is compacted by cleat  10 . Turf engaging protrusions  12   a ,  12   b ,  12   c  and  12   d  are folded or deflected upwardly by the relatively firm surface of the golf green and do not engage turf  40 , thereby preventing damage to the golf green. The turf engaging protrusions also fold upwardly when walking on solid surfaces such as on asphalt or indoor flooring and will not damage such surfaces. 
     FIG. 11 depicts another preferred cleat  50  which differs from cleat  10  in that cleat  50  includes a slot  52  for tightening cleat  50  onto the sole  30   a  of shoe golf  30  with a screw driver. Slot  52  can be made large enough to be tightened with the edge of a coin such as a dime. 
     FIG. 12 depicts still another preferred cleat  54  which differs from cleat  10  in that cleat  54  includes two holes  56  for tightening cleat  54  onto sole  30   a  of golf shoe  30 . A tool having two protrusions mating with holes  56  is used for tightening cleat  54 . 
     FIG. 13 depicts yet another preferred cleat  70  which differs from cleat  10  in that engaging protrusions  72   a ,  72   b ,  72   c , and  72   d  are wider and extend from hub portion  20  substantially perpendicular to each other. In addition, cleat  70  includes a triangular hole  74  for tightening cleat  70  with a triangular shaped tool. 
     FIGS. 14 and 15 depict another preferred cleat  76  which differs from cleat t 0  in that turf engaging protrusions  78   a ,  78   b ,  78   c  and  78   d  have parallel edges  82  and flat tips  80  so that the turf engaging protrusions  78   a ,  78   b ,  78   c  and  78   d  extend outwardly and downwardly beyond the hub in a relatively straight manner instead of spiraling outwardly. In addition, cleat  76  includes a hexagonal hole  79  for tightening cleat  76  with a hexagonal wrench. 
     EQUIVALENTS 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For example, holes having other suitable shapes such as square holes or star-shaped holes can be formed in the present invention cleats for accommodating other common types of driving tools. In addition, although the present invention cleats have been described for providing traction for golf shoes, alternatively, the use of the cleats is not limited to golf shoes but can be employed for other suitable purposes such as soccer or football as well as surfaces other than grass. Furthermore, although each preferred cleat has been depicted with four protrusions, alternatively, more than four or less than four protrusions can be employed.