Patent Publication Number: US-6701645-B1

Title: Rotatable traction pad for athletic shoe

Description:
FIELD OF THE INVENTION 
     This invention relates to athletic shoes, and particularly to athletic shoes having rotatable traction pads that facilitate quick turning maneuvers. The invention has application to various types of athletic shoes, including basketball shoes, tennis shoes, baseball shoes, football shoes, dance shoes, cheerleader shoes, aerobic workout shoes, and specialized work boots. 
     BACKGROUND OF THE INVENTION 
     In various sports activities a person may be required to swivel his foot to execute a change of direction. My U.S. Pat. No. 5,566,478 discloses a sports shoe equipped with a rotatable traction pad for enabling the person to execute a directional change without unduly stressing the person&#39;s ankle. During a turning maneuver the traction pad becomes anchored to the ground (or floor surface, while the shoe rotates around the traction pad rotational axis, whereby the person&#39;s foot can rotate with the rest of his body. The traction pad has features, whereby it can be easily removed from the shoe for cleaning the pad or removing debris that might interfere with pad rotation. Another traction pad is shown in U.S. Pat. No. 3,354,561 issued to B. M. Cameron. 
     SUMMARY OF THE INVENTION 
     In U.S. Pat. No. 5,566,478 the mechanism for rotatably mounting the traction pad is located in a circular cavity formed in the bottom surface of the shoe sole. In some cases, particularly with shoe soles that are relatively thin or lack strength, the cavity might unduly weaken the sole. In some cases the cavity might enable the traction pad to punch through or deform the sole, making the shoe uncomfortable to wear. 
     The present invention is concerned with an athletic shoe having a rotatable traction pad that is at least partially contained within a circular cavity formed in the bottom surface of the shoe sole, with the cavity being relatively shallow so that the cavity does not unduly weaken the shoe sole. In preferred practice of the invention the traction pad is rotatably supported by means of an anti-friction bearing that is contained within an annular bearing housing that is adhesively bonded to the circular side surface of the cavity. 
     With such an arrangement the load forces on the traction pad are largely distributed to relatively thick areas of the shoe sole surrounding the circular cavity (not to the roof area of the cavity). By spreading the load forces into relatively thick areas of the sole it comes possible to maintain the overall strength of the shoe sole, the ensure a comfortable fit of the shoe on the person&#39;s foot. The invention has particular application to shoes that have relatively thin soles. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a shoe having rotatable traction pads of the present invention mounted in the toe area and heel area of the shoe sole. 
     FIG. 2 is a bottom plan view of the shoe illustrated in FIG.  1 . 
     FIG. 3 is a fragmentary sectional view taken on line  3 — 3  in FIG.  2 . 
     FIG. 4 is a sectional view taken in the same direction as FIG. 3, but showing another traction pad constructed according to the invention. 
     FIG. 5 is a sectional view, taken the same direction as FIGS. 3 and 4, but showing another traction pad embodying the invention. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     FIGS. 1 and 2 show a generally conventional sports shoe  10  having a sole  12  formed of rubber or similar elastomeric materials having cushioning properties and traction capabilities. In some cases, such as a football shoe or a dance shoe, the sole might be formed of leather or a composition material. Botton surface  18  of the sole can have grooves or slots therein for improving the traction on a ground or pavement or floor surface. 
     The invention is more particularly concerned with a rotatable traction pad  20  located within a circular cavity  22  formed in the bottom surface  18  of the shoe sole. The rotatable nature of the traction pad enables the pad to be anchored to the ground surface during a shoe turning maneuver, thereby enabling the shoe to more easily turn with the person&#39;s foot so as to minimize stress on the person&#39;s ankle. 
     FIGS. 1 and 2 show the shoe equipped with two rotatable traction pads  20 , one located on the toe area of the shoe sole and the other located on the heel area of the shoe sole. FIGS. 1 and 2 are merely illustrative of the traction pad locations that can be employed in practice of the invention. In a given instance (e.g. a tennis shoe or a basketball shoe) the rotary traction pad can be incorporated into the toe area of the shoe sole. In another instance (e.g. a dance shoe), the rotary traction pad can be mounted in the heel area of a shoe sole. 
     As shown in FIGS. 1 and 2, the two rotary traction pads  20  are the same size. However, they can be of different sizes in accordance with the available sole surface area and pad area required to achieve the desired anchorage on a particular terrain. The two rotary traction pads can be similarly constructed. In each case, the rotatable traction pad is located within a circular cavity  22  formed in the shoe sole bottom surface  18 . Each traction pad is mounted for relative rotation around a central axis  24  that coincides with the central axis of circular cavity  22 . 
     FIGS. 3,  4  and  5  show different pad constructions that can be employed in practice of the invention. As shown in FIG. 3, the traction pad  20  comprises a rigid flat circular plate  26  having a circular edge  28  in close clearance relation to circular side surface  30  of the associated cavity  22 , for minimizing the entry of dirt into cavity  22 . Traction pad  20  further includes a circular post  32  extending upwardly from plate  26  so that it&#39;s free end  34  is in close proximity to roof surface  36  of cavity  22 . 
     Traction pad  20  is preferably a one piece structure, wherein circular plate  26  and post  32  are integrated together as a unit. The lower face of plate  26  carries a traction disk  38 , preferably of the same material as shoe sole  12 . 
     Traction pad  20  is a rigid one piece unit, formed of a material that is non-deformable and resistance to compression forces. The one piece unit can, for example, be formed of aluminum (for lightness) or a rigid polymer (e.g. nylon), or a composite material having reproducible dimensional qualities. Resistance to deformation under compressive forces is a principal requirement for the traction pad material. 
     As previously noted, cavity  22  has a roof surface  36  and a cylindrical side surface  30  extending from the roof surface to the shoe sole bottom surface  18 . Cavity  22  is preferably a relatively shallow cavity having a depth dimension A that is relatively small in relation to the vertical thickness of shoe sole  12 . Typically, cavity  22  has a depth dimension A that measures about 0.33 inch, whereas shoe sole  12  has a vertical thickness varying from about three fourth inch to one inch or more (depending on the type of shoe). 
     By keeping the depth dimension A of the circular cavity  22  small in relation to the shoe sole thickness, it is possible to minimize the weakening effect of the cavity on the overall strength of the shoe sole. 
     The diameter dimension B of the circular cavity is also kept reasonably small in order to maintain the overall strength of the shoe sole. Typically, the cavity diameter is about one and three quarter inch. 
     Traction pad  20  is rotatably mounted for rotation around central axis  24 , by means of an anti-friction bearing  40  that is supported on an annular housing  42 . As shown in FIG. 3, the housing is a one piece rigid structure that includes an upper end surface  44  abutting the cavity roof surface  36 , an annular circular side surface  46  mated to the cavity side surface  30 , and a lower end surface  48  having a close clearance relation to the upper surface  50  of circular plate  26 . The housing further includes a radial flange  51  that projects radially inwardly toward post  32 . 
     Housing  42  can be formed of various rigid materials, e.g. aluminum, or a rigid polymer, or a high strength composite. The housing is adhesively bonded to the circular side surface  30  of cavity  22 , so that axial loads on housing  42  are distributed to cavity side surface  30  and the areas of shoe sole  12  surrounding cavity  22 . This minimizes the loadings on cavity roof surface  36 , and indirectly prevents undesired vertical deformation of the shoe sole (especially the sole material that defines cavity roof surface  36 ). 
     The anti-friction bearing  40  shown in FIG. 3 is a thrust bearing that includes an array of rollers  52  floatably mounted in a separator that is located between an upper anti-friction disk  53  and a lower anti-friction disk  54 . Each disk can be formed of polytetrafluoroethylene or other polymer having low surface friction properties. The disks are optional. 
     Traction pad  20  is retained in an operating position by a retainer  56  that is releasably secured to circular post  32  near the post free end  34 . As shown in FIG. 3, retainer  56  includes a snap ring seated in a mating groove in the post  32  side surface so as to vertically overlap the inner edge area of housing flange  51 . Other retainer constructions can be employed, e.g. a lock nut threaded onto the end of post  32 , or a sleeve press fit on the post free end. 
     Retainer  56  prevents axial play of traction pad  20  toward or away from cavity roof surface  36 , so that the traction pad is retained in an operating position wherein rollers  52  have firm rolling contact with the bearing surfaces on disks  53  and  54 . 
     Retainer  56  is spaced a predetermined axial distance from plate  26 , so that housing end surface  48  has only a slight running clearance relative to the upper surface  50  of plate  26 , e.g. on the order of 0.001 inch. A slight running clearance is beneficial in that it tends to prevent undesired migration of dirt into cavity  22  (where such dirt could clog the bearing). 
     Traction pad  20 , anti-friction bearing  40  and housing  42  are assembled together prior to insertion of the operating components into circular cavity  22 . Retainer  56  is inserted onto post  32  to retain components  20 ,  40  and  42  together as a sub-assembly. The sub-assembly is then inserted into cavity  22  and fixed in place by an adhesive extending along the interface between housing side surface  46  and cavity side surface  30 . 
     As shown in FIG. 3, the vertical (axial) thickness dimension of annular housing  42  is almost as great as the cavity depth dimension A. This ensures that there is a substantial adhesive bond area between surfaces  46  and  30 , even though cavity depth dimension A is relatively small in an absolute sense, e.g. only about one third inch. 
     During operation of the rotary traction pad, axial load forces on the traction surface (disk  38 ) tend to displace traction pad  20  upwardly relative to shoe sole  12 , so that the adhesive bond between surfaces  46  and  30  is under a shear stress. Some of the axial load on the traction pad is transferred via the adhesive bond to the areas of sole  12  surrounding cavity  22 , so as to somewhat reduce the axial loadings on cavity roof surface  36 . 
     The axial thickness dimension of annular housing  42  is preferably at least sixty percent of the cavity depth dimension A, in order to maximize the adhesive bond area and minimize forces tending to distort the shoe sole  12 . In the FIG. 3 arrangement, the axial thickness of housing  42  is approximately eighty percent of cavity depth dimension A. 
     Traction pad  20  is a rigid one piece structure in order to minimize traction pad distortion that could produce undesired frictional interferences between the traction pad and housing  42  (or the cavity surfaces). Housing  42  is located radially outwardly from central post  32  in order to minimize the depth of cavity  22  (typically the cavity has a depth of about 0.33 inch). Components  20 ,  40  and  42  are held together as a sub-assembly (by retainer  56 ) so that the sub-assembly can be adhesively secured to shoe sole  12  without forming fastener holes in the shoe sole (that could constitute weak points in the shoe sole). 
     FIG. 3 represents a presently preferred embodiment of the invention. FIGS. 4 and 5 show other forms that the invention can take. 
     FIG. 4 shows an arrangement wherein annular housing  42  is a radially thickened sleeve having flat upper and lower ends. The housing does not have an inwardly radiating flange, as in the FIG. 3 arrangement. 
     The anti-friction bearing  40  is a radial bearing that includes an inner race  58  having a close fit on post  32 , an outer race  60  adhesively bonded to the inner surface of housing  42 , and an array of anti-friction balls  62  interposed between the two races. The grooves in races  58  and  60  are deep enough so that bearing  40  can act as a thrust bearing. Bearing  40  can be a commercially available sealed anti-friction bearing. 
     In the operation of assembling the FIG. 4 traction pad, anti-friction bearing  40  is initially bonded to annular housing  42 . After the bearing has been placed on post  32 , retainer  56  is installed on post  32  to position traction pad  20  in operative connection with bearing  40  and housing  42 . The sub-assembly of components  20 ,  40  and  42  is installed as a unit in cavity  22 . As in the FIG. 3 arrangement, the annular side surface  46  of housing  42  is adhesively bonded to cavity side surface  30  to retain the rotatable traction pad in its operation position. 
     In the FIG. 4 arrangement, the axial thickness dimension of annular housing  42  is approximately sixty percent of the cavity depth dimension A. While this percentage is less than the eighty percent in FIG. 3, nevertheless there is sufficient surface area on housing side surface  46  to obtain a satisfactory adhesive bond between housing  42  and cavity surface  30 . 
     In an operational sense, the FIG. 4 construction operates in the same general fashion as the FIG. 3 arrangement. 
     The construction depicted in FIG. 5 is the same as that shown in FIG. 3 except for the type of anti-friction bearing that is used. In FIG. 5 the anti-friction bearing comprises an annular disk  64  formed of polytetrafluoroethylene or similar anti-friction bearing material. The disk can have a press fit in housing  42 . 
     The lower surface of anti-friction disk  64  is in rotary sliding contact with a thin wafer  66  that is adhesively bonded to the upper surface of plate  26 . Wafer  66  can also be formed of polytetrafluoraethylene. Disk  64  can have an axial thickness of about 0.14 inch; wafer  66  can have an axial thickness of about 0.005 inch. The thickness dimensions are selected, at least partly, so that lower end surface  48  on housing  42  has only a slight running clearance with respect to the upper surface  50  of circular place  26 . 
     In the FIG. 5 arrangement, traction pad  20  is operatively connected to housing  42  by means of a retainer  56  that may be similar to the retainer shown in FIG.  3 . The FIG. 5 construction operates in essentially the same fashion as the FIG. 3 construction. 
     The drawings show illustrative forms that the invention can take. However, it will be appreciated that the invention can be practiced in other forms and configurations.