Athletic shoe sole with cleats having threaded exchangeable gripping elements
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to an outer sole for an athletic shoe of the type having cleats with exchangeable gripping elements that are screwed onto sole-mounted threaded studs. 
     An athletic shoe having a sole of this kind is described in U.S. Pat. No. 2,302,471, where a kind of flat headed screw is inserted through the shoe sole from the inside, and a washer and locking disk are secured by a nut onto the exteriorly projecting threaded shaft. Moreover, a cone-shaped gripping element, having teeth at its base, is screwed onto the projecting threaded shaft. The teeth at the base of the gripping element form a locking engagement, when screwed onto the shoe sole, with the grip members punched out from the washer. To ensure locking action, the washer has exteriorly toothed ring elements that cut into the shoe sole. A threaded sleeve is molded into the bore of the cap, which consists of deformable material, like rubber, to ensure firm anchoring thereof. 
     However, this known construction has several disadvantages. Firstly, the continuous flat headed screw causes considerable weakening of the sole, which may tear at the bore edges when frequently deformed. A similar effect is caused by the sharp toothed ring elements cutting into the sole. Another drawback of the known arrangement is the necessity of the special threaded sleeve in the cap. 
     A similar arrangement of gripping elements is disclosed in U.S. Pat. No. 3,054,197, as can be seen from the drawings of this patent. 
     German O. S. No. 2,542,116 shows a grip element in the form of a conventional screw-in cleat, which additionally can be screwed onto a shallow threaded study by way of an interior thread. This threaded stud has cylindrical shape. As the gripping elements, however, advantageously should be cone shaped, this creates a thin area in the vicinity of the threaded stud in the cleat wall, which may result in breakage of the cleat due to cold weather and correspondingly stiff material. 
     It is the objective of the present invention to provide an outer sole for an athletic shoe having cleats with exchangeable gripping elements of the foregoing kind that are designed for easy and cost-effective manufacture, yet a premature tearing, breaking, or breaking away of the sole is prevented, while at the same time, the caps can be removed from the studs without damaging or destroying them. 
     Furthermore, a cone shaped stud and snap-on cap are described in German Patent GM No. 1,888,123. However, the stud and cap are nailed on, and a screw-lock engagement is not featured. 
     This objective is achieved by employing the special features of the invention wherein a cone shaped threaded stud projects from a ground contacting surface of the sole and a hollow, tapered screw-on cap is threadingly engageable thereon with the broad base of the cap facing the sole, wherein the threading of the stud and the cap extends for less than a full turn and wherein the cap is provided with locking elements that interact with locking elements of the sole, said locking elements forming a ratchet-like locking assembly and having run-on surfaces that are less inclined relative to a plane of a bottom surface of the sole than inclined locking surfaces of the locking elements. 
     The present invention provides large area contact between the threaded stud and the cap, whereby the use of special threaded sleeves is not necessary. The partial screw threads permit a quick fastening and removal with low rotational effort of the cap, and the special inclined configuration of the teeth permits a soft screwing on, while the screwing off action necessitates high rotational moment, without, however, causing any marring or damage of the locking elements. When the threaded studs are molded to the sole, only the caps, without additional components, are to be screwed on. 
     These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a vertical cross sectional view of a portion of a sole in accordance with the present invention, part of a stud thereof being shown in elevation; 
     FIG. 1a is an enlarged cross section of a threaded portion of a stud; and 
     FIG. 2 is an exploded view depicting interacting contact areas of sole or stud and cap or cap member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Numeral 1 designates a shoe sole, particularly an outsole of an athletic shoe, e.g., football, hockey or baseball shoe. Generally, this outsole consists of a single component made of injection molded or cast synthetic material, like polyurethane, polyethylene, polyamide, hexamethylenediamine adipic acid polycondensate or similar material, and extends over the entire bottom of a shoe, i.e., from the toe to the heel of the shoe. The heel and sole portions, may, however, be two separate parts. The shoe sole or the sole portion and the heel are provided with studs 2 which, preferably, form a single structural element therewith. Alternatively, the studs may consist of individual studs, possible with stamped flanges, which studs can be inserted, snap locked, or advantageously, molded into the sole or into the sole member and heel. 
     In accordance with the invention, a thread 4, specifically a multiple thread having, preferably, a short or steep thread course, which consists of only partial turns of screw threads, is molded on the outer surface 3 of stud 2. Preferably, the partial screw thread turns constitute approximately 25% to 50% of a complete thread turn, so that the caps (cap members which will be subsequently described) can engage the short or steep threads in the manner of a quick action lock. Caps 5 or cap members 5a are screwed onto stud 2 with a corresponding counter thread. Threads 4, preferably, are threads of rectangular or trapezoidal shape. Advantageously, the flanks 6 of threads 4, facing in the direction of shoe sole 1, are parallel, or nearly parallel, to the plane of the bottom surface 7 of sole 1 to obtain a high degree of screw-on stability (FIG. 1a). 
     Advantageously, interacting areas are provided at shoe sole 1 and at caps 5 or cap members 5a, respectively, (FIG. 2) to prevent loosening of the screw engagement during athletic activity. This is achieved, in accordance with the illustrated embodiment, by lock elements 10, 11 (FIG. 2), provided on the facing contact surfaces, preferably in the shape of saw teeth, lock elements 10 being located within an annular recess 8 in the bottom surface 7 of sole 1 and lock elements 11 being formed on an annular flange 9 that is received within recess 8. The tooth flanks serving as run-on surfaces 12, 13 during screw on are less inclined relative to bottom surface 7 than the tooth flanks 14, 15 serving as locking surfaces. By this arrangement a ratchet-like effect is provided whereby the torsional moment for the screw-on engagement of the cap 5, cap member 5a is reduced, but the torsional force required for disengagement is increased so as to practically eliminate self-disengagement. 
     In order to facilitate screw-on and screw-off action, cap 5 or cap member 5a have inset areas to receive a tool, e.g., cut-outs 16, multiple exterior surfaces, or shoulders. 
     Cap 5, as a single homogeneous component, may consist of an abrasion resistant synthetic material, like hard PVC, hard polyurethane, polyethylene, polycarbonate, or similar material, or may consist of a metal like aluminum, copper, brass, bronze, or steel, or it may be made of a ceramic, like steatite, aluminum, oxide, zirconium dioxide, or corundum, that, where appropriate, is combined with organic or inorganic binders. The cap may, furthermore, be comprised of textile, glass-metal or reinforced coal-fiber synthetic material, and/or abrasion resistant particles of metal or ceramic may be admixed into a synthetic plastic material or may be embedded into the stress areas, preferably by pressing-in. 
     However, as depicted in the drawing, cap 5 may be comprised of a cap member 5a having a wear-resistant grip element 17 mounted thereover. Advantageously, stud 2 and cap member 5a are designed as truncated cones, in which case, grip element 17 has the shape of a disk secured on the truncated cone-shaped cap member 5a, or may have the shape of an overlapping bell. Alternatively, particularly, when studs 2 are cylindrical, grip element 17 may have a sleeve-shaped design, in which case, cap members 5a and grip element 17 may consist of the same material as cap 5, namely of a single homogeneous material. Appropriately, however, cap member 5a is somewhat softer, and specifically may consist of synthetic material which renders it somewhat resilient, facilitating an easier friction fit. 
     Cap member 5a and grip element 17 are interconnected by way of lock and/or centering elements, e.g., projection 18 and bore 19, and may, additionally, be glued. Alternatively, it is possible to directly mold grip element 17 to cap 5a when fashioning cap member 5a. 
     While we have shown and described various embodiments in accordance with the present invention, it is understood that the same is not limited thereto, but is susceptible of numerous changes and modifications as known to those skilled in the art, and I, therefore, do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.