Abstract:
A cable anchor has ball surfaces that permit misalignment between the cable and a stem of the anchor, and a fitting that permits the introduction of a corrosion inhibitor to the interior of the anchor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/120,503 filed May 14, 2008, now allowed, which claims the benefit of U.S. Provisional Patent Application No. 60/938,366 filed May 16, 2007, both of which are hereby incorporated by reference. 
     
    
     STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       FIELD OF THE INVENTION 
       [0003]    This invention relates to an apparatus for anchoring the end of a cable to a structure such as a concrete pillar, post, or the like. 
       BACKGROUND OF THE INVENTION 
       [0004]    This invention relates to cable anchors of the type disclosed in U.S. Pat. No. 4,899,499, the disclosure of which is hereby incorporated by reference. The anchor disclosed has a body with a wedge-shaped (conical) internal bore surface, cable grippers with wedge-shaped (conical) external surfaces received in the bore, a cable gripped by the grippers and extending from one end of the body, a cap at the opposite end attached to the body through which a stem extends outside of the body and the stem having a head that is captured against a facing surface of the cap. The stem is threaded into an insert that is embedded in a concrete structure. The facing surfaces of the cap and head are generally flat such that in this structure it is desirable that the axis of the stem and the axis of the cable be aligned. While that is ideal, that is not always the case in practice. In practice, there are often at least slight deviations between the axis of the cable and the axis of the stem, which stress the components of the connection. In addition, as the cables that are anchored oftentimes form barriers, even if the cable is initially aligned, at least generally, with the stem, an impact to the cable can result in significant stresses and deviations from aligned axes, which, even if temporary, can damage or even break the assembly. Corrosion inside the anchor, for example between the grippers and the body, the cable and the grippers and the cap and the stem, exacerbates the problem. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides an apparatus for anchoring the end of a cable to a structure with the head of the stem and the facing surface of the cap being shaped to allow articulation between the head of the stem and the cap while maintaining surface contact. Preferably, the mating surfaces of the head and cap are frusto-spherical in shape. Thereby, an anchor of the invention can accommodate misalignments between the axis of the cable and the axis of the stem, either upon initial construction, impact to the cable, or other changes that may occur during the life of the structure, such as vibrations and settling. 
         [0006]    The foregoing and other objects and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a cross-sectional view of an anchor of the invention installed in an insert embedded in a concrete structure and gripping the end of a cable; 
           [0008]      FIG. 2  is an exploded perspective view of an anchor of the invention; 
           [0009]      FIG. 3  is a perspective view of the cap of  FIG. 2  viewed in the opposite direction of  FIG. 2 ; and 
           [0010]      FIG. 4  is a detail cross-sectional view illustrating the mating surfaces between the stem and cap. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0011]    Referring to  FIG. 1 , an anchor  10  of the invention is illustrated including a chuck body  12 , a stem  14 , a cap  16  attached to the chuck body and capturing the head  18  of the stem, grippers  20  securing the end of a cable  22  in the bore of the chuck body, and a spring  24  in the bore of the chuck body urging the grippers  20  into engagement with the cable  22 . Also illustrated in  FIG. 1  is an insert  26  embedded in a concrete structure  28  into which a shank  15  of the stem  14  is threadedly fastened. 
         [0012]    Referring to  FIGS. 2 and 3 , the head  18  of the stem  14  has a frusto-spherical surface  30  that mates with a frusto-spherical surface  32  of the cap  16 . The mating frusto-spherical surfaces  30  and  32  permit articulation for 360° about the axis of the stem  14  relative to the cap  16 . The range of articulation permitted from the aligned position illustrated is sufficient to accommodate typical impacts, vibrations and construction imperfections. Thereby, the anchor  10  can accommodate misalignments between the axis of the cable  22  and the axis of the stem  14  that may result from many different causes. 
         [0013]    While it is preferred that frusto-spherical surfaces be formed on both of the head  18  and the cap  16 , it may be possible to accomplish the advantages of the invention with other combinations of surfaces, for example, with just a frusto-spherical surface on the head  18  and a frusto-conical surface on the cap  16 , or just line contact at the end of a circular bore of the cap  16 . 
         [0014]    The stem  14  also has a neck section  38  that extends through bore  40  of the cap  16  and is significantly smaller in diameter than the bore  40  so as to provide clearance to accommodate articulating motions of the stem  14  relative to the cap  16 . This clearance is what determines the range of articulation permitted by the construction. In addition, preferably, where the stem  14  exits the cap  16  and is exposed, the stem  14  has flats  44  that can be engaged by a wrench to turn the stem  14  so as to threadedly engage the shank  15  with the insert  26 . It is noted that the shank  15  as illustrated is externally threaded, but could alternatively be internally threaded. 
         [0015]    The cable grippers  20  are conventional, for example, a set of two or three wedge-shaped jaws. Typically, the interior surface of the grippers  20  is formed with teeth, which may be formed by a thread cutting operation, and the exterior is a frusto-conical surface or a portion of a frusto-conical surface. The bore of the body  12  is a mating frusto-conical surface such that when the grippers  20  are urged leftwardly as viewed in  FIG. 1 , they clamp down on the end of the cable  22  and bite into it to firmly grip it. The spring  24  biases the grippers  20  in this direction to aid in initial gripping of the cable  22 . 
         [0016]    Preferably, the mating surfaces  30  and  32  are lubricated so as to reduce friction therebetween to take full advantage of the invention. Particularly when so lubricated, an anchor of the invention can accommodate and absorb even small misalignments between the cable  22  and the stem  14 , such as may be caused by vibrations, to prevent vibrations from being transmitted either to or from the cable to the stem  14 . Lubrication also reduces the stress on the assembly which may be caused by larger articulations, for example, from an impact, from the building settling, or during initial installation. 
         [0017]    To assure adequate corrosion protection to protect the wedges  20 , housing  12  and strand  22  interface, which is the most vulnerable area for corrosion to start, and also to lubricate and protect against corrosion of the mating surfaces of the head and cap, a grease zerc fitting  50  ( FIG. 1 ) is preferably provided in the body  12 , through which grease or another corrosion inhibitor may be introduced into the body  12 . This also helps lubricate the surfaces  30  and  32  as discussed above. 
         [0018]    A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiment described, but should be defined by the claims that follow.