Patent Document

[0001]     The present application claims the benefit of U.S. Provisional Application Ser. No. 60/777,692, filed Feb. 27, 2006, which application is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to securing the ends of cables and in particular to force distributing ends for securing the ends of cable.  
         [0003]     Light weight cables have been developed which replace heavy steel cores with light weight cores, such as a carbon fiber core with a fiberglass sheath. Such light weight cores may be damaged by cable ends which concentrate holding forces over a small area of the cable surface.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     The present invention addresses the above and other needs by providing a dead cable end which distributes holding force over a length of a cable end to reduce or eliminate damage to cables. The dead cable end includes a housing containing a plurality of collets each residing in a collet receptacle. Each collet includes conical exterior and a lengthwise collet gap and each collet receptacle includes a conical interior. The collets and collet receptacle are held inside the housing by a retaining nut, and the collet and collet receptacle pairs are compressed between the retaining nut and a spring inside the housing. The cable end resides inside the collets, and compressive force on each collet and collet receptacle pair causes each collet to compress radially and hold the cable end. The holding force is thereby distributed over the length of each collet and over the plurality of collet and receptacle pairs to avoid damage to the cable.  
         [0005]     In accordance with one aspect of the invention, there is provided a dead cable end including a housing, a retainer, and a multiplicity of collets and collet receptacles residing in series in the housing for holding a cable end. The housing includes a housing interior opening to a housing mouth and the retainer includes a retainer cable passage for allowing a cable to pass through the retainer and into the housing interior. The retainer is connectable to the housing at the housing mouth. A first collet has a conical exterior, a lengthwise collet gap, a collet cable passage for allowing the cable to pass through the collets freely when the collets are in a relaxed state, and a collet small end facing the retainer in an assembled dead cable end comprising. A first collet receptacle has a conical cavity for cooperation with the conical exterior of the first collet. A multiplicity of additional collets and additional collet receptacles reside serially between the first collet and the first collet receptacle and the retainer with the collet small ends of the additional collets facing away from the retainer. A spring residing serially with the first collet and the first collet receptacle opposite the additional collets and collet receptacles. The collets and collet receptacles reside serially in compression in the housing between the spring and the retainer for advancing each collet into the respective collet receptacle to urge the collets to a compressed state to squeeze the cable residing in the collet cable passages to resist removing the cable from the dead cable end.  
         [0006]     In accordance with another aspect of the invention, there is provided a dead cable end including a housing, a retainer, a spring, a first collet and first collet retainer, and at least one additional collet and collet retainer. The housing has a housing interior opening to a housing mouth and the retainer is connectable to the housing mouth and includes a retainer cable passage for allowing a cable to pass through the retainer and into the housing interior. The first collet has a conical exterior, a lengthwise collet gap, and a collet cable passage to allow the cable to pass through the first collet freely when the first collet is in a relaxed state. The collet cable passage has outwardly rounded ends for preventing damage to the cable and a collet small end of the first collet faces the retainer in an assembled dead cable end. The first collet receptacle includes a conical cavity for cooperation with the conical exterior of the first collet. The additional collet and additional collet receptacle residing serially between the first collet and the first collet receptacle and the retainer with the collet small end of the additional collet facing away from the retainer. The spring resides serially with the first collet and the first collet receptacle opposite the retainer. The collets and collet receptacles reside serially in compression in the housing between the spring and the retainer for advancing each collet into the respective collet recpetical to urge the collets to a compressed state to squeeze the cable residing in the collet cable passages to resist removing the cable from the dead cable end.  
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0007]     The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:  
         [0008]      FIG. 1  is an exploded view of a dead cable end assembly according to the present invention.  
         [0009]      FIG. 2  is an end view of the dead cable end assembly.  
         [0010]      FIG. 2A  is a cross-sectional view of the dead cable end assembly taken along line  2 A- 2 A of  FIG. 2 .  
         [0011]      FIG. 2B  is a detailed view of the cooperation of a collet and collet receptacle according to the present invention.  
         [0012]      FIG. 3  is a perspective view of a dead cable end housing according to the present invention.  
         [0013]      FIG. 4A  is an end view of the dead cable end housing.  
         [0014]      FIG. 4B  is a side view of the dead cable end housing.  
         [0015]      FIG. 5  is a cross-sectional view of the dead cable end housing taken along line  5 - 5  of  FIG. 4A .  
         [0016]      FIG. 6  is a perspective view of the collet only.  
         [0017]      FIG. 7A  is a side view of the collet according to the present invention.  
         [0018]      FIG. 7B  is an end view of the collet.  
         [0019]      FIG. 8  is a cross-sectional view of the collet taken along line  8 - 8  of  FIG. 7A .  
         [0020]      FIG. 9  is a view of detail  9  of  FIG. 7B  showing a collet gap according to the present invention.  
         [0021]      FIG. 10  is a perspective view of the collet receptacle.  
         [0022]      FIG. 11A  is an end view of the collet receptacle according to the present invention.  
         [0023]      FIG. 11B  is a side view of the collet receptacle  
         [0024]      FIG. 12  is a cross-sectional view of the collet receptacle taken along line  12 - 12  of  FIG. 11A .  
         [0025]      FIG. 13  is an end view of a spring according to the present invention.  
         [0026]      FIG. 14  is a cross-sectional view of the spring taken along line  14 - 14  of  FIG. 13 .  
         [0027]      FIG. 15  is a perspective view of a screw-in retainer according to the present invention.  
         [0028]      FIG. 16A  is an end view of a threaded end of the screw-in retainer.  
         [0029]      FIG. 16B  is a side view of the screw-in retainer.  
         [0030]      FIG. 17  is a cross-sectional view of the screw-in retainer taken along line  17 - 17  of  FIG. 16A .  
         [0031]      FIG. 18  is a side view of a cable end coupler according to the present invention.  
         [0032]      FIG. 19  is a cross-sectional view of the cable coupler according to the present invention taken along line  19 - 19  of  FIG. 18 .  
         [0033]      FIG. 20  is a perspective view of a second collet according to the present invention.  
         [0034]      FIG. 21A  is a side view of the second collet.  
         [0035]      FIG. 21   b  is an end view of the second collet.  
         [0036]      FIG. 22  is a cross-sectional view of the second collet taken along line  22 - 22  of  FIG. 21A .  
         [0037]      FIG. 23  is a cross-sectional view of a second dead cable end assembly according to the present invention.  
         [0038]      FIG. 24  is a cross-sectional view of a third dead cable end assembly according to the present invention. 
     
    
       [0039]     Corresponding reference characters indicate corresponding components throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0040]     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims.  
         [0041]     An exploded view of a dead cable end assembly  10  according to the present invention for securing a cable  18  is shown in  FIG. 1 . An end view of the dead cable end assembly  10  is shown in  FIG. 2 , a cross-sectional view of the dead cable end assembly  10  taken along line  2 A- 2 A of  FIG. 2  is shown in  FIG. 2A , and a detailed view of a general collet  22  and collet receptacle  20  is shown in  FIG. 2B . The dead cable end assembly  10  secures the cable  18  through a multiplicity of collets  22   a - 22   h  cooperating with a multiplicity of collet receptacles  20   a - 20   h . The collets  22   a - 22   e  and the collet receptacles  20   a - 20   h  are contained in a dead cable end assembly housing  12  within which the collets  22   a - 22   h  are compressed, using screw-in retainer  16  into the collet receptacles  20   a - 20   h  thereby forcing the reduction of diameter of the collets  22   a - 22   h  to exert a pressure on the cable  18 . Multiple collets  22   a - 22   h  are used in order to distribute securing forces, thereby reducing the concentration of pressures exerted on the cable  18 . Each collet  22   a - 22   h  is be designed to hold a portion of the total tensile load applied. Once a collet  22   a - 22   h  has reached it&#39;s predetermined holding capacity, the cable  18  will slip within the collet  22   a - 22   h  at which point another collet  22   a - 22   h  will begin retaining the remaining load.  
         [0042]     The in-series collets  22   a - 22   h  and collet receptacles  20   a - 20   h  are held in compression between the screw-in retainer  16  and a spring  14  at the opposite end of the collets  22   a - 22   h  and collet receptacles  20   a . The screw-in retainer  16  is preferably tightened to approximately 80 foot pounds of torque, and the collets  22   a - 22   h  and collet receptacles  20   a - 20   h  are under approximately 2700 pounds of compression. The tensile load capacity of the dead cable end assembly  10  is a function of the collet angle (or taper), collet length, and collet diameter. The maximum collet taper for the arrangement of collets  22  in the dead cable end assembly  10  is preferably approximately 18 degrees and more preferably, the collet tapers for the arrangement of collets  22  in the dead cable end assembly  10  are between approximately six degrees and approximately 16 degrees from the collet axis. Such preferred tapers provide the desired clamping pressure and are easily manufactured. Other dead cable ends having other arrangements of collets may utilize other tapers. For example, a dead cable end with all of the collet small ends  23   a  facing the screw-in retainer may use collets with up to a 26 degree taper.  
         [0043]     The smaller the taper, the greater the clamping pressure on the cable  18 . To determine the minimum collet taper the coefficient of friction between the collet  22   a - 22   h  and cable  18  is used as well as the coefficient of friction between the collet and collet receptacle. As the coefficient of friction between the collet  22   a - 22   h  and cable  18  decreases, more collet taper is required. As the coefficient of friction between the collet  22   a - 22   h  and collet receptacle  20   a - 20   h  increases so will the collet taper. Preferably, the friction between the collet and collet receptacle is minimized by manufacturing the collets and collet receptacles from 17-4 stainless steel and using a low friction coating such as dry lubricant molybdenum disulfide or a Casidaim coating between the collet and collet receptacle.  
         [0044]     The collet  22   a  is oriented with the collet small end  23   a  (and thus the face of the conical exterior  31  (see  FIG. 6 ) of the collet) facing the screw-in retainer  16 , and the collets  22   b - 22   h  are oriented with the collet small end  23   a  facing away from the screw-in retainer  16 . By orienting collets  22   a  and  22   b  with opposing collet small ends  23   a  facing each other, the collets  22   a  and  22   b  maintain a gripping force even if the cable load has been released. Also, by orienting collet  22   a , the furthest from the screw-in retainer  16 , with the collet small end  23   a  facing the screw-in retainer  16 , increased gripping force is generated with increase cabled load, thereby, increasing the compression of the preceding collets  22   b - 22   h  resulting in increased gripping forces by the collets  22   b - 22   h.    
         [0045]     Various angles for the collets  22  and collet receptacles  20  may be utilized to provide more even pressures on the cable  18  surface. When comparing the forces collinear to the cable load, collet  22   h  nearest the screw-in retainer  16  exerts a force onto screw-in retainer  16  equal to cable load. Collet receptacle  20   a  is furthest from screw-in retainer  16  and exerts the smallest force, only a fraction of the cable load, onto the collet receptacle  20   b . Since the forces collinear to the cable load at each contacting surface increase from collet receptacle  20   a  to the screw-in retainer  16 , the tapers of the conical surfaces  31  preferably are also increased to ensure even pressure on the cable  18  surface. An example of a set of preferred collet tapers for the collets  22   a - 22   h  of the dead cable end assembly  10  (see  FIG. 2A ) are approximately 6 degrees, approximately 8 degrees, approximately 10 degrees, approximately 13 degrees, approximately 13 degrees, approximately 14.5 degrees, approximately 14.5 degrees, and approximately 16 degrees respectively. The preferred collet tapers are directed to a 0.280 inch diameter carbon fiber cable.  
         [0046]     With increased collet  22  length the pressure on the cable  18  is reduced for a given collet taper and cable load, though, the total force exerted onto the cable  18  remains approximately constant. Gripping force is a function of force exerted onto the cable  18  and the coefficient of friction between the cable  18  and collet  22 . Therefore, the reduction of pressure does not significantly affect the gripping force but does reduce cable failure caused by crushing.  
         [0047]     Further, if collet tapers are the same, by stacking N number of collets in series and applying a given compression load, each collet  22  and collet receptacle  20  assembly will exert the same cable gripping force (friction between collet  22  and collet receptacle  20  is ignored in this example but may generate uneven gripping forces). For instance, if a given compression load of X pounds produces Y pounds of gripping force, the collets  22  in series will produce a gripping load of N multiplied by Y. Further, while trying to maximize collet length, length and diameter restrictions of the assembly envelope must also be considered. In the instance where one long collet is desired, the angle has to be shallow enough and/or load large enough to produce the desire clamping forces.  
         [0048]     A gap, seen as a recess  21  of the collet small end  23   a  in  FIG. 2B , between the adjacent collets  22  is provided to prevent touching. The gap is preferably between approximately 0.04 inches and approximately 0.10 inches with the lower tapered collets having a larger gap due to the increased movement per unit of radial deflection. For example, for a 6 taper degree collet, a gap of approximately 0.09 inches is preferred, and for a 16 degree taper collet, a gap of approximately 0.04 inches is preferred. The collet  22  has a collet small end  23   a  and a collet base  23   b  opposite the collet small end  23   a.    
         [0049]     A pin  17  resides in the housing  12  and intersects a groove  45  (see  FIG. 16B ) in the screw-in retainer  16 . The dead cable end assembly  10  may be preassembled at the manufacturer and the pin  17  inserted to prevent tampering. The groove  45  which the pin  17  fits in is large enough to allow the screw-in retainer  16  to be loosened and relax the collets  22  so to allow the cable  18  may slip through the collets  22 . Once the cable  18  is in place, the screw-in retainer  16  may be tightened to 80 ft-lbs.  
         [0050]     A perspective view of a dead cable end housing  12  according to the present invention is shown in  FIG. 3 , an end view of the dead cable end housing  12  is shown in  FIG. 4A , a side view of the dead cable end housing  12  is shown in  FIG. 4B , and a cross-sectional view of the dead cable end housing  12  taken along line  5 - 5  of  FIG. 4A  is shown in  FIG. 5 . The dead cable end housing  12  includes an attaching feature  26 , a housing interior  32  and inside threads  24  for connecting the screw-in retainer  16  (see  FIG. 2A ). The housing interior  32  is generally cylindrical with a constant inside diameter. The housing  12  is generally cast while the remaining components are machined.  
         [0051]     A perspective view of the collet  22  only is shown in  FIG. 6 , a side view of the collet  22  is shown in  FIG. 7A , an end view of the collet  22  is shown in  FIG. 7B , a cross-sectional view of the collet  22  taken along line  8 - 8  of  FIG. 7A  is shown in  FIG. 8 , and a view of detail  9  of  FIG. 7B  showing a collet gap according to the present invention is shown in  FIG. 9 . The collet  22  has a tapered conical exterior  31 , a collet cable passage  36  with rounded ends  34   a  and  34   b , and a stepped lengthwise collet gap  28 . The rounded ends  34   a  and  34   b  are provided to limit or prevent damage to a portion of the cable  18  residing in the collet cable passage  36  and preferably have an approximately 0.03 inch radius. The collet cable passage  36  preferably has a surface roughness between approximately 32 and approximately 63, and more preferably has a surface roughness of approximately 63.  
         [0052]     The lengthwise collet gap  28  is preferably a stepped gap with a narrow portion  30  having a preferred width W g1  of approximately 0.016 inches for a 0.28 inch diameter cable and the inside edge of the narrow portion  30  has a rounded edge  34   c  to avoid damage to the cable  18 , which rounded edge  34   c  is preferably approximately 0.010 inches. The wider portion may, for example, have a preferred width W g2  of approximately 0.062 inches. The preferred width W g1  of approximately 0.016 inches has been found to be narrow enough to provide good gripping area onto the cable  18  while being wide enough to allow the needed radial deflection of the collet  22  to grip the cable  18 . The width W g1  may further be fine tuned to prevent the crushing of the cable.  
         [0053]     The collet gaps  28  of an in series set of collets  22  are preferably oriented within the housing  12  to prevent the collet gaps  28  of adjacent collets  22  from sharing the same orienting plane. A preferred orientation the collet gaps  28  is at approximately 90 degree, approximately 180 degree, and approximately 270 degree increments.  
         [0054]     In general, the collet taper T c  (see  FIG. 8 ) may be between approximately 1 degree and approximately 30 degrees. This range of tapers is based on the dead cable end assembly  10  applied to a 0.28″ diameter cable. Different cable diameters may also fall within this range. Based on testing, a more preferred range of collet tapers T is between approximately four degrees and approximately 20 degrees. The length L c  of the collet  22  is preferably between approximately 0.75 inches and approximately 1.25 inches. The diameters D c  of the collet  22  is preferably between approximately 0.5 inches and approximately 0.9 inches. The preferred length L c  and diameter D c  of the collet  22  are determined by the diameter and length of the housing interior  32  (see  FIG. 5 ) as well as the taper T of the collet  22 . In general, it is preferred to maximize the collet length L c  for a given housing interior diameter in order to reduce the pressures exerted onto the cable  18 . For example, a collet  22  with a large taper T, for example 30 degrees, will be shorter in length then a collet  22  with a small taper, for example 5 degrees, when the allowable diameter D c  is the same. When the taper T is large, the collet&#39;s resistance to deflection increases substantially and therefore the higher taper collet&#39;s diameters can be reduced in order to minimize the resistance and allow more clamping force on the cable  18 .  
         [0055]     A perspective view of the general collet receptacle  20  according to the present invention is shown in  FIG. 10 , an end view of the collet receptacle  20  is shown in  FIG. 11A , a side view of the collet receptacle  20  is shown in  FIG. 11B , and a cross-sectional view of the collet receptacle  20  taken along line  12 - 12  of  FIG. 11A  is shown in  FIG. 12 . The collet receptacle  20  has a receptacle diameter D r , and a receptacle length L r . The receptacle diameter D r  is selected to allow the collet receptacle  20  to slide easily within the housing interior  32  (see  FIG. 5 ). The receptacle length L r  is selected to approximately match the length L c  of the corresponding collet  22  so that the base  23   b  (see  FIG. 2B ) of the collet  22  always protrudes from the collet receptacle  20  under all loading. Such protrusion of the base  23   b  is approximately the same distance as the recess  21  of the collet small end  23   a  and the relative outside diameter of the conical exterior  31  (see  FIG. 6 ) and the conical cavity  38  (see  FIG. 12 ) must be selected accordingly. The collet receptacle  20  includes a conical cavity  38  for receiving the collet  22 , with the conical cavity  38  including a relief cut  40  provided to prevent contact of the conical cavity  38  with the cable  18  to, for example, prevent possible damage to the cable  18 .  
         [0056]     An end view of the spring  14  according to the present invention is shown in  FIG. 13 , and a cross-sectional view of the spring  14  taken along line  14 - 14  of  FIG. 13  is shown in  FIG. 14 . The spring  14  has a spring inside diameter D s1 (also a diameter of a spring cable passage  15 ) and a spring outside diameter D s2 . The spring outside diameter D s2  is selected to allow the spring  14  to slide easily within the housing interior  32  (see  FIG. 5 ) and the spring inside diameter D s1  is selected to allow the cable  18  to slide easily inside the spring cable passage  15 . A preferred spring  14  is a combination of in-series pairs of spring washers. A preferred spring  14  comprises a relaxed length (before assembly of the dead cable end assembly  10 ) of approximately 0.70 inches and a compressed length (after assembly of the dead cable end assembly  10 ) of approximately 0.624 inches corresponding to an initial load of approximately 2700 pounds without cable tension.  
         [0057]     A perspective view of the screw-in retainer  16  according to the present invention is shown in  FIG. 15 , an end view of a threaded end of the screw-in retainer  16  is shown in  FIG. 16A , a side view of the screw-in retainer  16  is shown in  FIG. 16B , and a cross-sectional view of the screw-in retainer  16  taken along line  17 - 17  of  FIG. 16A  is shown in  FIG. 17 . The screw-in retainer  16  includes outside threads  44  to cooperate with the inside threads  24  of the housing  12  (see  FIG. 5 ), a groove  45  for cooperation with the pin  17  (see  FIG. 2A ), and a retainer cable passage  42  for the cable  18 . The retainer cable passage  42  has a diameter D r2  of a size to allow the cable  18  to slide freely through the retainer passage  42 , and a rounded entrance  43  to reduce or prevent damage to the cable  18 . The retainer  16  includes lands  46  for a tightening tool.  
         [0058]     A side view of a cable end coupler  50  according to the present invention is shown in  FIG. 18  and a cross-sectional view of the cable coupler  50  taken along line  19 - 19  of  FIG. 18 . The arrangement of the spring  14 , collets  22  and collet receptacles  20  in each end of the coupler  50  may be the same as the dead cable end assembly  10 , or of other embodiments of the present invention.  
         [0059]     A perspective view of a second collet  60  according to the present invention is shown in  FIG. 20 , a side view of the second collet  60  is shown in  FIG. 21A , an end view of the second collet  60  is shown in  FIG. 21B , and a cross-sectional view of the second collet  60  taken along line  22 - 22  of  FIG. 21A  is shown in  FIG. 22 .  
         [0060]     A cross-sectional view of a second dead cable end assembly  10   a  according to the present invention is shown in  FIG. 23 . The second dead cable end assembly  10   a  includes two collets  22  and collet receptacles  20 , both having the collet small end facing the screw-in retainer  16 , and second springs  14   a  at the base of each collet  22 .  
         [0061]     A cross-sectional view of a third dead cable end assembly  10   b  according to the present invention is shown in  FIG. 24 . The third dead cable end assembly  10   b  includes five collets  22  and three collets  60 , all of the collet small ends facing the screw-in retainer  16 . The third dead cable end assembly  10   b  may provide advantages because holding force is increased by increased cable tension, but may require more fine tuning to obtain the advantages.  
         [0062]     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.

Technology Category: 5