Abstract:
A process for producing a potting transition which is more nearly planar and which is more repeatable from assembly to assembly. Devices for carrying out the process are also disclosed. A stranded cable comprising a containment jacket is stripped of its containment jacket for a short length to expose the end strands for termination (Obviously, in the case of a cable having no jacket, no stripping is required). The exposed strands are then placed in a barrier device to separate them into a region of exposed strands and a region of guarded strands. Potting compound is then applied to the exposed region. The barrier device prevents the potting compound from penetrating into the guarded region. The result is a distinct transition between a region of strands which have been wetted by the liquid potting compound (“wetted region”) and a region of strands which have not been wetted by the liquid potting compound (“unwetted region”).

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     Pursuant to the provisions of 37 CFR §1.53(c), this application claims the benefit of an earlier-filed provisional application. The provisional application was assigned Ser. No. 60/426,085. It was filed on Nov. 13, 2002. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of rope and cable. More specifically, the invention comprises a method for potting cable terminations, along with devices for carrying out the method. 
     2. Description of the Related Art 
     Devices for mounting a termination on the end of a rope or cable are disclosed in detail in copending U.S. application Ser. No. 60/404,973 to Campbell, which is incorporated herein by reference. Generally, the strands proximate the end of a cable are wetted with a potting compound to affix them to an anchor (The term “anchor” is used to refer generally to any object affixed to a cable in order to transmit a load to or from the cable). 
       FIG. 1  shows a cable  10  ready for the application of a potting process. Those skilled in the art will know that a cable is generally composed of a bundle of smaller strands. Over most of its length, the strands within cable  10  will generally be held in place by a containment jacket  12  (which may be an extruded plastic jacket, a braided strand jacket, or similar encircling sheath). In other cases, no encircling jacket will be present. For these, a tape sheath or other compressing method such as a string wrap must be used to organize the strands for potting. However it is done, a length of strands must be exposed for potting (meaning that they can be infused with potting resin). In the view, these are designated as exposed strands  14 . 
     In order to lock the cable to an anchor, exposed strands  14  must be wetted with a potting compound. This is typically done in one of two ways: (1) An anchor is pulled around the exposed strands to hold them in place while a potting compound is poured into them, or (2) The exposed strands are wetted and then an anchor is pulled over the exposed strands to form them into the proper shape.  FIG. 2  shows a completed termination, with anchor  40  being locked to potted region  22 . 
     However the potting compound is applied, there will be a transition between the unpotted strands and the potted strands. This is referenced as potting transition  20  in the figure. The reader will note that potting transition  20  is irregular. It is difficult for the potting compound to penetrate to the center of the cable. Even though the strands are splayed prior to potting, those strands near the center tend to remain bunched together, inhibiting the penetration of the liquid potting resin (designated as central strand region  16 ). The bunching lessens toward the periphery of the cable and in the vicinity of the end of the cable (designated as end strand region  18 ). Because of this variation in strand density, uneven penetration of the potting compound often results. This fact introduces inconsistency from assembly to assembly, since the location and shape of potting transition  20  varies significantly. When attempting to pre-wet the strands, the center strands also tend to be guarded somewhat by the cable itself. Consistency in the application of the potting compound therefore suffers. 
     Throughout this disclosure, the term “strand” will be used to describe the constituents of synthetic cables, natural-fiber cables, and wire ropes. Although synthetic cables are used for the illustrations, the reader should understand that the methods and devices disclosed are equally applicable to any type of stranded cable. 
     BRIEF SUMMARY OF THE PRESENT INVENTION 
     The present invention comprises a process for producing a potting transition which is more nearly planar and which is more repeatable from assembly to assembly. Devices for carrying out the process are also disclosed. A stranded cable comprising a containment jacket is stripped of its containment jacket for a short length to expose the end strands for termination (Obviously, in the case of a cable having no jacket, no stripping is required). The exposed strands are then placed in a barrier device to separate them into an exposed region and a guarded region. Potting compound is then applied to the exposed region. The barrier device prevents the potting compound from penetrating into the guarded region. The result is a distinct transition between a region of strands which have been wetted by the liquid potting compound (“wetted region”) and a region of strands which have not been wetted by the liquid potting compound (“unwetted region”). 
     Once the application of the potting compound is complete, the stranded cable is removed from the barrier device and an anchor is applied over the wetted region. The potting compound then turns from a liquid to a solid over a period of time. Once the potting compound has turned solid, the wetted region of strands are said to be the “potted region” (meaning a region where the strands are locked within a solid mass of hardened potting compound). The unwetted region—in which the strands remain dry and free—is said to be the “unpotted region.” The result is a more uniform distribution of potting compound and a more nearly planar transition from unpotted region to potted region. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is an isometric view, showing a prior art cable ready for termination. 
         FIG. 2  is an isometric section view, showing a prior art cable termination. 
         FIG. 3  is an isometric section view, showing a potted cable according to the present invention. 
         FIG. 4  is an isometric view, showing the proposed process. 
         FIG. 5  is an isometric view, showing the proposed process. 
         FIG. 6  is an isometric section view, showing the proposed process. 
         FIG. 7  is an isometric section view, showing the proposed process. 
         FIG. 8  is an isometric section view, showing the proposed process. 
         FIG. 9  is an isometric view, showing the application of the proposed process to an intermediate termination. 
         FIG. 10  is an isometric view, showing the application of the proposed process to an intermediate termination. 
         FIG. 11  is an isometric view, showing the application of the proposed process to an intermediate termination. 
         FIG. 12  is an isometric view, showing a conical barrier surface. 
         FIG. 13  is an isometric view, showing a planar barrier surface. 
         FIG. 14  is an isometric view, showing the use of cylindrical clamps. 
         FIG. 14B  is an isometric view, showing the use of eve clamps. 
         FIG. 15  is an isometric view, showing the use of a curved linear barrier. 
         FIG. 16  is an isometric view, showing a clamp designed for strands which have been folded back over the cable. 
         FIG. 17  is an isometric view, showing a collar designed to hold strands which have been folded back over the cable. 
         FIG. 18  is an isometric view, showing a collar designed to hold strands which have been folded back over the cable. 
         FIG. 19  is an isometric view, showing clamps designed for use when wetting a portion of strands exposed in the middle of a cable. 
         FIG. 20  is an isometric view, showing a clamping system incorporating an O-ring and a groove. 
         FIG. 21  is an isometric view, showing a clamping system incorporating a molding cavity. 
         FIG. 22  is an isometric view, showing clamps designed for use when wetting a portion of strands exposed in the middle of a cable. 
     
    
    
     REFERENCE NUMERALS IN THE DRAWINGS 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 10 
                 cable 
               
               
                 12 
                 containment jacket 
               
               
                 14 
                 exposed strands 
               
               
                 16 
                 central strand region 
               
               
                 18 
                 end strand region 
               
               
                 20 
                 potting transition 
               
               
                 22 
                 potted region 
               
               
                 24 
                 splayed strands 
               
               
                 26 
                 upper barrier 
               
               
                 28 
                 lower barrier 
               
               
                 30 
                 barrier edge 
               
               
                 32 
                 exposed region 
               
               
                 34 
                 guarded region 
               
               
                 36 
                 linear barrier 
               
               
                 38 
                 strand slot 
               
               
                 40 
                 anchor 
               
               
                 42 
                 conical barrier surface 
               
               
                 44 
                 flat barrier surface 
               
               
                 46 
                 cylindrical clamp 
               
               
                 48 
                 curve barrier 
               
               
                 50 
                 collar 
               
               
                 52 
                 O-ring 
               
               
                 54 
                 groove 
               
               
                 56 
                 vee clamp 
               
               
                 58 
                 mold cavity 
               
               
                 60 
                 injection port 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 3  shows an idealized potting transition  20  which is more nearly planar, and consistent in its saturation and density. It is also displaced from the end of containment jacket  12  (or compression tape unit or string binding unit in the case of an unjacketed cable). In this particular anchor, potted region  22  only consumes a portion of the region of exposed strands  14 . The potting compound is only applied to the relatively loose strands lying near the cable&#39;s end. The strand spacing in this region is relatively uniform (and dispersed), resulting in a thorough and even penetration of the potting compound. The present invention primarily concerns how to achieve this result. The present invention also provides the opportunity to use thicker potting compounds and processes which can be more easily automated. 
     In  FIG. 4 , a length of strands on one end of a cable has been exposed. This length naturally has a free end and a fixed end which is affixed to the cable itself. The free end can be bent and flexed, while the fixed end is generally held in place by the cable. Cable  10  has been passed upward through upper barrier  26  (which may conventionally be attached to a jig or fixture). The free end of exposed strands  14  have then been splayed by conventional means into the form of splayed strands  24 . The fixed end merges into the cylindrical shape of the cable. Upper barrier  26  and lower barrier  28  are then moved together to clamp over splayed strands  24 .  FIG. 5  shows upper barrier  26  and lower barrier  28  holding splayed strands  24  (Throughout this disclosure, the terms “upper” and “lower” will be understood to refer only to the orientations shown in the views, and not to any limitation on the scope of the invention. The devices shown can obviously be applied in many different orientations). 
       FIG. 6  is a section view showing internal details. The reader will observe that—in this particular embodiment, the two barriers have hollow interiors. The result is that they only contact splayed strands  24  along barrier edges  30 . The two barriers could also be solid—thereby contacting the splayed strands over a plane (although the upper barrier must also have a through-hole to allow the cable itself to pass through). However, the use of an edge contact helps to hold the splayed strands at the point of contact. Splayed strands  24  have thereby been divided into two separate regions—exposed region  32  and guarded region  34 . 
     While held in the position shown, potting compound is applied to exposed region  32 . This can be done by dispensing the compound through a pressurized dispenser, dipping the entire assembly into a vat, painting the compound on manually, spraying the compound, or using other conventional means. However it is applied, the barrier devices prevent the potting compound from seeping into guarded region  34 . The cable is then removed from the barrier devices and an anchor is slid into position over the wetted strands, resulting in the assembly shown in  FIG. 3 . 
     Upper barrier  26  is shown in  FIG. 6  as a solid piece, which requires that the cable be slipped through a hole in its center. This approach may be undesirable on some occasions, since passing the cable through a central hole could fray the exposed strands. To alleviate this concern, the upper barrier can be split into two or more pieces (like a mold), which clamp together over the cable. 
     Barrier devices similar to those disclosed in  FIGS. 4–6  can be configured to carry out the strand wetting process in a variety of ways. Altered versions of the two barriers are shown in  FIG. 7 . The conical shape of the joint between upper barrier  26  and lower barrier  28  clamp the splayed strands into a truncated cone shape (The downward facing and upward facing barrier edges  30  assume the shape of a truncated cone). Such a shape may be advantageous for dipping or other processes. 
     In  FIG. 8 , third versions of upper barrier  26  and lower barrier  28  are shown. These embodiments clamp the splayed strands in an inverted truncated cone shape, which may be advantageous for painting on the potting compound or other processes. 
     The shape of the lower barrier can be improved to facilitate the splaying of the strands.  FIG. 12  shows a lower barrier  28  incorporating a conical barrier surface  42 . When the upper and lower barriers are clamped together, the shape of the conical barrier surface helps to ease the strands into the splayed conical shape. 
     A simple flat surface can also be used for the lower barrier.  FIG. 13  shows a lower barrier incorporating flat barrier surface  44 . 
     An alternative to using barrier edges  30  would be to employ two flat plates with an incorporated O-ring or O-rings to form the seal. A cooperating O-ring in one plate and groove in the other could also be used. The result would be essentially the same, in that the strands would be divided into a guarded and unguarded region. It is also possible to incorporate a dish holding the liquid potting resin into the lower barrier. 
       FIG. 20  shows a clamping system incorporating an O-ring and corresponding groove. Upper barrier  26  has flat barrier surface  44  facing downward. O-ring  52 , which is made of pliable material, is located on this downward facing surface. Lower barrier  28  has a corresponding flat barrier surface  44  facing upward. This surface optionally includes a groove  54  placed to align with O-ring  52 . When the two barriers clamp together, the exposed strands are separated into exposed region  32  and guarded region  34 . A version of lower barrier  28  which omits groove  54  is also possible. In this version, O-ring  52  simply compresses the strands against flat barrier surface  44  on lower barrier  28 . Although the O-ring is shown as having a circular cross section, flat O-rings, square O-rings, or other shapes can be used as well. 
     Those skilled in the art will realize that many types of barrier devices are possible. Radially symmetric devices have been shown, but planar devices are possible as well.  FIG. 9  shows exposed strands being held between two linear barriers  36 . Each linear barrier  36  can optionally have a strand slot  38  positioned to clamp the exposed strands into an approximately planar fan. This action also creates an exposed region  32  and a guarded region  34 . 
     The linear barrier need not be straight.  FIG. 15  shows two curved barriers  48  being clamped over a region of fanned strands. Like the straight version, curved barriers  48  optionally include strand slots  38 . 
     The same type of guarding system can be applied to unfanned strands.  FIG. 14  shows a cable with exposed strands  14  ready for wetting. Two cylindrical clamps  46  are pressed around a portion of the exposed strands (and optionally a portion of the cable jacket, if there is one) to divide the strands into guarded and unguarded regions. 
       FIG. 14B  shows the use of vee clamps  56 . These incorporate “vee” notches which are capable of closing over cables of varying diameter. The two vee clamps  56  are offset (The upper clamp in the view is slightly forward of the lower clamp) so that the vee notches can overlap. Those skilled in the art will realize that the type of vee notches shown can be adapted for use in most of the other clamping devices in this disclosure. 
     Although the devices disclosed are most commonly used in attaching an anchor to an end of a cable, they can also be used for attaching an anchor somewhere in the middle of a cable.  FIG. 10  shows a cable wherein containment jacket  12  has been stripped away in a middle portion to reveal exposed strands. The region of exposed strands is divided from the rest of the cable by a first boundary (The upper boundary in the view) and a second boundary (The lower boundary in the view). Two sets of linear barriers  36  are clamped to the exposed strands in order to create an exposed region  32  and a guarded region  34 . As for the radially symmetric applications, the potting compound is applied to exposed region  32  and an anchor is then potted (i.e., bonded) to these strands. 
       FIG. 11  shows another type of intermediate termination. The strands of cable  10  have been exposed for a longer span and pulled into two opposing loops. These loops are then held in place by a different embodiment of linear barrier  36 . The embodiment shown has two strand slots  38 . The exposed loops (projecting outward) are wetted for potting. Although a jacketed cable is shown in the illustration, the devices would work for an unjacketed cable as well (true for the balance of this disclosure as well). 
       FIG. 19  shows a simpler type of intermediate termination. A portion of the containment jacket is stripped away to reveal exposed strands  14 . The cable is then placed under compression to “upset” the exposed strands into a bulge as shown (This is an optional step, but it does promote strand wetting since it increases the space between the strands). Two sets of cylindrical clamps  46  are then applied to segregate the portion of the strands that will receive the potting compound (the bulged area) from the rest of the cable. 
       FIG. 22  shows another approach to the same problem. After stripping away a portion of the containment jacket, the cable has been compressed to form a bulge in the region of the exposed strands. Upper barrier  26  and lower barrier  28  are then pressed together to clamp over the bulge. Exposed region  32  lies outside (in the radial direction) of the two barriers, while guarded region  34  lies inside the two barriers. Liquid potting compound is then infused through the exposed strands. 
     Other methods of exposing the strands for potting compound infusion may be needed.  FIG. 16  shows a cable with a length of exposed strands  14  on its end (The cable is shown sectioned for visual clarity). The free ends of these strands have been fanned and bent back to form a “collar” around the cable itself. Two cylindrical clamps  46  are placed on either side of the “strand collar” and pressed together to hold the strand collar against the cable. The region of strands above the cylindrical clamps (in the context of the orientation shown in the view) are then within the exposed region and the portion of the strands lying beneath the clamps comprise the guarded region. The exposed region therefore lies between the clamps and the free end of the exposed strands. 
     Other devices can be used to hold the strand collar in place.  FIG. 17  shows another cable with its exposed strands folded backward to form a strand collar. Collar  50 , which has a bore through its center, is then slid upward to the position shown in  FIG. 18  (A chamfer on the upper surface of the collar eases its passage over the strands). The strands exposed above collar  50  in  FIG. 18  then comprise exposed region  32  (the portion lying between collar  50  and the free end of the exposed strands). The potting compound can be applied to these exposed strands using known techniques. 
     In the field of synthetic cables, which typically feature small strands, the potting compounds used would often be liquid polymers which harden over time (reactive resins, air-drying resins, etc.). For wire rope, the potting compounds may also include molten metals. Thermoplastics have also been used as potting compounds. The reader will appreciate that the methods and devices disclosed are not dependent upon the type of potting compound nor the type of cable. Although the illustrations are focused on small-strand cables, the invention is not limited to this application. 
     Those skilled in the art will also realize that the barrier devices could be incorporated into the anchor itself Thus, the barrier might not be removed but rather left to form part of the potted termination. The devices shown could also be adapted to non-round cable shapes (such as square cable). 
     Pressurized injection may optionally be used to achieve complete strand infusion.  FIG. 21  shows a modified version of the upper and lower barriers designed to accomplish pressurized infusion. The upper and lower barriers incorporate barrier edges  30  which are the same as the version shown in  FIG. 6 . However, an annular cavity has been added to both the barriers. When the two barriers are clamped together—as shown—mold cavity  58  is formed around exposed region  32 . Liquid potting compound is then injected under pressure through injection port  60 . Vents are provided to vent the air in the mold cavity, in order to allow the liquid potting compound to fill the cavity and completely infuse the strands. 
     Although the preceding description contains significant detail, it should not be construed as limiting the scope of the invention but rather as providing illustrations of the preferred embodiments of the invention.