Abstract:
A sealing boot for protecting an electrical interconnection includes: a main body having a cavity configured to house an interconnection of two electrical connectors; and a neck merging with one end of the main body and having a cylindrical inner surface that defines a bore that is continuous with the cavity of the main body, the inner surface having an inner diameter that is less than an inner diameter of the cavity of the main body. The inner surface of the neck includes a helical projection comprising a main artery and two tributaries, the tributaries each intersecting a section of the main artery at one end and merging with an end of the main artery at an opposite end.

Description:
RELATED APPLICATION 
       [0001]    The present application claims priority from and the benefit of U.S. Provisional Patent Application No. 62/240,263, filed Oct. 12, 2015, the disclosure of which is hereby incorporated herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a device for environmentally sealing and securing the interconnection between electrical cables. 
       BACKGROUND 
       [0003]    Interconnections between electrical connectors, such as the interconnection between two cables or a cable and a piece of electronic equipment, may be subject to degradation from environmental factors such as moisture, vibration and repeated expansion and contraction from daily temperature changes. Outer sealing enclosures that surround or enclose an electrical interconnection have been used to protect such interconnections. Enclosures often apply rigid clamshell configurations that, once closed, may be difficult to open, especially when installed in exposed or remote locations, such as atop radio towers; gaskets or gel seals may be applied at the enclosure ends and/or along a sealing perimeter of the shell. 
         [0004]    Elastomeric sealing covers for protecting electrical interconnections are also known. Elastic sealing covers can be advantageous because they may be more easily installed over the typically uneven contours of an electrical interconnection. Exemplary configurations are described in U.S. Pat. No. 6,429,373 to Scrimpshire and U.S. patent application Ser. No. 13/646952, filed Oct. 8, 2012; U.S. Ser. No. 13/938,475, filed Jul. 10, 2013; and U.S. Ser. No. 14/245,443, filed Apr. 4, 2015, the disclosures of which are hereby incorporated by reference herein. 
         [0005]    The elastomeric sealing covers discussed above typically have a neck section that seals snugly against the jacket of a cable attached to a connector that resides within the cavity of the cover. Often the neck section has a smooth inner diameter, which provides maximum contact for sealing purposes, but which makes the neck section more difficult to slide relative to the cable jacket during installation. U.S. Pat. No. 7,838,775to Montena (also incorporated herein by reference) proposes a cover that has annular grooves on the inner surface of the neck section to facilitate installation; however, this configuration can make the neck section more susceptible to moisture ingress, particularly if the cable has a corrugated outer conductor, as the presence of the corrugations can form shallow ridges and valleys in the jacket of the cable. As such, it may be desirable to provide a sealing cover having an alternative configuration. 
       SUMMARY 
       [0006]    As a first aspect, embodiments of the invention are directed to a sealing boot for protecting an electrical interconnection, comprising: a main body having a cavity configured to house an interconnection of two electrical connectors; and a neck merging with one end of the main body and having a cylindrical inner surface that defines a bore that is continuous with the cavity of the main body, the inner surface having an inner diameter that is less than an inner diameter of the cavity of the main body. The inner surface of the neck includes a helical feature comprising a main artery and two tributaries. The tributaries each intersect a section of the main artery at one end and merge with an end of the main artery at an opposite end. 
         [0007]    As a second aspect, embodiments of the invention are directed to a sealing boot for protecting an electrical interconnection, comprising: a main body having a cavity configured to house an interconnection of two electrical connectors; and a neck merging with one end of the main body and having a cylindrical inner surface that defines a bore that is continuous with the cavity of the main body, the inner surface having an inner diameter that is less than an inner diameter of the cavity of the main body. The inner surface of the neck includes a helical feature having first and second ends, wherein the first and second ends are spaced from a free end of the neck. 
         [0008]    As a third aspect, embodiments of the invention are directed to an interconnection assembly, comprising: (a) a cable having a helically corrugated outer conductor, the outer conductor defining a helix having a first rotative direction; and (b) a sealing boot. The sealing boot comprises: a main body having a cavity configured to house an interconnection of two electrical connectors; and a neck merging with one end of the main body and having a cylindrical inner surface that defines a bore that is continuous with the cavity of the main body, the inner surface having an inner diameter that is less than an inner diameter of the cavity of the main body. The inner surface of the neck includes a helical feature that defines a helix having a second rotative direction that is opposite the first rotative direction. The inner surface of the neck grips the cable. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]      FIG. 1  is a front view of a cover boot for an electrical interconnection according to embodiments of the invention. 
           [0010]      FIG. 2  is a front section view of the cover boot of  FIG. 1 . 
           [0011]      FIG. 3  is a greatly enlarged view of a neck section of a cover boot and the surface of the jacket of a coaxial cable with a corrugated outer conductor. 
           [0012]      FIG. 4  is a front view of a coaxial cable having an annularly corrugated outer conductor. 
           [0013]      FIG. 5  is a front view of a coaxial cable having a helically corrugated outer conductor. 
           [0014]      FIG. 6  is a front partial section view of a cover boot with annular grooves in the neck section inserted over a helically corrugated coaxial cable as in  FIG. 5 . 
           [0015]      FIGS. 7A and 7B  are front partial section views of a cover boot with helical grooves in the neck section inserted over a helically corrugated coaxial cable as in  FIG. 5 , wherein both the helical grooves of the neck and the corrugations of the coaxial cable follow a “right-handed” helix.  FIG. 7A  shows the grooves and corrugations “in phase”, and  FIG. 7B  shows the groove and corrugations out of phase. 
           [0016]      FIG. 8  is a front partial section view of the neck section of a cover boot according to embodiments of the invention inserted over a helically corrugated cable as in  FIG. 5 . 
           [0017]      FIGS. 9A and 9B  are schematic diagrams illustrating the cylindrical coordinate system used in  FIGS. 10 and 11 . 
           [0018]      FIG. 10  is a layflat view of a groove pattern for the neck section of a cover boot according to embodiments of the invention. 
           [0019]      FIG. 11  is a layflat view of a groove pattern for the neck section of a cover boot according to alternative embodiments of the invention. 
           [0020]      FIGS. 12A and 12B  are greatly enlarged front section views of exemplary features (grooves and projections) that may be employed in the patterns shown in  FIGS. 10 and 11 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The present invention is described with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments that are pictured and described herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It will also be appreciated that the embodiments disclosed herein can be combined in any way and/or combination to provide many additional embodiments. 
         [0022]    Unless otherwise defined, all technical and scientific terms that are used in this disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this disclosure, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when an element (e.g., a device, circuit, etc.) is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
         [0023]    Referring now to the figures, a cover boot for an interconnection of coaxial connectors, designated broadly at  10 , is illustrated in  FIGS. 1 and 2 . The boot  10  includes a generally cylindrical main section  12  that is tapered on one end. A generally cylindrical cable neck  14  is somewhat smaller in diameter than the main section  12  and extends from the tapered end of the main section  12 . The opposite end of the main section  12  merges with a collar  16  that extends radially inwardly. The resulting structure is hollow and defines a continuous bore  18  that passes through each of the substantially coaxial sections  12 ,  14 ,  16 . Annular ribs  20  are formed on the outer surface of the boot  10  to enhance an installer&#39;s grip. 
         [0024]    The boot  10  may be formed of any number of materials, but is typically formed of an elastomeric material, such as rubber, that can recover to its original shape after significant deformation. The boot  10  is typically formed as a unitary member, and in particular may be formed via injection molding. 
         [0025]    As discussed above, when a coaxial cable has a corrugated outer conductor, the overlying jacket may have shallow ridges and valleys formed by the crests and roots of the corrugations. This structure can be seen in  FIG. 3 , in which a cable  50  has a jacket  52  with projecting ridges  54  and recessed valleys  56  formed by the corrugations of the underlying outer conductor. The outer conductor of a coaxial cable may have annular or helical corrugations: cable  100  of  FIG. 4  has annular corrugations that create annular ridges  104  and valleys  106 , whereas cable  200  shown in  FIG. 5  has an outer conductor with helical corrugations that create helical ridges  204  and valleys  206  in the jacket  202 . 
         [0026]    When annular grooves and projections are included in the portion of a sealing boot (such as the neck  14  discussed above) that seals a cable in order to ease sliding of the boot along the cable jacket, the interaction of the helical ridges  204  and valleys  206  in the jacket  202  and the projections and grooves of the boot can create voids between the inner surface of the neck  14  and the jacket  202 . As can be seen in  FIG. 6 , a seal (denoted “B”) is formed wherever a projection  304  of a boot  300  crosses a ridge  204 , as such contact compresses the projection  304  and provides a seal. However, voids (denoted “A”) are formed wherever a projection  304  (or a groove  306 ) spans a valley  206  between two ridges  204 . The voids A can create a path through which moisture can seep into the interconnection within the boot  300 . 
         [0027]    Such voids “A” can be even more pronounced when, as shown in  FIGS. 7A and 7B , the protections  404  and grooves  406  in the inner surface of the neck  414  of a boot  400  are helical in the same direction as the helix of the cable  200  (e.g., both the cable and the grooves/projections in the boot have a right-handed thread). There should be no voids A when the projections  404  and recesses  406  of the boot  400  and the ridges  204  and the valleys  206  of the cable  200  are “in phase” ( FIG. 7A ), but significant voids A are present when the projections/grooves  404 / 406  and the ridges/valleys  204 / 206  are out of phase, which can easily occur when the boot  400  is slipped onto the cable  200 . Moreover, voids A created by an out of phase cable helix/projection interface are also helical and can create a spiral pathway for moisture to reach the interconnection protected by the boot  400 . 
         [0028]    A solution to the void problem is offered by the boot  500  shown in  FIG. 8 , which has a projection  504  that is routed in the opposite direction of the helix of the cable  200  (e.g., the cable  200  has a right-handed helix and the projection  504  follows a left-handed helix). As can be seen in  FIG. 8 , an oppositely-directed helical projection  504  cannot be positioned to be out of phase with the helix of the cable  200 . Thus, many high compression areas B between the projection  504  and the cable  200  can be generated, as can high compression areas B between the ridges  204  of the cable  200  and the recesses  506  of the boot  500 . Moreover, these high compression areas B intersect one another, with the result that potential spiral leak paths are blocked as long as the helix of the projection  504  does not extend for the entire length of the neck  514  of the boot  500 . 
         [0029]    Referring now to  FIGS. 9A, 9B and 10 , an exemplary pattern for a projection  604  for a boot  600  is shown therein. By way of explanation,  FIGS. 9A and 9B  establish a cylindrical coordinate system for the neck  614  of the boot  600 , with axial length along the neck  614  being denoted “c-j” and angular position on the neck  614  denoted “1-12” in the manner of a clock face.  FIG. 10  illustrates the inner surface of the neck  614  in “layflat” form as it would be unfurled or unwrapped so that it can be shown in two dimensions. As can be seen in  FIG. 10 , the projection  604  includes a helical main artery  622  that is routed  360  degrees about the inner surface of the neck  614  as it traverses axially from “e” to “h”. In the illustrated embodiment, the main artery  622  has a “left-handed” helix angle based on the assumption that a cable that the boot  600  would seal would have a right-handed helix. At each end, the main artery  622  meets a respective tributary  624 ,  626 . The tributary  624  extends between the “h” end of the artery  622  toward an intermediate portion of the artery  622  relatively near the “e” end of the artery  622  (i.e., near position “9f”), and the tributary  626  extends between the “e” end of the artery  622  toward an intermediate portion of the artery  622  near the “h” end of the artery  622  (near position “3g”). Thus, the resulting projection  604  describes, in three-dimensions, a ring with a diamond-shaped “loop” over approximately half of the diameter of the ring. The helix angle α of the main artery  622  may vary, but typically would be between about 5 and 30 degrees. 
         [0030]    Referring now to  FIG. 11 , another projection  720  for a boot  700  is shown therein in layflat form. The projection  720  comprises a single continuous left-handed helix that extends for approximately 480 degrees along the inner surface of the neck  714  between the “e” and “h” positions. The helix angle α of the projection  720  may vary, but may typically be between about 5 and 30 degrees. The ends of the projection  720  terminate well short of the end of the neck  714 . 
         [0031]    Both of the projections  620 ,  720  can facilitate the installation of the boots  600 ,  700  onto a cable by reducing the friction between the inner surface of the neck  614 ,  714  of the boot and the cable jacket. However, the projections  620 ,  720  can also prevent moisture from seeping into the interconnection residing in the boot because, as oppositely-directed helices, they seal voids in helically corrugated cables as described above. 
         [0032]    Those of skill in this art will appreciate that, although relatively narrow projections  620 ,  720  are shown herein separated by wider recesses (see  FIG. 12A ), the inner surface can also be constructed such that the projections are relatively wider and are separated by relatively narrower recesses/grooves (see  FIG. 12B ), or the projections/recesses may be of similar width. Thus, either of the features of the inner surface of the neck (i.e., projections or recesses) may follow the paths of the projections discussed above. 
         [0033]    The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.