Patent Publication Number: US-2012037419-A1

Title: Cable termination apparatus and related methods

Description:
REFERENCE TO REALTED APPLICATION  
     This application claims priority from U.S. patent application No. 61/162159 filed on 20 Mar. 2009 and entitled 
     TERMINATION APPARATUS FOR HIGH TEMPERATURE HEATING CABLES. For the Purposes of the United States of America, this application claims the benefit under 35 U.S.C. §119 of U.S. application No. 61/162159 filed on 20 Mar. 2009 and entitled TERMINATION APPARATUS FOR HIGH TEMPERATURE HEATING CABLES which is hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD  
     The invention relates to terminating cables. Particular embodiments generally relate to termination apparatus for heating cables. 
     BACKGROUND  
     Heating, power and other types of cables need to be safely terminated in a wide variety of environments. In some situations, cables must be electrically connected to other cables, either of the same type or different types, or connected to other electrical components. Such connections are often made within a protected electrical enclosure. In other situations cables need to be simply terminated without connecting to other cables or other components. 
     Prior art systems for connecting and/or terminating cables include:
         United States Patent Application Publication No. 2010/0035457 to Holliday;   U.S. Pat. No. 7,648,373 to Dixon et al.;   U.S. Pat. No. 6,267,621 to Pitschi et al.;   U.S. Pat. No. 5,789,706 to Perkins;   U.S. Pat. No. 5,518,420 to Pitschi;   U.S. Pat. No. 4,538,053 to Morrow et al.;   U.S. Pat. No. 4,387,267 to Becker;   U.S. Pat. No. 4,022,966 to Gajajiva;   U.S. Pat. No. 4,030,741 to Fidrych;   U.S. Pat. No. 3,567,843 to Collins et al.;   U.S. Pat. No. 3,371,150 to Bachman;   U.S. Pat. No. 3,176,064 to Browne; and,   U.S. Pat. No. 1,345,473 to Benjamin.       

     The inventors have determined a need for improved apparatus and methods for terminating cables. 
     SUMMARY  
     One aspect of the invention provides an apparatus for terminating a cable having a corrugated sheath. The apparatus comprises a body having a terminating portion and a cable receiving portion. The terminating portion has an aperture defined therethrough. The cable receiving portion comprises an extension projecting outwardly in a direction away from the terminating portion. The extension has an extension channel defined in a central portion thereof and one or more locking features protruding into the extension channel near an outward end thereof. The apparatus also comprises a cap configured to be secured to the extension of the body and one or more fasteners for securing the cap to the extension of the body. The cap has a cap channel defined in a central portion thereof and one or more locking features protruding into the cap channel near an outward end thereof. When the cap is secured to the extension the extension channel and the cap channel cooperate to define a compression chamber therebetween. The compression chamber is generally aligned with the aperture through the terminating portion, and the locking features protruding into the extension channel and the cap channel are configured to engage the corrugated sheath of the cable. 
     Another aspect of the invention provides a method of terminating a cable having a corrugated sheath. The method comprises providing a body having a terminating portion and a cable receiving portion, the terminating portion having an aperture defined therethrough, the cable receiving portion comprising an extension projecting outwardly in a direction away from the terminating portion, the extension having an extension channel defined in a central portion thereof and one or more locking features protruding into the extension channel near an outward end thereof, and a cap configured to be secured to the extension of the body, the cap having a cap channel defined in a central portion thereof and one or more locking features protruding into the cap channel near an outward end thereof, coupling the terminating portion to an electrical enclosure, inserting an end of the corrugated sheath through the aperture in the terminating portion and positioning the corrugated sheath in the extension channel such that the one or more locking features of the extension engage a corrugation of the corrugated sheath, and, securing the cap to the extension using one or more fasteners, such that the extension channel and the cap channel cooperate to define a compression chamber around the corrugated sheath, the compression chamber being generally aligned with the aperture through the terminating portion, and such that the one or more locking features of the cap engage a corrugation of the corrugated sheath. 
     Further aspects and details of example embodiments are set out below. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. 
         FIG. 1  shows a termination apparatus according to one embodiment. 
         FIG. 2  is a longitudinal sectional view of the termination apparatus of  FIG. 1 . 
         FIG. 3  shows the cap and the body of the termination apparatus of  FIG. 1 . 
         FIGS. 4A-C  show example fasteners for termination apparatus according to various embodiments. 
         FIGS. 5A-C  show example compression chamber shapes according to various embodiments. 
         FIGS. 6A-6D  and  7 A-C show example locking features according to various embodiments. 
         FIG. 8  shows a termination apparatus according to one embodiment. 
         FIGS. 9A and 9B  are sectional views taken along lines A-A and B-B of  FIG. 8 , respectively. 
         FIG. 10  shows a termination apparatus according to another embodiment. 
     
    
    
     DESCRIPTION  
     Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
     Termination apparatus according to some embodiments comprise a metal body and a metal cap which together form a half shell metal fitting assembly. The half shell metal fitting assembly grips the metal sheath of a heating cable by raised indentations on the inner surfaces of the body and cap (referred to as “locking ridges” below), or by other locking features, and also compresses the interface between the shell and the sheath by the action of the approaching two half shells being tightened. Particular embodiments provide a combination of gripping, compressing and sealing of the oval, corrugated sheath. Particular embodiments also provide a combination of sealing boots and sealants with the half shell assembly applying pressure on them to affect the sealing. Particular embodiments also provide electrical grounding of the sheath. 
     Termination apparatus according to some embodiments provide one or more of the following functions:
         To maintain the environmental integrity of the sheath.   To prevent the entry of water into the core of the heating cable.   To provide strain relief for the heating cable such that any loads that are imposed on the cable as it enters the electrical connection means are spread out and not concentrated such that the sheath of the heating cable cracks, etc.   To provide an electrical ground path from the heating cable metallic sheath to the system electrical ground.   To prevent the entry of explosive gases into either the heating cable or an electrical enclosure where a spark may occur during energizing of the heating cable resulting in explosion.       

     Termination apparatus according to some embodiments comprise a universal fitting with a compression chamber within which an end of a heating cable is terminated and which has a threaded nipple, allowing the termination apparatus to be joined to any number of electrical enclosures, junction boxes, or electrical connectors. In such embodiments, the compression chamber is accessed by a removable cap in the form of a split half collar that allows the metallic sheath of the prepared heating cable, which has annular corrugations, to be positioned and captured by a locking ridge. The locking ridge provides mechanical strain relief thereby preventing the heating cable from being pulled out of the termination apparatus by axial load. In some situations, the end of the heating cable is de-energized prior to being positioned in the termination apparatus, such that the portion of heating cable in and/or near the termination apparatus does not produce heat. In other situations the end of the heating cable may remain energized. 
     Some embodiments provide a termination apparatus uniquely designed to fit onto, as well as provide strain relief and sealing on an oval, corrugated metal sheath of high temperature heater products. For example, some embodiments are particularly suitable for use with CMH heater products such as those described in United States Patent Application Publications No. 2009/0283513, No. 2009/02835134 and No. 2009/02835135, all of which are hereby incorporated herein by reference. 
     Particular embodiments can be used in a range of products designated as CMH. This range includes generally and is not limited to:
         wattages of from 5 to 30 watts/foot of heater   voltages of from 120 to 600 VAC   three sizes of sheath— 5/16″, ⅜″, and ½″ nominal round diameter   corrugations of about 10/inch of heater length       

     In some embodiments, a sealing boot made of silicone rubber, elastomer, polymer or other similar material is designed to fit over the prepared cable. The use of elastomers to terminate a high temperature heater is acceptable here due to characteristics of the CMH heating cable. Due to the design of CMH heating cables, the preparation method of the cable for termination de-energizes the heater proximate to the termination apparatus, resulting in much lower temperatures in the de-energized zone than those temperatures in the operating zone. This dead length of heating cable is a short de-energized length of the entire heating cable being terminated, thereby having the function of a cold lead assembly. This dead length is created in the field through preparation of the stock cable, and not by factory assembly of a separate unit or field installation of a separate component. In some embodiments, the termination apparatus may be used to terminate a lower temperature heater, or another type of cable such as, for example, a cable providing electrical power, or a cable providing electromagnetic signals. 
     Termination apparatus according to some embodiments are designed so that the boot provides a gas tight environmental seal when positioned in the chamber. The tip of the boot penetrates an aperture such as, for example a machined chamber through a threaded nipple that closely matches the oblong dimension of the heater assembly, while the tail of the boot is compressed by the split half collar, thereby sealing the boot at each crest of the annular corrugations in the heating cable. The apparatus can be suitably modified to function with heater sheaths having helical corrugations by designing an angled offset to the locking ridge also. The apparatus is sealed when the removable split half collar is positioned and secured in position using one or more fasteners such as, for example threaded fasteners, thereby applying radial compression on the silicone rubber boot. Use of field applied silicone sealant aids in lubricating the boot during installation, and sealing the completed assembly after the sealant sets. 
       FIGS. 1 to 3  show a termination apparatus  100  according to an example embodiment. Apparatus  100  comprises a body  110  and a cap  120  removably secured thereto by one or more fasteners (not shown in 
       FIGS. 1 to 3 , see  FIGS. 4A-C ). Apparatus  100  may be used for terminating cables such as, for example a heating cable  10  having an annularly corrugated sheath  12 . Within sheath  12 , heating cable  10  comprises a heating element (not shown) and bus wires  14  for providing electrical power to the heating element, as well as other elements such as spacers and one or more insulation layers (not shown). 
     In embodiments wherein grounding of sheath  12  is required, body  110  and cap  120  are made from an electrically conductive material. In some embodiments, body  110  and cap  120  may be made from metallic materials selected to ensure absence of galvanic corrosion due to dissimilar metals. For example, when apparatus  100  is configured for use with a stainless steel sheath  12 , body  110  and cap  120  may be made from nickel-plated brass or stainless steel. Those skilled in the art will recognize that other materials may be used in other situations (for example, aluminum can be used for cables with aluminum sheaths and so on). 
     Body  110  comprises a terminating portion  111  and a cable receiving portion  112 . Terminating portion  111  is configured to be coupled to an electrical enclosure or the like, and has an aperture defined therethrough for allowing cable  10  and boot  130  to pass into the electrical enclosure. The aperture through terminating portion  110  may comprise, for example, a machined aperture which is slightly larger in cross section than sheath  12 , such that an interference fit with boot  130  is created to form a seal. In some embodiments, terminating portion  111  is configured to be coupled to a variety of standard electrical enclosures or boxes, or to other connection apparatus such as, for example and without limitation, those described in PCT Publication No. WO 2009/082815 entitled MULTIPURPOSE CABLE CONNECTOR, which is hereby incorporated by reference herein. If cable  10  does not need to be connected to any other elements, and simply needs to be safely terminated, apparatus  100  may be used to form an end seal by insulating bus wires  14  and screwing a pipe cap onto threaded coupler  113 , such that the pipe cap serves as the electrical enclosure. 
     In the illustrated embodiment, terminating portion  111  comprises a standard threaded coupler  113  such as, for example a NPT thread. Terminating portion  111  may also comprise a hexagonal portion  114  to facilitate tightening of threaded coupler  113  into a suitable receptacle in an electrical enclosure or the like by a wrench or other tool. 
     Cable receiving portion  112  of body  110  comprises an extension  115  projecting outwardly away from terminating portion  111 . As best seen in  FIG. 3 , extension  115  has a channel  116  defined therein. On either side of channel  116 , extension  115  comprises coplanar flat surfaces  117 . Cap  120  likewise has a channel  121  defined therein, with coplanar flat surfaces  122  on either side of channel  121 . When cap  120  is secured to extension  115  of body  110 , flat surfaces  117  and  122  are held flush against each other, and channels  116  and  121  cooperate to define a compression chamber therebetween. The compression chamber is generally aligned with the aperture through terminating portion  111  such that cable  10  may extend through the compression chamber and the aperture. 
     Locking features for engaging sheath  12  of cable  10  are provided in the form of a locking ridge  118  near the outer end of channel  116  and a locking ridge  128  near the outer end channel  121 . In the embodiment of  FIGS. 1 to 3 , locking ridge  118  is integrally formed as part of extension  115  and locking ridge  128  is integrally formed as part of cap  120 , but other types of locking features are also possible, as discussed below. In embodiments wherein grounding of sheath  12  is required, locking ridges  118  and  128  are made from electrically conductive material to provide a ground path through terminating portion  111  of body  110  to an electrical enclosure or the like. 
     A boot  130  is positioned over the end of cable  10 , with bus wires  14  protruding from an opening (or from two separate openings) in the end of boot  130 . Boot  130  is made of a compressible material such as, for example silicone rubber, elastomer, polymer or other similar material. When apparatus  100  is in use, boot  130  is compressed against sheath  12  between body  110  and cap  120 , thereby establishing an environmental seal around cable  10 . Alternatively, in some embodiments, an environmental seal may be established without the use of boot  130  by wrapping tape such as, for example, self-amalgamating rubber tape around the portion of sheath  12  which is to be received in apparatus  100 . 
     When apparatus  100  is installed, bus wires  14  can be connected to appropriate conductors within an electrical enclosure using any acceptable connection method including but not limited to crimp connectors, screw terminals, cage clamps, soldering, Marr™ connectors, or other connectors. 
     In the embodiment of  FIGS. 1 to 3 , extension  115  of body  110  has a plurality of threaded holes  119  extending therethrough, and cap  120  has a plurality of correspondingly located holes  129  extending therethrough, such that cap  120  may be secured to extension  115  using threaded fasteners  140 , as shown in  FIG. 4A . Holes  119  and  129  are located around the periphery of extension  115  and cap  120 , respectively, so as to avoid penetrating the compression chamber, and to evenly distribute clamping forces over flat surfaces  117  and  122 . 
     Other types fasteners could also be used to secure cap  120  to extension  115 . For example,  FIGS. 4B and 4C  show embodiments wherein straps  142  are used to secure cap  120  to extension  115 . Straps  142  may comprise, for example, steel straps, pipe straps, nylon ties, or the like. 
     In the  FIG. 4B  embodiment, straps  142  pass through slots  144  defined through cap  120  and extension  115 . In the  FIG. 4C  embodiment, straps  142  are received in grooves  146  defined in cap  120  and extension  115 . As one skilled in the art will appreciate, other types fasteners could also be used. 
     The shapes and sizes of channels  116  and  121  are selected based on the configuration of the sheath of the cable to be terminated by apparatus  100 . For example, in the embodiment of  FIGS. 1 to 3 , channels  116  and  121  have semi-oval shapes such that they cooperate to form a compression chamber having an oval-shaped cross section, as shown in  FIG. 5A . Channels  116  and  121  are sized such that when cable  10  and boot  130  are therebetween and cap  120  is secured to extension  115 , boot  130  is compressed against sheath of cable. Also, the clamping force exerted on the sheath of the cable is prevented from exceeding some predetermined maximum, since once flat surfaces  117  and  122  contact each other further tightening of the fasteners securing cap  120  to extension  115  is prevented. 
     The channels in cap  120  and extension  115  may also have other shapes and sized. For example,  FIG. 5B  shows semi-circular channels  116 B and  121 B which cooperate to form a compression chamber having a circular cross section.  FIG. 5C  shows channels  116 C and  121 C which cooperate to form a compression chamber having a triangular cross section. 
     The locking features provided in channels  116  and  121  are also selected based on the configuration of the sheath of the cable to be terminated by apparatus  100 . For example, where the sheath has annular corrugations, the locking features may comprise locking ridges  118  and  128  as described above. As shown in  FIG. 6A , locking ridge  128  extends laterally across channel  116 . Locking ridge  118  may be correspondingly positioned. Where the sheath has helical corrugations, an angled locking ridge  128 B may be provided in channel  121  of cap  120 , as shown in  FIG. 6B , and a correspondingly positioned locking ridge (not shown) may be provided in channel  116  of extension  115 . 
     Other types of locking features may also be provided. For example,  FIG. 6C  shows an embodiment wherein a plurality of protrusions  128 C extend into channel  121  of cap  120  to act as the locking features. Similar protrusions  118 C may also extend into channel  116  of extension  115 , as shown in  FIG. 6D , which is an end view. 
     As noted above, locking ridges  118  and  128  may be integrally formed with extension  115  and cap  120 , respectively, as shown in  FIG. 7A .  FIGS. 7B and 7C  show another embodiment wherein the locking features comprise grooves  118 D and  128 D defined in extension  115  and cap  120 , respectively, and a split washer comprising washer portions  118 E and  128 E configured to be received in grooves  118 D and  128 D, respectively. Other variations of the locking features are also possible. For example, an O-ring could be provided instead of a split washer in some embodiments having grooves  118 D and  128 D, wherein the O-ring is positioned over the sheath of the cable before installation. 
     FIGS.  8  and  9 A-B show a termination apparatus  100 A according to another embodiment. Termination apparatus  100 A has a similar construction to that of termination apparatus  100  of  FIGS. 1 to 3 , and as such only differences between apparatus  100 A and apparatus  100  are described herein to avoid repetition. Apparatus  100 A differs from apparatus  100  in that cap  120 A and extension  115 A have compressible portions  132  and  134  along their respective channels and opposed flat surfaces (see  FIG. 9A ), and terminating portion  111 A has a compressible portion  136  lining the inside of the aperture (see  FIG. 9B ). Compressible portions  132 ,  134  and  136  provide an environmental seal against the sheath of a cable without requiring a separate boot. In the embodiment of FIGS.  8  and  9 A-B, body  110 A and cap  120 A may be made, for example from a hard plastic material, and compressible portions  132 ,  134  and  136  may be made from a lower durometer plastic, or from rubber. 
       FIG. 10  shows a termination apparatus  100 B according to another embodiment. Termination apparatus  100 B has a similar construction to that of termination apparatus  100  of  FIGS. 1 to 3 , and as such only differences between apparatus  100 B and apparatus  100  are described herein to avoid repetition. Apparatus  100 B differs from apparatus  100  in that cap  120 B is pivotally coupled to body  110 B by a hinge  148 . Hinge  148  may be formed, for example, by providing interleaved protrusions extending from both cap  120 B and body  110 B with lateral holes therein, through which a hinge pin may be inserted to couple cap  120 B to body  110 B. One or more fasteners (not shown in  FIG. 10 ) may be provided at or near the cable-receiving end of apparatus  100 B for securing cap  120 B against extension  115 B. Suitable fasteners include threaded fasteners, a steel strap, a pipe strap, a nylon tie, or other types of fasteners. 
     Although the description has been described with respect to particular embodiments thereof, these particular embodiments are merely illustrative, and not restrictive. 
     It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. 
     As used in the description herein and throughout the claims that follow, “a”, “an”, and “the” includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
     While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.