Patent Publication Number: US-6664473-B2

Title: Connector assembly for armored cable

Description:
THIS APPLICATION IS A CONTINUATION OF PROVISIONAL APPLICATION No. 60/277,828 FILED Mar. 22, 2001, NOW PENDING. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a connector assembly for armored cable that provides a secure and steady grounding path across the connection for false and other stray voltage. 
     BACKGROUND OF THE INVENTION 
     Providing reliable connections to ground for industrial machinery is vital to the safe and continued operation of that machinery. Should a short circuit or fault condition arise in a piece of industrial machinery, it is all too possible that an operator or maintenance person working on that machine may be injured. In addition, fault conditions in the control system of an industrial machine may cause that machine to malfunction in a way that can cause injury to persons in the vicinity of the machine or can destroy product being processed by that machine. 
     One method of providing a grounding connection to an industrial machine or other type of device involves connecting a wire between the chassis of the machine or device in question and true ground. This connection may be made using a grounding path formed by a conductive rod driven into the soil and preferably into the water table. Another manner in which a grounding connection is provided to an industrial machine is through the cable that provides power or controlling signals to that machine. This may be accomplished by running an extra conductor through the cable that is connected between the chassis of the device in question and true ground or by forming a conductive sheath around the conductors that form the control or power cable itself. 
     An example of this former means for providing a ground is the apiaceous three pronged plug used on common household appliances. An example of the latter means of grounding is given in U.S. Pat. No. 5,631,444 to Rook. Rook&#39;s coupling device comprises an inner hollow support body and a separate ground sleeve that is received thereover. The grounding sleeve is sized to be received over the inner hollow support body in a coaxial relationship thereto. Furthermore, the grounding sleeve is sufficiently large that a wire mesh hose formed around an electrical cable may be received therebetween. The grounding sleeve of the Rook coupling is deformed as by crimping so as lock the wire mesh hose of the cable to the inner hollow support body of the coupling. A spring ring is used to rotatively secure a coupling nut to the inner hollow support body of the coupling. Rook does not disclose the formation of a continuous grounding connection from a coupling through the armor of an armored cable. Nor does Rook address how ground currents are to be reliably passed between the male and female components of coupling. Rather, Rook focuses on providing alternative grounding means in the form of lugs that are formed integral with the grounding sleeve. Independent grounding connections are made between the lugs to form the necessary grounding path. 
     Another shortcoming of the prior art is that heavy conductors of type disclosed in Rook are specifically designed to be assembled in the field by an operator using simple hand tools. While this is useful in that connectors can be assembled where and as needed, forming these connectors by hand results in less than reliable results with respect to the strength and grounding ability of these connectors. Should any of the hand assembly operations be incompletely or incorrectly carried out, the connector may not function as intended and a dangerous fault condition may result. 
     In industrial control and power supply applications, it is important that a coupling be extremely sturdy so as to physically protect the point at which the electric connections are made within the coupling itself. Failure to protect the electrical connection made within the coupling can result in failure of the coupling and can result in harm to the industrial device that is being controlled or to which power is being supplied or to that device&#39;s operator. One way in which this can occur is if the cable is allowed to bend too near the point at which the electrical connections are made within the coupling. Flexing of the cable tensions the conductors within the cable and can cause the electrical connections to fail. Furthermore, pressure or tension applied to the cord adjacent the coupling as where the cord is step on, bumped or run over by an object such as a fork lift may cause the connectors within a cable to pull away from the electrical connections made within the couple. Another problem with electrical supply and control connections is that the couplings used may themselves be damaged through impact or through the gnawing of vermin such as rats. 
     In light of the shortcomings of the prior art, it is an objective of the present invention to provide a coupling suitable for use with armored cable that provides an extremely reliable and durable grounding connection through a coupling connection. Another objective of the present invention is to provide a coupling that has a simple structure and is easy to assemble and that rigidly protects the connectors within a cable through the coupling. It is a further object of the present invention to provide a fully shielded and fully insulated electrical connector that can be inexpensively and quickly manufactured. There is yet another object of the invention to provide a coupling that does not rely on a pin and socket connection to form a ground connection through the armor of a grounded cable. Another objective of the present invention is to provide a coupling that is fully armored throughout so as to be impact resistant, impervious to vermin, and preventative of bending stresses that may cause tension on the conductors within a cable to which the couplings are attached. A final objective of the present invention is to provide a cable that can be rapidly, inexpensively, and reliably produced using dependable machine assembly operations. 
     These and other objectives and advantages of the invention will appear more fully from the following description made in conjunction with the accompanying drawings where like reference characters refer to the same or similar parts throughout the several views. 
     SUMMARY OF THE INVENTION 
     The objects of the present invention are realized in an armored coupling that has an integral ground connection formed therethrough. This coupling is attached to an armored cable comprising a conductor that is disposed within a conductive sheath. 
     A substantially rigid sleeve is sized to receive therein the armored cable. The sheath is secured to the cable by at least one set screw that is threaded through the wall of the sleeve and into the conductive sheath of the cable so as form a conduction path from the conductive sheath of the cable through the set screw and into the sleeve. A contact holder is received within a distal end of the sleeve and is constructed and arranged to receive therein the conductor of the armored cable. A substantially rigid jacket is formed over the sleeve and at least a portion of the cable extending from the sleeve. In order to facilitate a strong bond between the jacket, sleeve, and conductive cable, it is preferred to form at least one relief hole through the sleeve so that the material from which the jacket is made can enter between the sleeve and conductive cable to form a unitary structure. A slip ring is received over the sleeve to be longitudinally slidable on the sleeve between a flange extending from the distal end of the sleeve and a shoulder formed by the jacket. The slip ring is fashioned of an electrically conductive material and accordingly extends the conduction path from the sleeve to a coupling nut that is joined to the slip ring. 
     The armored coupling may be plugged into an outlet or coupling on a machine or may be joined to a mating or complementary coupling. The conductive cable typically comprises a plurality of conductors, though it is envisioned that in high current applications, only a single conductor will pass through the conductive cable. 
     The present invention may alternatively be characterized as a cable coupling having an integral ground connection formed thereacross. Each half of the coupling has a set screw that is threadedly received within a sleeve received over a first cable. The set screw forms an electrical connection between a conductive sheath of the first cable and the sleeve within which the set screw is threadedly received. A slip ring is received and retained around the sleeve and a coupling nut is secured to slip ring by means of a retaining ridge formed within the coupling nut. The retaining ridge of the coupling nut is received in a groove formed around the slip ring. Note that the retaining ridge and the groove are interchangeable vis-à-vis their relative locations on the slip ring and the coupling nut. The coupling nut is constructed and arranged to mate with a complementary coupling nut on a second coupling, e.g. a male-female coupling arrangement or an outlet of an electrically operated machine. The conduction path for grounding the conductor extends from the conductive sheath of the cable, through the set screw to the sleeve received over the cable, from the sleeve to the slip ring received therearound, and from the slip ring to the coupling nut received over the sleeve and slip ring. Preferably each half of the coupling is provided with a rigid jacket that covers at least a portion of the sleeve and the cable that extends therefrom. 
     The present invention also embodies a method of forming an armored cable connector that starts with the step of providing a conductor cable having a conductive sheath and at least one conductor housed within the conductive sheath. A predetermined length of the at least one conductor is then exposed. 
     A substantially rigid conductive sleeve is slipped over the conductor cable and an electrically conductive pathway between the conductive sleeve and the conductive sheath of the conductor cable is created by driving at least one set screw through the conductive sleeve into the conductive sheath. It is preferable to form at least one relief hole through the sleeve prior to its installation. A contact holder is attached to the at least one conductor of the conductor cable for making an electrical connection to a mating conductor cable. Once all of the conductors of the conductor cable have been connected to the contact holder, the plug end of the contact holder is inserted into the distal end of the conductive sleeve. 
     A rigid jacket is molded over at least a portion of the rigid sleeve and the conductor cable to strengthen the coupling and prevent unwanted tension on the conductors of the conductor cable. A slip ring is next emplaced over the rigid sleeve between the rigid jacket and a flange of the rigid sleeve. It must be noted that the slip ring can be placed over the conductor cable prior to slipping the sleeve over the conductor cable and over-molding the jacket in place. 
     Finally, a coupling nut is joined to the slip ring such that the coupling nut can mechanically fix the cable connector to a complementary cable connector while providing a reliable electrical connection from the conductive sheath of the conductor cable, through the at least one set screw to the rigid sleeve, and from the rigid sleeve through the slip ring and to the coupling nut joined to the slip ring. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of an armored cable having respective male and female coupling portions constructed and arranged according to the present invention; 
     FIG. 2 is a partial cutaway view of the female coupling portion taken along cutting lines  2 — 2  of FIG. 1; 
     FIGS. 3-6 illustrate steps in the assembly of a female coupling portion of the present invention. 
     FIG. 7 is a partial cut away view of a pair of male and female coupling portions of the present invention illustrating how the coupling portions fit together. 
    
    
     DETAILED DESCRIPTION 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
     FIG. 1 illustrates a cable  16  having a male coupling portion  12  and a female coupling portion  14  secured to the respective ends of the cable  16 . A male coupling portion  12  and a female coupling portion  14  together comprise a complete connector assembly  10 . FIG. 2 is a partial cutaway view of the female coupling portion  14  that is taken along cutting lines  2 — 2  of FIG.  1 . 
     The connector assembly  10  of the present invention is typically used with a armored cable  16  of the type illustrated in FIG.  2 . The armored cable  16  comprises an inner cable  18  comprising a plurality of conductors  22  housed within a flexible insulating layer  20 . Received over the inner cable  18  is a metal jacket  24  that, while being substantially rigid to lateral forces that would otherwise crush the cable  16 , is sufficiently flexible to allow the cable  16  to be bent or coiled as needed. Over the metal jacket  24  is disposed an outer cable jacket  26  that renders the armored cable  16  water proof and which also provides added protection to abrasion and to corrosive materials that might otherwise come into contact with the metal jacket  24  or inner cable  18  of the armored cable  16 . It is to be noted that armored cable  16  may comprise any suitable number of conductors  22  within the inner cable  18  without exceeding the scope of the present invention. Furthermore, it is anticipated that the present invention may be adapted for used with un-armored cables (not shown). 
     The male and female coupling portions  12 ,  14  have similar structures. The main differences between the two coupling portions being that the male coupling portion  12  in FIG. 1 has a male coupling nut  28 A and the female coupling portion  14  illustrated in FIGS. 1 and 2 has a female coupling nut  28 B. Where a specific coupling nut is referred to, the reference characters  28 A or  28 B will be used. Where coupling nuts in general are referred to, the reference numeral  28  will be used. 
     The respective male and female coupling portions  12 ,  14  typically have male and female versions of a contact holder  30  as illustrated in FIG.  2 . Note that the contact holder  30  described herein is specifically designed for use with multiple conductors  22 . Various types of contact holders  30  may be used without exceeding the scope of the present invention. However, in general, the contact holder  30  will have generally the same shape as is illustrated in the Figures. 
     Referring to FIG. 2, there is illustrated a partial cutaway view of a female coupling portion  14 . As indicated above, male and female coupling portions  14  differ only in the use of male and female coupling nuts  28 A and  28 B and in the use of male and female contact holders  30 , respectively. Therefore, for the sake of simplicity, only a female coupling portion  14  will be described in detail herein. The female coupling portion  14  essentially comprises a sleeve  32  that is received over the armored cable  16 . The sleeve  32  is substantially rigid and electrically conductive. What is more, the sleeve is preferably made of steel, though other conductive materials such as copper and other metals and conductive ceramics, composites or other moldable materials may also be used. 
     A forward end of the sleeve  32  has a flange  34  extending therefrom. Preferably a number of relief holes  36  will be formed through the sleeve  32 . The sleeve  32  is preferably secured over the armored cable  16  by one or more set screws  38  that are threadedly received within a corresponding number of bores  38 A formed through the sleeve  32 . The set screws  38  may have a pointed tip  39  that engages the armor  24  of the armored cable  16  thereby creating a secure and reliable electrical connection between the conductive armor  24  of the armored cable  16  and the electrically conductive sleeve  32 . In addition, the use of pointed set screws  38  lends itself to a higher degree of confidence in the formation of an electrical pathway from the armor  24  of the cable  16  to the sleeve  32 . Another benefit to the use of the set screws  38  with the sleeve  32  is that the armored cable  16  is also securely retained within the sleeve  32 . It is to be understood that set screws  38  may also comprise tips  39  that are flat, rounded, and any other useful shape. 
     The contact holder  30  is preferably fashioned from a non-conductive material such as a molded plastic. The contact holder  30  is constructed and arranged to have disposed therein a plurality of pins (in a male contact holder) or pin contacts (in a female contact holder such as that illustrated in FIG.  2 ). Generally the contact holders  30  have a generic shape that is designed to be inserted into the sleeve  32 . The contact holders  30  will differ greatly in the arrangement of the pins, pin contacts, and other contacts and connectors that are disposed therein depending on the type and nature of the application for which the connector assembly  10  is intended. Because the contact holders are essentially the same with regard to their overall configuration and differ only in the arrangement of the pins, and pin contacts, the reference numeral  60  will be used to refer to all pins and the pin contacts. 
     The contact holder  30  comprises a body having a plug end  40  that is constructed and arranged to be received within the front end of the sleeve  32 . While the plug end  40  of the contact holder  30  may be retained within the sleeve  32  using an adhesive, a crimp, or a set screw, it is preferred to size the plug in  40  of the contact holder  30  so that there exists a press fit between the plug end  40  and the sleeve  32 . Contact holder  30  has a flange  42  extending from the body thereof that limits the insertion of the plug end  40  of the contact holder  30  into the sleeve  32 . The outer diameter of the flange  42  of the contact holder is roughly the same as that of the flange  34  formed on the sleeve  32 . A forward receptacle portion  44  of the contact holder  30  is constructed and arranged to house therein pins or pin contacts  60 , depending on whether the contact holder  30  is a male or female version. Because there exist many different structures for making electrical connections in couplings, a specific structure of the present invention is not to be limited to a contact holder having pins or pin contacts  60  as disclosed herein. 
     Formed over and around a sleeve  32  and a length of the armored cable  16  that extends therefrom is an over-molded jacket  46 . This over-molded jacket  46  is preferably made from a non-conductive plastic material that is substantially rigid when cured. The relief holes  36  formed through the sleeve  32  act to allow the over molding material from which sleeve  46  is fashioned to flow into the interior of the sleeve  32  between the sleeve  32  and the armored cable  16 . In this manner, the cable  16  is securely locked within the sleeve  32 . In addition, because the jacket  46  extends past the end of the sleeve  32 , any bending of the cable  16 , which might otherwise tension the conductors  22  is mitigated or even prevented. The jacket  46  is molded in such a manner that there exists a gap  47  between a forward shoulder  48  of the jacket  46  and the flange  34  of the sleeve  32 . 
     Once the jacket  46  has been emplaced, a slip ring  50  is placed in the gap  47  between the shoulder  48  of the jacket  46  and the flange  34  of the sleeve  32 . The slip ring  50  has a slightly larger inner diameter than the outer diameter of the sleeve  32  and therefore, the slip ring  50  may move freely between the shoulder  48  and the flange  34  within gap  47 . The slip ring  50  also has a gap or slot  52  formed therein so that the ring may be expanded slightly to fit it over the flange  42  of the contact holder  30  and the flange  34  of the sleeve  32 . Alternatively, it is envisioned that that slip ring could be slipped over the cable  16  before sleeve  32  is placed over the cable  16  and them moved into its place adjacent the flange  34  before the jacket  46  is molded around the sleeve  32  and cable  16 . The inner surface of the slip ring  50  is preferably smooth while the outer surface has a groove  54  formed therein. This groove is sized to receive an inwardly extending ridge  56  that is formed within coupling nut  28 . The ridge  56  of coupling nut  28  is the same for the male and female embodiments of the coupling nuts  28 . Note that the location of groove  54  and ridge  56  may be exchanged, i.e. the groove may be formed within the coupling nut  28  and the ridge  56  formed in the outer surface of the slip ring  50 . 
     The retaining ring  50  also has formed therein a forwardly orientated beveled surface  58 . The beveled surface  58  of the slip ring has a generally frustoconical shape and allows the ridge  56  within the coupling nuts  28  to be more easily inserted into the groove  54  formed in a slip ring. It is to be noted that both the slip ring  50  and the coupling nuts  28  must be made from an electrically conductive material, preferably from a metallic material such as steel, copper, brass or the like. 
     FIGS. 3-6 illustrate how one portion of the connector assembly  10  of the present invention is assembled. The first step in assembling a portion of the coupling  10  of the present invention is to expose the conductors  22  within the inner sheath  18  of the armored cable  16 . To do this, a portion of the outer covering  26  of the armored cable and a portion of the armor  24  of the armored cable  16  are cut back from the inner cable  20 . A portion of the inner cable  20  is itself cut back to expose the individual conductors  22 . The relative exposures of the respective cable coverings  26 ,  24 , and  20  is best seen in FIG.  2 . Once an appropriate length of cable  16  has been stripped, the sleeve  32 , having set screws  38  retracted to a first retracted position, is slid onto cable  16  past the exposed conductors  22 . Suitable pins or pin contacts  60  are then attached to the ends of the exposed conductors  22  in a known manner, preferably by crimping or soldering. The pin or pin contacts  60  are then inserted into the appropriate contact holder  30 . The pin or pin contacts  60  are typically retained within the contact holder  30  within respective bores formed therethrough by means of a friction fit or snap fit. Another manner of securing a pin or pin contact  60  within the contact holder  30  is to mold the pin or pin contact  60  into the contact holder  30 . Alternatively, the pins or pin contacts  60  may be retained within the bores formed through the contact holder  30  by means of a non-conductive adhesive. The bores formed through the contact holder  30  are not illustrated herein as the size, arrangement, and number of these bores will be related directly to the number of conductors  22  of the cable  16  that are to be used and to the nature of the application to which the connector assembly of the present invention is adapted. 
     Once the pin or pin contacts  60  are emplaced within the contact holder  30 , sleeve  32  is press fit onto the plug end  40  of the contact holders  30  such that the flanges  34  and  42  of the respective sleeve  32  and contact holder  30  are in contact with one another. FIG.  3 . Note that the length of the inner cable  18  that is stripped must be such that the set screws  38  of the sleeve  32  may contact the armor  24  of the cable  16 . 
     As can be seen in FIG. 4, the next step in assembling the coupling portion is to seat set screws  38  of sleeve  32  into the conductive armor  24  of the armor cable  16 . The set screws  38  are driven to their second, extended position in which the tip  39  of the set screws  38  securely contact the armor  24  of the armored cable  16 . Note that where a set screw  38  having a pointed tip  39  is used, the tip  39  may slightly penetrate the armor  24  of cable  16 . While a pointed set screw  38  may be driven completely through the armor  24  of the cable  16 , it is preferred that any penetration of the tip  39  into the armor  24  be superficial. Care must be taken not to unnecessarily deform the armor  34  of the cable  16 . In this manner, a secure and reliable electrical connection is made from the armor  24  of the armored cable  16  through the set screws  38  into the sleeve  32 . 
     Referring next to FIG. 5, the jacket  46  is over-molded over the sleeve  32  and cable  16  that extends therefrom. In the over-molding process, the molten material from which the jacket  46  is made will be caused to flow through holes  36  formed through sleeve  32 . In this manner, the material of the jacket  46  solidly encases the sleeve  32  and cable  16  so as to firmly lock the cable  16  within the sleeve. As noted above, the jacket  46  also acts to stiffen the juncture between the cable  16  and the coupling portion  12  or  14 , thereby reducing tension on the conductors  22 . 
     Next, the slip ring  50  is inserted over the flanges  34  and  42  of the sleeve  32  and contact holder  30 , respectively. This is done by expanding the inner diameter of the slip ring  50  somewhat to fit over the flanges  34 ,  42 . As indicated above, the slip ring  50  could be placed on the cable  16  behind the sleeve  32  prior to the placement of the sleeve  32  over the cable  16 . 
     Referring next to FIG. 6, a coupling nut  28  is press fit onto the coupling portion such that the small retaining ridge  56  formed on the interior of the coupling nut  28  is received within the groove  54  formed around the slip ring  50 . This results in the structure illustrated in FIG. 2 wherein a female coupling nut  28 B is utilized. 
     FIG. 7 is a partial cutaway view of an entire coupling assembly  10  of the present invention wherein a male coupling portion  12  is connected to a female coupling portion  14 . Specifically, FIG. 7 illustrates how a grounding connection is made through the coupling nuts  28 A and  28 B. The respective slip rings  50  on the male and female coupling portions  12 ,  14  are free to slide longitudinally in gap  47  between the jacket  46  and the flange  34  of the sleeve  32 . The longitudinal travel of the slip rings  50 , and of the coupling nuts  28 , facilitates the mating of the threaded portion  29 A of the male coupling nut  28 A with the threaded portion  29 B of the female coupling nut  28 B. Preferably, the lengths of the respective threaded portions  29 A and  29 B of the male and female coupling nuts  28  are sized such that the threaded portions  29 A and  29 B will not bottom out when the male and female coupling portions  12 ,  14  are connected. Rather, as the male coupling nut  28 A is threaded into the female coupling nut  28 B, the retaining ridges  56  formed within each of the respective coupling nuts  28  bear against the grooves  54  formed around the slip rings  50  of the respective coupling portions. The pressure exerted by the coupling nuts  28  upon the slip rings  50  causes each of the respective slip rings  50  to bear against the flanges  34  of the respective sleeves  32  of each coupling portion. Consequently, a continuous, reliable, and extremely sturdy grounding connection is formed between the respective coupling portions of the coupling  10 . Alternatively, or in addition, the end  62  of the threaded portion  29 A of the male coupling nut  28 A may be arranged to come into contact with the beveled surface  58  of the slip ring  50  of the female coupling portion  14  when the respective coupling portions are connected. However, it is important to arrange the threaded portions  29 A and  29 B of the coupling nuts  28  so that the slip ring  50  will not be forced away from the flange  34  of sleeve  32 . 
     The grounding path through the connector assembly  10  can be traced from the armor  24  of the cable  16 , through the set screws  38  and to the sleeves  32 . From the sleeves  32 , the grounding path continues through the flange  34  of the sleeve  32 , into the slip ring  50 , and thence to the retaining ridge  56  formed within the coupling nuts  28 . The grounding path continues from the retaining ridge  56  of a coupling nut (either male or female)  28  through the threaded portions thereof and into the retaining ridge  56  of the complementary coupling nut. As can be appreciated, the grounding path continues from the retaining ridge  56  of the complementary coupling nut  28 , through the slip ring  50 , sleeve  32 , and set screw  38  to the conductive armor  24  of a second portion of cable  16 . 
     Where either the male or female coupling portion  12 ,  14  of the coupling  10  is constructed and arranged as a receptacle mounted in an industrial machine or other device, the grounding path will function in much the same manner. However, rather than the grounding path moving from a first cable  16  through a connector assembly  10  to a second cable  16  as indicated above, the grounding path may move from a first cable  16  through the coupling  10  to the chassis of the industrial machine or other device in a known manner. 
     The coupling  10  of the present invention, because of its simple design, may easily be manipulated in the field under various conditions, including cold conditions where a user of the connector assembly  10  may be wearing gloves. Furthermore, because of the sturdy nature of grounding path, the coupling  10  may be connected and disconnected repeatedly without failure of the grounding path. 
     The armored coupling  10  of the present convention comprises a coupling structure that has a secured, reliable, and repeatable grounding connection through the coupling itself, while simultaneously providing rigid mechanical protection to the two cables being connected through the coupling  10 . 
     The invention described above may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description and all changes, which come within the meaning and range of equivalency of the claims, are intended to be embraced therein.