Abstract:
A connector for an armored cable including a connector body having an opening extending therethrough and a gland nut telescopically engageable with the connector body. The gland nut has an aperture for receiving the armored cable. The connector further includes a sealing ring positionable within the gland nut and has an inner annular surface engageable with the armored cable for sealing about same on an opposed outer annular surface. The sealing ring includes an annular groove formed about an outer surface thereof, and the groove permits the sealing ring to diametrically contract upon linear compression of the sealing ring. In addition, an isolating device is provided that is positionable about the sealing ring for frictionally isolating the sealing ring from the gland nut and permitting the gland nut to rotate substantially independently of the sealing ring.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a connector for electrical cables and, more particularly, to a connector for attaching armored electrical cables to enclosures. 
     BACKGROUND OF THE INVENTION 
     Armored electrical cables may be used in a wide variety of applications. They are particularly suited for environments in which it is essential for the wiring to be isolated from the surrounding environment. The conventional construction of such cable permits it to be used in environments which are referred to as hazardous locations. Such locations had traditionally been serviced with rigid metal conduit. In recent years, however, when permitted by applicable electrical code, armored cable may be used in place of rigid conduit. Rigid conduit is typically more difficult and more expensive to install than armored cable, therefore, it is desirable to use such cable when permitted. 
     Armored cable typically includes an electrically conductive flexible metal casing which protects the conductors running within from abrasion, impacts and the like. In addition, the metal casing permits the cable to be grounded throughout its length. An outer plastic or rubber sheath typically covers the metal casing thereby adding water proof protection to the cable as well as protecting the metal sheathing from corrosive elements. 
     When armored cables are connected to, or terminated in, metal enclosures, special connectors are typically employed. As is usually required by the applicable electrical code, such connectors provide electrical grounding continuity between the flexible metal casing and the enclosures. In addition, such connectors provide adequate physical retention of the cable and sealing moisture and dust from the enclosure. 
     Existing armored cable connectors are typically bulky in size. Such connectors often have numerous parts making the connector expensive to manufacture and time consuming to install. In addition, cable connectors typically can only accommodate a limited range of cable sizes. This requires a manufacturer to produce a wide variety of connectors in order to have a suitable connector available to accommodate the wide range of commercially available armored cables. Additionally, prior art armored cable connectors typically have two portions, a connector body and gland nut, which are threadedly engaged. As the two portions are threaded together, the armored cable has a tendency to twist. 
     Prior art armored cable connectors typically employ an elastomeric O-ring in order to provide the necessary sealing between the outer diameter of the cable and the connector. Such a design contributes to the two significant problems set forth above. The O-rings typically have an inside diameter substantially similar to the outside diameter of the cable and an outside diameter similar to the inside diameter of the connector piece in which it is disposed. When the connector body and gland nut are threaded together, the O-ring is deformed into forced sealing engagement with the cable. However, since an O-ring may only be slightly diametrically contracted without being damaged, only a narrow range of cable size may be accommodated by a particular connector. Additionally, as the gland nut portion of the connector is rotated onto the body portion of the connector and the O-ring begins to engage the cable, a torque is applied to the cable causing it to rotate. This rotation of the cable may result in its being damaged especially its outer sheathing. 
     Accordingly, there is a need for an armored cable connector which is capable of accommodating a wide range of cable sizes and which does not rotate the cable upon securing the connector components. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a connector for securing armored cable. 
     It is a further object of the present invention to provide a connector having a body portion, gland nut and a sealing ring for sealing about an armored cable. 
     It is still a further object of the present invention to provide a connector having a friction isolation device surrounding the sealing ring for preventing the transmission of torque from the gland nut to the cable when the gland nut is treaded onto the body. 
     It is yet a further object of the invention to provide a connector having a sealing ring with a U-shaped groove annularly extending about an outer surface of the sealing ring. 
     In the efficient attainment of these and other object, the present invention provides a connector for an armored cable including a connector body having a generally longitudinal opening extending therethrough and having a first end, a gland nut telescopically engageable with the first end of the connector body, the gland nut having a first end, the gland nut first end having an aperture for receiving the armored cable. The connector further includes a sealing ring positionable within the gland nut and having an inner annular surface engagable with the armored cable for seating about same on an opposed outer annular surface. The sealing ring has an annular groove formed about an outer surface thereof, and the groove permits the sealing ring to diametrically contract upon linear compression of the sealing ring. In addition an isolating device is provided that is positionable about the sealing ring for frictionally isolating the sealing ring from the gland nut and permitting the gland nut to rotate substantially independently ofthe sealing ring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the able connector of the present invention. 
     FIG. 2 is a cross-sectional view of the connector of FIG. 1 showing the connector in the unsecured position. 
     FIG. 3 is a cross-sectional view of the connector of FIG. 1 showing the connector in the secured position. 
     FIG. 4a is a cross-sectional view showing the sealing ring of the present invention in an uncompressed state. 
     FIG. 4b is a cross-sectional view showing the sealing ring of FIG. 4a in a compressed state. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, armored cable connector  10  of the present invention is shown. Connector  10  includes, a connector body  20 , gland nut  40 , electrically conductive spring  60 , beveled washer  70 , sealing ring  80  and sealing ring isolation assembly  90 . Connector  10  is used to secure an armored cable  100  to an enclosure or other structure  110  and is capable of preventing moisture and other contaminants from entering enclosure  110 , as will be described below. 
     As shown in FIGS. 2 and 3, armored cable  100  is of the type commercially available and includes electrical conductors  108  encased in an internal polymer sheath  106  all of which is covered by a flexible armor casing  104 . In addition, armor casing  104  may be covered by a plastic or rubber sheath  102  which prevents contaminants such as dirt or moisture from entering the cable and protects the armor casing  104  from corrosion. The construction of cable  100  allows it to be used in damp environments and where corrosive gases and elements are present. Such cables are available in a variety of sizes having various numbers and sizes of conductors in order to accommodate a variety of circuit requirements. Connector  10  may also be manufactured in a variety of sizes in order to accommodate the range of cable sizes. Referring again to FIGS. 1 and 2, the connector body  20  is of a generally unitary construction and is made of an electrically conductive material preferably aluminum or zinc plated steel. Body  20  is a generally annular body having an inner bore  30  extending longitudinally through the center of body  20 . A front end  22  includes a substantially planar front surface  24 . External threads  26  are formed about the body adjacent front end  22 . Body  20  further includes a back end  28  which includes external threads  29  formed to cooperate with threads  112  formed on enclosure  110  thereby securing connector  10  to a structure  110  in a moisture and dust tight manner. When body  20  is attached to sheet metal enclosure, a locknut (not shown) can be used to secure the connector. Such structures  110  may include junction boxes, panel boards, motor control enclosures, electrical distribution equipment, and the like. 
     External threads  26  are formed to cooperate with and secure gland nut  40  to body  20 . Gland nut  40  is preferably an annular hollow housing having a side wall  44  extending upwardly from a back wall  46 . The inner surface of gland nut side wall  44  includes threads  48  formed adjacent gland nut front end  50 . Gland nut threads  48  cooperate with external threads  26  formed on connector body  20  thereby allowing gland nut  40  to be securing to the connector body. In addition, gland nut back wall  46  includes an aperture  52  formed therethrough to allow the passage of armored cable  100  into connector  10 . 
     In a preferred embodiment, body  20  and gland nut  40  are formed from generally hexagonal or octagonal stock. Parts are preferably machined in a manner well known to those skilled in the art. Forming of threads  26  and  29 ,  48 , and the desired openings can be done while leaving portions of the hexagonal or octagonal stock intact lower as locations where the connector may be engaged for tightening the connector into the enclosure and/or tightening gland nut  40  onto body  20 . 
     Referring additionally to FIG. 4a, connector  10  further includes an annular sealing ring  80  formed of a deformable elastomeric material such as neoprene or other rubber-like elastomeric material. Sealing ring  80  is sized to fit within gland nut  40  and may be positioned adjacent back wall  46 . Sealing ring  80  includes a side wall  86  extending between two planar end walls  88 . Sealing ring  80  preferably includes, a U-shaped annular groove  82  extending about the outer surface of side wall  86 , as shown in FIGS. 2 and 4a. Sealing ring  80  has an inner diameter surface  84  which is substantially uniform in an uncompressed state and is sized to allow the passage of armored cable  100 . Groove  82  permits the sealing ring&#39;s inner diameter to be radially contracted a significant amount when sealing ring  80  is axially compressed as shown in FIG.  4 b. Upon such axial compression, inner diameter surface  84  deflects radially inward and is brought into physical sealing engagement with armored cable  100  thereby providing a moisture and dust tight seal between cable  100  and connector  10 . Sealing ring  80  is shown in its relaxed uncompressed state in FIG.  4 a. 
     In order to permit for sufficient contraction of the inner diameter of sealing ring  80 , groove  82  preferably has a depth, d, at least ½ the wall thickness, t, when in the uncompressed state. With such a depth, the side wall thickness at the bottom  83  of groove  82  is thin enough to permit a wide range of radial deflection. By permitting such a range of radial deflection, connector  10  is capable of accommodating a relatively wide range of cable sizes as described below. 
     A beveled washer a ring  70  may be placed within gland nut  40  adjacent sealing ring  80 , as shown in FIG.  2 . Beveled washer  70  preferably has an outside diameter equal to or less than the outside diameter of sealing ring  80 . Beveled washer  70  has a generally inward beveled surface  72  on one side and a generally planar surface  74  forming the opposing side surface. Beveled washer  70  is preferably positioned within gland nut  40  such that planar surface  74  is adjacent sealing ring  80 . Planar surface  74  may be brought into formed engagement with sealing ring  80  resulting in the axial compression of sealing ring  80  in a manner which will be described in detail below. 
     As shown in FIGS. 2 and 3, beveled surface  72  forms a seat for spring  60 . Spring  60  is preferably a coil spring which is deformable to form a generally circular structure. Spring  60  is preferably formed of an electrically conductive material and has an operative position such that it is in electrical contact with the armored casing  104  of armored cable  100  and with gland nut  40 , as shown in FIG.  3 . Spring  60  provides electrical continuity for grounding the armored cable through the connector  10 . 
     Referring to FIG. 3, gland nut  40  may be threaded onto connector body  20  so that the length of the connector is telescopically reduced and the various components within gland nut  40  are compressed. More specifically, connector body planar surface  24  engages spring  66  which is then driven into its beveled seat causing the spring&#39;s diameter to constrict thereby bringing spring  60  into electrical and physical contact with cable armor  104 . In addition, upon securement of gland nut  40  onto body  20 , beveled washer  70  is urged against sealing ring  80 . This results in axial compression of sealing ring  80  which in turn causes the inside diameter of sealing ring  80  to diametrically contract. The inside diameter  84  is, therefore, brought into sealing engagement with the armored cable sheath  102  thereby providing a moister tight and dust tight seal. 
     Since groove  82  allows for significant diametrical contraction of sealing ring  80 , a relatively wide range of cable sizes may be properly accommodated and sealed within a particular size connector. For example, a connector of the prior art may require 12 different sizes in order to accommodate a range of cable outer diameters from 0.50 inches to 2.620. In contrast, a connector type formed in accordance with the present invention can properly accommodate such a cable range with only 7 connector sizes. Therefore, a manufacturer needs only produce a relatively small number of connector sizes in order to accommodate the wide range of commercially available cable sizes. In addition, a distributor is not burdened with stocking a wide assortment of connectors. Accordingly, the ability of connector  10  to accommodated a wide range of cable sizes results in considerable savings in manufacturing and distribution. 
     Connector  10  further includes a friction isolation assembly  90 . In prior art connectors when the gland nut is threaded onto the connector body, the gland nut tends to rotate the sealing ring placed within. As the sealing ring is brought into engagement with the cable, the torque generated by the turning of the gland nut is imparted to the cable resulting in cable twisting which is undesirable. The amount of frictional force between the sealing ring and the cable is especially pronounced when the sealing ring is highly compressed. The present invention overcomes such problems by the inclusion of the friction isolation assembly  90  which substantially isolates sealing ring  80  from gland nut  40  thereby reducing any transmission of torque to the cable. 
     Isolation assembly  90  preferably includes a thin walled cylinder  92  which is sized to receive sealing ring  80 . Cylinder  92  has a length preferably equal to or slightly larger than the axial length of sealing ring  80  so that the entire side wall  86  of the sealing ring is covered, as shown in FIG.  2 . Cylinder  92  also preferably has an inside diameter which is slightly larger than beveled washer  70 . Therefore, beveled washer  70  may extend within cylinder  92  to permit axial compression of sealing ring  80 , as described above. 
     Isolation assembly  90  also preferably includes a planar washer  94  which is insertable within gland nut  40  such that it sits between gland nut end wall  46  and the adjacently disposed sealing ring end wall  88 . Accordingly, washer  94  frictionally isolates sealing ring end wall  88  from gland nut back wall  46 . 
     Cylinder  92  and washer  94  are preferably formed of a smooth polymer material such as nylon. The isolation assembly  90  greatly reduces the friction between gland nut  40  and sealing ring  80  by providing a low friction barrier surface which allows gland nut  40  to be rotated substantially independently of sealing ring  80 . Therefore, upon securing gland nut  40  to body  20 , no significant amount of torque will be imparted to sealing ring  80  or cable  100  thereby eliminating cable twisting. 
     In an alternative embodiment (not shown), the sealing ring side wall  86  and end wall  88  may include friction reducing material molded therein. 
     The operation of connector  10  will now be described. In order to attach an armored cable  10  to an enclosure or other structure  110 , connector body  20 , with gland nut  40 , spring  60 , beveled ring washer  70 , sealing ring  80  and isolation assembly  90  all relatively loosely connected thereto, is screwed into an opening in the enclosure using threads  29 . Armored cable  100  is inserted through aperture  52  in gland nut  40  and through bore  30  in connector body  20 . In a preferred embodiment shown in FIG. 3, inner bore  30  includes a large diameter portion  32  and a small diameter portion  34  connected by a beveled cable stop  36 . Large diameter portion  32  extends from front end  22  to cable stop  36  and small diameter portion  34  extends from cable stop  36  to back end  28 . The free end of cable  100  inserted into connector  10  abuts cable stop  36 . Preferably, the end of armor casing  104  will abut cable stop  36 . It will be appreciated that the outer diameter of armor casing  104  will preferably, but not necessarily, be larger than the diameter of small diameter portion  34  of bore  30 . The conductors  108  of cable  100  extend past cable stop  36 , through small diameter portion  34  and exit connector  10  through back end  28 . 
     Once cable  100  is fully inserted, gland nut  40  may be tightened, thereby compressing spring  60 , beveled washer  70  and sealing ring  80  to insure the desired electrical connection and seal. Upon tightening of the gland nut  40 , gland nut back wall  46  urges against one of the sealing ring end walls  88 . The front surface  24  of body  20  urges spring  60  and beveled washer  70  into the other end of sealing ring  80  thereby axially compressing sealing ring  80  causing diametrical contraction thereof. In addition, the compression of spring  60  between connector body front surface  24  and beveled surface  72  of beveled washer  70  pushes spring  60  against cable  100 , which holds cable  100  tightly within connector  10  thereby increasing cable pullout resistance. 
     As the sealing ring  80  is compressed, its side wall  86  and end wall  88  is retained between cylinder  92  and washer  94  respectively. Due to the minimal friction between gland nut  40  and cylinder  92  and washer  94 , no significant amount of torque will be transmitted to cable  100 . Therefore, as sealing ring  80  grips cable  100 , gland nut  40  will rotate independently of cylinder  90  and sealing ring  80 . 
     It will be appreciated that once connector  10  is in place in the enclosure and secured thereto, only gland nut  40  needs to be tightened to provide the necessary compression to achieve the desired electrical connection, dust and water seal and cable pullout resistance. 
     Whereas, particular embodiments of this invention have been described for purposes of illustration, it will be evident to those skilled in the art that numerous variations may be made without departing from the invention as described in the claims.