Abstract:
A moisture proof, telescoping coupler assembly for electric metal tubes with an enhanced grounding arrangement for electrically grounding the telescoping tube to the coupler body, and a modified arrangement thereof utilizing a snap fitting retaining ring for securing an electric metal tube to the coupler body to provide for unidirectional insertion of an electric metal tube into the open end of a coupler body in a manner that prohibits unintentional separation of the tube and/or retainer ring from the coupler body.

Description:
FIELD OF INVENTION 
   This invention is generally directed to an expansion or telescoping coupler assembly for electrical metal tubes and more specifically to a moisture proof telescoping or expanding coupler assembly with an enhanced electrical grounding arrangement for coupling an electric metal tube that is in relative sliding relationship to a coupler body. 
   BACKGROUND OF THE INVENTION 
   Heretofore, there exists various known types of coupler fittings for attaching an electric metal tube (EMT) to an electrical installation such as an electric box or panel or for joining at least two electrical metal tubes in an end-to-end relationship. Such known coupler assemblies include a coupler body to which the electrical metal tubes are rigidly connected to the coupler body, e.g. as disclosed in U.S. Pat. Nos. 268,686; 3,976,314; 4,073,514; 4,091,523. Other known coupler assemblies include a coupler body wherein at least one connected electrical metal tube is permitted to telescope or slide relative to the coupler body or relative to another electrical metal tube fixedly connected to the coupler body, e.g. as disclosed in U.S. Pat. Nos. 5,141,258 and 6,715,803. 
   With respect to such known sliding or telescoping coupler assemblies, it has been noted that because of the relatively free or sliding relationship between the moveable electrical metal tube relative to the coupler body, the optimal electrical grounding effect therebetween is substantially diminished because of insufficient contact between the complementary surfaces of the movable electrical metal tube and the associated coupler body due to the required tolerance necessary to permit the desired telescoping between the moveable electric tube and the associated coupler body. Thus, the optimum desired amount of the electrical grounding effect therebetween is not achieved. 
   SUMMARY OF INVENTION 
   It is therefore an object of the present invention to provide a coupler assembly that has a coupler body with and inlet end portion arranged for telescopically receiving an electric metal tube in sliding relationship relative thereto and wherein the optimum desired amount of an electrical grounding is achieved. 
   Another object is to provide a telescoping coupler assembly having an arrangement for prohibiting the seepage of moisture into the coupler assembly and the relative telescoping members. 
   Another object is to provide a telescoping coupler assembly having a coupler body for slidably receiving an electric metal tube connected thereto that is positively electrically grounded to the coupler body. 
   Another object is to provide a telescoping coupler assembly for electrical metal tubes which is relatively simple in structure, easy to manufacture, positive in operation, and moisture proof. 
   The foregoing objects and other features and advantages are attained by a telescoping coupler assembly that includes a coupler body for securing an electrical metal tube to an electrical structure such as an electrical box or panel or for connecting at least a pair of electrical metal tubes in end-to-end relationship wherein at least one of the electric metal tubes is rendered movable relative to the other. The coupler body includes a bore extending therethrough to define opposed open ends. One open end of the coupler body may be adapted to be fixedly connected to an electric box, panel, or adapted to receive another electric metal tube. The other open end of the coupler body for receiving an electric metallic tube is sized and shaped to telescopically receive an end portion of the electric metal tube for relative sliding or telescoping movement with respect thereto. The end of the coupler body adapted for securing the coupler body to an electrical box or panel may be formed to accommodate a lock nut or a snap fit adaptor such as disclosed in U.S. Pat. Nos. 6,555,750, 6,737,584, 6,916,688, 6,935,891 or other like patents. Alternatively, each of the opposed ends of the coupler body may be formed to snugly receive electric metal tube wherein one electric metal tube is fixedly secured to the coupler body by means of a fastener, and the other electric metal tube is telescopically mounted relative to the other end of the coupler body, as illustrated herein. 
   Connected adjacent to the end of the coupler body for receiving the telescoping tube is a grounding means that includes a grounding ring which is arranged to be slipped onto and fixedly secured to an end portion of the electrical metal tube telescopically fitted into the corresponding open end of the coupler body. 
   The grounding ring is connected to the coupler body by a wire mesh grounding strap of a predetermined length sufficient to provide for the relative sliding or telescoping movement of the moveable electric metal tube relative to the coupler body. The arrangement is such that the moveable electric metal tube is positively electrically grounded to the coupler body throughout its entire range of movement to provide for optimal electrical grounding between the coupler body and the associated telescoping electric metal tube. 
   Disposed within the bore of the coupler body are sealing rings for rendering the coupler assembly moisture proof without seriously limiting the relative sliding relationship between the telescoping electric metal tube and the associated coupler body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a telescoping coupler assembly for an electric metal tube embodying the present invention. 
       FIG. 2  is a perspective view of the coupler body, absent the moveable electric metal tubes. 
       FIG. 3  is a top view of  FIG. 2 . 
       FIG. 4  is a section view of the coupler body taken along line  4 - 4  on  FIG. 3 . 
       FIG. 5  is a longitudinal sectional view of the coupler assembly of  FIG. 1 . 
       FIG. 6  is a detail perspective view of a modified tube retainer for fixedly securing an electric metal tube to the coupler body. 
       FIG. 7  is a fragmentary sectional view of a modified form of the invention utilizing the modified tube retainer of  FIG. 6  wherein the limiting tang and retainer tang are shown in their operative positions. 
       FIG. 8  is a sectional view similar to  FIG. 7 , wherein the tube retaining tang is shown in the operative position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings there is illustrated in  FIG. 1  a telescoping coupler assembly  10  embodying the invention. As shown, the coupler assembly  10  includes a coupler body  11  comprising an elongated tube or cylinder of a predetermined length defining a bore  13  extending therethrough that is opened at the opposed ends  11 A,  11 B of the coupler body  11 . In the illustrated embodiment of  FIG. 1  the coupler body  11  is configured to connect at least two electric metal tubes  14  and  15  in end-to-end relationship wherein one electric metal tube, e.g. tube  14 , is arranged to be received within the end opening  11 B of the coupler body  11  and fixedly secured thereto by means of suitable fasteners e.g. one or more set screws  16 . The other electric metal tube  15  is adapted to be slidably received within the other open end  11 A of the coupler body  11 . The arrangement is such that tube  15  is rendered slidably or telescopically mounted within the open end  11 A of the coupler body  11  to accommodate any protracting or retracting movement of the electric metal tube  15  relative to the coupler body  11  or the other metallic electric tube  14  fixedly connected to the coupler body  11 . 
   As best seen in  FIG. 4 , the coupler body  11  is provided with a circumscribing inwardly projecting external groove  17  to define an internal stop shoulder  17 A. The shoulder stop  17 A functions to limit the distance that the fixed tube  14  may be inserted into the open end  11 B of the coupler body  11  as noted in  FIG. 5 . As shown in  FIG. 5 , the stop shoulder  17 A is located along the length of the coupler body  11  at a point closer to the end opening  11 B than to end opening  11 A. The arrangement is such that the longer portion A of the coupler body  11  to the right of the stop shoulder  17 A has a length sufficient for the electric metal tube  15  to be telescopically mounted relative thereto so as to be slidably displaced therein as the tube  15  telescopes relative to the coupler body  11  so as to not allow the movable tube  15  to separate from the coupler body  11 . 
   To prohibit any moisture or water from entering into the coupler assembly and the tubes connected thereto, the coupler body is provided with end seals  18 - 18 . As shown at least two such end seals  18 - 18  are provided, one to either side of the stop shoulder  17 A. 
   The seat  18 A for accommodating the respective seals  18 - 18  is defined by a circumscribing internal grove  18 A which is formed in any suitable manner, e.g. by swedging, pressure rolling or molding to deform the material of the coupler body as illustrated in  FIG. 5 . While the illustrated embodiment of  FIG. 5  is described as having one seal  18  on opposite sides of the internal stop  17 A, it will be understood that the number of such seals may be varied as required. 
   As shown in  FIG. 1 , the insertion of electric metal tube  14  into the opened end  11 B of the coupler body  11  is limited by the internal stop  17 A. With the tube  14  properly seated in the open end  11 B of the coupler body  11 , the tube  14  is fixedly secured thereto by means of a suitable fastener, e.g. set screw  16 . 
   The slidable or telescoping tube  15  is inserted into the other open end  11 A of the coupler body  11 . The length A of the coupler body  11  is sufficient to permit tube  15  to be slidably disposed relative thereto without causing the tube  15  to be separated therefrom. In other words, the length A of the coupler body is greater than the maximum permitted linear displacement of the tube  15  within the coupler body  11 . 
   Because tube  15  is slidably disposed within the coupler body  11 , the coupler body is provided with a means for insuring the maximum optimizing of a positive electrical ground between telescoping tube  15  and the coupling body  11 . In the illustrated embodiment, this is attained by a grounding ring  19  which is sized and shaped so as to be snugly fitted onto an end portion of the slidable or telescoping tube  15 . Suitable fasteners such as set screws  20  fixedly secure the grounding ring  19  to the telescoping metal tube  15 . 
   A grounding strap  21  connects the grounding ring  19  to the coupler body  11 . A mounting plate  21 A and  21 B is connected to each end of the grounding strap  21  to provide the means whereby the grounding strap  21  is securely fixed to the grounding ring  21  and coupler body  11  by suitable fasteners, such as bolts or screws  22 - 22 . Preferably the grounding strap portion  21 C connected between the opposed end mounting plates  21 A and  21 B comprises a woven wire mesh strap  21 C that renders the grounding strap  21  flexible for accommodating the telescoping or sliding movement of tube  15  relative to the coupler body. Thus the grounding strap  21  is free to flex or stretch in accordance with the linear or telescoping displacement of the electric metal tube  15  as the tube  15  telescopes or slides relative to the coupler body  11 . In doing so, the grounding effect of the movable tube relative to the coupler body  11  is maximized throughout the entire telescoping range of the coupler assembly. 
   By providing seals  18  between the coupler body  11  and the respective associated electric tubes  14  and  15 , the coupler assembly  10 , described, also prohibits moisture or water from seeping into the coupler assembly  10  and the electrical tubes  14 ,  15  associated therewith. 
   While the embodiments illustrate the coupler body  11  having opposed end openings  11 A,  11 B of substantially equal diameters, it will be understood that the coupler body  11  may have opposed end openings with different sized diameters for connecting electric metal tubes of corresponding different diameters in end-to-end relationship. 
   It will also be noted that the short end B of the connector body  11  may be formed for accommodating a snap fit locking ring (not shown) of the type disclosed in U.S. Pat. Nos. 6,555,750, 6,737,584, 6,860,758, 6,935,891 and 6,916,988 and the like whereby one end of the coupler body  11  may be formed to be snap fitted or secured to an electronic box or panel in the manner described in the foregoing noted U.S. Patents which are incorporated by reference herein in the event it is desirable to couple a telescoping electric metal tube directly to an electric box or panel. 
   With the foregoing described structures it will be noted that the electrical grounding effect between the telescoping electric metal tube  15  and the coupler body  11  is rendered more positive than simply relying merely upon the sliding motion of the telescoping metal tube relative to the coupler body to produce the electrical ground effect, which may be problematic due to a space tolerance required between the sliding tube and the coupler body. 
     FIGS. 6 and 7  are directed to a modified form of the invention. The coupler assembly  10 A is similar to the coupler assembly  10  herein described with the exception that the means for fixedly securing the fixed electric metal tube  25  to the coupler body  26  is achieved by a retainer ring  27  constructed to permit the fixed tube  25  to be snap fitted into one end  26 A of the coupler body  26  that will also resist any unintentional separation of the fixed tube  25  from the coupler body  26  by an unintentionally applied force tending to cause separation of the fixed tube  25  from the coupler body  26 . 
   As illustrated in  FIG. 6 , the retaining ring  27  is preferably formed of spring steel with a circular configuration capable of being inserted into the end opening  26 A of the coupler body  26 . In the illustrated embodiment, the retaining ring  27  has its opposed ends  27 A and  27 B slighted spaced apart to form a split ring. As the material of the retainer ring  27  is formed of spring steel, the described retainer ring  27  has an inherent resiliency which in its relaxed state is provided with an outer diameter that is slightly greater than the internal diameter D of the open end  26 A of the coupler body  26 . 
   Referring to  FIG. 6 , the split ring retainer  27  is provided with a leading edge  27 C, a trailing edge  27 D, and a plane surface  27 E therebetween. Blanked or formed out of the plane surface  27 E are one or more tube retaining tangs,  28 , one or more locking tangs  29 , and one or more limit tangs  30 . As shown in  FIG. 6  the tube retaining tangs  28 , the locking tangs  29  and limit tangs  30  are alternating and circumferentially spaced about the circumference of the retaining ring  27 . 
   The tube retaining tangs  28  are inwardly bent out of the plane surface  27 E and are inclined or angled in the direction of the leading edge  27 A of the retainer ring  27 . The locking tangs  29  are outwardly bent relative to the plane surface  27 E of the retainer ring  27  and are oppositely inclined or angled toward the trailing edge  27 D of the retainer ring  27 . The limit tangs  30  are also blanked or formed out of the plane surface and outwardly bent relative to the plane surface  27 E and are angled or inclined toward the leading edge of the retaining ring  27 . 
   As illustrated in  FIG. 7 , the retainer ring  27  being split may be compressed to permit the retainer ring  27  to be inserted into the open end  26 A of the coupler body  26 . The arrangement is such that with the retainer ring in its compressed state when inserted into the end opening  26 A, will cause the outwardly bent limit tang  30  to engage an internal surface portion of the coupler body upon the removal of the compressing force thereon to limit the distance the retainer ring  27  may be inserted into said end opening  26 A. 
   Upon releasing the compression force acting on the retainer ring  27 , the inherent resiliency of the split retainer ring  27  will cause the diameter of the retainer ring  27  to expand with a sufficient force to fixedly secure the retainer ring  27  within the end opening  26 A whereby the outwardly bent locking tangs  29  will impart an additional “bite” force against the inner surface of the end opening to resist any unintentional pull out force that may be applied on the retainer ring. 
   With the retainer ring  27  frictionally secure within the open end  26 A of the connector body  26 , as above described, the arrangement is such that the electric metal tube  25  can be fixedly secured to the end opening  26 A of the coupler body  26  by simply pushing the end portion of electric tube  25  into the end opening  26 A and through the retainer ring  27  until the end of the tube  25  engages the internal stop  31 . As the end of the electric metal tube  25  passes through the retainer ring  27  the tube retaining tangs  29 , which are inwardly bent as described herein, will inherently exert a holding or biting force on the electric metal tube sufficient to resist an unintentional pulling force imparted onto the electric metal tube  25 . In all other respects, the embodiment disclosed and described with the embodiment of  FIGS. 6 and 7  is similar to the embodiments herein before described with respect to  FIGS. 1 to 5 . 
   The locking tangs  29 , being outwardly bent, are sufficiently resilient so as to flex inwardly permitting the retainer ring to also pass through the end opening  26  of the coupler body  26  and spring outwardly, when ring  27  is fully seated, to bite into the internal surface of the bore of the coupler body to resist or prohibit unintentional separation of the retaining ring  27  from the coupler body in the assembled position. 
   With the retainer ring  27  described, installation of the electric metal tube  25  to the coupler body  26  may also be effected by positioning the retaining ring  27  onto the end of the electric metal tube  25 , and then inserting the electric metal tube with the retainer ring  27  secured thereto into the end opening  26 A of the coupler body  26  until the end of the tube engages the stop shoulder  30  as noted in  FIG. 7 . In this assembled position, as seen in  FIG. 7 , the tube retaining tangs  28 , which are inwardly bent and inclined in the direction of the leading edge  27 C of the retaining ring  27 , are bias to exert a biting force onto the metal tube  26  with a force sufficient to prohibit unintentional separation of the tube  25  therefrom. At the same time the outwardly bent locking tangs  29 , inclined in the direction of the trailing edge  27 D, will exert a biting force onto the internal surface of the bore  32  to resist unintentional withdrawal of the retainer ring  27  and the associated tube  25  from the open end  26 A of the coupler body  26 . 
   While the invention has been described with respect to the described embodiments, other variations and modifications can be made without departing from the spirit or scope of the invention.