Abstract:
An electrical fitting having a gripping device with a plurality of gripping tabs forming a helix or spiral. The electrical fitting permits electrical metallic tubing or EMT to be quickly attached to and removed from the electrical fitting without disassembling the fitting or cutting the tubing. A body with a locking end having a plurality of griping tabs receives an end of the tubing pushed into the fitting. The gripping tabs securely hold the tubing preventing loosening or removal. The helix or spiral formation of the griping tabs permits easy removal of the tubing by rotating the tubing counter-clockwise.

Description:
FIELD OF THE INVENTION 
     The present invention relates in general to an electrical fitting, and more particularly to a push fitting, connector, or coupler for attaching electrical metallic tubing or EMT that is easily removable without disassembly of the fitting. 
     BACKGROUND OF THE INVENTION 
     There are many electrical fittings and connectors that are used in construction. Pipes or tubing have been used to contain conductors or electrical wires. The pipes or tubing containing electrical wires are connected to electrical boxes through electrical fittings, such as connectors or couplers. Often electrical metallic tubing is used, much like pipe, to act as a conduit through which electrical wires or conductors are run. Due to the large number of connections typically made with electrical wires in construction, there is a need for an easy to use fitting, connector, or coupler for connecting tubing to an electrical box or coupling two tubes together. Accordingly there are many devices that are used to connect or couple tubing, with each connector or coupler having some particular advantage. 
     One such connector is disclosed in U.S. Pat. No. 3,312,483 entitled “Pipe Connector” and issuing to Ledbetter et al on Apr. 4, 1960. Therein disclosed is a pipe connector using a ring provided with a series of radially and axially extending slits which define a plurality of tabs. The tabs swing inwardly, thus biting into the plastic pipe. 
     Another pipe fitting is disclosed in U.S. Pat. No. 4,073,514 entitled “Combination Pipe Fitting and Retainer Ring” issuing to Pate on Feb. 14, 1978. Therein disclosed is a retainer ring having tabs. The retainer ring is held into the fitting by a groove or recess and an anchor tab. 
     Another fitting is disclosed in U.S. Pat. No. 6,670,553 entitled “Snap Engagement Electrical Fitting for EMT” issuing to Gretz on Dec. 30, 2003. Therein disclosed is a fitting that provides a snap-in engagement with electrical metallic tubing. A plurality of locking tangs are lanced longitudinally and bent inwardly. Arcuate edges on the leading ends of the locking tangs dig into the outer surface of the electrical metallic tubing thereby holding it fast to the trailing end of the connector. 
     Yet another fitting is disclosed in U.S. Pat. No. 6,913,298 entitled “Mechanical Pipe Coupling Derived from a Standard Fitting”, and issuing to Snyder, Sr. et al on Jul. 5, 2005. Therein disclosed is a retainer having a plurality of radial teeth angularly oriented to engage a pipe and prevent its removal from the coupling. 
     While all of these fittings or connectors have performed well in permitting the inserting of a pipe or tubing that is relatively securely held, they have not permitted easy removal of the pipe or tubing should it be desired to uncouple the pipe or tubing. Generally, once these connectors have been assembled, if a change or modification is required, the pipe or tubing cannot be removed without cutting the tubing or disassembling the fitting. This is often a time consuming and difficult process which makes any subsequent modification of the configuration of the pipe or tubing difficult. 
     Therefore, there is the need for a simple, easy to use electrical fitting, connector, or coupler in which electrical metallic tubing may be simply pushed into the connector or coupler with the electrical metallic tubing being securely held and yet that permits easily removable of the electrical metallic tubing from the fitting, connector, or coupler when desired. 
     SUMMARY OF THE INVENTION 
     The present invention permits easy assembly of electrical metallic tubing used for running wire or conductors for making electrical connections that can be assembled by simply pushing the electrical metallic tubing into the fitting, connector, or coupler and yet that is easily removable without disassembling the fitting, connector, or coupler. The present invention is an electrical fitting comprising a connector body having a gripping device securely held therein. The gripping device has a plurality of gripping tabs that are arranged along a helix or spiral. The gripping tabs are of equal lengths and are equally spaced along a circle and originate from a ramp. The gripping tabs are positioned along the ramp at a different position relative to the longitudinal axis of the connector body of the fitting, connector, or coupler. The gripping tabs flex away from an opening in the fitting permitting the electrical matallic tubing to be pushed into the fitting through the opening. The angled gripping tabs prevent the electrical metallic tubing from being pulled away from the fitting. However, the helical or spiral positioning of the gripping tabs permits the electrical matallic tubing to be removed by simply twisting or turning the electrical metallic tubing. A contact rib is placed within the connector body to contact the electrical metallic tubing which improves continuity. 
     Accordingly it is an object of the present invention to provide an easy to use fitting or connector for use with electrical metallic tubing that can securely hold the electrical metallic tubing and yet be readily removable without disassembling the fitting or cutting the electrical metallic tubing. 
     It is another object of the present invention to provide good electrical continuity and to provide a relatively low voltage drop across the electrical fitting, connector, or coupler. 
     It is an advantage of the present invention that the electrical metallic tubing may be simply pushed into the electrical fitting, connector, or coupler. 
     It is another advantage of the present invention that the electrical metallic tubing is securely held and yet is easily removed from the electrical fitting, connector or coupler when desired. 
     It is yet another advantage of the present invention that the electrical metallic tubing fits tightly into the connector body despite variances in the outside diameter of the electrical metallic tubing. 
     It is a feature of the present invention that gripping tabs are formed along a helix or spiral. 
     It is another feature of the present invention that rounded corners are utilized on the highest and lowest gripping tabs. 
     It is yet another feature of the present invention that a contact rib is used, improving continuity between the electrical metallic tubing and the electrical fitting. 
     These and other objects, advantages, and features will become more readily apparent in view of the following, more detailed, description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating an embodiment of the present invention. 
         FIG. 2  is a perspective view illustrating an embodiment of the present invention with an electrical metallic tube placed therein. 
         FIG. 3  is a cross-section of an embodiment of the present invention. 
         FIG. 4A  is a front elevational view of a gripping or locking device utilized in the present invention. 
         FIG. 4B  is a side elevational view illustration the gripping or locking device utilized in the present invention. 
         FIG. 4C  is a perspective view illustrating the gripping or locking device utilized in the present invention. 
         FIG. 4D  is a perspective view taken at a different angle illustrating the gripping or locking device utilized in the present invention. 
         FIG. 5  illustrates a coupling embodiment of the present invention for connecting two tubes together. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an embodiment of the present invention assembled. The electrical metallic tubing connector  10  has a generally cylindrical body  12  having a flange  14  thereon. Adjacent the flange  14  is a threaded end  16 . The body  12  may be made of a zinc alloy. The gripping or locking end  18  contains a gripping or locking device  20 . A washer  22  is held within the electrical metallic tubing connector  10  by crimped lip  24 . Pressed within the crimped lip  24  are a plurality of dimples  26  that provide pressure to prevent the washer  24  and the gripping or locking device  20  from rotating relative to the body  12  of the electrical metallic tubing connector  10 . The washer  22  has a cylindrical aperture or opening  23  therein. The diameter of the cylindrical aperture or opening  23  should be substantially the same as that of the outside diameter of the electrical metallic tubing intended to be connected. The washer  22  provides a point of support for the electrical metallic tubing. 
       FIG. 2  illustrates the electrical metallic tubing connector  10  having the electrical metallic tubing  30  inserted therein. Locknut  28  is threaded on to the threaded end  16 . The threaded end  16  is typically placed within an aperture of an electrical box, not shown, with the sides of the electrical box securely held between the locknut  28  and the flange  14 . 
       FIG. 3  is a cross section more clearly illustrating the construction of the electrical metallic tubing connector  10  of the present invention. The body  12  has a body bore  32  with a first diameter. The threaded end  16  has a threaded end bore  34  with a second diameter. Between the body bore  32  and the threaded end bore  34  is an intermediate shoulder stop  36 . Adjacent the intermediate shoulder stop  36  is at least one contact rib  38 . The contact rib  38  extends radially into the body bore  32 , effectively reducing the diameter of the body bore  32  within the body  12 . The contact rib  38  extends radially into the body  12  by an increasing radial dimension while progressing axially or longitudinally relative to the body  12 . Preferably, there are three contact ribs equally spaced one hundred and twenty degrees apart within the body bore  32 . Adjacent the body  12  is conical portion  40 . Near the large open end of the conical portion  40  is a shoulder  42 . The shoulder  42  is adapted to receive a flat rim  44  of the gripping or locking device  20 . Attached to the flat rim  44  is a tapered angled portion  46  which is attached to a flat ramp  48  on which the gripping tabs  50  are placed. One end of the flat ramp  48  is displaced approximately two degrees (2°) from the plane of the flat rim  44 . Accordingly, the flat ramp  48  has a slope or pitch of approximately two degrees (2°). The gripping tabs  50  are equally spaced and have an equal length but are displaced axially relative to the longitudinal axis of the body  12  thereby forming a helix or spiral. The equal length of the plurality of gripping tabs  50  helps to uniformly hold the electrical metallic tubing. The gripping tabs  50  flex slightly and are angled inward away from the circular aperture or opening  23 . 
       FIGS. 4A-D  illustrate different views of the gripping or locking device  20 , more clearly illustrating the positioning of the plurality of gripping tabs  50 . The gripping tabs  50  are positioned or placed in a helix or spiral and are equally spaced around the inside perimeter of the gripping or locking device  20 . Accordingly, there is a high end gripping tab  52  and a low end gripping tab  54  that are axially displaced and separated by edge  58 . The high end gripping tab  52  and the low end gripping tab  54  have rounded corners  56  that are adjacent or facing each other. The rounded corners  56  may by shaped or have a metal cutting edge so as to cut or tap metal. As seen in  FIG. 4B  the flat ramp  48  is displaced by angle  60  form the flat rim  44 . Angle  60  is preferably two degrees. Therefore, the helix or spiral has a pitch of approximately two degrees. The gripping or locking device  20  is preferably made of a spring metal and may be made of stainless steel, and is harder than the material of the electrical metallic tubing. 
       FIG. 5  illustrates another embodiment of the present invention and is a coupling utilized to connect two sections of electrical metallic tubing or EMT together. The electrical metallic tubing coupler  110  has a body  112  adapted to receive a respective end of two sections of electrical metallic tubing  30 . The ends of the electrical metallic tubing  30  are positioned adjacent intermediate stop  136 . Adjacent intermediate stop  136  are contact ribs  138 . Preferably, there are three contact ribs  138  equally spaced one hundred and twenty degrees apart within the bore of the body  112 . Placed within each end of the electrical metallic tubing coupler are gripping or locking devices  120  and washers  122 . The construction of each end of the electrical metallic tubing coupler is the same as that described for the electrical metallic tubing connector  10  illustrated in  FIGS. 1-4D . 
     The operation and advantages of the present invention can readily be appreciated by referring to  FIGS. 1-4D . The electrical metallic tubing connector or fitting may be pre-assembled and easily attached, in a conventional way, to an electrical box opening by inserting the threaded end  16  into an electrical box opening, not shown, and tightening locknut  28 . An electrical metallic tubing  30  may then be pushed into the circular aperture  23  so that the gripping tabs  50  of the gripping or locking device  20  flex slightly inward, permitting the electrical metallic tubing to move forward, or inward, contacting the contact rib  38  and the intermediate shoulder stop  36 . The contact rib  38  permits improved electrical contact or continuity between the electrical metallic tubing  30  and the body  12  of the electrical fitting or connector  10 , thus reducing a voltage drop across the electrical fitting or connector  10 . Additionally the contact rib  38  assures that the outer diameter of the electrical metallic tubing  30  is snugly held within the body bore  32  and adjacent the intermediate shoulder stop  36  and provides a point of contact assuring no movement or wobble of the electrical metallic tubing  30  within the body  12 . The circular aperture  23  in washer  22  provides another point of contact for the electrical metallic tubing  30  that is spaced from the contact with the contact rib  38 . These multiple, separated contact points assure that the electrical metallic tubing  30  does not wobble within the electrical metallic tubing connector or fitting  10 . Additionally, the gripping tabs  50  prevent the electrical metallic tubing  30  from being pulled from or withdrawn from the body  12  simply by pulling longitudinally on the electrical metallic tubing  30 . Therefore, the electrical metallic tubing  30  is securely held within the electrical metallic tubing fitting or connector  10  and provides a secure connection simply by pushing in the electrical metallic tubing  30  through the circular aperture  23 . Therefore, the present invention provides a secure electrical fitting for dry locations, as there are no seals for weatherproofing. 
     Should it be necessary to disassemble or remove the electrical metallic tubing  30  from the electrical metallic tubing fitting or connector  10 , this can easily be done without having to cut the electrical metallic tubing  30  or disassemble the electrical metallic tubing fitting or connector  10 . Due to the gripping tabs  50  being positioned in a helical or spiral position, the electrical metallic tubing  30  can easily be removed simply by rotating the electrical metallic tubing  30 , preferably counter-clockwise, causing it to follow the helical or spiral pattern of the gripping tabs, thereby forcing the electrical metallic tubing  30  to be backed out of the electrical metallic tubing fitting or connector  10 . The gripping or locking device  20  is prevented from rotating by the dimples  26  placed in the crimped lip  24  and resulting pressure exerted on the washer  22  and the shoulder  42  of the gripping or locking device  20 . The rounded corners  56  formed on the high and low end gripping tabs  52  and  54  may have a metal cutting edge and aid in cutting or tapping in to the electrical metallic tubing  30 , essentially cutting or tapping threads so that the electrical metallic tubing  30  may be reversed out of the electrical metallic tubing fitting or connector  10  upon the electrical metallic tubing being rotated counter-clockwise. Therefore, the electrical metallic tubing  30  can be easily removed from the fitting or connector  10  without disassembling the fitting or connector  10 . The electrical metallic tubing coupler  110  illustrated in  FIG. 5  functions in an analogues way. 
     Therefore, the present invention provides a pre-assembled electrical fitting, connector, or coupler that is easily installed on an electrical box and permits an electrical metallic tubing or EMT to be securely connected to the electrical fitting without assembly or tools simply by pushing the end of the EMT into the fitting. The present invention therefore saves considerable time in not requiring time consuming assembly of the electrical fitting for each of the numerous electrical connections often required in construction. Yet should a change or different connection be required or desired the electrical metallic tubing can be easily removed from the fitting without cutting the EMT or disassembling the electrical fitting. This saves considerable time in, and therefore reduces the cost of construction advancing the electrical fitting arts. 
     While the present invention has been described with respect to several different embodiments, it will be obvious that various modifications may be made without departing from the spirit and scope of this invention.