Snap engagement electrical fitting for EMT

• US 6,670,553 B1
• Filed: 11/01/2002
• Issued: 12/30/2003
• Est. Priority Date: 01/15/1998
• Status: Expired due to Term

• Current Assignee: Arlington Industries Incorporated
• Original Assignee: Arlington Industries Incorporated
• Inventors: Gretz, Thomas J.
• Primary Examiner(s): PATEL, DHIRUBHAI R
• Application Number:
  US10/286,228
• Time in Patent Office: 424 Days
• Field of Search: 174/65.R, 174/65.SS, 174/65.G, 174/135, 174/152.G, 174/153.G, 248/56, 439/439, 439/460, 439/98, 439/92, 16/21, 294/50, 285/194, 285/921, 285/154.1, 285/140.1
• US Class Current: 174/664
• CPC Class Codes: H02G 15/04 Cable-end sealings
• CPC Class Codes: H02G 3/0616 Joints for connecting tubing to casing
• CPC Class Codes: H02G 3/0691 Fixing tubing to casing by auxiliary means co-operating with indentations of the tubing, e.g. with tubing-convolutions
• CPC Class Codes: H02G 3/083 Inlets
• CPC Class Codes: H02G 3/18 providing line outlets
• CPC Class Codes: H02G 3/22 Installations of cables or lines through walls, floors or ceilings, e.g. into buildings

Abstract

A fitting that provides snap-in engagement of EMT to a panel. The fitting includes a hollow, tubular, electrically conductive electrical connector including a fastening arrangement on the leading end to allow snap-in engagement to a panel and a resilient, electrically conductive, cylindrical-shaped split ring within the trailing end to allow snap-in engagement of EMT. A plurality of locking tangs on the split ring are lanced longitudinally and bent inwardly to a smaller diameter than the outer diameter of EMT that the fitting will be used in conjunction with. Arcuate edges included on the leading ends of the locking tangs dig into the outer surface of the EMT thereby holding it fast to the trailing end of connector. The large contact area between the locking tangs and the EMT provide a large amount of surface contact between the locking tangs and the EMT, thereby improving continuity and lowering the millivolt drop. The fastening arrangement on the leading end of the fitting is typically a split ring affixed to the nose of the connector.

Claims

1. A fitting for securing electrical metallic tubing to a panel comprising:

a hollow, tubular, electrically conductive electrical connector including a leading end, a trailing end, a central bore, and a fastening arrangement on said leading end for fastening said connector to an aperture in a panel;

a resilient, electrically conductive, cylindrical-shaped split ring secured within said trailing end, said split ring having a longitudinal axis there through;

a securing arrangement on said trailing end for resisting removal of said split ring from said connector;

a plurality of locking tangs lanced longitudinally from said split ring, said locking tangs bent inwardly from said split ring thereby forming a trailing end cantilevered from said split ring and a free leading end;

said locking tangs bent inwardly to a smaller diameter than the outer diameter of an electrical metallic tube that said fitting will be used in conjunction with; and

arcuate edges on said leading ends of said locking tangs, said arcuate edges capable of digging into said tube.

2. The fitting of claim 1 wherein said arcuate edges on said locking tangs form a circular engagement surface for engaging said tubing.

3. The fitting of claim 2 wherein said split ring includes a total of eight of said locking tangs.

4. The fitting of claim 1 wherein said split ring is formed of spring steel to a thickness of 0.020 inch.

5. The fitting of claim 4 wherein said spring steel is AISI (American Iron and Steel Institute) 1050 CRS (cold rolled steel), annealed #3 edge, hardened to a Rockwell C hardness of between 42 and 44.

6. The fitting of claim 1 wherein said fastening arrangement includes a seat on said leading end and an electrically conductive leading split ring disposed on said seat, said leading split ring including tangs for engaging the walls of said panel.

7. The fitting of claim 6 wherein said fastening arrangement includes panel engagement tangs for engaging said panel and grounding tangs for biasing against the walls of said aperture in said panel for providing good electrical continuity between said panel and said connector.

8. The fitting of claim 1 wherein said securing arrangement includes

one or more securing tangs lanced longitudinally from said split ring and bent outwardly of said split ring, said securing tangs including a leading end cantilevered from said split ring and a free trailing end; and

a complementary number of tang apertures in said trailing end of said connector, whereby compression and insertion of said split ring into said trailing end of said connector enables said securing tangs to engage said tang apertures.

9. The fitting of claim 1 wherein said securing arrangement includes an annular flange at said trailing end of said connector, said annular flange extending into said central bore, said annular flange capturing said split ring and securing it therein when said split ring is compressed and inserted therein.

10. The fitting of claim 1 wherein said locking tangs are formed in pairs, with each of said pairs staggered different distances from the edge of said split ring, and each of said pairs approximately aligning with an opposing pair across said split ring, thereby insuring that said pairs will apply pressure equally to opposing sides of said tube.

11. The fitting of claim 10 wherein said opposing pairs of said locking tangs include opposing arcuate edges that are approximately 0.060 inch less than the outer diameter of said tube.

12. The fitting of claim 1 wherein said split ring includes a leading edge and a trailing edge and a plurality of raised areas pressed inwards of said split ring near said trailing edge, said raised areas providing stabilizers for effectively narrowing the effective inner diameter of said split ring near said trailing edge and thereby stabilizing said tube from excessive movement within said trailing end.

13. The fitting of claim 1 wherein said fastening arrangement includes a threaded nose on said leading end and a threaded lock nut on said threaded nose for engaging the walls of said panel.

14. A method for quickly connecting EMT to an aperture in a panel, comprising:

providing an electrically conductive electrical junction box with an aperture;

providing a conduit;

providing an electrically conductive connector having a leading end for insertion in said aperture, a trailing end for connection to said conduit, and a face limiting the distance said leading end may be inserted in said hole;

providing an electrically conductive snap ring secured to said leading end of said connector with said snap ring having a leading portion and a trailing portion;

providing at least one panel engagement tang on said snap ring that has a relaxed outer dimension greater than the diameter of said aperture;

providing at least one grounding tang integral with and supported at one end from said snap ring and free at its opposite end; and

providing a cylindrical-shaped electrically conductive split ring secured to said trailing end, said split ring including inward extending locking tangs;

inserting said leading end of said electrical connector with said snap ring into said aperture until said crest of said panel engagement tang clears said aperture and said grounding tang draws said face of said electrical connector against said junction box; and

inserting said conduit into said trailing end of said connector containing said split ring until said locking tangs engage the outer periphery of said conduit.