Threaded snap in connector

[0002] The present invention relates to devices for connecting cables and electrical tubing to electrical panels or junction boxes and specifically to a device that is easier to use in a more universal manner than current connectors that are commonly used in the trade.

[0003] It is common in the electrical industry to connect cable and electrical tubing to electrical junction boxes by means of a variety of standard threaded connectors. The exterior threaded portion of the connectors are pushed into a standard access hole in a junction box or electrical panel and held in the hole by a standard lock nut. This standard lock nut has an interior-thread, which is screwed onto the exterior-threaded electrical connector that extends into the junction box. The lock nut typically has one or more individual threads on its interior circumference to create a locking grip against the wall of the junction box. Sometimes the access hole has internal threads into which the connector is threaded. In that case, no lock nut is needed. Lock nuts used in the electrical trade are commonly formed of metal that is 0.130 inches or more in thickness.

[0004] Also, snap fitting connectors are becoming more popular in situations that do not require a threaded lock nut.

[0005] While snap fitting connectors have become important, they are still limited to those installations where a locking nut is not desired or a threaded receiver access hole are not present.

[0006] Therefore, an acceptable and versatile snap fitting connector or snap ring that can also be removed for use with threaded lock nuts or threaded receptacles is very much needed. Efforts have been made in the past to achieve these goals, but the prior efforts are not believed to have been successful.

[0007] This invention provides a snap ring and threaded electrical connector that is much easier to use in a universal and versatile manner than the current connectors used in the trade. The snap ring is stamped from a single thin piece of spring steel or its equivalent. In the stamping procedure, locking tabs are formed to define portions that are bent inward to form locks for mating with apertures located in the leading end of a special connector and portions that form snap locking tangs. The stamped piece of spring steel is formed into a circular or annular shape thereby creating a ring shaped snap ring with snap locking tangs slanted to the rear and outward to snap in an access hole in an electrical junction box to prevent pull out. The snap ring also has inward and forward slanting locking tabs around its outer periphery to lock the locking tabs to an aperture in the forward portion of the electrical fitting. The locking tabs within the snap ring are sized, positioned and shaped to fit into the mating aperture in a manner it cannot be pulled forward or rotated relative to the connector. As used herein, the aperture is defined to include an opening or a locking recess as the aperture can be either open at the bottom or have a thin bottom wall. The thickness of the snap ring and its shape is critical as it must fit into the space between the outside diameter of the threaded portion of the connector with standard threads and the inside diameter of the standard access holes in the electrical junction box or panel. Grounding tangs are also lanced rearwardly and outwardly to provide a grounding contact.

[0008] To apply the snap ring with the threaded connector, the snap ring is placed over the threaded leading end with the locking tabs located in the locking apertures. The assembled connector and snap ring is then ready for use. When used, the installer simply has to insert the assembled connector into the access hole in the junction box until the flange prevents further insertion. During insertion, the snap locking tangs are forced inwardly by the sidewalls of the junction box hole until the tangs are completely through the hole at which time they snap back and prevent withdrawal. This is a single hand job and makes installation efficient and easy, even in difficult positions. The invention permits the use of the special connector of the invention with standard cable and electrical tubing with standard electrical junction boxes having standard holes.

[0009] In the event, it is desired to remove the snap ring, such can readily be done by a screwdriver or other tool or manually to unlock and remove the ring from the remainder of the fitting. This exposes the screw thread for use with a standard lock nut either when there is no thread opening in an electrical box or permits the connector to be threaded into a threaded receptacle.

[0010] Other advantages of the present invention will be better understood from the following description when read in conjunction with the appropriate drawings.

[0011] FIG. 1 is a view of the annular snap ring in place on a connector and mounted in the outer wall of an electrical junction box.

[0012] FIG. 2 is a view of the connector of FIG. 1 with the annular snap ring and junction box wall omitted.

[0013] FIG. 3 is a plan view of the blank used to form the snap ring of the present invention.

[0014] FIG. 4 is an end view of the annular shaped snap ring formed from the blank shown in FIG. 1.

[0015] FIG. 5 is a side view of FIG. 4 with the leading end on the right.

[0016] FIG. 6 is a side view similar to FIG. 5 with the trailing end on the right.

[0017] FIG. 7 is a view similar to FIG. 4 except viewed from the opposite side.

[0018] FIG. 8 is a cross sectional view of the connector of FIG. 2.

[0019] FIG. 9 is a cross sectional view similar to FIG. 8 but rotated ninety degrees.

[0020] FIG. 10 is a view similar to FIG. 9 but showing a lock nut prior to being assembled to lock the connector into position.

[0021] FIGS. 11 to 13 show an alternative preferred embodiment similar to FIGS. 3 to 5.

[0022] The present invention comprises an annular snap ring and threaded electrical connectors for use with standard electrical junction boxes, including electrical panels and the like.

[0023] With reference to FIG. 3, there is shown a plan view of the blank 11 used to form the snap ring.

[0024] The blank is typically stamped from a thin piece of spring steel, such as 1050 spring steel or equivalent, preferably 0.017 to 0.018 inches in thickness but may be 0.013 to 0.022 inches in thickness. The blank 11 has a tongue 12 on one end and a groove 14 on the opposite end. U-shaped openings 30 in the blank 11 define tabs or tangs, which are lanced from the body of the blank. The U-shaped openings have relatively wide slots 32 on each side of the tabs or tangs and a narrow slot or shear line 31 at the bottom of the U-shape. The snap locking tangs 16 are bent outwardly and rearwardly. Locking tab 18 is bent inward and forwardly. Two slits or narrow openings 34 in blank 11 define grounding tangs 36 that are bent outward and rearwardly adjacent the trailing edge 35. The flat front surface of blank 11 shown in FIG. 3 will become the outer circumference 26 when it is formed into the annular shape of the snap ring.

[0025] As shown in FIG. 1, edge 22 is the forward or leading end of the snap ring facing into the interior of a junction box and edge 24 is the rearward or trailing edge facing away from the junction box.

[0026] FIG. 4 depicts an end view of blank 11 after it has been formed in a circle or annular shape. Snap locking tangs 16 are angled outwardly and rearwardly from the face 25 of blank 11. The locking tab 18 is angled inwardly and forwardly from face 25. Grounding tang 36 is angled outwardly and rearwardly.

[0027] When blank 11 is formed into an annular shape, tongue 12 loosely fits into groove 14. The blank formed into an annular snap ring 50 is depicted in FIG. 4. Usually, the spring steel is heat treated after the forming operation so that the steel will have the correct properties and so that it will hold the annular shape. The blank 11 is approximately 0.375 inches wide and 2.750 inches long prior to being formed in the annular shape.

[0028] Snap locking tangs 16 with outer or abutment edges 38 extend and are angled outwardly and rearwardly from the outer circumference 26 of the snap ring 50 and are located preferably at approximately 180 degrees from each other.

[0029] The snap locking tangs form an outermost diameter of 1.00 inches for a ½ trade size connector. Except when specifically indicated otherwise herein, all dimensions are with reference to a ½-inch trade size fitting.

[0030] The locking tabs 18 are located approximately 180 degrees apart and extend inwardly and forwardly from the inner circumference 28 at the approximate angle shown. The locking tabs 18 project typically 0.06 inches inwardly and are each approximately 0.125 inches in width.

[0031] The locking tabs 18 drop into the apertures 20 so that the abutment edge contacts the vertical or forward wall 21 so that the snap ring is prevented from linear movement with respect to the connector in the forward or leading direction. The snap ring is prevented from linear movement in the opposite direction by the forward wall 43 of flange 45. The locking tabs 18 are also prevented from rotating relative to the connector by the side walls 17 of the locking tabs 18 being in contact with the vertical side walls 19 of the apertures 20. Thus, the snap ring is locked onto the connector unless a tool or fingers are used to raise the locking tab 18 out of the aperture.

[0032] FIG. 1 depicts the annular snap ring 50 and connector 40 fastened to an electrical junction box wall 46. To apply the snap ring 50, it is first fastened on the external threaded end 42 of the connector 40. This usually slightly stretches the diameter of the ring.

[0033] The connector 40 has a trailing end 37, which represents the entire range of various electrical connectors that may be used for clamping a cable or conduit. For illustrative purposes, there is shown a body 44 with a threaded screw hole 68 for receiving a clamping screw.

[0034] The abutment edge 64 of locking tabs 18 engage the forward wall 21 (See FIG. 9) of apertures 20 located in the leading end of the connector. The sides 19 (See FIG. 10) of the aperture 20 keep the locking tabs 18 from rotating relative to the connector 40. The aperture is approximately 0.020 inches wide and 0.020 long and may be bottomless or may have a thin bottom.

[0035] As the connector 40 and snap ring 50 is pushed into the access hole or knock-out 48, the locking tangs 16 are forced inward toward the central axis of the annular snap ring. The spring steel material of construction of the snap ring 50 allows the locking tangs to flex inwardly toward the central axis. When the snap ring 50 is advanced sufficiently into the access hole 48, the locking tangs spring outward as their abutment edges 38 pass completely through the electrical junction box wall 46. As a result, the connector 40 is locked tightly into place on each side of the wall 46 between the forward wall 43 of flange 45 of the connector 40 on one side abutted with the outer surface 60 of the junction box wall 46 and the locking tangs 16 abutted with their abutment edges 38 against the inner surface 58 of the junction box wall 46.

[0036] When installed in a junction box, as depicted in FIG. 1, the leading edge 22 of the snap ring is inside the junction box and the outer or trailing edge 24 is within the confines of the access hole 48 and facing flange 44 of the connector. The grounding tangs 36 extend outward approximately 0.020 inches and are forced inward by the inside wall of access hole 48 so that the trailing grounding edge 35 of the grounding tang makes firm contact with the side walls of the access hole 48 of the electrical junction box. The connector is highly resistive to pull out forces when the connector 40 and snap ring 50 are locked in place.

[0037] The outer diameter of the annular snap lock ring in its relaxed or unstretched shape is preferably circular and, as measured from its outer surface 52, is approximately 0.875 inches in diameter for ½-inch nominal trade size threads. The dimensions of the snap lock ring mentioned herein are for use with a threaded connector having ½ inch NPS (National Pipe Straight) or NPT (National Pipe Taper) trade size threads.

[0038] As seen in FIG. 5, the ring is slightly bowed outward with a dividing line 54 for the outward bow approximately 0.145 inches from the right end. The outside diameter of the leading end 56 has an outward diameter of approximately 0.836 inches and the outside diameter of the trailing end 62 is approximately 0.836 inches.

[0039] With reference to FIG. 10, there is shown the connector of this invention with nominal size threads 66, which have been slightly truncated at 67. The threads are of standard pitch and depth but the slight truncation at 67 which is flat or slightly rounded to reduce the normal maximum diameter of the threaded portion. This is typically approximately {fraction (1/32)}″ in width. As used herein a truncated thread is meant to be a nominal trade size thread which has the crest of the thread slightly flattened or rounded to reduce the major diameter. Otherwise, the thread is unchanged and when the snap ring is removed, can be readily threaded into the threaded opening of a junction box or can be used with a standard lock nut 70.

[0040] The nominal knockout or access hole for an electrical junction box is 0.875 inches in diameter. Usually the manufacturer provides an opening 0.870 to 0.880 inches in diameter. However, the access hole can be as small as 0.859 inches in diameter (including tolerances).

[0041] The snap ring could be constructed for other standard trade size threads by scaling these dimensions appropriate to the nominal trade sizes such as for nominal trade sizes ¾ inch or 1 inch.

[0042] With reference to FIGS. 11, 12 and 13, there is showed views similar to FIGS. 3, 4 and 5 and similar numbers are used. The alternative and preferred embodiment is shown in these figures where the snap locking tang 16 and locking tab 18 share a common shear line 72 which defines a narrow separation line. There is also provided a small half-circular cutout 74 at each end of the shear line located adjacent narrow slot 31 and 33, respectively. A singular relatively wide slot 32 is provided adjacent each snap locking tang 16 and locking tab 18 on the opposite side from common shear line 72. Shown on FIG. 12 is the central axis 76 of the snap ring.

[0043] The nominal major diameter of the threads 66 is normally approximately 0.803 to 0.806 inches but in actuality approximately 0.798 to 0.799 inches after this has been reduced by the truncated crest 67. This leaves sufficient space between the major truncated diameter and the minimum diameter of 0.859 inches for the access hole to accommodate the thickness of the wall of the snap ring.

[0044] Thus, the invention defines a versatile threaded snap in connector that is readily utilized by electricians to connect cable and electrical tubing to electrical junction boxes by the easily applied snap in feature; but, at the same time can be utilized to make the connection by lock nut or by threaded access holes. To expose the threads for the threaded connection, it is only necessary to remove the snap ring. Because of this arrangement, the electrician can minimize the inventory and only take one threaded snap in connector for a job.

[0045] Having thus described the invention with reference to preferred embodiment, it is to be understood that the invention is not so limited by the description herein but is defined as follows by the appended claims.