US 3651245 A
An electrical receptacle or the like is grounded directly and positively by means of a screw extending through axially shortenable spacer means positioned between the metallic frame of the receptacle and a portion of the metallic junction box on which it is mounted. The junction box is also provided with a cover member having a tubular portion whose length can be reduced as required in order to provide a plane that is substantially flush with the finished wall surface.
Claims available in
Description (OCR text may contain errors)
United States Patent Moll [ 1 Mar. 21, 1972  JUNCTION BOX AND GROUNDING MEANS THEREFOR  Inventor: Oswin C. Moll, 1640 Chippendale Circle,
Bethlehem, Pa. 18017  Filed: Dec. 22, 1969 211 Appl. No.: 887,077
 US. Cl ..l74/5l, 174/53, 174/57, 174/66, 220/32, 220/37, 339/14 R  Int. Cl. ..H05k 5/02  Field of Search ..l74/51, 53-57, 174/58, 208; 220/32, 3.7; 339/13, 14
 References Cited UNITED STATES PATENTS 1,688,518 10/1928 Bennett ...174/57 UX l,767,339 6/1930 Beerhalter 174/57 Primary Examiner-Darrell L. Clay Attorney-Leonard H. King 57] ABSTRACT An electrical receptacle or the like is grounded directly and positively by means of a screw extending through axially shortenable spacer means positioned between the metallic frame of the receptacle and a portion of the metallic junction box on which it is mounted. The junction box is also provided with a cover member having a tubular portion whose length can be reduced as required in order to provide a plane that is substantially flush with the finished wall surface.
The aforementioned abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.
9 Claims, 6 Drawing Figures PLANE F or FINISHED mu;
FINISHED WA 11 PATENTEDMARZ] I972 3,651,245
(1021014 ART) FINISHED WALL FINISHED WALL INVENTOR. 05W! C. MOLL ATTORNEY FIGZ JUNCTION BOX AND GROUNDING MEANS THEREFOR This invention relates generally to outlet or junction boxes such as used in commercial or residential buildings and more particularly to improved means for grounding the receptacle associated with thejunction box.
BACKGROUND OF THE INVENTION The National Electrical Code at present requires that a ground conductor be connected directly between the junction box and the metallic frame or yoke of the receptacle or other such device mounted therein. A grounding connection must then be made to the external wiring. A second conductor may be utilized for the latter function.
It has been found from experience that the prior art practice outlined very briefly above is excessively time consuming. It is, at best, an awkward procedure that is frequently executed poorly. Unfortunately, improper or incomplete workmanship is not readily detected visually and when it is an extensive and costly rework of a finished wall is frequently required. In addition, the prior art construction presents the possibility a bare portion of the grounding conductor coming into contact with live conductor terminals, either during installation or thereafter.
The patent literature available in this art shows an apparent recognition of the basic problem. However, the solutions provided by the prior art to the problem at hand fall short. For example, in US. Pat. No. 2,378,861, issued to L. H. Pewey on June 18, 1945, special hollow screws are provided for securing a tubular body to inwardly turned, tapped lips of an outlet box. Conventional screws are then used to mount an electrical fixture, such as a receptacle, on the special screws. It should be particularly noted that intermediate members namely the special hollow screws and the tubular member are used as part of the grounding circuit so that the grounding path is not direct. Corrosion, improper fitting and the like will all contribute to a reduction of the grounding effectiveness of the prior art because of the indirect construction.
By way of contrast, the present invention provides means for mounting the yoke of a receptacle or the like directly on a junction box to thereby form a direct or continuous ground path. If desired, a conductor is used in the conventional manner to provide a ground path-between the junction box and the external wiring secured thereto. It will be appreciated from the following discussion that the present invention simplifies assembly and installation time. A dual grounding circuit is provided between the grounding lug of the yoke of the device and the junction box. The grounding paths are protected from corrosion by wet plaster, for example, since they are entirely within the cover member which is not part of the grounding path. An installation made in accordance with the teachings of this invention may be easily viewed for inspection purposes. In addition the present invention eliminates any possibility of accidental contact between a bare grounding wire and a live terminal of the receptacle or the like.
The present invention, in its broadest aspect, provides tubular metallic spacer means intermediate the junction box mounting lugs and the mounting lugs of an electrical device such as a receptacle, a switch or the like. The tubular spacer means as well as the screws therein provide the dual grounding path between the metal yoke of the electrical device and the junction box. The wall thickness of the tubular spacer means is circumferentially reduced in a plurality of places along the length thereof in order to provide means for adjusting the position of the electrical device relative to the junction box this structure thereby assures that the electrical device can be mounted flush with the room side surface of a finished wall regardless of the depth of the junction box.
Another novel aspect of the present invention is the provision of a junction box cover member having a tubular extension whose length can be varied to suit the depth of junction box relative to the finished wall surface. In contrast to the prior art wherein similar tubular members serve as the ground path as well as the support means for the receptacle, the present invention provides a non-conductive tubular member than can readily be shortened with electricians pliers but which does not serve either any support or grounding function. The length of the prior art tubular member is shortened at the inside end since the outer end carries the-receptacle mounting tab. No such tabs are needed with the present invention so that the tubular member can be shortened, as required, from the room side in order to make it flush with the finished wall surface.
Accordingly, it is a primary object of this invention to provide improved grounding means for an electrical device such as a receptacle, a switch or the like that is mounted in a junction box.
Another object of this invention is to provide the improved grounding means as described above, wherein a screw provides the grounding path directly between the grounding lug of the receptacle and junction box.
A further object of this invention is to provide a dual grounding path between the grounding lug of the receptacle and the junction box by means of tubular metallic spacer means extending therebetween and through which metallic screws pass.
A particular object of this invention is to provide spacer means between the yoke of the receptacle and a mounting lug on the junction box, the spacer means including means for facilitating the shortening thereof as required for flush mounting of the receptacle.
An advantage of this invention is that the spacer means described above serve as an alternate grounding path between the receptacle yoke and the junction box.
A feature of this invention is the provision of a junction box cover having a shortenable, tubular extension thereon that does not support the electrical device.
These andother objects features and advantages of the invention will, in part, be seen with particularity, and will, in part, become obvious from the following more detailed description of the inyention, taken in conjunction with the accompanying drawing which forms an integral part thereof.
DESCRIPTION OF THE DRAWING In the various figures of the drawing like reference characters designate the like parts.
In the drawings:
FIG. 1 is a perspective view, partially broken away, illustrating a receptacle grounded to the junction box in accordance with the teachings of the prior art;
FIG. 2 is a perspective view, partially broken away and similar in orientation to FIG. 1 but illustrating a receptacle grounded to a junction box in accordance with the teachings of the present invention;
FIG. 3 is an exploded, perspective view, partially broken away illustrating an alternative embodiment of this invention, the basic concept thereof being applied to a junction box adapted to accommodate either one or two, side-by-side electrical devices such as a receptacle and a switch;
FIG. 4 is a fragmentary, sectional view illustrating, in elevation, an alternative embodiment of a cover member that may be used with the present invention;
FIG. 5 is a fragmentary, sectional view illustrating, in elevation, another alternative embodiment for a cover member that may be used with the present invention; and
FIG. 6 is a fragmentary sectional view illustrating, in elevation, still another alternative embodiment of a cover member that may be used with the present invention.
In order to be clearly distinguished from the present invention the prior art is illustrated in FIG. 1. There is shown a junction box 10 one wall of which serves as a terminal for the external wiring 12. A cover member 14 having a tubular extension 16 is suitably secured to the junction box 10 by any conventional fastener means. lnwardly turned lips 18 at'the room side end of the tubular extension provide means for supporting an electrical device, for example a receptacle 20.
To comply with Article 250 (grounding) of the National Electrical Code grounding conductor 22 is secured by a screw 24 to the metallic yoke 26 of the receptacle 20. The other end of the grounding conductor 22 is secured to the base wall of the junction box by means of a screw 28. Under the code it is optional to use another grounding conductor 30 extending between the screw 28 and the external wiring 12.
As explained above and as is evident from FIG. 1, the assembly procedure for the prior art is unnecessarily time consuming. The awkwardness involved in making the connection frequently results in poor and even in incomplete installation that is very difficult to detect. Furthermore when a faulty ground connection is discovered by an inspector after a wall is finished the correction of the error is extremely expensive.
The present invention, as illustrated by one embodiment in FIG. 2 overcomes the shortcomings of the prior art. A function box 32 is provided with conventional means for securing the end of external wiring 34 thereto. A pair of the tabs 36 and 38 are bent inwardly from the room-side end of opposed junction box walls 40 and 42, respectively. The tabs 36 and 38 may be tapped or conventional captive type sheet metal nuts (not shown) may be clipped thereon in the usual manner. A pair of tubular, metallic spacers 44 and 46 are placed on the tabs 36 and 38, respectively, to support a receptacle 48 having a conventional metallic yoke 49 with clearance holes therein. Screws 50 and 52 that pass through the clearance holes in the yoke 49 and the spacers 44 and 46, respectively, are threadably engaged in the tapped holes of the tabs 36 and 38 respectively and thereby secure the receptacle 48 to the junction box 32. v
It will be appreciated that the grounding conductor used with the prior art structure is not required by the present invention since the screws 50 and 52 contact the metallic yoke of the receptacle 48 and the junction box 32. Thus a direct grounding path is provided that can readily be inspected. As will be explained hereinafter the grounding path is substantially enclosed by a cover member and therefore is not subjected to corrosion that may otherwise result from contact with moisture laden plaster.
At this time it should be noted that the spacers 44 and 46 are provided with a plurality of axially spaced, circumferential cuts 54 and 56," respectively, that substantially weaken the wall. This construction permits the onsite selection of the length of the spacers 44 and 46 that will provide for mounting of the receptacle 48 flush with the plane F ofthe finished wall (FIG. 2) A pair of electricians pliers may be used to snap off the unwanted length of the spacers 44 and 46. It should now be appreciated that dual grounding paths are provided by the tubular, metallic spacers 44, 46 and the screws 50, 52, all of which extend between and are in direct contact with the metallic yoke of the receptacle 48 and the junction box 32.
FIG. 2 may also be used to illustrate another feature of this invention. A non-conductive cover member 58 having a tubular extension 60 is secured to appropriately located tabs (not shown) on the open or room-side end of the junction box 32 by any conventional means. Unlike the prior art, the cover member 58 is not part of the grounding path and does not support the receptacle 48. Accordingly, it need not be conductive and may be fabricated from non-flammable plastics such as high impact polystyrene or polycarbonate or phenylformaldehyde. Preferably the extension 60 is molded with a plurality of axially spaced, peripheral grooves 62 that facilitate adjusting the length of the extension 60 so as to be flush with the plane F of the finished wall. An electricians pliers may be used to snap off the unwanted portion 64 shown in phantom outline in FIG. 2.
Although not illustrated a conventional cover plate may be secured by a screw to the receptacle 48 in the usual manner using the tapped hole provided for this purpose.
FIG. 3 illustrates one alternative embodiment of this invention wherein either one or two electrical devices may be mounted. Since the basic concept is the same as that described in connection with the embodiment shown in FIG. 2, the advantage of this structure will not be repeated. However, for.
.the sake of clarity, the grounding of both a receptacle 66 and a switch 68 to a junction box 70 will be discussed.
Three pairs of tabs 72, 74, 76, 78 and 80, 82 are bent inwardly from the open, room-side end of the junction box 70. Tubular, metallic spacers 84, 86 are positioned over the tabs 72 and 74, respectively, in order to receive screws 88 and 90, respectively, and thereby secure the metallic yoke of the receptacle 66 to the junction box 70. The same procedure is applied to spacers 92 and 94 and screws 96 and 98 with respect to the tabs 76 and 78, respectively, and the switch 68. The spacers 84 and 86, 92 and 94 have axially spaced, circumferential lines of weakness for the same purpose as described in connection with the embodiment of FIG. 2. Similarly, and for the same purpose, a cover member-100 having a grooved tubular extension 102 is also provided.
When only one electrical device is to be mounted in the junction box 70, then the tabs 80 and 82 are utilized with appropriately positioned spacer means. All of the spacer means as well as the cover member extension may have the unwanted length removed with a simple tool such as a pair of electricians pliers.
Turning now to FIGS. 4, 5 and 6, there are shown, fragmentarily, several alternative embodiments of the cover member and particularly the tubular extension thereof. In FIG. 4, for example, the tubular extension 104 is provided with a plurality of axially spaced, angularly positioned grooves 106 that are filled with a fire retardant compound 108. This construction maintains the fire retarding integrity of the installed portion of the cover member. In FIG. 5 the cover member is provided with a tubular extension 110 comprised of a continuous length of welded wire 112. The FIG. 6 embodiment provides a cover member having a tubular extension 114 in which are formed a plurality of axially spaced internal grooves 116 that are filled with cuttable, spot welded wire 118 for providing support and rigidity.
There has been disclosed heretofore the best embodiment of the invention presently contemplated. However, it is to be understood that various changes and modifications may be made thereto without departing from the spirit'of the invention.
What I claim as new and desire to secure by Letters Patent 1. Improved grounding means of an electrical device having a metallic yoke, the electrical device being mounted on a metallic junction box, said grounding means comprising:
a. elongated, tubular spacer means extending between the metallic yoke portion of the electrical device and the junction box, wherein said spacer means are provided with a plurality of axially spaced lines of weakness in the walls thereof to thereby permit shortening of said spacer means as required by mounting the electrical device substantially flush with the room side plane of the finished wall; and
b. metallic fastener means passing through spacer means, said fastener means being in direct contact with both the metallic yoke of the electrical device and the junction box.
2. The grounding meansin accordance with claim 1 wherein said lines of weakness are grooves formed in the outside face of said tubular spacer means. I
3. An improved junction box for supporting an electrical device having a metallic grounding yoke, the junction box comprising: i i
a. a cup-shaped metallic housing having a plurality of tabs formed at the open end thereof; 7
b. elongated, tubular spacer means extending outwardly from at least some of said tabs and into contact with the I metallic yoke of the electrical device; I ,c. metallic .fastener means passing through said spacer means, said fastener means being in direct contact with both the metallic yoke portion of the electrical device and at least some of the tabs; and
d. a cover member secured to and enclosing the open end of 6. The junction box in accordance with claim 5 wherein said said housing and a tubular extension depending from said ro ve re filled with a fire retardant compound. Cover member a direction y from Said housing, Said 7. The junction box'in accordance with claim 3 wherein said extension having a plurality axially p Peripheral sections of said tubular extension are defined by a coiled sections at least one of which is adapted to be broken off 5 length of wire, at least some adjacent portions of said wire whereby the outermost portion of said extension is flush being welded to each omen with the Plane of the finished wall in which said junction 8. The junction box in accordance with claim 3 wherein said box is mounted.
sections of said tubular extension are defined by grooves 4. The jLll'lCllOl'l box in accordance with claim 3 wherein said formed on the inside surface thereof.
cover member andsaid extension is non-metallic.
5. The junction box in accordance with claim 3 wherein said The Juncuon box m accordance claim 8 wherem grooves are filled by a cuttable wire.
sections of said tubular extension are defined by grooves formed on the outside surface thereof.