US3423724A - Terminal means - Google Patents

Description

R. c. CLEMENT TERMINAL MEANS Jan. 21, 1969 Filed July 25, 1966 KALP/ c. azz/wz/yr arfazwzy United States Patent 3,423,724 TERMINAL MEANS Ralph C. Clement, St. Clair Shores, Mich, assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed July 25, 1966, Ser. No. 567,539 US. Cl. 339-269 3 Claims Int. Cl. H011" 7/16, 3/06, 9/10 ABSTRACT OF THE DISCLOSURE This invention relates to means for electrically connecting a plurality of electrical conductors to a common potential.

In panelboards for light industrial and home applications a single phase three wire energizing system is often used. In such an arrangement there is a neutral bar at a potential intermediate the potential existing between the so-called hot wires. Whether or not the neutral bar is grounded, separate equipment grounding means are often provided in order to individually ground equipment energized through the panelboard.

Equipment grounding at panelboards is accomplished by utilizing screw tightened connections. The prior art has provided a so-called pressure wire connector wherein a screw tip engages the wire and presses it against a ground plate as in the device of US. Patent 2,967,287, which issued Jan. 3, 1961, to S. Sori for a Neutral Bar Assembly. The prior art has also provided a screw type connector in which the screw head presses the wire against a ground plate. In order to facilitate the making of socalled screw type connections, certain ground plates of the prior art have been provided with embossments to position and hold the equipment grounding wire adjacent to the screw shank while the screw is being tightened. This has proven successful when copper wire is utilized but has proven to be a failure for use with aluminum wire whose use is being increased in view of price advantages gained by utilizing aluminum and a growing shortage of copper.

More particularly, in prior art constructions where the ground plate is provided with embossments to locate the wire only a very short length of wire is engaged by the screw. Since aluminum is relatively soft unless a substantial portion of the wire is engaged by the screw head, the wire flattens out too much and breaks.

In order to overcome this disadvantage of the prior art screw type connectors, the instant invention provides a ground plate having a clearance aperture adjacent to the threaded aperture for the screw. The clearance aperture receives the free end of the grounding wire and as this wire is bent toward the ground plate to move under the screw head, the grounding wire end becomes frictionally held in the clearance aperture. This permits the portion of the grounding wire to be curved around the screw shank so that as the screw is tightened a substantial portion of the grounding wire is positioned under the screw head thereby distributing the forces clamping the grounding wire against the ground plate. Thus, excessive flattening of the grounding wire is prevented and a mechanically secure reliable ground connection is achieved.

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Accordingly, a primary object of this invention is to provide a novel terminal means for connecting a plurality of electrical conductors to a common potential.

Another object is to provide a terminal means of this type having provisions to simplify the making of electrical connections.

Still another object is to provide a terminal means of this type which utilizes a screw type connection without damage to aluminum conductors.

A further object is to provide a terminal means of this type having a clearance aperture operatively positioned in close proximity to the screw so that the free end of the grounding wire may be inserted into the clearance aperture and be frictionally held therein as the grounding wire is curved around the threaded shank of the screw and is held in this position during tightening of the screw.

These as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a fragmentary perspective showing that portion of a panelboard enclosure having the grounding terminal means of the instant invention mounted thereto.

FIGURE 2 is a plan view of the grounding terminal means of FIGURE 1.

FIGURE 3 is an end view of the grounding terminal means looking in the direction of arrows 33 of FIG- URE 2.

FIGURE 4 is a fragmentary end view of the grounding terminal means illustrating the position of the grounding wire immediately after insertion thereof into the locating and holding clearance aperture adjacent to the screw.

FIGURE 5 is a plan view of the elements of FIGURE 4 at a time after the grounding wire is curved around the shank of the screw. In FIGURE 5 the head of the screw is removed for the sake of clarity.

FIGURE 6 is an electrical schematic of an application of the grounding terminal means to a single phase three wire electrical system.

Now referring to the figures and more particularly to FIGURE 6, power transformer 20 includes a center tapped secondary winding which energizes first and second loads 24, 26, respectively, through circuit interrupting devices 28, 30, respectively. Wire 32 connected to the center tap of the secondary winding, as well as leads 34, 36 to loads 24, 26, respectively, are connected to a common potential at neutral bar 40. Equipment grounding conductors 44, 46 extending from loads 24, 26, respectively, are connected to grounding terminal means 50 which in turn is grounded through conductor 38. Coventionally, circuit interruptors 28, 30 are mounted within a common enclosure or panelboard indicated schematically by the dotted box 31, with wires 32, 34, 36 being connected within box 31 as seen in FIGURE 6. In some installations neutral bar 40 is also grounded.

The instant invention resides in ground terminal means 50 which is constructed in such a manner that the cost thereof is relatively low and the making of connections thereto is relatively simple.

More particularly, terminal means 50 includes elongated bus bar 51 constructed of conductive material formed into a channel which, in cross-section, includes arms that are considerably shorter than the web 52 thereof. Mounted to the channel web 52 are a plurality of post screws each having a head 55a and a threaded shank 55b (see FIG- URE 3). Each of the threaded shanks 55b extends through an individual threaded aperture in web 52 with each of the heads 55a being positioned in front of web 52. An individual clearance aperture 56, extending through web 52, is associated with each of the threaded apertures for screws 55. Each of these clearance apertures 56 is positioned adjacent to its associated threaded aperture for which reasons will hereinafter *be explained.

At the upper left portion of web 52, as viewed in FIG- URE 2, there is a tubular wire grip 58 mounted to the front surface of web 52 by screw 59 (FIGURE 3) extending through a clearance aperture in web 52 from the rear thereof. The tubular portion of wire grip 58 is provided with a rearward keying extension (not shown) which is entered into a cooperating formation in web 52 to prevent rotation of wire grip 58 with respect to web 52, in a manner well known to the art.

As seen in FIGURE 1, terminal means 50 is mounted to rear wall 31a of box 31 and is positioned with one of the channel arms adjacent to side wall 31b of box 31 and the free ends of the channel arms resting against rear wall 31a. Screw 61 extends through clearance aperture 62 (see FIGURE 2) in web 52 and is received by a threaded aperture (not shown) in rear wall 31a to mechanically secure terminal means 50. Wire grip 58 is provided to receive grounding lead 38 in a manner well known to the art.

The equipment grounding leads from the individual loads, such as leads 44, 46, are connected to terminal means 50 by engagement with screws 55. More particularly, as best seen in FIGURES 5 and 6, for connection of equipment grounding lead 44 to terminal means 50, the free end 44a of lead 44 is entered into one of the clearance apertures 56 after the post screw 55 associated with this particular aperture 56 is backed out so that its head 55a is spaced from the front surface of web 52.

As wire 44 is bent toward web 52 to move under head 55a and then be curved around shank 55b, the free end of wire 44a frictionally engages the sharp boundary edges of clearance aperture 56 at the front and back surfaces of web 52 thereby frictionally holding free ends 44a. Thus, as screw 55 is tightened on the portion 44b of wire 44 which is looped about shank 5517, free end 44a is held against being withdrawn through clearance aperture 56. During the tightening of screw 55 the electrician has one hand free to hold wire 44 looped about shank 55b so that a significant portion of head 55a engages loop 44b. Thus, even when aluminum wire is used for equipment grounding the clamping force exerted by screw head 55a against wire 44 assures high pressure contact and the clamping force is distributed over relatively long loop portion 44b and good electrical contact is made with bus bar 51.

It should now be apparent to those skilled in the art that terminal means 50 may be used as a neutral 40 insulated from box 31. This is accomplished by utilized screw 61 to mount bar 51 on the forward end of insulator 99 shown in phantom in FIGURE 2.

Thus, it is seen that the instant invention provides novel construction for an electric terminal means which is relatively economical to produce, facilitate the making of electrical connections, and permits the use of aluminum conductors.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is cleamed are defined as follows.

I claim:

1. An electric terminal means including a bar having a first threaded aperture and an associated first clearance aperture in a first surface thereof, a screw including a threaded shank and an enlarged head, said shank in threaded engagement with said first threaded aperture, said head positioned in front of said first surface in confronting relationship therewith, said first clearance aperture positioned in close proximity to said head when said screw is in a clamping position wherein said head bears against an electrical conductor having an end frictionally held in said first clearance aperture and a portion adjacent such end curved about said shank and clamped against said first surface by said head, said bar additionally provided with a plurality of threaded apertures in said first surface each associated with an individual clearance aperture in the same manner as the association between said first clearance aperture and said first threaded aperture, an individual screw threadably mounted in each aperture of said plurality of threaded apertures, said first surface being on a thin-walled portion of said bar, said bar being an elongated channel member including generally parallel arms connected by a web having said first surface, said arms extending to the rear of said web, whereby said arms serve to support the entire terminal means, provide for screw clearance, and space the clearance apertures a limited distance from a surface to which the terminal means is mounted so that an excessive amount of said conductor is not used.

2. A terminal means as set forth in claim 1 also including a wire grip mounted to said first surface.

3. A terminal means as set forth in claim 1 in which the bar is of a cross-section in which the arms are substantially of equal height and said height is less than the spacing between said arms.

References Cited UNITED STATES PATENTS 1,905,121 4/1933 Adam 339242 X 2,260,219 10/1941 Gates 339269 2,371,446 3/1945 Jensen. 2,693,586 11/1954 Dorfman et a1. 339269 X 2,707,761 5/1955 Page 33917 X 2,735,080 2/1956 Littman 339269 2,967,287 1/1961 Sori.

FOREIGN PATENTS 864,287 1/1953 Germany. 673,907 6/1952 Great Britain.

MARVIN A. CHAMPION, Primary Examiner.

PERRY TEITELBAUM, Assistant Examiner.

US. Cl. X.R.

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