US3806856A

US3806856A - Electrical receptacle with self-grounding element

Info

Publication number: US3806856A
Application number: US00294762A
Authority: US
Inventors: G Virani; F Gelzheiser
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1972-10-03
Filing date: 1972-10-03
Publication date: 1974-04-23
Anticipated expiration: 1991-04-23
Also published as: CA993534A

Abstract

A receptacle for mounting in a metal wall box is provided with a ground contact element with a first portion within the insulating housing of the receptacle for receiving the ground prong of a plug and a second portion, unitary with the first portion, that extends away from the housing for contacting a fastener located in the extended portion of the mounting yoke of the device. For duplex receptacles, the ground contact element can provide portions for contacting the ground prongs of two plugs, as well as the extended portion for self-grounding with a fastener mounting the yoke, in a unitary piece of material.

Description

Virani et al.

[ ELECTRICAL RECEPTACLE WITH SELF-GROUNDING ELEMENT [75] Inventors: Gopal J. Virani, Bridgeport; Francis L. Gelzheiser, Fairfield, both of Conn.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22 Filed: Oct. 3, 1972 [21] App]. No.: 294,762

[52] US. Cl 339/14 R [51] Int. Cl H0lr 3/06 [58] Field of Search 339/14 R, 132 R, 132 B, 7 339/133 R, 134; 174/51, 53 [56] References Cited UNITED STATES PATENTS 3,694,790 9/1972 Martin 339/14 R 3,723,942 3/1973 Dennison 339/14 R 3,723,941 3/1973 Schumacher et al. 339/14 R 5] Apr. 23, 1974 3,713,071 l/l973 Poliak et al. 339/14 R 3,663,919 5/1972 .laconette.... 3,714,614 1/1973 Ludwig 339/14 R Primary Examiner-Bobby R. Gay Assistant ExaminerRobert A. Hafer Attorney, Agent, or Firm-G. H. Telfer [5 7] ABSTRACT A receptacle for mounting in a metal wall box is pro- 7 Claims, 4 Drawing Figures 32 21 I5 33 I8 ITA h 34 if 20 at i I IO :rl9 22 ELECTRICAL RECEPTACLE WITH SELF-GROUNDING ELEMENT BACKGROUND OF THE INVENTION This invention relates to electrical receptacles such as those in common usage in commercial establishments and households.

Self-grounding receptacles are known to the priorart. Such devices provide a grounding connection between an internal contact element that receives the ground prong of an inserted male plug and a metal wall box to which the the device is secured by a mounting yoke. In self-grounding devices the completion of the desired grounding connection is made simultaneously with the placement and fastening of the device in the metal wall box. Means for this purpose generally include one of various types of spring elements secured to the mounting yoke and extending to a location where it contacts a fastener used to secure the mounting yoke to the wall box.

For further background on the art of self-grounding wiring devices, reference is made to copending application Ser. No. 266,791 filed June 27, 1972, by C.M. Smith and assigned to the assignee of the present invention. Specific examples of representative prior art are cited in the copending application. Prior art approaches have generally entailed the addition of a selfgrounding element to an otherwise conventional wiring device. Expense and complication of assembly are drawbacks to such approaches.

The present invention came about in an effort to design a receptacle with self-grounding functions while minimizing the number of elements of the device and the complexity of their assembly.

It is acknowledged that prior art relating to duplex grounding receptacles includes such receptacles in which the internal ground contacts are portions of a unitary member. However, no suggestion regarding the provision of a self-grounding element unitary with one or more internal grounding contacts is known.

SUMMARY OF THE INVENTION In accordance with this invention, an electrical receptacle for mounting in a metal wall box is provided with a unitary ground contact element having a first portion within the insulating housing of the receptacle for receiving the ground prong of a plug and a second portion that extends away from the housing for contacting a fastener located in the extended portion of the mounting yoke of the device. For duplex receptacles, the ground contact element has portions for contacting the ground prongs of two plugs, as well as the extended portion for self-grounding with'a fastener mounting the yoke, in a unitary piece of material. The unitary member is in intimate electrical contact with the mounting yoke over a principal portion of the formers length in duplex receptacles.

The invention, therefore, reduces the number of elements required in the device as compared with other receptacles with self-grounding elements for improved economical assembly while ensuring the existence of an excellent conductive path between internal contacts and the external self-grounding element.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of an embodiment of the present invention;

FIG. 2 is a sectional view taken along line IIII of FIG. 1;

FIG. 3 is a plan view of the device of FIG. 1 with the housing cover absent; and

FIG. 4 is a sectional view of an alternate embodiment 0 of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. l-3, a device is shown which is characterized in the art as a duplex receptacle of the two-pole, three-wire grounding type. The invention may, however, be applied to receptacles for one, or more than two, plugs and may also be applied to grounding receptacles for systems other than two-pole, three-wire systems.

The device of FIGS. 1-3 includes an insulating housing 10 comprising a cover or upper housing portion 11 and a base or lower housing portion 12. Cover 11 is provided with openings 21 for receiving the blades of a three-pronged plug, not shown. Base 12 is provided with chambers 22 for the location of female contact elements for mating with male plug blades. Only two of such chambers 22 are shown in FIG. 2, one in each half of the duplex device. A metal mounting yoke 14 is located between the two housing portions 11 and 12 and these three

elements

11, 12 and 14 are mutually secured by means such as a fastener 15 holding the housing portions together and sandwiching the mounting yoke between them.

The mounting yoke 14 comprises a principal portion 16 that is generally flat and straight and is located intermediate the two housing portions 11 and 12. The yoke 14 also has additional portions 17A and 178 which extend respectively from opposite ends of the principal portion 16. Extended portions 17A and 178 include, insofar as is relevant to this invention, an aperture 18 through which a fastener 19 passes for securing the mounting yoke to a metal wall box 20 (FIG. 2). For convenience and economy in the practice of this invention, self-grounding is provided only at one end of the device.

A ground contact element 30 is provided in accordance with the present invention. Ground contact element 30 has portions 31A and 318 that are located within chambers 22 of the base 12 and which serve as the internal contacts that mate with ground prongs of inserted plugs. Portions 31A and 31B are unitary and are joined by a bridging portion 32 that extends over, and in contactwith, part of the yoke portion 16 between the two portions 31A and 318. A further portion 33 of the ground contact element 30 extends away from portion 31A over part of the extended yoke portion 17A to the fastener aperture 18. An extremity 34 of the contact element engages the fastener 19 to secure the mounting yoke to the wall box.

The ground contact element 30 is preferably a flat strip of flexible sheet metal, such as of brass, which is stamped to a desired configuration including a generally U-shaped portion 31A for one of the plug receiving portions, a single leaf spring portion 318 for the other curving up and around part of the extended yoke portion with a curl at the extremity 34 that engages the fastener. It is also suitable to employ a straight edge termination for contacting the .fastener rather than a curled edge. The curled edge 34, extending within opening 18 and in the plane of yoke portion 17A, is preferred in order that fastener 19 is held perpendicular to yoke portion 17A prior to fastening in the wall box 20.

It is apparent from the foregoing description that the inventive combination provides a distinct improvement in uniting into the single member 30 the contact portions for the ground contacts of a duplex receptacle as well as the self-grounding portion which insures ground continuity from the device. Furthermore, it is also the case that the element 30 provides a more secure ground path from the ground contact portions 31A and 313 because of the unitary structure insuring electrical continuity and also because a substantial portion of element 30, namely

portions

32 and 33, are in direct contact with the yoke 14, in effect providing an extra parallel electrical path therethrough that gives full assurance of a low resistance ground. The facility in providing a low resistance ground is aided by not requiring any fasteners, such as rivets or the like, to conduct current from ground elements such as would be in the cations of 31A or 318 to the metal yoke. In embodiments of the invention as shown in FIGS. 1 to 3 it is not required to employ any separate fasteners to secure the element 30 within the structure, it being held merely by its location between housing portions 11 and 12. Rivets or other fasteners give rise to a possibility of high resistance if not making secure contact between the fastened elements. It can also be seen that the low resistance grounding connection has substantial current carrying capacity which minimizes any danger of fire in the event of a high current grounding short.

The embodiment of FIGS. 1-3 is a form of the invention of immediate and practical applicability although not the only form in which the invention may be practiced. For example, the device of FIGS. l-3 is one in which the mounting yoke 14 extends between housing portions 11 and 12. An additional type of device with which the invention may be practiced is illustrated in FIG. 4 in which corresponding although not necessarily identical, elements are identified by the same reference numerals as those employed in FIGS. l- 3.

In FIG. 4 the yoke 14 is a U-shaped member encircling the base 12 of the housing. Suitable means, such as a fastener 15, holds together the housing portions 1 l and 12 with the yoke. Additionally, a ground contact element 30 is configured to be located within the appropriate ground receiving chambers 22 for contacting ground prongs as well as extending over and in electrical contact with the yoke portion 17A and out to the fastener aperture 18. Consequently, it may be stated that a general concept applicable to the forms which the invention can take in duplex receptacles is that the ground element 30, with the contact portions 31A and 318 located as required by the plug configuration, has a bridging portion 32 that follows the yoke 14 whether that yoke is located between the housing portions or underlying and encircling the base thereof.

We claim as our invention:

1. An electrical receptacle for mounting in a metal wall box and comprising: an insulating housing; a metal mounting yoke secured to said housing, said yoke having a portion extending away from said housing for mounting the receptacle in the wall box, said yoke portion having a fastener aperture; a plurality of electrical contact elements within said housing, with corresponding openings in said housing to receive plug elements therein to mate with said contact elements, said contact elements including a ground contact element which is a distinct element from said yoke, including a first portion which extend into the housing for receiving the ground prong of a plug and a second portion, which is an integral extension of said first portion, that extends away from said housing towards said fastener aperture of said yoke portion and contacts a fastener located in said fastener aperture.

2. The subject matter of claim 1 wherein: the receptacle is a duplex receptacle with openings and internal contact elements for receiving a pair of three-pronged plugs, each including a ground prong; and said ground contact element includes an additional portion, integral with and extending from said first and second portions, that is located for receiving the ground prong of a second plug.

3. The subject matter of claim 1 wherein: said metal mounting yoke has a substantially flat principal portion located between upper and lower portions of said housing with extended portions at each end of said principal portion; and said ground contact element is a shaped fiat strip with said first portion being a generally U- shaped portion, and said second portion is an extension of one side of said U-shaped first portion extending over, and in contact with, said extended yoke portion to an extremity in said fastener aperture.

4. The subject of claim 2 whereinzsaid metal mounting yoke has a substantially flat principal portion located between upper and lower portions of said housing with extended portions at each end of said principal portion; and said ground contact element is a shaped flat strip with said first portion being a generally U- shaped portion, said second portion is an extension of one side of said U-shaped first portion extending over, and in contact with, said extended yoke portion to an extremity in said fastener aperture, and said additional portion is an extension of the other side of said U- shaped portion, and a bridging portion of said ground contact element extends over, and in contact with, said yoke between said first portion and said additional portion. I

5. The subject matter of claim 1 wherein: said metal mounting yoke is a U-shaped member encircling said housing and said ground contact element includes a portion lying immediately adjacent said U-shaped member with at least one contact portion extending upwardly therefrom into a housing chamber.

6. The subject matter of claim 1 wherein: said ground contact element, including said first and second portions, is a single, continuous, flat strip of flexible sheet metal.

7. The subject matter of claim 2 wherein: said ground contact element, including said first, second and additional'portions, is a single, continuous, flat strip of flexible sheet metal.

Claims

3. The subject matter of claim 1 wherein: said metal mounting yoke has a substantially flat principal portion located between upper and lower portions of said housing with extended portions at each end of said principal portion; and said ground contact element is a shaped flat strip with said first portion being a generally U-shaped portion, and said second portion is an extension of one side of said U-shaped first portion extending over, and in contact with, said extended yoke portion to an extremity in said fastener aperture.

4. The subject of claim 2 wherein: said metal mounting yoke has a substantially flat principal portion located between upper and lower portions of said housing with extended portions at each end of said principal portion; and said ground contact element is a shaped flat strip with said first portion being a generally U-shaped portion, said second portion is an extension of one side of said U-shaped first portion extending over, and in contact with, said extended yoke portion to an extremity in said fastener aperture, and said additional portion is an extension of the other side of said U-shaped portion, and a bridging portion of said ground contact element extends over, and in contact with, said yoke between said first portion and said additional portion.

7. The subject matter of claim 2 wherein: said ground contact element, including said first, second and additional portions, is a single, continuous, flat strip of flexible sheet metal.