US 3369211 A
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Description (OCR text may contain errors)
Feb. 13, 1968 J. A. SUNDQUIST GROUNDING RECEPTACLE Filed May 12, 1966 NM ummy INVENTOR.
United States Patent 3,369,211 GROUNDING REQEPTACLE John A. Sundquist, Trumbull, Conn, assignor to Harvey Hubbell, Incorporated, Bridgeport, Conn., a corporation of Connecticut Filed May 12, 1966, Ser. No. 549,705 10 Claims. (Cl. 339-14) This invention relates to a grounding electrical receptacle and, more particularly, to such a receptacle wherein the grounding elements are isolated from the mounting strap.
A common type of receptacle which is widely used in electrical wiring includes a pair of slots and associated female contacts for receiving the line blades of a male plug and a third semi-circular opening associated with the female grounding contact for receiving a grounding prong on the plug. In receptacles of this type, it is customary to mount the female grounding contact on the metallic mounting strap which encircles the rear portion of the receptacle and is used for mechanically mounting the receptacle in an outlet box. The grounding connection is thus made through the outlet box and the metallic sheathed cable, or conduit, to a water pipe.
In certain electronic and communication installations, such a system ground often introduces unwanted interference which creates noise or distortion in sensitive apparatus. In these installations a separate grounding Wire is required and this often necessitates the use of specially designed receptacles, outlets, boxes, or plates.
Accordingly, it is a primary object of the present invention to provide an improved grounding receptacle. Other objects are to provide such a receptacle wherein the grounding contacts are electrically isolated from the mounting strap; wherein a separate grounding connection may be made to the grounding contact; and wherein the receptacle may be mounted in a standard outlet box and covered by a standard plate.
The manner in which the foregoing objects are achieved will be apparent from the following description, the appended claims and the figures of the attached drawing wherein:
FIG. 1 is a back view, partially broken away, of a duplex receptacle constructed in accordance with the present invention;
FIG. 2 is a right side view of the receptacle of FIG. 1, partially broken away to illustrate its internal construction;
FIG. 3 is a perspective view illustrating the construction of the ground contacts of the receptacle of FIGS. 1 and 2;
FIG. 4 is a back view, partially broken away, of a single receptacle constructed in accordance with the present invention;
FIG. 5 is a left side view of the receptacle of FIG. 4, partially broken away to illustrate its internal construction; and
FIG. 6 is a perspective view illustrating the construction of the grounding contact of the receptacle of FIGS. 4 and 5.
The objects of the present invention are achieved by means of an electrical grounding receptacle which comprises a body of insulating material defining chambers therein. The body includes a face portion which defines openings communicating with the chambers. A plurality of female electrical contacts are positioned Within the chambers and are aligned to receive male contacts inserted through the openings. A grounding terminal is mounted on the body and an electrical conductor joins the grounding terminal and at least one of the female electrical contacts. A metallic mounting strap is provided on the body and insulating means isolate the conductor from the mounting strap.
With particular reference to FIGS. l-3, there is illustrated a duplex receptacle comprising a body 10 of the usual insulating material. On its front surface the body 10 is provided with faces 12, 14 for receiving the two line blades and the grounding prong of a male plug P. Intermediate the faces, a circular hole 15 extends through body 10. The grounding opening 16 of the upper face and the similar opening 18 of the lower face are illustrated inFIG. 2. Each of these openings communicates with an internal chamber, such as chamber 20 communieating with grounding opening 16, and chamber 21 communicating with grounding opening 18. These chambers extend completely through the body 10. The back of body 10 is closed by means of an insulating back plate 22. The back plate 22 includes the usual back wiring openings 24 and is provided with a groove 25 of rectangular cross section which extends longitudinally along the entire length of the back surface. A rectangular opening 26 within the groove 25 is aligned with chamber 20 and a circular opening 27 is aligned with hole 15. At its lower right hand corner, as seen in FIG. 1, the back plate 22 is cut away to form a notch 28, which extends into alignment with the chamber 21. A passage 30 in the side Wall of body 10 extends from the rear surface of the body and communicates with the chamber 21. In addition, the side Wall is provided with a recess 32 for receiving the wiring terminal plate, as will be later disclosed.
Housed within chamber 20 is a U-shaped spring grounding contact 34 and within chamber 21 is a U- shaped spring grounding contact 36. In receptacles constructed in accordance with the prior art, the grounding contacts are riveted directly to the mounting strap. However, in the present construction they are riveted to the end of an electrically conductive bridging member 38 which is shown in detail in FIG. 3.
The bridging member 38 is substantially L-shaped, the leg 40 of the L terminating in a Wiring terminal plate 42 which is bent downwardly as shown. The terminal plate 42 is drilled and tapped to receive a binding screw 44. Extending from the terminal plate 42 is a locking lug 46 and an outwardly bent conductor retaining tab 48. The main body of the bridging'member 38 is provided with an enlarged portion 50 which defines an opening 52 which is larger than the opening 27 in the back plate 22. The grounding contacts 34, 36 on bridging member 38 are inserted, respectively, through the opening 26 and notch 28 in the back plate into the chambers 20, 21. The terminal plate 42 slides Within the recess 32 on the side of the body 10 and the locking lug 46 enters a locking opening formed in the body adjacent the recess 32. When fully inserted, the main body portion of the bridging member 38 is positioned within the recess 25 with its large opening 52 concentric with the smaller opening 27 in the back plate.
Mounted against the bridging member 38 and also contained within the groove 25 is a rectangular insulating strip 54. The insulating strip defines a circular opening 56 of substantially the same size as the opening 27 in the back plate but considerably smaller than the opening 52 in the bridging member with which it is aligned.
The U-shaped metal mounting strap 58 is next mounted within the recess 25 and against the insulating strip 54. The mounting strap extends around the ends of the body 10 Where it is retained by molded locking lugs in the usual manner and includes an opening 6t] aligned with the hole 15 of the body It} and flanked by a pair of raised bosses 62. A bushing 64 is inserted through the opening 60 in the mounting strap and into the hole 15 in body 19. This bushing is drilled and tapped at one end and includes a square head 66 at the other end which is positioned between the bosses 62 to resist rotation. A screw 68 extends into the drilled and tapped end of bushing 64 between the faces 12, 14 on the front of the receptacle and may be used to secure the cover plate.
It will now be seen that the receptacle of FIGS. 1-3 provides a novel construction for receiving the threeprong grounding plugs commonly in use. However, the female grounding contacts are completely isolated electrically from the mounting strap by reason of the insulating strip 54 and the clearance between opening 52 and bushing 64. The contacts may be grounded only by a separate grounding conductor connected to binding screw In FIGS. 4-6 there is illustrated a modification of the invention as applied to a single receptacle. In this modification the body 70 is approximately cubic and has a single face 72 which defines a grounding opening 74 communicating with a chamber 76. A hole 78 extends through the body 79 from front to back. The corners of the body 70 are mitered, as seen in FIG. 4, but the lower left hand corner is cut away even more so as to define a recess 80 in the rearward portion of the body 76.
The back of the body 70 is closed by a back plate 82 which includes the usual wiring openings 84. It also defines a groove 36 which extends longitudinally of the base plate from top to bottom as seen in FIG. 4. In addition the back plate also defines an auxiliary groove 88 which extends diagonally from the main groove to the recess 80. Within the groove 86 there is a rectangular opening 90 which communicates with the chamber 76 and a central opening 92 aligned with, and of substantially the same size as, hole 78.
An angled ground strap 94 is mounted within the groove 86 and supports a grounding contact 96 which is riveted thereto and positioned within the chamber 76. The ground strap 94 defines an enlarged opening 98 concentric with, but larger than, the opening 92. The angled end of the ground strap is bent downwardly to form a wiring terminal plate 100 which is positioned within the recess 80. The terminal plate is drilled and tapped to receive a binding screw 102. The body 70 is apertured to provide clearance for the end of screw 102.
Also mounted within the groove 86 and auxiliary groove 88 and atop the ground strap 94 is an insulating strip 104. As seen in FIG. 6, this strip has a shape similar to that of the ground strap 94 and defines an opening 106 which is aligned with, but smaller than, the opening 98. The metal mounting strap 108 is mounted within the groove 86 and against the major portion of the insulating strip 104. The mounting strap extends around the top and bottom of the body in the usual manner and the entire assembly is held together by means of a bolt 1163 extending through the hole 78 and the various aligned openings and retained by a nut 112. It will thus be seen that, in a manner similar to that of the duplex receptacle, the grounding contact 96 is completely isolated from the mounting strap 108, the sole connection thereto being made by means of binding screw 102. It will also be obvious that bolt 110 and nut 112 may be replaced by a rivet.
It is believed that the many advantages of this invention will now be apparent to those skilled in the art. It is also believed that many variations and modifications will be apparent which do not depart from the spirit and scope of the invention. Accordingly, the foregoing description is to be construed as illustrative only, rather than limiting. This invention is limited only by the scope of the following claims.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. An electrical grounding receptacle which comprises: a body of insulating material defining chambers therein and including a face portion defining openings communicating with said chambers; a plurality of female electrical cont-acts within said chambers aligned to receive male contacts inserted through said openings; grounding terminal means on said body; an electrical conductor joining said grounding terminal means and at least one of said female electrical contacts; a metallic mounting strap on said body; and insulating means for electrically isolating said conductor from said mounting strap.
2. The receptacle of claim 1 wherein said body includes a detachable back plate defining a groove on its outer surface and wherein said electrical conductor comprises a metallic strip positioned in said groove.
3. The receptacle of claim 2 wherein said insulating means comprises a strip of insulating material positioned in said groove atop said electrical conductor.
4. The receptacle of claim 3 wherein said mounting strap is positioned in said groove atop said insulating material.
5. The receptacle of claim 4 wherein all of said body, back plate, electrical conductor, insulating means, and mounting strap are secured by locking means extending therethrough.
6. The receptacle of claim 5 wherein said electrical conductor defines an opening surrounding but spaced from said locking means.
7. The receptacle of claim 1 wherein said receptacle is duplex and wherein said electrical conductor comprises a bridging member having a grounding contact secured at substantially each end thereof.
8. The receptacle of claim 7 wherein said bridging member includes a laterally extending portion extending across the back of said body and including a forwardly bent portion positioned on the side of said body to form said grounding terminal means.
9. The receptacle of claim 1 wherein said receptacle is single and defines a recess extending from its back surf-ace and wherein said conductor is a metallic strip having said female contact mounted at one end thereof, the other end being forwardly bent to lie in said recess and defining said grounding terminal means.
10. The receptacle of claim 9 wherein said strip includes a major portion extending longitudinally of said body and an angled portion extending to said recess.
References Cited UNITED STATES PATENTS 1,591,707 7/1926 Harrington 339-133 3,032,736 5/1962 Howells 33914 3,096,132 7/1963 Hubbell 339-44 X 3,218,597 11/1965 Oehlerking et a1. 339l4 MARVIN A. CHAMPION, Primary Examiner.
P. A, CLIFFORD, Examiner.