US3835437A

US3835437A - Grounding plug

Info

Publication number: US3835437A
Application number: US00262715A
Authority: US
Inventors: A Gartland; V Carissimi; G Riley
Original assignee: Harvey Hubbell Inc
Current assignee: Hubbell Inc
Priority date: 1972-06-14
Filing date: 1972-06-14
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10
Also published as: CA986604A

Abstract

Apparatus for containing the blades of an electrical plug, especially where the plug includes a ground blade. A highly reliable ground is provided for the non-conducting metal structure of the plug by permanently connecting the ground blade thereto. The wiring terminal on the ground blade is externally disposed on the plug to facilitate verification of the ground wire connection to the plug. To avoid the safety hazard otherwise presented thereby, the wiring terminals on the power blades are structurally enveloped within the plug.

Description

[ Sept. 10, 1974 United States Patent 1191 Gartland Jr. et al.

[54]. GROUNDING PLUG 3,025,486 3/1962 Falconer............................. 339/208 [75] lnvenmrsi Albert E f Trumbull 3,461,417 8/1969 Schumacher et 31...... 339/14 P Vincent L. Carlssmu, Fairfield;

George Riley Bridgeport an of Primary .Examiner-Paul R. Gilliam Conn Assistant ExaminerRobert A. Hafer [73] A ignee; Harvey H t b ll I r t d, Attorney, Agent, or F [rm-Wooster. Davis & Cifelli Bridgeport, Conn.

June 14, 1972 [21] Appl. No.: 262,715

[57] ABSTRACT Apparatus for containing the blades of an electrical plug, especially where the plug includes a ground [22] Filed:

blade. A highly reliable ground is provided for the non-conducting metal structure of the plug by permanently connecting the ground blade thereto. The wir- [52] US. 339/14 P, 339/206 R [51] Int.

H01r 3/06 339/ 14 R, 14 P, 14 RP, ing terminal on the ground blade is externally disposed 339/14 L, 62, 63 R 63 M, 206 R, 206 P, 207 on the plug to facilitate verification of the ground wire [58] Field of Search connection to the plug. To avoid the safety hazard otherwise presented thereby, the wiring terminals on the power blades are structurally enveloped within the plug.

[56] References Cited UNITED STATES PATENTS 2,682,646 6/1964 Hubbell............................. 339/14 R 10 Claims, 6 Drawing Figures GROUNDING PLUG BACKGROUND OF THE INVENTION The present invention relates to container apparatus for a grounded plug and particularly to such apparatus for enclosing the wiring terminals on the power blades within the structure of the plug while permanently affixing the ground blade electrically to the nonconducting metal structure of the plug. Hitherto, many different devices have been used to contain the terminal blades of a grounded plug. Generally, all grounded plugs provided for the electrical cord to enter from the rear and contain power and ground blades which protrude from the front. Existing codes require that all non-conducting metal structure on grounded plugs, such as cord clamps, must be electrically connected to the ground blade.

In some plugs, the wiring terminals on all blades are accessible through an opening in the front (hereinafter open front type), while in other plugs such accessibility is only attained after removing a blade holder to which all blades are secured (hereinafter dead-front type). The open front plugs are advantageous because the ground blade is permanently affixed electrically to the non-conducting metal structure of the plug. Also, the integrity of the ground wire connection to the plug may be verified without disassembling the plug. These open front plugs, however, present a safety hazard in some applications because the wiring terminals on the power blades are not completely enclosed by the structure of the plug. The dead-front plugs are advantageous because the wiring terminals on the power blades are completely enclosed by the structure of the plug. However, the removable nature of the blade holder makes it necessary to incorporate a disconnecting electrical interface between the ground blade and the nonconducting metal structure of the plug. Also, to verify integrity of the ground wire connection in a dead-front plug, the blade holder must be detached from the plug.

SUMMARY OF THE INVENTION It is, therefore, a general object of the present invention to provide a grounded plug having a container apparatus which minimizes and obviates the disadvantages of the prior art.

' It is a specific object of the present invention to provide a grounded plug having a container apparatus which structurally encloses the wiring terminals on the power blades while permanently connecting the ground blade electrically to the non-conducting metal structure of the plug.

It is a more specific object of the present invention to provide a grounded plug having a container apparatus in which the integrity of the ground wire connection may be verified without disassembly of the plug.

These objects are accomplished according to the present invention by partitioning a plug body into an open compartment and an elevated surface. Power blades having wiring terminals are secured in an insulated holder which is retained to the plug body with the wiring terminals disposed in the open compartment. The power blades extend externally from the holder which is configured to close off the open compartment. A ground blade is permanently connected electrically to the non-conducting metal structure of the plug and is disposed within the plug body to extend from the eleis disposed to be externally exposed on the plug.

BRIEF DESCRIPTION OF THE DRAWING The manner in which these and other objects of the invention are achieved will be best understood by reference to the following description, the appended claims, and the attached drawing wherein:

FIG. 1 is a perspective view of a grounded plug incorporating the container apparatus of this invention;

FIG. 2 is an exploded view thereof without the cable and with portions of the plug body cut away to illustrate the separate mounting provisions utilized for the power blades and the ground blade;

FIG. 3 is a perspective view of the blade holder to which the power blades are secured;

FIG. 4 is a front elevational view of the grounded plug illustrating the external connection of the ground wire to the wiring terminal on the ground blade;

FIG. 5 is a sectional view thereof taken substantially along line 55 of FIG. 4 to illustrate the structural en closure provided for the wiring terminals of the power blades and the permanent electrical connection provided between the ground blade and the binding plate; and

FIG. 6 is a sectional view thereof taken substantially along line 6-6 of FIG. 5 to illustrate the interior construction of the plug.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawing, and more particularly to FIG. 1, there is illustrated a grounded plug l0-into which the improvements of this invention have been incorporated. Generally, the grounded plug 10 is used to connect the wires of-an electrical cord 12 to a source of power from an outlet (not shown). The grounded plug 10 includes a plug body I4 from which two power blades 16 and a ground blade 18 extend. A ground wire 20 of the cord 12 passes from the interior of the plug 10 through a conduit means and connects to the ground blade 18. At its other end, the ground wire 20 is usually connected to the housing of the electrical equipment utilizing the power, to thereby eliminate the safety hazard presented when short circuit conditions exist in the equipment. To relieve stress on the electrical connections within the plug 10, a conventional cord clamp 22 is secured to the plug body 14 by suitable means such as discussed below. Typically, the cord clamp 22 has a pair of jaw members 23 which are interconnected by screws 24.

As illustrated in FIG. 2, the plug body 14 is generally cylindrical in shape and is interiorly partitioned to provide an elevated surface 25 in a contiguous location to an open compartment 26. The ground blade 18 is disposed to extend from the elevated surface 25 and is permanently fixed to the plug 10. The power blades 16 are secured within a blade holder 28 which is configured for insertion into the plug body 14 over the open compartment 26.

Support surfaces

30, 32, 34 and a gripping lip 36 are disposed within the plug body 14 to align and retain the blade holder 28 upon full insertion, as shown in FIG. 4. Any suitable means may be utilized to secure the blade holder 28 to the plug body 14, such as a binding screw 38.

means on each power blade 16 is a screw 44 threaded into a lug head 46' which is an integrally formed portion of the power blade 16 as shown in FIGS. 2 6.

The plug body 14 ismade from an electrically insulating, elastomeric material and has a particular interior configuration. In addition to the open compartment 26, the elevated surface 25,' the

support surfaces

30,32, 34,- and the gripping lip 36 previously discussed,

the plug body 14 containsa rear entrarice48 as illus- I trated in FIG. 5. The cord-l2 passesinto the open compartment 26 through the rear entrance 48 and contains power conducting wires 49 in addition'to the ground wire 20. Perpendicularly across the rear entrance 48, the exteriorof the plug'body 14 is recessed to accommodate mounting ears 50 on the jaw members 23 of the cord clamp 22, whichare retained to the plug body 14 under an annular binding plate 52. i

The cord clamp 22*andbinding plate 52 are made of metal but they areinon-conducting and only a structur'al part ofthe plug 10. Many safety codes require that thenon-conducting metal'structure on grounded 3 plugs must be electrically connected to the ground blade 18. When complying with such codes, it is most desirable to permanentlyaffix the ground blade 18 in the plug 10, whichthereby avoidsthe need 'of-a detachable ground .connectionfAny suitablefasteningmeans can be utilized to permanently, affix and electrically f: connect the ground blade 18 to theplug 10. A most convenient arrangement is to secure the ground'blade 18 to the binding plate 521with a rivet-54 ,extending through ajload-ibearing, eyelet 56'which is disposed fin 68 abuts against the support surface 30 and thef bulkhead 58 abuts against both

support surfaces

32 and 34. When the blade holder 28 is fully inserted into the plug body 14, the gripping lip 36 on the plug body 14 snaps over the raised lip 76 on the blade holder 28 to provide limited retention thereto. Thereafter, the bind- 1 ing screw 38 is inserted into aperture 74 and tightened to secure the blade holder 28 to the plug 10. The terminal means on the power blades 16 are then structurally enveloped by the plug 10.

To connect the cord 12 to the plug 10, the binding screw 38 isloosened and the blade holder 28 is'removed from the plug body 14. The screws 24 are manipulated to open the jaw members 23. of the cord clamp 22. One end of the cord 12 is then directed through the, rear entrance 48 and open compartment 26 of the plug body 14, until the plug body 14 is disposed well back from the end of the cord 12. The

through the plugbody 'l4,,as' shown in =FlG. 5.- The binding screw 38 securing the blade holder '28 to'the plug body 14 also threads through and secures tothe binding plate 52. 1

tends perpendicularly back from (the, bulkhead 58, as

shown in FIGS. 2 3, andlias' a legportion 64 and' a crossportion 66. The lug heads' 46 andf'screws 44 on the power blades 16a're separated by'the' legportion 64 .The top surface of' the cross portion 66 is configured to have a protruding fin 68 and a groove 70 which Detailed'construction of the-blade holder 28 isillustrated in .FlGS. 2 4 6,-where eachpowerblade,l6f extends perpendicularly through'a partially cylindrical bulkhead 58 of an insulated'base 60. {AjiT' web.62 'ex-Y 3 umn 72 on the blade holder 28 between the support surfaces 32 and 34 within the plug body 14. The blade holder 28 is then forced into the plug body 14 until the the plug. J u r It; should 'be understood that the present disclosure has-beenimade only by way ofexample and that numer.-"-

jacket on the cord 12 is then removed for an appropriate length to expose the

wires

20 and 49. The insulation f is then stripped from the power conducting 'wiresi49 which are then connected to the appropriate power. blades 16 on theblade holder 28. The ground wire-20 R is disposed within the groove 'on the blade holder-28 which serves as the conduit means from the interior of 5- the assembled plug 10. The cord 12 .is directedback: y through-thecompartment 26;and' rearent r'an'ce' 48 of l the plug body 14 until the blade holder 28 is joined to 7 the plug body 14 in .the manner. previously described.

After this jointure, the binding screw 38 is tighten ed to secure the blade holder 28 to the plug body. 14 with the, ground wire 20 extending from the plug 10in a similar direction to the

blades

16 and 18. The ground; wire20 1 is then stripped of insulation andconnected to the ground blade 18 under the externally disposed tei 'rninfal screw 40.

. lt jshouldbereadily appre'ciated'by those sk'illediri; F: this art that the plug container'apparatus embodiedbyi' t' i this invention structurally e'njvelops the wiring terminals on the power blades to avoid short 'circuitsfiwhil j lii ably affixing the ground-blade permanentl'y'to the non: conduc'tingmetal structure of thef 'plug. Furthermore," the wiring terminal on the groundblade is. disposed ex ternally on the'plug-which permits the integrity of the ground connectionto be v'erifiedwithout disassembling ous changes in details of construction and the combinations or arrangements of parts may be resorted to without departing from the true spirit and scope of the invention and therefore, the present disclosure should be construed as illustrative rather than limiting.

What we claim is:

1. An electrical plug comprising:

a blade holder, said blade holder having power blades disposed therethrough and supported thereby, said power blades including terminal means for connecting to electrical wires;

a plug body, said plug body including non-conducting metal structure and being configured to detachably secure said blade holder with said terminal means structurally enclosed therein; and

a ground blade, said ground blade being permanently affixed to said plug body in electrical continuity with said non-conducting metal structure.

2. The electrical plug of claim 1 wherein conduit means for passing a ground wire from within said plug body is included on said electrical plug and wherein said ground blade includes terminal means for connecting to electrical wires, said ground blade terminal means being externally accessible on said electrical plug.

3. The electrical plug of claim 2 wherein said conduit means includes a groove disposed on said blade holder.

4. The electrical plug of claim 1 wherein said terminal means includes a screw threading into each said power blade.

5. The electrical plug of claim 1 wherein said plug body includes an open compartment and an elevated surface contiguous to said open compartment, said ter' minal means on said power blades being disposed within said compartment and said ground blade being disposed to extend from said elevated surface 6. The electrical plug of claim 5 wherein said blade holder is configured to close off said open compartment.

7. The electrical plug of claim 1 wherein said nonconducting metal structure includes a binding plate, said ground blade being secured to said plug body by fastening means for attaching to said binding plate.

8. The electrical plug of claim 7 wherein said fastening means includes a rivet.

9. The electrical plug of claim 1 wherein conduit means for passing a ground wire from within said plug body is included on said electrical plug and said ground blade includes terminal means for connecting to electrical wires, said ground blade terminal means being externally accessible on said electrical plug; wherein said plug body includes an open compartment and an elevated surface contiguous to said open compartment and said non-conducting metal structure thereof includes a binding plate, said power blade terminal means being disposed within said compartment, said ground blade being disposed to extend from said elevated surface and being secured to said plug body by fastening means for attaching to said binding plate; and wherein said blade holder is configured to close off said open compartment.

10. The electrical plug of claim 9 wherein said power blade terminal means and said ground blade terminal means include screws threading into said blades; wherein said conduit means includes a groove disposed on said blade holder; and wherein said fastening means includes a rivet.

Claims

1. An electrical plug comprising: a blade holder, said blade holder having power blades disposed therethrough and supported thereby, said power blades including terminal means for connecting to electrical wires; a plug body, said plug body including non-conducting metal structure and being configured to detachably secure said blade holder with said terminal means structurally enclosed therein; and a ground blade, said ground blade being permanently affixed to said plug body in electrical continuity with said nonconducting metal structure.

5. The electrical plug of claim 1 wherein said plug body includes an open compartment and an elevated surface contiguous to said open compartment, said terminal means on said power blades being disposed within said compartment and said ground blade being disposed to extend from said elevated surface.

6. The electrical plug of claim 5 wherein said blade holder is configured to close off said open compartment.

7. The electrical plug of claim 1 wherein said non-conducting metal structure includes a binding plate, said ground blade being secured to said plug body by fastening means for attaching to said binding plate.