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Publication numberUS2579538 A
Publication typeGrant
Publication dateDec 25, 1951
Filing dateFeb 19, 1948
Priority dateFeb 19, 1948
Publication numberUS 2579538 A, US 2579538A, US-A-2579538, US2579538 A, US2579538A
InventorsBierce Burton B
Original AssigneeElwin A Andrus
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrical outlet with insulating closures
US 2579538 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

Dec. 25, 1951 B, BIERCE ,2,579,53s

ELECTRICAL OUTLET WITH INSULATING CLOSURE Filed Feb. 19, 1948 an 5 u I INVENTOR. @4212 flaw Patented Dec. 25, 1951 ELECTRICAL OUTLET WITH INSULATING CLOSURES Burton B. Bierce, Pewaukee, Wis., assignor of one-half to Elwin A. Andrus, Milwaukee, Wis.

Application February 19, 1948, Serial No. 9,551

4 Claims.

This invention relates to electrical connecting plugs for domestic appliances and the like and to wall outlet receptacles to receive the same.

One of the objects of the invention is to provide a plug receptacle having slots to receive the prongs of the plug which are normally closed and are opened only by inserting the plug therein.

Another object is to provide a receptacle of this type which will open upon the direct insertion of the plug without turning of the plug in either direction.

Another object of the invention is to provide a receptacle having a ground connection adapted to function with a plug having a ground prong for grounding appliances and the like.

Another object of the invention is to provide a plug and a wall receptacle therefor which when receiving the plug makes a ground contact therewith well in advance of any electrical connection and having apertures for the prongs which are normally maintained closed and which are opened automatically by the ground contact means.

Another object is to provide such a plug and plug receptacle which is of inexpensive, simple, and durable construction and will not wear out after a short period of service.

Another object is to provide such a receptacle that can be adjusted for use as a conventional receptacle with conventional plugs.

These and other objects and advantages of the invention will be more fully set forth in the following description of a preferred embodiment of the invention illustrated in the accompanying drawings.

In the drawings:

Figure 1 shows the receptacle in side elevation with parts broken away and sectioned to show the construction thereof;

Fig. 2 is a transverse cross-section through one socket of the wall receptacle and a plug therefor in position for assembly together;

Fig. 3 is a view similar to Fig. 2 with the plug partially inserted in the receptacle;

Fig. 4 is a view similar to Fig. 2 with the plug fully inserted in the receptacle;

Fig. 5 is a transverse sectional view taken on line 5-5 of Fig. 2; and

Fig. 6 is a transverse sectional view taken on lines 66 of Fig. 4.

The plug may be constructed as disclosed in applicants co-pending application Serial No. 680,600, filed July 1, 1946, now abandoned.

In this construction the body I carries three prongs disposed with the two electrical contact prongs 2 spaced apart to fit a standard outlet receptacle, and with the third prong 3 centrally disposed between prongs 2 and providing the ground connection with the outlet receptacle.

A three wire cord 4 leads from the prongs 2 and 3 to the appliance.

The ground prong 3 may be made retractable as set forth in the co-pending application referred to so that by manual adjustment the prong may be made inoperative to avoid interference with the use of the plug with conventional nongrounding receptacles. In considering the present invention, it is assumed that ground prong 3 is in extended position for functioning with the outlet receptacle herein disclosed, and for this purpose it should be adjusted to non-retractable position or be made entirely non-retractable, as shown.

The outlet receptacle of the present invention comprises a base 5 of suitable insulating material made in two parts providing a hollow interior and which are riveted together by means of the hollow ground rivets 6 disposed centrally of the two socket faces 1 for the outlet.

The receptacle is of standard size to fit the usual outlet box and has a metal strip 8 extending beneath the same and bent upwardly and flanged at the ends for securing the receptacle in place to the outlet box.

Strip 8 is secured to the receptacle by means of rivets 6 and completes the ground connection from the rivets to the outlet box.

The electrical connections are provided by a contact strip 9 extending along each side of the lower section of the base and having its opposite ends I0 extending upwardly toward the face 1 of the corresponding socket to provide a contact for receiving one of the-prongs 2 of the plug.

The central portion of strip 9 is exposed laterally from the receptacle and has a pair of binding post screws Ii thereon for securing the end of a lead wire thereto. The strips 9 are disposed in slots formed in the lower part of base 5 and may be additionally secured thereto by means of rivets or the like, if desired.

The free contact ends ID of strips 9 are disposed for registering with slots l2 in the corresponding faces I of the receptacle.

Each end 10 carried an insulating cap 13 which covers the upper end thereof and extends outwardly to cover the underside of the corresponding slot l2 when the contacts are in inoperative position. The cap I 3 encircles the end I0 and is spaced from the inner surface to provide a recess l4 for receiving the corresponding prong 2 of the plug when in operative position so that electrical contact may be completed between contact I and prong 2.

Each cap l3 also has a thin cam projection I extending through a vertical slot It in hollow rivet 6. The two cam projections [5 for a given socket face each other and may engage each other when the parts are in normal inoperative position. I 7

Theground' prong3 is adapted to enter the hollow rivet E and to push projections outwardly, thereby registering recesses M with the corresponding slots l2 for receiving-prongs Zas the plug is pushed farther into the socket.

The ground prong 3 should fit the hollow rivet 5 snugly to make proper ground contact therewith. The prong 3 is generally longer than prongs 2 and completes theground contact with rivet 6 prior to completion of the electrical contact between prongs 2 and contacts In. This provides a safety construction which makes certain that the appliance will be grounded at all times when current is applied thereto.

When the plugis removed, the resilience in strips 9 and ends I0 spring the latter back to inoperative position, as shown in Fig. 2, where the slots l2 are closed by caps l3 and cam mem bers l5 extend into the hollow rivet 6.

Ordinarily the receptacle cannot be employed with a plug that does not have a ground prong 3. However, where conventional non-grounding plugs must be used with a given receptacle it is possible to insert a member, not shown, into the hollow rivet B for spreading the contacts in to operative position prior to assembly of the plug therewith.

The principal advantages of the present invention lie in the safety of the construction. The contacts I9 are covered by insulation and slots l2 are closed during normal exposure of the socket face 1 so that small children cannot accidentally connect a terminal In with the ground. When in use the appliance is always grounded through the plug so that it can be used safely in kitchens, bathrooms and the like without danger of excessive shock to the user.

The invention may have various embodiments within the scope of the accompanying claims.

I claim:

1. An electrical outlet comprising a hollow base having a face and openings therein to receive the three prongs of a connecting plug, said openings being disposed in a line with the central opening directly between the outer two openings, a pair of metal spring biased contact strips disposed in said base with one end of each strip free to move into alignment with 2. corresponding outer opening in the face of the receptacle, means to secure the opposite end of each strip rigidly to an electric terminal in said base, an insulating member secured to each strip to cover the free end thereof and disposed between the strip and the corresponding opening to close the opening when the strip is in inoperative position, and a cam carried by each of said strips and disposed normally within said central opening to be engaged by the central prong of a plug as it enters the opening and thereby move said strips outwardly of said base against the biasing of the strips and into a position of contact with two other prongs of the plug.

2. In an electrical plug receptacle for receiv- 4 ing a central pin and two electrical conductin prongs, a pair of movable contact members disposed within the receptable opposite openings in the receptacle for receiving the prongs of the plug, a ground contact sleeve disposed centrally between said contact members in the receptacle to receive said pin, insulating members secured to said contact members, biasing means normally securing said insulating members in a position closing said openings in the receptacle, and cam means secured to said insulating members normally extending into said sleeve and disposed to be engaged by the pin entering the sleeve to move said insulating members and uncover said slots for positioning said contact members in operative relation to contact said prongs.

3. An electrical outlet receptacle tor receiving a plug having two spaced contact prongs and a third central ground pin, comprising a base having slots in the face thereof to receive said prongs, contact members yieldably secured within said base substantially in alignment-with said slots, a ground contact sleeve disposed centrally between said strips and opening in the face of said base to receive said pin, insulating closure means secured to said yieldable contact members and normally closing said slots, and cam members carried by and normally extending from said yieldable contact members into said sleeve and disposed to be engaged by the pin entering the sleeve to move said closure means and uncover said slots for positioning said contact members in operative relation to contact therewith by said prongs.

4. An electrical outlet receptacle for receiving a plug having two spaced contact prongs and a third central ground pin, comprising a base having slots in the face thereof to receive said prongs, contact members yieldably secured within said base substantially in alignment with said slots, a ground contact sleeve disposed centrally between said strips and opening in the face of said base to receive said pin, insulating closure means secured to said yieldable contact members and normally closing said slots, and cammem bers extending into said sleeve and disposed to efiect a yielding movement of said contact members upon separation of said cam members by insertion of a pin into the sleeve whereby said closure means uncovers said slots and said contact members are positioned inoperative relation to said slots to be engaged by said prongs.


REFERENCES CITED The following, references "are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,288,922 Klein Dec. 24, 1918 1,522,574 Benjamin Jan. 13, 1925 FOREIGN PATENTS Number Country Date 364,797 England Jan. 14, 1932 377,352 England July 28, 1932 435,330 England Sept. 19, 1935 492,268 Germany May 8, 1927 658,827 Germany June 7, 1936

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Referenced by
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US2770786 *Oct 11, 1952Nov 13, 1956Victor Chelton MacDouble safety electrical receptacle
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U.S. Classification439/137, 174/67
International ClassificationH01R13/453, H01R13/44
Cooperative ClassificationH01R13/453
European ClassificationH01R13/453