US2704831A

US2704831A - Electric outlet having means to lock the prongs of an attachment plug therein

Info

Publication number: US2704831A
Application number: US431827A
Authority: US
Inventors: Wilbur R Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-05-24
Filing date: 1954-05-24
Publication date: 1955-03-22
Anticipated expiration: 1972-03-22

Description

March 22, 1955 R.. SMITH ELECTRIC OUTLET HAVING MEANS TO LOCK THE PRONGS OF AN ATTACHMENT PLUG Tl-IEREIN Filed lay 24, 1954 2 Sheets-Sheet l f Wffgg E M /3 1 2/ 23 /6 7 .19 3 gm 6 J v 3/ Z6 iFZLZZ I I I 6 INVENTOR.

Wilbur 7?. 3/77/27? .March22, 1955 w. R. SMITH 2,704,831

ELECTRIC OUTLET'HAVING MEANS TO LOCK THE PRQNGS N OF AN ATTACHMENT PLUG THEREI 2 Sheets-Sheet 2 Filed May 24, 1954 Wilbur 2291 559933 7;

United States Patent ELECTRIC OUTLET HAVING MEANS TO LOCK THE PRONGS OF AN A'ITACHlVlENT PLUG THEREIN Wilbur R. Smith, Clarkston, Wash.

Application May 24, 1954, Serial No. 431,827

4 Claims. (Cl. 339-91) This invention relates to an electrical outlet.

One object of the invention is to provide an outlet of such construction that a person will not be liable to receive an electric shock by careless handling of a plug.

Another object of the invention is to provide an electric outlet with a cylinder adapted to receive a terminal plug, the cylinder being rotatable about its axis from a normal position wherein the circuit is broken, to a position wherein the circuit is made to the plug and danger of accidental shorting of the circuit eliminated.

Another object of the invention is to provide an electric outlet having a rotatable cylinder of such construction that when the terminal plug is inserted and the cylinder rotated, plungers are moved into locking engagement with the plug prongs and danger of accidental removal of the plug from the outlet is eliminated.

Another object of the invention lies in the provision of an electric outlet including a rotatable cylinder having contact bars adapted to electrically connect with contact strips carried by the outlet body when the cylinder is I0- tated, by means of a plug having its prongs disposed withing the sockets formed in the cylinder, so that electrical connecting and disconnecting is accomplished between the contact bars and contact strips instead of between the plugs of the prong and the sockets as in conventional outlets.

Another object of the invention lies in the provision of an electrical outlet having a rotatable cylinder adapted to receive the prongs of a terminal plug and having means for locking the prongs in the cylinder during the period that contact is made between the contact bars of the cylinder and contact strips of the outlet and releasing the prongs only after contact is broken between said bars and strips.

These and other objects of the invention will become apparent during the course of the following description.

In conventional electric outlets where the prongs of the terminal plug are admitted to the contact bars within the outlet which are permanently connected to the electric wiring system, it is possible to receive an electric shock by touching the prongs during the insertion or removal of the terminal plug with relation to the outlet. Also, when heavy loads are being carried by the circuit, the making and breaking of the electrical connection between the prongs and the contact bars causes arcing and burning of the elements and in addition the terminal plug is held into the outlet by frictional engagement only and often is accidentally removed therefrom. The present invention seeks to overcome all of these undesirable conditions.

In the accompanying drawing, forming a part of this specification, and in which like numerals are employed to designate like parts,

Figure 1 is a face view of a wall outlet having a cover plate secured in place;

Figure 2 is a vertical cross section taken through the outlet and including a terminal plug in one cylinder;

Figure 3 is a rear elevation of the improved outlet with the rear cover removed;

Figure 4 is a transverse cross section taken through the outlet midway its length;

Figure 5 is a fragmentary longitudinal cross section on a plane 90 degrees from that of Figure 2 and showing one cylinder; and

Figure 6 is a perspective view of the rear and one side of the outlet with the rear cover removed.

Referring now more particularly to the drawing, the improved outlet has been shown as a double electric outlet and has a body 10 formed from insulating material. This body, like conventional outlets, is adapted to be secured within an outlet box (not shown) and has a face plate 11 releasably secured thereto to conceal the box. In the body are formed longitudinally spaced annular cavities 12 open at their front and rear ends and having reduced front end portions 13 defined from the enlarged rear end portions 14 by an intermediate annular shoulder 15. Disposed within each cavity is a cylinder 16 which has an enlarged rear end portion 17 and a reduced front end portion 18 and having an intermediate shoulder 19 which bears against the shoulder 15 and prevents removal of the cylinder forwardly out of the cavity 12 and yet permits axial rotation of the cylinder therein. The cylinders are of dimensions to have close tolerance within their respective cavity 12.

Inspection of Figures 2, 3, and 5 will reveal that the enlarged portions 14 of the cavities 12 are provided with diametrically opposed crescent shaped recesses constituting cam surfaces 20, thus causing the enlarged portion 14 to appear eliptical or oblong in cross section.

Each cylinder 16 is provided with a pair of sockets 21 spaced and disposed to receive the prongs 22 of conventional terminal plugs as 23. It will here be noted that the conventional prongs 22 of plugs 23 are provided with axially aligned apertures at 24 and these are employed in the exercise of this invention and the manner of use will be more particularly disclosed hereinafter.

Each socket 22 is provided with a contact bar 25 which is formed from a strip of conductive material folded upon itself midway its length and the resulting bar has the folded end bent at substantially a right angle to form a lip 26. The contact bars 25 are inserted into the sockets 21 from the rear end of the cylinder 16 with the spaced open ends toward the front of the cylinder 16 and the right angle lips 26 extending radially at the rear end of the cylinder 16 and disposed diametrically opposed to each other.

Substantially midway the length of the cylinder 16 I provide radial bores 27 which communicate from the peripheral face of the annular cylinder 16 one with each socket 21. It will also be noted that one leaf of the bars 25 is drilled or otherwise provided with an aperture 28 to admit a plunger 29 into the socket 21. The plunger is disclosed as having a substantially hemispherical end face 30 and it will be seen that the rear end of the plunger extends into the crescent shaped recesses or cam areas 20 so that the faces 30 are retracted from the sockets 21 a sufiicient distance to permit admission of the prongs 22 of the terminal plug 23. However, when the cylinder 16 is rotated substantially degrees the cam surfaces 20 cause the plungers 29 to shift inwardly into the sockets 21 and lock the prongs 22 therein. Obviously, the plungers 29 may enter into the apertures 24 as disclosed in Figure 5 to lock the prongs or the hemispherical end face 30 may enter a smaller aperture only insofar as it is physically capable and still lock the prong in the sockets. If no aperture 24 is provided the plungers then are forced against the side faces of the prongs 22 to lock them therein by clamping action. This use is disclosed since it is conceivable that prongs having no aperture 24 may be manufactured and their use would not be obviated by the change in the structure.

On its rear face the body 10 is provided with a pair of opposed contact strips 31 and these strips are carried by the body and tangentially arranged at the rear end of the cavities 12 in such position that when the cylinders 16 are rotated 90 degrees from their normal position, wherein the lips 26 are disposed in longitudinal alignment with the longitudinal dimension of the body 10, to a contacting position, wherein the lips 26 are disposed laterally of the body 10, they are frictionally engaged with the contact strips 31 for electrical connection thereto. It will thus be seen that when the contact bars 25 are electrically connected to the contact strips 31 the plungers 29 are forced inwardly and the prongs 22 of the terminal plug 23 are locked within the sockets 21 of the cylinder 16 against accidental removal, therefore,

making and breaking of the electrical connection is accomplished between the contact strips 31 and the lips 26 and these may be made of sufiiciently heavy material to prevent burning or damage by this action. The contact strips are provided with bifurcations 31a which are defined by upper and lower bars 31b and 310 and the lips 26 pass intermediate these bars and into the bifurcations where electrical contact is made. The electrical contact strips 31 are secured to the body by means of screws 32 and by this means also the cylinders 16 are secured against removal from the body rearwardly since the contact strips cover a portion of the cavities 12.

It will be seen in Figure 4 that the bolts 32 thread into a metal connector 33 carried by the body and this connector is provided with circuit connecting bolts 34 to which the conventional house wiring is secured.

A rear cover plate 35 is secured by bolt 36 to an internally threaded boss 37 carried by the body 10 and is removable for access to the rear of the outlet.

The body is provided with longitudinally extending wedge shaped stops 38 which bind the lips 26 when the cylinders are rotated to their normal position and prevent rotation beyond a position wherein the lips 26 are disposed longitudinally of the body 10. To prevent movement beyond the contact position shown in Figure 6 the rear end face of the cylinders 16 are provided with bosses 39 which are adapted to strike the stops 38 and limit the rotational movement of the cylinder 16 to substantially 90 degrees from the normal position.

Having thus described my invention, I claim:

1. An electric outlet comprising a body of insulation formed with a cavity open at its front end; a pair of opposed spaced contact strips carried by the body and diametrically arranged at the rear end of said cavity; a revolvable cylinder in said cavity and having a pair of contact bars disposed in spaced sockets for receiving and electrically contacting the prongs of a conventional electric plug; said contact bars having lips at the rear end of said cylinder for electrically connecting to said contact strips when said cylinder is rotated from its normal position; a plunger carried by the cylinder and radially movable therein into and out of locking relation with respect to a plug prong disposed for the time being in one said socket; and means operable when said cylinder is rotated to move said plunger inwardly to the locking position when the cylinder is rotated from its normal position.

2. An electric outlet comprising a body of insulation formed with a cavity open at its front and rear ends; a pair of opposed spaced contact strips carried by the body at opposite sides of the cavity and diametrically arranged at the rear end thereof; a revolvable cylinder in said cavity and having a pair of contact bars disposed in spaced sockets for receiving and electrically contacting the prongs of a conventional electric plug; said contact bars having radially extending diametrically opposed lips at the rear end of said cylinder and adapted to electrically connect to said contact strips when said cylinder is rotated substantially 90 degrees from its normal position; a plunger slidably carried by said cylinder and movable diametrically thereof into one said socket and through an aperture in one said contact bar into and out of locking relation with respect to a plug prong disposed within said socket; said cavity having an eliptical cross sectional configuration constituting a cam surface; and said plunger engaging said cam surface and thereby moved inwardly to the locking position when the cylinder is rotated substantially 90 degrees from its normal position.

3. An electric outlet comprising a body of insulation formed with a cavity open at its front and rear ends; said cavity being annular and having a reduced forward end portion and an enlarged rear end portion defined by an intermediate annular shoulder; a pair of opposed spaced contact strips carried by the body at opposite sides of the cavity and tangentially arranged at the rear end thereof; a revolvable cylinder in said cavity and having a pair of contact bars disposed in spaced sockets for receiving and electrically contacting the prongs of a conventional electric plug; said cylinder having a reduced forward end portion and an enlarged rear end portion defined by an intermediate shoulder and adapted to fit into said cavity with close tolerance for rotation therein; said contact bars having means for electrically connecting to said contact strips when said cylinder is rotated substantially 90 degrees from its normal position; a plunger slidably carried by said cylinder and movable diametrically thereof into one said socket through an aperture in one said contact bar into and out of locking relation with respect to a plug prong disposed within said socket; said cavity having a cam face cooperating with said plunger for moving said plunger inwardly to the locking position as the cylinder is rotated substantially degrees from its normal position.

4. In an electric outlet having a rotatable cylinder normally disconnected from an electrical circuit and adapted to receive and electrically contact the prongs of a conventional electric plug; means for securing said prongs in said cylinder comprising a plunger carried by the cylinder and movable radially therein into and out of locking relation with respect to a plug prong disposed for the time being therein; and means including a cam surface engageable with said plunger operable when said cylinder isrotated to move said plunger inwardly to the locking position as the cylinder is rotated substantially 90 degrees from its normal position.

References Cited in the file of this patent UNITED STATES PATENTS 1,657,004 Douglas Jan. 24, 1928 1,669,666 Laub May 15, 1928 1,774,230 Fagerlund Aug. 26, 1930 2,040,113 Von Holtz May 12, 1936 2,175,472 Kuhlman Oct. 10, 1939 2,215,316 Benander Sept. 17, 1940