US 3161450 A
Description (OCR text may contain errors)
Dec. 1964 B. A. GOODENOUGH 3, 0
PILFERPROQF WALL PLUG Filed Oct. 17. 1961 IN VEN TOR. BRADFORD A.Goooslvauan 3%M United States Patent 0 3,161,450 PILFERPROOF WALL PLUG Bradford A. Goodenough, Athens, Ga., assignor to General Time Corporation, New York, N.Y., a corporation of Delaware Filed Oct. 17, 1961, Ser. No. 145,577 1 Claim. (Cl. 339--80) This invention relates to electrical appliance plug and socket connections and more particularly to a securing assembly for locking the plug and socket together.
The conventional electrical cord plug is easily inserted into or removed from a receptacle socket so as to provide for quick and convenient connection with a source of electrical power. This ease in making electrical connections is not, however, an advantage when the appliance carrying the cord is located in a hotel, motel or the like and subject to pilferring. Also, accidental removal of a plug by children is a problem where power failure in appliances such as freezers or refrigerators may cause food spoilage. Furthermore, a safety problem with children is partial removal of a plug leaving exposed bare, current carrying prongs.
It is an object of the present invention to provide a locking assembly for an appliance cord plug which will lock the plug in electrical engagement with a receptacle socket.
It is an additional object of the invention to provide a locking assembly of the above type which can be used with conventional electrical receptacles.
It is an overall object of the present invention to provide a locking assembly of the aforementioned type which is simple and inexpensive to manufacture, easily installable and durable in use, while providing protection against pilferring or accidental removal of a cord plug.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:
FIGURE 1 is an exploded perspective showing the plug and locking means constructed in accordance with the present invention;
FIG. 2 is a perspective showing the parts assembled together;
FIG. 3 is a vertical section taken along line 3-3 in FIG. 2; and
FIG. 4 is an enlarged face view of the head for the fastening screw.
While the invention will be described in connection with a preferred embodiment, it will be understood that I do not intend to limit the invention to such embodiment, on the contrary, it is intended to cover all of the alternatives, modifications and equivalents, falling within the spirit and scope of the invention as defined by the appended claim.
Turning to the drawings, shown in FIG. 1 is a preferred embodiment of the present invention for securing a plug 10 to a receptacle 11. The plug 10 is carried on a conventional electrical cord 12 having an appliance (not shown) connected thereto. For providing an easily accessible source of electrical power, the duplex receptacle 11 has sockets 14, 15. Slidably engageable into these sockets are a pair of conductive prongs 16 projecting from the plug face 17.
The receptacle 11 is mounted in the wall 18 and has a conventional escutcheon plate 19 with appropriate aper- 3,161,450 Patented Dec. 15, 1964 ice tures 20, 21 exposing the sockets 14, 15. For fastening the escutcheon plate 19 to the receptacle 11, a fastening screw 22 is passed through an escutcheon plate opening 24 and threaded in a tapped aperture 25.
In accordance with the present invention, the plug 10 includes an integral extension which lies fiat against the escutcheon plate overlying the screw opening so that the screw seems to lock the plug in place. In the preferred embodiment, the assembly 26 takes the form of a reinforced integral tab 28 locked to the receptacle 11 by the screw 22 having a non-backout head 29. The plug tab 28 is preferably molded integrally with the plug 11 so as to constitute an offset extension of the plug face 17. The screw 22 is passed through an opening 30 in the tab 28, and upon rotation of it, the tab is drawn against the receptacle. As can be observed in FIG. 3, the screw head 29 has a screwdriver slot 31 of the ordinary type except for the diagonally opposite half sides 32, 33 of the slot being chamfered or beveled. The chamfering is done so that a screwdriver or like implement can be used to tighten the screw 22 down, but the same implement is ineffective to backout the screw. Consequently, the plug cannot be removed without special effort such as drilling out the screw and therefore, as long as the appliance and attendant cord are intact, the appliance cannot be carried away.
Explaining the tab 28 construction in more detail, it is reinforced with a backing plate 35 having a periphery following the outlines of the tab 28 and is carried behind the tab in a transverse notch or recess 36. Because the plug and tab are generally constructed of pliable material, for example rubber, the backing plate 35 provides the necessary rigidity for the tab to assure that the latter is not, viewing the installation in FIG. 2, bent around and the plug 16 unlocked from the receptacle 11 by tearing the tab. Furthermore, the backing plate 35 allows the holding force from the tightening of the screw 22 to be distributed over all the tab.
The installation of the plug of the present invention is simple. One only need remove the ordinary screw retaining the escutcheon plate 19 in place, electrically engage the plug 16 in either socket 14 or 15, pass the screw 22 through tab opening 30 and thread the screw in the receptacle tapped aperture 25. Because of the non-backout head 29, once tightened, the screw cooperates with tab 23 to lock the plug 10 to the receptacle 11.
It is clear that the present invention performs a useful function in guarding either intentional or accidental removal of cord plugs. This is achieved while maintaining simplicity and economy in manufacture and ease in installation with commonly used electrical outlet receptacles.
It is not necessary to replace the regular escutcheon plate and since the locking feature may be optionally used, appliances equipped as here described need not be made special but may be sold to the entire market.
I claim as my invention:
For use with an electrical receptacle having a tapped aperture and an outlet socket, a lockable cord comprising, in combination, a molded plug on the cord having a face with projecting conductive prongs slidable into the outlet socket, a tab molded integrally with said plug to constitute an offset extension of said plug face, a rigid backing plate for stiffening said tab for withstanding transverse bending forces applied to said plug, said plate being carried in a transverse recess in said plug behind said tab,
and a screw fastener with a non-backout head, said screw passing through an opening in said tab and said backing plate and threaded into the receptacle tapped aperture so that upon rotation of said screw said tab and backing plate are drawn against the receptacle to lock said plug in the socket with said backing plate distributing the holding forces effected by said screw to prevent pivoting of the plug upon said prongs slidably engaged within the socket.
References Cited in the file of this patent UNITED STATES PATENTS Brooks Oct. 1, 1872 Eisner Oct. 11, 1949 Dalton Sept. 25, 1951 Johnson Nov. 10, 1953 Kobler et al Jan. 3, 1956