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Publication numberUS3524029 A
Publication typeGrant
Publication dateAug 11, 1970
Filing dateJul 22, 1968
Priority dateJul 22, 1968
Publication numberUS 3524029 A, US 3524029A, US-A-3524029, US3524029 A, US3524029A
InventorsLaff Robert M
Original AssigneeLaff Robert M
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Keylock for electrical plugs
US 3524029 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)


United States Patent O 3,524,029 KEYLOCK FOR ELECTRICAL PLUGS Robert M. Latf, 2844 W. Gregory St., Chicago, Ill. 60625 Filed July 22, 1968, Ser. No. 746,603 Int. Cl. H01h 9/28; H01r 13/70 US. Cl. 200-44 6 Claims ABSTRACT OF THE DISCLOSURE A locking device comprising a housing having a compartment for enclosing an electrical plug, such as an appliance plug. A socket is mounted in the housing adjacent the compartment and is connected to a line cord which in turn is connected to a conventional electrical power source. The socket is adapted to receive the electrical plug. A key-actuated switch is mounted in the housing and interposed between the socket and power source for opening or closing the electrical circuit. The device is provided with means for permanently sealing the electrical plug within the housing compartment after the plug is inserted into the socket.

BACKGROUND OF THE INVENTION This invention relates generally to electrical connectors and circuit breakers with unauthorized-use preventing means. In particular, this invention pertains to a locking device for use with electrical appliance plug to prevent the unauthorized use of the appliances.

The closest prior art includes many devices for preventing the unauthorized use of appliances. These devices fall generally into two groups: 1) keylock receptacles for appliance cord plugs; and (2) plugs which contain key-operated disabling means. The devices of the first group have the disadvantage of being too cumbersome to use because whenever the appliance is to be operated, the plug must be removed from the receptacle and inserted into an electrical outlet. The second group of articles have the disadvantage of having to be substituted for the conventional plug normally found on the appliance, by either the manufacturer or the consumer of the appliance.

Therefore, an object of this invention is to provide a locking device which can be permanently connected to existing electrical plugs and which is easy to install and operate. A further object of this invention is to provide a locking device which can be economically manufactured and sold to the consuming public at a relatively low price. Additional objects of this invention will become manifest from the description, drawings, and claims.

SUMMARY OF THE INVENTION The device of this invention includes a housing containing a compartment for retaining a conventional electrical appliance plug and a socket mounted in the housing adjacent the compartment. The socket is electrically connected to a line cord which terminates in a conventional plug, and a key-actuated switch is interposed in the line between the socket and the cord. The switch is mounted in the housing with the keyhole being externally accessible. The appliance plug is inserted into the socket and is enclosed within the compartment provided for it. A cover is permanently secured to the compartment by drive screws or like means so that the appliance plug cannot be removed without destroying the locking device. When the device is connected to a nappliance, the applitime can be controlled by the key-operated switch so that the appliance can be secured against unauthorized use.

3,524,029 Patented Aug. 11, 1970 "ice BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawings, an appliancelocking device 10 of this invention is shown. This device includes a housing 12 having a compartment 14 for holding a conventional appliance plug, such as the threepronged plug 16 shown in FIG. 3. The housing 12 is preferably constructed of plastic or other suitable non-conductive material. The plug 16 is inserted into a socket 18 which is retained by a mounting plate 20. The cord 17 of the appliance is guided about a post 19 (see FIG. 3) and through an opening 21 in the housing 12. While a three-hole grounded type socket 18 and three-prong grounded type plugs 16 and 24 are shown, a two-hole ungrounded receptacle and ungrounded two-prong plugs may be employed for use with conventional two-pronged electrical plugs. In the latter system, two wire connections would be employed so that the ground connection 28 would be eliminated.

Referring to FIG. 3, it will be seen that the socket 18 is electrically connected to a line cord 22 which terminates in a plug 24. The socket 18 is connected to the line 22 by wire 26 and wire nut 30. A ground wire 28, shown in dotted lines in FIG. 3, extends between the socket 18 and the line 22, wire 28 being connected to the line 22 by a wire nut 32, also shown in dotted lines in FIG. 3.

Interposed between the socket and the line 22 is a switch 34. The switch is electrically connected to the socket at terminal 35 by wire 36 and is connected to the line 22 at terminal 38. The line cord 22 extends from the switch 34 about a post 37, through guides 39, into the compartment 14, and out of an opening 40 in the housing 12. The switch is actuated by a removable key 42, which is movable between open and closed positions. The switch is mounted within the housing 12 and the keyhole a is externally accessible. While any suitable key-operated switch may be employed in this invention, I have found that a 15 amp., to 277 volt A.C. single pole, lock-type switch manufactured by Pass and Seymour, Inc., Catalog No. ACDl1-L, gives satisfactory performance.

In FIG. 1 a cover 44 is shown for the compartment 14. After the appliance cord is connected to the socket 18, the cover 44 is placed on the ledges 45 provided therefor and is permanently fastened to the housing 12 by drive screws 46 and 48 or other suitable means. The drive screws 46 and 48 are inserted through openings 50 and 52 in the cover 44 and into holes 54 and 56 provided in the housing 12. The screws are tapped into place (as shown in FIG. 2) by a hammer or other suitable means, and once inserted cannot be removed without destroying the device. Only two screws are necessary in the illustrated embodiment because one end 58 of the cover is inserted under an overhanging portion 60 (FIG. 2) of the top of the portion of the housing adjacent the compartment 14.

Although drive screws are specifically disclosed, other suitable permanent fastening means may be employed. Also, the cover may be connected to the housing in other convenient ways than the one described hereinbefore.

While a specific embodiment of this invention has been described above, it should be understood that the invention is not limited thereto since many modifications may be made; and it is contemplated, therefore, to cover by 3 the following claims any such modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A locking device for an electrical plug comprising:

(1) a housing;

(2) a compartment in said housing for enclosing said elcetrical plug, said compartment having an opening in one side to insert said plug;

(3) a socket in said housing adjacent said compartment adapted to receive said electrical plug;

(4) means disposed in said housing for supporting said socket;

(5) an electric line cord connected to said socket, said cord extending out of said housing through an opening therein and terminating in a plug which is adapted to be inserted into a conventional electrical outlet;

(6) a key-actuated switch in said line intermediate said socket and said line cord plug, said switch being movable between open and closed positions and being mounted in said housing with the keyhole externally accessible;

(7) means for electrically connecting said socket with said switch so that when said switch is open said socket will be disabled;

(8) means for permanently sealing said electrical plug within said housing, said means including a cover which fits over the opening in said compartment for said appliance plug and at least one fastening means which is adapted to permanently fasten said cover to said housing.

2. The apparatus of claim 1 wherein the housing has a top portion which extends part way across the top; the means for supporting said socket is a wall located intermediate the ends of said housing and under said housing top portion so that a part of said housing top portion overhangs said wall, said wall supporting said socket so that the apertures in said socket for receiving the appliance plug face the plug enclosing compartment; and the cover which fits over the opening in said compartment has one end which extends under the overhanging part of said housing top portion and has an aperture adjacent the opposite end thereof, said housing having an aperture which corresponds to the aperture in said cover,

both of said apertures being adapted to receive said permanent fastening means.

3. The apparatus of claim 2 wherein said housing and said compartment cover each have a plurality of corresponding apertures which are adapted to receive a plurality of fastening means.

4. The apparatus of claim 3 wherein said housing and said compartment cover each have two corresponding apertures which are adapted to receive the fastening means and said fastening means comprises two drive screws.

5. The apparatus of claim 1 wherein the wall located in the housing describes a second compartment in said housing, said second compartment containing said keyactuated switch and the means for electrically connecting said socket to said switch, said second compartment also containing that part of said electric line cord which is connected to said socket.

6. The apparatus of claim 5 wherein the wall has an opening through which the electric line cord passes into the plug enclosing compartment, said line cord passing out of said plug enclosing compartment through said opening in said housing for said line cord.

References Cited UNITED STATES PATENTS 1,588,984 6/1926 Nutting 200-44 X 1,656,586 I/ 1928 Hemingway ZOO-44 2,643,787 6/1953 Rockman.

2,654,073 9/ 1953 Katz.

2,733,416 1/1956 Bualt.

2,759,159 8/ 1956 Teetor.

2,761,028 8/ -6 Teetor.

2,879,494 3/ 1959 Teetor.

2,955,272 10/ 1960 Gallaudo.

3,345,603 10/ 1967 Cohen.

ROBERT K. SCHAEFER, Primary Examiner H. J. HOHAUSER, Assistant Examiner US. Cl. X.R. 200-51; 307--114

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1588984 *Sep 3, 1925Jun 15, 1926William B NuttingSafety ignition lock
US1656586 *Apr 2, 1924Jan 17, 1928Electrolock Mfg CompanyElectric switch
US2643787 *Nov 24, 1950Jun 30, 1953Rockman Benjamin WLockable container for electrical connectors
US2654073 *Jul 29, 1950Sep 29, 1953Rudi KatzLocking device for electric plugs
US2733416 *Apr 5, 1955Jan 31, 1956 Locking device for use with electrical
US2759159 *Mar 7, 1955Aug 14, 1956Teetor Herman CElectric plug with disabling means
US2761028 *Mar 9, 1955Aug 28, 1956Teetor Herman CElectric plug with disabling means
US2879494 *Mar 9, 1955Mar 24, 1959Teetor Herman CElectric plug with disabling means
US2955272 *Mar 10, 1959Oct 4, 1960Juan GallardoTelevision and electric appliance lock
US3345603 *Sep 2, 1965Oct 3, 1967Alan Cohen StanleyElectrical plug key lock
Referenced by
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US4063110 *Jan 12, 1976Dec 13, 1977Glick Michael BSecurity device
US4135171 *Jun 2, 1977Jan 16, 1979The J. B. Foote Foundry Co.Cement mixer with switch harness
US4167658 *Mar 20, 1978Sep 11, 1979Sherman Robert SSafety and security outlet
US4247743 *Oct 10, 1979Jan 27, 1981Hinton David ODevice for preventing unauthorized usage of appliance
US4323762 *May 7, 1980Apr 6, 1982Ervin Ron EEnergy-temperature occupant monitor apparatus
US4463228 *Jan 7, 1983Jul 31, 1984Mcgill Manufacturing Company, Inc.Portable electrical switch and outlet unit
US4479688 *Dec 24, 1981Oct 30, 1984Jennings Gordon BWall outlet lock apparatus
US4482789 *Sep 27, 1982Nov 13, 1984Mcvey Jack LApparatus for preventing unauthorized use of electrically powered equipment
US4828452 *Sep 17, 1987May 9, 1989The Gradall CompanySingle engine excavator capable of railroad use
US5408924 *Feb 19, 1993Apr 25, 1995Food Sciences, Inc.Apparatus for the extraction of edible oils
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US5488208 *Sep 23, 1994Jan 30, 1996Seewald; GerhardMultiple electrical outlet box with locking cover and power interrupt switch
US7910833May 27, 2008Mar 22, 2011Voltstar Technologies, Inc.Energy-saving power adapter/charger
US7910834Jul 18, 2008Mar 22, 2011Voltstar Technologies, Inc.Energy saving cable assemblies
US7960648Oct 15, 2008Jun 14, 2011Voltstar Technologies, Inc.Energy saving cable assemblies
US7984852Sep 18, 2008Jul 26, 2011Liberty Plugins, Inc.Recharge electrical apparatus and method for electric vehicles
US8622759 *Jan 12, 2009Jan 7, 2014Dormina Uk LimitedElectrical fitting and safety cover
US20130003297 *Jun 29, 2011Jan 3, 2013Mrs. Julie Quyen Du-HensonGame Lock Box
DE3203925A1 *Feb 5, 1982Aug 18, 1983Triumph Adler AgVorrichtung mit zugentlastung zum halten eines flachbandkabels mit mindestens einem steckverbinder
DE3327087C1 *Jul 27, 1983Aug 16, 1984Franz LechnerAdaptor for protecting mains plugs against unauthorised apparatus use
DE3534457A1 *Sep 27, 1985Apr 2, 1987Schwoerer ArturPlug connector strip
U.S. Classification200/43.2, 439/133, 200/51.00R, 307/114, 200/43.4
International ClassificationH01R13/639
Cooperative ClassificationH01R13/639
European ClassificationH01R13/639