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Publication numberUS2733416 A
Publication typeGrant
Publication dateJan 31, 1956
Filing dateApr 5, 1955
Publication numberUS 2733416 A, US 2733416A, US-A-2733416, US2733416 A, US2733416A
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Locking device for use with electrical
US 2733416 A
Abstract  available in
Images(1)
Previous page
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Claims  available in
Description  (OCR text may contain errors)

Jan. 31, 1956 G. J. EVALT 2,733,415

LOCKING DEVICE FOR USE WITH ELECTRICAL PLUGS Filed April 5, 1955 LOCG DEVICE FOR USE WITH ELECTRICAL PLUGS George J. Evalt, Philadelphia, Pa. Application April 5, 1955, Serial No. 499,275

r 8 Claims. (Cl. 339-37) This invention relates to locking devices for use with electrical plugs to prevent unauthorized use of electrical appliances. 1

With the wide and increasing use of power tools, there is-an increasing need for such locking devices, especially in homes where children may be injured by power tools. The locking devices heretofore proposed for this purpose have not been satisfactory and have not been commercially acceptable for one reason or another, usually because they are of complex structure and are costly to manufacture and, therefore, must be sold at a high price.

. When it is considered thatfan owner of power tools re quires a locking device for each tool, and many persons now own various power tools, it may be appreciated that the cost of the locking device is a significant factor. A need has existed for a simple and inexpensive locking device, in which cost is minimized without sacrificing effectiveness to prevent children from plugging in power tools in the home.

The principal object of the present invention is to provide a simple, inexpensive and commercially practical locking device to meet this need.

Another object of the invention is to provide a locking device which can be made practically entirely of plastic material, white metal, or any other desired material.

A further object of the invention is to provide a looking device which is easy to use and yet provides adequate protection against the unauthorized use of electrical appliances such as power tools.

7 Other objects and features of the invention will be apparent from the detailed description to follow.

In the accompanying drawing:

. Fig. 1 is a perspective view of one embodiment of the locking device provided by this invention, showing an electrical plug in association with the device;

Fig. 2 is a side elevational view of the device and associated plug; I

.Fig. 3 is a sectional plan view taken along line 3-3 of Fig. 2 showing the device in the unlocked condition;

Fig. 4 is a view similar to Fig. 3 showing the device in the locked condition;

Fig. 5 is a transverse sectional view taken along line 5-5 of Fig. 3;

Fig. 6 is a sectional view of a modified form of the device, taken along a central vertical plane longitudinally of the device; and

Fig. 7, is a cross-sectional view of the same device taken along the transverse vertical plane indicated by line 77 of Fig. 6. A

Referring moreparticularly to the drawing, as shown in Fig. 1, the locking device 10 preferably comprises a rectangular casing comprising a main part 11 and a cover 12. While these parts may be formed of any suitable material, they are preferably formed of plastic material. Any suitable arrangement may be employed to effect secure attachment of the cover 12 to the main casing part 11. For example,.the main part 11 may be provided with dove-tail recesses 13, and the cover 12 may be pro- .7 nited States Patent 0 2 vided with projections 14 which are forced into the recesses,

Figs. 3 and 4 are effectively plan views with the cover 12 removed. As may be seen in these figures, the casing has openings 15 to receive the prongs 16 of a conventional electrical plug 17. The most common electrical plug has two prongs and, therefore, the casing 10 is shown with two openings to receive. the prongs of such a plug. However, the device may be adapted for use with plugs having any number of prongs, e. g. plugs having three prongs.

The device provided by. the invention effects locking of an electrical plug by locking engagement of at least one of the plug prongs through the aperture which is present in each of the prongs. In the embodiments illustrated, which are adapted for use with plugs having two prongs, locking is efiected through the apertures of both prongs, and therefore two locking members are provided as hereinafter described. However, the invention contemplates the provision of one or more locking members to elfect locking through one or more of the prongs of an electrical plug.

As shown in Figs. 3 and 4, a pair of opposed locking members 18 and 19 are arranged within the casing 10 for translational movement from outer positions to inner positions to effect locking action. the casing has opposed recesses 20 and 21 to slidably support the locking members 18 and 19 which are shaped as shown. These members are urged to their outer positions, as shown in Fig. 3, by a helical spring 22, the end portions of which are seated in recesses 23 and 24, of the locking members. Manual elements 25 and 26, in the form of button-like projections, are provided on the locking members 18 and 19 and they extend through openings 27 and 23 in the opposed sides of the casing.

The locking action is effected by means of pins 29 and 30 provided respectively on the locking members 18 and 19. As may be clearly seen in Fig. 3, these pins are in opposed relation to one another and they are aligned with the apertures 31 of the inserted plug prongs 16. When the locking members 18 and 19 are moved to the inner positions, as shown in Fig. 4, the pins 29 and 30 are projected through the prong apertures 31. Recesses 32. and 33 serve to receive the end portions of the pins 29 and 39 so as to protect them against shearing in the event that a pulling force is exerted on the plug 17. The movement of the locking members to their inner locking positions is effected simply by exerting a squeezing force with two fingers on the manual elements 25 and 26.

The locking members 18 and 19 are locked in their inner positions by key-releasable detent means. As

shown in Figs. 3 and 4, a spring detent finger 34 has one end secured to thelocking member 18 at 35 as by riveting or by means of a screw. The said end is seated in a shallow recess of member 18 to prevent turning of the finger 34 which extends transversely between the two locking members. The other end 36 of finger 34 is shaped for engagement behind stationary detent elements 37 formed integrally with the casing. As best shown in Fig. 1, the adjacent end of the casing has an opening 38 to receive a key 39 having opposed projections 40 thereon. The inner portion of the casing adjacent the opening 38 is constructed to provide a space 41 through which the key projects, and the raised central section of the casing has a recess 42 to receive the end of the key and to serve as a bearing support when the key is turned. This section of the casing also has recesses 43 and 44 to serve as retaining guides for the detent finger 34.

When the locking members 18 and 19 are moved to their inner locking positions, the spring finger 34 is deflated sufiiciently so that the portion 36 rides over the detent projections 37 and falls behind them. The plug The main part 11 of.

position, whereupon spring 22 moves the locking members lfiand 19 to their outer positions shown in Fig. 3.

As previously mentioned the device may be adapted to engage only one of the plug prongs. In such case, locking member 19 could be eliminated and one end of spring 22 would engage a part of the casing. Detents 37 would then be provided on the casing.

From the foregoing description, it will be seen that the device provided by this invention is extremely simple in construction and is easy to assemble. The device comprises a minimum of individual parts ideally suited for mass production. All of these parts can readily be formed of plastic material with the exception of the spring, the detent finger and the engaging pins, which may be simple metal parts.

Furthermore, in the form of the device shown in Figs. 1 to 5, the simple key 39 serves for unlocking and no key barrel is needed. Such device is adequate for most purposes, such as the protection of small children against injury by power tools.

Figs. 6 and 7 show a modified form of the device which is identical with the first described embodiment but is provided with a lock barrel 45 of conventional form having a rotatable cylinder 46 which is turned by key 47 The barrel 46 carries an element 48 which serves to deflect the spring detent finger 34a. Apart from this modification, this embodiment is the same as that previously described, and the parts are designated by similar reference numerals with the sufiix a. This modified form of the device may be employed where it is desired to provide positive insurance against unlocking of the device by older persons Who might tamper with the device.

While the device is shown at a portable unit, it could be built into a stationary structure, such as a wall socket. Thus, the device could be provided in place of one of the usual receptacles of a multi-receptable wall unit. In such case, the casing would be built into the wall unit or would be adapted to be inserted therein.

Although exemplary embodiments have been illustrated and described for the purpose of disclosure, it will be understood that the invention is not limited thereto but contemplates such further embodiments as may be provided within the scope of the invention.

I claim:

1. A locking device for use with an electrical plug having prongs, comprising a casing having openings to receive the prongs, locking means within said casing movable translationally from an outer position to an inner position to lockingly engage one of the inserted prongs, spring means for normally retaining said locking means in the outer position, manual means for moving said locking means to the inner position, and key-releasable detent means for holding said locking means in the inner position.

2. A locking device for use with an electrical plug having prongs, comprising a casing having openings to 'receive the prongs, a locking member within said casing movable translationally from an outer position to an inner position to lockingly engage one of the inserted prongs, spring means for normally retaining said locking member in the outer position, a manual element on said locking member extending externally of said casing for moving said locking member to the inner position, and key-releasable detent means for holding said locking member in the inner position.

3. A locking device for use with an electrical plug having prongs, comprising a casing having openings to receive the prongs, a locking member within said casing movable translationally from an outer position to an inner position to lockingly-engage one of the inserted prongs,

spring means for normally retaining said locking member in the outer position, a manual element on said locking member extending externally of said casing for moving said locking member to the inner position, and a keyreleasable spring detent element for holding said locking member in the inner position.

4. A locking device for use with an electrical plug having a plurality of apertured prongs, comprising a casing having openings to receive the prongs, a plurality of locking members within said casing each having a pin thereon to enter the aperture of one of the prongs, said members being movable translationally from outer positions to inner positions to efiect entry of the pins on said members into the apertures of the prongs, spring means for normally retaining said members in their outer positions, a manual element on each of said members extending externally of said casing for moving each member to its inner position, and key-releasable detent means for holding said members in their inner positions.

5. A locking device for use with an electrical plug having a pair of apertured prongs, comprising a casing having openings to receive the prongs, a pair of opposed locking members within said casing each having a pin thereon to enter the aperture of one of the prongs, said members being movable translationally from outer positions to inner positions to effect entry of the pins on said members into the apertures of the prongs, spring means for normally retaining said members in their outer positions, a manual element on each of said members extending externally of said casing for moving each member to its inner position, and key-releasable detent means for holding said. members in their inner positions.

6. A locking device for use with an electrical plug having a pair of apertured prongs, comprising a casing having openings to receive the prongs, a pair of opposed locking members within said casing each having a pin thereon to enter the aperture of one of the prongs, said members being movable translationally from outer positions to inner positions to effect entry of the pins on said members into the apertures of the prongs, spring means for normally retaining said members in their outer positions, a manual element on each of said members extending externally of said casing for moving each member to its inner position, and a key-releasable spring detent finger secured to one of said members and engageable with the other member for holding said members in their inner positions.

7. A locking device for use with an electrical plug having a pair of apertured prongs, a rectangular casing having openings at one end to receive the prongs and having key receptacle means at the other end, a pair of opposed locking members within said casing adjacent the opposed sides thereof, inwardly-extending pins on said members aligned with the apertures of the inserted prongs, said members being movable translationally from outer positions to inner positions to efiect entry of said pins into said apertures, spring means arranged between said members to normally force them apart and to retain them in their outer positions, a manual element on each of said members extending through the adjacent side of said casing for moving each member to its inner position, and key-releasable detent means adjacent said other end of said casing for holding said members in their inner positions.

8.'A locking device for use with an electrical plug having a pair' of apertured prongs, a rectangular casing having openings at one end to receive the prongs and having key receptacle means at the other end, a pair of opposed locking members within said casing adjacent the opposed sides thereof, inwardly-extending pins on saidmembers aligned with the apertures of the inserted prongs, said members being movable translationally from outer positions to inner positions .to effect entry of said pins into said apertures, spring means arranged between said members to normally force them apart and to retain 5 them in their outer positions, a manual element on each of said members extending through the adjacent side of said casing for moving each member to its inner position, and a key-releasable spring detent finger secured to one of said members and engageable with the other member 5 2654073 for holding said members in their inner positions.

2,643,787 Rockman June 30, 1953 Katz Sept. 29, 1953 2,664,734 McEneaney Jan. 5, 1954 FOREIGN PATENTS 699,833 Germany Dec. 7, 1940

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2643787 *Nov 24, 1950Jun 30, 1953Rockman Benjamin WLockable container for electrical connectors
US2654073 *Jul 29, 1950Sep 29, 1953Rudi KatzLocking device for electric plugs
US2664734 *Jun 2, 1949Jan 5, 1954Mceneaney Hugh GLocking device for electrical connections
DE699833C *Jun 26, 1938Dec 7, 1940Alexander Pichlerdfunkgeraeten oder elektrischen Apparaten an das Stromnetz mittels eines Steckers durch Unberufene
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2844805 *Feb 17, 1956Jul 22, 1958Darrell George HPlug locking and protecting device
US2946841 *May 7, 1957Jul 26, 1960Wagner Charlie MElectrical insulator contamination shield
US3416123 *Feb 28, 1966Dec 10, 1968James L. HuseboPlug block
US3524029 *Jul 22, 1968Aug 11, 1970Laff Robert MKeylock for electrical plugs
US3543544 *Aug 19, 1968Dec 1, 1970Efston Evan NLocking device for use with an electric plug
US3662320 *Dec 24, 1970May 9, 1972Marx Arthur JPlug lock
US4060297 *Nov 29, 1976Nov 29, 1977Marshall Bruce HPlug cap
US4413488 *Dec 22, 1980Nov 8, 1983Iowa State University Research Foundation, Inc.Electrical appliance lock
US4445738 *Sep 29, 1982May 1, 1984Wiencke Erich KLocking device for electrical plugs
US4494143 *Mar 29, 1982Jan 15, 1985Rca CorporationTelevision descrambler with security plug having folded flexible printed circuit board providing tier tag memory
US4533189 *Oct 21, 1983Aug 6, 1985General Dynamics Pomona DivisionZero insertion force connector
US4563048 *Jan 11, 1985Jan 7, 1986Im Kwan SLocking device for an electrical plug
US4566297 *Jul 22, 1983Jan 28, 1986Hawley Robert CElectrical plug locking device
US4640107 *Dec 12, 1985Feb 3, 1987Slade Luman CSafety lock apparatus for an electrical plug
US4972690 *Feb 14, 1990Nov 27, 1990Sullivan Daniel J OLocking cassette case
US5055057 *Oct 9, 1990Oct 8, 1991Boyer Paul LElectric plug lock
US5169326 *Feb 3, 1992Dec 8, 1992Werner Theodore JElectric plug lock
US5176527 *Dec 14, 1990Jan 5, 1993E. I. Du Pont De Nemours And CompanyApparatus for preventing the use of an electrical device
US5277599 *Oct 23, 1992Jan 11, 1994Nilson Donald LLockable container for securing an electrical connector
US5288239 *Nov 12, 1992Feb 22, 1994Johnson Jack LDevice for preventing the theft of electrical appliances
US5330361 *Aug 20, 1993Jul 19, 1994Brend Gary WElectrical plug locking device
US5507656 *Oct 28, 1994Apr 16, 1996Ales; Matthew W.Electrical male plug lock
US5666829 *Feb 20, 1996Sep 16, 1997Aikens; IsaacPlug lock
US6142797 *Nov 10, 1999Nov 7, 2000Bailey; CraigElectrical plug locking device
US6508654 *Mar 13, 2002Jan 21, 2003Eliezer TatzMale electrical plug locking device
US6773277 *Dec 31, 2002Aug 10, 2004Antoine IssaSecurity cap for electrical plugs
US7497705Sep 12, 2007Mar 3, 2009Master Lock Company LlcLockout device
Classifications
U.S. Classification439/134, 70/57
International ClassificationH01R13/639
Cooperative ClassificationH01R13/6397
European ClassificationH01R13/639E