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Publication numberUS3575684 A
Publication typeGrant
Publication dateApr 20, 1971
Filing dateAug 22, 1969
Priority dateAug 22, 1969
Publication numberUS 3575684 A, US 3575684A, US-A-3575684, US3575684 A, US3575684A
InventorsMcintyre Charles S
Original AssigneeMcintyre Charles S
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrical safety plug assembly
US 3575684 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

[45] Patented United States Patent Charles S. Mclntyre R. 4, Box 73B, Greenfield, Ind. 46140 [21] AppLNo. 852,181

[22] Filed Aug. 22, 1969 Apr. 20, 1971 [72] Inventor [54] ELECTRICAL SAFETY PLUG ASSEMBLY 3 Claims, 3 Drawing Figs.

[52] US. Cl 339/42, 339/170 [51] Int. Cl 11011 13/44 [50] Field of Search 339/42, 170

[56] References Cited UNITED STATES PATENTS 2,396,901 3/ 1946 Tiffany 339/42 2,459,032 1/ 1949 Korth 339/ 1 70X 3,167,373 1/1965 Kostich 339/42 FOREIGN PATENTS 1,353,307 l/ 1964 France 339/42 658,827 4/1938 Germany 339/42 Primary Examiner-Marvin A. Champion Assistant Examiner-Terrell P. Lewis Attorney-Woodard, Weikart, Emhardt and Naughton ABSTRACT: Disclosed is an electrical plug for use in a conventional, electrical plu'g-in outlet which can be attached to an electrical appliance cord, for example, or used as an adapter. Both types have an insulating sheath which is spring biased to a position covering the current-carrying prongs of the plug and which retreats, baring the prongs, as it is inserted into an electrical outlet.

VJ. I,

'PATENTEU meow 3575584 LNVENTOR CHARLES M INTYRE BY UMAMAMMZM @Mm ATTORNEYS ELECTRICAL SAFETY PLUG ASSEMBLY BACKGROUND OF THE INVENTION Various types of lock-in or latch-in electrical plugs are well known in the prior art, the object of these devices being, primarily, to prevent plugging or unplugging or dangerous tampering with an electrical connection by children. These devices do not protect against shock caused by accidental SUMMARY OF THE INVENTION The inventive concept is that of a pronged electrical plug having a cavity in which a prong-insulating sheath is free to move, the sheath being biased into a position shielding the prongs and retreating to bare the prongs only as they are inserted into an electrical outlet.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an end view of a safety plug assembly embodying the present invention.

FIG. 2 is a side sectional view of the plug assembly taken generally along the line 2-2 of FIG. I.

FIG. 3 is a side sectional view, similar to FIG. 2, but illustrating a modified form of the assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to FIGS. 1 and 2, the structure includes a housing fomted by two matching halves, a and 10b which are held together by screws 11 (FIG. 2) or other suitable fastening means. The housing may be molded from any suitable material, such as nylon or a similar plastic material.

The mating halves of the housing are undercut to provide an interior cavity 12 (FIG. 2) and an insulating sheath or block 13 is slidably received within the cavity. As may best be seen in FIG. 1, opposite sides of the'sheath 13 are provided with longitudinal ribs [3a which fit within a groove I4 formed in the housing.

The sheath 13 is generally U-shaped in configuration and is preferably formed of nylon or other suitable durable material. Registering abutments l7 and 18 extended from the housing halves and across the transverse portion of the sheath to limit extension of the sheath from the housing. An indentation 19 in each of the abutments l7 and 18 fon'ns a seat for a pen 21. The pen 21 extends freely through an aperture in the transverse portion of the sheath l3 and extends longitudinally of the housing to bottom in an indentation formed in a boss 22 (FIG. 2) extending from the sidewall of each of the mating housing halves (only the boss 22 of the housing portion 10a being shown in FIG. 2). I

Resilient means, taking the form of the compressions spring 23 encircles the guide pen 21 and extends from a seat 24 in the abutment 22 to bear against the transverse portion of the sheath l3, urging the sheaths into its maximum extended position. Extending through the legs of the sheath 13 are electrical conductors taking the form of prongs 26 and 27. The inner ends of the prongs extend through longitudinal slots 28 and 29 formed in the housing halves and abut against shoulders 31 formed in the abutments 22. The inner ends of the exposed prongs,

the prongs are adapted to have electrical wiring connected to them by means of the screws 32, the" wiring being accommodated in aperture 33 in the housing-end.

In operation, when the parts are in their positions of FIG. 2, all but the tip portion of the prongs are masked by the sheath 13. When the prongs are inserted into an electrical outlet, the face of the outlet engages the ends of the leg portions of the sheath moving it toward its retracted position within the cavity In the housing, this movement taking place against the force exerted by the spring 23. As the plug is inserted in an electrical outlet, the prongs are covered, during insertion, by the sheath andthe possibility of bridging the prongs by the hand or fingers of the user is eliminated.

Referring to FIG. 3 a modified form of the structure is shown, this structure difiering from that of FIGS, 1 and 2 only in that the inner ends of the prongs 41 and 42 are adapted for receiving and holding prongs from an adjacent conventional plug which may be inserted through the apertures 43 and 44 in the housing. In FIG. 3 parts identical to those in FIG. 2 are given the same reference numerals.

Rivetted to the offset inner ends of the prongs 41 and 42 are somewhat resilient leaves 46 and 47, these cooperating with the extendingends 41a and 42a of the prongs to grasp the prongs or other conductors inserted between them. A tooth 48, struck from each of the prongs, serves to retain the inserted conductors. The operation of this form of the device is the same as that of the structure of FIGS. 1 and 2, the structure of FIG. 3 serving merely as an adapter for interposing between a conventional plug and a conventional electrical outlet receptacle.


I. An electrical safety plug adapted to plug into an electrical outlet, said plug comprising a housing, electrical prongs rigidly supported adjacent their inner ends within the housing and extending from the exterior thereof adapted for insertion into an electrical outlet, said housing having acavity therein through which said prongs extend, an insulating sheath slidably received within said cavity and moveable therein parallel to said prongs from a retracted position wherein the sheath is within the housing to an extended position wherein the sheath extends from the housing to mask all but the tip portions of said prongs, said insulating sheath being generally U-shaped' in configuration with the legs of the U enclosing said prongs, said housing having an abutment extending into said cavity and engageable with the base portion of said U-shaped sheath to limit extension of the sheath from the cavity and define said extended position thereof, and resilient means within the housing urging the sheath into its said extended position, whereby as the prongs of said plug are inserted into an electrical outlet said sheath is moved from its extended toward its retracted position against the force exerted by said resilient means to prevent exposure of any substantial portion of said prongs during insertion or removal of the plug prongs with respect to an electrical receptacle. 1

2. An electrical safety plug as claimed in claim I in which the supported inner end portions of said prongs are adapted for attachment of electrical wiring.

3. An electrical safety plug as claimed in claim I in which the supported inner end portions of said prongs are adapted to

Patent Citations
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US2396901 *Jan 2, 1943Mar 19, 1946Lockheed Aircraft CorpDetachable plug
US2459032 *Oct 3, 1946Jan 11, 1949Sam W LevineElectrical connector
US3167373 *May 14, 1962Jan 26, 1965Northrop CorpMulti-pin connector with protective shield
*DE658827A Title not available
FR1353307A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3737835 *Jul 21, 1971Jun 5, 1973Clement CSelf-ejecting line plug
US3754205 *May 19, 1971Aug 21, 1973Lenmark Enterprises IncProtected connector plug
US3839697 *Jan 24, 1973Oct 1, 1974Burndy Electra SpaConnector for automatically establishing electric connections between vehicles, particularly between railroad vehicles
US4128739 *Sep 13, 1977Dec 5, 1978Communications Technology CorporationFront tap shoe for mounting on test block for telephone conductor pairs
US4340267 *Jun 13, 1980Jul 20, 1982Tokuji NukagaSafety electrical plug
US4959609 *Jan 23, 1989Sep 25, 1990Manfred ProkoppElectrical connecting apparatus for an electrical or electronic testing unit
US5030119 *Sep 27, 1989Jul 9, 1991Safe Care Products, Inc.Safety plug
US5076656 *Nov 17, 1989Dec 31, 1991Briggs Robert CHigh precision optical fiber connectors
US5166995 *Jan 7, 1992Nov 24, 1992Amp IncorporatedPolarized connector
US5518411 *Jun 1, 1994May 21, 1996Belleci; Sal J.Electrical plug with retractable prong shield
US5599196 *May 1, 1995Feb 4, 1997Powell; Patti J.Electrical plug safety cover
US6106311 *Apr 9, 1999Aug 22, 2000Scientific-Atlanta, Inc.Electrical connector including spring mechanism for covering leads in open position
US6767228 *May 31, 2002Jul 27, 2004Irwin G. KatzInternal safety cover and method to prevent electrical shock
US7517235Dec 28, 2006Apr 14, 2009General Electric CompanyPress fit connection for mounting electrical plug-in outlet insulator to a busway aluminum housing
US8162697Dec 10, 2010Apr 24, 2012Amphenol Australia Pty LtdTip-sleeve silent plug with 360 sliding ring contact
US8277237Oct 2, 2012Nicholas CherishElectrical plug having retractable prongs
US8702435 *Nov 12, 2009Apr 22, 2014Sony CorporationPlug, plug receptacle and electric power supplying system
US8770994Sep 25, 2012Jul 8, 2014Brett FaganChild resistant safety plug accessory
US20080160812 *Dec 28, 2006Jul 3, 2008Bagewadi Sandeep PPress fit connection for mounting electrical plug-in outlet insulator to a busway aluminum housing
US20110237098 *Nov 12, 2009Sep 29, 2011Shigeru TajimaPlug, plug receptacle and electric power supplying system
US20150364866 *Aug 24, 2015Dec 17, 2015Brainwave Research CorporationElectrical cord plug eject mechanism
WO2013061560A1 *Oct 22, 2012May 2, 2013Yazaki CorporationConnector
U.S. Classification439/140
International ClassificationH01R13/453
Cooperative ClassificationH01R13/4538
European ClassificationH01R13/453H