US3891289A - Lockable electrical outlet - Google Patents

Abstract

An electrical outlet for the reception of both grounded and ungrounded plugs. A locking member manually positionable within an outlet housing and having surfaces thereon for biasing the contact finger assemblies of the housing into locking engagement with each of the plug prongs preventing inadvertent plug separation.

Description

United States Patent 1191 Hanke LOCKABLE ELECTRICAL OUTLET [76] Inventor: Edward F. Hanke, 550 E. 33rd St.,

Eugene, Oreg. 97405 [22] Filed: Feb. 7, 1974 21 App]. No.: 440,397

[52] US. Cl. 339/14 P; 339/75 P [51] Int. Cl HOlr 13/54 [58] Field of Search..... 339/14 R, 14 P, 74 R, 75 R,

339/75 P, 75 M, 75 MP, 270 R, 274

[56] References Cited UNITED STATES PATENTS 3,559,156 l/l97l Coley 339/274 X 3,588,786 6/1971 Alfiero 339/75 M 1 June 24, 1975 1/1973 Warner et a1. 339/74 R 7/1973 lversen 339/75 M Primary ExaminerR0y Lake Assistant ExaminerNeil Abrams Attorney, Agent, or FirmJames D. Givnan, Jr.

[5 7] ABSTRACT An electrical outlet for the reception of both grounded and ungrounded plugs. A locking member manually positionable within an outlet housing and having surfaces thereon for biasing the contact finger assemblies of the housing into locking engagement with each of the plug prongs preventing inadvertent plug separation.

2 Claims, 8 Drawing Figures SHEET PATENTED JUN 24 I975 LOCKABLE ELECTRICAL OUTLET BACKGROUND OF THE INVENTION I The present invention concerns electrical outlet or receptacle structure within which may be locked a conventional plug of the two or three prong type. Said structure may be embodied in a wall mounted outlet or an outlet located at the end of an extension cord.

Within the prior art are electrical outlet embodiments which have the stated purpose of locking standard or modified electrical plugs in place therewithin. An intended objective of such outlets is to prevent accidental separation of the plug member while simultaneously providing for a secure electrical connection between the plug prongs and the cooperating electrical contacts. Examples of the prior art structures are found in US. Pat. Nos. 2,872,654 and 3,710,304.

Known receptacle structure, while directed toward objectives similar to the present invention, are complex incurring a high cost of manufacture as well as questionable reliability. Further, no provision is made for locking all of the inserted prongs of the plug within the electrical outlet.

SUMMARY OF THE INVENTION The present invention is embodied within components, few in number, which are desirably of simplified cast or molded construction to provide a lockable outlet of low manufacturing cost and yet of high reliability. A unitary locking member includes a threaded portion with a pair of opposite camming surfaces and an end surface for movement into and out of biasing contact with yieldable outlet contacts. Accordingly said contacts are each biased into firm engagement with their respective prongs of an inserted plug member. Said flexible contacts, in addition to being in locked engagement with said prongs, are held thereagainst to affect a positive electrical connection therebetween. Since the contacts are displaced into prong engagement, wear of the contact surfaces which normally results in a loose connection, is compensated for.

Important objects of the present invention include the provision of a receptacle for the reception of two or three prong plugs wherein a one-piece member serves to bias flexible contacts into gripping engagement with each prong of a plug; an outlet of simplified construction and highly reliable operation; an outlet of low manufacturing cost; an outlet for the reception and locking in place of all conventional two or three prong plugs with the capability of locking each of said prongs against accidental separation; an outlet constructed primarily of molded dielectric material with a minimum of conductive components to provide a high degree of safety.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a side elevational view of an outlet embodying the present invention with a conventional plug member disengaged therefrom,

FIG. 2 is a plan view of FIG. 1,

FIG. 3 is an exploded side elevational view of the outlet,

FIG. 4 is an elevational view of the outlet locking member rotated clockwise through 90 from its FIG. 3 position,

FIG. 5 is a horizontal sectional view taken approximately along line 5-5 of FIG. 1,

FIG. 6 is a side elevational view of the outlet main housing with fragments broken away and with a terminal cap removed,

FIG. 7 is a side elevational view of a modified form of the invention in place within a wall outlet, and

FIG. 8 is an elevational view taken from the right hand side of FIG. 7 and terminating at the horizontal centerline of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With continuing attention to the accompanying drawings, the reference numeral 1 indicates generally an electrical outlet embodying one form of the present invention, said outlet being located at the end of an electrical cord 2. Indicated at 3 is a conventional threeprong electrical plug having a pair of prongs or blade contacts 4 and a ground prong 5. As will be later understood, the present outlet is equally adaptable to the reception of plug members'having only a pair of blade contacts.

Outlet 1 comprises a main housing 6 having a cap member 7 both formed of a suitable dielectric material of a type lending itself to economical molding operations. Machine screws 8 extend through housing 6 and into cap 7 removably mounting the latter to housing 6 to permit access to concealed terminals. A ring member at 10 is disposed about the forward end of the main housing and includes flanges apertured for the passage of said machine screws. Said ring is received within an inset area 6A extending about housing 6.

With joint attention to FIGS. 3 and 5, a pair of contact assemblies are indicated at 14 each adapted to receive the inserted blade contact of a conventional plug. The following brief description of one outlet contact assembly is equally applicable to the remaining contact assembly. Spring contact fingers 15 are disposed within a cavity 17 in housing 6 and jointly terminate rearwardly in a binding post structure 18. Said binding post structure includes a transverse portion 20 of a size greater than the opening to cavity 17 to permit seating of portion 20 against the rear wall 6B of the housing. A retainer plate 21 with screws 22 secures the contact assembly 14 in place.

With attention to FIGS. 3 and 6, a ground contact finger assembly generally at 23 includes fingers 24 within a housing cavity 26 between which is received the ground prong 5 of a plug member. The metallic fingers 24 terminate rearwardly in a binding post structure 25 which, in similarity to the earlier described contact assembly, is of a dimension greater than the opening of cavity 26 to provide a seating surface for the binding post for retention of the post against the rear wall 6B of housing 6. Retainer plate 21, of a durable dielectric material, also engages binding post structure 25 holding same into abutment against housing wall 6B.

With attention to main housing 6, an internal bore 13 extends downwardly into communication with the pair of cavities 17 and with cavity 26. A locking member indicated generally at 28 and best viewed in FIGS. 3 and 4 includes a fingergrip 29 having a threaded segment at 30 therebelow in threaded engagement within internally threaded bore 13 in housing 6. Threads at 30A are of a steep pitch to achieve the desired vertical travel of the locking member with only arcuate rotation of the locking member. Integral with threaded portion 30 is a cam 31 having camming surfaces 32. Said cam terminates in an end portion 33. The operation of said locking member is hereinafter described.

With locking member 28 in place within housing 6, cam 31 is disposed intermediate the innermost fingers of contact assemblies 14. As viewed in FIG. 5, the cam is oblong in section and when in parallel relationship to the. fingers 15 is spaced therefrom. Arcuate rotation of the locking member and hence cam 31 into perpendicular relationship to contact fingers 15 results in cam surfaces 32 urging said fingers laterally into locking engagement with the inserted blade contact of a plug. Accordingly, the contact fingers 15 of each contact assembly and the blade contact therebetween are biased outwardly in opposite directions.

Simultaneous with the locking of contact fingers 15 with blade contacts 4 I accomplish locking of ground prong in place within ground contact fingers 24. Such is accomplished by the downward or inward movement of locking member 28 and specifically end portion 33 thereof. As viewed in the unlocked position of FIG. 6, end portion 33 moves downwardly to bias the uppermost ground contact finger into locking engagement against the ground prong. It will be apparent that the earlier described operation of cam 31 will take place whether or not the plug being secured includes a ground prong.

Adequate travel of locking member 28 is achieved with only partial rotation of same as for example arcuate rotation to'the broken line position of FIG. 2. A stop 34 is included on ring to prevent removal of locking element 28.

In FIGS. 7 and 8, a modified housing for the present invention is disclosed, adapted for use with a wall mounted double outlet box indicated at 35.

A main housing 36 includes cars at 36A for screwed attachment to outlet box 35. A cap 37 is affixed to housing 36 by machine screw 38 and conceals binding posts for the upper and lower pairs of contact assemblies generally at 40 and 41. The binding post structures for said assemblies are indicated at 42-43 and may be bridged at 44 for the sake of convenient assembly. While contact assemblies 40 and 41 are as shown and described in the earlier described embodiment of the invention, the ground contact assemblies, generally at 45 and 46, may be paired at their respective binding post structures 47-48 for the sake of housing size. Insulated leads at 49-50 terminate at binding post structure 42 while a ground wire at 51 terminates at either binding post 47-48. A retainer plate 54 holds the binding post structures in place against housing 36.

Locking members, generally at 52 and 53, are as earlier described with slightly modifiedfingergrips 55, 56.

The operation of each locking member 52, 53 is independent of the other and as earlier described.

While I have shown but two embodiments of the invention it will be apparent to those skilled in the art that the invention may be embodied still otherwise without departing from the spirit and scope of the invention.

Having thus described the invention, what is desired to be secured under a Letters Patent is:

1. An electrical outlet for the lockable reception of both two and three prong plugs of the type associated with household appliances, the latter-type plug having a ground prong, said outlet comprising,

a main housing defining multiple cavities each for the reception of contact finger assemblies, an internally threaded bore within said housing extending intermediate a pair of said cavities and terminating in communication with an additional cavity within the housing,

contact finger assemblies disposed within each of said cavities and adapted for engagement with the inserted prongs of an electrical plug,

a threaded locking member rotatably mounted within the housing bore and terminating outwardly of the housing in an exposed fingergrip, said locking member threaded for a portion of its length, cam surfaces oppositely formed on said locking member for laterally biasing a pair of contact finger assemblies into positive contact with plug prongs, said locking member terminating inwardly in an end portion disposed within said additional cavity'for biasing a ground contact finger against the ground prong of a plug whereby the plug prongs are frictionally engaged by each contact finger assembly and by a ground contact finger assembly to assure positive electrical contact and to prevent inadvertent plug separation from the outlet.

2. The electrical outlet as claimed in claim 1 wherein each of the contact finger assemblies comprise opposed flexible contact fingers between which a plug prong is received.

Claims (2)

1. An electrical outlet for the lockable reception of both two and three prong plugs of the type associated with household appliances, the latter type plug having a ground prong, said outlet comprising, a main housing defining multiple cavities each for the reception of contact finger assemblies, an internally threaded bore within said housing extending intermediate a pair of said cavities and terminating in communication with an additional cavity within the housing, contact finger assemblies disposed within each of said cavities and adapted for engagement with the inserted prongs of an electrical plug, a threaded locking member rotatably mounted within the housing bore and terminating outwardly of the housing in an exposed fingergrip, said locking member threaded for a portion of its length, cam surfaces oppositely formed on said locking member for laterally biasing a pair of contact finger assemblies into positive contact with plug prongs, said locking member terminating inwardly in an end portion disposed within said additional cavity for biasing a ground contact finger against the ground prong of a plug whereby the plug prongs are frictionally engaged by each contact finger assembly and by a ground contact finger assembly to assure positive electrical contact and to prevent inadvertent plug separation from the outlet.

2. The electrical outlet as claimed in claim 1 wherein each of the contact finger assemblies comprise opposed flexible contact fingers between which a plug prong Is received.

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