US3736547A

US3736547A - Three wire grounded receptacle with safety lock

Info

Publication number: US3736547A
Application number: US00182592A
Authority: US
Inventors: G Koenig
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-09-22
Filing date: 1971-09-22
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29

Abstract

A grounded receptacle to receive a conventional plug with two live sockets to receive the two live prongs of the plug and a grounded socket to receive the ground prong of the plug. Previous grounded receptacles of this type had the disadvantage that they were as equally suited to be used with plugs without a ground prong as with plugs with a ground prong. The grounded socket of this receptacle has at least one blocking plate which normally extends to a position blocking insertion of one of the live prongs of the plug into the corresponding live sockets of the receptacle, but which is resiliently displaced by insertion of a ground prong into the grounded socket to a position in which such insertion of the live prong is permitted.

Description

UIlItGd States Patent 1 [1 1 3,736,547 Koenig [45] May 29, 1973 THREE WIRE GROUNDED Primary ExaminerMarvin A. Champion RECEPTACLE WITH SAFETY LOCK [76] Inventor: Gerhard Koenig, 58 Westview Crescent, Elliot Lake, Ontario, Canada [22] Filed: Sept. 22, 1971 [21] Appl. No.: 182,592

[52] US. Cl. ..339/14 R, 339/40 [51] Int. Cl. ..II01r 3/06 [58] Field of Search ..339/14, 74, 36, 37, 339/40, 41, 42, 43

[56] References Cited UNITED STATES PATENTS 3,173,731 3/1965 Anderson ..339/14 R 2,579,538 12/1951 Bierce 339/14 R 3,238,492 3/1966 Houston ..339/40 3,206,705 9/l965 Smith ...339/l4 R 3,363,215 l/1968 Smith ..339/14 R FOREIGN PATENTS OR APPLICATIONS 377,352 7/l932 Great Britain ..339/43 Assistant ExaminerRobert A. Hafer AttorneyGeorge H. Riches [5 7] ABSTRACT A grounded receptacle to receive a conventional plug with two live sockets to receive the two live prongs of the plug and a grounded socket to receive the ground prong of the plug. Previous grounded receptacles of this type had I the disadvantage that they were as equally suited to be used with plugs without a ground prong as with plugs with a ground prong. The grounded socket of this receptacle has at least one blocking plate which normally extends to a position blocking insertion of one of the live prongs of the plug into the corresponding live sockets of the receptacle,

but which is resiliently displaced by insertion of a ground prong into the grounded socket to a position in which such insertion of the live prong is permitted.

10 Claims, 4 Drawing Figures PATENTEDMAYZB 1975 INVENTOR. GER HARD KOENIG THREE WIRE GROUNDED RECEPTACLE WITH SAFETY LOCK BACKGROUND OF THE INVENTION This invention relates generally to a grounded receptacle for receiving a conventional three prong grounded electrical plug and more particularly to such a grounded receptacle having a Safety lock.

In the past electrical plugs having only two prongs and receptacles having two sockets to receive these prongs have been widely used to connect various appliances or devices to a sourceof power. This arrangement has the disadvantage that it is not generally convenient to independently connect the appliance or device to an electrical ground, while it is generally known that a lesser number of electrical fires occur in appliances and wiring when provision is made for electrically grounding the appliance or wiring.

More recently this disadvantage has been overcome to some extent by the use of electrical plugs having a third prong called a ground prong with receptacles having a third socket called a grounded socket. As is well known, the ground prong is connected through a third wire to the appliance or device with which it is used, while the grounded socket is connected to an electrical ground. The term live prong is used to refer to either of the prongs of such a plug other than the ground prong, while the term live socket is used to refer to either of the sockets of such a receptacle other than the grounded socket. The ground prong of these conventional three prong plugs is generally shaped so that it cannot be inadvertently inserted into one of the live sockets of these conventional grounded receptacles. This method of providing an electrical ground has proven to be such a significant advantage that in certain installations in some areas only such grounded receptacles are permitted to be installed. However these conventional grounded receptacles still have the disadvantage that plugs which are not provided with a ground prong or plugs with the ground prong broken off may still be used in conjunction with them in which case the appliance or device which is plugged in is still not grounded.

In addition conventional grounded receptacles have the further disadvantage that persons who are not aware of the danger involved, such as small children, may receive a severe electrical shock resulting in injury or death by inserting conductive objects into such a receptacle when it is not in use to make contact with the live sockets. One of the attempts to overcome this further disadvantage has been to provide a cap for each receptacle, but these caps have the disadvantage that if they are removable they are often eventually lost and if they are not removable they must be hinged or have some other way of being opened in which case they are often broken off. Also, such caps do not provide protection to children who are old enough to be able to remove or open them.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to at least partially overcome these disadvantages to provide a safer grounded receptacle having a lock which restricts the live prongs of a plug or any other conductive object from making contact with the live sockets of the receptacle unless the ground plug or other object is inserted into the grounded socket of the receptacle.

To this end, in one of its aspects, the invention provides a grounded receptacle to receive a conventional electrical plug which has first and second live prongs and a ground prong, comprising first and second live prong socket means adapted to contact said first and second live prongs, and grounded socket means having ground prong receiving means and at least one live prong blocking means, said ground prong receiving means adapted to resiliently receive said ground prong,

said blocking means having a first position blocking contact of said first live prong with said first live prong socket means, and a second position unblocking said contact, said blocking means being moved from the first position to the second position by partial entry of the ground prong into the ground prong receiving means and returned from the second position to the first position upon removal of the ground prong.

In another of its aspects, the invention further provides a grounded receptacle to receive a conventional electrical plug which has first and second live prongs and a ground prong, comprising (a) a non-conductive body having a non-conductive cover, said cover having first and second openings adapted to respectively receive said first and second live prongs, and a further opening adapted to receive said ground prong, (b) first and second live prong sockets each having a rear portion and two arms extending from said rear portion in opposed relation to form a mouth, said first and second live prong sockets securedly located by said body to respectively engageably receive said first and second live prongs inserted through said openings in said cover and through said mouths, and (c) a grounded socket having a rear portion, two arms extending from said rear portion in opposed relation to form a mouth, said grounded socket securedly located by said body to resiliently receive through said mouth said ground prong inserted through said further opening in said cover, and one blocking plate extending from one of said arms to a normal position between said first opening in said cover and the mouth of said first live prong socket blocking insertion of said first live prong into said first live prong socket, said one arm being sufficiently resiliently displaced by insertion of the ground prong through the mouth of the grounded socket to displace said blocking plate to a displaced position in which insertion of said first live prong into said first live prong socket is permitted.

Further objects and advantages of the invention will appear from the following description, taken together with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cut-away perspective view of the main component parts of a single grounded receptacle according to a preferred embodiment of the invention with a conventional three prong grounded electrical plug shown in position to be inserted into the receptacle,

FIG. 2 is a partially cut-away plan view of the embodiment of the invention shown in FIG. 1,

FIG. 3 is a sectional view along lines III-III of FIG. 2, and

FIG. 4 is a similar view to FIG. 3, additionally showing a conventional three prong grounded electrical plug partially inserted in said receptacle.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is first made to FIGS. 1 to 3 which show a single grounded receptacle according to the invention having the main component parts of two

live sockets

12 and 12 and a grounded socket 14. As best seen in FIG. 1, these sockets are formed having appropriate dimensions and suitably located with respect with each other so as to be able to receive a conventional three prong grounded electrical plug 16 having two live prongs l8 and 18' and one ground prong 20. In practice, receptacles according to the invention are seen as being used primarily with conventional voltages of 115 or 220 volts and currents up to 50 amperes although they could be constructed to withstand substantially higher voltages and currents. It may be desirable to combine the components described herein in multiples to form double or triple receptacles rather than the single receptacledescribed herein.

The sockets are held in place by a body 22 formed of a suitable non-conducting material, havinga cover 24. As seen in FIG. 2, the cover 24 has two

slots

26, 26 and a circular opening 28 to permit insertion of the prongs of the plug 16 into the corresponding sockets of the receptacle 10.

The live sockets l2 and 12' are each formed of relatively thin conductive material to have a rear portion 30, 30' and a first arm 31, 31' and a second arm 32, 32' extending from the

rear portion

30, 30 to form a mouth 33, 33'. As shown, extending from the rear portions 30, 30', the arms of each of the live sockets consist of a pair of first portions 34, 34' extending substantially parallel to each other, a pair of second portions 35, 35' converging towards each other and a pair of

third portions

36, 36 diverging from each other to form the mouth 33, 33'. Each live socket 12, 12' also has a terminal 37, 37' to which an appropriate wire is connected to supply an electrical power supply to the receptacle. The live sockets 12 and 12' may be formed of any suitable material and in any suitable shape to provide electrical contact between them and the respective

live prongs

18 and 18 when the plug 16 is fully inserted into the receptacle 10. These may take the form of a variety of electrical contacts known to those familiar with the art.

The grounded socket 14 which is shown as being somewhat larger than the

live sockets

12, 12, is similarly formed of relatively thin material to have a rear portion 38 and a first arm 39 and a second arm 40 which extends from the rear portion 38 to form a mouth 41. The

arms

39,40 of the grounded socket 14 are similarly formed to have a pair of first portions 42 extending substantially parallel to each other, a pair of second portions 43 converging towards each other and a pair of third portions 44 diverging from each other to form the mouth 41. The grounded socket 14 also has a connection 45 to which a grounding lead is connected.

The grounded socket 14 additionally is shown having blocking

plates

46 and 47 extending respectively from

arms

39 and 40. When the plug 16 is in position for insertion into the receptacle l0, blocking plate 46 is located in a position between live prong 18 and the mouth 33 of the corresponding live socket 12, and blocking plate 47 is located in a position between live prong l8 and the mouth 33' of the corresponding live socket 12. Although a

blocking plate

46, 47 is shown extending from each 39, 40 of the grounded socket 14, the grounded socket 14 may be constructed to have the two blocking plates extending from a single arm or alternately even with a single blocking plate extending from a single arm (although this is not as advantageous as it leaves one of the

live sockets

12, 12 open to insertion of a conductive object).

There are a variety of materials of which the grounded socket 14 may be formed in a variety of shapes to provide electrical contact with the ground prong 20 when the plug 16 is fully inserted into the receptacle 10 in addition to being sufficiently resilient to provide that the blocking plates, which are resiliently displaced by insertion of the ground prong 20 as described below, return to their original position'when the ground plug is withdrawn.

As an alternate to the embodiment of the invention shown in the drawings, the grounded socket 14 may be located in the body 22 somewhat higher than shown with respect to the live sockets 12, 12' and constructed to have the

blocking plates

46, 47 attached to the

respective arms

39, 40 of the grounded socket 14 so as to locate the

blocking plates

46, 47 at a level somewhat below the mouth 41 of the grounded socket 14. This enables the receptacle to be used with a three prong plug having a ground prong 20 of a different length with respect to the live prongs 20 than that shown. In fact, such a receptacle may even be used with a plug having a ground prong 20 shorter in length than the

live prongs

18, 18 in which case the grounded socket 14 may be smaller than the

live sockets

12, 12.

The

blocking plates

46, 47 are shown as being formed of the same piece of thin conductive material as the

arms

39, 40 and the rear portion 38 of the grounded socket 14, and as being located in a plane perpendicular to the direction of insertion (shown by arrow M in FIG. 1) of the plug 16 into the receptacle 10. While the

blocking plates

46, 47 need not necessarily be of this shape nor located in this plane, they must be shaped and normally located so as to contacted by an object which is inserted through one of the slots 26, 26' in the cover 24 and not readily moved aside by pressure on such object to permit such object to contact one of the live sockets 12, 12'. Therefore, as is apparent from the foregoing, the location or position of the

blocking plates

46, 47 is to some extent dependent upon their shape.

It is preferable that the

blocking plates

46, 47 not be conductive so that when the plug 16 is in place in the receptacle 10, the possibility is reduced of one of the

live prongs

18, 18 shorting to ground through one of the

blocking plates

46, 47. This may be achieved by covering the

blocking plates

46, 47 with a suitable insulating covering 48 as shown or alternately by forming the

blocking plates

46, 47 of a suitable insulating material and attaching them to the

arms

39, 40 of the grounded socket 14.

In use, a receptacle according to the invention performs a form of locking function in that it is necessary to insert an object, such as a ground prong of a conventional three prong plug, into the grounded socket 14 in order to gain access to the live sockets l2, 12. As best seen in FIG. 3, each of the

blocking plates

46, 47 is normally located between one of the slots 26, 26' in the cover 24 and the corresponding one of the

mouths

33, 33 of the live sockets 12, 12' in which position insertion of one of the live prongs 18, 18' or other conductive object through that slot to make contact with the live socket is blocked. However, as seen in FIG. 4, when the ground prong 20 is inserted through the circular opening 28 in the cover 24 into the mouth 41 of the grounded socket 14, the

arms

39, 40 of the grounded socket 14 are pushed apart by the ground prong 20. This motion of the arms moves the

blocking plates

46, 47 which are attached to the arms, to the positions shown in FIG. 4, wherein entry of the

live prongs

18, 18 into the mouths 33, 33' of the respective live sockets l2, 12 is not blocked. The grounded socket 14 has sufficient resilience that when the ground prong 20 is removed from the mouth 41 of the grounded socket 14, the

arms

39, 40 and the

blocking plates

46, 47 of the grounded socket 14 return to their original or normal positions blocking access to the live sockets 12, 12'.

What I claim is:

1. A grounded receptacle to receive a conventional electrical plug which has first and second live prongs and a ground prong, comprising:

first and second live prong socket means adapted to contact said first and second live prongs, and grounded socket means having ground prong receiving means and at least one live prong blocking means comprised of an integral extension of the ground prong receiving means, said ground prong receiving means adapted to resiliently receive said ground prong, said blocking means having a first position blocking contact of said first live prong with said first live prong socket means, and a second position unblocking said contact, said blocking means being moved from the first position to the second position by partial entry of the ground prong into the ground prong receiving means and returned from the second position to the first position upon removal of the ground prong.

2. A grounded receptacle as claimed in claim 1, wherein said grounded socket means has second integral live prong blocking means, said second blocking means having a first position blocking contact of said second live prong with said second live prong socket means, and a second position unblocking said contact, said second blocking means being moved from the first position to the second position by partial entry of said ground prong into the ground prong receiving means and returned from the second position to the first position upon removal of the ground prong.

3. A grounded receptacle as claimed in claim 1 wherein said live prong blocking means is located in a plane substantially perpendicular to the direction of insertion of said plug into said receptacle.

4. A grounded receptacle as claimed in claim 2 wherein said live prong blocking means is coated with a suitable insulating material.

5. A grounded receptacle as claimed in claim 1 wherein said ground prong receiving means and said live prong blocking means are formed of thin conductive material, said live prong blocking means being covered with suitable insulating material. A

6. A grounded receptacle to receive a conventional electrical plug which has first and second live prongs and a ground prong, comprising:

a. a non-conductive body having a non-conductive cover, said cover having first and second openings adapted to respectively receive said first and second live prongs, and a further opening adapted to receive said ground prong,

b. first and second live prong sockets each having a rear portion and two arms extending from said rear portion in opposed relation to form a mouth, said first and second live prong sockets securedly located by said body to respectively engageably receive said first and second live prongs inserted through said openings in said cover and through said mouths, and

c. a grounded socket having a rear portion, two arms extending from said rear portion in opposed relation to form a mouth, said grounded socket securedly located by said body to resiliently receive throughsaid mouth said ground prong inserted through said further opening in said cover, and one blocking plate integral with and extending from one of said arms to a normal position between said first opening in said cover and the mouth of said first live prong socket blocking insertion of said first live prong into said first live prong socket, said one arm being sufficiently resiliently displaced by insertion of the ground prong through the mouth of the grounded socket to displace said blocking plate to a displaced position in said insertion of said first live prong into said first live prong socket is permitted.

7. A grounded receptacle as claimed in claim 6 wherein said grounded socket has a second blocking plate integral with and extending from a second of said arms to a normal position between said second opening in said cover and the mouth of said second live prong socket blocking insertion of said second live prong into said second live prong socket, said second arm being sufficiently resiliently displaced by insertion of the ground prong through the mouth of the grounded socket to displace said second blocking plate to a displaced position in which insertion of said second live prong into said second live prong socket is permitted.

8. A grounded receptacle as claimed in claim 7 wherein said blocking plates are located in a plane substantially perpendicular to the direction of insertion of said plug into said receptacle.

9. A grounded receptacle as clamed in claim 7 wherein said blocking plates are coated with a suitable insulating material.

10. A grounded receptacle as claimed in claim 7 wherein said grounded socket is formed of a thin conductive material, said blocking plates being covered with a suitable insulating material. l 4

Claims

1. A grounded receptacle to receive a conventional electrical plug which has first and second live prongs and a ground prong, comprising: first and second live prong socket means adapted to contact saId first and second live prongs, and grounded socket means having ground prong receiving means and at least one live prong blocking means comprised of an integral extension of the ground prong receiving means, said ground prong receiving means adapted to resiliently receive said ground prong, said blocking means having a first position blocking contact of said first live prong with said first live prong socket means, and a second position unblocking said contact, said blocking means being moved from the first position to the second position by partial entry of the ground prong into the ground prong receiving means and returned from the second position to the first position upon removal of the ground prong.

5. A grounded receptacle as claimed in claim 1 wherein said ground prong receiving means and said live prong blocking means are formed of thin conductive material, said live prong blocking means being covered with suitable insulating material.

6. A grounded receptacle to receive a conventional electrical plug which has first and second live prongs and a ground prong, comprising: a. a non-conductive body having a non-conductive cover, said cover having first and second openings adapted to respectively receive said first and second live prongs, and a further opening adapted to receive said ground prong, b. first and second live prong sockets each having a rear portion and two arms extending from said rear portion in opposed relation to form a mouth, said first and second live prong sockets securedly located by said body to respectively engageably receive said first and second live prongs inserted through said openings in said cover and through said mouths, and c. a grounded socket having a rear portion, two arms extending from said rear portion in opposed relation to form a mouth, said grounded socket securedly located by said body to resiliently receive through said mouth said ground prong inserted through said further opening in said cover, and one blocking plate integral with and extending from one of said arms to a normal position between said first opening in said cover and the mouth of said first live prong socket blocking insertion of said first live prong into said first live prong socket, said one arm being sufficiently resiliently displaced by insertion of the ground prong through the mouth of the grounded socket to displace said blocking plate to a displaced position in which insertion of said first live prong into said first live prong socket is permitted.

8. A grounded receptacle as claimed in claim 8 wherein said blocking plates are located in a plane substantially perpendicular to the direction of insertion of said plug into said receptacle.

10. A grounded receptacle as claimed in claim 7 wherein said grounded socket is formed of a thin conductive material, said blocking plates being covered with a suitable insulating material.