U.S. patent number 3,736,547 [Application Number 05/182,592] was granted by the patent office on 1973-05-29 for three wire grounded receptacle with safety lock.
Invention is credited to Gerhard Koenig.
United States Patent |
3,736,547 |
Koenig |
May 29, 1973 |
THREE WIRE GROUNDED RECEPTACLE WITH SAFETY LOCK
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.
Inventors: |
Koenig; Gerhard (Elliot Lake,
Ontario, CA) |
Family
ID: |
22669133 |
Appl.
No.: |
05/182,592 |
Filed: |
September 22, 1971 |
Current U.S.
Class: |
439/93;
439/137 |
Current CPC
Class: |
H01R
13/453 (20130101) |
Current International
Class: |
H01R
13/44 (20060101); H01R 13/453 (20060101); H01r
003/06 () |
Field of
Search: |
;339/14,74,36,37,40,41,42,43 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Champion; Marvin A.
Assistant Examiner: Hafer; Robert A.
Claims
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.
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.
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 8 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.
Description
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 those prongs have been widely used to
connect various appliances or devices to a source of 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 10 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 18 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 receptacle described herein.
The sockets are held in place by a body 22 formed of a suitable
non-conducting material, having a 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 12 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 10, 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 18' 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 be 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 12,
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 that 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 12, 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'.
* * * * *