Note: Descriptions are shown in the official language in which they were submitted.
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TWIST-LOCK CONNECTOR FOR ELECTRICAL PLUG AND WALL SOCKET
INTRODUCTION
[0001] The present invention relates to locking apparatus for electrical
connectors, and
more particularly, to a twist-lock connector assembly for maintaining
engagement between
an engaged electrical plug and a wall socket.
BACKGROUND OF THE INVENTION
[0002] When using electric powered appliances or power tools, it is necessary
to maintain
firm engagement between an engaged electrical plug and a wall outlet or power
box in
order to ensure an uninterrupted source of power to the appliance or power
tool.
Unintentional unplugging of an engaged electric power cord from a wall outlet
can cause
frustration and contribute to decreased productivity. For example, most people
have
experienced the common frustration of having the power cord of a vacuum
cleaner
unintentionally pulled loose from the wall socket several times while
vacuuming. As a
further example, a computer plug which comes loose from its connection to a
wall socket
can result in loss of data. As another example, construction workers at a job
site
experience production losses each time they must replug a power tool that has
come loose
from a wall socket or power box during use.
[0003] Various techniques and devices have been proposed for ensuring
engagement
between an engaged electrical plug and wall outlet or power box. For example,
in
accordance with one prior art technique, the electrical plug is provided with
a metal loop
or fork tongue flange which is designed to be fastened by a screw to the
center hole of the
cover plate of the electrical outlet.
[0004] A disadvantage with this technique is that the cover plate center screw
be loosened
each time the electric plug is to be engaged or disengaged from the wall
socket. Thus, this
technique is extremely impractical for uses in which the electric plug will
only be engaged
for short time periods, such as is the case with the use of vacuum cleaners,
gardening
tools, power tools, etc. Further, this technique requires use of a screw
driver each time the
electric plug is to be locked in engagement with and unlocked from engagement
with the
wall socket. Further still, in the case where the electric plug to be engaged
is a three prong
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plug, the presence of the third "ground" prong of the three prong plug means
that the plug
can only be inserted into the wall socket in one orientation. Since there is
usually only one
center screw hole located between the two socket access openings of the cover
plate, only
one electric plug having the metal loop or forked tongue flange can be screwed
in place to
the wall socket at a time. Accordingly, a connector arrangement for securing
an engaged
electric plug to a wall socket which does not require use of additional tools
to make the
locking connection and which can lockingly engage more than one electric plug
to the
respective socket portions of an electrical outlet at a time would be a big
advance in the
art.
[0005] In the case of exposed outlet boxes of the type commonly found on boat
docks, it is
the common practice to use leather straps, string or even tape to ensure that
an engaged
electric plug remains connected to the socket portion of the outlet box. It is
also the
common practice to bend or deform the conductor prongs of an electric plug to
create a
tighter fit inside the outlet. Obviously such practices are only temporary
fixes and do not
provide a long lasting secure engagement between and engaged electric plug and
an
electrical outlet.
[0006] My previous approach to solving this problem is disclosed in U.S. Pat.
No.
5,344,333. This approach proposes to use a rotatable cylindrical sleeve for
twist-locking
an engaged electric plug to a cover plate of a wall outlet. In this design the
cylindrical
sleeve is provided with a first end adapted for snap fit insertion within a
socket opening of
the cover plate and a second end provided with grooves along an inner
cylindrical surface
thereof. The electric plug is provided with a circular face plate having
threads formed
along its outer surface. In use, the plug is engaged within the socket and the
sleeve is
rotated such that the grooves of the sleeve lockingly engage with the threads
of the face
plate on the electric plug.
[0007] While my earlier design works well and offers many advantages over the
prior art
techniques discussed above, there is still a problem since dirt and debris
tends to collect in
the sleeve over time and this can inhibit positive locking engagement. Also,
in my earlier
design, two hands are required to complete the locking engagement between the
engaged
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electrical plug and the wall outlet. Accordingly, a twist-locking connector
arrangement
which overcomes these problems would be extremely desirable.
SUMMARY OF THE INVENTION
[0008] It is therefore a principle object of the present invention to provide
a simple, low
cost twist-lock connector assembly for securing an engaged electrical plug to
a wall outlet
or power box.
[0009] It is a related object of the invention to provide a twist-lock
connector assembly of
the type described herein which permits convenient single handed-locking
operation and
which does not require any tools to perform the locking operation.
[0010] Briefly, in accordance with a preferred embodiment, the twist-lock
connector
assembly of the present invention comprises two primary components including
an axially
rotatable cylindrical sleeve for enclosing the insulator body portion of an
electrical plug
and a modified cover plate which replaces the conventional cover plate that
covers the
metal electrical box of a wall socket. The cylindrical sleeve has a first
sleeve end that
extends a distance beyond the insulator body portion of the electrical plug in
the direction
of the protruding electrical conductors or prongs and a second sleeve end that
is rotatably
mounted to the insulator body portion of the electric plug. In use, the
cylindrical sleeve is
freely rotatable about the long axis of the electric plug. The first sleeve
end includes a
plurality of radially inwardly projecting nubs provided along an inner
cylindrical surface
thereof.
[0011] The modified cover plate is similar in design to a conventional cover
plate except
that it includes an upstanding cylindrical wall disposed about a periphery of
each socket
access opening. Each of the upstanding cylindrical walls is provided with a
plurality of
spaced apart discontinuous thread members formed along their respective
exterior wall
surfaces. The diameter of each upstanding cylindrical wall is dimensioned to
provide a
close tolerance fit within the first sleeve end of the cylindrical sleeve.
Also, the thread
members on the exterior wall surfaces are designed to matingly engage the nubs
on the
inner cylindrical surface of the first sleeve end as the sleeve is twist-
rotated over the
upstanding cylindrical wall.
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[0012] In use, the electrical plug is inserted into the socket portion of the
wall outlet and
the cylindrical sleeve is rotated about a 1/4 turn. This causes the inner
disposed nubs of the
sleeve to lockingly engage the outer disposed threads of the upstanding
cylindrical wall of
the cover plate. The electrical plug is prevented from being accidentally
pulled loose from
the outlet by its connection with the second sleeve end of the cylindrical
sleeve.
[0013] An advantage of the present invention over of the thread-in-groove
twist-lock
connector designs of the prior art is that the use of projecting nubs on the
sleeve instead
receiving grooves substantially eliminates the aforementioned problem of dirt
and debris
collecting in the sleeve and inhibiting positive twist-locking engagement of
the locking
structure.
[0014] The location of the rotatable sleeve on the electrical plug also
advantageously
facilitates single-handed twist-locking operation by a user.
[0015] In an alternate embodiment of the invention, the twist-lock connector
assembly
comprises three components: namely, a cover plate for attaching to a wall
socket, a
shortened cylindrical sleeve, and an adapter or face plate that attaches to or
forms an
integral part of the prong end of the electrical plug. The shortened
cylindrical sleeve
includes a first sleeve end adapted for snap fit insertion into the socket
access openings of
the cover plate and a second sleeve end having a plurality of spaced apart
nubs disposed
along an inner cylindrical surface thereof. Once snap fitted in place on the
cover plate, the
shortened cylindrical sleeve is permitted to axially rotate with respect to
the cover plate.
The face plate on the prong end of the electrical plug is provided with a
plurality of
external threads. In use, the electrical plug is plugged into the socket
portion of the wall
outlet and the shortened cylindrical sleeve is rotated so that the internally
disposed nubs on
the second sleeve inner cylindrical surface lockingly engage the external
threads on the
face plate of the electrical plug.
[0016] In still another embodiment of the invention, the twist-lock connector
assembly
includes a rotatable sleeve housing for enclosing the electrical plug. The
rotatable sleeve
includes external threads formed along a forward end portion thereof. The
twist-lock
connector assembly also includes a modified wall socket cover plate having
socket
receiving holes provided with spaced apart, inwardly projecting nubs formed
integrally
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along an inner cylindrical wall surrounding each of the socket receiving
holes. In use, the
conductor prongs of the electrical plug are inserted into the corresponding
receiving holes
of the wall socket and the sleeve is rotated thereby causing the external
threads of the
rotatable sleeve to lockingly engage the nubs of the cover plate.
[0017) In yet another embodiment of the invention, the twist-lock connector
assembly is
adapted for maintaining engagement of an electrical plug with a female socket
end of an
extension cord. This embodiment is directly specifically towards maintaining
engagement
between extension cords and power tools and/or appliances having a male
electrical
connector or prong end that is attached by a whip portion to, or is formed
integral with, the
handle structure of a power tool or appliance. For example, such connectors
are commonly
found on most outdoor garden tools, such as, leaf blowers and vacuums, hedge
clippers,
etc. In this embodiment, the male or prong end of the electrical connector on
the whip or
in the handle is provided with a face plate member having a cylindrical outer
wall with a
plurality of threads formed thereon. As before, the female or socket end of
the connector
assembly is provided with a twist rotatable and retractable sleeve having the
inwardly
projecting nubs formed integral along a forwardmost portion of the inner
sleeve wall. In
use, the conductor prongs of the electrical plug are inserted into the
corresponding
receiving holes of the female socket portion and the sleeve is rotated thereby
causing the
inwardly projecting nubs of the rotatable sleeve to lockingly engage the
threads on the
cover plate member. The cover plate member may be formed integral with the
male
insulator body portion of may be provided as an after market piece.
[0018] Another advantage afforded by the present invention is the extended
operating life
and reliability of the electrical contacting components of the electrical plug
and socket
assemblies since the twist-lock feature of the connector assembly
substantially reduces
tensional forces on the electrical plug and thereby prevents excess wear of
the electrical
contact surfaces of the female socket and male electrical plug assemblies.
[0019] Methods and apparatus which incorporate the features described above
and which
are effective to function as described above constitute specific objects of
this invention.
[0020] Other and further objects of the present invention will be apparent
from the
following description and claims and are illustrated in the accompanying
drawings, which
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by way of illustration, show preferred embodiments of the present invention
and the
principles thereof and what are now considered to be the best modes
contemplated for
applying these principles. Other embodiments of the invention embodying the
same or
equivalent principles may be used and structural changes may be made as
desired by those
skilled in the art without departing from the present invention and the
purview of the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings incorporated in and forming a part of the
specification, illustrate several aspects of the present invention, and
together with the
description serve to explain the principles of the invention.
[0022] FIG. 1 is an isometric perspective view of a twist-lock connector
assembly in
accordance with one embodiment of the present invention and which shows an
electrical
plug in locking engagement with a wall socket.
[0023] FIG. 2 is an isometric perspective view similar to that of FIG. 1 but
showing the
electrical plug disengaged from the wall socket.
[0024] FIG. 3 is a cross sectional side elevation view of the twist-lock
connector assembly
of FIG. 2.
[0025] FIG. 4 is an isometric perspective view of a twist-lock connector
assembly in
accordance with a second embodiment of the present invention and which shows
an
electrical plug in locking engagement with a wall socket.
[0026] FIG. 5 is an isometric perspective view of a second embodiment of the
present
invention similar to FIG. 4 but showing the electrical plug disengaged from
the wall
socket.
[0027] FIG. 6 is a front elevation view of a wall socket cover plate
constructed in
accordance with a second embodiment of the present invention.
[0028] FIG. 7 is an isometric perspective view of a twist-lock connector
assembly for
maintaining engagement between an engaged electrical plug and a wall socket in
accordance with a third embodiment of the present invention.
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[0029] FIG. 8 is a cross sectional view through the wall socket plate assembly
and
rotatable sleeve taken along the line and in the direction of arrows 8-8 of
FIG. 7.
[0030] FIGS. 9 and 10 show a series of front views illustrating the retracted,
open position
(FIG. 9) and closed position (FIG. 10) of a wall socket cover plate assembly
in accordance
with another embodiment of the invention.
[0031] FIG. 11 is a sectional view through the wall socket cover plate
assembly taken
along the line and in the direction of arrows 11-11 of FIG. 10.
[0032] FIG. 12 is an isometric perspective view of a twist-lock connector
assembly for
maintaining engagement between an engaged electrical plug and a female socket
portion
of an electrical extension cord in accordance with a fourth embodiment of the
present
invention.
[0033] FIG. 13 is an exploded isometric cross sectional view through the
connector
housing assembly of the female socket taken along the line and in the
direction of arrows
13-13 of FIG. 12.
[0034] FIG. 14 is a side elevation view of the twist-lock electrical connector
assembly
shown in FIG. 12 showing, in cross section, the twist-lock connecting
structure provided
to the female and male plug assemblies.
[0035] FIG. 14A is a detail fragmentary view of the region encircled by arrows
14A-14A
of FIG. 14.
[0036] FIG. 15 is a side elevation view of twist-lock connecting structure for
male and
female electrical plug assemblies and which shows conforming tapered regions
at the
regions of engagement for providing a compression fit.
[0037] FIG. 16 is a partial cross sectional view through an electrical
connector or prong
end of a handle or whip portion of a garden tool in accordance with the prior
art.
[0038] FIG. 17 is an isometric perspective view in partial cut away of a twist-
lock
connector assembly for maintaining engagement between an electrical plug and a
female
socket portion of an electrical extension cord in accordance with a fifth
embodiment of the
present invention.
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[0039] FIG. 18 is a side elevation cross sectional view of the of the twist-
lock electrical
connector assembly of FIG. 17.
[0040] FIG. 19 is a cross sectional view through the prong end of the
connector assembly
taken along the line and in the directions of arrows 19-19 of FIG. 18.
[0041] FIG. 20 is an detail sectional view of the region encircled by arrows
20-20 in FIG.
19.
[0042] Reference will now be made in detail to various present preferred
embodiments of
the invention, examples of which are illustrated in the accompanying drawings.
DETAILED DESCRIPTION OF THE INVENTION
(0043] A twist-lock connector assembly for use in maintaining engagement
between and
engaged electrical plug and a wall socket constructed in accordance with one
embodiment
of the present invention is generally designated by reference numeral 10 in
FIGS. 1-3.
[0044] The twist-lock connector assembly 10 includes a generally cylindrical
sleeve 12
which encloses the insulator body portion 14 of the electrical plug 16. As
best seen in FIG.
3, the sleeve 12 includes a first sleeve end 13 which extends in a forward
direction a
distance beyond the insulator body portion 14 such that it partially encloses
the electrical
conductors or prongs (shown in phantom) of the electrical plug 16. The first
sleeve end 13
has an inner cylindrical surface provided with a plurality of evenly spaced
apart nubs 15.
[0045] The sleeve 12 also includes a second sleeve end 17 having rotatable
mounting
means for rotatably mounting the sleeve 12 to the electrical plug 16 so that
the sleeve 12 is
freely axially rotatable about the long axis of the electrical plug 16 as
indicated by
directional arrow A. The rotatable mounting means also serve to attach or
tether the sleeve
12 to the electrical plug 16 in a way which keeps the sleeve 12 in a preferred
axial
relationship with the insulator body portion 14 as shown. In a preferred
embodiment, the
rotatable mounting means include a notched key way 18 disposed at a
rearwardmost end
of the sleeve 12. The key way 18 is adapted to be slidably received within an
annular slot
or gap 20 provided to the electrical plug 16. In this example, the gap 20 is
formed by the
presence of the insulator body portion 14 on one side and a fixed conical
housing portion
22 on the other side.
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(0046] There are, of course, many other possible alternative structural
arrangements for
rotatably mounting the sleeve to the electrical plug in a way that keeps the
sleeve in a
desired axial relationship with the electrical plug (i.e., where the first
sleeve end 13 with
the nubs 15 is positioned just forwardly of the insulator body portion 14 of
the electrical
plug 16). For example, the conical end portion 22 may be formed integral with
the
cylindrical sleeve 12 (in this case the conical end portion would not be fixed
or held by
screws to the electrical plug 16). The tapered end of the conical end portion
of such a
modified sleeve would include a hole for receiving the power cord of the
electrical plug.
An additional keeper, such as a ring or similar member (not shown) could be
installed on
the power cord to restrain rearward displacement of the conical end portion
relative to the
electrical plug 16 and thus keep the sleeve in a desired axial relationship
with the electrical
plug.
[0047] The twist-lock connector assembly 10 also includes a modified cover
plate 30
which replaces the conventional cover plate of a wall socket. The modified
cover plate 30
preferably includes a center hole 32 for receiving a fastening screw (not
shown) to secure
the cover plate 30 to the conventional center screw location of the wall
socket. This is best
seen in FIGS. 2 and 3. Alternatively, as is shown in FIG. 1, the cover plate
may include
top and bottom screw holes 34 (shown in phantom) for attaching the cover plate
30 to the
top and bottom screw mounts of the metal box that houses the electrical socket
portions 35
of the wall socket.
[0048] The cover plate 30 is provided with socket access openings 36 which are
formed
with a surrounding upstanding perimeter wall 38. Each wall 38 defines a
cylindrical
opening having a diameter sized for close tolerance fit within the cylindrical
opening of
the first sleeve end 13. The outer surface of wall 38 includes a plurality of
external threads
40 which, in use, engage the nubs 15 of the first sleeve end 13 as the
electrical plug is
inserted into the socket portion 35 and the sleeve 12 is rotated in a locking.
In this manner
the rotatable sleeve 12 is twist-locked onto the grooved upstanding
cylindrical wall 38 of
the cover plate 30 and therefore provides a positive locked engagement between
the
engaged electrical plug 16 and the socket portion 35 of the wall socket. To
disengage the
electrical plug from the wall socket, the sleeve 12 is simply rotated in a
reverse orientation
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which, in turn, frees the nubs 15 from locking engagement with the external
threads 40 of
the upstanding cylindrical wall 38 of the cover plate 30.
[0049] In a preferred embodiment of the invention, there are four nubs 15 and
there are
four discontinuous threads 40 which are arranged in a conventional four (4)
point thread
configuration of the cross hair type. This simple arrangement permits twist-
locking and
unlocking operation with only about a 1/4 turn of the sleeve in either
direction required. A
greater number of threads and nubs may be used if desired.
[0050] A twist-lock connector assembly constructed in accordance with a second
embodiment of the present invention is designated generally by reference
numeral 50 in
FIGS. 4 and 5.
[0051] The twist-lock connector assembly 50 includes: a face plate 52 attached
to or
formed integral with a prong end of an electrical plug 16; a modified cover
plate 56 for
replacing the conventional cover plate of a wall socket or power box; and a
cylindrical
sleeve 54 for rotatably securing the face plate 52 to the cover plate 56. The
sleeve 54 is a
modified and shortened version of the sleeve 13 of the embodiment described
above with
reference to FIGS. 1-3 and includes a first sleeve end having perimeter rib
segments 58
adapted for snap fit insertion within the socket access openings 60 of the
cover plate 56.
Each of the socket access openings 60 preferably include at least one inwardly
extended
tab or stop member 62 which, in use, abuts against axial stops 64 provided to
the first
sleeve end to limit the range of axial rotation of the sleeve 54 within the
socket access
openings.60. This feature will be discussed in more detail below with
reference to FIG. 6.
[0052] The sleeve 54 also includes a second sleeve end having an inner
cylindrical surface
formed with a plurality of spaced nubs 66. The inner cylindrical surface of
the sleeve
second end is sized for close tolerance fit over the face plate 52 of the
electrical plug 16.
Upon engagement of the conductors elements 68 (shown in phantom) of the
electrical plug
16 by the corresponding receiving slots of the socket portion 35 of the wall
socket, the
sleeve is twist-rotated as indicated by arrow A in FIG. 4. This causes the
nubs 66 to
lockingly engage external threads 70 provided on the face plate 52, thereby
locking the
electrical plug 16 to the cover plate 56. The rotatable sleeve 54 preferably
includes finger
tabs 72 to facilitate the twist-lock operation by a user.
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[0053] Referring now to FIG. 6, the two finger tabs 72 on each of the sleeves
54 are
preferably oriented diagonally opposite to one another such that they lie at
about the two
o'clock and eight o'clock positions of the socket access openings when the
sleeve 54 is in
the unlocked position. When the sleeve is rotated to the locked position, the
finger tabs 72
move to about the four o'clock and ten o'clock positions, respectively. A
greater or lesser
range of axial rotation of the sleeve 54 within each socket access opening 60
can be made
by adjusting the placement of the axial stops 64 of the sleeve first end which
abut against
the tab 62 at the fully locked and unlocked positions of the rotatable sleeve.
The placement
of the axial stops 64 with respect to finger tabs 72 of each sleeve is also
selected to ensure
that the finger tabs of the top and bottom sleeve do not overlap and interfere
with one
another.
[0054] A twist-lock connector assembly for maintaining engagement between an
engaged
electrical plug and a wall socket constructed in accordance with a third
embodiment of the
present invention is designated generally by reference numeral 80 in Figs. 7-
8.
[0055] The twist-lock connector assembly 80 includes a wall socket cover plate
82 for
replacing the con en Tonal cover plate of a wall socket or power box. The
cover plate
includes openings 84 sized and positioned to permit plug-in access by a male
electrical
plug assembly 16 to the wall socket portions 86 of the wall outlet. Each
opening 84 has an
inner cylindrical wall provided with a plurality of spaced apart, radially
inwardly
projecting nubs with four nubs spaced at regular intervals being preferred.
The depth of
the inner cylindrical wall of each opening 84 is sufficient to permit full
twist-locking
engagement with the external threads of the rotatable sleeve member provided
to the male
electrical connector assembly (described below).
[0056] The twist-lock connector assembly 80 further includes a rotatable
cylindrical
sleeve 90 for enclosing the insulator body portion 14 of male electrical plug
assembly 16.
The axial rotation of the sleeve 90 about a long axis of the electrical plug
16 as indicated
by direction arrow A. The sleeve 90 is provided with a plurality of external
threads 92 at a
first, forward end thereof. The threads 94 are configured in size and number
to facilitate
cooperative twist-locking engagement with the nubs 88 of the access openings
84 of wall
socket cover plate 82. The sleeve 90 also includes means for retaining
rotatable
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engagement with the male plug assembly 16. In the exemplary embodiment shown,
the
retaining means includes a notched key way 94 disposed at a second rearward
end of the
sleeve 90.
[0057] Just as in the embodiment described above with reference to Fig. 3, the
notched
key way 94 is adapted to be rotatably secured within an annular slot or gap 20
formed in
the insulator body portion 14 of the electrical plug assembly 16. As before,
the electrical
plug assembly may include a fixed conical housing portion 22 to complete the
cosmetically pleasing tapered outer appearance of the electrical plug assembly
16.
[0058] Also, in the preferred embodiment of the invention, there are four nubs
88 and
there are four discontinuous threads 92 which are arranged in a four (4) point
thread
configuration of the cross hair type. This simple arrangement permits twist-
locking and
unlocking operation only about a 1/4 turn of the sleeve in either direction
required. A
greater number of threads and nubs may be used if desired.
[0059] The wall socket cover plate 82 of the present invention is intended to
a permanent
replacement for conventional wall socket cover plates presently in use in the
home or
business. It is recognized that users will continue to use the wall outlet for
plugging in
conventional electrical plugs (i.e., those plugs not provided with twist-lock
engaging
structure) in additional to electrical plugs provided with the specially
configured twist-lock
connecting structure of the present invention. It is also recognized that the
inwardly
projecting nubs 88 provided to the openings 84 of the cover plate 82 may
inhibit proper
plug-to-socket engagement with certain of the large diameter male plug
configurations in
use today.
[0060] With reference to Figs. 10-1 l, this potential problem is overcome by
designing the
cover plate 82 as a retractable cover plate assembly including retractable
outer cover plate
portions 96a, 96b and inner cover plate 98. The nubs 88 are formed along the
inner
cylindrical wall of the openings 84 of the outer cover plate portions 96a,
96b. The access
openings and thickness of the inner cover plate 98 are the same as a
conventional cover
plate so as to be fully plug-in compatible with conventional electrical plug
configurations.
The firmer cover plate 98 is secured to the wall socket 99 by a center screw
fastener 99 in
the conventional way (see Fig. 11 ).
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(0061] Suitable tongue-in-groove retractable sliding means are provided to the
mating
surfaces of the inner cover plate 98 and outer cover plate portions 96a, 96b
(e.g., tongue
100 on inner cover plate 98 and groove 102 on outer cover plate portions 96a,
96b) to
facilitate movement of the outer cover plate portions out of position so as to
expose the
inner cover plate. The above described retractable feature of the outer cover
plate portions
permits any conventional electrical plug unobstructed plug-in access to the
wall socket.
Detents or nubs 104 and conforming receiving indents 106 may be provided to
the
respective groove 102 and tongue 100 surfaces to lock the outer cover plate
portions 96a,
96b in either the fully retracted, open (Fig. 9) or closed positions (Fig.
10). The outer
cover plate portions 96a, 96b my further include ribbed or serrated edge
regions 108 to
facilitate handling by a user when moving the outer cover-plate portions 96a,
96b into or
out of position.
[0062] It is understood that the above described embodiment for the
retractable, twist-
lockable cover plate assembly is capable of variation and modification while
still
achieving the basic objective of moving the outer plate portion or portions
out of the way
to permit unobstructed plug-in access by a conventional electrical plug to the
female
socket portion underneath. For example, the outer plate portions of the cover
plate
assembly may be pivotally attached to the inner plate either by a suitable
hinge or other
conventional pivot structure. In addition, the cover plate portions could be
configured as a
single outer plate member that is rotatably, pivotally or otherwise removably
attached
(e.g.. by snap-fit attachment) to the inner plate portion.
[0063] With reference to Figs. 12-13, there is shown a twist-lock connector
assembly for
maintaining engagement between an engaged electrical plug and a female socket
portion
of an electrical extension cord in accordance with a fourth embodiment of the
present
invent ion. In this embodiment, the insulator body portion 14 of the male
electrical plug
assembly 16 is provided with the same twist-lock connecting structure as
described above
in connection with the embodiment shown in Figs. 7 and 8. That is to say, the
insulator
body portion 14 is enclosed by the rotatable sleeve 90 with the external
threads 92
disposed at the forward or prong end of the electrical plug assembly 16.
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[0064] The female socket 110 is enclosed by a retractable sleeve 112 and a
fixed conical
end housing 114. The retractable sleeve 112 is retractably coupled to the
female socket
110 to permit a desired amount of translational movement of the sleeve 112
between a
first, fully retractable position wherein a forward end 112a of sleeve 112
lies substantially
flush with the front face 1 l0a of the female socket 110 and a second,
extended position
wherein the forward end 112b of the sleeve 112 extends a distance beyond the
front face
1 l0a of the female socket 110. This range of translational movement is
indicated by
direction arrow B in Fig. 12. The forward end 112a of the sleeve 112 is
provided wit a
plurality of spaced apart, radially inwardly projecting nubs 116.
[0065] As best seen in Fig. 13, the underside of sleeve 112 includes one or
more tab
members 112 that ride within corresponding slots 1 l Ob provided to the
exterior surface of
the female socket 110. Alternately, the tab member 112b may be configured as a
single
annular protrusion and the slot may be configured as a single annular slot. In
this case, the
retractable sleeve 112 would also be permitted to rotate axially about the
female socket
110. The tab and slot dimensions are configured so as to provide a desired
range of
translational motion to the forward end 112a of the sleeve 112 beyond the face
11 Oa of the
female socket 110. Also, as an option the retractable sleeve 112 may be biased
into a
normally extended position by a spring 118.
[0066] In operation, twist-lock engagement of the male electrical plug to the
female socket
is performed as follows. First, the conductor prongs of the male electrical
plug assembly
16 are inserted in the corresponding receiving holes of the female socket 110.
The sleeve
112 is then moved into its extended position (if not already biased into the
extended
position by spring 1180) so that nubs 116 extend beyond the front face 1 l0a
of the female
socket a distance sufficient to provide full engagement with the threads 92 of
the rotatable
sleeve 90 of the male electrical plug assembly 16. Next, the user simply
rotates the sleeve
90 in a tightening direction (e.g., clockwise for right hand thread, counter
clockwise for a
left hand thread). The tightening rotation of sleeve 90 draws the threads 92
into
engagement with the nubs 116 which pulls the conductor prongs of the male
electrical
plug 16 the remaining distance into the corresponding receiving holes of the
female socket
110. To disengage the male electrical plug 16 from the female socket 110, the
rotation of
rotatable sleeve 90 is reversed so that the threads 92 disengage from the nubs
116.
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[0067] As is best seen in Figs. 14 and 14a, either or both of the forward and
rear ends of
the rotatable sleeve 90 and the retractable sleeve 112 may be thinned and
tapered to
provide a seal against dust, moisture and like contaminants. Such "dust seals"
may also be
provided to any or all of the previously described embodiments.
[0068] With reference to Fig. 15, the respective engaging surfaces at the
forward ends of
the rotatable sleeve 90 and the retractable sleeve may be conformingly tapered
to provide
a desired compression fit upon twist lock engagement. In the example shown,
the
receiving inner cylindrical wall 120 at the forward end 112a of retractable
sleeve 112 and
the outer cylindrical wall 122 at the threaded end 92 of rotatable sleeve 90
are matingly
frusto-conical. The inner cylindrical wall surrounding each access opening 84
of the face
plate 82 of the embodiments shown in Figs. 7-11 may also be conically tapered
to provide
a desired compression fit with an electrical plug having the appropriately
configured twist-
lock engagement structure.
[0069] Fig. 16 shows the recessed prong end 130 typically found in the handle
or whip
portions of outdoor garden tools. The male insulator body portion 132 is
contained in a
housing 134 that is either formed integral with the handle for the garden tool
or provided
as a short whip portion connected to the handle of the garden tool. The prongs
136 (they
may include just two prongs or a third ground prong) are set back within a
recessed area
138 of the housing 134. In use, the female socket portion of an electrical
cord (not shown)
is received within the recessed area 138 for receiving engagement with the
prongs 136.
[0070] Fig. 17 shows an adaptation of the present invention for twist-locking
engagement
with the whip end of a garden tool in accordance with a fifth embodiment of
the present
invention. In this embodiment, the insulator body portion of the male
electrical plug
assembly 216 is provided with a face plate member 218 having a plurality of
threads 292
formed along an outer cylindrical wall of the face plate member 218. The
threads 292
preferably comprise four or five discrete thread members like those shown in
the previous
embodiments. In this embodiment, the face plate member 218 is connected to the
male
insulator body and may be removably fixed thereto by screws, or like
mechanical
fasteners, or may be formed integral with the male insulator body or formed
integral with
the housing 222 that encloses the male insulator body. Here, the male
electrical plug
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assembly 216 is embodied as a recessed connection formed as part of a whip
connector
end or handle portion of a conventional outdoor garden power tool. The housing
224 of
the whip connector end or outdoor garden tool handle structure extends around
the face
plate member 218 and prongs or conductors 236 and is sized sufficiently large
in diameter
to enclosed the leading edge portion of the rotatable and retractable sleeve
112.
[0071] Just as described above in connection with the embodiment shown in
Figs. 12-13,
the female socket 210 is enclosed by a sleeve 212 and a fixed conical end
housing 214.
The sleeve 212 is retractably coupled to the female socket 210 to permit a
desired amount
of translational movement (indicated by arrow B) of the sleeve 212 between a
first, fully
retracted position wherein a forward end 212a of sleeve 212 lies substantially
flush with
the front face 210a of the female socket 210 and a second, extended position
wherein the
forward end 212b of the sleeve 212 extends a distance beyond the front face
210a of the
female socket 210. The underside of sleeve 212 includes radially inwardly
extending tab
members 212b that are received within corresponding annular slot 210b provided
to the
exterior surface of the female socket210. Alternately, the tab members 212b
may be
configured as a single annular protrusion. In this case, the retractable
sleeve 212 is also
permitted to rotate axially about the female socket 210 as indicated by
direction arrow A.
The tab (or single protrusion) and slot dimensions are configured so as to
provide a desired
range of translational motion to the forward end 212a of the sleeve 212 beyond
the face
210a of the female socket 210. The forward end 212a of the sleeve 212 is
provided with a
plurality of spaced apart, radially inwardly projecting nubs 216.
[0072] In operation, twist-lock engagement of the male electrical plug to the
female socket
is preformed as follows. First, the conductor prongs 236 of the male
electrical plug
assembly 216 are inserted into the corresponding receiving holes of the female
socket 210.
The translatable and rotatable sleeve 212 is then moved into its extended
position so that
nubs 216 extend beyond the front face 210a of the female socket a distance
sufficient to
provide full engagement with the threads 292 of the face plate member 218 on
the forward
end of the male electrical plug assembly 216. Next, the user simply rotates
the sleeve 212
in a tightening direction (e.g., clockwise for right hand thread, counter
clockwise for a left
hand thread). The tightening rotation of sleeve 212 rotates the nubs 216 into
engagement
with the threads 292, which pulls the conductor prongs 236 of the male
electrical plug 216
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the remaining distance into the corresponding receiving holes of the female
socket 210. To
disengage the male electrical plug 216 from the female socket 210, the
rotation of
rotatable sleeve 212 is reversed so that the threads 292 disengage from the
nubs 216.
[0073] The sleeve 212 preferably retracts a sufficient distance out of the way
to permit use
with convention oversize plug connectors. The connecting structure of the
embodiments
shown in Figs. 17 and 18 may be modified as desired to include the tapered
dust seals of
Figs. 14-14A and the matching frusto-conical compression fit structure of Fig.
15.
[0074] Referring now to Figs. 19-20, the outer perimeter surface of face plate
218
preferably includes one or more valleys or depressions 294 formed therein. The
depressions 294 are configured to matingly receive a respective one of the
projecting nubs
216 of the female sleeve 212 as the sleeve is rotated to engage the threads
292. The
depressions 294 are positioned relative to the thread members 292 so as to
define the end
of the twist lock engagement between the sleeve 212 and the face plate member
218. In
this way, the user can readily determine by feel whether a locked engagement
exists so
that over tightening of the connector assembly can be avoided.
[0075] While I have illustrated and described the preferred embodiments of my
invention,
it is to be understood that these are capable of variation and modification,
and I therefore
do not wish to be limited to the precise details set forth, but desire to
avail ourselves of
such changes and alterations as fall within the purview of the following
claims.
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