Note: Descriptions are shown in the official language in which they were submitted.
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Power Cord Strain Relief
This invention relates to arrangements for inhibiting
the passage of strain, on a power cord, from the internal elements
of a device cord by the power cord.
While power cord strain relief of the invention is
described specifically with respect to use on a microwave oven,
it is of course apparent that the invention is not limited to
this application of the relief device, the relief device being
readily adaptable to other electric appliances and electric
devices.
In one type of strain relief device for a power cord,
a plastic bushing is arranged to be fit around the cord and
snapped or otherwise held in an enlarged hole in an external wall
of the device powered by the cord. Closing of the bushing forms
a slight bend in the cord so that it cannot be withdrawn through
the hushing. In power cord relief assemblies of this type, the
wires of the cord must extend into the device for interconnection
at the proper location, and the assembly thereof requires the
steps of encircling the cord with the bushing at the proper
distance from the end thereof, inserting the cord and bushing
into the hole in the device, compressing the bushing to snap it
into place, and then feeding the wires in the device to the proper
location and connecting them. This latter step would of course
be done in a manner to avoid interfering with other components
of the device, especially if the wires terminate at some distance
from the relief, or to couple the power cord to the device at
an early stage in the assembly.
In another form of strain relief, as disclosed in US.
Patent No. 4~272,6~5, a strain relief enlargement is molded on
the power cord at the proper location from its end, the
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enlargement being especially configured and elastic to enable
it to be forced into a specially designed aperture in the de-
vice, by a special tool. In the arrangement of this reference,
the wires of the power cord extend directly into the device for
connections at locations which may be remote from the entry
point thereof.
The present invention is directed to the provision
of an easily produced power gore strain relief arrangement
which simplifies the installation thereof, as well as mini-
mixing the effort and expense required to protect the device from excess current or other faults within the appliance.
Briefly stated, in accordance with specific embody-
mints of the invention, these objects are achieved by providing
a power cord having an enlarged molded extremity on one end
thereof. The power cord extends into the molded end, and is
attached to spade lugs projecting from the plug for intercom-
section within the electrical device. The molded end is pro-
voided with a pair of parallel grooves or the like on opposite
sides thereof, to enable it to be slid into a slot in, for
example, a metal panel of an appliance. Preferably such panel
is arranged in the electrical device to have its slot covered
by a further element, such as another panel in subsequent
assembly steps, to inhibit removal of the mounted end from the
slot. In addition, a laterally extending lug extends generally
parallel to the plane of the grooves of the molded end, the Jug
having a hole enabling the firm interconnection of the lug with
the panel by means of a screw or the like. This lug is pro-
fireball coupled to the ground wire of the power cord, thereby
enabling grounding of the device in a simple and effective
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In further embodiments of the invention, further
spade lugs may be provided for connecting a fault sensor
thereto, in order to interrupt the current spade lugs in the
event of excess current. This feature serves to protect the
device in a simple manner, without the necessity of providing
further arrangements, such as fuses in the electrical appliance.
More generally, according to one broad aspect, the
invention provides a strain relief for a power cord of an elect
trig device, wherein the power cord has at Yeast three leads,
one of which is adapted to be grounded, said strain relief
comprising an insulating body into which said power cord
extends, a grounding lug extending from said body and connect
ted to said one lead of said power cord, at least one external
groove in said body in a plane adjacent the plane of said
grounding lug, or engaging the walls of a slot in said elect
trig device, and a pair of connectors extending from said body
and connected to separate other leads of said power cord, for
connecting conductors of said device thereto.
According to another broad aspect, the invention
provides a strain relief for a power cord of an electric de-
vice, wherein the power cord has at least three leads, the
first of which is adapted to be grounded; said strain relief
comprising an insulating body, said power cord extending into
one end of said insulating body, a grounding lug extending from
the end of said body opposite one end, and connected internally
of said body to said first lead of said power cord, first and
second parallel grooves in opposite sides of said body extend-
. in between said ends and in a plane parallel to and adjacent
the plane of said ground lugs, said body hazing a first portion
into which said power cord extends and from which said grounding
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lug extends, and a second portion on the side of said grooves
opposite said first portion, and first and second connectors
extending from said second portion of said body, at least said
first connector being connected to another lead of said power
cord.
In order that the invention will be more clearly
understood, it will now be disclosed in greater detail with
reference to the accompanying drawings, wherein:
FIG. 1 is a perspective view of a microwave oven,
one side being cut away to show the use of the strain relief
of the invention;
FIG. 2 is a perspective view of one embodiment of a
strain relief in accordance with the invention;
: FIG. 3 is an end view of the relief of FIG. l;
FIG. 4 is a bottom view of the strain relief of
FIG. 2;
FIG. 5 is a side view of the strain relief of FIG. 2;
FIG. 6 is a view of the strain relief of FIG. 2
taken from the side from which the cord thereof extends;
FIG. 7 is a cross section of the strain relief of
FIG. 1 taken along the lines 7-7 of FIG. S;
FIG. 8 is a cross sectional view of the strain relief
of FIG. 2 taken along the lines 8-8 of FOG. 7;
FIG. 9 is an exploded view of a further modification
of a strain relief in combination with a fault sensor;
FIG. 10 isaperspective view corresponding to FIG.
Jo 9, with the fault sensor connected to the strain relief;
FIG. 11 is an end view of the strain relief of
FIG. 10;
FIG. 12 is a bottom view of the strain relief of
FIG. 10;
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FIG. 13 is a side view of the strain relief of FIG.
10;
FIG. 14 is a view of the strain relief of FIG. 10
from the side to which the cable is connected,
IT. 15 is a cross sectional view of the strain
relief of FIG. 10 taken along the lines 15-15 of FIG. 13; and
FIG. 16 is a cross sectional view of the strain
relief of FIG. 10 taken along the lines 16-16 of FIG. 15.
FIG. 1 illustrates a microwave oven 10 having a
wall 11. The wall 11 may be an interior wall as illustrated,
; or it may be an exterior wall. A parallel sided slot (not
shown) is provided in the wall for receiving a power cord strain
relief device 12 in accordance with the invention. A line
cord 13 extends from the strain relief 12 externally of the
oven, the strain relief having a pair of spade connectors 32
Andy adapted to receive conventional connectors for applying
power to internal systems in the oven. The edge 16 in which
the slot for receiving the strain relief extends may be adapted,
in a final assembly of the microwave oven, to abut another wall,
such as external wall 17 of the microwave oven, thereby to
inhibit removal of the strain relief from the slot. In addition,
a hole 18 in the wall 11 is shown at the end of the slot to
receive a screw extending through a grounding lug of the strain
relief, thereby to ground the microwave oven as well as to
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further inhibit release of the power relief from the microwave
oven.
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While the strain relief in accordance with the invent
lion has been illustrated in use in a microwave oven, it is
apparent that the strain relief may be employed similarly in
other electrical appliances and devices, within the scope of
the invention. in the embodiment of the strain relief of the
invention illustrated in FIGS. 2 through 3, the strain relief
has an insulating body 20, for example of molded rubber or
plastic. The power cord 13 extends into one end of the body
portion 20. A grounding lug 21 is molded -to extend out of the
the body 20 and is connected internally of the body 20 to the
grounding wire 22 of the three wire power cord 13.
The body 20 has a pair of parallel grooves 24, 25 on
opposite sides thereof, in a plane just adjacent the plane of
the grounding lug 21, the grooves 24~ 25 being joined by a groove
26 at the end of the body 20. The grooves 24, 25 are adapted
to receive the sides of the slot in a sheet metal wall of the
appliance, the end groove 26 thereby engaging the end of such
slot. Since the grooves 24-26 are adjacent the grounding lug
21, the grounding lug 21 may be readily aligned with a suitable
hole in the appliance, to receive a screw for grounding the
appliance as well as holding the strain relief firmly in the
appliance.
The portion 30 of the body on the opposite side of
the grooves 24-26 from the grounding lug 21 has a surface 31
toward the power cord 13 that is in a plane perpendicular to
the plane of the slots and the axis of the power cord as it
enters the strain relief. This planar surface 31 is positioned
to be generally in line with the open end of the slot into which
the strain relief is inserted, so that the surface 31 may abut
a further sheet metal wall later assembled in the appliance,
to further hold the strain relief in position.
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A pair of spade Lowe 32, 33 extend from the side of
the portion 30 of the body 20, these spade lugs being internally
connected to the wires 34, 35 respectively of the power cord.
The spade lugs I 33 are hence adapted to be connected to the
internal components of the appliance by conventional connectors.
The spade lugs might also be wires or other devices to engage
the external electrical circuit.
In the modification of the invention illustrated in
FIGS. ~-16, the strain relief in accordance with the invention
is also readily adapted to protect the components of the
appliance from excess current. In this embodiment, a pair of
connectors 40, 41 are provided on surface 30 of the body 20
opposite the power cord 13. The connectors 40, 41 are adapted
to receive the spade lugs 42, 43 respectively of a fault sensor
device 44, such as an automotive type fuse. In this embodiment
of the invention the line 35 on the power cord is connected
internally of the body 20 to the connector 40, the connector 41
being connected internally of the body portion 30 to the spade
lug 33'. The other power cord connector 34 is connected intern-
ally of the body 20 to the spade lug 32'. The spade lugs 32'
and 33' or other devices are hence adapted to be connected
internally of the appliance to the electrical components thereof.
While the fault sensor 44 serves to protect the
components of the appliance by interrupting the current from
the power cord, for example by the melting of a fusible element,
the fault sensor is located completely internally of the
appliance and is hence not adapted to be changed by the user
of the appliance upon the occurrence of a fault. Since the fault
sensor is hence not exposed, it may be designed primarily from
the standpoint of the current at which the fusible element will
open. The operating voltage of the appliance need not be a prime
consideration, as in the case of conventional appliance fusing,
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devices. It is for this reason that conventional automotive
type fuses, designed for low voltage, may be economically
employed for the fault sensor.
It is of course apparent -that the connectors 40, 41
for receiving the spade lugs of an automotive type fuse will
be replaced by connectors for receiving cartridge fuses or the
like, and that the location for the connectors for such fault
sensing devices may be disposed elsewhere on the portion 30 of
the howdy 20. Alternatively, a space may be recessed in the
strain relief for receiving a cartridge type fuse, although such
a modification of the invention increases the cost of the strain
relief and may require the provision of a special tool for
replacement of the fault sensor.
The present invention thereby provides a strain relief
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device especially adapted for electrical appliances, wherein
the cost of the device and its installation is minimized, while
providing ensured grounding of the appliance as well as minimum
interference with the internal wiring of the appliance. The
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strain relief may also advantageously include a fault sensing
device for protecting the appliance from over current.
While the invention has been disclosed and described
with reference to a limited number of embodiments, it is apparent
that variations and modifications may be made therein, and it
is therefore intended in the following claims to cover each such
variation and modification as falls within the true spirit and
scope of the invention.
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