CA1229140A - Power cord strain relief - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A strain relief for a power cord for electric devices includes a molded insulating body into which the power cord extends? a grounding lug extending from another side of the body and connected to the ground lead of the power cord. Grooves are provided in the sides of the body to enable the body to be assembled in a slot of the electric device, with the grounding lug of the strain relief adjacent a wall of the electric device, so that the grounding lug may be held to the wall of the device by a screw. The ground-ing lug may be used to function as a strain relief or auxiliary metal may be provided as a retainer. Connectors extending from the device on the portion opposite the grounding lug are adapted to be connected to leads within the electric device, the connectors being for example spade lugs. A fault sensing device such as an automotive fuse may be coupled to additional connectors on the body.

Description

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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 Closing of the bushing forms a slight bend in the cord so that it cannot be withdrawn through the hushing.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 !

--l--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 ; 30 manner.

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-2-8~09-20 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

-3 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;

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 :
further inhibit release of the power relief from the microwave oven.
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I, -pa-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.

- -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, go 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 ::
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 :- :
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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Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A strain relief for a power cord of an electric device, wherein the power cord has at least three leads, one of which is adapted to be grounded, said strain relief compris-ing an insulating body into which said power cord extends, a grounding lug extending from said body and connected 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, for engaging the walls of a slot in said electric device, and a pair of connectors extending from said body and connected to separate other leads of said power cord, for connecting conduc-tors of said device thereto.

2. The strain relief of claim 1 wherein said body is a molded insulating body.

3. The strain relief of claim 1 wherein said connect-ors are spade lugs.

4. The strain relief of claim 1 wherein said power cord extends into one end of said body and said ground lug extends from the opposite end thereof.

5. The strain relief of claim 4 wherein said one exter-nal groove extends on said body between said ends, and further comprising a second external groove parallel to said one groove on the side of said body opposite thereto, said connectors ex-tending from the portion of said body on the side of said grooves opposite said grounding lug.

6. The strain relief of claim 5 further comprising an additional groove interconnecting said one and second groove adjacent grounding lug.

7. The strain relief of claim 5 wherein the portion of said body on the side thereof from which said connectors extend has a planar surface on the side thereof directed to the end of said body into which said power cord extends.

8. A strain relief for a power cord of an electric device, 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 extending between said ends and in a plane parallel to and adjacent the plane of said ground lugs, said body having a first portion into which said power cord extends and from which said grounding 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.

9. The strain relief of claim 8 wherein said first and second connectors are spade lugs, and said second connector is connected to separate other lead of said power cord.

10. The strain relief of claim 8 further comprising third and fourth connectors extending from said second portion, said second and third connectors being connected internally of said body, said third and fourth connectors being adapted to receive fault sensing means, and said fourth connector being connected to a separate other lead of said power cord.

11. The strain relief of claim 10 wherein said first and second connectors are spade lugs adapted to be connected to said electric device.

12. The strain relief of claim 11 further comprising a fault sensor connected to said third and fourth connectors.

13. The strain relief of claim 12 wherein said fault sensor is an automotive type fuse.

14. The strain relief of claim 8 wherein said connect-ors extend from said body in a direction normal to the plane of said grooves.