US3714614A

US3714614A - Apparatus for improving the grounding connection for an electrical unit

Info

Publication number: US3714614A
Application number: US00187285A
Authority: US
Inventors: L Ludwig
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-10-07
Filing date: 1971-10-07
Publication date: 1973-01-30
Anticipated expiration: 1990-01-30

Abstract

Apparatus for making a low resistance electrical connection between a metal mounting yoke and a metal flush box. The yoke is attached to an electrical unit and has a slotted portion for receiving a screw. A metal member is provided, said member having a first leg fixed to the slotted portion of the yoke. The member has a second cantilevered leg positioned parallel to the first leg, wherein the second leg is resiliently movable in the transverse direction. The second leg is at least partially positioned over a slot in the slotted portion to provide a yieldable pressure contact with the screw when the screw is inserted through the slot so as to provide a low resistance electrical connection between the yoke and the flush box when the screw is threaded to the flush box.

Description

United States Patent 1191 Ludwig Jan. 30, 1973 154] APPARATUS FOR IMPROVING THE GROUNDING CONNECTION FOR AN ELECTRICAL UNIT [76] lnventor; Louis Ludwig, 310 East 44th Street,

[51] Int. Cl. ..H01r 3/06 [58] Field of Search .339/14, 133,164

[56] References Cited UNITED STATES PATENTS 1/1964 Ludwig ..339/133R 5/1972 Jaconette ..339/14R Primary Examiner-Joseph H. McGlynn Attorney-Morris Kirschstein et a1.

{57] ABSTRACT Apparatus for making a'low resistance electrical connection between a metal mounting yoke and a metal flush box. The yoke is attached to an electrical unit and has a slotted portion for receiving a screw. A metal member is provided, said member having a first leg fixed to the slotted portion of the yoke. The member has a second cantilevered leg positioned parallel to the first leg, wherein the second leg is resiliently movable in the transverse direction. The second leg is at least partially positioned over a slot in the slotted portion to provide a yieldable pressure contact with the screw when the screw is inserted through the slot so as to provide a low resistance electrical connection between theyoke and the flush box when the screw is threaded to the flush box.

8 Claims, 5 Drawing Figures Patented Jan. 30, 1973 3,714,614

l NVEN TOR. 100/5 [vow/a APPARATUS FOR IMPROVING THE GROUNDING CONNECTION FOR AN ELECTRICAL UNIT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to apparatus for providing grounding connections for an electrical unit and more particularly relates to apparatus for insuring a ground connection between a metal mounting yoke attached to the electrical unit and a metal flush box in which the electrical unit is mounted.

2. Description of the Prior Art In present duplex three-socket plug receptacles which are generally mounted within a wall, power is supplied to two of the sockets so that current flows to an activated appliance when its plug is properly inserted in the live sockets of the receptacle. The third socket is connected to circuit ground and provides the ground path for the casing of the appliance via a third prong of the plug. This ground path is necessary to prevent the operator of the appliance from receiving a dangerous electrical shock in the event that one of the hot power leads of the appliance becomes exposed and touches the casing of the appliance. In the event that the appliance is rendered electrically hot, the circuit ground will provide a safety path which will prevent harm to the user of the appliance until a circuit fuse blows, thus rendering the appliance inoperative until repairs are made.

connect the mounting yoke to the flush box. The flush box, in turn, is then electrically connected to piping which ultimately leads to circuit or earth ground. If the screw is loosely fitted within the slot in the yoke, a poor electrical connection may. result therebetween, thus providing a high resistance path to circuitground. If in fact a high resistance path'to circuit ground is thus formed, great heat and "arcing might be created between the screw and the yoke which might in fact result in the causing of an electrical fire. Still further, an appliance which is plugged into the receptacle will not be provided with agood low resistance path to circuit ground, and if the casing of the appliance should be rendered electrically hot, it would pose a great safety hazard to anyone who is in close proximity of the appliance.

Previously, electrical units, which were packed by the manufacturer, had their mounting screws held in their respective slots by small cardboard washers. Since these washers were made of an insulating material, if they weren't removed when the unit was mounted in the flush box, an open circuit in the circuit ground path would result. I

In order to insure agood low resistance connection between the mounting yoke and the metal flush box, and to eliminate the need for insulating holding washers, there has been described in U. S. Pat. No. 3,432,793 a metal clip which is attached to a slotted portion of the yoke. The clip consists of two spring wires, both of which overlap the slot. The wires are bent and their ends are spot-welded to the yoke. The screw fits between both wires of the clip and is screwed into the metal box. The resiliency of the spring members provides for a good pressure and electrical connection between the screw and the clip so as to insure a good low resistance path between the mounting yoke and the metal flush box. It should be noted, however, that the clip is comprised of two separate components which require critical positioning in .order to insure good electrical connection to the screw. Since each component of the clip consists of a separate spring wire, handling and positioning of the wires can be timeconsuming and thus costly. Still further, the spot-welding of the wires can be cumbersome and if the welding is not performed properly, the springs might be out of position, snap off, or form a high resistance electrical connection with the yoke. A high resistance electrical connection between the yoke and the clip can result in a poor ground connection between the yoke and the screw, and also the yoke and the flush box, since the screw, which is held between the two spring wires of the clip, may never directly electrically contact the yoke thereby placing the high resistance connection in series with the ground path. Still further, if either one of the two spring members are distorted. by the screw beyond its elastic limit, a poor electrical connection might be formed between the screw and the clip, thus 1 again creating a poor circuit ground path.

SUMMARY OF THE INVENTION 1. Purpose of the Invention It is, therefore, an object of this invention to provide an improved apparatus for insuring a good low-resistance path for the ground terminal in an electrical wall unit.

It is a further object of this invention to provide for a more reliable and less expensive ground assembly for an electrical recepticle. I

It is a still further object of this invention to provide an improved grounding assembly having a reduced number of parts, which parts require less critical positioning for final assembly.

It is a still further object of the invention to provide a grounding assembly which eliminates the need for a manufacturers cardboard washer to hold the screw in the slot in the yoke.

Other objects of the invention will in part be obvious and'in part be pointed out hereinafter.

2. Brief Description of the Invention According to a broad aspect of the invention, there is provided an apparatus'for making a low resistance electrical connection between a metal mounting yoke and a metal flush box, said yoke being attached to an electrical unit, said yoke having a slotted portion for receiving a screw, wherein the improvement comprises a one piece metal member having a first leg fixed to the slotted portion of said yoke, said member having a second cantilevered leg parallel to said first leg, said second leg being resiliently movable in the transverse I direction and at least partially positioned over a slot in said slotted portion to provide a yieldable pressure contact with the screw when the screw is inserted through the slot, so as to provide a low resistance electrical connection between the yoke and the flush box when the screw is threaded to the flush box.

A feature of the invention provides that said first leg is so positioned on the slotted portion of said yoke that the screw will only be squeezed between an edge of the slot and said second leg.

Another feature of the invention provides that the distance between said first and second leg is at least equal to or greater than the width of the slot.

A further feature of the invention provides that said second leg has a portion extending over and around an outer edge of said slotted portion so as to prevent said second leg from being pulled away from said slotted portion when the screw is being removed from the flush box.

A still further feature of the invention provides that said slotted portion contains at least two raised parts extending from a remaining part of said slotted portion, and said first leg has two holes aligned with and receiving the respective raised parts, said raised parts having a pressed head for fastening said first leg between the respective pressed heads and the remaining part of the slotted portion.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings in which are shown various possible embodiments of my invention,

FIG. 1 is a top view showing a duplex receptacle and its mounting yoke attached to a metal flush box;

FIG. 2 is a back view of the mounting yoke having a metal member fixed to each slotted portion of the mounting yoke;

FIG. 3 is the reverse view of the mounting yoke shown in FIG. 2 illustrating the overhanging portion of one of the legs of the metal member;

FIG. 4 is a perspective view of the metal member illustrated in FIGS. 2 and 3; and

FIG. 5 is an enlarged fragmentary perspective view of the slotted portion of the yoke showing raised parts I extending from a remaining part thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS should be understood that the invention can be used effectively with other electrical units.

Each receptacle of socket contains three sockets (notshown), for mating with corresponding prongs of an electrical plug, which plug is connected to the end of a three wire cable that is attached to an electrical appliance. As previously described, two of the prongs and their mating sockets are in the circuit path for providing current to the electrical appliance, while the third prong and corresponding mating socket are connected to a pre-cautionary grounding path for the appliance. The receptacle has a rigid metal mounting yoke 12 attached thereto. Terminals l3 and 14 are internally electrically connected to the respective electrically activated sockets of the receptacle (not shown) and are externally connected to two respective electrically hot lines of a power cable (not shown). Terminal 15 on mounting yoke 12 is'internally electrically connected to the ground sockets of the receptacle (not shown), and externally connected to a third or ground line of the power cable (not shown). Yoke 12 is shown also to Although FIGS. 2 and 3 show a mounting yoke having two slotted portions and grounding arrangements, the following discussion will be limited to the slotted portion and grounding arrangement shown at the right side of FIGS. 2 and 3. In FIG. 2, metal member is shown to have a first leg 24 and a second leg 26. Leg 24 is firmly fixed to slotted portion 16 in such a manner as to not overlie a slot 28 in slotted portion 16. Leg 26 is cantilevered and parallel to leg 24. Leg 26 is also resiliently transversely movable in same plane as

legs

24 and 26, and is at least partially or wholly positioned over slot 28, so that screw 17 can pass through slot 26 and form a yieldable pressure contact with leg 26 so as to insure a good low-resistance connection between screw 17 and yoke 12, and ultimately yoke 12 and metal flush box 18 (shown in FIG. 1

As shown in FIG. 2, edge of leg 24, does not overlap slot 28 so that screw 17 is actually squeezed between edge 32 of slot 28 and leg 26. In a preferred fon'n of the embodiment the actual distance between leg 24 and leg 26 is at least equal to or greater than the width of slot 28, so as to insure that a good electrical contact is formed between screw 17 and yoke 12 when screw 17 is pushed against edge 32 of slot 28 by leg 26. If, on the other hand, edge 30 of leg 24 overlaps edge 32 of slot 28, electrical connection would be made directly between screw 17 and

legs

24 and 26, rather than directly between screw 17 and edge 32 of slot 28, and, therefore, if there were a poor electrical connection formed between member 24 and slotted portion 16 of yoke 12, a poor low resistance path would be formed between screw 17 and yoke 12, and thus ultimately between yoke 12 and metal box 18. Therefore, in view of the above, it is clear that a more reliable low resistance connection is formed between yoke 12 and metal box 18 when screw 17 is forced against edge 32 of slot 28, by leg 26.

In a further feature of the invention, as shown in FIG 4, leg 26 has an extended portion34, which portion includes a bent lip 36. As shown in FIG. 3, lip 36 extends past and around outer edge 38 of slotted portion 16, and overlaps a portion of a front side 40 of slotted portion 16, so as to prevent leg 26 from pulling away from the underside 22 of slotted portion 16 when screw 17 is being removed from the metal box 18 and/or from yoke 12.

Leg 24 of member 20 can have at least two holes 42 and 43 therein (shown in FIG. 4) so as to coincide with respective raised parts 44 and 45 (shown in FIG. 5), which raised parts extend from a remaining part 46 and result from indentations 47 and 48 (shown in FIG. 3)

formed in slotted portion 16. After leg 24 is placed over slotted portion 16 to coincide with raised

parts

44 and 45 described above, these parts can be pressed or riveted to form pressed heads 50 and 52 shown in FIG. 2, thereby fastening leg 24 between underside 22 of slotted member 16 and respective

pressed heads

50 and 52. Other alternative means could be used to fasten leg 24 to slotted member 16, such as staking slotted portion 16 to leg 24 at

indentations

47 and 48.

It should be noted that metal member 20 has a solid one piece construction which can be stamped out of a sheet of metal and bent into its final shape as shown in FIG. 4. Metal member 20 can be made of brass and can be a flat piece which lies in one plane except for bent lip 36. The use of metal member 20 in the final as sembly results in a cheaper and more reliable low resistance ground connection than what was used previously.

It is thus seen that there is provided an improved ground connection which achieves the several objects of the invention and is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the'above invention, and as various changes might be made in the embodiments, above set forth, it is to be understood that all matter herein described, or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

Having now described the invention, there is claimed:

1. In apparatus for making a low resistance electrical connection between a self-form maintaining electrically conductive mounting yoke and a self-form maintaining electrically conductive flush box, said yoke being attached to an electrical unit, said yoke having a slotted portion for receiving a screw, that improvement comprising a one-piece self-form maintaining electrically conductive member having a first leg fixed to the slotted portion of said yoke, said member having a second cantilevered leg parallel to said first leg, said second leg being resiliently movable in the transverse direction and at least partially positioned over a slot in said slotted portion to provide a yieldable pressure contact with the screw when the screw is inserted through the slot, so as to provide a low resistance electrical connection between the yoke and the flush box when the screw is threaded to the flush box.

2. An apparatus according to claim 1 wherein said first leg is so positioned on the slotted portion of said yoke that the screw will only be squeezed between an edge of the slot and said second leg.

3. An apparatus according to claim 1 wherein the distance between said first and second leg is at least equal to or greater than the width of the slot.

4. An apparatus according to claim 1 wherein said second leg has a portion extending over and around an outer edge of said slotted portion so as to prevent said leg from being pulled away from said slotted portion when the screw is being removed from the flush box.

5. An apparatus according to claim 1 wherein said slotted portion is staked to said first leg.

6. An apparatus according to claim 1 wherein said I tending portion of said second leg.

8. An apparatus according to claim 7 wherein said member is comprised of brass.

Claims

6. An apparatus according to claim 1 wherein said slotted portion contains at least two raised parts extending from a remaining part of said slotted portion and said first leg has two holes aligned with and receiving the respective raised parts, said raised parts having a pressed head for fastening said first leg between the respective pressed heads and the remaining part of the slotted portion.

7. An apparatus according to claim 4 wherein said member is a flat stamped structure except for the extending portion of said second leg.