Electrical device having an improved mounting strap

[57] ABSTRACT

An improved mounting strap is provided for electrical devices, such as outlet receptacles and switches which are mounted in wall outlet boxes. The improved mounting strap includes a substantially T-shaped keylock stamped from the mounting extension and the side portion adjacent thereto of the mounting strap for engaging a complementary shaped recess in the insulative cover of the electrical device. In addition, the side portion further includes laterally extended flanges on each side which engage shoulders formed in the side of the housing. If the side portion of the moimting strap includes a grounding flange then that side in addition to being secured by the grounding screw is locked to the body of the device by an upward projection on the grounding flange which is engaged in a recess in the cover and by a D-shaped projection in the side of the housing which is received in a complimentary shaped cavity in the mounting cavity.

Claims, 5 Drawing Figures

<img file="US3688239A_D0001.tif" />

Patented Aug. 29, 1972

3,688,239

<img file="US3688239A_D0002.tif" />

3,688,239

ELECTRICAL DEVICE HAVING AN IMPROVED MOUNTING STRAP

BACKGROUND OF THE INVENTION

This invention relates to electrical devices of the type to be mounted in a wall outlet box, and more particularly, to an improved mounting strap therefor.

Heretofore, conventional electrical devices to be mounted in an outlet box usually include a mounting strap which is secured to the bottom of the housing of the electrical device either by a center rivet or by the screw which secures the cover to the body of the housing. The conventional mounting straps include side portions which extend along the sides of the housing and mounting extensions extending outwardly from the ends of the side portion parallel to the face of the device for securing it to an outlet box. Such mounting straps have been subject to distortion and separation from the housing of the device during or prior to installation by careless handling, and after installation by distorting forces applied to the device during use. The latter type of distortion is especially true in locking type electrical devices.

Various attempts have been made to solve this problem. For example, in U.S. Pat. No. 3,310,770, combination of upward projections on laterally and inwardly turned flanges of the side portions of the mounting strap which engage the cover of the housing and inclined tongues which engage recesses on the sides of the housing are provided to eliminate such distortion. This arrangement, however, increases the complexity of the electrical device by requiring extra flanges on the mounting strap, locking surfaces in the cover, and recesses formed in the sides of the housing. In addition, the inclined tongues protect against distortion mainly by means of frictional engagement with the inner surface of the recess which does not provide a good gripping action against distortions of greater force. U.S. Pat. Nos. 1,540,330 and 1,631,507 also utilize frictional grips. Finally, in U.S. Pat. Nos. 2,231,976 and 2,857,452 shoulders formed in the lateral edges of the side portions of the mounting strap or cavities formed therein are provided to engage complimentary shoulders or projections formed in the sides of the housing to prevent distortion. These, however, only protect against distortion forces which are applied in a direction perpendicular to the face of the receptacle and do not prevent distortion where the forces are inclined to the face of the receptacle. Thus, a simple and adequate solution to the distortion problem has not been provided by the prior art.

SUMMARY OF THE INVENTION

The present invention provides such a solution by providing a T-shaped key-lock stamped out of the mounting extension and side portion adjacent thereto which is received in a complimentary shaped recess formed in the body of the receptacle. In addition laterally extending shoulders in the side portions may be provided to engage complimentary shaped shoulders in the side of the body. If a grounding flange is provided at one side of the mounting strap, that side may be locked to the body of the receptacle by an upward projection on the ground flange which engages a recess in the cover of the body an by a D-shaped cavity in the side portion of the mounting strap which engages a complimentary shaped projection in the side of the body.

It is, therefore, a general object of the present invention to obviate and minimize the disadvantages of prior known mounting straps for mounting electrical devices in outlet boxes.

It is a more specific object of the present invention to provide a mounting strap for an electrical device which positively engages the body of the device at both sides to prevent distortion of the mounting strap away from the body.

It is another object of the present invention to provide a mounting strap for an electrical device having a key-lock extending from the side portion thereof to positively engage the body of the electrical device to prevent distortion.

BRIEF DESCRIPTION OF THE DRAWINGS

These as well as other objects and advantages of the present invention will become apparent to those skilled in the art from a perusal of the appended claims and the following description when read in conjunction with the attached drawings in which:

FIG. 1 is a top plan view of an electrical device having the improved mounting strap of the present invention;

FIG. 2 is a side elevation thereof;

FIG. 3 is a cross sectional view thereof taken along lines 3—3 of FIG. 2;

FIG. 4 is an exploded perspective view of an electrical device and the improved mounting device of the present invention; and

FIG. 5 is an illustration of the distortion problem of conventional mounting straps which the present invention obviates.

detailed description of the preferred embodiment

Referring to the drawings, the improved mounting strap 10 of the present invention is shown for illustrative purposes only as being used with a duplex outlet receptacle 12. It will be apparent that other electrical devices may also be provided with the improved mounting strap of the present invention. The duplex receptacle includes a housing 14 and a cover 16 which is secured to the housing by a center rivet 18. The duplex receptacle is illustrated as including the conventional openings 20 for receiving a male plug and is provided with contact terminals 22 for wiring purposes. Further details of the receptacle are not shown inasmuch as they do not form part of the present invention.

The mounting strap 10 includes a bottom section 24, side portions 26 and 28 extending from either end of the bottom section 24 and mounting extensions 30 and 32 extending from the ends of the side portions 26 and 28, respectively remote from the bottom section 24. The side portions 26 and 28 extend parallel to the face of the receptacle 12 and may include openings 34 or ears 36 for securing the receptacle into a conventional outlet box. One side portion 28 may also include a grounding flange 38 which is secured to a longitudinal side of the housing 14 by means of a grounding screw 40 to which a grounding wire may be attached. The mounting strap is generally secured to the receptacle through the center rivet 18 which may include an inter3,688,239 nally threaded post 42 in which a plate securing screw is threadably engaged.

Thus far described, the mounting strap 10 is completely conventional. As such it would be subject to distortion during, or before installation by careless handling or by distortion forces during use as illustrated in FIG. 5 in which the side 44 in which the grounding flange is provided may be slightly distorted away from the body of the receptacle inasmuch as the grounding flange tends to hold it in place to some degree and may be more severely distorted at the other side 46.

To overcome this problem, the improved mounting strap 10 of the present invention is provided with a Tshaped key-lock 48 which is Stamped out of the mounting extension 30 and the side portion 26 adjacent thereto to extend inwardly towards the body of the receptacle 12. The T-shaped key-lock 48 is received in a complimentary shaped recess 50 formed in the cover 16 of the receptacle 12 to positively lock the strap to the body of the receptacle 12. In addition, the side portion 26 is provided with flanges 52 which engage complimentary shaped shoulders 53 in the side of the housing 14. On the opposite side portion 28 of the mounting strap 10 positive locking is provided by an upward stepped projection 54 formed at the upper edge of the grounding flange 38 which engages a complimentary shaped recess in the cover 16 and by providing a Dshaped opening or cavity 56 in the side portion 28 in which a complimentary shaped projection 58 in the side of the housing 14 is received.

The T-shaped key-lock 48 provides a positive lock between the mounting strap and the side of the body of the receptacle 12 and prevents distortion of the side portion 26 of the mounting strap 10 therefrom. The upper projection 54 of the grounding flange 38 also provides a positive lock between the side portion 28 of mounting strap 10 and the body of the receptacle and prevents distortion of the mounting strap 10 therefrom. The engagement of the flanges 52 with the complimentary shaped shoulders 53 in the side of the housing 14 and the D-shaped projection 58 received in the cavity 56 also cooperate to prevent distortion of the mounting strap especially due to the component of distortion forces perpendicular to the face of the receptacle. In all, these various elements cooperate to prevent any distortion whatsoever of the mounting strap away from the body of the receptacle regardless of the direction of the distortion forces or the magnitude. Also it will be readily apparent that where no grounding flange is provided a T-shaped key-lock could be provided in both side portions of the mounting strap.

Thus, an improved mounting strap for an electrical device has been provided which overcomes the problems of distortion of the mounting strap before and during installation of the device in an outlet box and during use thereafter.

It is believed that the many advantages of the present invention will now be apparent to those skilled in the art. It will also be apparent that a number of variations and modifications may be made without departing from its spirit and scope. Accordingly, the foregoing description is to be construed as illustrative only rather than limiting.