Electrical boxes have been produced for many years in a variety of shapes and dimensions to accommodate various electrical devices such as switches, connectors and receptacles. The electrical boxes require a suitable mounting member for coupling the electrical device to the box. Metal electrical boxes have a tab or flange with a threaded hole for receiving mounting screws for mounting the electrical device directly to the box.
Electrical boxes are commonly made of metal that can be stamped as a one-piece unit or formed from different components that can be ganged and assembled to the desired dimensions. Metal electrical boxes can be grounded directly to a ground wire. The electrical device can also be grounded directly to the electrical box.
Electrical boxes are also made of plastic. Plastic electrical boxes are desirable from the standpoint of being inexpensive, lightweight and easy to manufacture. Plastic and other non-metallic materials used for making non-metallic electrical boxes cannot be grounded directly and require a suitable ground connection for the electrical device. Electrical codes require the electrical device to be grounded. A separate grounding member or ground wire is usually required to ground the electrical device properly.
Non-metallic electrical boxes are known to have metal ground members attached to the box for providing a ground connection to the electrical device. Many of these non-metallic electrical boxes have metal components attached to the box for mounting the electrical device.
One example of a ground strap in a non-metallic electrical box is disclosed in U.S. Pat. No. 4,315,100 to Haslbeck et al. This device includes a non-metallic electrical box with a metal ground strap attached to the top end of the electrical box. The ground strap has an opening for receiving a threaded fastener for coupling directly to the electrical box. A second threaded opening is provided at the opposite end of the ground strap for receiving a fastener for coupling directly to a ground wire. The ground strap is attached to the electrical box after the electrical box is formed.
Another example is disclosed in U.S. Pat. No. 3,210,458 to Palmer. This device includes a metallic strap attached to the side wall of the electrical box. The ground strap has a top portion with a threaded hole for receiving a mounting screw of an electrical device. The end of the top portion has a downwardly extending anchoring lug in a hole in the box to attach the ground strap to the box. The bottom portion of the ground strap has a tab that extends through a hole in the bottom wall of the electrical box. The tab is bent to attach the ground strap to the bottom of the electrical box.
Another example of a non-metallic electrical box with a ground strap is disclosed in U.S. Pat. No. 6,369,323 to Wright. This electrical box includes a metallic ground strap supported within the box by screws that extend into the bottom wall of the box. The ground strap has an L-shape with a top portion for supporting the electrical device. A top end has a downwardly extending hook-shaped member received in a hole formed in a top edge of the box.
Examples of other non-metallic electrical boxes having metal grounding components are disclosed in U.S. Pat. No. 4,960,964 to Schnell et al. and U.S. Pat. No. 6,403,880 to Elford et al. The '880 patent discloses a metal ground strap that is attached to the inner surface of the electrical box by a friction fit with inner struts molded within the box. The ground strap is assembled by positioning the ground strap into the cavity of the previously molded electrical box. The ground strap is held in place by forcing the ground strap into the box between the struts. The '964 patent discloses a grounding assembly for a non-metallic electrical box having a metallic grounding plate and a conducting clip. The grounding plate has a central portion with a downward extending coupling flange that frictionally engages a slot formed in a molded lug.
The prior non-metallic electrical boxes have metallic ground members that are assembled with the preformed molded box. The ground members require fasteners to couple the ground member to the box and an additional assembly step.
While the prior electrical boxes have been suitable for their intended use, there is a continuing need in the industry for improved non-metallic electrical boxes and methods of producing non-metallic electrical boxes.
USPTO Backgrounds
USPTO Backgrounds