Typically, electrical connectors and other wiring devices have cable clamps for gripping and coupling an electrical cable thereto. These cable clamps are conventionally designed to have at least one clamping member movable substantially perpendicular to the longitudinal axis of the cable. The clamping member, which may be a screw, a rib, or a series of ribs, extends into the passageway of the connector and engages and thereby couples a cable within the connector.
More than one member may be used. When this is done, the members often oppose one another and thus, engage opposite sides of the cable.
However, when significant longitudinal force is applied to a cable coupled within one of these typical connectors, the cable tends to slip because the clamp is unable to satisfactorily grip and hold the cable within the connector. In other words, the gripping force produced by the members on the cord is insufficient to securely hold the cable within the connector.
Furthermore, conventional cable clamps have a relatively small area that engages the cable. Thus, the gripping force on the cable is concentrated in a small area and the stress on the cable is high. The concentrated stress may cut, deform or otherwise damage the cable. Also, the highly concentrated gripping stress produces high stress at the cable exit point. Thus, when the cable is flexed cable fatigue failure may result.
Examples of some prior electrical connectors with cable clamps are disclosed in the following U.S. Pat. Nos.: 2,577,748 to Gillespie; 2,911,616 to Townsend; 3,402,382 to De Tar; 3,437,980 to Smith; 3,784,961 to Gartland; 3,865,461 to Ludwig; 4,080,036 to Hagel; 4,178,056 to Lee; 4,213,667 to Wittes; and 5,021,006 to Fargeaud et al.
Thus, there exists a need to provide an improved electrical wiring device with cord clamping mechanisms which distribute a uniform force over a wide area on the cable, thereby resisting cord slippage and damage. This invention addresses this need in the art, along with other needs which will become apparent to those skilled in the art once given this disclosure.
USPTO Backgrounds
USPTO Backgrounds