1. Field of the Related Art
The present disclosure relates to wiring devices, and more particularly, to a wire clamp for a wiring device.
2. Background of the Related Art
Most countries utilize an alternating current based power source to power their electric grid infrastructure (referred to herein as an “AC source”). These systems can be either balanced or unbalanced and may include one or more phases, e.g., a three-phase AC source may include a first wire that provides a zero phase AC source, a second wire that provides a 120-degree phase AC source, a third wire that provides a 240-degree phase AC source and a return path (usually referred to as a “neutral” wire). The “neutral” wire may be used as a return path for the AC source supplied by the first, second and third wires. A wire includes (or is considered to be) a conductive path that can also be referred to as a “line.” The terms “line,” “conductive line” and “wire” are considered herein to be synonymous, and all include (or is equivalent to) a conductive path.
However, many AC wiring systems (e.g., those found in typical dwellings) also utilize an alternative return path called an earth ground. The earth ground, sometimes referred to as “the ground wire,” is generally used as a safety feature by providing an alternative return path to the return path provided by the neutral wire. The earth ground may include several conductive rods that are sufficiently driven into the earth. A number of rods of sufficient length are used to provide a high current capacity conductive connection to the earth with sufficiently low impedance.
Many dwellings and office buildings use either a single-phase, two-phase, or three-phase AC source and/or some combination thereof. The AC source may be accessed by standardized connections (referred to as “plugs”) that prevent a user from improperly connecting to an AC source, e.g., a three-phase AC plug cannot connect to a two-phase AC outlet. Additionally, many AC sources may selectively apply electricity to a load based upon whether a switch is turned on or off, e.g., a light switch.
To route, install and otherwise use AC electrical power, manufactures produce many different kinds of devices. These devices are referred to herein as wiring devices. Examples of wiring devices include electrical receptacles, switches, wiring boxes, ground fault circuit interrupters and the like. Typically, these wiring devices have a conductive strap or frame that can be grounded. By grounding the conductive strap, any AC source that unintentionally touches the conductive strap will return the AC current to the earth facilitating the detection of the unsafe condition while mitigating the risk of electric shock.
One method of grounding a wiring device is to ground the conductive frame or strap via a ground terminal. The ground terminal may be a piece of metal, such as a plate that includes a threaded opening for receiving a screw. The ground wire is stripped to expose the conductive layer (i.e., the outer insulating material is removed to expose the inner conductor). The stripped portion of the wire must then be bent or wrapped around the screw in some termination techniques. This is sometimes done using pliers and/or other tools. After the stripped portion of the wire is bent or wrapped around the screw's body, the screw can be tightened. The head of the screw secures the wire to the piece of metal grounding the ground terminal. Some prior art ground terminals have a limited torque capacity because the ground terminal is sometimes an extended thin piece of metal without additional structural support and are difficult to install because rigid wires can be difficult to bend or wrap around the screw.
Other wiring device terminals are also available for terminating wires. In addition to the ground terminals mentioned above, the other terminal types include load or line terminals, and/or neutral terminals. Together these terminals, depending on the mechanical configuration, may be wired using several different standard termination techniques. One such terminal is referred to as “side-wire” (sometimes referred to as “wrap-wire”) terminals that are conducive to a termination technique with the same name. To terminate a wire using a side-wire terminal, the wire is initially stripped and the exposed portion of the wire is wrapped around a screw. The screw is then tightened causing the head of the screw to bind the exposed wire between the head of the screw and a metallic plate (e.g., a brass terminal).
Another type of wiring technique is referred to as “back-wire” (also referred to as “clamp-wire”). In back-wire terminals, a screw engages a metallic plate with a second metallic place (referred to as a clamp) to compress a wire therebetween. The metallic plate (or brass terminal) has a threaded opening and the clamp is a second metallic place that slides along the shaft of the screw between the brass terminal and the head of the screw. A stripped wire is placed between the two metallic plates and the screw is tightened to compress the wire.
Yet another type of wiring terminal technique is referred to as a “push-in” technique. Push-in terminals are terminals in which a small hole is available for insertion of a stripped wire. A #14 AWG solid-metal wire is initially stripped about five-eights of an inch from the cut end and the stripped portion is inserted into the hole. A locking mechanism presses down on the wire and maintains electrical contact with the wire for use by the wiring device. The locking mechanism prevents the wire from being pulled out of the hole. To release the wire, a screwdriver is used to press into a release slot releasing the wire.
USPTO Backgrounds
USPTO Backgrounds