1. Field of the Invention
This invention relates to power supply cord to be used by electricians preforming domestic or commercial electric service change or upgrade and more particularly to connection means for temporarily supplying power to circuit breaker and ground fault current interrupter protected circuits.
2. Description of Prior Art
It is generally accepted as common practice to disconnect power from the electrical service that is to be changed or upgraded. This is accomplished by cutting the supply conductors between the street utility pole and the Watt meter in domestic applications. After power has been disconnected there is need for electrical power to operate temporary lights and construction tools such as drills, saws and compressors in the construction area. In order to supply power to these tools it is necessary to connect an extension cord to the supply cable at the point at which it was cut. To accomplish this connection it has been necessary to strip the insulation from the ends of live power lines and mechanically connect the un-insulated ends of the power cable and the extension cord. In most cases this connection is made at a point that is exposed to the elements, in some instances in rain or snow, increasing the hazard to the person making the connection. The tools to be powered usually have a maximum load of 12 amps at 120 volts. The incoming power to most homes is 100 amps minimum at 120 volts on each of two power legs. It is necessary therefore to limit the current delivered by the extension cord to prevent incineration of the tools or the extension cord in the case of a short circuit. Due to the relatively unsafe conditions in most construction areas it has been found advisable to use a ground fault current interrupter to protect workers and equipment from undesired ground fault currents.
Electric plugs with built in fuse devices have been developed as a way to protect appliance cords from overheating due to excessive current flow. U.S. Pat. No. 2,636,096 describes a plug in receptacle. A conventional tubular glass bodied fuse is incorporated into the circuitry. U.S. Pat. No. 2,988,617 and 4,275,374 utilize a similar arrangement with the same type of fuse in an insertion and injection channel, making removal and replacement of the fuse relatively simple. U.S. Pat. No. 5,109,316 provides an extension cord with multiple outlet receptacle receiving power from a conductor connected to a standard electrical plug and fitted with a circuit breaker for protection from over heating due to excessive current flow. The design objectives of each of the above devices is convenience and simplicity of use, however, none of the above designs provide for ground fault current protection for operators or equipment. U.S. Pat. No. 4,567,456 provides a ground fault current interrupter protected extension cord fitted with a standard male electrical plug, but offers no protection from over heating due to excessive current flow.