Patent Application
20140060889
The inventions described below relate to the field of electrical construction components and more specifically to removable shields for protecting electrical terminals.
Lighting control devices are available that can be powered from line (hot) and neutral power connections or from line (hot) and earth ground connections, the latter are commonly referred to as leakage to ground devices. Leakage to ground devices are restricted under Underwriters Laboratories (UL) standards to a maximum of 0.5 mA of leakage current. In residential and older commercial applications it is uncommon for neutral wires to be available, but an earth ground wire is available for safety purposes.
Due to the proliferation of such leakage devices which are used particularly in large buildings, there may literally be thousands of such devices in a single building. In large buildings, the earth ground connection is made unreliable because all the leakage current may alter the voltage potential at the earth ground connection for the building. This may interfere with certain equipment that requires a zero potential earth ground. Building codes and regulations are changing such that neutral wire connections will be required in all new construction. As these codes roll out, manufacturers of lighting controls are required to have both neutral connection and leakage to ground connection products available in order to compete in the lighting controls market. However, maintaining separate models of these devices is costly and takes up valuable shelf space, e.g., at an electrical supply distributor.
UL standards forbid providing both a neutral and ground connection for power in lighting controls for safety reasons. One approach in the art (SensorSwitch WSD NGX) is to make a product convertible in the field from a ground connection to a neutral connection by putting a green (ground) cover slip over a white (neutral) wire (or flying lead as is known in the industry). The wire with the green cover slip is considered an earth connection for a leakage to ground installation. If the installer sees that a neutral connection is available, he/she removes the green cover slip (by first cutting off a wire terminal that helps hold the slip into place over the wire), thereby exposing the white wire that can then be connected to neutral. This approach requires multiple steps on the part of the installer, which can lengthen the time to complete an installation involving hundreds of devices.
Slidable or rotatable covers are well known in the art, particularly for receptacle outlets. Such covers are not approved by UL as safety coverings because they may fail and slid out of the way, thereby exposing a neutral terminal to which could be miswired a ground wire, causing a safety hazard.
The devices and methods described below provide for a snap-off or breakaway cap that is molded into the plastic enclosure of a lighting control device that covers the neutral wire input hole and, if desired, the head of the terminal screw used to tighten the terminal to the wire after it is inserted into the hole. The terminal input or connection is securely protected until it is determined that an alternative wiring option is available and then the terminal shield is easily removable.
For example, the cap may be held to the surface of an enclosure by at least one, preferably at least two, plastic linkages. Preferably, the snap-off cap has molded in features to engage a common screwdriver or similar tool, e.g., a Philips screwdriver but could be straight edge screwdriver or a hex socket for an Allen wrench or similar. The tool is engaged into the mating features in the cap and the tool is used to break off the cap. Alternatively, the snap-off cap may be designed to allow a tool, such as a flat blade screwdriver, to be inserted under the cap, and the screwdriver to apply a lever motion to pop the cap off of the enclosure. The neutral terminal connection is then exposed for wiring to a neutral power wire. The ground wire may be left connected or disconnected and simply capped off, e.g., using a wire nut as is known in the industry.
Technically, if the terminal screw is designed such that it is not possible to place a wire under the head of the screw, e.g., by recessing the terminal assembly inside of the enclosure and only exposing a portion of the head of the screw in an opening, then all that is needed is to place the snap-off cap over the hole into which the wire would be placed. If the terminal screw head is more exposed, then a snap-off cap may be provided that covers the head and prevents insertion of a wire underneath of the head.
Electrical control device 10 of
Electrical control device 20 of
Terminal shield 30 is illustrated in
Terminal shield 40 is illustrated in
While the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the inventions. The elements of the various embodiments may be incorporated into each of the other species to obtain the benefits of those elements in combination with such other species, and the various beneficial features may be employed in embodiments alone or in combination with each other. Other embodiments and configurations may be devised without departing from the spirit of the inventions and the scope of the appended claims.
