The invention relates to a dead-front electrical connector which is inexpensive to manufacture and safe to use.
There are two broad categories of electrical plug connectors: live-front and dead-front type. In the live-front type, the screws for securing the cord conductors to the terminals are reached through the face or front of the connector. After the screws are tightened the front is usually covered by a removable insulating disc. This type of connector has few parts and is simple and inexpensive. It requires, however, a high level of care in wiring and maintenance to ensure safety. One common danger of such connectors is that the removable insulating disc covering the front may become damaged or lost and the live terminals may thereby be exposed. In connectors of the dead-front type there is a heavy insulating base at the front of the connector and the terminal screws are accessed from behind this base. The wiring area is usually fully enclosed after wiring. Such connectors can accommodate greater variations in the quality of wiring and maintenance without loss of safety or service. However, prior art electrical connectors of the dead-front type generally have had more parts and have been more costly to produce than connectors of the live-front type.
One of the many ways of connecting insulated conductors to terminals of wiring devices is the so-called insulation displacement technique which typically involves pushing a conductor into a terminal slot by a pair of hand pliers such that the slot cuts through the insulation and makes electrical contact with the conductor wire. This technique typically requires skillful operators and convenient access to the terminal slots permitting the use of hand pliers.
The invented connector is of the dead-front type and makes use of a particularly convenient and effective combination of pivoted side covers, locking means and insulation-displacement terminals. One embodiment of the connector comprises a housing made up of a dead-front base and a pair of side covers having front ends pivotally connected to the base by web hinges. The base and side covers are integrally molded as a one-piece structure made of an electrically insulating material. The base supports terminals, such as a pair of power terminals and a ground terminal, which have wiring ends extending back of the base. The terminals may have male contacts, such as a pair of power blades and a ground pin extending through suitable openings in the dead-front base, or they may have female contacts receiving male contacts passing through suitable openings in the dead-front base, or both types of contacts. There are locking portions molded integrally with the dead-front base and the side covers which engage when the connector is closed and the back ends of the side cover are secured to each other, which locking portions resist relative motion between the side covers and the dead-front base so as to supplement and even replace, if needed, the holding action provided by the web hinges. The electrical cord may be wired to the terminals in the course of folding the side covers to close the connector by having the wiring ends of the terminals in the form of insulation displacement slots opening toward one of the side covers. The intact insulated conductor wires of the cord are laid against the open ends of the terminal slots and the conductors are pushed into the slots, as the side cover facing the open ends of the slots is being closed, by a pusher shelf or shelves integrally formed with that side cover and suitably disposed with respect to the terminal slots. The terminal slots may be curved to be along an arc centered at one of the hinges so as to facilitate the insulation displacement connection. Their open ends may be staggered such that one of the cord conductors would start being pushed into its slot before another. The dead-front base may have barrier walls which surround the wiring parts of the terminals to keep them out of electrical contact with each other and, moreover, to prevent the terminal slots from being undesirably widened when the insulated conductors are being pushed into them. The locking means which resist relative motion between the side covers and the dead-front base when the connector is closed may include integrally formed means for locking, in a permanently closed position, the side cover which does not face the open ends of the terminal slots so as to use the permanently locked side cover as a shelf against which the cord conductors can be laid prior to closing the other cover so as to make the insulation displacement connection.
The objects of the invention include providing a high strength, one-piece housing for a dead-front electrical connector, providing a housing of this type which fully insulates the wiring area of the connector, providing a dead-front electrical connector which affords great ease of wiring and assembly, providing a dead-front connector which eliminates the variability of workmanship associated with screw-type terminal wiring and stripping of conductor ends for screw-type terminals, providing a connector having a housing made up of a dead-front base and web-hinged side covers which lock to the housing when closed so as to remain locked even in the absence of the holding action of the web hinges, and providing a dead-front connector which is particularly simple and inexpensive to make, assemble and use. These and other objects of the invention are discussed in more detail in the appended Detailed Description.