For many years, trade shows and exhibitions have used what are termed "stringer" boxes to help deliver electrical power to the myriad of booths which are to be found at such shows and exhibits. Initially, such boxes can be described as a one-piece molded rubber junction box having thick walls with opposite ends of the box provided with hollow, nipple-like rubber extensions to receive the main power cable and with openings on opposed sides of the box to receive conventional electrical receptacles, switches and the like. A series of such boxes is usually mounted on a single power cable, each for delivery of power to one or more booths or exhibits. The wiring of even a single such early boxes to a power cable was both difficult and time consuming since the power cable needed to be pulled, usually with considerable difficulty, through the nipple-like extension at one end of the box, through the box and then through and out the opening at the opposite end of the box.
My U.S. Pat. No. 4,818,822 provides a junction or stringer box readily adapted to be installed on electrical power cable and which comprises interlocking box sections which may be joined together over the cable at any appropriate point to enclose the cable connections or in-line taps and to securely clamp the junction box to the cable. Such box, when constructed to be used as a stringer box, is made up of two identical sections and thus only a single cavity mold is needed to manufacture the box sections. The preferred material from which such boxes is made is an electrically non-conductive material such as PVC, ABS or a bisphenol A polycarbonate polymer, commercially available under the trademarks Lexan and Merlon.
The box of the aforementioned "822" patent is basically used in situations where a series of such boxes is mounted to a single power cable, which cable enters at one end of the box and exits at the opposite end. Although such boxes have proved to work extremely well, there is no provision in the box for sealing off an unused end of the box.
Moreover, many junction and outlet boxes used in electric wiring are provided with so-called knock-out plugs, which, when removed, provide an opening to allow for entry and exit of a power cable. Once such plugs have been removed, it is not possible to replace the plug.