Explosion-proof switching installation with a bus bar duct

In an electric switching installation of explosion-proof design with a bus bar duct on the input side and switching and control devices accommodated in housings designed to meet the requirements of the protective class "explosion-proof enclosure", wherein an explosion-proof plug connection, having a plug part and a jack part, and a safety element for the mutual locking of both parts, are arranged between each housing and the bus bar duct, wherein the safety element prevents removal of said housing from said bus bar duct when voltage is present in the bus bar duct, the improvement comprising:

• (a) the jack parts arranged on the bus bar duct, and the plug parts on the housings;
• (b) the safety element formed by a threaded insert and an end switch mounted on said bus bar duct next to each jack part and a fastening screw on each enclosure, cooperating with the threaded insert to mechanically connect said housings to said bus bar duct and after such connection is made, actuating said end switch such as to effect voltage supply to the bus bar duct when said housing is connected to said bus bar duct and to cut off voltage supply when said housing is removed from said bus bar duct;
• and
• (c) a protective lid movable fastened at the bus bar duct near the jack pat, said lid in its rest position exposing the jack part and in its operating position covering the jack part and said lid having a passage opening for a screw for cooperating with said threaded sleeve and said end switch.