Insulated cable for safety switch - avoids adverse effects caused by crushing of cable and shorting of wires by using controlled shorting to operate fuse and de-excite relay

摘要

The cable has at least two wires to connect e.g. a safety switch (1) to a controlled device such as a power-disconnecting relay (T) coupled across a dc supply (5). The insulation (9) of one of the wires has an electrically-conducting sheath (11). The conducting sheath is connected electrically to the switch and via a fuse (4) to one dc-supply pole (5). If the cable (2) is damaged by crushing such that the core of the first wire (3) and/or the core (10) of the second wire (6) contacts the conducting sheath (11) (which itself consists of wires (11), then a short circuit bridges the relay excitation coil (7) and causes the fuse (4) to open-circuit. This open circuit interrupts the supply to the excitation coil and causes the relay to de-excite. USE/ADVANTAGE - Provides protection where control cables are exposed to likelihood of mechanical damage (e.g. due to squashing by passing vehicle).