Cutler-Hammer Safety Products Key Interlock Switches: KSCdirect.com is an authorized Cutler-Hammer wholesale distributor.

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Often the need arises for a device to provide a signal indicating that a door has been closed or that a machine guard is in place before a machine can be turned on or a sequence of operations can begin. While a standard limit switch would probably be able to do this function, the possibility exists that the unit could be false tripped or false actuated either accidentally or deliberately, thereby posing a danger to the person operating the machine.

In response to this problem, many switch manufacturers offer what is known as a key interlock switch. These switches look and operate similar to standard limit switches except for the operating heads. Instead of a rotary or plunger operating head, there is a key slot. In addition to being difficult to override, the safety interlock is also designed to fail to a safe mode. If, by chance, the contacts were to become welded together, removal of the key will physically tear the contacts apart, resulting in a safe condition.

Cutler-Hammer Key Interlock Switches by Eaton electrical business are available in both NEMA and DIN style housings. NEMA Style Key Interlock Switches feature durable metal housings, which removes power to the machine when the guard is opened. DIN Style Key Interlock Switches feature a reduced size and economical plastic housings. They remove power to the machine when the guard is opened.

Actuation of the interlock switch occurs only when the corresponding key is inserted into the key slot. The key is usually mounted on a door or machine guard in such a way that when the door or guard is closed, the key fits into the slot actuating the switch. The special design of the key makes the safety interlock switch extremely difficult to defeat. When inserted into the slot, the key performs three separate mechanical functions.