CH 4 - Operating principles and typical forms of intrlocking devices associated with guards

Interlocking devices can be classified using a great variety of criteria, e.g. the nature of the link between guard and output system, or the technological type (electromechanical, pneumatic, electronic, etc.) of the output system.

They have a guard position monitoring function that sense wheter the guard is closed or not and produce a stop command when the guard is not in the closed position. An interlocking device can also be used in the control of other function e.g. application of a brake to stop hazardous machine functions before acess is possible. Some interlocking device also have a guard locking function to keep the guard locked while hazardous machine function is present.

Table 1 and the figures below show the classification of interlocking device based on the actuation principle and the type of actuator.

In absence of interlocking, the shelter may be opened at any time, but the time required for access to the Danger Zone must be longer than that of the interlocking system triggered by the stop signal from the interlock.