Last edit: 06/07/2023
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 senses whether the guard is closed or not and produces 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.
4.2 Interlocked guards without locking
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.
4.3 Interlocked Guards with Locking
When locked, the guard is prevented from opening until all hazardous machine operations have been stopped.
In this configuration, unlocking can take place:
- At any time by an operator, subsequently generating the stop command. The unlocking time must be longer than the stopping time of the hazardous functions (unconditional unlocking);
- Only after the hazardous functions of the machine have been stopped (conditional unlocking).