Safety switches
Protection of machine operators
Safety limiters break the control circuit of the machine start-up when the protective guard is opened or removed. Using operating contacts, they stop machine movement that could be dangerous to the operator.
Safety switches
Protection of machine operators
Safety limiters break the control circuit of the machine start-up when the protective guard is opened or removed. Using operating contacts, they stop machine movement that could be dangerous to the operator.
What is and how does a safety switch work?
The safety switch is one of the components of the safety system, which immobilizes, stops or shuts down the machine when a danger appears. Triggering of the signal must be forced by the machine's limiting element, such as a guard, so it is necessary to select and install the limiter in such a way that pressure is created on the activator when the guard is opened.
Removal/opening of the guard (after the hazardous movement has stopped) can
either be:
- at the time the machine is switched off for low inertia machines (machines where the rundown time is less than the time it takes for the operator to access the hazardous zone),
- delayed for high inertia machines (machines where the rundown time is greater than the time it takes for the operator to access the hazardous zone).
The start command for the machine can only be initiated following correct operation of the safety interlock switch. On its release, the NC safety contacts are opened by positive action or, for coded magnetic switches, change state (this should be monitored using a Schneider Electric safety control unit).
There are 3 types of safety switches:
- mechanical safety switches,
- magnetic safety switches,
- RFID safety switches.
What is and how does a safety switch work?
The safety switch is one of the components of the safety system, which immobilizes, stops or shuts down the machine when a danger appears. Triggering of the signal must be forced by the machine's limiting element, such as a guard, so it is necessary to select and install the limiter in such a way that pressure is created on the activator when the guard is opened.
Removal/opening of the guard (after the hazardous movement has stopped) can
either be:
- at the time the machine is switched off for low inertia machines (machines where the rundown time is less than the time it takes for the operator to access the hazardous zone),
- delayed for high inertia machines (machines where the rundown time is greater than the time it takes for the operator to access the hazardous zone).
The start command for the machine can only be initiated following correct operation of the safety interlock switch. On its release, the NC safety contacts are opened by positive action or, for coded magnetic switches, change state (this should be monitored using a Schneider Electric safety control unit).
There are 3 types of safety switches:
- mechanical safety switches,
- magnetic safety switches,
- RFID safety switches.
Mechanical safety switches
Switches with head for linear (plunger)
or rotary movement (lever)
For use on machines with low inertia and also on machines with high inertia, when used in conjunction with key-operated safety interlock switches with solenoid for monitoring access doors and/or guards. When used on their own, they are always installed in “positive mode” or combined in pairs, with one switch being in “positive mode” and the other in “negative mode”.
Switches with head for rotary movement
(lever or spindle)
Specifically designed for small industrial machines with low inertia fitted with small hinged doors, covers or protective guards. They help protect the operator by immediately stopping the hazardous movement of the machine as soon as the rotary lever or spindle displacement reaches an angle of 5°.
Magnetic safety switches
Specifically designed for industrial machines fitted with doors, covers or guards with imprecise guiding. They are ideally suited for machines subjected to frequent washing or liquid spray. They help protect the operator by immediately stopping any hazardous movement, as soon as the distance between the switch and its magnet is greater than 5 or 8 mm, depending on the switch model.