Belt off-track switch and pull-cord emergency switch for conveyors

Belt off-track switch

If a belt conveyor’s belt runs off track, it could be damaged. Often the whole facility will stop. To prevent this, a belt track switch signals that the belt is running off track in several stages.

The actuator of the belt off-track switch is connected to the roller levers of multiple microswitches. If a certain deviation is reached, the first switch sends a signal to the controller to correct the belt tracking. If the belt is so far off track that it could be damaged, another switch causes the conveyor system to stop.

Pull-cord emergency switch

Above all it is important to protect the safety of people who are working on the belt conveyor. So a pull-cord is installed parallel to the belt, which allows any employee to stop the conveyor immediately if they or a colleague are in danger.

The pull-cord is connected to the actuator of a pull-cord emergency switch, which in turn actuates the roller lever or push-button of a microswitch as soon as the cord is pulled. The microswitch opens a power circuit and the controller stops the drive immediately.

Which snap-action switches were chosen?

The manufacturer Dittelbach und Kerzler fits two different Schaltbau microswitches in its belt off-track and pull-cord emergency switches. The S800 snap-action switch is used to switch loads directly, the S826 has self-cleaning contacts that also reliably transmit small signal currents. Both microswitches have these features:

• Positive opening operation of the break contact (VDE approved)
• Suitable for safety-relevant applications (Machinery Directive, ISO EN 13849)
• High shock and vibration resistance
• Ambient temperature: -40 °C … +85 °C