The belt sway switch and pull cord switch are two of the protective devices for the belt system, and its working principle is simple to understand. There is a micro switch inside of the device, the mechanical unit will drive the micro switch, to complete connecting and breaking the circuit, then the control loop of the driving system will make the protection action, when a failure occurs to the belt conveyor system. However, in the production process, the failure is not referred to the maintenance downtime, it’s more like that the self-fault in the belt sway switch and the pull cord switch. Here are two common failures:
1. the belt sway switch is placed in a hostile environments, the short circuit would take place because of the worn control cable;
2. The control contact is rusted, which result to the short circuit fault to ground. This is the two faults that often occurs and leads to a more breakdown due to the short circuit. There will be an auto-circuit breaker in the circuit design of the belt sway switch, to avoid the above failures, then the relay will be controlled by the contact to display and drive the circuit, although this method can solve out the circuit deficiency of the belt sway switch and the pull cord switch, it wastes plenty of control cables and takes up electric component space. In order to deal with this technical problem, a new design is put forward: the contact will connect to the divide-shut brake with the iron core coil. The divide-shut brake contains the armature and the switch-plate that can break the contact of the belt sway switch. This is a simple, reliable and low power consumed protective device which also can diagnostics the related short circuit to cut down the circuit, increasing the safety factor to the belt conveyor system. The working current is small when the belt sway switch runs normally, the magnetic force generated by the iron core coil cannot catch up the armature, and the divide-shut brake will not proceed to the next action; but as the shut-circuit or the circuit grow quickly, the electric current passing through the iron core coil will increase, then armature will close to the coil to trigger the divide-shut brake, next the switch plate will press the main contact of the belt sway switch, In this series of rapid process, the circuit loop is broke up, which can guarantee the normal running of the belt system.
To the belt sway switch, the iron core coil is a detachable current coil, it changes the size of winding to adapt to the current of the device, which can slowly reduce the current in step, and achieve the protective movement at the short-circuit current fault point. At the meantime, there will be the lighting and alarming function, when the short-circuit presents to the belt sway switch. As the iron core coil sucks in the armature, there would not be power in the induction device, this is, no electromagnetism induction phenomenon, the photoelectric switch will inaction, while its contact closed, then the acoustic alarm sends out the warning message. At that time, the maintainer will find out the fault point of the belt sway switch according to the sound.