Emergency stop button can also be called "emergency stop push button switch", the industry referred to as the emergency stop button. As the name implies, the emergency stop button is when an emergency occurs, people can quickly press this button to achieve protective measures.
In various factories, some large and medium-sized machinery and equipment or electrical appliances can be seen on the eye-catching red button, the standard should be marked with "emergency stop" meaning the same red font. This button can be collectively referred to as the emergency stop button. This button is simply pressed down directly. It can quickly make the whole equipment immediately stop or release some transmission parts. To start the equipment again, you must release the button, that is, just turn it clockwise about 45 ° and release it, the pressed part will pop up. That is, "release".
In the industrial safety inside the requirements of some transmission parts will be directly or indirectly in the event of abnormalities will produce harm to the body of the machine must be protected measures, emergency stop button is one of them. Therefore, in the design of some machines with transmission parts must be added to the emergency stop button function. And to be set on the surface of the machine can be easily pressed by personnel, there can not be any obstructions exist
(1) from the action time normally closed contacts from closed to open time than normally open contacts from the natural state to close the time is much shorter. Maybe you want to say, which can be less how much ah? Such a short time does not matter. But I have to say, this is particularly important in the event of a dangerous need for emergency stop. At this time, even a short time, even milliseconds or even microseconds is also very important. You know, accidents happen in a very short period of time. You can think about it, in such a short period of time, you use normally open contacts may not stop the machine or disconnect the switch, resulting in major machine damage or personal injury or death accident. But the use of normally closed contacts it is possible to stop the machine or let people electrocuted for a shorter period of time to avoid all this.
(2) from the button mechanism We know that the emergency stop button, whether normally closed or normally open contacts, will spring back up without pressing in place (press to the end), thus rendering the action ineffective. When using normally open contacts, in the emergency stop button is not pressed in place, the emergency stop is not played any role (because the normally open contacts are not closed); and the use of normally closed contacts is different, regardless of the emergency stop button is not pressed in place, only by the contact action, the emergency stop will work.
(3) from its control line Needless to say, the most basic role of the emergency stop button is the emergency stop in case of emergency, to avoid mechanical accidents or personal accidents. However, due to the long operation of the machine, the line, especially the emergency stop line part, may cause a fault break. At this time, if the emergency stop button using normally open contacts, the emergency stop part of the line failure will not be found, if the time to use the emergency stop button and then found it is already too late. When the normally closed contact is used, when the line of the emergency stop part fails, it will cause the machine to stop at most, and the loss will be relatively small. It is for the above reasons, in the design of the electrical control system, the emergency stop button is best to also use normally closed contacts.
(4) When an area of the emergency stop button is pressed, one pair of contacts goes to cut off the operation of the power equipment that needs to be stopped in that area, and the other pair of contacts goes to the PLC to cut off the starting circuit of the power equipment controlled by the PLC.
