Analysis and prevention of common faults in travel switches

1. Classic fault of travel switch

Generally speaking, the number of actions of the limit switch is 30,000 times, but when the limit switch used in some parts reaches about 10,000 times, the spring of the limit switch has failed and cannot rebound normally after the action. After replacement, use about 10,000 times, the travel switch spring fails again and cannot be used. The travel switches in other positions have been used normally 20,000 times.

2. The reason for the failure of the travel switch

The action of the general-purpose travel switch is 45 degrees, and the size of the roller is generally 17.4mm-17.5mm. For a general travel switch, when the driving rod moves 45 degrees, the upper surface of the roller and the center point of the roller when the driving rod is in the original position are on the same horizontal line. . If the striker is in contact with the travel switch at the initial position, the lower surface of the striker is lower than the center point of the travel switch roller, as shown in Figure 3-3, and the equipment does not stop immediately after the collision (for example, a delayed stop is set, or a mechanical stroke is set) There is a delay in stopping), the roller drive rod is compressed beyond the 45-degree approach travel, reaching the over-travel area, which damages the drive rod spring. At the initial position of the drive rod, the lower surface of the striker is lower than the center point of the roller, and the overtravel after being pressed is how much. In the long run, the service life of the travel switch will be reduced.

3. Travel switch failure prevention

The approach stroke of the roller drive rod is 45 degrees, and the action position is about 1/2 of the approach stroke and 1/4 of the roller. Therefore, when adjusting the universal roller-driven lever-type travel switch, the lower surface of the striker should be at the 1/4-1/2 position of the roller.

What is the basis for the selection and use of the travel switch?

1. Select the protection form according to the installation environment, whether it is an open type or a protective type;

2. According to the voltage and current of the control loop, choose which type of travel switch to use;

3. Select the appropriate head structure according to the force transmission and displacement relationship between the machine and the travel switch.  

4. The position of the position switch should be accurate when installing, otherwise the purpose of position control and limit cannot be achieved;

5. The position switch should be checked regularly to avoid poor contact of the contacts and failure to ac

hieve the purpose of stroke and limit control.

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