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TECHNICAL DESCRIPTION FOR LIMIT SWITCH AND DRIVE MECHANISM



What Is Limit Switch?
A Limit Switch is enclosed in a case to protect a built-in basic switch from external force, water, oil, gas, and dust. Limit Switches are made to be particularly suited for applications that require mechanical strength or environmental resistance.


The shapes of Limit Switches are broadly classified into
1. Horizontal,
2.Vertical, and
3.Multiple Limit Switches. 

Limit Switches are generally composed of five components.
1. Seals
2. Enclouser case
3. Built-in basic switch.
4. Connectors
5. Actuator

Drive Mechanism of Limit Switch:
The drive mechanism of the Limit switch is an important part of the Limit Switch and is directly linked to seal performance and operating characteristics. Drive mechanisms are classified into three types,.

1.Plunger
There are two types of plunger (types A and B) depending on the sealing method. With type A, an O-ring or a rubber diaphragm is used for sealing. The rubber seal is not externally exposed, and so resistance is provided against cutting debris from machine tools, but sand and fine shavings may become stuck on the sliding surface of the plunger. 
                                            
With type B, sand and fine shavings will not become stuck, and the sealing performance is superior to type A, but hot cutting debris striking the Switch may damage the rubber cap. Whether type A or type B is required depends on the location in which the Switch is to be used. 

2.Hinge Lever
The amount of plunger movement is increased at the end of the lever (i.e., roller) by the lever ratio, and so an absorption mechanism is generally not used.
                                         

3.Roller Lever
The structure of the WL is shown as a typical example. Other drives include those in which the plunger performs the function of the reset plunger and those in which a coil spring is used for the reset force and a cam is used to move the auxiliary plunger.
                                       ROLLER LEVER

Advantage´s of Limit Switch:
1.Can be used in almost any industrial environment
2.Very precise in terms of accuracy and repeatability
3.Consume little electrical energy
4.Can switch loads with high inductance
5.Can control multiple loads

Disadvantage´s of Limit Switch:
1.Generally restricted to equipment operating at relatively low speeds.
2.Must make direct contact with target.
3.Moving mechanical parts will wear out.

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