Limit Switch, Degree Of Protection: IP67, Omron

Product Details

What Is a 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 Horizontal, Vertical, and Multiple Limit Switches. The structure of a typical vertical Limit Switch is shown in the following figure as an example. Limit Switches are generally composed of five components.Drive Mechanism of Limit SwitchThe 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, as shown in the following figure.(1) Plunger There are two types of plunger (types A and B in the figure) 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.With the plunger drive, the movement of the plunger piston enables air to be compressed and taken in.Therefore, if the plunger is left pushed in for a long time, the air in the Limit Switch will escape and the internal pressure will become equivalent to atmospheric pressure. This will causethe plunger to tend to reset slowly even if an attempt is made to quickly reset it. To prevent this problem from occurring, design the system to limit the amount of air compressed by pushing in the plunger to 20% or less of the total air pressure in the Limit Switch. To extend the service life of the Limit switch, the plunger drive includes an OT absorption mechanism that absorbs the remaining plunger movement using an OT absorption spring and stops the movement of an auxiliary plunger that pushes the Built-in switch according to the movement of the plunger.(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.