Travel switch, also known as limit switch, is used to control the travel of mechanical equipment and limit protection. In the actual production, the travel switch is installed in the pre-arranged position. When the module installed on the moving parts of the production machinery hits the travel switch, the contact action of the travel switch is realized to switch the circuit. Therefore, the travel switch is a kind of electric appliance that switches the circuit according to the travel position of the moving parts, and its action principle is similar to that of a button. Travel switch is widely used in all kinds of machine tools and lifting machinery to control their travel, terminal limit protection. In the control circuit of the elevator, the travel switch is also used to control the speed of opening and closing the car door, the limit of automatic opening and closing, and the upper and lower limits of the car protection.
According to its structure, the travel switch can be divided into direct moving type, roller type, micro moving type and combined type.
1-push rod 2-spring 3-moving break contact 4- moving bonding contact
(1) The structure principle of the direct-acting travel switch is shown in FIG. 1. Its action principle is the same as that of the button switch, but the opening and closing speed of the contact depends on the running speed of the production machine, so it is not suitable for the place where the speed is lower than 0.4m/min.
1- roller 2- upper arm 3, 5, 11- Spring 4- frame 6- pulley 7- press plate 8, 9- contact 10- horizontal plate
(2) The structure principle of roller type travel switch is shown in FIG. When the controlled mechanical bump block hits the bump bar with roller, the bump bar turns to the right, drives the CAM to rotate, and pushes the lever under the top to make the contact in the micro switch move quickly. When the moving machine returns, under the action of the reset spring, each part of the moving parts reset.
Roller type travel switch is divided into single roller automatic reset and double roller (horn type) non-automatic reset, double roller moving switch has two steady position, "memory" function, in some cases can simplify the line.
1 push rod 2. Spring 3. Compression spring 4. Moving break contact 5. Moving contact
(3) The structure of micro switch travel switch is shown in FIG. 3. Lxw-11 series products are commonly used.
