A limit switch is an electrical device designed to restrict the movement of mechanical equipment. These switches come in two types: contact and non-contact. The contact type is the more straightforward option. A travel switch is installed on the moving parts of the machinery, while a limit position block is fixed at a point of relative movement, or at the opposite installation position. When the mechanical contact of the travel switch strikes the block, it cuts off (or modifies) the control circuit, causing the machine to either stop or alter its operation. Due to the inertia of the machine's movement, this travel switch includes a certain amount of "overtravel" to protect the switch from potential damage. Several non-contact methods exist; commonly used types include reed switches, photoelectric switches, and inductive switches.
Limit switches, commonly referred to as travel switches, can be mounted on static objects (such as fixed frames or door frames) or moving objects (such as vehicles or doors). When a moving object approaches a static one, the connecting rod of the switch actuates the switch contacts, either breaking a closed contact or closing an open contact. This change in the state of the switch contacts allows for control over the circuit and motor operation.
The limit switch is a frequently utilized low-current master electrical gadget. The impact of moving parts in production machinery prompts the switch contacts to either connect or disconnect the control circuit, fulfilling a specific control objective. Primarily, these switches are employed to govern the position or stroke of mechanical movements, which ensures that moving machines can automatically stop, reverse, alter speeds, or move back and forth within established limits. In electrical control systems, the limit switch serves to accomplish sequential control, positioning control, and position state detection. It ultimately governs the stroke and protective limits of mechanical equipment.
The limit switch comprises an operating head, a contact system, and a protective shell. In actual production settings, the limit switch is positioned in a predetermined location. When the module attached to the moving components of the production machinery makes contact with the stroke switch, it activates the movement of the limit switch contacts and facilitates circuit switching.
Therefore, the travel switch functions as an electrical device that activates the circuit based on the position of moving parts. Its operating principle is akin to that of a standard button. Limit switches are extensively used in various machine tools and lifting machinery to manage their stroke and provide terminal limit protection. In elevator control circuits, travel switches are deployed to regulate the speed at which car doors open and close, determine the limits of automatic door functions, and provide upper and lower limit protection for the elevator cab. Limit switches can be affixed to static objects (like door frames) or dynamic objects (such as vehicles). Throughout their operation, these switches control the action of circuits and mechanisms based on the open and closed states of their contacts.
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