The limit switch box is a housing device used to install and protect the limit switch. As a mechanical control electrical component, the limit switch is used to detect the position or range of motion of an object. When the object reaches the predetermined position, the limit switch will trigger a signal to control the operating status of related equipment. The limit switch box provides physical protection for the limit switch, protecting it from external environmental factors (such as dust, water, oil, mechanical collision, etc.), and can easily install the limit switch on various equipment.
Structure and composition of limit switch box
The structure and composition of the limit switch box are relatively complex, but it mainly includes the following key parts:
1. Shell
• Material: The housing is usually made of metal (such as aluminum alloy, stainless steel) and engineering plastics (such as polycarbonate, ABS plastic). The metal shell has high strength and can withstand large external impacts, making it suitable for harsh industrial environments. Engineering plastic shell are characterized by light weight and good insulation performance, and are widely used in equipment with high quality and insulation requirements.
• Shape & design: The shape of the shell is generally a cuboid or a cylinder, which is easy to install and fix. There are mounting holes on the surface of the shell. The specifications and positions of the mounting holes are determined according to different application scenarios and installation requirements, such as standard M4 or M5 threaded holes, which are convenient for installing them on the bracket, guide rail and other positions of the equipment with screws. Some shells also have transparent viewing windows for viewing the status of the internal limit switches.
2. Internal support and fixing structure
• Bracket Function: The internal bracket is used to fix the switch and ensure its stable position in the box. The shape and size of the bracket are designed according to the appearance of the limit switch and are usually made of metal (such as galvanized steel plate) or high-strength plastic. In some high-precision equipment, the bracket may also have a fine-tuning device for making small adjustments to the position of the limit switch.
• Fixing method: The limit switch can be fixed on the bracket by slot fixing and screw fixing. The slot-type fixing is convenient for installation and is suitable for small limit switches. The screw fixing is firm and suitable for high vibration and high impact environments.
3. Sealing structure
• Seal types: Mainly include sealing gaskets and sealants. The sealing gasket is generally made of rubber(such as nitrile rubber, silicone rubber ) or soft plastic, and its shape and size match the sealing part of the housing. Sealant is used to further enhance the sealing effect, especially in areas prone to leakage such as cable inlets and box joints.
• Inlet sealing: The cable inlet is one of the key sealing parts. Usually a rubber sealing sleeve or a sealant is used for sealing. The rubber sealing sleeve is put on the outside of the wire, with one end fitting tightly against the inner wall of the wire inlet and the other end tightly wrapping the wire to form a sealed channel to prevent moisture, dust, etc. from entering the box along the wire.
4. Wiring terminals and wiring channels
• Wiring terminals: Wiring terminals are components that connect limit switches to external circuits and generally include terminal blocks and connecting screws. There are multiple wiring positions on the terminal block, and each wiring position corresponds to a pin of the limit switch. By tightening the connecting screws, the metal core of the wire can be tightly connected to the wiring position to ensure good electrical conductivity.
• Wiring channels: Wiring channels are used to guide and organize wires so that the wires in the box are arranged neatly and orderly. It can be a wire trough designed inside the box, or it can be a channel formed by means of plastic clips, etc., to prevent the wires from being entangled and squeezed with each other, and reduce the risk of damage to the insulation layer caused by friction between the wires.
How does the sealing structure of the limit switch box achieve waterproof and dust-proof properties?
The sealing structure of the limit switch box is mainly waterproof and dust-proof by the following methods:
- Sealing gasket: Sealing gasket is usually made of rubber or soft plastic, and its shape and size match the sealing part of the housing. When the cover of the switch limit box is closed, the sealing gasket is squeezed between the cover and the box body, thereby filling the gap and playing a role in waterproofing and dust-proofing.
- Sealant: Sealant is used to further enhance the sealing effect, especially in some occasions where high sealing requirements are required. Sealant is usually applied to areas prone to leakage, such as cable inlets, box joints, etc. After curing, a tough sealing layer is formed to effectively prevent the intrusion of external substances.
- Inlet sealing: In order to prevent leakage around the wires, rubber sealing sleeves or sealants are usually used to seal the cable inlet. The rubber sealing sleeve is put on the outside of the wire and fits tightly with the inner wall of the wire inlet to form a sealed channel to ensure that moisture, dust, etc. will not enter the box along the wire.
Function and effect of switch limit box
1. Function and effect:
• Protect limit switches: Provide a protective housing to prevent the limit switches from being disturbed and damaged by the external environment.
• Fixing and Supporting: Ensure the limit switch maintains a stable position in the box through internal brackets and fixing structures.
• Sealed waterproof and dust–proof: The sealed structure prevents the intrusion of moisture, dust and other foreign substances to ensure the normal operation of the limit switch.
2. Working principle:
• When the object being measured reaches the preset position, the mechanical structure or sensing device inside the limit switch is triggered.
• Changes in the mechanical structure or sensing device are converted into electrical signals and output to the external circuit through the wiring terminals.
• The external circuit performs corresponding control operations based on the electrical signals received, such as starting, stopping or reversing the motor.
Application areas of switch limit boxes
Limit switch boxes are widely used in various occasions where the position of objects needs to be detected and controlled, such as:
- Automated production line: Used to detect the position of the workbench and workpiece and trigger the action of the next process.
- Machine tool equipment: Used to detect the stroke and position of the machine tool to prevent the machine tool from moving beyond the predetermined range.
- Lifting equipment: Used to detect the upper and lower limits of equipment such as lifts and cranes to ensure safe operation of the equipment.
- Door control system: Used to detect the open and close status of doors in automatic door, rolling door and other systems.
- Dangerous occasions protection: In chemical plants, mines and other places where hazardous substances exist, it is used to monitor equipment movement to prevent equipment operation errors or accidental triggering of potential dangerous events.
HNUAMN product recommendations
APL-210N Limit Switch Box
HANUMNA would like to recommend to you APL-210N limit switch box，which with limit switch box valve position indicator G1/2 inch port 4 to 20mA 250VAC 3A 125V 5A 250VDC 0.2A 125V 0.4A 30V 4A mounting bracket and fixing bolt.
APL-210N limit switch box is a kind of site instrument which can check the valve status in automatic control system through signal output of switch input under the ON or OFF valve position. The PLC will get this signal and later confirm and execute the next program.
APL-210N limit switch box features:
- The indicator is intuitive and striking, water-proof, and reliable.
- It owns multiple contact of terminal board, eight standard connecting points, and standard double dual interfaces.
- It is equipped with mounting bracket and bolt.
HANUMAN can offer you with limit switch box and limit switch box valve position indicator, such as the APL-210N, APL-310N, and APL-410N-EX, with optional connection port sizes of G1/2” and G3/4”.
Please consult HANUMAN if you have any needs!
