Keys for limit switches

Keys for limit switches

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Keys for limit switches

Key limit switches are widely used in industry, especially in production processes, wherever there are machines that pose a threat to human health and life. Thanks to the key adapted to the switch and acting as a physical interlock, the limit switch does not allow access to the live parts of machines due to safety or due to the necessity to maintain the continuity of a specific process.

Safety zone protection and machine control

Key limit switches used in industrial plants may protect the casing against opening, eg in the case of machines with a long run-on time, when they block access to the device before its complete stopping. They perform a similar function as protection of security zones separated by fences, preventing the opening of partitions when it is dangerous or harmful to the process being carried out.

Limit switches with safety element

Machine control in the production process usually has to integrate their work with securing free access to live parts of machines and specific danger zones. The protection most often consists of various sensors and switches, e.g. limit switches, the status of which is monitored by a safety relay or a PLC controller. In this way, the work of the machines is coordinated with the security measures.

Key switch

Keys for limit switches are small pieces of various shapes to fit the most common industrial covers. They are attached to the leading edge of the cover (e.g. in hinged covers, similarly to regular doors, the key is attached where the lock bolt is located in the leaf) so that when it is closed, it rests in the opening of the limit switch head. In the offer of manufacturers such as Schneider Electric or Siemens , you can find both simple, rigid and flexible keys (activators).

The keyed limit switches are usually made of metal bonded to the plastic, which is formed in such a way as to allow the best possible attachment to the cover. They are perfect for applications where the closed state of guards is required until the potential hazard is no longer present, or until a predetermined safety condition occurs. Their presence in the system reduces the risk of opening the cover during hazardous machine operation and protects against unnecessary interruptions in production. The devices provide electrical coupling between the control circuit and the shield, are easy to install and economical.

Hinge limit switches

Hinge limit switches have a securing element in the form of a metal pin. They are attached directly to the cover hinge and are ideal for use in machines where the product is distributed through a hinge cover - for example conveyor belts with baffles used due to dust, water or other process fluids in specific areas. The side mounting position has the advantage that the limit switch does not block transport through the cover. Hinge fasteners are also used in security fencing.

Non-contact interlocking connectors

The limit switch keys are a kind of mechanical interlock. However, the group of limit switches also includes devices that communicate by radio in the RIFID coding technology. Activation of the safety switches does not require physical contact of the device with the actuator, and the large detection field guarantees operation even in the event of the door not being aligned with the frame or inaccurate fitting of the movable cover with the fixed part of the fence. Due to the uncomplicated housing compared to key switches, the use of RIFID locks is recommended wherever the fence and the device are exposed to dirt. Although non-contact switches have many advantages, sometimes their proper functioning requires the use of control modules, which increases the cost of purchase.