Types of switches as safety devices in mechanical engineering

Safety switches play an important role in mechanical engineering. They minimize accidents by reliably interrupting or preventing hazardous movements and processes in the event of an emergency. Depending on the application, different types of safety switches are used. This article provides an overview of various safety switches, their functions and their applications.

What is a safety switch?

A safety switch differs from conventional switches by its special design features. These include forced-guided contacts that ensure a reliable disconnect even in the event of errors, as well as self-monitoring mechanisms for early error detection. Safety switches are designed to provide maximum reliability even in harsh conditions. They are subject to strict legal requirements, in particular the Machinery Directive 2006/42/EC, and must comply with relevant standards such as EN ISO 13849-1/-2 or IEC 60947. For more information on safety devices in mechanical engineering, see this blog.

Types of Mechanical Safety Switches

Depending on the application, there are different types of safety switches in mechanical engineering, which differ in their operation.

Emergency Stop Button

The ISO 13850 emergency stop button is one of the central safety devices on machines. In the event of danger, it must trigger the immediate and complete shutdown of the machine to protect people or equipment against injury and damage. Common designs include mushroom push-buttons that are quickly recognizable and easily accessible due to their shape and color (red on yellow background). Large-scale systems use rip cord switches, which can be tensioned over long distances. It is important that the switch can only be reset by a deliberate action to prevent an unintentional restart of the machine.

Two-hand control

Two-hand control in accordance with ISO 13851 is a safety system that requires the simultaneous actuation of two spatially separated push buttons. The machine process will be started only if both buttons are pressed within a certain time window. This ensures that the operator’s hands are not in the hazardous zone. This measure is particularly common in stamping presses, presses or similar machines with a high risk of injury.

Safety footswitch

Safety footswitches are used if manual operation is not possible or impractical. This is often the case with large or heavy machines where the operator needs their hands for other activities. These switches usually have special protective mechanisms such as protective hoods to prevent accidental tripping.

Load disconnectors and protective circuits

Load disconnectors are used to safely shut down electrical equipment under load, especially during maintenance or in emergencies. Together with protective circuits, they enable safe isolation and prevent the risk of residual voltages or unintentional restart.

Safety mechanisms to prevent errors

Safety switches are usually used in combination with various safety mechanisms. These include:

Guards

Switches in safety-critical applications are often provided with mechanical guards. These prevent accidental operation and protect against unauthorized access. Covers can be transparent to allow visual inspection, or lockable to allow controlled access.

Dual Contacts

Dual contact switches are often used in safety-related applications. This redundancy ensures that the safety function is maintained even in the event of a switch contact failure. At the same time, it enables fault detection by a safety relay or controllers, which increases failure protection.

Start-up protection after machine failure

Another important safety feature is start-up protection. After a power failure or technical malfunction, a machine must not restart automatically. Safety switches with start-up lockout or additional reset buttons prevent this unintended restart. The machine process can only be continued after a controlled reset by the operator.

Sensor-based safety devices

In addition to mechanical safety switches, sensor-based systems according to IEC 62046 are increasingly being used, which enable contactless monitoring.

Light barriers

IEC 61496-2 light barriers detect when an object or person enters a defined hazardous zone and immediately trigger a machine shutdown. Light barriers or light curtains are an effective safety measure, especially for open work areas or machines without fixed enclosures.

Distance Sensors

Distance sensors continuously monitor the distance to objects or people. If a defined minimum distance is not maintained, a warning or shutdown is triggered. They are used particularly in robots and automated systems.

Proximity Switches

Proximity switches contactlessly detect the position of machine components or operators. In safety-relevant applications, they act as a component of safety door monitoring or end position detection. For more information, check out our blog post about proximity switch vs. limit switch.