Foolproof emergency-stops and emergency-stop switches – safety that cannot be manipulated
Foolproof emergency-stops and emergency-stop switches, such as emergency-stop mushroom heads, are a central safety component for machine controls and industrial plants. Unlike simple emergency switches, they prevent manipulation, malfunction and unintended handling. For critical applications, e.g. in the machine building, robotics, packing or conveyor industry, they guarantee that in a case of emergency, a machine is being stopped without fail.
In this blog, you will learn what defines a foolproof switches, how they can be realised technically, why they are crucial for modern plants and in which application cases they are especially relevant.
What is the meaning of "foolproof"?
An emergency-stop or emergency-stop switch is considered to be foolproof if its safety function does not disappear through manipulation. Theoretically, normal switches can be "outwitted" – for example by consciously actuating and latching the mushroom head without opening the contacts. This is being prevented successfully in the case of foolproof devices, as is a requirement of the standard EN 60947-5-5.
Technical realisation of the foolproof function
Mechanical positive opening
A movement of the red mushroom head is directly being transferred to the contacts. Springs or rubber elements that could fail in the case of malfunction are being avoided.
It must be ensured by appropriate mechanical measures that the mushroom head of the emergency-stop only latches when the contacts are definitely activated. On the other hand, the contacts may only activate if it is guaranteed that the mushroom head will latch in safely.
Why the foolproof function is decisive
Foolproof switches are necessary, because they ...
detect manipulation attempts,
bring the plant into a safe state,
fulfil the standards: they are in accordance with DIN EN ISO 13850 regarding the control of safety-oriented applications and with EN 60947-5-5.
Application of foolproof switches
Foolproof emergency-stops and emergency-stop switches are used everywhere, where highest safety requirements apply, such as:
Robotics: industrial robot cells with direct human-machine interfaces
Productions with big numbers of staff: logistics and intra logistics
In these areas, foolproof switches prevent that a necessary safety precaution is being avoided unintentionally through manipulation.
Foolproof emergency-stops / emergency-stop switches from Schlegel – selection, features and applications
Georg Schlegel GmbH & Co. KG from Duermentingen offers a broad portfolio of control units with worldwide product certifications. This also includes emergency-stops and emergency-stop switches made from high-quality plastics that are designed for high safety requirements – including foolproof variants.
Special features of Schlegel solutions
Certified safety: Schlegel emergency-stops and emergency-stop switches are certified in accordance with the standards EN 60947‑5‑5 and DIN EN ISO 13850 and approved by TÜV.
Contact blocks with positive opening: The contact blocks are with positive opening according to IEC 60947‑5‑1 and are available with one or two channels – an integral part of safe emergency-stop solutions.
Robust construction: Degree of protection from IP65 to IP69K make the switches suitable for demanding industrial environments.
Versatile variants: Schlegel offers various shapes, sizes and release types (twist or pull to release) and combinations with AS-Interface-Safety@Work.
Self-monitoring contact blocks: They can detect errors like loose mounting or mechanical damage and automatically trigger the emergency-stop signal in such cases.
Labelling: The switches from Schlegel are available with standardised labelling options ("EMERGENCY-STOP" lettering or symbol) to ensure quick identification and operation according to the standard.
Concrete product examples
Emergency-stop mushroom heads FRVKOO / FRVKOOI: Emergency-stops or emergency-stop switches with round shape from the SHORTRON series with foolproof versions, degree of protection IP65/67, mechanical lifetime of more than ten thousand switching cycles and conformity to standards.
Other variants: There are also illuminated versions with status indication (active/inactive) available to improve perceptibility and operability.
Summary
Foolproof emergency-stops and emergency-stop switches prevent that safety functions are bypassed and ensure a reliable protection of humans, machines and processes. They offer highest operational safety as standard devices, are in accordance with standards such as EN ISO 13850 and EN 60947‑5‑5 and are indispensable for industrial plants.
