The DIN EN ISO 13849-1 machine directive tightens the safety rules for machines and equipment. In order to achieve the required safety integrity levels, the safety-related components of the control systems must, in some circumstances, be designed redundantly. To accomplish this, safety switches can, for example, be installed doubled or additional PLCs installed for monitoring.
Schaltbau offers an economical alternative with its S850 snap-action switches: the double NC contact switch unites two safety switches in one compact housing. It is an elegant solution for control system constructors who want to increase the safety level without having to invest in additional hardware, installation or programming.
The S850 can simultaneously open two galvanically separated safety circuits with a delay of less than 3 milliseconds. The two fixed contact pairs are closed by one bridge each when inactive. The two contact bridges are attached to one plunger and therefore mechanically linked. As soon as the switch is actuated, the snap-action mechanism is activated and pulls the plunger and the contact bridges upward. If the contacts become welded together and the snap mechanism is made ineffective due to a short circuit, the positive opening levers push the plunger upwards so that both circuits can be opened reliably in any event.