An “Attractive” New Interlock Design

SCHMERSAL recently introduced an innovative new switch, the MZM 100, a safety interlock with a non-mechanical operating principle - no actuator key or positive-linked solenoid latching mechanism.

The MZM 100 is a magnetic interlock: it uses a powerful electromagnet to generate a 500 N holding force, locking the machine guard. Additionally, the switch detects and monitors the actuator plate through an integrated non-contact sensor that uses SCHMERSAL’s patented pulse-echo technology.

The unique combination of the magnetic operating principle and the pulse-echo sensing offers multiple advantages: Since there are no moving parts, the switch is not subject to mechanical wear; The noncontact sensor tolerates larger door misalignments; Also, the pulse echo technology allows a single safety controller to monitor multiple units - not only other MZM 100, but other pulse-echo units such as the AZM 200 interlock and the CSS 180 and CSS 34 safety sensors, without detriment to the safety level.

Even without a positive-linked mechanical locking mechanism, the MZM 100 fulfils the requirements of Control Category 4 (EN 954-1) or SIL 3 (IEC 61508). The magnetic locking principle complies with EN 60947-5-1.

Additionally, the actuator plate was designed with a flexible mounting which absorbs vibration. This neutralizes undesired rattling noises, even on machines with high vibrations. The tolerance to vibration makes the MZM 100 perfectly suitable for light safety guards, such as on packaging and wrapping machines. The MZM 100 was also designed with smooth surfaces where dust and dirt cannot deposit. This is of particular advantage in cases where extremely dirty conditions occur. The MZM 100 has an IP 67 protection class rating, making it suitable for the food-processing industry or wherever high hygienic standards need to be maintained.