Sensors & Transducers


Contacts feature self-control function for optimum safety

September 2001 Sensors & Transducers

Rockwell Automation says that its new contacts for the 800E series pushbutton programme increase the safety of emergency-stop applications considerably.

In case of a fault, a reliable emergency stop switch can become the most important part of the entire affected system: one push of the emergency button and the plant stops immediately. But this is not the case if the mechanical connection between front and contact elements does not work correctly: pushing the button shows no effect, the contact block's openers remain closed and the system continues to run. In case of incorrect installation, mechanical overload, vandalism or carelessness during start-up, this scenario can become reality.

In this case, the new self-controlling 800E series contact blocks offer effective prevention. Due to their innovative construction (patent applied for) these elements recognise the correct connection between the emergency stop push button's operating and switch components. If this connection is faulty - for whatever reason - the switch trips and opens the connected machine's control circuit. This is made possible by a self-controlling NO-contact that is wired in series to an NC-contact. If the contact block is correctly connected to the operating element, the emergency stop pushbutton must be operated in the usual way to interrupt the control circuit via the NC-contacts. If, however, the connection between the operating element and the coupling element is broken, the pre-switched NO-contact closes automatically and switches the system off. The user can be assured that operating personnel and equipment are given optimum protection at all times.

As already demonstrated by other 800E series' products, these new contact blocks can also be installed quickly and are also finger-secure in accordance with IPX2. Safety-conscious users can easily optimise existing systems with conventional emergency stop pushbuttons by installing the new self-controlling contact blocks.



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