Safety switches prevent trapping for machinery directive compliance

2nd March 2009
Posted By : ES Admin
Safety switches prevent trapping for machinery directive compliance
The TP and STP range of safety switches manufactured by Euchner enable machine builders and both production and process engineers to ensure compliance of individual machines and production installations with the latest European Machinery Directive regarding ‘risk of being trapped in a machine (code 1.5.14)’. The new Directive (2006/42/EC) is due to become effective on 29th December 2009 and states ‘machinery must be designed, constructed or fitted with a means of preventing an exposed person from being enclosed within it or, if that is impossible, with a means of summoning help’.
The standard TP and STP range of safety switches are designed to ensure that guard devices cannot be opened with machines in operation, and remain closed until all potentially hazardous moving parts have become static. These switches are provided as an option with a manual emergency release mechanism located at the rear of the switch housing.

To prevent the unintentional locking-in of personnel within an individual machine or machining-cell enclosure, however, adaptations of these switches can be provided which incorporate an integrated bistable solenoid, operated from a separate supply voltage, which provides both actuation and condition monitoring of the guard locking. With varying combinations of the mains power and control voltage being ON or OFF either collectively or separately, the necessary conditions of OPEN/CLOSED safety devices with locking mechanisms ACTIVATED/DEACTIVATED can be achieved. This ensures appropriate safeguards for personnel, together with the ability of obtaining exit from machine enclosures.

Versions of the Euchner safety switch range incorporating the bistable solenoid feature are designated as the TP-Bi and STP-Bi types, with the STA and twin-headed switches also being capable of the same adaptation, without alteration to their original housing dimensions.

Other provisions must be made, however, where switches are fitted in inaccessible positions, or where guard devices could trap personnel outside the reaching distance of appropriate safety devices. In these circumstances, switches can be provided which incorporate a flexible Bowden cable for escape or emergency release of the guard locking mechanism. The cable, combining inner wire and sleeve can be supplied in lengths up to five metres and can be routed to cover individual installation requirements. The cable is supplied with a convenient ring-pull, but this can be replaced with a more substantial pull handle if it is necessary to route the cable through a machine bulkhead, rigid partition or guarding.

A pre-assembled Bowden cable emergency release mechanism incorporating replacement switch cover is also available as a retro-fit item for Euchner TP and STP switches where they have already been built into existing safety circuitry. This will ensure that even currently operating machine installations can be easily upgraded to comply with the latest Machinery Directive requirements.

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