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Automated guard is always alert to human entry

A Leuze Electronic product story
Edited by the Engineeringtalk editorial team Sep 13, 2004

The new Entry Exit FT-Muting Guard developed by Leuze Mayser enables a simple but essential safety function to be added to many handling and warehousing operations.

The new Entry Exit FT-Muting Guard developed by Leuze Mayser enables a simple but essential safety function to be added to many handling and warehousing operations - preventing persons becoming entwined in machinery such as shrink-wrappers but allowing the free-flow of approved items.

In many handling applications fork lift trucks (FLTs) are deployed to remove or place palletised loads onto conveying systems or other in-feeds to automated machines.

There is a legal obligation on the company to provide safety guards that will stop the machine's operation should a person move too close to the hazard zone for whatever reason.

Fixed guards may be in place either side of the conveyor-run, the problem area is the load/unload point where clear access is needed.

A hinged door across the entry and exit points would add considerable time to a production schedule therefore the natural product choice for protecting staff is to have safety light barriers monitoring across the openings.

Unfortunately, as the palletised load is placed on the conveyor it will trigger the safety light barrier and close all machinery functions unless the FT-Muting Guard is used.

Leuze Mayser's FT-Muting Guard momentarily negates or "mutes" the action of the safety light barrier during the load and collection operations.

It achieves this by linking the light barrier via muting controls to inductive loops in the floor.

As the fork truck arrives at the drop-off or pickup points its mass is detected by inductive loops, these mute the operation of the safety beam allowing the infeed/discharge of a pallet without affecting the action of the shrink wrap machine.

Design of the overall conveyor system must be such that during removal or placement of the palletised load it "blocks" the access point onto the conveyor thus preventing human access.

Any person within the inductive field will not be detected by the inductive loops and will thus not initiate a mute but by breaking the safety beam they trip the system to safe mode.

To improve the safety integrity of this system Leuze Mayser uses two separate inductive loop controllers giving the mandatory two muting channels.

The output signals from each loop controller are cross-checked against each other, so that a failure in either loop controller will be detected and muting will be inhibited.

The FT-Muting Guard incorporates a contact in its control box which opens when the two inductive loops are occupied by an FLT.

This signal is primarily used to inhibit the infeed/discharge conveyor from running while the FLT is loading/discharging a pallet.

Also a "loop occupied" timer overrides the mute when an FLT is parked on the inductive loops for a length of time.

The ability to distinguish between products and personnel is achieved using the concept of "muting" as provided by the new FT-Muting Guard.

The many customer benefits include a serious reduction in on-site time-consuming configurations over the more traditional forms of machine guarding.

This is brought about by its plug-and-play concept making for a far easier and faster installation.

Another feature is that of self-diagnostics, enabling potential component failure to be easily identified without recourse to individual component analysis.

With the FT-Muting Guard an extremely high level of safety is achieved whilst allowing free, uninterrupted product flow.

This safety system is part of an expanding machine guarding product portfolio developed by Leuze Mayser in the UK to satisfy many unique industrial applications.

Find out more about this article. Request a brochure, download technical specifications and request samples here.
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