Presence-Sensing Device

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Interlocks into the machine’s control system to stop operation when the sensing filed (photoelectric, radio frequency, or electromagnetic) is disturbed.

Advantages: adjust to fit different stock sizes; allows access to load and unload the machine; and allows access to the guarded area for maintenance and set-up activities.

Disadvantages: Restricted to machines that stop operating cycle before operator can reach into danger area (e.g., machines with partial revolution clutches or hydraulic machines); Must be carefully maintained and adjusted; does not protect operator in the event of a mechanical failure; and operator may make device ineffective.

There are also presence-sensing mats that interlock into machine’s control system to stop operation when a predetermined weight is applied to the mat.  A manual reset switch must be located outside the protected zone.