(57) A timed safety switch, particularly for accident-prevention doors of machines and
apparatus, includes an enclosure (2) which can be anchored to the machine and internally
accommodates a series of fixed electrical contacts (3) and of moving electrical contacts
(3'), devices (4, 5) for locking the door which includes a safety key (4) which can
be anchored to the door and can be inserted in a slot (7) of the enclosure (2), delay
devices (11) which can move between an active position and an inactive position and
are suitable to anticipate or delay the operation of the locking devices (4, 5) with
respect to the actuation of the switch, clearance-providing devices (8) which can
move to allow the insertion/extraction of the key (4) through the slot (7) only when
the delay devices (11) are in their inactive position, so as to prevent accidental
actuations of the switch when the door is open. The delay devices, the locking devices
and the clearance-providing devices are of a mechanical type in order to ensure maximum
reliability and safety.
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