ELEVATOR WITH SAFETY CHAIN OVERLAY CONTROL UNIT COMPRISING A SAFETY PLC MONITORING SAFETY SWITCHES AND MIRRORING A SWITCHING STATE TO AN ELEVATOR CONTROL

摘要

An elevator (1) is proposed, the elevator comprisinga drive unit (11) for effectuating displacing an elevator cabin(5) in an elevator hoistway (3), an elevator controller (13) for controlling an operation of components of the drive unit(11) and multiple safety switches (17) being switchable upon occurrence of safety relevant events. Furthermore, the elevator comprises a safety chain overlay control unit (31) comprising a safety PLC(43). The safety PLC (43) comprises first connectors (47) via which it is connected to contacts (45) of at least one of a single safety switch (17) and a plurality of safety switches (17) connected in series to form a safety chain(18). The safety PLC (43) is adapted to monitoring a current safety status of the elevator (1) and identifyinga safety critical status of the elevator based on detecting when one of the safety switches (17) changes its switching state. The safety PLC (43) is adapted to cause interruption of a main energy supply to the drive unit (11) upon identifying the safety critical status of the elevator(1). Furthermore, the safety PLC (43) comprises second connectors (51) via which it is connected to contacts of the elevator controller (13). The safety PLC (43) is adapted to communicate the current safety status to the elevator controller (13) via the second connectors.Using the safety chain overlay control unit (31), an existing elevator may be modernized and its safety may be increased, possibly even enabling additional functionalities such as re-levelling of the cabin (5) or pre-opening of elevator doors (21, 27).