DEVICE TO PROVIDE SAFE OPERATION OF LIFT Russian patent published in 2000 - IPC

FIELD: passenger lifts; safety devices. SUBSTANCE: lift electric circuit provided with contacts of monitor sensors with two parallel-connected free contacts of lift shaft doors. Monitor sensor contacts are series- connected separately for each floor. Contacts close monitoring relays when monitor sensor contact is closed at no lift cabin with check shunt on floor and at closed contact of shaft door when the door is opened by hand. Check shunt installed on lift cabin, whose length is reduced to 120 mm, switches off monitor sensor only within the limits of accurate stopping from 0 to ± 50 mm. This provided automatic opening of shaft and cabin doors without closing of monitoring relay. Beyond the limits of accurate stopping, all monitor sensors are closed by permanent magnets providing control over those doors of shaft behind which no lift cabin with check shunt is present. EFFECT: enhanced reliability of lift circuit owing to disconnection of lift from supply source when unauthorized persons get into lift shaft through shaft doors opened by hand. 1 dwg