GB1241406A - Elevator control system safety arrangement - Google Patents

Abstract

1,241,406. Lift control systems. OTIS ELEVATOR CO. 29 April, 1970, No. 20704/70. Heading B8L. [Also in Division H2] When a lift-car upwardly approaches a second floor landing at which it is to stop, contacts SPDS1 close to energize relay HXB, whereby the control system is transferred from main to levelling operation. Movement of the car under levelling operation brings it within a first predetermined distance from the landing (defining an outer zone), whereupon brush 20DB bridges contacts ODC. The car and hoistway doors are opened, and door relay GDS is de-energized to release relay CY1. Continued levelling of the car brings it within a second predetermined distance from the landing (defining an inner zone) and a signal from a selector machine falls below a set value so that a comparator operates to re-energize relay CY1, while a relay CY2 is released. If the car is located at the landing with the doors open and a misoperation causes it to move beyond the inner zone, relay CY1 is released. This causes potential-switch C to be released and prevents the car from making a trip to another landing. Additionally, movement to another floor is inhibited if the car is prevented from entering the inner zone. Under these circumstances, contacts CY1 11-12, and 1DZ 7-8 remain open to release the switch C. If the doors try to close to enable the car to make such a trip, relay GDS is energized to interrupt the circuit for the switch C. Under the foregoing condition, that is failure of the car to enter the inner zone, if the car attempts to make a trip from the second landing without closing the doors, the switch C again releases to stop the car. The control system is also protected against failure of its own components. For example, failure of a relay to respond when the car enters the inner zone causes the car to stop. The reliability circuit also provides protection against failure of outer zone relay ODZ and door relay GDS. If the speed in the up or down direction is exceeded, the voltage from a tachometer generator overcomes a bias to release a relay. The car is then stopped provided that any of the doors are opened at the time. The tachometer generator is monitored during each trip of the car. If the speed of the car has exceeded a predetermined magnitude in a particular direction, a selector machine advancer carriage must be a prescribed distance from the synchronous panel, or else the switch C is released to stop the car. If the rate of change of acceleration exceeds a predetermined amount, a sensing coil, having a saturable core associated with a conductor conveying the armature current of the lift-motor, responds to render a transistor conductive. A relay is released to open contacts DADT 1-2 whereby the circuit for the switch C is interrupted if the doors are open.