Patent GB-1437268-A (GB)
Title: Elevator system
IPC: B66B1/52
Filed: 1973-05-18
Abstract: 1437268 Automatic control of elevators WESTINGHOUSE ELECTRIC CORP 18 May 1973 [30 May 1972] 23733/73 Heading B8L In an elevator system, the acceleration pattern is modified in response to a request for the car to stop, to reduce the acceleration magnitude; delay means 500 sensitive to a voltage decreasing as car speed increases ensuring that the modification can take place only for higher velocity portions of the acceleration schedule; to aid transition to deceleration without excessive jerk. As shown, car speed during acceleration is related to current provided, to the winding of a pattern motor (not shown) by rectifier 359, supplied from constant voltage source 361L, 361A, via back-toback controlled rectifiers 371, 373 and an impedance UM, or DM, whose coils UMC, DMC are on the advancer of a floor selector (23), Fig. 1 (not shown), armatures UMA, DMA passing within the respective coils and being mounted on the selector synchronous carriage, the impedances of UM, DM thus varying with synchronous carriage-advancer spacing and being least when the advancer is fully advanced. The rate of current growth in the pattern motor supply is adjusted by controlling the firing angle of controlled rectifiers 371, 373, unijunction transistor 379 being driven by transistor 377 whose conduction, enabling charging of capacitor 411 to fire the unijunction is controlled by a command current I c  set in magnitude by rheostat 387 and establishing a desired acceleration pattern, opposed by feedback current L F  proportional to the rate of change of pattern motor winding supply current. Rectifiers 371, 373 are non-conductive initially, contacts A1, A2 being closed, the latter opening when car acceleration is desired, the firing angle of the rectifiers 371, 373 progressively decreasing until they are both fully on when full car speed is reached. For higher speeds, Zener 383 conducts at a point set by potentiometer 417, I F  being correspondingly increased to decrease car acceleration. Modification of acceleration magnitude.-The magnitude is decreased by inserting variable resistor 512 in the resistance chain defining the value of I c , to decrease the latter, insertion of 512 being controlled by either of contacts UPL6, DPL6, closed during initial acceleration of the car, and one of them being opened when the advancer encounters a floor requiring service, or by contacts XL1 of relay coil XL controlled by the voltage, inversely proportional to car speed, across controlled rectifiers 371, 373. A. Trip of one floor.-The advancer is at the destination floor, so that one of UPL6, DPL6; UPL5, DPL5 are open. Since car speed is low initially, voltage across 371, 373 is high, energizing relay coil XL keeping contacts XL1 closed, thus delaying acceleration modification, acceleration magnitude remaining high, until voltage across 371, 373 drops sufficiently for coil XL to drop, at a value preset by rheostat 510, decreasing the acceleration. B. Two or three floors.-Acceleration is decreased when one of UPL6, DPL6 open, coil XL being de-energized at the time rheostat 510 ceases to be shorted by UPL5, and DPL5, car speed already being high in view of the higher speed prevailing. The advancer synchronous carriage is driven by synchronous motor (SM) receiving signals from synchronous generator (SG) coupled to idler pulley (9) of the hoist system, Fig. 1 (not shown). An advancer motor (AM) is provided,