Patent GB-701845-A (GB)
Title: Improvements in or relating to elevator systems
IPC: B66B1/20
Filed: 1951-07-19
Abstract: 701,845. Lifts. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. July 19, 1951 [Aug. 19, 1950], No. 17137/51. Class 78 (3) [Also in Group XXXVIII] In a multi-car elevator system of the kind in which the cars are attendant-controlled and after each trip are brought back to a dispatching floor, the dispatching interval is varied in accordance with the number of calls on the system, and with the rate of change in the number of calls. Allotting arrangements.-As each car arrives at the dispatching (top) floor, its relay AU-DU (the system shown having 4 cars), provided that no car has already been allotted as "next" car,. completes a circuit for a clutch magnet AC which couples a cam 40 to a constantly running motor. Contacts RA-RD are thus closed in succession until a "next" relay AN--DN is operated whereupon the clutch magnet is disconnected and hall and car lamps of the car corresponding to the operated "next " relay are lit. Normal timing arrangements.-As each car leaves, a circuit is made for a clutch magnet SC and motor M then drives a timing cam 42 from a normal position until contact S is operated whereupon the common start relay ST pulls up and locks, releases the clutch magnet to allow the cam to return to normal and operates the starting signal ASL--DSL of the allotted car by energizing the corresponding individual starting relay AS--DS. ST is thus unlocked but the operated relay AS--DS remains locked up until the car has left and its relay AU--DU, accordingly, has fallen back. Modifying dispatching interval in accordance with weight of traffic and number of cars in service.-The armature of the timing motor M is fed from a generator G which is driven at constant speed but has its field current varied to make the motor speed vary inversely with the traffic load. The field winding GF is supplied over a network with as many parallel branches as there are cars in service, contacts 52 being opened to disconnect the corresponding branch while any particular car is out of action. As each car button ICB-20CB is actuated, it inserts an additional section of a resistor in the corresponding branch. As each "down" call registering relay 2DR--19DR operates, it inserts a corresponding section in all the branches. The resulting reduction in the generator field current reduces the motor speed and increases the dispatching interval to make it agree with the slower average speed of the cars when a number of stops have to be made. Modifying dispatching interval in accordance with rate of change of demand.-In the case of a sudden increase in the traffic demand, the dispatching interval is reduced and in the case of a sudden reduction it is increased. This is brought about with the aid of a. pair of sensitive relays ID, 2D in series with a condenser 60, ID 'being more sensitive than 2D and being polarized. The relays and condenser are connected between points on a pair of potential dividers associated respectively with the upper and lower half of the floors. Normally the condenser is charged, but as sections of the resistors 62, 64 in the potential dividers are shunted by the "down" call registering relays, it discharges through the relays and may charge in the reverse direction. If the discharge (or reverse charge) rate is sufficiently high both relays operate and 2D causes the immediate operation of the common start relay if or as soon as the cam shaft is slightly off normal via cam contact S<SP>1</SP>. If ID only is operated, the timing motor is speeded up by the shunting of the four-branched network over contact 1D1. If the demand suddenly falls so that the condenser charges sufficiently quickly in the other direction, 1D closes its other contacts 1D2 to cut in extra resistance 54 in the generator field circuit and slow down the timing motor. Modifications not described in detail.-The system may be adapted for the case in which both top and bottom floors are dispatching floors and relay 1D may modify the dispatching interval at both floors, or the bottom floor may be the sole dispatching floor. As further alternatives the dispatches may be controlled in accordance with car button calls only or with landing calls only.