Patent GB-719831-A (GB)
Title: Improvements in or relating to lifts
IPC: B66B1/20
Filed: 1952-06-23
Abstract: 719,831. Push button lifts. EXPRESS LIFT Co., Ltd., and HUNT, S. T. June 15, 1953 [June 23, 1952], No. 15803/52. Class 40 (1). A lift control system for a plurality of lift cars each serving both a high zone and a low zone, has a provision for automatically despatching a car to provide service in the low zone, whereby it answers only down calls in that zone, when due to the operation in one or more of the cars of either a pass switch pass (1) or a weight responsive switch LW(1), one or more of the cars is conditioned to pass a down call originating in the low zone. The control arrangement ensures that the car selected for service in the low zone is the car having a starting priority from the parking floor except when one or more calls have been registered for that particular car for a destination in the high zone, in which case the next available car is selected. Also, provision is made for selecting only one of: the lifts to provide a low zone service until the selected car either returns to the parking floor or is conditioned to pass a down call in the low zone. When a car has been selected for low zone service the normal indication, showing that this is the next car to leave the parking floor, is cancelled. In the drawings, which relate to a system of four lifts serving 12 floors with floors 7-12 considered as the high zone and the remainder as the low zone, suffixes (1)-(4) are added to apparatus particular to one of the lifts 1-4, whilst no suffixes are used for apparatus common to all lifts; and all contacts have the same references as their associated relays. Operation.-Assuming the system to be conditioned as follows: (a) Lift No. 1 is parked at the main floor and is the next to leave but is being held back from starting by operation of the holdback push button H(1). (b) Lift No. 2 is parked at the main floor. (c) Lift No. 3 is travelling in the down direction and is passing down calls in the low zone. (d) Lift No. 4 is answering calls behind Lift No. 3. Condition (c) above causes the relay PP(3) and then the relay PL(3) to be energised to close normally open contacts PL(3) to energise the relay PLC which self holds. The changeover contacts PLC prepare the circuit to the relays such as NL2(1) and NL2(2), but this cannot operate on lift No. 1 since the relay NL1(1) is' operated by the allocation of starting priority to lift No. 1. Since lift No. 1 is being held back' by the holdback relay HB(1) the associated low zone relay LZR(1) will not operate owing to the' normally closed contacts HB(1) and NL1(1) both being open. Normally closed contacts NL1(1) and PLC open to release a relay AB(1) fed through normally open contacts AR(1) and normally closed contacts SR2(1). The operation of the relay AB(1) is controlled by normally open contacts AR(1) of a relay AR(1) which is energised when lift No. 1 is parked; the system is, however, arranged to release the relay AB(1) under down peak conditions as above described When the relay AB(1) is released a selector switch having contacts S(1) associated with lift No. 1 and similar to contacts S(2), S(3) and S(4) associated with the other lifts is arranged to drive to close the contacts such as S(1) selectively to select another lift since lift No. 1 is not available owing to the operation of the holdback relay HB(1). Under these conditions, the selector will close the contacts S(2) associated with lift No. 2. The circuit to the relay NL2(2), will be completed through normally open contacts AR(2), S(2), changeover contacts PLC and normally closed contacts NL1(2). The energisation of the relay NL2(2) closes the normally open contacts NL2(2) to energise the starting relay SR2(2) so that lift No. 2 starts immediately to provide low zone service without providing any indication that it is the next lift to leave the main floor owing to the fact that relay NL1(2) is not energised. At the same time, the normally open contacts NL2(2) complete a circuit to energise the low zone relay LZR(2) and normally closed contacts associated with the relay NL2(2) in the car call circuit of lift No. 2 are arranged to prevent the possibility of any car calls being registered for the second lift. The operation of the low zone.relay LZR(2) is arranged to open normally closed contacts LZR(2) in circuits for feeding relays such as 312(2)-307(2) associated with down calling pushes 12D(2)-7D(2) respectively. It will be noted that all these relays and down calling pushes are associated with the high zone being similar to the relays 312(1) &c., and down calling pushes 12D(1) &c., shown in Fig. 1. Other normally closed contacts LZR(2) are arranged to prevent the completion of control circuits through calling pushes 11U(2)-1U(2) associated with relays 211(2)-201(2). This has the effect of preventing the registration of any up calls from both the high and low zones for lift No. 2, it will be noted that the. control circuits shown in the lower part of Fig. 1 of the drawings allow down calls from landings in the low zone to be registered by the closing of down calling pushes such as 6D(2)-2D(2) to energise their associated relays 306(2)-302(2) respectively. The relays 306(2) &c., have associated normally open contacts 306(2) &c., which when any one or more of them is closed energises a relay 62 thereby causing the normally open contacts 62 in the circuit of the relay PL(2) to be closed. The above described arrangement of the control circuits causes lift car No. 2 to provide low zone service and to reverse at the highest landing in the low zone for which a down call has ben registered. The opening of normally closed contacts LZR(2) and normally closed contacts SR2(2) de-energises the relay PLC when the second: lift car has been despatched to provide low zone service. The relay LZR(2) is released either when the second lift car returns to the main floor or if the second lift car passes down calls in the low zone. The release of the relay LZR(2) enables another lift to be allocated to. provide low zone service if the condition of down peak still.exists.