US2581245A - Elevator dispatching system - Google Patents

Description

Jan. 1, 1952 w. F. EAMES ELEVATOR DISPATCHING SYSTEM 2 SHEETSSHEET l Filed Aug. 19

R D 3 R D Y 2 Fig.l.

INVENTOR Fig2.

WITNESSES: 7%

Jan. 1, 1952 w. EAMES ELEVATOR DISPATCHING SYSTEM 2 SHEETSSHEET 2 Filed Aug. 19, 1950 INVENTOR William F.E es. 74/

ATT RNEY WITNESSES: 47y

Patented Jan. I, 1952 UNITED STATES PATENT OFFICE ELEVATOR DISPATCHING SYSTEM William; F;- -Ea-mes, Westfiqld, N. .I., assignor to Westinghouse; Electric Corporation, East Pittsburgh, Pa., a corporation, of' Pennsylvania ApplicationAugust 19, 1950, Serial No. 180,400

19 Claims.

The invention relates to elevator systems in which a pluralityofcars o-perateas-a bank, and particularly to a dispatching: system for. an installation of suchtype for individually. dispatchlllg the cars at suitable intervals from a' dispatching floor.

There have been many elevator dispatching systems suggested, and many are now in :use, including .the rotational dispatcher for abank ofcars, in which the cars are'dispatched from a terminal floor in a predetermined invariable sequence, and the non-rotational dispatchenrin' which the-cars are dispatched from the terminal in the order of their arrival.

In both of these cases the dispatching signal is given to the operator attheexpiration of a period-of time after arrival at thedispatching floor depending upon estimated traffic conditions. However, for a given building tr'alfic conditions do not remain. constant throughout the day, and asa result there'may be undesirable delays in answering calls 'for service under some conditions'becausethe dispatching schedule issuch that-two or more cars of the bank may be at the dispatching terminal at the same time, thereby reducing the number of cars available for servicing the intermediate floors of the building.

In another type of dispatching system designed to improve this situation when more than one car is present at the dispatchingterminaL the dispatching time, or interval, of the first car under steady load conditions the cars of the sys-.

tern will become properly spaced, but with variations in loading there-will be an undesirable time lag in the realignment of the dispatchingschedule responsive to the resulting bunching of the cars, and the situation is worsened if thechange in loading occurs suddenly.

In accordance with the present invention a dispatching system is provided in which the dispatching interval is'varied continuously in accordance with thenumber of calls for service on the elevator system and rate of I change in the number of calls for service. For example, where a bank of elevators has substantially equal up'anddown loading, which may be classed as heavy, which'tapers oil over 'a'short-periodi to a, light loading and then increases toanother period of heavy loading, the present invention will respond by first decreasing the dispatching interval to prevent cars 'bunching at the dispatching terminal during the light load period,

and then, increasing the interval again as the loading becomes heavy. The dispatching interval is kept continually in phase-with the-load demand as it changes, and in the event of a sudden change in the rate of'loading bya, predetermined-amount the dispatch-signal may be given substantially instantaneously.

It is, therefore, an object ofthe invention to providea dispatching system in which the elevator cars of a bank aredispatched from a tervminal, or dispatching'floor, in a period of time after arrival which continuously varies in accordance with anumber of calls for'servioe registered on the systemas-well as the rate of change in the number of such registrations.

It isafurther object of the invention toprovide-an elevator dispatcher which is responsive to..the registered car calls'and/orhall calls to continuously vary the-dispatching interval in accordance Wi-th variations in the number of calls enhelev tor syst m.

- Other; objects of theinvention-willbe apparent from the following description andthe accompany n d awi whi h:

Figure l is a-schematic view of an elevator system illustrative of the type-to which the inent n may-b pp i d;

Fig. 2; is a schematiccircuit in straight-line .form-of the dispatching system of the invention, and

Fi 2A isa schematic key-sheet indica in the location of the relays-and contacts'of Fig. 2-when pierced-besidev Fig. 2.

The invention, of course, -is primarily applicable to banks of two or moreelevator cars, al-

though it may have some application to a. single car. By way-of illustration the invention-will be-described with respect to a bank of four cars,

one of which is schematically illustrated in :Fig. 1. As indicated in the circuit diagram, Fig. 2,

the invention may be'applied abank of four cars designated as A, B, C and D.

Referring to Fig. 1, car-A of the bank is suspended from one or more ropes or cables 2 which .extendover a hoisting sheave 4 and'are cona conventional type having a plurality of fixed contacts i mounted in insulated relation and Spaced in accordance with the spacin of the floors of the building, and a movable cross-head or carriage i2 having contact brushes 14 mounted on it for engaging the stationary contacts H] as the cross head moves up and down the face of the selector in accordance with car movement, as governed by threaded shaft [6 driven from the motor 6 through suitable reduction gearing l8. A contact A28] is also on the selector at a position corresponding to the top terminal of the elevator shaft to be engaged by brush A22 when the car reaches that position. Similarly, contactAZl corresponds to the lower terminal, the position of the carriage 12 as shown corresponds to the car being at basement level.

The motor 6 may be controlled in any of a number of ways which are conventional, such as by a car switch CS to be manipulated by the operator in the car to start the car, and the car may be stopped automatically by car buttons CB mounted in the car, and push-button stations HR in the hall or corridor at each floor. Usually, of course, there is one car button corresponding to each floor of the building, and at each-intermediate fioor the push-button stations HB comprise an up button and a down button. The automatic stopping of the car in response to these buttons is so well known that a detailed description thereof is not considered necessary. Of course, the system may be such that the stopping is controlled manually by the car switch CS in response to signals to the operator effected by the push-buttons. The carbuttons upon being pressed will remain in circuit-closing position until the car stops at the designated floor or until the car completes its trip in a given direction, and the hall buttons upon being pressed energize call registering relays which remain in energized or contact-closed condition until the call is answered by the car.

The above-described apparatus for car A is duplicated for cars B, C and D, it being understood, of course, that for the group or bank of cars, only one set of hall buttons H at each fioor is required because cross-connections between the floor selectors of the four cars insure that the nearest car moving in the desired direction of travel will answer and cancel the hall call, in accordance with usual practice.

Referring to Fig. 2, the dispatching timer of the invention includes a variable speed motor M, the armature 3d of which is connected in a loop circuit with the armature 32 of a generator G which is driven by a constant speed alternating current motor 34. The motor M is provided with a separately energized field MF. The generator G is provided with a shunt field winding GF, the degree of excitation of which determines the output of the generator, and, accordingly, the speed of the timing motor 30. This is usually termed a variable-voltage or Ward-Leonard type of motor control system.

The generator G is mechanically connected through an electromagnetic clutch AC to a cam it which sequentially closes a plurality of pairs of contacts RA, RB, RC and RD. Suitable gearing 6i may be interposed between the clutch and cam to provide a desired rate of rotation of the cam.

The timing motor M is connected through a second electromagnetic clutch SC to timing cams 52 and A l for a purpose to be described.

In the dispatching sequencea car upon selection as the next car to leave receives a next" light ANL and after a time interval a start light ASL. These are shown in Fig. 1 as mounted in the car to indicate to the operator that his car is next and he can begin to receive passengers. Preferably a hall lantern AHL is lit at this time to signal to intending passengers that the car is available. When the operator receives the starting signal ASL he may proceed on his trip.

For the purposes of this description the dispatching floor will be considered to be the upper terminal, and the dispatching interval will be controlled by car and hall calls for service in the down direction.

If car A is the first to arrive adjacent to the terminal, and assuming that a car has just left the terminal as car A arrives, floor selector contacts A22 and A20 engage and relay AU will be energized (Fig. 2) and will remain energized so long as car A is at the terminal. With relay AU energized, contacts AUl close which completes a circuit through the winding of clutch AC and the series of break contacts ANI through DNI thereby engaging the clutch AC and rotating selector cam 40,,whose purpose is to select the next car to leave in the event that two or more cars should be at the dispatching floor at the same time.

Contacts AUZ also close preparing a circuit for next relay AN through break contacts ASZ and open contacts RA of the switch operated by cam 40. A circuit is also prepared for the start relay AS which is incomplete at this time by reason of the open contacts ANZ and ST3.

As the cam 40 advances, with a relatively rapid rotation which may be assumed to be one revolution per second, contactor RA will be closed and thereby complete the circuit to relay AN. The energization of relay AN opens contacts ANI in the circuit of the winding of clutch AC, thereby stopping cam 4% It also closes contacts AN3 in circuit with the next light ANL and the hall lantern AHL for car A, and it closes contacts ANZ in the circuit of start relay AS.

With the winding of clutch SC energized through break contacts ST! and the series of break contacts ASI through DSi, cam switch S will be closed in a predetermined time depending upon the speed of the timing motor 30. With the closure of contacts of cam switch S, relay ST is energized. The relay picks up and establishes a holding circuit for itself through contacts STZ. At the same time break contacts STl open and deenergize the clutch SC, permitting the cam 41. to return to its starting position under the influence of spring 43.

Relay ST upon energization closes its contacts ST3 thereby completing the circuit to relay coil AS, the circuit comprising Relay AS closes its contacts ASA to energize the start signal ASL. It also closes contacts ASS which establish a holding circuit for itself. Contacts ASI will open, breaking the circuit to the relay winding ST and the clutch winding SC. Contacts ASA, in addition to energizing the start signal ASL, may also be effective to control a circuit for starting the car, as indicated, in the event that the elevators are of the automatic pushbutton type.

As the car leaves the terminal in response to the starting signal, the engagement of the floor selector contacts A20 and A22 is broken and the system is ready to respond to the next car at the terminal, assuming-that-cars B, Cor D arrived 1 during theabovedescribed-dispatching sequence for car A. -In-thatcase'selectorcontacts B- B22, or C20-C22,-or D20-D22will be in engagementand the respective relays BU, CU or DU will pick up andthe above described next and start sequence will be repeated.

1 Of course, while car A is waiting for-its start signal after receiving its next signal, the arrival-of-subsequent cars do not affectthe dispatch operation-of car A because even though the relays BU, CU or DU become energized and close their contacts BUI, etc. the circuit through clutch winding-AC -is broken by contacts AN! which do not reelose until AN-is deenergized by the pickup of start relay AS of car A which opens its contacts A52.

Assuming further that there are no cars at-the terminal, that is, none of the relays AU through -DU are energized, the winding of clutch SC is energized (ST! beingclosed) and upon rotation of cam 42 switch S will close. Relay ST will then be energized and hold-in through its contacts STZ. Clutch winding SC will be deenergized by the opening of ST! and cam- 42 will be returned to its'starting position by spring 43. The contacts ST3 in the circuit of start relays AS to DS will close, so that uponthe arrival of the next car,

that field winding GB of generator has been energized to any required degree for operating the timing-motor M. Howeversuch energization in accordance with the invention will be varied in proportion tothe number of calls for service on the system, and the rate of registration of said 7 calls.

For example, in Fig. 2 the field winding GF may be energized through four parallel resistance circuits a, b, c and d corresponding tothe four cars A, B, C and D. Each resistancecircuit is divided into equal sections corresponding to the number of floors to be served inresponse to the car buttons CB, andthe floors to be served in response to down. hall buttons at the floors. Assuming a building of twenty floors, there will be twenty resistor sections corresponding to the number of car buttons and nineteen sections corresponding to the number of down hall buttons. The resistor sections are normally shunted, when there are no calls on the system, by break contacts to be operated by the car buttons ICB through 20GB, and break contacts 2DR through IBDR on the down call registering relays (not shown) which operate in response to the down hall buttons, and are held in. operated condition until a car answers the call.

.A fixed resistor is in series with each of theresistance circuits a, b, c and d to provide a desired minimum value, and contacts 52 are provided in each branch and are closed when the respective cars are placed in service. The four resistance circuits are connected in parallel through a series resistance 54 to the generator shunt field winding GF. The resistor 54 is shunted by break contacts ID2 for a purpose described hereinafter.

By way of example and not limitation, the fixed resistors 51) may be of the order of ohms, and each of the segments of the resistance circuits a, b, c and d may be 20 ohms.

Assuming that car A isithe only car in service, if there are no registered callson'the system, resistance a will be shunted bythe closedcontacts of car buttons CB and. the DR contacts. of the hall call storing relays. The. only resistance in circuit with the field winding GEwill. berepresented by fixed resistors 50 and..54. .This. will afiord a relatively high...energization, of GE and accordingly, a relatively highspeed. of the timer motor M. When passengers enter car A. and car buttons are pressed indicating the desired. destination floors, corresponding sections, of resistance a are placed in the circuit of GE, and as down floor-calls are registered corresponding contacts DR will open thereby cutting in more resistance to further decrease the energization of GE and accordingly increasethe timer interval to correspond to an expected longer through-triptime of the car.

If car B is placed in -service,nclosing its contacts 52, its DR contacts .correspondingto the hall calis registered. will also open, andhcarbutton contacts corresponding tothe desires of passengers entering car B willopen. ,With the. two

' resistance paths. a and b in parallel, GEwill be energized to a higher degree therebyincreasing the speed of motor, M and .decreasingthetimer interval. Similarly, as cars C and'D are brought into service, the additional resistors c andd bei come efiective, the hall calls. onthe system being common to all the cars, and car hallsbeingefiective to modify the resistor associated. only-with the car in which they areregistered.

From the foregoing it is apparent that the speed of the dispatcher motor M, and hence-the length of the dispatching-interval, is a continually varying quantity depending upon the number of car calls and hall calls registered at any given instant. That is, with asteady balanced loading of calls, an interval of 30 seconds for dispatching cars from-the top terminal may be adequate. However, if the loading decreases, thereby decreasing the round-trip time of the cars, the cars may start to bunch or accumulate at the I dispatching terminal unless the dispatch interval is shortened. This is automatically taken care of in the present system because as the number of calls decrease, fewer of the DR, contacts will be open and hence the energization of the gener-- ator field GF will increase. The reverse is true of course for an increase of loading on the system resulting in an increased round-trip time, making a longer dispatch interval desirable to insure a proper distribution of the cars.

Also as cars are taken out of service, or brought into service, opening or closing the respective contacts 52, the dispatch interval will. automatically varyto adapt the cars in .service to the loading on the system at that time.

At the lower part of Fig. 2 is shown a circuit which is responsive to the rate of change inthe registration of calls, in this case downhall-calls for example, including a capacitor 63, relays ED and 2D, sectionalized resistors. 62 and Y64, and fixed resistors .65 and 68.

The capacitor 60, which may he of the order of 300 or 400 microfarads capacity, is connected in series with the windings of relays ID and 2D in a circuit connected between the junction of resistors 52-66 and 64-B8.

The segments or resistor 62 are provided with shunts including the normally open contacts ZDRl through iliDRi of down call registering relays (not shown) which are operated in response to the registration of calls for service at the second through tenth floors.

Similarly, the segments of resistor 64 are shunted by circuits including the normally open contacts IIDRI through IBDRI corresponding to the call storing relays for the eleventh through nineteenth floors.

The relays ID and 2D are of the instrumenttype operating upon a fraction of a watt, and are polarized so that they are responsive to the direction of current flow through their windings. Relay ID is set to operate at a lower current than 2D.

Relay ID in operation closes its contacts ID! in a circuit which shunts the resistance circuits a, b, c and d, and open its contacts [D2 which are in shunt circuit for the resistor 54 in series with the generator field winding GF. Relay 2D upon energization closes its contacts ZDI which are in circuit with contactor S controlled by the cam wheel 44 of the timer.

Assuming that there are no calls on the system and the contacts ZDRI through IQDRI are open as shown, the condenser 60 will be charged from LI, resistor 68, condenser 60, relay windings ID and 2D, resistor 66 and L2, because the total resistance of the sectionalized resistors is substantially larger than that of the fixed resistors 66 and 68. The relay side of the condenser 63 will therefore be charged negatively, and no current will be flowing through the relay circuit because it is assumed that the condition existed long enough to have charged the condenser.

As down-calls are registered, corresponding segments of the resistors 62 and 64 will be shunted by the DRI contacts, thereby decreasing the total values of these resistors. If we assume an extreme case, by way of example, where suddenly from a period of no down-calls on a system there are suddently registered fifteen down-calls, the values of resistances 62 and 64 will decrease to a point where the current through the condenser will reverse in direction, namely from LI through the few remaining segments of resistor 62, the relay windings 2D, ID and condenser 50 through the remaining segments of resistor 64 to L2.

Under this extreme condition, there would be sufiicient current flowing through the directional relay windings ID and 2D to operate both of them. The complete charging of the condenser 60 will of course be delayed in accordance with the resistance remaining in the circuit.

The operation of ID, closing IDI, speeds up the dispatcher timer by increasing the energization of shunt field GP to dispatch a car from the terminal sooner than the car otherwise would be dispatched. At this point the normally closed contacts IDZ do not open.

The operation of relay 2D closes ZDI to energize relay ST to give a start signal immediately to a car at the terminal provided that a minimum interval has elapsed since the last start signal has been given, which is determined by contact S operated by cam wheel 44. That is,

' if a car is present at the top terminal, it will receive an immediate dispatch signal assuming that S is closed, but if no car is there, the signal will be stored until a, car does arrive because relay ST will remain energized through its holding contacts STZ and upon the arrival of the car the car will immediately receive its "next and start signals.

In the operation just described the operation of relay ID is of no great consequence because of the simultaneous operation of relay 2D. However, if there are a smaller number of down calls, than the fifteen assumed above, there will be a smaller current flow through the relays ID and 2D which may not be sufficient to operate relay 2D, and an immediate start signal will therefore not be available. However, there may be sufiicient current to operate the more sensitive relay ID for a time, and speed up the dispatcher by closing contacts IDI which shunt the resistor circuits a, b, c and d. Therefore, a smaller increase in down hall-calls causing suflicient current to flow to operate relay ID only, will effect a speeding up of the dispatcher signal which will move cars from the upper terminal more rapidly to take care of the increase in down calls.

When the increase of down calls is satisfied, resulting in many or most of the DRI contacts opening, the current through the condenser will again reverse, making the relay side negative, causing a reversal in the current flow through the relay coils. The reversal will have no effect upon relay D2 but it will cause relay DI to open contacts IDZ, and will leave contacts IDI normally open. The normally closed contacts ID2, when open, remove the shunt around resistor 54 in series with the field GF which will lengthen the dispatching interval.

If desired, this contact ID2 may be employed to speed up the dispatcher at the opposite terminal to decrease the dispatching interval at that point and thereby speed the dispatch of cars in the up direction. That is, although the foregoing description has been specific to dispatching from the top terminal in connection with "down calls for service, it may be desirable to have a bottom floor dispatcher in connection with up calls. Such an up dispatcher would be substantially in accordance with Fig. 2 except that segmental resistors a, b, c and (1 would be controlled by contacts on the call registering relays DU which are controlled by the up corridor push buttons.

On the other hand, the requirements of a given installation may render it more expedient to dispatch from the bottom floor only, omitting the top floor dispatcher.

Further, it may be expedient to control either or both top and bottom dispatchers in accordance with car button calls only, in a situation where up or down corridor calls are infrequent, or if most of the passengers collected in response to corridor calls normally desire to proceed to one terminal or the other, the dispatcher may be controlled entirely by the number and rate of registration of corridor calls.

Quite obviously many aspects and modifications of the system disclosed will present themselves and it is intended that the invention be limited only by spirit and scope of the appended claims.

I claim as my invention:

1. In an elevator system including a bank of cars for serving a plurality of floors and provided with means for registering calls for service for said floors; means for individually dispatching said cars from one of said floors at periodic intervals including a timing device and means controlled thereby for giving dispatch signal to said cars, and means for varying the operation of said timing device to vary the interval between dispatch signals in accordance with the number of registered calls for service on said system and the rate of registration of said calls.

2. In an elevator system including a bank of cars for serving a plurality of floors and provided with means for registering calls for service for said floors; means for individually dispatching said cars'irom ione'of said floors at periodic intervals including a timing device and means controlled thereby for-giving a dispatch signal to said cars, and means for varyingthe operation of said timingdevice'to vary the interval between dispatch signalsin accordance with the number of registered calls for service on said system, and means for furthervarying the operation of said timing device in response to a rate of registration of said calls above a predetermined amount for decreasing the interval as determined by said last named means.

3. In an elevator system including a bank of carsfor serving a plurality of floors" and provided with means for registering calls forservice for said floors; means'for individually dispatching said cars from one of said floors at periodic intervals including a timing device and means controlled thereby for giving a-dispatch signal to said cars, and means'fo'r varying the-operation of said timing device to vary the interval between dispatch signals in accordance with'th'e number of registered calls for service on said system, and means responsive to a rate of registration of said calls above a predetermined amount for giving a dispatch signal substantially instantaneously.

4. In an elevator system including a plurality of cars servinga plurality-of floors and means-for registering callsfor service by the cars with respect to the floors, one of said floors being a dispatching floor, means forsequentially dispatch ing the cars from the dispatching floor at con-' tinuously variable-intervals comprising a variable speed voltage responsive timing device, and means for energizing it at a variable voltage continuously proportional in magnitude to the number of registered calls for service on said system.

5. In an elevator system including a plurality ofcars serving a plurality of'floors and means for registering calls for service by the cars with respect to the floors, one of said floors being a dispatching floor, means for sequentially dispatching the cars from the dispatching floor at continuously variable intervals comprising a variable speed electric timing motor, an electric generator having its armature connected in a loop circuit with the armature of said motor and a separately excited shunt field winding, means for exciting said winding including means for varying the excitation thereof in accordance with the number of registered callson said system.

6. In an elevator system including a plurality of cars serving a plurality of floors and means for registering calls for service by the cars with respect to the floors, one of said floors being a dispatching floor, means for sequentially dispatching the cars from the dispatching floor with a continuously variable time delay comprising a variable speed electric timing motor, an electric generator having its armature connected in a loop circuit 'With the armature of said motor and a separately excited shunt field winding, means for exciting said winding comprising means for varying the excitation thereof in accordance with the number of registered calls on said system and the duration of such calls.

7. In an elevator system including a plurality of cars serving a plurality of floors and means for registering calls for service by the cars with respect to the floors, one of said floors being a dispatching floor, means for sequentially dis patching the cars from the dispatching floor with a continuously variable'time delay comprising a variable speed electric timing motor, an electric generator having its armature connected in a loop circuit with thearmature of said motor and a separately excited shunt field winding, means for exciting said winding comprising means'for varying the excitation thereof in accordance with the number of regis-teredcalls-on said system and means responsive to the-rate of registration of such calls for further varying the energization of said winding.

8. In an elevator system including a plurality of cars serving a plurality of floors and means for registering calls for service by the cars with respect to the floors, one of said floors being a dispatching floor, means for sequentially 'dispatching the cars from the dispatching floor witha continuously variable time delay after arrival thereof at such floor comprising a variable speed electric timing motor, an electric'generator having its armature connected in a loop circuit with the armature of said motor and a separately excited shunt field winding, means for exciting said winding comprising means for varying the excitation thereof in accordance with the number of registered calls onsaid system and the duration of such calls and means responsive to the rate of registration of such calls f0r-further varying the energization ofsaid winding.

9.-In an elevator system including a plurality of cars serving a'plural-ityof floors and call means at said floors-forregistering calls for service in the-down direction and call means in each car for each floorserved thereby, means a ,for dispatching saidcars in sequence from an upper floor comprising a dispatching signal and an electric timing motor for effecting the energization thereof, means for automatically and continuously var-ying the speed of such motor including a 1 constant speed electric generator electrically'connected-thereto and having a separately excited field winding, means for variably exciting said winding including a plurality of sectionalized resistors, one corresponding-to each car, and means connecting them in parallel circuit relation with each other and'all in'series circuit relation with said winding and a source ofvol'tage, separate shunt cicrcuits for the sections of said-resistor each including a normally closed contact, such contacts to be opened in response to the operation of said call registering means -to-vary the resistance of the circuit of said winding. 7

10. In an elevator installation including a bank of cars serving a plurality of floors and means at each of said floors for registering a call for service by the-cars for that floor; a system for dispatching saidcars from one of said floors including: means for selectinga car at that floor to be the next to be dispatched, a dispatch signal,-andmeans iorenergizing said signal for the car so selected after a time interval or variable duration depending upon the number of unanswered registered callsfor service on thebank of cars.

11. In an elevator system in which a plurality of cars are sequentially dispatched from one floor to serve a plurality of other floors and in which means are provided for registering calls for service to said floors by said cars, means at said one floor for giving periodic dispatch signals, means for continuously varying the period between dispatching signals in accordance with the number of registered calls for service on said system, and means for further varying such period in rell sponse to the rate of change in the number of calls registered.

12. In an elevator system in which a plurality of cars are sequentially dispatched from one floor to serve a plurality of other floors and in which means are provided for registering calls for service to said floors by said cars, means at said one floor for giving periodic dispatch signals, means for continuously varying the period between dispatching signals comprising a voltage responsive timing device, a source of variable voltage therefor, and age of said source in accordance with the number of registered calls for service on the elevator system.

13. In an elevator system in which a plurality of cars are sequentially dispatched from one floor to serve a plurality of other floors and in which means are provided for registering calls for service to said floors by said cars, means at said one floor for giving periodic dispatch signals, means for continuously varying the period between dispatching signals in accordance with the number of registered calls for service on said system, and means for further varying such period in response to the rate of change in the number of calls registered, and additional means responsive to the rate of registration of said calls for further varying the voltage of said source.

14. In an elevator system in which a plurality of cars serve a plurality of floors and which are provided with means responsive to calls for service registered by push-buttons at said floors and push-buttons in each car corresponding to the floors served thereby; means for dispatching said cars sequentially from one of said floors comprising selecting means for determining the next car to be dispatched, a dispatching signal and means operable with a time delay for energizing said signal for a car so selected, said last named means including timing mechanism and means for varying continuously the timing operation thereof in accordance with the number of calls for service registered on the elevator system by said push-buttons.

15. In an elevator system including a plurality of cars serving a plurality of floors and which are provided with means responsive to calls for service registered by switches at said floors and switches in each car corresponding to the floors served thereby, means for dispatching said cars sequentially from one of said floors comprising selecting means for determining the next car to be dispatched therefrom, a dispatch signal and means operable with a time delay for energizing said signal for a car so selected, said last named means including a variable speed electric timing motor, a variable-voltage generator for energizing said motor, and means for exciting said generator with a voltage continuously variable in magnitude in proportion to the number and duration of calls registered by said push-buttons in said cars.

16. In an elevator system including a plurality means for continuously varying the volt- I 12 of cars serving a plurality of floors and call registering means at each floor for registering calls for service in one direction of travel with re spect to a dispatching floor, and means for sequentially dispatching said cars from said floor including a dispatch signal in each car, a variable speed timing device and a contactor operated thereby for energizing said signals, means for varying the speed of said timing device in accordance with the number and duration of calls registered, and means responsive to an increase in the rate of registration of said calls above a predetermined amount for increasing the speed of said timing motor, and means responsive to a further increase in the rate of registration for energizing the dispatching signal for a car at the dispatching floor substantially instantaneously.

17. In an elevator system including a plurality of cars serving a plurality of floors and call registering means in each car'for registering calls for service in the direction of travel of the car toward a dispatching floor, and dispatching means at such floor for dispatching cars therefrom in sequential intervals including a timing device, and means for varying continuously the operation of said device in accordance with the number of calls registered on said call registering means. i

18. In an elevator system including a plurality of cars serving a plurality of floors and call registering means at each floor for registering calls for service by such cars and means for sequentially dispatching said cars from one of said floors including a dispatch signal for each car, a variable speed timing device and contactor operated thereby for energizing said signals, means for varying the speed of said timing device in accordance with the number and duration of calls registered, and means responsive to the rate at which said calls are registered to increase or decrease the speed of said timing motor as such rate of registration increases or decreases a pre determined amount.

19. In an elevator system in which a plurality of cars serve a plurality of floors and which are individually provided with stopping means responsive to calls for service registered by pushbuttons at said floors and push-buttons in each car corresponding to the floors served thereby, means for dispatching said cars sequentially from one of said floors comprising selecting means for determining the next car to be dispatched, a starting signal and means operable with a time delay for energizing said signal, said last named means including a variable speed electric timing motor, a variable-voltage generator for energizing said motor, and means for exciting said generator with a voltage continuously variable in magnitude in accordance with the number and duration of calls for service registered by said push-buttons at said floors.

WILLIAM F. EAMES.

No references cited.

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