US2889010A - Elevator controls - Google Patents

Description

June 1959 J. H. BORDEN ET AL 2,339,010

ELEVATOR CONTROLS Filed Feb. 21, 1957 2 Sheets-Sheet 1 JOSEPH H. BORDEN YRAYMOND A. BURGY B ATTORNEYS June 2, 1959 J. H. BORDEN ET AL 7 2,839,010

ELEVATOR CONTROLS Filed Feb. 21, 1957 2 Sheets-Sheet 2 INVENTORS JOSEPH H. BORDEN igg YMOND A. BURGY ATTORNEYS United States Patent 2,889,010 ELEVATOR CONTROLS Joseph H. Borden, Toledo, and Raymond A. Burgy, Maumee, Ohio, assignors to Toledo Scale Corporation, a corporation of Ohio Application February 21, 1957, Serial No.'641,693 11 Claims. (Cl. 187-29) This invention relates to signal and control equipment for elevator systems and more particularly to such equipment for indicating or establishing a desired operating pattern for one or more elevator cars in response to the current pattern of car operation. The subject matter embraced is related to that disclosed in R. A. Burgy application Serial No. 641,600, entitled Elevator Controls and filed herewith.

Heretofore attempts have been made to control the operation of elevator cars either singly or in combination by sensing certain conditions in the system. Usually the conditions sensed have been the number of car or landing calls in registration, the rate of registration, the accumulated time calls have remained unanswered, the number of cars present at a landing, the existence of special service calls, the loading of the cars, and even their operation as compared to a predetermined or idealized schedule. In particular, attempts have been made to improve the distribution of cars by indicating or establishing starting intervals from landings which have been designated dispatching landings. Dispatching has been eifected on a number of bases including uniform intervals between dispatch signals or from the departure of a next preceding car, intervals of altered duration as determined by a supervisor, intervals which vary with the number of unanswered calls for service or the accumulated time registered calls remain unanswered. Since a prime objective of dispatching devices is to avoid the bunching of cars, another technique employed frequently is to issue dispatch signals to cars as the number present at a dispatching terminal increases either by shortening the dispatching interval or by issuing dispatch signals to at least one car immediately upon the number of cars exceeding a predetermined level. Other approaches have involved mechanisms which monitor the travel of the cars and alter dispatching in accordance therewith. These latter approaches have included means insuring that the number of cars traveling in each direction are maintained in a predetermined ratio and issuing dispatch signals to cars so as to maintain that ratio, and means to establish an idealized car trip schedule and comparethe actual travel of the car with that schedule so that a car ahead of schedule is caused to travel at a slower speed than one on time, a car behind schedule travels at a faster rate than one that is on time. The dispatch intervals in this type of system tend to be increased by cars behind time and to be decreased by cars ahead of schedule.

The present invention is directed to means for generating dispatching signals at intervals dictated by the travel pattern of the cars in service. Its prime object is to improve upon the dispatching and general operating techniques, equipment, and results of those systems of the prior art.

Another object is to simplify the equipment required to issue dispatch signals in response to car travel.

A further object is to facilitate the integration of dis patch control equipment which is responsive to car travel with existing equipment.

An additional object is to measure the travel time between selected points or to measure the variables in such time, as stopping time of one or more cars, and actuate car and system controls in accordance therewith.

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Ideally the cars in an elevator system should be distributed in time throughout the system so that a car is available at a landing at the end of a regular interval following the next preceding car. The present invention achieves a distribution approaching this ideal by establishing a regular dispatch interval on the basis of the travel time, for example, the round trip time of a car plus a given amount of time for car loading and unloading at the terminals. The system is arranged to continuously correct operation as the operating pattern changes even during a single trip of but one car. This time interval is increased as trafiic increases as a function of the integrated stopping time of the cars at intermediate floors. The dispatch time interval is based upon the round trip time of a car as a function of the number of cars in service. Thus, if a basic round trip plus a reasonable loading time at the terminals required seconds and four cars were in operation a dispatch interval of 20 seconds might be employed. If the number of stops at intermediate landings increased to an average of three for each car, each landing stop requiring approximately 12 seconds so that the round trip time is increased to 116 seconds, the dispatch interval can be increased to 29 seconds or one quarter of the round trip time. Similarly if only three cars were in service, the interval can be altered to a third of the round trip time.

In accordance with the above objects, one feature of this invention resides in monitoring the stopping time of operating cars.

Another feature involves altering one or more controls determining the operating pattern of a car or system, such as the dispatch time, as a function of round trip time and the number of cars in service, and ancillary thereto, altering the fraction of the round trip time establishing the dispatching interval between cars from a basic value in response to the stopping time of the cars.

Another feature utilizes means adjusting the dispatch ing interval of cars as a fraction of the integrated stop ping time of elevator cars.

A fourth feature includes means for changing the speed of a dispatch timer motor in response to landing stops by elevator cars.

Another feature resides in an integrating electrostatic, stop timer for one or more cars of an elevator system which controls the operating pattern of the system.

An additional feature involves an integrating, electrostatic timerof car stops which employs readily available circuit elements including an electron discharge tube, relays, resistors, and a condenser to effect variations in an operating pattern of an elevator system as a function of variations in the car stops within the system. This timer is particularly well suited for incorporation with equipment of the type currently employed to alter the dispatching interval of cars in the system.

The above and additionalobjects and features of this invention will be appreciated more fully from the following detailed description when read with reference to the accompanying drawings wherein:

Fig. I is a diagrammatic representation of a dispatch timer motor suitable for utilization with this invention;

Fig. II is an across the line schematic circuit diagram of the stopping time monitoring and dispatcher control equipment of one embodiment of this invention;

Fig. H1 is adispatch timer control circuit utilizing this invention set forth in across the line schematic form.

Before proceeding with a detailed discussion of the illustrative embodiment of the invention, it should be noted that the invention is not to be read as restricted to the present disclosures and that numerous alternatives are available to those skilled in-the art. Further alternatives include timing devices utilizing flux decay mechanisms to establish delays. i

The mode of operation afforded by this invention is suited particularly to systems wherein the cars operate without attend-ants. However, it should be appreciated that the control actuated as taught here might also be employed to signal attendants. Similarly, in the nstant example applied to control of a dispatcher machine the dispatch interval is measured from the departure of the next preceding car. Alternatively, the dispatch rnterval can be initiated from any convenient point such as the instant the dispatch signal of the next preceding car to be dispatched from the landing is issued or from some predetermined instant in the dispatching operation at another dispatching landing.

Correlation between the relay actuated contacts and their actuating coils has been maintained in this description by employing the same reference characters for the several elements and indicating the spatial relationship by a marginal index on the drawings. Each actuating coil is positioned on an index line numbered at the rlght of the circuit diagram and its reference character is repeated in a marginal column adjacent the line number. The contacts illustrated which are actuated by that coil are listed by the number of the line in which they are located in the index column to the right of the reference character. The form of the contact location numbers in the index also indicates the nature of the contact, back contacts, those which are closed when the actuating coil is deenergized and are opened when the coil is energized, having their location numbers underlined, while front contacts, those normally opened and closed by the energization of their actuating coils, are not underlined. All contacts are illustrated in the positions they assume when their actuating means are deenergized.

The present disclosure embraces only a portion of an elevator system and illustrates only those elements considered necessary to an understanding of the invention. These elements are combined in a multicar system with the usual controls for stopping and starting the individual cars, registering car and landing calls, dispatching the cars from suitable locations and setting operating patterns for the cars. The dispatching functions contemplated can include means for selecting a car from a plurality available at a dispatching landing and means for issuing a dispatching signal to the car either to start it in operation away from the landing or for issuing a signal to an attendant indicating that the dispatch interval has expired. The automatic features of this invention particularly adapt it for integration in known operatorless elevator systems; however, they also offer advantages when incorporated in systems operating under attendant control or to systems that can run with or without attendants.

In the illustrative embodiment a conventional motor driven dispatch timer is shown in Fig. I. It comprises a motor 1, advantageously of the direct current type to facilitate speed control, having an armature shaft 2 driving a gear train within gear box 3 to rotate shaft 4 at a reduced speed. A cam disk 5 having a protuberance 6, arranged to engage successively followers 7 and 8 of contacts 9 and 10, is rotated by shaft 4 to issue dispatch signals in a well known manner as illustrated, for example, in I. H. Borden Patent 2,759,564, of August 21, 1956, entitled Elevator Dispatchers.

As set forth in the Borden patent, motor 1 is controlled by a circuit of the type shown in Fig. HI wherein rectified current is applied to the motor arrnatures 12 and 13 for the lower and upper dispatch timers respectively. The current is derived from a multivoltage source so that it can be applied to the armatures at different levels of voltage as established for example by a selector switch 34 which can be connected to the several taps 14 through 19 of an autotransformer 20. These currents are fed to transformers 22 through 27 which in turn each feed respective rectifier bridges 28 through 33 supplying direct current to the armatures 12 and 13. Field windings (not shown) for armatures 12 and 13 are supplied from a source of direct current so that the speed of the motors is detennined by the voltage applied to the transformers 22 through 27 and the number of. transformers which are effective.

The current to the armatures 12 and 13 derived from contact arm 34 of the autotransforrner tap selector is fed to the transformers 22, 23 and 24 supplying armature 12 through the normally closed contacts FLD of a full load dispatch relay (not shown) at line 128 and back contacts DFU at line 1290f the up dispatch timer holding relay (not shown) while down dispatch armature 13 is fed through back contacts DFD of a down displatch timer holding relay (not shown) and back contacts I-I4A of a program relay (not shown) at line 127. The full load dispatch relay is energized when the load in the car while at the lower terminal exceeds a predetermined level to increase the speed of the up dispatch timer. When the load reaches a level actuating the full load dispatch relay, contacts FLD at line 129 are closed and back contacts FLD at line 128 are opened to supplant the voltage from contact arm 34 with a higher voltage from lead 35 connected to the end of the autotransformer 20. The current at junction point 36 is fed through back contacts DFU of an up displatch timer holding relay which deenergizes that timer if no car is available for dispatching at the lower terminal or if the system is arranged to dispatch cars only while there is a demand for service, on call operation, and the requisite demand is absent.

The portion of the voltage at junction 36 which is effective to drive armature 12 depends upon the number of transformers 22, 23 and 24 which are in circuit and is greatest when all are effective. Operation of the full load dispatch relay energizes them all by closing contacts FLD at lines 128 and 131 to complete the circuits for transformers 24 and 23, respectively, to lead 37 and thus source 38. These transformers are also operated in response to the accumulation of cars at the terminals so that the up dispatch timer armature 12 rotates faster to shorten the dispatch interval when three or more cars are at the lower terminal by the closing of contacts BU2 at line 129 of an up three car relay (not shown). This operation also reduces the rate at which additional cars arrive at the lower dispatching landing by retarding the dispatching at the upper terminal. Down dispatch timer 13 is slowed by opening back contacts BUZ at line 126 to disconnect transformer 26 and reduce the voltage applied to its armature. Conversely an accumulation of three or more cars at the upper terminal shortens the dispatch interval by closing contacts BD2 of a down three car relay (not shown) at line to energize transformer 27 thereby increasing the voltage applied to armature 13 and increasing the speed of the down dispatch timer while the up dispatch timer is retarded by opening back contacts BD2 at line to reduce the voltage applied to armature 12 unless a full load dispatch relay has been actuated.

In accordance with the present invention the voltage at contact arm 34 can be altered in response to the integrated stopping time of the system by engaging contact 39 with arm 34. This enables the contacts D81 through DS4 at lines 122 and 123 to effect the connection of arm 34 to various taps of autotransformer 20 as the operating pattern of the active or in service cars change and thereby change the speed of the dispatching motors as a function of that pattern.

Connection of contact arm 34 to contact 39 in Fig. Ill places full line voltage across the circuits driving armatures 12 and 13 from lead 40 connected to source 38 through back contacts D51, DS2, D53 and D84 of dispatcher speed control relays in line 122, lead 42, contact 39 and the circuits outlined above. Dispatch speed control relays are successively energized as the integrated stopping time of the operating cars increases to reduce sesame the voltage applied to arm 34. Operation of these relays can best be understood by reference to Fig. II.

Integration of the stopping time of elevators is effected in the circuit of Fig. H to develop successively higher grid potentials in a cathode follower amplifier as the stopping time of the several cars increases so that the dispatcher speed control relays D81 to DS4 are energized successively to lengthen the dispatch intervals. This circuit is supplied from transformer 43 having secondaries 44 for the plate supply and 45 for the heater filament supply of triode connected pentode 46. Secondary 45 is connected directly to filament 47. Secondary 44 provides a plate supply through rectifier 4-8 and across smoothing condenser 49 developing a potential at junction 51 which is slightly below the peak voltage from secondary 44.

Pentode 46 is connected as a cathode follower amplifier having a series of four relays DSll to D84 connected between ground and cathode resistor 52.. These relays are each arranged to pull in at a given current and drop out at a lower current, the several threshold currents for the individual relays ascending in the order of their designations. The current flowing in the cathode follower circuit is controlled by the potential between cathode 53 and control grid 5 of pentode 46 and this in turn is a function of the potential at junction 55 at the upper terminal of condenser 56. This potential is derived from a voltage divider connected between the plate and ground and having parallel resistances 57 (A), 57 (B), 57(C) and 57 (D) (the parenthetical letter suffix is applied to the reference characters for elements individual to particular cars of the same designation, as cars A, B, C and D in the exemplary four car system) connectedto resistance 58. A lead from junction 55 is connected through a parallel combination of a unidirectionally conductive element or rectifier 59 and a resistor 61 to junction 62. to complete the condenser charging path.

Condenser 56 is charged as a result of the stopping of elevator cars. The amount of charge accumulated is a function of the total stopping time of the several cars as a result of the selective introduction of resistors 57 (A), 57 (B), 57(C) and 57(1)) into the voltage divider circuit. In the illustrated arrangement the resistors are inserted in response to stops by the respective cars A, B, C or D at landings between the lower and upper dispatching terminals, however, if desired the stops at one or both of those terminals might also be sensed. The conditions necessary to connect a resistor into the charging circuit in the present embodiment include the closure of back contacts MG and MGi for the car, these contacts being actuated by car position relays (not shown) which are energized to indicate the car is at the lower dispatching terminal during the interval the car is below a point just below the landing immediately above the lower dispatching terminal in the case of contacts MG or to indicate the car is at the upper dispatching terminal during the interval the car is above a point just above the landing immediately below the upper dispatching terminal in the case of contacts M61. The car also must be conditioned to provide service as indicated by the closure of contacts OE of an in-service relay (not shown) to enable resistors 57(A), 57(B), 57(C) and 57(D) to be made effective. When these conditions are met, the stoppage of a car at a landing closes its contacts AMR by virtue of the deenergization of the advance motor relay (not shown) for the car. The advance motor relay is deenergized when the car is set to stop while traveling toward a landing for which it has received a stopping assignment, while the car is stopped, and until it is started.

The introduction of one or more resistors in the upper portion of the voltage divider completes the path be tween lead 63 and ground so that junction 62 has four quiescent, fixed or stable potentials depending upon how many cars are stopped simultaneously. Stoppage of one car develops the lowest potential at junction 62 since the resistance between it and lead 63 is at a maximum for a completed circuit. When a second resistance is paralleled with the first, the resistance in the upper portion of the voltage divider is halved and the potential drop in lower resistance 56 increases to increase the potential of junction 62 with respect to ground. Similarly, the addition of a third resistance reduces the upper portion of the voltage divider to one third of its original value and further increases the potential at junction 62 as does the introduction of the fourth resistance by the simultaneous stopping of all four cars.

When junction 62 is raised above ground potential charge flows through resistance 61 and into condenser 56 at a rate dependent upon their magnitudes and the potential level. The accumulation of a charge on condenser 56 raises the potential of junction 55 and control grid 54. The increase of the resistance between junction 62 and lead 63 as occasioned by the reduction of the number of resistors in the upper portion of the voltage divider enables condenser 56 to discharge, at least partially, by the passage of charge through rectifier 59 and resistor 58 to ground at a rate determined in essence by the value of capacitance of condenser 56 and the resistance of resistor 58. It is to be noted that in addition to the adjustment of the charging and discharging rate available by appropriate choice or" values for the components shown additional adjustments can be attained by the inclusion of a resistance in series with rectifier 59 so that the series combination is paralleled by resistor 61, by the reversal of the rectifier polarity where a rapid chang ing rate is desired to reduce or effectively eliminate the resistance 61 in series with condenser 56 during charging, and by the inclusion of resistance in series with condenser 56 and the parallel rectifier 59 resistor 61 group.

In the illustrated system excursions of the potential of control grid 54 are almost continuously changing to some slight degree since the changes in the stop monitoring circuit follow the car operating pattern to cause an immediate response. However, the rise and decay of the potential is tempered by establishing component values which introduce appropriate time constants for these excursions to become efiective. As is well known a resistance-capacitance circuit as shown has a charging and a discharging characteristic with respect to time which follows a logarithmic function wherein time is proportional to the capacity and resistance so that the voltage across the condenser reaches 1/ e of its maximum in a number of seconds represented by the product of the capacitance in farads and the resistance in ohms. This time constant holds for both charging and dis charging of the circuit in the absence of modifying means such as the rectifier 59 and resistance 61. In practice the system has operated very satisfactorily in a four car bank employing resistors 57 (A), 57 (B), 57(0) and 57(D) of 22 megohms, a resistor 58 of four megohms, a silicon diode for rectifier 59 having a peak back voltage in excess of 200 volts, a resistor 61 of 8 megohms and a capacitor 56 of 9 microfarads. A plate voltage of about 200 volts was applied to a sharp cut ofi pentode connected in a triode connection through a selenium rectifier 48 having a peak back voltage of 240 volts and across a 2 microfarad smoothing condenser 49.

The circuit from cathode 53 to ground includes four relays DS1 to D54 and a resistor 52 all in series. Relays DS]!. to D84 alter the Voltage applied to dispatch timer motor armatures 12 and 13 to provide four additional steps in dispatching timer motor speed control. The resistance of the operating coils of the relays DSI to DS4 can all be the same, in the example they were of about 5,000 ohms and resistor 52 is of a similar value. Each of the relays 1351 to DS4 are arranged to pull in at diiferent cathode to ground voltages i.e. different cathode currents. Since the relays are of the same type and it is desired to encompass a substantial operating range, the magnitude of the operating current through the third and fourth relays D83 and D84 is maintained in the same range as for relays D51 and D52 by by-passing a portion of the current through resistors 64 and 65 paralleling the operating coils of relays D53 and D54. In order to enable a wider range of drop out currents to be utilized with relays D53 and D54 additional resistors 66 and 67 are respectively paralleled with their operating coils when they are energized by the closure of contacts D53 at line 114 to connect resistor 66 around relay D53 and by the closure of contacts D54 at line 111 to connect resistor 67 around relay DS4. In the operative embodiment discussed above resistors 64 and 65 are each of 5000 ohms while resistors 66 and 67 are each of 25,000 ohms.

A circuit as shown, having components of the magnitudes suggested, picks up relay DSl at a cathode to ground voltage of 24 volts, a current of 1.2 milliampcres. and drops out at 18 volts, a current of 0.9 inilliampcrc. Similarly relay D52 picks up at 43 volts or 2.2 milli amperes and drops out at 35.5 volts or 1.8 milliamperes, relay D53 picks up at 57 volts or 2.9 milliamperes through the series circuit and 1.5 milliamperes through the relay coil and drops out at 48 volts or 1.1 milliamperes through the coil, and relay D54 picks up at 67.5 volts or 1.7 milliamperes drops out at 61.5 volts or 1.5 milliamperes. These energization levels for the pull in and drop out of the relays are established by adjustment of the spacing between the pole piece and the armature of each relay at its respective limits of travel. The pull in level depends upon the separation of the armature from the pole piece or core when the relay is deenergized while the drop out level depends upon that separation when it is energized. The means for establishing these limits of armature travel are well known.

Integration of the stopping time as measured from the instant a car picks up its stopping assignment to the instant its starting is initiated and its effect on relays D51 to D54 is illustrated in the following table which was derived from the operation of the circuit of Fig. II by imposing a stop signal for four cars simultaneously and measuring the intervals required to energize relays D51 through D54 from the completely dormant condition. A second set of values was obtained by simultane ously removing the four stop signals at a time the circuit was passing its maximum plate current and measuring the intervals from that instant which were required to deenergize relays D54 through D51. With a 25 microfarad condenser 56 connected across resistor 58 and the parallel combination of resistor 61 and rectifier 59 eliminated, the following times were obtained:

Pull-in interval, seconds Drop-out interval, seconds Relay Pull-in interval, seconds Drop-out interval, Seconds While it is extremely unlikely that all four cars of a four car system would stop simultaneously or all remain stopped for the intervals set forth above, it is to be recognized that the idealized conditions utilized in obtaining the above data illustrate an initial rapid correcting action followed by the need of a greater and greater integrated stopping interval to effect corrections. It is evident that a logarithmic function is involved in the relationship between energization of the relays and the stopping time of cars. Operating experience has indicated for example that traflic conditions can vary from a condition wherein but one stop per car is required for each round trip to a stop at each landing. Thus conditions can range from that where stops are made only intermittently to a condition where several stops are sensed in the voltage divider continuously.

When the prevailing service demand is sufiicient to warrant regular dispatching of one or more cars but insufficient to disrupt the average round trip interval from the basic value from which the dispatch motor timer speed was established, none of relays D51 to D54 are energized since the circuit is adjusted so that the threshold level of anode current is not reached in Fig. II. As the travel time is increased by additional stops, the condenser attains and retains a greater charge thereby increasing the anode current above the threshold of one or more of the relays D51 to D54. The effect of these relays, when energized, is to alter the potential applied to the selector arm 34. In the example set forth above, the circuit of Fig. III is so adjusted that line voltage, that applied to the timer motors when none of relays D51 to D54 are energized, drives the motors at a speed which rotates disk 5 through a complete revolution in 18 seconds to issue a dispatch signal with that frequency. An increase in the stopping time of cars at floors intermediate the dispatching terminals to an extent energizing relay D51 connects arm 34 to tap 18 by opening back contacts D51 at line 122 and closing contacts D51 at line 123 to decrease the voltage to dispatch timer motor armatures 12 and 13 an amount reducing their speed to a dispatch interval of 25 seconds. In the same manner energization of relay D52 establishes a 31 second interval, relay D53 establishes a 38 second interval and relay D54 21 45 second interval.

The above dispatcher control thus enables a pattern to be set up with a great deal of flexibility as to the number of cars, number of landings, stopping time at landings, running speed of cars and choice of landings effective in the stop sensing circuits by choice of circuit components as taught here. The use of such circuits correlates the dispatch interval with the trip time by taking account of the major variable in trip time, the stopping time, continuously averaging that stopping time and continuously altering the dispatch interval in accordance therewith. While the interrelating function between stopping time and the dispatch interval is a matter of choice and falls within a wide range so far as the capacities of the present circuit are concerned it has been found desirable to smooth the peaks and valleys of the operating pattern. Thus the increases in dispatch interval, particularly those for the longest intervals, have been chosen somewhat less than the proportional increase in average round trip time and a lag in the reversion to the next lower relay in the dispatcher speed control group has been introduced by establishing a drop out level somewhat below that required for pull in.

In one installation involving service by four cars to twelve landings and including dispatching both upward and downward the basic round trip time has been set at about 72 seconds. This is determined from a running time in each direction of about 24 seconds when the door closing interval, and acceleration and deceleration at the terminals are considered, a minimum standing time at each terminal of about 5 seconds, and a single stop of 14 seconds at a landing intermediate the terminals. This indicated a dispatch interval for four cars of 18 seconds.

Each additional stop consumes about 14 seconds so that the system is arranged to introduce the first change in dispatch timer motor speed, raising the dispatch interval to 25 seconds, when each car on the average makes somewhat greater than three stops per round trip. A second step is eflfected when the number of stops increases to about five per average round trip so that a dispatching interval of 31 seconds is set up, while a 38 second interval is appropriate for about seven stops and a 45 second interval is utilized when nine or more stops are required in an average round trip.

While the above description has been directed to alteration of the dispatching interval in accordance with the trafiic pattern and particularly the integrated trip time for elevator cars, the concepts embraced here can be employed to efiect other changes in the control of the operating pattern of an elevator car or group: of cars in response to changes in that pattern such as are indicated by the stopping time during a trip. Further the trip over which stopping time is monitored can be for a single car or a plurality of cars, and can be limited to only a single direction of travel or only a selected portion of an overall trip. Where stopping time at terminals is a significant variable this also can be monitored and indicated to the controls.

From the above it is apparent that many equivalents and modifications will occur to those skilled in the art as a. consequence of the present disclosure. Accordingly, it is to be understood that this disclosure is intended merely to illustrate the invention and is. not to be read as limiting either the spirit or scope of this invention.

What is claimed is:

1. In an elevator system including a car serving a plurality of landings, an electron discharge device, means to alter the signal from said device in response to changes in the time of travel of a car over a given path, and means responsive to said signal for controlling the operating pattern of said car.

2. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device, means to alter the signal from said device in response to changes in time of travel of said cars over respective given paths, and means responsive to said signal for controlling the operating patterns of said cars.

3. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device, means to alter the signal from said device in response to changes in the stopping time of said cars, and means responsive to said signal for controlling the operating patterns of said cars.

4. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device, means to alter the signal from said device in response to changes in the stopping time of said cars, means for issuing dispatch signals at intervals to said cars, and means responsive to said device signal to alter the dispatch signal interval.

5. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device, means to alter the signal from said device in response to changes of a given sign in the stopping time of said cars, means for issuing dispatch signals at intervals to said cars, and means responsive to said device signal to alter in the same direction as said given sign the dispatch signal interval.

6. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device having an anode, a cathode and a control electrode, means to alter the potential of said control electrode with respect to said cathode in response to car stops, a dispatch timer, means responsive to the output of said device to control said dispatch timer.

7. In an elevator system including a plurality of cars service a plurality of landings, an electron discharge device having an anode, a cathode and a control electrode, a voltage divider between said anode and said cathode, a tap on said voltage divider connected to said control electrode, means responsive to car stops to alter the resistance of said voltage divider and the potential of said control electrode with respect to said cathode, a dispatch timer, means responsive to the cathode current in said device to control said dispatch timer.

8. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device having an anode, a cathode and a control electrode, a voltage divider between said anode and said cathode, a tap on said voltage divider connected to said control electrode, a parallel group of resistors between one of said electrodes and said tap, means to connect one of said resistors in circuit during each car stop, thereby altering the potential at said tap, a dispatch timer, means responsive to the cathode current in said device to control said dispatch timer.

9. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device having an anode, a cathode and a control electrode, a condenser connected to said control electrode, means to develop a voltage across said condenser which is a function of the car stopping time, a dispatch timer, means responsive to the output of said device to control said dispatch timer.

10. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device, means to alter the current through said device as a function of car stopping time, a dispatch timer, a plurality of control means responsive to successively higher levels of current connected in series with said device, each of said control means when responsive altering the speed of said timer.

11. In an elevator system including a plurality of cars serving a plurality of landings, an electron discharge device having an anode, a cathode and a control electrode, a voltage divider connected between said cathode and anode, a tap on said voltage divider connected to said control electrode, a resistor for each car in said system, means connecting said resistors between said anode and said tap while respective cars are stopped, a condenser between said tap and the cathode end of said voltage divider, a plurality of current sensitive relays connected in series to said cathode and each arranged to be activated in response to a unique current level in said cathode, a multiple voltage source, a dispatch timer motor, and means actuated by the activation of said relays to alter the value of voltage applied to said motor from said source.

No references cited.

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