US3741347A

US3741347A - Static elevator supervisory system

Info

Publication number: US3741347A
Application number: US00179644A
Authority: US
Inventors: A Kirsch
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1971-09-13
Filing date: 1971-09-13
Publication date: 1973-06-26
Anticipated expiration: 1990-06-26
Also published as: CA951443A; FR2152909B1; FR2152909A1; BE788724A

Abstract

In a scanning type elevator control system, various control signals associated with the individual landings are serially stored in shift registers in the order of the landings. Circulation of the signals through the shift registers is synchronized with the scanner so that the signals associated with a particular landing are presented to the supervisory control each time the scanner is scanning the particular landing. When a shift register is utilized as a floor selector a signal representing the position of the car is advanced or retarded in the scanning sequence as the car moves from one floor to the next.

Description

United States Patent [1 1 Kirsch STATIC ELEVATOR SUPERVISORY SYSTEM v[ 1 June 26, 1973 Primary Examiner--Bernard A. Gilheany A ttorney- A. T. Stratton and Donald R. Lackey [75] Inventor: Andrew F. Kirsch, Edison, NJ.

[73] Assignee: Westinghouse Electric Corporation, [57] ABSTRACT Pmsburgh in a scanning type elevator control system, various con- [22] Filed: Sept. 13, 1971 trol signals associated with the individual landings are serially stored in shift registers in the order of the land- [21] Appl' 179644 ings. Circulation of the signals through the shift registers is synchronized with the scanner so that the signals [52] U.S. Cl 187/29 R associated it a pa ticular landing are presented to [51] Int. Cl B66b 1/18 the sup is y ontr l ea h time the scanner is scan- [58] Field of Search 187/29 ng the p ti ula landing- When a shift register is utilized as a floor selector a signal representing the posi- [56] References Cit d tion of the car is advanced or retarded in the scanning UNITED STATES PATENTS sequence as the car moves from one floor to the next.

3,443,668 5/1969 Hall et al. 187/29 21 Claims, 10 Drawing Figures 573 NOT (Fls No1"c H DN 566 574 NOR T69 NOT I 56 8 561 W DELAY NOR 3- NOT r- NOR {562 576 READ (FlS cLocK- 2ND 3RD (N+2 mews) OUT B69 575 BIT BIT BIT BIT NOT l i 5647 TO I NOR NOR NOT NOR SCAN l NOTCH DN NOTCH UP NORMAL PAIENIEUJUNZS ms SHEET 1 BF 5 2P7 18TH FLOOR E 7TH FLOOR D T gogg uPs 2Uv -1.

zD/LJ DOWN CALL STORAGE m ocs SUPERVISORY CONTROL 2ND FLOOR CAR CALL STORAGE L" 0A M ccs SELECTOR m v Q IST FLOOR v s- FIGJ.

ammal; ms

SHEEN! 0F 5 S3 S2 s2 I 33 I Sl B2 SCAN8 R NOT 0- 1 ,530 80C K509 LAHLQ NOT I 0 8C 529 sec 0 NOT NOR o 7U f5l8 /528 (UC 7D /527 70c kw-i519 NOT I NOR 7C f jszs me i Y SCAN 7' 2U ,fsls [525 z [506 S 1,-1.- 0 NOT g NORM 2D /5|4 20C 1 Li Q NOT l NOR O i 4 5:3 {523 gcc A 0 NOT g NOR O S 522 IUC J 0 NOT NOR Lg 5|| 52| 31?] 0 NOT I NOR l 504 W SCANI BINARY "CLOCK COUNTER [5m Fl G. 2.

PAIENIEB Jill 2 6 B73 SHEET 5 OF 5 547 L 5E f 554 F-F CLOCK-n NOJPCH NOR & N'oTcT UP NOR 2A 548 552 SHIFT NOR l; UP F L L NOR v 555 TFTS 557 558 549 NOR !NOTCH DN NOR v 555) F-F cLocK- F-F IA 53 BL 5 -A NOR NOR NOR F NOTCH DN {5 L5 559 56o 5m .NOT NOR ADVANCE 574 NOR T69. NOT I 568 557 HURT-M L DELAY NOR NOT f NOR $562 (576 lST 2ND 3RD READ (ms c CK+ 569 NOT 575 BIT BlT BIT (MZD'G'TS) g I L. To I NOR NOR NOT NOR %%m R%E SCAN! NOT 5?! 570 L NOTCH DN NOTCH UP NORMAL FIG STATIC ELEVATOR SUPERVISORY SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to supervisory controls for transportation systems and more particularly to vertical transportation systems such as elevators.

2. Prior Art In the real time control of a vehicular system such as an elevator system, it is necessary to retain selected sig nals for various intervals to effectuate the dynamic control of the system. Conventionally, signals such as calls for service, are memorized by electromechanical relays. Various types of relays have been utilized for the purpose, such as latching type relays which maintain a given state until electrically energized to another position, however, the most widely used arrangement is to provide a holding circuit for the relay through a set of its own contacts. In recent years, solid state devices such as flip-flops have been increasingly utilized in the elevator field for storing bits of information.

Conventionally, elevator circuits have operated in parallel. However, with the development of solid state technology, scanning type systems wherein the various signals are rapidly processed in serial form have found increasing acceptance. In such systems, as in the relay systems,a separate storage device is provided for each signal. For instance, a flip-flop or relay is provided to register a car call for each floor served by the car.

Elevator. systems also incorporate a floor selector which provides a supervisory control system with the position of the car relative to the landings. Generally floor selectors are of two types. In the analog type, a number of brushes are mounted on a carriage which moves in synchronism with the car. The brushes make contact with stationary contact segments mounted on the floor selector at positions corresponding to the location of the landings in the hoistway. The other general type of floor selector is the notching type in which signals are generated as the car passes from one landing to the next. Conventionally, the'notching signals are utilized to successively energize relays as the car moves past the landings. More recently, reversible digital counters have been utilized in notching type selectors to follow the position of the car.

SUMMARY OF THE INVENTION In accordance with the invention, various signals utilized in the control of a vehicular system are serially stored in storage means which comprises a plurality of serially connected signal storage units. The signals are shifted from one storage unit to the next in synchronism with scanning means which scans the various signal generating means in rapid succession. The scanning means also coordinates the utilization of the stored signals by supervisory control means which controls the movement of the vehicle.

As applied to an elevator system, the invention contemplates the serial storage of per floor information in the storage means which may take the form of shift registers. The signals are recirculated through the shift registers by recirculating means which couples the output back to the input. The recirculation is synchronized by the scanning means so that the appropriate signal will appear in a read-out unit each time the scanner is scanning the associated landing. This effects memorization of the signal despite termination of the original signal. The signal may be removed from the shift register by a cancelling signal which is generated under predetermined conditions. With respect to calls for service in an elevator system, the indication of the call is retained in the shift register by the recirculating means despite the release of the car or hall call button by the passenger and is cancelled when the car stops for the call.

In the preferred embodiment of the invention, gating means responsive to either the generation of a signal by the signal generating means being scanned or the recirculating means is operative to insert a signal into an input storage unit in the shift register in the absence of the cancelling signal. Also preferably, the shift register includes one more storage unit than the number of landings to be scanned, so that the last unit in the shift register represents the same landing as the first unit and supplies the read-out to the supervisory means. Alternatively, the shift register may be provided with the same number of storage units as the number of landings, but with means operative to synchronize the inser-. tion of the signal shifted out of the last signal storage unit into the first signal storage unit. In this arrangement, the first signal storage unit becomes the read-out unit for the supervisory control means.

The invention further includes the use of a shift register in a floor selector, with the signal represenative of the position of the car being recirculated through the shift register in synchronization with the scan. The length of the loop, which is closed by the recirculating means, is varied in length as the car moves from one landing to the next to reflect this change in position relative to the scan. In a preferred embodiment of the invention, the shift register incorporates two more units than the number of landings served by the car. The loop is lengthened to cause the position of the car to be delayed one landing by inserting the recirculating signal into the first unit in the series when the car moves from one landing to the next in the direction of the scan. The loop is shortened by one unit when the car moves from one landing to the next while traveling in the direction opposite to the direction of scan by inserting the recirculated signal into the third unit in the series. In the absence of a notching signal, the recirculated signal is inserted into the second unit to reflect no change in position. The extra unit on the end of the shift register is utilized as a read-out unit for the supervisory control.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an elevator system embodying the invention;

FIGS. 2 and 3 are schematic circuit diagrams'of call storage circuits according to the invention;

FIGS. 4a through d are schematic diagrams illustrating the operation of the storage units used in FIG. 3;

FIGS. 5 and 6 are schematic circuit diagrams of a floor selector according to the invention; and

FIG. 7 is a schematic diagram of another embodiment of the call storage units utilized inn FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION- the various landings are rapidly and continuously scanned in the order of the landings. The resulting serially generated signalsare processed by solid state circuits which control the movement of the cars and the stopping of the cars at selected landings. Since the circuits associated with the individual cars are identical, only circuits associated with one car will be shown. Where applicable, components and signals which are identical to those used in the patent will be identified by like reference characters. Although the system described in the patent serves only five landings, it could easily be expanded to serve the eight landings in the structure shown in this system.

Referring to FIG. 1, there is shown an elevator system l constructed according to the teachings of the invention. Elevator system includes an elevator car CA and a counterweight 16 are suspended from opposite ends of a wire rope R0 which is trained over a traction sheave 13. A motor control system MC rotates the sheave 13 to move the car CA up and down in a hoistway to serve a structure having eight landings.

The elevator car'CA carries an inductor notching relay Z which is utilized to produce notching signals as the elevator car travels in the hoistway. This relay may be of a conventional type that is mounted on the car in a position to pass adjacent each of a plurality of inductor plates ZPl, and ZP2 through ZP7 of magnetic material mounted in the hoistway. The inductor plates are so positioned that the inductor notching relay Z comes into horizontal alignment with one of the plates when the elevator car is halfway between landings.

The relay Z has two. break contacts'ALl and BLl. If the coil of the inductor notching relay is energized,

' such energization alone is insufficient to open either of the contacts ALI or 81.1. If the inductor relay, while its coil is energized, reaches one of the inductor plates ZPl, ZPS, ZPS orZP7, a magnetic circuit is completed which results in opening of the break contacts ALI. The contacts-ALI momentarily open while the relay Z is opposite one of the inductor plates ZPl, 2P3, 2P5 or ZP7, but immediately reclose when the inductor relay passes beyond such plate. Similarly, if the inductor relay Z while its coil is energized reaches one of the inductor plates 2P2, ZP4, or ZP6, a magnetic circuit is completed which results in opening of the break contacts BLl. It will be appreciated, therefore, that as the elevator car moves between the terminal floors the break contacts ALI and BM alternately open as the car proceeds from the position halfway between a pair of adjacentlandings to a position halfway between the next pair of adjacent landings in the direction of car travel. The signals generated by the contacts AL] and BM serve to operate the selector SL as will be hereinafter described.

The elevator car CA also contains a car station CS provided with a plurality of car call pushbuttons 1C through 8C which may be operated by the passengers to register calls for landings desired by the passengers within the elevator car. The car call buttons supply signals to the car call storage circuit identified in FIG. 1 by the block CCS.

Hall call stations are provided at each of the landings to afford prospective passengers the opportunity to register calls for service. The intermediate floors are provided with up hall call buttons identified by the floor number and the letter U, and down hall call buttons identified by the floor number and the letter D. For instance, the up hall call button for the second floor is identified by the reference character 2U, and the down hall call button for this floor is represented by the reference character 2D. The upper and lower terminal floors are provided only with the down hall call button 8D, and theup hall call button 1U, respectively. All of the down hall call buttons supply signals to the down hall call storage circuits identified by the reference character DCS, while the up hall call button supplies signals to the up hall call storage circuits UPS. The hall call storage circuits, car call storage circuits and selector supply signals to a supervisory control system 11, which in turn controls the movement and stopping of the cars through the motor control MC.

Although other types of logic circuits could be utilized, NOR logic is employed in describing the invention, since this is the type of logic utilized in the patent. The basis of NOR logic is the NOR element exemplified by the block labeled 503 in FIG. 2. The NOR element may have a plurality of inputs such as the three shown for NOR 503 in FIG. 2, but has a single output. The circuits for NOR elements are well known, therefore, it is sufficient at this point to say that the operating characteristics of a NOR element are such that a signal will appear at the output only when no signal appears at each of the inputs. In binary terms, the NOR element will have a ONE output onlywhen all of'the inputs are ZERO. If any of the input signals is a ONE, the output is ZERO. ANOR element with only one input, such as element 504 in FIG. 2, is also referred to as a NOT element, since it generates the reciprocal of the input signal.

Another common logic element utilized is the OR element, such as the element 531 in FIG. 3. Again the circuits for OR elements are well known. The characteristics of an OR element are such. that it will have a ONE output if any one of the inputs is a ONE.

An additional common logic element which will be found in the disclosed circuits is the flip-flop memory element represented bythe divided rectangle with the lettersF-F in the upper portion, such as element 546 in FIG. 5. It is unnecessary to describe the circuit diagram of this well known logic element. The inputs appear on the leftside of the rectangle representing the flip-flop, while the outputs appear on the right side. A flip-flop will always have at least one upper and one lower input, but may have multiple upper and lower inputs. It may have an upper and/or lower output, but it may only have one upper and one lower output. When a ONE signal is applied to the upper input of the flipflop, a ONE signal will appear on the lower output of the flip-flop and a ZERO willappear on the upper output. The flip-flop will remain in this state even though the input signal goes to ZERO until a ONE is applied to one of the lower inputs which will cause the lower output to go to ZERO and the upper output to go to ONE.

FIG. 2 illustrates the circuits for generating the time synchronized call signals. Busses B1 and B2 supply current for the car call and hall call buttons, respectively. Pressing of the car call button 2C by a passenger applies a ONE to the input of the NOT element 513 thereby causing its output to go to ZERO. The ZERO signal generated by NOT element 513 is applied to the input of NOR element 523, however, a signal 2CC generated by this NOR element can only go to ONE if the other input namely the signal SCAN 2 simultaneously this point, the scanner is again scanning the second floor. Assuming that at this point the passenger has released the car call button so that the signal MCC is equal to ZERO. The output of NOR element 544 will thus go to ZERO, and NOR 543 will insert a ONE into the first or input bit of the shift register 542 by the signal E which appears in the last bit of the shift register. Thus, the previously inserted signal is reinsertedinto the first bit of the shift register through the recirculating means which includes the lead 57 8 between the last bit and the NOR element 544. In this configuration, both the first and the last bit in the shift register represent the floor being scanned. Of course in reality the passenger would hold the car call button depressed for several cycles by the scanner, however, it can be seen from FIG. 3 that with the signal E and/or the signal MCC equal to ONE, a ONE will be insertedinto the first bit of the shift register. It can be appreciated that with the car call button released, the signal representing the car call is memorized or stored in the shift register.

As indicated in connection with the discussion of FIG. 3, when the car approaches the second floor and a stop signal and door open signal are generated the CANCEL signal will go to ONE when the scanner is scanning the second floor. Under these conditions, even though the ONE signal stored in the last bit of the shift register 542 causes the output of NOR element 544 to go to ZERO, the output of NOR element 543 is forced to ZERO by the CANCEL signaL'Therefore, although a ONE remains in the last bit of the shift register, a ZERO, indicating a cancellation of the call, now appears in the first bit. This condition is shown in FIG. 4d. When the clock causes the shift register to shift all signals one unit to the right on the next pulse, the ONE signal stored in the last bit will be lost and therefore the next time the scanner is scanning the second floor a ZERO will appear in the read-out bit of the shift register. Although it is apparent from the above discussion that the E signal, which is an indication to the supervisory control system of a car call, will not go to ONE until a full scan after the floor is interrogated while the button is depressed, and will not return to ZERO until one fullscan after the car cancels the call, this slight delay of approximately 8 milliseconds is of no consequence in the time frame of the control system.

An alternative arrangement in which the shift register comprises a number of digits equal to the number of landings is shown in FIG. 7. Like reference numerals in FIGS. 3 and 7 indicate like components, while like reference numerals except for a prime mark indicate modified components. In this circuit, the lead 578 is connected tothe shift out terminal of the last bit of the shift register 542' rather than to the read terminal. In addition the lead 578 is connected to the input of the NOR element 544 through delay means whichincludes NOT element 580 and a pulse generator 579. The pulse generator or differentiator 579'is a well known static device which produces a signal at its output for a given time interval after it appears at the input. The element 579 may have a suitable pulse interval such as 250 microseconds. Now when the clock generates a pulse causing the scanner to advance to the next landing, the signal which was stored in the last digit of the shift register will be applied to the input of the NOR element 544, for a duration of 250 microseconds after the clock pulse. This delay provides the scanner sufficient time to assume the new position and for the system to cancel the signal if conditions so warrant. In no CANCEL signal is generated and a ONE had previously been stored in the last bit of the shift register, a ONE will be inserted into the first bit during the delay interval. In this configuration the first unit also serves as the readout unit which generates the signal E.

Returning to FIG. 3, it can be seen that down corridor calls are stored in the shift register 538 by generating a master down call signal MDC in OR element 532 and that thissignal is inserted into to the first bit of the shift register 538 through NOR

elements

540 and 539. Corridor calls once registered are recirculated through the shift register by the lead 580 which connects the last bit of the shift register 538 to the NOR element 540. As in the case of the car calls, the down corridor calls are shifted through the shift register 538 by clock pulses. The signal stored in the last bit of shift register 538 is the multiplexed down corridor signal D which corresponds to the similarly identified signal in the pa tent. This signal is applied to the supervisory control system of the patent for controlling the movement of the cars. I

As in the case of car calls, down corridor calls are cancelled by a car hich stops at the floor with its doors open (signals 34, ii and (F)S equal to ZERO) through NOR element 541. However, in addition, a down corridor call can only be cancelled by such a car which is set for down travel (81D equal to ZERO).

In a similar manner up corridor calls are stored in shift register 534 by a master up call signal MUC which is generated in OR element 531 and applied to the input unit of shift register 534 through NOR

elements

536 and 535. The up corridor calls are shifted through the shift register 534 by clock pulses and are recirculated through the recirculating line 581. The signal appearing in the last bit of the shift register 534 represents up hall calls at the floor being scanned and supplies the multiplexed up corridor call signal C corresponding to the similarly identified signal in the patent. Again this signal is utilized by the supervisory control circuit to control the movement and stopping of the cars. Up corridor calls are cancelled by a car which stops with its doors open at the associated landing (signals 3i,4 l and (m all equal ZERO) only if the car is set for up travel (T117 equal ZERO) through NOR element 537.

FIGS. 5 and 6 illustrate the application of the invention to a floor selector which generates signals for the supervisory system representative of the position of the car relative to the landings. The selector is of the notching type utilizing the two lane notching scheme common in the elevator field and utilized in the patent. As described above in connection with the description of FIG. 1, signals are alternately generated by contacts ALl and BLl of the inductor relay Z as the car passes halfway between landings. For instance, as the car passes between the first and second landings, the contacts ALl generate a signal and then as the car passes between the second and third landings, the contacts BLl generate a signal. As shown in the circuits of the patent, a signal AL is equal to ONE when the contacts ALl are closed and goes to ZERO when the contacts ALl open as the car passes halfway betwefl the first and second landings. Similarly, the signal BL is equal to ONE except when the contacts BLI are opened as the car passes between the second and third landings goes to ZERO. It can be appreciated that when the car call button 2C is not depressed so that the input to the NOT element 513 is a ZERO, the ONE signal generated by the NOT element 513 maintains the signal 2CC equal to ZERO.

In a similar manner the hall call buttons 2U and 2D each control the output of a NOR element through a NOT element in cooperation with the signal SCAN 2. As a consequence, the signals 2UC, 2DC and 2CC can only to to ONE when the appropriate call button is depressed and the signal SCAN 2 is equal to ZERO.

Similarly, all of the other call buttons control the output of a NOR element through a NOT element in conjunction with a SCAN signal associated with that landmg. t

The SCAN signals can be generated by circuits similar to those disclosed in the patent, or they may be generated in any other suitable manner such as through the circuit shown in FIG. 2. In this arrangement, a clock 501' generates periodic pulses which drive a binary counter 502. A reasonable frequency for this clock is in the range of 1 kilohertz. The binary counter 502 is a three digit counter capable of counting from zero through seven thereby having eight states. Of course, a binary counter capable of counting the number of landings in the building is required.

The binary counter generates signals on the busses S1, S2 and S3 corresponding to the first, second and third digits in accordance with the number in the counter. The complementary signals are generated on the complementary busses S1, S2 and S3. Thus, when the binary number 001 is in the counter, ZERO signals appear on busses S3 and S2 and a ONE signal appears on bus S1. Concurrently, a ZERO signal appears on bus S1 while a ONE signal appears on busses S3 and S2. Thethree inputs to a NOR element 503 are connected to busses S3, S2 and S1 so that when the binary number 00l appears in the binary counter all the inputs to this NOR element will be equal to ZERO and the output will go to ONE. The output of NOR element 503 is inverted by the NOT element 504 so that the signal SCAN 1 will go to ZERO when abinary number 001 appears in the binary counter.

Similarly, the three inputs to NOR element 505 are connected to the busses S3, S2 and S1 so that the signal'SC AN 2 will go to ZERO when the binary number 010 which is equivalent to the decimal number 2 appears in the binary counter 502. In a similar manner, NOR elements associated with each landing are connected to the outputs of the binary counter so that their outputs go to ONE when the associated binary number appears'in the binary counter. Each of the signals is inverted by a NOT element to generate the appropriate SCAN signal.

Recalling the previous discussion, it can be seen that the signal 2CC can go to ONE only while the car call button 2C is depressed and the binary number for the decimal number 2 appears in the binary counter. As the clock 501 continues to generate pulses, the binary counter 502 will continuously count from zero through seven, and each time the number 2 appears in the counter, the signal 2CC will go to ONE as long as the button 2C remains depressed. Since the signal SCAN 2 will goto ZERO approximately every 8 milliseconds, and since a passenger will hold the button 2C down for a period longer than this interval, there is no difficulty in generating a signal 2CC. If several car call buttons are depressed, the CC signal associated with a particular landing will only go to ONE during the l millisecond interval that the scanner is scanning the associated landing. It can be appreciated then that the scanner serves to time synchronize the car call, the up hall call and the down hall call signals separately with respect to time.

Turning to FIG. 3, all of the time synchronized car call signals ICC through 8CC are fed into the OR element 533 which generates the time multiplexed master car call signal MCC at its output. Therefore, as the scanner scans past the landings, the signal MCC will go to ONE each time the scanner passes a landing for which a car call button is held depressed.

The master car call signal MCC serially feeds the car calls into shift register 542 through NOR

elements

543 and 544. The output of the shift register 542, which is the signal E, also serves as an input to the NOR element 544 while a CANCEL signal generated by the NOR element 545 serves as an additional input to the NOR element 543. The CANCEL signal will go to ONE when a stop signal and a door open signal are generated 3 and II equal ZERO) and the car is at the floor being scanned ((TYS equals ZERO).

Reference to FIG. 4a will lead to a better understanding of the operation of the shift register 542. The shift register 542, which may be of any suitable type, such as General Instrument MEM3021, is composed of a number'of serially connected storage units or binary bits. The shift register is provided with shift means which when triggered causes the signal stored in each of the bits to be shifted to the next succeeding bit. The shift is from left to right as shown in FIG. 4a. The signal stored in the last bit is lost in the shift. It should be noted that there is one more bit in the shift register than there are landings so that shift register 542 contains nine bits.

When a car call is registered at the floor at which the scanner is scanning, the signal MMC, shown in FIG. 3, will go to ONE to cause the output of the NOR 544 to go to ZERO. If the CANCEL signal is also equal to ZERO, the output of NOR element 543 will go to ONE, to insert a ONE into the firstbit of the shift register 542. If the scanner is scanning the second floor, the first bit in the shift register represents the second floor at this instant. The shift means is operated by pulses from a clock so that whenthe clock generates a pulse to cause the scanner to advance to the third floor, all of the signals in the shift register 542 are shifted one unit to the right. As a result, the signals stored in the shift register 542 appear as in FIG. 4b. At this instant in time, with the scanner scanning the third floor, the first bit in the shift register represents a car call at the third floor, and the second bit in the sequence represents the car call at the second floor. Since it will be assumed that MCC is equal to ZERO at this point, indicating that the car call button 3C is not depressed and since it will be assumed at the present that the other input to the NOR element 544 is equal to ZERO, the output of NOR 544 will go to ONE to force the output of NOR 543 to go to ZERO. In this manner a ZERO is inserted into the first bit of the shift register indicating that no car call is registered at the third floor.

As the scanner scans up through the floors the ONE signal associated with the car call at the second floor is successively shifted one unit to the right until it appears in the last bit in the series, as illustrated in FIG. 4c. At

and the fourth and fifth landings etc., when it goes to ZERO.

As can be seen from FIG. 5, these A L and El: signals are utilized to alternately set and reset the flip-flop 546.

For instance, when the car is'set for travel in the up direction (signal TA equal to ZERO) the output of NOR element 549 will go to ONE to reset the flip-flop 546 when the contacts ALI open, to cause the signal H to go to ZERO as the car passes between the first and second floors. As the car continues to travel in the upward direction, the output of NOR element 548 will go to ONE to set the flip-flop 546 as the car passes between the second and third floors and the signal at goes to ZERO. It can be seen then that the flip-flop- 546 alternates between its set and reset conditions as the car travels upward in the hoistway. As the car travels downward (signal 2A equal to ZERO) NOR

elements

547 and 550 alternately set and reset the flip-flop 546 as the car passes halfway between the landings. If the car which resets the flip-flop 546 through NOR ele-' ment 549 in traveling from the first to the second floor reverses direction at the second floor, it will set the flipflop again with the contacts ALI through the NOR element 547 as the car passes halfway between the second floor and the first floor traveling in the down direction.

The set and reset outputs of the flip-flop 546'serve as inputs to a'NOR element 551 through pulse generators 552 and 553, respectively. These pulse generators are well known logic elements which generate an output pulse whenever a signal is applied to the input. The duration of the output pulse is fixed despite the continuous application of an input signal. A suitable interval for the output pulse in this application is on the order of 150 microseconds. The output of NOR element 551 serves as an input to NOR

element

554 and 555. A second input to NOR element 554 is the up direction signal I while the second input to the NOR element 555 is the down direction signal 2A. With the output of the pulse generators 552 and 553 normally equal to ZERO, the ONE output of NOR element 551 normally maintains the output of NOR

elements

554 and 555 equal to ZERO. However, whenever the car passes halfway between floors and a notching signal is generated to cause the flip-flop 546 to change states, one of the inputs to NOR element55l goes to ONE for the duration of the pulse to cause the output of NOR element 551 to go to ZERO. If the cg was traveling in the up direction so that the signal 1A is equal to ZERO, the output of NOR element 554 will change to ONE. On the other hand, if the car is traveling in the down direction so that the signal 2A is equal to ZERO, the output of the NOR element 555 will go to ONE for the duration of the pulse. Since the NOR element 554 goes to ONE momentarily when the car passes between floors going in the up direction, the output of this element is designated the SHIFT UP signal. On the other hand, the output of NOR element-555 is referred to as the SHIFT DN signal.

The momentary SHIFT UP signal resets the flip-flop 556 which as a result applies a ZERO to the upper input of a NOR element 557. The SHIFT UP signal is synchronized with the scanner through the application of a second input to NOR element 557 in the form of the inverted car position signal This latter signal is equal to ONE except when the scanner is scanning the last floor at which the car was located.

When the output of the NOR element 557 goes to ONE it resets the flip-flop 558 to cause the NOTCH UP signal to go to ONE. The NOTCH UP signal sets the flip-flop 556 to inhibit the NOR element 557 so that its output cannot go to ONE each time the scanner scans past the position of the car. A pulse from the clock sets the flip-flop 558 to cause the NOTCH UP signal to go to ZERO and the NOTCH UP equal to ONE when the scanner advances to the next landing.

The notching signals generated as the car travels downward in the hoistway are similarly synchronized with the scanner to cause the NOTCH DN signal to go to ONE only when the scanner isscanning at the last floor at which the car was located. The NOTCH DN signal sets the flip-flop 559 so that the NOTCH DN signal only goes to ONE on the first scan after the notching signal is generated.

Turning to FIG. 6, the shift register 562 which stores the position of the elevator car relative to the landings is similar to the shift registers used to store the calls for service. However, this shift register is provided with N 2 storage units or bits, where N is the number oflandings. One of the extra storage units is the last unit which serves as the read-out bit. A ONE appears in this unit when the scanner is scanning at the floor at which the car is located. This signal (F)S is fed to the supervisory control and also serves as an input to the NOT element 569. When the scanner is scanning at the floor at which the car was located on the previous scan, the output of NOT element 569, the signal (I E, will go to ZERO. As long as the car is not located at the top or bottom terminal so that the signals T69 and B69, respectively, are equal to ZERO (see the patent for the generation of these signals) the output of NOR element 568 will go to ONE. This signal is inverted by the NOT element 567 to cause the inverted signal to go to ZERO. If no notching signals were generated on this scan so that the NOTCH UP and NOTCH DN signals are both equal to ZERO, the output of NOR element 564 will go to ONE which in turn causes the output of OR element 563, which is the NORMAL signal, to go to ONE. When the NORMAL signal goes to ONE, it inserts a ONE into the second storage unit of the shift register 562. It can be appreciated that since the shift register 562 contains N 2 units, and since the clock pulses cause the signal to be shifted one unit to the right each time the scanner advances to another landing, the ONE signal inserted into the second unit of the shift register will appear in the readout bit when the scanner is again scanning that landing. It will also be clear from the above discussion that if no notching signals are again generated, that a ONE signal will again be inserted into the second unit of the shift register 562. In this manner, it willbe understood that a ONE signal will be recirculated through the shift register 562 and appear in the read-out bit each time the scanner is canning the landing at which the car is located.

Assuming that on a subsequent scan a notching signal is generated while the car is traveling in the up direction, the NOTCH UP signal will goto ONE when the scanner is scanning the landing at which the car was noted to be located on the previous scan. With the NOTCH UP signal equal to ONE, the NORMAL signal cannot go to ONE to insert a signal into the second unit of the shift register. On the other hand, the NOTCH UP signal will go to ZERO to cause the output of the NOR element 565, which is the DELAY signal to go to ONE.

Under these conditions the DELAY signal will insert a ONE into the first unit of the shift register. Since the ONE signal must now be shifted one extra unit before it appears in the read-out bit, the signal (F)S will not go to ONE until the scanner has scanned one floor past the previous position of the car. To illustrate, if the car had been located at the first floor (F)S would go to ONE each time the scanner was scanning the first floor. However, with the ONE inserted in the first unit of the shift register, the signal (F)S will not go to ONE on the next scan until the scanner is scanning at the second floor.

If a notching signal is generated while the car is traveling in the down direction, the NOTCH DN signal will go to ONE when the scanner is scanning the floor at which the car was located on the previous scan. This will prevent the NORMAL signal from inserting a ONE into the second unit of the shift register 562. However, the NOTCH DN signal will go to ZERO to cause the output of the NOR element 566 which is the AD- VANCE signal, to go to ONE. When the ADVANCE signal goes to ONE, a ONE signal is inserted into the third unit of shift register 562. Under these conditions, the ONE signal will appear in the readout digit one scan position sooner on the next scan.

Therefore, it can beseen that if no notching signal is generated a ONE signal will be inserted into the second unit of the shift register 562 to cause the signal (F)S to go to ONE at the same position each scan. If however, a notching signal is generated while the car is traveling in the up direction, which is the same direction as the direction of scan, a ONE signal will be inserted into the first unit of the shift register thereby causing the signal (F)S to goto ONE when the scanner is scanning the next higher floor. On the other hand, when the notching signal is generated as the car is traveling in the down direction a ONE signal will be inserted into the third unit of the shift register so that the signal (F)S will go to ONE while the scanner is scanning the next lower floor.

When the elevator car is'located at the top terminal ineffective. The signal T69 causes the output of NOT element 574 to go to ZERO, so'that when the output of NOT element 573 goes to ZERO when the scanner is scanning the eighth or top floor, the output of NOR element 572 goes to ONE. Similarly, if the car is located at the lower terminal the output of NOR element 575 will go to ONE when the scanner is scanning the first floor. If either the output of NOR element 572 or 575 is equal to ONE, the NORMAL signal will go to ONE to insert a ONE into the second unit of the shift register 562. Since'the generation ofthe NORMAL signal under these circumstances is directly synchronized with the scan, it is assured that the correct car position is maintained in shift register 562. This arrangement provides for positive resynchronization of the selector each time the car reaches the top or the bottom terminal. It is also useful in the event of power failure, wherein a car can be run to the terminal and the selector reset.

It can be understood from the above discussion that in a scanning type of supervisory system, wherein the bits of information are serially processed, signals associated with particular landings can be efficiently stored in shift registers thereby doing away with the necessity of having a separate memory device for each signal for each floor. In view of the advances in integrated circuit technology, all of the up calls or down calls, etc. can be stored on a single chip which can lead to considerable savings.

I claim as my invention:

1. In an elevator control system adapted for controlling the movement of an elevator car to serve a plurality of landings, signal generating means operative for generating a plurality of signals indicative of predetermined conditions in the system, signal storage means operative for storing selected signals generated by said signal generating means, control means operative to control the movement of the car and the stopping of said car at selected landings in response to the signals generated by the signal generating means including the signals stored in the signal storage means, and scanning means continuously and repetitively providing scan signals assigned to the plurality of landings which are operative to coordinate the operation of the control means and the signal storage means, said combination characterized in that the signal storage means includes a plurality of serially connected signal storage units each operative to store a selected signal and shift means operative when activated to shift the signal stored in each signalstorage unit into the next succeeding signal storage unit, said scan signals provided by the scanning means being operative to activate the shift means.

2. The system of claim 1 wherein said signal generating means include means for generatinga plurality of signals each of which is associated with a different one of said landings, wherein said scanning means includes means for rapidly and continually scanning said signal generating means-in the order of the landings and for inserting selected of said signals into an input storage unit of said signal storage means in the order that they appear in the scan, and wherein the control means includes means responsive to the sequence in which the signals are stored in the signal storage means.

3. The system of claim 2 including recirculating means operative to reinsert a particular signal associated with a particular landing back into the input storage unit of the storage means when said scanning means is again scanning the signal generating means associated with a particular landing, whereby said particular signal will appear in the input storage unit each time the scanning means is scanning the particular landing despite the termination of the condition which originally generated the particular signal.

4. The system of claim 3 including cancelling means operative under predeterminedconditions for rendering the recirculating means inoperative to reinsert a particular signal into said input storage unit.

5. The system of claim 3 wherein said signal generating means includes call registering means operative in response to a passenger operation for registering a call for service to a particular landing, said passenger initiated call signal being recirculated through said storage means by the recirculating means despite termination of the passenger operation.

6. The system of claim 5 including cancelling means responsive to the stopping of the car at said particular landing for rendering the recirculating means inoperative to reinsert said particular signal into said input storage unit.

7. The system of claim 4 wherein said scanning means includes coincident signal generating means operative to generate a coincident signal each time the scanning means scans a signal generating means which is generating a signal, said combination including gating means operative in response to a signal generated by either the coincident signal generating means or the recirculating means in the absence of a signal from said cancelling means for inserting a signal into said input storage unit.

8. In an elevator control system adapted for controlling the movement of an elevator car to serve a plurality of landings,

signal generating means operative for generating a plurality of signals indicative of predetermined conditions in the system, said signal generating means including means for generating a plurality of signals each of which is associated with a different one of said landings,.

signal storage means operative for storing selected signals generated by said signal generating means, control means operative to control the movement of the car and the stopping of said car at selected landings in response to the signals generatedby the signal generating means including the signals stored in the signal storage means,

scanning means operative to coordinate the operation of the control means and the signal storage means, said scanning means including means for rapidly and continually scanning said signal generating means in the order of the landings and for inserting selected of said signals into an input storage unit of said signal storage means in the order that they appear in the scan,

said control means including means responsive to the sequence in which the signals are stored in the signal storage means,

recirculating means operative to reinsert a particular signal associated with a particular landing back into the input storage unit of the signal storage means when said scanning means is again scanning the signal generating means associated with a particular landing, whereby said particular signal will appear in the input storage unit each time the scanningmeans is scanning the particular landing despite the termination of the condition which originally generated the particular signal, said scanning means including coincident signal generating means operative to generate a coincident signal each time the scanning means scans a signal generating means which is generating a signal,

cancelling means operative under predetermined conditions forrendering the recirculating means inoperative to reinsert a particular signal into said input storage unit,

gating means operative in response to a signal generated by either the coincident signal generating means or the recirculating means in the absence of a signal from said cancelling means for inserting a signal into said input storage unit,

said signal storage means including a plurality of serially connected signal storage units each operative to store a selected signal,

shift means operative when activated to shift the signal stored in each signal storage unit into the next succeeding signal storage unit,

9. In an elevator control system adapted'for control- I ling the movement of an elevator car to serve a plurality of landings,

signal generating means operative for generating a plurality of signals indicative of predetermined conditions in the system,

said signal generating means including means for generating a plurality of signals each of which is associated with a different one of said landings,

signal storage means operative for storing selected signals generated by said signal generating means,

control means operative to control the movement of the car and the stopping of said car at selected landings in response to the signals generated by the signal generating means including the signals stored in the signal storage means,

scanning means operative to coordinate the operation of the control means and the signal storage means,

said scanning means including means for rapidly and continually scanning said signal generating means in the order of the landingsand for inserting selected of said signals into an input storage unit of said signal storage means in the order that they appear in the scan,

recirculating means operative to reinsert a particular signal associated with a particular landing back into the input storage unit of the signal storage means when said scanning means is again scanning the signal generating means associated with a particular landing, whereby said particular signal will appear in the input storage unit each time the scanning means is scanning the particular landing despite the termination of the condition which originally generated the particular signal,

said scanning means including coincident signal generating means operative to generate a coincident signal each time the scanning means scans a signal generating means which is generating a signal,

cancelling means operative under predetermined conditions for rendering the recirculating means inoperative to reinsert a particular signal into said input storage unit,

gating means operative in response to asignal generated by either the coincident signal generating means or the recirculating means in the absence of a signal from saidcancelling means for inserting a signalinto said input storage unit,

said scanning means being operative to activate said shift means,

wherein the number of serially connected signal storage units is equal to said plurality of landings and wherein the recirculating means includes means for applying the signal shifted out of said last signalstorage unit in the series to said gating means to be reinserted in said input storage unit, andincluding means for applying the signal stored in said input storage unit to said control means.

10. The system of claim 1 adapted for storing a signal representative of the position of the car relative to the landings, wherein the scan means has a plurality of scan positions corresponding to said landings which are rapidly and continually scanned in the order of the landings, said combination including recirculating means for closing the loop of said serially connected storage units, the length of the loop being such that the signal representative of the position of the car appears in a selected one of said storage units each time the scanning means is scanning the landing at which the car is located.

11. In an elevator control system adapted for controlling the movement of an elevator car to serve a plurality of landings and for storing a signal representative of the position of the car relativeto the landings,

signal generating means operative for generating a plurality of signals indicative of predetermined conditions in the system, signal storage means operative for storing selected signals generated by said signal generating means, said signal storage means including a plurality of serially connected signal storage units each operative to store a selected signal, control means operative to control the movement of the car and the stopping of said car at selected landings in response to the signals generated by the signal generating means including the signals stored in the signal storage means, scanning means operative to coordinate the operation of the control means and the signal storage means, said scanning means having a plurality of scan positions corresponding to said landings which are rapidly and continually scanned in the order of the landings,

shift means operative when activated to shift the signal stored in each signal storage unit into the next succeeding signal storage unit, said scanning means being operative to activate the shift means,

recirculating means for closing the loop of said serially connected storage units, the length of the loop being such that the signal representative of the position of the car appears in a selected one of said storage units each time the scanning means is scanning the landing at which the car is located, said signal generating means including means for generating an advance signal each time said car passes from one landing to the next, and means responsive to said advance signal for altering the progress of said signal representative of car position through the storage means, whereby the signal representative of car position will appear in said selected storage unit when the scanning means is scanning the new landing at which the car is located.

12. The system of claim 11 wherein the means for altering the progress of the signal representative of car position comprises means for varying the length of said loop.

13. The system of claim 12 including means responsive to the presence of said car at a selected landing and operative to cause the signal representative of the car position to appear in a selected storage unit when the scanning means is scanning said selected landing.

14. The system of claim 13 wherein said means responsive to the presence of said car at a selected landing includes means for preventing a signal representative of the car position from appearing in said selected storage unit when the scanning means is scanning any landing other than said selected landing.

15. The system of claim 12 including direction means responsive to the direction of travel of the car and operative to a first condition when the car is traveling in a first direction and operative to a second condition when the car is traveling in the opposite direction, said combination wherein the means for varying the length of said loop is responsive to the condition of said direction means and is operative to'lengthen said loop in the presence of an advance signal when the direction means is in the first condition and operative to shorten said loop in the presence of an advance signal when the direction means is in the second condition.

16. The system of claim 15 wherein the number of serially connected storage units in the storage'means exceeds the number of landings served by the car.by two, wherein the last storage unit in the series is a readout unit, said read-out unit being connected to the control means and to the recirculating means including the means for varying the length of said loop, said combination wherein said means for varying the length of said loop includes means to insert the signal stored in the read-out unit into the first storage unit in said series in the presence of an advance signal when the direction means is in the first condition, means to insert the signal stored in the read-out unit into the third storage unit in the series in the presence of an advance signal when the direction means is in the second condition and means to insert the signal stored in the read-out unit into the second storage unit in the series in the ab sence of an advance signal.

17. The system of claim 16 including resynchronizing means operative in response to the presence of the car at a selected landing for inserting a signal into the second storage unit in said series when said scanning means is scanning said selected landing.

18. The system of claim 17 wherein the resynchronizing means is also operative in response to the presence of the car at the selected landing to render the recirculating means inoperative to insert signals stored in said read-out unit into said serially connected storage units.

19. An elevator control system, comprising:

a structure having a plurality of landings,

an elevator car mounted for movement relative to the structure to serve the landings,

shift storage means having aplurality of memory elements including input and output memory elements,

output terminal means connected to a predetermined one of the elements of said shift means, logic means connected to the input element of said shift means,

signal means for providing landing related signals in response to requests for elevator service,

scan counter means continuously and repetitively providing scan counter signals assigned to the landings,

means connected to said logic means and responsive to said scan counter means and said signal means for serially introducing said landing related signals into said shift means and shift the landing related signals from element to element thereof in response to saidscan counter signals such that a landin'g related signal at the output terminal means at any instant is related to the floor assigned to the scan counter signals being provided by the scan counter'means,

and means connecting the output element of said shift means to said logic means to store said landing related signals in said shift means by recirculating them.

20. The elevator control system of claim 19 including reset means connected to the logic means operative under predetermined conditions for rendering the logic means inoperative to recirculate a particular landing related signal through the shift means.

21. The elevator control system of claim 19 wherein the signal means provides a landing related signal only while arequest for elevator service is being registered, and wherein the landing related signals are stored in the shift means by providing a cycle rate for the scan counter means which is short compared with the duration of the landing related signal provided by the signal means.

Claims

1. In an elevator control system adapted for controlling the movement of an elevator car to serve a plurality of landings, signal generating means operative for generating a plurality of signals indicative of predetermined conditions in the system, signal storage means operative for storing selected signals generated by said signal generating means, control means operative to control the movement of the car and the stopping of said car at selected landings in response to the signals generated by the signal generating means including the signals stored in the signal storage means, and scanning means continuously and repetitively providing scan signals assigned to the plurality of landings which are operative to coordinate the operation of the control means and the signal storage means, said combination characterized in that the signal storage means includes a plurality of serially connected signal storage units each operative to store a selected signal and shift means operative when activated to shift the signal stored in each signal storage unit into the next succeeding signal storage unit, said scan signals provided by the scanning means being operative to activate the shift means.

2. The system of claim 1 wherein said signal generating means include means for generating a plurality of signals each of which is associated with a different one of said landings, wherein said scanning means includes means for rapidly and continually scanning said signal generating means in the order of the landings and for inserting selected of said signals into an input storage unit of said signal storage means in the order that they appear in the scan, and wherein the control means includes means responsive to the sequence in which the signals are stored in the signal storage means.

4. The system of claim 3 including cancelling means operative under predetermined conditions for rendering the recirculating means inoperative to reinsert a particular signal into said input storage unit.

8. In an elevator control system adapted for controlling the movement of an elevator car to serve a plurality of landings, signal generating means operative for generating a plurality of signals indicative of predetermined conditions in the system, said signal generating means including means for generating a plurality of signals each of which is associated with a different one of said landings, signal storage means operative for storing selected signals generated by said signal generating means, control means operative to control the movement of the car and the stopping of said car at selected landings in response to the signals generated by the signal generating means including the signals stored in the signal storage means, scanning means operative to coordinate the operation of the control means and the signal storage means, said scanning means including means for rapidly and continually scanning said signal generating means in the order of the landings and for inserting selected of said signals into an input storage unit of said signal storage means in the order that they appear in the scan, said control means including means responsive to the sequence in which the signals are stored in the signal storage means, recirculating means operative to reinsert a particular signal associated with a particular landing back into the input storage unit of the signal storage means when said scanning means is again scanning the signal generating means associated with a particular landing, whereby said particular signal will appear in the input storage unit each time the scanning means is scanning the particular landing despite the termination of the condition which originally generated the particular signal, said scanning means including coincident signal generating means operative to generate a coincident signal each time the scanning means scans a signal generating means which is generating a signal, cancelling means operative under predetermined conditions for rendering the recirculating means inoperative to reinsert a particular signal into said input storage unit, gating means operative in response to a signal generated by either the coincident signal generating means or the recirculating means in the absence of a signal from said cancelling means for inserting a signal into said input storage unit, said signal storage means including a plurality of serially connected signal storage units each operative to store a selected signal, shift means operative when activated to shift the signal stored in each signal storage unit into the next succeeding signal storage unit, said scanning means being operative to activate said shift means, wherein the number of serially connected storage units exceeds the number of signal generating means associated with landings by one, and wherein the recirculating means includes means for applying the signal stored in the last signal storage unit in the series to said gating means, and including means for also applying the signal stored in said last signal storage unit to said control means.

9. In an elevator control system adapted for controlling the movement of an elevator car to serve a plurality of landings, signal generating means operative for generating a plurality of signals indicative of predetermined conditions in the system, said signal generating means including means for generating a plurality of signals each of which is associated with a different one of said landings, signal storage means operative for storing selected signals generated by said signal generating means, control means operative to control the movement of the car and the stopping of saiD car at selected landings in response to the signals generated by the signal generating means including the signals stored in the signal storage means, scanning means operative to coordinate the operation of the control means and the signal storage means, said scanning means including means for rapidly and continually scanning said signal generating means in the order of the landings and for inserting selected of said signals into an input storage unit of said signal storage means in the order that they appear in the scan, said control means including means responsive to the sequence in which the signals are stored in the signal storage means, recirculating means operative to reinsert a particular signal associated with a particular landing back into the input storage unit of the signal storage means when said scanning means is again scanning the signal generating means associated with a particular landing, whereby said particular signal will appear in the input storage unit each time the scanning means is scanning the particular landing despite the termination of the condition which originally generated the particular signal, said scanning means including coincident signal generating means operative to generate a coincident signal each time the scanning means scans a signal generating means which is generating a signal, cancelling means operative under predetermined conditions for rendering the recirculating means inoperative to reinsert a particular signal into said input storage unit, gating means operative in response to a signal generated by either the coincident signal generating means or the recirculating means in the absence of a signal from said cancelling means for inserting a signal into said input storage unit, said signal storage means including a plurality of serially connected signal storage units each operative to store a selected signal, shift means operative when activated to shift the signal stored in each signal storage unit into the next succeeding signal storage unit, said scanning means being operative to activate said shift means, wherein the number of serially connected signal storage units is equal to said plurality of landings and wherein the recirculating means includes means for applying the signal shifted out of said last signal-storage unit in the series to said gating means to be reinserted in said input storage unit, and including means for applying the signal stored in said input storage unit to said control means.

11. In an elevator control system adapted for controlling the movement of an elevator car to serve a plurality of landings and for storing a signal representative of the position of the car relative to the landings, signal generating means operative for generating a plurality of signals indicative of predetermined conditions in the system, signal storage means operative for storing selected signals generated by said signal generating means, said signal storage means including a plurality of serially connected signal storage units each operative to store a selected signal, control means operative to control the movement of the car and the stopping of said car at selected landings in response to the signals generated by the signal generating means including the signals stored in the signal storage means, scanning means operative to coordinate the operation oF the control means and the signal storage means, said scanning means having a plurality of scan positions corresponding to said landings which are rapidly and continually scanned in the order of the landings, shift means operative when activated to shift the signal stored in each signal storage unit into the next succeeding signal storage unit, said scanning means being operative to activate the shift means, recirculating means for closing the loop of said serially connected storage units, the length of the loop being such that the signal representative of the position of the car appears in a selected one of said storage units each time the scanning means is scanning the landing at which the car is located, said signal generating means including means for generating an advance signal each time said car passes from one landing to the next, and means responsive to said advance signal for altering the progress of said signal representative of car position through the storage means, whereby the signal representative of car position will appear in said selected storage unit when the scanning means is scanning the new landing at which the car is located.

15. The system of claim 12 including direction means responsive to the direction of travel of the car and operative to a first condition when the car is traveling in a first direction and operative to a second condition when the car is traveling in the opposite direction, said combination wherein the means for varying the length of said loop is responsive to the condition of said direction means and is operative to lengthen said loop in the presence of an advance signal when the direction means is in the first condition and operative to shorten said loop in the presence of an advance signal when the direction means is in the second condition.

16. The system of claim 15 wherein the number of serially connected storage units in the storage means exceeds the number of landings served by the car by two, wherein the last storage unit in the series is a read-out unit, said read-out unit being connected to the control means and to the recirculating means including the means for varying the length of said loop, said combination wherein said means for varying the length of said loop includes means to insert the signal stored in the read-out unit into the first storage unit in said series in the presence of an advance signal when the direction means is in the first condition, means to insert the signal stored in the read-out unit into the third storage unit in the series in the presence of an advance signal when the direction means is in the second condition and means to insert the signal stored in the read-out unit into the second storage unit in the series in the absence of an advance signal.

19. An elevator control system, comprising: a structure having a plurality of landings, an elevator car mounted for movement relative to the structure to serve the landings, shift storage means having a plurality of memory elements including input and output memory elements, output terminal means connected to a predetermined one of the elements of said shift means, logic means connected to the input element of said shift means, signal means for providing landing related signals in response to requests for elevator service, scan counter means continuously and repetitively providing scan counter signals assigned to the landings, means connected to said logic means and responsive to said scan counter means and said signal means for serially introducing said landing related signals into said shift means and shift the landing related signals from element to element thereof in response to said scan counter signals such that a landing related signal at the output terminal means at any instant is related to the floor assigned to the scan counter signals being provided by the scan counter means, and means connecting the output element of said shift means to said logic means to store said landing related signals in said shift means by recirculating them.

21. The elevator control system of claim 19 wherein the signal means provides a landing related signal only while a request for elevator service is being registered, and wherein the landing related signals are stored in the shift means by providing a cycle rate for the scan counter means which is short compared with the duration of the landing related signal provided by the signal means.