US3407905A - Control system for elevators including reed switch detectors for position and speed control - Google Patents

Description

Oct. 29, 1968 J. A. GINGRICH CONTROL SYSTEM FOR ELEVATORS INCLUDING REED SWITCH DETECTORS FOR POSITION AND SPEED CONTROL Filed Feb. 5, 1965 4 Sheets-Sheet l .-4* "(H I 0-; R! "L.

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4? JOHN A. GINGRICH Fl 6. 1 Y r ATTORN EYS Oct. 29, 1968 J. A. GINGRICH 3,407,905 CONTROL SYSTEM FOR ELEVATORS INCLUDING REED SWITCH DETECTORS FOR POSITION AND SPEED CONTROL FIG. 3

JOHN A. GINGRICH ATTORNEYS Oct. 29, 1968 J. A. GINGRICH 3,407,905

CONTROL SYSTEM FOR ELEVATORS INCLUDING REED SWITCH DETECTORS FOR POSITION AND SPEED CONTROL JOHN A. GINGRICH ATTORN EYS United States Patent Oflice 3,407,905 Patented Oct. 29, 1968 CONTROL SYSTEM FOR ELEVATORS INCLUDING REED SWITCH DETECTORS FOR POSITION AND SPEED CONTROL John Alvin Gingrich, Toronto, Ontario, Canada, assignor, by mesne assignments, to Dover Corporation, New York, N.Y.

Filed Feb. 5, 1965, Ser. No. 430,529 8 Claims. (Cl. 187-29) ABSTRACT THE DISCLOSURE An elevator control system comprises a plurality of electromagnetic coils arranged in a line at respective floors, a stepping switch for selectively actuating the coils in accordance with the floor-s at which the elevator car is to stop, and a plurality of spaced reed contacts movable with the car past the coils so that the reed contacts can be operated successively by an actuated coil at a particular floor to provide indications of the distance of the car from that particular floor. Means for slowing down and stopping the elevator car are controlled by the successively operated reed contacts.

This invention relates to an improved control system for elevators, and in particular, to the part of an elevator system that provides the necessary indications of car position in the hoistway, and of the distance between the car and the floor at which the car is landing.

In order to satisfy all of the requirements for controlling the movement of an elevator, two types of information are required: (1) information indicating which floor the car is approaching, landing at, stopped at, or relevelling at, and (2) information indicating the distance between the car and the floor being approached, landed at, or at which the car is stopped or relevelling. The first type of information may be called position information, and the second may be called proximity information.

Ideally, the position information should correctly indicate the destination floor at the commencement of slowdown, and should hold this indication during the entire slowdown, so that when the car is stopped at, or relievelling at said floor, the position information indicates the correct floor. This should occur even if the slowdown begins several floors away from the destination, as it may on high speed elevators. Moreover, when the car is in motion, the position information should preferably keep always far enough ahead of the true car position so that a normal stop can still be made, if necessary, at the floor indicated by the position information. This information is required for such purposes as: detecting the presence of car or hall calls, for stopping the car and opening the doors when required; cancelling car or hall calls; detecting car or hall calls above and below the car position, in order to determine the direction of travel; and illuminating the appropriate position indicator or hall lantern when required.

The proximity information should accurately indicate the distance between the car and the floor indicated by the position information, and not other floors, regardless of any intervening floors between the car and its destination. This information is required to control the various steps of slowdown, the final stopping, and, if necessary, the relevelling. For simple speed control systems, only one or two indications of proximity are required. For high speed variable voltage speed control systems, many indications are desirable in order to control many small steps of speed reduction.

A commonly used device for obtaining both of these types of information is an advance selector such as described in the Crane et al. Canadian Patent No. 669,267. However, such selectors have disadvantages: a considerable amount of mechanical and electrical complication is required to cause the advancing operation to function properly; the proximity information is not full scale; the height of the selector increases with the travel of the elevator, and in buildings where express elevators travel long distances without any stops, much space is wasted in representing thisexpress done to scale; and the position information is often not continuous since the moving fingers usually meet a gap between adjacent stationary fingers.

A, commonly used method of obtaining the position information is to use a device called a notching selector. This may consist of a bidirectional stepping switch, or it may be a device operated by an electric motor which can move a carriage to various positions. Each position represents a floor in the building, and various contacts associated with each position are either opened or closed when the carriage is present. In either case, the distance between adjacent positions is the same, regardless of the actual distance between the two corresponding adjacent floors in the building. When a notching selector is used, further equipment is required to provide the proximity information and to provide signals for notching the selector. This is commonly done with inductor relays mounted on the car and each consisting of an electromagnet or permanent magnets, and a contact. Vanes of magnetic conducting material are located in the hoistway in such a manner than when an inductor relay passes close to a vane its contact is opened or closed. 'One line of vanes is normally positioned to actuate an inductor relay each time the car is half way between adjacent floors. This causes the notching selector to advance one step in the desired direction, so that the selector always indicates which floor the car is nearest. Another arrangement uses two lines of vanes, with two vanes between adjacent floors, to cause notching to occur earlier than half way between floors. In either case, further inductor relays and vanes are required to provide the proximity information.

Systems which drive the notching selector in the way described above have the following disadvantages: the selector can get out of step, and thus indicate the wrong floor, the position information is not always advanced ahead of the true car position, but is often representing a floor already passed, the system can normally be used for only slower speeds where the slowdown distance is less than half the minimum floor to fioor distance, or at most for speeds where the slowdown distance is less than the minimum floor to floor distance if earlier notching is used, the proximity information requires much hoistway space if many steps of slowdown are used, and the proximity information is confused since an inductor contact may operate during slowdown to indicate the proximity of a fioor other than the floor at which the car is landing.

The system of the present invention overcomes the foregoing disadvantages of the two above mentioned systems, and provides improved position and proximity information. The position information is obtained from a notching selector (or other means for selectivity actuating sources of energy), but the selector is driven in a different manner. The proximity information is obtained by devices (for example, magnetically operated contacts) carried on the car, but the sources of energy (for example, electromagnets) for operating these devices are not on the car, as with conventional inductor relays, but are in the hoistway, and there is a separate energy source for each floor. Except for terminal floors, only one of these sources is energized at a time, and the one which is energized corresponds always to the floor indicated by the notching selector.

car carrying a column of proximity devices,

The devices on the car which indicate the proximity information are arranged in a vertical line or column so for the different floors are similarly arranged in a vertical line so that any one of "them, when energized, is capable of actuating the devices on the car, when the car passes said energized source. 'In the accompanying drawings:

FIGURES l, 2 and 3 illustrate schematically three portions of a control circuit for a variable'voltage elevator control, FIGURE 1 showing in side elevation an elevator FIGURE 4 is an enlarged side elevation ofthe colum of -proximity devices showing. the relationship of the column to an electromagnetic energy source when the elevator car is level with the floor corresponding to that source;

FIGURE "is a further enlarged horizontal section taken on the line 55 of FIGURE 4;

FIGURE 6 is a reduced and diagrammatic view of the apparatus of FIGURE 4 viewed from the right hand side;

' FIGURE 7 is a view similar to FIGURE 6 of a modified arrangement; and

FIGURE 8is a view similar to FIGURE 7 of another modified arrangement.

1 The variable voltage control circuit of FIGURES 1 to 3 has, for clarity, been simplified by the elimination of such well known and conventional elements as a regulator, suicide circuit, overload relays, etc. A variable voltage system is shown since it best illustrates the advantages of the invention,'but the invention is not restricted to variable .voltage elevators, and can be used with any type ofspeed control system, and is of particular utility for those systems which require a large number of steps of slowdown.

FIGURE 1 shows a generator consisting of an armature GA, series field GSF and shunt field GF. This generator is rotated at essentially constant speed by a prime mover such as an alternating current induction motor which is not shown. The generator field GF is supplied with direct current from supply lines L+ and L- through reversing contacts U-1, U-2, or D-1, D2, through resistance R1, and contact M-1. Adjustable taps ATI through AT8 can be made elfective by contacts VL1 and V31 through V8-1 to short out portions of the resistor to control the generator field current in steps, as is well known in the. art.

The output of the generator armature is applied, through the series field GSF, to the armature HMA of a hoist motor, which is directly coupled to brake drum BD, and is connected either directly or through reducing gears to sheave 1. The shunt field HMF of the hoist motor is connected to supply lines L+ and L- through resistor R2. Contact MF-l, when closed, applies full voltage to the motor field. If contacts M-2 and either U-3 or D-3 are closed, brake magnet BM is energized and pulls brake shoe BS, which is spring applied, away from brake drum BD to allow rotation. An elevator car 4 and a counterweight 3 are connected by a hoist cable 2 passing over sheave 1.

Mounted on the car 4 by brackets 5 is a column 6 which carries proximity contacts (hereinafter described) that can be actuated by stationary position electromagnetsv 1PM, 2PM, 3PM, 4PM, 5PM and TPM mounted in vertically spaced apart relationship in the hoistway. A position electromagnet is provided for each of the'fioors F1 to F6 of the building, and the car 4 is shown level with the bottom floor F1. A stepping switch S has a wiper 7 movable over contacts S1 to S12. For the six floor system shown only the contacts S1 to S6 are utilized, and as will be explained in greater detail below the contacts S1 to S6 are connected for selected energization of the position magnets 1PM to TPM respectively. The pp Switch S can be Provided with levels in addition to the one illustrated, such other levelshaving their wipers and contacts wired as may be desired to suit the requirements of various types of control such as single automatic, selective collective, duplex, triplex or multicar group systems, all of which are known and are not part of this invention. i

i As shown in FIGURES 4 and 5, a typical position'magnet 1PM may consist of a pair of electromagnetic coils 8 and '9 mounted by means of bolts 10 between two ferromagnetic side plates 11 and 12. Two coils providea more even distribution of flux than one. The coils may be connected in series or parallel, butwith similar polarity so that if coil 9 makes plate 11 a north pole, and plate 12 a south pole, coil 8 must also make plate 11 a north pole and plate 12 a south .pole. If current is flowing through the coils, magnetic flux flows in substantially straight lines across the air gap (flux path) between the side plates 11 and 12. I W

The column'6 consists of an elongated nonmagnetic casing 13 within which are several vertically spaced apart proximity devices typified by the proximity contact PCC of FIGURE 5. The contact PCC is of the dry sealed reed type. Such a contact is ideally suited for systems embodying this invention, but other types of magnetically operated contacts could be used instead. The contact PCC consists of a glass envelope 14 into which two reads 15 and 16 are fused. The envelope is filled with an inert'gas, and sealed. The reeds form both the magnetic and the electrical circuits. When sufiicient magnetic fiux flows lengthwise through the reeds, it crosses the small air gap 17 in the centre, and the two reeds are magnetically attracted. The reeds bend until they touch, and thereby complete an electric-circuit between terminals 18 and 19 from which the contact PCC is supported on insulated strip 19a. The outer ends 15a and 16a of the reeds are bent approximately at right angles to reduce the necessary spacing between the plates 11 and 12 and to collect moremagnetic flux.

The magnetic circuit of FIGURE 5 allows the column 6, mounted on the car, to wander horizontally to some extent with respect to the stationary position magnets, either closer to or farther from the coils 8 and 9, or closer to one of the side plates 11 or 12, or in both such directions, without appreciably affecting the amount of flux flowing through the reeds. Thus the vertical position of the car at which a particular contact closes is not particularly influencedby wandering of the car in its guides.

FIGURE 4 shows the column 6 carrying a plurality of proximity contacts (designated PCU, PC8U, etc.), in the position that is assumed relative to a typical position magnet lPM when the car is level at the floor corresponding that that magnet. The number and position of the con tacts can be varied to suit the requirements of various speed control systems, and various slowdown distances, but is shown here to agree with the particular circuits shown in FIGURES 1, 2 and 3. The height of the plates 11 and 12 can be varied to suit the requirements of any installation, but should preferably be the same for all types of installations, and is identical for all floors ina given installation. For the purpose'of the present de* scription it will be assumed that these plates 11 and 12 are ten inches in height to define a flux path ten inches high. Also it will be assumed that a contact closes when it first comes level with the top or bottom edges of the plates 11 and 12 of an energized position magnet. I Contact PCC is centered in the position magnet when the car is level with the corresponding floor. In this position of the car, contacts PCB and PCA are two inches from the top and bottom edges of the plates respectively, contacts PCDS and PCUS are one-half an inch from said edges but within the space between the plates, and contacts PCLU and PCLD are one-half an inch away from said edges but outside said space. The remaining con tacts are locatedas shown in FIGURE 4, but it isnot necessary to specify particular distances for them.

All of these proximity contacts are preferably adjustable vertically in the column 6 to adjust the positions of the car at which they operate. The centre contact PCC, however, would normally not be adjusted up or down from its central position.

When the car is going up at full speed and approaches a position magnet, contact PCU is the first to enter the position magnet. As will be more fully described below, the closing of contact PCU causes the stepping switch S to advance one step (i.e., to notch) if a landing is not to be made at the floor corresponding to that position magnet. The advancing of the stepping switch causes de-energization of the position magnet which caused notching, andthe next position magnet (for the next floor above) is energized. This continues until the necessity for making a landing is detected. Then, the stepping switch makes no further notches, the position magnet for the destination floor remains energized, and the closing of the contacts PCU, PCSU, PC7U, PC6U, PCSU, PCDS, FCC and PCA provide indications of proximity, each such indication causing a reduction in speed. The closing of contact PCUS causes the final stopping.

Similarly, when the car is going down at full speed, contact PCD indicates when the stepping switch should be advanced one notch in the down direction. The advancing of the stepping switch then causes de-energization of the position magnet which caused notching, and the next position magnet below is energized. Again, this continues until it is necessary to make a landing at a given floor. Then, with the position magnet for the last mentioned floor maintained energized, the closing of contacts PCD, PC8D, PC7D, PC6D, PCSD, PCUS, PCC, PCB and PCDS provide the proximity indications for slowing down and stopping.

In either case, full speed up or full speed down, only contacts PCU or PCD close for each floor at which a landing is not to be made; the remaining contacts do not close until a landing is being made since the stepping switch keeps notching ahead, and thus the position magnet which is currently energized keeps changing in the direction ahead of car movement.

For the stepping switch to accomplish the notching sequence just described, the stepping switch must be advanced one step when the car first starts to leave a floor at which it has been stopped. Such a notching results in de-energization of the position magnet for the floor the car is leaving, and then the next magnet ahead (either above or below depending on the direction the car is going) is energized. In many cases, this newly energized position magnet will not cause contact PCU (or PCD) to close because the latter has already moved past the magnet. Instead, one of contacts PCSU, PC7U, PC6U or PCSU (or PC8D, PC7D, PC6D or PCSD) will be closed, or will close after a small amount of car movement. The circuit is arranged to cause notching under these circumstances, after the car has attained partial speed, if there is no need to stop at the next floor. If there is a need to stop at the next floor, the position magnet for that floor remains energized, and the slowdown and stopping is controlled by the proximity contacts as before, for full speed, except that the sequence now begins not with contact PCU or PCD but at some other point such as PC7U (or PC7D). The partial speed at which notching can occur is dependent on which contact is closed. For example, contact PCSU (or PCSD) can cause notching at a lower speed than contact PC6U (or PC6D). In some instances, for example with high speed elevators or closely spaced floors, the next notching operations may still result in contacts PCU or PCD being unable to cause further notching. The circuit is arranged to handle this situation in the same way as just described, where the first notching resulted in this situation. Thus, contacts PCU and PCD can cause notching, or can initiate slowdown when the car is at or near full speed, but the remaining contacts from PCSU and PCSD out to PC8U and PC8D can cause notching or initiate slowdown whenever an appropriately high speed has been attained.

FIGURE 6 shows diagrammatically the location of a proximity contact column 6 in relation to a typical position magnet 1PM when the car is level at a floor. If the column 6 were ten feet long, and there were a floor four feet above the one shown, its position magnet would be about four feet above magnet 1PM, i.e., one foot down from the top of column 6 in FIGURE 6. The arrangement 0n FIGURE 6 is normally used where possible, but the vertical length of the column 6 must be essentially twice the slowdown distance required for the elevator car. For high speeds, this length may be too great for practical mounting on the car.

FIGURE 7 shows an alternative arrangement which may be used if a single position contact column is 'too long. There are two proximity contact columns in FIG- URE 7, namely a down column 6D and an up column 6U. Two position magnets DPM and UPM are now required at each floor, and are normally wired in series or in parallel so that both are energized together. The down column 6D could contain all the contacts required for the down direction, and up column 6U could contain all the contacts for the up direction; a preferred arrangement, however, is to put in the down column all of the contacts for the last ten inches of travel in both directions, so that fine vertical adjustments to the position magnet DPM can be made without the necessity of maintaining an accurate spacing between magnets DPM and UPM. As in FIGURE 6, FIGURE 7 shows the relative positions of the columns 6D and 6U with respect to the magnets DPM and UPM when the car is level at a floor. This arrangement allows the length of the columns to be essentially equal to the slowdown distance, instead of twice the slowdown distance as in FIGURE 6.

Further proximity contact columns can be added, as required, to handle longer slowdown distances, but an additional line of position magnets must of course be provided for each additional assembly. FIGURE 8 shows an arrangement for three columns. The column 6DA controls the first two-thirds of slowdown in the down direction as it passes through position magnet PMD. The column 6UA controls the first two-thirds of slowdown in the up direction as it passes through position magnet PMU. The remaining one-third of slowdown, in either direction, is controlled by column 6C as it enters magnet PMC. The columns are shown in FIGURE 8 at the elevation that they occupy when the car is level at the floor for which the three position magnets PMD, PMC and PMU are provided, these magnets being energized together.

The following description will assume that the arrangement of FIGURE 6 is used; however, the arrangement of FIGURES 7 or 8 could be used with no essential change except to substitute the plural for the singular wherever a position magnet is mentioned. Each proximity contact column can contain as many proximity contacts as required to suit the speed control system.

Before the sequence of events for a typical trip of the car is described, reference should be made to some of the contacts in FIGURE 2. The contacts X-l, X-2 and X-3 are closed when the coil (not shown) of relay X is energized. The circuit for the coil of relay X is not shown since it may be different for various types of operation such as single automatic, selective collective, duplex, triplex or multicar group operation, and this coil circuit is not associated with the control of the speed of the elevator, with which this invention is concerned. The circuitry for the coil of relay X is relatively simple, and a relay such as relay X frequently is used in conventional control circuits.

Relay X must be energized in preparation for a run, and with variable voltage speed control, should be energized only while the doors are closing, or are fully closed before a run. It will be shown later that this allows the motorfield to' be fully energized while the doors are closing so that the motor field'current is at its maximum value by the timethe car starts to move. Once the run has commenced, relay X must remain energized, in spite of any interruptions to the safety circuit such as the pressing of a stop button in the car, until a need to stop is detected at the floor represented by the position information. Such need to stop could be caused by a car call or a hall'call at that floor, or by the absence of any calls beyond that floor. Once relay X has been de-energized in this manner, it must remain de-energized until after the car has made anorrnal landing. Frequently, such need tostop is detected immediately after the stepping switch S has moved to a new position representing a floor at which there is a car or ball call which must be answered. Occasionally, such as when a car or hall call is registered late, the relay X will drop out some time after the stepping switch has. moved to a new position, but, if such a call is too late to be answered, the stepping switch will have moved on an additional step, and the relay F is controlled by conditions at the new floor.

Contact CA-l of FIGURE 2 closes when there are unanswered calls above the floor represented by the position of stepping switch S, and contact CB1 of FIGURE 2 closes when there are unanswered calls below the floor represented by the position of stepping switch S. The relay arrangements for operating such contacts are well known in the art and need not be described.

Limit switches LU11 and DL11 (bottom of FIGURE 3) are set to open when the car is within nine inches of the top or bottom floor respectively. Thus, with the car level at the bottom floor F 1:

(1); Limit switch DL11 is open but UL11 is closed. Thus the coil of relay UL is energized.

(2) Proximity contacts PCDS, PCB, PCC, PCA and PCUS (FIGURE 6) are closed. These contacts are shown near the top of FIGURE 3, and being closed they energize the coils of relays DS, Z, VL and US. Thus, in the circuit of magnet 1PM of FIGURE 1, contacts DS-3 and US-3 are open.

(3) Proximity contacts PCLU and PCLD (FIGURE 6) are open. These contacts are shown near the top of FIGURE 3; since they are open, the coils of relays LD, LU and LV are not energized. Thus, in FIGURE 1, contact LV-1 is closed. With the stepping switch wiper 7 at contact S1, the coil of relay BP is energized, and thus contact BP-l in FIGURE 1 is closed.

(4) Magnet 1PM is energized through contacts BP-l, LV-l and P-2, the latter being closed because the circuits to relay P near the bottom of FIGURE 2 are open: as already mentioned (paragraph (1) above) relay UL is energized and consequently contact UL3 is open, and paragraph (3) above) relay BP is energized and consequently contact BP-2 is open.

To summarize, with the car level at the bottom fioor, the relays that are energized are relays UL, DS, Z, VL, US and BP, and magnet 1PM is energized.

The sequence of events for an up trip will now be described. Assurne that a call is registered at the fifth floor. Contact CA-l is then closed. The relay X will be energized provided that the doors are closing, or are fully closed, and contact X-1 (top of FIGURE 2) will energize relay A and also relay AA through contact MRA-4. Relay MP is then energized through contacts A-2 and V8-3. 'The motor field HMF is increased to full strength by the closing of contact MF-1 in FIGURE 1, in preparation for the run.

When the doors are fully closed, auxiliary gate contact GC (FIGURE 2) closes and energizes relays UR and MR through GC, X-2, CA-l, DR- and up limit switch UL10, which is open only if the car is above the top floor.

The closing of contact UR-l (FIGURE 1) causes the top position magnet TPM to be energized; this is not required for a run to the fifth floor, but magnet TPM is always energized during up travel to assure a proper land- 8 ing at the top floor it" there is any failure in the other position magnets or in the circuits associated with them.

The closing of contacts UR3 and MR2 (FIGURE 2) results in the energization of relays U and M through a safety circuit (which contains such devices as overtravel switches, a governor contact, a safety contact, and a stop'button), through contacts D-7, A-3,'UR-3, the usual door and gate contacts, and contacts MR2, AA-2 and MT-Z.

Contacts M-2 and U-3 (FIGURE 1) energize the brake magnet EM, and at the same time contacts U-l', U-2 and M-1 (FIGURE 1) cause current, as determined by tap ATl on resistance R1, to flow through the generator shunt field GF. At the same time, contact M-6 (FIGURE 2) energizes relay MT. While the brake shoe BS is lifting, contact MT-1 (FIGURE 2) energizes relay MRA through contacts MR-3 and MT-l. Contact MRA 1( bottom of FIGURE 2) energizes relay P through contacts DS-2 or US-2, MRA-1 and X-3. Th opening of contact P-2 (FIGURE 1) de-energizes position magnet 1PM, and thus proximity contacts PCDS, PCB, PCC, PCA and PCUS in FIGURE 3 open. Relays DS, Z, VL and US are all de-energized, but because of capacitors C3, C4, C5 and C6 (which must discharge through these relays and the resistors R5, R6, R7 and R8) these relays are slightly delayed in dropping out.

The closing of contact P-1 in FIGURE 3 causes the up coil SU of stepping switch S to be energized through contacts P-l, T P-3, UR-4 and UL-2. This causes wiper 7 in FIGURE 1 to move so that it now connects to contact S2, but since contact P2 is'still open the position magnet 2PM is not yet energized. Relay BP is now deenergized.

By now the brake shoe BS is clear of brake drum BD, and the hoist motor has begun to rotate. Relay VL, which (because of capacitor C5 and resistor R7) delayed dropping out when magnet 1PM was de-energized, now closes contact VL1 in FIGURE 1), and this increases the generator field current. Also, relay Z (which was likewise delayed in dropping out) now closes contact Z-l (FIG- URE 3) and thus relay V3 is energized through contacts MRA-2, Z-l, and VL2.

At the same time, relays DS and US open contacts DS2 and US-2 (bottom of FIGURE 2) and relay P is de-energized. The opening of contact P1 de-energizes the up coil SU of stepping switch S and the ratchet of the switch (not shown) returns to its original position without any further movement of the wiper 7. The closing of contact P-2 energizes position magnet 2PM through th wiper 7 and contact S2 of stepping switch S, and through contacts LV-1 or US3 or DS3 and P-2. Let us assume that position magnet 2PM is far enough away from magnet 1PM that proximity contact PCU will not close until the car has reached full speed. This is normal with slower speed elevators (e.g., 200 feet per minute) with normally spaced floors.

In the meantime, relay V3 closes contact V31 (FIG- URE l) to give another increase in generator field current, and contact V32 (FIGURE 3) energizes relay V4 through contacts MRA-2, V3-2, DS-6, US-6, U-4 and UL-l. The closing of contact V4-1 causes another increase in generator field current.

The remaining speed relays V5, V6, V7 and V8 are energized in sequence, but are preferably delayed slightly by dashpots (not shown) so that the generator field current is not increased too rapidly. Relay V5 is energized through contacts MRA-2, V3-2, V4-2, and AA-3, and resistor R9. Relay V6 is energized through additional contacts V5-2, U-5, up limit switch UL12, contact AA-4, and resistor R10. Relay V7 is energized through additional contacts V6-2 and AA-S and through resistor R11. Relay V8 is energized through additional contacts V7-2, U-6, up limit switch UL13, contact AA-6, and resistor R12.

Thus, in FIGURE 1, the closing of contacts VL-l,

V3-1 and V4-1 in sequence is followed by similar sequential closing of contacts V-1, V6-1, V7-1 and V8-1. Each such closing causes an increase in generator field current, and thus the car speed is gradually increased. The opening of contacts V8-3 (FIGURE 2) de-energizes relay MF, and condenser C1 discharges through resistor R3 and the coil of relay MF. When contact MF-1 opens in FIGURE 1, the motor field current is reduced by the insertion of resistor R2. This causes a final increase in speed, and the car is now running at full speed.

The opening of contact MF-Z (FIGURE 2) de-energizes relay AA. Contacts AA-3, AA-4, AA-S and AA-6 open (FIGURE 3) without de-energizing relays V5, V6, V7 or V8 since their contacts V5-3, V6-3, V7-3 and V8-2 are now closed.

After the car has moved nine inches away from the bottom floor, limit switch DL11 (bottom of FIGURE 3) closes and energizes relay DL. Further upward movement of the car causes down limit switches DL12 and DL13 to close, but they have no effect on up travel.

It is assumed that there are no calls except at the fifth floor. Thus the relay X remains energized. When proximity contact PCU closes, relay CP (FIGURE 3) is energized through contacts MRA-Z, V3-2, V42, V5-2, V6-2, V7-2, U-6, UL13, AA-6, resistor R12 and proximity contact PCU. This lowers the voltage on the coil of relay V8, due to the higher current through resistor R12, but relay V8 does not drop out, and relay CP is designed to operate on this lower voltage.

The opening of contact CP2 does not de-energize relay A in FIGURE 2 since contact X1 is still closed. The closing of contact CP-l (bottom of FIGURE 2) energizes relay P through contacts CP-l, MRA-l and X-3. The opening of contact P-2 de-energizes the coils of position magnet 2PM, and thus contact PCU opens. This drops out relay CP (FIGURE 3) and the opening of contact CP-l de-energizes relay P, which has just picked up. Rectifier D1 provides a discharge path for the inductive current of relay P, and thus delays slightly its dropout. Thus relay P remains in the energized position long enough for contact P-l to apply a pulse to the up coil SU of stepping switch S, through the same contacts as before. Wiper 7 thus moves to the next position and when contact P-2 closes position magnet 3PM is energized. No other proximity contacts close since the top of the proximity contact column 6 is just entering position magnet 2PM, which is no longer energized.

The car has now passed the point at which a landing could have been made at the second floor, and the wipers of the stepping switch are now indicating the third floor, so that any calls there, which require a stop, can be detected. The car, however, is still below the second fioor, but too close to stop there. During the time that the car is approaching and passing the second floor, and up until the time that proximity contact PCU is closed by position magnet 3PM, a call requiring a stop at the third floor would de-energize relay X and (as explained below with reference to the fifth floor) cause a stop to be made there.

. For this trip, however, it is assumed that there is no call except at the fifth floor. Thus the closing of contact PCU from energized position magnet 3PM results in another advance of stepping switch S similar to the previous advance, causing position magnet 3PM to be deenergized and magnet 4PM to be energized.

Similarly when proximity contact PCU is closed by position magnet 4PM, stepping switch S is advanced to its fifth position, and now position magnet 5PM is energized. The top position magnet TPM is still energized through UR-l. Since there is a call at the fifth floor, relay X drops out shortly after the stepping switch S advances to its fifth position. Also, contact CA-l opens if there are no calls at the top floor. The opening of contact X-l does not de-energize relay A because contacts MR-l, CP-2 and A-1 are still closed. The opening of 10 contacts X-2 or CA-1 does not de-energize relays UR and MR since contacts M4 and UR-Z are still closed.

Thus the car continues to run at full speed until proximity contact PCU is closed by position magnet 5PM. Then relay CP is energized as before, but now the closing of contact CP-l does not energize relay P since contact X-3 is open. Instead, the opening of contact CP-Z de-energizes relay A since X-1 and MRA-3 are both open.

The closing of contact A5 in FIGURE 2 energizes relay MF through contacts M-3 and A-5. Contact MF-l in FIGURE 1 then increases the motor field to full strength and causes a reduction in car speed. The opening of contact A-1 assures that relay A will remain de energized after contact CP-Z closes again when relay CP is de-energized by the opening of proximity contact PCU after it has passed through position magnet 5PM. The opening of contact A-3 does not de-energize relays U and M since contact US5 is closed.

Contact AA-8 (FIGURE 3) has been closed since the car first reached full speed, and thus when proximity contact PC8U closes, the coil of relay V8 is shorted out through PC8U and AA-S. Relay V8 then opens contact VS-l in FIGURE 1 to cause areduction in generator field current. The opening of contact V8-2 assures that relay V8 remains de-energized even after proximity contact PCSU opens.

Similarly, the closing of proximity contacts PC7U, PC6U and PCSU cause the dropping out of the associated relays V7, V6 and V5 in sequence at the appropriate distances from the fifth floor, and the opening of contacts V7-1, V6-1, and V5-1 in FIGURE 1 cause the generator field current and hence the elevator speed to be reduced in steps. If any proximity contact should fail to drop out the associated relay, the dropping out ofthe next relay will take care of this through contacts V4-2, V5-2, V6-2 or V7-2. The resistors R9, R10, R11 and R12 allow the relay coils to be shorted out without draw: ing excessive current from supply lines L+ and L.

When the car reaches a position ten and one-half inches below the fifth floor, proximity contact PCLU closes and energizes relay LU and LV (FIGURE 3). The closing of contact LU-l (FIGURE 2) partially completes a bypass around the door and gate contacts; the opening of contact LV1 (FIGURE 1) does no de-energize the position magnet 5PM since contacts US-3 and DS3 are still closed. No reduction in generator field occurs.

When the car has moved one inch or more, so that it is nine and one-half inches below the fifth floor, proximity contact PCDS closes and energizes relay DS (FIGURE 3). The opening of contact DS-6 (FIGURE 3) de-energizes relay V4, and the opening of contact V4-1causes a further reduction in generator field current. The closing of contacts DS-l and V4-3 (FIGURE 2) completes a circuit which bypasses the door and gate contacts so that the doors may be opened at this point, if desired.

When the car has reached a position five inches below the fifth floor, proximity contact PCC closes and energizes relay Z, Although proximity contact PCB closed earlier, PCA is not yet closed, anr relay VL is not energized. The opening of contact Z-1 (FIGURE 3) de-energizes relay V3, and the opening of contact V3-1 causes another reduction in generator field current.

When the car reaches a position two inches below the fifth floor, proximity contact PCA closes, and relay VL is energized through proximity contacts PCB, which closed earlier, and PCA. The opening of contact VL-l causes the generator field to be reduced to the value required for landing speed.

When the car reaches a point one-half an inch below the fifth floor, position contact PCUS closes and energizes relay US. The opening of contact US-S (FIGURE 2) deenergizes relays U and M since contacts UR-6 and A-3 are both open. The opening of contacts M-l, U-1 and U-2 de-energizes the generator field GF, and the opening of contacts M-2 and U3 de-energizes brake magnet BM, allowing brake shoe BS to be force against brake drum BD by the brake spring. Thus the car slides to a stop. Assuming that it slides one-half an inch, it will then be level with the fifth floor.

,At this position, proximity contact PCLU should not be closed, since it is just outside the flux path of the position magnet for the fifth floor. However, were it not for an arrangement to be described below, contact PCLU would probably remain closed at this position since most magnetically operated contacts open at a much lower magnetic flux density than that required to close them, and, if PCLU is correctly set to close if the car should be more than one-half an inch below flood level, it will not open until the car is well above the floor level, perhaps two inches, where the fringing flux from the position magnet is weaker. The opening of contact PCLU is taken care of by contacts LV1,-US-3 and DS-3 at the bottom of FIGURE 1. When contact US-3 opens, and the car thus begins its slide to a stop, the position magnet 5PM at the fifth floor is tie-energized since contacts LV-l and DS-3 are already open. This causes all the proximity contacts which are closed to open, and thus contacts PCLU, PCDS, PCB, PCC, PCA and PCUS open. Relays DS, Z, VL and US do not drop out since condensers C3, C4, C5 and C6 discharge through resistors R5, R6, R7 and R8 and through the coils of these relays. Also, relay LU is delayed slightly by rectifier D2, Relay LV, 'however, drops out and contact LV-l energizes the position magnet 5PM again so that proximity contacts PCDS, PCB, PCC, PCA and PCUS all close again before relays DS, Z, VL and US drop out. Proximity contact PCLU should not close again since the car should now be within onehalf an inch of level with the fifth floor. Thus relays LU and LV drop out and stay out as long as the car does not drift down to one-half an inch below the floor.

The opening of contact M-4 (FIGURE 2) de-energizes relaysUR and MR since contacts X-2, DS4 and US-4 are open. The opening of contact M-6 (FIGURE 2) deenergizes relay MT but this relay does not drop out until condenser C2 has discharged through resistor R4 and through the coil of relay MT. Similarly the opening of contact M-3 (FIGURE 2) de-energizes relay MF which drops out later when condenser C1 'has discharged through resistor R3 and through the coil of relay MP.

The opening of contact UR-l (FIGURE 1) de-energizes the top position magnet TPM which played no part in the run just described, but was energized to assure a normal stop at the top floor in case of failures at other floors. In addition, limit switches UL13, UL12, UL11 and UL open at various distances from the top floor to reduce the speed in coarse steps if other methods fail. The opening of contact MR-3 (FIGURE 2) de-energizes relay MRA. If relevelling does not occur immediately, contact MF-l (FIGURE 1) opens a few seconds after relay MF was de-energized, and thus the motor field current is reduced to the standing value.

The closing of contact UR-6 (FIGURE 2) would allow the car to relevel up if contact LU-1 were still closed, as would occur if the car dropped down more than one-half an inch below the floor. What is more likely to happen is that the car overshoots the fifth floor so that it goes more than one-half an inch above the floor. Assume that such an overshoot occurs, or that for some other reason, such as passengers exiting from the car, the car rises up more than one-half an inch above the floor. If the car goes high enough above, perhaps two inches, proximity contact PCDS will-open, and relay D5 will be de-energized. When this occurs, the position magnet is held energized during the relevelling operation through DS3 and P-2 until the car has been brought back down to one-half on inch above the floor where contact PCDS closes.

Usually, however, the car does not go far enough above the-floor to open proximity contact PCDS, and thus relays DS and US are energized while the car relevels. Therefore relay LV will be rapidly energized and de-energized: with US-3 and DS-3 (FIGURE 1) both open, each time LV-1 opens it de-energizes the position magnet which then opens proximity contact PCLD and de-energizes relay LV, closing LV-l so that the position'magnet is re-energized, proximity contact PCLD recloses, and relay LV is ire-energized again to start the whole cycle over again. Relay LD is also energized intermittently, but rectifier D3 provides enough timing to hold in relay LD during the brief period of cle-energization. Also, proximity contacts PCDS, PCB, PC'C, PCA and PCUS are opened intermittently, but capacitors C3, C4, C5 and C6 prevent relays DS, Z, VL and US from dropping out.

The purpose of this rapid opening and closing of the proximity contacts during a down relevelling operation is to detect the descent of the car to within one-half an inch from the fioor by the opening of proximity contact PCLD which, if set to close when the car is one-half an inch high,'would open only when the car is much lower, perhaps two inches below the floor. While relay LD is energized, contact LD-l causes relays D and M to be energized through the safety circuit and contacts U7, DR-6, US-l, LD1, and V4-3.

The closing of contacts D-1, D-2, and M-1 causes generator field current to fiow in the direction required for down travel. The closing of contacts M2 and D-3 energizes brake magnet BM. Since relay MR is now not energized, relay MRA is also not energized, and relays V3, V4, V5, V6, V7 and V8 cannot be energized. Thus the amount of generator field current is determined by adjustable tap AT1 unless the car is far enough away from the floor to open proximity contact PCB, in which case relay VL will be de-energized, and adjustable tap AT2 will give a higher speed until the car gets within two inches of level.

Also during a relevelling operation, relay MP is energized through contacts M-3and A-5 or V8-3. Contact MF-l shorts out resistor R2 to give full motor field current during the relevelling operation, and for a short time afterward.

When the car has relevelled back down to within onehalf an inch of the floor, the opening of proximity contact PCLD by the rapid vibration of relay LV causes relay LD to be de-energized (if PCLD does not reclose) and thus after a short relay due to rectifier D3 the contact LD1 opens and tie-energizes relays D and M. This causes the car to stop as a result of the de-energization of the brake magnet BM and the generator field GF.

The sequence of events for an up relevelling operation is similar to the down relevelling sequence just described, and need not be described. If there is any failure in the relevelling operation, resulting in movement of the car away from the floor, proximity contacts PCLU and PCDS open as the car moves up above the floor, and proximity contacts PCLD and PCUS open as the car moves down below the floor. This causes either relays LU and DS, or LD and US, to open contacts DS-l and LU-l, or US-l and LD1, to de-energize relays U and M or D and M, to stop such unsafe movement. The failure of any one proximity contact to open does not result in an unsafe condition.

The up trip from the bottom floor to the fifth floor has been described on the assumption that the car reached full speed before it had moved far enough to close proximity contact PCU. Now it will be assumed that after the stepping switch wiper 7 is advanced to contact S2, and position magnet 2PM is energized, proximity contact PC7U closes because it is situated between the plates 11 and 12 of position magnet 2PM. As the car accelerates, proximity contact PC7U moves up and out of the magnet, and proximity contact PC6U moves up into the magnet. It is possible that'these contacts may be spaced closer than twelve inches apart, and thus both may be closed for a short time. Rectifier D5 in FIGURE 3 is provided to prevent the closing of both PC6U and PC7U from falsely energizing relay V7 when relay V6 is energized during the acceleration. A similar rectifier D4 prevents relay V6 from being falsely energized with relay V if contacts PCSU and PC6U are simultaneously closed. It is assumed that proximity contacts PC7U and PC8U are far enough apart that they will never close together, but a further rectifier similar to D4 and D5 could be added if necessary if these contacts are too close together.

It is assumed that when the acceleration has progressed far enough for relay V6 to be energized, proximity contact PC6U is closed. Then relay CP will be energized through contacts MRA-Z, V3-2, V4-2, V5-2, U-5, UL12, AA-4, resistor R10, rectifier D4 and contacts PC6U and AA-7. If there is no need to stop at the second fioor, relay X is still energized, and since X-1 is closed, the opening of contact CP-Z (top of FIGURE 2) does nothing. The closing of contact CP-l (bottom of FIGURE 2) causes stepping switch S to advance to its third position, resulting in the de-energization of position magnet 2PM and the energization of position magnet 3PM, in the same manner as described earlier when notching occurred after the car had reached full speed. This notching operation does not alter or interfere in any way with the accelerating sequence, which continues in the same way as described earlier.

Thus it can be seen that a notching operation can be caused by relay CP picking up from various proximity contacts, but only if the speed relays V5, V6, or V7 etc., for the corresponding proximity contacts, are energized. In other words, the indications of car speed, provides by closing of speed relay contacts V5-2, V6-2, etc., and indications of car distance, provided by closing of contacts PCSU, PC6U, etc., are used to notch the stepping switch ahead if the car speed is excessive to achieve a satisfactory stop at the floor corresponding to the position magnet which is currently energized. This assures that the stepping switch S will always be far enough head that a stop can still be made at the floor it is indicating, but each advance of the stepping switch is delayed as long as possible so that any car or hall call which is registered late may still be accepted if the car is capable of making a normal stop at that floor.

Now assume that the car starts up from the bottom floor with a call at the second floor, rather than at the fifth floor, or perhaps in addition to the call at the fifth floor. The accelerating sequence commences as before, but now, when stepping switch S advances to its second position, relay X is de-energized by circuits not shown. Assume also that, as in the preceding example, when relay V6 is energized, proximity contact PC6U is closed. Then, as before, relay CP is energized. Now the closing of contact CP-l cannot energize relay P since contact X-3 is open. Thus stepping switch S does not advance, but remains at its second position and position magnet 2PM remains energized.

The opening of contact CP-2 causes relays A and AA to be de-energized since contacts X-l and MRA-3 are open. The opening of contact AA-7 de-energizes relay CP, but since contact A-l is now open the closing of contact CP-2 does not energize relays A or AA again. The closing of contact AA-S shorts out the coil of relay V6, which was only briefly energized, the shorting occurring through rectifier D4 and contacts PC6U and AA-8. The contacts of relay V6 have probaly not changed from the de-energized condition since relay V6 is nor mally delayed slightly in its pickup by a dashpot or other means. Thus contact V61 in the generator field probably does not close, or, if it does, it closes for only a very short time.

As the car continues to move, relays V5 and V4 are dropped out in the same manner as described earlier, and the remainder of the slowdown continues as before, and need not be described again. On such a run as this, the acceleration is interrupted part way through, and slowdown is immediately commenced; relay MF remains in for the entire run, whereas previously it dropped out at full speed, and picked up again as the first step of slowdown.

In the last example, speed relay V6 was only briefly energized since proximity contact PC6U was already closed when relay V6 was energized. If proximity contact PC6U closes after relay V6 is energized, but before relay V7 is energized, then relay V6 will be energized for a longer period. In any case, on a single floor run, all these speed relays are dropped out at the same distance from the floor as they would have been on a normal slowdown from full speed, except for the first one which may be delayed slightly.

Thus the system causes notching to occur, or causes slowdown to commence, at the correct car position in the hoistway for all types of runs, from one floor to the adjacent fioor, for two floor runs, or for longer runs, regardless of the spacing between floors. Although the up direction of travel has been referred to in the examples, the operation in the down direction is similar and need not be described.

An important advantage of the system is that the car can slow down and stop at only the floor indicated by stepping switch S, or at a terminal floor, since the position magnets for all other floors are de-energized. Thus the car does not falsely cancel calls at floors where it does not stop, or illuminate the wrong hall lantern, as occurs in other systems which use a notching selector when the selector gets out of step with the position of the car.

Assume that the car is going up, and that due to a fault, such as failure of wiper 7 to make a connection with contact S4, position magnet 4PM does not become energized. The proximity contacts cannot close at magnet 4PM, and thus no further notching occurs. The car continues to the top floor, where position magnet TPM is energized through UR-l, LV-l and P-2, and the car is brought to a landing at the top floor.

When the car gets within nine inches of the top floor, up limit switch UL11 opens and de-energizes relay UL. Then, when contact MR-4 closes just after the car has stopped, relay P is energized through contacts MR-4, SU-l, SD-l, TP-Z and UL-3. (This does not occur on a normal stop at the top fioor, because for a normal stop the contact TP-2 is open, the wiper 7 connecting to contact S6 to energize relay TP.) The closing of contact P-1 energizes the down coil SD (FIGURE 3) of stepping switch S through contacts P-l, TP-3, UL-4, and DL-2. This causes switch S to advance one step in the down direction (from contact S4 where it was stopped) and to open contact SD-l. Relay P is thus de-energized and the coil SD is de-energized by the opening of P-l. The ratchet of the stepping switch returns to its original position, and because SD is de-energized contact SD-l closes again, relay P is energized and the sequence repeats itself until the wiper 7 has passed contacts S3, S2 and S1, and then continues while the other end of wiper 7 has passed contacts S12, S11, S10, S9, S8 and S7. Finally, when the wiper arrives at contact S6, relay T P is energized through the wiper and contact S6, and the opening of contacts TP-2 and TP-3 stops this resetting sequence by deenergiz-ing relay P and the coil SD. The stepping switch S has now been reset to the correct position to suit the car, which is at the top floor, and the opposite end of wiper 7 has been brought into action in case the fault was caused by failure of the previously used part of the wiper.

A similar sequence of events will reset the stepping switch S to the bottom floor position if the car arrives there and opens down limit switch DL11 without relay BP being energized. In this case, the coil SU of the stepping switch causes the switch to step in the opposite direction. The remainder of the control circuits can easily be arranged (by using contacts of relays TP, BP, DL and l 'UL) to prevent cancellation of any car or liallj calls while the stepping switchis being reset."

' If stepping switch S should advance two" stops instead of one, due to a mechanical or electrical failure, the car will not stop at the floor which has "been so passed over, but the car will get back in step with the stepping switch again when the position contact column 6 enters the position magnet which is energized,

Assume that the car is beginning to make, a landing at the fifth floor, in the up direction, when the stop button in the car is pressed. The stop button is in the safety circuit (FIGURE 2) and thus relays U'and M are deenergized. This causes the generator'field current to be interrupted, and the brake to be applied so that the car comes to a more abrupt stop than normal. The opening of contact M-S assures that relays U and M cannot pick up again until the car has come completely to a stop, and perhaps longer, as indicated by the timing of relay MT which is de-energized by the opening of contact M-6. The opening of contacts U-4, U-S and U-6 causes relays V4, V6, and V8 to be de-energized, and they then deenergize relays V5 and V7.

If the car slides until it is Within nine and one-half inches of the fifth floor, proximity contact PCDS closes and energizes relay DS. This causes relays UR and MR to be de-energized since contacts M4 and X-2 are open. The car is then not necessarily level with the floor, but it is close enough for the doors to open, and the car is able to make a normal start from this position.

However, if the car stops more than nine and one-half inches from the floor, relay DS is not energized, and relays UR and MR are held energized through DS-4, US-4, UR-2, DR-S and UL10. Then when relay MT drops out, relay MRA is de-energized by the Opening of contact MT-l. Relay V3- is de-energized by the opening of contact MRA-2. Relays A and AA are energized through contacts MR-1, MRA-3 and MRA-4. When the stop button is released, relays U and M are energized as before, and the car accelerates. Proximity contacts PCSU, PC6U or PC7U initiate slowdown as described before, and the car lands level at the floor it was originally approaching. This sequence of events occurs regardless of whether or not there are any calls above, and in spite of the fact that the calls at the floor being approached have already been cancelled. Such operation is desirable for two reasons: first, if the car were allowed to start down after such an emergencystop below a floor, the stepping switch would be behind, and thus out of step; secondly, the operation assures that intending passengers waiting in the hall are not bypassed, and left waiting for the next trip, by the pressing of the stop button in the car. With conventional systems of the kind previously discussed, once the car has made an emergency stop near a floor, it cannot stop at that floor until the next trip. A further advantage of the present system is that calls can be cancelled and hall lanterns can be illuminated earlier than in the conventional systems that have been mentioned. When the stepping switch S first moves to a new position, the distance between the position of the car and the floor indicated by the stepping switch is equal to the slowdown distance plus one floor to floor distance, and the stepping switch maintains its position while the car approaches and lands at the floor corresponding to its position. If this system is used in a building where express elevators serve upper floors, with a long travel where there are no entrances, two extra position magnets can be used, one near the upper end of the express zone and arranged to be energized only in the up direction, and one near the bottom of such express zone and arranged to be energized only in the down direction. An extra position is used on the stepping switch to illuminate an express position indicator in the car, and also to energize these two extra position magnets. Q

Although a twelve positions stepping switch is shown in FIGURE 1, a stepping switch with any number of position can be used, provided that there are at least as many positions as there are floors served theelevator. The system can be used, with little or no modification, for very closely spaced adjacent floors, suchas sometimes are served by elevators with entrance at both the front and rear. With position magnet plates 11 and 12 having a height or ten inches, floors twelve inches or more apart can be handled with'no change. For floors ino're closely spaced than this, and ten inch magnet plates, a separate proximity contact column would have to be used in a separate 'line of position magnets. H

While the use of positiongmagnets and magnetically operated contacts has been described, the invention fis equally suited to the use of lamps instead of magnets' and photocells instead of contacts. I In fact, any form of energy producer, for example radio frequency antennae, or audio speakers, could be used to create response in suitable receivers or microphones carried on the car. Also, the position magnets could produce alternating flux to induce voltages in coils on the car.

Also, although a bidirectional stepping switch has been described as the notching selector,'one could employ a ring counter or a binary counter, having vacuum tubes, transistors, or magnetic logic elements, or one could employ a mechanical device driven by an electric motor, or any other device which can be driven one step at a time in either direction.

What I claim as my invention is:

1. An elevator control system for stopping an elevator in car serving a plurality of floors, comprising a plurality of electromagnetic coils spaced apart from one another in a line and each representing a different floor, means for selectively actuating the electromagnetic coils, a plurality of magnetically operated reed contacts each of which When moved adjacent to an actuated electromagnetic coil is operable thereby, the reed contacts being arranged in a line and movable with the car past the electromagnetic coils whereby the reed contacts can be operated successively by an electromagnetic coil to provide indications of the distance of the car from the floor represented by the electromagnetic coil, and car slowdown and stopping means controlled by the successively operated reed contacts.

2. A system as claimed in claim 1, wherein each coil has a pair of magnetizable plates between which the magnetic flux extends to define the flux path.

3. A system as claimed in claim 1, including a normally open magnetically operated contact located so as to be just outside the path of magnetic flux of the coil representing a floor with which the car is level, car relevelling means operable when said contact closes as a result of travel of said contact into said path, and means for deactuating said coil While said contact is closed whereby said contact can open and close intermittently during relevelling of the car to ensure that said contact is open when the car is level with said floor.

'4. A system as claimed in claim 1, wherein the means for selectively actuating the electromagnetic coils comprise notching means for successively actuating the electromagnetic coils ahead of the car in the direction of car travel until there is reached a coil representing a floor at which the car is to stop.

5. A system as claimed in claim 4, wherein the notching means comprise a stepping switch.

6. A system as claimed in claim 4, wherein one of the reed contacts when operated by an actuated electromagnetic coil operates the notching means to deactuate said coil and actuate the next coil in the direction of car travel.

7. A system as claimed in claim 4, including means providing indications of car speed, the means for selectively actuating the electromagnetic coils including means resonsive to said indications of car speed and to said indications of car distance from the floor represented by an actuated coil to cause the notching means to deactuate said coil and actuate the next electromagnetic coil in the 17 direction of car travel when the car speed is excessive for stopping at said floor.

8. An elevator control system for stopping an elevator car that travels in a hoistway to serve a plurality of floors, comprising a plurality of electromagnetic coils arranged in a vertical line in the hoistway, one for each floor, a plurality of magnetically operated reed contacts arranged in a column on the car to be carried thereby past each electromagnetic coil whereby the contacts can be operated successively by the coil, when the latter is energized, at different distances of the car from the floor of the energized coil, a plurality of additional reed contacts that operate at different car speeds, and means responsive to operation of the reed contacts for de-energizing said energized coil and energizing the next coil in the direction 15 18 of the car travel when the car is too close to the last mentioned floor to make a satisfactory stop there from the speed at which it is travelling.

References Cited UNITED STATES PATENTS 2,666,110 1/1954 Berkovitz l8729 X 2,674,348 4/ 1954 Sautini et al 187-29 2,840,188 6/ 1958 Savage l87---29 10 2,875,853 3/ 1959 Borden et al 187-29 ORIS L. RADER, Primary Examiner.

T. LYNCH, Assistant Examiner.

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