US1919014A - Elevator control system - Google Patents

Description

July 18, 1933. W F EAMEs 1,919,014-

ELEVATOR CONTROL SYSTEM Filed Nov. 50, 1927 2 Sheets-Sheet l INVENTOR /.l/ ///dfl7 Ffames.

July 18, 1933. w. F. EAMES 1,919,014

ELEVATOR CONTROL SYSTEM Filed Nov. 50, 1927 2 Sheets-Sheet 2 Patented July 18, 1933 UNITED STATES 1,919,014 PATENT OFFICE WILLIAM F. EAMES, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA ELEVATOR CONTROL SYSTEM.

Application filed November 30, 1927. Serial No. 236,772.

tained constant under varying-load condi-' tions.

Another object of my invention is to provide a control system for motor-driven matained substantially constant under variations of load.

invention consists particularly in providing a motor-generator control system of the Ward-Leonard type with means for varying the voltage produced by the generator to compensate for variations in load upon the driven motor.

My invention is described with reference to the accompanying drawings, wherein,

Figure 1 is a diagrammatic view of my control system, as applied to an elevator drive, an 1 Figs. 2, 3 and 4 are diagrammatic views showlng the speed curves obtained with my compensating devices.

Referring to the drawings, I have illustrated an elevator car- C- suspended in the usual manner upon a cable Ca, which passes over a hoisting drum D to a suitable counter weight Cw. Directly coupled to the hoisting drum D is an armature EM of an elevator motor EM which is provided with, a separately-cXcited-field winding EMF. The armature EM is connected in loop circuit with the armature G of a generator G. The generator G is of the cumulative-compoundwound type including a series field winding GSF and a separately excited field winding GF. A motor M, having its armature M directly coupled to the armature G of the generator G, acts as a driving means for the generator. The motor M is illustrated as being of the shunt-wound type having its field winding MF connected in parallel relation to the armature M.

The direction and speed of operation of the elevator motor EM is suitably controlled, in the usual manner, by means of an updirection switch 1, a down-direction switch 2 and a plurality of speed relays 3, 5 and 6. The speed relays determine the three predetermined operating speeds at which the elevator may be driven.

The "illustrated control system is of the so-called automatic-landin type wherein the accurate stopping of the efiavator car 0 level with any of the floors served by the car is determined by the operation of suitable inductor relays carried by the car, which cooperate with inductor-plates mounted in the hatchway adjacent to each of the floors. A control system of this type is illustrated in the copending application of E. M. Bouton, Serial No. 7 31,921, filed August 14, 1924 and assigned to the Westinghouse Electric & Mfg. Co.

The inductor-relays illustrated in the present drawings comprlse a high-speed-up relay 10, a high-speed-down relay 9, an up-intermediate-speed relay 8 and a down-intermediatespeed relay 7. The final stopping of the elevator car is accomplished through the oper ation of a mechanical landing switch 11, operable, as hereinafter described, by a retiring magnet 12 and cams 13, one of which is mounted in the hatchway adjacent to each of the floors, but only one of which is illustrated in the drawings.

For maintaining the motor speed constant under varying load at low speeds, the seriesfield winding GSF on the generator G is so proportioned that cumulative compounding of the generator is achieved to increase the voltage supplied to the motor under increase in load and to decrease the voltage supplied to the motor under light or overhauling loads in such proportions as to counteract the nor mal characteristic of the elevaton-motor to reduce its speed as the load thereon increases. At hi her speeds, it is noted that the compoun ing of the generator is not suflicient to maintain an accurate speed regulation, and I, therefore, provide an additional means for regulating the speed of the motor by varying the excitation current supplied to the sepa rately-excited-generator-field winding GF in some proportion to the load on the elevator car.

The form of apparatus used for accomplishing the resultant speed regulation is illustrated as a multiple-fin er relay designated, generally, by the re erence character 14. This relay comprises a suitable magnet structure including an upper magnetic plate 15 and a lower magnetic plate 16 between which a series coil 17 and a shunt coil 18 are so mounted as to exert a magnetizing influence upon the plates 15 and 16. The series coil 17 is connected in series relation with the generator armature G and the motor armature EM, while the shunt coil 18 is connected in parallel relation to the motor and generator armatures for a purpose hereinafter described.

Pivotally mounted upon the lower plate 16 are a plurality of movable contact fingers 19, 20, 21 and 22. While only four of these fingers are illustrated, it is obvious that the number may be varied to suit the particular condition under which the-control system is to operate. The extreme ends of the contact fingers are suitably insulated from the main body of the relay, as at 23, thereby forming four distinct and separate contact members 24, 25, 26 and 27, which may be moved into engagement, respectively, with cooperating stationary contact members 28, .29, 30 and 31. As will be hereinafter set forth, under certain conditions of operation, it is desirable to have all of the contact members 24, 25 etc. in engagement with their cooperating contact members 28, 29 etc. A locking bar 32, normally spring biased to contactengaging position by means of a spring 33, is disposed adjacent to the contact arms 19, 20 etc. but is movable to open-contact position under the influence of a releasing magnet 34 cooperating with a lever 35 to cause a movement of the locking bar to the left when the magnet 34 is energized.

The operation of the system disclosed may best be described with reference to an assumed elevator operation. Assuming the elevator to be standing at the lower-most floor and that it is desired to start the car upwardly, ,the attendant on the car C moves the car switch handle C8 to the left to supply current to the lip-direction switch 1 through the engagement of contact members 40, 41 and 42. The circuit for the switch 1 extends from line conductor L1 through conductors 43 and 44, contact members 41. 40 and 42, conductor 45, the coil of rip-direction switch 1. and conductors 46. 47 and 48 to line conductor L2. ITp-direction switch 1 completes a circuit for energizing the separately-excited-field-winding GF with current in one direction, which circuit extends from line conductor L1 through conductors 49 and 50, contact members b of UP-(llIECtlOfl switch 1, conductors 51 and 52, separatelyeXcitedfield-winding GF, conductor 53, contacts members a of updirection switch 1, conductors .54 and 55, re-

sistor sections 56, 57,58, 59, 60, 61, 62 and 63 and conductors 64 and 48 to line conductor L2.

The generator G now sup lies a voltage to the elevator motor armature elevator to start upwardly. In order to cause the car to accelerate to a higher speed the car switch Cs may be moved further to the left to complete a circuit for speed relay 5 which extends from line conductor L1 through conductors 43 and 44, contact memhere 41, 40 and 65 on the car switch C8, conductors 66 and 67, contact members 68 0b,, up intermediate-speed relay 8, conductor 69, the coil of a holding relay 70, conductor 71, the coil of speed relay 5, conductor 72, doorswitch devices 73 and 74, such as are usually provided to be operated to open-circuit position whenever the hatchway doors are opened, conductor 75, contact members of a gate switch 76, and conductor 77 to line conductor L2. Speed relay 5 operates to shortcircuit resistor section 58 by way of conductor 78, contact members a of 'rela 5, conductors 79, 80 and 81, contact mem ers b of relay 5 and conductors 82 and 83, and also section 57 through conductor 78, contacts a of speed relay 5, conductors 79, 80, and con-. tacts b of speed relay 4, thus causing the elevator to run at its lower intermediate speed. 0

The operation of speed relay 5 completes a. circuit for energizing the retiring magnet 12 of the landing switch 11 to move the landing switch to its retired position. The circuit for the magnet 12 extends from line conductor L1 through conductors 85 and 86, the coil of magnet 12, conductor 87, contact members a of speed relay 5, and conductors 88 and 48 to line conductor L2.

When the landing switch 11 is retired, its contact member 91 engages its contact members 89 and 90 to complete, first, a self-holding circuit for up-direction switch 1 and, second, a circuit for energizing speed relay 3. The self-holding circuit for up-direction switch 1 extends from line conductor L1 through conductor 85, contact members 89 and 91 on landing switch 11, conductors 92 and 93, contact members (1 on up-direction switch 1 and thence, by way of conductors 45, 46 etc., as previously traced for up-direction switch 1. The circuit for speed relay 3 extends from line conductor L1 through conductor 85, contact members 90 and 91 of landing switch 11, conductor 94, the coil of speed relay 3, and conductors 95 and 48 to line conductor L2.

The operation of relay 3 performs two functions: first that of short-circuiting rcsistor section 59 by way of conductors 83 and 96, contact members a of speed relay 3 and conductor 97, and second the short-circuiting of a portion of a discharge resistor 98 connected in parallel relation to the separately M to cause the 70 excited field winding GF by way of conductor 99, contact members I; of speed relay 3 and conductor 100. The effect of short-circuiting a portion of discharge resistor 98 will be set forth hereinafter.

Excluding resistor section 59 causes an increased amount of current to be supplied to the separately excited field winding GF, to thereby cause the elevator motor EM,to be accelerated to its next higher speed. The motor is now running at the second intermediate speed.

Assuming now that the car switch C8 is moved to its extreme position, a circuit will be partially completed for energizing speed relay 6, which circuit extends from line conductor L1 through conductors 43 and 44, contact members 41, 40 and 101, conductors 102 and 103, contact members 104 of high-speed up-inductor relay 10, conductor 105, the coil of a holding relay 106, and conductor 107 to a junction-point 108, whence one branch extends by wayof conductor109, the coilof speed relay 6, conductor 110, contact members a of a counter E. M. F. relay 111, and conductors 112 and 72, door switches 73, 74 etc., as previously traced, to line conductor L2, and the other branch extends by way of conductor 113, the coil of motor-field relay 114, conductor 115, contact members a of a second counter E. M. F. relay 116, conductor 117, contact members of counter E. M. F. relay 111 to conductors 112 and 72 etc., as previously traced for these conductors.

It should be noted that counter E. M. F. relay 111 is designed to delay the operation of the high-speed relay 6, thereby delaying the time in the acceleration period when full voltage will be supplied to the separatelyexcited-field winding GF for the purpose of preventing the over-shooting of speed as the elevator motor accelerates to its highest speed.

In Fig. 2, is shown an acceleration curve showing the time at which the counter E. M. F. relays 111 and 116 will operate to produce a substantially smooth acceleration curve without over-speeding. This curve is designated by the reference character 117 and .is shown in comparison with an acceleration curve 118. which is the result of omitting the time delay occasioned by relays 111 and 116. It will be observed that, without the time delay, the elevator motor will be accelerated from zero speed to a high speed illustrated by the portion 119 of the curve 117. However, in accelerating to this high speed, it is a characteristic of the motorgenerator drive of the Ward Leonard type that full field excitation will cause an overshooting of the high speed, as indicated by the portion 120 of the curve 118. This is an undesirable condition, since it causes an unpleasant sensationtopassengers riding in the elevator car. It has been discovered that the time relay provided by relays 111 and 116 will cause a smoothing out of the acceleration to attain the high speed (line 119) without causing such over-speeding.

If the relay 111 is so selected that it will operate upon receiving a counter E. M. F. of a predetermined value, for example, '100 volts, this relay may be so adjusted that it will. be energized at some point in the acceleration curve represented by the character 121. As was previously described, the pration of relay 111 completes the partially closed circuit for speed relay 6, permitting this relay to operate to thus further reduce the resistance in circuit with the separatelyexcited-field winding GF.

Relay 6, therefore, operates at this time to short-circuit resistor section 56 from the generator field circuit, thereby permitting the elevator to accelerate to its highest speed.

Relay 116 should be so selected that it will operate at a higher value of counter E. M. F., for example, 200 volts. Relay 116 will, therefore, operate at some predetermined time after the operation of relay 111 and, when so operated, will complete the partially closed circuit for motor-field relay 114.

As will be observed from an inspection of Figure 1, the field winding EMF for motor EM is permanently connected to line conductors L1 and L2 by way of conductors 123, 124, resistor 125 and conductor 126. The contact members of relay 114 normally short-circuit the resistor 125, thereby insuring full field strength in the elevator motor field. However, upon the operation of relay 114, the resistor 125 will be inserted in the circuit of the elevator motor field winding EMF, to cause a weakening of the field strength and a consequent speeding up of the. motor EM.

Referring again to Fig. 2, it will be observed that the point in the acceleration curve at which relays 116 and 114 should operate is indicated by the reference character 127. The result of the operations of relays 111 and 116 in the control system described is such as to produce a substantially smooth acceleration of the elevator to its predetermined high speed without overspeeding.

By delaying the operation of high-speed relay 6 until the voltage supplied to the terminals of the elevator motor EM builds up to a predetermined value, another desirable result is accomplished, namely, an automatic selection of a one-floor run or a two-floor run, dependent upon the time during whichthe car switch is held at full-speed position. It is undesirable to force the attendant to carefully operate the car switch when making a one-floor run to such a position as will not engage contact members and 101, it being preferable that he be permitted to operate the car switch to its extreme position, re-

ardless of the distance the car is to travel. Vithout the delay imposed by relay 111, movement of the car switch to the high-speed position would cause the car to accelerate to its highest speed from which it would be impossible to decelerate, as hereinafter described, to stop at the next adjacent floor. However, by employing the relay described, the attendant may move the car switch to its full-speed position and then return it to neutral position, without the possibility of energizing higlrspeed relay 6, and the car will accelerate only to the intermediate speed, preparatory to decelerating to make a stop at the next floor.

It will be observed that the closing of relay 6 will energize speed relay 4, causing this relay to open ites contact members b, thus permitting relay 6 to thereafter control the exclusion of both resistor sections 56 and 57 for a purpose hereinafter described.

As previously described, the speed regulation imposed upon the system by use of the series-field winding GSF on the generator G is not as effective at high speeds as at low speeds, and, for this reason, I provide the multiple-finger relay 14 to improve the regulation of the system under high-speed conditions.

Resistor sections 60, 61, 62 and 63, in circuit with the separately excited field winding GF, are connected to be short-circuited by the operation of the four contact fingers 24, 25, 26 and 27, respectively.

When. the elevator motor EM is first energized to start and accelerate the elevator to high speed the acceleration current is obviously of a relatively high value, while the voltage supplied to the elevator motor is relatively low. The locking bar 32 holds the fingers in closed-circuit position, thereby exeluding resistors 60 to 63, inclusive, from the generator field circuit and permitting full field excitation during the accelerating period.

As the voltage supplied to the elevator motor armature EM builds up, release magnet 34.- Will be energized to release the locking bar 32. However, the acceleration current is of such high value at this time that the series coil 17 will exert such a magnetizing influence upon the plates 15 and 16 that the arms 19 to 22, inclusive, will remain in circuitclosing position. As the elevator is brought up to speed, the acceleration current is reduced, thereby reducing the magnetic influence upon the arms 19 to 22, inclusive. It will be observed that the plate 15 is provided with projecting portions 130, 131, 182 and 133, which projections are preferably of adjustable length, for the purpose of adjusting the normal air gap between the extended portions'of these projections and the levers 19, 20, 21 and 22, respectively, with which they cooperate. By suitably adjusting the air gap between the projections and their fingers, it follows that different values of energizing current in the coil 17 will cause certain of the fingers 19, 20, etc., to remain in circuit-closing position while the others will be dropped out.

It will be observed that, if the load upon the elevator car is heavy, for example, a heavy lifting load, the value of current in the coil 17 at the expiration of the acceleration period will be of such value as to maintain all of the fingers in circuit-closing position, thereby sup lying full field excitation to the generator 3 and, consequently, a high voltage to the elevator motor EM. However, if the load is light, the current in the coil 17 will not be suflicient to hold fin 811 19 in closed-circuit position, and this nger will drop out to insert resistor section 60 in the field circuit, thus reducing the voltage supplied to the motor EM, whereby the elevator car will be moved at the same speed as when it was fully loaded. I

With a balanced car, that is, the condition wherein the load upon the car just equals the balancing force exerted by the counterweight, the current in coil 17 will only be of such value as is required to overcome the frictional losses in the machine. Under these conditions, finger 20 will be dropped out in addition to finger 19, and resistor sections 60 and 61 will be inserted in the field-winding circuit to cause a proportionate reduction in the voltage supplied to the elevator motor EM, whereby the car will travel at the same speed as when the load was extremely heavy.

In case the elevator is traveling downwardly under relatively light load, that is, with a load just exceeding the force exerted by the counter-weight, the current in coil 17 will be a regenerative current and, under these conditions, finger 21, as well as fingers 19 and 20, will be dropped out to insert resistor sections 60, 61 and 62 in the field-wind ing circuit.

It will be noted that, under these conditions, it would appear that a reversal of the flux through plates 15 and 16 would occur and that the current in coil 17 would be increased over the value at balanced-car condition.

In order to maintain the flux in the same direction, under all conditions of loading, a coil 18, connected across the terminals of the elevator-motor armature EM is disposed between the plates 15 and 16 and is selected of such magnetizing value as to exert a biasing influence upon the coil 17, that is, the ampere-turns in the coil 18 always exceed the ampere-turns in the coil 17, so that, under heavy loading conditions, the coil 17 adds its influence to that of the coil 18, while under overhauling load conditions, the coil 17 bucks the influence of the coil 18, thereby giving a resultant magnetizing value in the plates 15 and 16 which is continuously in one direction and is reduced as the load changes from a peagy lifting load to a heavy overha 'ng Therefore, under the condition of a light overhauling load, as described above, the eii'ective flux in the plates 15 and 16 will be so weak as to permit fingers 19, 20 and 21 to be dropped.

Under the extreme overhauling loads, the flux value in the plates 15 and 16 will be further reduced to drop all four of the fingers 19 to 22, inclusive, thereby inserting the tour resistor sections 60 to 68, inclusive, thus proportionately reducing the ,efiective field citation of the generator G.

Fig. 3 illustrates the motor speed curve, first without, and second, with, the correction imposed by the relay 14. Assuming that the zero point for both curves represents zero amperes, with increase toward the right with lifting load and regenerative or negative load in amperes toward the left, a speed curve, such as is represented by the line 135, is the result. As will be observed this curve shows a drooping speed characteristic as the positive load increases.

However, with the correction imposed by the relay 14, the speed, though falling along lines parallel to the line 135, is increased in value in four distinct steps, as the finger to 22, inclusive, are moved to closed-circuit position. The result of this curve is a speed characteristic such as is represented by the broken line 136, producing an average speed characteristic such as'is represented by the dotted line 137. It will be seen, therefore, 1 that the variations in load are compensated for to maintain a substantially flat speed characteristic at high speeds as well low speeds.

Assuming now that it is i stop the elevator car a given door attendant will-center. car switch Ga cause energiaat'ion the coils of the inductor relays 7, 8,

9 and The circuit for high-speed inductor relays 9 and 10 extends from line conductor L1 through conductors 43 and 44, contact members 41, 40 and 138, and conductor 139 to junction-joint 140, whence one branch ear tends through the coil of relay 9 and ductor 141 to line conductor L2, while the other branch extends by way of conductor 142, the coil of relay 10 and conductor 143 to line conductor L2.

Immediately upon centering the car switch Cs, the original circuit for speed relay 6 and field relay 114 will be broken. However, this operation will not cause deenergization of these relays, since a holding circuit has been completed through the operation of holding relay 106, which circuit extends from line conductor L1 through conductors 43 and 144.;

contact members a of relay 106, conductors 145 and 103, contact members 104 of relay 10 and thence as previously described for this circuit. The elevator car will, therefore, con tinue to run at high speed until the 10 passes the inductor-plate 146 associated with the floor at which it is desired to stop.

Inductor relay 10, the coil which is now energized, passesinductor plate 146 and operates to open its contact members 104, deenergizing relays 106, 6, and 114, thereby re-insorting resistor sections 56 and57 in the circuit of separately-excited field-winding GF to cause deceleration of the elevator motor EM.

it has been observed that, in the type of control illustrated, smooth and rapid accelerand deceleration between zero speed and predetermined intermediate speeds can only be accomplished within the shortest travel distance, rovided the excitation of the field winding h on the generator G is so selected for certain of its speed values as to cause the car to attain a continuous speed in excess of the desired speed it such excitation were permitted to continue for a predator mined length of time.

It is a desirable characteristic, in elevator operation, that the elevator be accelerated from zero speed to its highest running speed within the shortest distance of travel which will ensure operation that is comfortable for the passengers. Assuming an elevator operable at 600 feet pe minute, the shortest dis tance in which s: iactory acceleration to this speed may occ s 11 feet. The average distance on ad acent floors in a building ately 11 feet. Therefore, the sc- .1. n and deceleration distances for this elevator are the distances between adjacent noors.

The most economical arrangement is to have the acceleration distance the same whether the elevator is to travel only the distance between adjacent floors or is to travel through a further distance. The problem presents itself, therefore, of causing the elevator to attain the highest possible speed in starting from one floor from which'it may be decelerated comfortably to make a stop at the next adjacent floor. This should be an intermediate speed, such as is illustrated as being controlled by actuation of relay 5.

Under the'assumed conditions of 11 feet distance between floors, the highest practical speed which the elevator may attain in male ing a one-floor run is approximately 300 feet per minute. By making the acceleration distance 5 feet and deceleration distance feet the elevator car may make the one floor run in the most efi'icient time.

The reason for allowing the extra foot for deceleration is that with the lowest steps oi speed, those steps controlled by the landing switch 11 consume a greater length or time than is required to accelerate to the speeds controlled by this switch.

llld

In Fig. 4, are shown the acceleration and deceleration curves for an elevator operating under the assumed conditions. Assuming that the point 0 represents the elevator standing at a floor and it is desired to have the car travel to the next floor, acceleration of the elevator will be along the line 150. It is assumed that the car switch will be moved only so far as to make contact with contact member 65 controlling speed relay 5, when a one-floor run is to be made. Should the re sistor 58 normally under the control of relay 5, be excluded from the field-winding circuit. the elevator would accelerate to maintain a continuous running speed of 300 feet per minute. But this acceleration to a speed of 800 feet per minute represented by the curve 151, drops as the speed of the elevator ap proaches a continuous 800-foot speed, and the elevator car will not be running at 300 feet, until the car has traveled to a point 152 on the curve 151. It will readily be observed that the point 152 also represents the travel distance of approximately 7 feet, leaving only 4 feet in which deceleration may occur to bring the car to a stop at the next floor.

When the car passes the point between the floors (represented by the line 153) at which inductor relay 8 will be actuated to initiate deceleration, the speed of the elevator car will not be 300 feet per minute, but will be a lower value, such as is represented by the point 154, at which curve 151 crosses the deceleration line 153. This speed will be approximately 275 feet per minute and, when inductor relay 8 operates, the elevator will be decelerated along line 155 to make the stop at the next floor. It will be observed that the speed of the elevator car, as it approaches the floor along curve 155, is slow, and the car appears to drag to the floor. In order, therefore, that the most efficient deceleration may be used, it is necessary that the excitation of the generator field GF should be slightly in excess of that required to obtain a continuous running speed of 300 feet per minute and if the excitation value is properly selected the car will accelerate along curve 150. This curve 156 crosses the deceleration line 153 at a point 156, at which time the elevator car wit] be traveling at 300 feet per minute and, when inductor relay aperates, the car will be decelerated alon, .e 157, representing the most eflicient (It ation for the elevator. If (iQCCltEEittltL. not initiated, the car wou attain a continuous running speed of t per minute. wever, if it is desired to stop the elevator car at the same door when approached from a greater distance than the next adjacent floor, the car will have been operating at its maximum speed of 600 feet per minute. The most ethcient deceleration from this speed is along curve 157, starting from a deceleration-initiation point 158, approximately 11 feet from the floor at which it is desired to stop.

Referring now to Fig. 1, it will be observed that the actuation of speed relay 5 excludes I both resistor sections 57 and 58, since the con- 1 ute. The effect of excluding both resistor sections 57 and 58 therefore causes acceleration along the curve 150, leaving only resistor section 56 to be controlled by the high-speed relay 6 when it is desired to have the elevator car travel at its maximum speed of 600 feet per minute.

However, on deceleration, deenergization of relay 6 would insert only resistor section 56 in the field-winding circuit and the car would decelerate along curve 158 to attain a continuous operating speed of 325 feet per minute, never reaching the desired speed of 300 feet per minute. The point at which curve 158 passes the deceleration line 153, representing initiation of the second step of slow-down, also represents a speed of the elevator car of 350 feet per minute, and this is greater than the speed at which the second step of slow-down should be initiated.

In order to compensate for this over-speeding on deceleration, relay, 4 is arranged to transfer the control of resistor section 57 from low-speed relay 5 to high-speed relay 6, when high-speed relay 6 is operated. The circuit for relay 4 extends from line conductor L1 through conductors 49 and 50, contact members 0 on up-direction switch 1, conductor 159, contact members I) on high-speed relay 6, conductor 160, the coil of relay 4 and conductor 48 to line conductor L2.

Relay 4, when actuated, completes a selfholding circuit, by way of contact members a thereof and conductor 161, to maintain this relay energized until up-direction switch 1 is dropped out. The opening of contact members 5 of relay 4 opens the circuit for resistor section 57, normally controlled by relay 5, and places both resistor sections 56 and 57 in condition to be controlled by high-speed relay 6, through conductors 79 and 78.

Thus, upon initiation of deceleration from high speed by dropping out relay 6, both resistor sections 56 and 57 are inserted in the field-winding circuit for the generator G, causingthe car to decelerate to attain a continuous running speed of 275 feet per minute,

instead of 300 feet, and this deceleration will be. along curve 157, passing the second slow down point 158 when the speed is 300 feet per minute.

In other words, in order to attain maximum etliciency, it is necessary to over-shoot the speed desired on acceleration and undershoot the speed desired on deceleration, and initiate the intermediate-speed slow-down at a point prior to the time at which the elevator attains a continuous running speed for the selected values of field excitation. This is ac complished in a very simple manner by providing the relay 4, effective, upon acceleration,- for placing two sections of the acceler ating resistor under the control of the lowspeed relay 5 and efi ective, upon deceleration, to place two sections of the resistor under the control of high-speed relay 6.

In our assumed operating condition, the

- deenergization of speed relay 6, when the inductor relay 10 passes its inductor plate 146, will insert resistor sections 56 and 57 in circuit with the separately excited field winding GF, and the motor will be caused to slow down to an intermediate speed within the prescribed distance of travel. At this time, the inductor relay 8, controlling the intermediate speed, will pass inductor plate 146, thereby opening contact members 68 to deenergize relay 5. It will be noted that the energizing circuit for the coil of inductor relay 8 passes through normally closed contact members of holding relay 106, thus preventing actuation of relay 8 until after the actuation of relay 10. The circuit for the coil of relay 8 extends from line conductor L1 through conductors 13 and 162, cpntact members b of relay 106, conductor 163. the coil of relay 8 and conductor 164 to line conductor L2.

The opening of contact members 68 on inductor relay 8 will cause deenergization of holding coil 70 and speed relay 5, thereby causing speed relay 5 to re-insert resistor section 58 in the separately-eXcited-field-winding circuit and the car will be decelerated along the curve 157 (Fig. 4) to the landing speed, that is, the speed controlled by land ing switch 11 and relay 3. il/hen contact members 0 on speed relay 5 are opened, the retiring magnet 12 on the landing switch 11 is deenergized, permitting the roller 165 to touch the cam 13. The cam 13 should be of such length that, at such times as relay 5 will be deenergized, the roller 165 on the landing switch 11 will be adjacent to the outermost or highest portion of the cam 13.

As the car C continues to travel toward the floor at which it is desired to stop, the roller 165 will move from the outermost portion of the cam 13 to the'next portion, thereby causing the contact arm 91 to be moved out of engagement with the contact member 90, thus opening the circuit for speed relay 3.

As has previously been described, relay 3, when actuated, short-circuits a portion of the discharge resistor 98, normally connected across the terminals of the separately-excitedfield-winding GF to provide a time constant for the decay of the field flux when it is desired to decelerate the motor EM. However, when the elevator is slowing down to make a stop at the floor, relay 3, in dropping out,

opens this short-circuit to cause insertion of all of the resistor 98 to thereby increase the resistance of the closed circuit for the field winding GF.

It has been observed that, should the entire stabilizing resistor 98 be left in circuit during the first portion of the slow-down or deceleration period, the change of flux in the field winding GF would be so rapid as to cause an unstable operation of the motor EM. The

motor wouldtend to slow down too rapidly and then increase its speed, and then again slow down in a series of steps. However, if only a small portion of the resistor 98 is in circuit with the field winding during the first portion or" the deceleration period, the decay of the field will be slower and the deceleration will, therefore, be more smooth.

I However, the small section of the resistor 98 required to accomplish the smooth deceleration during the early portion of the period, is not sufficient during the latter portion of the period, when the elevator is travelling at its lowest speed, since, at this low speed, it is desirable that the decay of the field shall be at a more rapid rate to insure complete demagnetization when the elevator arrives level with the floor. By re-inserting the short-circuited portion of the resistor 98 when relay 3 is deenergized, the rate of decay at this slow speed, is proportionately in creased.

The opening of peed relay 3 inserts resistor section 59 in the separately-excited field-winding circuit to further decelerate the car. The speed at which the car will' move when all the resistor sections 56 to 59, inclusive, are inserted in the circuit, is a very slow landing speed, for example, 20 to 25 feet per minute.

As the car approaches closer to the floor level, the roller 165 will be moved to the lowermost or right hand face of" the cam 13, which is illustrated as being of substantially V-shape. lVben the roller 165 is in this position, contact member 91 will be moved from engagement with contact member 89, thereby breaking the holding circuit for up-direction switch 1 and causing the elevator motor to be stopped.

lln order that the generator field may-be completely demagnetized, I provide an extra field winding, GAF- preferably in the form of a differentially wound coil. to oppose the effect of the residual magnetism in the gen erator iron and the effect of the series-field winding G-SF when the elevator is to be brought to a stop. The circuit for the extrafield winding/GAF extends from conductor 170, connecting the one terminal of each of the generator armatures G and the elevator motor armature EM through conductor 171, the extra field winding GAF, conductor 172, normally closed contact members e on downdirection switch 2, conductor 173, the contact members of up-direction switch 1, and conductor 174 to conductor 175, connecting theop-posite terminals of the generator armature G and the elevator-motor armature El /l. The effect of the winding GAF will be to exert a demagnetizing force upon the field of the generator G which is equal and opposite to the force created by the series field winding GSF and the residual magnetism in the generator field iron, thereby preventing creepage after the usual brake {not shown) is applied and thereby causing the elevator to be brought to a stop. It is assumed that the elevator car will be held t tionary at the floor by the application of the usual suitabl mechanical brake.

it will be seen, therefore, that I have ro- 'ded a motor-generator drive of the ardonard type, especially adapted for elevator rvice, wherein the essential characteristic constant speed under varying load conditions is accomplished, thereby permitting accurate landing of the elevator car level with the floors which it serves. The speed com pensation includes the series field winding the multiple-finger relay 14, the field lay 114', a relay 4, with connections veen speed relays -5 and 6, and counter E. h F, relays 111 and 116 for controllin the me of actuation of field relay 114: and the nighest-Speed relay 6.

The embodiment of my invention herein escribed is merely illustrative and I do not desire to be limited to the details of the apparatus shown except as set forth in the appended claims.

I claim as my invention: 1. In a motor control system, a motor; a generator; electrical connections between d motor and said generator, means for vallably controlling the voltage of said genertor to control the speed of said motor; means hiding an element responsive to the curent in said connections, means disposed to 3 controlled by said current responsive ans for further varying the voltage of said aerator, and means to limit the effect of d current responsive means to a predeterned range of voltages of said generator.

trol system, a motor; a nnections between said nor; means for variably ge of said generator to the specs or said motor; and addii means for controlling the voltage of nerator, said additional means comising a contact element, means including an cment responsive to the current in said conions adapted to control said contact element, and means to limit the control of said contact element by said last-mentioned means to predetermined range of voltages of said generator.

3. In a motor control system, a motor; a enerator; electrical connections between said F2, in a motor con generatomelectric motor a motor and said generator; means for variably controlling the voltage of said generator to control the speed of said motor; and addi tional means for controlling the voltage of said generator, said additional means comprising a contact element, means including an element responsive to the current in said connections adapted to control said contact element, and means comprising an element responsive to the voltage of said generator for limiting the control of said contact element by said last-mentioned means to a predetermined range ofvoltages of said generator.

In an elevator-control system, an elevator motor, a generator for supplying voltage to said motor, said generator including a separately excited field winding and a circuit therefor, means responsive to changes in the effective load on said motor for correspondingly varying the excitation current supplied to said field winding to maintain. the speed of said motor uniform, said means comprising a resistor associated with the circuit for said field winding, means for respectively including and excluding said resistor in and from said circuit, and means for rendering said load-responsive means ineffective when the voltage of said generator is below a prcdetermined value.

5. In an elevator-control system, an elevator motor, a generator for supplying voltage to said motor, said generator including a separately excited field winding and a circuit therefor, means responsive to changes in the effective load on said motor for correspondingly varying the excitation current supplied to said field winding to maintain the speed of said motor uniform, said means comprising a resistor associated with the circuit for said field winding, means for respectively includin and excluding said resistor in and from said circuit, and means for rendering said load responsive means ineffective during the first portion of the acceleration of said motor.

6. In a motor control system, a motor; a generator having a field winding; electrical connections between said motor and said generator; means including a circuit having resistance associated therewith for variably exciting said winding to cause said motor to operate at speeds within a first range and a higher range; a switch comprising contact members having normal and operated positions, means to bias said contact members to said normal position, means comprising a coil responsive to the current in said connections efiective, if said current exceeds a predetermined v ue, to maintain said contact members in said operated position, and additional means effective while said motor is operating in said first speed range to maintain said contact members in said operated position; and means controlled by said contact members and effective while said contact members occopy said operated position to reduce the resistance of said circuit.

7. In a motor control system, a motor; a generator; electrical connections between said motor and said generator; means for variably controlling the vo tage of said generator to cause said motor to operate at corresponding speeds; a switch comprising contact members having normal and operated positions, means to bias said contact members to said normal position, means comprising a coil responsive to the current in said connections eiiective, if said current exceeds a predetermined value. to maintain said contact members in said operated position, and additional means effective while the voltage of said generator is below a predetermined value to maintain said contact members in said operated position; and means controlled by said contact members and eii'ective while said contact members occupy said operated position to effect an increase in the voltage of said generator.

8. In an elevator control system, motive means for the elevator, and control means for,

said motive means comprising a manually operable switch in said elevator, said switch being movable to a plurality of different positions. a plurality of control circuits, each of said circuits being associated with one of said positions, means adapted to complete each of said circuits in response to movement of said switch to the corresponding position, main taining means for each circuit responsive'to completion of the associated circuit, and means to delay the completion of certain of said circuits to thereby prevent completion ot'said certain of said circuits in response to a momentary actuation of said switch.

9. In an elevator control system, motive means for said elevator, and control means for said n'lotive means comprising a manually operable swit-"h in said car. said switch being movable to a plurality ot different posi tions including a high speed position, a plurality of control circuits, each of said circuits being associated with one of said positions, means adapted to complete each oi said circuits in response to movement of said switch to the corresponding position. maintaining means for each circuit responsive to completion of the asso iated circuit. and means to delay completion of said high speed circuit, whereby operation oi said elevator at high speed is not ctl' ccted in response to momentary movement of said switch to said high speed position.

10 In an elevat n'-control system. an elevator motor, a control device. control means operably responsive to actuation oi said control device including a slow-speed means and higl1-;-1 ":eed means tor causing said elevator (0 operate at (OIIOSIIOYMllNQ speeds. means responsive to actuation of said slow-speed and high-speed means, respectively, for maintainingthe associated means active, and means for delaying the acuation of said high-speed means whereby n'ioinentary operation of said control device will cause said elevator to operate only at said slow speed.

11. In a motor control system, a motor; a generator for supplying power to said m0- tor: and means for controlling the voltage of said generator to accelerate and decelerate said motor, said controlling means including a resistance having a plurality of sections. a first switch for controlling one section of said resistance, a second switch for controlling a second section of said resistanco, and means including a transfer element disposed to render athird section of said resistance subject to control by said tirst switch during acceleration of said motor and subject to control by said second switch during deceleration of said motor.

12. In a motor control system, a motor; a generator for supplying power to said motor; and means for controlling the voltage of said generator to accelerate and decelerate said motor, said controlling means including a resistance having a plurality of sections, a first switch for controlling one section of said resistance, a second switch for controlling a second section of said resistance, and means including a transfer element responsive to the voltage of said generator disposed to render a third section of said resistance subject to control by said first switch during acceleration of said motor and subject to control by said second switch during deceleration of said motor.

13. In a control system for elevators, an elevator operable past a plurality of adjacent floors, a motor therefor, and means for controlling the power supplied to said motor for accelerating and decelerating said motor, in cluding a resistor formodifying the voltage supplied to said motor, a first switch, actuable to effect a low operating speed of said motor, for controlling a portion of said resistor, a second switch, actuable to efl'ect a higher operating speed of said motor, for controlling another portion of said resistor, and means for controlling a third portion of said resistor operable during acceleration of said motor to place said third portion under the control of said first switch, and operable during deceleration to place the third portion of said resistor under the control of said second switch.

.4. In a control system for elevators, an elevator. a motor therefor, a generator for supplving voltage to said motor, said generator having a separately excited field winding, and means for controlling the voltage supplied to said motor for acceleratlng and decelerating said motor, including a resistor in circuit with said separately excited field winding. a first switch actuable t9 exclude one portion of said resistor from said circuit,

a second switch actuable to exclude another portion of said resistor from said circuit, and means for controlling a third portion of said resistor operable during acceleration to place said third portion under the control of said first switch and operable during deceleration to place said third portion under the control of said second switch.

15. In an elevator system of the type in which the distance between certain selected starting and stopping points is such that the decelerating point, in advance of said selected stopping point, at which deceleration must be initiated, is reached before the elevator attains the maximum operating speed,

' a motor for driving the elevator, a source of excitation for said motor, and means for controlling said source to accelerate and decelerate said motor, said controlling means including switching mechanism operable, in starting the elevator from said selected starting point, to fix a value of excitation for said motor adapted to cause said motor to attain substantially a predetermined operating speed when said decelerating pointv is reached, and additional switching mechanism operable, in decelerating said motor from said maximum speed to stop the elevator at said selected stopping point, to fix a 3o/value of excitation for said motor adapted to speed, a motor for driving the elevator, a-

cause said motor to attain substantially said predetermined operating speed when said decelerating point is reached.

16. In an elevator system of the type in which the distance between certain selected starting and stopping points is such that the decelerating point, in advance of said selected stopping point, at which deceleration must be initiated, is' reached before the elevator attains the maximum operating generator for supplying power to said motor,.;and means for controlling the voltage ofs'aid generator to accelerate and decelerate said; motor and to cause said motor to attartainisubstantially a predetermined operating till speed when passing said decelerating point, either on acceleration or deceleration, said control means comprising switching means to increase the voltage of said generator to accelerate said motor, additional switching meanslto decrease the voltage of said generator to decelerate said motor, and regulatingtmeans effective, during acceleration to said; predetermined speed, to increase the voltage of said generator to a value in excess ofuthat required to cause said motor to operate continuously at said predetermined speed 17.1 11 ,an elevator system of the type in :awhich ithe distance between certain selected starting and stopping points is such that the decelerating point 1n advance of said selectedgstopping point, at which deceleration voltage of said generator to accelerate said motor, additional switching means to decrease the voltage of said generator to decelerate said motor, and regulating means efiective, during deceleration to said predetermined speed, to decrease the voltage of said generator to a value lower than the value required to cause said motor to operate continuously at said predetermined speed.

18. In an elevator control system, an elevator operable in a hatchway between a plurality of stopping points, a motor therefor, means defining a point in advance of each of said stopping points at which deceleration from a-predetermined speed must be initiated in order that the elevator may be stopped at that point, and means for either accelerating said elevator to said predetermined speed from zero speed at the next adjacent stopping point or decelerating said elevator to said predetermined speed from a higher speed from a more remote point in said hatchway, including means effective during acceleration for applying voltage to said motor in excess 1 vator operable between two or more adjacent floors, means for defining a point adyacent each of said floors at which deceleration from W ing spaced from that floor by not less than I one-half the distance between floors, and means for accelerating the elevator from zero speed at one of said floors, to said predetermined speed within the distance between said one of said floors and the deceleration point for the next of said floors approached by said elevator, including means for apply ing power to said elevator in excess of that required to attain a continuous running "speed equal to said predetermined speed.

WILLIAM E. IEAMESQJV

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