US2557179A

US2557179A - Automatic elevator system

Info

Publication number: US2557179A
Application number: US107688A
Authority: US
Inventors: Walter S Fish; Rawley D Mccoy
Original assignee: SERVO CONTROL Co Inc
Current assignee: SERVO CONTROL Co Inc; SERVO CONTROL COMPANY Inc
Priority date: 1949-07-30
Filing date: 1949-07-30
Publication date: 1951-06-19
Anticipated expiration: 1968-06-19

Description

June 19, 1951 w. s. FISH ETAL AUTOMATIC ELEvAToR SYSTEM 3 Sheets-Sheet 1 Filed July 30. 1949 M WN INVENTORS WHL vE/P s. F/s Awa/.Er o. M Ccc'y/ BY WATTORNE June 19, 1951 w s. FISH ErAL 2,557,179 AUTOMATIC ELEVATOR SYSTEM Filed July .'50, 1949 3 Sheets-Sheet 2 fig.

E 6 i TZ/FATTORNEYQM faz 706 03 fra INVENTORS A 75%? S. F/Sf/ 5V /V/CCO Y /fATTORNE June I9, 1951 w. s. FISH ETAL AUTOMATIC ELEvAToR SYSTEM 3 Sheets-Sheet 3 Filed July 30, 1949 HYDRUL /C 8005 TER iff Ptenred June 19, 1951 2,557,179 AUTOMATIC ELEVATOR SYSTEM Walter S. Fish, Pelham,

Bronxville, N. Y Company, Inc.,

assignors to Servo a corporation of New York and Rawley D.

Control Application July 30, 1949, Serial No. 107,688 21 Claims. (Cl. IS7-29) This invention relates to an improved and simplified automatic elevator control system in which many of the complex relays heretofore employed are eliminated by a system employing balanced potentials or signals based upon a comparison of voltages representing each oor level with a voltage variable with the car level.

A further improvement is the use or adaptation of a hydraulic valve and a self-locking hydraulic motor to motivate the elevator car. In this system, the control is effected by controlling the stroke of a constantly driven pump, so that a variable supply is delivered to a reversible motor connected to the elevator cables. Such a system is self-locking, light, and of maximum reliability.

The electric controls operate on the principle of having a signal generating means which produces a definite signal or voltage representing each floor level and which is matched against a variable signal or voltage producing means turned or positioned by the elevator car, so that the elevator car is always moved to a position at which these two signals are matched before corning to rest, and such position is at the floor level signaled by one of the call buttons. Thus, there is produced an elevator system which may be fully automatic or semi-automatic and which is self-levelling with a minimum number of interlocking relays and parts. This system also automatically provides for uniform rapid acceleration of the car since the initial signal delivered is proportional to the difference between the oor levels at which the car is positioned at the time and to which it is signaled, subject, of course, to a safe maximum speed, which is controlled by an additional signal generator producing a countervoltage proportional to elevator speed. For smooth decelerating, an additional signal generator responsive to the rate deceleration may be provided to limit this rate Within safe and comfortable limits.

Other features will be apparent from the following description and claims.

Referring to the drawings in which a preferred embodiment of the invention is shown,

Fig. 1 is a simplified wiring diagram of the call button and step switch control circuits;

Fig. 2 shows an additional portion of the wiring diagram showing a third unit of the step switch and the balanced potentiometer system which produces a net signal which is fed to the amplier and servomotor;

Fig. 3 is a wiring diagram of the amplifier and counter-signal producing means to which the net signal is fed, and a diagrammatic representation of the servomotor system which actuates the elevator car; and

Fig. 4 is a wiring diagram showing the apparatus of Figs. 2 and 3 modified so that an alternating current power source is employed to energize the apparatus which produces the control signals,

In the diagram of Fig. 1 there is shown our system applied to a five-story building. One set of call buttons is shown, but it will be understood that the same system may be applied to any number of floors desired and a duplicate set of up and down call buttons will be provided on the cars as well as at each door.

Referring now to Fig. l, call buttons l0, Il, I2, I3, I4, I5, I6 and |'l are located on the various floors and' serve to produce the fifth floor down, fourth floor up, third floor up, second floor up, fourth floor down, third floor down, second floor down and the first floor up signals respectively. Identical relays 20, 2|, 22, 23, 24, 25, 29 and 27 are respectively operated by means of call buttons IIJ-Il and battery 28. Each of these relays is of the hold-in type so that after it is operated it will remain operated until released by a control circuit which is described hereinafter. Indicating lights 29 are preferably provided in parallel with the windings of relays 2U-21 to indicate whenthese relays are operated.

Three step switch sections 3|, 32 and 33 are mounted on a common shaft 35 and the shaft 35 is actuated by means of pawl and ratchet mechanism 3l. When solenoid 39 is energized it pulls armature 4| and pawl 42 down, thereby opening contacts 44 and de-energizing solenoid 39 so that spring 46 restores armature 4| and pawl 42 and causes ratchet wheel 48 to rotate one notch. This rotates shaft 35 and causes the rotors of switches 3|, 32 and 33 to advance one position.

Switch 49 is momentarily closed each time the elevator door is closed. This switch 49 may be located in the elevator cab or a switch may be provided for each floor. For the latter arrangement, the switches for the various floors are connected in parallel.

The windings of relays 50, 5|, 52, 53, 54, 55, 59 and 51 are energized by switch 49 and battery 53 through step switch 32, and these relays serve to release relays 20-21 respectively.

The winding of relay 59 is connected in series with each of the windings of relays 59-51 so that the winding of relay 59 is also energized by means of switch 49.

Fig. 2 shows a bridge circuit which is employed to produce the signals which control the movement of the elevator cab.

Potentiometers 6| and 62 are connected across battery 63. Potentiometer 6| has five taps and each tap provides a reference voltage which designates one fioor.

For example, the fifth floor is represented by tap 64 which is 85 volts above ground, the fourth fioor by tap 65 which is 65 volts above ground. the third oor by tap 66 which is 45 volts above ground, the second floor by tap 61 which is 25 volts above ground, and the rst oorby tap 68 which is three volts above ground potential. After the taps 64--68 are adjusted to supply the various voltages required, no further adjustment is required.

The rotor of potentiometer 62 is rotated by shaft 10 which in turn is rotated by means of a mechanical linkage connected to the elevator car (Fig. 3). When the elevator car is at the first floor, the rotor of potentiometer 62 is at the same potential as tap 68 on potentiometer 6|. When the elevator car is at the second floor the rotor of potentiometer 6| is at the same potential as tap 61 on potentiometer 6|, and so on to the fifth floor, where the rotor of potentiometer 6| is at the same potential as tap 64.

'Ihe rotor of potentiometer 62 is connected to one side of resistor 12 and the taps of potentiometer 6| are selectively connected by means of switch 33 to the other side of resistor 12.

The voltage across resistor 12 is applied over

conductors

16 and 11 to a servo amplifier 14 (Fig. 3) which serves to actuate the elevator car moving mechanism. As will be explained hereinafter, amplifier 14 and the car moving mechanism constitute a servo apparatus which actuates the armature of potentiometer 62 so that potentiometer 62 is caused to produce a voltage equal to the voltage on the tap of potentiometer 6| asselected by step switch section 33.

Referring now to Fig. 3, the control signal across

leads

16 and 11 is applied to the servo amplifier input resistor 19 through an R.C. network comprising resistor 80 and condenser 82, a linear potentiometer 8| and resistor 83.

The direct current signal across resistor 19 is converted to an alternating current signal by means of vibrator 85 and transformer 81 in a conventional manner. The winding of vibrator `85 is energized by an alternating current from source 89 which may be a 60 cycle power line.

The signal induced in the secondary of transformer 81 is amplified by power amplifier 14 and applied to field winding 9| of a two-phase A. C. motor 92 through transformer 94. 'Ihe other field Winding 96 of motor 92 is separately excited from source 98 which is of the same frequency as source 89 and may be a 60 cycle power line.

While motor 92 might be used directly to raise and lower the elevator car or to control an electric motor driven system, I prefer to interpose a hydraulic'motor system in order to achieve maximum safety. Accordingly, motor 92 is coupled through gears to gear |02 which actuates gear |03 and arm |04 about pivot |05. Stops |06 are provided to limit the movement of gear |03 and arm |04. The force applied to hydraulic booster |06 is increased by booster |06 and applied to a variable delivery hydraulic valve and pump |08. When arm |09 of the hydraulic valve and pump |08 is moved off center in one direction, the hydraulic valve and pump |08 permits the hydraulic fiuid to iiow clockwise through the hydraulic valve and pump |06, pipes and hydraulic motor ||3; and when arm |09 is moved oli center in the other direction, the hydraulic valve and pump |08 permits the hydraulic fluid to flow counterclockwise through the hydraulic system. When arm |09 is at its central or neutral position, the hydraulic fluid is not permitted to circulate and the hydraulic motor ||3 is locked.

Constant speed motor I5 serves to actuate the hydraulic pump of unit |08, and motor ||5 is preferably energized with three-phase alternating current.

Hydraulic motor ||3 and pump |08 may be a variable delivery reversible, self-locking type such as shown in 'the patent to T. B. Doe, 2,177,098, dated October 24, 1939.

The rotary output of hydraulic motor ||3 is applied to reduction gearing ||1 which actuates pulley ||9 which in turn moves the elevator car |20 up and down by means of cables |22.

Tachometer |30 is actuated by the shaft of motor 92 and serves to produce a D. C. voltage which is applied through potentiometer |3|, resistor |32 and condenser |33 to resistor 83 in the same polarity as the D. C. signal applied to the amplifier input resistor 19 through resistor c 83 by means of

leads

16 and 11.

When the elevator car |20 is moved from one floor to another, motor 92 first rotates until gear |03 strikes one of the stops |06 and later, due to the action of

potentiometers

62 and 8|, as explained hereinafter, motor 92 is caused to rotate in the opposite direction until gear |03 is centered between stops |06. Thus, each time motor 92 rotates, a D. C. signal is produced by tachometer |30 which aidsv the main control signal produced across leads 16 and 11. In this manner the rate of acceleration and the rate of deceleration of elevator car |20 is controlled, the amount of `control being determined by the voltage produced by tachometer |30, the setting of potentiometer |3| and the time constant of resistor |32 and condenser |33, so as to limit the rate within safe andcomfortable limits.

The rotor of potentiometer 8|; is actuated by the shaft of motor 92 through gears |00, gears |35 and shaft |31. When a signal is applied to amplifier 14 over

leads

16 and 11, motor 92 is caused to rotate first in one direction and this causes the rotor of potentiometer 8| to be olset from its center position to produce a voltage which is applied to the amplifier input resistor 19 in opposite polarity to the main control signal across leads 16 and 11. When motor 92 is caused to rotate in the other direction and is restored to its initial position, the rotor of potentiometer 8| is slowly restored to the midpoint of the resistance element.

Thus, two auxiliary signals are algebraically added to the main control signal supplied by

leads

16 and 11. The rst of these auxiliary signals is produced by tachometer |30 and the magnitude of this auxiliary signal is proportional to the acceleration or deceleration of the elevator car |20.A The second auxiliary signal is produced by potentiometer 8| and the magnitudev of this signal is proportional to the car speed.

The system operates as follows: Assuming the` if the fourth floor up call button is pressed (for example), the winding of relay 2| will be energized by current flowing from battery 28 through button the winding of relay 2|, t e normally closed contacts of relay 5|, and the winding of relay 59 to ground, thus operating the armatures of relays 2| and 59. The connection between the armature and front contact of relay 2| serves to maintain relays 2| and 59 in an operated condition after button is released. 'I'he back contact of relay 2|, which is connected to contact 39 on switch 3|, is now de-energized.

Assuming that the second and third floors have no up calls, contacts I4| and |43 will be energized by battery 28 and the released armatures of

relays

22 and 23 respectively. The armature of relay 21 is operated since the car is at the first floor and, hence, contacts |45 and |46 of switch 3| are de-energized. When the elevator car doors are closed by the operator, switch 49 will close momentarily and energize the winding of relay 51 through contacts |48 and |49 of switch 32. Thus, the armature of relay 51 operates momentarily and de-energizes the winding of relay 21 so that the armature of relay 21 is released.

Solenoid 39 is now energized by battery 28 through the armature and back contact of relay 21, contacts |45 and |46 of switch 3|, contacts 44, and the contacts of relay 59. lThe stepping mechanism will now step shaft 35 around to move the rotors of switches 3|, 32 and 33 from contact to contact until a de-energized contact on switch 3| is reached. For the example under consideration, contact |39 is the first de-energized contact on switch 3|. Since stepping switches are available which operate as fast as one step per one-tenth second, the rotor of step switch 3| can reach contact 39 before the car door is completely closed.

When the rotor of switch 3| reaches Contact |39 the stepping mechanism is stopped since the back contact of relay 2| is not in contact with the operated armature of relay 2| and the circuit between solenoid 39 and battery 28 is open at that point.

Thus, the armatures of switches 3|, 32 and 33 stop on contacts |39, |50 and |52 respectively.

The rotor of switch 33 now connects tap 65 on potentiometer 6| to lead 11. Since tap 65 is at a potential of 65 volts above ground and since the elevator car is at the first iioor so that the rotor of potentiometer 62 is at a potential of 3 volts above ground, a control signal of approximately 62 volts is applied across resistor 12 s0 that lead 11 is of positive polarity with respect to lead 16.

This control signal is applied to vibrator 85 and transformer 81 through delay network 80, 82, potentiometer 8| and resistor 83. While the elevator car |20 is still at rest at the first floor, the rotor of potentiometer 8| is at the midpoint of the resistance element of the potentiometer, no voltage is produced by tachometer' |30, and the main control signal across leads 16 and 11 is not affected by the auxiliary signal circuits.

The main control signal is converted to an A. C. signal by vibrator 85 and transformer 81, and the A. C. signal is amplified by power amplifier 14 and applied to field winding 9| of motor 92 to cause the shaft of motor 92 to rotate in a counter-clockwise direction until gear |03 strikes stop |06 at which timel the shaft of motor 92 stops rotating and remains stationary until it is restored to its initial position as explained hereinafter.

' ably controlled by the 'I'his counter-clockwise rotation of motor 32' causes control arms |04 and |09 to move to the left, thereby activating hydraulic motor ||3 and causing the elevator car |20 to be raised.

The counter-clockwise rotation of motor 92 also causes the rotor of potentiometer 8| to rotate in a clockwise direction to a position near the upper end of the resistance element o1' potentiometer 8|. In this manner a counter-signal is introduced in series with lead 16 which opposes the main control signal conveyed by

leads

16 and 11. For the embodiment of the invention disclosed herein, the maximum opposing voltage may be 12 volts, for example, so that the main control signal is thereby reduced to volts.

The rotation of motor 92 also causes tachometer 130 to produce a D. C. voltage across resistor 83 in series with lead 11, which increases the control signal conveyed by

leads

16 and 11 by a small amount. 'I'he primary purpose of tachometer |30' is to control the rate of deceleration as discussed hereinafter. The rate of acceleration is prefer- R.C. delay network 80, 82 across

lines

16 and 11 which retards the rate of increase of the control signal.

Thus, the control signal applied to amplifier 14 is initially retarded by the delay network 80, 82

. and reduced by the auxiliary signal produced by potentiometer 8| and increased slightly by the auxiliary signal produced by tachometer |30 so that the initial A. C. signal produced by amplifier 14 and consequently the speed of motor 92 and the acceleration of elevator car |20 are determined by the algebraic sum of the three signals. When gear |03 strikes stop |06, the auxiliary signal produced by tachometer |30 begins to decrease exponentially at a rate dependent upon the time-constant of resistor |32 and condenser |33. The decrease of this auxiliary signal is preferably fairly rapid.

As the elevator car |20 rises, the rotor of potentiometer 62 is rotated pulley |26, gears |28 and shaft 10 so that the voltage applied to lead 16 approaches the voltage applied to lead 11. When the voltage between leads 16 and 11 is reduced to 12 volts by the rise of elevator car |20, the net control signal applied to amplifier 14 across resistor 19 will be zero since potentiometer 8| produces a counter-signal of 12 volts and since the auxiliary signal produced by tachometer |30 will have decayed to zero by this time. The elevator car |20 will still be rising at its maximum rate of speed at this time. However, at the next instant, the signal applied to amplifier 14 across resistor 19 will reverse in polarity because the counter-signal from potentiometer 8| will exceed the signal across leads 16 and 11. An A. C. signal which differs in phase from the initial signal by is now produced by amplifier 14 and applied to field winding 9| of motor 92 so that motor 92 rotates in a clockwise direction and slowly closes valve |08 so as to stop motor ||3 and the elevator car |20.

The speed of elevator car |20 will decrease slowly as the rotor of potentiometer 8| is restored to its central position. When the rotor of potentiometer 8| is completely restored to its central position, the elevator cab |20 will stop at the fourth floor, since for this condition no signal is applied to amplifier 14 and no hydraulic fluid will flow through valve |08 and motor ||3.

During the deceleration period tachometer |30 will generate a signal which opposes the deceleration. The amount of deceleration is determined by the time-constant of resistor |32 and conby means of cable |24,

If the load in the elevator car |20 is changed by a large amount sol that the car is raised or lowered a small distance, the rotor of potentiometer 62 will rotate a corresponding amount, and a. signal will be applied to amplifier 14 which will cause motor 92 to drive off center and then back to center, thereby re-leveling the elevator car.

The operation of the hydraulic motor ||3 is controlled by the displacement of relatively incompressible hydraulic fluid. When hydraulic valve |08 is in its central or neutral position, the hydraulic fluid can not flow through lines and the hydraulic motor |3 is locked. T hus no power is required to hold the elevator car |20 at rest.

After the elevator car door is opened and closed by the operator, switch 49 serves to momentarily energize the winding of relay 5| through the circuit from battery 58, through switch 49, the rotor of switch 32, contact |50, the winding of relay 5|, and the winding of relay 59 to ground. When the armature of relay 5| operates, the circuit which energizes the winding of relay 2| is opened and the amature of relay 2| is restored to the back contact of relay 2|. Since the rotor of switch 3| is at contact |39, solenoid 39 is connected to battery 28 through the back contact and released armature of relay 2|, contact |39, the rotor of switch 3|, armature 4|, and contacts 44. If one or more of the other call buttons have been pressed, relay 59 will be operated and the stepping mechanism 31 will step until the armature of switch 3| encounters a contact which is de-energized.

If the fifth floor down call button |0 has been pressed the apparatus will function in a manner analogous to that described above to raise the elevator car |20.

If one of the lower call buttons has been pressed, the bridge circuit formed by potentiometers 6| and 62 and switch'33 will produce a control signal which causes lead 16 to be of positive polarity with respect to lead 11. This control signal will cause motor 92 to rotate in a clockwise direction, thereby causing the hydraulic system to lower the elevator cab 20.

Preferably a mechanical brake should be provided 'in order to hold the elevator car |20 at rest in case of electric power failure or hydraulic failure. Such a brake may be one of the types already known in the elevator art and it is not disclosed herein since it is not part of my invention.

Fig. 4 shows the apparatus of Figs. 2 and 3 modified so that an alternating current power source 98 is employed to energize the apparatus which produces the control signals.

A pair of step switch sections |60 and |62 are actuated by the shaft 35 which, as explained above with reference to Fig. 1, is actuated by means of the call buttons located on the various floors. The rotors of the switches |60 and |62 serve to selectively connect the stator windings of two of the Selsyns |64|13 across an alternating current source of potential 98 which may be a 60-cycle power line.

The rotors of the two groups of Selsyns, |64- |68 and |69-|13, are respectively positioned to produce signals having magnitudes which increase by increments and represent the oor levels to 5, and then the rotors are locked in these positions and no further adjustment is required.

The two Selsyns |15 and |16 serve to produce alternating current signals having amplitudes proportional to the distance which the elevator car is to be moved.

The rotor windingsof Selsyn |15 are connected across the locked rotor windings of Selsyns |64- |68 and the rotor windings of Selsyn |16 are connected across the locked rotor windings of Selsyns |69|13.

The rotor of 4Selsyn |115 is turned through 1'15 degrees as the elevator car moves from the first to the fifth floor, the rotor being actuated by means of the shaft 10 which is connected to the elevator car by the mechanical linkage described above with reference to Fig. 3. The rotor of the Selsyn |16 is connected to the shaft 10 by gears |18 which cause the rotor of Selsyn |16 to make 15 revolutions for each 175 degree rotation of the Selsyn |15.

Thus, Selsyn |15 serves to produce a coarse control signal having an amplitude proportional to the distance the elevator car is to be moved as determined by the position of the rotor of Selsyn |15 and by the signal produced by Selsyns |64 to |68. This coarse control signal is employed to control the movement of the elevator car until the car is almost at the floor level to which it has been called. Then the fine control signal produced across the stator winding of Selsyn |16 is employed to control the movement of the elevator car until the car stops at the floor level to which it has been called. The amplitude of the fine control signal is determined by the position of the rotor of Selsyn |16 and by the signal produced by Selsyns |69 to |13. i

The coarse control signal produced across the stator winding of Selsyn |15 is applied to a diode rectifier tube through an R.C. network |82, |84, and the direct current voltage developed across the R.C. network |82, |84 is applied between the grid and cathode of an amplifier tube Cathode bias for tube |86 is obtained by means of resistors |88 and |90 connected across battery |92. Thus, when the signal developed across the R.C. network |82, |84 exceeds the cathode bias developed across resistor |88, the amplifier tube |86 draws current from battery |92 through the winding of relay |94, and the armature of relay |94 operates to connect the signal produced by the stator of Selsyn |15 across the primary winding of the amplifier input transformer 81. This signal is amplified by amplifier 14 which serves to energize the winding 9| of motor 92. The winding 96 of twophase motor 92 is energized from the source 98 through a condenser |95 which serves to produce the necessary phase shift between the respective signals applied to the windings 9| and 99.

The rotation of the shaft of motor 92 serves to actuate the hydraulic system which in turn serves to move the elevator car as explained above with reference to Fig. 3.

As the elevator car approaches the i'loor to which it has been called, the magnitude of the voltage across resistor |82 decreases, and when the cathode bias across resistor |88 exceeds the voltage across resistor |82, tube |86 ceases to asumir draw current and the winding of reiay |94 is deenergized. If further control over the operation of relay |94 is desired, a condenser 20|! may be provided across the relay winding.

When the armature of relay |94 releases, the coarse control signal is disconnected from the amplier 14 and the line control signal produced across the stator of Selsyn |16 is applied to the amplifier 14 through a potentiometer '202. The circuit constants are proportioned so that the coarse and ne control signals are of approximately the same amplitude at the instant when the armature of relay |94 releases.

The elevator car continues to move with decreasing speed towards the floor to which it has been called until no signal is produced across the stator of Selsyn |16 at which instant the elevator car stops at the level of the iloor to which it has been called.

The potentiometer |93 (which corresponds to the potentiometer 8| of Fig. 3) is connected to the source 98 through a transformer |98 and serves to produce a signal between its rotor and grounded center tap which is 180 out of phase with the main control signals produced by Selsyns |15 and |16.

The amplitude of the signal produced by the potentiometer |96 is proportional to the speed of the elevator car, and this signal is employed to partially `counteract the main control signal applied to amplifier 14 as before.

The rotor of potentiometer |96 is initially oliset almost to one end of its resistance element to produce a counter-signal proportional to the speed of the elevator car and then the rotor is slowly restored to the center of the resistance element as the car decelerates and stops at the desired floor level.

In this embodiment of the invention the rates of acceleration and deceleration of the elevator car are controlled by means of an inertia wheel 2M and an electromagnetic damper comprising a copper disc 206 and a magnet 208 which serve to control the acceleration and deceleration of the shaft of motor 92.

It will be apparent that various modifications can be made in the apparatus disclosed herein. For example, electric motive means may be employed instead of the hydraulic motor system. and the resistance element of potentiometer 8| or potentiometer |99 may be made non-linear. If extremely high speed elevator operation is desired, the counter-voltage introduced by the displacement of the rotor of potentiometer 8| or potentiometer 98 may be caused to vary as the square root `of its displacement.

.Since many changes could be made in the above construction and many apparently widely ditlerent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An elevator control system comprising a motor for raising and lowering the elevator car, energizing means for said motor. means for varying the output of said energizing means, said last named means having a movable control arm, a servo system for controlling the position of said arm, a. signal generator connected to the control circuit of said servo system for producing a variable signal having a magnitude proportional to the distance the elevator car is to be moved, and

means for limiting the rates of acceleration and deceleration of the car.

2. An elevator control system comprising a signal source adapted to produce signals which increase by an increment for each iloor level, a variable signal source adapted to produce a second signal variable with the height of the elevator car, means for selectively comparing said first signals with said variable signal and producing control signals proportional to the vector sum of said first and second signals, and means responsive to said control'signals for actuating the elevator car.

3. The apparatus of claim 2 further including means responsive to the speed of the elevator cab for reducing said control voltage an amount proportional to said speed.

4. An elevator control system comprising a signal source adapted to produce a plurality of signals, each signal representing a iioor level and the signals increasing in strength or amplitude by an increment for each floor, a variable signal source controlled by the height of the elevator cab for producing an auxiliary signal, call means located on each floor, a step switch actuated by said call means for selectively connecting said iirst signals in series with said auxiliary signal in opposite polarity to produce control signals, and servo means responsive to said control signals for actuating the elevator cari 5. In an elevator control system, a reversible motor for raising and lowering the elevator car, variable energizing means for said motor, a servo system connected to said energizing means for controlling the output thereof, a source of potential, a first resistance connected across said source of potential and having taps representing the various floor levels. which produce signals which increase in magnitude by an increment for each floor level, a second resistance connected across said source of potential, said second resistance having an adjustable tap, means for moving said tap along said resistance in one direction as said motor rotates in one direction and in the other direction as said motor rotates in the other direction, and means connecting said slider and for selectively connecting said taps across an impedance in said servo system to control said servo system and thereby control the rotation of said motor.

6. In an elevator system having signalling means located at the various oors and a motor for raising and lowering the elevator car and a variable energizing circuit for said motor having an input circuit responsive to a control signal, apparatus for producing a control signal comprising a source of potential, a first impedance connected across said source of potential, a movable slider on said first impedance connected to one terminal of said input circuit, means for moving said slider in one direction along said rst impedance as the elevator car is moved in one direction and for moving the slider in the other direction along the impedance as the elevator car is moved in the other direction, a second impedance connected across said source of potential, said second impedance having a plurality of taps thereon, and meansresponsive to said signalling means for selectively connecting predetermined ones of said taps to the other terminal of said input circuit.

7. In an elevator control system, means for producing a first signal having a, magnitude proportional to a predetermined oor level, means for producing a second signal having a magnitude proportional to the height of the elevator car, means for producing a control signal proportional to the diierence in magnitude between said rst and second signals, means for producing an auxiliary signal having a magnitude proportional to the speed of the elevator car and a polarity determined by the direction which the elevator car is moved, a motor for moving the elevator car up and down, variable energizing means for said motor, said energizing means having an input circuit and being adapted to cause said motor to rotate in one direction in response to an input signal of one polarity and in the opposite direction in response to an input signal of the other polarity, and means serially connecting said control and auxiliary signal producing means in opposite polarity across said input circuit.

8. In combination, a reversible motor for raising and lowering an elevator car, variable energizing means for said motor, said energizing means being adapted to cause said motor to rotate in one direction in response to a signal of one polarity and in the opposite direction in response to a signal of the opposite polarity, a bridge circuit for producing a variable control signal having a variable amplitude proportional to the distance and a polarity determined by the direction said elevator car is to be moved, interconnecting means between the output of said bridge circuit and the input of said energizing means, said interconnecting means including an impedance, and means for producing an auxiliary signal across said impedance of opposite polarity to the said control signal, said auxiliary signal having a magnitude proportional to the speed of said motor.

9. In combination, means for raising and lowering an elevator car including a reversible, selflocking hydraulic motor, a circulating system for circulating hydraulic iluid through said motor, said system including a valve adapted to control the quantity and direction 'of circulation of said hydraulic uid, an electric signal source for producing a control signal having a variable amplitude proportional to the distance and a polarity determined'by the direction which said elevator car is to be moved, and means responsive to the control signal produced at the output of said signal source for controlling the position of said valve.

10. In combination, means for raising and lowering an elevator car including a reversible, selfv locking hydraulic motor, a closed circulating system for circulating hydraulic uid through said motor, said system including a valve adapted to control the quantity and direction of circulation of said hydraulic fluid, a servo system for moving said valve, a source of potential, a first resistance connected across said source of potential and having taps representing the various floor levels which produce signals which increase in magnitude by an increment for each floor level, a second resistance connected across said source of potential and having a slider, means responsive to the movement of said elevator car for moving said slider along said resistance in one direction as the elevator car is moved upward and in the other direction as the elevator car is moved downward, means connecting said slider and for selectively connecting said taps across an impedance in said servo system to control said servo system and thereby control the position of said valve.

11. In combination, means for raising and lowering an object including a reversible, self-lock- 12, ing hydraulic motor, means for circulating hydraulic iiuid through said motor, an adjustable control for said circulating means having a neutral position for preventing the circulation of iluid through said motor, said adjustable control being adapted to cause the hydraulic fluid to circulate in one direction through said motor when displaced in a iirst direction and adapted to cause the hydraulic fluid to circulate in the opposite direction through said motor when displaced in a second direction, a bridge circuit for producing a control signal having a. variable amplitude proportional to the distance which said object is to be moved, said signal being of one polarity when the object is to be moved up and of the opposite polarity when the Objectis to be moved down, and servo means responsive to said control signal for actuating said adjustable control.

12. The apparatus of claim 11 further including means responsive to the displacement of said adjustable control for reducing the amplitude of said control signal an amount proportional to the displacement of said adjustable control.

13. The apparatus 'of claim 11 further including means responsive to said servo means for increasing said control signal an amount proportional to the acceleration and the deceleration of said hydraulic motor.

14. In an elevator control system, means for producing a D. C. -signal having a variable magnitude proportional to the distance and a polarity determined by the direction the elevator car is to be moved, means for converting said D. C. sigamplifier actuated thereby, and means for moving the elevator car from the output of said amplifier. y

15. The apparatus of claim 14, wherein said moving means includes a two-phase A. C. motor having one field winding'connected to said A. C. signal and the other iield winding connected to a second'A. C. signal having a xed phase and a frequency equal to the frequency of said A. C. signal. 'i

16. In Ian elevator control system having a motorfor raising and lowering the elevator car and an energizing circuit for said motor controlled by a control signal produced by the signalling means for the elevator car, a signal generator for producing an auxiliary signal proportional to the acceleration and deceleration of said motor, and means interconnecting said signal generator and said energizing circuit for increasing said control signal by an amount proportional to the magnitude of said auxiliary signal.

17. In an elevator control, call buttons for up and down operation for any floor to any other iloor, a step switch set into operation by the pressing of any button, means for stopping said switch upon its reaching a position corresponding to the oor button pressed including means producing a distinctive voltage for that iioor, avariable opposing voltage producing means turned by the elevator which matches said other voltage only when the elevator is at that floor, and a reversible elevator motor controlled by net volthaving a magnitude which varies in accordance with the distance whichthe elevator c ab is to be moved, means for producing a second variable voltage having a magnitude which varies in accordance with the speed of the elevator cab, a motor for raising and lowering the elevator cab, and means responsive to the difference between said rst and second voltages for controlling said motor.

19. In an elevator system having means for signaling the elevator cab, a signal source responsive to said signaling means for selectively producing A. C. signals having amplitudes which vary in accordance with the iloor level to which the elevator cab is signaled, a Selsyn having its rotor connected by a mechanical linkage to the elevator cab and turned by the movement of the cab, one winding of said Selsyn being connected to said signal source, and motive means responsive to the signal produced across the other winding of said Selsyn for raising and lowering the elevator cab.

20. In an elevator system having means for signaling the elevator cab, a signal source responsive to said signaling means for selectively producing A. C. control signals having amplitudes which vary in accordance with the floor level to which the elevator cab is signaled, a Selsyn having its rotor connected by a mechanical linkage to the elevator cab and turned by the movement of the cab, one winding of said Selsyn being connected to said signal source, means for producing an auxiliary A. C. signal having an amplitude which varies in accordance with the speed of the elevator cab, and means responsive to the 8l diilerence between the amplitude of each signal produced across the other winding of said Selsyn and the amplitude of said auxiliary signal for controlling the movement of the4 elevator cab.

21. An elevator control system comprising a signal source adapted to produce signals which increase by an increment for each floor level, a variable signal source adapted to produce a Second signal variable with the height of the elevator car, means for selectively comparing said rst signals with said variable signal and producing control signals proportional to the vector sum of said rst and second signals, means responsive to said control signals for actuating the elevator car lat a speed proportional thereto, and means responsive to the deceleration of the elevator cab for lessening the rate of decrease of said control voltage, thereby limiting the rate of deceleration.

WALTER S. FISH. RAWLEY D. McCOY.

The following references are of record in the le of this patent:

UNrrED STATES PATENTS Number Name Date 1,971,811 Chadbourne Aug. 28, 1934 2,015,799 Hoffman Oct. 1, 1935 2,072,282 Smart et al. Mar. 2. 1937 2,105,598 Hubbard Jan. 18, 1938 2,113,436 Williams, Jr. Apr. 5, 1938 I 2,189,193 Brown Feb. 6, 1940 2,266.240 Nyberg Dec. 16. 1941 2,367,746 Williams, Jr. Jan. 23, 1945