US2676673A

US2676673A - Elevator control system

Info

Publication number: US2676673A
Application number: US185521A
Authority: US
Inventors: Edgar M Bouton
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1950-09-19
Filing date: 1950-09-19
Publication date: 1954-04-27
Anticipated expiration: 1971-04-27

Description

April 27, 1954 E. M. BOUTON 2,676,673

ELEVATOR CONTROL SYSTEM Filed Sept. 19, 1950 2 Sheets-Sheet 1 Reduction Fi I TGF I M3 M3 (M3 2. UL

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ATTO EY April 27, 1954 E. M. BOUTON 2,676,673

ELEVATOR CONTROL SYSTEM Filed Sept. 19. 1950 2 Sheets-Sheet 2 Fig.2A. Fig.2.

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0 us V WITNESSES: 9 INVENTOR r' Edgar M.B0ufon. BY 7 /w-' I f//// ATT i EY Patented Apr. 27, 1954 UNITED STATES TENT OFFICE ELEVATOR CONTROL SYSTEM Edgar M. Bouton, Nutley, inghouse Electric Corpo Pa., a corporation of P N. J assignor to Westration, East Pittsburgh, ennsylvania 9 Claims. 1

The invention relates to motor control systems and more particularly to a system for controlling .the speed of an elevator car during the retardation thereof prior to stopping.

In elevator systems, particularly those employing a single-speed alternating-current hoisting motor, slowdown r retardation and automatic stopping of the car level with a floor presents a vproblem because stopping is usually initiated at a fixed point in the hatchway with respect to the door, and varying loading conditions of the car result in varying car speeds during the stopping operation. Accordingly, a system adjusted for a certain car load may result in over-shooting or stopping short of floor level with difierent car loads on different directions of car travel.

It is an object of the invention, therefore, to provide an improved control system for elevators in which the elevator car may be slowed and stopped accurately at floor level regardless of the load on the car.

It is a further object of the invention to pro- :vide a control system for a single-speed alterhating-current motor in which the motor may be smoothly decelerated and stopped regardless of [variations in loading conditions on the motor.

Another object of the invention is to provide an improved control system for an electric elevator motor which will bring the car to an accurate stop in accordance with the motor speed during slow-down regardless of the load on the car.

Other advantages will be apparent from the following description and accompanying drawings, in which:

Figure 1 is a schematic illustration of an elevator system in connection with which the present invention may be used;

Fig. 2 is a schematic diagram of a control circuit for the apparatus illustrated in Fig. 1;

Fig. 2A is a key-diagram which indicates the positions of the various relays and their contacts as shown in Fig. 2, and

Fig. 3 is a schematic view of an inductor relay used in connection with the invention.

Referring more particularly to Fig. 1, an elevator driving motor 2 may be of the single-speed alternating-current squirrel-cage type including an armature 3 and a three-phase Y-connected stator having windings a, b and c.

The shaft of armature 3 extends into a reduction gearing 4, which may be of a worm-gear type, the output of which drives a hoisting sheave .6, about which the hoisting rope or cable 8 extends, connecting a suitable counterweight 9 with the elevator car I0.

A service brake l2 includes a brake drum mounted on the motor shaft and has associated with it a brake shoe H, which is spring-pressed [into braking engagement by a spring [5. A brake winding 0, to be energized when the elevator is in operation, is effective to release the brake against the force of spring l5. Normally, winddng C will be deenergized during the stopping operation to permit the application of the brake shoe I i, which will stop the car and hold it in its stopped position.

The motor shaft is provided with a second brake H, the operation of which is variably controlled, as described later, by a winding B reacting on a piston [4 in a fluid system including a second piston I6 which operates to force a brake shoe l 3 against its brake drum which is mounted i011 the motor shaft. Upon deenergization of winding B, the brake IE will be released by spring :26, which was compressed when the brake shoe !8 was applied.

A tachometer generator TG is also mounted on the motor shaft to be driven in accordance with the motor speed, and includes separately excited field winding TGF.

An inductor relay 26 is mounted on the car I!) for movement therewith past a plurality of

plates

22 and 23, of magnetic material, mounted :in the hatchway at fixed points with respect to the various floors to be served. This type of relay is indicated more clearly in Fig. 4, and is of a well known type as shown, for example, in Santini Patent 2,298,174. Briefly, the relay includes a winding I and normally closed contacts DL and UL. The magnetic circuit of the relay is such that even though the winding I is energized, the contacts UL and DL will remain closed until the relay registers with a

plate

22 or 23, at lWhiCh point the magnetic circuit is completed by such plates to open the respective contacts DL :or UL. For example, as shown in Fig. 4, the posirtion of the relay indicates that the car is stopped accurately at floor level, at which point both

plates

22 and 23 are efiective to open the contacts UL and DL, respectively. However, upon movement of the relay with respect to the plates, suficient to clear the relay from the magnetic influence of the plates, the contacts DL and UL will close. In other words, if the car and its relay move upward, as. indicated by the arrow in Fig. 3, a relatively small movement will cause the contact DL to close, and the converse is true for contact UL for downward car movement.

The windings a, b and c of the hoisting motor 2 are energized from a three-phase alternatingcurrent supply including leads LI, L2 and L3.

The energization of the motor is primarily con trolled by the contacts M3, and the direction oi rotation of the motor armature is controlled by the contacts U2 and D2 which are effective to reverse the connections to the motor windings a and b.

An iron core reactor 30 is connected in ser es with the lead L2 and is shunted by a circuit including normally open contact VI. The reactor 30 is of the saturable type, including a control winding A which is energized as hereinafter described.

The starting and stopping of the elevator car is controlled. by the circuit shown in 2. Referring particularly to the lower portion of the diagram, the alternating-current leads Li L2 constitute the input to a full-wave rectifier 36, which may be a bridge of copper oxide rectifiers, and the output of the rectifier is connected to provide positive lead I(+) and a negative lead II(- across which the control relay windings are connected.

There are many conventional types of elevator starting and stopping circuits which may be employed, but as a relatively simple example, it will be assumed that the car will e started and its stopping initiated by a car switch CS mounted in the elevator car. Up direction switch U and down direction switch D are provided to control the direction of rotation of the elevator motor 2 depending upon the direction of movement of the car switch handle, and the stopping of the car after the car switch handle ha the been centered will be controlled by the inductor relay 2%; as it passes a plate 22 or a plate depending upon the direction of car movement, to open respectively its contacts UL or DL.

As an assumed operation, with the elevator car standing at a floor and with its door open, if the operator desires to travel to a higher door, he will first close the door. This will complete the circuit through the door interlocks and the winding of relay DR, assuming all the other door contacts or" the installation are closed. Winding of relay DR will then close its contacts D'Rl effecting a connection between the positive lead I+ to the movable contact of the car switch C'S When the operator moves the car switch handle in a counter-clockwise direction, for upward car movement, contact 38 will be engaged completing a circuit through the up direction switch U, closed contact Di and the car running relay lx l.

Relay U will open its contact Ui in the circuit of the clown direction switch D to prevent energization thereof, and will close its contacts U2 in the motor leads Li and L2, which will permit appropriate rotation of the motor for the up direction.

Relay M will close its contacts M3 in the leads Ll, L2 and L3 to complete the circuit for the motor and at the same time will close contacts M2 to energize the winding C or" service 2, to release the brake, contacts U3 being already closed. The car will now move in the up direction, but at a relatively low speed because of the reactor 39 in lead L2 of the motor which inter poses a relatively high impedance and results in a reduction of motor torque to substantially its single phase characteristics.

Further movement of the car switch handle in the counter-clockwise direction will bring the car up to normal speed. Contact it is engaged by the car switch to energize relay V, contacts DB2 having already been closed upon energization of relay DR when the door interlock circuit was completed.

Relay V will close its contacts VI in the shunt circuit around the reactor 3% which restores com-- piste energization of the motor lead L2 and brings the motor up to synchronous speed. It will also open its contact V2, which controls the one tion of the slow-down brake coil B as hereinafter described, and it will open contacts V to clean ergize the coil I of the inductor relay. Contacts V l will also be opened for a purpose to be described.

Assuming that the car is now traveling up at full speed, and a stop is intended, the operator centers the car-switch CS thereby breaking the circuit to

contacts

38 and 46. Qpeni cuit at 40 deenergizes high-speed relay V, results in (1) opening VI which renders reactor to effective to reduce motor energization, (2) closes V3 to energize inductor winding 1, and (3) closes V4 to complete a holding circuit for direction switch U and running relay l l through closed inductor contacts UL.

Disregarding for the moment the of brake coil B and the bias coil A of the 1 the car will proceed until a plate 22 adjacent to the desired landing becomes effective to open the contacts UL. Contacts UL when open will deem ergize the up direction switch U which will open the contacts U3 in the circuit of coil C oi the service brake l2 and permit application of the brake under the influence of its operating spring to stop the car and hold it in stopped posi on. Contacts U2 in the motor winding leads will re open and relay M being deenergized along "h switch U, contacts M3 in the motor leads will open, completely disconnecting the motor from the source of supply.

It is contemplated that during slow-down the brake H actuated by hydraulically applied pres sure will be applied to assist in the slow-down operation by absorbing the stored energy in the system. The actuation of brake ii is eil'eeted by coil B in a circuit shown in the upper portion of Fig. 2. The circuit 44 includes series connected iron-core reactors it and 48, a full-wave rectifier bridge 50, and the contact V2 wl on closed when relay V dropped. The output of the bridge 55 includes windings 52 and 55, connected in opposition, ior the reactors B8 and respectively, and th brake coil B.

The impedance of reactors it and it is normally such that brake coil B would not be effectively energized, but such impedance may be reduced by the biasing coils $0 and. 622 for these reactors, which coils are also connected in opposition. The energization of biasing coils 8t and 62 is controlled in the following manner.

At the point of initiating slow-down (when car switch CS is centered), the tachometer generator T6 is operating at substantially full with its field TGF connected across the direct current leads 1+ and II-. Assuming that at this time, with the car travelling up, the right hand output terminal of TG is positive, contact U4 being closed, the full output of TG is impressed on the biasing coils fill and 62 through a circuit including a one-way rectifier 66, thereby decreasing the impedance of reactors i3 and 48 to a minimum, and permitting maximum energization of the brake coil B.

Coil B then operates, through pistons 14 and i6 and the fluid system therebetween, to apply brake shoe l8 to its drum to slow the elevator, in addition to the retarding effect of reactor 30 in lead L2, to further overcome the inertia of the system.

As the elevator speed decreases, the output of TG also decreases until its voltage is balanced against an opposing voltage, or pattern voltage, from the voltage divider, the tap R being preferably so set that such balance occurs at full speed of the elevator, but, of course, other speeds may be chosen as desired depending upon the operation required. When the two voltages are equal, no current will flow in the biasing coils 60 and 62, thereby rendering the impedance of reactors 45 and 48 of maximum value, and hence, a minimum energization of brake coil B. Accordingly, brake H initially has a maximum retarding eifect which decreases as the elevator speed decreases to a minimum retarding action at the 10% speed point.

During the slow-down of the car to the 10% optimum, biasing coil A of reactor at has been substantially deenergized because the positive output of TG has been blocked by a rectifier or valve 68. Accordingly, coil A has had no effect on the high impedance of reactor 35, maintaining a slow-speed energization of the motor 2.

If the elevator speed tends to fall below the 10% optimum because of load on the car, the output of TG further decreases to a point where the voltage divider component will predominate, whereupon the direction of current fiow through the armature of TG reverses. This will not aifect the biasing coils EU and 52 because of the rectifier- 56, but it will energize the winding A of reactor 32) in accordance with the output of 'I'G which will have the effect of reducing the impedance of reactor 30, causing an increase in motor torque to tend to bring the motor speed back to the 10% value. The motor will then arrive at a speed where the torque equals the load on the car, or at least be sufiicient to maintain the desired landing speed without regard to the load on the car.

At a higher load, the speed of the car and hence the output of TG would further decrease, thereby increasing the energizati-on of bias coil A, which further decreases the impedance of reactor 30, which in turn provides an increased motor torque to take care of the higher load.

With the apparatus and system disclosed, an automatic landing system for an elevator has been provided which is substantially independent of variations in loading conditions on the car over a rather wide range. By reason of the reactor 30 and its biasing winding, effective slowdown speed is readily obtained, and the stopping action is facilitated by the auxiliary hydraulic brake H which provides a smooth braking torque applied at a maximum force upon initiation of slow-down and gradually decreases as the car slows to a desired speed, the rate of decrease depending upon the speed of the car which, of course, is a function of the load on the car.

As previously indicated, although the elevator control system is shown as a relatively simple car-switch start and inductor-relay stop arrangement, quite obviously the invention may be applied to automatic push-button systems of various known types for passenger and freight elevators operating at speeds up to 250 or 300 feet per minute in which smooth retardation and accurate stops at floor level are desired factors.

I claim as my invention:

1. In an elevator system including an elevator car for serving a plurality of floors, a hoisting motor for said car having a brake for stopping the car at a floor and means for controlling said motor to start said car and to initiate retarda tion thereof prior to stopping it at a floor; means for controlling automatically the retardation of said motor including means responsive to the initiation of retardation to decrease the energization of said motor to decrease the speed thereof, and means exerting a variable force in opposition to the torque of said motor for further decreasing the speed thereof to a desired predetermined speed, and means operable at a fixed point in the travel of the car with respect to said floor for deenergizing said motor and applying said brake to stop the car at said floor.

2. In an elevator system including an elevator car for serving a plurality of floors, a hoisting motor for said car having a brake for stopping the car at a floor and means for controlling said motor to start said car and to initiate retardation thereof prior to stopping it at a floor; means for controlling automatically the retardation of said motor including means responsive to the initiation of retardation to decrease the enerlgization of said motor to decrease the speed thereof, means exerting a variable force in opposition to the torque of said motor for further decreasing the speed thereof to a predetermined desired speed, and means for increasing the energization of said motor in response to the speed thereof dropping below said predetermined speed prior to arrival of the car at a fixed point in the travel of said car.

3. In an elevator system including an elevator car for serving a plurality of floors, a hoisting motor for said car having a brake for stopping the car at a floor and means for controlling said motor to start said car and to initiate retardation thereof prior to stopping it at a floor; means for controlling automatically the retardation of said motor including means responsive to the initiation of retardation to decrease the energization of said motor to decrease the speed thereof, means exerting a variable force in opposition to the torque of said motor for further decreasing the speed thereof to a predetermined speed, and means for increasing the energization of said motor a variable amount in response to the speed thereof dropping to said predetermined speed prior to the arrival of the car at a fixed point in the travel of said car, said variable amount of increase in energization depending upon the difference between said speeds.

4. In an elevator system comprising an elevator car, an alternating current hoisting motor therefor having a brake to stop the motor and a control system for said motor to start the car and initiate retardation thereof prior to making a stop at a floor; means for automatically controlling the retardation of said car including means responsive to said initiation of retardation to increase the impedance of the energizing circuit of said motor to decrease the speed thereof, an

electrically operated brake for said motor, and means responsive to said initiation of retardation to actuate said brake to exert a force on said motor proportional to the speed thereof to further decrease the speed of the motor until a desired predetermined low speed is attained, and means operable at a fixed point in the travel of the car with respect to said floor for deenergizing said motor and applying said brake to stop said car level with said floor.

5. In an elevator system comprising an elevator car, an alternatin current hoisting motor therefor having a brake to stop the motor and a control system for said motor to start the car aevae're and initiate retardation thereof prior to making a stop at a floor; means for automatically controlling the retardation of said car including means responsive to said initiation of retardation to increase th impedance of the energizing circuit of said motor to decrease the speed thereof, an electrically operated brake for said motor, and means responsive to said initiation of retardation to actuate said brake to exert a braking force on said motor proportional to the speed thereof, said last-named means including means responsive to the speed of said motor for generating a control voltage for aiiecting the degree of energization of said brake.

6. In an elevator system comprising an elevator car, an alternating current hoisting motor therefor having a brake to stop the motor and a control system for said motor to start the car and initiate retardation thereof prior to making a stop at a floor; means for automatically controlling the retardation of said car including means responsive to said initiation of retardation to increase the impedance of the energizing circuit of said motor to decrease the speed thereof, an electrically operated brake for said motor, means responsive to said initiation of retardation to actuate said brake to exert a force on said motor proportional to the speed thereof to further decrease the speed of the motor until a desired predetermined speed is attained, and means responsiv to a speed below said predetermined low speed for decreasing the impedance of the energizing circuit of said motor by an amount prop-ortional to the difference between said speeds.

'7. In an elevator system including an elevator car and an alternating current induction motor therefor having an energizing circuit, means for decreasing the speed of said motor to a desired low speed substantially below synchronous speed including an electrically operated brake for the motor, a variable reactor for varying the impedance of said motor circuit, means for generating an electrical potential proportional to t e speed. of said motor, means for establishing a pattern potential corresponding to said desired low speed, and means responsive to a comparison of said potentials for varying the energization of said brake and for varying the impedance of said reactor to maintain said desired low speed.

8. In an elevator system including an elevator car and an alternating current hoisting motor having an energizing circuit, means for starting said motor, means for controlling the speed of said motor to bring the car substantially level with a floor comprising means for varying the impedance of the motor energizing circuit to vary the speed of the motor, an electrically operated brake for retarding said motor, andmeans for applying it with a force which is a function of the motor speed, means for generating an electrical potential proportional to the speed of said motor, means for establishing a pattern potential corresponding to a desired low speed of said car, means responsive to a comparison of said potentials for decreasing the value of impedance when the speed of the motor falls below said pattern potential and for increasing the value of said impedance when the motor speed exceeds said pattern potential.

In an elevator system comprising elevator car, a hoisting motor therefor having a brake to stop the motor and a control system for said motor to start the car and control the stopping thereof level with a selected floor; means for initiating the retardation of said for stopping at such floor including means responsive thereto to decrease the energization of said motor to the speed thereof, a second brake for motor and means responsive to said initia" tion of retardation for ctuating it to exert a braking force proportional to the speed of said motor to further decrease the speed thereof to desired predetermined speed, means responsive to a difference between the actual. motor speed and said desired speed for varying tie energization of said motor toattain such despeed, and means operable at a fixed point the travel of said car to deenergize said motor and apply said first mentioned brake to stop the car at said floor.

References Cited in the file of this patent UNITED STATES PATENTS