US2361170A - Elevator control system - Google Patents

Description

Oct. 24, 1944. E. M. BOUTON ELEVATOR CONTROL SYSTEM Filed Aug. 6, 1942 INVENTOR [dyvrMBoufo Z Patented Oct. 24, 1944 ELEVATOR CONTROL SYSTEM Edgar M. Bouton, Nutlcy,,N. J ass'ignor toWestinghouse Electric Elevator Company, Jersey City, N. J., a corporation oflllinois Application August 6, 1942, Serial No. 453,768 teams. (01. 187-29) My invention relates to elevator control systems, and moreparticularly, to such systems as are provided with leveling means for causing the cars to stop approximately level with the floors and to maintain such position while they are loading and unloading.

One object of my' invention is to provide for applying such a braking effect to a single speed elevator motor as will hold'the car at a desirable landing speed While it is being'leveled with the floor at which it is being stopped, regardless of theload carried. by the car and its direction of operation. I

A furtherobject is to provide for applying a dragging brake effect to an elevator car having asingle speed motor for reducing the speed of I the car to a desirable landing and leveling speed.

For a better understanding of my invention reference may be had to the accompanying drawing in which:

Figure 1 is a diagrammatic representation (in what is known as the straight line style) of an elevator system embodyingmy invention;

Fig. 1A is a keyrepresentation of the relays embodied in Fig. l, with their coil and contact members disposed in horizontal alignment with their positions in the straight line circuit so that their locations therein may be readily deter mined;

Fig. 2 is a diagrammatic representation of the inductor relay mounted on the elevator car in Fi 1.

The following" is a list of the relays illustrated in the drawing:

=brake v =up direction switch :down direction switch :car running relay :leveling circuit relay =inductor relay 1T first time delay relay 2T =second time delay relay 3T :third time delay relay 4T :fourth time delay relay 5T =fifth time delay relay TG=speed responsive device mechanism I5 connects the shaft 14 with the holding the car at the floor landings.

-stop thereat.

motor IE to secure an appropriate speed for the car when the motor is in operation. An electromechanical brake B is provided for engaging a brake drum BD-on the shaft l4 for stopping and The brake 7 may be the usual electromagnetically released type of brake, such as isprovided with a magnetizing coil Bi and a brake-applying spring B2.

The hoisting motor [6 is illustrated as a three- :phase single-speed alternating current electric motor comprising a stator having windings I8,

I9 and 20 and a rotor ISA. The stator windings may be connected to a suitable alternating 1 current supply represented by the conductors, I,

. II and III by means of a car running'relay M U and aclown direcand an updirection switch tion switch D. I

The I energy for operating the direction switches,-the relay M, and such additional con- :trol apparatus. as is used in the system may be secured from supply conductors L+ and L which may be connected to any suitable source of electrical energy such as arectifier.

Any suitable arrangement may be provided for controlling the direction switches to start and stop the car. However, for the sake of. simplicity I have illustrated a simple car switch CS for starting the car in either direction and for initiating its stopping action at the floors.

Aninductor relay Q. is provided for stopping the car when it arrives at a floor for which the car switch CS has been operated to effect the stopping of the car. The inductor relay Q includes an electro-responsive or energization coil -or core with a down contact member DQ and an upcontact member UQ-mounted. on the car in position to be operated when energized, by the influence of adjacent inductor plates of magnetic material mounted in the hatchway. The plates include an up directionplate UP and a down direction plate DP mounted-on the hatch- Way wall at eachfloor for opening the inductor relay contacts when the car brings the inductor relay opposite the plates at a floor in making a Inductor relays are old anclwell known in the art but further information regarding. them, if desired, may be had from the White and- Hearn Patent 1,884,446 dated October 25, 1932.

A leveling relay L is provided for'energizing therelay Q and for conditioning the control circuits to eiiect the leveling of the car with a landing floor when a stop is made thereat. The leveling relay L is controlled by the car switch JCS. Whenthecar switch is centered for a stop at a floor it energizes the leveling relay L which, in turn, energizes the inductor relay Q to effect the stopping and leveling of the car with the floor. This is effected because during a leveling operation, the inductor relay Q controls the circuits to the up direction switch U and the down direction switch D and the car running relay M 'for cutting off the power to the hoisting motor and applying the brake to stop the car.

In practicing my invention, I provide a control means for causing the brake to be applied with sufficient force to stop the car and then, if the car undershoots or overshoots the floor, to relieve the brake pressure sufficiently to permit the hoisting motor to pull the car through it to a position level with the floor, at a predetermined leveling speed. Furthermore, when the car drifts away from the floor, for any reason, while making a stop thereat, I provide for controlling the brake by the leveling apparatus in a manner to bring the car back level with the floor at a predetermined leveling speed. In other words, I provide a dragging brake so adjusted in response to the speed of the car that it will hold the speed of the car to a predetermined leveling speed when a leveling operation is being made. I

In the present instance it is assumed that the hoisting motor will operate the car at a constant speed of approximately 100 feet per minute, and that the leveling means will cause the car to level into the floor at a speed of approximately 20 feet per minute. However, the system may be designed for any other running or leveling speeds desired Thebrake control means comprises a resistance including a plurality of resistors TI, r2, r3, T4 and r5 disposed in the brake circu t, a plurality of time delay relays IT. 2T, 3T, 4T and ET for controll ng the use of the resistors, a pickup circuit 33 for the t me delay relays, and a speed responsive device TG for opening the p ckup circuit to stop the operat on of the time delay relavs when the car reaches the desired leveling speed during a leveling operation.

The time delay re ays are arran ed t operate in seouence to render the resisto s in the brake circuit ineffec ive in a predetermined order. A holding coil HIT is prov ded for the relav IT so that w en the relay is energi ed and closes its contacts. a ter a predetermined t me delay those contacts will be held in their clo ed position until the levelin operation is comple ed. A sim lar holdin coil is prov ded for each of the other time delay relays. When a leveling ope at on is completed. the holding coils and l kewise the time delay relays are deenergized so that they may return to their normal cond tion ready for the next operation. The period of delay may be of such length as desired. A delay of one second can be used and will probably be most suitable for the usual installation.

The speed r sponsive device TG comprises a copper disc 21 fixed on the shaft I4 to be rotated thereby n accordance with the movement of the car by the mo or IS. A permanent magnet 28 is pivotallv mounted adjacent to the copper disc in pos tion to control a pair of contacts 9. When the motor rotates the copper disc it will effect a drag upon the permanent ma net 28 in accordance with the speed with which it rotates. In the present case, it is assumed that the disc and the permanent magnet are so designed that the disc will drag the permanent magnet sufficiently far to open the contacts 29 when the car reaches a speed of 20 feet per minute. The contacts 29 control the pickup circuit 33 for the time delay relays IT, etc., in such manner that no additional time delay relay can be picked up after the speed responsive device opens its contacts 29.

The following operation of the apparatus described will be assumed, with the car standing at the first floor of its hatchway (not shown) and with the system readyfor operation. In this condition the inductor relay Q and the leveling relay L are energized. It will be assumed now that an attendant enters the car and moves the car switch CS in a clockwise direction, thereby energizing the up direction switch U and the car running relay M to move the car upwardly. The circuit for relays U and M extends: L+, CS, 30, U, D4, M, L. The operation of the car switch also opens the circuit for the leveling relay L thus deenergizing that relay which in turn, deenergizes the inductor relay Q. The deenergized relay L closes its contacts L2, thereby completing a shunt circuit around the resistors TI to r5 in the brake circuit and thus rendering them ineffective in the brake circuit.

The energized relay U opens its contacts U4 and closes its contacts UI U2 and U3. The energized relay M closes its contacts MI, M2, M3 and M4. The closing of the contacts U3 energizes the brake coil BI by the circuit L+, BI, L2, U3, L- to release the brake B. The closin of the contacts UI and U2 in conjunction with the closing of the contacts MI, M2 and M3 energizes the field windings l8, I9 and 20 of the hoisting motor I6 to operate the hoisting drum II to move the car upwardly from the first floor. The car now operates at its predetermined top running speed which remains at approximately feet per minute by reason of the single speed motor I6.

It will be assumed now that the car is approaching a floor at which the attendant desires to make a stop and that the attendant centers the car switch CS to make the desired stop. The centering of the car switch CS energizes the leveling relay' L, by the circuit L+, CS, 3|, L, L, to close ts contacts LI, L3 and L4 and open its contacts L2.

The closing of the contacts LI prepares the pickup circuit 33 for the time delay relays IT, etc.. for operation. The opening of the contacts L2 in the brake circuit inserts the resistors TI to T5 in the brake circuit, thus decreasing the current in the brake coil sufilciently to cause the brake to be applied to stop the car. The closing of contacts L3 transfers the circuit for relays U and M from the car switch and this circuit now extends: L+. L3, UQ, U, D4, M, L. The closing of the contacts L4 energizes the inductor relay Q to deenergize the up direction switch U and the relay M when the car is level with the floor. In this operation it will be assumed that the ear is normally loaded and that the car switch is centered at the exact point where the application of the brake is such as to stop the car level with the floor at which the stop is being made. As the car drifts into the floor after the application of the brake, the up inductor contacts UQ- come opposite the lower end of the plate UP and are thereby opened to deenergize the up direction switch U and the car running relay M. The deenergizing up direction switch U opens its contacts UI and U2 thus deenergizing the field winding of the motor l6 and opens its contacts U3 thereby deenergizing the brake coil BI to fully apply the brake B to hold the car at its position level with the floor at which the stop is being made.

' As the car is stopped bythe inductor relay contacts coming opposite the plate UP, the down" inductor relay contacts DQ 'are also opened by coming'opposite the plate DP; Hence, if the deenergized'relay U recloses its contacts U4 in the direction switch circuit, the down relay D cannot be energized because the down-inductor relay contacts DQ" are open.

The foregoing described operation illustrates how the car may be'started' and stopped level with its landingfloor by the apparatus illustrated in tlie'drawing. when its load and other conditions are normal.

A leveling operation of the car will be assumed Assuming that the car, during a stop at a now. floor, goes below that floor for some reason; such as stretching" of the cables or overshooting the floor landing; then the inductor relays will be moved'below the inductor plate'UP such a distance that the inductor contacts UQ, coming outlrorn under the influence of the inductor plate UP; reclose and thereby energize the up direction switch U and the car running relay M by the sufilcient force to prevent the motor l6 from Starting the car back to the floor; that is, the brake is dragging so hard on the motor that the motor cannot move the car.

I When the car running relay M was energized it closedits contact members M4 which thereupon energized the time delay relay' IT by the circuit L+, Ll, 29, 33, ET, M4, U3, L-p However, in View of the time delay used with this relay, its contacts ET! and 1T2 remain openior a predetermined periodor time after the relay is energized,

say, 1 second. After this delay'of 1 second the The closed contactscontacts lTi and 1T2 close. I Tl render the resistor rl ineffective in the brake circuit. This increases the electromotive force in the brake coil Bl and thereby decreases the force applied by the brake shoes of brake B. However, the retarding force is still too strong to permit the motor to move the car. The closing of the contacts lT2 energized the relay 2T and after a predetermined time delay of 1 second that time delay relay closes its contacts ZTI and 2T2. The closing of the contacts 2T| renders the resistor r2 inefiective in the brake circuit, hence the current through the brake coil is now stronger and the brake torque, is consequently weaker so that the motor starts to pull the car through the dragging brake.

When the contacts 2T2 closed, they energized the relay 3T and after the expiration of the time delay for that relay 3T it closes its contacts 31! and 3T2. The closed contacts 3T1 eliminate the resistor r3 from the brake circuit thus increasing the current through the brake coil BI and further weakening the brake B thus permitting the motor It to move the car faster. The closed contacts 3T2 energize the time delay relay 4T so that it will be ready for its operation after the expiration of its predetermined time delay.

It is assumed now that motor I5 is pulling the car through the weakened brake more rapidly and that, as the speed of the car increases to the desired predetermined leveling speed of feet per minute, itrotates thecopperdisc 21 at such a rate that 'it exerts sufficient pull on the permanent magnet 28 tomove it until it opens the contacts 29 in the circuit of the time delay relays, thereby preventing the energization of additional time delay relays during thisleveling operation. However, the contacts of the time delay relays IT, 2T, and'3T are still held in their closed position-by the "holding coils HlT, HZT and 1-HT and hence the resistors 'rl, r2 and r3 remain inefiective in the brake circuit and the car now remains atitspresent speed because the motor torque isjust balanced by the load torque plus the brake drag: As there is no excess torque, acceleration cannot'occur'and' the car will move with uniform lowspeed; The operation willbe stable, as any increase in speed will be accompaniedby a slight diminishing'of' the-motor torque; and a slight'reduc'tion of speed; by a slight increase of motor torque.-

Th car is now running at its predeterminedspeed ofsay 20 feet per minute and, when it carries the inductorrelay contacts UQ upwardly adjacent to thelower edge of the plate UP, those 1 contacts are opened by the influence of the plate and thereby open the'circuit for the up direction switch U, thusdeenergizing that switch to open its contacts Ul, U2 andU3 and to close its contacts U4; Theopening of the-contacts UI and U2 deenergizes the hoisting motor" to stop the carand the opening of the contacts U3 deenergizesthe brake coil Bl thus causing full application of'the brake Bto hold the carat the floor; The car is now stopped and held level withjhe floor. The opening of the contacts U3 also deenergizes'the holding coils HIT, HZT, H3T, etc.,

so thatthe contacts of the time delay relays IT. 2T and 3T are returned to normal condition for use in the next leveling operation.

Inasmuch as the inductor contacts DQ are also open because they are opposite the down plate DP, the closed contacts U4 restore the levelingv circuits for'use if another leveling operav tion is necessary during this stop.

By the foregoing assumed operation it is seen that I have provided a releveling'system which will effectively level a car and when the car is moving under the influence of the leveling circuits it willkeep it at a predetermined leveling speed. It will also be apparent that I have provided a simple and inexpensive leveling system which may be easily installed, operated and maintained in operation and that the speed at which the cars are leveled will be kept at such a rate that the cars will not overshoot the floors to which they are releveled.

Although I have illustrated and described only one embodiment of my invention, it is to be understood that modifications thereof and changes therein may be made without departing from the spirit and scope of the invention.

I claim as my invention:

1. In an elevator system, a car, a single-speed hoisting motor for operating the car at a normal high running speed, an electromechanical brake for the motor, a circuit for connecting the brake to a supply of electric energy, a leveling means for the car, and means for controlling the leveling speed of the car to a predetermined speed, comprising a resistance, means responsive to operation of the leveling means for inserting the resistance in the brake circuit, a timing means for sequentially decreasing the efiective resistance in the circuit, and a speed means responsive to operation of the car for controlling the action of the timing means to bring the car to and hold it at a predetermined leveling speed until it is stopped at the floor at which it is landing.

2. In an elevator system, a car, a single-speed motor for operating the car, an electromechanical brake for the car, a circuit for connecting the brake to a supply of electric energy, a leveling means for the car, and means for controlling the leveling speed of the car comprising a resistance, means responsive to operation of the leveling means for rendering the resistance effective in the'brake circuit while the brake is applied to the motor to cause the brake to drag, a timing means for varyin the amount of eifective resistance in the circuit and speed means responsive to operation of the car for stopping further operation of the timing means when the drag of the brake on the motor is reduced sufficiently to permit th motor to move the car at a predetermined leveling speed.

3. In an elevator system, a car for serving a landing floor, a single-speed motor for operating the car at a predetermined running speed, control means for operating the motor, an electromechanical brake, a circuit for connecting the brake to a source of electric energy, a leveling means responsive to the car not being level with the landing floor during a stop thereat for causing the motor to level the car with the landing floor, and means for maintaining the car at a predetermined leveling speed during a leveling operation comprising a plurality of resistors, means responsive to operation of the leveling means for inserting said resistors in series in the brake circuit to cause application of the brake at a predetermined strength at the start of the leveling operation, a plurality of time delay relays, one for each resistor, a pick-up circuit for causing the time delay relays to be energized in sequence after predetermined time delays for sequentially rendering the resistors in-the brake circuit ineffective, means for holding each en-.

ergized time delay relay in its energized position after it is energized, and a speed device responsive to the speed of the car for rendering the pick-up circuit ineffective to energize additional time delay relays when the car reaches said predetermined leveling speed to hold said car at said leveling speed until its leveling operation is completed.

4. In an elevator system, a car for serving a landing floor, a single-speed motor for operating the car at a predetermined running speed, control means for operating the motor, an electromagnetic brake, a circuit for connecting the brake to a source of electric energy, a leveling means responsive to the car not being level with the landing floor during a stop thereat forcausing the motor to level the car with the landing floor, and means for maintaining the car at a predetermined leveling speed during a leveling operation comprising a pluralit of resistors, means responsive to operation of the leveling means for inserting said resistors in series in the brake circuit to cause application of the brake at a predetermined strength at the start or the leveling operation, means responsive to operation of the leveling means for sequentially rendering the resistors ineifective at predetermined intervals during the leveling operation, and means responsive to the speed of the car for stopping the operation of the sequential means at the predetermined leveling speed of the car to hold the car at that speed until the leveling operation is completed.

5. In a control system for a single-speed elevator car serving a floor landing, a motor for driving the car at a predetermined high speed corresponding to a rated motor speed, a brake for the motor, means for applying the brake with suflicient torque to stop the car, a plurality of timing devices for decreasing said torque in predetermined sequential steps, means responsive to operation of the brake applying means for starting said timing devices in operation, and means responsive to the speed of the car for stopping the operation of the timing devices when the value of the brake torque becomes proportional to the load driven by said motor when it is moving the car at a constant predetermined low speed, whereby said car will be reduced to a predetermined constant low speed as it approaches the point where the motor is to be deepergized for a stop at the landing regardless of the I load on said elevator.

EDGAR M BOUTON.

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