US2323652A - Elevator control system - Google Patents

Description

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f TQQ July 6, 1943. w. F. EAMES 2,323,652

ELEVATOH CONTROL SYSTEM Fned March 12, 1942 2 sheets-sheet 1 6 3 r 5 nu 3 M F A' 2 y E 1/mm d z f n e n J 2l 7 W. o $5 mw C y C .T e M a D U P M w w n. p ull@ a 0.1 um Wl n. Mm n I INVENTOR M/am-fmes.

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w. F. EAMES 2,323,652

ELEVATOR CONTROL SYSTEM Filed March 12, 1942 2 Sheets-Sheet 2 July 6, 1943.

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Patented July 6, 1943 ELEVATOR CONTROL SYSTEM William F. Eames. Westfield. N. J., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 12, 1942, Serial No. 434,323

(Cl. IS7-29) 9 Claims.

My invention relates to elevator control systems in which the cars are stopped at the floors by suitable automatic means dependent on the position and operation of the cars with reference to the oors and, more particularly, to such systems of this character as are operated at relatively low speeds of the order of 100 to 150 feet per minute.

Although not limited thereto, my invention is particularly applicable to elevators of the geared-drive type in which the hoisting sheave is driven through suitable gearing by a constant speed motor, sometimes called an induction motor. The motors usually provided in such installations have dropping speed-torque characteristics resulting in a variation of the car speed dependent upon the elevator load. If the motor is disconnected and the brake applied at the same fixed distance in advance of the floor each time, the car will coast or drift against the retarding torque of the brake for different distances before it stops, depending upon the car load and its direction of operation. Hence, the car may stop level at the floor when bearing one load and may stop short of or beyond the door when bearing other loads, unless some arrangement is provided for varying the distance of the car drift in accordance with the speed or load.

One object of my invention is to provide a means for causing the control apparatus of a constant speed elevator motor to cut ofi the motor and apply the brake at varying distances from the iioor in accordance with the load on the car and its direction of operation, so that the car will coast or drift into a stop approximately level with the floor landing at which it is to load or unload.

Another object is to provide a stopping system for elevator cars which shall be simple and inexpensive to install, operate and maintain in operation, and which will be eiective and long lived in service.

A further object is to provide an elevator stopping system which shall stop the cars approximately level with the floor landings without requiring moving parts on the car.

A still further object is to provide an elevator stopping system which may be constructed of rugged apparatus which will stand up well under hard usage and which can be easily and inexpensivelyv enclosed and protected from tampering or damage.

It is also an object to provide a stopping system in which the circuits will not be overly sensitive to speed, time or temperature changes and in which it will not be necessary to work to close tolerances in adjusting the system for operation.

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

Figure 1 is a diagrammatic representation of an elevator installation embodying my invention;

Fig. 2 is a straight-line representation of the power and control circuits for the car illustrated in Fig 1;

Fig. 2A is a key representation of the relays embodied in Fig. 2, illustrating the coils and contact members disposed in horizontal alignment with their positions in the straight-line circuits so that their locations therein may be readily determined;

Fig, 3 is a diagram of a curve showing the pull of two of the load relays embodied in Fig. 2; and

Fig. 4 is a diagram of curves showing the levels made at the stops without correction and with correction.

Referring more particularly to the drawings, I have illustrated an elevator car 9 disposed in a hatchway i0 and supported by a cable Il passing over a hoisting drum I2 to a suitable counterweight i3. The hoisting drum is mounted upon a shaft it driven by an electric motor H. A suitable gear reducing mechanism I5 is connected with the shaft i4 to secure an appropriate speed of the car when the motor H is in operation. A brake il operated by an electromagnetic coil i8 and a spring i9 is provided for stopping the car and holding it at any floor at which a stop is made.

The hoisting motor H is illustrated as a threephase single speed alternating-current motor comprising a stator having windings 2|, 22, and 23 and a rotor 24. The stator windings 2i, 22, and 23 may be connected to a suitable alternating current supply represented by the conductors Li, L2, and L3 by means of an up direction switch U and a down direction switch D and a car running relay M.

A car switch CS is mounted in the car for starting and stopping it. Rotation of the car switch in clockwise direction will energize the down direction switch D to connect the motor windings to move the car downwardly and rotation of the switch in counterclockwise direction will energize the up direction switch to connect the motor windings to move the car upwardly. Centering the car switch will cause its stopping system to stop it at the next floor.

The energy for operating the direction switches, the relay M and the stopping system may be supplied through a pair of conductors L+ and L- which are connected for energization through a full-wave rectifier 25 and a transformer 26 to the supply conductors Ll and L3.

In order to cause the elevator, when making a stop at a oor, to cut on its motor and apply its brake at a distance from the floor which will have a definite proportion to the load on the car so that the car will land approximately level with the floor, I have provided a novel stopping system comprising a pair of stopping circuits 21 and 29 for controlling the direction switches U and D in making a stop, a plurality of switching devices such as stopping inductor relays AR, BR and CR for operating the stopping circuits, and a pair of control relays E and F for selectively controlling the effectiveness of the stopping circuits in accordance with the load on the car when a stop is being made.

The up stopping circuit 29 is connected to the coil of the up direction switch U in parallel with the up contacts 31 on the car switch CS and is provided with a shunt circuit 30 around one part and a shunt circuit 3| around another part. The down stopping circuit 21 is connected to the coil of the down direction switch D in parallel with the down contacts 34 on the car switch CS and is `provided with a shunt circuit 32 around one part and a shunt circuit 33 around another part. The shunt circuits are controlled by the control relays E and F. The circuits 21, 29, 30, 3|, 32 and 33 may be termed stopping circuits.

The inductor relay AR is mounted on the top of the car and at one side thereof in position to pass between an up inductor plate AUP and a down inductor plate ADP when the car moves up and down in the hatchway. The relay has an energizing coil A, a normally closed pair of up contacts AU and a normally closed pair of down contacts AD. The inductor plates are constructed of magnetic material and are mounted in the hatchway in position to cooperate with the relay and open its contacts when it is in an energized condition as the car approaches the inductor plates. The inductor relay BR with its coil B is similar to the relay AR and is disposed to cooperate with an up inductor plate BUP for opening its up contacts BU and a down inductor plate BDP for opening its down contacts BD. The inductor relay CR with its coil C is also s'imilar to the relay AR and is disposed to cooperate with an up inductor plate CUP for opening its up contacts CU and a down inductor plate CDP for opening its down contacts CD.

Referring to the plates for the third floor, the position of the up plate BUP should be slightly higher than that of the up plate AUP and the position of the up plate CUP should be slightly higher than that of the up plate BUP. The position of the down plate BDP should be lower than that of the down plate CDP and the position of the down plate ADP should be lower than that of the down plate BDP. The distances of the plates from the floor should be predetermined in accordance with the design of the car, its loading and its counterweight. The plates ADP2, etc., for the second floor should be disposed in the same relation for the second iloor.

The plates may be made of light sheet iron welded to a support bracket 28 to constitute a unitary structure to be mounted n the Wall 0f the hatchway. In welding the plates on the frame, they may be placed in their predetermined positions with relation to each other so that when the unit is mounted in the hatchway with its position correct for one plate, the positions of all the plates will be correct and it will not be necessary to adjust each plate individually.

I have illustrated inductor plates for only two iloors, but it is to be understood that similar inductor plates will be mounted at each floor.

The coils A, B and C of the inductor relays are connected in series through the center contact 35 of the car switch CS so that centering the car switch will cause all of the inductor relay coils to be energized simultaneously for a stop at the next floor.

When the car comes into a floor stop in the up direction with the inductor coils energized, the contacts AU passing plate AUP open rst; later contacts BU passing plate BUP open and nally when the car is nearly at the floor level, the contacts CU passing the plates CUP open. These contacts always operate in this sequence on an up stop and at predetermined distances from the floor at which the stop is to be made and they are disposed in series in the up stopping circuit 29.

On a down stop, rst the down contacts CD pass the plate CDP and open. Next, the down contacts BD pass the plate BDP and open, and lastly the contacts AD pass the down plate ADP and open. Hence, it is seen that the down contacts open in sequence at predetermined distances from the door. These contacts are included in series in the down stopping circuit 21.

The control relay E is a current responsive relay of the moving coil type with an adjustable drop out. It has a stationary coil ES connected across the supply conductors L2 and L3 for the hoisting motor H and its moving coil E is connected in series with the secondary winding of a current transformer CT the primary winding of which is connected with the supply conductor L2 for the motor H. The control relay F is similar to relay E and its coils are connected to the supply conductors in the same manner.

Inasmuch as moving coil relays are old and well known in the art, no further description thereof will be given, but if further detailed information is desired, reference may be had to Patent No. 1,820,712, issued to Walter Schaelchlin on August 25, 1931, and assigned to the Westinghouse Electric 8: Manufacturing Company, which patent shows a moving coil magnetic device which is used as a regulator but which may be used as a relay for controlling any circuit, as desired.

The normally open contacts of the control relays are disposed in the shunt circuits 30, 3l, 32 and 33.

The relays E and F are so designed and adjusted that both of them will be energized to close their contacts when the car starts, because of the large amount of current used in accelerating the car. The relay F is designed to drop out and open its contacts FI and F2 in the shunt circuits 3| and 32 when the amount of current taken by the hoisting motor decreases beyond a predetermined value as the load on it decreases by reason of decrease of the elevator loading and the influence of the direction of elevator operation. The relay E is designed and connected to' drop ou-t and open* its contacts El and E2 in the shunt circuits 30 and 33 when the current taken by the motor decreases still further by reason of still less loading of the elevator and the influence of the direction of elevator operation.

The direction of operation of the car influences the load on the motor, as the counterweight is usually heavier than the empty car. The usual practice is to load the counterweight so that it equals the weight of the empty car and then add to the counterweight a weight equal to 40% of the normal load for which the car is designed. For example, with a car weighing 5,000 pounds designed to carry a load of 2500 pounds the counterweight would be ilrst loaded with 5,000 pounds to equal the weight of the car, and then an additional thousand pounds (40% of the 2500 pounds load for which the car was designed) would be added to the counterweight, making the total weight of the counterweight 6,000 pounds, while the car without load would weigh 5,000 pounds, but with full load would weigh '7500 pounds.

With the above described weighting of the counterweight, the car with full load in the up direction will be a heavy load for the motor than medium load on the motor because the counterweight helps to pull the car upwardly thus causing the motor to use less than the medium amount of current. A car running in the down direction with full load will cause the motor to pull the least amount of current. Under these circumstances the relay F may be so designed and adjusted that it will open its contacts when the motor is responding to that condition between an empty car down and a balanced up or down car, and the relay E may be designed and adjusted to open its contacts when the motor is responding to a condition between a balanced up or down car and a full load down, as indicated by the curve in Fig. 3.

In the usual system, stops initiated at a definite point in the approach of the car to the floor with a medium strong brake, may vary as much as five inches with the load range. For example, an empty car down may stop one and one-half inches above the landing floor and a loaded car down may stop as much as three inches below the landing floor. With my system, the control relays and the diilerent positions of -the inductor plates may be used to vary the point at which the motor is cut off and the brake applied in accordance with the load on the car or motor and its direction of operation so that stops with loads up to 60% will not vary more than three-fourths of an inch from the floor level and stops with greater loads up to full load will not exceed one inch from iioor level.

It is believed that the invention may be best understood from an assumed operation of the apparatus described. It will be assumed now that the car is in the lower part of the shaft and is fully loaded and that the attendant in the car has rotated the car switch in counterclockwise direction, thus energizing the relay M and the up direction switch to start the car upwardly by the circuit L+, M, U, 31, 36, L-. The energized up direction switch closes its contact members Ui, U2 and U3 and the energized relay M closes its MI, M2 and M3. The closing of the contacts UI and U2 and MI, M2 and M3 causes the operation of the hoisting motor H by energizing its field windings 2l, 22, and 23, the circuit extending through the conductor Li, Mi, UI, 2l, to a point 39, through the conductor L2, CT, M2, U2, 22 to the point 39 and through conductor L3, M3, 23, to the point 39. The closing of the contacts UI and U2 and Mi and M2 also energizes the brake winding I8 to release the brake Il. The closing of the contacts U3 provides a self-holding circuit for the up direction switch U and the car running relay M through the up stopping circuit 29. These contacts U3 may be termed the holding means for causing the car to keep in motion after the car switch has been centered for a stop until the stopping circuit is deenergized and the brake applied.

The energization of the motor and the release of the brake causes the car to move upwardly. The control relays E and F are also fully energzed because the motor is pulling a heavy current in accelerating the car.

It will be assumed now that, as the loaded car approaches the third floor in the up direction, the attendant centers the car switch CS to cause the car to stop at the third iloor.

The centering of the car switch closes its contacts 35 and 36, thereby energizing the coils A, B and C of the inductor relays AR, BR. and CR on the car by the circuit L+, A, B, C, 35, 36, L-.

As the loaded car approaches the third floor with its inductor coils energizedI both control relays E and F will remain energized sufficiently by the heavy current being pulled by the hoisting motor to prevent them from opening, and hence, their contact members El and FI in the stopping circuit 29 will remain closed. However, this will not initiate the stopping of the car. Inasmuch as the car is fully loaded, it will be easily stopped, but the hoisting motor will be pulling such a considerable amount of current, that the relays E and F will remain energized, and, consequently, their contacts El and FI in the stopping circuit will remain closed. Hence, when the up car nears the third floor and causes the contacts AU to open rst. that does not affect the stopping circuit because the contacts Fl are closed, providing a shunt circuit around the contacts AU. Inasmuch as the relay E remains energized, its contacts El are closed, and as the car approaches still closer to the iloor, its contacts BU are opened by the plate BUP1 but the up direction switch still remains energized because the contacts El still remain closed in the circuit 26. As the car comes still cio-ser to the floor, the inductor relay contacts CU come opposite the up plate CUP and are opened thereby. The opening of the contacts CU deenergizes the up direction switch U, and the car running relay M to open their contact members and thus deenergize the hoisting motor H and the brake coil l0 of the brake Il. The cutting oil' of the motor decelerates it and the deenergization of the brake il causes it to be applied to the hoisting drum I2 to stcp the car. The car with its heavy load does not drift very far, but, inasmuch as its inductor relay contacts have been cut off at the proper drift distance from the floor, the car stops approximately level with the iloor.

Let it be assumed now that an up stop is made with the car loaded sufiiciently to balance the weight of the counterweight. Under such circumstances, the approach of the car to its third floor stop will cause the control relay F to drop out by reason of the lower amount of current pulled by the hoisting motor, and thus the contacts are open in the shunt circuit around the contacts BU. As the car nears the oor under these conditions, the up contacts AU come opposite the up plate AUP and are opened in the control circuit 29, but this does not affect the up direction switch because the control contacts El are still closed. As the car with its balanced load continues its approach to the third oor, the up contacts BU on the relay BR come opposite the up plate BUP and are opened in the up stopping circuit 29. This opening of the contacts BU deenergizes the up direction switch U because the contacts Fl are open. The deenergizing of the up direction switch U and the car running relay M cuts ofi" the motor and applies the brake while the car is at a predetermined distance from the third floor, which distance is the predetermined distance from the oor at which the car with a balanced load will drift into and stop approximately level with the floor after its motor is cut oil' and its brake is applied.

Assuming now that the car is making the same up stop without any load. Inasmuch as the counterweight is heavier than the empty car, it is pulling the car up the hatchway without the assistance of the hoisting motor H, and, hence, the car will require a greater distance in which to drift to a stop after the motor is cut ofi and the brake is applied than it would if the car were balanced or were loaded to full capacity. The control relays E and F will both be opened, thus opening their contacts El and Fl in the control circuit 29. As the empty car approaches the up stop at the third floor, its contacts AU come opposite the plate AUP and are opened in the stopping circuit 29. Inasmuch as the contacts Fl are open, the opening of the contacts AU deenergizcs the up direction switch U and the car running relay M to cut off the motor and apply the brake at the predetermined distance from the third oor at which the empty up car will drift into and stop approximately level with the third oor.

It will be assumed now that the car not loaded is above the third floor, and that the attendant moves the car switch in counterclockwise direction to cause the car to move downwardly towards the third oor. 'I'his movement of the car switch closes its contacts 33 and 3l, thereby energizing the car running relay M and the down direction switch D by the circuit L+, M, D, 34, 36, L The energized relay D closes its contact members DI, D2, and D3. The closing of the contact members D3 establishes a self-holding circuit for the down direction switch D through the normally closed inductor relay contacts AD, BD, and CD to L-.

It will be assumed now that the attendant on the car centers the car switch CS to cause the car to make a down stop at the third oor. The centering of the car switch energizes the inductor coils A, B, and C, as previously described to cause the car to stop at the third floor.

As the empty car approaches the down stop at the third floor, the down contacts CD of inductor relay CR first approach the down inductor plate CDP and are opened thereby. The contacts CD are in the stopping circuit 21, but inasmuch as the empty car down is causing the hoisting motor to pull considerable current to move it downwardly by reason of the fact that the counterweight is heavier than the empty car, the control relays E and F are closed, thus their contacts E2 and F2 are closed in the circuits around the contacts BD and CD. Therefore, the opening of the contacts CD does not aiTect the energization of the down switch D.

As the empty car approaches still closer to the down stop at the third oor, the contacts BD of the inductor relay BR are opened as they come opposite the down inductor plate BDP. However, inasmuch as the contacts E2 are still closed, the opening of the contacts BD does not affect the stopping circuit 21.

As the empty down car approaches still closer to the third floor, the contacts AD come opposite the plate ADP and are opened thereby, thus opening and stopping circuit 21 to deenergize the car running relay M and the down direction switch D. The deenergization of the down direction switch D and the relay M cuts 01T the hoisting motor H and applies the brake I1 to stop the car, and this action takes place at just the right distance from the third floor to cause the empty car with its motor cut 01T and its brake applied to drift into and stop approximately level with the third floor landing.

It will be assumed now that the car is on a down trip above the third floor, and is partly loaded with passengers whose weight plus that of the car balances the counterweight so that the car is in a balanced condition. It will also be f' assumed that the attendant centers the car switch as before described to cause the car to stop at the third iloor. Under these conditions, the hoisting motor H will be pulling such a. current that the control relay F will have dropped out and the control relay E remains energized, thus leaving the contacts F2 open and the contacts E2 closed in the stopping circuit 21.

As the car approaches within a predetermined distance of the down stop at the third oor, the contacts CD come opposite the down plate CDP and are opened, but inasmuch as the contacts E2 are closed in the stopping circuit 21, thus the opening of the contacts CD has no effect on the car. As the balanced car approaches closer to the down stop at the third floor, the contacts BD come opposite the down plate BDP and are opened. Inasmuch as the contacts F2 are open, the opening of the contacts BD deenergizes the down direction switch D and the car running relay M, thereby cutting off the motor H and applying the brake l1 to stop the car. This action takes place at the predetermined distance from the third floor which will cause the car with a balanced load to drift into and stop approximately level with the third oor.

It will be assumed now that the car with full load is above the third floor and that the attendant in moving it down, centers the car switch to cause another down stop at the third floor. The centering of the car switch energizes the inductor coils A, B, and C, as previously described, and inasmuch as thel car is heavily loaded and is moving down, the hoisting motor has little work to do. Therefore, both the control relays E and F are deenergized to open their contacts E2 and F2. As the car approaches the down stop at the third floor, the contacts CD are rst opened by the inductor plate CUP thus deenergizing the down direction'switch D and the car running relay Mr to cut off the motor and apply the brake to stop the car. The tendency of the fully loaded car, of course, is to move downwardly thus requiring a long drift into the landing and it will be obvious that the contacts CD have opened at the right distance from the lioor to permit the car to drift in and stop level with the floor.

The curves in Fig. 4 are provided to illustrate the action of my invention in correcting the accuracy of the stops at the floors. The horizontal line 40 represents a floor level. Ordinates measured vertically from this line to the curve lines indicate the inaccuracy of stop for various loads. Light load accuracies, including that for empty car, are shown on the left side; those for heavy loads, including full load, are shown on the right. Balanced car occurs to the left of the center. With balanced load the car stops level and the oor level line 40 and the accuracy line 4l cross here, indicating no inaccuracy.

superimposed on line 4| is a broken solid line 42 to show the effect on the accuracy of stopping when my invention is applied. Empty cars cause stops 1/ inch high and light loads cause stops to 1/2 inch low. At a certain load, which is approximately half-way between empty car and balanced load, the first correction occurs with the opening ci F. Stops are initiated by contacts BU and BD, and, with loads in excess of balanced car accuracies, are produced in the range of 1% inch high to 3A inch low. When sufficient car load occurs to cause the second correction to occur by opening E, then loads to full load cause inaccuracies in the range of 1 inch high to 1 inch low, as indicated by curve 43.

The corrections could be caused to occur at other loads. With slightly diierent plate locations, all loads could be caused to stop in a range of 3A inch high to 3A inch low. I prefer the adjustment indicated. In the average elevator approximately 60% of the loads carried are less than balanced car and an additional 30% approximately are between balanced car and 3A load. With this adjustment, the greatest accuracy of stopping is obtained with the loads that occur most frequently.

The circuits are, for the sake of simplicity, shown as those of a car switch start system with automatic stop by a stopping inductor, but the invention may be applied to any push-button f control system where the push-buttons are used to start the car, a selector determines when it should be stopped, and a car carried inductor relay stops it.

Although I have illustrated and described only one speciiic embodiment of my invention, it is to be understood that changes therein and modifications thereof 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 serving a plurality of floors in a hatchway, a motor for operating the car, means for energizing the motor by connecting it to a source of electrical energy, a plurality of switch devices mounted on the car, means mounted on the wall of the hatchway adjacent to each floor for eiTecting operation of the switch devices in consecutive order as the car approaches a stop at a oor, a control device controlled by the loading of the motor, and means responsive to consecutive operation of the switch devices when a stop is to be made and to the condition of the control device for deenergizing the motor when the car approaches within a. predetermined distance of the floor at which the stop is to be made proportional to the loading of the motor and its direction of operation.

2. In an elevator system, a car serving a floor in a hatchway, a motor for operating the car, means for energizing the motor by connecting it to a source of electrica1 energy, a plurality of switch devices mounted in side by side relation in a horizontal plane on the car, means for operating the switch devices '1n consecutive order lwhen the car approaches a stop at the floor, a

control device controlled by the loading of the motor, and means responsive to the consecutive operation of the switch devices when a stop is to be made, and to the operation of the control device for deenergizing the motor when the car approaches within a predetermined distance of the floor at which the stop is to be made proportional to the loading of the motor and its direction of operation.

3. An elevator system comprising a car operable to servie a plurality of floors in a hatchway, a motor for operating the car, switch means for connecting the motor to a source of electrical energy, and a stopping means for deenergizing the motor comprising a plurality of stopping relays mounted in side by side relation in a horizontal plane on the car, a plurality of inductor plates for each floor for operating the relays when the car is to stop thereat, means for mounting the inductor plates for each tioor in diierent positions corresponding to the loadings on the car and its direction of operation to effect operation of the relays in consecutive order when a stop is being made, a control device controlled by the loading of the motor, and means responsive to operation of the control device and the consecutive operation of the relays for deenergizing the motor when the car approaches within a predetermined distance of a iloor at which a stop is to be made.

4. An elevator system comprising a car operable to serve a floor landing in a hatchway, a motor, means for energizing the motor to operate the car, a plurality of stopping switches mounted in a horizontal plane on the car, means for simultaneously preparing the switches for operation when a stop is to be made, means for operating the switches in consecutive order as the car approaches a stop at the floor, a plurality of stopping means controlled by said switches for effecting stopping of the car, and control means responsive to the loading of the motor for selecting the stopping means to be operated in accordance with the loading and direction of operation of the car.

5. An elevator system comprising a car operable to serve a landing floor in a hatchway, a motor for operating the car, an up direction switch for connecting the motor for up operation, a down direction switch for connecting the motor for down operation, a stopping circuit, for each switch, a plurality of stopping relays mounted in a horizontal plane on the car for controlling the stopping circuits, each relay having a pair of contacts disposed in each stopping circuit, a plurality of short circuits disposed around portions of each stopping circuit, means for simultaneously energizing the relays when a stop is to be made, a plurality of inductor plates mounted on the hatchway wall at different distances from the landing floor in proportion to diiferent loadings of the car for causing operation of the relays in consecutive order when the car approaches a stop at the landing floor, a pair of control relays associated with the hoisting motor and responsive to the load thereon for controlling the shunt circuits around portions of the stopping circuits to render effective that relay which corresponds to the load on the motor.

6. An elevator system comprising a car operable to serve a landing floor in a hatchway, a motor for operating the car, direction switches for connecting the motor for operation, a plurality of stopping circuits, a plurality of stopping relays mounted side by side in a horizontal plane on the car for controlling the stopping circuits, means for simultaneously energizing the relays when a stop is to be made at the floor, a plurality of inductor plates mounted in the hatchway at different distances from the landing floor in proportion to different loadings of the car for causing operation of the relays in consecutive order, a plurality of control devices responsive to the load on the motor for controlling the stopping circuits to render effective the stopping circuit which corresponds to the load 0n the motor and its direction of operation.

'1. An elevator system comprising a car operable to serve a landing floor in a hatchway, a motor for operating the car, an up direction switch for connecting the motor for up operation, a down direction switch for connecting the motor for down operation, a plurality of stopping circuits for each switch, a switch means for selectively energizing the direction switches to start the car and for preparing them for deenergization when a stop is to be made, self-holding means operated by the direction switches for connecting the stopping circuits to control the switches when the car is to be stopped at a iloor, a plurality of stopping relays mounted in a horizontal plane on the car for controlling the stopping circuits, means for simultaneously energizing the relays when a stop is to be made, a plurality of inductor plates mounted on the hatchway wall at different distances from the landing floor in proportion to different loadings on the car and its direction of operation for causing operation of the relays in consecutive order, a

pair of control relays associated with the hoisting motor and responsive to the loading of the car and its direction of operation for controlling the stopping circuits to render eiective that stopping circuit which corresponds to the load on the car and its direction of operation.

8. In an elevator, a hatchway, a floor landing in the hatchway, a car disposed for operation in the hatchway to serve the landing, a motor for operating the car, a brake for stopping and holding the car, a plurality of switching devices mounted on the car, a plurality of switch-operating devices mounted on the hatchway wall in position to effect operation of the switching devices in consecutive order and at predetermined distances from the landing as the car approaches a stop at the landing, a plurality of circuits controlled by the switches for eiecting the stopping of the motor and application on the brake, and control means responsive to the load on the motor for rendering effective the stopping circuit corresponding to the load on the car and its direction of operation to cause the car to land approximately level with the floor in making a stop thereat.

9. In a control system for a motor driving an elevator; means for starting said motor to move said elevator; holding means associated with said starting means for causing said elevator to continue in motion; stopping means for said motor comprising a plurality of pairs of members, each pair comprising a member movable with the motion of said motor and a stationary member cooperating therewith, any pair of members being capable of rendering ineffective said holding means to cause said motor to stop; means for rendering all of said pairs of members effective to initiate a stop of said elevator at a selected floor; and means responsive to the load current to said motor for determining which pair of members will initiate said stop. whereby said elevator will be caused to stop substantially level with said floor regardless of the load in said elevator.

WILLIAM F. EAMES.

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