US2359092A - Elevator control system - Google Patents

Description

2 Sheets-Sheet l INVENTOR-s M'l/z'am T 90785 W. F. EAMES EIAL ELEVATOR CONTROU SYSTEM Filed Nov. 4, 1942 /VI V// Se t. 26, 1944.

WITNESSES Z? H/"nes. 0/ TT and E/rney Patented Sept. 26, 1944 ELEVATOR CONTROL SYSTEM William F. Eames, West Hines, Wilkinsburg, house Electric Eleva N. J., a corporation field, N. J., and Birney Pa., assignors to Westingtor Company, Jersey City, of Illinois Application November 4, 1942, Serial No. 464,434

8 Claims.

Our invention relates to elevator control systems and, more particularly, to low-speed elevators and the means for stopping them at the floors they serve.

Our invention is more particularly applicable to elevators of the geared drive type, in which the hoisting sheave is driven through suitable gearing by a constant speed motor, and which are usually designed for operation at a speed of between 100 and 175 feet per minute. The motors usually provided in such installations have drooping 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 point 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 a floor when bearing one load, and may stop short of or beyond it when bearing another load or when operating in another direction, unless some arrangement is provided for selecting the point at which to start the car drift in accordance with the speed or load.

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

Another object is to reduce the amount of space usually required for mounting the stopping apparatus on the top of the elevator car and to also reduce the amount of cooperating parts of the stopping apparatus to be mounted on the elevator hatchway walls.

It is also an object to reduce the number of electrical contact members needed in the control system and to also secure finer and more variations in the points at which the deceleration of the car will start in accordance with the load on the car and its direction of operation in making stops at the floors.

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

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

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

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

Fig. 3 is an enlarged representation of the inductor relay device mounted on the roof of the car in Fig. 1;

Fig. 4 represents a curve illustrating the results obtained by the three load relays embodied in Fig. 2; and

Fig. 5 is a group of curves showing the distances from the floors at which the car will stop under certain conditions without correction and with the correction provided by our invention.

Referring more particularl to the drawings, we have illustrated an elevator car [0 as disposed in a hatchway I l and supported by a cable [2 passing over a hoisting drum I3 to a suitable counterweight 14. The hoisting drum is mounted upon a shaft l5 driven by an electric motor H. A suitable gear reducing mechanism 16 connects the shaft l4 and the motor H to secure an appropriate speed of the car when the motor is in operation. A brake I! released by an electromagnetic coil 18 and applied by 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 2U, 21 and 22 and a rotor 23. The stator windings may be connected to a suitable alternating-current supply represented by the conductors I, II and III by means of an up-direction switch U and a downdirection switch D in connection with a car running relay M.

'A car switch CS is mounted in the car for starting it and for initiating the stopping action thereof. Rotation of the car switch in a clockwise direction will energize the down-direction switch D to connect the motor windings to move the car downwardly, and rotation in counterclockwise direction will energize the up-direction switch U 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 may be connected for energization, through a full-wave rectifier 25 and a transformer 28, to the supply conductors I and III.

In order to cause the elevator, when making a stop at a floor, to cut off its motor and apply its brak at a distance from th floor which will have a definite proportion to the load on the car and its direction of operation so that the car will land approximately level with the floor, we have provided a stopping system comprising a stopping circuit 30 for controlling the direction switches U and D in making a stop, stopping inductor relay device L for rendering the stopping circuit efiective to stop the car, and three control relays E, F and G for selectively controlling the point at which the stopping circuit becomes effective to stop the car in accordance with the load on the car and its direction of operation when the stop is being made.

One end of the single stopping circuit 30 is connected to the supply conductor L-I- either through the up-direction switch U by the contacts U3 or through the down-direction switch D by the contacts D5. The other end of the circuit 38 is connected to the supply conductor L. The section of the stopping circuit intermediate itsends 30 and 30a is provided with 'a plurality of shunt circuits disposed to be controlled by the direction switches U and D, the inductor device L and the control relays E, F and G in accordance with the loading of the car and its direction of operation,

The inductor relay device L is mounted on 'top of the car and at one side thereof by a supporting member, 33 (Fig. 3) in position to pass be tween an up inductor plate UPI and a down in ductor plate DPI on one side, and an up inductor plate UP2 and a down inductor plate DPZ on the other side. A similar group of plates is disposed at each floor for making stops thereat. In appreaching a stop at a floor in the up-directidh, the inductor device passes between the up plate UPI and the up plate UP2.

device passes between the down plate DPI and the down plate DP2.

The inductor device L comprises two relays LA and LB. The relay LA is provided with two con tact switches LI and L3 on its upper end and the relay LB is provided with two contact switches L2 and LA on its lower end. That is, the relays are mounted end to end with their contact members adjacent to each other and with their north poles adjacent to each other, so that the contact switches on the relays will be only a small distance apart, say, one and one-quarter inches. The inductor plates for operating the contact switches have a predetermined length, say, of five inches and are placed at predetermined distances from a line 34 corresponding to the position of the car when its floor is level with the landing floor; that is, the plates are so mounted on the hatchway wall that, when the inductor device L on the car is centrally disposed between. the vertical positions of the plates, the floor of the car will be exactly level with the floor of the landing.

The inductor plates are constructed of magnetic material and are mounted in the hatchway in position to cooperate with the relay device and open its contact switches when it is in an energized condition as the car moves it along and between the inductor plates. The inductor plates are mounted on the hatchway wall at such dis tances from each other that the contact switches on the inductor device will be operated by the down plates in the predetermined order of LI, L2, L3 and L4 when the car approaches a down stop, and in the predetermined order L2, LI, L4

In approaching a' stop at a floor in the down direction, the inductor and L3 by the up plates when the car approaches an up stop.

The relay coils LA and LB of the inductor device are connected in series through the center contacts 35 of the car switch CS so that centering the car switch will cause the inductor device to be energized for a stop at the next floor.

When the car comes into a floor stop in the up direction with the inductor device coils energized, the contacts L2, passing plate UPI, open first when the car floor is 11% inches from the landing floor level; next the contacts LI, passing plate UPI, open when the car floor is 10 /2 inches from the landing floor level; next the contacts L4, passing plate UPZ, open when the car floor is 9%, inches from the landing floor level and finally the contacts L3 pass the plates UP2 and are opened when the car floor is 8 inches from the landing floor level.

On a down stop, first the contacts LI pass the plate DPI and are opened when the car floor is 11% inches from the landing floor; next the contacts L2 pass the plate DP! and are opened when the car floor is 10 inches from the landing floor; next the down contacts L3 pass the plate DPZ and are opened when the car floor is 9 inches from the landing floor; and last the contacts L4 pass the plate DP2 and are opened when the car floor is 8 inches from the landing fioor.

Hence it is seen that the'contact switches on the inductor device open in predetermined order at predetermined distances in accordance with the direction of the car when it is being stopped at a floor.

The control relays E, F and G are current responsive relays of the stationary type with adjustable drop out. The control relay E has a Sta- 7 i moving coil E connected in series with the secondary Winding of a current transformer CT, the primary windin of which is connected with the supply conductor II for the motor H. The control relays F and G are similar to the relay E and their coils are connected to the supply conductor II through the same'circuit.

Inasmuch as moving coil relays are old and well known in the art, no further description thereof will be given but further detailed information if desired may be had in Patent No. 1,820,712 issued to Walter Schaelchlin on August 25, 1931, which patent shows a moving coil magnet device used as a regulator but which may be used as a relay for controlling a circuit. Each of the control relays is provided with a normally open switch which is disposed in the shunt circuits associated with the central portion of the stopping circuit 30.

The control relays E, F and G are so designed and adjusted that they will be energized to close their contact switches when the hoisting motor is using a large amount of current to operate the car. The relay G is designed to drop out and open its contact switch GI in the stopping circuit 30 when the amount of current taken by the hoisting motor decreases from its maximum to a predetermined value as the load on the car decreases and by the influence of the direction of elevator operation. The relay F is designed to drop out and open its contact switch Fl in the stoppin circuit 30 when the current taken by the hoisting motor decreases still further by reason of still less loading of the elevator and the influence of its direction of operation. The relay E is designed to drop out and open its contact switch El in the stopping circuit 30 when the current taken by the motor decreases still further by reason of still less loading of the elevator and the influence of its direction operation. The direction of operation of the car influences the load on the motor, a th 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.

With the above described weighting of the counterweight, a car with full load in the up direction will be a heavy load for its motor and cause it to use a heavy current. An empty down car will be nearly as heavy a load on the motor and cause it to pull a somewhat less amount of current. When the car i loaded just enough to balance the counterweight it is a balanced car with the load on the motor the same for either direction of operation and it uses a medium amount of current. An empty car in the up direction will place a less than medium load on the motor because the counterweight helps to pull the car upwardly. The car running in th down direction with a full load will cause the motor to use the least amount of current.

Under these circumstances the relay G may be so designed and adjusted that it will open its contact switch when the motor is responding to that condition between an empty car down and a balanced up or down car, the relay F may be designed and adjusted to open its contact switch when the motor is responding to a condition where the car is a balanced car for either the up or the down direction, and the relay E may be so designed and adjusted that it will open its contact switch El when the car has a full load in the down direction, as indicated by the curve in Fig, 4.

In the usual system, stop initiated at a definite point in the approach of the car to the fioor with a medium strong brake, may cause the car to stop at different distances from the landing and they may vary as much as 5 inches with the load range. For example, an empty car down may stop 1 /2 inches above the landing floor and a loaded car may stop as much as 3 inches below the landing floor. With our system, the control relays, the selected position of th inductor switches in vertical alignment and the positions of the inductor plates may be used to vary the point at which the motor is cut oil and the brake applied in accordance with the load on the car motor and its direction of operation so that stops will be approximately level with the floor and not often more than of an inch above or below even under the most unsatisfactory loading conditions.

It is believed that the invention may be better understood from the following assumed operation.

It will be assumed now that the car is at the lower part of its shaft and is fully loaded and that the attendant in the car has rotated the car switch in a counterclockwise direction thus energizing the up-direction switch to start the car upwardly by the circuit L+, M, U, cs, L-

The energized up direction switch closes it contact members Ul, U2, U3, U4, U5 and U5. The closing of the contacts Ul and U2 i conjunction with the closed contacts Ml, M2 and M3 of the car running relay M causes operation of the hoisting motor H by energizing its field windings 20, 2| and 22, the circuit extendin through I, MI,

UI, 20, to a point 38, also through the conductor II, CT, M2, U2 to the point 38, and also through conductor III, M3, 22 to the point 38. The energization of the conductors I and II also energizes the brake winding [8 to release the brake H. The closing of the contacts U3 provides a self-holding circuit for the up direction relay U and the car running relay M through the single stopping circuit 30. The holding circuit will cause 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 relays of the brake cause the car to move upwardly. The control relays E, F and G are also now fully energized because the motor is using a heavy current in accelerating the car.

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

The centering of the car switch closes its contacts 35, thereby energizing the inductor device coils LA and LB by the circuit L+, LA, LB, 35, cs, L

While the loaded up car approaches the stop at the floor with its inductor coils energized, the control relays E, F and G will remain energized sufiiciently by the heavy current being used by the hoisting motor to prevent them from opening, and hence, their contacts El, F! and GI in the stopping circuit will remain closed. Inasmuch as the car is fully loaded it will be easily stopped, and in making this stop it will drift about 8 inches after the motor is cut off and the brake applied. When the up car nears the floor and causes the contacts L2 to open first, that does not affect the stopping circuit because, after the contacts L2 open, the stopping circuit still carries current through the circuit at, U6, Fl, U4, L3, GI, U5, sea, L

providing a shunt circuit around the contacts L2.

As the car approaches still closer to the stopping floor the contact switch Ll moves adjacent to the up plate UPI and is opened, However, the shunt circuit just described extends around the contact switch LI and keeps the up direction switch U energized.

As the car approaches still closer to the stopping floor, the contact switch L4 comes opposite the up plates UP2 and is opened thereby. However, no action results because the shunt circuit still remains complete for maintaining the updirection switch U energized.

As the car approaches still closer to the stopping floor the contact switch L3 is brought opposite the up plates UP2 and is thereby opened. The opening of the contact switch L3 opens the holding circuit described, and thereby deenergizes the Lip-direction switch U and the car running relay M to open their contact members and thus deenergize the hoisting motor H and car brake ll. The deenergization of the hoisting motor decelerates the car and the deenergization of the brake coil l8 causes the brake to be applied to the hoisting drum l3 to stop the car and hold it at the floor. The up car with its full load has a drift of approximately 8 inches and, inasmuch as its effective inductor relay contacts open when the car is 8 inches from the floor, the car will stop approximately level with the floor.

Let it be assumed now that the car completes its stop and continues its up trip to another stop with a load between full load and a balanced load. Under these conditions, the decreased current used by the motor causes the control relay G to open its contacts Gl in the stopping circuit, thereby leaving the holding path through the stopping circuit controlled by the contact switch L4 as follows:

As the car approaches the stopping floor, its inductor contact switch L2 opens first but that does not affect the holding circuit. Next, the contact switch Ll opens as the car approaches still closer to the fioor but that does not affect the stopping circuit. However, as the car approaches still closer to the floor, the contact switch L4 is oened by the plate UP2 and this opens the holding path through the stopping circuit, thus deenergizing the up-direction switch U and the car running relay M to cause the car to drift into and stop level with the floor. Inasmuchas the car is moving upwardly and has a loadless than full load but greater than a balanced load, its drifting distance will be approximately 9 A; inches, and inasmuch as the contact switch L4 opens when the car is 9% inches from the floor, the drift of the car will cause it to stop level with the floor.

Assuming now that the car completes its stop and continues its up trip with a balanced load to the next s op, then the current used by the hoisting motor will decrease to such an extent that the control relay F will open its contacts Fl in the stopping circuit, thereby leaving the holding path through the stopping circuit controlled by the inductor device contacts Ll as follows:

L+, M, U, U3, Ll, El, U4, L3, L4, 30a, L

As the car approaches the stoppin fl or, i s inductor switches L2 open without affecting the holding circuit. Next, the inductor switch Ll opens. Inasmuch as the only holding path is through this contact switch, its opening deenergizes the up-direction switch U to effect the stopping of the car when the car is 10 /2 inches from the floor level. Inasmuch as the normal drift of the car is 10 inches, it will stop level with the floor.

Assuming now that the car unloads and then resumes its up trip in an empty condition to the upper terminal, the empty up car will cause still less current to be used by the hoisting motor and therefore the energization of the control relay E is reduced to such a value that it opens its contacts El 'in the stoppingcircuit. The effective holding circuit path is now controlled by switch L2 and extends as follows:

an, Ll, L2, L3 and La As the car approaches the stop at the upper terminal with its inductor device energized, its inductor switch L2 will be opened as it approaches the up plate UPI for the upper terminal when the car is 11% inches from the landing floor. Inasmuch as the drift of an empty up car amounts to 11 /4 inches, the car will drift into and stop level with the floor.

It will be assumecl'now that the car takes on a full load at the upper terminal and that the attendant moves the car switch CS in clockwise direction to energize the down switch D to start the car downwardly. Under these conditions, the hoisting motor will be using so little current that the control relays E, F andG will be energized to such a small degree that they will open 3!), LI, L2, L3, L4, 3.6a

As the car approaches a down stop with its inductor device energized, the inductor contact switch Ll is first to approach the down plate DPl for that stop and is thereby opened, thus opening the holding path through the stopping circuit and deenergi'zing the down-direction switch D. The contact switch Ll opens when the car is 11% inches from the stopping floor level and inasmuch as a down full loaded car willdrift ll% inches after the motor is deenergized and the brake applied, it will stop approximately level with the stopping floor.

It will be assumed now that the car completes its stop and continues its down trip with a load between full load and a balanced load. Under these conditions, the current used by the hoisting motor will energize the contro1 relay E sufficiently to close its contacts E l, thus placing the effective holding path through the stopping circuit under the control of switch L2, by extending it through:

30, D3, El, L2, L3, L4, Ella As the down car approaches the next down stop, its contact switch Ll is first opened by passing the down plate DPl for that stop but that does not affect the stopping circuit. As the car continues downwardly, the next contact switch L2 passes thedown plate D-Pl and is opened, thereby thus opening the holding path through the stopping circuit which deenergizes the down direction switch D to stop the car. The contact switch L2 opens when the car is 10 inches from the floor, and inasmuch as the down drift of the car having between a balanced load and a full load is 10 /2 inches, the car will stop level with the floor.

It will be assumed now that the car completes its stop and resumes its down trip with a balanced load. Under these conditions the hoisting motor uses sufficient current to energize the re lay F to a point where it closes its contacts Fl. Therefore the'holding path through the stopping circuit is controlled by switch L3 and now extends:

as, D3, Fl, 136,134, Gl, L4, 38a

As the car moves downwardly to the next stop at a landing floor, its contacts Ll are first to approach the down plate DPl for that floor and are opened, but they do not affect the holding circuit. Next, the contacts L2 are opened by the down plate DPl for that floor, but they do not affect the holding circuit. Next, the contacts L3 are opened by the plate DP2 for that floor, thereby opening the stopping circuit when the car is 9 inches from the stopping floor. Inasmuch as the balanced down car has a normal drift of 9 inches and its motor is cut off and its brake applied when it is 9 inches from the floor, itwill be stopped level with the floor.

Assuming now that the car unloads at the stop just described and starts on down in an empty condition, under this condition the control relays E, F and G will be energized because of the increased current used by the hoisting motor and therefore the holding path through the stopping circuit will be controlled by switch L4 and will extend:

30, D3, Fl, D6, D4, GI, L4, 30a

As the car approaches closely to the stopping floor the contact switches will be operated in the order Ll, L2 and L3. However, these do not afiect the holding circuit and it is not until the fnovement of the car causes the contact switch L4 to open that the stopping circuit is opened to deenergize the down-direction switch for stopping the car. Inasmuch as the contact switch L4 opens when the car is 8 inches away from the floor and the down drift of the empty car after its motor is cut off and its brake applied is 8 inches, the car will be stopped level with the floor.

It is" to be understood that the distances given are approximate, and that they will vary some with variations in load and operating condition:

By the foregoing operations it will be seen that we have provided a stopping system for a single speed elevator which will cause the car'motor to be cut off and the brake applied at a point a distance from the stopping floor corresponding to the distance the car will drift by reason of it loaded or unloaded condition and its direction of operation, It will also be apparent that this system embodies only one inducto relay device' taking up a width of only one inductor relay on the top of the car and also requiring a small number of inductor plates mounted in the hatchway. Furthermore, the points at which the motor is cut off and. the brake applied are only 1 /2 inches apart so that the plus or minus error at the floor level will be only half that amount or of an inch. From this it will be apparent that we have provided a system with such a large number of points at which the motor may be cut off and the brake applied that the possible errors in variations in the amount of drift of the car under various loaded and unloaded conditions in connection with its direction of operation will be so small that the car will stop approximately level with the floor under any condition;

It will'also be apparent that each control relay will require only one pair of contacts and that the number of relays and inductor plates are kept at a minimum so that the expense of construction and maintenance is kept at a low point.

Although we have illustrated and described only one specific embodiment of our 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.

We claim as our invention:

1. In an elevator system, a car for serving a plurality of floors in a hatchway, a motor for operating the car, a plurality of stopping switches mounted in a vertical plane on the car, means responsive to the approach of the car to a stop at a floor for operating the stopping switches in a predetermined order, and means responsive to the loading of the car and its direction of operation for rendering effective for stopping the motor that stopping switch corresponding to the normal drifting distance of the car resulting from its loading and direction of operation.

2. In an elevator system, a car for serving a plurality of floors in a hatchway, a motor, means for connecting the motor to a source of electrical energy for operating the car, a plurality of stopping switches mounted in a vertical plane on the car, means for simultaneously preparing the switches for operation when a stop is to be made,

means responsive to movement of the car for operating the switches in a predetermined consecutive order as thecar approaches a stop at a floor, a stopping circuit including the stopping switches, a plurality of shunt circuits associated with the stopping circuit, and control means responsive to the loading of the motor for controlling the shunt circuits to render efiective for stopping the motor that stopping switch corresponding to the loading of the car.

3; In an elevator system, a car for serving a plurality of floors in a hatchway, a motor, means for connecting the motor to a source of electrical energy for operating the car and means for stopping the car comprising a brake for the motor, a plurality of switch devices mounted one above the other in an approximately vertical plane on the car, switches on the switch devices, means for operating the switches in a predetermined consecutive order when the car approaches a stop at a floor, a plurality of control devices controlled by the loading of the motor, and means responsive to the operation of the control devices and to the direction of operation of the car for rendaring one of the switches efiective for disconnecting the motor from its source of energy and for applying the brake to stop the car when the car approaches within a distance of that floor substantially proportional to the loading of the motor and its direction of operation.

fl. In an elevator system, a car for serving a plurality of floors in a hatchway, a motor, means for connecting the motor to a source of electrical energy for operating the car, and means for stopping the car comprising a brake, a switching kl i e mounted on the car, said switching device having a plurality of relays disposed one above the other in approximately a vertical plane, a plurality of stopping switches mounted on the relays, means for simultaneously preparing the relays 'for operation, means responsive to the prepared condition of the relays and movement of the car for operating the switches in one predetermined consecutive order in up direction operation and in another predetermined consecutive order in down direction operation, a plurality of control devices controlled by the loading of the motor, and means responsive to the operation of the control devices and the direction of operation of the car for rendering one of the switches efiective to cause disconnection of the motor from its source of energy and application of the brake at a distance from that floor corresponding to the loading of the motor and its direction of operation.

5. In an elevator system, a car for serving a plurality of floors in a hatchway, a motor, means for connecting the motor to a source of electrical energy for operating the car, and means for stopping the car comprising a brake, and a switching device mounted on the car, said switching device having a plurality of relays disposed one above the other in approximately a vertical plane with their north poles adjacent to each other, a plurality of stopping switches mounted on the adjacent ends of the relays, means for simultaneously preparing the relays for operation, means responsive to the prepared condition of the relays and movement of the car for operating the switches in one predetermined consecutive order in up direction operation and in another predetermined consecutive order in down direction operation, a plurality of control devices controlled by the loading of the motor, and means responsive to th operation of the control devices and the direction of operation of the car for rendering one of the switches effective to cause disconnection of the motor from its source of energy and application of the brake at a distance from that floor corresponding to the loading of the motor and its direction of operation;

6. I -n an elevator system, a car for serving a plurality of floors in a hatchway, a single speed motor for operating the car, an up-direction switch and a down-direction switch for starting the motor, an up starting circuit for the up switch, a down starting circuit for the down switch, a single stopping circuit, said stopping circuit having shunt circuits intermediate its ends, means for disconnecting-an operated starting circuit "from its starting switch and connecting the single stopping circuit thereto, a plurality of stopping switches mounted on the car and connected in said stopping circuit, means responsive to the approach of the car to a stop at a floor for operating the stopping switches in consecutive order, and means responsive to the loading of the car and its direction of operation for Controlling the shunt circuits in accordance with the loading and direction of operation of the car to render effective the stopping switch which will initiate the stopping of the car at a distance from the floor corresponding to its normal stopping drift resulting from its loading and direction of operation.

7. In an elevator system, a car for serving a plurality of floors in a hatchway, a single speed motor for operating the car, an up-direction switch and a down-direction switch for starting the motor, an up starting circuit for the up switch, a down starting circuit for the down switch, a single stopping circuit, said stopping circuit having shunt circuits intermediate its ends, means for disconnecting an operated start--. ing circuit from its starting switch and connecting the single stopping circuit thereto; a plurality of stopping switch devices mounted one above the other in approximately a vertical plane on the car, a plurality of stopping switches on the switch devices and connected in said stopping circuit, a

direction of operation.

8. In an elevator system, a car for serving a plurality of floors in a hatchway, a single speed motor, a brake for the motor, means for connecting the motor to a source of electrical energy for operating the car, and means for stopping the car comprising an inductor device mounted on the car, said inductor device having a pair of relays disposed one above the other in approximately a vertical plane with their like poles facing each other, a pair of stopping switches mounted on each of the relays, said stopping switches being disposed with one pair above the other and in approximately vertical alignmenttherewith, an up pair of inductor plates anda down pair of inductor plates mounted on the hatchway wall adjacent to each floor, each of the plates in each pair being displaced both horizontally and vertically with reference to each other and a sufiicient distance apart to permit the relays to be moved therebetween by movement of the car to secure consecutive operation of the stopping switches in one order for up direction and in another order for down operation, a plurality of control devices floor proportional to the drift of the car depending on its loading and direction of operation.

WILLIAM F. EAMES. BIRNEY HINES.

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