US1072083A - Motor-controlling system. - Google Patents

Description

E. R. GARICHOFF. MOTOR CONTROLLING SYSTEM.

APPLICATION FILED MAY 18, 1905.

Patented Sept. 2, 1913.

WITNESSES:

ATTORNEY COLUMBM IYLANOGRAPH CO.,WASHINGTDN, D. c.

UNITED STATES, PATENT ornron.

EUGENE R. CARICHOFF, OF EAST ORANGE, NEW JERSEY, ASSIGNOR T0 OTIS ELEVATOR COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF J ERSEY.

MOTOR-CONTROLLING SYSTEML.

Specification of Letters Patent.

Patented Sept. 2, 1913.

Application filed May 18, 1905. Serial No. 260,922.

To all whom it may concern Be it known that I, EUGENE R. CARICHOFF,

a citizen of the United States, residing at, East Orange, in the county of Essex and The main object of my invention is to provide means for automatically reducing the speed of an electric motor to a predetermined value irrespective of the load and maintaining such reduced speed until the motor is stopped.

Another object of my invention is the provision of means for automatically reducing the speed of an elevator car, as it approaches a desired landing, to a predetermined value irrespective of the load, speed or direction of travel of the car, so that the car shall stop more nearly level with the desired landing floor than is usual in elevators now in operation.

In electric elevator systems in use at the present time, and more particularly that designated landing, will frequently overoeed to such floor and stop there, the entire run or fall short of the exact floor level.

Nearly all of the electric elevators now in use employ a motor whose stunt field alone is excited when the car is traveling cally the same speed upon ap )roac ing a floor landing with varlous loacs upon the Now the brake which is used to stop.

car. such a car is applied by a spring and the braking eflect at each stop is always the same.

It will readily be seen from the foregoing that where an elevator car is heavily loaded and approaches a landlng where it is desired to stop, if the car is descending there will be a tendency to over-run the floor level due to the momentum of the load. In a similar manner if the car be going in an upward direction, the load on the car being heavy, the latter will fall short of the floor level. lVith such machines, the brake spring is adjusted to stop the car with an average load at the floor level, and it becomes apparent that with other than a certain fixed load, a condition which is seldom if ever met with, the elevator car will not stop level with a predetermined floor landing. My invention provides for just this emergency.

A further object of my invention is the provision of signaling means at the landlngs.

Other objects of the invention will appear hereinafter, the novel combinations be ing pointed out in the claims.

Referring now to the accompanying drawing, which illustrates a push-button electric elevator system, E designates the usual car. Any suitable hoisting mechanism may be used.

In general, the system illustrates one in which a number of push-buttons are located at each floor landing. The number of buttons P at each floor correspond to the number of floors, thus making it possible to call the elevator car from any floor to any one articular fioor, or to send the car from any oor to any other floor. It is merely necessary to push a button on any floor corresponding to the floor at which it is desired to have the car stop. The elevator will then prooperation outside of pushing a button being automatic. 1

The switch L is an ordinary double pole switch. The floor relays A, B, C, andD are exactly alike in construction, and by referring more particularly to relay Dit will be seen that each comprises a solenoid, 3, adapted when energized to raise the plunger or core 4 to which are rigidly connected the parts 10 and 15 shown in this instance as rods. The lower end of the rod 10 has a collar 12 firmly attached to it while the rod 15 has fastened at its lower end a collar 16. Ufipon these rods 10 and 15 are loosely mount- .e the contact-makers 9 and 13, respectively.

11 designates a spring which limits the downward movement of the contact-maker 9. The lower contact-maker 13 normally rests upon the contacts 17 and 14. Directly above, and in the path of travel of, the disk 9 are four fixed contacts 5, 6, 7, and 8 which are engaged and connected by the contact-maker 9 when the latter is in its raised position. This relay is more clearly illustrated in Fig. 3 of my Patent N 0. 677,891, granted July 9, 1901, for an improvement in controlling apparatus for elevators. relays, it will be seen that as soon as the solenoid 3 is sufficiently energized to raise the plunger 4, the contact-maker 9 will be carried upwardly by the collar 12 and spring 11 until it bridges or makes contact with the four contacts shown directly above. The rod 15 is at the same time raised upwardly, sliding freely through the contact-maker 13, the latter remaining stationary until the collar 16 engages it, when it will be raised out of engagement with the contacts 17 and 14. The spring 11 having been compressed during this operation, will firmly hold the upper disk 9 against its contacts. The main object of this construction is to insure the engagement of the upper disk with its contacts before the lower disk has been raised out of engagement with the contacts 17 and 14.

The motor reversing switches R and R are of similar construction. A description of one applies equally as well to the other. The reversing switch R comprises a solenoid 20 adapted when energized to raise the plunger 21 to which are rigidly fastened the insulated contact-makers or contact-bridges 22 and 23. Directly above the contact-maker 22 and in a position to be engaged thereby, are three fixed contacts 24, 25 and 26, and directly above contact-maker 23 and arranged to be engaged thereby, are three fixed contacts 27, 28 and 29. The contactmaker 23 when in its lower position, rests on and bridges the fixed contacts 30 and 31.

r designates a resistance, one end being connected to the contacts 28 and 28 and the other end being connected to contacts 31 and 30.

S designates a magnet switch and comprises a plunger carrying a contact plate 18 which is in contact with the fixed contacts 19, 32 and 33 except at such times as it is raised by the solenoid 34 into contact with the fixed contacts 35 and 36, the latter contacts being connected together by the resistance 37.

H designates a magnet-controlled rheostat operated by the solenoid 38 through the plunger 39, the latter carrying two contact pieces 45 which are held in engagement with the contact strip 47 and contacts 48 by the compression spring 46. A piece of insulation 43 is rigidly mounted upon the plunger 39 and serves to operate the bell-crank levers Owing to the construction of these 40 and 40 which latter serve to establish electrical connections between the contacts 41 and 42 and 41 and 42, respectively. A contact disk 44 is also fastened to the plunger 39 but insulated from it and when in its lowermost position bridges the fixed contacts 50.

I designates a magnet switch whose operating solenoid is connected across the armature brushes and which is adapted to control a circuit to the solenoid 38 of rheostat H through the contacts 54.

M is the hoisting motor, its armature being designated by 55, shunt field by 56, and

the armature brushes by 57 and 58, respectively. While the motor M is shown as shunt wound, it is to be understood that any type of electric motor may be used, a shunt motor being shown merely for the purpose of illustrating one application of my invention and at the same time to make the various electrical connections as. simple as possible and thereby avoid complexities.

G designates the conventional brake which may be applied to a friction pulley on the motor shaft by a spring when it is desired to stop the hoisting machine, and released by a magnet when the elevator car is to be started either up or down.

0, O, O, O' designate the landing door contacts, one for each landing, and are shown connected in series. Thus upon opening any one of the doors the connection between them is broken.

P, P, P and P designate push-buttons which are what is known as open-circuit buttons. A set of these buttons is at each floor landing and each set has as many buttons as there are floor landings. In the present case this number is four.

F designates a floor controller and in general comprises sets or groups of contacts each group controlling electrical circuits relative to the different floor landings. These groups may be divided into two halves, one half operating to control the motions of the car in an upward direction and the other half operating in a similar manner when the car is descending. The floor controller is preferably connected to the shaft of the ele vator hoist-ing drum by a sprocket chain. The floor controller will therefore always be in an exact relative position to that of the car.

The different sets in each group, indicated by parentheses, are similar in construction, only differing in the manner in which they are connected electrically. The lowermost set on the Down side, for example, comprises four contacts 68, 69 and 60, 59, which are adapted to be bridged by the contact pieces 70 and 61, respectively. The same applies to any other set. The Up set of contacts on the Up side are shown connected, z. 6., bridge piece 64 engages contacts is raised out of engagement with its contacts.

62 and 63, and bridge piece'67 engages the" their res ective contacts. The bridge 61 closing rst, then brid e 70. Next, the bridges and 81 on to Up side are moved awa from their respective contacts, the piece 8 being the first to move. Next, the bridge 83 closes and directly afterward the bridgle 82. This operation is repeated at the di erent sets of contacts in a similar. manner as the car rises, until finally when the car hasreached the top landing, the'{ bridge pieces on the Down side are/all in engagement with their respective contacts, while the bridge pieces on the Up side arei all out of engagement with their respective contacts. Should the car go down again,

25 the same operation is gone through witlu only in a reverse manner, and upon the car reaching the bottom landing the same conditions exist as before, i. 6., the bridge pieces on the Down side are all out of engagement with their respective contacts while: the bridge pieces on the Up side are all in an engaging position with their respective contacts.

The operation of such a system as has just been described can be best shown by pressing one of the buttons, say the top button of the set P. The car being at the bottom landing? and the main line switch L closed, a circuit;

will at once be established from the positive 1 main by wires 2 and 84 throu h the landing; door contacts 0, O, O" and (thedoorsi must be in their closed position); and by y the wire .85 to the contacts 14 and 8 of the g floor relay D. Now as the lower contactmakers of the floor relays are all in their lower positions, the circuit is closed through I the lower contacts of these relays to the wire 3 86 which latter is common to all of the push buttons P, P, P, P'. The top button of the set P having been pushed, the circuit iscompleted through that button by the wire, 87, the solenoid '3 of relay D, wire .88, hall light 114, and by the wire 1 to the negative main. The circuit just pointed out includes the door contacts, the lower contacts of the: floor relays, a pushbutton, the solenoid 3 of floor relay D and the hall lamp 114. The

solenoid 3 will now be energized to raise its plunger 4 I together with the contact-makers 9 and 13. The contact-maker 9 will engage, the contact 8 before the contact-maker 13' The operation of the relay D opens the circuit through the wire 86 to the hall but- 85, and contacts 8 and 7 to the contact 66 on the floor controller. This contact 66 is contons, at thecontacts 17 and 14, but not until the circuit to the solenoid of floor relay D has been completed through the contacts 8 and 5. The solenoid of D is now in a selfholding circuit including the door contacts 0, O, O" and O' At this juncture it would be manifestly impossible to operate the other relays since the common wire 86 of all the buttons is open circuited at contact 17 Therefore, all the push-buttons are deenergized. When the upper contactmaker of relay D bridges the contacts 5, 6, 7 and 8, the positive main is connected through the door contacts by wires 84 and nected by the bridge piece 67 and contact 65 to the lowerterminal of the solenoid 34 of the slow down switch S, the upper terminal of this solenoid being connected by wire 92 through the contacts 50 (the contact-maker 44 at this time being in its lowermost position), and wire 89 to the wire 1 and the negative main. A circuit is thus completed through the solenoid 34 and the contact-maker 18 is thereby raised into engagement with the fixed contacts 35 and 36. The operation of the relay D also completed a circuit to the reversing switch R, this circuit being traced from the positive main by wires 84,85, contacts 8 and 6, wire 90, contacts 63 and 62 and bridge-piece 64 of the floor controller to the solenoid 20 of switch R. The other terminal of this solenoid is connected to the negative main by the wire 91, contacts 30 and 31, contact-maker 23, contact 30, wire 92, contacts 50, and the wires 89 and 1 to the negative main. The solenoid of R is thereby energized to raise its plunger together with its contact-makers '22 and 23. Thecontact-maker 22 bridges the contacts 24, 25 and 26, while the contact-maker 23 bridges the contacts 27, 28" and 29 and at the same time is raised out of engagement with the contacts 30 and 31. The solenoid of switch R is now open-circuited at 31', thus making it impossible to energize it so long as the solenoid of switch R is getting current. In a similar manner it is impossible to get current to the solenoid of switch R when the solenoid of switch R is energized.

The operation of switch It closes a circuit to the hoisting motor M, this circuit being traced as follows: From the positive main current flows by wire 2, contacts 36 and 35 (the resistance 37 being shortcircuited by the contact-maker 18), contacts 26 and 24, and contact-maker 22, and by wire 93 to the motor armature by the brush 58. Thecircuit continues to the opposite brush 57 which is connected to the contact strip 47 of the rheostat H, the plunger 3-9 being in its lowermost position. The strip 47 is in electrical connection with the resistance 49 through the lowest of the con' is connected by wire 96, contacts 41 and 42 of switch 40, and by wires 89 and 1 to the negative main. The field, therefore, receives current at the full line potential, and since the brake G is connected inparallel to the motor field, it follows that it will be en ergized to release the brake. The motor now receives current from the line limited by the resistance 49. The motor field is fully excited and the brake released. The motor is free to operate the hoisting ma:

chinery to raise the elevator car.

Upon the operation of the switches R and S, a circuit is closed to the solenoid 38' of the rheostat H. This circuit may be traced from the positive main through contact 25, and byvwire 95 to the contacts 54 of switch I, solenoid 38, contacts 41 and 42 of switch 40, to the wire 89 and negative main 1. The solenoid will therefore be energized to raise the plunger 39, the sliding wipers 45 operated thereby cutting out the resistance 49 in a well-known way. If desired, a dash-pot of any suitable construetion may be used to regulate the speed of the plunger as it rises. This cutting out of the resistance 49 allows the motor to run at a higher speed, its armature being connected across the mains. 49 has all been cut out a further upward movement of the plunger 39 causes the insulation piece 43 to strike and operate the small bell-crank levers40 and 40 which at all other times are closed, thereby breaking the connection between the contacts 41 and 42, and 41 and 42, respectively. The circuit to the shunt field of the motor is now forced to traverse the resistance 52, since a circuit from wire 96 by way of contacts 41 and 42 to wire 89 and negative main 1 is broken at the contacts 41, 42, current now flowing from wire 96 to wire 97, resistance 52, wire 98, to wires 87 and 89 to the negative main. This will cause a reduction in the current strength and consequent weakening of the motor field which operates to As soon as the resistance,

to prevent any over-heating and waste of energy after the solenoid 38 has raised its core or plunger 9, the current required to raise the plunger 39 being greatly in excess of that required to hold the plunger in its uppermost position. i

The operation of the rheostat H opens at the contacts 50, the circuit through the solenoids 34 and 20of the switches S and R by way of wire 92. The circuit now supplying these solenoids may be traced from the positive main to the contacts and upper contact-maker of floor relay D, through, the floor-controller F, and through the solenoids 20 and 34. The circuit from the solenoid 20 continues through wire 91, contacts 30 and 31 and contact-maker 23, re-

sistanoe 7, contacts 28 and 29 and contactmaker 23, wire 1 to the negative main, while that from the solenoid 34 continues through a portion of wire 92, to wire 99, contact 30, resistance r, to the negative main as before. The current passing through the solenoids 20 and 34 is therefore reduced by the presence of the resistance r in the circuit of each. The position that the various parts have I10W assumed, together with the arrangement of the circuits in accordance with the foregoing, correspond to normal full speed, the car traveling upwardly. Shortly before the car reaches the desired landing, in this case the top floor, the bridge piece 67 on the floor controller is moved out of contact with,

the two fixed contacts and 66, interrupting the circuit between them. Now this circuit includes the solenoid 34 of slow-speed switch S. The solenoid 34 will be deenergized and allow the contact-maker 18 to drop and electrically connect the contacts 19 and 33. This is productive of three results; first, the resistance 37 is inserted in the circuit supplying the motor with current from the main line; and second, a shunt circuit is closed around the motorarmature through the resistances 51 and 49; and third, the solenoid of switch I is connected across the armature brushes, one end of the solenoid being permanently connected to brush 57 and the other end being now connected by contacts 19 and 32 to the brush 58.

The insertion of the resistance 37 into the armature circuit cuts down the amount of current flowing from the main line to the motor, causing the latter to run at a reduced speed. The shunt around the motor armature through the resistances 51 and 49 further reduces the amount of current passing through the armature thereby producing a still slower speed.

At the time that the solenoid 100 of switch I is connected in circuit, the motor is developing a counter-electromotive force of relatively high value. The solenoid 100 will therefore receive sufficient current to door at the top landin energize the same and raise its contactmaker 101 from the contacts 54 which results in opening the circuit to the solenoid 38 of the rheostat H. The sliding wipers 46 will therefore be allowed to descend to cut out the resistance 49 but the resistance 51 remains in circuit. When the core 39 begins to descend, the contacts 41, 42 and 41 42 crank levers 40 and 40, respectively, thereby short-circuiting the resistances 52 and 53.

The cutting out of the resistance 49 from the shunt circuit produces a gradual slowing down of the motor until its speed and counter-electromotive force assumes a value so low that the solenoid 100 becomes deenergized to such an-extent that it no longer has suflicient power to hold its plunger in its upper position. Upon the plunger 102 dropping, the contacts 54 are again placed in electrical connection, thereby closing the circuit including the solenoid 38 of rheostat H, which will operate to re-insert the resistance 49 in the shunt circuit across the armature brushes. As the resistance 49 is being re-inserted, the motor speed and resultant counter-electro-motive force rises again, energizing solenoid 100 of governor switch I causing it to again open-circuit the solenoid of rheostat H. The latter again cuts out of circuit more or less of the re sistance 49.

The switch I by virtue of its connections depends for its operation upon the counterelectro-motive force of the revolving armature. This counter-electro-motive force is proportional to the speed and load of the motor, and since the insertion or cutting out of resistance 49 is controlled by the rheostat Hand the latter is dependent for itsoperation upon switch I, it necessarily follows that the motor automatically acts as its own governor, causing its armature to revolve at a constant low speed regardless of the load. By the time the car has reached the desired landing at the top floor, the floor controller operates to open the circuit to the solenoid 20 of the reversing switch R by removing the bridging piece 64 from the contacts 62 and 63. The core 21 of the reversing switch It now drops, cutting off all current supply to the motor and at the same time applying the brake by open-circuiting its releasing coil and allowing the spring to apply the brake shoes. The relay D remains energized, maintaining its own circuit the same bein closed throu h the door contacts. In orc er to restore the system to its normal condition it is necessary to open one of the doors; in this case the would be opened, breaking the circuit fee ing relay D, allowing it to drop and thereby restoring the system to a proper condition for any further operation by the push-buttons.

are again connected by the bell If it be desired to bring the car to the bottom landing, it is only necessary to push a corresponding button. In such case the relay A is energized to operate in a manner similar to that of relay D. In this case, however, a circuit to reversing switch It is closed through the floor-controller contacts 59 and 60 and to the switch S through the contacts 68 and 69. Circuits to the motorarmature, field and brake are closed as before, except that now the current to the armature flows in a reverse direction, causing the elevator car to descend. The armature circuit now extends from the positive main by contacts 36 and 35, 24 and 26, resistance 49, to brush 57 passing through the armature to brush 58, the circuit continues by wire 93 and contacts 29 and 27 to the negative main, the current traversing the motorarmature in a direction reverse to that when the car was ascending. As the car approaches the lower landing, the floor controller operates to open the circuit of slowspeed magnetic switch S at the contacts 68 and 69 and finally by opening the contacts 60 and 59 to stop the car at the desired floor. The automatic operations of the rheostat H and governor switch I takes place as before and causes a reduction in motorspeed to a low constant regardless of the load so that as the car approaches the land ing the ultimate efiectis to stop the car substantially level with the floor landing. As before, a landing door, as 0 must be opened and shut before another operation is possible.

In order to have either of the reversing switches operate to raise their plungers and to close a circuit to the motor, it is necessary that all of the resistance 49 is first inserted in the armature circuit. This is accomplished by the circuit-closer including the small contacts 50. When any button is pushed, the corresponding relay operates to close a circuit to the operating solenoid of either of the reversing switches R or It. This circuit must be completed through the contacts 50, and as the plunger 39 and disk 44 must be in their lowermost position to do this, it is apparent that it would be impossible to start the motor unless the resistance 49 was in circuit.

The operation of the system when it is desired to move the car to an intermediate ifloor landing is similar to the foregoing description in connection with the top or bottom landings, the floor controller in every case controlling circuits leading to the re versing switches R and R and the slowdown magnet S, while a relay magnet corre sponding to the predetermined button closes circuits through contacts on the floor controller which corresponds to the selected button. M

It will be seen from the drawing that the hall lamps or signal devices 111, 112, 113 and 114 are in series respectively with the coils of the floor relays A, B, C and D and have a common return wire 104 to the negative main. lVhenever the uppermost pushbutton at any floor landing is operated the signal device 114: at the uppermost landing and only that signal device, will be immediately operated no matter where the car may be at the time. Furthermore, the signal device, shown as a lamp in this instance, will remain in its indicating position until the car is brought to the top floor and the door is opened to break the circuit. So also if the 15' third floor push-button at any floor be pressed the lamp 113 at the third floor will be lighted and remain lighted until the car arrives at that floor, is stopped, and the door is opened. The lamps 111 and 112 will be operated in a similar manner by the first and second floor push-buttons.

While I have described my invention in connection with an electric elevator system 1 and have shown its operation when applied thereto, and while it is particularly adapted to such a system, I do not wish to limit myself to such a system or to any other particular system in which an electric motor is used for hoisting or other purposes, my invention being applicable to any and all systems in which it may be desired to produce an automatic governing or slowing down of an electric motor to a constant value irrespective of its load.

Having fully described my invent-ion, what I claim and desire to secure by Letters Patent is:

1. In combination with a motor, of a starting resistance in circuit therewith, an electro-responsive device for varying said resistance, means for closing a circuit to said device, a normally short-circuited resistance in series with the winding of said electroresponsive device, means operated by said device for opening the short-circuit around said last named resistance to reduce the current in said winding, an additional resistance in series with said starting resistance, means comprising an electro-magnet for short-circuiting said additional resistance, a shunt circuit for said electro-magnet, said shunt circuit containing resistance to reduce the current through said electro-magnet after said additional resistance has been short-circuited, and a circuit closer connected to said electro-responsive device for controlling a circuit to said electro-magnet.

2. The combination with a motor, of resistance, means for varying said resistance, an electro-responsive device for controlling said resistance-varying means, means for closing a circuit through said electro-responsive device, an additional resistance, means for establishing a circuit including the motor and said first-named resistance and for closing a local circuit including said motor and said resistances in series, and

means for interrupting the first-named circuit through said electro-responsive device to control the speed of the motor.

3. The combination with a motor, of motor starting resistance, additional resistance arranged to be placed in series therewith, means including an electro-magnet for conance connected across the motor armature,

means comprising an electro-magnet for varying sa1d resistance, and means for interrupting the circuit through said electro-magnet when the motor exceeds a predetermined speed.

5. The combination with a motor and a main line circuit, of sectional resistance normally in series with the motor-armature, connecting-mechanism for sa1d resistance, a

solenoid connected across said main line, a core or plunger for the solenoid and secured to said connecting-mechanism, a second solenoid connected across the armature, a core for said second solenoid, a switch secured to said last-named core actuated by said second solenoid to interrupt the circuit to the first-named solenoid upon the motor-armature attaining excesssive speed.

6. The combination with a motor, of starting resistance therefor, means for varying said resistance, additional resistance in a circuit connected in parallel with said motor when the latter is at rest, an electro-responsive device for influencing said resistancevarying-means, and means for interrupting said circuit upon starting of the motor and for closing the same to reduce the speed thereof and also connecting said electro-responsive device across the armature to control said reduction of speed.

7. The combination with a motor, of starting resistance therefor, means for varying said resistance, a second resistance arranged to be connected in series with the motor to reduce the speed thereof, and a third resistance arranged to be connected to said starting resistance and to still further reduce the speed of the motor.

8. The combination with an electric motor, of sectional resistance normally in series with said motor, means for varying said resist-ance, an electro-magnet for actuating said varying-means, an additional resistance and a switch in a circuit in shunt to said motor and sectional resistance, an electro-responsive device, means for operating said switch to interrupt said circuit upon starting the motor and for closing the same to reduce the speed of the motor before stopping and also for connecting said electroresponsive device across the armature to control the said resistance-varying means.

9. The combination with a motor, of resistance in circuit therewith, movable contacts for cutting out said resistance to increase the speed of the motor, an electromagnet operating at constant potential for controlling said contacts, a switch in circuit with said electro-magnet, a governing magnet for actuating said switch to effect a deenergization of said electromagnet to allow the latter to reinsert and gradually vary said resistance or a part thereof to reduce the speed of the motor, and means for connecting said governing magnet across the motorarmature to be controlled by the varying potential thereof.

10. The combination with a motor, of resistance in circuit therewith, movable contacts for varying said resistance, an electromagnet for operating said contacts, a switch in series therewith, an additional electromagnet for cont-rolling said switch, an additional resistance and an additional switch in parallel with said motor and first-named resistance, and means for opening said additional switch on starting and closing same on stopping and also connecting said additional electro-magnet across the motor-armature so as to be controlled by the potential thereof.

11. In motor-controlling apparatus, the combination with a resistance, of movable contacts for varying said resistance, an electro-magnet operating at constant potential for operating said contacts, a switch in series with said electro-magnet, an additional electro-magnet for controlling said switch to eifect a variation in the reduction of speed of the motor in accordance with the load.

12. In motor-controlling apparatus, the combination with resistance in a controlled circuit, an electro-magnetic device operating at constant potential for varying said resistance, an additional electro-magnetic device for controlling said resistance-varying device to efiect the same reduction of speed of the motor with varying loads.

13. The combination with an electric motor, of reversing switches for the same, a resistance in circuit with the reversing switches, a variable resistance for the motorarmature, an electro-magnetic device for controlling the same, an additional electromagnetic device for controlling the aforesaid electro-magnetic device; and means for inserting said first-named resistance in series with the motor to reduce the speed thereof, and connecting said additional electro-magnetic device across the motor-armature to effect the same reduction of speed of the motor before stopping with varying loads.

14. In a push-button electric elevator system, the combination wit-h a car and its motor, of push-buttons corresponding to the various landings, reversing switches for the motor, circuits and connections for automatically controlling said reversing switches, means for varying the resistance of the m0- tor-armature circuit, an electro-magnet for controlling said means, an electro-magnetic switch for controlling said electro-magnet, and means for automatically controlling said electro-magnetic switch to effect a reduction of speed of the motor to a predetermined low value irrespective of the load as the car approaches a predetermined landing, so that the car shall stop substantially level with the desired floor.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

EUGENE R. GARIOI-IOFF.

'Witnessses CHAS. M. NISSEN, W. H. STOKES.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G.

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