US716953A

US716953A - Electric elevator.

Info

Publication number: US716953A
Application number: US52717494A
Authority: US
Inventors: Frank J Sprague
Original assignee: Sprague Electric Co
Current assignee: Sprague Electric Co
Priority date: 1894-10-29
Filing date: 1894-10-29
Publication date: 1902-12-30
Anticipated expiration: 1919-12-30

Description

Patented Dec. 30,1902. F; J. SPRAGUE.

ELECTRIC ELEVATOR.

(Application filed Oct. 29, 1894.)

8 Sheets-Sheet I.

' (No Model.)

WITNESSES:

mvrnron flank J5 in ya. BY. I W j I ATTOR s @d wzz No. 7l6,953. Patented Dec. 30, I902.

F.- J. SPRAGUE.

ELECTRIC ELEVATOR.

- (Application filed Oct. 29, 1894.} (No Model.) 8 Sheets-Sheet 2.

m: "cams PE'KRS no, vuoTo-uwo.. WASHINGYGN, u c

' No. 716,953. Patented Dan. 30, I902.

F. J. SPRAGUE;

, ELECTRIC ELEVATOR.

- (Application filed Oct. 29, 1894.) v (No Model.) 8 $heets-Sheet 3.

I! II II I! I! II [In WITNESSES: V INVEN TOR TNE uoams PUERS co. Pnoio-umo" wAsmNo'rom n. u.

No. 7l6,953. v Patented Dec. 30, I902.

F. J. SPBAGUE.

ELECTRIC ELEVATOR.

{Application filed Oct. 29, 1894.)

8 Sheets-Sheet 4.

(No Model.)

W/ TNESSES.

ATTORNEY THE mums PETERS co. Pum'uuma. wAsnmcYcn, u. c.,

Patented Dec. 30, I902. F. J. SPRAGUE.

ELECTRIC. ELEVATOR. (Application filed Oct. 29, 1894.

8 Sheets-Sheet (No Model.)

INVEI'ITOR WI TNESSES Patented Dec. 30, I902.

No. 7|s,953.

F. J. SPRAGUE.

ELECTRIC ELEVATOR. (Application filed Oct. 29, 1894.) (No Model.) 8 Sheets-Shed! 6.

WITNESSES. @az wzt aw/ a i lffikraymg.

6%M47/flM v4 v gi g y) INVEN TOR TNE mums PETERS c0, Puorounym WASHINGTON. u. c.

P atented Dec. so, 1902.

F. J. SPRAGUE.

ELECTRIC ELEVATOR.

(Application filed Oct. 29, 1894.)

8 Sheets-Sheet 7.

(No Model.)

IN VE N TUB WITNESSES ATTORNEY m: uoams "ETERs w PHuYO-LITO-IQ. WASHINGTON, D. c.

No; 716,953. Patented Dec. 30,1902,

- F. J. SPRAGUE.

ELECTRIC ELEVATOR.

{Application filed. Oct. 29 1894.)

(No Model.) 8 Sheets-Sheet 8.

WITNESSES: INVENT OR 11 TTORNEY.

m: Nomvs PETERS c'o. PnoTaumou WASNKNGTON, I:v c.

UNITED STATES PATENT OFFICE.

FRANK J. SPRAGUE, OF NEW YORK, N. Y., ASSIGNOR TO THE SPRAGUE ELECTRIC COMPANY, A CORPORATION OF NEW JERSEY.

ELECTRIC ELEVATOR.

SPECIFICATION forming part of Letters Patent No. 716,953, dated December 30, 1902.

Application filed October 2911894- Serial No. 527,1 7 1. (No model.)

To all whom it may concern:

Be it known that I, FRANK J. SPRAGUE, a citizen of the United States of America, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Electric Elevators, of which the following is a specification.

The invention is an improvement upon the systems shown in United States Patents No. -l72,909, dated April 12, 1892, and No. 509,397, dated November 28, 1893. Many of its broad features are described in the Electrical Englneer, New York, April 18, 1894, Vol. XVII, No. 311, beginning on page 350 and ending on page 356. 1

The improvements consist mainly in substituting an improved pilot-motor and circuit for controlling the connections and operation of the main motor, whereby the number of wires carried to the car are reduced to four; the substitution of an improved form of main or working motor; the simplification of the main regulator; the substitution of an electromechanical,for a purely mechanical brakerelieving device; the addition of an entirely new choking-shunt for the working motor,

and an entirely new circuit for controlling the brake; and the further modification of the systems shown in the patents named above, and in certain other features of construction and arrangement, as hereinafter fully described and claimed.

In the accompanying eight sheets of draw ings, which form a part of this specification, Figure 1 shows the main mechanical parts of the elevator, including the car-hoistway and hoisting mechanism, in about the relations in which they are constructed. Fig. 2 shows the hoisting mechanism, together with a diagrammatic representation of the controlling and regulating mechanism and electrical circuits. Fig. 2 is a detail of the monitor centrifugal governor for opening the brake-magnet circuit. Fig. 3 is a detail showing a modification of the rheostat. Fig. 4: is a diagram of the circuits as they are when the car is ascending at moderate speed. Fig. 5 shows the Fig. 6 is a diagram of the circuits as they are when the car is descending at moderate speed, and Fig. 7 shows the circuits of the preceding diagram as modified by the closing of the lower'automatic to automatically check the car at the bottom of the hoistway and also the centrifugal opened by high speed and the choking-shunt closed. Figs. 8 and 9 are respectively top and front views of the car-switch as it is preferably constructed. Fig. 10 shows a modified form of car-switch repeated in three positions, together with the pilot-motor and pilot-motorswitch block controlled by it. Fig. 11 shows the same elements enlarged, but with a simpler form of car-switch, the parts being in the position to which they are brought when the down contact is held closed. Fig. 12 shows the same elements in the position to which they are brought by closing the stop-contact, and Fig. 13 shows the position assumed on closing the up contact. Fig. 14 shows the connections of the car-switches of three elevators connected to their pilot-motors through a common-control switchboard. Fig. 15 is a view similar to Fig. 2, but showing a modification of the brake-magnet and its circuit.

General Construction.

The elevator is of a type in which the load is lifted by an electric motor and descends by gravity under control of the same motor, which is reversed in direction and driven by the car as a retarding-dynamo. The car is therefore necessarily heavier than the counterweight, even with the minimum load. It can therefore properly be called an underbalanced car. The machine is of the horizontal multiple-sheave type. The sheave and overhead work is of a style common in hydraulic and other plants. The rope multiplication and cross-head movement are similar to the horizontal type of hydraulic elevators. From the car 1 the hoisting-ropes 2 lead over an overhead sheave 3 to the inner of the sheaves 4 on the fixed cross-head 5 of the hoistingmachine and, dividing on either side of the cross-head and screw, lead to the traveling sheaves 6 on the traveling cross-head, pass back and forth between the two sets of sheaves and are anchored to the fixed end of themachine. Inpracticevariablechaincounterweights 8, with one end anchored in the hoistway, are used on the car or counterweight to make the pull equal at all points of the hoistway for any given load. The hoisting mechanism has a cross-head and frictionless nut 9, running upon a screw 10, instead of being attached to a piston operating in a water-cylinder, as in the hydraulic elevator. A heavy main girder 11 supports and guides the traveling cross-head and carries the outboard screw-bearing 1:2. The fixed crosshead is a casting bolted to one end of this girder, and at the other end is the motor bedframe 13, on which is the brake, the main or working motor, and the thrust-bearing of the screw. The nut and screw are of the general type of that of the United States Patent No. 438,320 and the nut is of the particular form described in United States Patent No. 476,304. The nut is mounted in the cross-head in the manner described in United States Patent No. 448,788. The screw is directly connected to the armature 14 of the working motor. This motor is preferably a multipolar slowspeed motor, with strongly compounded winding, part of the field-coils, hereinafter called the shunt field-coils 15, being connected in ashunt-circuit S to the main leads in parallel with the armature, and part of the field-coils, hereinafter called the series field-coils 16, being connected in series with the armature. These coils are superimposed on each pole. The working motor is regulated by a rheostat 17 and the main circuit-changing switch, consisting of a movable member 18 and contacts, controlled by a suitable controlling device on the car. As shown, this car device is a switch l9,which controls a pilot-motor 20 and through it controls the rheostat and switch of the working motor.

Like the hydraulic, this elevator always works against gravity. The shunt field-coils are normally connected to the main leads A B through a shunt-circuit S. While hoisting the car, the motor-armature and series fieldcoils are connected through a feed or hoist circuit C to the main leads and take current therefrom. In lowering the armature the series field-coils are cut off from the main lines and closed on the down regulating-circuit D. The working motor is driven as a dynamo in a reversed direction by the weight of the descending car and acts as a brake on the car in descent. The direction of the current in the field and armature of the working motor is substantially never reversed and the machine never demagnetized, for in hoisting the main line electromotive force predominates and in lowering the direction of the current in the shunt field-coils is unchanged and the reversed electromotive force of the motor-armature is the only active electromotive force in the circuit of the armature and series field-coils; but, as stated, the motor is then being driven in a direction the reverse of that of hoisting and the current developed traverses the armature and series fieldcoils in the same direction as the hoisting current traverses them. This current would traverse the series field-coils and excite the field, even if the shuntfield-coils were broken. The force which resists gravity while the car is descending is the sum of the friction and inertia of the hoisting mechanism and the torque of the armature due to the current generated therein by its own revolution. The torque exists whether the car be going slow or fast and is practically the same with any given load and a steady speed, whatever be the speed. In this respect this present system is unlike those electric elevators having an approximate balance between the car and counterweight, in which the working motor is connected to the main leads during both ascent and descent and takes current from or gives current to the lines according to the preponderance of weight and the speed of operation. The car 1 is held at rest at any point by an electromechanical brake 21,which holds the screw 10. The brake-band is of steel and is preferably wood-lined. It is anchored at one end on the side of the motor bed-frame away from which the screw turns in lowering, and at the other end is continually drawn down by a powerful spring 22 under compression. The mechanical movement in opposition is effected through the medium of a magnet, which in one form herein shown has a single coil, Fig. 15, and in a second form, Fig. 2, has a double winding. In this latter form of magnet one coil, called the series brake-coil 23, consists of a few turns of coarse wire and is in line in series with the working-motor armature and series field-coils and holds off the brake while the car is being hoisted. The other coil, called the shunt brake-coil 24, consisting of many turns of fine wire, is directly supplied from the lines through a circuit G, containing a suitablyoperated switch, and holds oilf the brake while the car is being lowered. The brake helps to stop the screw and locks it when at rest. The magnet which controls the brake also controls a cooperating automatic chokingshunt closer 25 in a derived circuit with the armature of theworking motor, herein called the choking-shunt E. The brake and automatic choking-shunt are not used to vary the car speed, but merely to help stop and hold the screw. The car speed, both in ascent and descent, is controlled by controlling the amount of resistance in circuit with the working motor, and this is true also as to graduating the stop and start of the car. To operate this system, I provide one general regulating device, called herein the main regulator, which is controlled, as shown, by a pilot-motor through a circuit called herein the car-circuit F, in which is a small switch handled by the conductor on the car. This car-switch is provided with hoist, lowering, and stop contacts, and the main regulator is provided with cooperating circuit-controllers included in the car-circuit. The main regu- IIO lator also has a contact in the hoist or feed circuit, which cooperates with the main rheostat to supply the working motor and main brake from the lines during ascent and also contacts in the down-regulating circuit, which regulates the working motor during the descent of the car, and in a circuit which is called the brakemagnet circuit G. This circuit may control the brake during both ascent and descent, as in Fig. 15, or it may control the brake only during descent, as in Fig. 2. In the latter the circuit includes the shunt brake-coil, which controls the electromechanical brake during the descent of the car. In both forms the brake can be applied during descent by means of a switch opened and closed by a circuit-opener, called the monitor centrifugal 26, which-is driven by the main screw. In both forms this centrifugal applies the brake only during descent. The term monitor is used to indicate that the switch warns the conductor if the car runs too fast, but does not limit his control of the car after the car slows down or stops. The term centrifugal is used in the broad sense of speed-governed.

Upon failure of the current, for any reason, whether in ascent or descent, the brake is applied; also to prevent attaining too high a speed on the down run the brake is applied by the monitor centrifugal opening the brakemagnet circuit. This governor may be of the Pickering or any other standard type of speedgovernor. Its construction is illustrated in detail in Fig. 2. There are strap-springs carryinggovernor-ballsaboutmidway. These springs are hinged at their lower ends to a fixed collar on the governor-shaft, and at their upper ends they are hinged to a sliding collar. Nuts limit the travel of the sliding collar and so determine the range of travel of the governor-balls to and from the axis. In order that the governor shall act to open at one speed and not close again until a lower speed is reached, it is over compensated. This is effected by having the strap-springs so bent before the governor is assembled that the springs would carry the balls in beyond the axis of the governor if all obstacles were removed. In all positions of the balls when the governor is together the springs will therefore have a deflection from their normal position that is greater than the distance of the balls from the axis. Under these conditions, when a speed sufficient to start the balls out is reached the centrifugal force, which increases,as is well known,proportionatelyto the distance from the axis, will rise more rapidly than the tension of the springs and the balls will at once fly out to their-outer limit,even though the speed of the governor remains constant, and remains there until the speed is checked sufficiently to bring the centrifugal force below the spring tension,when they will return. In Fig. 2 the length of the arrowsmrepresent the spring tension tending to hold the balls at their inner positions.

The arrows 0 represent a centrifugal just in excess of the springs to start out the balls. The arrow m shows what the spring force will become when the balls reach their outer position. force and centrifugal force will become without increase of speed of the governor when the balls reach their outer position. The centrifugal force being, as will be seen,in excess of the spring force, the balls will remain out until the centrifugal falls below the spring force through a reduction of the former by the slackening of the speed.

From the-foregoing it will be seen that the governor is constructed to open the switch when the screw exceeds a certain maximum and close it when the speed falls to a certain slower rate or the screw comes to a stop. Attached to the girder,near the outboard end of the screw, is the lower automatic switch 27. This is a rheostat-switch, operated by a roller 28 on the frame attached to the traveling cross-head, to close and gradually cut down the resistance of a shunting-circuit for the working motor when the car reaches its lowest limit. This circuit is called the lower automatic shunting-circuit H, or called, briefly, the lower automatic circuit. Attached at the otherend of the girder is the upper automatic switch 29, which is a rheostatic switch, operated by a roller 30 on the frame of the traveling cross-heads to increase the resistance in and finally open the feedcircuit when the car reaches its upper limit.

The main regulatoris independent and selfcontained and can be set at any convenient place. It is, in brief, as shown, a pilot-motor 20, with a magnetic brake 31 and having a shaft 32, which is threaded to carrya switchblock; a rheostat l7, composed of castiron grids (merely indicated) mounted in a circle or partial circle in a suitable frame (not shown) and connected with contact-clips; a rheostat-arm 33, having teeth 34 engaging with a worm 35 on the pilot-motor shaft, by which the arm is made to travel around the clips and opens and closes the circuit, and the movable member 18, one end of which is in the path of the arm and by it is thrown into contact with contact-points in the hoist and lowering circuits.

Generally speaking, the features of the mechanical construction of the parts are not herein claimed. The description, therefore, of mechanical construction is brief. Many of the features of mechanical construction, however, are novel and will be claimed in other applications.

Switches.

The more elaborate and complicated switches will now be described. This involves a description of the main regulator, which is composed in part of several of the switches.

The car-swttch-The car-switch, which may also be called an auxiliary or sub- The arrow 0 shows what the s rin sidiary controlling-switch, since it controls the pilot motor which operates the main switch, is operated by the conductor on the car to hoist, lower, and stop the car. It has a stop-contact 36, a hoist-contact 37, and a lowering-contact 38, through which can be closed, respectively, the stop branch f, the hoist branch f, and the lowering branch f of the car-circuit F. The contact 36is called a stop-contact, because if it is closed and held closed in any position of the system eX- cept when the car is already at rest the car will be brought to rest. The contact 37 is called a hoist contact, because if it is closed and held closed in any position of the system except when the car is already being hoisted at full speed the system will be brought into position to hoist the car, for should the car he descending continued closure of the hoist-contact while it would first bring the car to rest would cause the car to be hoisted, and contact 38 is called a lowering-contact, because if itis closed and held closed it will cause the system to be brought into condition to lower the car in the same way that closure of the hoist-contact operates to cause the car to be hoisted. In other words, the operator in order to cause the car to ascend, no matter what may be the condition of the system, has onlyto close the hoist-contact of the car-switch and hold it closed; in order to cause the car to descend has only to close the lowering-contact and hold it closed, and in order to cause the car to come to a rest has only to close the stop-contact and hold it closed. In fact, as the car-switches are constructed in order to bring the car to rest it is only necessary to let go of the car-switch altogether, whereupon a spring provided for that purpose will operate to close the stopcontact and hold it closed. Three alternative forms are shown. In that shown in Figs. 8 and 9 the stop-contact is opened by pulling a stop-lever 39 held in the fingers, and the other two contacts are closed by pressing push-buttons e0 41 with the thumb. Normally the stop-contact is closed and the other two contacts are open. This is the stop position of the switch and is maintained by the force of springs. When either of the push-buttons is pressed to close the hoist or lowering contact, it will open the stop-contact if the stop-contact is not already opened. The normal operation in starting is to open the stop-contact and then press the hoist push-button, thus bringing the switch into the hoist position, or press the lowering push-button, thus bringing the switch into the, lowering position, according as the car is to go up or down, and to hold the stop-contact open and the hoist or lowering contact closed until the main rheostat is brought into the position which corresponds to the desired car speed. The button may then be released and its contact allowed to open, the stop-contact being meanwhile held open. This brings the switch into the steady position-that is, the position of the switch which corresponds to continued uniform movement of the car. As will appear later, there is also provided in the car-circuit a compound automatic circuit-breaker which if a contact of the car-switch is held closed breaks the car-circuit when the main rheostat attains any limiting position, whether of up, down, or stop. The stop-contact must be held open so long as the car is to travel continuously in one direction. An alternative form is shown in Fig. 10. In this are also the hoist, lowering, and stop contacts, with springs to hold the stop-contact closed and the other contacts open. To close the-line through the hoist or lowering contacts, the stopping-lever 39 must first be carried to the right or left to a contact against which the up or down lever 40 or 4.1 is likewise closed, the up and down levers being operated to close with the stop-lever contact with opposite mechanical movements. The features of likeness in these two forms are that they have essentially the same contacts, that the stopcontact is opened and the others closed against a force, shown as a spring tension, and when released the stop-contact closes and the other two open, that to close the line through the hoist or lowering contact the stop-contact must first be opened, and that the stop-contact is operated by a movement distinct from that required to operate the other two contacts.

The third form is that shown in all of the diagrammaticfigures. Theessential features which it has in common with the other forms are that the switch can be brought into stop, hoist, lowering, or steady position, but is moved from stop position against a force, shown as a spring tension, to close either the hoist or lowering con tacts, which can be closed independently of each other, but only on opening the stop-contact, and automatically return to stop position when released. It is obvious that this feature of automatic return to stop position is applicable to car-controlling devices generally, whether they be switches or levers or other devices for operating circuits or valves in electric, hydraulic, or steam elevators. I therefore claim this feature broadly. It will be seen that I have in this car-switch which controls the pilot-motor a switch that may be brought into any one of three positions, in each of which it will close a circuit and cause the pilot-motor to be operated. The switch may be closed through the hoistcontact and will then cause the pilot-motor to run in such direction that the working motor shall cause the elevator to ascend, or it may be closed at the lowering-contact, in which case the pilot-motor will so arrange the connections of the working motor that the elevator shall descend, and the switch can be brought into either of these two positions only when moved out of the third position-that is, when the stop-contact is open, there being a spring provided automatically to close the stop-contact. Moreover, the circuit cannot be closed through the hoist and the lowering contacts at the same time. Thenever the circuit is closed at the stop-contact, the direction in which the pilot-motor has been driven is reversed, and in due course the pilot-motor is brought to rest, whether the hoist-contact or the lowering-contact has been closed.

The common-control switc7zb0ctrcZ.lVhen there is in a building a set of two or more elevators each operated by an electrical system such as is herein shown, there is preferably and almost necessarily provided at some convenient point, as in the room occupied by the multiplying machines and regulators, a common control switchboard, Fig. 14, to which all the car-circuits of the whole set of elevators are connected in multiple and on which is a separate switch 42 for each car. Each switch 42 consists of three levers which are thrown simultaneously, but are insulated from each other, but connected by three contacts to the pilot-motor belonging to the corresponding elevator. In their usual position each connects the stop, hoist, and lowering branches fff of the car-circuit F to the switch of the pilot-motor for the car, as shown for car No. 2; but each can be thrown, as shown for car No. 1, so as to connect its pilotmotor with a common-control switch 43. In the first-mentioned case the regulator and working mechanism for the car are controlled from the car by the car-switch, and in the second the regulator is controlled in the engine-room by the common-control switch. When any system has its three-lever switch in the middle position, as shown for car No. 3, it is disconnected both from its car-switch and from the common-control switch. The common-control switchboard is used for the purpose of general inspection, cleaning, testing, and manipulating the machines or when undergoing repairs. It is also useful for hoisting safes or for any other purpose when it is desired to run the elevators without a conductor in the cars.

The main reguZctt0r.The entire main regulator is controlled by the operator indirectly through the car-switch or the common-control switch. It comprises contacts in the carcircuit F, herein called the pilot-motor switch, contacts in the brake-magnet circuit G, herein called the brake-magnet switch 44, and the main circuit-changing switch, which has contacts in all but one of the circuits through the armature of the working motor and which, together with main rheostat, is called the working-motor switch. These three switches, which together constitute the main regulator, are all synchronously operated by the pilot-motor, to the shaft of which their movable members are geared. Fig. 2 shows the position of the switches which corresponds to the position of rest for the car. When the switch-block is moved to either side of its stop position, connections are established, as illustrated in positional off of the lowering-plate.

views and hereinafter explained, which result in establishing the hoist or lowering conditions of the circuits of the system. This is herein described as operation of the switchblock or the switches of the system in opposite senses.

The pilot-motor switch-The circuits of the pilot-motor are shown in detail apart from all the other circuits of the system. in Figs. 11, 12, and 13. On the switch-block are two like insulated plates, which, with cooperating contact-points, control the pilot-motor. The lefthand plate of the two is the lowering-contact plate 45, which, with the cooperating contacts,is called the lowering branch of the switch, and the right-handplate is the hoistcontact plate 46, which, with the cooperating contacts, is called the hoist branch of the switch. As to the hoist and lowering branches the switch is merely an automatic circuitbreaker. The third point is the stop-contact point. As to this the switch is an automatic circuit-changer and circuit-breaker. There might be three separate circuit-breakers. As shown, all the breaks, however, occur at a single insulation 45, which cooperates with all the contacts. The stop-contact is the middle contact, but is not exactly midway between the other two, being somewhat nearer the lowering than the hoist contact. This is because the main-rheostat arm 33 makes a complete revolution in turning from stop to full-hoist position and less than a complete revolution in turning from stop to full-lowering position, as will hereinafter appear more fully. In'the stop position, Fig. 12, the stop-contact rests on the insulation-piece 45, where it is out of circuit. In this position the other two contacts are distant from the middle contact less than half the distance from the ends of their respective plates to the stop-contact. As soon as the hoist-circuit is closed and the switch-block starts to move the lowering-plate comes in contact with the stop-contact, and similarly when the lowering-contact is closed the hoist-plate comes in contact with the stop-contact. If the car and pilot-motor switches are closed at the hoist-contacts, the circuit is automatically broken at the pilot-motor switch when the hoist-contact runs off of the hoist=plate. This occurs when the switch-block reaches its extreme position at the right, Fig. 13. In this position the lowering-contact is still closed, because of the unsymmetrical arrangement of the hoist and lowering contacts with reference to their plates above stated. It, on the other hand, the car and pilot-motor switches are closed at the lowering-contacts, the circuit is automatically broken in the pilot-motor switch when the lowering-contact runs This occurs when the switch-block reaches its extreme position to the left, Fig. 11. In this position the hoistcontact is still closed, because of the unsymmetrical arrangement of the hoist and lowering contacts and plates above stated. The

length of the contacts conforms to the intended travel of the rheostat-arm and determines the number of revolutions of the pilotmotor armature. The passage of the current through the pilot-motor armature releases its brake, and when the current is cut off the brake automatically stops the armature from running too far by its moment-um.

The car-switch 19 or common-control switch 43 and the pilot-motor switch form a compound sWitch consisting of two independent branches-to wit, the hoist branch, which controls the start in ascent and the stop in descent, and the lowering branch, which controls the start in descent and the stop in as cent, as will be hereinafter set forth. Each branch has a circuit-closer controlled by the operator, which controlled circuit-closer is the hoist or lowering contact of the car-switch or common-control switch. Each branch has also an automatic circuit-breaker on the pilotmotor switch, the branch being broken when the hoist or lowering contact point of the pilot-motor switch passes off of "its plate. \(Vith these branches are combined the controlled stop-contact of the car or commoncontrol switch, which the operator can open and close directly at will, and on the pilotmotor switch the stop-contact. In its intermediate position this acts as a circuit-changer to change the circuit from one branch to the other whenever the stop-contact of the carswitch is closed in any but the stop position and as an automatic circuit-breaker to open the circuit when the switch-block returns to the middle or stop position. The stop-contact on the car and pilot-motor switches and the con necting-wirefconstitute a stop branch of the compound switch. It will be seen that by this arrangement the car-switch is connected in circuit with the pilot-motor without the intervention of relays. The con nection is through the pilot-motor switch. The compound switch formed by the car-switch and the pilot-motor switch is directly connected to the pilot-motor. This is of great importance, because in my system the regulator is operated by the pilot-motor, which must therefore respond instantly and with absolute certainty upon the operation of the car-switch. This is insured by the electrical connection shown between the car-switch and the pilot-motor.

The working-motor switch.-The main or working-motor switch is made up of a'rheostat and a circuit-changing switch. The rheostat consists of a number of contact-clips arranged to form an arc of a circle and connected to each other in series, with one end of the series connected to the armature of the working motor, and a. rheostat-arm' 33 electrically connected to the movable member 18 of the circuit-changing switch and pivoted so that it can be revolved around the circle of the rheostat in either direction. The gap be tween the lowest clip 50, connected to the motor-armature, and the highest clip 5llat the other end of the series prevents the current from passing from any other clip of the series to the lowest clip by any path except through the intermediate clips. The gap between the highest and the lowest clip can be filled with insulated clips connected'to intermediate clips of the series, as shown in Fig. 3, so that the arm shall never break contact in the rheostat. The upper end of the movable member of the circuit-changing switch lies in the path of the main-rheostat arm 33 and is moved by the arm between a contact 47 in the hoist-circuit on one side and two contacts on the other side, one of which, 48, isiin the down regulating-circuit'and the other of which, 49, is in the lower automatic circuit. The movable member is always normally in contact either with the hoist side or the lowering side of this switch and should never be left in the intermediate position. "When released from either side, it is thrown by a spring to the other side. As it is a snap-switch, the contact is made and broken quickly.

When the machine is at rest, the circuitchanging switch is preferably closed on the lowering side, with the rheostat-arm on the lowest clip 50, which lies next to the motor armature, so that the resistance of the rheostat is reduced to a minimum. It is not absolutely necessary that this switch should be closed on the lowering side nor that the arm should contact with the lowest clip when the machine is at rest. The circuitchanging switch might be closed on the hoist-contact and the arm might be entirely out of contact with the rheostat, in which case the mere 010- sureof the circuit-changingswitch on the hoist side would not close the line. As will be seen hereinafter, itis desirable that in the normal stop position the arm should rest on the lowest clip and the circuit-changing switch be closed on the lowering side, which is the position shown, since this places the apparatus in position when at rest such that the armature is short-circuited at the main rheostat, and the closure of the lower automatic closes a circuit on the working motor which is independent of resistance of the main rheostat. The armature so short-circuited will prevent the car from running away even if the brake is actually removed.

When the pilot-motor is operated to effect the hoisting of the car,it rotates the main-rheostat arm from the lowest clip in the direction of the hands of a watch, which is hereinafter called right rotation, and so brings it in contact with the highest clip of the rheostat and then closes the hoisting-circuit by closing the circuit-changing switch on the hoist-contact. The arm will then continue its movement in the same direction until the hoist branch of the car-circuit is opened, either manually at the car-switch or automatically at the pilot-motor. switch. The positions of the hoist, stop, and lowering contacts of the pilot-motor switch thus determine how far the rheostat-arm can be revolved in either direction from the stop positions. As shown, if the car-circuit is not broken until it is broken automatically at the pilot motor switch the rheostat-arm will have traveled until it contacts with the lowest clip of the main rheostat. The operator on the car can readily bring the arm to any position which he may wish by holding open the stop-contact and playing the hoist-contact open and shut, thus moving the rheostat-arm step by step until the position is attained which corresponds to the desired car speed, for momentary closure of either branch of the car-circuit starts the rheostat-arm in rotation. Then the pilotmotor is operated to slacken the car or stop it, the rheostat-arm is rotated in the opposite direction to the hands of'a watch, herein called left rotation. If the stop-contact of the carswitch is held closed long enough, the arm is brought back to the stop position, and before passing off of the highest clip of the rheostat the arm breaks the hoist-circuit by throwing the circuit-changing switch to the lowering side and acts to check the rotation of the armature. The arm then moves from the highest to the lowest clip.

lVhen the pilot-motor is operated to effect the lowering of the car, the rheostat-arm rotates in left rotation from the lowest clip 50 through a distance which is determined by how long the lowering branch of the car-circuit is held closed. As it travels it throws more and more resistance of the main rheostat into the down regulating-circuit, and if the lowering branch of the car-circuit is held closed until automatically broken at the pilotmotor switch the arm travels until it reaches the highest clip 51 of the main rheost-at. On stopping from lowering the arm returns from the highest to the lowest clip without operating the movable member of the main circuitchanging switch.

The rheostat-arm can be rotated from the stop position shown in Fig. 2 almost completely around the circle in left rotation when the car is to descend, in which movement the arm does not operate the movable member, and can be rotated completely around the circle in right rotation when the car is to ascend, in which movement it throws the movable member from the lowering side to the hoist side of the main circuit-changing switch. This difference in the length of travel is due to the difference in the distances from the hoist and lowering contacts to the insulating-piece in the pilot-motor switch. The rheostat-arm can travel in right rotation from the extreme of lowering position on the highest clip back to the stop position on the lowest clip, and continuing in the same direction can travel once again around the whole circuit to the lowest clip 50, this being the extreme of hoist position, throwing the movable member from the down side to the hoist side on passing from stop to hoist. This changes the movement of the elevator from down at full speed to up at full speed. When the rheostat-arm was in the extreme of lowering position on the highest clip 50, the hoistplate 46 on the pilot-motor switch was in contact with its cooperating contacts in the hoist and stop branches of tlte car-circuit, and the lowering branch of that circuit was broken at the pilotmotor switch. (See Fig. 11.) During the described movement of the arm the lowering plate 45 contacts with its cobpcrating contacts in the lowering circuit, and the stop-circuit is first broken at the insulation 45 (see Fig. 12) and is then transferred to the lowering branch, and finally the hoist branch is broken by the hoist-plate moving out of contact with its cooperating contacts in the hoist-circuit, this being position for hoist at extreme speed. (See Fig. 13.) The rheostat-arm can travel from the extreme of hoist on the lowest clip in left rotation once around the circle to the stop position, and then continuing in the same direction pass to the extreme of lowering at the highest clip, throwing the movable member from the hoist to the lowering side on passing from the hoist to the stop position, the contacts in the car-circuits being made and broken in the reverse order to that before described. In any of these movements it will be understood that the rheostat-arm can be stopped at any intermediate position on the rheostat by merely opening the car-circuit at the car or commoncontrol switch. These intermediate positions of the rheostatarm correspond to intermediate rates of speed of ascentordescent and are called steady positions. Fig. 4 shows the steady position of ascent at moderate speed, and Fig. 6 shows the steady position of descent at moderate speed. As the conductor approaches a floor and wishes to stop he can slow down the speed by bringing the arm to successive steady positions, corresponding to slower and slower speeds, by simply holding the stop-contact open and playing the button which corresponds to movement in the opposite direction to that in which he is traveling or by leaving both buttons open and playing the stop-contact open and shut.

The brakamagnet switch.-Two forms are showna down brake-magnet switch (shown in Fig. 2 and certain other figures) and an up and down brake-magnet switch. (Shown in Fig. 15.) The former will be described first. On the left end of the main switchblock, Fig. 2, is a plate 4A, which, with cooperating contact-points, constitutes the down brake-magnet switch. The switch is closed during descent and open when the car is at rest and during ascent. There is also provided a shunt around this switch, in which is a circuit-closer that can be operated manually to relieve the brake when the machine is at rest.

In Fig. 15 the brake-magnet switch is represented as a pivoted member 44, connected to line and having teeth engaging with a Worm on the pilot-motor shaft, whereby it is moved to right and left. The switch has an interare in parallel with each other.

mediate stop position, in which the circuit is broken in the switch, and a hoist-plate 52 and resistances and a lowering-plate 53 and resistances, the resistances beingintended to prevent the current from being turned on too quickly.

Reviewing the entire main regulator, it is seen to be made up of the pilot-motor switch, the brake-magnet switch, and the workingmotor switch. All the foregoing parts, except the car-switch and, perhaps, the source of supply, are preferably placed in the engineroom. The three switches of the main regulator have common stop, hoist, and lowering positions--that is, their movements are codrdinated and interrelated, so that by operating the car or com in on-con trol switch they can all be brought at once each to its stop or hoist or lowering position. The open position is both the stop and the hoist position of the brakernagnet switch shown in Fig. 2.

While I have shown the regulator mounted in the car under the direct manual control and in the reach of the hands of the conductor in the car, I do not limit my invention, which I claim broadly, to any specified location of the regulator or any specified means of control thereof.

circuits are (l) the shunt field-circuit S to supply to the working motor a field which is independent of the main switch; (2) the feed circuit 0, also properly called the main circuit, the hoist-circuit, or the up regulating-circuit, to control the working motor, choking-shunt, and brake during ascent; (3) the brake-magnet circuit Gr to control the brake and closure of the automatic chokingshunt for the working motor in descent, Fig. 2, or in both ascent and descent, Fig. 15; (4) a circuit to control the entire system, so as to place the hoisting, lowering, and stopping of the car under normal operation at the will of the operator, called the car-circuit F. These are connected to the source of supply. Circuits numbered 2, 3, and 4 may be called operative-line circuits, and 5 a compound circuit, made up of the two branches, herein called the down regulating-circuit D and the lower automatic circuit H, which Neither of these branches is under any circumstances connected with the source of supply. They are closed only during descent, when they control the speed of the car by controlling the output of the working motor, which the descending car drives as a dynamo. This compound circuit can be called the brake or braking or the retarding circuit. The

term brake-circuit is herein used because in United States Patent No. 472,909 it is applied to an analogous circuit, and certain generic claims of that patent are drawn in the general form adopted in more specific claims of the present application. In that patent a mechanical brake was used to hold the main screw. The adoption of an electromechanical brake in the present case gives rise to the danger of misunderstanding of the term brakecircuit. It is therefore explicitly stated that, as shown, the circuitherein called the brakecircuit in no way and under no conditions controls the electromechanical brake for the main screw; but its branches control the speed of the working motor during descent. This statement is not intended as a limitation of the invention, but is inserted merely to avoid possible confusion of terms.

The feed-circuit and brake-circuit together constitute a compound circuit, which may be broadly called the working-motor circuit. In addition to the foregoing circuits there is provided an automatic choking shunt and resistance E, which is electrically operated. When closed, it shunts the armature and series coils of the working motor, but not the brake-magnet, and is so connected that it is independent of the WOIking-l'IlOiOl switch. It is controlled by a contact opened and closed by the brake-magnet. It is a part of both the feed-circuit and the brake-circuit.

The shunt field-circuit S is normally closed. The car and feed circuits are used in hoisting. The other circuits are always open in hoisting, except that in Fig. 15 the up side of the brake-magnetis closed. The car, down brakemagnet, and the brake-circuits are used in lowerin The other circuits are always open in lowering. In the stop position, which is assumed when the machine is stopped by the operation of the car-switch, the down regulating-circuit and the automatic choking-shunt are closed; but the other circuits of the, system are opened. If the car is stopped by arriving at the lower limit without operating the car-switch, the down regu lating brake-magnet and lower automatic circuits are closed and the other circuits are open. If the car-switch is then brought to stop position, the condition is established in which the down regulating and lower automatic retarding-circuits and the automatic choking-shunt are closed and the other circuits of the system are open.

At the bottom of the diagram of Fig. 2 are two main or general bars A B, herein called bus-bars, to which are connected all the elevator systems and the dynamo or other suitable source of electricity belonging to the outfit of the building. One elevator system is shown connected to the bars; but others can be connected in parallel therewith.

Following up either of the leads a b there will be found a point in each where the wire divides into four branches. These four branches are the fourcircuits above described as connected to the source of supply. They can be connected, if desired, each to an independent source of supply.

One of the leads of each dynamo or other ICC IIO

source of electricity includes, in series with the hoist-contact of the working-motor switch, a fuse 54: or other suitable overload circuitopener to open the circuit in'case of overload of the circuit throughout or locally. As shown, the lead branches between this fuse and the bus-bar into three wires. One of these wires is in the shunt field-circuit, a second is in the car-circuit, and the third is in the brake magnet circuit. These three branches are not affected by blowing the fuse. As will be seen more fully hereinafter, the purpose of this connection, whereby these branches are independent of the fuse, is to enable the operator to lower and control the car in case the fuse is blown. By the arrangement shown the car cannot be hung up between landings by blowing the fuse, but though disabled for hoisting can be normally lowered.

The different circuits will now be described and such description given of the parts included therein as may be necessary.

The shunt fieZd-circuit.'lhe shunt fieldcircuit S contains only the shunt field-coils and a rheostat-switch, by which it can be opened and closed, and its resistance, and hence the strength of the shunt-field, can be varied. These coils have a steadying effect on the working-motor field,particularly when the motor is driven as a dynamo in descent. It is shown as normally closed while the system is in operative condition; but I do not limit my claims to a normally closed shunt field-circuit. Variation of the field can be made to determine in part the hoisting and lowering speeds, weakening it increasing the speed with any given load and position of the rheostat-arm. These shunt field-coils differ from the shunt field-coils of an ordinary compound-wound orshunt-wound motor, because the connections of this shunt field-circuit are independent of the other connections of the motor.

The feecZ-circztt'h-The feed, main, hoist, or up-regulating circuit 0 includes the upper automatic snap switch and rheostat, the working-motor armature and the series fieldcoils thereof, the main rheostat, the hoist side of the working-motor switch, and the fuse above referred to, and in the construction of Fig. 2 the series brake-coil. At the moment of closing this circuit the armature and series field-coils are shunted through the automatic choking-shunt, which consists of a rheostat, preferably of greater resistance than that of the armature and series field-coils. The moment the brake-magnet is energized and the brake lifted this circuit is opened at a low potential, and consequently without sparking, and remains open until the current is interrupted. In the construction of Fig. 2 the armature and series field-coils should be connected to the working-motor switchindependently of the series brake-magnet coils, but not independently of the automatic chokingshunt, so that the armature and series fieldcoils can be divided off from the series brakecoils and connected independently thereof in the brake-circuit during descent, but without disturbing the connections of the automatic choking-shunt. By reference to Fig. 2 it will be seen that this is accomplished by branching the wire 2', which is led from the contact 48 on the down side of the working-motor switch, into three branchese-one, branch i, going to the series field-coils and armature, another, i to the series brake-coil, and the third, 2' to the automatic choking-shunt circuit-opener. This choking-shunt is closed whenever for any cause the current fails in the feed-circuit in ascent or in the down brake-magnet in descent, in the construction of Fig. 2, and whenever the current fails in the brake-magnet circuit of Fig. 15. It is closed and shunts the working motor whenever the car stops, except, as will be seen, in the single instance when the car is stopped at the lower limit without operating the carswitch, in which case it remains open until the car-switch is closed at the stop-contact.

It is closed to shunt the working motor and helps to bring it to rest under seven conditions-to wit, during hoisting on failure of the current from any cause, as, first, when the circuit is opened in normal stop; second, when the circuit is opened at the upper automatic; third, when the safety-fuse is blown in the main circuit, (not true of Fig. 15;) fourth, on total failure of current in the leads and, during lowering, on failure of the current in the brake-magnet circuit from any cause, as, first, when the circuit is opened in normal stop; second, when the circuit is opened by the centrifugal; third, when for any reason there is failure of currentin the safety-circuit or in the leads.

T he brake-magnet circuit-This circuit is shown in two forms. In one, shown in Fig. 2 and certain other figures, it is a down brakemag'net circuit only, the brake-magnet being controlled during ascent by the feed-circuit. In the other form (shown in Fig. 15) it is an up-and-down brake-magnet circuit. Referring first to the form shown in Fig. 2, the down brake-magnet circuit G is intended in the normal operation of the system to lift off the brake from the main screw and open the contact of the automatic choking-shunt when the car is to start down, to maintain this condition so long as the car runs down at aspeed which does not exceed the established maximum, and to apply the brake and close the choking -shunt on the working motor when the car is to stop normally. It also contains a circuit-opener operated by a centrifugal governor to apply the brake and shunt the working motor when the car runs down too fast. The automatic circuit-opener is of the construction before described and is driven from the shaft of the working motor and is opened whenever the main screw rotates too rapidly. It should be set to open at one determined speed and closeat a lower the safety-circuit is opened and also to delay and soften the brake operation, a shunt around it is provided, which is adjustable and, as shown, consists of lamps through which the coils can discharge. Should the car acquire too fast a speed in descending, the down brake-magnet circuit is opened by the centrifugal governor; but it will merely be necessary for the speed of the car to be slowed down to the determined limit or the car to be stopped bythe strap-brake and choking-shunt to enable the operator by operating the carswitch in the ordinary way again to relieve the brake and open the choking-shunt, Fig.7. In hydraulic elevators there are no centrifugal safeties except those operating the catches on the car, and to avoid the annoyance of operation from temporary excess of speed these are frequently set for so high a speed as to be inoperative when required. This additional monitor centrifugal safety, herein described, does not interfere with the use or operation of car centrifugal catches. The essential point of the modification of Fig. 15 is that a single-coil brake-magnet is substituted for the double-coil brake-magnet of Fig. 2. The hoist-plate 52 of the brake-magnet switch 44 is connected directly to the line on the motor side of the upper automatic switch, so that the hoist branch g of the brake-magnet circuit shall include this upper automatic switch and the brake-magnet shall be denergized when the upper automatic switch is opened. The lowering-plate 53 of the switch is connected to the line on the line side of the upper automatic switch, but through the centrifugal circuit-opener, so that the lowering branch 9 of the brake-magnet circuit shall be independent of the upper automatic and shall be opened to demagnetize the brakemagnet by the centrifugal circuit-opener. In this system the monitor centrifugal circuitopener is not in operation during ascent that is, in both forms there is a compound brake-magnet circuit having one branch which includes the upper automatic switch and another branchwhich includes the monitor centrifugal circuit-opener. This singlecoil brake-magnet is introduced merely to enlarge the scope of the invention, so that the claims, which do not specify a double-coil brake-magnet, shall be broadly construed.

If the monitor centrifugal circuit-opener is omitted from either form of brake-operating circuit, the circuit will become a mere brakeoperating and motor-shunting circuit. If the automatic choking-shunt feature is omitted, the circuit will become a mere brake-operating circuit. I use the terms brake-magnet circuit and brake-operating circuit in a broad sense.

The car-czrcmt.The car-circuit F is provided with instr'u'mentalities intended to put it in the power of the car-conductor or the engineer to rotate the arm of the main rheostat in either direction and to bring it to rest and hold it as long as desired at any point on the rheostat, and it is also provided with instrumentalities which automatically bring it to rest at or near opposite ends of the rheostat when the car is being hoisted or lowered and at stop position when the car is stopped. With this object the car-circuit includes the armature of the pilot-motor and the electromagnet of a magnetic brake to prevent the pilot-motor armature from spinning, and thus unduly shifting the switch-block andrheostat after the current is out off. The circuit divides into two branches, which traverse the field-magnet of the pilot-motor in opposite directions. Changing the circuit from one branch to the other reverses the direction of rotation of the pilot-motor by reversing the polarity of the field. This method of reversal of direction of the pilot-motoris novel, being a'departure from the ordinary method of reversing the current in the armature or in a single field-circuit. Instead there are two field-coils wound in opposition. The two coils are never used together. A modification of this method would be to use two oppositely-wound coils in series, one or the other of which is short-circuited when thrown into line, according to the direction of rotation required.

*One branch of the car-circuit, herein called the hoist branch f, includes a rheostatswitch, the hoist-contact of the pilot-motor switch,and the hoist-contact of the car-switch. The other branch, herein called the lowering branch f, includes a rheostat-switch, the lowering-contact of the pilot-motor switch, and the lowering-contact of the car-switch. The operating position of the car-circuit to start the elevator up or down is with the stopcontacts open and the hoist or lowering contactsclosed. The steady position is with the stop-contact and at least one of the other contacts of the pilot-motor switch closed, but with all the contacts of the car-switch open, and hence with all branches of the car-circuit open. Closing the stop-contact of the carswitch except when the pilot-motorswitch is at the stop position changes the car-circuit fmm one of the branches to the other, and thus reverses the pilot-motor, and if the stopcontact is closed long enough brings the switch to stop position, at which point the circuit is automatically opened at the stopcontact of the pilot-motor switch.

It will be seen that the lowering branch f of the car-circuit controls the starting of the car down from Stop and the stopping of the ascending car, for in order to move the rheostat and circuit-changing switch from; say, the position shown in Fig. 4, which corresponds to ascent of car, to the position shown in Fig. 2, which corresponds to the stopping of the car, itis necessary to turn the rheostatarm in left rotation, and this is effected by closing circuit through the lowering-contact 38 or the stopping-contact 86, the loweringplate 45, and the corresponding field-winding of the motor, these parts being in the position shown in Fig. 4 in the lowering branch f, and that the hoist branch controls the starting of the car up and the stopping of the descending car, for in order to move the rheostat-switch from, say, the position shown in Fig. 6 (descent of car) to the position shown in Fig. 2 (car stopped) it is necessary to turn the rheostat-arm in the right rotation, and this is effected by closing circuit through the stopping-contact 36 or the hoist-contact 37, the hoisting-plate 46, and the corresponding field-winding of the motor, these parts being in the position shown in Fig. 6 in the lowering branch f. It is desirable that these two branches should be independently adjustable, particularly with an underbalanced car, for when the car starts down the main rheostat-arm can be operated very quickly and the car quickly got under way without jar on account of the mechanical conditions of the down movement, and when the car stops in ascent the current can be cut oif very promptly and the car allowed to stop in the height determined by the gravity equivalent without jar. Therefore the lowering branch of the car-circuit should rotate the pilot-motor armature and through it the main rheostat-arm rapidly; but if the car stops in descending too rapidly there results a jerk on the ropes and a strain on the machine, besides an unpleasant personal experience in the passengers, and if the current is put on to hoist too quickly the increase of current affects unpleasant-ly other translating devices in circuit, such as lamps, as well as unnecessarily straining the machine and shaking up the passengers. Therefore the two fields of the pilot-motor are in shunt to each other and independently adjustable, each having its own rheostat, as shown, and they are wound so as to give the highest permissible speed when the rheostats are cut out.

The brake-circuit.The brake, braking, or

retarding circuit has two branches which are in multiple with each other. One branch, which is the lowering or down regulatingcircuit D, includes the armature and series field-coils of the working motor, a switch to control the speed of the car in descending, preferably,but not necessarily,the main rheostat, and one point on the lowering side of the working-motor switch. This branch is closed when the lowering-contact of the car-switch is closed. The other branch, which is the lower automatic circuit H, includes the contact 49 on the lowering side of the working motor switch and the lower automatic switch 27. This switch is automatically closed through its entire resistance and its resistance gradually cut out when the car approaches its lowermost position, as already described. This so far short-circuits the working motor that the car can scarcely drive the motor, and it is brought automatically and gradually very nearly to a stop. It comes to a full stop when the operator lets his controlling-switch go to Stop or the traveling cross-head 7 is stopped by the buffer-nut at the end of the screw 10.

All these various circuits and branches of circuits are independent of each other. The shunt field-circuit is obviously not influenced by the other circuits. The feed-circuit would operate to hoist the car independently of any operation of the car-circuit it, as above suggested, the main regulator were operated mechanically. The down regulating-circuit and lower automatic circuit are similarly independent of the car-circuit, and the feed and brake and feed and down brake-magnet circuits are mutually independent of each other, because each is open when the other is closed, so that they cannot interfere, and the brakecircuit is independent of the brake-magnet circuit, since it and the brake-magnet circuit in both forms each has a separate switch. The brake-circuit can be used alone to lower the car if the brake is operated mechanically instead of magnetically. The car and brakemagnet circuits obviously perform their functions independently of each other and of any other circuits of the system. By operating the monitor centrifugal manually the car can be lowered without using the carcircuit, for by opening and closing the brake-magnet circuit the brake can be lifted off and applied and the descent thus regulated. This can also be accomplished without a brake-magnet circuit if the brake is operated mechanically. This, however, of course differs from the normal method of regulating the descent by the resistance in the circuit with the working motor. In specifying operation of the brake I include also mechanical operation of the circuit-closer of the choking-shunt.

A consideration of the foregoing description will make it clear that this is a gravityelevator system with an underbalanced car in which there is substantially no reversal of the currentin any of the circuits. The current always flows in the same direction through each branch of the car-circuit, through each branch of the brake-magnet circuit of Fig. 15, through the shunt field-circuit, and through the feed-circuit and the two branches of the brake-circuit, and, as already explained, the current is not reversed through the motor on changing from the feed-circuit to the brakecircuit. iVhen, however, the car in traveling up opens the upper automatic, thereby cutting off the line-current and closing the automatic choking-shunt for an instant while the car continues to rise, a reversed current is developed which traverses the armature and series field coils and the choking-shunt.

It is well at this point to indicate a few broad features of the invention, which will be clear-from the foregoing full description. The pilot-motor is connected to the car-switch without the intervention of relays. The carswitch and the pilot-motor switch together constitute a compound switch with two branches, in each of which is a controlled circuit-closernamely, the hoist and lowering contacts of the car-switch-in combination with a circuit-changernamely, the stopcontact of the car-switch and the corresponding connection on the pilot-motor switchactiug to change the circuit from one branch to the other. In the invention herein disclosed this circuit-changer acts to change the circuit from either branch to the other, according to the position of the pilot-motor switch, and there are provided means for automatically opening the circuit at the limit and stop contacts on the pilot-motor switch. There are also means for automatically operating the circuit-changer, such means being the springs which return the car-switch to stop position when it is released. WVhen the car-switch is brought thus automatically to the stop position, one of the branches is opened and the other is closed. By this it is not meant that the other contact of the car-switch is closed, but that the corresponding branch leading from the pilot-motor switch to the pilot-motor is closed through the stop-contact of the carswitch, and if we consider the rheostat as a part of the combination there is provided means for operating itnamely, the pilotmotor and connections-a suitable circuit for controlling the rheostat-operating means namely, the car-circuit and the connections with the pilot-mot0ra circuit changer operating to bring the rheostat to a definite positionnamely, the stop or initial position and means for automatically operating the circuit-changer, as above explained, together with the automatic circuit-openers, whereby the rheostat can be brought to certain other definite positions-nan1ely, the full-hoist or full-lowering position.

In certain of the claims I use the term current-controller as a generic term to cover either a simple rheostat or any form of circuit-varying switch to control the drivingmotor. The term thus covers a series mul tiple switch or a reversing-switch.

Operation.

except the shunt field-circuit S, the chokingshunt E, and the down regulating-circuit D. The conductor opens the stop-contact 36 and closes the hoist-contact 37 of the car-switch This closes the hoist branch f of the car-circuit F through the pilot-motor 20 and the pilot-motor switch. The pilot-motor drives the main-switch block to the right and rotates the rheostat-arm 33 of the main rheostat 17 in right rotation. The rheostat-arm contacts with the highest clip 51 of the rheostat, and the hoist-circuit O is then closed by the movable member 18 of the circuit-changing switch, which is thrown by the arm from the lowering-contacts to the hoist-contact 47. The line-current then traverses the feed-circuit (1, including the whole of the main rheostat and momentarily including the automatic choking-shunt E. The brake 21 is then lifted oif and the choking-shunt is opened. It the hoist-contact of the car-switch is held closed, the main-rheostat arm travels on in right rotation, cutting out more and more of the rheostat. All the circuits of the system are open except the shunt field-circuit S and the feed-circuit G, which must be closed, and the car-circuit 1*, both. branches of which may be open or which may be temporarily closed in either branch f or f to move the rheostat-arm forward or backward, and thus control the rate of ascent. This is the condition throughout an uninterrupted hoisting unless the hoist-contact of the car-switch is held closed untii the main -switch block is pushed far enough to the right to break the hoist branch f at the pilot-motor switch. In this position the rheostat-arm will rest upon the lowest clip 50, the main rheostat will be entirely out out, and the rate of ascent will be the maximum permitted speed, and when the parts are in this position the hoist branch f of the car-circuit cannot be closed. As soon as the current through the pilot-motor is out off by opening the car-circuit at the car-switch 19 or pilot-motor switch, or both, the magnetic brake 31 stops its armature, and the main-switch block and main-rheostat arm are stopped. The position illustrated in Fig. 4 is that in which the hoist branch of the carcircuit is opened at the hoist-contact 37 of the car-switch before the car-circuit is automatically broken at the pilot-motor switch and before the entire resistance of the rheostat is out out of the hoist-circuit O. This is a position of steady speed of ascent slower than the maximum speed of ascent permitted. When the conductor of the car wishes to slow down before stopping, he plays the stop-contact 36 of the car-switch open and shut, or holding this open plays the lowering-contact 38 open and shut, thus reversing the connection in the car-circuit from the hoist to the lowering branch and moving the rheostatarm in left rotation, and thus throws in more and more of the resistance of the rheostat. Momentarily the circuits are as they would be in Fig. 6 if in that figure the car-switch were closedat the stop or lowering contacts. The main-switch block is then brought by the pilot-motor to stop position, where either branch of the car-circuit when closed through the stop-contact is automatically broken.