US1052587A - System of electrical control. - Google Patents

Description

J. D. IHLDER. SYSTEM OF ELECTRICAL CONTROL. APPLICATION FILED JUNE 12,1908.

Patented Feb. 11,1913.

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QVL-h-woaco GHoznm JQD. IHLDER.

SYSTEMOP ELECTRICAL CONTROL.

APPLICATION FILED JUNE 12, 1908. v 1 52 5837 Patented Feb. 1 1, 191.3.

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' q/v f aoo co r v M472 "J. 1). IHLDER.

SYSTEM OF ELEOTRIGAL CONTROL.

APPLICATION FILED JUNE 12, 1908.

Patented Feb. 11, 1913.

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aw/{M00000 J. D. IHLDER. SYSTEMOF ELECTRICAL CONTROL.

APRJLOATION FILED JUNE 12, 1908.

Patented Feb. 11, 191-3.

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o I Svwewto-z attozmm 1d ti /Y @MA/w tinrrnn sir-acres Parana canton JOHN D. IHLDER, OF NEW' YORK, N. Y., ASSIGNOR TO OTIS ELEVATOR COMPANY, OF

JERSEY CITY, NEW JERSEY A CORPORATION OF NEW JERSEY.

SYSTEM OF ELECTRICAL CONTROL.

Specification of Letters Patent. Patented Feb, 11, 1913.,

Application filed June 12, 1908. Serial No. 438,080.

To all 2 17101721 it may concern:

3e itknown that T, JOHN D. IHLDER, a citizen of the United States, residing in New York city, in the county of New York and State of New York, have invented a new and useful Improvement in 'Syste'ms of Electrical Control, of which the following is a specification.

The present invention relates to hoisting mechanism and electrical operating and controlling mechanism therefor, and is more particularly adapted to ammunition hoists of that type in which the ammunition is lifted by a carrier to a position opposite the breech of the gun, and the carrier held in its elevated position by means of a. reduced and-d0 and down to the winding drum 11.

current supplied tothe hoisting motor.

One of the objects of the invention is 0 provide means for reducing the current as the carrier approaches 1ts upper limit oi travel to an amount substantially proporupper end of the tracks 6 in position to form tional to-or varying with the load.

Another object .of the invention is the provision of improved means for limiting the speed of descent of the-car or carrier.

A further object of the invention is the provision of means for overcoming any excessive startingfriction of the descending load by supplying an initial current to the motor which is automatically cut off as the load commences its descent.

Still another object is to provide means for automatically slowing down the carrier during any desined portions of its travel either ascendingor descending.

()ther objects of the invention will ap-- pear hereinafter, the novel combinations of elements being set forth in the appended claims.

Referring to the accompanying drawings, Figure 1 is an elevational view of a gunand ammunition hoisting mechanism; Fig. 2 is a view showing mechanism for simultaneously adjusting the gun elevation and the position of the bufl'er; Fig. 3 is a rear elevation of the buffer and ammunition carrier; Fig. 4; is a diagrammatic view of the, electrical system of control; Fig. 5 shows a modification of the controlling mechanism adapted to a shunt wound motor.

.The invention'is herein shown in connection with agun as used on a war vessel.

The gun-Grismounted in a rotating turret rails 6.

T supported on rollers 1 adapted to travel on a track 2 on the framework 3. The gun is mounted on its carriage 4 in the usual way. by means of horizontal trunnions 5 journaled in the gun carriage. The ammunition is elevated from the hold of the ship to the gun'by a can or carrier '0 adapted to travel on the tracks 6. The upper ends of these tracksare fixed to the turret and the nected at one end to the carrier and ex tending up and over the guide sheaves 9 A gear wheel 12 connected to the winding drum meshes with the driving pinion 13 on the shaft of the hoisting motor M.

An adjustable buffer B is located near the a stop for thecarrier at its upper limit of travel. This buffer comprises a cross beam 14 and guides 15 slidable vertically on the Abutment-s 16 normally projected by springs 17 form yielding stops for the carrier C.

The mechanism for adjusting the elevation of the gun comprises a bracket 18. bolted to the under surface of the turret floor, and having a hollow cylindrical body portion to receive a rotatable member 19. A 'miter gear 20 on the upper end of the member 19 meshes with a pinion 21 on the shaft of an electric motor A. A screw-threaded rod 22 works in a threaded recess in the. 'men'iber 19. nected at 1ts lower end to the mass,

nism for automatically adjusting the position of the buffer B as the gun elevation'is adjusted, forms a feature of the present invention. A screw-threaded rod 25 is swiveled'in a cross-beam 26 which is secured to the-rails 6. The rod 25 is held against.

vertical movement by disks 27 secured to the rod on opposite sides of the beam' 26.

rod cannot move vertically the sleeve 38.

and buffer B will be moved up or down, depending on the direction of rotation of the motor armature. The gearing is so arranged and proportioned that the buffer moves up and down with the breech of the gun and to substantially the same extent, so that whatever the gun elevation may be the buffer is in position to stop the carrier G with the charge in proper position for loadmg.

In connection with the buffer B, l have shown an electromagnetic locking device L adapted to lock the carrier C in its elevated position during the loading of the gun. This device comprises a .catch (Fig. 4) adapted to engage below a bracket 36 secured to the carrier C, the under surface of the catch being beveled to permit the same to be moved out of the way the carrier nears its upper limit of travel, the catch then returning to normal posltion to hold a the carrier suspended. In order to permit the carrier to descend, the catch is released by energizing the electro-magnet comprising the solenoid 38, the frame 37 and the core or plunger 38.

An automatic floor controller F is connected for rotation to the motor M, or some movable part of the hoisting mechanism. As shown in Fig. 1, the controller F is provided with a sprocket wheel 40 geared by a chain 41' to a sprocket wheel 42 on the shaft of the hoisting drum, so that the controller will move in unison with the carrier C. As shswn diagrammatically in Fig. 4 the controller carries aseries of arc-shaped movable contact strips 43, 44, 45, etc., adapted to engage a series of stationary brushes 4-9, 50, etc. The brushes, or those controlling the motor circuits as the, carrier C is lifted, maybe carried by an arm 62 journaled at one end on the shaft of the controller. A rope or cord 63 is connected at one end to the arm 62 and passes over direction sheaves 64, 65 and is secured at its other end to the gun. .A coil spring 66 keeps the rope 63 taut. The position of the brushes carried by the arm'62 will therefore be changed whenever the gun elevation is changed, and the arrangement is such that the'relative position of the brushes and contact strips is always substantially the same .168 to the minus line.

for any given position of the carrier C relatively to the buffer B and breech otthe gun. The specific construction of the'controller F maybe the same as that fully shown and described in my former Patent No. 879,387, dated February 18,1908. If it is desired to give the controller more than one revolution, the construction disclosed in my Patent No. 710,914, dated October 7, 1902, may be used.

In Fig. 4 the controller F is shown in the position assumed when the car C is at its normal upper limit of travel. The lever of the car switch S has been brought to center and the machine is at rest with the car held by the locking device L. The power is cut off from all parts except the brake magnet. To start the car on its downward travel from this position, the car switch handle is moved to the right to bring the contact plate 71 into engagement with the stationary contacts 69, 76, 77 and 78. It is assumed that the car is not sufficiently heavy to overcome the friction of rest of all 'the parts, but that after being" set in motion it will ac celerate and continue running downward without requiring power from the source of pp y- The circuits established are as follows: from the plus line 67 through conductor 68 to car switch contact 69, plate 71 and contact 76, through conductors 158, 158,-

the contacts 100 and 163, and thereby closing a main line circuit through the motor, which circuit is from the plus line to the armature brush 98, through the armature 97, brush 96, conductor 165, switch 160, coil 166 of magnet LM, and resistances 167 and The switch 160 is closed at this time sinceits magnet spool 156 is energized, being in a parallel circuit with the spool 157' of magnet X which circuit may be traced from the conductor 158 through spool 156, conductors 159, 128, conline. Current is admitted to the brake magnet 112 by way of car switch contact 77 through conductor 155, contact 49, spiral 45, contact 50, conductor 111 to the brake spool 112, and through conductor' 91 to the minus line. A parallel circuit through the brake magnet may be tracedfrom the plus line through conductor 150, contact conductor 151, contact 52, spiral 46, contact 51, conductor 152, resistance 153 to conductor 111 and the brake coil 112. The purpose of this latter circuit will be pointed out later. The car switch contact 78 controls the circuitthrough the magnet coil 38 of the'locktact/s 187, and conductor 127 to the minus ing device L which is therefore operated to disengage the catch and permit the car to descend. As the switch lever is thrown over to the right, the plate 71 momentarily engages the contact 79 and closes a circuit through the magnet FS which may cause the latter to operate, but this is merely inci' dental and has no effect on the operation of the motor and hoistingmechanism.

Briefly stated, the effect of moving the lever of the switch S over to the right is to release the locking device L and supply current to the armature in a direction to 'start the carrier downward. This current is only supplied during the initial downward movement of the carrier, however, and is for the purpose of overcoming the excessive starting friction which in some cases the weight of the carrier may not be able to overcome. The carrier now commences its downward movement and the increasing speed of the armature quickly develops sufficient counterelectro-motive force to cause the lower magnet 169, which is connected ture, to pull its core down against the pull of the upper magnet 157. l The contact strip 48 also leaves the brush 60 when the carrier has moved downwardly a short distance and opens the circuit through the upper magnet 157, thereby limiting the distance the car can travel before the magnet is operated; The operation of the magnet 169 opens the circuit from the main line through the motor armature at the contact 163 and closes a local circuit through the armature. This latter circuit may be traced from the armature brush 08 through conductor 99, con tacts 100, 101, series field coil 102, resistances 1'03, 10%, 105, coil of magnet 05, resistances 106. 107, conductor 81+, resistances 168, 167,

- coil 166 of the ,load magnet LM switch 160, conductor 165 to the armature brush 96. The car now drives the motor as.a generator and the current in this local circuit produces an electro-dynamic braking effect which limits the speed of the car in its descent. The magnet 05 acts during the descent of the car to regulate the speed for diilerent loads. That is, if the load is heavy and accelerates the motor above a predetermined limit, the magnet 05 receives sutlicient current to close the switch 108 and short-circuit the resistance 107, thereby increasing the current in the local circuit and thus increasing the electro-dynamic braking action sufficiently to bring the speed down again. If the load is light, it will not tend to produce an excessive speed and the magnet will not operate to short-circuit the resistance 107, and the co braking action will be correspondinglylimited. If a heavy'lcad has caused the magnet 95 toclose the switch108 and as a result the speed falls below a given limit, the mag-.

7 net will be weakened and the switch will open again to reduce the braking cfiect.

conductors 180 and 99 to the brush 98.

across the arma- The load magnet LM operates a switch 186 in the same way to control the resistance 167, so that the speed is regulated during the descent of the carrier and kept substantially the same or within predetermined limits for different loads. As the car descends, the spiral contacts of the controller F are turned in a clockwise direction and when the car reaches afpoint in its travel where it is necessary or desirable to reduce the speed temporarily, as for example, where it has to pass over a sharp curve in the tracks or through a hatchway port, the spiral 47 'makes connection between the contacts 177 and 176. This introduces a magnet coil 175 into a circuit across the armature as follows,

from'the armature brush 96, through conductors 165,. 178, magnet coil 175, conductor 179. contact 176, spiral 17, contact 177, and The magnet coil 17 5, if the speed of the armature is sufficiently high depending on the load, closes the switch 181 andshort-circuits the resistance 168 which is at this time in the local circuit of the motor armature. The electrodynamic brake action is thus increased and slows down the carrier until the obstruction has been passed, when the spiral 47 leaves the brush 17 7 and opens the circuit through the magnet coil 175 to reinsertthe resistance 168 and permit the motor to run up to full speed again.

During the descent of the carrier, the controller F makes somewhat less than a complete revolution. The first step in slowing down the motor asthe carrier approaches its lowermost position takes place when the contact strip 47 of the floor controller reaches the position where it bridges the contacts 55 and 57. This closes a circuit from the positive main through conductor 150, brush 55, strip 47, brush 57, conductors 117, 82, coil of magnet FS, and conductor 8 1 to the negative main. The magnet FS now closes the switch '87 and short-circuits the resistances 106- and 107, increasing the elec'tro-dynamic braking effect and slowing down the motor. The next step in the control of the motor occurs when the strip 17 reaches the brush 58, the strip 47 still rotating clockwise. This establishes a circuit from the positive main through conductor 150, brush 55, contact strip 47, brush 58, conductor, 85, coil of magnet SS, and conductors 86 and 8 1 to the negative main. The magnet SS closes the switch 88 and short-circuits the load magnet LM, ances 167, 168 and the magnet 95, leaving only the resistances -103,' 104, 105, and the" series field coil 102,'-in circuit with the motor resistand the. dy-- circuit the resistance 103.

the switch 125 also brings the auxiliarycomnamic braking action quickly brings the motor and hoisting mechanism also to rest. In case the motor does not stop immediately, a slight further movement separates the spiral 45 and contact 49 of the controller]? and interrupts the circuit of the brake magnet 112,' so that the brake assists in stopping the motor.- Genera y the dynamic brake action will be sufficient to effect a prompt stop without the mechanical brake being applied. The carswitch handle may then be brought to the stop position.

To lift the car, the handle of the car switch S is turned to the left, causing the contact plate 71 to make connection between the contacts 70, 72, 73, 74 and 75. This establishes. the following circuits: from the plus line through conductor 68, contact 70, plate 71, contact 72, conductor 89, main line magnet spool 90, and conductor 91 to the minus line. The main line magnet closes the switch 92, establishing a. motor circuit from the plus line through switch 92, conductor 93 to armature brush 96, through the armature 97, brush 98, conductor 99, contacts 100, 101, conductor 126, series field winding 102, resistances 103, 104, 105, spool 95, and resistances 106, 107: to the minus line, circuit is made from the plus line through conductor 68, contact 70, plate 71, contact 73, conductorllO, contact 50, conductor 111, brake spool 112 and conductor 91 to the minus line, energizing the spool and lifting the brake. A connection is also made through the previously traced conductors to plate 71,'contact 74, conductor 115, contact 54, spiral 43, contact 59, conductors 116, 117, 82, through the winding of the magnet FS and to the minus line. This energizes the magnet FS and closes the switch 87. A further circuit is made at the car switch which may be traced from the plate 71 through contact 7 5, conductor 119, contact 53, spiral 44, contact 56, conductoi 120, accelerating magnet spool 118, conductor 121 to the junction 126, which energizes the accelerating magnet spool according to the potential of the motor armature. The magnet FS, having closed the switch 87, thereby short-circuiting the resistances 106 and 107,'has. reducedthe starting resistance to the amount contained in the seriesfield 102, resistances 103,104, 105 and the spool 95; These resistances are so proportioned that the current admitted by them will start the maximum load.

As the speed of the armature increases and the accelerating magnet gradually increases in power, it first closes the switch 123, short circuiting the resistance 105; and as the speed further increases the switch 124 is closed toshort-circuit the resistance 104; and finally the switch 125 is closed to short- The closing of Another motor now reaches maximum speed, the

starting resistance being all short-circuited. The armature circuit at this time is as follows: from the plus line through contacts 92, conductor 93, armature brush 9G, armature 97, brush 98, contacts 100, 101, conductor 144, contacts 138, conductors 143, 141, 122, switch 125, conductor 128, contacts 187 and conductor 127 to the minus line. During the upward travel of the car, the spirals of the controller F move in an anti-clockwise direction. \Vhen the car reaches the hatchway or position for which a slower speed is desired, the spiral 48 makes connection between the contacts 184 and 183, energizing thespool 182, which opens the normally closed switch 187 and introduces the resistance 188 in the armature circuit, thereby reducing the speed of the motor. After the car'has passed such position, the spiral 48 breaks connection between the contacts 184 and 183, denergizing the spool 182, closing the switch 187 and permitting the motor to again attain full speed. As the car approaches the upper limitof its travel the spiral 44 breaks connection between the contacts 53 and 56, interrupting the circuit of the accelerating magnet 118, causing the switches 123,124 and 125 to open, introducing the resistances 103, 104, 105 and also the spool'95 into the armature circuit, and thereby reducing the speed of the armature. The switch 87 is closed at this time and the resistances 106 and 107 therefore short-circuited. The current through the magnet 95 which has just been excited by the operation of the accelerating magnet, is proportional to the load being lifted by the motor, and this magnet is so designed that with aheavy load it will close the switch 108, but with a light load the switch 108 will remain open.

The second step in slowing down the motor takes place when the controller has rotated a short distance farther and the contact strip 43 runs off the brush 59 and opens the circuit through the magnet FS. This efiects the opening of switch 87 and in troduces the resistance 106 into the armature circuit, and if the load is light so that the the load is heavy. It is thus seen that the magnet 95 and resistance controlled thereby form a means for varying the current in the motor in accordance with the load as the latter is being brought to rest at its upper limit of travel. Although the magnet 95 provides for only one variation in the current, it is obvious that the number of magnets and resistances may be increased to se-' cure any degree of refinement of control desired. The speed of the motor now re-.

duced'so that the carrier C is moving slowly as this brought up against the butler B and comes/ 0 rest without any undue jar or strain on any or the parts. The hook or catch carried by the butter will be engaged by the carrier asthe latter is being brought to rest and hold the same until. the hook is re-.

leased by its magnet.

in order to insure the brake being off during the time the carrier is opposite the gun, the following meansmay be provided. A contact strip 16 on the floor controller is so located as to engage the brush 52 when the carrier reaches the lowest position of the or the gun; This closes a circuit breach through the brake magnet, which may be traced from the positive main through conductor 150, conductor 151, brush 52, contact strip 46, brush 51, conductor 152, resistance 153, conductor 111, brake magnet coil 112, and conductors 91, 8% to the negative main.

' This circuit is entirely independent of the manual switch S and is maintained until the carrier has descended below the gun. The operator is thereby prevented from opening the brake circuit and applying the brake to the motor when the carrier is moved while locked to the butter. Without this provision the brake might be applied when the carrier was locked to the bufier and the breech of the gun then moved, carrying with it the buffer and carrier C which would be :Eorccddown against the holding power of the brake. Or, the carrier might be raised when the brake was applied, thereby producing slack in the hoisting cable so that the carrier would drop when the brake was released. In either case, the cable might be broken or other injurious results follow.

In some cases it is not only necessary to provide sutficient torque to hold the car, but a surplus torque must be provided to enable the motor to follow up the movement of the gun. In order to give the motor this addi tional torque with the least increase of current I make use of the magnet 131 which has short-circuited the series field, this magnet being connected to the terminals of the motor armature through the circuit which has been traced. hen the connection was made during the acceleration, the motor had nearly reached full potential. This magnet is designed to hold the switches 137, 138 closed until the motor has nearly come to rest, when it will open said switches, introducing the series field into the circuit. The

strength of the series field is preferably so proportioned that it is sufiicient to overcome the extra friction of rest.

To prevent magnet 131 becoming deenergized when contacts 129 and 130 open, and thereby separating contacts 137 and 138, 1 use magnet 139 to keep the spool 131 energiZed, as long as the motor armature is generating a moderate counter-electromotive force. The circuit for spool 139 can be traced from brush 98, through conductor 99, contacts 100, 101, conductor 1 6, series field 102, conductor 1-11, conductor 1e10, spool 139, conductor 136 to brush 96. The switch 112 for spool 139 is closed as soon as the arrna ture makes proper potential, and after contacts 129 and 130 have energized spool 131, causing it to close the switch 137, it will be seen that the separating or contacts 129 and 130 does not de'e'nergize spool 131, its circuit remaining established from conductor 126 through spool 131, conductor 132, contacts 1-12, conductor 115, contacts 137, conductors 135 and 136, conductor 165 to armature brush 9G. The magnets 131 and 139 will only become deenergized when the armature potential drops below a predetermined point.

and while the compound field winding has advantages over the shunt field winding in hoisting motors, a motor with a shunt field winding may be used llf desired as illustrated in Fig. 5. In this case the series winding 102 is omitted and a resistance 113 is placed in circuit with the shunt field winding 113. This resistance is short circuited by the contacts 138 which are arranged to be separated when the magnet 131 is energized. The circuit for the spool 139 may be traced from the brush 98 through conductor 99, contacts 100, 101, conductors 126, 140, spool 139, conductor 136 to brush 96. The magnet 139 closes the contacts 142 and maintains a holding circuit for the mag net coil 131 as before pointed out. The operation is substantially like that described in connection with Fig. 1, except that the magnet 1.31 when energized separates the contacts 133 to introduce the resistance 131- in the field circuit instead of the contacts being closed to short-circuit a series coil as in Fig. 4. In either case slowing down of the motor so that the magnet 131 drops its core. eiiects an increase in the strength of the motor field so that the torque is sui'licient to enable the nidtor to follow up the movement of the gun.

in my Patent 879,387, above referred to, T have disclosed means for stopping the carrier automatically at different positions, varying with the position of the breech of the gun. The same device used there can oi I have shown in Fig. 4: a compound motor course be employed in this case in connection with controller F. Also, though It show controller F in the form .of splrals, 1 do not limit myself to this construction. Anyother suitable form, such as switches opened bycams, or equivalent construction, can be used, if desired.

'It is understood that the position and length of the spirals and the location'of the brushes is to ba'determined according to the travel of the car, and .the movement provided for the spirals. The contacts and con- ,tact plate .on the car switch also are-to be located tb suit the desired movementof the car switch handle. The spacing may be irregular, and the movement of the handle does not necessarily have to be to the center position for stopping. The position of the contacts is shown on the wiring diagram symmetrical, for clearness sake.

Slow speed can be produced by the operatora't any time during the run by moving the handle of switch S from extreme position toward the stop position, opening on the up motion the accelerating magnet contacts, while with such movement of the switch S during the down'motion the contaste of magnet FS are closed. A stop can bemade by the operator at any time by bringing the switch handle to stop position for either up or down, thereby cutting off the power and applying the brake.

I'wish not to be limited to the exact construction disclosed, as various changes in the ya details of construction and arrangement of at its upper limit by means of a reduced curparts may be made Without departing from the spiritand scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

" 1. The combination with an electric motor,

rent.

3. The combination with a car or carrier, of an electric motor for lifting the car, and automatic controlling means 'for reduclng {the speed of the car as it approaches its upper hmit of travel to an extent varying with the load on the car undto maintain the motor energized to hold the car in its elevated position. 1 e

4. The combination with a load-carrying device, of an electric motor for lifting said its upper limit by-the torqueL-otthe motor,

and means for increasing the field strength tion.

$5. In hoistin mechanism, the combinaof the motor while the car is in such position with an e ectric motor comprising a q 7 series field winding, of a car, power-transmitting mechanism between the car and motor, starting resistance, means for introducing said resistance in the motor ClICllll and short-circuiting the seriesfield winding .as the car approaches its upper limit of travel, and means for automatically introducing the series field winding into the' motor circuit while the car is being brought to rest inits elevated position. 7. The combination, with an electric motor comprising a series field winding, of starting resistance in the motor circuit, an accelcrating magnet operable to short-circuit said resistance, means controlled by said magnet for effecting the closing of a short circuit across the series field winding, and means independent of the accelerating magnet for maintaining the series field winding shortcircuited. i

8. The combination with an electric motor comprising a seriesfield winding, of an elec-. tro-responsive device controlling a short circuit across the series field winding, means for effecting the operation of said device to short circuit the field winding when the speed of the motor reaches a predetermined limit, and means for retaining the field windingshortcircuited until the speed of the motor is reduced to a point materially below said limit.

I 9. Thecombination with an electric motor comprising a series field winding, of starting resistance, an accelerating'ma i'1et,-an electro-magnet, a switch in the circuit of the electro-magnet operated 'by theaccelerating -magnet, a short circuit across the series field 4 .motor, and operable toshort-circuit said ad "ditional resistance only when the speed of the motor is excessive.

11. The combination with an electric motor, of starting resistance therefor, means for controlling said resistance, additional resistance, means for closing a local circuit including the motor armature. and said resistances, an electro-magnet having its winding in said local circuit, and means operated by said magnet for controlling said additional resistance.

12. The combination with a car, of a motor for lifting the car, means-for supplying current to the motor in a direction to start the ear dqwnward from its elevated position, and means for automatically cutting off the supply of current when the car has started downward.

13. The combination with a motor, of a deviceoperated by' the motor in one direction and operative to drive the motor as a generator in the pposite direction, means for supplying cur ent to the motor to start it in said last-named direction, and means for cutting off the supply of current when the motor has started and permitting it to be run as agenerator.

14, The combination with 'a' car, of an electric motor, driving connections between the car and motor, means for supplying current to the motor in a direction to lift the car, means for reversing the direction of the current through the motor when the car is in its elevated position, and means for automatically cutting-off the current supply and establishing a local circuit for the motor when the car has developed a' predetermined speed in its initial downward travel and maintaining said local circuit during the remaining downward travel of the car.

15. The combination with a car, of an electric motor, power-transmitting connections between the car and motor, means for supplying current to the motor to lift the car, and means for supplying current to the motor in direction and quantity to overcome the starting friction when the car is in its elevated position and start the car downward and then permittingit to be low ered by gravity.

16. The combination with a car, of an electric motor, power-transmitting connections between the car andmotor, means for supplying current to the motor in a direction to lift the car, mechanism for reversing the current throu h the motor and starting the car do\vnwar fro1n its elevated position, and means for automatically cutting off the current supply when the car has reached a given point a short distance below its upper limit of travel.

17. The combination with a car and a lifting motor, of means for supplying current to the motor in a direction to lift the car, a device for reversing the current while 'the car is elevated and starting the car downward, and means for cutting off said switch in the motor circuit, mechanism foroperating said switch when the car is in its elevated position, and means for cutting off the supply of current to. the motor when the car has started downward.

19. The combination with a car, of an electric motor, an electro-magnetic Ieversing switch normally closed in a direction 'to supply current to the motor for lifting the car, a floor controller, and circuit connections between the magnet winding of the reversing switch and the floor controller for reversingsaid switch only when the car is at its upper limit of travel and during its initial downward movement. v

20. The combinationwith a car, of an electric motor for lifting the car, a switch in the motor circuit, a switch-operating electro-magnet, a floor controller, circuit connections between the floor controller and the winding of said magnet for closing the magnet circuit only while the car is near its upper limit of travel.

21. The combination with an electric motor and hoisting mechanism, of a reversing switch an electro-ma net for ooeratin said 7 C 1 b switch having differential windings, the current in one of said windings being dependent on the speed ofthe motor armature,

-a floor controiler, and circuit connections between the floor controller-and the other of said windings. a

22. The combination with an electric motor, of a switch, circuit connections for establishing a line circuit througlrthe motor armature when the switch is in one position and for opening the line circuit and establishing a local circuit through-thennotor armature when the switch is in another position, a differentially wound electro-magnet for operating the switch, and a floor controller automatically controlling one ofthe circuits of't e magnet winding 23. The combination with a hoisting m0- tor, of a load-carrying device, means for supplying current to the motor in a direction to lift said device, mechanism operable when the car is at its upper limit of travel to supply current in a direction to start the car downward, means for cutting off the current supply when the motor has developed a given speed in' its downward travel, and additional means ,for cutting off the current supply when the car has moved downwardly a given distance independently of the speed.

24. The combination with an electric hoisting motor, of a car, means for operating the motor, floor controller and eicc tro-responsive means controlled thereby for automatically varying the speed of the car at an intermediate point in its travel and again bringing it back to normal speed during the operation of the motor.

The combination of an electric motor, a car operated thereby, electrically operated means for automatically reducing the speed of the car and again bringing it back to normal speed at predetermined intermediate points in its travel.

26. The combination with a car, of an electric hoisting motor, and an automatically operable electro-responsive device electrically controlled and operated to effect a temporary reduction in the speed of the car and again bring it back to normal.

27'. The combination with a car, of an electric hoisting motor, and electro-responsive means to effect a change in the current strength in a circuit of the motor during an intermediate period in thetravel of the car and thereby produce a temporary change in' the speed of the car.

.28. The combination with a car, of -a hoisting motor, a resistance in a circuit of the motor, a normally closed electro-magnet-ic switch in a short circuit across said resistance, and automatic means for energizlng the switch magnet and lntroduclng' said resistance in the motor circuit for a limited period in the travel of the car.

29. The combination with a car, of an electric motor, a floor controller, and means controlled thereby for eifecting a temporary reduction in the speed of the car.

30. The combination with a car, of an electric motor, a floor controller, an electromagnetic device controlled thereby operative to automatically effect a temporary slowing down of the car at an intermediate point in its travel and circuit connections between said device and the floor controller.

31. The combination with a car, of an cuit, a normally open switch in a short cir-' cuit across said resistance, an operating electromagnet for saidswitch, and means operable automatically at a predetermined point in the travel of the car to excite said magnet and close the switch during a limited period in the travel of the car and then de'e' nergize said magnet and reopen the switch and permit the continued travel of the car at normal speed' 33..The combination 'with a car, of a hoisting motor, means for effecting automatically a reduction in the speed of the car throughout a predetermined period in its upward travel, and additional means for automatically reducing the speed of the carat a corresponding period in its downward travel.

34. The combination with a car, of a hoisting motor, means for operating the mo-- tor, mechanism for automatically reducing the speed as the car approaches its limit of travel, and independent means for efiecting a'temporary reduction in the speed While the car is at an intermediate point.

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

JOHN D. -IHLDER. Witnesses WALTER C. STRANG, JAMES G. BETHELL.

Copies 6f this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. (1.?

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