US1050554A - Motor-controlling apparatus. - Google Patents

Description

D. L. LINDQUIST.

MOTOR CONTROLLING APPARATUS.

APPLIOATION FILED JULY 6, 1907. D A 1 1 5 55 Aatented. Jan. 1, 19;).

2 SHEETS-SHEET l.

5mm We a D. L. LINDQUIST. MOTOR CONTROLLING APPARATUS.

APPLIOATION FILED JULY 6, 1907.

Patented Jan. 14, 1913.

2 $HEETSSHEET 2.

QN kSkm w MEM 35 UNI E STATES PATENT OFFICE.

DAVID L. LInnoUIs'r, or YONKERS, NEW YORK, ASSIGNOR To one nnnvnron com-- IPANY, F JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

Specification of Letters Iatent.

' Patented Jan. 14., 1913.

Application filed July 6, 1907. Serial No. 382,498.

To all whom it may concern.-

Be it known that I, DAVID L. LIND UIST, a citizen of the United States, residing in Yonkers, in the county of Westchester and Stateof New York, have invented a newand useful Improvement in Motor-Control ling Apparatus, of which the following is a specification.

My invention relates to motor controlling apparatus, particularly that used for trac- The specific objects of the invention will' appear hereinafter, the novel combinations of elements being set forth in the appended. claims. I

In theaccompanyingdrawings, Figure 1 represents a traction elevator system to which my invention may be applied; and Fig. 2 represents a wiring diagram and a system of control including my invention.

Referring to Fig. 1, G designates an elevator car which may be suitably uided to move up and down in the elevator atchway or elevator well in the usual way. S desig nates a controlling switch in the car, and SW a safety switch in the car.- 1 are the cables which are secured to the top of the car and extend upwardly over the frictional driving sheave or drum 2 and thence downwardly over the direction sheave 3, upwardly over the sheave 2 and finally downwardly to the counterweight W which is associated with the fixed -guides 4, i. In some instances the driving sheave 2 may be at'the lower end of the elevator well, instead of at the upper end as shown. Furthermore, the sheave 3 for securing additional friction may sometimes be omitted. It should be noted that this sheave 3 is preferably placed at one side. so as to act also as a deflection sheave for the cables extending from the car upwardly or those extending downwardly to the counterweight. Ar-

ranged in the path of travel of a moving.

part of the elevator, in this instance the cams 5 and 5' carried by the car, are a series of limit switches 6 at the upper limit of travel ofrthe car and a series of additional limit switches 6' at the lower limit of the car'traveh The journals of the shafts of the direction sheave 3 areprovided with fixed bearings 7, 7 at the upper end of the hatchway or elevator well. Adjacent thereto isthe fixed bed-plate 8 for the electric motor M and for the standards 9, 9 and 10. The standards 9, 9 are provided with bearlugs for the motor shaft 11, to which are connected the driving drum 2 and the brake pulley 12. To the standard 10 are pivoted the brake bands 13 which carry the brake shoes arranged to be brou 'ht against the pulley 12 by the brake springs 14 and released therefrom by the electro-magnet 15.

The latter may be supported by a bracket 16 fastened to and extending from the uppermost end of the standard 9. It should. be understood that the frictional driving apparatus associated with the power transmitting cables connecting the car and counterweight may be varied in details and arrangement as desired; so also the brake ap' paratus and the type of the motor. Preferably, however, the motor is of the multipolar type with a series connected armature and a shunt field. On account of the slow motor speed, and consequent small momentum of the armature, comparatively little power is needed for accelerating the armature up to'full speed. B designates the 0on troller board of slate or other insulating -material for carrying most of the switches,

electro-magnets, and the circuits and connections illustrated in Fig. 2. L is the main line switch for controlling the continuity of the main circuit from the source of current supply through the main lines a, b. P designates the potential switch, R, R the reversing switches, A the accelerating 'magnet, ALM the auxiliary loadmagnet, EPSM the excess potential safety magnet. SFSM the shunt field safety magnet, and FSM the fast speed magnet. 17, 18, 19 and 20 and 21, 22,- 23 and 24 are speed controlling switches arranged to be operated by electro-magnets.

' Similar characters of reference are used onboth figures of the drawing.

' Referring now to Fig. 2, it will be seen that in addition'to the parts already mentioned there are represented a governor G for controlling the shunt field resistance SFR and the potential switch P; also a switch 25 which may be associated with brake solenoid, and 26 designates an electric switch operated by movement of the plunger 27 illustrated in Fig. 1. 28 designates the shunt field Winding, 29 the motor armature,

30 the main or'maximum starting current resistance, 31 the minimum starting current resistance and '32 the by-pass resistance. 33 and 33' are auxiliary switches associated with the reversing switches to control the brake magnet. 34 and 34" designate limit, switches which are operated when the car goes beyond its normal limits of travel. When the'motor is at rest I prefer to have the shunt field winding 28 connected in series with the shunt field resistance SFR, so that when the main line switch L is closed as in: dicated a circuit may be traced from the positive main a through the blade 35, con-. ductors 36, 37, shunt field resistance SFR, shunt field winding 28, conductor 38, shunt field safety magnet SFSM, conductor 39, conductor 40, switch blade 41, out to the negative main bQfThe shunt field will thereforc'be permanently: excited, but its strength will vary according to the amount of the resistance SFR and the potential across the mains. The shunt field corresponding to full car speed is left on permanently for the sake of safety, and also to prevent too sudden acceleration with heavy load on down motion of the car or light load on up motion. Connected across the shunt field winding 28 is a high resistance 42 to take up the shunt field discharge in the event that the shunt field circuit should be interrupted. This high resistance is shown variable, for the reason that it may be omitted if desired. Some of the other resistances in Fig.2 are also shown as variable to indicate that they may be omitted if desired. On account of the self-induction in the shunt field and the retarding effect when solid steel poles are used in the motor, it is possible to make a whole change in the excitation in the shunt field in one step without any jar or too sudden. change in speed. The shunt field resistance SFR being in circuitwith the shunt field winding when the motor is at rest, the field will be comparatively weak, and it will therefore take sufiicient time for the shunt field to build up to its full strength to insure the acceleration of the motor not being too sudden and therefore insuring a smooth and easy start of the car.

The construction of the motor is such that the constant losses are small and the efficiency of the motor therefore high at light load, the maximum efliciency occurring at about .onekhalf load which is about the average'load. in general elevator practice. Almost all losses in the motor at full load are in the armature winding. The resistance of the latter can therefore be comparatively high, which permits a saving of copper but stillmaintaining high efliciency. The pur- .ment in electric elevator apparatus, although any other type of switch may be used if desired, the one herein shown being merely forillustrative purposes.

43 designates the controller lever which is pivoted at 44 and connected thereto so as to oscillatetherewith is the arc-shaped rack 45 which is in engagement with the gear 46. The latter is pivoted to the casing and is operatively connected to the conducting segments 47 and 48, the former being arranged to move into engagement with the fixed contacts or spring-pressed contacts 49 and 50 and the latter being arranged to engage the fixed contacts or spring-pressed contacts 51, 52, 53, 54, 55, 56, 57 and 51, 52, 53, 54, 55, 56 and 57. It will therefore be seen that when the lever 43 is moved in the direction of the arrow marked Up the segment 47 will engage the contact 49 and the segment 48- will engage one or more of the contacts 51 to 57, inclusive.

Let it be assumed that the main line switch L is closed, as also the potential switch P, and that there is proper potential across the mains for the desired operation of the electric motor. Then if the lever 43 is moved for operating the car in the up direction segment 48 will first engage the contact 51, and thereafter or at substantially the same time segment 47 Will engage the contact 49, when a circuit will be closed from the positive main a through the blade 35 and conductor 36, and thence through the fuse 58, blade 59, contact 60, conductor 61, limit-switches 62, 62, conductor 63, resistance 64, individual switch 65, solenoid 15 of the brake magnet, conductor 66, contact 51, segment 48, plate 67, segment 47, contact 49, conductor 68, switch 25, conductor 69, blade of the safety switch SW, conductor 71, fuse 72, conductor 73, contact 74, blade of the potential switch P, conductor 40, blade 41 of the main line switch L, out to the negative main 5.. The relative position of the contact 49 is shown, however, such that segment 47 does notengage the same until the segment 48 engages the contact 52, so that the brake apparatus will be released substantially at the same time that the reversing switch is operated to establish the motor circuits in a direction corresponding to the desired direction of the 59, conductor 76, resistance 77, conductors 78, 79, limit switch 80, conductors 81, 82, the solenoid 83 of the electro-magnet for operating theswitch R", conductor 84, limit switch 85,.conductor 86, contact 52, plate 67 contact 49, conductor 68, switch 25, conductor 69, blade 70, conductors 71, 73, contact 74, and thence to the negative main. It will now be seen that the brakemagnet solenoid 15 is placed across the-mains with the resistance 64 in series therewith and that the solenoid 83 is placed across the mains.

7 hen the latter receives current'itwill actuate its core or plunger 87, and thereby lift v the contacts 88 and 89 into engagement with the contacts 90 and 91, respectively, and

separate the contacts 92 and 93 from the contacts 94 and 95. The motor circuit indicated by the heavy lines will now be closed and may be traced from the positive main to conductor 76 and thence through the windings of the blow-out coil 96, contacts 90, 88, conductor 97, contacts98, 99, conductor 100, minimum starting resistance'31, conductors 101, 102, brush 103 of the motor armature 29, brush'104, conductors105, 106, coil 107 for holding the plunger 108' in its lowermost position. to secure firm connection I between the contacts 98, 99 and contacts 108 and 109. I through the latter contacts and by conduc- Thence the circuit continues tor 110 to and through conductor 111, main starting resistance .30, conductor 112 to the blade 75 which is connected to the negative main. From the junction 113 a shunt path leads by conductor 114 through'the plural ity of blow-out coils 115, the series of closed switches 24., 23, 22 and 21, conductor 116, section 117 of the by-pass resistance 32, and thence by conductor 118 to the motor armature brush 104. It will now be seen that the starting resistances 31 and 30 are placed in 3 series with the motor armature and that the section 117 of the by-pass resistance 32 is placed in shunt to the motor armature.

When the switch R is closed the auxlliary switch 33 is also closed, in this instance being connected to operate substantially at the same time. The circuit controlled by the switch 33 may be traced from the positive main to and through conductor 76, contacts 90, 88, conductor 97, contact 119, switch 33, conductor 120, individual switch 121, and through the brake solenoid 15 and thence by conductor 66 to contact 51, plate 67, contact 49, conductor 68, switch 25, conductor 69, blade 70, conductors 71, 73, contact '74, blade 7 5, and thence to the negative main. It will therefore be seen that a path is established in parallel to the resist-- ance (i land that therefore the latter is shortcircuited so that'the brake magnet is not closed. As soon as the brake magnet is operated the switches 65 and 121 are opened to insert the resistances 123 and 124 in the re-.

spective branches of the brake magnet circuit leading from the positive main to the junction 122. It should be noted therefore that the resistance 6 1 may he suflicient to prevent the brake from being released when the controlling switch in the car is initially operated, and that not until the reversing switch R is operated does the brake magnet solenoid receive sufiicient current to operate the brake apparatus.

After the brake has been operated, however, the resistances 123 and 12 1 are inserted in series therewith so as to minimize the consumption of current after the brake magnet has done its work, as it requires less power for the brake magnet to hold its plunger in its uppermost position, and consequently the brake mechanism in released position, than to initially lift the said plunger and actuate the'brake mechanism connected thereto. It should also be noted that the terminals of the brake magnet circuit are at the contacts 60 and 74 which are .isolated with .re'spect to the other contacts of the potential switch P, so that when the latter is opened the brake magnet circuit will be entirely disconnected from both mains and also from the motor. The brake magnet is'therefore entirely disconnected from any possible source of current which would tend to hold the brake mechanism released, for instance, when the motor acts as a generator although the potential switch is open. This arrangement insures the application of the mechanical brake to stop the motor shaft and-the frictional driving drum connected thereto, in any event.

The insertion of the resistances in series with the brake magnet coil decreases the amount of current taken by the brake magnet, thereby lessening the current consumption and decreasing heating. Furthermore, when the resistances are thus inserted the magnet will release the brake apparatus more quickly when the current from the mains thereto is interrupted. In order to apply the brake shoes gradually the motion of the magnet cores is electrically retarded by shunting the brake coil with the high re sistance 125. Upon the interruption of the brake, magnet circuit the counter-electrw motive force of self-induction of the brake magnet will produce a current through the resistance 125. This will tend to maintain the brake magnet energized so that the brake shoes will be applied gradually. Such brake resistance around the brake magnet may be a variable resistance, or omitted if desired, or such resistance may be in an open circuit and automatically controlled to produce the effect desired at the proper time. In order to effect a quick release of the brake mechanism when the brake-magnet is energized the plunger or core of the latter is preferably slotted longitudinally.

When the main line switch L is closed and current flows through the shunt field resistance SFR and the shunt field winding 28, the shunt field safety magnet will also receive current to close the switch 126 which controls the continuity of circuit of the magnet 127 which holds the potential switch in closed position. The circuit controlled by the switch 126 may be traced from the junction 128 through conductor 129, switch 130, conductor 131, switch 126, conductor 132,

individual switches 133 and 134, conductor 135 and the resistance 136 therein, and thence through the electro-magnet 127, switch 137, conductor 138, individual switches 139 and 140, conductor 141, governor switch 142, conductor 143, blade 144 of the safety switch SWin the car, conductors 71, 73, to the contact 74. It will therefore be seen that this circuit is connected across the positive and negative terminals and, includes the switches 130, 126, 137, 133, 134, 142, SW, and theelectro-magnet 127. The opening of any one of these switches, therefore, will effect the denergization of the potential switch magnet 127 and the consequent opening of the potential switch which will cause a slowing down and the stoppmg of the motor and the car. If the current through the shunt field should decrease to a predetermined value such that the I operation of the car should become unsafe andthat the speed would tend to become excesslve, the shunt field safety magnet SFSM would not have suflicient strength to maintain the switch 126 closed. Upon the open- 'ing of the latter the potential switch magnet 127 would be deenergized, with the result already stated. Furthermore, if the car should travel beyond its normal limits of travel the cam 5 on the car would strike the roller on the lever operating the switch 34 on up motion or on the roller of the lever for the switch 34 on down motion, and therefore either the switch 133 or 134 would be opened and consequently the circuit of the potential switch magnet interrupted. Should the operator in the car lose control of the holsting apparatus, the opening of the safety switch SW in the car would also open the potential switch magnet circuit and cause the stopping of the car. If during the normal running of the car the speed should exceed a predetermined limit, the governor device G would open the switch 142 to break the circuit of the potential switch magnet and thereby bring the car to rest.

Should the potential applied to the mains a and Z) from the source of electric current supply exceed a predetermined limit then other conductors so that there will be no pos-' sibility of maintaining the magnet 127 energized by the motor acting as a generator.

Should the mainline current become interrupted while the motor is operating, the latter might be converted into a generator and tend to supply current to the potential switch magnet 127 to hold the potential switch P closed, but the current through the shunt field safety magnet SFSM will be decreased at this time to permit the opening of the switch 126 so that thecircuit of the potential switch magnet will be interrupted, wit-h the consequent eflect'of stopping the car gradually. Should it happen, however,

that the switch 126 is not opened before the car gains excessive speed or before the motor acting as a generator furnishes sufficient current to the magnet SFSM to cause the latter to hold the switch 126 closed, then the excess potential from the motor as the same speeds up will operate the magnet EPSM. The switch 130 will be opened by the latter and the motor stopped. Should the acquired speed become excessive then the governor will be operated. This is the preferred arrangement but the order of operation may be varied by readjustments, as desired.

Upon the closing of the reversing switch R in the manner heretofore stated, a circuit will be immediately closed through the fast speed magnet FSM from the conductor 97 through the conductor 148, resistances 149 and 150, solenoid 151, conductor 152, to the junction 153, and thence by the conductor 69 to the blade 7 0 of the safety switch SW and through the same to conductors 71, 73 and finally to the contact 74. The fast speed magnet FSM will therefore be in a circuit connected directly across the mains and will operate the switch 154 to close the and most of the by-pass resistance short circuited. Hence when the lever 43 of the car switch S is moved in the direction of the up arrow and the, contacts 51, 52 and 49 are electrically connected together, the motor may start at slow speed and will .continue to operate at such speed until the lever receives additional actuation to cause the -seg-.

ment 48 to engage the contact 53. When this occurs a circuit will be closed from the positivemain through the conductor 76, conswitch 25, blade 70, conductors 71, 73 to contact74 and thence to the negative main. \Vhen the solenoid 159 is thus supplied with current it will lift its plunger 164 and close the switch 17 and open-the switch21. The opening of the switch 21 will insert an additional section165 of the by-pass resistance in parallel-to the motor armature, and the closing of the switch 17 will short circuit a section 166 of the minimum starting resistance 31. The motor will therefore increase in speed to another predetermined value. v

When the switch 17 is closed the auxiliary contacts 167 and 168 are brought into engagement with each other so that when the lever 43 receives an additional movement to bring the plate -67 into engagement with the contact 54,'the next solenoid 169 will receive current to close the switch 18 and open the switch 22. The remaining section of the minimum starting resistance 31 will therefore be short circuited and an additional section of the bypass resistance inserted. The closing of the switch 18 will permit the closure of the switch 19 when the plate 67 engages the contact 55; and the closure of .the switch 19 will permit the solenoid 170 to receive current to close the switch 20 and open .the switch 24 when the plate 67 engages the contact 56. Upon the closure of the switch 19 the solenoid 159 receives current independently of the car switch through the circuit from the positive main through the reversing switch R, conductor 158, solenoid 159, resistance 160, conductor 171, contacts 172, 173, conductor 174, switch 25, conductor 69, blade 70, conductors '71, 73, to the contact 74 and thence to the negative main. When the switch 19 is closed and the switch 23 opened the entire'by-pass resistance is inserted across the armature, and when the switch 20 is closed and the switch 24 opened the by-pass resistance circuit is entirely interrupted.

When the switch 20 is closed the circuit of the accelerating magnet A is closed across the armature when the switch plate 67 engages the contact 57. This circuit may be traced from the armature brush 103 through the'conductors 102, 175, contacts 99, 98, conductors 97, 176, resistance 177, accelerating magnet A, switch 20, conductor 178, section 179 of the main starting resistance 30, conductors 111, 110, contacts 108,,109, solenoid 107, and conductors 106, 105 to the other armature brush 104. Now after the by-pass resistance circuit has been opened the motor will increase in speed while the accelerating magnet is connected across the armature. Associated with the accelerating magnet are aseries of switches 180, &c., for gradually cutting out the main starting resistance as the motor increases in speed in the well known manner.

When the last switch is closed an aux- .iliary switch 181 is also closed so as to short circuit the fast speed magnet FSM and cause the latter to open the switch cont-rolled thereby and thus insert the shunt field resistance SFR and still further increase the speed of the motor by weakening the shunt field. The short circuit around the solenoid 151 may betraced from the junction 182 through the conductor 183, switch 181, conductor 184, the auxiliary contacts of the switch 20, conductor 185, contact 57, switch plate 67, contact 49, conductor 68, .switch 25, conductor 69, to the junction 153. The

motor, hoisting apparatus and car will 'now operate at full speed, but if this speed should exceed a predetermined value the governor G will close the switch 186 and thus short circuit the section 155 of the shunt field resistance by the conductors 187 and 188, The short circuiting'of the section 155 will have the efiect of strengthening the field and thus slowing down the motor. If, however, this slowing down is not suficient the continued speeding of the car will cause the governor- G to open the switch 142 after the switch'186 has been closed. As before explained, when the switch 142 is opened the circuit of the potential switch magnet 127 is interrupted, and when this occurs the potential switch will drop open and the conductor 189 connected thereto will electrically connect the clips 190 and 191. This will close a short circuit or local 'circuit across the motor armature through the conductors 102, 192, 118, 105, and a small section of the by-pass resistance 32. This will cause an electro-dynamic braking action to slow down-the motor while the mechanical brake is being gradually applied, the contacts 60 and 74 being entirely disconnected from any source of current sup-ply when the potential switch P is opened. I prefer to permanently connect the shunt field terminals'between the main line switch L and the potential switch P so that a weak shunt field is left on continuously to lessen the liability of accidental opening of the field circuit, and, furthermore, leaves the shunt field excited even when the potential switch opens,

thereby always insuring a strong electrodynamic braking eflect 1n bringing the car automatically to a gradual stop. It should also be noted that when the potential switch P opens and the current is cut oif from the electro-magnets controlling the switches 21, 22, 23 and 24 a local circuit is also closed from the armature brush 103 by way of conductors 102, 114, switches 24, 23, 22 and 21,

1 conductor 116, section 117 of the by-pass resistance 32, conductors 118, 105, to the other armature brush 104. The local armature circuit just traced insures additional electro-dynamic braking action upon stopping and also when the car switch is moved back toward central position to reduce the speed of the motor. It should be particularly noted that not only are theterminals of the brake magnet atthe contacts 60 and 74, but

that the negative terminal of the reversing switch magnet solenoids and of the speed controlling solenoids are also at the contact 74, so that when the potential switch is opened all current is entirely cut off from such solenoids.

The circuits thus far traced have been upon the operation of the lever 43 in the directlon of the up arrow for the operation of the reversing switch R, but it will be 30 apparent that upon movement of the lever 43- in the direction of the down arrow the reversing switch R will be operated to establish motor circuits in the opposite direction, but the successive operation of the 3, speed controlling electro-magnets and the consequent insertion of the by-pass resistance and. the cutting out of the minimum starting resistance will be the same, and that finally the accelerating magnet will graduzally cut out the startin resistance and eifect the'operation of the ast speed magnet to Insert the shunt field resistance. After the switch lever 43 has been moved to its extreme limit so that the plate 67 engages the 45 contact- 57 and it is desired to reduce the speed of the car the segment 48 is 'moved off the contact 57 but still left in engagement with the contact 56. The short circuiting pat-h around the fast speed magnet will so thereupon become broken and the latter will therefore again be energized. to short circuit the shunt field resistance and thereby strengthen the field and cause the motor speed to decrease. Further movement of the 55., switch lever 43 toward central position leaving the segment 48 in engagement with the contact will effect the interruption of the circuit for the solenoid 170 and the consequent opening of the switch 20 and the 60 closure of the switch 24. The opening of the switch 20 will interrupt the circuit of the accelerating magnet, and consequently the entire maximum starting resistance 30 will be reinserted in series with the motor armature. The closure of the switch 24 will insert the entire by-pass resistance 32 across the motor armature. This will still further reduce the speed of the motor. Upon the movement of the segment 48 off the contact 55 the circuit of the solenoid 193 will be interrupted to open the switch 19 andclose the switch 23. This operation may insert a section of the minimum starting resistance or by the closure of the switch 23 only short circuit a portion of the by-pass resistance, with the result of still further reducing the speed of the motor.

Upon the segment 48 leaving the contact 54 the circuit of the solenoid 169 will be interrupted to effect the opening of the switch 18 andthe closure of the switch 22. The opening of the switch 18 will insert in series with the armature a portion of the minimum starting resistance and the closure of the switch 22 will short circuit an additional section of the by-pass resistance. When the segment 48 leaves the contact 53 the circuit of the solenoid 159 is broken, the path from the conductor 174 having already been broken by the opening of the s itch 19. The switch 17 will therefore open 0 insert the remaining section of the minimum starting resistance and the switch 21 will close to short circuit the section 165 of the by pass resistance, leaving only the section 117 in shunt to the armature. When the switch plate 67 electrically connects the three contacts 49, 51 and 52, the minimum by-pass resistance is connected acrossl'the armature and all of the starting resistances are connected in series with the motor armature and the shunt field resistance is short circuited, so that the motor will run at minimum speed at such time.

When the car switch is moved toward centralposition to stop the motor and the segment 48 leaves the contact 52 the circuit of the reversing switch solenoid 83 will be interrupted and the main line current supply to the motor therefore cut off upon the opening of the switch R. At the same time that the reversing switch R is opened the switch 33 is opened, thereby interrupting the path including the conductor 120 and the resistance 124. Preferably when the seg ment 48 leaves the contact 52 the segment 47- also leaves the contact 49, so that when the switch 33 is opened the circuit of the brake magnet'is also opened, and as heretofore explained, if the shunt resistance 125 is employed the brake shoes will be applied gradually. Preferably the switches 33 and 33' comprise contacts separated or isolated from the reversing switch contacts so that- .the counterelectro -motive force of the armature cannot effect the energization of the brake magnet and the consequent holding of? of the brake apparatus. It will be evident, however, that after the segment 48 leaives the contact 52 the contacts 49 and 51 may still be electrically connected by the switch plate 67 and the brake magnet still receive current through the resistances 64 and 123.- If this current is sufiicient the brake apparatus will still be held in released position, but it will be seen that when the reversing switch It is opened the local circuit including the armature and the. minimum startin resistance is closed to establish an electroynamic brake circuit. This brake circuit may be traced from the brush 103 through the conductor 102 to the junction 113, and thence through conductor 101, resistance 31, conductor 175, contacts 95, 93, conductor 110, contacts 108, 109, holding solenoid 107, conductors 106, 105, to the brush 104; also through conductor 100, contacts- 99, 98, conductor 97, conductor 157, contacts 92, 94, solenoid 87 and conductors 194, 105, to the armature brush 104. Therefore the ,electro-dynamic brake may be applied either while the mechanical brake is being applied or before the same is released to permit its application. In the latter event when the circuit of the brake magnet is interrupted at the contact 51 the current will be reduced from a value dependent upon the resistance 64. The higher this resistance, the less current will be flowing for holding the brake in released position, but when the circuit is interrupted the current will be reduced to the point where the solenoid 15 will release its core in a shorter space of time than if the resistance 64 were lower, it being understood that the brake shoes while being applied are retarded nevertheless, due to the local current in the brake solenoid.

The series of limit switches 6 and 6 are so connected to the car switch-that they will have substantially the same efiect' as the movement of the car switch from its extreme position to its limiting position. These limit switches are arranged to be operated by some moving partof the hoisting apparatus and in this instance I have shown them arranged in the hatchway so as to be operated successively by cams 5, 5 carried by the car. WVhen the car approaches the upper limit of its travel the switch 195 will be opened first by the cam 5' which has the same effect as the'moving of the switch plate 67 oil the contact 56. The next limit switch to be operated, by the cam 5, is that designated 196 which effects a further reduction in speed of the motor as explained when the segment 48 leaves the contact 54 of the car switch. When the switches 80 and 85 are opened both terminals of the reversing switch solenoid 83 will be disconnected from any source of current supply and the reversing switch R will be 7 opened and the brake magnet denergized brake apparatus to positively stop the car sufiiciently to cause the application of the at its upper limit of travel. Or in case the path including the-resistance 64 is employed, an additional limit switch 62 is opened upon further movement of the car after being slowed down to veryslow speed. The opening of the switch 62 will entirely disconnect the brake magnet from the positive main and the brake apparatus will therefore be applied. Should the car have obtained such great momentum that the force of slowing down and stopping is not sufiicient to bring the car to rest at its normal limit of travel,

but the car goesbeyond a short distance, the

cam 5 will open the switches 133and 140 to disconnect both terminals of the potential switch magnet 127 from the mains and thus effect the opening of the potential switch magnet.

It will be noticed that an auxiliary load magnet ALM and a resistance 197 in series therewith are connected across the motor armature between the junctions 198 and 199 by means of the conductor 200. This magnet controls a switch 201 which is connected by the conductor 202 to the solenoid 193 and by the conductor 203 to the conductor 204 which leads to the contact 55 of the car switch. Ordinarily when the motor is optermined value, the car would tendto stop before reaching the level of the floor landing. The armature would be slowed down to such a speed, however, that the potential across the latter would not be suflicient to cause the auxiliary load magnet ALM to hold the switch 201. open. Therefore upon the closing of the latter a circuit would be established from the positive main through the reversing switch R, conductor 158, solenoid 193, conductor 202, switch 201, conductors 203, 204, contact 55, plate 67, contact 49, conductor 68, switch 25, conductor 69, blade 70, conductors 71, 73, to the negative main. It should be noted that the conductor 204 has no limit switch therein.

Therefore when the switch 201 is closed and the solenoid 193 receives current the switch "19 is closed 'or held closed so that the minimum starting resistance 31 will remain short circuited and the opening of the switch 23 will cause the entire by-pass resistance to be inserted if the switches 22 and 21 are still open. If the switch 22 or 21, or both, are already closed then only the closing of the switch 19 will cause the resistance 31 to be short circuited The purpose of maintaining current in the solenoid 193 or reestablishing current therein is to vary the slowing down resistance so that more ouro 8 '1,oso,o64

rent can be received by the motor armature than when an average load is being moved, so that the car will be carried automatically to its normal limits of travel although the load in the car may exceed a predetermined value on the up motion or fall below a predetermined, value on the down motion. This is also true as to the stopping of the car at an intermediate landing. I

Obviously those skilled in the art may make various changes in the details and arrangement of part-s without departing from the spirit and scope ofmy invention and I desire therefore not to be limited to the precise construction herein disclosed.

Having thus fully described my invention and the mode of its application, what I desire to have protected by Letters Patent of the United States is 1 1. The combination with an electric motor, of an electromagnetic main line potential switch, and a relay operated by the field current for permitting said switch to be held closed.

2. The combination with an electric motor, of an electro-magnetic potential switch, an additional switch to control the operation of said potential switch, and an electro-magnet in the field circuit normally holding said additional switch closed but permitting the same to open to effect the opening of said potential switch when the current in said field circuit falls below a predetermined value.

3. The combination with a shunt motor, of a switch for controlling'the continuity of the conductors leading from the source of supply to said motor, an electro-magnet for holding said switch closed, an additional switch for controlling said electro magnet, and a safety magnet in the shunt field cir-. cuit and normally closing said additional switch but permitting the same to open to effect the opening of said first-named switch and the consequent cuttin off of the current from the motor when t e current in the shunt field circuit falls too low.

4. The combination with an electric shunt motor, of a resistance, devices to insert said resistance in circuit with the shunt field windings to increase the speed of the motor, a governor, and a switch operated by said governor to out out a portion of said resistance to reduce the speed of the motor when such speed exceeds a predetermined value.

5. In motor-controlling apparatus, the

combination with a brake magnet, of a resistance in circuit with said magnet, means for cutting out said resistance to cause the magnet to operate, and means actuated by said magnet for again increasing the resistance of the magnet circuit after the magnet has operated. i

6. In I motor-controlling apparatus, the combination with a brake magnet, of a resistance in circuit therewithto prevent sufficient current to flow to operate the said magnet, means for short-circuiting said resistance to cause the magnet to operate, an additional resistance, and a switch operated by said magnet to insert said additional resistance.

7. The combination with an electric motor, of reversing switch mechanism therefor, a brake magnet, a resistance in circuit with the latter, auxiliary switches operated by the reversing switch mechanism to short-circuit said resistance to permit said brake. magnet to operate, additional resistances, and switches operated by the brake magnet to insert said additional resistances.

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

' AVID L. LINDQUIST. Witnesses:

CHAS. M. WISSEN, ALFRED E. Bnormr.

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