US1848563A - Hoxjse electric - Google Patents

Description

March 8, 1932. -hm I 1,848,563

CONTROL SYSTEM Filed May 11, 1928 INYENTOR Damlo Sanhm ATfORNEY 4 systems and more particularl Patented Mar. 8, 1932 PATENT OFFICE nnuro sun-1m, or EAST rxr'rsnonon, .xoosn mare a mmirac'ruame vama Application filed Kay 11,

The invention relates generally to control to control systems for electric motors w ich may be utilized for operating hoisting a paratus or devices having similar characteristics.

The object of the invention, generally stated, is to provide a control s stem for hoisting motors which shall be simple and eflicient in operation and economical to manufacture and install.

A more s ecific object of the invention is to .provide or controlling the operation of a hoist motor to insure a predetermined movement of the hoist in a selected direction,

irrespective of interruptions in power supply or the stopping of the motor.

Other objects will become evident from the followin description, taken in conjunction with t e accompanying drawing, in

which the single figure is a diagrammatic view of a control system embodying the invention.

Referring to the drawing, 10 designates, generally, an electric motor suitable for operating a hoist of the particular kind known as a skip hoist which is not illustrated, since hoists and the means for driving them by motors are well known in the art. In this particular instance, a direct-current motor, having an armature 11, shunt field windin 12, and a series field winding 13, is utilize The motor 10 may be operated from any suitable source of direct-current power which may, in this instance, be illustrated by line.

conductors 14 and 15.

In order to control the direction of operation of the motor 10, a pair of reversing switches 16 and 17 and a line switch 18 are provided. As shown, the reversing switch 16 is provided with a plurality of main con tact members 19, 20, and 21 and back contact members 22 and 23. Likewise, the other reversing switch 17 is provided with main contact members 24, 25 and 26 and back contact members 27 and 28.

The starting current of the motor 10 is controlled, in a well known manner, by means of a series resistor 29 which may be shunted in any desired manner, to increase the motor speed. In this instance, accelerating PENNSYLVANIA, assmnoa 1'0 wns'rmocourm, a conroaa'rron or rmmsyncomaor. mm

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switches 30 and 31 are provided for this urpose. The accelerating switches 30 an 31 are provided with operating coils 32 and 33, respectively, and also with restraining coils 34 and 35, and are arranged to provide for current limit acceleration. Since accelerating systems of this type are well known, itis deemed sufiicient to say that the motor current is led through the restraining coils which hold the accelerating switches in their 69 open positions until the motor-current decreases to a predetermined value, wherc on V the operating coils, being energized, e ect the closure. of the switches.

It will be readily understood that, in operating hoists of this character, it is desirable to definitely establish and maintain the direction in which the hoist is to operate until a complete cycle has been completed. In apparatus of this character, it is common practice to provide a carriage or skip,for lifting material from one level to another. Generall in operating hoists, the load is carried on y when the carriage is moved upwardly, and no great expenditure of power is required 75 to control it when it is moved downwardly. If a loaded hoisting carriage or skip is stopped while it is being moved upwardly, as a result of failure of power, then u on the re-establishment of' the power supp y, it is desirable'to be ableto effect starting and'operation of the motor in the proper direction to continue the upward movement of the carriage; otherwise, the carriage may begin to descend and, if the lifting apparatus is not designed for the lowering of heavy-loads, the

.hoist ma be damaged.

hereinafter. Since the relay 36 controls the operating circuit for the up-reversing switch 16, and the relay 37 controls the operating circuit for the down-reversing switch 17, they will be referred to hereinafter as the up rela 36 and down relay 37.

T e operation of the system may be manually controlled by ush-button switches 38 and 39, which will e referred to as stop and start push buttons, respective y. However, after the system is once set in operation, it is desirable to control the movements of the hoist automatically, which, in this instance, is effected b a plurality of limit switches 40 to 45, inc usive, which are disposed to control the energization of the various switch-operating circuits in res onse to predetermined movements of the hoist or ski he limit switches are shown schematically in the drawing as simple trip-type switches which are well known and which are usually installed along the path of the hoist carriage so that they are actuated when the hoist carriage passes predetermlned points. A drum-type limit switch may be used instead of trip-type switches and operated through reduction gearing or a chain drive from the motor, if desired.

The limit switches 40 and 41 are disposed to control the operating circuits for the up relay 36 and the down relay 37, switch 40 being closed and switch 41 bein open when the skip is in the down or loading position. The limit switches 42 and 43 are disposed to control the operation of the reversing switches 16 and 17 and the line switch 18 in response to movements of the skip, switch 43 being closed and switch 42 open when the skip is in the down or loading position. The limit switches 44 and 45 are disposed to control the operation of the motor-accelerating switches 30 and 31, the switch 45 being open and switch 44 being closed, when the skip is in the down position.

In describing the system and its operation, it will be assumed that the skip is in its lowermost position. The circuits established and the switches operated in order to manipulate the skip will be explained in the proper sequence. When the limit switches 40, 43 and 44 are closed, the hoist motor 10 may be set in operation to move the skip upwardly by actuating the start push-button switch 39 to its closed position. Current then flows from the line conductor 14 through conductor 48, limit switches 46 and 47, conductor 48a, stop push-button switch 38, start push-button switch 39, conductor 49, operating coil 50 of the switch 51 and conductors 52 and 53 to the line conductor 15.

Upon the closure of the switch 51, a holding circuit is established comprising conductors 54, contact members of the switch 51 and coil 50 which bridges the start push-button switch 39 and maintains the switch 51 in its closed position. Upon the closure of switch 51, an operating circuit for the up relay 36 is established which extends from the energized conductor 48a, through stop pushutton switch 38, conductor 54, contact members of the rela 51, conductor 55, operating coil of the up relay 36, conductor 56, limit switch 40 and conductors 57, 58, 76, 52 and 53 to the line conductor 15.

It will be observed that the up relay 36 is provided with a latching device 59 comprising a plunger 60 and an actuating spring 61 which is disposed to actuate the plunger 60 into a latching position which, as shown, engages in the slot 62 in the armature of the rela 36, when in its closed position. The late ing device 59 is also rovlded with a releasing coil 63 which, w en energized, unlatches the plunger of the switch 36 permitting it to drop to the open position, when its operating coil is deener ized. Likewise the down relay 37 is provided with a latchin device 64 having an actuating spring 65 and releasing coil 66.

It will be observed that, when the oper-.

ating coil of the up relay 36 was energized, an energizing circuit for the releasing coil 66 of the latching device 64 was established which caused the releasing of the armature member of the down relay 37, permitting it to fall to the open positlon. Therefore, it will be readily understood that, since the relay 36 controls the operating circuit of the up reversing switch 16 and is securely latched in the closed position when the hoist is being moved upwardly, then the operating circuit will not be interrupted upon the failure of power until the skip reaches its uppermost position where the pro r limit switches are operated to effect the ownward movement of the skip.

Upon the closure of the up relay 36, an operating circuit for the up reversin switch 16 and line switch 18 is establishe which may be traced from the energized conductor 48a, through push-button switch 38,

conductor 54, the contact members of the relay 51, conductors 49 and 67, the operatin coil of the line switch 18, conductors 68 an 69, contacts of relay 70, conductor 71, back contact member 28 of the reversing switch 17, conductor 72, the contact members of the up relay 36, conductor 73, the operating coil of the up reversing switch 16, conductor 74, limit switch 43, which is closed, conductors 75, 7 6, 52 and 53 to the line conductor 15.

Upon the closure of the up reversing switch 16 and the line switch 18, an energizing circuit for the hoist motor 10 is established which may be traced from the line conductor 14 through conductors 48 and 7 7 contact members 19 of the switch 16, conductor 78, armature 11, conductors 79 and 80, contact members 20 of switch 16, conductors 81, 82 and 83, series field winding 13, conductor 84, starting resistor 29, restraining coil 34 of the accelerating switch 30, conductor 85, contact members of the line switch 18 and conductor 53 to theline conductor 15.

In accordance with common practice in installations of this kind, a spring-pressed brake shoe 86 is utilized to stop the motor when the motor circuit is open. For the purpose of illustration, the brake shoe 86 is shown engaging the armature 11 of the motor 10 although it is to be understood that, actually, a separate brake wheel is provided on the motor shaft for this purpose. In order to withdraw the brake shoe 86 from the engaging or braking position when the motor is started, an'electromagnet, disposed to be energized upon the closure of the motor circuit, is provided.

As shown, the electromagnet comprises an iron core 87 connected to the brake shoe 86 and disposed to be actuated by a coil 88.

In this particular embodiment of the invention, the motor-is provided with a dynamic-braking resistor 89 which is shunted directly across the armature 11 when the reversing switches 16' and 17 are both in their open positions, the dynamic-braking circuit being established through the back-contact members 22 and 27 of the reversing switches 16 and 17 respectively.

It will be readily understood that, as only one of the reversing switches is closed at any one time,energizing current may be obtained for the brake-actuating coil 88 by connecting it to the dynamic braking resistor 89. When the reversing switch 17 is in the open position, current flows from the line conductor 14 through conductors 48 and 77, the contact members 19 of the up reversing switch 16, the back contact members 27 of the down reversing switch 17 dynamicbraking resistor 89, conductor90, brake-actuating coil 88, conductors 91, 92 and 93, line switch 18 and conductor 53 to the line conductor 15. Therefore, when the motor circuit is closed by means of the up reversing switch 16, the coil 88 is energized and the brake shoe 86 is withdrawn. Likewise, when the down reversing switch 17 is closed, a brake-actuating circuit is established through the back contact members 22 of the up reversing switch 16. a

In order to provide for reducing the speed v of the motor before dynamic braking begins, a slow-down resistor 94 is provided which is also connected in shunt relation to the armature 11 during the acceleration or deceleration of the motor.

In order to control the connection of the slow-down resistor 94, a transfer switch 95 is provided. As shown, the actuating coil of the transfer switch 95 is connected in series with the limit switches 44 and 45 and, as

.is closed and limit switch 45 is open when the skip is in the down position. Therefore, I

the transfer switch 95 is deenergized and the lower contact members 96 are bridged,thereby establishing an actuating circuit for the slow-down switch 97 which may be traced from the dynamic-braking resistor 89 which is connected to the line conductor 14, through the back contact members 27 of the switch 17, conductor 98, contact member 96 of the transfer switch 95, conductor 99, operating coil of the slow-down switch 97, conductors 100 and 101, line switch 18, and conductor 53, to the line conductor 15. The closure of the switch 97 connects the slow-down resistor 94 in shunt relation to the motor armature 11, through a circuit extending from one side of the armature 11, conductor 102, resistor 94, conductor 103, contact members of the switch 97 to the other armature terminal.

The motor 10, therefore, operates to move the skip upwardly and, since it is desirable to accelerate the motor to full speed as quickly as possible, the limit switch 45 is disposed to be closed after the skip has been raised a predetermined distance in the upward direction. Upon the closure of the limit switch 45, an energizing circuit for the transfer switch 95 is established, which may be traced from the energized dynamic-braking resistor 89, conductor 104, the operating coil of the transfer switch 95, limit switches 44 and 45 and conductors 76, 52 and 53, to the line conductor 15. The transfer switch 95, is accordingly, actuated to its up position to bridge contact members 105 and thereby interrupt the energizing circuit for the slow-down switch 97 which opens its contact members to disconnect the slow-down resistor 94 from the motor armature.

Simultaneously with the operation of the slow-down switch 97 an energizing circuit flowing through the restraining coil 34 of the accelerating switch 30, it is maintained in the open position until such time as the motor current decreases to a predetermined value. Upon the closure of the accelerating switch 30,'the first section of the resistor 29 is shunted through a circuit comprising contact members 108 of the accelerating switch 30 and the restraining coil 35 of the accelerat- 'ing switch 31. Simultaneously, an energizing circuit for the actuating coil 33 of the accelerating coil 31 is established from the conductor 107, through contact members 109 of the accelerating switch 30, coil 33, conductors 92 and 93 and the line switch 18, to the line conductor 15. After the motor current again decreases to a predetermined minimum value, the second section of the resistor 29 is shunted by the closure of the accelerating switch 31.

Inorder to operate the motor 10 at a maximum rate of s ed, provision is made for shunting the series field winding 13, in which event, the motor operates as a shunt motor. In order to provide fonshunting the series field winding 13, a switch 110 is-provided. As shown, the accelerating switch 31 is provided with contact members 111 which, upon the closure of the switch 31, establishes an energizing circuit for the switch 110. Upon the closure of the switch 110, a shunting circuit is established around the series field winding 13 which may be traced from the junction point of the line conductors 81 and 82, through conductor 112, the contact members of the switch 110 and conductor 85, directly to the line switch 18. As will be observed, this shunt circuit also completely shunts the starting resistor 29. The speed of the motor 10 is, therefore, entirely dependent upon the strength of the shunt field winding 12 which, as shown, is connected, directly across the line conductors 14 and 15, in shunt relation to a resistor 113 which may be utilized to control the excitation current flowing in the field winding.

Since it is desirable to reduce the speed of the skip as it nears the limits of its upward travel, the limit switch '44, which is now closed, is disposed to open at approximately the same distance from the upper limit of the travel of the skip as the limit switch 45 was closed from the beginning of its travel.

In this instance, the transfer switch 95 is deenergized, which, as described hereinbefore, establishes an energizing circuit for the slow-down switch 97, and the slow-down resistor 94 is again connected in shunt relation to the armature 11 which reduces the speed of the motor prior to the establishment of the dynamic-braking circuit. When the skip reaches the limit of its upward travel, the limit switch 43 is opened, thereby deenergizing the operating circuit for the up reversing switch 16 and the line switch 18 Upon the opening of the contact members 19 of the reversing'switch 16, the operating circuit for the brake coil 88 is interrupted, which permits the brake to close. Simultaneously with the brake-closing operation, dynamic braking of the motor 10 is-efi'ected since the back contact member 22 of the reversing switch 16 is now closed, to establish the dynamic-braking circuit hereinbefore described.

In operating hoists of this character, it is necessary to provide sufli'cient time delay 7 after the skip reaches the limit of its upward travel to provide sufiicient time for an unloading operation.

When the skip is in its uppermost position, the limit switch. 42 is closed and the limit switch 43 is o ened. The closure of the limit switch 42 esta lishes an ener 'zing circuit for the down-reversing switch 1 and line switch 18 which depends, for its complete establishment, upon the down relay 37 and the switch 7 O which are in their closed positions.

In this instance, the switch 7 0 is provided with a dash pot 115 in order to ensure a time delay in its closing operation and, therefore, the switch is utilized to control the enerthe line switch 18 after the down relay 37 'has been actuated to its closed position.

Since the limit switch 40 was maintained in a closed position until the skip reached its uppermost position, the up relay 36 is held in its closed position both magnetically and mechanically. The limit switch 41, being open until the skip reaches its uppermost position, the operating coil 63 of the latching device 59 is deenergized, which causes the latching device 59 to securely hold the up relay 36 closed, even though a power failure occurred which would deenergize its actuating coil. The limit switch 40, being opened at this time, deenergizes the operating coil of the up relay 36 which cannot open until the latching device 59 has been actuated. The

closing of the limit switch 41, which starts the skip in a downward direction, energizes the actuating coil 63 of the locking device 59 through a circuit extending from the energized conductor 48, through push-button switch 38, conductor 54, switch 51, conductor 55, resistor 116, coil 63, conductors 117 and 118, limit switch 41, conductors 58, 76, 52 and 53, to the line conductor 15. An energizing circuit for the down relay 37 is also established to extend from the energized conductor 118, through conductor 119, operating coil of the relay 37, to the energized conductor 55.

As described hereinbefore, the relay 7 0 was in its closed position when the starting push-button switch was actuated. However, upon the closure of the reversing switch 16 and the line switch 18, the operating coil of the relay 70 was energized through a circuit extending from the line conductor 14, through conductors 48 and 77, contact member 19,

back contact members 27, resistor 89, conductor 98, operating coil of the switch 7 O, conductor 101, line switch 18 and conductor 53, to the line conductor 15. The switch 70 is, therefore, actuated to its open position and, since the contact members 21 of the reversing switch 16 are bridged, the energizing circuit for the reversing switch 16 and the line switch 18 is maintained which would otherwise have been interrupted by the opening of the switch circuit for the reversing switch 17 whic It will be readily understood that, so lon as the motor is energized, the switch 70 wifi be maintained in its open position and, since its initial closure is necessary in order to establish an energizing circuit for either of the reversing switches 16 and 17, the ener izing connects the motor 10 to operate in a direction to lower the skip cannot be established until the time-delay switch 70 closes after it has been deenergized by the opening of the re- .versing switch 16. Since the dash pot 115 may be regulated to give any desired time element, the final establishment of the energizing circuit for the down reversin switch 17 and line switch 18 may be delaye to provide sufiicient time for unloading the skip.

With the down relay 37 in the closed position and securel locked b the locking mechanism 64, the clbsure of t e time-delay relay 7 0 establishes an energizing circuit for the reversing switch 17 and the line switch 18 which may be traced from the 'line conductor 15, through conductors 53, 52 and 76, limit switch 42, conductor 120, operating coil of the switch 17, contact members of the down relay 37, the back contact members 23 of the switch 16, contact members of the time-delay switch 70, conductors 69 and 68, the operating coil of the line switch 18, conductors 67 and 49, switch 51, conductor 54 and push-button switch 38, to the energized conductor 48.

Since the skip stands in its uppermost position, the limit switch 44 is open and, consequently, the transfer switch 95 is in the down position, bridging contact members 96 and thereby establlshlng an operating circuit for the slow-down switch 97 which, as described hereinbefore, connects the slow-down resistor 94 in shunt relation to the armature 11. After a predetermined movement of the skip downwardly, limit switch 44 closes to energize the operating coil of the transfer switch 95, which, upon its operation, initiates the acceleration of the motor, as described hereinbefore in detail.

It will be readily understood that the skip continues to move in the downward direction until it reaches its lowermost position, in which event, the limit switches 41 and 42,

which are now closed, are actuated to their open positions, and the limit switches 40 and 43, which are now open, areactuated to their closed atione the skip and the starting of it in the upward direction again, which movement is initiated only upon the operation of the time-delay relay 70.

As has been pointed out hereinbefore, a dominant feature of this control system is positions, and their simultaneous operects the slowing down and stoppingof the provision of means for maintaining the initially established control circuits to insure that the initially closed switches,wh1ch power failure, will in response to the may be opened because of automatically be closed return of the power. It will be apparent that this important function is performed by the utilizat1on of the up relay 36 and down rela 37, the operation of which, in connection wit the directional controlling switches, has been described in detail in the preceding paragraphs.

Since certain changes may be made in the above construction, and difierent embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the 'aboYe description and shown in the accompanying drawing shall be interpreted as illustrative and not 1n a limiting sense.

I claim as my invention:

1. In a control system for hoists,-.in combination, a hoist motor, electro-magneticallyoperated switches for establishing motor circuits to operate the motor in either direction, limit switches for reversing the motor, and means for locking the electro-magneticallyoperated switches, said locking means being disposed to be operated only 1n response to the operation of a limit switch.

2. In a control system, in combination, an

magnetic switches for establishing circuits to operate the motor in either direction, a plurality of limit switches and auxiliary switches provided with electrically-controlled latching devices for controlling the operation of the electromagnetic-motor-circuit switches, and other limit switches for effecting the operation of the auxiliary switches and their respective latching devices to insure the reestablishing of a selected motor circuit in case the motor is stopped before a reversing limit switch is operated.

4. In a motor-control system, in combination, a motor for operating a skip hoist, reversing switches for the motor, limit switches disposed to be operated in accordance with the movements of the skip for controlling the operation of said reversing switches, auxiliary switches disposed to co-operate in the control of the reversing switches, electrically-cont'rolled locking-means for said auxili ary switches, and means for controlling the locking means in accordance with the position of the skip, thereby to maintain the proper auxiliary switch eflective, regardless of power failure until the skip is actuated to predetermined positions.

5. In a motor-control system, in combination, a motor for actuating a skip hoist, a source of power, reversing switches and a line switch for connecting the motor to the power source, circuits for controlling said switches, limit switches disposed to be actuated in accordance with the position of the skip for controlling the switch-actuating circuits, a directional-controlling switch for each switch-actuating circuit, spring-biased-locking devices for each directional-controlling switch, said devices being provided with releasin coils, and limit switches for controllin e energization of said directional-contro lin switches and the releasing coils of the loc ing devices, thereby to prevent the release of either locking device until its res ective limit switch has been actuated by the movement of the skip to predetermined positions.

6. In a control system for a skip hoist in combination, a motor for actuating a skip hoist, a source of power for the motor, reversing switches for connecting the motor to the power source, manual control means for stopping and starting the motor when the skip is in any position, limit switches for controlling the operation of the reversing switches, a directional switch cooperative with each limit switch for further controlling the operation of the reversing switches, spring-biased latching means disposed to hold the directional switches in the closed position, said latching means being provided with releasing coils, and other limit switches for controlling the operation of the directional switches and the latching means, said other limit switches being disposed to alternatel close and release the directional switc es at the end of the skip travel in either direction.

7. In a control system for hoist motors, in combination, a motor for actuating a skip hoist, a source of power, reversing switches for connecting the motor to the power source, starting and slow-down resistors for the motor, bridging switches for the starting resistor, a switch disposed to connect the slowdown resistor across the motor armature, a

terrufited prior to the operation of any limit switc 8. In a control s stem for hoists, in combination, a motor or actuating the hoist, a source of power for the motor, reversing switches for connecting the motor to the power source to cause the hoist to be actuated in upward and downward directions, a plurality of limit switches disposed to be operated b the movements of the hoist certain of sai limit switches being disposed to control the operation of the reversing switches, and means res onsive only to other of said limit switches lsposed to coo crate with said first limit switches in control ing the reversing switches, said means being effective to cause the initially-operated reversing switch to reclose in the event that the motor has been disconnected from the power source before the hoist has completed its travel in either direction.

9. In a control system for hoists, in combination, a hoist motor, reversing switches for establishing motor circuits to operate the motor in either direction, limit switches for controlling the energization of the reversing switches to eliect a reversal of the motor at the end of the hoist travel in either direction, and means disposed tocooperate with said limit switches in controlling the energization of the reversing switches to insure the reclosure of the initially closed reversing switch in the event that the initially-established energizing circuit for the hoist motor is interrupted before the hoist has completed its downward or upward travel.

In testimony whereof, I have hereunto subscribed my name this first da of May, 1928.

DANIL SANTINI.

transfer switch for controlling said bridging switches and the switchfor connecting the slow-down resistor, limit switches for controlling the operation of the reversing switches, other limit switches for controlling the operation of the transfer switch to alternately disconnect the slow-down resistor and bridge the starting resistor, and means disposed to cooperate with said limit switches for controlling the reversing switches to cause said switches to reestablish a preselected motor circuit if the motor circuit is in-

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