US1299924A

US1299924A - Motor-control system.

Info

Publication number: US1299924A
Application number: US26941719A
Authority: US
Inventors: John Easton
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1919-01-03
Filing date: 1919-01-03
Publication date: 1919-04-08
Anticipated expiration: 1936-04-08

Description

JIEATON.

NlOTQRCONTROL SYSTEM. APPLICATION FILED APR.23, 1915. RENEWED JAN. 3,1919.

1,299,924. Patented Apr. 8,1919.

Iri-Q 7'0 POSITION SHOW Y Inventor": Jo hn Eaton,

His Jitter-Beg.

UNITED STATES i rnrnnr onmon.

JoHn Enron, or scnnnncranv, NEW YORK, AssIGNon no GENERAL nnnc'rnrc comm, a conronn'rron' on NEW max. I

moroa-con'rnon-srsrnm.

Specification of Letters Patent.

Patented Apr. 8, 1919.

Application filed April 23, 1915, Serial No.23,339. Renewed January 3,1919. Serial No. 269,417.

To all whom it may concern: 7

Be it known that I, JOHN Enron, a sub ject of the King of Great Britain, residing at Schenectady, county of Schenectady, State of New York, have invented certain the like and has for its object the provision of means whereby the control of such operation is effected in a reliable and eificient manner. r

My invention relates more specifically to combined hand and automatic control for electric motors for driving planers and the like. In the operation of electrically driven planers, it is frequently desirable to be able to control the planer from positions remote from the master controller or reversing switch, which is actuated by. dogs on the platen of the machine.

Heretofore it has been necessary forithe operator to manipulate the reversing switch in order to get the required small movements or inching necessary in adjustin' the work. To make it possible to operate t e reversing switch from both sides of the ma chine, it is necessary thatan operating shaft for the. reversing switch extend across the machine and the operator is then limited to these two positions on opposite sides of the machine for manipulation. In large planers this is extremely awkward, since the operator may be machining a'large casting which I will be of considerab height,"so as to make it necessary for him in order to see the work, to climb upon the machine. Under these circumstances, when the operator isadjusting the work, he may have to climb up and down a number of times before hegets the work adjusted. In other words, he cannot see the work while he ismanipulating the reversing switch. Another difficulty with this arrangement lies in-the 'fact that the operator has to very carefully consider which way to throw the reversing switch, since if he makes a mistake, it may be very serious. He must also look carefully to the position of the reversing switch before he 1 the control from automatic to manual and vice versa and a switch mechanism plainly marked to indicate the out and return movement. This control may take the form of push buttons, one of which when pressed will cause the motor to travel in the cutting? direction as long as the button is held 1n the closed position, but upon releasing.

the button the machine will stop. Likewise, on pressing the return button the reverse operation will be accomplished. The arran'gement is such that the speed at which the motoroperatesunder the. manual conthe starting resistance in the motor circuit.

With my arrangement the operator, in any position in which it may be necessary for him to be located in orderto inspect the work, may have complete control 'athand. He may stop the motor at anytime under normal operation by simply throwing switch which changes from automatlc to hand operation. 7 He may then start the motor in either direction at a slow 5 eed and continue it as long as desired. Furt ermore the operator need never be concerned about which way the machine will move when he closes' the circuit breaker, since the machine cannot be started under any condition until one of the push buttons .is operated which will fix the direction of operation.

- In one form of my invention, this result is brought about by employing a master conthe troller or reversing switch which is normally biasedto return to a neutral or intermediate position. When the master switch is thrown to either position by the planer dogs, it only remains in that position for an instant and then returns to its normal position. This arrangement is made possi le by having maintainin' circuits for the switches controlled by t e master controller, so that after the switches are .once operated, they will be held in closed position by a circuit closed at contacts in the neutral position or the troller. To my previous application Ser. No. 817,365 filed February 7th, 1914;, T have described and claimed a system in which there is a manual control for planer operating motors in addition to the automatic control. While in general this is satisiactory, it does not give the complete and safe control then quickly climb up again to see that every thing is working satisfactorily. With my present control, he never needs to leave his point of observation nor does he need to be concerned about which way the machine will operate when the'circuitbreaker is closed.

Tn the agcompanying drawing, 1 have shown my invention applied to a planer control system of the general type described in the patent to Murphy and Eaton, #1,0tl,84c5. Tn addition to the features disclosed in the said patent, my present system also discloses additional features which are described and claimed in my previous applications above relierred to. in order, however, that the operation of my system as a whole may be cleanl shall describe it in its entirety and then point out the features of novelty. 4

Referring to the drawing which shows diagrammatically. one embodiment of my invention, A. represents the armature and F the shunt held of an electric motor for driving a planer or the like. The direction of rotation of this motor is controlled by four electromagnetic switches or contactors, two for each direction of rotation. Two oi these switches are designated as C and (3', respectively for driving in the forward or cutting direction, while the other two switches, designated as R and lit respectively, when closed drive the planer in the opposite or return direction. These four switches are operated by shunt windings controlled by a master switch S which is biased to assume the intermediate or neutral position shown in the drawings of the apparatus hereinafter described. In the drawing the parts are shown in the position they assume when the circuit breaker is open and all parts deenergized. When the line is energized by the closing of the circuit breaker CB andthe master controller S is moved so as to engage the finger 10, the windings of the mo em connected so as to close and short circuit the resistance when the counter-electromotive iorce oi the motor rises to a predetermined value. For varying the speed or the motor, I have provided two rheostats, one of which has a resistance T, which is controlled by the arm 13, while the other has a resistance 1" controlled by the arm is. When the motor is started, the switch 12 'is open and both of the resistances 1' and .r are short circuited through the wire 15 and the switch 16, which isspring closed. When the switch 12 closes the switch 16 is-opcned so as to break the short circuit. With the master switch S in engagement with the finger it), that is, in the cutting position, a portion of the resistance r, the amount of which will depend upon the position of the lever 13, will be connected in'the field circuit. When the master switch is moved to the opposite position, the connection to the arm 13 ot the rheostat is broken by the closing of the line contactor it so that through the connection at the arm it all of the resistance r as well as a portion of the resistance r will now be in the field circuit.

In order to bring the motor armature to rest quickly, ll provide a brake resistance through which the motor armature is short circuited. This brake resistance is divided into two sections BR and B'R. pose of these two sections otresistance is to aduate the dynamic braking current as the field builds up and the motor slows down. For making the dynamic braking connections, ll provide the contactor B. This contactor is normally held closed by a spring 17. The winding of this contactor is connected across the armature of the motor so that while the motor is operating the winding tends to close the switch. T have likewise provided a series winding 18 which is not energized until the contactor is closed. The five contactors R, R, G, C and B being arranged as shown in the drawings are provided with tour mechanical interlocks, 19, 20, 21, and 22, cotiperating with the contactors so as to compel operation in a predetermined manner. The structure of these interlocks forms no part of my invention, but for purposes of illustration, T have shown them pivoted at their middle points and engaged by upwardly projecting stems of two adjacent contactors in the The pur- I out further description. While the contactor B is closed by' a spring, this spring is not sufliciently'stifi', to. apply any considerable pressure to the contacts, since electromagnetic means are'provided for holding the contacts tightly closed.

The line contactors are provided with means for preventing their closure except when the field of the motor is of a predetermined strength. This means consists of resistances 23 and 24 interlocked as hereinafter described with the contactor which controls the brake resistance BR. Electromagnetic switch or relay 25 is provided with a winding having one terminal connected with the shunt field F while the other end is connected with the resistance r. The winding of this relay is divided into two halves which are differential or oppose each other, so that when the two halves are energized they neutralize each other and the relay will not close. It is obvious that when the switch 16 is opened, the field current must pass through the two diiferential portions of the relay winding and through any field resistance-which may be in circuit, to the negative side of the line. The relay is therefore inoperativeunder this condition. When however, the=switch 16 is closed the upper half of the relay winding and the resistance are short-circuited so that one half the winding is energized and the relay becomes active. The winding of this relay is so adjusted that when the field current approaches a maximum, that is when the field is nearly full strength, therelay will close, but when the field is weak, the relay will not close even though only one of the windings isenergized. When the switch 16 closes, the field resistance is short-circuited so as to strengthen the field, but the field increases gradually due to the inductive effect and until the field current rises to the predetermined value, which is preferable near the maximum, the relay 25 will not operate. When it does operate, it short circuits a section of brake resistance BR. This relay 25 is provided with an interlocking contact 26 connected with the resistance 2 k in parallel with the line contactors so that when the -relay 25 closes, the circuit of the resistance 2 1 will be open to permit the line contactors to close.

In order to obtain the same dynamic brak- 55 ing effect when the motor is reversed from high speed as when it is reversed from low speed, I provide means whereby a portion of the braking resistance is short circuited when the motor is dynamically braked from 60 one direction of rotation so that dynamic braking takes place only through a portion of the braking resistance, while when the motor is reversed from the opposite direction of rotation, the braking occurs through 65 the whole braking resistance. For accomhas two windings, one-of which, 28, is con- .closed by the-potential coil alone so that ranged thatwhen the dynamic braking circuit is closed with the motor rotating in the cutting or forward-direction, it will be closed, but will not be closed when the dynamic braking circuit is closed with the motor rotating in the opposite or return direction. To this end the magnetic switch nected across the line, while the other winding, 29, is connected across the motor armature. These two windings are so proportioned that when the .counter-electromotive force of the motor opposes the voltage applied to the winding 28 the switch will remain open, but when the counter-electromotive force is reversed, the relay will close. Furthermore, this relay is arranged to be when the counter-electromotive winding29 is opposing the winding 28, the switch will not close until the counter electromotive force reaches a low value, that is, when the motor speed drops to a proper point.

In order to immediately stop the motor upon the failure of voltage, I provide a circuit breaker CB which is so arranged as to apply an effective dynamic brake to the mo-, tor when the circuit breaker opens. To this end, in the particular form illustrated, I have provided two

contacts

32 and 33 which move into and out of engagement with fixed contacts asthe circuit breaker closes and opens. The contact 33 engages with three contacts, two of which close a dynamicbraking circuit through the motor and a portion of the brake resistance BR while the other is connected with the shunt field. The contact 32 engages with two contacts, one of which is connected with the field terminal while the other is connected with the armature circuit during the dynamic braking. When the circuit breaker is opened the armature circuit is immediately closed through a portion of the resistance BR and the field circuit is closed across the armature in parallel with the section of braking resistance.

As thus far described, the arrangement is the same as that disclosed in my patent application above referred to. I will now de scribe my improvements whereby the manual control is effected. As before stated the master controller or reversing switch S is biased to the neutralposition shownin the drawing so that it returns to this neutral position as soon as the platen of the planer starts to return. The line contactors for thecutting direction C and-C are energized at the contact 10 and the contactors for the return direct-ion R and R" are energized at the contact 11. In order to hold the contactors closed when the reversing switch returns to this neutral position, I have provided holding circuits which are madethrough the reversing switch in this neutral position. The holding circuit for the contactors C and C is made at contact when the contact is raised, the relay will open and insert the starting resistance l into the motor armature circuita its upper-position contact 40 makes the manual control circuit through manual controlled switches 42 and 43. These switches are shown as normally open, switches or pushhuttons, those marked 42 being causing operation in the cutting direction while those marked 43 cause the motor to operate in the return direction The circuit through'the push huttons i2 is through the interlock 37 on reversing contactor lit, and the circuit through push huttons is through the interlock 35 on oontactor CC This makes it necessary that the reversing contactor for one direction. of rotation should he closed. A switch mechanism composed of two switches and 45 is provided for changing from automatic to manual con trol. T have shown this switch mechanism as composed of two switches so that the change may be made from either of two positions althougholbviously this arrangement is not an essential part of my invention. The arrangement is such that the operation of either one of the switches will stop the motor and throw the control from hand to automatic and vice versa. The operation of either switchmay undo what has been accomplished by the operation of the other switch. One switch is intended to he on each side of. the planer so that if for instance the manual control is thrown in by operating a switch on one side of the planer,

the manual control can be thrown out and the automatic thrownin by operating the switch on the opposite side of the planer. Or one switch may be located at the master controller and the other be a pendant switch convenient to the operator from the upper part of the machine. The return circuit through the line contactors is through the sw'tches 44 and 45 both actuating and holdi g circuits returning through these switchesto the negative side of the line.

As thus constructed and arranged, the mode of operation of my system is as follows: Assuming switches 4d and 45 in the incense position shown in full lines in the drawing and assuming that the reversing switch or controller S has been moved by the dog on the planer into engagement with contact 10, contactors C and C will he energized from the positive side or the line through resistance 23, thence through the windings oi contactors C and C in parallel, through the interlock 37 on contactor lit to the contact 10 on the master. controlleigthence through contact to back to the negative side of the line through the switches re and 4:5. liesistance 2d is in a parallel circuit with the contactors C and C and resistance 23 the circuit through this resistance 24 extending through the interlock 26 and back to the negative side of the line through wire 4:7. These resistances arevso adjusted that the contactors C and C will not close until the parallel circuit through the resistance 24 is open. The field circuit is made from the positive side or the line through the wire.

48, wire 4 through the field winding and the lower winding of? the relay 25 wire 15 and switch 16 to the negative side of the line. The relay :25 will therefore close hut not until the iield has hecome energized at substantially full strength. The closing of the main contacts or the relay 25 has no effect hut the opening of the interlock 25 opens the circuit of the parallel resistance 24 and causes contactors G and G to close. line contactors therefore do not close until the field has reached substantially full strength. Te relay 2'? will also close since its lower winding 28 is connected across the line and the winding 29 which has a minute"- lelectromotive force coil gradually becomes energized in a direction to assist winding 28. Contactors C and C as well as relay '25 and relay 3? are now. closed and the arma- The ture circuit of the motor is therefore closed through the contacts of contactors C and C and resistance 5D. The motor willnow start in the cutting direction and as the armature speeds up contactor 12 will close and short circuit the resistance D of the armature circuit. The closing or this contactor 12 causes a portion of the resistance.

r to be inserted in the field circuit of'the motor, the-field -circuit now being through the two windings of relay-25, This causes the motor to speed up due to the insertion tactor B thereupon closes thereby closing the dynamic brake clrcuit through the motor and the brake resistance BR, causing the contactor 27 to close by reason of thefact of the resistance r in the field circuit and I that the counter electromotive force of the stopping the motor in case it should be run motor is "in a directionto amist the winding 28 which is across the line. As the field there y short. circuiting the brake resist .ance BR and bringing the motor to rest quickly. Upon the closing of relay 25 the circuit of the resistance 24 is opened at the interlock 26 so that the contactors Rand It may close. These contactors can only close therefore Whenthe motor is brought substantially to rest-for. the additional reason that the contactor'It' cannot close until the brake contactor is opened. The motor now starts on'its return stroke, the operation being the same as beforeexcept that the motor is brought up to a higher speed by reason of the fact that the resistancer. and a portion of the resistance 4- depending upon the position of the lever 14'will be inserted in the field circuit. of the motor uponthe closing of relay 12. Likewise when the end of the stroke is reached, the operation will be as before but in this case all of the brake resistance :BR and BR will initially be included in the dynamic'brake circuit. This will be the normal mode of operation under automatic conditions.

If now it is decided to'operatemanually, thismay be done by throwing either one of the switches 44 or 45 to' its opposite position. This will have the effect of immediately ning' and causing the relay 38 to operate. When the relay 38 closes it completes a hold- .ing' circuit for self, from the positive side of the line through the winding of the relay,

contact 39, segment 41 onthe master controller S and back to thenegative side of theline. The operation of the relay 38 also denergizes the relay 12 and inserts the starting resistance in the armature circuit. Thisis done by the lifting of contact 40 out of engagement with its lower contacts. When the contact 40 engages its upper contacts, "a. circuit is completed through the push buttons '42 and 43, this circuit being motor for operatin through wire 50, contacts 40, 39,- and switches '44 and 45. By the operation of one of the switches 44 or 45, the motor has been stopped. If new one of the push buttons as for instance the cutting push button 42 is pressed, the contactors C and C will be closed, the circuit now passing from the interlock 37 through the push button 42 and wire 50 to the contacts 39 and 40 on the rela 38 in this upper position and throu'g switches 44 and 45. There is also a circuit from contact 39 through the segment 41 on the master switch to the negative side of the line. The motor will therefore start in the cutting direction. By opening and closing the push button 42', the motor may be stopped and'started at will. The'motor willing in the wrong direction.

ditions since. both sections of brake resistance are short-circuited- In fact it will stop instantly, this being what is wanted on manual control. When-the end of the stroke is reached, the master switch will be operthe return circuit of the contactors C and-(Y will still be made at the switch 44 and 45. Likewise upon pressing one of the push buttons 43, the motor may start inthe opposite direction and continue at will. :If now it is" .70 ated but the motor-will'not be-stopped since decided to return to automatic, one, of the switches 44 or 45 is operated.

tion should start in a return direction, one of the push, buttons 43 is pressed. This Supposing that it is desired that the automatic operacauses contactors R and R to close and make a maintaining circu'it for themselves as previously described. The operation will now continue independently of the push button butat slow speed because the relay 12 is open'and resistance D in the motor 'cir--' buit. When the end of the stroke is reached,

the relay 38 will bedenergized at the seg-- ment 41, the relay 12 will close and the automatic operation will continue in its normal way- With'this arrangement upon chang- I ing toautomatic the operator can fix the direction which he shall go, without refer ence to the master controller. Furthermore when he closes his circuitbreaker, the motor will n'ot start until one of the push buttons is pressedso thatthere, is no danger Ofstart will suggest themselves to those skilled in the art without departingfrom the spirit.

of my invention. the? scope'of which is set forth in the annexed claims.

What I claima's new and desire to secure by Letters Patent of the United States, is

1. In combination, a reversible electric planer, manually operated switches for controlling the motor for either direction of r0- tation and means independent of the relny. invention as a planer or the like, a reversing switch or the motor automatically. operated at the limits of travel of the' versin switch for changing from manual contro to automatic control in either direction of rotation as-desired. 2. In combinatlon, a reversible electrlc motor for operating a planer or the like, a reversing switch 'for the motor automatically operated .at the limits of-travel of the planer, manually operated switches for con,-

trolling the motor in either direction of rotation and connections whereby the direction in which the motor starts under automatic control is controlled by the manual switches.

3. In combination, 'a' reversible electric motor for operating a planer or the like a reversing switch for the motor automatically operated at the limits of travel of the planer, manually operated switches for controlling the motor for either direction of rotation, a switch for changing from manual to automatic control and connections whereby the direction in which the motor starts when the control is changed to automatic is controlled by the manual switches.

4. In combination, a reversible electric motor for operatinoa planer or the like, a reversing switch for the motor automatically operated at the limits of travel of the planer and biased to an intermediate position during the main portion of the travel, manually operated switches for controlling the motor for either direction of rotation and a switch in circuit with the reversing switch in its neutral position for changing from manual to automatic control.

5. In combination, a reversible electric motor for operati a planer or the like, a reversing switch l dr the motor automatically operated at the limits of travel of the planer and biased to an intermediate position'which it occupies during the main portion of the travel and manually operated switches for controlling the motor for either direction of rotation and starting the motor in either direction for automatic control with the reversing switch in its neutral position.

6. In combination, a reversible electric motor for operating aplaner or the like, a reversing switch for the motor automatically operated at the limits of travel of the planer and biased to a neutral position which it occupies during the main portion of the travel, electromagnetic switches for controlling the direction of rotation of the motor having actuating and maintaining circuits made res ective in the operated and neutral posi-- tlons of the reversing switch and manually operated means for controlling the motor in elther direction of rotation and starting the motor in either direction for automatic control with the reversing switch in the-neutralposition.

7. In combination, a reversible electric motor for operating a planer or the like a reversing'switch for the motor automatically operated at the limits of travel of the planer and biased to. an intermediate position durmg the main portion of the travel, electro:

magnetic switchesfor controlling the direcmotor for operating a planer or the like, a

reversing switch automatically operated at the limits of travel of the planer magnetic switches for controlling the direction of rotation of the motor controlled by the reversin switch and having actuating and maintaining circuits, manually operated switches for controlling the actuating.

circuits of Said electromagnetic switches, a switch for changing over from manual to automatic control and connections whereby a holding circuit for said electromagnetic switches is made through the reversing switch when the said changeover switch is in position for automatic operation.

9. In combination, a reversible electric motor for operating a planer or the like, a reversing switch automatically operated at the limits of travel of the planer and biased to an intermediate position during the main portion of the travel, electromagnetic switches for controlling the direction of rotation of the motor having actuating circuits made when the reversing switch is operated and maintaining circuits made in. the intermediate position of the reversing switch, manually operated switches for controlling the 'actuating circuit of the electromagnetic switches a relay controlling the circuit through the manual switches and a change over switch having connections for completing the maintaining circuit of the electromagnetic switch in one position and energizing the relay in another position.

In witness whereof, I have hereunto set my hand this 22nd day of April, 1915.

JOHN EATON.

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