US1792287A - Control system - Google Patents

Description

D. W. DEAN CONTROL SYSTEM Feb, 10, 1931.

Filed Sept. 30, 1927 INVENTOR Dale W Deon ATTORNEY Patented Feb. 10, 1931 PATENT oFricE DALE w. DEAN, ,or WILKINSBURG, PENNSYLVANIA, ASSIGNOR 'ro WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA CONTROL srs'rfsm Application filed September so, 1927." serial No. 222,965.

My invention relates generally to systems of control and particularly to control systems for rolling mills and the like.

The object of my invention, generally stated is'to provide a control system which shall be simple and elficient in operation and readily and economically manufactured and installed, and further to provide means for rendering the s ed adjustment of the component parts-of a rolling mill equipment more need automatic than tofore been possible,

A more specific object of my invention is toprovide for maintaining a definite speed relation between the reducing rolls and the roll tables, throughout a comparatively wide range of. operation.

7 Another object of myvinvention is to provide for automatically changing the speed of the roll tables concurrently with the change in s eed of-the reduci n rolls, as the speed of t e reducing rolls 1s varied,rto maintain certain operating schedules and to accommodate thevvariousshapes and thicknesses of metal which isbeing worked.

Other objects of my invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawing, in which, 4 i

The single figure'is a diagrammatic view of a rolling mill provided with the usual driving motors and control system, arranged for operation in accordance with the pres ent invention.

Referring now to the drawing, the structure shown comprises a rolling. mill 5- provided with reducing -rolls8 and feed rolls 9, in accordance with the usual-practice;

In order to drive the reducing rolls 8. a motor 12, having a separately excited field winding 13, is provided, As is usual practice, the speed of the reducing-roll motor 12 may be varied by the manipulation of a manually operated rheostat 14 which is has hereshownconnected in series relation to the field winding 13. The reducing-roll motor 12 is shown connected to a supply source 1.3 and it may be controlled in any manner well known in the art.

In accordance with the usual practice the feed rolls 9 are actuated from a driven shaft 16 whichis disposed to extend longitudinally to the roll tableand provided with a plurality of beveled gear wheels which, as'

shown, mesh with beveled gear wheels mounted onthe table'roller shafts.

The shaft 16 may be driven in any -suitable manner and, in this particular instance,

a separately excited motor 17 is'provided which actuates the shaft 16 by means of the gear train-18.

' To control the operation of the motor 17, a controller 19 is provided which is interposed between the motor and" a source of I power-supply, here shown as line'conductors 20 and 21. a 1

The field winding 22 of-the'auxiliary mo.- torl7 is energized from an'exciter 23 which is mechanically connected to a motor 24 by means of the shaft 25. A variableresistor 26. is connected in circuit with the field winding 22lfor the purpose of partly-controlling the energizingeurrent which is further conthe excite! 23.

The m0t0r'24 is controlled, in'a' well known manner, by-means of a start=:push-button switch 27 and afstop push-button switch 28, which, upon operation. establish or interrupt the operating circuit for a plurality of line switches 31 and 32 having contact members 33 to 36,:i-nclusive.

lnzorder to prevent the motor 24 from belDQHCHllP-(Kftfill'lO the line, unlessthe shunt field winding 37 is sufficiently energized to prevent excessive speeds, a relay 38 is provided. The relay 38 hasa movable armature member 39 which is biased to the illustrated position by the coil spring 41 and isdisposed to be actuated by an operating coil 42 which is energizeilfrom the shunt-field circuit of the motor 24.

The contact members 43 of the relay 38 are adapted to interrupt the-push-button-control circuit in case the field circuit of the motor 24 becomes (lo-energized and thus to pre\ mt the-establishment of an operating circuit f r the line switches 3i and 32 unless the lil winding 37 is properly energized;

A sectional starting resistor 40, which trolled bv varving the generated voltageof connected in serieswith the armature of the motor 24, is controlled by electromagnetic switches 44 and 45. V The switches-44 and 45 are respectivelyprovided with actuating coils 46 and 47'W'hich are adapted'to be energized successively upon the operation of' thelin'e switch 31. e

To provide "for controlling-the excitation of the'field winding -48 of the exciter 28, a motor-actuated rheostat 49 is utilized. The rheostat =49 comprises a resistor 5-1 and a"rotatable arm 52 which isadaptedto'ex'clude very small sections ofthe 'resistor 51...fmm the energizing circuit of t'hefield windingf4 3 for a purpose which will be'set forth -more in detail hereinafter.

The rotatable-arm-52 is actu-ated-bymeans of a pilot motor-53 'connec'ted thereto through a worm and worm-wheeldrive 54. 'Ihe series field winding of -the pilot motor 53-is -c'omposed of twosections '5-5 and 56 whither-e connected in-series' relation-and-adapted to be alternately energized to effect the rotation of the pilot motor in either direction.

In order to control-the direction of rotation of the pilot-motor 53, electromagnetic switches 57 and 58'are provided which may be utilized to reversethe line connections to the motor in a well known manner. Each of'the switches 57 and 58 is connected in circuit/with a section of the field winding andonebf-a pair of limit switches 59 and 61 which are disposed to be operatedby the rotatable ar-m 52 as it approaches the end of its travel i-neither aclockwise or counter-clockwise direction.

The control of the motor-operatedrheostat 49 may be effected manually o'r-automatically to control the generated voltage of th'e e'x citer 23 and thereby the speed of the roll-table motor 17.

For manual control, push-button -switches 62 and 63, each having "a pair of closed and a pair of o n'contact members, are rovided to establis operating circuits fort e pilotmotor- control switches 57 and 5 8,'in a'manner which will be described in detail hereinafter.

The upper contact members of each of the ush-button switches 62 and 63 are normally Eridged by the movable elements and are connected in series relation, as shown. The bridged contact members are also connected in circuit with a voltage relay 68.

The volta e relay 68 has a movablemember 69 biase toward theillustrated position by a suitable coil spring 71 anddisposed to be actuated by' the operating coil-73 toefiect the engagement of contact members 72.

The operatin coil 73 is connectedin shunt relation to the field winding 13 of the reducing-roll motor 12 and is, therefore, responsive to the voltage impressed upon the field winding 13. The contacts of relay 68 are connected in the circuit which controls the operation of the motor-operated rheostat-4'9,=-but tables.

since the operating-coil 13 isconnected as just stated, it is evident that the operating coil 73 must be energized and thusthe contact In the rolling of di'fi'erent-shapesand thick- 'nesses"of metal, it is necessary to frequently change the speed of the reducing rolls to obtain the proper rate of reduction and to maintain certain operating-schedules.

As the speed of the red'ucin rolls is changed, inany suitable manner, it is desirable to also change the speed of the roll tablesto conform closelyto the speed ofthe reducing rolls in order to prevent strains being imparted to the metal as it passes through the reducing rolls.

Heretofore, the practice has been toeiiect the change in speed of both thereducing rolls and the rolltables by manual means. It will be readily understood that, when manual means for synchronizing speeds is'resorted to, a great deal of timeis expended in adjusting the speeds of the two se )arately driven parts of the mill, and that t o utilization of speecl-indicating instrumentsand the like is necessary. Therefore,to 'automatically effect a change in s eed of the roll-table motors, concurrently-with a change in speed of the reducing-roll motorg'a fluttering-type relay 74 is interposed between the separately excited fieldwinding 13 of the reducing-roll motor 12 and the-exciter 23.

The relay 74, in the'simple form which is utilized to illustrate the invention, iscomposed of a movable element 75 responsive to actuating coils 76 and 77 oppositely disposed to effect the movement of the movable member 75 either to-the right or to the left, as shown.

The operating coil 76 of the relay 74 is connected across the armature of the exciter 23 and is, therefore, responsive to the generated voltage of the excit'er'23, which is impressed upon the field winding 22 of the roll-table or'auxiliary motor 17 and, consequently, operating coi 77 is responsive to the operating speed of motor 17, in a wellknown manner.

The operating coil 77 of the oppositely disposed portion of relay 74 is connected in shunt relation to the separately excited shunt field winding 13 of the reducing-roll motor 12 and is, therefore, responsive to the voltage impressed on the field winding 13 and, subsequently, to the speed of the motor-12.

The movable member 75 is dis osed to engage fixed contact fingers 78 an 79, as it is sand the roll' actuated to the right or left-hand ositions by the actuating coils 76 and 77, as escribed hereinbefore.

The fixed contact fingers 78 and 79 are, therefore, utilized for establishin an o erating circuit to effect the operation of the motor-operated rheostat 49 to vary the generated voltage of the .exciter 23.

It will be observed that a variable resistor 82 is in circuit with .the operating coil 77 of the relay 74 and is, therefore, utilized for controlling the current flowing therein in the event that the normal voltage impressed upon the field winding 13 is eater than the voltage generated by the exciter 23 when the reducin rolls 8 and table rolls 9 are rotatin at t e same speed.

he operation of the rolling mill in accordance with the invention, will now be set forth.

In order to set the exciter 23 in operation, the start push-button switch 27 is closed to establish an operatin circuit for the line switches 31 and 32 w ich extends from the positive conductor 21, through conductors 83 and 84, contact members 43 of the relay 38, conductor 85, the operating coils of switches 32 and 31, .conductors 86 and 87, push- button switches 27 and 28 and conductor 88, to the negative line conductor 20. In this instance, it will be assumed that the relay 38 is sufliciently energized from the shunt field circuit of the motor 24 to cause the contact members 43 to engage and thus complete the push-button control circuit. The operating circuit of the relay 38 extends from the ne ative conductor 20, through conductor 89, fie d winding 37 of the motor 24, conductor 91, operating coil 42 of the relay 38 and Couductors 84 and 83, to the positive line conductor 21.

In case the relay circuit is not properly established, the contact members 43 of relay 38 will remain in their open positions and it is impossible to establish the o crating circuit for the line switches 31 an 32.

Upon the closure of the line switches 31 and 32, a holding circuit for them is established which may be traced from the negative line conductor 20, through conductor 88 and push-button 28, conductors 92, closed contact members 36, conductors 93 and 86, the operating coils of the line switches 31 and 32, conductor 85, contact members 43 or the relay 38 and conductors 84 and 83 to the positive line conductor 21. This permits the start push-button 27 to be released by the operator and maintains the line switches 31 and 32 in their closed positions.

' The energizing circuit for the motor 24 extends from the positive line conductor 21, through conductor 118 and 83 to contact members of the line switch 32, conductors 94, 95 and 96, the armature of the motor 24, conductors 97 and 98, resistor 40, conductor 99, contact members 33 of the line switch 31 and conductor 101, to the negative line conductor 20.

The contact members 34 of the line switch 31, when in the closed osition, establish an operating circuit for t e resistor-short-circuiting contactor 44 which extends from the energized conductor '98, through the contact mem ers 34, conductor 102, operating coil 46 of the contactor 44, to the energized conductor 95. The lower contact members of the contactor 44 are bridged, thereby short-circuitin the portion of the resistor which accel erates the motor 24 a predetermined degree.

The upper and lower contact members of the contactor 44 are bridged at the same time, thereby establishing an operating circuit for the second resistor-short-circuiting contactor 45, which extends from the energized conductor 97, through conductor 103, upper contact members of the contactor 44, operating coil 47 and conductor 95 to the energized conductor 96. Upon the closure of the contactor 45, the second portion of the resistor 40, is short-circuited, which allows the motor 24 to accelerate to full speed.

Assuming now that the movable arm 52 of the motor-operated rheostat 49 is in the position illustrated, it establishes the proper circuit for energizing the field winding 48 of the exciter 23, which extends from the posi tive line conductor 21, through conductor 104, a portion of the resistor 61, conductor 105, field winding 48, conductors 106 and 101, to the negative line conductor 20.

Therefore, the proper voltage is built up in the exciter armature for energizing the field winding 22 on the auxiliary motor 17 by means of the circuit extending from the positive armature terminal of the exciter 23, through conductor 107, field winding 22, resistor 26 and conductor 108, to the negative armature terminal of the exciter 23. The roll table may now be put in operation by starting the motor 17 by means of the startor 19.

For the purpose of explanation, it will be assumed that the reducing-roll motor is completely deenergized and, therefore, the operating coil 77 is also deenergized and has no effect upon the movable member 75 of the relay 74.

As set forth hereinbefore, the operating coil 76 of the relay 74 is connected directly across the armature of the exciter 23. which generates sufiicient voltage to energize the coil 76 which actuates the movable member 75 of the relay 74 to the left and establishes an operating circuit for the pilot-motor line switch 58. However, it will be observed that the contact members 72 of the relay 68, which are in the operating circuit of the line switch 57, are not in engagement and, therefore, it is impossible to complete the energizing circuit for the pilot motor 53 until the field 13 of the reducing-roll motor 12 and, consequently, the coils 73 and 77 havebeenenergized. The simultaneous energization ofboth the coils 73 and 77 insures that the proper de tee of opposition. .to the coil 76 will be-esta lished to prevent the pilot-motor-operating circuit, which was esta lishedwhen the coil 7 6 was energized, from remaining; closed long enough to effect the maximum. travel of the rotatable arm 52 oithe rheostat 49.

Since. in order toisimplify the drawing, the controlmeans for the reducing roll motor 12 is not shown, itwill be assumed that itis operated tostart the v, notor312, after the'energizing circuit forthefield winding13has been established by the closure of the switch 80. The energizing circu it for the field windingf 13 exten s from, the positive line conductor 21, through ,conductor 109,-switch 80, variable resistor- 14, conductor 1'11, field winding 13,. conductors 112, 113 and 123, to negativeline conductor 20.

w eathefi ld motor 12 'becomes ,energized, the operating coil '77 of the relay-74 is ,also energized through acircuit eatending from the energize'd, conductor 113, conductor 114,:variable resistorj82, theoperating coil 77 and-conductor 115 ,tothe energized conductor 111.

' The, coils 76'and77of the relay 74 are, in this instance,energi zcd to a degree depending upon'the relative valuesof voltage which is being generated by the .exciter 23 and that which is being impressed upon-the field winding13. A t

In order to clearly explain the operation of the relay 74, it will first. be assumed that the voltage impressed upon ,coil 77 is slightly greater than that generated by the exciter 23. Insuch event, the movable armature member 75 of therelay- 74 is actuated to the right, into engagementwithi-the fixed contact member 79. Ari-operating circuit is established for the pilot-moton-line-switch 58, which extends from the positive conductor 21 through conductor 118, push-button switches 62 and 63, 'conductor 119, relav 68,

contact member 79, conductors 121 and 122, the operating coil of the line switch 58 and conductor 123 to'the negativeline conductor 20. 4

Upon the closing ofthe'pilot-motor line switch 58, an energizing circuit for the pilot motor 53 is established which extends from the positive conductor 21, through conductor 104, the armature of thepilot motor 53, field winding 55, limit switch 59, conductor 60, switch 58, conductor 123, to the negative line conductor 20. 4

The energizing circuit thus established causes the pilot motor 53 to operate in a direction to actuate the rotatable arm 52 counter-clockwise, thus decreasing the amount of the resistor 51 which is connected in series circuitoi the reducing-rolla :It will be-readily understood that,so loug as the "oltage impressed upon the operating" ;coil 7 7 "is sufiicient to maintain themovable contact member 75 in engagement \vith'the fixed contact member 79, the operating circuit for the pilot motor 53 will be maintained.

The generated voltage of the exciter 23 -will, therefore, gradually increase, as herein before set forth, until such time as the .pull 2! the (20117621111815 thatof the electromagnet l.f=.=II1 this event, a state of'equilibriuin will exist, and the movable contact member wi ll,:consequentl y, return to the midposition and interrupt'th-e operating circuit for the pilot r'notor line switch 58.

Atthis point in the cycle of operation, the

:rotata'ble arm 52 or the motor-operated rheostat 49v is'sto'pped' in'some such position'as shown, and thena'n appreciable portion of the resistor 51 will have been gradually removed from-the field 'circuit of the'excit'er 23.

It will now be noted' that't-he' voltage impressed upon the field winding 22 of the auxiliary or roll-table motor 17 has been increased and, consequently, a reduction in speed of the motor 17 is obtained which causes the feed rolls 9 to nevolvc' at approximately the same I speed as that ofthe reducing rolls 8.' Let-it be further assumed that the operator desires to increase the speed of the reducingrollmotor-12 which may-be accomplished by manipulating the variable resistor 14 to reduce the voltage impressed upon the field wniding-l3.

- In such event, the current flowihg in the operating coil of the coil 77 will'be reduced to a value lower than the current. flowing in the operating coil 76 and the movable member 75 will beactuated to the left into engagement with the fixed contact finger 78. The operation of the-member 75 establishes an operating circuit for the pilot-motor line switch 57, which extends from the positive conductor 21, through conductor 118, pushbutton switches 62 and 63, conductor 119, contact member 72 0f the relay 68, the fixed con-. tact member 78, conductors 120 and 124, the operating coil of the line switch 57 and conductor-123, to the negative line conductor 20;

Upon the closure of the line switch 57, an energizing-circuit for the pilot motor 53 is established which extends from the positive conductor 21, through conductor 104, the armature of the pilot-motor 53, field winding 56, conductor 125, limit switch 61, line switch 57 and conductor 123, to the negative line conductor 20. It will be noted that. in this case, the second portion of the series field Winding 56 of the pilot-motor 53 was included in the motor circuit and that it was energized in such direction as to cause the reverse operation of the pilot motor 53, thereby actuating the rotative arm 52 clockwise to gradually increase the amount of the resistor 51 contained in the field circuit of the exciter 23.

It can be readily understood that the exciler voltage will be decreased to a point where the voltage impressed upon the coil 76 will equal that which is impressed upon the opposing coil 77, and, consequently, a state of equilibrium will again be obtained, and the pilot-motor circuit be deenergized in the manner described hereinbefore.

As the voltage generated by the exciter 23 is gradually decreased, the voltage impressed upon the field winding 22 of the auxiliary motor 17 is decreased, and consequently, the speed of the auxiliary motor 17 is increased to raise the speed of the table rollers 9 to that of the increased reducing roll speed.

As mentioned hereinbefore, the motoroperated rheostat, operating in con unct1on with the relay 74. may be controlled manually by means of the push-button switches 62 and 63.

In the event that the operator wishes to increase or reduce the speed of the auxiliary motor 17 for any reason, this may be accomplished by depressing the fast push-button 62 or the slow push-button 63.

In order to clearly illustrate the facility with which this control system may be adapted for either automatic or manual speed regulation between the reducing-roll motor 12 and the auxiliary or roll-table motor 17, it will be assumed that if the operator wishes to decrease the speed of the table rolls 9 below that of the reducing rolls 8, he will proceed in the following manner.

The push-button switch 63 is depressed, which bridges the lower contact members and establishes an operating circuit for the pilot motor line switch 58, extending from the positive line conductor 21, through conductor 118, lower contact members of the push-button switch 63, conductor 122, operating coil of the switch 58 and conductor 123, to the negative line conductor 20.

Upon the closure of the switch 58, an energizing circuit for the pilot-motor 53 is established in exactly the same manner described hereinbefore and, the rotatable arm 52 is revolved counter-clockwise to increase the generated voltage of the exciter 23 and, consequently, to decrease the speed of the auxiliary motor 17.

Since certain changes may be made in the above described system and different embodiments of the invention may be made without departing from the scope thereof, it is intended that all the matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a control system for rolling mills rovided with reducing rolls and roll tables,

in combination, a motor for actuating the reducing rolls, an auxiliary motor for actuating the roll tables, means for varying the excitation of the motor driving the reducing rolls to vary the speed of the reducing rolls, and means responsive to changes in excitation of said reducing-roll driving motor to vary the speed of the auxiliary motor, to prevent the application of undesirable strains to tlhe metal as it passes through the rolling mil 2. In a control system for rolling mills provided with reducing rolls and roll tables, in combination, a motor for actuating the reducing-rolls, an auxiliary motor for actuating theroll tables, means for varying the excitation of the motor driving the reducing rolls, and electrically-operable means responsive to the degree of excitation of said reducing-roll driving motor to vary the speed of the auxiliary motor, thereby to prevent the application of undesirable strains to the metal as it passes through the rolling mill.

3. In a control system for rolling mills provided with reducing rolls and roll tables, in combination, a motor for actuating the reducing rolls, an auxiliary motor for actuating the roll tables, means for varying the speed of the motor driving the reducing rolls, a relay responsive to changes in speed of the reducing-roll driving motor and means controlled by said relay for varying the speed of the auxiliary motor to prevent the application of undesirable strains to the metal as it passes through the rolling mill.

4. In a control system for rolling mills provided with reducing rolls and roll tables, in combination, a motor for actuating the reducing rolls, an auxiliary motor for actuating the roll tables, means for varying the speed of the motor driving the reducing rolls, a relay responsive to changes in speed of the reducingroll driving motor, a motor-generator set for controlling the speed of the auxiliary motor, and means responsive to the action of the relay for controlling the excitation of the generator of the motor-generator set and, therefore, the speed of the auxiliary motor to prevent the application of undesirable strains to thel1 metal as it passes through the rolling m1 5.- In a control system for rolling mills provided with reducing rolls, and roll tables, in combination, a motor for actuatin the reducing rolls, said motor having a fie d winding, means for energizing the field winding, an auxiliary motor for actuatin the roll tables, said motor having a fiel windin a motor-generator set for exciting the eld Win i g f he auxiliary motor, and means interposed between the motor driving the reducing rolls and the motor-generator set for controlling the excitation of the generator, said means being responsive to the change in excitation of the motor driving the reducing rolls and thereby controlling the generator voltage to vary the speed of the auxiliary motor to prevent the applications of undesirable strains to the metal as it passes through the rolling mill.

6. In av control system for rolling mills provided with reducing rolls and roll tables, in combination, a motor for actuating the reducing rolls, said motor having a field winding. means for energizing the field winding. an auxiliary motor for actuating the roll tables. said motor having a field winding, a generator for exciting the field winding of the auxiliary motor, a motor-actuated rheostat for controlling the generator voltage, and a relay interposed between the generator armature and the field of the reducing-roll driving motor, said relay being responsive to changes in the excitation of the reducingroll driving motor and the generator voltage to control the operation of the motoractuated rheostat to vary the excitation of the generator and. consequently. the speed of the auxiliary motor in accordance with changes in speed of the reducing-roll driving motor to prevent the application of undesirable strains to the metal as it passes through the rolling mills.

7. In a control system for rolling mills provided with reducing rolls and roll tables, in combination, a motor for actuating the reducing rolls, said motor having a field wind ing, means for energizing the field winding, an auxiliary motor for actuating the roll tables, said motor having a field winding, a generator for exciting the field winding of the auxiliary motor, means for varying the generator voltage, and a relay having a plurality of operating coils and a balanced armature disposed to be actuated by the operating coils, one of said coils being connected across the generator armature, another coil being connected across the field of the reducing-roll driving motor, said relay bein responsive to the generator voltage and the field voltage of the reducing-roll driving motor, res ectively, to control the means for varying the generator voltage, thereby varyin the speed of the auxiliary motor in accordance with any change made in the speed of the reducing-roll driving motor to prevent the applications of undesirable strains to the metal as it passes through the rolling mill.

8. In a control system for rolling mills provided with reducing rolls and roll tables, in combination, a motor for actuating the reducing rolls, an auxiliary motor for actuating the roll tables, means for varying the speed of the motor driving the reducing rolls, means for controlling the speed of the auxil- DALE W. DEAN.

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