US2084035A - Rolling mill drive and control system - Google Patents

Description

June 15, 1937. KENYON ETIAL 2,084,035

ROLLING MILL DRIVE AND CONTROL SYSTEM Filed Jan. 3, 1954 6 Sheets-Sheet l WITNESSES; V INVENTORS N Alonzo F Kenyan &

(758M .v I Wil/argYfil Ca June 15, 1937. A. F. KENYON ET AL 2,084,035

ROLLING MILL DRIVE AND CONTROL SYSTEM Filed Jan. 3, 1934 6 Sheets-Sheet 2 WITNESSES INVENTORS W I g 0% ATTO EY June 15, 1937. A. F. KENYON ET AL 2,084,035

-ROLLING MILL DRIVE AND CONTROL SYSTEM Filed Jan. 3, 1934 6 Sheets-Sheet 3 June 15, 1937. A. F. KENYON ET AL ROLLING MILL DRIVE AND CONTROL SYSTEM Filed Jan. 3, 1954 6 Sheets-Sheet 4 x &

Y mk m myo Nn 0 w Gl r1,10 or o m AW/ WITNESSES @m/ 0 Z June 15, 1937. A. F. KENYON in AL ROLLING MILL DRIVE AND CONTROL SYSTEM Filed Jan. 3, 1934 6 Sheets-Sheet 5 INVENTORS I Alonzo Kenyon & W/l/ara' C0222 WITNE'SSES: WM (5 MW June'15, 1937. A. F. KENYO N ET AL 7 2,084,035

ROLLING MILL DRIVE AND CONTROL SYSTEM Filed Jan. 3, 1934 6 Sheets-Sheet 6 WITNESSES: INVENTORL TORY ran tea aorantc Irma. naive Ann oo'nrnon s s'rnin Alonzo F. Kenyon, W .1

slbnrg, and Willard G.

Cook, Forest Hills, Pa assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation oi Pennsylvania Application January 3,

Our invention relates, generally, to electric drives and control systems for rolling mills and more particularly to an electric drive and control system for driving and controlling the operation 5 of a cold roll mill having a reel on each side of the main roll stand, commonly known as a single stand reversible mill.

During the pastfew years, notable advances have been made in the design of cold roll mills m of the above type making it possible to roll. at

very'high speeds as compared to the speeds obtained on the older mills.

The increased speed of rolling thin strip material has made it necessarfto provide electric t5 drives andcontrol systems for these mills of such nature= that the high speeds be readily obtainable and that the mill motor and reel motors be so controlled as to accurately control both the entry and wind-up tensions under all conditions regard- 20 less of speed, thickness of the material being rolled and the reduction being made on each pass.

The tension control must so operate as to maintain the proper tension underconditions of acceleration and deceleration and must also be ca able 25 of easy and ready adjustment to changethetem sions when desired.

The control in general must be flexible in operation and provide for effecting the operation of the reel motors individually to set-up the mill 30 and thereafter maintain tension or for effecting the operation of one reel,motor and the main.

mill motor or to control all of the motors in unison from. any one of two operating stations during the rolling operations when .the strip material is being 35 ,unwound from the entry reel under tension, I passed through the rolls and rewound under tension on the wind-up reel and the operation reversed and repeated until the'desired reduction is made.

The object is to provide anelectric drivefor a rolling mill which shall be simple and efiicient in operation and which may be economically manufactured and installed.

A more specific object of our invention is'tq provide for driving electrically a rolling millcomprising a rollstand and winding reels on either side of the roll stand, in either direction, or successively in opposite directions and automatically 50 maintaining a predetermined constant tension on the metal as it entersandlleaves the roll stand. Another object of our invention is to provide,

in an'electric mill drive of the hereinbefore described character, for maintainingsubstantially 5.3 the same winding and unwinding tensions on the of'our invention, generally stated,

193 i, Seriall lo. 105,073

metal during periods of acceleration and deceleration as during constant speed; operation of the mill. I 7

A further object of our, invention is to provide for operating the mill over any one of several speed ranges and for preventing a change from one speed range toanother unless the mill is stopped.

A still furtherobject of our invention is to provide for controlling the operation of a mill of the above-described character from any one of a plurality of control stations, for selecting the direction of operation of the mill and for rendering only one control station efiective dependent upon the direction selected. Another object of our invention is to provide for utilizing a booster generator in conjunction with the motor on eithenof the two reels which is functioning as the unwinding reel in order that motors or generators: whichever they may be, to

maintain substantially constant tension. on both; sides of the mill and for automatically recalibrat-' ingthe regulators dependent upon the speed A still further object of our invention is to provide for causing the current regulators to maintain substantially constant entry and windup tensions regardless of whether or not the reel motors may change from generators to motors range selected and during periods of acceleration and deceleration of the mill.

or vice versa during periods of acceleration and deceleration of the mill.

Other objects of our invention will become apparent from the following detailed description of its structural and operating features and the drawings, in which Figures 1 to fi inclusive, when placed together ,side to side form the complete diagram of the electric drive and control system of our invention. In practicing the invention, the main mill motor J receives power from a generator and its speed passes i. e. the first, third, fifth, etc., the reel motor on the entry side of the mill functions as a drag generator to subject the metal to a back tension while the motor on the wind-up side functions as a motor to subject the metal to a pulling tension.

The drag generator is disposed to be connected generator circuit so that its excitation both as to direction and amount is dependent upon the generator voltage. i

The excitation of the reel motors is controlled by booster exciter generators having their armatures connected in series with the reel motor field windings, respectively, across the excitation circuit. The excitation of the booster exciters is controlled. by current .regulators responsive to the load currents flowing in, the reel motor circults. One regulator is always used on the entry side and the otheron the wind-up side and suitable switches are provided for shifting fromone reel motor circuit to the other dependent upon the direction of the pass through the mill.

The regulators may be adjusted to maintain any :desired current in the reel motor circuits corresponding to the tensions desired by varying the resistance of their coil circuits. Provision is also made to change the resistance of the coil circuits dependent upon the speed range in which'the mill is to operate and also when it is desired to accelerate. or decelerate.

The mill is accelerated or decelerated by varying the main generator voltage through the'operation of a motor-operated rheostat controlling the excitation of the generator. Whenever the motor-operated rheostat is functioning to vary the generator voltage to accelerate the mill,- the resistance of the regulator coil circuit on the delivery reel motor is increased so that an additional amount of current may fiow in the delivery reel motor circuit to accelerate the reel while still maintaining the necessary amount 01 current for constant tension. During this time, the resistance of the regulator coil circuit on theentry side controlling the drag generator is decreased in order to reduce the generator torque suflicient- 1y to compensate for the extra pull or tension placed on the strip by the main mill to accelerate the generator to the higher speeds.

During periods of deceleration, the resistances of the regulator coil circuits are changed in the reverse order since in this case the inertia of the reel and motor on the wind-up side tend to increase the tension while on the entry side the inertia of the reel and drag generator tend to reduce the tension.

The direction of the pass through the mill is controlled by a pass selector master switch located on one side of the mill stand such, for example, as at the left control desk. The operation of this switch to itsfleft position connects ,the generator field in the proper direction and operates certainirelays to connect the regulators to the desired speed range.

proper reel motor circuits and booster excitei' fields for the odd numberedpasses whileits op-' necessary circuit setups for the even passes.

The actual operation of the mill is controlled by means of speed selector, main, reel and mill master switches, and inch, tension and release tension push buttons, located on both sides of switches function eration to the "right position establishes the to make all the necessary circuit set-ups for the proper resistance is placed in the mill motor shunt field circuit, the reel motor shunt field circuits,

I That is, by their operation, -the proper'amount of resistance is inserted in the main booster generator auxiliary and mam any desired position. These masters also-have a stop position which stops the mill with the strip under tension.

The reel master switches control the reel motors individually when it is desired to position the reel for any reason. --Likewlse, the mill master switches control the mill motor separately of the reel motors;

Referring now to the drawings, and particularly to Fig. 1, there is illustrated diagrammatically a mill of the kind for which the present invention is particularly adapted, which comprises a roll stand l0 and right and left reels H and I2, respectively. The reels H and I! are provided with electro-magnetic brakes I3 and I4,

respectively. The roll stand I may be dl'lvenby a suitable direct current motor l5 through suitable gearing IS in a well known manner. Likewise, the reels may be drivenor braked by means of direct currentmotors "and [8 connected through gears as shown.

Power may be supplied to the mill motor I5 and reel motors I I and [8 by a direct. current generator 19, provided with a field winding H,

which may be driven in any suitable manner, such as by a synchronous or other constant speed motor. 1

In the operation of mills of this type, it is desirable to operate the mill over a wide speed range oi. possibly from to 250 R. P. M. to provide a delivery speed of from 500 to 1000 feet per min ute if the mill working roll diameter is around 16 inches. Then, assuming that the reel drums are about 30 inches in diameter when empty and the coilof strip may build up to 48 inches in diameter andthat reductions up to 50% per pass aredesired, the entry or unwinding reel must operate over a speed range of from 20,to 125R. P. M-

This is a 6 to 1 ratio and since it is impractical to build large capacity direct current motors to operate over such a wide speed range by shunt field control, a main booster generator is provided and connected in series with whichever one of the reel motors that is functioning as a drag generator to the generator circuit in order that the drag generator will only be required to develop a low voltage at low speeds, this voltage'being increased by the main booster generator to a value such as to feed back into the main generator circuit. may be driven in any suitable manner.

As shown, the main booster generator 22 is pro- I one armature terminal connected directly to the generator bus'25 througha resistor 26'. v In order to provide for connecting the opposite terminal of the main booster generator in series with either reel motor switches 21 and 3B are provided. The reel motor circuits may be completed by means of switches 29 and 26, which connect the opposite terminals of the reel motor annatures to the opposite generator bus 3i. Switches 32 and 33 are provided for connecting the reel motor armatures directly to the generator bus'25. I

When it is desired to roll from right to left, reel II becomes the entry reel and Subjects the unwinding strip to a back tension. Therefore, switches 21 and 28 are closed to connect themain booster generator 22 in series with the reel motor i l, which now operates as a generator, across the generator busses 25 and 3i. For thisdirection of rolling, reel 12 becomes the wind-up reel and switches 29 and 33 are closed to connect the reel motor l8 directly across the generator busses 26 and 3|. v V

Hereinafter, the pass through the mill from right to left, as viewed in Fig. 1, will be referred to as the odd pass, whereas the pass in the opposite direction will be the "even pass The first pass through the mill is, of course, the first odd pass." Each time the direction of pass is reversed, the reel'which was formerly the entry reel .becomes the wind-up reel and the other reel becomes the entry'reel. r 1 A switch 34 is provided for connecting the mill motor -I5 to the generator. The mill motor is provided with a dynamic braking resistor 35 which may be connected across the armature by means of a switch 36 inc, well known manner.

In order to provide for maintaining the desired tension on the strip material, provision is made for controlling the excitation, of the reel motors in such manner as to maintain a constant armature current corresponding to the desired tension. (In this embodiment of the invention, the field windings 31 and 38 of reel motors l1 and I8, respectively, are connected in series with the armatures of auxiliary booster exciters '39 and 40, respectively, across 'the source of excitation,

many of the circuits through cables BI and 42. y

In order to identify the circuits extending through the cables and 42, the points of entry and exit of the conductors will be designated by like letters. The connections from the booster exciters The main booster generator 22 wind-up reel motor. lators are alternately connected to opposite 3 in Fig. reel-motor field windings in Fig. l.

is carried through the cable so to the A source of constant potential voltage tor furnishing excitation current to the various machines and operating currents for the relays is provided in'the form of a generator did Fig. .1,

which may be connected to supply conductors X- and Y which extend on either side of the diagram. The voltages of the boosterexciters 33 and 46 are varied to control the excitation voltages impressed upon the field windings of the reel motors;

by meansof current regulators 66 and t5,respec.= tively, shown in Figs. 2 and 3. The current regulators it and Wiimay be of any suitable type. The particular kind illussuch manner as to alternately increase and de crease theeffefit of the resistors 52 to 65, inclusive, which are connected in circuit across the excitation source with whichever one "of.v the boosterexciter fields that is associated with the In other words, the regubooster exciter fields as the direction of operation of the mill is reversed.

The regulator 45, which is always used to control the booster exciter associated with the entry reel motonalso comprisesra core 66, magnetizing 5 7 69 which actuates the movable contacts 5! in to 66, exactly, in the same manner asin the case of regulator 56. v

The moving coils t9 and 69 of the regulators the load currents of the reel motorsor generators 4" are disposed to be energized in accordance with to hold these currents and, therefore, the strip the mill is operating in one direction, and which,

when energized, reverses the coil connection.

The set-up relay 66, when deenergized, also connectsthe' moving coil of the wind-up side regulator 44 across a resistor 61 in the armature-cir= cuit of the right reel motor, and when energized switches this connection to a similar resistor 68 in the armature circuit of the-left reel motor.

The setup relay 66, when deenergized also connects the contacts of the entry sideregulator 45 to the booster exciter field associated with the entry reel motor and the contacts of the wind-up side regulator to the oppositebooster exciter field.

When the relay is energized, the foregoing contact connections are reversed. .I'his set-up relay has other functions in connection with making the 1 proper circuit set-ups depending on the direction of pass as will appear as the description proceeds.

As will be readily understood, the regulators and 45 may be'caused to maintain predetermined constant armature currents in the machines to which they are connected, depending upon the resistances of their movable coil circuits.

In order that the resistances of the regulator co'il circuits may be controlled in such manner as tohlways maintain the desired constant tension on the strip regardless of whether or not the mill is operating in one speed range or. another, and at low or high speed in anyspeedmange, and

accelerating or decelerating under any condition,'resistors 69 and 69a bias batteries and 10a, tension adjusting resistances .H, Ha and 12, 12a 'andcompensating switches 14 to 11, inclusive, are provided.

In the case of. the wind-up the resistor 69 is disposed to be connected in series with the'coil 49,*bias battery 10 and either one of l5 the tension adjusting resistors H and Ha. across either one of the resistors 61 and 68 in the reel motor circuits depending upon the position of the set-up switch 66. The resistors II and Ha are utilized to adjust the regulator coil circuit to maintain any desired tension on the strip during constant speed operation, resistor H being efiective on the odd numbered passes and resistor Ha onthe even numbered passes.

In the case of the entry side regulator 45, the

resistor 69a. is disposed to be connected in series with the coil 59, bias battery 10a and either one f of the tension adjusting resistors vin and 12a across theresistor 'lfiin the main booster generator circuit. The connection is made'to resistor 25 through the tension adjusting -rheostat J2 for the odd passes and reversed for the even passes. J M

It will be apparent that .when the mill is accelerated \or decelerated, the regulator coil cir- Lil cuits must be changed or'compensated accordingly. That is, when the mill is being accelerated, the wind-up reel motormust develop additional torque to overcome its own inertia and that of the reel to which it is connected, and at thesame time develop suflicient torque co maintain the desired constant strip tension. This requires that the wind up reel motor be caused to draw more current and, therefore, the regulator coil circuit must be readjusted in order to permit this addi--v T tional current to flow.

In the case of the entry reel under accelerating conditions, the situation is reversed as the iner-, tia'of the drag generator and the reel increases the strip tension and, therefore, the current flowing in the generator armature must be reduced sufficiently to still maintain the strip tension constant: In this instance, the regulator coil circuit must be readjusted to cause the regulator associated with the entry reel generator to reduce its excitation. I I 7 It will be readily understood that in. the case of deceleration, thereadjustments of the regulator I coil circuitsmust be made in the opposite manner aswthe inertia forces during deceleration are working in the opposite way.

effectiveness of the resistors 69 and 68a, which is accomplished by means of compensating switches 1 "to 11, inclusive.

' Before describing the operation of the compenside regulator 44, Q

- speed range switches 81 and 88, the switch 81 sive to the operation of the time delay relay 19.

through resistor 12a relay 18 is causedto open its contact menrbers 'for the purpose of insuring that there will .al-

This readjustment or compensation of the regulators during the accelerating and decelerating periods is effected in this instance by yarying the .us'ted or compen resulting when themill motor is operating on weak field. R

In this instance, the compensating switches 14 and 16 are effective in the low speed range while switches 15 and II are ei fective in the highspeed range only. The operation of switches I4 to H is controlled by suitable time delay relays 18; and i9, relay 18 being used under conditions of accel eration while relay 'lfis for deceleration. Since. these time delay relays are of well known con- 10 struction they will "not be described in detail other than to state that they are provided with neutralizing .coils 8| and 82 connected in series acrossconductors X and Y as shown and magnetizing coils 83 and 84, which when energized, operate .the relay contacts 85 and 86 to the opposite positions from that shown. e

As to whether or not the relay J8 operates switch 14 or"'l5 depends uponthe position of the being closed when operating on low speed range and switch 88 being closed when operating on high speed range. These switches also determine which one of switches 16 and I1 is respon-' As will appear more clearly hereinafter, during constant speed operation in the low speed range, for example, the compensating switch 14 will be energized to open its contact members 1411 and close contact members 14!) which places a certain amount of resistance in the coil circuit of the regulator 45 and shorts a portion of the resistance in the coil circuit of regulator 44. These resistance values being such as to maintain a desired constant tension at constant speed.

When the ,mill islaccelerat ed, the time delay 85 to deenergize the compensating switch 14 which closesits contact member 14a to reduce the resistance of the regulator coil circuit 45 and toincrease the resistance of the coil circuit of t the regulator 44, which, as described hereinbefore, readjusts the regulator settings -to compensate forthe inertia forces in the reels and reel motors. In this" instance, the resistance (15 change of the regulator coil circuits is madein one step. However, it is evident that-as, many steps as desired may be made.

When the mill is running-at constant speed .50

and is then decelerated, the time delay relay I9 is operated to effect the operation of switch 16,

which opens its contact members 16a to further increase the resistance of the coil circuit of the entryregulator and closes its" contact member 16b tofurther decrease the resistance of the coil circuit of the delivery regulator 44, which is the opposite readjustment to that described hereinbefore in the case of acceleration. r The biasing batteries 'Ilhand 10a. are provided though it must i'unctlon at times to reduce the load currents of the reel motors to very low values or actually reverse them in order topompensate for the inertia forces which may develop when the mill is rapidly accelerated or decelerated. In other words these batteries place a positive voltage bias on the regulator coilwhich causes the regulators to function in the required manner under any operating condition that may When operating the mill with very low tensions on the strip, the amount by-which the load currents of the reel motors must be reduced during periods of deceleration may be greater than the total load currents during constant and 58 in the reel motor circuits is actually reversed and without the positive biasing voltage on the regulator coils the regulators could not function to control the tensions on the strip.

It is to ,be understood, however, that the bias- 15 ing voltage may be obtained from other sources and that the use of batteries for this purpose is merely illustrative.

In this instance the magnetizing or stationary coil ill of theentry side regulator 45 is connected go directly across conductor X or Y overa circuit which extends from conductor X in Fig. 2, conductor 89, coil conductor 9d and resistor 9i to conductor Y Likewise the magnetizing or stationary coil ill 25 of regulator all is connected from conductor X in Fig. 3 through conductor 92, resistor 88, coil ill and conductor 235 to conductor Y. J

In order to control the excitation of the field winding 2i of the main generator, there is pro- 30 vided a motor operated rheostat 93 having an operating motor 9d and a resistance element 95 disposed to 'be connected in series circuit relation with the field winding 2i across the excitation source through either one of two reversing 35 switches 96 and '91- As will be described'more fully hereinafter, the generator field reversing switches 9t and ti are operated in accordance with the direction of pass through the mill. The operation of the rheostat motor 96 may be controlled by switches 98 and lie-,the closure of switch, 99 beingefiective to energize the motor 9% in such direction as to drive the rheostat'arm I00 in a direction to raise the generator voltage and switch 93 be- 45 ing operable to effect the opposite result.

The rheostat 93 is provided with limit switches llll and H12 which function to deenergize the relays 93 and ile to stop the motor when the arm loll reaches its limit of travel.

50 In order to provide for increasing the generator voltage in a single step for certain purposes, as will appear hereinafter, a shunting relay !63 is provided which, when operated, short.

circuits a portion of the resistor 95 as shown. 55 The energization of the control relays 98 and 99 may be controlled by a relay I04 which is controlled in a manner to be described hereinafter.

In order to control the energization and direction of current flow through the auxiliary field 26 of the main booster generator 22, reversing switches I05 and I06 are provided. When switch 105 is closed, the fleld-2l is connected across the supply conductors X and Y through a variable resistor in! and a fixed resistance Hi8 which is controlled by the speed selector switches 8'l and 88. Resistor'llll'is used to vary the voltgenerator busses 26 and ti through a resistor ill. I The'complete control-ofthe mill, in this embodiment of the invention, is effected through the operation of a plurality of master switches and push button switches located on both sides of 5 the roll stand 60. With. the exception of one master switch known as the pass selector which is located on the left sideonly, all of the other switches are duplicated in both the right and left control positions thereby providing two control stations permitting the operator to control the mill from the entry side while setting it up and later transferring his control to the wind-upside to connect up the wind-up reel and operate the mill in one direction.

In "this instance, l M is the pass selector switc having right and left operating positions. he will be described more fully hereinafter, the operation or this switch to the left position efiects,

among other things, the energization of the setup relay at to establish the necessary control circuit set=ups to make an odd pass'and when operated to the right position operates a. sec- 0nd set-up relay H5 which makes the necessary circuit set-ups for the even passes.

As described hereinbefore, itis desirable to operate themill at: various speed ranges and in order to accomplish this, a pair of speed selector master switches lit and i ll having slow and fast operating positions are provided, switch lit being located on the left side and ill on the right side of the roll'stand it, These master switches control the operation of the speed' selector relays dl and as in order to make the 5 necessary circuit/set-ups for the desired speed ranges. j I

The operation of the completelmill including the roll stand and reels after the mill has been set up and initial tension established, may be 40 switch, the slow position effecting the operations of the complete mill at a slow speed,the raise position being effective to control the relay Illt in Fig; 3, which controls the operation of the relays 98 and 99, which control the motoroperated rheostat 93. When this master switch is operated to the raise position, the motor-operatedrheostat 93} is caused to increase the generator voltage and thereby accelerate the mill. The

'motor-operated rheostat to reduce the generator voltage. The generator voltage, and, consequently, the mill speed may be held at any desired value byoperating this master switch to the hold position which stops and holds the motor-- operated rheostat in any desired position.

Left and right reel master switches l2l and :22, respectively, are provided for individually 'order that'the reel may' be positioned to attach the metal strip during the set-up .process for the, odd pass.

1 In order to control the mill motor' I5 sepa- 5 rately, there are provided left and right mill mas- 1 ter switches I23 and I24, respectively, which are g established, in order to attach the strip to the utilized, as will be described more fully hereinafter, to operate the mill motor to run'the metal through the rolls after bak tension has been delivery reel. 9

In addition to the master switches, right andleft inch push-button switches I25 and I26 are provided for controlling the operation of the en-' 15 try reel motor. when setting up the mill. -When inch button I25is pressed, theright reel motor I1 is caused to rotate the reel II toward the mill 'to; pay dut the strip which is to be; inserted between the mill-rolls. Likewise, when inch button 20126 is pressed, the 6 reel motor is caused rotate the reel I2 toward the, mill. 3 After the strip has been inserted'between the mill rolls and the screw down mechanisms, (not shown) operated'to set the rolls, it is then'desir- 25 able to establish-aback-tension on the entry side of the 'mill, and it is for this purpose that push 'buttons I21 and I29 are provided. When push .button I21 is"operated, the right reel motor I1 is connected in series with the main Lbooster generator 22 across the generator bus'ses which causes this motor to' operate in a direction .to rotate the reel II away from the mill until the slack is taken up which causes the motor to stall. This, establishes what is known as the stalled tension and 35 when the mill is started, thennetal strip is un wound from the entry reel thereby driving the entry reel motor as a generator developing sufficient torque to subject the strip tothe desired back tension.

In order that a more comprehensive understanding of the features of the invention may be obtained, a description of the operation of the mill will now be set forth.

In describing the operation, it at, be assumed :45 that the main generator I9 is being driven at required speed, that the constant voltage exciter 43 is also in operation so that switches I3I and I32 may be closed to'energize the conductors X and Y and also, that tliemain booster generator 22 and the booster exciters as and 40 are. being. driven at the required speeds. 1 In order for the systemic become operative,

the low voltage relay; I33 must be closed which will occur if the; various control relays, push 55 buttons and master switches are closedwith exception of. thepass selector switch 4', which must .be'operated to either the even or odd pass position before the low voltage relay may become energized. A v A 60 Assuming in this instance that the pass selec tor 'II4 is operated to the odd pass position, thereby establishing an. energizing circuit for the set-up relay 66 which; extends from conductor K through contacts I34, bridged'by segment I35,

65 conductor l36,coil I31 of the set-up relay ,66

for the odd pass.

us and m, of the mill masters in and m,

.conductor I49, through the closed contact members of' push buttons I25 to I29, inclusive, conductor I49, to point A in the cable 4|, through .the cable to point A in Fig.1, conductor II, the 5 tors I56 and I51 to'the energized conductor X. 10

Upon the closure of the low voltage relay I33, its--contacts I58 and I59 are closed to establish its own holding circuit through-the closed contact member of the set-up relay 66 and the emergency stop buttons I39 and I49. The closure of contact- I59 also connects conductor X,.to a sec- "ond control conductor Z which now becomes energized. It is now evident that the master switches, push button switches and other control apparatus through which the original pick-up circuit from the low voltage relay extended may 7 now be operated to perform their other functions without deenergizing the low voltagerelay. When the pass selector H4 is operated to the odd position, it sets up, in addition to operating the set-uprelay 66, certain circuits through its contact members to render-the speed selectorswitches H6 and II1,eilective to operate the speedselector relays 91 and 89. In addition to this, it energized, through its own contacts, generator field cp'ntactor 91 to cause the generator I9 todevelop voltage in the proper direction The circuit, for operating the field switch 91 k extends in Fig. 4 from conductor Z through conductor I62,'- contact'fingers I63, bridged by the segment I64, conductor I65 to point .B-in the cable 42, through the cable to the point B in Fig. 2, conductor I66, the coil of relay 91, closed contact members of the QPhBlIrfiEld switch 96, and con- 40 ducto'r I61 to conductor Y. v

In response to the closure of the set-up relay 66, the entry side regulator is connected to the entry reel motor circuit which, in this case, is

motor "and to the field wlndingofthe auxiliary 45 booster exciter 39 which is associated with the, right reel motor whichis now on the entry side of the mill. J

J The circuit for connecting the coil. of the ,en-

try side regulator 45 across the resistor 26 in the circuit connecting the mainbooster generator and reel motor I1 across the generator busses may be traced from the upper end of the resistor- 26 in" Fig. 1 through conductor I69, variable resistor 12, contact members I", bia's battery 19a, resistor 69a, movable coil 59 ofthe regulator, conductor I12, contact members I13 and conductor I14 to the lower side of the resistor 26. v

The movable contact ,members of the entry regulator '45 are connected to the field winding 60 of-the booster exciter 39 through a circuit which extends from conductor Y in Fig. 3 through conductor I15 to the bridge circuit comprising resis- I tors 62, 63, 64 and 65, The field winding of the booster exciterf39 is connected to opposite sides 65 of this bridge circuit through contact members I16 and I 11 of the set-up relay 66 and the movable contacts 6| of theregulator connected 4 acsacss bias battery it, resistance ll, contact members its and conductor-ml to the lower end of the resistor 63. 1

In'this instance, conductor M8 in Fig. 3 connects conductor Y to the bridge circuit comprising resistors 52, 53, 541 and 55. The field winding of the booster exciter QB is connected to opposite the regulators respond to the load currents fiow-.-

ing in the reel motor circuits to. which they are corrected and operate their movable contacts to continually vary the voltageimpressed on the fields of the auxiliary booster exciters in such manner as to maintain the load current of the reel motor circuitssubs tantially constant.

The closureof. set-up relay be also operates relay i 06 to connect the fields of the main booster generator 22. The energizing circuit for relay its extends from conductor Y in Fig. 6 through coil I95, conductor W6, closed contact unembers it? of the inching relay 6%, conductor m9, contact members 2% of the set-up relay 6t and conductors 262 and 2 277 to conductor Z.

' Upon the operation of relay we, the main field Winding 23 of the booster generator this connected from the generator bus. 25 through con-- ductor 203, field winding 23, resistor iii, conductor 205 to point C in the cable ill and through the cable to point C in Fig. 4, conductor 2%, contact members 2%, conductor Eiil, to point D in cable ill back through the cable to point- D in Fig. 1 andto the opposite generator bus iii.

The energizing circuits established for the auxiliary field winding 241 of the booster 22 by the closure of relay Hit extends from conductor Y in 4 through conductor 208, contact members through the cable to point E in Fig. 1, field wind- 299, conductor 2m to point LE in the cable M ing 2t to point F in the cabledl and through the cable to point F in Fig.4, conductor 25!, conthrough-the cableto point G in Fig. 6, conductor tact members 2i 2, conductor 2 l3,-variable resistor H89 and speed resistor its to conductor X.

At this time, the closure of. set-up relay 6% also operates switch 21 in Fig.. 1 to connect the main booster generator 22 in series with the entry reel motor ill. The operating circuit for this switch extends'from conductor Y in Fig. 1 through the coil of switch zl, to point G in the cable at 2H3, contacts 29! of relay 66. and conductors 202 and 227 to conductor Z.

It is now necessary to run off strip from the entry reel I I in order that itinay be inserted be- .tween the rolls of the mill It. This requires an inching operation of the entry reel motor ll which maybe efiected by the operation of the inch push button H25. The closure of the inch button to bridge its lower contact members establishes an obvious energizing circuit through the coil 2 l5 of the inching switch I98 and closed contact members 2H5 of the deenergized set-up relay H5 to conductor Y.

' The operation ofthe inching switch i923 interrupts at contacts I91 the previously completed energized circuit for the field switch Hit thereby causing this switchto drop out and disconnect the flelds of the maiubooster generator 22. However, the opening of contacts l9l does not interrupt the previously completed operating circuit for the switch 21 and, therefore, the main booster generator is still connected in series with the entry reel motor H.

The closure of the inching switch I98 also establishes'a circuit for releasing .the brake it on the right reel motor Ill and for operating switch 23 in Fig. 1 to complete the connection of the reel contact members 222 of the inching relay, closed contact members 223 of relay. 8%, which is now deenergized, to point I in cable 6i. through the cable to point I in Fig. 1 and the coil of switch 28 to conductor Y. Upon the completion of these circuits, the reel motor 5? operates to rotate the reel it toward the roll stand as. e I

At this time also, the inching switch 5% efiects the operation of a, time delay relay 22:?! which after a predetermined time closes its contact members 225 to effect the operation of relay I83 7 in Fig. 3 to step up the generator voltage. The

time delay relay 226 has a neutralizing winding 225 which is connected directly across the control conductors Z and Y through conductor 2Z1, Winding 225 and conductor 228 to conductor" Y.

The relay is also provided with a magnetizing winding 229 which is also connected across the conductors Z and if in parallel with winding 225, which causes the relay armature to be operated to open contacts 225.

When the inching switch 898 is closed, its contact members 23! short circuit the magnetizing coil 22% thereby causing the relay to drop out after a predetermined time to close contacts 225. Upon the closure of contacts 225, the generator field step up relay 6&3 is operated over a circuit which extends from conductor Z in Fig. 6 through contact members 225 of the time delay relay, conductors 232 and 233 to point J in the cable 52 through the cable to point '3 in Fig. 3', coil of relay its, and conductors 23d arid 235 to .con-

ductor Y.

After the strip has been entered in the mill rolls, back tension may be placed on the strip by operating the tension button 121 in Fig. 6. In the meantime, however, the inch button I25 has been released and the inching switch I98 returns to ductor 23?, closed contact members 238 of set-up relay 6%, conductor 239, coil of the tension relay 2% and'a release tension button 24! to conductor Y. 4

The operation of tension relay 235 again establishesan energizing circuit for the switch 28 in Fig. 1, which was interrupted when the inch button 525 was released, .which extends in this The operation of tension relay 236 also again a releases the brake I3, which was setwhen the 1 inch button I25 was released, over a circuit exi tending from conductors Z in Fig. 6 through conductor 242, contact members 244, n the tension relay topointK on the-cable (I through the cable to pointI-I in Fig. 1, conductor 2|.8, and the coil of relay 2I 9-t0 conductor Y.

The -tension relay 236 is also provided with a contact 245 which bridges the lower contact members of the tension button I21 and obviously establishes a holding circuit for the tension relay when the pushbotton is released.

At this time, the roll stand I0 is idle, the generator I9 is developing a lowvoltage of possibly 50 volts while the booster generator 22 is developing .a higher voltage of possibly 90' volts, thus 25 subjecting the right.reel motor I1 to a voltage of possibly volts in a direction to cause it to rotate away from the mill thereby taking up i any slack'in the strip, and'then-placing a stalling tension on. the strip. J

In order to complete the setting up operation ,and 33 to connect the wind-up reel motor I8 to of the mill, either one of the mill master switches effects the operatibn ofthe motor control switch '40 34 in Fig. 1 fpr cgzinnecting the mill motor I5 across the generator buses. -The circuit for operating the: control relay 246 extends {from conductor Z in Fig. 5 through contact members 241, bridged by thesegnient 248 or master switch I23, conductor .249, coil of control relay 246, and

' conductor '25I to conductor Y.

the generator buses and release the magnetic brake I4 onthe reel I2. V

Theoperation of the reel master I2I to the slow position establishes a circuit for operating a second tensionrelay 26I in Fig. 6 similar to relay 236 whichextends from conductor Z in Fig. 5 through contacts 282 of master switch I-2'I,

conductor 263, closed contactmembers 264'of ductors 261, and 268, closed contact members 269 of relay 26I ''to point M in the cable 4I. through tension button 266 to conthe cable to point M in Fig. 1, coil of switch 29, and conductor 255 to conductor Y.

The circuit for switch 33 also extends through contact members 269 of the tension relay 26l, contacts 218 of set-up relay 66 to point N in the cable 4I and through the cable to point N in Figrl, coil of relay 33', and conductor 255 to conductor Y. f

Thecircuit for operating ,the brake I4 extends from conductor Z in Fig. 6,,through conductor 2I5, contact members 21I oi the; tension relay 26I, conductors 212 and 213 to point 0 in cable 42, through the cableto point-O in Fig; 2, conductor 214, coil of'relay 215 and conductor 216 to conductor Y. The operation of relay 215 establishes an obvious energizing leasingv the brake I4. v

The strip is now secured to the wind-up real and the mill is completely set up for making the first, which, in this case,'is the odd pass. Before,

the mill is startedfhowever, the speed range In which it is desired tooperate should be selected by operating, in this instance,' the left speed selector master H6 in Fig. 4 to either the slow or fast position, to operate relay 81 or 88, as the The closure of relay 246 establishes an operating circuit for the motor control switch 34 in Fig. 1 which extends from conductor Z,in Fig. 5

through conductor 252, fcontact members253,

' conductor 254 to point "L in the .cable H, and

through the cable topoint L in,-Fig. 1, the coil of switch 34 and conductor 255 to conductor'Y.

The operation 01' the-left mill master-I23 tov the fast-'position establishes a shunting circuit around the magnetizing coil of time delay relay 224 which has again been picked up, which after a time interval causes this relay to close its contact members 225 to effect the operation of g relay I83 to again increase thegenerator voltage" as described hereinbefore. This shunting circuit extends from contact 256 on the mill master through conductors 251*a11d V258 to point 258 which obviously connects both sides of the coil 229 to conductbr Z r I The m 11 is permitted to' fun untii'enough strip is r n through for connection to the windup reel I2, whereupon the mill master I23 is operated to the 011' position to stop themill' ductor I51 to conductor 2:

slow speed range, which means that the millmotor I5 operates at full field excitation, master switch I, I 6 is operated to its "slow" position'which circuit for recauses its contact segment 219 to bridge contacts pass selector which are now bridged by segment 284, conductor 285 to'point P on cable 4 I, through the.cable*t,o point Pin the cable in Fig.1. closed contacts 286 on the motor switch 34 and con- 286 on the motor switch-84, the speed range se-.

lected cannot be changed after the 'motor "has been started unless it isagain deenergized to permit the switch 34 to close -interlock 286. Furthermore, when the low speed relay 81 closes, its lower contacts 281 establish a holding circuit through conductor 288, closed contacts 288 of the high speed relay 88 and conductor'flfl. Likewise, when the high speed relay 88 is closed;

by. operating the speedselectorgl I8 to the fast position, its contacts 289 establish. a holding circuit through conductor 888, the normally closed I c v Attention is directed to the fact that since the energizing circuit for either oneof the speed relays 81 and 88 extends through the interlock ductor 29 I.

circuit changes for efiecting the operation of the mill in the low speed range.

Its contacts 292 close to short circuit a portion of the resistor III in the main field winding 23 of booster generator 22. the booster generator 22 to develop a high voltage for the slow speed operation when the entry reel II is operating at a low speed and its drag generator developing a low voltage. Its contacts 293 are closed to shunt a portion of the resistor 294 connected in series with the mill motor field winding 295. This subjects the motor to full field excitation. Contacts 296 are closed to render the compensating relay 14 responsive to the closed position of the time delay relay 18. Upon the closure of the contacts 296, the compensating relay 14 is energized over an obvious energizing circuit which causes its contact members 14a to. open and insert a block of resistance in the coil circuit of the entry side regulator 45. Contacts 14b are also closed to shunt out a portion of the resistance 69 in thecoil circuit of the wind-up sideregulator 44. The resistances now in the coil circuits are those necessaryto maintain the desired constant tension on the slow speed range for constant speed operation. Closure of contact members 291 on the speed relay 81 set up the operating circuit for compensating relay 16 in order that it may be operated in response to the closure of relay,19 under conditions of deceleration.

In connection with the operation of the com--- peosating relays 14 to 11, it should be noted that in case the speed relay 88 has been closed, its contacts 298 would have caused the compensating relay 15 to be picked up instead of relay M, which would have inserted a larger amount of resistance in the coil circuitof the entry side a motor l8 extends from conductor X through re I regulator 35 and shunted a larger amount'of resistance in the coil circuit of thewind-up side regulator 44. The closure of. its contact mem- Contact members 305 and 306 of low speed rep lay 81 also set up the proper resistances in the field circuits ofthe reel motors which also include the armatures of the auxiliary booster exciters 39 and 40. As shown in Fig. 4, the energizing circuit for the field winding of the reel sistor 301, armature of auxiliary booster exciter 40 to point Q in cable 4| and through the cable to point Q in Fig. 1, field winding 38 and conductor 255 to conductor Y.

The circuit for energizing the field winding or the reel motor 11 extends from conductor X in Fig. 4 through resistor 308, armature of auxiliary boosterexciter. 39- to point B in cable 4| through the cable to point R in Fig. 1 and field winding 31 to conductor Y. i

In order that the resistors 301 and 308 may be automatically set up to the proper value depending upon the direction of pass, relays 309 and of the. speed relay 81 makes the necessary set ups and This permits I of the rheostat-mo- 3l0 are. provided and controlled in accordance with the position of the set-up switch H5 which is energized only on' the even pass. Since the odd pass is now being described, it is evident that contact 3 of the set-up*switch H5 is closed to establish an obvious energizing circuit for relay 309, which closes its contacts 3I2-to shunt out a portion of the, resistor-301 and it closes its contacts 3l3 to complete the shunting circuit set up by contacts 306 of thelow speed relay '81. It will be noted that the closure of contacts 305 of the low speed relay have no efiect on the resistor 301 at this time since relay 3I0' isdeenergized. On the even passes, however, contacts 3l4-of relay 5 would be closed to operate relay 3|0 thereby closing its contacts 3l5 to. complete the shunting circuit set up by contacts 305 and contacts 3l6 also closed to shunt out a portion of the resistor 308.

The closure of low speed relay 81 also increases the resistance of the energizing circuit for the auxiliary field winding 2d of the main booster generator 22 by opening" contacts 3!! thereby inserting a portion'of resistor I08 in the field circuit. Section 3 l 8 of the resistor W8 is now shorted over a circuitwhich extends through conductor 3I9, 320 togpoint S in cable dl, through the cable to point S in Fig. 1, through the normally closed contacts of relay 32! and cond lctor I51 back to the conductor X. When the relay 32! is opened in response to the energization of the mill motor l5, the resistor section 3 I 8 is also inserted and the auxiliary field winding 2d of the booster generator is practically rendered inefi'ective because of the resistance l00.

These latter connections are for the purpose of I rendering the auxiliary field of the main booster generator efiective to establish and maintain back tension when the main generator voltage is low and therefore, does not have an appreciable efiect upon the main field of the main booster generator and to render the auxiliary field winding of the main booster substantially ineffective after the mill motor starts.

After the speed range selection has been made,

the mill may be set in operation to roll the odd 1 pass by operating the main master H8 to the slow position. The operation of thismaster to the "slow position efiects a number of switch operations simultaneously in order to release the brake on the wind-up reel and establish the circuit connections for the'mill motor l5 and windup reel motor l8.

The circuit for releasing the brake I4 extends from conductor Z in Fig. 5 throughconductor Contact finger 33] of the main master H0 is bridged to establish a circuit for operating a running relay 332 which functions to close the connecting switches 29 and 33 for reel motor i8,and also a second running relay 333 to close the connecting switch 34 for the mill motor l5. The circuit for operating relays 332 and 333 extends from contact finger 33l .on the main master, switch through closed contacts 334 of the set up relay H5, conductor 335, and through the coils of the relays in parallel to conductor Y.

Upon the closure of relay 333, its contacts 336, connects point L of the cable 4| directly to conductor .2 through conductors 331 and 252 which again completes the previously described energizing circuit for the main motorswitch 34. Its contacts 338 are closed to complete an obvious energizing circuit for the magnetizing coil 339 of time delay relay 340, which upon energization closes its contacts 34I to establish an obvious energizing circuit for a relay 342 which closes its contact members 343 to establish a parallel shunt connection across contacts 336 of relay 333. The purpose of this shunt connection is to permit relay 333 to be opened when it is desired to stop the mill without actually opening the main motor switch 34, this switch being held in until the opening of switch 342 which is controlled by the time delay relay 340. The time delay relay 340 is caused to function when the relay 333 .is deenergized. This. permits the roll stand to operate for a short interval after the wind-up reel has been stopped in order to provide slack in the strip.

The closure of contacts 344 of relay 332 connects points M and N on the cable M to conductors Z, through conductors 345 and 261, thus reestablishing the previously described energizing circuit for the connecting switches 29 and 33 of the wind-up reel motor I8, As will be recalled, this circuit was completed once before in response to the operation of the tension relay 26I controlled by the tension button I28 during the setting up operation.

Relay 332 is also provided with contacts 346 which are closed'to establish an obvious holding circuit for the relays 332 and 333 which extends back through conductor 341, the closed contacts 348 of a stop relay 349 and conductor 252 to conductor Z. The stop relay 349 is energized from a circuit which extends from contact finger 35I on the main master I I8 only when the main master is in the stop position, as shown, through conductor 352, closed contacts 353 of the set-up switch II5, coil of stop relay 349, and conductor 354 to conductor Y.

Relay 332 also closes its contacts 355 which are in parallel with the contacts 243 of the tension switch 236 which is now energized and, therefore, have no efiect'in connection with the control of switches 21 and 28 of the entry reel .motor I1 at this time.

The mill is now running at slow speed in the low speed range and if it is desired to accelerate the mill, the main master switch H8 is actuated to the raised position to bridge contact finger 358 and establish a circuit for operating relays I04 and 99 to increase the generator voltage. The circuit thus established extends from contact finger 358 in Fig. 5, conductor 359, contacts 36I, conductor 362, to point T in cable M and through the cable to point T in Fig. 3, conductor 363, coil of relay I04, and conductor 364 to conductor Y.

As explained hereinbefore, this efiects the operation of relay I04 which closes its contacts 365 to establish an energizing circuit for the raise relay 99, which closes its contacts 366 and 361 to connect the rheostat motor 94 across the conductors X and Y so as to rotate the rheostat arm I in a direction to decrease the resistance of the generator field circuit. The circuit forv operating the raise relay 99 extends fromconductor X through contacts 365, coil, of relay 93, normally closed limit switch I02 on the rheostat and conductor 235 to conductor Y. The energizing circuit for the motor 94 established by the closure of relay 99 extends from conductor Z through conductors 315 and 368, contacts 361,

armature'of motor 94, contacts 30I .of the low speed switch 81 which are now-closed, contacts 366, and conductor 364 to conductor Y.

The motor-operated rheostat 93 will continue to raise the generator voltage until the main master switch H8 is actuated to the "stop position which will, stop the mill or to the "slow position which will deenergize the relay I04 thereby deenergizing the raise relay 99 and enthe hold position which interrupts the energizing circuit for the lower relay 98 even though the relay -I04 has attempted to close its circuit.

The circuits thus established for accomplishing these functions will now be described. the event that the main master II 8 isactuated to the slow position, the energizing circuit thus established for the lower relay 98 extends fromconductor X in Fig. 5 through contacts 31I of the right main master switch II9, contacts 312 of the left main master switch H8 bridged by segment 313 to point Ujn cable 42 and through the cable to point U in Fig. 3, contacts 369, coil of lower relay 98, limit switch IM and conductor 235 to conductor Y. The establishment of this circuit causes the rheostat motor 94 to operate the generator rheostat 93 in the opposite direction to reduce the voltage. eration will continue until the motor 94 is stopped by the limit switch IOI or the operation of the main master II8 to either the stop or hold" position;

In order to hold the generator voltage at any desired value when being raised or lowered the master switch may be actuated to the hold" position. In this'position its contact members 312 are not bridged by the segment 313 and, therefore, the previously traced energizing circuit for the lower relay 98 is not established and the rheostat motor 94, upon being deenergized in response to the opening of the raise relay 99, is stopped in any desired position.

As described hereinbefore, the compensating relays 14 to 11 in Fig. 2 become efiective during periods of acceleration and deceleration to change thesettings of the regulators 44 and 45 to compensate for the inertia forces of the reels and reel motors.

When the raise relay 99 was closed to raise the generator voltage, it also, by the closure of its contacts 314, established an energizing circuit for the magnetizing coil 83 of time delay relay 18, which controls the compensating switch 14 when operating in the low speed range. This circuit extends from conductors Z ,in Fig. 3, through conductor315, contacts 314 01' the raise relay, conductor 316, magnetizing coil 83,- conductors 311 and 318 to conductor Y. The establishment of this circuit operates relay 18, thereby opening its contacts 85 to deenergize the compensating switch 14 which permits contacts 14a to close and 14b to open. The closure of contacts 14a decreases the resistance of the coilcircuit of the regulator 45 on the entry'reel motor in order to reduce the generator torque at sumcient amount to compensate for the extra tension that will be applied to the strip in accelerating the inertia of the reel and the reel motor. The opening of contact 1417 increases the resistance of the coil This opcircuit of the regulator 44 on the wind-up side in order to cause the regulator to respond to a greater armature current and thereby produce the additional torque required to accelerate the inertia of the reel and the reel motor.

When the lower relay 98 was operated to decelerate the mill, a circuit was established for operating the time delay relay I9 which controls the operation of the compensating switch I6 when operating in the low speed range. The circuit thus established for the time delay relay I9 ex.- tends from conductors Z in Fig. 3 through conductor 315, contacts 319 on the lower relay 98 to point V in cable 42 through the cable to point V in Fig. 2, magnetizing coil 84 and conductor 318 to conductor Y. This energizes the relay causing it to close its contacts 86, which establishes an energizing circuit for the compensating switch I6 extending from conductor X through contacts 86, closed contacts 291 and the coil of switch I6 to conductor Y. Switch I6 opens contacts 'IBa to now increase the resistance of the coil circuit of the regulator onthe entry side since in this instance, the inertia forces are tending to release the tension on the strip and additional back torque must be developed by the braking generator to compensate for this. This switch closes its contacts 16b to decrease the resistance of the coil circuit of the regulator 44 on the delivery side, since in this instance the inertia forces are acting, so as to increase the tension and, therefore, the torque developed by the reel motor must be reduced a corresponding amount. It is to be understood that during the decelerating periods the compensating switch I4 is energized and contacts I la open and 14b closed.

When it is desired to stop the mill at the end of the pass, the main master switch H8 is actuated to the stop position, 'as shown. At this time, contact finger 330 is disengaged which interrupts the circuit of the brake relay 215 which opens to deenergize the brake It on the delivery reel. 1

When the main master switch I I8 was actuated to the stop position, relay 333, is ,deenergized and. opens its contact 336. However, since these contacts are. bridged by contacts 343 of the relay 342, the energizing circuit for the main motor switch 34 is not interrupted. The opening of contacts 338, however, on switch 333 deenergizes the magnetizing coilof time delay relay 340 thereby causing this relay to open its contact 34I after a predetermined time to deenergize relay 342 which thereupon opens its contacts 343 to interrupt the energizing circuit for the main motor switch 34.

The relay 332, however, was deenergized imme diately upon the actuation of the master switch to the stop position and opened its contacts 344 to interrupt the operating circuit for the reel motor switches 29 and 33. It is, therefore, apparent that the wind-up reel I2 was stopped slightly in advance of the stopping of the main rolls in order to provide sufficient slack in the strip to prevent injury thereto.

. The mill is now stopped with back tension still being applied by the entry reel II. Back tension is still applied because of the fact that the pass selector switch H4 is still in the odd pass position which maintains the set-up relay 66 closed. As will be recalled, this set-up relay was closed before the right reel II was inched to set up the mill and later its motor connected in series with the main booster generator to establish back tension. After this back tension has once been In order now to reverse the mill for the even pass, the pass selector switch H4 must be actuated to the even pass position which deenergizes the set-up relay 66 for the odd pass and energizes the set-up relay I I5 for the even pass.

When the set-up relay 66 is deenergized, it drops open to close all of the back contacts which function to reverse the regulator connections to the booster exciters 39 and 40 and the circuits of the reel motors I1 and I8. That is, the regue lator 45 is now used on the opposite side which becomes the entry side of the mill and its coil'59 is connected across the resistor 26in the main booster generator circuit in the opposite direction through back contacts I]0a and H311. The contact members 5| of the regulator 44 are now connected to the field winding of the auxiliary booster exciter through back contacts I92a and I9Ia. Likewise, the coil 49 of the regulator 44 is now connected across the resistor 61 in the armature circuit of the reel motor II, through back contacts I83a and I86a.

Back" contacts 385 of the set-up relay 66 in Fig. 5, are closed to render the tension relay 236 responsive to the operation of the right reel motor master switch I22 and its back contacts .386 are closed to energize the booster generator switch 30 in Fig. 1 to connect the armature of the'reel motor I8 inseries with the main booster generator 22 in order that this motor may now become the drag generator. This circuit extends from conductor Z in Fig. 6 through conductors 221 and 202, back contacts 386, conductor38'l,

to point X in Fig. 1, ;coil of booster switch 30 and conductor 255 to conductor Y.

Back contacts 386 of set-up relay 66. also esf tablish a circuit for operating relay I05 to reto point X in the cable 4| and through the cable verse the connection of the auxiliary field 24 on and 308 in the auxiliary booster exciter circuits.

Contacts 353, 36I and 334 are'opened to render the left main master II8 ineffective and contacts 353a, 36Iu, and 3340. are closed to render the right main master switch II9 effective to control the operation of the mill. The circuits closed by the operation of the master switch II9. are otherwise the same as described hereinbefore'in connection with the odd pass operation.

The speed selector master switch III on the right side would now be used instead of master 7 switch H6 and assuming that operation in the low speed range was desired, its operation to this position would operate the speed relay 81 to set up exactly the same circuits as described hereinbefore for the odd pass.

Before the even pass may be made, it is again necessary to establish tension on the entry side of the mill. This may be accomplished by the operation of the tension push button I28 which establishes a circuit from conductors Z through the lower contacts of push button I28, conductor 386, closed contacts 381 of the set-up relay H5,

conductor 388, coil of tension relay 26] and tension release pushbutton 266 to conductor Y.

The closure of contacts 269 on tension relay 26! again complete the previously traced ener gizing circuit through the point M on cable 4| and through the cable to point M in Fig. 1 for the switch 29, but switch 33 is not closed in this instance because contacts 270 of the set-up relay 66 are now open. The operation of the switch 29 completes the connection of the armature oi the reel motor I8 and main booster generator 22 to the generator buses.

At this time, the generator is again developing possibly 50 volts in the opposite direction while the booster is developing a higher voltage possibly 90 volts thereby subjecting the reel motor l8 to approximately 40 volts tending to rotate it away from the mill and establish back tension on the strip in the same manner as described in connection with reel motor I! for the odd pass. The tension relay 26I also closes its contacts 21! to again establish the previously traced operating circuit for the brake I 4 on reel l2. closes an interlock 389 to establish an obvious holding circuit in order that it may be held energized when the tension push button I28 is released.

The operation of the mill from this'point on for the even pass is controlled by the master switch H9 over the circuits which have been set up by the opening of the set-up relay 66 and the closure of the opposite set-up relay I I5.

- Operation of the'main master switch H9 to the slow'position sets the mill in operation at its minimum speed in the same manner as described in connection with the odd pass. Acceleration of the mill is effective by operating the master switch to the raise position and to the hold position if it is desired to maintain any particular speed. Since these circuits have already been described in detail in connection with the odd pass, it is deemed to be unnecessary to repeat'the description.

It may be stated in conclusion, that, while the illustrated example constitutes a practical embodiment of my invention, we do not wish to limit ourselves strictly to the exact details herein illustrated, since modifications of the same may be made without departing from the spirit of the invention, as defined in the appended. claims.

We claim as our invention:

1. In a rolling mill, winding and unwinding reels for handling strip material being worked by the mill, dynamo-electric machines for driving the reels, a power source, a booster generator, and means whereby either of said dynamo-electric machines may be connected to the power source to operate as a motor and the other connected to the power source in series with-the booster generator to operate as a braking generator to tension the material, as it is being worked by the mill.

2. The combination with a rolling mill for rollingstrip material having winding reels disposed on opposite sides thereof for winding up and unwinding the strip, of a motor for driving the rolling mill, a source of power, a motor for driving one of said reels to wind upthe strip, a braking generator having driving connection with.

the other reel for exerting a tension on the unwinding strip, and a booster generator having an armature connected in series with the braking generator armature for causing the braking gen- It also erator to return energy to the power source regardless of its speed of operation.

3. The combination with a rolling mill and winding and unwinding strip-handling reels located on opposite sides thereof, of a dynamo-electric machine connected to each reel disposed to function as a driving motor. or a regenerative ing reels positioned on opposite sides of the roll stand for subjecting the material being rolled to tension on both sides of the roll stand, of a motor for driving the roll stand, motors for driving the reels, 2. generator for supplying power to said motors, a booster generator, means for connecting the roll stand motor and one reel motor to the power source, means for connecting the other reel motor to the power source in series with the booster generator, and means including a regulator for each reel motor forcontrolling the excitation of the reel motors to maintain predetermined tensions on the material passing through the roll stand.

5. In combination, a stand of reducing rolls, a main motor for driving the reducing rolls, winding reels on opposite sides of the roll stand for passing strip material back and forth through the roll stand, dynamo-electric machines for driving the reels, 2. ,source of power, a booster generator, means operable to alternatelyconnect one dynamo-electric machine and the main motor to the power source and the other dynamoelectric machine to the power source in series with the booster generator, whereby the dynamoelectric machines on the reels alternately function as motors and back-tension generators to maintain tension on the strip material as it passes back and forth through the reducing rolls,,

and means associated with each dynamo-electric machine and operable in response to the load currents thereof to cause said machines to maintain substantially constant tension on the material.

6. In combination, a stand of reducing rolls, a

main motor for driving the reducing rolls, windmotor to the power source and the other dynamo-electric machine to the power source in series with the booster generator, whereby the dynamo-electric machines on the reels alternately function, as motors and back-tension rial as it passes back and forth through the reducing rolls, and means including a current regulator associated with each dynamo-electric machine operable to regulate the excitation of said machines to maintain a substantially constant tension on the strip material as it passes generators to maintain tension on the strip matewinding reel, a source of variable voltage power for the motors, means for connecting the roll stand motor and one of the reel motors to the power source, a booster generator, and means for connecting the booster generator in series with the other reel motor across the power source, whereby said reel motormay be operated as a drag generator at a voltage less than the power supply voltage and return 1 energy to the power source. 7

8. In combination, a roll stand for working strip material, a main motor for driving the roll stand, winding reels on. opposite sides of the roll stand, dynamo-electric machines connected to said reels, a source of variable Voltage power, a booster generator disposed to be connected in series with eitherone of said dynamo-electric machines across the power source, means operable to connecteither one of the dynamo-electric machines directly across the power source to rotate the reel toward the roll stand while the rolLstand is in a non-operating condition, means operable to connect either one of the dynamo--' electric machines across the power source in series with the booster generator to cause said dynamo-electric machine to function as a motor to rotate the reel away from theroll stand to v exert a back tension on the material before the roll stand is set in operation, and means operable to connect the other dynamo-electric gnachine and the main motor across the power sourceto start the mill-stand, whereby the reel driven by said other-dynamo-e'lectric machine is caused to subject the strip material to apulling tension as it comes through the roll stand and the other reel is caused to drive the dynamo-electric machine in series'with' the booster as a generator to exert a back tension on the material.

9. The combination with a roll standand adapted to alternately wind and unwind material being passed through 'and worked by the /roll stand, a main motor for driving the roll stand, motors connected to each reel adapted to alternately function-as generators and motors dependent upon the direction inwhich the material is moving through the roll stand, a booster generator, a power source, means operable to connect the booster generator in series with the I motor on the unwinding reel across the power source, saidmotor then functioning as a drag generator when the roll stand is operated, means operable to connect the main motor and the winding reel motor to the power source to efifect a rolling operation, a source of excitation for the reel motors, a booster exciter connected in. series with the field 'winding'on each reel motor across the excitation source, and regulators responsive to the load currents of their respective reel booster exciters and thereby theexcitation of the reel motors to maintain predetermined constant tensions on the material between each reel and the roll stand during rolling operations. 1

winding reels on: opposite sides of the stand motors for controlling the excitation of the'.

motor on the unwinding reel across the power source, said motor then functioning as'a drag generator'when the vroll stand is operated, means operable to connect the main. motor and the winding reel motor to the power source to effect citers and thereby the excitation of the reel motors to maintain predetermined constant tensions on the material between each reel and the roll stand during rolling, means operable to change the speed of the main motor, ang the motor on the winding reel, and means responsive to the operation of said speed changing means for changing the characteristics of the regulators to compensate for the inertia forces of the reels and reel motors so that tension on the material will not be varied during periods of acceleration connected to each. reel disposed to alternately function as generators and motors dependent upon the direction of movement of the strip through the roll stand, a variable voltage generator for supplying power to the main motor and dynamo-electric machines, a booster generator, means for connecting the booster genera tor in series with the unwinding reel-dynamoelectri'c machine across the generator to cause the unwinding reel to exert a back tensionvon the strip, means including a master controller operable to one position to connect the main mow tor and the dynamo-electric machine on the winding reel to the generator to cause the strip material to be unwound from the unwinding reel against the drag of the dynamo-electric machine and passed through the roll stand under a back tension while subjected to a pulling tension by the winding reel, and means responsive to the operation of the master controller vto a second position for increasing the generator ,switchesfor connecting the generator field winding to the excitation source in opposite directions, a motor-operated rheostat for controlling the ex-,

citation of the generator, switches operable to connect the main motor to the generator, switches operable to connect the reel motors directly across the generator or either one across the generaj tor in series with the booster generator, whereby the motor connected directly across the generator functions as a winding'motor and the other connected in series with the booster functions as a drag generator when the material is unwound from its associated reel, means including a ourcuits and their field winding circuits, and a main master switch operable to a plurality of positions to start, stop and vary the speed of the mill, said main master switch being operable to a slow position to close the main motor switches and the switches connecting one reel motor directly to the generator and the other reel motor to the generator through the booster generator de raise position to cause the motor-operated rheostat,to raise the generator voltage and change the regulator settings to compensate for inertia forces of the reels and reel motors during acceleration, and back to slow position to cause the motor-operated rheostat to lower the generator voltage and to change the regulator settings to compensate for the inertia forces of the reels and reel motors during deceleration or to a hold position to cause the motor-operated rheostat to hold the voltage at a predetermined value,

- 3 or to a stop position to stop the mill.

13. The combination, with a rolling mill "for rolling stripmaterial and winding and unwinding reels on opposite sides thereof, of a motor connected in driving engagement with each reel toalternately function as motors to place a tension on the strip material as it leaves the mill and as'regenerative braking generators to. place a tension on the material as it enters the mill,

each of said 'reel motors being provided with a I 40 field winding connected across a constant voltage connect one regulator to the circuit of the motor.

driving the winding up reel and its associated booster exciter generator and the other regulator to the'braking generator and its associated boost- 50 or exciter generator, said means having a normal position which connects the regulators to the motors in opposite relation'thereby to always use one regulator on the winding up reel motor and the other on the unwinding reel motor, and means 55 associated with each current regulator for changing its normal adjustment I for different speed ranges of operation of the mill and during periods of acceleration and deceleration of the mill, whereby the tension in the strip on both sides 60 of the mill is maintained constant for all mill speeds and regardless of the inertia forces of the reels and their motors during periods of'acceleration and deceleration of the mill. e 14. In combination, a rolling mill for rolling 65 strip material, a motor for driving the mill, winding and unwinding reels on opposite sides of the mill for handling the strip material, motors connected to the reels, 9. generator for supplying power to mill and reel motors, a booster generator 7odisposed to be connected in series with the reel motor on the entry side of the mill, said reel motor then functioning-as a brakin' generator to tension the strip on the entry si e,-means operable to connect the booster generator and either reel "'5 motor in series across the generator to subject the rent regulator disposed to be associated with each strip to a back tension, means operable to connect the other reel motor and mill motor across the generator circuit to start the mill and cause the reel on the delivery side of the mill to likewise exert a tension on the strip, means includ- 5 ing a current regulator for controlling the excitation of each reel motor, said regulators having operating coils connected to their associated reel motor circuits through resistors to be energized in accordance with the load currents, the resistors 0 being normally adjusted to cause the regulators to maintain constant load currents to maintain constant tension on the strip for constant speed operation, control means for raising and lowering the main generator voltage to accelerate and del5 celerate the mill, means responsive to the operation of said control means to raise thegene'rator pending on the direction of the pass, and toe,

voltage and accelerate the mill for increasing the resistance of the coil circuit of the regulator on the wind-up reel motor and for simultaneously de- 20 creasing the resistance of the coil circuit or the regulator on the entry 'reel generator, and'means responsive to the operation of the control means to decelerate the mill for changing the resistances of the regulator coil circuits in the opposite 25 manner. 15. In combination, a rolling mill for rolling strip material, a motor for driving the'milLa reel for holding the strip material to b unwound from the reel by the mill, a generator connected to said reel disposed to function as a regenerative brake, a main generator for supplying power to the mill motor, said reel generator being connected to the main generator, means including a current regulator for controlling the reelgenerator excitation to control the tension of the strip in accordance with the load current of the reel generator, said regulator being adjusted to maintain a predetermined constant generator current corresponding to the strip tension desired; means operable to vary the maingenerator voltage to accelerate and decelerate the mill motor, and means responsive to said means operable to change the regulator adjustment during the accelerating and decelerating periods to permit an increase in the generator current during deceleration to compensateifor theinertia of the reel and generator and a decrease in generator current during acceleration to compensate 16. In combination, a rolling mill for rolling strip material, a motor for driving the mill, a

reel for holding the strip material to be unwound from the reel by the mill, a generator connected to saidreel disposed to function as a regenerative brake, a main generator for supplying power to the mill motor, said reel generator being connected to the main generator, means including a current regulator for controlling the excitation of the reel generator, said regulator having an operating coil energized through a resistor in accordance with the reel generator current and the resistor normally adjusted to maintain a predetermined constant tension on the strip during constant speed operation of the mill, control means for varying the main generator-voltage to accelerate and decelerate the mm to different speeds, means responsive to ,the operation "01 the control means to accelerate the mill for decreas-' ing the resistance ofthe regulator coil circuit, and means responsive to the operation of the control means to decelerate themill for increasing the resistance of the regulator coil circuit, thereby to compensate. for the additional braking inertia force in the first instance and the additional 15

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