US2223728A - Control system for reversible rolling mills - Google Patents

Description

Dec. 3, 1940. A. F. KENYON I I CONTROL SYSTEM FOR REVERSIBLE ROLLING MILLS Filed July 16, 1938 2 Sheets-Sheet 1 ATTOR Y Dec. 3, 1940. A. F. KENYON- CONTROL SYSTEM FOR REVERSIBLE ROLLING MILLS Filed July 16, 1938 v 2 Sheets-Sheet 2 &

INVENTOR [0/720 Patented Dec. 3, 1940 7 2,223,728 CONTROL SYSTEM ron REVERSIBLE ROLLING MILLS Alonzo F. Kenyon, Wilkinsburg, Pa., assignor to Westinghouse Electric & Man

ufacturlng Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 16, 1938, Serial No. 219,530

14 Claims.

My invention relates, generally, to electric drives and control systems tor rolling mills and, more particularly, to an electric drive and control system for a single stand reversible strip J mill having a reel on each side of the main roll stand.

The present invention is an improvement of the invention disclosed in Patent No; 2,084,035, issued June 15, 1937, to A..F. Kenyon and W. G. Cook. In the system described in the aforesaid patent, a booster generator, of approximately half the voltage rating or the main generator and reel motors, is connected in series with the reel motor that is operating as a braking generator on the unwinding reel to permit the unwinding reel to run at the slower speed than the winding reel necessitated by the reduction in the strip thickness during the passage through the mill rolls. The booster generator must be of the same ampere capacity and approximately half the voltage rating as the reel motors and, therefore, of relatively large size.

An object oi my invention is to provide for reducing the voltage rating and the size of the booster generator in a reversible rolling mill drive.

Another object of my invention is to. provide an electric drive for a rolling mill which is in-. herently suitable for making predetermined reductions in the thickness of the inaterial during each pass through the mill.

A more general object of my .invention is to provide an electric drive for a rolling mill which shall be simple and emcient in operation and which may be economically manufactured and installed.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In practicing my invention, the reel motors of a reversible rolling mill are made double or triple armature, depending upon whether it is ,desired to make reductions up to approximately 50% or 33%% in the thickness of the strip durlng each pass. When the reel motors are-provided with two armatures, they may be so connected. thatkboth armatures are in series on the low speed unwinding reel, and only one armature is utilized on the higher speed winding reel, thus establishing conditions to make reductions up to Likewise, when triple armature reel motors are utilized, they are so connected that the three armatii'res are in series when operating on the unwinding reel and two armatures are connected in series, and the third riotused, 7

on the winding reel, thus establishing conditions to make reductions up to 33.36%. In this manner, the booster generator may be of a low voltage rating, as it is only utilized for RI drop compensation, and for inching and stalled tension during the starting operations.

For a fuller understanding of thenature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a diagrammatic view of one embodiment of my invention wherein double arma ture reel motors are utilized; and,

Fig. 2 is also a diagrammatic view of a modi- 10 fication of my invention in which the reel mo tors are provided with three armatures.

Referring now the drawings, and particularly to Fig. 1, the rolling mill shown therein comprises a roll stand it! and right and left reels H and i2, respectively, for handling a strip of material l3 while it is being worked by the'rolls I0. The roll stand l0 may be driven by a suit-- able direct current motor I havlng'a field winding i5. Likewise, the reels H and 12 may be driven or braked by dynamo-electric machines 16 and II, respectively, which will be described more fully hereinafter. The power for operating the mill motor i4 and the dynamo-electric machines i6 and I1 is supplied by a direct current generator I! having a field winding 19. The current for exciting the field windings of the generator it, the motor 14 and the dynamoelectric machines i6 and II, as well as for operating the control equipment, may be supplied by an exciter 20 or any other suitable power source. The generator l8, the exciter 20, and the booster generator 2!, described later, may be driven by a synchronous motor (not shown) or by any other suitable means.

As explained hereinbeiore, it is desirable to provide a booster generator ii to operate in series with whichever of the reel motors is functioning as a braking generator on the unwinding reel to permit the. unwinding reel to operate at 45 a slower speed than the winding reel. In order to reduce the voltage rating and the size of the booster generator 28, as well as the size of the machines which drive the reels, the-"dynamoelectric machines it and II are each provided so with a plurality of armature windings.

As shown in Fig. 1, the machine It has two armature windings 22 and 23 and two field windings 24 and 25. Likewise, the machine II has two armaturewindings 28 and 21 and two field windings 28 and 29. The armature windings for each machine are mounted on the same shaft. However,

if desired, the machines may be provided with individual shafts which may be coupled together. 5 When the, reel II is operating as the unwind ing reel the armatures 22 and 23 are connected in series-circuit relationand in series with the booster generator 2| across the main generator I8. The armature 21, which drives the winding reel I2 is connected directly across the generator I8, and the armature 26 is not used; If desired, the armature's 26 and 21 may be connected in parallel-circuit relation across the generator I8 to increase the torque on the winding reel. Likewise, when the reel II is the winding reel and the reel I2 the unwinding reel, the armatures 26 and 21 are connected in seriescircuit relation and in series with the booster 2| across the generator I8 while the armature 23, or armatures 22 and 23in parallel, is connected directly across the generator l8.

In this manner, the machines which operate the reels are so connected that the mill is in-- herently suitable for making a reduction of 50% in the thickness of the strip at each pass through the reducing rolls I since the unwinding reel can operate at half the speed of the windin reel and the dynamo-electric machines on the unwinding reel still develop sufficient voltage to 30 regenerate current into the power system, since the armatures of these machines are connected in series.

Therefore, the booster generator is required only for RI drop compensation and for inching and stalledv tension. Hence it can be of a low voltage rating and kilowatt'capacity. As will be explained more fully hereinafter, the booster generator 2| may be utilized for certain-of the inching and stalled tension operations required 40 when thestrip is being threaded through the mill.-

The booster generator 2| is provided with a field winding 3| which is energized from the exciter 20 through a variable resistor 32. Reversing switches 33 and 34 are provided for controlling 45 the polarity of the booster generator. A revers- Jing switch 35 of the drum type is provided for I reversing the polarity of the main generator I8 to control the direction of operation of the mill. The excitation of the generator field I9 and,

50 therefore, the voltage of the generator may be controlled by a variable resistor 36.

Dynamic braking resistors 31, 38 and 39 are provided for stopping the mill motor I4 and the reel motors I6 and II, respectively, in a well 55 known manner. A plurality of electrically oper-, ated switches or contactors 4| to 46 inclusive, are provided for establishing the proper motor and generator connections during the operation of the mill; The operation of the foregoing contactors 60 may be controlled by a drum switch 48. The

usual; inching and stalled tension operations for' threading the strip I3 through the mill stand may, be controlled by push-button switches 41, 52; and 53.

65 In order to hold. the strip tension at a predetermined amount, the excitation of the field wi n dings of the reel motors is governed by cur-" rent regulators 54 and 55, which maybe of any suitable type, as, for example, the well known 70 vibrating regulator. The actuating'coils of the regulators 54 and 55 are energized from shunts 56 and' 51, respectively, in accordance with the load currents of the reel motors or generators, thereby holding thesecurrents and, therefore, 75 the strip tension within predetermined limits.

In order that the functioning of the foregoing apparatus may be more clearly understood, the operation of the system will now be described in more detail.

It may be assumed that the main generator I8,

the exciter 20, and the booster generator 2| are operating-at the required speed. It is also assumed' that 'a variable resistor 58 has been adjusted to provide the proper voltage on the exciter 20 for the excitation of the machines utilized during the operation of the mill. It is further assumed that a coil of strip material to be rolled has been placed on the reel driven by the dynamo-electric machine I6. Therefore, the,

first pass through the mill will be from right to left, as viewed in Fig. 1. Accordingly, the drum switch 35 is actuated to the'left to provide the proper polarity of the main generator I8 for rolling the strip from right to left, Furthermore, the variable resistor 36 should be adjusted to provide a reduced voltage on the main generator I8. during the inching operations which are required for threading the strip I3 through the mill.

The reel I I may be inched to permit the end of the strip I3 to be advanced to the rolls ID by closing the push-button switch 5|, thereby closing the contactors 44 and 46 and the field reversing switch 34 to cause the main generator I8 and the booster generator 2| to supply power for driving the reel I I in the desired direction. The energizing circuit for the actuating coil of the contactor 44 may be traced from the positive terminal of the exciter 20 through conductor 6|, the actuating coil of the switch 44,

conductor 62, contact members 63 of the pushbutton switch 5|, conductor 64 and conductor 65 to the negative terminal of the exciter 20. The energizing circuit for the actuating coil ,of the switch 46 extends from the previously energized conductor 6| through conductor 96, the coil of the switch 46, conductors 91 and 61, contact members 68 of the push-button switch 5|, and conductor 64 to the negative conductor 65. The

energizing circuit for the actuating coil of the reversing switch 34 extends from the positive 'conductor 6| through conductor 69, the coil of the switch 34, conductors II and I2, contact members I3 on the switch 5| and conductor 64 to the negative conductor65. I V

The closing of the field reversing switch 34 connects the field winding 3| ofthe booster generator 2| across the exciter 20 through a circuit 4 which may be traced from the positive terminal of the exciter through conductors 6| and "I4, the adjustable rheostat 32, contact members I5 of the reversing switch 34, conductor I6, the field winding 3|, a conductor I1, contact members I8 and conductor 19' to the negative conductor 65.

Ther'eforathe field winding 3| of the booster the contact members 86 of the switch 44, con

ductor 85, the armature winding 22, conductor 84, the armature winding 23, conductor I35, the shunt 56, conductor I64, the switch 46 and connerwinding 25, conductor 88, the field winding 24,

conductor 89, a variable resistor 3| and the conductor 65 to the' negative terminal of the exciter 20. At this time the rheostat 32 should be adjusted to cause the booster 2| to generate a relatively low voltage since the booster voltage is added to the main generator voltage, which is below normal.

When it is desired to thread the strip I3 through the rolls II), the mill motor I4 may be inched by closing the push-button switch 52 to operate the contactors 4| and 46. The energizing circuit for the actuating coil of the contactor 4| may be traced from the positive conductor 6| through conductor 92, the coil of the switch 4|, conductor 93, contact members 94 of the push-button switch 52 and conductor 96 to the negative conductor 66. The energizing circuit for the actuating coil of the switch 46 extends from the positive conductor 6| through conductor 66, the actuating coil of the switch' 46, conductor 91, contact members 68 and conductor 96 to the negative conductor 66.

The closing of the switches 4| and 46 connects the armature winding of the mill motor I4 across the main generator I8 to drive the rolls ill. However, in view of the reduced voltage of the generator I3, the rolls are driven at a relatively slow speed. The energizing circuit for the armature vanced to the winding. reel I2.

winding I4 may be traced from the one terminal of the main generator "through conductors IIII and 8| to the armature of the mill motor I4, conductor I02, the contact members I33 of the switch 4|, conductor I04, the switch 46 and conductor I05 to the other terminal of the generator II. The field winding I! of the mill motor I4 is connected across the exciter 20 through a circuit which extends from' the positive terminal of the exciter 20 through conductor 6|, the field winding I5 and conductor 65 to the negative terminal of the exciter 23.

By inching the mill motor in the manner just described, the end of the strip I3 may be ad- If it is necessary to rotate the reel I2 in order that the strip may be properly clamped in the reel in the usual manner, the left reel motor may be inched by closing the push-button switch 63 to operate the switches 42 and 46, thereby connecting the armature winding 21 across the main generator I3. The energizing circuit for the switch 42 may be traced from the positive conductor 6| through conductor I36, the actuating coil of the switch 42, conductor I", contact members I08 of the push-button switch 53 and conductor I 39 to the negative conductor 66, The energizing circuit for the switch 46 extends from the previously'energized conductor 36 through the actuating coil of the switch 46, conductor 31, contact members 8, and the conductor I03 to thenegative conductor 46.

The closing of the switches 42 and 46 energizes the armature winding 21 of the dynamo-electric machine I'I through a circuit which extends from the one terminal of the main generator I3 through conductors IOI, 8| and 82, contact members III of the switch 42, conductor 2', the armature winding 21, conductor I I3, the shunt II, conductor I34, the switch 46 and conductor I36 to the other terminal of the generator I8. At this time, the field winding 23 of the dynamo-electric machine I1 is energized through a circuit which extends from the positive conductor 6| through conductor II4, the field winding 29, conductor II5, contact members II6 of the switch 42, conductor III, a

variable resistor H6 and conductor 9 to the negative conductor 65.

As soon as the end of the strip has been entered into the mill, the stalled tension pushbooster to a higher value than the main generator in order to reverse the current in the reel motor I6.

After the strip 43 is clamped in the reel I2, the rolling operation may be performed. As explained hereinbefore, the dynamo-electric machine I! functions as a motor to wind the strip I3 on the reel l2 and the machine I6 functions as a braking generator to apply tension on the strip I3 during the rolling operation. Furthermore, the armature windings 22 and 23 of the dynamo-electric machine I6 are connected in series-circuit relation in order that the reel I I may operate at onehalf the speed of the reel I2 and the machines I6 still generate sufiicient voltage to cause current to be returned to the power system. In this manner, the booster generator 2| which is connected in the circuit with the armatures 22 and 23 is required only for RI drop compensation as the strip is transferred from one reel to the other during a rolling operation in which a reduction of approximately 50% in the thickness of the strip is obtained for each pass through the rolls ID.

The operation of the mill at this time is controlled bythe drum switch 48 which is actuated toward the left, as indicated on the drawings, when the strip is being rolled from the right to the left. At this time, the contactors 4|, 42, 44 and 46 and the booster field reversing switch 33 are closed to establish the necessary-connections tive conductor 6| through conductor I06, the actuating coil of the switch 42, conductor I01, contact segment I24, and conductors I22 and I23 to the negative conductor 65. The energizing circult for the contactor 44 extends from the positive conductor 6| through the actuating coil of the switch 44, conductor 62, contact segment I25,

conductors I26 and I23 to the negative conductor 66. The energizing circuit for the switch 46 may be traced from the positive conductor 6| through conductor 36, the actuating coil of the switch 46, conductor 31, contact segment I21 and conductor I23 to the negative conductor 65. The actuating coilof the reversing switch 33 is energized through a circuit which extends from a positive conductor 6| through conductor 69, the coil of the switch 33. conductor I23, contact segment I23 and conductor-s I26 and I23 to the negative conductor 65..

The closing of the switch 33 energizes the field winding 3| tocause thebooster generator 2| to generate a potential which is'added to that produced by the dynamo-electric machine I6 which is connected across the main generator I3 and terminal of the generator I8 through conductors IIII and 8|, the armature winding, I4, conductor I82, thecontact members I 83 of the switch 4|, conductor I84, the switch 46, and conductor I to the other terminal of the generator I8. At this time, the resistor 36 should be adjusted to raise the generator voltage I8 to its normal value, thereby maintaining normal speed of the mill motor I4 during the rollingoperation.

The closing of the contactor 42 connects the armature winding 21 of the dynamo-electric machine I1 across the main generator I8 to oper- Since the energizing circuit -for'the armature 21,

established by the closing of the switch 42, has

' been previously traced, it will not be retraced at this time.

The closing of the switch 44 connects the armature windings 22 and 23 inseries-circuit relation and in series with the booster generator 2| across the main generator I8, thereby causing the dynamo-electric machine I6 to function as a braking generator, The circuit through the armatures 22 and 23 may be traced from the one terminal of the armature 22 through conductor" 85, the contact members 86 on the switch 44, conductor 81, the booster'generator 2|, conductor IIII, the main generator I 8, conductor I05, the

switch 46, conductor I 04, the shunt 56, conductor I35, the armature 23 and conductor 84 to the other terminal of the armature 22.

As explained hereinbefore, the regulators 54 and control the field excitation of the dynamo-electric machines I6 and I1 during the rolling operation to maintain the motor,current within a predetermined limits, thereby regulating the tension on the strip I3. As shown, the actuating coil of the regulator 54 is connected across .the

shunt 56 and it, therefore, responds to the current flowing through the armatures 22 and 23. The contact members of the regulator are disposed to shunt the resistor 9| from the field ex- 55 citation circuit of these machines when in the position shown in thedrawing, thereby providing maximum excitation on the machines and causing them to generate maximum current. The shunt circuit around the resistor 9| extends from 86 the terminal of the resistor 9| through conductor I36, contact members I31 and I38 of the regulator 54, conductor I39, contact segment I of the drum switch 48 and conductors I42 and I23 to the negative'conductor 65. When the current in the shunt 56 exceeds a predetermined value, the actuating coil of the regulator opens the contact members I31 and I38, thereby inserting the resistor 9| in the field winding circuit and reducing the excitation on the machines to reduce the generated current.

Likewise, the regulator 55 functions to control the current flowing through the armature 21, thereby controlling the tension applied to the strip I3 by the motor I1. When the regulator 55 is in the positionshown in the drawings, the reaaaavas functions as a braking generatorduring the roll- Theclosing of'the switches 4| and 45 connects ate the reel I2 to wind the strip I3 on the reel.

sistor H8 is connected in' the excitation circuit for the field winding 29 of the motor I1, thereby providing minimum excitation and maximumspeed of the motor. It the current drawn by the motor flowing through the shunt 51 exceeds a predetermined value, the actuating coil otthe regulator 55 closes contact members I43 and I44 of the regulator to shuntthe resistor '8 from the field winding circuit, thereby increasing the excitation on the motor and decreasing its speed .which, in turn, decreases the tension applied to the strip I3. The shunt circuit for the resistor I I8 extends from the conductor I I1 through conductor I45, the contact members I43 and I44 of the regulator 55, conductor I46, contact segment I41, and conductors I48 and I23 to the, negative conductor 65. In this manner, a tension on the strip I3 is maintainedwithin, predetermined limits during the rolling operation.

When it is desired to stop the mill at the end of thepass, the main control switch 48 may be actuated to the off position thereby deenergizing the switches 4|, 42, 44 and 45 to disconnect the machines I5 and I1 and the mill motor I4 from the main generator I8 and also to apply dynamic braking to'the mill motor I4 and the machines I6 and I1. Atthis time, the switch 35 may. also be actuated to the 011 position to remove the excitation from the main generator I8.

The dynamic braking circuit for the mill motor I4 may be traced from one terminal of the. armature I4 through conductor 8|, the dynamic braking resistor 31, contactmembers I5I of'the switch 4| and conductor I02 to theot'her terminal of the armature I4. The dynamic braking circuit 35 for the dynamo-electric machine .I1 may be traced from one terminal of the armature 21 I through conductor II2, the'armature 26, conductor II3 to the other terminal of the armature 21. The dynamic braking circuit for the dynamo-electric machine I6 may be traced from one terminal otthe armature 22 through conductor 85, the'dynamic braking resistor 38, contact members I56 of the switch 45, conductor I51, contact members I58 of the switch 44, conductor I35, the armature winding 23 and conductor 84 to the other terminal of the armature 22. v

Assuming that the mill has been stopped before the .end of the strip I3 has left the reel I I, the' mill may be reversed to r 11 from left to right by simply actuating the switch 35 toward the right to reverse the polarity of the maingenerator I8, thereby reversing the direction of operation of the mill motor I4 and the reelmotors I6 and I1, and also actuating the switch 48 toward the right to energize the actuating coils of the switches 4 I, '43, 45, 46 and the reversing switch 34 to establish the proper connections for rolling from left to right. The energizing circuit for the switch'4I may be traced from the positive conductor 6| through conductor 92, the actuating coil of theswitch 4|,conduotor 93, a contact segment I6I on the switch 48 and conductors I22 and I23 to the negative conductor 65. The energizing circuit for the switch. 43 may be traced from the positive conductor 6| through conductor I62, the actuating coil of the switch 43, conductor I63, contact segment I64 and conductors I65 and {I23 tothe negative conductor 65. The energizing circuit for the switch 45 extends from the positive conductor 6| through conductor 66, theactuating coil of the switch 45, conductor I66, contact seg- 14 ment I61, and conductors I68 and I23 to the .ductor 6| through conductor 69, the actuating coil of the switch 34, conductors 1i and 12, contact segment I?! and conductors W5 and I23 to the negative conductor 65.

The closing of the switches 4| and 46 connects the mill motor 54 across the generator I8 in the manner described hereinbefore to operate the rolls I0. The closing of the switch 45 connects the armature winding 23 across the generator I8 to drive the reel I i, which now becomes the winding reel. The-circuit for the armature winding 23 may be traced from one terminal of the generator I8 through conductors 1|, 6|, and 82, contact members I12 of the switch 45, conductors I13 and 84, the armature winding 23, conductor I35, the shunt 56, conductor I05, the switch 46 and conductor I05 to the other terminal of the generator I8. At this time, the field winding 25 is energized through a circuit which extends fromthe positive conductor 6| through the field winding 25, conductor 88, contact members I14 of the switch 45, conductor 89 and the resistor 9| to the negative conductor 65.

Since the reel I2 now becomes the unwinding reel, the armatures 26 and 21 of the dynamoelectricmachine I1 are connected in series-circuit relation in order that the machine I1 will function as a braking generator in the manner hereinbefore described to apply a tension on the strip I3. The circuit through the armature windings 26 and 21 may be traced from one terminal of-the armature 26 through conductor I52, contact members I15 of the switch' 43, conductor 81, the booster generator 2|, conductor "II, the generator I8, conductor I05, the switch 46, the shunt 51, conductor 3, the armature winding 21 and conductor I I2 to the other terminal of the armature winding 26.

The regulators 54 and 55 function to control the motor current during the rolling operation in the manner hereinbefore described. The contact members I43 and I16 of the regulator 55, which is now controlling the dynamo-electric machine I1 which is now functioning as a generator, es-

tablish a shunt' circuit for the resistor ||8,

conductor I11, contact segment I18 and con-.

ductors I48 and I23 to the negative conductor 65.

When the current through the armature winding 23 of the reel motor I6 is sufficient to cause the regulator 54 to close its contact members I31 and I19, a shunting circuit is established for the resistor 9| to increase the excitation of the motor 23, thereby reducing its speed and decreasing the tension applied to the strip I3 in the manner previously described. The shunting circuit for the resistor 9| may be traced from the conductor 89 through conductor I36, contact members I31 and I19, conductor |8| contact segment I82, and conductors I42 and I23 to' the negative conductor 65'.

The mill may be stopped at the endof the pass by actuating the switch 48 to the oil position to v in Fig. 1.

apply dynamic braking to the motors in the manner hereinbefore described. If it is desired to reverse the mill in order to perform another rolling operation upon the strip of material,|3,'

the switches 35 and 48 are actuated toward the left. If the strip has been reduced to the desired thickness, the reel containing the strip may vtionis performed as previously explained.

The modification of the invention shown in Fig. 2 is similar to the structure shown in Fig. l, with the exception that the dynamo-electric machines I6 and I1 are eachlrovided with three armature windings instead of two, ,as in the system shown During the rolling operation, two of the armature windings on the winding reel are connected in series and all three of the armature windings on the unwinding reel are connected in series, thereby establishing conditions to make reductions up to 33 in the thickness of the strip I3 during each pass through the mill instead of 50% as in the system shown in Fig. 1, in which double armatures are used. In the system shown in Fig. '2, the elements of apparatus which are similar in structure and perform the same functions as in the system shown in Fig. l are designated by the same reference characters. Therefore, it is believed to be unnecessary to repeat the description of this apparatus at this time.

In addition to the swtich 4| which connects the mill motor I9 across the generator I8 as hereinbefore described, switches I83, I85, I81, I88, I89 and I96 are provided for establishing the proper connections for the machines during the operation of the mill. The dynamo-electric machine I6 is provided with armature windings I9I, I92, and I93 and field windings I94, I95 and I96.

' Likewise, the dynamo-electric machine I1 is provided with armature windings I91, I98 and I99 and field windings 20I, 202 and 203.

In addition to the push-button switches 5|, 52 and 53, which may be utilized to control the inching operations, the push-button switch 41 may be utilized to provide a stalled tension condition of the unwinding reel II when the mill is being put into operation. The current for operating the reel motor I6 is supplied by'the booster generator 2| during the stalled tension-condition. The current for inching the reel motors I6 and I1 is also supplied by the booster generator 2|.

Assuming that the reel containing the strip of material I3 which is to be rolled by the rolls I0 has been placedon the shaft driven by the motors l6 and that the generator I8, the exciter 20 and the booster generator 2| are being driven at the proper speed, it is first necessary to actuate the switch 35 toward the left to provide the proper polarity of the generator I8 for rolling from right to left. Furthermore, the voltage of the generator I8 should be set at a relatively low value by means of the resistor 36 during the inching operations, after which the voltage should be raised to the normal value to perform the rolling operations.

The reel I I may be inched to advance the strip I90, conductor 206, contact members 201 of the switch 5| and conductor 209 to the negative conductor 65. The energizing circuit for the switch 34 may be traced from the positive conductor 6| to conductor 209, the actuating coil of the switch 34, conductor 2| I and contact members 2 I 2 oi'the switch 5| to the negative conductor 65.

The closing of the switch 34 connects the field winding 3| of the booster generator across the exciter 20, thereby providing excitation for the booster generator. The energizing. circuit for the field winding 3| maybe traced from the positive conductor 6| through conductors 2 I3- and 2|4, contact members 2|5 oi the switch 34, the field winding 3|, contact members 2|6, conductor 2 I 1, the resistor 32 and conductor 2 I 9 to the negative conductor 65. The closing of the switch I90 'from one terminal of the booster generator through conductor 22I, contact members 222 of the switch I90, conductor 223, the armature winding I93, conductor 224 to the armature winding I92, conductor 225, the armature winding I9I, conductor 220, the shunt 56, conductors 226 and 221 to the other terminal of the booster generator 2|.

At this time, the field windings for the machine I6 are connected across the exciter 29 through a circuit which may be traced from the positive conductor 6| through the resistor 9|, conductor 229, field winding I99, conductor 229, field winding I95, conductor 23L the field winding I96 and conductor 232 to the negative conductor 65. Therefore,'the machine I6 will operate the reel II to advance the strip I3 toward the rolls I0. I

When it is desired to thread the strip I3' through the rolls III, the mill motor It may be inched by closing the push-button switch 52, thereby energizing the actuating coil of the switch 9| and causing this switch to connect the mill motor across the main generator I9. The energizing circuit for the switch 9| may be traced from the positive conductor 6| through conductor 233, the actuating coil of the switch 9|, conductor 239, the push-button switch 52, and conductor 209 to the negative conductor 65.

The closing of the switch 9| connects the mill motor I9 across the'generator I9 through a circuit which may be traced from one terminal'of the generator I9 through conductor 295, the armature of the mill motor I9, conductor 236, contact member I03 of the switch II I and conductors 231 and 239 to the other terminal of the generator I9.

At this time, tension may be applied to the I strip I9 by closing the push-button switch 91 to energize the switches I90 and 99, thereby connecting the reel motor I9 across the booster generator 2| and reversing the polarity of the booster to reverse the direction of operation of the reel II. The energizing circuit for the switch I99 extends from the positive conductor 9| through conductor 295, the actuating coil of the switch I90,'conductor 296, the contact members 2* of the push-button switch 91 and conductor 292 to the negative conductor 95. The energizing circuit for the reversing switch 99 may be traced from the positive conductor 9| through conductor 299, the actuating coil of the switch 99, conductor 293, contact members 299 and conductor 292 to the negative conductor 55. Closing the switch I99 connects the motor I6 across the boostergenerator 2| through a circuit previously traced. Therefore, the motor will operate to take actuating coil of the switch I99, contact members 246 of the push-button switch-53 and conductor 241 to the negative conductor 65. The energizing circuit for the switch 34 extends from the positive conductor 6| through conductor 209, the actuating coil of the switch 34, conductors 2| I and 246, the contact members 249 of the switch 53 and conductor 241 to the negative conductor 65.

The closing of the switch 34 energizes the field winding 3| through a circuit previously traced.

The closing of the switch I99 connects the motor I1 across the booster generator 2| through a circuit which may be traced from one terminal of the booster-generator through conductors 22| and main generator I9 to drive the winding reel I2 and also connecting the three armatures of the dynmo-electric machine I6 in series-circuit relation and in series with the booster generator 2| acrdss the main generator I9 to function as braking generator for the reel II. The energizing circuit for the switch 4| extends from the positive conductor 6| through conductor 233, the actuating coil of the switch 9|, conductor 234, a contact segment 258, on the switch 49, and conductor 2 59 to the negative conductor 65. The energizing circuit for the switch. I93 extends from the positive conductor 6| through conductor 245, the actuating coil of the switch I93, conductor 26 I, the contact segment 262 and conductor 259 to the negative conductor 65. The energizing circuit for the switch I91 may be traced from the positiveconductor 6| through conductor 263, the actuating coil .of the switch I91, conductor 264, a contact segment 265, and conductor 266 to the negative conductor 65.

The closing of the switch 4| connects the mill motor I9 across the main generator I9 through a circuit previously traced. The closing of the switch I99 connects the armatures I91 and I99 of the dynamo-electric machine I1 in series-circuit'relation and across the generator I9 through a circuit which may be traced from one terminal of the generator through conductors 235, 251 and 299, contact members 269 of the switch I93, conductors HI and 255, the armature winding I99, conductor 259, the armature winding I91, conductor 252, the shunt '51, conductor 212, contact members 219 of the switch I93, conductors-214 the main generator I8 thereby causing this machine to regenerate current into the power system andfunctionas abrakeon the coil II to apply tension to the strip I3 during the rolling operation. The circuit through the armature windings of the machine I6 may be traced from one terminal of the generator I8 through the conductors 238, 281 and 268, the contact members 288 of the switch I83, conductors 2H and 215, contact members 218 of the switch I81, conductors 211 and 223, the armature winding I83, cond ctor 24, armature winding I82, conductor 225, t e armature winding I9I, conductor 228, the shunt 55, conductors 228 and 221, the booster generator 2i, conductors 22I, 25I and 212, contact members 218 of the switch I83 and conductors 214 and 238 to the generator I8.

In this manner, the machine I1 drives the reel I2 to wind the strip on this reel and the machine I8 functions as a braking generator for the reel Ii. of the armatures of the machine H are connected in series while three of th armatur windings of the machine It are connected in series during the rolling operation from right to left, the system is inherently suitable for reductions up to 33 /3% in the thickness of the material for each pass through the rolls I8, since the machine I8 will operate at of the speed of the motor I 1 with the same voltage. As in the system shown in Fig. 1, the booster generator is, therefore, required only for the RI' drop compensation and for variations in the size of the reels as a result of the transfer of material from one reel to the other. The booster is also utilized for the inching and stalled tension operations, as described hereinbefore.

It will be noted that the armature I88 is not utilized when the mill is rolling from right to to apply dynamic braking to the mill motor I4 and the reel motors I6 and I1. The dynamic braking circuit for the mill motor I4 extends from one terminal of the motor through conductor 238, contact members I5I of the switch,

the resistor 31 and conductor 281 to the other terminal of the motor I4. The dynamic braking circuit for the reel motor I1 may be traced from one terminal of the armature winding I88 through conductors 255 and 28 I contact members 282 on the switch I81, conductor 283, contact members 284 on the switch I88, conductor 285,

contact members 288 on the switch I83, conductor 281, the resistor 38, conductor 252, the armature winding I81, conductor 253, armature winding I88 and conductor 254 to the other terminal of the armature winding I88. The braking circuit for the motor I8 may be traced from one terminal of the armature winding I83 through conductors 223, 211 and 288, contact members 288 on the switch I88, conductor 28I, contact members 282 on the switch I88, conductor 283, contact members 294 on the switch I85, conductor 285, the resistor 38, conductor 228, armature winding I8I, conductor 225, the armature winding I82 and conductor 224 to the other terminal of the armature winding I83.

roll the material from left to right by actuating In view of the fact that only two the switch 48 to the right and also the switch 35 to the right to reverse the polarity of the main generator I8. When the mill-is rolling from left to right, the reel II becomes the winding reel and the reel i2 the unwinding reel and the operation of the switch 48 to the right energizes switches 4i, I85 and W8 to connect the mill motor M to the main generator and establish the proper connections for the machines I6 andi1..

The energizingcircuit for the switch 85 may be traced from the positive conductor 8! through conductor 238, the actuating coil of the switch 59,

conductor 238, a contact segment 285 on the switch 48 and conductor 258 to the negative conductor 55. The energizing circuit for the switch I85 may be traced from the positive conductor 5i through conductor 285, the actuating coil of the switch i85, conductor 28?, contact segment 288 on the switch 88 and conductor 288 to the negative conductor 85. The energizing circuit for the switch i88 extends from the positive conductor 5i through conductor 283, the actuating coil of the switch I88, conductor 88H, a contact segment 882, and conductor 288 to the negative conductor 85.

The closing of the switch 89 connects the mill motor Id across the generator I8 through a circuit previously traced. The closing of the switch I85 connectstwo of the armature windings of the machine I8 across the main generator to drive the reel ii. The circuit for the motor I8 may be traced from one terminal of the generator I8 through conductors 235, 281, and 268, contact members 883 on the switch I85, conductors384 and 228, the armature winding E92,

conductor 225, the armature winding I8I, c0n' ductor 228, the shunt 56, conductor 385, contact members 386 on the switch I85 and conductor 238 to the other terminal of the generator Q8.

The closing of the switch I88 connects all three of the armature windings of the machine I1 in series-circuit relation and in series with the booster generator 2I across the main generator I8. The circuit through the machine I1 may be traced from one terminal of the generator I8 through conductors 235, 281 and 288, the contact members 383 of the switch I85, conductors 38.4 and 381, contact members 888 on the switch I88, conductors 388, 28I and 255, the armature winding I88, conductor 254, the armature winding I88, conductor 253, the armature winding I81, conductor 252, the shunt 51, conductors 212, 25I and HI, the booster generator 2I, conductors 221,228 385, the contact members 388 of the switch I85 'andconductor-238 to the other terminal of the generaton wl i In this manner, the. dynamo-electric machine I8 functions .as a motor to drive the reel II and the machine I1 functions as a braking generator for the reel I2, thereby applying tension to the strip I3. The armature winding I83 does not function during this operation since its corresponding field winding I88 is shunted fromthe excitation circuit by a contact member 3 on the switch I85.

The switches 33 and 34 function to reverse the polarityof the booster generator in the manner hereinbefore described. Therefore, it is believed to be unnecessary to describe further their operation at this time. Likewise, the regulators 54 and 55 control the tension applied to the strip I3 by regulating the current in the excitation circuits for the machines I8 and I1 during the operation of the mill, as described hereinbefore.

The mill may ,be stopped at the end of the pass by actuating the switch 48 to theofi position to apply dynamic braking to the motors as previously described. Ifit is desired to reverse the operation of the mill to roll the sheet again from right to left, the switches 35 and 48' areactuated to the left and the operation of the mill repeated. In this manner, the strip may be rolled until the desired thickness is attained, it being' understood that the rolls l0 may be screwed down between passes by any suitable means.

From the foregoing description, it is apparent that I have provided a rolling mill drive which is inherently suitable for making predetermined reductions in the thickness of the strip for each pass through the. mill. Furthermore, I have provided a system of operation which makes it possible to utilize a booster generator of a relatively low voltage rating and also to utilize machines of a smaller dimension for operating the winding reels.

Since many modifications may be made in the apparatus and arrangement of parts, without' departing from the-spiritof my invention, I do not wish to be limited other than by the scope of the appended claims.

I claim as my invention:

1. In a rolling mill, in combination, win and unwinding reels for handling strip material being worked by the mill, a power source, dynamo-electric m.achines for driving the reels, each of said machines having a plurality of armatures, and means for connecting certain ones of the armatures of either of said machines to the power source to operate as motors only and certain ones of the armatures of the other machine to the power source to operate as braking generators to tension the material while it is being worked by the mill.

2. In a rolling mill, in combination, winding and unwinding reels forhandling strip material being worked by the mill, a power source, a plurality of dynamo-electric machines for driving each of the reels, and means for connecting certain ones of the machines for either of said reels to the power source to operate as motors only and certain ones of the machines for the other reel to the power source to operate as braking generators to tension the material while it is being worked by the mill.

3. In a rolling mill, in combination, winding and unwinding 'reels for handling strip material being worked by the mill, a power source, dynamo-electric machines for driving the reels, each of said machines having a plurality of armatures, and means for connecting a portion of the armatures of either machine to the power source to operate as motors only and all of the armatures of the other machine to the power source operate .as braking generators to tension the material while it is being worked by the mill.

4. In a rolling .mill, in combination, winding and unwinding reels for handling strip material being worked by the mill, a power source, a plurality of dynamo-electric machines for driving each of the reels, and means for connecting a portion of the machines for either of said reels to the power source to operate as motors only and all of the machines for the other reel to the power source to operate as braking generators to tension the material while it is being worked by the mill. v

5. In a. rolling mill, in combination, winding and unwinding reels for handling strip material being worked by themill, a power source,

. dynamo-electric machines for driving the reels,

escapes armatures, and means for connecting a portion or the armatures or either machine to the power source to operate as a motor and for connecting the armatures of the other machine to the power 6. In a rolling mill, in combination, winding and unwinding reels for handling strip mate-, rial being worked by'the mill, 9. power source, a

, plurality of dynamo-electric machines for driving each of the reels, and means for connecting a portion of the machines for either of said reels to the power source to operate as motors, and for connecting all of the machines for the other reel to the power source in series-circuit relation to operate as braking generators to tension the material while it is being worked by the mill.

7. In a rolling mill, in combination, winding and unwinding reels for handling strip material being worked by the mill, a'power source, a booster generator, dynamo-electric machines for driving the reels, each of said machines'having a plurality of armatures, and means for connecting a portion or the armatures or either machine directly to the power sourceto operate as motors and for connecting the armatures of the other machine to the power source in series-circuit relation and in series with the booster generator to operate as braking generators to tension the material while it is being worked by the mill.

8. In a rolling mill, in combination, winding and unwinding reels for handling strip material being worked by the mill, a power source, a booster generator, a plurality of dynamo-electric machines ior driving each of the reels, andmeans for connecting a portionoi the machines for either 01' said reels directly to the power source to operateas motors and for connecting all of the machines for the other reel to the power source in series-circuit relation and in series with the the other machine as a braking generator, the armatures of the machine which is operating as a generator being connected to the power source in series-circuit relation.

v10. In a rolling mill, in combination, ng and unwinding reels for handling strip material being worked by the mill, a power source, a booster generator, dynamo-electric machines for driving the reels, each of said machines having a plurality of armatures, and means for operating either of said machines as a motor at the voltage of the power source and the other machine as a braking generator, the armatures of the machine which is operating as a generator being. connected to the power source in series-circuit relation and in series, with said booster generator. I

11. The combination with a. rolling mill and winding and unwinding reels on opposite sides thereof, of a dynamo-electric machine connected to each of said reels adapted to serve as a driv-' ing motor or as a regenerative brake therefor,

each of said machines having a plurality of armatures, a source of power, a booster generator, and

means for connecting the booster g'ra across of the armature windings oi the dynamo-electric machine functioning as the regenerative brake to cause the voltages developed by each to be added,

thereby permitting the braking machine to operate at a slower speed than the motoring machine. 12. The combination with a rolling mill and winding and unwinding reels on opposite sides thereof, of a dynamo-electric machine connected to each of said reels adapted to serve as a driving motor or as a regenerative brake therefor, each of said machines having a plurality of armatures, a source of power, a booster generator, means for operating the dynamo-electric machine functioning as a motor at the voltage of the power source, and means for connecting the booster generator across the power source in series-circuit relation with all of the armature windings or the dynamo-electric machine functioning as the regenerative brake to cause the voltages developed by each to be added, whereby said braking machine may operate at a slower speed than the motoring machine and regenerate power into the power source.

13. The combination with a rolling mill and winding and unwinding reels for handling strip material being worked by the mill, of a dynamoelectric machine connected to each of said reels, one oi said machines functioning as a motor and the other as a braking generator, each of said machines having a plurality of armatures, a source of power. a booster generaton'and means for connecting said machines to the power source, said generating machine having a greater number of armatures connected to the power source in series-circuit relation than said motoring machine, said booster generator being also connected 10 in series-circuit relation with the armatures of said generating machine.

14. The combination with a rolling mill and winding and unwinding reels for handling strip material being worked by the mill, 0! a dynamoelectric machine connected to each of said reels, one of said machines functioning as a motor and the other as a braking generator, each of said machineshaving a plurality of armatures, a

source of power, a booster generator, means for operating the motoring machine at the voltage or the power source, and means for connecting the armatures of the generating machine to the power source in series-circuit relation and in series with the booster generator.

ALONZO F. KENYON.

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