US2281063A - Control system - Google Patents

Description

Apfil 28, 1942. w. G. COOK CONTROL SYSTEM Filed Nov. 29, 1939 2 Sheets-Sheet l ti Q INVENTOR 1 ///0/'a G. 600K.

WITNESSES:

: It! ATTORNEY April 28, 1942. w. e. COOK 2,281,063

CONTROL SYSTEM Filed Nov. 29, 1939 2 Sheets-Sheet 2 WITNESSES: INVENTOR MWO/"O G 60 OK, fi I Patented Apr. 28, 1942 UNITED STATES PATENT OFFICE CONTROL SYSTEM Willard G. Cook, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania 13 Claims.

This invention relates, generally, to control systems, and, more particularly, to systems for controlling the tension on strip material as it is being passed through a rolling mill.

In the operation of steel strip rolling mills it is desirable that back and front tensions be applied to the strip as it enters and leaves the working rolls. In some instances it is highly desirable to maintain front and back tensions on the strip of greater magnitude than can be applied through the winding and unwinding reels. It has become the practice, therefore, to provide tensioning devices between the unwinding reel and the working rolls and between the working rolls and the winding reel which will function to provide much higher front and back tensions at the working rolls than the winding and unwinding reel tensions. One such tensioning device for providing front tension on the strip as it leaves the roll stand has been in the form of a pulling device comprising a pair of driven rolls over which a partial wrap of the strip is taken in passing from the roll stand to the winding reel. These two rolls provide the front tension on the strip while the winding tension is independent of the front tension.

Heretofore, the rolls of such pulling devices have been geared together and driven by a single motor. This method of operation has been found unsatisfactory for the reason that small :7;

differences in the diameters of the rolls of the pulling device cause slippage and buckling of the strip on the rolls and sometimes cause one .of the rolls to carry most of the pulling load.

An object of the invention is to provide a 5 :control system for strip tensioning rolls which .shall function to distribute the tensioning load between the rolls in a predetermined adjustable proportion which shall maintain the desired tension distribution between the tensioning rolls regardless of the speed of the mill, and which shall be simple and efiicient in operation, and inexpensive to manufacture, install, operate, and maintain.

These and other objects and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic view of a portion of a strip rolling mill embodying the principal features of a preferred embodiment of the invention, and r Fig. 2 is a diagrammatic view of a portion of a strip rolling mill embodying the principal features of another embodiment of the invention.

In practicing the invention, tensioning rolls driven by separate motors are positioned to en gage the strip between the winding reel, and a roll stand of a strip rolling mill. Substantially constant excitation is provided for the tensioning roll motors and their relative excitations are adjusted in accordance with the relative tensioning torques that it is desired to have the tensioning rolls exert upon the strip. The armatures oi the tensioning roll motors are connected in series circuit relation and energized by the same source of adjustable voltage power as the reel motor and the reducing roll stand motor. An auxiliary generator is connected in series circuit relation with the tensioning roll motors and is so controlled in accordance with armature current of the tensioning roll motors as to maintain the armature current substantially constant. The constant armature current of the tensioning roll motors together with constant excitation of these motors results in the application of a substantially constant tension to the strip.

In the embodiment of Fig. 2 a tensiometer or tension responsive device controls the excitation of the auxiliary generator to maintain the torques of the tensioning roll motors substantially constant.

Referring to Figure l for a more detailed description of the invention, the tensioning rolls 2 and 4 driven by the motors 6 and 8, respectively, are positioned to subject the strip ID to tension as it extends or passes from the rolls of the mill stand I2 to a reel M. The rolls of the mill stand 12 and the reel 14 are driven by the motors I6 and 18, respectively.

The motors I6 and [B are supplied with power by a main generator 20 which is continuously driven by any suitable means such as the motor 22. The generator 20 is connected to energize a power bus comprising the conductors 24 and 26. The armature of the roll stand motor I6 is connected to the power bus by a circuit which extends from the conductor 24 through the condoctor 28, the armature of the motor I6, and the conductor 30, to the conductor 26. The reel motor I is connected to the power bus through a circuit which extends from the conductor 24 through the conductor 32, a controller, as indicated, and a conductor 34 to the conductor 26. The controller is merely indicated and not shown in detail for the reason that any type of controller well known in the art which will function to control the reel motor l8 to maintain substantially constant strip tension may be used. The speed of the motors l6 and I8 is controlled of the solenoid I00. Likewise, the energization of the circuit of the field winding 96 will cause an impulse to be transmitted through the transformer IIO to the circuit of the solenoid I00. The secondary windings I24 and I28 of the transformers III! and I30, respectively, are so connected that the impulses transmitted therethrough by changes of excitation and output potential of the generator 80 will cause movement of the solenoid I in the opposite direction to that in which the solenoid I00 previously moved to cause the hereinbefore described changes of excitation and output potential of the generator 80. Thus, after the contact elements I46 and I48 have closed, the impulses transmitted through the transformers H0 and I30 to the solenoid I00 will be such as to cause these contact elements to open and the contact elements I44 and I48 to close. The closure of contact elements I44 and I48 will act to energize the field winding 96 of the generator 80 in the opposite direction, which in turn, will cause the solenoid I00 to move the arm I40 in the direction to open the contact elements I44 and I48 and to close the contact elements I46 and I48. Thus, the contact elements I44 and I46 will be continuously vibrated to excite the generator 80, first in one direction, and then the other. The relative lengths of the alternate periods of energization or" the field winding 96 of the generator 60 will be controlled by the armature current of the motors 6 and 8 and the generator 80, which is the main source of energization of the winding of the solenoid I00, and it controls the average position of the arm I40, and, therefore, the relative length of the time of engagement of the contact element I44 with the contact element I48 and the contact element I46 with the contact element I48.

As the mill is started and brought up to speed by variation of the output potential of the main generator 20, the tension on the strip I0 applied by the tensioning rolls 2 and 4 will remain constant because of the constant current regulating effect of the generator 60 in series circuit relation with the armatures of the motors 6 and 8, regardless of the value of the output potential of the generator 20.

It is usually desired to have a greater tension on the strip I0 between roll stand I2 and the tensioning roll 2 than between the reel I4 and the tensioning roll 4. The tensioning roll 2 will have a greater strip pressure upon it, therefore, than the tension roll 4 and will be able to carry a greater part of the tensioning load without slippage upon the strip. To cause the tensioning roller 2 to carry a greater load than the tensioning roller 4, the relative excitations of the motors 6 and 8 may be adjusted by the variable resistor 68 to provide the desired ratio of motor torques. These motor torques will be maintained throughout the range of operation of the mill since their armature currents are maintained constant, and they have a constant field excitation.

The embodiment of the invention shown in Fig. 2 is substantially the same as that of Fig. l with the exception that the regulator which controls the excitation of the generator 80 is made responsive to a tension responsive device I19 and constant strip tension is maintained in response to the tension responsive device rather than a current responsive device. Like reference characters designate similar or identical elements of the two systems.

Referring to Fig. 2, a shunting circuit for the rangement 98 extends from the junction I53 through the conductors I02, B, I64 and I66, the contact element I48 which is mounted upon the movable arm I40 actuated by the solenoid I00, contact element I44, and conductor I68 to the junction I05. A similar shunting circuit for the resistor leg I52 of the Wheatstone bridge arrangement 98 extends from the junction I53 through the conductors I 02, B, I64 and I66 to the contact element I48, the contact element I46, and the conductors I10 and I I8 to the junction II9.

In this embodiment of the invention, the solenoid I00 is merely provided to vibrate the movable contact element I48 between the movable contact elements I44 and I46. The energizing circuit for the Winding of solenoid I00 extends from the conductor A through the conductor I12, the variable resistor I96, conductor H4, the secondary I28 of the transformer I30, conductor I26, the secondary winding I24 of the transformer II 0, conductor N6, the winding of the solenoid I00, and conductors I16, I66, and I64 to the conductor 13.

The engagement of contact element I48 with contact element I46 will close the shunting circuit for the resistor leg I52 causing an unbalance of the Wheatstone bridge 98. This will energize the field winding 96 of the auxiliary generator to change its output potential. The energization of the field Winding 96 of the generator and the change of its output potential will cause impulses to be transmitted through the transformers H0 and I30 to the energizing circuit of the Winding of the solenoid I00 in such a direction as to cause the contact element I48 to disengage the contact element I46 and to engage contact element I44. This will cause energization of the field winding 96 in the opposite direction which will result in movement of the contact element I48 out of engagement with contact element I44 and into engagement with contact element I46. Thus, the contact element I48 will be made to vibrate continuously and continuous regulation is eilected eliminating hunting or excessive variations of strip tension.

The positioning of the contact elements I44 and I46 with respect to the vibrating contact element I48 is controlled by the tension responsive device I19 which comprises a tensioning roller I80 mounted upon an arm of a bell crank I82 in such position as to engage the strip I0 and deflect it from its normal pass line, and a suitable actuating means, such as a fluid pressure operated piston and cylinder arrangement I84. The contact elements I44 and I46 may be actuated in accordance with the movement of the bell crank of the tension responsive device by means of the arm I86 attached thereto. The tension responsive device is so adjusted that variations in strip tension will vary the deflection of the strip and, therefore, the position of the contact elements I44 and I46 with respect to the vibrating contact element I48. Thus, the relative lengths of excitation of the generator 80 in one direction and the other are controlled by the tension of the strip and automatically function to maintain a substantially constant strip tension.

It is to be understood that the application of the control system to a rolling mill between the roll stand and a winding reel is merely illustrative and that the system may be used equally well to control the tension between two roll stands of a tandem mill or between an unwinding reel and resistor leg I50 of the Wheatstone bridge ara roll stand. In the event that the system is used to control the back tension on the strip between an unwinding reel and a roll stand, the dynamoelectric machines 6, 8 and I8 would be operated as drag generators and the system would function to control the amount of braking torque applied to the strip by these drag generators.

It is to be further understood that as many tensioning rolls and their associated dynamoelectric machines as desired may be provided, the system being applicable to several tensioning rolls in the same manner as it is applied to tWo tensioning rolls in the illustrated embodiments of the invention.

It will be seen that I have provided a control system for a strip tensioning device which shall function to distribute and maintain the desired strip tension between a plurality of driven tensioning rolls regardless of the speed of the mill, which shall compensate for the I. R. drop in the dynamo-electric machines connected to the tensioning rolls, which shall be simple and efiicient in operation, and inexpensive to manufacture, install, operate and maintain.

In compliance with the requirements of the patent statutes, I have shown and described herein the preferred embodiments of my invention. It is to be understood, however, that the invention is not limited to the precise constructions shown and described, but is capable of modification by one skilled in the art, the embodiments herein shown being merely illustrative of the principles of my invention.

I claim as my invention:

1. In a strip tension control system for a pair of tensioning rolls over which the strip passes in travelling between a roll stand and a reel of a strip rolling mill, in combination, a separate dynamo-electric machine connected in driving relation with each of the tensioning rolls, means connecting the armatures of said dynamo-electric machines to a source of potential to which the roll stand and reel motors are connected and which is selectively variable to vary the speed of the mill, and auxiliary generator connected in series circuit relation with said dynamo-electric machines, means providing selectively adjustable substantially constant excitations for said dynaom-electric machines, and means for so controlling the said auxiliary generator as to cause said dynamo-electric machines to exert substantially constant torques on the strip regardless of variations in the value of the potential of the source of potential which energizes the reel and roll stand motors.

2. In a control system for a plurality of tensioning rollers over which a strip of material passes in a partial wrap as it extends between adjacent work devices for controlling the tension on the strip of material as it passes between the work devices which are connected in driving relation with dynamo-electric machines whose armatures are energized from a. power source of selectively adjustable potential, in combination, a separate dynamo-electrio machine connected in driving relation with each of the rollers, means connecting the armatures of said roller dynamo-electric macl es the source of adjustable potential to which the work device dynamo-electric machines are connected, means providing separately selectively adjustable sub stantially constant excitations for said roller dynamo-electric machines, a generator connected in series circuit relation with said roller dynamoelectric machines, and means for so controlling aasncca said generator as to cause said roller dynamoelectric machines to exert substantially constant torques on the strip regardless of variations in the value of the potential of the power source.

3. In a control system for a plurality of tensioning rollers over which a strip passes in a partial wrap as it extends between adjacent work devices for controlling the tension on the strip as it passes between the work devices which are connected in driving relation with dynamoelectric machines whose armatures are energized from a power source oi selectively adjustable potential, the combination of a separate dynamoelectric machine connected in driving relation with each of the rollers, means connecting the armatures of said roller dynamo-electric machines to the source of adjustable potential to which the work device dynamo-electric machines are connected, means for providing and maintaining substantially constant ratios between the excitations of the roller dynamo-electric machines, a generator, means connecting said generator armature in circuit with the armatures of said roller dynamo-electric machines, and

. means for so controlling said generator as to cause said roller dynamo-electric machines to exert substantially constant torques on the strip regardless of variations in the potential of the power source.

4. In a control system for a plurality of tensioning rollers over which a strip passes in a partial wrap as it extends between adjacent work devices for controlling the tension on the strip as it passes between the work devices which are connected in driving relation with dynamo-electric machines whose armatures are energized from a power source of selectively adjustable potential, the combination of a separate dynamoelectric machine connected in driving relation with each of the rollers, means connecting the armatures of said roller dynamo-electric ma chines to the source of adjustable potential to which the work device dynamo-electric machines are connected, means providing selectively adjustable substantially constant excitations for said roller dynamo-electric machines, a generator, means connecting said generator in circuit with said roller dynamo-electric machines, and means responsive to the armature current of said roller dynamo-electric machines for so controlling said generator as to maintain substantially constant current in the armatures of said roller dynamo-electric machines regardless of variations of the potential of the said power SOLH'CB.

5. In a control system for a plurality of tensioning rollers over which a strip passes in a partial wrap as it extends between adjacent Work devices for controlling the tension on the strip as it passes between the work devices whichare connected in driving relation with dynamoelectric machines whose armatures are energized from a source of selectively adjustable potential, the combination of a separate dynamo-electric machine connected in driving relation with each of the rollers, means. connecting the armatures of said roller dynamo-electric machines to the source of adjustable potential to which the work device dynamo-electric machines are connected, :means providing selectively adjustable substantially constant excitations for said roller dynamoei'e'ctric machines, a generator connected in cir- 'cuit with said roller dynamo-electric machines, and means responsive to the strip tension for .so controlling said generator as to maintain subelectric machines, a generator, means connecting stantially constant tension on the strip regardless of variations of the potential of the said power source.

6. In a control system for a plurality of tensioning rollers over which a strip passes in a partial wrap as it extends between adjacent work devices for controlling the tension on the strip as it passes between the adjacent work devices which are connected in driving relation with dynamo-electric machines whose armatures are energized from a power source of selectively adjustable potential, the combination of a separate dynamo-electric machine connected in driving relation with each of the rollers, means connecting the armatures of said roller dynamo-electric machines to the source of adjustable potential to which the work device dynamo-electric machines are connected, means for providing and maintaining substantially constant ratios between the excitations of the roller dynamo-electric machines, a generator, compensating means providing an excitation for said generator proportional to the armature currents of said roller dynamo-electric machines, means connecting said generator armature in circuit with the armature of said roller dynamo-electric machines, and means for so controlling said generator as to cause said roller dynamo-electric machines to exert substantially constant torques on the strip regardless of variations in the potential of the power source.

7. In a control system for a plurality of tensioning rollers over which a strip passes in a partial wrap as it extends between adjacent work devices for controlling the tension on the strip as it passes between the work devices which are connected in driving relation with dynamoelectric machines whose armatures are energized from a power source of selectively adjustable potential, the combination of a separate dynamoelectric machine connected in driving relation with each of the rollers, means connecting the armatures of said roller dynamo-electric machines to the source of adjustable potential to which the work device dynamo-electric machines are connected, means providing selectively adjustable substantially constant excitations for said roller dynamo-electric machines, a generator, means connecting said generator in circuit with said roller dynamo-electric machines, compensating means providing an excitation for said generator proportional to the armature currents of said roller dynamo-electric machines, and means responsive to the armature current of said roller dynamo-electric machines for so controlling said generator as to maintain substantially constant current in the armatures of said roller dynamo-electric machines regardless of variations of the potential of the said power source.

8. In a control system for a plurality of tensioning rollers over which a strip passes in a partial wrap as it extends between adjacent work devices for controlling the tension on the strip as it passes between the work devices which are connected in driving relation with dynamoelectric machines whose armatures are energized from a source of selectively adjustable potential, the combination of a separate dynamo-electric machine connected in driving relation with each of the rollers, means connecting the armatures of said roller dynamo-electric machines to the source of adjustable potential to which the work device dynamo-electric machines are connected, means providing selectively adjustable substantially constant excitations for said roller dynamosaid generator in circuit with said roller dynamoelectric machines, compensating means providing an excitation for said generator proportional to the armature currents of said roller dynamoelectric machines, and means responsive to the strip tension for so controlling said generator as to maintain substantially constant tension on the strip regardless of variations of the potential of the said power source.

9. In a control system for a pair of tensioning rollers over which a strip of material passes in a partial wrap as it passes between a rolling mill and a winding reel for controlling the tension on the strip of material as it is delivered from the rolling mill and wound onto the winding reel which mill and reel are connected in driving relation with motors whose armatures are energized from a power source of selectively adjustable potential, the combination of a separate drive motor for each of the rollers, means connecting the armatures of said roller motors to the power source to which the mill and reel motors are connected, means providing selectively adjustable substantially constant excitations for said roller motors, a generator, means connecting said generator in circuit with said roller motors, and means for so controlling said generator as to cause said roller motors to exert substantially constant torques on the strip regardless of variations in the potential of the power source.

10. In a control system for a pair of rollers over which a strip of material passes in a partial wrap as it passes from an unwinding reel to a rolling mill for controlling the tension on the strip of material as it is fed to the rolling mill from the unwinding reel which mill and reel are connected in driving relation with a drive motor and a drag generator, respectively, which drive motor and drag generator are connected to a power source of selectively adjustable potential, the combination of a separate drag generator driven by each of the rollers, means connecting the armatures of said roller drag generators to the power source to which the reel drag generator and the mill motor are connected, means providing selectively adjustable substantially constant excitations for said roller drag generators, an auxiliary generator, means connecting said auxiliary generator in circuit with said roller drag generators, and means for so controlling said auxiliary generator as to cause said roller drag generators to exert substantially constant torques on the strip regardless of variations in the potential of the power source.

11. In a system for controlling the tension on a strip of material as it is delivered from a rolling mill and wound onto a winding reel which mill and reel are connected in driving relation with motors whose armatures are energized from a power source of selectively adjustable potential, the combination of a pair of rollers over which the strip passes in a partial wrap as it passes from the mill to the reel, a separate drive motor for each of said rollers, means connecting the armatures of said roller motors to the power source to which the mill and reel motors are connected, means providing selectively adjustable substantially constant excitations for said roller motors, a generator, means connecting said generator in circuit with said roller motors, and means responsive to the strip tension for so controlling said generator as to maintain substantially constant tension on the strip regardless of variations of the potential of the said powersource.

12. In a system for controlling the tension on a strip of material as it is delivered from a rolling mill and wound onto a winding reel which mill and reel are connected in driving relation with motors whose armatures are energized from a power source of selectively adjustable potential, the combination of a pair of rollers over which the strip passes in a partial wrap as it passes from the mill to the reel, a separate drive motor for each of said rollers, means connecting the armatures of said roller motors to the power source to which the mill and reel motors are connected, means providing selectively adjustable substantially constant excitations for said roller motors, a generator, means connecting said generator in circuit with said roller motors, and means responsive to the strip tension for so controlling said auxiliary generator as to maintain substantially constant tension on the strip regardless of variations of the potential of the said power source.

13. In a system for controlling the tension on a strip of material as it is delivered from a rolling mill and wound onto a winding reel which mill and reel are connected in driving relation with motors whose armatures are energized from a power source of selectively adjustable potential, the combination of a pair of rollers over which the strip passes in a partial wrap as it passes from the mill to the reel, a separate drive motor for each of said rollers, means connecting the armatures of said roller motors to the power source to which the mill and reel motors are connected, means providing selectively adjustable substantially constant excitations for said roller motors, a generator, means connecting said generator in circuit with said roller motors, and means responsive to the armature current of said roller motors for so controlling said generator as to maintain substantially constant current in the armatures of said roller motors regardless of variations of the potential of the said power source.

WILLARD G. COCK.

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