US2043208A - Motor control system for coiling mechanisms - Google Patents

Description

June 2, 1936.

D. I. BOHN MOTOR CONTROL SYSTEM" FOR COILING MECHANISMS Filed May 51, 1932 INVENTOR ing mechanism and to regulate-the tension as- Patented June 2, 1936 MOTOR CONTROL SYSTEM FOR COILING MECHANISMS Donald I. Bohn, Pittsburgh, Pa., assignor to Aluminum Company of America,.Pittsburgl1, Pa., a corporation of Pennsylvania Application May 31, 1932, Serial No. 614,600 n Claims. (oi. 242-75) This invention relates in general to material coiling mechanisms used in conjunction with sheet-processing and/or feeding mechanisms, such as rolling mills or the like, and in particular to electrical control systems for coiling mechanisms capable of producing constant tension on material delivered from a rolling mill.

In the operation of rolling mills, wherein the material rolled is coilediupon' a rewind block or drum, the quality of the. material produced is materially improved whenla predetermined constant tension is exerted on the material being coiled. To satisfactorily accomplish such a result it is essential to allow for the increasing diameter of the rewind coil, and in the present forms of apparatus, slip gears or clutch mechanisms areused to adjust the torque of the coilthe coil increases indiameter. Mechanical means of this nature, however, have not proved very satisfactory because of their low degree of accuracy and because of lost motion and sluggish operation resulting from wear of the various mechanical parts. For this and other reasons electrically controlled systems have for the most part replaced these earlier forms of mechanical devices.

The electricallycontrolled systems which have supplanted the above-mentioned mechanical de- Vices operate on a common fundamental principle in that the motor driving the rewind drum or coiler and the main mill motor are coordinated, by means of the rewind motor armature receiving its voltage from a suitable generator driven by the main mill motor, to produce the required constant tension. In arrangements such as these the voltage impressed on the rewind motor armature is approximately proportional at all times to the speed of the mill motor and, assuming the excitation of the rewind motor. field-magnet winding is adjusted to maintain constant current through the armature circuit, such an arrangement insures an approximate constant power input to the rewind or coiler motor. Such arrangements, however, offer numerous disadvantages in that losses in the rewind motor, particularly when the rolling mill is slowed down from normal operating speed, introduce errors in the tension exerted by the rewind or coiling mechanism and when the rolling mill is eventually stopped, the tension is entirely removed from the material unless auxiliary electrical equipment is employed to provide a separate source of power in the rewind motor circuit.

Furthermore, if such a system is provided with auxiliary equipment, which usually takes the form of relays and electrically operated contactors in the rewind motor circuit adapted to function as the main mill motor slows down, the resultant interruption in the current flow causes fluctu- ,5 ations in the values of torque applied to the coiler, which action produces uneven tension in the ,material being processed.

mill is slowed down to and including zero mill speed. i

A further object of my invention is to provide an electrical control system by means of which a constant tension is maintained on the material discharged from the rolling mill in such a manner that the rewind motor automatically takes up and maintains any desired preset tension on the material being rolled.

This and various other objects, as well as other novel features and advantages of the invention, will be more apparent when the following detailed description is considered in conjunction with the accompanying drawing in which:

Fig. '1 represents, in diagrammatic form, my improved arrangement of constant tension coiling mechanism; v

Fig. 2 represents an illustration of a particular portion of the apparatus shown in Fig. 1.

Referring to. the drawing, the invention is illustrated as applied to the control of a rewind or coiling mechanism employed in combination with a rolling mill.

The apparatus shown in the drawing comprises a rolling mill, althoughany suitable feeding mechanism, or the like, can quite manifestly be substituted therefor, represented'as a pair of working rolls Ill and ii, to which suitable driving means, such as a compound-wound motor i2, is coupled in any well known manner. The material or stock l3 torbe processed is passed between the rolls l0 and ii in the usual fashion and is engaged on the discharge side of the rolling mill upon a coiler or rewind drum l4 of any suitable construction. The coiler is likewise provided with a suitable driving motor I5, a shunt-wound, fully compensated motor being considered preferable.

In accordance with this invention, provision is made for automaticaly controlling the operation of motor I5 in response to variations in the diameter of the reel I4, whereby the power output of the motor I5 is at all times proportional to the speed of the main mill motor I2 for any desired preset value of tension on the material I3 being processed.

In accomplishing this result separately excited pilot generators I6 and ll of relatively small size are direct-connected to the motors I2 and I5 respectively. Generator I6 is equipped with a separately excited field-magnet winding I8, adjustable by means of a rheostat I9, whereas generator I! is equipped with a field-magnet winding 20 the excitation control of which will be hereinafter described. These generators are similar in all respects as to their electrical characteristics and when driven at the same speed, with equal field excitation, generate equivalent voltages. As will be seen from the drawing, the pilot generators I6 and H are electrically connected, in opposed relationship, by means of theconductors 2|, 22 and 23. The coil 24 of a suitable relay in the form of a polarized, contactmaking, zero-center voltmeter 25 completes, the circuit between the conductors 22 and 23. The voltmeter 25 may be of any suitable construction and is herein shown as comprising a circuit controlling bridging member 26, a permanent magnet 21, the aforementioned coil 24, and contact members 26 and 29. In operation the bridging member 26 remains midway between the contact members 26 and 29 when the voltages generated by the pilot generators I6 and I] are equal and opposite. Any difference in the voltages generated by the pilot generators I6 and I1 energizes the coil 24, at which time the bridging member 26 is attracted by the permanent magnet 21 into contact with either one or the other 01. the contact members 26 and 29.

Completion of the circuit through the medium of bridging member 26 and either of the contactors 28 and 29 serves to connect a reversible, split-field, series motor 30 across the conductors L1 and L2. This is accomplished by means of the conductors 3|, 32 and 33 through field-magnet winding 34; or 3|, 35 and 33 through fieldmagnet winding 36 in accordance with the particular'direction in which the bridging member 26 is rotated. The field - magnet windings 34 and 36 of motor 30 are oppositely wound and reverse the direction of rotation of this motor. The motor 30 is direct-connected to rheostats A and B, which are suitably designed in accordance with the characteristics of the field-magnet windings 31 and 20 of motor I5 and generator II, respectively, the purpose of which willbe hereinafter described. By means of the conductors 38, 39 and 4D rheostat A is connected across the field-magnet winding 20 of pilot generator II from the main leads L1 and L2. Similarly, by means of conductors 4|, 42 and 43, field-magnet winding 31 of motor I5 is connected across the leads L1 and L2.

A suitable three-phase synchronous motor 44 i is direct-connected to two generators, 45 and 46,

motor I5. The generator 46 and the various elements included in a loop-circuit formed by this generator and the armature of motor I5 are provided for the purpose of applying a constant armature current to the motor I5 in accordance with any desired preset value of tension upon the material being processed.

Also a circuit comprising a suitable current regulator, which for purposes of illustration has been shown as a compressible carbon pile regulator 5|, is connected in series with the fieldmagnet winding 41 of the generator 46, the purpose of which is to control the magnitude of the constant current through the armature of motor I5 for any given setting of the rheostat 55. Conductors 4B, 49 and 52 complete the field circuit of generator 46 with busbars L1 and L2, an adjustable rheostat being provided for adjustably controlling the excitation of field-magnet winding 41. The loop-circuit comprising generator 46 and motor I5 is completed through the medium of conductors 53 and 54, and a suitable shunt R of constant predetermined resistance is inserted in the conductor 54. Shunted around the shunt R is a circuit comprising the rheostat 55 and an electromagnet coil 56 which cooperates with the compressible pile regulator 5| in a manner to be described.

In the operation of the electrical control system above described, material or stock having been introduced between the rolls I 0 and II of the rolling mill, the mill is set in operation by 'means of any suitable starter mechanism 66 across the leads 6| and 62 to the mill motor I2. The three-phase synchronous motor 44 directconnected to the D. C. generators 45 and 46 is also set in motion, which action energizes the re- 1 wind system. The motor 44 is equipped with any suitable separately'excited field-magnet winding 63, this excitation being shown as supplied from the conductors L1 and La. Likewise, generator 45 is equipped with field-magnet winding 64 and rheostat 65, conductors 66 and 61 being provided to conduct the generated power into the busbars L1 and L2.

To obtain a desired torque on the rewind reel I4 the current applied to the armature of motor I5 is maintained constant for the particular torque desired. This is accomplished by means of the circuit comprising the rheostat 55 and the electromagnet coil 56 in combination with the compressible pile regulator 5| in the fieldmagnet winding 41 of generator 46'.

For example, when the motor I5 is operating at zero speed the voltage generated by generator 46 is just sufllcient to provide a current in the armature circuit of motor I5 as determined by the setting of the rheostat 55. As the mill motor I2 accelerates motor I5 also accelerates and during this period the carbon pile regulator functions to increase the excitation of field-magnet winding 41 of generator 46 to maintain a con-' stant current through the annature of motor I5. This constant current is maintained by regulator 5| as determined by the initial setting of rheostat 55 and the electromagnet coil 56, the amount of current through this circuit being inversely proportional to the resistance of this circuit with respect to the resistance of the shunt R. The additional current through the rheostat 55 energizes the coil 56 and attracts the core 51 which, through the medium of the pivoted bar 58, relieves the pressure on the compressible pile regulator 5| against the tension of spring 59. This action permits the discs of the regulator 5| to separate and thereby increases the resistance of the field'circuit of the generator 46.

It will be readily seen that as the motor l5 slows down because of the increased diameter of the coil l4, generator i1 will also slow down and will generate a lower voltage than generator l6.

4 This differentiation in the voltages generated by is strengthened as its speed decreases.

It will thus be seen that, byproperly designing rheostats A and B, and by maintaining a constant current through the armature of motor I5, the power output of motor l5 will be constant for a given mill speed. These conditions will result in a constant tension on the material being processed regardless of the mill speed down to and including a full stop. The behavior of rheostat B is the same as though it 'were mechanically operated, as shown diagrammatically in Fig. 2,

wherein a roller 68, supported upon a fulcrumed.

arm 69, rides in contact with the reel lid and through the medium of a suitable link I0 actuates the rheostat B, the contactor arm of which is shown in the form of a bell crank, to cut out resistance in the filed-magnet winding 3'! as the reel diameter increases. That is, rheostats A and B have definite positions for every outside diameter of the material on reel M.

It will be seen that the electrical control system incorporated in this invention does not include auxiliary equipment in the armature cir cult of the rewind motor which has heretofore caused intermittent current supply resulting in fluctuations in the torque attendant withpreviously employed. electrical control systems.

Having thus described and explained my invention and its mode of operation, it is to be understood that the apparatus described was selected merely for purposes of illustration and that numerous variations in the form and arra'ngement of parts shown and described herein may be made without departing from the nature and scope of my invention except as defined in the appended claims.

I claim:

1. In an apparatus for processing strip material, a feeding mechanism; means for driving said feeding mechanism, a coiler mechanism, an electric motor for driving said coiler mechanism, a generator driven by said feeding mechanism driving means and electrically connected in opposed relationship with a similar generator driven by the coiler mechanism electric motor, said similar generators when generating different voltages being adapted to control the excitation of the coiler motor field-magnet winding, an electrical means incorporated in the coiler motor armature circuit, whereby a constant torque is developed by said coiler motor. 1

2. In an apparatus for processing strip material, a feeding mechanism,means for driving said feeding mechanism, a coiler mechanism, an electric motor for driving said coiler mechanism, a generator driven by said feeding mechanism driving means and electrically connected in opposed relationship with a similar generator driven by said coiler mechanism electric motor, a reversible 7,

driving means, a controllingemeans for said reversible driving means, said controlling means being positioned in the electrical connection between the similar generators and adapted to operate the reversible driving means when the similar generators generate different voltages, said reversible driving means being adapted to control the excitation of the coiler motor fieldmagnet winding, and electrical means incorporated in said coiler motor armature circuit to maintain constant current therein.

3. An apparatus for processing strip material comprising a feeding mechanism and a coiler mechanism, means for driving the feeding mechanism, an electric motor for driving the coiler mechanism, said electric motor having a fieldmagnet winding'and an armature circuit, means operated by different-iations in the speed of the feeding mechanism. and the speed of the coiler mechanism to control the excitation of the fieldmagnet winding, and means in the armature cir-' cult comprising a generator adapted to provide a constant current t o-said coiler motor armature.

4. In an apparatus for processing strip mate-' rial, a feeding mechanism and means for driving the same, a coiler mechanism and an electric motor for driving the same, electrically-operated means for controlling the strength of the electric motor field, electrically-operated means for maintaining a constant current in the armature n of the electric motor, both of said electricallyoperated means being adapted to maintain the power output of the coiler mechanism proportional to the speed of the feeding mechanism.

5. In an apparatus for processing strip material, a feeding mechanism and means for driving the same, a coiler mechanism and an electric motor for driving the same, similar generators driven by said feeding mechanism driving means and said coiler motor, said similar gen- 6. In an apparatus for processing strip mate- 0 rial, a feeding mechanism, means for driving said feeding mechanism, a coiler mechanism, an electric motor for driving said coiler mechanism, a

generator driven by said feeding mechanism driving means and electrically connected in opposed relationship with a similar generator driven by the coiler mechanism electric motor, said similar generators, when generating diiferent voltages, being adapted to control the excitation of the coiler motor field-magnet winding, and adjustable means in said coiler motor armature circuit to maintain any preset constant current therein.

'7. In an apparatus for processing strip material, a feeding mechanism, means for driving said feeding mechanism, a coiler mechanism, an electric motor for driving said coiler mechanism, a generator driven by said feeding mechanism driving means andelectrically connected in opposed relationship with a similar generator driven by said coiler mechanism electric motor, a reversible driving means, a controlling means for said reversible driving means, said controlling means being positioned in electrical connection between the similar generators and adapted to operate the reversible driving means when the similar generators generate difiere'nt voltages, said reversible driving means being adapted to control the excitation of the coiler motor fieldmagnet winding, and adjustable electrical means incorporated in said coiler motor armature circuit adapted to maintain constant current therein.

8. In an apparatus for processing strip material, a coiler mechanism-adapted to coil the strip material, said coiler mechanism being driven by an electric motor, means for exciting the electric motor filed-magnet winding in response to a differentiation between speeds of the processing apparatus and coiler, and an armature circuit for said electric motor, including adjustable electrical means for providing constant current thereto to ;maintain uniform torque.

9. In an apparatus for processing strip material, a feeding mechanism, means for driving said feeding mechanism, a coiler and an electric motor for driving the same, two similar generators one of which is driven by the feeding mechanism and the other of which is driven by the coiler motor, said similar generators being connected in opposed relationship and adapted to generate equal voltages for all difierentiations in speed between the feeding mechanism and the coiler, an armature circuit for said coiler motor including a generator connected in loop-circuit therewith, and a resistance'having a circuit shunted around the same in said loop-circuit, said last-mentioned circuit comprising a .rheostat and a current regulator, said loop-circuit being adapted to maintain a constant current supply .to the armature of the coiler motor for all speeds thereof.

10. In an apparatus for processing strip material, a reel for receiving and coiling the strip, said reel being driven by an electric motor, means for exciting the electric motor field-magnet winding in response to a difierentiation between speeds of the processing apparatus and reel, and a loopcircuit including the motor armature and a generator, said loop-circuit being provided with a carbon pile current regulator for controllingv the excitation of the generator to maintainv a constant preset current through the motor arms/.- ture for all speeds of the reel.

DONALD I. BOHN.

Images