US2485757A - Unwind reel control - Google Patents

Description

Oct. 25, 1949. M. MICHEL UNWIND REEL CONTROL Filed July 31, 1948 Q WW 3 AW 7/ 1 3 w: m m M w \m I; Q\I 2 Patented Oct. 25, 1949 UNITED STATES PATENT OFFICE UNWIND REEL CONTROL Mathias Michel, Pittsburgh, Pa.

Application July 31, 1948, Serial No. 41,787

This invention relates to control systems for unwind reels adapted to unwind strip material under tension as it is fed to a strip processing machine, such as a rolling mill, trimmer, slitter, leveler, or the like. The term strip is used generally, as the invention is applicable to unwind reel controls for wide or narrow strip, band, wire or other forms of material unwound in long lengths from reels.

It is recognized that it is desirable to main-' tain strip, unwinding from a coil on a reel to a strip processing machine, under a substantially constant tension regardless of changes in processing speed or changes in coil diameter (with consequent changes in speed of rotation of the coil and reel). Mechanical devices for restraining the rotation of unwind reels are inherently sluggish in operation, if not incapable of properly controlling the tension developed in the unwinding strip. Electrical controls for this purpose have been developed to a high degree of accuracy, but are usually expensive to install and/or to maintain.

One object f this invention is to provide an inexpensive electrical unwind reel control capable of ready adjustment for the maintenance of substantially constant selected values of tension on strip material fed from the unwind reel. The control system of the invention is simple and efficient, and yet it is highly accurate in operation. It is also an object of the invention to avoid the use of current and voltage regulators of the contact or vibrating contact type, since they require considerable maintenance.

Other objects and advantages of the invention will become apparent upon a reading of the following detailed description of a preferred embodiment of the invention, which description has reference to the two figures of the accompanying drawing.

Figure 1 shows a mechanical arrangement of the various elements of the invention. Figure 2 is a schematic diagram of the electrical connections.

Fig. 1 shows, by way of example, a mechanical arrangement of the various instrumentalities for the application of the unwind control system to a rolling mill. In this figure an unwind reel I is shown supporting a coil II from which strip material l2-is fed to a rolling mill l5. The unwind reel I0 is coupled, through suitable shafts, couplings and gears, to a direct current drag generator 20. The rolling mill I5 is coupled, through suitable couplings, spindles, pinions, and gears to a main mill motor 25. To the main mill motor 25, a direct current feed-back motor 35 is suitably coupled; and to the feed-back motor. 35. a direct current control exciter 45 is suitably coupled. Feed-back motors 35 and control exciter 45 may, however, be separately operated at speeds pro- 5 Claims. (Cl. 242-75) 2 portional to the mill speed, without being coupled directly or indirectly thereto.

The arrangement of motor, exciter, and genera or with the unwind reel and mill, as shown in Fig. 1, permits the following mode of operation. Mill motor 25 drives rolling mill l5 which pulls the strip |2 off coil held on unwind reel It), thus imparting rotation to unwind reel III (which drives drag generator 20) and creating tension in the strip l2. The power developed by drag generator 20 is delivered to feed-back motor 25 Which can take some of the load of driving mill I5. Control exciter 45 is electrically associated with drag generator 20 in a manner which will be explained by reference to Fig. 2.

Fig. 2 shows the electrical arrangement of the motors, exciter, and generator shown in Fig. 1. It will be noted from this figure that drag generator 20 and feed-back motor 35 have their armatures connected in loop circuit by lines l3 and H. A booster generator l6 may be inserted in this loop circuit, for a purpose to be referred to later, but it is not essential that it be employed. A contact switch I! is also preferably provided in this loop circuit. The feed-back motor 35 is preferably series wound, being provided with a series-field 36.

The drag generator 20 is provided with a control field 2|. One side of control field 2| is con nected through a portion of line |3 with one armature terminal of drag generator 20; the other side of control field 2| is connected with that armature terminal of control exciter 4 5 which is of polarity corresponding to that of the armature terminal of drag generator 20 to which the firstmentioned side of control field 2| is connected as above-described. The other armature terminal of control exciter 45 is connected through a portion of line l4 with the second armature terminal of drag generator 2|l, these terminals also being of corresponding polarity.

The control exciter 45 is preferably provided with a series field 4G, and has a separatel excited shunt field 41.

The shunt field 41 is controlled by a rheostat 48. The drag generator. is also preferably provided with a separately excited shunt field 22, which may be controlled by a rheostat 23. Rheostats 48 and 23 may be so arranged as to be commonly adjusted by a single rheostat shaft, as shown.

The unwind control system functions as follows: The separately excited shunt field 22 for drag generator 20 is given a fixed excitation for a given tension condition by adjustment of rheostat 23. Likewise, the separately excited. shunt field 41 for control exciter 45 is given a fixed excitation by adjustment of rheostat 48. Control exciter 45-.

will develop a potential on control field 2| generall proportional to the speed of the strip |2 passing through the mill l5, while drag generaassays? tor 20 will tend to develop a potential proportional to the speed of rotation of the unwind reel iii. If a higher potential is developed across the armature of drag generator 20 than across the armature or control exciter 45, then current will flow through the control field 2i, opposing shunt field 22 and reducing the excitation of drag generator 20. Contrarily, ii a lower potential is developed by drag generator 20 than by the control exciter 45, then current will flow through the control field 2| in an opposite direction, increasing the excitation of drag generator 20. The system tends to keep the same voltage on drag generator 20 as is developed by control exciter 45, regardless of the speed of unwind reel i and the corresponding speed of drag generator 20. Since control exciter 45 is driven at a speed proportional to the speed of the strip l2, then for a given external excitation thereof determined by the setting of rheostat 48, its potential is always proportional to strip speed. Likewise, the potential on drag generator is proportional to strip speed and not unwind speed. Thus tension can be maintained at a substantially constant selected value on strip ii.

The series field 46 for the control exciter 45 reduces the output of control exciter 45 where current flows through its armature in order to compensate for the IR drop in the control field 2i oi. drag generator 20 and in the armature of control exciter 45, so as to maintain as nearly constant potential on drag generator 20 as possible when the control system is operating.

The booster generator I 6 supplies added potential to compensate for the IR drop in the loop circuit containing drag generator 20 and feed-back motor 35, and can be regulated for different amounts of compensating effect in accordance with requirements of the system.

Rheostats 48 and 23 can be commonly adjusted to establish a new value of strip tension, since they permit new values of excitation of drag generator 20 and control exciter 45 to be established.

to maintain substantially constant tension on strip material red therefrom to a driven process-' ing machine comprising a drag generator driven by the unwind reel, a feed-back motor arranged to be operated at a speed proportional to that of the driven processing machine, said drag generator and said feed-back motor having their armatures connected in loop circuit, a control exciter.

for said drag generator driven at a speed proportional to that of the driven processing machine, and a control field for said drag generator, said control exciter having its armature terminals connected, in series with said control field, across the armature terminals of corresponding polarity of said drag generator.

2. A control system for an unwind reel adapted to maintain substantially constant tension on strip 4 material fed therefrom to a driven processing machine comprising a drag generator driven by the unwind reel, a feed-back motor arranged to be operated at a speed proportional to that of the driven processing machine, said drag generator and said feed-back motor having their armatures connected in loop circuit, a separately excited shunt field for said drag generator, a control exciter for said drag generator driven at a speed proportional to that of the driven processing machine, and a control field for said drag generator, said control exciter having its armature terminals connected, in series with said control field, across the armature terminals of corresponding polarity of said drag generator.

3. A control system for an unwind reel adapted to maintain substantially constant tension on strip material fed therefrom to a driven processing machine comprising a drag generator driven by the unwind reel, a feed-back motor arranged to be operated at a speed proportional to that of the driven processing machine, said drag generator and said feed-back motor having their armatures connected in loop circuit, a separately excited shunt field for said drag generator, a control exciter for said drag generator driven at a speed proportional to that of the driven processing machine having aseparately excited shunt field and a series field in its armature circuit, and a control field-for said drag generator, said control exciter havingits armature terminals connected, in series with said control field, across the ,armature terminals of corresponding polarity 01 said drag generator.

4. A control system for an unwind reel adapted to maintain substantially constant tension on strip material fed therefrom to a driven processing machine comprising a drag generator driven by the unwind reel, a feed-back motor arranged to be operated at a speed proportional to that of the driven processing machine, said drag generatorand said feed-back motor having their armatures' connected in loop circuit, a booster generator in said loop circuit, a control exciter for said drag generator driven at a speed proportional to that of the driven processing machine, and a control field for said drag generator, said control exciter having its armature terminals connected, in series with said control field, across the armature terminals of corresponding polarity of said drag generator.

5.,--A control system for an unwind reel adapted to maintain substantially constant selected valves of tension on strip material fed therefrom to a driven strip processing machine such as a motor driven rolling mill comprising a direct current drag generator coupled to the unwind reel, 8. direct current series wound feed-back motor 'coupled to the driven strip processing machine,

No references cited.

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