US2180635A - Method and apparatus for cold rolling strip metal - Google Patents

Description

Nov. 21, 1939 L. IVERSEN 2.1 80,635

METHOD AND APPARATUS FOR COLD ROLLING STRIP METAL Filed July 15, 1935 3 Sheets-Sheet 1 INVENTOR Nov. 21, 1939. L. IVERSEN 2,180,

' METHOD AND APPARATUS FOR com) ROLLING STRIP METAL Filed July 15, 1935 3 Sheets-Sheet 2 Patented Nov. 21, 19:39

METHOD PATENT OFFICE AND APPARATUS FOR COLD ROLL- ING STRIP METAL Lorenz Iversen, Pittsburgh, Pa., assignor to Mesta Machine Company, Pittsburgh, Pa., a corporation of Pennsylvama Application July 15, 1935, Serial No. 31,432

13 Claims.

This invention relates to, the cold rolling of strip metal in a continuousjmill; that is to say, in a mill consisting of a series of stands adapted to work successively on the metal, different portions of the strip being acted upon by two or more stands of the mill at the same time. It is now well recognized that in cold rolling the compressive force of the rolls and tension on the strip are both important factors afiecting the reduction. With increasingly close gauge tolerances it becomes necessary to effect a close control of these factors. It has heretofore been proposed (Bedell Patent 1,964,241, dated June 26, 1934), to deflect the strip from a straight-line path as it travels between 'successivestands of a tandem mill so as to maintain a substantially constant tension on the strip. It has also been proposed to maintain a substantially unvarying tension by using electric driving motors for the mill stands,

which motors have suitable characteristics, as,

for example, a drooping power curve. The difllculty with these prior systems has been that they presuppose a uniform and unvarying quality of strip. As a matter of fact, however, the hot rolled strip which is used as a starting material in a cold rolling operation may for a variety of reasons be non-uniform. For example,"it may-have hard spots which offer undue resistance to reduction, and unless special treatment is accorded to these. hard spots there will inevitably be variations more-or less serious in the gauge of the strip. The systems heretofore employed have not been adequate to meet situations such as that just described,. and a further difflculty attendant 35 upon electric motor control or regulation is that the inertia of the moving parts is such as to destroyany possibility of instantaneous response to a changed condition. In consequence systems of that sort have not only failed to overcome the difflculties but hafle induced additional gauge variations by reason ofthe hunting which occurs.

I have found that superior resultsmay be obtained by deflecting the strip out of a straightline path between stands and subjecting it to a varying tension, the amount of tension being automatically adjusted in accordance with the characteristics of successive portions of the strip as it travels through the mill. Preferably the degree of pressure variation is lessened in the later stages 0 of reduction. At this time the differences in hardness between successive portions of strip will have been lessened in some degree by reason of the eifect of cold work.

I so arrange the mill and its associated parts 55 that a relatively short length of strip is subjected to deflection at any time. This not only makes for accuracy of tension effect but, what is more important, limits the effect of the varied tension to that portion of the strip which, because of its special characteristics, requiresan adjustment of the reducing forces. Suppose that there be a hard spot in a strip, the hard portion having a length, say, of five feet. It isnecessary to increase the tensile force which is applied to the strip .in order to reduce this hard spotin the same amount as the adjacent portions of the strip. Obviously the increased tension should be applied for only a relatively limited period of time as otherwise its effect will be applied to the portions of the strip adjacent the hard spot and will reduce them unduly. I therefore place the roll stands relatively close togethernot more than twelve work roll diameters apartand preferably'limit the span overwhich the advancing strip is deflected to not more than six work roll diameters.

In the accompanyingdrawings illustrating a present preferred embodiment of the invention,

Figure l is a diagrammatic view of a continuous mill employing the invention;

Figure 2 is a longitudinal section to enlarged scale of a portion of one of the mill stands, and

the associated tensioning mechanism;

Figure 3 isa section on the line IIIlII of Figure 2; and Figures 4 to 7 inclusive are diagrammatic views showing the various tension cifects which may be secured by suitable adjustment of the tension device.

The mill shown in Figure 1 comprises a series of stands 2, 3, 4 and 5 adapted to successively engage and cold roll steel strip fed from a coil holder 6. Each of the stands is shown as being of the well-known 4-high type having working rolls I and backing rolls 8 of larger diameter. The working rolls are driven through gear reductions 9 by strip passes out of the last stand, it is coiled on a reel I2 driven by a motor l3 through gearing 13a.

7 In the mill shown the working rolls are 18 motors ID of the constant speed type. After them spaced approxi- The tensioning rollers it are actuated and controlled by mechanism illustrated in detail in Figures 2 and 3. The same structure is employed between each two successive mill stands and a de- 5 scription of one will suffice for all. However, as hereinafter explaineddifferent adjustments are employed in different cases.

The tension roller I6 is mounted in a lever l1 pivoted on a cross shaft 3 mounted in the housing 10 IQ of the mill stand. The lever Ill has an arm 20 which is connected by a link 2| to a lever 22. The lever 22 is provided with three holes A, B and C arranged to accommodate a pin 23 which makes the pivotal connection between the link 2| and the lever 22. By placing the pin in different holes different effective lever links can be obtained. The lever 22 rocks on'a fulcrum pin 24 mounted on a base 25. The fulcrum pin is movable to any one of a variety of positions, four of which are indicated at W, X, Y and Z. The

mounting of the fulcrum pin is best shown in Figure 3. It is formed with roller portions 26 run- I ning on tracks 2! formed on the base and carries pinions 28 meshing with racks 29 fixed in 25 the base. Rotation of the fulcrum pin causes it to move along the tracks 21, the rack and pinion construction insuring positiveness of movement. Rotation of the fulcrum pin is effected by an adiusting lever 30 having a latch connection 3| 30 with an extension 32 of the fulcrum pin. A

thumb button 33 permits of engaging or disengaging the latch connection, as desired, so that the operating lever 30 can be conveniently. used. Operation of the main lever 22 does not exert any 5 force tending to displace the fulcrum pin 28 from any adjusted position, and any inconsequential forces which may tend to move it are effectually resisted by the mere weight of the operating lever 30 which, when the fulcrum pin has been moved to the desired adjusted position, is allowed to rest against a cross bar 38. The tensioning roller I6 is urged upwardly through the mechanism just described by means of a weight W attached to a plunger 35 and oper- The plunger 35 is carried in a bearing sleeve 31 line between successive stands, and'have also indicated more or less arbitrarily top, bottom and middle positions which the roller l6 may take.

Figures 4 to 6 inclusive show the tension exerted on the strip for different settings of .the several elements above enumerated. Figure 4, for example, shows the amount of tension in different positions of the roller it with the fulcrum pin located at W. There are three curves in this figure lettered A, B andC corresponding to positioning of the pin 23 in each of the holes A, B

and C.

In the earlier stages of reduction the apparatus will be so adjusted as to exert considerable force, lesser forces being employed as the reduction proceeds. The total magnitude of the force, as well as the amount of variation'therein for any given movement of the roller it may be ating in a cylinder 36 connected to the base 25.

readily fixed by the adjustments heretofore ric scribed.

In operation, if, say, the stand 2 fails to reduce a given portion of the strip in the same amount as adjacentportions, as, for example, if a hard spot is encountered, there is a corresponding decrease in elongation and as the hard spot travels over the span between the stand in which it was just rolled and the succeeding stand, the roller It will be deflected downwardly, thus increasing the tension on the strip and correspondingly increasing the amount of reduction effected on the hard spot in the succeeding stand because of the increased back tension which is applied. Similarly, if an undue reduction is effected in a stand there is a corresponding increase in elongation with consequent decrease in the tension.

The apparatus functions promptly whenever a condition such as this is encountered, and its effect is substantially limited to that portion of the strip which requires correction. Even though the effect be reflected in some small measure on portions of the strip at either side of the iard or soft spot, nevertheless the desired gauge is more closely approximated throughout the strip, and as successive stands and successive tension devices operate on the strip all irregularities are minimized or eliminated. This is especially so if the tension variations are reduced as the strip progresses through the mill.

An important feature of my invention is that thezcontrol is effected independently of the drive. The stands are driven, each at constant speed, and the necessity for complex electrical controls supposedly functioning to correct variations in the strip may be dispensed with.

I have illustrated and described a present preferred embodiment of the invention, but it will be understood that the same is not limited thereto but may be otherwise embodied or practiced within the scope of the following claims.

I claim:

1. In the method of cold rolling strip metal in a tandem mill having a plurality of driven stands, the steps consisting in driving the stands each at constant speed, subjecting the strip to successive cold reductions in the several stands, maintaining the strip under tension between two successive stands, and varying the tension between such stands independently of the driving of the stands.

2. In the method of cold rolling strip metal in a tandem mill having a plurality of -driven stands, the steps consisting in driving the several stands each at constant speed, subjecting the strip to successive cold reductions in the stands, main- ,taining the strip under tension between stands,

and varying such tension.

3. In the method of cold rolling strip metal in a tandem mill having a plurality of driven stands, the steps consisting in driving the stands each at constant speed-subjecting the strip to successive cold reductions in the several stands, maintaining the strip under a varying tension between successive stands, to compensate for irregularities in the strip, the amount of variation being less between later stands of the mill than between preceding stands. a

4. Apparatus for the cold rolling of metal strip 1 comprising spaced substantially constant speed roll stands adapted for the continuous rolling of the strip, means between the stands for deflecting the strip from a straight-line path, and means biasing the deflecting means and 'efiective for imposing a tension on the strip which decreases with increasing departure of the strip from a straight-line path between stands.

6. Apparatus for the cold rolling of metal strip comprising a pair of mills adapted for the continuous rolling of the strip, means for driving the mills each at constant speed, and means arranged to engage the strip between two suchmills and subject it to a varying tension.

7. Apparatusfor the cold rolling of metal strip comprising a pair of mills adapted for the continuous rolling of the strip, means for driving the mills each at constant speed, and means adapted to engage the strip between the mills and deflect it from a straight-line path, said means being effective for imposing a tension on the strip which decreases with increasing departure. of the strip from the straight-line path.

8. Apparatus for the cold rolling of metal strip comprising a plurality of mills adapted for the continuous rolling of the strip, tensioning means arranged between two successive stands adapted to engage the strip and deflect it from a straight line path between the stands and impose a varying tension thereon, and a second tensioning means arranged between stands at a point closer to the delivery end of the mill than the firstmentioned tensioning device, the second tensioning device being also adapted to impose a varying tension on the strip but less in amount than the first-mentioned tensioning device.

. 9. In the method of cold rolling strip metal in; a tandem mill having a plurality of driven stands, the steps consisting in driving the several'stands each at constant speed, subjecting the strip to successive cold reductions in the stands, maintaining the strip under tension between stands, deflecting the strip from a straight line path in its passage between stands by the application of a deflecting force, and varying such tension by varying the deflecting force.

10. In the method of cold rolling strip metal in a tandem mill having a plurality of driven stands,

the steps consisting indriving the several stands each at constant speed, subjecting the strip to successive cold reductions in the stands, maintaining the strip under tension between stands,

increased when a relatively hard portion of the,

strip travels between such stands.

11. In the method of cold rolling strip metal in a tandem mill having a plurality of driven stands, the steps consisting in driving the several stands, feeding a strip therethrough and subjecting the strip to successive cold reductions in the several stands, maintain g the strip under ,tension between stands, an compensating for local irregularities in the strip by varying the amount of tension between two successive stands as the portion in question, is being reduced in such stands while maintaining the speed of such stands substantially constant.

12. Apparatus for the cold rolling of metal strip comprising spaced roll stands adapted for support. I

13. Apparatus for the cold rolling of metal strip comprising spaced roll stands adapted for the continuous rolling of the strip, means between the stands for deflecting the strip from a straight line path, said means being movable toward or from operative position, means for urging the deflecting means toward operative cluding a lever having one arm operatively connected to the deflectingmeans and'the other arm operatively connected to the urging means, a fulcrum upon which the lever is rockably mounted, a fixed support, the fulcrum being movable thereon, and means for adjusting the position of the fulcrum on the support.

LORENZ IVERSEN.

40 pos tion, and connections between said means in-

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