US3461705A - Apparatus for controlling the deflection of the rolls of a rolling mill - Google Patents

Description

Aug. 19, 1969 K. J. NEUMANN 3,461,705 APPARATUS FOR CONTROLLING THE DEFLECTION OF THE ROLLS OF A ROLLING MILL Filed Nov. 14, 1966 :5 Sheets-Sheet 1 usN laL INVENTOR. KARLIJ. NEUMANN ATTORNEYS.

Aug. 19., 1969v K. J. NEUMANN 3,461,705

APPARATUS FOR CONTROLLING THE DEF'LECTION OF THE ROLLS OF A ROLLING MILL' Filed Nov. 14,1966 3 Sheets-Sheet 2 INVENTOR. HQ 5 KARL. J. N'EUMANN BY Maya, 7M 5 80:14;

ATTORNEYS.

Aug. 19, 1969 NEUMANN 3,461,705

APPARATUS FOR CONTROLLING THE DEF'LECTION OF THE ROLLS OF A ROLLING MILL Filed Nov. 14, 1966 5 Sheets-Sheet 3 INVENTOR.

KARL J. NEUMANN ATTORNEYS.

United States Patent 3,461,705 APPARATUS FOR CONTROLLING THE DEFLEC- TION OF THE ROLLS OF A ROLLING MILL Karl Josef Neumann, St. Ingbert-Saar, Germany, assignor to Verwaltungsgesellschaft Moeller und Neumann Offene Handelsgesellschaft Filed Nov. 14, 1966, Ser. No. 593,955 Claims priority, application Germany, Nov. 17, 1965,

Int. 01.13211) 59/00, 31/16 US. Cl. 72-243 Claims ABSTRACT OF THE DISCLOSURE The present invention pertains to the art of rolling mills, and more particularly to an improved apparatus for controlling the deflection of the rolls of a rolling mill.

The invention is particularly applicable for use in fourhigh rolling mills of the type used in the production of metal sheets and strips in cold and hot rolling processes, and it will be described with particular reference thereto; however, it is appreciated that the invention is capable of broader application and could be used on a variety of rolling apparatus used in the production of a variety of products.

As commonly used in the rolling art, the term fourbig when used to describe a rolling mill, refers to a mill having a pair of opposed working rolls each provided with a back-up roll positioned directly opposite its work contacting side. Other types of mills are known in which one or more intermediate rolls are positioned between the working rolls and their respective back-up rolls. As used in the following specification and claims, the term back-up rolls will denote those rolls that are directly in contact with the working rolls, without regard to whether they would normally be considered back-up or intermediate rolls.

As is well known, the rolls of a rolling mill tend to deflect or bend during the rolling of material into plates or sheets. As a consequence, the resulting product is thicker at the center than at the outer edges. Because of the continuously increasing tolerance requirements as to flatness and uniformity of thickness, especially with regard to cold rolled sheets and strips, numerous suggestions have been made to provide a uniform sheet or strip by controlling the bending or deflection of the rolls in accordance with the rolling pressure. Generally, these suggestions have involved applying corrective bending moments to the back-up rolls so that the resulting product is fiat and has a uniform thickness across its entire width.

Correcting or compensating bending or deflecting moments having different directions or senses of rotation may be applied to control the uniformity of the strip. In the present specification, the term positive bending moments is used to denote those applied bending moments which have a direction or sense of rotation opposite to the bending moments resulting from the rolling force. Conversely, applied bending moments, which have the same direction or rotational sense as the moments resulting from the rolling force, will be hereinafter referred to as negative bending moments.

It is common knowledge that a four-high mill is often provided with a mechanism which produces positive, as well as negative, bending moments in the rolls to compensate for moments caused by the rolling operation. These prior mechanisms exert the bending moments either at only the back-up rolls or the working rolls alone.

When the correcting or compensating moments are applied to the rolls, in the manner disclosed above, certain disadvantages are experienced. For instance, the working rolls make contact with the back-up rolls at selected small areas either the ends of the rolls (in the case of positive bending moments applied to the working rolls or of negative bending moments applied to the back-up rolls) or at the middle of the rolls (in the case of negative bending moments applied to work-rolls or positive moments applied to the back-up rolls). Consequently, when rolling pressure is applied by the mill, pressure between the working rolls and their respective back-up rolls is increased at the small contact areas at either the ends of the rolls or the middle of the rolls. This is because the pressure contact between the rolls, which results from the pre-set correcting moments, is on the limited contact areas of the rolls and the pressure resulting from the rolling force is also on these same limited contact areas. Consequently, increased rolling wear is produced at the contact areas. Additionally, in the case of driven back-up rolls, the friction contact between the back-up rolls and the working rolls is at a maximum along these contact areas.

In the past these difficulties have been eliminated by crowning the rolls; however, as is well known, each particular crowning is applicable for only one particular product width, rolling force, rolling speed, etc. Consequently, roll crowning is generally unsatisfactory because of the limited range in which any particular degree of crowning is useful.

In the case of known four-high rolling mill stands include means for correcting the bending curvature of the rolls, the forces which produce the bending moment are applied to the extended necks of the back-up rolls. The back-up rolls, as well as the work rolls, are of cylindrical form. The driven work rolls have to drive the heavy backup rolls by frictional contact and for this reason they must be pressed with sufficiently high force against the backup rolls. In the case where the back-up rolls are pre-bent opposite to the bending action which may be expected from the rolling pressure, the pre-bending forces produce a locally limited contact between the work rolls and the back-up rolls which are mechanically curved by the bending forces. Consequently, no optimum frictional contact can be expected since the rolls contact each other during the idle run merely at the center of their roll surfaces over a more or less extended area. In this way one is forced, during the reverse operation of the mill stand, and particularly during rolling of metal plates, where a frequent reversing is necessary in comparison with strip rolling, to disconnect the pre-bending of the rolls during the idle run in order to maintain the rolls in frictional contact over their entire roll surface lengths. This requires complicated control devices since the counter-bending forces must be connected and disconnected exactly at the moment when the rolled goods are seized by the rolls or leave the roll gap in order to produce the optimum friction contact over the entire roll surface length by the rolling pressure.

Aside from these special idle run conditions a pressing action between the work rolls and the pre-bent back-up rolls, which is locally limited during the idle run, has also an unfavorable effect during the rolling operation. For example, due to the rolling pressure which is distributed over the width of the flat product, when the work rolls following the contour of the back-up rolls are pressed against the latter, it may be noted that the pressing action between the work rolls and the backup rolls is increased at the center of the roll surfaces because the pressing action from bending moments for correcting the bending curvature is already limited locally during the idle run, and because during rolling supplemental forces are added at the points of the locally limited contacts, while towards the edges of the roll surfaces there exist only the forces from the rolling pressure. This produces not only a locally increased rolling wear, but also, a roll flattening action, which depends on the forces which are transmitted from a work roll to the associated backup roll during their cooperation, becomes variable. In the case where during the idle run a friction contact exists only in the center of the rolls a roll flattening etfect is produced during rolling which decreases towards the edges of the rolled goods, i.e. a narrower roll gap so that the rolled goods are thinner at the edges than at the center,

The present invention eliminates the aforementioned difliculties and provides a method and apparatus for adjusting the bending moments acting on the back-up or intermediate rolls, as well as on the working rolls. By the use of the present invention for correcting the bending curves of the rolls, the rolling force is distributed uniformly over the width of the sheet or strip being rolled. Additionally, because of the manner in which the bending curves of the rolls are adjusted, the locally limited pressure contact areas between the back-up or intermediate rolls and the working rolls is eliminated and the rolls have generally uniform pressure contact throughout their length.

In accordance with the one aspect of the present invention, a method is provided for adjusting the deflecting of the rolls of a rolling mill of the general type described. This method comprises applying predetermined bending moments to both the working roll and the back-up roll in contact therewith, to produce a desired deflection in the rolls. The bending moments are chosen so that the deflection resulting in the rolls produces a substantially uniform pressure contact throughout their length. In this manner increased wear between the rolls is eliminated.

In accordance with another aspect of the present invention, apparatus is provided for adjusting the deflection of the rolls of a rolling mill of the general type described. This apparatus includes first means for applying a predetermined bending moment to the working roll, and second means associated with the backup roll for applying a corresponding bending moment thereto. The bending moments applied are such that the deflections resulting in the rolls produces a substantially uniform pressure contact along the axial lengths of the rolls.

A primary object of the present invention is the provision of a method of controlling the deflection of the rolls of a rolling mill in a manner which eliminates the problems previously encountered with limited areas of high pressure contact between the working rolls and their back-up rolls.

An additional object is the provision of a method which permits the production of rolled sheet products that are of substantially uniform thickness.

A further object is the provision of apparatus for controling the deflection of the rolls of a rolling mill so that the rolling force is distributed uniformly throughout the line of contact between the working roll and the back-up roll.

A still further object is the provision of apparatus to produce a variable predetermined deflection in the rolls of a rolling mill.

These and other objects and advantages will become apparent from the following description used to illustrate the preferred embodiments of the invention as read in connection with the accompanying drawings in which:

FIGURE 1 is an elevational view, somewhat diagrammatic, of a four-high rolling mill and showing a first embodiment of the present invention;

FIGURES 2 and 3 are partial elevational perspective views, somewhat diagrammatic, showing two additional embodiments of the present invention;

FIGURES 4 and 5 are elevational views of a four-high rolling mill showing, in somewhat diagrammatic form, two additional embodiments of the present invention; and

FIGURES 6-9 are partial elevational views, somewhat diagrammatic, showing four additional embodiments of the present invention.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIGURE 1 shows a four-high stand comprising the back-up rolls 1 and 2, the opposed work rolls 3 and 4, the frames 5 and 6, the back-up roll chocks 7 and 8, or 9 and 10, and the work roll chocks 11 and 12, or 13 and 14. The extensions of the roll necks as well as the rod parts are merely indicated by solid lines. Throughout the: remaining figures the same reference numerals are used to denote the same or corresponding parts.

In FIGURE 1, one preferred embodiment of a device for influencing the bending curve of the rolls is illustrated. This device is comprised of hydraulic power units 15, for example, double acting pistions, mounted on the frames 5 and 6. The pulling or pushing rods 16 of these power units act on the extended necks 1a or 2a of the back-up rolls 1 and 2. This portion of the device is already known in the art.

The invention is characterized by length adjustable pull or push rods 17 which extend between the necks 1a, 2a of the back-up rolls and the necks 3a, 4a of the work rolls 3, 4. The rods 17 are of adjustable length in order to take into account changes in roll diameter resulting from the grinding off of the rolls. It is readily seen that not only at the back-up roll necks 1a, 2a, but also at the work roll necks 3a, 4a, positive bending moments are exerted when the pressure chambers 15a of the hydraulic power units are placed under pressure. These positive bending moments are indicated by solid arrows. The dashline arrows indicate negative bending moments which are produced when the outer pressure chambers of the hydraulic power units 15 are pressurized.

In View of the fact that the resistance moments of the back-up rolls and work rolls are different, supplemental hydraulic power units 20 are added to the pulling or pushing rods 17 between the back-up and the work rolls. The pistons of these power units are pressure contacted on both sides and adapted to be locked. In this manner it is possible to adjust the ratio of the bending moments which are applied to the back-up rolls and the work rolls. In the normal case where positive bending moments are to be produced not only are the pistons of the supplemental hydraulic power units 20 locked, but the pressure in the pressure chambers 15a of the main power units 15 are increased. In special cases it would of course be possible to produce, by the supplemental power units 20, oppositely directed bending moments at the back-up and work rolls.

In the embodiment according to FIGURE 7, right side, the length adjustable pull or push rods 17 with their power units 20 are missing. Their effect is replaced by known hydraulic power units 22 between the chocks 12 and 14 of the work rolls 3 and 4. These pressure cylinders, known for the balancing of the upper work roll 3, must be designed, within the scope of the invention, with suflicient power to influence the bending curve of the work rolls. With this arrangement positive as well as negative bending moments may be created at the back-up rolls 1 and 2; however, at the work rolls 3 and 4, only positive moments can be produced.

In FIGURE 2, the arrangement according to FIGURE 7 has been further developed with the use of a known arrangement. At the upper frame yoke only a single hydraulic power unit 15 is arranged. This unit is guided in a vfloating manner over the guide bars 24 of the stand.

The piston rod of the power unit is pivotally connected at rod 16 at the extended necks 1a of the back-up roll 1. As the perspective view shows, the cylinder of the power unit is positively connected through a cross-beam 26 to which is attached a pair of push rods 28 connected through a cross-beam 30 to the extended necks 2a of the other back-up roll. If the pressure chamber 15a of the hydraulic power unit is put under pressure, positive bending moments are introduced into both of the back-up rolls. The bending curve of the work rolls 3, 4 is influenced, as shown in the example of FIGURE 7, by hydraulic power units 22 acting between the chocks of the work rolls.

The embodiment of FIGURE 3 is similar to that shown in FIGURE 2. However, in this embodiment supplemental hydraulic power units are utilized to apply bending moments to the work rolls, instead of the power units 22. As shown, hydraulic power units 20 are associated with pull or push rods 17 which travel as an extension of the rods 16 between the extended necks 1a or 2a of the back-up rolls and the necks 3a or 4a of the work rolls. In this way, the sense of rotation of the correcting bending moments to be introduced may be selectively set, for this purpose the main power unit 15 must be adapted to be pressurized on both sides. With reference to FIGURE 3 a further development according to the invention consists in that instead of the power units 22 between the chocks 12, 14 of the work rolls the piston rod 16 of the floating power unit 15 is connected as an extension beyond its contact point at the back-up roll with the necks 3a of the subsequent work roll 3 and the necks 4a of the other work roll 4 over a supplemental power unit 20 with the pair of pull or push rods 28 to the other back-up roll. The pistons of the supplemental power units 20 are adapted to be pressurized on both sides and locked in a desired position.

FIGURES 4 and 8 show embodiments in which the supplemental hydraulic power units 20 are eliminated without loss of the ability of selectively reversing the sense of rotation of the correcting bending moments. In these embodiments the hydraulic power units 15 may be fixed to the frames 5 (FIGURE 4) or arranged in a floating manner at the frames 6 (FIGURE 8). The pull and push rods 16 of the hydraulic power units of both of these embodiments are pivotally connected approximately at the level of the work rolls 3, 4, to an oscillating or twoarm lever 30. The outer ends of the levers 30 are connected to the extended necks 1a or 2a of the backup rolls. The two-arm levers 30 are otherwise positioned by intermediate supports 32 which lead to the contact points of the back-up roll into an approximately horizontal position. In this way it is possible to make the ratio of the effective levers 30 variable by displacing the rods' 34 between the levers and the pull or push rods 16. For this purpose the rods 34 are adjustably guided as slide members in slots 36 of the levers. It is understood that the pull or push rods 16 cannot cross the extended backup roll necks 1a, 2a, and for this purpose they are constructed as double rods in a manner not shown in detail. The double rods being supported by cross-beams and connected to a pair of levers 30 each. The inner ends of the levers 30 are pivotally connected to the ends of the work roll chocks 11, 13 or 12, 14. The chocks are provided withslots or openings into which the levers extend for operative engagement.

Due to the arrangement of the levers 30 the pull or push forces of the power units 15 are fed in a simple manner and in the same direction as bending forces in a regular distribution to the back-up and work rolls. The relative bending moments applied to the work rolls and back-up rolls is, of course, determined by the set lever ratio of the levers. This adjustability of the lever transmission makes it necessary that the pressure units 15 be supported at 38 in a pivoting manner on the frames 5.

For the embodiment according to FIGURE 8, the

above-mentioned applies to the full extent except that for each frame side only, one hydraulic power unit is provided in a floating manner as described with respect to FIGURES 2 and 3.

In all embodiments of the invention of the rolling mill described so far, the reaction of the bending forces goes into the screws of the screw-down or setting device. This makes the initial setting under load, as it is usually done during cold rolling, more diflicult. Complications are also encountered when the rolling mill is provided with an automatic roll gap control in which the roll forces are measured by means of pressure gauges placed under the pressure screws. The reaction forces of the device for correcting the bending curves must then be made ineflfective to permit the automatic roll gap control to function properly. These relationships have already been recognized and between the' pressure screws of the screw-down devices and the chocks of the back-up rolls beams which are resistant to bending have been disposed by means of which the correcting bending forces are backed up in a closed system. In using this known measure and in accordance with FIGURE 5, the invention proposes that the beams 40 between the pressure screws 42 of the screw-down device and the chocks 7 of the backup rolls 1 constitute supports for the hydraulic power units 15. In FIGURE 5, these hydraulic power units are pivotally supported in slots 40a of beams 40 at 44. The transfer of the bending forces by means of levers 30 corresponds to the embodiment of FIGURE 4. Of course the construction with the support beams 40 can be applied to all other embodiments described so far.

A further possibility of maintaining the bending forces in a closed system, as discussed with reference to FIG- URE 5, is shown in FIGURE 9. Here the hydraulic power units 15 are arranged laterally of the chocks 8 of the back-up rolls 1 and the chocks of each back-up roll are connected to each other by a bridge 46 in a manner which prevents them from tilting or twisting. It is also true here that besides the beam construction shown any other power transfer is applicable including the arrangement of floating hydraulic power units 15.

FIGURE 6 shows an embodiment without hydraulic power units connected at the frames so that the disassembly of the rolls is facilitated and the rod arrangement is simplified. The device for producing the correcting bending moments according to this embodiment of the invention consists merely of length-adjustable pull or push rods 50, 52 with built-in power units 20. The rods extend between the extended necks 1a or 2a of the back-up rolls 1, 2 and the necks 4a or 3a, or 11 and 13, of those work rolls 4 or 3, which, as viewed from the particular back-up roll, are located on the outer side of the rolling gap. The stroke of the power units 20 must, in this case, comprise the entire adjusting distance of the rolls because the rods 50, 52 cross the rolling gaps. As the rods 50, 52 cross each other in the side view, a rod, in the embodiment shown, the lower rod 52, is suitably provided behind the power unit 20 with a cross-beam 54 which is connected to the piston rod and over a rod pair 52a and an additional cross-beam 56 to the necks 3a of the upper work roll 3.

The arrangement according to FIGURE 6 also permits correcting bending moments of either direction or rotation to be applied to both rolls on the same side of the roll gap. If, for example, the outer pressure chamber 20a of the power units 20 is placed under pressure the rods 50, 52 are pressure rods and exert forces on the roll necks which produce positive bending moments for correcting the bending line of the rolls. In case the other pressure chamber is pressurized negative bending moments arise. Due to the coupling of the rolls of different gap sides, positive or negative bending moments in the same direction are produced in the rolls on each roll gap side in spite of oppositely directed push or pull forces in the rods 50, 52.

A third possibility of operation of the embodiment of FIGURE 6 exists. The pistons of the hydraulic power units 20 can be hydraulically locked, if desired, after a certain preliminary pressure is provided to produce positive bending moments. Then, if during rolling the backup rolls bend under the roll forces, the extended necks 1a, 2a of the back-up rolls push through the push rods 50, 52 and the locked power, units 20, in the sense of producing positive bending moments on the necks 4a or 3a of the work rolls. Depending on the work rolls resistance to bending moments, or the given lever ratios, there arises a reverse efiect of the forces from the work rolls into the push rods 50, 52 in the sense of producing positive bending moments at the pins 1a, 2a of the backup rolls. Due to the fact that according to the invention the push or pull rods 50, 52 attack at the back-up roll necks 1a, 2a, with a larger lever arm than at the work rolls, as FIGURE 6 shows, the bending moments introduced into the back-up rolls are increased corresponding to their higher resistance moment with respect to the resistance moment of the work rolls.

In order to take into consideration in all embodiments of the invention that the work rolls must be disassembled often, and the back-up rolls at larger intervals for a regrinding, means could be provided to permit the pull or push rods to be easily pivoted away by means of intermediate rods at least at the drive free ends or those ends of the work rolls which are first pulled from the frame during the roll change.

As far as the operation of the devices for correcting the roll bending curves is concerned one may operate in a known manner with a prebending of the rolls, although the hydraulic forces can be set only upon starting of the rolling operation and may be regulated or controlled with reference to the roll force. The regulation may be adjusted by thickness measuring devices distributed over the width of the flat products. Since during cold rolling deviations of the strips from the plane condition are easily recognizable with the naked eye a visual control alone would be suflicient here.

In all the embodiments it is a particular advantage of the arrangement according to the invention for correcting the bending curve of the rolls that no special suspension means for balancing the upper rolls must be provided.

The invention has been described in great detail sufficient to enable one of ordinary skill in the rolling mill art to duplicate the invention. Obviously, modifications and alterations of the preferred embodiments described will occur to others upon a reading and understanding of this specification and it is my intention to include all such modifications and alterations as part of my inventions insofar as they come within the scope of the appended claims.

Having thus described my invention, I claim:

1. In a rolling mill including a frame, a pair of opposed work contacting rolls and at least two back-up rolls carried by said frame, and means for varying the spacing of said work contacting rolls, the improvement comprising: first means for adjustably applying a pre determined bending moment to said work contacting rolls,

and second means for adjustably applying a predetermined bending moment to said back-up rolls, the first means and second means being related so the bending moments applied to each of said back-up rolls and their associated work contacting rolls produce substantially uniform pressure contact between the associated rolls.

2. The improvement as defined in claim 1 wherein said second means include a movable piston carried by said frame and having a connection between said piston and at least one of the ends of said back-up rolls, and wherein said first means include an adjustable connecting member extending between the said at least one end of said one back-up roll and at least one end of one of said work contacting rolls.

3. The improvement as defined in claim 2 wherein said adjustable connecting member comprises a cylinder and piston means.

4. The improvement as defined in claim 1 wherein said second means includes a movable piston carried by said frame and having a connection between said piston and at least one of the ends of said back-up rolls, and wherein said first means includes piston means positioned between the ends of said work contacting rolls.

5. The improvement as defined in claim 4 wherein said second means comprises a vertically extending cylinder and piston unit flOatingly carried on said frame with a first force transmitting member extending between said piston and one end of one of said back-up rolls, and a second force transmitting member extending between said cylinder and one end of the other of said backup rolls.

6. The improvement as defined in claim 1 wherein said second means includes a lever having one end drivingly connected with the end of one of said work contacting rolls, and said first means includes means drivingly connecting the other end of said lever with the end of one of said back-up rolls, and adjustable force producing means connected to said lever at a point intermediate the ends thereof.

7. A method of controlling the deflection of the rolls of a rolling mill having a pair of opposed work contacting rolls and a backup roll associated with each of said work contacting rolls, said method comprising: applying a first predetermined bending moment to at least one of said work contacting rolls, and a second predetermined bending moment to said back-up roll associated with said one work contacting roll, said bending moments being chosen so that the deflection resulting in said one work contacting roll and its associated back-up roll produces a substantially uniform pressure contact therebetween.

8. The improvement as defined in claim 1 wherein said second means includes at least one cylinder and piston means.

9. The improvement as defined in claim 1 wherein said second means is connected to the ends of said backup rolls, and said first means is connected to the ends of said work contacting rolls.

10. The improvement as defined in claim 1 wherein said first and second means include piston and cylinder power means.

References Cited UNITED STATES PATENTS 5/1966 Stone 72-245 5/ 1967 Plaisted 72-8

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