US3535902A

US3535902A - Method and apparatus for straightening sheet materials

Info

Publication number: US3535902A
Application number: US709351A
Authority: US
Inventors: Theodor Sevenich; Peter Zens
Original assignee: Hoesch AG
Current assignee: Fried Krupp AG Hoesch Krupp
Priority date: 1967-03-06
Filing date: 1968-02-29
Publication date: 1970-10-27
Anticipated expiration: 1987-10-27
Also published as: BE711733A; GB1217013A; FR1555335A

Description

Oct. 27, 1970 1-. SEVENICH EI'AL 3,535,902

METHOD AND APPARATUS FOR STRAIGHTENING SHEET MATERIALS Filed Feb. 29, 1968 T E QOK SEVtE V IQH PE'FER ZEN-5 United States Patent Ofice 3,535,902 METHOD AND APPARATUS FOR STRAIGHTEN- ING SHEET MATERIALS Theodor Sevenich, Dortmund, and Peter Zens, Dortmund-Kirchderne, Germany, assignors to Hoesch Aktiengesellschaft, Dortmund, Germany Filed Feb. 29, 1968, Ser. No. 709,351 Claims priority, application Germany, Mar. 6, 1967,

1,602,461; Sept. 21, 1967, 1,602,468

Int. Cl. B21d 1/02 US. Cl. 72-160 8 Claims ABSTRACT OF THE DISCLOSURE Straightening sheet materials, especially sheet metal having at least a curvature in the transverse direction, by passing the sheet in a continuous movement in its longitudinal direction between two sets of straightening rollers having concave and convex outer surfaces, respectively, which act under pressure upon the convex and concave sides of the sheet, respectively, so as to eliminate said curvature.

The present invention relates to a method and an apparatus for straightening sheet materials and especially sheet metal which has a curvature extending transverse to the direction in which the material has been rolled in a hot-rolling mill.

In the production of sheet metal of any width it is the conventional procedure to wind the rolled sheet coming from the rolling train and while still in a hot condition into a coil and then, after it has cooled, to unwind it from the coil in a cutting apparatus in which it is cut transversely and/or longitudinally to the rolling direction to the desired dimensions. While being unwound from the coil, the sheet material is straightened and thereby plastically deformed in the longitudinal direction. This straightening operation, however, cannot prevent that residual stresses remain in the longitudinal direction of the sheet material and that the transverse components of these longitudinal stresses will cause the material to curve in the transverse direction. These transverse curvatures must be thereafter eliminated in a separate straightening operation outside of the cutting apparatus.

For straightening uneven parts of metal sheets, these sheets are generally passed through straightening machines which may be of different types. In one type of these machines the sheet material is passed between two superimposed rows of cylindrical straightening rollers which are rotatable in opposite directions and apply a pressure upon the opposite sides of the sheet. Another known type of these straightening machines comprises cylindrical straightening rollers which are bent by means of bracing rollers so that the sheet material running therethrough will be stretched longitudinally at certain areas whereby the waviness of adjacent areas of the sheet will be eliminated. Still another known type of straightening machines comprises short cambered straightening rollers which may be shifted axially on their shafts and act upon the particular areas of the sheet which are to be straightened. There is also a straightening method known in which two different types of these machines are combined so that the sheet metal is at first straightened in its longitudinal direction and thereafter in a separate operation in the transverse direction by means of a flexible straightening roller or a short straightening roller.

In all of these known methods the sheets to be straightened will be deformed in their direction of travel while the deformation which is attainable in the transverse direction is very small as compared with the longitudinal deformation. If it is necessary to eliminate transverse Patented Oct. 27, 1970 curvatures in the sheets, the latter must be passed several times through the straightening machine. Since repeated straightening operations cannot be carried out at all or only with great difiiculty in a cutting apparatus, the known straightening methods and the machines for carrying out these methods are unsuitable for continuously eliminating the transverse curvatures of metal sheets.

It is an object of the present invention to overcome the above-mentioned disadvantages of the known straightening methods and apparatus and to provide a new straightening method in which sheets or strips of metal or other materials will be completely straightened in the longitudinal and transverse directions by being passed only once through a new type and arrangement of straightening rollers.

For attaining this object, the invention provides that the sheets or strips to be straightened are given an initial stress contrary to the transverse curvature and are deformed beyond the elastic limit of the sheet material by a rolling operation in the longitudinal direction in which they are produced by the rolling train of the mill. The extent to which the elastic limit of the material is to be exceeded in the transverse direction of the sheet is preferably determined by the sum of the transverse components of the longitudinal stresses and of the initial stress itself which the sheet has in its transverse direction.

The stresses which according to the invention are produced in the transverse direction of the sheet should, however, preferably be kept far :below the elastic limit of the material since they are not needed to effect a plastic deformation of the material in the transverse direction. The transverse curvature of the sheets is therefore eliminated merely by plastically deforming the material in the longitudinal direction to such an extent that the transverse components of the stresses which are produced by this longitudinal plastic deformation will be sufficiently increased by the transverse stresses themselves.

For straightening sheets or strips especially of metal by a single continuous operation, the invention provides an apparatus which comprises two rows of associated straightening rollers which are disposed within two different levels and are provided with concave or convex outer surfaces, respectively. The straightening rollers with convex surfaces are preferably provided in the upper row and the straightening rollers with concave surfaces in the lower row since the sheets are preferably passed through these rollers with their transverse curvature extending in the upward direction. Since according to the new method only a small stress is to be produced in the transverse direction of the sheet or strip material, the degree of curvature in the axial direction of the straightening rollers is prefera bly made very large. The diameter of these straightening rollers and their distances from each other therefore have to be only slightly larger than those of the conventional cylindrical straightening rollers in order to attain the required permanent plastic deformation of the sheets in their longitudinal rolling direction for completely straightening the sheets in all directions.

The features and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying diagrammatic drawings, in which FIG. 1 shows a perspective view of a complete set of straightening rollers according to the invention;

FIG. 2 shows a perspective view of a plate, for example, of sheet metal which has been wound from a coil and cut off transversely;

FIG. 3 shows a perspective view of a set of straightening rollers consisting of two upper convex rollers and one lower concave roller for carrying out the first stage of the straightening operation;

FIG. 4 shows the lines of force in a sheet while the sheet is being bent about the lower concave straightening roller according to FIG. 3;

FIG, shows a perspective view of a set of straightening rollers consisting of one upper convex and two lower concave rollers for carrying out the second stage of the straightening operation; while FIG. 6 shows the lines of force in a sheet, for example, of metal, while the sheet is being bent about the upper convex straightening roller according to FIG. 5.

For carrying out the new method of straightening sheets or strips, for example, of metal, the invention provides a set of straightening rollers, as diagrammatically illustrated in FIG. 1, which comprises a row of lower rollers 1 with concave outer surfaces and a row of upper rollers 2 with convex outer surfaces. All of these straightening rollers l and 2 are ground so as to have substantially equal concave or convex curvatures 0, respectively, as indicated in FIG. 3.

FIG. 2 illustrates a sheet, for example, of metal 3 which has been unwound from a coil and has then been cut transversely to the desired length. This sheet has a curvature a in its longitudinal direction and a curvature b in the transverse direction. Both these curvatures a and b are to be straightened so that the sheet will be completely plane. For this purpose, the invention provides that in a first working stage the sheet is passed through the set of straightening rollers as shown in FIG. 3. This first part of the straightening operation gives the sheet an initial tension in the direction opposite to the original transverse curvature b by bending it for the distance b+c. This results in a compressive stress A on the upper side of sheet 3 and in a tensile stress A on its lower side, as indicated by the solid arrow heads in FIG. 4. These stresses A and A by themselves do not exceed the elastic limit of the material. In the longitudinal direction of sheet 3, the stresses A and A produce the stress components B and B as indicated in FIG. 4 by ordinary open arrow heads. The stress component B on the upper side of the sheet forms a tensile stress and the stress component B on the lower side of the sheet a compressive stress. The stress components B and B by themselves likewise do not reach the elastic limit of the material.

When the sheet 3 runs through the system of straightening rollers according to FIG. 3, it will be plastically deformed in the longitudinal direction about the lower concave straightening roller. This results in a tensile stress C on the upper side of the sheet and a compressive stress C on its lower side, as indicated by the double open arrow heads in FIG. 4. In the transverse direction of the sheet, the stresses C and C produce the stress components D and D as indicated by triple open arrow heads in FIG. 4. Since the stress component D on the upper side of the sheet is a compressive stress, it is added to the initial stress A while the stress component D is a tensile stress and therefore likewise added to the initial stress A If the sheet is plastically deformed to a sufficient extent in the longitudinal direction of the stresses C and C the sums of the stresses of the components A and D and of the components A and D will also exceed the elastic limit of the material in the transverse direction and a plastic deformation of the sheet will take place in the transverse direction which eliminates the original curvature b of the sheet. The curvature a in the longitudinal direction of the sheet will, however, at first be increased by the straightening operation by means of the straightening rollers according to FIG. 3.

Since the entire roller arrangement as illustrated in FIG. 1 consists of several convex straightening rollers in the upper row and several concave straightening rollers in the lower row, the first stage of the straightening operation as above described will be followed immediately by the second stage by means of the roller arrangement according to FIG. 5. In this second straightening stage, the sheet will be stressed in the transverse direction in the same manner as in the first straightening stage according to FIG. 3. By bending the sheet in the transverse direction, the compressive stress E will be produced on the upper side of the sheet and the tensile stress E on its lower side. These stresses are indicated in FIG. 6 by single open arrow heads. When runing through the roller arrangement according to FIG. 5, sheet 3 will be bent in the longitudinal direction about an upper convex roller 2. The stresses G and G which are then produced are indicated in FIG. 6 by double open arrow heads. These longitudinal stresses G and G produce the transverse components H and H in the transverse direction, as indicated in FIG. 6 by triple open arrow heads. As may also be seen in FIG. 6, the stresses E and E extend in the opposite direction to the transverse components H and H Therefore the transverse components H and H will reach the elastic limit of the material only after the latter has been plastically deformed in the direction of the longitudinal stresses G and G to a greater extent than that which occurs during the passage of the sheet through the roller arrangement according to FIG. 3 in which the transverse components D and D are formed which are produced by the longitudinal stresses B and B as indicated in FIG. 4. The roller arrangement according to FIG. 5 thus not only bends back the sheet so as to eliminate its deformation in the longitudinal direction which was produced by the preceding straightening stage by means of the roller arrangement according to FIG. 3, but it also eliminates the curvature a which originally existed in the longitudinal direction. The order of succession in which the individual straightening stages may be carried out may also be reversed and, if necessary or desirable, they may be repeated several times.

The considerable advantage of the straightening method according to the present invention over the straightening methods as heretofore known is particularly the fact that the transverse curvature of a sheet or strip of metal of other material may be completely eliminated by passing it only once through the set of straightening rollers according to FIG. 1. It is another advantage of the new method that it also permits the different transverse curvatures of sheets and strips of different thicknesses to be completely eliminated by means of the same uniformly ground straightening rollers and by merely adjusting the upper and lower straightening rollers relative to each other so as to exert the required pressures upon the sheets or strips in accordance with their different thicknesses. If the method according to the invention is applied, it is therefore no longer necessary to carry out any additional expensive straightening operations outside of the cutting apparatus.

Although our invention has been illustrated and described with reference to the preferred embodiment thereof, we wish to have it understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed our invention, what we claim is:

1. A method of straightening sheets or strips of metal or other materials having at least a curvature transverse to their longitudinal direction of travel through a rolling train or other apparatus in which they have been produced, wherein a pressure is exerted upon said sheets in the direction opposite to said transverse curvature and said sheets are deformed in said longitudinal direction beyond the elastic limit of their material, whereby said sheets are bent so as permanently to eliminate said transverse curvature.

2. A method as defined in claim 1, wherein said pressure is exerted upon said sheets and said sheets are deformed by passing said sheets in one continuous movement in said longitudinal direction between two sets of rotating straightening rollers having concave and convex outer surfaces, respectively, and pressing said convex rollers upon the concave side of said sheets and said concave rollers upon the convex side of said sheets.

3. A method as defined in claim 1, wherein said elas tic limit is exceeded to an extent determined by the sum of the transverse components of the longitudinal stresses and the transverse stresses of said sheets.

4. An apparatus for straightening sheets or strips of metal or other materials having at least a curvature transverse to their longitudinal direction comprising a set of at least two upper straightening rollers and a set of at least two lower straightening rollers rotatable about substantially parallel axes, each roller of one set being positioned closely adjacent a roller of the other set, each roller of one of said sets having a concave outer surface and each roller of the other set having a convex outer surface, whereby when said sheets or strips are passed in a continuous movement between said two sets of rollers in said longitudinal direction and substantially transverse to the axes of said rollers, they are straightened in the longitudinal and transverse directions thereof.

5. An apparatus as defined in claim 4, wherein said concave and convex rollers have substantially the same degree of curvature.

6. An apparatus as defined in claim 4, wherein said rollers of said upper row have a convex outer surface and said rollers of said lower row have a concave outer surface.

7. An apparatus as defined in claim 4, wherein one of said sets has at least three rollers, two of said three rollers cooperating with each of the rollers of the other set.

8. An apparatus as defined in claim 4, wherein each roll of one set has two rolls of another set cooperating therewith and the axes of the rolls of each set are located substantially in a single plane, the planes being parallel.

References Cited UNITED STATES PATENTS 1,584,499 5/1926 Zachhuber 72-176 X 1,854,021 4/1932 Derby 72-176 X 2,240,548 5/1941 Cairns 72179 X 2,337,047 12/1943 Hunter 72-179 2,348,539 5/1944 Harper 72176 2,470,235 5/ 1949 Burrell 72-179 X 2,692,003 10/1954 Nieman et a1. 72-179 2,854,056 9/1958 Stanius 72-176 X MILTON S. MEHR, Primary Examiner US. Cl. X.R.