Patent Publication Number: US-2012028068-A1

Title: Method for producing profiled metal sheets

Description:
The present invention relates to a method for producing a profiled metal sheet according to the features of claim  1 . 
     Roll forming (cold roll fowling) is a continuous process in which a profile is manufactured from a sheet metal strip. With this method, several processing steps can be performed simultaneously, such as embossing, cutting, decorating, perforating etc. This differentiates roll forming from other techniques, such as extruding, trimming or bending pressing. An advantage of roll forming is that large series with the same cross-section can be manufactured within a relatively short time. Different metals can be used during this process. 
     This method can also be employed for manufacturing profiles with variable cross-sections, but considerable efforts are needed for this purpose. If profiles with variable cross-sections are profiled, i. e. profiles which have cross-sections differing over their length, this can be called flexible profiling. 
     Bending is a shaping manufacturing method. A bending moment is applied to the material and causes a permanent deformation. Metal sheets are bent basically by folding of a surface portion with respect to the remaining surface of a sheet-metal strip. Depending on the methods and machines employed, relevant characteristics of the workpiece, such as bending edge, bending angle or bending radius, are defined and reproducible. 
     The disadvantages of the prior art producing profiled metal sheets can be summarized as follows. Flexible profiling cannot be achieved easily and an easy guidance of a profile is not possible since contours to be guided must first be formed. Also, roll forming and variability in height are coupled to another. Furthermore, with roll forming, the necessary upsetting and extension deformations, for example, cannot be easily introduced into a flexible cross-section. Also, it has not been possible to easily adapt the shape of the parts to the load up to this point. In addition, the machines used for bending, in particular the presses, are relatively expensive. 
     The aim of the present invention is therefore to provide an easy-to-implement, resource-conserving conserving and cost-effective method by means of which the disadvantages of the prior art described above can be eliminated. 
     This aim is achieved by a method with the characterizing features of claim  1 . 
     Advantageous further developments of the invention are indicated in the dependent claims. 
    
    
     
       A detailed description of the invention by means of the appended drawings will now follow wherein: 
         FIG. 1  shows some variants according to the invention and their forming methods; 
         FIG. 2  shows some variants according to the invention from  FIG. 1  and perspective views thereof, and 
         FIG. 3  shows a schematic presentation of a forming process according to one embodiment of the present invention. 
     
    
    
     The present invention refers to a method for producing a profiled metal sheet. The method comprises the following steps in the indicated order. In step a), roll forming of a sheet metal strip by means of a conventional or rigid roll forming unit or a flexible roll forming unit operated like a conventional or rigid roll forming unit is performed. The sheet metal strip determines a first working plane of the roll forming unit in respect to which parts of the sheet metal strip are bent up to form the profiled metal sheet. In addition, the bent parts of the sheet metal strip are curved at least partially in respect to the first working plane. In step b), bending of the profiled metal sheet by means of a bending unit is performed. In doing so, the bent up parts of the profiled metal sheet are bent such that a second working plane is formed and the first working plane is curved. 
     The profiled metal sheets produced with the method according to the invention can be open or closed. They can furthermore have a variable cross-section in the direction of their longitudinal axis. In addition, the profiles can be straight or bent. 
     In one embodiment, the method furthermore comprises a step c) after step b). In step c), roll forming of the profiled metal sheet is carried out using a conventional or rigid roll forming unit or a flexible roll forming unit operated like a conventional or rigid roll forming unit. Here as well, parts of the profiled metal sheet are bent up with respect to the second working plane. Also, in this step, roll forming comprises a supporting measure. In one embodiment, the supporting measure can be carried out at the first working plane. For this purpose, individual rollers or roller pairs movable in at least one axis can follow the profile contour in a controlled manner. During this process, the profile must be supported after the (first) bending so that it can be guided through the roll forming unit without any problems, such as deformation, during the subsequent roll forming process. There are different supporting possibilities. 
     One possibility is guiding or supporting in the roll forming unit by means of rollers or roller pairs. During this process, the rollers/roller pairs must follow the new bent contour, i. e. they must be movable at least in one axis and able to track the contour with a corresponding control. With reference to the following embodiment, with the top-hat profile, the bottom must be supported, depending on the current height, with rollers which can track the longitudinal section in the vertical direction. In each stand of the roll forming unit following the bending, the rollers or roller pairs can thus be moved in height for support. 
     Alternatively, the bent profile can also be placed and clamped in a kind of “negative mold” and guided through the roll forming unit on a linear guide. However, in this case, a continuously guided process is not possible and the mold or molds must permanently be returned to the head of the unit. 
     In another embodiment, the method further comprises a step d) after step c). In step d), the profiled metal sheet is bent by means of a bending unit. During this process, the first and the second working plane are at least partially curved. 
     In one embodiment, the bending in step b) can take place on one plane. In another embodiment, the bending in step d) can take place on one plane, on two planes or on three planes. If bending takes place on two planes, for instance, new roll forming lines can be aligned at the bottom and on the side, which are then bent or formed, respectively, in the subsequent roll forming process. If bending takes place on three planes, a torsion can be introduced into the profile. 
     In the method according to the invention, at least one dimension of the cross-section of the profiled metal sheet can be kept constant or vary. A repetitive combination of roll forming and bending allows the production of profiles and cross-sections in any desired variants. The width and height can vary. Furthermore, angles can also be varied over the length. Also, for example, in one roll forming step only one half of the metal sheet or the cross-section can be processed and in a subsequent roll forming step the other half. Only the order of the roll forming steps is important. Furthermore, as mentioned above, bending can also take place in two or three dimensions (e. g. right/left, up/down and torsion). 
     In the method according to the invention, the profiled metal sheets comprise the following profiles: straight or bent profiles, U-shaped profiles with or without flanges, V-shaped profiles with or without flanges, C-shaped profiles, top-hat profiles, M-shaped profiles, oval profiles, rectangular profiles and combinations thereof Oval and rectangular profiles occur, for instance, in oval pipes or rectangular pipes, respectively. 
     In the method according to the invention, bending can comprise a supporting measure. As a supporting measure in the bending process, a core, a drawing die, a mold or glide-draw bending can be employed. The bending process can also take place by means of a simple tool with interior and exterior part in combination with a hydraulic press. Also, the rollers for a 3-roller bending process can contain suitable recesses, brims and shoulders. Furthermore, the workpiece can also be filled with an elastic plastic material (e. g. silicone). In case of wind instruments, for example, the pipe is filled with liquid lead before bending. 
     In the methods according to the invention, bending comprises the processes 3-roller bending, glide bending, bending with form shoe and stretch-bending. The present invention also envisages combinations of these processes. 
     With reference to  FIG. 1 , some variants according to the invention and their forming methods are shown. For manufacturing the profile A shown in cross-section four steps are required, namely a roll forming step  1 , followed by a bending step  2 , followed by another roll forming step  3  and an additional bending step  4 . These steps are explained in more detail with reference to  FIG. 3 . In addition, the first two steps for producing the profile B are analogous to those for producing profile A, followed by an additional roll forming step  3  and another bending step  4 . Similarly, steps  1  and  2  for manufacturing the profile C are analogous to steps  1  and  2  for producing profile A, followed in turn by another roll forming step  3  or bending step  4 . Profile D in  FIG. 1  is produced by means of a roll fowling step  1 , followed by a bending step  2  and another bending step  4 . Additionally, at the bottom of  FIG. 1 , a lateral view of profiles C and D is shown, with pleats on the profile sides formed parallel to the bottom or the rim (flange). 
     In another embodiment which is not shown pleats are provided on the profile sides in any position. These pleats also form a new roll forming line or plane. The orientation and position of the pleats is determined by the definition of the new roll forming line (plane). 
     With reference to  FIG. 2 , the profiles A, B and C from  FIG. 1  are shown as well as perspective views thereof, where the perspective views a 1 , a 2  show different bending variants of the profile A, the perspective view b shows a bending variant of the profile B and the perspective view e shows a bending variant of the profile C. 
     The profiled metal sheets produced according to the invention can be used in different industries, e. g. in the automotive industry, especially for frame longitudinal and transverse members, bumpers, door stiffenings, preforms for inner high-pressure metal forming; in shipbuilding, particularly for masts; in road construction, especially for lanterns; and in architecture, especially for structural steel profiles. 
     The present invention further envisages a unit by means of which the method according to the invention can be implemented. An embodiment of the unit can be as follows: in one module  1  of the unit, there can be a conventional roll forming unit which forms the sheet metal strip, cut to size, according to step a) of the present invention (e. g. to a U profile). In a follow-up module  2 , there can be a bending unit which bends the profiled metal sheet from step a) according to step b) of the present invention. In another embodiment of the unit, there can be another conventional roll forming unit in a module  3  downstream of module  2 , which further forms the profiled metal sheet from step b) according to step c) of the present invention (e. g. from a U profile to a top-hat profile). In another embodiment of the unit, a further bending unit can be located in a module  4  downstream of module  3 , which further bends the profiled metal sheet from step c) according to step d) of the present invention. In case the unit comprises the modules  1  through  4  described above, a method according to the invention can be implemented which is explained in the following example of embodiment. 
     However, the unit according to the invention is neither limited to the above-mentioned number of modules nor to the types thereof. In one embodiment of the unit, for example, a feeding module and/or a cutting module can be provided before the method according to the invention is carried out. Furthermore, another cutting module can be provided e. g. after the method according to the invention has been completed. 
     The method according to the invention can be carried out in the unit in a continuous or a discontinuous process. As mentioned above, the profiled metal sheets can also be bent, where the position of the bending line is critical for the process to be performed. If the bending line is to be located in the cross-section of the metal sheet to be profiled, a continuous process can take place (continuous unit). If, on the other hand, the bending line is to be positioned outside the cross-section of the profiled metal sheet, a discontinuous process is to take place (discontinuous unit). 
     Exemplary Embodiment 
     With reference to  FIG. 3 , a schematic representation of a forming process according to an embodiment of the present invention is shown. Step  0  shows a top view of the respective profile A 0  of a flat sheet metal strip cut to size. Steps  1 - 4  show corresponding lateral views of the profile A 1 -A 4  during forming. On the left side, the cross-sections of profiles A 1 -A 4  are represented. 
     In step  1 , the lateral wings can be bent, for instance, to a “U profile” on a first working plane  11  of a conventional roll forming unit. By cutting the sheet metal to size, a U profile with variable a height of the lateral wings is produced. 
     In step  2 , a variable bending process can be implemented, for instance, with an adapted COPRA® Flexform stand. The bending radius changes continuously during this process. The strip edge lies flat against a second working plane  21  over its entire length. It should be noted that the term “strip edge” refers to the presented example. In general, it should be said that the new roll forming line(s) is/are brought to one level and aligned horizontally for the subsequent roll forming unit, respectively. 
     In step  3  of a conventional roll forming unit, the bent U profile can be bent, for example, to a “top-hat profile”. The rim of the “hat” lies on one plane and the lateral faces of the top-hat profile receive a variable height. Possibly, a discontinuous guidance of the bottom  33 , e. g. with a simplified COPRA® Flexform stand, may be necessary. 
     In step  2  of the present example, the metal sheet is bent in only one dimension (up/down); however, it is also conceivable to bend the metal sheet in two or three dimensions. If the metal sheet is now bent in two dimensions, the new roll forming line, as in the case of bending in one dimension, passes horizontally through the roll forming unit in step  3 , but due to the additional curvature in the second dimension, the stands of the subsequent roll forming unit must be adapted to this second dimension. 
     In step  4 , a variable bending process can be performed, for instance, by means of an adapted COPRA® Flexform stand. During bending, the bending radius changes continuously. Eventually, the desired final profile shown in cross-section on the right side can be obtained. 
     The advantages achieved by the present invention can be summarized as follows: 
     The methods roll forming (or respectively cold roll faulting) and bending are well-known and easy-to-implement methods, resulting in an easy-to-implement method according to the invention. 
     In production, the profile to be formed can more easily be bent than flexibly profiled. 
     In the bending process, a core or other supporting measures can be employed. 
     Necessary upsetting and stretching processes in the flexible cross-section are introduced by the bending process, resulting in a cost-effective method according to the invention. In this way, the required guiding of the cross-section or of the profile, respectively, can also be implemented more cost-effectively. 
     A shape of the components which is adapted to the load (savings in terms of weight and expenditure of energy) can be obtained easily, resulting in a resource-conserving method according to the invention. 
     Roll forming and variability in height are decoupled. 
     Easier guidance of the profile is possible since the contour to be guided already exists. In contrast, the contour necessary for guiding is only being produced in the course of a flexible profiling process. 
     By appropriate selection of the forming steps, a very wide range of profiles can be produced with the methods according to the invention, wherein it is irrelevant whether the profile is open or closed since only the order of the roll forming steps is important. 
     If technical features mentioned in any one of the claims are marked by a reference number, these reference numbers have been merely included to improve comprehensibility of the claims. Accordingly, these reference numbers have no limiting effect on the scope of protection of each element indicated by way of example by such reference numbers.