Abstract:
When roll-forming a blank into a profile having varying width and upright sides, the vertical position of at least any one of the forming roll pairs ( 21, 22; 23, 24 ) is varied 5 on either side during the roll-forming operation while the lateral and rotational positions thereof are simultaneously varied. The profile can thus be given a flat bottom during the roll-forming operation itself.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a method of forming a flat blank into a product with a central bottom part having a width that varies along the length of the product and upright sides and to a roll-forming machine comprising two rows of forming roll pairs which are movable laterally and rotationally. 
       BACKGROUND OF THE INVENTION 
       [0002]    Roll-forming machines for roll-forming operations of this kind are known from a number of publications. DE 20 2009 007 527 U1 describes a roll-forming machine of this kind provided with separate devices for making the central bottom part flat in the longitudinal direction since the roll-forming operation does not produce a flat central bottom part. Other patent publications also describe devices for making the bottom part flat with the aid of devices separate from the forming roll pairs. 
         [0003]    Aim of the invention and brief description of the invention The aim of the invention is to reduce or completely eliminate the incidence of the roll-forming pairs producing a central bottom part that is not flat in the longitudinal direction. This is achieved in principle by varying the vertical position of any one or more of the forming roll pairs during the roll-forming operation while simultaneously varying the lateral and rotational positions thereof. The invention is defined by the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  shows several steps for the manufacture of a profile from a flat blank by roll-forming. 
           [0005]      FIG. 2  is a diagrammatic view showing four roll-forming pairs in two working positions. 
           [0006]      FIG. 3  is a diagrammatic view showing four roll-forming units in two working positions. 
           [0007]      FIG. 4  is a cross section through a roll-forming station as viewed in the direction indicated by the arrows  4 - 4  in  FIG. 5 . 
           [0008]      FIG. 5  is a partly sectional top view as viewed in the direction indicated by the arrows  5 - 5  in  FIG. 4 . 
           [0009]      FIG. 6  shows a flat blank for a product having a convexly curved shape by way of example. 
           [0010]      FIG. 7  is a longitudinal view of a finished product having a convex shape manufactured without using the invention. 
           [0011]      FIG. 8  shows a blank for a product having a concavely curved shape by way of example. 
           [0012]      FIG. 9  is a longitudinal view of a finished product having a concave shape manufactured without using the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]      FIG. 1  shows by way of example three of the forming steps when roll-forming a flat blank  11  into a product in the form of a sheet-metal beam  12  with a flat bottom  13  and two upright sides  14 ,  15 . In practice, there are often more steps than those shown. A product of this kind is normally bent in, e.g. six steps.  FIGS. 6 and 8  show blanks  11  the outer edges of which have a radius and the broken lines  18 ,  19  show the lines along which the corners  18 ,  19  in  FIG. 1  are to be bent. 
         [0014]      FIG. 4  shows one of the forming stations. It has two pairs of forming rolls  21 ,  22  and  23 ,  24  which clamp the semi-formed blank  11  between them. The forming station has two stand units  25 ,  26  and the forming roll pairs are mounted therein. The stand units have vertical journals  27 ,  28  which support the stand units and are mounted in a base (not shown) in such a manner that the stand units can rotate about vertical axes I and II. The journals  27 ,  28  can be displaced laterally in the base as indicated by the arrows  30 ,  31  and they are movable vertically as indicated by the arrows  32 ,  33 . All of the movements are motor-driven and computer-controlled, although the driving devices are not shown. The forming roll pairs  21 ,  22  and  23 ,  24  can thus be displaced laterally and vertically during the roll-forming process and they can moreover be rotated about the axes I and II. Any one or more of the forming rolls is/are driven and advance/s the blank through the machine. 
         [0015]    The stand units are provided with measuring wheels  34 ,  35  mounted in the stand units in such a manner that they follow all of the movements of the forming roll pairs. The measuring wheels bear against the blank  11  and measure the displacement of the blank through the roll pairs. The positions of the forming roll pairs are controlled by the position of the blank in the respective roll pairs and at least the first and the last roll pairs should be provided with measuring wheels. The guiding operation is simplified if all of the roll pairs are provided with measuring wheels. 
         [0016]      FIG. 6  shows a blank  11  having a convex shape, wherein the lines along which the corners  18 ,  19  are to be formed are indicated by broken lines designated by the same reference numerals as the corners. In this example, the blank has a convexly curved shape with a constant radius. A blank of this kind having a convex shape in order to produce a profile  12  having upright sides as shown in  FIG. 1  tends to give the finished product an upwardly curved shape when viewed from the side, as shown in  FIG. 7 . 
         [0017]      FIG. 8  shows a blank  11  which instead has a concave shape. A blank of this kind having a concave shape in order to produce a profile having upwardly bent sides tends instead to give the finished profile  12  according to  FIG. 1  a downwardly curved shape when viewed from the side, as shown in  FIG. 9 . 
         [0018]    In order to prevent the finished product from being curved in the vertical plane, i.e. in order to prevent its bottom  13  in  FIG. 1  from being curved, as shown in  FIGS. 7 and 9 , according to the invention, any one or more of the forming roll pairs can be displaced vertically during the roll-forming process. 
         [0019]      FIG. 2  shows the roll-forming in four roll pairs  1 ,  2 ,  3 ,  4  of a blank having a convex shape according to  FIG. 6  which tends to be curved downwards, i.e. to result in an upwardly curved shape as shown in  FIG. 7 . Raising the last forming roll pair in each row, i.e. the roll pairs  4 , during the roll-forming operation and thereby bending the product upwards prevents the formation of the curved shape and the finished product has a flat bottom. 
         [0020]      FIG. 3  shows an alternative method of preventing the product from being curved. Instead of raising the last roll pairs  4 , the roll pairs  2  and  3  situated between the first and the last roll pairs are lowered, thereby bending the blank upwards during the forming operation, i.e. into a downwardly curved shape, before it is given its final shape and the finished product has a flat bottom. 
         [0021]    When roll-forming a blank having a concave shape according to  FIG. 8  instead of a blank having a convex shape according to  FIG. 6 , the forming roll pairs are guided in the opposite manner to that shown in  FIGS. 2 and 3 .