Method for the production of a metal tube, in particular a gas distributor tube for vehicle airbags

Abstract

The invention relates to a method for the production of a metal tube, particularly a gas distributor tube for vehicle airbags. The tube mantle is punched out as a planar metal blank, the outside contour of which corresponds to the developed view of the tube. The planar metal blank is then formed into a profile having a U-shaped cross-section. The U-shaped profile is pressed to form a tube-shaped semi-finished piece that still has an open longitudinal slit. The longitudinal slit, which extends without interruption with an essentially constant gap width over the entire length of the tube, is finally welded closed. In the production of gas distributor tubes, the outside contour of the metal blank corresponds to a developed view of the gas distributor tube, whereby the parting plane for the developed view is laid through the exit openings.

1 . Method for the production of a metal tube, which has at least one change in cross-section, wherein 
 the tube mantle is punched out as a planar metal blank ( 4 ), the outside contour of which corresponds to the developed view of the tube ( 1 ,  1 ′),    the planar metal blank ( 4 ) is formed into a profile ( 5 ) having a U-shaped cross-section,    the U-shaped profile ( 5 ) is pressed to form a tube-shaped semi-finished piece ( 7 ) that still has an open longitudinal slit, and    the longitudinal slit, which extends without interruption with an essentially constant gap width over the entire length of the tube, is welded closed.    
   
   
       2 . Method according to  claim 1 , characterized in that the metal blank ( 4 ) has segments of different width, which are connected by means of constant transition segments.  
   
   
       3 . Method according to  claim 1  or  2 , characterized in that the metal blank is punched out in a width that corresponds to the outside diameter of the tube, multiplied by the number π.  
   
   
       4 . Method according to one of  claims 1  to  3 , characterized in that press die-plates ( 6 ,  6 ′) configured as half-shells are used for the production of the tube-shaped semi-finished piece ( 7 ) and that the shank ends of the U-shaped profile ( 5 ) are held at a distance that forms the longitudinal slit, by means of a tongue ( 8 ), during the shaping.  
   
   
       5 . Method according to one of  claims 1  to  4 , characterized in that a welding tool, for example one controlled by an automatic welding machine, is guided along the longitudinal slit of the tube-shaped semi-finished piece ( 7 ), which follows the spatial progression and the contour of the tube and welds the longitudinal seam closed.  
   
   
       6 . Method according to one of  claims 1  to  5 , characterized in that within the course of the deformation of the metal blank ( 4 ), functional elements ( 9 ) are inserted, which are fixed in place with a positive lock, by means of the wall profile, after completion of the tube ( 1 ,  1 ′).  
   
   
       7 . Method according to  claim 6 , characterized in that projections are formed on the lengthwise sides of the metal blank ( 4 ), which form an annular space for holding a functional element ( 9 ), after deformation to produce a tube-shaped semi-finished piece, and that the contour forming the annular space is finished with external shaping tools.  
   
   
       8 . Method according to  claim 6  or  7 , characterized in that projections are formed on the lengthwise sides of the metal blank ( 4 ), which form a bead-shaped widened tube region to hold a disk ( 10 ), after deformation to produce a tube-shaped semi-finished piece ( 7 ), and that the widened tube region is pressed to form a collar ( 11 ), using shaping tools, in which the disk ( 10 ) is fixed in place with a positive lock.  
   
   
       9 . Method according to one of  claims 6  to  8 , characterized in that a flow insert ( 9 ) arranged between two support disks ( 10 ) is laid into the profile within the course of the deformation process, and that the support disks are fixed in place, with a positive lock, in collars ( 11 ) that are formed during the course of the deformation of the metal blank ( 4 ), and finished using shaping tools.  
   
   
       10 . Method according to one of  claims 1  to  9 , characterized in that the lengthwise edges of the metal blank ( 4 ) have a profile with back-sets ( 16 ), which complement one another during the deformation of the metal blank ( 4 ) to form a tube ( 1 ′), to form exit openings ( 13 ) on the mantle, which are in a row in the longitudinal direction.  
   
   
       11 . Method according to one of  claims 1  to  10 , characterized in that the lengthwise edges of the metal blank ( 4 ) have a profile with projections ( 15 ), from which a collar ( 3 ) and a connector cuff ( 2 ) are formed during the deformation of the metal blank ( 4 ) to form a tube ( 1 ′).  
   
   
       12 . Method according to one of  claims 1  to  11 , characterized in that the metal blank ( 4 ) has a segment with a lesser width, which forms a narrowed cross-section of the tube after deformation of the metal blank.  
   
   
       13 . Method according to one of  claims 10  to  12 , characterized in that the metal blank ( 4 ) is punched out of a piece of sheet metal, in segments, whereby the length of the segments is selected to be such that the transitions lie in the region of the back-sets ( 16 ) on the edges of the metal blank ( 4 ) that form the exit openings ( 13 ).  
   
   
       14 . Method according to one of  claims 1  to  13 , characterized in that the tube that has been produced from the planar metal blank ( 4 ) and welded longitudinally is given a predetermined spatial progression adapted to the application, by means of bending.  
   
   
       15 . Method according to one of  claims 1  to  13 , characterized in that a bending deformation that shapes the work piece in the longitudinal direction takes place at the same time with deformation of the metal blank ( 4 ) and/or with the subsequent pressing to form a tube-shaped semi-finished piece ( 7 ), and that in this way, the work piece is given a spatial progression adapted to the application, before the longitudinal slit of the tube-shaped semi-finished piece ( 7 ) is welded closed.  
   
   
       16 . Method according to  claim 15 , characterized in that the metal blank ( 4 ) is deformed into a work piece having a U-shaped cross-section, by means of bending in a forging die or edge rolling, which piece is curved in the longitudinal direction and subsequently pressed into a tube shape using press die-plates ( 6 ,  6 ′), the shaping cavity of which is adapted to the shape of the work piece.  
   
   
       17 . Method according to  claim 15  or  16 , characterized in that segments curved in arc shape are deformed subsequently, by means of bending of the tube that has already been shaped three-dimensionally and welded at the longitudinal seam.