Roll form apparatus, method to manufacture crush tubes

Abstract

An apparatus comprises an uncoiling device for unrolling sheet material, an embossing device for embossing a series of crush initiating embossments into the sheet, a slitter to remove deformed edges of the sheet to facilitate welding, and a roll former with rolls configured to deform the sheet into a continuous tubular beam with walls each including some of the embossments, with the rolls being configured to clear the embossments but accurately form corners joining the walls. The apparatus further includes a welder welding abutting edges of the sheet together to fix the tubular beam, with the abutting edges being located inboard of an adjacent one of the corners but outboard of an outboard edge of adjacent ones of the embossments, and a cutoff device for cutting the continuous tubular beam into beam segments. A related method is also disclosed.

The invention claimed is: 
     
         1 . A roll form apparatus comprising:
 an uncoiler device for unrolling an elongated sheet of material from a roll of the material;   an embossing device for embossing a series of crush initiating embossments into the sheet;   a roll former with rolls configured to deform the sheet into a continuous tubular beam defined by walls, each wall defining a plane with some of the embossments extending from the plane in at least one of the walls, the walls being joined by corners with the embossments spaced from the corners;   a welder welding abutting edges of the sheet together to fix the tubular beam, with the abutting edges being located inboard of an adjacent one of the corners but outboard of an outboard edge of adjacent ones of the embossments;   a cutoff device for cutting the continuous tubular beam into beam segments, with the beam segments being substantially finally formed as crush tubes.   
     
     
         2 . The apparatus of  claim 1 , including an end trimmer between the embossing device and the roll former to trim edges of the sheet that are deformed when forming the crush initiating embossments. 
     
     
         3 . The apparatus of  claim 1 , including a wall-trimming device that shortens some of the walls but leaves a longitudinally-extending flange on at least one of the walls. 
     
     
         4 . The apparatus of  claim 1 , wherein the embossing device forms embossments in each of the walls, and wherein the rolls are configured to clear the embossments when deforming the sheet. 
     
     
         5 . A method comprising:
 uncoiling an elongated sheet of material from a roll of the material;   embossing a series of crush initiating embossments into the sheet;   roll forming deform the sheet into a continuous tubular beam defined by walls, each wall defining a plane with some of the embossments extending from the plane in at least one of the walls, the walls being joined by corners with the embossments spaced from the corners;   welding abutting edges of the sheet together to fix the tubular beam, with the abutting edges being located inboard of an adjacent one of the corners but outboard of an outboard edge of adjacent ones of the embossments;   cutting the continuous tubular beam into beam segments, with the beam segments being substantially finally formed as crush tubes.   
     
     
         6 . The method of  claim 5 , including a step of trimming edges of the sheet between the steps of embossing and roll forming, the step of trimming eliminating deformed portions of the sheet caused when the crush initiating embossments are formed. 
     
     
         7 . A roll form apparatus comprising:
 an embossing device for embossing a series of crush initiators into a sheet;   a roll former with rolls configured to deform the sheet into a continuous tubular beam defined by walls, the walls being joined by corners with the crush initiators spaced from the corners, the rolls being configured to avoid contact with portions of the sheet having the crush initiators placed therein;   a welder welding edges of the sheet together at a location inboard of the corners but outboard of an outboard edge of adjacent ones of the crush initiators; and   a cutoff device for cutting the continuous tubular beam into crush tubes.   
     
     
         8 . A crush tube product made by a roll form process comprising:
 a sheet having opposing edges that is deformed to have embossed crush initiators and that is roll formed into a tubular shape and cut to length for use as a crush tube for mounting a bumper beam on a vehicle front end;   the crush initiators being formed perpendicularly into the sheet inboard of the opposing edges;   the elongated tubular shape having a longitudinal centerline caused by roll forming the sheet so that the opposing edges abut, with the tubular shape having a constant cross section except for the crush initiators, the constant cross section having side walls defining corners;   a weld securing the opposing edges together to fix the elongated tubular shape, with some of the crush initiators being between the weld line and an adjacent one of the corners; and   a section of the elongated tubular shape being cut into a desired length to thus form a crush tube configured to support a bumper beam on a vehicle frame and configured to longitudinally crush with a predictable force/deflection curve when impacted parallel the longitudinal centerline.