Tubular beam with single center leg

Abstract

A reinforcement beam for a vehicle bumper system comprises a single sheet deformed to define first and second tubes sharing a common single center wall. A channel rib is formed on each tubes and a crevice rib over the center leg forms a third rib. Edges of the sheet are deformed to a radius so that their surface consistently engages an associated radiused corner formed on ends of the center leg, which facilitates consistent abutting line engagement of material surfaces, and thus facilitates consistent welding. In a preferred beam, front wall sections of each tube are coplanar and form a face of the beam, with each channel rib and crevice rib providing added stiffness to the beam, and yet nothing extends forward of the coplanar front wall sections. Related apparatus and methods are also disclosed.

1 . A reinforcement beam comprising:
 a beam formed from a single sheet and including first and second tubes sharing a common wall and having coplanar aligned front walls and coplanar aligned rear walls, each front wall including a channel rib therein, the sheet including a first edge with a first radiused portion and first tip, a second edge with a second radiused portion and second tip, a third radiused portion connecting one of the aligned front walls with one end of the common wall, and a fourth radiused portion connecting one of the rear walls with another end of the common wall, the first and third radiused portions being welded together at a first weld and forming a front crevice rib having a cavity depth at least two times a thickness of the sheet, and the second and fourth radiused portions being welded together at a second weld and forming a rear crevice having a cavity depth at least two times the thickness of the sheet, the channel ribs and the front crevice rib forming ribs that stiffen a front face of the beam.   
     
     
         2 . The reinforcement beam defined in  claim 1 , wherein the front crevice is generally centered over the aligned wall, and forms with said channel ribs a three rib reinforced front face on the beam. 
     
     
         3 . The reinforcement beam defined in  claim 1 , wherein the front weld is formed at a bottom of the first crevice immediately adjacent a location where the first and third radiused portions first come into abutting contact, the first tip extending inside the beam and away from the weld less than about 4 mm. 
     
     
         4 . The reinforcement beam defined in  claim 1 , wherein the front weld is a continuous strip of bonded material formed by laser welding. 
     
     
         5 . The reinforcement beam defined in  claim 1 , wherein the sheet has a material thickness of is less than about 1.2 mm. 
     
     
         6 . The reinforcement beam defined in  claim 1 , wherein the sheet has a tensile strength of greater than 250 ksi. 
     
     
         7 . The reinforcement beam defined in  claim 1 , wherein the channel ribs have a same shape and have a depth equal to their width. 
     
     
         8 . An apparatus for forming a sheet into a beam having four exterior walls and a common center leg extending between an opposing two of the walls, the four exterior walls defining a rectangular cross section, and the center leg dividing the cross section into first and second adjacent tubes, the center leg having radiused ends each defining slip planes perpendicular to the center leg, and the sheet having edges that abut the radiused ends, comprising:
 a roll former including roll form stations with rollers for forming the sheet into the beam with the four exterior walls and the common center leg, the roll former including a welding station with welders and a weld box fixture, the weld box fixture including a fixture frame, external mandrels supported by the fixture frame and supporting the four exterior walls in a desired accurate shape, two of the external mandrels being movable and opposing, and including at least one actuator operably connected to the two opposing external mandrels for moving the opposing external mandrels into engagement with associated opposing ones of the four exterior walls; and   internal mandrels in each of the first and second adjacent tubes that are supported by upstream anchor lines so that the internal mandrels remain generally adjacent the external mandrels;   whereby, the internal and external mandrels, in combination with a bias of the springs and a counter bias of the two opposing external mandrels, control a shape of the beam by flexure and movement of material of the sheet along the slip planes to thus actively maintain an accurate shape when in the weld box fixture during a welding process of the welder.   
     
     
         9 . The apparatus defined in  claim 8 , wherein the at least one actuator includes an adjustable threaded member. 
     
     
         10 . The apparatus defined in  claim 8 , wherein the internal mandrels each have opposing halves and a spring biasing the opposing halves apart against the external mandrels and against a force of the actuator. 
     
     
         11 . An apparatus for forming a sheet into a beam having four exterior walls and a common center leg extending between an opposing two of the walls, the four exterior walls defining a rectangular cross section, and the center leg dividing the cross section into first and second adjacent tubes, the center leg having radiused ends each defining slip planes perpendicular to the center leg, and the sheet having edges that abut the radiused ends, comprising:
 a roll former including roll form stations with rollers for forming the sheet into the beam with the four exterior walls and the common center leg, the roll former including a welding station with welders and a weld box fixture, the weld box fixture including a fixture frame, external mandrels supported by the fixture frame and supporting the four exterior walls in a desired accurate shape, two of the external mandrels being movable and opposing, and including at least one actuator operably connected to the two opposing external mandrels for moving the opposing external mandrels into engagement with associated opposing ones of the four exterior walls, two others of the external mandrels being fixed and opposing such that the two other external mandrels generally fix a distance between the opposing two walls between which the center leg extends;   whereby, the external mandrels in combination with a bias of the two opposing external mandrels, control a shape of the beam by flexure and movement of material of the sheet along the slip planes to thus actively maintain an accurate shape when in the weld box fixture during a welding process of the welder.   
     
     
         12 . An apparatus for forming a sheet into a beam having four exterior walls and a common center leg extending between an opposing two of the walls, the four exterior walls defining a rectangular cross section, and the center leg dividing the cross section into first and second adjacent tubes, the center leg having radiused ends each defining slip planes perpendicular to the center leg, and the sheet having radiused edges that abut the radiused ends, comprising:
 a roll former including roll form stations with rollers for forming the sheet into the continuous beam with the four exterior walls and the common center leg, the roll former including a welding station with a welder and a weld box fixture, the welder generating an upwardly-angled laser beam for welding the continuous beam to permanently fix the cross section and being positioned under the continuous beam at a location upstream or downstream from the weld box fixture so that the laser beam welds within a down-facing crevice formed by one of the radiused edges abutting one of the radiused ends;   whereby, the welder welds the continuous beam from a position under the continuous beam yet is positioned away from falling debris.   
     
     
         13 . An apparatus for forming a sheet into a beam having four exterior walls and a common center leg extending between an opposing two of the walls, the four exterior walls defining a rectangular cross section, and the center leg dividing the cross section into first and second adjacent tubes, the center leg having radiused ends each defining slip planes perpendicular to the center leg, and the sheet having radiused edges that abut the radiused ends, comprising:
 a roll former including roll form stations with rollers for forming the sheet into the continuous beam with the four exterior walls and the common center leg, the roll former including a single welding station with a top welder and a bottom welder and a weld box fixture, the welders welding the continuous beam to permanently fix the cross section by welding simultaneously in the welding station at upper and location locations on the beam;   whereby welding is done in the single welding station and not in multiple weld stations.   
     
     
         14 . An apparatus for forming a sheet into a beam having four exterior walls and a common center leg extending between an opposing two of the walls, the four exterior walls defining a rectangular cross section, and the center leg dividing the cross section into first and second adjacent tubes, the center leg having radiused ends each defining slip planes perpendicular to the center leg, and the sheet having radiused edges that abut the radiused ends, comprising:
 a roll former including first roll form stations with first sets of rollers forming the center leg of the sheet and outboard wings of the sheet, with the outboard wings having portions adjacent the center leg that extend perpendicular to the center leg and that are joined to the center leg by the radiused ends, and with the outboard wings also having the radiused edges formed thereon;   the roll former further including additional roll form stations with additional sets of rollers forming the outboard wings into first and second tubes with the center leg being a common wall forming part of each of the first and second tubes; and   top and bottom welders welding the radiused edges to the radiused ends.