Vehicle bumper beam with non-uniform cross section

A bumper construction for vehicles comprising:

• a rollformed tubular beam made from sheet material having a constant thickness and having a length and a longitudinal cross section that varies along the length, the tubular beam including a rear wall having a center section that defines a longitudinally extending arcuate surface, a mounting section on each end of the center section formed from material of the rear wall that defines a flat co-planar mounting surface, and a corner section on each outer end of the respective mounting sections that sweeps rearwardly from the associated flat mounting surface, and including flat top and bottom walls that connect the front and rear walls.

A method comprising steps of:

• forming a sheet of material having a constant wall thickness into a tubular beam having a length and a longitudinal cross section that varies along the length, including forming front and rear walls to have center sections with longitudinally extending arcuate surfaces defining different radii that extend around different centerpoints, and forming flat top and bottom walls that connect the front and rear walls and that extend generally horizontally when in a car-mounted position, the step of forming the front wall including hydroforming areas at ends of the center section and reforming an outer end section of the front wall outward of the center section of the front wall to cause the outer end section to define a compound angle with an end of the center section of the front wall while maintaining a flat shape of the top and bottom walls.

A method comprising steps of:

• rollforming a sheet of material having a constant wall thickness into a tubular beam with a constant B-shaped longitudinal cross section, the B-shaped longitudinal cross section, when in a car-mounted position, including material forming top and bottom lobes and a center region that define a B-shaped cavity;
• and
• reshaping portions of the tubular beam at locations spaced from ends of the tubular beam to form a non-uniform cross section along a length of the tubular beam, including enlarging portions of the beam to form an increased internal cavity size.

A method comprising steps of:

• providing a longitudinally curved tubular beam with a constant longitudinal cross section, the tubular beam having a front wall and a back wall spaced from the front wall, the front wall having top, bottom, and center areas defining a constant B-shaped internal cavity with the back wall;
• and
• outwardly forming the center area in the front wall at locations spaced longitudinally from a mid point of the tubular beam to form a non-uniform cross section along a length of the tubular beam where the internal cavity remains B-shaped in center and end locations but is approximately rectangularly shaped in mounting locations adapted for mounting to a vehicle frame.

A bumper construction for vehicles comprising:

• a tubular beam having a length and a longitudinal cross section that varies along the length and further having spaced-apart mounts adapted for mounting to a vehicle frame, the tubular beam, when oriented in a car-mounted position, including front and rear walls that have center sections with longitudinally extending arcuate surfaces defining different radii and that extend around different centerpoints, and including relatively flat top and bottom walls that connect the front and rear walls, the longitudinal cross section being generally rectangularly shaped at the mounts but B-shaped at a central location and at end locations.

A method comprising steps of:

• rollforming a sheet of material having a constant wall thickness of less than about 2.4 mm into a tubular beam having a length and a longitudinal cross section that varies along the length, including forming front and rear walls to have center sections with longitudinally extending arcuate surfaces defining different radii that extend around different centerpoints, and forming flat top and bottom walls that connect the front and rear walls and that extend generally horizontally when in a car-mounted position, the step of forming the front wall including hydroforming areas at ends of the center section with at least a 3% stretch in some areas to cause permanent deformation and a set in the front wall.

A method comprising steps of:

• rollforming a sheet of material having a constant wall thickness and a tensile strength of at least 70KSI to form a tubular beam with a constant longitudinal cross section;
• and
• reforming the tubular beam to reshape portions of the tubular beam to form a non-uniform cross section along a length of the tubular beam, including shaping portions of the beam to form an increased internal cavity size.