Patent ID: 7430890

Claim:
A method of manufacturing a tube having a polygonal cross-section with at least one side wall opening therein comprising: providing a sheet of metal having a length and a width; providing male and female press brake tools for forming corners in the tube, the press brake tools having a width conforming to the length of the metal sheet, the male press brake tool having an offset axis along which forming force may be applied to the metal sheet to form the tube corners; forming at least one opening in the metal sheet conforming to the at least one tube side wall opening; after forming the at least one opening in the metal sheet, aligning the press brake tools along the length of the metal sheet at a first width location and forming a first corner of the tube; aligning the press brake tools along the length of the metal sheet at a second width location and forming a second corner of the tube; aligning the press brake tools along the length of the metal sheet at a third width location and forming a third corner of the tube; and aligning the press brake tools along the length of the metal sheet at a fourth width location and forming a fourth corner of the tube, wherein the width locations closest to edges along the width of the metal sheet are less than the dimension of the tube between the corners formed at such width locations such that, after forming of the last corner, an opening remains along the length of the tube between the corners formed at such width locations, and wherein the press brake male tool axis is offset sufficiently to permit the tool to apply forming force to the last corner of the tube through the opening remaining along the length of the tube.