| 摘要 |
PCT No. PCT/SE92/00071 Sec. 371 Date Oct. 14, 1993 Sec. 102(e) Date Oct. 14, 1993 PCT Filed Feb. 6, 1992 PCT Pub. No. WO92/13658 PCT Pub. Date Aug. 20, 1992A supporting crossbar construction is made from thin metal strip by feeding the strip lengthwise to a punching station, and forming in the punching station four parallel rows of slits extending lengthwise of the strip so that five parallel plate fields are formed extending lengthwise of the strip. The strip is then deformed so that the strip is expanded into a construction having two outer straight plate fields and a straight middle plate field between the two outer plate fields, the middle plate field being interconnected with each of the two outer plate fields by a plurality of diagonal members that are spaced apart and are formed by the deformation of the plate fields between the middle and outer plate fields, whereby the middle and outer plate fields are spaced a greater distance apart from each other. The middle plate field is then bent about at least one longitudinal bend line so as to bring together the two outer plate fields. The two outer plate fields are then secured together, thereby to form a supporting crossbar construction in which one flange is comprised by the middle plate field and another flange is comprised by the secured-together outer plate fields, there then being a plurality of alternately oppositely inclined crossbars interconnecting the flanges. The expanding is performed by forcing the middle and outer plate fields to follow diverging circular arcs of different radii of curvature, and then straightening them. |
