METHOD OF MAKING MULTIHEDRAL CONE TUBES Russian patent published in 1998 - IPC

FIELD: processes for manufacturing electrically welded tubes, namely production of multihedral cone tubes of predetermined length. SUBSTANCE: method comprises steps of cutting out sheet material to two trapezoidal blank-carts, forming predetermined shapes of said blanks, rotating one blank by 180 degrees in horizontal plane, assembling blanks and welding their lengthwise edges. Before shaping compression effort is applied along bending lines on inner surface of trapezoidal blank. Shaping is realized by successive steps along blank in such a way that length of shaped portion is proportional to value of applied effort. EFFECT: production of high-efficient equal-strength (relative to efforts acting upon support) tubes for illumination and contact networks. 3 cl