| 摘要 |
The invention relates to a method and apparatus for the manufacture of a screw-line shaped reinforcement spiral out of metal wire for the reinforcement of concrete pipes or columns. The wire is, while subject to tensile stress, wound onto a cylindrical last whose diameter is equal to the inner diameter of the spiral. The wire, before coming onto the last, passes over a roll that prestresses the wire to a curve of such a small diameter that, after the wire has been taken off the curve, a tension tending to bend the wire in the direction of bending of the reinforcement spiral remains in the wire. The winding takes place so that at the immediate proximity of the initial end of the last the wire passes over rolls. The first roll, whose projection is partly outside the projection of the mantle of the last and which gives the wire a curve radius smaller than the radius of the last, makes a tension bending in the wire in the direction of bending of the reinforcement spiral which bended remain in the wire. The subsequent rolls whose projections are inside the mantle of the last or are in contact with same, jointly provide a curvature whose curve radius is at the beginning larger than the radius of the last but becomes gradually smaller and, at the last roller becomes the same. The wire is wound onto the last as guided by rolls placed at the initial end of the last and positioned radially in relation to the last. The rolls provide the winding with an opening tension effective in the axial direction of the spiral, because the rise of the winding is at the beginning or at a part of the first winding, larger than the diameter of the wire but after a few windings, the rise is the same as the diameter of the wire. One or some of these last-mentioned windings are pressed against the last by means of a roll. The roll is, at the end of the roll facing towards the final end of the last, provided with a flange that penetrates between the windings and thereby causes gliding of the windings placed behind the flange on the last by the width of the flange and at the same time bending the windings in the axial direction of the spiral.
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