Method and blank for producing a screw-tube conveyor and screw-tube conveyor produced in this way

A method of making a screw-tube conveyor in the form of a cylindrical rotatable tube having an internal helix for conveying and mixing bulk material, the method comprising the following steps:

• providing a unitary blank comprising an elongated base strip having a longitudinal row of lateral fins, the base strip having two first opposite longitudinal edges and two second transverse end edges bridging ends of the longitudinal edges, the strip having longitudinally spaced and transversely extending bend lines extending between the first longitudinal edges and extending parallel to the second transverse edges, the fins each being formed unitarily with one of the longitudinal edges between two adjacent bend lines or between one of the transverse end edges and an adjacent one of the bend lines;
• bending each of the fins about a fin bend angle relative to the base strip along the one longitudinal edge at which the fins are unitarily connected to the base strip;
• and
• bending the base strip along the bend lines about a base bend angle such that the base strip forms between the bend lines a helical row of base zones of the rotatable tube and the previously bent fin forms a segment of a helix inside the rotatable tube or a ridge projecting radially outward from the helical row of base zones.