Patent ID: 7918026

Claim:
A method for production of a mast comprising at least three identical extruded mast elements having opposing side edges, the mast elements are interconnected along the side edges at corners of the mast, each of the mast elements having a straight elongated channel section along one of the side edges and a straight elongated rail section along the opposing one of the side edges, the rail section of one of the mast elements being inserted into the channel section of an adjacent one of the mast elements for establishing a joint between the one of the mast elements and the adjacent one of the mast elements, wherein the method comprises: providing the channel section with inwardly tapered inner wall sections formed during the extrusion process of forming the extruded mast elements, an inner distance between the inner wall sections at a bottom end of the channel section is equal to or larger than a width of the rail section; inserting at least a part of the rail section of the one of the mast elements into the channel section on the adjacent one of the mast elements; and moving, in a substantially continuous motion, a roller type tool in longitudinal direction of and on the exterior of the channel section, the roller type tool having rollers arranged on opposing sides of the channel section, the rollers having outwardly projecting knobs to be pressed onto the joint, the rollers providing sufficient force to clamp the channel section and the rail section together, causing permanent deformation of the channel section around the rail section, and forming one of the corners of the mast, wherein the knobs form spot strengthened areas on both opposing sides of the joint.