US Patent 10138921 Connecting element, use and method

A connecting element, the use thereof and a method for connecting plate shaped workpieces are proposed. The connecting element comprises a multiplicity of closed encircling annular projections, which are arranged in such a way that the spacing between adjacent annular projections changes along a circumference or that adjacent annular projections are arranged parallel to one another or obliquely to the longitudinal axis. The connecting element is rotated and pressed into contact to produce a hole and, after the production of the hole, is subjected only to axial contact pressure and is then twisted to lock.