US Patent 10165727 Trimmer head

A trimmer head that includes a casing to be coupled to a driveshaft. The casing includes an upper shell and a lower shell, with the lower shell including a second toothing that protrudes upwardly. The trimmer head further includes an upper disk and a lower disk within the casing, with the lower disk including a first toothing that protrudes downwardly. A spool of cutting wire is positioned between the lower disk and the upper disk. In an engagement position, the first toothing and the second toothing are engaged and the upper disk and lower disk rotate with the lower shell. In a free position, the first toothing and the second toothing are disengaged and the upper disk and lower disk rotate with respect to the lower shell.