US Patent 10537057 Spool assembly for a trimmer head

A spool assembly includes a spool formed of a central section including a core wall containing a core and passages extending through the core wall, an upper flange located at an upper portion of the central section, a lower flange located at a lower portion of the central section, and a protrusion section integral with the central section and extending above the upper flange. The protrusion section includes a cut-out formed inside the protrusion section, the cut-out having a non-circular shape adapted to be securely engaged to a drive member of a motor.