US Patent 8025249 Bi-directional trimmer head spool with curved trimmer line guide

In an embodiment, a spool for a trimmer head has a structure for guiding the trimmer line around a region for a driveshaft. In an embodiment, a component (e.g., a turn knob or a stop) is attached to the spool so that after determining the orientation in which to install the spool, the user is unlikely to install the spool in another orientation, even though the spool is invertible. In an embodiment, the turn knob also includes a structure that allows the turn knob to be used as a tool (e.g., as a wrench or screw driver) that facilitates disassembling the trimmer head.