Patent ID: 7640668

Claim:
A cutting head for a rotary trimmer comprising: two diametrically opposed cutting flails which extend outwardly from a spinning, generally cylindrical housing having an axis of rotation; a bumper for engagement with the ground; means to allow predetermined lengths of flail to feed outwardly in response to the engagement of the bumper on the ground; a cam member having a first and second set of radially spaced radially extending tangs, wherein the first set of tangs is spaced along said axis of rotation from the second set of said tangs to define a serpentinous cam slot; a generally cylindrical follower member disposed over the cam member and having at least two diametrically opposed tangs extending radially inwardly adjacent an upper surface of said generally cylindrical follower member positioned to ride in said cam slot of the cam member, the generally cylindrical follower member including a plurality of ribs disposed on a lower circumferential surface; a spool member having a generally cylindrical body including a plurality of flanges on an upper portion of the generally cylindrical body configured for supporting each of said cutting flails and a lower portion of the generally cylindrical body configured as the bumper, the upper portion of the spool member being disposed in the housing and the lower portion extending through an opening in the housing, the cam member and the generally cylindrical follower member being disposed in the spool member and the spool member including a plurality of ramps disposed along a peripheral inner surface of the generally cylindrical body corresponding to the plurality of ribs disposed on the lower circumferential surface of the generally cylindrical follower member; and a biasing means acting on the generally cylindrical follower member to urge the generally cylindrical follower member into stable positions on said cam slot of the cam member and into engagement with the spool member when undisturbed by a force applied to said bumper by said biasing means, and adapted to be overcome by a suitable force applied to said bumper, the cam slot being generally parallel to the force applied by said biasing means, wherein upon loading the two cutting flails, the spool member is rotated via the bumper in one direction along the axis of rotation and the generally cylindrical follower member is fixed due to the interaction with the cam member preventing the spool member from traveling in an opposite direction.