A grass trimmer includes a grass trimmer head, a brushless motor, a drive circuit, and a controller. The grass trimmer head includes a spool and a head housing. The spool is configured to wind a grass trimmer rope. The head housing is configured to accommodate the spool. The grass trimmer has an automatic winding mode. In the automatic winding mode, the brushless motor drives at least one of the spool and the head housing so that the spool and the head housing rotate relatively and the grass trimmer rope is automatically wound onto the spool. The controller is configured to: in the automatic winding mode, output a control signal to the drive circuit according to at least one of the given voltage and the given current so that the rotation speed of the brushless motor is basically constant.

A strand trimmer and method of use thereof. The strand trimmer includes a pair of pivotable arms each having a motor, a follower wheel, and a cutter-spindle assembly disposed thereon. The arms are biased toward one another and are guided by the follower wheels to pivot around obstacles passing between the arms. The motor rotates the cutter-spindle assembly to move cutting strands extending therefrom through a cutting path with sufficient rotational velocity to cut vegetation. The cutter-spindle assembly includes a reloadable spool and a strand-feed mechanism. The strand-feed mechanism includes a solenoid actuated plunger within a shaft of the cutter-spindle assembly which operates to non-contactingly actuate the plunger to feed out a length of strand. The solenoid is non-rotatably carried on the trimmer arm while the shaft of the cutter-spindle assembly is encircled by and rotated within the solenoid.

A string trimmer includes a trimmer head and a driving device having a motor for driving the trimmer head to rotate around a rotation axis. The trimmer head includes a spool, a head housing formed with an accommodating space, and a transmission member mounted to the spool. The spool is at least partially accommodated in the accommodating space. The transmission member includes a driving portion. The head housing is formed with a mating portion to mate with the driving portion.

A string trimmer includes a trimming head, a driving device, and an operating device. The trimming head includes a spool, a head housing formed with an accommodating space, and a transmission member mounted to the spool that can move freely between the head housing and the spool in the direction of a straight line perpendicular to the direction of the rotation axis. The trimming line has an effective portion extending from the accommodating space. When the length of the effective portion of the trimming line is larger than a preset value, the transmission member automatically releases the head housing. When the length of the effective portion of the trimming line is less than the preset value, the transmission member locks the head housing.

Trimmers and auto advancing trimmer lines are provided. A trimmer includes a trimmer head disposed on a connecting member, a user interface disposed on the connecting member, wherein the user interface is configured to operate the trimmer head, a sensor configured to determine a length of a trimmer line extending from the trimmer head, and an auto advance mechanism configured to extend the trimmer line extending from the trimmer head based on feedback from the sensor.

A grass trimmer includes a grass trimmer head, a brushless motor, a drive circuit, and a controller. The grass trimmer head includes a spool and a head housing. The spool is configured to wind a grass trimmer rope. The head housing is configured to accommodate the spool. The grass trimmer has an automatic winding mode. In the automatic winding mode, the brushless motor drives at least one of the spool and the head housing so that the spool and the head housing rotate relatively and the grass trimmer rope is automatically wound onto the spool. The controller is configured to: in the automatic winding mode, output a control signal to the drive circuit according to at least one of the given voltage and the given current so that the rotation speed of the brushless motor is basically constant.

A grass trimmer includes a grass cutting head and a driving mechanism. The grass cutting head includes a head housing, a spool, and a clutch mechanism. The clutch mechanism is configured to implement power transmission between the head housing and the spool. The clutch mechanism includes an elastic member which is elastically deformable.

A string trimmer head includes a spool, a head housing, an automatic line release device, and an operating member. The automatic line release device is configured to enable the spool and the head housing to generate a first relative rotation so that the string trimmer head releases a string trimmer line, where the string trimmer line has an effective length extending out of the accommodation space; and the automatic line release device is further configured to make the string trimmer head release the string trimmer line when the effective length of the string trimmer line is less than a preset value. The operating member is configured to be operable by a user to drive the spool and the head housing to generate a second relative rotation so that the string trimmer line is wound around the spool.

A grass trimmer includes a grass cutting head and a driving mechanism. The grass cutting head includes a head housing, a spool, and a clutch mechanism. The clutch mechanism is configured to implement power transmission between the head housing and the spool. The clutch mechanism includes an elastic member which is elastically deformable.

A trimmer head arranged to be driven to rotate a trimmer line, where the trimmer head includes a housing and an inner body connected to a trimmer line spool. The inner body is arranged to be movable relative the housing so that a trimmer line spooled around the trimmer line spool is released and pulled out by a centrifugal force caused by the rotation of the trimmer head, thereby allowing feed of the trimmer line. The trimmer further includes drive means for driving the trimmer head to rotate, and the trimmer is arranged to cause a relative movement of the inner body relative the housing by changing the rotation speed of the trimmer head.