US Patent 7797915 System to clear stuck reels on grass mowing machine

A system to clear stuck reels on a grass mowing machine with a reversible electric or hydraulic motor connected to a cutting reel. The reel motor can rotate in a forward direction and a reverse direction. A controller provides electric signals to the reel motor, and commands the motor to reverse direction if the reel motor does not rotate in the forward direction at a rotational speed at least as high as a preset minimum speed, or rotate a pre-specified number of revolutions.