Cap screwing device and cap screwing method

The invention belongs to the technical field of cap screwing, and particularly relates to a cap screwing device and a cap screwing method. The cap screwing device comprises a driving shaft, a coupler and a rotating shaft which are coaxially arranged, the lower end of the rotating shaft is provided with a pre-positioning sleeve and a cap screwing part, the periphery of the coupler is sleeved with a restoration spring, the rotating shaft and the driving shaft are flexibly connected through the coupler, and the pre-positioning sleeve located at the lower end of the rotating shaft and a filling opening can be allowed to be adaptively positioned; the restoring spring can restore the bent coupling to be in a vertical state after the pre-positioning sleeve is separated from the filling opening; in other words, the cap screwing device can conduct self-adaptive compensation through the pre-positioning sleeve when the cap screwing part deviates from the filling opening, and can reset automatically. Besides, on the basi