Cardboard boxes by the front-end sealing machine sealing up and down the middle, the 90-degree corner machine, pushed by the pushing box board into the corner side sealing machine, photoelectric detector to the machine according to the carton, and automatically adjust the machine width and height. Manpower do not need to adjust the machine is simple, convenient and fast. Automatic adjustment of the carton, to automatically seal the carton up and down the four corners of the edges, smooth, fast, smooth; machine adopts PLC control, easy operation, easy maintenance, more stable performance.