METHOD AND DEVICE FOR JOINING SHEET

PROBLEM TO BE SOLVED: To shorten the joining time of a preceding sheet and a new sheet with a simple mechanism and to reuse scraps without using an adhesive tape and the like, when long sheet rolls are switched.SOLUTION: When a sheet is unwound from the long winding roll and the roll is switched to a new long winding roll if the rest of sheets is running out, the rear ends of the remaining sheets are sucked and held to two upper and lower sheet suction pads 1, 2 provided in series and lower ends are partly projected on the center groove 7 of the lower suction pad 2. Then, the lower suction pad 2 is released while the upper suction pad 1 is moved upward, and the rest of the remaining sheets is removed. Next, the sheet tip of the new long winding roll is sucked to the lower suction pad 2 and the upper portion of the upper groove 6 of the suction pads is cut out. The upper suction pad 1 is moved downward. The protrusion of the rear end of the remaining sheets sucked to the upper suction pad 1 and the sheet tip part of the new long winding roll sucked to the lower suction pad 2 are overlapped with each other. The tip of a welding unit 8 is brought into contact with the overlapping portion center for welding and joining.