A method and a device for joining ends of fiber webs in a parent roll change of an unwinder

The invention relates to a method for joining ends of fiber webs in a parent roll change of an unwinder, which method is configured to be performed by a device comprising a tool element (11) with a gripping device and a traversing punching device (13), whereby at a stage, in which a parent roll in the unwinder (10) is almost empty, the run of the fiber web (W) from the emptying parent roll is moved to a joining position at the tool element (11) and the trailing end of the fiber web (W) from the emptying parent roll is cut upstream from the joining position and the fiber web (W) is attached to the tool element (11) by means of gripping effect created by the gripping device of the tool element (11), at a next stage a beginning end of a new fiber web (WN) from a new parent roll is guided to contact with and to an overlapping position with the trailing end of the fiber web (W) from the emptying parent roll and the rotating movement of the new parent roll in the unwinder (10) is stopped, at a next stage the traversing punching device (13) is moved across the width direction of the fiber webs (W, WN) and is configured to make at least one joint cut to the overlapping ends of the fiber webs (W, WN) and to join the ends of the fiber webs (W, WN) to each other, the beginning end of the new fiber web (WN) from the new parent roll in the unwinder (10) is cut downstream from the joint for removing the beginning end simultaneously or after making the at least one joint cut, and at a next control of tension of the joined fiber webs (W, WN) is turned on and the joint joining the ends of the fiber webs (W, WN) is ready. The invention also relates to a device for joining ends of fiber webs in a parent roll change of an unwinder comprises a tool element (11) with a gripping device for attaching a trailing end of a fiber web (W) from an emptying parent roll in the unwinder (10) to a beginning end of a fiber web from a new parent roll. The tool element (11) further comprises a traversing punching device (13) configured to move across overlapping ends of the trailing end of the fiber web (W) from the emptying parent roll and of a beginning end of a fiber web from a new parent roll in width direction of the fiber webs (W, WN) to make at least one joint cut to the overlapping ends of the fiber webs (W, WN) and to join the ends of the fiber webs (W, WN). Keksinnön kohteena on menetelmä kuiturainojen päiden liittämiseksi yhteen aukirullaimen konerullan vaihdon yhteydessä, joka men