Method and device for joining plies of paper

Method for joining plies of paper comprising steps of embossing a first ply by an embossing roller provided with protuberances and a pressure roller cooperating with said embossing roller;

• feeding said first ply and a second ply according to a longitudinal direction of advancement through a ply-bonding nip between the embossing roller and a set of ply-bonding wheels, said ply-bonding wheels being separated and spaced apart from one another in a cross-machine direction transverse to said direction of advancement so as to provide (1) first areas which can receive localized pressure from said ply-bonding wheels and (2) second areas between respective ones of said ply-bonding wheels which do not receive pressure from said ply-bonding wheels, when said ply-bonding wheels are positioned to exert localized pressure on said embossing roller;
• bonding said first ply and said second ply together by localized pressure in said ply-bonding nip;
• wherein at least one of said first ply and said second ply is moistened only in said first areas in which said localized pressure is to be exerted along longitudinal areas separate and in a spaced relation from one another in said cross-machine direction and extending parallel to an advancement direction of said first ply and said second ply, and wherein on said longitudinal areas following moistening thereof, said localized pressure is exerted on said first areas by said ply-bonding wheels so that said first ply and said second ply are bonded by moisture in said longitudinal areas which have been moistened and by said localized pressure in absence of any adhesive material.