Compressive treatment of web materials

Abstract

Improved machine and method for longitudinal compressive treatment of webs employing a two roll drive nip. Specially arranged initial parts of one or a pair of stationary retarding members are positioned at the exit side of the drive nip in the region of minor divergence of the roll surfaces to provide damming forces. The initial part of the retarding member, preferably a curved, resilient nipping element, is shaped to oppose the flow of the web. By its construction and position close to the line of centers of the rolls, it establishes a very compacted column extending upstream to an initial treatment point continually located in the drive nip, between the moving surfaces of the rolls. In this region, longitudinal compressive action occurs upon the web in a continuous and uniform manner, preferably with compensatory action in response to variations in the forces exerted by the compacted column of web. This compensatory action is provided by resilient deformation of a retarding member in the direction normal to the plane of the web, resilient adjustment movement of a retarding member in the direction away from the nip roll center line, and in some cases, by resilient response of the compacted material itself. The retarding members may accomplish their resilient movement by swinging about the roll axes and by moving longitudinally of the web flow path. The retarding member, or the leading member of a pair, preferably, in the start-up position, has its initial part located upstream of the running position.