Compressive treatment of web materials

In a machine for longitudinal compressive treatment of a web, comprising a drive nip for driving the web along a web path formed by stable surfaces of a pair of oppositely rotating rolls, and a retarding device on the exit side of the nip, the improvement wherein said retarding device is formed by a pair of relatively stationary retarding members between which the web is pushed by the nip, said pair of retarding members having substantially parallel opposed web-contacting surfaces defining a retarding path aligned with the plane of tangency defined by the two rolls at their nip, said surfaces positioned to support the faces of said web to prevent gross pleating, the initial part of at least one of said retarding members defining a dam means, said dam means capable of presenting a frontal surface inclined to the direction of web travel immediately as it approaches said dam means, said dam means constructed to enable continual flow of the web thereover while imposing resistance to said flow, and said dam means shaped to be positioned in the region of minor divergence of said roll surfaces downstream from the line of centers of said pair of rolls at a distance less than about 5% of the sum of the diameters of said rolls, to terminate therebetween a longitudinal compression cavity of correspondingly short length and height, means for continually maintaining said dam means at said position for steady state running conditions, said dam means cooperative with the adjacent surfaces of said drive rolls and the opposite retarding member to continually maintain in position in advance of said dam means, between the moving surfaces of said two rolls, a longitudinally compacted moving column of web against which fresh web delivered by said nip is progressively compressed, said roll surfaces at said cavity effective to continually intimately contact the faces of the web, to support the web against folding upon itself, whereby said web remains continually within its original general plane without gross pleating throughout its longitudinal compressive treatment.

In a machine for longitudinal compressive treatment of a web, comprising a drive nip for driving the web along a web path formed by stable surfaces of a pair of oppositely rotating rolls, and a retarding device on the exit side of the nip, formed by at least one relatively stationary retarding member held next to a given roll, the improvement wherein the initial part of said retarding member, for providing damming forces, defines a resilient nipping surface which is resilient in the direction normal to the plane of tangency defined by the two rolls at their nip, said nipping surface constructed to enable continual flow of the web thereover while imposing resistance to said flow, and said nipping surface shaped to be positioned in the region of minor divergence of said roll surfaces downstream from the line of centers of said pair of rolls at a distance less than about 5% of the sum of the diameters of said rolls, to terminate therebetween a longitudinal compression cavity of correspondingly short length and height, means for continually maintaining said nipping surface at said position for steady state running conditions, said nipping surface thereby cooperative with the adjacent surfaces of said drive rolls to continually maintain in position in advance of said nipping surface, between the moving surfaces of said two rolls, a longitudinally compacted moving column of web against which fresh web delivered by said nip is progressively compressed, said roll surfaces at said cavity effective to continually intimately contact the faces of the web, to support the web against folding upon itself, whereby said web remains continually within its original general plane without gross pleating throughout its longitudinal compressive treatment, and said resilient nipping surface effective to enable resilient accomodation of said column as it moves past said nipping surface while said nipping surface remains at a steady position relative to said line of centers.

In a machine for longitudinal compressive treatment of a web, comprising a drive nip for driving the web along a web path formed by stable surfaces of a pair of oppositely rotating rolls, and a retarding device on the exit side of the nip, formed by at least one relatively stationary retarding member held next to a given roll, the improvement wherein the initial part of said retarding member defines means providing damming forces, said dam means being resilient in the direction normal to the plane of tangency defined by the two rolls at their nip to provide a resilient nipping surface inclined to the direction of web travel, downstream thereof said retarding member defining a material-engaging surface lying relatively more parallel to said web direction, said dam means constructed to enable continual flow of the web thereover while imposing resistance to said flow, said dam means positioned adjacent to the line of centers of said nip to terminate therebetween a longitudinal compression cavity of correspondingly short length, said dam means thereby cooperative with the adjacent surfaces of said drive rolls to continually maintain in position in advance of said dam means, between the moving surfaces of said two rolls, a longitudinally compacted moving column of web against which fresh web delivered by said nip is progressively compressed, said dam means comprising a resilient spring member terminating at a free end directed upstream relative to the moving web, the terminal part of said spring element curving upstream from a direction generally parallel to the plane of tangency defined by the two rolls at the nip to a direction at said free end forming an acute angle .alpha. therewith, in a manner converging upstream toward the surface of said given roll that lies on the respective side of the web.

In a machine for longitudinal compressive treatment of a web, comprising a drive nip for driving the web along a web path formed by stable surfaces of a pair of oppositely rotating rolls, and a retarding device on the exit side of the nip, formed by a pair of relatively stationary retarding members each held next to a respective roll, and between which the web is pushed by the nip, the improvement wherein the initial part of at least one of said retarding members defines a dam means for providing damming forces, said dam means capable of presenting a frontal surface inclined to the direction of web travel immediately as it approaches said dam means and downstream thereof said retarding member defines a material-engaging surface lying relatively more parallel to said web direction, said dam means constructed to enable continual flow of the web thereover while imposing resistance to said flow, said dam means positioned adjacent to the line of centers of said nip to terminate therebetween a longitudinal compression cavity of correspondingly short length, said dam means cooperative with the adjacent surfaces of said drive rolls and the opposite retarding member to continually maintain in position in advance of said dam means, between the moving surfaces of said two rolls, a longitudinally compacted moving column of web against which fresh web delivered by said nip is progressively compressed, said retarding members being connected together for dependent opposite movement from a first position in which one retarding member has its leading edge immediately adjacent to the line of centers of said pair of rolls and that of the other is spaced a greater distance from said line of centers, whereby the nip defined by said rolls is substantially filled by said retarding members to a second position in which the said spacings of said retarding members are more nearly equal.

In a method of longitudinal compressive treatment of a webb, comprising driving the web forward along a web path by a pair of oppositely rotating, stable-surfaced rolls forming a nip, and retarding the web on the exit side of the nip by the positioning of at least one relatively stationary retarding member held next to a given roll, the improvement comprising opposing the flow of the web from the nip by a dam means on the initial part of said retarding member providing damming forces, said dam means capable of presenting a frontal surface inclined to the direction of said web travel immediately approaching said dam means, and engaging the web downstream thereof with a web-engaging surface lying relatively more parallel to said web direction, said dam means enabling continual flow of the web thereover while imposing resistance to said flow, the position of said dam means being maintained in a steady state running position in the region of minor divergence of said roll surfaces downstream from the line of centers of said pair of rolls at a distance less than about 5% of the sum of the diameters of said rolls, to terminate therebetween a longitudinal compression cavity of correspondingly short length and height, said dam means cooperating with the adjacent surfaces of said drive rolls to continually maintain in position in advance of said dam means, between the moving surface of said two rolls, a longitudinally compacted moving column of web against which fresh web delivered by said nip is progressively compressed, said roll surfaces at said cavity effective to continually intimately contact the faces of the web, to support the web against folding upon itself, whereby said web remains continually within its original general plane without gross pleating throughout its longitudinal compressive treatment.