Arrangement for conveying web material through a treating plant

An arrangement for conveying a web such as a foil of metal, plastics or another material, which upon single curving shows stiffness transverse to the direction of curving, and which preferably is coated on one or both sides, through a treatment plant, comprising a plurality of blower boxes, arranged adjacent each other with perforations providing blow-on apertures in a first plane above and a second plane below the web, said boxes extending transversely to the web, said blow-on apertures having a certain degree of perforation for blowing a medium, such as air, perpendicularly against the web, and outlet apertures for draining the treating medium between said boxes, characterized in that the blower boxes are arranged in periodically repeated groups located adjacent each other, one group thereof comprising blower boxes with a high perforation degree and the other group comprising blower boxes with a low perforation degree, and that a group with high perforation degree in one plane is located directly in front of a group with low perforation degree in the other plane so that the web assumes a wave shape between the first and second planes, said wave staying with its nodes in definite positions closer to the one plane opposite the highly perforated groups in the second plane, and closer to the second plane opposite the highly perforated groups in the one plane.