Apparatus in a drying section of a paper machine

Claim 1

In a drying section of a paper machine including at least one drying group wherein a web in contact with a supporting fabric runs from a drying cylinder in one line of drying cylinders to a drying cylinder in another line of drying cylinders, apparatus for preventing conditions tending to deteriorate the support contact between the web and the fabric including the generation of positive pressures in the narrowing gaps defined by the surfaces of the drying cylinders and the web supporting fabric as it approaches and/or moves away therefrom, comprising: at least one blow box adapted to be connected to a source of blow gas, said blow box being situated adjacent to a respective run of the web supporting fabric and extending transversely thereto substantially over the width of the web, said blow box including at least two transversely extending blow gas discharge aperture means having respective widths and between which a substantially planar carrying surface is provided, said carrying surface being in opposed substantially parallel relationship to the web carrying fabric and spaced a first distance therefrom which is in the range of between about 10 to 30 times the width of at least one of said blow gas discharge aperture means, a space being defined between said carrying surface and the opposed web carrying fabric, at least one of said blow gas discharge aperture means being situtated proximate to the web carrying fabric and spaced a second distance therefrom, said first distance at which said carrying surface is spaced from said web carrying fabric being greater than said second distance at which said at least one blow gas discharge aperture means is spaced from said web carrying fabric, and wherein said blow gas discharge aperture means comprise means for directing blow gas away from said space defined between said carrying surface and opposed web carrying fabric to generate a negative pressure in said space.