Prevention of web floating at wrapped transport and guide rollers

Abstract

Increasing productivity of web converting machines requires constructive improvements for the prevention of web floating at transport and guide rollers. Existing solutions which carry off the air like vacuum or grooved rollers as well as rough layers at the roller surfaces are on the one hand complicated and on the other hand limited in their effect.

On this background a novel principle, the so-called "gap throttle effect", which was discovered at the institute of engineering design at the Ruhr-Universitat-Bochum (LMK) is presented.

The following analysis contains initial practically orientated investigations of pressure development resp. air entrainment for the conventional system ,,wrapped roller" and subsequent investigations for the novel system "gap throttle". The aim is to analyse the influence parameters with aid of a developed simulation program based on the finite differences method as well as to verify the results with experimental investigations at a test rig.

To show the influence and the potential of the "gap throttle effect'', LWC, SC, Tissue and Newsprint with different material properties especially, air permeability and surface roughness, are analysed by variation of relevant process, gap throttle and machine parameters.

The results prove, that the effect can be used to achieve higher transferable friction forces and therefore higher web speed. Subsequent investigations show, that the effect amount and it's stability can be increased considerably by an additional small pressure on the web surface at the mounting area of the web. The innovation potential and the usefulness of this novel principle for web handling machines should be used for later research work, to increase the range of application, especially for winding and coating.