PERFEZIONAMENTO NEI SISTEMI DI GUIDA SENZA CONTATTO DI MATERIALE A NASTRO SU PERCORSI CURVI

摘要

A guide for contactless support of a running web as the latter changes directions. The guide is formed as a drum-like member having an arcuately curved surface which can be variable as to the length of its arc depending on the degree of turn or change of direction desired for the running web. A series of parallel grooves are formed in the arcuate surface of the drum-like member, which grooves extend in the direction of web travel. An air nozzle extends along the length of the drum-like member and at each end of the grooves in the drum-like member and pressurized air is fed through the nozzles so as to form a pneumatic cushion between the web and the arcuate surface of the drum-like member to thereby float the web in its turning direction over the drum-like member and without contact therewith. The grooves in the arcuate surface act as labyrinth seals in inhibiting transverse air flow out of the cushion and towards the edges of the running web. A barrier extends transversely of the direction of the web travel and across the grooves and blocks them intermediate their length to thereby form a barrier to the air flow in the grooves. This barrier ensures flow stability by preventing one slot from dominating the other which would lead to a non-symmetrical air flow pattern and reduced cushion pressure as well as result in non-uniform cushion pressure.