Double wall silencer for IC engine - has helical corrugations formed in concentric pipes and packed with steel wool

摘要

A silencer for an internal combustion engine has an inner pipe (1) with a perforated wall (4) which is supported inside an outer pipe (2). The annular gap between the pipes is filled with heat and corrosion resisting steel wool (3). In addition, helical corrugations are formed in the walls of both tubes. The outer tube is first formed with a smooth outer surface and the inner tube which is already corrugated is fitted inside and held centrally by helical spacers. The steel wool is inserted and the corrugations are then formed in the outer tube so that the steel wool is compressed and retained in position.