Back-flow prevention device, for exhaust gas line, has floating body with central section and outer section raised in succession dependent on power range

摘要

The back-flow prevention device has a tubular body (1) inserted in a vertical section of the exhaust gas line, provided with a valve seat (5) for a floating body which is lifted from the valve seat by a gas flow in the forwards direction. The floating body has an annular outer section (4) cooperating with the valve seat and a central section (3) cooperating with a secondary valve seat (6) provided by the outer section. The central section is raised in the lower power range, with partial or full lifting of the outer section with increasing power.