F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
F01N1/00—Silencing apparatus characterised by method of silencing
F01N1/16—Silencing apparatus characterised by method of silencing by using movable parts
F01N1/165—Silencing apparatus characterised by method of silencing by using movable parts for adjusting flow area
B—PERFORMING OPERATIONS; TRANSPORTING
B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
B21D51/00—Making hollow objects
B21D51/02—Making hollow objects characterised by the structure of the objects
B21D51/10—Making hollow objects characterised by the structure of the objects conically or cylindrically shaped objects
Procede d'elaboration d'une tole ou d'une bande en acier pour la realisation d'une boite et tole ou bande en acier obtenue par ce procede