Flap device

The flap device (1) has flap housing (2) enclosing channel portion (7) in circumferential direction (6). A flap (3) controls fluid flow cross-section (9) of channel portion around pivotal axis (10) in flap housing. A positioning unit (4) drives flap and has hydraulic or pneumatic pressure capsule (16) or temperature-controlled wax element. A coupling unit (5) couples flap shaft (14) coaxially extended to pivotal axis with linear adjustable drive shaft (11) coaxially aligned to pivotal axis so that linear motions (12) of drive shaft are converted to rotating movements (15) of flap shaft.