Patent ID: 7429231

Claim:
A rotary drive for a belt tensioner, including a housing, a pinion ( 32 ; 78 ) rotatably mounted therein, and at least one driving gear coupled to the pinion ( 32 ; 78 ), the driving gear being mounted in the housing and being adapted to be driven by pressurized gas introduced into a pressure chamber ( 20 ; 68 ), in the driving gear there being formed a cavity ( 24 ; 70 ) having a substantially radially extending wall ( 38 ; 72 ) which, in the installed state, is opposite to a protrusion which projects into the cavity ( 24 ; 70 ) and is rigidly connected to the housing, the wall ( 38 ; 72 ) of the cavity ( 24 ; 70 ) and the protrusion forming part of a wall of the pressure chamber ( 20 ; 68 ).