Shut-off or throttle valve with pivotal flap

A shut-off or throttle valve for an exhaust gas conduit of an internal combustion engine for generating a ram pressure therein, comprising:

• a housing comprising a tubular sleeve and a pair of cylindrical conduit portions of said exhaust gas conduit closed by said tubular sleeve;
• a valve flap mounted in said housing so as to be pivotal between open and closed positions, said valve flap allowing flow of exhaust gas through said conduit when in said open position, said valve flap prohibiting substantially all flow of exhaust gas through said conduit when in said closed position, said valve flap comprising an axis of rotation and a flap plate divided by said axis of rotation into a pair of plate sections, said flap plate being disposed in a closing plane extending transversely to a longitudinal axis of said exhaust gas conduit, when said valve flap is in its closed position;
• a pair of abutment edges provided on the housing at opposite sides of said valve flap and facing towards each other such that when the valve flap moves to its closed position one of said plate sections has a peripheral area thereof sealingly engage one of said abutment edges and the other of said plate sections has a peripheral area thereof sealingly engage the other of said abutment edges so as to close said exhaust gas conduit, said conduit portions having end faces facing said valve flap and serving as said abutment edges;
• one of said plate sections having a larger surface area than the other of said plate sections and said valve flap being arranged such that ram pressure generated by said valve flap in said exhaust gas conduit exerts upon said valve flap pressure forces resulting in torque tending to move said valve flap towards said open position;
• and
• actuating means selectively operable to move said valve flap between open and closed positions.