Patent ID: 7028979

Claim:
A servo-assisted butterfly valve ( 1 ) comprising a valve body ( 2 ), a valve seat ( 4 ) formed in the valve body ( 2 ), a butterfly disc ( 5 ) adapted to engage the valve seat ( 4 ), a shaft ( 6 ) on which the butterfly disc ( 5 ) is keyed, an electric motor ( 3 ) coupled to the shaft ( 6 ) by means of a gear transmission ( 8 ) comprising at least a first toothed wheel ( 17 ) in order to rotate the butterfly disc ( 5 ) between a position of maximum opening and a closed position of the valve seat ( 4 ), a spiral return spring ( 35 ) adapted to rotate the butterfly disc ( 5 ) towards the closed position, and an opposing spring ( 36 ) adapted to rotate the butterfly disc ( 5 ) towards a partially open or limp-home position defined by an abutment body ( 37 ) against the action of the return spring ( 35 ); the butterfly valve ( 1 ) being characterised in that the opposing spring ( 36 ) is a flat leaf spring and is mounted on a moving member ( 40 ) which is mounted coaxially and idly on the shaft ( 6 ) and comprises a projection ( 42 ) adapted to engage in abutment against the abutment body ( 37 ), a first end ( 43 ) of the opposing spring ( 36 ) being free and being disposed alongside the first toothed wheel ( 17 ) so as to face an inner surface ( 44 ) of this first toothed wheel ( 17 ), this first toothed wheel ( 17 ) comprising a projection ( 45 ) which projects in a perpendicular manner with respect to the inner surface ( 44 ) so as to bear against the first end ( 43 ) of the opposing spring ( 36 ) during the rotation of the first toothed wheel ( 17 ).