Servo assisted butterfly valve provided with a flat leaf spring and a spiral spring to establish the limp-home position

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).