An air bleed device for cooling components in a turbine engine, including an annular conduit having a substantially rectangular cross-section formed in a housing and having a radially internal wall swept by an airflow is disclosed. The device includes an air inlet orifice, and a flap valve for controlling the airflow entering through the orifice, formed by a plate borne by a maneuvering member mobile in translation parallel to the axis of the orifice between a position in which the plate closes off the orifice and a position in which the plate opens the orifice.