The dipping device blocks part of the beam provided by the light source and comprises a plate with a single carrier arm (2), lying above or below the optical axis (3) having an end (5) fitted in an opening (6) of the headlamp reflector (7).The carrier arm is doubled over throughout its length, its wide side faces lying in a vertical plane, the transverse arm (8) of the plate supporting a hollow cylinder (9) at its optical axis end comprising 2 half shells with symmetrical halves joined together by a bridge divided by the fold line for the symmetrical halves.
