Motor vehicle screen wiping apparatus including means for varying wiping pressure

A screen wiping apparatus comprising:

• a drive head having a pivot axis;
• a wiper arm for carrying at least one wiper blade, said wiper arm pivotally mounted on the drive head for movement with respect to the drive head about the pivot axis;
• and wiping torque-applying means coupled between the drive head and the wiper arm for applying a wiping torque to the wiper arm, the wiping torque applying means having a substantially constant torque-applying means which includes at least one spring coupled to the wiper arm and drive head for applying to the wiper arm a substantially constant nominal wiping torque;
• and said torque-applying means further including complementary torque-applying means for applying a complementary torque, said complementary torque applying means having an actuator, the actuator having an actuator body and an output member movable in the actuator body, the actuator body being mounted on the drive head and the output member being connected to the wiper arm, the complementary torque applying means further having a coupling member coupling the wiper to the output member of the actuator;
• said output member mounting the coupling member for movement therewith in a direction of displacement at right angles to the pivot axis, the coupling member having a working surface, the wiper arm carrying an elongated pin that has an axis parallel to the pivot axis, and the apparatus further including a roller rotatably mounted on the wiper arm pin for rotation about the wiper arm pin axis and for engagement with the working surface of the coupling member whereby movement of the coupling member varies the magnitude of the complementary torque.