A screen cleaning assembly (10) for cleaning a rectangular material catching screen (9) comprises a hollow arm (42, 50) movable over a surface of the screen (9), the arm (42, 50) having an aperture in a first side which is adjacent to the surface of the screen (9) a hollow duct (32) for connecting the arm (42, 50) to a source (33) of vacuum pressure and an actuator mechanism for moving the arm (42, 50) so that the aperture draws material off of the screen (9) as the arm (42, 50) moves over the screen (9). The arm (42, 50) comprises an inner arm (42) pivotally coupled to the duct and an outer arm (50) which is movable with respect to the inner arm (42).
