Rotation is transmitted from shaft 1 to shafts 2 and 3 through bevel gears 4, 5 and 6. Masses m₁ and m₂ are mounted on shafts 2 and 3 by means of guides a and b and springs 7. Masses m₁ and m₂, together with their guides, rotate in opposite directions. By the action of unbalanced masses m₁ and m₂, frame 8 of the screen has vibratory motion in the direction shown by the arrow.
$2150$EL,VM$