q Dancer roll control w Air brake control As the diameter of the roll increases, tension on the dancer roll decreases. (Drooping or straining of the film is corrected, and tensile force is maintained.) A low friction cylinder, etc. with less mechanical loss is used. The diameter is detected, deformation is reported to an electro-pneumatic converter, and the air brake is activated. E P Low friction cylinder Electro-pneumatic regulator E P Air brake Diameter detection Front matter 8