To unnecessitate holding a back face shielding head for a rotary drum tube by a worker, to correctly position it, to facilitate carrying it into or carrying it away from the rotary drum tube and to adapt it to the variable size of the diameter of the drum tube.
In a back face gas shielding device wherein three-leg members 4-6 are combined to a leg base 1, a rotary base 8 is connected to the leg based by a rotary axis body 7, and a back face shielding head 100 and a weight 110 are supported by the rotary base 8, respective leg members 4-6 are extendable and contractible in the radial direction of the drum tube 3 and provided with a shoe 45 which abuts on the inner peripheral surface 31 of the body tube 3 at the leg end. Or a rotation driving mechanism including an electric motor and reduction gear is used in place of the weight 110. The inclination of the head 100 is detected by an inclination detector, and the speed of revolution of the electric motor is adjusted by a motor driving device so that the inclination becomes zero.
FUJITA TAKASHI
MARUYAMA TOSHIHIKO
