PURPOSE: To descale a contacting material and to cool and replace a brush easily by locking a holding member, which bundles steel wires with a protecting board, by many holes of a cylindrical stay ring and rotating the stay ring by holding it with a perforated cylindrical body.

CONSTITUTION: A bundle of steel wires 15 is attached in a U-shape to a holding member 13 by a binding band 17. Brushes are inserted into many holes 11 of a stay ring 5 fixed to the flanges 3, 3' of rotating shafts 2, 2' by bolts 6, and are locked by the holding members 13, and are restricted by a perforated cylindrical body 10 of the innter surface so as not to come out. The brushes 3 are bulged outside by a centrifugal force caused by the rotation of the shafts 2, 2', to descale a contacting material. The brush 3 is cooled by a cooling-water-containing air sucked from windows 4 to prolong its service life. Further, the brush 3 is easily replaced by dismantling the stay rings 5.