A dirt scrapper assembly (200) comprising an annular stiffening structure (205) adapted to connect with a tube for sealing the tube is disclosed. The annular stiffening structure comprises a plurality of first axial sections (215) equally spaced and extended along axial direction on an outer side of the tube. Curvature of corresponding radii is provided on the outer surface of the first axial sections. The annular stiffening structure (205) further comprises a second axial section (220) extended along axial direction of the tube on inner side of the tube. The plurality of first axial sections (215) and the second axial section (220) are connected by a connection section (225) of the stiffening structure to get into contact with an end surface of the tube. The connection section (225) comprises a cut section (235) at the bottom surface extended over the length of each of the plurality of first axial sections (215) to provide flex to the plurality of first axial sections.

嵌合部（８）に保護部材（５）の周縁部（７）を嵌め、止め輪溝（９）に止め輪（６）を嵌着することにより、保護部材（５）を軌道輪（２）に固定する。止め輪溝（９）の軸方向外側の溝肩部（１２）における直径φＢは、保護部材（５）の周縁部（７）を径方向に受ける嵌合部（８）の周面（８ａ）の直径φＡと同径の寸法、又は、φＡに対して保護部材（５）の周縁部（７）から遠くなる方へ径差をもった寸法に設定した転がり軸受である。