Armstrong, Westerman, Hattori, McLeland & Naughton
Cylinder tube and process for producing same
 A cylinder tube comprising an aluminum tube formed on its outer surface with an outside oxide film having a hardness of not lower than 150 HV to less than 350 HV and on its inner surface with an inside oxide film having a hardness of not lower than 350 HV to not higher than 650 HV. 
Showa Aluminum Corporation
F
F16J
inventional
Masaaki Minobu Akira Masakazu Tatsuo
Ooide Sukimoto Sakayori Shimaguchi Otsuka