Oblon, Fisher, Spivak, McClelland & Maier
Rotor assembly of roots pump
 A Roots pump having a plurality of rotor assemblies each including a light-alloy rotor, a steel shaft press-fitted in a bore of the rotor and a lock pin which is inserted through the rotor and the shaft to prevent removal of the shaft from the rotor. The lock pin is located substantially at an axial center of a press-fitted portion of the shaft accommodated the axial bore. The shaft has a timing gear at one end thereof for meshing with a timing gear of the shaft of the adjacent rotor assembly. The shaft further has a plurality of engagement teeth provided at one of opposite ends of the press-fitted portion on the side of the timing gear. The engagement teeth are at least partially embedded in an inner surface defining the axial bore of the rotor, upon press-fitting of the press-fitted portion in the axis bore, to thereby prevent a rotational movement of the shaft relative to the rotor. 
Toyota Jidosha Kabushiki Kaisha
F Y Y F Y F
F04C Y10T Y10T F01C Y10T F04C
inventional additional additional inventional additional inventional
Katsuro Yoshio Naofumi Hisao Takuo Kichiro
Harada Kuroiwa Masuda Shirai Sibata Kato