Nikaido, Marmelstein, Murray & Oram LLP
Ball screw for vacuum apparatus
 A ball screw for a vacuum apparatus which includes a screw shaft having a spiral inner raceway formed on an outer peripheral surface thereof, a ball nut having a spiral outer raceway formed on an inner peripheral surface thereof, a plurality of balls disposed in a spiral space defined between the inner raceway and the outer raceway, and circulating members connecting ends of the spiral space to each other to define a continuous ball circulating passage. The plurality of balls are first balls formed of high polymer material containing polytetrafluoroethylene as a main component and second balls formed of either a metallic material or a ceramic material. The first balls circulate through the circulating passage together with the second balls. The second balls have lubricating films of crystalline polytetrafluoroethylene formed on the surface thereof. 
NTN Corporation
F F F F Y
F16H F16C F16C F16C Y10T
inventional inventional inventional additional additional
Tokumasa Michiyoshi Hiroshi Masahiro Hiromitsu
Nakamura Ishimaru Yamada Nobutomo Kondo