| 摘要 |
PURPOSE:To facilitate a relative motion by providing a rotor in a space portion between a tooth portion of a shaft and a tooth portion of a cylinder to reduce the friction therebetween. CONSTITUTION:Grooves 6 for receiving tooth portions 5 of a shaft at the central portion are formed on the inner peripheral surface of a cylinder 3 corresponding to grooves 4. Accordingly tooth portions 7 of the cylinder are projected between the grooves 6, and the tooth portions 7 of the cylinder are respectively positioned at the central portions of the grooves 4 of the shaft 2. A suitable number of rotors 8 like balls are disposed in the respective space portions formed between the tooth portions 5 of the shaft and the tooth portions 7 of the cylinder 7 in the axial direction. In this arrangement, when the members are about to be relatively moved in the axial direction, there is no loss of power because the rotors 8 interposed between the moving members are adapted to roll, so that the relative motion is facilitated.
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