| 摘要 |
PURPOSE: To raise the support ability between a roller and a guide surface and reduce the roller cost by forming a roller nearly cylindrical and the cross section of the wall of the guide groove of an outside element relating to at least one side rotation direction in a projected crown shape. CONSTITUTION: Three cylindrical rollers 31 are installed on an inside element 20 so as to be fixed axially on three arms 22 fixed radially and a roller 31 is mounted so as to be positioned in the guide groove of an outside element 1. The cross section of the wall 13 of the counter-clockwise direction of the guide groove of the outside element 1 is formed in a projected crown shape. Therefore, the roller 31 is nearly cylindrical and cheap and the bearing between the roller 31 and the arm 22 and the support ability between the roller 31 and the crown shape surface of the guide groove 13 can be improved.
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