| 摘要 |
PURPOSE:To prevent the play of a helicoid screw due to the wear of a helicoid, by providing a spring part for preventing the play of the helicoid screw on the outside circumference of a helicoid member of a lens. CONSTITUTION:On the outside circumference of a helicoid cylinder part 11, three divided discontinuous screws helicoid 14 are provided, and play preventing springs 12 are protruded in break parts between helicoid screws 14. By this constitution, in case that a member, which is engaged threadedly with helicoid screws 14 of this helicoid member for a lens, named an inside helicoid is slided while meshing with helicoid screws 14, screw threads of the inside helicoid press play preventing springs 12 to cause a bending elastic deformation in the radial direction. Consequently, helicoid screws 14 and the inside helicoid continue always press mutually by the force of play preventing springs 12 when both of them mesh with each other and slide, and thus, the play of helicoid screws 14 is prevented. |
