| 摘要 |
PURPOSE:To avoid the need of a guide shaft and reduce the dimension and weight by forming a sliding-contact surface for shift-guiding a driven member free from eccentricity and chattering onto a screw shaft body for shifting the driving member, in the straight advancing mechanism for camera, etc. CONSTITUTION:When a zoom motor 7 is revolution-driven, also a variator driving shaft 5 having a V-shaped screw groove 5a revolves, and a lens group 3 shifts in the axis center X direction in the state free from chattering, allowing the inner peripheral surface 3b of a cylindrical part 3B to sliding-contact the cylindrical surface 5b of a driving shaft 5. The cylindrical surface 5b of the driving shaft 5 is formed over nearly the full length of the part having the V-shaped screw part 5a formed, and a ball body 21 is pressed into the V-shaped groove 5a by a spring 22, and since the chattering of the driving shaft 5 in the axial direction is regulated by the spring 20, the tilt in shift can be reduced, securing a large operation distance of the lens groups 3. Therefore, a guide shaft can be omitted, and the dimension and weight can be reduced.
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