| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw thread mechanism having improved screw forwarding operability compared with conventional mechanisms. SOLUTION: The mechanism is provided with a male screw member having a male screw composed of a spiral groove having nearly constant width on the outer circumference and a rotary member fit on the outer circumference of the male screw and rotated relative to the male screw member. The male screw has a varying pitch region to continuously change the pitch between the grooves of at least a part of the male screw. The mechanism is further provided with an engaging means to engage with a part of the length of the groove to meet the change of the pitch between the grooves. The engaging means is rotated together with the rotary member according to the rotation of the rotary member and, at the same time, shifted in longitudinal direction in the groove to shift the rotary member along the axial direction in a state guided with the groove. COPYRIGHT: (C)2003,JPO
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