| 摘要 |
PURPOSE: To heighten the combining strength of a nut member with a lower rail by bringing the nut member into contact with the lower rail, and forming the distance from the center of a second screw hole to the end edge of a lead screw larger than the distance from the center of a first screw hole to the lower rail. CONSTITUTION: When stress F is applied to a first lead screw 7 in the longitudinal direction, components of force Fb1, Fb2 are applied to a point of force (c), and angular moment Fv applied to a point of application (d) is the component of Fb2. Namely they are expressed in Fv=F2sinθb, F2=Fsinθ/ sin 180-(θ+θb)}. Therefore because the angleθb of a supporting point (b) against the direction of the stress F is determined smaller than the angleθa of a supporting point (a) against the direction of the stress F50, the angular moment Fv applied to the point of application (d) becomes small, the tensile force applied to a female screw hole 9a7 for fixing does not become larger than the shearing force, and hence the combining strength against a lower rail is heightened.
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