| 摘要 |
PURPOSE:To measure the outside diameter of a steel pipe in an on-line manner, by providing an outside-diameter measuring apparatus with a screw mechanism having thread parts different in pitch for moving phtodetectors disposed opposite to a projector in opposite directions according to the diameter of a steel pipe to be measured. CONSTITUTION:The pitch of a thread part 11 for moving one detector 2a is made large, while the pitch of a thread part 12 for moving the other detector 2b is made small, and the thread parts are opposite in thread direction to each other. If the projection angle of light from a projector 1 is theta with respect to a fixing rest 5 and the radius of a steel pipe X is (r), the distances between the positions where the detectors 2a and 2b are set in measuring the steel pipe outside diameter on one hand and a reference line alpha on the other are represented by (1+costheta)r and (1-costheta)r, respectively. Therefore, if a ball screw 10 is employed having the thread parts 11, 12 with a pitch ratio of (1+costheta):(1-costheta), it is possible to set the detectors 2a, 2b at their respective predetermined reference positions by means of a single driver 4 at all times even if the diameter of the steel pipe X to be measured changes and the central position thereof changes. |
