DETECTION DEVICE FOR CROSS-SECTIONAL AREA CHANGE

摘要

PROBLEM TO BE SOLVED: To accurately detect a change in the cross-sectional area of a steel material.SOLUTION: A detection device for cross-sectional area change includes: a cylindrical body 1A surrounding a steel material 10; an inflated state bag body 2 having a bag body portion 2A brought into an intimate contact with the steel material 10 and the cylindrical body 1A and sandwiched therebetween; an electrode 3 provided at each point for the purpose of measuring a resistance value between two points sandwiching the cross-section in the bag body portion 2A which changes according to a cross-sectional area of the bag body portion 2A changing with a change in the cross-sectional area of the steel material 10; and an electric wire 3a electrically connected to the electrode 3 and pulled out of the bag body 2. The resistance value is in inverse proportion to the cross-sectional area of the bag body portion 2A. As the cross-sectional area of the steel material 10 increases, the cross-sectional area of a cross-section e of the bag body portion 2A decreases, and the resistance vale increases. A resistance measurement device 7 makes a current flow in the electric wire 3a, and measures the resistance value based on the current value.SELECTED DRAWING: Figure 2