| 摘要 |
PROBLEM TO BE SOLVED: To make detachment from a leg difficult after being fitted by turning the inclination angle of an inclined wall to the axis of a fitting cylinder part to be tightly fitted to the end part outer peripheral surface of the leg to a specified range. SOLUTION: An inclined cylinder part 3 in a truncated cone shape is constituted of a cylindrical fitting cylinder part 2 tightly fittable to the lower end part outer peripheral surface of the leg 1 composed of a cylindrical pipe and the inclined wall 30 whose diameter is widened from one end. The inclination angleθ2 of the inclined wall 30 to the axis of the fitting cylinder part 2 is turned to be more than about 20 degrees and less than about 35 degrees. By elastically tightly fitting the fitting cylinder part 2 to the end part outer periphery of the leg 1, the end part outer peripheral surface and end edge of the leg 1 are covered with this entire protective cap. Even in the case that force in the direction of being detached from the leg 1 acts on the protective cap fitted to the end part of the leg 1, the inclined wall 30 of the inclined cylinder part 3 is hardly displaced to the direction of turning to the same direction as the axis L of the fitting cylinder part 2 to the fitting cylinder part 2 and a seat part 4. Thus, the phenomenon of pulling a boundary part 2a with the inclined cylinder part 3 in the fitting cylinder part 2 in the direction of separating from the outer peripheral surface of the leg 1 is suppressed.
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