| 摘要 |
PURPOSE:To facilitate process by providing an intermediate plate forming a curved shape, two end plates forming a flat shape, and a connection member for connecting the intermediate plate with the end plates. CONSTITUTION:A tread 14 is formed out of a center 14a buckling in arc, straight end parts 14b, 14b, a center part 14C recessed into arc, and of straight end parts 14d, 14d. A riser 15 is formed out of an intermediate plate 10 curved into arc, first and second flat end plates 17, 18, and of first and second connection members 19, 20. Both end parts 14b, 14b of the tread 14 are fitted to a fitting groove 12 for each tread of right and left side plates 11 from the rear side, while both end plates 17, 18 of the riser 15 are fitted to a fitting groove 13 for each riser of the right and left side plates 11 from below, and a staircase is thus formed. The setting of the width size as well as the depth size of the fitting groove 13 and the process thereof are facilitated by fitting the end plates 17, 18 of the riser 15 almost perpendicular to and in the fitting groove 13. |
