To enhance the production efficiency of a tread connected to an bridge board, for constructing stairs, to achieve fixture of connectors to the tread easily and with sufficient strength, and to simplify separation of the tread when discarded.
In production of the tread, a plate member 23 formed with through holes 25 extending in a longitudinal direction is extrusion-molded, and each connector 30 having a bolt portion 31 or a nut portion formed at one end thereof and an anchor fixing portion 35 formed at the other end, is inserted into the through hole 25 beginning from the anchor fixing portion 35. By driving a rod member into a tapered bore 33 opening at the center of the bolt portion 31 or the nut portion, a peripheral wall of the tapered bore having a slit 36 formed therein, is expanded like a skirt, and therefore the rod member engages in a through hole wall surface 25a. In this manner the tread 20 is formed by fixing the connector 30 to the plate member 23. Then the plurality of treads 20 are fixed to the two bridge boards opposed to each other to construct the stairs.
YAMAMOTO HIDEKI
TOGAWA HIROSHI
Atsushi Maeda