| 摘要 |
<p>PURPOSE:To shorten a cycle time of production to improve the productivity by filling molding sand into a space to be filled with the sheathing material, and thereafter, blowing carbon deoxide gas into the molding sand from ventilation holes and an opening of a sheathing pipe. CONSTITUTION:A sheathing steel pipe 14 has multiple ventilation holes 16 in the pipe wall, and a ventilation hole 15 is formed by punching and a part of the surroundings are left, and a tong piece 18 generated by punching is folded inside of the pipe 14. Molding sand 20 as the sheathing material is filled from an upper opening 19 of the sheathing pipe 14 into the space 15 to be filled with the sheathing material, and next, carbon deoxide gas 21 is blown from the ventilation holes 16 and the opening 19 of the sheathing pipe 14 into the molding sand 20 to harden the molding sand 20. The molding sand 20 is hardened instantly by blowing the carbon deoxide gas 21. Since the molding sand 20 is hardened instantly by blowing the carbon deoxide gas 21, a cycle time of production is shortened remarkably to improve the productivity remarkably.</p> |
