| 摘要 |
PROBLEM TO BE SOLVED: To prevent an overheat phenomenon and temperature irregularities from occurring and thereby upgrade the homogeneity of a foaming state by first injecting steam into a chamber to perform a preliminary evacuation of air, then boosting an internal pressure to a set pressure level to cause the mutual fusion of foamable raw material beads, and further, forming the skin of a foamed molding while lowering the internal pressure. SOLUTION: In a preliminary evacuation step, steam valves 41, 51, suction valves 42, 52, 42b, 52b and drain valves 43, 53 are operated ON/OFF, then the air in chambers 2, 3 and between the raw material beads is evacuated by a steam to cause the replacement of the air with the steam. Next, in a pressure boosting/fusion step, evacuation apertures in the chambers 2, 3 are closed to inject the steam, so that a steam pressure at a temperature to cause the mutual fusion of the raw material beads is boosted to a second set pressure value. In this case, the internal pressure of the chambers 2, 3 is set below a first set pressure value to control the internal pressure in such a manner that a partial fusion reaction between the raw material beads does not occur. After that, the skin of a foamed molding is formed at a fourth set pressure value which is lower than the pressure value set below the first set pressure value. Even at this low pressure, the fusion of the surface part advances. |
