초록 ▼

A flow molding process and associated molding apparatus for making plastic parts employing a radio-frequency heating field. In a two-piece mold, a diaphragm is supported thereacross and over a foam plastic compound that is disposed in the bottom half of the mold. A fluid is adapted to be introduced

A flow molding process and associated molding apparatus for making plastic parts employing a radio-frequency heating field. In a two-piece mold, a diaphragm is supported thereacross and over a foam plastic compound that is disposed in the bottom half of the mold. A fluid is adapted to be introduced into the mold against the diaphragm. The introduction of this fluid is controlled to initially inject the fluid into the mold to cause deflection of the diaphragm to thus expel substantially all air from the mold and to thereafter extract the fluid from the mold during the heating cycle as the material expands, the extraction causing a vacuum that assists in the plastic foam compound expansion.

대표청구항 ▼

A flow molding process using radio-frequency dielectric heating of a foamable plastic material that is adapted to be expanded into a finished foam piece and that is disposed in a mold cavity, said process comprising the steps of, supporting a flexible and deformable diaphragm across the mold cavity,

A flow molding process using radio-frequency dielectric heating of a foamable plastic material that is adapted to be expanded into a finished foam piece and that is disposed in a mold cavity, said process comprising the steps of, supporting a flexible and deformable diaphragm across the mold cavity, disposing a foamable plastic material in the mold cavity under the diaphragm, applying a pressure by controllably forcing a liquid into the mold cavity against the diaphragm on a surface thereof opposite to the material side of the diaphragm to cause the diaphragm to deflect against the material while permitting air to be removed from the cavity, applying radio-frequency heating to the mold cavity over a heating cycle, and concurrent with said heating releasing the pressure imposed by said liquid against the diaphragm, the applied pressure being released at a predetermined rate comparable to the rate of material expansion, said diaphragm, upon release, deflecting against a surface of the cavity.