| 摘要 |
<p>A hot sprue valve assembly is provided for controlling flow of molten material into the mold cavity of an injection molding machine. The valve assembly is particularly designed for use with an injection molding machine for molding centrally apertured record discs, such as video information discs. The valve assembly includes a hot sprue bushing defining a heated flow path for passage of molten material toward a stationary dispersion head positioned centrally within the mold cavity. The dispersion head directs the molten material to flow in a generally radially outward direction with substantially uniform radial distribution into the mold cavity. A cylindrical sleeve valve is carried about the hot sprue bushing for reciprocal movement between an open position retracted from the mold cavity to permit flow of the molten material into the mold cavity, and a closed position projecting into the mold cavity in seated engagement with the dispersion head simultaneously to prevent flow of the molten material into the mold cavity and to mold a central aperture in the disc.</p> |
