| 摘要 |
Injection molding device for the prodn. of record discs includes a sprue bushing defining a hot runner, and a poppet valve that is located at the end of the bushing and can move between a runner closing and a runner opening position. The bushing is spring biased to the closed position and a ram is located opposite the poppet valve. Injection pressure opens the valve against its spring bias to facilitate injection. After injection, the working material pressure is reduced to a holding pressure still sufficient to keep the valve open. After the end of a holding period the ram is actuated to move the valve through the still soft material to the closing position against the bias of the spring. |
