| 摘要 |
<p>This invention relates to a nozzle seal to be used in multi-cavity valve-gated injection molding. A heater cast with a lower nozzle portion is spaced from a cavity plate by an insulating air space and the valve pin reciprocates vertically in the heater cast bore into a gate in the cavity plate. A hollow generally cylindrical nozzle seal is provided across the air space between the lower tip of the nozzle portion and the cavity plate around the gate. The cylindrical seal provides additional heat transfer from the heater to the area of the gate to facilitate operation of the valve pin, particularly seating of the valve pin in the gate, during molding of certain plastic materials with high temperature characteristics. The nozzle seal is formed of a high yield strength titanium alloy and structured to avoid leakage or breakage in this critical area due to high injection pressure and both vertical and lateral relative movement between the nozzle and the cavity plate due to thermal expansion and contraction. In a second embodiment, a lower portion of the seal is tapered to improve sealing at high pressures and heat transfer to the immediate gate area and to avoid a "dead spot" for the accumulation of molten plastic material adjacent the gate.</p> |
