| 摘要 |
A mold for hollow injection molding has an inlet for admitting a fluid into the molten resin when injected to form an interior hollow in the molded product. The inlet is opened and closed by retraction and advancement of a movable pin having at least a portion to fill the inlet and close it. When the inlet is closed, while the resin is being injected, the pin has a portion which projects out of the inlet into the space where the resin is injected. When the inlet is opened, the retraction of the pin leaves a short passageway in the injected resin leading from the fluid inlet for flow thereinto of the hollow-forming fluid. Preferably, the pin is stepped with an inlet-closing large rear portion and a smaller projecting forward portion which is located in and has an annular clearance with the inlet when it is open. The pin may be detachably connected to a movable plunger, operated by fluid or spring pressure, to enable replacement by pins of different lengths, sizes, etc.
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