| 摘要 |
PURPOSE:To prevent sinking from developing without being effected by the height of a boss and at the same time under the state that the height of the boss is stabilized by a method wherein a mold part, which is located at the outer periphery of a resin molded item and has a hollow cylinder activable in the axial direction of the boss, is provided so as to be shifted for pressurizing in the direction toward the position at which sinking develops after injection molding. CONSTITUTION:Molten resin is filled through a sprue 5 in a product part 7 and a boss part 8. A center pin, which forms the hollow part of the boss 8, is fixed relative to a core 10. A sleeve pin 14 is fitted onto the center pin to the tip of the boss so as to eject the boss part at the time of the release of a product from a mold. A hollow pin 20 having a hollow tubular form, into which the form of the boss and the sleeve pin 14 is fitted, is provided at the outer periphery of the boss. The hollow pin 20 is so constituted as to be pushed up by means of a cam 17 and a hydraulic cylinder 18. Molten resin IS injected under the state that the hollow pin 20 is lowered. After the filling of the resin the hydraulic cylinder 18 and the cam 17 are put into actuation so as to push up the hollow pin 20 in order to press the root of the boss, resulting in completely preventing sinking from developing. |
