PRESSURE INJECTION DEVICE FOR PRESSURIZING LIQUID FOR HOLLOW INJECTION MOLDING AND MANUFACTURE OF HOLLOW INJECTION MOLDING

摘要

PROBLEM TO BE SOLVED: To positively enable the pressure injection of a pressurizing liquid into a molten resin without the back flow of the molten resin by providing a gap for the passage of a pressurizing liquid a plug with a recessed part in the tip part and a gap of such a size that allows the passage of the pressurizing liquid but does not allow the entry of the molten resin, formed on the tip side of a sleeve, and further, installing a check valve at the rear end of the sleeve. ;SOLUTION: A mold 1 with an opening for forward/backward movement is clamped into a movable half of a mold, and the tip of a sleeve 4 is moved forward until it reaches the interior of a mold cavity 2 by the hydraulic pressure of a hydraulic cylinder 8. After injecting a molten resin into the mold cavity 2, a pressurizing liquid is injected under pressure along the front and back faces of a molding to form a uniform hollow part 10a stably and the molten resin is pressed to the front face of the mold cavity 2. As a recessed part is present on the tip face of the sleeve 4, the pressure of the pressurizing liquid can be positively retained and therefore, the pressurizing liquid is prevented from leaking halfway through the cooling of a hollow molding. A back flow is prevented from running into a pressurizing liquid pipe 7 by a check valve 4 at the rear end part of the sleeve 4. After the cold setting of the molten resin, the pressurizing liquid is drained from the opening for forward/backward movement of the sleeve 4.;COPYRIGHT: (C)1998,JPO