| 摘要 |
PURPOSE:To uniformize the speed distribution of resin flow in the peripheral direction of a passage and to prevent the local reduction of the wall thickness of a tubular molded body caused by the presence of bridges by providing projections on the downstream side of the bridge parts so as to further divide the resin flow divided by bridges. CONSTITUTION:A core 2 is supported within a land 1 by bridges 3 provided in the peripheral direction at the end part on the upstream side of resin flow. Projections 4 are provided to the outer surface of the core 2 on the downstream side of the bridge parts to divide the widths of the passages between the bridges 3, 3 into equal parts. The flow velocity of the resin flow coming into contact with the side surfaces of the bridges 3 is relatively low because of friction resistance and becomes fast toward the central parts between the bridges 3, 3. However, respective divided flows are further divided by the projections 4 at the central part between bridges on the downstream side of the bridge parts to urge the uniformity of the speed distribution of the resin flow. |
