| 摘要 |
PURPOSE:To prevent any decrease in strength of a packing, and enhance the liquid-leakage resistance of the packing by providing a projection at the position where a weld is produced, and making the weld to be formed within the projection when the packing is formed through injection molding. CONSTITUTION:A molten resin injected from a gate 3 is distributed in two directions, flows through a cavity, and reaches a point X on the surface opposite to the gate 3. Here since a metal mold is provided with a concave part, which corresponds to a projection 2, a cooled resin containing firing grade and an impurity such as a parting agent flows into the projection 2 and is solidified into a weld 4. As a result, a packing 1 consists of a solidified body of a resin which has a high temperature and contains no impurities, no decrease in binding strength arises in the packing 1, and the strength of the packing 1 is rather increased since it has an increased cross section. The former projection 2 is preferred to be provided on the inner side of the packing 1. |
