| 摘要 |
PURPOSE:To obtain a subject ball which is prevented from leakage of inside air, by a method wherein, after a particular valve seat is secured on a small projection formed on an inner wall surface of a rotary mold, a molding material charged thereinto and the valve seat are rotated monolithically for molding, and a particular valve is then inserted into the valve seat firmly. CONSTITUTION:A small mushroom-shaped projection a' is formed on an inner wall surface of a mold (a). A conical top of said small projection a' is mated with a valve seat b. The valve seat b consists of a rigid plastic resin made base portion b2 and a soft plastic resin made top portion b1. A mating hole 1 is made in the base portion b2, and a fine perforation 2 is formed in the top portion b1. A molding material is charged into the mold (a) for rotation-molding therein. A ball proper C is demolded together with the valve seat b, and a portion corresponding to the small projection a' becomes a hook hole 3. A nozzle of an filler is inserted therefrom through the valve seat b, and air is filled into the ball proper C. After the nozzle is pulled out, a valve d is firmly fitted in the hook hole 3 to prevent from leakage of air. |
