| 摘要 |
PURPOSE:To enhance roundness of a bobbin by furnishing a ring-shaped gate in communication with a ring-shaped cavity outside the wind-up shaft, when manufacturing bobbins consisting of a metal shaft with plastic flanges at its ends, and by molding said flanges through injection of resin material from the gate. CONSTITUTION:When a flange 3 is molded at each end of a wind-up shaft 2 made of metal, first the circumferential surface is contracted by, for ex., applying a roller to the right-hand outside circumference of the wind-up shaft 2, to form a ring-shaped groove 5, in whch two or more circumferentially stretching through-holes 6 are excavated at a certain constant spacing. Then the end of shaft 2 is fitted in a metal die 7, and the edge 2a of shaft 2 is butted against the inner surface 7a of the die 7 to make location of the wind-up shaft 2. After a core 12 is inserted from the other end of the shaft 2, a molten resin material is placed by pressure from a spool 11. It shall be poured into cavities 10, 13 in the wind-up shaft 2 and a cavity 13 outside the shaft 2 as well as fully into a cavity 8 through the through-hole 6. Then the metal die 7 and core 12 are taken away when the resin has hardened. Now the molding is ready. |
