| 摘要 |
PURPOSE:To eliminate waste of edge blank material and to reduce the material cost, by expanding a cylinder made of a thermoplastic resin having flexibility and heat forming the resin into the edge shape. CONSTITUTION:The cylinder 4 is formed by adhering ends of the edge blank material 3 made of a urethane resin strip being a thermoplastic resin and having flexibility. Further, the cylinder 8 is inserted to a cylinder section 7 implanted from the center of a lower metallic die 6 having a ring recessed groove 5. Then, an upper metallic die 9 having a ring projection 8 opposing to the recessed groove 5 is used, and a through-hole 10 penetrated at the center of the die 9 is coupled with the cylinder section 7 of the die 6 and the cylinder 4 is pressed and inserted with the dies 6 and 9. The upper end of the cylinder 4 brought into contact with the die 9 is extended by softening the cylinder 4 together with the dies 9 and 6. Then, the expanded cylinder 4' is inserted and held closely between the dies 6 and 9, and heated, pressed and formed into the edge shape having a corrugation 11 with the recessed groove 5 and the projection 8 of both dies 6 and 9, and the edge 12 for the speaker diaphragm is obtained. |
