PURPOSE: To shorten the heating time and to save the energy required for the heating process, by heating directly the metallic foils on both surfaces of a diaphragm substrate by the heating of electromagnetic induction.
CONSTITUTION: An adhesive layer 3 containing a heat fusing adhesive sheet, an urethane sheet 2, an adhesive sheet 3' containing a heat fusing adhesive sheet, and a metallic foil 4 are laminated and put between the holding plates are stuck on the opposite faces of the press molds of an electromagnetic induction heater. Then both the press molds are put close to each other, and at the same time a magnetic field generated by the electromagnetic induction heater is applied. An eddy current is produced to the foil 4 by a magnetic field formed by the above- mentioned magnetic filed. Then the foil 4 is heated to fuse the layers 3' and 3. The layers 3' and 3 are then cooled, and the layer 3 is stuck to the sheet 2. Furthermore the foil 4 is adhered to the sheet 2 via the layer 3' to obtained a unified metallic foil member 13. The member 13 is attached to both surfaces of a diaphragm substrate 1 with the layer 3 side used as a contact surface and then pressed. Thus an eddy current is produced in the foil 4, and the foil 4 is heated to fuse the layers 3' and 3. After this, the layers 3' and 3 are cooled to be adhered to each other.
IKEDA TAMON
SUZUKI TOSHIO
FUJIWARA NOBUHIRO
SODA KAZUHIKO
