PURPOSE: To form spiral wave patterns on a metallic foil blank material by imposing and fixing the metallic foil blank material via an elastic material layer on an anvil, pressing a freely rotatable ball tip into pressurized contact with the surface thereof and moving the ball tip relative to the anvil so as to move the tip along the above-mentioned spiral wave patterns.
CONSTITUTION: The stainless steel foil (a) molded to a truncated circular cone shape is imposed onto the anvil 2 and is pressed and fixed by a pressure disk 4. The arm 6 is then rotated to bring this ball tip 7 into pressurized contact with the part near the center of the stainless steel foil (a) and thereafter, the anvil 2 is rotated while ultrasonic vibration is applied in the axial direction of the anvil. The spiral grooves P are formed on the stainless steel foil (a) by the rotation of the anvil 2 and the movement of the ball tip 7, by which the diaphragm D is formed. The degree of the relative movement of the ball tip 7 and the anvil 7 is properly selected, by which the diaphragms with the various spiral wave patterns are easily produced.
SHIMADA TOSHINORI
WATANABE TERUO
ONISHI KIHACHI
