| 摘要 |
PROBLEM TO BE SOLVED: To maintain the spacing between a diaphragm placed atop a ring and an iron core within a prescribed size value at all times and to eliminate the variations in timbre between products by removing the shock line made in the plane part of a yoke, making the thickness of the plane part to uniform and assuring the smoothness of the plane part. SOLUTION: This buzzer has the flat planar yoke 3 integrally and projectingly provided with the iron core 4, a coil wound around the iron core 4, a magnet, the ring placed on the plane part 7 of the yoke 3 and the diaphragm which is placed atop this ring and forms a slight spacing with the top surface of the iron core 4. Very small hollow grooves 15 are press formed over approximately the entire surface of the under surface 7a of the plane part 7 of the yoke 3. The very small hollow grooves 15 are plastically deformed by press forming in the plane part 7 of the yoke 3 in the manner described above, by which the material for the recessed components is moved and the shock line is negated by this material. In addition, the thickness of the plane part 7 is made uniform.
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