| 摘要 |
PURPOSE:To install no separate top plate to a magnetic circuit, by using the center of the crossing of a frame which is made of crossed band-like thin plate stays of a magnetic material as the top plate of the magnetic circuit to enable to use a frame of a small area. CONSTITUTION:Iron thin plate stays 71 and 71 cross diagonally to each other to constitute a frame 70. Each of center parts 72 and 72 is superposed to form a ring like circular plate shape which is provided with a through-hole 73 in its center part. They are directly placed on a ring magnet 3 on a bottom plate 2 to act as a top plate of a magnetic circuit 60, and a magnetic gap 50 is formed between the through-hole 73 and a center pole 1. A ring like member 12 for jointing an end part is adhered on a flat part 76... of each end part of an arm part 75..., and a cone type diaphragm 8 is adhered between a gasket 9 on the ring like member 12 and the ring like member 12. The ring like member 12 and gasket 9 are made of a paper tube laminated and wound with a thin plate by slicing it. On both sides of the arm part 75..., reinforcing pieces 77 and 77... are bent and formed. |
