| 摘要 |
PURPOSE:To prevent fine metal powder from entering the magnetic gap of field path by applying a thermoplastic resin or an adhesive film between a frame and a top plate before welding. CONSTITUTION:On the surface of the top plate 1 to be stuck to the frame 2, the thermoplastic resin 6 is coated over all around circumference so as to be a little higher than the small projection 3 at the inside of the pitch circle of the small projection 3. Then, the relative position of the frame 2 and plate 1 is fixed to become concentric and they are pressure-welded at the position of the small projection 3 of the frame 2 with the electrodes 4 and 5. When the resin 6 is pressure-welded with the upper and lower electrodes 4 and 5, it is compressed and extended to completely fill the gap between the frame 2 and plate 1, thus capturing the fine metal powders and preventing powders from entering the magnetic gap of the field path. |
