| 摘要 |
<p>The disclosed method consists in shaping metal sheet, preferably hard aluminium or beryllium to form a cone 1. The smaller perimeter of the cone obtained in this way has a constituent fold or step 2 at a first reinforcement member, whilst the larger perimeter of the cone is provided with a fold 3 which forms a second reinforcement member. The fold 3 lies in a plane perpendicular to the axis of rotation of the membrane, and a resilient ring is attached to the fold 3 to facilitate vibration of the membrane. <IMAGE></p> |
