| 摘要 |
<p>For tensioning a drum head, a counter hoop bearing on the rim of the drum head is formed to define an annular channel between itself and the drum shell over which the drum head is stretched. Co-operating camming means extend into this annular channel from the inner surface of the counter hoop and from the outer surface of the drum shell, respectively, so that upon rotation of the counter hoop about the axis of the drum, the counter hoop is simultaneously moved parallel to that axis to alter the tension in the drum head.</p> |
