| 摘要 |
<p>The stand has an inner pipe inserted in an outer pipe and flexibly sliding in the outer pipe. The inner pipe is shifted to a maximum width by a compression spring. A ball channel is attached on the outer pipe, and a freely moveable ball is supported in the channel. The ball rolls in the channel as soon as the ball is moved out from horizontals. Specially formed kerb cuttings are detected in the inner pipe.</p> |
