| 摘要 |
<p>Pneumatic cleaning devices (12, 32, 36) producing plural jets of air do so such as to produce an imbalance of forces on the cleaning device in a transverse plane to their direction of operation. Duct cleaning devices involve a ring of nozzles (34-57) about the axis of the cleaning device (32) with an irregular placement of one or more nozzles to break the general symmetry. Riser cleaning devices (36, 45) involve a plurality of randomly moving tubes (41, 47) whose sum effects a random thrust on the device.</p> |
