| 摘要 |
The downward-pointing jets (21,22,23) constitute a horizontal ring around a vertical (ZZ) suction tube (51A). This assembly is motor-driven (92) through a casing (9) having rotary seals passing water (31A) down to the jets and water-borne excavated material e.g. earth or gravel up, via a suction pipe (51) to a settling tank. The jet ring is self-rotated by water reaction forces around a stationary suction nozzle. Jet cone angles depend on soil types. Water pressure and flow rate, suction flows and tool positions are regulated, via a central controller, by the operator, permitting him to react appropriately immediately on encountering buried pipes, etc. Typically, an equipment carrier (12) has transverse (131) and vertical (134) positioning rails, and provides tilting (132,133) of the tool axis (ZZ).
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