| 摘要 |
Moling apparatus for forming a generally horizontal underground passage in soil for a utility conduit or the like includes tool head structure with a base portion and a nose portion mounted on the base portion such that an interface region is formed between nose portion and base portion surfaces. The base portion is movable along that interface relative to the nose portion between a first position in which nose portion surfaces are symmetrical with respect to the tool axis so that the tool will tend to move along a straight line path and a second position in which nose portion surfaces are in asymmetrical position with respect to the tool axis so that the tool will tend to move along a curved path. The apparatus includes structure for creating positive pressure during system operation in the interface region between the base portion and nose portion such that relative movement of the nose and base portions between the first and second positions is not significantly impaired.
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