| 摘要 |
For installing a cable duct around a cable buried in the ground, the duct is propelled by a propelling device formed of a solenoid and a corresponding core member of a magnetic material, and a duct transporting device. The core member is provided with a coupling which couples to a free end of the cable. The solenoid is driven by a current so as to maintain, during operation, the free end of the longitudinal member, coupled to the core member, in a fixed position with respect to the transporting device. The propelling operation is supported by feeding a fluid under pressure through the duct, with the foremost end of the duct being provided with a spouting member. Suitable design of the core member in combination with a suitably varying current for driving the solenoid allows increased dynamic propelling operation and consequently improved performance.
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