| 摘要 |
A method of and an apparatus for relieving ground pressure surrounding pvc vent pipes which have been displaced from their T-fitting traps in sewer systems. The round tubular nature of a semi-rigid pipe is changed to an elliptical or oval shape with initial insertion and rotation of a special tool. The tool being connected to a drive-shaft and rotated by an external source such as a drill motor. The rotation of the tool within the pipe progressively causes the pvc pipe to have momentary elliptical cross-sectional shape as the tool rotates within the previously round pipe, without rotating the pipe. As the tool passes down (or "screws down") through the pipe, the pipe re-assumes its circular cross-sectional shape, and original diameter, but only after its larger-dimension elliptical cross-section has pressurized the earth duct and increased its diameter to about an inch greater than its initial (unpressured) circular diameter. The tool includes angled rollers for exerting pressure against the interior wall of the pvc pipe to reduce friction between the rollers and the interior wall of the pipe. While the circumference of the pvc pipe in its prior round shape and its forced elliptical shape remain equal, the maximum cross-section dimension of the elliptical shape of the pipe, caused momentarily by the tool as it is screwed into the pipe, is greater than the diameter of its circular shape, thus progressively enlarging the earth duct which surrounds the buried pipe as the tool is being operated and rotated by the drill motor.
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