Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Repair – replacement – or improvement
Patent
1985-08-28
1987-03-10
Taylor, Dennis L.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Repair, replacement, or improvement
405154, 175 19, 138 97, 173 91, F16L 100
Patent
active
046487468
DESCRIPTION:
BRIEF SUMMARY
This invention relates to apparatus for use in the laying and replacement of pipes underground.
It is known, for example, from British Patent Specification No. 2113795 to replace existing underground pipework by driving an expander into an existing pipeline with sufficient force to deform the pipe outwardly so that it is compressed into the surrounding ground and by feeding a new pipe into the space formerly occupied by the existing pipeline.
An entirely new pipeline can be installed by the same method except that in this case the expander compresses the soil to form a passage therein for the pipe which is to be inserted.
In either case, the expander should be driven with sufficient force to ensure that the existing pipe or soil can be deformed radially outwardly and compressed into the surrounding material which may be concrete or soil.
A known apparatus for performing the above-described method of pipe replacement comprises a conical or frusto-conical member adapted to engage the end of an existing pipe with its smaller end having a smaller diameter than the internal diameter of the pipe and its larger end having a diameter which is at least as great as the external diameter of the pipe, a jacket secured to the larger end of the conical or frusto-conical member and means for driving the said member into the pipe to cause the latter to be forced radially outwards and compressed into the surrounding ground by the forward movement of the conical or frusto-conical member and jacket.
The other end of the jacket was provided with a locking ring which was screwed into the jacket, or to an interconnecting spacer member, an the leading end of a replacement pipe was secured to the locking ring by means of co-operating screw-threads.
The drive means took the form of a pneumatic percussive device referred to in the art as an impact mole. Now it has been found that such devices tend to rotate in operation, the direction of rotation in the northern hemisphere being clockwise. As a result of this rotation, conventional right-hand screw-threads tend to become loosened when the apparatus is in operation so that the replacement pipe can work loose and even become detached from the apparatus. This problem could be overcome by using left-hand screw-threads but in that case the screw connection would be tightened and it could prove difficult to remove the apparatus from the pipe at the end of the pipe laying operation. Moreover, the rotation of the apparatus in the ground is conveyed to the following pipeline so that the sections of pipe also tend to rotate causing drag and impeding the progress of the apparatus through the ground which is a considerable disadvantage. In severe cases, twisting of the pipe can occur and this should be avoided if at all possible.
The present invention aims to provide an apparatus for use in the laying and replacement of underground pipes which overcomes the above-mentioned disadvantage.
According to the invention, there is provided an apparatus for use in the laying and/or replacement of pipes underground which comprises a cylindrical casing, a conical or frusto-conical member secured to one end of the casing and adapted to form an underground passage for the casing when the apparatus is being driven through the ground, a piston reciprocally mounted in the casing and arranged to be driven by a source of compressed air or other fluid to engage said conical or frusto-conical member with a series of impacts to drive said member through the ground, means for connecting the interior of the casing to a source of compressed air or other fluid, valve means to ensure that the piston is reciprocated in the casing by said compressed air or other fluid, a pipe fitting for clamping the leading end of a pipeline which is to be laid in the underground passage formed by said conical or frusto-conical member and a connection between the pipe fitting and the said other end of the casing, said connection comprising a sleeve connected to the said other end of the casing and having an internal flange, the pipe fit
REFERENCES:
patent: 3995702 (1976-12-01), Klimashko et al.
patent: 4132277 (1979-01-01), Tupitsyn et al.
patent: 4284147 (1981-08-01), Jenne
patent: 4377984 (1983-03-01), Donnelly
patent: 4505302 (1985-03-01), Streatfield et al.
patent: 4507019 (1985-03-01), Thompson
patent: 4537265 (1985-08-01), Cox et al.
Stodola Nancy J.
Taylor Dennis L.
Water Research Centre
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