Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Repair – replacement – or improvement
Patent
1991-04-11
1992-11-24
Taylor, Dennis L.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Repair, replacement, or improvement
405154, F16L 100
Patent
active
051658224
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a pipe joint for driving pipes laid underground.
It has recently become more and more customary to lay sewage pipes and the like underground using the so-called "driving technique." The driving technique involves driving the pipes from a central shaft or pit in the desired direction up to another shaft, whereby the current laying distance of the pipes is about 75 to 100 m, but will increase further. This driving technique can be used expediently in particular to lay pipes with nominal diameters of 250 to 1000 mm. The advantage of this driving technique is that it is no longer necessary to dig shafts over the entire laying length when laying sewage pipes underground. One can thus not only dispense with troublesome digging work but also keep the necessary blockage of streets to a minimum.
However, the lengths of the pipes laid underground by the driving technique are limited by the diameter of the central shaft. With a shaft diameter of 2 m one can drive pipes out of the shaft that have a length of about 1 m. With a shaft diameter of 3 m it is possible to drive pipes having a length of 2 m. That is, the driving technique limits the length of the pipes to be laid so that a great number of pipe joints are required for joining the pipes into a conduit.
For pipes laid underground by the driving technique, however, the pipe joints are of particular importance since the pipe joints should not protrude beyond the pipe either outwardly or inwardly. They should not protrude inwardly because sewage pipes are regularly laid on a small slope and the projections within the pipe would constitute barriers for the sewerage. Projections of the pipe joint outwardly interfere with the rough-pressing of the pipes, since frictional forces of 1 to 4 p/m.sup.2 must be taken up. The forces that build up due to outer projections from pipe joints would be so great that there would be a danger of the outward projections shearing off. Furthermore, outwardly projecting ribs cause earth material to be carried along during driving of the pipes, so that earth masses may cave in when the pipes are laid underground. The forces can be reduced by employing lubricants but, firstly, this involves a surplus effort and, secondly, the resulting reduction of forces is insufficient in particular in view of the long laying distance of 100 m and more.
For the driving technique one very often uses concrete pipes with a length of 1 m, in particular asbestos cement pipes. Compared to cast iron pipes these concrete pipes are ten times as thick, so that pipe joints can readily be accommodated within them without any projections outwardly or inwardly. Such thick concrete pipes permit good axial force transmission, but the large outside diameters of the pipes mean that a very great amount of material must be moved aside when the pipes are driven. The thickness of the pipes also causes a very high buildup of forces in the case of large laying distances.
One has therefore begun to use cast iron pipes that are encased with concrete pipes (German patent no. 36 18 334). The cast iron pipes serve here to transmit the forces of pressure. The cast iron pipes are connected by conventional socket joints, the cast iron pipes being formed at one end with a bell to produce a socket and at the other end as an inserting end for the socket. However, the encasing of the cast iron pipes is elaborate to produce because a steel mat is laid about the cast iron pipe and concrete is cast thereabove and then jolted on. An expensive and elaborate method is therefore required to hide the projections of the pipe joint on the outside. A further disadvantage is that cast iron pipes must be produced with a small length of 1 m and different end formations, namely a socket and an inserting end. In practice, however, one attempts to produce cast iron pipes with a great length of 6 to 7 m for reasons of production technology. It would be less expensive here to cut these pipes to lengths of 1 m and to employ such shortened pipes for laying by the driving techni
REFERENCES:
patent: 4552485 (1985-11-01), Hammer
patent: 4801222 (1989-01-01), Froblick
patent: 4808032 (1989-02-01), John
patent: 4966494 (1990-10-01), Inagaski et al.
Halbergerhutte GmbH
Taylor Dennis L.
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