The present invention relates generally to pipes and pipe cladding, and in particular to pipes of the sort used for conveying liquids underground, with special reference to the conveyance of water for drainage purposes.

It is known that when installing pipelines underground it is necessary to make provision for the fact that ground movement, for example as a result of temperature variations or variations in moisture (especially seasonal variations between wet and dry seasons) can result in relative movement of parts of the ground through which the pipeline passes. Likewise, in areas over which traffic passes, the load on the ground may vary, and cause movement, as individual vehicles pass over the location of the pipeline. This can cause damage or even fracture of a pipe if special measures are not taken to protect the pipe.

In order to accommodate such ground movements and to isolate the pipe from any effects thereof it is conventional to surround the pipeline with a substantially incompressible material in particulate form the particles of which can move in relation to one another thereby isolating the pipe from any ground movements. The particulate material most commonly used is called "pea gravel" and although this functions satisfactorily it is expensive to quarry, transport, store and install, and installation is not always undertaken entirely satisfactorily, especially in circumstances where economies may be sought in which case an insufficiently thick layer of pea gravel may be used.

Traditionally, pipelines were made from lengths of rigid baked clay or concrete, and these materials have considerable strength in themselves. More recently, plastics materials have been used for making pipelines, and although these materials are durable they have relatively less physical strength and are more readily subject to rupture either as a result of ground movement or traffic passing over them, or from localised pressures exerted, for example, by projecting stones which may be present in the soil backfilled around the pipe after installation.

Moreover, should any modifications to the pipeline be needed, or even if the ground is excavated around the pipeline for other purposes, for example to gain access to other services in the close vicinity (such as telephone cables or gas pipes) the protective filling of particulate material is disturbed and frequently lost, and special efforts must be made to reintroduce the same particulate material, or at least one compatible therewith, when the excavated ground is reinstated otherwise there is a risk that, without it, the pipe may be damaged by the loads applied locally or by subsequent ground movement.

The present invention seeks to overcome the disadvantages of the use of traditional materials by providing a pipe having a cladding of modern material which will not necessarily be lost or disturbed if the pipe is excavated after its initial installation.

One attempt to achieve this objective is described in US published Patent Application US 2004/0089361A1 published on 13 May 2004, which describes a

flexible pipe, such as a plastics pipe having a flexible perforated netting containing an aggregation of lightweight elements such as expanded polystyrene beads capable of wrapping around the pipe, preferably in helical fashion along the length of the pipe. The lengths of pipe are manufactured with this cladding in place, and the ends of the pipes left exposed to allow junctions to be made upon installation. Although this provides protection which adequately replaces the traditional pea gravel over most of the length of the pipe, the junction regions, which in many respects are the most sensitive parts of the pipeline and the most likely to suffer damage due to subterranean movement, are left exposed.

The present invention seeks to provide means by which this disadvantage can be overcome. The present invention also provides means for improving the drainage properties of perforated drainage pipe, and, in another aspect, improves the performance of underground pipelines generally, regardless of whether they are perforated or not and/or regardless of whether they are intended for drainage of water from the ground or for conveying water (or indeed other liquid) underground.

According, therefore, to one aspect of the present invention, there is provided a cladding unit for use with a drainage pipe of the type having a substantially cylindrical permeable or impermeable pipe body surrounded by a cladding of a permeable material capable of withstanding and/or distributing the loads imposed on the pipe when installed underground whilst allowing the passage of liquid therethrough, the pipe body having means for connecting it to an adjacent such

pipe body in the formation of a pipeline, and the cladding unit being so formed that it can be fitted into position so as to enclose the junction region between adjacent pipe bodies after the said junction has been made, the said cladding unit being substantially permeable at least longitudinally thereof.

The cladding unit may be composed of two or more bodies so shaped as to have interpenetrating or interlocking parts or portions by which the bodies can be snap- engaged together around the junction region between two adjacent pipe sections of a pipeline.

Preferably, the cladding unit comprises an outer layer of flexible laminar material enclosing a loose fill of particulate elements or beads. The elements or beads need not necessarily be crushable or resilient, although these properties are useful in many circumstances.

The outer layer may comprise a mesh or grid the mesh size of which is smaller than the size of the particulate elements or beads of which the loose fill is composed. Alternatively, however, the said outer layer may comprise a flexible membrane and need not necessarily be permeable, although permeable or semi- permeable membranes have properties which often make them particularly suitable.

As mentioned above, although this is not essential within the scope of the present invention, the particulate elements or beads may be composed of a resilient or

crushable material. This allows the cladding layer to absorb forces due to relative movement of the ground with respect to the pipe not only by displacement of the particles themselves, but also by compression of adjacent particles when in contact with one another and/or the ground or the pipe.

It is considered that the material used for the particulate elements may very conveniently be a foamed or expanded plastics material and expanded polystyrene is both readily available, lightweight and suitable for this purpose.

Cladding units in accordance with the principles of the present invention may, therefore, be formed as a cuff covering the otherwise exposed junction region between two adjacent pipe sections when utilised with a system such as that described in the above-mentioned US Patent Application.

As an alternative to the use of a loose fill of particulate material within an enclosing mesh or membrane, at least a portion of the unit may be formed by a single or composite body of crush-resistant plastics material. Such plastics material may be open cell or closed cell foam and may be formed as a single elementary unit or fabricated from a number of cooperating units.

In such a system the outer surface of the cladding unit does not require to have a separate mesh or membrane, although an outer skin of the same material as the plastics forming the body, or a different material may be utilised, especially in circumstances where containment of a liquid is of particular importance.

Alternatively, the body of the cladding unit may be composed of agglomerated or adhered beads of material, especially beads of plastics material.

Regardless of the form of the body of the unit (that is whether it is a unitary body of foam, an assembly of particles, or a fabricated unit of relatively large foam bodies, the overall shape of the cladding unit may be in the form of a flexible pad or panel which is generally flat in its relaxed state and which can be wrapped around the junction region between two pipes on installation.

In an alternative embodiment a major part of the body of the cladding unit is shaped with a curvature to fit partly around the junction between two pipes, with a longitudinal opening allowing passage of the pipe upon installation. This opening may be closed after installation and held in position by adhesive or by an external band.

A further alternative embodiment of the cladding unit may be composed of a plurality of elementary parts assembled together to form the cladding unit upon installation onto the junction region between two pipes.

In another aspect the present invention provides a method of producing a cladding for length of pipe comprising the steps of surrounding the said length of pipe with containment means, or introducing the said length of pipe into containment means, and then introducing a foaming, aggregating or agglomerating material into the

containment means and causing it to foam, aggregate or agglomerate to form a self-supporting body around the said length of pipe.

Because the pipe is entirely surrounded by the cladding this latter holds itself in position without it necessarily being adherent to the pipe itself although, clearly, in the case of pipes made of plastics material it would be entirely possible to select foaming materials which will also adhere to the pipe.

The method of the invention may further include the step of removing the said containment means, or removing the thus-clad length of pipe form the said containment means. In such an embodiment the said containment means may comprise a flexible member of define shape corresponding to that of the length of pipe, and the said containment means may be left in situ after the foaming, aggregating or agglomerating material has cured, set or otherwise hardened.

It is particularly convenient if at least the step of introducing the foaming, aggregating or agglomerating material into the containment means is undertaken with the said length of pipe in situ in a trench or other subterranean location in which it is intended to remain after application of the cladding.

Indeed, if the pipe is to be laid in a trench the walls and/or bottom of the said trench or other subterranean location may form at least part of the said containment means in which case, as mentioned above, such containment means are naturally left in place once the foaming material has cured, set or hardened.

Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view illustrating a first embodiment of the invention formed as an improvement over the prior art clad pipe;

Figure 2 is an axial sectional view of the junction between two prior art clad pipes;

Figure 3 is a partial axial sectional view illustrating the junction between two clad pipes provided with a cladding unit of the invention;

Figure 4 is a perspective view showing a cladding unit in a preparatory state for application to the junction between two clad pipes;

Figure 5 is a partial axial sectional view of an alternative embodiment of the invention adapted for use with a pipe having a flanged end coupling; Figure 6 is an axial sectional vie of a clad pipe formed as an alternative embodiment of the invention;

Figure 7 is a similar axial sectional view of an alternative embodiment of the invention;

Figure 8 is a schematic diagram illustrating the application of the method of the invention;

Figure 9 is a perspective view of a further alternative embodiment; and

Figure 10 is an exploded perspective view of yet another embodiment.

Referring now to Figure 1, the clad pipe is generally indicated with the reference numeral 10, comprising a tubular body 11 of plastics or other material having

opposite ends one of which has a tapered spigot section 14 and the other of which has an enlarged or flared section 15 allowing the tapered or spigot section 14 of one pipe 11 to be fitted into the flared end section 15 of an adjacent pipe as illustrated in Figure 2. Around the outside of the netting envelope is an outer sleeve layer 12 of a geotextile material having a finer mesh size than that of the netting envelope. The opposite ends 13 A, 13B of the outer layer 12 project slightly beyond the ends of the netting envelope.

Around the main body of the pipe 12 is a net or mesh envelope 16 enclosing a loose filled mass of particulate elements 17, typically expanded polystyrene granules or beads.

The pipe 11 illustrated in Figure 1 is imperforate although for land drain purposes a perforated pipe may be utilised as illustrated in Figure 2 where the junction between two adjacent pipes H ₁ and H ₂ is illustrated in cross-section. As can be seen in Figure 2 although the main body section of the two pipes H ₁ and H ₂ are protected from ground movement by the cladding arrangement comprising the mesh 16 and the granules 17 this does not cover the junction region generally indicated 18 between the two pipes where the spigot 14 is fitted into the flared end portion 15. The exposure of this junction region would be a significant disadvantage in the protection of the land drain, and in Figure 3 there is shown a structure in which the cladding element of the present invention is fitted over the junction region 18 (see Fig. 4) to provide a substantially continuous cladding layer over the entirety of the pipe assembly. Here, the junction cladding element is

generally indicated 19 and, as can be seen, the ends of the outer sleeve layer 12 overlap the ends of a corresponding outer layer 9 of the junction-cladding element 20. As illustrated in Figure 4, this may be formed as a flat panel-like structure of mesh material 20 filled with a loose fill of particles or granules (represented by the particles 21) and of dimensions such that it can be wrapped around the junction region 18 of a clad pipe and illustrated by the arrows A and B. The wrapped panel 19 may be secured in position, for example, by a band generally indicated 22 or other means (not shown) such as a Velcro (RTM) fastener or a simple tie strap. The securing of the panel 19 in position does not have to be extremely secure since, one the trench containing the pipeline is backfilled the soil itself will retain the cuff formed by the wrapped panel 19 in position providing its protective effect around the junction region 18 of the pipeline.

Figure 5 illustrates an alternative arrangement in which two pipes 23, 24 have respective flanges 25, 26 at each end. Flanged couplings as such are known, but in this case since it is desirable for there to be a longitudinal flow of water around the outside of the pipe, the flanges 25, 26 are provided with respective sets of apertures

27, 28 passing therethrough, in addition to the apertures 29, 30 provided for reception of the fixing bolts 31 by which the pipes are clamped in end-to-end relationship with one another. Again, the pipes 23, 24 are illustrated having mesh sleeves 32, 33 respectively each housing a loose fill of polystyrene beads 34, 35 respectively.

The region between the ends of the sleeves 32, 33 at which the flanges 25, 26 are exposed is covered by a cuff or junction cladding element 36 which itself comprises a shaped mesh 37 housing a plurality of polystyrene or other beads 38.

As an alternative to the loose fill of polystyrene beads, a pipe may be provided with a sleeve in the form of a solid foam structure as illustrated in Figures 6 and 6a. Here, a pipe 40, again having tapered and flared opposite ends 41, 42 for connection to adjacent such pipes is provided with a sleeve 43 of resilient closed- cell foam material with an outer skin 44 of the same material formed during foaming. Such a foam sleeve may be formed in situ utilising a suitable mould, or may be moulded separately and fitted on to the tube or pipe 40 by introducing the pipe into a central opening in the sleeve 43. The exposed junction region where the tapered end 41 is introduced into the flared end 42 of an adjacent pipe can be covered by a cuff in the form of two horseshoe shaped foam elements 45, a typical one of which is illustrated in Figure 6a. Fitting two such elements in face to face relation over the junction region forms a short sleeve section or annular portion spanning the junction and filling the gap between the sleeves 43, 44 of adjacent pipes 40. In an alternative embodiment, not illustrated, the foam body 43 has no skin and an open cell foam structure to allow ingress and egress of water through the wall of the pipe 40 which, obviously, would need to be correspondingly perforated.

Figure 7 illustrates a further alternative embodiment in which a protective sleeve is made of agglomerated particles pressed together to make a composite body of agglomerated particles 46.

Figure 8 illustrates one way in which the foam body 43, 44 can be formed in situ in a trench, by providing an outer membrane 44' closed at one end 50 and secured around a pipe 51, leaving an open end 52 into which foaming material, represented by the arrow 53 can be introduced into the containment membrane 44' and allowed to foam with the open end 52 being closed, hi this way the side walls 54, 55 of the trench can also act as guides to shape the foam as it fills the membrane 44'.

Figure 9 illustrates an alternative form of junction cuff in the form of a sleeve generally indicated 60 of cylindrical form with a longitudinal slot 61 defined by two opposite radial faces 62, 63. This body can be preliminarily formed ready to be fitted over or "sprang" into position over a junction region 18 such as that shown in Figure 4 and then held closed with the faces 62, 36 in contact with one another either by adhesive or by an external clamp.

A further embodiment is illustrated in Figure 10. This comprises two semi-circular elements 70, 71 of crushable or resilient foam material the facing surfaces 74, 75 of which have correspondingly shaped projections 76 and cavities 77 so shaped that when fitted together they snap-engage to retain the two members together. Each member has an arcuate array of axial passages 78.

In use the two half-collars 70, 71 are fitted over the junction region of a pipe and between the facing ends of the sleeves of particles which surround them, whereby to insulate and protect the junction from mechanical crushing and stresses resulting from ground movement. Water movement in the ground immediately surrounding the pipeline can infiltrate into the sleeves of particles and move longitudinally of the pipe through the passages 78.