GB2040151A - Liquid channelling member - Google Patents

Abstract

A liquid channelling member includes a plurality of tubular core members 2 each having a helical gap (4) along its length and an envelope constituted by a longitudinally extending liquid impermeable portion 1 and a filter portion 3, whereby, in use, the core members are contained within the envelope to provide the channelling member. <IMAGE>

Description

SPECIFICATION Liquid channelling member This invention relates to a liquid channelling membey which is particularly suitable for use in a land drainage system.

Existing land drains employ porous clay, cement, or rigid or flexible plastics pipes in which there are holes and/or slots. The holes and/or slots cannot easily be matched in size to the particular soil structure in which they are laid. Therefore these drains tend to block as a result of the migration of small soil particles into the drainage system.

Attempts to solve this problem by wrapping the drain with some kind of filter medium, such as coconut matting, straw, felt or non-woven mesh fabric have not been successful in solving this problem. The present invention provides a liquid channelling member which is particularly suitable for use in a land drainage system and which is more adaptable than the known drains. Furthermore, the channelling members of the present invention are easierto handle and less likely to breakage than are those at present known. The space required for storing and the carriage of channelling members made in accordance with the present invention is less than that required for conventional drains and the problems of blockage are minimised in arrangements in accordance with the present invention.

In the preferred embodiment of the present invention, a channelling member has a plurality of tubular core members, each core member having a gap in the wall of the tube, the said gap extending along the tube and around the circumference of the core. In use, the core members are arranged between a lower impermeable sheet and an upper sheet of filter material, the channel member being laid in a trench which has a gradient with the impermeable sheet lying on the floor of the trench. The soil is back filled over the exposed sheet of filter material.An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 is an end view of a channel member; Figure 2 is a side view of a core member; and Figures 3(a) and 3KbJ are exploded perspective views of coupling members.

Referring to Figure 1,there is shown a channel member constituted by a water-impermeable lower sheet 1, a plurality of tubular core members 2, each having a helical gap along its length, and an upper sheet of filter material 3.

A suitable filter material 3 is the filter material 6 described in our Patent Specification No, 1,536,551.

The filter material has a coefficient Mo/D50 as herein defined related to a bridging coefficient Cb as herein defined of the surrounding material as determined by the co-ordinates of a point which lies in a region on a graph between the ordinate axis, when the ordinate represents values of the bridging coefficient Ob, and a line defined by the following respective co-ordinate points of the bridging coefficient Cb and the coefficient Mo/Dsot 1.00, 2.10; 1.25,2.60; 1.75, 3.20; 2.50,4.15; 3.75, 5.00; 7.00, 6.66; 12.50, 8.1; 25.50, 10.05 and where Cb = D90/D40r where D40 D50 and D90 are the minimum dimensions of apertures in given units through which particles constitute respectively 40%, 50% and 90% by dry weight of the material in which the filter material is to be used can pass and Mo is the minimum dimension of the opening in the filter material in the same given units.

The impermeable sheet 1, which functions as a carry-away conduit for the drained liquid can be made of any impervious, non-degradable resistant material, such as polythene, or any other plasticised plastic film.

The tubular core members 2 act as spacers between the sheets 1 and 3 and give the channelling member the required pipe shape and volume capacity necessary to carry away the drained liquid. The tubular core members 2 also act as ducts themselves.

Referring to Figure 2, there is shown a core member 2 having a helical gap 4 along its length.

The width of the gap 4, indicated art a is, in preferred embodiments, between 2mm and 4mm. The pitch b of the gap 4 is, in preferred embodiments, between 5mm and 1 Omm. The tubular core 2 has, in preferred embodiments, an internal diameter c between 6mm and 12mm. The diameter of the core members 2 and the number of core members employed determines the size of the channel member. For example a channel member equivalent to a 25mm diameter drain might use core members having an internal diameter of 6mm while a channel member equivalent to a drain having a diameter of 150mm might use core members having an internal diameter of 12mm.

The wall thickness dofthe tubular core member 2 is, in preferred embodiments, between 0.5mm and 2mm. It will be appreciated that these dimensions can be varied. The wall thickness dofthe core member 2 may differ according to the compressive strength of the material employed.

The pitch of the gap 4 in the core member 2 can be adjusted to take into account not only the volume of liquid entering the space between the sheets 1 and 3, but also the amount of compression to which the whole channel member is submitted when buried in a trench.

It will be appreciated that a core member 2 can be formed from a pipe in which the helical gap 4 is cut or from a tape or filament wound or extruded to form a helical tubular core from a thermosetting plastics material such as polypropylene or from a ferrous or non-ferrous metal.

The filter material 3 has openings that initially allow a proportion of the finer particles of the adjacent soil material to pass into the channel member and be flushed away. Under these condi tions there will remain a thin layer of soil next to the filter material 3 which has a much higher permeability to the liquid to be drained than the mass of the surrounding soil which remains intact. As a result of this action a natural filter is formed.

The present invention enables a land drainage system to be provided in which the random nature of the previously employed filter medium, for example slots and/or holes in pipes, is replaced by a filter material having a mesh characteristic which is specifically designed to match the structure of the soil surrounding it.

The characteristics of a suitable filter material 3 have been set out above and are also set out in the specification of out Patent No. 1,536,551.

In the preferred embodiment of the invention the filter material 3 has a mesh structure which is formed by weaving. It is possible when manufacturing a woven fabric material to adjust comparatively easily the mesh opening of the material so that a range of filter materials, each of which is suitable for use in draining soils having particular particle size distribution, can be manufactured more easily and more precisely. The strands of the woven material which extend in one direction can be positioned relative to one another at intervals corresponding to the largest mesh opening dimension required and the spacings between the strands extending in the other direction can easily be changed during different production runs to give different filter criteria, as required.

The sheet of filter material 3 shown in Figure 1 is bonded to the sheet 1 of impermeable material along its edges 5 and 6 in such a way that the core members 2 located in the space between the sheets 1 and 3 are compressed transversely. The sheets 1 and 2 form a sheath about the core members 2 binding the core members 2 together and giving strength to the channel members so formed.

The channel member can, however, be formed into the shape shown subsequent to its manufacture on site during installation. For example, the sheet 3 can be bonded to the sheet 1 along the line 5 during manufacture with, for example, five of the tubular core members 2 attached to the sheet 3 and four of the tubular core members 2 attached to the sheet 1, and the assembly can be transported with the sheets 1 and 3 laid out in a substantially planar manner. It is possible by this means to utilize storage space for the channel members to the full. Upon arrival at the site for installation, the member can be folded about the line 5 and the edges of the sheets 3 and 1 can be clipped together along the line 6.If necessary, inner sheets of wide mesh material can be used to hold the respective tubular cores 2 attached to the sheets 3 and 1 before the assembly is folded into the shape shown in Figure 1.

It will be appreciated that the filter material 3 can be fabricated in other ways than by weaving. For example the strands of the mesh can be made by any well known extrusion welding process.

Referring to Figures 3a and 3b, there are shown respectively in-line and T-junction coupling members. These coupling members consist of upper and lower preformed sections 8 and 9 of plastics material or metal. The internal diameters of the coupling members when the sections 8 and 9 are pressed togetherformatubewhich is some l0mmsmaller than the diameter of the channel member shown in Figure 1 when it is in its "relaxed" state.

The two preformed sections 8 and 9 each have flanges 10 and 11,the upper flanges 10 having holes 12 in which press-studs 13 on the lower flanges 11 locate.

Holes 14 are provided in the upper sections 8.

In use, the pre-formed sections 8 and 9 are positioned equi-distantfrom the ends of two channel members to be joined together so that when pressure is applied between the sections 8 and 9 on opposite sides of a channel member the press-studs 13 locate in the holes 12 and hold the structure together. When the channel members have been installed in a trench and coupled together nails are driven through the holes 14, the drain assembly within the coupling members and into the sub-soil in order to hold the assembly together even more firmly.

It will be appreciated that the coupling members can be reinforced by binding them for example with wire or tape of plastics material.

Although the invention has been described with reference to particular embodiments, it will be appreciated that variations and modifications can be made within the scope of the invention.

The assembled channel member which has been described with reference to Figure 1 is particularly suitable for installation by mole-draining techniques, since, although, it is sufficiently rigid to enable it to be handle easily, it is sufficiently flexible to enable it to be wound on a drum and to be installed.on curves.

It will also be appreciated that it can be installed at angles with reference to the horizontal, including being installed with its longitudinal axis vertical.

Furthermore, although the tubular core member 2 having a helical gap along its length is shown in the preferred embodiment to be formed from an element having a solid wall, it is possible for the wall of the member 2 to contain apertures provided, for example, by perforations or by a mesh structure, the gap together with the apertures in the wall occupying between 10% and 75% of the surface of the wall of the tubular core member.

The tubular core can for example be made from a member having a lattice structure.

It will be appreciated that, as long as the gap, together with the apertures in the wall which are provided, for example by perforations or a mesh structure, constitute between 10% and 75% of the surface of the wall of the tubular core, it is possible to reduce the width of the gap until it is a slit.

It will be appreciated that the tube formed by the sections 8 and 9 when pressed together could be a cylinder or have any other suitable cross section for accommodating the channel member.

Claims (11)

1. A liquid channelling member including a plurality of liquid permeable tubular core members and - an envelope for containing the core members, the envelope comprising a first portion which is impermeable to liquids and which extends along the length of the channelling member and a second liquid permeable filter portion.

2. A channelling member as claimed in claim 1 wherein a tubular core member has a solid wall and a helical gap along its length.

3. A channelling member as claimed in claim 1, wherein a tubular core member has an apertured wall and a helical gap along its length.

4. A channelling member as claimed in claim 2 or claim 3 wherein the helical gap or the helical gap plus the apertures in the wall occupy between 10% and 75% of the surface of the wall of a tubular core member.

5. A channelling member as claimed in any one of the preceding claims wherein the first and second envelope portions are bonded together along one respective edge.

6. A channelling member as claimed in claim 5 wherein a number of the plurality of tubular core members is attached to the first portion of the envelope and the remainder of the plurality is attached to the second portion of the envelope.

7. A channelling member as claimed in any one of the preceding claims having the envelope formed into a tube about the core members.

8. A channelling member as claimed in claim 5 and claim 7 having each of the other respective edges of the envelope portions clipped together.

9. A liquid channelling member substantially as described herein with reference to Figures 1 and 2 of the accompanying drawings.

10. A liquid channelling member as claimed in any one of the preceding claims wherein the second liquid permeable filter portion of the envelope has filter characteristics falling within the scope of the filter claimed in claim 1 of Patent Specification No.

1,536,551.

11. An arrangement including liquid channelling members as claimed in any one of the preceding claims when coupled together by coupling members substantially as described herein with reference to Figures 3a or 3b of the accompanying drawings.