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(11) | EP 1 247 912 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Channel sections |
| (57) A drainage system is constructed from plastics sections (2) having a uniform U-shaped
cross section. A slotted grid (4) closes an open mouth of the channel. Adjacent channel
sections (2) are joined by means of an external joining sleeve member (6) which engages
with formations (26) at either side of the channel sections in the lower portion in
both adjacent channel sections (2). The channel sections are self-supporting and made
of a closed cell structure PVC foam. An outlet sleeve (8) is provided which engages
with formations (26) at either side of the channel sections in the lower portion of
the channel section (2). The outlet sleeve (8) is provided so that the channel section
(2) can be easily coupled to a downward drainpipe at any point along its length. Channel
sections (2) as described can also be used with a solid cover in ducting applications
for cabling. |
Background of the Invention
[0001] The present invention relates to plastics channel sections that can be used as enclosed ducting or in drainage systems made up of plastics drainage channel sections closed by slotted grids.
Technical Background
[0002] The use of plastics material makes for a lightweight channel, which is particularly suitable for use in interior and in light-duty applications in situations where non-corrosive fluids are to be drained, for example, around swimming pools, patios and in domestic driveways.
[0003] As with many linear drainage systems, the channels are formed by placing U-shaped open mouth channel sections end-to-end in order to provide channels of the appropriate length. Typically special channel sections are provided with vertical outlet connections. These are inserted in the run of standard channel sections as required.
Prior art
[0004] GB-A-2 351 992 describes such a plastics channel. This channel has been extruded with hollow section side walls. The same technique has been shown in US-A 5 181 793. These types of structure have limited torsional rigidity. The flexibility of the channel structure also makes it necessary to devise mechanisms for supporting the slotted grid in the open mouth of the channel. The many cavities in the hollow section side walls allow for the entry of ground water, which could freeze, expand and damage the channel.
[0005] Another technical problem with plastics channel sections is posed by the need to provide additional lugs at one end face of the channel to plug into sockets formed in the other end face in order to connect channel sections together. These formations must be added to the channel section after extrusion. This makes for a more complex manufacturing process. Therefore, there is a need for a convenient system for joining channel sections so that they can be kept aligned during installation.
[0006] The present invention also addresses the technical problem of eliminating the need for specially fabricated channel sections with outlet connectors.
Solution of the invention
[0007] The present invention provides a self-supporting plastics channel section having a uniform U- shaped open mouthed cross-section made of a foamed plastics material having a closed cell structure.
[0008] The advantage of using a closed cell foam for the channel section are substantial. A closed as opposed to an open cell foam structure is made up of cells which do not connect with one another. In an open cell structure such as a bath sponge the cells are connected so that water and air can pass from cell to cell. Because the closed cell structure consists of cells that each form an enclosed cavity the resulting structure is similar to that described in GB-A- 2 351 992 but on a much smaller scale. The structure can therefore be made such that it has sufficient stiffness to be self supporting. Such a channel section is preferably formed by extrusion so the sections can be made of any length.
[0009] The use of plastics foam in drainage systems has been proposed in GB-A-2 348 913 (Nattrass). However in that case the foam material is used to provide a foldable flat structure that can be used as a formwork when a drainage channel section of concrete is created in situ. The material is injection moulded from structurally foamed plastics to produce a flat section. This structure is not required to be self supporting and there is no disclosure of the cell structure of the foam.
[0010] Because the closed cell foamed plastics is stiffer than prior art plastics channels of comparable weight, it can be used to provide recesses to support a slotted grid in the open mouth in the same way as is used for polymer concrete or metal channel sections. The use of closed cell foamed plastics material also enables the channel to function independently and cope with vehicle loads in its own right without a concrete haunch if need be.
[0011] Moreover a closed cell structure foam created by the use of PVC chips produces a channel section that is not vulnerable to penetration by ground water. This eliminates the problems created by water freezing in the hollow side walls of the prior art channel sections.
Brief Description of the Drawings
[0012] In order that the invention may be well understood, some embodiments thereof will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which:
- Figure 1
- shows an exploded perspective view of the components of a drainage system;
- Figure 2
- is a perspective view of a short length of channel section;
- Figure 3
- is a front view of an end plate;
- Figure 4
- is a top view of the end plate of Figure 3;
- Figure 5
- shows a cross section through a joining sleeve component;
- Figure 6
- shows a partial cross section side view of an outlet sleeve component; and
- Figure 7
- shows a top view of the outlet sleeve component of Figure 6.
Description of a Preferred Embodiment
[0013] The channel sections to be described can be used with a solid cover to provide a ducting system or with a slotted grid as part of a drainage system. The application of the channel sections in drainage systems will be exclusively described in more detail below but it will be appreciated that the channel sections may be put to other uses.
[0014] A drainage system can be assembled from a small number of components as shown in Figure 1. These are a U shaped channel section 2, a slotted grid 4, a sleeve component 6 with an outlet connection 8 and an end plate 10. The embodiment shown in Figure 1 uses a single design of sleeve component 6 for joining sections 2 and positioning an outlet. The remaining figures show an embodiment in which a different design of sleeve component is used for each purpose.
[0015] The channel section 2 is made as an extrusion of foamed plastics material. The channel section 2 has a uniform cross section, flat end faces 16 and an open mouth 18. The channel section 2 has a base 20 and two facing upstanding side walls 22. An internal surface of the section defines a curved U-shaped channel to provide good drainage flow characteristics. Externally the profile is substantially rectangular and the base 20 is flat so that the sections can be easily handled and seated. At either side of the base 20 in a lower portion of the channel section 2 lateral projections 24 are provided. The projections 24 merge with the side walls by means of sloping faces 26.
[0016] Each side wall 22 terminates in an edge 30. An internal recess 32 is formed adjacent the open mouth 18 of the channel section 2 just below the mouth. The recess 32 defines a ledge 34 that can support the slotted grid 4. Upstands 36 at either edge of the mouth effectively provide a protected edge for the grid 4 and aid line and level installation. These upstands 36 and the ledges 34 can be co-extruded with a harder more dense material to resist wear. An internal bead 38 is formed just beneath the upper edge of each upstand 36 in order to seat above the top of the grid 4.
[0018] A circular opening 40 is shown in the base 20 of the channel section 2. Such an opening can be created on site at any position along the length of the channel section 2 in order to cooperate with an outlet connection 8.
[0019] The joining sleeve component 6 is used to join adjacent channel sections 2 together end-to-end. The sleeve 6 is a laminar piece having a flat base 42 with raised edges 44 shaped to fit snugly around the projections 24 of the channel section 2. The edges 44 are inturned to seat against the walls 26 so that the sleeve 6 can slide along the channel section 2 using the projections 24 effectively as tracks. The sleeve enters the tracks by being engaged from one end face 16. The edges 44 are radiused at each end 46 so as to facilitate engagement with the channel sections before the sleeve is slid into place.
[0020] In the embodiment illustrated in Figure 1 the sleeve component 6 also serves to provide a connection for an outlet connection 8. In this case, the base 42 will be provided with a circular witness 48 that can be knocked out when the multipurpose component is to be used to couple to a drain. However, in a preferred embodiment separate sleeve components are provided for the purpose of joining the channel sections and for coupling to an outlet. The joining sleeve component is shown in Figure 5 and the outlet sleeve component shown in Figures 6 and 7. In addition, the end plate 10 is also adapted to be connected to the end face 16 of a channel section by means of its own sleeve component shown in Figures 3 and 4. Each sleeve component is constructed in the same way with a base and raised edges so that it can slide onto projections 24. The corresponding parts are given the same reference numerals.
[0021] The outlet sleeve component has a circular opening 50 in its flat base 42. A depending tubular wall 54 surrounds the opening 50 and projects in the opposite direction from the edges 44. The wall 54 provides a socket that serves as an outlet connection 8. A second, larger, tubular wall 56 surrounds the tubular wall 54 concentrically. Each wall 54, 56 acts as a socket for a respective standard diameter drainpipe. The inner wall 54 has a diameter of 75mm to cooperate with standard European drainpipes whereas the outer wall 56 has a diameter of 110mm to cooperate with the standard UK drainpipe. The lower edges of each wall 54, 56 are preferably chamfered to facilitate engagement with the end of the drainpipe. When an outlet sleeve component is used along a channel section the opening 50 must be aligned with an opening 40 created in the base 20 of the channel section 2 during assembly.
[0022] A perforated leaf guard (not shown) can be formed in the upper tubular part to prevent leaves and the like passing from the drainage channel into a drain pipe coupled to the outlet connection.
[0024] The end plate 10 as shown in Figure 3 is shaped to correspond to the outer profile of the cross section of the channel section 2. The thickness of the end plate 10 is reduced by means of v-shaped indents 60 on either face of the plate to outline areas 62 spaced over the surface of the end plate. This allows the outlined areas 62 of the end plate within these outlines to be knocked out during installation to leave apertures so that the drained water can flow into a soak away if desired.
[0025] Most required configurations of drainage arrangement for domestic application can easily be formed from the described components. However, for the block pavior installations, it may be necessary to provide 90° comer units. These are preferably assembled in a factory by mitring together two channel sections at 90° to each other and securing them together by solvent welding.
Manufacture
[0026] The channel sections 2 are preferably made of expanded PVC foam that has a closed cell structure. The extrusion process will create a continuous smooth skin all on the exposed surfaces of the product. This skin will aid hydraulic flow and also improves the aesthetic appearance of the channel sections 2. The extrusion method is not novel of itself but it has not previously been used in the field of manufacture of drainage channel sections.
[0027] The process for making a channel section 2 uses a plastics polymer, for instance a PVC compound as the raw-material. Such a PVC compound can be used in granular or powder form. The polymer compound can typically contain some or all the following components:
i) basic polymer homopolymer, copolymer and/or a polymeralloy;
ii) heat (temperature) and light stabilising agents as required for outdoor use; and
iii) high-polymeric additives to provide greater physical strength against impact;
iv) colour pigments as required to produce the desired colour and to provide greater light stability;
v) lubricants as an extrusion process aid; and
vi) blowing or foaming agents.
[0028] These components are fed into an extrusion moulding machine. A suitable extrusion moulding machine is manufactured by Battenfeld. However, it will be appreciated that machines made by other manufacturers may be equally suitable. The extrusion moulding machine is fitted with a forming die that has been specifically manufactured to mould a channel section of the desired profile. The foaming of the material takes place during the moulding process. Foaming is caused by gas bubbles produced as the blowing agent thermally dissociates during the heating of the polymer compound when this is being melted. The gases produced by the heated blowing agent could be nitrogen, carbon dioxide, ammonium or water vapour depending on the blowing agent used. Examples of suitable blowing agents are Sodium bicarbonate or azodicarbonamide. A combination of more than one blowing agent might be used.
[0029] During the heating process in the extrusion machine, the gas produced by the blowing agent dissolves in the polymer matrix. Once the polymer compound has become fully molten it passes through the extrusion machine to the forming die where it is extruded according to the profile of the channel section. As the polymer material leaves the forming die it is under reduced pressure which allows the dissolved gas or gases to evaporate forming cavities or cells in the polymer matrix.
[0030] Care must be taken to ensure that the correct amount of blowing agent is added to the polymer compound. If the level of blowing agent is too low, there will be insufficient foaming which will result in a channel section having insufficient rigidity. If the level of the blowing agent is too high this might lead to cell collapse producing an open cell structure. A channel section with an open cell structure would not have the same structural strength and would also be vulnerable to water damage within the body of the channel section.
[0031] With the cross sectional shape illustrated a good closed cell foam structure can be created throughout the body of the section. A one metre section of channel would be virtually rigid and display minimal bending when supported at one point. One metre PVC channel can be constructed with a weight as low as 2.6 kilograms. Cell dimensions in the range 5.0µm to 0.5mm throughout the body of the section provide a good degree of stiffness whilst maintaining low weight.
[0032] PVC compound is used in the preferred embodiment. However, other suitable plastics materials may be used. Co-extrusion of a harder more dense material to define the edges of the mouth is an option where this would be an advantage.
Installation
[0033] The channel sections 2 are positioned end to end to create channels of the required length. Each section is connected to the next by a joining sleeve component 6 which slides onto the projections 24 of the adjacent sections 2. Where an outlet connection is required a hole 40 is cut on site in the base 20 of the channel. An outlet sleeve component is slid into position under the hole 20 and a drainpipe fitted to the appropriate socket wall 54, 56 from below.
[0034] The components may be solvent welded together if necessary to provide greater watertightness and to prevent movement of the components while the surface adjacent to the channel is constructed.
[0035] The open mouths 18 of the channels 2 are closed by placing slotted grids 4 in the mouths of the channel. Edges of the grids 4 rest on the ledges 34 at either side of the channel.
1. A self-supporting plastics channel section having a uniform U- shaped open mouthed
cross-section and made of a foamed plastics material having a closed cell structure.
2. A plastics channel section as claimed in claim 1, made of PVC foam.
3. A plastics channel section as claimed in claim 1 or 2, made by extrusion.
4. A plastics channel section as claimed in claim 3, wherein parts of the channel section
are co-extruded with a harder material.
5. A plastics channel section as claimed in any one of the preceding claims, having side
walls having recesses to support a slotted grid or solid cover in the open mouth.
6. A plastics channel section as claimed in any one of the preceding claims, having external
formations provided at either side of the U shaped channel section in order to engage
with a sleeve member adapted to surround a lower portion of the channel section.