AU2012261627B2 - Trench Drainage System - Google Patents

Abstract

The present invention relates to drainage systems. In particular, the invention relates to trench drains able to be embedded in the ground, comprising: two substantially parallel frames formed from a plurality of bars of L-shaped cross-section arranged in two substantially parallel lines, the bars being arranged with vertical portions extending upwards from horizontal portions, the horizontal portions of each parallel line of bars facing inwards towards each other; a trough suspended below the frames and coupled thereto such that the horizontal portions of the frames extend inwards from inner surfaces of the trough to form two lips; a grate spanning between the frames and supported by the upper side of the horizontal portion of each frame; and at least one clip having a first portion extending over a part of the grate and further portions extending under the two lips to hold the grate in position. The invention also relates to a method of forming the said drainage system. Figure 1

Description

099 1'46 760 iP Australia TRENCH DRAINAGE SYSTEM 17 SEP 2012 RECEIVED FEP FAX Field of Invention The present invention relates to drainage systems. In particular, the invention relates to trench drains able to be embedded in the ground. Background to the Invention Trench drains are drains placed in the ground or floor and act to drain surface water. Usually roughly linear in shape, trench drains consist of a main trough-shaped channel with a grate over the top through which fluid can drain into the channel. The grate is often flush with the adjoining surface. One existing type of trench drain is made by pouring concrete around a former or mould. The former may be constructed on site, for example out of wood or out of pre-made modules made from lightweight expanded polystyrene or cardboard. After the concrete has dried, the former is removed to leave a channel moulded in the concrete. Making a wooden former on site is very labour intensive and can lead to difficulties in positioning outlet pipes in the drain and levelling the grate. Pre-made formers are far quicker to use but any method using a removable former leaves a drain channel made of concrete alone. This is susceptible to cracking and shifting as a result of ground movement, which can adversely affect the ability of the drain to function as intended. This is particularly a problem in areas suffering from frequent tectonic activity. Another type of trench drain uses pre-made concrete channel sections that are inserted into a dug trench and then have concrete poured around them to set the drain in place. Installations commonly require haunching concrete to be poured, which needs to be compressed a section at a time around the base of the channel sections. Once set, further concrete must be added to bring it up flush to the top of the drain. In some instances, a concrete polymer.is used which improves on the strength and resilience of traditional concrete. One problem with drains made of pre-made concrete sections set in concrete is the difficulty of installation. Sections are installed one at a time onto wet concrete and the height of each 1 0991'46760 section needs to be maintained to ensure correct alignment. Some people attempt to address this difficulty by using concrete containing little water so that the drain sections do not sink. However, this can lead to installations with poor quality concrete containing lots of holes or voids. There can be drainage issues is cracks occur in the drain sections and water can seep through the voids in the setting concrete. Furthermore expansion and contraction of concrete over the course of time can lead to a separation between the channel sections and the setting concrete. This can cause the drain to become unstably installed, prone to misalignment and incorrect functioning. Again, ground movement can also cause problems. Figure 1 is an isometric view illustration of a prior art drainage system - the Steel Trench Drain System from MultiDrain Systems Inc. This system is a trench drain formed from two parallel frames 1 to which is attached a square-shaped metal former 2, typically made from galvanised or stainless steel. The frames I are formed from flat sheets of stainless steel bent into a Z shaped cross-section. The former 2 is attached to the bottom vertical portion of the frames 1 by means of screws 3. The screws also connect spacer bars 4 between the frames 1 to strengthen the drain structure. A grate 5 is placed over the drain, supported by the horizontal section of the frames 1. To install, the frames and former are inserted into a trench and supported by rods 6, which are placed vertically in the trench. The frames 1 comprise anchor arms 7 that engage with the rods 6 and hold the drain in place. Concrete is poured into the trench around the drain up to the level of the grate. Further anchor arms 8 also hold the drain in place within the surrounding concrete. The drainage system shown in Figure 1 has a number of drawbacks. The frames and former lack rigidity, which can make installation of the drain difficult and means the drain is prone to failure over time through ground movement and other external influences. In addition, the system is made up of lengths of frame and former that are limited in size based on the availability of materials from which they are made. For example, the steel sheets from which the frame sections of the system in Figure 1 are made are typically only available in lengths 2.4m or 8 feet long. This limits the length of frame that is possible, therefore meaning more sections are required for a given length of drain than if frame sections were available in longer lengths. The more components that need to be connected together, the greater the complexity of installation. There is a need for a drainage system that improves on existing systems and, in particular, addresses one or more of the drawbacks of existing systems, such as discussed above. 2 099146760 Furthermore, many drainage systems are designed to deal with run-off of water and it may not be desirable if other materials, including liquid or solid waste products are able to enter certain parts of a drainage system. For example, it is preferable that drainage systems with outflow to rivers, lakes or seas do not allow unwanted materials to pass downstream in the system. Solid materials can be particularly problematic if they cause blockages. There is also a need for an improved filtration device or sump able to collect and manage runoff in a drainage system to prevent undesirable material from passing through. Alternatively, it is an object of the invention to at least provide the public with a useful choice. Summary of the Invention According to a first aspect of the invention, there is provided a trench drainage system for embedding in a ground surface comprising: two substantially parallel frames formed from a plurality of bars of L-shaped cross section arranged in two substantially parallel lines, the bars being arranged with vertical portions extending upwards from horizontal portions, the horizontal portions of each parallel line of bars facing inwards towards each other; a trough suspended below the frames and coupled thereto such that the horizontal portions of the frames extend inwards from inner surfaces of the trough to form two lips; a grate spanning between the frames and supported by the upper side of the horizontal portion of each frame; and at least one clip having a first portion extending over a part of the grate and further portions extending under the two lips to hold the grate in position. Preferably, the clip is in the form of a 'W' shape. Preferably the clip comprises one or more resilient members which are deformed when the clip is in position to act to hold the grate in position. More preferably, the clip comprises a single strip which may, for example, be formed of metal. Preferably, the drainage system comprises a plurality of support members adapted to support the frames in spaced apart relation to a trench surface prior to a settable medium being 3 099I46760 introduced around the drainage system and forming the ground surface. An upper surface of the grate may be substantially flush with the ground surface. In a preferred embodiment of the invention, the plurality of support members comprises a plurality of vertical support members, each vertical support member having a first end adapted to connect to one of the frames and a second end adapted to be inserted into a ground material. It will be understood that a vertical support member is operable to support a frame or part thereof in a vertical direction. Vertical support members may be arranged vertically or in any other orientation. Preferably, the bars comprise means for receiving the vertical support members coupled to the outer side of the bars. The means for receiving the vertical support members may comprise vertically oriented tubes having an opening in the bottom into which the vertical support members may be received. Furthermore, the tubes may comprise a tapering upper section configured to frictionally engage the vertical support members. The plurality of support members may also comprise a plurality of lateral support members connected to two or more vertical support members and configured to provide structural rigidity thereto. Preferably, at least some of the bars are at least 6m in length. In preferred embodiments, the flanges of the trough are welded to the frames. Preferably, the trough comprises a plurality of trough members arranged end-to-end. Preferably, the grate comprises a plurality of grate members arranged end-to-end on the frames. Preferably, the trough has a rounded bottom. Preferably, the drainage system comprises one or more braces coupled to each frame. According to a second aspect of the invention, there is provided a method of forming a drainage system in a trench comprising: 4 099146760 coupling a trough to the underside of a plurality of bars of L-shaped cross-section, the plurality of bars being arranged in two substantially parallel lines to form two substantially parallel frames, the bars being arranged with vertical portions extending upwards from horizontal portions, the horizontal portions of each parallel line of bars facing inwards towards each other, wherein the trough is coupled to the bars such that the horizontal portions of the frames extend inwards from inner surfaces of the trough to form two lips; mounting the plurality of bars on a plurality of support members in spaced apart relation to a surface of the trench, introducing a settable medium into the trench; allowing said settable medium to set, thereby holding the drainage system in place in the trench; positioning a grate on the upper side of the horizontal portion of each frame to span between the frames; and positioning a first portion of a clip over a part of the grate and further portions of the clip under the two lips to hold the grate in position. Preferably, the method comprises welding the trough to the underside of the frames. Preferably, the method further comprises coupling a first end of each support member to one of the frames. Furthermore, the method may comprise inserting a second end of each support member into the trench surface. More preferably, the step of coupling a first end of each support member to one of the frames comprises inserting the respective support member into a vertically oriented tube coupled to an outer side of one of the frames. Furthermore, the method may comprise frictionally fitting the support member into a narrower upper section of the tube. According to a third aspect of the invention, there is provided a sump for a drainage system, the sump comprising: a housing defining a cavity, the housing having an open or openable upper side; a fluid inlet to the cavity in a first wall of the housing, a fluid outlet to the cavity in a second wall of the housing, wherein the fluid outlet is positioned lower than the fluid inlet; and cavity partitioning means extending across the housing to divide the cavity into a first side in which the fluid inlet is situated and a second side in which the fluid outlet is situated, 5 099146760 wherein the cavity partitioning means defines at least in part an opening below the level of the fluid outlet and extends up to a level above the fluid inlet. Preferably, the cavity partitioning means comprises a baffle plate. More preferably, the baffle plate is substantially vertically oriented. Preferably, the housing has a rectangular horizontal cross-section, the fluid inlet being located in an end wall of the housing. More preferably, the housing has a width substantially equal to a width of a trench drain to which it is fluidly connected. Further aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the invention. Brief Description of the Drawings One or more embodiments of the invention will be described below by way of example only, and without intending to be limiting, with reference to the following drawings, in which: Figure 1 is an isometric view illustration of a prior art drainage system; Figure 2 is an isometric view illustration of a drainage system according to an embodiment of the invention; Figure 3 is an end cross-sectional view of the drainage system shown in Figure 2; Figure 4 is an isometric view illustration of a frame bar according to another embodiment of the invention; Figure 5 is an isometric, cross-sectional view illustration of a sump according to another embodiment of the invention; and 6 099146760 Figure 6 is an isometric view illustration of a drainage system according to another embodiment of the invention. Detailed Description of Preferred Embodiments of the Invention Figure 2 is an isometric view illustration of a drainage system 10 according to an embodiment of the invention. The front section of drainage system 10 is shown in cross-section. Figure 3 is an end cross-sectional view of the same drainage system 10. Figure 2 shows drainage system 10 installed in the ground as a trench drain with its upper surface being flush with the surrounding ground level. The structure of an installed drain in one embodiment will first be described, followed by an exemplary method of installation. Structure of a drain Drain 10 comprises two frames 11 arranged substantially parallel to each other. The frames are each formed from one or more bars having an L-shaped cross section. The bars are oriented with their vertical portions extending upwards from the horizontal portions and the horizontal portions of each parallel line of bars face inwards towards each other. In this way, the outer sides of the horizontal portions of the bars abut the surrounding ground and an opening to the drainage channel is defined between the frames 11. The bars forming the frames may be formed of any suitable material but, in preferred embodiments, are lengths of angle iron. Embodiments of the invention comprise angle iron lengths of approximately 6 metres or more, thus enabling a drain of a given length of be made of fewer frame lengths than existing drains in which the frames are constructed from 2.4 metre lengths of bent stainless steel sheets. The frames of such existing drains are limited in length by the size of stainless steel sheeting commercially available, whereas the use of angle irons has no such restriction. Longer sections of frame are also more rigid, giving greater strength to the system and making it easier and quicker to install. The drainage channel is formed by a trough 12 suspended below the frames 11. The trough may be formed of one or more individual trough members arranged end-to-end. The trough members have flanges on their upper ends which are coupled to the underside of the horizontal portions of frames 11 by an appropriate means. In some embodiments of the invention, the 7 099 146760 trough members are welded to the frames 11, for example spot welded. Again, welding the trough 12 to the frames 11 provides a high level of rigidity to the overall structure of the drainage system. The trough sections are preferably constructed from galvanised or stainless steel but other suitable materials may also be used. The frames 11 and trough 12 are arranged with a gradient sufficient to allow water to drain along the bottom of the trough 12 to a drain fluid outlet (not shown). In the embodiment shown in Figure 2, the trough 12 has a rounded bottom. In other embodiments, the trough may have a different cross-sectional profile, including a square shaped bottom. One advantage of troughs having a rounded bottom profile is better flow and cleaning of the trough when water is flowing. Troughs of differing depths may be available to suit the needs of a particular installation, as shown by dotted lines 20 in Figure 3. Within the same installation, trough sections of differing heights can be installed adjacent to one another so that the trench drain includes a continuous fall along its length while enabling the top of the drain to be horizontal. A grate 13 is positioned over the top of the drain, preferably with its upper side substantially flush with the surrounding ground surface. The grate 13 may be formed of one or more grate members arranged end-to-end, the grate members spanning across the drainage channel and being supported by the upper side of the horizontal portions of each of the frames 11. As shown in Figure 3, braces 19 may span between the two frames 11. Braces 19 are typically formed of stainless or galvanised steel and are coupled to frames 11 at each end. The braces act to maintain the distance between frames 11 during installation and following ground movement and increase the strength of the drainage system 10. The drain 10 is embedded in the surrounding ground, for example within concrete 14 or other settable ground material. A supporting structure is used to support the drain in spaced apart relation to the surface of a trench 15 that may be dug- or prepared in a ground material 16 prior to installation. The supporting structure shown in Figure 2 comprises a plurality of support members or rods 17, each attached at one end to one of the frames 11 and having its other end inserted into ground material 16. In the embodiment shown, the rods 17 comprise steel rods welded to the outer side of frames 11. The rods 17 support the frames vertically and act to distribute the load of the drain and its contents evenly to the surrounding ground. The rods 17 8 099146760 may comprise notches or grooves on their surface to prevent slippage in the ground material 16 and concrete 14. The supporting structure may also comprise lateral support members, for example rods 18 spanning horizontally between one or more of the vertical rods 17. The lateral support members significantly add to the strength of the drainage system, particularly providing strength against cave-ins. In other embodiments of the invention, the support members may be attached to the frames in other ways. For example, Figure 4 is an isometric view illustration of a frame bar 30 according to another embodiment of the invention. Frame bar 30 is a length of angle iron 31 having an L shaped cross-section. Coupled to the outer side of the bar is means for receiving a supporting rod in the form of a vertically oriented tube 32. Tube 32 has an opening in its bottom end which, in use, receives one end of a supporting rod, such as rod 17 shown in Figure 2. Tube 32 may have a tapering upper end 33 into which the end of a supporting rod can be frictionally fitted. In one example, rods 17 have a diameter of 12mm and tubes 32 have a diameter of 13mm. The tube may be tapered by crimping or another similar method to a diameter of less than 12mm so that the rod can frictionally fit therein. Similar tubes may be coupled to each frame bar at regular distances apart, for example every 600-700mm. A frame bar such as is shown in Figure 4 may be advantageous because the supporting rods can be easily and securely fitted on site. This removes the need to transport frames having supporting rods also attached, which may be cumbersome and dangerous to transport. It also negates the need to weld the supporting rods to the frames on site, which is relatively more difficult and time consuming. Referring again to the drainage system 10 shown in Figure 2, the load of the drain and fluid within the trough acts is supported by the surrounding concrete and ground material 16 through the underside of the frames 11 and supporting rods 17 respectively. The width of the underside of the horizontal portion of frames 11 is sufficiently large that a significant proportion of the weight of the system is supported by the surrounding concrete at this point. This has the advantage over existing systems where the load is supported through the bottom of the trough or channel in that it makes the drainage system 10 resilient to significant amounts of ground movement, as has been observed by the applicant in testing of the invention. In addition, the supporting structure of the rods 17 and 18 can flex as the surrounding concrete 14 expands or 9 099146760 contracts with temperature fluctuations, maintain the integrity of the system. Therefore the drainage system of the present invention has a longer life span than existing systems, notably in areas of high levels of ground movement, for example areas prone to tectonic activity. Method of installing the drain There will now be described a method of forming or installing a drainage system such as the embodiment shown in Figures 2 and 3, in accordance with another embodiment of the invention. Firstly, a trench is formed in a material in which the trench drain is to be installed. Typically, this involves digging a trench in existing ground.. As shown in Figure 2, the size of the trench 15 may be larger than the size of the trench drain to allow room for concrete to be poured around it. Once the appropriately sized trench has been dug a string line may be erected to act as a guide for putting up the drain. The string line may include the desired gradient for water to drain along the trough. Next, the bars of L-shaped cross-section are mounted on the support rods 17 and in spaced apart relation to the surface of the trench 15 to form two substantially parallel frames 11. The string line may be used to guide the position of frames 11 along the length of the drain. Generally, the trough members 12 are coupled to the frames 11 prior to delivery to the installation site to form trough 12 or in any case prior to the frames being mounted on the support rods 17. The support rods 17 may be fixed to the frames 11 prior to being positioned in the trench or the supporting structure of rods 17 and 18 may first be erected in the trench before the frames 11 are coupled to the rods 17. If frames 30 such as shown in Figure 4 are used, the step of coupling the rods to the frames simply requires the rods to be inserted into the bottom of tubes 32. The tubes may be hammered down on the rods to ensure a strong frictional fit of the rods in the tapered upper section 33 of tubes 32. The bottom ends of rods 17 are easily slid into most ground materials 16. 10 099146760 If required, the braces 19 may be coupled between the frames 11. In some embodiments, lengths of parallel frames may be coupled together with braces prior to installation. This aids in ensuring the frames are spaced the correct distance apart. Once in place, a settable medium, for example concrete 14, is introduced into the trench 15. The settable medium is filled up to the desired level, typically flush level with the top of frames 11 and/or grate 13, which may be positioned on top of the frames at any stage. In some embodiments a top surface may be laid on top of concrete 14. For example, a layer of asphalt 21 or the like may be added, in which case the level of concrete 14 will allow for the height of the asphalt layer 21 to allow the asphalt layer 21 to be flush with the top of the grate 13. The concrete 14 is allowed to set to thereby hold the trench drain in position. Grating lip and clip Figure 6 is an isometric view illustration of a drainage system 60 according to another embodiment of the invention. Similarly to the embodiment shown in Figures 2 and 3, drainage system 60 comprises two substantially L-shaped frames 61 facing towards each other. Trough 62 is suspended below frames 61 and may be similar to the trough described in relation to Figures 2 and 3. Drainage system 60 also comprises a grate 63 sitting on the horizontal portions of L-shaped frames 61 and spanning between them. In the embodiment shown in Figure 6, the L-shaped frames 61 extend inwards beyond the vertical inner surfaces of trough 62 extending down from the frames such that a lip 64 is formed on the underside of each L-shaped member 61. Put another way, compared to the embodiment of Figures 2 and 3, the trough 62 connects to L-shaped frames sufficiently far from their inner edge to form such a lip 64. Drainage system 60 further comprises a resilient clip 65 that acts to hold the grate 63 in position. Clip 65 has a W' shape with a central peak extending higher than the edge portions 66. In use, the centre of clip 65 is placed over a part of the grate 63, such as a longitudinally extending part of the grate, while the edge portions 66 are positioned under the lips 64 formed by the L-shaped frames 61. The size and shape of the clip 65 is configured such that the clip is deformed slightly to be placed in the position shown in Figure 6. As such, the dip is held under tension- with the edge portions 66 being resiliently biased upwards against the underside of lips 11 099146760 64 to hold the grate 63 in position. Clip 65 may be made from one or more resilient members although in the embodiment show in Figure 6 it is formed from a single metal strip. In another embodiment, the clip may comprise two or more central peaks to hook over an appropriately positioned part of the grate. Any troughs formed between the central peaks may hook under part of the grate. Compared to drainage systems in which a grate sits on L-shaped frames without any means to hold it in place, the system described above helps to ensure the grate remains in position and is not displaced by vibrations (such as may be caused by traffic or seismic movement) or impact from vehicles or the like passing over the trench drain. The presently described system also provides advantages over drainage systems that use other forms of engagement to hold the grate in place. For example, nuts and bolts are fiddly and time consuming to fasten and the threads of the bolt can easily get congested with dirt or grime, making their removal difficult and sometimes necessitating their replacement. In contrast, the presently described clip can be quickly and easily put in place and removed by squeezing either side of the central peak and it holds the grate in place in a strong, effective way. Another advantage is that clips such as clip 65 shown in Figure 6 allow a grate to be secured to the frames of the trench drain at any point along its length. This allows considerable flexibility in positioning and securing grates compared to other drainage systems in which grates may only be able to be secured at pre-defined points along its length, for example where bolt holes have been made. In these systems, the grates need to line up with the pre-defined points to be secured. Misalignment of one section of grate can therefore cause misalignment of other sections. The flexibility provided by the clip disclosed herein avoids these problems. Drain sump Figure 5 is an isometric, cross-sectional view illustration of a sump 40 according to another embodiment of the invention. Sump 40 is suitable for installation in a drainage system comprising a trench drain as described above and is adapted to assist in preventing unwanted materials entering into a drainage outlet. 12 0991t46 760 Sump 40 comprises a housing 41 which, in the embodiment shown in Figure 5 is generally cuboid in shape and has a width similar to that of the trench drain 10 shown in Figure 2 so that sump 40 can be installed at the end of the trench drain. The upper side of housing 41 is open so that the cavity inside housing 41 may be easily accessed. In some embodiments, an openable lid may cover housing 41 to provide access to the cavity when desired. For example, the housing 41 may be adapted to be covered by a grate similar to the grate 13 covering the trench drain of Figure 2 so that, from above, sump 40 looks like any other part of the trench drain. One wall of the housing 41 comprises a fluid inlet 42 to the cavity in the sump. In the embodiment shown, the fluid inlet 42 is located in an upper portion of one of the end walls of housing 41. Fluid inlet 42 may be appropriately sized to fluidly communicate with the trough 12 of the trench drain 10 shown in Figure 2. The depth of inlet 42 may be able to be cut to accommodate troughs of differing sizes, as depicted by dotted lines 43. Another wall of the housing 41 comprises a fluid outlet 44. In the embodiment of Figure 5, fluid outlet 44 is shown as a circular hole in one of the side walls of the housing, but the outlet can be positioned to suit the size and position of an outlet drain. Both the fluid inlet and outlet may be cut on site to suit the configuration of the drainage system into which the sump is to be installed. Fluid outlet 44 is positioned lower on housing 41 than fluid inlet 42. This allows the sump 40 to filter material from the drain, as will be explained shortly. Sump 40 further comprises a cavity partition which, in the embodiment of Figure 5, takes the form of a vertically oriented baffle plate 45. Baffle plate 45 extends across the width of the housing and divides the cavity vertically into two sides. The fluid inlet 42 is situated on, and in fluid communication with, the first side of the cavity and the fluid outlet 44 is situated on, and in fluid communication with, the second side of the cavity. Baffle plate 45 does not divide the two sides of the cavity in a sealing manner. An opening is defined at least in part by the baffle plate 45. For example, as shown in Figure 5, baffle plate 45 does not extend to the bottom of housing 41 but leaves an opening defined by the sides of the 13 0991'46760 housing 41 and the bottom of the baffle plate 45. In other embodiments, the baffle plate may extend to the bottom of the housing 41 but have one or more openings therein. The top of the opening under the baffle plate is below the level of fluid outlet 44 so that floating material is not able to pass through the fluid outlet 44. Furthermore, the baffle plate 45 extends up to a level above the fluid inlet 42, typically at least as far as a level at which water commonly enters the sump housing 41. The baffle plate operates to prevent material floating on or near the top of water collected in a drain from passing into the fluid outlet. Typically, sump housing 41 has a certain level of water in it, preferably at least up to the level of the bottom of baffle plate 45. Fluid passing into the sump through fluid inlet 42, for example from a drain trough, enters to the side of baffle plate 45 and therefore material floating on or near the top of the water is trapped behind the baffle plate. This may include solid debris such as leaves and litter but also fluid contaminants like oil and other hydrocarbons. In the meantime, the water is able to drain out of the sump through outlet 44. Periodically the sump 40 can be cleaned of debris manually by removal through the open top of the housing 41. Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to". The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference. Reference to any prior art in this specification Is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world. The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features. 14 099146760 Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth. It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention. 15

Claims (18)

1. A trench drainage system for embedding in a ground surface comprising: two substantially parallel frames formed from a plurality of bars of L-shaped cross-section arranged in two substantially parallel lines, the bars being arranged with vertical portions extending upwards from horizontal portions, the horizontal portions of each parallel line of bars facing inwards towards each other; a trough suspended below the frames and coupled thereto such that the horizontal portions of the frames extend inwards from inner surfaces of the trough to form two lips; a grate spanning between the frames and supported by the upper side of the horizontal portion of each frame; and at least one clip having a first portion extending over a part of the grate and further portions extending under the two lips to hold the grate in position.

2. A trench drainage system as claimed in claim 1, wherein the clip is in the form of a 'W' shape.

3. A trench drainage system as claimed in claim 1 or 2, wherein the clip comprises one or more resilient members which are deformed when the clip is in position to act to hold the grate in position.

4. A trench drainage system as claimed in any one of claims 1-3, wherein the drainage system comprises a plurality of support members adapted to support the frames in spaced apart relation to a trench surface prior to a settable medium being introduced around the drainage system and forming the ground surface.

5. A trench drainage system as claimed in claim 4, wherein the plurality of support members comprises a plurality of vertical support members, each vertical support member having a first end adapted to connect to one of the frames and a second end adapted to be inserted into a ground material.

6. A trench drainage system as claimed in claim 5, wherein the bars comprise means for receiving the vertical support members coupled to the outer side of the bars.

7. A trench drainage system as claimed in claim 6, wherein the means for receiving the vertical support members comprise vertically oriented tubes having an opening in the bottom into which the vertical support members are received. 16

8. A trench drainage system as claimed in claim 7, wherein the tubes comprise a tapering upper section configured to frictionally engage the vertical support members.

9. A trench drainage system as claimed in any one of claims 4-8, wherein the plurality of support members also comprise a plurality of lateral support members connected to two or more vertical support members and configured to provide structural rigidity thereto.

10. A trench drainage system as claimed in any one of the preceding claims, wherein at least some of the bars are at least 6m in length.

11. A trench drainage system as claimed in any one of the preceding claims, wherein the flanges of the trough are welded to the frames.

12. A trench drainage system as claimed in any one of the preceding claims, wherein the trough has a rounded bottom.

13. A method of forming a drainage system in a trench comprising: coupling flanges of a trough to the underside of a plurality of bars of L-shaped cross section, the plurality of bars being arranged in two substantially parallel lines to form two substantially parallel frames, the bars being arranged with vertical portions extending upwards from horizontal portions, the horizontal portions of each parallel line of bars facing inwards towards each other, wherein the trough is coupled to the bars such that the horizontal portions of the frames extend inwards from inner surfaces of the trough to form two lips; mounting the plurality of bars on a plurality of support members in spaced apart relation to a surface of the trench, the plurality of bars being arranged in two substantially parallel lines to form two substantially parallel frames, the bars being arranged with vertical portions extending upwards from horizontal portions, the horizontal portions of each parallel line of bars facing inwards towards each other; introducing a settable medium into the trench; allowing said settable medium to set, thereby holding the drainage system in place in the trench; positioning a grate on the upper side of the horizontal portion of each frame to span between the frames; and positioning a first portion of a clip over a part of the grate and further portions of the clip under the two lips to hold the grate in position.

14. A method as claimed in claim 13, wherein the method comprises welding the trough to the underside of the frames. 17

15. A method as claimed in any one of claims 13-14, wherein the method further comprises coupling a first end of each support member to one of the frames.

16. A method as claimed in claim 15, wherein the method comprises inserting a second end of each support member into the trench surface.

17. A method as claimed in claim 15 or 16, wherein the step of coupling a first end of each support member to one of the frames comprises inserting the respective support member into a vertically oriented tube coupled to an outer side of one of the frames.

18. A method as claimed in claim 17, wherein the method comprises frictionally fitting the support member into a narrower upper section of the tube. 18