The present invention relates to a slotted drain. In particular, but not exclusively, the present invention relates to a slotted drain comprising an elongate drain pipe having a drainage slot extending in a direction along a length of the pipe and an adjustable height throat coupled to the drain pipe and which provides access for fluid into the drain pipe.

Many different types of drainage systems have been developed for collecting and directing rainwater. 'Slotted drains' or 'slot drains', developed in recent years, have a particular utility in collecting and draining water from large, hard-surfaced areas such as car parks, roads and airport runways. These drains comprise elongate pipes having a drainage slot which extends along a length of the pipe and which provides access for water running off the land into the pipe. A number of the pipes are connected together end-to-end and direct the water either straight into a sewer system, or into an intermediate holding tank from which the water flows into the sewer system.

The provision of such slotted drain pipes offers advantages over other, more conventional drainage systems. For example, slotted drain pipes permit collection of large volumes of water when compared to drainage systems in which water flows into a drain pipe through a number of spaced, vertical drain shafts. Also, the slot assists in restricting entry of large solids into the drain pipe, which may otherwise cause a blockage.

Where a slotted drainage system is to be employed, it is necessary to provide a throat which facilitates passage of water from surface level down to the pipe, which is provided at depth below the surface. These throats are typically formed from a pair of spaced elongate plates, which are coupled together and secured to the drain pipe. The throats include upper openings which are provided at or near surface level, and lower openings which communicate with the slot in the drain pipe.

As is well know n. the drain pipes of any drainage system must provide a fall to the sewer or holding tank, in order to provide for efficient drainage and to promote increased tlow velocities within the drain pipe, which helps prevent solids in the water carried by the pipe from falling out of suspension and, over time, blocking the pipe. Typically a fall of around 1 : 100 to 1 :500 will be built-in to slotted drainage systems. To achieve this, it is necessary to dig an inclined trench for the pipe, which progressively falls towards the sewer/holding tank, so that the trench is deepest at a point adjacent the sewer/tank.

Early slotted drains incorporated throats of fixed heights, and thus of fixed slopes or angles of inclination relative to their drain pipes. Accordingly, a fall of a known height was provided from one end of a pipe to the next, and it was necessary to carefully select the adjacent pipe section so as to match up with the first pipe and to continue with the desired fall. Any errors in calculating the fall, discovered during laying of the drainage system, can be major problem as it is necessary to pre-order and stock the drain pipes on site. Also, if work has progressed to the stage where the incorrect drain pipes have been cemented in the trench, the pipes would become damaged and unusable when dug-up, and would need to be discarded.

Modified drains have therefore been developed incorporating adjustable height throats. One such slotted drain is disclosed in US Patent no.5380121 to Contech Construction Products, Inc., which incorporates upper and lower grates. The height of the upper grate relative to the lower grate can be adjusted to vary the height of the throat. However, it is necessary to weld the grates together following adjustment, which is difficult and time-consuming, and does not address the issue of accidental selection of an incorrect height. It is also difficult to maintain the selected throat height during the welding process, which can lead to errors or undesired variations.

It is therefore amongst the objects of embodiments of the present invention to obviate or mitigate at least one of the foregoing disadvantages.

According to a first aspect of the present invention, there is provided a slotted drain comprising: an elongate drain pipe having drainage slot extending in a direction along a length of the pipe; an adjustable height throat assembly coupled to the drain pipe and which provides access for fluid into the drain pipe through the slot, the adjustable height throat assembly comprising a first throat section coupled to the drain pipe and at least one further throat section which is movably mounted relative to the first throat section to facilitate adjustment of a height and angular inclination of the throat assembly relative to the drain pipe; and at least one securing arrangement for releasably securing the further throat section against movement relative to the first throat section so that the height and angular inclination of the throat assembly relative to the drain pipe can be fixed.

In this fashion, the present invention enables the height and angular inclination of the throat assembly relative to the slotted drain pipe to be adjusted, and then set at desired levels by securing the first and further throat sections together. The invention may allow for repeated adjustment and securing of the throat sections, if required or desired, and thus may allow for a number of adjustments to be made. Providing the slotted drain including first and further throat sections may facilitate manufacturing cost efficiencies. For example, it may be possible to manufacture the further throat section (on which surface loads are directly imparted) from thicker materials and/or from materials having a higher yield strength than the first throat section. Providing the slotted dram including first and further throat sections may also facilitate any likely surface slope to be accommodated.

The securing arrangement may be for releasably securing the first and further throat sections together to fix the height and angular inclination of the throat assembly relative to the drain pipe. The securing arrangement may alternatively be for releasably securing the further throat section to or relative to the drain pipe or to another component of the slotted drain.

The first and further throat sections may each comprise spaced elongate plates which define respective throats therebetween. The throat of one of the first and further throat sections may be shaped and/or dimensioned to receive the other one of the first and further throat sections.

The securing arrangement may comprise a rod, bar or the like which extends through the throat assembly and which serves for coupling the first and further throat sections together. This may facilitate adjustment of a position of the further throat section relative to the first throat section, and thus of a height and inclination of the throat assembly, without separation of the further throat section from the first throat section. The first and further throat sections may each comprise a slot, track, channel or the like in which said rod is received and within which said rod is movable during movement of the further throat section relative to the first throat section. One or both of said slots in the first and further throat sections may have ends defining extreme extents of movement of said rod, and thus defining extreme extents of movement of the further throat section relative to the first throat section.

Said slot in the first throat section may cooperate with said slot in the further throat section such that the slots, or portions of the slots, align or overlap so that said rod may pass through the throat sections. The first throat section may be an outer throat section and said first section slot may be inclined with respect to a main axis of the first throat section. The further throat section may be an inner throat section and said further section slot may be disposed horizontally/parallel to a main axis of the further throat section. Alternatively, the first throat section may be an inner throat section and said first section slot may be disposed horizontally/parallel to a main axis of the first throat section. The further throat section may be an outer throat section and said further section slot may be inclined with respect to a main axis of the further throat section. The drain may comprise a plurality of securing arrangements, and there may be a respective slot in each throat section for the rod of each securing arrangement.

Providing inclined slots on one of the throat sections and horizontal slots on the other may facilitate in preventing passage of concrete (or other materials used to secure the drain) into the drain. This is because the slots may be arranged to cooperate so as to present a very small dimension leak path for fluids through the slots, and which may be sufficiently small as to prevent (or at least substantially restrict) passage of viscous solids-bearing fluids such as concrete.

Where there are a plurality of inclined slots, the slots may be of corresponding incline. The slots may all incline in corresponding directions, and may incline towards a common end of the drain. Providing inclined slots may offer a number of advantages. For example, inclined slots may facilitate movement of the further throat section relative to the first throat section, as the incline will encourage the securing arrangement to travel down the slot during lowering of the further throat section. Also, as the first and further throat sections may be coupled through a rod in the slots, providing inclined slots (as opposed, say. to vertical slots) results in the load of the further throat section on the first throat section having both vertical and horizontal components. Consequently, there will be a degree of resistance to movement of the further throat section relative to the first throat section, so that friction between the throat section and the rod will provide a degree of resistance which will facilitate positioning of the further throat section by an operator. Also and where there are a plurality of rods/slots, providing inclined slots may facilitate adjustment of the further throat section relative to the first throat section. This is because, for example, slots which are purely vertical/ perpendicular to a main axis of the drain pipe could restrict the degree of adjustment, and could cause the further throat section to stick, particularly where relatively large inclinations of the further throat section relative to the drain pipe are to be accommodated.

The securing arrangement may comprise or may take the form of a clamping assembly for releasably clamping the first and further throat sections together. The clamping assembly may be movable between: a release position in which the clamping assembly permits movement of the further throat section relative to the first throat section; and a clamping position in which the clamping assembly clamps the first and further throat sections together so as to restrict movement of the further throat section relative to the first throat section. In the clamping position, the clamping assembly may impart a clamping force on the first and further throat sections, to urge the first and further throat sections into abutment and thereby clamp them together. Providing a clamping assembly of this type may facilitate positioning of the further throat section relative to the first throat section at any desired point between two extreme extents of motion.

The clamping assembly may comprise: a rod which extends through the first and further throat sections (and which may define the rod described above), in particular through ox ciiapping slots in the first and further throat sections; at least one lever, arm or the like coupled to the rod, the lever being movable between release and clamping positions and defining a throat abutment surface; and a restraint provided on the rod spaced along a length of the rod from the lever; and the lever may be arranged such that, on movement from the release position to the clamping position, a distance between the abutment surface of the lever and the restraint on the rod is reduced, so as to clamp the first and further throat sections, located between the lever and the restraint, together. This may be achieved by appropriate shaping and/or dimensioning of the lever/the abutment surface of the lever. Where there are a plurality of clamping assemblies, each clamping assembly may be capable of being located at any point along a length of respective inclined slots, between extreme ends of the slots, which may facilitate accurate adjustment of a height of the throat assembly.

The lever abutment surface may be adapted to indirectly abut the throat assembly, or to directly abut the throat assembly. Where the abutment surface is adapted to indirectly abut the throat assembly, the clamping assembly may comprise a collar, washer or the like moveably mounted on the rod, and the lever may be adapted to exert a force on the collar to thereby urge the collar to clamp the throat assembly. The collar and/or the restraint may define one or more protrusions, such as teeth, adapted to engage one of the throat sections of the throat assembly, to thereby restrict movement of the respective throat section relative to the collar and thus relative to the clamping assembly.

The clamping assembly may comprise a throat support element which may be provided on or coupled to the rod, and which may be located between the lever and the restraint. The support element may be shaped to support the throat assembly to resist deformation of the throat assembly when the clamping assembly is moved to the clamping position. In particular, the support element may be shaped to support the throat section which is provided innermost of the throat assembly. The support element may define support surfaces at opposite ends thereof, which support surfaces may be adapted to support respective inner surfaces of the one of the first and further throat sections which is provided innermost of the throat assembly. The support surfaces may define one or more protrusions, such as teeth, adapted to engage the throat section to enhance the clamping force exerted on the respective throat section. The securing arrangement may be fluid (optionally hydraulically) operated and may comprise at least one piston mounted in a cylinder and which can be actuated to raise and/or lower the further throat section relative to the first throat section. The securing arrangement be a mechanical or electro-mechanical system for raising and/or lowering the further throat section.

The drain may comprise a plurality of securing arrangements spaced at intervals along a length of the throat assembly. The securing arrangements may be shaped to receive a reinforcing bar (or rebar). Where the securing arrangements take the form of the clamping assembly defined above, the levers of the clamping assemblies may comprise apertures shaped to receive a reinforcing bar. The levers of adjacent clamping assemblies may be provided on alternate sides of the throat assembly. This may facilitate provision of reinforcing bars on both sides of the throat assembly.

The clamping assembly may each comprise a further lever defining the restraint, and levers may be provided on both ends of the rod.

The securing arrangement may facilitate positioning of the further throat section relative to the first throat section in any one of a number of discrete positions. The securing arrangement may comprise or take the form of a ratchet assembly such as a ratchet strip provided on one of the first and further throat sections and which defines a plurality of detent positions or detents, and a ratchet element provided on the other one of the first and further throat sections and which is adapted to engage in a selected one of the detents for restricting movement of the further throat section relative to the first throat section. The ratchet element may be resilient, or may be biased (for example, spring biased) for engagement with the ratchet strip detents.

The throat assembly may comprise the first throat section, a second throat section movably mounted relative to the first throat section, and a third throat section movably mounted relative to the second throat section.

The slot in the drain pipe may be continuous, or may comprise a number of slot portions which together define the slot. Strengthening members or braces may be provided at intervals along the length of the slot, thereby dividing the slot up into such slot portions.

Interlocking elements such as locking tabs may be provided on the throat assemblies, for engaging with corresponding recesses, channels or the like on the throat assemblies of adjacent drains.

According to a second aspect of the present invention, there is provided a kit of parts to be assembled to form a slotted drain, the kit comprising: an elongate drain pipe having a drainage slot extending in a direction along a length of the pipe; an adjustable height throat assembly coupled to the drain pipe and which provides access for fluid into the drain pipe through the slot, the adjustable height throat assembly comprising: a first throat section adapted to be coupled to the drain pipe; and at least one further throat section, the further throat section selected from a plurality of further throat sections of different heights, and the selected further throat section adapted to be movably mounted relative to the first throat section to facilitate adjustment of a height and angular inclination of the throat assembly relative to the drain pipe; and at least one securing arrangement for releasably securing the further throat section against movement relative to the first throat section so that the height and angular inclination of the throat assembly relative to the drain pipe can be fixed.

The first throat section may be selected from a plurality of first throat sections of different heights. The drain pipe may be selected from a plurality of drain pipes of different external diameters, internal diameters, wall thicknesses and/or materials.

Further features of the parts forming the kit of the second aspect of the invention in common with the slotted drain of the first aspect of the invention are defined above.

According to a third aspect of the present invention, there is provided a method of forming a slotted drainage system comprising the steps of: excavating a trench in preparation for receiving a slotted drain including providing the trench with a desired fall in height along a length thereof to promote the flow of fluid through the slotted drain; laying the slotted drain in the trench, the slotted drain comprising: an elongate drain pipe having a drainage slot extending in a direction along a length of the pipe; an adjustable height throat assembly coupled to the drain pipe and which provides access for fluid into the drain pipe through the slot, the adjustable height throat assembly comprising a first throat section coupled to the drain pipe and at least one further throat section which is movably mounted relative to the first throat section; adjusting a height and inclination of the throat assembly relative to the drain pipe by adjusting a position of the further throat section relative to the first throat section; and fixing the height and angular inclination of the throat assembly by releasably securing the further throat section against movement relative to the first throat section using a securing arrangement of the slotted drain.

The method may comprise the step of cementing or otherwise securing the drain pipe in the trench prior to adjusting the height and inclination of the throat assembly. Following adjustment and fixing of the height and angular inclination of the throat assembly, the throat assembly may be cemented or otherwise secured within the trench. This allows for the height/inclination of the throat assembly to be set and checked prior to cementation of the throat assembly (thereby allowing for correcting adjustments), this being performed following cementing of the drain pipe and thus from a strong, stable platform. It will be understood that references herein to cementing the dram pipe and 'or throat assembly are to securing the drain pipe and/or throat assembly using a ccmentitious (typically concrete) material, but that many other types of material may be employed, including asphalt/asphaltic concrete (tarmacadam) and combinations thereof, depending upon particular construction and/or use requirements.

The method may comprise adjusting the height of the throat assembly so that an upper opening of the throat assembly, defined by the further throat section, is provided at anticipated or planned ground surface level. On cementing the throat assembly, the cementitious (or like) material may be poured up to a level not higher than the opening and is typically poured up to the level of the opening.

The step of laying the slotted drain may comprise laying a first drain section in the trench; laying a second drain section in the trench; coupling the second drain section to an end of the first drain section; and then coupling at least one further drain section to the second section. Additional drain sections may be added as required to form a slotted drain of desired length. The heights and inclinations of the throat assemblies of the drain sections located in the trench may be adjusted (if required) and fixed prior to coupling of a further drain section thereto; or all of the drain sections may be laid and coupled together prior to adjustment (if required) and fixing of the heights of the throat assemblies of the drain sections.

Reference is made herein to the inclination of the throat assembly relative to the drain pipe. It will be understood that there will typically be a fall in the height of the drain pipe from one end to the other, to provide a natural flow along the pipe, as described above. Thus the drain pipe will be inclined relative to the ground surface level. However, it is generally desired to provide an upper opening of the throat assembly at ground surface level. Accordingly, the further throat section (defining the upper opening) will typically be at a non-parallel angle (and thus inclined) relative to the drain pipe. However, in certain circumstances, such as where there is a natural or planned slope at ground level, the further throat may be parallel to the drain pipe and thus there may be zero inclination of the further throat relative to the drain pipe. Thus setting the inclination of the throat assembly may involve setting the further throat section such that the upper opening is parallel to the drain pipe (or to a main axis of the pipe).

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1, there is a perspective view of a slotted drain in accordance with an embodiment of the present invention; Figures 2, 3 and 4 are side, end and plan views, respectively, of the drain shown in Figure 1 ;

Figures 5 and 6 are schematic cross-sectional views of the drain of Figure 1 illustrating steps in a method of installing the drain;

Figure 7 is an enlarged view of part of the drain shown in Figure 1, illustrating the connection between a throat assembly and a drain pipe 12 of the drain;

Figure 8 is a view of a plate forming part of an outer throat of the throat assembly, drawn to a different scale from that shown in Figure 1 ;

Figure 9 is a view of a plate forming part of an inner throat of the throat assembly, drawn to a different scale from that shown in Figure 1;

Figure 10 is a perspective view a spacer for inner plates of the inner throat, again drawn to a different scale from Figure 1 ;

Figures 1 1 and 12 are enlarged perspective views of a clamping assembly of the drain shown in Figure 1 , shown in release and clamping positions, respectively;

Figures 13 and 14 are enlarged plan views of the clamping assembly, shown in the release and clamping positions, respectively;

Figure 15 is a perspective view of part of a slotted drain in accordance with an alternative embodiment of the present invention;

Figure 16 is a view of a throat assembly of a drain in accordance with a further alternative embodiment of the present invention, the throat assembly shown sectioned in a direction perpendicular to a main axis of the assembly;

Figure 17 is an external view of the throat assembly shown in Figure 16, illustrating a ratchet strip and ratchet element forming part of a securing assembly of the drain in more detail; Figure 18 is a view of a throat assembly of a drain in accordance with a further alternative embodiment of the present invention, the throat assembly shown sectioned in a direction perpendicular to a main axis of the assembly; and

Figure 19 is an internal view of the throat assembly shown in Figure 18, illustrating a ratchet strip forming part of a securing assembly of the drain in more detail.

Turning firstly to Figure 1 , there is shown a perspective view of a slotted drain in accordance with an embodiment of the present invention, the slotted drain indicated generally by reference numeral 10. The drain 10 is also shown in the side, end and plan views, respectively, of Figures 2, 3 and 4. The slotted drain 10 has a particular utility in collecting and draining water from large, hard-surfaced areas such as car parks, roads and airport runways.

The drain 10 generally comprises an elongate drain pipe 12 which has a drainage slot 14 (Figures 1 and 3) extending in a direction along a length of the pipe. The drain 10 also comprises an adjustable height throat assembly, indicated generally by reference numeral 16, and which is coupled to the drain pipe 12. The throat assembly 16 provides access for fluid into the drain pipe 12 through the slot 14. and comprises a first throat section in the foπn of an outer throat section 18 and at least one further throat section in the form of a second, inner throat section 20. The inner throat section 20 is movably mounted relative to the outer throat section 18, to facilitate adjustment of a height and angular inclination of the throat assembly 16 relative to the drain pipe 12. The drain 10 also comprises at least one securing arrangement, and in the illustrated embodiment includes three securing arrangements 22. for releasably securing the outer and inner throat sections 18. 20 together so that the height and angular inclination of the throat assembly 16 relatix e to the drain pipe 12 can be fixed. In the illustrated embodiment, the securing arrangements 22 take the form of clamping assemblies which will be shown and described in more detail below.

Typically, the slotted drain 10 will be provided in 3 metre lengths with four clamping assemblies 22 (only three shown) per three metre lengths. A number of lengths or sections of the drain 10 will be coupled together end-to-end to foπn a dram of desired length. It will be understood that the drains 10 may be provided in alternative lengths, depending upon particular circumstances including transportation restrictions, design restrictions and/or particular use requirements.

Referring now to Figures 5 and 6, there are shown steps in a method of installing the slotted drain 10. Firstly, a trench 24 is excavated in the ground and a layer of hardcore/concrete 26 is laid in a base 28 of the trench. The hardcore/concrete 26 is carefully laid so as to provide a desired fall along a length of the trench 24. A number of the slotted drains 10 are then located within the trench, feet 30 of the drain resting on the hardcore/concrete 26, and are coupled together end-to-end to form a pipe of desired length, but only the first slotted drain 10 is shown in the Figures. A first layer of concrete 32 is then poured into the trench 24 and, when set, provides a secure foundation and locates the drain pipes 12 within the trench. The progressive fall along the length of the trench 24 ensures that a corresponding fall is provided in the drain pipe 12, so that water entering the pipe will flow along a length of the pipe to a discharge location (not shown), which may be into a sewer or holding tank.

The adjustable throat 16 of the first drain 10 is then adjusted to set a height and inclination relative to the drain pipe 12. This is achieved by raising the inner throat section 20 relative to the outer throat section 18. The throat assembly 16 is shown following such adjustment in Figure 6. The clamping assemblies 22 are then operated to clamp the outer and inner throat sections 18, 20 together and thus to fix the position of the inner throat section relative to the outer throat section. This holds the inner throat section 20 at the height/inclination which has been selected until such time as it can be cemented in place. The height of the throat assembly 16 is then carefully checked to ensure that an upper opening 34 of the inner throat section 20 is provided at final ground surface level 36 (Figure 6). Any errors which are discovered can be corrected by releasing the clamping assemblies 22 and repositioning the inner throat section 20 before rechecking the height/inclination.

The throat assemblies of the remaining drains are then adjusted in a similar fashion, progressively along the length of the pipe. Following checking, reinforcing bars 38 are located extending through the clamping assemblies 22 and a second layer of concrete 40 is then poured into the trench 24 up to finished surface level 46, to secure the inner throat section 20 relative to the outer throat section 18, and thus to set the throat assembly 16 in the position shown in Figure 6. The concrete 40 will come up to and abut lips 114 of the inner throat 20, and will sit underneath and support the lips. This will assist in reducing 'spalling' of the concrete (or indeed any alternative surface finishing material), which may occur under heavy loading such as may occur in, for instance, an airport runway. Rainwater falling on the finished surface 46 will flow into the inner throat section upper opening 34, down through the inner and outer throat sections 20 and 18, through the slot 14 and into the drain pipe 12 for passage to the sewer/holding tank.

The structure and method of operation of the slotted drain 10 will now be described in more detail.

The drain pipe 12 is a reinforced structured wall pipe with a smooth internal bore 48. The connection between the throat assembly 16 and the drain pipe 12 is best shown in the enlarged view of Figure 7, which illustrates part of an end 52 of the drain 10. The outer throat section 18 of the throat assembly 16 is connected to the drain pipe 12 and comprises two spaced elongate plates 54a and 54b. The plate 54a is also shown in the view of Figure 8, drawn to a different scale from that shown in Figure 1. It will be understood that the plates 54a and 54b are of similar construction, save that lips 56a, 56b of the respective plates (which serve for connecting the outer throat section 18 to the drain pipe 12) extend in opposite directions. Outer throat section spacers 58 (Figure 3) are provided at intervals along a length of the outer throat section, and serve for spacing and securing the plates 54a, 54b together by means of rivets which pass through apertures 60 (only those for the plates 54a are shown in the Figures). Other fixing methods may be employed. For example, the inner throat 20 may slidably engage the outer throat 18 by means of suitable cooperating engaging elements (not shown - for example a tongue-and-groove arrangement) on each of the throat sections. The inner throat 20 may be detachable from the outer throat 18. Rivets are similarly used for securing the plates 54a, 54b to the drain pipe 12, the rivets passing down through a wall 62 of the drain pipe 12 and the lips 56a, 56b of the plates 54a, 54b. The inner throat section 20 is similarly made up from two spaced elongate plates 64a, 64b. The plate 64a is shown in more detail in Figure 9, again drawn to a different scale from Figure 1. In the illustrated embodiment, two different types of spacers 66 and 68 are provided for coupling the inner throat section plates 64a, 64b together, and are spaced alternately along a length of the throat section. One of the spacers 68 is shown also in the perspective view of Figure 10, again drawn to a different scale from Figure 1. The spacers 66 and 68 engage in slots 70 in the plates 64a and 64b and each include tabs 72 which protrude from the slots 70 and which are bent over so as to retain the plates 64a, 64b in engagement. In addition however, the spacers 66 include reinforcing bar support arms 76 through which reinforcing bars (not shown) pass, to provide reinforcement within the concrete layer 40. In less heavy-duty applications, the spacers 66 including the support arms 76 (and the associated reinforcing bars) may be dispensed with, and only the spacers 68 used.

As best shown in Figure 7, the inner throat section 20 is dimensioned such that it fits within the outer throat section 18, and such that it can slide up and down within and relative to the outer throat section 18. In this way, the height and inclination of the inner throat section (and thus of the throat assembly 16), relative to the drain pipe 12, can be adjusted and set to desired levels. Slots 69 (Figure 9) may be provided in a lower part of the inner throat 20 enabling it to pass over the spacers 58. Additionally, the portion of the inner throat section 20 which protrudes from the top of the outer throat section 18 tapers in cross-section towards the upper opening 34. This helps to ensure that any solids entering the opening 34 do not block the inner throat section 20. as the throat effectively increases in width from the top down.

The clamping assembly 22 will now be described, with reference to the enlarged perspective views of Figures 1 1 and 12, and the plan views of Figures 13 and 14. Figures 1 1 and 13 show the clamping assemblies 22 in a release position, whilst Figures 12 and 14 show the clamping assembly in a clamping position. It will be understood that each clamping assembly 22 is of the same structure, and operates in a similar fashion to that shown in Figures 1 1 to 14. The clamping assembly 22 comprises a rod 78 which extends through the outer and inner throat sections 18, 20. To facilitate this, inclined slots 80a, 80b are provided in the corresponding plates 54a, 54b. Similar, horizontal slots 82a, 82b, (parallel to a main axis of the drain pipe 12) are provided in the inner throat plates 64a, 64b. A retainer 84 is provided on the rod 78, and comprises a first, locking nut 86 and a second, abutment nut 88 which carries a number of teeth 90. The first nut 86 serves for locating the second nut 88 in a desired position on the rod 78, which is threaded (not shown) to permit adjustment. A lever 91 is provided at an end 92 of the rod 78, and is shaped to define an abutment surface 94. A collar 96 is mounted on the rod 78, and carries teeth 98 similar to the teeth 90 on the nut 88. The lever 91 pivots about a pin 100 on the rod 78 between the release and clamping positions. The lever 91 is shaped such that a distance A between the abutment surface 94 and a centre of the pin 100 when the lever is in the release position (Figure 13) is less than a distance B between the abutment surface 94 and the centre of the pin 100 when the lever 91 is in the clamping position (Figure 14). A throat support element in the form of a cylindrical tube 102 is movably mounted on the rod 78, and defines abutment surfaces 104, 106 at opposite ends thereof each of which includes teeth similar to those on the collar 96.

In use, and when the lever 91 is moved from the release to the clamping position, the lever draws the rod 78 through the tube 102, thereby shortening a distance between the nut 88 and the collar 96. This movement securely clamps the outer and inner throat sections 18, 20 together. Specifically, the plate 54a of outer throat section 18 and plate 64a of inner throat section 20, which are located between the collar 96 and the surface 104, are securely clamped together and the teeth on the collar 96 and on the surface 104 bite into the (typically galvanised steel) platen to provide a secure engagement. In a similar fashion, the plates 54b and 64b are clamped between the nut 88 and the surface 106, the teeth 90 on the nut 88 and on the surface 106 biting into the plates to provide a secure engagement. The clamping arrangements 22 therefore each clamp the outer and inner throat sections 18. 20. as shown in Figure 6.

Additionally, the shape of the lever 91 is such that the reinforcing bar 38 may be easily located extending along apertures 108 defined by the lex ers. Typically an operator will adjust the height of the throat assembly 16 as follows. Initially, all of the clamping assemblies 22 will be in their release positions of Figures 1 1 and 13. The inner throat section 20 will then be freely moveably within and relative to the outer throat section 18 within the constraints of the inclined slots 80a, 80b. Specifically, the clamping assembly rods 78 will abut ends 110, 112 (Figure 7) of the slots 80a, 80b to thereby restrict the extent of movement. Initially therefore, the self-weight of the inner throat section 20 will be such that the clamping assembly rods 78 reside towards a lower end 1 12 of the slots 80a, 80b. The inner throat section 20 will then be raised to the approximate ground surface level 36, and a first one of the clamping assemblies 22 moved to the clamping position by rotating the lever 91 to the position of Figures 12 and 14. This will typically be the clamping assembly provided at one of the ends of the drain 10, for example the end 52 (Figure 1). The operator will then move to the opposite end of the drain 10, and will raise the other end of the inner throat section 20, fixing this using the clamping assembly 22 adjacent this other end. The operator will then check the height and inclination to ensure that this is correct and corresponds to the planned, finished ground level 36, making any adjustments as necessary by releasing and reactivating the clamping assemblies 22. Once verified, the further clamping assembly 22 is activated, and the reinforcing bar 38 then located through the lever apertures 108 on each side of the throat assembly 16.

Further, similar slotted drain sections are then provided in the trench 24, coupled together end-to-end by means of a spigot joiner profile (not shown) on the ends of the drains. It will be understood that, due to the progressively increasing fall along the length of the trench 24. the heights of the adjustable throat assemblies 16 will progressively increase along the length of the trench. Depending upon the desired fall and thus the required heights of the throat assemblies of the further drains, it may be necessary to provide the further drains with throat assemblies of greater height. Interlocking elements such as locking tabs (not shown) may be provided on the throat assemblies, for engaging with corresponding recesses or channels (not shown) on the throat assemblies of adjacent drains. The tabs will typically be releasable to permit for adjustment/ release. When all of the slotted drains 10 have been installed in the trench 24 and coupled together, and tied into a sewer system, final checks will be carried out and the trench 24 filled in and surface finishing carried out as described above with reference to Figures 5 and 6.

Turning now to Figure 15, there is shown a slotted drain 10' in accordance with an alternative embodiment of the present invention. Like components of the slotted drain 10' with the drain 10 of Figures 1 to 14 share the same reference numerals, with the addition of the suffix '.

The drain 10' is in fact of identical construction to the drain 10, save that an adjustable height throat assembly 16'of the drain 10' includes an alternative inner throat section 20'. The inner throat section 20' tapers towards an upper opening 34' in a similar fashion to the inner throat section 20. However, the drain 10' is designed for a less heavy-duty application than the drain 10, and is shaped differently in the region of the upper opening 34. Specifically, plates 64a ^" and 64b' of the inner throat section 20' are bent inwardly at the upper end, rather than outwardly as is the case with the throat section 20. This may provide a different surface finish. Specifically, a finishing, wearing course of asphalt (tarmacadam) - not shown - of around 30 to 50mm depth may be laid up to the desired ground surface level 36. Alternatively concrete may be provided to surface level, or other wearing courses such as block paving may be utilised.

Turning now to Figure 16, there is shown part of a slotted drain 10" in accordance with a further alternative embodiment of the present invention. Like components of the slotted drain 10" with the drain 10 of Figures 1 to 14 share the same reference numerals, with the addition of the suffix ^" . The slotted drain 10 ^" is in fact of similar construction to the drain 10, save that the drain 10 ^" includes alternative securing arrangements to the clamping assemblies 22. Only the alternative securing arrangements 22" are shown and described herein in detail.

Figure 16 is a view of a throat assembly 16 ^{" "} of the drain 10 ^{" "} , which has been sectioned in a direction perpendicular to a main axis of the throat assembly. Inner and outer throat sections 18" and 20 ^{" "} are shown. The securing arrangement 22 ^" " facilitates positioning of the inner throat section 20" relative to the outer throat section 18" in one of a number of discrete positions. The securing arrangement 22" comprises a ratchet assembly having ratchet strips 116a, 116b provided respectively on plates 54a, 54b of the outer throat section 18" and which define a plurality of detents 1 18a, 1 18b. The detents 118a, 118b are provided as apertures in the respective plates 54a, 54b. Resilient ratchet elements in the form of tabs 120a, 120b are provided on plates 64a, 64b of the inner throat section 20" and engage in a selected one of the corresponding detents 118a, 118b for restricting movement of the inner throat section 20" relative to the outer throat section 18". The ratchet strip 116a and tab 120a are illustrated in more detail in the external view of the throat assembly shown in Figure 17. The tabs 120a, 120b are deflected inwardly as the inner throat section 20" is raised relative to the outer throat section 18" to engage in a higher detent. The tabs 120a, 120b are shaped to resist return movement of the inner throat section 20" back down relative to the outer throat section 18" and thus retain a selected position of the inner throat. If required, the tabs 120a, 120b can be pushed back in using a screwdriver or similar tool, to facilitate downward movement of the inner throat section 20". A number of the ratchet strips 116a, 116b and corresponding tabs 120a, 120b will typically be provided, spaced along a length of the throat assembly 16" in a similar fashion to the clamping assemblies 22.

Figure 18 shows part of a slotted drain 10"' in accordance with a further alternative embodiment of the present invention. Like components of the slotted drain 10"' with the drain 10 of Figures 1 to 14 share the same reference numerals, with the addition of the suffix " ^" . The slotted drain 10'" is in fact of similar construction to the drain 10", save that the drain 10" ^' includes alternative ratchet-type securing arrangements 22'" having ratchet strips 1 16a"' and 1 16b'". The ratchet strips 1 16a'" and 1 16b ^{" " "} comprise a larger number of teeth and define a greater number of detent positions for tabs 120a'" and 120b'". The ratchet strip 116a'" is illustrated in more detail in the internal view of the throat assembly shown in Figure 19.

The present invention offers numerous advantages over prior drains. For example, the securing arrangement, which in at least one embodiment may be considered to be a 'slide-lock/release' type mechanism, may offers repeated opportunities to set and adjust the height/angle of the inner/upper throat section, either at a later stage during construction, or even after the system has been in use for some time. Also, the drain can be quickly and easily set to the required height thus offering advantages in speed of construction of a drainage system incorporating the drain.

Other benefits include the ability to set the drainage channel (drain pipe) to correct line and level, but to then allow the top throat section to be dropped during other phases of construction and then raised immediately prior to surfacing, thus providing valuable protection and prevention of damage to the top edge of the channel during construction activities on site. Also, the drain provides the ability to re-set the height of the upper throat section in the event of a mistake being made in respect of the height of the channel drain (drain pipe) or the surrounding surface levels. Furthermore, the drain offers advantages in terms of the ease and speed of setting and subsequently re- adjusting the height/angle of the upper throat section. Additionally, the drain offers an ability for contractors to return to the location in subsequent years to carry out re-surfacing of the surrounding area whilst retaining the existing channel drain system. For example, the 'slide-lock/release' mechanism may allow the contractor to release the upper throat section and re-set it to the height/angle of the resurfaced finished level. This may require the inclusion of a specific cover/casing over the securing arrangement (for example, over the release lex ers of the clamping assemblies) to keep it clean and enable it to be accessed and operated at a future point in time. Additionally and as shown in the accompanying drawings, the drain may incorporate an inner/upper throat section that may be trapezoidal and a lower portion that may be straight (parallel sides), thus providing the benefits of a trapezoidal shape at the top (that will allow debris to fall into the channel w ithout getting stuck in the throat), whilst still enabling sufficient variation in height via the lower straight portion (where the securing arrangements are provided).

Various modifications may be made to the foregoing without departing from the spirit and scope of the present invention.

For example, the first throat section may be an inner throat section and said first section slot may be disposed horizontally/parallel to a mam axis of the first throat section. The further throat section may be an outer throat section and said further section slot may be inclined with respect to a main axis of the further throat section. Where the drain comprises a securing arrangement in the form of a clamping assembly, the clamping assembly may comprise a further lever defining the restraint, and levers may be provided on both ends of the rod.

The throat assembly may comprise the first throat section, a second throat section movably mounted relative to the first throat section, and a third throat section movably mounted relative to the second throat section.

The heights and inclinations of the throat assembly of a drain section located in a trench may be adjusted (if required) and fixed prior to coupling of a further drain section thereto; or all of the drain sections may be laid and coupled together prior to adjustment (if required) and fixing of the heights of the throat assemblies of the drain sections.