BACKGROUND OF THE INVENTION Shutters are commonly used in the construction industry for forming concrete structures. Concrete channels are formed at the base of manholes to carry the flow of liquids from one or more inlet pipes to one or more outlet pipes. Such channels must comply with building regulation specification.

The current practice is to construct wooden shuttering for each individual manhole channel. This is an expensive practice with regard to both materials and time.

Our co-pending patent application GB2300663 describes a method for forming a concrete channel between two or more pipe ends in a manhole base. The method comprising the steps: (i) interconnecting said pipe ends by at least one pre-formed channel- section shutter; (ii) locating further pre-formed shutters on said channel-section shutters upwardly to extend the shuttering between said pipe ends ; (iii) applying concrete around the assembled shutters; and (iv) allowing said concrete at least partially to set and removing the pre- formed shutters.

The pipe ends may be of different diameters. The pre-formed shutters include at least two channel-section shutters of different dimensions to correspond to respective pipe end diameters.

The pre-formed shutters may include at least two channel-section shutters and at least one further curved shutter having relatively inclined transverse ends. Such shutters allow the assembled shuttering to extend between two non-aligned pipe ends.

The shutters may be made of any suitable material, for example, plastic or glass- reinforced plastic.

STATEMENTS OF INVENTION The above-mentioned method, as disclosed in GB2300663, makes use of lower and upper pre-formed shutters. Using such pre-formed shutters, a shuttering assembly can be easily installed. However, this shuttering assembly can be difficult to remove once the concrete has been introduced and allowed at least partially to set.

The present invention provides a method for forming a concrete channel between two or more pipe ends in a manhole base, the method comprising the steps: (i) interconnecting said pipe ends by means of at least three pre-formed channel- section shutters, one of said shutters extending into one of said pipe ends and another of said shutters extending into the other of said pipe ends; (ii) extending upwardly by means of opposed, pre-formed side shutters the or each channel-section shutter located between those channel-section shutters which extend into the pipe ends, said side shutters being mounted on the channel-section shutters so as laterally to overhang said channel-section shutters; (iii) extending upwardly those channel section shutters which extend into the pipe ends by means of in situ formed side shutters. said side shutters also being mounted on the channel-section shutters so as laterally to overhang said channel-section shutters;

(iv) applying concrete around the assembled shutters; and (v) allowing said concrete at least partially to set and removing the pre-formed and in situ formed side shutters.

By using a combination of lower channel-section shutters and upper side shutters which extend laterally beyond the lateral extension of the pre-formed channel-section shutters, easy removal of the shuttering is ensured. The side shutters can be individually removed and the channel-section shutters can be easily be pulled upwardly out of the channel formed by the concrete without becoming stuck between the sides of the concrete, due to the greater width of the concrete channel formed around the side shutters.

Preferably, the in situ formed side shutters are mounted on the channel-section shutters only outside the pipe, thereby filling the gaps between the pipe end and the side shutters which extend over the next adjacent channel-section shutter. Panels may be cut to a length sufficient to fill the gaps and these panels are preferably mounted on support elements which are connected to the shutters which define the gap. More preferably, each support element is in the form of a right-angle bracket which is attached to the upper surface of the channel-section shutters which extend into the pipe ends and to the vertical edge of the next adjacent side shutter.

Such an arrangement gives great flexibility in that the panels can be cut to size to suit the requirements and, in particular, the extent to which the channel-section shutters extend out of the pipe end.

In addition, the present invention provides a kit for use in forming a concrete channel between two or more pipe ends, the kit comprising at least three pre-formed channel- section shutters, a pair or pairs of pre-formed side shutters, the or each pair for use with a respective pre-formed channel-section shutter apart from two such shutters intended for insertion into the pipe ends and means for forming in situ side shutters for use with said two pre-formed channel-section shutters.

The present invention allows smooth channels to be created in concrete by using a combination of pre-formed shutters and side shutters, both pre-formed and in situ formed. The pre-formed shutters may be of different sizes and may be re-used.

The lower pre-formed shutters are of generally channel-section and are referred to hereinafter as boat shutters. These boat shutters form the curved cross-section of the channel and the shutters sit on top of the boat shutters and form the sides of the channel. The shutters may be secured releasably to each other, for instance, by being bolted together or by the use of pin wedges. Each boat shutter may include a pipe extending longitudinally therethrough to carry any existing liquid flow between the inlet and outlet pipes.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings, in which:- Figure 1 shows an arrangement of shutters forming part of an assembly to interconnect the two pipe ends; Figure 2 shows part of another arrangement for interconnecting two pipe ends of different diameters; Figure 3 illustrates upper and lower shuttering for use with the method of the present invention; Figure 4 shows another example of upper and lower shutters for use with a method of the present invention; Figure 5 shows a more complete arrangement of upper and lower shuttering for use with a method in accordance with the present invention; and Figure 6 shows components for a further shuttering assembly of use in the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1 of the accompanying drawings, there is illustrated an arrangement, comprising two boat shutters 1 and 3 and two items of side or wall shuttering 5 and 7 which serve to upwardly extend the boat shutter 3.

Boat shutter 1 includes end walls 9 and 11, each having a hole 13 located therein.

The end walls 9,11 are of substantially semi-circular shape and they are interconnected by semi-cylindrical wall 15. Extending radially inwardly from the upper longitudinal edges of wall 15 are flanges 17 and 19. Small holes 21 are provided in flanges 17,19 and the end wall 9 in order to allow this boat shutter 1 to be connected to other items of shuttering.

As will be seen in Figure 1, boat shutter 3 is generally of the same shape and structure as boat shutter 1 but in this case the shutter is curved, the"longitudinal" sides being curved and one longitudinal side being shorter than the opposite longitudinal side. As a result boat shutter 3 provides a bend in the shuttering. Wall shutters 5 and 7 are both curved and have lengths corresponding to the flanges 23 and 25 of boat shutter 3. Each of these wall shutters 5,7 includes a solid wall 27 and relatively shallow side walls 29 of a width substantially the same as that of flanges 23,25. The actual width of side walls 29 is slightly greater than that of flanges 23, 25 so providing an overhang of the wall shuttering 5,7 laterally beyond the boat shutter 3 to allow easy removal of the boat shutter 3 after the concreting has taken place. In another embodiment, the width of the side walls is essentially the same as that of the flanges, but the side walls are mounted in a slightly offset manner on the boat shutter to create the overhang.

As illustrated in Figure 1, boat shutter 1 will, in the method of the present invention, be inserted at least partly into the end 31 of a pipe which extends into a manhole base. Boat shutter 3 will be connected to boat shutter 1 by being bolted thereto or by the use of pin wedges. Wall shuttering 5.7 is secured to boat shutter 3 to extend the

shuttering upwardly. Further shuttering elements are provided in the method of the invention and examples of such elements and the method of installation will be described below with reference to other accompanying drawings.

Referring to Figure 2 of the accompanying drawings, there is illustrated two pipe ends 41,43 and, extending therebetween, three boat shutters 45,47,49. Boat shutters 45 and 49 are of different diameters to each other but in general are similar to the boat shutter 1 shown in Figure 1. Boat shutter 47 is a straight but tapered boat shutter and allows the shuttering to extend between boat shutters of different dimensions.

Referring to Figure 3 of the accompanying drawings, a boat shutter 51 is depicted which is similar to boat shutter 1 of Figure 1. In addition, Figure 3 illustrates the upper shuttering associated with this boat shutter in the case where it is to be used at least partially inserted within a pipe end, in other words, in the situation illustrated in Figure 1 with respect to boat shutter 1. Right angled bracket or L-bars 53,55 are secured to the flanges 57,59 of boat shutter 51. The horizontal arms of L-bars 53 and 55 extend along essentially the entire length of the flanges 57 and 59 and at least partially within the pipe end. To provide in situ shuttering above boat shutter 51 and outside the pipe end, timber boards 61 and 63 are cut to the appropriate length and then secured to the L-bars 53,55 in positions abutting against integral ribs 65,67 extending longitudinally from the horizontal and vertical arms of the L-bars.

Although the timber boards 61,63 are illustrated in Figure 3 extending along substantially the whole of the length of the horizontal arms of L-bars 53,55, it will be appreciated that, in practice, the timber boards 61,63 will be cut to a length significantly less than that of the horizontal arms of L-bars 53,55, the remainder of these L-bars extending within the pipe end. Timber boards 61,63 protrude laterally beyond the L-bars to provide the required overhangs.

Referring now to Figure 4 of the accompanying drawings, there is illustrated a boat shutter 71 with associated upper wall shuttering 73,75, the boat shutter 71 being a

curved boat shutter and the upper wall shuttering 73 and 75 both also being curved.

Also illustrated in this Figure is a bracing device 77 comprising a timber board 79, shaped to bridge the gap between wall shutters 73 and 75 at the upper ends thereof.

Attached to timber board 79 and downwardly extending therefrom are two bracing members 81,83 which are each of a length equal to the gap between wall shutters 73 and 75 and which prevent these wall shutters moving towards each other under the pressure of the concrete which is to be located about the shuttering.

Referring to Figure 5 of the accompanying drawings, there is illustrated an assembly of shuttering elements including straight boat shutters 91 and 93 and three curved boat shutters 95,97,99. These curved boat shutters provide bends of 45°, 22and 1 1 1/4° respectively. A narrow, solid element 101 bridges the small gap between boat shutter 93 and curved shutter 99. This narrow solid element is substantially of U- shape having a bight portion 101 corresponding to adjacent boat shutters and two upwardly extending arms 103 of a length corresponding to that of the wall shuttering to be located on the boat shutters. Although not clearly shown in Figure 5, the arms 103 extend laterally outwards of bight portion 101 to provide the required overhang.

Also illustrated in Figure 5 are curved wall shutters such as 105 which serve to upwardly extend the shuttering providing by curved boat shutters 95,97 and 99. The straight boat shutters 91 and 93 are for insertion in the pipe ends to be joined by the shuttering assembly. Located above these boat shutters are timber board panels 107 and 109 which are located on L-bars 111 and 113, the latter being in turn fixed to the boat shutters 91 and 93.

Referring to Figure 6 of the accompanying drawings, another shuttering assembly is illustrated. This includes straight boat shutters 121 and 123 and curved boat shutter 125. The latter boat shutter has fixed thereto upper wall shutters 127 and 129 and a bracing device 131. The straight boat shutters 121,123 are upwardly extended by means of L-bars 133 and timber board panels 135.

Within the pipe end, a jack may be located in order to stop floating or twisting of the shuttering relative to the pipe end. A horizontal beam or bar may be secured across the boat shutter within the pipe end by fixing it to each of the opposite upper flanges.

The jack may then be positioned between this horizontal beam and the inside upper surface of the pipe end.

The various boat shutters and wall shutters may be each made of a single piece of plastics material. However, other suitable materials may be used including, for instance, glass fibre formed on a metal frame.

Once all the shuttering has been fixed in place, all the shutter joints are covered with tape and the entire outer surface of the shuttering assembly is coated with release agent. The resultant assembly provides a rigid mould for a concrete channel between the inlet and outlet pipe. The concrete is poured around the assembled shuttering and is allowed at least partially to set. The shuttering is then removed in the reverse order to that of the assembly of the shuttering in order to leave a smooth channel joining the inlet and outlet pipes.