WO1993019258A1

WO1993019258A1 - Manholes and inspection chambers

Info

Publication number: WO1993019258A1
Application number: PCT/GB1993/000554
Authority: WO
Inventors: Christopher John Cawte
Original assignee: Caswick Ltd
Current assignee: Caswick Ltd
Priority date: 1992-03-19
Filing date: 1993-03-18
Publication date: 1993-09-30
Anticipated expiration: 1994-09-19
Also published as: GB2279373B; AU3760193A; GB9206034D0; GB2279373A; GB9418094D0

Abstract

A modular system forming an inspection chamber or manhole for a drainage system comprises a base portion (1), an insert portion (5) adapted to lie at least partly upon said base and having one or more drainage channels fabricated within it, a plurality of support segments (15) of desired arc lengths, the insert portion being supported at its edges between the top of the support segments and a stack of shaft rings (11), wherein each piece is preformed and the structure is adapted to be assembled in situ and to be connected to the ends of drainage pipes.

Description

MANHOLES AND INSPECTION CHAMBERS

This invention relates to manholes and inspection chambers. In particular, it relates to the base portions thereof. In all underground drainage systems, it is important that access points be provided for inspection, clearage of blockages and maintenance. This access is generally provided by manholes or inspection chambers which are accessible from a roadway or other surface. Traditionally, these have been constructed in situ of brick or concrete. More recently, in the UK, plastics have been used for small diameter shafts of up to about 450 mm and shallow depths of less than about 1 m. Where man entry is required the minimum shaft diameter is about 900 mm and it is usual to use precast concrete sections to form the sides of the chamber. The manhole bases are, however, made in situ. This takes time and labour and the quality is dependent upon the skill of the workers and site conditions. According to the present invention there is provided an inspection chamber or manhole for a drainage system, comprising a base portion, an insert portion adapted to lie at least partly upon said base and having one or more drainage channels fabricated within it, a plurality of support segments of desired arc lengths, the insert portion being supported at its edges between the top of the support, segments and a stack of shaft rings, wherein each piece is preformed and the structure is adapted to be assembled in situ and to be connected to the ends of drainage pipes.

The drainage pipes may.be installed at the same time as the chamber or manhole. Alternatively, the chamber or manhole may be a replacement for an older installation, in which case it may be connected to drainage pipes which already exist in situ. In some embodiments one or more or indeed all of the support segments may be integral with the base.

The insert portion may be in more than one piece. According to the present invention, in a second aspect, there is provided a kit of parts for an inspection chamber or manhole for a drainage system, comprising a base portion, an insert portion adapted to lie at least partly upon said base and having one or more drainage channels fabricated within it, a plurality of support segments of desired arc lengths, the insert portion being supported at its edges between the top of the support segments and a stack of shaft rings, wherein each piece is performed and the structure is adapted to be assembled in situ and to be connected to the ends of drainage pipes.

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

Figure 1 shows schematically a plan view of a first embodiment of a manhole;

Figure 2 shows a cross-section through X-X; Figure 3 shows schematically a partly cutaway plan view of an alternative embodiment of a manhole; and Figure 4 shows a cross-section through Y-Y. Referring to the figures, a manhole is assembled from pre-formed components in.situ.

The invention is equally applicable to manholes or any other type of inspection chamber. A manhole is described below. The manhole comprises a base l, which is usually circular but may be shaped otherwise, eg rectangular, square or octagonal, and which may be reinforced by a steel mesh 14. The base may be flat. The mesh provides additional strength to the base. Lifting eyes 3 may be included in the upper surface of base 1. In the example shown, the eyes are set in a recessed portion la of the base. The slab may contain one or more channels 2 for locating an insert portion 5. The insert 5 forms, in situ, the base portion of the manhole and extends to partially or completely cover the top surface of base 1. Insert 5 will therefore generally be of approximately the same geometric shape as the base. Insert portion 5 is preferably moulded of a plastics material, in one example this may be a polyolefin. Alternatively, it may be of metal, ceramics, glass, glass reinforced plastics or any other material. Portion 5 contains the drainage channels for the device and is formed with the required benching, invert and soffits. In the appropriate terminology, the invert is generally defined as the level of the bottom of flow and the soffit as the top of the flow level. The benching is the curvature or undulations which ensure that the flow travels in the correct direction and ensures that the detritus carried in the flow does not stick along its path. Along its circumferential edge, the base 1 includes a groove 4.

A plurality of circumferential generally arcuate segments 15 are spaced around the edge of base 1 in the manner shown by dashed lines in Figure 1. As shown, the segments extend up to the site of the channels formed in moulded piece 5 and are therefore of different arc lengths as shown. In practice, a large number of segments 15 of different arc lengths may be fabricated such that any combination may be selected "off the shelf" to suite any desired combination of drainage channels. Segments 15 include a similarly curved longitudinal protrusion or tongue 15a adapted to be received in groove 4 to locate the segments with respect to base l.

A further groove 15b is located on the top of each of the segments for receiving the edge of portion 5, which preferably but not necessarily, has a matched profile to that of the segments, and/or the bottom of the lowermost one of a plurality of shaft rings 11 which form the sides of the manhole. These rings may be made of concrete or of plastics for example. A spreader ring, of metal for example, may be included to facilitate an even distribution of loads upon the segments and base.

To install the manhole, after pipes 13 have been placed in position, opening into the region in which the manhole is to be situated, the base 1 is positioned at the bottom of a prepared hole. The plastic insert 5 is placed in position and the inlet and outlet pipes 6, 7 and 8 are checked for alignment. These should obviously register with the openings of pipes such as pipe 13. In the example shown in Figure 1, the flow is from left to right in the main pipe and the pipes 8 are branches flowing into the main pipe. In Figure 2, the bottommost level of branch 8 is seen to be at the same level as the bottom of branch 7. However, in certain embodiments it is preferred that the branch enters a main flow path a distance up from the bottom of the path.

The drainage channel pattern shown in the figures is by way of example only and many variations are possible.

The plastics insert 5 is then lifted a small amount to allow positioning of the segments 25 (although in some embodiments one or all of the segments may be integral with, and therefore, non-removable from, the base) . As described above, a range of segments in different arc lengths are different sizes is made to allow numerous combinations of base l and insert 5 to suit numerous drainage designs. The insert 5 is then located at the top of the segments 15. The inlet and outlet pipes 6, 7 and 8 are then connected to a structure by any convenient manner. The method used should preferably be one which is as watertight as possible, to avoid or reduce to a minimum any leakage. In the example shown, elastomeric sealing rings 13 located in sockets 12 are used. An alternative method is by welding. The jointing of the inlet and outlet pipes may be internally or externally depending upon base complexity and size for example. The shaft rings 11 are then placed concentrically on top of the plastics insert 5 and therefore locking it into the segments 15 by virtue of a matching joint profile 16 and 15b. Thus the edges of portion 5 and segments 15 are preferably of matching profile. It is desirable to make this area watertight by using an elastomeric seal or a sealing compound for example. The joint between the base and segments may also be watertight. As shown at 9, the surface of insert 5 is tapered towards the channels, to facilitate drainage into the channels. The edges of insert 5 may extend part way along the top surface of segments 15, into groove 15b for example, or may extend further, to the rear of the segments. They may even extend upwardly a distance up the outsides of rings 11. The precise structure may be varied widely but is preferably one which ensures that any fluid present on the inside of rings 11 is directed onto insert 5 and into the drainage channels. Insert 5 may be in several pieces. One example of an embodiment taking advantage of having the insert in several pieces is shown in Figures 3, 4 and 5. In this embodiment the insert comprises a central portion 31 (shown in Figure 5) and an outer adaptor ring portion 32. The body of central portion 31 may typically be of diameter 450 mm. In the embodiment shown, it has two 90° junctions. Other versions may have, for example, 45° junctions or other configurations. The central portion 31 includes the required benching, soffits and inverts and is provided with connectors 36 for connection to pipes 34. The method of connection can be any one which is substantially watertight. Portion 31 sits on a, substantially flat, base slab 33.

Adaptor ring 32 has an outside diameter equivalent to the normal diameter of the manhole or inspection chamber, eg 900 or 1200 mm. Its internal diameter is equal to the diameter of the central portion, typically 450 mm. The adaptor ring 32 is has a gentle slope, typically of 1 in 12 (8%) downwards from its perimeter so that water or other fluids can drain into the central portion and therefore into the connected drainage pipes. The central portion is also preferably gently sloped, at the same or a different angle towards the drainage channels fabricated within it, to ensure that fluids flow into the drainage channels. The adaptor ring is sealed by any suitable means to the centre portion and to the bottom chamber ring 38. Ring 12 may be of generally constant thickness, as shown in Figure 4. The embodiment shown has an inner flange 39 for sealing with the side wall of central part 31.

In the embodiment shown, eight support segments 35 are provided. These are shown in cross-section in Figure 4 and in dashed lines in Figure 3 where they are hidden by adaptor ring 32 which sits upon, and partially supported by, them. Two segments 35a and 35b are mounted side by side between adjacent pipes 34a and 34b, and this construction is repeated around the structure. As indicated by longitudinal cavity 40 the segments 35a may be hollow cored or otherwise be as lightweight as possible. Preferably, however, they are sufficiently strong to support adaptor ring 32 so that this can withstand the weight of a human standing on ring 32 who is inspecting or maintaining the open well formed by central portion 31. Typically, they might be expected to support a load equivalent to a 7 m head of water. Sealing and joints, where appropriate, are also preferably watertight to a pressure corresponding to this.

In this embodiment, the pipes extend into the interior of the chamber as shown and are connected to the central portion 31 at flanges 37, by o-rings and/or other sealing means. This embodiment may therefore be easier to assemble, and therefore preferable in some environments, than the embodiment of Figures 1 and 2.

In practice, a plurality of different centre pieces and adaptors may be made and/or purchased, of which a selected centre is matched with an appropriate base at the point of installation. Eg, different centres may have two inputs and two outputs at 90°, or two outputs at 45°, or two, five or any other selected number of inlets/ outlets at selected angles. Adaptor rings may be 450 mm to 1000 mm, 450 to 1200 mm or any other diameters. Where two of the inlets are at, say, 45° to one of the inlets, it may be necessary to have one segment portion 35 between the centraL inlet and each of the two inlets at 45°, and three segments between each of the 'angled' inlets and the outlet. The segments may, as in this embodiment, all be identical or may be of different sizes.

Claims

1. An inspection chamber or manhole for a drainage system, comprising a base portion, an insert portion adapted to lie at least partly upon said base and having one or more drainage channels fabricated within it, a plurality of support segments of desired arc lengths, the insert portion being at least partially supported at its edges between the top of the support segments and a stack of shaft rings, wherein each piece is preformed and the structure is adapted to be assembled in situ and to be connected to the ends of drainage pipes.

2. An inspection chamber or manhole as claimed in Claim 1, wherein at least one of the support segments is integral with the base.

3. An inspection chamber or manhole as claimed in

Claim^'l or Claim 2, wherein the insert portion comprises a plurality of pieces.

4. An inspection chamber or manhole as claimed in Claim 3, wherein the insert portion comprises a central portion to which the pipes are connected and having the drainage channels, and an adaptor ring between the periphery of the central portion and the perimeter of the manhole.

5. An inspection chamber or manhole as claimed in Claim 4, wherein, it situ, the adaptor ring lies above the pipes and is at least partially supported by one or more segments.

6. An inspection chamber or manhole as claimed in any preceding claim, wherein each support segment is generally fan-shaped.

7. An inspection chamber or manhole as claimed in any one of the preceding claims, wherein each support segment is shaped to extend along at least part of the space between adjacent drainage portions of the insert portion or between adjacent pipes.

8. An inspection chamber or manhole as claimed in any one of the preceding claims, wherein the support segments and base include complementary means for securing each segment to the base.

9. An inspection chamber or manhole wherein the complementary means comprises complementary protrusions and channels.

10. An inspection chamber or manhole as claimed in any one of the preceding claims, wherein the support segments each have a profile for receiving a corresponding profile on part of the insert and/or the lowermost shaft ring.

11. An inspection chamber or manhole as claimed in any one of.the preceding claims, including a spreader ring.

12. An inspection chamber or manhole as claimed in any one of the preceding claims, wherein the surface of the insert is sloped towards the drainage channels, to facilitate drainage into the channels.

13. An inspection chamber or manhole as claimed in any one of the preceding claims, wherein the edges of the insert extend to the external edge of the segments.

14. An inspection chamber or manhole as claimed in Claim 13, wherein the edges of the insert extend further a distance parallel to the external surfaces of the shaft ring or rings.

15. An inspection chamber or manhole as claimed in ' any one of the preceding claims including elastomeric sealing means positioned to seal the joint between the pipes and the drainage channels.

16. An inspection chamber or manhole as claimed in Claim 15 wherein the sealing means at each joint comprises a sealing ring located in a socket.

17. An inspection chamber or manhole as claimed in any one of the preceding claims further including sealing means at part of the edges of the insert and/or the support segments.

18. An inspection chamber or manhole as claimed in any preceding claim, wherein the insert is of plastics material.

19. An inspection chamber or manhole as claimed in any preceding claim wherein the shaft rings are of concrete or of a plastics material.

20. A kit of parts for an inspection chamber or manhole for a drainage system, comprising a base portion, an insert portion adapted to lie at least partly upon said base and having one or more drainage channels fabricated within it, a plurality of support segments of desired arc lengths, the insert portion being at least partially supported at its edges between the top of the support segments and a stack of shaft rings, wherein each piece is performed and the structure is adapted to be assembled in situ and to be connected to the ends of pre-existing drainage pipes.