WO2005056930A1

WO2005056930A1 - Improvements in and relating to manholes

Info

Publication number: WO2005056930A1
Application number: PCT/GB2004/005177
Authority: WO
Inventors: John Lunt
Original assignee: John Lunt
Priority date: 2003-12-09
Filing date: 2004-12-09
Publication date: 2005-06-23
Also published as: GB2421972B; GB0328554D0; GB2421972A; EP1709253A1

Abstract

A manhole affording safe access to drain conduits and comprising a manhole chamber defined at least in part by peripheral walling and having at its lower end base walling accommodating flow channelling at least part of which is open into the chamber. The improvement comprising a landing area provided by staging separate from and spaced above the base walling. The preferred staging comprises a grating occupying the entire cross-section of the chamber and is supported from the peripheral walling. The preferred grating has at least one movable portion to facilitate access underneath the staging.

Description

Title: Improvements in and relating to manholes

DESCRIPTION The present invention relates to manholes. Manholes are used in drainage schemes for foul and surface water and provide a means of man access to the drains as well as a means of linking one or more drain conduits to another. Typically, they comprise pre-cast concrete (p.c.c.) rings that are available in many standard sizes, (for example 1200mm diameter, 1350, 1500, 1800, 2100 and so on) or they may be purpose built from masonry and/or concrete. The manhole has a chamber defined in part by a peripheral walling and has a base to the lower end that accommodates flow channelling at least part of which opens into the chamber. A suitable removable access lid is provided to close off the top of the chamber. Traditionally part of the base between the channelling is formed by concrete and is constructed to serve as a landing area for someone standing in the

manhole. For health and safety reasons there has to be a minimum safe landing area, which typically is of the order of 500mm x 500mm. This minimum safe landing area along with the size of the conduits running through the manhole determines the necessary size (horizontal cross-sectional area) of the manhole to be used. Frequently any given size of manhole may have the physical capacity to incorporate more flow conduits, but a larger size has to be used in order to provide the necessary safe landing area or alternatively a number of smaller manholes have to be provided to connect the desired number of flow conduits. Having to provide more manholes or larger manholes necessarily increases the cost of providing the infrastructure. Furthermore, when a development is being extended and more flow conduits have to be connected into an existing drainage system, it is often the case that whilst an existing manhole has the capacity to accept another flow conduit, doing so would result in the manhole failing to provide the necessary safe landing area. In such an instance, the existing manhole would have to be replaced with a larger one, at considerable expense, or an additional manhole provided. The present invention aims to provide a solution. Accordingly the present invention provides a manhole comprising a manhole chamber defined in part by peripheral walling and having at its lower end base walling accommodating flow channelling at least part of which is open into the chamber, and wherein a landing area is provided by staging separate from and spaced above the base walling. The staging conveniently comprises a grid like structure. It may be supported from the base walling or from supports fitted to the peripheral walling, or by a cross-section of said support options. The staging occupies at least part of the base area of the manhole; equal to the minimum safe landing area. More preferably it occupies the whole of the horizontal cross-sectional area of the manhole. Square, rectangular or circular staging is envisaged to mirror the usual shape of manholes. The staging is conveniently movably located either entirely or at least in part. A preferred construction comprises a combination of fixed and movable grating

means. Preferably the movable grating means is mounted for hinged movement between a lowered support position, and a raised position affording access underneath the staging. The present invention will now be described further hereinafter, by way of example only, with reference to the accompanying drawings; in which:- Figure 1 is a horizontal sectional plan view of a manhole looking toward its base walling according to the prior art, Figure 2 is a horizontal sectional plan view of a first embodiment of manhole according to the invention, Figure 3 is a partial section on AA of figure 2, and Figure 4 is a horizontal sectional plan view of a second embodiment of manhole-according to the invention. Figure 1, illustrates the base of a manhole construction (for the case of a Y conduit configuration) according to current practice and which provides an acceptable safe landing area as denoted by the area 1 outlined by dotted lines. The illustrated manhole is formed from concrete rings 3 stacked one upon the other to the required height. Benching areas 7a, 7b and 7c between the flow conduits 5 are fonτted by concrete and extend above the flow conduits 5 and slope down at between 1 in 10 and 1 in 30 to the flow conduits. The benching provides the landing

area in the illustrated construction. However, it will be seen that whilst there is space for introducing more flow conduits, no conduits could be in introduced in the safe landing area. According to the invention the safe landing area is provided by staging that is separate from and spaced above the base walling.- Accordingly all of the area of the base walling can be used for flow conduits. Figure 2 illustrates a first embodiment of the invention applied to a manhole made from p.c.c. rings 8 and in which the staging occupies the whole of the horizontal cross-sectional area of the manhole chamber.^' In this embodiment the staging comprises a metal ring 10 dimensioned to fit within the cross-section of the rings 8 and includes cross-bars 12 and 14a, 14b, cross-bar 12 intersects cross-bars 14a, 14b at 90° in the illustrated embodiment. The ring 10 is supported on support brackets 16 that are conveniently secured tlirough lifting holes provided in the wall of the p.c.c. ring. The brackets 16 are disposed at spaced positions around the internal periphery of the p.c.c. ring. The area between the ring and the respective cross-bars 14a, 14b define fixed sections 18a, 18b that are covered with an open mesh grating, whilst the space between the cross-bars 14a, 14b is occupied by two manhole gratings 28a,28b having their own peripheral framework which engage hingedly with the cross-bar 12. They are arranged to pivot upwardly and conveniently each is provided with a liftmg eye bracket 22 to receive a hook 24 of a steel wire lifting rope 26 - see figure 3 for a diagrammatic representation. The ring and/or the cross-bars and/or support lugs attached to the p.c.c. ring act as stops to hold the movable gratings in- the horizontal position when not held up for access below the staging.

Figure 2 shows a simple straight-through flow conduit arrangement 25. On the other hand figure 4 shows a more complex herring bone pattern flow conduit arrangement having 5 inlet channels 25' and one outlet 25" to illustrate how the full conduit capacity of a given section of p.c.c. ring can be utilised when constructed according to the present invention. In this embodiment the staging comprises a central diametrical bridge section 30 defined by rails 32,33,34 forming a fixed platform and covered with a grating (not illustrated), an intersecting cross-bar 36, and four hinged flaps 38,40,42,44. A peripheral ring 46 is also provided in the same manner as the previous embodiment and arranged to be supported by support brackets (not illustrated) in the same manner as illustrated with reference to figure 3. Hinges from the respective flaps are shown at 48 co-operating with the rails 32,34 as the case may be. Again lifting lugs 22' are provided to enable the flaps to be lifted individually or simultaneously. Again the flaps are covered with a grating material. It will be appreciated that the configuration of the staging may take any convenient fonri and is not limited to the two illustrated embodiments. Preferably the staging is fabricated from steel and galvanised. The provision of the staging is a considerable safety benefit, and especially so where it extends across the whole of the cross-sectional area of the manhole. Not only does the staging have the advantage of providing the necessary safe landing area, it can also act to prevent discharge upwardly of some solid sewer contents in the event of sewer surcharging, by virtue of the fact that the grating acts as a sieve for large solids.

Claims

CLAIMS 1. A manhole comprising a manhole chamber defined at least in part by peripheral walling and having at its lower end base walling accommodating flow channelling at least part of which is open into the chamber, and wherein a landing area is provided by staging separate from and spaced above the base walling.

2. A manhole as claimed in claim 1 in which the staging comprises a grid like structure.

3. A manhole as claimed in claim 1 or 2 in which the staging occupies at least part of the base area of the manhole.

4. A manhole as claimed in claim 1, 2 or 3 in which the staging occupies the whole of the horizontal cross-sectional area of the manhole.

5. A manhole as claimed in any one of claims 1 to 4 in which the staging is movably located either entirely or at least in part.

6. A manhole as claimed in any one of claims 1 to 4 and comprising a combination of fixed and movable gratmg means.

7. A manhole as claimed in claim 6 in which the manhole grating means is mounted for hinged movement between a lowered support position, and a raised position affording access underneath the staging.

8. A manhole as claimed in any one of the preceding claims in which the staging is supported from the base walling or from the peripheral walling or from a combination of such options.

9. A manhole as claimed in claim 6 and comprising a plurality of movable gratmg means.