GB2301610A

GB2301610A - Manhole arrangement

Info

Publication number: GB2301610A
Application number: GB9511064A
Authority: GB
Inventors: Barry Turner; David Henry Edmonds
Original assignee: C I S
Current assignee: C I S
Priority date: 1995-06-01
Filing date: 1995-06-01
Publication date: 1996-12-11
Anticipated expiration: 2015-06-01
Also published as: GB2301610B; GB9511064D0

Abstract

A manhole arrangement has a frame 10 for supporting a manhole cover 18. The latter has side walls 20 and a cover tray 22 and is preferably formed of mild steel. The cover is reinforced by elongate beams 26 applied to the underside of the cover tray 22, each of the beams 26 being preferably formed of ductile iron and being connected to a central annular beam 28. The latter has the maximum dimension in a direction downwardly of the tray 22 to provide the cover with the required load bearing characteristics. The materials used enable the cover to be relatively easily constructed to any required size, the reinforcing beams providing long-term corrosion resistance. In an alternative construction there are two sets of two beams at right angles to each other, Figs 4 and 5, which form a lattice work at the centre of the cover.

Description

Manhole Arrangements This invention relates to manhole/access hole arrangements and more particularly to covers therefor.

Existing manhole covers are usually manufactured from steel. It is advantageous to use steel, principally because it is normally possible with steel to relatively easily vary the size of the manhole cover for use on access holes of various sizes, by cutting, welding and galvanizing. New Standards require manhole covers to have such load bearing characteristics that, where covers are made from commercial grades of welding steel, an enormous level of reinforcement would be required, because steel has a long stress/strain curve, being subject to plastic deformation at relatively low stress levels. Such a level of reinforcement would generally cause steel covers to be uncompetitive compared with covers of iron.

According to the present invention there is provided apparatus for use as a manhole cover, the apparatus comprising a cover member for seating on a frame arrangement, and reinforcing means which is formed of a material having improved load bearing characteristics relative to the material of the cover member, and which is so positioned on the latter as to provide the apparatus with desired load bearing characteristics.

Preferably the reinforcing means comprises a plurality of elongate members connected to one face of the cover member, the elongate members being connected together towards a central area of the cover member and extending outwardly of the cover member in different directions from the central area. Preferably also the cover member has a substantially rectangular configuration and the reinforcing means comprises elongate members extending between the central area and respective side edges of the cover member, whereby to be able to seat on the frame arrangement. The length of the or each elongate member may be adjusted to the respective dimension of the cover member by cutting off a respective length from a free end section thereof before connecting the reinforcing means to the cover member.

The cover member is preferably formed primarily from steel, with the reinforcing means being formed of iron, preferably ductile iron.

The elongate members of the reinforcing means may be interconnected to define a structure which is connected to the central area of the cover member. The interconnecting structure may have the form of an annular reinforcing member, or may be defined by the elongate members being interconnected to define a lattice arrangement. The interconnecting structure preferably has a width greater than the width of the free end section of each elongate member, the width of each elongate member reducing gradually from the interconnecting structure to the respective end section.

Each elongate member of the reinforcing means may have a channel section with the upstanding channel sides connecting to said one face of the cover member.

Alternatively each of the elongate members may have a T section with the leg of the T connecting to said one face of the cover member.

The invention also provides a manhole arrangement comprising cover apparatus as described in any of the five preceding paragraphs, and a frame arrangement for connecting to a foundation.

Seating means may be provided on the frame arrangement at each location where a free end of a respective elongate member is arranged to seat on the frame arrangement.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a partial top perspective view of a manhole cover and frame arrangement; Fig. 2 is a section on A-A of Fig. 1; Fig. 3 is a side elevation of a reinforcing part of the arrangement of Figs. 1 and 2; Fig. 4 is a plan of another embodiment of the reinforcing part; and Fig. 5 is a section on A-A of the reinforcing part of Fig. 4.

Referring to Figs. 1 to 3 of the drawings, a frame 10, designed to define the upper end of a manhole, has a substantially square configuration and includes upstanding side walls 12 secured at lower ends thereof to respective horizontal base plates 14, the latter extending inwardly of the walls 12 to define seatings 16 for a manhole cover 18.

The cover 18 is of substantially square configuration dimensioned to locate on the frame 10 within the side walls 12 thereof. The frame 16 and the cover 18 are each preferably formed of mild steel which is cut into sections as required, the sections being welded to define a frame and cover of dimensions suitable for the respective manhole. It should be appreciated that the frame 16 and cover 18 can therefore be relatively easily formed of varying dimensions to cover manholes of various sizes. The mild steel of both the frame 10 and the cover 18 is finished by being hot dip galvanized.

The cover 18 is defined by upstanding side walls 20 and a cover tray 22 which connects between the side walls 20 at a location between upper and lower edges thereof whereby, in use, to define a lower section 24 of each wall 20 below the cover tray 22, the lower edge of each section 24 being supported by the seating 16 of the respective frame base plate 14. An airtight seal is formed between the lower edge of each section 24 and the base plate 14.

In view of the fact that steel has a long stress/ strain curve and is subject to plastic deformation at low stress levels, it is necessary to reinforce the steel cover 18 in order to meet the new load classification standards following the introduction of British Standard EN 124:1994. The method of testing required by this Standard involves a principal part of the test load applied centrally of the cover at a specified rate.

The cover 18 is reinforced by a configuration of elongate beams 26 applied to the underside of the cover tray 22. Each of the beams 26 is preferably formed of ductile iron and has a channel section, with the free edges of the channel legs being secured to the cover tray 22 by any suitable means. At a central location underneath the cover tray 22, the reinforcing arrangement includes an annular beam 28, with each of the elongate beams 26 being integrally connected at one end to the beam 28 and extending outwardly therefrom to a respective side of the cover tray 22, along an axis substantially at right angles to the latter, but terminating short of the respective wall 20. As the annular beam 28 reacts to the test load which is applied centrally, the annular beam 28 has the maximum width, i.e. the dimension in a direction downwardly of the cover tray 22. Each of the elongate beams 26 has an outer end section 30 of minimum width where the stress is primarily shear, with an inner section 32 increasing gradually in width from that of the section 30 to that of the annular beam 28. Each elongate beam 26 has therefore the greatest width at the high tensile section of its length.

A seating block 34 is welded to the upper surface of the seating 16 of each frame base plate 14 at the appropriate location to seat the outer end of the respective elongate beam 26. A grease retaining lip 36 is provided around the inner edges of the frame base plates 14.

In another embodiment, reinforcement for the cover 18 is by way of a different configuration of beams, as shown in Figs. 4 and 5.

This reinforcing arrangement includes a first pair of spaced parallel elongate beams 36 extending substantially between one pair of opposed sides of the cover tray 22 along axes substantially at right angles to the latter, but each terminating short of the respective walls 20. A second pair of spaced parallel elongate beams 38 extends substantially between the other opposed sides of the cover tray 22 along axes substantially at right angles thereto, but again terminating short of the respective walls 20. Each of the elongate beams of one pair integrally connects with the beams of the other pair to thereby define a lattice structure 39 at a central location underneath the cover tray 22. As the structure 39 reacts to the test load which is applied centrally, the lattice structure 39 has the maximum width, i.e. the dimension in a direction downwardly of the cover tray 22.

Each of the elongate beams 36, 38 is preferably formed of ductile iron and has a channel section, and also has an outer end section 40 of minimum width where the stress is primarily shear, with an inner section 42 increasing gradually in width from that of the section 40 to that of the lattice structure 39. Sections 44 of the channel legs, which are secured to the cover tray 22 by any suitable means, each increase in thickness inwardly of the channel from a location on each inner section 42 approaching the outer end section 40, to the beginning of the section 40, and then reduce gradually in thickness to the original dimension of the channel leg at the outer end of the section 40.A section 46 of the base of each channel flares outwardly from each side from the same location on each inner section 42, to the beginning of the respective outer end section 40, and thereafter retains the same lateral direction to the outer end of the section 40.

In each embodiment, the outer end section of each elongate beam allows the beam to be cut in that section to a required length before being connected to the galvanized tray 22. The manhole cover is therefore able to be of different sizes to meet the demand for unusual sizes without the need for pattern modifications or special castings. Such a reinforced cover is designed to meet the load test at sizes of cover from 600 mm square up to 900 mm square.

There is therefore provided a manhole cover assembly which can be principally formed of mild steel for ease of manufacture, but which can meet the required load bearing characteristics by the use of a ductile iron reinforcement, the latter in itself being adjustable in size whereby the cover assembly can be constructed for use with manholes and other access holes of various sizes and various load bearing requirements.

In a modification, the elongate beams may each be formed of a T section with the leg of the T connected to the underside of the cover plate 22. The use of a channel section or T section for the elongate beams has the advantage of moving more material to the tensile side of the neutral axis.

Various other modifications may be made without departing from the invention.

Whilst endeavouring in the foregoing Specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Uatnis:

1. Apparatus for use as a manhole cover, the apparatus comprising a cover member for seating on a frame arrangement, and reinforcing means which is formed of a material having improved load bearing characteristics relative to the material of the cover member, and which is so positioned on the latter as to provide the apparatus with desired load bearing characteristics.

2. Apparatus according to Claim 1, wherein the reinforcing means comprises a plurality of elongate members connected to one face of the cover member the elongate members being connected together towards a central area of the cover member and extending outwardly of the cover member in different directions from the central area.

3. Apparatus according to Claim 2, wherein the cover member has a substantially rectangular configuration and the reinforcing means comprises elongate members extending between the central area and respective side edges of the cover member1 whereby to be able to seat on the frame arrangement.

4. Apparatus according to Claim 2 or 3, wherein the length of the or each elongate member is adjusted to the respective dimension of the cover member by cutting off a respective length from a free end section thereof before connecting the reinforcing means to the cover member.

Apparatus according to any of Claims 2 to 4, wherein the elongate members of the reinforcing means are interconnected to define a structure which is connected to the central area of the cover member.

6. Apparatus according to Claim 5, wherein the interconnecting structure has the form of an annular reinforcing member.

7. Apparatus according to Claim 5, wherein the interconnecting structure is defined by the elongate members being interconnected to define a lattice arrangement.

8. Apparatus according to any of Claims 5 to 7, wherein the interconnecting structure has a width greater than the width of the free end section of each elongate member, the width of each elongate member reducing gradually from the interconnecting structure to the respective end section.

9. Apparatus according to any of Claims 2 to 8, wherein each elongate member of the reinforcing means has a channel section with the upstanding channel sides connecting to said one face of the cover member.

10. Apparatus according to any of Claims 2 to 8, wherein each of the elongate members has a T section with the leg of the T connecting to said one face of the cover member.

11. Apparatus according to any of the preceding Claims, wherein the cover member is formed primarily from steel.

12. Apparatus according to any of the preceding Claims, wherein the reinforcing means is formed of iron.

13. Apparatus according to Claim 12, wherein the reinforcing means is formed of ductile iron.

14. A manhole arrangement comprising cover apparatus according to any of the preceding Claims, and a frame arrangement for connecting to a foundation.

15. An arrangement according to Claim 14, wherein seating means is provided on the frame arrangement at each location where a free end of a respective elongate member is arranged to seat on the frame arrangement.

16. Apparatus for use as a manhole cover, substantially as hereinbefore described with reference to the accompanying drawings.

17. A manhole arrangement substantially as hereinbefore described with reference to the accompanying drawings.

18. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding Claims.