GB2348665A

GB2348665A - A frame for manhole assembly with improved grip

Info

Publication number: GB2348665A
Application number: GB9930296A
Authority: GB
Inventors: Barry Turner
Original assignee: C I S
Current assignee: C I S
Priority date: 1999-12-23
Filing date: 1999-12-23
Publication date: 2000-10-11
Anticipated expiration: 2019-12-23
Also published as: GB9930296D0; GB2348665B; GB2369143A; GB0026974D0

Abstract

Manhole assembly 10, Fig 2 includes a frame 12 comprising an upstanding wall 26, Fig 3 provided with projecting seats 28, Fig 3 for mounting a cover member 14. The frame 12 further includes a flange 30, Fig 3 extending outwardly from the upstanding wall 26. The undersurface 33 of the flange 30 has projections or nodules 42. The projections 42 improve the grip between the flange 30 and the mortar 40, Fig 3 in which it is embedded. The outer edge of the flange 30 may have a protruding bead 44.

Description

Ground Surface Access Assemblies The invention relates to ground surface access assemblies, such as manhole assemblies and gully gratings. Such assemblies allow access to sewers, water hydrants and other below surface installations, via openings in the roads, pavements, etc. above.

A manhole assembly typically includes a generally rectangular frame and a cover member mountable on the frame. The frame may include upstanding walls and flanges extending outwardly from the bases of the walls.

Conventionally, the flanges are mounted within a mortar bed to retain the manhole assembly in place.

According to the invention, there is provided a frame arrangement for a ground surface access assembly, the frame arrangement including a support portion for mounting a cover member and a flange extending outwardly from the support portion, wherein an undersurface of the flange is provided with a plurality of projections.

Preferably the projections result in the profile of the undersurface having alternating peaks and troughs in each of two mutually perpendicular directions.

The projections on the undersurface of the flange preferably provide a smoothly undulating profile in each of the two mutually perpendicular directions. The undulations may be regular or periodic. The undersurface of the flange may be provided with a plurality of protruding nodules. The nodules preferably protrude in a direction substantially perpendicular to a general plane of the undersurface of the flange. The nodules may be substantially conical in shape, with blunt or curved peaks. The peaks of the nodules may be approximately 10mm apart and the peaks may extend between 1.5 and 5 mm, and preferably about 3 mm, beyond the troughs. The nodules may be provided over substantially the whole of the undersurface of the flange. Preferably the nodules terminate smoothly near an outer edge of the flange.

The support portion may include an upstanding wall and one or more seats protruding inwardly therefrom. A cover member supported on the support member may be supported on the seats, inwardly of the upstanding wall.

The flange may extend outwardly from a lower part of the upstanding wall. The flange may be generally planar and may lie approximately parallel to a cover member mounted on the support portion. The flange may have a thickness of about 10mm to 20mm. A central region of an upper surface of the flange may be substantially smooth.

The wall may be generally rectangular in plan view, including substantially straight side portions and curved corner portions. The flange may include foot portions extending outwardly from the corner portions of the wall and edge portions extending outwardly from the side portions of the wall. The foot portions may extend further outwardly than do the edge portions of the flange. The foot portions may extend outwardly a maximum of about 100 mm from the wall and the edge portions may extend a maximum of about 50 mm from the wall. Each foot portion may include one or more openings passing therethrough. Preferably each foot portion includes three openings passing therethrough.

An elongate bead may extend around at least a part of the outer edge of the flange. The bead may protrude upwardly beyond the upper surface of the flange. The bead may have a substantially circular section, having a radius of about 10mm. The bead preferably extends around the whole of the outer edge of the flange. The bead may define an edge of the substantially smooth central region of the top face of the flange.

An embodiment of the invention will be described for the purpose of illustration only with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic plan view of a manhole assembly frame; Fig. 2 is a diagrammatic plan view of a manhole assembly including a frame and a cover member; Fig. 3 is a diagrammatic partial cross-section through a prior art manhole assembly; Fig. 4 is a diagrammatic partial cross-section through the manhole assembly of Fig. 3, after exposure to traffic; Fig. 5 is a diagrammatic partial plan view of the underside of a frame for a manhole assembly, according to the invention; Fig. 6 is a diagrammatic partial cross-section through a manhole assembly according to the invention; and Fig. 7 is an enlarged diagrammatic cross-sectional detail of a bead of the frame of Fig. 6.

Referring to the drawings, a manhole assembly 10 includes a frame 12 and a cover member 14. Referring to Fig. 2, the cover member is formed of cast metal and comprises two substantially planar triangular parts 16 provided with triangular projections 18 on their upper surfaces. The triangular projections 18 provide for a high friction upper surface of the cover member 14, to allow traffic to pass over the manhole assembly 10 without skidding.

The cover member 14 is supported at its edges 20 by the frame 12. The frame 12 is generally square in plan view, including straight sides 22 and curved corner regions 24. Referring to Fig. 3, the frame 12 includes an upstanding wall 26, provided with seats 28 projecting therefrom in an inward direction. The edges 20 of the cover member 14 are supported on the seats 28.

Extending outwardly from a base region of the upstanding wall 26 is a generally planar flange 30. The flange has a thickness of about 8mm, and has smooth upper and lower surfaces 31 and 33 respectively. Referring to Fig. 1, the flange 30 includes relatively narrow side portions 32, extending about 20 to 30 mm outwardly from the upstanding walls 26, and splayed corner portions 34 which extend about 10mm outwardly from the upstanding walls 26 at the curved corner regions 24 of the frame. Each corner portion 34 includes three openings 36 passing therethrough.

A square section bead 38 extends around the perimeter of the flange, along the edges of the side portions 32 and around the splayed corner portions 34.

In use, the flanges 30 are embedded in a mortar bed 40 which retains the manhole assembly in place in the road, etc.

When a vehicle travels over the manhole assembly, a force is applied to the cover member 14, and hence to the frame 12 via the seats 28 in a downward direction. However, it has been realised by the applicant that, because the vehicle is often braking or accelerating, a force is also applied to the manhole assembly in a direction substantially parallel to the cover member 14 and to the flanges 30, in the direction of the arrow in Fig. 4. This applies a shear stress to the mortar at the interface between the mortar and the underside of the flange 30. Movement at this interface is resisted by the effectiveness of the mortar adhesion or, in the event of failure of this mechanism, friction between the material of the flange 30 and the mortar. Where the friction is not sufficient to resist small movement between the mortar and the flange 30, the bead 38 applies a load to the encapsulating mortar. The conventional bead profile is generally square in section and it has been appreciated by the applicant that the load is therefore concentrated in the mortar at the corners of this square profile. This may increase the stress levels in these regions beyond the tensile capacity of the mortar, which is generally strong in compression but not particularly strong in tension. Cracks 41 may form at the corners of the bead 38 and be propagated through the mortar until the cracked section eventually detaches itself from the main body of the mortar. This renders the manhole assembly installation a failed structure and subsequent deterioration of the mortar and the assembly occurs rapidly (see Fig. 4).

Referring to Figs. 5 and 6, a manhole assembly according to the invention includes a frame 12 having a flange 30 which is of a generally similar overall shape to the previously described prior art flange. However, according t the invention, the flange 30 is provided with protruding nodules 42 on its lower surface 33. The nodules 42 are generally conical in shape, but have curved peaks. The nodules 42 result in the flange having an undulating profile (see Fig.

6) in each of two mutually perpendicular directions.

At a perimeter of the flange 30, a generally circular cross-section bead 44 is provided.

When a vehicle applies a shear force to the frame 12, the nodules 42 act as mechanical"keys"so that the grip between the flange 30 and the mortar bed 40 is not solely reliant on friction between the flange and the mortar but also on the shear, tensile and compression properties of the mortar. Friction is also significantly increased by the increase in effective contact area between the mortar and the flange undersurface.

The circular section of the bead 44 also helps to minimise the likelihood of failure of the mortar. The bead has no corners to concentrate stress or form initiation sites for cracks.

There is thus provided a manhole frame which minimises the possibility of failure of the mortar bed.

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

Claims :- 1. A frame arrangement for a ground surface access assembly, the frame arrangement including a support portion for mounting a cover member and a flange extending outwardly from the support portion, wherein an undersurface of the flange is provided with a plurality of projections.
2. A frame arrangement according to claim 1, wherein the projections result in the profile of the undersurface having alternating peaks and troughs in each of two mutually perpendicular directions.
3. A frame arrangement according to claim 2, wherein the projections on the undersurface of the flange provide a smoothly undulating profile in each of the two mutually perpendicular directions.
4. A frame arrangement according to claim 3, wherein the undulations are regular.
5. A frame arrangement according to claim 3 or claim 4, wherein the undulations are periodic.
6. A frame arrangement according to any preceding claim, wherein the undersurface of the flange is provided with a plurality of protruding nodules.
7. A frame arrangement according to claim 6, wherein the nodules protrude in a direction substantially perpendicular to a general plane of the undersurface of the flange.
8. A frame arrangement according to claim 6 or claim 7, wherein the nodules are substantially conical in shape, with blunt or curved peaks.
9. A frame arrangement according to claim 8, wherein the peaks of the nodules are approximately 10 mm apart.
10. A frame arrangement according to claim 8 or claim 9, wherein the peaks extend between 1.5 and 5 mm beyond the troughs.
11. A frame arrangement according to claim 10, wherein the peaks extend about 3 mm beyond the troughs.
12. A frame arrangement according to any of claims 6 to 11, wherein the nodules are provided over substantially the whole of the undersurface of the flange.
13. A frame arrangement according to any of claims 6 to 12, wherein the nodules terminate smoothly near an outer edge of the flange.
14. A frame arrangement according to any preceding claim, wherein the support portion includes an upstanding wall and one or more seats protruding inwardly therefrom.
15. A frame arrangement according to claim 14, wherein a cover member supported on the support member may be supported on the seats, inwardly of the upstanding wall.
16. A frame arrangement according to claim 14 or claim 15, wherein the flange extends outwardly from a lower part of the upstanding wall.
17. A frame arrangement according to any of claims 14 to 16, wherein the wall is generally rectangular in plan view, including substantially straight side portions and curved corner portions.
18. A frame arrangement according to any of claims 14 to 17, wherein the flange includes foot portions extending outwardly from the corner portions of the wall and edge portions extending outwardly from the side portions of the wall.
19. A frame arrangement according to claim 18, wherein the foot portions extend further outwardly than do the edge portions of the flange.
20. A frame arrangement according to claim 19, wherein the foot portions extend outwardly a maximum of about 100 mm from the wall and the edge portions extend a maximum of about 50 mm from the wall.
21. A frame arrangement according to any of claims 18 to 20, wherein each foot portion includes one or more openings passing therethrough.
22. A frame arrangement according to claim 21, wherein each foot portion includes three openings passing therethrough.
23. A frame arrangement according to any preceding claim, wherein the flange is generally planar and lies approximately parallel to a cover member mounted on the support portion.
24. A frame arrangement according to any preceding claim, wherein the flange has a thickness of between 10 mm and 20 mm.
2 5. A frame arrangement according to any preceding claim, wherein a central region of an upper surface of the flange is substantially smooth.
26. A frame arrangement according to any preceding claim, wherein an elongate bead extends around at least a part of the outer edge of the flange.
27. A frame arrangement according to claim 26, wherein the bead protrudes upwardly beyond the upper surface of the flange.
28. A frame arrangement according to claim 26 or claim 27, wherein the bead has a substantially circular section, having a radius of about 10 mm.
29. A frame arrangement according to any of claims 26 to 28, wherein the bead extends around the whole of the outer edge of the flange.
30. A frame arrangement according to any of claims 25 to 29, wherein the bead defines an edge of the substantially smooth central region of the top face of the flange.
31. A frame arrangement substantially as herein described with reference to Figs. 1, 2,5,6 and 7 of the drawings.
32. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.