GB2369143A

GB2369143A - Frame arrangement for ground surface access assembly

Info

Publication number: GB2369143A
Application number: GB0026974A
Authority: GB
Inventors: Barry Turner
Original assignee: C I S
Current assignee: C I S
Priority date: 1999-12-23
Filing date: 2000-11-04
Publication date: 2002-05-22
Also published as: GB0026974D0; GB2348665B; GB9930296D0; GB2348665A

Abstract

The frame assembly 12, for use with manholes, gully gratings etc., includes a support portion for mounting a cover member and a flange 30 extending generally outwards from the support portion in use, wherein the flange has a fully curved profile which includes no sharp edges or sharp corners. In use the flange may curve generally downwardly and outwardly away from the support and an outer part of the flange may curve upwardly and outwardly so that the flange is generally u-shaped with the lower profile of the flange forming part of an arc of a circle. The flange may extend around the whole of the support portion and may form a channel shape there around. There may be a plurality of flanges extending from the support portion. The underside of the flange may be provided with a plurality of projections 42 formed from alternating peaks and troughs or a multitude of projecting nodules which may be provided over the whole of the underside of the flange or which may terminate smoothly near the outer edge of the flange. The support portion may include an upstanding wall 26 from which one or more seats protrude inwards upon which the cover member is mounted. The upstanding wall may be generally rectangular in plan view with corner portions from where the flange extends outwards further than from the interconnecting straight portions. The flange may extend outwardly from the lower portion of the wall, with which it merges smoothly, and an elongate smooth bead 44 may extend around at least a portion of the outer edge of the flange.

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 cover member can be lifted from the frame or pivoted relative to the frame in order to allow access to the below surface installation. The frame may include an upstanding wall and a flange extending outwardly from the base of the wall. Conventionally, the flange is mounted in 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 generally outwardly from the support portion in use, wherein the flange has a fully curved profile including no sharp edges or sharp corners.

The flange may curve generally downwardly and outwardly away from the support portion in use. An outer part of the flange may curve upwardly and outwardly away from the support portion.

A lower profile of the flange in use may form part of an arc of a circle in section. The flange may be generally U-shaped in section.

The flange may extend substantially around the whole of the support portion. Alternatively a plurality of flanges may extend from the support portion.

The flange may form a channel shape, extending substantially around the support portion.

Preferably 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 any two mutually perpendicular directions.

The projections on the undersurface of the flange preferably provide a smoothly undulating profile on 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 generally downwards in use. The nodules may be substantially conical in shape, with blunt or curved peaks. The peaks of the nodules may be approximately lOmm apart and the peaks may extend between 1.5mm and 5mm, and preferably about 3mm, 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 upstanding wall may be generally rectangular in plan view, including corner portions and straight portions. The flange may extend further outwardly away from the wall at the corner portions than at the straight portions.

The flange may extend generally outwardly from a lower part of the upstanding wall. The flange preferably merges smoothly into the lower part of the wall. The flange may have a thickness of between 8mm and 1 5mm.

An elongate bead may extend around at least a part of an outer edge of the flange, remote from the support portion.

The bead is preferably smoothly curved in shape. The bead may have a substantially circular section, and may have a radius of between Smm and 15mm and preferably about lOmm. The radius of the bead may be greater than the thickness of an adjacent part of the flange. The bead may extend around substantially the whole of an outer edge of the flange. The bead may be shaped to merge smoothly into the remainder of the flange.

According to the invention there is further 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 generally outwardly from the support portion, wherein an elongate bead extends around at least a part of an outer edge of the flange, remote from the support portion.

The bead is preferably smoothly curved in shape. The bead may have a substantially circular section, and may have a radius of between 5mm and 1 5mm and preferably about lOmm. The radius of the bead may be greater than the thickness of an adjacent part of the flange. The bead may extend around substantially the whole of an outer edge of the flange. The bead may be shaped to merge smoothly into the remainder 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 prior art manhole assembly

frame; Fig. 2 is a diagrammatic plan view of a prior art manhole assembly

including a frame and a cover member; Fig. 3 is a diagrammatic partial cross section through the prior art

manhole assembly of Fig. 2;

Fig. 4 is a diagrammatic partial cross section through the manhole assembly of Fig. 3, after exposure to traffic; and Fig. 5 is a diagrammatic cross section through a manhole assembly according to the invention.

Referring to the drawings, a manhole assembly 10 includes a frame 12 and a cover member 14. As shown in 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 100mm 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. The splayed corner portions 34 provide additional strength and rigidity below the supporting seats 28.

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

s 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 Fig. 5, a manhole assembly 10 according to the invention includes a frame 12 having a flange 30 which has a fully curved shape. The flange 30 is generally U-shaped in vertical section. The thickness of the flange is about 8mm to lOmm and the flange extends outwardly up to about lOOmm from the upstanding wall 26. The flange may extend about lOOmm from the upstanding wall in its corner regions and about 50mm from the upstanding wall in mid regions.

The flange 30 is also provided with a smooth circular section bead 44 which extends around an outer edge of the flange 30. The bead 44 merges smoothly into an adjacent part of the flange, and includes no corners or sharp edges. The flange 30 is further 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 in each of any two mutually perpendicular directions.

The flange 30 is preferably embedded in use in polymer mortar 45, which has greater tensile strength than conventional mortars.

When a vehicle applies a shear force to the frame 12, the rounded shape of the flange avoids the concentration of stresses at its outer edge, in that some of the energy is absorbed by compressing the sub-structure, rather than trying to split it. The overall curved profile reduces stress raisers at all locations. The curved profile also improves the vertical rigidity of the frame, i.e. its ability to withstand forces without flexing and causing damage to the mortar bed. In addition, the circular section of the bead 44 helps to minimise the likelihood of failure of the mortar around the outer edge of the flange. The bead 44 has no corners to concentrate stress or form initiation sites for cracks.

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

Various modifications may be made to the above described embodiment without departing from the scope of the invention. In particular, the exact profile of the flange may be altered provided there are no sharp edges. A junction between the flange and the base region of the wall 26 need not be arc shaped as in the above described embodiment but may be generally right angled, with edges of the right angled corner being smoothed off.

The frame has been illustrated as generally rectangular, but could be circular in plan view.

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

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 generally outwardly from the support portion in use, wherein the flange has a fully curved profile including no sharp edges or sharp corners.

2. A frame arrangement according to Claim 1 wherein the flange curves

generally downwardly and outwardly away from the support portion in use.

3. A frame arrangement according to Claim 1 or Claim 2 wherein an outer part of the flange curves upwardly and outwardly away from the support portion.

4. A frame arrangement according to any preceding claim wherein a lower profile of the flange in use forms part of an arc of a circle in section.

5. A frame arrangement according to any preceding claim wherein the flange is generally U-shaped in section.

6. A frame arrangement according to any preceding claim wherein the flange extends substantially around the whole of the support portion.

7. A frame arrangement according to any of Claims 1 to 5 wherein a plurality of flanges extend from the support portion.

8. A frame arrangement according to any preceding claim wherein the flange forms a channel shape, extending substantially around the support portion.

9. A frame arrangement according to any preceding claim wherein an undersurface of the flange is provided with a plurality of projections.

10. A frame arrangement according to Claim 9 wherein the projections result in the profile of the undersurface having alternating peaks and troughs in each of any two mutually perpendicular directions.

11. A frame arrangement according to Claim 10 wherein the undersurface of the flange is provided with a plurality of protruding nodules.

12. A frame arrangement according to Claim 11 wherein the nodules are provided over substantially the whole of the undersurface of the flange.

13. A frame arrangement according to Claim 11 or Claim 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, such that a cover member supported on the support portion may be supported on the seats, inwardly of the upstanding wall.

15. A frame arrangement according to Claim 14 wherein the upstanding wall is generally rectangular in plan view, including corner portions and straight portions and the flange extends further outwardly away from the wall at the corner portions than at the straight portions.

16. A frame arrangement according to Claim 14 or Claim 15 wherein the flange extends generally outwardly from a lower part of the upstanding wall, and merges smoothly into the lower part of the wall.

17. A frame arrangement according to any preceding claim wherein an elongate bead extends around at least a part of an outer edge of the flange, remote from the support portion.

18. A frame arrangement according to Claim 17 wherein the bead is smoothly curved in shape.

19. A frame arrangement according to Claim 17 or Claim 18 wherein the bead is shaped to merge smoothly into the remainder of the flange.

20. A frame arrangement for a ground surface access assembly, the frame arrangement being substantially as herein described with reference to Fig. 5 of the drawings.

21. 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.