GB1571824A - Manhole assemblies - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO MANHOLE ASSEMBLIES (71) We, BRITISH STEEL CORPORATION, a Corporation incorporated and existing under the Iron and Steel Act 1967 whose principal office is at 33 Grosvenor Place, London, S.W. 1 do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to manhole assemblies.

It is to be understood that the expression "manhole assemblies" as used herein includes inspection and access openings and assemblies for sewers, drains, wiring pits and conduits and similar installations.

In certain cases it is desirable that such assemblies be sealed against the passage of liquids and/or gases. Thus with regard to manhole assemblies covering for example drainage installations located in roadways it is often desirable to effect a sealed closure to prevent a sudden upsurge of floodwater, for example, lifting and displacing the cover of the manhole assembly which could present a road hazard to vehicles or pedestrians. Again it is often desirable with regard to sewer installations, for example, to prevent the escape of noxious gases. Similarly, it can be desirable to prevent the ingress of dirt or other unwanted material into a pipe, conduit or like system below a manhole assembly.

It is an object of the present invention to provide a convenient and effective sealed closure for such assemblies.

According to the Invention there is provided a manhole assembly comprising a frame surround and defining an inspection or access opening, the frame include a continuous inward-facing surface substantially at right angles to the general plane of the frame; a closure member covering the opening and secured to the frame and including a continuous outward-facing surface corresponding to and disposed alongside the continuous inwardfacing surface of the frame; and a resilient sealing member compressed between said continuous inward-facing surface and said continuous outward-facing surface to effect a seal between the two surfaces.

Said continuous outward-facing surface of the frame may comprise the inner edge surface of the frame.

The closure member may be in the general form of a plate, an outer peripheral portion of which overlies part of the frame, and may include a recessed portion located within the opening defined by the frame. In this case the outer surface of a part of the plate linking the recessed portion with the remainder of the plate may constitute said outward facing continuous surface of the closure member.

The sealing member may be in any desired form and conveniently comprises a resilient '0' ring of rubber or similar elastomeric material.

In order that the invention may be more readily understood, one embodiment thereof will now be described by way of example with reference to the laccompanying drawings in which: Fig. 1 is a top plan view of a manhole assembly according to the invention; Fig. 2 is a sectional isometric view of part of the manhole closure.

As can be seen in the drawings the manhole assembly includes a cast iron frame 1. The frame 1 includes an inner flange portion 2 which surrounds and defines a circular manhole opening. Located in association with the flange portion 2 is a closure member in the form of a plate of mild steel 3 secured around a peripheral portion 10 thereof to the flange portion 2 by means of a plurality of bolts 4 spaced around the plate. As can be seen most clearly in figure 2 the plate 3 includes a recessed portion 5 fitting within the opening defined by the flange 2.

It is to be noted that the wall portion of the plate 3 upstanding from its recessed portion 5 corresponds to and is disposed alongside the inner edge 7 of the flanged portion to define an annular gap therebetween. Thus it will be seen that in this embodiment of the invention the outer surface of the wall 6 and the inner surface of the wall 7 define said continuous outer surface of the closure member and said continuous inner surface of the frame respectively.

Located between wall 6 and edge 7 is a natural rubber '0' ring 8 which in practice is a compression fit between them, and is therefore, in the assembled position of the closure, in a compressed and sealing configuration. A plurality of small steel taps 9 are welded at spaced points between the lower end of wall 6 and serve to retain the '0' ring 8 in place about the wall 6 so preventing it from being dislodged down the manhole opening during removal of the closure member.

For assembly therefore the '0' ring 8 is placed about the wall 6 of the plate 3, the plate 3 is placed over the flange portion 2 of the frame and then urged downwardly so as to cause sealing engagement of the '0' ring between the wall 6 and edge 7. Bolts 4 are then applied to secure the closure in position.

Two inverted 'U' shaped tabs 11 are welded to the upper surface of the plate 3 to enable it to be lifted from the manhole opening if required.

The assembly is completed by the fitting into the frame 1 of two triangular shaped manhole covers one of which is shown at 12.

It is to be observed that with a closure of the kind disclosed, pressure within the manhole opening will not reduce the sealing effect afforded by the '0' ring 8, since the sealing forces caused by the compressed '0' ring will not be reduced by any tendency of pressure below the closure trying to lift the plate 3. Indeed increase the pressure below the closure member can tend to force the '0' ring 8 more firmly into sealing engagement with the respective surfaces of the closure member and the frame. This advantageous feature compares most favourably with previous known arrangements in which an essentially flat rubber gasket is interposed between respective horizontal surfaces of the frame and the superposed closure member.With such arrangements, the gasket is prone to creep thereby reducing the applied securing bolt load resulting in a relaxation of the compression of the gasket and the possibility of leakage of the seal.

It is further to be observed that the closure member and its associated assembly in no way interferes with the location or seating of the covers 12 which in use form part of a roadway or pavement surface.

Again it is to be observed that the sealing closure assembly does not provide any restriction, after its simple removal, of the manhole opening defined by the manhole frame.

It will be seen therefore that by means of the invention there- is provided an effective, convenient and simple sealed closure for a manhole assembly.

WHAT WE CLAIM IS: 1. A manhole assembly comprising a frame surrounding and defining an inspection or access opening, the frame including a continuous inward-facing surface substantially at right angles to the general plane of the frame; a closure member covering the opening and secured to the frame and including a continuous outward-facing surface corresponding to and disposed alongside the continuous inward-facing surface of the frame, and a resilient sealing member compressed between said continuous inward-facing surface and said continuous outward-facing surface to effect a seal between the two surfaces.

2. A manhole assembly according to Claim 1 wherein the continuous inwardfacing surface of the frame comprises the inner edge surface of the frame.

3. A manhole assembly according to any one of the preceding claims wherein the frame defines a generally circular opening.

4. A manhole assembly according to any one of the preceding claims in which the closure member is in the general form of a plate, an outer peripheral portion of which overlies part of the frame.

5. A manhole assembly according to Claim 4 wherein the closure member includes a recessed portion located within the opening defined by the frame.

6. A manhole assembly according to Claim 5 wherein a part of the plate linking the recessed portion with the remainder of the plate constitutes, on its outer surface, said outward-facing continuous surface of the closure member.

7. A manhole assembly according to Claims 4, 5 or 6 wherein the outer peripheral portion of the plate is secured to the frame.

8. A manhole assembly according to any one of the preceding claims in which the sealing member comprises an '0' ring

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. by means of a plurality of bolts 4 spaced around the plate. As can be seen most clearly in figure 2 the plate 3 includes a recessed portion 5 fitting within the opening defined by the flange 2. It is to be noted that the wall portion of the plate 3 upstanding from its recessed portion 5 corresponds to and is disposed alongside the inner edge 7 of the flanged portion to define an annular gap therebetween. Thus it will be seen that in this embodiment of the invention the outer surface of the wall 6 and the inner surface of the wall 7 define said continuous outer surface of the closure member and said continuous inner surface of the frame respectively. Located between wall 6 and edge 7 is a natural rubber '0' ring 8 which in practice is a compression fit between them, and is therefore, in the assembled position of the closure, in a compressed and sealing configuration. A plurality of small steel taps 9 are welded at spaced points between the lower end of wall 6 and serve to retain the '0' ring 8 in place about the wall 6 so preventing it from being dislodged down the manhole opening during removal of the closure member. For assembly therefore the '0' ring 8 is placed about the wall 6 of the plate 3, the plate 3 is placed over the flange portion 2 of the frame and then urged downwardly so as to cause sealing engagement of the '0' ring between the wall 6 and edge 7. Bolts 4 are then applied to secure the closure in position. Two inverted 'U' shaped tabs 11 are welded to the upper surface of the plate 3 to enable it to be lifted from the manhole opening if required. The assembly is completed by the fitting into the frame 1 of two triangular shaped manhole covers one of which is shown at 12. It is to be observed that with a closure of the kind disclosed, pressure within the manhole opening will not reduce the sealing effect afforded by the '0' ring 8, since the sealing forces caused by the compressed '0' ring will not be reduced by any tendency of pressure below the closure trying to lift the plate 3. Indeed increase the pressure below the closure member can tend to force the '0' ring 8 more firmly into sealing engagement with the respective surfaces of the closure member and the frame. This advantageous feature compares most favourably with previous known arrangements in which an essentially flat rubber gasket is interposed between respective horizontal surfaces of the frame and the superposed closure member.With such arrangements, the gasket is prone to creep thereby reducing the applied securing bolt load resulting in a relaxation of the compression of the gasket and the possibility of leakage of the seal. It is further to be observed that the closure member and its associated assembly in no way interferes with the location or seating of the covers 12 which in use form part of a roadway or pavement surface. Again it is to be observed that the sealing closure assembly does not provide any restriction, after its simple removal, of the manhole opening defined by the manhole frame. It will be seen therefore that by means of the invention there- is provided an effective, convenient and simple sealed closure for a manhole assembly. WHAT WE CLAIM IS:

1. A manhole assembly comprising a frame surrounding and defining an inspection or access opening, the frame including a continuous inward-facing surface substantially at right angles to the general plane of the frame; a closure member covering the opening and secured to the frame and including a continuous outward-facing surface corresponding to and disposed alongside the continuous inward-facing surface of the frame, and a resilient sealing member compressed between said continuous inward-facing surface and said continuous outward-facing surface to effect a seal between the two surfaces.

2. A manhole assembly according to Claim 1 wherein the continuous inwardfacing surface of the frame comprises the inner edge surface of the frame.

3. A manhole assembly according to any one of the preceding claims wherein the frame defines a generally circular opening.

4. A manhole assembly according to any one of the preceding claims in which the closure member is in the general form of a plate, an outer peripheral portion of which overlies part of the frame.

5. A manhole assembly according to Claim 4 wherein the closure member includes a recessed portion located within the opening defined by the frame.

6. A manhole assembly according to Claim 5 wherein a part of the plate linking the recessed portion with the remainder of the plate constitutes, on its outer surface, said outward-facing continuous surface of the closure member.

7. A manhole assembly according to Claims 4, 5 or 6 wherein the outer peripheral portion of the plate is secured to the frame.

8. A manhole assembly according to any one of the preceding claims in which the sealing member comprises an '0' ring

of elastomeric material.

9. A manhole assembly substantially as shown in and as hereinbefore described with reference to the accompanying drawings.