GB1599409A - Manhole or inspection chambers - Google Patents

Description

(54) IMPROVEMENTS IN MANHOLE OR INSPECTION CHAMBERS (71) We, MONO CONCRETE LIMI TED, a British Company of Western House, Dingwall Road, Croydon, CR9 2TU, 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 or inspection chambers.

Known manhole or inspection chambers are built by superimposing a plurality of rectangular rings of concrete or like material so as to form a vertical chamber extending upwardly from a drain, pit or the like to ground level, the upper and lower surfaces of the rings being formed e.g. with oppositely offset lips or with tongues and grooves so as to impart lateral rigidity to the built up chamber, the top of which is closed by a manhole cover.

One known form of chamber of the above type consists of a plurality of rings of rectangular contour, and the area of its interior opening towards the top of the chamber is reduced by providing a transition ring, the outer surface of which tapers upwardly and which taper ring is located to engage on to a ring therebelow and support a ring thereabove, the latter having an opening area less than that of the ring below. The outer surface of the taper ring may taper on only one side or two or more outer surfaces may taper. In another known arrangement the reduction in area is achieved by using a corbel slab comprising an annular frame which is interposed between rings of different opening area with a solid slab portion at one side of the frame to bridge the gap which would otherwise exist between said rings.The reduction in area may be in one or more locations vertically spaced along the chamber by using the appropriate numbers of taper rings or corbel slabs.

An object of this invention is to provide a simple means to blank off space between immediately-adjacent rings of different sizes which will be smaller, lighter and easier to handle than previously known corbel slabs.

Another object is to provide a corbel slab enabling rings of different opening sizes to be built up directly on top of each other and the resulting gap blanked off without the interposition of known corbel or taper units.

A further object is to facilitate the construction of a manhole or inspection chamber or the like.

According to this invention there is provided a manhole chamber comprising two superimposed, immediately-adjacent annular elements having interengaged formations in their adjacent surfaces, one opposed pair of walls of the upper of said elements being less widely spaced than the corresponding opposed pair of walls of the lower element so that there is a gap extemal to the upper element between one wall thereof and a parallel wall of the lower element, and a corbal slab bridging said gap, said slab having formations on three sides of its under-surface to interengage with the formations in the upper surface of the lower element exposed from the upper element, being stepped down on a fourth side thereof to pass beneath said one wall of the upper element and having a formation in the upper surface of its stepped down portion to interengage with that on said one wall of the upper element.

By this means the need is avoided for a relatively heavy and unmanageable corbel slab or taper unit comprising an annular portion of the same dimensions as the upper element and interposed between the upper and lower elements.

The upper surface of the corbel slab is preferably flat and at right angles to the walls of said elements between which it extends.

Said interengaged formations of said elements are preferably overlapped, offset lips and said formations of the slab preferably comprise downwardly opening grooves in said three sides of its undersurface to receive the lip upstanding from the lower element exposed from the upper element and said formation in the upper surface of its stepped down portion preferably comprises an upwardly opening groove to receive the lip depending from said one wall of the upper element.

The stepped down portion of the corbel slab is preferably constituted by a thickened end of a central portion of the slab which has an undersurface inclined with respect to the upper surface of the slab.

Said lower element may be the uppermost of a stack of similarly-dimensioned elements all having interengaged formations in their adjacent surfaces and said upper element may be the lowermost of a stack of similarly dimensioned elements all having interengaged formations in their adjacent surfaces.

The corbel slab and annular elements may be made of reinforced concrete. Normally the annular elements will be oblong, and the gap bridged by the corbel slab will be in the greater linear dimension of the lower element.

Chambers built up utilising corbel slabs according to this invention can utilise only one corbel slab so that one reduction in opening area is obtained, or more than one corbel slab can be used, a lower one providing a first chamber interior opening area reduction from a lowermost stack of elements to an intermediate stack of elements and an upper one providing a further chamber interior opening area reduction from the intermediate stack to a further stack of annular elements of smallest opening area.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a plan view of an uppermost or smallest chamber ring, Figure 2 is a section on the line 11-11 of Figure 1, Figure 3 is a plan view of an intermediate chamber ring, Figure 4 is a plan view of a lowermost chamber ring, Figure 5 is a plan view of one form of corbel slab unit, Figure 6 is a section on the line VI-VI, of Figure 5, Figure 7 is a section on the line VII--W of Figure 5, Figure 8 is a plan view of a second form of corbel slab unit, Figure 9 is a section on the line IX-IX of Figure 8, Figure 10 is a plan view of a third form of a corbel slab, Figure 11 is a section on the line XI--XI of Figure 10, Figure 12 is a plan view of one manhole chamber arrangement, Figure 13 is a section of elevation on the line XII-xII of Figure 12, Figure 14 is a sectional elevation similar to Figure 13 of an alternative manhole chamber arrangement, and Figure 15 is an exploded view of the components of the chamber shown in Figure 13.

Referring first to Figures 1 to 4, there are shown three oblong rings A, B and C. These rings have lips 10, 11 top and bottom which are relatively staggered enabling identical rings to be built up superimposed as will be clear from Figures 13 and 14. Ring B has a pair of opposite notches 12 in the lip 10 along opposite longitudinal sides, whilst the ring C has two such pairs 12, 12a, to facilitate the seating or stacking of rings of different sizes.

Referring now to Figures 5 to 11, three forms of corbel slab units 13, 14 and 15 are shown which enable chamber opening area reduction between stacks of different rings.

The corbel slab 13 is for use between a ring C and a ring B, the corbel slab 14 for use between a ring B and a ring A and the corbel slab 15 for use directly between a ring C and a ring A (see Figures 13 and 14). Each corbel slab has a fiat upper surface 16, which is horizontal in use, i.e. at right angles to the walls of the rings between which it extends (see Figures 13 and 14) and has a lip and groove 17, 18 respectively along one end. A central portion of the slab thickens from said one end to project downwardly and outwardly at the opposite end of the slab and has a groove 19 along the upper surface at this stepped down end. The two other sides of the under-surface of the slab are grooved at 20 as shown in Figures 6, 8 and 10.

Referring now to Figures 12 to 14, Figures 12 and 13 show the use of two corbel slabs 13 and 14, the slab 13 bridging the gap between the upper ring C of a stack of lowermost rings and a lower intermediate ring B thereabove, and the slab 14 bridging the gap between an upper intermediate ring B and the lowest ring A of an uppermost stack of rings thereabove. Figure 14 shows how a single corbel slab 15 may bridge the gap between a ring C and a ring A thereabove.

It will be understood that mortar will be laid between the rings and between the rings and corbel slabs.

The corbel slabs illustrated are lighter in weight, easier to produce and easier to handle than conventional taper rings and corbel units.

It will be understood that although Figure 13 shows only two rings A, B and C in each stack the number of rings in any one stack will vary according to circumstances. In the exploded view of Figure 15 only one ring B is shown.

WHAT WE CLAIM IS: 1. A manhole chamber comprising two super-imposed, immediately-adjacent annular elements having interengaged formations in their adjacent surfaces, one opposed pair of walls of the upper of said elements being less widely spaced than the corresponding opposed pair of walls of the lower element so that there is a gap external to the upper element between

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

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. comprises an upwardly opening groove to receive the lip depending from said one wall of the upper element. The stepped down portion of the corbel slab is preferably constituted by a thickened end of a central portion of the slab which has an undersurface inclined with respect to the upper surface of the slab. Said lower element may be the uppermost of a stack of similarly-dimensioned elements all having interengaged formations in their adjacent surfaces and said upper element may be the lowermost of a stack of similarly dimensioned elements all having interengaged formations in their adjacent surfaces. The corbel slab and annular elements may be made of reinforced concrete. Normally the annular elements will be oblong, and the gap bridged by the corbel slab will be in the greater linear dimension of the lower element. Chambers built up utilising corbel slabs according to this invention can utilise only one corbel slab so that one reduction in opening area is obtained, or more than one corbel slab can be used, a lower one providing a first chamber interior opening area reduction from a lowermost stack of elements to an intermediate stack of elements and an upper one providing a further chamber interior opening area reduction from the intermediate stack to a further stack of annular elements of smallest opening area. Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a plan view of an uppermost or smallest chamber ring, Figure 2 is a section on the line 11-11 of Figure 1, Figure 3 is a plan view of an intermediate chamber ring, Figure 4 is a plan view of a lowermost chamber ring, Figure 5 is a plan view of one form of corbel slab unit, Figure 6 is a section on the line VI-VI, of Figure 5, Figure 7 is a section on the line VII--W of Figure 5, Figure 8 is a plan view of a second form of corbel slab unit, Figure 9 is a section on the line IX-IX of Figure 8, Figure 10 is a plan view of a third form of a corbel slab, Figure 11 is a section on the line XI--XI of Figure 10, Figure 12 is a plan view of one manhole chamber arrangement, Figure 13 is a section of elevation on the line XII-xII of Figure 12, Figure 14 is a sectional elevation similar to Figure 13 of an alternative manhole chamber arrangement, and Figure 15 is an exploded view of the components of the chamber shown in Figure 13. Referring first to Figures 1 to 4, there are shown three oblong rings A, B and C. These rings have lips 10, 11 top and bottom which are relatively staggered enabling identical rings to be built up superimposed as will be clear from Figures 13 and 14. Ring B has a pair of opposite notches 12 in the lip 10 along opposite longitudinal sides, whilst the ring C has two such pairs 12, 12a, to facilitate the seating or stacking of rings of different sizes. Referring now to Figures 5 to 11, three forms of corbel slab units 13, 14 and 15 are shown which enable chamber opening area reduction between stacks of different rings. The corbel slab 13 is for use between a ring C and a ring B, the corbel slab 14 for use between a ring B and a ring A and the corbel slab 15 for use directly between a ring C and a ring A (see Figures 13 and 14). Each corbel slab has a fiat upper surface 16, which is horizontal in use, i.e. at right angles to the walls of the rings between which it extends (see Figures 13 and 14) and has a lip and groove 17, 18 respectively along one end. A central portion of the slab thickens from said one end to project downwardly and outwardly at the opposite end of the slab and has a groove 19 along the upper surface at this stepped down end. The two other sides of the under-surface of the slab are grooved at 20 as shown in Figures 6, 8 and 10. Referring now to Figures 12 to 14, Figures 12 and 13 show the use of two corbel slabs 13 and 14, the slab 13 bridging the gap between the upper ring C of a stack of lowermost rings and a lower intermediate ring B thereabove, and the slab 14 bridging the gap between an upper intermediate ring B and the lowest ring A of an uppermost stack of rings thereabove. Figure 14 shows how a single corbel slab 15 may bridge the gap between a ring C and a ring A thereabove. It will be understood that mortar will be laid between the rings and between the rings and corbel slabs. The corbel slabs illustrated are lighter in weight, easier to produce and easier to handle than conventional taper rings and corbel units. It will be understood that although Figure 13 shows only two rings A, B and C in each stack the number of rings in any one stack will vary according to circumstances. In the exploded view of Figure 15 only one ring B is shown. WHAT WE CLAIM IS:

1. A manhole chamber comprising two super-imposed, immediately-adjacent annular elements having interengaged formations in their adjacent surfaces, one opposed pair of walls of the upper of said elements being less widely spaced than the corresponding opposed pair of walls of the lower element so that there is a gap external to the upper element between

one wall thereof and a parallel wall of the lower element, and a corbel slab bridging said gap, said slab having formations on three sides of its undersurface to interengage with the formations in the upper surface of the lower element exposed from the upper element, being stepped down on a fourth side thereof to pass beneath said one wall of the upper element and having a formation in the upper surface of its stepped down portion to interengage with that on said one wall of the upper element.

2. A chamber as claimed in claim 1, wherein the upper surface of the corbel slab is flat and at right angles to the walls of said elements between which it extends.

3. A manhole chamber as claimed in either preceding claim, wherein said interengaged formations of said elements are overlapped, offset lips and wherein said formations of the slab comprise downwardly opening grooves in said three sides of its under-surface to receive the lip upstanding from the lower element exposed from the upper element and wherein said formation in the upper surface of its stepped down portion comprises an upwardly opening groove to receive the lip depending from said one wall of the upper element.

4. A manhole chamber as claimed in any one of the preceding claims, wherein the stepped down portion of the corbel slab is constituted by a thickened end of a central portion of the slab which has an undersurface inclined with respect to the upper surface of the slab.

5. A manhole chamber as claimed in any one of the preceding claims, wherein said lower element is the uppermost of a stack of similarly-dimensioned elements all having interengaged formations in their adjacent surfaces and said upper element is the lowermost of a stack of similarly-dimensioned elements all having interengaged formations in their adjacent surfaces.

6. A manhole chamber substantitially as herein described with reference to and as illustrated in Figures 12, 13 and 15 of Figure 14 of the accompanying drawings.

7. A corbel slab substantially as herein described with reference to and as shown in Figures 5-7, Figures 8 and 9 or Figures 10 and 11 of the accompanying drawings.