Inspection chamber system

Abstract

An inspection chamber unit 10 having at least one inlet 14 and outlet 14 is connected to a pipe network that may be a sewer, water supply or gas network. An opening 16 in the inspection chamber unit 1

Description

FIELD The present disclosure relates to an inspection chamber unit, an inspection chamber base and a guide component for an inspection chamber base. The present invention also relates to an inspection system including an inspection chamber unit, a riser conduit and a manhole cover assembly. BACKGROUND Inspection systems are commonly used in pipe networks (e.g. sewer, water supply or gas networks). Such systems typically include an underground inspection chamber base connected to the pipe network. The inspection chamber base has an opening for visually inspecting a property of the pipe network (e.g. checking for standing water indicative of a blocked drain) and / or for providing access for equipment such as CCTV apparatus, drain cleaning apparatus or testing apparatus. In such inspection systems, a riser conduit (e.g. a pipe) is coupled at a first end to the opening of the underground inspection chamber base and at a second end to a manhole cover assembly, which is typically flush with a ground surface (e.g. a road or pavement surface). The manhole cover assembly typically has a frame which defines an access bore in communication with the riser conduit, and a cover placed over the access bore. The cover is typically removable for inspection / access. It is desirable to prevent leakage from the pipe network to the surrounding ground and / or to prevent ingress of groundwater or debris into the pipe network via the opening of the inspection chamber base. In order to achieve this, the riser conduit is typically sized to be a tight fit with the inspection chamber base and / or to include a seal component such as an O-ring which is a tight fit with the inspection chamber base. However, this can make it difficult to insert the riser conduit through the opening, particularly when the inspection chamber base is located deep in the ground. Moreover, inspection chamber bases typically have thin wall thickness relative to their overall size, which makes them prone to warping (e.g. during cooling, storage, transport and / or other stages of manufacturing or distribution). This can change the shape of the opening, which can further inhibit insertion of the riser conduit into the inspection chamber base. The present disclosure seeks to overcome, or at least mitigate, one or more problems of the prior art. SUMMARY Aspects and embodiments of the invention provide an inspection chamber base, a guide component, an inspection chamber kit of parts, and an inspection system kit of parts according to the appended claims. According to an aspect of the disclosure, there is provided an inspection chamber unit comprising at least one inlet and at least one outlet for connection to a pipe network (e.g. a sewer, water supply or gas network), wherein the inspection chamber unit defines an opening for receiving a riser conduit, and wherein the unit comprises one or more guide surfaces adjacent the opening for guiding a riser conduit into the opening. The use of one or more guide surfaces adjacent the opening facilitates easier coupling of a riser conduit with the inspection chamber unit. Optionally, the inspection chamber unit comprises an inspection chamber base which includes the at least one inlet and at least one outlet; and wherein the one or more guide surfaces are mounted on the inspection chamber base. It will be understood that more complex mould tooling would be required to produce an inspection chamber unit as a single piece with one or more guide surfaces. Therefore, mounting the one or more guide surfaces on the inspection chamber base provides a simpler method of manufacturing the inspection chamber unit. Optionally, the or each guide surface defines a free end, and wherein the unit comprises an underside having a stacking formation complementary to the shape of the free end of the or each guide surface, such that a first inspection chamber unit can be stacked with a second inspection chamber unit of the same shape and configuration by positioning the or each free end of a subjacent or superjacent inspection chamber unit in a respective stacking formation of the other inspection chamber unit. Such a stacking formation allows multiple inspection chamber units to be stacked on top of each other for easier storage and / or transportation. Optionally, the one or more guide surfaces comprise a single annular guide surface, or wherein the one or more guide surfaces comprise a plurality of guide surfaces spaced apart around the opening. A single annular guide surface or a plurality of guide surfaces spaced around the opening facilitate guiding of a riser conduit from all directions as it is inserted into the opening in use. In other words, these arrangements facilitate coaxial alignment of a riser conduit with the opening. In exemplary embodiments, the opening is circular for receiving a riser conduit of circular cross-section. Such a circular opening is suitable for coupling to a riser conduit of circular cross-section which is typically used in the field. Optionally, the or each guide surface comprises a ramp which extends from the opening to a free end radially outboard of the opening; optionally, wherein the ramp is substantially linear in cross-section or wherein the ramp is concave in cross-section. Such a ramp has been found to be particular effective for guiding a riser conduit into the opening. According to an aspect of the disclosure, there is provided an inspection chamber base comprising a body having at least one inlet and at least one outlet for connection to a pipe network (e.g. a sewer, water supply or gas network); wherein the body defines an opening for receiving a riser conduit and a connection arrangement proximal the opening; wherein the connection arrangement is configured for engagement with a corresponding connection arrangement on a guide component having one or more guide surfaces configured to guide a riser conduit into the opening, such that the body and a guide component can be coupled together via the respective connection arrangements. It can be difficult to fit a riser conduit within the opening of an inspection chamber base, and so such a connection arrangement allows a guide component with one or more guide surfaces to be coupled to the base to facilitate easier insertion of a riser conduit into the inspection chamber base. In addition, it will be understood that more complex mould tooling would be required to produce an inspection chamber unit as a single piece with one or more guide surfaces. Therefore, providing an inspection chamber base with a connection arrangement configured for engagement with a corresponding connection arrangement of a guide component with one or more guide surfaces provides a simpler method of manufacturing an inspection chamber unit. Furthermore, due to the thin wall thickness relative to their size, inspection chamber bases are prone to warping (e.g. during cooling, storage, transport and / or other stages of manufacturing or distribution) which can change the shape of the opening and make it difficult to receive a riser conduit. It has been found that when a guide component (e.g. a collar) is attached to the inspection chamber base via the connection formations, this helps to return the opening to its intended shape, which further facilitates easier insertion of a riser conduit into the inspection chamber base. Optionally, the connection arrangement of the body comprises a plurality of spaced apart connection formations for engagement with a corresponding plurality of connection formations of a guide component; optionally, wherein the connection formations of the body are distributed evenly about the periphery of the opening. Such a plurality of spaced apart connection formations facilitates attachment of a guide component at multiple points around the opening which provides a secure connection. The plurality of connection formations being distributed evenly about the periphery of the opening facilitates attachment of one or more guide components at even points about an entire periphery of the opening, which provides a secure connection. In exemplary embodiments, the connection formations of the body each comprise a recess or aperture for engagement with a complementary projection of a guide component, optionally wherein each recess or aperture extends radially with respect to a longitudinal axis of the opening; or the connection formations of the body each comprise a projection for engagement with a complementary recess or aperture of a guide component, optionally wherein each projection extends radially with respect to a longitudinal axis of the opening. Optionally, the connection arrangement of the body comprises a series of first formations for interdigitation with a series of second formations on a guide component. Such an interdigitation improves the connection between the body and the guide component. Furthermore, this interdigitation allows for rotational alignment of a guide component (e.g. a collar) with the inspection chamber base. This helps to ensure that any complementary connection formations on the guide component and inspection chamber base are rotationally aligned. Optionally, the body comprises an annular side wall having a rim which defines the opening and the first formations comprise a series of castellations provided on an interior surface of the side wall, wherein the castellations comprise troughs which are recessed axially away from the rim for receiving said second formations in the form of axially-projecting tabs of a guide component; optionally, wherein the connection arrangement of the body further comprises a plurality of connection formations which are circumferentially aligned with the troughs of the castellations. Such castellations improve the connection between the body and the guide component. Optionally, the body comprises a side wall having a rim which defines the opening, wherein the body further comprises an underside having a first stacking formation complementary to the shape of the rim, such that a first inspection chamber base can be stacked with a second inspection chamber base of the same shape and configuration by positioning the rim of a subjacent or superjacent inspection chamber base in the first stacking formation of the other inspection chamber base. Such a first stacking formation allows multiple inspection chamber bases to be stacked on top of each other for easier storage and / or transportation. Optionally, the underside of the body comprises a second stacking formation located radially outside the first stacking formation, such that the inspection chamber base can be stacked with a guide component having a free end which is radially outboard of the rim of the body by positioning a free end of a subjacent or superjacent guide component in the second stacking formation. Having such a combination of first and second stacking formations allows multiple inspection chamber bases to be stacked on top of each other in an unassembled state (i.e. without any corresponding guide component(s) attached) or in an assembled state (i.e. with one or more corresponding guide components attached). This facilitates easier storage and / or transportation regardless of the assembly state of the inspection chamber base. In exemplary embodiments, the opening is circular for receiving a riser conduit of circular cross-section. Such a circular opening is suitable for coupling to a riser conduit of circular cross-section which is typically used in the field. According to an aspect of the disclosure, there is provided a guide component for coupling to an inspection chamber base having an opening for receiving a riser conduit, the guide component comprising: a skirt portion comprising a connection arrangement configured for engagement with a corresponding connection arrangement proximal an opening of an inspection chamber base, such that the guide component can be coupled with an inspection chamber base via the respective connection arrangements; and a guide surface which defines a ramp which extends outwards from a fixed end at the skirt portion to a free end of the guide component, for guiding a riser conduit into an opening of an inspection chamber base with which the guide component is coupled in use. It can be difficult to fit a riser conduit within the opening of an inspection chamber base. Therefore, such a guide component, which can be coupled with an inspection chamber base and which includes a guide surface for guiding a riser conduit into an opening of said inspection chamber base, facilitates easier coupling of a riser conduit with the inspection chamber base. In addition, it will be understood that more complex mould tooling would be required to produce an inspection chamber unit as a single piece with one or more guide surfaces. Therefore, providing a separate guide component with a connection arrangement for coupling together with an inspection chamber base provides a simpler method of manufacturing an inspection chamber unit. Furthermore, due to the thin wall thickness relative to their size, inspection chamber bases are prone to warping (e.g. during cooling, storage, transport and / or other stages of manufacturing or distribution) which can change the shape of the opening and make it difficult to receive a riser conduit. It has been found that when one or more of such guide components are attached to an inspection chamber base via the connection arrangements, this helps to return the opening to its intended shape, which further facilitates easier insertion of a riser conduit into said inspection chamber base. Optionally, the ramp is substantially linear in cross-section or the ramp is concave in crosssection. Such a ramp has been found to be particular effective for guiding a riser conduit into an opening. Optionally, the skirt portion comprises an inner formation which is configured to fit radially inside a rim defining an opening of an inspection chamber base; optionally, wherein the inner formation comprises a series of second formations for interdigitation with a series of first formations on an inspection chamber base; optionally, wherein the series of second formations comprise an inner group of spaced apart tabs. Such an inner formation facilitates alignment of the guide component with a rim defining an opening of an inspection chamber unit. In addition, the inner formation facilitates re-shaping of an opening of an inspection chamber base when it is fitted radially inside a rim defining the opening. Such an interdigitation (e.g. via spaced apart tabs engaged with corresponding troughs of a castellation formation inside a rim of an inspection chamber base) improves the connection between the guide component and an inspection chamber base. Such an interdigitation also allows for rotational alignment of the guide component with an inspection chamber base. This helps to ensure that any complementary connection formations on the guide component and inspection chamber base are rotationally aligned. Optionally, the inner formation comprises the connection arrangement; optionally, wherein the inner formation comprises an inner group of spaced apart tabs which each comprise a connection formation (e.g. projection or recess) for engagement with a complementary connection formation (e.g. recess or projection) of an inspection chamber base. Optionally, the guide component further comprises an outer formation which is configured to fit radially outside of a rim of an inspection chamber base, such that said inner and outer formations define a space therebetween for receiving a rim of an inspection chamber base; optionally, wherein the outer formation comprises an outer group of spaced apart tabs; optionally, wherein the outer group of spaced apart tabs are interspersed between the inner group of spaced apart tabs along a periphery of the guide component. Such an outer formation facilitates alignment of the guide component with a rim defining an opening of an inspection chamber unit. The outer formation also facilitates re-shaping of an opening of an inspection chamber base when it is fitted radially outside a rim defining the opening. Optionally, a distance between the inner and outer formations decreases from a free end of the inner and outer formations to a fixed end of the inner and outer formations; optionally, wherein the inner formation is configured to extend parallel to a longitudinal axis of an opening of an inspection chamber base and the outer formation is configured to flare radially outwards relative to said longitudinal axis when the guide component is fitted to an inspection chamber base in use. Such a configuration means that the space between the inner and outer formations is greater at the free ends (which facilitates insertion of a more warped rim of an inspection chamber base) and reduces towards the fixed ends (which facilitates better re-shaping of the rim as it is pushed further inside the space between the inner and outer formations). The inner formation being configured to extend parallel to a longitudinal axis of said opening and the outer formation being configured to flare radially outwards relative to said longitudinal axis provides a flared receiving space whilst ensuring that the inner formation does not substantially reduce a width of an opening of the inspection chamber base (e.g. as opposed to a configuration in which the outer formation was configured to extend parallel to the longitudinal axis and the inner formation was configured to flare radially inwards relative to the longitudinal axis). Optionally, the connection arrangement of the skirt portion comprises a plurality of spaced apart connection formations for engagement with a corresponding plurality of connection formations proximal an opening of an inspection chamber base; optionally, wherein the connection formations of the guide component are distributed evenly along the skirt. Such a plurality of spaced apart connection formations facilitates attachment of the guide component at multiple points around an opening of an inspection chamber base, which provides a secure connection. The plurality of connection formations being distributed evenly around the skirt facilitates attachment of the guide component along an entire periphery of the skirt, which provides a secure connection. In exemplary embodiments, the or each connection formation of the guide component comprises a projection for engagement with a complementary recess or aperture of a body of an inspection chamber base, optionally wherein the or each projection is configured to extend radially with respect to an opening of an inspection chamber base when the guide component is coupled to said inspection chamber base in use; or the or each connection formation of the guide component comprises a recess or aperture for engagement with a complementary projection of an inspection chamber body, optionally wherein the or each recess or aperture is configured to extend radially with respect to an opening of an inspection chamber base when the guide component is coupled to said inspection chamber base in use. Optionally, the skirt portion is annular for receiving a riser conduit therethrough, optionally, wherein the skirt portion is circular for receiving a riser conduit of circular crosssection. The skirt portion being annular allows a single guide component to be coupled to an inspection chamber base (e.g. as opposed to multiple guide components distributed around the opening). This facilitates simpler assembly. Optionally, the guide surface is annular. Optionally, the guide component comprises a plurality of guide surfaces spaced apart along the skirt portion. An annular guide surface or a plurality of guide surfaces spaced along the skirt portion (e.g. along an annular skirt portion) facilitate guiding of a riser conduit from all directions (i.e. coaxial alignment) as it is inserted into the opening of an inspection chamber base in use. Optionally, the guide component comprises a segment of an annular shape (e.g. an arcuate segment of a circular annular shape). The guide component comprising a segment of an annular shape allows multiple guide components of the same shape and configuration to be coupled to an inspection chamber base (e.g. with the guide components touching each other to define a continuous annular shape, or with the guide components spaced apart to define a discontinuous annular shape). Optionally, the guide component further comprises one or more location formations (e.g. recesses or projections) proximal the free end of the guide surface, for co-operation with a corresponding one or more location formations (e.g. projections or recesses) of an assembly jig. Such location formations allow the guide component to be correctly positioned within an assembly jig (e.g. in the correct angular orientation), which makes it simpler to couple with an inspection chamber base in an automated factory operation. According to an aspect of the disclosure, there is provided an inspection chamber kit of parts comprising an inspection chamber base as disclosed herein and a guide component as disclosed herein. According to an aspect of the disclosure, there is provided an inspection chamber system comprising: an inspection chamber unit comprising at least one inlet and at least one outlet for connection to a pipe network (e.g. a sewer, water supply or gas network), wherein the inspection chamber unit defines an opening for receiving a riser conduit, and wherein the unit comprises one or more guide surfaces adjacent the opening for guiding a riser conduit into the opening; a manhole cover assembly comprising a frame and a cover configured to be attached to the frame; and a riser conduit comprising a first end configured for coupling to the opening of the inspection chamber unit or base and a second end configured for coupling to the frame of the manhole cover assembly. Optionally, the inspection chamber system further comprises an intermediate component having a first portion configured to be located within the second end of the riser conduit and a second portion configured for connection to the frame of the manhole cover assembly. In exemplary embodiments, the riser conduit comprises a seal component proximal the first end for forming a seal between the riser conduit and the inspection chamber unit or base. According to an aspect of the disclosure, there is provided an inspection system kit of parts comprising: an inspection chamber unit as disclosed herein or an inspection chamber kit of parts as disclosed herein; a manhole cover assembly comprising a frame and a cover configured to be attached to the frame; and a riser conduit comprising a first end configured for coupling to the opening of the inspection chamber unit or base and a second end configured for coupling to the frame of the manhole cover assembly. In exemplary embodiments, the inspection chamber kit of parts further comprises an intermediate component having a first portion configured to be located within the second end of the riser conduit and a second portion configured for connection to the frame of the manhole cover assembly. In exemplary embodiments, the riser conduit comprises a seal component proximal the first end for forming a seal between the riser conduit and the inspection chamber unit or base. BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will now be described, by way of example only, with reference to the following figures in which: Figure 1 is an exploded isometric view of an inspection system according to an embodiment; Figure 2 is an isometric view of an inspection chamber unit of the inspection system of Figure 1; Figure 3 is a side sectional view of the inspection chamber unit of Figure 2; Figure 4 is an isometric view of an inspection chamber base of the inspection chamber unit of Figures 2 and 3; Figures 5a and 5b are isometric views of a guide component for coupling to the inspection chamber base of Figure 4 to form the inspection chamber unit of Figures 2 and 3; Figure 6 is a side sectional view of two inspection chamber bases of Figure 4 stacked one atop the other; and Figure 7 is a side sectional view of two inspection chamber units of Figures 2 and 3 stacked one atop the other. DETAILED DESCRIPTION Referring firstly to Figure 1, an inspection system is indicated at 1000. The inspection system 1000 includes an inspection chamber unit 100 having an opening 16, a manhole cover assembly 102 and a riser conduit 104. The manhole cover assembly 102 includes a frame and a cover configured to be attached to the frame. In particular, the manhole cover assembly 102 is of the kind described in GB2558211. However, other suitable manhole cover assemblies may be used. The riser conduit 104 has a first end 104a configured for coupling to the opening 16 of the inspection chamber unit 100, and a second end 104b configured for coupling to the frame of the manhole cover assembly 102. In the illustrated embodiment, the riser conduit 104 also includes a seal component 104c (e.g. a compressible annular seal, such as an O-ring) proximal the first end 104a, for forming a seal between the riser conduit 104 and the inspection chamber base 10. In the illustrated embodiment, the riser conduit 104 is a single integrally formed conduit. In alternative embodiments, the riser conduit 104 is formed of a plurality of riser conduit sections which are coupled together via suitable means. In the illustrated embodiment, the inspection system 1000 also includes an intermediate component 106 having a first portion 106a configured to be located within the second end 104b of the riser conduit 104 and a second portion 106b configured for connection to the frame of the manhole cover assembly 102. In other words, the second end 104b of the riser conduit 104 is configured for coupling to the frame of the manhole cover assembly 102 via the intermediate component 106. In the illustrated embodiment, the riser conduit 104 is a circular pipe (i.e. has a circular cross-section). Accordingly, the opening 16 of the inspection chamber unit 100 and the first portion 106a of the intermediate component 106 are also circular. However, it will be understood that riser conduits of different shape / configuration may be used (e.g. a riser conduit of square cross-section). In such embodiments, the shape of the opening 16 of the inspection chamber unit 100 and the first portion 106a of the intermediate component 106 would change accordingly, to complement the cross-section of the riser conduit 104. Referring now to Figures 2 and 3, the inspection chamber unit 100 has a plurality of inlets and outlets 14 for connection to a pipe network (e.g. a sewer, water supply or gas network). The inspection chamber unit 100 also has a guide surface 52 adjacent the opening 16. It will be understood that the guide surface 52 is configured for guiding the riser conduit 104 into the opening 16. In particular, the guide surface 52 defines a ramp which extends from the opening 16 to a free end radially outboard of the opening. It will be understood that when the riser conduit 104 is offset with respect to the opening 16 whilst trying to insert the riser conduit 104 into the opening 16, the first end 104a of the riser conduit 104 contacts and moves along the ramp defined by the guide surface 52 to come into alignment with the opening 16. This facilitates easier insertion of the riser conduit 104 into the opening 16. In the illustrated embodiment, the ramp defined by the guide surface 52 is substantially linear in cross-section (i.e. the ramp 52 is flat). In alternative embodiments, the ramp defined by the guide surface 52 is concave in cross-section (i.e. the ramp 52 is curved). It will be understood that when the seal component 104c of the riser conduit 104 is inserted through the opening 16, the shape of the ramp 52 results in a gradual compression of the seal component 104c as it is guided along the ramp 52. In the illustrated embodiment, the ramp 52 has a substantially constant cross-sectional profile along a circumferential length of the ramp 52. Therefore, as the riser conduit 104 is inserted into the opening 16, the shape of the ramp 52 leads to substantially equal compression of the seal component 104c along the circumferential length of the ramp 52. In alternative embodiments, a cross-sectional profile of the ramp 52 varies along a circumferential length of the ramp 52. When the riser conduit 104 is inserted into the opening 16 in such embodiments, the shape of the ramp 52 results in varied rates of compression of the seal component 104c along the circumferential length of the ramp 52, which reduces the force required to insert the riser conduit 104 into the opening 16. In one such embodiment, the ramp 52 includes one or more first portions which are substantially linear in cross-section (i.e. substantially flat portions) and one or more second portions which are concave in cross-section (i.e. curved portions). In another such embodiment, the ramp 52 includes one or more first portions which are arranged at a first angle with respect to a longitudinal axis of the opening 16 and one or more second portions which are arranged at a second angle with respect to the longitudinal axis of the opening 16, where the second angle is less than the first angle. It will be understood that in embodiments where the cross-sectional profile of the ramp 52 various along a circumferential length of the ramp 52, there may be a smooth transition region between adjacent portions of the ramp to avoid sharp edges which could damage the seal component 104c. In the illustrated embodiment, the guide surface 52 is annular (i.e. it surrounds the opening 16). This facilitates guiding of the riser conduit 104 from all directions as it is inserted into the opening 16 in use. In other words, this facilitates coaxial alignment of the riser conduit 104 with the opening 16. In alternative embodiments, there are a plurality of guide surfaces spaced apart around the opening 16 (e.g. two opposing guide surfaces, or greater than two guide surfaces evenly spaced apart around the opening 16). In such embodiments, the guide surfaces may each define an arcuate segment (e.g. of 10 to 90 degrees). In such embodiments, the spacing between the guide surfaces is preferably equidistant. It will be understood that the spacing between the guide surfaces in such embodiments allows for varying rates of compression of the seal component 104c of the riser conduit 104, in a similar way to having a ramp with a cross-sectional profile which varies along a circumferential length of the ramp, as is described above. It will be understood that a single arcuate guide surface (e.g. a 10 to 180 degree arc) would also be suitable because this would still, to a certain extent, guide the riser conduit 104 from multiple directions (e.g. at multiple positions along the arc) as the riser conduit 104 is inserted into the opening 16. As will be described in more detail below, the inspection chamber unit 100 has an inspection chamber base 10 which defines the opening 16 and includes the inlets and outlets 14. As will be described below, the guide surface 52 is mounted on the inspection chamber base. In particular, the inspection chamber unit 100 also includes a guide component 50 which defines the guide surface 52. The inspection chamber base 10 and the guide component 10 are coupled together. As best illustrated in Figure 3, the inspection chamber base 10 has a thin wall thickness relative to a width of the opening 16. This makes the inspection chamber base 10 prone to warping (e.g. during cooling, storage, transport and / or other stages of manufacturing or distribution) which can change the shape of the opening 16 and inhibit insertion of the riser conduit 104 into the opening 16. However, when the guide component 50 is attached to the inspection chamber base 10, it helps to return the opening 16 to its intended (e.g. circular) shape, which makes it easier for the riser conduit 104 to be inserted. In alternative embodiments, the inspection chamber unit 100 is a single item (e.g. with an integrally formed base and guide surface 52). Referring now to Figure 4, the inspection chamber base 10 will be described in more detail. The inspection chamber base 10 has a body 12 which includes the inlets and outlets 14 and defines the opening 16. The inspection chamber base 10 also has a connection arrangement 18 proximal the opening 16. The connection arrangement 18 is configured for engagement with a corresponding connection arrangement 56 on the guide component 50, such that the body 12 and the guide component 50 can be coupled together via the respective connection arrangements 18, 56. In alternative embodiments, the guide component 50 is mounted on the inspection chamber base 10 via laser welding, adhesive or any other suitable means. In the illustrated embodiment, the connection arrangement 18 of the body 12 includes a plurality of spaced apart connection formations 20 for engagement with a corresponding plurality of connection formations 62 of the guide component 50. In the illustrated embodiment, the connection formations 20 of the body 12 are distributed evenly about the periphery of the opening 16. In alternative embodiments, the connection arrangement 18 includes a single connection formation (e.g. an annular connection formation). In the illustrated embodiment, the connection formations 20 of the body 12 are apertures for engagement with complementary projections 62 of the guide component. The apertures extend radially with respect to a longitudinal axis of the opening 16 (i.e. through an annular side wall 22 of the body 12). In alternative embodiments, the connection formations 20 of the body 12 are recesses which do not extend fully through the side wall 22. In alternative embodiments, the connection formations 20 of the body 12 are projections for engagement with complementary apertures / recesses on the guide component 50. In the illustrated embodiment, the connection arrangement 18 also has a series of first formations 24a, 24b for interdigitation with a series of second formations 60 on the guide component 50. In particular, the first formations 24a, 24b are in the form of a series of castellations provided on an interior surface of the side wall 22. The castellations have troughs 24b which are recessed axially away from a rim 26 of the side wall 22. As best illustrated in Figures 2 and 3, when the inspection chamber base 10 and guide component 50 are coupled together, the troughs 24b receive the second formations 60 of the guide component 50, which are provided in the form of axially-projecting tabs. In the embodiment illustrated in Figure 4, the connection formations 20 of the body are circumferentially aligned with the troughs 24b. In particular, each connection formation 20 is aligned with in a different trough 24b. Referring now to Figures 5a and 5b, the guide component 50 will be described in more detail. The guide component 50 has a skirt portion 54 with a connection arrangement 56 configured for engagement with the connection arrangement 18 of the inspection chamber base 10, such that the body 12 and the guide component 50 can be coupled together via the respective connection arrangements 18, 56. The guide component 50 also includes the guide surface 52 mentioned above, which defines a ramp which extends outwards from a fixed end at the skirt portion 54 to a free end 55 of the guide component 50. In the illustrated embodiment, the skirt portion 54 defines an inner formation 58 which is configured to fit radially inside the rim 26 of the inspection chamber base 10. In particular, the inner formation includes a series of second formations 60 for interdigitation with the first formations 24a, 24b of the inspection chamber base 10. In the illustrated embodiment, the series of second formations 60 are in the form of an inner group of spaced apart tabs. In the illustrated embodiment, the inner formation 58 includes the connection arrangement 56 of the guide component. In particular, each spaced apart tab 60 of the inner formation 58 has a connection formation 62 for engagement with one of the complementary connection formations 20 of the inspection chamber base 10. In the illustrated embodiment, the connection formations 62 of the guide component 50 are projections for engagement with complementary apertures 20 of the inspection chamber base. The projections 62 extend radially with respect to a longitudinal axis of the opening 16, so that they can be received in the apertures 20 through the side wall 22 of the body 12. In alternative embodiments, the connection formations 62 of the guide component 50 are apertures / recesses for engagement with complementary projections on the body 12 of the inspection chamber base 10. In the illustrated embodiment, the inner group of tabs 60 are evenly spaced apart. Thus, the connection formations 62 provided on the inner group of tabs 60 are also evenly spaced-apart. In the illustrated embodiment, the guide component 50 also has an outer formation 64 which is configured to fit radially outside of the rim 26 of the inspection chamber base 10, such that the inner and outer formations 58, 64 define a space 66 therebetween for receiving the rim 26 of the inspection chamber base 10. In the illustrated embodiment, the outer formation 64 includes an outer group of spaced apart tabs which are interspersed between the inner group of spaced apart tabs 60 along a periphery of the guide component 50. In the illustrated embodiment, a distance between the inner and outer formations 58, 64 decreases from a free end of the inner and outer formations 58, 64 to a fixed end of the inner and outer formations. Such a configuration means that the space 66 between the inner and outer formations 58, 64 is greater at the free ends (which facilitates insertion of a more warped rim 26 of the inspection chamber base 10) and reduces towards the fixed ends (which facilitates better re-shaping of the rim 26 as it is pushed further inside the space between the inner and outer formations 58, 64). In some embodiments, the inner formation 58 is configured to extend parallel to a longitudinal axis of the opening 16 of the inspection chamber base so that it sits flush against the side wall 22 in use (as illustrated in Figure 3) and the outer formation 64 is configured to flare radially outwards relative to the longitudinal axis when the guide component 50 is fitted to the inspection chamber base 10. Such a configuration provides a flared receiving space 66 whilst ensuring that the inner formation 58 does not substantially reduce the width of an opening 16 of the inspection chamber base 10 (e.g. as opposed to a configuration in which the outer formation 64 was configured to extend parallel to the longitudinal axis to sit flush with the outside of side wall 22, and the inner formation 58 was configured to flare radially inwards relative to the longitudinal axis). In the illustrated embodiment, the skirt portion 54 is annular for receiving the riser conduit 104 therethrough. In other words, the skirt portion 54 is a collar for the inspection chamber base 10. In this way, only a single guide component 50 is needed to surround the opening 16 of the inspection chamber base 10. In alternative embodiments, the guide component 50, and thus the skirt portion 54 and guide surface 52, is a segment of an annular shape (e.g. an arcuate segment of a circular annular shape). In such embodiments, it will be understood that multiple guide components 50 may be coupled to the inspection chamber base 10 (e.g. with the guide components 50 touching each other to define a continuous annular shape, or with the guide components 50 spaced apart to define a discontinuous annular shape). In the illustrated embodiment, the guide surface 52 is also annular. In alternative embodiments there are a plurality of guide surfaces 52 spaced apart around an annular skirt portion 54 (e.g. two opposing guide surfaces, or greater than two guide surfaces evenly spaced apart around the skirt portion 54). In such embodiments, the guide surfaces may each define an arcuate segment (e.g. of 10 to 90 degrees). In such embodiments, the spacing between the guide surfaces is preferably equidistant. In the illustrated embodiment, the guide component 50 has a plurality of location formations 68 proximal the free end 55 of the guide surface 52. The location formations 68 are in the form of recesses for co-operation with a corresponding plurality of projections of an assembly jig (not shown). In alternative embodiments, the location formations 68 are projections for co-operation with a corresponding recess of an assembly jig. Such location formations 68 allow the guide component 50 to be correctly positioned within an assembly jig (e.g. in the correct angular orientation), which makes it simpler to couple with the inspection chamber base 10 in an automated factory operation. Referring now to Figure 6, the body 12 of the inspection chamber base 10 has an underside 28 having a first stacking formation 30 complementary to the shape of the rim 26, such that a first inspection chamber base 10A can be stacked with a second inspection chamber base 10B of the same shape and configuration by positioning the rim 26 of the first inspection chamber base 10A in the first stacking formation 30 of the second inspection chamber base 10B. In Figure 6, the first inspection chamber base 10A is subjacent the second inspection chamber base 10B, but it will be understood that the first and second inspection chamber bases 10A, 10B can also be stacked the other way up with the first inspection chamber base 10A superjacent the second inspection chamber base 10B (i.e. with the openings 16 of the inspection chamber bases 10A, 10B facing downwards). In the illustrated embodiment, the first stacking formation 30 consists of a plurality of recesses 32 distributed around the underside 28 of the inspection chamber base 10. In alternative embodiments, the first stacking formation 30 is an annular groove or one or more arcuate grooves in the underside 28 of the inspection chamber base 10. Referring now to Figure 7, the underside 28 of the body 12 also has a second stacking formation 34 located radially outside the first stacking formation 30, such that a first inspection chamber unit 100A can be stacked with a second inspection chamber unit 100B by positioning the free end 55 of the guide of the first inspection chamber unit 100A in the second stacking formation 34 of the inspection chamber base 10 of the second inspection chamber unit 100B. In Figure 7, the first inspection chamber unit 100A is subjacent the second inspection chamber unit 100B, but it will be understood that the first and second inspection chamber units 100A, 100B can also be stacked the other way up with the first inspection chamber unit 100A superjacent the second inspection chamber unit 100B (i.e. with the openings 16 of the inspection chamber units 100A, 100B facing downwards). In the illustrated embodiment, the second stacking formation 34 consists of a plurality of recesses 36 distributed around the underside 28 of the inspection chamber base 10, radially outboard of the recesses 32 of the first stacking formation 30. In alternative embodiments, the second stacking formation 34 is an annular groove or one or more arcuate grooves in the underside 28 of the inspection chamber base 10. Having such a combination of first and second stacking formations 30, 34 allows multiple inspection chamber bases 10A, 10B to be stacked on top of each other in an unassembled state (i.e. without any corresponding guide component(s) 50 attached, as shown in Figure 6) or in an assembled state (i.e. with the corresponding guide component(s) 50 attached, as shown in Figure 7). It will be understood that in some embodiments where the inspection chamber unit 100 is a single item (e.g. with an integrally formed base and guide surface 52), only a single stacking formation is provided (i.e. the first stacking formation 30 is omitted). Although the invention has been described in relation to one or more embodiments, it will be appreciated that various changes or modifications can be made without departing from the scope of the invention as defined in the appended claims. It should also be noted that whilst the appended claims set out particular combinations of features described above, the scope of the present disclosure is not limited to the particular combinations hereafter claimed, but instead extends to encompass any combination of features herein disclosed.

Claims

1. An inspection chamber base comprising a body having at least one inlet and at least one outlet for connection to a pipe network;wherein the body defines an opening for receiving a riser conduit and a connection arrangement proximal the opening;wherein the connection arrangement is configured for engagement with a corresponding connection arrangement on a guide component having one or more guide surfaces configured to guide a riser conduit into the opening, such that the body and a guide component can be coupled together via the respective connection arrangements,wherein the connection arrangement of the body comprises a plurality of spaced apart connection formations for engagement with a corresponding plurality of connection formations of a guide component.

2. The inspection chamber base of claim 1, wherein the connection formations of the body are distributed evenly about the periphery of the opening.

3. The inspection chamber base of claim 1 or 2, wherein the connection arrangement of the body comprises a series of first formations for interdigitation with a series of second formations on a guide component.

4. The inspection chamber base of claim 3, wherein the body comprises an annular side wall having a rim which defines the opening and the first formations comprise a series of castellations provided on an interior surface of the side wall, wherein the castellations comprise troughs which are recessed axially away from the rim for receiving said second formations in the form of axially-projecting tabs of a guide component.

5. The inspection chamber base of claim 4, wherein the connection arrangement of the body further comprises a plurality of connection formations which are circumferentially aligned with the troughs of the castellations.

6. The inspection chamber base of any preceding claim, wherein the body comprises a side wall having a rim which defines the opening, wherein the body further comprises an underside having a first stacking formation complementary to the shape of the rim, such that a first inspection chamber base can be stacked with a second inspection chamber base of the same shape and configuration by positioning the rim of a subjacent or superjacent inspection chamber base in the first stacking formation of the other inspection chamber base.

7. The inspection chamber base of claim 6, wherein the underside of the body comprises a second stacking formation located radially outside the first stacking formation, such that the inspection chamber base can be stacked with a guide component having a free end which is radially outboard of the rim of the body by positioning a free end of a subjacent or superjacent guide component in the second stacking formation.

8. A guide component for coupling to an inspection chamber base having an opening for receiving a riser conduit, the guide component comprising:a skirt portion comprising a connection arrangement configured for engagement with a corresponding connection arrangement proximal an opening of an inspection chamber base, such that the guide component can be coupled with an inspection chamber base via the respective connection arrangements; anda guide surface which defines a ramp which extends outwards from a fixed end at the skirt portion to a free end of the guide component, for guiding a riser conduit into an opening of an inspection chamber base with which the guide component is coupled in use.

9. The guide component of claim 8, wherein the ramp is substantially linear in crosssection or wherein the ramp is concave in cross-section.

10. The guide component of claim 8 or 9, wherein the skirt portion comprises an inner formation which is configured to fit radially inside a rim defining an opening of an inspection chamber base.

11. The guide component of claim 10, wherein the inner formation comprises a series of second formations for interdigitation with a series of first formations on an inspection chamber base.

12. The guide component of claim 10, wherein the inner formation comprises the connection arrangement.

13. The guide component of any of claims 10 to 12, further comprising an outer formation which is configured to fit radially outside of a rim of an inspection chamber base, such that said inner and outer formations define a space therebetween for receiving a rim of an inspection chamber base.

14. The guide component of claim 13, wherein a distance between the inner and outer formations decreases from a free end of the inner and outer formations to a fixed end of the inner and outer formations.

15. The guide component of claim 14, wherein the inner formation is configured to extend parallel to a longitudinal axis of an opening of an inspection chamber base and the outer formation is configured to flare radially outwards relative to said longitudinal axis when the guide component is fitted to an inspection chamber base in use.

16. The guide component of any of claims 8 to 15, wherein the connection arrangement of the skirt portion comprises a plurality of spaced apart connection formations for engagement with a corresponding plurality of connection formations proximal an opening of an inspection chamber base.

17. The guide component of claim 16, wherein the connection formations of the guide component are distributed evenly along the skirt.

18. The guide component of any of claims 8 to 17, wherein the skirt portion is annular for receiving a riser conduit therethrough.

19. The guide component of claim 18, wherein the skirt portion is circular for receiving a riser conduit of circular cross-section.

20. The guide component of any of claims 8 to 19, wherein the guide surface is annular.

21. The guide component of any of claims 8 to 19, comprising a plurality of guide surfaces spaced apart along the skirt portion.

22. The guide component of any of claims 8 to 17, wherein the guide component comprises a segment of an annular shape.

23. The guide component of any of claims 8 to 22, further comprising one or more location formations proximal the free end of the guide surface, for co-operation with a corresponding one or more location formations of an assembly jig.

24. An inspection chamber kit of parts comprising the inspection chamber base of any of claims 1 to 7 and the guide component of any of claims 8 to 23.

25. An inspection system kit of parts comprising:the kit of parts of claim 24;a manhole cover assembly comprising a frame and a cover configured to be attached to the frame; and5 a riser conduit comprising a first end configured for coupling to the opening of theinspection chamber base and a second end configured for coupling to the frame of the manhole cover assembly.

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