It is known to install optical fibres into underground ducts using a blowing technique, such cables typically comprising a bundle of tubes: it is also known to install optical fibres into these tubes subsequently, using the same blowing technique. In this blowing technique, a blowing head is used, at a convenient access point, to blow the cables through the duct (or the fibres through a cable tube), the leading end of the cable (or fibres) being retrieved downstream at an interceptor point: typically, the cable or a further cable is blown along another duct leading away from that interceptor point to a further interceptor point, and so on.

Enclosures for use as interceptors on optical fibre cable networks are known. However, these suffer various drawbacks, either being unsuited to a range of different uses encountered in a network or requiring breaking of a seal with an existing duct in order to open the enclosure for access.

We have now devised an enclosure which is suited to use as an intercept and which serves a wide variety of different uses.

In accordance with the present invention, there is provided an enclosure for use on an optical fibre network, the enclosure comprising a hollow body having an open top, a cover for fitting over said open top, and a plurality of ports formed in the side or sides of said body.

Preferably at least two of the ports of the enclosure are directe at right angles to each other, so that cables can enter and leave at 90° to each other. Preferably the hollow body is circular in plan view and at least one of the ports is directe generally tangentially, to facilitate cables entering and leaving at 90°. Preferably the enclosure has four sets of ports directe outwardly at 90° intervals around the enclosure: each such set may comprise two ports directe generally

tangentially; optionally each set may include a third port, dispose between the first two ports of the set and directe radially of the enclosure. Preferably all of the ports are positioned in a common plane extending transversely of the enclosure, preferably adjacent the bottom of the enclosure.

It will be appreciated that the cover of the enclosure can be removed, to provide access for a blowing head, without disturbing ducts already coupled to the ports of the enclosure and thereby without disturbing the seals between the enclosure and such ducts.

Often enclosures are expensive to manufacture.

However, we have now devised a method of manufacture which is relatively straightforward and results in an enclosure of relatively low cost.

Thus, in accordance with the present invention, there is provided a method of manufacturing an enclosure which comprises a body part and a removable lid, the method comprising forming a hollow body of plastics material within a mould by a rotational moulding process, then severing said hollow body to form a body part having an open top and a lid for fitting onto the open top of the body part.

Preferably the method further comprises the step of severing the hollow moulded body to form the body part with an open lower end and provide a separate bottom part for fitting onto the open lower end of the body part.

In carrying out the rotational moulding process, plastics material is introduced into the mould through an aperture in an end of the mould, corresponding to an aperture formed in the lid of the enclosure. Conveniently, this aperture may receive a pressure relief valve in the final enclosure.

Preferably the mould comprises a plurality of mould parts which separate along axes parallel to the axes of respective ports provided in the side or sides of the body part of the enclosure.

It is often required to install an interceptor enclosure to couple into an already-laid cable duct. We have devised an enclosure which enables this to be achieved in a simple and relatively quick manner.

Thus, also in accordance with the present invention, there is provided an enclosure for use in an optical fibre network, the enclosure comprising a hollow body including a bottom portion which is split into upper and lower half-shells which define a plurality of radiating passages communicating with the interior of the hollow body, enabling the lower half- shell to be separated from the upper half-shell and the two half-shells then to be embraced about an existing cable duct.

Preferably the two half-shells define two passages radiating in diametrically opposite directions from the enclosure.

Preferably the upper half-shell is formed as an adaptor arrange to be fitted onto the open lower end of a body part of the enclosure. In this case, the two half-shells can be clamped onto an existing duct, then the required length of the duct opened up and the necessary work carried out on its cables, before the body part is fitted onto the top of the upper half-shell or adaptor.

The two half-shells may be formed of metal, whilst the enclosure body part and its lid may be formed of plastics.

The enclosure may be marketed in a standard form consisting of a body part, lid and bottom part. For the occasions where, in the field, it is found that the enclosure requires fitting to an existing duct, then the bottom part can be discarded and an adaptor assembly used in its place (to clamp around the existing duct and then have the enclosure body part fitted to it).

Preferably the enclosure body part is arrange so that two or more of such body parts may be fitted one-on-top-of- another, the lid part then being fitted over the uppermost body part.

The upper half-shell may be formed with one or more cable entry ports, which are preferably directe tangentially.

The enclosure may, in this case, comprise three parts only, the upper half-shell, the lower half-shell and a lid which fits across the open top of the upper half-shell. Cables from the main duct may run out through the port or ports of the upper half-shell.

It is often necessary for an enclosure to be capable of

receiving ducts or cables of widely differing diameters. We have now devised an enclosure having this capability.

Thus, in accordance with the present invention, there is provided an enclosure which comprises a hollow body having one or more ports to receive cables or cable ducts, the or each port comprises a radially-outer tubular portion projecting from said hollow body and a radially-inner tubular portion extending axially inwardly from the outer end of the radially-outer tubular portion.

For relatively large diameter cables or ducts, an end portion of the port can be cut away, leaving a desired length of the radially-outer tubular portion only. Smaller diameter cables or ducts may be inserted through the radially-inner tubular portion (cafter the inner end thereof, which is preferably closed in the enclosure as manufacture, is cut out).

Preferably the radially-outer tubular portion inclues a tapering section, and the length of the port which is cut away (when installing the larger-diameter cables or ducts) is selected according to the diameter of the cable or duct to be installe.

Embodiments of the present invention will now be described by way of examples only and with reference to the accompanying drawings, in which: FIGURE 1 is a plan view of an enclosure in accordance with the present invention; FIGURE 2 is a side view, partly in section, of the enclosure of Figure 1 in the direction of the arrow A; FIGURE 3 is a side view partly in section, of a rotationally-moulded hollow body from which the enclosure of Figures 1 and 2 is formed; FIGURE 4 is a similar side view of the hollow body of Figure 3, showing the manner in which the body is divided to form the enclosure of Figures 1 and 2; FIGURE 5 is a similar side view to Figure 2 of the enclosure, shown with its bottom provided with an adaptor for fitting the enclosure onto an existing duct; FIGURE 6 is a side view, partly in section, of the enclosure of Figure 5, from the direction of arrow B of Figure 5 ;

FIGURE 7 is a series of sections through a port of the enclosure, showing the port cut through transversely at different points to accommodate ducts or cables of different diameters; FIGURE 8 is a further series of sections through a port of the enclosure, showing the centre of the port cut through axially to accommodate cables of different diameters; FIGURE 9 is a side-view, partly in section, of a modifie enclosure in accordance with the present invention; FIGURE 10 is an underside view, partly in section, of the enclosure of Figure 9; and FIGURE 11 is an end view partly in section, of the enclosure of Figure 9.

Referring to Figures 1 and 2 of the drawings, there is shown an enclosure which comprises a generally cylindrical body 10 which has an open top provided on the outside with a peripheral flange 11. The enclosure further comprises a circular lid 20 which fits over the open top of the body part 10: the lid 20 has a peripheral flange 21 which seats on the flange 11 of the body part 10, with the interposition of an annular seal or gasket 8, and a depending peripheral skirt 22 which locates within the open top of the body part 10. The lid is fastened in place by a clamp ring 6 which engages over the flanges 11,21 of the body part 10 and lid 20. The lid 20 is formed at its centre with a well 24, which has an orifice in which a pressure relief valve 26 is mounted: this valve opens to vent the interior of the enclosure should the internal pressure inadvertently exceed a predetermined value (e. g.

5p. s. i).

The body 10 of the enclosure also has an open lower end and a bottom part 30 is provided to close it. The bottom part 30 is generally flat and has an upstanding peripheral wall 32 with an outwardly-projecting flange 31 at its top, corresponding to the flange 11 at the top of the body part 10.

The lower end of the body part 10 is formed with a flange 13 and a depending skirt 12, corresponding to the flange 21 and skirt 22 of the lid 20. The body part 10 accordingly fits onto the bottom part 30 in identical manner to the manner in which the lid 20 fits onto the top of the body part 10, an annular

gasket 32 being interpose between the flanges 13 and 31 and a removable clamp ring 4 being engaged around these flanges to fasten the body part and bottom part together.

The body part 10 of the enclosure is formed with four sets of ports, directe outwardly from the side of the enclosure, the four sets being positioned at 90° intervals.

Each set of ports, e. g. set 40,41,42, comprises three ports, a centre port 41 being directe radially of the enclosure and the other two ports 40,42 being positioned either side of the centre port and directe parallel to it. By being offset either side from the centre port 41 in this manner, the two ports 40,42 are directe generally tangentially to the inner surface of the body part 10 of the enclosure. It will be noted that all of the ports are positioned in a common transverse plane adjacent the bottom of the body part 10.

It will be appreciated that any selected port or ports of the enclosure can be used for coupling to ducts for optical fibres or fibre tubes to be fed into the enclosure, or fed outwardly from the enclosure, using conventional blowing techniques. For example, the cover of the enclosure can be removed and a blowing head used to blow fibres or fibre tubes outwardly through any selected port of the enclosure.

Furthermore, excess lengths of fibre-containing tubes can be coiled around and stored within the enclosure: for this purpose, the inner surface of the body part 10 of the enclosure is formed, at spaced intervals around the enclosure, with a number of series of projecting ledges 16, to locate different coils of fibre-containing tubes. If desired, fibres or fibre tubes may enter and leave the enclosure at 90°, using any one of the tangential ports and one of the ports at 90° to it.

The body part 10, lid 20 and bottom 30 of the enclosure are manufactured by forming a single hollow body by a rotational moulding process, then severing this hollow body to form the three separate components. The rotationally-moulded hollow body is shown in Figure 3: the mould, in which the hollow body is formed, inclues four sections which separate along respective axes parallel to the axes of the respective sets of ports of the enclosure, the four sections of the mould meeting each other along vertical planes at 45° to the sets of

ports. During the rotational moulding process, plastics material is fed into the mould through an aperture in one end, corresponding to the aperture on the central well of the lid which is used, in the final product, for receiving the pressure relief valve.

The mould also inclues a ring structure to define the space between the flanges 21 and 11 of the lid and body part respectively. This ring structure comprises two metal rings M1 and M2, separated by a split ring R1 of plastics material, the latter being positioned in a plane intermediate the two flanges: thus, once the hollow body is removed from the mould, the two semi-circular halves of the split ring R1 can be removed, then the hollow body severed over that plane (P1 in Figure 3) using a cutting tool inserted between the two metal rings M1, M2 of the mould. This process effectively separates the lid 20 from the moulded hollow body, as shown in Figure 4: the metal rings M1, M2 are slid off and an annular piece S1 is then cut from the top of the hollow body (the cut being made along a cylindrical surface), to form the top of the body part of the enclosure, the piece S1 being discarded.

A corresponding ring structure is employed in the mould, to define the space between the flanges 13 and 31 of the body part and bottom part. In a similar manner to that just described, the moulded hollow body is severed over a plane P2, intermediate the flanges 13 and 31, to separate the body part from the bottom part, then an annular piece S2 is cut from the bottom part and discarded.

It is often required to install an interceptor enclosure to couple into an already-laid cable duct. For this purpose, and referring to Figure 5 and 6, an adaptor assembly can be provided for fitting onto the existing cable duct and then to receive the lower end of the body part 10 of the enclosure of Figures 1 and 2. The adaptor assembly comprises a generally dish-shaped hollow shell 50 having a circular wall at its top, formed with a peripheral flange 51 and corresponding to the top of the body part 10 of the enclosure.

Thus, the lower end of the body part 10 fits onto the top of the adaptor shell 50 and is fastened in position using the clamp ring 4.

The underside of the adaptor shell 50 is formed with a raised floor section 52 extending diametrically across it. The adaptor assembly further comprises a trough-shaped clamp member 60 for fitting against the underside of the raised floor section 52. In use, the clamp member 60 is placed under the existing duct D (Figure 5): then the adaptor shell 50 is placed over the duct D and clamp member 60, upstanding threaded studs 62 of the member 60 passing through corresponding holes in the floor 52 of the shell 50 to receive nuts for holding the shell 50 and clamp member 60 together. The opposite ends of the clamp member 60 are formed with semi-circular extensions 64 to fit against the underside of the duct D: the adaptor shell 50 is formed with corresponding semi-circular extensions 54 to fit against the upperside of the duct D. The adaptor shell 50 and clamp member 60 accordingly embrace the duct D at its diametrically opposed entry and exit points. A seal 66 is interpose between the adaptor shell 50 and the clamp member 60.

Once the adaptor shell 50 and clamp member 60 have been clamped onto the duct D, then, working through the top of the shallow adaptor shell 50, a length of the duct D is cut away to gain access to the cables etc. within it. The relatively large open top of the adaptor shell, and the fact that it is shallow in height, allows good access to the duct D and subsequently its cables for the necessary work to be carried out on these. The body part 10 of the enclosure can be fitted once this work has been completed.

It will be appreciated that because the body part 10 and the top of the adaptor shell 50 are circular, the body part 10 can be fitted onto the adaptor shell in any desired rotary portion. In this way, the body part 10 can be turned for a selected one of its ports to align in a required direction, for example to suit the line along which a new duct must be installe. Similarly, where the enclosure is fitted into a standard rectangular pit, the body part may be positioned such that its ports are directe at 45° to the length of the pit, so giving access to all ports of the enclosure, rather than positioning it with two opposed sets of ports directe longitudinally and the other two opposed sets of ports directe

transversely (in which case there would be insufficient access to the latter sets of ports).

Referring to Figure 8a, it will be noted that each port comprises a radially outer tubular portion, extending axially outwardly from the enclosure, and a radially inner tubular portion which extends axially inwards from the outer end of the radially outer tubular portion. The radially outer tubular portion comprises a cylindrical section 72 projecting outwardly from the side wall of the body part 10 of the enclosure, then a tapering section 74 extending from the outer end of the cylindrical section 72, then a short cylindrical section 76 extending from the outer end of the tapering portion 74. The radially inner tubular portion comprises a cylindrical section 78 which extends axially inwards from the outer end of the section 76, and an end section 80 which closes its inner end.

There is a step-reduction in diameter between the cylindrical section 72 and the tapering section 74 of the radially outer tubular portion of the port. The end of the port can be cut off at this point if a relatively large- diameter duct D1 or D2 is to be installe, as shown in Figure 7a, 7b. For a duct D3 of smaller diameter or a 19-tube cable C, for example, the end of the port can be cut off on the axially outer cylindrical section 76, leaving the tapering section 74 in place (Figures 7c, 7d): in each of these cases, a heat shrink sleeve 82 is applied over the port and the duct or cable, to form a seal. In Figure 7e, two small-diameter cables are installe and the heat shrink sleeve 82 applied, but opposed portions of the sleeve between the two cables are pinched together at 84 (either using a clip applied before heat-shrinking, or using a camping tool).

If the port is to receive a single cable of small diameter, the inner end of the radially inner tubular portion of the port can be cut away, using a hole saw inserted axially into this portion of the port. Figures 8b and 8c show 7-tube and 4-tube cables inserted, with heat shrink sleeves 82 subsequently applied. Figure 8d shows a cable of yet smaller diameter (e. g. a 4-, 2-or 1-tube cable) inserted, a sealing and locking device 86 in accordance with our UK patent No.

2,277,206 being used.

In manufacturing the enclosure, the radially-inner tubular portion of each port may be deflected to position its axis at angle to the axis of the radially-outer tubular portion: in this way, the radially-inner tubular portion of the port can be aligned more nearly tangentially to the enclosure inner surface. This deflection of the radially-inner tubular portion of each port may be achieved by inserting a mandrel into it, immediately after the enclosure is removed from its mould, and angularly displacing the mandrel.

Figures 9 to 11 show an enclosure which comprises the upper half-shell 90 and a lower half-shell 92, corresponding to the adaptor 50 and clamp 60 of the enclosure of Figures 5 and 6. However, the upper half-shell 90 is formed with two pairs of tubular-able entry ports 94,96 located at diametrically opposite positions around the circumference of the half-shell 90, and directe tangentially thereof and parallel to the main through-passage defined by the two half- shells. The enclosure further comprises a generally flat lid 98 fitted across the open top of the upper half-shell 90. The enclosure can be fitted onto a cable duct D, in the same manner as previously described with reference to Figures 5 and 6: cables can then be run from the main duct and through one or more of the cable entry ports 94,96; these cables can be sealed in their ports using a sealing and locking device in accordance with our UK patent No. 2,277,206.