WO2005101079A1

WO2005101079A1 - Protective housing

Info

Publication number: WO2005101079A1
Application number: PCT/GB2005/001380
Authority: WO
Inventors: George Henry Platt Brown; Kevin Thomas Cockburn
Original assignee: Emtelle Uk Limited
Priority date: 2004-04-14
Filing date: 2005-04-11
Publication date: 2005-10-27
Also published as: GB0408268D0

Abstract

A protective housing (1) for a connection between at least one pair of tubes for accommodating one or more optical fibres comprises: - a first sealing element (2) having at least one aperture (5) therethrough for receiving at least one first tube (7) for accommodating one or more optical fibres; a second sealing element (3) having at least one aperture (6) therethrough for receiving at least one second tube (8) for accommodating one or more optical fibres; a cover element (4) for engaging said first (2) and second (3) sealing elements to define an enclosure enclosing a connection between at least one said first tube (7) and at least one said second tube (8); anal clamping means (13, 14) for causing at least one said sealing element to form a seal with said cover element (4) and with the or each said first (7) or second (8) tube passing through said sealing element.

Description

PROTECTIVE HOUSING

The present invention relates to an improved protective housing for a connection between a pair of elements. The present invention relates particularly, but not exclusively, to a housing for use with a connection between at least one pair of tubes for accommodating one or more optical fibres to provide telecommunications, internet services, and the like.

Optical fibre cables carry data at very high speeds and as the demand for ^Broadband' internet access grows, there is an increasing requirement for optical fibre cables to be deployed either directly into individual homes or business premises, or at least to a roadside cabinet sufficiently close to the subscriber to provide the bandwidth required. Increasingly, optical fibre networks are constructed by setting up a network of small tubes, typically having a diameter of between 3 mm and 12 mm, and then subsequently installing the optical fibre cables into the tube network usually by means of a combination of blowing and pushing. The small tubes from which the optical fibre network is created are generally assembled into bundles so that they can be more easily managed and installed. Currently, the number of tubes in a commercially available tube bundle ranges from between one and twenty five, and consequently tube bundles have a wide range of different outside diameters.

It is known for tubes and tube bundles to be provided with an outer sheath, which protects the tubes and which incorporates a moisture barrier layer to prevent water ingress, which might adversely affect the performance of the tubes and the optical fibre cables contained inside the tubes. Tube bundles may be provided with a range of different outer sheaths depending on the environment in which they will have to operate. For example, some outer sheaths incorporate glass reinforcement, others have aluminium water barriers, and others have metal-free water barriers.

In constructing the network, it might be the case that one or more tube bundles containing twenty five tubes are installed by the service provider. Along the route it is usually the case that these tube bundles containing twenty five tubes are broken down into tube bundles comprising fewer tubes, so that one or more tubes can be conveniently branched out at various points along the route to feed various subscribers. At these branch points the tubes need to be cut and connected to another tube. The individual tubes are connected using commercially available push fit pneumatic tube connectors. In order to make this connection, the outer sheath has first to be removed and it is necessary therefore to fit a protective housing around the connection to provide the protection which has been lost as a result of the removal of the outer sheath.

Such a protective housing needs to be able to accommodate a large number of different diameter tube bundles, provide a good degree of mechanical protection, and prevent the ingress of water. Furthermore, the diameter of protective housings for tubes and tube bundles are preferably large to accommodate large diameter tubes. Large diameter tubes minimise friction at bends when the optical fibre cable is installed by blowing, thereby facilitating installation of optical fibre cable over longer distances. There are many different types of protective housing commercially available. Known protective housings generally consist of two halves which may be fitted together and over the connection to form the housing, and are generally manufactured by injection moulding. The protective housing is generally provided with a suitable rubber seal between the two halves, and some means, screws or otherwise, for clamping the two halves together. The clamping process compresses the rubber seal in an attempt to create a watertight joint. Further, such known protective housings are usually provided with one or more apertures through which the items to be joined, in this case tubes or tube bundles, may pass. There is also provided a means of clamping and securing the tube bundles inside the housing to reduce the possibility of accidentally dislocating the connection between tubes inside the protective housing. Each housing is provided with a means of forming a seal around each tube or tube bundle and between the two halves of the housing.

There are significant disadvantages associated with this type of protective housing. For example, it is expensive to make protective housings large enough to provide adequately generous bend radii (particularly for larger tubes carrying larger, stiffer optical fibre cables), using injection moulding processes. The reason for this is that firstly, the mould needs to be large, and secondly, the machine that the protective housing is moulded on needs a very high clamping force in order to resist the injection pressure over the large surface area of the mould. Furthermore, each tube or tube bundle needs to be accommodated in the protective housing in a manner which provides a watertight seal. The fact that the housing is manufactured in two halves makes sealing the housing against water ingress difficult. Not only do the two halves of the housing need to be sealed one against the other, but in addition, each of the apertures has to be sealed relative to the housing and this is very difficult to achieve at the point where two separate seals, one between the two halves of the housing and one between the aperture and the tubes, meet. An alternative is to manufacture a complicated one-piece seal, which again, requires a large and expensive mould.

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.

According to the present invention there is provided a protective housing for a connection between at least one pair of tubes for accommodating one or more optical fibres, the housing comprising: - (i) a first sealing element having at least one aperture therethrough for receiving at least one first tube for accommodating one or more optical fibres; (ii) a second sealing element having at least one aperture therethrough for receiving at least one second tube for accommodating one or more optical fibres; (iii) a cover element for engaging said first and second sealing elements to define an enclosure enclosing a connection between at least one said first tube and at least one said second tube ; and (iv) clamping means for causing at least one said sealing element to form a seal with said cover element and with the or each said first or second tube passing through said sealing element .

By providing a cover element for engaging the first and second sealing elements to define an enclosure enclosing a connection between at least one pair of said tubes, and clamping means for causing at least one sealing element to form a seal between the sealing element and said cover element and between the sealing element and the or each tube passing through said sealing element, this provides the advantage of enabling the housing to be of simple and inexpensive construction.

In a preferred embodiment, at least one said first and/or second sealing element comprises a compressible member adapted to be compressed in a first direction by means of said clamping means, to cause said compressible member to expand in a second direction to form a seal with said cover element and with the or each said tube passing through at least one said aperture through said sealing element .

In this way, only one sealing element is required to form a seal at one end of the housing and provides a seal between both the sealing element and said cover element and between the sealing element and the or each said tube .

Preferably, said clamping means comprises first and second plates disposed on opposite sides of at least one said compressible member, said first and second plates being adapted to be urged together to compress the compressible member to form a seal with said cover element and with the or each said tube passing through at least one said aperture through said sealing element^".

By having the clamping means in the form of first and second plates, pressure is applied evenly across the area of the compressible member when the plates are urged together.

The housing may comprise two elongate spacer elements further defining said clamping means, each elongate spacer element engaging the first and second sealing elements and being adapted to compress at least one said compressible member to form a seal with said cover element and with the or each said tube passing through at least one said aperture through said sealing element.

It is preferred that the housing further comprises at least one elongate spacer element engaging the first and second sealing elements for fixing the sealing elements in position relative to each other.

Preferably, the first and second sealing elements each comprise through holes for engaging the said elongate spacer elements, the said elongate spacer elements being screw threaded at each end for engagement with a nut, such that when the nuts at each end of the elongate spacer element are tightened, and said clamping means compresses at least one said compressible member to form a seal with said cover element and with the or each said tube passing through at least one said aperture through said sealing element. In this way, the elongate spacer elements fulfil a dual purpose, which reduces the number of parts required for the protective housing.

It is preferable that the cover element comprises a one- piece tubular member which is slidable over the first and second sealing elements.

The advantages of such a one-piece arrangement are that manufacturing costs are kept to a minimum, and the chances of water penetrating the protective housing are reduced.

Preferably, the one-piece tubular member is manufactured by extrusion.

The benefits of manufacturing the cover element by extrusion are that the length of the cover element may be varied simply by changing the cut length. This can be achieved using modern extrusion equipment simply by changing the operation of a saw without the need to stop the process or fit a new mould. Extrusion is much cheaper than injection moulding as a means of manufacturing such components as the cover element, since raw materials for extrusion are often less expensive than raw materials for injection moulding. This is particularly true in the case of PVC, which is a suitable material for the cover element. Furthermore, extrusion dies are much cheaper than injection moulds and the speed of manufacture using extrusion techniques is much greater than the speed of manufacture using injection moulding techniques. The benefits of having a cover element which is circular in cross-section are that it provides a strong structure which uses less material than is the case with other types of shape. Furthermore, structures having circular cross-sections are easier to extrude than structures having non- circular cross-sections.

The clamping means may comprise first and second plates for compressing said first sealing element to form a seal with said cover element and with the or each said first tube, and said cover element may be adapted to compress said second sealing element to form a seal with said cover element and with the or each said second tube.

The cover element may comprise two portions adapted to be clamped together to form a tubular member and to compress said second sealing element.

This- provides the advantage that a much more simple seal may be formed at one end of the housing. It is often the case as shown in Figures 1, 3 and 4 that a single tube or tube assembly enters the housing at one end and multiple tubes or tube assemblies exit the housing at the other end. In view of this, the entry end of the housing may be conveniently sealed using a simple injection-moulded second sealing element adapted to fit around the tube or tube assembly entering the housing. This simple seal can then be placed under pressure by the act of closing and clamping together the two portions of the cover element, thereby avoiding the need for a multi-part seal. In this way, the second sealing element forms a seal with said cover element and with the or. each said second tube when, the two portions of the cover element are clamped together. Preferably, each of the two portions of the cover element comprises a peripheral channel along its length, inside of which a third sealing element is disposed.

In this way, when the two portions of the cover element are clamped together, the third sealing element, which may be in the form of an O-ring, abuts the periphery of the first and second sealing elements to thereby form an additional seal between the O-ring and the first and second sealing elements. This provides a further barrier to the ingress of water into the housing.

The first and second sealing elements and said clamping means may comprise at least one slit to facilitate location of the protective housing over a tube bundle in which not all of the tubes have been cut.

This provides the advantage that the housing may be used both in the case where all of the tubes have been cut, and also the case where at least some of the tubes have not been cut.

A preferred embodiment of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings in which: -

Figure 1 is a perspective view from the end and one side of a protective housing embodying a first embodiment of the present invention, with the cover element removed;

Figure 2 is a perspective view from the end and one side of the cover element of the protective housing of Figure 1; Figure 3 is a perspective view from the end and one side of a further embodiment of a protective housing embodying the present invention, with one portion of the cover element removed;

Figure 4 is a perspective view from the end and one side of the embodiment of the protective housing of Figure 3 with two portions of the cover element in situ; and

Figure 5 is a perspective view from the end and one side of part of the embodiment of a protective housing of Figure 3.

With reference to Figures 1 and 2, a protective housing 1 comprises a first sealing element in the form of a first compressible member 2, a second sealing element in the form of a second compressible member 3, a cover element 4, a first clamping means in the form of first and second plates 13 and 14, and a second clamping means in the form of first and second plates 17 and 18.

The first compressible member 2 and the plates 13 and 14 each include one aperture 5 in which a bundle 7 of twenty five optical fibre tubes is retained. Further, the second compressible member 3 and the plates 17 and 18 each include a plurality of apertures 6 in which separate optical fibre tubes 8 are retained. However, it is to be appreciated that any number of bundles of optical fibre tubes or separate optical fibre tubes may be retained in the protective housing 1. The separate tubes making up the tube bundle 7 may be connected to the separate tubes 8 using commercially available push fit pneumatic tube connectors, which are not shown for the sake of clarity. The tubes 8 and tube bundle 7 are secured in place using jubilee clips 16 or any other suitable means. The jubilee clips 16 ensure that any strain on the tubes 8 or tube bundle 7 does not cause the connections between the tubes inside the protective housing 1 to dislocate.

The cover element 4 is an elongate tubular member having dimensions which enable it to pass freely over the first and second sealing elements 2 and 3 when in their uncompressed state. The cover element 4 is circular in cross-section and has openings of the same size and shape at either end. Further, the cover element 4 is manufactured by extrusion. The cover element 4 as shown in Figure 2 is a one-piece element. However, it is to be appreciated that the cover element 4 may alternatively be of a clam shell-type arrangement having two halves with a suitable seal therebetween. Such a two-piece arrangement may also be extruded, and benefits from the advantages of such a manufacturing process as discussed above.

The plates 13, 14 and 17,18 and the compressible members 2 and 3 are each of a circular shape. The compressible members 2 and 3 are made from a resilien^'tly deformable material such as a soft thermoplastic material or a thermosetting rubber or the like, and may be advantageously cut from a sheet using water jet cutting techniques. The first and second plates 13, 14 and 17,18 respectively are made from a rigid material such as metal, hard thermoplastic or any other material which is capable of compressing the compressible member. Furthermore, the first 13 and second 14 plates are mirror images of each other so that they can be manufactured using the same mould. Similarly, the first and second plates 17 and 18 are mirror images of each other for the same reason. The first and second plates 13, 17 and 14, 18 respectively are of the same size and shape and as such may be moulded from the same mould by providing change inserts to create different configurations of apertures 5 and 6 through which the tubes 8 or tube bundles 7 pass. This significantly reduces the cost of the moulds required. Alternatively, the first 13, 17 and second 14, 18 plates could be moulded as blanks and then drilled or machined to create a number of different size apertures greatly increasing flexibility and reducing the requirement for stock holding.

The protective housing 1 also comprises elongate spacer elements in the form of rods 9a, 9b and 9c, which are attached at one end to first and second plates 13 and 14 and at the other end to first and second plates 17 and 18. The rods 9a, 9b and 9c fix the sealing elements 2 and 3 in position relative to each other and facilitate easy access to the inside of the protective housing 1 and attachment of the connector (not shown) . The rods 9a, 9b and 9c may also be used to attach a bracket to the housing 1 in the event that the housing 1 is to be fixed in a manhole or suspended from an overhead catenary wire. The rods 9a, 9b and 9c are made from a suitably hard material such as steel. The attachment of the spacer elements 9a, 9b and 9c to the plates is facilitated by a number of through holes 10 around the periphery of the first and second plates 13 and 14 and sealing element 2, and a number of through holes 11 around the periphery of the first and second plates 17 and 18 and sealing element 3. The rods 9a, 9b and 9c are engageable with the first 13 and second 14 plates and sealing element 2 via through holes 10. Similarly, the rods 9a, 9b and 9c are engageable with the first and second plates 17,- 18 and sealing element 3 via through holes 11. The rods 9a, 9b and 9c are screw threaded at each end and are fixed in place in the holes 10 and 11 by means of nuts 12.

In order to install the protective housing 1, the cover element 4 is first placed over the tube bundle 7, and the end of the tube bundle 7 is then inserted through the aperture 5 of the protective housing 1. The ends of the separate tubes 8 are then inserted through the holes 6 of the protective housing 1, and a connector (not shown) is then used to connect the separate tubes of the tube bundle 7 to the separate tubes 8. The jubilee clips 16 are then fixed to the tube bundle 7 and the separate tubes 8, and the cover element 4 is then slid over the assembly such that the gap between the first 2 and second 3 sealing elements, and more particularly the connector (not shown) between the tubes, is covered. The nuts 12 are then tightened, which urges the first 13 and second 14 plates together such that they compress the compressible member 2, and which urges the first 17 and second 18 plates together such that they compress the compressible member 3. As the compressible member 2 is compressed in this first direction, it expands in a second direction to form a seal around the tube bundle 7, and between the plates 13 and 14 and the inside of the cover element 4. In a similar fashion, as the compressible member 3 is compressed in the first direction, it expands to form a seal in a second direction around the individual tubes 8 and between the first and second plates 17 and 18 and the inside of the cover element 4. In this way, a substantially robust and watertight seal is provided around the connection (not shown) between the tubes. A further embodiment of a protective housing is shown in Figures 3 to 5, and is represented generally by reference numeral la.

The protective housing la comprises a first sealing element in the form of a first compressible member 2a, and a second sealing element in the form of a second compressible member 3a. The housing la further comprises a cover element 4a, and a clamping means in the form of first and second plates 13a and 14a respectively for compressing the first compressible member 2a. The first compressible member 2a and the plates 13a and 14a each include a plurality of apertures 5a in which optical fibre tubes 7a are retained. Further, the second compressible member 3a includes a single aperture 6a in which a single optical fibre tube 8a is retained. However, it is to be understood that any number of optical fibre tubes, or bundles of optical fibre tubes, may be retained in the protective housing la. The tubes 7a and 8a may be connected inside the housing la using commercially available push fit pneumatic tube connectors, which are not shown for the sake of clarity.

The tubes 7a and 8a are secured in place using clips lβa or any other suitable means, which ensure that any strain on the tubes 7a or 8a does not cause the connections between the tubes inside the protective housing la to dislocate .

The plates 13a and 14a may be clamped together by means of clamping bolts 28, which, when tightened, compress the plates 13a and 14a in one direction to cause the first compressible member 2a to expand in an outwardly direction to form a seal with the cover element 4a and with the tubes 7a.

The cover element 4a is formed of a first clam-shell portion 4a' and a second clam-shell portion 4a' ' , whereby the two portions 4a' and 4a' ' fit together along their length to form a tubular member having a generally circular shaped cross-section at a first end 30, and a generally lozenge shaped cross-section at a second end 32. The two portions 4a' and 4a'' may be clamped together by means of bolts 22, and apertures 24 disposed at intervals along the length of the cover element 4a.

Further, the two portions 4a' and 4a' ' each comprise a peripheral channel 26 along their length, in which a third seal in the form of an O-ring (not shown) may locate. This feature is best shown in Figure 5. The 0- ring forms a seal along the length of the cover element 4a. When the two portions 4a' and 4a'' of the cover element 4a are clamped together, and the plates 13a and 14a are clamped together, the O-ring abuts against the periphery of the first and second sealing elements 2a and 3a, and thereby forms an additional seal to prevent the ingress of water into the protective housing la.

The plates 13a and 14a and the first compressible member 2a are each generally lozenge shaped, and the second compressible member 3a is of a generally circular shape. The plates 13a and 14a and first and second compressible members 2a and 3a may be made from similar materials to the plates 13, 14, 15 and 16, and compressible members 2 and 3, respectively, of the embodiment of Figures 1 and 2. The plates 13a and 14a, and first and second compressible members 2a and 3a each comprise a slit 20, to enable the plates 13a and 14a and the first and second compressible members 2a and 3a to locate over tubes which have not been cut .

In order to install the protective housing la, the first sealing element 2a, plates 13a and 14a, and second sealing element 3a are located over the tubes 7a and 8a to be connected. The tubes 7a and 8a are then connected using a conventional connector, for example, and then the two portions 4a' and 4a' ' of the cover element 4a are placed over the tubes 7a and 8a, and the first and second sealing elements 2a and 3a respectively. The two portions 4a' and 4a' ' of the cover element 4a are then clamped together using bolts 22 and apertures 24 disposed at intervals along the length of the cover element 4a. In clamping the two pieces 4a' and 4a' ' together, the 0- ring and the second sealing element 3a are compressed, thereby forming a substantially watertight seal along the length of the cover element 4a, and at the first end 30 of the protective housing la between the cover element 4a and the tubes 8a.

In order to form a substantially watertight seal at the other end 32 of the protective housing 4a, the clamping bolts 28 are tightened, which compresses the first compressible member 2a to cause the first compressible member to expand outwardly to abut the O-ring and the cover element 4a, to thereby form a substantially watertight seal.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense, and that various alternatives and modifications are possible without departing from the scope of the invention as defined by the appended claims.

Claims

1. A protective housing for a connection between at least one pair of tubes for accommodating one or more optical fibres, the housing comprising: -

(i) a first sealing element having at least one aperture therethrough for receiving at least one first tube for accommodating one or more optical fibres;

(ii) a second sealing element having at least one aperture therethrough for receiving at least one second tube for accommodating one or more optical fibres;

(iii) a cover element for engaging said first and second sealing elements to define an enclosure enclosing a connection between at least one said first tube and at least one said second tube; and

(iv) clamping means for causing at least one said sealing element to form a seal with said cover element and with the or each said first or second tube passing through said sealing element .

2. A housing as claimed in claim 1, wherein at least one said first and/or second sealing element comprises a compressible member adapted to be compressed in a first direction by means of said clamping means, to cause said member to expand in a second direction to form a seal with said cover element and with the or each said tube passing through at least one said aperture through said sealing element.

3. A housing as claimed in claim 2, wherein said clamping means comprises first and second plates disposed on opposite sides of at least one said compressible member, said first and second plates being adapted to be urged together to compress the compressible member to form a seal with said cover element and with the or each said tube passing through at least one said aperture through said sealing element.

4. A housing as claimed in claim 2 or 3, comprising two elongate spacer elements further defining said clamping means, each elongate spacer element engaging the first and second sealing elements and being adapted to compress at least one said compressible member to form a seal with said cover element and with the or each said tube passing through at least one said aperture through said sealing element.

5. A housing as claimed in any one of the preceding claims, further comprising at least one elongate spacer element engaging the first and second sealing elements for fixing the sealing elements in position relative to each other.

6. A housing as claimed in any one of claims 2 to 4 and claim 5, wherein the first and second sealing elements each comprise through holes for engaging the said elongate spacer elements, the said elongate spacer elements being screw threaded at each end for engagement with a nut, such that when the nuts at each end of the elongate spacer element are tightened, and said clamping means compresses at least one said compressible member to form a seal with said cover element and with the or each said tube passing through at least one said aperture through said sealing element.

7. A housing as claimed in any one of the preceding claims, wherein the cover element comprises a one-piece tubular member which is slidable over the first and second sealing elements.

8. A housing as claimed in claim 7, wherein the one- piece tubular member is manufactured by extrusion.

9. A housing as claimed in any of claims 1 to 6, wherein said clamping means comprises first and second plates for compressing said first sealing element to form a seal with said cover element and with the or each said first tube, and said cover element is adapted to compress said second sealing element to form a seal with said cover element and with the or each said second tube.

10. A housing as claimed in claim 9, wherein the cover element comprises two portions adapted to be clamped together to form a tubular member and to compress said second sealing element.

11. A housing as claimed in claim 10, wherein each of the two portions of the cover element comprises a peripheral channel along its length inside of which an 0- ring is disposed.

12. A housing as claimed in any one of the preceding claims, wherein the first and second sealing elements and said clamping means comprise at least one slit to facilitate location of the protective housing over a tube bundle in which not all of the tubes have been cut.

13. A protective housing for a connection between at least one pair of tubes for accommodating one or more optical fibres, the housing substantially as hereinbefore described with reference to the accompanying drawings.