GB2221736A

GB2221736A - Sealing a service duct

Info

Publication number: GB2221736A
Application number: GB8818990A
Authority: GB
Inventors: Carl Jackson; Michael Twist
Original assignee: Hawke Cable Glands Ltd
Current assignee: Hawke Cable Glands Ltd
Priority date: 1988-08-10
Filing date: 1988-08-10
Publication date: 1990-02-14
Anticipated expiration: 2008-08-10
Also published as: HK1000073A1; GB8818990D0; GB2221736B

Abstract

A service duct assembly for a plurality of leads 5 for service commodities such as gas, electricity, oil, water, telecommunications and the like comprises an outer main duct 1 and a respective inner sub-duct 2 extending longitudinally within the main duct 1 for passage of each lead 5. Each sub-duct 2 is sealed relative to the main duct 1 by a respective common duct seal 3 at each end of the main duct 1 and, each lead 5 is sealed relative to the associated sub-duct 2 by a respective lead seal 6 at each end of the sub-duct 2. Each lead seal 6 (Figure 4) comprises an outer sleeve 17 engageable in the end of the associated sub-duct 2 and an inner liner 16 releasably secured in the sleeve 17 and having a through bore 18 for passage of the associated lead 5. A range of liners 16 having bores 18 of different sizes may be selectively assembled with a common sleeve 17 to accommodate leads 5 of different sizes and, the liner 16 may be replaced by a solid plug 24 (Figure 5) for selectively blanking off a sub-duct. <IMAGE>

Description

APPARATUS FOR SEALING A SERVICE DUCT This invention relates to apparatus for sealing a service duct for commodity services such as gas, electricity, oil, water, telecommunications etc.

For convenience herein, the term "lead" is used and should be interpreted in the context to include a cable, wire, pipe, tube or like elongate element as used in conducting commodity services.

Service ducts are often buried underground and a typical arrangement consists of an elongate outer or main duct embedded in concrete or clay and a plurality of elongate inner or sub-ducts extending longitudinally within the outer duct for separate passage of individual leads.

The main duct is commonly a hollow pipe or tube of circular section providing a throughway for the subducts each of which is a smaller hollow pipe or tube providing a throughway for one lead. In this way, a multitude of service leads can be located in a common main duct whilst each lead is confined in its own subduct so as to be isolated from the other leads.

Such assembly facilitates installation of a number of leads as well as subsequent maintenance or replacement of individual leads or addition of further leads.

It is often a requirement for service ducts to be sealed on entry and exit of the leads to and from the ducts so as to provide a barrier against fluid, fire and small animals and the present invention is particularly concerned with apparatus for this purpose.

It is an object of the present invention therefore to provide apparatus for sealing a service duct which is of simple construction capable of assembly with the service duct in situ.

It is a further object of the present invention to provide apparatus for sealing a service duct which enables different sizes of sub-ducts and/or leads to be sealed within the main duct.

According to the present invention we provide apparatus for sealing a service duct assembly of the type comprising an elongate outer or main duct and an elongate inner or sub-duct extending longitudinally within the outer duct for passage of a lead, the apparatus comprising a duct seal adapted to be received in the main duct and defining an opening in which the sub-duct is received to seal the sub-duct relative to the main duct, and a lead seal adapted to be received in the sub-duct and defining an aperture through which the lead extends to seal the lead relative to the subduct.

The duct seal preferably comprises a resiliently compressible body for insertion in the end of the main duct. The body may be an interference fit to seal the sub-duct relative to the main duct but preferably compression means is provided for axially compressing the body to seal the sub-duct relative to the main duct.

The compression means conveniently comprises at least one pair of compression plates arranged at opposed ends of the body and connected by a compression bolt extending through the body parallel to the longitudinal axis.

With this arrangement the sub-duct is firmly secured within the main duct so as to resist displacement by the significant push-out forces which arise when a lead is pulled through the sub-duct.

The lead seal advantageously comprises an inner liner extending around the lead and engageable within an outer sleeve received in the end of the sub-duct.

In this way the lead seal can be adapted to accommodate different sizes and/or shapes of lead in a simple manner by selection and fitment of an appropriate liner within a common outer sleeve.

Preferably the inner liner has internal ribs for sealing engagement with the lead and the sleeve has external ribs for sealing engagement with the sub-duct.

Advantageously, the opposed surfaces of the liner and sleeve have co-operating formations to locate the liner within the sleeve, for example interengageable fir-tree formations.

The liner may be replaced by an end plug engageable within the outer sleeve to blank-off the sub-duct if required. Such end plug is conveniently adapted for connection to the end of a lead to facilitate pulling the lead through the sub-duct.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, wherein: FIGURE 1 is a partly sectioned side view of a service duct shown in the assembled condition with leads in situ and sealed by apparatus according to this invention; FIGURE 2 is a front elevation of the service duct shown in Figure 1; FIGURE 3 is an exploded isometric view of the duct seal shown in Figures 1 and 2; FIGURE 4 is an exploded isometric view of the lead seal shown in Figures 1 and 2; and FIGURE 5 is a side view of a modification of the lead seal shown in Figure 4.

Referring first to Figures 1 and 2 of the accompanying drawings, one end of a service duct for telecommunication leads is shown comprising an elongate outer or main duct 1 of circular section through which three smaller elongate inner or sub-ducts 2 extend parallel to the longitudinal axis of the main duct.

The sub-ducts 2 are located in spaced apart relationship and sealed relative to the main duct 1 by a duct seal 3 disposed within the end of the main duct and having three separate openings 4 in which the ends of the sub-ducts 2 are received so as to project a short distance outwards from the end of the main duct 1.

A separate lead 5 extends through each sub-duct 2 and is sealed relative to the sub-duct 2 by a lead seal 6 extending around the lead 5 and received in the end of the sub-duct 2.

As will be understood, a similar arrangement of duct and lead seals will be provided for sealing the other end of the service duct so that water or other fluids as well as small animals are prevented from entering the duct.

Referring now to Figure 3, the duct seal 3 is shown in more detail and comprises an annular body 7 moulded from neoprene or other suitable material in which the openings 4 for the sub-ducts are formed. The openings 4 are all of the same size for receiving subducts 2 of the same size but it will be understood this is not essential and the openings 4 may be of different sizes and/or shapes for accommodating different sizes and/or shapes of sub-ducts 4.

The body 7 is also formed with three axially extending bolt holes 8 uniformly spaced in the circumferential direction between the openings 4. At each end of the body 7, the bolt holes 8 open into a recess 9 of generally triangular shape in which a compression plate 10 having a square aperture 11 aligned with the bolt hole 8 is received.

Extending through each bolt hole 8 between the compression plates 10 is a compression bolt 12 having a square shank portion 13 on the underside of the bolt head and an externally threaded tail portion 14 at the free end for engagement with a threaded nut 15.

In the assembled condition, the square shank portion 13 engages the aperture 11 of the inner or rear compression plate 10 thereby preventing rotation of the bolt 12 and the threaded tail portion 14 projects through the aperture of the outer or front compression plate 10 so as to be accessible externally of the service duct for tightening the compression nut 15.

In use, the duct seal 3 with the compression plates 10 and associated bolts 12 fitted to the body 7 and loosely secured by the nuts 15 is eased over the ends of the sub-ducts 2 into the end of the main duct 1 whereupon the nuts 15 are tightened to compress axially the body 7 causing the body 7 to expand radially to seal tightly the sub-ducts 2 relative to the main duct 1.

With this arrangement the sub-ducts 2 are firmly secured within the main duct 1 so as to resist any tendency for the sub-ducts 2 to be pulled out of the main duct 1 when pulling the leads 5 therethrough.

Referring now to Figure 4, each lead seal 6 is similar and comprises an inner liner 16 engageable within an outer sleeve 17.

The liner 16 has a central aperture 18 for passage of the lead 5 and is formed with internal ribs 19 for sealing engagement with the lead and external ribs 20 of fir-tree section for sealing engagement with internal ribs 21 of fir-tree section on the sleeve 17.

The lead seal 6 is a push fit in the end of the sub-duct 2 and the sleeve 17 has a collar 22 at one end to limit insertion and external ribs 23 to seal against the inner surface of the sub-duct 2.

With this two-part construction of lead seal 6, a common outer sleeve 17 may be combined with any one of a range of inner liners 16 having central apertures 18 of different sizes and/or shapes enabling the lead seal 6 to be adapted to different lead sizes and/or shapes in a simple manner.

Referring now to Figure 5, there is shown an end plug 24 for adapting the lead seal 6 of Figure 4 to blank-off the end of a sub-duct 2, for example if a lead 5 is removed or if the number of sub-ducts exceeds the number of leads so that additional leads may later be installed as required.

The end plug 24 is engageable within the outer sleeve 17 of the lead seal 6 in place of the inner liner 16 and has external ribs 25 of fir-tree section for engagement with the internal ribs 21 of the sleeve in similar manner to the liner 16.

The end plug 24 also has integral rings 26 at each end which facilitate manual removal of the end plug 24 when it is desired to insert a lead 5 through the subduct 2 and to which the end of the lead 5 may be attached to facilitate pulling the lead 5 through the sub-duct 2.

It will be understood that the invention is not limited to the embodiment above-described, for example, where the service duct and leads are already installed, the duct and lead seals may be axially split to allow assembly around the leads for fitment as above-described.

In certain applications the compression plates and bolts for compressing the body may be dispensed with and the body formed with ribs or the like providing an interference fit of the body in the main duct for effective sealing engagement with the main and subducts.

Finally, although in the embodiment above-described there are three sub-ducts disposed within the main duct, it will be appreciated the number of sub-ducts may be chosen to suit any particular application and that one or more sub-ducts may be blanked off.

Claims

Claims:

1. Apparatus for sealing a service duct assembly of the type comprising an elongate outer or main duct and an elongate inner or sub-duct extending longitudinally within the outer duct for passage of a lead, the apparatus comprising a duct seal adapted to be received in the main duct and defining an opening in which the sub-duct is received to seal the sub-duct relative to the main duct, and a lead seal adapted to be received in the sub-duct and defining an aperture through which the lead extends to seal the lead relative to the sub-duct.

2. Apparatus according to Claim 1 wherein the duct seal comprises a resiliently compressible body for mounting in the end of the main duct.

3. Apparatus according to Claim 2 wherein the body is an interference fit to seal the sub-duct relative to the main duct.

4. Apparatus according to Claim 2 wherein compression means is provided for axially compressing the body to seal the sub-duct relative to the main duct.

5. Apparatus according to Claim 4 wherein the compression means comprises at least one pair of compression plates arranged at opposed ends of the body and connected by a compression bolt.

6. Apparatus according to Claim 5 wherein the bolt has a portion of non-circular section arranged to co-operate with one of the plates to prevent rotation of the bolt.

7. Apparatus according to Claim 5 or Claim 6 wherein the compression plates are received in respective recesses in the opposed ends of the body.

8. Apparatus according to any one of the preceding Claims wherein the lead seal comprises an outer part for mounting in the end of the sub-duct and an inner part for sealing around a lead or for blanking-off the sub-duct.

9. Apparatus according to Claim 8 wherein the outer part comprises a sleeve member having a sealing rib on the outer surface for engagement with the inner surface of the subduct.

10. Apparatus according to Claim 8 or Claim 9 wherein the outer and inner parts have co-operating interengageable formations for releasably securing the inner part within the outer part.

11. Apparatus according to Claim 10 wherein the interengable formations comprise interengageable fir-tree formations.

12. Apparatus according to any one of Claims 8 to 11 wherein the inner part comprises a liner having a through bore for passage of a lead.

13. Apparatus according to Claim 12 including a plurality of liners for selective mounting in a common outer part with each liner having a respective through bore for passage of a lead and the bores being of different sizes for passage of a corresponding range of leads of different sizes by selection and fitment of the matching liner.

14. Apparatus according to Claim 12 or Claim 13 wherein the or each liner has a sealing rib on the inner surface of the bore for engagement with the outer surface of the lead.

15. Apparatus according to any one of Claims 8 to 11 wherein the inner part comprises a solid plug for blankingoff the end of the sub-duct.

16. Apparatus according to Claim 15 wherein the plug is adapted for connection to the end of a lead.

17. Apparatus according to any one of the preceding Claims wherein the duct seal and/or lead seal is axially split.

18. Apparatus according to any one of the preceding Claims wherein the duct seal has a plurality of openings for a plurality of sub-ducts.

19. Apparatus for sealing a service duct assembly substantially as hereinbefore described with reference to the accompanying drawings.

20. Apparatus for sealing a service duct assembly of the type comprising an elongate outer or main duct and at least one elongate inner or sub-duct extending longitudinally within the outer duct for passage of a lead, the apparatus comprising a duct seal at or adjacent to one end of the main duct for sealing around the sub-duct within the main duct, and a lead seal at or adjacent to one end of the sub-duct for sealing around a lead extending longitudinally within the sub-duct or for blanking-off the sub-duct.

21. Apparatus according to Claim 20 wherein the lead seal comprises an outer part for sealing engagement with the inner surface of the sub-duct and a separate inner part releasably secured therein for sealing engagement with the outer surface of a lead or for blanking-off the sub-duct.

22. Apparatus according to Claim 20 or Claim 21 wherein the duct seal has a plurality of spaced apart openings for passage of respective sub-ducts.

23. A service duct assembly comprising an elongate outer or main duct and at least one elongate inner or sub-duct extending longitudinally within the outer duct for passage of a lead, a duct seal at or adjacent to one end of the main duct through which the sub-duct extends for sealing the subduct relative to the main duct, and a lead seal at or adjacent to one end of the sub-duct for sealing a lead extending through the sub-duct relative to the sub-duct or for blanking-off the end of the sub-duct.

24. A service duct assembly according to Claim 23 including a respective duct seal at or adjacent to each end of the main duct and a respective lead seal at or adjacent to each end of the sub-duct.