GB2292018A

GB2292018A - Cable ducting junction

Info

Publication number: GB2292018A
Application number: GB9415558A
Authority: GB
Inventors: Ronald David Broughton
Original assignee: B & H Ltd
Current assignee: B & H Ltd
Priority date: 1994-08-02
Filing date: 1994-08-02
Publication date: 1996-02-07
Anticipated expiration: 2014-08-02
Also published as: GB2292018B; GB9415558D0; GB2292018A8

Abstract

A cable duct junction piece 22 for joining a branch cable duct to a main cable duct comprises a main limb 24 having an internal diameter substantially equal to that of the main duct and enlarged open ends 30, 32 to receive with a close fit the ends of main ducts, and a branch limb 26 extending at an acute angle from the main limb 24. The longitudinal axis of the enlarged open end 32 towards which the branch limb 26 is directed is offset by a distance D-D (Figure 3) from the longitudinal axis of the main limb 24, away from the branch limb 26. <IMAGE>

Description

Title: Cable Ductina The present invention relates to tubular members such as cable ducting and in particular to junction pieces for the connection of a branch line to a main cable duct line.

Ducting is used, for example, for carrying communications cables for cable television transmission to cable TV subscribers from a main receiving aerial. The ducting generally comprises a main line typically 96mm in diameter, which has a number of smaller branch lines typically 54mm in diameter leading off to subscribers' houses. The main line is normally laid a few feet beneath a pavement or pathway with each branch line extending to the subscriber's house where it is brought to the surface and capped, ready to take the communications cables. These are inserted at the subscriber end of the ducting and fed along the branch line into the main line towards a terminal. To ensure that the cable enters the main line from the branch line feeding in the correct direction, each branch line diverges from the main line at a relatively shallow angle.

Connection of a branch line to a main line is usually by means of a junction piece. Main line ducting is received within each end of the body of the junction piece and the end of a branch duct is received within a smaller diameter limb extending, as mentioned above, from the body at a relatively shallow angle.

However, one of the problems which is encountered is that occasionally the end of a cable fed through the branch line may catch on the junction between the junction piece and the main line duct into which the cable is supposed to pass. The application of force to overcome this may cause damage to the cable or even result in the end of the cable being driven right through the wall of the duct.

There has now been devised an improved form of cable duct junction piece which overcomes or substantially mitigates the above-mentioned disadvantage.

According to the present invention, there is provided a cable duct junction piece for joining a branch cable duct to a main cable duct, the junction piece comprising a main limb having an internal diameter substantially equal to that of the main cable duct and enlarged open ends to receive with a close fit the ends of main cable ducts, and a branch limb extending at an acute angle from the main limb, the longitudinal axis of the enlarged open end towards which the branch limb is directed being offset from the longitudinal axis of the main limb, away from the branch limb.

The junction piece according to the invention is advantageous primarily in that the offset of the open end of the main limb into which a cable is fed from the branch limb reduces or eliminates the possibility of the cable becoming fouled on the end of the main duct into which it is to be passed.

The extent to which the longitudinal axis of the enlarged open end is offset may be quite small. For example, where the internal diameter of the open end is 108mm, the offset may be less than lmm, eg 0.5mm.

The junction piece according to the invention and the ducts with which it is used may incorporate complementary formations to ensure that the junction piece is correctly installed as described in British Patent Application No 2267183-A, the teaching of which is incorporated herein by reference.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic plan view of telecommunications cable ducting laid to several buildings; Figure 2 is a plan view of a tubular member forming a junction for the ducting of Figure 1; and Figure 3 is an enlarged sectional view of the tubular member of Figure 2.

Referring to the drawings, Figure 1 shows part of the layout of ducting 10 for carrying communications cables to buildings 12 and 14. These buildings are typically detached or semi-detached domestic houses. The ducting comprises a main line 16 with branch lines 18 and 20 leading to the buildings 12, 14. Each branch line 18, 20 branches from the main line 16 via a junction 22 which is shown in more detail in Figure 2. As can be seen, the junction 22 is formed by a tubular member which has a ribbed main limb 24 connected in the main line 16 of the ducting and a branch limb 26 which. extends from the main limb at a relatively shallow angle of typically 22.50.

As can be seen from Figure 2 a free end of the branch limb 26 is formed with a cylindrical end portion 28 of an increased diameter sufficient to receive one end of a ducting branch limb as a reasonably close fit.

Similarly, the ends of the main limb 24 are formed with cylindrical end portions 30,32 of an increased diameter sufficient to receive one end of a main line duct as a reasonably close fit.

The main limb 24 has an internal diameter which is substantially equal to the internal diameter of the main cable ducts received within the end portions 30,32. The first end portion 30 has an internal diameter substantially equal to the external diameter of the main line duct received within it, and is concentric with the main limb 24.

The second end portion 32, on the other hand, whilst it has the same internal diameter as the first end portion 30, is eccentric to the main limb 24. As can be seen in Figure 3, the centre line A of the second end portion 32 is displaced from the centre line B of the main limb 24 by a distance D-D of 0.5mm. The displacement of the second end portion 32 is diametrically away from the side of the main limb 24 which carries the branch limb 26.

The eccentricity of the second end portion 32 relative to the main limb 24 reduces the chance of the end of a main cable duct inserted into that end portion standing proud of the internal surface of the main limb 24 at the point at which a cable inserted through the branch limb 26 is likely to contact that surface. This lessens the likelihood of the cable end becoming fouled on the end of the main cable duct and facilitates smooth passage of the cable into the main line ducting.

Claims

1. A cable duct junction piece for joining a branch cable duct to a main cable duct, the junction piece comprising a main limb having an internal diameter substantially equal to that of the main cable duct and enlarged open ends to receive with a close fit the ends of main cable ducts, and a branch limb extending at an acute angle from the main limb, the longitudinal axis of the enlarged open end towards which the branch limb is directed being offset from the longitudinal axis of the main limb, away from the branch limb.

2. A cable duct junction piece as claimed in claim 1, wherein the offset of the longitudinal axis of the open end towards which the branch limb is directed from the longitudinal axis of the main limb is less than imam.

3. A cable duct junction piece as claimed in claim 1 or claim 2, wherein the main limb is a tubular member with a ribbed outer surface.

4. A cable duct junction piece as claimed in any preceding claim, wherein the enlarged open ends are cylindrical.

5. A cable duct junction piece as claimed in any preceding claim, wherein the main limb has an internal diameter which is substantially equal to the internal diameter of the main cable ducts received within the open ends.

6. A cable duct junction piece substantially as hereinbefore described and as illustrated in the accompanying figures.