GB2267183A

GB2267183A - Cable ducting

Info

Publication number: GB2267183A
Application number: GB9309770A
Authority: GB
Inventors: Arthur Robert Swan
Original assignee: B & H Ltd
Current assignee: B & H Ltd
Priority date: 1992-05-12
Filing date: 1993-05-12
Publication date: 1993-11-24
Also published as: GB9210146D0; GB9309770D0

Abstract

A ducting system (Figure 1) for communications cables has a plurality of tubular members the end portions of which engage in one preselected angular position. In an embodiment the rib 50 on tubular member 32 slots into groove 48 on junction 22 to locate the member in a preselected angular position. Other tubular members, curved (38, Fig. 7) or straight (44, Fig. 9), with one or two slots, may be provided. A cap (46, Figs. 11 to 13) is provided for closing off the tubular member; the cap has a locating rib (50) and indicia to show cable direction. <IMAGE>

Description

Title : Cable Ducking The present invention relates to tubular members such as cable ducting.

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.

However, one of the problems which is encountered is that occasionally the tubular members actually forming the junctions are laid in the wrong, reverse direction so that when the cable is fed from the branch line into the main line, instead of, for example, the cable being fed upstream along the main line towards the terminal it is directed upstream away from the terminal.

Since connection of subscribers often takes place several years after the ducting has been laid, the correcting of such a fault causes considerable upheaval and delay for the subscriber. In addition, since the work of laying the ducting is normally guaranteed by the contractor for a maximum of only two years, correcting the incorrectly laid junction often has to be carried out at the expense of the cable company.

Hitherto, once the cable ducting had been buried there was no simple way of checking whether or not the junction had been correctly installed.

Accordingly, the present invention provides a ducting system for communications cables having a plurality of axially engageable tubular members, wherein adjacent engageable end portions of said members have co-operating means for enabling axial engagement of said end portions in one pre-selected relative angular position about the axes of said members.

In a preferred form of the invention said adjacent end portions are adapted to engage one within the other and have complementary co-operating means for angularly locking said one member to the other in a pre-selected angular position.

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 sectional plan view of a tubular member forming a junction for the ducting of figure 1; Figure 3 is a view in the direction of arrow A of figure 2; Figure 4 is a view of a tubular member forming a shallow bend for the ducting; Figure 5 is an end elevation of one end of the tubular member of Figure 4; Figure 6 is an end elevation of the opposite end of the tubular member of Figure 4; Figure 7 is a view of a tubular member forming a 900 bend for the ducting:: Figure 8 is an end elevation of one end of the tubular member of Figure 7; Figure 9 is a side elevation of a straight tubular member for the ducting; Figure 10 is an end elevation of the tubular member of Figure 9; Figure 11 is a side elevation of an end cap for the ducting; Figure 12 is an end elevation of an inner end of the cap of figure 11; and Figure 13 is an end elevation of the outer end of the cap of figure 11.

Referring now 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 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 figures 2 and 3 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 30 of a further ducting branch limb 32 as a reasonably close fit. The end 30 of the limb 32 is plane, ie of the same diameter as the body of the limb 32, whilst its other end is formed by an enlarged diameter end portion 34 similar to the end portion 28. The limb 32 extends through an angle of typically 67.50 such that when it is coupled to the branch limb 26 the end portion 34 extends at right angles to the main line 24 of the ducting. At the end 36 of each branch line remote from the main line 16 the ducting is brought to the surface by a further curved limb 38 which extends generally through 900.The curved limb 38 also has enlarged diameter end portions 40, 42, one end portion 42 being connected to the end portion 34 of the limb 32 by a suitable length 44 of straight ducting. The ducting 44 has plane ends so that it can simply be cut to the required length on site.

Finally, a cap 46 is provided to close the open end portion 40 of the limb 38.

Referring again to figures 2 and 3, the end portion 28 of the branch limb 26 is formed with an axially extending recess or key 48 in its radially inner wall which engages with a co-operating rib 50 which is formed as an axially extending rib on the radially outer surface of the limb 32. Corresponding recesses or keys 48 are formed in the end portions 34, 40 and 42 and a corresponding rib is formed on the straight length 44 of ducting.

Finally, the end cap 46 also has an axially extending rib 50 which engages with the co-operating recess in the end portion 40.

The outer end 52 of the cap 46 is provided with an arrow to indicate the direction of the cable run along the main line 24 from its source to the subscriber. As will be appreciated, because the recesses 48 and ribs 50 allow for only one relative angular position in which two tubular members may be connected, if the junction 22 is correctly positioned in the main line 16 then the arrow on the end cap 46 will point in one direction.

If the junction 22 is incorrectly positioned, ie with the branch limb 26 extending to the right as seen in figure 2, then the end cap 46 will only fit on the end portion 40 when the arrow is moved through 1800 to point in the reverse direction.

It will be appreciated that a simple inspection of the end cap of each branch line gives a clear indication of whether or not the associated junction 22 is correctly installed.

Although the illustrated tubular members have been shown having linear recesses 48 and ribs 50, it will be appreciated that any suitable form of co-operating key which allows engagement of two members in only one relative angular position may be provided.

Claims

1. A ducting system for communications cables having a plurality of axially engageable tubular members, wherein adjacent engageable end portions of said members have co operating means for enabling axial engagement of said end portions in one pre-selected relative angular position about the axes of said members.

2. A ducting system as claimed in claim 1 wherein said adjacent end portions are adapted to engage one within the other and have complementary co-operating means for angularly locking said one member to the other in a pre selected angular position.

3. A ducting system as claimed in claim 2 wherein said co operating means comprise respective co-operating projecting means and recess means on said adjacent end portions.

4. A ducting system as claimed in claim 3 wherein said projecting means is formed on one of said end portions and said recess means comprises an axially extending recess formed in the adjacent end portion.

5. A ducting system as claimed in claim 4 wherein said projecting means is formed externally of said end portion and said recess is internally of said adjacent end portion.

6. A ducting system as claimed in claim 5 wherein said projecting means is an axially extending rib.

7. A ducting system as claimed in any of the preceding claims wherein one of said tubular members is a closure member having a closed end portion and indicia means on said closed end portion for indicating the angular position of said closure member relative to the remaining tubular members.

8. A ducting system as claimed in claim 7 having a main duct line and a branch duct line branching from said main duct line at an acute angle thereto, wherein said branch duct line is formed by said plurality of tubular members and closed by said closure member and said indicia means indicates the direction of flow of said branch duct line into said main duct line.

9. A ducting system substantially as hereinbefore described with reference to the accompanying drawings.