GB2104309A - Universal jointing box for telecommunication or power cables - Google Patents

Abstract

A jointing box for jointing telecommunication or power cables (14), comprising a protective tube (1) provided at each end with an end plate (3) having a lead-in terminal for a cable, a securing ring (2) in screw-threaded engagement with each end plate (3), and between the ring (2) and each plate (3) a sealing ring (4) which sealingly contacts the end face of the protective tube (1), the outer periphery of the end plate (3) and the inner periphery of the ring (2). Metal inserts 10 are provided in the end plates 3 which with conductive crossbars 6 or a conductive cylinder (5, Fig. 3 not shown) and conductors 11 interconnect the cable armours 15. <IMAGE>

Description

SPECIFICATION Universal jointing box for telecommunication or power cables This invention relates to a universal jointing box for jointing telecommunication or power cables, which is intended for the termination of a cable and for mutual connection of two cables. A jointing box for cables has to accomplish two basic tasks, i.e. to make possible a mechanical connection and an electrical connection of cables.At each of these connections the jointing box has to fulfil several tasks, e.g. at the mechanical connection there has to be achieved a mechanical protection of the connection point, protection against the entering of humidity into the cable, relieving of the conductors of the axial pull, hermetical sealing of the space in which electrical connections between cable conductors are executed, electrical protection of the connection points of the cables and filling of the jointing box with a sealing material, oil etc., depending on the type of the jointing box. At the electrical connection the jointing box has to ensure a proper mutual connection of the cable conductors and at the same time a sufficient mutual insulation at the connection points.

An important component of such a jointing box is the lead-in terminal, which, on one hand, has to be universal at least within a certain range concerning all construction of cables as well as the diameter of the cable, i.e. a certain type of the lead-in terminal can be used for all cables, whose diameter is within a defined range, and on the other hand, it has to ensure a sufficient mechanical force onto the cable, whereby a uniform axial pull, bending and torsion of the cable are achieved.

Jointing boxes as construction components have been known for a long time and have been manufactured in several different ways.

There are known metal jointing boxes, which are very heavy and not universal and cannot be used with all types of cables. Another type of a jointing box is based on sealing resins, i.e. special resins, with which the interior of the box is filled. The greatest disadvantage of such jointing boxes lies in the fact that they cannot be re-opened, and they are directly used for cables with PE cable sheathing. Recently, jointing boxes have been made available, which are constructed on the basis of shrinkage tubes. These jointing boxes are ruined if re-opened and they are rather expensive. Another group of jointing boxes is characterized in that the sealing of the jointing box is achieved by radial pressure of the sheathing of the cable against the lead-in terminal through which the cable is fed.The technology of these jointing boxes is rather complicated and connected with rather high costs.

All the stated types of jointing boxes with the exception of the oldest, very heavy types cannot withstand high mechanical loads on the cables and cannot be exposed to high gas pressure.

According to the present invention there is provided a jointing box for jointing telecommunication or power cables, comprising a protective tube provided at each end with an end plate having a lead-in terminal for a cable, a securing nut or ring in screwthreaded engagement with each end plate, and provided between the tightening nut or ring and end plate a sealing ring gasket which sealingly abuts against the end face of the protective tube, the outer circumference of the end plate and the inner circumference of the tightening nut or ring.

The inventors aimed to construct a jointing box which would be universal to the greatest possible extent, i.e. which would receive and connect cables of different types, constructions and diameters, which would be universal for telecommunication as well as for power cables, whose production would be simple and not expensive and whose assembling would be fast, with basic hand tools and without the need for a specially skilled worker.

Besides, this jointing box should be easily reopened an closed, it should ensure a high degree of mechanical safety and be able to withstand high gas pressure.

Two embodiments of a jointing box for telecommunication or power cables according to the invention will now be described in detail hereinafter, by way of examples, with reference to the accompanying drawings, in which: Figure 1 illustrates a jointing box according to the invention in a partial cross-section, Figure 2 illustrates another embodiment of the inner part of the lead-in terminal in the cross-section of the jointing box according to the invention, and Figure 3 is a perspective view of a partially assembled jointing box according to the invention.

As it can be seen from Fig. 1, the outside of the jointing box according to the invention is formed by a protective tube 1, which can be made of plastics material, rubber or metal, at each end there is an end plate having a universal cable lead-in terminal 3 and two retaining nuts or rings 2. As it can be seen from Fg. 1 of the drawings, the end faces of the tube 1 are chamfered, and the chamfering starts on the outer circumference of the tube 1 and terminates at the inner circumference of said tube 1. In the first embodiment the universal lead-in terminals 3, extend into the tube 1 from each side and they are each connected with a crossbar 6. This connecton is executed in such a manner that at least three metal inserts 10 reach from the front side of the terminals 3 through the terminal itself up to the interior of the jointing box and are screwed into the crossbar 6.The inserts 10 and the crossbar 6 form an electrically conductive connection between the front side of the terminals 3 so that through conductors 11 fixed to the inserts 10, an electrical connection can be formed between the armours 1 5 of the cables 1 4 entering the jointing box.

Each end plate provided with a terminal 3 has an external screw-thread onto which the tightening nut or ring 2 is threaded by means of its internal screw-thread. Each nut or ring 2 is formed in such a manner that a part of it extends over the tube 1, and in the space formed between the nut or ring 2 and the terminal 3 a sealing ring gasket 4 is positioned.

In Fig. 3 there is shown an embodiment of the jointing box according to the invention in which the crossbar 6 is substituted by a cylinder 5 made of an electrically conductive material, preferably of sheet metal. The cylinder 5 is composed of two halves, which have openings 5' on their circumference directed towards the terminal 3, through which openings there extend connecting teeth 5" positioned on the circumference of the terminal 3, which teeth engage into the openings 5' on the cylinder 5. Thus, cylinder 5 is in electrical connection with the insert 10 by a part (not specially marked), which protrudes from the cylinder 5.

At the passage of the cable through the lead-in terminal 3, two requirements have to be fulfilled as it has already been stated in the introduction. On one hand, the cable 14 has to be mechanically unloaded, which is executed in the zone 1 2 of the cable, and on the other hand, the contact between the cable 14 and the terminal 3 has to be water-and gastight, which is executed in the tightening zone 13.

If the zone 1 2 as shown in Fig. 1 is considered, it can be seen that part of the cable sheathing and a part of the armour 1 5 of the cable 14 is removed. On its projecting tube-like part, the end plate having the lead-in terminal 3 is cut in such a manner that this tube-like part forms spring ribs or fingers, which are surrounded by a compressible clamp 16. On the inside of the end plate having the terminal 3, a connecting bridge 1 7 is positioned, which is either formed as shown in Fig. 1, whereas in Fig 2 a second embodiment of this bridge 1 7 is shown.By means of a connector 11' said bridge 1 7 is connected either with the crossbar 6 or with the cylinder 5 and, because it is at the same time also in an electrically conductive contact with the armour 1 5 of the cable 14, the connection, which is otherwise made by the conductor 11, is substituted thereby.

It is characteristic for the tightening zone 1 3 that between the extreme inner end of the tube-like part of the end plate having the terminal 3 and the bridge 1 7 a sealing ring gasket 22 is positioned, and extending over the bridge 1 7 and the sheathing 1 8 of the cable 1 4 there is placed a sleeve 19, which is impermeable to gas and water and which tightly contacts the bridge 1 7 as well as the sheathing 1 8. The sleeve 1 9 can be made of one piece, but it can also be made by wrapping the cable with a convenient insulating material.Into the interior of the tube-like part of the end plate having the terminal 3 btween its inner wall and the sheathing 18 of the cable 14, sealing material 20 can be inserted.

The assembling of the jointing box according to the invention is very simple. Onto both ends of cables 1 4 there are positioned tightening nuts or rings 2 with the ring gaskets 4 and in addition, onto one end of the cable thee is put the protection tube 1. Depending on the length of the protection tube 1, defined by the type of the cables 1 4 to be connected, the outer sheathing, the armours 1 5 and the water-impermeable sheathing 1 8 are removed from both ends of the cables 14.

Both ends of the cables 1 4 are inserted into the plates provided with the terminal 3 and are fixed with the clamp 1 6 and then they are sealed with the sleeve 1 9 and/or sealing material 20. The mutual mechanical connection of both terminals 3 is executed by the insertion of the crossbars 6, into which the inserts 10 are screwed, whereafter there are executed the final electrical connection points 7 of the cable conductors, which are mutually insulated.In the second embodiment one half of the cylinder 5 with the openings 5' is put onto the connecting teeth 5" of the terminals 3, whereafter the connection points 7 and the final contact between the insert 10 and cylinder 5 or the connection between the bridge 1 7 and the cross bar 6 or the cylinder 5 is made by means of the conductor 11' and the second half of the cylinder 5 is fixed to both terminals 3.Thereby a firm mechanical connection between both terminals 3 is achieved, whereafter the protection tube 1, the ring gaskets 4 and the tightening nuts or rings 2 are pulled over the cylinder and the tightening nuts 2 are tighened, so that by the compression of the ring gasket 4 and its abutting on the front wall of the protecting tube 1, the outer circumference of the terminal 3 and the inner circumference of the tightening nut 2, a complete sealing of the interior of the jointing box is achieved. If the electrical connection of both armours 1 5 of the cable 14 has not been made in the interior of the jointing box according to the invention as it has been described above, this connection can be made by conductors 11, which on one side are connected to the armours 1 5 of the cable 14 and on the other side to the insert 10 in the terminal 3.

In cases where the crossbar 6 is used for the connection of the terminals 3 and that at the same time it is necessary that the interior of the jointing box is electrically screened, it is possible to surround the jointing box, before the protection tube 1 is assembled, with a metal shield 5"', which is electrically connected to the crossbar 6 in a convenient way.

The protection tube 1 can be provided with an opening 9, through which the interior of the jointing box according to the invention can be filled with sealing material or oil, and a valve 8 for the introduction of compressed air or nitrogen into the interior of the jointing box can be positioned on the terminal 3.

It is evident from the foregoing that the jointing box according to the invention is a constructional component, whose manufacturing is simple and which in a novel manner makes possible a simple and reliable connection of cables electrically as well as mechanically, and at the same time a repeated opening of the jointing box is possible without difficulties if any new work has to be done at the connection points of the cables ih the jointing box.

Claims (7)

1. A jointing box for jointing telecommunication or power cables, comprising a protective tube provided at each end with an end plate having a lead-in terminal for a cable, a securing nut or ring in screw-threaded engagement with each end plate, and provided between the tightening nut or ring and end plate a sealing ring gasket which sealingly abuts against the end face of the protective tube, the outer circumference of the end plate and the inner circumference of the tightening nut or ring.

2. A jointing box as claimed in claim 1, in which several metal inserts are provided in the end plates, which inserts are rigidly connected with an electrically conductive crossbar or a cylinder and which by means of a conductor is connected with the armour of the cables.

3. A jointing box as claimed in claim 1, in which the armours of both cable ends are in mutual electrical contact via a bridge, a conductor, an electrically conductive cylinder or a crossbar.

4. A jointing box as claimed in any precedng claim, in which the sheathing of the cable and the bridge, which abouts thereon and is positioned on the inner side of the terminal, are surrounded by a water- and gasimpermeable sleeve.

5. A jointing box as claimed in any preceding claim, in which the space between a tube-like part of the end plate and the sheathing of the cable is filled with sealing material.

6. A jointing box as claimed in any of the preceding claims, in which an outer tube-like part of the end plate is surrounded by a clamp which abuts on the armour of the cable.

7. A jointing box for cables substantially as hereinbefore described with reference to and as illusrated in the accompanying drawings.