Patent Application
20090045591
The present invention relates to the general field of telecommunications. It relates more particularly to a device for sealed connection of telecommunications cables, for example optical fibers, the device being for use in a protective box used for distribution lines.
The optical fiber cables that are used to construct telecommunications lines are connected by means of connectors and splices. In order to protect them from moisture and other ambient agents (oils, acids, or other pollutants), cable ends and connectors are generally placed in sealed protective boxes which are themselves placed in telecommunications structures (underground chambers, cabinets, raceways, etc.).
Such protective boxes, which are generally tubular or parallelepipedal in shape, present inlets that are usually situated in two opposite faces. These inlets need to be thoroughly sealed, both with respect to their own closure devices and with respect to their cable inlets.
Furthermore, the cable inlets of such boxes are bulky because they are constituted by tubular plugs that are leaktight and strong. The number thereof must therefore limited for any one box. Thus, for a protective box dedicated to optical fiber cables, the maximum number of inlets is generally of the order of six to 12, for 100 to 200 spliced optical fibers. This number of cable inlets is sufficient for transport links where the cable division ratio is small (of the order of 2 to 3 at most).
In contrast, with a distribution optical network, it is frequently necessary to serve a large number of users from a single point. Thus, there exists a network architecture known as a passive optical network (PON) that consists in separating a single optical fiber by means of a coupler into eight, 16, or 32 optical fibers in order to serve a corresponding number of users, thereby exponentially increasing the number of cable inlets that are needed.
Document EP 0 695 900 provides for dividing a cable inlet having a diameter of 20 millimeters (mm) into two or four inlets each having a diameter of 3 mm to 4 mm. The protective box that initially had six cable inlets can then be transformed into a box presenting a large-diameter inlet enabling a large-diameter cable to be subdivided into 20 small cables.
Not only do the cable inlets of that document fail to achieve cable densification that is sufficient for an application to an distribution optical network, they also present the drawback of being interdependent. Thus, when it is necessary to act on one of those inlets (to install or replace a cable), the other inlets are also involved. In particular, the elastomer washers that provide sealing for one inlet are common to all of the inlets, so that any operation on one of them breaks sealing on all of them. They also present the drawback of retaining cables only weakly in the elastomer washers.
A main object of the present invention is thus to mitigate such drawbacks by proposing a device for sealed connection of telecommunications cables that enables cable density for a given protective box volume to be increased significantly, while conserving independence between the cable inlets.
To this end, the invention provides a sealed connection device for telecommunications cables, the device comprising a tubular plug for being received in an inlet of a protective box for telecommunications, and a plurality of tubes each designed to receive at least one telecommunications cable, said tubes being disposed longitudinally in the plug so as to pass right through it, the device being characterized in that it further comprises a resin that is cast between the tubes so as to ensure both mechanical retention of the tubes in the plug and sealing of the connection device.
The use of a plurality of tubes housed in the plug makes it possible to increase cable density significantly. For example, a single plug can receive as many 36 tubes, i.e. at least as many telecommunications cables. It is possible to make such connection devices independent firstly because each plug that is to be received in an inlet of a protective box presents its own sealing, and secondly because the cables are placed in the tubes without slack and without interfering with the sealing that exists between the tubes or between the tubes and the cables already in place.
Furthermore, such a connection device presents reliability (in terms of mechanical strength, leaktightness, and ability to withstand pollutants) that is well adapted to the environment of a protective box for telecommunications.
Another advantage of such a connection device is that it is possible to conserve existing boxes in the same conditions of use, thereby enabling costs to be kept down, in particular in terms of training staff.
According to an advantageous disposition of the invention, the plug includes a reduction in section at an inlet end so as to prevent the tubes from moving longitudinally in the plug.
According to another advantageous disposition of the invention, the plug has at least two distinct annular compartments, each designed to have a plurality of tubes passing therethrough.
The invention also provides a method of manufacturing such a connection device. The method is characterized in that it consists: in using a tubular plug designed to be received in an inlet of a protective box for telecommunications; in using a plurality of tubes each designed to receive at least one telecommunications cable; in disposing the tubes longitudinally in the plug so that the tubes pass right through the plug; and in casting a resin between the tubes in such a manner as to ensure both mechanical retention of the tubes in the plug and sealing of the connection device.
The resin may be cast into the plug via an injection tube that opens out between the tubes. Under such circumstances, the tubes are advantageously spaced apart from one another by means of rings so as to facilitate distribution of the resin while it is being cast.
Other characteristics and advantages of the present invention appear from the following description made with reference to the accompanying drawings which show an embodiment having no limiting character. In the figures:
The box 10 is substantially in the form of a rectangular parallelepiped presenting at opposite ends an inlet face 12 and an outlet face 14. The inlet face 12 presents at least one inlet orifice 16 for passing optical fiber telecommunications cables.
Additional orifices 17 are also provided in the inlet face 12 of the box. These additional orifices 17 serve to enable single telecommunications cables to enter or leave the box.
With reference to
The connection device 18 of the invention comprises in particular a tubular plug 20 and a plurality of tubes 22 each serving to receive at least one telecommunications cable (also referred to as telecommunications cable transport tubes).
The tubular plug 20 presents an inlet wall 20a that is to be positioned in the protective box, and an outlet wall 20b that is opposite from its inlet wall 20a.
In the embodiment of
The plug 20 is also provided with a flange 26 that comes to bear against the inlet face 12 of the protective box 10 when the connection device is mounted in the box.
The telecommunications cable transport tubes 22, e.g. presenting an inside diameter of 4 mm for an outside diameter of 6 mm, can be made of polyolefin or polyamide. They are disposed longitudinally in the compartments 24a, 24b of the plug 20 so as to pass right through it.
More precisely, at an inlet end 22a, each of the tubes 22 is flush with the inlet wall 20a of the plug 20. At its opposite end 22b (outlet end), each tube projects longitudinally from the outlet wall 20b of the plug 20.
The connection device 18 further comprises a resin 28 which is cast between the tubes 22 so as to serve firstly to hold the tubes mechanically in the plug 20 and secondly to provide the connection device with overall sealing.
The resin 28 is cast into each of the compartments 24a, 24b of the plug 20 between its inlet and outlet walls 20a and 20b. In order to ensure that the tubes 22 are held securely in the plug 20 with good sealing, the resin 28 is distributed between the tubes and between the tubes and the inside walls of the plug.
The resin may be of the single-component or two-component type. For example, it may be constituted by polyester or polyurethane. Its composition needs to comply with certain standards that are in force for protecting telecommunications cable splices. In particular, it must present a setting time that is relatively short.
In an advantageous disposition of the invention, the plug 20 has a reduction in section 30 in each of its compartments 24a, 24b at the inlet end thereof so as to prevent the tubes 22 from moving longitudinally in the plug.
Furthermore, at their outlet end 22b, the tubes 22 may have respective covers 32 serving to make the tubes leaktight in the absence of telecommunications cables.
When a cable 34 is inserted in a tube, its cover 32 is removed and sealing is provided, e.g. by means of a heat-shrink sleeve.
When not in use for installing a unit cable, the additional orifices 17 may also receive respective tubular plugs of the type described above, preferably plugs having a single compartment only.
A method of manufacturing such a connection device is described below with reference to
In the absence of telecommunications cables, such a plug 20 is designed to close one of the inlet orifices of the protective box. For this purpose, each compartment 24a, 24b presents a wall 36 in the form of a capsule that can be removed, e.g. using a screwdriver and a hammer (only one wall 36 is shown in
With reference to
An injection tube 40 is also provided. This tube 40 enables resin to be injected into the compartments 24a, 24b using an operating technique described below. It is provided with a plurality of holes 42 at its inlet end 40a.
As shown in
These operations are repeated for each set of tubes 22, 40 that is to be housed in the compartments 24a, 24b of the plug 20.
The following step (
A sealing bead 46 (e.g. of butyl sealant) is then placed at the outlet ends 22a of the tubes 22 so as to close them. An additional sealing bead 48 may also be disposed around the tubes 22 against the inlet wall 20a of the plug 20.
A cap-forming endpiece 50 is then put into place around the outlet ends 22a of the tubes 22 (
In order to make it easier to cast the resin, the plug 20 and the tubes 22 as positioned in this way are disposed vertically with the endpiece 50 pointing downwards. The resin 28 is then cast into the compartments 24a, 24b using the injection tubes 40 provided with the holes 42 (
Once the resin 28 has polymerized, the endpieces 50 are withdrawn and the excess lengths of tube 22 projecting from the inlet wall 20a of the plug are cut off (e.g. by sawing) as shown in
Beside this inlet wall 20a, after the ends of the tubes 22 have been cut, they are trimmed and smoothed. Beside the outlet wall 20b of the plug, the tubes 22, 40 can be cut to the same length.
Finally, as described with reference to
| Number | Date | Country | Kind |
|---|---|---|---|
| 0500030 | Jan 2005 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR06/50001 | 1/2/2006 | WO | 00 | 3/21/2008 |
