Patent Application
20150114682
The invention relates to cables and to cable pulling methods. A pulling element may be fixed at an end of the cable. The cable is pulled by exerting a pulling force on the pulling element.
According to a first prior art, for example described in
Cable 1 can be installed in a duct or in a casing by exerting a pulling force on a pulling wire that is attached to a pulling eye itself attached to the end 10 of the cable 1. When installing a cable 1 in this manner, the pulling force is exerted by the pulling grip 20 on the outer surface 12 of the cable 1, that is to say on the outer sheath 12 or on the outer jacket 12 of the cable 1.
In some cable designs, especially in optical cables without or with a limited amount of aramide underneath the outer jacket 12 and where internal elements of cable core 11 are rather loose in the design, such as for example high fiber count Flextube® cables, the pulling forces are not transferred or practically not transferred on the internal components of the cable core 11. Consequently, most of the pulling force is supported by the outer jacket 12 and the outer jacket 12 may fail, that is to say be torn, under these circumstances. The pulling grip 20, or the pulling nail which can be used instead, gets disconnected from the cable 1.
In other cable designs, especially in optical cables where internal elements of cable core 11 are rather tight in the design, the pulling forces are somewhat transferred on the internal components of the cable core 11. Consequently, only a part of the pulling force is supported by the outer jacket 12, but the outer jacket 12 may however fail, that is to say be torn, under these circumstances. The pulling grip 20, or the pulling nail which can be used instead, can get disconnected from the cable 1, even if it is for a higher pulling force than for a cable with a loose design.
In a second prior art, for example described in application WO 2000/60714 A1, it is disclosed a device for connecting the end of a wire or of a cable. This device comprises a ring provided with one or more longitudinal grooves and an end piece provided with the same number of longitudinal grooves. The grooves in the ring and the end piece form a chamber into which a wire of a cable can be inserted. When the ring is rotated over the end piece the wire(s) are grasped and locked. This device can be used for drawing wires or cables in ducts or casings. A drawback of this second prior art is a relative complexity. Indeed, it is needed to directly connect pulling element to the internal components of cable core rather than merely on the cable outer sheath.
In a third prior art, for example described in application CN101359817A, it is disclosed an integrated pulling eye with a pulling grip where slipping of the cable is prevented by using a special clamping structure in the pulling grip. A drawback of this third prior art is a relative complexity. Indeed, it is needed a specific structure of the pulling grip. Moreover, the clamping of the pulling grip on outer sheath of cable may not avoid the outer sheath to be torn if pulling force exceeds a threshold, even a relatively low one, since here again cable outer sheath is alone to bear the effect of the pulling force.
The object of the present invention is to alleviate at least partly the above mentioned drawbacks.
More particularly, the invention aims to help transferring more of a pulling force exerted on cable outer sheath, to a cable core, that is to say to at least some internal components or elements of cable core. That way, the failure threshold of cable outer sheath, for example when cable outer sheath is torn, is increased, thanks to a more equitable repartition of the pulling force between cable outer sheath and cable core.
According to some embodiments of the invention, in the cable, there will be a coupling of the inner elements of the cable all together with the outer jacket or with the outer sheath in order to have the pulling load distributed over all the cable elements.
According to some embodiments of the invention, this better repartition of the pulling load is performed through better coupling of cable outer sheath and cable core, by increasing pressure of cable outer sheath on cable core. In optical cables, the optical fibers then participate significantly to absorb the pulling effort when the cable is pulled in the duct.
According to some embodiments of the invention, at least the respective elongations of internal components of cable core, like optical fibers, on the one side and of cable outer sheath on the other side, will be reduced too. This helps avoiding deterioration of the cable design.
According to some embodiments of the invention, the use of one or more rings surrounding cable outer sheath will increase the pulling force that can be exerted on the cable without failing of the outer sheath and disconnection of the pulling grip, or even of a pulling nail, from the cable.
One object of the invention is achieved with a cable comprising a cable outer sheath surrounding a cable core and at least a ring surrounding partly said cable outer sheath so that said ring presses said cable outer sheath on said cable core in a way adapted to increase a transfer of a pulling effort exerted on said cable outer sheath to said cable core.
Another object of the invention is achieved with a method of cable pulling including a step of pulling a pulling element fixed on a cable end comprising a cable outer sheath surrounding a cable core and at least a ring surrounding partly said cable outer sheath so that said ring presses said cable outer sheath on said cable core so that a transfer of a pulling effort exerted on said cable outer sheath to said cable core, is increased.
Preferred embodiments comprise one or more of the following features:
Further features and advantages of the invention will appear from the following description of embodiments of the invention, given as non-limiting examples, with reference to the accompanying drawings listed hereunder.
On all
A pulling grip is a flexible socket of braided material, for example made of metal, aramide, or other high strength synthetic materials, that is placed around an end of a cable. If a soft pulling grip is used, the maximum length of the pulling grip should be limited to easily go through bended ducts. In this case, for example for a 16 mm diameter cable, length for pulling grip should not be more than 900 mm.
A pulling eye is an element made of metal, aramide, or other high strength synthetic material, that forms an eye to which a pulling wire can be attached so that a pulling force can be exerted on a cable. A pulling eye may also be attached to a pulling grip so as to form an integral part with the pulling grip.
If a rigid pulling nail is used instead, the maximum length of the pulling nail should be limited to easily go through bended ducts. In this case, for example for a 16 mm diameter cable, length for pulling nail should not be more than 180 mm.
Here, a ring 21, presenting a width W21 of about 7 cm, is located at about 20 cm of the very end 13 of cable 1. A ring or a couple of rings presenting much lower width could be used instead, for example two rings large of 15 mm separated by a distance of 15 mm could be used instead. This ring 21 is so wide that it can be called a sleeve. This ring 21 is crimped on the cable outer sheath 12. This ring 21 couples, at ring 21 level, cable core 11 with cable outer sheath 12. A pulling grip 20 will surround this ring 21. The pulling grip 20 will grip on the ring 21 as well as on the cable outer sheath 12 of cable end 10, on both sides of the ring 21. Thanks to said coupling, because of ring 21 presence, a bigger part of the pulling force exerted on outer sheath 12 will be transferred to cable core 11, than if there were no such ring. Indeed, the ring 21 presses cable outer sheath 12 on cable core 11 in a way adapted to increase a transfer, to cable core 11, of a pulling effort exerted on cable outer sheath 12.
Since it is easier to pull the cable by exerting a pulling force on one of its ends, the ring 21 surrounds partly cable end 10 outer sheath 12. The ring 21 is shrunk or crimped on cable outer sheath 12 to better couple cable outer sheath 12 with cable core 11. Shrinking or crimping will both be used in following texts, they are considered to vehicle the same idea. The crimped ring 21 has an external diameter close to the nominal cable external diameter in order not to have too prominent protrusions from cable outer sheath in order to avoid gripping within the duct while pulling the cable. The crimped ring 21 practically does not affect the cable 1 external diameter.
Preferably, the ring 21 is shrunk on cable outer sheath 12 in such a way that the ring 21 external diameter is reduced by at least 5%, preferably by at least 10%. In an example, a ring presenting an original internal diameter of 21.5 mm and of external diameter of 25.5 mm is slide first around a cable presenting an external diameter of 21 mm After crimping on cable outer sheath 12, the external diameter of the ring 21 is around 21 mm and the internal diameter of the ring 21 is around 19 mm.
In order to make easier shrinking or crimping of ring 21 on cable outer sheath 12, the ring 21 is made of ductile material. For example ring 21 can be made of aluminum or of copper.
In a preferred structure of cable 1, for which one or more rings are especially useful, the cable core 11 includes internal elements which are loose with respect to one another at a position along the cable where there is no ring on the outer sheath and which are tight with respect to one another at a position along the cable where there is a ring on the outer sheath, for example at ring 21 level. Preferably, this cable core 11 includes radial strength members with no aramide or with very little aramide. Such relatively loose cable design can be a cable including one or more Flextube®. This Flextube® cable is an optical cable in which the optical fibers are grouped in one or more modules, each module comprising multiple optical fibers covered by a thin flexible layer of polymer material and a single outer sheath surrounding the one or more modules. This single outer sheath may include two embedded strength members.
Space 24 lying between rings 23 and 25 presents excess material thickness due to neighbor crimping of rings 23 and 25 on cable outer sheath 12. The pulling grip will grip all the more this exceeding material which will in turn transfer more easily pulling force due to presence of neighbor rings 23 and 25.
Space 26 lying between series of rings 23 and 25 on the one side and sleeve 21 on the other side, is relatively long as well as well coupled to cable core 11 due to rings 23 and 25 and sleeve 21. The pulling grip will grip the outer sheath 12 in space 26 which will in turn transfer more easily pulling force due to effective coupling to cable core 11 thanks to presence of relatively close rings 23 and 25 and relatively close sleeve 21.
In cable 1 of
A distance 26 between at least two of said rings, between for example ring 23 and ring 30 on
Tests have been made with cables corresponding respectively to
Results of pulling efforts application on cable of
Results of pulling efforts application on cable of
Results of pulling efforts application on cable of
Results of pulling efforts application on cable of
As already said, cable of
The strength members are the strength members of the cable outer sheath. In tables 2 and 3, the outer sheath elongation follows a diameter reduction of the outer sheath. In table 4, the outer sheath elongation is followed by a tear of the outer sheath.
In ring sliding step S1, one or more rings are slide around the outer sheath of a classical cable comprising a cable core surrounded by the outer sheath.
In ring crimping step S2, the ring or the rings are crimped on the outer sheath of cable so that outer sheath is coupled to cable core.
In pulling grip fixing step S3, the pulling grip is put around the outer sheath and the rings located at the end of the cable. At the end of the pulling grip is fixed a pulling eye. Instead of the pulling grip, there could be a pulling nail, but this is less efficient, because pulling nail does not surround all the different rings.
In pulling grip shrinking step S4, a pulling effort starts to be exerted on the pulling element so that the pulling grip, which is preferably a flexible socket of braided material, shrinks on the cable end outer sheath and on the cable end ring(s) so that cable end is tight within pulling grip.
In cable pulling step S5, a pulling effort continues to be exerted on the pulling element so that the cable is pulled. During cable pulling, the ring or the rings press the cable outer sheath on the cable core so that the transfer, to the cable core, of the pulling effort exerted on said cable outer sheath is increased.
The invention has been described with reference to preferred embodiments. However, many variations are possible within the scope of the invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2011/003299 | 10/28/2011 | WO | 00 | 4/28/2014 |
