Technical field

The present invention relates to the field of optical cables and in particular 5 to a tool for safely and precisely making an access window on an optical cable.

In the present description and claims, the expression "optical cable stripping tool" or "a tool for stripping an optical cable" or any other similar expression will designate a tool configured for making an access window on0 an optical cable, namely a tool for removing a portion of optical cable sheath and creating an access window without cutting any fibers inside the cable. Through such a window an access to optical fibers is provided. On the opposite side of the cut window the sheath is not removed.

Background art 5 A possible scenario of use of the present invention is in passive optical networks, for instance in a Fiber-to-the-Home network (briefly FTTH).

A FTTH network is an optical access network providing a number of end users with communication services, e.g. with services requiring data transmission at a rate of some hundreds of Mbit/s or more. 0 Typically, a FTTH network comprises a distribution cabinet cooperating with a transport network. The distribution cabinet is often located in the basement of the building where the end users reside and is connected with termination boxes arranged, for example, at the various building floors via optical cables, housing one or more optical fibers. 5 An optical cable comprising a plurality of optical fibers typically departs from the distribution cabinet. Typically, an optical cable exiting a distribution cabinet and serving each floor of a given building to reach each end user is indicated as "in-line optical cable". Similarly, each optical fiber of an in-line optical cable is typically indicated as "in-line optical fiber". 0 Typically, the in-line optical cable vertically runs through the building from the basement up to all the building floors. The in-line optical cable is typically laid down within a duct, which is substantially vertically fixed to or within a building wall and which mechanically protects the in-line optical cable or simply installed on the wall without mechanical protection. The duct which receives an in-line optical cable is typically indicated as "in-line cable duct". The in-line optical cable can also be installed substantially "horizontally" to serve more workstations on the same floor.

Typically, an in-line optical fiber comprising one or more optical fibers, (generally two), branches out the in-line optical cable at a certain floor and exits a termination box for connecting the end user. Typically, the optical cable branching out the in-line optical cable is indicated as "drop cable". Each optical fiber of a drop cable is generally indicated as "drop optical fiber".

Connecting the distribution cabinet to a termination box requires extracting at least one in-line optical fiber from the in-line optical cable and connecting, typically by splicing, such an in-line optical fiber to a drop optical fiber of said drop cable exiting the termination box or taking directly the in-line optical fiber to the end-user. The optical connection between the in-line optical cable and the drop cable is typically made in a so-called "optical transition box".

In order to access in-line optical fibers within an in-line optical cable an optical cable stripping tool is used. US 2007/0286564 discloses a tool and method for accessing fibers within an in-line optical fiber cable. The tool can be used to access optical fibers within buffer tubes held in distribution cables. In one embodiment, the tool is clamped over a buffer tube and a blade is slid across a blade guide of the tool to facilitate the cutting of a fiber access window in the buffer tube. The method of accessing fibers within a fiber optic cable includes supporting a section of buffer tube and sliding a blade across the mid-portion of the supported section thereby creating optical fiber access windows therein.

The Italian patent application MI2008000008 (in the Applicant's name) discloses a tool for accessing optical fiber contained in a cable, said tool comprising a body with a longitudinal recess for partially housing a portion of said cable, and a blade transversely secured in said recess with a predetermined slant with respect to the longitudinal axis of said recess. The tool is positioned over the optical cable to house the cable into the longitudinal recess. Exerting a controlled pressure on the cable, the tool is tracked along the cable in the cutting direction parallel to the cable axis.

Summary of the invention The Applicant has noticed that the above known tools and methods for accessing fibers within an optical fiber cable has some problems.

In the case of the tool of US 2007/0286564, in order to cut a window a separate blade has to be provided. The tool, in fact, only provides a blade guide to facilitate the cutting of a fiber access window into a buffer tube. However, such tool requires a lot of free space around the in-line optical cable, such a space being not always available.

As the cutting of the sheath is made by the operator by a separate tool, it is possible that the sheath removal is made through more than one cut. This results in a corresponding number of small chips which are sometimes left on the site where the stripping operation is carried out. This has negative effect on the environment.

In addition, the tool according to US 2007/0286564 is rather bulky and a buffer tube has to be separated rather far from the other buffer tubes in order to be clamped by the tool. The tool of MI2008000008 may not always provide an accurate window access. The depth and the size of the cut depend on the pressure exerted by the operator, which can be either excessive or insufficient. Furthermore the cable has to be fixed or held steady during the cutting because of the axial traction force applied thereupon for opening the window access would cause the cable to move thus making the cutting difficult if not impossible.

The Applicant faced the problem of providing a tool for accessing optical fibers contained within an optical cable, said tool being handy, easy to use and more efficient than the known tools and apt for making a precise and safe stripping of an optical cable without the necessity of keeping the cable steady during the operation.

For the purpose of the present description and of the appended claims, an optical cable is any tubular arrangement containing, directly or indirectly, optical fibers and comprising a sheath.

According to the present invention, the Applicant found that a tool provided with cutting devices connected to arms hinged to move said devices according to opposed trajectories, could produce a continuous cutting path enabling to open a window access in a single, simple and accurate maneuver with no stress or undesirable movement of the cable containing the optical fibers to be accessed.

In particular, the present invention provides a tool for cutting an access window on an optical cable, wherein the optical cable comprises a sheath. The tool comprises: a first arm and a second arm, said first and second arms being hinged at a pivot axis, said first and second arms having a first handle and jaw and a second handle and jaw, respectively; - a first jaw head and a second jaw head respectively connected to the first and second jaws; and a first cutting device rigidly connected to the first jaw head and a second cutting device rigidly connected to the second jaw head for cutting a window in the sheath of the cable to be accessed when the handles are rotated to a closing configuration.

The tool may comprise a first backing device and a second backing device, wherein said first and second backing devices are configured for backing the cable when the window is cut in the sheath.

The first backing device may be rotatably connected to the first jaw head and the second backing device may be rotatably connected to the second jaw head.

Preferably, the first and second backing devices are configured for engaging the cable from a side which is substantially opposite to the cut window in the sheath. Preferably, each of said first and second backing devices comprises at least one pin. The at least one pin may be rotatable.

Each of said first and second backing devices may be hinged at a pivot axis.

In one embodiment, the pivot axis can be changed for adjusting the tool to two or more cable sizes. For instance, the position of the pivot axis can be changed in three positions corresponding to three cable sizes. The tool may further comprise a depth guide for limiting the penetration depth of the cutting device in the sheath of the cable.

The depth guide may comprise a tongue.

Preferably, the depth guide is rigidly arranged with respect to the cutting device. In one embodiment, the tool further comprise an adjusting device for adjusting the maximum angle of the arms.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include any combination of the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Brief description of the drawings

The present invention will become fully clear by reading the following detailed description to be read by referring to the accompanying drawings, wherein:

- Figure 1 is an axonomethc schematic view of an optical cable stripping tool according to one embodiment of the present invention;

- Figure 1 .1 is an axonometric schematic view of an optical cable stripping tool according to a further embodiment of the present invention;

- Figure 2 is a detail of the optical cable stripping tool of Figure 1 ;

- Figure 3 is a view similar to Figure 1 with the tool which is engaging a cable just before starting stripping thereof;

- Figure 4 is an axonometric schematic view similar to Figure 3, taken from a different angle;

- Figure 5 is a detail of the optical cable stripping tool of Figure 4; - Figure 6 is an axonometric schematic view of the tool of Figure 1 in an intermediate position of cable stripping;

- Figure 7 is an axonometric schematic view of the tool of Figure 1 in a final position of cable stripping. Detailed description of preferred embodiments of the invention

The stripping tool according to embodiments of the present invention is schematically shown in the various Figures. However, the tool can have a shape different from the one which is shown.

With first reference to Figures 1 and 1.1 , the tool (either according to the one or further embodiment) is designed by the reference number 1. Stripping tool 1 preferably comprises a first arm and a second arm 2A, 2B hinged at a pivot axis 8. A portion of each of the arms 2A, 2B represents a first and a second handle 21 A, 21 B, respectively. Another portion of each of the arms 2A, 2B represents a first and a second jaw 22A, 22B, and comprises a first and a second cutting device 4A, 4B, respectively. Preferably the portion representing the handles 21 A, 21 B is longer than the portion representing the jaws 22A, 22B.

In both the embodiments shown in Figures 1 and 1.1 , the jaws 22A, 22B comprise respectively a first and a second head 3A, 3B. Said heads 3A, 3B can be substantially U- or joke- shaped.

With reference to Figure 2, an exemplary description of second head 3B is given. Head 3B comprises two legs 31 B, 33B connected at one end to the arm 2B. Preferably, at the opposite ends, they are connected to the above mentioned cutting device 4B. Preferably, the area which is delimited by the two legs 31 B, 33B and by the cutting device 4B is an empty area. This results in a convenient space for passing through of the removed portion of cable sheath 91 as it will be shown below.

In the embodiments shown in Figures 1 and 1.1 (and in the detail of Figure 2), a first leg 31 B is preferably provided with a cavity 32B for receiving a corresponding projecting part 34A of the head 3A of the second jaw 22A. Similarly, the second leg 33B is preferably provided with a projecting part 34B which can be received in a corresponding cavity 32A of the head 3A of the second jaw 22A.

In the embodiment of Figure 1 (differently from the embodiment of Figure

1.1 ), a backing device 5B is provided in the head 3B. The backing device 5B is configured for engaging the cable 9 to be accessed from an opposite side than the stripping side (namely the side where the cutting devices operate) as it will be clear with reference to Figures 3 to 6.

Preferably, as shown in the embodiment of Figures 3 to 6, a first and second pivotable backing device 5A, 5B is provided respectively to the first and second head 3A, 3B. In one embodiment, the backing devices 5A, 5B comprise a first and second L-shaped bracket 51 A, 51 B hinged at a first and second hinge axis 54A, 54B in the projecting part 34A, 34B of the head 3A,

3B.

At the short end of the L-shaped bracket 51 B at least one guiding pin 52B, 53B is provided for engaging the back of the cable 9 to be accessed. In one embodiment a single guiding pin is provided. In another embodiment (as shown in Figure 2), two guiding pins 52B, 53B are provided. In such another embodiment, one first pin 52B has preferably a first length whilst the second pin 53B has a second length shorter than the first length of the guiding pin 52B. Preferably, the second length is half of the first length for reasons which will become clearer in the following. The pin(s) 52B, 53B of the first head can be rotatable or fixed, namely not rotatable. The first option is more preferred.

The whole applies to L-shaped bracket 51A, too.

The following description is referred to the head 3B and to the portions thereof {e.g., the pivotable backing device 5B), but the same features and functions can be shown by the head 3A and by the portions thereof (e.g., the pivotable backing device 5A).

Preferably, the pivotable backing device 5B is adjustable for adjusting the tool 1 to a plurality of cable sizes. In the shown embodiment, the pivotable backing device 5B is adjustable in correspondence of three different positions for accommodating the use of the tool 1 for three cable sizes. Typically, a first cable size corresponds to a 12 optical fiber cable and has an outer diameter of 8 mm, a second cable size corresponds to a 24 optical fiber cable and has an outer diameter of 12 mm and a third cable size corresponds to a 48 optical fiber cable and has an outer diameter of 14.5 mm. The adjustment is preferably provided by three holes (341 B to 343B) in the projecting part 34B of the head 3B. Such three holes 341 B to 343B provide three positions for the pivotable backing device 5B. The upper hole 341 B (namely the one closer to the cutting device 4B) is adapted to operate on larger diameter optical cables 9 whilst the lower hole 343B (namely, the one which is more distant from the cutting device 4B) is adapted to operate on smaller diameter optical cables 9. The head 3B, as said above, comprises a cutting device 4B. In one embodiment, the cutting device 4B comprises a plane blade with a wedge cutting edge. Preferably, the plane blade 4B is fixed to the ends of the two legs 31 B, 33B as shown in Figure 2. Advantageously, the blade 4B is made of stainless steel or the like. In one embodiment, the head 3B comprises a depth guide 7B as a safety measure for limiting the penetration depth of the cutting device 4B. Preferably, such a depth guide 7B comprises a tongue connected to the two legs 31 B, 33B. A distance is provided between the cutting device 4B and the tongue 7B. Such a distance cooperates to define the maximum depth of the cutting device 4B in the sheath 91. Preferably, the depth guide 7B is rigidly connected to the two legs 31 B, 33B of the head 3B at a blocking screw axis 71 B.

Preferably, each of the jaws 22a, 22B is shaped in a complementary manner so that the cutting edges of the cutting devices 4A, 4B, respectively, touch when the handles 21 A, 21 B are rotated and become closer (see Figures 6 and 7).

As said above, the other head 3A is shaped in a complementary manner with respect to head 3B. The same or similar parts of head 3A have been designed by the same reference numbers, but with the letter "A" in the place of "B".

Just to mention, the length of the second (shorter) pin 53A, 53B of each head 3A, 3B, respectively, has to be such that they do not interfere one with the other when the handles close.

In one embodiment, the tool 1 according to the present invention comprises an adjusting device 6 for adjusting the maximum angle of the arms

2A, 2B. Such an adjusting device 6 could comprise a screw device as schematically shown in Figures 1 , 1.1 , 3, 4, 6 and 7. The larger the maximum angle, the longer the open window 92 in the cable sheath 91.

Figure 3 shows the stripping tool 1 of Figure 1 ready for removing a portion of a sheath 91 of an optical cable 9 for creating a sheath window 92. Through such a sheath window 92 access to optical fibers is provided. Figure 4 is similar to Figure 3 but it shows the tool 1 and the optical cable 9 from a different angle.

Figure 5 shows a detail of Figure 4.

Figure 6 shows the tool 1 of Figure 3 at an intermediate stage of the sheath stripping. The penetration depth starts from zero at the edges of the sheath window 92 and increases until the depth guide 7A, 7B begins working: from that point going towards the center of said window the penetration depth will be substantially constant. Indeed, in a very first portion of the window the optical fibers are not accessible because the penetration depth is lower than the sheath thickness. As it is clear for a skilled in the art, the cable sheath 91 is peeled by closing the arms of the tool. Figure 6 shows an aperture angle which is lower than the aperture angle of the tool 1 shown in Figure 5.

Finally, Figure 7 shows the tool of Figure 3 at a final stage of the sheath stripping. The aperture angle has now become null and the two heads 3A and 3B are nested together. In this final position, the cutting edges of the heads

92 touch and the window in the sheath is completed. Through the inner portion of the sheath window 92 access to the optical fibers is provided.

Through the arrangement according to the present invention, a precise open window is created in the sheath of the optical cable. Profitably, according to the present invention, the stripping is performed in a very precise manner without the risk to damage the optical fibers during the stripping operation and without using highly skilled technicians. The tool is robust and relatively compact. In particular, only a relatively reduced space is required at the cable side opposite to the stripping side.