SPECIAL END PIECE FOR A NEEDLE INTENDED TO BE PUSHED INTO A SHEATH OCCUPIED BY CABLES

Abstract

An end piece is provided for guiding a needle intended to be inserted in a sheath occupied by at least one installed cable. The end piece includes: a free first end referred to as a head of a shape suited to slipping in between an internal wall of the sheath and the at least one installed cable; a second end fixed to the needle; and a part connecting the two ends and referred to as a shank. The shank has a flexibility that increases toward the head.

Claims

1-15. (canceled)

16. An end piece for guiding a needle intended to be inserted in a sheath occupied by at least one installed cable, the end piece comprising: a free first end referred to as a head, of a shape suited to slipping in between an internal wall of the sheath and the at least one installed cable, a second end fixed to the needle, and a shank connecting the two ends, the shank having a flexibility that increases toward the head.

17. The end piece as claimed in claim 16, in which the head comprises a partially cylindrical convex upper face and a partially cylindrical concave lower face.

18. The end piece as claimed in claim 17, in which the convex upper face has a radius of curvature that is less than an interior radius of the sheath.

19. The end piece as claimed in claim 17, in which the concave lower face has a the radius of curvature that is greater than a radius of a section of a bundle formed by the at least one installed cable.

20. The end piece as claimed in claim 17, in which the upper face comprises, at the free end of the head, a rounded edge.

21. The end piece as claimed in claim 17, in which the free end of the head has a B-shaped profile.

22. The end piece as claimed in claim 17, in which a maximum thickness between the upper face and the lower face is greater than or equal to a maximum of the thickness of the shank and of a thickness of the needle.

23. The end piece as claimed in claim 16, in which the head has a length along an axis of the shank that is less than three times an inside diameter of the sheath.

24. The end piece as claimed in claim 16, in which the head is pierced with a hole.

25. The end piece as claimed in claim 16, in which the shank is of oblong cross section.

26. The end piece as claimed in claim 16, in which the flexibility of the shank, at the second end, is substantially equal to that of the needle.

27. The end piece as claimed in claim 16, in which the second end is fixed to the needle removably.

28. A method of inserting a needle in a sheath occupied by at least one previously installed cable, comprising the following acts: inserting a determined length of the needle into the sheath via an inlet of the sheath, wherein an end piece is fixed to the needle, the end piece comprising: a free first end referred to as a head, of a shape suited to slipping in between an internal wall of the sheath and the at least one installed cable, a second end fixed to the needle, and a shank connecting the two ends, the shank having a flexibility that increases toward the head, wherein act of inserting is preceded by an act of positioning the end piece at the inlet of the sheath, in an empty space situated between an internal wall of the sheath and the at least one installed cable, the positioning being adapted to respective shapes of the free space and of the end piece.

Description

4. INTRODUCTION TO THE FIGURES

[0054] Further advantages and features of the invention will become more clearly apparent from reading the following description of one particular embodiment of the invention, given by way of simple illustrative and nonlimiting example, and from studying the attached drawings, among which:

[0055] FIG. 1 shows an overall view of one example of an end piece according to the invention, in a situation of use with a needle, a sheath and a cable,

[0056] FIG. 2 shows an example of an end piece according to one aspect of the invention,

[0057] FIG. 3 is a view in cross section on A-A of FIG. 1,

[0058] FIG. 4 shows a detailed view of the inside of a corrugated sheath with an example of an end piece head according to one aspect of the invention,

[0059] FIG. 5 shows an example of the path of a sheath comprising several turns in different planes.

5. DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

[0060] In the remainder of the description examples are given of various embodiments of the invention based on a corrugated sheath that is small in size and on an already-installed cable of the coaxial type of large size, but the invention also applies to other types of sheath and to several cables already installed in the same sheath.

[0061] When a single installed cable is mentioned, it must also be understood that this extends to several installed cables, and when an installed-cable size or diameter is mentioned, this means the size or diameter of the circle in which the cables bunched together can be inscribed.

[0062] FIG. 1 shows an overall view of one example of an end piece according to the invention, in a situation of use with a needle, a sheath and a cable.

[0063] The cable 9 is installed definitively in the sheath 7, prior to the insertion of the needle 10. Fixed to the end of the needle 10 is an end piece 1. The needle 10 is pushed into the sheath 7 from outside the sheath 7. As it is being inserted, the needle 10 is preceded and guided by the end piece 1, which slips into the space left free inside the sheath 7 by the cable 9. A view of this space left free is given in FIG. 3, from a different viewpoint. The end piece 1 and its three parts 2, 3 and 4 is shown in greater detail in FIG. 2.

[0064] FIG. 2 shows one example of an end piece according to one aspect of the invention.

[0065] The end piece 1 comprises a head 2, an end 3 fixed to the needle 10, and a shank 4. The head has an upper face 5 and a lower face 6. The upper face 5, opposite to the lower face 6, is not visible in FIG. 2 but is visible in FIGS. 3 and 4, with reference to which the head 2 is described in greater detail.

[0066] The shank 4 is flexible and has a preferred plane of curvature which is the same as that of the needle 10. Specifically, the cross section of a needle is often rectangular which imposes greater flexibility on it in one plane than the others in which the flexibility may even be zero, and prevents the needle from twisting on itself as it is inserted into a sheath. Advantageously, the cross section of the shank 4 is flat, or, more precisely, not radially symmetrical, so as to give it a preferred plane of curvature which is substantially the same as that of the needle. Various shapes of flat cross section are suitable, for example rectangular, oval or more generally oblong. The end 3 of the end piece 1 is fixed to the needle 10 securely, which means to say without the freedom of the end piece to rotate with respect to the needle. The end piece 1 may potentially be removable in relation to the needle, if the end 3 of the end piece 1 and the end of the needle 10 are each equipped with a suitable fixing mechanism.

[0067] The flexibility of the shank 4 increases from the end 3 of the end piece 1, toward the head 2. The flexibility of the shank 4 is both in curvature in the preferred plane of curvature, and in torsion along the axis of its length. At the end 3, the flexibility is preferably identical to that of the needle. The flexibility is greater at the end 2 than at the end 3, something which allows the end piece 1 to enter changes in direction more easily as it advances along the sheath.

[0068] FIG. 3 is a view in cross section on A-A of FIG. 1.

[0069] The cable 9 previously installed in the sheath 7 is of a diameter less than the interior diameter of the sheath. In this cross-sectional view, it may be seen that when the cable touches the interior wall of the sheath, a free space is created, in the shape of a lunar crescent. The head 2 of the end piece occupies part of this free space by adopting a similar shape. When the head 2 is made from a material with a low friction coefficient, the dimensions of the head 2 may come close to, without equaling or exceeding, those of the free space, without the head becoming jammed in its progress through the occupied sheath. Preferably, the rest of the end piece and the needle therefore must not exceed the dimensions of the head.

[0070] A tile- or gutter-shaped profile is therefore suitable for the head, which therefore has an upper face and a lower face which are partially cylindrical. Preferably, the convex upper face 5 of this “tile” does not have exactly the same profile as its lower face 6.

[0071] Specifically, the radius of curvature of the upper face 5 is preferably less than that of a circle delimiting the interior wall of the sheath, so as to limit the points of contact between the head and the sheath, and therefore limit the friction as the head slides along inside the sheath.

[0072] The radius of curvature of the lower face 6 is itself preferably greater than that of a circle delimiting the perimeter of the cable, again so as to limit points of contact between the head and the cable, and therefore limit the friction as the head slides along the cable.

[0073] It will be appreciated that the crescent-shaped profile best suited to the head 2 may vary between a very slender crescent and a half-moon, depending on the number of cables installed in the sheath and depending on whether or not they are the same diameter.

[0074] FIG. 4 shows a detailed view of the inside of a corrugated sheath with one example of an end piece head according to one aspect of the invention.

[0075] Most of the sheaths used for cabling, whether this is for electricity, television, telephone or the Internet, are what are referred to as “corrugated” sheaths. These sheaths have rings on the outside as on the inside, the succession of which rings gives the sheath a tube shape. In the segments of the path followed by the sheath 7 which are not straight lines, the rings 12 on the inside of the sheath 7 are liable to place themselves directly in the path of the head 2 when the end piece 1 is progressing along the sheath 7. In order for the head 2 to be able to slide from one ring 12 to another unimpeded in the turns taken by the sheath 7, the free tip 11 of the head 2 is rounded on its upper face 5. The rounding of the free tip 11 can be inscribed inside an imaginary circle, depicted in dotted line in FIG. 4, the diameter of which is preferably greater than the spacing between two rings 12.

[0076] It will be appreciated that there is no need for the lower face 6 of the head 2 to have such a rounding because this face never comes into contact with the interior wall of the sheath but slips over the installed cable or cables, which are smooth.

[0077] If the thickness between the upper face 5 and the lower face 6 of the head 2 is insufficient to obtain a rounding that can be inscribed in a sufficiently large circle, one variation of the end piece according to the invention makes it possible to avoid the upper face from jamming against a ring. In this alternative form, in which the head adopts the shape of a very slender tile, the rounding needed is obtained by cutting the free tip of the head into the shape of an upper-case letter B. When the B is curved from the bottom upwards, the top of the tile thus obtained lies between the two curves of the B, and the lateral profile of the tile is rounded on the top.

[0078] FIG. 5 gives an example of the path of a sheath comprising several turns in different planes.

[0079] The path in this example starts off horizontal forward, then has a first bend C1 to the right in the plane {x, z}, followed by a second bend C2 upwards in the plane {x, y} perpendicular to the plane {x, z}. When the needle 10 is pushed in a sheath (not illustrated) following such a path, the succession of turns C1 and C2 therefore introduces torsion into the needle 10. Because the needle 10 has a certain torsional flexibility being elastic, its end is therefore pushed laterally toward the cable or cables (not illustrated) which need to be moved aside in order for the needle 10 to be able to continue to progress along the sheath.

[0080] The special quarter-moon shape of the head of the end piece 1 allows it to insinuate itself between the internal wall of the sheath and the cable or cables, even when the end piece 1 is attracted laterally by the elastic torsion return force of the needle 10. Thus, the needle 10 does not remain under torsion and its torsion is not accentuated to breaking point if sequences of turns in different planes are strung together.

[0081] The invention also relates to a method of inserting a needle into a sheath occupied by at least one already installed cable. This method uses a needle to the end of which is fixed an end piece as just described, and comprises: [0082] a step of positioning the end piece at the entrance to the sheath, in a free space situated between the internal wall of the sheath and the at least one installed cable, the positioning being such that the convex upper face 5 of the head 2 of the end piece 1 is in contact with the internal wall of the sheath, [0083] a step of inserting an end of the needle into an entrance of the sheath, at least until the end piece is fully inside the sheath, [0084] a step of pushing, from outside the entrance to the sheath, a sufficient length of needle in the sheath, so that the head of the end piece reaches a determined point in the path of the sheath, which may be the exit from the sheath.

[0085] Once the determined point on the sheath has been achieved, generally the exit at the opposite end to the inlet, there are several known options that present themselves. If the needle is a cable which was intended to be installed and to remain in the sheath, the end piece is detached and kept for future use with another needle.

[0086] If not, the new cable to be installed is fixed to the needle emerging from the sheath at the determined point. This can be done in a number of alternative ways: [0087] either the end piece is removed from the needle and the new cable is fixed to the needle using a known means, such as a sleeve for example, [0088] or the new cable is attached to the head of the end piece fixed to the needle, using a known means employing the hole 12 in the end piece, for example a string, [0089] or a second end piece is fixed to the cable and the two end pieces are attached to one another via their respective hole 12, using a known means.

[0090] Thereafter, the needle is pulled from the entrance of the sheath, with the consequence that the new cable is pulled through into the sheath.

[0091] It will be appreciated that if a second end piece is fixed to the cable and everything pulled into the sheath using the needle, the insertion method described hereinabove may also be used. In this case, the cable in the phase intended to be inserted acts as a needle, and the pushing step is replaced by a pulling step.

[0092] By virtue of the end piece according to the invention, the method of inserting a needle according to the invention allows a new cable to be inserted into a sheath already occupied by at least one already installed cable without the needle becoming jammed during the insertion phase.

[0093] An additional advantage of the end piece according to the invention is that it is also suitable for inserting a needle into a free cable sheath, by virtue amongst other things of the shape of its head which has no roughness on its free tip.