Method and device for pulling optical fiber into a metallic sheath.

Abstract

A method for drawing a first element (30) into a sleeve (10), comprising the following steps: attaching a guide (2) made of a first magnetic material to a first end (31) of the first element (30); engaging the guide (2) inside the sleeve (10); using a guide (20) made of a second magnetic material to induce a magnetic interaction between the guide (2) and the guide (20) in order to cause the guide (2) to move inside the sleeve (10). The invention also relates to a device for drawing the first element (30) into a sleeve (10) comprising a guide (2) made of a first magnetic material provided with means for attaching it to the first element (30) and a guide (20) made of a second magnetic material. Figure for the abstract: 3

Description

Title of the invention: Method and device for pulling optical fiber in a metallic sheath. technical field

[0001] The present invention relates to the field of optical fiber communications and more particularly to the production of harnesses comprising small diameter sheaths intended to accommodate a single optical fiber. PREVIOUS STATE OF THE ART

[0002] Installing optical fiber in a conduit is a common operation in telecommunications networks. The conduit's function is to mechanically protect the optical fiber it contains. However, the method of installing the optical fiber in the conduit must guarantee the integrity of the optical fiber at the end of the operation.

[0003] The main methods used to pass the optical fiber through a conduit are pulling and blowing.

[0004] Fiber pulling consists of manually pulling the optical fiber through a conduit using a pull cable. It is suitable for short distances and conduits with slight curves. However, it is laborious and presents a risk of damaging the fiber, particularly when the pulling forces are not properly controlled. In some installations, a cable guide (also called a "pulling rod" or "wire puller") is first inserted into the conduit. This guide is then used to pull the optical fiber through the conduit. The rod can be made of steel, semi-rigid plastic, or fiberglass and is used to pull or push cables through conduits or ducts. It is often used to guide the optical fiber through more complex routes.

[0005] Alternatively, blowing (or jetting) is a more modern and efficient technique for installing optical fibers in a conduit. This method involves injecting the fiber into the conduit using an air compressor. The airflow helps propel the fiber while reducing the mechanical forces applied to it. Blowing is generally used for longer distances and when conduits are already in place with complex shapes. The pressurized airflow allows the fiber to move smoothly inside the conduit. The use of compressors is optimized by blowing machines that regulate the compressed air and ensure installation without risk of damaging the fiber. It is also possible to implement the same technique by applying a vacuum to the conduit.

[0006] It has the advantage of reducing the risk of fiber breakage by allowing fiber to be pulled over greater distances. This method is costly and requires the use of specific equipment (blowing machine, compressor).

[0007] In cases where friction may be excessive (particularly in complex passages), specific cable lubricants can be used to reduce pulling forces and prevent breakage. These lubricants are designed to be non-conductive and not affect the materials of the fibers or sheaths.

[0008] In the Telecom field, optical fiber is generally protected by different layers of plastics (ETFE). In critical applications such as aeronautics, space, medical or energy, this single fiber can be subjected to extremely severe environments (thermal, vibrational, ...) requiring protection by a metallic tube or sheath (generally stainless steel or another non-magnetic material) with an inner diameter ranging from half a millimeter to a few millimeters - typically an inner diameter between two and twenty times the diameter of the fiber - and over significant distances, of several tens of meters.

[0009] Existing techniques are unsuitable for small diameter ducts and optical fibers. Indeed, blowing technologies have proven ineffective for small diameters and long lengths due to pressure limitations imposed by the duct structure (mechanical strength, lack of sealing). Pulling technologies require pre-fitting the duct with a pull wire, which poses constraints identical to those encountered during fiber passage. SUBJECT OF THE INVENTION

[0010] An object of the present invention is to improve the reliability of a method and a device for pulling a small number of optical fibers - ideally only one - in sheaths, tubes and sleeves of small diameters and particularly sleeves made of a non-magnetic material. Description of the invention

[0011] To this end, a method for drawing a first element into a sleeve is provided, comprising the following steps: attaching a guide made of a first magnetic material to a first end of the first element; engaging the guide inside the sleeve; using a passer made of a second magnetic material to cause a magnetic interaction between the guide and the passer in order to cause a displacement of the guide relative to the sleeve.

[0012] According to other specific, non-exclusive and optional embodiments of the invention: • the step of attaching a magnetic material guide to one end of the first element includes the creation of a tubular guide, the introduction of a guide wire into an internal volume of the guide and the attachment of the guide to the guide wire; • the additional step consists of securing the guide strand with the first end of the first element; • the guide strand is an optical fiber; • the step of securing the magnetic material guide to one end of the first element includes a gluing operation; • the shunt is annular in shape with a central orifice whose diameter is significantly larger than the diameter of the sheath; • the step of using the feeder includes a step of engaging the feeder on the sheath, so that the sheath extends into the central orifice of the feeder; • The first element comprises a first optical fiber.

[0013] The invention also relates to a device for pulling a first optical fiber through a sheath, comprising: • a guide made of a first magnetic material provided with means for its attachment to the first element; • a conduit into a second magnetic material.

[0014] Advantageously, • the guide is attached to a guidance device comprising a first and a second guide, intended to cooperate with the sheath in order to guide the movement of the guidance device along the sheath; • a first drum intended to receive a plurality of windings of the first element and a second drum provided with an indexing device of a second rotation of the second drum with a first rotation of the first drum, the second drum receiving a traction element functionally connected to the changer; • a trolley mounted on bearings on a frame of the pulling device; • a chassis attached to the frame and on which a drum is mounted for rotation double compartment, the double compartment drum comprising a first section on which the plurality of windings are wound and a second section to which the traction element is connected, the traction device comprising at least one return element of the first element or of the traction element.

[0015] Other features and advantages of the invention will become apparent from the following description of a particular, non-limiting embodiment of the invention. Brief description of the drawings

[0016] Reference will be made to the attached figures, among which: • [Fig.1]: [Fig.1] is a schematic representation of part of the drawing device according to a first embodiment of the invention. • [Fig.2]: [Fig.2] is a schematic cross-sectional representation of the device in [Fig.1]. • [Fig.3]: [Fig.3] is a schematic representation of the entire device of [Fig.1] in application in a situation of use. • [Fig.4]: [Fig.4] is a schematic representation illustrating a first step of the process according to the invention. • [Fig.5]: [Fig.5] is a schematic representation illustrating a second step of the process according to the invention. • [Fig.6]: [Fig.6] is a schematic representation illustrating a third step of the process according to the invention. • [Fig.7]: [Fig.7] is a schematic perspective representation of the drawing device according to a second embodiment of the invention.

[0017] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0018] With reference to Figures 1 to 3, and according to a first embodiment, the pulling device 100 is designed to insert a first optical fiber 30 into a small-diameter sleeve 10, intended to protect it. This device is based on an innovative magnetic guidance mechanism that reduces the mechanical stresses exerted on the fiber and ensures smooth passage, essential for critical applications.

[0019] The optical fiber 30 is provided with a guide 2 at a first end 31—here, a spiral made of iron. This guide 2, made of a first magnetic material, is designed to allow magnetic interaction with a transmitter 20 located outside the sheath 10. The transmitter 20, also magnetic, is annular in shape and is made of a second, distinct material (here, a neodymium magnet) in order to create an attractive force between the guide 2 and the transmitter 20. This magnetic interaction is precisely adjusted to move the guide 2 and, consequently, draw the optical fiber 30 into the sheath 10 along its entire length, without exposing it to mechanical stresses that could damage or break it.

[0020] The guide 2 is tubular, having an internal volume 4, as illustrated in Figures 1 and 2, thus allowing one end 3 of a guide strand 1 to be received. The end 3 is inserted into the internal volume 4 of the tubular guide 2 and is secured to it, thereby providing mechanical support while ensuring the centering required for the fiber's progression. The attachment between the tubular guide 2 and the guide strand 1 can be achieved by an adhesive bond or other means. fixing allowing sufficient cohesion to resist the tensile forces generated by magnetic interaction.

[0021] In the device, the adapter 20, illustrated in detail in [Fig. 3], is configured to surround the sleeve 10, creating a targeted magnetic force that attracts or repels the waveguide 2. This configuration of the adapter 20, with its central orifice 21, allows the adapter 20 to be threaded around the sleeve 10, positioning the latter inside the central orifice 21. Thus, the adapter 20 can move along the sleeve 10 while maintaining a constant magnetic interaction with the waveguide 2 inside. This approach makes it possible to efficiently guide the optical fiber 30 through the sleeve 10 without direct friction and over long distances.

[0022] With reference to figures 4 to 7, the process according to the invention will be described.

[0023] According to a first step, the end 31 of the optical fiber 30 (or the associated guide strand 1) is inserted into the inner volume 4 of the guide 2. Once this insertion has been made, several fastening options can be used to ensure a robust and durable bond between the guide 2 and the optical fiber 30. For example, a suitable adhesive can be applied to create a homogeneous bond between the guide 2 and the fiber 31. Alternatively, a mechanical fastening, such as a light crimp or pressure adjustment, can be considered to hold the fiber in position within the guide 2 without causing deformation or excessive stress on the optical fiber.

[0024] This securing step ensures that the guide 2 remains firmly attached to the end of the optical fiber 30 throughout the pulling process. Thanks to this attachment, the guide 2 can interact effectively with the guide 20 without risk of detachment, ensuring the accuracy and safety of the optical fiber 30's movement within the conduit 10.

[0025] The next step of the process consists of engaging the guide 2 inside the sleeve 10, as illustrated in [Fig. 5]. This second step takes place once the guide 2 has been secured to the end 31 of the optical fiber 30, thus ensuring that the pulling device 100 is ready for insertion, and that the sleeve 10 has been engaged in the orifice 21 of the adapter 20.

[0026] For this operation, the guide 2 is positioned upstream of the opening of the sleeve 10, so that its alignment with the conduit is optimal. Thanks to its tubular shape and adapted diameter, the guide 2 can be smoothly inserted into the sleeve 10 without exerting excessive pressure or causing significant friction against the inner walls of the sleeve. This initial positioning is essential to minimize the risk of damage to the optical fiber 30 during its passage.

[0027] The configuration of this step ensures a precise, centered and secure initial insertion of the guide 2 and the optical fiber 30, laying the foundation for the pulling steps subsequent steps that will allow the fiber to be routed to the other end of the sheath 10.

[0028] The guide 20, made of a second magnetic material, is used to create a controlled magnetic interaction with the guide 2, already inserted inside the sleeve 10, in order to cause the progressive movement of the guide along the sleeve 10. [Fig. 6] illustrates this interaction where the ring-shaped guide 20 with a central orifice 21 maintains precise alignment between the guide 20 and the guide 2 inside the sleeve 10. The movement of the guide 20 relative to the sleeve 10 then causes a movement of the guide 2—and therefore of the fiber 30—inside the sleeve 10.

[0029] This arrangement allows the guide 20 to remain in constant interaction with the waveguide 2, generating a magnetic force of attraction or repulsion that pushes or pulls the waveguide 2 through the sleeve 10. This method of movement without direct contact with the optical fiber 30 considerably reduces the risk of damage, as no mechanical pressure is exerted directly on the fiber. The controlled movement of the waveguide 2, thanks to the magnetic interaction of the guide 20, allows for smooth and regular progression of the optical fiber 30 in the sleeve 10 over lengths of several tens of meters.

[0030] To ensure efficient transmission of magnetic forces, the slider 20 is adjusted to enclose the sleeve 10, ensuring stable positioning throughout the drawing process. This stability of the slider 20 around the sleeve prevents any deviation or variation in the magnetic force applied to the guide 2, thus optimizing the linear displacement of the guide 2 along the axis of the sleeve 10.

[0031] Thanks to this configuration, the device 100 allows the optical fiber 30 to be pulled while minimizing the risks of stress and damage, ensuring a reliable and delicate insertion process, ideal for applications requiring increased protection of the fiber 30.

[0032] Elements identical or analogous to those previously described shall bear a numerical reference identical to that in the following description of a second embodiment of the invention.

[0033] With reference to [Fig. 7], the pulling device 100 comprises a frame 71 integral with a frame 70 of the pulling device 100, which provides stable support for the entire system. A double-compartment drum 80 is mounted on this frame 71 and comprises two distinct sections.

[0034] The first section 81 forms a first drum 50 and the second section 82 a second drum 60. The first drum 50 is intended to receive a series of windings 32 of the optical fiber 30, allowing for organized storage of the fiber 30 and controlled unwinding. The second drum 60 receives an element of The traction element 61—here a metal cable—is attached to the first drum 50, so its second rotation is indexed with the first rotation of the drum 50. The device 100 thus coordinates the winding of the traction element 61 and the unwinding of the optical fiber 30. The traction element 61 is functionally connected to the guide 20 and is wound onto the second drum 60. Depending on the controlled rotation of the drum, this traction element 61 ensures a precise pulling force on the guide 20, and consequently on the guide 2 and the optical fiber 30, while maintaining stability of movement. This mechanism allows the guide 2 to advance along the duct 10 without tension variations, thus ensuring a smooth and safe passage for the optical fiber 30.Indexing the rotations of drums 50 and 60 allows a constant and measured tension to be maintained on the optical fiber 30 during pulling, which is essential to avoid any excessive stretching or slack that could damage the fiber 30 or cause a separation of the guide 2 and the fiber 30.

[0035] The pulling device 100 also includes a carriage 40 mounted on bearings on the frame 70 by means of four wheels 43. The carriage 40 includes a first front guide 41 and a second rear guide 42 mounted to slide on the sleeve 10 in order to guide the movement of the carriage 40 along the sleeve 10 and to ensure its position inside the guide 20. The pulling element 61 has a free end 62 provided with a ring 63 which cooperates with a hook 44 integral with the carriage 40 to connect the carriage 40—and incidentally the guide 20—to the pulling element 61.

[0036] The device 100 includes at least one guide element - here a pulley 75, positioned opposite the frame 71, at one terminal end of the sleeve 10, to guide and redirect the trajectory of the traction element 61. The pulley 75 ensures optimal alignment of the fiber throughout the process, ensuring that it remains in the axis of the sleeve 10 and minimizing any friction or undesirable pressure on the optical fiber.

[0037] During operation, the drum 80 is rotated. This rotation causes the first length of the pulling element 61 to be wound around the section 81. The first length of the pulling element 61 to be wound around the section 81 causes the carriage 40 to move a first distance equal to this first length. Similarly, at the same time as the first length of the pulling element 61 is wound, a second length, equal to the first length, of optical fiber 30 is unwound from the section 82 and carried by the feeder 20 into the conduit 10 during the movement of the carriage 40. This pulling device 100, with its coordinated drums 50 and 60, provides complete and precise control over the optical fiber 30 pulling process, thus ensuring a secure and damage-free installation of the optical fiber 30 in the conduit 10.

[0038] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention.

[0039] In particular, - although here the gluing operation is described to secure the guide with the guide strand, the invention also applies to other gluing configurations, such as for example a direct gluing of the guide onto the first optical fiber or a double gluing involving both the fixing of the guide onto the guide strand and that of the guide fiber onto the optical fiber. Although here the bonding operation is performed to hold the guide in position relative to the guide strand, the invention also applies to variants where the bonding can be limited solely to fixing the guide fiber to the first optical fiber, without direct bonding between the guide and the guide strand. This configuration allows the overall strength to be adjusted according to specific pulling constraints. - although here the gluing is described as a single operation ensuring the fixing of the guide to the guide strand, the invention also covers variants where the guide and the guide strand are joined by a first gluing, while a second gluing is carried out to fix the guide fiber directly to the first optical fiber. - although here the bonding step includes a gluing operation, the invention also applies to a bonding step including a fiber fusion operation (also known as "splicing"). Although the carriage is described here as being mounted on a rotating device, the invention also applies to configurations where the carriage is coupled to a non-rotating movement device, such as a linear slide system. In this variant, the linear movement of the carriage is indexed to the movement of the first drum, allowing precise positioning control without rotation. Although the invention here provides for the carriage to be connected to a rotating mechanism for fiber pulling, it also applies to variants where the carriage is connected to a non-rotating translation device, such as a rack and pinion system or a hydraulic cylinder. In this configuration, the movement of the carriage, and not a rotation, is synchronized with the rotation of the first drum, ensuring coordinated fiber progression. - although here the trolley is described as being driven by a rotary motion, the invention also covers variants in which the trolley is moved by a non-rotating moving device, such as a linear motor. In this variant, the linear movement of the carriage is indexed to the first drum, allowing direct control of the synchronization of the draw without rotary conversion; Although here the optical fiber guide is described as a magnetic iron spiral, the invention also applies to other guide shapes and materials. The guide could thus take the form of a helix, a spring, or even a flexible sheath with similar characteristics. Regarding materials, it is conceivable to use other magnetizable metals, suitable alloys, or composite materials exhibiting similar properties of flexibility and magnetism; Although the drawing device in this case comprises a wheeled carriage, the invention also applies to other types of guiding devices. For example, the device could include a set of guides attached to the feeder, bearing against an external surface of the sheath to ensure increased stability. It is also possible to use a cam device guided in a rail or structure parallel to the sheath, offering more precise control of the movement. Furthermore, the guidance could be achieved by slides, bearings, or low-friction surfaces, allowing for smooth and controlled movement of the device, depending on the requirements of the specific application. Although here the invention has been described in connection with the passage of a first optical fiber through a sheath, the invention also applies to other types of first element passed through a sheath such as, for example, a pull wire or a plurality of optical fibers.

Claims

Demands

1. Method of drawing a first element (30) into a sleeve (10) comprising the following steps: - Attaching a guide (2) made of a first magnetic material to a first end (31) of the first element (30); - Engaging the guide (2) inside the sleeve (10); - Using a passer (20) made of a second magnetic material to cause a magnetic interaction between the guide (2) and the passer (20) in order to cause a displacement of the guide (2) relative to the sleeve (10).

2. A method according to claim 1, wherein the step of attaching a guide (2) made of a first magnetic material to a first end (31) of the first element (30) comprises the following steps: - making the guide (2) in the form of a tubular guide made of a first magnetic material; - introducing one end (3) of a guide strand (1) into an internal volume (4) of the tubular guide (2); - attaching the tubular guide (2) to the guide strand (1).

3. Method according to claim 2, comprising an additional step of securing the guide strand (1) with the first end (31) of the first element (30).

4. A method according to any one of claims 2 or 3, wherein the guide strand (1) is an optical fiber.

5. A method according to any one of the preceding claims, wherein the step of securing the magnetic material guide (2) to a first end (31) of the first element (30) includes a gluing operation.

6. A method according to any one of the preceding claims, wherein the passer (20) is annular in shape comprising a central orifice (21).

7. A method according to claim 6, wherein the step of using the changer (20) to induce a magnetic interaction between the guide (2) and the changer (20) in order to cause a displacement of the guide (2) relative to the sleeve (10) comprises a step to engage the sling (20) on the sheath (10) so that the sheath (10) extends into the central orifice (21).

8. A method according to any one of the preceding claims, wherein the first element comprises a first optical fiber (30).

9. Device (100) for drawing a first element (30) into a sheath (10) comprising: - A guide (2) in a first magnetic material provided with means for its attachment to the first element (30) - A passer (20) in a second magnetic material.

10. Pulling device (100) according to claim 9, in which the passer (20) is integral with a guiding device (40) comprising a first guide (41) and a second guide (42) arranged to cooperate with the sleeve (10) in order to guide the movement of the guiding device (40) along the sleeve (10).

11. A pulling device (100) according to claim 9 or 10, comprising a first drum (50) intended to receive a plurality of windings (32) of the first element (30) and a second drum (60) provided with an indexing device of a second rotation of the second drum (60) with a first rotation of the first drum (50), the second drum (60) receiving a pulling element (61) functionally connected to the changer (20).

12. Pulling device (100) according to claim 11, wherein the guiding device (40) comprises a carriage mounted on bearings on a frame (70) of the pulling device (100).

13. Pulling device (100) according to claim 12, comprising a frame (71) integral with the frame (70) and on which is rotatably mounted a double compartment drum (80), the double compartment drum (80) comprising a first section (81) on which the plurality of windings (32) are wound and a second section (82) to which the traction element (61) is connected, the pulling device (100) comprising at least one return element (75) of the first element (30) or of the traction element (61).

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