Device for pulling in cables

Abstract

The invention relates to a device for pulling in cables or the like, having a flexible pull-in spring (1) and a coupling element located at a front end of the pull-in spring (1), wherein the pull-in spring (1) comprises a flexible rod (7), to the front end of which an adhesive sleeve (9) is fastened. High strength is achieved in that the adhesive sleeve (9) comprises a tensile-force transmission element (9a), on which a union sleeve (11) for transmitting tensile forces is supported.

Description

[0001] Device for pulling in cables

[0002] The present invention relates to a device for pulling in cables or the like, comprising a flexible, elastic retraction spring and a coupling element arranged at a front end of the retraction spring, wherein the retraction spring comprises a flexible, elastic rod, to the front end of which an adhesive sleeve is fastened.

[0003] For pulling cables into empty conduits, flexible retraction springs are typically used. To facilitate the insertion of such a retraction spring into the empty conduit, retraction spring tips are increasingly being used. These are arranged via a coupling element at the front end of the actual retraction spring and are particularly flexible in order to optimally follow the curves of the empty conduit. Such a device, consisting of a retraction spring and a retraction spring tip, is known from EP 3 114 739 A.

[0004] Although existing devices already significantly facilitate the insertion of a retractor spring into the empty pipework, the problem still exists that the transition from the retractor spring to the retractor spring tip represents a weak point where the device can break relatively easily. However, simply reinforcing it is not effective, as this would lead to stiffening in the transition area, which would significantly complicate its use in empty pipework with sharp bends. A similar problem arises when other accessories are attached to the coupling element.

[0005] In general, as with all retractable springs, a particular challenge is to enable the advancement to be as simple and smooth as possible, even under difficult conditions.

[0006] DE 20 2016 100 068 U1 describes a coupling that connects a flexible retracting spring to a guide element. A sleeve connected to a rod has a section with an external thread at its end, onto which the guide element can be screwed. While this allows for good tensile force transmission, it creates a rigid area in the area of ​​the screw connection, making it difficult to insert the retracting spring.

[0007] The object of the present invention is to further develop known devices in such a way that, despite sufficient flexibility, high strength is achieved and the insertion of the retraction spring into empty piping is as smooth as possible. According to the invention, the adhesive sleeve comprises a tensile force transmission element on which a cap sleeve is supported for transmitting tensile forces.

[0008] In contrast to known devices, a coupling element, such as a thread, for attaching a retractable spring tip is not attached directly to the adhesive sleeve, but is arranged on a separate component, namely the cap sleeve.

[0009] The solution according to the invention makes it possible to minimize the rigid area at the transition point between the retraction spring and an accessory part attached thereto, such as the flexible retraction spring tip, which is essentially formed by the cap sleeve, and at the same time to increase the tensile strength and kink resistance.

[0010] A particularly maintenance-friendly solution is also achieved because the accessory is easily replaceable and, in the unlikely event of breakage, the retraction spring can be shortened, fitted with a new adhesive sleeve and reassembled.

[0011] However, a particular advantage of the solution according to the invention is that the cap sleeve can be rotated relative to the adhesive sleeve and thus relative to the rod, so that a retractable spring tip or another accessory element can rotate automatically when inserted, which considerably facilitates the process.

[0012] Simplified handling is achieved by the coupling element being designed as a thread, preferably as an internal thread.

[0013] The coupling sleeve preferably has a tubular end section that forms a receiving space, with the front end of the rod, together with a portion of the adhesive sleeve, projecting into the receiving space. This allows the rigid section of the rod caused by the adhesive sleeve to be at least partially accommodated within the equally rigid coupling sleeve, so that the flexibility of the entire assembly is only minimally impaired. In addition, the loose connection of the coupling sleeve to the tensile force transmission element allows the rod to pivot in a joint-like manner relative to the coupling sleeve.

[0014] A particularly preferred embodiment provides a plastic sleeve that is firmly connected to the coupling sleeve at its front end. Preferably, the coupling sleeve also projects beyond the adhesive sleeve in the axial direction in at least one direction, and preferably in both directions. As a result, the area of ​​the rod that is particularly vulnerable to breakage, namely the transition from the adhesive sleeve to the sheath layer, is secured by the coupling sleeve. On the opposite side, the end of the retraction spring tip is allowed to protrude into the coupling sleeve, allowing the rigid section, which is essentially formed by the main part of the coupling sleeve (excluding the connecting section) and the end sleeve, to be kept as short as possible.

[0015] It is also advantageous if the coupling sleeve has a structured connecting section embedded in the plastic sleeve. This makes it possible to continuously increase the flexural rigidity of the retracting spring toward its end, thus minimizing the risk of breakage. Particularly preferably, the connecting section is tubular, has perforations, and is overmolded with the plastic sleeve.

[0016] The rod can preferably be protected by a sheathing layer, which usually extends over the entire length of the rod. An important function of the sheathing layer is to facilitate sliding in the empty conduit by providing a smooth, sliding surface. It is advantageous if such a sheathing layer is provided between the rod and the plastic sheath. Good sliding properties are also important here, as the plastic sheath must be easily twistable relative to the rod. The production of the retraction spring is particularly simplified if the sheathing layer is directly connected to the adhesive sleeve and preferably has the same outer diameter.

[0017] It has proven effective to design the tensile force transmission element of the adhesive sleeve as a radially circumferential projection, and for the coupling sleeve to have a shoulder that rests on the projection. This allows for optimal transfer of the tensile forces from the retraction spring tip to the retraction spring rod.

[0018] The retractable spring tip can be optimized by having a central wire element that is sheathed on the outside.

[0019] The device according to the invention is easy to disassemble because the retractable spring tip can be screwed onto the cap sleeve. This also increases flexibility, as alternative retractable spring tips or other components can be attached.

[0020] The retractable spring tip can be made particularly robust by providing a compression sleeve at one end of the central wire element, which is pressed onto the central wire element. A flange-like projection is preferably provided on the compression sleeve, on which the end sleeve is particularly preferably supported. A particularly advantageous design solution provides for the compression sleeve to be supported on a shoulder of the end sleeve, which is preferably arranged at the end of the end sleeve facing the retractable spring. This allows the jacket of the retractable spring tip to be designed such that it projects into the area between the compression sleeve and the end sleeve, which increases overall robustness. At the same time, this protects the end of the jacket, thereby increasing the service life of the retractable spring tip.

[0021] It has been found that a slight twistability of the retraction spring tip has a particularly beneficial effect on the smooth movement of the device when inserting it into an empty conduit, especially when the conduit has tight radii. This smooth movement is particularly preferably achieved by allowing the end sleeve to be twisted relative to the central wire element.

[0022] A further shortening of the rigid area in the transition from the retraction spring to the retraction spring tip can be achieved by the end sleeve of the retraction spring tip projecting axially into the union sleeve in the assembled state.

[0023] In order to increase the flexibility of the retraction spring, it can be provided in particular that the central recess of the end sleeve of the retraction spring tip, in the assembled state, receives the end section of the rod together with a part of the adhesive sleeve with radial play.

[0024] A particularly advantageous embodiment of the present invention provides for the plastic sleeve to be rotatable and displaceable relative to the rod. As explained above, the ability to easily rotate the retractable spring tip is particularly advantageous when inserting the device into an empty conduit.

[0025] An optimal design combines this measure with the end sleeve of the retractable spring tip, which is designed to be rotatable relative to the central wire element, thus creating two independent pivot joints. This has proven particularly advantageous because, in the case of a sharp bend in the area of ​​a pivot joint, rotation can be hindered by tension in the components. The double pivot joint described above ensures that the retractable spring tip can practically always be rotated relatively smoothly.

[0026] The invention will now be explained in more detail by means of the embodiment shown in the figures. They show:

[0027] Fig. 1 shows an end section of a device according to the invention with a retractable spring and a retractable spring tip in a longitudinal section; Fig. 2 shows a detail of the connection point between the retractable spring and the flexible retractable spring tip;

[0028] Fig. 3 shows a detail of the end section of the retraction spring of a slightly modified embodiment;

[0029] Fig. 4 shows the cap sleeve of Fig. 3 in an oblique view; and

[0030] Fig. 5 and Fig. 6 show further embodiments of the invention, each in longitudinal section.

[0031] The device shown in Fig. 1 consists of a retraction spring 1, of which only the distal section is shown. At its end, a flexible retraction spring tip 2 is removably attached via a screw connection 3. The retraction spring tip 2 has a central wire element 4, which serves to transmit tensile forces. At the distal end of the retraction spring tip 2, an eyelet 5 is provided, to which a cable (not shown) can be attached, which is to be pulled into an empty conduit. The central wire element 4 is covered with a sheath 6, which tapers conically towards the front and, due to its relatively low flexural rigidity, regulates the flexibility of the flexible retraction spring tip 2.

[0032] The retraction spring 1 consists of a flexible rod 7 made of fiber-reinforced plastic, for example fiberglass, on which a conical plastic sleeve 8 is provided in its end section.

[0033] Fig. 2 shows in detail the connection area between the retraction spring 1 and the retraction spring tip 2 of a first embodiment. At its distal end, an adhesive sleeve 9 is firmly glued to the flexible rod 7. The adhesive sleeve 9 is essentially cylindrical and has an annular, circumferential tensile force transmission element 9a. Proximally, the adhesive sleeve 9 is adjoined by a sheath layer 10, which preferably has the same thickness as the adhesive sleeve 9. Axially adjoining the plastic sleeve 8 is a cap sleeve 11 made of stainless steel, which has a structured connecting section 19 that creates a resilient connection with the plastic sleeve 8. At its front end, opposite the connecting section 19, the cap sleeve 11 has a thread 12 that serves to fasten the retraction spring tip 2.

[0034] The retraction spring tip 2 is also designed to transmit tensile forces to enable cables to be pulled through the empty piping. The forces are transmitted from the eyelet 5 (not visible in Fig. 2) to the central wire element 4, which has a compression sleeve 13 at its end. This compression sleeve is cylindrical and has a flange-like projection 13a at its proximal end. An end sleeve 14 sits on this compression sleeve 13. The end sleeve 14 is supported on the flange-like projection 13a to transmit tensile forces and is screwed into the thread 12 proximally thereto. Distal thereto is a cover section 14b whose outer diameter approximately corresponds to the outer diameter of the cap sleeve 11. The sheath 6 is firmly connected to the central wire element 4 and to the compression sleeve 13 and has an end section 6a that projects into the space between the compression sleeve and the end sleeve 14.The end sleeve 14 is rotatable relative to the assembly consisting of the eyelet 5, the casing 6, the central wire element 4, and the compression sleeve 13. The rotation is possible because the end sleeve 14 can slide along the inner cylindrical surface 17 on the casing 6.

[0035] In addition to the above-described rotation of the retractable spring tip 2 around the cylindrical surface 17, it is also possible to rotate the cap sleeve 11, including the plastic sheath 8 firmly connected to it, relative to the rod 7, including the adhesive sleeve 9 and the sheath layer 10 attached thereto. This rotation occurs along the outer surfaces 18 of the adhesive sleeve 9 and the sheath layer 10.

[0036] The embodiment shown in Fig. 3 differs from the device shown above in that the thread 12 of the coupling sleeve 11 directly adjoins the area that receives the tensile force transmission element 9a of the adhesive sleeve 9. The thread 12 is also slightly shortened in the axial direction, so that the end face 7a of the rod 7 projects beyond the end face 20a of the threaded portion 20 of the coupling sleeve 11. In this way, particularly high flexibility can be achieved.

[0037] Fig. 3 shows the distal end of the retraction spring 1 without the retraction spring tip 2. It can be seen that the union sleeve 11 is firmly connected to the plastic sleeve 8 via a structured connecting section 19. The connection is created by several openings 11a in the essentially cylindrical connecting section 19, which on the one hand enable a positive interlocking with the plastic of the plastic sleeve 8 and on the other hand reduce the flexural rigidity of the entire assembly so that a limited curvature of the retraction spring 1 is already possible immediately proximal to the circumferential tensile force transmission element 9a. If necessary, axially running incisions can reduce the flexural rigidity of the assembly even further. At the distal end of the union sleeve 11, a threaded section 20 is provided, into which the end sleeve 14 of the retraction spring tip 2 can be screwed.Furthermore, a receiving space 16 is formed inside the threaded portion 20, which is intended to partially receive the end sleeve 14.

[0038] As already shown in Fig. 2, the compression sleeve 13 also partially projects into the receiving space 16 in the assembled state, with the flange-like projection 13a lying inside the threaded portion 20. However, the end sleeve 14 and the compression sleeve 13 do not completely fill the receiving space 16. A free space remains between the adhesive sleeve 9 and an extension 14a of the end sleeve 14, so that a limited pivoting of the rod 7 together with the adhesive sleeve 9 relative to the cap sleeve 11 is possible at this point as well. The extension 14a of the end sleeve 14 partially accommodates the adhesive sleeve 9 with play in a central recess 22.

[0039] Fig. 3 also shows in detail how the coupling sleeve 11 is supported on the tensile force transmission element 9a of the adhesive sleeve 9 via the shoulder 21. The above-described limited pivoting of the rod 7 together with the adhesive sleeve 9 relative to the coupling sleeve 11 can also be achieved in particular by the tensile force transmission element 9a partially lifting off the shoulder 21.

[0040] Fig. 4 shows a cap sleeve 11, wherein in particular the structured connecting section 19 is visible.

[0041] In the following, the manufacture of the described components of the device according to the invention is briefly explained.

[0042] First, the retraction spring 1 is prepared by exposing the end of the flexible rod 7 covered by the sheath layer 10. Then, from the distal end, an assembly consisting of the cap sleeve 11 and the plastic sheath 8 is pushed on. This assembly was previously produced by overmolding the plastic sheath 8 inserted into the shape of the cap sleeve 11, so that these components are permanently connected to one another via the structured connecting section 19. The adhesive sleeve 9 is then firmly glued in place of the removed sheath layer 10 to create a connection that transmits the tensile force. Thus, the cap sleeve 11 is held captive in the distal direction by the adhesive sleeve 9, since the cap sleeve 11 is secured at its shoulder 21 by the tensile force transmission element 9a of the adhesive sleeve 9.

[0043] The retractable spring tip 2 is manufactured by pressing a press sleeve 13 onto the wire element 4 opposite the eyelet 5 so that the flange-like projection 13a is flush with the end face of the wire element 4.

[0044] The end sleeve 14 is then pushed on, and the entire assembly is inserted into a mold and overmolded with plastic to form the jacket 6. Since the inner cylindrical surface 17 of the end sleeve 14 is smooth, the jacket 6 does not bond to the stainless steel of the end sleeve 14. In contrast, the outer surface of the compression sleeve 13 is structured during pressing, for example, to obtain a polygonal prismatic or generally rough shape, so that a positive connection to the jacket 6 is achieved. Thus, the end sleeve 14 is ultimately rotatable but axially immovable connected to the other components of the retraction spring tip 2.

[0045] In the embodiment shown in Fig. 5, the cap sleeve 11 is slightly extended in the axial direction, although no plastic cover is provided here. The design of the adhesive sleeve 9, including the tensile force transmission element 9a, corresponds to the embodiments shown above. The thread 12 is also designed as an internal thread, as before.

[0046] The embodiment variant of Fig. 6 differs in that the tensile force transmission element 9a is arranged at the distal end of the adhesive sleeve 9. The threaded portion 20 of the cap sleeve 11 has a reduced outer diameter and carries a thread 12 in the form of an external thread, onto which a correspondingly adapted end sleeve 14 can be screwed, which then carries a corresponding internal thread.

[0047] The twistability and limited pivotability of the union sleeve 11 are also present in the last-described variants, which ensures excellent applicability.

Claims

PATENT CLAIMS Device for pulling in cables or the like, with a flexurally elastic retraction spring (1) and a coupling element arranged at a front end of the retraction spring (1), wherein the retraction spring (1) has a flexurally elastic rod (7), to the front end of which an adhesive sleeve (9) is fastened, characterized in that the adhesive sleeve (9) has a tensile force transmission element (9a) on which a union sleeve (11) is supported for transmitting tensile forces. Device according to claim 1, characterized in that the coupling element is designed as a thread (12), preferably as an internal thread. Device according to one of claims 1 or 2, characterized in that the union sleeve (11) is rotatable and displaceable relative to the rod (7).Device according to one of claims 1 to 3, characterized in that the cap sleeve (11) has a tubular end section (20) which forms a receiving space (16), and in that the front end of the rod (7) together with a part of the adhesive sleeve (9) projects into the receiving space (16). Device according to claim 4, characterized in that the cap sleeve (11) projects beyond the adhesive sleeve (9) in the axial direction in at least one direction and preferably in both directions. Device according to one of claims 1 to 5, characterized in that a plastic sleeve (8) is provided, to which the front end is firmly connected to the cap sleeve (11). Device according to claim 6, characterized in that the cap sleeve (11) has a structured connecting section (19) which is embedded in the plastic sleeve (8).Device according to claim 7, characterized in that the connecting section (19) is tubular and has openings (11a). Device according to one of claims 7 or 8, characterized in that the connecting section (19) is overmolded by the plastic sleeve (8). Device according to one of claims 7 to 9, characterized in that a sheath layer (10) is provided between the rod (7) and the plastic sleeve (8). Device according to claim 10, characterized in that the sheath layer (10) directly adjoins the adhesive sleeve (9) and preferably has the same outer diameter. Device according to one of claims 1 to 11, characterized in that the tensile force transmission element (9a) of the adhesive sleeve (9) is designed as a radially circumferential projection, and in that the coupling sleeve (11) has a shoulder (21) that is supported on the projection. Device according to one of claims 1 to 12, characterized in that the end face (7a) of the rod (7) projects beyond the end face (20a) of the threaded portion (20) of the coupling sleeve (11). Device according to one of claims 1 to 13, characterized in that a flexible retraction spring tip (2) is detachably attached to the tubular end portion (20).Device according to claim 14, characterized in that the flexible retractable spring tip (2) has an end sleeve (14) that can be detachably connected to the cap sleeve (11). Device according to claim 15, characterized in that the end sleeve (14) has an extension (14a) that, in the assembled state, is connected externally to the cap sleeve (11) and that has a central recess (22) for receiving an end section of the rod (7) together with the adhesive sleeve (9). Device according to one of claims 14 to 16, characterized in that the retractable spring tip (2) has a central wire element (4) that is sheathed on the outside. Device according to claim 17, characterized in that a press sleeve (13) is provided at one end of the central wire element (4), which press sleeve is pressed onto the central wire element (4).Device according to claim 18, characterized in that a flange-like projection (13a) is provided on the press sleeve (13), on which the end sleeve (14) is preferably supported.

20. Device according to one of claims 18 or 19, characterized in that the compression sleeve (13) is supported on a shoulder of the end sleeve (14), which is preferably arranged at the end of the end sleeve (14) facing the retraction spring (1).

21. Device according to one of claims 18 to 20, characterized in that a sheath (6) surrounding the central wire element (4) is provided, which has an end portion (6a) arranged between the compression sleeve (13) and the end sleeve (14).

22. Device according to one of claims 17 to 21, characterized in that the end sleeve (14) is rotatable relative to the central wire element (4).

23. Device according to one of claims 14 to 22, characterized in that the end sleeve (14) in the assembled state projects in the axial direction into the cap sleeve (11).

24. Device according to one of claims 16 to 23, characterized in that the central recess (22) of the end sleeve (14) in the assembled state receives the end section of the rod (7) together with the adhesive sleeve (9) with radial play.

25. Device according to one of claims 14 to 24, characterized in that the retraction spring (1) is rotatable relative to the retraction spring tip (2) at least two points. 2023 09 06 Ba

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