Method and device for deicing a sheath of a structural cable

Abstract

A deicing device (30) for a sheath (20) of a structural cable (10) is disclosed. The deicing device (30) comprises: a support body (32) rotatable about a first axis; and at least one eccentric contact member (34) attached to the support body (32) and extending transversally to the first axis.

Description

METHOD AND DEVICE FOR DEICING A SHEATH OF A STRUCTURAL CABLE

[0001] The present invention relates to a deicing device for a sheath of a structural cable and to a method for deicing the sheath.BACKGROUND

[0002] Structural cables, for example stay cables, are widely used to support suspended structures such as bridge decks or roofs. They can also be used to stabilize erected structures such as towers or masts.

[0003] A typical stay cable includes a bundle of tendons, for example wires or strands, housed in a collective duct, or sheath. The sheath is intended to protect the metallic tendons of the bundle.

[0004] The sheath is in contact with the surrounding environment. As such, it is susceptible to the formation of frost, rime, ice or snow thereon.

[0005] Addressing this phenomenon is important, as the presence of frost, rime, ice or snow on the sheath may significantly alter the aerodynamic properties of the stay cable, which in turn may lead to vibrations of the cable. Ice chunks falling from the cables may also cause problems.

[0006] Several approaches have been developed to address this, such as an approach relying on a metallic collar configured to break ice and frost by being moved along the sheath. This is not fully satisfactory, as it tends to erode the sheath, and it may become unusable in certain circumstances. Another approach is known from WO 2019 / 064042 Al wherein the sheath comprises heating components. WO 2018 / 142174 A discloses a sheath with a cavity that may receive a vibration module to break superficial ice or frost deposits.

[0007] US 10,113,278 Bl discloses a module for deicing a cable sheath with a mass and a vibrator. This solution causes vibrations along the cable that removes the ice or snow covering the cable. However, such solution requires a lot of power.

[0008] WO 2020 / 229867 Al discloses a deicing device arranged in the interstitial space left free from tendons within the sheath. In use, the deicing device bears on the tendons and on sheath to cause a local deformation of the sheath. In order to remove ice along the sheath, the deicing device is movable longitudinally within the interstitial space.SUMMARY

[0009] There is proposed a deicing device for a sheath of a structural cable, the deicing device comprising: a support body rotatable about a first axis; and at least one eccentric contact member attached to the support body and extending transversally to the first axis.

[0010] Since the support body is rotatable about the first axis, and the eccentric contact member is attached thereto, rotation of the support body causes a simultaneous rotation of the at least one contact member. During this rotation, the support body stores elastic energy which is subsequently released, causing an abrupt rotation of the support member and the eccentric contact member and shaking the sheath with respect to the bundle of tendons. This abrupt rotation produces impacts and jolts of the eccentric contact member and the support body against the sheath in which the deicing device is installed. Such impacts and jolts allow to remove ice and other matter accumulated on the outside of the sheath.

[0011] Such a deicing device is robust, compact and provides a simplified solution compared to those known in the prior art. It enables satisfactory ice removal without the need for a powerful power supply.

[0012] Installation of the deicing device is also facilitated because it is possible to install the deicing device in its entirety by inserting the preformed deicing device (i.e., comprising the support body and the one or more eccentric contact member) into the sheath. The replacement of the deicing device is likewise facilitated: it is sufficient to remove from the sheath the worn deicing device, and to insert a new preformed one.

[0013] In an embodiment, the deicing device comprises a plurality of eccentric contact members spaced apart along the first axis.

[0014] In an embodiment, the eccentric contact members are angularly aligned about the first axis. In another embodiment, the eccentric contact members have mutual angular misalignments about the first axis.

[0015] The at least one eccentric contact member may have a circular or elliptical shape.

[0016] In an embodiment, the deicing device further comprises a power system configured to rotate the support body about the first axis.

[0017] The support body may comprise a rope. In an embodiment, the rope comprises a steel strand.

[0018] A first end of the rope may be configured to be driven in rotation about the first axis while a second end of the rope opposite to the first end may be configured to be guided in rotation about the first axis.

[0019] In an embodiment, the at least one eccentric contact member is made of high-density polyethylene.

[0020] In another aspect, it is proposed a structural cable comprising a sheath, tendons housed in the sheath, and at least one deicing device as defined above inserted in the sheath.

[0021] In another aspect, it is proposed a method of deicing a sheath of a structural cable, the structural cable comprising tendons housed in the sheath, the method comprising: providing a deicing device within the sheath of the structural cable, the deicing device comprising a support body rotatable about a first axis and at least one eccentric contact member attached to the support body and extending transversally to the first axis; driving the support body in rotation about the first axis so that the at least one eccentric contact member in contact with an inner surface of the sheath causes vibration of the sheath relative to the tendons.BRIEF DESCRIPTION THE DRAWINGS

[0022] Other features and advantages of the deicing device disclosed herein will become apparent from the following description of non-limiting embodiments, with reference to the appended drawings, in which:- Fig. 1 is a schematic side view of a stay cable;- Fig. 2 is a schematic cross-sectional view of a stay cable;- Fig. 3 is a schematic perspective view of a deicing device according to a first example;- Fig. 4 is a schematic perspective view of a deicing device according to a second example;- Fig. 5 is a schematic front view of a possible configuration of a contact member of a deicing device of the kind illustrated in Figs. 3 and 4; and- Fig. 6A-D are schematical cross-sectional views of the stay cable of Figs. 1 and 2 provided with the deicing device of Fig. 3 in different positions.DESCRIPTION OF EMBODIMENTS

[0023] Fig. 1 shows a structural cable 10 that may be equipped with a deicing device according to the invention.

[0024] The cable 10 is configured to take up efforts applied to a structure to which it is anchored. The cable 10 is, for example, a stay extending along an oblique path between first and second parts 12, 14 where it is anchored using respective anchoring devices 16, 18. The stay cable is used to suspend the second part 14 (e.g., a bridge deck) from the first part 12 (e.g., a pylon), or to stabilize a tall structure forming the first part 12 from the ground or some lower structure forming the second part 14.

[0025] The structural cable 10 comprises tendons 22 disposed parallel to each other (Fig. 2) and contained in a collective sheath 20. For example, the tendons may be steel strands each protected by a substance such as grease or wax and individually contained in a respective plastic sleeve.

[0026] The collective sheath 20 forms a protective cover for the tendons 22. It is in the form of a duct which internally defines a cavity 24 running along the length of the cable 10 and within which the tendons 22 are arranged. The cross-section of the sheath 20 is typically circular. Other shapes, e.g. polygonal, elliptical, etc., are possible. The sheath 20 comprises an inner surface 28 facing the tendons 22. The inner surface 28 may be circular like the cross-section of the sheath 20, but the present disclosure is not limited thereto.

[0027] The tendons 22 are arranged within the cavity 24 so that an interstitial space 26 unoccupied inside the sheath 20 is left accessible. The interstitial space 26 extends within the sheath 20 and over the entire length of the sheath 20. Since the tendons 22 normally support the sheath 20, the interstitial space 26 is generally located below the tendons 22 within the sheath 20.

[0028] The cable 10 may have a length of up to several hundred meters. The bundle may include a few tens of tendons 22.

[0029] The sheath 20 is typically made of plastic material such as high-density polyethylene (HDPE).

[0030] Figs. 3 and 4 show schematically a deicing device 30 that is configured to be placed within the sheath 20 to remove ice, snow, frost, or any other deposit of material present onthe outer surface of the sheath. It should be understood that the word “deicing” is meant here to cover the removal of any matter present on the sheath 20, specially on its outer surface.

[0031] As it will be detailed, the deicing device 30 extends longitudinally along the sheath 20, between the two ends of the sheath 20. As shown in Figs. 6A-D, the deicing device 30 is advantageously disposed in the interstitial space 26. It is installed underneath the bundle of tendons 22, so that it does not have to support the weight of the sheath 30.

[0032] The deicing device 30 comprises a support body 32 and one or more eccentric contact member(s) 34.

[0033] The support body 32 may comprise a rope that is for example made of a metallic material. Conveniently, the rope 32 is a steel strand.

[0034] The rope 32 extends along a longitudinal axis L, substantially parallel to the tendons 22. It comprises a first end 36 and a second end 38 longitudinally opposed.

[0035] The rope 32 is installed in the interstitial space 26 with moderate tension. It runs substantially parallel to the catenary curve of the tendons since it is contained in the sheath 20. The rope 32 is mounted rotatable about the longitudinal axis L. In a non-limiting embodiment, one among the first end 36 and the second end 38 is configured to be driven in rotation about the longitudinal axis L, while the opposite end 38, 36 is configured to be guided in rotation about the longitudinal axis L, for example using a ball bearing 44 or a similar device. For this purpose, the end 36, 38 configured to be driven in rotation may be connected to a power system 40 configured to rotate the rope 32 about the longitudinal axis L. The power system 40 may be connected to the support body 32 either directly or via a motion transmission mechanism (e.g. via a cardan shaft, gears or similar).

[0036] In the exemplary embodiments of Figs. 3 and 4, the first end 36 is driven in rotation about the longitudinal axis L by the power system 40, while the second end 38 is guided in rotation about this axis L.

[0037] The eccentric contact member 34 has a general shape about the axis L which may be convex, circular, elliptical, etc.

[0038] In the non-limiting embodiment of Fig. 5, the contact member 34 has a first zone 48 and a second zone 50.

[0039] The first zone 48 comprises a through hole 52 shaped to receive the rope 32 tightly. The eccentric contact member 34 is attached to the rope 32 and extends transversally to the longitudinal axis L.

[0040] The second zone 50 comprises a contact face 54 that is free. The contact face 54 advantageously has a convex shape. The second zone 50, and in particular its contact face 54, are configured to come into contact with the inner surface 28 of the sheath 20 at defined frequencies when the rope 32 is rotated about the longitudinal axis L.

[0041] Advantageously, the eccentric contact member 34, or at least its contact face 54, are made of a material that prevents or limits wear of the area of the inner surface 28 against which the contact face 54 comes into contact during the rotation of the rope 32. For example, the contact member 34, or at least its contact face 54, may be made of the same material of the sheath 20, typically HDPE. Alternatively, the eccentric contact member 34, or at least its contact face 54, may be made of rubber.

[0042] In order to deice the sheath 20, the rope 32 is driven in rotation about the longitudinal axis L at the end 36 that is connected to the power system 40, while the opposite end 38 is guided in rotation about the longitudinal axis L. At one point during this rotation, the eccentric contact member 34, namely its contact face 54, comes into contact with the inner surface 28 of the sheath 20, as shown in figure 6A. Further rotation of the rope 32, with the eccentric contact member 34 acting as a cam (figure 6B), causes an increase of the distance d between the rope 32 and the inner surface 28 of the sheath 20, and also some twisting of the rope 32. Hence, elastic energy is being stored in the rope 32. The stored elastic energy is released when further rotation occurs (figure 6C). This causes the eccentric contact member 34 to rotate abruptly about the longitudinal axis L (figure 6D) and impact against the inner surface 28 of the sheath 20. This results in a jolt in the sheath 20. The impact of the eccentric contact member 34 together with the jolt caused by the rope 32 results in vibration of the sheath 20 with respect to the tendons 22 and creates a local mechanical force on the sheath 20 capable of removing accumulations of ice or any other matter from at least part of its surface. The frequency of the impacts and jolts applied to the sheath 20 varies with the speed of rotation of the rope 32.

[0043] In the non-limiting embodiments shown in Figs. 3 and 4, a plurality of eccentric contact members 34 spaced apart along the longitudinal axis L are attached to the rope 32. In some cases, all the eccentric contact elements 34 may be identical to each other. They may also have different shapes.

[0044] By attaching a plurality of eccentric contact members 34 to the rope 32, a mechanical force capable of removing accumulations of ice or other matter present on the sheath 20 is created along the entire length of the rope 32.

[0045] The eccentric contact members 34 can be spaced apart at constant distances or at different distances. Advantageously, the distance between eccentric contact members 34 is chosen so that every point of the sheath is reached by the mechanical force created by the impacts of the eccentric contact members 34 or the jolts of the rope 32, so as to ensure that there is no part of the sheath 20 where ice or other matter tends to accumulate.

[0046] In the exemplary embodiment of Fig. 3, all the eccentric contact members 34 are angularly aligned about the longitudinal axis L, i.e., they are all arranged at the same angular position around the rope 32. The frequency of the impacts and jolts applied on the sheath 20 varies with the speed of rotation of the rope 32.

[0047] In the exemplary embodiment of Fig. 4, the eccentric contact members 34 have mutual angular misalignments about the longitudinal axis, i.e., they are arranged at different angular positions around the rope 32. In this way, each eccentric contact member 34 impacts against the inner surface 28 of the sheath 20 at different times. In this case, the frequency of the impacts and jolts applied on the sheath 20 varies with the speed of rotation of the rope 32, but also with the position of each eccentric contact member 34.

[0048] It should be noted that the deicing device 30 and the deicing method described above enable deicing using a robust, compact and simplified solution. In addition, thanks the combination of the impact of the eccentric contact members 34 and the jolts of the rope 32, the mechanical force capable of remove matter accumulated on the sheath 20 can be exerted along the entire length of the sheath 20 without the need for a complex mechanism requiring a large power supply. Finally, as already mentioned, the installation and replacement of the deicing device 30 are made easily as all that is required is to insert the deicing device 30 formed by the rope 32 and the eccentric contact members 34 into the sheath 20, after having extracted eventually a worn deicing device 30 if necessary.

[0049] It will be appreciated that the embodiments described above are illustrative of the invention disclosed herein and that various modifications can be made without departing from the scope as defined in the appended claims.

Claims

CLAIMS1. A deicing device (30) for a sheath (20) of a structural cable (10), the deicing device (30) comprising: a support body (32) rotatable about a first axis (L); and at least one eccentric contact member (34) attached to the support body (32) and extending transversally to the first axis (L).

2. The deicing device (30) of claim 1, comprising a plurality of eccentric contact members (34) spaced apart along the first axis (L).

3. The deicing device (30) of claim 2, wherein the eccentric contact members (34) are angularly aligned about the first axis (L).

4. The deicing device (30) of claim 2, wherein the eccentric contact members (34) have mutual angular misalignments about the first axis (L).

5. The deicing device (30) of any one of the preceding claims, wherein the at least one eccentric contact member (34) has a circular or elliptical shape.

6. The deicing device (30) of any one of the preceding claims, further comprising a power system (40) configured to rotate the support body (32) about the first axis (L).

7. The deicing device (30) of any one of the preceding claims, wherein the support body (32) comprises a rope.

8. The deicing device (30) of any one of the preceding claims, wherein the rope(32) comprises a steel strand.

9. The deicing device (30) of claim 7 or 8, wherein a first end (36, 38) of the rope (32) is configured to be driven in rotation about the first axis (L) while a second end (38, 36) of the rope (32) opposite to the first end (36, 38) is configured to be guided in rotation about the first axis (L).

10. The deicing device (30) of any one of the preceding claims, wherein the at least one eccentric contact member (34) is made of high-density polyethylene.

11. A structural cable (10) comprising a sheath (20), tendons (22) housed in the sheath (20), and at least one deicing device (30) as claimed in any one of the preceding claims inserted in the sheath (20).

12. A method of deicing a sheath (20) of a structural cable (10), the structural cable (10) comprising tendons (22) housed in the sheath (20), the method comprising: providing a deicing device (30) within the sheath (20) of the structural cable (10), the deicing device (30) comprising a support body (32) rotatable about a first axis (L) and at least one eccentric contact member (34) attached to the support body (32) and extending transversally to the first axis (L); driving the support body (32) in rotation about the first axis (L) so that the at least one eccentric contact member (34) in contact with an inner surface (28) of the sheath (20) causes vibration of the sheath relative to the tendons.

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