A FIRST CORD AND A SECOND CORD

Description

Technical Field

[0001] The invention relates to a method to provide a connection between two cords that may withstand a pull force of at least 10 000 N. The method is in particular suitable to provide a connection between monostrand cords (strands).

Background Art

[0002] There has always been a need to connect the ends of cords to one

another in order to make a long or endless cord. By connecting the ends of two cords constant continuous lengths of cords can be coiled for example on spools or spoolless coils.

However, in order to allow coiling or uncoiling of cords, the connection or temporary connection should withstand a pull force sufficient to allow coiling or uncoiling of the connected cords.

[0003] Connection of the ends of two cords can for example be realised by

knotting, by welding two ends of two cords to each other or by using a Chinese trap system.

However, the connecting methods known in the art do not result in connections that may withstand a pull force sufficient to allow proper coiling or uncoiling of the connected cords.

Disclosure of Invention

[0004] It is an object of the present invention to provide a method to provide a connection between two cords avoiding the drawbacks of the prior art. It is another object of the present invention to provide a method allowing the coiling and uncoiling of a cord having a connection or a temporary connection.

[0005] According to a first aspect of the present invention, a method to provide a connection between a first cord and a second cord is provided. The connection may withstand a pull force of at least 10000 N. More preferably, the connection may withstand a pull force of at least 20000 N or a pull force of at least 30000 N.

The first and the second cord comprise a group of twisted steel filaments, a polymer coating around said group of twisted steel filaments and a filling compound filling at least partially internal interstices between the twisted steel filaments of the group and a peripheral interstice lying between a periphery of the group of twisted steel filaments and an inner face of the polymer coating. The method comprises the steps of

- connecting a first connection means at one end of said first cord;

- connecting a second connection means at one end of said second cord;

- interconnecting said first connection means and said second connection means by means of a chain.

[0006] For the purpose of this invention a chain is considered to be a series of objects connected one after the other, usually in the form of a series of metal links or metal rings passing through one another.

[0007] With connection is meant either a temporary connection or a permanent connection.

[0008] Preferably, the method comprises the additional step of

- protecting said first connection means, said second connection means and said chain with a protective sheath.

[0009] The first cord and the second cord may comprise any type of cord

comprising a group of twisted steel filaments.

The first and second cord may comprise a monostrand cord (a strand) or a multistrand cord. Preferred cords comprise cords having a 2x1

construction, a 3x1 construction, a 1 +6 construction or a 1 +6+12 construction.

Preferably, the first cord and the second cord are of the same type. [0010] The description of the construction follows the sequence of manufacturing the cord i.e. starting with the inner most filament or strand and moving outwards.

The full description of the cord is given by the following formula :

(NxF) + (NxF) + (NxF)

whereby N = number of strands;

F = number of filaments.

(when N or F equals 1 , they should not be included)

[001 1] The construction can be completed with the diameter of the filaments and is then given by the formula:

(NxF)xD + (NxF)xD + (NxF)xD

whereby D = nominal diameter of filaments, expressed in mm.

[0012] The diameter of the steel filaments ranges preferably between 0.5 mm and 10 mm. More preferably, the diameter of the steel filaments ranges between 2 mm and 8 mm, for example between 3.5 mm and 6.5 mm.

[0013] The steel filaments are preferably plain carbon steel filaments. Such a steel generally comprises a minimum carbon content of 0.40wt% C or at least 0.70 wt% C but most preferably at least 0.80wt% C with a maximum of 1.1 wt% C, a manganese content ranging from 0.10 to 0.90 wt% Mn, the sulphur and phosphorus contents are each preferably kept below 0.030 wt%; additional micro-alloying elements such a chromium (up to 0.20 to 0.4 wt%), boron, cobalt, nickel, vanadium -a non-exhaustive enumeration- may also be added. Also preferred are stainless steels. Stainless steels contain a minimum of 12wt%Cr and a substantial amount of nickel. More preferred are austenitic stainless steels, which lend themselves more to cold forming. The most preferred compositions are known in the art as AISI (American Iron and Steel Institute) 302, AISI 301 , AISI 304 and AISI [0014] The steel filaments preferably have a tensile strength higher than 1000 MPa. More preferably the steel filaments have a tensile strength higher than 1500 MPa, higher than 1800 MPa, higher than 2000 MPa or higher than 2200 MPa.

[0015] The steel filaments can be coated for example with a coating comprising zinc, aluminium, magnesium or alloys thereof. Preferred coatings comprise zinc or zinc alloy coatings for example Zn-Fe, Zn-Ni, Zn-AI, Zn- Mg, Zn-Mg-AI alloys.

A preferred zinc alloy coating is a Zn-AI alloy coating comprising between 2 and 15 % Al.

Possibly, between 0.1 and 0.4 % of a rare earth element such as Ce and/or La can be added.

[0016] Internal interstices are created between the twisted filaments of the cords.

Between the peripheral surface of the cord and the inner face of the polymer coating a peripheral interstice is created. The internal interstices and the peripheral interstice of the first cord and the second cord are at least partially filled with a filling compound.

[0017] The filling compound has preferably lubricating properties. The filling

compound comprises for example a wax, a grease or a polymer.

Preferably, the filling compound is applied just before the application of the polymer coating.

The filling compound can be applied by any technique known in the art, for example by dipping.

[0018] The filling compound may enhance the corrosion protection and/or the fatigue behaviour of the cord by lubricating the contacts between neighbouring steel filaments. Furthermore the filling compound may prevent shear and/or tensile stress concentration in certain portions of the cords, which may cause cracks in the polymer coating. [0019] The first and the second cord comprising the filling compound are provided with a polymer coating. The polymer coating forms a jacket around the first and the second cord comprising the filling compound. The polymer coating comprises for example a polyolefin coating, for example

polyethylene (PE) or polypropylene (PP), a polyamide coating (PA) or an epoxy coating. A preferred polymer coating comprises high density polyethylene (HDPE).

[0020] The polymer coating can be applied on the first and second cord by any technique known in the art. Preferred techniques comprise extrusion and electrostatic deposition.

[0021] The polymer coating has preferably a thickness of at least 100 μηη.

Preferably, the thickness of the polymer coating ranges between 1 mm and 2.5 mm and is for example equal to 1.2 mm.

[0022] To connect the first connection means to one end of the first cord and to connect the second connection means to one end of the second cord any technique can be considered. Preferred techniques comprise welding or gluing or mechanical fixation. The welding comprises for example resistance welding, arc welding or flame welding. For a person skilled in the art it is clear that other types of welding can be considered.

[0023] The first connection means and the second connection means preferably comprise metal, for example steel. The first connection means and the second connection means can be coated with a coating comprising zinc, aluminium, magnesium or alloys thereof.

[0024] In preferred embodiments the first connection means and the second

connection means have an eye shape allowing to introduce one end of the chain, more particularly one link or ring of the chain. [0025] The first connection means comprises for example a steel wire welded to one end of the first cord and the second connection means comprises for example a steel wire welded to one end of the second cord. The wire welded to one end of the first cord and the wire welded to one end of the second cord have for example an eye shape.

[0026] In a preferred method the polymer coating is removed from one end of the first cord, i.e. the end of the first cord that will be connected to the second cord, before the first connection means is connected to this one end of the first cord. The polymer coating is preferably removed over a length L, with L ranging between 1 and 20 cm, more preferably between 5 and 20 cm. Similarly, the polymer coating is preferably removed from one end of the second cord, i.e. the end of the second cord that will be connected to the first cord, before the second connection means is welded at one end of the second cord. Preferably, the polymer coating is removed over a length L, with L ranging between 1 and 20 cm, more preferably between 5 and 20 cm.

By removing the polymer coating at this one end of the first cord and the second cord, the connection between the first connection means and the one end of the first cord or the connection between the second connection means and the one end of the second cord is improved, for example because a better welding contact between the end of the first and the second cord and the first and second connection means is obtained.

[0027] The first connection means and the second connection means are

interconnected by means of a chain. The chain comprises preferably metal, for example steel.

The chain or the links or rings of the chain can be coated with a coating comprising zinc, aluminium, magnesium or alloys thereof.

[0028] Preferably, the chain may withstand a pull force of at least 10000 N. More preferably, the chain may withstand a pull force of at least 20000 N or of at least 30000 N. [0029] In preferred embodiments the chain has a tensile strength similar to the tensile strength of the first and the second cord.

[0030] In a preferred embodiment the connection between the first and the

second cord, more particularly the first connection means, the chain and the second connection means, is protected by means of a protective sheath.

The application of a protective sheath on the connection between the first and the second cord, more particularly on the first connection means, the chain and the second connection means, has the advantage that possible damages caused by the first connection means, the chain and/or the second connection means on the coiled cord or cords is avoided.

Preferably, the protective sheath is applied over the length L at the end of the first cord and at the end of the second cord where the polymer coating is removed.

[0031] The protective sheet comprises preferably a polymer material.

The protective sheet can be applied by any technique known in the art. Preferred techniques comprise wrapping or coiling of a material around the connection, for example wrapping or coiling a strip, tape or foil around the connection.

Other preferred techniques comprise coating techniques such as extrusion or electrostatic deposition.

[0032] The polymer material comprises for example polyolefins such as

polyethylene (PE) or polypropylene (PP), polyamide (PA) or epoxy.

[0033] In a preferred embodiment the protective sheet comprises a heat

shrinkable foil, for example a polyolefin heat shrinkable foil.

[0034] Preferably, the location of the connections is indicated for example by colouring the connections. This can be realised by applying a coloured protective sheath or by colouring the connections, for example by painting the connections.

[0035] The method to provide a connection between a first cord and a second cord according to the present invention allows providing spools with continuous lengths of cord.

As the connection may withstand a pull force of at least 10000 N, and more preferably a pull force of at least 20000 N or even at least 30000 N, the connection allows coiling and uncoiling of the connected cords.

[0036] The method according to the present invention is suitable to connect cords having a high diameter and stiffness. The method according to the present invention is in particular suitable to connect cords having a diameter higher than 10 mm, for example higher than 20 mm.

[0037] The method according to the present invention is in particular suitable for cords or strands for use in prestressed concrete structures or for cords or strands for use as stay cable.

Prestressed concrete structure are structures comprising concrete that has been compressed by either pretensioning or posttensioning of high tensile steel strands or steel cods.

Brief Description of Figures in the Drawings

[0038] The invention will now be described into more detail with reference to the accompanying drawings whereby

- Figure 1 is an illustration of a first embodiment of a connection between a first cord and a second cord according to the present invention;

- Figure 2 is an illustration of a second embodiment of a connection

between a first cord and a second cord according to the present invention;

- Figure 3 is an illustration of the cross-section of the first cord and the second cord shown in Figure 1. Mode(s) for Carrying Out the Invention

[0039] The present invention will be described with respect to particular

embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0040] Figure 1 is an illustration of a connection 100 between a first cord 102 and a second cord 104. A cross-section of the first cord 102 and of the second cord 104 is shown in Figure 3. Both the first cord 102 and the second cord 104 are single strand cords having one central filament 106 and six peripheral filaments 108 helically wrapped around this central filament 106. The central filament 106 and the peripheral filament 108 have for example a diameter of respectively 5.4 mm and 5.2 mm and a tensile strength of at least 1860 MPa.

[0041] Both the first cord 102 and the second cord 104 comprise a polymer

coating 1 10. The polymer coating 1 10 comprises for example high density polyethylene (HDPE). The polymer coating has preferably a thickness ranging between 1.5 mm and 2 mm. The polymer coating 1 10 is preferably applied by extrusion.

The interstices 1 12 lying between the filaments (the central filament 106 and the peripheral filaments 108) and the peripheral interstice 1 14 lying between the periphery of the peripheral filaments 108 and the polymer coating 1 10 are filled with a filling compound 1 16. The filling compound comprises for example a grease.

[0042] One end of the first cord 102 is provided with a first connection means

1 18. In order to obtain a good connection between the first cord 102 and the first connection means 1 18 it can be preferred to remove the polymer coating 1 10 over a length L at the end of the first cord 102. The length L ranges preferably between 1 and 20 cm, for example between 5 and 20 cm.

The first connection means 1 18 has preferably an eye shape.

[0043] Similarly, one end of the second cord 104 is provided with a second

connection means 120. In order to obtain a good connection between the second cord 104 and the first connection means 1 18 it can be preferred to remove the polymer coating 1 10 over a length L at the end of the second cord 104. The length L ranges preferably between 1 and 20 cm, for example between 5 and 20cm.

The second connection means 120 has preferably an eye shape.

[0044] The first connection means 1 18 and the second connection means are interconnected with a chain 122.

[0045] Figure 2 is an illustration of a connection between a first cord and a

second cord as shown in Figure 1 provided with a protective sheath 124. The protective sheath 124 comprises for example a heat shrinkable foil coiled around the first connection means 1 18, the chain 122 and the second connection means 120.