EP1115941B1 - Composite cable with synthetic core for lifting or traction - Google Patents

Abstract

The invention includes a composite cable having a plurality of strands (10, 12) stranded around a composite synthetic core (5) with a concentric structure. The core (5) has a nucleus (11) formed by a bundle of parallel synthetic fibers extending along the cable longitudinal direction, and of a compact thermoplastic sheath (13) enclosing the nucleus (11) and serving as winding support for the strands.

Description

The present invention relates to hoisting ropes or traction, including elevator cables, that is to say the cables that support the cabin elevator and transmit the movement of the drum drive.

The characteristics required for these cables are notably a great flexibility, a good regularity diametrically ensuring a regular permanent elongation, and good resistance to abrasion, since the training is ensured by friction between the cable and the drum. For further explanations on the characteristics required for such cables and constraints to which they must respond, we will be able to postpone, for example, the French patent application filed under No. 93 08648.

The type of cable conventionally used for such applications is a mixed cable with eight strands of steel wires wound helically on a textile core natural hard fibers, such as sisal. We know also a similar cable but whose soul itself is combination of metal strands and textile fiber filling.

Elevator traction cables can also be cables with metal strands on a soul metallic, independent or not. We thus know cables with twelve outer strands wound on a core independent Warrington type, or cables to nine outer strands on a metal core independent itself to nine strands.

In other lifting applications, we use also cables with natural fibers of the type sisal, or synthetic (polypropylene), whose role is to form a mattress inserted between the different layers of strands. The aim is to avoid or at least limit the friction of the strands or strands against each other, and the risks of indentation, in order to improve and maintain the flexibility of the cable, and avoid breaks of son.

We also know, by the patent application International WO 89/11559; a cable whose central core of polymeric or elastomeric material serves as a support winding to the metal strands and includes effect of the spiral grooves intended to receive them. The soul can be hollow in the center to receive reinforcing elements.

A common point of these inserts in non materials metal is that they do not participate directly in voltage recovery in the cable, that is to say they do not contribute directly to increasing resistance pulling the cable.

It is also known, for example from US-A-5566786, cables intended to serve as cable traction for lifts, and which consist of only synthetic fibers likely to transmit a tensile force. Such a cable presents in particular the advantage of a more linear density weaker than a steel or composite cable, with equivalent. However, it has the disadvantage of require significant changes in relation to more conventional cables with regard to its implementation work and its control. For example, an anchoring system special, very complex, is necessary to him. In addition, can not control the state of wear of fibers synthetic materials, as is the case for steel wires, electrical or electromagnetic methods. He has been planned to include synthetic fibers in electrically conductive carbon fibers, the Conductivity control makes it possible to obtain a state of cable wear. But this increases the complexity of the cable, and therefore the cost. Moreover, these cables can still have other disadvantages, for example a poor transmission by adhesion between the cable and the drum drive, or increased risk of cutoff voluntary by vandalism.

The present invention aims to solve problems mentioned above. In particular, it aims to provide a lifting or pulling cable that equal weight, a breaking strength considerably increased compared to all-steel cables or cables known mixes, allowing in particular, with equal mass, to increase the payload as well as the height of lifts, or, at equal charge, to reduce the number of strands or the diameter of the cables used.

With these objectives in view, the object of the invention is a mixed cable having a plurality of strands wired around a synthetic core, characterized in that the core is constituted by a core formed of a bundle of parallel synthetic fibers between they extend in the longitudinal direction of the cable, and by a compact sheath made of thermoplastic material enclosing said core and serving as a winding support to the strands.

The principle of the invention can also be apply identically to a cable in its constitution the simplest, that is to say a simple strand, the inventions also relates to a mixed strand having a plurality of outer strands stranded around a core synthetic material, this strand being characterized in that the soul is constituted by a nucleus formed of a beam of parallel synthetic fibers extending between them longitudinal direction of the strand, and by a sheath thermoplastic material enclosing said core and serving of winding support to the wires.

As will be understood, the invention lies in its essential characteristics, in the presence of a two-component synthetic composite core arranged concentrically: a compact but deformable sheath radial compression (a thermoplastic) that surrounds tightly a central core formed of a bundle of individual fibers, also of synthetic material, substantially continuous along the length of the cable, and arranged in such a way as to participate effectively in all tensile force exerted on the cable by a load.

Unlike this, in mixed cables known, the synthetic material serves as padding, for maintain the strands or wires, one for each relationship to each other in the cable section, and so avoid, for example, friction of metal wires on one another or even indentations caused by the radial pressure that can be exerted between wires or strands when the cable is turned on, but it makes virtually no additional contribution to traction.

To effectively participate in resistance to traction, the section and the number of fibers of the cable or strand according to the invention are determined so that the soul forms with the wires or metal strands a assembly such as deformations under load, mainly in elongation, are substantially equivalent for the synthetic fiber core and for strands or external metal wires, despite the differences in mechanical characteristics of these materials. Moreover, the sheath surrounding the fibers is a deformable but not very compressible material, so that this material flows during the manufacture of the cable or strand until filling the free spaces between the soul and the strands or wires of the surrounding layer directly the soul. It results from this a pressure radial force exerted by the outer strands or wires on the sheath, and from there on the peripheral layer of the fibers of the soul, which creates a strong bond, or a kind of mechanical cohesion, between wires or strands and the so-called fibers, capable of ensuring a transmission between them of pulling forces. In addition, friction between fiber, which is actually increased by the effect of radial compression exerted by the strands or wires outside, allows at least part of closer and closer to the heart of the soul, the efforts of traction experienced by the peripheral layer, so that the whole section of the soul can participate in the recovery of the tensile load to which the cable is subjected.

The sheath serves in particular to maintain the fibers parallel together, ensuring the compactness of the soul.

It should be noted that the transmission of efforts between strands or outer threads and the soul is all the better ensured by friction between the sheath and said strands or outer threads that these penetrate into the material of the sheath, since this increases the contact area.

Moreover, the sheath constitutes a layer intermediate between the outer strands or wires and the fibers of the soul, which avoids or at least limits the effect of shearing fibers, which extend according to the axial direction, by the outer threads, or the threads outer strands, which are transverse to the so-called axial direction.

Whether it's the cable or the single strand, the fibers are preferably made of polyethylene or aramid, and the sheath is for example polyamide extruded.

The outer strands of the cable according to the invention may be entirely metallic, that is to say made entirely of wire, or mixed, and in particular made of mixed strands conforming themselves to the invention.

Other features and benefits will appear in the description that will be made of strands and cables according to the invention.

• la figure 1 est une section d'un toron mixte selon l'invention ;
• la figure 2 est une section d'un câble conforme à l'invention selon un premier mode de réalisation ;
• la figure 3 est une section d'un câble conforme à l'invention selon un deuxième mode de réalisation.

Reference is made to the accompanying drawings in which:

• Figure 1 is a section of a mixed strand according to the invention;
• Figure 2 is a section of a cable according to the invention according to a first embodiment;
• Figure 3 is a section of a cable according to the invention according to a second embodiment.

The strand shown in section in FIG. comprises a composite synthetic core 4 with a structure concentric: a central core 1 formed by a beam of free and parallel fibers, the cohesion of which is ensured by a monolithic sheath 3 which corsets the beam. This soul is surrounded by a layer of threads of steel 2 (here ten in number) wound spirally on the sheath 3, and which presses around the core 1 in him thus giving their footprints, as we see on the drawing.

The constituent fibers of the core are by example of polyethylene fibers, aramid, Kevlar®, Twaron®, etc. Sheath 3 is made of a material thermoplastic, for example a polyamide, having good adhesion properties with the fibers of the core.

The cable shown in section in FIG. composed of a core 5 of synthetic fibers similar to the soul 4 previously described and surrounded by twelve strands seventeen steel wires. Between the core 11 and the layer outer strand 12, is interposed a layer thermoplastic material, constituting a compact sheath 13 which is pressed around the soul by the 12. As can be seen from the drawing, the threads strands, located towards the inside of the cable, are embedded in the thermoplastic material of the sheath 13, thus providing a large contact area and therefore a strong adhesion. The latter is still reinforced by the effect of centripetal radial compression exerted by the strands on the sheath when a tension is exerted on the cable.

The constituent materials of the core 5, the core 11 and sheath 13, are of the same type as those indicated for the strand of Figure 1.

FIG. 3 represents yet another cable, having a synthetic fiber core 5 having a central beam 11 of synthetic fibers and a sheath thermoplastic material 13. Unlike the previous example, the eight strands 10 are not entirely made of steel, but are actually strands in accordance with that shown in Figure 1.

The three examples above are by no means The breaking load of a conventional cable, even mixed, is essentially dependent on the section metallic which is the sum of the sections of all the wires component cable. It hardly depends on existing nonmetallic inserts in mixed cables, and in particular synthetic fibers which, having no mainly that a filling function of the voids between strands or strands, do not include any part of the charge.

On the other hand, the weight of the cables is due first instead of the weight of the steel wires composing it. So, the ratio breaking load / weight of steel ropes is substantially constant, relying mainly on the construction of the cable and not of its diameter.

The comparative table below indicates the R / P ratio of the breaking load R to the weight per meter P, for two types of cables, 8x19 and 12x17, in a current embodiment (col.2) and produced according to the invention ( col.3) respectively.

We can easily see the increase in the ratio R / P with corresponding cable structure. Relative to all-steel cables, and equal cable weight, the load useful can be increased, or vice versa, for the same load, weight and diameter of the cables can be diminished, making it possible to reduce the dimensions of machines or frames of elevators or apparatus Similar. Also, the life of the cables according to the invention is increased compared to cables while steel.

Compared to cables made entirely of fiber, the implementation of the cables according to the invention does not require no modification of the existing installations: the anchors and cable terminations are identical to conventional applications of steel cables; the interface between the drums of the machineries and the cable is always a steel contact on drum material, which does not change the conditions for a transmission of adhesion movement; the criteria for removal and replacement are similar, based on the decrease diameter and the number of broken steel wires; and the cables of the invention are not more sensitive to acts of vandalism as all-steel cables.

The invention is not limited to the modes of realization which have been described above only to as an example. The number of wires of each strand, and the number of strands of the cable can obviously be changed. Also, the use of these cables is not not limited to their application as cables lifts, and they can also be used as hoisting ropes, lines, for applications in mountain or in the maritime domain, etc.

Claims (8)

1. Composite cable comprising a plurality of strands (10, 12) wound around a core of synthetic material, constituted by a nucleus (11) and by a compact sheath (13) of thermoplastic material enclosing said nucleus and serving as a support for winding said strand (10, 12), characterized in that said nucleus (11) is formed by a bundle of synthetic fibers parallel among them extending in the longitudinal direction of the cable.
2. Composite strand comprising a plurality of wires (2) stranded around a core (4) of synthetic material, constituted by a nucleus (1) and by a compact sheath (3) of thermoplastic material enclosing said nucleus and serving as a support for winding said wires, characterized in that said nucleus (1) is formed by a bundle of synthetic fibers parallel among them extending in the longitudinal direction of the strand.
3. Strand according to claim 2, characterized in that the fibers constituting the nucleus (1) are of polyethylene or aramide.
4. Strand according to claim 2, characterized in that the sheath (3) is of polyamide.
5. Cable according to claim 1, characterized in that the fibers constituting the nucleus (11) are of polyethylene or aramide.
6. Cable according to claim 1, characterized in that the sheath (13) is of polyamide.
7. Cable according to claim 1, characterized in that the strands (12) are constituted by metallic wires.
8. Cable according to claim 1, characterized in that the strands (10) are strands according to claim 2.

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