EP0633350B1 - Hoisting cable - Google Patents

Abstract

The cable comprises a central core (3) and outer strands (2) formed from at least one layer of wires (21) made of metal, especially steel, which are stranded on a foundation (22) made of synthetic, preferably thermoplastic material, this taking place according to a pitch similar to that of the strands (5, 6) from which is formed the core (3) which can be completely metallic or composite. These cables are intended particularly for use as hoisting cables, especially lift cables, or other multi-cable installations with transmission by adhesion. <IMAGE>

Description

The present invention relates to lifting cables multi-channel, in particular intended to work in adhesion transmission, such as cables for lifts.

These cables are currently being formed either fully with outer strands and steel core, either with strands metallic exteriors and non-metallic central core or partially metallic.

The core must ensure correct geometry of the architecture of the outer strands that it supports, and in particular ensuring sufficient functional clearance between these strands to prevent them from coming into mutual contact intimate, which would cause friction and wear of the wires in contact, with risks of seizure, indentation, contact corrosion and breakage.

In the case of all-metal cables, the core steel ensures this correct geometry, because that the core is not radially deformable. But, the mass linearity of these all-steel cables is important. Through elsewhere, the outer strands also being made of steel (therefore also slightly radially deformable), the pressures of contact exerted by these external strands on the core are very important, especially when winding on pulleys or drums. This results in wear risks and indentation between the outer strands and the core. Of even the high contact pressure of the outer strands on pulleys or drums can cause deterioration of these.

This is why we commonly use in applications of this type, especially as cable elevators, steel strand cables, and core in natural textile with hard fibers, such as sisal.

• l'âme en fibres naturelles constitue un réservoir pour le lubrifiant dont elle est imprégné, et qui en est extrudé lors de la compression de l'âme par les torons extérieurs ;
• le frottement des torons extérieurs sur l'âme est faible, ce qui confère à ce type de câble une grande souplesse ;

These cables have a lower linear mass than all-steel cables and combine different advantages:

• the natural fiber core constitutes a reservoir for the lubricant with which it is impregnated, and which is extruded therefrom during the compression of the core by the outer strands;
• the friction of the outer strands on the core is low, which gives this type of cable great flexibility;

In elevator installations, cables are generally mounted on the same drive pulley in ply of several cables, or "strands", parallel. So that the total load is durably distributed over all these strands, it is necessary that all the strands have a homogeneity of behavior in service, in particular in with regard to their diameter and, correspondingly, their permanent extension. Indeed, so that the tensions of each of the strands are equivalent, it is imperative that their diameters are equal and constant. if it's not the case, some strands are in tension and others are relaxed, which generates vibrations and differential crawling (localized catching up of displacement of one strand relative to the other) which cause wear of the cables and grooves of the driving pulley.

From this point of view, sisal core cables have the disadvantage of their diametrical irregularity and their compressibility under tension and under cycles of associated alternating tension-bending operation, which cause variations in elongation and their consequences indicated above.

In addition, we are currently faced with increasing difficulties in supplying the fibers of sisal, from a plant whose culture is in the process of disappearance.

We tried to substitute sisal for fibers synthetic, but on the one hand these fibers are less effective than sisal in its reservoir function lubricant and, on the other hand, the characteristics of friction of the core on the outer strands are significantly less. As a result, these cables are less resistant to fatigue, due to abrasion in service the soul by the strands, which, moreover caused a wear of the core, the reduction in cable diameter, and the elongation resulting permanent.

We also know from document US 3,729,921 a cable composed of a plurality of strands exteriors comprising metallic wires stranded on a synthetic material core and wired on a central core itself comprising strands wired on a central core.

The object of the invention is to propose a new cable
lifting, particularly suitable for elevators or
similar lifting devices,
which, in order to enable the various problems indicated above to be resolved, has a reduced permanent elongation, and a nearly ideal distribution of contact pressures, in particular during winding on pulleys or drums.

With these objectives in view, the invention relates to a cable composed of a plurality of strands exteriors comprising metallic wires stranded on a synthetic material core and wired on a central core itself comprising strands wired on a central core characterized in that the outer strands are wired at the same pitch as, and parallel to, the core strands that the soul is entirely metallic.

The cable according to the invention thus has a large geometric stability, thanks to very little metallic core compressible, and therefore a permanent extension in service significantly reduced. Its linear density is equal to, or at less very close to that of a cable equivalent to strands metallic exteriors on textile fiber core natural, and therefore lower than that of a cable entirely metallic of the same diameter.

In addition, the synthetic plastic material of the heart outer strands, allows them to deform when winding on pulleys or drums, by marrying the shape of the groove where the cable rests. This ensures a almost ideal distribution of contact pressures, therefore a strong reduction of these pressures between the strands exterior and soul, which decreases the risks indentation since the core strands and these strands exteriors are wound in a similar step. A strong pressure reduction thus also takes place between outer strands and winding members, which reduces the risk of damage to these organs. It results in fatigue resistance of the cable according to the invention very much improved compared to that of a cable on textile core.

In addition due to the realization on soul dimensionally stable metal, and the layer or layers of metallic wires of the outer strands, the tolerance of manufacturing on the cable diameter can be significantly reduced, going to - 0, + 3% of the nominal diameter, against - 0, + 5 or 6% for a textile core cable.

Other characteristics and advantages will appear in the description which will be given by way of example a lifting cable according to the invention, particularly intended for use as a cable elevator, or for multi-cable installations adhesion transmission.

Reference is made to the appended drawing which represents the cross section of this cable.

The cable 1 comprises several external strands 2, eight in the example shown, surrounding a soul 3. The soul 3 itself comprises a central core 4 (advantageously formed of a strand itself); four main strands 5, and four secondary strands 6. All the strands of the core are made of steel and assembled with Lang wiring.

The outer strands 2 are assembled in wiring crossed, parallel and at the same pace as the strands of soul which are themselves assembled so that all inter-layer contacts and between the different strands are linear, which reduces the contact pressures and therefore the risks of indentation.

The outer strands 2 are formed of a layer external of steel wires 21, stranded on a support central 22 made of synthetic material with good qualities mechanical, for example polyethylene, polypropylene, polyamide or other similar substances, preferably of thermoplastic nature.

The central support can also include fibers aromatics, carbon fibers or glass fibers or other fibers with high mechanical resistance, covered with a polyethylene, polypropylene, polyamide or other sheath analogous substances.

Preferably the outer strands 2 are made by placing the wires 21 of the outer layer on a rod of said synthetic material softened by heating so that the wires 21 become embedded in the synthetic material and that it flows between the wires filling all the gaps between them.

Although in the example shown in the figure, it there is only one layer of wires 21, we can also form the outer strands 2 with several layers of these wires, by example two, assembled as shown above so that the synthetic material fills the spaces between the son in contact with him.

The manufacture of the outer strands may in particular be done similarly to the method described for non-metallic core cables in the document FR-A-1601293 to which reference may be made for more information.

It is however recalled that, in accordance with this method, the strand of synthetic material intended for constitute the central support 22, is, prior to the placement of external wires, at least partially conforms to the internal profile of the layer of wires which it will support after stranding, which allows to control the strand geometry, by automatic prepositioning wires on said strand.

As already indicated above, the outer strands 2 are wired at the same pitch as the strands 5, 6 of the core and parallel to these. This preferential provision also has the advantage of allowing the manufacture of cable in a single wiring operation, during which all strands, core strands and strands exterior, are assembled simultaneously in the same phase wiring.

The synthetic material of the central support 22 of the outer strands 2 allows a very good distribution of contact pressures of these strands on the organs winding such as pulleys or drum, because said material allows the outer strands to deform elastically in their section and to marry as well as possible the profile of the grooves or bearing surfaces of the organs winding.

For the same reasons, the distribution of pressures contact of the outer strands on the core strands is greatly improved compared to stranded cables all-metal exteriors on an equally metallic core or mixed. This results in very little wear of the core metallic.

In addition to the advantages indicated above, relating to conditions of use of the cable, the invention allows also, thanks to the use of a metallic core, reduce the tolerance on the nominal diameter which can be halved compared to textile core cables equivalent for the intended application.

Furthermore, the structure of the cable according to the invention, by limiting its diametral settlement in service, allows considerably reduce the permanent elongation by service. The tests carried out revealed a permanent elongation three to six times less than that cables of the prior art with a sisal textile core.

As an example we give below a table comparison of test results carried out on a cable textile core according to the prior art and on a cable according to the invention.

These data are measured before, then in progress and after a conventional fatigue test on a pulley of 300 mm in diameter and relate to cables with nominal diameter 13 mm:

The invention is however not limited to the realization of the cable described above by way of example. In particular, the composition of the soul can be different from that indicated above, the number, the constitution and relative position of the strands of the core metallic that can be changed without harming the benefits resulting from the use of strands exteriors according to the invention.

The number of these outer strands can also be amended.

Claims (6)

1. Cable composed of a plurality of outer strands (2) including metal wires (21) that are stranded over a core element (22) made from synthetic material and cabled over a central core (3) that itself includes strands (5, 6) cabled over a central core member (4), characterized in that the outer strands (2) are cabled at the same pitch as the strands (5, 6) of the central core (3) and parallel to the latter, and in that said central core (3) is entirely metallic.
2. Cable according to claim 1, characterized in that the synthetic material making up the core element (22) of the outer strands (2) is thermoplastic.
3. Cable according to claim 1, characterized in that the core element (22) of the outer strands (2) includes aromatic fibres, carbon fibres or glass fibres.
4. Cable according to claim 1, characterized in that the core element (22) of the outer strands (2) includes synthetic fibres with high mechanical strength which are coated with a sheath of thermoplastic material.
5. Cable according to claim 1, characterized in that the synthetic material making up the core element (22) of the outer strands (2) is polyethylene, polypropylene or polyamide.
6. Cable according to claim 1, characterized in that the central core member (4) is itself made up of a strand.

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