ES2550527B1 - Suspension and traction element, lift and control procedure of the adhesion of said element to a pulley - Google Patents

Abstract

Suspension and traction element, elevator and method of controlling the adhesion of said element to a pulley. # The present invention relates to a suspension and traction element with active adhesion control comprising a load bearing section (1) provided of at least one thread and a sheath (2) that at least partially covers the supporting section, characterized in that the sheath comprises a matrix of polymeric and paramagnetic material and magnetic particles dispersed in said matrix in a proportion of at least 10% by volume . The invention also relates to a system and an elevator incorporating said element and a method of adhesion control.

Description

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DESCRIPTION

Suspension and traction element, lift and control procedure of the adhesion of said element to a pulley.

TECHNICAL SECTOR

The present invention relates to cables, belts, belts or other suspension and traction elements used in elevators, teleferic and funicular cabins. In particular, the invention relates to a suspension and traction element where the load bearing section is at least partially covered with a sheath, said sheath comprising a paramagnetic polymer matrix and magnetic particles.

STATE OF THE TECHNIQUE

During normal operation of suspension and traction systems, for example elevators, it is desirable that the adhesion between suspension and traction elements and traction pulleys be very high, as this increases the traction capacity. However, there are cases in which it is important to minimize such traction capacity:

1. To avoid the possible winding of the cab outside its nominal travel, it is of interest that in certain cases the cables slide over the tractor pulley. The best known case is the one mentioned in the EN81-1 standard “Counterweight supported by shock absorbers.” The cab being on the upper floor, even though the traction sheave is still moving upwards from the cab, the cable must slide on the pulley so that the cab does not go up, therefore, in this case it is important that the adhesion between the tractor pulley and the cable is low, so that the cable slides and thus avoid accidents.

2. When there is a deflection pulley in the system, the alignment of the cable with respect to the throats of the deflection pulley must be maximum, since any angle of deflection (fleet angle) causes a rotation in the cable that causes torsional stresses unwanted (figures 1a and 1b), especially in the case of cables covered with a polymeric sheath. In practice it is not always possible to totally avoid these deviations. In these cases, the cable when coming into contact with the pulley, first touches one side of the throat (at a higher or lower point depending on the magnitude of the angle of deviation) and then, sliding and rotating, reach the bottom from the throat Cable rotation is undesirable, since there are

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rotations, the cable is subjected to stresses for which it has not been designed. Therefore, it is advantageous that the adhesion between cable and pulley in these cases is minimal, as explained in EP1657208A1.

Another problem known in the state of the art is that which occurs in deflection pulleys due to the unequal tension between the different cables. This difference in tension causes the cables to advance tangentially differently in the throats of the pulley, which can be accentuated due to the adhesion between cable and pulley. This phenomenon is undesirable particularly in coated cables since among other phenomena, noise is produced.

It is therefore desirable to have systems where the adhesion between suspension and traction elements and pulleys is variable and controllable.

The magnetorheological materials respond to the application of a magnetic field with a change in its mechanical behavior and are formed by magnetizable particles in a paramagnetic matrix. This change is due to the magnetic forces caused by the interactions between the magnetic dipoles caused by the application of an external magnetic field.

OBJECT OF THE INVENTION

The object of the present invention is to provide a traction and suspension element whose adhesion can be actively controlled depending on the type of contact (between element and suspension or traction pulley), contact area (function of the pulley diameter, geometry of the throats of the pulley and hugging angle) and the working conditions of the element (normal operation or winding). The suspension and traction element of the invention comprises a load bearing section provided with at least one wire and a sheath that at least partially covers the bearing section, where the sheath comprises a matrix of polymeric and paramagnetic material and dispersed magnetic particles. in said matrix in a proportion of at least 10% by volume, in a preferential example, at least 15%. Preferably, but not necessarily, the particles will be spherical and will have a dimension of between 10 and 105 nm., And the matrix will be made of elastomeric thermoplastic polyurethane. The magnetic particles may be of one or more of the following materials: iron, ferrites, magnetites, garnets, nickel, cobalt, or mixtures thereof. The invention also comprises a system incorporating pulleys and said element, an elevator and an adhesion control procedure.

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BRIEF DESCRIPTION OF THE FIGURES

In order to help a better understanding of the characteristics of the invention in accordance with a preferred example of practical realization thereof, the following description of a set of drawings is attached, where the following has been represented by way of illustration:

Figure 1 illustrates the rotation of a cable in the deflection pulley due to cable deviations.

Figure 2 is an implementation of the invention in the form of a cable.

Figure 3 shows different possible suspension and traction element sections of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As can be seen in Figure 2, the traction and suspension element of the invention comprises a load bearing section (1) totally or partially covered with a sheath of paramagnetic polymeric material (2) to which magnetic grids are added in a proportion of at least 10% by volume.

Within the polymeric materials the matrix will be elastomeric since its elasticity allows the magnetorheological effect to be important. Preferably, a matrix of TPU (elastomeric thermoplastic polyurethane) is used since it exhibits good performance from the point of view of adhesion in cable-pulley systems.

The load bearing section may include a single thread or a plurality thereof, with the same or different characteristics (material, coating, hardness, stiffness ...).

The size of the grids is, preferably but not necessarily, between 10 and 105 nm. They can be acicular, spherical, octahedral, cubic, of scales. In a preferential example, the spherical shape is preferred, since from the point of view of fatigue of the suspension and traction element it presents the best compromise of life-properties.

Figure 2 shows an implementation of the invention in the form of a cable, where the sheath surrounds the supporting section. The supporting section is made up of several strands formed by threads. Figure 3 shows other implementations: a cable where the

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cover not only surrounds the supporting section, but is also present between cords and an implementation where the suspension and traction element is a tape.

The suspension and traction element can be manufactured using different processes. The selection will depend on the type of polymeric material used in the matrix:

- Extrusion process with thermoplastic material with magnetic particles.

- Pultrusion process applied to a polymer matrix with magnetic particles whose curing is carried out with a vulcanizing agent.

- Pultrusion process applied to a polymer matrix with magnetic particles whose curing is carried out at room temperature.

For the complete system, there are the following possibilities (we will refer to cables although the same put into practice are applicable to all types of suspension and traction elements):

Traction Pulley:

During normal operation of an elevator, it is desired that there is good adhesion, so that the entire motor torque is transmitted to the cable. For this, a radial magnetic field (with respect to the pulley) will be applied from inside the pulley by means of the use of an electro-magnet.

However, outside the nominal cab travel, in order to avoid the winding of the car, low adhesion is required. To control the adhesion, electromagnets are placed on the outside of the pulley along an arc of length equal to the length of the cable in contact with the pulley. The length of the cable in contact with the pulley depends on the diameter of the pulley and the angle of hugging.

Deflection Pulley:

In the case of the deflection pulley, it is always interesting that the minimum adhesion. Therefore, the electromagnet will be placed on the outside of the pulley and will surround the cable portion in contact with the pulley, so that a magnetic field is applied perpendicular to it (the same configuration as in the case of the pulley traction in winding conditions).

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For both the traction and deflection pulley, the application of a magnetic field greater than 1 mT in the radial direction of the pulley modifies the cable-pulley adhesion depending on the operating needs.

Since the hardness is a parameter much easier to quantify than the adhesion, tests have been carried out on the first one by applying a magnetic field perpendicular to the suspension and traction element from outside the pulley (deflection pulley). These tests are shown in the following table;

 Material

 Magnetic field Sh A 1 Sh A 2 Sh A 3 Media Sh A

 0% particles

 0 mT 33 33 34 33.33

 15% particles

 0 mT 48 48 45 47.00

 15% particles

 130 mT 55 55 57 55.67

 15% particles

 0 mT (after previous withdrawal) 50 48 48 48.67

 15% particles

 180 mT 55 57 57 56.33

 15% particles

 0 mT (after previous withdrawal) 50 47 45 47.33

The tests were carried out with a suspension and traction element without magnetic particles (first line of the table) and then an element according to the invention was used with 15% of magnetic particles in volume. The hardness measurement according to the Shore A scale was performed three times, obtaining an average to minimize errors. The matrix used was a WACKER Elastosil® M 4644 silicone consisting of two components: silicone (WACKER Elastosil® M 4644 A) and the vulcanizing agent (WACKER Elastosil® M 4644 B). The proportion between the vulcanizer and the matrix is 1:10 respectively. The selection of this matrix is due to the fact that the curing is carried out at room temperature and also, the beginning of said process is controlled with the vulcanizing agent.

The magnetic particles used were iron, CIP (Carbonyl Iron Powder), of an average size of 1.27 ± 0.54 ^ m and shape is spherical.

First, the hardness was studied according to the Shore A scale for an element to which no magnetic field (0mT) was applied. Subsequently, a perpendicular field of 130mT was applied to the element. After removing said field, a measurement was made again. In a fourth step a field was reapplied, this time of 180mT. Finally the field was withdrawn and a last measurement was made. As can be seen, after

the removal of the magnetic field the hardness returns to values very close to the initials. With the application of a field, the hardness increases. As any expert in the field will appreciate, a change in hardness implies a change in stiffness and adhesion.

Claims (10)

5 10 fifteen twenty 25 30 35 1. Suspension and traction element with active adhesion control comprising a load bearing section (1) provided with at least one thread and a sheath (2) that at least partially covers the bearing section, characterized in that the sheath comprises a die of polymeric and paramagnetic material and magnetic particles dispersed in said matrix in a proportion of at least 10% by volume. 2. Suspension element according to claim 1 characterized in that the proportion of magnetic particles is at least 15% by volume. 3. Suspension and traction element according to claims 1 or 2, characterized in that the particles are spherical. 4. Suspension and traction element according to claims 1-3 characterized in that the particles have a dimension between 10 and 105 nm. 5. Suspension and traction element according to any of the preceding claims characterized in that the matrix is made of elastomeric thermoplastic polyurethane. 6. Suspension and traction element according to any of the preceding claims, characterized in that the magnetic particles are of one or more of the following materials: iron, ferrites, magnetites, garnets, nickel, cobalt, or mixtures thereof. 7. Suspension system comprising a traction and / or deflection pulley and a suspension and traction element according to any of the preceding claims, characterized in that the pulley or pulleys are provided on their outer and / or inner part of electromagnets capable of producing a variable magnetic field perpendicular to the suspension element along the entire length of the element in contact with the pulley. 8. System according to claim 7 characterized in that the magnetic field produced by the electromagnets is at least 1mT. 9. Elevator comprising a suspension and traction system according to any of claims 6-8. 10. Procedure for controlling the adhesion to a pulley of a suspension and traction element according to the preceding claims characterized in that a controllable magnetic field is applied perpendicular to the suspension and traction element.