Metal cord and process and apparatus for manufacturing a metal cord

The invention relates to a metal cable and a method for producing a metal rope.

[0002] The invention particularly relates to a metal rope usually used as a reinforcing element in elastomeric products comprising at least one pre-shaped basic metal wire.

[0003] The invention further relates to a method for producing a metal cable.

[0004] The invention also relates to a device for producing a metal rope.

[0005] The above-mentioned metal rope can be used to produce reinforced industrial elastomer products, such as, for example, tires, high-pressure liquid pipes, belts, belt conveyors and the like.

[0006] It is known that metal cables are usually used as reinforcement for industrial elastomer products and are generally made of several basic metal wires, twisted together along an axis coincident with the longitudinal path of the ropes themselves.

[0007] These metal ropes, in particular when used in the manufacture of tires, must have a generally high mechanical strength and should enable to obtain the appropriate physical-chemical adhesion properties to the elastomeric material in which they have been incorporated. In addition, the ropes should have adequate penetration of the space between the adjacent basic metal wires of the metal ropes through the elastomeric material.

[0008] In fact, it is known that in order to avoid the occurrence of an undesirable corrosion phenomenon of metal ropes once they are incorporated into the elastomeric product, it is essential that the basic metal wires forming the metal ropes are completely covered over their entire surface with the elastomeric material.

[0009] Such a solution, which is more difficult to achieve with the use of more complex metal ropes, is not easy to obtain even if there are metal ropes consisting of a small number of basic metal wires.

[0010] In fact, to give the metal ropes the appropriate geometrical and structural stability, the individual metal wires forming the ropes are compacted, i.e. they are located so close to each other as to be in contact. This leads to the formation of at least one closed hollow area within these steel ropes, which extends over its length.

[0011] These voids are closed and are therefore inaccessible to the elastomeric material during the standard phases of rubberizing the wire rope. As a result, corrosion can occur inside these cavities and spread along the length of individual wires that make up the rope.

Thus, this means that, for example, as a result of the formation of cuts in the reinforced elastomer material of the product, moisture and / or other external factors can enter these closed voids, inevitably causing the corrosion process of the basic steel wires to accelerate, to a serious extent thus deteriorating the structural strength of the wire ropes themselves and, as a consequence, also the reinforced elastomeric product.

[0013] Furthermore, the presence of these inaccessible, closed to elastomeric materials means the reduction of the contact surface of the metal wires with the elastomeric material, which may cause an unwanted tendency for the wires to separate from the elastomeric material.

[0014] An additional disadvantage resulting from the insufficient surrounding of the metal wires with the rubber material as a result of the formation of these voids is the galling corrosion of the metal wires as a result of their mutual contact. This phenomenon causes the inevitable reduction of fatigue strength of metal wires and consequently of metal ropes.

[0015] It has already been attempted in the field of the above-mentioned attempts to solve the above-mentioned problems.

[0016] For example, the use of so-called "open" ropes has already been described. In these "open" ropes, metal wires (typically three to five) are loosely connected and spaced apart, and the distance is kept constant during the guming phase, e.g. by attaching a small load to the rope (usually not exceeding five kilograms).

[0017] Ropes of the type described above, i.e. so-called "open" ropes, are disclosed, for example, in US Pat. No. 4,258, 543 to the applicant. The ropes described in it are designed to allow excellent penetration of the elastomeric material into spaces between adjacent metal wires forming ropes.

[0018] International patent application WO 95/16816 relates to a steel rope comprising steel fibers, wherein at least one of said steel fibers is polygonal. This steel rope is to be characterized by full penetration of the rubber material and low elongation at partial load.

[0019] International patent application WO 99/28547 relates to a steel rope comprising at least one steel fiber, wherein at least one of said steel fibers is corrugated in one plane and in a second plane substantially different from the first corrugated plane. These steel ropes are to be characterized by a better penetration of the rubber material or a greater elongation at break.

U.S. Patent No. 6, 698, 179 to the Applicant relates to a method for producing a wire rope comprising the step of permanently deforming the at least one wire to a substantially sinusoidal form in one plane, by splicing at least one wire with at least one other wire by twisting the wires. along the longitudinal axis of the wire ropes and with the rope obtained. This metal rope is to be characterized by a good penetration of the rubber material and a better elongation at break.

[0021] However, the metal ropes described above have certain disadvantages.

For example, in the case of so-called "open" ropes, the stresses to which they are subjected before they reach the device responsible for rubberizing may cause compaction of the wires relative to each other, thus impeding the penetration of areas between adjacent wires of steel ropes through the elastomeric material . As a result, despite the high elongation at partial load, i.e. a high elongation value for small loads (less than or equal to 50N), these ropes may not allow adequate penetration of the elastomeric material, causing corrosion of the metal wires, thereby seriously limiting the structural strength both ropes as well as reinforced elastomeric products containing metal ropes.

[0023] On the other hand, metallic ropes known in the art, such as, for example, the ropes disclosed in international patent application WO 95/16816, WO 99/28547 or in US patent 6 698 179 as described above, although they are characterized by high value of elongation at break and good penetration of the elastomeric material, may show a low value of elongation at partial load. This low value of elongation at partial load can cause problems when producing reinforced elastomeric products containing these ropes, particularly when used in the manufacture of tires, wherein particularly favorable values ​​for elongation of metal ropes are required in particular production steps.

[0024] Furthermore, the applicant has observed that after the vulcanization and vulcanisation of the metal ropes, the values ​​of both elongation at break and elongation at partial load are significantly reduced.

The applicant has now invented a metal wire comprising at least one metallic base wire characterized by both a high elongation at break and a high value of elongation at partial load, these features essentially unaffected even after rubberizing and vulcanizing the metal cable. . Furthermore, this steel rope is characterized by a better penetration of space between adjacent metal primary wires forming a metal rope through the elastomeric material.

[0026] According to a first subject, the invention relates to a metal wire according to claim 1.

[0027] According to the invention, this metal rope comprises at least one preformed metal primary wire, while the remaining primary wires forming this metal rope do not have to be pre-shaped. Before their initial design, the metallic primary wires are straight in shape.

For the purposes of this description and the description of the claims below, the term "preform" means the distortion of the metal primary wire along its longitudinal axis by applying at substantially equal intervals lateral forces greater than the elastic limit of the material from which the basic metal wires have been made for the distortion to be permanent after deducting the applied force.

[0029] This metallic base wire is pre-shaped so as to obtain a substantially sinusoidal wave shape; then this pre-shaped metal base wire is spirally shaped along its longitudinal axis so that it obtains a wave-spiral shape (henceforth referred to as a "doubly pre-shaped metallic wire"). The result of this double preform is a metal wire shaped in three dimensions.

[0030] According to a preferred embodiment, these sine waves have a length (or pitch) of 1.0 mm to 15 mm, more preferably of 2.0 mm to 8.0 mm.

[0031] According to a further advantageous embodiment, these sine waves have an amplitude of 0.10 mm to 1.0 mm, more preferably from 0.20 mm to 0.50 mm.

[0032] The ranges of the wavelengths and amplitudes discussed above can be measured directly on a non-silent, metal base wire before it is introduced into the elastomeric material to be subsequently vulcanised. It is advantageous to measure these parameters on a metal primary wire using magnifying lenses and graduations (for example a ruler scale). If it is necessary to investigate an industrial vulcanized product with reinforcement, it is necessary to remove the elastomeric material with solvents, for example by using dichlorobenzene at a temperature of at least 100 ° C, preferably 140 ° C, for at least 12 hours.

[0033] According to a preferred embodiment, the metallic base wire has a diameter (D) from 0.10 mm to 0.50 mm, preferably from 0.12 to 0.40 mm.

[0034] According to a preferred embodiment, the metallic base wire is made of steel. Where the diameter of the metallic base wire is between 0.10 mm and 0.50 mm, the tensile strength of standard tensile strength steel (NT) ranges from approximately 2 600 N / mm² (or 2,600 MPa - megapascals) up to about 3,200 N / mm2, the tensile strength of high tenacity steel (HT) ranges from about 3,000 N / mm2 to about 3,600 N / mm2, the tensile strength of steel with a very high tensile strength (SHT) in the range from approximately 3,300 N / mm2 to approximately 3,900 N / mm2, the breaking strength of ultra high tensile steel (UHT) is in the range of approximately 3,600 N / mm2 up to approximately 4,200 N / mm2. The above values ​​of breaking strength depend in particular on the amount of carbon contained in the steel. The above-described types of basic metal wires HT, SHT, UHT are preferably made of steel with a very high carbon content, usually greater than 0.9%.

[0035] Generally, this metallic base wire is covered with a brass coating (Cu from 60% to 75% by weight, Zn from 40% to 25% by weight) with a thickness of 0.10 to 0.50 gm. The above coating provides better adhesion of the metal base wire to the rubberized compound as well as protecting the metal against corrosion, both during the manufacture of reinforced elastomer industrial articles as well as during their operation. If it is necessary to provide a higher degree of corrosion protection, this metal base wire can be used to improve the coating properties with an anti-corrosive coating other than brass, which is able to provide better corrosion resistance, such as zinc-based coating, zinc-manganese alloys (ZnMn), zinc-cobalt (ZnCo), or zinc-cobalt-manganese (ZnCoMn).

[0036] According to a preferred embodiment, the metal rope has a structure of type nx D, where n is the number of metallic primary wires forming the rope and D is the diameter of each metallic base wire. The number n is preferably from 2 to 6. Particularly preferred is n equal to 5.

Preferred constructions of steel ropes are, for example, 2x (i.e., two metal basic wires twisted with each other), 3x, 4x, 5x, 6x, 2 + 1 (i.e. one weave of two metal wires and one weave with one metal wire, both strands twisted together), 2 + 2, 3 + 2, 1 + 4.

[0038] According to a preferred embodiment, the length of the weave of this metal rope is between 2.5 mm and 25 mm, more preferably between 6 mm and 18 mm.

[0039] According to a preferred embodiment, this metal rope has the following features:

- a gap field that satisfies the following equation:

gap field> nD²/ 4 where D is the diameter of the metal base wire,

- the sum of the distances between each pair of adjacent metal primary wires in cross-section (£ sn) that satisfies the following equation:

Zsn> D / 2 where n is the number of metallic primary wires, D is the diameter of the metallic base wire;

and the above features are fixed along the entire length of the metal rope.

For the purposes of this description and the claims below, the term "fracture field" means an area in the cross-sectional area of ​​the rope, bounded by polygonal segments connected together, in which the end points of each segment are located on the outer peripheries adjacent to each other. metal basic wires.

For purposes of this description and description of the claims below, the term "distance between each pair of adjacent metal primary wires" means the distance calculated as follows:

S = 1 - (r + r ') where 1 is the distance between the centers of the cross-sections of two adjacent metal base wires, r and r' are radii of cross-sections of two adjacent metal base wires. Preferably, the rir 'rays have the same value.

According to a further object, the invention relates to a method for producing a metal rope, comprising the steps of:

(a) permanently deflecting at least one metallic base wire to obtain a substantially sinusoidal deformation located in a plane comprising a pre-shaped metallic wire;

(b) permanently deforming the preformed metal base wire obtained in step (a) in a spiral form along its longitudinal axis, thereby obtaining twice a pre-shaped metallic base wire;

(c) a braiding of at least twice the preformed metal base wire obtained in step (b) with at least one additional metallic base wire by twisting, thereby obtaining a metal wire.

[0043] The preformed metal wire obtained in steps (a) and (b) is substantially free of any sharp edges and / or discontinuities of curvatures over its entire length. The above feature is particularly advantageous because the absence of sharp edges / corners results in a favorable increase in the breaking load value of the metal primary wire.

According to a further object, the invention also relates to a device for producing a metal rope comprising:

- at least one rotor attached to the supporting structure and rotating around the axis of rotation,

- feeding devices for feeding a plurality of metal basic wires from individual feed rolls, said metal primary wires being fed to the rotor in accordance with the splice route, the end sections of which are convergent with the axis of rotation of the rotor and the central section being offset from this axis of rotation,

- at least one device for a first pre-formation, arranged in a section before the first end section of the braiding route, for machining one of said metallic base wires, said at least one first pre-formating device providing said metal base wire with a substantially sinusoidal deformation,

- at least one device for a second preform, arranged downstream of said first pre-configuration device, upstream of the first end section of the splice path, for machining the same metal base wire, wherein the at least one second preform provides this metal the basic wire has a permanent deformation substantially spiral along its longitudinal axis.

[0045] This device may comprise at least one device for a first pre-formation for each metal wire of a base metal cable.

[0046] According to a further advantageous embodiment, the at least one first pre-formation device comprises first and second pulleys, each pulley having a plurality of pins arranged circumferentially, the pulleys being spaced apart such that during their rotation, the pins of the first and second wheels mutually overlap to cause a substantially sinusoidal deformation without the sharp edges of the wire extending through the space between the pins of the first wheel and the corresponding pins of the other wheel.

[0047] According to a preferred embodiment, the at least one second pre-forming device comprises a pulley and a pivot pin, the pivot pin being positioned between this pulley and the first end section of the braiding route so that the inside angle (α) formed between the entry of the metal primary wire to the pivot pin and the output of the metal base wire from the pivot pin is less than or equal to 180 °, preferably from 45 ° to 90 °. Preferably, the pivot pin may have at least one groove, more preferably a plurality of parallel grooves. Preferably, the pulley is adjustable.

[0048] This device may comprise at least one device for a second pre-formation for each metallic base wire.

[0049] Further features and advantages of the invention will be better explained by the following detailed description of some preferred embodiments thereof, presented with reference to the accompanying drawings, wherein:

- Fig. 1 shows a side view of the device according to the invention,

- Figures 2a and 2b show the details of the second pre-embodiment device according to the invention in the form of a partial top view,

- Fig. 3 shows a cross section of a metal cable according to one embodiment of the invention,

- Fig. 4 is a photograph of a top view of a metal rope according to the invention

- Fig. 5 shows the elongation at partial load for different metal ropes.

[0050] With reference to Figure 1, the reference mark 1 means the metal rope 1. The metal rope 1, as stated above, comprises several metal primary wires (not shown in Figure 1), preferably made of steel, and more preferably covered with a brass coating. , with a diameter (D) ranging from 0.10 mm to 0.50 mm, preferably from 0.12 mm to 0.40 mm, twisted along the longitudinal axis of the metal cable.

[0051] The characteristic and constructive features of the steel rope 1 according to the invention will be better understood in the form of the following description, both with respect to the device used for its manufacture and the procedure for its production.

[0052] Fig. 1 shows an example of a device 10 for shaping a metal rope 1 comprising five metal primary wires.

[0053] The apparatus 10 for producing the metal rope 1 in a known configuration comprises a support structure 100 into which the rotor 5 is rotatably mounted. The latter is rotated by means of a motor or similar device (not visible in fig. 1). Furthermore, a cradle (not visible in FIG. 1) is fastened to this support structure, which can sway around the rotational axis of the rotor 5. Several feed rollers 8 are connected to the cradle, allowing their operation. One or more metal primary wires of a metal rope 1 are wound onto each of the feed rollers 8.

Furthermore, the developing devices (not visible in FIG. 1, as they are considered to be obvious and contractual) are connected to feed rollers 8, which are mounted on the cradle to guide metal primary wires exiting the feed rollers 8.

The basic metal wires are routed in a known manner from the cradle mouth to the rotor 5 according to the previously determined braiding route, along which the metal rope 1 is shaped by rotor 5 being rotated by means of the above-mentioned motor or equivalent device, in combination with the movement of the metal wire 1 caused by the receiving devices (not visible in Fig. 1 because they are known and not included in the scope of the invention).

[0056] More specifically, the braiding route comprises a first terminal section 10a substantially coincident with the axis of rotation of the rotor 5, the limit of which is determined by the first rotary conveyor device 12 directly attached to the rotor 5 and the assembly 11 in a known manner consisting of a five-hole plate directly mounted to the cradle and consequently immobile.

During the course of the first end section 10a, the metal primary wires are subjected to the first twisting about the rotational axis of the rotor 5 by stretching and rotation, which the rotor 5 exerts on the first rotatable transmission device 12.

After passing the first rotary conveyor device 12, the metallic primary wires extend along a central section of the splice route 10b which has a beginning on the rotor 5 and which is arranged radially around the axis of rotation of the rotor to omit the cradle (not visible in FIG. 1) and which this section closes the second rotary conveyor device 13 directly attached to the rotor 5 on the opposite side of the axis.

[0059] Finally, the braiding route also includes a second end section 10c substantially coincident with the axis of rotation of the rotor 5 and terminating after the second rotatable transfer device 13. At this second end section, as a result of the tensile and rotational forces induced by the rotor 5 on the second rotary the conveying device 13, a second twisting of the basic wires follows, thus terminating the shaping of the metal rope 1, which is gradually extended from the device through the above-mentioned receiving devices.

[0060] The ratio between the rotation speed of the rotor 5, preferably from 2000 rpm to

6000 rpm, and the speed of pulling the metal rope 1 and consistently the metal primary wires forming this rope, preferably between 60 m / min and 250 m / min, determines the length of the weave, i.e. the length of the weave, according to which the metal basic wires are twisted made of metal rope 1.

Preferably, this weave length is maintained at a value between 2.5 mm and 25 mm, preferably between 6 mm and 18 mm.

The following elements are functionally arranged in order for each metallic base wire along the path of the metallic primary wires within the cradle, and more particularly in front of the assembly 11: input alignment pulleys 14, first pre-forming devices 15, output alignment pulley 16 comprising a wheel rotated by 90 ° relative to the pair of pulleys at the first pre-forming device. This rotated pulley is intended to bring the metallic primary wires exiting from the first pre-forming devices 15 to the second preform apparatus, comprising an adjustable pulley 17 and a rotating peg 18 according to the invention (shown in detail in Fig. 2a and Fig. 2b) . In FIG.

At the end of the pivot pin 18, the metallic base wires are transferred to the assembly 11. Optionally, a second output pulley may be provided between the pivot pin 18 and the assembly assembly (not shown in Fig. 1).

[0064] A detailed description of the first preforming device can be found in the above-described US Patent No. 6, 698, 179.

[0065] Fig. 2a shows a partial top view of a pivot pin 18 of a second pre-embodiment device according to the invention comprising a plurality of grooves. Reference mark 201 means five metallic primary wires exiting from the adjustable pulley 17. This rotating stud is preferably made of steel.

Fig. 2b is a partial top view of the second embodiment of the device according to the invention comprising an adjustable pulley 17 and a pivot pin 18, wherein A is the distance between the central axis of the adjustable pulley 17 and the central axis of the pivot pin 18, where the distance is preferably is from 5 mm to 50 mm, d is the cross-sectional diameter of the pivot pin 18, where the diameter is preferably from 1 mm to 10 mm and (α) is the internal angle formed between the entry of the metal base wire and the pivot pin the basic wire from the pivot pin. By changing both the distance A, the diameter d and the internal angle (α), it is possible to obtain metal primary wires with different wavelength and wave amplitude. Also in FIG.

[0067] Finally, the device 10 comprises a tensioning device (capstan), a device for receiving the produced wire rope and typical devices for straightening metal primary wires, such as a torsion device, which serve to eliminate residual stresses present in the steel line being made. These devices are not shown in Fig. 1 because they are known, typical and not particularly relevant to the invention.

[0068] The first and second pre-formers according to the invention can be used together with all known splice systems, for example with a twofold twist system or with an arrangement system. In particular, a twofold twisting system may allow internal reception (if the roller receiving the finished products is located inside the cradle, between the rotors) or external reception (if the feed rollers are inside the cradle, while the receiving roll of the finished products is located on the outside of the cradle). On the other hand, the distributed system differs from a double twisting system in that every rotating machine corresponds to one weave length, whereas in a twisting system two rotors turn one increment equal to two weave lengths.

[0069] As noted earlier, the metallic primary wire preferably has a wavelength (or plexus length) of 1.0 mm to 15 mm, more preferably of 2.0 mm to 8.0 mm and a wave amplitude of 0.10 mm to 1. , 0 mm, more preferably from 0.20 mm to 0.50 mm.

[0070] Fig. 3 shows a cross-section of a 5 x 0.25 metal cable (i.e. five base metal wires 0.25 mm in diameter, braided together and forming a metal rope), where h, l, l, u and l5 means the distances between the centers of two adjacent metal primary wires in the cross-section, s1, s2, s3, s4 and s5 are the distances between each pair of adjacent metal primary wires in cross-section, this is the area of ​​the gap. In the particular embodiment shown in Fig. 3, all metallic primary wires have the same diameter D (not visible in Fig. 3).

[0071] Fig. 4 is a photographic illustration of a particular embodiment of a metal rope according to the invention, wherein the metal rope comprises five double pre-shaped metal primary wires.

[0072] The invention is further illustrated below by means of exemplary illustrations presented only for demonstrations, without limiting the scope of the invention. EXAMPLES 1-3 [0073] Three different steel ropes were tested with the following features.

Example 1: 5 x 0.25 steel wire, where all five steel primary wires have been doubly pre-shaped according to the invention,

Example 2 (comparative): 5 x 0.25 "steel" wire rope (OC),

Example 3 (comparative): 3 x 3 x 0.20 steel rope with a high HE elongation

HT [0074] A breaking load, elongation at break and elongation at partial load for a force of 50 N, both for a bare wire rope and for a rubberized / vulcanized rope (i.e. a steel wire which has been previously incorporated into the elastomeric material and subjected to the test) was tested. vulcanization according to methods compatible with art). The above measurements were carried out according to the BISFA method as above, and the data obtained are presented in Table 1.

[0075] Elongation at partial load for 50 N was defined as an increase in the length of the wire rope due to the wire rope being subjected to a force of 50 N and expressed as a percentage of the initial pre-tensioned rope pre-tension (e.g. 2.5 N) .

[0076] In a particular case of a rubberized / vulcanized steel rope, a strip of rubberized fabric reinforced with steel ropes spaced at 100 lin / dm was used.

Table 1

<td rowspan="2"></td><td>Example 1</td><td>Example 2^(and)</td><td>Example 3^(and)</td><td>Example 1</td><td>Example 2^(and)</td><td>Przykład_3 (^and)</td>

<td colspan="3">The rope was bare</td><td colspan="2">Lina gumowana / wu</td><td>kanizowana</td>

<td>Length plexus (Mm)</td><td>12.5 S</td><td>10 S.</td><td>3.15 / 6.3 S / S</td><td>12.5 S</td><td>10 S.</td><td>3.15 / 6.3 S / S</td>

<td>Load Breaking?) (N)</td><td>602</td><td>698</td><td>780</td><td>598</td><td>703</td><td>790</td>

<td>Elongation p^governmenty * break⁽*) (MPa)</td><td>4.25</td><td>2.49</td><td>3.55</td><td>4.15</td><td>1.50</td><td>3.00</td>

<td>Elongation p^governments partial load for 50 N (%)⁽**)</td><td>0.557</td><td>0.492</td><td>1,155</td><td>0.552</td><td>0.256</td><td>0.967</td>

<td colspan="7">(a): comparative, (*): the BISFA E6 method, 5 (**): BISFA E7.</td>

[0077] The analysis of the data shown in Table 1 showed that the steel rope according to the invention (example 1) is characterized by both high elongation at break and high elongation at partial load and that these features are also maintained for the rubberized / vulcanized rope.

EXAMPLES 4-5 [0078] Two different steel ropes were tested with the following features.

Example 4: 5 x 0.25 steel wire, all five of the basic steel wires being doubly pre-shaped according to the invention, Example 5 (comparative): 5 x 0.25 coplanar steel rope, obtained by the method of the above-mentioned US 6 patent 698 179.

[0079] Break load, elongation at break and elongation at partial load were measured for bare steel wire: measurements were made according to the BISFA method as described above, and the data obtained are shown in table 2.

[0080] The elongation values ​​for the partial load are also given in Fig. 5, where the load value (expressed in kN) is given on the y axis and the elongation (%) is given on the x axis. In Figure 5, curve A corresponds to example 5 (comparative) and curve B corresponds to example 4 according to the invention.

In addition, the above-mentioned wire ropes have been subjected to an attempt to penetrate a rubber material that measures the degree of penetration of the elastomeric material after the rubberization of the area between the steel wires forming the ropes and consequently to the quality of the elastomer coating around each of these steel wires. At the bottom of the bowl containing the ethyl alcohol, an inverted funnel is preferably made of glass. The funnel had a scale along the cylinder-shaped shaft and was equipped with a suction device positioned at the free end of the funnel and basically operated by the operator. Switching on the suction unit resulted in raising the ethyl alcohol in the cylindrical body until reaching a predetermined level, called the zero level. During this stage, a test sample consisting of the 5 cm x 5 cm belt described above was immersed in the bowl, which was then placed at the inlet to the funnel. Ethyl alcohol has the property of stripping the air that may be in the elastomer material and take up its space. This fact caused the reduction of the level of ethyl alcohol in the shaft with the scale in relation to this zero level. This measurement allowed to determine the volume of air contained in the elastomeric material into which the steel wires are embedded and, consequently, to determine the degree of penetration through the rubber area between the steel wires forming the steel rope. Ethyl alcohol has the property of stripping the air that may be in the elastomer material and take up its space. This fact caused the reduction of the level of ethyl alcohol in the shaft with the scale in relation to this zero level. This measurement allowed to determine the volume of air contained in the elastomeric material into which the steel wires are embedded and, consequently, to determine the degree of penetration through the rubber area between the steel wires forming the steel rope. Ethyl alcohol has the property of stripping the air that may be in the elastomer material and take up its space. This fact caused the reduction of the level of ethyl alcohol in the shaft with the scale in relation to this zero level. This measurement allowed to determine the volume of air contained in the elastomeric material into which the steel wires are embedded and, consequently, to determine the degree of penetration through the rubber area between the steel wires forming the steel rope.

Table 2

<td></td><td>Example 4</td><td>Example 5^(and)</td>

<td>Length of the weave (mm)</td><td>12.5 S</td><td>12.5 S</td>

<td>Breaking load · * (N)</td><td>596</td><td>558</td>

<td>Elongation at break · * (MPa)</td><td>4.20</td><td>4.04</td>

<td>Elongation at partial load for 50 N (%) (**&gt;</td><td>0.605</td><td>0,240</td>

<td>Penetration of rubber (mm³/ cm rope)</td><td>0.28</td><td>0.10</td>

<td colspan="3">(a): comparative, (*): the BISFA E6 method, (**): BISFA E7.</td>

[0082] Analysis of the data shown in Table 2 showed that the steel rope according to the invention (example 4) has better mechanical characteristics (especially elongation at partial load - see also Fig. 5) than the steel cable according to the prior art (example 5). In addition, the steel rope according to the invention (example 4) is characterized by a better penetration through the rubber material than the steel rope according to the prior art (example 5). EXAMPLE 6 [0083] A 5 x 0.25 steel rope with a weave length (mm) of 12.5 S, all five basic steel wires being doubly pre-shaped according to the invention, has been measured both at the angle of the gap (PS) as and the sum of the distances between each pair of adjacent metal primary wires in a cross-section (£ s_n).

[0084] To this end, three different sections (A to C) were randomly selected on the length of the steel wire (each section had a length corresponding to three weave lengths). Five cross-sections were sequentially made in each section (in particular one length of the weave of each section was subjected to five cross-sections of the same length), and for each cross-section the above-mentioned measurements were made. The measurements were made using a magnifying lens and a graduated ruler: the obtained data is presented in Table 3.

Table 3

<td>AND</td><td>B</td><td>C</td>

<td>(PS) = 0.325 (Zsj) = 1.0 x nd²/ 4</td><td>(PS) = 0.950 (Zsj) = 3.0 x nd^:/ 4</td><td>(PS) = 0.525 (Zsj) = 2.0 x nd^:/ 4</td>

<td>(PS) = 0.900 (Zsj) = 2.0 x nd²/ 4</td><td>(PS) = 0.650 (Zsj) = 2.0 x nd^:/ 4</td><td>(PS) = 0.450 (Zsj) = 1.5 x nd^:/ 4</td>

<td>(PS) = 0.755 (Zsj) = 2.0 x nd²/ 4</td><td>(PS) = 0.325 (Zsj) = 1.5 x nd^:/ 4</td><td>(PS) = 0.450 (Zsj) = 1.5 x nd^:/ 4</td>

<td>(PS) = 0.200 (Zsj) = 1.0 x nd^:/ 4</td><td>(PS) = 0.450 (Zsj) = 1.5 x nd^:/ 4</td><td>(PS) = 0.675 (Zsj) = 2.0 x nd^:/ 4</td>

<td>(PS) = 0.625 (Zsj) = 2.0 x nd^:/ 4</td><td>(PS) = 0.450 (Zsj) = 1.5 x nd^:/ 4</td><td>(PS) = 0.650 (Zsj) = 2.0 x nd^:/ 4</td>

[0085] The analysis of the data shown in Table 3 showed that the steel cable according to the invention retains the features described above, i.e. the gap area (PS) and the sum of the distances between each pair of adjacent metal primary wires in cross-section (£ sn), throughout its length.

Grażyna Palka Patent attorney