Description

Technical Field

[1] The invention relates to a rope for use in a hoisting system or for use as control cable in a drive system such as a window elevator system.

Background Art

[2] Ropes for use in hoisting systems or in window elevator systems must meet several high-level standards. These ropes must have a long life time since they are subjected to repeated bends and these ropes must be corrosion resistant since they often have to operate in aggressive environments.

[3] A rope which has become the benchmark in the industry has following construction: 19 + 8x7, this means a core strand of nineteen steel filaments and eight strands of each seven steel filaments.

Disclosure of Invention

[4] The primary object of the invention is to provide an alternative rope which is cheaper than the 19 + 8x7 rope construction.

[5] Another object of the invention is to provide a rope which has a long life time.

[6] Still another object of the invention is to provide a rope which has good penetration for a thermoplastic or for an elastomer.

[7] According a first aspect of the invention there is provided a rope for use in a hoisting system or for use in drive system such as a window elevator system. The rope comprises a core strand and only seven layer strands. These seven layer strands are twisted around the core strand and form an unsaturated layer around the core strand.

[8] The terms "unsaturated layer" refer to a layer around the core strand where penetration of an elastomer or a polymer is possible during a normal extrusion process.

[9] The use of only seven layer strands allows to reduce the diameter of the core strand and at the same time to reduce the number of strand twisting steps. In this way a cheaper rope can be made.

[10] The formation of an unsaturated layer around the core strand allows thermoplastics or elastomers to penetrate. This penetration has a triple effect. First of all, the rope becomes mechanically anchored in the thermoplastic or elastomer. Secondly the thermoplastic or elastomer provides corrosion protection for the rope, in addition to the corrosion protection already offered by the individual coatings on the filaments of the rope. Thirdly, in operation, the thermoplastic or the elastomer functions as a type of cushion between two neighbouring layer strands and thus avoid or at least mitigate any fretting of these two neighbouring strands.

[1 1] In a preferable embodiment of the first aspect of the invention, at least one of the layer strands and most preferably all of the layer strands comprise one steel filament functioning as core of the layer strand and six steel filaments twisted around this one steel filament.

[12] In order to further increase the degree of penetration for polymers or elastomers, most preferably the one steel filament has a filament diameter d ₃ and the six steel filaments each have the same filament diameter d ₄ , and d ₄ is smaller than d ₃ in order to create an unsaturated layer around the one steel filament. The difference between d ₃ and d ₄ is preferably greater than 0.01 mm. Due to the unsaturated layer in the layer strands the polymer or the elastomer not only penetrates between the layer strands but also inside the layer strands. In addition, since this unsaturated layer has been reached by decreasing the diameter of the steel filaments in the layer and these steel filaments are the filaments positioned at the radially outer side of a cross -section of the rope according to the invention, the life time of the rope is increased, since bending stresses created in thin filament are smaller than bending stresses created in a thick filament.

[13] According to a preferable embodiment of the first aspect, the core strand has three steel filaments functioning as core of the core strand and nine steel filaments twisted around the three steel filaments.

[14] In order to further increase the degree of penetration for polymers or elastomers, most preferably the three steel filaments have a diameter di and the nine steel filaments all have a diameter d2, and d2 is smaller than di in order to create an unsaturated layer around the three steel filaments. Preferably the difference between di and d2 is greater than 0.01 mm. Due to the unsaturated layer in the core strand the polymer or elastomer also penetrates inside the core strand.

[15] A preferred embodiment of the rope according to the first aspect of the invention has following construction: 3xdi + 9xd ₂ + 7 x (lxd ₃ + 6xd ₄ )

[16] Preferably the filament diameter d ₃ is smaller than or equal to di and greater than or equal to d ₂ .

[17] So summarizing the preferred relationships between the four filament diameters of a 3xdi + 9xd ₂ + 7 x (lxd ₃ + 6xd ₄ ) construction: d ₃ > d ₄

3xdi + 9xd ₂ + 7 x (lxd ₃ + 6xd ₄ )

The two preferable embodiments are:

di = d ₃ and d ₂ = d ₃

since this choice allows the reduce the number of different filaments.

[18] Preferably the diameters di, d ₂ , d ₃ and d ₄ are all ranging from 0.08 mm to 0.26 mm, most preferably from 0.10 mm to 0.24 mm, e.g. from 0.10 mm to 0.22 mm. The small filament diameter guarantees a high resistance against fatigue and a long life time.

[19] In a preferable embodiment, the directions of lay of the rope according to the first aspect are either SSZS or ZZSZ. This means following two embodiments:

3xdi + 9xd ₂ + 7 x (lxd ₃ + 6xd ₄ )

S S S Z

z z z s

The layer strands are individually twisted in a direction opposite to the twisting of the layer strands around the core strand.

[20] In order to provide a resistance against corrosion, the filaments of the layer strands of the rope and preferably all the filaments of the rope are provided with a corrosion-resistant coating such as a zinc or zinc alloy coating. The zinc alloy coating may be a zinc aluminium coating. A zinc aluminium coating may have an aluminium content ranging from 2 per cent by weight to 12 per cent by weight, e.g. ranging from 3 % to 11%, e.g. around 5 % or around 10%, the remainder being zinc. Instead of zinc a tin (Sn) may also be applied.

[21] In order to further increase the corrosion resistance the steel filaments may have magnesium oxide particles in a liquid carrier on their surface.

[22] Alternatively to the magnesium oxide particles, the rope may further comprise a coating of a thermoplastic or an elastomer. Examples of suitable thermoplastic materials are : polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyethylene napthalate (PEN), polybuteen terephthalate (PBT) polyvinylchloride (PVC), polyamide (PA), polyester (PES), polyimide (PI), polycarbonate (PC) , styrene acrilonitryl (SAN), acrylonitril- butadiene-styrene (ABS), thermoplastic polyurethane (TPU), thermoplastic polyolefins (TPO), thermoplastic copolyetheresters , copolymers of these polymers or similar materials. A preferable elastomer is a polyurethane.

[23] The rope as such, coated with a thermoplastic or elastomer or not coated, may be used in a hoisting system such as an elevator for persons or for goods.

[24] According a second aspect of the invention, there is provided a hoisting belt. This belt has a polymer or an elastomer as matrix material. The belt further comprises one or more ropes according to the first aspect of the invention. These one or more ropes function as reinforcing elements and load bearing elements of the belt.

[25] According to a third aspect of the invention, there is provided a drive system such as a window elevator in a car door, a drive system for a sliding door, or a canvas roof drive, or a garage door opener drive system. This drive system has a rope according to the first aspect of the invention to function as a transmission member or a control element.

Brief Description of Figures in the Drawings

[26] Figure 1 is a cross-section of an uncoated rope according to the first aspect of the invention.

[27] Figure 2 is a cross-section of a coated rope according to the first aspect of the invention.

[28] Figure 3 illustrates a window elevator system according to the third aspect of the invention.

[29] Figure 4 is a cross-section of a hoisting belt according to the second aspect of the invention.

Mode(s) for Carrying Out the Invention

[30] Starting material to manufacture a rope according to the first aspect of the invention is a steel wire rod with a composition along following lines: a minimum carbon content of 0.65%, a manganese content ranging from 0.40% to 0.70%, a silicon content ranging from 0.15% to 0.30%, a maximum sulfur content of 0.03%, a maximum phosphorus content of 0.30%, all percentages being percentages by weight.

Usually the carbon content is less than 1.10%. Common percentages for carbon are 0.70% and 0.80%.

[31] One or more of the following elements may be added to the steel composition:

- chromium (%Cr): in amounts ranging from 0.10% to 1.0%, e.g. from 0.10 to 0.50%;

- nickel (%Ni): in amounts ranging from 0.05% to 2.0%, e.g. from 0.10% to 0.60%;

- cobalt (%Co): in amounts ranging from 0.05% to 3.0%; e.g. from 0.10% to 0.60%;

- vanadium (%V): in amounts ranging from 0.05% to 1.0%, e.g. from 0.05% to 0.30%;

- molybdenum (%Mo): in amounts ranging from 0.05% to 0.60%, e.g. from 0.10% to 0.30%;

- copper (%Cu): in amounts ranging from 0.10% to 0.40%, e.g. from 0.15% to 0.30%;

- boron (%B): in amounts ranging from 0.001% to 0.010%, e.g. from 0.002% to 0.006%;

- niobium (%Nb): in amounts ranging from 0.001% to 0.50%, e.g. from 0.02% to 0.05%;

- titanium (%Ti): in amounts ranging from 0.001% to 0.50%, e.g. from 0.001% to 0.010%;

- antimony (%Sb): in amounts ranging from 0.0005% to 0.08%, e.g. from 0.0005% to 0.05%;

- calcium (%Ca): in amounts ranging from 0.001% to 0.05%, e.g. from 0.0001% to 0.01%;

- tungsten (%W): e.g. in an amount of about 0.20%;

- zirconium (%Zr): e.g. in an amount ranging from 0.01% to 0.10%;

- aluminum (%A1): preferably in amounts lower than 0.035%, e.g. lower than 0.015%, e.g. lower than 0.005%;

- nitrogen (%N): in amounts less than 0.005%;

- rare earth metals (%REM): in amounts ranging from 0.010% to 0.050%.

[32] The wire rod is cold drawn to the desired filament diameters in various subsequent cold drawing steps. The subsequent cold drawing steps may be alternated by one or more suitable thermal treatments such as patenting, in order to allow for further drawing.

[33] A corrosion resistant coating such as a zinc or zinc alloy coating may be provided at the level of the end drawn final steel filament or as an intermediate step at an intermediate diameter before the final drawing operations.

[34] The zinc coating may be applied by means of an electroplating process or by means of a hot dip process. Preferably a hot dip process as described in WO-A1-2001/86058 or in WO-A1- 2008/101831 may be applied as this provides a thin zinc layer with a good anchorage to the steel filaments thanks to the zinc -iron alloy between the steel and the zinc.

[35] The resistance against corrosion may be further increased by treating the steel filaments with a liquid carrier such as an aliphatic mineral containing magnesium oxide particles, as disclosed in WO-A1- 2007/071340.

[36] Having reached the various final filament diameters, the rope according to the first aspect of the invention is made in following steps:

1. Twisting of three steel filaments of the core of the core strand:

2. Twisting of nine steel filaments around the three twisted steel filaments to form the core strand: 3xdi + 9xd ₂ ;

3. Twisting of seven layer strands, i.e. twisting six steel filaments around a central steel filament lxd ₃ + 6xd ₄ ;

4. Finally twisting the seven layer strands around the core strand: 3xdi + 9xd ₂ + 7 x (lxd ₃ + 6xd ₄ ).

The various twisting steps may be done by means of a double- twisting device (sometimes referred to as a buncher) or by means of a tubular twisting machine (sometimes referred to as a cabling machine).

[37] A cross-section of a rope 100 according to the first aspect of the present invention is shown in Figure 1. Rope 100 comprises a core strand 102. Core strand 102 has a core 104 of three filaments 106 with filament diameter di which are twisted together and a layer 108 of nine filaments 110 with diameter d ₂ which are twisted around the three filaments 106. The rope 100 further comprises a layer of seven layer strands 112 which are twisted around the core strand 102 and which form an unsaturated layer around this core strand 102. Each layer strand 1 12 has a 1x7 or 1+6 construction with a core filament 114 of diameter d ₃ and six layer filaments 116 of diameter d ₄ twisted around core filament 1 14. Figure 1 shows a preferable embodiment with di > d ₂ , d ₃ > d ₄ and di = d ₃ .In case these relationships of filament diameters are met, an open rope construction is obtained with openings between the layer strands 112, with openings between the layer filaments 116 of the layer strands 112 and with openings between the layer filaments 110 of the core strand 102.

[38] This brings us to Figure 2 which shows the cross-section of a coated rope 200. The steel rope 100 is provided with a coating of a polyurethane 202. This may be done by means of an extrusion process.

[39] Due to the open rope construction the polyurethane 202 is able to penetrate inside the rope 100 until it reaches and contacts the three core filaments of the core strand.

[40] Example 1:

A first rope construction has been made and tested:

- 3x0.175 + 9x0.16 + 7 x (0.175 + 6x0.15)

- zinc coated

- lay lengths 4.0 mm/ 8.0 mm/ 12.0 mm/ 12.5 mm

- lay direction: SSZS (hereinafter referred to as S) and ZZSZ (Z)

- diameter: about 1.6 mm (see table)

- LLE low length elongation between 54.82 N and 274.1 N: 0.2 %

- PLE part length elongation between 2.5 N and 50 N: 0.1 %

- breaking load: minimum 2800 N

- tensile strength: between 2440 MPa and 2500 MPa

Table 1

Sample Diameter Rope(mm) Ovality (mm) Rubberpenetration(%)

1 - S 1.531 0.030

2 - S 1.542 0.031

94

3 - S 1.532 0.029

one out of five samples giving 69% the other give 100%

4 - S 1.532 0.030 100

5 - Z 1.538 0.033

6 - Z 1.536 0.028 100

7 - Z 1.535 0.026 100

8 - Z 1.538 0.031 100

The lay length is the axial distance required to make a 360 degree revolution of any element in a strand or a cord. The length of lay is expressed in millimeters (mm). The recommended lengths of lay are based on the ISO recommendation R-388-R20 series, ranging from 2.50 mm to 25.00 mm. The direction of lay is the helical disposition of the components of a strand or a cord.

The strand or cord has an 'S' or left-hand lay if, when held vertically, the spirals around the central axis of the strand or cord conform in direction and slope to the central portion of the letter 'S\

The strand or cord has an 'Z' or right-hand lay if, when held vertically, the spirals around the central axis of the strand or cord conform in direction and slope to the central portion of the letter 'Ζ'.

The diameter of the rope is measured optically or by means of a micrometer. The ovality is the difference between the greatest diameter of the cross-section of the rope and the smallest diameter of the cross- section of the rope and is expressed in mm. The percentage of rubber penetration is determined by measuring the degree of air wicking along the steel rope cured in rubber under controlled conditions of temperature, time and curing pressure. The amount of air passing through a rubber block in which the steel rope is embedded, is measured at 4 bar air pressure difference. 100% rubber penetration means that no air is passing. The degree of rubber penetration is a measure for the degree of penetration by a thermoplastic or by an elastomer. [41] Example 2

A second rope construction has been made and tested:

- 3x0.21 + 9x0.19 + 7 x (0.19 + 6x0.175)

- zinc coated

- lay lengths 4.0 mm/ 8.0 mm/ 12.0 mm/ 16.0 mm

- lay direction: SSZS (S) and ZZSZ (Z)

- diameter: about 1.9 mm (see table)

- LLE low length elongation between 75.46 N and 377.3 N: 0.2 %

- PLE part length elongation between 2.5 N and 50 N: 0.06%

- breaking load: minimum 4000 N

- tensile strength: between 2520 MPa and 2560 MPa

Table 2

[42] Figure 3 illustrates the use of a rope as control cable in a window elevator system 300. Driving drum 302 may be electrically driven or may be manually operated. The rotational movement of the driving drum 302 is translated in a to and fro movement of the rope 100 which is the transmission or control member. The to and fro movement of the rope 100 is in its turn translated in an upward or downward movement of window 304. A carriage 306 is attached to the rope 100. This carriage 306 carries the window 304 in its upward and downward movement thereby helped by means of a guide 308. One or more pulleys 310 guide the rope 100 in its trajectory. [43] Figure 4 illustrates a cross-section of a hoisting belt 400 where several ropes 100 are embedded. The hoisting belt 400 may have a matrix of rubber or of polyurethane 402. The polyurethane 402 is penetrating between the layer strands 112 until and even inside the core strand 102 of the rope 100. Hoisting belt 400 may be used in elevators, harbor cranes, mining shafts, sucker rods...

List of Reference Numbers 100 rope 102 core strand 104 core of core strand 106 filaments of core of core strand 108 layer of core strand 1 10 filaments of layer of core strand 112 layer strand 114 core filament of layer strand 116 filaments of layer of layer strand 200 coated rope 202 polyurethane 300 window elevator system 302 driving drum 304 window 306 carriage 308 guide 310 pulleys 400 hoisting belt 402 matrix material.