FI75372C - Cable and means for its manufacture. - Google Patents

Description

75372

Cable and method of making it

The invention relates to cables (ropes) and in particular to cables in which the strands are coated with individual coatings of plastic or rubber material.

In previously proposed cables, the strands or individual strand cores therein are generally round in cross section. There are several disadvantages to such a cable structure. The geometry of the cable is not particularly stable because.

the individual strands are able to deform and rotate relative to each other. Since the degree to which this occurs is unpredictable, the efficiency of such a cable cannot be accurately predicted. In addition, the contact between the strands takes place in a very small area and thus the pressures between the strands are high, which together with the movement of the strands relative to each other leads to the wear of the strands. This wear increases if the cable runs around the pulley because such bending of the cable produces relative movements of the strands. In addition, the contact area between the thread cover and the pulley is limited, with sharp variations producing large loads. In fact, the forces between the strands of such a rope allow only limited bending for such a cable. This type of cable also allows only limited load transfer between the strands.

The state of the art is described in DE-A-1,510,095, GB-A-2,040,063 and U.S. Pat. No. 4,059,951.

It is an object of the invention to provide a cable formed of one or more layers of braided strands, each strand of the layer or each strand of at least one layer being coated with an individual coating of plastic or rubber material, and the cross-section of at least some of the strands is circular. the aberrant and the coating extend helically along said strand before the strands are braided together, the strands of the strands of the braided layer being such as to lock the strands together to determine their relative position in the cable.

It is a further object of the invention to provide a method of making a cable, the method comprising forming a plurality of strands, coating at least some of the strands with an individual coating of plastic or rubber material and braiding the coated fibers together to form a cable. an associated strand prior to braiding the strands together, wherein the adjacent strands, when braided together, are arranged so that their coatings engage to provide a layer in which the strands have a generally fixed relative position to each other and to the cable.

Some embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 shows a part of a thread connected to a first cable, Fig. 2 is a schematic elevational view of an extruder nozzle for pressing a coating over a strand of Fig. 1, Fig. 3 is a cross-sectional view , Fig. 4 is a side elevational view of a coated strand, and Fig. 5 is a sectional view of a first cable having coated strands, Fig. 6 is a sectional view of a second form of cable having coated strands, and Fig. 7 is a sectional view of a third strand having coated strands.

In the first cable according to Figure 1, the strand 10 is formed of a plurality of elements 11 intertwined. The elements may be metal wires or bundles of synthetic material, or a combination of such wires or bundles. Suitable metal wires are steel wires, especially wires made of tough steel. Bundles made of synthetic material are preferably formed of yarn spun from, for example, a plastic material such as aromatic polyamide (e.g. KELVAR (trademark)). Alternatively, the strands may be made of different materials or different combinations of materials and / or different amounts of braids to improve load distribution.

All elements 11 or alternating elements 11 may be coated with a coating of plastic or rubber material before being formed into a fiber. This reduces friction between the fibers and also increases the load transfer between the fibers.

The thread 10 need not be formed of yarns and / or bundles intertwined. Alternatively, the thread 10 may be formed of a plurality of bundles or strands of yarn of synthetic material arranged in parallel (not shown). The thread 10 thus formed may have a cover which is shrunk or extruded on bundles or threads to hold them together.

After the thread is formed, it is passed through an extrusion nozzle 12 (Figure 2). A suitable molten plastic 75372 or rubber material is fed to the nozzle from a pressure-heated screw feed in a conventional manner. Suitable materials may be thermoplastic materials, either alone or in combination, such as polyesters, polyethers, polypropylenes, polyether ether ketones, nylon and polyvinyl chlorides; thermosetting and vulcanized materials such as polychloroprene, natural and synthetic rubbers, polyurethane, HYPALON (trademark) and EPDM, and chemical curable materials.

The nozzle 12 is generally trapezoidal in shape with straight but tapered sides 13 connected at its proximal ends by a short convex end 14 and at their distal ends by a concave curved end 15. The nozzle has dimensions such that it has a larger area than the thread 10 the cross-sectional area and the thread 10 are guided through the nozzle so that there is a gap between the outer surface of the thread and the surfaces delimiting the nozzle (as shown in Figure 2). The convergence of the sides 13 and the curvature of the curved ends 14, 15 have been chosen according to the ideas given below.

The thread is fed through a nozzle at a predetermined linear feed rate. The nozzle 12 is simultaneously rotated at a predetermined rotational speed, the direction of rotation of which is the same as the direction of the thread or it is arranged in the direction of the cable.

As a result, the coating 20 is extruded around a thread having a shape similar to that of a nozzle and running helically along the thread. This is shown more clearly in Figures 3 and 4, which show that the coating 20 has tapered sides 16, a concave narrower end side 17 and a convex wider end side 18. The taper of the sides 16 is selected as shown below.

The extruded coating 20 penetrates the spaces between the elements 11 and the sub-strands to lock the coating into the strands. However, this locking can be increased by arranging gaps between the elements to allow deeper penetration of the coating into the thread. Alternatively or in addition, a chemical binder may be placed on top of the filament prior to extrusion to form a bond between the filament and the coating.

In addition, the lubricant may be placed in the thread prior to application of the coating 20 so that the lubricant remains in the thread by the coating 20 after it has been extruded.

As best seen in Figure 4, the rotation of the nozzle 12 causes the coating to spiral around the filament. Since the linear feed rate of the thread and the rotational speed of the nozzle are adjusted, the pitch of this thread can be arranged as the required pitch. The manner in which the required pitch is determined is described in more detail below.

The coated strands are then assembled to form a cable. Figure 5 shows a 1 + 6 cable (i.e. the cable has a coated core strand 21 surrounded by six equidistantly spaced strands 22). However, any suitable cable structure can be used, although preferably the size, number and geometry of the strands are such that they can be folded, thus allowing the cable to be extended. For example, two or more layers of strands may be provided, as shown in broken lines in Figure 5.

In each strand 22, the tapered angle of the side surfaces 16 and the curvature and shape of the curved surfaces 17 and 18 are selected according to the diameter of the cable and the diameter of the core. However, it is clear that no core thread 21 needs to be placed, in which case the side surfaces 16 of the coating 20 may converge at one point. Additionally or alternatively, several layers of strands can be provided, whereby the convergence angles of the side surfaces 16 and the curvature of the wider and narrower surfaces 17, 18 are selected accordingly.

6 75372 The strands 22 are assembled by feeding the required number of strands through a conventional cable braiding machine. The pitch angle of the thread of the extrudable coating is selected to be the same as the pitch angle of the strands 22 when assembled into cables.

It will be appreciated that by using a slightly different pitch angle for the thread of the strand sheath than that determined by the cable layer, as well as by using back or front braiding in the braiding process, forces can be applied to the strands 10 which then tend to lock the rope structure together. When using such braiding variations, it may be desirable to thermoset the coatings after assembly to secure the coating braid.

It will be seen that in the assembled cable the side surfaces 16 of adjacent coatings face each other. In addition, the wider surfaces of the strands form a continuous cylindrical outer surface for the cable. This structure has several advantages, including: 1. The cable has a stable geometry because the spatial relationship between all the strands is fixed due to the coatings so that no strand can move substantially with respect to the other and cannot change its position in the cable. Thus, the operating characteristics of the cable are stable and predictable.

2. Because the forces between the strands are spread over a relatively large area, this reduces the pressure between the strands and thus increases the age of the strand and thus the age of the cable.

3. As a result, the strands are able to move easily with respect to each other, and thus allow the cable to bend easily around the hoist, thus reducing the increase in forces between the strands caused by such bending.

4. The cylindrical outer surface provides a large area for frictional adhesion between the cable and the drive wheel, for example, and thus reduces the load on the coating as torsion is transferred from the drive wheel to the cable.

7 75372 5. The cylindrical outer surface provides a large support area for the support wheel and provides a reduced support pressure between such pulley and cable, or allows higher or lower loads to be applied at the same support pressure. This advantage allows the use of such a cable with a v-shear that cannot be used with previous cables due to the high support pressures between such a pulley and the individual strands, which compress such a cable and force the strands from their geometric structure, i. the cable tends to flatten.

6. Due to the substantially fixed cross-section of the cable, it is difficult for dirt and other damaging material to enter the inside of the cable.

7. Compared to cables in which a single strand is not coated, but in which the entire outer part of the cable is coated, it is easier to extend the cable shown with reference to the drawings above.

8. In addition, compared to such cables, damage to a single sheath does not cause corrosion of all strands.

9. The interconnection of all strands (including the core strand) allows for increased load transfer between the strands so that the load is evenly transferred between the strands.

It will be appreciated that various variations or modifications may be made to the above arrangement, including the following.

The coatings of the strands 10 need not all have the same cross-section. Referring to Fig. 6, in one embodiment, the alternating strands 10a are provided with coatings 20a having a circular cross-section, the intermediate strands 10b being provided with coatings 20b having concave side surfaces 16b to which the round coatings 20a of adjacent strands 10a are received. In this way, the strands 10a, 10b of the layer 75372 are interlocked in the same manner as the strands 10 of the embodiment of Figures 1-5. The intermediate outer surfaces 18b of the strands 10b have an elongated curved length to cover the adjacent strands 10a and provide the cable with a cylindrical outer surface.

The structure of the strands 10a, 10b and the shape of the coatings 20a, 20b are the same as shown above with reference to Figures 1-5.

The outer surfaces 18 of the coatings may be provided with structures to prevent water from entering between the cable and a surface, such as a pulley, over which the cable passes. For example, the coating may be formed by grooves 25 (Figure 5) at angles between the outer surfaces 18 and the side surfaces 16. These wipe the pulley over the surface, thus removing both water and dirt.

Additionally or alternatively, the grooves or channels 26 (Figure 5) may be extruded or cut into surfaces 18 for this purpose. Another possibility is to apply a tread pattern to this surface.

Friction between the strands can be further reduced by providing the side surfaces 16 with grooves 21 (Figure 5) containing oil to provide a lubricant between the contact surfaces 16. Adjacent surfaces may be provided with grooves 27 that are offset from each other and have an overlap between them, resulting in limited lubricant removal in the grooves. Additionally or alternatively, pieces of low friction material 28 (Figure 5), such as polytetrafluoroethylene, may be provided between adjacent surfaces 16.

The core thread may be provided with a coating having structures that engage the structures formed on the inner surfaces 17 of the coatings. This positively allows locking between the core thread and other strands.

Adjacent strands or strands of strands may be arranged in opposite directions to reduce rotation.

9 75372 Coatings may be provided with closed air cells 29 (Figure 5) to make a cable capable of floating in whole or in part in water.

Referring now to Figure 7, the third cable comprises seven strands arranged as a central strand 35 and six outer strands 36, all strands being helically braided together. It is not essential that there are seven threads here, but this is advantageous to facilitate continuation. These seven threads are coated with a cured outer coating 38 made of rubber or the like.

In one form of cable, each strand 35, 36 is made of a plurality of fibers of aromatic polyamide, such as "KELVAR" (trademark, manufactured by Du Pont de Nemours International S.A.). In particular, each thread may comprise a plurality (e.g., 200) of braids 37 (only one shown), each of which in turn consists of one or more (e.g., 3, 5, or 7) yarns. Each yarn may contain several "KELVAR" (trademark) fibers, e.g., 1500 fibers. The method of manufacture is explained in more detail below, but it should be noted that each braid 37 of the thread 35, 36 is individually surrounded by a rubber or similar material 39.

In addition, each thread 35, 36 itself is surrounded by a coating 40, which may be any of those shown above with reference to Figures 1-4. The coatings 40 of the six outer threads 36 are formed by straight sides 40a connected by curved inner and outer surfaces 40b, 40c. The side surfaces 40a of the adjacent coatings 36 face each other. In addition, the roughened outer surfaces 40c form a continuous cylindrical outer surface, and the curved inner surfaces 40b cooperate with the coating 40 of the core thread 35. This has the advantages shown in connection with the cable of Figures 1-5.

Preferably, the bond strength between the outer coating 38 and the individual fiber coatings 40 is lower than the tensile strength of the rubber or similar material of the fiber coatings 40372 10, which facilitates peeling of the outer coating 38 from the fibers. In addition, the bond between the strands is less than the tensile strength of the rubber or similar material 39 of the strands. The fact that these two requirements are met facilitates the continuation, as it allows the outer coating 38 to be easily peeled off the strands and the strands to be easily separated.

It is desirable for the cable to be arranged so as to see the deterioration or incipient damage caused by the rupture of the braid or strands. This can be arranged in many ways, some of which are exemplified below and which can be used individually or in any suitable combination.

The outer coating 38 may be given a color that contrasts with the color of the coatings 40 of the strands 35, 36. In this way, tearing or cutting of the outer coating 38 or other damage that keeps the contrast color of the coating 40 visible from the outside becomes immediately apparent.

Weakening of the cable can produce a local decrease in its diameter and thus increase the length of the cable.

A local decrease in cable diameter can be observed by arranging a series of cuts through the outer sheath 38, which cuts are spaced along the length of the cable and each passes along the length of the small length cable. The cuts are arranged to show the contrast color of the filament coating 40. Therefore, if a local decrease in cable diameter occurs, this tends to close the cuts and is indicated locally by the loss of contrast color of the coating 40.

The increase in cable length can be shown by another series of short cuts divided by the length of the cable, each of which runs a very short distance around its circumference. These cuts are normally invisible, but they open as the length of the cable increases and indicate the contrast color of the filament coatings 40.

11 7 5 3 7 2

The method by which the cable shown in Fig. 7 can be manufactured will now be briefly explained.

First, the aromatic polyamide material that forms the base of the rope may be in the form of yarns, each of which comprises several, e.g., 1,500 fibers.

Early in the process, there is braiding to turn the yarns into braids. Each braid 37 may consist of only one yarn or may comprise more than one yarn, for example three, five or seven yarns. Although each braid 37 consists of only one yarn, the braiding is performed. Braiding may be preceded by the step of dipping the yarn or yarns into the binder.

The strands 35, 36 are then made of braids 37. Each strand 35, 36 consists of a relatively large number of braids 37, e.g. 60 to 200 braids. In each strand 35, 36, the braids 37 are parallel to each other and embedded in a rubber or similar material individually surrounding the braids 37. In the process of converting braids 37 into strands 35, 36, a crosshead extruder of the type shown above in Figure 2 may be used. and into which rubber or similar material is simultaneously fed at right angles and individually surrounds the braids 37 and holds them all together. Braids are not braided together. This process thus forms an outer filament coating 40. The filament exiting the extruder then passes into a continuous heating chamber which cures the rubber.

The seven strands thus formed are then put together as shown in the figure and assembled to form a cable. The outer coating 38 is then added using extrusion.

Finally, the cable is then subjected to heat and pressure to tie it all together. A hydraulic press can be used for this purpose, making it large enough to accommodate several sets of ropes at a time.

12 75 372

In one variation, the braids are braided together in each thread or arranged in bundles braided together in each thread.

Another way to immerse the braids in the rubber is a dipping process where the braid passes through a liquid elastomer bath which is then dried to form a solid elastomer that adheres to the braid.

Such a cable, shown with reference to Figure 7, has several applications. When it passes around or partially around a pulley or similar member and a force transfer between the member and the cable by friction between them is required, it may be desirable to provide a groove in the outer sheath 38 of the cable to increase this friction.

The use of "KEVLAR" (trademark) material as the main component of the cable is advantageous because "KELVAR" (trademark) material has a similar volume / strength ratio as steel and a much lower weight / volume ratio. However, other forms of cable according to the invention can be made in which the main components of the rope are not aromatic polyamide or "KEVLAR" (trademark) fibers but are some other material. For example, steel wires could be used. In such a case, the steel wires would be arranged in the same way into braids 37, as described above.

In each of the embodiments shown with reference to the figures above, the pressure acting inwardly on the central strand depends in part on the tension of the cable. For this reason, by using suitable means for measuring the pressure on the central thread, it is possible to provide an indication of the rope tension and thus a warning of overvoltage. Such pressure can be monitored, for example, electronically. Synthetic materials are available whose conductivity changes drastically as a function of pressure, and such materials could thus be arranged in a central thread to control its pressure.

7 5 3 7 2 13 An electrically conductive wire or wires could be arranged in the cable to run along its length, whereby the wire or wires would be arranged to break when the rope is excessively elongated, and thus this allows electrical monitoring of the rope elongation.

In all embodiments of the invention shown with reference to the above drawings, the coatings are threaded into associated strands to account for the braiding of the strands into a cable. However, it is clear that such a helical coating does not need to be used. The coating can be applied to the strands in a straight formation (i.e., without braiding) and braided into the coatings when the cable is assembled. In this case, the coatings can be heat-cured after assembly to secure the braid.

Claims (9)

1. A cable formed by one or more layers of co-wound card parts, each card part of the layer or at least one layer being covered with a single sheath of a plastic or rubber material, characterized in that at least some of the card parts (10; 36 ) has a non-circular cross-sectional sheath (20; 40) extending in a spiral along the respective shaft before twisting the sheaves together, wherein the sheaths (20; 40) of the sheaves (10; 36) of the twisted layer are so shaped that they intervene in each case to fix the interrelationship in the space between the strands of the cable. Cable according to claim 1, characterized in that each sheath (20) has a cross-section which is non-circular to form two spaced apart lateral surfaces (16) which are substantially straight in plane perpendicular to the cable shaft and which engage with corresponding surfaces of the sheaths of the adjacent cartilages. Cable according to Claim 1, characterized in that alternately located card parts (10a) are provided with a sheath (20a) of circular cross-section, while each card part (10b) between said alternating parts is provided with a sheath (20b) with two concave side surfaces (16b), which receive the sheaths of said adjacent strands with a circular cross-section. 4. A cable according to claim 1, characterized in that the card parts forming the outer layer of the cable are sheathed and that the outer surfaces of said sheaths are provided with formations (25; 26) for interaction with the surface over which the cable passes to remove water. between the cable and the surface. Cable according to any one of claims 1-4, characterized in that it comprises a core cable.