WO2018231063A2

WO2018231063A2 - A chain formed of linked flexible loops, and an apparatus and a method of manufacture of said loops

Info

Publication number: WO2018231063A2
Application number: PCT/NO2018/050150
Authority: WO
Inventors: Kjell Magne VEKA
Original assignee: Van Beest Norway As
Priority date: 2017-06-13
Filing date: 2018-06-08
Publication date: 2018-12-20
Also published as: EP3638844A2; NO20170954A1; WO2018231063A3

Abstract

A method of forming a flexible loop (6") comprising one or more continuous flexible strands (1), comprises coiling the strand (1) upon itself multiple revolutions (R) to form a plurality of coils (1b) which collectively form a bundle (23) of a predetermined thickness (t1); and for each revolution (R), passing the strand (1) around an imaginary centre line CL at least once so as to form a twisted bundle (23). In one embodiment, the method comprises forming a mantle (18) applying a stitching procedure. A strand (1) winding apparatus (8), comprises a ring member (11) rotatably arranged in a body (12), said body(12) having a tubular ring shape dimensioned such that the ring member (11) may rotate (R) inside said body; said body comprising a helical slit (9). A plurality of strand guides (10) having a strand-conveying member (10c) fixedly connected to the ring member (11) extend through the slit (9) and comprise at least one strand-conveying member (10c). A chain may be formed by interconnecting a plurality of the flexible loop.

Description

A chain formed of linked flexible loops, and an apparatus and a method of manufacture of said loops

Field of the invention

The invention concerns a flexible loop, a chain formed of a plurality of linked flexible loops, and an apparatus for forming a flexible loop. The flexible loop is made up of fibers, such as polymeric fibres, synthetic plastic material, such as polyester, nylon or Kevlar having extremely high tensile strength to weight ratio. The chain is useful for mooring or anchoring boats and other floating vessels, to lash cargo in road, rail, water and air transportation or for conveying, hoisting, suspending or lifting applications.

Background of the invention

Chains made up of non-metallic lifting loops are well known and increasingly used for lifting, suspending, hoisting and securing cargo, as well as for anchoring purposes at sea.

The prior art includes RU 2130421 CI, which describes methods of making a twisted rope, in which strand elements are twisted around a core.

The prior art also includes US 4 779 411, which describes a non-metallic rigging chain formed with a plurality of linked flexible loops. Each loop has a core which consists of a continuous strand of non-metallic material coiled upon itself. The coiled core material is enclosed in a sheath of a woven outer fabric. The sheath may be heavy canvas or a synthetic plastic fabric, such as nylon or polyester. The core is preferably synthetic plastic material, such as polyester, nylon or Kevlar having extremely high tensile strength to weight ratio. The sheath may be wrapped about the core, its ends overlapped and its side edges stitched longitudinally. Except for the two terminal loops of each chain, one loop is formed by coiling a continuous strand of core material in linked relation within a pair of completed loops. The length of each chain is determined by the diameter of its loops and the number of loops linked together.

The prior art also includes WO 2008/089798, which describes a chain suitable to moor or anchor boats, to lash cargo in road, rail, water and air transportation or for conveying, hoisting, suspending or lifting applications. The chain comprises a plurality of interconnected links, and at least part of the links comprise polyolefin multifilament yarns. In particular, the yarns comprise ultrahigh molecular weight polyethylene (UHMWPE) fibers. A method of enhancing the strength of such a chain is also described, in which the chain is subjected to a number of load cycles. The number of load cycles may range between 2 and 25, and the maximum load applied is lower than 45 % of the breaking load of the chain.

The prior art also includes WO 2009/115249, which describes a chain having a plurality of first links interconnected with a plurality of adjacent links. The first links comprise polymeric multifilament yarns and have a first thickness at least at the portion where they interconnect with the adjacent links, and the adjacent links have a second thickness at least at the portion where they interconnect with the first links. The ratio between the first and second thicknesses is at least 1.2. The invention further relates to the use of the chain for storing, securing, and handling cargo, e.g. in lifting, hauling and rigging.

The prior art also includes WO 2015/086627, which describes a chain having a plurality of chain links comprising a polymeric fibre. The chain also comprises at least one spacer having a thickness Δ at the contact location through which loads are directly transmitted between the chain links and a ratio Δ/τ = f, with τ being the thickness of any of the chain links at the contact location through which loads are directly transmitted between said chain links and f being in a range between 0.10 and 2.50. The invention described further relates to the use said chain for storing, securing, lashing and tying down for handling and transporting cargo, in lifting and hoisting, logging, hauling and rigging, propulsion and driving, mooring, cargo-hold of an aircraft or naval ship.

The present invention provides certain improvements over the prior art, both in the manufacturing process and the load-bearing capabilities.

Summary of the invention

The invention is set forth and characterized in the main claims, while the dependent claims describe other characteristics of the invention.

It is thus provided a method of forming a flexible loop comprising one or more continuous flexible strands, characterized by

- coiling the strand upon itself multiple revolutions to form a plurality of coils which collectively form a bundle of a predetermined thickness; and

- for each revolution, passing the strand around an imaginary centre line at least once so as to form a twisted bundle.

In one embodiment, the method comprises either

a) winding a tape or thread around the flexible loop bundle to form a protective mantle, utilizing a toroidal winding process; or

b) forming a mantle by applying a stitching procedure; or

c) winding one or more threads around the flexible loop bundle to form a protective mantle.

It is also provided a method of forming a flexible loop comprising one or more continuous flexible strands, characterized by coiling the strand upon itself multiple revolutions to form a plurality of coils which collectively form a bundle of a predetermined thickness; and forming a mantle by applying a stitching procedure or a thread winding procedure. The stitching procedure may employ a puller-feed sewing technique.

In one embodiment , the methods comprise forming at least one region of increased thickness, having a maximum thickness. In one embodiment, two regions of increased thickness are formed at diametrically opposite sides of a flexible loop.

In one embodiment, the thickness ratio (t₂/ti) is in the range between 1.5 and 2.0.

The strand may be selected from the group comprising a string, single filament, yarn, multifilament yarn, rope, line, and pre-twisted lines.

The strand material may be a fibre material, such as a high-performance fibre, such as a polymeric fibre.

It is also provided a method of forming a chain comprising a plurality of flexible loops formed by the methods according to the invention, characterized by forming a subsequent flexible loop comprising one or more continuous flexible strands, and coiling the strand upon itself multiple revolutions and for each revolution passing the strand through a prior made flexible loop. In one embodiment, the chain of flexible loops is subjected to a stretching force. It is also provided a flexible loop comprising one or more continuous flexible strands, manufactured according to the methods according to the invention.

It is also provided a strand winding apparatus, comprising

- strand guiding means, and

- twisting means configured and operable to move the strand guiding means a given number of times around itself per revolution around a twisted means periphery.

In one embodiment,

- the twisting means comprises a ring member rotatably arranged in a body,

- said body having a tubular ring shape, dimensioned such that the ring member may rotate inside said body; said body comprising a helical slit;

- the strand guiding means comprises a plurality of strand guides having a strand- conveying member fixedly connected to the ring member and extending through the slit and comprising at least one strand-conveying member.

In one embodiment, the strand-conveying member is arranged outside of the body.

In one embodiment, the helical slit makes a plurality of turns around the body per revolution around said body.

It is also provided a twisted flexible loop formed by the method according to the invention. It is also provided a flexible loop comprising one or more continuous flexible strands, characterized in that the strands are twisted and arranged in a helical fashion around an imaginary centre line to form a plurality of coils which collectively form a bundle of a predetermined thickness.

The invention provides a process of manufacturing a flexible loop and a chain made up of such loops, which is considerably more efficient the prior art methods. The process is suitable for automation. Also, the invented flexible loop comprises an integrated spacer (radius controller) which contributes to maintaining the loop opening geometry when the loop is subjected to loads. Brief description of the drawings

These and other characteristics of the invention will become clear from the following description of various forms of embodiment, given as non-restrictive examples, with reference to the attached drawings, wherein:

Figure 1 is a perspective view of a loop winding apparatus of a first

embodiment, at the inception of a loop winding process according to a first method;

Figure 2 corresponds to figure 1, and shows a partial build-up of a flexible loop of a first embodiment;

Figure 3 is a perspective view of a variant of the loop winding apparatus illustrated in figures 1 and 2, at the inception of a loop winding process according to a second method;

Figure 4 corresponds to figure 3, and shows a partial build-up of a flexible loop of the first embodiment;

Figure 5 is a perspective view of a loop winding apparatus of a second embodiment;

Figure 6 is a perspective view of a variant of the loop winding apparatus illustrated in figure 5;

Figure 7 is a side view of the loop winding apparatus illustrated in figure 6;

Figure 8 is a sectional view along section line A-A in figure 7;

Figure 9 is a perspective view of the loop winding apparatus illustrated in figure 5, at the inception of a loop winding process according to a third method;

Figure 10 corresponds to figure 9, and shows a partial build-up of a flexible loop of a second embodiment;

Figure 11 is a perspective view of a flexible loop formed by the loop winding process according to the third method; Figure 12 is a sectional side view along section line B-B in figure 11, in the plane of the flexible loop;

Figure 13 is a perspective view of a flexible loop formed by the loop winding process according to the first or second method, and illustrates two methods of applying an outer mantle;

Figure 14 is a perspective view of a stitching procedure to form a mantle on a flexible loop;

Figure 15 is an enlarged view of the dotted square in figure 14;

Figures 16 and 17 correspond to figure 15, and illustrate further steps in the stitching procedure;

Figure 18 is a perspective view of a flexible loop formed by the loop winding process according to the first or second method, and a stitching procedure

corresponding to the stitching procedure illustrated in figures 14-17;

Figures 19 and 20 are schematic side views of two linked flexible loops, in which at least one of the loops has been subjected to a stitching procedure to form regions of increased thickness on the loop;

Figure 21 is a perspective view of a gripper device arranged above a loop winding apparatus of the first embodiment, wherein the winding apparatus has completed the forming of a flexible loop according to the first or second method;

Figures 22 and 23 are a top view and a perspective view, respectively, of the gripper device removing the completed flexible loop from the loop winding apparatus;

Figure 24 is a perspective view of the loop winding apparatus of the first embodiment in the process of forming a second flexible loop of a first embodiment, while the first flexible loop is supported by the gripper device and arranged such that the second flexible loop is linked to the first flexible loop as the second flexible loop is being formed;

Figure 25 is corresponds to figure 24, and illustrates a subsequent step in which a fourth flexible loop is formed and linked to a third flexible loop; and Figure 26 is a schematic side view illustrating a procedure of forming chain of flexible loops according to the invention, and illustrates also a stretching procedure.

Detailed description of a preferential embodiment

The following description will use terms such as "horizontal", "vertical", "lateral", "back and forth", "up and down", "upper", "lower", "inner", "outer", "forward", "rear", etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader's convenience only and shall not be limiting.

Figure 1 shows a loop winding apparatus 3 of a first embodiment, comprising four rotatable spools 4 arranged on a base 5 and having a fixed guiding eye 2 for a strand 1. It should be understood that the apparatus may comprise fewer or more spools.

Although the invention in the following will be described with reference to a strand 1, it should be understood that the invention is equally applicable to any thread, string, strand, filament, yarn, multifilament yarn, core yarn, rope, line, cord, and pre-twisted lines.

It should be understood that, although not illustrated, several fixed guiding eyes may be provided, allowing different strands to be fed into the winding apparatus

simultaneously. The flexible loop may thus comprise one or more strands. Required power and control means, motors, gears, etc., are not shown as these are well known in the art. The strand 1 has been placed around the spools 4 and the free end 1 ' has been connected to the strand by cluing, welding, tying or any other means or process known in the art, thereby forming an initial coil la. The loop winding process is accomplished by rotating the spools a number of revolutions as indicated by arrows R in figure 2, thereby forming plurality of coils lb to make up a flexible loop 6' of a first

embodiment. The strand 1 is supplied from a bobbin (not shown) and the tension in the strand is controlled in a manner which is known in the art. It should be understood that the number of revolutions R will determine the number of coils lb (i.e. number of times the strand is arranged around the spools), and hence the thickness of the flexible loop body (also referred to as a bundle 23, see e.g. figure 13). When the winding process is finished, and the flexible loop is of the desired thickness (ti, see figure 19), the strand supplied from the bobbin is cut and the free end is secured to the loop by cluing, welding, tying or any other means or process known in the art.

Figures 3 and 4 show a variant of the loop winding apparatus illustrated in figures 1 and 2, in which the spools are stationary but a rotating ring 7 is arranged around the spools. The rotating ring 7 comprises a hole 7a through which the strand 1 is inserted prior to commencing the loop winding process. Then, the strand free end is arranged around the spools and connected to the strand as described above with reference to figure 1, forming an initial coil la, and the rotating ring 7 is rotated. It should be understood that, although not illustrated, several fixed guiding eyes may be provided, allowing different strands to be fed into the winding apparatus simultaneously. The flexible loop may thus comprise one or more strands. Required power and control means, motors, gears, etc. for the rotating ring, are not shown as these are well known in the art. During the winding procedure, the strand 1 is supplied from a bobbin (not shown) and the tension in the strand is controlled in a manner which is known in the art. It should be understood that the number of revolutions R will determine the number of coils lb (i.e. number of times the strand is arranged around the spools), and hence the thickness of the flexible loop body (also referred to as a bundle 23, see e.g. figure 13). When the winding process is finished, and the flexible loop is of the desired thickness (ti, see figure 19), the strand supplied from the bobbin is cut and the free end is secured to the loop by cluing, welding, tying or any other means or process known in the art.

Figures 5 to 8 show another embodiment of a loop winding apparatus 8 according to the invention. This loop winding apparatus 8 comprises a ring-shaped and tubular outer body 12 (configured for being supported by a base 5, see figure 9). A helical slit 9 is formed in the body 12, and an inner ring member 11 is arranged inside the outer body 12 and arranged to move inside the body. Required power and control means, motors, gears, etc. for rotating the inner ring member 11 inside the outer body, are not shown as these are well known in the art. Connected to and supported by the inner ring member 11 are a plurality of strand guides 10. Each strand guide 10 comprises a base 10a which is connected to the ring member 11, a stem 10b which is connected to the base 10a and extending through the helical slit 9, and a strand-conveying member 10c protruding beyond the slit (see figure 8). In the illustrated embodiment, the strand-conveying member 10c is an arc-formed member with a gap lOd through which a tread may be passed. However, it should be understood that the strand-conveying member may have other shapes.

Figure 5 shows a variant in which the helical slit 9 makes three turns (a helical pattern with three spirals) around the outer body 12 tubular. In other words, the slit 9 spirals three times around the tubular per revolution around the outer body. A revolution in this context should be understood as movement along the outer body 12 circumference (see reference letter R in figure 10).

Figures 6-8 show a variant in which the helical slit 9 makes one turn (a helical pattern with one spiral) around the outer body 12. The invention shall not, however, be limited to number of helical slit turns (spirals). Also, in a practical application, fewer or more strand guides 10 than those illustrated, may be used. The invention shall not be limited to a specific number of strand guides.

In figure 9, the loop winding apparatus 8 is supported by a base 5. A strand 1 has been entered through a fixed guiding eye 2 and arranged in the multiple strand guides 10 around the outer body 12. The strand free end (not shown in figure 9) has been connected to the strand in a manner known in the art, such that the strand 1 forms an initial coil la. It should be understood that, although not illustrated, several fixed guiding eyes may be provided, allowing different strands to be fed into the winding apparatus simultaneously. The flexible loop may thus comprise one or more strands. In the illustrated embodiment, the slit 9 spirals four times around outer body 12 tubular, i.e. the outer tubular circumferential axis. However, the invention shall not be limited to this number. It shall be understood that the number of turns (spirals) that the slit makes, determines the number of times a strand is twisted around itself during the formation of the flexible loop.

It should be understood that other embodiments of a loop winding apparatus are conceivable. For example, the aforementioned tubular outer body (and its associated helical slit) may be replaced by a twisted, ring-shaped structure, and strand guides may be configured to move along the twisted, ring-shaped structure. It should also be understood that the strand guides may be replaced by grooves in the ring member 11. Thus, each strand guide (or groove) will spiral a given number (n) of times around the twisted structure per revolution (R) around the twisted structure periphery; the number n being equal to the number of twists in the ring-shaped structure. In general, therefore, the strand guide 10 or groove, or any other technically equivalent device or structure, may be referred to as a strand guiding means 10, and the tubular outer body 12, its associated helical slit 9 and inner ring member 11, or any other technically equivalent devices or structure, may collectively be referred to as twisting means 9, 1 1, 12.

In figure 10, the inner ring member 11 (not shown in figure 10) is rotated, causing also the strand guides 10 to rotate (indicated by arrow "R") around the outer body 12, following the helical slit 9. The strand 1 is supplied from a bobbin (not shown) and the tension in the strand is controlled in a manner which is known in the art. The rotational movement (revolutions) R of the strand guides 10 causes the formation of a twisted flexible loop 6" of a second embodiment. It will be understood that the number of turns (spirals) that the slit makes around the outer body tubular per revolution R determines the number of times the strand 1 is twisted around the tubular during the formation of the flexible loop. This embodiment of the flexible loop 6" is thus twisted and will in the following be referred to as such. It should also be understood that the number of revolutions R of the strand guides will determine the number of coils lb (i.e. the number of times the strand is arranged around the tubular outer body 12), and hence the thickness of the flexible loop body (also referred to as a bundle 23, see e.g. figure 15). When winding process is finished, and the flexible loop is of the desired thickness (ti, see figure 11 or figure 19), the strand supplied from the bobbin is cut and the free end is secured to the loop by cluing, welding, tying or any other means or process known in the art.

As a clarification, the flexible loop 6' of the first embodiment, described above, will in the following be referred to as a non-twisted flexible loop. A reference to a flexible loop 6 in general shall imply that the flexible loop may be either a twisted flexible loop or a non-twisted flexible loop.

Lines 13 in figures 9 and 10 indicate that the outer body 12 may be split into two parts 12a,b. Although not illustrated, it should be understood that the inner ring member 11 may be split into two parts in a similar manner. The methods and means by which the outer body parts and ring member parts may be connected and disconnected need not be discussed here, as they are known in the art.

Figure 11 shows a twisted flexible loop 6" in a completed state after the outer body parts and the inner ring member parts have been split, and the twisted flexible loop 6" has been removed from the winding apparatus. Reference number 1" denotes a portion of the strand 1 which has been coloured grey, in order to visualize how the strands are twisted.

This is also illustrated in figure 12, which illustrates a half of a twisted flexible loop 6", cut to visualize how the strands are twisted and arranged in a helical fashion around an imaginary centre line CL. This imaginary centre line corresponds to the circumferential centre line of the outer body 12 tubular, i.e. the circumferential centre line around which the strand guides 10 rotate in the above mentioned helical pattern.

Some post-winding processes will now be described, with reference to figures 13 to 20.

Figure 13 illustrates how a non-twisted flexible loop 6' is wrapped with a tape 14 and a wrapping thread 15 around the body (also referred to as a bundle) 23, utilizing a toroidal winding technique, in order to form respective mantles 18 to protect the individual strands and preserve the integrity of the loop. It should be understood that only the tape 14 or only the wrapping thread 15 may be applied to the flexible loop, in other words, they are independent alternatives. Although not illustrated, it should be understood that similar tape and wrapping thread may be applied to the twisted flexible loop, when the flexible loop has been removed from the winding apparatus 8.

Figures 14 to 17 illustrate a stitching procedure on a twisted flexible loop 6" to form a mantle 18 on the entire flexible loop (not shown) or on portions of it. The mantle 18 is formed by winding or stitching one or more threads around (not through) the flexible loop body 23. In the illustrated embodiment, a stitching procedure is illustrated, which comprises a so-called "puller-feed sewing" technique, which per se is known in the art. The needle 16 moves in a zig-zag pattern Z across the flexible loop body (also referred to as a bundle) 23, feeding a first sewing thread 17a and picking up a second sewing thread 17b. Figure 18 illustrates a similar stitching procedure applied on a non-twisted flexible loop 6' . The mantle 18 serves to protect the loop body 23 and to provide a structural outer body for the loop body.

A problem associated with chains made up of flexible loops is a tendency of the loops to lose their original geometry. This may lead to stress hot spots when the chain is subjected to loads. This phenomenon is well known in the design of wire rope and associated drums (onto which the wire rope is to be spooled): In that context, the relationship between the wire rope diameter d as it is bent around the drum of a diameter D is expressed as a Old ratio. The smaller the ratio, the sharper the bend a wire rope must make as it spools around a drum. Thus, a system having a small Old ratio, aggravates the wire rope bending motion, which may cause fatigue, irregular wear and accelerated deterioration. This is also a problem with chains made up of flexible loops.

Furthermore, this distortion of loop geometry may make it difficult or time consuming to enter hooks, shackles, etc. into the loop. The geometry problem and the stress hot spot problem may be mitigated by an embodiment of the invented flexible loop, illustrated in figures 19 and 20.

In the flexible loops 6i, 62 illustrated in figure 20, the portions K indicate regions of increased thickness, hereinafter referred to as bundle thickness. In the regions K, the flexible loop is less susceptible to loop geometry change, due to the material added here, and therefore contributes to maintaining a comparably high thickness ratio (comparable to the analogous Old ratio describe above). In addition to mitigating stress hot spots, the regions K, typically at opposite ends of each flexible loop, serve as radius control means and contribute to maintaining an "open" loop, illustrated by the arrows W in figures 19 and 20. More specifically, referring to figure 19, the bundle thickness is increased from ti, which is the thickness of the flexible loop bundle as formed (e.g. as described above with reference to figures 1 to 10) to a maximum bundle thickness t₂. The increase in thickness is preferably gradual, providing a suitable taper between ti and t₂. The skilled person will understand that the absolute values of ti and t₂ is determined based on the intended use of the chain of flexible loops. Favourable thickness ratios (t₂/ti) are, however, considered to be in the range between 1.5 and 2.0. The invention shall, however, not be limited to this range. The regions K of increased loop thickness may be formed by winding one or more threads around the loop body 23, or by the stitching procedure described above with reference to figures 14 to 18, or by the toroidal winding procedure described above with reference to figure 13, using thread, tape or a combination of both. It should be understood that the formation of regions K of increased loop bundle thickness is equally applicable to any of the flexible loops (i.e. non-twisted 6' and twisted 6") described above, and may be performed while the flexible loop is supported by its winding apparatus (i.e. 3 or 8), or after it has been removed from its winding apparatus. The finished flexible loop may be subjected to coating or impregnation by a resin, controlled heat-setting, or similar. Such coating or impregnation may be applicable even to flexible loops in which no regions of increased loop bundle thickness have been formed.

Referring now to figures 21 to 23, a gripper device 19 with movable gripper arms 20 is arranged above the loop winding apparatus 3. The arrows indicate the movements of the gripper device 19, gripper arms 20 and spools 4, so as to remove a completed flexible loop 6' from the winding apparatus 3. Once the flexible loop has been removed from the winding apparatus, it may be released from the gripper device, or it may be held by the gripper device as shown in figure 24. Then, a new flexible loop 6'₂ may be formed by the same process as described above with reference to figures 1 to 4 and 13 to 20. Figure 25 illustrates a chain forming sequence, in which consecutive flexible links 6'_2-4 are formed and linked to a preceding flexible link.

Although the chain forming procedure described above refers to figures 21 to 24, which illustrate a non-twisted flexible loop 6', it should be understood that a similar chain forming procedure may be performed for the twisted flexible loop 6".

Figure 26 illustrates a procedure of forming a chain of flexible loops 6_1-n. It should be understood that this procedure is applicable to both non-twisted flexible loops 6' and twisted flexible loops 6". Arrow M indicate chain movement, and arrows T indicate tension provided by cogwheels 21a,b, intermittently rotating in opposing direction Ri, R₂ to impose a stretching force on (and hence shape) the individual flexible loops. The tension T is dimensioned according to the loop material type, loop thickness, and intended use. In order to improve the stability of the strands in the loop, a resin may be applied to the stretched flexible loop, for example in a processing facility 22. Controlled heat-setting may also be used to increase the loop's tenacity and to fixate the shape of the loops.

Although the invention has been described with reference to a strand 1, , it should be understood that the invention is equally applicable to any string, strand, single filament, yarn, multifilament yarn, rope, line, and pre-twisted lines. While a suitable strand material is a high-performance fibre, such as a polymeric fibre, the invention is applicable to any fibre type. A preferred material for flexible loops intended for load- carrying applications is polyethylene, such as ultrahigh molecular weight polyethylene (UHMWPE), but the invention shall not be limited to this material.

Claims

1. A method of forming a flexible loop (6") comprising one or more continuous flexible strands (1), characterized by

- coiling the strand (1) upon itself multiple revolutions (R) to form a plurality of coils (lb) which collectively form a bundle (23) of a predetermined thickness (ti); and

- for each revolution (R), passing the strand (1) around an imaginary centre line CL at least once so as to form a twisted bundle (23).

2. The method of claim 1, further comprising either

a) winding a tape (14) or thread (15) around the flexible loop bundle (23) to form a protective mantle (18), utilizing a toroidal winding process; or

b) forming a mantle (18) by applying a stitching procedure; or

c) winding one or more threads around the flexible loop bundle (23) to form a protective mantle (18).

3. The method of claim 2, wherein the stitching procedure employs a puller-feed sewing technique.

4. The method of claims 2 or 3, further comprising forming at least one region of increased thickness (K), having a maximum thickness (t₂).

5. The method of claim 4, wherein two regions of increased thickness (K) are formed at diametrically opposite sides of a flexible loop.

6. The method of claims 4 or 5, wherein the thickness ratio (t₂/ti) is in the range between 1.5 and 2.0.

7. A method of forming a flexible loop (6; 6'; 6") comprising one or more continuous flexible strands (1), characterized by coiling the strand (1) upon itself multiple revolutions (R) to form a plurality of coils (lb) which collectively form a bundle (23) of a predetermined thickness (ti); and forming a mantle (18) by applying a stitching procedure or a thread winding procedure.

8. The method of claim 7, wherein the stitching procedure employs a puller-feed sewing technique.

9. The method of claims 7 or 8, further comprising forming at least one region of increased thickness (K), having a maximum thickness (t₂).

10. The method of claim 9, wherein two regions of increased thickness (K) are formed at diametrically opposite sides of a flexible loop.

11. The method of claims 9 or 10, wherein the thickness ratio (t₂/ti) is in the range between 1.5 and 2.0.

12. The method of any one of claims 1-11, wherein the strand (1) is selected from the group comprising a string, single filament, yarn, multifilament yarn, rope, line, and pre-twisted lines.

13. The method of any one of claims 1-12, wherein the strand material is a fibre material, such as a high-performance fibre, such as a polymeric fibre.

14. A method of forming a chain comprising a plurality of flexible loops (6i_-n) formed by the method of any one of claims 1-13, characterized by forming a subsequent flexible loop (6₂) comprising one or more continuous flexible strands (1), and coiling the strand (1) upon itself multiple revolutions (R) and for each revolution passing the strand through a prior made flexible loop (6i).

15. The method of forming a chain of claim 14, wherein the chain of flexible loops is subjected to a stretching force (T).

16. A flexible loop (6; 6'; 6") comprising one or more continuous flexible strands (1), manufactured according to the method of any one of claims 1-6, or according to the method of any one of claims 7-11.

17. A strand (1) winding apparatus (8), comprising

- strand guiding means (10), and

- twisting means (9, 11, 12) configured and operable to move the strand guiding means (10) a given number (n) of times around itself per revolution (R) around a twisted means periphery.

18. The strand winding apparatus of claim 17, wherein

- the twisting means comprises a ring member (11) rotatably arranged in a body (12) said body (12) having a tubular ring shape, dimensioned such that the ring member (11) may rotate (R) inside said body; said body comprising a helical slit (9);

- the strand guiding means comprises a plurality of strand guides (10) having a strand- conveying member (10c) fixedly connected to the ring member (11) and extending through the slit (9) and comprising at least one strand-conveying member (10c).

19. The strand winding apparatus (8) of claim 18; wherein the strand-conveying member (10c) is arranged outside of the body (12).

20. The strand winding apparatus (8) of claims 18 or 19; wherein the helical slit (9) makes a plurality of turns around the body (12) per revolution around said body.

21. A twisted flexible loop (6"), formed by the method of any one of claims 1-6.

22. A flexible loop (6") comprising one or more continuous flexible strands (1), characterized in that the strands are twisted and arranged in a helical fashion around an imaginary centre line CL to form a plurality of coils (lb) which collectively form a bundle (23) of a predetermined thickness (ti).