Background Hawsers are designed for long-lasting, large strains, especially hawsers for maritime environments, for instance when used for offshore moorings. There are high requirements to wear resistance and longevity.

Cables with binding agent in the core (US patent 4312260), sheathing braiding giving reduced inner friction (US patent 4640178), ropes intended to have high exterior friction (US patent 5934168) and ropes with an especially dense surface to prevent penetration of pollution (US patent 6099961) are known. None of these attempt to meet the demand for high wear resistance by improving the outer structure.

From US patent 4,534, 163 (New England Ropes, 1985), it is known to cross spoole a rope core of parallel fibres with tape. To ensure enhanced wear resistance, this spooling construction is coated with a layer of plastic. However, this is not a satisfactory solution, neither in regard to cost, nor for satisfying the need for wear resistance for demanding use.

Objectives The main object of the invention is to provide a method which yields a wear resistant hawser and to produce a longevity hawser for demanding application purposes.

In particular, an object is to create a hawser which has an even and hard-wearing outer surface, and thus can tolerate more wearing and strain, as for instance buckling, than other known hawsers.

Furthermore, it is an object create a hawser with a surface so dense that the penetration of contaminants, such as sand and plancton, or the risk of hooking a foreign body, as for instance fishing hooks, is considerably reduced.

The invention The invention is indicated in patent claim 1. This hawser has a sheathing with extreme wear resistance and resistance to penetration of foreign matter, as well as simultaneously tolerating a much smaller bending radius than hawsers with conventional plastic layers. Because of the sheathing construction, it will not burst at a small bending radius. In claim 2, a particularly preferred embodiment is indicated.

In addition, the invention comprises a method of producing hawsers, as indicated in claim 3.

After short period of use, the sheathing will get a hairy surface. This makes the sheathing more resistant than known hawsers to mechanical wearing and penetration of foreign matter, as for instance sand and dirt.

A more detailed description of the invention will follow below.

Example The invention will be further described with reference to the drawings, where Fig. I is a schematic illustration of an installation for manufacturing hawsers according to the invention, Fig. 2 is a schematic front elevation view of the braiding machine of the installation in Fig. 1, Fig. 3 and 4 are side elevation views of the braid zone for two hawsers with different cores, Fig. 5 is a plane view of a ribbon which can be used for manufacturing a hawser according to the invention, Fig. 6 is an end elevation view of the ribbon in Fig. 5, while Fig. 7 is a side elevation view of a used hawser according to the invention, for illustration of the term "fairing".

Fig. 1 schematic illustrates an installation 11 for manufacturing of a hawser. The installation, the principle of which is known, comprises a number of not shown spools with parallel or braided strands 12, which may be 3-, 4-, 8-or 12-fold, and which are guided through a guide disk 13 with a hole for each strand, and further together to form a hawser core 14 at the entrance 15 of a braiding machine 16 with spools 17 of sheath ribbons 18 which are braided as a dense sheath 19 onto the core 14. The hawser core 14 and the sheath 19 form together the final hawser 20. The final hawser 20 is spooled onto a reel 21.

The braiding machine 16 has a rotatable journal led carrying disk 22, which supports a number of rotating spool holders 23. The spool holders 23 may be operated by gear wheels for performing a cyclic movement relative to the adjacent spools, when the braiding machine 16 rotates. The number of spool holders and accordingly the number of sheath ribbons 18 may vary between 4 and 32, depending on ribbon broadness and hawser diameter.

Fig. 2 is a front elevation view of the braiding machine 16 with the spool holders 23, which illustrates how the sheath ribbons 18 are arranged in equal numbers in each direction (left-and rightwards). This is part of prior art, and will not be further described here.

In Fig. 3 and 4, two hawsers 20 are shown, which are spooled with a braided core 24 (Fig. 3) and a parallel core 25 ("multicore") (Fig. 4), respectively.

Fig. 5 is a side view of a sheath ribbon 18 which is woven together with six parallel, twisted fibre parts 26. Each such twisted fibre part 26 is formed of a number of fibres 27 and the sheath ribbon 18 is held together by transverse inwrought threads 28. The threads 28 are very hard-wearing, for instance Dyneema (trademark). If the thread 28 should burst, the construction of the sheathing will prevent it to loosen. This is because ribbon crosses ribbon and mutually lock one another. Plastic material may be extruded onto the sheathing/sheath ribbon.

Fig. 6 is an end elevation view of the sheath ribbon 18 in Fig. 5, which illustrates how the weaving influences the fibre material.

The sheath ribbon 18 may be of polyester fibre, which is especially resistant to sunlight. Aramid fibre (nylon) may also be used, such as Kevlar (trademark), which is particularly heat-resistant. A third alternative is HM-polyethylene fibres, such as Dyneema (trademark), which are extreme mechanical strong fibres. The assembly of sheath ribbons in this manner can be done in a particular machine.

Fig. 7 is a section view of a hawser 20 which has a sheathing with fairing. Some of the sheath ribbons are provided with cutted threads to form threads 29 hanging out, or nap, which are called"fairing" and which contribute to stabilize the hawser movement when pulled through the water. Fairing is used to prevent vibration in the hawser and to reduce the drag factor. The fairing may especially be made of"Danline"or"Dyneema" (trademarks).

By a known process, the hawser 20 may be impregnated or coated with plastic coating of a suitable material.

Advantages of the invention 1. The hawser may be used with special winches where existing constructions do not have sufficient resistance to mechanical wearing.

2. It can be combined with"fairing". This reduces vibrations and the drag factor.

3. The dense sheathing prevents penetration of sand/dirt when anchoring makes the hawser lie on the sea floor.

4. It tolerates less bending radius than known hawsers.

5. In some cases, the sheathing can substitute steel eyelets because of its resistance to mechanical wearing.

6. Hawsers with such a sheathing have in some cases sufficient wear resistance to replace wire.

7. The ribbon construction gives the sheathing large resistance to mechanical wearing and to cutting by sharp objects, especially when using polyethylene fibres, such as Dyneema (trademark).

8. The sheathing will not open if a ribbon is cut.

9. The sheathing can be braided with various numbers of ribbons. The smallest number of sheath ribbons is 4.

10. Length and angle of the ribbon deposition can be adjusted according to application.