WO1989008210A1

WO1989008210A1 - Hawser socket

Info

Publication number: WO1989008210A1
Application number: PCT/NO1988/000018
Authority: WO
Inventors: Ivar Krogstad
Original assignee: Mocos - Marine And Offshore Consulting Services, A
Priority date: 1988-03-03
Filing date: 1988-03-03
Publication date: 1989-09-08

Abstract

A hawser attachment comprises an outer, internally conical socket (5) and a concentric inner, externally conical sleeve divided into segments (6). The strands of a rope (1) to be attached between the socket and sleeve are divided into groups (2, 3), one of the groups (2) being guided through the hollow space of the inner sleeve (6) from its narrowest end, over its broad end (14) and back along the inside of the outer socket (5), while the other group (3) is guided, overlapping the first group (2), in the opposite direction along the outside of the inner sleeve (6), around its broad end (14) and back through its hollow space.

Description

HAWSER SOCKET

The invention relates to a sleeve-like end attachment or socket for ropes, preferably fiber ropes, and particularly double-braided ropes having a core and an outer layer. End attachments for fiber ropes are usually an eye splice. If the end attachment is to be subjected to higher loads, the eye is provided with a thimble which provides good support for about half of the circumference of the rope and a reasonably large bending radius. The ultimate strength of the rope at the eye splice is usually lower than for the rope itself. An eye splice comprises a relatively large part of the length of the rope.

For fiber ropes having parallel fibers without strands arranged in a hose-like sheath holding the fibers in place, conical metal sleeves or sockets with a central conical plug are used. The cone in the socket and the plug must be relatively long in order for the friction between the rope and socket to be sufficiently large for the rope not to slide out. This results in large radial forces and, thus, large dimensions of the socket relative to the rope.

For fiber ropes there is also an internally conical metal socket with an internal plastic socket which is conical on the outside. Here the rope is separated so that the core is guided through the axial cylindrical bore in the plastic sleeve, is bent around the rear thickest part of the sleeve, which is well rounded, and back on the outside along the conical part. The outer layer of the rope is guided on the outside of the core so that both parts of the rope are clamped against each other and between the plastic sleeve and the metal socket when the plastic sleeve with the rope is pressed into the metal socket (DE-OS 24 18 880).

For steel rope it is also used conical sockets as end attachments. The strands are spread outwards like a brush inside the socket and is thereupon cast in zink or thermosetting plastic. For steel rope there are also various conical sockets having internal clamping^'- sleeves where the strands either are clamped inside the inner sleeve or between the sleeve and socket.

All of these structures, where an internal socket with an internal cone is used together with a conical plug or internal sleeve conical on the outside, have a rela¬ tively slender cone in order to obtain a large clamping force.

By the end attachment according to the invention it is obtained that one can use a relatively short socket as end attachment, while concurrently the clamping action on the rope and the bursting effect on the socket are moderate.

In comparison it can be mentioned that a socket for 600 tons rope tension in accordance with the invention becomes about 30 cm long, while a 30 cm socket of the above-mentioned design having a conical plug will hold only. 15 tons. Both these designs are for fiber rope.

The moderate socket dimensions and the large hold¬ ing force are obtained according to the invention by dividing the strands of the rope into two groups, each taking about half the ultimate load. These two groups are guided in opposite directions back and forth along seg¬ ments which together constitute a sleeve which is cylind¬ rical on the inside and conical on the outside and rounded like half of a toroid at the rear where the sleeve is thickest. Each group of strands is divided into as many sub-groups as there are segments and is guided mainly along the surfaces of these segments. One of the groups of strands is guided from the forward edge of the sleeve along the conical outside, around the back and further back to the forward edge on the inside of the sleeve. The other group of strands is also led from the forward edge of the sleeve, but in the opposite direction and with the best possible contact with the first group. When the sleeve with the rope strands wrapped around it is pulled by the rope down into the internally conical metal socket, which approximately fits the conicity of the first sleeve with the rope wrapped around, the two groups of rope are pressed against each other over the entire contact length between the two cones, over the toroidal rear and through the middle of the cylinder. Thus, the two rope groups are locked against each other by friction and the harder the higher the rope force becomes. In addition comes the frictional force between the rope and the socket and sleeve along the entire length of contact between these parts .

In order to obtain the effect described, the seg¬ ments of the inner sleeve must be radially compressible so that the strands in the middle are subjected to about the same force as the strands between the sleeve and socket. The internal diameter of the sleeve must therefore be sufficiently small to allow the necessary compression. Thus, gaps will exist between the segments as long as the rope force has not reached the maximum.

The effect of the locking of the strands against each other becomes even better if the strands are arranged in more than two layers, where the tensional force in each layer is the opposite with respect to the preceding layer.

The outer sleeve or socket, which is to absorb the radial bursting force as tensile force and transmit the rope force further, is preferably made of metallic material. The inner sleeve generally takes up compres- sional forces only and may advantagelusly be plastic. it is therefore preferably made of plastic material.

Due to. the conicity the inner sleeve has a fairly high material thickness towards the rear, which can be utilized to provide a large bending radius for the strands of the rope passing over the semi-toroidal surface.

This is of advantage when it comes to giving the rope even loading. Small bending radii give local stress concentration in the outer fibers of the bent strand.

Since the inner sleeve is divided in segments, it is preferable to place guiding plates along the bounding surfaces in order to keep the rope strands in place before all the segments are placed in the outer socket. In addi¬ tion, one may also use elastic tape to keep the strands in place along the inner and the outer surface of the inner sleeve before the parts are finally placed in the outer socket.

When the rope is subjected to tension, the inner sleeve will be pulled radially farther into the outer socket and the rope strands will interlock gradually. Preferably, the tension in the various strands should be allowed to equalize as much as possible when the strands are locked more firmly. All the strands have to pass a cylindrical area at the center and an annular area bounded by the two cones . Since the same amount of rope has to pass through both areas, these have to be of about the same size. This is also true in the longitudinal direction, and the external cone of the inner sleeve will therefore be steeper than the internal cone of the outer socket. When the inner sleeve is displaced axially with respect to the socket, the relationship between the annular areas changes, but this may be utilized in order to improve the balance between the strands of the rope.

By carefully choosing the dimensions the strands will be compressed the most closest to the inlet or the leading edge, where the diameter is the least when the tensioning of the rope is commenced for the first time. The strands having the highest loading will in this situation extend over the entire length from the inlet, where the clamping load is relatively high but still mode¬ rate, further to the rear of the sleeve, around the bend and back towards the inlet. On this distance the clamping load will be less, while it increases towards the inlet on the return path. The clamping force in the center and in the annular space automatically will be equalized since the inner sleeve is free to adjust radially.

As the rope force increases and the inner sleeve is pulled farther into the outer socket, the annular area towards the rear of the sleeve becomes relatively smaller and the clamping force higher.

Thus, the major part of the frictional force for locking the rope will occur towards the rear of the sleeves, while the most critical part of the hawser attachment closest to the inlet for the rope provides only moderate clamping action on the rope. High clamping force will reduce the ultimate strength of the rope in the same area and it is therefore advantageous to have a moderate clamping action where the tensile load in the rope is the highest.

The method for assembling the rope in the hawser attachment becomes as follows, but the sequence of the various steps may be changed.

The rope is lashed some distance from the end and the braiding or twisting of the strands outside the lashing is opened. The loose strands are collected and pulled through the outer socket until also the lashing is through the socket. The strands are divided into two main groups, both of which represent about half of the tensile strength of the rope. For double braided ropes having a core and an outer layer this becomes very simple since each of these normally carries half the ultimate load and forms a natural main group.

Thereafter the groups are divided into the same number of sub-groups as there are segments in the inner sleeve and also as symmetrically as possible along the periphery of the rope. Advantageously the sub-grbups may be divided in further small groups of strands arranged as symmetrically as possible within the part of the periphery of the rope allocated to the segment.

The first segment is held approximately axially with respect to the rope at a predetermined distance between the lashing and the forward or thinest part of the segment. A sub-group of strands is run along the outside of the segment, over the rounded rear part and back along the inside of the segment. The strands are partly held in place by the guide plates extending in the radial exten¬ sion of the bounding surface between the segments, but in order to ascertain the correct length with respect to the lashing, it is advantageous also to secure the strands by means of elastic tape. A good safeguarding is to secure the end of the sub-group to itself by means of the tape just outside the leading edge of the segment. The second sub-group is thereafter run in the opposite direction of the first between the guiding plates on the inside of the segment, around the rear part and back along the outside until it has passed the forward or leading edge of the segment and is secured by means of tape to all the other strands, which thus run both forwards and backwards at this point. It will be necessary to somewhat bend aside the guide plates on the inside of the segment in order to make room for the la.st sub-group of strands .

If the sub-groups are further divided into small groups, the method becomes much the same. The strands in each small group are run in opposite direction as descri¬ bed above. In order to obtain the best effect of the sub¬ dividing, care is taken that the layers become as even as possible so that strands running in opposite directions obtain the best possible contact with each other. In order for this to be obtained, the strands may be flattened or partially opened. On the outside of the segment it is relatively simple to obtain good stratifi¬ cation, while on the inside good contact may also be obtained between the strands from the two main groups when they are pressed between the guide plates. When the strands are sufficiently secured by means of e.g. elastic tape, the segment may be released and the next segment be placed in the corresponding position with respect to the lashing. This segment and the remaining segments are covered with strands in a corresponding manner. Thereupon the segments are placed axially and symmetrically with respect to the rope as well as possible, and the segments are mutually secured temporarily by means of elastic tape. Then the rope is pulled back through the outer socket until the cone of the segments meets the internally conical surface of the outer socket . When the rope is subjected to tension, the segments will be pulled further into the socket and normally be locked therein .

The figures show an exemplifying embodiment of the invention, where Fig. 1 shows a longitudinal section, Fig. 2 shows a cross-section and Figs. 3 and 4 cross-sections of a segment without rope and with rope, respectively, before it is placed in the outer socket. Fig. 5 is a detail of the strands at the forward edge of the segments before they are pressed into the outer socket.

Fig. 1 shows a section through a hawser attachment after fastening of the hawser. At the bottom of the drawing the hawser 1 is seen from the outside. The hawser is a double-braided artificial fibre hawser having core 2 and outer layer 3, which each takes about half the ulti¬ mate load of the hawser. The outer layer 3 and the further course of the strands of the same are shown in black where they are shown in section in the drawings, while the core 2 is dotted. The rope is lashed 4 and above the lashing the braiding is loosened so that all the strands are free. The outer socket 5 is preferably made of steel in order to have moderate dimensions. Internally the socket 5 is conical 10, except from the lowest part at the inlet, which is shown cylindrical 9.

The internal sleeve consists of several segments 6 with leading or forward edge 7, conical outer surface 11, semitoroidal rear part 14 and cylindrical inner surface 12. The segments 6 are preferably made of plastic material which is deformable without damaging the rope.

The strands from the outer layer 3 are guided along the conical outer surface 11 of the segments 6, over the toroidal rear part 14 and back to the leading edge 7 along the inside 12 of the segments 6. The strands from the core 2 of the rope are guided centrally of the segments 6, on the outside of the outer layer 3, over the toroidal rear part 14 of the segments 6 and back towards the inlet 9 of the outer socket 5.

The figure also shows that the unloaded ends of the strands of the core 2 provide protection for the most highly loaded parts of the outer layer 3 in the area 9 at the inlet of the socket 5. Similarly, the unloaded end of the strands of the outer layer 3 provides protection of the most highly loaded parts of the core 2 at the leading edge 7 of the segments 6.

Fig. 2 is a cross-section along the line I - I in Fig. 1. The inner sleeve is divided axially into four identical segments 6.

Guide plates 8, 8' are shown in the bounding sur- faces adjacent the next segment and these guide plates are radially extended on the inside and outside of the seg¬ ment. The purpose is to hold the strands in place in the segments 6 before these are placed in the outer socket 5. The drawing shows that the inner parts of the guide plates 8, 8' have been deformed when the segments 6 were pulled into the outer socket 5.

The guide plates 8, 8' are glued to the segments, but they may also be made in one piece.

Fig. 3 shows a similar cross-section as Fig. 2 through a segment 6 having guide plates 8, 8' before the rope strands are assembled.

Pig. 4 shows a cross-section of the same segment after the rope strands 2, 3 have been assembled but before the segments 6 are pulled into the outer socket. In this section the rope strands 2, 3 are further divided into small groups 2', 2", 3' , 3" of the core 2 and outer layer 3. These small groups lie in layers 2' , 3' and 2", 3", and the strands 2 and 3 have opposite tension directions. As compared to Fig. 2, the number of contact surfaces between the layers have been increased from one to three and, since the compression force is about the same, the frictional forces locking the rope in the hawser attach¬ ment is about tripled.

In order for the rope strands 2, 3, which here are not compressed, to have sufficient room on the inside 12 of the segments 6, the guide plates 8, 8' must be deformed in this area. This deformation was identical for the arrangement in Fig. 2 before the segments 6 were in- serted in the socket 5.

Fig. 5 shows a longitudinal section through the segments 6 at the leading edge 7 before the segments are arranged in the outer socket 5. The figure shows, with exaggerated thickness, elastic tapes 15 and 16 holding the strands together in the outer layer 3 and the core 2, respectively, for each segment 6. Since here the outer layers 3 lie between the core strands 2, also the outer strands become surrounded by the tape 16. More tape 17 holds all the segments with the strands together ahead of the leading edge 7 and further up along the conical surface.

Claims

C l a i m s

1. A hawser attachment, comprising an outer, internally conical socket (5), from which the rope force is to be transmitted, and an inner, externally conical sleeve (6) being well rounded at the thickest end of the sleeve, where the strands or the like of a rope (1) are divided into two groups (2, 3), the first group (2) being guided from the narrow end of the inner sleeve (6) through its generally cylindrical hollow space, over the well rounded broad end (14) and back into the annular space between the socket and sleeve (5, 6), while the second group (3) is guided into the annular space between the socket and sleeve (5, 6) and overlaps the first group (2), c h a r a c t e r i z e d in that the inner sleeve is sub-divided into segments (6), the diameter of its generally cylindrical hollow space, in the closely spaced position of the segments, being smaller than the diameter of the rope (1) and in that the second group (3) further is guided over said broad end (14) and back in said generally cylindrical hollow space.

2. A hawser attachment according to claim 1, c h a r a c t e r i z e d in that at least parts of the second group (3) are guided on the iriside of the first group (2) in the annular space between the socket and sleeve (5, 6) and on the outside of the first group (2) in the inner space of the segments (6).

3. A hawser attachment according to claim 1 or 2, c h a r a c t e r i z e d in that guide plates (8, 8' ) are arranged in the extension of the radial end surfaces of the segments (6), said guide plates separating the segments (6) for holding the strands (2, 3) in place before they are arranged in the outer socket (5).

4. A hawser attachment according to claim 1, 2 or 3, c h a r a c t e r i z e d in that the outer socket (5) is made of metallic material.

5. A hawser attachment according to one of the preceding claims, c h a r a c t e r i z e d in that the segments (6) are made of plastic material.

6. A hawser attachment according to one of the preceding claims, c h a r a c t e r i z e d in that the cone angle for the internal conical surface (10) of the outer socket (5) is smaller than that of the outer conical surface (11) of the segments (6).

7. A method for attaching a rope (1) to an end attachment comprising an outer internally conical socket

(5) and a concentric inner, externally conical sleeve (6), where the strands or the like of the rope (1) are divided into two groups (2, 3) and the first group (2) is guided from the narrow end of the inner sleeve (6) through its generally cylindrical inner space, over its well rounded broad end (14) and back in an annular space between the socket and sleeve (5, 6), while the second group (3) is guided into the annular space for overlapping the first group (2), whereupon the inner sleeve (6) is forced into the outer socket (5) in order to press the two groups (2, 3) against each other and against the conical surfaces (10, 11) of the socket and sleeve (5, 6), c h a r a c t e r i z e d by the use of an inner sleeve which is divided into segments (6), and in that the second group (3) is guided further over the broad end (14) of the segments and back through the generally cylindrical hollow space formed by the inner surfaces (12) of the segments

(6) .

8. A method according to claim 7, c h a r a c t e¬ r i z e d in that at least parts of the second group (3) are guided along the surface (11, 14, 12) of the segments ( 6 ) .

9. A method according to claim 7 or 8, c h a r a c t e r i z e d in that the two groups (2, 3) are divided into several small groups (2¹ , 2", 3', 3") which are intermixed around the segments (6).

10. A method according to claim 7, 8 or 9, c h a r a c t e r i z e d in that at least one of the groups (2, 3) or small groups (2', 2", 3', 3") are lashed, preferably by means of adhesive tape (15, 16, 17) at the narrow end of the segments (6).