WO1993018997A1

WO1993018997A1 - Rope splice

Info

Publication number: WO1993018997A1
Application number: PCT/GB1993/000565
Authority: WO
Inventors: John Mawson Walton; Michael Thomas Burtoft
Original assignee: Bridon Plc
Priority date: 1992-03-20
Filing date: 1993-03-19
Publication date: 1993-09-30
Also published as: ZA931947B; AU3761093A; GB9206094D0; GB2265162B; GB2265162A

Abstract

An end portion (3a) of each strand tail of one length of rope is connected end-to-end to an end portion (3b) of a strand tail (or core portion) of the other length of rope, by a connector (1) having terminal socket portions, with interposed adhesive (4).

Description

Rope Splice

There are many materials handling and transportation systems around the world which operate with an endless loop of wire rope. Typically these members are formed by manufacturing one or more ropes of finite length, which are then jointed into an endless loop of the requisite size. A technique known as ' long splicing' is used to effect the necessary connections, producing what may be regarded as an invisible joint.

The technique of long splicing is, of course, well known to those skilled in the art of wire rope manufacture, but it will be convenient to give a brief description here.

Figures 7 and 8 of the accompanying drawings illustrate a known method of splicing together two rope lengths A and B (which may be two ends of one rope), the rope being 26 mm in diameter, for example, and having a core strand and six outer strands (each strand consisting of twisted wires). Bindings are applied to the rope lengths and then the six strands (referred to as strands Al, A2, A3, A4, A5 and A6 for rope length A, and Bl, B2, B3, B4, B5 and B6 for rope, length B) are unwound back to the bindings. The core strand 2 of each rope length A and B is then cut off at the respective binding.

The ends of the rope lengths A and B are now brought together with the strands interlocking in regular order as shown in Figure 7 and the binding on the rope length A is removed.

Strand Al is then gradually unwound from the rope length A, and the corresponding strand Bl of the rope B is laid in its place until only a short length of Bl remains unwound. The unwound strand Al is cut off, leaving a loose end similar to that of strand Bl. A temporary binding may be placed over the junction of the strands Al and Bl.

Strand A3 is then unwound from the rope length A and strand B3 laid in its place, in similar fashion to strands Al and Bl, and this process is carried back to a separate point. The loose ends of strands A3 and B3 are cut off to a short length, and again a temporary binding can be placed over the junction of the strands A3 and B3. The same procedure is then carried out for strands A5 and B5.

The binding is then removed from the rope length B and the procedure described above with regard to unwinding and winding of strands is then followed; that is, strand B2 is unwound and strand A2 wound in its place, strand B4 is unwound and strand A4 wound in its place back to a different point, and strand B6 is unwound and strand A6 is wound in its place. The loose end of each of these strands is cut off to a short length. Figure 8 shows the state of the splice at this stage. It is now necessary to deal with the strand ends, and in fact these can be dealt with in a variety of ways.

In particular, each strand end is tucked into the centre of the rope. This process involves temporary opening out of the strands of the rope and removal of a short length of the core strand. Each strand end is butted up to another strand end or to a portion of the remaining core strand.

Long splicing is an effective and well proven technique, but it is known that, under the dynamic loading conditions to which it is usually subjected, the splice may "draw", that is the endless rope loop may elongate, due to gradual and progressive slip of the splice. Various treatments of the splice tails have been developed to minimise this effect and to prolong the useful life of the splice, but none of these have proved fully effective.

The present invention provides a long splice connecting two portions of a rope, and means for connecting together the strand tails from the adjacent tucks in the long splice, to resist relative movement (separation) of the tails when the rope is loaded and worked.

In this way it becomes possible to greatly reduce or totally obviate the occurrence of splice draw, which is expected to substantially improve the potential service life of endless rope haulage systems. An anticipated additional benefit is that appreciably shorter splice lengths will prove effective, with consequent savings in cost.

Accordingly, the invention provides a rope splice formed between two lengths of rope of similar construction, each length of rope comprising strands extending helically around the rope axis, and optionally a core extending along the rope axis, the two lengths of rope overlapping in the region of the splice, where their strands form strand tails of finite length and their cores, if any, form core portions of finite length, characterised in that an end portion of each strand tail of one length of rope is connected end-to-end to an end portion of a strand tail or core portion of the other length of rope, by a connector having terminal socket portions in which the said end portions are respectively secured.

The invention will be described further, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a longitudinal section through a connection between two strands of a long splice;

Figure 2 is a similar view of another embodiment of the connection; Figure 3 is a similar view of a further embodiment of the connection;

Figure 4 is a side view of an articulated connector;

Figure 5 is a plan view of the articulated connector;

Figure 6 is a part cut-away side view of a long splice, showing an articulated connector at the centre;

Figure 7 is a fragmentary side view of two rope lengths prepared for making a long splice; and

Figure 8 is a diagrammatic side view illustrating an intermediate stage during the formation of the splice and indicating dimensions by way of example.

In its most basic form, the connection may be provided by a rigid tubular connector which extends longitudinally over the two strand ends, and is secured to them by a suitable bonding agent, such as an adhesive or thermosetting resin compound. Two exemplary forms of connector are illustrated in Figures 1 and 2. Figure 1 illustrates a connector 1 in the form of a ferrule with a parallel bore 2, the ferrule having terminal socket portions la, lb which fit closely around the respective strand ends 3a, 3b with interposition of a suitable adhesive compound 4, capable of transmitting axial load by means of shear transfer. Figure 2 is a variation of the concept and incorporates a conical taper 6 converging towards the outer end of each socket portion la, lb, which entraps the bonding agent 7 (e. g. a • thermosetting resin compound) and generates an additional radial gripping force when axial load is subsequently applied to the strands, by virtue of the wedging action of the (resin) cone.

The joints referred to above are located within the core of the rope (not shown), the strands 3a, 3b being introduced into the ferrule 1 and positioned before the adhesive/resin curing takes place.

A recognised limitation of the foregoing connection means is that the ferrule will be subjected to bending stresses when the rope is worked over sheaves and pulleys. An alternative design of ferrule is therefore proposed which substantially reduces the ferrule stiffness and hence the stresses due to bending. Figure 3 illustrates part of a tubular ferrule 1 which incorporates a waisted central section 8, which may be introduced into the ferrule by machining, pressing, or swaging (or in composite form, by filament winding). For example a reduction of 25% in the diameter of the tube, at the waist, will reduce the flexural stiffness by more than 50% without any loss in sectional area, as illustrated in Table 1.

Table 1. Effect of aistin on Ferrule Stiffness*

% Reduction in diameter 0 10 15 20 25 30 35 40 at waist

Relative

Flexural 100 77 66 56 47 38 30 22

Stiffness

* Assume 10% wall thickness and constant cross-sectional area of ferrule at waist.

For applications where severe and frequently repeated bending is involved, the rigid tubular ferrule may be replaced by an articulated connector 1 comprising two shorter closed ferrules la, lb flexibly linked together at their closed ends, as part-illustrated, for example, in Figures 4 and 5, although various other detailed arrangements are possible. The ferrules la, lb are again secured to the respective strand ends by the means described earlier and illustrated in Figures 1 and ^"1.

Figure 6 shows an articulated connector 1 which has two mutually orthogonal pivot pins 11 and 12 and is located in the centre of the rope splice 9, being coaxial with the two lengths of rope which have been spliced together.

The degree of articulation required will depend upon the severity of bending, and the length of ferrule. Examples of typical service conditions are given in Table 2, together with the optimum range of joint articulation (for an assumed ferrule length of 1.5 x the rope diameter).

Table 2 Required Articulation of Ferrule Joint

Bending ratio: Sheave dia.

24 32 40 48

Rope dia.

Angular freedom

(degrees) +7.2 +5.4 +4.3 +3.6

It is observed that from a design viewpoint the articulation requirement is in conflict with the need to maximise the tensile strength of the joint. The angular freedom of the joint should therefore be kept to an absolute minimum, i.e. say +5^* for a bending ratio of 40:1 (allowing for manufacturing tolerances).

Using the techniques described above, it is possible to provide:

(a) A wire rope splice incorporating a connecting means between the tails of adjacent strand tucks capable of transmitting axial load and resisting the separation of the strand tails as the rope is worked.

(b) A wire rope splice incorporating a connecting means between the tails of adjacent strand tucks, comprising a rigid tubular ferrule within which the two ends of strand are secured.

(c) A splice as in (b), with internal parallel bore and adhesive bonding. (d) A splice as in (b), with internal tapering section and potting compound to generate self-wedging gripping action.

(e) A splice as in (a) to (e), with a waisted central section.

(f) A wire rope splice incorporating a connecting means between the tails of adjacent strand tucks, comprising a pair of flexibly coupled tubular ferrules within which the ends of the strands are secured.

(g)- A splice as in (f), with a means of articulation between the two interconnected ferrules. (h) A splice as in (g) in which the articulation is limited to +5^*. (i) A splice as in (a) to (h), in which the ferrule(s) is/are metallic. (j ) A splice as in (a) to (h), in which the ferrule(s) is/are manufactured from composite material, such as CFRP (carbon fibre reinforced plastics), (k) A splice as in (a) to (j), in which the connecting means are located in the centre of and coaxial with the rope, and are surrounded by the outer strands. The above-described method of splice enhancement is most applicable to ropes of 6 to 9 strand construction where the core accommodation within the rope is larger than the diameter of the outer strands. The lengths of strand tail not covered by the connector, may be built up to support the outer strands, in the usual way. In addition to being used to connect adjacent strand tails to one another, the method may also be used to connect the first and last strand tucks of the splice to the adjacent core ends, if the core is capable of carrying an appreciable load and can be reduced to a size which is compatible with the connector.

The preferred length of ferrule should be sufficient to accommodate strand ends of length equivalent to 4-8 times their own diameter, although alternative gripping lengths of etween 2x and lOx the strand diameter may be considered, depending on the service duty.

The taper angle of the conical bore section of the ferrule, if used, is preferably.2-6^* (i.e. 4-12" included angle), although a wider range of angles could be considered, depending on detailed design considerations. The resin or adhesive bonding compound may be introduced into the ferrule bore or after the strand insertion. Injection holes may be provided in the ferrule if the potting material is to be introduced last. If the resin injection is not the final operation, then all necessary adjustments must be completed before the potting material begins to set.

The connector will ordinarily be manufactured from metal(which term includes alloys) e.g. high strength steel, but alternatively non-metallic materials, such as carbon fibre reinforced plastics, may be considered for some duties, for example where the rope itself is fabricated from such advanced fibre material.

To assist bonding, the area of the strand tail that will be located within the. connection means, is thoroughly cleaned and degreased. Similarly, the internal bore of the.parallel ferrule shown in Figure 1 will also be thoroughly cleaned and for some adhesive systems the surfaces may be advantageously pre-treated with a priming agent. Additional gripping advantages may be obtained by grooving the internal bore of the ferrule in a substantially transverse (or hoop) direction (not shown).

Where the tapered or conical ferrule is adopted, then a bond to the ferrule is no longer desirable as it would resist the movement required to achieve the wedging action. The internal bore of the ferrule 1 shown in Figure 2 may therefore be advantageously pre-treated with a release agent which prevents the potting material adhering to it, whilst not impairing the bond to the strand.

It will be appreciated that, by means of the above-described connectors, it is possible to achieve a connection whose breaking strength approaches the breaking strength of the individual strands.

Claims

CLAIMS:

1. A rope splice formed between two lengths of rope of similar construction, each length of rope comprising strands extending helically around the rope axis, and optionally a core extending along the rope axis, the two lengths of rope overlapping in the region of the splice, where their strands form strand tails of finite length and their cores, if any, form core portions of finite length, characterised in that an end portion (3a) of each strand tail of one length of rope is connected end-to-end to an end portion (3b) of a strand tail or core portion of the other length of rope, by a connector (1) having terminal socket portions (la, lb) in which the said end portions (3a, 3b) are respectively secured..

2. A rope splice as claimed in claim 1, in which each socket portion (la, lb) has a parallel bore (2) and is adhesively bonded to the corresponding end portion (3a, 3b).

3. A rope splice as claimed in claim 1, in which each socket portion (la, lb) has a bore (6) which tapers towards its outer end and potting compound (7) is interposed between the bore (6) and the corresponding end portion (3a, 3b).

4. A rope splice as claimed in claim 1, in which the connector (1) comprises a rigid tubular ferrule.

5. A rope splice as claimed in claim 4, in which the ferrule (1) has a waisted central section (8).

6. A rope splice as claimed in claim 1, in which the connector (1) comprises a pair of flexibly coupled ferrules (la, lb).

7. A rope splice as claimed in claim 6, including means for permitting articulation of the ferrules (la, lb).

8. A rope splice as claimed in claim 7, in which the articulation is limited to a range of at most ± 5".

9. A rope splice as claimed in claim 1, in which the connector (1) is metallic.

10. A rope splice as claimed in claim 1, in which the connector (1) is of composite material.

11. A rope splice as claimed in claim 1, in which the length of each said end portion within the connector is equal to 2 to 10 times, preferably 4 to 8 times, the diameter of the said end portion.

12. A rope splice as claimed in claim 1, in which the connector (1) is located in the centre of the rope splice and is coaxial with the two lengths of rope.