GB2228776A

GB2228776A - Rod or cable fastening

Info

Publication number: GB2228776A
Application number: GB8928911A
Authority: GB
Inventors: Renan Lochouarn
Original assignee: EPI ETUDES PROD IND
Current assignee: EPI ETUDES PROD IND
Priority date: 1989-01-10
Filing date: 1989-12-21
Publication date: 1990-09-05
Anticipated expiration: 2009-12-21
Also published as: FR2642446A1; NL9000015A; GB8928911D0; DE3942535A1; FR2642446B1; GB2228776B

Abstract

An end fastening 1 for a cable or rod 3 made by pultrusion of carbon or synthetic fibres is secured to the rod by first surrounding the rod end with a fabric or braid 2 of mineral or synthetic material of a length at least equal to the length of the end fastening and being impregnated with a polymerizable adhesive, then inserting this into the end fastening and then heating in the temperature range 60 to 120 DEG set the adhesive. The resulting cable can be used as a carrier or guy. <IMAGE>

Description

PROCESS AND ASSEMBLY FOR FIXING CABLES The present invention relates to cables and cable carriers and more particularly to a process for fixing or securing extruded rods to end fastenings or mechanical attachments.

It should first of all be recalled that pultrusion, a die extrusion technique in which the material undergoes a drawing process at the same time, provides a means of producing composite rods or cables of different materials, e.g. with a carbon fibre or synthetic fibre base such as aramide or the like.

Synthetic textile fibres of high mechanical performance and with a high elasticity modulus are being used with increasing frequen~ > in place of steel In certain fields of application, i.e. oceanographic, maritime, submarine and eronanticel, as all as on land, as supports for electromechanical cables an for cables with optical fibres, or again, as guy.: for pylons of transmission and receiving riajs or #uyin# elements on racing boats or pleasure craft (with ei.h one or more hulls).This enables considerabl@ increase in power to be obtained together with noticeable reduction in weight, particularly at the masF head.

These supporting devices are at present mave ~ assembled and sheathed synthetic fibres or else of singie- wire or single-strand stainless steel or of ordinary steel wire. Such cables or guys, in consequence of their weight, the space they occupy and their torque, prevent the required performance from being obtained in the guying system as a whole.

Up to the present the use of pultruded rods of carbon or synthetic fibres, of which the excellent performance is known, has#not been considered, the main reason being the difficulty or impossibility of connecting these rods firmly to end fastenings or attachments only occupying very limited space and producing assemblies having considerable breaking strength. Attempts to use adhesive such as resins or polymerizable or similar compositions for the ends of the rods before and during their introduction into a fastening or attachment body have only given mediocre and disappointing results, both as regards the adhesion of the substance employed and as regards the mechanical properties obtained, particularly the tensile strength.

The invention provides a solution to this technical problem, its purpose being to produce assemblies of rods and attachment bodies with high mechanical performance, with the characteristics usually required in the aforementioned fields of application as regards lightness, limited elongation and aerodynamic properties.

Accordingly the invention provides a process for fixing or securing a pultruded rod with a natural or synthetic fibre base to end fastening(s) or attachment(s) in which a piece of fabric or a braid of a mineral or synthetic material, imprenated in advance with a polymerizable adhesive composition, is placed on the rod, in a position for attachment to the attachment body and over a length at least equal to that of the attachment body (b) this assembly is inserted, with the exertion of traction, into the attachment body; and (c) the fabric or braided portion and the attachment body are then heated to a temperature substantially in the range 60 to l2O0C.

The invention extends to a rod or cable assembly so produced.

The pultruded rod, here regarded as known per se, can be selected from among existing materials, such as synthetic fibres of high physical and mechanical performance, e.g.

aramide fibres. With reference to a preferred but not limitative version of the invention the following description will be confined to the case of carbon fibres rods produced by the pultrusion of sets of cores of highstrength carbon filaments in a die of synthetic impregnation resin.

The invention provides that in the zone adjacent to the attachment body which will serve to secure the rod the latter is provided with a piece of fabric or braiding of natural or synthetic material. In practice it has been found convenient, particularly in the case of the carbon rod, to use a braiding of glass fibres capable of being fitted around the rod or cable like a stocking, starting from one end. This braiding is impregnated in advance with a resin or polymerizable synthetic composition capable of serving as an adhesive, such as compositions with an epoxy and amine resin base.

In a preferred embodiment of the invention the length of braiding placed on the rod in the vicinity of the attachment body is at least equal to three times the length of this latter.

Further characteristics of the invention will emerge from the following description, relating to a non-limitative embodiment illustrated in the accompanying drawings, consisting of the following schematic diagrams: Fig. 1: a section through the end fastening assembly mounted by the process to which the invention relates.

Fig. 2: a more detailed view, in half-section, of the end attachment body.

Fig. 3: a section through a complete assembly consisting of a rod fitted at both ends with an attachment device.

As may be seen from Figs. 1 and 3, a system assembled in accordance with the invention consists essentially of the pultruded rod 3, the braid 2,2' over a certain length and the end fastening or attachment body, 1,1'.

In one particularly advantageous example of the invention the rod used, with a resistance of 4600 daN, consists of a combination of 32 strands of 12000 filaments of high-strength carbon, impregnated with a heat-hardening resin with 100 parts (by weight) of epoxy resin to 27.5 parts (by weight) of amine as the hardening agent. After the rod has been produced to the right length for the particular purpose in view and then treated with the abrasive the portion to be covered with the braid is cleaned with a solvent (such as acetone). The braid, e.g. of glass fibres, is impregnated beforehand with polymerizable resin, such as that already mentioned and having an epoxy/amine base, after which it is cut to a length at least equal to that of the attachment body. In practice this length of braid is important, being the means of determining the final resistance of the cable thus produced.In most cases it is about three to four times the length of the attachment body. In the case of the aforementioned carbon fibre, for instance, knowing that the heat-hardening resin has a combined tension and shear resistance of 2.4 daN/mm2, we find that an "adhesion length" of 94mm represents a resistance of 4610 daN, which is thus compatible with the carbon rod of 4600 daN. This length of 94mm will therefore be that selected for attachment body or bodies.

The use of a braid, e.g. of carbon fibre as in the present case, offers particular advantages owing to the angle of inclination of the fibres in relation to the axis of the rod. These fibres are wound spirally around the periphery of the rod, which assists the automatic tightening effect accompanying the traction exerted on the attachment body and enables the assembly prepared in accordance with the invention to be rendered more resistant.

In one variant of the invention the braid can be covered, before the polymerization of the resin with which it is impregnated, with a sheath of heat-shrinking material which by reason of its shrinkage enables the surplus impregnation agent and also any adhesion faults to be eliminated.

The braid thus cut and impregnated is then placed on the rod, after which the assembly is drawn into the attachment body as far as the end of the braid. The attachment body is then moved until it is on a level with the end of the pultruded rod and the length of braiding extending beyond the attachment body is cut off. Finally, the entire system is kept at a temperature generally between 600 and 1200 in order to ensure the polymerization and hardening of the impregnation resin and the adhesive.

The attachment body 1, which may be of metal (such as titanium), of metal alloy or of synthetic polymer (such as aramide), can with advantage consist of a tube of which the internal wall may be either smooth or provided with circular grooves over all or part of its length. In one version these grooves may likewise be helicoidal. In the preferred example illustrated in the detailed diagram in Fig. 2 the attachment body is provided, on a level with the flat portion 4 enabling it to be tightened up, with a slightly shouldered portion 5 continuing in the form of a screw-threaded element 6 by which it can be connected to any securing device or end cap serving to take the strain.

With the process to which the invention relates very reliable high-strength carrier cable assemblies can be produced. By way of comparison, for example, the conventional method by which a pultrude- rod of carbon fibres with a diameter of 4mm is secured with the use of an adhesive provides a breaking strength of the order of 1500 daN, whereas that provided by the invention will resist a load of at least 2400 daN, in addition to the greatly improved ageing resistance of the system.

There are numerous applications for this process, among which mention may be made of the following: the construction of carrier cables and traction cables, the guying of masts for vessels or the reinforcement of frameworks, such as those of surgical operating tables. The attachment system according to the invention can also be used on supports of electronic cables or of cables with optical fibres, where the electrical or optical part can be tightly connected to the attachment body described.

Claims

1. A process for fixing or securing a pultruded rod with a natural or synthetic fibre base to end fastening(s) or attachment(s) in which a piece of fabric or a braid of a mineral or synthetic material, imprenated in advance with a polymerizable adhesive composition, is placed on the rod, in a position for attachment to the attachment body and over a length at least equal to that of the attachment body (b) this assembly is inserted, with the exertion of traction, into the attachment body; and (c) the fabric or braided portion and the attachment body are then heated to a temperature substantially in the range 60 to 1200C.

2. A process in accordance wtih Claim 1, in which the pultruded rod consists of carbon fibres while the braid or fabric comprises either glass fibres, carbon fibres or synthetic polymers.

3. A process in accordance with Claim 1 or Claim 2, in which the attachment body is formed by a hollow element of metal such as titanium, metal alloy or synthetic polymer.

4. A process in accordance with Claim 3, in which the hollow element is a tube of which the internal wall is either smooth or provided over the whole or part of its length with circular or helicoidal grooves.

5. A process according to any of Claims 1 to 4 in which the fabric or braid extends over a length at least three times the length of the attachment body.

6. A process in accordance with any one of Claims 1 to 5, in which the fabric or braid is covered, before being inserted into the attachment body and prior to the polymerization, with a sheath of heat-shrinking plastics material.

7. A process substantially as described herein with reference to the accompanying drawings.

8. An assembly comprising a pultruded rod, a covering braid and an attachment body or end fastening, produced in accordance with any of Claims 1 to 7.

9. A carrier cable according to Claim 8 in which the attachment body is connected to an electromagnetic cable or to a cable with optical fibres.