GB2262470A - Process and apparatus for the formation of elongate composite pultrusions - Google Patents

Abstract

Elongate composite pultrusions of curable material are manufactured by forming a first, solid, rod-like or hollow, sleeve- like inner member 2 of the composite; curing or partially curing said member; forming a second, outer member 12 around said inner member 2 and curing, or partially curing the second, outer member 12. Optionally, additional outer members may be applied by repeating the forming and curing steps to obtain a composite product of desired dimension. The invention also includes apparatus for carrying out the process, consisting of separate means to form and cure the first, inner member (not shown); means 8 to form a second, outer, member 12 around the inner member 2, e.g. from unidirectional reinforcing strands applied after passage through resin bath 10; means such as heated die 11 to cure the outer member 12 and, optionally, means 13 to apply a final winding of tape 14 to the composite. <IMAGE>

Description

PULTRUDED COMPOSITES This invention relates to amethod of manufacturing a composite by the pultrusion method, to apparatus for carrying out the method, and to composites produced by the method and/or apparatus.

Such composites are cured by heating of one form or another and whilst composites of relatively small section can be produced satisfactorily from both the economic and technical viewpoints, composites of a larger cross section give rise to difficulties in that the rate of pultrusion must be slowed, with attendant production losses, to provide sufficient time for heat penetration to achieve curing, in order tc avoid a reduction in strength and fle: ility of the composite.

Considering specificll the manufacture of a cable or hose which comprises at or near its nazis at least one inner core or other elongate means (for the transmission of e.g.

electrical or light signals or fluid flows), and an outer sleeve or annulus constructed from a composite material consisting of reinforcement fibres contained in a matrix which requires curing, the elongate core mentioned above is frequently damaged by the shrinkage and/or adherence of the composite sleeve which occurs during processing. Similar damage or displacement of fluids which may be an integral part of the inner core is known as a result of the pressure applied during processing. Such fluids have been known to burst the inner elongate core as a result of processing pressure and invade the surrounding uncured, partially cured or cured matrix resulting in overall degradation of the composite structure and interruptions to production.

In the case of composite materials which contain an elongate core(s) at or near their axes, the composite is usually provided to protect the elongate core(s) from axially applied loads which can result during installation or service, as in for example an underground cable or a suspended (aerial) cable, or other transmission means that is subject to for example catenary loads.

A basic object of the invention is to provide a method of manufacturing pultruded composites and suitable apparatus for carrying out the method whereby, even for larger section composites, the method and apparatus need not be slowed for curing reasons.

According to a first aspect of the invention , there is provided a method of manufacturing an elongate pultrusion composite of curable material comprising: 1. forming a first, inner member of the composite; 2. curing, or partially curing, the inner member; 3. forming a second, outer member around the inner member; and 4. curing, or partially curing, the second, outer member.

According to a second aspect of the invention, there is provided apparatus for carrying out the method of the first aspect comprising: 1. means to form the first, inner member of the composite; 2. means to cure, or partially cure, the inner member; 3. means to form a second, outer members(s) around the inner member; and 4. means to effect curing, or partial curing, of the second, outer member.

The invention also includes a pultruded composite manufactured by the above defined method and/or apparatus.

Thus, the invention departs from conventional techniques in that the composite is built up, in stages, from members of relatively small wall thickness, that can be fully cured, or partially cured, at relatively high pultrusion speeds resulting in substantially increased production possibly 50% or more - than has been possible with conventional, prior art techniques. Thus, composites may be produced to any desired final section, with the extent of curing assured, as no attempt is made to cure a final composite of finished section in one "pass". On the contrary, in accordance with the invention, the composite is produced in multiple curing, or partial curing, stages.

Furthermore, any required number of additional outer members may be produced, applied to the previous outer member, and cured, or partially cured, until a composite of required final section has been attained. Thus, should a composite be required of such final section that its production is not possible by one "pass" through the means (3) and (4) above, then either second or additional forming means (3) and curing means (4) may be provided downstream, or alternatively, the part finished composite may be passed for a second, third, etc. time through the first mentioned means (3) and (4).

The inner member may be a solid, rod-like member if the composite being produced is a bar such as a reinforcing bar or, alternatively, may be a hollow, sleeve-like member, particularly if the composite being produced is for example for an optical fibre cable, with an optical fibre core intended to be located within the inner sleeve-like member.

In the manufacture of a composite required to contain an inner core, for example a cable or hose within the sleevelike member, insertion of the core is rendered possible by the inner sleeve-like member preferably being formed initially as a plurality of separate elongate elements, which when assembled together, e.g. at a first forming station, form a hollow, e.g. circular section, sleeve. If, for instance, the plurality is two, then each elongate element is of semicircular section.In detail, the elongate element(s) constituting the inner sleeve-like member may be formed by drawing a plurality of uni-directional glass fibre reinforcing strands through an upstream, primary resin bath and then through heated dies, the latter providing both curing, or partial curing, and the profile section required, with the inner core introduced into the interior of the part-formed, inner sleeve-like member as the elements of the inner sleeve are brought together "cold", e.g. at an assembling head. The plurality of elongate elements adapted to form the inner sleeve-like member may conveniently be bonded together using for example a "hot melt" adhesive to form a complete concentric sleeve e.g. containing an inner core.

If required, the external surface of the inner member may be roughened to aid keying of the second and subsequent members before such sleeves are applied, e.g. by drawing glass fibre reinforcing strands through a secondary resin bath, and then cured, or partially cured, e.g. in a heated die. The surface of the finished composite can finally be helically overwound by one or more filaments to provide a "key", while a jacket, e.g. of polyethylene, may be applied at a later stage.

The composite when in the form of an optical fibre cable enables a jelly filling to be used without the attendant problems of jelly migration described earlier, as the first sleeve provide adequate eial protection to the core, e. r. optical fibres constrained within containment tubes.

Apart from preventing the core being squeezed, the inner sleeve assembly avoids mechanical loading being applied to the core.

The uni-directional reinforcing strands drawn through the secondary resin bath are applied to the assembled inner sleeve, or previous cured, or partially cured composite layer, before the composite enters the second (or subsequent) curing die. For this purpose, a bobbin may be provided with a number of radially spaced guide holes arranged axially with respect to the composite, to guide the strands into the secondary or subsequent curing die.

The bobbin may be partially rotated or oscillated in each direction about the axis of the composite to lay the reinforcing fibres in an alternate left hand and right hand helix to provide a partial binding effect, thus improving the resistance of the finished composite to fatigue and longitudinal splitting.

Although, as indicated previously, it is preferred that the plurality of elongate elements to form an inner sleeve consists of two 'C'-shaped elements adapted to be butted together to form the first sleeve, this first sleeve may be assembled from three elements, each subtending 1200 or four elements, each subtending 900 or more. Conventional adhesive e.g. hot melt adhesive, may be applied to appropriate surfaces of the elements to ensure temporary assembly.

One example of the method and apparatus for producing an optical fibre cable is shown by way of example in the schematic accompanying drawing of which Figure 1 is a plan view and Figure 2 a side elevation.

Conventionally, a plurality of uni-directional glass fibre reinforcing strands (not shown) are drawn through a primary resin bath (not shown) and then through heated dies (not shown) to provide both curing of the resin and profiling to form two semi-circular, elongate halves 1 adapted to be brought together downstream (as will be described later) to the form of a hollow sleeve 2 constituting the first, inner member of the composite containing an optical fibre core 3.

The core 3 is introduced into the part-formed sleeve 2 with the core and the two sleeve halves 1 firstly passed through a guide 4, and at a downstream station 5, hot melt adhesive is applied to the intended abutting surfaces of the semi-circular halves 1 to retain temporarily the halves in their sleeve 2 configuration with the three elements then being passed into an assembling head 6. Downstream of the latter is a station 7 to apply a roughened external surface to the emerging sleeve 2. Downstream of the station 7 is an oscillating bobbin 8 receiving a plurality of uni-directional, glass fibre reinforcing strands 9 from supply reels (not shown) after passage through a secondary resin bath 10, so that the strands 9 are layed in a sinuous manner around the sleeve 2 and the resin carried by the strands 9 is curd in a downstream heated die Ii to form an elongate, outer member 12 of annular section, downstream of which die 11 is a conventional puller or haulage unit (not shown), and beyond the puller overwinding units 13 are provided for applying a final winding of tape 14 to the composite.

Claims (31)

1. A method of manufacturing an elongate pultrusion composite of curable material comprising: (1) forming a first, inner member of the composite; (2) curing, or partially curing, the inner member; (3) forming a second, outer member around the inner member; and (4) curing, or partially curing the second, outer member.

2. A method as claimed in Claim 1, wherein steps (3) and (4) are repeated by applying any required number of additional outer members to the previous outer member, and curing or partially curing the additional outer member until a composite of required final section has been attained.

3. A method as claimed in Claim 1 or Claim 2, wherein the inner member takes the form of a solid, rod-like member.

4. A method as claimed in Claim 1 or Claim 2, wherein inner member is a hollow, sleeve-like member.

5. A method as claimed in Claim 4, wherein the sleeve-like member is formed initially as a plurality of separate elongate elements, which when assembled together form a hollow, e.g. circular section, sleeve.

6. A method as claimed in Claim 5, wherein two elongate elements are employed, each of semi-circular section.

7. A method as claimed in Claim 5 or Claim 6, wherein the elongate element(s) consituting the inner sleeve-like member is/are formed by drawing a plurality of uni directional glass fibre reinforcing strands through an upstream, primary resin bath and then through heated dies, the latter providing both curing, or partial curing, and the profile section required, with the inner core introduced into the interior of the part-formed inner sleeve-like member as the elements of the inner sleeve are brought together "cold".

8. A method as claimed in any one of Claims 5 to 7, wherein the plurality of elongate elements adapted to form the inner, sleeve-like member are bonded together using for example a "hot melt" adhesive to form a complete concentric sleeve.

9. A method as claimed in any preceding Claim, wherein the external surface of the inner member is roughened to aid keying of the second and subsequent members before such sleeves are applied.

10. A method as claimed in any preceding Claim, wherein the second outer member, and subsequent outer member(s) is/are formed by drawing glass fibre reinforcing strands through a secondary resin bath, and then by curing, or partially curing the strands and resin, e.g. in a heated die.

11. A method as claimed any preceding Claim, wherein the surface of the finished composite is helically overwound by one or more filaments to provide a "key".

12. A method as claimed in any preceding Claim, wherein an outer jacket, e.g. of polyethylene, is applied to the composite.

13. A method as claimed in Claim 7 and any claim appendant thereto, wherein the uni-directional reinforcing strands drawn through the secondary resin bath are applied to the assembled inner sleeve, or previous cured, or partially cured composite layer, before the composite enters the second (or subsequent) curing die using a bobbin provided with a number of radially spaced guide holes arranged axially with respect to the composite, to guide the strands into the secondary (or subsequent) curing die.

14. A method as claimed in Claim 13, wherein the bobbin is partially rotated or oscillated in each direction about the axis of the composite to lay the reinforcing fibres in an alternate left hand and right hand helix to provide a partial binding effect.

15. A method as claimed in Claim 5 and any Claim appendant thereto, wherein conventional adhesive e.g. hot melt adhesive s applied to appropriate surfaces of the elements to ensure temporary assembly.

16. A method of manufacturing an elongate pultrusion composite substantially as hereinbefore described with reference to the accompanying drawing.

17. Apparatus for carrying out the above defined method, comprising: (1) means to form the first, inner member of the composite; (2) means to cure, or partially cure, the inner member; (3) means to form a second, outer members(s) around the inner member; and (4) means to effect curing, or partial curing, of the second, outer member.

18. Apparatus as claimed in Claim 18, wherein second or additional forming means (3) and curing means (4) provided downstream.

19. Apparatus as claimed in Claim 17 or 18 comprising an upstream, primary resin bath followed by heated dies serving both to cure, or partially cure, and also to profile, the inner member.

20. Apparatus as claimed in any one of Claims 17 to 19, comprising a station at which adhesive is applied to intended abutting surfaces of elongate elements adapted to form a sleeve-like inner member.

21. Apparatus as claimed in Claim 20, comprising an assembly head, downstream of the adhesive station, at which a plurality of elongate elements adapted to constitute the inner, sleet like members are brought together.

22. Apparatus as claimed in Claim 21, comprising a surface roughening station, downstream of the assembling head.

23. Apparatus as ciaimed in Claim 22, comprising an oscillating bobbin downstream of the surface roughening station, and an associated secondary, resin bath.

24. Apparatus as claimed in Claim 23, comprising a heated die downstream of the bobbin.

25. Apparatus as claimed in Claim 24, comprising a puller downstream of the die.

26. Apparatus as claimed in Claim 25, comprising at least one wrapping station downstream of the puller.

27. Apparatus for carrying out the method of Claims 1-16, substantially as hereinbefore described with reference to the accompanying drawings.

28. A pultruded composite manufactured by the method of Claims 1 to 16.

29. A composite as claimed in Claim 28, wherein the inner member is a solid, rod-like member.

30. A composite as claimed in Claim 28, wherein the inner member is a hollow, sleeve-like member.

31. A composite as claimed in Claim 30, wherein the hollow, sleeve-like member contains a core.