CA1301038C

CA1301038C - Process and apparatus for the continuous production of fibre-reinforcedplastic hollow sections and plastic hollow sections

Info

Publication number: CA1301038C
Application number: CA000527945A
Authority: CA
Inventors: Norbert Lona
Original assignee: FUTURTECH AG.
Current assignee: ARUNDO TECHNOLOGY AG
Priority date: 1986-02-07
Filing date: 1987-01-22
Publication date: 1992-05-19
Anticipated expiration: 2009-05-19
Also published as: BR8700545A; DK162151B; DE3664282D1; AU6793087A; FI870442A0; ZA87740B; AU596634B2; ATE44488T1; FI88372C; IL81372A0; JPS62191129A; FI870442A; NO870464D0; JPH07115420B2; EP0233439A1; DK162151C; IL81372A; ES2009805B3; GR3000112T3; MX168582B

Abstract

A b s t r a c t A stationary mandrel (1) is wrapped in a separat-ing film (3) at the front, as seen in the draw-off direc-tion (A). A gel coat layer is coated onto the film (3) and partly gelled by means of a heater (12). The gel coat layer is coated with liquid polyester, wrapped in a longitudinally extending glass-fibre fabric (20) in an overlapping manner and wound helically in a glass sliver (21). These layers are hardened by means of a further heater (24,25), so that a structural supporting profile for coating on the follow-ing layers is obtained. The mandrel (1) is set off after the further heater (24,25). For coating on the further layers, liquid polyester, a fibre fabric (34) and a helic-ally wound sliver (37) are applied alternately. These layers are fulled and coated with an outer gel coat layer. The polyester is hardened in an oven (50). A grab device (52) draws the section off continuously from the mandrel (1).
Finally, the section is cut to length. A hollow section of high strength is produced by means of this process.

(Figures 1a and 1b)

Description

1301~38 OM/rii Process and apparatus for the continuous production of fibre-reinforced plastic hollow sections and plastic hollow sections US Patent Specification 3,689,343 discloses a process and an apparatus according to the precharacterizing clause of claims 1 and 9 for the production of fibre-reinforced hol-low sections. In this known process, a gel coat layer is coated over part of the width of a separating film drawn off from a supply roll and is partly gelled. A fibre fabric is pressed onto the gel coat layer. This laminate is wrapped round a mandrel in such a way that the longitudinal edges of the gel coat layer and of the fibre fabric butt against one another. The pLojecting free longitudinal edges of the separating film are received in a slit in the mandrel. Resin-impregnated longitudinal roving strands are laid onto the hollow-section inner wall formed in this way. In a forming tool, these roving strands are wrapped in an outer wall, which likewise consists of a separating film, of a gel coat 130:~3;~3 layer coated onto the latter and partly gelled and of a pressed-on fibre fabric, and are compressed radially. The resin sets in a heating device at the end of the forming tool. The hollow section is drawn off continuously at the rear end of the apparatus by a grab device and is cut to length by a crosscutting device.

The gel coat layer gives the hollow section produced a smooth surface and high corrosion resistance. A disadvan-tage of the hollow sections produced by this process is the abutting side edges of the gel coat layers which are only incompletely connected to one another after gelling. The unconnected longitudinal edges of the fibre fabrics also butt together at the same seam point, so that this seam point is vulnerable. Although the hollow section is pressed radially in the forming tool, nevertheless the pressing forces cannot be very high, because otherwise the friction in the forming tool and on the fixed mandrel would exceed the tensile strength of the hollow section. It is there-fore impossible to prevent air intrusions, and this impairs the strength of the hollow section. The roving strands are only connected to one another by means of the synthetic resin. Although they increase the bending resistance and tensile strength of the hollow section, they nevertheless make no contribution to its strength against internal pres-sure. This is only moderate because of the seam points of the fibre fabrics.

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The object of the invention is to provide a process and an apparatus for the continuous production of fibre-reinforced hollow sections, by means of which it is possible to pro-duce hollow sections of high strength. This object is achieved by the characterizing features of claims 1 and 9.
The hollow section according to the invention is described in claim 18.

Because the inner gel coat layer is coated onto the separat-ing film on the mandrel, it is seamless and guarantees re-liable protection of the fibre-reinforced plastic layers.
The overlapping of the innermost fibre layer and the harden-ing of the plastic contained in it give the hollow section sufficient strength, so that the mandrel can be offset after the third heating device. It is then no longer neces-sary for the mandrel to provide support in order to apply the further fibre layers impregnated with plastic, so that the air inclusions in these layers can be largely removed, especially by fulling, without the friction on the mandrel thereby being increased. It is possible, in addition, to wind at least some of the further layers, without conse-quently increasing the friction on the mandrel. A high strength against internal pressure of the hollow section can therefore be achieved.

GB Patent Specification 1,350,298 likewise makes known a process and an apparatus for producing fibre-reinforced t3~3 plastic sections. On a flat plane web, a continuously supp-lied separating film is coated with gel coat and the gel coat is partly gelled. Liquid synthetic resin and a fibre ribbon are applied to the gel coat layer. Subsequently, the laminate, plane up to then, is shaped into a section, and the synthetic resin is hardened in a continuous oven.
GB Patent Specification 1,350,298 mentions that the longi-tudinal edges of the laminate could be overlapped and therefore a hollow section produced. However, this is not possible because the separating film would prevent the overlapped longitudinal edges from being connected. A pres-sure-resistant hollow section of high strength cannot be produced in this way.

US Patent Specification 3,033,729 discloses a process and an apparatus for the continuous production of glass-fibre-reinforced plastic pipes. Here, roving strands are con-veyed through a bath containing liquid synthetic resin and are fed peripherally to a heated mandrel in an approximately axial direction. The synthetic resin is hardened partially as a result of this heating. Roving strands are wound onto the semy-hardened synthetic resin, and finally the synthetic resin is set in a continuous oven. In this process, it is impossible to provide the pipe with an inner gel coat layer. The semy-hardened synthetic resin is insufficiently stable, so that the roving strands can only be wound loosely, but on the other hand is not liquid enough to ensure that 13~1~38 the wound roving strands would bond reliably with the resin.
For these reasons, the pipe produced by this process con-tains many air inclusions, is leaky and has only moderate strength.

An exemplary embodiment of the invention is explained below with reference to the drawing. In the drawing:

igures la and lb show a diagrammatic representation of the apparatus, Figure 2 shows a longitudinal section through the mandrel, Figure 3 shows a cross-section along the line III - III in Figure 1, and Figure 4 shows a cross-section along the line IV - IV in Figure 1.

In Figure 1, the apparatus is shown diagrammatically for a better understanding of the individual process steps, Figure lb following Figure la on the right.

A separating film 3 drawn off from a strip magazine 2 moun-ted fixed in place is first applied to a stationary mandrel 1. The film 3 wraps round the mandrel 1. Its longitudinal edges overlap one another. The outer overlapping longitu-dinal edge is fixed to the overlapped longitudinal edge bymeans of an adhesive tape 5 drawn off from a supply roll 4.
The adhesive tape 5 is pressed on by means of a roller 6.
The separating film 3 thus forms a tubular separating layer which slides on the mandrel 1.

Behind the roller 6, liquid gel coat is coated in a thick-ness of approximately 0.4 mm onto the separating film 3 via an annular feed device 7 with an annular gap and is cali-brated by means of an annular orifice plate 8, so that a seamless gel coat layer forms round the film 3. A duro-plastic, for example a polyester with a high softener fraction, is suitable as a gel coat. The gel coat layer is more elastic than the fibre-reinforced duroplastic to be applied subsequently and because of its composition can be adapted to the intended use. The liquid gel coat is supplied to the feed device 7 from a vessel 9.

Behind the annular orifice plate 8 in the draw-off direc-tion A of the section, the mandrel 1 is heated by a heater 12, so that the gel coat layer is partially gelled here.
The heat transmission is very good as a result of direct contact between the film 3 and the mandrel 1, so that the temperature necessary for the gelling of the gel coat layer can be reached over a short distance and this layer can be prevented from overheating. After the heater 12, the mandrel 1 is cooled by means of a cooling coil 13.

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When larger layer thicknesses of the gel coat layer are de-sired, by means of nozzles 11 pivotable about the mandrel axis a second layer is sprayed over the first layer, app-lied by means of the feed device 7, in the region of the heater 12, that is to say at a point where the viscosity of the first layer is already substantially highèr. The liquid gel coat is supplied to the nozzles 11 from the vessel 9 by means of a pump 10. For even larger wall thick-nesses, several of these spray devices can be arranged in succession, the heater 12 being extended correspondingly.
Applying the gel coat layer in several layers ensures that, despite the effect of gravity, the layer has a uniform wall thickness over the circumference.

Via an annular feed device 17 with an annular gap, liquid duroplastic from a vessel 18 is now coated onto the gelled-on gel coat layer. A woven glass fabric 20 is drawn off from a supply roll 19 with a fixed axle. This glass fabric is applied to the duroplastic layer in the longitudinal direction of the hollow section with overlapping longitu-dinal edges. A further woven glass fabric 21 is drawn off from a supply roll 22, mounted in a magazine 23 rotatable about the mandrel axis, and is looped helically round the fabric 20 in an overlapping manner. Behind this magazine 23 in the draw-off direction A, the mandrel 1 is heated by a further heater 24, 25, a first heating coil 24 utilizing the waste heat from the cooling coil 13 and/or a subsequent further cooling coil 26. In this way, the energy consump-tion for heating can be kept low. Heat recovery becomes possible as a result of the direct heat transmission via the mandrel. During transit through the heaters 24, 25, the duroplastic is hardened, so that a thin-walled fibre-rein-forced duroplastic hollow section is obtained as a support-ing section for the layers to be applied subsequently. This supporting section is supported via supporting rollers 27 which run on the already hardened fibre-reinforced duro-plastic. After the heater 25, the mandrel has the above-mentioned further cooling coil 26, in order to cool the supporting profile so that the duroplastic layers to be applied subsequently do not harden prematurely. The sup-porting section is sufficiently rigid for the following operations, so that after the cooling coil 26 a step 28 is provided on the mandrel so as to reduce the latter to a smaller diameter. The mandrel 1 can also end at this point.

In each of several successive stages a, b, liquid duro-plastic, a longitudinally extending glass-fibre fabric 34 and a helically wound glass-fibre sliver 37 are applied to the now inherently stable supporting section. Here, the feed devices 31a, 31b for duroplastic, with the exception of the inside diameter, correspond to the device 17, and the vessels 32a, 32b correspond to the vessel 18. The woven glass-fibre fabrics 34a, 34b, like the fabric 20, are drawn off from supply rolls 33a, 33b mounted fixed in place. Their longitudinal edges likewise overlap one another, the overlap points being offset relative to one another in the peripheral direction. For this purpose, the axes of rotation of the supply rolls 19, 33a, 33b are also arranged distributed round the mandrel axis. In Figure lb, merely for the sake of greater clarity, they are shown arranged successively in line in the axial direction of the mandrel. A woven glass-fibre sliver 37a, 37b is looped helically round each glass fibre fabric 34a, 34b in an overlapping manner and is pressed radially as a result of the sliver tension, so that the layers 34a, 37a and 34b, 37b are impregnated with the previously applied duroplastic and air inclusions are substantially forced out. This pur-pose is also served by a fulling device 35 rotatable about the mandrel axis and having several rollers 36 distributed uniformly over the periphery of the hollow section. The fulling device 35 can be arranged in front of or behind the last sliver station 37b, 38b, 39b. The hollow section is now drawn through a calibrating orifice plate 40, in which the section wall is compressed and excess duroplastic is stripped off. Behind the calibrating orifice plate 40, an outer gel coat layer is sprayed on by means of several nozzles 44 pivotable about the mandrel axis and is cali-brated in a further calibrating orifice plate 45. The ~3~1~38 liquid gel coat, for example once again a polyester with a high softener fraction, is fed to the nozzles 44 from a vessel 47 via a pump 46.

The hollow section then passes through a continuous oven 50, in which the duroplastic and the outer gel coat layer are heated from outside and hardened, and through several measuring stations 51 for checking the diameter, wall thick-ness and hardness.

The now finished hollow section is drawn off continuously from the mandrel 1 by a grab device 52 and is cut to the desired section length by a crosscutting device 53. Suit-able grab and crosscutting devices are known from extrusion machines for solid sections.

Figure 2 shows a longitudinal section through the mandrel 1 with the heating and cooling devices. The mandrel 1 is clamped in a bearing stand 57 and consists of a steel tube, through which are guided a feed pipe S9 and a return pipe 60 for cooling water and electrical leads 61 for the heat-ing. The heaters 12 and 25 each comprise an aluminium or copper sleeve 62 resting against the inside of the tube 58 and having several thermostatically controlled electrical heating bars 63 distributed uniformly over the periphery.
The heating bars 63 are connected electrically to one another in each heater 12, 25 and are each connected to ~3~

one of the leads 61. The cooling devices 13 and 26 each consist of a coiled tube 64 which is connected to the tube 58 in a thermally conductive manner and of which the rear end, as seen in the draw-off direction A, is connec-ted to the feed pipe 59 and the front end is connected to the rear end of a further coiled tube 65 forming the pre-heater 24. The front end of the coil 65 is connected to the return pipe 60. The preheater 24 thus utilizes the waste heat of the two cooling devices 13, 26.

Figure 3 shows a cross-section through the device 11 for coating on the inner gel coat layer. An annular carrier 68 is mounted on rollers 69 so as to be rotatable about the axis of the mandrel 1. Four spray nozzles 70 directed radially inwards are fastened in a uniform distribution on the periphery of the carrier 68. The spray nozzles 80 are supplied with liquid gel coat through a distributor pipe 71 via a flexible hose 72 by the pump 9. Furthermore, a compressed-air line (not shown) for atomizing the gel coat material is connected to the spray nozzles 70. The nozzles 70 can be fastened to the carrier 68 so as to be radially adjustable, to make it possible to produce hollow sections of differing inner dimensions after the mandrel 1 has been exchanged. The gel coat material emerges from the nozzles 70 as a fine spray jet 73. To obtain a uniform thickness of the gel coat layer, the carrier 68 is pivoted 13~ 3~

to and fro about the mandrel a~is by means of a motor 74 ancl a crank mechanism 75. The device 44 for coating on the outer gel coat layer is of the same design as the device 11 shown in Figure 3.

Figure 4 illustrates the feed of the glass-fibre sliver 21 from the sliver magazine 23. The sliver magazine 23 com-prises a tubular carrier 77 which is arranged coaxially relative to the mandrel l and which is mounted so as to be rotatable about the mandrel axis, for example by means of rollers 78, and is driven via a toothed ring 79 by means of the pinion 80 of a motor 81. Welded to the carrier 77 so as to project radially is a carrier plate 82. Fastened to this so as to be rotatable about an axle 84 are a holder 83 for the supply roll 22 and a reserve roll 22a. The holder 83 engages in the position shown and in a position rotated through 180. The sliver 21 is guided via a deflecting roller 85, a pair of rollers 86 and a further pair of rollers 87 braked in order to regulate the sliver tension.
The pair of rollers 86 is fastened to a slide 90 displace-able along a rod 88 and biassed into the basic position shown by a spring 89. The slide 90 has a press surface 91 over which the sliver 21 is guided. Opposite the press sur-face 91, a pressing beam 92 is mounted displaceably on the slide 90. The beam 92 can be pressed against the press sur-face 91 by means of a solenoid 93. The sliver start 21a 1301~3~

of the reserve roll 22a is guided round a further deflect-ing roller 94. The front end of the sliver start 21a is fastened to the beam 92 so as to be easily releasable. A
double-sided unsupported adhesive tape 95 is glued onto its underside, facing the sliver 21.

During operation, the carrier 77, and with it the entire sliver magazine 23, rotates at a uniform speed about the axis of the mandrel 1 according to the draw-off speed of the section from the mandrel l, in such a way that the longitudinal edges of the sliver 21 overlap one another.
When the supply roll 22 is used up, the sliver end is de-tected by a light barrier 96 and the solenoid 93 is conse-quently actuated. The beam 92 now presses the front end of the sliver start 21a of the reserve roll 22a, together with the adhesive strip 95, against the rear end of the sliver 21 and connects these two ends to one another. During press-ing, the slide 90 runs together with the sliver 21 against to the force of the spring 89. The solenoid 93 is cut off again with a predetermined delay, so that the slide 90 re-turns to the basic position illustrated. The sliver magazine 23 rotates relatively slowly about the mandrel axis, so that the following operations to introduce a new reserve roll can be carried out by hand. The holder 83 is first pivoted 180~ in the clockwise direction, and the sliver start 21a is transferred from the deflecting roller 94 to the deflecting roller 85 and threaded into the light bar-rier 96. A new reserve roll 22a is attached onto the now empty mandrel of the holder 83, an adhesive tape 95 is glued onto the front end of its sliver start, and this end is fastened to the beam 92. The sliver magazine 23 is thus ready once again for the next sliver change.

The sliver magazines 38a and 38b are of the same design as the magazine 23 shown in Figure 4. The automatic connec-tion, shown in Figure 4, between the sliver end of a supply roll and the sliver start of a reserve roll is basically also possible for the glass-fibre fabrics 20, 34a and 34b and for the separating film 3 and the adhesive tape S. How-ever, since the draw-off speeds of the fabrics 20, 34, the film 3 and the adhesive tape 5 are substantially lower than the draw-off speed of the sliver 21, it is more ex-pedient here to exchange the supply rolls and connect the sliver ends purely manually.

For fibre reinforcement, instead of glass fibres, for ex-ample also carbon fibres, aramide fibres or silicate fibres are suitable. Duroplastics, especially polyesters, are basically suitable as binders. Hollow sections of any outline can be produced by means of the process, provided that the outer contour does not have any concavities. The process is particularly suitable for producing pipes of circular cross-section.

Claims

1. Process for the continuous production of fibre-reinforced plastic hollow sections, in which a separating film (3), an inner gel coat layer and a first fibre mat-erial layer (20,21) are applied round a stationary mandrel (1), subsequently further layers (34,37) of fibre material and liquid plastic are placed round the first fibre mate-rial layer (20,21), and the hollow section is calibrated in a forming tool (40) and subsequently heated, so that the plastic hardens, and in which the hardened hollow sec-tion is drawn off continuously from the mandrel (1) by a grab device (52) and is finally cut to length, character-ized in that the inner gel coat layer is coated onto the separating film (3) on the mandrel (1) and is partly gelled by heating, in that the first fibre material layer (20,21) together with liquid plastic is laid onto the inner gel coat layer in an overlapping manner, and in that, before the further layers (34,37) of fibre material are applied, the hollow section is heated and the plastic in the first fibre material layer (20,21) is hardened.

2. Process according to claim 1, characterized in that the inner gel coat layer is composed of at least two layers, the layer or layers following the first layer being sprayed on after the start of heating of the gel coat layer.

3. Process according to claim 2, characterized in that the inner gel coat layer is cooled after heating and before the first fibre material layer (20,21) is app-lied.

4. Process according to claim 2 or 3, character-ized in that liquid plastic is coated onto the gel coat layer before the first fibre material layer (20,21) is applied.

5. Process according to one of claims 1, 2 or 3 characterized in that the hollow section is heated from the inside after the first fibre material layer (20,21) has been applied.

6. Process acccording to one of claims 1, 2 or 3 characterized in that the hollow section is cooled before the further fibre material layers (34,37) together with the plastic are applied.

7. Process according to one of claims 1, 2 or 3 characterized in that, in order to apply the further fibre material layers (34,37), for each at least one liquid plastic layer, a fibre fabric (34) extending in the long-itudinal direction of the hollow section and having over-lapping longitudinal edges, and a helically wound sliver (37) are applied in succession and in that the further fibre material layers (34,37) are fulled.

8. Process according to one of claims 1, 2 or 3 characterized in that the hollow section is calibrated after the further fibre material layers (34,37) have been applied, and in that before final heating an outer gel coat layer is coated onto the calibrated hollow section, preferably sprayed onto it, and is likewise calibrated.

9. Apparatus for the continuous production of fibre-reinforced plastic hollow sections, with a stationary mandrel (1), a feed device (2) for a separating film (3), a device (7,11) for coating an inner gel coat layer onto the separating film (3), a feed device (19,23) for a first fibre material layer (20,21), further feed devices (31,33, 38) for further fibre material layers (34,37) and liquid plastic, a calibrating device (40), a first heating device (50), a grab device (52) for continuously drawing off the hollow section from the mandrel (1), and a crosscutting device (53), characterized in that, as seen in the draw-off direction of the hollow section, the device (7,11) for coating on the inner gel coat layer round the mandrel (1) and a second heating device (12) are arranged behind the separating-film feed device (2) and a third heating device (24,25) is arranged behind the feed device (19,23) for the first fibre material layer (20,21), and in that the mandrel (1) is set off behind the third heating device (24,25) and in front of the further feed devices (33,38) for further fibre material layers.

10. Apparatus according to claim 9, characterized in that the second and third heating devices (12,24,25) are arranged in the mandrel (1).

11. Apparatus according to claim 10, characterized in that a cooling device (13,26) is arranged behind both the second and the third heating device (12,24,25).

12. Apparatus according to one of claims 9, 10 or 11 characterized in that, as seen in the draw-off direction of the hollow section, a device (17) for coating the gel coat layer with liquid plastic is arranged in front of the feed device (19,23) for the first fibre material layer (20,21).

13. Apparatus according to one of claims 9, 10 or 11 characterized in that a fulling device (35) is arranged in front of the calibrating device (40).

14. Apparatus according to one of claims 9, 10 or 11 characterized in that at least one (38) of the further feed devices (33,38) for further fibre material layers (34,37) comprises a sliver magazine (38) rotatable about the mandrel axis.

15. Apparatus according to one of claims 9, 10 or 11 characterized in that, as seen in the draw-off direction of the hollow section, a device (44) for coating on an outer gel coat layer is arranged in front of the first heating device (50).

16. Apparatus according to one of claims 9, 10 or 11 characterized in that the feed device (19,23) for the first fibre material layer (20,21) comprises a sliver magazine (23) rotatable about the mandrel axis.

17. Apparatus according to one of claims 9, 10 or 11 characterized in that, as seen in the draw-off direction of the hollow section, supporting rollers (27) for the hollow section are arranged behind the third heating de-vice (24,25).

18. Fibre-reinforced hollow section, with an inner and an outer gel coat layer and with layers of fibre material and duroplastic located between them, characterized in that, following the inner gel coat layer, the fibre material layers (20,21,34,37) comprise several layers, each with a fibre fabric (20,34) extending in the longitudinal direction of the hollow section and having overlapped longitudinal edges, and with a sliver (21,37) wound helically in an overlapping manner.

19. Hollow section according to claim 18, charac-terized in that both the fibre fabrics (20,34) and the slivers (21,37) consist of woven material.

20. Hollow section according to claim 18 or 19, characterized in that the overlaps of the various layers of fibre fabrics (20,34) are offset relative to one another in the peripheral direction.