Pultrusion Process and Arrangement for the Continuous Production of Blanks from a Fibre-Plastic Composite Material

Abstract

The invention relates to a pultrusion process for the continuous production of blanks from a fibre-plastic composite material (23), an arrangement for carrying out a pultrusion process and use of the pultrusion process according to the invention and the arrangement according to the invention. The pultrusion process comprises at least the following process steps: i. providing a strand of unimpregnated fibres (21); ii. feeding the strand of unimpregnated fibres (21) to a vacuum device (5, 5, 5), which has at least one vacuum chamber (52, 52, 52); iii. generating a negative relative pressure in the at least one vacuum chamber (52, 52, 52) of the vacuum device (5, 5, 5), whereby air (200) escapes from the strand of unimpregnated fibres (21); iv. removing the almost airless strand of unimpregnated fibres (22) from the vacuum device (5, 5, 5) and feeding the almost airless strand of unimpregnated fibres (22) to an injection device (6, 6), which has at least one injection chamber (61, 61), wherein the vacuum device (5, 5, 5) and the injection device (6, 6) are connected to one another in an airtight manner, at least with respect to the surroundings; v. injecting matrix material (230) in a flowable state into the at least one injection chamber (61, 61) of the injection device (6, 6) and impregnating the strand (2) with the matrix material (230); vi. removing of the blank (23) from the injection device (6, 6). With the process according to the invention, a homogeneous and complete wetting of the fibres of the strand is advantageously achieved at a high drawing rate. Furthermore, the fibre-plastic composite is not pressed in the process.

Claims

1. Pultrusion process for the continuous production of blanks from fibre-reinforced plastics composite material (23), comprising at least the following process steps: i. providing a strand of unsaturated fibres (21); ii. feeding the strand of unsaturated fibres (21) to a vacuum unit (5, 5, 5) that comprises at least one vacuum chamber (52, 52, 52); iii. generating a negative relative pressure in the at least one vacuum chamber (52, 52, 52) of the vacuum unit (5, 5, 5), as a result of which air (200) escapes from the strand of unsaturated fibres (21); iv. removing the virtually evacuated strand of unsaturated fibres (22) from the vacuum unit (5, 5, 5) and feeding the virtually evacuated strand of unsaturated fibres (22) to an injection unit (6, 6) that comprises at least one injection chamber (61, 61), the vacuum unit (5, 5, 5) and injection unit (6, 6) being interconnected so as to be airtight at least with respect to the surroundings; v. injecting matrix material (230), in fluid state, into the at least one injection chamber (61, 61) of the injection unit (6, 6), and impregnating the strand (2) with the matrix material (230); vi. removing the blank (23) from the injection unit (6, 6).

2. Pultrusion process according to claim 1, characterised in that the following process steps follow process step vi.: vii. feeding the blank (23) to a coating unit (7); viii. forming a coated surface of the blank (23) in the coating unit (7), the coating (711) being designed to ensure the air tightness of the surface during further process steps which the blank (24) may undergo; ix. removing the blank (24), comprising the coating, from the coating unit (7).

3. Pultrusion process according to claim 1, characterised in that either, following process step vi., the blank (23), or, following process step ix., the blank (24) comprising a coating, passes through a cutting unit (9), the blank (23) or the blank (24) comprising a coating being cut to length in the cutting unit (9).

4. Pultrusion process according to claim 1, characterised in that the strand channel of the vacuum unit (5) comprises a friction-reducing surface.

5. Pultrusion process according to claim 1, characterised in that the vacuum unit (5, 5) comprises at least two chambers (52, 520, 52) that are interconnected in an airtight manner.

6. Pultrusion process according to claim 1, characterised in that the vacuum unit (5, 5) comprises at least one annular element (53) that is arranged in a stationary manner around the strand of unsaturated fibres (21), or comprises rotating roller seal elements (56).

7. Pultrusion process according to claim 1, characterised in that the vacuum unit (5) comprises at least two arrangements (58) of rotating roller seal elements (56), at least two rotating roller seal elements (56) arranged in succession in the pultrusion direction (11) being interconnected, in one arrangement (58), in the manner of a conveyor belt, by means of a sealing strip (581).

8. Pultrusion process according to claim 1, characterised in that the injection unit (6, 6) comprises at least two chambers (61, 61, 62, 62) that are interconnected so as to be airtight at least with respect to the surroundings.

9. Pultrusion process according to claim 1, characterised in that the injection unit (6, 6) comprises at least one drainage chamber (62, 62) that is arranged upstream and/or downstream of the at least one injection chamber (61, 61) and/or between two chambers (61, 61) of the injection unit (6, 6).

10. Pultrusion process according to claim 1, characterised in that the injection unit (6) is formed as an integral component.

11. Pultrusion process according to claim 1, characterised in that the injection unit (6) is formed as a modular component, the modules (67, 68) of the injection unit (6) being interconnected so as to be airtight at least with respect to the surroundings.

12. Pultrusion process according to claim 1, characterised in that the strand channel of the injection unit (6, 6) is provided with a wear protection layer.

13. Pultrusion process according to claim 1, characterised in that at least one temperature-control element (64, 64) is arranged on the injection unit (6, 6).

14. Pultrusion process according to claim 1, characterised in that at least the elements of the vacuum unit (5) and/or of the injection unit (6) which have a region (531, 631) of contact with the strand (2) perform a rotational movement around the strand (2), the strand (2) being rotationally symmetrical about a strand axis (27).

15. Pultrusion process according to claim 2, characterised in that the injection unit (6, 6) and the coating unit (7) are interconnected so as to be airtight at least with respect to the surroundings.

16. Pultrusion process according to claim 2, characterised in that a coated surface of the blank (23) is formed by means of partial consolidation of matrix material (230) in regions close to the surface, or by means of cooling regions close to the surface to a temperature that is lower than or equal to the glass transition temperature of the matrix material (230), at a sufficiently high cooling rate.

17. Pultrusion process according to claim 2, characterised in that a coated surface of the blank (23) is formed by means of a sprinkling unit or an immersion bath or an extruder, or by means of wrapping or encasing the blank in a film (711), or by means of rolling up the blank in a film (711).

18. Arrangement for carrying out a pultrusion process for the continuous production of blanks from fibre-reinforced plastics composite material (23), comprising: a vacuum unit (5, 5, 5) that comprises at least one vacuum chamber (52, 52, 52), the vacuum unit (5, 5, 5) comprising at least one connection element (54, 54, 54) that is suitable for connecting a vacuum pump, and the vacuum unit (5, 5, 5) being designed such that a negative relative pressure is generated in a strand of unsaturated fibres (21), and an injection unit (6, 6) comprising at least one injection chamber (61, 61) for injecting matrix material (230), in a fluid state, which injection chamber is designed for impregnating the strand (2) with the matrix material (230), the vacuum unit (5, 5, 5) being arranged upstream of the injection unit (6, 6) in the pultrusion direction (11).

19. Arrangement for carrying out a pultrusion process for the continuous production of blanks from fibre-reinforced plastics composite material (24) according to claim 18, characterised in that the arrangement comprises elements (500, 65) which are designed to set the vacuum unit (5) and/or the injection unit (6) or at least the elements of the vacuum unit (5) and/or of the injection unit (6) which have a region (531, 631) of contact with the strand (2), into a rotational movement around the strand (2).

20. Arrangement for carrying out a pultrusion process for the continuous production of blanks from fibre-reinforced plastics composite material (24) according to claim 18, characterised in that a coating unit (7) is arranged downstream of the injection unit (6, 6) in the pultrusion direction (11).

21. (canceled)

22. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0129] In the drawings:

[0130] FIG. 1 is a schematic view of a pultrusion facility which comprises an embodiment of an arrangement according to the invention and is suitable for carrying out the process according to the invention;

[0131] FIG. 2a shows an embodiment of an arrangement according to the invention;

[0132] FIG. 2b shows a further embodiment of an arrangement according to the invention which comprises a coating unit;

[0133] FIG. 3a is a longitudinal section of an embodiment of a vacuum unit comprising a plurality of vacuum chambers in a modular construction, the cutting plane corresponding to the centre plane of the strand and being in parallel with the pultrusion direction, and the vacuum unit comprising stationary annular elements;

[0134] FIG. 3b shows an embodiment of a modular vacuum unit comprising a plurality of vacuum chambers and stationary annular elements, as in FIG. 3a, the vacuum unit comprising elements for performing a rotation about the strand axis;

[0135] FIG. 3c shows an embodiment of an integral vacuum unit comprising a plurality of vacuum chambers and stationary annular elements, shown as in FIG. 3a, the vacuum unit comprising elements for performing a rotation about the strand axis;

[0136] FIG. 4a is the side view of an alternative embodiment of a vacuum unit comprising a plurality of vacuum chambers, the vacuum unit comprising rotating rollers as sealing elements;

[0137] FIG. 4b shows the cross sectional view shown in FIG. 4a, along the line A-A perpendicularly to the pultrusion direction of the embodiment of a vacuum unit shown in FIG. 4a;

[0138] FIG. 5a is the side view of a further alternative embodiment of a vacuum unit comprising a plurality of vacuum chambers, the vacuum unit comprising two conveyor belt-like arrangements having rotating rollers that are connected by means of a sealing strip;

[0139] FIG. 5b shows the cross sectional view shown in FIG. 5a, along the line A-A perpendicularly to the pultrusion direction of the embodiment of a vacuum unit shown in FIG. 5a;

[0140] FIG. 6a is a longitudinal section of an embodiment of an injection unit in an integral construction, the cutting plane corresponding to the centre plane of the strand and being in parallel with the pultrusion direction;

[0141] FIG. 6b shows an embodiment of an integral injection unit, as in FIG. 6a, the injection unit comprising elements for performing a rotation about the strand axis;

[0142] FIG. 7 is a longitudinal section of an alternative embodiment of an injection unit in a modular construction, the cutting plane corresponding to the centre plane of the strand and being in parallel with the pultrusion direction;

[0143] FIG. 8a is a plan view of an embodiment of a coating unit, the FRP blank being coated in a film by means of rolling up.

[0144] FIG. 8b shows the cross sectional view of the coating unit shown in FIG. 8a, along the line A-A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0145] FIG. 1 is a schematic view of a pultrusion facility 1 which is suitable for continuously producing an FRP blank 23 in accordance with the pultrusion process according to the invention. The FRP blank may have a round, oval or polygonal, e.g. T-shaped, cross section. The strand 2 that passes through the pultrusion facility 1 comprises bundled fibres or semi-finished fibre products which are arranged in a supply region 3. The supply region 3 comprises, by way of example, a creel 31 comprising a plurality of spools 310 from which continuous fibres or rovings 311 are drawn off in the pultrusion direction 11 and bundled in a guide unit 4. The supply region 3 further comprises, by way of example, a winding wheel 32 by means of which for example rovings 321 can be laid on the strand 2 at an adjustable angle relative to the pultrusion direction, and a number of fibre strip spools 33 from which for example fibre strips 331, mats or unbonded webs are laid on the strand 2 for the purpose of reinforcement.

[0146] The strand of unsaturated fibres 21 is drawn into a vacuum unit 5, in the pultrusion direction 11, which vacuum unit said strand leaves as a virtually evacuated strand of unsaturated fibres 22. At least one vacuum pump (not shown) is connected to the vacuum unit 5 in order to generate a negative relative pressure in the vacuum unit 5. The virtually evacuated strand of unsaturated fibres 22 is then drawn into an injection unit 6 in which said strand is impregnated. The vacuum unit 5 and injection unit 6 are interconnected by means of the connecting element 51, for example a flange sealed by an elastomer O-ring, so as to be airtight with respect to the surroundings of the pultrusion facility 1, such that no ambient air penetrates into the virtually evacuated strand of unsaturated fibres 22 during the transition from the vacuum unit 5 into the injection unit 6. The strand leaves the injection unit fully impregnated with matrix material, in the form of an FRP blank 23. The injection unit 6 and a coating unit 7 are interconnected by means of the connecting element 60, which is sealed by an elastomer O-ring for example, so as to be airtight with respect to the surroundings of the pultrusion facility 1, such that it is ensured that no ambient air penetrates into the FRP blank 23 during the transition from the injection unit 6 into the coating unit 7. Since the FRP blank 23 is generally fully impregnated, a pultrusion facility 1 can also be operated without a connecting element 60 between the injection unit 6 and the coating unit 7. Following impregnation, the FRP blank is fed to the coating unit 7 in which a coated surface of the FRP blank 23 is formed, the coated surface also being airtight when stretched, compressed or shaped in another manner. The FRP blank 24 comprising a coated surface then passes through the draw-off unit, by means of which unit the strand 2 is drawn through the pultrusion facility 1. The embodiment shows a strip draw-off unit 8. Following the strip draw-off unit 8, the FRP blank 24 comprising a coated surface is cut to length, to appropriate dimensions, by means of a cutting unit 9, for example a saw, and can be fed to further process steps (not shown).

[0147] FIG. 2a shows an embodiment of an arrangement according to the invention. The arrangement comprises the portion of a pultrusion facility from the vacuum unit 5 as far as the injection unit 6, the vacuum unit 5 being connected to the injection unit 6, by means of the connecting element 51, so as to be airtight with respect to the surroundings, and being suitable for continuously producing an FRP blank 23 in the form of a solid profile, in accordance with the pultrusion process according to the invention.

[0148] A strand of unsaturated fibres 21 is guided into the vacuum unit 5, air bubbles 200 being trapped in the strand of unsaturated fibres 21 upon entry into the vacuum unit 5. The air bubbles 200 escape in the vacuum unit 5 owing to the negative relative pressure that is generated in the vacuum unit 5 by means of a vacuum pump (not shown), such that a virtually evacuated strand of unsaturated fibres 22 leaves the vacuum unit 5 and is drawn into the injection unit 6. The virtually evacuated strand of unsaturated fibres 22 is impregnated with matrix material 230 in the injection unit 6. A fully impregnated FRP blank 23 leaves the injection unit 6.

[0149] FIG. 2b shows an alternative embodiment of an arrangement according to the invention. Said figure schematically shows a detail of a pultrusion facility which is suitable for continuously producing an FRP blank 23 in the form of a hollow profile in accordance with an embodiment of the pultrusion process according to the invention, and for providing said blank with a coated surface. The detail comprises the portion of the pultrusion facility from the vacuum unit 5, which is connected to the injection unit 6, by means of the connecting element 51, so as to be airtight with respect to the surroundings, as far as the coating unit 7, which is connected to the injection unit 6, by means of the connecting element 60, so as to be airtight with respect to the surroundings, the airtight connection between the injection unit 6 and the coating unit 7 being optional.

[0150] In order to manufacture a FRP blank 23 in the form of a hollow profile, a mould core 25 that may consist of solid material or may be tubular, is arranged in the strand 2. The mould core 25 is removed following possible shaping (not shown) and following curing of the matrix material 230, for example by means of being pressed out, drilled out or melted out, or remains in the component. As shown in FIG. 2b, a strand of unsaturated fibres 21, the fibres being bundled around the mould core 25, is first guided into the vacuum unit 5, air bubbles 200 being trapped in the strand of unsaturated fibres 21 upon entry into the vacuum unit 5. The air bubbles 200 escape in the vacuum unit 5 owing to the negative relative pressure that is generated in the vacuum unit 5 by means of a vacuum pump (not shown), such that a virtually evacuated strand of unsaturated fibres 22 comprising a mould core 25 leaves the vacuum unit 5 and is drawn into the injection unit 6. The virtually evacuated strand of unsaturated fibres 22 is impregnated with matrix material 230 an the injection unit 6. A fully impregnated FRP blank 23, on the surface of which an airtight coating (shown here as a film 711) is arranged in the coating unit 7, leaves the injection unit 6. The FRP blank 24 comprising a coated surface is fed to further process steps (not shown here).

[0151] FIG. 3a is a cross section, in the pultrusion direction 11, of an embodiment of a vacuum unit 5 comprising a plurality of vacuum chambers 52 arranged in succession, the vacuum unit 5 comprising a cascade of stationary annular elements 53 that is formed in a modular manner. The components of the vacuum unit 5 are arranged so as to be substantially symmetrical with respect to a longitudinal plane through the centre axis of the strand 2, in the pultrusion direction 11, and therefore, for reasons of clarity, mutually symmetrical components of the vacuum unit 5 are provided with a reference sign just once in each case.

[0152] As in all the embodiments of the vacuum unit, the strand 2 enters the vacuum unit 5 as a strand of unsaturated fibres 21, and leaves said unit as a virtually evacuated strand of unsaturated fibres 22. Each stationary annular element 53 comprises a region 531 in which contact takes place between the inner surface 532 thereof (for the sake of improved clarity, the contact region 531 and the inner surface 532 are denoted in FIG. 3a only on the first stationary annular element 53) and the strand 2, such that airtight sealing results between the vacuum chambers 52. The contact region 531 of the first stationary annular element 53 furthermore seals the strand channel of the vacuum unit 5 with respect to the surroundings. The inner surface 532 of a stationary annular element 53 is preferably designed so as to be friction-reducing, since the contact region 531 is subjected to friction with the strand 2 that is moved in the strand channel. The friction-reducing design can for example achieve a lubricating effect between the strand 2 and the inner surface 532, and/or minimise the contact surfaces between the strand 2 and the inner surface 532, as a result of which fibre damage and abrasion of the inner surface 532 are reduced. In order to achieve the friction-reducing design, the inner surface can be formed so as to be hemispherical on a microscopic scale (not shown), for example by means of sandblasting or coating processes. Furthermore, in each case two stationary annular elements 53, arranged in succession, are interconnected by means of an O-ring 533 and a flange or another suitable connection, in this case by means of clamping elements 535 (shown schematically), so as to be airtight with respect to the surroundings. The connecting element 51 sealed by an O-ring 511, which element for example comprises a flange, achieves a connection between the vacuum unit 5 and the following injection unit (not shown) that is airtight with respect to the surroundings. The connecting element 51 also comprises a contact region 512, by means of which the final vacuum chamber 52 is sealed off from the injection unit (not shown) in an airtight manner.

[0153] Each vacuum chamber 52 comprises a separate connection 54 for one vacuum pump in each case. It is thus possible to connect vacuum pumps of different types and/or different suction capacities, and to achieve different absolute pressure values in the individual chambers 52, the absolute pressure reducing in the pultrusion direction 11. It is likewise possible for one or more of the chambers shown here as vacuum chambers 52 to be designed as an inactive chamber, in that the connection 54 is closed in an airtight manner, for example by means of a blank flange, after air has been pumped once, and in a manner only to be repeated in specified intervals, into the inactive chamber.

[0154] The dimensions 534 of the strand channel in the contact region 531 perpendicularly to the pultrusion direction 11 are selected so as to be smaller, at least at the final two stationary annular elements 53 in the pultrusion direction 11, than the corresponding dimensions 26, i.e. in this case smaller than the diameter, of the strand 2. The sealing of the final vacuum chamber 52 is therefore particularly good, with the result that it is possible to achieve a particularly low absolute pressure value in said vacuum chamber 52. The dimensions 534 of the preceding stationary annular elements 53 are selected so as to be approximately equal to or slightly greater than the corresponding dimensions 26 of the strand, in order to keep the friction between the strand and the inner surface 532 of the stationary annular element lower.

[0155] FIG. 3b shows a vacuum unit 5 as a modular cascade of stationary annular elements 53, similar to that in FIG. 3a, drive elements 500 being arranged on the embodiment shown in FIG. 3b in order to perform a rotation of the vacuum unit 5 about the strand axis 27. The strand 2 is designed so as to be rotationally symmetrical about the strand axis 27. The rotation prevents possible accumulation of the fibres on the surface of the strand 2 in the entry region into the respective contact regions 531 of the stationary annular elements 53. Access to the vacuum chambers 52, the boundary 532 of which rotates, is provided, for the process of pumping out using a stationary vacuum pump (not shown) is provided by means of rotary unions 541 that are arranged on a peripheral groove 542.

[0156] In FIG. 3b, an inactive chamber 520 is arranged between two vacuum chambers 52, which inactive chamber does not have any access to a vacuum pump. The inactive chamber 520 functions in the manner of a labyrinth seal by lengthening the flow path, such that a lower absolute pressure can advantageously be achieved in the vacuum chamber 52 that is to the rear in the pultrusion direction 11.

[0157] FIG. 3c shows an embodiment of a vacuum unit 5 as a cascade of stationary annular elements 53, similar to the drawings in FIG. 3a and FIG. 3b. The vacuum unit 5 is not modular, but instead integral. Said unit can be manufactured for example by means of hollow turning or erosion of solid material, such that advantageously no, in particular no axial, joints are arranged in the strand channel, which joints could lead to fibre damage.

[0158] Similarly to the embodiment of FIG. 3b, the vacuum unit 5 shown comprises elements 500, 541, 542 by means of which the vacuum unit 5 can rotate about the strand axis 27.

[0159] Owing to the friction in the entry region into the contact region, the rotational movement is transmitted to the fibres on the surface of the strand in part. The translational movement and the rotational movement result in a force on the fibres on the surface of the strand. Said resulting force causes a slight displacement of the fibres on the surface of the strand, which displacement promotes constriction of the strand and thus reduces the diameter of the strand, as a result of which the fibres are subjected to additional tensile stress.

[0160] The constriction-promoting effect of the resulting force on a fibre on the strand surface is present apart from in the case in which the direction of the resulting force corresponds to the fibre direction vector in the relevant associated defined point of the entry region into the contact region. In this case the fibre direction vector corresponds to the unit vector, the direction of which reflects the orientation of the fibres on the strand surface. The rotational speed should therefore preferably be selected such that the situation described above does not arise, at least in the case of most of the defined points. Particularly preferably, the rotational speed should be selected such that the situation described above does not arise in the case of more than 80% of the defined points. Said rotational speed or said rotational speeds should be excluded from the range available for the selection of the rotational speed, which range comprises all speeds which cause a resulting force to occur on the fibres on the strand surface.

[0161] In this case, the reduction in the diameter of the strand owing to the resulting force is very small compared with the diameter of the strand. After leaving the contact region, the displacement of the fibres is almost completely reversed again by restoring forces owing to the tensile stress. The rotational movement thus at least does not change target geometry of the strand to an inadmissible extent.

[0162] The described embodiment is advantageous in that an accumulation of fibres on the surface of the strand, in the entry region into the elements of the vacuum unit and/or of the injection unit which comprise a region of contact with the strand, is at least significantly reduced.

[0163] FIGS. 4a and 4b show an alternative embodiment for a vacuum unit 5 comprising a plurality of vacuum chambers 52 that are arranged in succession and are located in an airtight housing 55 comprising a plurality of connection elements, e.g. small flanges, for vacuum pumps 54. FIG. 4a is a side view of the vacuum unit 5 shown in the pultrusion direction 11, the side wall of the housing 55 being removed, and FIG. 4b is a cross section through the vacuum unit 5 perpendicularly to the pultrusion direction 11, or the plan view of a section through the vacuum unit 5 along the line A-A shown in FIG. 4a. The components of the vacuum unit 5 are arranged so as to be substantially symmetrical with respect to a longitudinal plane through the centre axis of the strand 2, in the pultrusion direction 11, and therefore, for reasons of clarity, mutually symmetrical components of the vacuum unit 5 are provided with a reference sign just once in each case.

[0164] In order to seal the vacuum chambers 52 in an airtight manner with respect to one another and to seal the first vacuum chamber 52 in an airtight manner with respect to the surroundings of the vacuum unit 5, the vacuum unit 5 comprises rollers 56 that are rotatably mounted on respective shafts 561 sealed off from the housing 55 and are in the shape of cotton reels. As can be seen in the plan view of the contact region 562 shown in FIG. 4b, the contact region 562 between a roller 56 and the strand 2 surrounds the relevant surface of the strand 2 in the manner of a half shell. The contact region 562 forms the sealing surface between the roller 56 and the strand 2. Each of the rollers 56 rotates about the shaft 561 thereof owing to rolling friction in the contact region 562 resulting from the uniform movement of the strand 2 in the pultrusion direction 11. Owing to the opposing directions of rotation thereof, two rollers 56 roll against one another in the contact region 563 between said two rollers 56, the contact region 563 forming the sealing surface between the two rollers 56.

[0165] Stationary sealing elements 57 are arranged on the housing 55 of the vacuum unit 5 in a rigid and airtight manner. A stationary sealing element 57 comprises a region 571 of contact with one roller 56 in each case, the roller 56 rolling against the stationary sealing element 57 in the contact region 571. The sealing of a roller 56 with respect to the housing 55 is achieved in the contact region 564 between the roller 56 and the housing 55, the surfaces of the roller 56 and housing 55 being ground and polished in the contact region 564 and being equipped with sealing means suitable for a vacuum, for example vacuum grease.

[0166] The sealing of the vacuum unit 5 with respect to the injection unit (not shown) is achieved by means of the connecting element 51 which comprises an O-ring 511 for sealing purposes.

[0167] FIGS. 5a and 5b show a further alternative embodiment for a vacuum unit 5 comprising a vacuum chamber 52 in an airtight housing 55 comprising a connection element, e.g. a small flange, for a vacuum pump 54. FIG. 5a is a side view of the vacuum unit 5 shown in the pultrusion direction 11, the side wall of the housing 55 being removed, and FIG. 5b is a cross section through the vacuum unit 5 perpendicularly to the pultrusion direction 11, or the plan view of a section through the vacuum unit 5 along the line A-A shown in FIG. 5a. The components of the vacuum unit 5 are arranged so as to be substantially symmetrical with respect to a longitudinal plane through the centre axis of the strand 2, in the pultrusion direction 11, and therefore, for reasons of clarity, mutually symmetrical components of the vacuum unit 5 are provided with a reference sign just once in each case.

[0168] The vacuum unit 5 comprises two arrangements 58 that consist in each case of two rotating rollers 56 that are arranged in succession in the pultrusion direction 11 and are interconnected in a conveyor belt-like manner by means of a sealing strip 581 comprising a drive roller 582 and a tensioning roller 583. The sealing strip 581 in the conveyor belt-like arrangement 58 can be actively set into motion by means of the drive roller 582, the portion of the sealing strip 581 arranged on the strand 2 moving in the pultrusion direction 11. The vacuum chamber 52 is located between the two rotating rollers 56, arranged in succession, of the two conveyor belt-like arrangements 58. In order to arrange an additional vacuum chamber upstream or downstream of the existing vacuum chamber 56, an additional rotating roller per conveyor belt-like arrangement 58 is to be arranged upstream or downstream of one of the two existing rotating rollers 56 per arrangement 58.

[0169] The rotating rollers 56 that are rotatably mounted on a shaft 561 are rotationally symmetrical and in the shape of a cotton reel. Two rotating rollers 56 in each case are arranged relative to one another in the manner of half shells. The sealing strips 581 of the arrangements 58 are arranged in the contact region 562 between the rotating roller 56 and the strand and in the contact region 563 between the rotating rollers 56. Accordingly, contact between the strand 2 and the rotating rollers 56 and between two rotating rollers 56, which contact forms a sealing surface, occurs indirectly via the sealing strip 581.

[0170] There is no sealing contact between the sealing strips 581 of the two conveyor belt-like arrangements 58 in the vacuum chamber 52, and therefore air can escape from the strand in the vacuum chamber 52.

[0171] Each rotating roller 56 in the conveyor belt-like arrangements 58 rolls in a sealing manner against a counter roller 59 that is rotatably mounted on a shaft 591, such that a sealing surface results, in the contact region 565, between the sealing strip 581 arranged on the rotating roller 56 and the counter roller 59.

[0172] Stationary sealing elements 57 are arranged on the airtight housing 55 of the vacuum unit 5 in a rigid and airtight manner. A stationary sealing element 57 comprises a region 571 of contact with one counter roller 59 in each case, the counter roller 59 rolling against the stationary sealing element 57 in the contact region 571. The sealing of the rollers 56, 582, 583, 59 with respect to the housing 55 is achieved in the contact region 564, 592 (the contact region between the drive and tensioning rollers and the housing is not shown) between the rollers 56, 582, 583, 59 and the housing 55, the surfaces of the rollers 56, 582, 583 59 and of the housing 55 being ground and polished in the contact region 564, 592 and being equipped with sealing means suitable for a vacuum, for example vacuum grease.

[0173] The sealing of the vacuum unit 5 with respect to the injection unit (not shown) is achieved by means of the connecting element 51 which comprises an O-ring 511 for sealing purposes.

[0174] FIG. 6a is a cross section, in the pultrusion direction 11, of an embodiment of an integral injection unit 6. The components of the injection unit 6 are arranged so as to be substantially symmetrical with respect to a longitudinal plane through the centre axis of the strand 2, in the pultrusion direction 11, and therefore, for reasons of clarity, mutually symmetrical components of the injection unit 6 are provided with a reference sign just once in each case.

[0175] The strand 2 is fed to the injection unit 6, proceeding from the vacuum unit (not shown), as a virtually evacuated strand of unsaturated fibres 22, and leaves the injection unit 6 fully impregnated with matrix material, as an FRP blank 23. The injection unit 6 comprises a plurality of injection chambers 61 arranged in succession, which chambers are each connected to a reservoir for matrix material (not shown) by means of an injection channel 611. The wall 63 of the injection unit 6 is formed as a integral component, e.g. a cast part or turned part, without dividing seams. The injection chambers 61 are mutually separated by means of contact regions 631 between the wall 63 and the strand 2. As a result, matrix material can be injected into the individual injection chambers 61 at different absolute pressures, the absolute pressure generally increasing in the pultrusion direction 11 from one injection chamber 61 to the next injection chamber 61 in the pultrusion direction 11. In this case, it is expedient for the absolute pressure of the injection into the first injection chamber 61 to be selected so as to be low enough to prevent, by means of the pressure difference, the matrix material from penetrating into the vacuum unit (not shown) which is arranged upstream of the injection unit 6 and is connected thereto by means of a seal provided with an O-ring 511.

[0176] Owing to the friction present in the contact regions 631, the strand channel is provided with a preferably break-free wear protection layer (not shown) in the contact regions 631 and over the entire inner surface 632 of the wall 63.

[0177] A plurality of temperature-control elements 64 are arranged on the injection unit 6 in order for it to be possible to influence the temperature-dependent viscosity of the matrix material in a desired manner. In this case, the temperature-control elements may be used for heating or cooling and may be for example resistance heaters or heating cartridges or coolant channels or electrical cooling elements.

[0178] The injection unit 6 is sealed off with respect to a coating unit (not shown) that follows in the pultrusion direction 11, by means of an O-ring 600 and a suitable connecting element 60 such as a flange element or connecting element.

[0179] An integral injection unit 6 can be manufactured for example by means of hollow turning or erosion of solid material. Cleaning baths, for example, can be used for cleaning.

[0180] FIG. 6b shows an integral injection unit 6, similar to that in FIG. 6a, drive elements 65 being arranged on the injection unit 6 in order for it to be possible to perform a rotation of the injection unit 6 about the strand axis 27. The strand 2 is designed so as to be rotationally symmetrical about the strand axis 27. The rotation prevents possible accumulation of the fibres on the surface of the strand 2 in the entry region into the respective contact regions 631 between the inner surface 632 and the strand 2. The stationary matrix reservoir (not shown) is connected to the co-rotating injection channels 611 and drainage channels 621 arranged on the drainage chambers 62 by means of rotary unions 660 that are arranged on a peripheral groove 661. The electrical power is transmitted to the temperature-control elements 64, in the form of electric heaters, for example by means of sliding contacts 662.

[0181] Owing to the friction in the entry region into the contact region, the rotational movement is transmitted to the fibres on the surface of the strand in part. The translational movement and the rotational movement result in a force on the fibres on the surface of the strand. Said resulting force causes a slight displacement of the fibres on the surface of the strand, which displacement promotes constriction of the strand and thus reduces the diameter of the strand, as a result of which the fibres are subjected to additional tensile stress.

[0182] The constriction-promoting effect of the resulting force on a fibre on the strand surface is present apart from in the case in which the direction of the resulting force corresponds to the fibre direction vector in the relevant associated defined point of the entry region into the contact region. In this case the fibre direction vector corresponds to the unit vector, the direction of which reflects the orientation of the fibres on the strand surface. The rotational speed should therefore preferably be selected such that the situation described above does not arise, at least in the case of most of the defined points. Particularly preferably, the rotational speed should be selected such that the situation described above does not arise in the case of more than 80% of the defined points. Said rotational speed or said rotational speeds should be excluded from the range available for the selection of the rotational speed, which range comprises all speeds which cause a resulting force to occur on the fibres on the strand surface.

[0183] In this case, the reduction in the diameter of the strand owing to the resulting force is very small compared with the diameter of the strand. After leaving the contact region, the displacement of the fibres is almost completely reversed again by restoring forces owing to the tensile stress. The rotational movement thus at least does not change target geometry of the strand to an inadmissible extent.

[0184] The described embodiment is advantageous in that an accumulation of fibres on the surface of the strand, in the entry region into the elements of the vacuum unit and/or of the injection unit which comprise a region of contact with the strand, is at least significantly reduced.

[0185] FIG. 7 is a cross section, in the pultrusion direction 11, of an alternative embodiment of a modular injection unit 6. The components of the injection unit 6 are arranged so as to be substantially symmetrical with respect to a longitudinal plane through the centre axis of the strand 2, in the pultrusion direction 11, and therefore, for reasons of clarity, mutually symmetrical components of the injection unit 6 are provided with a reference sign just once in each case.

[0186] The injection unit 6 is in a modular construction, consisting of a plurality of mutually separated modules 67, 68. The number of modules 67, 68 can be selected and adjusted in a simple manner, in accordance with the process parameters of the process according to the invention. In each case, two modules 67, or one module 67 and one module 68, are sealed off with respect to the surroundings of the injection unit 6 by means of an O-ring 670 and by means of clamping all of the modules 67, 68 using clamping elements 69. The inner surface 671 of a module 67 is shaped such that a cavity forms around the strand 2, as the injection chamber 61. Each injection chamber 61 comprises injection channels 611 which are connected to a reservoir for matrix material (not shown). The inner surface 681 of a module 68 is shaped such that a cavity forms around the strand 2, as the drainage chamber 62. Each drainage chamber 62 comprises a drainage channel 621 which is connected to an outlet gulley (not shown) for excess matrix material. In each case, a drainage module 68 is arranged upstream and downstream of the number of injection modules 67 selected in a manner matched to the process parameters. It is also possible to insert modules into the arrangement that function as inactive chambers. A temperature-control element 64, e.g. in the form of an electrical heater, is arranged on each injection module 67 in order to influence the viscosity properties of the matrix material by means of purposeful temperature adjustment.

[0187] The modules 67, 68 are sealed off with respect to one another by means of sealing elements 672, 682, for example elastomer sealing lips, which are oriented in the pultrusion direction 11 owing to the directed movement of the strand 2 through the strand channel, and are pressed against the strand 2 in a sealing manner by means of the positive relative pressure prevailing in the injection chambers 67. Owing to the modular construction of the injection unit 6, the sealing elements 672, 682 can be exchanged in a simple manner if said elements are worn and the sealing effect decreases due to abrasion owing to the movement of the strand 2.

[0188] FIGS. 8a and 8b show an embodiment of a coating unit 7, FIG. 8a being a plan view and FIG. 8b showing the cross sectional view shown in FIG. 8a, along the line A-A. The surface of the FRP blank 23 is coated by means of being rolled up in a film 711 from a film storage means 71 that is axially parallel with the FRP blank 23 and is rotatably mounted on a shaft 712. The film feed takes place over the entire length of the FRP blank 23; the width of the film 711, i.e. the dimension thereof in parallel with the shaft 712, corresponds at least to the length of the FRP blank 23. The film 711 is drawn off from the film storage means 71 and introduced, into a guided manner, into a region in which a plurality of rollers 72 are rotatably arranged.

[0189] The FRP blank 23 leaves the pultrusion facility 1 fully impregnated with matrix material and is transported by a conveyor belt 80 to the cutting unit 9, e.g. a saw, and cut to length. After being cut to length, the FRP blank 23 is also transported, in a freely suspended manner, into the roller region, and the film 711 is pressed onto the surface in a portion of the surface of the FRP blank 23. Rotation of the rollers 72 in the direction of rotation indicated by arrows in FIG. 7b causes the FRP blank 23 to rotate in the opposing direction of rotation shown. The film storage means 71 thus also rotates in this direction of rotation that opposes the rollers 72, and therefore the film 711 is drawn further into the roller region and is laid completely around the surface of the FRP blank 23, until a slight overlap is achieved. In order to seal the overlap, the film 711 may be self-adhesive for example. Subsequently, the film 711 is trimmed by the tool 73 and laid on the surface of the FRP blank 23 in a crease-free and rigid manner by means of further rotation of the rollers 72 and of the FRP blank 23. The coated FRP blank is removed from the roller region by means of an ejector 74.

LIST OF REFERENCE NUMERALS

[0190] 1, 1 pultrusion facility [0191] 2 strand [0192] 200 air bubbles [0193] 21 strand of unsaturated fibres [0194] 22 virtually evacuated strand of unsaturated fibres [0195] 23 FRP blank [0196] 230 matrix material [0197] 24 FRP blank comprising a coating [0198] 25 mould core [0199] 26 dimensions of the strand [0200] 27 strand axis [0201] 3 supply region [0202] 31 creel [0203] 310 spool [0204] 311 roving [0205] 32 winding wheel [0206] 321 roving [0207] 33 fibre strip spool [0208] 331 fibre strip [0209] 4 guide unit [0210] 5, 5, 5 vacuum unit [0211] 500 drive element for rotation [0212] 51, 51, 51 connecting element [0213] 511, 511, 511 O-ring [0214] 512 contact region [0215] 513 dimension of the strand channel in the contact region [0216] 52, 52, 52 vacuum chamber [0217] 520 inactive chamber [0218] 53 stationary annular element [0219] 531 contact region between the stationary annular element and the strand [0220] 532 inner surface of a stationary annular element [0221] 533 O-ring [0222] 534 dimension of the strand channel in the contact region [0223] 535 clamping element [0224] 54, 54, 54 connection element for a vacuum pump [0225] 541 rotary union [0226] 542 groove [0227] 55, 55 housing of the vacuum unit [0228] 56, 56 rotating roller [0229] 561, 561 shaft of the rotating roller [0230] 562, 562 contact region between the rotating roller and the strand [0231] 563, 563 contact region between two rotating rollers [0232] 564, 564 contact region between the rotating roller and the housing [0233] 565 contact region between the rotating roller and a counter roller [0234] 57, 57 stationary sealing element [0235] 571, 571 contact region between the stationary sealing element and a roller [0236] 58 conveyor belt-like arrangement [0237] 581 sealing strip [0238] 582 drive roller [0239] 583 tensioning roller [0240] 59 counter roller [0241] 591 shaft of the counter roller [0242] 592 contact region between the counter roller and the housing [0243] 6, 6 injection unit [0244] 60 connecting element [0245] 600, 600 O-ring [0246] 61, 61 injection chamber [0247] 611, 611 injection channel [0248] 62, 62 drainage chamber [0249] 621, 621 drainage channel [0250] 63 wall [0251] 631 contact region between the wall and the strand [0252] 632 inner surface of the wall [0253] 64, 64 temperature-control element [0254] 65 drive element for rotation [0255] 660 rotary union [0256] 661 sliding contact [0257] 662 groove [0258] 67 injection module [0259] 670 O-ring [0260] 671 inner surface of the injection module [0261] 672 sealing element [0262] 68 drainage module [0263] 681 inner surface of the drainage module [0264] 682 sealing element [0265] 69 clamping element [0266] 7 coating unit [0267] 71 film storage means [0268] 711 film [0269] 712 shaft of the film storage means [0270] 72 rollers [0271] 73 tool for film trimming [0272] 74 ejector [0273] 8 strip draw-off unit [0274] 80 conveyor belt [0275] 9 cutting unit