Device and method for continuously blow molding fiber-reinforced thermoplastic hollow profiles having a constant or changing cross-section

Abstract

The invention relates to a device and a method for semi-continuous blow moulding of fiber-reinforced, thermoplastic, endless, hollow-profile-shaped components with longitudinally constant or varying cross-sections, consisting of at least one consolidation tool, which, in its closed state, encloses a preform enclosing an elastically moldable pressure chamber.

Claims

1. A device for the semi-continuous blow moulding of fiber-reinforced, thermoplastic, endless, hollow-profile components with cross sections that are constant or varying in a longitudinal direction, comprising at least one consolidating tool which, in a closed state, encloses a preform, which encloses an elastically deformable pressure chamber, wherein: a) a preforming unit and the at least one consolidating tool are arranged directly one after another; b) the preforming unit provides the preform; c) the preform enclosed by the at least one consolidating tool is a preform segment; d) a central axis of the preforming unit, the at least one consolidating tool, the preform segment, and the pressure chamber are arranged congruently; e) the at least one consolidating tool is designed in at least two parts; and f) the at least one consolidating tool corresponds to a contour of the component; wherein: the at least one consolidating tool has at least two independently isothermal-tempered tool segments, and in that the tool segments are arranged along a middle axis; dimensions of the at least one consolidating tool, the pressure chamber, and the preform segment for processing are identical along the central axis; the device has a feed device which is capable of repeatedly moving the preform by an amount of a length of one of the tool segments into a machining direction directed along the central axis; the pressure chamber is formed from: an endless, deformable pressure membrane and sealing elements, or a pressure membrane that is a deformable hose firmly attached to sealing elements; and the pressure chamber is pressurizable.

2. The device according to claim 1, wherein, on an inner cavity wall, the tool segments comprise exchangeable modules which deviate from the final contour of the component.

3. The device according to claim 1, wherein, on an inner cavity wall, the tool segments comprise at least one exchangeable module, having an inner contour that corresponds to the outer contour of the component.

4. The device according to claim 1, wherein the tool segments have an identical length.

5. The device according to claim 1, wherein the tool segments are thermally decoupled from one another by heat transfer barriers.

6. The device according to claim 1, wherein: the pressure chamber comprises at least two sealing elements which have a distance from each other, and which have a pressure-tight connection to a coupling element; and each having a seal pressing radially against the pressure membrane at a pressure p1 thus forming the pressure chamber.

7. The device according to claim 6, wherein the coupling element: is fixed in an area of the preforming unit; and has an air duct along its longitudinal axis that runs along an entire length of the coupling element, wherein the air duct has in the area of the at least two sealing elements radially arranged air outlets that are provided for applying the pressure p1.

8. The device according to claim 1, wherein a material of the pressure membrane: corresponds to a same class of materials as an embedding matrix of the preform; and has a higher degree of polymerization, and a thickness between 50 and 60 μm.

9. The device according to claim 1, wherein: a consolidation pressure p2 lies in a range between 4 and 10 bar, and a sealing pressure p1, acting on the pressure membrane between the at least two sealing elements, is greater than the consolidation pressure p2.

10. The device according to claim 1, wherein: a consolidation pressure p2 lies in a range between 5 and 9 bar, and a sealing pressure p1, acting on the tubular pressure membrane between the sealing elements, is greater than the consolidation pressure p2.

11. A method for semi-continuous blow moulding of fibre-reinforced thermoplastic hollow profiles with cross-sections that are constant or varying in longitudinal direction, comprising at least the steps: a) providing a tubular pressure membrane which is coated or enclosed with a preform comprising thermoplastic matrix material; b) providing a device for the semi-continuous blow moulding of fiber-reinforced, thermoplastic, endless, hollow-profile components with cross sections that are constant or varying in the longitudinal direction, comprising at least one consolidating tool which, in a closed state, encloses a preform, which encloses an elastically deformable pressure chamber; c) positioning of the tubular pressure membrane and the preform such that it extends over an entire length of the at least one consolidating tool and covers sealing elements, d) closing the at least one consolidating tool; e) compressing a preform segment by enlarging a diameter of the tubular pressure membrane through pressurization, and nestling the preform segment against an inner wall of the least one consolidating tool; f) heating a first preform segment in the first tool segment of the at least one consolidating tool to a temperature below a melting temperature of the thermoplastic, heating a second preform segment in the second tool segment of the at least one consolidating tool to a temperature which at least reaches the melting temperature of the matrix material, cooling and shaping a third preform segment in a third tool segment of the at least one consolidating tool to a temperature which is below a solidification temperature of the matrix material; g) terminating the pressurization of the tubular pressure membrane; h) opening the at least one consolidating tool and, subsequently, advancing the preform by the length of one tool segment and subsequently closing the at least one consolidating tool; and i) repeating steps e) to h).

12. The method of claim 11, wherein: the pressurization via a consolidation pressure (P2) is in a range between 4 bar and 10 bar; and a sealing pressure (P1) is larger than the consolidation pressure (P2) and acts between the sealing elements and the tubular pressure membrane.

13. The method according to claim 11, wherein reinforcement filaments of the fiber-reinforced thermoplastic hollow profiles of the preform are glass, carbon, basalt and/or thermoplastic filaments which have a higher melting point than a surrounding embedding matrix of the preform.

14. The method according to claim 11, wherein the thermoplastic matrix materials of the preform are organic polymers having melting temperatures in a range between 70° C. and 380° C.

15. The method of claim 11, wherein: the pressurization via a consolidation pressure (P2) is in the range between 5 bar and 9 bar; and a sealing pressure (P1) is larger than the consolidation pressure (P2) and acts between the sealing elements and the tubular pressure membrane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail below with reference to drawings and an exemplary embodiment, without being restricted thereto. For the sake of clarity, only the tool (4) is displayed hatched in the sectional views.

(2) FIG. 1 shows a side view of the consolidation tool according to the invention.

(3) FIG. 1a shows a side view of the consolidation tool according to the invention in a first method step, in a pressureless and open state to convey the preform segment.

(4) FIG. 1b shows a side view of the consolidation tool according to the invention in a second method step in a closed and pressurized state, together with temperature zones.

(5) FIG. 1c shows a side view of the consolidation tool according to the invention in a third method step, in the open, pressure-free state, for the feed motion of the preform segment.

(6) FIG. 2a shows an alternative embodiment of the consolidation tool with a variable cross-section of the resulting component.

(7) FIG. 2b shows a 3D representation of a preform segment.

(8) FIG. 3 shows cross-sections of variable-manufacturable cross-section geometries.

(9) FIG. 4 shows a detailed cross-section of the material transition between the preheating zone and melting zone.

(10) FIG. 5 shows a detailed cross-section of a sealing element.

(11) FIG. 6 shows detailed cross-sections of a sealing element unpressurized (left) and pressurized (right).

(12) FIG. 7a shows a top view of a preforming unit based on the braiding process.

(13) FIG. 7b shows a side view of a preforming unit based on the braiding process.

(14) FIG. 7c shows a top view of a preforming unit based on the spiralization process

(15) FIG. 7d: shows a side view of a preforming unit based on the spiralization process.

(16) FIG. 8 shows a schematic representation of the cycles of the method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(17) FIG. 1 shows a side view of a consolidation device (11), in which a tube-shaped preform (1), which is applied to a tube-shaped pressure membrane (9) with the help of a textile-technological preforming unit (13), is consolidated into a component (6) in several process steps. In a first embodiment according to the invention component 6 has a constant cross-section. For the purposes of this application, the length L corresponds to the distance between the sealing elements (2) and the partial length s is the length of a tool segment (4.1, 4.2, 4.3).

(18) FIG. 1a shows a side view of the consolidation device according to the invention in a first step of the method in which the preform segment (14) is moved into the consolidation device in the feed direction (7). According to the invention, the hose-shaped pressure membrane (9) is pulled over the sealing elements (2) in the feed direction (7). The feed travel of the preform segment corresponds to the partial length s.

(19) To enable the feed motion, the pressure chamber (3), comprising the pressure membrane (10) and the sealing elements (2), is opened in an unpressurized state (p1=p2=0) and the separable forming tool (4) is separated in the radial direction of the preform segment by the opening path (12). The amount of the opening path (12) must be selected in a way that the preform segment (14) can be moved in an axial direction without contact to the tool (4).

(20) FIG. 1b shows a side view of the consolidation device according to the invention in a further method step with a closed tool (4) and a pressurized pressure chamber (3).

(21) The pressure chamber (3) according to the invention is made of the sealing elements (2), which are subjected to a pressure p1, and the pressure membrane (9), which is subjected to a pressure p2. The length of the pressure chamber corresponds to the distance L in between the sealing elements (2), which are connected in a pressure-tight manner to a coupling element (8). This coupling element (8) according to the invention has a longitudinal bore extending over its entire length and radial bores in the area of the sealing elements (2), which make it possible to generate a pressure p in the sealing elements (2). The mode of action of the sealing elements (2) is described in detail in connection with FIGS. 5 and 6. In the area of the preforming unit (13), the coupling element (8) is arranged concentrically to the central axis of the consolidation device (11).

(22) The consolidation pressure p2 is kept constant between 4 bar and 9 bar for the consolidation time of the material. The sealing pressure p1 is higher than the consolidation pressure p2.

(23) The tool segment of the heating zone (4.1) is heated to a temperature below the melting temperature of the embedded matrix material used (T<TS).

(24) The tool segment of the melting zone (4.2) has a temperature above the melting temperature of the embedded matrix material used (T>TS).

(25) The tool segment of the consolidation and solidification zone (4.3) has a temperature below the melting temperature of the embedded matrix material used (T<TS), which is selected so that the embedding material solidifies in such a way that the resulting component can be handled.

(26) For the purposes of this application, isothermal refers to the fact that the tools have constant temperatures in the respective temperature zones (4.1, 4.2 and 4.3) regardless of the method step.

(27) The duration of the pressure application corresponds to the matrix-specific flow time in the melting state.

(28) FIG. 1c shows a side view of the consolidation device according to the invention in a further method step with an open tool (4) and a pressureless pressure chamber (3). In this method step after the consolidation process, the preform segment (14) is subject to a feed motion (7) by the partial length s, corresponding to the temperature zone lengths defined by the tool segments of the temperature zones (4.1, 4.2 and 4.3).

(29) FIG. 2a shows an alternative, particularly preferred consolidation device in a closed state with several interchangeable modules (16) of the tool segments (4.1, 4.2, 4.3) inside the tool (4). In this embodiment, the inner tool walls of the tool segment of the solidification zone (4.3) consist of three interchangeable modules (16).

(30) FIG. 2b shows a three-dimensional view of a preform segment (14) in a subsection L of the consolidation device (11) with a part of the multi-part tool (4) in touch with the preform segment (14). A section of the preform segment (14) is shown, which is in contact with the tool wall of the melting zone tool (4.2), as well as a section of the preform segment (14), which is in contact with the cavity wall of the consolidation and solidification zone tool (4.3). The respective temperature zones of the tool are thermally decoupled by heat transfer barriers (10).

(31) FIG. 3 shows exemplary cross-sections of a preform segment with varying cross-sections in axial and radial directions, which may be adjusted over the length L of the consolidation device (11). In section 0, this part of the preform segment is positioned in the tool segment of the heating zone (4.2), and the preform (1) does not yet undergo forming, but is heated to its melting temperature by contact with the tool wall of the tool segment of the heating zone. In the subsequent part of the preform segment, marked by the sections A, B and C, the preform segment is formed into the varying cross-sections of the resulting component (6), and the material is cooled down below the melting temperature of the matrix material.

(32) FIG. 4 shows a detailed view of the transition between the preform (1) and the component (6) of the preform segment (14) in the area of the tools preheating zone (4.1) and heating zone (4.2). Both temperature zones are thermally decoupled from each other by heat transfer barriers (10).

(33) FIG. 5 exemplarily shows a detailed view of a sealing element (2) in the area of the resulting component (6). In order to separate the pressure chamber (3) from the ambient pressure to allow for the application of the consolidation pressure, a pressure p1 must be applied in the intermediate space formed in between the elastic radial seal (2.3) and the sidewalls (2.1) and (2.2). The sealing effect of the sealing element (2) arises as soon as the radial seal (2.3) locks against the pressure membrane (9), the preform (1) or the component (6), and the tool walls (4.1 and 4.3). For this, the pressure p1 must be greater than the pressure p2. The pressure p1 can be applied to the sealing elements (2) via a channel that extends over the longitudinal axis and over the entire length of the coupling element (8), and which is respectively connected to at least one bore arranged in a radial direction and between the sidewalls (2.1) and (2.2).

(34) The left side of FIG. 6 shows a detail of the sealing element (2) with the radial seal (2.3) in its pressurized state. Here, the pressure p1, which is greater than the pressure p2, is effective in the sealing elements and pushes the pressure membrane (9) against the preform (1) in the area of the sealing elements. As a result, the pressure chamber (3) is temporarily formed over the length L of the consolidation device (11) and is subjected to the pressure p2, which presses the pressure membrane (9) against the preform (1).

(35) The right-hand side shows the unpressurized sealing element (2) and the unpressurized pressure chamber (3). The distance d between the pressure diaphragm (9) and the preform (1) is greater than zero.

(36) FIG. 7 a to d show preferred preforming units (13). Such preferred braiding or spiralizing machines are suitable for depositing endless textile semi-finished products on a core, thereby enabling the forming of the Preform (1).

(37) FIG. 8 schematically shows the first three relevant cycles according to the invention at the beginning of the method, which cycles are passed by the preform segment (14) in order to consolidate the preform (1) into a component (6) with the help of the forming tool (4).

(38) In a first cycle, the preform segment (14) is positioned inside the forming tool (4) in such a way that it is completely covered by it, and is at the same time heated or cooled to the respective temperatures in the sections 14.1, 14.2 and 14.3 by contact with the tool segments (4.1, 4.2, 4.2).

(39) In a second cycle, the preform segment is positioned inside the forming tool (4) in such a way that the previous section 14.1 becomes the new section 14.2 and the previous section 14.2 becomes the new section 14.3.

(40) In a third cycle of the method, the preform is again positioned in a way that the previous section 14-A becomes the new section 14.1 and the previous section 14.2 becomes the new section 14.3. During the sequence of cycles, the preform (1) is supplied endlessly and guided to the section 14.1 in every cycle.

(41) The finished component (6) corresponds to the previous section 14.3. As a result of the process, after the execution of the first two cycles at the beginning of the process, a scrap is created from sections 14.2 and 14.3 on which the complete temperature regime has not yet acted.

LIST OF REFERENCE SIGNS

(42) 1 preform 2 sealing element 2.1 internal wall of the sealing element 2.2 external wall of the sealing element 2.3 pressure chamber in the sealing element 2.4 elastic seal 3 pressure chamber for the application of the consolidation pressure 4 separable tool 4.1 separable tool of the preheating zone 4.2 separable tool of the melting zone 4.3 separable tool of the consolidation and solidification zone 6 component 7 feed and/or pull-off direction 8 coupling element of sealing elements 9 pressure membrane 10 heat transfer barrier 11 consolidation device of length L 12 travel of the upper tool 13 preforming unit 14 preform segment 15 exchangeable modules of the solidification zone 16 exchangeable modules of the preheating and heating zone