DE102010062870B4 - Method and device for producing a fiber composite component in integral construction - Google Patents

Abstract

Method for producing a fiber composite component (1) in an integral construction, comprising the steps of: positioning a sheet-like semi-finished fiber product (36) on a molding tool (12) predetermining an outer contour of the fiber composite component (1), arranging dimensionally stable semi-finished fiber products (40) produced to final dimensions on the sheet-like semi-finished fiber product (36), stabilizing and fixing the dimensionally stable semifinished fiber products (40) with tool cores (20) which have at least two core parts (26, 28) forming the respective tool core (20), laterally of the dimensionally stable semi-finished fiber product ( 40) and extend over the sheet-like semi-finished fiber product (36), wherein they rest on the end of the mold (12) and for receiving the respective dimensionally stable semifinished fiber product (40) each define a receiving space (50, 52), - resin infiltration, wherein a ) a sprue on the tool cores (20) on the head side of the dimensionally stable semi-finished fiber products (40) takes place and an extraction in the region of the molding tool (12), or b) a sprue in the region of the molding tool (12) and an extraction via the tool cores (20) at the head side of the dimensionally stable semifinished fiber products (40), - hardening of the structure (36, 40), and - removing the structure (36, 40), wherein the tool cores (20) are removed.

Description

The invention relates to a method for producing a fiber composite component in Integralbauweise and an apparatus for performing such a method.

Conventionally, fuselage segments of metal-clad aircraft are made from skin shells. The skin shells each consist of a sheet-like skin panel, which is reinforced by a Hinterbaustruktur of extending in the longitudinal and circumferential reinforcing elements. The connection of the longitudinal stiffeners to the metal body takes place directly by riveting. The connection of the peripheral stiffeners is indirectly via riveted fittings.

Recently, however, there is an increased use of fiber composites such as carbon fiber reinforced or glass fiber reinforced plastic components for the production of the fuselage segments. In a known construction, the skin panels and the stiffening elements as well as the fittings made of impregnated with a resin web-like fiber layers such as prepregs are made separately and riveted after a mechanical finishing. The production of large-scale skin field is easy to automate and therefore cost. Cost-cutting, however, is the production of the stiffening elements and the fittings because of the required reworking on final measure and their subsequent integration into the skin by riveting.

Due to very high costs for the rivets, in particular for rivets for use in carbon fiber reinforced plastic compounds, a very low tolerance compensation, which can lead to assembly problems especially for large component dimensions, as well as a complex mechanical finishing of the stiffening elements and fittings is increasingly trying to make the fuselage segments integral with a Trailing structure form. In this so-called integral construction, at least most of the longitudinally extending stiffening elements are made integral with the skin shell. This known method is characterized by the production in one shot, d. H. there is no subsequent riveting necessary at least for the longitudinal stiffeners.

An infusion process is for example in the DE 10 2008 029 518 A1 shown. In this case, by means of a thermoplastic binder dimensionally stable executed semi-finished fiber products are positioned on a non-dimensionally stable sheet-like semi-finished fiber representing the skin panel and used as a support for semi-rigid fiber semi-finished products. The non-dimensionally stable semi-finished fiber products are connected in a resin infusion process and in a subsequent curing process with the dimensionally stable semifinished fiber products to the skin shell with integrated framework structure. The dimensionally stable semi-finished products acting as tool cores each have, in a central region spaced apart from a component head in the vertical direction, a longitudinally extending inner or resin supply channel which, after curing, forms an integral component of the skin shell filled with resin residues. During the infusion, the resin is driven from the resin supply channel upwards in the direction of the component head and in an opposite direction downwards in the direction of the flat foot-like semi-finished fiber product. However, the problem is the positioning of the non-dimensionally stable or dry semi-finished fiber products on the tool cores and the associated high manufacturing complexity and a repeatable component quality, for example, with respect to a uniform resin distribution. In addition, fiber-free component areas are formed by the resin residues arranged and hardened in the integral supply channels, which lead to a reduction in component stability.

The EP 2 119 544 A1 describes a method for producing a fiber composite component. Here, a dimensionally stable semifinished fiber product is arranged on a sheet-like semi-finished fiber, wherein the dimensionally stable semifinished fiber product is stabilized with tool cores and fixed in position. Then, the semifinished fiber product is infiltrated with resin, wherein the sprue in the region of the mold and the suction via the tool cores on the head side of the dimensionally stable semifinished fiber products. Finally, the structure is cured and demolded, with the tool cores are removed.

The US 2002/0 185 785 A1 describes a process for producing a fiber composite structure consisting of various independent semifinished fiber products, the process being carried out by a single production step. In this case, several frame-like semi-finished fiber products are arranged on a sheet-like semifinished fiber product. Then there is a resin infusion, the sprue on the tool cores on the head side of the dimensionally stable semi-finished fiber products and the suction takes place in the region of the mold.

The object of the invention is to provide a method and an apparatus for producing a fiber composite component in Integralbauweise that eliminate the aforementioned disadvantages and allow high process reliability and repeatable component quality.

This object is achieved by a method having the steps of patent claim 1 and by a device having the features of patent claim 7.

In a method according to the invention for the production of a fiber composite component in an integral construction, first a sheet-like semifinished fiber product is positioned on a molding tool which predetermines an outer contour of the fiber composite component. Then dimensionally stable semi-finished fiber products manufactured to final dimensions are arranged on the sheet-like semifinished fiber product in accordance with a course of stiffening elements. Subsequently, the dimensionally stable semifinished fiber products are stabilized with tool cores and fixed in position. Thereafter, a resin infusion, wherein a sprue on the tool cores on the head side of the dimensionally stable semi-finished fiber products takes place and the suction in the region of the mold or the sprue in the region of the mold and the suction on the tool cores on the head side of the dimensionally stable semifinished fiber products. Finally, a hardening and demolding of the structure, whereby the tool cores are removed. The tool cores have at least two core parts forming the respective tool core, which are laterally positioned laterally of the dimensionally stable semifinished fiber product and extend over the sheet-like semifinished fiber product, wherein they rest on the end of the molding tool and each define a receiving space for receiving the respective dimensionally stable semifinished fiber product. It is advantageous in the method according to the invention that the fiber semi-finished products are completely positioned between the sprue and the suction due to the arrangement of the sprue and the suction, and thus a resin or matrix material is reliably guided into each component area. A formation of resin-free, the component quality lowering cavities is not possible. In addition, it is advantageous that at least the semifinished products forming the stiffening elements are already made to final dimensions, so that a costly reworking after removal of the structure is eliminated. Furthermore, it is advantageous in the method according to the invention that the semifinished products which form the stiffening elements can be handled simply and precisely due to their dimensional stability and can be positioned on the flat semi-finished fiber product. Dimensionally stable means that the semi-finished fiber products are provided with a thermoplastic binder, for example, which is only solidified and softened by a temperature, whereby the semi-finished fiber lose its inherent stability. When falling below a certain solidification temperature, however, they are returned to their dimensionally stable state. In addition, in contrast to the aforementioned prior art, no fiber-free component regions are formed, so that the fiber composite components produced according to the invention have optimum stability.

In a preferred embodiment, the sprue is punctiform or linear in the sheet-like semi-finished fiber.

In an alternative variant, the sprue is punctiform or linear over at least one lateral edge region of the flat semi-finished fiber product.

In another preferred embodiment, the suction is punctiform or linear in the sheet-like fiber semi-finished product.

In an alternative variant, the suction is punctiform or linear over at least one lateral edge region of the flat semi-finished fiber product.

In one embodiment, the sheet-like semi-finished fiber is positioned in a frame on the mold. The frame can already be integrated in the mold or can be built up on this almost flexible. The frame defines a cavity in which the semi-finished fiber is guided laterally safe and also prevents resin or vacuum leakage. In particular, the size or areal extent of the cavity corresponds to a final dimension or nominal dimension of the sheet-like semifinished fiber product, so that likewise expensive reworking with respect to the flat semifinished fiber product is dispensed with. By extending the tool cores over the sheet-like fiber semi-finished and the end-side support on the mold, a stable position thereof is achieved.

Especially with large-area and / or concavely curved fiber composite components, it may be advantageous if the tool cores are supported in addition to their end-side support on the mold on at least one adjacent tool core.

An inventive device for carrying out such a method has a mold for receiving a flat semi-finished fiber tool and tool cores for supporting dimensionally stable fiber semi-finished products for forming stiffening elements integral with the flat semi-finished fiber product. The tool cores each have at least one integral receiving space for receiving the dimensionally stable semifinished fiber products and in each case at least one component-side-side integral supply channel which is open directly or indirectly to the receiving space and forms a sprue or a suction. The tool cores have at least two core parts, which are positioned laterally in the transverse direction of the dimensionally stable semifinished fiber product and extend over the sheet-like semifinished fiber product, wherein they rest on the end of the mold. Such a device enables a uniform matrix material distribution in the semifinished fiber products and via the outside of the dimensionally stable semi-finished fiber tools tool cores a correspondingly high and reproducible component quality.

In one embodiment, the respective supply channel is in fluid communication with the receiving space via a longitudinal gap or a hole pattern. As a result, the demolding of the cured composite component is facilitated because the hardened in the supply channels resin is thus connected only via a thin resin film with the stiffening elements and thus can be easily removed accordingly. In addition, the sprue or the suction can be controlled via the gap, for example with regard to course and amount of resin.

In a particularly robust device, the supply channels are formed closed on one side. In principle, however, it is also possible to connect the supply channels, for example in a meandering manner.

The positioning of the tool cores can be simplified, and the respective gap is formed in a parting plane of the two tool core parts.

The positioning of the tool cores is particularly simple if they are divided symmetrically to the longitudinal axis of the trainees stiffening elements in their core parts. In addition, the core parts can be combined in the symmetrical separation of the tool cores to any one tool core.

Other advantageous embodiments of the invention are the subject of further subclaims.

In the following, preferred embodiments of the invention will be explained in more detail with reference to highly simplified schematic illustrations. Show it

1 a perspective view of a fiber composite component according to the invention, and

2 to 22 Process steps for the production of the composite component 1 and a stepwise structure of a device according to the invention.

In the figures, the same structural elements bear the same reference numerals, for reasons of clarity in some figures, only a few elements are provided with a reference numeral.

In 1 is a fiber composite component produced according to the invention 1 shown. This is a skin shell of an aircraft fuselage, which has just been shown for the purpose of simplified drawing, consisting of a skin panel 2 and an integrally attached hindleg structure for strengthening the skin panel 2 , The rear structure has at least a plurality of stiffening elements arranged parallel next to one another and extending in the longitudinal direction 4 on. The stiffening elements 4 are each T-shaped with one on the skin panel 2 Tailed foot 6 and one centered and orthogonal to the foot 6 extending footbridge 8th educated. One for the production of the skin shell 1 Required device according to the invention has a mold 12 , two longitudinal strips 14 , two transverse bars 16 , Tool cores or plungers 20 , Spacers 22 , Patches 24 , Printing inserts 30 and pipe socket 32 on.

At the beginning of the procedure, as in the 2 to 6 shown on the forming an outer contour of the respective fuselage segment molding tool 12 a cavity 34 for receiving a sheet-like semi-finished fiber product 36 for the formation of the skin shell 2 educated. The areal extent or size of the cavity 34 corresponds in principle to the areal extent of the skin shell 1 so that the skin field 2 does not have to be laboriously reworked, but already has final dimensions. For this purpose, the longitudinal bars 14 and the transverse bars 16 frame-like to each other on the mold 12 arranged ( 2 and 3 ). This is located in a horizontal or horizontal orientation. Then be along the opposite transverse strips 16 within the frame 18 the spacers 22 positioned, each in the area of a crossbar 16 be spaced apart so that between them a gap 38 for end support of the tool cores 20 is created ( 4 ). After positioning the spacers 22 However, first the filling pieces 24 in the interstices 38 arranged ( 5 ). After formation of the longitudinal strips 14 in the transverse direction and from the spacers 22 as well as the filling pieces 24 longitudinally limited cavity 34 then becomes the sheet-like semi-finished fiber 36 fitted and recut if necessary ( 6 ). The semi-finished fiber product preferably consists of a plurality of carbon fibers, which are combined to form a clutch, tissue, knit or the like. Preferably, it is carried out with dry bindered or unbonded fibers.

Then the stiffening elements are individually one after the other 4 on the sheet-like semi-finished fiber 36 built up. For this purpose, as in 7 shown a filler pair consisting of two opposing filler pieces 24 from the corresponding spaces 38 between the spacers 22 taken and according to 8th one dimensionally stable semifinished fiber product 40 to form the first stiffening element 4 between the now free Zwischenraumpaar on the flat semi-finished fiber 36 positioned. The dimensionally stable semifinished fiber product 40 has according to the stiffening element 4 a T-shaped cross-section with a foot 6 and a jetty 8th , It is already made to final gauge and consists of a plurality of carbon fibers, which are converted in a clutch, fabric, knit or the like by means of a thermoplastic binder in their T-shaped, final gauge-like shape.

The exact positioning and exact adherence to the shape geometry of the dimensionally stable semifinished fiber product 40 takes place as in the 9 and 10 represented by one of the tool cores 20 consisting of two core parts 26 . 28 in the transverse direction laterally of the dimensionally stable semifinished fiber product 40 be positioned.

As in 11 The core parts are supported 26 . 28 each with a support surface 42 . 44 on the flat semi-finished fiber 36 and are in the range of a vertical parting plane with their longitudinal surfaces 46 . 48 in Appendix. The vertical parting plane extends in the longitudinal direction of the stiffening element to be formed 4 so this with its core parts 26 . 28 mirror-symmetrical to the longitudinal axis of the stiffening element 4 is trained. For receiving the respective dimensionally stable semifinished fiber product 40 with his foot 6 as well as his jetty 8th each limit a recording room 50 . 52 ,

Seen in a vertical direction above the web-side receiving space 52 arranged head portion of the tool core 20 is a supply channel 54 educated. The supply channel extends along a bridge head 55 or a component head edge and stands over a preferably only a few tenths of a millimeter wide gap 56 with the web-side recording room 52 in fluid communication such that the semifinished fiber product 40 over the bridge head 55 is infiltrated with a resin.

As in the 12a . 12b and 13a . 13b shown have the core parts 26 . 28 one half each 58 the web-side recording room 52 on. Likewise, they have a half 60 of the supply channel 54 on. In this case, the supply channel extends 54 or its halves 60 in the longitudinal direction over the web-side receiving space 52 also and is closed on one side. Further, in the core parts 26 . 28 one half each 62 of the gap 56 formed, which extends substantially over the entire length of the web-side receiving space 52 or its halves 58 extends. For end support of the core parts 26 . 28 on the mold 12 in the area of interstices 38 have these ends each one opposite the support surface 42 . 44 projecting support surface 64 . 66 on. The foot-side recording room 50 does not exist like the web-side recording frame 52 from two cross-section reduced halves 58 but each one subspace 68 to fully absorb a transversely from the web 8th away extending side foot section 70 . 72 ( 11 ). The core parts 26 . 28 thus form two identical L-shaped receiving areas 58 . 68 , Which seen in the transverse direction, the dimensionally stable semi-finished fiber 40 each in equal proportions in the core parts 26 . 28 is included. The foot 6 of the dimensionally stable semifinished fiber product exemplified here 40 has no smooth transition to the sheet-like semi-finished fiber 36 or skin field 2 , At a footstep 6 are the subspaces 68 in the core parts 26 . 28 according to the lengths and thicknesses of the semifinished fiber product 40 customized.

After positioning the core parts 26 . 28 for supporting the first dimensionally stable semifinished fiber product 40 takes place to form the further stiffening elements 4 the positioning of the other dimensionally stable semi-finished fiber products 40 on the sheet-like semi-finished fiber 36 analogous. First, as in 14 shown the next two opposite patches 24 from the interstices 38 removed and a second dimensionally stable semifinished fiber product 40 on the flat semi-finished fiber 36 arranged. This is then according to the 15 and 16 by means of the core parts 25 . 26 a second tool core 20 exactly aligned.

Then be like in the 17 and 18 shown for forming a third stiffening element 4 the remaining opposing patches 24 from the interstices 38 taken. After removal of the filling pieces 24 is again a dimensionally stable semi-finished fiber 40 between the spaces 38 on the sheet-like semi-finished fiber 36 prepositioned and by means of two core parts 26 . 28 exactly aligned. After the arrangement of all tool cores 20 are not numbered joints between their respective core parts 26 . 28 sealed.

To a deformation or change in position of the tool cores 20 to avoid resinous infusion, as in 19 shown especially in large stiffening element lengths and / or curved skin fields 2 the tool cores 20 or their core parts 26 . 28 on both sides by means of pressure supplements 30 at their respective adjacent tool core 20 or on the longitudinal strips 14 supported. The printing supplements 30 extend transversely between the tool cores 20 and are positively connected to these.

Subsequently, as in 20 each one of the pipe socket illustrates 32 in one of the supply channels 54 used. The pipe socket 32 be connected by means of preferably flexible piping to a resin supply or suction, which open into a central line as needed. A necessary in the production of components according to the infusion vacuum construction is not shown for reasons of clarity.

The now completed structure can be used for the following variants of the infusion process according to the invention, wherein in principle two process groups each with two variants exist. All variants is equal to either the sprue over the bridge heads 55 or upper component regions and the extraction takes place on the component side via at least one lower component region, or the extraction via the web heads 55 or upper component regions and the sprue takes place on the component side at least over a lower component region. Likewise, all variants is the same that with a horizontal orientation of the mold 12 starting from the supply channels 54 the resin in just one vertical direction the bridge 8th flows through and not at the same time as in the cited prior art in a vertical opposite direction. This is especially due to the sprue or the suction on the web heads 55 achieved. Furthermore, the variants are the same that the connecting channels 54 indirectly via a cross-section-reduced gap 56 with one of the web-side recording rooms 52 keep in touch. This can be very advantageous, for example, to be produced fiber composite components with varying cross-sections, as over the column 56 or their opening cross-sections, for example, the amount of resin required per each supply channel-side component area per time can be set individually. In addition, it is preferred in all variants with linienartigem sprue and line-like suction when the sprue and the suction are oriented in different horizontal planes parallel to each other, so that the forming resin fronts are virtually no pivoting, as in a relative horizontal displacement of the sprue and the suction would take place, for example, 90 °.

In the first group of methods, the sprue is made in the area of the molding tool 12 and the suction line over the bars 8th in the area of tool cores 20 , In this case, according to a first variant of the sprue line along one or more lower foot-side component edge / component edges, for example. Along the longitudinal bars 14 , and the suction through the supply channels 54 or pipe socket 32 respectively. According to a second variant, the sprue is punctiform or linear in the flat semi-finished fiber product 36 and the suction also via the supply channels 54 ,

In the second group of methods, the sprue is linear over the web heads 55 in the area of tool cores 20 and the suction in the area of the mold 12 , In this case, according to a first variant of the sprue on the supply channels 54 or pipe socket 32 and the suction line along one or more lower foot-side component edge / component edges, eg. Along the longitudinal bars 14 respectively. According to a second variant, the sprue also takes place via the supply channels 54 and the suction point or line in the flat semi-finished fiber 36 ,

After the infusion process with subsequent hardening of the fiber composite component 1 Under temperature action, the resin pipes, the pipe socket 32 and the vacuum build-up removed. Then be like in 21 shown for demolding the composite component 1 the printing supplements 30 , the spacers 22 and finally the core parts 26 . 28 away. As in 22 each one is illustrated in the supply channels 54 cured resin residue 74 on the stiffening elements 4 on the head over a resin film 76 tethered. Because the gap widths in the core parts 26 . 28 However, only a few tenths of a millimeter, these resin residues 74 lightly along the thin resin film 76 on the respective stiffening element head 55 be canceled. Due to the provision of semi-finished fiber products 36 . 40 according to their final dimensions can be omitted in principle further post-processing steps.

Of course, the invention is not limited to T-shaped stiffening elements 4 limited, but for example, in L-shaped, omega-like or hat-shaped stiffening elements 4 and drgl. applicable. In addition, the invention is not limited to carbon fiber reinforced composite components, but as a fiber material is, for example, also glass, aramid or UHMWPE vorstellber. Also conceivable as semi-finished fiber prepreg "SQRTM".

Disclosed is a method for producing a fiber composite component in Integralbauweise, are arranged at least to final dimension dimensionally stable semi-finished fiber on a sheet-like semi-finished fiber and a Harzanguss either via the tool cores along each head of the dimensionally stable semi-finished fiber semi-finished and an extraction in the region of a mold or the sprue in the region of the mold and the suction over the tool cores along each of a component head of dimensionally stable semifinished fiber products, and an apparatus for performing such a method, wherein the tool cores each having an integral receiving space for receiving the semi-finished fiber and an integral component head side supply channel, which opens to the receiving space is and with a sprue or suction is connectable.

LIST OF REFERENCE NUMBERS

1

Fiber composite component

2

skin panel

4

stiffener

6

foot

8th

web

10

contraption

12

mold

14

longitudinal bar

16

cleat

18

frame

20

tool core

22

spacer

24

filling

26

core part

28

core part

30

pressure supplement

32

pipe socket

34

cavity

36

sheet-like semi-finished fiber

38

gap

40

dimensionally stable semifinished fiber product

42

bearing surface

44

bearing surface

46

contact area

48

contact area

50

Recording room foot

52

Recording room footbridge

54

supply channel

55

web head

56

gap

58

Half reception room

60

Half supply channel

62

Half gap

64

support surface

66

support surface

68

subspace

70

foot section

72

foot section

74

resin residue

76

resin film

Claims (12)

Method for producing a fiber composite component ( 1 ) in integral construction, with the steps: - Positioning of a sheet-like semifinished fiber product ( 36 ) on an outer contour of the fiber composite component ( 1 ) predetermining mold ( 12 ), - arranging dimensionally stable semifinished fiber products ( 40 ) on the sheet-like semi-finished fiber product ( 36 ), Stabilizing and fixing the dimensionally stable semifinished fiber products ( 40 ) with tool cores ( 20 ), at least two of the respective tool core ( 20 ) forming core parts ( 26 . 28 ), which in the transverse direction laterally of the dimensionally stable semifinished fiber product ( 40 ) and over the sheet-like semi-finished fiber ( 36 ), wherein they end up on the mold ( 12 ) and for receiving the respective dimensionally stable semifinished fiber product ( 40 ) each have a receiving space ( 50 . 52 ), resin infiltration, wherein a) a sprue over the tool cores ( 20 ) at the head end of the dimensionally stable semi-finished fiber products ( 40 ) and an extraction in the region of the mold ( 12 ), or b) a sprue in the area of the mold ( 12 ) and an extraction via the tool cores ( 20 ) at the head end of the dimensionally stable semi-finished fiber products ( 40 ), - hardening of the structure ( 36 . 40 ), and - removal of the structure ( 36 . 40 ), with the tool cores ( 20 ) are removed. Method according to claim 1, wherein the sprue is punctiform or linear in the sheet-like semi-finished fiber product ( 36 ) he follows. Method according to claim 1, wherein the sprue is punctiform or linear over at least one lateral edge region (FIG. 14 ) of the flat semi-finished fiber product ( 36 ) he follows. The method of claim 1, wherein the suction point or line in the sheet-like semi-finished fiber products ( 36 ) he follows. The method of claim 1, wherein the suction point or line over at least one lateral edge region ( 14 ) of the flat semi-finished fiber product ( 36 ) he follows. Method according to one of the preceding claims, wherein the sheet-like semifinished fiber product ( 36 ) in a framework ( 18 ) on the mold ( 12 ) is positioned. Device for carrying out a method according to one of the preceding claims, with a molding tool ( 12 ) for receiving a flat semi-finished fiber product ( 36 ), Tool cores ( 20 ) for the support of dimensionally stable semifinished fiber products ( 40 ) for the formation of stiffening elements ( 4 ) integral with the flat semi-finished fiber product ( 36 ), with the tool cores ( 20 ) at least two core parts ( 26 . 28 ), which in the transverse direction laterally of the dimensionally stable semifinished fiber product ( 40 ) are positioned and over the sheet-like semi-finished fiber ( 36 ), wherein they end up on the mold ( 12 ) and in each case at least one integral receiving space ( 50 . 52 ) for receiving the dimensionally stable semi-finished fiber products ( 40 ) and at least one component head-side integral supply channel ( 54 ) leading to the receiving space ( 50 . 52 ) and forms a sprue or suction. Apparatus according to claim 7, wherein the respective supply channel over a longitudinal gap ( 56 ) or a hole pattern with the respective receiving space ( 50 . 52 ). Apparatus according to claim 7 or 8, wherein the supply channels ( 54 ) are closed on one side. Device according to one of claims 7 to 9, wherein the tool cores ( 20 ) at least at an adjacent tool core ( 20 ) are supported. Device according to one of claims 8 to 10, wherein the respective gap ( 56 ) in a parting plane of the core parts ( 26 . 28 ) is trained. Device according to one of claims 7 to 11, wherein the tool cores ( 20 ) symmetrical to the longitudinal axis of the stiffening elements ( 4 ) into the core parts ( 26 . 28 ) are divided.

Images