Resin pipe formed of bellows

Abstract

The invention relates to a resin line (2) formed from a bellows (4), which has individual through-holes arranged on the circumference side in a wall (6). In order to improve the resin line (2), it is provided that the bellows (4) has a non-rotationally symmetrical cross-sectional shape around the closed wall (6) in at least a section transverse to the longitudinal center axis (10), wherein the wall (6) is divided into a first portion having a truncated base (8) which extends over the length of the bellows (4) in a direction transverse to the longitudinal center axis (10) and a second portion having an arc (12) which extends over the length of the bellows (4) transverse to the longitudinal center axis (10) to a height (H), and wherein, for said cross-sectional shape, the width (B) of the truncated base (8) as first portion of said wall (6) is greater than the height (H) of the second portion of said wall (6) configured as an arc (12).

Description

TECHNICAL FIELD

[0001] The present application relates to a resin line formed from a bellows, which has individual through-holes arranged on the circumference side in the wall. BACKGROUND

[0002] A vacuum infusion method is described, for example, in document DE 102 39 325 B4. In order to produce a fiber composite component, a resin line is placed into a mold in order to transport a liquid matrix material under vacuum into the reinforcing fibers placed into the tool. The reinforcing fibers can be present as fiber semifinished products in the form of rovings, mats, gelege, textiles, multiaxial materials, knits and braids and are made from very different fiber materials, such as carbon fibers, glass fibers, aramid fibers, boron fibers or hybrid materials, also in arbitrary combinations. The reinforcing fibers are impregnated by the matrix material transported through the resin line. Here, the matrix material also fills the mold. As matrix material different suitable resin systems can be used, which have a suitable viscosity in the working temperature range and which connect well with the reinforcing fibers. After complete impregnation of the reinforcing fibers and filling of the forming cavity in the mold, the matrix material hardens. The finished component can then be removed from the mold.

[0003] A resin line formed from a bellows of this type is known from document DE 10 2016 121 245 A1. By the wave shape of the wall, the resin line can be flexibly laid out. The wall of the resin line formed from a bellows has a diameter which varies in a wave shape over its length. The corrugations of the bellows achieve an increased stiffness and load capacity in the radial direction of the bellows relative to a smooth wall surface. In the longitudinal direction, however, the bellows can also be easily deformed on the bending radius which the bellows must assume in order to be able to be inserted into a predetermined mold, due to the wave shape of the wall. The bellows is thus an ideal material which can meet the requirements of stiffness under vacuum and the flexible requirement of simple layability of the resin line in the mold. Depending on the material used, the wall thickness of the bellows can be reduced to a thickness of up to 0.2 mm to 0.4 mm. The bellows material can be simply stored and transported as an extruded continuous material on a spool. The bellows material can be cut from the continuous strip to an arbitrary length. The cutting waste is thereby reduced to a minimum. Typically, the bellows has a circular cross-sectional shape.

[0004] The bellows has individual through-holes arranged on the circumferential side, through which the matrix material can be discharged from the interior of the bellows to the outside. The through-holes are dimensioned and shaped in such a way that, depending on the viscosity and flow properties of the matrix material used and the desired course of the flow front during the impregnation phase in the mold, an exactly adapted amount of matrix material is discharged at the individual desired locations. The through-holes can be configured in the troughs or on the crests or extend over the length of one or more bellows. The through-holes are arranged along the longitudinal axis of the bellows at such a distance that, locally in the region of the through-holes, a smaller proportion of the matrix material conveyed in the bellows flows into the mold and a larger proportion of the matrix material is guided through the through-holes in the direction of the end of the resin channel in the direction of transport in order to achieve as uniform a distribution of the matrix material as possible in the mold over the length of the resin channel.

[0005] A distribution system for matrix material is also known from the document WO 2009 / 003476, in which the resin channel has an omega-shaped cross-sectional shape. The resin channel is placed with the legs onto the mold structure. The matrix material is discharged downward from the channel cross-section in the region of the legs through slits on the underside extending over the entire length of the resin channel. This resin channel is unsuitable for longer conveying sections of matrix material in the mold, since it distributes the matrix material unevenly. While a large amount of matrix material enters the mold directly in the front section of the resin channel, the matrix material hardly reaches the distal end of the resin channel, and the matrix material that overflows in the front section has already begun to solidify, while the matrix material does not reach the distal end of the resin channel at all. The resin channel with an omega-shaped cross-section is also not particularly loadable, since it expands in the region of the longitudinal slit under pressure and then collapses.

[0006] In the known bellows, it has proven disadvantageous that the bellows leaves a material imprint in the matrix material of the component. Resin channels with an omega-shaped cross-sectional shape can only be obtained as rods, since they are not sufficiently flexible to be rolled up. It is also not possible to lay out such resin channels in an arc-shaped course in the mold. SUMMARY

[0007] It is the task of the present invention to provide a resin channel which can be manufactured cost-advantageously, which meets the static requirements under vacuum, which leaves as inconspicuous an imprint as possible in the matrix material, and which can be rolled up and also laid out flexibly in an arc-shaped course.

[0008] For this type of resin line, the task is solved in that the at least in sections circumferentially closed wall of the bellows has a non-rotationally symmetrical cross-sectional shape transverse to the longitudinal center axis, wherein the wall is divided into a first portion having a truncated base extending over the length of the bellows in a direction transverse to the longitudinal center axis and a second portion having an arc shape extending over the length of the bellows to a certain height in a direction transverse to the longitudinal center axis, and for said cross-sectional shape the width of the truncated base of the first portion of the wall is greater than the height of the second portion of the wall configured as an arc.

[0009] By the special cross-sectional shape of the resin line, the resin line rests with the truncated base on a larger contact surface on the component lying thereunder. Due to the larger contact surface of the truncated base, the resin line does not easily slip when being laid. When the mold is filled with the matrix material, the resin line is not pressed too deeply into the material of the component and the matrix material on its underside by the larger contact surface when there is a vacuum on the mold. When the final component is later demolded, the resin line can be easily torn from the hardened surrounding matrix material without leaving a clearly visible trace of the resin line there, as in the case of a circular resin line. The imprint left by the resin line in the matrix material is shallower and less conspicuous than in the case of a circular cross section of the resin line.

[0010] The at least in sections circumferentially closed wall of the bellows is characterized in that the resin line has at least no through-going slit extending in the longitudinal direction of the resin line there, as is the case with a resin line having an Ω-shaped line cross section, so that the pressure and tension forces acting on the resin line in these sections are received and distributed over the circumference of the resin line. Thus, the resin line does not expand under load as much as a resin line having an Ω-shaped line cross section, and also collapses less quickly. The wall that is circumferentially closed in sections still has local through-holes arranged at a distance from one another, through which the matrix material can flow from the resin line into the mold. However, the through-holes do not weaken the resin line as much as the through-going slit in a resin line having an Ω-shaped line cross section, since the resin line is at least circumferentially closed around the through-holes. The pressing forces acting on the resin line by the vacuum can likewise be very well conducted out into the material lying thereunder, for example reinforcing fibers of the component to be manufactured, designed into the mold, by the corrugation of the bellows and the arc shape of the wall, without the resin line collapsing there or being interrupted or at least significantly hindered by the resin flow of the resin line.

[0011] The resin pipe with the described cross-sectional shape can also easily be wound onto a roll as a continuous material and unwound again from the roll and cut to the desired length when required. At component lengths of, for example, more than 100 meters, as occur in fiber-reinforced rotor blades for wind turbines, a significant advantage is that the working material from the roll is processed, so that it is not necessary to connect many short pieces to one another. Due to the flexibility of the resin pipe along the longitudinal center axis, the resin pipe can also be laid in the mold very well, locally or in an arc shape over the entire length, which additionally simplifies the processing.

[0012] The wall of the bellows is preferably composed of a rigid material. The bellows can be made of a thermoplastic plastic material, for example polyamide, polyethylene, polyvinyl chloride, polytetrafluoroethylene or polypropylene. The plastic material used should have sufficient strength at least in the working temperature range of the matrix material when the matrix material begins to flow into the component, so as not to collapse under the active vacuum in the mold and / or soften or liquefy due to the heat from the matrix material or the solvent contained therein, so that the matrix material is no longer reliably distributed in the mold or the matrix material is contaminated by the material of the bellows.

[0013] Due to the resin pipe lying flat locally on the material lying thereunder, the matrix material can directly seep from the resin pipe into the material lying thereunder in the mold. In order to allow the matrix material to seep from the resin pipe into the material lying thereunder in the mold, there are advantageously also through-holes in the wall in the region of the truncated base. The distance of the through-holes from one another and the shape, size and position of the through-holes are derived, inter alia, from the matrix material used and the size of the component volume which is to be filled with matrix material using the resin pipe. The viscosity and hardening speed of the matrix material used and the delivery path via which the matrix material is to be delivered are also important for the selection of the correct arrangement of the through-holes. Cavities in the wedge-shaped region, which is in the region of the lateral recess of the resin pipe with a circular cross-section facing the material lying thereunder, are easily produced by a cover which does not lie completely flat against the outer surface of the resin pipe. These cavities can be avoided by the resin pipe configured according to the application.

[0014] A further advantage of the resin pipe according to the application is that, due to the greater width of the resin pipe relative to its height, less matrix material is wasted in production. In order to supply the matrix material to all regions in the mold, the smaller cross-section of the resin pipe is sufficient for the distribution of the matrix material. After the mold has been completely filled with matrix material, less unused volume of matrix material remains in the resin pipe, which is then removed with the used resin pipe.

[0015] According to an embodiment of the application, the truncated base forms a flat surface. This flat surface provides a stable possibility of placement and a good contact with the material lying thereunder. Through the through-holes in the flat surface, the matrix material delivered through the resin channel can well directly penetrate into the material lying thereunder. The resin channel can be more easily torn off the hardened component on the flat surface after the matrix material has hardened.

[0016] According to an embodiment of the application, in the shape of the truncated base there is an uneven shaping which forms at least one flow channel on the outer side of the bellows, which flow channel faces away from the through-holes. After the matrix material has been discharged from the bellows through the through-holes, the matrix material is guided away from the respective through-hole through the flow channel. When the bellows with its base rests on the material lying thereunder, the material lying thereunder can clog the through-holes or at least hinder the matrix material from flowing out of the bellows. This applies in particular when the bellows is pressed by the vacuum acting thereon onto the material lying thereunder. The flow channel simplifies the diffusion of the matrix material in the region of the through-holes. The flow channel can extend to the side edges of the base in order to introduce the matrix material (which has been discharged from the bellows through the through-holes) likewise in a direction transverse to the longitudinal extension of the bellows into the mold. However, it can also already be sufficient that the flow channel guides the matrix material only over a partial width of the base, however, whereby this surface (through which the matrix material can penetrate into the mold after passing through the through-holes) has already significantly increased. Here, the flow channel can be configured such that it extends in its surface at least also obliquely to the longitudinal extension of the bellows and / or in the direction of the longitudinal extension of the bellows in order to cover a larger surface for the penetration of the matrix material into the mold.

[0017] According to an embodiment of the application, the second portion of the wall, which is configured in an arc shape, has a cross-sectional shape which is at least approximately or exactly semicircular. The semicircular shape is optimal from a static point of view, since by this shape the force acting on the resin channel by the vacuum in the mold is well transmitted into the material lying thereunder. The wall of the resin channel can be designed with a relatively small wall thickness, whereby a large amount of plastic material for the resin channel can be saved, which reduces the material outlay and costs as well as the environmental burden. The semicircular shape also constitutes a good compromise between good distribution in the region of the matrix material next to the resin channel laterally of the mold and the delivery capacity of the matrix material in the direction of extension of the resin channel.

[0018] According to an embodiment of the application, the ratio of the width to the height of the resin duct is at least approximately or exactly 2:1. The at least approximately square ratio enables a sufficiently high flow capacity of the resin duct with a good delivery and guidance of the matrix material in a direction transverse to the longitudinal center axis of the resin duct. For example, the resin duct can have a width of 35 mm and a height of 17.5 mm. With such a resin duct, the mold can be supplied with matrix material very effectively.

[0019] According to an embodiment of the application, the wall of the resin duct is made of polyvinyl chloride. Since the wall made of polyvinyl chloride softens at a relatively large amount of heat acting on it and is penetrable for the matrix material, the wall collapses due to the heat at the exothermic reaction of the matrix material in the mold. The PVC and / or the matrix material can be set such that the exothermic reaction does not start until after the injection of the matrix material into the mold has ended. The remaining matrix material still in the resin duct is pressed out of the resin duct when the resin duct collapses. This matrix material can thus flow unhindered into the mold and also be used for the production of the component. The resin duct itself collapses here. Since the resin duct often no longer or at least hardly still protrudes above the surrounding surface of the mold, the pressure per unit area acting on the resin duct from the vacuum decreases. As a result, the resin duct no longer presses its underside to such an extent into the surface of the component that hardly any pressure traces of the resin duct can be found there after the resin duct has been removed therefrom after the matrix material has hardened.

[0020] According to an embodiment of the application, the wall is made of polypropylene. Polypropylene as a raw material is more resistant to heat than other plastic materials, so that a resin duct made of it does not collapse even at a relatively large amount of heat in the mold, for example due to the exothermic reaction of the matrix material and the resulting heating of the wall. This material selection is advantageous when the resin duct has to deliver the matrix material over a relatively large delivery path and / or a large amount of heat is generated by the exothermic reaction of the matrix material and the resin duct cannot collapse here.

[0021] It is expressly pointed out that the above-mentioned embodiments of the application can be combined with the subject matter of claim 1, respectively individually, but also in any combination with one another.

[0022] Further advantageous variants and embodiments of the application can be gathered from the following detailed description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] The application is described in more detail by means of examples. The drawings show:

[0024] Figure 1 : View of the bellow forming the resin duct from an oblique top view;

[0025] Figure 2 Side view of a bellows;

[0026] Figure 3 Front view of the bellows;

[0027] Figure 4 Bottom view of a bellows;

[0028] Figure 5 Top view of a bellows; and

[0029] Figure 6 : Cross-sectional view of the bellows along section line AA. Detailed Implementation

[0030] exist Figure 1 The diagram shows a section of resin conduit 2 comprised of a corrugated pipe 4. The corrugated pipe 4 has walls made of a corrugated material. Here, these corrugations can be constructed in a circular shape or, as in the embodiment, in an angular cross-sectional shape with corrugations. Importantly, the wall 6 is not constructed to be smooth, but rather its wavy shape allows the corrugated pipe 4 to bend without any bends in the wall 6 that would interfere with good flow and potentially cause leaks in the wall 6.

[0031] As can be seen from an obliquely upward view, the bellows 4 has a non-rotationally symmetric cross-sectional shape transverse to the longitudinal central axis 10 by dividing the wall 6 into two parts. In the first part, the wall 6 has a flattened base 8 extending transversely to the longitudinal central axis 10 along the length of the bellows 4 along its circumference. In the second part, the wall 6 is constructed in the circumferential direction as an arc 12 extending transversely to the longitudinal central axis at a height H along the length of the bellows 4. Here, for the cross-sectional shape, the width B of the flattened base 8, which is the first part of the wall 6, is greater than the height H of the second part of the wall 6, which is constructed as an arc 12.

[0032] The wall 6 of the bellows 4 is closed around the longitudinal central axis 10 in at least some sections. However, through-holes 14 are present in some locations, through which matrix material can be discharged from the inner cavity of the bellows 4 into the mold. In this embodiment, one row of through-holes 14 is located at the uppermost end of the arc 12, and another row of through-holes is located in the middle region of the base 8. Depending on the application, more or fewer through-holes 14 can be constructed in the bellows 4, wherein the through-holes 14 can also be arranged at other locations along the circumference of the bellows 4, and multiple through-holes 14 can also be arranged around the circumference of the bellows 4 and in alternating positions and / or alternating distances.

[0033] The matrix material flows through the bellows 4 along the longitudinal centre axis 10. By means of a vacuum in the mould, the matrix material is sucked through the through-holes 14 into the mould. However, the through-holes 14 are so small in comparison with the cross-section of the channels of the bellows 4 that only a part of the matrix material flowing through the bellows 4 can reach the mould at this location. The remainder of the matrix material flow, which flows through the bellows 4, continues to move through the bellows 4 to a further through-hole 14 which is located downstream, so that the matrix material also reaches the region of the mould which is remote in the flow direction. By arranging the bellows 4 accordingly in the mould, it is possible to use the bellows 4 to bring the matrix material to all regions of the mould and to fill the mould with matrix material.

[0034] In Figure 2 The bellows 4 is shown in a side view. The corrugated structure, in which the second portion of the wall 6 is implemented in an arc shape, is well visible in this side view. By means of the recess of the wall 6 in the region of the individual corrugations, it is possible to arrange the bellows 4 to extend in an arc shape, without a kink being formed in the wall 6 of the bellows 4 here. The bellows 4 can thus also be transported and supported as a continuous material, for example wound on a reel. When processing, the continuous strip of the bellows 4 can be pulled off the reel. This leads to a very easy processing of the bellows 4 when producing the mould for the transport of the matrix material.

[0035] In Figure 3 A front view of the bellows 4 is shown in

[0036] In Figure 4The diagram shows a bottom view of the flattened base 8 of the bellows 4. From the bottom view of the flattened base 8, it can be seen that a slight unevenness is formed in the bottom, through which flow channels 16 are formed. Therefore, an uneven forming portion exists in the shape of the flattened base 8, which forms at least one flow channel 16 on the outer surface of the bellows 4, pointing away from the through-hole 14. After the matrix material is discharged from the bellows 4 through the through-hole 14, the matrix material is guided away from the corresponding through-hole 14 through the flow channels 16. When the bellows 4 rests with its base 8 on the material below it in the mold, the material below it can block the through-hole 14 or at least prevent the matrix material from flowing out of the bellows 4. The flow channels 16 facilitate the diffusion of the matrix material in the area of ​​the through-hole 14. The flow channels 16 can extend to the side edges of the base 8 to facilitate the introduction of the matrix material (which is discharged from the bellows 4 through the through-hole 14) into the mold in a direction transverse to the longitudinal extension of the bellows 4. However, it may be sufficient for the flow channel 14 to guide the matrix material only across a portion of the width of the base 8, but this significantly increases the surface area through which the matrix material can penetrate into the mold after passing through the through-hole 14. Here, the flow channel 16 can be configured such that it extends at least in its surface in a direction inclined to and / or along the longitudinal extension of the bellows 4, to cover a larger surface area for penetrating the matrix material into the mold. A portion of the flattened bottom surface of the base 8 is configured as protrusions 18 along which the matrix material can flow out. The protrusions 18 form the channel walls of the flow channel 16. The protrusions do not necessarily extend transversely to the longitudinal axis of the bellows 4, but can also be arranged at steeper or flatter angles, thus forming a type of top on the flow channel 16, the free cross-section of which differs in length due to this type of top.

[0037] exist Figure 5 The diagram shows a top view of the bellows 4. In the top view, it can be seen that the through-hole 14 is only located in a portion of the wall 6. In the section of the bellows 4 between the through-holes 14, the wall 6 is closed around the circumference.

[0038] from Figure 6 Along shown in Figure 4 The cross-sectional view of section line AA shows, with the aid of the drawn arrows, how the matrix material is discharged outward into the mold through the through hole 14 as it passes through the bellows 4.

[0039] In the above-described embodiments, the bellows 4 has a semi-circular cross-sectional shape. Instead of an exact semi-circle, the cross-section can of course also be constructed compressed or stretched, whereby the height / width ratio between the first and second portions of the wall 6 changes. Deviations from the semi-circle can advantageously influence the processability of the bellows 4 and the distribution of the matrix material in the mould.

[0040] In the present embodiment, the ratio of the width B to the height H of the resin tube is 2:1. If the cross-sectional shape of the bellows is changed accordingly, the ratio will change.

[0041] The application is not limited to the above-described embodiments. It will be no difficulty for the person skilled in the art to modify the embodiments in a manner that appears suitable to him in order to adapt the embodiment to the specific requirements of the application case.

Claims

1. A resin pipe (2) formed of a bellows (4) having respective through holes (14) arranged on a circumferential side in a wall (6), characterized by, The at least in sections closed wall (6) of the bellows (4) has a non-rotationally symmetrical cross-sectional shape transverse to the longitudinal center axis (10), wherein the wall (6) is divided into a first portion having a truncated base (8) extending in a direction transverse to the longitudinal center axis (10) over the length of the bellows (4) and a second portion having an arc (12) extending transverse to the longitudinal center axis (10) to a height (H) over the length of the bellows (4), and for the cross-sectional shape the width (B) of the truncated base (8) as first portion of the wall (6) is greater than the height (H) of the second portion of the wall (6) configured as arc (12), wherein in the shape of the truncated base (8) there is an uneven shaping which forms at least one flow channel (16) on the outer side of the bellows pointing away from the through-hole (14).

2. The resin line (2) according to claim 1, characterized in that The truncated base (8) constitutes a flat surface.

3. The resin line (2) according to claim 1 or 2, characterized in that The second portion of the wall (6) configured as arc (12) has an at least approximately or exactly semicircular cross-sectional shape.

4. The resin line (2) according to claim 1 or 2, characterized in that, The ratio of the width (B) to the height (H) of the resin line (2) is at least approximately or exactly 2:

1.

5. The resin line (2) according to claim 1 or 2, characterized in that, The wall (6) is made of polyvinyl chloride.

6. The resin line (2) according to claim 1 or 2, characterized in that, The wall (6) is made of polypropylene.

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