Method, device and backflow preventer for impregnating at least one fiber material

Abstract

Impregnation device (100) for impregnating at least one quasi-endless fiber material (10) with a plastic material (12) that is melted at a corresponding process temperature, comprising at least one fiber feed channel (240) with a fiber inlet (111) for supplying the quasi-endless fiber material (10) to the impregnation device (100), and at least one plastic feed channel (250) with a plastic inlet separate from the fiber inlet (111) for supplying the plastic material (12) separately to the fiber material (10) of the impregnation device (100), wherein the at least one fiber feed channel (240) and the at least one plastic feed channel (250) are at least partially separate and open into a common impregnation cavity (123) for impregnating the quasi-endless fiber material (10) with the supplied and melted plastic material (12), characterized in thatthat the impregnation device (100) has a backflow prevention zone in which the fiber feed channel (240) has at least a section-wise S-shaped course formed by two bends (240a, 240b) with opposite directions of curvature, between which the fiber feed channel (240) merges with the at least one plastic feed channel (250), so that a common channel section is subsequently formed.

Description

The invention relates to an impregnation device for impregnating at least one quasi-endless fiber material with a plastic material. The invention also relates to a backflow preventer component for this purpose. The invention further relates to a method for this purpose. Due to their exceptional strength-to-weight ratio and stiffness, fiber-reinforced composites have become indispensable as modern materials. The combination of fiber and polymer materials in 3D printing also opens up new possibilities for the production of complex structures without the need for isotropic materials. Both in the production of fiber-reinforced composite components and in 3D printing with fiber reinforcement, fiber rovings are very frequently used. These rovings are bundles of fibers made up of numerous continuous fibers, also known as filaments. Besides additive manufacturing processes (e.g., 3D printing) for the production of fiber-reinforced components, a number of other manufacturing methods currently exist for producing fiber-reinforced composites. These include tape laying, thermoforming, winding, pultrusion, autoclave and infusion processes, and overmoulding. Especially in continuous or intermittently continuous processes, such as the extrusion of continuous fiber-reinforced semi-finished products or the 3D printing (FFF, DED) of continuous fiber-reinforced structures, the high-quality and continuous incorporation of the rovings into the plastic presents a significant challenge. The fiber bundles (e.g., carbon fibers or glass fibers) often consist of several thousand to ten thousand individual fibers with a diameter between 3 µm and 8 µm and must be impregnated with the liquid plastic (completely penetrated or each individual fiber coated) and subsequently consolidated (the final geometric contour should be achieved as free as possible from foreign matter and air inclusions through the solidification of the plastic). From Hauke ​​Prüß and Thomas Vietor's article, "New Design Freedoms Through 3D-Printed Fiber-Reinforced Plastics," published in the Forum for Rapid Technology, issue 12 / 2015, a 3D printhead is described that receives a central feed of virtually endless fiber material. Additionally, a plastic material is fed to the 3D printhead via two feed channels, with the fiber and plastic material converging in a common mixing chamber. Here, the fiber material is mixed with the plastic material, and the resulting material mixture is dispensed. This allows for the development of virtually any structure with an integrated load-bearing filament. In addition, DE 10 2017 124 352 A1 discloses a system for producing 3-dimensional structures with a 3D print head, in which 3 or more feed channels are provided that are arranged around an axial course of the channel for the fiber material, which makes it possible in particular to realize the 3D printing of a fiber-plastic mixture with different plastic materials. From the subsequently published DE 10 2019 106 355 A1, an impregnation device for the production of continuous fiber-reinforced semi-finished products with plastic impregnation is further disclosed, in which the quasi-continuous fiber material and the plastic material are fed separately to the impregnation device. In a mixing chamber, the quasi-continuous fiber material is then drawn through the pressurized plastic material, whereby sound energy is introduced into the plastic material of the mixing chamber by means of a sonotrode for improved impregnation. The disadvantage of these known 3D print heads or impregnation devices lies in the fact that feeding the thermoplastic material into the mixing chamber creates pressure within the chamber. This pressure forces the molten plastic into the fiber feed channel, causing it to rise and move against the direction of flow of the virtually endless fiber material. In the worst-case scenario, this can lead to the plastic escaping at the point where the fiber material enters the impregnation device's feed channel, resulting in an unwanted leak. There is also the risk that the rising molten plastic within the feed channel will cool and solidify, ultimately interrupting the fiber material feed and thus terminating the process.German patent DE 10 2017 124 353 A1 discloses, similarly to DE 10 2017 124 352 A1, a system for producing three-dimensional structures with a 3D printhead. In this system, an additional feature is the connection of an overpressure source at the inlet of the fiber material. This overpressure is intended to prevent plastic material from rising into the fiber feed channel and thus causing the problems described above. A disadvantage of this system is its high complexity and the limited mobility of the 3D printhead, particularly at high printing speeds. This is because the fiber material, along with its fiber magazine, must be housed in a closed pressure vessel to create a completely enclosed system.Furthermore, the use of compressed air increases the risk of air inclusions forming in the matrix material, which can then lead to defects within the component. From EP 0 712 716 A1, a method and a device for impregnating continuous fibers or fiber bundles with a molten thermoplastic are further disclosed, wherein the fibers or rovings pass through an impregnation zone that has the form of a damped vibration. This is intended to improve the spreading of the rovings and thus the impregnation result. Furthermore, a split tool is provided to improve the insertion of the rovings and the cleaning of the tool. However, even with this device, it cannot be prevented that the plastic material fed into the tool escapes at the inlet of the fiber material feed due to the feed pressure. Especially when impregnating rovings (fiber bundles) with high-viscosity plastics, such as thermoplastics, increased melt pressures are necessary for efficient impregnation and process control. Particularly when continuously introducing fiber bundles into a pressurized liquid plastic, it is a significant challenge to prevent liquid plastic from rising into the fiber feed channel and subsequently blocking it. A high-viscosity plastic material is defined here as one that has a viscosity of significantly more than 8000 mPas (millipascal-seconds) at a given process temperature. This is distinct from low-viscosity plastic materials, which have a viscosity up to 300 mPas. Viscosities between 300 mPas and 8000 mPas are considered medium.Thermoplastic polymers, commonly used in hybrid 3D printing, often have a viscosity of 300 Pa to 10,000 Pa. Depending on the degree of shear stress exerted on the polymer material when it comes into contact with the fiber, the viscosity can also be significantly below the typical zero viscosity (3,000–10,000 Pa). The specified process temperature refers to the temperature at which the polymer material is used for impregnation. For thermoplastic polymers, this is specifically the temperature at which the polymer material is melted and can thus impregnate the fiber bundle. German patent DE 10 2016 219 289 A1 discloses a method for impregnating fiber rovings. In this method, the fiber roving is guided through a roving impregnation device. For impregnation, a matrix material in a quantity adapted to the throughput speed of the fiber roving is introduced into a cavity of the roving impregnation device via a matrix feeder. DE 38 35 574 A1 discloses an extrusion impregnation device for the continuous production of fiber-reinforced molded parts. The extrusion impregnation device has a split housing with a split heating jacket, an extruder connection with a melt feed, a split impregnation insert, an inlet nozzle for fiber material, and an outlet nozzle for the fiber-reinforced linear profiles. WO 02 / 030 657 A1 discloses a method and a device for manufacturing composite components, in which a matrix is ​​melted by energizing electrically conductive fibers contained in the matrix and the component is hot-pressed. Another challenge in the continuous impregnation of rovings using an automated impregnation device is the insertion of the fiber bundle at the very beginning of the process. The feed channel provided for the fiber material must be capable of threading the fiber material into the impregnation device at the entry point. It is therefore an object of the present invention to provide an improved device with which a fiber material (in particular rovings) can be continuously impregnated with a plastic material. It is also an object of the present invention to provide an improved method for this purpose. The problem is solved according to the invention by the impregnation device mentioned at the outset, having the features of claim 1. Advantageous embodiments of the impregnation device are found in the corresponding dependent claims. According to claim 1, an impregnation device for impregnating at least one quasi-endless fiber material is claimed, wherein the quasi-endless fiber material is impregnated with a plastic material that is melted at a corresponding process temperature. The fiber material can be, in particular, rovings or fiber bundles consisting of a multitude of individual, quasi-endless fibers or filaments. The fiber material can be, for example, carbon fibers or glass fibers. However, other fiber materials are certainly conceivable. The fiber material can be, in particular, the fiber material that is a component of a fiber-reinforced composite material used to manufacture a fiber-reinforced composite component. This can especially include fiber materials used in additive or generative manufacturing processes, such as 3D printing using a 3D printing system. The plastic material can be a thermoplastic or thermosetting plastic. In particular, it can be a high-viscosity plastic. It can also be a plastic material that forms part of a fiber-reinforced composite used to manufacture a fiber-reinforced component. Such plastic materials are also referred to as matrix materials. The impregnation device according to the invention has, by design, at least one fiber feed channel with a fiber inlet for supplying the quasi-endless fiber material to the impregnation device. Furthermore, the impregnation device has, by design, at least one plastic feed channel with a plastic inlet separate from the fiber inlet, in order to supply the required plastic material, with which the fiber material is to be impregnated by the impregnation device, separately to the fiber material of the impregnation device. The plastic inlet of the plastic feed channel can have a closure device for connecting the impregnation device to a reservoir for the plastic material.The closure device allows a particularly flexible supply hose to be connected to the impregnation device, which at the opposite end is equipped with the storage container and, if necessary, with a pressure source to generate transport pressure. The at least one fiber feed channel and the at least one plastic feed channel are at least partially separated within the impregnation device. Both the fiber feed channel and the plastic feed channel then open into a common impregnation cavity to impregnate the quasi-endless fiber material with the supplied and melted plastic material. The impregnation takes place mainly and preferably completely within the impregnation cavity. However, this does not preclude the possibility that the fiber feed channel and the polymer feed channel are routed in a common channel section upstream of the impregnation cavity, which then leads into the impregnation cavity. In this case, both the fiber feed channel and the polymer feed channel have a first section where the two feed channels are separate and at least one second section where the fiber material and the polymer material are routed in a common channel section. Thus, in the second section, the fiber feed channel and the polymer feed channel are formed by a common channel. According to the invention, the impregnation device now has a backflow prevention area in which the fiber feed channel has at least a section-wise S-shaped course formed by two bends with opposite directions of curvature, between which the fiber feed channel is joined with the at least one plastic feed channel, so that a common channel section is subsequently formed. This backflow prevention zone (section-wise S-shaped course of the fiber feed channel) is preferably located in the remaining part of the impregnation device and not in the fiber inlet or in the impregnation cavity. Due to the S-shaped course, the fiber material rests against the respective radius of curvature of the S-shaped section, whereby the direction of curvature changes because of the S-shaped course, and thus the fiber material rests against a first inner surface and then against an opposing second inner surface during transport through the fiber feed channel (conveying direction, extrusion direction). The fiber material itself thus forms a backflow preventer, as the fiber material, due to the change of sides, is always in contact with an inner surface and therefore forms a natural backflow barrier for the plastic material. It has been shown that, due to the continuous movement of the fiber material, which acts upon the plastic material in the conveying direction as it rises, the melt pressure against the conveying direction is reduced to such an extent that the plastic material cannot be forced between the inner surface of the fiber feed channel, where the fiber material rests, and the fiber material itself.For the continuous conveying of the fiber material, a tensile stress is applied to the fiber material, which causes the fiber material to be pulled through the feed channel and pressed against the inside of the fiber feed channel in the S-shaped course with a force that is greater than the counterforce caused by the rising plastic material. It was surprisingly found that a natural backflow barrier formed by an S-shaped curve can effectively prevent the supplied plastic material from rising into the fiber feed channel. Due to the continuous conveying of the fiber material and the associated tensile stress on it, the pressurized plastic material cannot reach the section of the fiber feed channel located above (in the conveying direction) the first bend. Furthermore, the continuous conveying of the fiber material prevents the plastic material from penetrating and permeating the fiber material at the point where the plastic feed channel meets the fiber feed channel, which would otherwise allow the plastic material to breach the backflow preventer. The continuous conveying of the fiber material prevents complete saturation at this point, thus ensuring that the plastic material cannot overcome the backflow preventer. However, this knowledge can be used to ensure partial pre-impregnation of the fiber material without complete penetration. This can improve the impregnation result. Such an impregnation device can be part of a system for printing quasi-endless, plastic-impregnated fiber materials. According to one embodiment, the curvatures of the fiber feed channel are designed such that the fiber material is guided in contact along a first inner surface of the fiber feed channel at the first curvature and along a second inner surface of the fiber feed channel opposite the first inner surface at the second curvature. According to one embodiment, the at least one plastic feed channel opens into the fiber feed channel on the first inner side of the fiber feed channel between the first and second bends. The plastic feed channel opens into the fiber feed channel on the inside, where the fiber material rests against the first bend located above (in relation to the conveying direction) the opening. Thus, starting from the opening into the fiber feed channel, the fiber material blocks the fiber feed channel against the conveying direction. According to one embodiment, the impregnation device has at least one heating device designed to temper the fiber material and / or the plastic material. Tempering the plastic material keeps it at the process temperature to accelerate the impregnation process. Tempering the fiber material ensures that the process temperature remains constant, or essentially constant, even when the plastic material comes into contact with the fiber material, preventing negative properties from developing due to cooling of the plastic material against the fiber material. According to one embodiment, the heating device has an electrode arranged in the fiber feed channel at a position where the fiber material is guided along the electrode in contact, wherein the heating device is configured to generate a current flow in an electrically conductive fiber material by means of the electrode. Such an electrode can preferably be arranged in a curve, more precisely on the inside of the curve, within the fiber feed channel. For the sake of completeness, it should be mentioned that the heating device also includes a counter electrode, which can either be provided within the impregnation device or arranged outside of it (for example, in the fiber magazine or at the outlet of the impregnation device). A current is thereby induced between the electrode and the counter electrode in the electrically conductive fiber material, causing the fiber material to heat up in a manner similar to resistance heating. This current flow is achieved by applying an electrical voltage to the electrode and / or counter electrode. According to one embodiment, the width of the fiber feed channel essentially corresponds to the width of the fiber material. This allows the fiber material to block the fiber feed channel even more effectively in the area where it intersects the plastic feed channel, thus preventing the plastic material from rising up the fiber. According to one embodiment, the fiber feeder is a component separate from the rest of the impregnation device, designed for detachable attachment to the impregnation device, and comprising at least two individual elements that can be moved from an open state to a closed state, which in the closed state form at least a section of the fiber feed channel. Accordingly, the fiber feeder is a separate component that can be detachably attached to the impregnation device. The component can therefore be moved from an unassembled to an assembled state and back again. Thus, the separate component can be detachably mounted to and removed from the impregnation device. The "open" state refers to an unassembled or unmounted state, while the "closed" state refers to an assembled or mounted state. The fiber feeder, in the form of a component separate from the rest of the impregnation device, comprises at least two individual elements that can be moved from an open to a closed state. In the closed state, the component can then be mounted on the impregnation device. In the open state, access to the interior of the section of the fiber feed channel formed by the fiber feeder is possible. The individual elements can be separate components that are physically assembled and moved into the closed state only when the fiber feeder is mounted on the impregnation device. Alternatively, the individual elements could be connected by a hinge or pivot device designed to allow the individual elements to be moved from an open to a closed state and back again. This also makes it possible to simplify fiber insertion when threading the fiber material into the impregnation device at the beginning of the process, while simultaneously preventing the molten plastic material from rising and escaping from the fiber insertion point. Thanks to the separately available component, which consists of several individual elements, the fiber insertion point can now be detached from the impregnation device, the fiber material inserted into the impregnation device, and then the inserted fiber material enclosed by the fiber insertion point when the fiber insertion point is assembled and mounted on the impregnation device. This is particularly advantageous if the section of the fiber feed channel formed by the fiber inlet in the closed state has a cross-sectional shape that essentially corresponds to the cross-sectional shape of the fiber material to be fed. In particular, this section of the fiber feed channel has a cross-sectional area that is only insignificantly larger than the cross-sectional area formed by the fiber material. It has proven advantageous if the cross-sectional area of ​​the fiber feed channel section of the fiber inlet, perpendicular to the conveying direction of the fiber material, corresponds to a maximum of 30 times (preferably a maximum of 20 times, and especially preferably a maximum of 10 times) the theoretical cross-sectional area of ​​the fiber bundle or the fiber material.The theoretical cross-sectional area of ​​a fiber bundle is the sum of the cross-sectional areas of the individual fibers, which results from the number of individual fibers and the cross-sectional area of ​​a single fiber layer or filament. The significantly reduced cross-sectional area perpendicular to the conveying direction reliably prevents the plastic material fed under pressure into the impregnation device from rising, while the modular design of the fiber introduction makes threading a roving easy. According to one embodiment, the dividing plane of the individual fiber feeder elements lies on the axis of the section of the fiber feed channel formed by the fiber feeder. Thus, when the fiber feeder is open, each individual element contains a portion of the inner surface of the section of the fiber feed channel formed by the fiber feeder. By assembling the individual elements in the closed position, the section of the fiber feed channel formed by the fiber feeder is then created. This particularly facilitates loading the impregnation device with the fiber material and cleaning relevant components. According to one embodiment, a locking device is provided for the form-fitting and / or force-fit arrangement of the individual fiber feed elements on the impregnation device. Such a locking device can include a centering element (for example, by means of locking elements and / or tongue-and-groove elements) into which the individual elements are inserted, and the individual elements can be fixed to the impregnation device by means of a cap nut. Clamping devices in which the individual elements are pressed together are also conceivable.The closure device has the further advantage that the section of the fiber feed channel formed by the fiber introduction is centered at the mechanical interface with respect to the subsequent section of the fiber feed channel in the rest of the impregnation device, so that the fiber material can be continuously conveyed from the first section of the fiber feed channel (in the fiber introduction) to the second section of the fiber feed channel (in the rest of the impregnation device, the main assembly) without any problems. According to one embodiment, the cross-sectional area of ​​the section formed by the fiber feeder, as the first section of the fiber feed channel, is smaller than that of a second section of the fiber feed channel immediately following the fiber feeder in the rest of the impregnation device. The fiber feeder thus has a narrower section of fiber feed channel than the rest of the impregnation device, which makes threading the fiber material into the impregnation device particularly easy, while reliably preventing the migration of plastic material into the fiber feed channel of the fiber feeder. According to one embodiment, the section formed by the fiber feed is essentially straight, wavy, or double-S shaped, or the first section formed by the fiber feed has at least one curve. The cross-sectional shape (perpendicular to the fiber guide) is preferably rectangular (advantageous if the fiber material (roving) is fed in already spread) or round or oval (advantageous if the fiber material has not been spread beforehand). However, other cross-sectional shapes are also conceivable, such as multiple curves. With a straight course of the section of the fiber feed channel formed by the fiber introduction, the fiber material is guided through the fiber introduction particularly gently, as the friction of the fiber material on the inner wall of the fiber feed channel is minimized. In contrast, a wavy profile increases the friction of the fiber material against the inner wall of the fiber feed channel. However, the alternating directions of the fiber guidance can both promote the spreading of the fiber material, which improves the impregnation of the fiber material with the plastic material, and further prevent the plastic material from rising into the section of the fiber feed channel formed by the fiber insertion. Particularly with a double-S-shaped profile, it can be achieved that the fiber material itself always forms a barrier against the further upward movement of the liquid plastic material.Because of the change in direction of the curves in a double-S-shaped profile, the fiber material lies at least once on the first inner side and at least once on the opposite second inner side, so that the plastic material is prevented from rising further by the fiber material itself. In conjunction with a wavy or double-S-shaped fiber feed channel at the fiber inlet, and optionally a significantly tapered cross-section of this section, it is possible to prevent the plastic material from rising against the conveying direction and negatively impacting the impregnation process, even at high melt pressures. This provides additional protection even at high melt pressures. According to one embodiment, the backflow prevention zone is arranged in the conveying direction of the fiber material upstream of the impregnation cavity. According to one embodiment, the backflow prevention zone is provided in a backflow prevention component, which is detachably attached or attachable to an impregnation component having the impregnation cavity, wherein the fiber feed is arranged or can be arranged as a separate component on the backflow prevention component. This allows the entire impregnation device to be constructed modularly. The conveying speed of the fiber material can range from 0.3 m / min to 50 m / min (preferably 3 m / min to 15 m / min). The conveying speed of the plastic material can be identical to or differ from the conveying speed of the fiber material (by up to 30%). The fiber bundles of carbon fiber, glass fiber, natural fiber, etc., as roving, can comprise 1,000 to 50,000 individual fibers. It is also conceivable that several fiber bundles are fed simultaneously or sequentially via multiple feeding units. Furthermore, it is conceivable that a plurality of fiber bundles are spread out and fed as a wide band. The fiber bundles can be spread out, particularly flattened, by the impregnation device before entering the impregnation cavity. The impregnation device has corresponding spreading elements for this purpose.It is advantageous if the fiber bundle is pre-heated or pre-heated by the impregnation device's heating element to a temperature between 50°C and 1000°C (150°C to 500°C). The actual process temperature depends on the type of plastic used and, in particular, on the rheological properties of the liquid plastic. The fiber bundles can be pre-stressed with a force of more than 5 Newtons and below the critical tensile force at which fiber damage would occur, and then continuously conveyed through the impregnation device. The pressure of the liquid plastic (melt pressure) can be between 5 bar and 1000 bar (preferably between 5 bar and 400 bar). With the help of the impregnation device, it becomes possible to achieve a fiber volume content of the final semi-finished product or the extruded profile / strand (3D printing) of between 30% and 80% after exiting a nozzle. The impregnation device has an outlet or outlet channel downstream of the impregnation cavity in the conveying direction, through which the impregnated fiber material is discharged. A nozzle can be connected to the impregnation device here to extrude the impregnated fiber material (extrusion impregnation). Another aspect of the present invention relates to a non-return valve component for use in an impregnation device for impregnating a quasi-endless fiber material with a plastic material, wherein the non-return valve component has at least one fiber feed channel with a fiber inlet for feeding the quasi-endless fiber material, and at least one plastic feed channel with a plastic inlet separate from the fiber inlet for feeding the plastic material separately to the fiber material, wherein the at least one fiber feed channel and the at least one plastic feed channel are separated at least sectionally.The impregnation device has a backflow prevention zone in which the fiber feed channel has at least a section of an S-shaped profile formed by two bends with opposite directions of curvature, between which the fiber feed channel is joined with the at least one plastic feed channel, so that a common channel section is subsequently formed. The statements made regarding the impregnation device in connection with the features of the backflow preventer can be applied accordingly to this aspect of the invention. This applies in particular to all features provided upstream of the impregnation cavity. The backflow preventer according to the invention specifically does not have an impregnation cavity as defined in the present invention. The problem is also solved according to the invention by the method of the type mentioned at the outset, wherein the method comprises the following steps: - providing an impregnation device according to one of claims 1 to 13, - introducing the quasi-endless fiber material into the provided impregnation device, and - continuously feeding the plastic material and the quasi-endless fiber material into the impregnation cavity of the impregnation device in order to impregnate the quasi-endless fiber material with the plastic material, - wherein in a backflow prevention area provided in the impregnation device the fiber material is guided through an S-shaped course of the fiber feed channel, wherein between the two bends of the S-shaped course the plastic material is pressed through the plastic feed channel opening in between into the common channel section. The invention is explained in more detail by way of example with reference to the accompanying figures. These show, without limitation of generality: Fig. 1 Representation of an impregnation device according to the invention; Fig. 2 Representation of a backflow preventer component; Fig. 3 Representation of the backflow preventer component in an isometric view; Fig. 4 Representation of the fiber feed in a further embodiment; Fig. 5 Representation of the fiber feed in a further embodiment; Fig. 6 Representation of the fiber feed with temperature control elements; Fig. 7 Representation of a fiber spreader prior to the fiber feed; Fig. 8 Representation of a further embodiment for temperature control; Fig. 9 Schematic representation of a backflow preventer using fiber material. Fig. 1 shows in a complete view the impregnation device 100 with a backflow preventer component 110, an impregnation component 120 and a spreading component 130 for spreading the fiber material 10 to be introduced. The fiber material 10 (fiber bundle) contained in a fiber magazine is guided through the spreading component 130, which has a roller system 131 designed to spread the fiber bundle. The fiber material 10 is then introduced into the non-return valve component 110. A liquid plastic 12 is also fed into this non-return valve component 110, where it mixes with the introduced fiber material 10 and is intended to completely impregnate the fiber material 10 within the impregnation component 120. The fiber material 10, now impregnated with the plastic 12, is then extruded from a die 121. As will be shown in detail later, the non-return valve component 110 has several non-return valves 112. At the upper end of the backflow preventer 110 in the area where the fiber material 10 is introduced into the backflow preventer 110, there is the fiber introduction 111, which will also be explained in detail later. The impregnation component 120 contains an ultrasonic sonotrode 122 to apply sound energy to the plastic material 12 located in the impregnation cavity 123. This is intended to improve the impregnation result. Positioning elements 124 are located in front of and behind the impregnation cavity 123 so that the fiber material is guided along the ultrasonic sonotrode 122 at a precisely defined position relative to it. The ultrasonic sonotrode 122 may have a passage through which the fiber material is guided. The entire impregnation device 100 has a modular design, allowing the individual components to be assembled as needed. For example, if an impregnation component 120 is required that does not include an ultrasonic sonotrode 122, the impregnation component 120 can simply be replaced by another component, provided the mechanical interfaces are compatible. Fig. 2 shows in detail the backflow preventer 200, designated 110 in Fig. 1. Fig. 3 shows an isometric view of this component. In the area where the fiber material 10 is inserted, there is a fiber feed-in 210, which can be detachably attached to the backflow preventer 200 as a separate component. In the embodiments shown in Figs. 2 and 3, the separate component of the fiber feed-in 210 has two individual elements 220, which can be attached to the backflow preventer 200 by a centering locking device 230. In the embodiment shown in Fig. 2, the individual elements 220 are shown in a closed state on the backflow preventer 200, while in Fig. 3, the individual elements 220 are shown in an open state. The closure device 230 also includes a clamping element 231 in the form of a union nut, which, in conjunction with a centering device 233 of the closure device 230, allows the individual elements 220 of the fiber feeder 210 to be connected to the backflow preventer 200 in a form-fit and / or force-fit manner. This can be achieved, for example, by means of a fine thread located on a collar of the backflow preventer 200. A conical inner shape of the clamping element 231, which interacts with a conical outer shape of the individual elements 220, allows the fiber feeder to be firmly attached to the backflow preventer 200. Simultaneously, the two halves are clamped against each other. The angled surface generates a downward force (fastening the individual elements to the component) and an inward force (radially, to press the individual elements together) when the union nut is tightened. Centering, as used here, means that the channel outlet of the fiber feeder 210 is positioned above the channel inlet of the backflow preventer 200. The individual elements 220 have projections and recesses (in the form of a tongue-and-groove connection) that interlock and fix the individual elements against each other. Additionally, a corresponding fit is provided on the backflow preventer 200, into which the individual elements 220 engage, thus centering the fiber feeder 210 on the component. The clamping element 231 fixes the individual elements 220 both to each other and to the component. Furthermore, a heating device 270 can be provided at the fiber entry point 210 in order to temper the introduced fiber material 10 accordingly. Inside the non-return valve component are a fiber feed channel 240 and a plastic feed channel 250. The fiber feed channel begins at the upper end of the fiber inlet 210 and terminates at a common outlet channel 260, which then leads into the impregnation cavity of the impregnating component. The same applies to the plastic feed channel 250, which begins at a plastic inlet 251 and also terminates in the common outlet channel 260. In the embodiment shown in Figures 2 and 3, the fiber feed channel has a first channel section 241, which is formed by the section of the fiber feed channel through the fiber inlet 210. A second channel section 242 adjoins this, located within the backflow preventer and separate from the plastic feed channel 250. Finally, there is a third channel section 243, within which the fiber material 10 and the plastic material 12 are guided together and which opens into the common outlet channel 260. The plastic feed channel 250 has a main section 252 and a secondary section 253. Both the main section 252 and the secondary section 253 lead to the common outlet channel 260, so that in the third channel section 243 of the fiber feed channel 240 the plastic material is guided together with the fiber material in a common channel. The inner surfaces of at least part of the fiber feed channel 240 should have very low surface roughness and high wear resistance, since the fiber material 10 comes into contact with the inner surfaces of the fiber feed channel 240. This applies in particular to the first and second channel sections 241 and 242, whereby the first channel section 241 has a significantly smaller cross-section than the second channel section 242. Fig. 4 shows an embodiment in which the fiber inlet 210 consists of a total of 3 individual elements 220. Each individual element forms an axial part of the inner surface of the first channel section 241 of the fiber feed channel 240, and in the assembled state, the complete first channel section 241 of the fiber feed channel 240 is formed. Preferably, the first channel section 241 has a rectangular cross-sectional shape. In the embodiments shown in Figs. 1, 2, 3 to 4, the first channel section 241 is straight and, in particular, has no curves or waviness. In the embodiment shown in Fig. 5, a fiber feed-in 210 is depicted which, in its assembled state, shows a wavy first channel section 241 of the fiber feed channel. Fig. 6 shows an enlarged view of the fiber inlet 210, which is slotted in a region 211. This creates two sections of the fiber inlet 210. Each section can be equipped with a separate temperature control element 270 to create different temperature zones within the fiber inlet area. For example, the temperature of one zone can be deliberately set below the temperature of the liquid plastic to increase its viscosity and thus prevent it from rising and leaking out. Fig. 7 shows a detailed view of the attached spreading component 130, which is intended to spread the fiber material 10 before it is introduced into the impregnation device 100 or into the fiber feeder 210. For this purpose, the fiber material 10 is guided by a roller system 131, so that the fiber material constantly changes its direction. An electrode in the form of a roller electrode 132 can be arranged on one of the rollers, interacting with a counter electrode 133 in such a way that a current flow is induced between the roller electrode 132 and the counter electrode 133 in the electrically conductive fiber material. This current flow leads to heating of the fiber material and thus to temperature control. A sensor 134 can be provided to continuously monitor the temperature of the fiber material. Fig. 8 shows the channel layout of the fiber feed channel and the plastic feed channel of the backflow preventer component 200. It can be seen that the fiber feed channel 240 has an S-shaped path, with a first bend 240a and a second bend 240b forming the S-shaped path of the fiber feed channel 240. Between the first bend 240a and the second bend 240b, the secondary section 253 of the plastic feed channel opens into the fiber feed channel 240. The first bend 240a is designed such that the fiber material 10 rests against a first inner surface of the fiber feed channel 240, where the secondary section 253 of the plastic feed channel also opens into the fiber feed channel 240. The fiber material is then guided from the first inner side at the first curvature 240a to the opposite second inner side at the second curvature 240b.As can be seen, the fiber material between the first bend and the second bend thus forms a backflow barrier, since the plastic material would have to be pressed against the conveying direction between the fiber material and the first inner side along the first bend. In Fig. 8, an electrode 271 of the heating device 270 (not shown in this figure) is provided at a third bend 240c, which interacts with a counter electrode 272 to generate a current flow. The fiber material is heated in the area through which the current flows. Fig. 9 shows the operating principle of the backflow preventer, which is effected by the fiber material, in a schematically simplified representation. The tensile force applied to the fiber material for continuous conveying in the extrusion direction presses the fiber material against the first inner surface 244a of the first bend 240a. This contact force results from the tensile force used to convey the fiber material. Similarly, the fiber material is pressed against the second inner surface 244b of the second bend 240b. Since the plastic material now enters the fiber feed channel 240 at the first inner surface 244a between the first bend 240a and the second bend 240b, the path of the plastic material against the conveying direction is blocked by the fiber material 10.The plastic material would have to overcome the force acting on it due to the conveying of the fiber material, as well as the pressure exerted by the fiber material at the first bend 240a, in order to rise in the fiber feed channel. Although the fiber material is wetted by the plastic material, a sufficient, at least partially continuous, conveying of the fiber material prevents complete penetration until the exit point or the backflow preventer is overcome. Reference symbol list 10 Fiber material 12 Plastic material 100 Impregnation device 110 Non-return valve component 111 Fiber feed 112 Non-return valve 120 Impregnation component 121 Outlet nozzle 122 Ultrasonic sonotrode 123 Impregnation cavity 124 Positioning elements 130 Spreading component 131 Roller system 132 Roller electrode 133 Counter electrode 134 Temperature sensor 200 Non-return valve component 210 Fiber feed 211 Slotted areas 220 Individual fiber feed elements 230 Closure device 231 Clamping element 232 Fine thread 240 Fiber feed channel 240a First bend 240b Second bend 240c Third bend 241 First channel section 242 Second channel section 243 Third channel section 244a First inner side 244b second inner side 250 plastic feed channel 251 plastic feed 252 main section 253 secondary section 260 common outlet channel 270 heating device 271 electrode of the heating device 272 against electrode of the heating device

Claims

Impregnation device (100) for impregnating at least one quasi-endless fiber material (10) with a plastic material (12) that is melted at a corresponding process temperature, comprising at least one fiber feed channel (240) with a fiber inlet (111) for supplying the quasi-endless fiber material (10) to the impregnation device (100), and at least one plastic feed channel (250) with a plastic inlet separate from the fiber inlet (111) for supplying the plastic material (12) separately to the fiber material (10) of the impregnation device (100), wherein the at least one fiber feed channel (240) and the at least one plastic feed channel (250) are at least partially separate and open into a common impregnation cavity (123) for impregnating the quasi-endless fiber material (10) with the supplied and melted plastic material (12), characterized in thatthat the impregnation device (100) has a backflow prevention zone in which the fiber feed channel (240) has at least a section-wise S-shaped course formed by two bends (240a, 240b) with opposite directions of curvature, between which the fiber feed channel (240) merges with the at least one plastic feed channel (250), so that a common channel section is subsequently formed. Impregnation device (100) according to claim 1, characterized in that the curvatures (240a, 240b) of the fiber feed channel (240) are designed such that the fiber material (10) is guided in contact along a first inner side (244a) of the fiber feed channel (240) at the first curvature (240a) and along a second inner side (244b) of the fiber feed channel (240) opposite the first inner side (244a) at the second curvature (240b). Impregnation device (100) according to claim 2, characterized in that the at least one plastic feed channel (250) opens into the fiber feed channel (240) between the first and second curvature (240a, 240b) at the first inner side (244a) of the fiber feed channel (240). Impregnation device (100) according to one of the preceding claims, characterized in that the impregnation device (100) has at least one heating device (270) designed for tempering the fiber material (10) and / or the plastic material (12). Impregnation device (100) according to claim 4, characterized in that the heating device (270) has an electrode (271) arranged in the fiber feed channel (240) at a position where the fiber material (10) is guided along the electrode (271) in contact with it, wherein the heating device (270) is configured to generate a current flow in an electrically conductive fiber material (10) by means of the electrode (271). Impregnation device (100) according to one of the preceding claims, characterized in that the width of the fiber feed channel (240) corresponds substantially to the width of the fiber material (10). Impregnation device (100) according to one of the preceding claims, characterized in that the fiber introduction (111) is a component separate from the rest of the impregnation device (100), which is designed for detachable arrangement on the impregnation device (100) and which has at least two individual elements (220) that can be moved from an open state to a closed state, which in the closed state form at least a section of the fiber feed channel (240). Impregnation device (100) according to claim 7, characterized in that the parting plane of the individual elements (220) of the fiber introduction (111) lies in the axis of the section of the fiber feed channel (240) formed by the fiber introduction (111). Impregnation device (100) according to claim 7 or 8, characterized in that a closure device (230) is provided which is designed for the form-fitting and / or force-fitting arrangement of the individual elements (220) of the fiber introduction (111) on the impregnation device (100). Impregnation device (100) according to one of claims 7 to 9, characterized in that the cross-sectional area of ​​the section formed by the fiber introduction (111) as the first section of the fiber feed channel (240) is smaller than a second section of the fiber feed channel (240) immediately adjoining the fiber introduction (111). Impregnation device (100) according to one of claims 7 to 10, characterized in that the section formed by the fiber introduction (111) is essentially straight, wavy or double-S shaped, or that the first section formed by the fiber introduction (111) has at least one curvature. Impregnation device (100) according to one of the preceding claims, characterized in that the backflow prevention area is arranged in the conveying direction of the fiber material (10) upstream of the impregnation cavity (123). Impregnation device (100) according to claim 12, characterized in that the backflow prevention area is provided in a backflow prevention component (110) which is detachably attached or attachable to an impregnation component (120) having the impregnation cavity (123). A non-return valve component (110) for use in an impregnation device (100) for impregnating a quasi-endless fiber material (10) with a plastic material (12), wherein the non-return valve component (110) has at least one fiber feed channel (240) with a fiber inlet (111) for feeding the quasi-endless fiber material (10), and at least one plastic feed channel (250) with a plastic inlet separate from the fiber inlet (111) for feeding the plastic material (12) separately to the fiber material (10), wherein the at least one fiber feed channel (240) and the at least one plastic feed channel (250) are separated at least section by section, characterized in that the non-return valve component (110) has a non-return zone in which the fiber feed channel (240) has an S-shaped profile at least section by two bends (240a, 240b) is formed with opposite directions of curvature,between which the fiber feed channel (240) is joined with the at least one plastic feed channel (250), so that a common channel section is subsequently formed. A method for impregnating at least one quasi-endless fiber material (10) with a plastic material (12), the method comprising the following steps: - providing an impregnation device (100) according to any one of claims 1 to 13, - introducing the quasi-endless fiber material (10) into the provided impregnation device (100), and - continuously feeding the plastic material (12) and the quasi-endless fiber material (10) into the impregnation cavity (123) of the impregnation device (100) in order to impregnate the quasi-endless fiber material (10) with the plastic material (12), - wherein in a backflow prevention area provided in the impregnation device (100), the fiber material (10) is guided through an S-shaped section of the fiber feed channel (240), wherein the plastic material is guided between the two bends (240a, 240b) of the S-shaped section. (12) is pressed into the common channel section through the intervening plastic feed channel (250).

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