DE102023101604A1 - Method for connecting towpregs and winding machine with connection station - Google Patents

Abstract

Method for connecting two Towpreg tapes (21, 22) during a spool change in a winding machine (1) for producing a component (9) made of fiber-reinforced plastic by winding Towpreg tapes around a winding core (4), wherein the Towpreg tapes (21, 22) are fiber tapes made of continuous fibers which are already impregnated with matrix material and are provided on spools (7, 8), and wherein the end (23) of a first Towpreg tape (21) from a first spool (7) is connected to the beginning (24) of a second Towpreg tape (22) from a second spool (8), wherein the beginning (24) and the end (23) are brought substantially parallel to one another, wherein a polymerization adhesive is applied to the beginning (24) and/or to the end (23) using an adhesive application unit (11), and wherein a pressing device (13) presses the beginning (24) and Press the end (23) together, whereby the two Towpreg bands (21,22) are connected to each other in a tension-resistant manner.

Description

The invention relates to a method for connecting towpregs in a winding machine for producing a component made of fiber-reinforced plastic. Such components are, for example, gas tanks for vehicles, rollers for paper machines or other rotationally symmetrical components that are made in particular from carbon fiber-reinforced plastic (CFRP).

Such wound fiber-reinforced plastic components are usually manufactured using the so-called wet winding process. The fiber tapes are wound dry onto spools. The fibers used are preferably carbon fibers in the form of continuous fibers. The individual fiber tapes are, for example, rovings, which consist of several thousand parallel individual fibers. A duromer, for example epoxy resin, is used as the matrix material, which is available as a liquid in a resin bath to impregnate the fiber tapes online. After unwinding from the spool, the still dry fiber tapes are first passed through the resin bath, in which they are soaked in the liquid matrix material and thus impregnated. The impregnated fiber tapes are then wound wet-on-wet onto the winding core.

Such winding machines are known in the state of the art. In the DE 102016122522 A1 A winding machine for wet winding is described. Another design for a winding machine is described in the WO 2022/136812 A1 shown. Winding machines are also known that process so-called Towpreg tapes. Towpreg tapes are fiber tapes that are pre-impregnated with matrix material and are wound onto spools. At room temperature in the winding process, the matrix material is a very tough, somewhat sticky epoxy resin and not as thin as the resin that is used for online impregnation in the tempered resin bath. The tough resin makes it easy to unwind the Towpreg fiber tapes from the spool and guide them over the rollers. The processing and winding of the component can take place at a much higher speed.

This provides an advantage in terms of increased productivity, reliability and improved quality compared to wet winding machines, so that manufacturing costs can be significantly reduced.

The components made of fiber-reinforced plastic are manufactured by winding wet-impregnated rovings or towpreg tapes onto a winding core. The winding core is equipped with a drive and pulls the rovings or towpreg tapes off the spool through rotation.

Up to now, the bobbin change on these winding machines has been carried out by tying the beginning of the new bobbin to the end of the previous bobbin. The machine operators do this by hand and it is very time-consuming and inefficient, especially on winding machines in which several fiber ribbons are processed in parallel. The knots often have to be cut out manually afterwards to avoid local quality losses.

A proposal for an automated process for joining Towpreg tapes is, for example, in the DE 102022104803 A1 The two Towpreg tapes are to be connected by locally hardening the existing matrix material in the area of overlap between the start of the new coil and the end of the previous coil. However, several problems arise that prevent this from being used effectively. Firstly, the curing time of the matrix material is too long, so that really efficient operation is not possible. Secondly, the hardened areas become stiff and inflexible, which can lead to defects and corresponding losses in quality during subsequent winding.

The object of the invention is to develop an improved and automatable method for connecting Towpreg tapes when changing spools, with which the beginning of a new spool can be reliably connected to the end of a previous spool. As well as to provide a corresponding winding machine that can implement this method.

The object is achieved for the method according to the invention by an embodiment according to independent claim 1. Further advantageous embodiments of the present invention can be found in the subclaims. The method according to the invention is characterized in that the beginning and the end are brought essentially parallel to one another, that a polymerization adhesive is applied to the beginning and/or the end using an adhesive application unit, and that a pressing device presses the beginning and the end together, whereby the two Towpreg tapes are connected to one another in a tensile manner.

The advantage of this process is that the polymerization adhesive in development is an adhesive that is suitable for the matrix materials used and at the same time reacts quickly enough to produce a sufficiently tensile bond in a short time when pressed. connection between the Towpreg tapes, while at the same time creating a sufficiently flexible connection point that does not interfere with winding. This, together with the essentially parallel alignment of the Towpreg tapes to be connected, means that the connection point does not cause any disturbances in the quality of the wound component.

No deterioration in quality is acceptable, especially for the gas tanks for vehicles mentioned above, as these gas tanks must meet very high safety requirements and at the same time be manufactured as lightly as possible and with as little material as possible. In addition, production must be reliable and as cost-effective as possible.

The method according to the invention thus offers for the first time a reliable, quality-compliant and automatable option for joining Towpreg tapes when changing spools. Thanks to this improvement, the inherently more efficient Towpreg winding is now also more efficient when changing spools than the wet winding method.

During development, cyanoacrylate adhesives have proven to be particularly suitable polymerization adhesives. They are relatively thin, easy to apply, adhere well to the Towpreg tapes and, under suitable conditions, develop the necessary strength particularly quickly.

The curing of the polymerization adhesive is even faster if an activator substance is also applied to the beginning and/or the end, so that the polymerization adhesive and activator substance react chemically with each other when pressed together and the polymerization takes place more quickly. Acetone can be used in particular for this, which works together with a cyanoacrylate adhesive as an activator substance by providing the required carbions. Acetone is also thin and can be applied easily.

The connection of the Towpreg tapes achieves the required strength when the beginning and the end are pressed together for at least 3 seconds, preferably at least 10 seconds, after the polymerization adhesive has been applied. To ensure appropriate safety, a pressing time of at least 20 seconds or at least 30 seconds is preferred.

A simple and even application of the polymerization adhesive and/or the activator substance is preferably carried out by spraying or squirting or as a droplet application using an air stream directed at the Towpreg belt(s). This allows the application and dosing to be easily automated.

In order to enable precise application and better parallel alignment of the Towpreg tapes, it is advantageous to fix the beginning of the second Towpreg tape to or using a holding device before applying the polymerization adhesive. A gripper, a vacuum plate or another holding plate can be used as a holding device, for example. In this way, the beginning of the second Towpreg tape can be brought in a controlled manner next to the still taut end of the first Towpreg tape.

In a further advantageous embodiment, the first Towpreg belt is deflected sideways from its normal running direction during operation by means of a gripper before the polymerization adhesive is applied and is thereby brought into an area of an adhesive application unit. For example, this can be combined with the holding device for the start of the second Towpreg belt. The advantage of this deflection is that the adhesive application can be arranged stationary outside the running area of the Towpreg belts during normal operation. This means that the adhesive application unit and the pressing device do not interfere. An alternative would be for these units to be designed to be pivotable or movable and only brought into the desired position for the connection when changing the spool.

A further improvement is achieved if the relative humidity in the area around the start and end is between 40% and 80%, preferably between 55% and 70%, at least after the polymerization adhesive has been applied. The humidity can be measured and/or adjusted or maintained in the desired range, for example by spraying water or steam. If necessary, the connection point can also be shielded or enclosed to make it easier to adjust the humidity.

In order to have even less impact on the quality of the wound components, the first Towpreg tape can be cut after pressing between the first coil and the pressing device. This ensures that the end of the first Towpreg tape after the connection point is as short as possible and that the untensioned Towpreg tape residue is not wound up in an uncontrolled manner.

For the device, the task is accomplished by a winding machine according to the invention. accordingly fulfilled in the independent claim 10. Further advantageous embodiments of the present invention can be found in the associated subclaims. The design of the winding machine according to the invention is characterized in that the winding machine has a connecting station with an adhesive application unit and with a pressing device. In the connecting station, when changing the spool, the end of a first Towpreg tape from a first spool can be connected in a tensile manner to the beginning of a second Towpreg tape from a second spool. The connecting station is designed such that the beginning and the end can be brought essentially parallel to one another, that the adhesive application unit can apply a polymerization adhesive to the beginning and/or the end, and that the pressing device can press the beginning and the end together.

The winding machine is further improved if an additional application unit is present for applying an activator, in particular acetone, to the beginning and/or the end.

Preferably, the adhesive application unit is designed such that it applies the polymerization adhesive as a liquid, in particular by splashing or spraying it on or by applying it as droplets by means of an air stream.

The pressing device preferably comprises a pressing roller and/or a pressing plate. This enables controlled pressing, in particular a pressing plate can be used to achieve a flat pressing. If necessary, a point-like or strip-like pressing is also sufficient.

Alternatively, the pressure can also be applied via air streams onto the Towpreg belts.

It is also advantageous to provide a sensor unit that detects the correct position of the first and second Towpreg belts in the connecting station. This makes it possible to check and ensure that the beginning and end are essentially parallel.

In a further preferred embodiment, a holding device is provided which is intended to fix the beginning of the second Towpreg tape before the polymerization adhesive is applied. In this way, the beginning can be fixed in the appropriate position and aligned essentially parallel to the first Towpreg.

Due to the design of the winding machines according to the invention, the developed method for joining Towpreg tapes during spool changes can be carried out optimally, so that the advantages of the method can be fully utilized.

• 1 Erfindungsgemäße Wickelmaschine mit Verbindungsstation zu Durchführen des erfindungsgemäßen Verfahrens
• 2 Detaildarstellung zum erfindungsgemäßen Verfahren (Draufsicht)
• 3 weitere Detaildarstellung zum erfindungsgemäßen Verfahren (Draufsicht)
• 4a, b noch weitere Detaildarstellungen zum erfindungsgemäßen Verfahren (Seitenansicht)
• 5 Detaildarstellung zum erfindungsgemäßen Verfahren (Rückansicht)

Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. The features mentioned can not only be advantageously implemented in the combination shown, but can also be combined individually with one another. The figures show in detail:

• 1 Winding machine according to the invention with connecting station for carrying out the method according to the invention
• 2 Detailed representation of the method according to the invention (top view)
• 3 Further detailed representation of the method according to the invention (top view)
• 4a , b further detailed representations of the method according to the invention (side view)
• 5 Detailed representation of the method according to the invention (rear view)

The figures are described in more detail below. The same reference numbers denote the same or similar parts or components. The various features of the embodiments shown and described can also be advantageously combined with one another individually.

The 1 shows the winding machine 1 according to the invention. The winding core 4 is driven and its rotation causes the Towpreg tapes 20 to be wound around the winding core 4. The component 9 made of fiber-reinforced plastic - for example a gas tank or a roller shell - is produced by winding various layers onto the winding core 4.

The Towpreg tapes 20, 21 are fiber tapes made of rovings that are already impregnated with matrix material. They are provided on the spools 7. The fiber material is preferably carbon fibers, alternatively other materials can also be used such as glass fibers or basalt fibers. Duromers are used as the matrix material, preferably epoxy resins.

The Towpreg tapes 21 are pulled off the spools 7 and guided to the thread eye 2 via deflection rollers 5, 6. The thread eye 2 in turn comprises deflection rollers 3 and guides the individual Towpreg tapes 21 next to one another to form the Towpreg tape 20, which is laid down on the winding core 4. The thread eye 2 can be tilted about its longitudinal axis so that the Towpreg tapes 20 can be laid down on the winding core 4 at an adjustable angle.

Shortly before the respective first spool 7 is empty, the machine must be stopped and a second spool (not shown separately here) must be provided. Then the beginning of the towpreg tape from the new second spool must be connected to the end of the first towpreg tape 21 so that the towpreg tape from the second spool can be threaded into the winding machine and production can continue.

The winding machine 1 according to the invention is designed in such a way that it can implement the method according to the invention for connecting two Towpreg tapes. For this purpose, it comprises at least one connecting station 10 for this connection, which can connect the two Towpreg tapes to one another when changing the spool. The connecting station 10 has an adhesive application unit 11 and a pressing unit 13. It preferably also comprises a further application unit 12 for applying an activator substance and a holding device 14 for holding at least the beginning of the second Towpreg tape.

2 shows a detailed view of a section to illustrate a variant of the method for joining two Towpreg tapes.

As soon as the spool 7 is almost empty, production is interrupted and the start 24 of the second Towpreg tape 22 is unwound from the second spool 8. Then the end 23 of the first Towpreg tape 21 is brought essentially parallel to the start 24 of the second (new) Towpreg tape 22. In the illustration they are drawn next to each other for clarity, but they are preferably arranged one above the other so that they can be connected to each other flat. Preferably at least the start 24, and possibly also the end 23, is held in position by the holding device 14. In order to detect the correct position of the start 24 and/or end 24, a sensor unit can optionally be present. This is advantageous in particular for the automation of the process and corresponding quality control.

The polymerization adhesive, preferably in the form of a cyanoacrylate adhesive, is then applied to the beginning 24 and/or the end 23 by the adhesive application device 11. The application is preferably carried out in liquid form, for example sprayed or squirted on as droplets. To further improve the process, an activator substance, preferably acetone, for example, can also be applied to the beginning 24 and/or the end 23 using a further application unit 12. This means that the polymerization process is started more quickly or accelerated upon contact by creating so-called carbides.

The pressing device 13 then presses the beginning 24 and the end 23 together. It is advantageous if the pressing is maintained for at least 3 seconds, preferably at least 10 seconds. The pressing does not have to be particularly strong. After this pressing, the connection between the two Towpreg tapes 21, 22 has sufficient tensile strength to continue production, with the second Towpreg 22 being threaded from the second spool 8 into the winding machine. In addition, the connection point is only slightly thicker than the single Towpreg tape and is so flexible that it can be wound into the component 9 without causing quality problems.

In order to avoid disruptions caused by a residual strip of the first Towpreg strip 21 that is too long, the first Towpreg strip 21 is advantageously cut between the first spool 7 and the pressing device 13, for example at the cutting point 17 shown. In this way, only a short residual strip of the first Towpreg strip 21 is wound up.

In 3 Another variant is shown schematically. Here, the gripper(s) 15 are present, which deflect the first Towpreg belt 21 from its normal running direction 25 during operation so that the Towpreg belt 21 is brought into the area of the connecting station 10. This has the advantage that the connecting station 10 can be positioned stationary outside the normal running direction and thus does not interfere with normal operation. The grippers 15 can be part of the holding device 14 or can be provided separately on or next to the connecting station 10.

In the side view of the connection station 10 in 4a ,b shows a variant of the holding device 14 and the pressing device 13 in which these two components are combined. It also shows how several consecutive coil changes can be carried out easily and efficiently.

First, the first bobbin change in 4a The upper reel is the first reel 7, which is almost empty. The beginning 24 of the second Towpreg tape 22 from the second reel 8, which is full, is threaded through and held by the lower holding device 14. After the application of the polymer adhesive and, if necessary, the activator substance, the beginning 24 and end 23 are pressed together by the pressing device 13 and held for a short time. For this purpose, at least one of the shown plates are moved or both plates are moved.

Then the first Towpreg tape 21 is separated between the first reel 7 and the pressing device 13 (separation point 17) and production can continue.

In 4b 1 shows a further subsequent spool change when the lower spool is now almost empty. The lower spool is then the first spool 7 in the sense of the method according to the invention. The upper spool is the second spool 8, which is full and provides the second towpreg band 22. The start 24 is threaded and held in position by the upper holding device 14. The method for joining is then carried out as described above.

In general, as an alternative to the pressing devices 13 shown, which provide one or more pressing plates, the pressing device can also be designed differently. For example, the pressing device 13 can be designed with a pressing roller that presses against a plate or a holding device and is rolled over the connection point. In another design, the pressing device 13 can work with air pressure, so that the beginning 24 and the end 23 are pressed together with the help of air streams.

5 shows a detail with the connection station 10 in rear view to illustrate the application of the adhesive. The beginning 24 and the end 23 are brought essentially parallel to each other. The polymer adhesive is then sprayed onto the beginning 24 and/or the end 23 by the adhesive application unit 11, for example with an air stream. The activator substance can be sprayed on at a different time or at the same time by the additional application unit 12, which can optionally also be designed as a joint application unit with the adhesive application unit 11. To improve the application, this can take place in a type of chamber or with a shield, which are not separately shown here.

The pressing device 13 then presses the end 23 and the beginning 24 together. And the process is continued as described above.

List of reference symbols

1

Winding machine

2

Thread eye

3

Pulleys

4

Winding core

5

Pulleys

6

Pulleys

7

first coil

8th

second coil

9

Component

10

Connection station

11

Adhesive application unit

12

additional order unit

13

Pressing device

14

Holding device

15

Gripper

16

Sensor unit

17

Separation point

20

Towpreg tapes

21

first Towpreg volume

22

second Towpreg volume

23

End of the first Towpreg volume

24

Beginning of the second Towpreg volume

25

Towpreg running direction during operation

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102016122522 A1 [0003]
• WO 2022136812 A1 [0003]
• DE 102022104803 A1 [0007]

Claims (15)

Method for connecting two Towpreg tapes (21, 22) during a spool change in a winding machine (1) for producing a component (9) made of fiber-reinforced plastic by winding Towpreg tapes around a winding core (4), wherein the Towpreg tapes (21, 22) are fiber tapes made of continuous fibers which are already impregnated with matrix material and are provided on spools (7, 8), and wherein the end (23) of a first Towpreg tape (21) from a first spool (7) is connected to the beginning (24) of a second Towpreg tape (22) from a second spool (8), characterized in that the beginning (24) and the end (23) are brought substantially parallel to one another, that a polymerization adhesive is applied to the beginning (24) and/or to the end (23) using an adhesive application unit (11), and that a pressing device (13) presses the beginning (24) and the end (23) together, whereby the two Towpreg bands (21,22) are connected to each other in a tension-resistant manner. Procedure according to Claim 1 characterized in that the polymerization adhesive is a cyanoacrylate adhesive. Procedure according to one of the Claims 1 or 2 characterized in that in addition to the polymerization adhesive, an activator substance, in particular acetone, is applied to the beginning (24) and/or the end (23). Method according to one of the preceding claims, characterized in that the beginning (24) and the end (23) are pressed together for at least 3 seconds, preferably at least 10 seconds, after the application of the polymerization adhesive. Method according to one of the preceding claims, characterized in that the application of the polymerization adhesive and/or the activator substance is carried out by spraying or squirting or as a droplet application with the aid of an air stream directed onto the Towpreg tape(s) (21, 22). Method according to one of the preceding claims, characterized in that the beginning (24) of the second Towpreg tape is fixed to or by a holding device (14) before the application of the polymerization adhesive. Method according to one of the preceding claims, characterized in that the first Towpreg belt (21) is deflected laterally from its normal running direction (25) during operation by means of a gripper before the application of the polymerization adhesive and is thereby brought into an area of the adhesive application unit (11). Method according to one of the preceding claims, characterized in that the relative humidity in the vicinity of the beginning (24) and the end (23) is, in particular maintained or adjusted, between 40% and 80%, preferably between 55% and 70%, at least after the application of the polymerization adhesive. Method according to one of the preceding claims, characterized in that the first Towpreg band (21) is severed after the beginning (24) and the end (23) have been pressed together between the first coil (7) and the pressing device (13). Winding machine (1) for producing a component (9) made of fiber-reinforced plastic by winding Towpreg tapes onto a winding core (4), wherein the Towpreg tapes (21, 22) are fiber tapes made of continuous fibers which are already impregnated with matrix material and are provided on spools (7, 8), characterized in that the winding machine (1) has a connecting station (10) with an adhesive application unit (11) and with a pressing device (13) in which, when changing spools, the end (23) of a first Towpreg tape (21) from a first spool (7) can be connected in a tensile manner to the beginning (24) of a second Towpreg tape (22) from a second spool (8), wherein the connecting station (10) is designed such that the beginning (24) and the end (23) can be brought substantially parallel to one another, such that the adhesive application unit (11) applies a polymerization adhesive to the beginning (24) and/or to the end (23), and that the pressing device (13) can press the beginning (24) and the end (23) together. Winding machine (1) to Claim 10 characterized in that a further application unit (12) is present for applying an activator, in particular acetone, to the beginning (24) and/or the end (23). Winding machine (1) to Claim 10 or 11 characterized in that the adhesive application unit (11) is designed such that it applies the polymerization adhesive as a liquid, in particular by splashing or spraying it on or by applying it as droplets by means of an air stream. Winding machine (1) according to one of the Claims 10 until 12 characterized in that the pressing device (13) comprises a pressing roller and/or a pressing plate. Winding machine (1) according to one of the Claims 10 until 13 characterized in that a sensor unit (16) is present which detects the correct position of the first and second towpreg belts (21,22) in the connecting station (10). Winding machine (1) according to one of the Claims 10 until 14 characterized in that a holding device (13) is provided which is intended to fix the beginning (24) of the second Towpreg tape before the application of the polymerization adhesive takes place.

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