Patent Application
20160368168
The invention relates to a device for separating fibrous material, in particular strand-shaped or tape-shaped fibrous material, into portions, and for depositing the portions, having a separation roller having a plurality of cutters which are disposed on the circumference, a counter roller, and a portion carrier, wherein the separation roller and the counter roller are rotatable in opposite directions and are disposed such that the fibrous material is guided through between the separation roller and the counter roller and thereby may be severed by one of the cutters interacting with the counter roller such that, on account thereof, a portion is created. Separating is performed by cutting or breaking the fibers over an edge. The interaction between the cutter and the counter roller does not necessitate mutual contact.
Rovings, fiber strands, or tapes, in particular fabric tapes, cross-laid structure tapes, or non-woven tapes, for example, may be considered as fibrous material. The fibers for the fibrous material may be carbon fibers, glass fibers, aramid fibers, or other fibers. A fiber strand may be composed of twisted or spun fibers. A fiber strand from numerous fibers which in a non-twisted form are simultaneously unwound from a wound package or a ball, is referred to as a yarn bundle or a roving. The rovings here may be composed of up to a plurality of ten thousand endless individual fibers which are disposed in parallel and which are also referred to as filaments. Such rovings or tapes are used particularly for manufacturing fiber-reinforced plastics components. There is often the necessity for the fibrous material which is available in a more or less endless state to be cut to a certain length. A respective device to this end is described in the publication WO 02/055770 A1. Said device has a separation roller having cutters which are axially disposed on the circumference, and a counter roller. The fibrous material is cut into short pieces and after cutting falls downward out of the device. Attention is paid to configuring the cutting process such that the fiber pieces are constantly cut to the correct length as exactly as possible. It is disadvantageous that the fiber pieces simply fall downward by gravity alone and thus cannot be deposited in a targeted manner. Certain variations in terms of density and alignment cannot be avoided when depositing.
It is now the object of the invention to refine a device of this type or a method of this type, respectively, such that portions may be separated from the fibrous material and be deposited in a better controlled manner with high productivity.
The object is achieved according to the invention by a device according to claim 1. To this end, the device on the counter roller or on the separation roller has a plurality of integrated retaining elements which are configured such that in each case at least one of the retaining elements exerts a retaining force on a respective portion, on account of which the portion may be retained on the roller having the retaining elements and, after severing, may be moved by a distance conjointly with the roller circumference of this roller, and configured such that the respective portion after this conjoint movement may be deposited onto the portion carrier. In this context, integrated means that the retaining elements corotate with the corresponding roller. The retaining elements here differ from the clamping elements known to date, which only press the fibrous material onto the counter roller, so as to be able to better and more accurately cut said fibrous material, but do not retain the fibrous material on the roller by way of a retaining force.
On account of a retaining element which after separating holds the portion on the roller being present, the portion is moved onward in a controlled manner by the rotation of the roller. It is particularly advantageous that, on account thereof, the portion may be moved away from the region of the other roller so far that said portion may be released from the roller and be deposited in a controlled manner onto the portion carrier. Moreover, controlled depositing is improved in that the retaining elements are embodied so as to be displaceable in a substantially radial manner, specifically in such a manner that said retaining elements may move the portion away from the roller circumference for depositing. If and when the substantially radial outward displacement is carried out with a sufficient impulse and is abruptly stopped, the portion may then, on account thereof and counter to the retaining force, be released from the retaining element and be deposited.
On account thereof, the alignment of the portions, which in the case of fiber-reinforced plastics components is particularly decisive, may be accurately established when depositing. In relation to multiaxial depositing robots the device has the advantage of a significantly higher rate of productivity (depositing rate) being possible. A further advantage is that the portions may also be deposited beside one another transversely to the longitudinal direction thereof with the device according to the invention. By virtue of the assembly for separating and controlled deposition, combined in one device, particularly high productivity and at the same time high quality in terms of alignment may be achieved.
A device according to the invention is particularly suitable for manufacturing preforms or semi-finished products for fiber-reinforced plastics components. In particular, tape-shaped semi-finished products, having inter alia fibers which are aligned so as to be transverse to the tape direction, or planar semi-finished products, having for example also non-rectangular contours, may be manufactured particularly readily and rapidly in this way.
Two cutters or two retaining elements, for example, may also constitute a plurality of cutters or a plurality of retaining elements. The separation roller preferably has at least four cutters on the roller circumference, and at least four integrated retaining elements are preferably present on the counter roller or on the separation roller.
The portion carrier may be a conveyor belt or else be a forming tool or a component onto which the portions are directly deposited. The forming tool or the component may be disposed on a traversable X-Y-table, for example, so that the portions are deposited at the desired position. The X-Y-table may also be height adjustable. The portions may likewise be deposited directly onto such a table. The forming tool or the component onto which depositing takes place may also have a three-dimensional surface.
If and when a roving is employed as fibrous material, the former prior to separating is preferably spread such that the fibers lie beside one another and are retained by the retaining element in this position and are subsequently deposited.
The fibrous material is preferably for the largest part or largely completely composed of fibers. Said fibrous material may however readily also contain binder material or matrix material. And the fibrous material may also contain substantial amounts of binder or matrix material, for example when so-called prepregs, in particular thermoplastics prepregs are processed. A prepreg is a fibrous material which has already been impregnated with matrix material which later, after forming, for example, is cured or consolidated.
A plurality of rovings or fiber strands or tapes may likewise be simultaneously infed beside one another, separated and the portions be deposited with the device. In particular, comparatively long portions may also be manufactured and deposited at a high depositing rate with the device according to the invention. Lengths for the portions are preferably between 10 and 300 mm, particularly preferably between 40 and 80 mm. The spacings of the adjacent cutters on the roller circumference of the separation roller have to correspond therewith.
Further advantageous features of the embodiment according to the invention, which improve productivity or controlled depositing are to be found in the dependent claims and in the following description.
In each case one retaining element is preferably provided between two adjacent cutters. In the case of fibers which are somewhat more flexurally rigid, such as carbon fibers or glass fibers, for example, this is sufficient to be able to retain and deposit the portion in a controlled manner. If and when comparatively long portions are to be separated and deposited, or if and when flexurally less rigid fibers are to be processed, two or more retaining elements may also be provided between two adjacent cutters. The cutters on the circumference of the separation roller are preferably disposed in a substantially axial direction.
Vacuum retaining elements are particularly suitable as retaining elements, wherein a vacuum supply which in that circumferential region in which the portion is to be deposited is deactivatable or may be interrupted is provided. The connection of the vacuum retaining elements to the vacuum supply is performed by way of at least one vacuum connector on the vacuum retaining elements. The vacuum retaining elements have a bored or perforated surface, for example, by way of which the portion is suctioned. On account thereof, a retaining force is exerted. If the portion is to be deposited, the vacuum supply may be interrupted or deactivated such that the retaining force is reduced or is entirely cut off. The portion may then be released from the roller in a controlled manner and be deposited.
It is furthermore advantageous for the vacuum supply to be performed by way of a stationary vacuum port which is connected to a negative-pressure source and which is configured such that said vacuum port in that circumferential region in which the portion is to be held connects the vacuum connectors of the respective retaining elements to the vacuum supply, and in that circumferential region in which the portion is to be deposited vacates the vacuum connectors. A particularly simple implementation having a low regulating investment results on account thereof.
It is generally also of advantage for the retaining elements, in particular the vacuum retaining elements, to be embodied such that the portion in that region in which said portion is to be deposited may be blown down by an air stream from the retaining element. To this end, for example, a further connection port which connects the vacuum connectors to a compressed-air source may be provided specifically in that region in which the portion is to be deposited. Alternatively, the retaining elements may also be embodied as electrostatic retaining elements or as mechanical retaining elements. The electrostatic charge may likewise be readily produced and discharged again, so that the retaining force for depositing is reduced or cut off. The mechanical embodiment may have movable clamps or retaining brackets or needles, for example. Deactivation of the retaining force in this case may be performed by moving away, rotating, or retracting the clamps, retaining brackets, or needles.
The radial movement of the retaining elements during rotation of the rollers is controlled in a particularly simple and effective manner by way of a gate-type guide, in particular in such a manner that the gate-type guide in that circumferential region in which the portion is to be deposited has a substantially radially outward increment.
Moreover, one or a plurality of sprung elements which urge the retaining elements in a substantially radial manner outward up to a stop edge may be provided. An impulse for releasing the portion may be, for example, produced in this way, in particular in combination with a gate-type guide which forms the stop edge and which has an outward increment.
The angle along the roller circumference between that point at which the cutter can sever the fibrous material up to that point at which the portion is deposited is preferably between 20° and 180°, and particularly preferably between 45° and 135°. On account thereof, the portion is sufficiently far from the other roller and may be disposed without interference and in a well-controlled manner. In one preferred embodiment, the two axes of the rollers are horizontal, and the portion carrier by way of the depositing face thereof is also aligned so as to be substantially horizontal. The angle mentioned above then is embodied so large that the portion after cutting is conjointly moved until said portion is aligned in a substantially horizontal manner, being deposited only then. Particularly controlled depositing is possible by depositing at an alignment which is substantially horizontal.
The accuracy of depositing is also improved in that the arrangement of the portion carrier is chosen such that the minimum spacing (d) between the retaining element and the portion carrier when depositing is between 0 and 70 mm, preferably between 0 and 10 mm. By way of such a minor spacing across which the portion falls onto the portion carrier or is transferred thereto it is ensured that the desired orientation is maintained. A spacing of 0 mm means that the retaining element when depositing urges the portion onto the portion carrier. The intensity of the contact pressure, or the slightness thereof, may be chosen depending on the application. Spreading of the individual fibers of the portion in relation to one another may be produced in this way if and when the portion is urged onto the portion carrier with a comparatively great force. In the case of a spacing of more than 0 mm any deformation of the portion carrier is avoided which may be of advantage in particular when depositing onto forming tools or components.
In order for the portion after depositing to be fixed in the alignment thereof it may be of advantage for the portion carrier to be configured as a vacuum conveyor belt. If and when the vacuum conveyor belt is disposed such that the former may transport the portions after depositing in a manner substantially transverse to the longitudinal direction of said portions, preferably at an angle in relation to the longitudinal direction thereof of 60° to 90°, particularly preferably at an angle of in relation to the longitudinal direction thereof of 80° to 90°, tapes may be produced having portions which are aligned so as to be transverse to the longitudinal direction of the tapes. The longitudinal direction of the portion is the longitudinal direction of the fibrous material in correspondence with which, the latter is infed to the device.
However, transportation of the deposited portions may also be performed at an angle of 0° or at any other angle in relation to the longitudinal direction.
In terms of the method for separating fibrous material, in particular strand-shaped or tape-shaped fibrous material, into portions, and for depositing the portions, the object according to the invention is achieved by a method as claimed in claim 11. To this end, a device according to the invention is used, and the following steps are sequentially carried out:
a) separating a portion from the fibrous material;
b) retaining the portion on the counter roller or on the separation roller, and moving the portion conjointly with the roller circumference of this roller;
c) depositing the portion on a portion carrier.
The retaining element shortly prior to the separation procedure here may advantageously also exert a retaining force on that part of the fibrous material that will be separated. The sequence of separating, retaining and moving onward, and depositing is performed sequentially for a plurality of portions, so as correspond to the rotation of the rollers and of the spacing of the cutters in a temporally offset manner. Continuous production is achieved in this way.
Depositing may be particularly well checked if and when the portion, from that point at which said portion is separated from the fibrous material up to that point at which said portion is deposited, is moved conjointly with the roller circumference across an angle between 20° and 180°, preferably between 45° and 135°. To be moved conjointly with the roller circumference means that the portion is moved conjointly so as to correspond to the rotation of the roller; for this, said portion need not fully bear on the roller circumference. It suffices for said portion to be adequately fixed by the retaining force by way of a retaining element such that said portion is conjointly moved.
In order for the portion to be reliably released from the retaining element, an impulse in the outward radial direction may be exerted on the portion between steps b) and c). This impulse may be introduced by way of sprung elements, for example, which urge the retaining elements outward. The impulse may also be utilized for transferring the portion across a certain spacing between the retaining element and the portion carrier onto the latter.
A further variant for exerting a retaining force on the portion is the application of binder material onto one or a plurality of retaining elements before the latter come into contact with the portion. A binder application device may be used to this end. An adhesive or a thermoplastics material or a matrix material are to be considered as binder material, for example. A matrix material may be a duromer plastics or a thermoplastics material, such as is used for manufacturing fiber-reinforced plastics components. The binder material may be applied as a solution or as a melt or as a resin or as a powder. Activating the binder may, for example, optionally be performed by heating prior to the portion coming into contact with the retaining element. The retaining force is produced by way of adhesion and may be controlled by way of the amount of the binder material or by way of the type of activation, for example. An outwardly directed impulse or blowing down may be utilized in order for the portion to be released and to be deposited in a controlled manner. The binder material which is present and which remains on the portion may be utilized for fixing the portion after the latter has been deposited.
It may furthermore be advantageous to provide a binder application installation which applies binder material (as mentioned above) onto the portions, after the latter have been deposited onto the portion carriers. The deposited portions may thus be interconnected to form a tape or a planar semi-finished product, for example. The arrangement and the alignment of the portions is fixed with a view to further processing. On account thereof, the deposited portions may also be connected to a layer of fibrous material that has already been deposited, or be connected to another base material.
In particular in order to be able to manufacture tapes having a fiber orientation which is transverse to the longitudinal tape direction thereof, it is of advantage for the portions after the latter have been deposited onto the portion carrier to be transported away in a manner substantially perpendicular to the longitudinal direction of said portions, preferably at an angle in relation to the longitudinal direction thereof of 60° to 90°, particularly preferably at an angle in relation to the longitudinal direction thereof of 80° to 90°. In the case of rovings the fiber direction and the longitudinal direction of the portion are identical.
Further advantageous features of the invention will be explained by means of exemplary embodiments with reference to the drawings. The mentioned features may not only be advantageously implemented in the combination illustrated but may also be individually combined with one another. In the drawings:
The figures will be described in more detail hereunder.
A more detailed illustration of an embodiment according to the invention can be seen in
A device as in
The gate-type guide 36 may be present on one side or preferably on the front and rear side of the device. Tilting of the retaining elements 27 is reliably avoided by way of an embodiment on both sides.
The device according to the invention in
In one further advantageous embodiment a device according to the invention may be configured such that the length of the portions may be modified during operation. This may be performed in that the roving 21 by way of a slowing of the cycle in relation to that of the counter roller 23 and of the separation roller 24 is retracted after a portion 22 has been cut. That is to say that the portion, on account thereof, becomes somewhat shorter than the spacing between the cutters 26. In order for the retraction to be produced, the contact roller 40 may run at a slower cycle or be decelerated, for example, so that the roving 21 is provided with slippage in relation to the counter roller 23. However, the modification of the portion length is also possible without a contact roller in the case of the other embodiments according to the invention in that the tape tension of the roving is increased by way of other means such that said roving is held back in relation to the counter roller and to the separation roller.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 224 835.0 | Dec 2013 | DE | national |
| 10 2014 221 085.2 | Oct 2014 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/076070 | 12/1/2014 | WO | 00 |
