Patent Publication Number: US-2018043563-A1

Title: Cutting Unit Comprising a Blade For Cutting at Least One Fiber, Particularly For Producing Fiber Preforms

Description:
The invention relates to a cutting unit comprising a blade for cutting at least one fiber, in particular for producing fiber preforms which provide, in particular, a preliminary stage in the production of fiber-reinforced plastics material components. In addition, the invention relates to a device for producing fiber preforms which provide, in particular, a preliminary stage in the production of fiber-reinforced plastics material components. 
     DE 10 2011 007 018 A1 describes in a preferred technical area a device for producing fiber preforms which provide, in particular, a preliminary stage in the production of fiber-reinforced plastics material components. A cutting device is named for cutting off fibers. 
     When cutting fibers, in particular fiber bands, as a rule cutting systems where the cutting unit cuts fibers according to a scissor principle are used. In addition, there are systems comprising a cutting unit which carries out the cutting using knives which are fastened on a roller and penetrate into a soft counter roller. If a repeated cutting operation is required, where it is necessary to open the cutting unit wide between cutting operations, e.g. to reach through for transporting a fiber material, the existing systems can only be used in a limited manner. In particular, where there is very little installation space available, it is technically very expensive to design conventional cutting systems in such a way that a cutting unit, in particular the blade thereof, is able to be opened in a sufficiently wide manner. 
     Consequently, it is the object of the invention to provide a modified cutting unit which, in particular with simple kinematics, enables a reliable cutting operation and a sufficiently large opening. A device for producing fiber preforms with a modified cutting unit is also to be provided. 
     The solution according to the invention is characterized by the features of claim  1  or  11 . Advantageous designs are reproduced in the subclaims. 
     Preferred is, accordingly, a cutting unit comprising a blade for cutting at least one fiber in particular on a cutting base, in particular for producing fiber preforms which provide, in particular, a preliminary stage in the production of fiber-reinforced plastics material components, wherein a guide device is arranged to guide at least either of the blade or a cutting base, which is movable relative to the blade, along a linear path for cutting. 
     A first variant consequently provides guiding the blade along a linear path for cutting the fiber, wherein the fiber is pressed against a cutting base during the cutting operation or, where a cutting base is not used, the fiber is tensioned in this case by means of the blade. A second variant provides that the blade is arranged, in particular, in a fixed manner and a cutting base for cutting the fiber is guided along a linear path toward the blade. According to a third variant, both the blade and a cutting base are guided along a linear path toward one another and against one another for cutting the fiber. 
     In particular, consequently one of the two components—blade and cutting base—is arranged in a fixed manner or both components are consequently moved along a common path. 
     The cutting unit is designed in a preferred manner for cutting reinforcement fibers for producing fiber-reinforced plastics material components or corresponding preforms, i.e. preliminary forms produced from a fiber composite material. 
     An advantage compared to scissors or cutting rollers is that as a result of the blade being guided in a linear or straight-lined manner, fibers which are arranged in particular side by side are not displaced sideways. The precise positioning of the fibers is very important to the strength of CFRP components (CFRP: carbon fiber reinforced plastic) and is advantageously made possible. 
     Guiding the blade in a linear manner additionally enables a cutting unit which only requires a small amount of space and is thus usable in particular for cutting reinforcement fibers in an advantageous manner in a device for producing fiber-reinforced plastics material components or corresponding preforms, in particular semi-finished fiber products. Guiding in a linear manner also allows for a large space between blade and cutting base for picking up the fibers or a band. The necessary installation space for such a cutting unit is additionally extremely small with reference to an achievable cutting force. 
     Fibers are also to be understood here, in particular, as multiple fibers which are arranged adjacent one another, fiber bands which comprise fibers and fiber materials. In particular, fibers are also to be understood here as yarns and so-called rovings, i.e. a strand, bundle or multi-filament yarn produced from filaments or continuous fibers arranged in parallel. Fibers are also to be understood in this case as semi-finished products, thermoplastic or thermosetting prepegs. The cutting or severing method or a corresponding cutting unit can also be used in particular in a roving applicator. 
     A preferred further development consists in that the linear path leads in a direction at least substantially transversely to an extension of the cutting base or to a cutting edge of the blade. 
     In particular, the cutting edge extends in such a manner transversely or substantially transversely to the linear path that the cutting edge is pressed with its longitudinal extension through the fibers and against and/or into the cutting base. 
     In particular, the linear path extends at least substantially perpendicularly to a plane spanned by the cutting base. The severing or cutting edge of the blade is guided up to the fiber in such a manner for cutting, in particular transversely or perpendicularly to the longitudinal extension of a fiber to be cut through as a result of the cutting process. In the event of a fiber arranged horizontally on the cutting base, the blade is consequently pressed from above or below against the fiber. 
     At least substantially transversely means that not only guiding transversely to the cutting base but, where applicable, also a deviation of a few angular degrees, in particular up to 5°, in particular up to 10° is tolerable. A more inclined portion of the band is advantageous with reference to wastage. A more inclined cut from above or in the cut longitudinal direction with such a tolerance can be advantageous technically for reasons of installation space. 
     A preferred further development consists in that the cutting base is realized from a soft material or at least comprises a soft surface. 
     The opposite side of the blade consequently provides a soft cutting base, e.g. a PU material (PU: polyurethane). A soft or yielding surface enables a cutting principle with the blade on a soft cutting base, wherein the blade or the cutting edge thereof consists of a material that is rigid relative to the base. This results, when the blade is pressed onto the fiber, in filaments of the fiber to be cut through breaking and thus enables effective and reliable cutting which is sufficiently tolerant in particular also in the case of a blunt blade. 
     A preferred further development consists in that the blade and/or the cutting base is fixed so as to be adjustable in relation to a fastening point by means of a drive arrangement and the guide device guides a component of the drive arrangement, which is adjustable between the fastening point and the blade and/or the cutting base, in such a manner along a guide path with a predetermined path progression that the blade and/or the cutting base is adjustable only along the linear path. 
     A fastening point, in this case, is, for example, a frame of a device in which the cutting unit is inserted, in particular a fixed component part of a device for the production of fiber reinforced plastics material components or corresponding preforms. The adjustable component is, in particular, a rigid linkage element which drives the blade, a further joint which is adjustable relative to the fastening point or the blade or a blade mounting. 
     The guide path can have a linear progression when, for example, the blade or a joint on the blade or the blade mounting thereof is guided by the guide device. In particular, in such a case the guide path and the linear path can coincide. The guide path, however, can also have a non-linear, for example arcuate progression when, for example, an adjustable component, which is at a spacing from the joint on the blade, is guided by the guide device. 
     A preferred further development consists in that the adjustable component is a component part of a lever arrangement, in particular a toggle lever arrangement. 
     A lever arrangement provides a redirection of force as indirect drive means and thus enables a particularly small requirement for installation space. A lever arrangement preferred for this comprises a linkage and joint arrangement produced from rigid linkage elements and joints which connect them, at least one linkage element or joint realizing the adjustable component. The in particular two linkage elements are connected together in an articulated manner by a joint. A drive, for example a cylinder drive, for example a pneumatic cylinder is arranged on, in particular, one of the joints such that the components of the toggle lever arrangement are adjustable relative to one another by means of the drive. In the case of a toggle lever arrangement preferred for this, one joint is fastened on a fastening point and one joint is assigned to the blade, in particular is fastened in an articulated manner on the blade or on a blade mounting. 
     The guide device, in this case, is, for example, a guide unit with a guide path which guides one of the joints or the blade or the blade mounting thereof along a predetermined path progression. Where there is, in particular, lateral guiding of the joint on the blade, of the blade or of the blade mounting, the guide path runs, in particular, in a linear manner in order to bring about a linear blade path. Where there is, in particular, lateral guiding of a joint which is arranged between linkage elements, in a preferred manner the guide path runs in a non-linear manner in order to bring about a linear blade path. 
     In particular, such a toggle lever principle enables a very compact and easy method of construction with reference to the achievable cutting force. Thus, in a particularly preferred manner, an opening movement can be carried out quickly and with little expenditure of force, whilst a cutting movement can be carried out slowly with a high level of expenditure of force. 
     In particular, attaching the blade in a central and pivotably mounted manner enables the cutting forces of the blade to be distributed uniformly onto the cutting base. Even when the base deflects slightly, for example on account of limited rigidity, a cut that is more reliable is made possible. This additionally keeps any tolerance demand on a guide or the guide device very small. 
     A preferred further development consists in that the adjustable component is a drive element, which is adjustable in relation to the fastening point, of a drive which drives the blade and/or the cutting base directly in relation to the fastening point. 
     Such a drive is, for example, a drive cylinder or motor fastened on an, in particular, fixed frame of the cutting unit, for example a crank mechanism, the drive cylinder or motor being fastened, for example, directly by means of its adjustable drive element or by means of a joint to the blade or the blade mounting thereof. 
     The guide device, in this case, is, for example, once again a drive unit with a drive path which guides either the joint or the blade or the blade mounting thereof along a predetermined path progression. In the event of a cylinder which directly drives the blade with its piston linkage, the guide device is realizable as an option by the cylinder arrangement itself. 
     A preferred further development consists in that the blade and/or the cutting base is adjustable by means of a momentum drive device. 
     A momentum drive device is, for example, a crank mechanism or a different drive comprising, between the same and the blade, a gear unit or pivotably connected linkage in a design which accelerates the blade during the movement for cutting. The blade is accelerated and cuts off the fiber as a result of such a momentum principle. 
     A preferred further development consists in that the blade and/or the cutting base is adjustable by means of a pulse drive device. 
     A pulse drive device is, for example, a drive comprising, between the same and the blade, a gear unit or pivotably connected linkage in a design which deposits the blade on the material during the movement for cutting and cuts the fiber as a result of a pulse or impact acting on the blade. 
     A preferred further development consists in that a holding device is arranged on the cutting unit, in particular on a component adjusting the blade and/or the cutting base, for holding a fiber to be cut through adjacent to the blade and/or the cutting base during cutting. 
     As a result, the fiber can be held in particular behind the cutting unit during the cutting operation. This is designable in particular by a gripper in addition to the gripper holding the fiber or by a combined mechanism which is connected to the cutting unit. In particular, such a mechanism can comprise a spring-loaded holding-down device as the holding element. 
     A preferred further development consists in that a holding device is arranged on the cutting unit to hold a fiber to be cut through in a defined position during cutting and after cutting. 
     The defined position serves for the purpose of holding the fiber in a defined position during an in particular subsequent pick-up operation. To this end, as the holding device, in particular restoring elements such as, for example, thin spring plates can be used as the holding element in the cutting unit or adjacent to the same. In particular, the holding device fixes the fibers in the defined position on the cutting base or on a component adjacent to the same. 
     In particular, the above statements regarding an adjustable blade also apply correspondingly to an accordingly adjustable cutting base. 
     Preferred is additionally a device for producing fiber preforms which provide, in particular, a preliminary stage in the production of fiber-reinforced plastics material components, wherein the device comprises at least one unwinding station and at least one yarn transfer point for the provision of at least one fiber, and at least one gripper which can grip individual or multiple fibers at its beginning, and at least one cutting device for cutting the at least one fiber, wherein the at least one cutting device is or comprises at least one cutting unit. 
     In a preferred manner, the cutting units are arranged between the gripper and the receiving table or mold in devices for producing fiber preforms. 
     A preferred further development consists in that the device comprises multiple such unwinding stations for the provision of multiple fibers, in particular yarns or rovings, and multiple grippers which in each case can grip individual or multiple yarns or rovings at their beginning, wherein each gripper is movable to and fro along a path between a maximum position and a pick-up position, wherein the pick-up position is provided at a yarn transfer point and is closer to the unwinding station than the maximum position, wherein each gripper has an own maximum position and is assigned to an own yarn transfer point and wherein the grippers are each movable individually along paths which are substantially parallel to one another. 
     In a particularly preferred manner, one or multiple such cutting units will be or are used in a device, as is described, for example, in DE 10 2011 007 018 A1. The cutting device thereof, in this case, is realized by one or multiple such cutting units. 
     A preferred further development consists in that the at least one cutting unit for cutting the at least one fiber, yarns or rovings is arranged between a mold and the at least one gripper and/or the at least one cutting unit for cutting the at least one fiber, yarns or rovings is arranged between a mold and the at least one yarn transfer point. 
     Other drive forms which are operated, for example, hydraulically, electrically or electromagnetically can also be used as drive means along with the pneumatic cylinders named as an example. 
     Such a cutting unit or a device with such a cutting unit is advantageous compared to the scissor principle as a result of the considerably smaller installation space and as a result of the cut transversely through the fiber against the cutting base, which avoids displacing and, where applicable, compressing fibers that are adjacent one another. Compared to the scissor principle of a guillotine, the requirements for guiding the cuts are very minimal as a cutting gap, which would not be tolerable in the case of fiber material, is avoided. A cutting unit which is light and of a size that is dimensioned in a structurally compact manner is accordingly produced as a result. 
    
    
     
       The solution according to the invention is explained below by way of figures, in which in detail: 
         FIG. 1  shows a partially sectioned view of a schematically simplified representation of the basic structure of a cutting unit for cutting a fiber during a first operating position, 
         FIG. 2  shows a further side view compared to  FIG. 1  of the basic structure during a second operating position, 
         FIG. 3  shows a side view of a schematically simplified representation of a basic structure of a device for producing fiber preforms, which provide, in particular, a preliminary stage in the production of fiber-reinforced plastics material components, 
         FIG. 4  shows a top view of the basic structure of the device from  FIG. 3 , 
         FIG. 5  shows a partially sectioned view of a schematically simplified representation of a basic structure, modified in relation to  FIG. 1 , of a cutting unit for cutting a fiber during a first operating position and 
         FIG. 6  shows a schematized representation of a detail of a basic structure according to  FIG. 2  with a modified cutting base. 
     
    
    
       FIGS. 1 and 2  show a cutting unit  1  with a blade  2  for cutting a fiber  3  or a plurality of such fibers  3 .  FIG. 1  shows a first operating position prior to cutting with the blade  2  above the fiber  3 .  FIG. 2  shows a second operating position during or after cutting with the blade  2  in the fiber  3 . 
     A cutting base  4  is arranged underneath the blade  2 . The cutting base  4  extends in a plane which is arranged parallel or substantially parallel to a cutting edge of the blade  2 . The blade  2  is arranged so as to be adjustable along a linear path b for cutting through the fibers  3 . The linear path b runs transversely or substantially transversely to the longitudinal extension of the cutting edge or perpendicularly or substantially perpendicularly to the extension of the plane of the cutting base  4 . 
     The cutting unit  1  comprises a fastening point  8 , in particular a fixed point which is stationary in relation to the cutting base  4  and/or in relation to a frame. The blade  2  is mounted so as to be adjustable in relation to the fastening point  8  by means of a drive arrangement. 
     A lever arrangement, in particular a toggle lever arrangement  6 , is shown as an example of a drive arrangement. It consists of a joint  7 , by means of which a linkage element  11  is pivotably connected to the fastening point  8 . A further linkage element  10  is pivotably connected to the oppositely situated end of the linkage element  11  by means of a further joint  12 . The blade  2  is pivotably connected to the oppositely situated end of the further linkage element  10  by means of yet another joint  9 . 
     A guide device  5  is arranged in such a manner on the cutting unit  1  in the region of the drive arrangement that an adjustment of the components of the drive arrangement, that is to say, in particular, of the joints  7 ,  9 ,  12  and of the linkage elements  10 ,  11 , is possible only such that the blade  2  is adjustable in particular only along the linear path b. 
     In the case of the toggle lever arrangement  6  shown, the guide device  5  comprises a guide path which, for example, guides a bolt which protrudes laterally in the region of the central joint  12 . The guide path comprises, in this case, a non-linear, in particular arcuate progression. 
     The cutting unit  1  additionally comprises a drive  13  which is realized, for example, as a pneumatic cylinder. A linkage  14 , which is adjustably drivable by means of the drive  13 , is connected to the central joint  12  in such a manner that, by means of the drive  13 , the blade  2  with its cutting edge is adjustable in the direction of the cutting base  4  or in the opposite direction via the toggle lever arrangement  6 . 
     In a particularly preferred manner, by means of the toggle lever principle, an opening movement can be carried out quickly and with little force expended, whilst a cutting movement can be carried out slowly and with a large amount of force expended. According to a preferred method of control, the drive  13  is actuated correspondingly in such a manner that an opening movement, that is to say an adjustment of the blade  2  away from the cutting base  4 , is actuated quickly, whilst a cutting movement in the opposite direction is actuated slowly. 
     A gripper  16  serves for transporting the fibers  3 . 
       FIG. 2  additionally shows a yarn pick-up point  15  which comprises, in particular, an unwinding station and a yarn transfer point for providing at least one such fiber  3 . The gripper  16 , which is adjustable in and counter the direction to the yarn pick-up point  15  and is realized to receive at least one fiber  3  at the yarn transfer point and to pull it over an operating region, is outlined situated opposite. In this case, the cutting unit  1  is situated in such a manner over the operating region that the at least one fiber  3  can be cut through by means of the blade  2 . 
     A holding device  17 , which is designed to hold the fiber  3  adjacent the blade  2  during the cutting-through process by way of a holding element  18 , is additionally outlined. A further position of the holding device  17  as an example is outlined by a dotted line. As an example, the holding element  18  is connected by means of an, in particular, elastic connecting mechanism  19  to a component which adjusts the blade  2 . Before the blade  2  reaches the fiber  3 , the holding element  18  clamps the fiber  3  against the cutting base  4 . On account of the elasticity of the connecting mechanism  19 , the blade  2  can be adjusted further in the direction of the cutting base  4  in order to cut through the fiber  3 . 
     In a preferred manner, the cutting base  4  is realized from a soft or elastic material and enables the cutting edge of the blade  2  to press-in the surface of the cutting base  4  somewhat or to penetrate somewhat into the surface of the cutting base  4 . 
     A further holding device  20 , which holds the at least one fiber  3  in particular adjacent to the yarn pick-up point  15  for a pick-up operation, is additionally outlined. A holding element  21  is fastened by means of an, in particular, elastic connecting mechanism  22  on or opposite the operating region and/or the cutting base  4  in such a manner that the at least one fiber  3  is able to be held sufficiently firmly. 
       FIGS. 3 and 4  show a device  30  for producing fiber preforms which, in particular, provide a preliminary stage in the production of fiber-reinforced plastics material components, according to 10 2011 007 018 A1. Insofar as components and functions which are described in  FIG. 1 or 2  are used, in particular also by way of reference symbols, corresponding statements with regard to the components and functions are applicable in  FIGS. 3 and 4 . 
     The fibers  3 , in particular yarns or rovings, are provided by means of a plurality of unwinding stations  31 , in which the fiber material is provided in the form of spools or balls of yarn (so-called bobbins). The unwinding stations  31  are arranged in several rows side by side, one behind another or one above another. The beginnings of the fibers  3  are shown schematically only in the region in use in each case for the unwinding stations  31  in use. All these other beginnings of fibers  3  are threaded to corresponding yarn transfer points  32  such that they can be grasped by the associated grippers  16  in assigned pick-up positions. Such an arrangement is designated together as a creel. 
     On the other side, the grippers  16 , apart from one gripper  16 , are shown in their maximum positions, which, in this case, also correspond to the start positions. Even if only grippers  16  of identical widths are shown, grippers  16  with different widths which can grip, in particular, a correspondingly other number of fibers  3 , are also possible. The grippers  16  do not necessarily also have to have their maximum and pick-up positions in a line. In addition, a first mold  33  is shown on a table, in particular a lifting table  34 , and a second mold  35 , which is realized as a hood, is shown in the removal position, that is to say outside the path of the grippers  16 . The second mold  35  is not shown in  FIG. 4 . A corresponding moving or lowering device for the second mold  35  is not shown either. In addition, there is a binder material supply  36 , which is arranged, for example, between the rows of unwinding stations  31 . 
     One of the grippers  16  is situated in the pick-up position and fetches the fibers  3  corresponding to its arrangement in the device by gripping the beginnings thereof. The gripper  16  is displaceable by means of a guide device  37 , for example a linkage or a piston. The grippers  16  are moveable individually between the pick-up position and the maximum position, but in particularly only linearly and side by side along parallel paths. This enables simple automation and quick parallel movement. As shown, multiple unwinding stations  31  can be combined to form a group and can be assigned to one gripper  16 . In a preferred manner, there are at least as many unwinding stations  31  as grippers  16 . 
     Binder material  18 , for example in the form of binder fibers or binder non-woven fabrics, can also be clamped by the gripper  16  together with the fibers  3 , in particular yarns or rovings. 
     The device is shown after a first draping stage of a first layer produced from fibers  3  or yarns or rovings. The first mold  33  has been moved into the draping position by the lifting table  34 . As a result, the fibers  3  are deflected and draped over the mold  33 . The gripper  16  fixes the beginnings of the fibers  3  close to the outside contour of the mold  33 . After said stage, as an alternative to this or in addition to it, binder material can be applied or sprayed onto the fibers  3 . In the next stage, the fibers  3  are draped further or shaped by means of the second mold  35 , which has been moved into its draping position. Precise shaping is possible as a result of the interaction between the two molds  33 ,  35  between which the layer of fibers  3  is situated. 
     At the same time as or after fixing, the fibers  3  are cut on both sides of the molds by means of a cutting device, that is to say between gripper  16  and mold  33  or  35  and between yarn transfer points  32  and mold  33  or  35 . In one embodiment, the cutting device can be connected to the first or second mold. It is advantageous when the cut is effected close to the mold  33  at least on the side of the yarn transfer points  32 . As a result, little wastage of expensive fiber material occurs and less post-processing of the fiber preform is necessary. 
     As an example, two cutting units  1 , described here, in particular according to  FIGS. 1 and 2 , are used as cutting devices in said device  30 . The cutting unit outlined on the left-hand side of the cutting units  1  is fastened, for example, on the lifting table  34 . The cutting unit outlined on the right-hand side of the cutting units  1  is fastened, for example, on the upper mold  35 . A large opening width w or lift height between the blade  2  and the cutting base  4 , with the cutting unit  1  having at the same time a small lateral extension and a small installation height, can be seen in  FIG. 3 . 
     The cut fibers  3  can be pulled back again and wound by means of a rewinding device or can be stored temporarily by means of corresponding yarn guiding. The rewinding is effected such that once again beginnings of the fibers  3  lie in the region of the yarn transfer points  32  such that they are able to be picked up by the grippers  16  without there being too much wastage material. It is possible to use sensors for detecting the beginnings. The holding device  20  for the pick-up operation from  FIGS. 1 and 2  can also be used in place of or in addition to such rewinding devices. 
     Using such a device, it is also possible to carry out, in particular, a method for producing fiber preforms, which, for example, provide a preliminary stage in the production of fiber-reinforced plastics material components, said method comprising the following method stages: tensioning fibers  3 , in particular yarns or rovings, draping the fibers  3  over a mold  33 , fixing the draped fibers  3  to form a fiber preform, wherein multiple separate grippers  16  at multiple yarn transfer points  32 , assigned in each case to the individual grippers  16 , grip individual or multiple fibers  3 , wherein the grippers  16  are then moved toward one another along substantially parallel paths and wherein, as a result, the fibers  3  are clamped side by side. Once the fibers  3  have been fixed by means of a further mold  35  placed thereon, the laterally protruding fibers  3  between mold  33  or  35  and gripper  16  and/or between mold  33  or  35  and yarn transfer point  32  are cut through. 
     A modification as an example provides that the guide device  5  is set up in a fixed manner in the arrangement and the blade is set up guided in a positively guided manner. Fixed guiding of the joint  12  in the guide path  5  is sufficient in such a case. Components arranged above this in the drawing in  FIG. 1 , such as the fastening point  8 , the linkage  11  and the joint  7 , can be omitted. Further modifications can provide a different component or another two different components as fixed fastening points. 
     According to various designs, only the cutting base is moved toward the fiber and the blade or only the blade is moved toward the fiber or both, i.e. blade and cutting base, are moved toward one another and in this case, both are also moved toward the fiber that is located in between. 
       FIG. 5  shows a partially sectioned view of a schematized simplified representation of a basic structure, modified in relation to  FIG. 1 , of a cutting unit  1 * for cutting a fiber during a first operating position. In particular, differences compared to  FIG. 1  will be described below with reference to the statements concerning  FIG. 1 . 
     As an example, the drive  13  and the guide device  5  are arranged in a fixed manner in the overall arrangement. The blade  2  is guided in a positively guided guide  38 . 
     The components arranged on the other side of the joint  12  when seen from the blade  2 , such as the fastening point  8 , the linkage  11  and the joint  7 , are arranged with a further linkage  39  for adjusting the cutting base  4  such that the blade  2  and the cutting base  4  are moved along the linear path b in a reciprocal manner, i.e. toward one another or away from one another. Moved along the linear path b is to be understood in this case once again as the blade  2  with its cutting edge being guided so as to be movable transversely or substantially transversely to the fiber  3  and the cutting base  4  with its extension parallel in particular to the cutting edge of the blade  2  being guided so as to be movable transversely or substantially transversely to the fiber  3 . 
     The linkage  39  is fastened on the joint  7  for example and extends along or implicitly also parallel to the linear path b to the cutting base  4 , on which the linkage  39  is fixedly or pivotably fastened by way of, in particular, its oppositely situated end. In a preferred manner, in this case, the joint  37  or the cutting base  4  is guided in a further guide  38 , the guide  38  guiding the further linkage  39  and/or the cutting base  4  along the linear path b. 
       FIG. 6  shows a schematized representation of a detail of a basic structure according to  FIG. 2  with a modified cutting base  4 . A recess  40  is realized in the cutting base  4 . The recess  40  leads into the cutting base  4  in the region in which the blade  2  contacts the upper plane of the cutting base  4  when cutting. 
     In order to be able to cut through the fiber  3 , two holding elements  18 , in particular, are arranged for tensioning the fiber  3  against a surface of the cutting base  4  adjacent to the recess  40 . In particular, such holding elements  18  are connected elastically to the blade  2  by means of one or in each case one holding device  17  or are connected to the blade  2  by means of one or in each case one, in particular, elastic connecting mechanism  19 . The blade  2  is guidable through the fiber  3  between the holding elements  18 . 
     Further modifications provide, in particular, combinations of the design elements alternatively described above. Thus, for example, the holding devices can be arranged alternatively or additionally on the cutting base which is adjustable, in particular, along the path. 
     LIST OF REFERENCES 
     
         
           1 ;  1 * Cutting unit 
           2  Blade 
           3  Fiber 
           4  Cutting base 
           5  Guide device 
           6  Drive arrangement, in particular toggle lever arrangement 
           7  Joint 
           8  Fastening point 
           9  Joint 
           10  Linkage 
           11  Linkage 
           12  Joint 
           13  Drive 
           14  Linkage 
           15  Yarn pick-up point, in particular unwinding station 
           16  Gripper, adjustably drivable 
           17  Holding device 
           18  Holding element 
           19  Connecting mechanism 
           20  Holding device 
           21  Holding element 
           22  Connecting mechanism 
           30  Device for producing fiber preforms 
           31  Unwinding stations 
           32  Yarn transfer points 
           33  First mold 
           34  Lifting table 
           36  Binder material supply 
           37  Guide device 
           38  Guides 
           39  Linkage on cutting base 
           40  Recess 
         b Linear path 
         w Opening width or lifting height of the blade