Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    Field of the Invention 
         [0002]    This invention relates to a coextrusion adapter, such as for an extrusion system equipped with a plurality of extruders and a die that is fed by them in order to produce a coextrusion composite out of a thermoplastic material. Such a coextrusion adapter includes a central conduit having an inlet end for connecting to an extruder and an outlet end for connecting to the die as well as bottom and top walls that define the height of the central conduit and side walls that define the width of the central conduit. The coextrusion adapter also includes at least one coextrusion conduit having an inlet end and an outlet end. The inlet end can be respectively connected to another extruder and the outlet end feeds into the central conduit downstream of the inlet end of the central conduit and adjusting devices are provided and allocated to each outlet end of the at least one coextrusion conduit and are composed of a plurality of adjusting elements, which collectively extend across the width of the outlet end and by actuating drives, are adjustable independently of one another so that it is possible to change the inner width of the respective width section of the outlet end. 
         [0003]    Discussion of Related Art 
         [0004]    Coextrusion adapters of this kind are used for bringing together melt strands composed of a thermoplastic material coming from a plurality of extruders, for example when producing films, plates, and boards. In this context, the individual melts of thermoplastic materials prepared by the extruders are conveyed against one another in the desired layer position in the coextrusion adapter and then together, are conveyed to the extrusion die for the production of the coextrusion composite. 
         [0005]    In the layering of different plastics onto one another inside the coextrusion adapter, as is frequently the intended use in practice, it is necessary to compensate for different properties of the plastics, in particular different viscosities or also deviations in the selected mass flow conditions of the individual extruder. 
         [0006]    A coextrusion adapter of this kind is known from European Patent Reference EP 1 621 320 A1. 
         [0007]    When manufacturing multi-layered films with a coextrusion adapter of this kind, the layers that are conveyed against one another from a die connected downstream of the coextrusion adapter, frequently a sheet die, are extruded to produce the multi-layered film. Ideally, all of the layers emerge with a uniform, desired layer thickness across the entire width of the die. In practice, however, fluctuations in the layer thickness and in the resulting film quality occur in the edge regions, among other things due to viscosity differences and friction losses so that edge strips with a width of approx. 30 to 50 mm are not suitable for the end product and are cut off and preferably fed back directly into the extrusion. Depending on the raw material of the individual layers, however, this is disadvantageous since it has a negative impact on the reusability and/or since the raw material used can be very cost-intensive. 
         [0008]    There have thus already been various proposals for the edge region that is to be cut away to be produced only out of less expensive, easily reusable plastics so that the actually desired multi-layered composite is encapsulated and is obtained in the desired configuration only after the edge trimming. 
         [0009]    It is known from U.S. Pat. No. 5,120,484 A to feed the edge region of a sheet die from a separate melt conduit with a connected extruder for an edge polymer so that between the edge regions, the multi-layered composite can be extruded unimpeded and is available for use once the edge regions are cut off. This is very complex and inflexible. In particular, only constant widths of the edge strips and of the entire extrudate can be produced. 
         [0010]    U.S. Pat. No. 4,784,815 and U.S. Pat. No. 4,289,560 disclose coextrusion adapters in which the melt stream flowing in the central conduit is united with separately supplied melt streams for the edge regions prior to the entry into the subsequent die, with the supplied melt streams for the edge regions pushing the melt stream flowing in the central conduit back from the edge. Systems of this kind with symmetrical composites, however, only function satisfactorily if all of the utilized raw materials of all layers have similar viscosities. But if they have different viscosities or temperatures or if the desired layered composite is asymmetrical, then layer boundary shifts frequently occur in the edge region and the multi-layered melt stream in the central conduit cannot be displaced out of the edge region, which leaves room for improvement. 
         [0011]    European Patent Reference EP 0 315 304 A1 describes a coextrusion adapter in which between the central conduit and a coextrusion conduit, adjustable separating elements are provided, which have a smaller width than the central conduit and also, the coextrusion conduit is limited to a correspondingly narrower width than the central conduit. In this way, it is possible to produce symmetrical composites with an encapsulation at the edges, which is produced from the melt stream that has been previously supplied in the central conduit. The flexibility with regard to the selective displacement of individual or multiple layers of the multi-layered coextrusion composite to be produced, however, still leaves room for improvement. 
       SUMMARY OF THE INVENTION 
       [0012]    One object of this invention is to modify a coextrusion adapter so that regardless of the sequence and number of layers placed on top of one another in the coextrusion adapter, individual or multiple layers can be reliably displaced from the edge region in a simple and flexible way and can be omitted from the edge trimming in order to increase both the reusability of the cut off edges and the economy of production. 
         [0013]    To attain the stated object, this invention proposes the embodiment of a coextrusion adapter according to the features described in this specification and in the claims. 
         [0014]    Advantageous embodiments and modifications of this invention are also discussed in this specification and in the claims. 
         [0015]    The above and other objects of this invention are achieved if adjacent to the outlet end of the respective coextrusion conduit, in at least one of the side walls of the central conduit, a receiving bore is provided, into which it is possible to insert a displacing element that protrudes beyond the side wall into the central conduit. 
         [0016]    According to this invention, it is thus possible to use the inward-protruding displacing element to selectively displace one or more layers of the extrudate flowing in the central conduit away from the side walls situated in the width direction and to fill the resulting empty space with the supplied melt from the coextrusion conduit in order to form the correspondingly desired coextrusion layer. 
         [0017]    In this regard, regardless of the positioning of one or more unwanted layers in the edge region, it is possible to selectively displace them from the edge region. The unwanted layers can, for example, be difficult-to-reuse adhesive layers or very cost-intensive raw materials such as EVOH. 
         [0018]    In one embodiment of this invention, the displacing element is embodied as a displacing bolt, such as with a cylindrical basic form, is inserted into a corresponding cylindrical receiving bore and at its end oriented toward the central conduit, has a displacing protrusion that protrudes a suitable amount into the central conduit and displaces the melt from the edges in the central conduit. 
         [0019]    A range from approximately 1 to 10 mm, preferably approximately 2 to 4 mm, is considered to be a suitable dimension for the protrusion of the displacing protrusion into the central conduit. With a width of the central conduit of approximately 100 mm and a nozzle width of the subsequent sheet die of 2,000 mm, this results in an edge strip formation with selectively displaced layers of approximately 30 to 50 mm wide. Through the indicated range of approximately 1 to 10 mm for the protrusion of the displacing protrusion, it is possible to obtain suitable widths of the edge strips with nozzle widths of approximately 500 to 5,000 mm. 
         [0020]    Furthermore, the receiving bore is preferably embodied so that it passes through the side wall in the form of a through bore and it is possible for the displacing element to be inserted into this through bore from the outside and in a sealed fashion. In this way, it is possible, for example, to adjust different-sized displacement regions or positionings, depending on the sequence of layers, while the system is not in operation after a product change by correspondingly exchanging displacing bolts for ones that have a displacing protrusion that protrudes by a different distance, without requiring a labor-intensive disassembly or cleaning of the entire coextrusion adapter. 
         [0021]    In the event of unwanted displacement of the melt from the central conduit, it is also possible, at an outlet end of a coextrusion conduit, to insert a closing element into the receiving bore provided adjacent to the outlet end, which in lieu of a displacing bolt, only closes the receiving bore, but does not protrude into the central conduit, instead ending flush at the side wall. 
         [0022]    It is also preferable if the two side walls of the central conduit have or are embodied with receiving bores that are flush with each other respectively adjacent to the outlet end of the coextrusion conduits so that both edge regions lying in the width direction are selectively processed in the above-described way and the corresponding melt is displaced at the edge. 
         [0023]    At their ends facing the outlet end, the adjusting elements can have a wedge-shaped adjusting section whose one wedge surface faces the central conduit and whose other wedge surface faces the outlet end of the coextrusion conduit in order to be able to control the thickness of the supplied coextrusion layer, as is known from European Patent Reference EP 1 621 320 A1. Thus, with this invention it is possible for the wedge surface facing the central conduit to be placed against the protruding displacing element or against its displacing protrusion, thus further improving the selective displacement of the layer flowing in the central conduit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    This invention is explained in greater detail below in view of exemplary embodiments shown in the drawings, wherein: 
           [0025]      FIG. 1  shows a schematic depiction of a basic function of a coextrusion adapter according to this invention; 
           [0026]      FIG. 2  shows an enlarged depiction of the detail X according to  FIG. 1 ; 
           [0027]      FIG. 3  shows a vertical sectional schematic diagram of the coextrusion adapter according to this invention; 
           [0028]      FIG. 4  shows a section taken through the coextrusion adapter according to this invention along the line V-V shown in  FIG. 3 ; 
           [0029]      FIG. 5  is a perspective depiction of an embodiment of the coextrusion adapter according to this invention; 
           [0030]      FIG. 6  shows a top view of the coextrusion adapter according to this invention according to  FIG. 5 ; 
           [0031]      FIG. 7  shows a sectional view extending through the central conduit of the coextrusion adapter according to this invention according to  FIG. 5 ; 
           [0032]      FIG. 8  shows a partial section taken through the coextrusion adapter according to  FIG. 5  in an orientation that is rotated by 90° relative to  FIG. 7 ; 
           [0033]      FIG. 9  shows a schematic section taken through a coextrusion composite according to the prior art; 
           [0034]      FIG. 10  shows another schematic section taken through a coextrusion composite according to the prior art; and 
           [0035]      FIG. 11  shows a schematic section taken through a coextrusion composite according to this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]      FIG. 1  shows a basic function of a coextrusion adapter for producing a multi-layered coextrusion composite out of a thermoplastic material. From two different extruders that are not shown in detail here, two different melt streams S 1 , S 2  of or composed of the same or different thermoplastic materials are produced and supplied at high pressure to a coextrusion adapter. In this case, the melt stream S 1  is supplied essentially in a straight line without deflection through a central conduit of the coextrusion adapter, which conduit will be explained in greater detail below, in the direction toward a die. 
         [0037]    By contrast with this, the melt stream S 2  is divided into two partial streams S 2 . 1  and S 2 . 2  and is supplied via coextrusion conduits on both sides to the stream S 1  flowing in the central conduit and forming a three-layered composite as shown in  FIG. 2  that are stacked on top of one another, with the melt streams S 2  forming the outer layers and the melt stream S 1  forming the inner layer of the thus produced overall stream G, which is subsequently supplied to the die, not shown, for example, a sheet die for producing a multi-layered film. Because of possible rheological differences in the individual plastics of the melt strands S 1 , S 2  and/or different mass flows, a great deal of attention must be paid to the moment when the melt strands S 1 , S 2  and S 2 . 1  and S 2 . 2  are brought together. 
         [0038]      FIGS. 3 and 4  show an exemplary embodiment of a coextrusion adapter  1 , which is basically described above and includes two conduit parts  2 ,  3  that are spaced apart from each other, forming the central conduit  10 , in each of which a respective coextrusion conduit  11  is formed. The conduit parts  2 ,  3  are embodied as mirror-symmetrical to the central axis of the central conduit  10  and delimit it in the vertical direction, forming a bottom wall  102  and corresponding top wall  103 . 
         [0039]    The two conduit parts  2 ,  3  are connected by side plates  4 ,  5 , which simultaneously also form the side walls  104 ,  105  thereof, lying in the width direction of the central conduit  10 . In this regard, the central conduit has a rectangular cross-section that is delimited by the bottom wall  102 , the top wall  103 , and the side walls  104 ,  105 . 
         [0040]    Because of an existing axial symmetry to the central axis M, it is now possible to explain other details based on one conduit part and the other components positioned therein. They correspondingly also apply to the mirror-symmetrically embodied other conduit part. 
         [0041]    In accordance with the explanations relating to  FIG. 1 , the melt stream S 1  conveyed by a first extruder enters into the central conduit  10  at an inlet end  100  and initially flows alone through this central conduit  10  to the region in which the two coextrusion conduits  11  in the side parts  2 ,  3  feed into the central conduit  10  with their respective outlet ends  112 . The partial streams S 2 . 1  and S 2 . 2  of the melt stream S 2  that have been previously divided by a dividing element, not shown here, first travel via inlet ends  110 , for example, provided in the side part  4 , into a distributing region  111  in which they are spread out to the entire width of the outlet end  112  and then across the entire width of the outlet end  112 , travel into the central conduit  10  that is embodied with the same width. The melt streams S 2 . 1  and S 2 . 2  conveyed by the coextrusion conduits  11  enclose the melt stream S 1 , which has been previously supplied in the central conduit  10 , on both sides so that the layered composite shown in  FIG. 2  is produced, which then exits the central conduit  10  via the outlet end  101  at a connected die, not shown here, for producing a coextrusion composite. Correspondingly, in the supply region of the two coextrusion conduits  11 , the central conduit  10  is embodied as stepped in order to have enough room for the supplied melt streams. 
         [0042]    In order to compensate for fluctuations in the mass flow of the melt streams S 1 , S 2  and possibly existing different rheological properties of the individual plastics, adjusting elements  6  that are associated with each outlet end  112  of the coextrusion conduits  11  are provided, which are positioned next to one another in the width direction of the outlet end  112  and in the width direction of the central conduit  10  that is embodied with the same width, as is particularly visible from the top view according to  FIG. 4 . In the exemplary embodiment shown, a total of three adjusting elements  6  are situated next to one another, or behind one another in the depiction according to  FIG. 3 , in order to cover the entire width of the outlet end  112  of the coextrusion conduits  11  and the entire width of the central conduit  10 . 
         [0043]    Each adjusting element  6  in this case, at its end oriented toward the outlet end  112 , includes a wedge-shaped adjusting section  60 , which comes to a point and tapers in the flow direction through the central conduit  10  and whose one wedge surface  60   a  faces the central conduit  10  and whose other wedge surface  60   b  faces the outlet end  112  of the coextrusion conduit  11 . Consequently, the adjusting section  60  in the region of its two wedge surfaces  60   a,    60   b  remains in contact with melt on both sides, namely in the region of the wedge surface  60   a,  it remains in contact with the melt being conveyed in the central conduit  10  and in the region of the wedge surface  60   b,  it remains in contact with the melt from the coextrusion conduit  11  emerging from the outlet end  112 . The unification of the melt streams from the central conduit  10  and the coextrusion conduit  11  takes place at the wedge tip of the adjusting section  60 . 
         [0044]    In order to avoid an excessively sharp change in direction in this case, the outlet end  112  of the coextrusion conduit  11  is embodied as already inclined toward the flow direction through the central conduit  10 . 
         [0045]    Adjacent to the adjusting section  60 , each adjusting element  6  then includes a cylindrically expanded bearing section  61  with which the adjusting elements  6  are inserted into corresponding recesses  21  in the respective conduit parts  2 ,  3  of the coextrusion adapter  1 . This cylindrically expanded bearing section  61  is matched exactly to the recesses  21  in the conduit parts  2 ,  3  thus preventing melt from penetrating from the central conduit  10  and/or the coextrusion conduit  11  along the joint between the bearing section  61  and the recess  21 , while at the same time ensuring that the bearing section and the adjusting section  60  formed onto it are able to pivot about the axis A that is visible in  FIG. 4  and extends out in the width direction of the outlet ends  112  of the coextrusion conduit  11 . In this case, the central axis of the bearing section  61  simultaneously constitutes or forms the pivot axis A. 
         [0046]    The pivoting support of the bearing section  61  inside the conduit parts  2 ,  3  enables a pivoting motion of the wedge-shaped adjusting section  60  about the pivot axis A according to arrow P 2 . 
         [0047]    This results in the fact that depending on the pivoting motion in the direction of arrow P 2 , the inner width of the respective width section of the outlet end  112  spanned by an adjusting section  60  can be enlarged or reduced and in corresponding opposition thereto, the inner width of the respective width section of the central conduit  10  can be reduced or enlarged. 
         [0048]    Thus, if the inner width of the outlet end  112  is enlarged by pivoting the adjusting section  60  to the left in the direction of arrow P 2  according to  FIG. 3 , then at the same time, the inner width of the central conduit  10  in this width section is correspondingly reduced and vice versa. This is due to the fact that the wedge surfaces  60   a,    60   b  of the adjusting section  60  are in contact with the melt stream in the central conduit  10  on the one hand and with the melt stream in the coextrusion conduit  11  and its outlet end  112  on the other, thus enabling the corresponding alternating influence. 
         [0049]    For the corresponding adjusting or pivoting of the adjusting sections  60 , at the end of each adjusting element  6  oriented away from the adjusting section  60 , an adjusting lever  63  is provided, which is operatively connected to an actuating drive  7 . 
         [0050]    The actuating drive  7  comprises or is composed of a threaded rod  71  that is positioned so that it extends out externally from the conduit parts  2 ,  3  of the coextrusion adapter  1 , and, with the engagement of a rotating tool in the direction of arrow P 1 , can be screwed into or out of the respective conduit part  2  or  3 . At its end oriented toward the adjusting element  6 , the threaded rod  71  has a driving element  70 , which is connected to the adjusting lever  63  so that by actuating the threaded rod  71  in the direction of arrow P 1 , it is possible to produce the desired pivoting motion of the adjusting element  60  in the direction of arrow P 2 . 
         [0051]    The screwing in and out of the threaded rods  71  is made possible by a threaded nut  72 , which is kept stationary by a counter plate  74  and screws  75  and through which the threaded rod  71  is screwed. 
         [0052]    The respective movement path of the threaded rod  71  can also be directly read and assessed from the outside at any time by a measurement spindle  73  that is rigidly affixed to the driving element  70 . 
         [0053]    In order to achieve a sufficient mobility of the actuating drive  7  and adjusting element  6 , the two conduit parts  2 ,  3  can each have or be provided with sufficiently large recesses  20 , which receive the above-mentioned components in accordance with their possible movement. 
         [0054]      FIGS. 5 and 6  show an embodiment of a coextrusion adapter in which parts of the coextrusion adapter, which has been described above and whose operating principle has been shown in  FIGS. 3 and 4 , that are the same have been provided with the same reference numerals and are not separately described again below, to avoid repetition. 
         [0055]    By contrast with the coextrusion adapter shown in  FIGS. 3 and 4 , which has only one coextrusion conduit  11  in each conduit part  2 ,  3  so that on the whole, an at most three-layered coextrusion composite can be produced, the coextrusion adapter  1  shown in  FIGS. 5 and 6  has three coextrusion conduits  11 ,  12 ,  13  in each of its conduit parts  2 ,  3 , with corresponding outlet ends  112 ,  122 ,  132  positioned or situated one after the other in the flow direction through the central conduit  10  so that on the whole, an at most seven-layered coextrusion composite can be produced in this depicted coextrusion adapter  1 , but this composite can also have even more layers or fewer layers with a corresponding variation of the coextrusion conduits. 
         [0056]    The conduit parts  2 ,  3  are positioned between side parts  4 ,  5 . In the depiction according to  FIG. 5 , the side part  4  is removed. 
         [0057]    The configuration and embodiment of the conduit parts  2 ,  3  and the coextrusion conduits, adjusting elements, and actuating drives they contain have been selected to coincide with the embodiments in  FIGS. 3 and 4  so that they are respectively embodied to be mirror-symmetrical to the central axis M extending through the central conduit  10  so that their embodiment can be explained by proxy based on one coextrusion conduit. 
         [0058]    From the perspective depiction according to  FIG. 5  and also the top view according to  FIG. 6 , it is clear that the respective adjusting elements  6  allocated to an outlet end  112 ,  122 ,  132  of the coextrusion conduits  11 ,  12 ,  13  can be embodied in different widths. The middle adjusting elements  6  have a greater width than the outer adjusting elements  6 , which is particularly apparent from the adjusting sections of the coextrusion conduit  13  labeled with the reference numeral  60 . Preferably, the adjusting sections  60  can have a width of 5-30 mm, in particular 10-25 mm. 
         [0059]    During operation of the coextrusion adapter shown in  FIGS. 5 and 6 , a melt stream S 1  first travels via an inlet end  100  into the central conduit  10 , whereupon melt streams conveyed in the conduit parts  2 ,  3  via the coextrusion conduits  11  are applied to it from the outside. The melt stream, which now has three layers and is conveyed in a correspondingly widened section of the central conduit  10 , then has another outer layer from the coextrusion conduits  12  applied to it on each side and after this, the now five-layered coextrusion composite then once again has another outer layer from the coextrusion conduits  13  applied to it so that altogether, a seven-layered coextrusion composite is formed and can be supplied via the outlet end  101  to a die that is not shown. In this case, in the above-described way, the individual adjusting elements  6  provided at the outlet ends  112 ,  122 ,  132  of the coextrusion conduits  13  enable an individual profiling, which can be different as needed across the width direction, of the respective incoming melt stream from the coextrusion conduits  11 ,  12 ,  13  and a simultaneous, opposite profiling of the melt stream traveling in the central conduit  10 . 
         [0060]    The respective supply of the individual melts to the inlet end  100  of the central conduit and the coextrusion conduits  11 ,  12 ,  13  is particularly apparent from the top view according to  FIG. 6 . 
         [0061]    By an adapter that is connected upstream of the coextrusion adapter  1 , but not shown here, a first melt stream travels from a first extruder directly to the open inlet end  100  of the central conduit  10  and from there, travels into the coextrusion adapter  1  from the top. 
         [0062]    The melts to be supplied to the coextrusion conduits  11 ,  12 ,  13  in the respective conduit parts  2 ,  3  are each introduced into the coextrusion adapter  1  via inlet ends  110 ,  120 ,  130  and travel via an internal conduit system into a distributing region which is not shown separately here, but has been explained in connection with  FIGS. 3 and 4 , from which the respective melt travels to the outlet end  112 ,  122 ,  132  of the coextrusion conduits  11 ,  12 ,  13  and finally into the central conduit  10 . In order to compensate for possibly existing rheological differences between the individual melts, upstream of each outlet end  112 ,  122 ,  132  of the coextrusion conduits  11 ,  12 ,  13 , damming elements  8  are provided, over which the melts are conveyed before entry into the respective outlet end  112 ,  122 ,  132 . Through selection of an appropriate contour, these damming elements  8  can be individually adapted to the respective rheological properties of the supplied plastic melt and the mass flow and, by formed-on base parts  80 , are interchangeably secured in corresponding insertion grooves of the conduit parts  2 ,  3  so that a respective individual adaptation to the processed thermoplastic materials can take place. 
         [0063]    In order to be able to produce the conduit system already mentioned above from the inlet ends  110 ,  120 ,  130  to the outlet ends  112 ,  122 ,  132  in a particularly simple fashion, the inlet ends  110 ,  120 ,  130  and the continuing conduit section in the region of the interstices T between the side parts  4 ,  5  and the conduit parts  2 ,  3  are each inserted half-way so that they can be produced for a low production cost during the production of the side parts  4 ,  5  and conduit parts  2 ,  3  by milled slots in the respective surface oriented toward the subsequent interstice T. In this way, when forming the inlet ends  110 ,  120 ,  130  and the subsequent conduit sections of the respective coextrusion conduits  11 ,  12 ,  13 , it is possible to eliminate the use of complex methods such as erosion. 
         [0064]    For a coextrusion composite produced by coextrusion adapters of this kind, for example a multi-layered coextruded film, it is characteristic for the film to have a cross-section that is visible in  FIG. 9 , in which, due to viscosity fluctuations and/or friction losses, and the like, the edge regions R lying on both sides of the central axis M 1  do not achieve the desired thickness tolerance and in this regard, are not usable for the desired end product. Since this has been technically unavoidable up to this point, the edge regions R are cut off with a width of approximately 30 to 50 mm and are preferably reused, while the remaining film satisfies the specifications. 
         [0065]    But if individual layers that are shown by way of example with hatching in  FIG. 9  can only be reused with difficulty, such as adhesive layers, or are of or composed of costly raw materials such as EVOH, then this edge trimming is accompanied by corresponding disadvantages. 
         [0066]    In the event that largely similar properties of all of the layers are present, then it is possible, for example, to perform an encapsulation with a suitable edge material, as shown in  FIG. 10 . Such a solution, however, is not possible with large differences in viscosity and/or temperature of the individual layers and their raw materials. 
         [0067]    In the coextrusion adapter  1  shown in the drawings, in the region labeled reference letter E in  FIG. 7  of the infeed of one, several, or all of the coextrusion conduits  11 ,  12 ,  13 , described here by proxy based on the coextrusion conduit  12 , receiving bores  90  that are flush with one another are introduced into the central conduit  10  in the side walls  104 ,  105  thereof, adjacent to the outlet end  122 . Displacing elements  9  in the form of displacing bolts are inserted into these receiving bores  90  and sealed by seals that are not shown. At their end oriented toward the central conduit  10 , they have a displacing protrusion  91  that protrudes into this central conduit by approximately 3 to 5 mm here, and also see the depiction in  FIG. 8 , to the left of the central axis M. 
         [0068]    The displacing protrusion  91  rises in wedge-shaped fashion in the flow direction of the central conduit  10  and the wedge surface  60   a  of the adjusting element  60  oriented toward the central conduit  10  is positioned so that it rests against the displacing protrusion  91 . 
         [0069]    The displacing protrusion  91  that protrudes into the central conduit by the corresponding amount makes it possible, in a selective fashion by choosing the appropriate receiving bore  90  and by appropriately dimensioning the displacing protrusion  91 , to mechanically and reliably displace the melt flowing in the central conduit  10  away from the edge region of the central conduit  10  before the application of the melt stream coming from the corresponding coextrusion conduit  10 ,  11 ,  12  so that the empty space produced at the edge is immediately occupied by the incoming melt flowing from the respective coextrusion conduit. 
         [0070]    As a result, it is thus possible, as clear from  FIG. 11 , to selectively displace from the edge region R individual or multiple layers that are not wanted in the edge trimming, regardless of the symmetry and layer sequence of the entire coextrusion composite and regardless of the rheology of the individual layers, and to inexpensively and simply reuse the edge region R. 
         [0071]    For this purpose, it is naturally preferable for the receiving bores  90  that are flush with one another adjacent to one of the coextrusion conduits  10 ,  11 ,  12  to be equipped with congruently embodied displacing elements  9 , though this is not absolutely necessary. Alternatively, it is also possible, as shown by way of example in  FIG. 8 , to the right of the central axis M, to close the receiving bore by a closing element  9   a  that is embodied similarly to the displacing bolt  9 , but that does not protrude into the central conduit  10 , instead ending flush with the side wall  105 . This is advisable, for example, if no displacement of individual layers from the edge region of the central conduit  10  is to take place in the region of the supply of melt from the corresponding coextrusion conduit  10 ,  11 ,  12  into the central conduit. 
         [0072]    In any case, the receiving bores  90  are embodied as through bores in the side plates  4 ,  5  and pass through them so that after removal of covers that are not shown in detail, for example when the system is not in operation, it is possible to exchange displacing bolts  9  and/or closing bolts  9   a  from the outside without disassembling the coextrusion adapter and to adapt to altered production requirements, for example in that displacing bolts  9  with a differently dimensioned displacing protrusion  91  are used or in that displacing bolts  9  are exchanged for closing bolts  9   a  or closing bolts  9   a  are exchanged for suitable displacing bolts  9 . 
         [0073]    The drawing according to  FIG. 6  also shows still further bores  40 ,  50  in the side parts  4 ,  5 , in which temperature control elements can be accommodated and/or adapters for the extruders can be mounted. 
         [0074]    Naturally, the individual inlet ends  110 ,  120 , and  130  of the coextrusion conduits  11 ,  12 ,  13  embodied in both conduit parts  2 ,  3  and arranged mirror-symmetrically relative to one another can each be supplied with a melt stream that comes from an extruder and is also divided according to  FIG. 1  and it is equally possible to respectively supply each inlet end  110 ,  120 ,  130  of a coextrusion conduit  11 ,  12 ,  13  in the two side parts  2 ,  3  with different melt streams from separate extruders. 
         [0075]    Finally, when not in use, it is also possible to seal individual coextrusion conduits  11  off from the central conduit  10  by correspondingly closing the outlet end  112 ,  122 ,  132  by a corresponding movement of the adjusting elements  6  and it is also possible to seal the adjacent receiving bores  9  by closing elements  9   a  so that despite the fact that in this case, six coextrusion conduits  11 ,  12 ,  13  are provided for the correspondingly seven-layer coextrusion composites, it is also possible to produce coextrusion composites with a smaller number of layers and to use the adjusting elements  6  and the closing elements  9   a  to simply close the coextrusion conduits  11  that are not needed for this process. This minimizes changeover times in the coextrusion adapter  1 . 
         [0076]    European Patent Application EP 16159939.4, filed 11 Mar. 2016, the priority document corresponding to this invention, to which a foreign priority benefit is claimed under Title 35, United States Code, Section 119, and its entire teachings are incorporated, by reference, into this specification.

Technology Category: 7