Abstract:
A method of producing a reinforced plastic profile ( 10 ) with a uniform profile cross section, in which the transverse reinforcement ( 12 ) is formed by a linked, knitted, sewn or woven tube. Such a tube can be seamlessly formed continuously during the production of the plastic profile ( 10 ), which is preferably performed by pultrusion.

Description:
STATEMENT OF RELATED APPLICATIONS  
       [0001]     This patent application claims convention priority on and is based on German Patent Application No. 10 2005 057 487.4, having a filing date of 30 Nov. 2005, and German Patent Application No. 10 2006 042 920.6, having a filing date of 13 Sep. 2006, both of which are incorporated herein in their entireties by this reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     The invention relates to a method of producing a reinforced plastic profile, at least one reinforcement being provided with plastic by drawing in a drawing direction.  
         [0004]     2. Related Art  
         [0005]     Plastic profiles are reinforced to improve the mechanical properties, in particular to improve their strength. In the simplest case, one reinforcement is provided for this purpose. If one reinforcement alone is not adequate, an additional transverse reinforcement is provided.  
         [0006]     It is known to form reinforcements or transverse reinforcements from prefabricated nonwoven or woven fabrics. These prefabricated nonwoven or woven fabrics are laid together with an overlap at a seam. This causes a lack of symmetry, which is disadvantageous in particular in the case of rotationally symmetrical plastic profiles and those for which dimensional stability is important.  
         [0007]     Furthermore, the incorporation of prefabricated woven and nonwoven fabrics can only be integrated in the production process of the plastic profile with great effort.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The invention is based on the object of providing a method of producing a reinforced plastic profile which allows simple formation of the reinforcement, in particular the transverse reinforcement, and great accuracy, particularly of rotationally symmetrical plastic profiles.  
         [0009]     A method to achieve this object comprises a method of producing a reinforced plastic profile, at least one reinforcement being provided with plastic by drawing in a drawing direction, wherein the at least one reinforcement is formed entirely or partly from at least one row of stitches and/or loops of at least one yarn or thread and/or by weaving structures obtained. This envisages forming the reinforcement at least partly from at least one row of stitches and/or loops of at least one yarn or a thread. Alternatively or in addition, it is envisaged to form the reinforcement at least partly from structures that have been produced by weaving technologies. With preference, a transverse reinforcement surrounding a longitudinal reinforcement is produced in this way. The stitches, loops and/or structures form around the longitudinally running reinforcing strands of the longitudinal reinforcement a homogeneous transverse reinforcement, which gives the plastic profile good strength and good dimensional stability, in particular the plastic profile is provided with outstanding symmetry by virtue of the uniformity of the transverse reinforcement that can be achieved with stitches, structures or loops.  
         [0010]     With preference, it is envisaged to create from the at least one row of stitches, loops, structures or the like a tube-like covering or encapsulation of the reinforcing strands. The tube-like covering forms in particular an especially uniform transverse reinforcement. The tube-like covering for forming the transverse reinforcement is arranged with preference tightly around the longitudinal reinforcement; it may, however, also loosely surround the longitudinal reinforcement or be provided as a single reinforcement.  
         [0011]     In the case of a preferred method, it is envisaged to form the tube-like encapsulation or covering from a number of layers each of a row of stitches, structures and/or loops, the stitches, structures or loops being formed with preference from a yarn or thread of the material provided for the longitudinal reinforcement. In this way, a reinforcement, in particular transverse reinforcement, that satisfies the requirements can be formed, the multiple layers altogether forming a tube-like encapsulation that is approximately the same thickness all around, as a result of which rotationally symmetrical plastic profiles can be produced with great precision, in particular great roundness, even in the case of multilayer transverse reinforcements.  
         [0012]     According to a preferred development of the method, it is envisaged to produce the tube-like encapsulation or covering for forming the reinforcement, in particular the transverse reinforcement, continuously as the longitudinally directed reinforcing strands are being further transported in the drawing direction. As a result, the formation of the reinforcement can be integrated as it were “in line” in the production process. This makes it possible to dispense with preceding production stages or intermediate stages, as are required in the case of the known prefabrication of woven and nonwoven fabrics to form reinforcements.  
         [0013]     According to a further proposal of the invention, the tube-like covering for forming the reinforcement, in particular the transverse reinforcement, is produced using needles which can move back and forth. With preference, the stitches, structures and/or loops of each layer of the tube-like covering are produced by knitting, in particular circular knitting, sewing, linking or weaving. With the known methods, a particularly uniform tube-like covering can be produced, to be precise with yarns or threads of all suitable materials. In particular, the tube-like covering can be continuously produced by knitting, linking, sewing our weaving simply with needles which can move back and forth, to be precise at a drawing rate correspondingly the rate of production.  
         [0014]     If, in particular, the transverse reinforcement is produced by sewing or weaving with warp and weft threads, the weft threads run in the longitudinal direction of the strands of the longitudinal reinforcement. In this case, at least some of the weft threads of the transverse reinforcement may be formed by some or all of the longitudinal strands of the longitudinal reinforcement. It is also possible to interweave, interlace or intertwine, at least partially, the longitudinal strands of the longitudinal reinforcement, in the form of weft threads, and the weft threads of the transverse reinforcement, also running in the longitudinal direction of the longitudinal strands. In the case of the previously described refinement of the invention, parts of the longitudinal reinforcement are formed by the transverse reinforcement, or vice versa. The longitudinal reinforcement and the transverse reinforcement are interconnected in this way to form a single reinforcement.  
         [0015]     The threads or yarns for producing the tube-like covering of the reinforcement or transverse reinforcement are preferably formed from the material of the reinforcing strands of the longitudinal reinforcement running in the drawing direction. These may be yarns or threads of organic and inorganic fibers, that is to say both natural fibers and synthetic fibers, for example glass fibers or carbon fibers.  
         [0016]     According to a preferred refinement of the invention, it is envisaged to draw the yarns or threads for producing the tube-like encapsulation or covering from reels or drums, these reels or drums preferably being assigned in an unchanging location to the apparatus serving for drawing the strands, to be precise at such a point that the yarns or threads for producing the tube-like covering are fed to the longitudinally running reinforcing strands and entangled, linked or interwoven with the encapsulation before the plastics material is applied to the reinforcing strands of the longitudinal reinforcement and the tube-like covering of the transverse reinforcement.  
         [0017]     The method according to the invention is used with preference in the pultrusion of plastic profiles. In the case of this special drawing process, the invention can be integrated particularly advantageously in the production process, in that the stitched, linked or woven covering is produced “in line” in the pultrusion.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     Preferred exemplary embodiments of the invention are explained in more detail below on the basis of the drawing, in which:  
         [0019]      FIG. 1  shows a simplified perspective representation of a pultrusion apparatus.  
         [0020]      FIG. 2  shows a plan view of apparatus for producing a transverse reinforcement.  
         [0021]      FIG. 3  shows a sectional representation of part of a plastic profile produced by the method according to the invention, with the only schematically (symbolically) represented transverse reinforcement.  
         [0022]      FIG. 4  shows a perspective representation of part of a woven transverse reinforcement. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]     The invention concerns the production of an extruded plastic profile  10 . The exemplary embodiment shown relates to the production of the plastic profile  10  by pultrusion. The invention may, however, also be used in connection with other strand-drawing processes for producing the plastic profile  10 .  
         [0024]     The plastic profile  10  shown in  FIG. 3  has an approximately oval cross section. In the case of the method according to the invention, however, plastic profiles of any other desired cross sections, both rotationally symmetrical cross sections and asymmetrical cross sections, including those with undercuts, may also be produced.  
         [0025]     The plastic profile  10  shown has a longitudinal reinforcement  11  and a transverse reinforcement  12 . In  FIGS. 1 and 3 , the transverse reinforcement is represented only in a simplified form, that is say is only indicated. Both the longitudinal reinforcement  11  and the transverse reinforcement  12  are impregnated at least partially, preferably completely, with plastic and completely surrounded by the plastic, which is preferably a thermosetting material  13 . The single- or multilayer transverse reinforcement  12  surrounds the longitudinal reinforcement  11  in a tube-like manner, the transverse reinforcement  12  preferably tightly surrounding the longitudinal reinforcement  11 .  
         [0026]     The longitudinal reinforcement  11  is formed by individual reinforcing strands  14  running continuously in the longitudinal direction of the plastic profile  10 . Reinforcing strands  14  may, if appropriate, also be interlaced, spun or connected in some other way. The transverse reinforcement  12  is formed by fibers or yarns, which surround the longitudinal reinforcement  11  in a tube-like manner in at least one row of stitches and/or loops running in the longitudinal direction of the transverse profile  10 . It is conceivable to form the transverse reinforcement  12  from a number of threads or yarns, the tube-like transverse reinforcement  12  then preferably being formed from a number of layers each of a row of stitches or loops or combinations of stitches and/or loops. In addition or as an alternative, the transverse reinforcement  12  may also be formed from structures which have been obtained for example by weaving technologies.  
         [0027]     It is also possible to provide an only partial transverse reinforcement, in regions of the plastic profile that are particularly subjected to loading. Such partial transverse reinforcements surround the longitudinal reinforcement  11  only partially, that is to say they do not form a closed tube-like covering of the longitudinal reinforcement  11 .  
         [0028]     The yarns or threads of the transverse reinforcement  12  are formed with preference from the same material as the strands of the longitudinal reinforcement  11 . These are strands of a natural material, for example hemp or flax, or else a synthetic material, for example glass or carbon fibers. Similarly, the fibers and yarns of the transverse reinforcement  12  may be formed from hemp, flax or other natural materials, but also from synthetic fibers, for example carbon or glass fibers. It is also conceivable to form the strands from fibers of different materials, and similarly the yarns and threads. The yarns and threads may also be formed from different materials than the strands of the longitudinal reinforcement  11 . With regard to the materials of the longitudinal reinforcement  11  and of the transverse reinforcement  12 , there are no limits in the case of the method according to the invention.  
         [0029]     The pultrusion apparatus shown in  FIG. 2  has, seen in the direction of pultrusion  15 , an impregnating mold  16 , which is laterally assigned an extruder  17 , a then following impregnating zone  18 , arranged behind that a mold  19  and finally a cooling zone  20  at the end. Upstream of the impregnating mold  16  there is an apparatus for producing the transverse reinforcement  12 , surrounding the longitudinal reinforcement  11  in a tube-like manner. In the exemplary embodiment shown, this apparatus is a linking apparatus  21 . In place of the linking apparatus  21 , a knitting apparatus, in particular a circular knitting apparatus, a sewing apparatus or a weaving apparatus may also be arranged upstream of the impregnating mold  16 . The individual connected or unconnected strands of the longitudinal reinforcement  11  run continuously through the linking apparatus  21  and the subsequent pultrusion apparatus, that is to say the impregnating mold  16 , the impregnating zone  18 , the mold  19  and the cooling zone  20 . The seamless, tube-like covering for forming the transverse reinforcement  12  is produced around the longitudinal reinforcement  11  by the linking apparatus  21 , before the longitudinal reinforcement  11  and the transverse enforcement  12  are impregnated with plastic. Accordingly, the longitudinal reinforcement  11  and the transverse reinforcement  12 , arranged preferably tightly around it, run together in the direction of pultrusion  15  through the impregnating mold  16 , where polymer plasticated by the extruder  17  is fed in, and subsequently through the impregnating zone  18 , the mold  19  and the cooling zone  20 .  
         [0030]     The linking apparatus  21  arranged upstream of the impregnating mold  16  provides the longitudinal reinforcement  11  continuously with the transverse reinforcement  12 , for which purpose the operating speed of the linking apparatus  21  corresponds to the rate at which the longitudinal reinforcement  11  and the transverse reinforcement  12  provided around it are drawn through the pultrusion apparatus in the direction of pultrusion  15 .  
         [0031]     The linking apparatus  21  shown in  FIGS. 2 and 3  serves for producing the transverse reinforcement  12  from a number of layers. The linking apparatus  21  has four needles  22 , which in each case provide a yarn or a thread with an elongated row of stitches or loops running in the direction of pultrusion  15 . However, the invention can also be realized with a greater or smaller number of needles  22 . In the exemplary embodiment shown, all the needles  22  are arranged obliquely in relation to the direction of pultrusion  15 , such that a needle  22  is located on each side next to the longitudinal reinforcement  11 . The straight needles  22  can be moved up and down or back and forth on a straight path. In this case, all the needles  22  move laterally past the longitudinal reinforcement  11 , without touching it. The four needles  22  arranged around the longitudinal reinforcement  11  lie in a plane which intersects the direction of pultrusion  15 , that is to say the direction of the longitudinal reinforcement  11 , perpendicularly or at an oblique angle. It is also conceivable, however, if need be to orient the needles  22  differently, in order to produce transverse reinforcements  12  with some other pattern of stitches or loops.  
         [0032]     Each of the needles  22 , all of a straight form, is assigned a pressure medium cylinder  23 , which is preferably a pneumatic cylinder. The straight needles  22  can be moved by the pressure medium cylinder  23  transversely in relation to the direction of pultrusion  15  on a path running straight in the longitudinal direction of said needles, to be precise from one side of the bundle of strands of the longitudinal reinforcement  11  to the opposite side.  
         [0033]     In the case of the linking apparatus  21  shown in  FIG. 3 , which is arranged upstream of the impregnating mold  16  of the pultrusion apparatus, all the pressure medium cylinders  23  are arranged on one side of the longitudinal reinforcement  11 . Since the needles  22  move in pairs from opposite sides of the longitudinal reinforcement  11 , from one side of the longitudinal reinforcement  11  to the other, two needles  22  directed the other way round are arranged at one end of a distance sleeve  25  extending a piston rod  24  of the pressure medium cylinder  23  concerned. The tips  26  of these two needles  22  thereby point toward the pressure medium cylinder  23 , while the tips  26  of the two other needles are directed away from the pressure medium cylinders  23 , extending the piston rods  24  of the pressure medium cylinder  23  concerned. If all four pressure medium cylinders  23  are extended, the two needles  22  move from one side and two needles  22  move from the other side over or under the longitudinal reinforcement  11 .  
         [0034]     All four pressure medium cylinders  23  with the needles  22  are mounted on a common planar support plate  27 . The support plate  27  has a laterally open cutout  28 . The longitudinal strands of the longitudinal reinforcement  11  transported further in the direction of pultrusion  15  run through this cutout  28 . The linking apparatus  21  shown in  FIG. 3  is assigned to the direction of pultrusion  15  in such a way that the plane of the support plate  27  intersects the direction of pultrusion  15 , and consequently the longitudinal reinforcement  11 , perpendicularly, the longitudinal reinforcement  11  running through the cutout  28  in the support plate  27  in the direction of pultrusion  15 .  
         [0035]     The method according to the invention proceeds as follows:  
         [0036]     Before the actual pultrusion operation takes place, that is to say before the reinforcement is impregnated and/or encapsulated with preferably thermosetting material, the transverse reinforcement  12  is produced continuously from at least one row of structures, stitches or loops around the strands of the longitudinal reinforcement  11  running in the direction of pultrusion  15 . For this purpose, the strands of the longitudinal reinforcement  11  are provided with the seamless tube-shaped covering for forming the transverse reinforcement  12  by the linking apparatus  21  upstream of the impregnating mold  16  of the pultrusion apparatus. In the exemplary embodiment shown, the tube-shaped covering is formed from a number of threads or yarns, namely four threads or yarns, by linking. This involves creating the uniform tube-shaped covering of the transverse reinforcement  12  surrounding the longitudinal reinforcement  11 , which transverse reinforcement comprises four layers in the exemplary embodiment shown with the linking apparatus  21  having four needles  22 . The transverse reinforcement  12  surrounds the longitudinal reinforcement  11  from the outside, surrounding it tightly. In the exemplary embodiment shown, the stitches or loops run transversely in relation to the longitudinal direction of the strands of the longitudinal reinforcement  11 .  
         [0037]     The strands of the longitudinal reinforcement  11  are continuously linked in a looping formation, to be precise at a rate of advancement which corresponds to the rate of pultrusion. In other words, the linking takes place at the same rate at which the strands of the longitudinal reinforcement  11  are drawn through the pultrusion apparatus in the direction of pultrusion  15 .  
         [0038]     The strands of the longitudinal reinforcement  11  surrounded on the outside by the seamless tube-like transverse reinforcement  12  are continuously moved together at the same rate through the impregnating mold  16  in the direction of pultrusion  15 . In the impregnating mold  16 , liquid polymer produced by the extruder  17  is fed to the longitudinal reinforcement  11  and the transverse reinforcement  12  surrounding the latter. This causes the encapsulation, and also at least partial impregnation, of the strands or fibers or yarns of the longitudinal reinforcement  11  and of the transverse reinforcement  12 . Following the impregnating mold  16 , the longitudinal reinforcement  11  and transverse reinforcement  12  provided with plastic are moved further in the direction of pultrusion  15  through the impregnating zone  18 , the then following mold  19 , in which the plastic profile  10  is given its final outer shape, and finally through the cooling zone  20 . At the end of the cooling zone  20 , the finished plastic profile  10  leaves the pultrusion apparatus as a continuous strand. Plastic profiles  10  of appropriate length are cut off from this strand by means of a cutting-to-length apparatus.  
         [0039]     In the case of the method according to the invention, the transverse reinforcement  12 , that is to say the tube-like covering of the longitudinal reinforcement  11 , may also be produced by knitting, in particular circular knitting, sewing or weaving. In this case, as in the case of linking, the tube-shaped or only partial transverse reinforcement  12  may also comprise a number of layers by using a corresponding number of needles.  
         [0040]      FIG. 4  perspectively shows part of a woven transverse reinforcement  29 . The woven transverse reinforcement  29  has warp threads  30  and weft threads  31 . The warp threads  30  run parallel to one another along the direction of pultrusion  32 . Accordingly, the weft threads  31  run transversely in relation to the direction of pultrusion  32 . The warp threads  30  may be some or all of the longitudinal strands of the longitudinal reinforcement (not shown in the figure), which is at least partially enclosed by the transverse reinforcement  29 . It is also conceivable to interlace, intertwine or interweave the warp threads  30  of the transverse reinforcement  29  with the longitudinal strands of the longitudinal reinforcement running parallel to the warp threads  30 .  
         [0041]     The partly shown transverse reinforcement  29  has warp threads  30  in an approximately horizontal plane and weft threads  30  in an approximately vertical plane. The weft threads  31  meet in the corner between the horizontal and vertical warp threads  30 . To form a corner connection of the weft threads  31 , the warp thread  30  of the corner is used jointly and alternately by the continuous weft threads  31 . This involves weaving in a looping formation the weft thread  30  forming a corner, which leads to a corner connection  33  of the transverse reinforcement  29 .  
         [0042]     The woven transverse reinforcement  29  partly shown in  FIG. 4  is produced in the way described above as it were “in line” in the production of the profile, to be precise at the rate of pultrusion of the plastic profile. The warp threads and the weft threads  31  are drawn from supply reels which are assigned in a stationary manner, that is to say at a fixed location, to the pultrusion apparatus. The supply reels are only freely rotatable about stationary axes of rotation, for drawing off the warp threads  30  and the weft threads  31 .  
         [0043]     The exemplary embodiments of the invention described above are formed on a plastic profile with at least one longitudinal reinforcement  11  and at least one transverse reinforcement  12  or  29  entirely or partially surrounding the latter. However, it is also conceivable to provide the plastic profile only with one reinforcement, which however is preferably formed as a transverse reinforcement  12  or  29 , so that the longitudinal reinforcement  11  is absent. The single reinforcement is then formed in a way according to the invention by knitting, in particular circular knitting, sewing, linking or weaving, and has at least one row of structures, stitches and/or loops of at least one yarn or thread.  
       LIST OF DESIGNATIONS  
       [0000]    
       
           10  plastic profile  
           11  longitudinal reinforcement  
           12  transverse reinforcement  
           13  polymer  
           14  reinforcing strand  
           15  direction of pultrusion  
           16  impregnating mold  
           17  extruder  
           18  impregnating zone  
           19  mold  
           20  cooling zone  
           21  linking apparatus  
           22  needle  
           23  pressure medium cylinder  
           24  piston rod  
           25  distance sleeve  
           26  tip  
           27  support plate  
           28  cutout  
           29  transverse reinforcement  
           30  warp thread  
           31  weft thread  
           32  direction of pultrusion  
           33  corner connection