Abstract:
A radial braiding machine includes a bobbin gear through which stationary yarns and braiding yarns are fed, a braiding ring through which the stationary yarns and braiding yarns are guided, and at least one transport device for transporting a core to be over-braided. The braiding ring has a non-round internal cross-section when projected onto a yarn outlet plane spanned by the bobbin gear. A braiding ring, a flat braid and a method of producing the flat braid are also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation application, under 35 U.S.C. §120, of copending International Application PCT/EP2015/053414, filed Feb. 18, 2015, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2014 202 970.8, filed Feb. 18, 2014; the prior applications are herewith incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a radial braiding machine including a bobbin gear through which stationary yarn and braiding yarn are fed, a braiding ring through which the stationary and braiding yarns are guided, a core to be over-braided and at least one transportation device for transporting the core. The invention also relates to a braiding ring for use in a radial braiding machine and to a flat braid obtained by over-braiding a core using a radial braiding machine with a braiding ring through which yarns are guided by a bobbin gear. The flat braid includes stationary yarns extending in the longitudinal direction of the braid, and braiding yarns interwoven with the stationary yarns and extending at an oblique angle to the stationary yarns, the course of the braiding yarns differing from an ideal, straight course of a nominal layer by an angle of twist and each stationary yarn being at a distance from an adjacent stationary yarn. The invention additionally relates to a method of producing the flat braid. 
         [0003]    A generic radial braiding machine is disclosed, for example, in German Patent Application DE 2 112 499, corresponding to U.S. Pat. No. 3,599,529, and is equipped with a bobbin gear, through the use of which stationary yarns and braiding yarns are guided to a braiding ring and guided therethrough. Furthermore, a transportation device for transporting a core to be over-braided must be present. The device is likewise moved through the braiding ring. Conventionally, the braiding ring which is always perpendicular to a core having a round cross section, also has a round inside diameter. 
         [0004]    In practice, by using a radial or round braiding machine of that type, solely round braided sleeves could be produced, which had high requirements in terms of uniformity and yarn course. However, when producing braids for diameters which are not circular, the yarns warp and irregularities occur. That applies in particular to flat braids which are produced on such machines, for which a tubular round braid which is created is merely flattened. Undesirable warping of the yarns occurs in particular at the edges of the resulting flat braid. 
       SUMMARY OF THE INVENTION 
       [0005]    It is accordingly an object of the invention to provide a radial braiding machine, a braiding ring, a flat braid and a method of producing the flat braid, which overcome the hereinafore-mentioned disadvantages of the heretofore-known machines, rings, braids and methods of this general type, which allow the precise production of various braids and which provide an improved flat braid. 
         [0006]    With the foregoing and other objects in view there is provided, in accordance with the invention, a radial braiding machine, comprising a bobbin gear through which stationary yarn and braiding yarn are fed, the bobbin gear spanning a yarn outlet plane, a braiding ring through which the stationary and braiding yarns are guided, the braiding ring having a non-round internal cross section when projected onto the yarn outlet plane, a core to be over-braided, and at least one transportation device for transporting the core. 
         [0007]    In this case, the point of the deposition of the braiding yarns on the core to be over-braided and the tension of the yarns is influenced by the braiding ring having a non-round internal cross section, that is to say an internal cross section which differs from the circular shape, and more specifically when projected onto a yarn outlet plane which is spanned by the bobbin gear. This can, of course, preferably be brought about by a braiding ring, which itself has a non-round internal cross section, but also by a ring having a round cross section which is mounted in an oblique or twisted manner with respect to the bobbin gear in such a way that only the projection of the internal cross section thereof is not round. This likewise has the effect of a non-round internal cross section. Good results can be achieved by using a braiding ring having an internal cross section with an oval or elliptical shape when projected onto the yarn outlet plane. However, it is preferable for the braiding ring itself to have an oval or elliptical internal cross section. 
         [0008]    Another influence on the yarn tension and deposition position of the yarns on the core to improve the braid properties can be achieved on a braiding machine in which the front side of the braiding ring, through which the yarns are substantially diverted, protrudes in regions from the yarn outlet plane which is spanned by the bobbin gear or from a plane which is parallel thereto. As a result of the fact that the front side protrudes only in regions, but not completely, and to different extents from the yarn outlet plane or the parallel plane in the opposite direction to the transportation direction of the braid core, specific regions of the braiding and stationary yarns are guided in a controlled manner in such a way that they come to rest on the core sooner or later than other yarns, or obtain another tension. Another adjustment and/or fine adjustment can take place by placing the braiding ring in the radial or round braiding machine in a pivoted manner, and more specifically about at least one of two pivot axes which are orthogonal to one another, so that the yarn diverter protrudes to different extents at the points of intersection with one or both of the pivot axes on each side of the braiding ring. The configuration can be selected in such a way that the yarn diverter protrudes to different extents or projects at different heights at all four points of intersection of the pivot axes with the braiding ring. 
         [0009]    With the objects of the invention in view, there is also provided a braiding ring for use in radial or round braiding machines, the front side of which that diverts the stationary and braiding yarns, referred to as the yarn diverter, according to the invention spans an imaginary surface which is curved at least in regions. That is to say that a surface which would be in contact with all of the points of the yarn diversion of the braiding ring would not be a planar, straight surface. A braiding ring of this type can also have in particular an inner contour which differs from the circular shape, preferably an elliptical inner contour. The yarn diverter of a braiding ring of this type can also protrude to different extents at the points of intersection of two intersecting inside diameter axes. 
         [0010]    With the objects of the invention in view, there is additionally provided a flat braid obtained by over-braiding a core using a radial braiding machine with a braiding ring through which yarns are guided by a bobbin gear. The flat braid comprises stationary yarns extending in a longitudinal direction of the braid, each of the stationary yarns being disposed at a distance from a respective adjacent stationary yarn, and braiding yarns being interwoven with the stationary yarns and extending at an oblique angle to the stationary yarns, the braiding yarns following a course differing from an ideal, straight course of a nominal layer by an angle of twist. The angle of twist is at most +/−3° and is obtained by influencing a position and a time of deposition of the stationary and braiding yarns on the core by modifying the braiding ring from a circular shape taking into consideration a shape of the core, providing the braiding ring with an internal cross section having a non-round shape when projected onto a yarn outlet plane being spanned by the bobbin gear and providing the braiding ring with an inner contour being at a different distance from an outer contour of the core to be over-braided. 
         [0011]    In this case, braiding errors or deviations from the ideal braiding yarn course, which are referred to as an S twist or Z twist, are reduced to an angle of twist of at most +/−3°. This can be produced by a braiding method in which the position and time of deposition and the yarn tension are influenced by modifying the braiding ring of the braiding machine from a circular shape, while taking into consideration a core shape to be selected in such a way that the internal cross section of the braiding ring has a non-round shape when projected at least onto the yarn outlet plane which is spanned by the bobbin gear, and the inner contour of the braiding ring is at a different distance from the outer contour of the core to be over-braided. For this purpose, substantially rectangular braiding cores can also be selected, which can also be very flat and thus already come close to the later shape of the flat braid. The differences in tension in the braiding yarns at the outer edges of the flat braid, which are unavoidable in the prior art, are avoided or minimized in this case. Preferably, a flat braid is thus achieved having distances between the stationary yarns with an average standard deviation of only at most 5%, more preferably at most 2%. With the specification of the average standard deviation, the fact has also been taken into account that the distance between two stationary yarns is never 100% constant over the length of the flat braid. The distance between two stationary yarns is therefore accordingly specified as an average. The average standard deviation is thus the standard deviation of the average distances between the stationary yarns in the flat braid. 
         [0012]    The deposition of the yarns on the core including the yarn tension can in this case be influenced by using a special construction and/or mounting of the braiding ring so that the front side thereof which diverts the braiding yarns (yarn diverter) protrudes at various positions to different extents over the yarn outlet plane or a plane which is parallel thereto. 
         [0013]    When using a non-round core having different cross-sectional dimensions of a maximum height and a maximum width, the braid properties can be influenced in a positive manner when the internal cross section of the braiding ring (when projected at least onto the yarn outlet plane El) differs in an inverse manner from the circular shape, that is to say that the distance thereof from the core at the position of the maximum core cross-sectional dimension is selected so as to be smaller than at the position of the minimum core cross-sectional dimension. It also has a positive effect when the yarn diverter on the front side of the braiding ring protrudes further at the position of the maximum cross-sectional dimension of the core than at the position of the minimum core cross-sectional dimension. 
         [0014]    A braiding ring having a front side which protrudes to different extents on each side of the maximum and/or minimum cross-sectional dimension of the core, or mounting a braiding ring in such a way that a spatial positioning of this type occurs can also influence the braid in a positive way, in particular when using braiding cores having a longitudinal axis which is not straight. One way of achieving this influence by using the mounting of the braiding ring is to mount the ring in a tilted and/or pivoted manner with respect to the yarn outlet plane. 
         [0015]    All of the embodiments of the braiding ring which are disclosed in relation to the braiding machine can be combined with the method according to the invention and vice versa. 
         [0016]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0017]    Although the invention is illustrated and described herein as embodied in a radial braiding machine, a braiding ring, a flat braid and a method of producing the flat braid, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0018]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0019]      FIG. 1  is a diagrammatic, side-elevational view of a radial braiding machine according to the invention; 
           [0020]      FIG. 2  is a perspective view as seen in the direction II of  FIG. 1 ; 
           [0021]      FIG. 3  is a perspective view and two side-elevational views of the braiding ring of  FIG. 1 ; 
           [0022]      FIG. 4  is a perspective view as seen in the direction IV of  FIG. 1 ; 
           [0023]      FIG. 5  is a diagrammatic, plan view of a flat braid according to the invention; and 
           [0024]      FIG. 6  is a diagrammatic, perspective view of an angle of twist in a braid. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a simplified view of a radial braiding machine which has a bobbin gear  1  from which stationary yarns and braiding yarns  2 ,  3  are guided through a yarn-diverting front side  4 , also referred to as a yarn diverter, of a braiding ring  5  and subsequently guided therethrough. In order to create the braid, a core  6  to be over-braided is pushed through the braiding ring  5  in a transport direction  7  by a transportation device  10 . In so doing, the then interweaving yarns  2 ,  3  are located on the core  6  as a braid, which is only suggested in  FIG. 1 . The bobbin gear  1  is annular and spans a yarn outlet plane E 1 . The yarns  2 ,  3  emerge from the inside of the bobbin gear  1 , which is only diagrammatically indicated in  FIG. 1 . 
         [0026]      FIG. 2  is an oblique front view as seen from a position II in  FIG. 1 , which shows only part of the bobbin gear  1 , but in a much more detailed and perspective view. It can be seen in this figure that the core  6  has a flat, rectangular cross section which is disposed so as to be opposed to an elliptical internal cross section of the braiding ring  5  in the embodiment shown. 
         [0027]      FIG. 3  is a detailed view of the braiding ring  5  and four retaining elements  8  thereof, through the use of which the ring is attached to the non-illustrated bobbin gear. The braiding ring  5  has not only an oval inside diameter, but also outwardly curved sides  15  on the front side  4  thereof, which protrude from a plane (E 2 ) that is parallel to the yarn outlet plane E 1  (see also  FIG. 1 ) which is spanned by the bobbin gear. By contrast, upper and lower ends  25  of the front side  4  of the braiding ring  5  are aligned with the plane (E 2 ) so that the front side  4  of the braiding ring  5  protrudes from the plane (E 2 ) only in regions, but not all over. Through the use of this construction, the deposition of the braiding and stationary yarns  2 ,  3  on the core  6  to be over-braided can be influenced in a targeted manner. The yarn-diverting front side  4  of the braiding ring  5  thus spans an imaginary surface which is curved at least in regions and which clearly differs from a planar, straight surface of conventional braiding rings. 
         [0028]    A particularity of the braiding machine according to the invention is the fact that the braiding ring  5  as shown in  FIG. 4  can be disposed so as to be pivoted by an angle α with respect to the planes E 1  and (E 2 ). As a result, the deposition of the yarns  2 ,  3  can be influenced to a greater extent, in particular when using braiding cores  6  which have no straight longitudinal extension or longitudinal axis L, but rather have, for example, a curved one. For the sake of clarity, neither the core nor the yarns are shown in  FIG. 4 . 
         [0029]    Preferably, the braiding ring  5  can be mounted so as to be pivoted about pivot axes S 1  and S 2  (see  FIG. 3 ) which are orthogonal to one another. The pivoted mounting in  FIG. 4  corresponds in this case to a mounting in which a distance A 4  between the plane E 1  and the point of intersection of the yarn-diverting front side  4  of the braiding ring  5  with the pivot axis S 2  protrudes the furthest. A distance A 3  on the opposite side is slightly smaller due to the pivoting, and distances A 1  and A 2  (points of intersection with the pivot axis S 1 ) are even smaller due to the special construction of the yarn-diverting front side  4  of the braiding ring  5 . 
         [0030]    In the perspective view of  FIG. 3 , the braiding core  6  is further shown diagrammatically in order to show how the geometry thereof is preferably to be constructed with respect to the braiding ring  5 . In order to achieve a flat braid, an already flat core  6  having a preferably rectangular diameter can be selected. Contrary to what may be assumed, in this case, the construction and configuration of the braiding ring  5  with respect to the braiding core  6  has an advantageous effect on the uniformity of the braid to be obtained, in which distances k 1  between a maximum width B of the core  6  are smaller than, preferably substantially smaller, than distances K 2  between the core  6  in the case of a maximum height H of the core  6  and the inside diameter of the braiding ring at each position. Likewise, the braiding ring  5  is disposed in such a way that the further protruding side regions  15  thereof are to be found at the maximum cross-sectional dimensions of the core  6 , in this case the width B, and the less protruding upper and lower faces  25  are to be found at the positions of the minimum cross-sectional dimension, in this case the height H, of the core  6 . 
         [0031]      FIG. 5  is a diagrammatic view of a flat braid which is produced on the braiding machine according to the invention. This flat braid can be obtained by flattening the braided sleeve which is produced or by cutting open the sleeve on one or both sides. 
         [0032]    The width, the distance and the angle of twist of the yarns  2  and  3  are not shown to scale in this figure. In this case, stationary yarns  2  extend in the longitudinal direction L of the braid, and braiding yarns  3  extend at an oblique angle to the stationary yarns  2 . Distances G (also referred to as gaps) are located between each of the stationary yarns. In the case of the braid which is produced, a uniformity can be achieved so that the average value of the distances G between the stationary yarns  2  is at most 5%. 
         [0033]      FIG. 6  is a likewise purely diagrammatic illustration of a braid which can be obtained according to the prior art and includes a circular braiding ring, which is located in a plane that is parallel to the plane E 1 . In  FIG. 6 , braiding yarns  3  are only shown in one direction, whereas the braiding yarns which are oblique in the opposite direction are not shown therein. The stationary yarns  2  extend in parallel and are aligned only in the perspective shown. On one hand, it can be seen that the braiding yarns  3  do not have an ideal straight course, which is referred to as a nominal position N, but rather differ from that nominal position N, which is the straight line that cuts through the braiding yarn  3  in the center of the flat braid in the manner of a cross section and extends at a tangent to the braiding yarn  3 , in that they have a curved course in the manner of a stretched letter S. This is referred to as an S twist. An inverse curvature, which is not shown therein, is referred to as a Z twist. The size of the twist is measured in an angle of twist β which is defined between the nominal position N and a straight line W that is lain through the points at which the braiding yarn  3  is in contact with the two outer stationary yarns  2 . The angle which is spanned between N and W is the angle of twist β. In the case of the braid according to the invention, the uniformity is so high that the angle of twist β is at most +/−3°. On the other hand, it can be seen in  FIG. 6  that the distances between the stationary yarns  2  clearly decrease from the center of the flat braid towards the outside. In the case of the braid according to the invention, the uniformity is so high that the distances between the stationary yarns  2  have an average standard deviation of only at most 5%, preferably at most 2%. 
         [0034]    Through the use of the configuration of the radial braiding machine and the braiding ring  5  thereof according to the invention, the flat braid according to the invention can be produced, which thus meets the high requirements in terms of uniformity. In this case, taking into consideration a shape of the core  6  which is selected in each case, it is possible to influence the position and time of deposition of the yarns  2 ,  3  in order to optimize the braid.