Abstract:
A net, in particular for protection, safety, water-rearing or architectural purposes, is braided together from individual helically curved longitudinal elements ( 3 ) to form a braided structure. Individual longitudinal elements ( 3 ) curved into a cylinder or screw shape are twisted one inside the other with adjacent ones and compressed such that the braided structure is in more or less planar sheet-like form and the longitudinal elements ( 3 ) here each form more or less rectilinear limbs ( 8   a,    8   b;    9   a,    9   b ) and curves ( 10   a,    10   b;    11   a,    11   b ) therebetween. The curves ( 10   a,    10   b;    11   a,    1   b ) between elongate limbs ( 8   a,    8   b;    9   a,    9   b ) are inflected in kink form. This gives a net design with unexpectedly high strength values.

Description:
FIELD OF THE INVENTION 
     The invention relates to a net, in particular for protection, safety, water-rearing or architectural purposes which is twisted together from individual helically or similarly bent longitudinal elements, such as wires, to form a woven structure, individual longitudinal elements curved into a cylinder or screw shape or similar being twisted one inside the other with adjacent ones and being compressed such that the braided structure forms a substantially planar sheet-like form and the longitudinal elements each form substantially rectilinear limbs and curves in between, and an apparatus for producing the net. 
     BACKGROUND OF THE INVENTION 
     Protective nets of this type are characterised in that they have a high tear strength and good deformability, and on this basis can be stressed to a considerable extent. This type of protective net is disclosed in WO 2010/049089 which relates to a high-strength braided structure composed of wire spirals twisted one inside the other and which are pressed flat to form three-dimensional rows of loops. This procedure enables inexpensive production of the braided structure. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The object underlying the invention is to improve the strength values of the net with simple structural measures while retaining these advantages, and moreover to enable faultless production of such nets or braided structures. 
     The object is achieved according to the invention by a net including a plurality of individual, bent longitudinal elements coupled together to form a woven structure. Each longitudinal elements is individually curved into a cylinder or screw shape to provide a first set of spaced apart curves on a first side of the longitudinal element and a second set of spaced apart curves on a second side of the longitudinal element, the curves in the first and second sets of curves alternating with one another in a longitudinal direction of the longitudinal element such that each curve of the first set is between two curves of the second set and each curve of the second set is between two curves of the first set. A first one of the longitudinal elements is twisted on one side with an adjacent second one of the longitudinal elements such that each curve of the first set of curves of the first longitudinal element passes around and inside of a respective curve of the second set of curves of the second longitudinal element to form knots each between one of the curves of the first set of curves of the first longitudinal element and a respective curve of the second set of curves of the second longitudinal element. The first longitudinal element is twisted on another side with an adjacent third one of the longitudinal elements such that each curve of the second set of curves of the first longitudinal element passes around and inside of a respective curve of the first set of curves of the third longitudinal element to form knots each between one of the curves of the second set of curves of the first longitudinal element and the respective curve of the first set of curves of the third longitudinal element. The longitudinal elements are compressed such that the woven structure has a substantially planar form. Each longitudinal element include elongate limbs between adjacent curves such that each limb is situated between one of the curves of the first set of curves and one of the curves of the second set of curves. The curves between the elongate limbs are kinks. The object is also achieved by an apparatus including stamps arranged in rows and which are adjustable in relation to one another transversely to the longitudinal extension of the longitudinal elements, each stamp including a guide groove for centering the longitudinal element on a front face side, and which run according to a gradient angle of the limbs. The stamps have an initial position in which one of the bent longitudinal elements is turned or inserted in the guide grooves of the stamps, and a final position in which the longitudinal element is compressed. The respective kinked shape of the curves is produced by the elongate limbs being guided through the stamps over substantially their entire length and the longitudinal elements respectively only projecting out of the stamps at the curve. 
     Advantageously, these curves respectively made in the form of kinks between the elongate limbs are produced such that the respectively adjacent limbs are compressed against one another transversely to their longitudinal extension until the planar sheet-like form plus an additional angle is achieved. 
     In the apparatus according to the invention the elongate limbs that are produced upon achieving the planar sheet-like form are guided over almost their entire length through stamps and the longitudinal elements respectively only project from the stamps at the curve. 
     The kinks in the limb regions according to the invention increase the flexibility of the net and to some extent loosen the geometry of the net, and in nature this leads to a visually advantageous camouflaging effect. Since these nets according to the invention are used above all in nature to counter natural hazards, this is an advantage with respect to conventional nets. 
     The kinks in the nets lead, moreover, to a loose, three-dimensional structure which for architectural applications achieves novel visual effects which can be used, for example, for large-scale façade coverings. 
     For the purpose of a mostly mirror-symmetrical design of the braided structure the invention makes provision such that the longitudinal elements are provided with kinks bent alternately in opposite directions transversely to the surface of the net. This measure is particularly advantageous if the longitudinal elements form diamond-shaped loops the limbs of which have kinks bent in opposite directions. 
     With regard to the use of the protective net in environmentally adverse conditions, the invention also makes provision such that the longitudinal elements are produced from wires, cords or strands made of corrosion-resistant, rust-proof and corrosion protection-coated steel. Advantageously the wires, cords or strands are produced from high strength steel with a strength of 1000 N/mm 2  to 3200 N/mm 2 . 
     For the purpose of flexible end connection of the longitudinal elements it is advantageous if the wires, cords or strands are knotted at the end to form loops by means of which they can be connected with one another in pairs to wire clips, wire hooks or similar connection elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the invention will be described in more detail by means of exemplary embodiments with reference to the drawings. These show as follows: 
         FIG. 1  is a net according to the invention, shown in simplified form in the front view, 
         FIG. 2  is a perspectively illustrated longitudinal element of the protective net according to  FIG. 1 , 
         FIG. 3  and  FIG. 4  are respective embodiments of the longitudinal element from  FIG. 2 , shown in the direction of arrow  1  in  FIG. 1 , 
         FIG. 5  is a perspective diagrammatic view of two stamps of an apparatus according to the invention for the production of the net; 
         FIGS. 6, 7 and 8  each show two stamps respectively shown diagrammatically in a diagrammatic view and which are shown, collectively, in three different positions adjusted in relation to one another and which here are pressing flat a wire bent in helical form. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows part of a net  1  which can be used in particular as a net that protects against rockfall, landslides, avalanches, unstable embankments and similar natural hazards. Moreover, it can be used for safety purposes or for aesthetic purposes in architecture. For example, they are used as fencing systems, shut-off and safety barriers, shatter protection, break-in and break-out protection, thoroughfare blocks for vehicles or ships and for further safety-relevant net solutions. This type of net is also suitable, however, as a protective net for baskets or covers for the rearing of fish, mussels or molluscs in bodies of water. 
     The net  1  is made up of a wire mesh braided structure  2  that is produced from longitudinal elements  3  in the form of helically bent steel wires  4 ,  5 ,  6 ,  7  according to  FIG. 5 . The wires  4 ,  5 ,  6 ,  7  bent in the form of spirals are twisted one inside the other in pairs, are braided together and pressed flat here such that at the end of the shaping process they obtain the form shown in  FIG. 2  with regularly successive limbs  8   a ,  8   b ;  9   a ,  9   b  and curves  10 ,  10   b ;  11   a ,  11   b . Here the wound longitudinal elements  3  are compressed in the limb regions  8   a ,  8   b ;  9   a ,  9   b  such that they are more or less rectilinear. 
     The wire mesh braided structure  2  produced in this way has diamond-shaped meshes  12  the flexible knots  13  of which define the net surface  14  drawn in by dots and dashes in  FIG. 3  and  FIG. 4  with an approximately planar sheet-like form A. 
     At their ends the wires of the longitudinal elements  3  are bent or knotted to form loops  17   a ,  17   b ;  18 ,  18   b  which make it possible to connect the wires at the end by means of wire clips or wire hooks guided in pairs through the loops  17   a ,  17   b  and  18   a ,  18   b  or by means of similar elements at the end. The knotted wire ends additionally enable inexpensive connection to the adjacent net sections of the protective net. Needless to say other comparable end connections for the wire ends of the longitudinal elements can also be used instead of knots. 
     According to the invention the wound longitudinal elements  3  are shaped into a more or less planar sheet-like form A in the net surface  14 , the curves  10   a ,  10   b ;  11   a ,  11   b  respectively being produced in the form of kinks. These kink-like curves  10   a ,  10   b ;  11   a ,  11   b  are formed such that the radius of curvature is very small or almost zero on the inside of each respective curve  10   a ,  10   b ;  11   a ,  11   b.    
     Moreover, within the framework of the invention the longitudinal elements  3  are formed such that they are more or less planar in the net surface  14  and are each provided with a slight kink  15   a ,  15   b ;  16   a ,  16   b  transversely to the net surface  14  in the limb region. The effect of this simple measure is that the net has higher tensile and tear strength values and clearly greater deformability than without the kinks. In this way, if there is an impact from a heavy object it can absorb more kinetic energy. 
     The kinks  15   a ,  15   b ;  16   a ,  16   b  are arranged approximately in the middle of the limbs  8   a ,  8   b ;  9   a ,  9   b , alternately in opposite directions transverse to the net surface  14 . They have a height of at most a few millimeters which is advantageously determined dependently upon the diameter of the longitudinal elements  3 . 
     It is also possible within the framework of the invention to provide a number of kinks in each limb running in the same or in opposite directions. Even very slight kinks enable advantageous elastic or plastic springing functions depending on the application. 
     As can be seen from  FIG. 3  and  FIG. 4 , it is also possible within the framework of the invention to vary the geometry of the wire braided structure  2  provided its longitudinal elements  3  are more or less planar in the net surface  14  and their limbs  8   a ,  8   b ;  9   a ,  9   b  are provided with slight kinks transversely to the net surface  14 . Depending on the conditions of use, a braided structure made up of cords or strands can also be used instead of the wire braided structure. 
     The flexible connections  13  between the wires  3  make it possible to roll up or fold up the braided structure. This is advantageous for transportation and storage of the net. 
       FIG. 5  to  FIG. 8  show diagrammatically two of the stamps  21 ,  22  of an apparatus according to the invention arranged in rows. These stamps  21 ,  22  are respectively provided with a guide groove  21 ′,  22 ′ receiving the wire  3  on the front face side and are arranged in relation to one another such that the guide grooves  21 ′,  22 ′ are alternately directed towards one another and run according to the gradient angle of the limbs  8   a ,  8   b ;  9   a ,  9   b . These stamps  21 ,  22  can be adjusted here backwards and forwards transversely to the longitudinal extension of the helically bent longitudinal elements  3  a specific distance apart from one another by means of driveable rods. 
       FIG. 6  illustrates the initial position of two of the stamps  21 ,  22  arranged in rows which are spaced apart depending upon the gradient height of the individual wire helix. Here, the helically bent wire  3  is turned along its longitudinal axis into the guide grooves  21 ′,  22 ′ similarly to screwing in and, moreover, is at the same time threaded into an adjacent wire that has already been pressed flat, but which is not detailed. In this way the net can be produced continuously. 
       FIG. 7  shows the two stamps  21 ,  22  in a position displaced in relation to one another and compressing the wire  3 . 
     It emerges from the final position of the stamps  21 ,  22  according to  FIG. 8  how the curves  10   a , respectively made in a kink shape, of the longitudinal elements are produced between the elongate limbs  8   a ,  8   b . The elongate limbs  8   a ,  8   b  produced upon achieving the planar sheet-like form are guided more or less over their entire length by the stamps  21 ,  22 , as can also be gathered from  FIG. 5 . Here the longitudinal elements  3  respectively only project from the stamps  21 ,  22  at the curve  10   a ,  10   b.    
     The respectively adjacent limbs  8   a ,  8   b  are compressed against one another transversely to their longitudinal extension until achieving the planar sheet-like form A plus an additional angle α. With this over-expansion of the limbs the respective kink shape of the curves is additionally favoured because in this way a type of strength increase is brought about to a certain extent, this angle α, which is preferably between 10° and 30°, becoming smaller when the stamps are drawn back and the longitudinal element is released by the springing back of the limbs. 
     In order to produce the kinks  15   a ,  15   b ;  16   a ,  16   b  in the longitudinal elements  3  the stamps  21 ,  22  are equipped with pins  24 ,  25  that can also be moved backwards and forwards transversely to the longitudinal extension of the longitudinal elements  3 , and which are preferably moved perpendicularly towards the limbs  8   a ,  8   b  in this end position of the stamps  21 ,  22  shown in  FIG. 8  to such an extent that these permanent kinks are produced. 
     For nets made of a wire braided structure high-strength wires with strengths of between 1000 N/mm 2  and 3200 N/mm 2  are preferably used which withstand particularly high loading. 
     Depending on the application and the desired deformation characteristics, however, applications in the nominal strength range of between 350 N/mm 2  and 1000 N/mm 2  are also advantageous. 
     In consideration of the conditions of use in the open air rust-proof, corrosion-resistant steels or steels coated with corrosion protection are preferred. When using these nets as baskets or covers in the rearing of fish or mussels they are provided with an anti-fouling layer which may contain, for example, copper. When using cords or strands it is not necessary for them to be made exclusively of high-strength wires with the nominal strength values specified above. 
     With the net according to the invention it is additionally made possible to produce round, cylindrically closed net elements which can, for example, be placed over mussel rearing elements. Cube-like bodies made up of individual net elements can also be produced. 
     The corresponding wire diameters for the net according to the invention are preferably in the range of between 0.5 mm and 5.0 mm. Instead of individual wires, strands (e.g. consisting of 2 to 7 wires) can also be used. 
     The invention is sufficiently demonstrated by the above exemplary embodiment. However, it could also be illustrated by other versions. Thus, for example, a number of or theoretically no kinks could be provided for each limb element depending on the application. Here, preferably an odd number of kinks is advantageous. Instead of the previously mentioned kink, similar shapings also advantageously lead to improvements according to the invention. Such shapings can, similarly to kinks, be made to be slightly elongated and/or oval in shape. 
     Depending on the intended use of the net, the individual longitudinal elements can in principle also be made with different strengths.