Method for production of multi-planar stretched nets

Abstract

A process for production of a three-planar net has been conceived, which net consists of a plurality of thread-like elements ( 2 a ) of a first series ( 2 ) parallel to each other and secured to a plurality of thread-like elements ( 3 a ) of a second series ( 3 ) parallel to each other and transverse to the elements of the first series ( 2 ); the elements ( 3 a ) of the second series ( 3 ) are in turn secured to elements ( 4 a ) of a third series ( 4 ) parallel to each other and transverse to the elements of the two first series. The production process contemplates a step of stretching the three-planar-net article thus obtained ( 10 ) for modifying the weight features per unit of measurement of the net itself according to the specific requirements.

1 . A process for manufacturing multiplanar nets comprising the following steps:
 making a monobloc net-like article of manufacture by at least the following sub-steps:
 providing a first, a second and a third series ( 2 ,  3 ,  4 ) of thread-like elements ( 2   a ,  3   a ,  4   a ), each series ( 2 ,  3 ,  4 ) having thread-like elements ( 2   a ,  3   a ,  4   a ) parallel to each other; 
 coupling the first series ( 2 ) of thread-like elements ( 2   a ) to the second series ( 3 ) of thread-like elements ( 3   a ) in such a manner that the elements ( 2   a ) of the first series ( 2 ) are inclined to the elements ( 3   a ) of the second series ( 3 ), the elements of the first series ( 2 ) being in a lying plane (A) different from the elements of the second series ( 3 ), the coupling regions between the thread-like elements ( 2   a ) of the first series ( 2 ) and the thread-like elements ( 3   a ) of the second series ( 3 ) defining a plurality of knots ( 5 ) between the first and second series; 
 coupling said second series ( 3 ) of thread-like elements ( 3   a ) to said third series ( 4 ) of thread-like elements ( 4   a ) in such a manner that the elements of the second series ( 3 ) are inclined to the elements of the third series ( 4 ), the elements of the first series ( 2 ), the second series ( 3 ) and the third series ( 4 ) lying in different lying planes (A, B, C) respectively, the elements of the second series ( 3 ) being interposed between the elements of the first series ( 2 ) and the elements of the third series ( 4 ), the elements of the second series and the elements of the third series defining a plurality of connecting knots ( 6 ) between the second and third series ( 3 ,  4 ); characterised in that it further comprises a step of stretching the net-like article of manufacture ( 10 ) thus obtained in at least one first stretching direction ( 7 ). 
   
     
     
         2 . A process as claimed in the preceding claim, characterised in that the steps of making said first series ( 2 ), second series ( 3 ) and third series ( 4 ) of thread-like elements and the step of associating said first series with said second series and third series are substantially simultaneous. 
     
     
         3 . A process as claimed in anyone of the preceding claims, characterised in that said step of making a net-like article of manufacture ( 10 ) is obtained by an extrusion step, the thread-like elements ( 3   a ) of the second series ( 3 ) having an extension direction substantially parallel to the moving forward direction (MD) of the net-like article of manufacture ( 10 ) coming out of the extruder. 
     
     
         4 . A process as claimed in anyone of the preceding claims, characterised in that the thread-like elements of the first series ( 2 ) and the thread-like elements of the third series ( 4 ) are such made that they have mutually inclined extension axes ( 9 ,  11 ), the elements of the second series ( 3 ) being inclined to the elements of the first and third series ( 2 ,  4 ). 
     
     
         5 . A process as claimed in anyone of the preceding claims, characterised in that the connecting knots ( 5 ) between the first and second series ( 2 ,  3 ) and the connecting knots ( 6 ) between the second and third series ( 3 ,  4 ) are made in such a manner that they are at corresponding locations thus defining connecting knots between the first, second and third series. 
     
     
         6 . A process as claimed in anyone of the preceding claims, characterised in that the elements of the second series ( 3 ) substantially define a bisector of the angle (α) formed between the elements of the first and third series ( 2 ,  4 ). 
     
     
         7 . A process as claimed in anyone of the preceding claims, characterised in that it further comprises a further stretching step for stretching the net-like article of manufacture ( 10 ) in an additional direction ( 13 ) transverse to the first stretching direction ( 7 ), preferably the first stretching direction ( 7 ) is not parallel to any extension direction of the thread-like elements of the first, second and third series. 
     
     
         8 . A process as claimed in anyone of the preceding claims, characterised in that said first stretching direction ( 7 ) is substantially transverse and preferably orthogonal to the moving forward direction (MD) during manufacture, and to the longitudinal extension ( 8 ) of the thread-like elements of the second series ( 3 ). 
     
     
         9 . A process as claimed in anyone of the preceding claims, characterised in that said additional stretching direction ( 13 ) is transverse and preferably orthogonal to said first stretching direction ( 7 ), most preferably said additional stretching direction ( 13 ) being parallel to the longitudinal extension direction ( 8 ) of the thread-like elements of the second series ( 3 ). 
     
     
         10 . A process as claimed in anyone of the preceding claims, characterised in that it further comprises a step of associating at least one layer of filtering material ( 12 ) with the stretched net-like article of manufacture, said layer of filtering material ( 12 ) being preferably associated with said first series ( 2 ) of thread-like elements and/or said third series ( 4 ) of thread thread-like elements. 
     
     
         11 . A multiplanar net, in particular for draining fluids, comprising:
 at least one first, one second and one third series ( 2 ,  3 ,  4 ) of thread-like elements ( 2   a ,  3   a ,  4   a ), the thread-like elements ( 2   a ) of the first series ( 2 ) being parallel to each other, the thread-like elements ( 3   a ) of the second series ( 3 ) being parallel to each other and the thread-like elements ( 4   a ) of the third series ( 4 ) being parallel to each other, the thread-like elements of the first series ( 2 ) lying in a first lying plane (A), the thread-like elements of the second series ( 3 ) lying in a second lying plane (B) and the elements of the third series ( 4 ) lying in a third lying plane (C), said lying planes (A, B, C) being mutually offset,   connecting knots ( 5 ) between the thread-like elements of the first series ( 2 ) and the thread-like elements of the second series ( 3 );   connecting knots ( 6 ) between the thread-like elements of the second series ( 3 ) and the thread-like elements of the third series ( 4 ), characterised in that the thread-like elements ( 3   a ) of the second series ( 3 ) are stretched along their major extension direction ( 8 ), having a section, in a plane orthogonal to the major extension direction, decreasing and then increasing on moving from a knot to the next one.