Multi-stand rolling mill for rod-shaped bodies comprising three motorized-rollers stands

Abstract

The present invention relates to a multi-stand rolling mill for tubular bodies. The rolling mill comprises a first section for rolling on mandrel defined by a first plurality of rolling stands arranged in sequence along a rolling axis. According to the invention, the rolling mill also comprises a second rolling section without mandrel, arranged downstream of said first section, which comprises a second plurality of stands arranged in sequence along said rolling axis. Each stand of said second section comprises three rollers having rotation axes which are arranged at 120° from one another. The rotation axes for each stand are rotated by 180° with respect to corresponding rotation axes of an adjacent stand. According to the invention, at least one stand of said second section comprises a motorized roller having a vertical rotation axis.

What is claimed is: 
     
         1 . A rolling mill ( 1 ) for tubular bodies comprising a first section ( 10 ) for rolling on mandrel defined by a first plurality of rolling stands ( 15 ′,  15 ,  15 ″) arranged in sequence along a rolling axis ( 100 ),
 a second section ( 20 ) for extracting said mandrel, reducing and calibrating the diameter of said tubular bodies, said second section being downstream of said first section ( 10 ), wherein the distance between a last rolling stand of the first section ( 10 ) and a first rolling stand of the second section ( 20 ) in a range of 8 to 14 m, 
 wherein said tubular bodies exiting from said first section ( 10 ) have an external diameter equal or greater than 100 mm and 
 directly enter said second section ( 20 ), said second section ( 20 ) comprising a second plurality of rolling stands ( 25 ′,  25 ,  26 ,  27 ,  26 ′,  27 ′) without mandrel, arranged in sequence along said rolling axis ( 100 ), 
 wherein each stand ( 25 ′,  25 ,  26 ,  27 ,  26 ′,  27 ′) of said second section ( 20 ) comprises three rollers, the rotation axes of which are arranged at 120° relative to one another and 
 wherein, for each stand ( 25 ′,  25 ,  26 ,  27 ,  26 ′,  27 ′) of said second section, said rotation axes are rotated by 180° relative to corresponding rotation axes of an adjacent stand, said position of said rotation axes being assessed with respect to a vertical reference direction, and 
 wherein at least one stand of said second section ( 20 ) comprises a motorized roller having a vertical rotation axis, 
 wherein the second section ( 20 ) comprises first releasing thrust cylinders ( 290 ) positioned on the inlet side ( 20 ′) and 
 second locking thrust cylinders ( 291 ) being positioned on the outlet side ( 20 ″) of the second section ( 20 ) and capable of exerting an axial thrust on the stands ( 25 ′,  25 ,  26 ,  27 ,  26 ′,  27 ′) of the second section in a direction opposite to the rolling direction ( 200 ) for compacting the stands along the rolling direction and locking them axially. 
 
     
     
         2 . A rolling mill ( 1 ) according to  claim 1 , wherein said second section ( 20 ) comprises at least one fixed rollers stand ( 25 ′,  25 ) placed as the first rolling stand of the second section and at least one adjustable rollers stand ( 26 ,  27 ,  26 ′,  27 ′). 
     
     
         3 . A rolling mill ( 1 ) according to  claim 2 , wherein the total number of stands of the second section, is in the range from 8 to 16. 
     
     
         4 . A rolling mill ( 1 ) according to  claim 3 , wherein said second section ( 20 ) comprises a first series of fixed rollers stands ( 25 ′,  25 ) arranged in sequence along said rolling axis ( 100 ) starting from an inlet side ( 20 ′) of said second section ( 20 ), at least one of said fixed rollers stands ( 25 ′,  25 ) comprising mechanical drive means configured to transmit the motion from said motorized roller having vertical rotation axis to the other rollers of the same stand. 
     
     
         5 . A rolling mill ( 1 ) according to  claim 4 , wherein said second section ( 20 ) comprises at least one dummy stand ( 28 ) comprising at least one guide roller. 
     
     
         6 . A rolling mill ( 1 ) according to  claim 5 , wherein each stand ( 15 ′,  15 ,  15 ″) of said first section ( 10 ) comprises three rollers, the rotation axes of which are arranged at 120° relative to one another and wherein the rotation axes of the rollers of an outlet stand ( 15 ″) of said first section ( 10 ) are rotated by 180° with respect to the rotation axes of the rollers of an inlet stand ( 25 ′) of said second section ( 20 ). 
     
     
         7 . A rolling mill ( 1 ) according to  claim 6 , wherein said second section ( 20 ) comprises a first stretch ( 21 ) which defines a first plurality of lodging positions each of which configured for accommodating a fixed rollers stand or a dummy stand, said second section ( 20 ) comprising a second stretch ( 22 ), downstream of said first stretch ( 21 ), which defines a second plurality of lodging positions each of which configured for accommodating a fixed rollers stand or a dummy stand or an adjustable rollers stand. 
     
     
         8 . A rolling mill ( 1 ) according to  claim 7 , wherein said second section ( 20 ) comprises a group ( 60 ,  62 ) of adjustable rollers stands, said group ( 60 ,  62 ) comprising:
 a first stand ( 26 ,  26 ′) and a second stand ( 27 ,  27 ′) adjacent to said first stand ( 26 ,  26 ′), wherein said first stand ( 26 ,  26 ′) comprises at least one roller motorized by an actuating means;   a transmission device ( 91 ) which operatively connects said at least one roller ( 34 ,  35 ,  36 ) of said first stand ( 26 ,  26 ′) to at least one roller ( 34 ′,  35 ′,  36 ′) of said second stand ( 27 ,  27 ′) so that both the rollers are actuated by said actuating means.   
     
     
         9 . A rolling mill ( 1 ) according to  claim 8 , wherein said second stretch ( 22 ) of said second section ( 20 ) defines three lodging positions and wherein said group ( 62 ) of adjustable rollers stands is configured to occupy the first lodging position and the second lodging position downstream of said first stretch ( 21 ). 
     
     
         10 . A rolling mill ( 1 ) according to  claim 8 , wherein said second stretch ( 22 ) of said second section ( 20 ) defines three lodging positions and wherein said group ( 60 ) of adjustable rollers stands is configured to occupy the second lodging position and the third lodging position downstream of said first stretch ( 21 ). 
     
     
         11 . A rolling mill ( 1 ) according to  claim 10 , wherein said group ( 60 ,  62 ) comprises at least a first transmission device ( 91 ) which operatively connects a first vertical axis roller ( 34 ) of said first stand ( 26 ,  26 ′) to a first vertical axis roller ( 34 ′) of said second stand ( 27 ,  27 ′). 
     
     
         12 . A rolling mill ( 1 ) according to  claim 11 , wherein said first stand ( 26 ,  26 ′) and said second stand ( 27 ,  27 ′) of said group ( 60 ,  62 ) are integrated in a single body ( 60 ′) defining an operating recess inside which the rollers ( 34 ,  35 ,  36 ) of said first stand ( 26 ,  26 ′) and the rollers ( 34 ′,  35 ′,  36 ′) of said second stand ( 27 ,  27 ′) are accommodated. 
     
     
         13 . A rolling mill ( 1 ) according to  claim 12 , wherein said first stand ( 26 ,  26 ′) and said second stand ( 27 ,  27 ′) of said group ( 60 ,  62 ) each comprise:
 a first roller ( 34 ,  34 ′) having a vertical rotation axis ( 111 ,  111 ′); 
 a second roller ( 35 ,  35 ′) having a rotation axis ( 112 ,  112 ′) inclined by 120° with respect to said vertical rotation axis ( 111 ,  111 ′) of said first roller ( 34 ,  34 ′), said second roller ( 35 ,  35 ′) being operatively positioned above a horizontal reference plane ( 105 ) on which said rolling axis ( 100 ) lies; 
 a third roller ( 36 ,  36 ′) having a rotation axis ( 113 ,  113 ′) inclined by 120° with respect to said rotation axes of said first roller ( 34 ,  34 ′) and of said second roller ( 35 ,  35 ′), said third roller ( 36 ,  36 ′) being operatively positioned below said horizontal reference plane ( 105 ), and wherein said group ( 60 ,  62 ) comprises a second transmission device which operatively connects said third roller ( 36 ) of said first stand ( 26 ) to said second roller ( 35 ′) of said second stand ( 27 ,  26 ′), said third roller ( 36 ) of said first stand ( 26 ,  27 ′) being actuated by an actuating means. 
 
     
     
         14 . A rolling mill ( 1 ) according to  claim 13 , wherein said group ( 60 ,  62 ) comprises a further transmission device which operatively connects said second roller ( 35 ) of said first stand ( 26 ,  26 ′) to said third roller ( 36 ′) of said second stand ( 27 ,  27 ′), said third roller ( 36 ′) of said second stand ( 27 ,  27 ′) being actuated by a further actuating means.