Apparatus and method for pre-forming a metal strip for the manufacture of roll formed and welded tubes

Abstract

An apparatus and method for pre-forming a metal strip, having an embossing tool and a strip edge chamfering tool, the embossing tool having an embossing roll having a cylindrical surface with a central embossing portion, and the strip edge chamfering tool having an edge chamfering roll having a recessed central section and side sections on each side of the central section, and an anvil roll, the edge chamfering roll and the anvil roll being configured to receive and pass the metal strip in a clearance formed between the rolls, the clearance having a reduced height in the side sections, which are located in a position where the longitudinal side edges of the metal strip will pass, so that the longitudinal side edges on each side of the metal strip, and on the embossed side of the metal strip become chamfered when being passed between the pair of rolls.

1 . An apparatus for pre-forming a metal strip ( 40 ) for the manufacture of roll formed and welded tubes, comprising an embossing tool ( 20 ) and a strip edge chamfering tool ( 30 ) wherein
 the embossing tool comprises an embossing roll ( 1 ) having a cylindrical surface ( 2 ) with a central embossing portion ( 3 ,  3 ′), and   the strip edge chamfering tool comprises an edge chamfering roll ( 31 ) comprising a recessed central section ( 34 ) and side sections ( 35 ) on each side of the central section, and an anvil roll ( 32 ), wherein the edge chamfering roll ( 31 ) and the anvil roll ( 32 ) are configured to receive and pass the metal strip in a clearance ( 33 ) formed between the rolls, wherein the clearance ( 33 ) has a reduced height in the side sections, which are located in a position where the longitudinal side edges of the metal strip will pass, so that the longitudinal side edges on each side of the metal strip, and on the embossed side of the metal strip become chamfered when being passed between the pair of rolls ( 31 ,  32 ).   
     
     
         2 . The apparatus of  claim 1 , wherein
 the embossing tool comprises the cylindrical surface ( 2 ) of the embossing roll ( 1 ), said cylindrical surface comprising the central embossing portion ( 3 ) and side portions ( 4   a ,  4   b ) arranged on each side of the central portion, said central portion being provided with an embossing pattern ( 10 ) and said side portions being free from embossing pattern, and   the central section ( 34 ) of the strip edge chamfering tool ( 30 ) is dimensioned such that an embossed pattern of a metal strip passing between the pair of rolls through the edge chamfering clearance ( 33 ) is not affected by the rolls ( 31 ,  32 ).   
     
     
         3 . The apparatus of  claim 1 , wherein the embossing tool and the strip edge chamfering tool are integrated so as to comprise one combined embossing and edge chamfering roll, whereby the central embossing portion ( 3 ′) is comprised in the central section ( 34 ′) of the edge chamfering clearance ( 33 ). 
     
     
         4 . The apparatus of  claim 1 , wherein the embossing pattern ( 10 ) on the central embossing portion comprises a plurality of grooves ( 11 ) arranged in the cylindrical surface of the central portion ( 3 ), and wherein the cylindrical surface of each side portion ( 4   a ,  4   b ) is level with the cylindrical surface of the central portion ( 3 ) between the grooves, and wherein the strip edge chamfering tool ( 30 ) is arranged downstream of the embossing tool in a travel direction (T) of the strip to be pre-formed. 
     
     
         5 . The apparatus of  claim 4 , wherein the embossing roll ( 1 ) is comprised of a central embossing pattern roll pack ( 6 ) and side rolls ( 7   a ,  7   b ), said side rolls being arranged on each side of the central embossing pattern roll pack, and wherein the central embossing pattern roll pack has a cylindrical surface forming the central portion ( 3 ) and the side rolls have cylindrical surfaces forming the side portions ( 4   a ,  4   b ). 
     
     
         6 . The apparatus of  claim 1 , wherein the cylindrical surface of the embossing roll has a total width (W 1 ) of 15 mm or more, and the central portion of the embossing roll has a width (W 2 ), which is 85-99% of the total width (W 1 ). 
     
     
         7 . The apparatus of  claim 1 , wherein the central section ( 34 ) of the clearance ( 33 ) between the first and second rolls ( 31 ,  32 ) of the strip edge chamfering tool ( 30 ), has a width (W 3 ) which is equal to or greater than the width (W 2 ) of the central portion ( 3 ) of the embossing roll ( 1 ). 
     
     
         8 . The apparatus of  claim 1 , wherein the first roll ( 31 ) of the pair of rolls in the edge chamfering tool comprises a recess ( 37 ) having outwardly inclined side edges ( 36 ) on each side of the recess, running along the circumference of the cylindrical surface of the first roll. 
     
     
         9 . The apparatus of  claim 8 , wherein the inclined side edges ( 36 ) are inclined at an angle of 30-60°. 
     
     
         10 . The apparatus of  claim 1 , wherein the side sections ( 35 ) of the clearance ( 33 ) between the first and second rolls ( 31 ,  32 ) each have a width which is equal to or greater than half of the difference between the total width of embossing tool (W 1 ) and the width of the central portion of embossing tool (W 2 ). 
     
     
         11 . A method of pre-forming a metal strip ( 40 ) comprising
 embossing a pattern on a central portion ( 41 ) of the strip, in a longitudinal direction thereof, while side portions ( 42 ) on each side of the central portion of the strip are rolled without embossing pattern, and   chamfering the longitudinal side edges ( 43 ) of the strip on the side of the strip which is provided with the embossed pattern.   
     
     
         12 . The method of  claim 11 , wherein, during the chamfering, the strip material at the longitudinal side edges ( 43 ) of the strip are pressed down, up to 20-60% of the strip thickness, thereby forming an inclined edge surface along the longitudinal side edges of the strip. 
     
     
         13 . The method of  claim 11 , wherein the embossing pattern comprises protrusions ( 44 ), and the side portions of the strip are rolled during the embossing step to a strip thickness which is approximately level with the strip thickness between the protrusions of the embossing pattern, followed by chamfering of the side edges in a subsequent step. 
     
     
         14 . The method of  claim 11 , wherein the embossing and edge chamfering are performed simultaneously in an integrated embossing and edge chamfering tool. 
     
     
         15 . The apparatus of  claim 8 , wherein the inclined side edges ( 36 ) are inclined at an angle of 43-47°. 
     
     
         16 . The method of  claim 11 , wherein, during the chamfering, the strip material at the longitudinal side edges ( 43 ) of the strip are pressed down, up to 35-40% of the strip thickness, thereby forming an inclined edge surface along the longitudinal side edges of the strip.