Variable rake shear

Abstract

A variable rake shear comprises a housing ( 8 ), a first blade ( 1 ) mounted in a first blade mounting ( 4 ), a second blade ( 2 ) mounted in a second blade mounting ( 3 ); and a control device ( 5 ) to control movement of one blade mounting to shear the material. Each blade mounting is movable in at least one dimension relative to the housing. One blade is an active blade ( 1 ) and the other blade is a passive blade ( 2 ). A rake adjustment mechanism ( 6 a , 6 b ) for at least one of the mountings ( 3, 4 ) and the mounting ( 4 ) for the active blade ( 1 ) has a torque tube linkage mechanism ( 10, 11, 12 ).

What is claimed is: 
     
         1 . A method of operating a variable rake shear to shear material, the method comprising;
 mounting a first blade in a first blade mounting, mounting a second blade in a second blade mounting, wherein each blade mounting is movable in at least one dimension relative to the housing to move the blades toward and past each other for shearing;   applying a rake angle to one of the first and second blade mountings; wherein one blade is an active blade and the other blade is a passive blade; connecting the first blade mounting of the active blade to a torque tube linkage mechanism configured for; and controlling movement of the first blade mounting of the active blade to shear the material.   
     
     
         2 . A method according to  claim 1 , further comprising applying the rake to the active blade by disconnecting a clutch in the torque tube linkage mechanism of the blade mounting, adjusting the rake angle of the blade in the blade mounting; and reconnecting the clutch. 
     
     
         3 . A method according to  claim 1 , further comprising applying the rake to the passive blade by adjusting one or more mechanical adjusters connected between the housing and the blade mounting of the passive blade. 
     
     
         4 . A method according to  claim 3 , comprising setting a minimum vertical gap between the blades before shearing a material by using at least two of the adjusters. 
     
     
         5 . A method according to  claim 1 , comprising the adjusting of the rake angle is according to the thickness and strength of the material to be sheared. 
     
     
         6 . A method according to  claim 1 , comprising altering the rake of one or both blades between successive cuts on the same piece of material. 
     
     
         7 . A method according to  claim 1 , further comprising applying the rake to at least one of the first and second blade mountings. 
     
     
         8 . A method according to  claim 1 , further comprising applying the rake to the blade contacting a part of the material to be scrapped. 
     
     
         9 . A method according to  claim 1 , further comprising varying stroke of movement of the active blade according to at least one of the rake angle of the or each blade, the width of material being sheared, the position of the material relative to the centreline of the shear and the elongation to fracture of the material.