Cutting machine with a sharpening unit for a blade, sharpening method and blade for said machine

Abstract

The unit comprises a first grinding wheel ( 81 ) and a second grinding wheel ( 83 ) acting on a first side ( 207 ) and on a second side ( 209 ) of the bevel ( 205 ) of the blade ( 19 ). The first grinding wheel ( 81 ) has a finer grain than the second grinding wheel ( 83 ). Moreover, the first grinding wheel also has an inclination that is not parallel to the respective first side ( 207 ) of the bevel ( 205 ) of the blade ( 19 ), while the second grinding wheel ( 83 ) has an inclination essentially parallel to the second side ( 209 ) of said bevel.

1 . A sharpening unit to sharpen a disk-shaped cutting blade with a bevel with a continuous circular cutting edge, comprising a first grinding wheel and a second grinding wheel acting on a first side and on a second side of said bevel, wherein said first grinding wheel has a finer grain than said second grinding wheel said first grinding wheel has an inclination such that when the unit is in operation, said first grinding wheel is placed against the first side of the bevel at an inclination greater than the inclination of the first side, in respect to a lying plane of the a cutting edge of the blade, while said second grinding wheel has an inclination which is substantially parallel to the second side of said bevel, and said second grinding wheel is constructed and arranged to sharpen the bevel of the blade, while said first grinding wheel is constructed and arranged to apply a reaction force to said blade to prevent or reduce flexure of the blade in the a sharpening area and eliminating burrs produced by the second grinding wheel from the cutting edge.  
     
     
         2 . Sharpening unit as claimed in  claim 1 , wherein said first grinding wheel and said second grinding wheel are provided with a movement to move towards and away from the blade according to a direction essentially parallel to axes of rotation of the first grinding wheel and the second grinding wheel.  
     
     
         3 . Sharpening unit as claimed in  claim 2 , wherein the movement to move said first grinding wheel and said second grinding wheel towards the blade is controlled so that the first grinding wheel comes into contact with the first side of the bevel before the second grinding wheel comes into contact with the second side of the bevel, and moves out of contact with said first side of the bevel after the second grinding wheel has moved out of contact with the second side of the bevel.  
     
     
         4 . Sharpening unit as claimed in  claim 3 , wherein the movement to move the first grinding wheel and said second grinding wheel towards and away from the blade is controlled so that the first grinding wheel moves out of contact with the first side of the bevel after said blade has made at least one turn around its axis subsequent to the second grinding wheel moving away from the second side.  
     
     
         5 . Sharpening unit as claimed in  claim 1 , wherein said first grinding wheel and said second grinding wheel are motorized.  
     
     
         6 . Sharpening unit as claimed in  claim 1 , wherein the inclination of each said first grinding wheel and said second grinding wheel are equal and opposite in respect to the lying plane of the cutting edge of the blade; said lying plane being essentially orthogonal to the axis of rotation of the blade.  
     
     
         7 . Sharpening unit as claimed in  claim 1 , wherein said first grinding wheel has a fine grain of from 7 to 46 according to ISO standards.  
     
     
         8 . Sharpening unit as claimed in  claim 1 , wherein said second grinding wheel has a fine grain of between 45 and 91 according to ISO standards.  
     
     
         9 . A cutting machine to cut rolls of wound web material, comprising: 
 at least one disk-shaped blade rotating around an axis of rotation and having a cutting bevel, with a continuous cutting edge with a first side and a second side, the first side having a greater radial extension than the second side, and at least said first side having a surface hardening treatment;    at least one sharpening unit for said blade, with at least a first grinding wheel acting on said first side and a second grinding wheel acting on the second side;    wherein said at least one sharpening unit is produced according to  claim 1 .    
     
     
         10 . Cutting machine as claimed in  claim 9 , wherein the inclination of the first grinding wheel in respect of the first side of the bevel and thickness of said surface hardening treatment allow the cutting edge of the blade to remain within the thickness that has been subjected to hardening treatment.  
     
     
         11 . Cutting machine as claimed in  claim 9 , wherein said first grinding wheel and said second grinding wheel are equipped with a movement to move each towards and away from the blade according to a direction essentially parallel to a respective axis of rotation of said first grinding wheel and said second grinding wheel, said movement also recovering wear on the blade caused by successive sharpenings.  
     
     
         12 . Cutting machine as claimed in  claim 9 , wherein the inclination of each said first grinding wheel and said second grinding wheel are equal and opposed in respect to the lying plane of the cutting edge of the blade, said lying plane being essentially orthogonal to the axis of rotation of the blade, and wherein the inclination of each first said side and said second side of the bevel of the blade are different in respect to the lying plane of the cutting edge of the blade, the first side having, in respect to said lying plane, a lesser inclination than the second side.  
     
     
         13 . Cutting machine as claimed in  claim 9 , wherein said first side is substantially parallel to the lying plane of the cutting edge of the blade.  
     
     
         14 . Cutting machine as claimed in  claim 12 , wherein the difference in inclination between said first side and said second side is at least 1°.  
     
     
         15 . Cutting machine as claimed in  claim 10 , wherein the thickness of said hardening treatment of said first side is equal to or greater than 30 micrometers.  
     
     
         16 . Cutting machine as claimed in  claim 9 , wherein at least said first side of the bevel has a surface hardness greater than 70 HRC.  
     
     
         17 . Cutting machine as claimed in  claim 9 , wherein said blade is made of alloy steel.  
     
     
         18 . Cutting machine as claimed in  claim 9 , wherein at least said first side has a surface treatment obtained by penetration of molecules or atoms within structure of a base material forming the blade.  
     
     
         19 . Cutting machine as claimed in  claim 18 , wherein said surface treatment is a controlled nitriding treatment.  
     
     
         20 . Cutting machine as claimed in  claim 9 , wherein at least said first side has a surface treatment including a deposit of a material which is harder than a base material forming the blade.  
     
     
         21 . Cutting machine as claimed in  claim 17 , wherein said blade is made of chrome steel containing molybdenum.  
     
     
         22 . Cutting machine as claimed in  claim 9 , wherein the inclination of said first side is equal to or less than 9° in respect to said lying plane.  
     
     
         23 . Cutting machine as claimed in  claim 9 , wherein said blade has a body delimited by two planes essentially parallel to each other and essentially orthogonal to the axis of rotation of the blade.  
     
     
         24 . Method for sharpening a disk-shaped blade, to cut rolls of web material, comprising rotating around an axis of rotation said blade having a cutting bevel, with a continuous cutting edge, defined by a first side and a second side, the first side having an extension greater in a radial direction than the second side, and at least said first side having a surface hardening treatment; wherein a first grinding wheel acts on said first side and a second grinding wheel acts on said second side, wherein 
 said first grinding wheel has a finer grain than said second grinding wheel;    said first grinding wheel is placed against the first side of the bevel at an inclination greater than an inclination of the first side, in respect to a lying plane of the cutting edge of the blade;    said second grinding wheel is placed against the second side of the bevel at an inclination essentially corresponding to the inclination of said second side in respect to said lying plane;    wherein said second grinding wheel sharpens the cutting bevel, while said first grinding wheel applies a reaction force to said blade to prevent or reduce flexure of the blade in a sharpening area and eliminates burrs produced by the second grinding wheel from the cutting edge.    
     
     
         25 . Method as claimed in  claim 24 , further comprising using a blade whose surface hardening treatment has a thickness of at least 30 micrometers.  
     
     
         26 . Method as claimed in  claim 25 , wherein the inclination of the first grinding wheel in respect to the first side of the bevel and the thickness of said hardening treatment are such that the cutting edge of the blade remains within the thickness of the hardening treatment.  
     
     
         27 . Method as claimed in  claim 24 , wherein said first grinding wheel and said second grinding wheel are motorized.  
     
     
         28 . Method as claimed in  claim 24 , wherein said first grinding wheel and said second grinding wheel are moved against said blade with a movement essentially parallel to a respective axis of rotation, said movement also recovering wear of the blade caused by successive sharpenings.  
     
     
         29 . Method as claimed in  claim 28 , wherein the first grinding wheel comes into contact with the first side of the bevel before the second grinding wheel comes into contact with the second side of the bevel; and wherein the first grinding wheel moves out of contact with said first side of the bevel after the second grinding wheel has moved out of contact with the second side of the bevel.  
     
     
         30 . Method as claimed in  claim 29 , that wherein the movement to move the first grinding wheel and the second grinding wheel towards and away from the blade is controlled so that the first grinding wheel moves out of contact with the first side of the bevel after said blade has made at least one turn about its axis subsequent to the second grinding wheel moving away from the second side.  
     
     
         31 . Method as claimed in  claim 24 , wherein the inclination of each said first grinding wheel and said second grinding wheel are equal and opposed in respect of a lying plane of the cutting edge of the blade, essentially orthogonal to the axis of rotation of the blade, and wherein the inclination of each said first side and said second side of the bevel of the blade in respect of the lying plane (PG) of the cutting edge of the blade are different, the first side being inclined less in respect of said lying plane than the second side, and wherein said first grinding wheel and said second grinding wheel produce a symmetrical cutting edge in respect of the lying plane of the said cutting edge.  
     
     
         32 . Method as claimed in  claim 31 , wherein the difference in inclination between said first side and said second side is at least 1°.  
     
     
         33 . Method as claimed in  claim 24 , wherein said first grinding wheel has a fine grain of from 7 to 46 according to ISO standards.  
     
     
         34 . Method as claimed in  claim 24 , wherein said second grinding wheel has a fine grain of from 45 to 91 according to ISO standards.  
     
     
         35 . A disk-shaped blade to cut rolls of wound web material, comprising an axis of rotation, a body with flat parallel faces and a cutting bevel with a continuous cutting edge, defined by a first side and by a second side, the first side having, before sharpening, an extension greater in a radial direction, and at least said first side having a surface hardening treatment; wherein said surface treatment is a NITREG® treatment and has a thickness of at least 30 micrometers.  
     
     
         36 . Disk-shaped blade as claimed in  claim 35 , wherein at least said first side has a surface hardness of over 70 HRC.  
     
     
         37 . Disk-shaped blade as claimed in  claim 35 , wherein said blade is made of alloy steel.  
     
     
         38 . Disk-shaped blade as claimed in  claim 35 , wherein said blade is produced in molybdenum chrome steel.  
     
     
         39 . Disk-shaped blade as claimed in  claim 35 , wherein at least said first side has surface thermal treatment by means of penetration of atoms or molecules within structure of a base material forming the blade.  
     
     
         40 . Disk-shaped blade as claimed in  claim 35 , wherein the surface treatment is a controlled nitriding treatment.  
     
     
         41 . Disk-shaped blade as claimed  claim 40 , wherein said surface treatment includes a deposit of a material having a hardness greater than hardness of a base material forming the blade.  
     
     
         42 . Disk-shaped blade as claimed in  claim 35 , wherein said first side has, in respect of a lying plane of the cutting edge, an inclination less than the second side.  
     
     
         43 . Disk-shaped blade as claimed in  42 , wherein the first side is substantially parallel to the lying plane of the cutting edge of said blade.  
     
     
         44 . Disk-shaped blade as claimed in that  claim 42 , wherein difference in inclination between said first and said second side is at least 1°.  
     
     
         45 . Disk-shaped blade as claimed in  claim 42 , wherein said first side has an inclination equal to or less than around 9° in respect of said lying plane.  
     
     
         46 . Disk shaped blade as claimed in  claim 35 , wherein before sharpening said cutting edge lies on a lying line that does not coincide with a plane of a center line of the blade and in respect of the lying line is moved towards the first side.  
     
     
         47 . Disk-shaped blade as claimed in  claim 35 , wherein the blade has a body delimited by two planes essentially parallel to each other and essentially orthogonal to the axis of rotation of the blade.  
     
     
         48 . Disk-shaped blade as claimed in  claim 35 , wherein the thickness of said treatment is such that the cutting edge of the blade, once sharpened by the first grinding wheel and said second grinding wheel contacting the first side and the second side of the cutting bevel, remains within the thickness of said treatment.