Sharpening unit and cutting machine comprising at least one blade and said sharpening unit

Abstract

The sharpening unit ( 50 ) comprises a grinding wheel unit ( 80 ) with at least two grinding wheels ( 51, 53 ) opposed to act on two sides defining a cutting bevel of the blade ( 19 ). The grinding wheel unit is provided with at least a degree of freedom to center the grinding wheels ( 51, 53 ) in respect of a lying surface of the portion of the cutting bevel of the blade ( 19 ) on which said grinding wheels act.

1 . A sharpening unit for a blade, comprising a grinding wheel unit with at least two grinding wheels opposed to act on two sides defining a cutting bevel of said blade, wherein said grinding wheel unit is freely movable according to at least a first degree of freedom to center the grinding wheels in respect to a lying surface of a portion of the cutting bevel of the blade on which said grinding wheels act.  
     
     
         2 . Sharpening unit as claimed in  claim 1 , further comprising a system to move the grinding wheel unit towards the blade along a direction of forward movement.  
     
     
         3 . Sharpening unit as claimed in  claim 1  or  2 , wherein said grinding wheel unit is provided with a partly restricted movement according to a second degree of freedom to center said grinding wheels in respect to said lying surface.  
     
     
         4 . Sharpening unit as claimed in  claim 3 , wherein said grinding wheel unit can oscillate about an axis of oscillation disposed in an intermediate position between axes of rotation of the grinding wheels, and wherein movability about said axis of oscillation constitutes said second degree of freedom.  
     
     
         5 . Sharpening unit as claimed in  claim 4 , wherein said axis of oscillation lies essentially on a lying plane of the portion of the cutting bevel of the blade on which said grinding wheels act, or on a plane that approximates a lying surface of said portion of the cutting bevel of the blade.  
     
     
         6 . Sharpening unit as claimed in  claim 2 , wherein said direction of forward movement of the grinding wheel unit is parallel to an axis of oscillation of the grinding wheel unit.  
     
     
         7 . Sharpening unit as claimed in  claim 4 , wherein said grinding wheels are disposed essentially symmetrically to said axis of oscillation.  
     
     
         8 . Sharpening unit as claimed in  claim 1 , wherein said grinding wheel unit is freely movable along a direction of translation not parallel to the lying surface of the portion of said cutting bevel on which said grinding wheels act, wherein movement along said direction of translation constitutes said first degree of freedom.  
     
     
         9 . Sharpening unit as claimed in  claim 8 , wherein said direction of translation is approximately orthogonal to said lying surface.  
     
     
         10 . Sharpening unit as claimed in  claim 4 , wherein said axis of oscillation is orthogonal to a direction of translation of the grinding wheel unit.  
     
     
         11 . Sharpening unit as claimed in  claim 4 , wherein said grinding wheel unit has a center of gravity which lies on said axis of oscillation.  
     
     
         12 . Sharpening unit as claimed in  claim 8 , wherein a counterweight moving along said direction of translation is associated with said grinding wheel unit, linking means being provided to force the counterweight to move in a direction opposite to said grinding wheel unit along said direction of translation.  
     
     
         13 . Sharpening unit as claimed in  claim 4 , wherein said grinding wheel unit is stressed in a predetermined angular position in respect to said axis of oscillation.  
     
     
         14 . Sharpening unit as claimed in  claim 4 , further comprising means to bring said grinding wheels alternately into an operating position and into a non-operating position.  
     
     
         15 . Sharpening unit as claimed in  claim 14 , wherein said means comprise an actuator that produces a movement of oscillation of the grinding wheel unit around said axis of oscillation to move the grinding wheels against the blade in said operating position and hold the grinding wheels in contact with the blade, and wherein said grinding wheel unit is free to translate along a direction of translation to become centered in respect of to the blade.  
     
     
         16 . Sharpening unit as claimed in  claim 15 , wherein a control element operated by said actuator is associated with said grinding wheel unit, to act on the grinding wheel unit to move the grinding wheels against the blade and bring the grinding wheels into said operating position, said control element being irreversible, with stress exerted by the blade on the grinding wheels not producing an opposite movement to movement bringing the grinding wheel against the blade.  
     
     
         17 . Sharpening unit as claimed in  claim 16 , wherein said control element comprises a slider rotating around its an axis of the slider controlled by said actuator, and a mechanism that produces axial sliding of said slider in a support when said slider is made to rotate around said axis by said actuator, said axial sliding of the slider producing rotation of the grinding wheel unit in a direction to move the grinding wheels against the blade.  
     
     
         18 . Sharpening unit as claimed in  claim 4 , wherein said grinding wheel unit further comprises a plate rotatingly supported around said axis of oscillation by a slide sliding along a sliding guide parallel to a direction of translation.  
     
     
         19 . Sharpening unit as claimed in  claim 18 . wherein said sliding guide is carried by a carriage moving along said direction of forward movement of the grinding wheel unit.  
     
     
         20 . Sharpening unit as claimed in  claim 4 , further comprising an angular position sensor of the grinding wheel unit in respect to said angle of oscillation.  
     
     
         21 . A cutting machine for cutting elongated products comprising at least one path for the products to be cut; at least one device to feed the products along said at least one path; at least one blade provided with a cutting movement to cut said products; at least one sharpening unit for said at least one blade, which comprises a grinding wheel unit with at least two grinding wheels opposed to act on said at least one blade, wherein said sharpening unit is made according to  claim 1 .  
     
     
         22 . Cutting machine as claimed in  claim 21 , wherein said grinding wheel unit is oscillating around an axis of oscillation essentially orthogonal to a direction of feed of the products to be cut along said at least one path.  
     
     
         23 . Cutting machine as claimed in  claim 21  or  22 , wherein said grinding wheel unit is free to translate along a direction of translation essentially parallel to the direction of feed of the products to be cut.  
     
     
         24 . Cutting machine as claimed in  claim 21 , wherein said at least one blade is a disk-shaped blade rotating around a respective axis, carried by a unit rotating around its axis of rotation.  
     
     
         25 . Cutting machine as claimed in  claim 24 , wherein said disk-shaped rotating blade is provided with an alternate movement essentially parallel to a direction of feed of the products to be cut and further comprising a counterweight is associated with said grinding wheel unit moving along a direction of translation, and connection means to force the counterweight to move in the a direction opposite to said grinding wheel unit along said direction of translation.  
     
     
         26 . Cutting machine as claimed in  claim 21 , wherein two sharpening units are associated with said at least one blade.  
     
     
         27 . Cutting machine as claimed in  claim 26 , wherein a first one of said two sharpening units has idle grinding wheels and a second one of said two sharpening units has motorized grinding wheels, said idle grinding wheels unit and the motorized grinding wheels having different inclinations in respect to said blade.