Cutting Unit for Cutting Continuous Cigarette Rods

Abstract

A cutting unit for cutting continuous cigarette rods, wherein a cutting head is locked in position on a fixed supporting body by an automatically releasable locking device, and, to make a change in format, is rotated, with respect to the supporting body and after the locking device is released, about an axis of rotation by an actuating device negative-feedback-controlled by a detecting device for determining angular displacement of the cutting head about the axis of rotation.

1 ) A cutting unit for cutting continuous cigarette rods fed in a given travelling direction ( 6 ), the cutting unit ( 1 ) comprising a supporting body ( 9 ); a cutting head ( 12 ) fitted to the supporting body ( 9 ) to rotate about a first axis ( 20 ), the cutting body ( 12 ) comprising a cutting drum ( 15 ), which rotates about a second axis ( 16 ) forming a given angle with said travelling direction ( 6 ), and has at least one radial blade ( 8 ); a counter-cutting device ( 4 ), which is engaged by at least one said continuous cigarette rod ( 3 ), and through which said first axis ( 20 ) extends; and locking means ( 24 ) for angularly locking the cutting head ( 12 ) in position on said supporting body ( 9 ); and being characterized in that said locking means ( 24 ) comprise automatic release means ( 48 ) for releasing the cutting head ( 12 ) with respect to the supporting body ( 9 ); actuating means ( 27 ,  31 ,  32 ) being interposed between the supporting body ( 9 ) and the cutting head ( 12 ) to rotate the cutting head ( 12 ) about said first axis ( 20 ) to vary said angle.  
   
   
       2 ) A cutting unit as claimed in  claim 1 , and also comprising sensor means ( 23 ) for determining said angle and for negative-feedback-controlling said actuating means ( 27 ,  31 ,  32 ).  
   
   
       3 ) A cutting unit as claimed in  claim 2 , wherein said sensor means ( 23 ) comprise a scale ( 33 ) located on said cutting head ( 12 ); and a fixed optical reader ( 35 ) for determining said angle on said scale ( 33 ).  
   
   
       4 ) A cutting unit as claimed in  claim 3 , wherein said cutting head ( 12 ) comprises a curved lateral surface ( 34 ) coaxial with said first axis ( 20 ); said curved lateral surface ( 34 ) supporting said scale ( 33 ); and said optical reader ( 35 ) facing said scale and being positioned radially with respect to said first axis ( 20 ).  
   
   
       5 ) A cutting unit as claimed in any one of  claims 1  to  4 , and also comprising guide means ( 21 ) interposed between the cutting head ( 12 ) and the supporting body ( 9 ) to guide the cutting head ( 12 ) on the supporting body ( 9 ) during rotation about said first axis ( 20 ).  
   
   
       6 ) A cutting unit as claimed in  claim 5 , wherein said guide means ( 21 ) comprise a rib ( 25 ), which projects upwards from said supporting body ( 9 ) and extends, on the supporting body ( 9 ), along an arc coaxial with said first axis ( 20 ); and a slot ( 26 ), which is formed on said cutting head ( 12 ), extends along an arc coaxial with said first axis ( 20 ) and of the same radius as the arc of said rib ( 25 ), and is engaged in sliding manner by said rib ( 25 ).  
   
   
       7 ) A cutting unit as claimed in any one of  claims 1  to  6 , wherein said actuating means ( 27 ,  31 ,  32 ) comprise a motor reducer ( 27 ) fitted to said supporting body ( 9 ); a pinion ( 31 ) parallel to said first axis ( 20 ) and activated by said motor reducer ( 27 ); and a ring gear ( 32 ) coaxial with said first axis ( 20 ), fitted to said cutting head ( 12 ), and engaged by said pinion ( 31 ).  
   
   
       8 ) A cutting unit as claimed in any one of  claims 1  to  7 , wherein said supporting body ( 9 ) and said cutting head ( 12 ) comprise a first and, respectively, a second plate ( 11 ,  14 ) contacting each other; said locking means ( 24 ) comprising at least one pin ( 36 ) extending in axially sliding manner through said first plate ( 11 ) and fitted in transversely sliding and axially fixed manner to said second plate ( 14 ); elastic means ( 46 ) being interposed between said pin ( 36 ) and said first plate ( 11 ) to compress and lock said first and second plate ( 11 ,  14 ) against each other.  
   
   
       9 ) A cutting unit as claimed in  claim 8 , wherein said pin ( 36 ) has an end portion comprising an end plate ( 38 ); said second plate ( 14 ) having a curved, T-section groove ( 39 ) coaxial with said first axis ( 20 ); and said end portion engaging said groove ( 39 ) in transversely sliding manner.  
   
   
       10 ) A cutting unit as claimed in  claim 8  or  9 , wherein said automatic release means ( 48 ) comprise push means ( 51 ) carried by said supporting body ( 9 ) and acting on said pin ( 36 ) to move the pin ( 36 ) axially in opposition to said elastic means ( 46 ).  
   
   
       11 ) A cutting unit as claimed in  claim 10 , wherein said push means ( 51 ) are cam means acting axially on said pin ( 36 ).  
   
   
       12 ) A cutting unit as claimed in  claim 11 , wherein said locking means ( 24 ) comprise two pairs of said pins ( 36 ); said automatic release means ( 48 ) comprising, for each said pair of pins ( 36 ), a rod ( 50 ), which has a third axis ( 52 ) crosswise to the relative said pins ( 36 ), and is fitted with two cams ( 51 ), each of which cooperates with one end ( 47 ) of a respective said pin ( 36 ), and an actuating device ( 53 ,  54 ,  56 ) for rotating said rod ( 50 ) about said third axis ( 52 ).  
   
   
       13 ) A cutting unit as claimed in  claim 12 , wherein said actuating device ( 53 ,  54 ,  56 ) is common to said rods ( 50 ), and comprises a linear actuator ( 53 ); and an articulated quadrilateral, in turn comprising two cranks ( 55 ), each fitted to a respective said rod ( 50 ); said linear actuator ( 53 ) having an output ( 54 ) connected to one of said cranks ( 55 ).