Method and unit for simultaneously forming multiple tobacco mats

Abstract

A method and unit for simultaneously forming multiple tobacco mats on a multiple-rod cigarette manufacturing machine, whereby an input stream of shredded tobacco is fed to a switch conduit selectively alignable with the inputs of at least two downflow conduits, each of which communicates via a respective carding assembly with a respective upflow conduit closed by a respective conveyor belt for a respective tobacco mat; the switch conduit being switched between positions selectively aligned with the downflow conduits in response to a command signal generated in function of the tobacco level in the downflow conduits.

1 ) A method of simultaneously forming multiple mats ( 3 ) of tobacco on a multiple-rod cigarette manufacturing machine ( 1 ); the method comprising the step of: 
 feeding an input stream ( 7 ) of shredded tobacco to a switch conduit ( 22 ) selectively alignable with the inputs of at least two downflow conduits ( 9 ), each of which communicates via a respective carding assembly ( 10 ) with a respective upflow conduit ( 17 ) closed by a respective conveyor belt ( 4 ) for a respective mat ( 3 ) of tobacco;    determining the tobacco level, at least one said downflow conduit ( 9 );    generating a command signal in function of the tobacco level; and    switching the switch conduit ( 22 ) between positions selectively aligned with the downflow conduits ( 9 ) in response to said command signal.    
     
     
         2 ) A method as claimed in  claim 1 , wherein said command signal comprises a “minimum level” signal emitted upon a given minimum level being reached in one of said downflow conduits ( 9 ).  
     
     
         3 ) A method as claimed in  claim 1 , wherein said command signal comprises a “maximum level” signal emitted upon a given maximum level being reached in one of said downflow conduits ( 9 ).  
     
     
         4 ) A unit for simultaneously forming multiple mats ( 3 ) of tobacco on a multiple-rod cigarette manufacturing machine ( 1 ); the unit ( 2 ) comprising an input hopper ( 6 ) for shredded tobacco, at least two downflow conduits ( 9 ), two upflow conduits ( 17 ), each connected to a respective said downflow conduit ( 9 ), a carding assembly ( 10 ) interposed between each downflow conduit ( 9 ) and the relative upflow conduit ( 17 ), and a conveyor belt ( 4 ) for a respective mat ( 3 ) of tobacco, located at an output end of each upflow conduit ( 17 ); the unit ( 2 ) being characterized by comprising a switch device ( 21 ) interposed between said input hopper ( 6 ) and the downflow conduits ( 9 ), and in turn comprising a switch conduit ( 22 ) selectively alignable with respective inputs of the downflow conduits ( 9 ); control means ( 31 ) being provided to switch the switch conduit ( 22 ) between positions selectively aligned with said downflow conduits ( 9 ) in response to a command signal; and detecting device ( 32 ) being provided for determining the tobacco level at least one said downflow conduit ( 9 ) and for generating the command signal in function of the tobacco level.  
     
     
         5 ) A unit as claimed in  claim 4 , wherein said switch device ( 21 ) comprises two side by side valve members ( 24 ), which together define said switch conduit ( 22 ) and are mounted to oscillate about respective parallel axes ( 27 ) to switch said switch conduit ( 22 ) between said positions selectively aligned with said downflow conduits ( 9 ), and at the same time to close whichever one of said downflow conduits ( 9 ) is not aligned with the switch conduit ( 22 ).  
     
     
         6 ) A unit as claimed in  claim 4 , wherein said switch device ( 21 ) comprises two side by side valve members ( 24 ), which together define said switch conduit ( 22 ) and constitute the cranks of an articulated parallelogram ( 25 ) also comprising a connecting rod ( 26 ) connecting said two valve members ( 24 ); said two valve members ( 24 ) being mounted to oscillate, under the control of drive means ( 30 ), about respective parallel axes ( 27 ).  
     
     
         7 ) A unit as claimed in  claim 5 , wherein each said valve member ( 24 ), in section, is substantially in the form of an isosceles triangle mounted with one vertex facing upwards and to oscillate about the respective said axis ( 27 ) located at said vertex; each valve member ( 24 ) being bounded, on the opposite side to said vertex, by a cylindrical surface portion ( 29 ) which, as said switch device ( 21 ) oscillates, closes a respective downflow conduit ( 9 ) when said switch conduit ( 22 ) is aligned with the other said downflow conduit ( 9 ).  
     
     
         8 ) A unit as claimed in  claim 4 , wherein for each said downflow conduit ( 9 ) the detecting device ( 32 ) is able to emit a “minimum level” signal of the tobacco level.  
     
     
         9 ) A unit as claimed in  claim 4 , wherein for each said downflow conduit ( 9 ) the detecting device ( 32 ) is able to emit “maximum level” signal of the tobacco level.