Abstract:
A continuous cigarette rod is prepared by a unit comprising a looped conveyor on which a continuous stream of tobacco particles advances toward the entry point of a forming station where the rod is assembled. Also forming part of the unit, ordered in sequence along a predetermined feed path, are a first trimming device designed to produce a cyclical skimming action, a compactor device operating synchronously with the first trimming device, serving to increase the density of the stream selectively at points coinciding with the portions skimmed by the first trimming device, and a second trimming device by which the thickness of the stream is reduced uniformly to a prescribed value.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a unit and to a method for forming a continuous cigarette rod in a cigarette-making machine, whether equipped with a single processing line or with two such lines.  
         [0002]     A conventional cigarette maker of the type that operates by forming a continuous cigarette rod will generally comprise a vertical riser duct fed at the bottom end with a continuous flow of tobacco fibers and communicating at the top end with an aspirating conveyor belt on which a continuous stream of loose tobacco filler is formed.  
         [0003]     The stream of tobacco filler is carried by the aspirating belt along a predetermined path toward a feed unit supplying a continuous strip of paper, which is directed onto and along a forming block and wrapped progressively around the stream of tobacco to generate a continuous cigarette rod.  
         [0004]     To ensure that cigarettes have compact ends, thus minimizing the loss of tobacco during successive steps of the manufacturing process and when handled by the smoker, the cigarette maker is equipped with suitable compression means, positioned along the aforementioned path, of which the function is to densify and compact predetermined portions of the tobacco stream that will ultimately form the ends of the cigarettes.  
         [0005]     The tobacco is attracted by a bottom branch of the aspirating conveyor belt and gathered into a stream that does not present a uniform thickness, but will be of thickness greater at any given point than a prescribed value enabling it to be enveloped by the paper. This non-uniformity of thickness is attenuated at a first trimming station positioned upstream of the compression means, which removes a part of the tobacco so as to render the thickness of the stream more consistent and thus ensure that the compacted portions are of uniform density.  
         [0006]     Finally, the conventional machines in question comprise a second trimming station downstream of the compression means, of which the function is to adjust the stream of tobacco to the aforementioned prescribed thickness before it is enveloped by the paper strip.  
         [0007]     The tobacco removed at the two trimming stations is reclaimed by appropriate recovery means and put back into the cycle at a given point upstream of where the stream is formed, for example added to the continuous flow of tobacco fibers supplied to the riser duct.  
         [0008]     The reclaimed tobacco is however significantly degraded as the result of undergoing two trimming steps, the particles being unable to bind either with one another or with more fibrous material and thus easily lost from the cut ends of a cigarette, so that the compression step included precisely in order to prevent such losses is rendered fruitless.  
         [0009]     Due to the presence of extremely small particles, moreover, the reclaimed tobacco has limited filling capacity and is not of constant density, factors which jeopardize the quality of the cigarettes.  
         [0010]     In addition, the foregoing considerations apply for each of the single lines in a cigarette maker generating two cigarette rods, where the two lines run mutually parallel and at an extremely short distance one from another for accepted reasons of structural and functional optimization.  
         [0011]     The object of the present invention is to provide a unit and a method for forming a continuous rod in a cigarette maker such as will be unaffected wholly or at least in part by the aforementioned drawback.  
         [0012]     One object of the invention in particular is to provide a unit for forming a continuous cigarette rod in a cigarette maker, and a relative method, such as will ensure that the reclaimable degraded tobacco is not shredded to excess.  
       SUMMARY OF THE INVENTION  
       [0013]     The stated object and others besides are realized according to the present invention in a unit for forming a continuous cigarette rod in a cigarette maker, equipped with a conveyor serving to feed a continuous stream of tobacco particles toward the entry point of a station where the cigarette rod is formed, advancing in a predetermined direction along a predetermined feed path.  
         [0014]     Also forming part of the unit disclosed, ordered in sequence along the feed direction, are a first trimming device designed to reduce the thickness of the advancing stream, means serving to densify predetermined portions of the stream, and a second trimming device, of which the first trimming device operates cyclically and synchronously with the densifying means and serves to reduce the thickness of the stream at given portions corresponding to the predetermined densified portions. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which:  
         [0016]      FIG. 1  is a schematic elevation view of a unit for forming a continuous cigarette rod, embodied in accordance with the present invention;  
         [0017]      FIG. 2  shows a detail of the unit in  FIG. 1 , viewed from above with certain parts omitted better to reveal others;  
         [0018]      FIG. 3  is the section on III-III in  FIG. 2 ;  
         [0019]      FIGS. 4   a ,  4   b ,  4   c  and  4   d  illustrate successive processing steps performed on the tobacco rod by the unit according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]      FIG. 1  of the drawings illustrates a unit  1  for forming a continuous cigarette rod  2 , constituting part of a cigarette-making machine.  
         [0021]     Such a unit  1  comprises a conveyor  3  by which a continuous stream  4  of tobacco particles is fed toward the entry point  5  of a forming station  6  serving to generate a continuous cigarette rod  2 , advancing in a predetermined direction  7  along a predetermined path  8 . The forming station  6  is of conventional embodiment and therefore not described further.  
         [0022]     The conveyor  3  preferably takes the form of an aspirating belt  9  looped around rollers  10  at each end (one only of which is illustrated in  FIG. 1 ) rotatable about mutually parallel and horizontal axes. The aspirating belt  9  establishes a closed loop compassing a chamber  11  connected by way of a relative duct  12  to a source of negative pressure (not illustrated) and delimited at the bottom by a wall  13  pierced with suction holes  14 .  
         [0023]     The bottom branch  15  of the conveyor belt  9  runs in sliding contact with the wall  13  and is able to retain the fibrous tobacco particles P by suction as they emerge from a vertical riser duct  16  (of which only the left hand part is shown in  FIG. 1 ) positioned beneath the bottom branch  15 , so that the tobacco particles are formed into a continuous stream  4 .  
         [0024]     Operating at the entry point  5  of the station  6  where the continuous cigarette rod  2  is formed, the unit  1  comprises a looped conveyor  17  of which one branch extends beneath the bottom branch  15  of the aspirating belt  9 , occupying a zone of convergence with this same belt  9 .  
         [0025]     The looped conveyor  17  passes around rollers  18  (one only of which is illustrated in  FIG. 1 ) and includes a top branch  19  located in sliding contact with a table  20 , which serves to support a strip of cigarette paper  21  decoiled from a roll  22 .  
         [0026]     The stream  4  of tobacco filler is released by the aspirating conveyor  9  onto the strip of paper  21  and carried into the forming station  6 , where it is enveloped by the selfsame paper  21 .  
         [0027]     To prepare the stream  4  of tobacco filler for the subsequent step of being enveloped in the paper  21 , predetermined portions C of densified consistency are created (see  FIGS. 4   b  to  4   d ), such as will prevent the filler being shed from the cut ends of the single cigarettes during subsequent steps of the manufacturing process. Accordingly, the unit  1  comprises a first trimming device  23  installed on the predetermined path  8  followed by the stream  4  and operating upstream of the forming station  6 , also means  24  operating downstream of the first trimming device  23  relative to the feed direction  7  and serving to densify parts of the tobacco filler coinciding with the portions C aforementioned, and a second trimming device  25  operating downstream of the densifying means  24 .  
         [0028]     The first trimming device  23  brings about a first reduction in thickness of the stream  4  of tobacco filler at predetermined areas, as will become clear in due course.  
         [0029]     The densifying means  24  and the second trimming device  25  are of conventional type. In the example illustrated, the densifying means  24  consist in cam-operated forcing elements (one for each line) and the second trimming device  25  comprises a pair of contrarotating circular blades.  
         [0030]     Located in conventional manner beneath the first trimming device  23  and second trimming device  25  are respective recipients, indicated schematically as blocks denoted  26 , positioned to collect the shredded tobacco removed by the trimming operation. The reclaimable shredded tobacco is directed back into the processing cycle through the action of conventional recovery means not illustrated in the drawings.  
         [0031]     As illustrated in  FIGS. 2 and 3  and  FIG. 4 , the first trimming device  23  serves to reduce the thickness of the stream  4  at predetermined areas corresponding to the aforementioned predetermined densified portions C, and is therefore synchronized in operation with the densifying means  24 .  
         [0032]     The densifying means  24  and the first trimming device  23  operate synchronously with a cutter of familiar type, not illustrated, located downstream of the forming station  6  and timed to divide the continuous cigarette rod into single sticks in such a manner that the densified areas coincide with the cut ends of the sticks.  
         [0033]     More precisely, and referring to  FIGS. 4   a ,  4   b ,  4   c  and  4   d , because the stream  4  transported away from the riser duct  16  is of irregular thickness and presents a non-uniform profile, deliberately accentuated in  FIG. 4   a , it is subjected to a first trimming step ( FIG. 4   b ) only along the predetermined portions C destined to undergo the action of the densifying means  24 , in such a way as to render the thickness of these same portions C uniform at a predetermined value S 1  ( FIG. 4   c ).  
         [0034]     Following the compression step, the stream  4  undergoes a second trimming step ( FIG. 4   d ) along its entire length, in such a way as to establish a predetermined thickness denoted S 2 .  
         [0035]     In this way, the portions N not subjected to the action of the densifying means  24  are trimmed once only, with the result that the quantity of tobacco ultimately degraded is substantially reduced.  
         [0036]     Referring to  FIGS. 2 and 3 , the first trimming device  23 , designed to carry out the first trimming step, comprises a rotating knife  27  spaced apart from the bottom branch  15  of the aspirating belt  9  at a distance equivalent to the first thickness S 1 .  
         [0037]     More exactly, the rotating knife  27  comprises a disc  28  furnished with at least one blade  30  that extends radially from the peripheral edge  29  of the disc  28 .  
         [0038]     As illustrated in  FIG. 2 , the disc  28  presents just one blade  30  appearing as an arc to a circle concentric with the disc. The number of individual blades  30  presented by the disc  28 , the angular distance compassed by each blade  30  on the edge  29  of the disc  28 , and the radius of the blade  30 , are design parameters that can vary, without prejudice to the scope of the present invention, according to the characteristics of the cigarettes in production or to the specifications of the machine.  
         [0039]     The disc  28  rotates about an axis X coinciding with its center, extending at right angles to the wall  13  of the suction chamber  11  and the bottom branch  15  of the aspirating belt  9 .  
         [0040]     When the rotating knife  27  assumes the position of interference with the stream  4  of tobacco, the blade  30  brushes against a locating or striker element  31  afforded by a wall  32  set transversely to the plane occupied by the disc  28  and extending parallel to the stream  4 . To advantage, the striker element  31  is also capable of reciprocating motion in a direction parallel to the predetermined feed direction  7  followed by the stream  4  of tobacco, generated synchronously with the rotating knife  27 , so as to avoid sliding contact with the movement of the blade  30  by accompanying its movement.  
         [0041]     In effect, as the blade  30  skims the stream  4  of tobacco, the striker element  31  shifts in the same direction V 1  and at the same speed as the blade  30 . As the blade  30  then completes a full revolution and rotates toward the position of interference, the striker element  31  will shift in the opposite direction V 2  so as to regain its starting position ( FIG. 2 ).  
         [0042]     In the preferred embodiment illustrated, the stream  4  of tobacco advances along a confining channel  34  created between side walls denoted  33   a  and  33   b . With the knife  27  in the position of interference, the blade  30  functions as a third wall  35  enclosing the channel  34 .  
         [0043]     It will be evident that the drawbacks associated with the prior art are overcome by the invention and that the stated objects are realized in a first trimming device  23  as described and illustrated, which operates cyclically and synchronously with the densifying means  24  in such a way as to reduce the thickness of the stream  4  of tobacco filler at selected areas coinciding with the predetermined densified portions C aforementioned.  
         [0044]     The method and the unit according to the present invention are instrumental in improving the quality of reclaimed tobacco.  
         [0045]     In practice, the only parts of the stream  4  of tobacco filler subjected to two trimming actions are the compacted portions C.  
         [0046]     It follows that the average size of the recycled tobacco particles will be larger than that of the particles constituting the fraction removed by two successive trimming steps.  
         [0047]     Given the increased average size of the particles in question, the filling capacity of the tobacco is improved compared to the prior art and the finished cigarettes will present a more uniform distribution of tobacco filler from end to end.  
         [0048]     Finally, the generally larger reclaimed tobacco particles will bind more securely with the fibrous material, rather than being easily shed from the ends of the cigarette during subsequent processing operations or when handled by the smoker.  
         [0049]     It will be seen that in  FIGS. 2 and 3 , which refer to a cigarette maker with two cigarette rod forming lines, a second stream  4  of tobacco filler, a second channel  34  and a second knife  23  are shown in phantom lines.