Abstract:
Filters for cigarettes are manufactured on a machine by which a web of activated carbon fiber fabric is decoiled from a roll, fed into a fragmentation device and broken up into filaments or particles. The fragments are gathered by a first unit into a continuous flow directed up and through the top outlet of an ascent channel into a further unit with a slidable and air-permeable aspirating belt such as will attract and retain the filaments or particles rising through the channel and shape them progressively into a continuous stream which is then released by the belt to the infeed of a unit equipped with a garniture section along which a strip of paper is wrapped around the continuous stream to form a continuous filter rod. Finally, the rod is fed through a rotary cutter and divided into sticks that will provide the single filter plugs for attachment to cigarettes.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a method and to a machine for manufacturing filters applicable to tobacco products, in particular cigarettes.  
         [0002]     The prior art embraces the practice of attaching filters to cigarettes with tipping papers. Such filters are manufactured by a process in which a flow of filter material, usually cellulose acetate drawn from a supply such as a bale, is extended, stretched and treated with additives, in particular plasticizers. The flow is processed in such a way as to obtain a continuous stream of filter material and the stream then enveloped in a paper plugwrap to fashion a continuous filter rod, which will be divided ultimately into single filter plugs.  
         [0003]     Also embraced by the prior art are filters for cigarettes utilizing activated carbon granules as the filter material. In effect, activated carbon is an excellent filtration medium, that is to say with a high capacity for absorbing nicotine, tar and other harmful products contained in smoke.  
         [0004]     Owing to the relatively large particle size of the granules, however, filters of this type do not present a sufficiently compact structure.  
         [0005]     In effect, the interstitial spaces between the granules offer a path of least resistance to the smoke, thus significantly reducing the capacity of such filters to trap impurities.  
         [0006]     A further drawback consists in the fact that the equipment employed in manufacturing such filters is relatively complex, not least in view of the need to place the granular filters in question between two cellulose acetate filter plugs produced by the method outlined briefly above, which function not only as filters but also as a means of preventing the endmost granules of the activated carbon filter element from escaping during the various processing steps.  
         [0007]     The object of the present invention is to provide filters affording a high absorption capacity and guaranteed devoid of the drawbacks mentioned above.  
         [0008]     A further object of the invention is to provide a method and a system for the manufacture of such filters that will be unaffected by the drawbacks of conventional equipment as mentioned above, while affording simplicity and ease of implementation.  
       SUMMARY OF THE INVENTION  
       [0009]     The stated objects are realized according to the present invention in a method of manufacturing filters for tobacco products, which comprises the steps of feeding a continuous stream of filaments or particles consisting in activated carbon fibers to the infeed of a unit by which a continuous filter rod is formed, enveloping the continuous stream in a strip of wrapping material to form the continuous filter rod, and feeding the continuous rod to a cutter device by which it is divided into discrete filter sticks.  
         [0010]     The stated objects are realized similarly in a filter maker embodied according to the invention, comprising a reservoir that serves to collect and to contain a mass of filaments or particles of activated carbon fibers, also feed means supplying the reservoir, a unit by which the activated carbon filaments or particles are formed into at least one continuous stream, a unit by which the continuous stream is formed into a continuous filter rod, and cutter means by which the continuous rod is divided into discrete filter sticks. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which:  
         [0012]      FIG. 1  illustrates a portion of a machine for making filters applicable to tobacco products, embodied in accordance with the present invention, viewed schematically and in perspective and cut away in part;  
         [0013]      FIG. 2  illustrates the machine of  FIG. 1  with certain parts omitted and others added, viewed in elevation and on a different scale;  
         [0014]      FIG. 3  illustrates the machine of  FIG. 1  in a second embodiment, viewed schematically and in perspective, and cut away in part;  
         [0015]      FIG. 4  illustrates a variation in embodiment of the portion of the machine in  FIG. 3 , viewed schematically and in perspective;  
         [0016]      FIG. 5  illustrates the machine according to the present invention in a third embodiment, viewed in elevation;  
         [0017]      FIG. 6  illustrates a cigarette, in perspective, furnished with a filter manufactured by the method and employing a machine according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     Referring to  FIGS. 1 and 2  of the accompanying drawings,  1  denotes a filter making machine, in its entirety. Such a machine  1  comprises a reservoir  2  containing a mass  3  of filaments or particles of activated carbon fibers, also a unit  4  by which the filaments or particles of the mass  3  are formed into a continuous flow  5 , and a unit  6  by which the continuous flow  5  is formed into two continuous streams  7  of filaments or particles of activated carbon fibers.  
         [0019]     In addition, and as illustrated in  FIG. 2 , the machine  1  comprises a forming unit  8  on which two continuous filter rods  9  are assembled by wrapping each of the aforementioned continuous streams  7  of fibers in a respective strip  10  of paper decoiled by a relative feed device  11  from a corresponding roll  12 .  
         [0020]     The continuous filter rods  9  advance along a path denoted P to the outfeed end of the forming unit  8 , where they are divided into discrete sticks  13  by a cutter device  14 .  
         [0021]     Whilst the example described and illustrated relates to a machine with two processing lines, hence able to assemble two continuous filter rods simultaneously from respective streams of fibers, it will be appreciated that the disclosure applies equally to a machine with just one processing line.  
         [0022]      15  denotes a continuous web of fabric made from activated carbon fibers. More particularly, the material in question is obtained by a process of calcination in the absence of air or oxygen, known as carbonization, followed by an activating step consisting in oxidation at high temperature. The resulting fibers can be prepared for use, as in the case considered here, in the form of fabric.  
         [0023]     Also indicated in  FIG. 1  are decoil and guide means denoted  16 , in their entirety, constituting means by which to feed the web  15  of fabric along a predetermined path denoted P 1 . Such means comprise a device  17  serving to decoil a bulk roll  18  of the fabric  15  rotatable about a horizontal axis  18   a , also a roller  19  by which the fabric  15  is diverted onto a substantially vertical leg of the path P 1  toward a fragmentation device  20  positioned above the reservoir  2  and illustrated schematically as a pair of rollers  21  and  22  contrarotating about axes parallel to the aforementioned horizontal axis  18   a.    
         [0024]     The fragmentation device  20  serves to break up the fabric  15 , for example utilizing teeth or tines presented by the rollers  21  and  22 , and reduce it to filaments or particles having the consistency of fluff, accumulating to create the aforementioned mass  3  internally of the reservoir  2 .  
         [0025]     The unit  4  serving to form the continuous flow  5  of filaments or particles is housed in a vertically oriented enclosure denoted  23 , delimited laterally by two vertical walls  24  and  25 , and uppermost by a horizontal wall  26  presenting an opening  27  to the reservoir  2  through which the mass  3  of fluff can drop onto a power-driven toothed roller  28 .  
         [0026]     The mass  3  of fluff is directed by the roller  28  downwards and into a lower chamber  29  delimited at the bottom by a conveyor belt  30  which carries the fluff toward a carding device  31  equipped with a carding roller  32  rotatable about an axis  32   a  lying transversely to the vertical side walls  24  and  25  and operating in conjunction with a proportioning roller  33 .  
         [0027]     With the arrangement thus described, the mass  3  of fluff consisting in filaments or particles of activated carbon fibers is directed by the toothed roller  28  onto the belt  30 , and by the belt toward the carding roller  32 , from which a layer of fluff substantially equal in thickness to the radial dimension of the carding teeth is transferred away from the chamber  29  and beyond the position of the selfsame roller  32  tangential to the proportioning roller  33 .  
         [0028]     It will be seen that the toothed roller  28  and the belt  30  constitute first conveyor means serving to supply the carding device  31  with fluff from the reservoir  2 .  
         [0029]     The layer of filaments or particles of activated carbon fiber is taken up by an impeller roller  34  rotatable about an axis parallel to the axis  32   a  of the carding roller, and projected into a descent channel  35 .  
         [0030]     The descent channel  35  extends in a substantially vertical direction and is disposed with the bottom end facing the periphery of a toothed take-up unit denoted  36 , comprising a first and a second toothed roller combining one with another to transfer the layer of filaments or particles of activated carbon fibers onto a transfer belt  37 .  
         [0031]     The transfer belt  37  runs from right to left, as viewed in  FIG. 1 , and is angled upward with the runout end located beneath the inlet of an ascent channel  38  internally of which a continuous flow  5  of the filaments or particles of activated carbon fibers is entrained in an ascending air current generated by pneumatic means of conventional type (not illustrated).  
         [0032]     Accordingly, the descent channel  35 , the toothed take-up unit  36  and the transfer belt  37  combine to establish second conveyor means interposed between the carding device  31  and the ascent channel  38 .  
         [0033]     The top outlet end  39  of the ascent channel is enclosed by a pair of aspirating belts  40  made of air-permeable material and constituting a part of the unit  6  by which the aforementioned continuous streams  7  are formed. The two belts  40  are looped around two return pulleys  41  driven in rotation about respective horizontal axes. Compassed within the loop created by the belts  40  is a chamber  42  connected to a source of negative pressure (not illustrated) and delimited on the underside by a wall  43  pierced with suction holes  44 .  
         [0034]     Thus, filaments or particles of activated carbon fibers making up the continuous flow  5  are directed up through the ascent channel  38  and into contact with the bottom branches of the aspirating belts  40  as these slide against the aforementioned wall  43 , whereupon the fibers cling to the belts and gather progressively to form the aforementioned continuous streams  7 , which are conveyed to the infeed  45  of the unit  8  that will form them into continuous filter rods  9 .  
         [0035]     More precisely, and referring to  FIG. 2 , the continuous streams  7  of material are released onto respective strips  10  of paper supported by the top branches of respective looped conveyor belts  46 , of which one only is visible in  FIG. 2 , forming part of the aforementioned feed device  11  and fashioned from a textile material.  
         [0036]     The forming unit  8  further comprises a beam  47 , extending along the aforementioned path P, by which the paper strips  40  are constrained to wrap around the respective continuous streams  7  of filaments or particles of activated carbon fibers, thus bringing about the assembly of the two filter rods  9 . As the assembled components advance along the beam  47 , one longitudinal edge of each strip  10  will be gummed by applicator means (not illustrated) and stuck, so as to stabilize the wrap around the two rods  9 .  
         [0037]      FIG. 3  illustrates an embodiment of the machine differing from that of  FIG. 1  inasmuch as the reservoir  2  is placed at the outlet of a duct  48  of which the inlet is connected to a fragmentation device shown schematically as a block denoted  20 . Also, the unit  4  forming the continuous flow  5  of filaments or particles of activated carbon fibers is simplified in this embodiment, comprising only the toothed take-up unit  36 , placed at the bottom outlet end of the reservoir  2  in this instance, the transfer belt  37 , and the ascent channel  38 .  
         [0038]     It will be seen that the decoiling and guiding means  16  serving to direct a web  15  of fabric along a predetermined path P 1  in the example of  FIG. 1 , and the duct  48  in  FIG. 2 , are designed to act as feed means serving the reservoir  2 .  
         [0039]      FIG. 4  illustrates an embodiment of the machine differing from that of  FIG. 1  inasmuch as the reservoir  2  is fed by a conveyor belt  49  angled downward and toward the inlet of the reservoir  2 , onto which the mass  3  of filaments or particles of activated carbon fibers is released from above. More exactly, the top infeed end of the belt  49  is positioned beneath the fragmentation device  20  by which the web  15  of activated carbon fiber fabric will be broken up.  
         [0040]     In like manner to the example of  FIG. 3 , the unit  4  serving to form the continuous flow  5  of filaments or particles of activated carbon fibers is simplified in this embodiment, consisting only in the toothed take-up unit  36 , positioned at the bottom outlet end of the reservoir  2 , the transfer belt  37  and the ascent channel  38 .  
         [0041]     Referring to the example illustrated in  FIG. 5 , the block denoted  50  represents a spinning unit such as will produce a plurality of strands  51  consisting in filaments or particles of activated carbon fibers, obtainable from the web  15  of fabric or from a mass  3  of fluff containing filaments or particles of activated carbon fibers, or unwound from respective reels. The strands  51  emerging from the spinning unit  50  are fed into a forming unit shown as a block denoted  52 , and gathered by this same unit into a continuous stream  7  of filaments or particles of activated carbon fibers.  
         [0042]     Alternatively, the stream  7  could consist in a rope or braid of activated carbon filaments or particles unwound from a respective reel.  
         [0043]     In a further embodiment of the machine  1 , not illustrated in the drawings, the stream  7  could be processed directly by the forming unit  52  from a layer of fluff.  
         [0044]     Proceeding downstream of the forming unit  52 , the unit  8  by which the filter rods  9  are assembled is no different to that described with reference to the example of  FIG. 2 .  
         [0045]     Finally,  FIG. 6  illustrates a cigarette  53  with a filter  54  obtained from a stick  13  manufactured on the machine  1  by the methods described above. In particular, the filter  54  in question presents a much higher capacity for absorbing impurities than traditional filters made with cellulose acetate or activated carbon granules.  
         [0046]     In effect, the microporosity of the filter in question is such as to make it especially suitable for trapping pollutants of low molecular weight. The filter described and illustrated might also be utilized in conjunction with traditional cellulose filters to assemble composite filters.  
         [0047]     Furthermore, and in the light of the foregoing, a filter  54  obtained in this manner is considerably simpler to manufacture than a conventional filter.