Abstract:
Filters for tobacco products are manufactured by a device comprising a conveyor drum rotatable about a horizontal axis and furnished with peripheral grooves, each holding a leaf of paper material preassembled with a first filter element. The single groove is flanked by two tubular elements arranged symmetrically on either side of the drum, slidable axially between a first position located externally of the groove and a second position located internally of the groove, also by pushers slidable within the respective tubular elements and serving to direct second and third filter elements into contact with the end faces of the first filter element in such a way that the second filter element, which consists in a measure of powder or granular material deposited in each tubular element by way of a spool valve, remains interposed between the first and the third filter element. The leaf of paper material is engaged by a folder mechanism associated with the groove and closed around the two tubular elements to form a tubular wrap.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a method and a device for making filters applicable to tobacco products.  
         [0002]     The present invention finds useful application in the manufacturing sector concerned with tobacco products, typically cigarettes and the like.  
         [0003]     Conventional cigarette filters consist generally in a cylindrical plug of artificial fibers obtained by spinning concentrated solutions of cellulose acetate.  
         [0004]     The prior art also embraces composite filters that consist in a tubular plugwrap containing two or more component materials of dissimilar nature designed to improve filtration of the smoke.  
         [0005]     For example, the more common composite filters comprise a tubular wrap of paper material in which two components of artificial fiber (acetate) are accommodated together with a further component of powder or granular material, interposed between the two fiber components.  
         [0006]     Composite filters are fashioned by inserting the various filter components into the tubular wrap in ordered succession.  
         [0007]     In particular, the tubular wrap is positioned vertically on a relative support, at a location coinciding with a feed station, beneath a number of rotary devices each supplying one respective filter component. Each of the rotary devices presents at least one pocket able to contain a relative filter component and positionable cyclically in alignment with the feed station.  
         [0008]     Accordingly, the rotary devices will deposit the different filter components sequentially into the tubular wrap.  
         [0009]     Once the filling step is completed, the assembled filter components are compressed from the top end of the tubular wrap by a plunger.  
         [0010]     Whilst the conventional manufacturing devices outlined above are able to assemble composite type cigarette filters, such devices present certain drawbacks deriving in particular from the fact that they are unable to prevent the powder or granular material, during the feed step, from being released into the surrounding environment and thus causing damage to moving parts of the rotary devices.  
         [0011]     A further drawback derives from the fact that during the steps of inserting and then compressing the filter components, the plunger can damage the tubular plugwrap, not least due to the presence of powder or granular material that may lodge between the plunger and the wrap.  
         [0012]     Finally, another drawback affecting conventional devices for the assembly of composite filters is attributable to the method of feeding the component of powder or granular material. More exactly, the quantity of material inserted and compressed may be insufficient for the purpose and poorly compacted, with the result that its filtering properties are rendered ineffective.  
         [0013]     The object of the present invention is to provide a method and a device for making filters applicable to tobacco products such as will be unaffected by the aforementioned drawbacks.  
       SUMMARY OF THE INVENTION  
       [0014]     The stated object is realized in a method of making filters for tobacco products according to the present invention. The steps of such a method consist in feeding at least one leaf of paper material, inserting at least one filter component into at least one tubular element, placing the tubular element against an inner surface of the leaf, folding the leaf around the tubular element to form a tubular wrap, and finally, withdrawing the tubular element from the tubular wrap in such a way as to leave the at least one filter component lodged permanently within the wrap.  
         [0015]     The stated object is realized similarly in a device designed to implement the method of making filters for tobacco products described above, which comprises a transport conveyor set in motion along a predetermined path and presenting a plurality of grooves each able to accommodate at least one leaf of paper material, at least one tubular element associated with each groove of the conveyor and capable of axial movement between a first position outside of the groove and a second position within the groove, also pushing means capable of movement through the tubular element and serving to transfer at least one filter component onto a relative leaf of paper material, and a plurality of mechanisms, each associated with a respective groove, by which the leaf of paper material is wrapped around the tubular element. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which:  
         [0017]      FIG. 1  illustrates a device for the manufacture of filters for tobacco products according to the present invention, viewed schematically in a front elevation and with certain parts omitted;  
         [0018]      FIG. 2  shows a portion of the device in  FIG. 1  illustrated schematically in section from one side;  
         [0019]      FIG. 2   a  shows an enlarged detail of the portion of the device illustrated in  FIG. 2 ;  
         [0020]     FIGS.  3  to  12  are schematic side views showing a detail of the device in  FIG. 1 , illustrated in a succession of operating steps;  
         [0021]      FIGS. 3   a  to  11   a  are schematic sectional views showing a further detail of the device, seen from the same direction as in  FIG. 1  and illustrated in a succession of operating steps.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     Referring to  FIG. 1  of the drawings,  1  denotes a device, in its entirety, used in the manufacture of composite filters for tobacco products.  
         [0023]     The device  1  comprises a transport conveyor  2  embodied as a drum  3  rotatable clockwise, as viewed in  FIG. 1 , about a horizontal axis X. The drum  3  presents a plurality of grooves  4  arranged around a cylindrical surface  3   a  of revolution and set in motion along a circular path P.  
         [0024]     Operating above the conveying drum  3  is a loading drum  5  equipped with aspirating pockets denoted  5   a,  rotatable counterclockwise about an axis parallel to the axis X aforementioned in such a way as to revolve substantially tangential to the conveying drum  3  at a feed station denoted  6 .  
         [0025]      7  denotes a feed hopper dispensing first filter elements  8  of substantially cylindrical appearance obtained, for example, by spinning concentrated solutions of cellulose acetate.  
         [0026]     The first filter elements  8  are taken up from the hopper onto a train  9  of rollers of which the final roller  10  rotates substantially tangential to the feeder drum  5  at a point of release  11  where the selfsame filter elements  8  are directed singly and in succession into respective aspirating pockets  5   a  of the drum  5 .  
         [0027]      12  denotes a device, in its entirety, by which partially gummed leaves  13  of wrapping material are fed to the loading drum  5 . The single leaves  13  are separated from a continuous strip  14  by the action of a cutter unit  15  comprising a suction roller  16  that rotates tangentially to the feed drum  5  at a second point of release  17  downstream, considered relative to the rotation of the drum  5 , from the point of release  11  first mentioned. Thus, each leaf  13  can be tacked by way of an intermediate first gummed portion  18  to a corresponding first filter element  8  occupying one of the aspirating pockets  5   a.    
         [0028]     The preassembled first filter elements  8  and leaves  13  are advanced by the loading drum  5  toward the feed station  6  and there transferred into the aforementioned grooves  4  of the conveying drum  3 .  
         [0029]     In particular, and as illustrated in  FIGS. 3 and 3   a,  each groove  4  presents a cross section of substantially semicircular profile and is furnished with at least one suction hole  4   b  connected to a source of negative pressure not illustrated in the drawings.  
         [0030]     Following the transfer, an intermediate portion of the outermost surface presented by the leaf  13  will be breasted in contact with the bottom of the groove  4 , causing the leaf  13  to wrap partially around the respective first filter element  8  and assume a profile of U-shaped outline presenting two radially oriented members  13   a  and  13   b  ( FIG. 6   a ).  
         [0031]     As discernible in  FIG. 2  and FIGS.  3  to  12 , the transport conveyor  2  comprises a first and a second auxiliary roller denoted  19  and  20 , aligned coaxially with the drum  3  and placed symmetrically one on either side.  
         [0032]     With reference in particular to  FIG. 2 , the two auxiliary rollers  19  and  20  are rigidly associated with the drum  3 , presenting substantially the same radial proportions as those of the selfsame drum  3 , and mounted to respective fixed cylindrical hubs  23  with which they are also coaxial.  
         [0033]     Referring particularly to  FIG. 2   a,  which is a fragmentary view of the roller denoted  20 , and to FIGS.  3  to  12 , each roller  19  and  20  presents a peripheral portion furnished with axial ducts  21  corresponding in number to the grooves  4  of the conveying drum  3  and aligned coaxially with the selfsame grooves; each axial duct  21  presents a respective radial opening  22  communicating with the external environment.  
         [0034]     As discernible in  FIGS. 2 and 2   a  and FIGS.  3  to  12 , each duct  21  houses a coaxially aligned tubular element  24  invested with sliding motion in the axial direction by actuator means, denoted  25  in their entirety, between a first position located externally of the relative groove  4  ( FIGS. 3-6 ) and a second position located internally of the groove  4  ( FIGS. 7-10 ).  
         [0035]     Also associated with each axial duct  21 , and occupying a part of the roller  19  and  20  radially nearer to the horizontal axis X, is a cylindrical cavity  26  aligned on a relative axis parallel to the selfsame axis X and connecting with the duct  21  by way of a hole  27 .  
         [0036]     The rollers  19  and  20  are furnished internally with radial channels  28 , each connecting at one end with an intermediate part of a relative cylindrical cavity  26 , and opening at the opposite end onto a cylindrical surface  29  presented by a portion of the respective fixed cylindrical hub  23 .  
         [0037]     Each of the cylindrical cavities  26  is occupied by a dispensing valve element  30  caused to slide along the selfsame cavity  26  in a close fit through the agency of respective actuator means  31 .  
         [0038]     The valve element  30  consists in two cylindrical elements  32  and  33  interconnected by a rod  34  of diameter smaller than that of the two cylindrical elements  32  and  33 , in such a way that a space  35  is created between the cylindrical elements.  
         [0039]     As illustrated in  FIGS. 1 and 2 , the bottom half of each fixed cylindrical hub  23  incorporates a cavity  36  appearing as a sector to a circle and extending through an arc of predetermined width, of which the top part presents an opening  37  serving to admit a powder or granular material  38  designed to function as a second filter element  39 .  
         [0040]     Each cavity  36  also presents a bottom opening  40  that coincides with the aforementioned cylindrical surface  29  in such a way that when the rollers  19  and  20  are set in rotation, the cavities  36  will be connected in succession to the radial channels  28  communicating with the corresponding cylindrical cavities  26 .  
         [0041]     The dispensing valve element  30  is capable of movement, generated by the aforementioned actuator means  31 , between a receiving position, in which the space  35  is aligned with the outlet of the radial channel  28  and able to admit the powder or granular material  38  (as in  FIGS. 3, 4  and  12 ), and a dispensing position in which the space  35  is aligned with the hole  27  mentioned previously and able to release the material  38 .  
         [0042]      41  denotes a feed hopper supplying third filter elements  42  of substantially cylindrical appearance obtained, for example, by spinning concentrated solutions of cellulose acetate, which are conveyed in pairs by way of a train  43  of rollers to a pair of discs  44  furnished with aspirating pockets and set in rotation substantially tangential to the drum  3  at a point of release  45  located upstream of the feed station  6 , considered in relation to the rotation of the drum  3 . The filter elements  42  are transferred by the discs  44  into the aforementioned radial openings  22  presented by the axial ducts  21  of the rollers  19  and  20 .  
         [0043]     Each filter element  42  transferred to a radial opening  22  is placed at the mouth of the tubular element  24 , which presents a splayed entry portion denoted  46 .  
         [0044]     The third filter element  42  is engaged by pushing means  47  operating in coaxial alignment with the tubular element  24 ; such means  47  comprise a rod  48  of which the free end carries a wheel  49  positioned so as to roll, when the drum  3  is set in rotation, on a cam profile  50  presented by each of the fixed cylindrical hubs  23 .  
         [0045]     Similarly, the aforementioned actuator means  25  will comprise a wheel  51  carried by a first end of a sleeve  52  associated by way of a second end with the tubular element  24  and slidable thus internally of the axial duct  21 . When the drum  3  is set in rotation, the wheel  51  rolls on a cam profile  53  presented by the fixed cylindrical hub  23 .  
         [0046]     Finally, the aforementioned actuator means  31  associated with each dispensing valve element  30  include a rocker arm  54  anchored pivotably at one end to the relative auxiliary roller  19  and  20  and presenting a wheel  55  located at an intermediate point along its length. When the drum  3  is set in rotation, the wheel  55  rolls on a respective cam profile  56  afforded likewise by each of the fixed cylindrical hubs  23 , in such a way that the arm  54  will rock on its fulcrum pivot and thus cause the valve element  30  to reciprocate internally of the respective cylindrical cavity  26  against the action of a return spring  57 .  
         [0047]     As illustrated in  FIGS. 3   a  to  11   a,  the device  1  further comprises folder mechanisms  58  associated with each groove  4  of the drum  3  and invested with rocking motion by respective actuator means (not illustrated in the drawings), of which the function is to shape the leaf  13  of material into a tubular wrap around the filter. More exactly, the folder mechanisms  58  comprise a first folder  59  serving to flatten the member  13   a  of the U-shaped leaf  13  of material located upstream, considered relative to the rotation of the drum  3 , and a second folder  60  serving to flatten the downstream member  13   b  into partially overlapping contact with the member  13   a  flattened previously.  
         [0048]     It will be observed that the free edges of the first folder  59  and the second folder  60  are shaped with cylindrically concave surfaces of which the radius of curvature substantially matches that of the grooves  4 .  
         [0049]     In operation, with the drum  3  and the rollers  19  and  20  set in rotation and a groove  4  (any groove, for the sake of example) moving into alignment with the cavities  36 , a predetermined measure of powder or granular material  38  destined to provide the second filter elements  39 , as will be made clear in due course, passes down the channels  28  and fills the spaces  35  of the valve elements  30  associated with each roller  19  and  20 , as these occupy the receiving position of  FIGS. 3 and 4 .  
         [0050]     At the same time, two third filter elements  42  are brought to the point of release  45  by the pair of discs  44  and transferred through the radial openings  22  into each of the two sleeves  52 , which will have been drawn into a retracted position by the relative actuator means  25  and are fashioned each with a respective opening  61  aligned on the corresponding radial opening  22  ( FIG. 3 ).  
         [0051]     As the drum  3  continues rotating, the channels  28  of each roller  19  and  20  serving the particular groove  4  illustrated by way of example will pass beyond the limits of the openings  40  presented by the cavities  36  and each valve element  30 , subject to the action of the relative rocker arm  54 , is made to adopt the position of  FIG. 5 , closing off the radial channel  28  by means of the cylindrical element  32  and bringing the space  35  into alignment with the release hole  27 , also with a corresponding hole  62  presented by each sleeve  52 , through which a measure of the powder or granular material  38  constituting the second filter element  39  is able to drop into the sleeve  52 .  
         [0052]     In the same step, the third filter element  42  is forced inward by the rod  48  in such a way as to engage and lodge together with the second filter element  39  in the tubular element  24 .  
         [0053]     It will be observed that the forcible insertion of the second and third filter elements  39  and  42  into the tubular element  24  is facilitated by the splayed portion  46  of the mouth. Having located in the portion of the tubular element  24  that presents a constant diameter, the third filter element  42  functions as a stopper by sealing in the powder or granular material  38 .  
         [0054]     As the groove  4  under consideration passes into the feed station  6 , it will receive a preassembled first filter element  8  and corresponding leaf  13  of wrap material from the loading drum  5 , the leaf  13  assuming a U-profile as aforementioned.  
         [0055]     As the drum  3  and the rollers  19  and  20  continue rotating toward a transfer station  63  occupied by a further take-up conveyor  64 , the two sleeves  52  are caused by the relative actuator means  25  to move the tubular elements  24  into their second position, internally of the groove  4 , and substantially into contact with the opposite end faces of the first filter element  8  as illustrated in  FIG. 7 .  
         [0056]     Observing FIGS.  8  to  12 , the two rods  48  are caused by the respective wheels  49  moving along their cam profiles  50  to slide internally of the respective sleeves  52  and to force the respective second and third filter elements  39  and  42  through the respective tubular elements  24  until compacted against the opposite end faces of the first filter element  8  ( FIG. 11 ).  
         [0057]     As these steps proceed, the folder mechanisms  58  flatten the members  13   a  and  13   b  of the leaf one after the other, by means of the first folder  59  and the second folder  60 , along the portion of the tubular element  24  exhibiting a constant diameter, so as to fashion a tubular wrap  66  containing a central first filter element  8  and two pairs of respective second and third filter elements  39  and  42  positioned either side of the first element  8 . One edge of the outer member  13   b  presented by each leaf  13  is coated with a layer of gumming material such as will guarantee that the tubular wrap stays fastened.  
         [0058]     Immediately upstream of the transfer station  63 , as indicated in  FIG. 12 , the tubular elements  24  are retracted by the respective actuator means  25 , withdrawn from the tubular wrap  66  and returned to their initial position located externally of the groove  4 .  
         [0059]     Thereafter, the rods  48  likewise are retracted and the pushing means  47  returned to their initial position.  
         [0060]     It will be seen that when subject to the action of the return springs  57 , the valve elements  30  slide within the cylindrical cavities  26  back to the position in which the spaces  35  are able to receive the powder or granular material  38 .  
         [0061]     The device further comprises air ducts  65  formed both in the fixed cylindrical hubs  23  and in the auxiliary rollers  19  and  20 , which emerge into the cylindrical cavities  26 .  
         [0062]     Each of the filters assembled as described above is cut transversely to produce two single filters, each in turn combining with a single cigarette stick to create a filter tipped cigarette.