Abstract:
Cigarettes are manufactured on a machine that includes a filter tip attachment comprising a train of rollers with peripheral suction grooves, each proportioned to hold a single cigarette. The grooves are set parallel to the axis of rotation of the relative rollers and combine to establish a feed path along which the cigarettes are attracted and released, passing from one roller to the next and advancing through a succession of processing stations. To optimize the attraction and release steps, the cigarettes themselves are exploited in such a way as to create a chamber in each groove, compassed between the cylindrical surface of the cigarette and the bottom surface of the groove it occupies, and connected to the pneumatic circuits generating the suction.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a method and a machine for making filter cigarettes.  
           [0002]    In particular, the invention disclosed relates to a method of retaining and transferring cigarettes and relative filters by means of conveying rollers in an automatic cigarette manufacturing machine, described generally as a filter tip attachment, to which reference is made explicitly in the following specification albeit with no limitation implied.  
           [0003]    Such filter tip attachments comprise an infeed station interfaced with a cigarette maker turning out one or two continuous cigarette rods, and are equipped, departing from the infeed station, with a train of rollers rotatable about mutually parallel axes, along which a succession of cigarette sticks and filters are caused to advance through a series of process stations, emerging ultimately as filter tipped cigarettes. On reaching the outfeed end of the train of rollers, the finished cigarettes are directed into a packer.  
           [0004]    The outer surfaces of the rollers are typically fluted, fashioned with peripheral grooves such as will accommodate respective cigarette sticks and/or filters and retain them by suction. For the sake of simplicity, reference is made broadly to cigarettes in the following description.  
           [0005]    The grooves are disposed parallel to the axis of the roller and present a cross sectional profile appearing as an arc to a circle; the bottom surface of each groove incorporates a plurality of suction holes connected to a source of negative pressure by way of relative valves operating on the pneumatic circuit in such a way as to allow of transferring the cigarettes from one roller to the next.  
           [0006]    Each cigarette thus makes contact with the bottom surface of the respective groove along a straight line generator, and the portions of its cylindrical surface exposed to the force of suction are limited to the sum of the cross-sectional areas presented by the suction holes incorporated into the groove. The holes normally will be three or four in number, each approximately 0.15″ in diameter, and given the high speeds at which filter tip attachments of the current generation are able to operate, it becomes necessary to generate appreciably powerful suction forces in order to retain the advancing cigarettes. This in turn dictates the use of high power vacuum equipment, and of pneumatic circuits that tend to be highly complex and costly by reason of the fact that they are specified with notably high strength pipelines and seals. Moreover, the high rated power of the equipment results in correspondingly high electrical energy consumption and high noise levels generated by the pneumatic circuits, particularly at the moment when cigarettes pass from one roller to the next.  
           [0007]    Concerning this step, it will be observed that in the course of being transferred from one roller to the next, each cigarette makes a momentary radial flight from the releasing groove to the receiving groove. Accordingly, the aforementioned valves must be timed in such a way as to generate suction in the receiving groove before suction is deactivated in the releasing groove, so that the cigarette can pass from one to the other.  
           [0008]    In practice, the effect of generating suction marginally before the cigarette enters the groove is to intensify the noise produced by the pneumatic circuits, and moreover, the flight accompanying the passage from one roller to the other results in a violent impact that can degrade the cigarette, in particular by causing tobacco filler to dislodge and shed.  
           [0009]    The prior art includes a solution of adding slots to the groove in the neighborhood of the suction holes, so as to widen the area of those portions of the cylindrical surface of the cigarette that are exposed to the force of attraction. Nonetheless, using fluted rollers with suction surfaces of this kind can create problems of instability and cause the cigarettes to deform, due to the discontinuous nature of the supporting surface.  
           [0010]    The object of the present invention is to provide a method and a machine for making filter cigarettes from which the aforementioned drawbacks are absent.  
           [0011]    A further object of the invention is to provide a method and a relative machine that can maximize the cylindrical surface area of the cigarette exposed to the force of suction, while avoiding deformation of the cigarette itself.  
         SUMMARY OF THE INVENTION  
         [0012]    The stated object is realized in a method of making filter cigarettes according to the present invention, applicable to a machine comprising a plurality of rollers each furnished peripherally with a plurality of suction grooves accommodating respective cigarettes and aligned on axes parallel to the axis of rotation of the relative roller, in such a way as to establish a feed path along which the cigarettes are successively retained, released and transferred from a groove of one roller to a groove of a successive roller. The method disclosed includes a step of creating at least one negatively pressurized chamber within each groove of at least one of the rollers, compassed between the bottom surface of the groove and a cigarette occupying the selfsame groove.  
           [0013]    The stated object is realized similarly according to the present invention in a machine comprising a plurality of rollers each furnished peripherally with a plurality of suction grooves accommodating respective cigarettes and aligned on axes parallel to the axis of rotation of the relative roller, in such a way as to establish a feed path along which the cigarettes are successively retained, released and transferred from a groove of one roller to a groove of a successive roller. Advantageously, each groove of at least one roller comprises a bottom surface merging with two mutually opposed flank faces positioned so as to engage in contact along at least two longitudinal areas with a relative cigarette occupying the groove, thereby creating at least one chamber compassed between the bottom surface of the groove and the portion of the cylindrical surface of the cigarette directed toward the bottom surface of the groove, and connected to a source of negative pressure. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which:  
         [0015]    [0015]FIG. 1 illustrates a machine for making filter cigarettes by the method according to the present invention, viewed schematically in a fragmentary side elevation;  
         [0016]    [0016]FIG. 2 illustrates a roller of the machine in FIG. 1, viewed in an enlarged side elevation;  
         [0017]    [0017]FIG. 3 illustrates a detail of FIG. 2, viewed in an enlarged side elevation;  
         [0018]    FIGS.  4  to  6  are enlarged side elevations each showing two portions of two respective contiguous rollers forming part of the machine in FIG. 1, and in particular two mutually opposed grooves, illustrated in three successive operating steps;  
         [0019]    [0019]FIG. 7 shows a possible embodiment of the detail illustrated in FIG. 3, viewed schematically and in perspective;  
         [0020]    [0020]FIGS. 8 and 9 show a second embodiment of the detail illustrated in FIG. 3 viewed schematically from the side and in perspective, respectively;  
         [0021]    [0021]FIGS. 10 and 11 show a third embodiment of the detail illustrated in FIG. 3 viewed schematically from the side and in perspective, respectively;  
         [0022]    [0022]FIG. 12 shows a detail of FIG. 11, illustrated in perspective;  
         [0023]    [0023]FIGS. 13 and 14 show a fourth, and preferred embodiment of the detail illustrated in FIG. 3, viewed schematically from the side and in perspective, respectively;  
         [0024]    [0024]FIGS. 15, 16 and  17  illustrate three further embodiments of the grooves shown in FIGS. 8, 12 and  14 , respectively, viewed in perspective;  
         [0025]    [0025]FIGS. 18, 19,  20  and  21  illustrate two further embodiments of the grooves according to the present invention, viewed schematically from the side and from above. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    With reference to FIG. 1 of the accompanying drawings,  1  denotes a portion, in its entirety, of a machine known as a filter tip attachment, used in the manufacture of filter cigarettes. An infeed  2  of the attachment is coupled to the outfeed  3  of a beam  4  from which double length cigarette sticks  5  are directed in succession by a transfer unit  6  to the infeed  2  of the attachment, which will be seen to consist in a train of rollers rotatable about mutually parallel axes and furnished each with a plurality of suction grooves. In the interests of simplicity, the rollers are denoted R generically, except where identified by a specific numeral, and all the grooves are denoted  8 .  
         [0027]    The infeed  2  coincides with a first roller  7  set in rotation at a constant angular velocity, turning clockwise as viewed in FIG. 1 about a relative axis extending parallel to the predominating axis of the beam  4 , by which the double length cigarette sticks  5  are taken up in grooves  8  lying parallel to the axis of rotation. The sticks  5  are thereupon advanced transversely to their longitudinal axes and transferred in succession to relative grooves  8  afforded by the periphery of a second roller  9  set in rotation counterclockwise as viewed in FIG. 1.  
         [0028]    The double length sticks  5  are advanced by the second roller  9 , again transversely to their axes, toward a cutting unit  10  where each is divided in conventional manner to produce two single sticks  5   a  of length corresponding to the length of a normal cigarette; the two sticks  5   a  are then advanced in axial alignment and transferred to the grooves  8  of a third roller  11 , rotating clockwise, on which they will be distanced axially one from another.  
         [0029]    The separated sticks  5   a  are transferred to a fourth roller  12  forming part of a conventional assembly station  13  that also comprises a feed roller  14  conveying double length filter plugs  15 . As discernible in FIG. 1, the feed roller  14  is positioned substantially tangential to the fourth roller  12 , rotating in the opposite direction and at the same peripheral speed, and is designed to place each successive double length filter plug  15  in a central portion of a relative groove  8  offered by the fourth roller  12 . Each plug  15  transferred thus to a relative groove  8  of the fourth roller  12  will assume a position in between and in alignment with two single cigarette sticks  5   a  transferred to the selfsame groove  8 , thus forming an assembly  5   b  on the roller  12  composed of two axially aligned cigarette sticks  5   a  separated by one double length filter plug  15 . These assemblies  5   b  are then fed in succession from the fourth roller  12  to a fifth roller  16  coinciding with the infeed station of a finishing unit  17  of the type disclosed and claimed in Italian Patent n o  1 200 229, to which reference can be made for a full description.  
         [0030]    Besides the fifth roller  16 , as illustrated in FIG. 1, the finishing unit  17  comprises a feed roller  18  positioned to supply tipping papers  19  separated from a continuous strip  20  by a cutting unit  21 , of which the function is to join together the two cigarette sticks  5   a  and the double length filter plug  15  making up each assembly  5   b . Forming a part of this same unit  17  is a rolling unit  22 , including a respective roller  23 , designed to take up each successive assembly  5   b  together with the relative tipping paper  19  from the fifth roller  16  and thereupon roll the tipping paper  19  around the double length filter plug  15  and the corresponding ends of the two cigarette sticks  5   a  to fashion a double length cigarette, denoted  5   c . The double length cigarettes  5   c  pass in succession from the tipping roller  23  to a sixth roller  24  coinciding with the outfeed of the finishing unit  17 .  
         [0031]    At a given point while occupying the grooves  8  of the sixth roller  24 , each successive double length cigarette  5   c  is directed through a cutting unit  25  positioned to engage the double filter plug  15 , in such a manner as to generate respective pairs of axially aligned single cigarettes  26  that are then transferred from this same roller  24  onto further rollers  27  and  28 , thence to other machine units of the filter tip attachment indicated schematically by a block denoted  29 . One of the steps performed by these further units will be to order the cut cigarettes  26  in single file.  
         [0032]    [0032]FIGS. 2, 3 and  7  show a portion of a typical roller R illustrating the relative grooves  8 , each of which presents an arcuate profile with a concave face directed away from the axis of rotation of the roller R. More exactly, the groove  8  is fashioned with two mutually opposed flank faces  30  joined to a bottom surface  31  affording at least two holes  32  connected by way of radial ducts  33  to a source of negative pressure (conventional in embodiment, and not illustrated).  
         [0033]    As already intimated, each groove  8  of a given roller R is designed to accommodate a double length cigarette stick  5 , or a single cigarette stick  5   a , or an assembly  5   c  composed of two single sticks  5   a  separated by a double length filter plug  15 ; in the interests of simplicity however, reference will be made hereinafter simply to cigarettes  26 .  
         [0034]    With reference in particular to FIG. 3, the two flank faces  30  are flat and rectilinear, so that the groove  8  presents a cross-sectional profile of substantially shallow “U” outline. Moreover, the groove  8  is proportioned (see FIG. 3) so that a relative cigarette  26  will come to rest with two longitudinal areas  34  of its cylindrical surface offered in contact to two respective longitudinal areas of the flank faces  30 , in such a way as to create at least one chamber  35  between the bottom surface  31  of the groove  8  and a portion  26   a  of the cylindrical surface of the cigarette  26  directed toward the bottom surface  31 . Thus, the chamber  35  is compassed between the part of the cylindrical surface of the cigarette  26  delimited by the two longitudinal areas  34  of contact, and the part of the surface of the groove  8  delimited by these same two areas  34  of contact.  
         [0035]    The chamber  35  is connected to the aforementioned source of negative pressure by way of the relative holes  32  which, as discernible from FIG. 7, are located at points near to the two opposite ends of the groove  8  in such a way that the partial vacuum generated within the chamber  35  will be stronger in the central part, extending between the two suction holes  32 , than at the two endmost parts; thus, the part of the cigarette  26  exposed to the greatest force of attraction will be, correspondingly, that part of the portion  26   a  of the cylindrical surface extending between the two holes  32 .  
         [0036]    In the example of FIGS. 8 and 9, the two flank faces  30  of each groove  8  are joined to a bottom surface  36  presenting a cross-sectional profile of squarish outline, comprising a flat bottom face  37  extending between two flank walls  38  normal to the bottom face  37  and merged with the flank faces  30 . In this instance the chamber  35  is enlarged, and whilst the contact made between the cigarette  26  and the flank faces  30  remains the same as in the first example described, the distance separating the portion  26   a  of the cylindrical surface of the cigarette  26  from the bottom face  37  of the groove is increased, so that if tobacco particles are shed from the end of the cigarette  26 , this will not occasion any loss of grip between the cigarette  26  and the flank faces  30 .  
         [0037]    The groove  8  illustrated in FIGS. 10, 11 and  12  is fashioned with a bottom surface  39  presenting a longitudinal rib  40  positioned to make contact with an intermediate band  26   b  on the portion  26   a  of the cylindrical surface of the cigarette  26  directed toward the bottom surface  39 , and combining with the selfsame portion  26   a  of the cylindrical surface to create two half-chambers  35   a , as discernible in FIG. 10. Observing FIG. 12 in particular, the rib  40  in question presents transverse notches  41 , coinciding with the suction holes  32 , by which the holes  32  are connected with both half-chambers  35   a.    
         [0038]    [0038]FIGS. 4, 5 and  6  illustrate the steps by which a cigarette is transferred, in the portion  1  of the machine shown in FIG. 1, from a typical releasing roller R, rotating clockwise and indicated on the left in the three drawings, to a typical receiving roller R rotating counterclockwise. More precisely, FIG. 4 illustrates the mutual positions of two grooves  8 , releasing and receiving respectively, at a moment immediately preceding the transfer from left to right, in which the cigarette  26  is held by the partial vacuum generated in the chamber  35  of the groove  8  presented by the releasing roller R. FIG. 5 illustrates the mutual positions of the same two grooves  8  during the subsequent transfer step, in which the cigarette  26  remains in contact simultaneously with the two flank faces  30  of the releasing groove  8  and with the two flank faces  30  of the receiving groove  8 , along the respective longitudinal areas  34  and through a predetermined angular distance typically of 6°, as the rollers R rotate about their relative axes. Accordingly, the cigarette  26  makes contact simultaneously with four faces  30  of the two respective grooves  8  along four longitudinal areas  34  of its cylindrical surface.  
         [0039]    At a given point during the transfer sequence, suction is deactivated initially in the chamber  35  of the releasing groove  8 , through the agency of conventional valve means not shown in the drawings, and simultaneously activated in the chamber  35  of the receiving groove  8 . In this way, the transfer of a cigarette  26  from a releasing groove  8  to a receiving groove  8 , which concludes as illustrated in FIG. 6, can be effected gradually and without causing the cigarette  26  to be propelled through a radial flight between the two grooves  8  that might damage it in any way.  
         [0040]    To the end of ensuring that the position of the cigarettes  26  is correctly controlled throughout the entire operation of effecting a transfer from one roller R to the next, and as discernible in particular from FIG. 5, the diagonally opposed pairs of flank faces  30  presented respectively by the releasing and receiving grooves  8  are set apart one from another by a distance marginally less than the diameter of a single cigarette  26 , so that the selfsame cigarette will be lightly compressed along the four longitudinal areas  34  of contact with the four corresponding faces  30 .  
         [0041]    Where the grooves of two contiguous rollers R are embodied as in the example of FIGS. 10, 11 and  12 , the cigarette  26  will be held not only along the aforementioned four longitudinal areas  34  of contact during the transfer step, but also along the portions  26   b  in contact with the ribs  40 , so that there are six points of contact between the cylindrical surface and the grooves, four of which coinciding with the longitudinal areas  34  along the flank faces  30 , and two coinciding with areas  42  of the ribs  40  offered to the cigarette  26 .  
         [0042]    In the example of FIGS. 13 and 14, the flank faces  30  of each groove  8  are joined to a bottom surface  39  presenting a cross-sectional profile of squarish outline, comprising a flat bottom face  43  and two flank walls  44  substantially perpendicular to the bottom face  43 . The solution is therefore similar to that illustrated in FIGS. 8 and 9, though with the difference that the cigarette  26  is offered in contact both to the two flank faces  30  and to the flat bottom face  43 , thereby creating two half-chambers  35   a . Each hole  32  presents a countersunk mouth  45  communicating with both the half-chambers  35   a.    
         [0043]    It will be observed, in the examples of FIGS.  7  to  14 , that the two opposite ends of the groove  8  can be embodied either as illustrated in FIG. 3, or in familiar manner with a portion, denoted  46 , contoured in such a way as to minimize any loss of suction force from the chambers  35  or  35   a . In the examples of  15 ,  16  and  17 , the ends of the groove  8  are shaped in such a manner that the cigarette  26  engages fully in contact with the portions  46  lying between the two flank faces  30 .  
         [0044]    Finally, in the examples of FIGS.  18  to  21 , the single groove  8  is fashioned in such a manner that a cigarette  26  positioned on the bottom surface, denoted  48 , will enter into contact only with a substantially central area  49 . The central area  49  in question lies between two channels  50  presented by the bottom surface  48  and extending practically the full length of the groove  8 . The purpose of the channels  50  is to establish two half-chambers  47   a  of a chamber, denoted  47  in its entirety, created between the bottom surface  48  and the cylindrical surface of the cigarette  26 . The connection between the chamber  47  and the aforementioned source of negative pressure is provided by way of holes  32  in the bottom surface  48  located to coincide with the central area  49  of contact. Each hole  32  presents a countersunk mouth  52  communicating with both the channels  50 .  
         [0045]    The channels  50  might be fashioned with various cross-sectional profiles: the example of FIG. 18 shows a profile of squarish outline similar to that of FIG. 13, whilst the example of FIG. 20 shows a curved outline similar to that of FIGS. 10, 11 and  12 .  
         [0046]    It will be observed in the examples of FIGS.  18  to  21  that the partial vacuum is generated within a chamber  47  that has open sides, unlike the chamber denoted  35 . Accordingly, the inclusion of the two end portions  46  in the manner described above will be particularly advantageous in this instance, with the end in view of minimizing any loss of suction force from the chamber  47 .