Abstract:
A curling device for a filter tip attachment comprises at least one blade-like element offered to a continuous strip of paper material at a selected contact zone in such a way as to deform the material as it advances, so that single tipping papers separated from the strip by a cutting unit of the attachment are given a curved profile and as a result more easily wrapped around and affixed to the assembled filters and cigarette sticks when these are joined together; the curling device also comprises a delivery system by which the contact zone is flooded with a cushioning fluid designed to favor a smooth sliding contact between the curling element and the running strip, and at the same time equalize the tensions in the strip preceding and following the contact zone.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a curling device preferably for cigarette making machines.  
           [0002]    The invention finds application to advantage in the art field of cigarette making machinery, and in particular of filter tip attachments, that is to say machine units by which filters and cigarettes are assembled. Reference is made explicitly to this art field in the following specification, albeit with no limitation in general scope implied.  
           [0003]    Conventionally, cigarettes and filter tips are assembled by interposing a double length filter plug between two axially aligned cigarette sticks, then joining the filter to the sticks on each side by applying a previously gummed tipping paper, and ultimately cutting the double assembly in half to create two single filter-and-cigarette assemblies.  
           [0004]    A filter tip attachment generally comprises a feed station from which a continuous strip of paper material is advanced at a predetermined velocity and under a predetermined degree of tension along a feed path, likewise predetermined; the feed path passes both through a gumming station at which an adhesive substance is applied to one surface of the strip destined to engage the filter-and-cigarette assembly, and through a cutting unit by which the continuous strip is divided into discrete tipping papers ready for application.  
           [0005]    Each tipping paper separated by the cutting unit is positioned at an intermediate transfer station and there associated initially with a respective filter-and-cigarette assembly, before being affixed permanently to the selfsame assembly at a further station. The step of affixing the tipping paper permanently to the filter-and-cigarette assembly is accomplished normally by wrapping the paper around the assembly.  
           [0006]    This wrapping operation is much facilitated by a curling device installed between the feed station and the cutting unit, which engages the advancing strip and brings about a plastic deformation of the internal fibers. The material thus assumes a given curvature, when relieved of longitudinal tension, with the result that the application of the papers to the respective filter-and-cigarette assemblies is made easier.  
           [0007]    The prior art embraces curling devices embodied substantially as a sharp edged element or blade, offered in contact to the continuous strip and generating an action that is designed to weaken the selfsame strip in the transverse direction.  
           [0008]    Such curling devices betray certain drawbacks attributable principally to the friction generated at the area of contact between the strip and the aforementioned blade. In particular, it has been observed that the deforming action of the curling device generates high frictional forces tending often to degrade or to break the strip material, especially at the high operating speeds of filter tip attachments now in service.  
           [0009]    The object of the present invention is to provide a curling device from which the drawbacks mentioned above are absent.  
         SUMMARY OF THE INVENTION  
         [0010]    The stated object is realized according to the invention in a device for curling a continuous strip of paper material caused to advance along a predetermined feed path toward at least one cutting unit by which the strip is divided into discrete lengths. Such a device typically comprises at least one curling element interacting with an adhesion surface of the continuous strip at a contact zone, in such a way that the paper material is made to flex transversely to a longitudinal dimension of the advancing strip and assume a predetermined curvature.  
           [0011]    To advantage, the device disclosed also comprises friction reducing means associated with the curling element and interacting with the continuous strip at the contact zone in such a way as to favor a smooth sliding contact between the element and the strip. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which:  
         [0013]    [0013]FIG. 1 is a schematic illustration showing a portion of a cigarette maker equipped with a curling device embodied according to the present invention;  
         [0014]    [0014]FIG. 2 shows the curling device of FIG. 1, enlarged and in a preferred operating position.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    With reference to the two accompanying drawings,  1  denotes a curling device, in its entirety, shown associated with a cigarette maker illustrated in part in FIG. 1.  
         [0016]    In particular, the device is associated with a filter tip attachment comprising at least one feed station  2  from which a continuous strip  3  of paper or similar material is advanced steadily toward successive stations of the machine.  
         [0017]    The continuous strip  3  is decoiled from a roll  4 , subject to a predetermined tension and at a given velocity, and advanced along a predetermined feed path P that passes in succession through a gumming station  5  where an adhesive substance is applied to at least one adhesion surface  3   a  of the continuous strip  3 , and a cutting unit  6  by which the gummed strip is divided into discrete lengths, or tipping papers  7 , each serving to join at least one filter permanently to a respective cigarette stick.  
         [0018]    The adhesive substance in question is applied at the gumming station  5  by means of at least one gumming device  8  comprising an applicator roller  9  that acts directly on the adhesion surface  3   a  of the continuous strip  3 , and a reaction roller  10  acting on the surface of the strip opposite from the applicator roller  9 .  
         [0019]    As discernible in FIG. 1, the strip  3  passes over a guide roller  11  positioned upstream of the curling device  1 , then through a pair of pinch rolls  12  downstream of the selfsame device  1 .  
         [0020]    Needless to say, the rollers in question might be located and positioned in any given configuration, as dictated by the production and/or structural requirements of different filter tip attachments.  
         [0021]    The cutting unit  6  generates the aforementioned tipping papers  7  utilizing a suction roller  14  and an auxiliary roller  15  of which the respective axes of rotation  14   a  and  15   a  are disposed substantially horizontal and parallel one with another.  
         [0022]    The continuous strip  3  is taken up by the suction roller  14 , and directed through a cutting zone  16  at which the selfsame roller  14  interacts with the auxiliary roller  15  in such a way as to divide the strip  3  into single tipping papers  7 .  
         [0023]    The suction roller  14 , which presents a diameter greater than that of the auxiliary roller  15  and rotates at a peripheral velocity higher than the linear velocity of the advancing strip  3 , carries a plurality of angularly equispaced blades  17  with substantially straight cutting edges set skew to the axis of rotation  14   a.    
         [0024]    The auxiliary roller  15  rotates at a peripheral velocity substantially matching the linear velocity of the advancing strip  3 , and carries a plurality of substantially radial blades  18  equispaced around its surface of revolution. These blades  18  present cutting edges set substantially parallel to the axis of rotation  15   a  of the roller  15 .  
         [0025]    The cutting unit  6  is followed along the feed path P by a conveying roller  19  of conventional embodiment rotatable counterclockwise, as viewed in FIG. 1, about a relative axis denoted  19   a . The conveying roller  19  affords a plurality of fluted recesses  19   b  extending parallel to the straight line generators of the revolving surface, in which relative filter-and-cigarette assemblies  20 , each consisting in two cigarette sticks separated by a double length filter plug, are retained by suction in conventional manner. The filter-and-cigarette assemblies  20  are caused to advance broadside by the conveying roller  19  through a transfer zone  21  where each successive tipping paper  7  generated by the cutting unit  16  is offered to the surface of a respective assembly  20 .  
         [0026]    The curling device  1  comprises a curling element denoted  22 , designed to interact with the adhesion surface  3   a  of the continuous strip  3  in such a way as to flex the selfsame strip at a relative contact zone  23  extending transversely to its longitudinal dimension.  
         [0027]    In particular, the guide rollers  11  and pinch rolls  12  aforementioned are positioned along the feed path P, relative to the curling element  22 , in such a manner as to establish a leg presenting a Vee profile of which the vertex coincides with the edge  22   a  of the element  22 . The angle of the Vee thus created along this leg of the feed path P can hug the element  22  to a greater or lesser degree, according to the positions of this same element and of the rolling elements  11  and  12  one relative to another. FIG. 2 shows a preferred arrangement of the curling element  22  and the rolling elements  11  and  12 , with the strip  3  riding in close proximity to the side walls of the curling element  22 .  
         [0028]    With the strip  3  thus constrained to make a sharp change in direction over the curling element  22  at the contact zone  23 , the structure of the material is permanently deformed, assuming a predetermined curvature such that the gummed surface  7   a  of each tipping paper  7  separated by the cutting unit  6  and then offered in contact to a filter-and-cigarette assembly  20  will be concavely profiled. In other words, each tipping paper  7  is curled in such a way that it will cling to and wrap around the external surface of the filter-and-cigarette assembly  20  more easily.  
         [0029]    More exactly, the curling element  22  acts on the continuous strip  3  in such a way as to stretch the fibers on the side farthest from the element  22 , in relation to the fibers directed toward the selfsame element  22 .  
         [0030]    As discernible from the accompanying drawings, the curling device  1  presents a cross sectional profile of substantially triangular outline with one substantially sharp edge  22   a , referable to a longitudinal dimension that extends substantially parallel to the axis of rotation  14   a  of the suction roller  14  for a distance at least equal to the full transverse dimension of the continuous strip  3 .  
         [0031]    To advantage, the curling device  1  also comprises friction reducing means  24  associated with the curling element  22  and operating at the contact zone  23  in such a manner as to lessen the friction generated between the sharp edge  22   a  of the curling element  22  and the continuous strip  3 .  
         [0032]    Referring to FIG. 2, such friction reducing means  24  comprise fluid-hydraulic means  25  of which the function is to deliver at least one continuous stream of fluid  26  received from a suitable source, indicated in FIG. 2 by a block denoted  30 , at a predetermined and controllable pressure.  
         [0033]    The aforementioned friction reducing means  24  are associated with the curling element  22  in such a manner as to deliver the fluid  26  at the contact zone  23 . In a preferred embodiment, the means  24  in question will be set up to deliver the fluid  26  at a point upstream of the contact zone  23  occupied by the curling element  22 , considered in relation to the feed direction followed by the strip  3 , so that the emerging fluid  26  is drawn by the advancing strip  3  between the face of the selfsame strip  3  and the sharp edge  22   a  of the curling element  22 . Thus, the fluid  26  trapped between the continuous strip  3  and the curling element  22  functions as a cushion or bearing  27 , designed to ease the passage of the strip  3  by attenuating the strength of the frictional forces in play at the contact zone  23 .  
         [0034]    As discernible from FIGS. 1 and 2, the delivery means  25  include a main delivery duct  25   a  connected internally to the aforementioned source  30  and vented externally to the surrounding environment by way of orifices  25   b  directed toward the advancing strip  3 .  
         [0035]    More exactly, the delivery means  25  comprise a plurality of such orifices  25   b  arranged parallel one with the next along the longitudinal dimension of the curling element  2  and facing upstream from the selfsame element  22 , relative to the direction followed by the strip  3 .  
         [0036]    The problems associated with the prior are thus overcome by the present invention, and the stated object is duly realized.  
         [0037]    In effect, the curling device  1  according to the present invention allows the continuous strip  3  of paper material to be deformed in such a way that it will assume an ideal curvature, able to favor the application of the tipping papers  7  to the filter-and-cigarette assemblies  20  while guaranteeing the physical integrity of the assembly, and therefore the quality of the cigarettes ultimately obtained. In short, by achieving a notable reduction in the friction generated between the curling element  22  and the continuous strip  3 , the device  1  allows a smoother passage of the selfsame strip  3  along the feed path P.  
         [0038]    Finally, with the adoption of a curling device  1  according to the present invention, the treatment applied to the strip  3  in producing a given depth of curl at a given rate of feed is more delicate, any risk of tearing the material is avoided, and the tensions generated in the continuous strip  3  upstream and the downstream of the contact zone  23  can be equalized.  
         [0039]    In particular, the aforementioned fluid  26  could be water vapor or humidified air, suitably treated and maintained at temperatures such as will ensure the desired effects are obtained.