Abstract:
A curling device for a filter tip attachment comprises an element placed in contact with a strip of paper material advancing continuously along a given path, and serving to deform the strip in such a way that single tipping papers obtained by cutting the strip are invested with a curled profile; the curling device is associated with a mechanism such as will cause it to vibrate, describing rectilinear or looped trajectories at a predetermined frequency, so as to reduce friction between the curling element and the strip.

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]    Notwithstanding the application of tipping papers to filter-and-cigarette assemblies is assisted thus by the use of conventional curling devices, which consist essentially in a sharp-edged or blade-like element offered in contact to the continuous strip and designed to weaken the material transversely, it has been found that such devices betray certain drawbacks attributable principally to the friction generated at the area of contact between the device and the strip.  
           [0008]    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 at the high operating speeds of filter tip attachments now in service.  
           [0009]    The object of the present invention is to address and overcome the problems encountered in prior art solutions by setting forth a curling device for cigarette makers capable of deforming the fibers of a continuous strip in such a way as to facilitate the operation by which tipping papers are wrapped around filter-and-cigarette assemblies, while at the same time guaranteeing the integrity of the continuous strip and the quality of the finished cigarettes even at high operating tempos.  
         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 selfsame strip is divided into discrete lengths. Such a device presents at least one curling element operating on one surface of the advancing strip at a contact zone in such a manner as to deform the strip relative to its longitudinal dimension, and includes vibrator means associated with the curling element.  
         BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]    The invention will now be described in detail, by way of example, with the aid of the accompanying drawing, which is a schematic illustration showing one portion of a cigarette maker equipped with a curling device according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    Referring to the drawing,  1  denotes a curling device, in its entirety, embodied in accordance with the present invention. The curling device  1  is associated with a given portion  2  of a cigarette maker, and in particular with a filter tip attachment comprising at least one feed station A from which a continuous strip  3  of paper or similar material is advanced steadily toward successive stations of the machine.  
         [0013]    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 one or more adhesive substances are applied to at least one adhesion surface  3   a  of the continuous strip  3 , and a cutting unit  6  by which the gummed strip  3  is divided into discrete lengths, or tipping papers  7 , each serving to join at least one filter permanently to a respective cigarette stick.  
         [0014]    The adhesive substances in question are 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 .  
         [0015]    As discernible from the accompanying drawing, 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 .  
         [0016]    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.  
         [0017]    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 .  
         [0018]    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.    
         [0019]    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 .  
         [0020]    The cutting unit  6  is followed along the feed path P by a conveying roller  19  of conventional embodiment, rotatable counterclockwise as viewed in the drawing, about an axis  19   a  extending parallel to the axes  14   a  and  15   a  of the cutting rollers. 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  6  is offered to the surface of a respective assembly  20 .  
         [0021]    As discernible from the accompanying drawing, the curling device  1  is located upstream of the cutting unit  6 , considered relative to the feed direction D followed by the continuous strip  3 . In a preferred embodiment, the device  1  will be positioned between the feed station A and the cutting unit  6 , and more exactly between the feed station A and the gumming station  5 .  
         [0022]    In particular, and as intimated previously, the device  1  comprises a curling element  13 , embodied as a bar  22  appearing substantially triangular in section, of which one edge  13   a  is offered to the adhesion surface  3   a  of the continuous strip  3  at a contact zone denoted  23 .  
         [0023]    The aforementioned guide rollers  11  and pinch rolls  12  are positioned along on the feed path P, relative to the curling element  13 , in such a way as to establish a leg presenting a Vee profile of which the vertex coincides with the edge  13   a  of the bar  22 . With the strip  3  thus constrained to make a sharp change in direction at the contact zone  23 , the structure of the material becomes 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, the edge  13   a  of the curling element  13  is applied forcibly to the continuous strip  3  as it passes through the contact zone  23 , compressing the internal fibers beneath the surface directed toward the curling element  13 , while stretching the internal fibers beneath the surface directed away from the selfsame curling element.  
         [0024]    The curling element  13  is connected by a rod  24  to vibrator means indicated schematically as a block denoted  25 , such as will cause the bar  22  to vibrate at a predetermined frequency. Naturally enough, the rod  24  might be replaced by any other means of connection capable of transferring the energy from the vibrator means  25  to the bar  22 , or alternatively, the bar  22  could be coupled direct to the vibrator means  25 .  
         [0025]    The vibrator means  25  are of conventional type, for example electrical, mechanical or pneumatic in operation, and preferably will take the form of an ultrasound generator.  
         [0026]    The vibratory motion transmitted to the bar  22  by the vibrator means  25  can be rectilinear, oriented along an essentially rectilinear direction parallel to the rod  24 , hence transverse to the strip  3 , or oriented along a direction transverse to the rod  24  and coinciding with the direction followed by the strip  3  as it passes through the contact zone  23 .  
         [0027]    Finally, the vibratory motion can be generated by two directional components, one transverse to the other, in which case the trajectory described could be looped, elliptical or circular in outline.  
         [0028]    It has been observed that the motion transmitted by the vibrator means  25  to the bar  22  has the effect of reducing frictional forces in play at the contact zone  23  when the edge  13   a  of the curling element engages the adhesion surface  3   a  of the strip  3 , so that the tension values registering in the strip  3  upstream and downstream of the curling device  1  can be rendered uniform.  
         [0029]    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, and any risk of tearing the material is avoided.