Abstract:
A perforation apparatus of the tobacco-processing industry for perforating a wrapper of a rod-shaped article includes at least one optical radiation source to generate at least one primary beam. Optical elements are operative to split the at least one primary beam into at least four mutually non-overlapping partial beams to produce at least four perforation zones offset in an axial direction of the rod-shaped article. Partial beams arranged mirror symmetrically to each other with respect to a mirror plane of the rod-shaped article are derived from the same primary beam.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority of German Application No. 10 2006 013 929.1 filed Mar. 21, 2006, the subject matter of which is incorporated herein by reference, together with each and every U.S. and foreign patent and patent application mentioned below.  
       BACKGROUND OF THE INVENTION  
       [0002]     The invention concerns a perforation apparatus of the tobacco-processing industry for perforating a wrapper of a rod-shaped article, having at least one optical radiation source for generating at least one primary beam, and optical elements for splitting the primary beam into mutually non-overlapping partial beams for producing perforation zones offset in the axial direction of the rod-shaped article.  
         [0003]     Perforation apparatuses for producing a perforation zone in the tipping paper of a filter cigarette are known from German patent documents DE 33 21 800A1, DE 34 18 188A1, DE 37 05 627A, DE 195 30 216 A1 and DE 101 60 167 A1, and European patent document EP 0 578 385 A1. Usually, these apparatuses for perforating tipping paper are used in the manufacture of double-length cigarette rods. Therefore, it is known in the art to split the primary beam into two partial beams for producing identical perforations for each half of a double-length cigarette rod corresponding to one cigarette.  
       SUMMARY  
       [0004]     It is an object of the present invention to provide a perforation apparatus that allows differentiated influencing of the air permeability through the perforation in the wrapper of the rod-shaped article.  
         [0005]     The above and other objects are achieved according to the invention, wherein in one embodiment there is provided a perforation apparatus of the tobacco-processing industry for perforating a wrapper of a rod-shaped article, comprising: at least one optical radiation source to generate at least one primary beam; and optical elements operative to split the at least one primary beam into at least four mutually non-overlapping partial beams to produce at least four perforation zones offset in an axial direction of the rod-shaped article, wherein partial beams arranged mirror symmetrically to each other with respect to a mirror plane of the rod-shaped article are derived from the same primary beam.  
         [0006]     On account of the production of at least four independent partial beams, instead of the conventional production of two independent partial beams, at least two independent perforation zones can be produced in the tipping paper for each cigarette. This allows individual adjustment of the air permeability of the wrapper at several axially offset positions. This is especially important in connection with the development of cigarette filters of multi-stage construction, to allow individual adjustment of the air permeability of the tipping paper for each filter component.  
         [0007]     Due to the allocation of partial beams arranged mirror symmetrically to each other, with respect to a mirror plane of the rod-shaped article, to the same primary beam, an identical perforation structure of the two cigarettes of a double-length cigarette rod is ensured. This feature is different from the disclosure of German patent document DE 33 21 800 A1, which provides an asymmetrical allocation of the partial beams to the primary beams, with respect to the mirror plane of the rod-shaped article, which is contrary to the aim of providing identical perforations for each cigarette of a rod-shaped article in the form of a double length cigarette.  
         [0008]     According to the above described embodiment of the invention, at least four mutually non-overlapping partial beams are generated. This means that the bundles of light beams of at least four partial beams do not overlap each other geometrically in the region between the optical elements and the rod-shaped article. This allows individual, independent adjustment of the perforation properties produced by each partial beam, in particular the production of different perforation zones for a cigarette.  
         [0009]     The generation of four partial beams is known, for example, from German patent documents DE 3418188A1, DE 19530216A1 and DE 10160167A1. However, in each case two partial beams for producing a uniform perforation zone for a cigarette overlap. Each perforation zone therefore includes two separate, but closely spatially connected rows of perforations. These documents therefore disclose only two partial beams or partial beam regions which do not overlap each other.  
         [0010]     Within the scope of the present application the term “perforation zone” is used for all perforations which are produced with partial beams overlapping each other. According to the invention, therefore, at least four perforation zones (at least two perforation zones per cigarette) are produced, while the above-mentioned documents disclose the production of only two perforation zones (one perforation zone per cigarette).  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention is described below with the aid of advantageous practical examples with reference to the attached drawings.  
         [0012]      FIG. 1  shows a perforation apparatus in a first embodiment in a view perpendicular to the longitudinal axis of the rod-shaped article.  
         [0013]      FIG. 2  shows the perforation apparatus of the first embodiment in a view along the longitudinal axis of the rod-shaped article.  
         [0014]      FIG. 3  shows a perforation apparatus in a second embodiment in a view perpendicular to the longitudinal axis of the rod-shaped article.  
         [0015]      FIG. 4  shows the perforation apparatus of the second embodiment in a view along the longitudinal axis of the rod-shaped article.  
         [0016]      FIG. 5  shows a perforation apparatus in a third embodiment in a view perpendicular to the longitudinal axis of the rod-shaped article.  
         [0017]      FIG. 6  shows a perforation apparatus in a fourth embodiment in a view perpendicular to the longitudinal axis of the rod-shaped article.  
     
    
     DETAILED DESCRIPTION  
       [0018]     In the embodiment in  FIGS. 1 and 2 , the perforation apparatus  10  includes a beam generating device  11 , preferably a laser, for generating an optical primary beam  12 . Optical elements  13  to  16  split the primary beam  12  into partial beams (secondary beams)  17  to  20  and deflect the partial beams  17  to  20  in a direction towards a rod-shaped article  21 . Corresponding focusing elements  24  to  27  focus the partial beams  17  to  20  on the rod-shaped article  21  to produce corresponding perforations  28  to  31  in the tipping paper  32  of the rod-shaped article  21 . The rod-shaped article  21  is in the form of a double-length cigarette, i.e. it has two halves  22 ,  23  each forming one cigarette. The rod-shaped article  21  is cut into two single cigarettes  22 ,  23  in the mirror plane S in a subsequent production process.  
         [0019]     To produce the perforation, the laser radiation is pulsed, for example by a chopper disc, not shown, and the rod-shaped article  21  is rotated about its longitudinal axis at a fixed location. This takes place preferably by a corresponding rolling device in a filter assembler, as disclosed, for example, in German patent document DE 37 05 627 A1, particularly reference being made to  FIG. 1  thereof and its description, wherein there is shown and described a filter assembler apparatus  36  that includes a perforation apparatus  10 .  
         [0020]     Referring again to  FIG. 1  of the present application, the optical elements  13  to  15  are beam splitters in the form of semi-transmitting mirrors which each reflect a portion of the primary beam  12 , resulting in the partial beams  17  to  19 , and let through the remainder of the primary beam  12  to the subsequent optical element  16  to produce the partial beam  20 . The last optical element  16  as a rule has a reflectivity of 100% (non-transmitting mirror or purely deflecting element).  FIG. 2  shows the perforation apparatus of the  FIG. 1  in a view along the longitudinal axis of the rod-shaped article  
         [0021]     The partial beams  17  to  20  are extended beams, as illustrated by the example of the partial beam  17  in  FIG. 1 . For the other partial beams  18  to  20 , only the light cone behind the respective focusing lenses  25  to  27  has been shown. As can be seen from  FIG. 1 , the four beams behind the optical elements  13  to  16  are free from overlap with each other.  
         [0022]     If the optical elements  13  to  15  successively have a reflectivity of 25%, 33% and 50%, each of the partial beams  17  to  20  has the same intensity, so that identical perforations  28  to  31  are produced. However, this does not necessarily have to be the case. In general, the reflectivity of the optical elements  13  to  15  must only be coordinated with each other such that in each case mirror symmetrical partial beams have the same intensity, with reference to the mirror plane S between the cigarettes  22  and  23 , thus ensuring that the two cigarettes  22  and  23  have the same perforation structure. For example, the partial beams  17  and  18  can have different intensities in order to be able to individually adjust the air permeability of the perforations  28  and  29  of the cigarette  22 , the sum of intensities of the partial beams  17  and  18  in this case being appropriately 50%.  
         [0023]     In the embodiment according to  FIGS. 3 and 4 , the perforation apparatus includes two beam generating devices  11 A,  11 B, in particular two lasers, for generating two optical primary beams  12 A and  12 B. The optical elements  13  and  16  are located in the beam path of the primary beam  11 A, and the optical elements  14  and  15  are located in the beam path of the primary beam  11 B. In other words, the mirror symmetrical outer partial beams  17  and  20  are allocated to the same primary beam  12 A, and the inversely symmetrical inner partial beams  18  and  19  are allocated to the same primary beam  12 B. The use of two individually adjustable beam generating devices  11 A,  11 B to generate separate primary beams  12 A,  12 B allows the perforation properties, for example the number of holes or the ventilation, of the outer perforations  28 ,  31  to be individually adjusted independently of the perforation properties of the inner perforations  29 ,  30 .  
         [0024]      FIG. 4  shows the perforation apparatus of  FIG. 3  in a view along the longitudinal axis of the rod-shaped article. As can be seen from  FIG. 4 , the optical assembly  11 A,  13 ,  16 ,  24 ,  27  corresponding to the first primary beam  12 A is expediently offset by an azimuth angle ω from the optical assembly  11 B,  14 ,  15 ,  25 ,  26  corresponding to the second primary beam  12 B. In this case a low azimuth angle ω is preferred with a view to a compact size.  
         [0025]     The beam splitters  13  and  14  in this embodiment expediently have a reflectivity of 50%.  
         [0026]     In a modified embodiment, a plurality of primary beams can also be generated by a single beam generating device, for example a use of one or more pre-arranged beam splitters.  
         [0027]      FIG. 5  shows a view of another embodiment along the longitudinal axis of the rod-shaped article similar to the view shown in  FIG. 4 . Two rows of perforations  28 A,  28 B or  31 A,  31 B are produced in each of the two outer perforations zones  28 ,  31  of each cigarette  22 ,  23 , so that there is a total of six rows of perforations, including the two inner perforation zones  29 ,  30 . For this purpose the primary beam  12 A is split into two primary beams  33 ,  34 . This can be done for example by a diffractive element  35 , or some other suitable device, for example an arrangement as described in German patent document DE 195 30 216 A1. The primary beams  33 ,  34  are partially reflected by the beam splitter  13  in order to generate the partial beams  17 A,  17 B which in turn produce the rows of perforations  28 A,  28 B. The primary beams  33 ,  34  transmitted by the beam splitter  13  are reflected by the beam splitter  16  in order to generate the partial beams  20 A,  20 B which in turn produce the rows of perforations  31 A,  31 B.  
         [0028]     The light beams or cones corresponding to the partial beams  17 A,  17 B overlap spatially, as can be seen from  FIG. 5  by the example of the light cones corresponding to the partial beams  17 A,  17 B after the focusing element  24 . Similarly, the light beams or cones corresponding to the partial beams  20 A,  20 B overlap. The embodiment of  FIG. 5  therefore includes four perforation zones corresponding to four mutually non-overlapping partial beam regions  17  to  20  with a total of six partial beams  17 A,  17 B,  18 ,  19 ,  20 A,  20 B.  
         [0029]     In a further embodiment, alternatively or in addition in each of the inner perforation zones  29 ,  30  a plurality of rows of perforations can be produced.  
         [0030]     The invention is not restricted to producing two rows of perforations per perforation zone.  
         [0031]     The embodiment according to  FIG. 6  shows that the optical beam splitting means are not restricted to semi-transmitting mirrors and that a separate optical beam splitting device does not have to be provided for each independent partial beam. Here optical prisms  40 ,  41  made of a suitable material, for example ZnS, are provided as the beam splitting mechanism. The mutually independent partial beams  17  to  20  are here produced by reflection at the front and rear sides of the prisms  40 ,  41 .  
         [0032]     The distance from the inner perforation zones  29 ,  30  to the mirror plane S is preferably within the range from about 11 to about 15 mm and is further preferably approximately 13 mm, and the distance from the outer perforations zones  28 ,  31  to the mirror plane S is preferably within the range from about 19 to about 25 mm.  
         [0033]     The partial beams  17  to  20  are preferably incident on the wrapper of the rod-shaped article  21  at an angle of not more than 10°.  
         [0034]     The invention has been described in detail with respect to referred embodiments, and it will now be apparent from the foregoing to those skilled in the art, that changes and modifications may be made without departing from the invention in its broader aspects, and the invention, therefore, as defined in the appended claims, is intended to cover all such changes and modifications that fall within the true spirit of the invention.