Abstract:
Inner wrappers for packets of cigarettes are fashioned from a continuous strip of metal foil paper directed along a feed path internally of a cigarette packer, advancing through an embossing unit by which the metallic surface is textured, then through a rotary cutter such as will divide the material into leaves of specified length. The embossing unit is equipped with an assembly comprising a pair of rollers, also with a stabilizing mechanism that utilizes an aspirating roller to induce a controlled plastic deformation in the strip, canceling out the random deformations induced by the embossing action, and, with each revolution of the cutter, simultaneously advancing a portion of the embossed strip equivalent to the length of one leaf.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a unit for embossing a strip of wrapping material.  
         [0002]     In particular, the present invention relates to a unit serving to emboss a continuous strip of material, typically metal foil paper, that will be divided up ultimately into discrete lengths and fed to the wrapping mechanisms of a cigarette packer.  
         [0003]     In cigarette packers of conventional design, a strip of metal foil paper is drawn from a roll by decoiling means, directed along a predetermined feed path, taken up by cutting means and divided into single leaves each destined to envelop a group of cigarettes and thus provide an inner wrapper for a respective packet.  
         [0004]     At a given point upstream of the cutting means, likewise conventionally, the strip of material is subjected to the action of an embossing unit consisting in two rollers placed on opposite sides of the aforementioned feed path and contrarotating tangentially one relative to another.  
         [0005]     The two rollers are linked mechanically to the cutting means and present cylindrical surfaces with projections, generally of frustopyramidal shape, such as will indent the metallic strip passing between the rollers and cause it to assume the characteristic roughened texture adopted for inner foil wrappers.  
         [0006]     The cylindrical surface of each embossing roller, of which the circumferential measurement is equal substantially to the length of one leaf cut from the continuous strip, can present areas devoid of the aforementioned frustopyramidal projections, such as will combine to make up the letters of a word, “PULL”, or a selected graphic symbol.  
         [0007]     Accordingly, the “PULL” mark (or selected graphic symbol) is created by leaving areas of the surface unembossed and will appear on each leaf of the cut strip, placed to coincide with a portion of the inner wrapper destined to be removed at the moment of opening the packet of cigarettes.  
         [0008]     Before the packer is set in motion, an operator adjusts the positioning of the strip relative to the cutting means, so that the “PULL” mark will be correctly located on each leaf and therefore on the inner wrapper of the finished packet.  
         [0009]     In practice, it has been found that the embossing step is a direct cause of certain drawbacks.  
         [0010]     More particularly, it has been observed that when subjected to the action of the embossing unit, which results in plastic deformation, the strip of wrapping material tends to behave in an entirely unpredictable manner due to a number of different factors: environmental (temperature and humidity), physical (quality of the material), and mechanical (in particular, the tension to which the strip is subject when passing through the embossing unit).  
         [0011]     As a consequence of the plastic deformation in question, which is also the cause of microslippage induced in the strip relative to the embossing rollers, and the above noted fact that the cutting means are linked mechanically to the embossing unit, the length of the leaves separated from the strip becomes irregular and will in general differ randomly from the correct value.  
         [0012]     This variation in length also results in a loss of timing, with the “PULL” mark shifting from its correct position on the leaf and therefore on the inner wrapper of the finished packet.  
         [0013]     The object of the present invention is to provide a unit for embossing a strip of wrapping material, from which the drawbacks mentioned above will be absent.  
       SUMMARY OF THE INVENTION  
       [0014]     The stated object is realized in a unit according to the present invention for embossing a strip of wrapping material, which comprises a pair of embossing rollers positioned along a set feed path followed by the strip and establishing an embossing station, and incorporates means, positioned along the feed path, by which the strip is deformed plastically or stretched. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which:  
         [0016]      FIG. 1  illustrates an infeed portion of a cigarette packer, equipped with an embossing unit according to the present invention, viewed schematically and frontally in elevation and shown in a first embodiment;  
         [0017]      FIGS. 2 and 3  show a detail of  FIG. 1 , viewed in perspective;  
         [0018]      FIG. 4, 5  and  6  show three further embodiments of the unit according to the present invention, viewed schematically and frontally in elevation;  
         [0019]      FIG. 7  illustrates equipment for rewinding a strip of wrapping material, viewed frontally in elevation and equipped with an embossing unit according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     With reference to  FIG. 1 , numeral  1  denotes the infeed portion, in its entirety, of a cigarette packer incorporating a frame of which a frontal bulkhead  2  is illustrated.  
         [0021]     The infeed portion  1  comprises means, mounted to the bulkhead  2  and illustrated schematically as a block, denoted  3 , serving to guide and feed a continuous strip  4  of metal foil paper  4  decoiled from a roll  5 , also cutter means  6  by which the strip  4  is divided into single leaves  7  destined to provide inner wrappers, fashioned through the agency of wrapping means (not illustrated), for cigarette packets.  
         [0022]     Interposed between the guide and feed means  3  and the cutter means  6  is an embossing unit, denoted  8  in its entirety, mounted to a substantially rectangular vertical plate  8   a  carried by the bulkhead  2 .  
         [0023]     The embossing unit  8  combines with the guide and feed means  3  and the cutter means  6  to establish a feed path P along which the strip  4  advances in the direction indicated by the arrow denoted F.  
         [0024]     The cutter means  6  comprise two contrarotating rollers  9  and  10 , turning on respective horizontal axes  11  and  12  disposed transversely to the feed path P, equipped respectively with a blade  13  and with an anvil  14 .  
         [0025]     The embossing unit  8  comprises an embossing assembly  15  that consists of two contrarotating rollers  16  and  17  turning on respective axes  18  and  19  extending parallel to the axes  11  and  12  of the cutter rollers, and, at a given point downstream of the assembly  15  (in the direction of the arrow F), tension means  20  by which the advancing strip  4  is deformed plastically in the longitudinal direction, or stretched, composed of a decoiling roller  21  turning clockwise on an axis  21 ′ parallel to the axes  18  and  19  of the embossing rollers, and an idle diverter roller  22  located below the decoiling roller  21 .  
         [0026]     The blade roller  9  of the cutter means  6  is coupled directly to the anvil roller  10  and driven by a motor indicated schematically as a block  23 .  
         [0027]     Similarly, one embossing roller  17  is coupled directly to the other embossing roller  16  and driven by the aforementioned motor  23 , which also drives the decoiling roller  21 .  
         [0028]     With each single operating cycle of the embossing unit  8 , which corresponds to one full rotation of the cutter rollers  9  and  10 , the blade  13  and the anvil  14  strike together on the line of the feed path P and separate a leaf  7  of predetermined length L from the strip  4 , destined to form the inner wrapper of a packet of cigarettes.  
         [0029]     The two embossing rollers  16  and  17  are of circumferential length substantially equivalent to the linear length of one leaf  7 , or to a multiple thereof, and positioned mutually tangential at an embossing station  24 ; both rollers  16  and  17  present cylindrical surfaces  25  covered by frustopyramidal projections  26  such as will impress the strip  4  with the familiar rough or reeded texture of an inner foil wrapper as it passes through the embossing station  24 .  
         [0030]     As illustrated in  FIG. 2 , the cylindrical surfaces  25  of the embossing rollers  16  and  17  will present areas  27  devoid of the aforementioned frustopyramidal projections  26  and reproducing the word “PULL” (or a selected graphic symbol having the same significance).  
         [0031]     Accordingly, this same mark, created by virtue of the area remaining unembossed, will appear on each of the leaves  7  and therefore on the inner wrapper of each packet of cigarettes, positioned so as to be visible on opening the packet.  
         [0032]     Once beyond the embossing rollers  16  and  17 , the strip  4  passes through an arc substantially of 180° around the cylindrical surface  28  of the decoiling roller  21 , which is furnished with a plurality of holes  29  connected to a source of negative pressure (not illustrated), thence around the idle diverter roller  22  and toward the cutter means  6 .  
         [0033]     The circumference of the decoiling roller  21  is marginally greater than the circumference of the embossing rollers  16  and  17 .  
         [0034]     Passing through the embossing station  24 , the strip  4  undergoes a plastic deformation such that, with each cycle completed by the two rollers  16  and  17 , the length of the embossed portion of strip emerging from the assembly  15  is dissimilar (generally less, but sometimes greater) to that of the unembossed portion entering the assembly.  
         [0035]     This variance or error can vary unpredictably over time, dependent as it is on a multiplicity of factors, for example ambient temperature and humidity, the quality of the material used for the strip  4 , the degree of slippage between the strip  4  and the rollers  16  and  17  induced at the embossing station  24 , and the tensile force to which the strip  4  is subject.  
         [0036]     Given that the decoiling roller  21  rotates at a tangential velocity marginally greater than that of the embossing rollers  16  and  17 , due to its greater circumference, and that the embossed strip  4  clings to the cylindrical surface  28  without slipping, the advancing strip  4  will be subjected, along the stretch between the embossing station  24  and the cylindrical surface  28 , to a tensile force by which it is deformed plastically in a direction opposite to the force applied by the embossing rollers  16  and  17 , but in a perfectly controlled manner.  
         [0037]     Accordingly, the random deformations induced by the embossing step are cancelled out and, where the circumference of the decoiling roller  21  happens to coincide with the predetermined length L mentioned above, the portions of embossed strip  4  fed cyclically to the cutter means  6 , and ultimately the leaves  7  separated with each cycle of the selfsame cutter means  6 , will be of length that remains constant over time and equal to the predetermined length L (see  FIG. 2 ).  
         [0038]     Thus, the tension means  20  provide means (also denoted  20 ) by which to stabilize the length of the portions of embossed strip directed cyclically from the embossing assembly  15  to the cutter means  6 .  
         [0039]      FIG. 4  illustrates an embodiment of the unit differing from that described above in that the decoiling roller  21  is driven by an independent variable speed motor  30 , of which the operation is interlocked to a control circuit block denoted  31 .  
         [0040]     Where the strip  4  of wrapping material happens to be a preprinted type, for example procured from a paper mill and bearing printed images or logos, errors may occur in the positioning of the “PULL” mark relative to the images or logos.  
         [0041]     Such positioning errors could be occasioned by the aforementioned microslippages induced at the embossing station  24 , and/or by irregular spacing between the preprinted images, and/or by the elasticity of the material used for the strip  4 .  
         [0042]     In this instance, observing  FIG. 4 , a first input of the control circuit block  31  can be connected to means  32  capable of sensing the position of the images and/or the logo, typically a TV camera  33 , and a second input to means  47  that will emit a cyclical timing signal referenced to the embossing roller  16 .  
         [0043]     Thus, by controlling the speed of the decoiling roller  21 , the position of the preprinted images and/or logos relative to the “PULL” mark impressed by the embossing rollers  16  and  17  can be correctly adjusted and maintained steady over time.  
         [0044]     In addition, it will be seen that the independent drive system also serves, in conjunction with the facility of controlling the tangential velocity of the decoiling roller  21  and with the feedback from the sensing means  32 , to give exact and continuous control over the position of the “PULL” mark on each length of strip corresponding ultimately to a single leaf  7 . In this instance, clearly enough, the circumferential dimensions of the decoiling roller  21  are not critical in determining the length L of the leaf  7 .  
         [0045]     The embodiment of  FIG. 5  differs from that of  FIG. 1  in that the infeed portion  1  is equipped further with a feed unit  35 , interposed between the tension means  20  and the cutter means  6 , comprising a first roller  35 ′ power driven by a variable speed independent motor  36 , and an idle roller  37  by which the strip  4  is diverted directly into the cutter means  6 .  
         [0046]     Whilst the decoiling roller  21  serves to stabilize the length of the portions of embossed strip directed cyclically along the feed path P, as in the examples already illustrated, the function of the variable speed roller  35 ′ is to combine with the means illustrated in  FIG. 4  (control circuit block  31 , sensing means  32  and signal emitter means  34 ) in maintaining correct synchronization between the position of the “PULL” mark and the stroke of the cutter means  6 .  
         [0047]     Passing from the decoiling roller  21  to the feed unit  35 , the strip  4  is directed through a storage buffer  38  of the type comprising a negatively pressurized chamber  39  internally of which the running strip  4  forms a loop of variable length.  
         [0048]     The inclusion of the buffer  38 , which itself is of familiar embodiment, facilitates the adjustment and control operations described above by ensuring the strip  4  will run neither tight nor slack.  
         [0049]     With this precise end in view, the buffer  38  is equipped with relative sensing means  32 ′, typically a photocell  41 ′, such as will detect the level of the strip  4  internally of the chamber  39 .  
         [0050]     The sensing means  32 ′ are connected on the output side to a relative control circuit block  31 , to which the motor  23  driving the embossing roller  16  and the decoiling roller  23  is also interlocked.  
         [0051]     In this situation, the operation of the motor  23  can be piloted by the embossing unit  8  in response to signals received from the photocell  41 ′, in such a way as will maintain the loop of strip  4  at a constant and predetermined level internally of the buffer  38 .  
         [0052]     Likewise in this embodiment, the unit according to the invention can include a control circuit block  31  as in the example of  FIG. 4 , of which a first input is connected to a TV camera  33  capable of sensing the position of the images and/or logos on the strip  4 , and a second input to means  47  that will emit a cyclical timing signal referenced to the embossing roller  16 .  
         [0053]     Accordingly, and in like manner to the example of  FIG. 4 , by controlling the speed of the decoiling roller  21 , the positioning of the images and/or logos preprinted on the strip  4  can be adjusted and held steady relative to the “PULL” mark impressed with the embossing rollers  16  and  17 .  
         [0054]     Finally, it will be appreciated that in the example of  FIG. 5 , the decoiling roller  21  can be equipped with an independent motor  30 , rather than being driven by the same motor  23  as the embossing roller  16 .  
         [0055]     Referring again to  FIG. 2 , it will be seen that the word “PULL” impressed by the embossing rollers might be replaced by a reference mark  40  in the guise of a preprinted stripe or dash, that is to say a mark made on the strip by a printing device at intervals corresponding to the length of the single leaves  7 , before the strip itself is wound onto the roll  5 .  
         [0056]     Where printed reference marks  40  are used, the sensing means  32  illustrated in the examples of  FIGS. 4 and 5  could take the form of photocells  41  instead of TV cameras  33 .  
         [0057]     In the example of  FIG. 7 , the embossing unit  8  forms part of equipment  42  by which the embossed strip  4  is rewound onto a roll  5 ′.  
         [0058]     Instead of the aspirating roller  21 , tension means  20  serving to stabilize the strip  4  might consist in a pair of rollers  43  and  44  set in contrarotation substantially tangential one to the other, such as will decoil one length L of embossed strip with each cycle of rotation.  
         [0059]     In a further embodiment of the unit, illustrated in  FIG. 3 , the cylindrical surface  25  of at least one embossing roller  16  or  17  (that denoted  16  in  FIG. 3 ) presents an area, for example rectangular or circular in shape, devoid of frustopyramidal projections  10  and functioning as a die  45 .  
         [0060]     The sole function of the die  45  is to impress a succession of cyclical reference marks  46  on the strip  4  such as can be used to effect a positional adjustment, relative to the cutter means  6 , more accurate than that obtainable using the “PULL” mark and more reliable than that obtainable using a strip  4  with preprinted marks  40 .  
         [0061]     The reference marks  46 , impressed on the leaves  7  in such a way as to remain invisible when the packet is opened, are detectable by means of the photocell  41 .  
         [0062]     In the example of  FIG. 6 , the tension means  20  are located upstream of the embossing assembly  15 . The aspirating decoil roller  21  is driven by an independent variable speed motor  30 ′ interlocked in operation to a control circuit block  31 ′.  
         [0063]     A first input of the control circuit block  31 ′ is connected to sensing means  32 , located between the decoiling roller  21  and the embossing assembly  15  and consisting in a photocell  33  able to detect the position of preprinted marks  40  on the strip  4 . A second input of the circuit block  31 ′ is connected to means  34 ′ such as will emit a cyclical timing signal referenced to the embossing roller  17 .  
         [0064]     With this arrangement, it becomes possible to control the positioning of the preprinted marks  40  relative to the embossing rollers  16  and  17 .  
         [0065]     Finally, numeral  48  denotes a diverting roller located downstream of the embossing assembly  15 , by which the embossed strip  4  is directed toward the cutter means  6 .