Patent Publication Number: US-8992400-B2

Title: Machine and method for manufacturing composite filters

Description:
This application claims priority to Italian Patent Application B02010A000433 filed Jul. 8, 2010, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     This invention relates to a machine and a method for manufacturing composite filters, that is to say, filters comprising two or more filter plugs. 
     The term “composite filter” means a cigarette filter obtained by joining end-to-end two or more filter plugs having different filtration properties and/or made of different materials. 
     Document EP1787534, in the name of the same Applicant as this invention, discloses a twin-track machine for manufacturing composite filters. It involves dividing up at least two segments of filter material, supplied to respective reservoirs, to make filter plugs from them. 
     These filter plugs are transferred along a direction transverse to their longitudinal axes by a train of rotating transfer rollers of known type. 
     The machine comprises an assembling unit designed to place in axial end-to-end contact at least two plugs obtained from two different segments of filter material to obtain filter groups. 
     The filter groups are taken up and transferred in pairs by a single rotating member presenting circumferential carriers, each furnished with two flutes connected to suction means. 
     Each flute receives and accommodates a filter group. 
     The rotating member releases the filter groups in pairs to a pair of conveyors of a garniture tongue which forms two “filter rods”. 
     The garniture tongue affords two channels in which the filter rods supplied by the two conveyors are fashioned. 
     At the garniture tongue, the filter groups are wrapped in a strip of paper material to form two continuous filter rods. The rods feeding out of the garniture tongue are cut simultaneously at a single cutting station by a single cutting element. 
     The absolute and/or relative speeds of the garniture tongue are governed according to a signal from a sensor located upstream of the cutting station. 
     The sensor measures the relative phase between the two rods and between one of the two rods and the cutting element. 
     The expression “relative phase of the filter rods” means the relative distance of two predetermined filter plugs belonging to two different rods along the feed direction. For the rods to be cut correctly, this distance must be equal to a reference distance (at which the two rods are perfectly in phase with each other). 
     The expression “phase of one of the rods relative to the cutting element” means the relative position of a predetermined plug from one of the two rods relative to the position of the cutting element. For the rods to be cut correctly, this distance must be equal to a reference relative distance (at which the rod is in phase with the cutting head. 
     Governing the speeds of the two conveyors of the garniture tongue is necessary to make filters from dimensionally identical plugs, that is, in order to cut the filters correctly. 
     Thus, the absolute and/or relative speeds of the two conveyors are governed in real time in order to allow any phase differences between the two rods and between one of the two rods and the cutting head to be compensated. 
     During the release of the filter groups to the conveyors, the rotating member retains the two filter groups by keeping the suction means on in such a way that the two filter groups gently push—that is, by applying a slight force to—the other filter groups, which have already been placed on the garniture tongue conveyors. 
     That way, the rotating member compacts the filter groups positioned on the garniture tongue. In other words, it eliminates any gaps, or empty spaces, between the filter plugs in the same groups and forms two uninterrupted rows of filter groups. 
     One problem with this machine arises if the relative misalignment between the two rods is too high, that is to say, greater than a predetermined value. 
     In this condition, when the rotating member simultaneously transfers the two filter groups to the conveyors of the garniture tongue, one of the two filter groups being released may excessively compress the other groups already present on the conveyors and fall out of the flute on the rotating member, thus cancelling the effect of retaining the other filter group in the other flute. As a result, one or more filter groups are missing from the filter rod supplied to the garniture tongue and in the worst cases this may even cause a machine shutdown to allow the fault to be corrected. 
     This is worsened by the fact that the problem occurs relatively frequently because the filter segments supplied to the reservoirs have variable dimensions (typically of the order of a few tenths of a millimeter) on account of production tolerances. As a result, during machine operation, the two filter rods tend to go out of phase with each other and this can only be partly compensated by adjusting the relative speed of the garniture tongue conveyors. 
     SUMMARY OF THE INVENTION 
     The aim of this invention is to provide a machine and a method such as will be unaffected by the above mentioned drawback, that is to say, such as can guarantee the optimum operation of the garniture tongue. 
     Another aim of the invention is to provide a machine whereby any relative phase difference between the two filter rods at the cutting element can be easily eliminated. 
     The stated aims are achieved according to the invention in a machine for manufacturing composite filters whose features are as recited in one or more of the annexed claims, and in a method for manufacturing composite filters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The technical features of the invention, with reference to the above aims, are clearly described in the claims below and its advantages are apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate a preferred, non-limiting example embodiment of the invention, and in which: 
         FIG. 1  is a schematic perspective view of the machine for manufacturing composite filters according to this invention; 
         FIGS. 2 to 4  are side views of the machine of  FIG. 1  in as many operating configurations; 
         FIG. 5  is a side view of another embodiment of the machine for manufacturing composite filters according to this invention; 
         FIGS. 6 and 7  are side views of two different alternative embodiments of the machine for manufacturing composite filters according to this invention; 
         FIG. 8  shows a detail of a variant of the machine of  FIG. 1 ; 
         FIG. 9  shows a schematic plan view of yet another variant embodiment of the machine according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the accompanying drawings, the numeral  100  denotes in its entirety a machine for making composite filters from two or more filter plugs. 
     The term “filter plug” as used herein means a piece of substantially uniform filter material, obtained preferably by cutting a segment of filter material. In other words, a filter plug is a portion of a segment of filter material. 
     The term “filter group” as used herein means a group of filter plugs of different types, that is to say, made of different materials and/or having different filtration properties, lined up longitudinally with each other. 
     The machine  100  comprises a rotating member, denoted by the reference numeral  1 . 
     The rotating member  1 , which is of substantially known type, is described in patent document EP1787534 in the name of the same Applicant as this invention and incorporated herein by reference. 
     The rotating member  1  is represented schematically in  FIG. 1  and is shown more clearly in  FIG. 2 , and comprises a rotating body  2 . 
     The rotating body  2  rotates about a horizontal axis  2   a.    
     The rotating body  2  is equipped with a plurality of carriers  4 , spaced at equal angular intervals and rotatable about respective axes of rotation  4   a  (the carriers  4  are illustrated in  FIG. 2 ). 
     Each carrier  4  comprises a pick-up head  5  with two mutually parallel flutes  6 ,  7  for accommodating two distinct filter groups G 1 , G 2 . 
     The flutes  6 ,  7  of each pick-up head  5  are connected to a suction unit (not illustrated), which is turned on to hold the filter groups G 1 , G 2  within the flutes  6 ,  7  of the pick-up head  5  and turned off to release them. 
     The rotating member  1  is configured to convey the filter groups G 1 , G 2  while keeping the flutes  6 ,  7  of each carrier  4  substantially horizontal at all angular positions of the rotating body  2 , as shown clearly in  FIG. 2 . 
     The rotating member  1  also conveys the filter groups G 1 , G 2  longitudinally along their axes of longitudinal extension. 
     According to the invention, the rotating member  1  defines a feeder S for supplying pairs of filter groups G 1 , G 2 . 
     It should be noted that in other embodiments not illustrated the feeder S might be of a different type. 
     It should also be noted that the rotating member  1  is supplied by respective conveyors of known type forming part of an assembling unit (illustrated partly and schematically and labeled  50 ). 
     The assembling unit (not illustrated) is supplied with at least two segments of filter material of different types. 
     The segments are divided up to form a plurality of filter plugs which are conveyed transversally to their longitudinal axes by conveyor means. 
     The conveyors of the assembling unit combine the different filter plugs to form the filter groups G 1 , G 2  comprising at least two filter plugs SA, SB made from different types of filter material. 
     The filter groups G 1 , G 2  are then supplied to the rotating member  1 . 
     The machine  100  further comprises a conveyor  10  designed to take up the filter groups G 1 , G 2  from the feeder S (or rotating member  1 ) and to convey them along their direction X of longitudinal extension. 
     With reference to the preferred embodiment illustrated in  FIGS. 1-4 , the conveyor  10  is a pneumatic conveyor. 
     The pneumatic conveyor  10  comprises an element  11  presenting a pair of channels  12   a ,  12   b  extending along the direction X and nozzles  13  for blowing a stream of air. 
     Preferably, the channels  12   a ,  12   b  are transversally spaced by a distance equal to the spacing of the flutes  6 ,  7  of the pick-up head  5  of the rotating member  1 . 
     The rotating member  1 , as described in more detail below, releases each filter group G 1 , G 2  to a channel  12   a ,  12   b , that is to say, a first filter group G 1  is released to the channel  12   a  and a second filter group G 2  is released to the channel  12   b.    
     The nozzles  13  are positioned and oriented relative to the element  11  in such a way that the air issuing from the nozzles  13  applies a pushing action along the direction X on the filter groups G 1 , G 2  released by the feeder S. This allows the filter groups G 1 , G 2  to be pushed along inside the channels  12   a ,  12   b  of the element  11  and made to advance along the direction X. 
     The pneumatic conveyor  10  defines a filter group G 1 , G 2  transfer device DT by which the filter groups G 1 , G 2  are taken up from the feeder S in pairs and directed separately along two distinct feed channels or lines L 1 , L 2  along the direction X. 
     The machine  100  further comprises a wheel  3  which rotates about a respective central axis  3   a  and which is driven in rotation by drive means (not illustrated). 
     The axis  3   a  is parallel to the above mentioned axis  2   a.    
     Preferably, the wheel  3  is furnished with circumferential grooves  51  defining seats for receiving the filter groups G 1 ,G 2 . 
     As illustrated in  FIG. 1 , the wheel  3  comprises a pair of circumferential grooves  51 , namely, a first groove for taking up the first filter groups G 1  and a second groove for taking up the second filter groups G 2 . 
     The wheel  3  defines a release device R by which the filter groups G 1 , G 2  are released in phase with each other to a garniture tongue  8 . 
     In the preferred embodiment, the wheel  3  acts in conjunction with the transfer device DT to set the two filter groups G 1 , G 2  in phase one with the other, as described in more detail below. 
     The wheel  3  is driven in rotation about the axis  3   a  through the agency of motor means (not illustrated), controlled by a control unit  14  also forming part of the machine  100 . 
     The wheel  3  receives the filter groups G 1 , G 2  from the pneumatic conveyor  10  and releases them, that is, transfers them, to conveyors C 1 , C 2  of a garniture tongue  8  for forming two filter rods B 1 , B 2 . 
     The garniture tongue is denoted by the reference numeral  8  and also forms part of the machine  100 . 
     The garniture tongue  8  comprises two conveyors C 1 , C 2 , each designed to convey one of the two filter groups G 1 , G 2 . 
     The conveyors C 1 , C 2  direct the filter groups G 1 , G 2  along two feed lines L 1 , L 2  towards the garniture tongue  8 . 
     Preferably, the conveyors C 1 , C 2  of the garniture tongue  8  are conveyors of the type with belts. 
     The conveyors C 1 , C 2  are designed to take up the filter groups G 1 , G 2  released by the wheel  3  and to direct them to a garniture station  16  forming part of the garniture tongue  8 . 
     The filter groups G 1 , G 2  are progressively wrapped in a strip  25  of wrapping material placed above the conveyor belts C 1 , C 2  to make the two continuous filter rods B 1 , B 2  at the garniture station  16 . 
     The strip  25  is preferably of paper material. 
     The garniture station  16  comprises a folding device  24  (represented schematically in  FIG. 1 ) by which the strip  25  of wrapping material is fashioned around the filter groups G 1 , G 2  and a gumming device  26  (also represented schematically in  FIG. 1 ) for gluing to each other the longitudinal edges of the strip  25  of wrapping material. 
     In light of this, it should be noted that each filter rod B 1 , B 2  is composed of an alternating succession of filter plugs SA, SB having different filtration properties and/or of different types, or each rod B 1 , B 2  is composed of an aligned succession of first or second filter groups G 1 , G 2 . 
     The filter rods B 1 , B 2  are then transferred by the conveyors C 1 , C 2  of the garniture tongue  8  to a cutting station  9  downstream. 
     The cutting station  9  comprises a rotating cutting head  17  for dividing up the two filter rods B 1 , B 2  along a predetermined cutting line. 
     The cutting head  17  simultaneously cuts the two filter rods B 1 , B 2  to make composite filters F 1 , F 2 . 
     More specifically, the cutting head  17  comprises a rotating drum  19  driven by a respective motor (the latter not being illustrated). 
     The drum  19  rotates about an axis  19   a  which is substantially parallel to the feed direction X of the rods B 1 , B 2  and has on its outer surface of revolution one or more knives  27 . 
     Each knife  27  is inclined at an angle to the feed direction X of the continuous rods B 1 , B 2 . 
     The cutting head  17  is driven in such a way as to cut the rods B 1 , B 2  cyclically at regular intervals. 
     The cutting head  17  constitutes cyclic cutting means  20  driven by respective motor means to divide up the two rods B 1 , B 2  simultaneously into single composite filters F 1 , F 2 . 
     The machine  100  further comprises a sensor  21  which detects the passage of the plugs SA, SB of each filter rod B 1 , B 2  at a detection region  22 . 
     Preferably, the sensor  21  is configured to recognize the density and/or the color of the rod portion B 1 , B 2  in transit through the detection region  22 , in such a way as to identify the plugs SA, SB and send a corresponding signal to the control unit  14 . 
     It should be noted that the control unit  14  can derive from the detection signal received from the sensor  21  the relative phase between the two rods B 1 , B 2  and the relative phase between each rod B 1 , B 2  and the knives  27  of the cutting head  17 . 
     The expression “relative phase between the two filter rods” means the effective relative distance of two predetermined filter plugs SA, SB of one filter rod B 1  relative to those of the other rod B 2  along the feed direction X on the conveyors C 1 , C 2 . For cutting to be effected correctly, this distance must be equal to a reference distance corresponding to zero phase. 
     The expression “relative phase between one of the two rods and the cutting head” means the relative position of the plugs SA, SB constituting a filter rod B 1 , B 2  along the direction X relative to the position of the knives  27  of the cutting head  17 . For cutting to be effected correctly, this position, too, must be kept substantially equal to a reference position corresponding to zero phase. 
     According to the invention, the sensor  21  constitutes sensing means  23  serving to monitor the phase of at least one of the two rods B 1 , B 2 , preferably both rods, relative to the cutting means  20 . 
     The sensor  21  also constitutes sensing means  23  serving to monitor the relative phase between the filter rods B 1 , B 2 . 
     Below is a description of a preferred mode of operation of the machine  100  according to the invention, with reference to  FIGS. 2 to 4  which illustrate the steps performed in sequence by the machine  100  to release a pair of filter groups G 1 , G 2 . 
     In effect, it should be noted that the machine  100  is highly versatile and can operate in different modes depending on the driving speeds of its different component parts and/or on the configuration of the parts. 
     In light of this, it should be noted that the machine  100  can form one or two rows of filter groups G 1 , G 2  on the two lines L 1 , L 2  upstream of the wheel  3 . 
     In the example of  FIG. 2  the machine  100  is driven in such a way as to form, upstream of the wheel  3 , two rows of filter groups G 1  and G 2  on the two distinct lines L 1  and L 2  (it should be noticed that  FIGS. 2 to 4  show only the row of the first filter group G 1  because the drawings are side views and the row of the second filter group G 2  is hidden). 
     The rotating member  1  transfers the filter groups G 1 , G 2  of each pick-up unit  5  by rotation about its axis  2   a.    
     Each filter group G 1 , G 2  is released to the pneumatic conveyor  10  when the respective flute  6 ,  7  of the pick-up head  5  is aligned with the respective groove  12   a ,  12   b  of the conveyor  10  itself (as illustrated in  FIG. 2 ). 
     It should be noted that in  FIG. 2  the lowermost carrier  4  is at the position for releasing the respective filter groups G 1 , G 2  to the pneumatic conveyor  10 . 
     The suction element (not illustrated) of the pick-up head  5  of the carrier  4  in the release position is switched off. After being switched off, the filter groups G 1 , G 2  released by the rotating member  1  are pushed along the direction X by the stream of air issuing from the nozzles  13  ( FIG. 3 ). 
     The filter groups G 1 , G 2  released are pushed forward along the respective grooves  12   a ,  12   b  of the pneumatic conveyor  10  until coming into abutment with the filter groups G 1 , G 2  already present in the grooves  12   a ,  12   b  of the pneumatic conveyor  10  ( FIG. 4 ) or, if there are no filter groups G 1 , G 2  lined up in the grooves  12   a ,  12   b  of the pneumatic conveyor  10 , until coming into abutment with the walls of the grooves  51  of the wheel  3 . 
     It should be noted that the wheel  3  moves the plugs SA, SB making up the filter groups G 1 , G 2  substantially by friction, making the filter groups G 1 , G 2  advance until releasing them to the conveyors C 1 , C 2  of the garniture tongue  8 . 
     The conveyors C 1 , C 2  of the garniture tongue  8  are driven at a constant speed to feed the two continuous filter rods B 1 , B 2  towards the cutting station  9 . 
     In the cutting station  9 , the two filter rods B 1 , B 2  must be cut precisely at a predetermined position. 
     The sensor  21  of the machine  100  detects each plug SA, SB of the two filter rods B 1 , B 2  as it passes the detection region  22  and sends a corresponding signal to the control unit  14 . 
     From the signal of the sensor  21 , the control unit  14  derives a relative phase value of the two filter rods B 1 , B 2  and a phase value of one of the two filter rods B 1 , B 2  relative to the cutting head  17 . 
     According to the invention, the control unit  14  might also derive only the phase value of one of the two filter rods B 1 , B 2  relative to the cutting head  17 . 
     It should be noted that the control unit  14  is connected to the cutting head  17 , to the sensor  21 , to the wheel  3  and, preferably, as illustrated in  FIG. 1 , also to the conveyors C 1 , C 2  of the garniture tongue  8 . 
     The control unit  14  governs the speed of the wheel  3  as a function of the derived value of the phase between one of the two rods B 1 , B 2  and the cyclic cutting means  20 . Thus, the wheel  3  supplies the garniture tongue  8  at a rate controlled by the control unit  14 . 
     By way of an example, if the two filter rods are out of phase relative to the cutting head  17  (or the cutting lines of both filter rods B 1 , B 2  are displaced by the same amount relative to the reference position) and, more specifically, if a delay relative to the cutting head  17  is detected, the wheel  3  is accelerated to supply the conveyors C 1 , C 2  of the garniture tongue  8  at a faster rate. 
     According to another aspect of the invention, the control unit  14  is programmed to control also the speed of both conveyors C 1 , C 2  of the garniture tongue  8 . 
     More specifically, according to this aspect, the control unit coordinates the speed of both conveyors C 1 , C 2  of the garniture tongue  8  with the speed of the wheel  3  as a function of the phase signal of one of the two filter rods B 1 , B 2  relative to the cutting means  20 . 
     It should be noted that according to a yet further aspect, the control unit  14  also controls and governs the relative speeds of the two conveyors C 1 , C 2  of the garniture tongue  8  in such a way as to compensate for any relative phase difference between the two filter rods B 1 , B 2 , detected by the sensor  21 . 
     In this regard, it should be noted that if no phase differences between the two filter rods B 1 , B 2  and the cutting means  20  are detected, the wheel  3  is driven at a constant speed. 
     The advantages of the invention are described briefly below. 
     The main advantage of the machine  100  lies in the wheel  3  and in the pneumatic conveyor  10 , that is to say, in the release device R and transfer device DT. More specifically, the wheel  3  allows the filter groups G 1 , G 2  of the two distinct lines L 1 , L 2  to be set in phase with each other before completely releasing the groups G 1 , G 2  to the conveyors C 1 , C 2  of the garniture tongue  8 . 
     In effect, it should be noted, in this regard, that if one of the two filter groups G 1 , G 2  is released by the rotating member  1  in advance of the other, the wheel  3  can slow it down more than the other so as to align—that is, set at zero relative phase—the two groups released upstream of the conveyors C 1 , C 2  of the garniture tongue  8 . 
     The length of the two rows of filter groups G 1 , G 2  in the transfer device DT is modified as a function of the drive speed of the wheel  3 . Thus, the grooves  12   a  and  12   b  of the element  11  define, according to the invention, a buffer which can accommodate a variable length row of filter groups G 1 , G 2  to compensate for any slowdowns/accelerations of the wheel  3  relative to the rotating member  1 . 
     The release device R, in combination with the transfer device DT allows the operation of the rotating member  1  to be uncoupled from that of the conveyors C 1 , C 2  of the garniture tongue  8 . 
     In effect, it should be noted that in the machine  100  according to the invention, the rotating member  1  merely transfers the filter groups G 1 , G 2  to the pneumatic conveyor  10  without in any way compacting the filter groups G 1 , G 2 , as occurred, instead, in the prior art solutions. 
     The term “compacting” as used in this description means creating an uninterrupted row of filter plugs SA, SB placed in end-to-end contact, that is to say, creating a longitudinal row of filter plugs without gaps or empty spaces between them. 
     That way, during the step of releasing the filter groups G 1 , G 2 , the rotating member  1  of the machine  100  is unaffected by the drawbacks typical of the known solutions and, advantageously, its speed can be governed in such a way as to optimize it relative to the speed of the parts upstream. 
     In light of this, it should be noted that the effect of the control unit  14  governing the relative speed of the conveyors C 1 , C 2  to compensate for any phase differences between the two filter rods B 1 , B 2  is applied only to the wheel  3  and to the conveyor  10 —that is, to the length of the row of filter groups in the conveyor  10 . This avoids problems during the step of releasing the filter groups G 1 , G 2  by the rotating member  1 , overcoming the above described drawback of the prior art machines due to incorrect releasing and consequent incorrect supplying of the garniture tongue  8 . 
     In yet another embodiment, the control unit  14  governs the nozzles  13  and activates them according to a predetermined sequence to control the conveying speed of the pneumatic conveyor  10 . 
     Advantageously, the control unit  14  governs the nozzles  13  as a function of the monitored phase value of at least one filter rod B 1 , B 2  relative to the cutting means  20 . 
     In a further embodiment, the nozzles  13  are controlled independently in order to govern the relative conveying speed in the two lines L 1 , L 2  of the pneumatic conveyor  10 . 
     In a yet further embodiment, illustrated in  FIG. 7 , the machine  100  comprises, instead of the wheel  3  with the circumferential grooves  51 , a wheel  28  equipped with a plurality of paddles  29  by which the filter groups G 1 , G 2  released by the pick-up heads  5  are engaged in such a way as to bring about their release onto the conveyors C 1 , C 2  of the garniture tongue  8 . 
     The paddles  29  protrude radially and are preferably furnished with an axially projecting pin  30  by which the filter groups G 1 , G 2  are engaged in such a way as to push/retain them. 
     In this variant embodiment, the wheel  28  furnished with paddles  29 , hereinafter also referred to as paddle wheel  28 , constitutes the release device R described above with reference to the wheel  3  of the preferred embodiment. 
     This embodiment also preferably comprises, instead of the pneumatic conveyor  10 , a conveyor comprising a plurality of wheels  31 , hereinafter also referred to as wheel conveyor  31 . 
     The wheel conveyor  31  comprises a plurality of wheels  31  driven in rotation by respective drive means (not illustrated). 
     The wheels  31  are designed to engage the filter groups G 1 , G 2  released by the carriers of the rotating member  1  and to direct them along a predetermined conveyor path. 
     Preferably, the wheel conveyor  31  comprises first wheels, designed to engage and direct the first filter groups G 1 , and second wheels, designed to engage and direct the second filter groups G 2 . 
     Alternatively, the wheel conveyor  31  comprises a single group of wheels  31  designed to transfer both filter groups G 1 , G 2  to the release device R. 
     It should be noted that the wheels  31  can advantageously accelerate the filter groups G 1 , G 2  released by the rotating member  1  thereby spacing them from each other in such a way as to create a predetermined space LG 1 —or gap—between one filter group G 1 , G 2  and another. 
     This makes it possible to fill the gap LG 1  between one filter group and the next for example with granular material in order to make filters F 1 , F 2  comprising a filter portion made from granular material. 
     Thus, the machine  100  might advantageously also comprise a unit (not illustrated) for releasing granular material, located preferably downstream of the paddle wheel  28 . 
     Attention is thus drawn to the versatility of the machine  100 , which can be equipped with the wheel conveyor  31  and with the paddle wheel  29  in order to advantageously be able to space the filter groups from each other upstream of the wheel  28 . 
     Also, the gap LG 1  created between one filter group G 1 , G 2  and the next makes it possible to avoid breaking or damaging the filter plugs SA, SB making up the filter groups when a filter group G 1 , G 2  is engaged by a paddle  29 . 
     It should be noted that each paddle  29  is designed to engage a filter group G 1 , G 2  and direct it downstream of the wheel  28  to supply it to the conveyors C 1 , C 2  of the garniture tongue  8 . 
       FIG. 6  shows a variant where the machine  100  comprises a wheel  3  furnished with grooves  51 , and the wheel conveyor  31  described above. 
     This variant has the same technical and functional features as those described with reference to the preferred embodiment and will not therefore be further described. 
       FIG. 5  shows a variant embodiment where the machine  100  comprises, instead of the pneumatic conveyor  10 , a belt conveyor  34 . 
     The belt conveyor  34  comprises a pair of belts  35 ,  36 , namely, an upper belt  36  and a lower belt  35 . 
     Each belt  35 ,  36  is trained around respective end rollers  37 ,  38 ;  39 ,  40 , driven in rotation by drive means not illustrated. 
     The belt conveyor  34  serves the same function as the pneumatic conveyor  10 , that is to say, it allows transfer of the filter groups G 1 , G 2  released by the rotating member  1  to the release device R and acts in conjunction with the release device R to allow the two filter groups G 1 , G 2  of the two lines L 1 , L 2  to be aligned, that is to say, phased, with each other. 
     In a variant embodiment illustrated in  FIG. 8  the machine  100  comprises a pair of release devices R, each associated with one of the two lines L 1 , L 2 . 
     For clarity, the release devices R have been individually labeled R 1  and R 2 . 
     In particular, by way of a non-limiting example, the release devices R 1  and R 2  of  FIG. 8  are defined by a pair of wheels  3  having the same functional features as those described with reference to the wheel  3  of the preferred embodiment of the machine  100 . 
     In the variant illustrated in  FIG. 8  the wheels  3  are, at least on the surface of them, made of an elastic material which is deformable so that the filter groups G 1 , G 2  can be fed forward by friction. 
     The two release devices R 1 , R 2  are preferably driven by respective drive means which are independent of each other. In other words, the speed of each wheel  3  can advantageously be governed independently of the speed of the other. 
     In light of this, it should be noted that according to the invention the control unit  14  governs the speed of both wheels  3  as a function of the phase value between each filter rod B 1 , B 2  and the cutting head  17 . 
     It is also possible to govern the relative speed of the two wheels  3  as a function of the monitored relative phase value between the filter rods B 1 , B 2 . According to this aspect, any relative phase differences between the two filter rods B 1 , B 2  that might arise downstream of the garniture tongue  8  can advantageously be compensated. Advantageously, that means, unlike the solutions known up to now, that there is no need for any further adjustment of the speed of the conveyors C 1 , C 2  of the garniture tongue  8 . 
     In effect, as is known, adjusting the speed of the conveyors C 1 , C 2  of the garniture tongue  8  to reduce the relative phase difference between the two filter rods B 1 , B 2  is in many cases not very effective because the filter groups G 1 , G 2  are already partly wrapped in the strip  25  of wrapping material and thus any relative movement between the groups G 1  of one filter rod B 1  relative to the groups G 2  of the other filter rod B 2  along the direction X is not precise and is difficult to implement. 
     Advantageously, this variant therefore also allows the relative phase between the two filter rods B 1 , B 2  to be controlled highly effectively and precisely upstream of the conveyors C 1 , C 2  of the garniture tongue. 
     It should be noted, however, that the wheel  3  and the pneumatic conveyor  10  of the machine  100 , even without control of the relative speed of the two release devices R 1  and R 2 , make it possible to eliminate any phase differences between the filter rods downstream of the garniture tongue  8 . 
     Preferably, according to this variant, the machine  100  comprises, for each filter group G 1 , G 2 , an independent transfer device DT acting in conjunction with the respective release device R 1 , R 2 . 
     In short, it should be noted that according to this variant embodiment, there is a transfer device DT and a release device R for each filter group G 1 , G 2 - or line L 1 , L 2 . 
     In a further variant embodiment, illustrated in  FIG. 9 , the release device R comprises two variable pitch augers  42 , each independently driven in rotation about a respective axis of rotation. 
     For clarity, the two augers  42  of  FIG. 9 , namely a first auger and a second auger, are individually labeled  42   a  and  42   b , respectively. 
     Each auger  42  is configured to receive the filter groups G 1 , G 2  conveyed by the transfer device DT and to rotate about a respective central axis. 
     Preferably, in this variant embodiment, the transfer device DT comprises a vacuum type conveyor  43 . 
     Preferably and without limiting the invention, as illustrated by way of non-limiting example in  FIG. 9 , the machine  100  comprises a first  43   a  and a second  43   b  vacuum type conveyor  43 , each designed to carry and transfer a respective filter group G 1 , G 2  to one of the two augers  42   a ,  42   b.    
     It should be noted that each vacuum type conveyor  43   a ,  43   b  is furnished with a seat (denoted by the reference numeral  48 ) containing the filter groups G 1 , G 2  being fed forward. 
     Preferably, but not necessarily, each auger  42  is a screw with multiple starts which are substantially identical but angularly offset. In this regard, however, it should be noted that each auger  42  in  FIG. 9  has only one start. 
     Advantageously, with the rotating member  1  releasing filter groups G 1 , G 2  which are equal in number and size in a predetermined time interval, a multiple start auger  42  can be driven in rotation at a slower speed than a single-start auger to release the filter groups G 1 , G 2  to the conveyors C 1 , C 2  of the garniture tongue  8  at the same rate. 
     It should also be noted that in the embodiment shown in  FIG. 9 , the pitch of each auger  42   a ,  42   b , that is, the distance between the thread roots  44 , decreases along the axial direction of the auger  42  itself relative to the conveying direction of the filter groups G 1  and G 2  (in effect, the length LP 1 , corresponding to the pitch at the infeed end of the auger  42 , is greater than the length LP 2 , corresponding to the pitch at the outfeed end of the auger  42 ). 
     In other words, the pitch at the infeed end  46  of the auger  42  of  FIG. 9  is greater than the pitch at the outfeed end  47 . 
     Alternatively, the machine  100  may comprise a single auger (not illustrated), with at least two starts at a suitable angular offset, by which both filter groups are engaged simultaneously. 
     The operation of the machine  100  with the augers  42   a  and  42   b  is described briefly below with reference to the embodiment illustrated by way of non-limiting example in  FIG. 9 . 
     In  FIG. 9 , the filter groups G 1  and G 2  feeding into the respective augers  42   a ,  42   b  are not in phase with each other, that is to say, there is a longitudinal misalignment or phase difference, labeled D, between the two filter groups G 1 , G 2 . More specifically, the first group G 1  is ahead of the second group G 2 . 
       FIG. 9  shows the same filter groups G 1 , G 2  present at the infeed ends of the augers  42   a ,  42   b  at successive moments in time, that is to say, occupying successive positions, along the axial direction of the auger. 
     Between its infeed end  46  and its outfeed end  47 , the auger  42  applies a greater slowing action on the first group G 1 , that is to say, on the group which is ahead at the infeed end  46  of the auger  42 , and a smaller slowing action on the second group, that is to say, on the group which is behind at the infeed end  46  of the auger  42 . This advantageously allows the two groups G 1 , G 2  to be released at the outfeed ends of the augers  42   a  and  42   b  in phase with each other, that is, aligned, as may be seen in  FIG. 9 . 
     In effect, the rear portion of the threading of the auger  42  applies a slowing action on the filter groups G 1 , G 2  being fed forward by the respective vacuum type conveyor  43 . 
     The smaller pitch at the outfeed end  47  of each auger  42  advantageously allows the filter groups of each line L 1 , L 2  to be compacted before being released to the conveyors C 1 , C 2  of the garniture tongue  8 . 
     In the same way as the wheel  3 , the auger is advantageously controlled by the control unit  14 , which governs its speed as a function of the signal received from the sensor  21  and of the phase of the cutting head  17  according to the technical and functional features described above with reference to the wheel  3  of the preferred embodiment. 
     In variant embodiments not illustrated in the drawings, the variation of the pitch of the auger  42  may be distributed differently along the axial direction. 
     More specifically, the auger  42  may be designed to space the filter groups G 1 , G 2  from each other, that is, to space each first filter group G 1  from the next first filter group released by the rotating member  1  and to space each second filter group G 2  from the next second filter group released by the rotating member  1 . 
     In other words, according to this variant, the auger is designed to serve as an accelerating element that creates between one filter group and the next in each line L 1 , L 2  empty spaces which may or may not be filled, depending on the type of filter to be made. 
     According to this variant, the pitch at the outfeed end of the auger is greater than the pitch at the infeed end of the auger. 
     Set out in brief below are some general consideration regarding the machine  100 . 
     The release device R of the machine  100  may comprise, preferably and alternatively: 
     a wheel  3  furnished with circumferential grooves  51 ; 
     a wheel  3  of deformable material; 
     a paddle wheel  28 ; 
     a variable pitch auger  42 . 
     Further, the transfer device DT may comprise, preferably and alternatively: 
     a pneumatic conveyor  10 ; 
     a wheel conveyor  31 ; 
     a belt conveyor  34 ; 
     a vacuum type conveyor  43 . 
     The release and transfer devices R and DT can be combined in any way, all the possible combinations falling within the scope of the invention. 
     It should also be noted that the machine  100  may comprise either a single release device R operating on both filter groups G 1 , G 2  released by the rotating member  1  or a pair of release devices R 1 , R 2 , each operating on one of the two filter groups G 1 , G 2 . 
     Further, the machine  100  may also comprise either a single filter group G 1 , G 2  transfer device DT operating on both filter groups G 1 , G 2 , or a pair of filter group G 1 , G 2  transfer devices DT, each operating on one of the two filter groups G 1 , G 2 . 
     It should also be noted that the filters F 1 , F 2  made by the machine  100  according to the invention are supplied to a further unit  41 , illustrated schematically in  FIG. 1 , which attaches each filter F 1 , F 2  to a respective cigarette rod. 
     The invention described above is susceptible of industrial application and may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted by technically equivalent elements.