EP3328221B1

EP3328221B1 - Improved filter rod maker for handling stiff wrapping web material

Info

Publication number: EP3328221B1
Application number: EP16745738.1A
Authority: EP
Inventors: Cristiano Casale; Fabio Angelini; Luciano DI DOMENICO
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2015-07-31
Filing date: 2016-08-01
Publication date: 2019-10-02
Anticipated expiration: 2036-08-01
Also published as: JP2018521660A; WO2017021347A1; BR112017028513A2; KR102709576B1; CN107734980A; RU2017146616A; RU2017146616A3; CN107734980B; JP6976927B2; EP3328221A1; RU2703105C2; PL3328221T3; BR112017028513B1; KR20180034345A

Description

The present invention relates to an apparatus for making filter rods for use in the manufacture of smoking articles such as filter cigarettes.
Filter cigarettes typically comprise a rod of tobacco cut filler surrounded by a paper wrapper and a cylindrical filter aligned in end-to end relationship with the wrapped tobacco rod and attached thereto by tipping paper. The filter typically consists of one or more plugs of a fibrous filtration material. One suitable fibrous filtration material is cellulose acetate tow, that is often treated with a plasticizer like triacetin. The one or more plugs are circumscribed by a paper material typically referred to as "plug wrap".
The manufacture of filter rods from continuous fibre filter tow comprises moving the filter tow in a generally longitudinal direction through successive treatment steps for aligning tow fibres, applying plasticiser and/or other additives to the fibres before the tow is gathered, compressed and formed into a predetermined shape, such as a substantially cylindrical rod. In addition, the manufacturing process comprises wrapping the fibre tow rod with the plug wrap in order to produce a wrapped filter rod.
To this purpose, a filter rod maker includes a wrapping station for receiving the rod shaped fibre tow from a forming station and for wrapping the rod shaped fibre tow with filter paper to form a continuous filter rod. The wrapping station comprises an endless belt conveyor (provided, for example, as a garniture tape) configured to be advanced in a predetermined direction along an endless path, and a feeding device for supplying a filter paper ribbon onto the belt conveyor in a first portion of the path. Further, the wrapping station comprises guide elements for gradually converting the conveyor into a tube in a second portion of the path downstream of the first path portion by moving the side edges of the belt toward each other. Filter rod makers of this type are described for example in US 4768526 .
In more detail, the conveyor typically comprises a belt looped around two return rollers. One branch of the belt runs slidably along a longitudinal groove provided in a guide element or garniture. The groove has a cross section that varies continuously between an inlet end and an outlet end of the guide and which is substantially cylindrical at the outlet end. The belt sliding in the groove constitutes a garniture tape by which the filter paper ribbon advancing from the first path portion is guided and wrapped around the fibre tow rod in the second path portion. Thus, in the wrapping station, the filter paper ribbon is wound around the rod shaped fibre tow such that the marginal portions of the filter paper ribbon overlap.
Further, the filter rod maker comprises a gluing means for applying a suitable adhesive to one or both side edges of the filter paper ribbon so that, when they overlap, they are bonded to each other. The adhesive may be applied onto the wrapping web material in an applicator region along the wrapping garniture or, as an alternative, upstream from the entry of the wrapping web material into the garniture of the wrapping station.
By way of example, a heat-activatable adhesive may be applied onto one or both side edges of the filter paper ribbon, and the filter rod maker further comprises a heat source for activating the adhesive, the heat source being arranged at a position along the garniture.
In addition, the filter rod maker typically further comprises means for cooling the adhesive in order to cause the rapid setting of the adhesive. In particular, filter rod makers are known that comprise a cooling bar operatively coupled with the endless belt conveyor at a location along the wrapping web material path downstream of the heat source. One such cooling bar is typically configured to be, during use, at a temperature of from about -5 degrees Celsius to about 6 degrees Celsius. This ensures that, as the wrapped rod travels along the cooling bar, the adhesive sets and a sealed longitudinal seam is formed.
The wrapped filter rod thus produced may subsequently be cut into segments having a predetermined length to obtain filter plug elements. In particular, the filter maker comprises a cutting assembly at a location downstream of the cooling bar for cutting the continuous wrapped filter rod leaving the wrapping station into filter rod portions having a length corresponding to several filter plug elements. These filter rod portions may subsequently be transferred to a filter combiner or to a tipping machine for being attached to a tobacco rod. To this purpose, an exit station of the filter rod maker comprises a transfer drum comprising a plurality of flutes adapted to receive the filter rod portions leaving the wrapping station and for conveying the filter rod portions to another operating unit.
A filter rod maker disclosed in DE 10 2013 210634 , for example, comprises one such rotating transfer drum having a plurality of spaced apart flutes on an exterior surface of the drum. The flutes are constructed and arranged to receive filter rod segments as the drum rotates, and stop means are provided at one end in each of the flutes, the filter rod segments being positioned against such stop means when they are received into the flutes. Each stop means comprises a cylindrical pin extending along an axis of the flute between a first end, at which the pin is attached to a drum frame, and a second end opposite the first end.
For certain applications, it may be preferable to use a stiff, thicker wrapping web material, such as to impart a greater rigidity to the filter. This, however, may make forming a filter rod with low ovality difficult. Further, because friction between the stiff wrapping web material and parts of the filter rod maker along the wrapping web material path is increased, more heat is generated and so the sealing efficiency of the cooling bar may be impacted.
At the same time, because of the increased inherent tendency of the stiff, thicker wrapping web material to return elastically to its original, flat state, a greater amount of adhesive is necessary for correctly sealing the overlapping side edges of the wrapping web material being wound around the rod shaped fibre tow. However, this may have the undesirable effect that excess adhesive accumulates on the surfaces of the transfer drum receiving the wrapped filter rod portions at the exit of the wrapping station. Because of this, the filter rod maker may often have to be stopped and machine downtime is therefore undesirably increased.
Therefore, it would be desirable to provide an apparatus for making filter rods for use in the manufacture of smoking articles such that the drawbacks identified above may be effectively addressed. In particular, it would be desirable to provide one such apparatus such that machine downtime can be significantly reduced, whilst ensuring at the same time that the filter rods obtained by the apparatus meet the necessary production requirements, for example in terms of seal quality, ovality, visual impact, and so forth.
According to an aspect of the present invention, there is provided an apparatus for making a filter rod for use in the manufacture of smoking articles. The apparatus comprises an operating station for receiving filter plug material and wrapping web material and for forming a wrapped filter rod from the filter plug material and the wrapping web material. The apparatus also comprises at least one cutter blade for cutting the wrapped filter rod into elongate rod segments. Further, the apparatus comprises a transfer device comprising a rotating drum having a plurality of spaced apart flutes on an exterior surface of the drum, the flutes constructed and arranged to receive the elongate rod segments as the drum rotates. The drum further comprises stop means at one end of each of the flutes against which the elongate filter rods are positioned when they are received into the flutes. The stop means comprises a pin with a main cylindrical body having a first diameter (D1) and extending along an axis (F) of the flute between a first end, at which the pin is attached to a drum frame, and a second end opposite the first end. Further, the pin comprises an abutting portion extending along the axis (F) from the second end of the main cylindrical body, the abutting portion having a second diameter (D2) smaller than the first diameter (D1) and presenting a substantially flat surface for abutting an end of the elongate filter rod.
The term "ovality" is used in the present specification to describe the shape of a transverse section of the filter rod and, in particular, to describe its degree of deviation from a perfect circle. In the present case, ovality may be expressed as a length and its mathematical definition is given below:
$ovality = (b - a) .$
To determine the ovality of a segment of a filter rod, one end is viewed along the longitudinal direction of the filter rod. For example, the filter rod can be positioned on its end on a transparent stage so that an image of the end of the filter rod is recorded by a suitable imaging device located below the stage. Dimension "a" is taken to be the smallest external diameter of the segment at its downstream end and dimension "b" is taken to be the largest external diameter of the segment at its downstream end. The process is repeated for a total of ten filter rods having the same design and the number average of the ten ovality measurements is recorded as the ovality for that design of filter rod.
In contrast to known apparatus, a filter rod maker is provided that is equipped with an improved transfer device for delivering the newly formed filter rod segments. The transfer device comprises a rotating drum with a plurality of flutes spaced apart on an exterior surface of the drum, wherein the flutes are constructed and arranged to receive the elongate rod segments as the drum rotates. The drum comprises stop means at one end of each of the flutes, which the elongate filter rods abut when they are received into the flutes. The stop means comprises a pin presenting a substantially flat surface for abutting an end of the elongate filter rod. The pin comprises, at the end that, in use, comes into contact with the elongate filter rod, a portion having a reduced diameter compared with a main cylindrical body of the pin.
By providing one such stop means that presents a reduced surface area for direct contact with the freshly formed filter rod segments, the likelihood that adhesive accumulates on the stop means is advantageously significantly reduced. Without wishing to be bound to theory, it is understood that the abutting end of the pin contacts a radially central portion of the filter rod segments, where in general no adhesive is expected to be present. At the same time, a small gap is left between the stop means and the peripheral portion of the filter rod segment, that is the portion of the filter rod segment where the adhesive is most likely to be found, since it has been applied to form a seal between the overlapping longitudinal side edges of the wrapping web material.
Accordingly, the number and frequency of stops of the filter rod maker are significantly reduced, and machine downtime as a whole is therefore advantageously decreased. Thus, a filter rod maker in accordance with the present invention is particularly useful for the manufacture of filter rod comprising a stiff, thicker wrapper or any time that greater amounts of adhesive are required for reliably and safely sealing the wrapping web material around the filter plug material. As shall become apparent from the following description, with some preferred embodiments, further advantageous improvements relating to the characteristics of the filter rod, such as seal quality, ovality, and visual impact may be attained.
An apparatus according to the present invention comprises an operating station for receiving filter plug material and wrapping web material and for forming a wrapped filter rod from the filter plug material and the wrapping web material. In addition, the apparatus comprises at least one cutter blade for cutting the wrapped filter rod into elongate rod segments. Further, the apparatus comprises a transfer device for delivering the newly formed elongate rod segments. The transfer device comprises a rotating drum having a plurality of spaced apart flutes on an exterior surface of the drum, the flutes constructed and arranged to receive the elongate rod segments as the drum rotates. The drum further comprises stop means at one end of each of the flutes against which the elongate filter rods are positioned when they are received into the flutes. The stop means comprises a pin with a main cylindrical body having a first diameter (D1) and extending along an axis (F) of the flute between a first end, at which the pin is attached to a drum frame, and a second end opposite the first end. Further, the pin comprises an abutting portion extending along the axis (F) from the second end of the main cylindrical body, the abutting portion having a second diameter (D2) smaller than the first diameter (D1) and presenting a substantially flat surface for abutting an end of the elongate filter rod. Preferably, the abutting portion has a cylindrical shape.
The second diameter (D2) is preferably less than about 80 percent of the first diameter (D1). In addition, or as an alternative, the second diameter is at least about 50 percent of the first diameter (D1). These values are advantageous because a sufficiently wide annular region at the periphery of the filter rod segment does not abut the flat surface of the stop means, thereby minimising the likelihood that adhesive may be picked up by the drum. In some particularly preferred embodiments, the second diameter (D2) is about 75 percent of the first diameter. By way of example, the first diameter (D1) may be 8 mm and the second diameter (D2) may be 6 mm.
Preferably, a length (L) of the abutting portion measured along the axis (F) of the flute is at least about 0.5 mm. In addition, or as an alternative, a length (L) of the abutting portion measured along the axis (F) of the flute is less than about 2 mm. These values are advantageous because a sufficiently wide axial gap is thus left between a peripheral region of the filter rod segment and the flat surface of the stop means. This also contributes to minimising the likelihood that adhesive may be picked up by the drum. In some particularly preferred embodiments, the length (L) of the abutting portion measured along the axis (F) of the flute is about 1 mm.
The operating station of the apparatus typically comprises a garniture operatively coupled with an endless belt conveyor and configured to receive the filter plug material and the wrapping web material, and to wrap the wrapping web material around the filter plug material such that a first and a second longitudinal edges of the wrapping web material overlap to form the wrapped filter rod. In addition, the operating station comprises an applicator for supplying a heat-activatable adhesive for sealing the overlapping first and the second longitudinal edges of the wrapping web material. The heat-activatable adhesive may be applied onto one or both longitudinal side edges of the wrapping web material.
The operating station further comprises a heat source for activating the adhesive, the heat source being arranged at a position along the garniture. In more detail, the garniture is preferably operatively coupled with a heating bar adapted to supply heat to the overlapping first and the second longitudinal edges of the wrapping web material whilst supporting the longitudinal side edges of the endless belt conveyor slidably advancing within the garniture. The heating bar preferably comprises a groove having an arced profile for at least partially receiving the wrapped filter rod being sealed.
Even more preferably, the heating bar comprises a pair of heating bar ridges, each heating bar ridge delimiting the heating bar groove on one side and presenting a support surface on the other side, such that the support surfaces of the ridges are adapted to support the longitudinal side edges of the endless belt conveyor in a V-shaped arrangement (when seen in a transverse cross-section), as the belt slidably advances along the garniture.
In practice, the heating bar is arranged with the heating bar groove facing the upper surface of the belt advancing within the groove of the garniture. As the belt advances along the garniture, the longitudinal side edges of the belt slide against the (outer) support surfaces of the heating bar ridges, and the wrapped filter rod being sealed is substantially enclosed in a volume comprised between the upper surface of the belt and the surface of the heating bar groove. This is advantageous in that it prevents the belt from moving away from a correctly centred position within the garniture. Further, this advantageously favours the formation of a filter with low ovality.
Preferably, the heating bar ridges have a substantially triangular cross-section and the support surfaces are slanted such that the longitudinal side edges of the belt form between them (V-shaped arrangement) an angle of at least about 30 degrees. More preferably, the support surfaces are slanted such that the longitudinal side edges of the belt form between them an angle of at least about 45 degrees. In some preferred embodiments, the support surfaces are slanted such that the longitudinal side edges of the belt form an angle of about 60 degrees.
Further, the operating station preferably comprises a cooling bar operatively and thermally coupled with the garniture and the endless belt conveyor for cooling and causing the setting of the adhesive. The cooling bar is arranged downstream of the heat source. In preferred embodiments, the cooling bar is arranged immediately downstream of the heating bar and may be mounted on a same bracket.
The cooling bar comprises a longitudinal groove extending between a cooling bar inlet and a cooling bar outlet, and is arranged with the longitudinal groove facing the upper surface of the belt advancing within the groove of the garniture, such that the groove is adapted to at least partially receive the wrapped filter rod. Preferably, at the cooling bar inlet, the cross section of the groove is substantially hemi-circular.
In practice, the cooling bar is arranged at a distance from the garniture, such that a passageway for the belt is defined between the garniture and the cooling bar. The groove is preferably laterally delimited by side ridges presenting respective outer abutment surfaces adapted to cooperate with the longitudinal side edges of the belt advancing between the cooling bar and the garniture, and the surface area of the cross section of the groove preferably decreases between the cooling bar inlet and the cooling bar outlet.
Accordingly, as the belt advances along the garniture, the distance between the facing surfaces of the longitudinal side edges of the belt is increased as the belt reaches the cooling bar inlet and the longitudinal side edges of the belt come into contact with the side ridges of the cooling bar groove. This is advantageous because the belt is thus refrained from subsequently sliding against the remainder of the cooling bar, and so the cooling bar is not heated up by the friction of the belt against the cooling bar. In the meantime, the wrapped filter rod with the heat-activated adhesive sealing the overlapping side edges of the wrapping web material is maintained and advanced between the upper surface of the belt and the surface of the cooling bar groove. Thus, the adhesive provided between the overlapping longitudinal side edges of the wrapping web material and previously heated by the heat source is cooled and rapid setting of the adhesive may be achieved.
In some preferred embodiments, the apparatus further comprises a compressing means operatively coupled with the garniture, arranged at a downstream end of the garniture and adapted to cooperate with the wrapped filter rod at a location along the overlapping first and the second longitudinal edges of the wrapping web material. The compressing means is configured and arranged such as to apply to the wrapped filter rod a compressive load directed substantially along a radial direction of the wrapped filter rod. This is especially advantageous when stiff or thicker wrapping web material is used, because the provision of one such compressing means effectively counters the inherent tendency of the wounded wrapping web material to move away from a perfectly cylindrical arrangement around the filter plug material, which is understood to be one of the major causes of ovality.
Preferably, the compressing means comprises a cooperating portion having a substantially spherical shape. This is advantageous in that it provides for a rather smooth cooperation between the compressing means and the outer surface of the wrapped filter rod, such that the surface finish of the wrapped filter rod is not significantly impacted, whilst at the same time ovality is reduced. Accordingly, the overall visual impact of the wrapped filter rod is advantageously improved.
The invention will be further described, by way of example only, with reference to the drawings of the accompanying Figures, wherein:

Figure 1 illustrates a schematic perspective view of a detail of a transfer device of an apparatus according to the present invention;
Figure 2 shows a schematic perspective view of the drum frame of the transfer device of Figure 1;
Figure 3 shows a schematic side view of a stop means of the transfer device of Figure 1;
Figure 4 shows a schematic cross-sectional view of the garniture and heating bar of an operating station of a preferred embodiment of an apparatus according to the present invention;
Figure 5 shows a schematic perspective view of a cooling bar of a preferred embodiment of an apparatus according to the present invention; and
Figure 6 shows a schematic side view of a compressing means of a preferred embodiment of an apparatus according to the present invention.

Figure 1 illustrates a detail of a transfer device of an apparatus in accordance with the present invention. The transfer device comprises a rotating drum 100 having a plurality of spaced apart flutes 102 on an exterior surface of the drum 100. The flutes 102 are constructed and arranged to receive elongate rod segments 104 as the drum 100 rotates. The drum 100 further comprises stop means 106 at one end of each of the flutes 102 against which the elongate filter rod segments 104 are positioned when they are received into the flutes 102.
As also illustrated in more detail in Figure 3 the stop means 106 comprises a pin 108 with a main cylindrical body 110 having a first diameter D1 of about 8 mm and extending along an axis (F) of the flute between a first end 112, at which the pin is attached to a drum frame 116 (see Figure 2) which is mounted on the drum 100, and a second end 114 opposite the first end 112. Further, the pin 108 comprises an abutting portion 118 extending along the axis (F) from the second end 114 of the main cylindrical body 110. The abutting portion 118 has a second diameter D2 of about 6 mm. The abutting portion 118 presents a substantially flat surface 120 for abutting an end of the elongate filter rod segment 104. In the embodiment illustrated in Figures 1-3, the abutting portion 118 has a cylindrical shape and has a length L measured along the axis (F) of about 1 mm.
Figure 4 shows a schematic cross-sectional view of a garniture 200 and heating bar 202 of an operating station of a preferred embodiment of an apparatus according to the present invention. The garniture 200 is operatively coupled with an endless belt conveyor 204. Further, the garniture 200 is configured to receive filter plug material and wrapping web material, and to wrap the wrapping web material around the filter plug material such that a first and a second longitudinal edges of the wrapping web material overlap to form a wrapped filter rod. The garniture 200 is further operatively coupled with the heating bar 202, which supplies heat for activating an adhesive applied, at an upstream location, on one or both the longitudinal side edges of the wrapping web material. At the same time, the heating bar supports the longitudinal side edges of the endless belt 204 slidably advancing within the garniture 200. The heating bar 202 comprises a groove 206 having an arced profile for at least partially receiving the wrapped filter rod being heat-sealed. As illustrated in Figure 4 the heating bar 202 comprises a pair of heating bar ridges 208, 210, each heating bar ridge 208, 210 delimiting the heating bar groove 206 on one side and presenting a support surface 212, 214 on the other side. The support surfaces 212, 214 of the heating bar ridges 208, 210 are adapted to support the longitudinal side edges of the belt in a V-shaped arrangement, as the belt slidably advances along the garniture 200. A volume defined by the upper surface of the belt 204 and the surface of the heating bar groove 206 substantially encloses the wrapped filter rod being sealed. During use, this advantageously prevents the belt 204 from moving away from a correctly centred position, and favours the formation of a wrapped filter rod with a low ovality. In the embodiment of Figure 4, the hopper ridges 208, 210 have a substantially triangular cross-section and the support surfaces 212, 214 are slanted such that the longitudinal side edges of the belt form between them an angle α of about 60 degrees.
The operating station of an apparatus according to the present invention preferably further comprises a cooling bar operatively and thermally coupled with the garniture and the endless belt conveyor for cooling and causing the setting of the adhesive supplied to the longitudinal side edges of the wrapping web material for sealing it around the filter plug material. The cooling bar is arranged immediately downstream of the heating bar. Details of one such cooling bar 300 are illustrated in Figure 5. The cooling bar 300 comprises a longitudinal groove 302 extending between a cooling bar inlet 304 and a cooling bar outlet 306. The cooling bar groove 302 is adapted to at least partially receive the wrapped filter rod. In use, the cooling bar 300 is arranged with the longitudinal groove 302 facing the upper surface of the belt advancing within the groove of the garniture, and is arranged at a distance from the garniture (not shown), such that a passageway for the belt is defined between the garniture and the cooling bar. At the cooling bar inlet 304, the cross section of the cooling bar groove 302 is substantially hemi-circular. The cooling bar groove 302 is laterally delimited by side ridges 306, 308 presenting respective outer abutment surfaces adapted to cooperate with the longitudinal side edges of the belt advancing between the cooling bar 300 and the garniture. The surface area of the cross section of the groove 302 decreases between the cooling bar inlet 304 and the cooling bar outlet 306. Thus, as the belt advances along the garniture, the distance between the facing surfaces of the longitudinal side edges of the belt is increased as the belt reaches the cooling bar inlet 304 and the longitudinal side edges of the belt come into contact with the side ridges 306, 308 of the cooling bar 300. Accordingly, the belt is advantageously refrained from sliding against the remainder of the cooling bar 300 downstream of the cooling bar inlet 304, or at least cooperation between the belt and the cooling bar 300 is significantly limited. This is advantageous, in that the cooling bar 300 is not significantly heated up by the friction between the belt and the cooling bar 300. At the same time, the wrapped filter rod is advanced between the belt and the surface of the cooling bar groove, so that the adhesive activated by the heating bar becomes thermally coupled with the cooling bar, and rapid setting of the adhesive may be achieved.
A compressing means 400 for use in a preferred embodiment of an apparatus according to the present invention is illustrated in Figure 6. The compressing means 400 is operatively coupled with the garniture and is arranged at a downstream end of the garniture and adapted to cooperate with the wrapped filter rod at a location along the overlapping first and the second longitudinal edges of the wrapping web material. In more detail, the compressing means 400 is configured and arranged such as to a compressive load directed substantially along a radial direction of the wrapped filter rod. In the embodiment of Figure 5, the compressing means 400 comprises a cooperating portion 402 having a substantially spherical shape.
The compressing means advantageously counters the tendency of stiff or thicker wrapping web material to move away from a perfectly cylindrical arrangement around the filter plug material in the newly formed wrapped filter rod, which is understood to be a cause of ovality. Further, because of the spherical shape, the compressing means 400 provides for a smooth cooperation between the compressing means 400 and the outer surface of the wrapped filter rod. Accordingly, the surface finish of the wrapped filter rod substantially not impacted, and so the overall visual impact of the wrapped filter rod is advantageously improved.

Claims

Apparatus for making a filter rod for use in the manufacture of smoking articles, the apparatus comprising:
an operating station for receiving filter plug material and wrapping web material and for forming a wrapped filter rod from the filter plug material and the wrapping web material;

at least one cutter blade for cutting the wrapped filter rod into elongate rod segments (104); and a transfer device comprising a rotating drum (100) having a plurality of spaced apart flutes (102) on an exterior surface of the drum, the flutes (102) constructed and arranged to receive the elongate rod segments as the drum rotates, the drum (100) further comprising stop means (106) at one end of each of the flutes (102) against which the elongate rod segments (104) are positioned when they are received into the flutes (102);

wherein the stop means (106) comprises a pin (108) with a main cylindrical body having a first diameter (D1) and extending along an axis (F) of the flute (102) between a first end, at which the pin (108) is attached to a drum frame, and a second end opposite the first end; and

wherein the pin (108) comprises an abutting portion (118) extending along the axis (F) from the second end of the main cylindrical body, the abutting portion (118) having a second diameter (D2) smaller than the first diameter (D1) and presenting a substantially flat surface for abutting an end of the elongate rod segment (104).
Apparatus according to claim 1, wherein the second diameter (D2) is less than about 80 percent of the first diameter (D1).
Apparatus according to claim 1 or 2, wherein the second diameter (D2) is at least about 50 percent of the first diameter (D1).
Apparatus according to any one of claims 1 to 3, wherein a length (L) of the abutting portion measured along the axis (F) of the flute is at least about 0.5 mm.
Apparatus according to any one of the preceding claims, wherein a length (L) of the abutting portion (118) measured along the axis (F) of the flute is less than about 3 mm.
Apparatus according to any one of the preceding claims, wherein the operating station comprises:
a garniture (200) operatively coupled with an endless belt conveyor (204) and configured to receive the filter plug material and the wrapping web material, and to wrap the wrapping web material around the filter plug material such that a first and a second longitudinal edges of the wrapping web material overlap to form the wrapped filter rod; and

an applicator for supplying an adhesive for sealing the overlapping first and the second longitudinal edges of the wrapping web material.
Apparatus according to claim 6, wherein the garniture (200) is further operatively coupled with a heating bar (202) for supplying heat to the overlapping first and the second longitudinal edges of the wrapping web material and for supporting the longitudinal side edges of the endless belt conveyor slidably advancing within the garniture, wherein the heating bar comprises a groove (206) having an arced profile for at least partially receiving the wrapped filter rod being sealed.
Apparatus according to claim 7, wherein the heating bar (202) comprises a pair of heating bar ridges (208, 210), each heating bar ridge delimiting the groove (206) on one side and presenting a support surface on the other side, such that the support surfaces (212, 214) of the ridges (208, 210) are adapted to support the longitudinal side edges of the endless belt conveyor in a V-shaped arrangement, when seen in a transverse cross-section, and the edges of the endless belt conveyor slidably advance outside the groove, the belt thus being maintained in a substantially centred position within the garniture.
Apparatus according to claim 8, wherein the ridges (208, 210) have a substantially triangular cross-section and the support surfaces are slanted such that the longitudinal side edges of the belt form between them an angle of at least about 30 degrees.
Apparatus according to claim 6, wherein the apparatus further comprises a cooling bar (300) operatively and thermally coupled with the garniture (200) for cooling and causing the setting of the adhesive; the cooling bar (300) comprising a longitudinal cooling bar groove (302) extending between a cooling bar inlet and a cooling bar outlet, and being arranged with the longitudinal groove facing an upper surface of the belt advancing within the garniture to define a passageway for the belt, such that the groove is adapted to at least partially receive the wrapped filter rod; wherein the cooling bar groove is laterally delimited by side ridges (306, 308) presenting respective outer abutment surfaces adapted to cooperate with the longitudinal side edges of the belt, and the surface area of the cross section of the groove decreases between the cooling bar inlet and the cooling bar outlet.
Apparatus according to claim 6, comprising a compressing means (400) operatively coupled with the garniture (200), arranged at a downstream end of the garniture and adapted to cooperate with the wrapped filter rod at a location along the overlapping first and the second longitudinal edges of the wrapping web material, such as to apply to the wrapped filter rod a compressive load directed substantially along a radial direction of the wrapped filter rod.
Apparatus according to claim 11, wherein the compressing means (400) comprises a cooperating portion (402) having a substantially spherical shape.