EP0482634B1 - Method of manufacturing cigarette tubes for cigarettes without filter - Google Patents

Description

The invention relates to a method according to the preamble of claim 1.

In addition to industrially manufactured cigarettes (with and without a filter), it is known that there have always been "self-rolled" cigarettes and for some years now "self-stuffed" cigarettes, the latter made by smokers each from a tube and a so-called tobacco roll, in-house tobacco filling to be created.

When "rolling" cigarettes, previously only commercially available rectangular cigarette paper was used, one of the longitudinal edge sections was generally provided with a water-soluble adhesive layer, so that after the insertion of a tobacco portion into the essentially U-shaped hand-shaped cigarette paper and homogenization of the tobacco over the length of the (cigarette) paper strip after moistening the adhesive layer in mutual Overlap could be glued together.

In order to simplify the "rolling" of cigarettes, variously designed devices were developed and sold at least decades ago, by means of which the above-described "rolling" of a cigarette by hand was to be simplified (and in some cases was indeed to be simplified). , but the process described above was essentially the same and only the portioning, homogenization and the actual "turning process" were improved by (partial) mechanization.

Even today, so-called "self-rolled" or more recently "self-stuffed" (cigarettes) enjoy a certain (even increasing) popularity in smoking circles, although their share in total cigarette consumption is still comparatively low. This consumer acceptance of such cigarettes may partly be due to the fact that in certain circles it is considered "chic" or "in" to (at least partially) produce your own cigarette, but there is no doubt that the reason for this is that the so-called fine cut, which is generally used for this purpose, is tax privileged, so that such cigarettes are not insignificantly cheaper in relation to industrially manufactured ones, even if they are to be manufactured So-called tobacco rolls - that is, prefabricated tobacco rods - are used, which have long been offered for this purpose by the relevant industry.

Such tobacco rolls already have the essentially cylindrical shape of the tobacco rod of a (finished) cigarette, the actual tobacco rod being surrounded by a thin paper wrapper, the design of which, however, ensures that such tobacco rolls cannot be smoked as such. Rather, it is necessary to insert the tobacco rolls before smoking into a paper (cigarette) tube, the (cigarette) paper of which only ensures that a tobacco roll can be smoked after lighting. For this purpose, the relevant industry offers both cartridges with a filter for self-production of filter cigarettes and filterless casings for in-house production of filterless cigarettes.

Especially with filterless (cigarette) tubes, both the manufacture and the further handling (transport, packaging, storage, handling, filling with tobacco, etc.) are problematic because it is extremely difficult to find a paper strip without a "core" ( as is the case with filter sleeves) essentially cylindrical in order to deform a "nothing" and to connect its longitudinal edge sections, which then overlap one another.

For the aforementioned reasons, this connection can only be made by knurling anyway, but knurling is extremely disadvantageous simply because the throughput of such machines (in comparison to corresponding machines with gluing technology) is extremely low. A mutual gluing of the overlapping longitudinal edge sections of sleeves for filterless cigarettes did not appear possible for the reasons mentioned above.

This and other problems clearly do not occur with filter sleeves or only to a considerably lesser extent because - as already mentioned - not only is the cylindrical deformation of the cigarette paper around the cylindrical filter considerably easier, but also the further handling of the (filter) Sleeves after their manufacture during transport, packaging, when removing a filter sleeve from its packaging, etc., since a filter sleeve with the filter also has an essentially dimensionally stable grip section, which can be found, for example, during normal removal of a filter sleeve from a packaging with not excessive finger forces at least not significantly deformed when one grips a filter sleeve at the end of the filter, whereas when a filterless sleeve is removed from a package, even at relatively low pressures between the fingers removing a sleeve, the sleeve is damaged by kinking and the like. Like. Can come, which can then be extremely disadvantageous in further handling (especially when filling with tobacco), quite apart from the fact that a cigarette made from such a bent sleeve does not usually meet aesthetic requirements.

The known filterless sleeves also have numerous other disadvantages. For example, it happens more or less regularly that a tobacco roll used to "plug" a filterless sleeve arrives one end of the finished cigarette protrudes over the sleeve because further (and thus complete) insertion (e.g. due to sleeve deformation) is not possible. This is - quite apart from aesthetic considerations - highly undesirable at the mouth end because this causes tobacco to enter the smoker's mouth when smoking, and at the other (burning) end facing away from the mouth end because it ignites the cigarette glowing tobacco particles often fall, which can cause (burning) damage at their point of impact.

A very significant disadvantage of the known filterless (cigarette) tubes continues to be from a cost point of view that their production output per manufacturing unit is extremely low with a maximum of about 1000 tubes / min. This is based essentially on the disadvantages of extremely difficult handling, already mentioned above, when cylindrical shaping and subsequent connection of the overlapping longitudinal edge sections.

Furthermore, the known filterless (cigarette) sleeves are disadvantageous in the case of the so-called "ventilated" design because it is not ensured that the cigarettes made from them are smoked from the correct end. For ventilated cigarettes, as is known, a perforation of the cigarette paper is provided at a certain distance from the mouth-side end, which means that, when smoking (i.e. when negative pressure is applied in the smoker's mouth), air also enters the smoke stream in addition to the smoke that is sucked in and dilutes it accordingly. But if such a cigarette is accidentally on the intended Ignited at the mouth end and smoked from the other end, the ventilation is of course no longer required as soon as the perforation area located adjacent to the end of the burn has been smoked, so that immediately after the ventilation has ceased, a light cigarette spontaneously becomes a strong cigarette with correspondingly high nicotine and condensate values becomes. This danger exists even if a (advertising) print is provided at the mouth end of a filterless (cigarette) sleeve, as is the case with industrially manufactured cigarettes, since it has been proven that many smokers do not pay attention to this at all and often only with difficulty be careful if you light a cigarette you have made in the dark.

Furthermore, it is to be regarded as a disadvantage that the degree of ventilation that can be achieved with previously known filterless (cigarette) tubes is already limited by the fact that the perforation area causing the ventilation lies in the area of the tobacco rod.

Furthermore, it is often - especially by so-called "wet smokers" who smoke cigarettes with relatively moist lips - perceived as a disadvantage that there are no filterless (cigarette) sleeves available, which are wrapped at their mouth end with so-called covering paper. Such (cigarette) tubes, which are covered with covering paper at the mouth end (which, as can be seen, would also largely avoid the above-mentioned problem of a correct assignment of the mouth end and the burning end when smoking), have so far not been available because it is - at least with reasonable effort - previously seemed impossible with regard to their dimensional stability to cover extremely unstable filterless (cigarette) tubes with covering paper. The process practiced in the case of filter sleeves, in which the covering paper is wrapped around the sleeve without any particular technical difficulties in the area of the (dimensionally stable) filter, can clearly be discerned, whereby in the case of filter sleeves even the process known from industrial cigarette production can be used, in each case strands ( to produce at least) double sleeve length with a filter body arranged in the middle, twice the length of use, i.e. according to the filter attachment method, in which then with such strands covering paper of a length is wrapped around the double filter section, which is still slightly larger than the length of the double filter, so that the covering paper the sleeve paper overlaps at both ends and thus creates a (connection) connection between filter and cigarette paper. After the aforementioned steps, the double filter is then cut in the middle in the case of filter cigarettes or filter sleeves. However, this is obviously not possible with a conventional filterless sleeve because this would be compressed due to a lack of sufficient restoring forces.

From DE 33 00 302 a cigarette tube for filterless cigarettes is known (see FIG. 3), in which a support body provided with large through openings in the axial direction is inserted at the mouth end of the conically shaped cigarette paper, but such (conical) It is evident that (cigarette) tubes are not economically viable, because they have to be manufactured individually because of the taper and not - even as an intermediate product - they can be produced in one strand.

A finished filterless cigarette is known from DE 86 03 154 U1, which has a support body instead of a filter as in the case of the above-mentioned object, but here too there is no problem with the manufacture of filterless cigarette tubes because such cigarettes are made from Sections of a tobacco rod (tobacco rolls) previously produced separately and wrapped with cigarette paper are formed.

From DE 21 25 118 C3 a method and a device for producing filter cigarette tubes are known, in which adhesive spots are first applied to a running, flat (i.e. not deformed) cigarette paper, on which filter bodies are then attached, the initially spread out cigarette paper tape First rolled up essentially in a U-shape, deformed into a tube using a forming tape, glued and disassembled into filter cigarette tubes, the filter body glued to the cigarette paper tape being continuously pressed against the cigarette paper tape with increasing pressure against the cigarette paper tape - and thus the latter against the forming tape - Pressed, and the initially only approximately U-shaped rolled cigarette paper tape is finally wrapped completely around the filter body and glued tubular overlapping its longitudinal edges, and wherein the adhesive seam by means of a s - with little pressure on it - solidifies the brush.

These previously known measures for the formation of filter cigarette tubes obviously cannot be used for the production of filterless cigarette tubes and could not even provide the competent person with any information Give suggestions for the problem in question.

The present invention is therefore based on the object of creating a generic method for producing (in particular ventilated) generic tubes for filterless cigarettes while avoiding the aforementioned disadvantages or shortcomings, with which such tubes (namely tubes with a cylindrical shape) can be expediently and economically produced are, which are also much easier to handle during and especially after their manufacture, and which rot quickly after use (= smoking the cigarette in question).

This object is achieved according to the invention by the characterizing features of claim 1. Preferred embodiments of the invention are described in the subclaims.

Fig. 1 - 6

in einer teilweise schematisierten Darstellung die Herstellung erfindungsgemäßer filterloser (Zigaretten-)Hülsen gemäß einer ersten Verfahrensvariante;

Fig. 7 - 11

in einer teilweise schematisierten Darstellung die Herstellung erfindungsgemäßer (Zigaretten-) Hülsen gemäß einer zweiten Verfahrensvariante;

Fig. 12 - 16

in einer teilweise schematisierten, vergrößerten Darstellung die Herstellung eines (Rippen-)Stützkörpers für eine erfindungsgemäße (Zigaretten-)Hülse;

Fig. 17

einen unverdrillten (Rippen-) Stützkörper mit vier Rippen; und

Fig. 18

einen (Rippen-)Stützkörper gemäß Fig. 17 in um seine Längsmittelachse verdrilltem Zustand.

The invention is explained below using exemplary embodiments with reference to a drawing. Show it:

1-6

in a partially schematic representation, the production of filterless (cigarette) tubes according to the invention according to a first method variant;

Figures 7-11

in a partially schematic representation, the production of (cigarette) tubes according to the invention according to a second method variant;

Figures 12-16

in a partially schematic, enlarged representation, the production of a (rib) support body for a (cigarette) sleeve according to the invention;

Fig. 17

an untwisted (rib) support body with four ribs; and

Fig. 18

17 in a state twisted about its longitudinal central axis.

1 to 6 show (partly schematically for the sake of better understanding) the individual stages of a variant of the method according to the invention for producing (cigarette) tubes for self-made ("stuffing") filterless cigarettes, in which a paper strip 1, the Width B (see FIG. 2) is equal to the circumference of a sleeve 2 to be produced (see FIG. 6) plus an overlap surcharge 3, is deformed essentially cylindrically such that the predetermined clear diameter D (see FIG. 6) is achieved, and its longitudinal edge sections 4 and 5 (see FIG. 2) overlap, the overlapping longitudinal edge sections 4, 5 then being connected to one another by gluing.

In this case, mouthpiece-like sleeve reinforcements in the form of supporting body sections 6 ″ ″ with a cylindrical are formed on the upper side 1 ′ of the paper strip 1, which later forms the inside of the sleeve, with a mutual spacing l _H (see FIG. 1) Outline contour 7, which is indicated by dots in Fig. 2, arranged (3. Fig. 1 and 2). The paper strip 1 is then rolled up (with the support body sections 6 '''which form the "mold cores", the design of which is explained in more detail below) (see FIG. 3). whereby on the one hand the support body sections 6 '''are glued to their circumference at the top 1' of the paper strip, and on the other hand the overlapping longitudinal edge sections 4, 5 of the paper strip 1 are connected to one another by adhesive bonding (see FIGS. 3, 4, wherein Fig. 3 - schematically - shows the essentially finished wrapping process shortly before the longitudinal edge sections 4, 5 and FIG. 4 glue the finished sleeve strand 2 'in a frontal top view according to arrow II in FIG. 1).

The paper strip 1 is formed with a length n · L, which is equal to multiple (n times) the length (L) of a (finished) sleeve 2. The length l _{M of} the support body sections 6 '''is equal to the length l _{M of} the support body 6 of a finished sleeve 2.

From Fig. 1 it can also be seen that a first support body section 6 '' 'is arranged at one end (left in Fig. 1) 20 of the paper strip 1.

As indicated in FIG. 5 by corresponding sectional symbols, the sleeve strand 2 ′ formed according to FIGS. 1 to 4 is in each case on the end face 6 ″ facing the first (mouth-side) support body section 6 ″ of the longitudinal strand 15 of the sleeve strand 2 ′. subsequent support body section 6 ''', etc., so that ultimately filterless (cigarette) tubes according to the invention as shown in FIG. 6 2 arise into which a smoker when using such a sleeve 2 can insert a tobacco roll 8 designed as a tobacco roll from the end of the sleeve 2 facing away from the support body 6 in the direction of arrow 9 by hand or by means of a suitable device and thereby to a "self-stuffed "Cigarette comes, the attachment of topping paper 11 has not (yet) been shown and explained in this exemplary embodiment for the sake of a better overview, and reference is made to the fact that this is carried out in a manner analogous to that described below using the exemplary embodiment according to FIGS. 11 (see in particular FIGS. 9 to 11).

The tobacco portion 8 is a so-called. (Cylindrical) tobacco roll, which forms the tobacco rod in the finished cigarette, the tobacco 8 'of the tobacco roll 8 being surrounded by a very thin wrapping paper 10, which is such that the tobacco roll 8 taken on its own - that is, without a sleeve 2 - is non-smokable, but instead of this, in principle a sleeve, according to FIG. 6, could also be inserted (preferably with a suitable device), for example a fine-cut, appropriately dosed, cylindrically shaped tobacco portion , which was previously taken from a corresponding stock of tobacco and, if necessary, portioned and preformed cylindrically in the device mentioned.

, der gleich dem Doppelten der Stranglänge l_H einer (fertigen) Hülse 2 (bzw. einer hieraus zu bildenden Zigarette) ist, Stützkörperabschnitte 6''' angeordnet, deren (Ausgangs-)Länge ${\text{b = 2 · l}}_{\text{M}}$

gleich der doppelten Länge l_M eines fertigen Stützkörpers 6 einer fertigen Hülse 2 ist (s. Fig. 10).Before the supporting body 6 used is described in detail below, a procedure according to the invention is first described below with reference to FIGS. 7 to 11. In this method, the paper strips 1 are each at a mutual distance ${\text{a = 2 · l}}_{\text{H}}$

, which is twice the strand length l _H a (finished) sleeve 2 (or a cigarette to be formed therefrom), support body sections 6 '''are arranged, their (initial) length ${\text{b = 2 · l}}_{\text{M}}$

is equal to twice the length l _{M of} a finished support body 6 of a finished sleeve 2 (see FIG. 10).

The sleeve strand 2 'formed after the rolling in, which is formed in the same way as has been described in the method variant described above with reference to FIGS. 2 to 5, is in each case in the region of the support body sections 6' '' and symmetrical to this with covering paper 11 wrapped (see FIG. 9), the length B of which is somewhat greater than the length b of a support body section 6 ″ ″, the overlapping longitudinal edge sections of the covering paper 11 being connected to one another by adhesive and the sleeve strand 2 ′ wrapped in sections with covering paper 11 then on the support body sections 6 '' 'and the intermediate sections of the sleeve body 21, which do not have a support body section 6' '', in each case in the middle, as has been indicated in FIG. 9 with cut symbols and dash-dotted cut lines, so that thereafter finished sleeves 2 covered with covering paper 11 are produced, as shown in FIG. 10 to 11 are shown.

In this variant, as in the case of the method variants described with reference to FIGS. 1 and 6, the sleeve strand 2 'is already provided with ventilation openings 12 adjacent to a support body 6 by perforation, as is shown in FIG FIG. 5 is indicated, or preferably in the region of the support body sections 6 ″ ″, as is indicated in FIGS. 6 and 10. The ventilation openings 12 are formed using laser perforation.

In both the sleeve 2 according to FIG. 6 and the sleeve 2 according to FIG. 10, the support body 6 has ribs 13 which extend essentially radially to the longitudinal central axis 15. The ribs 13, of which there are eight in the exemplary embodiments according to FIGS. 1 to 11, preferably generally ten to twelve, are made of paper and are integrally formed. They each consist of two adjacent folding sections F₁, F₂; F₃, F₄ etc. of a leporello-like (second) rectangular paper strip 16 of length b and width l (see FIG. 12), which according to FIG. 12 has fold lines f₁ _, f₂, ... f _n running parallel to its narrow sides 13 - as explained leporello-like - is folded so that between the longitudinal edge f₀ and the adjacent fold lines f₁ or respectively between adjacent fold lines f₁, f₂; f₂, f₃ etc. or between the other longitudinal edge f _n and the adjacent fold line f _n-1 each fold sections arise which extend in the longitudinal direction of the strip-shaped paper section 16. With a length l _{M of} a (finished) sleeve reinforcement 6 or 6 'at a distance from the front edge of the paper strip 16, a broken line parallel to the front edge is drawn in FIG. 12 with a dashed line, and a further cutting line at this distance at a distance l _M etc., which divides the strip-shaped section 16 into sections, each of which forms a (rib) support body 14. These cutting lines 17 are already introduced at this point by definition because they divide the folding sections formed when folding the strip-shaped section 16 into folding sections F 1, F 2, etc., each of which as a pair form the layers of a rib 13 of a support body 6.

In order to achieve a sufficiently high manufacturing speed, the support bodies 6 are advantageously not produced from a single strip-shaped section 16 during mass production, but the strip-shaped material (paper) forming the support body 6 is removed from one by a corresponding device in the direction of the arrow 18 Pulled material supply forming bobbin and folded in the longitudinal direction, as described above.

13 folded (second paper) strip 16 (for example. About its longitudinal edge (f₀) pivoted as can be seen from Fig. 14, so each form two adjacent folding sections F₁ and F₂, F₃ and F₄ etc. a rib 13 consisting of two layers of paper, one layer (e.g. F₂) with a layer (F₃) of an adjacent rib 13 by integrally forming the folded sections (F₂, F₃, F₄, F₅) etc. on their base line connected is.

If the support body 6 were left in the state shown in FIG. 14, then, for example, a section 19 shown in dashed lines in FIG. 14 would have to be connected to the folding sections Fab, which section 19 folds the folding section F₈ with the folding section F₁ of the adjacent rib 13 (e.g. by gluing). In fact, the representation according to FIG. 14 corresponds only to an intermediate state during production, since the inner sides F _1i and F _2i or F _3i and F _4i etc. of the folded sections forming a rib 13 are connected to one another by gluing, so that the support body 6 (or initially a support body strand) with a cross section according to FIG. 15 is formed, the ribs 13 of which are each in two layers and are connected to one another by an integral design.

As has already been indicated, four ribs 13 were assumed for the sake of simplicity in the explanation of the support body production according to FIGS. 12 to 15, while a number of ten ribs 13 (see FIG. 16) has in fact proven to be particularly expedient (and - as stated - eight ribs 13 have been adopted in FIGS. 1 to 11 for the sake of simplicity).

It should be expressly pointed out that in the drawing (FIGS. 15, 16) there is an intermediate space between two folding sections, each forming a rib 13, in order to clarify in the illustration that it is a double-layer or two-layer ribs 13. In fact, the two folding sections, each forming a rib 13, lie flat against one another over the entire height of the rib and there is also no continuous (smoke) duct in the center of the (rib) support body 6, which would not be subjected to ventilation.

It should also be noted that the pitch angle α between adjacent ribs 13, 13 is essentially the same, that is, with ten ribs 13 (FIG. 16), in each case approximately 36 °.

1

(erster) Papierstreifen

1'

Oberseite (von 1)

2

Hülse

2'

Hülsenstrang

2''

Hülsenstrangabschnitte

3

Überlappungszuschlag (von 1)

4

Längsrandabschnitt (von 1)

5

Längsrandabschnitt (von 1)

6

Stützkörper

6''

Stirnseite

6'''

Stützkörperabschnitte

7

Umrißkontur (von 6)

8

strangförmige Tabakfüllung

8'

Tabak (von 8)

9

Pfeil

10

Umhüllungspapier (von 8)

11

Belagpapier

12

Ventilationsöffnungen

13

Rippen

14

15

Längsmittelachse

16

(zweiter) Papierstreifen

17

Schnittlinien

18

Pfeil

19

Abschnitt

20

21

Hülsenkörper

22

Anschlagfläche

17 shows a perspective view of a support body 6 with four ribs 13, between each of which there is a pitch angle α of 90 °, and FIG. 18 shows a similarly designed support body 6, the Ribs 13 are twisted about its longitudinal central axis 15 in the manner shown.

1

(first) paper strip

1'

Top (of 1)

2nd

Sleeve

2 '

Sleeve strand

2 ''

Sleeve strand sections

3rd

Overlap surcharge (from 1)

4th

Longitudinal edge section (from 1)

5

Longitudinal edge section (from 1)

6

Support body

6 ''

Face

6 '''

Support body sections

7

Outline contour (of 6)

8th

strand-like tobacco filling

8th'

Tobacco (of 8)

9

arrow

10th

Wrapping paper (of 8)

11

Covering paper

12th

Ventilation openings

13

Ribs

14

15

Longitudinal central axis

16

(second) paper strip

17th

Cutting lines

18th

arrow

19th

section

20th

21

Sleeve body

22

Abutment surface

Claims (9)

1. A process for the preparation of tubes (2) for non-filter cigarettes which are preferably ventilated by means of perforation and which are prepared by the smokers themselves from:

   a) such a tube (2), and

   b) a rod-like tobacco filling (8) devised more particularly as a so-called tobacco roll wherein:

   A) a rectangular paper strip (1) whose width (B) is equal to the periphery of a tube (2) plus an overlap (3) is deformed cylindrically, with its longitudinal edge parts (4, 5) overlapping and with an internal diameter corresponding to the predetermined external diameter of the rod-like tobacco filling (8) and with the use of support members (6),

   B) the overlapping longitudinal edge parts (4, 5) of the paper strip (1) being joined together,

   characterised in that:

   C) support member parts (6''') having a cylindrical contour (7) are disposed at a spacing (l_H) from one another on the paper strip (1) whose length is equal to a multiple of tube length (L) and are stuck on a part of their periphery to the paper strip (1);

   D) the paper strip (1) is wound around the support member parts (6'''), and

   E) its overlapping longitudinal edge parts (4, 5) are stuck together;

   F) the resulting tube strand (2') is wrapped around with covering paper (11) in the region of each support member part (6'''), the width of the paper (11) being equal to the periphery of the tube strand (2') plus an addition for overlap;

   G) the paper (11) is stuck to the outside of the tube strand (2');

   H) the overlapping longitudinal edge parts of the paper (11) are stuck together, and

   J) parts each forming a tube (2) are then parted off from the finished tube strand (2') thus formed.
2. A process according to claim 1, characterised in that when support member parts (6''') are used whose length (2 . 1_M) is equal to twice the length (l_M) of a support member (6) of a finished tube (2), the support member parts (6''') are secured on the paper strip (1) at a spacing (2 . l_H) from one another equal to twice the tobacco rod length (1_H) of a tube (2) and the tube strand (2') is severed centrally in the region of the support member parts (6''') and in the region of the tube strand parts (2''') disposed between two support member parts (6''', 6''') (Figs. 7 to 9).
3. A process according to claim 1, characterised in that when support member parts (6''') are used whose length (l_M) corresponds to the length (l_M) of a support member (6) of a finished tube (2), a first support member part (6''') is secured to one end (20) of the paper strip (1), the support member parts (6''') are secured on the paper strip (1) at a spacing from one another equal to the tobacco rod length (l_H), and the tube strand (2') is severed on that mouth-side end face (6''') of each subsequent support member part (6''') which faces the first support member part (6''') (Figs. 1 to 6).
4. A process according to one or more of the previous claims, characterised in that each support member (6) is formed from a second rectangular paper strip (16) which is so folded accordion-fashion in order to form ribs (13) which extend radially of the longitudinal central axis (15) of the tube (2) that the fold parts (F₁, F₂, ...) forming a rib (13) are disposed flat one on another substantially over the entire rib height (r).
5. A process according to claim 4, characterised in that two fold parts (e.g. F₁, F₂) forming a rib (13) are rigidly interconnected at least to some extent.
6. A process according to claim 4 or 5, characterised in that the ribs (13) are so twisted on at least one longitudinal part that their outer edge extends at least substantially helically relatively to the longitudinal central axis (15) of the tube (2).
7. A process according to claim 6, characterised in that one end of each support member (6) is twisted relatively to its other end by an angle (α) at least equal to the pitch angle (α) between adjacent ribs (13, 13).
8. A process according to one or more of claims 4 to 7, characterised in that the second paper strip is so folded that approximately ten ribs (13) are formed.
9. A process according to one or more of claims 4 to 8, characterised in that the pitch angle (α) between adjacent ribs (13, 13) is substantially the same in each case.

Images