EP0901898B1 - Device as well as process for the manufacture of corrugated paper - Google Patents

Description

An apparatus and method for manufacturing corrugated cardboard is provided.

Devices of this kind are produced with fluted rolls of shapes different, the profile being determined by the distance and the height of the teeth. During production, the paper strip is compressed under pressure and influence of heat between the profiles of the co-operating grooved rollers and then glued with a smooth covering strip. Usually this is done also under influence of heat and pressure by means of a roller support or compression roller.

The embossing process itself takes place between the fluted tops or profile tops of a grooved roller and the grooved base surfaces or respective profile valleys of the other grooved roller. Usually the sides do not participate in the embossing process. In constructions like this the difference between the radii of profile vertices and cooperating profile valleys play an important role.

With conventional grooved rollers, the profiles of the two rollers fluted are identical, so that the corrugation of the paper in both folding directions is identical and this results in a symmetrical profile of the final corrugated cardboard.

The contact between the profile vertices of the second grooved roller and the essentially cylindrical surface of the backing roller takes place in the slot support, i.e. in the contact area between the second roller grooved and the support roller. As a result, the distance between the axes of the two rollers defined by the contact of the grooved roller and the roller support constantly varies during the rotation of the rollers between a value maximum, when a profile vertex is located near a link plane containing the axes of the rollers, and a minimum value, when a valley in profile of the second grooved roller is located in the connection plane containing the axes of the rollers. These varying distances cause a permanent excitation of vibrations, the appearing amplitudes of vibration causing surface marking on the side of the backing roller of the smooth strip and can cause damage to the paper fibers in the support slot, especially in the area of resonances. The greater the grooved profile is large, more damaging vibration amplitudes may increase. To solve this problem, we could consider operations with reduced pressure values and a period of influence high between the second grooved roller and the support roller and allow by compensation a longer period of influence to obtain a intense bond between the wavy strip and the smooth strip.

It must be taken into account that the curvature and in particular the curvature apex of the profile tops of the second grooved roller is a factor essential which influences paper damage on the side of the roll support of the smooth strip. The greater the radius of curvature of the profile vertices the larger, the lower the Hertz pressure acting on the paper.

On the other hand, we cannot reduce the curvature at will or in other words, you cannot increase the radius of curvature in the apex area of the profile tops of the second grooved roller at will. Is that, the deviation given, the angle of the flank with respect to a partial circular circle of the profile rises with the radius of curvature. This easily leads to that a rolling of the profiles of the first and second fluted roller is embarrassed: the paper is overloaded and finally the teeth catch on in the others. The increase in flank angle can be compensated by an increase in the spread, but this measure is not effective if a defined gap is desired in view of the pressure stiffness of the compound tape formed by the smooth strip and the wavy strip.

In addition, the increase in the spread creates an increased risk of vibration excitation, because the deviation is also responsible for variations in the distance between the axes of the second grooved roller and the backing roller, because of a simple geometric reason: a gap increased causes increased variations in the radial distance between the axes of the second grooved roller and the support roller.

The idea of reducing damage to the side of the tape support roller smooth by increasing the radius of the vertices further causes also the disadvantageous effect of an increase in the consumption of paper, because the course of paper between a profile apex and a profile valley apex of the fluted rollers is moving further and further away of the straight line of connection between the two apex points representing the the shortest connecting line between these apex points.

US 5,419,796 discloses an apparatus for manufacturing corrugated cardboard. he has a first pair of fluted rollers and a second pair of fluted rollers which forms a support slot with a support roller. The first pair of fluted rollers consists of a roller at the top and a roller at the bottom, whose profile vertices and profile valleys cooperate for the wavy deformation of a continuous strip. The summits of profile of the grooved roller at the top are essentially smaller than the intermediate profile valleys. During the grooved roll at the bottom, the vertices in profile are larger than the profile valleys that lie between them. The profile valley areas of the two fluted rollers have no influence on the wavy deformation of the continuous strip and, therefore, are not suitable for areas of profile vertices that mesh. This realization of the two fluted rollers has for as a result an irregular walk of the device, which has negative effects on the corrugated cardboard to be manufactured.

The object of the invention is to arrange an apparatus for the production of cardboard. wavy so that the vibration excitation is reduced and the risk marking on the corresponding composite strip as well as damage fiber is reduced. In addition, the risk of mutual engagement, i.e. the risk of catching the cooperating teeth of the two rollers fluted is to be avoided.

The composite strip produced in an apparatus according to the invention can be single-sided corrugated board to use as it is, for example to wrap cylindrical articles. compound tape can also be a product preparation for two-sided or multi-layer corrugated cardboard. The expression “corrugated cardboard” notably comprises compound strips, which are manufactured using simple strips containing fibers and especially cellulose fibers. However, it is not excluded, that the band composed consists of other materials, for example strips of material synthetic, which can in principle be machined for the production of strips wavy compound single sided.

The invention is based on the idea, that an increased vibration excitation and increased charges appear mainly only where the profile ribs of the second grooved roller are in contact under pressure with the backing roller, the corrugated strip and the smooth strip being interspersed.

Near the more strongly curved profile tops of the first roller grooved with the arrangement according to the invention, crowns more strongly curved of the corrugated strip are formed. These peaks more strongly curved corrugated tape have no disadvantage for the product respective. Even if the corresponding compound tape is later machined from double-sided corrugated cardboard (Doubleface), the crowns more strongly curved corrugated tape are glued to a smooth strip of paper in an essentially flat junction line, where no vibration can not appear and where thus the influence of the vertex radius is limited.

Preferably, the two fluted rollers are arranged with an identical distance, that is, they have the same distance between successive apices of profile peaks and succeeding apexes of profile valleys.

The course of the flanks between peaks in profile and succeeding profile valleys is variable over a wide range, as long as it is assured, that there is no jamming. The idea of the invention can for example also be combined with the principle of the so-called "bone profiles", with which the vertices in profile are thickened in their extent along the partial circle by a concave arrangement of the sides. Such a "bone profile" is for example shown and described in the print "Die Einseitige Gruppe" (the simple group front), publication number 1 (793D) 0.5 from Peters Maschinenfabrik GmbH, Rondenbarg 9-17, 22525 Hamburg. As for the "bone profile", reference is also made to patent EP 0 098 936.

According to another aspect, the invention relates to a method for manufacturing of corrugated cardboard.

During this process, the difference between the radius of curvature of the valleys of profile of the second grooved roller and the radius of curvature of the tops of profile of the first grooved roller is approximately or preferably exactly equal to the difference between the radius of curvature of the valleys of profile of the first grooved roller and the radius of curvature of the tops of profile of the second grooved roller. In addition, a first smooth strip is glued against the peaks of the corrugated strip still in contact with the second grooved roller in a second roller slot between the second grooved roller and a support roller.

According to an advanced process, the first and second peaks have at least approximately circular cylindrical curvature in the apex area, and that of a larger radius of curvature in the area apex of the first wave crowns and a radius of curvature more small in the apex area of the second crowns.

The connecting flanks of the corrugated strip between the first and second successive and second and first wave crowns successive crowns can be formed essentially by straight line and essentially without pressure.

To obtain double-sided corrugated cardboard, a second smooth strip can be stuck to the apices of the second wavy peaks. It is true that these apex have a greater curvature or, in other words, a radius of curvature smaller. However, the appearance of the problems of excitation of vibrations and the risk of scarring is limited due to the attachment of the second smooth strip.

Corrugated cardboard can be produced according to the process described above, comprising a wavy band with first and second peaks of successive waves indicating opposite directions relative to the plane of the strip, and a first smooth strip in contact with the first tops of ripple and stuck to the apices, the first peaks of ripple having a smaller curvature than that of the second crowns.

The first wave crowns and the second wave peaks may have a circle arc curvature at least in the apex area respective, the radius of curvature of the first crowns of ripple being greater than the radius of curvature of the second peaks.

The connecting flanks of the corrugated strip can extend essentially in a straight line between a first and a second respective wave crown. The connecting flanks of the corrugated strip can be essentially without embossing between first and second crown respective, so that their rigidity is not affected.

Successive connecting flanks of the corrugated strip can form essentially identical angles with the plane of the wavy strip between a first wave crown and a respective second wave peak and between a second crown of ripple and a first crown of the wavy strip, respectively.

A second smooth strip can be in contact with and glued to the apexes of the second wavy peaks.

DE 26 11 325 B2

DE 82 17 295 U1

EP 06 81 909 A2

GB 22 84 433 A

US 54 19 796

US 30 53 309

Niemann, G.: Maschinenelemente , Springer-Verlag, Berlin et autres, 1960, Vol. 2, p. 25 - 28, 36 - 38.

As for the prior art, reference is made to the following documents:

DE 26 11 325 B2

DE 82 17 295 U1

EP 06 81 909 A2

GB 22 84 433 A

US 54 19 796

US 30 53 309

Niemann, G .: Maschinenelemente, Springer-Verlag, Berlin and others, 1960, Vol. 2, p. 25 - 28, 36 - 38.

The invention differs from all these objections essentially in that depending on the objections, essentially symmetrical profiles of the strip wavy are produced, while according to the invention, the first crowns corrugation of the final profiles of the corrugated strip have more curvature small and second wavy peaks have greater curvature or in other words: the peaks of undulation projecting from the plane of the corrugated strip in one direction have a different curvature than that of the tops corrugation projecting from the plane of the corrugated strip in the other direction.

Fig. 1

montre une vue d'ensemble d'un appareil selon l'invention pour la fabrication de carton ondulé simple face;

Fig. 2

montre les conditions d'engrènement entre les deux rouleaux cannelés d'un appareil selon l'invention et

Fig. 3

montre les conditions d'engrènement entre les deuxièmes rouleaux cannelés et le rouleau d'appui d'un appareil selon l'invention.

The appended figures illustrate the invention from an exemplary embodiment.

Fig. 1

shows an overview of an apparatus according to the invention for manufacturing single-sided corrugated cardboard;

Fig. 2

shows the meshing conditions between the two fluted rollers of an apparatus according to the invention and

Fig. 3

shows the meshing conditions between the second grooved rollers and the support roller of an apparatus according to the invention.

In Fig. 1, a frame is designated by 10; it is placed on a machine foundation 12. The frame houses a first grooved roller 1, a second roller grooved 2 and a support roller 4. The first grooved roller 1 is supported against the second grooved roller 2 and in addition the support roller 4 is pressed against the second canned roller 2 by means of support. The first and second grooved roll 1, 2 together form a slot ripple 3; the support roller 4 and the second grooved roller 2 form together a support slot 5.

From a reservoir shown at 14 in the block diagram, a continuous strip 16 short to the first grooved roller 1 by a deflection pulley 18 and along from the first grooved roller 1 to the corrugated slot 3. After its passage through the corrugated slot 3 the continuous strip 16, first of all smooth, is deformed into a wavy strip 20. Supported on the second roller grooved 2, this corrugated strip 20 runs in the direction of the support slot 5 which remains to be described in detail. From a reservoir 22 a smooth strip 24 short by a deflection roller 26 and by clamping means 28 up to the support roller 4 and supported thereon in the support slot 5. In the support slot 5, the corrugated strip 20 is joined with the smooth strip 24.

The deformation of the continuous strip 16 into a corrugated strip 20 is carried out by moistening the continuous strip 16 first smooth before entering in the corrugated slot 3 by a humidification device 30 schematically indicated and by heating it, for example by the pulley of bypass 18 heated by steam. The continuous strip thus moistened and then passes through the corrugated slot 3 formed by the rollers fluted 1, 2 heated to around 180 ° C. After passing through the corrugated slot 3, the corrugated strip 20 meanwhile born from the strip continuous 16 is so stabilized in its wavy shape that it crosses the distance to the support slot 5 supported on the grooved roller 2. The contact between the corrugated strip 20 and the grooved roller 2 can be improved pressing the corrugated strip 20 against the outside face of the roller grooved 2 by an external overpressure in an overpressure chamber not shown or causing a vacuum inside the roller grooved 2, which is for example applied by grooves circumferential with the profile valleys of the grooved roller 2, so that the corrugated strip 20 is pressed against the circumferential profile of the grooved roller 2 by this depression under the simultaneous influence of the atmospheric pressure on the outer radial side of the corrugated strip 20.

Schematically, Fig. 1 also shows a bonding device 32, whereby glue is applied to the outer radial side of the wavy strip 20, especially on the crowns radially indicating outside. The corrugated strip 20 carrying the adhesive and the smooth strip 24 enter in the support slot 5 together, to be pressed against one another, this support representing a first step of bonding. By maintaining a approximately constant tension the compound band 34, formed by the band corrugated 20 and the smooth strip 24, then runs through deflections 36, 38 in a transport device 40 which places the composite strip (cardboard corrugated single side) in loops on a longitudinal transport device 44, as illustrated in 46.

In this example, the profile vertices PS1 and PS2 and the profile valleys PT1 and PT2 extend essentially parallel to the axes of the rollers, but they can also be tilted relative to the latter.

In Fig. 2, the engagement conditions between the first grooved roller 1 and the second grooved roller 2 are shown in detail in linearized or unrolled representation. The grooved roller 1 has PS1 profile vertices and PT1 profile valleys as well as PF1 flanks linking these. Grooved roller 2 has profile tops PS2 and PT2 profile valleys as well as PF2 profile flanks linking these last. In the example, the construction is arranged so that the PS1 profile vertices have a circular cylindrical curvature with a radius of curvature RS1, the vertices of profile PS2 have a cylindrical curvature circular with a radius of curvature RS2, the valleys of profile PT1 have a circular cylindrical curvature with a radius of curvature RT1, the valleys of profile PT2 have a circular cylindrical curvature with a radius of RT2 curvature and that the side flanks PF1 and PF2 are each formed by tangents to neighboring circular cylindrical curvatures. The line in dashes is obtained by approximating the profile of the first grooved roller 1 to the profile of the second grooved roller 2. The distance between PF2 and PF1 ' corresponds approximately to the thickness of the paper of the corrugated strip 20, which is obtained by compression of the continuous strip 16 into a corrugated strip 20 in the apex areas of the corrugated slot 3, as shown in Fig. 1.

RS1 < RT2

RS2 < RT1

RS1 < RS2

RT2 < RT1.

We recognize without further that the following inequalities are satisfied:

RS1 <RT2

RS2 <RT1

RS1 <RS2

RT2 <RT1.

RS1 = 1,2 mm

RT2 = 1,5 mm

RS2 = 1,8 mm

RT1 = 2,1 mm.

In the example, the following values are valid for the radii of curvature:

RS1 = 1.2 mm

RT2 = 1.5 mm

RS2 = 1.8 mm

RT1 = 2.1 mm.

RT2 moins RS1 = 0,3 mm

RT1 moins RS2 = 0,3 mm.

We take into account the differences between the departments

RT2 minus RS1 = 0.3 mm

RT1 minus RS2 = 0.3 mm.

We also take into account that the difference t of the profiles of the grooved roller 1 and the fluted roller 2 is identical. Roller diameters grooved 1 and 2 can be identical or different.

Finally we take into consideration that the distance d between the flank PF2 and the flank PF1 'moved to operating position has a maximum value at height flanks average, which prevents jamming between the flanks when the rotation of the grooved rollers 1, 2.

In Fig. 3, we recognize a PS2 profile top of the grooved roller 2 in meshing with a cylindrical circumferential face U4 of the roller support 4 in linearized or unrolled representation. The smooth strip 24 is pressed against the corrugated strip 20 between the top of the PS2 profile of the grooved roller 2 and the circumferential face of the support roller 4, namely against a layer of glue 48 having been applied to the tops corrugation 50 of the corrugated strip 20 by the bonding device 32 according to Fig. 1.

Relatively large radii of curvature RS2 from the top of the PS2 profile and RT1 of the profile valley PT1 result in a radius of curvature relatively large (small curvature) of the wave crowns 50 where they are glued to the smooth strip 24 in the support slot 5, as recognize in FIG. 3. This results in a limited Hertz surface pressure at these positions.

The relatively strong curved peaks 52 are supported by a flat side of another flat strip not shown here, if a corrugated board double sided is formed later.

Machine operation is quieter due to pressure reduced surface and weaker knocks resulting between rollers 2 and 4.

During a possible gluing of the crowns 52 for an arrangement double-sided, glue consumption is low; thanks to the bonded surface reduced, "washboard effects" remain limited. The take-in factor remains practically equal to that of a corresponding symmetrical profile (the take-in factor is defined as the ratio of paper length tucked in with that of the corrugated paper, i.e. the length of the strip continues to that of the corrugated cardboard obtained). Despite the radii of curvature large RT1 and RS2 the flank angles α and β according to Fig. 2 can be maintained approximately equal to the angles of the sides with symmetrical profiles conventional.

It is also mentioned that the profile peaks PS1, PS2 and the valleys of profile PT1, PT2 cooperate for the wavy deformation, or in other words: that the deformation of the profile is obtained by subjecting the continuous strip 16 to the influence of the pressure between a top of profile PS2 of the second grooved roller 2 or lower grooved roller 2 and a profile valley PT1 of the first grooved roller 1 or upper grooved roller 1, or by subject to the influence of pressure between the PS1 profile vertices of the first grooved roller 1 or upper grooved roller 1 and the valleys of PT2 profile of the second grooved roller or lower grooved roller, respectively, as is evident from FIG. 2.

Another aspect of the invention can also be seen in the way next: We start again from an arrangement of fluted rollers with identical profiles of the two fluted rollers and it is assumed that the radius of curvature RS2 (being equal to radius of curvature RS1 in the case identical profiles of the grooved rollers) is large enough to limit excitations of vibrations and markings on the strip composed to admissible values. Now we reduce the radius of curvature RS1 of the upper grooved roller 1 without changing the radius of RS2 curvature of the lower grooved roller. In this case, the angle β does not vary not, but the angle α decreases. So the "walking capacity" of the profiles is improved, i.e. the risk of too close approximation of the profiles and too strong jamming of the continuous strip 16 is reduced.

Simultaneously, the take-up factor and thus the paper consumption are reduced.

In addition, following the reduction of the radius of curvature RS1, the radius of curvature RT2. Consequently, the angle β also decreases. A decrease in angle β means an additional change in the factor of re-entry in the sense of a reduction in paper consumption.

Claims (6)

1. Device for producing corrugated cardboard, comprising:

   a) a first fluted roller (1) and a second fluted roller (2), together forming a corrugating nip (3),

   b) a contact roller (4) forming a contact nip (5) together with the second fluted roller (2),

   c) feeding means (18) to feed a continuous strip (16) to the corrugating nip (3), in which the continuous strip (16) is formed into a corrugated strip (20),

   d) feeding means (26, 28) to feed a smooth strip (24) to the contact nip (5), in which the smooth strip (24) is pressed into contact with the corrugated strip (20) with interposition of adhesive means,

   e) advancing means (36, 38, 40) to advance the composite strip (34) formed by combination of the corrugated strip (20) and the smooth strip (24),

   f) each of the two fluted rollers (1, 2) having on its outer face a fluted profile with profile peaks (PS1, PS2) and profile valleys (PT1, PT2), which cooperate in order to provide the corrugated shaping,

   i) successive profile peaks (PS1, PS2) and profile valleys (PT1, PT2) of each fluted roller (1, 2) being joined to each other by profile flanks (PF1, PF2),

   ii) the profile peaks (PS1, PS2) of each fluted roller (1, 2) also having a tighter curvature than that of the profile valleys (PT2, PT1) of the other fluted roller cooperating with them in order to provide the corrugated shaping,

   iii) the profile peaks (PS1) of the first fluted roller (1) having a tighter curvature than the profile peaks (PS2) of the second fluted roller (2),

   iv) the profile valleys (PT1) of the first fluted roller (1) having a flatter curvature than that of the profile valleys (PT2) of the second fluted roller (2),

   v) the profile peaks (PS1, PS2) of the two fluted rollers (1, 2) being curved in circular arcs and the profile peaks (PS 1 ) of the first fluted roller (1) having a smaller radius of curvature (RS1) than that of the profile peaks (PS2) of the second fluted roller (2),

   vi) the profile valleys (PT1, PT2) of the two fluted rollers (1, 2) being curved in circular arcs and the profile valleys (PT1) of the first fluted roller (1) having a greater radius of curvature (RT1) than that of the profile valleys (PT2) of the second fluted roller (2),

   vii) the difference between the radius of curvature (RT2) of the profile valleys (PT2) of the second fluted roller (2) and the radius of curvature (RS1) of the profile peaks (PS1) of the first fluted roller (1) being approximately, or preferably exactly, equal to the difference between the radius of curvature (RT1) of the profile valleys (PT1) of the first fluted roller (1) and the radius of curvature (RS2) of the profile peaks (PS2) of the second fluted roller (2).
2. Device according to claim 1,
   characterised in that
   the two fluted rollers (1, 2) have an identical pitch, i.e. the same distance between successive profile peak vertices and successive profile valley vertices.
3. Method for the production of corrugated cardboard, in particular using a device according to any one of claims 1 or 2,

   a) in which a continuous strip (16) is passed through a first roller nip (3) between two cooperating fluted rollers (1, 2), i.e. a first fluted roller (1) and a second fluted roller (2), and is shaped to a corrugated strip (20) with first and second successive corrugations (50 and 52, respectively) pointing in opposite directions, thereby forming a first corrugation (50) between each profile valley (PT1) of the first fluted roller (1) and a respective profile peak (PS2) of the second fluted roller (2), then forming a second corrugation (52) between a profile peak (PS1) of the first fluted roller (1) and a profile valley (PT2) of the second fluted roller (2), then forming once again a first corrugation (50) between a profile valley (PT1) of the first fluted roller (1) and a profile peak (PS2) of the second fluted roller (2) etc.,

   b) the profile peaks (PS1, PS2) of the two fluted rollers (1, 2) being curved in circular arcs and the profile peaks (PS1) of the first fluted roller (1) having a smaller radius of curvature (RS1) than that of the profile peaks (PS2) of the second fluted roller (2),

   c) the profile valleys (PT1, PT2) of the two fluted rollers (1, 2) being curved in circular arcs and the profile valleys (PT1) of the first fluted roller (1) having a greater radius of curvature (RT1) than that of the profile valleys (PT2) of the second fluted roller (2),

   d) the first corrugations (50) having a smaller curvature between the profile valleys (PT1) of the first fluted roller (I), and the profile peaks (PS2) of the second fluted roller (2) and the second corrugations (52) having a larger curvature between the profile peaks (PS1) of the first fluted roller (1) and the profile valleys (PT2) of the second fluted roller (2),

   e) the difference between the radius of curvature (RT2) of the profile valleys (PT2) of the second fluted roller (2) and the radius of curvature (RS1) of the profile peaks (PS1) of the first fluted roller (1) being approximately, or preferably exactly, equal to the difference between the radius of curvature (RT1) of the profile valleys (PT1) of the first fluted roller (1) and the radius of curvature (RS2) of the profile peaks (PS2) of the second fluted roller (2), and

   f) a first smooth strip (24) being glued to the first corrugations (50) of the corrugated strip (20), which is still in contact with the second fluted roller (2) in a second roller nip (5) between the second fluted roller (2) and a contact roller (4).
4. Method according to claim 3,
   characterised in that
   the first (50) and the second (52) corrugations (50, 52) respectively have an approximately circular cylindrical curvature, at least in the vertex region, with a larger radius of curvature (RT1) in the vertex region of the first corrugations (50) and a smaller radius of curvature (RT2) in the vertex region of the second corrugations (52).
5. Method according to claim 3 or 4,
   characterised in that
   the flanks connecting the corrugated strip (20) between successive first and second corrugations (50 and 52, respectively) and first successive second and first corrugations (52 and 50, respectively) are formed substantially in a straight line and substantially without pressure.
6. Method according to any one of claims 3 to 5,
   characterised in that
   a second smooth strip is glued to the vertices of the second corrugations (52).

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