EP0485731B1 - Assembly device for machine for the production of corrugated cardboard - Google Patents

Abstract

A device, which assembles web-like workpieces consisting of superimposed glued layers to form a web of corrugated board material, includes three sections with a first section having a single heating plate and an upper blowing case, a second section including upper and lower transverse nozzles, as well as upper and lower suction chambers and a third section including the extension of the upper and lower suction chambers. The device includes a conveying arrangement which has an upper continuous mesh belt passing through the first, second and third sections, and a lower belt passing only through the second and third sections.

Description

The present invention relates to an assembly device for a strip element composed of superimposed and glued layers, constituting a station called "double-sided" of a machine for producing corrugated cardboard and in which said layers are of continuous passage. in strip form.

For the sake of convenience, this invention will be described more particularly in relation to a so-called "double-sided" station.

As a reminder, corrugated cardboard is made up of a first layer of cardboard called "single-sided" cardboard and consists of corrugated paper glued to flat cover paper, this first layer also being assembled by gluing to a second layer which can either be a second flat outer cover paper, to form a corrugated cardboard called "double-sided", or a second "single-sided" cardboard plus a cover paper to then form a corrugated cardboard called "double-double". Corrugated cardboards with "triple flute" are also known, manufactured in a similar manner. A machine for manufacturing such corrugated cardboard, also called "corrugator", usually comprises a first part called "wet" in which the cardboard is made and a second part called "dry" in which this cardboard is cut and stacked.

The first "wet" part begins with a station commonly known in the industry as "single-sided". In this station, the fluted paper, that is to say intended to be fluted, previously heated and humidified passes between two fluted trees, themselves heated with steam. The grooves thus formed are held against the lower grooved cylinder either by combs or by external means (relative to the cylinder) at overpressure or internal under vacuum. An adjacent sizing drum then deposits glue on the ridges of the grooves and the preheated cover paper is applied, under pressure and temperature, against the ridges by a second press drum adjacent to the sizing drum and also heated with steam. This pressure and this temperature immediately engage the adhesive.

The corrugated "single-sided" cardboard thus formed then passes through a station called "double-sided gluer" which deposits glue on the other ridges of the grooves, now visible. About a third of the water in this glue binds with the solids to form the adhesive, the other two thirds forming "free" water which increases the humidity of the paper at this stage.

The "single-sided" cardboard thus glued then enters a so-called "double-sided" station where it is applied either against the second cover paper, or against the second intermediate "single-sided" cardboard, itself applied against the cover sheet. The role of this "double-sided" station is therefore to put and maintain the layers in contact while providing them with the heat necessary for the glue to burst and for the evacuation of moisture, to advance this layer of continue removing moisture while keeping the cardboard flat while cooling.

Given the presence of the grooves, we realize that it is not possible to apply, in the "double-sided" station, a strong pressure between the layers, as was the case previously in the station "single-sided". This pressure reduction implies a decrease in temperature transmission and therefore a significant increase in the time for engaging the adhesive. In other words, given that at this stage of production the cardboard scrolls continuously in the form of a strip, this increase in setting time results in a corresponding increase in the length of this "double-sided" station.

The "double-sided" station generally consists of a heating section and a traction section also called a cooling section.

In the heating section, the various layers intended to form the corrugated cardboard are applied to a series of heating tables by means of an upper mat covering the entire station. This application force is exerted by support rollers acting on the upper belt. Another way of carrying out the pressurization of the various layers consists of blowing boxes placed above the upper carpet and exerting a uniform pressure on the entire upper face of the carpet and therefore of the various layers of corrugated cardboard. In general, this first section has between 18 and 24 heating tables distributed between three or four groups, each table having a transverse length, that is to say perpendicular to the passage of the corrugated board in formation, slightly greater than the useful width of the corrugator and a width of approximately 50 cm. These tables are supplied with steam on each of the groups.

The following traction section comprises a lower belt driven in synchronism with the upper belt, these two belts sandwiching the corrugated cardboard to frictionally pull it out of the heating section.

The major drawback of such a "double-sided" station lies in its considerable length. Indeed, the desired production speed conditions the number of heating tables necessary for the transfer of heat in the corrugated cardboard in order to set the glue and to evacuate the excess water contained in the corrugated cardboard, and therefore also, considering the friction forces involved, the length of the traction section. The mechanical power required to drive the carpets also becomes very important. In addition, impurities gradually accumulate at the junctions of the tables between them, impurities which can scratch the lower cover of the corrugated cardboard while it has been precisely subjected to ennobling surface treatments such as coating or printing. Finally, if one wishes to use blower boxes in the heating section, the upper carpet must almost be made of felt to obtain a sufficient friction force between this upper carpet and the corrugated cardboard. Indeed, if a mesh carpet which has the advantage of letting the air loaded with water, creates a pressure uniformly distributed on the corrugated cardboard, it does not however create, between the carpet and the corrugated cardboard, sufficient adhesion force for the traction effect. However, this adhesive force is generally useful for driving corrugated cardboard. On conventional devices, the large length of all the heating tables creates a braking force if important that all the adhesion forces between the upper and lower mat and between the upper mat and the corrugated board are necessary for the drive. A reduction in the adhesive force between the upper carpet and the corrugated cardboard in the area of the blowing boxes, by the use of a mesh carpet, is therefore not admissible. However, felt carpets have the great disadvantage of accumulating moisture instead of letting it pass. In the case of manufacturing corrugated cardboard of so-called "heavy" quality, this accumulation of moisture can limit the speed of production.

Patent US-A-3,217,425 proposes, for a "double-sided" station, an assembly device without a heating table, but comprising a lower belt bearing on support rollers, an upper belt passing under pressure rollers as well as under upper nozzles blowing hot air onto the corrugated board being formed, this air being immediately sucked into a vacuum box. However, given the excessively high efficiency of this device with regard to heating and drying, at the outlet the corrugated cardboard tends to quickly curl depending on the excess or insufficiency, at the input, of the humidity of the cardboard " single-sided "and / or various layers. There is therefore provided a complex device measuring the phenomenon of curling at the outlet to control individual preheating means for each of the layers at the inlet. However, stabilizing this feedback loop is very difficult to establish, with the secondary risk of overheating the adhesives while the layers are not yet assembled.

The document EP-A-0 077 186 mentions an upper mat common to all the sections of a "double-sided" station of a machine for producing corrugated cardboard.

The aim of the present invention is therefore to produce an assembly device for a station "double-sided" ensuring that the layers are kept in contact with one another and which is firm but without crushing, heating and drying of the corrugated board in formation correctly dosed for setting the adhesive, as well as sufficient cooling, so that the outgoing corrugated board is flat in both longitudinal and transverse directions. In addition to the flatness and the surface condition of the lower cover (that is to say on the outside on a package formed from this corrugated cardboard), the assembly device according to the invention must also be d 'a better yield than those known to date.

• soit à une diminution de la puissance installée pour une production donnée,
• soit à une longueur et puissance inchangées pour une augmentation de production.

These objects are achieved by means of an assembly device according to claim 1, in which the best efficiency is obtained by a reduction in the friction length, and therefore in the friction force, in the heating part. Numerous practical tests in the sector have shown that a length of 1 to 2 m, in the direction of travel, of the hot plates, is sufficient to guarantee a setting of glue and a flat surface of the external covering. This reduction in the length of friction leads to:

• either a reduction in the installed capacity for a given production,
• either at an unchanged length and power for an increase in production.

In addition, the relatively small length of the heating table compared to that of the drive section allows the use of a mesh belt which, in known manner, allows a better performance of the evacuation of moisture and therefore the removal of production speed limits imposed by the accumulation of moisture in the carpet when it is made of felt.

• la figure 1 est une vue en perspective schématique d'un dispositif d'assemblage selon l'invention et dans laquelle certaines parties supérieures du dispositif sont représentées en coupe pour mieux mettre en évidence d'autres parties inférieures, et
• la figure 2 est une vue en coupe du dispositif selon la plan I - I de la figure 1.

The invention will be better understood on studying an embodiment described below by way of nonlimiting example and with reference to the appended drawing in which:

• FIG. 1 is a schematic perspective view of an assembly device according to the invention and in which certain upper parts of the device are shown in section to better highlight other lower parts, and
• FIG. 2 is a sectional view of the device according to the plane I - I of FIG. 1.

• une première section dite "de chauffage" pour réaliser l'éclatement de la colle posée antérieurement sur les crêtes des cannelures d'une couche supérieure 20 dite "simple-face" et destinée à être assemblée avec une couche inférieure 30 dite de "couverture", les deux bandes 20, 30 étant de passage en continu sous forme de bande;
• une deuxième section dite "de séchage et de traction" pour extraire l'humidité résiduelle des deux couches 20, 30 et participant, au moins partiellement, également à l'entraînement du carton ondulé 10 en formation; et
• une troisième section dite "d'entraînement et de refroidissement" des deux couches 20, 30 assemblées, c'est-à-dire du carton ondulé 10 en formation.

The assembly device comprises three substantially distinct successive sections, namely:

• a first section called "heating" to achieve the bursting of the adhesive previously placed on the ridges of the grooves of an upper layer 20 called "single-sided" and intended to be assembled with a lower layer 30 called "covering" , the two bands 20, 30 being of continuous passage in the form of a band;
• a second section called "drying and traction" for extracting the residual moisture from the two layers 20, 30 and participating, at least partially, also in driving the corrugated cardboard 10 in formation; and
• a third section called "drive and cooling" of the two layers 20, 30 assembled, that is to say corrugated cardboard 10 in formation.

The first section consists essentially of a single horizontal heating table 250, lower, that is to say located below the passage of the strips 20, 30, and surmounted by a blowing box upper 150. This heating table 250 can be a cast iron or steel box, supplied with steam. Its transverse length is slightly greater than the useful width of the corrugator, that is to say of the machine for producing corrugated cardboard, and its width is approximately 2 m. To avoid its deformation, this table is internally reinforced by ribs and spacers which also form baffles improving the heat exchange between the steam and the box. The upper surface of this table is strictly flat to avoid the accumulation of impurities which could scratch the surface of the outer cover. The dimensions of the single heating table make its machining and assembly possible. The function of the upper blowing box 150 is to eject air downwards, that is to say on the upper face of the "single-sided" layer 20 to press the corrugated cardboard 10, in formation, uniformly against the heating table 250.

As illustrated in FIG. 1, the heating section comprises a series of identical upper nozzles 120, transverse, that is to say extending perpendicular to the direction of passage of the layers 20, 30 and at least over the entire width useful of the corrugator, parallel to each other and arranged one after the other in said direction of passage. Preferably, the heating section also comprises a series of lower nozzles 220 which are symmetrical and respectively in correspondence with the upper nozzles 120. All these nozzles 120, 220 have a generally oblique parallelepiped shape, that is to say, if we consider the upper nozzles 120, that they are higher on the lateral side through which the air arrives. The lower base of these upper nozzles 120 also has a frustoconical shape oriented downwards, which, due to the resulting reduction in the air flow section, slightly increases the speed of the outgoing air. The upper nozzles 120 are contained in an upper suction box 130 while the lower nozzles 220 are contained in a lower box 230.

As can be better understood in FIG. 2, the hot and dry air arrives from a duct 50 to be distributed by a series of lower supply pipes 52 into the corresponding lower nozzles 220 and by a series of supply pipes. upper supply 54 in the upper nozzles 120. This hot air is therefore projected from above against the upper face of the "single-sided" layer 20 and from below against the lower face of the cover layer 30, before being sucked upwards respectively by the upper box 130 and downwards by the bottom box 230. These two boxes 130, 230 are connected, by conduits 62, respectively 64, to an outlet 60 in the direction of a single pump not shown , creating sufficient depression in these boxes.

With reference to FIG. 1, it will be noted that the upper box 130 extends to the right, that is to say downstream, beyond the series of upper nozzles 120, this extension constituting in fact the part upper part of the third section called "drive and cooling". Similarly, the lower box 230 also extends to the right beyond the series of lower nozzles 220. The interior of these straight parts of boxes 130, 230 also being under vacuum caused by the outlet suction pump, a fresh air flows through the horizontal gap left at the level of the carton 10, between these two boxes and escapes through the conduit 60.

Still with reference to FIG. 1, the driving of the strips 20, 30, and therefore of the corrugated cardboard 10 in formation, is obtained by means of an upper mat 100 and a lower mat 200 movable in synchronism and without end.

Considering as a starting point an inlet drum 106 located upstream of the blowing box 150, the upper belt 100 passes first between this blowing box 150 and the heating table 250, then in the second section called "drying" under the upper nozzles 120 and also under first pressure rollers 115 each located between two parallel upper nozzles 120 and parallel thereto. The upper belt 100 then continues in the third section called "drive and cooling" under a series of other pressure rollers 110 parallel to each other and juxtaposed one after the other in the direction of passage of the carton 10 in training. All these rollers 110, 115 are transverse to the passage of the corrugated cardboard 10. At the exit of the third section, the upper belt 100 rotates upwards around a drum 105 to be taken up by a first upper pair of rollers 107a for placing under tension and back, supported by a second upper pair of rollers 107b located substantially in the middle of the device and by an upper guide roller 108 located substantially above the blower box 150, towards the inlet drum 106.

The lower belt 200 leaves an input drum 206 located downstream of the heating table 250 and enters directly into the second section. There, the carpet 200 passes over the lower nozzles 220 and also over the transverse support rollers 215, mutually parallel and each interposed between two consecutive lower nozzles 220. This belt 200 then continues in the third section called "drive and cooling" over a series of support rollers 210 facing the series of pressure rollers 110 described above. At the exit of the assembly device, the lower belt 200 rotates down around a lower drive drum 205 to be taken up by a lower pair of tensioning rollers 207, before being directed first backward on a lower guide roller 208, then return to the input roller 206.

During production, the "single-sided" layer 20 and the "cover" layer 30 which arrive from a previous station called "double-sided gluer", penetrate into the first section where the blowing box 150 applies the layer 20 against layer 30 and this one against the heating table 250 causing the bursting and setting of the glue.

The corrugated cardboard 10 thus formed, but still damp, is sandwiched at the entrance to the second station between the upper belt 100, which is pressed down by the pressure rollers 115 then 110, and the lower belt 200 maintained in place by the support rollers 215 and 210 successively. Given that the only friction forces to be overcome are those generated in the first heating section, the useful drive length which moreover corresponds to the length of the upper face of the lower belt 200, can be reduced to dimensions of far lower than those in progress to date.

Because the belts 100, 200 are formed of mesh, the air ejected from the nozzles easily passes through it. This air, once overloaded with moisture, is immediately taken up by the suction box 130, respectively 230. It should be noted that the useful suction section at the level of the corrugated board 10 is formed by the spaces between the nozzles minus the section apparent from the rollers 115 or 215 which is quite weak from an aerodynamic point of view.

Finally the cardboard 10, which continues to dry while cooling in the third section, is kept strictly plane between the two belts 100 and 200 guided by the series of rollers 110 and 210.

Given the high drying efficiency of the nozzles and suction boxes, it may be sufficient to provide only one series of these nozzles, either higher or lower. It is also possible to envisage having a control valve at the inlet of each of these nozzles so as to put only part of them into action, as necessary.

Many modifications can be made to the device described above, without departing from the scope of this invention. So, for example, the hot air used for heating / drying can be replaced by IR, microwave, UV, electron jet, etc. Combinations of such different systems are also possible. The heating systems also make it possible to heat in a differentiated manner in the transverse direction of the width in order to take account of possible transverse variations in humidity being in the form of bands oriented in the direction of passage of the various layers.

Claims (4)

1. Assembly device for weblike workpieces consisting of superposed and glued layers (20, 30), designed for being used in a so-called "single-face" or "double-face" section of a machine for the production of corrugated cardboard and in which the said layers (20, 30) continuously run in the form of webs, the said device comprising successive items arranged in the travelling direction, ie:

   - a first, so-called "heating" section consisting essentially of a single heating plate (250) provided with a smooth horizontal upper surface and topped by a blowing case (150) pulsing air downwardly onto the plate;

   - a second, so-called "drying and pulling" section comprising a row of upper slot-shaped parallel nozzles (120) arranged above, and perpendicularly to, the travelling direction of the corrugated cardboard (10) being produced with the said webs (20, 30) and on the upper side of which they blow hot air, the said upper nozzles (120) being located on an upper suction case (130);

   - a third, so-called "cooling and driving" section comprising the extension of the upper case (130) beyond the said row of upper nozzles, the conveyance from the second to the third section being achieved by means of two meshed belts (100, 200) both common to the two sections, ie:

   - by means of an upper belt (100) common to the said three sections, passing around an inlet drum (106) situated before the blowing case (150), then in the first section between the blowing case (150) and the heating plate (250) of the first section, then in the second section underneath the upper nozzles (120) and underneath a first range of transverse pressure rollers (115) each situated between two upper nozzles (120), then in the third section underneath a second range of transverse pressure rollers (110) juxtaposed in the travelling direction, then around an upper driving drum (105) in such a way as to ascend and return on upper supporting, tightening and guiding rollers (107, 108 respectively) towards the inlet drum (106), and

   - by means of a lower belt (200) passing around an inlet drum (206) situated after the heating plate (250), then in the second and third sections on a first range of transverse supporting rollers (210) juxtaposed in the travelling direction, then around a lower driving drum (205) in such a way as to descend and return on lower tightening and guiding rollers (207, 208 respectively) towards the inlet drum (206).
2. Assembly device according to claim 1, characterised by the fact that:

   - the second section comprises a row of lower slot-shaped transverse nozzles (220) situated underneath, and perpendicularly to, the said track of the corrugated cardboard (10) being produced and on the lower side of which the said nozzles blow hot air, the lower nozzles (220) being located on a lower suction case (230);

   - the lower part of the third section includes an extension directed to the downstream area of the lower suction case (230); and

   - the lower belt (200), when travelling through the second section, runs over the lower nozzles (220) and a second range of transverse supporting rollers (215) each situated between two lower nozzles (220), and then over supporting rollers (210) of the said first range.
3. Device according to claim 1 or 2, in which the hot air used for heating and drying purposes is substituted for by an infra-red, ultra-violet or micro-wave irradiation, electron-beam or other similar means.
4. Device according to one of the aforesaid claims, on which the heating plate consists of a single piece preventing the gathering of impurities between the various plates usually fitted in juxtaposed position on the double-face gluers.

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