JPH11170408A - Method for laminating corrugated fiberboard and laminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a corrugated fiberboard which enables its moisture content to be made uniform and adjusted effectively and also is almost free from a warping phenomenon. SOLUTION: A heating part is covered with chambers 17, 18 and the starched stepped center core of a single corrugated fiberboard and a liner are induction- heated by high frequency in such a state that both stepped center core and liner and lapped on each other. And at the same time, both faces of the center core and the liner are subjected to a negative pressure created by vacuumizing devices 19, 20. Thus the internal moisture of a corrugated fiberboard 10 is diffused and made uniform. Thus it is possible to obtain the corrugated fiberboard 10 which is hardly warped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for bonding cardboard, and more particularly to a method and apparatus for preventing cardboard from warping.

[0002]

2. Description of the Related Art In a conventional corrugated cardboard manufacturing apparatus, a single-sided corrugated cardboard in which a stepped core and a back liner are bonded is coated with glue on the step top of the core by a glue machine, and is superposed with a front liner to form a heater. While being conveyed while being clamped by the endless belt, the surface liner is adhered to the core and integrated by being heated by a heater to gelatinize the starch paste, and then cut into sheets of a predetermined size in the next step. A corrugated cardboard is produced. In the above manufacturing process,
It is required that the core and the liner be well adhered to each other, that a flat cardboard be obtained without warping, and that the cardboard be manufactured at a high speed. In order to obtain a flat cardboard without warpage, it is required that the water content of the liner itself be uniform and the water content of the front liner and the back liner be uniform. However, in the conventional method, since the water content on the liner surface is not uniform and the water content of the liners on both sides is easily unbalanced, warpage often occurs due to these factors.

[0003]

In particular, the unevenness (particularly in the width direction) of the water content of the front liner itself at the time of bonding, and the imbalance of the water content of the front liner and the back liner greatly affect the warpage of the cardboard. ing. Conventionally, in order to evaporate the moisture generated from the paste by heating with heat, various arrangements of a heating device have been proposed (for example,
JP-A-62-70034, JP-A-1-13673
No. 4) is still known to have special technical measures such as diffusing water in corrugated cardboard to make it uniform, or adjusting the water content of the front liner and back liner to maintain uniformity. Absent. In drying by heating, evaporation of moisture contained in the liner itself due to heat and evaporation of a large amount of moisture generated from the glue overlap, and furthermore, the environmental temperature, humidity, wind, etc. have a complex effect, so simply heating with a heater It is difficult to equalize the water content of the front liner and the back liner themselves and to balance them both alone.

The present invention is intended to solve the above-mentioned problems in the conventional corrugated cardboard manufacturing process, especially in the laminating process. It is an object of the present invention to provide a cardboard bonding method and a cardboard bonding method capable of manufacturing cardboard, which is less likely to cause cracks.

[0005]

According to the present invention, there is provided a cardboard laminating method for solving the above-mentioned problems, wherein the stepped core coated with the paste and the liner are heated while being superposed, and at least the step A technical means is adopted in which the pressure of the corrugated cardboard surface on the liner side to be bonded to the core is negative pressure. Various heating means such as a hot plate or microwave heating can be used for the heating, but it is preferable to use high-frequency dielectric heating. Also, make both sides of the cardboard negative pressure,
In addition, by controlling the degree of negative pressure acting on both side surfaces, the water content imbalance of the liners on both sides of the corrugated cardboard is adjusted, so that the water content imbalance of the liners on both sides of the corrugated cardboard can be arbitrarily adjusted. .

[0006] In the cardboard laminating apparatus of the present invention, which carries out the above cardboard laminating method, the stepped core coated with the glue and the liner are conveyed while being sandwiched between the heating device and the belt. In a corrugated cardboard laminating apparatus for bonding a corrugated cardboard by heating with a heating device, a chamber for covering at least a corrugated cardboard surface on the heating device side is provided, and the chamber is connected to an exhaust device. The heating device is preferably a dielectric heating device,
It is preferable to dispose a grid-type high-frequency dielectric heating electrode at least on the liner side on which the paste is applied. In that case, the high-frequency dielectric heating electrode is arranged so that the direction of the electric field by the electrode is inclined with respect to the traveling direction of the corrugated cardboard (the best direction is a right angle direction). To be heated.

[0007] The chamber is arranged on both sides of the cardboard,
Preferably, both chambers are respectively connected to an exhaust device. Then, by disposing the moisture sensors on both sides of the corrugated cardboard on the downstream side of the chamber, the exhaust devices on both sides are separately controlled by the output signals of the moisture sensors, and the imbalance of the moisture content on both sides is adjusted. It can be easily adjusted. Further, by providing a radiation thermometer for measuring the temperature of the cardboard at the downstream side of the chamber, the heating temperature of the cardboard can be appropriately controlled, which is desirable. Further, by providing a large number of holes in the heating device and the belt, steam generated during heating can be ventilated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. The illustrated apparatus shows a double facer section which is a post-process of a corrugated cardboard production line. In a pre-process, similarly to a conventional line, a core 2 and a back liner 3 which are corrugated by a corrugator are bonded together to form a single-faced corrugated cardboard 1. Is formed and continuously sent to the double facer section. In the double facer portion, the core is preheated by a heat roll 5, an adhesive is applied to the top of a single-sided corrugated cardboard by a glue machine 6, and bonded to the front liner 4 which is preheated and sent by a heat roll 7, After heating and drying in the heating section 8, the sheet passes through the cooling section 9 and is cut into a predetermined size by a cutter to produce a sheet-like double-faced cardboard 10 '. In the above manufacturing process, the present invention is particularly characterized by the heating unit 8 and the cooling unit 9.

In the heating section in this embodiment, a heating device is arranged along the front liner side of the conveying path through which the single-sided cardboard and the front liner overlap and pass, and the back liner side is an endless cotton extending to the cooling section. A belt 11 is arranged, and the cardboard is sandwiched between the dielectric electrode 21 of the heating device and the cotton belt 11 to be conveyed while being pressed. The dielectric electrode 21 and the cotton belt 11 are provided with a number of holes so that air and water vapor can flow. Then, chambers 15 and 16 are provided so as to respectively cover both surfaces of the cardboard in the heating section, and an exhaust device is connected to the chambers. By exhausting the inside of the chamber, moisture and air are removed together with the air. Moisture and pressure can be adjusted. In addition, by dividing the inside of the chamber into a plurality of sections as necessary on the front liner side (that is, the dielectric electrode side) and the back liner side, it is possible to provide and adjust an exhaust device for each section. it can. For example, the output can be arbitrarily adjusted, for example, by increasing the output of the exhaust device in the upstream section where the water portion from the glue occurs most, as compared with the downstream section. In the illustrated embodiment, the chamber is divided into six compartments on the front liner side and four compartments on the back liner side.
7 and 18 are provided and connected to the exhaust devices 19 and 20.

In the present embodiment, the heating device employs a high-frequency dielectric heating device. As shown in FIG. 2, a comb-shaped lattice-shaped dielectric electrode 21 is inclined by an electric field with respect to the traveling direction of the core and the liner. (Most preferably in the orthogonal direction). In high-frequency dielectric heating, when a high-frequency alternating voltage is applied between adjacent electrodes, the corrugated cardboard that is the object to be heated generates heat due to dielectric loss. Since the temperature of the heated portion is intensively increased in a short time, there is an advantage that the heating can be performed with high energy efficiency as compared with other heating methods and the heating can be controlled freely. In addition, since the top of the step with glue is located at right angles to the direction of movement of the cardboard, the dielectric electrodes should be arranged so that the direction of the electric field is inclined (at right angles) to the direction of travel of the core and liner. Thereby, the step top portion can be more effectively heated. 22 and 23 in the figure
Is a high frequency oscillator.

In the present invention, a moisture sensor and a radiation thermometer are provided so that heating and exhaustion (ie, negative pressure) can be controlled under optimum conditions while constantly monitoring the moisture of the cardboard. In the present embodiment, the first moisture sensor 24 is provided on the back liner side and the second moisture content is provided on the front liner side so that moisture on both sides of the cardboard which has been heated and dried in the heating unit and further conveyed through the cooling unit can be simultaneously detected. A sensor 25 is disposed, and the exhaust device 19 is operated according to the signal of each moisture sensor.
Or, by controlling the output of 20, the moisture on the back liner side and the front liner side can be adjusted.
Further, a radiation thermometer 26 is arranged downstream of the chamber so that the temperature of the cardboard after leaving the chamber can be measured in a non-contact manner. The output of the high-frequency oscillators 22 and 23 is controlled by the signal of the radiation thermometer 26 to heat to the optimum temperature. In the figure, 27 is the chamber 1
A feed belt is disposed in a cooling portion on the downstream side of the cotton belts 5, 16 and is opposed to a part of the downstream side of the cotton belt.

The corrugated cardboard laminating apparatus of the present embodiment is constructed as described above. The corrugated cardboard 10 which is coated with glue, superposed and pressed and conveyed is heated in a chamber at the same time as the evacuation devices 20 and 19 are operated. It drives to evacuate the chambers on both sides. As a result, a negative pressure is created in the chamber, so that moisture in the cardboard is diffused and uniformized. At the same time, steam generated by heating is forcibly discharged out of the chamber. Then, the moisture content of both sides of the cardboard is measured by the moisture sensors 24 and 25 on the downstream side, and based on the measurement result, the exhaust devices 19 and 20 are obtained so that a desired moisture content is obtained.
By controlling the water content, the water content of the liners on both sides can be appropriately adjusted. For example, if the back liner maintains a moderate moisture content, but the front liner has a high moisture content, only the exhaust device 19 is operated to eliminate the imbalance in the moisture content on both surfaces that causes warpage. be able to. Also, by measuring the temperature of the cardboard coming out of the chamber by the radiation thermometer 26, it is possible to determine whether the heating temperature in the chamber is appropriate, and by adjusting the output of the high-frequency oscillator based on the detected value, the desired value can be obtained. Can be controlled so as to reach the heating temperature.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various design changes can be made within the scope of the technical idea. For example, in the above-described embodiment, a plurality of exhaust devices are arranged in the chambers on both sides of the heating unit. However, it is not always necessary to provide a plurality of exhaust devices, and each may be one, or the entire front and back surfaces are made into one chamber. Thus, the entire exhaust can be performed by one exhaust device. Further, the chamber is not necessarily a closed type, and it is only necessary that the both sides of the cardboard can be evacuated. Therefore, an open type of a hood type is also possible.
Also, the first moisture sensor, the second moisture sensor, the radiation thermometer, the exhaust device, and the high-frequency oscillator are connected to the control device to set a predetermined corrugated cardboard temperature downstream of the heating unit and its water content on the front and back liner surfaces. Although it is desirable to automatically control the exhaust device and the high-frequency oscillator based on the two moisture sensors and the radiation thermometer so as to obtain the ratio, the exhaust device and the high-frequency oscillator may be manually controlled. Further, the moisture sensor may be provided not only on the downstream side of the heating unit but also on the upstream side to measure the moisture content in a preheated state and to cooperate with the moisture sensor on the downstream side.

Further, as the heating device, a dielectric heating device is desirable, but a suitable heating plate or heating box, a microwave heating device, or the like as in the related art can be employed. In the above embodiment, the case of the double-faced cardboard was shown, but it is needless to say that the present invention is not limited to the bonding of the double-faced cardboard, but can be applied to the bonding of the double-sided cardboard or the double-sided cardboard.

[0015]

As described above, according to the present invention, unlike the conventional method of simply evaporating moisture by heating to dry the cardboard, both sides of the cardboard are heated under a negative pressure. The moisture in the inside is diffused and uniform, and the amount of moisture can be adjusted optimally by adjusting the degree of negative pressure, so that the warpage of the cardboard can be effectively suppressed. In addition, since the degree of negative pressure on the front and back surfaces of the corrugated cardboard can be adjusted separately, the moisture imbalance of the liners on the front and back surfaces can be easily adjusted, and the liner moisture on the front and back surfaces, which is the biggest cause of warpage, can be adjusted. Can be eliminated, and a corrugated cardboard hardly warped can be obtained.

Further, by adopting a dielectric heating device as the heating device, it is possible to rapidly heat and thereby to quickly remove moisture generated from the paste by the exhaust device, so that the water content of the cardboard can be adjusted more easily. It is easy and can operate at a higher speed than before. In this case, the dielectric electrode is arranged so that the direction of the electric field by the electrode is inclined with respect to the traveling direction of the corrugated cardboard (the best direction is a perpendicular direction), so that the applied step top can be heated intensively, and the energy can be increased. Efficiency can be further improved. Furthermore, by disposing the moisture sensors on both sides of the corrugated cardboard, the exhaust devices on both sides are separately controlled by the output signals of the moisture sensors, so that the imbalance of the moisture content on both sides can be easily adjusted. it can. Further, by providing a radiation thermometer for measuring the temperature of the cardboard on the downstream side of the chamber, the heating temperature of the cardboard can be appropriately controlled.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cardboard laminating apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a high-frequency oscillator and a dielectric electrode according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 broken ball 11 cotton belt 15, 16 chamber 17, 18 exhaust duct 19, 20 exhaust device 21 dielectric electrode 22, 23 high frequency oscillator 24 first moisture sensor 25 second moisture sensor 26 radiation thermometer 27 feed belt

Claims (9)

[Claims] 1. Heating in a state in which a stepped core coated with glue and a liner are superimposed, and at the same time, applying a negative pressure to at least a corrugated cardboard surface on a liner side to be bonded to the stepped core. How to paste corrugated cardboard. 2. The method according to claim 1, wherein the heating is high-frequency dielectric heating. 3. The corrugated cardboard according to claim 1, wherein both sides of the corrugated cardboard are under negative pressure, and the degree of negative pressure acting on both sides of the corrugated cardboard is controlled to adjust the imbalance of the water content of the liners on both sides of the corrugated cardboard. Bonding method. 4. A corrugated cardboard laminating apparatus in which a stepped core coated with glue and a liner are stacked and conveyed while being sandwiched between a heating device and a belt, and heated by the heating device to bond the corrugated cardboard. And a chamber for covering at least a cardboard surface on the heating device side, wherein the chamber is connected to an exhaust device. 5. The heating device is a dielectric heating device, and has at least a grid-like shape (so that the direction of an electric field is inclined with respect to the direction of travel of the cardboard) on the cardboard surface side of the liner to be attached to the stepped core. 5. The corrugated cardboard bonding apparatus according to claim 4, wherein a high-frequency dielectric heating electrode is arranged. 6. The corrugated cardboard bonding apparatus according to claim 4, wherein the chambers are arranged on both sides of the corrugated cardboard, and both chambers are respectively connected to an exhaust device. 7. The corrugated cardboard laminating apparatus according to claim 6, wherein moisture sensors are respectively arranged on both sides of the corrugated cardboard downstream of the chamber. 8. A radiation thermometer for measuring the temperature of the cardboard is provided downstream of the chamber.
The cardboard bonding apparatus according to any one of the above. 9. The corrugated cardboard bonding apparatus according to claim 4, wherein the heating device and the belt are provided with a large number of holes.