JPH11216786A - Method and apparatus for laminating corrugated fiberboard without warp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a corrugated fiberboard without warp by generally and effectively removing a residual strain of a sheet fiber of the fiberboard generated based on a moisture contained in a paste. SOLUTION: The method for laminating a corrugated fiberboard comprises the steps of grasping the fiberboard in a warped state at a stage of a product, and sensing a residual strain of the fiberboard. And, the method further comprises the steps of feeding back a tension applied to a front liner 4 and one side surface corrugating fiberboard 3 to be controlled at the time of laminating the liner 4 and the fiberboard, and laminating the both, thereby eliminating the residual strain at the fiberboard to be a product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cardboard bonding method and apparatus, and more particularly to a cardboard bonding 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. By the way, the warpage of the corrugated board is caused by the distribution of fiber strain on the corrugated board surface at the time when the product is dried and becomes a product. The residual strain is largely affected by the difference in water content between the front liner and the back liner entering this step, and also affected by the surface distribution of the water content of the liner itself. Furthermore, in the manufacturing process, the paper fiber of the material is once stretched and bonded by the moisture contained in the glue in the manufacturing process, and then dried to form a product, but the warpage is once wetted by the moisture contained in the glue. It is also affected by being dried afterwards. Therefore, in order to obtain a flat cardboard without warpage conventionally,
It is required that the water content of the liner itself is uniform and the water content of the front liner and the back liner is also uniform.For example, in order to evaporate the water generated from the paste by heating with heat,
A device in which the arrangement of a heating device is devised (for example, see Japanese Unexamined Patent Application Publication No. Sho 62
Japanese Patent Application Laid-Open No. -70034, Japanese Patent Application Laid-Open No. 1-136634, etc.) have been proposed. However, none of the conventional methods can remove the warp comprehensively in response to various events that cause the residual strain that is the cause of the warp.

[0003]

By the way, the process of wetting and drying with moisture in the surface liner, especially in the width direction during bonding has a great influence on the warpage of the cardboard. This is because the core and the back liner that were corrugated in the previous step of the corrugated cardboard were first bonded, and in the next step the top of the core was coated with glue and the front liner was bonded, The location that will contain water will be the junction between the top of the core and the front liner mated with it, but the core is stepped while being held by the back liner that does not wet, This is because the wetted portion is in a so-called no-load state, whereas the front liner is formed of a single sheet of paper, so that the load tension applied to the liner directly extends to the wetted portion, causing the elongation of the paper.
Since the direction of the paper fibers of the liner is almost aligned in the transport direction, the deformation of the liner occurs more in the width direction than in the longitudinal direction. In addition, when there are many fibers in the oblique direction, a warp having an oblique component is generated.

[0004] The present invention is intended to solve the above problems in the conventional corrugated cardboard manufacturing process, particularly in the laminating process, and is intended to solve only the difference in water content between the front and rear liners and the water content distribution of the liner itself. Rather, it is intended to provide a cardboard laminating method and apparatus capable of producing a cardboard without warpage by comprehensively and effectively removing residual distortion of the cardboard caused by moisture contained in the paste. It is the purpose.

[0005]

SUMMARY OF THE INVENTION The present invention detects residual warping of corrugated cardboard by grasping the state of warpage of corrugated cardboard at the product stage, and when the front liner and single-sided corrugated cardboard are pasted together, the surface liner and the corrugated cardboard are bonded in advance. By applying feedback so as to control the tension applied to the single-sided cardboard and bonding them together, residual distortion is not generated in the cardboard as a product.

The back tension applied to the liner at the time of bonding is not only applied uniformly to the front liner and the single-sided cardboard, but also differently applied in the width direction. As a result, it is possible to prevent not only the warpage in the longitudinal direction but also the warp in the width direction and the oblique direction.

[0007]

The cardboard laminating step of the present invention, as shown in the apparatus shown in FIG. 1, corresponds to the double facer section which is a post-step of the cardboard production line. The back liner 1 is bonded to form a single-faced cardboard 3 and is continuously sent to the double facer portion. In this double facer portion, the core is preheated by a heat roll (not shown) in the previous process, an adhesive is applied to the top of the single-sided cardboard by the glue machine 6, and the surface liner is also preheated by the heat roll and sent. After laminating the sheet 4 and heating and drying in a heating unit 8, the sheet passes through a cooling unit 9 and is cut into a predetermined size by a cutter to produce a double-sided corrugated cardboard 5 in sheet form. In the above manufacturing process, the present invention is characterized in that, at the point of time when the single-sided corrugated cardboard and the surface liner are bonded to each other, a reverse stress is applied to both of the corrugated cardboard in advance so that no residual strain remains on the double-sided corrugated cardboard. Things. In short, the paper fiber is loosely bonded to the part where the liner stretches and warps the cardboard, and the loose part is stretched by applying tension to the loose part.

The method of applying the stress is as follows.
The back tension rollers 16 and 17 control the tension of the single-faced corrugated cardboard 3 and the front liner 4 which are sandwiched between the guide roll 10 and the pinch roller 13 at the upstream side. . Uniform distortion based on the water content difference between the front liner and the back liner can be eliminated by displacing the axis of a single back tension roller perpendicular to the transport direction, and it changes monotonically to the left and right with respect to distortion in the width direction If it is possible to change the amount of displacement of the left and right axes, it can be dealt with, but for those in which the strain is complicatedly changed in the width direction, the back tension roller is divided into multiple in the width direction and provided. This is dealt with by changing the amount of displacement and changing the degree of application of stress. By the way, since the single-sided cardboard has a structure in which the core is bonded to the back liner in a stepped state, if the tension is too large, the core will be pressed against the guide roller surface and will be deformed. It is preferable that the back tension is made substantially constant only by adjusting its own width direction component, and the back tension is controlled mainly on the front liner side.

The detection of the warpage of the cardboard is performed by the cooling unit 9.
A plurality of displacement sensors are arranged at least in the width direction at the downstream of the device, and the upward warp and the downward warp are determined in the longitudinal direction, the width direction, or the oblique direction. This sensor is preferably of a non-contact type such as an ultrasonic type or an optical type so that the measurement load does not affect the displacement amount. However, if the contact pressure is small, even a probe type sensor has no problem and is simple. The amount of displacement from each sensor is used to grasp the state of warpage, that is, which part of the cardboard is distorted in which direction, and by appropriately controlling the displacement of the back tension roller, the desired tension is applied to each part of the liner. And paste it. The state of warpage and the degree of back tension are grasped experimentally in advance,
It is appropriate to store the relationship in a ROM or the like.
In addition to the method of directly detecting warpage by the displacement sensor as described above, the difference in moisture content between the front liner and back liner, which is the main cause of warpage, is detected by the moisture sensor to predict the state of warpage. There is also a way to do it.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A single-faced corrugated cardboard 3 preheated in a previous step is appropriately tensioned by a back tension roller 16 disposed between guide rollers 18 and 19, and a guide roller is set on a step top of a single-sided corrugated cardboard core. 19 and 10
After the gluing is performed by the glue machine 6 disposed between the pinch roller 13 and the pinch roller 13 facing the entrance side guide roller 10 of the cotton belt 11, it is also preheated separately in the previous step and is appropriately operated by the action of the back tension roller 17. Is bonded to the front liner 4 to which tension is applied. In the process of passing through the heating unit 9, the cotton belt 1
1. Appropriate pressing force is applied by 1 and high frequency electrode 8-
1 to heat and dry, and the bonding of the double-faced cardboard 5 is completed. The pasted cardboard is pinched and conveyed by a pinch roller 14 facing the cotton belt exit side guide roller 12, and cut by a cutter 21 on the downstream side to complete the sheet-shaped double-faced cardboard 5. The state of warpage of the bonded double-faced cardboard is determined by a plurality of displacement sensors S1 (S
2), the detected value is input to the control operation unit 15, and the single-sided cardboard-side back tension roller is used by using the relation information of the warp state and the degree of back tension stored in the ROM in the control operation unit. 16 and the control signals CS1 and CS2 of the front liner side back tension roller 17 are indexed and output. Control signal CS1
, The back tension roller 16 is displaced in accordance with the control signal CS2, and the back tension roller 17 is displaced in accordance with the control signal CS2. If the back tension roller 17 on the front liner side is composed of two rollers that are separately displaced, the width of change in tension can be increased.

In the present embodiment, the heating device employs a high-frequency dielectric heating device 8-1.
The electric field is arranged so as to be inclined (most desirably at right angles) to the traveling direction of the core and the liner. 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. Moisture evaporated by heating is released to the outside by the exhaust device 22.

[0012]

Embodiment 1 FIG. 2 shows a specific example of the back tension roller. This is because the radial bearing of the roller is provided so that it can be displaced left and right.By setting the left and right bearing positions to the same amount of displacement, it is possible to apply uniform tension to the liner, When there is, it is possible to cope with it by adjusting the amount of displacement to the left and right (shown by broken lines). As the mechanism for displacing the bearing, a mechanism for displacing the spindle by a displacement motor in accordance with a control signal, or a mechanism for displacing the outer periphery of the bearing portion in a pinion shape and displacing the rack on the rack by applying a rotation amount according to the control signal. Can be applied.

[0013]

Embodiment 2 However, the embodiment shown in FIG. 2 can cope with the case where the distortion in the width direction is a monotone distortion which is monotonous to the left and right, but cannot deal with a distortion having a secondary component. FIG. 3 shows a specific example that can cope with this. This configuration is such that a roller is divided into a plurality of parts in the width direction and the axis of each roller is displaceably provided. With this configuration, since each roller can be individually displaced as shown by the broken line, it is possible to deal with a case where distortion is concentrated at the center with respect to the left and right and a case where distortion is concentrated at the opposite left and right. can do.

[0014]

Embodiment 3 Next, a specific example of a displacement sensor for detecting the distortion of a double-faced cardboard as a product is shown in FIG. When the bonding is completed, the double-sided corrugated cardboard cut by the cutter 21 on the downstream side and pinched in a cantilever state by the pinch roller 14 facing the cotton belt exit side guide roller 12 is positioned at a distance of L from the holding portion. A plurality of displacement sensors are arranged in a line in the width direction, and the displacement amount of the corrugated cardboard surface on one free end side, which is held linearly at one end, is measured. The type of the displacement sensor may be such that, for example, a probe is brought into contact with the surface of a cardboard and the displacement is detected by a differential transformer.

[0015]

Embodiment 4 Warpage can also be detected by measuring the amount of displacement of the surface of a double-faced cardboard that has been cut by the cutter 21 and has four sides on the belt. In this case, the sensors are arranged so as to be appropriately distributed on the cardboard surface. The example of FIG. 5 is an example in which sensors are arranged at nine locations to see the difference between the four corners and the center.

[0016]

[Embodiment 5] An embodiment will be described in which the state of warpage is detected by a moisture sensor by predicting the measured moisture content of the front liner and the back liner. Moisture sensor S that measures the water content of the back liner just before laminating one-sided cardboard and the front liner
3 and a moisture sensor S4 for measuring the moisture content of the front liner are provided, and the measured value is output to the control calculation unit. The arithmetic unit has a correspondence table between the water content and the warpage of the front liner and the back liner, which is created from the experimental data, that is, a residual strain. Further, a tension for removing the distortion is determined, and a feedback control signal to the back tension roller is determined. CS1,
Output CS2.

[0017]

According to the present invention, the distortion of the paper fiber, which is the cause of the warpage of the corrugated cardboard, is bonded by applying a reverse stress in the form of back tension to the single-faced corrugated cardboard and the front liner at the time of bonding. In order to eliminate warpage by removing residual strain, not only is the water content difference between the front and rear liners and the water content distribution of the liner itself, but also the residual cardboard produced by the moisture contained in the glue. The distortion can be removed comprehensively and effectively, and a cardboard without warpage can be manufactured.

A plurality of tension rollers for applying the back tension are divided and arranged in the width direction of the corrugated cardboard, and by giving a difference in how to apply the tension individually, an appropriate countermeasure against complicated warpage can be obtained. Can be taken.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a device for bonding a single-faced cardboard and a front liner according to the present invention.

FIG. 2 is a diagram showing one embodiment of a tension control device.

FIG. 3 is a diagram showing another embodiment of the tension control device.

FIG. 4 is a diagram showing an example of arrangement of displacement sensors.

FIG. 5 is a diagram showing another arrangement example of the displacement sensor.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 back liner 2 core 3 single-sided cardboard 4 front liner 5 double-sided cardboard 6 glue machine 8 heating unit 9 cooling unit 10,12 cotton belt guide roller 11 cotton belt 13,14 pinch roller 15 control operation unit 16,17 back tension roller S1 , S2
Displacement sensor S3, S4 Moisture sensor

Claims (4)

[Claims] 1. A method of detecting the degree of warpage of a double-sided cardboard and applying an appropriate back tension to the single-sided cardboard and a surface liner so as to eliminate the distortion of the paper fiber which causes the warp. How to paste corrugated cardboard. 2. A displacement detecting means for detecting a warpage of a double-faced cardboard after a cooling portion, a control calculating means for calculating a back tension control amount corresponding to the detected warping information, and a control signal output from the calculating means. And a tension control means for applying a back tension to the surface liner according to the above. 3. A moisture sensor for measuring the water content of each of the front liner and the back liner at a stage before the single-faced cardboard and the front liner are bonded, and predicting a degree of warpage based on a measurement value of the moisture sensor. Pasting a cardboard having control operation means for calculating a back tension control amount corresponding to predicted warpage information, and tension control means for applying back tension to a single-sided cardboard and a front liner in accordance with a control signal output from the operation means. Joint equipment. 4. A tension control means comprising a plurality of rollers divided and arranged in a width direction of a corrugated cardboard, wherein the axis of each roller can be adjusted separately.
2. The corrugated cardboard bonding apparatus according to item 1.