JP3935526B2 - Web or sheet conveying method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a web or sheet conveying method and apparatus, and more particularly, to a web or sheet conveying method such as a plastic film, paper, or cloth that contracts when dried (hereinafter described as a web).
[0002]
[Prior art]
For example, a web such as an undried plastic film, paper, or cloth formed by a solution casting method contains an evaporating liquid such as an organic solvent or water, and thus shrinks during the drying process. Flatness decreases. For this reason, in order to maintain and improve the flatness of the web, a conveying device called a tenter device is often used. This conveying device dries the web while applying a tensile force in the width direction of the web by conveying the both side edges of the web supported by holding members such as clips or pins (Japanese Patent Laid-Open No. Sho 62-62). 46625, JP-A 62-46626). As shown in FIG. 7, this transport device has a large number of pins on a pin plate 50 supported in a line by a pair of moving chains (not shown) arranged along the transport direction 51 of the web 16. 52 is implanted, and both side edges of the web 16 are supported by the pin 52. Therefore, most of the web 16 is conveyed in a non-contact state with respect to the object except for both side edges in the width direction.
[0003]
As shown in FIG. 8, the transfer device is often a one-stage type device 55 having a single transfer plane. However, in order to improve the efficiency of the device space, as shown in FIG. A multi-stage device 56 having 22 is advantageous. 8 and 9, 12 is a casting port, 14 is a rotating drum, and 18 is a peeling portion.
[0004]
[Problems to be solved by the invention]
By the way, the web 16 is supported by pins or the like on both side edges and stretched in the web width direction, and on the other hand, a constant tension is also applied in the running direction of the web. Therefore, when the undried web 16 having shrinkage is dried by the conveying device 56 having the reversing unit 22, the central portion of the web that is not supported due to the shrinking force of the web 16 is recessed in the reversing unit in FIG. Deforms into a drum shape as shown. Due to this deformation, a large tensile force is applied to both side edges of the web 16, so that the width of the web 16 is substantially expanded. As a result, the product finally obtained after drying has a drawback that the planarity of the web 16 becomes extremely poor because both side edges of the web 16 are loosened. Therefore, products that require flatness, even if the efficiency of the device space is sacrificed, if the single-stage transfer device 55 or the multi-stage transfer device 56 is used, the product over the entire width is used. Since it cannot be used, only the central part of the web 16 has to be made into a product, and there is a problem that productivity is extremely deteriorated.
[0005]
Further, since the width of the web 16 is expanded when the web 16 is deformed into a drum shape by the reversing unit 22, the clip or pin 52 of the transport device that supports both side edges of the web 16 has a flat surface. A large force acts in the width direction. Therefore, in the case of the web 16 having a small film thickness, there is a problem that the web 16 is broken at the clip or pin 52 portion.
[0006]
Thus, as a countermeasure for preventing the web 16 from contracting and deforming into a drum shape at the reversing portion 22, for example, a plurality of guide rollers 58 (FIG. 11) or a drum 60 (FIG. 12) are disposed inside the reversing portion 22. In some cases, the web 16 is prevented from being deformed into a drum shape by supporting the inner surface of the web 16. However, in this method, since the web 16 comes into contact with the guide roller 58 and the drum 60, there is a defect that surface defects such as scratches and dirt adhere to the web 16 frequently, and this is not an essential solution.
[0007]
The present invention has been made in view of such circumstances, and even when the web is dried by a multi-stage conveyance method having a plurality of reversing portions, the planarity of the web is not impaired in the reversing portions, and the surface shape is reduced. It is an object of the present invention to provide a web or sheet conveying method and apparatus that do not cause a failure.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention, when drying a shrinkable web or sheet, supports both side edges in the width direction of the web or sheet and stretches the web or sheet in the width direction. In the web or sheet transport method in which the web or sheet is transported in a state where the web or sheet is transported in the reversing section in the middle of transport, the web or sheet drum is caused by the contraction force generated in the web or sheet in the reversing section. Inverting the web or sheet in a state where a static pressure is generated by gas on the inner surface of the web or sheet so that surface pressure is applied to the entire reversal surface of the web or sheet It is characterized by making it.
[0009]
In order to achieve the above object, the present invention supports both side edges in the width direction of the web or sheet when drying the shrinkable web or sheet so that the web or sheet is moved in the width direction. In a web or sheet transport device that transports the web in a stretched state and reverses the transport direction of the web or sheet in a reversing section in the middle of transport, gas is applied to the inner surface of the web or sheet in the reversing section. A gas jetting means for applying a surface pressure to the entire surface of the reversing surface of the web or sheet, and a surrounding space is formed between the gas jetting means and the web or sheet, to the reversing surface of the web or sheet And a static pressure maintaining plate for generating a static pressure as the surface pressure .
[0010]
According to the present invention, in the reversing unit, a pressing force is generated on the inner surface of the web or the sheet by the gas ejected from the gas ejection means toward the inner surface of the web or the sheet, and the web or the sheet is reversed in this state. Since it did in this way, it prevents that a web or a sheet | seat shrink | contracts in a reversing part and deform | transforms into a drum shape.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a web or sheet conveying method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example in which a web transport apparatus 10 according to the present invention is applied as a transport apparatus for drying while transporting a web formed by a solution casting method.
[0012]
As shown in FIG. 1, a dope (high viscosity solution) is cast from the casting port 12 such as a hopper onto the surface of the rotating drum 14 to form a film-like web 16, and then the web 16 is peeled off by the stripping unit 18. take. The undried web 16 thus peeled off is conveyed through the dryer 20 by the conveying device 10 of the present invention. The conveying device 10 includes a pin implanted on a pin plate 21 (see FIG. 3) supported in a row on a pair of moving chains (not shown) arranged along the conveying direction of the web 16. The web 16 is transported in a state of being stretched in the width direction while being supported by a support member such as a clip. The transport device 10 is a multistage system so as not to take up device space, and has a plurality of reversing sections 22, 22, 22 in the middle of transport. The reversing unit 22 is provided with respective pulleys 24 with which the pair of moving chains are engaged, and the web 16 is reversed in the web conveyance direction in the reversing unit 22.
[0013]
FIG. 2 is a side sectional view showing the reversing unit 22 of the web or sheet conveying apparatus 10 of the present invention, and FIG. 3 is a front view of FIG. FIG. 4 is a perspective view showing a gas ejection duct 26 provided in the reversing unit 22. As shown in these drawings, a semi-doughnut-shaped gas ejection duct 26 is provided inside the reversing portion 22, and the web side surface 26 </ b> A is a reversing surface (approximately 180 ° of the web 16) reversing at the reversing portion 22. It has an area that can cover the entire surface. On the web side surface 26A of the gas ejection duct 26, slits 28 for ejecting air are formed in the width direction of the web 16, and a plurality of slits 28 are formed at predetermined intervals on the web side surface 26A of the duct 26. Established. Further, an auxiliary slit 30 having a shorter slit width than the slit 28 is formed between the slits 28 in the width direction of the web 16. Furthermore, substantially crescent-shaped first static pressure maintaining plates 32 and 32 projecting to the extent that they do not hit the reversing web 16 are disposed on both side edges in the web width direction of the web side surface 26A. On both side edges of the web conveying direction of 26A, second static pressure maintaining plates 34, 34 projecting to the extent that they do not hit the reversing web 16 are disposed. The first and second static pressure maintaining plates 32 and 34 form an enclosed space between the inner side surface of the web 16 and the web side surface 26 </ b> A of the gas ejection duct 26 so that air does not easily flow out. Accordingly, the air ejected from the slits 28 and 30 is less likely to flow out in the width direction and the conveyance direction of the web 16, and thus it is possible to easily maintain the static pressure. This static pressure makes it easy to generate a pressing force due to the surface pressure on the inner surface of the web 16 to be reversed, so that the pressing force at the reversing portion can be applied substantially evenly.
[0014]
In addition, a pressure sensor 36 that detects a pressing force that is the pressure of the air in the enclosed space and a floating amount (a floating position) at which the web 16 floats due to the pressing force are provided at the center of the web side surface 26A of the gas ejection duct 26. ) Is provided. As the flying height sensor 38, a reflection type optical sensor that reflects light on the inner surface of the web 16 can be used. In this case, when the web 16 is transparent and a reflection type optical sensor cannot be used, only the pressure sensor 36 may be used, and an ultrasonic sensor using a sound wave may be used instead of the optical sensor. ,
The detection values detected by the pressure sensor 36 and the flying height sensor 38 are input to the air amount control device 40, and the air amount control device 40 controls the amount of air ejected from the gas ejection duct 26 based on the detection values. To do. The controlled air is sent into the gas ejection duct 26 via the air pipe 41. Thereby, the pressing force with respect to the inner surface of the web 16 is appropriately adjusted so that an appropriate pressing force is applied to the inner surface side of the web 16. That is, from the gas ejection duct 26, an air ejection amount is generated that generates a pressing force that does not cause a drum-like deformation of the web 16 in the reversing portion 22.
[0015]
Here, an appropriate pressing force for preventing the drum 16 from being deformed in a drum shape at the reversing portion 22 will be described.
Basically, the flying height (floating position) of the web 16 of the reversing unit 22 is directly detected by the flying height sensor 38, and the air ejection from the gas ejection duct 26 is performed by the air amount control device 40 based on the detected value. The method of adjusting the pressing force by adjusting the amount is the best. However, if the web 16 cannot be confirmed due to large vibrations of the web 16, or if the web 16 is so transparent that the flying height of the web 16 cannot be detected by the optical sensor, the optical sensor detection unit is further soiled. If the optical sensor cannot be used because it tends to adhere, it is necessary to measure the shrinkage force of the web in the reversing unit 22 in advance from the web conditions (residual solvent, web film thickness, drying temperature, etc.). The pressure can be determined.
[0016]
For example, FIG. 5 shows shrinkage force data in the drying process of cellulose triacetate formed by the solution casting method. From the drying time on the horizontal axis corresponding to the position of the reversing unit 22, the contraction force of the web 16 at this time is read from the contraction force when the length of the vertical axis is constant. The contraction force F of the web 16 per full width is obtained by converting the read contraction force into the web width. In addition, in FIG. 5, the shrinkage force in the case where drying temperature is 30 degreeC and 75-80 degreeC was shown.
[0017]
The gas pressing force P of the reversing unit 22 for balancing with the contraction force F of the web 16 per full width is:
[0018]
[Expression 1]
P = F / WR (1) W: Web width R; P obtained here is an average pressing force in the reversing unit 22.
Actually, the pressing force in the width direction of the web 16 is not uniform, and gas flows out from both side edges of the web, so that the center of the web is high and the side edges are low. Further, the contraction force of the web 16 is not balanced by only the pressing force of the air, but is shared by the supporting members that support both side edges of the web 16 of the clip or pin. Further, the web 16 is continuous in the conveying direction, and the contraction force of the web 16 of the reversing unit 22 is not determined only by the contracting force in the vicinity of the reversing unit 22.
[0019]
Therefore, the pressing force P in the equation (1) needs to be corrected. For this reason, a coefficient K is given.
[0020]
[Expression 2]
P = K F / WR (2)
The value of K can vary depending on various situations (states) of the web 16 in the reversing unit 22. For example, if the web 16 has been dried considerably, the amount of shrinkage itself is small, and a large drum-like deformation does not occur in the reversing portion 22. Accordingly, the influence of the reversing unit 22 on the web at this time is small. That is, the problem of the drum-like deformation in the reversing unit 22 mainly occurs when the residual solvent of the web 16 is relatively large.
[0021]
Based on this point, the range of K was determined by various tests.
[0022]
[Equation 3]
0.4 ≦ K ≦ 2.0 is preferable, and more preferably
[Expression 4]
A range of 0.5 ≦ K ≦ 1.2 is preferable. If P is determined from Equation (2) using this coefficient K, an appropriate pressing force P can be obtained.
In addition, although the value of K was set in the range, since the strictness is required when the web 16 is soft, it is necessary to further narrow the range. This is because the absolute deformation amount is large.
[0024]
According to the web or sheet conveying apparatus 10 configured as described above, the gas ejection duct 26 is provided in the reversing portion 22 provided in the middle of the conveyance of the web 16 and is reversed by the air ejected from the gas ejection duct 26. Since the pressing force is generated on the inner surface of the web 16, it is possible to prevent the web 16 from being deformed into a drum shape at the reversing portion 22. Thereby, when the web 16 is dried, the planarity of the web 16 is not impaired even if a multistage transport device having the reversing unit 22 is used. Further, since the web 16 is supported by air, no surface failure occurs. Therefore, since the conveying apparatus 10 can be configured in a multistage system, the apparatus space can be reduced.
[0025]
In the present embodiment, air is ejected from the gas ejection duct 26, but is not limited to air. For example, in the case of a web that is easily oxidized by air, an inert gas such as nitrogen gas is used. Can be used. In the present embodiment, the air ejection amount is controlled based on the pressure detected by the sensor and the web flying height. However, either one of the sensors may be used, and further, the duct is connected in the direction of arrow 42 in FIG. The distance between the web 16 and the web side surface 26A of the gas ejection duct 26 may be adjusted by advancing and retreating.
[0026]
In this embodiment, air is ejected from the slit 28 and the auxiliary slit 30. However, the auxiliary slit 30 can be omitted, and the slit drilling position and the slit shape can be changed.
[0027]
【Example】
An embodiment in which the web 16 is transported and dried using the web or sheet transport apparatus 10 of the present invention in which the gas ejection duct 26 described above is disposed inside the reversing unit 22 will be described below.
Example 1
In the first embodiment, the flying height sensor 38 detects the flying height (floating position) of the web 16, and the air amount control device 40 adjusts the air ejection amount from the gas ejection duct 26 based on the detected value, and the web This is a case where 16 is not deformed into a drum shape.
[0028]
The conditions of the inversion part are as follows.
Type of web; film thickness of cellulose triacetate web; 150-160 μm
Residual solvent: methylene chloride, methanol, butanol drying conditions: 75 ° C. for 1 min over time (solvent content: 40-50 wt% by weight)
Web width; 1.6m
Inversion part diameter: 1.5m
Pressing force: 20 kg / m ²
Further, as a comparative example, the case of the conventional method in which air is not ejected from the gas ejection duct 26 was performed. The result is shown in FIG. In FIG. 6, h indicates the height (so-called ear tarmi) of both side edges of the web 16 when the web 16 after completion of drying is developed on a plane.
[0029]
As is clear from FIG. 6, in the first embodiment in which the pressing force is generated on the inner surface of the web 16 that is reversed by the air ejected from the gas ejection duct 26, the ear tarmi (h) is 0.2 to 1 mm. there were. On the other hand, in the comparative example in which air is not ejected, the ear tarmi (h) is 2 to 4 mm, and the present invention can greatly improve the flatness of the web 16 as compared with the comparative example. Further, according to the present invention, the web 16 is not broken at the reversing portion 22.
[0030]
As a result, even if a multistage conveying device having a plurality of reversing sections 22 is used, the full width of the web can be commercialized. Further, when the film thickness of the web 16 was 100 μm, in the comparative example in which air was not jetted, the web 16 was broken at the reversing portion 22, but in Example 1 of the present invention, the web 16 could be dried without breakage.
In this way, by continuously detecting the flying height (position) of the web 16 and controlling the pressing force, the product is stable and has good flatness even when the type and conditions of the web 16 are changed. It became possible to get. Furthermore, it is possible to efficiently use a multi-stage transport device, which dramatically improves productivity and enables production of low-cost products.
(Example 2)
Example 2 is a case where the optical sensor cannot be used because the vibration of the web 16 is large, the transparency of the web 16 is large, or dirt is easily attached to the detection part of the optical sensor. This is a case where the contraction force is read and the pressing force P is determined from the equation (2).
[0031]
The conditions of the inversion part are as follows.
Type of web; film thickness of cellulose triacetate web; 130-140 μm
Residual solvent; methylene chloride, methanol, butanol drying conditions; 75 to 80 ° C. for 2 min with time (solvent content; 15 to 25% by weight based on moisture)
Inversion part diameter: 1.5m
Web width; 1.6m
From FIG. 5, when the shrinkage force of the web when the drying time is 2 minutes is read and converted to the full width, F = 40 kg. Using equation (2) and calculating K with K = 0.8,
P = 0.8 × 40 / (1.6 × 0.75)
= 27 (kg / m ² )
From this calculated value, the pressing force was set to 27 kg / m ² (mmAq).
[0032]
Further, as a comparative example, the case where no air was ejected from the gas ejection duct 26 was performed. In the case of Example 2, the flatness of the web, which is the final product, can be greatly improved as compared with the comparative example in which air is not ejected, and the web 16 is not broken at the reversal part 22.
Basically, the best method is to directly detect the flying height (position) of the web of the reversing unit 22 and adjust the gas pressing force. I can substitute it enough. However, the measurement data of the contractile force in advance is essential at this time, and the measurement data is necessary every time the condition changes.
[0033]
【The invention's effect】
As described above, according to the web or sheet conveying method and apparatus of the present invention, in the reversing unit, the gas ejected from the gas ejecting means toward the inner surface of the web or sheet is applied to the inner surface of the web or sheet. Since the pressing force is generated and the web or sheet is reversed in this state, the web or sheet is prevented from being deformed into a drum shape due to the contraction force at the reversing portion.
[0034]
Thus, even when the web is dried by a multistage conveyance method having a plurality of reversing portions, the flatness of the web is not impaired in the reversing portion, and a sheet-like failure does not occur.
Therefore, it is possible to obtain a product that is stable and has good flatness even when the type and conditions of the web are changed. Furthermore, it is possible to efficiently use a multi-stage transport device, which dramatically improves productivity and enables production of low-cost products.
[Brief description of the drawings]
FIG. 1 is a configuration diagram in which a web or sheet conveying apparatus according to the present invention is applied as a conveying apparatus for drying while conveying a web formed by a solution casting method. FIG. 3 is a side sectional view of a reversing part of the web or sheet conveying apparatus of the present invention. FIG. 3 is a front view of FIG. 2 as viewed from the direction A. FIG. FIG. 5 is a graph showing the contraction force of cellulose triacetate formed by the solution casting method. FIG. 6 is a perspective view of a gas ejection duct disposed in the reversing part of the transport device of FIG. FIG. 7 is an explanatory view for explaining the effect of the web or sheet transport method and apparatus according to the present invention. FIG. 7 is an explanatory view for explaining a web support method for a tenter type transport apparatus. FIG. FIG. 9 is a block diagram of a multi-stage transfer device [FIG. 9]. FIG. 10 is a diagram for explaining a state where the web is deformed into a drum shape at the reversing unit. FIG. 11 is a diagram for explaining a conventional measure for preventing the web from being deformed into a drum shape at the reversing unit. FIG. 12 is another explanatory diagram for explaining a conventional measure for preventing the web from being deformed into a drum shape at the reversing portion.
DESCRIPTION OF SYMBOLS 10 ... Conveyance apparatus 12 ... Casting port 14 ... Rotary drum 16 ... Web 20 ... Dryer 22 ... Inversion part 24 ... Pulley 26 ... Gas ejection duct 28 ... Slit 30 ... Auxiliary slit 32 ... 1st static pressure maintenance board 34 ... Second static pressure maintaining plate 36 ... Pressure sensor 38 ... Flying height sensor 40 ... Air amount control device

Claims (5)

When drying a shrinkable web or sheet, the web or sheet is transported in a state where the web or sheet is stretched in the width direction while supporting both side edges in the width direction, In the web or sheet conveyance method for reversing the conveyance direction of the web or sheet,
The reversing unit generates a static pressure by a gas on the inner surface of the web or sheet so as to eliminate the drum-like deformation of the web or sheet due to the contraction force generated in the web or sheet. A method of conveying a web or sheet, wherein the web or sheet is reversed with surface pressure applied to the entire reversal surface of the sheet.   2. The method of transporting a web or sheet according to claim 1, wherein the pressing force by the gas is generated by jetting air onto the inner surface of the web or sheet. The pressing force P by the gas is given by the following formula: P = KF / WR
P: Gas pressure kg / m ²
F: Shrinking force in the traveling direction of the sheet or web kg / full width
W: Full width of sheet or web (direction perpendicular to traveling direction) m
R: radius of reversal part m
The method for conveying a web or sheet according to claim 1 or 2, wherein K is a coefficient, and the coefficient K is in a range of 0.4≤K≤2.0. When drying a shrinkable web or sheet, the web or sheet is supported while supporting both side edges in the width direction, and the web or sheet is stretched in the width direction. In the web or sheet conveying apparatus for reversing the conveying direction of the web or sheet,
A gas jetting means for applying a surface pressure to the entire reversing surface of the web or sheet by jetting a gas to the inner surface of the web or sheet at the reversing portion, and between the gas jetting means and the web or sheet A web or sheet conveying apparatus comprising: a static pressure maintaining plate that forms a surrounding space in the sheet and generates a static pressure as a surface pressure on the reversal surface of the web or sheet.   Providing a flying height detecting means for a web that is levitated by a pressing force generated by the gas ejected from the gas ejecting means, and adjusting an ejection amount of the gas ejected from the gas ejecting means based on the detected amount detected. The web or sheet conveying apparatus according to claim 4.

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