CN110049856B

CN110049856B - Longitudinal stretching device

Info

Publication number: CN110049856B
Application number: CN201780076171.4A
Authority: CN
Inventors: 金岛成光; 青木敦
Original assignee: Toray Engineering Co Ltd
Current assignee: Toray Engineering Co Ltd
Priority date: 2016-10-31
Filing date: 2017-10-05
Publication date: 2022-03-22
Anticipated expiration: 2037-10-05
Also published as: KR20190076016A; CN110049856A; JP2018069639A; WO2018079213A1; JP6622680B2

Abstract

Provided is a longitudinal stretching device capable of suppressing the occurrence of transfer scratches, and the like in a thermoplastic film during longitudinal stretching. Specifically, in a longitudinal stretching device (5) for stretching a thermoplastic film (F) heated by a heating roller (13) by a circumferential speed difference between a plurality of low-speed driving rollers (8) and a plurality of high-speed driving rollers (9), the plurality of low-speed driving rollers (8) and the plurality of high-speed driving rollers (9) are constituted by suction rollers having a plurality of low-speed side suction holes (8b) and high-speed side suction holes (9b) as suction holes on a conveying surface of the thermoplastic film (F), the plurality of heating rollers (13) are provided between the adjacent low-speed driving rollers (8) and high-speed driving rollers (9), the plurality of heating rollers (13) are each provided with a following electric motor (15) as an actuator, the plurality of heating rollers (13) are configured to be capable of independently rotationally driving the plurality of heating rollers (13), and the longitudinal stretching device is controlled so that an output torque of each following electric motor (15) coincides with a target value set for each following electric motor (15) .

Description

Longitudinal stretching device

Technical Field

The invention relates to a longitudinal stretching device. More specifically, the present invention relates to a longitudinal stretching apparatus for heating a thermoplastic film and stretching the thermoplastic film in a conveyance direction.

Background

Thermoplastic films composed of thermoplastic polymers such as polyester, triacetyl cellulose (TAC), polyolefin, and polyamide have been widely used as supports for packaging films, plate-making substrates, printing films, laminated films, magnetic recording media, optical disks, and the like. Such a thermoplastic film such as a polyester resin is known to have excellent physical properties by stretching, and is generally used as a uniaxially stretched film or a biaxially stretched film. The above biaxially stretched film is produced by stretching in the transverse direction after uniaxial stretching in the longitudinal direction. In the case of longitudinally stretching a thermoplastic film, stretching is performed in the flow direction by the speed difference between a low-speed roll on the upstream side and a high-speed roll on the downstream side. In this case, a method is known in which the stretching amount of the film per unit time is reduced by increasing the interval (increasing the pitch) between the low-speed roll on the upstream side and the high-speed roll on the downstream side so as to stably stretch the thermoplastic film without breaking the film. For example, as described in patent document 1.

In the longitudinal stretching device described in patent document 1, a heating furnace is provided between a low-speed roller on the upstream side and a high-speed roller on the downstream side, and a plurality of conveying rollers are provided in the heating furnace. The longitudinal stretching apparatus stretches a thermoplastic film heated by a heating furnace by low-speed rollers and high-speed rollers arranged with an increased pitch, and stretches wrinkles in the longitudinal direction of the film by a plurality of conveying rollers, thereby preventing wrinkling of the film and stably stretching the film. However, the technique described in patent document 1 causes wrinkles to spread by bringing the thermoplastic film into contact with a plurality of conveyance rollers, and therefore resistance during conveyance is large. Therefore, the longitudinal stretching apparatus conveys the thermoplastic film while pressing the thermoplastic film by the nip rollers so that the thermoplastic film does not slip between the high-speed roller and the low-speed roller. Therefore, the thermoplastic film may be scratched by a transfer scratch on the surface due to the pressing force of the nip roller or by sliding with the conveying roller.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2008-221722

Disclosure of Invention

Problems to be solved by the invention

The invention aims to provide a longitudinal stretching device which can prevent the generation of transfer scratches, scratches and the like in a thermoplastic film during longitudinal stretching.

Means for solving the problems

The problems to be solved by the present invention are as described above, and means for solving the problems will be described next.

That is, in a longitudinal stretching device for stretching a thermoplastic film heated by a heating roller by a circumferential speed difference between a plurality of low-speed driving rollers and a plurality of high-speed driving rollers having a circumferential speed greater than that of the low-speed driving rollers, the plurality of low-speed driving rollers and the plurality of high-speed driving rollers are constituted by suction rollers, the suction roller has a plurality of suction holes on a conveying surface of the thermoplastic film, a plurality of heating rollers are provided between the low-speed driving roller and the high-speed driving roller which are adjacent to each other, the plurality of low-speed driving rollers, the plurality of high-speed driving rollers, and the plurality of heating rollers are provided with actuators, respectively, and are configured to be capable of independently rotating and driving the plurality of low-speed driving rollers, the plurality of high-speed driving rollers, and the plurality of heating rollers, respectively, the longitudinal stretching device is controlled so that the output torque of each of the actuators coincides with a target value set for each of the actuators.

In the longitudinal stretching device, the actuators are connected to the plurality of low-speed driving rollers, the plurality of high-speed driving rollers, and the plurality of heating rollers via torque control devices, respectively, and the longitudinal stretching device is configured to: when the difference between the output torque and the target value is larger than a predetermined value, a rotational speed difference is generated between the input shaft and the output shaft of the torque control device so as to maintain the rotational speed of the output shaft of the torque control device connected to the actuator.

In the longitudinal stretching device, the torque control device is constituted by a powder clutch, and a torque transmission amount of the torque control device is controlled in accordance with the target value.

The longitudinal stretching device is configured to be capable of independently controlling the temperatures of the plurality of heating rollers.

Effects of the invention

The following effects are exhibited as the effects of the present invention.

In the longitudinal stretching device, since resistance of the heating roller to the thermoplastic film during conveyance is small, it is not necessary to apply friction by pressing the thermoplastic film with the nip roller between the low-speed driving roller and the high-speed driving roller. Further, no slip is generated between the plurality of heating rollers independently performing drive control and the thermoplastic film. This can suppress the occurrence of transfer scratches, and the like in the thermoplastic film during longitudinal stretching.

In the longitudinal stretching device, when the conveying speed of the thermoplastic film fluctuates, the heating roller rotates following the thermoplastic film regardless of the control of the actuator. This can suppress the occurrence of transfer scratches, and the like in the thermoplastic film during longitudinal stretching.

In the longitudinal stretching apparatus, the rotation speed of the heating roller is controlled according to the conveyance speed and stretching amount of the thermoplastic film. This can suppress the occurrence of transfer scratches, and the like in the thermoplastic film during longitudinal stretching.

In the longitudinal stretching device, since the thermoplastic film is stretched at a predetermined stretching ratio, speed variation is less likely to occur. This can suppress the occurrence of transfer scratches, and the like in the thermoplastic film during longitudinal stretching.

Drawings

Fig. 1 is a schematic diagram showing the overall configuration of one embodiment of a manufacturing apparatus having a longitudinal stretching apparatus.

Fig. 2 is a schematic view showing the overall structure of one embodiment of the longitudinal stretching device.

Fig. 3 is a front view showing the structure of a low-speed driving roller and a high-speed driving roller of one embodiment of the longitudinal stretching device.

FIG. 4 is a front view showing the structure of a heating roller and a cooling roller of one embodiment of the longitudinal stretching apparatus.

Fig. 5 is a block diagram showing a control structure of one embodiment of the longitudinal stretching device.

Fig. 6 is a schematic diagram showing an operation mode under the slip suppression control of the heating roller in one embodiment of the longitudinal stretching device.

Fig. 7 is a diagram showing a graph showing a variation in driving torque under the slip suppression control of the heating roller in one embodiment of the longitudinal stretching apparatus.

Detailed Description

First, a manufacturing apparatus 1 including a longitudinal stretching apparatus 5 as an embodiment of the longitudinal stretching apparatus of the present invention will be described with reference to fig. 1. The production apparatus 1 produces a thermoplastic film F made of a thermoplastic polymer such as polyester, triacetyl cellulose (TAC), polyolefin, or polyamide, and in the present embodiment, a case of producing the thermoplastic film F made of triacetyl cellulose (TAC) will be described.

As shown in fig. 1, the manufacturing apparatus 1 processes a thermoplastic polymer made of triacetyl cellulose (TAC) to manufacture a thermoplastic film F having a desired film thickness. The manufacturing apparatus 1 includes: a melt extrusion device 2, a slot die 3, a casting roll 4, a longitudinal stretching device 5, a transverse stretching device 6 and a coiling device 7.

The manufacturing apparatus 1 heats and melts a thermoplastic polymer in a sheet form by a melt extrusion apparatus 2 and extrudes the molten polymer from a slit die 3. The manufacturing apparatus 1 causes the thermoplastic polymer continuously extruded from the slot die 3 to adhere to the casting roll 4 and harden into a sheet shape. That is, the manufacturing apparatus 1 forms the unstretched thermoplastic film F from the sheet-like thermoplastic polymer. The manufacturing apparatus 1 continuously stretches the continuously formed unstretched thermoplastic film F in the conveyance direction (longitudinal direction) by the longitudinal stretching device 5 to form the longitudinally stretched thermoplastic film F. Next, the manufacturing apparatus 1 continuously stretches the thermoplastic film F in the width direction (transverse direction) by the transverse stretching apparatus 6 to form a biaxially stretched thermoplastic film F. The manufacturing apparatus 1 winds the formed thermoplastic film F around a core material by a winding apparatus 7.

With this configuration, the manufacturing apparatus 1 can continuously form the thermoplastic film F biaxially stretched in the longitudinal direction and the transverse direction from the sheet-like thermoplastic polymer.

Hereinafter, a longitudinal stretching apparatus 5 as an embodiment of the longitudinal stretching apparatus of the present invention will be described with reference to fig. 2 to 5. The longitudinal stretching device 5 stretches the unstretched thermoplastic film F in the conveyance direction (hereinafter referred to as the "longitudinal direction"). The longitudinal stretching device 5 has: a plurality of low-speed driving rollers 8, a plurality of high-speed driving rollers 9, a suction pump 10, a low-speed electric motor 11, a high-speed electric motor 12, a plurality of heating rollers 13, a plurality of cooling rollers 14, a plurality of follow-up electric motors 15, a plurality of powder clutches 16, and a control device 17.

As shown in fig. 2, the low-speed driving roller 8 stretches the unstretched thermoplastic film F in the longitudinal direction together with the high-speed driving roller 9. The low-speed drive roller 8 is disposed on the most upstream side of the longitudinal stretching device 5. In the present embodiment, a plurality of low-speed drive rollers 8 are disposed in the longitudinal stretching device 5. The low-speed drive roller 8 is a metal roller, and is subjected to surface treatment such as hard chrome plating, tungsten carbide spray, fluororesin coating, or ceramic coating. The low-speed driving roller 8 is arranged to wind the thermoplastic film F around the low-speed driving roller 8 at a predetermined wrap angle.

As shown in fig. 3, a plurality of holes penetrating into the low-speed side conveying surface 8a, which is a surface (hereinafter, simply referred to as "conveying surface") of the low-speed driving roller 8 that comes into contact with the thermoplastic film F, are formed. The low-speed drive roller 8 is configured to suck the inside of the roller by a suction pump 10 (see a light ink portion in fig. 2). Thus, the low-speed driving roller 8 is configured to be able to suction-hold the thermoplastic film F by functioning the holes of the low-speed side conveying surface 8a as the low-speed side suction holes 8 b.

As shown in fig. 2, the high-speed driving roller 9 stretches the unstretched thermoplastic film F in the longitudinal direction together with the low-speed driving roller 8. The high-speed drive roller 9 is disposed on the most downstream side of the longitudinal stretching device 5. In the present embodiment, a plurality of high-speed driving rollers 9 are disposed in the longitudinal stretching device 5. The high-speed drive roller 9 is a metal roller, and is subjected to surface treatment such as hard chrome plating, tungsten carbide spray, fluororesin coating, or ceramic coating. The high-speed driving roller 9 is arranged to wind the thermoplastic film F around the high-speed driving roller 9 at a predetermined wrap angle.

As shown in fig. 3, the high-speed driving roller 9 has a plurality of holes formed in a high-speed side conveying surface 9a that contacts the thermoplastic film F and penetrates into the roller. The plurality of high-speed driving rollers 9 are configured to suck the inside of the roller by a suction pump 10 (see a light ink portion in fig. 2). Thus, the plurality of high-speed driving rollers 9 are configured to be able to suction-hold the thermoplastic film F by functioning the holes of the high-speed side conveying surface 9a as the high-speed side suction holes 9 b.

The low-speed electric motor 11 and the high-speed electric motor 12 as actuators rotate and drive the plurality of low-speed driving rollers 8 and the plurality of high-speed driving rollers 9, respectively. The low-speed electric motor 11 and the high-speed electric motor 12 are connected to a vector inverter included in a control device 17 (see fig. 5), and are configured to independently perform torque control. The low-speed electric motor 11 is provided to each low-speed drive roller 8 via a powder clutch 16 as a torque control device, and the high-speed electric motor 12 is provided to each high-speed drive roller 9 via the powder clutch 16. That is, the plurality of low-speed electric motors 11 can independently control the driving of the low-speed drive rollers 8 connected thereto. Similarly, the plurality of high-speed electric motors 12 can independently control the driving of the plurality of low-speed drive rollers 8 connected thereto.

The high-speed drive rollers 9 perform traction control on the low-speed drive rollers 8. That is, the high-speed drive rollers 9 are driven so as to have a greater circumferential speed than the low-speed drive rollers 8. The thermoplastic film F is unwound from the upstream side by the plurality of low-speed drive rollers 8 at a predetermined unit unwinding speed, and is unwound toward the downstream side by the plurality of high-speed drive rollers 9 at a predetermined unit unwinding speed greater than the unwinding speed of the low-speed drive rollers 8. Thus, the plurality of low-speed driving rollers 8 and the plurality of high-speed driving rollers 9 are configured to stretch the thermoplastic film F at a distance therebetween by a difference between a unit take-up amount based on a predetermined take-out speed and a unit take-in amount based on a predetermined take-in speed.

As shown in fig. 2, the heating roller 13 heats the thermoplastic film F. The hot roller 13 is disposed between the low-speed drive roller 8 on the most downstream side and the high-speed drive roller 9 on the most upstream side. In the present embodiment, a plurality of heating rollers 13 are disposed in the longitudinal stretching device 5. The heating roller 13 is a metal roller, and is subjected to surface treatment such as hard chrome plating, tungsten carbide spray, fluororesin coating, or ceramic coating. The heating roller 13 is arranged to wind the thermoplastic film F around the heating roller 13 at a predetermined wrap angle.

As shown in fig. 4, each of the heating rollers 13 is provided with: a cartridge heater 13b as a heating unit; and a heating temperature sensor 13c that is temperature measuring means for measuring the temperature of the heating and conveying surface 13a of the heating roller 13 that is in contact with the thermoplastic film F. The cartridge heater 13b and the heating temperature sensor 13c provided in each of the hot rollers 13 are configured to independently heat and maintain the heating conveyance surface 13a of the hot roller 13 to a predetermined temperature by a control signal from the control device 17 (see fig. 5). In the present embodiment, the heating means of the hot roller 13 is the cartridge heater 13b, but the present invention is not limited to this, and may be a heating device, an induction heating device, or the like, based on circulation of a heat medium such as hot water, pressurized hot water, heating oil, or the like.

As shown in fig. 2, the cooling roll 14 cools the thermoplastic film F. The cooling roller 14 is disposed between the hot roller 13 on the most downstream side and the high-speed drive roller 9 on the most upstream side. In the present embodiment, a plurality of cooling rolls 14 are disposed in the longitudinal stretching device 5. The cooling roll 14 is a metal roll, and is subjected to surface treatment such as hard chrome plating, tungsten carbide spray coating, fluororesin coating, or ceramic coating. The cooling rolls 14 are arranged to wind the thermoplastic film F around the respective cooling rolls 14 at a predetermined wrap angle.

As shown in fig. 4, the plurality of cooling rolls 14 are respectively provided with: heat transfer pipe 14b as a cooling means; and a cooling temperature sensor 14c that is a temperature measuring means for measuring the cooling conveyance surface 14a of the cooling roller 14 that is in contact with the thermoplastic film F. The heat transfer pipe 14b and the cooling temperature sensor 14c provided in the plurality of cooling rollers 14 are configured to independently cool the cooling conveyance surface 14a of each cooling roller 14 by a control signal from the control device 17 (see fig. 5). In the present embodiment, the cooling means of the cooling roller 14 is the heat transfer pipe 14b, but the present invention is not limited to this, and may be a cooling device or the like based on circulation of a piezoelectric element or a heat medium.

The electric motor 15 for follow-up as an actuator rotationally drives the heating roller 13 and the cooling roller 14. The electric follow-up motors 15 are provided on the heating rollers 13 and the cooling rollers 14, respectively, via powder clutches 16 as torque control devices. The tracking electric motors 15 are connected to vector inverters included in the control device 17 (see fig. 5) and are configured to perform torque control independently. That is, the plurality of tracking electric motors 15 are configured to be able to independently drive and control the heating roller 13 or the cooling roller 14 connected thereto.

As shown in fig. 3 and 4, the plurality of powder clutches 16 as torque control devices limit the transmission torque between the low-speed drive roller 8 and the low-speed electric motor 11, the transmission torque between the high-speed drive roller 9 and the high-speed electric motor 12, the transmission torque between the heating roller 13 and the follow-up electric motor 15, or the transmission torque between the cooling roller 14 and the follow-up electric motor 15. The powder clutch 16 is switched to a state in which torque is transmitted between the input shaft 16a and the output shaft 16b by applying magnetic flux to magnetic iron powder (powder) interposed between the input shaft 16a and the output shaft 16b to generate friction. In the present embodiment, each of the powder clutches 16 has an input shaft 16a to which one of a plurality of low-speed electric motors 11, a plurality of high-speed electric motors 12, or a plurality of follow-up electric motors 15 is connected, and an output shaft 16b to which one of a plurality of low-speed drive rollers 8, a plurality of high-speed drive rollers 9, a plurality of heating rollers 13, or a plurality of cooling rollers 14 is connected. That is, each powder clutch 16 is configured to be able to arbitrarily set a transmission torque between the low-speed drive roller 8 and the low-speed electric motor 11, a transmission torque between the high-speed drive roller 9 and the high-speed electric motor 12, a transmission torque between the heating roller 13 and the follow-up electric motor 15, or a transmission torque between the cooling roller 14 and the follow-up electric motor 15. Each powder clutch 16 is connected to a control device 17 (see fig. 5), and is configured to be able to control the magnitude of the transmission torque independently of each other.

As shown in fig. 5, the control device 17 controls the longitudinal stretching device 5. The control device 17 may be substantially configured by connecting a CPU, a ROM, a RAM, an HDD, and the like with a bus, or may be configured by a monolithic LSI or the like. The control device 17 is connected to a control device of the manufacturing apparatus 1, not shown, and stores various programs and data for controlling the longitudinal stretching device 5 and the like.

The controller 17 is connected to the low-speed electric motor 11 of each low-speed drive roller 8 and the high-speed electric motor 12 of each high-speed drive roller 9, and controls the low-speed electric motors 11 and the high-speed electric motors 12 to output an arbitrary drive torque Td by transmitting a command value related to the drive torque to each of the low-speed electric motors 11 and the high-speed electric motors 12. The controller 17 can obtain actual drive torques from the low-speed electric motors 11 and the high-speed electric motors 12.

The control device 17 is connected to the suction pump 10 and can control the suction pump 10.

The controller 17 needs to be connected to the cartridge heaters 13b and the heating temperature sensors 13c provided in the heating rollers 13, and acquire the actual temperatures of the corresponding heating rollers 13 from the heating temperature sensors 13 c. The control device 17 can control the cartridge heaters 13b so as to transmit a temperature command value and maintain a predetermined temperature.

The controller 17 needs to be connected to each cooling temperature sensor 14c provided in each cooling roll 14, and acquire the actual temperature of the corresponding cooling roll 14 from each cooling temperature sensor 14 c.

The control device 17 is connected to the tracking electric motors 15 of the heating rollers 13 and the tracking electric motors 15 of the cooling drive rollers, and can perform control so as to output an arbitrary drive torque Td by transmitting a command value relating to the drive torque to each of the tracking electric motors 15. The controller 17 can acquire the actual drive torque from each of the tracking electric motors 15.

The controller 17 is connected to each powder clutch 16, and can control a state in which a command value for an arbitrary transmission torque is transmitted to transmit torque between the input shaft 16a and the output shaft 16b at or below the arbitrary transmission torque.

The longitudinal stretching device 5 configured as described above winds out the thermoplastic film F in a predetermined unit feeding amount while holding the thermoplastic film F by suction by the plurality of low-speed driving rollers 8. The longitudinal stretching device 5 heats the thermoplastic film F wound off from the low-speed driving roller 8 to a predetermined temperature by a plurality of heating rollers 13. On the other hand, the longitudinal stretching device 5 winds the thermoplastic film F by a predetermined unit winding amount while holding the thermoplastic film F heated by the heating roller 13 by suction by the plurality of high-speed driving rollers 9. Thus, the longitudinal stretching device 5 longitudinally stretches the heated thermoplastic film F by the difference between the unit take-up amount based on the predetermined take-up speed and the unit take-in amount based on the predetermined take-in speed. The longitudinal stretching device 5 cools the thermoplastic film F to a predetermined temperature by the plurality of cooling rollers 14. The longitudinal stretching device 5 stretches the thermoplastic film F by expanding the interval between the plurality of low-speed driving rollers 8 and the plurality of high-speed driving rollers 9, so that the amount of elongation per unit time of the thermoplastic film F can be reduced, and the load on the film during stretching can be reduced. In the present embodiment, the actuator is configured by an electric motor including the low-speed electric motor 11, the high-speed electric motor 12, and the follow-up electric motor 15, but the actuator is not limited to this and may be any drive device.

Hereinafter, a method of holding the thermoplastic film F by the plurality of low-speed driving rollers 8 and the plurality of high-speed driving rollers 9, and a method of stretching the thermoplastic film F by the low-speed driving rollers 8, the plurality of high-speed driving rollers 9, the plurality of heating rollers 13, and the plurality of cooling rollers 14 will be described with reference to fig. 3, 6, and 7. In the present embodiment, the longitudinal stretching device 5 includes four low-speed driving rollers 8, three high-speed driving rollers 9, four heating rollers 13, and four cooling rollers 14, but is not limited thereto.

As shown in fig. 3, the plurality of low-speed driving rollers 8 of the longitudinal stretching device 5 according to the present embodiment suction-hold the thermoplastic film F wound around each low-speed side conveyance surface 8a at a predetermined wrap angle through the holes formed in the entire conveyance surface. That is, each low-speed driving roller 8 sucks and holds the entire surface of the thermoplastic film F that is in contact with the low-speed side conveyance surface 8 a. Therefore, each low-speed driving roller 8 can hold the thermoplastic film F with a smaller pressure than in the case of pressing and holding by the nip roller. Further, each low-speed driving roller 8 presses the thermoplastic film F to the low-speed side conveyance surface 8a by air as a gas. Therefore, the low-speed driving rollers 8 can hold the thermoplastic film F with a uniform pressure, as compared with the case of pressing and holding by the nip roller as a solid. That is, each low-speed driving roller 8 is less likely to generate local pressure concentration on the thermoplastic film F. Thus, the low-speed driving roller 8 according to the present embodiment can prevent the occurrence of transfer scratches on the surface of the thermoplastic film F by suction-holding the thermoplastic film F. The same applies to the plurality of high-speed driving rollers 9.

Next, with reference to fig. 4, 6, and 7, slip suppression control in the plurality of low-speed drive rollers 8, the plurality of high-speed drive rollers 9, the plurality of hot rollers 13, and the plurality of cooling rollers 14 will be described. In the present embodiment, the slip suppression control in the hot roller 13 is explained, and the explanation of the plurality of low-speed drive rollers 8, the plurality of high-speed drive rollers 9, and the plurality of cooling rollers 14 that perform the same control is omitted.

As shown in fig. 6, each of the heating rollers 13 of the longitudinal stretching apparatus 5 in the present embodiment winds the thermoplastic film F around each of the heated conveyance surfaces 13a at a predetermined wrap angle. The plurality of heating rollers 13 are rotationally driven by a follow-up electric motor 15 (see fig. 4) connected thereto so as to follow the thermoplastic film F. That is, the heating roller 13 is controlled in synchronization with the conveyance speed Vt of the thermoplastic film F. The thermoplastic film F is stretched in the longitudinal direction and conveyed while increasing the conveyance speed Vt from a predetermined take-out speed of the low-speed drive roller 8 to a predetermined take-in speed of the high-speed drive roller 9. Therefore, the conveying speed Vt of the thermoplastic film F differs depending on the conveying path position. Therefore, the plurality of heating rollers 13 are configured such that the rotation speed Vr (circumferential speed) is independently controlled so as to be able to follow the conveyance speed Vt of the thermoplastic film F which differs for each arrangement.

As shown in fig. 4, the transmission torque between the plurality of heating rollers 13 and the electric follow-up motor 15 connected via the respective powder clutches 16 (see fig. 4) is limited. In each powder clutch 16, a drive torque Td of the tracking electric motor 15 is transmitted to the input shaft 16a, and a rotation torque Tr necessary for rotating the heating roller 13 at a predetermined speed is transmitted to the output shaft 16 b. In the powder clutch 16, when a difference of a predetermined value Tg or more is generated between the driving torque Td transmitted to the input shaft 16a and the rotational torque Tr transmitted to the output shaft 16b, the input shaft 16a and the output shaft 16b are displaced, and a rotational speed difference is generated between the input shaft 16a and the output shaft 16 b.

One of the heating rollers 13 disposed at an arbitrary position among the plurality of heating rollers 13 is rotationally driven by the tracking electric motor 15 so that a circumferential speed determined based on the rotation speed Vr thereof coincides with the conveyance speed Vt of the thermoplastic film F. When the conveyance speed Vt of the thermoplastic film F is the reference conveyance speed Vt0, the tracking electric motor 15 controls the drive torque Td required to match the circumferential speed determined according to the rotation speed Vr of the one heating roller 13 with the conveyance speed Vt of the thermoplastic film F as the reference drive torque Td 0.

As shown in fig. 6 (a), the conveyance speed Vt of the thermoplastic film F is the reference conveyance speed Vt0, and when the conveyance speed Vt matches the circumferential speed determined from the rotation speed Vr of one heating roller 13, the rotation speed Vr of the heating roller 13 is not affected by the conveyed thermoplastic film F.

As shown in fig. 7, during a time t1 until the thermoplastic film F is conveyed at a conveyance speed Vt0, the drive torque Td transmitted to the input shaft 16a and the output shaft 16b of the powder clutch 16 and the rotation torque Tr transmitted to the output shaft 16b become the reference drive torque Td0, respectively. That is, since a difference of the predetermined value Tg or more does not occur between the input shaft 16a and the output shaft 16b of the powder clutch 16, the input shaft 16a and the output shaft 16b do not deviate, and the respective shafts rotate at the same rotation speed Vr (see fig. 6 (a)). As a result, the heating roller 13 rotates following the conveyed thermoplastic film F, and thus the occurrence of slippage between the thermoplastic film F and the conveyance surface of the heating roller 13 can be suppressed.

As shown in fig. 6 (b), in the case where the conveyance speed Vt of the thermoplastic film F is greater than the reference conveyance speed Vt0 and reaches a conveyance speed Vt1 greater than the circumferential speed determined based on the rotation speed Vr of the one heating roller 13 in the one heating roller 13, the external force Fr1 is applied to the thermoplastic film F in the direction to increase the rotation speed Vr of the heating roller 13. As a result, the rotation torque Tr transmitted to the output shaft 16b of the powder clutch 16 varies in the output shaft 16 b. In the powder clutch 16, when a difference of a predetermined value Tg or more is generated between the drive torque Td transmitted to the input shaft 16a and the rotation torque Tr transmitted to the output shaft 16b of the powder clutch 16, the phases of the input shaft 16a and the output shaft 16b are shifted, and a rotation speed difference is generated between the input shaft 16a and the output shaft 16 b. That is, the rotation speed Vr (circumferential speed) of the one heating roller 13 is increased by the external force Fr1 from the thermoplastic film F to the rotation speed Vr1 that is the circumferential speed matching the conveyance speed Vt1 of the thermoplastic film F. As a result, although the conveyance speed Vt of the thermoplastic film F increases, the one heating roller 13 follows the thermoplastic film F by the external force Fr1 and the rotation speed Vr increases, so that the occurrence of slippage between the thermoplastic film F and the conveyance surface of the one heating roller 13 can be suppressed.

As shown in fig. 7, regarding the driving torque Td of one of the follow-up electric motors 15 that rotationally drives one of the heating rollers 13, the driving torque Td is reduced to the driving torque Td1 between time t1 and time t2 due to the external force Fr1 from the thermoplastic film F acting in a direction that assists the rotation of the one of the heating rollers 13. When the control device 17 detects that the drive torque Td of one of the follow-up electric motors 15 decreases, the control device performs control so as to increase the drive torque Td1 of the decreased one of the follow-up electric motors 15. That is, the control device 17 controls the drive torque Td so that the rotation speed Vr of the one heating roller 13 reaches the rotation speed Vr1 (see fig. 6 (b)). Thus, the heating roller 13 rotates to follow the conveyance speed Vt of the thermoplastic film F.

As shown in fig. 6 (c), when the conveyance speed Vt of the thermoplastic film F reaches a conveyance speed Vt2 that is lower than the circumferential speed determined based on the rotation speed Vr of the one heat roller 13 in the one heat roller 13, an external force Fr2 is applied to the thermoplastic film F in a direction to reduce the rotation speed Vr of the heat roller 13, and the rotation torque Tr transmitted to the output shaft 16b of the powder clutch 16 is varied. When a difference of a predetermined value Tg or more is generated between the drive torque Td transmitted to the input shaft 16a of the powder clutch 16 and the rotation torque Tr transmitted to the output shaft 16b of the powder clutch 16, the powder clutch 16 causes a phase shift between the input shaft 16a and the output shaft 16b, and a rotation speed difference is generated between the input shaft 16a and the output shaft 16 b. That is, the one heating roller 13 reduces the rotation speed Vr (circumferential speed) to the rotation speed Vr2 that is the circumferential speed matching the conveyance speed Vt2 of the thermoplastic film F by the external force Fr2 from the thermoplastic film F. As a result, although the conveyance speed Vt of the thermoplastic film F is reduced, the rotation speed Vr of the one heating roller 13 is reduced by the external force Fr2 following the thermoplastic film F, and thus the occurrence of slippage between the thermoplastic film F and the conveyance surface of the one heating roller 13 can be suppressed.

As shown in fig. 7, regarding the driving torque Td of the one follow-up electric motor 15 that rotationally drives the one heating roller 13, the driving torque Td increases to the driving torque Td2 between time t3 and time t4 due to the external force Fr2 from the thermoplastic film F acting in a direction that hinders the rotation of the one heating roller 13. When the control device 17 detects that the drive torque Td of one of the follow-up electric motors 15 increases, the control device performs control so as to decrease the increased drive torque Td2 of the one of the follow-up electric motors 15. That is, the control device 17 controls the rotation speed Vr of the one heating roller 13 to be the rotation speed Vr 2. Thus, the heating roller 13 rotates to follow the conveyance speed Vt of the thermoplastic film F.

With this configuration, the longitudinal stretching device 5 stretches the thermoplastic film F at a predetermined stretching ratio, and thus the speed variation is not easily generated. Further, since the longitudinal stretching device 5 is controlled so that the plurality of heating rollers 13 and the plurality of cooling rollers 14 actively follow the thermoplastic film F, the resistance of the heating rollers 13 and the cooling rollers 14 at the time of conveyance of the thermoplastic film F is small. Therefore, the longitudinal stretching device 5 does not need to apply a frictional force for suppressing the slip by pressing the thermoplastic film F with the nip roller in the low-speed driving roller 8 and the high-speed driving roller 9. The longitudinal stretching device 5 controls the torque of the rotation speed Vr of the plurality of heating rollers 13 and the plurality of cooling rollers 14 independently from the conveyance speed Vt of the thermoplastic film F. When the conveyance speed Vt of the thermoplastic film F varies, the heating roller 13 or the cooling roller 14 is rotated following the thermoplastic film F by the action of the powder clutch 16 regardless of the control of the electric motor 15 for following. Therefore, the longitudinal stretching device 5 does not generate slip between the heating roller 13 and the thermoplastic film F. This can suppress the occurrence of transfer scratches, and the like in the thermoplastic film F during longitudinal stretching.

As described above, the longitudinal stretching device 5 in the present embodiment uses the powder clutch 16 as a clutch, but is not limited thereto as long as the transmission torque can be controlled to an arbitrary value. The longitudinal stretching device 5 alternately heats the thermoplastic film F one surface at a time by bringing the thermoplastic film F into contact with the heating conveyance surface 13a of the heating roller 13, but is not limited to this, and the thermoplastic film F may be heated from both surfaces at the same time by heating of a closed air heating nozzle. The above-described embodiments are merely representative embodiments, and various modifications can be made without departing from the scope of the present invention. It is needless to say that the present invention can be implemented in various embodiments, and the scope of the present invention is shown by the description of the claims, and includes all modifications within the equivalent meaning and scope of the claims.

Description of the reference symbols

5: a longitudinal stretching device; 8: a low-speed drive roller; 9: a high-speed drive roller; 13: a heating roller; 8 a: a low-speed side conveying surface; 8 b: a low speed side suction hole; 9 a: a low-speed side conveying surface; 9 b: a high-speed side conveying surface; 15: an electric motor for tracking.

Claims

1. A longitudinal stretching device for stretching a thermoplastic film heated by a heating roller by a circumferential speed difference between a plurality of low-speed driving rollers and a plurality of high-speed driving rollers having a circumferential speed greater than that of the low-speed driving rollers,

the plurality of low-speed driving rollers and the plurality of high-speed driving rollers are suction rollers having a plurality of suction holes on a conveying surface of the thermoplastic film,

a plurality of heating rollers for heating the thermoplastic film are provided between the low-speed driving roller and the high-speed driving roller which are adjacent to each other,

the plurality of low-speed driving rollers, the plurality of high-speed driving rollers, and the plurality of heating rollers are provided with actuators, respectively, and are configured to be capable of independently rotating and driving the plurality of low-speed driving rollers, the plurality of high-speed driving rollers, and the plurality of heating rollers, respectively,

the longitudinal stretching means is controlled so that the output torque of each of the actuators coincides with a target value set for each of the actuators,

the actuators are connected to the low-speed drive rollers, the high-speed drive rollers, and the heating rollers via torque control devices, respectively,

the longitudinal stretching device is configured to: when the difference between the output torque and the target value is smaller than the predetermined value, the input shaft and the output shaft of the torque control device connected to the actuator are not offset, and the rotational speed difference is not generated between the input shaft and the output shaft of the torque control device connected to the actuator.

2. The longitudinal stretching device of claim 1,

the torque control device is constituted by a powder clutch, and the torque transmission amount of the torque control device is controlled in accordance with the target value.

3. The longitudinal stretching device of claim 1 or 2,

the plurality of heating rollers are configured to be capable of independently controlling temperature.