JP4290087B2 - Tension control device for plastic film - Google Patents

Description

  The present invention relates to a plastic film tension control device.

  In a bag making machine that manufactures a plastic bag with a plastic film, a dancer roller is normally engaged with the plastic film in a plastic film feeding path, and a pressure is applied to the dancer roller, and tension is applied to the plastic film. On the upstream side and downstream side of the dancer roller, the plastic film is engaged with the first and second feed rollers, the first and second feed rollers are rotated by the drive motor, and the plastic film is intermittently fed with different patterns, It may be absorbed by the dancer roller.

  For example, recently the applicant has developed a specially configured bag making machine. The bag making machine is what is called a double speed bag making machine. In the double speed bag making machine, the plastic film engages with the first feed roller on the upstream side of the dancer roller, the first feed roller is rotated by the drive motor, and the unit length of the plastic film is N times the size of the plastic bag. With this, it is sent intermittently at a fixed number of cycles. Then, for each intermittent feed, the plastic film is heat-sealed so that N times as many plastic bags are obtained. Further, on the downstream side of the dancer roller, the plastic film is engaged with the second feed roller, the second feed roller is rotated by the drive motor, and the plastic film has the first feed length with a unit feed length corresponding to the size of the plastic bag. It is sent intermittently at N times the number of rollers. For each intermittent feed, the plastic film is cut by a cutter, and a plastic bag is manufactured. Here, N is an integer of 2 or more. The number of cycles is the number of times the plastic film is sent per unit time.

  Therefore, regarding the plastic film of the double speed bag making machine, the feeding pattern is completely different between the upstream side and the downstream side of the dancer roller. And it is the dancer roller that absorbs it. When the plastic film is fed by the first feed roller on the upstream side of the dancer roller, the dancer roller moves thereby, and the plastic film is temporarily stored. Further, when the plastic film is fed by the second feed roller on the downstream side of the dancer roller, the dancer roller moves each time and the storage film is supplied.

  As a result, the speed of the bag making machine can be greatly increased, which is why it is called a double speed bag making machine, but the problem is the tension of the plastic film. In order to significantly increase the speed of the bag making machine, it is necessary to send the plastic film intermittently at a high speed on the upstream side and downstream side of the dancer roller. The dancer roller moves abruptly, which causes the tension to fluctuate. For this reason, the plastic film expands and contracts due to tension, and its unit feed length changes, which affects the quality of the plastic bag. When there is a printed pattern on a plastic film, the printed pattern may be displaced due to tension. Therefore, there is a strong demand for countermeasures.

  On the other hand, several tension-related devices have been proposed so far, but those of the feedback control system are common. An example is described in Japanese Patent Application Laid-Open No. 61-37653 (Patent Document 1). In the apparatus of the publication, a dancer roller is supported by a gear jack and a spring. Further, the drive motor is connected to the gear jack, the tension is detected by the detection device, and the drive motor is feedback-controlled by the control device based on the signal of the detection device to drive the gear jack.

  However, in the feedback control system, as the double speed bag making machine, when the dancer roller moves suddenly, it cannot accurately follow it, and the tension cannot be kept constant.

Therefore, the present invention fundamentally improves the tension control device for the plastic film so that the tension can be kept constant even when the dancer roller moves rapidly like a double speed bag making machine. It was made for the purpose.
JP-A-61-37653

According to the present invention, a dancer roller that engages the plastic film in a plastic film feed path that is intermittently fed with a predetermined feed pattern;
A support mechanism comprising an arm fixed to a rotating shaft, and supporting the dancer roller on the arm;
A tension applying servo motor that is coupled to the support mechanism, transmits torque to the support mechanism, applies pressure to the dancer roller, and applies tension to the plastic film;
Connected to the tension applying servo motor, sets the tension based on the input signal from the operator, calculates the appropriate torque of the tension applying servo motor in advance based on the set tension, and calculates the torque applied to the tension applying servo motor. There is provided a plastic film tension control device comprising a computer that controls torque to be generated, feedforward-controls according to the feed pattern, and maintains a constant tension of the plastic film .

  Further, a correction coefficient for the movement position of the dancer roller is calculated in advance in the calculation unit of the computer, and an appropriate torque of the tension applying servo motor is calculated in advance based on the calculation data. Then, the tension applying servomotor is torque-controlled so as to generate a calculation torque, and feedforward controlled.

  Further, in a preferred embodiment, the plastic film engages the first and second feed rollers upstream and downstream of the dancer roller. Further, the first and second feed servo motors are coupled to the first and second feed rollers, the computer is connected to the first and second feed servo motors, and the first and second feed servo motors cause the first and second feed servo motors to be connected. When the feed roller rotates and the plastic film is intermittently fed with different patterns, and the first and second feed rollers are accelerated and decelerated, the correction torque is added to the calculated torque, and the tension applying servo motor is added to the total torque The torque is controlled so as to be generated, and feedforward control is performed.

  Examples of the present invention will be described below.

  FIG. 1 shows an apparatus according to the present invention. This device is a tension control device for the plastic film 1 and has a dancer roller 2. And the plastic film 1 is intermittently sent with a predetermined pattern. The feeding direction is the length direction of the plastic film 1. Further, in the feeding path of the plastic film 1, the dancer roller 2 is supported by the support mechanism, and the dancer roller 2 is engaged with the plastic film 1. Further, a tension applying servo motor 3 is connected to the support mechanism, torque is transmitted to the support mechanism, pressure is applied to the dancer roller 2, and tension is applied to the plastic film 1.

  In this embodiment, as shown in FIG. 3, the support mechanism includes an arm 5 fixed to the rotating shaft 4. The armer 5 supports the dancer roller 2, and the tension applying servo motor 3 is directly connected to the rotating shaft 4. Therefore, the rotary shaft 4 is rotated by the tension applying servo motor 3 and the arm 5 is swung. The rotating shaft 4 extends in the width direction of the plastic film 1, and the arm 5 swings around the rotating shaft 5. Between the pair of guide rollers 6 and 7, the dancer roller 2 faces the plastic film 1 and engages with the upper surface thereof. Further, torque is transmitted to the rotating shaft 4, pressure is applied to the dancer roller 2, and tension is applied to the plastic film 1.

  Further, in this apparatus, the computer 8 is connected to the tension applying servomotor 3, and the tension applying servomotor 3 is feedforward controlled according to the feed pattern of the plastic film 1. Details thereof will be described later.

  This device is an accessory device of the bag making machine. Therefore, as shown in FIG. 2, the plastic bag 9 is manufactured by the plastic film 1. Further, the bag making machine is a double speed bag making machine. In the double speed bag making machine, the plastic film 1 is engaged with the first and second feed rollers 10 and 11 on the upstream side and the downstream side of the dancer roller 2. Further, in this embodiment, the first and second feed servo motors 12 and 13 are connected to the first and second feed rollers 10 and 11, and the computer 8 is connected to the first and second feed servo motors 12 and 13. The first and second feed servo motors 12 and 13 rotate the first and second feed rollers 10 and 11, and the plastic film 1 is intermittently fed with different patterns. The details are as follows.

  First, on the upstream side of the dancer roller 2, the first feed roller 10 is rotated by the first feed servo motor 12, and the plastic film 1 is intermittent at a constant cycle number with a unit feed length N times the size of the plastic bag 9. Sent. Each time the plastic film 1 is intermittently fed, the plastic film 1 is heat-sealed so that N times as many plastic bags 9 are obtained. Further, on the downstream side of the dancer roller 2, the second feed roller 11 is rotated by the second feed servomotor 13, and the plastic film 1 has a unit feed length corresponding to the size of the plastic bag 9 and the N of the first feed roller 10. It is sent intermittently at twice the number of cycles. And the plastic film 1 is cut by the cutter 14 for every intermittent feed, and the plastic bag 9 is manufactured. Here, N is an integer of 2 or more. The number of cycles is the number of times the plastic film 1 is sent per unit time.

  For example, on the upstream side of the dancer roller 2, the plastic film 1 is intermittently fed at a constant cycle number with a unit feed length L that is twice the size of the plastic bag 9. Further, the vertical sealing device 15 having a length four times the size of the plastic bag 9 is used, and the vertical sealing device 15 is driven by the drive mechanism every time the plastic film 1 is intermittently fed. The plastic film 1 is vertically sealed by 15, and the vertical seal portion 16 is formed on the plastic film 1. Thereafter, every time the plastic film 1 is intermittently fed, the vertical sealing device 15 is driven again, and the plastic film 1 is again vertically sealed. Further, a total of four sealing devices are used for the lateral sealing device 17, and each sealing device 17 is arranged at intervals corresponding to the size of the plastic bag 9, and is driven every intermittent feeding of the plastic film 1. The horizontal seal device 17 is driven by the mechanism, and the plastic film 1 is laterally sealed by the horizontal seal device 17, and the horizontal seal portion 18 is formed in the plastic film 1. Furthermore, after that, every time the plastic film 1 is intermittently fed, the lateral sealing device 17 is driven again, and the plastic film 1 is laterally sealed again. Therefore, every time the plastic film 1 is intermittently fed, the plastic film 1 is vertically and horizontally sealed so that twice as many plastic bags 9 are obtained. Further, a total of two cooling devices 19 are arranged at intervals corresponding to the size of the plastic bag 8, and the horizontal seal portion 18 is cooled by each cooling device 19 every time the plastic film 1 is intermittently fed.

  Further, after the heat sealing and cooling of the plastic film 1, the plastic film 1 intermittently has a unit feed length corresponding to the size of the plastic bag 8 and the number of cycles twice that of the first feed roller 10 on the downstream side of the dancer roller 2. Sent. And the plastic film 1 is cut with the cutter 14 for every intermittent feed, and the plastic bag 9 is manufactured.

  Further, this bag making machine is of a two-row type, and a slitter 20 is provided on the downstream side of the dancer roller 2, and the plastic film 1 is slit by slit lines 21 as the plastic film 1 is intermittently fed. Thereafter, the plastic film 1 is cut by the cutter 14, and two plastic bags 9 are produced and discharged. In addition, a punch 22 is provided on the downstream side of the dancer roller 2, and the plastic film 1 is punched by the punch 22 every time the plastic film 1 is intermittently fed, and a punched portion is formed in the plastic film 1 at the corner of the plastic bag 9. You can also The punch 22 is what is called a corner cutting device. It is also possible to use a punch for the notch device, which is provided on the downstream side of the dancer roller 2, punch the plastic film 1 with the punch, and form the notch in the plastic film 1.

  Therefore, for the plastic film 1 of this bag making machine, the feeding patterns are completely different on the upstream side and the downstream side of the dancer roller 2. Therefore, it is absorbed by the dancer roller 2. For example, when the plastic film 1 is fed by the first feed roller 10 on the upstream side of the dancer roller 2, the dancer roller 2 moves and descends thereby, and the plastic film 1 is temporarily stored. Further, on the downstream side of the dancer roller 2, when the plastic film 1 is fed by the second feed roller 11, the dancer roller 2 moves and rises each time, and the storage film 1 is supplied.

  As described above, when the plastic film 1 is fed by the first feed roller 10 on the upstream side of the dancer roller 2, the unit feed length is a unit feed length L that is N times the size of the plastic bag 9. It is as follows. On the other hand, when the plastic film 1 is fed by the second feed roller 11 on the downstream side of the dancer roller 2, the unit feed length is a unit feed length corresponding to the size of the plastic bag 2, and the number of cycles is the first. The number of cycles is N times that of the feed roller 10. Therefore, the entire feed length is kept the same on the upstream side and the downstream side of the dancer roller 2. As a result, when the plastic film 1 is stored and supplied by the dancer roller 2, the entire storage and supply amount are kept the same, and there is no excess or deficiency.

  Therefore, in the case of this bag making machine, when the heat sealing devices 15 and 17 are driven once and the plastic film 1 is heated and pressurized for a considerable time, it is simultaneously heat sealed in N times as many plastic bags 9. can do. For example, in double the number of plastic bags 9, it can be heat sealed simultaneously. As a result, the speed of the bag making machine can be greatly increased.

  However, the problem is the tension of the plastic film 1. In order to significantly increase the speed of the bag making machine, it is necessary to intermittently feed the plastic film at a high speed on the upstream side and the downstream side of the dancer roller 2. Further, the dancer roller 2 moves suddenly, descends and rises, and the tension varies accordingly. Therefore, the plastic film 1 expands and contracts due to the tension, and the unit feed length changes, which affects the quality of the plastic bag. When the plastic film 1 has a printed pattern, the printed pattern may be displaced due to tension. This device is intended to solve this problem.

  By the way, in this bag making machine, the dancer roller 2 is supported by the arm 5 and the tension applying servo motor 3 is directly connected to the rotating shaft 4 as described above. As described above, torque is transmitted to the rotating shaft 4, pressure is applied to the dancer roller 2, and tension is applied to the plastic film 1. Therefore, when tension is applied to the plastic film 1, the magnitude is proportional to the torque generated by the tension applying servomotor 3.

  Further, between the guide rollers 6 and 7, the dancer roller 2 is engaged with the plastic film 1 and thereby the plastic film 1 is inclined, but the inclination angle α is not constant. When the dancer roller 2 moves, descends and rises, the inclination angle α changes depending on the moving position, which affects the tension of the dancer roller 2. Therefore, the moving position of the dancer roller 2 affects the tension. Further, regarding the moving position of the dancer roller 2, the arm 5 swings around the rotating shaft 4, and the moving position is determined by the swing angle θ.

  When the generated torque of the tension applying servomotor 3 is Tr and the tension of the plastic film 1 is Ts, the relationship is obtained by the following equation.

  Tr = K (θ) × Ts

  Here, K (θ) is a function of the swing angle θ of the arm 5 and a correction coefficient thereof. Therefore, K (θ) is a correction coefficient for the movement position of the dancer roller 2.

  In this apparatus, first, the tension Ts is set by the computer 8 based on the input signal from the operator. Thereafter, the tension applying servomotor 3 is feedforward controlled by the computer 8. Prior to the feedforward control, the correction unit K (θ) for the moving position of the dancer roller 2 is calculated in advance in the calculation unit of the computer 8. Based on the calculation data, the appropriate torque Tr of the tension applying servomotor 3 is calculated in advance. As for the appropriate torque Tr of the tension applying servo motor 3, the appropriate torque Tr is obtained from the tension Ts and the correction coefficient K (θ). Thereafter, the tension applying servomotor 3 is torque-controlled so as to generate the calculation torque Tr, and feedforward-controlled.

  Further, in this apparatus, the computer 8 is connected to the first and second feed servo motors 12 and 13, and the first and second feed servo motors 12 and 13 perform the first feed on the upstream side and the downstream side of the dancer roller 2. As described above, the second feed rollers 10 and 11 rotate and the plastic film 1 is intermittently fed with different patterns. Therefore, at each intermittent feed, as shown in FIG. 4, the first feed servo motor 12 accelerates the first feed roller 10, which rotates at a constant speed V, and then the first feed servo motor 12 performs the first feed. Of course, when the roller 10 is decelerated, it will decrease the tension when it is accelerated, and it will increase when it is decelerated. On the other hand, as shown in FIG. 5, the second feed roller 11 is accelerated by the second feed servo motor 13 and rotated at a constant speed V, and then the second feed roller 11 is decelerated by the second feed servo motor 13. However, when accelerated, it increases tension, and when decelerated, it decreases tension.

  Therefore, in this apparatus, when the first and second feed rollers 10 and 11 are accelerated and decelerated, the correction torques Tr ′ and −Tr ′ are added to the calculated torque Tr, and the tension applying servomotor 3 is added to the total torque Tr + Tr. Torque control is performed to generate ', Tr + (-Tr'), and feedforward control is performed.

  As a result, the tension Ts is kept constant. Moreover, as described above, the dancer roller 2 moves suddenly, but in this apparatus, the tension applying servo motor 3 is not feedback-controlled by the computer 8. The tension applying servomotor 3 is feedforward controlled by the computer 8, and there is no problem of followability. Therefore, even if the dancer roller 2 moves suddenly, the tension Ts can be kept constant.

  The tension applying servo motor 3 can also be feedforward controlled by other control methods. In other control methods, the correction coefficient K (θ) for the movement position of the dancer roller 2 is calculated in advance, and the appropriate torque Tr of the tension applying servomotor 3 is calculated in advance based on the calculated data. Then, when the feeding of the plastic film 1 is stopped, the tension applying servo motor 3 is torque controlled so that the calculation torque Tr is generated. Further, the tension applying servo motor 3 is locked at that position at the start of feeding or just before that. Further, the feeding path of the plastic film 1 changes in the vicinity of the dancer roller 2, and based on this, the changing path of the plastic film 1 is calculated in advance in the calculation unit of the computer 8, and the appropriateness of the dancer roller 3 is determined based on the calculation data. The position is calculated in advance. Then, during the feeding, the tension applying servo motor 3 is position-controlled so that the dancer roller 2 moves to the calculation position and feed-forward controlled every minute time.

  As a result, even if the dancer roller 2 moves suddenly, the tension Ts can be kept constant.

  The computer 8 feed-forward-controls the tension applying servo motor 3 and simultaneously detects the tension Ts by the detection device. Then, the tension applying servomotor 3 may be feedback-controlled based on the signal from the detection device.

It is a side view which shows the Example of this invention. It is a top view of the plastic film of FIG. It is explanatory drawing which shows the relationship between the plastic film of FIG. 1, and a dancer roller. 2 is a graph showing the relationship between the speed of a first feed roller in FIG. 1 and the torque generated by a tension applying servo motor. 3 is a graph showing the relationship between the speed of a second feed roller in FIG. 1 and the torque generated by a tension applying servo motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plastic film 2 Dancer roller 3 Tension giving servo motor 4 Rotating shaft 5 Arm 8 Computer 10 1st feed roller 11 2nd feed roller 12 1st feed servo motor 13 2nd feed servo motor

Claims (4)

A dancer roller that engages the plastic film in a plastic film feed path that is intermittently fed with a predetermined feed pattern;
A support mechanism for supporting the dancer roller;
A tension applying servo motor that is coupled to the support mechanism, transmits torque to the support mechanism, applies pressure to the dancer roller, and applies tension to the plastic film;
Connected to the tension applying servo motor, sets the tension based on the input signal from the operator, calculates the appropriate torque of the tension applying servo motor in advance based on the set tension, and calculates the torque applied to the tension applying servo motor. A plastic film tension control device comprising: a computer that performs torque control to generate, feed-forward control according to the feed pattern, and keeps the tension of the plastic film constant. 2. The tension control according to claim 1, wherein the support mechanism includes an arm fixed to a rotating shaft, the dancer roller is supported by the arm, and the tension applying servo motor is directly connected to the rotating shaft. apparatus. In the calculation unit of the computer, a correction coefficient for the movement position of the dancer roller is calculated in advance, an appropriate torque of the tension applying servo motor is calculated in advance based on the calculation data, and an arithmetic torque is generated in the tension applying servo motor. 3. The tension control device according to claim 1, wherein torque control is performed so that feedforward control is performed. On the upstream side and downstream side of the dancer roller, the plastic film is engaged with the first and second feed rollers, the first and second feed servo motors are connected to the first and second feed rollers, and the computer is The first and second feed servo motors are connected to the first and second feed servo motors, the first and second feed servo motors are rotated, the plastic film is intermittently fed in different patterns, and the first and second feed servo motors are rotated. The feed-forward control is performed, wherein when the feed roller is accelerated and decelerated, a correction torque is added to the calculated torque, and the tension applying servo motor is torque-controlled so as to generate an added total torque. 4. The tension control device according to 3.

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