Control device, control method, and program for rotary screen printing machine

Abstract

To provide a control device which can reduce printing failures of a rotary screen printing machine.SOLUTION: A control device for a rotary screen printing machine includes a screen plate cylinder, a squeegee, ink recovery means, an ink amount sensor, a discharge pump, an external tank, and a supply pump. The control device includes: a storage part for recording ink amount change data indicating a secular change of an ink amount detected by the ink amount sensor, and state change time data indicating time when a state of the discharge pump or the supply pump is changed on the basis of the ink amount; a data processing part for calculating an ink change rate in the screen plate cylinder using the ink amount change data, and calculating a frequency of the state change of the discharge pump or the supply pump using the state change time data; and a drive control part for controlling the discharge pump and the supply pump on the basis of the ink amount, the ink change rate and the frequency.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device, a control method, and a program for a printing machine that performs rotary screen printing.

Background Art

[0002] In a rotary screen printing machine, in order to print high-definition picture lines at high speed, it is preferable that the viscosity of the ink is low. Patent Document 1 proposes a rotary screen printing machine including a printing mechanism in which a squeegee contacts the inner surface of a cylindrical screen plate cylinder upward. According to this printing machine, by adopting an upward squeegee mechanism, suitable printing quality can be obtained while controlling the ink amount.

[0003] In a rotary screen printing machine adopting an upward squeegee mechanism, the temperature of the ink may increase due to the friction generated between the squeegee and the screen plate cylinder and the heat generated by the printing machine, or the temperature of the ink may decrease due to the influence of the outside air. In this case, it is assumed that the viscosity of the ink changes and the printability is impaired. Therefore, the printing machine described in Patent Document 1 also includes an external tank connected to the inside of the screen plate cylinder and provided with a temperature adjustment mechanism. Further, in order to circulate the ink between the inside of the screen plate cylinder and the external tank, a supply pump for supplying the ink from the external tank into the screen plate cylinder and a discharge pump for discharging the ink from the inside of the screen plate cylinder to the external tank are also installed. The operations of the supply pump and the discharge pump are controlled according to the amount of ink in the screen plate cylinder.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to ensure good printing quality, it is desirable to continuously supply ink adjusted to a suitable temperature for printing from the above-described external tank into the screen printing cylinder, continuously discharge the ink in the screen printing cylinder to the external tank, and not vary the amount of ink in the screen printing cylinder.

[0006] For example, if the ink supply amount per unit time when the supply pump operates is equal to the sum of the ink discharge amount per unit time when the discharge pump operates and the ink consumption amount per unit time consumed by ink transfer to the printing substrate, suppressing the variation in the amount of ink in the screen printing cylinder can always be easily achieved by the continuous operation of the supply pump and the discharge pump.

[0007] However, in reality, since the ruled line area varies for each printing design, the amount of ink transferred to the printing substrate is different each time. In addition, there may be cases where the change in ink temperature caused by the room temperature during printing or the temperature change of the screen printing cylinder over time from the start of printing cannot be completely suppressed by the temperature adjustment mechanism of the external tank. In this case, the ink flow characteristics change, and accordingly, the balance between the supply amount and the discharge amount changes.

[0008] The amount of ink in the screen printing cylinder decreases or increases depending on the difference between the supply amount and the discharge amount of each pump. Also, the operation and stop of each pump are switched according to the set value. Therefore, the variation in the ink amount is within a certain range by switching the operation and stop of the pump based on the set value.

[0009] However, the switching of the operation and stop of each pump results in a state where the increase and decrease of the ink amount are repeated alternately, which is different from the stable state where the originally ideal supply amount and discharge amount are in opposition. Also, when the increase and decrease of the ink amount are repeated alternately, the amount of ink supplied to the squeegee tip will inevitably increase and decrease repeatedly.

[0010] When the amount of ink frequently increases and decreases within a short period of time in the screen cylinder, printing defects such as missing lines and roughness are likely to occur on the printing substrate.

[0011] Therefore, an object of the present invention is to provide a control device, a control method, and a program capable of reducing printing defects of a rotary screen printing machine.

Means for Solving the Problems

[0012] The control device according to the present invention includes a cylindrical screen cylinder, a squeegee that contacts the inner surface of the screen cylinder upward, an ink recovery means for recovering ink in the screen cylinder, an ink amount sensor for detecting the amount of ink staying in the ink recovery means, a discharge pump for discharging ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen cylinder. This control device includes a storage unit that stores ink amount change data indicating the change over time of the ink amount detected by the ink amount sensor and state change time data indicating the time when the states of the discharge pump and / or the supply pump change based on the ink amount, a data processing unit that calculates the ink change rate in the screen cylinder using the ink amount change data and calculates the frequency of state changes of the discharge pump and / or the supply pump using the state change time data, and a drive control unit that controls the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency.

[0013] In the above control device, the discharge pump stops when the ink amount falls below the lower limit value and operates when the ink amount exceeds the upper limit value. The data processing unit calculates the decrease rate of the ink using the ink amount change data and calculates the stop frequency of the discharge pump using the state change time data. When the stop frequency exceeds a predetermined number of times and the average value of the decrease rate exceeds a predetermined value, the drive control unit may control the supply pump so that the supply amount of the ink increases.

[0014] In the above control device, the supply pump stops when the ink amount exceeds the upper limit value, operates when the ink amount falls below the lower limit value, calculates the increase rate of the ink using the ink amount change data, and calculates the stop frequency of the supply pump using the state change time data. When the stop frequency exceeds a predetermined number of times and the average value of the increase rate exceeds a predetermined value, the drive control unit may control the discharge pump so that the discharge amount of the ink increases.

[0015] The control method according to the present invention is a control method for a rotary screen printing machine including a cylindrical screen plate cylinder, a squeegee that contacts the inner surface of the screen plate cylinder upward, an ink recovery means for recovering ink inside the screen plate cylinder, an ink amount sensor for detecting the amount of ink staying in the ink recovery means, a discharge pump for discharging ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen plate cylinder. Store ink amount change data indicating the change over time of the ink amount detected by the ink amount sensor, store state change time data indicating the time when the state of the discharge pump and / or the supply pump changes based on the ink amount, calculate the ink change rate inside the screen plate cylinder using the ink amount change data, calculate the frequency of state changes of the discharge pump and / or the supply pump using the state change time data, and control the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency.

[0016] In the above control method, The discharge pump stops when the ink amount falls below the lower limit value, operates when the ink amount exceeds the upper limit value, calculates the decrease rate of the ink using the ink amount change data, calculates the stop frequency of the discharge pump using the state change time data, and when the stop frequency exceeds a predetermined number of times and the average value of the decrease rate exceeds a predetermined value, the supply pump may be controlled so that the supply amount of the ink increases.

[0017] In the above control method, The supply pump stops when the ink amount exceeds the upper limit value, operates when the ink amount falls below the lower limit value, calculates the ink increase rate using the ink amount change data, calculates the stop frequency of the supply pump using the state change time data, and controls the discharge pump so that the ink discharge amount increases when the stop frequency exceeds a predetermined number of times and the average value of the increase rate exceeds a predetermined value.

[0018] The program according to the present invention causes a computer to execute a process for controlling a rotary screen printing machine including a cylindrical screen plate cylinder, a squeegee that contacts the inner surface of the screen plate cylinder upward, an ink recovery means for recovering ink inside the screen plate cylinder, an ink amount sensor for detecting the amount of ink staying in the ink recovery means, a discharge pump for discharging ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen plate cylinder. It stores ink amount change data indicating the change over time of the ink amount detected by the ink amount sensor, stores state change time data indicating the time when the state of the discharge pump and / or the supply pump changes based on the ink amount, calculates the ink change rate inside the screen plate cylinder using the ink amount change data, calculates the frequency of state changes of the discharge pump and / or the supply pump using the state change time data, and controls the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency.

Effect of the Invention

[0019] According to the present invention, it is possible to reduce printing defects of the rotary screen printing machine.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0021] Embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described below, and includes various other embodiments within the scope of the technical idea described in the claims.

[0022] (First Embodiment) FIG. 1 is a diagram showing a schematic configuration of a rotary screen printing machine according to the first embodiment of the present invention. The rotary screen printing machine 1 shown in FIG. 1 includes a printing mechanism 10, an ink circulation mechanism 20, and a control device 30. In addition to these, the rotary screen printing machine 1 also includes a paper feeding unit (not shown) for feeding the object to be printed to the printing mechanism 10, a paper discharging unit (not shown) for discharging the object to be printed from the printing mechanism 10, and the like.

[0023] First, the printing mechanism 10 will be described. The printing mechanism 10 has a screen cylinder 11, a squeegee 12, a retention tank 13, and an ink amount sensor 14. The screen cylinder 11 is a cylindrical member, and through holes are formed in its outer peripheral portion. During printing, the screen cylinder 11 rotates in one direction (clockwise in FIG. 1). As a result, the ink is discharged upward from the through holes. The discharged ink is transferred to the object to be printed sandwiched between the screen cylinder 11 and a pressure cylinder (not shown).

[0024] The squeegee 12 is provided inside the screen printing cylinder 11. The squeegee 12 is fixed to a support (not shown). The tip of the squeegee 12 is in upward contact with the inner surface of the screen printing cylinder 11 so that the ink is ejected upward. The squeegee 12 pushes the ink E into the through holes of the screen printing cylinder 11 and scrapes off the excess ink. The pushed ink E is transferred to the object to be printed as the screen printing cylinder 11 rotates. Thereby, an ink pattern is formed on the object to be printed.

[0025] The retention tank 13 is also provided inside the screen printing cylinder 11. The retention tank 13 is an example of an ink recovery means, and recovers the ink E scraped off by the squeegee 12 without being transferred to the object to be printed.

[0026] The ink amount sensor 14 detects the amount of ink retained in the retention tank 13. The ink amount sensor 14 is constituted by, for example, a pressure sensor. As the amount of ink retained in the retention tank 13 increases, the pressure value measured by this pressure sensor increases. That is, the ink amount sensor 14 detects the amount of ink retained in the retention tank 13 by converting the measured pressure value into the ink amount. Note that the method for detecting the ink amount is not limited to pressure, and other methods may be used.

[0027] Next, the ink circulation mechanism 20 provided outside the screen printing cylinder 11 will be described. The ink circulation mechanism 20 includes a discharge pump 21, an external tank 22, and a supply pump 23, which communicate with the retention tank 13 via a pipe 24.

[0028] The discharge pump 21 is connected to a recovery port 131 provided inside the retention tank 13 via the pipe 24. The discharge pump 21 discharges the ink from the retention tank 13. The discharged ink is stored in the external tank 22 through the pipe 24.

[0029] The external tank 22 stores the ink E discharged by the discharge pump 21 and the unused ink. A temperature control mechanism (not shown) is provided inside this external tank 22. The temperature control mechanism is, for example, a strip-shaped heater installed on the inner surface and bottom surface of the external tank 22. Note that the shape of this heater is not limited to a strip shape, and any shape that can be provided inside the external tank 22 is acceptable. Further, it is preferable that this temperature control mechanism has a function of controlling the temperature of the ink so that the viscosity of the ink stored in the external tank 22 is maintained at a preset value (for example, a value of 2 Pa·s or less). For example, the temperature of the ink in the external tank 22 is monitored, the heater is operated according to the temperature change, and the ink in the external tank 22 is cooled and heated. Also, the relationship between the temperature change and viscosity change of the ink may be grasped in advance, and the temperature of the ink may be managed in a temperature range where the required viscosity can be obtained.

[0030] The supply pump 23 supplies the ink stored in the external tank 22 into the screen printing cylinder 11 through the pipe 24. The supply pump 23 and the discharge pump 21 can adjust the ink feed amount per unit time by inverter control by the control device 30. That is, the supply pump 23 can adjust the ink supply amount per unit time into the screen printing cylinder 11, and the discharge pump 21 can adjust the ink discharge amount per unit time from the retention tank 13.

[0031] Next, the control device 30 that controls the ink circulation mechanism 20 will be described. The control device 30 includes a storage unit 31, a data processing unit 32, and a drive control unit 33. The control device 30 is configured by, for example, a PLC (Programmable Logic Controller) that controls the ink circulation mechanism 20 according to a predetermined program.

[0032] The storage unit 31 stores the above program and various data. Here, with reference to FIGS. 2(a) and 2(b), an example of the data stored in the storage unit 31 will be described.

[0033] Fig. 2(a) is a diagram showing an example of ink amount change data. The ink amount change data 311 shown in Fig. 2(a) shows the change over time of the ink amount stored in the retention tank 13 by associating and storing the ink amount detected by the ink amount sensor 14 with the detection time.

[0034] On the other hand, Fig. 2(b) is a diagram showing an example of state change time data. The state change time data 312 shown in Fig. 2(b) shows the state change times of the discharge pump 21 and the supply pump 23. This state change time is the time when each pump changes from the operating state to the stopped state, or the time when it changes from the stopped state to the operating state. Note that although the state change time data 312 stores the state change times of both the discharge pump 21 and the supply pump 23, only the state change time of either one of the pumps may be stored.

[0035] The data processing unit 32 calculates an ink change rate (ink increase rate or ink decrease rate) using the ink amount change data 311 stored in the storage unit 31. Also, the data processing unit 32 calculates the frequency of state changes of the discharge pump 21 and / or the supply pump 23 using the state change time data 312 stored in the storage unit 31.

[0036] The drive control unit 33 controls the discharge pump 21 and / or the supply pump 23 based on the ink amount detected by the ink amount sensor 14, and the ink change rate and the frequency of state changes calculated by the data processing unit 32.

[0037] Hereinafter, with reference to Figs. 3 and 4, the operation of the control device 30 according to the present embodiment will be described. Fig. 3 is a flowchart showing an example of the procedure of the control operation by the control device 30. Also, Fig. 4 is a timing chart showing an example of the relationship between the operation of the pump controlled by the control device 30 and the ink amount remaining in the retention tank 13.

[0038] When the printing mechanism 10 starts printing, the discharge pump 21 discharges ink quantitatively from the retention tank 13 to the external tank 22 based on a control signal SG1 (see FIG. 4) input from the drive control unit 33 of the control device 30. At this time, the supply pump 23 supplies ink quantitatively from the external tank 22 to the screen printing cylinder 11 based on a control signal SG2 (see FIG. 4) input from the drive control unit 33 of the control device 30.

[0039] Also, the data processing unit 32 of the control device 30 periodically acquires the ink amount detected by the ink amount sensor 14 (step S101). The acquired ink amount is stored in the storage unit 31 as ink amount change data (step S102).

[0040] As printing progresses, the amount of ink retained in the retention tank 13 also decreases. Therefore, the data processing unit 32 determines whether the acquired ink amount is less than the lower limit value LL (see FIG. 4) (step S103).

[0041] When the determination result that the ink amount is less than the lower limit value LL is notified from the data processing unit 32 to the drive control unit 33, the drive control unit 33 outputs a control signal SG1 for instructing the discharge pump 21 to stop (step S104). At this time, the output time of this control signal SG1 is stored in the storage unit 31 as state change time data indicating the stop time t11 of the discharge pump 21 (see FIG. 4) (step S105). Note that when the ink amount is not less than the lower limit value, the drive control unit 33 maintains the operation contents of the discharge pump 21 and the supply pump 23.

[0042] While the discharge pump 21 stops in step S104, the supply pump 23 continues to operate, so the amount of ink retained in the retention tank 13 increases. Therefore, the data processing unit 32 determines whether the acquired ink amount exceeds the upper limit value UL (see FIG. 4) (step S106).

[0043] When the determination result that the ink amount exceeds the upper limit value UL is notified from the data processing unit 32 to the drive control unit 33, the drive control unit 33 outputs a control signal SG1 for commanding the operation of the discharge pump 21 (step S107).

[0044] The operations of steps S103 to S107 described above, that is, the operation in which the drive control unit 33 controls the discharge pump 21 and / or the supply pump 23 based on the result of comparing the ink amount with the lower limit value and the upper limit value, is repeated to some extent as shown in FIG. 4. However, in the present embodiment, during the above operation, the data processing unit 32 calculates the decrease rate p of the ink amount using the ink amount change data 311 read from the storage unit 31 (step S108). The decrease rate p can be calculated by, for example, ΔA / Δt as shown in FIG. 4. Here, Δt is the elapsed time from the time when the ink amount reaches the maximum value MAX, that is, the time when the upper limit value UL is reached, and is preset. On the other hand, ΔA is the ink amount decreased during the period of Δt.

[0045] After calculating the decrease rate p as described above, the data processing unit 32 then calculates the stop frequency f of the discharge pump 21 using the state change time data 312 read from the storage unit 31 (step S109). The stop frequency f is, for example, the number of times the ink amount reaches the lower limit value LL within a predetermined period T as shown in FIG. 4. This number can be calculated by counting the number of stop times t11 to t14 shown in the state change time data 312.

[0046] Subsequently, the data processing unit 32 determines whether or not the stop frequency f exceeds a predetermined number N (step S110). In step S110, it is determined whether or not the stop frequency f of the discharge pump 21 between the current time and the time retrogressed by a predetermined period T from the current time is within the allowable range. If the stop frequency f exceeds the predetermined number N, the data processing unit 32 determines whether or not the average value m of the decrease rate p of the ink amount within the predetermined period T exceeds a predetermined value P (step S111).

[0047] When the average value m exceeds the predetermined value P, the data processing unit 32 notifies the drive control unit 33 of the determination result. In this case, as shown in FIG. 4, the drive control unit 33 outputs a control signal SG2 indicating a command to increase the ink supply amount during the operation period D1 of the discharge pump 21 to the supply pump 23 (step S112). As a result, the decrease rate p of the ink amount is suppressed.

[0048] Therefore, according to the present embodiment described above, in response to the variation in the ink amount in the screen printing cylinder 11, the supply pump 23 appropriately increases the ink supply amount during the operation of the discharge pump 21, thereby suppressing a rapid decrease in the ink amount in the screen printing cylinder 11. As a result, frequent increases and decreases in the ink amount can be avoided, and printing defects of the rotary screen printing machine can be reduced.

[0049] In addition, in the present embodiment, when the frequency of increase and decrease in the ink amount in the screen printing cylinder 11 increases, it can be automatically handled under the control of the control device 30, so that the possibility of incorrect operation of the pump by the operator can be eliminated.

[0050] Furthermore, even if conditions such as the type of ink, the ink pattern, the type of pump, and the ink path length are changed, by automatically controlling the discharge pump 21 and / or the supply pump 23 based on various parameters set each time, it is possible to provide an optimal ink circulation.

[0051] (Second Embodiment) Hereinafter, a second embodiment of the present invention will be described. Since the configuration of the rotary screen printing machine according to the present embodiment is the same as that of the rotary screen printing machine 1 according to the first embodiment described above, the description thereof will be omitted. In the present embodiment, the operation content of the control device 30 is different from that of the first embodiment. Here, with reference to FIGS. 5 and 6, the operation of the control device 30 of the present embodiment will be described.

[0052] FIG. 5 is a flowchart showing an example of the control operation procedure by the control device 30 of the second embodiment. FIG. 6 is a timing chart showing an example of the relationship between the operation of the pump controlled by the control device 30 of the second embodiment and the amount of ink staying in the retention tank 13.

[0053] When the printing mechanism 10 starts printing, in the same manner as in the first embodiment, the data processing unit 32 of the control device 30 periodically acquires the amount of ink detected by the ink amount sensor 14 (step S201). The acquired ink amount is stored in the storage unit 31 over time as ink amount change data (step S202).

[0054] During the printing by the printing mechanism 10, in the same manner as in the first embodiment, the drive control unit 33 repeatedly performs an operation of controlling the discharge pump 21 and the supply pump 23 based on the result of comparing the ink amount acquired from the ink amount sensor 14 with the lower limit value LL or the upper limit value UL.

[0055] However, in this embodiment, the data processing unit 32 determines whether the acquired ink amount exceeds the upper limit value UL (see FIG. 6) (step S203). As a result, when the ink amount exceeds the upper limit value UL, the drive control unit 33 outputs a control signal SG2 for instructing the supply pump 23 to stop (step S204). In this case, the output time of this control signal SG2 is stored in the storage unit 31 as state change time data indicating the stop time t21 of the supply pump 23 (see FIG. 6) (step S205). When the ink amount does not exceed the upper limit value, the drive control unit 33 maintains the operation contents of the discharge pump 21 and the supply pump 23.

[0056] While the supply pump 23 stops in step S204, the discharge pump 21 continues to operate, so the amount of ink staying in the retention tank 13 decreases. Therefore, the data processing unit 32 determines whether the acquired ink amount is less than the lower limit value LL (see FIG. 6) (step S206).

[0057] When the determination result that the ink amount has fallen below the lower limit value LL is notified from the data processing unit 32 to the drive control unit 33, the drive control unit 33 outputs a control signal SG2 for instructing the operation of the supply pump 23 (step S207).

[0058] Also, in the present embodiment, during the operations of steps S203 to S207 described above, the data processing unit 32 calculates the increase rate q of the ink amount using the ink amount change data 311 read from the storage unit 31 (step S208). The increase rate q can be calculated by ΔB / Δt as shown in FIG. 6, for example. Here, Δt is the elapsed time from the time when the ink amount becomes the minimum value MIN, that is, the time when the lower limit value LL is reached, and is preset. On the other hand, ΔB is the ink amount increased during the period of Δt.

[0059] After calculating the increase rate q as described above, the data processing unit 32 subsequently calculates the stop frequency f of the supply pump 23 using the state change time data 312 read from the storage unit 31 (step S209). The stop frequency f is, for example, the number of times the ink amount reaches the upper limit value UL within a predetermined period T as shown in FIG. 6. This number can be calculated by counting the number of stop times t21 to t24 shown in the state change time data 312.

[0060] Subsequently, the data processing unit 32 determines whether or not the stop frequency f exceeds a predetermined number N (step S210). In step S210, it is determined whether or not the stop frequency f of the supply pump 23 between the current time and the time retrogressed by a predetermined period T from the current time is within the allowable range. If the stop frequency f exceeds the predetermined number N, the data processing unit 32 determines whether or not the average value M of the increase rate q of the ink amount within the predetermined period T exceeds a predetermined value Q (step S211).

[0061] When the average value M exceeds the predetermined value Q, the data processing unit 32 notifies the drive control unit 33 of the determination result. In this case, as shown in FIG. 6, the drive control unit 33 outputs a control signal SG2 indicating a command to increase the ink discharge amount during the operation period D2 of the supply pump 23 to the discharge pump 21 (step S212). As a result, the increase rate q of the ink amount is suppressed.

[0062] Therefore, according to the present embodiment described above, in response to the variation in the ink amount in the screen printing cylinder 11, during the operation of the supply pump 23, the discharge pump 21 appropriately decreases the ink supply amount, thereby suppressing a rapid increase in the ink amount in the screen printing cylinder 11. As a result, frequent increases and decreases in the ink amount can be avoided, and printing defects of the rotary screen printing machine can be reduced.

[0063] In each of the above-described embodiments, the drive control unit 33 controls the discharge pump 21 and / or the supply pump 23 so as to suppress either the decrease rate or the increase rate of the ink amount in the screen printing cylinder 11. However, the pumps may be controlled by combining the first embodiment and the second embodiment so as to suppress both the decrease rate and the increase rate. In this case, since the frequency of increase and decrease of the ink amount can be further suppressed, it is possible to further reduce printing defects of the rotary screen printing machine.

[0064] Further, in the present embodiment, the data processing unit 32 calculates the stop frequency of the discharge pump 21 or the supply pump 23, but the operation frequency may be calculated based on the operation time when each pump changes from the stop state to the operation state. In this case, based on the operation frequency and the change rate (decrease rate or increase rate) of the ink amount, the drive control unit 33 controls the ink discharge amount through the discharge pump 21 and controls the ink supply amount through the supply pump 23. In this way, by appropriately controlling the discharge pump 21 and the supply pump 23 by the drive control unit 33, it is possible to reduce printing defects of the rotary screen printing machine.

[0065] In addition, it can also be realized by using a program for causing a computer having functions equivalent to those of the memory unit 31, the data processing unit 32, and the drive control unit 33 to execute the control of the ink supply and / or ink discharge of the rotary screen printing machine described above.

Explanation of Signs

[0066] 1: Rotary screen printing machine 11: Screen cylinder 12: Squeegee 13: Holding tank (ink recovery means) 14: Ink amount sensor 21: Discharge pump 22: External tank 23: Supply pump 30: Control device 31: Memory unit 32: Data processing unit 33: Drive control unit

Claims

1. A control device for a rotary screen printing machine, comprising: a cylindrical screen plate cylinder; a squeegee that contacts the inner surface of the screen plate cylinder upward; an ink recovery means for recovering ink inside the screen plate cylinder; an ink amount sensor for detecting the amount of ink staying in the ink recovery means; a discharge pump for discharging the ink from the ink recovery means; an external tank for storing the ink discharged by the discharge pump; and a supply pump for supplying the ink stored in the external tank into the screen plate cylinder, a storage unit that stores ink amount change data indicating a change over time of the ink amount detected by the ink amount sensor and state change time data indicating the time when the state of the discharge pump and / or the supply pump changes based on the ink amount; a data processing unit that calculates an ink change rate inside the screen plate cylinder using the ink amount change data and calculates the frequency of state changes of the discharge pump and / or the supply pump using the state change time data; a drive control unit that controls the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency; A control device comprising the above.

2. The discharge pump stops when the ink amount falls below a lower limit value and operates when the ink amount exceeds an upper limit value, The data processing unit calculates a reduction rate of the ink using the ink amount change data and calculates the stop frequency of the discharge pump using the state change time data, When the stop frequency exceeds a predetermined number of times and the average value of the reduction rate exceeds a predetermined value, the drive control unit controls the supply pump so that the supply amount of the ink increases. The control device according to claim 1.

3. The supply pump stops when the ink amount exceeds an upper limit value and operates when the ink amount falls below a lower limit value, The data processing unit calculates the increase rate of the ink using the ink amount change data, and calculates the stop frequency of the supply pump using the state change time data. When the stop frequency exceeds a predetermined number of times and the average value of the increase rate exceeds a predetermined value, the drive control unit controls the discharge pump so that the discharge amount of the ink increases. The control device according to claim 1 or 2.

4. A control method for a rotary screen printing machine including a cylindrical screen plate cylinder, a squeegee that contacts the inner surface of the screen plate cylinder upward, an ink recovery means for recovering ink inside the screen plate cylinder, an ink amount sensor for detecting the amount of ink staying in the ink recovery means, a discharge pump for discharging the ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen plate cylinder, Store ink amount change data indicating the change over time of the ink amount detected by the ink amount sensor. Store state change time data indicating the time when the state of the discharge pump and / or the supply pump changes based on the ink amount. Calculate the ink change rate inside the screen plate cylinder using the ink amount change data. Calculate the frequency of state changes of the discharge pump and / or the supply pump using the state change time data. Control the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency. Control method.

5. The discharge pump stops when the ink amount falls below the lower limit value and operates when the ink amount exceeds the upper limit value. Calculate the decrease rate of the ink using the ink amount change data. Calculate the stop frequency of the discharge pump using the state change time data. The control method according to claim 4, wherein when the stop frequency exceeds a predetermined number of times and the average value of the decrease rate exceeds a predetermined value, the supply pump is controlled so that the supply amount of the ink increases.

6. The supply pump stops when the ink amount exceeds the upper limit value, and operates when the ink amount falls below the lower limit value. Calculate the increase rate of the ink using the ink amount change data. Calculate the stop frequency of the supply pump using the state change time data. The control method according to claim 4 or 5, wherein when the stop frequency exceeds a predetermined number of times and the average value of the increase rate exceeds a predetermined value, the discharge pump is controlled so that the discharge amount of the ink increases.

7. A program for causing a computer to execute a process of controlling a rotary screen printing machine including a cylindrical screen printing cylinder, a squeegee that contacts the inner surface of the screen printing cylinder upward, an ink recovery means for recovering ink inside the screen printing cylinder, an ink amount sensor for detecting the amount of ink staying in the ink recovery means, a discharge pump for discharging the ink from the ink recovery means, an external tank for storing the ink discharged by the discharge pump, and a supply pump for supplying the ink stored in the external tank into the screen printing cylinder, Means for storing ink amount change data indicating the change over time of the ink amount detected by the ink amount sensor. Means for storing state change time data indicating the time when the state of the discharge pump and / or the supply pump changes based on the ink amount. Means for calculating the ink change rate inside the screen printing cylinder using the ink amount change data. Means for calculating the frequency of state change of the discharge pump and / or the supply pump using the state change time data. A program for causing the computer to function as means for controlling the discharge pump and the supply pump based on the ink amount, the ink change rate, and the frequency.

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