Parallel supply system and control method thereof

Abstract

To enable a parallel supply system to supply a stable amount of a raw material to a screw conveyor even when the amount of raw material discharged from a supply machine is not constant when the supply machine is filled with the raw material.SOLUTION: There is provided a parallel supply system that parallelly comprises: a first feeder A feeding a raw material S to a raw material inlet C1 of a screw conveyor C through a first raw material feeding line L1; and a second feeder B supplying the raw material S to the raw material inlet C1 through a second raw material feeding line L2. The parallel supply system also comprises: a replenishment machine R replenishing the raw material S through a replenishment line L3 to the feeders in which an amount of the raw material S is decreased; a replenishment destination switching valve V1 that sends raw material S to one of the first and second feeders in the replenishment line L3; a first supply destination switching valve V2 switching whether to send the raw material S from the first feeder A to the raw material inlet C1 or return to the replenishment machine R in the first raw material feeding line L1; a second supply destination switching valve V3 switching whether to send the raw material S from the second feeder B to the raw material inlet C1 or return to the replenishment machine R in the second raw material feeding line L2; and a control device.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a parallel supply system in which a plurality of supply machines are arranged in parallel, and a control method thereof. [Background technology]

[0002] For example, Patent Document 1 discloses an active material powder supply device for supplying active material powder from a hopper to a kneader, and this supply device includes: a plurality of parallel secondary supply lines connected to the hopper; a cylindrical container connected to the plurality of secondary supply lines; a helical screw member disposed inside the cylindrical container and rotating coaxially with the central axis of the cylindrical container in the longitudinal direction to feed out the active material powder; a main supply line connecting the cylindrical container to the kneader; filters provided on each of the plurality of secondary supply lines; and a selection means for selecting the secondary supply line through which the active material powder is to pass.

[0003] Also known is a so-called loss-in control type raw material supply system, which has a measuring device that measures the mass of a hopper and replenishes raw material from a replenisher when the amount of raw material in the hopper decreases. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-67398 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional loss-in control raw material supply systems, when the amount of raw material in the hopper decreases and the hopper is filled with raw material from a replenisher, the amount of raw material in the hopper increases suddenly, causing the amount of raw material dispensed from the hopper to become temporarily unstable for a while.

[0006] The present invention has been made in consideration of the above points, and its purpose is to enable a stable amount of raw material to be supplied to a supplied device even when the amount of raw material dispensed from the supply machine is not steady when the supply machine is filled with raw material. [Means for solving the problem]

[0007] In order to achieve the above object, in this invention, during an unsteady state in which at least one of the feeders is being replenished with raw material, raw material is supplied from the other feeder which is in a steady state and not filled with raw material.

[0008] Specifically, in the first invention, a first supplying device supplies raw material to a raw material inlet of a supplying device through a first raw material supplying line; a second supplying machine provided in parallel with the first supplying machine and supplying the raw material to the raw material inlet of the supply receiving device via a second raw material supplying line; a replenishing machine that replenishes raw material through a replenishing line to one of the first and second supply machines in which raw material has been depleted; a replenishment destination switching valve that is provided in the replenishment line and that is switched to send the raw material to one of the first supply device and the second supply device; a first supply destination switching valve that is provided in the first raw material supply line and switches whether the raw material from the first supply machine is sent to the raw material inlet or returned to the replenisher; a second supply destination switching valve provided in the second raw material supply line, which switches whether the raw material from the second supply machine is sent to the raw material inlet or returned to the replenishment machine; and a control device that switches the replenishment destination switching valve, the first supply destination switching valve, and the second supply destination switching valve.

[0009] According to the above configuration, by appropriately switching the switching valve using the control device, during the period when the amount of raw material dispensed becomes unstable due to the replenishment of raw material from one supply machine to the other supply machine, a stable amount of raw material can be continuously supplied to the supplied device.

[0010] In the second invention, in the first invention, The control device One of the first supply machine and the second supply machine is not allowed to supply raw material to the supplied device while the raw material is being replenished from the replenishment machine, The feed amount Y1 is stable, and the other of the first feeder and the second feeder supplies the raw material to the device to be supplied. The refill destination switching valve, the first supply destination switching valve, and the second supply destination switching valve are configured to be switched.

[0011] According to the above configuration, a stable amount of raw material can be continuously supplied to the supply destination device by simple control of appropriately switching each switching valve.

[0012] In a third aspect of the present invention, in the first or second aspect of the present invention, the replenisher is a powder / granular material discharger having a supply amount larger than the supply amounts of the first supplyer and the second supplyer, The first feeder and the second feeder are feeders with a weighing device that can measure the mass of the raw material in the hopper, and are configured so that a signal from the weighing device is sent to a control device.

[0013] According to the above configuration, by using a replenisher with a large supply volume, the replenishment time can be shortened and the unsteady period can be minimized. In addition, by having each replenisher equipped with a weighing device, the mass of raw material in the hopper is constantly transmitted to the control device, allowing for accurate control according to the measured value.

[0014] In a fourth aspect of the present invention, in the first or second aspect of the present invention, The device to be fed is a screw conveyor that feeds raw materials to a downstream kneader.

[0015] According to the above configuration, a stable amount of raw material is supplied to the screw conveyor, so that the amount of raw material supplied to the kneader downstream is stable, and stable, high-quality kneading can be performed in the kneader.

[0016] In a fifth aspect of the present invention, a first supplying device supplies raw material to a raw material inlet of a supplying device through a first raw material supplying line; a second supplying machine provided in parallel with the first supplying machine and supplying the raw material to the raw material inlet of the supply receiving device via a second raw material supplying line; a replenishing machine that replenishes raw material through a replenishing line to one of the first and second supply machines in which raw material has been depleted; a replenishment destination switching valve that is provided in the replenishment line and that is switched to send the raw material to one of the first supply device and the second supply device; a first supply destination switching valve that is provided in the first raw material supply line and switches whether the raw material from the first supply machine is sent to the raw material inlet or returned to the replenisher; The present invention relates to a control method for a parallel supply system including a second supply destination switching valve that is provided in the second raw material supply line and switches whether the raw material from the second supply machine is sent to the raw material inlet or returned to the replenishment machine.

[0017] In the control method, preparing the parallel supply system to replenish the replenisher, the first supplyer, and the second supplyer with raw materials; Start the parallel supply system; The raw material is supplied from the first supply device to the raw material inlet of the supplied device through a first raw material supply line; When the remaining amount of raw material in the first supplier falls below a first threshold, the first supply destination switching valve is switched to a side returning the raw material to the replenisher, and the second supply destination switching valve is switched to a side sending the raw material to the raw material inlet, so that the raw material is supplied from the second supplier to the raw material inlet; The replenishment destination switching valve is switched to a side for sending raw material to the first supply device, and the raw material is replenished to the first supply device; After a first predetermined time has elapsed, the replenishment destination switching valve is switched to stop the supply of raw material to the first supplier; Further, by continuing the operation of returning the raw material from the first supply device to the replenisher and supplying the raw material from the second supply device to the raw material inlet for a second predetermined time, the amount of raw material returned from the first supply device to the replenisher becomes stable, When the operation is further continued and the remaining amount of raw material in the second supply device falls below a second threshold, the second supply destination switching valve is switched to a side returning the raw material to the replenisher, and the first supply destination switching valve is switched to a side sending the raw material to the raw material inlet, and the raw material is supplied from the first supply device to the raw material inlet, The replenishment destination switching valve is switched to a side for sending raw material to the second supply device, and the raw material is replenished to the second supply device; After a third predetermined time has elapsed, the replenishment destination switching valve is switched to stop the supply of raw material to the second supply device; Further, by continuing the operation of returning the raw material from the second supply machine to the replenisher and supplying the raw material from the first supply machine to the raw material inlet for a fourth predetermined time, the amount of raw material returned from the second supply machine to the replenisher becomes stable. Repeat a series of steps.

[0018] According to the above configuration, by appropriately switching the switching valve using the control device, during the period when the amount of raw material dispensed becomes unstable due to the replenishment of raw material from one supply machine to the other supply machine, a stable amount of raw material can be continuously supplied by supplying raw material to the supplied device. [Effects of the Invention]

[0019] As described above, according to the present invention, even when the amount of raw material dispensed from a supplying machine is not steady when the supplying machine is filled with raw material, a stable amount of raw material can be continuously supplied to the supplied device by supplying raw material from the other supplying machine whose amount of dispensing is steady. [Brief explanation of the drawings]

[0020] [Figure 1A] FIG. 1 shows the first step of a parallel supply system. [Figure 1B] FIG. 10 shows a second step of the parallel supply system. [Figure 1C] FIG. 10 shows a third step of the parallel supply system. [Figure 1D] FIG. 10 illustrates a fourth step of the parallel supply system. [Figure 1E]FIG. 5 illustrates a fifth step of the parallel supply system. [Figure 1F] FIG. 6 illustrates the sixth step of the parallel supply system. [Figure 1G] FIG. 7 illustrates the seventh step of the parallel supply system. [Figure 1H] FIG. 8 shows the eighth step of the parallel supply system. [Figure 1I] FIG. 9 illustrates the ninth step of the parallel supply system. [Figure 1J] FIG. 10 illustrates the tenth step of the parallel supply system. [Figure 1K] FIG. 11 shows the eleventh step of the parallel supply system. [Figure 2] 10 is a time chart showing the amounts dispensed by the first supply machine, the second supply machine, and the replenishment machine. [Figure 3] FIG. 2 is a block diagram showing an outline of a control configuration of the parallel supply system. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0022] 1A to 1K show steps 1 to 11 of a parallel supply system 1 according to an embodiment of the present invention. The parallel supply system 1 of this embodiment includes a first supply machine A and a second supply machine B arranged in parallel.

[0023] The first feeder A serves to supply the raw material S to a raw material inlet C1 of a screw conveyor C as a supplied device via a first raw material supply line L1 made of hollow piping, etc. Note that the supplied device is not limited to the screw conveyor.

[0024] The second feeder B is installed in parallel with the first feeder A and serves to supply raw material S to the raw material inlet C1 of the screw conveyor C via a second raw material supply line L2, such as a hollow pipe. As shown in FIG. 3, the first feeder A and the second feeder B are feeders equipped with weighing devices, each equipped with a first load cell WA and a second load cell WB, respectively, capable of measuring the raw material mass in their respective internal hoppers. The measured values ​​of the first and second load cells WA and WB are transmitted continuously or at predetermined intervals to a control device PLC2 (described later) via first and second feeder controllers 4A and 4B. The first feeder A and the second feeder B each have a level gauge for detecting the remaining amount of raw material S, and are capable of detecting a first threshold value TH1 and a second threshold value TH2, respectively, as lower limits. The detection signals are transmitted to the PLC2. PLC2 is configured to send signals to the first and second feeder controllers 4A and 4B, respectively, to rotate the first and second feeder motors MA and MB so as to feed raw material S from the first feeder A and the second feeder B. The first feeder A and the second feeder B are arranged in parallel, but in this embodiment, raw material is not fed from both feeders at the same time. In order to stabilize the amount of material fed to the raw material inlet C1, the steady-state feed rates Y1 of the first feeder A and the second feeder B are set to be equal.

[0025] The screw conveyor C is, for example, a screw conveyor that supplies raw materials S to a twin-screw continuous kneader located downstream. Any device may be provided downstream of the screw conveyor C depending on the raw materials to be supplied.

[0026] The parallel supply system 1 is equipped with a replenisher R upstream of the first supplyer A and the second supplyer B. This replenisher R serves to replenish the raw material S via a replenishment line L3 made of hollow piping or the like to the first supplyer A or the second supplyer B that has run out of raw material S. The replenisher R is a powder / granular material discharger that has a larger supply amount than the first supplyer A and the second supplyer B, and is configured to be able to replenish, for example, about 10 times the amount of raw material.

[0027] This replenishment line L3 is provided with a replenishment destination switching valve V1 that can be switched to send the raw material S to either the first supplier A or the second supplier B. Although not shown in detail, the replenishment destination switching valve V1 includes, for example, a T-shaped or other branch pipe, a valve body disposed therein, an actuator that opens and closes the valve body, and a solenoid valve that sends high-pressure air or high-pressure oil to the actuator. This actuator is composed of, for example, an air motor, an air cylinder, a hydraulic motor, a hydraulic cylinder, or the like.

[0028] The first raw material supply line L1 is provided with a first supply destination switching valve V2 that switches whether the raw material S from the first supply machine A is sent to the raw material inlet C1 or returned to the replenishment machine R via the first return line R1.

[0029] Similarly, the second raw material supply line L2 is provided with a second supply destination switching valve V3 that switches whether the raw material S from the second supply machine B is sent to the raw material inlet C1 or returned to the replenishment machine R via the second return line R2.

[0030] The first supply destination switching valve V2 and the second supply destination switching valve V3 each include, for example, a branch pipe, a valve element disposed therein, an actuator for opening and closing the valve element, and a solenoid valve for supplying high-pressure air or high-pressure oil to the actuator. This actuator is also composed of, for example, an air motor, an air cylinder, a hydraulic motor, a hydraulic cylinder, etc. The first supply destination switching valve V2 and the second supply destination switching valve V3 supply less oil than the replenishment destination switching valve V1, so the valve size and the actuator size can be smaller than those of the replenishment destination switching valve V1.

[0031] The electromagnetic switching valves of the replenishment destination switching valve V1, the first supply destination switching valve V2, and the second supply destination switching valve V3 are appropriately switched by a programmable logic controller (PLC2) as a control device, so that the replenishment destination switching valve V1, the first supply destination switching valve V2, and the second supply destination switching valve V3 are controlled to open and close.

[0032] 3, as will be described later, PLC2 is configured to appropriately switch the replenishment destination switching valve V1, the first supply destination switching valve V2, and the second supply destination switching valve V3 so as to prevent one of the first supply machine A and the second supply machine B from supplying raw material S to the screw conveyor C while the raw material S is being replenished from the replenishment machine R, and to supply raw material S to the screw conveyor C from the other of the first supply machine A and the second supply machine B, where the discharge amount Y1 is stable. Power is supplied to PLC2, the first and second motor controllers 3A and 3B, and the first and second feeder controllers 4A and 4B from a power source P.

[0033] Next, a control method for the parallel supply system 1 according to the embodiment of the present invention will be described. Although detailed description will be omitted, each control is performed by the PLC 2, the first and second motor controllers 3A and 3B, the first and second feeder controllers 4A and 4B, etc.

[0034] First, the above-described parallel supply system 1 is prepared.

[0035] Then, an appropriate amount of raw material S is replenished to the replenisher R, the first feeder A, and the second feeder B. The raw material S is not particularly limited. For example, it differs depending on the application, and examples include polyacetal, polyamide, polyurethane, etc. in the polymerization and reaction of engineering plastics, epoxy, polyamide, polyester, etc. in the kneading of plastics, sealants, powder coatings, etc. in the kneading of chemical industrial products, chocolate, candy, etc. in the mixing, kneading, and grinding of food industries, and battery raw materials, ceramics, carbon, EMC, etc. in the kneading of electronic parts.

[0036] When the parallel supply system 1 starts operating, as shown in FIGS. 1A and 2, in the first step, the first supply destination switching valve V2 is switched to the delivery side, and raw material S is supplied from the first supply device A to the raw material inlet C1 of the screw conveyor C via the first raw material supply line L1. As shown in FIG. 2(a), the supply rate (discharge rate) is set to a predetermined value Y1 kg / hr. At this time, the second supply destination switching valve V3 is switched to the return side, and the raw material is returned to the replenisher R at the discharge rate Y1 via the second return line R2. The replenishment destination switching valve V1 is closed. As shown in FIG. 2(c), the supply rate sent to the screw conveyor C is also constant at Y1.

[0037] If this state continues, as shown in the second step in Figure 1B, the amount of raw material S in the hopper of the first feeder A decreases, and the amount of raw material S in the hopper of the second feeder B also gradually decreases. As shown in Figure 2(a), the amount of raw material S fed to the screw conveyor C remains constant at Y1.

[0038] As shown in the third step in Figure 1C, when the remaining amount of raw material S in the first feeder A falls below the first threshold TH1, the first supply destination switching valve V2 is switched to return the raw material S to the replenisher R via the first return line R1, the second supply destination switching valve V3 is switched to send the raw material S to the raw material inlet C1, and the raw material S is supplied from the second feeder B to the raw material inlet C1. As shown in Figure 2(b), the supply rate (discharge rate) is set to a predetermined value Y1 kg / hr per hour. As shown in Figure 2(c), the supply rate sent to the screw conveyor C is also constant at Y1.

[0039] As shown in the fourth step in Figure 1D, the replenishment destination switching valve V1 is switched to the side that sends out raw material S to the first feeder A, and raw material S is replenished to the first feeder A. The discharge rate Y2 kg / hr at this time is, for example, about 10 times Y1. At this time, a large amount of raw material S is charged into the hopper of the first feeder A all at once, so the amount Y3 of raw material S discharged from the first supply destination switching valve V2 becomes unstable and may be more or less than Y1.

[0040] As shown in the fifth step in Figure 1E, after the first predetermined time has elapsed, the hopper of the first feeder A is sufficiently filled with raw material S, and the replenishment destination switching valve V1 is switched to stop the delivery of raw material S to the first feeder A. For a while after the stoppage, the amount Y3 of raw material S dispensed from the first supply destination switching valve V2 remains unstable. The first predetermined time is determined by the amount Y2 dispensed by the replenisher R and the amount replenished to the hopper of the first feeder A.

[0041] Furthermore, for a second predetermined time, as shown in the sixth step in FIG. 1F, the operation of returning raw material S from the first supply device A to the replenisher R via the first return line R1 at a feed rate Y1 and supplying raw material S from the second supply device B to the raw material inlet C1 at a feed rate Y1 continues. After a while, the feed rate of raw material S returned from the first supply device A to the replenisher R becomes stable at Y1. As shown in FIG. 2(c), the feed rate sent to the screw conveyor C is also constant at Y1. The second predetermined time is determined by the time it takes for the amount Y3 of raw material S fed from the first supply destination switching valve V2 toward the first return line R1 to return from an unsteady state to a steady state.

[0042] As shown in the seventh step in FIG. 1G, when this steady operation is continued for a predetermined time, the remaining amount of raw material S in the second supplier B decreases below the second threshold value TH2.

[0043] Then, as shown in the eighth step in Figure 1H, the second supply destination switching valve V3 is switched to the side returning the raw material S to the replenisher R via the second return line R2, the first supply destination switching valve V2 is switched to the side sending the raw material S to the raw material inlet C1, and the raw material S is supplied from the first supply machine A to the raw material inlet C1 by the discharge amount Y1.

[0044] Then, as shown in the ninth step in Figure 1I, the replenishment destination switching valve V1 is switched to the side that sends out raw material S to the second supply device B, and raw material S is replenished to the second supply device B at a feed rate Y2. During this time, the amount of raw material in the hopper of the second supply device B increases rapidly, and the feed rate Y3 returned to the replenishment device R via the second return line R2 becomes unsteady, fluctuating between increases and decreases compared to Y1. Nevertheless, raw material S is supplied from the first supply device A to the raw material inlet C1 at the feed rate Y1.

[0045] As shown in the tenth step in Figure 1J, after the third predetermined time has elapsed, the replenishment destination switching valve V1 is switched to stop the delivery of raw material S to the second supply device B. The third predetermined time is determined by the feed rate Y2 of the replenishment device R and the replenishment rate to the hopper of the first supply device A, just like the first predetermined time.

[0046] As shown in the 11th step in Fig. 1K, after a fourth predetermined time has elapsed, the feed amount Y3 returned from the second supply device B to the replenisher R via the second return line R2 becomes equal to the steady feed amount Y1. The fourth predetermined time is determined by the time it takes for the amount Y3 of raw material S fed from the second supply destination switching valve V3 toward the second return line R2 to return from an unsteady state to a steady state.

[0047] Then, the process returns from step 11 to step 1. This series of operations from step 1 to step 11 is repeated. During this time, as shown in Figures 2(a) and 2(b), the feed rate Y3 from the first feeder A or the second feeder B may become unsteady, but this does not affect the feed rate from the screw conveyor C, as this is raw material being returned to the replenisher R via the first return line R1 or the second return line R2, and the feed rate is always maintained at the steady value Y1, as shown in Figure 2(c).

[0048] In this way, in this embodiment, by appropriately switching the switching valves V1, V2, and V3 using PLC2, even when the feed rate becomes unstable due to the replenishment of raw material from the replenishment machine R to one of the feeders, a stable feed rate Y1 of raw material can be continuously supplied to the screw conveyor C from the other feeder.

[0049] Since a stable amount of raw material is supplied to the screw conveyor, for example, the amount of raw material supplied to a kneader downstream is stable, allowing stable, high-quality kneading to be performed in the kneader.

[0050] Furthermore, by using a replenisher R with a large supply volume, the replenishment time can be shortened, and the non-steady time period can be shortened.

[0051] Furthermore, since each of the feeders A and B has the first and second load cells WA and WB, the mass of the raw material in the hopper is constantly transmitted to the PLC 2, allowing for accurate and rapid control.

[0052] As described above, according to the present invention, even when the amount of raw material S dispensed from one of the first supply device A and the second supply device B is not steady when the raw material S is being filled into one of the first supply device A and the second supply device B, a stable amount of raw material S can be continuously supplied to the screw conveyor C from the other of the first supply device A and the second supply device B, which has a steady amount of dispensed raw material S.

[0053] (Other embodiments) The present invention may be configured as follows in relation to the above embodiment.

[0054] That is, in the above embodiment, a PLC has been described as an example of the control device. However, the control device may be physically configured in any way as long as it controls the "parallel supply system 1." For example, the control device may be one that uses software (programs), such as a microcomputer. Alternatively, the control device may be realized by combining hardware (circuit components).

[0055] It should be noted that the above-described embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses. [Explanation of symbols]

[0056] 1. Parallel supply system 2 PLC (control device) 3A 1st motor controller 3B Second motor controller 4A 1st Feeder Controller 4B 1st feeder controller A 1st supply machine B 2nd supply machine C Screw Conveyor C1 Raw material input port R replenishment machine R1 First return line R2 Second return line V1 Refill target switching valve V2 1st supply destination switching valve V3 Second supply destination switching valve L1 First raw material supply line L2 Second raw material supply line L3 Refill Line MA 1st cutting motor MB 2nd cutting motor WA No. 1 load cell (weighing instrument) WB Second load cell (weighing device) Y1 Cutting amount Y2 Cutting amount Y3 Cutting amount TH1 First threshold TH2 Second threshold

Claims

1. a first feeder that feeds the raw material to a raw material inlet of a feed receiving device via a first raw material feed line; a second supply device provided in parallel with the first supply device and configured to supply raw material to a raw material inlet of the supply receiving device via a second raw material supply line; a replenishing machine that replenishes raw material via a replenishing line to one of the first and second supply machines when the raw material inside the supply machine is depleted; a replenishment destination switching valve that is provided in the replenishment line and that is switched to send the raw material to one of the first supplier and the second supplier; a first supply destination switching valve provided in the first raw material supply line for switching whether the raw material from the first supply machine is sent to the raw material inlet or returned to the replenishment machine; a second supply destination switching valve provided in the second raw material supply line for switching whether the raw material from the second supply machine is sent to the raw material inlet or returned to the replenishment machine; a control device that switches the replenishment destination switching valve, the first supply destination switching valve, and the second supply destination switching valve; A parallel supply system.

2. The control device one of the first supply machine and the second supply machine is not allowed to supply raw material to the supplied device while the raw material is being replenished from the replenishment machine; The other of the first and second feeders is configured to feed the raw material to a feed device, the feed amount of which is stable. The refill destination switching valve, the first supply destination switching valve, and the second supply destination switching valve are configured to be switched.

2. The parallel supply system of claim 1.

3. the replenisher is a powder / granular material discharger having a supply amount greater than the supply amounts of the first supplyer and the second supplyer, The first feeder and the second feeder are feeders with a weighing device that can measure the mass of the raw material in the hopper, and are configured so that a signal from the weighing device is sent to a control device.

3. The parallel supply system according to claim 1 or 2.

4. The supplied device is a screw conveyor that supplies raw materials to the downstream kneader.

3. The parallel supply system according to claim 1 or 2.

5. a first feeder that feeds the raw material to a raw material inlet of a feed receiving device via a first raw material feed line; a second supply device provided in parallel with the first supply device and configured to supply raw material to a raw material inlet of the supply receiving device via a second raw material supply line; a replenishing machine that replenishes raw material via a replenishing line to one of the first and second supply machines when the raw material inside the supply machine is depleted; a replenishment destination switching valve that is provided in the replenishment line and that is switched to send the raw material to one of the first supplier and the second supplier; a first supply destination switching valve provided in the first raw material supply line for switching whether the raw material from the first supply machine is sent to the raw material inlet or returned to the replenishment machine; a parallel supply system including a second supply destination switching valve that is provided on the second raw material supply line and switches whether the raw material from the second supply machine is sent to the raw material inlet or returned to the replenishment machine, and the replenishment machine, the first supply machine, and the second supply machine are replenished with raw material; Start the parallel supply system; supplying the raw material from the first supply device to the raw material inlet of the supplied device through a first raw material supply line; When the remaining amount of raw material in the first supplier falls below a first threshold, the first supply destination switching valve is switched to a side returning the raw material to the replenisher, and the second supply destination switching valve is switched to a side sending the raw material to the raw material inlet, so that the raw material is supplied from the second supplier to the raw material inlet; The replenishment destination switching valve is switched to a side for sending raw material to the first supply device, and the raw material is replenished to the first supply device; After a first predetermined time has elapsed, the replenishment destination switching valve is switched to stop the supply of raw material to the first supplier; Further, by continuing the operation of returning the raw material from the first supply device to the replenisher and supplying the raw material from the second supply device to the raw material inlet for a second predetermined time, the amount of raw material returned from the first supply device to the replenisher becomes stable, When the operation is further continued and the remaining amount of raw material in the second supplier falls below a second threshold, the second supply destination switching valve is switched to a side returning the raw material to the replenisher, and the first supply destination switching valve is switched to a side sending the raw material to the raw material inlet, and the raw material is supplied from the first supplier to the raw material inlet, The replenishment destination switching valve is switched to a side for sending raw material to the second supply device, and the raw material is replenished to the second supply device; After a third predetermined time has elapsed, the replenishment destination switching valve is switched to stop the supply of raw material to the second supply device; Further, by continuing the operation of returning the raw material from the second supply machine to the replenisher and supplying the raw material from the first supply machine to the raw material inlet for a fourth predetermined time, the amount of raw material returned from the second supply machine to the replenisher becomes stable. Repeat a series of tasks A method for controlling a parallel supply system.

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