Loss-in-weight type weighing instrument and its control method

Abstract

To provide a loss-in-weight type weighing device that does not leave raw material inside a weighing tank when a target amount of raw material is taken out. The loss-in-weight weighing device includes a measuring tank (2), a raw material supplying means (4) for supplying raw material (9) to the measuring tank (2), a raw material discharging means (5) for discharging the raw material (9) from the measuring tank (2), a weighing means (3) for measuring the weight of the measuring tank (2), and a control unit (6). The control unit (6) calculates the cumulative weight W of the raw material (9) discharged from the measuring tank (2). S1 When the accumulated weight W reaches a predetermined threshold value P, a first control is performed to control the raw material supply means 4 so that the raw material supply flow rate and the raw material discharge flow rate coincide with each other. A second control is performed to measure the remaining raw material weight A of the raw material 9 remaining in the measuring tank 2 at this time. S1 is the target amount of raw material to be taken out from the weighing tank 2, which is the set take-out weight W E and a third control in which, when the difference in the weight of the raw material 9 reaches the difference in the weight of the remaining raw material A, the supply of the raw material 9 to the weighing tank 2 is stopped and all of the raw material 9 remaining in the weighing tank 2 is discharged.

Description

[Technical Field]

[0001] The present invention relates to a loss-in-weight type weighing machine that does not leave any raw material inside a measuring tank when a target amount of raw material is taken out, and a control method thereof. [Background technology]

[0002] BACKGROUND ART Loss-in-weight scales have been known as devices for taking out a target amount of powdered or granular raw material. In general, a loss-in-weight weighing device supplies powdered or granular raw material into a weighing tank equipped with a weighing means, and then adjusts the raw material discharge flow rate by utilizing the amount of weight loss in the weighing tank when the raw material is discharged downstream from the weighing tank, thereby controlling the raw material discharge flow rate from the metering tank to maintain it at a predetermined set flow rate. A prior application relating to such a loss-in-weight type weighing instrument is known, for example, from Patent Document 1 shown below.

[0003] Patent Document 1 discloses an invention entitled "Loss-in-Weight Type Fixed Quantity Supply Device" that relates to a technique for supplying articles to a measuring tank that contains the articles as objects to be weighed. The loss-in-weight constant quantity feeder disclosed in Patent Document 1 comprises a metering tank having a metering means, a supplying means provided above the metering tank for supplying the metering tank with articles as weighed objects in accordance with a supplying control signal, a discharging means provided in the metering tank for discharging the articles in the metering tank in accordance with a discharging control signal, a supplying control means for repeatedly generating the supplying control signal so that when the amount of the articles in the metering tank becomes low, the supplying of the articles by the supplying means is started and the supplying is stopped when the amount of the articles in the metering tank has nearly reached a predetermined upper limit, and a discharging control means for discharging the articles at a predetermined manipulated variable during a supplying period during which the discharging means is supplying the articles, and a control means for controlling a period during the discharge period following the supplying period in which a signal due to the supplying is displayed in the measurement signal of the metering means. and a discharge control means for repeatedly generating the discharge control signal based on the metering signal so that the measured value of the discharge flow rate of the discharge means matches the target flow rate during a period from after a stabilization period required for the vibration components generated by the metering signal to attenuate until the end of the discharge period, wherein the replenishment control signal is generated so that during the replenishment period, the replenishment flow rate of the article by the replenishment means first becomes greater than the target flow rate for a predetermined first time, and then the replenishment flow rate remains greater than the target flow rate for a predetermined second time while continuously decreasing gradually over time, and finally the replenishment flow rate becomes zero, and the replenishment control means generates the replenishment control signal so that the replenishment flow rate becomes approximately equivalent to the target flow rate when the amount of the article in the metering tank is about to reach the upper limit value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6433727 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent document 1 discloses the following regarding the timing of stopping the supply of items when controlling a loss-in-weight type constant volume supply device: "Incidentally, the time t3 at which the supply of items 100 is stopped is unrelated to the weight measurement value Wx'. In other words, the supply of items 100 is finally stopped based on equation 4, regardless of the weight measurement value Wx'" (see paragraph

[0052] of the specification of Patent document 1). Therefore, in the invention disclosed in Patent Document 1, there is an extremely high probability that articles will remain inside the metering tank when the discharge of articles from the metering tank is stopped. Furthermore, once the target amount of goods has been discharged, any goods remaining in the measuring tank are usually discarded without being used, or are supplied to the market as low-quality goods at a price significantly lower than their original price. Therefore, when the loss-in-weight constant volume feeder disclosed in Patent Document 1 is used, there is a problem in that all or almost all of the articles fed into the measuring tank cannot be used effectively.

[0006] The present invention has been made in response to the above-mentioned conventional circumstances, and its object is to provide a loss-in-weight type weighing machine and a control method thereof that does not leave any raw material in the measuring tank when a target amount of powdered or granular raw material is taken out. [Means for solving the problem]

[0007] A first invention for solving the above problems is a loss-in-weight weighing device comprising a weighing tank having an upper opening and a lower opening and capable of storing powdered or granular raw material therein, raw material supplying means for dropping and supplying the raw material into the inside of the weighing tank through the upper opening, raw material discharging means for dropping and discharging the raw material from the inside of the weighing tank through the lower opening, weighing means for measuring the weight of the raw material stored in the weighing tank, and a control unit for controlling the raw material supply flow rate and raw material discharge flow rate of the raw material supplying means and raw material discharge means, the control unit being configured to be able to calculate the raw material discharge flow rate based on changes in the weight values ​​measured by the weighing means, and the control unit is a loss-in-weight weighing device comprising: an integrated weight W of the raw material sequentially discharged from the raw material discharge means; S1reaches a predetermined threshold P, a first control controls the raw material supply means so that the raw material supply flow rate and the raw material discharge flow rate become equal or approximate to each other; a second control controls the measuring means in a state in which the raw material supply flow rate and the raw material discharge flow rate become equal or approximate to each other by the first control, thereby measuring the remaining raw material weight A of the raw material remaining in the measuring tank; and S1 is the target amount of material to be discharged from the weighing tank, the set take-out weight W E and a third control that, when the difference between the weight of the raw material remaining in the measuring tank and the weight of the raw material remaining in the measuring tank reaches the difference between the weight of the raw material remaining in the measuring tank and the weight of the raw material remaining in the measuring tank, stops the supply of the raw material to the measuring tank by the raw material supply means and continues the discharge operation of the raw material discharge means so as to discharge all of the raw material remaining in the measuring tank. By performing the first control in the first invention having the above configuration, the raw material can be discharged downstream of the metering tank while maintaining a preset flow rate in the raw material discharge means, and the weight of the raw material stored inside the metering tank can be kept constant. Next, in the second control, by weighing the weight of the raw material that is kept constant inside the metering tank, it is possible to determine the weight A of the remaining raw material remaining inside the metering tank when the supply of raw material to the metering tank is stopped while the raw material supply flow rate into the metering tank and the raw material discharge flow rate downstream of the metering tank are the same or similar. Furthermore, by performing the third control, the weight of the raw material taken out from the measuring tank can be set to W E When only 100g of the raw material is discharged, the weight of the raw material remaining in the measuring tank can be reduced to zero. That is, according to the first aspect of the present invention, all of the raw material supplied from the raw material supply means to the inside of the measuring tank is taken out at a set take-out weight W E It can be extracted as a raw material for constituting the above.

[0008] A second invention is the first invention, wherein the threshold value P is set as follows when the upper limit value of the weight of the raw material stored inside the measuring tank is M1: 0 <P<(W E -M1) The present invention is characterized in that: In the second aspect of the invention having the above configuration, by setting the threshold value P within the above range, it is possible to ensure a necessary and sufficient time for performing the first control and the second control. In other words, when the remaining raw material weight A has not yet been determined, the cumulative weight W of the raw material discharged from the raw material discharge means is S1 The set take-out weight W E This has the effect of preventing the occurrence of a problem in which the difference between the weight of the remaining raw material and the weight of the unknown raw material A is reached, which causes the timing to perform the third control to be missed, that is, the timing to stop the supply of raw material to the inside of the measuring tank to be missed.

[0009] The third invention is the second invention, wherein the threshold value P is set to a value W when the maximum weight of the raw material that can be stored in the measuring tank is W M (However, M1 <W M ), then 0 <P≦(W E -W M ) The present invention is characterized in that: In the third invention having the above configuration, by setting the threshold value P within the above range, it is possible to prevent the occurrence of a problem in which the timing for performing the third control is missed, even if it takes longer to determine the remaining raw material weight A than in the second invention described above.

[0010] The fourth invention is the first or second invention described above, characterized in that the raw material supply means comprises a hopper provided above the upper opening of the metering tank and having an outlet for supplying raw material into the interior of the metering tank, and a supply gate for adjusting the flow rate of raw material supplied into the interior of the metering tank by changing the opening of the outlet to change the amount of raw material falling, and the raw material discharge means comprises a discharge gate for adjusting the flow rate of raw material discharged downstream of the metering tank by changing the opening of the lower opening to change the amount of raw material falling. The fourth invention having the above configuration comprises a hopper having an outlet and a supply gate as the raw material supply means, and a lower opening of the metering tank and a discharge gate as the raw material discharge means, i.e., by unifying the operating mechanisms of the raw material supply means and the raw material discharge means, it has the effect of minimizing the time required to adjust the opening of the outlet of the hopper or the lower opening of the metering tank, and minimizing the difference in response time when operating the raw material supply means and the raw material discharge means. Therefore, according to the fourth aspect of the present invention, the first to third controls can be performed smoothly and quickly.

[0011] A fifth invention is a control method for a loss-in-weight weighing device, which includes a weighing tank having an upper opening and a lower opening and capable of storing powdered or granular raw material therein, raw material supplying means for dropping the raw material into the inside of the weighing tank through the upper opening, raw material discharging means for dropping the raw material from the inside of the weighing tank through the lower opening, weighing means for measuring the weight of the raw material stored in the weighing tank, and a control unit for controlling the raw material supply flow rate and raw material discharge flow rate of the raw material supplying means and the raw material discharge means, and wherein the control unit is configured to be able to calculate the raw material discharge flow rate based on changes in the weight value measured by the weighing means, and E A control method for a loss-in-weight type weighing device that controls so that no raw material remains inside the weighing tank when only raw material is taken out, and S1 When the flow rate of the raw material reaches a predetermined threshold value P, the raw material supply means starts to supply the raw material until the raw material supply flow rate matches or approximates the raw material discharge flow rate. Then, when the raw material supply flow rate and the raw material discharge flow rate match or approximate, the weighing means measures the remaining raw material weight A of the raw material remaining in the weighing tank, and then the integrated weight W S1 The set take-out weight W E When the difference between the weight of the raw material and the weight of the remaining raw material A is reached, the raw material supply means stops supplying the raw material to the inside of the measuring tank, and then the raw material discharge means discharges all of the raw material remaining in the measuring tank. The fifth invention having the above-mentioned configuration is a specification of the first invention as a method invention, and its operation is the same as that of the first invention. [Effects of the Invention]

[0012] According to the first and fifth aspects of the present invention, all of the raw material supplied from the raw material supply means to the inside of the measuring tank is taken out at a set take-out weight W E It can be discharged from the measuring tank and taken out as a raw material constituting the above. That is, the first invention, the loss-in-weight type weighing device, is used to set the raw material take-out weight WE When only the raw material is removed, the amount of raw material remaining inside the measuring tank can be reduced to zero. For this reason, for example, when the raw material supplied from the raw material supply means to the inside of the measuring tank is grain and lot switching is performed, the set take-out weight W E Once the raw material is removed, there is no need to remove and discard any remaining grain in the weighing tank, or to sell it to the market as a low-quality blended product at a price significantly lower than its original value. Therefore, according to the first and fifth aspects of the present invention, it is possible to provide a high-performance loss-in-weight weighing machine and a control method thereof that can effectively use all of the raw material supplied from the raw material supply means to the inside of the measuring tank.

[0013] According to the second invention, the raw material is set to a weight W using a loss-in-weight weighing device. E This reduces the risk of not being able to perform the third control when extracting only the remaining part. Therefore, according to the second aspect of the present invention, it is possible to provide a high-performance loss-in-weight weighing instrument that can perform the first to third controls with high reliability.

[0014] According to the third invention, compared to the second invention, even if it takes time to determine the remaining raw material weight A, the risk of not being able to perform the third control can be reduced. Therefore, according to the third aspect of the present invention, a loss-in-weight type weighing instrument that is highly reliable during operation can be provided.

[0015] According to the fourth aspect of the present invention, the structure of the loss-in-weight weighing instrument can be simplified. This makes it easier to reduce the size of the loss-in-weight weighing instrument. Furthermore, by unifying the operating mechanisms of the raw material supply means and raw material discharge means, the difference in response time when operating the raw material supply means and raw material discharge means can be minimized compared to when these operating mechanisms are different. This makes it possible to minimize errors when adjusting the raw material supply flow rate and raw material discharge flow rate. Therefore, according to the fourth aspect of the present invention, a loss-in-weight weighing instrument with high performance can be provided in this respect as well. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a system configuration diagram of a loss-in-weight type weighing instrument according to an embodiment of the present invention. [Figure 2] 1 is the first half of a flowchart showing the operation of the loss-in-weight weighing instrument according to the present embodiment. [Figure 3] 10 is a second half of a flowchart showing the operation of the loss-in-weight weighing instrument according to the present embodiment. [Figure 4] 10 is a graph showing the change over time in the raw material weight WX (kg) during the fixed quantity discharge operation of the loss-in-weight weighing device according to the present embodiment. [Figure 5] 10 is a graph showing the change over time in the raw material weight WX (kg) at the time of the final operation of the loss-in-weight weighing device according to the present embodiment. [Figure 6] FIG. 2 is a cross-sectional view showing the state before the start of operation of the loss-in-weight type weighing device according to the present embodiment. [Figure 7] FIG. 2 is a cross-sectional view showing the state of the loss-in-weight type weighing device according to the present embodiment when raw material is being supplied. [Figure 8] FIG. 2 is a cross-sectional view showing the state of the loss-in-weight type weighing device according to the present embodiment when discharging a fixed amount. [Figure 9] FIG. 10 is a cross-sectional view showing the state when raw material is added to the loss-in-weight type weighing device according to the present embodiment. [Figure 10] FIG. 2 is a cross-sectional view showing the state when first and second controls are being performed in the loss-in-weight type weighing instrument according to the present embodiment. [Figure 11] FIG. 10 is a cross-sectional view showing the state when third control is being performed in the loss-in-weight type weighing instrument according to the present embodiment. [Figure 12] FIG. 10 is a cross-sectional view showing the state when third control is being performed in the loss-in-weight type weighing instrument according to the present embodiment. [Figure 13] 10 is a flowchart showing steps performed after the fixed quantity discharging operation is completed and before the finishing operation is started. DETAILED DESCRIPTION OF THE INVENTION

[0017] A loss-in-weight weighing machine and a control method thereof according to an embodiment of the present invention will be described in detail with reference to Figures 1 to 13. It should be noted that the following description of the preferred embodiment is merely exemplary in nature.

[0018] The structure of a loss-in-weight type weighing instrument according to a representative embodiment of the present invention (hereinafter referred to as this embodiment) will be described. As shown in FIG. 1, the loss-in-weight weighing device 1 according to this embodiment includes a roughly bowl-shaped weighing tank 2 capable of storing powdered or granular raw material 9 therein, raw material supply means 4 disposed above the weighing tank 2, raw material discharge means 5 disposed below the weighing tank 2, weighing means 3 disposed on the outer periphery of the weighing tank 2, a control unit 6 connected to the weighing means 3, raw material supply means 4, and raw material discharge means 5, and a memory unit 7 connected to the control unit 6.

[0019] The metering tank 2 has an upper opening 2a that opens upward at the center of the top surface and communicates with the interior, while the lower half is tapered, the diameter of which decreases as it goes downward, and a lower opening 2b that communicates with the interior is formed at the lower end of the lower half.

[0020] The raw material supply means 4 comprises a hopper 4A having an outlet 41 at its lower end, a cylindrical shape with a centerline facing up and down, and capable of guiding the raw material 9 downward, a supply gate 4B arranged below the hopper 4A and having a plate-like surface facing up and down, and a first cylinder 4C arranged to the side of the supply gate 4B and consisting of an electric cylinder that slides the supply gate 4B horizontally, and the outlet 41 can be switched between an open state and a closed state by the extension and retraction action of the first cylinder 4C. That is, the raw material supply means 4 is capable of adjusting the raw material supply flow rate of the raw material 9 supplied into the inside of the metering tank 2 through the upper opening 2a by changing the opening of the outlet 41 using the first cylinder 4C to change the amount of raw material 9 that falls.

[0021] The raw material discharge means 5 comprises a discharge gate 5A, which is disposed below the metering tank 2 and has a plate-like surface facing up and down, and a second cylinder 5B, which is disposed to the side of the discharge gate 5A and is composed of an electric cylinder that slides the discharge gate 5A horizontally, and the second cylinder 5B is disposed directly below the first cylinder 4C. Raw material discharge means 5 can switch between a state in which lower opening 2b is opened and a state in which it is closed by discharge gate 5A through the extension and contraction action of second cylinder 5B. That is, raw material discharge means 5 can adjust the raw material discharge flow rate of raw material 9 that drops from inside metering tank 2 through lower opening 2b and is discharged downstream of metering tank 2 by changing the opening degree of lower opening 2b with second cylinder 5B to change the amount of raw material 9 that falls.

[0022] The weighing means 3 is a load cell attached to the side of the upper half of the weighing tank 2 symmetrically across the center line, and is capable of measuring the weight of the raw material 9 stored inside the weighing tank 2 as well as the weight of the weighing tank 2 itself.

[0023] The memory unit 7 stores the total weight W of the measuring tank 2 measured by the measuring means 3. T , the wind in measuring tank 2 W0, weight W T The raw material weight W minus the wind weight W0 X , the raw material weight W during the fixed quantity discharge operation 100 described later X The upper limit M1 and the lower limit M2 of the raw material 9 that can be stored in the measuring tank 2 are expressed as the maximum weight W M , the set take-out weight W which is the target amount of the raw material 9 to be discharged and taken out from the weighing tank 2 E It is possible to memorize the following. The storage unit 7 also stores the cumulative weight W of the raw material 9 sequentially discharged from the raw material discharge means 5. S1 Furthermore, the storage unit 7 can store the accumulated weight W S1 The threshold value P is stored.

[0024] The control unit 6 outputs an actuation signal to the raw material supply means 4 to slide the supply gate 4B, thereby changing the opening degree of the outlet 41 and controlling the raw material supply flow rate. Furthermore, the control unit 6 outputs an actuation signal to the raw material discharge means 5 to slide the discharge gate 5A, thereby changing the opening of the lower opening 2b and controlling the raw material discharge flow rate.

[0025] Furthermore, the control unit 6 calculates the cumulative weight W of the raw material 9 sequentially discharged from the raw material discharge means 5 when the raw material 9 is discharged from the discharge gate 5A at a preset flow rate. S1 reaches the threshold value P, the first control is performed to control the raw material supply means 4 so that the raw material supply flow rate coincides with or approximates the set flow rate. Furthermore, the control unit 6 calculates the raw material weight W when the raw material supply flow rate is equal to or close to the set flow rate. X The second control is performed to control the weighing means 3 so as to measure the remaining raw material weight A of the raw material 9 remaining inside the measuring tank 2. Furthermore, the control unit 6 calculates the cumulative weight W of the raw material 9. S1 is the set take-out weight W E When the difference between the weight of raw material 9 and the weight of remaining raw material A is reached, the raw material supply means 4 is controlled so as to stop the supply of raw material 9 into the weighing tank 2, and the raw material discharge means 5 is controlled so as to discharge all of the raw material 9 of the weight of remaining raw material A remaining inside the weighing tank 2, which is a third control.

[0026] For example, the set take-out weight W E 1000kg, maximum value W M is 50 kg and the threshold P is 900 kg, the control unit 6 calculates the accumulated weight W S1 The raw material supply means 4 intermittently supplies the raw material 9 into the metering tank 2 until the accumulated weight W reaches 900 kg, which is the threshold value P, while the raw material discharge means 5 and the raw material supply means 4 are controlled so that the raw material 9 is discharged from the metering tank 2 at a set flow rate by the raw material discharge means 5. S1 When the raw material discharge amount reaches 900 kg, the raw material supply means 4 is controlled so that the raw material discharge flow rate by the raw material discharge means 5 and the raw material supply flow rate by the raw material supply means 4 become equal to or approximate each other. When the raw material discharge flow rate and the raw material supply flow rate become equal or approximate to each other, the control unit 6 measures the weight A of the remaining raw material remaining in the measuring tank 2, for example, 30 kg, and calculates the cumulative weight W S1 When the cumulative weight W of the raw material 9 discharged from the measuring tank 2 reaches (1000-30) = 970 kg, the raw material supplying means 4 is controlled to stop the supply of the raw material 9 to the inside of the measuring tank 2, leaving 30 kg of the raw material 9 inside the measuring tank 2, and finally, the raw material discharging means 5 is controlled to discharge all of the raw material 9 (30 kg) from the inside of the measuring tank 2. Then, the cumulative weight W of the raw material 9 discharged from the measuring tank 2 is S1 The set take-out weight is (970 + 30) = 1000 kg. E It is designed to match.

[0027] Next, an example of the operation of the loss-in-weight weighing instrument 1 according to this embodiment will be described with reference to FIGS.

[0028] The operation of the loss-in-weight weighing device 1 according to this embodiment is mainly to calculate the cumulative weight W of the raw material 9 discharged from the raw material discharge means 5. S1 The fixed-quantity discharge operation 100 (see FIGS. 2 and 4) is performed until the accumulated weight W reaches the threshold value P. S1 reaches a threshold P.

[0029] The fixed quantity discharging operation 100 in the loss-in-weight weighing instrument 1 according to this embodiment will be described with reference to FIGS. 2, 4, and 6 to 9. FIG. In step S1 of the fixed quantity discharge operation 100 shown in FIG. 2, the weighing means 3 measures the weight of the empty measuring tank 2 (see FIG. 6) and stores it in the memory unit 7 as a weight W0 (kg). At any point T in the subsequent steps, the weight W of the measuring tank 2 is measured by the measuring means 3. T When weighing (kg), the weight value W T The weight of the raw material at any point in time T is W minus the weight W0 of the measuring tank 2 measured in step S1. X (kg). Figures 4 and 5 show graphs plotting these values ​​over time.

[0030] After step S1, the process proceeds to step S2 shown in FIG. 2, where the supply gate 4B provided above the upper opening 2a of the metering tank 2 is opened (see FIG. 7), and the supply of the raw material 9 into the metering tank 2 begins (see time T1 in FIG. 4). By this operation, the weight W of the raw material stored inside the metering tank 2 is X increases (see Figure 4). Thereafter, the process proceeds to step S3, and the weight W of the raw material stored inside the measuring tank 2 is calculated. X It is determined whether or not the weight W of the raw material stored inside the measuring tank 2 reaches the upper limit value M1. If the determination in step S3 is NO, X The determination in step S3 is repeated until the upper limit M1 is reached. If the determination in step S3 is YES, the process proceeds to step S4, where supply gate 4B is closed (see FIG. 8) to stop the supply of raw material 9 into metering tank 2 (see time T2 in FIG. 4). After step S4, the process proceeds to step S5 shown in FIG. 2, where discharge gate 5A provided at lower opening 2b of metering tank 2 is opened (see FIG. 8), and discharge of raw material 9 from lower opening 2b of metering tank 2 begins (see time T2 in FIG. 4).

[0031] In the loss-in-weight weighing device 1 according to this embodiment, the raw material discharge flow rate when the raw material 9 is discharged from the lower opening 2b of the measuring tank 2 needs to be maintained at a preset set flow rate. For this reason, in step S5, although not specifically shown in the flow of FIG. 2, discharge gate 5A is gradually opened to start discharging raw material 9 downstream of metering tank 2, and the raw material discharge flow rate to be discharged from discharge gate 5A is calculated based on the amount of decrease in the measured value of metering tank 2 by metering means 3, and the opening of discharge gate 5A is adjusted so that this raw material discharge flow rate becomes the above-mentioned set flow rate.

[0032] Furthermore, after step S5, the process proceeds to step S6, and the cumulative weight W of the raw material 9 discharged from the measuring tank 2 is calculated. S1 It is determined whether or not has reached a threshold value P. In this step S6, it is determined whether it is time to start the finishing operation 200, which will be described later. If the determination in step S6 is NO, the process proceeds to step S7, and the weight W of the raw material stored inside the measuring tank 2 is calculated. X It is determined whether or not the value reaches the lower limit M2. If the determination in step S7 is YES (see time T3 in Figure 4), proceed to step S8, open supply gate 4B (see Figure 9), and start supplying raw material 9 into the inside of metering tank 2 (see time T3 in Figure 4). If the determination in step S7 is NO, the process returns to step S6 and the subsequent steps are repeated.

[0033] The threshold P (kg) is the set take-out weight W E is set based on the upper limit value M1 of the weight of the raw material 9 stored inside the measuring tank 2, so as to satisfy, for example, the following formula. 0 <P<(W E -M1)

[0034] After step S8, the process proceeds to step S9, where the cumulative weight W of the raw material 9 discharged from the weighing tank 2 is calculated again. S1 It is determined whether or not has reached a threshold value P. If the determination in step S9 is NO, the process proceeds to step S10, and the weight W of the raw material stored inside the measuring tank 2 is calculated. X It is determined whether or not the upper limit M1 has been reached. If the determination in step S10 is YES (see time T4 in FIG. 4), the process proceeds to step S11, where supply gate 4B is closed to stop the supply of raw material 9 into metering tank 2 (see time T4 in FIG. 4). If the determination in step S10 is NO, the process returns to step S9 and the subsequent steps are repeated.

[0035] If the determination in the previous step S6 or step S9 is YES, it is time to start the ending operation 200, so the process proceeds to the ending operation 200 shown in FIGS.

[0036] 2, the raw material supply means 4 and the raw material discharge means 5 are controlled to discharge the raw material 9 downstream of the metering tank 2 while maintaining a set flow rate in the raw material discharge means 5. In addition to the above operation, in the fixed-quantity discharge operation 100, the control unit 6 calculates the cumulative weight W of the raw material 9 discharged from the metering tank 2. S1 reaches a threshold P, and determines whether it is time to start the finishing operation 200. That is, in the fixed-quantity discharge operation 100, as shown in FIG. 4, for example, a process α in which the raw material 9 is supplied into the inside of the metering tank 2 while being discharged downstream of the metering tank 2 at a set flow rate, and a process β in which the supply of the raw material 9 into the inside of the metering tank 2 is stopped and the raw material 9 is discharged downstream of the metering tank 2 at a set flow rate are combined to obtain an accumulated weight W of the raw material 9 discharged from the metering tank 2. S1 are alternately repeated until a threshold P is reached.

[0037] The ending operation 200 in the loss-in-weight weighing instrument 1 according to this embodiment will be described with reference to FIGS. 3, 5, and 10 to 12. The cumulative weight W of the raw material 9 discharged from the measuring tank 2 S1 When the threshold value P is reached, the following termination operation 200 is performed. If the determination in step S6 or step S9 shown in FIG. 2 is YES, the process proceeds to step S12 shown in FIG. 3, where supply gate 4B is opened (see FIG. 10), and the supply of raw material 9 into the metering tank 2 begins (see time T5 in FIG. 5). Thereafter, the process proceeds to step S13, where it is determined whether the weight change in the measuring tank 2 is zero or close to zero. If the determination in step S13 is NO, the process proceeds to step S14, where the opening of the supply gate 4B is finely adjusted, and then the process returns to step S13 and the subsequent steps are repeated. If the determination in step S13 is YES (see FIG. 10), the process proceeds to step S15 shown in FIG. 3, where the weight W of the raw material stored inside the measuring tank 2 is calculated. X The remaining raw material weight A is determined by weighing the remaining raw material (see time point T6 in FIG. 10 and FIG. 5).

[0038] While the raw material 9 is being discharged from the discharge gate 5A at a preset flow rate, the supply gate 4B is opened (step S12) to make the raw material supply flow rate into the metering tank 2 equal to or approximate the set flow rate (steps S13 and S14). This causes the amount of raw material 9 entering and leaving the metering tank 2 to become balanced (see FIG. 10), and the weight W of raw material stored inside the metering tank 2 becomes equal to or approximates the set flow rate. X becomes constant (see Figure 5). And the weight of the raw material in this state W X By measuring the amount of raw material (step S15), the weight A of the remaining raw material remaining inside the metering tank 2 is determined when the supply gate 4B is closed in a state where the raw material supply flow rate into the metering tank 2 and the raw material discharge flow rate downstream of the metering tank 2 are the same or similar.

[0039] Furthermore, after step S15, the process proceeds to step S16 shown in FIG. 3, and the accumulated weight W of the raw material 9 discharged from the measuring tank 2 is calculated. S1 is the target amount of raw material 9 to be discharged and taken out from the weighing tank 2, which is the set take-out weight W E It is determined whether the difference in the remaining raw material weight A has been reached. If the determination in step S16 is NO, the process returns to step S16 and the subsequent steps are repeated. Also, if the determination in step S16 is YES, the process proceeds to step S17 shown in FIG. 3, where supply gate 4B is closed (see FIG. 11), and the supply of raw material 9 into metering tank 2 is stopped (see time T7 in FIG. 5).

[0040] That is, when the determination in step S16 is YES, the preset take-out weight W E The amount of raw material 9 obtained by subtracting the remaining raw material weight A from the total amount of raw material 9 has been discharged from the measuring tank 2. At this time, the raw material weight W remaining inside the measuring tank 2 X is the weight of the remaining raw material A. Therefore, when the determination in step S16 is YES, the supply of raw material 9 into the inside of the measuring tank 2 is stopped (step S17), and all of the raw material 9 remaining in the measuring tank 2 with a weight A of the raw material is discharged. S1 Set the take-out weight W E can be matched to

[0041] Therefore, after step S17, the process proceeds to step S18, and the weight W of the raw material stored inside the measuring tank 2 is calculated. X is zero, and if the determination in step S18 is NO, the process returns to step S18 and repeats the subsequent steps. Also, if the determination in step S18 is YES (see FIG. 12), the process proceeds to step S19, where the discharge gate 5A is closed to terminate the discharge operation of the raw material 9 by the loss-in-weight weighing device 1 (see time T8 in FIG. 5).

[0042] Note that steps S12 to S14 in the ending operation 200 shown in FIG. 3 correspond to the first control. Also, step S15 in this ending operation 200 corresponds to the second control. Furthermore, steps S16 to S19 in the above-mentioned ending operation 200 correspond to the third control.

[0043] The loss-in-weight weighing instrument 1 according to this embodiment has the following advantages. That is, according to the loss-in-weight weighing device 1 of this embodiment, the raw material 9 is taken out from the weighing tank 2 at a set weight W E At the time when only the raw material 9 remaining inside the measuring tank 2 is removed, the raw material 9 remaining inside the measuring tank 2 can be reduced to zero. That is, by operating the loss-in-weight weighing device 1 according to this embodiment shown in FIG. 1 as described above, all of the raw material 9 supplied from the raw material supply means 4 to the inside of the measuring tank 2 is taken out at a set take-out weight W E The raw material 9 constituting the above can be discharged and taken out from the measuring tank 2.

[0044] More specifically, when the raw material 9 supplied from the raw material supply means 4 to the inside of the weighing tank 2 is, for example, grain, and when the lot is changed, the set take-out weight W E When the removal of the raw material 9 is completed, there is no raw material 9 remaining inside the measuring tank 2. This eliminates the need to remove and discard the grain remaining inside the weighing tank 2, or to supply it to the market as a low-quality blended product at a price significantly lower than its original price. That is, by operating the loss-in-weight weighing instrument 1 according to this embodiment as described above, the stopping accuracy Q of the loss-in-weight weighing instrument 1 can be improved.

[0045] The stopping accuracy Q (%) is the set take-out weight W E (kg), the cumulative weight of the raw material supplied from the raw material supply means is W S2 (kg), it can be calculated using the following formula: Stopping accuracy Q(%)=(W S2 -W E ) / W E ×100 However, W S2 =W E +B In addition, B (kg) in the above formula is the cumulative weight W of the raw material discharged from the measuring tank 2. S1 is the set take-out weight W E is the weight of the raw material 9 remaining in the measuring tank 2 when the weight reaches In addition, a large value of the stopping accuracy Q (%) means that the set take-out weight W of the raw material 9 supplied from the raw material supply means 4 is E This means that the weight ratio of raw material 9 that could not be extracted as a raw material constituting the product is large.

[0046] Therefore, by operating the loss-in-weight weighing instrument 1 according to this embodiment shown in FIG. 1 as described above, a high-performance loss-in-weight weighing instrument can be provided that can effectively use all of the raw material 9 supplied from the raw material supply means 4 to the inside of the metering tank 2.

[0047] Here, the threshold value P will be explained. The threshold value P (kg) set in steps S6 and S9 in the flowchart shown in FIG. 2 is the set take-out weight W E The upper limit M1 of the weight of the raw material 9 stored inside the measuring tank 2 may be set so as to satisfy the following formula: 0 <P<(WE -M1)

[0048] In this case, it is possible to ensure a necessary and sufficient time to perform steps S12 to S15 in the ending operation 200 shown in FIG. In other words, the upper limit of the threshold P is set to (W E By setting the value close to the value of the remaining raw material weight A, the cumulative weight W of the raw material 9 discharged from the measuring tank 2 can be calculated at a time when the remaining raw material weight A has not yet been determined. S1 The set take-out weight W E This makes it less likely that the timing to perform steps S16 to S19 will be missed, i.e., the timing to stop the supply of raw material to the inside of the measuring tank 2 (step S17) will be missed, as a result of the difference in the weight of the remaining raw material reaching an unknown value A. Therefore, by setting the threshold value P (kg) within the above range, it is possible to provide a high-performance loss-in-weight weighing instrument 1 that can perform steps S12 to S19, that is, the first to third controls, with high reliability.

[0049] In order to safely ensure a necessary and sufficient time for performing steps S12 to S15, the threshold value P can be set to satisfy the following formula. 0 <P≦(W E -W M )

[0050] Also, the set take-out weight W E The value of W is the maximum weight of the raw material 9 that can be stored in the measuring tank 2. M If it is large enough for, say, (10 × W M )≦W E In this case, the threshold P may be set to satisfy the following formula: (W E -2W M )≦P≦(W E -W M ) The reason for this is explained below.

[0051] As described above, in the loss-in-weight weighing device 1 according to this embodiment, the raw material discharge flow rate is calculated based on the amount of decrease in the weight measurement value of the measuring tank 2, and the opening of the discharge gate 5A is adjusted so that the raw material discharge flow rate from the discharge gate 5A becomes the set flow rate, thereby improving the accuracy of adjusting the raw material discharge flow rate. On the other hand, while steps S12 to S14 in the termination operation 200 shown in Figure 3 are being performed, the change in the weight measurement value of the metering tank 2 becomes zero or approaches zero, and the impact caused by the raw material 9 falling inside the metering tank 2 affects the weight measurement value of the metering tank 2, so it may be difficult to calculate the raw material discharge flow rate discharged from the discharge gate 5A with high accuracy. Therefore, while steps S12 to S14 in the finishing operation 200 are being performed, the accuracy of adjusting the discharge flow rate of the raw material discharged from the discharge gate 5A tends to be low.

[0052] That is, the longer the time t (see FIG. 5) required for steps S12 to S17 in the finishing operation 200 shown in FIG. 3, the longer the set take-out weight W of the raw material 9 from the measuring tank 2. E There is a risk that the weighing error will be large when only the sample is taken out. Therefore, in the loss-in-weight weighing device 1 according to this embodiment, the threshold value P, which is the criterion for determining the timing to start the termination operation 200, is set to the set take-out weight W E It is preferable to set it to a value close to

[0053] On the other hand, when the opening degree of the supply gate 4B in the loss-in-weight weighing device 1 according to this embodiment and the parameters of the raw material supply flow rate corresponding to that opening degree are clear, it may be possible to predict with high accuracy the opening degree of the supply gate 4B corresponding to the raw material discharge flow rate of the raw material 9 discharged from the discharge gate 5A. In this case, steps S12 to S15 in the ending operation 200 shown in FIG. 3 can be completed in a few seconds, so the threshold value P is (W E -2W M ) beyond W E Even if the threshold P is set to a value closer to (W E -2W M)≦P≦(W E -W M ) is satisfied, the ending operation 200 shown in FIG. 3 can be performed without any problems.

[0054] When operating the loss-in-weight weighing instrument 1 according to this embodiment, a step shown in FIG. 13 may be added as necessary. As described above, in the loss-in-weight weighing device 1 according to this embodiment, the raw material discharge flow rate is calculated based on the amount of decrease in the weight measurement value of the weighing tank 2, and the opening of the discharge gate 5A is adjusted so that the raw material discharge flow rate from the discharge gate 5A becomes the set flow rate. In addition, the raw material weight W of the raw material 9 stored inside the measuring tank 2 X After the weight of the weighing tank 2 reaches the lower limit M2 (step S7 in FIG. 2), and while the raw material 9 is being resupplied into the weighing tank 2 by the raw material supply means 4 (step S8 in FIG. 2), that is, while step α is being performed, the measured value of the weight of the weighing tank 2 increases rapidly. Therefore, while the step α is being performed, it may be difficult to accurately grasp the weight of the measuring tank 2 accompanying the discharge of the raw material 9. For this reason, it may be difficult to calculate the raw material discharge flow rate at the discharge gate 5A with high accuracy while the step α is being performed.

[0055] When the loss-in-weight weighing device 1 according to this embodiment is operated, the accumulated weight W of the raw material 9 discharged from the weighing tank 2 while the raw material 9 is being resupplied into the weighing tank 2, that is, while the process α is being performed, is calculated. S1 reaches the threshold P (step S9). In this case, it may be difficult to adjust the opening of supply gate 4B so that the raw material supply flow rate at supply gate 4B matches or approximates the raw material discharge flow rate at discharge gate 5A. That is, while the process α shown in FIGS. 4 and 5 is being performed, the cumulative weight W of the raw material 9 discharged from the measuring tank 2 is S1 When the weight W reaches the threshold value P, the process immediately shifts to the termination operation 200 shown in FIG. 3, and the set weight W is taken out from the weighing tank 2. EThere is a risk that the weighing error will be large when taking out the raw material 9.

[0056] Therefore, when the loss-in-weight weighing device 1 according to this embodiment is operated under the above-described circumstances, the cumulative weight W of the raw material 9 discharged from the weighing tank 2 during the process α is S1 reaches the threshold value P, the loss-in-weight weighing instrument 1 may be controlled so as to proceed to the termination operation 200 after the step α is completed. That is, after the fixed amount discharging operation 100 is completed and before the ending operation 200 is started, the loss-in-weight weighing instrument 1 may be controlled to perform the steps shown in FIG.

[0057] Specifically, when the determination in step S9 of the fixed amount discharging operation 100 shown in FIG. 2 is YES, the process proceeds to step S21 shown in FIG. 13, where it is determined whether or not the supply gate 4B is closed. If the determination in step S21 is NO, the process proceeds to step S22, where the raw material weight W of the raw material 9 stored in the measuring tank 2 is calculated. X It is determined whether or not the upper limit M1 has been reached. If the determination in step S22 is YES, the process proceeds to step S23, where the supply gate 4B is closed. If the determination in step S21 is YES, or after step S23, the process proceeds to step S12 in the ending operation 200 shown in FIG.

[0058] In this case, since it is possible to reliably avoid transitioning to the final operation 200 shown in FIG. 3 while the process α is being performed, the set take-out weight W E This can prevent the measurement error that occurs when discharging the raw material 9 from becoming large.

[0059] The loss-in-weight weighing device 1 according to this embodiment includes a hopper 4A having an outlet 41, a supply gate 4B, and a first cylinder 4C as the raw material supply means 4, as shown in FIG. 1, for example, and includes a discharge gate 5A and a second cylinder 5B as the raw material discharge means 5, as shown in FIG. 1, for example, so that the time required to adjust the outlet 41 of the hopper 4A or the opening of the lower opening 2b of the metering tank 2 can be shortened as much as possible. Furthermore, by unifying the operating mechanisms of the raw material supply means 4 and the raw material discharge means 5, the difference in response time when the raw material supply means 4 and the raw material discharge means 5 are operated can be minimized.

[0060] As a result, it is possible to provide a high-performance loss-in-weight weighing instrument 1 that can smoothly and quickly perform each step shown in FIGS. 2 and 3, that is, the first to third controls. Furthermore, if the flow rate adjusting mechanisms of both the raw material supply means 4 and the raw material discharge means 5 are unified into a shutter type as shown in FIG. 1, it is easy to reduce the size of the loss-in-weight weighing instrument 1 according to this embodiment.

[0061] The flow rate adjusting mechanisms in the raw material supply means 4 and raw material discharge means 5 do not need to be shutter-type as shown in FIG. 1, and any mechanism may be used as long as it can adjust the flow rate of the raw material 9 as desired. More specifically, as the flow rate adjusting mechanism in the raw material supply means 4 and the raw material discharge means 5, for example, a screw feeder, a cut gate valve, or the like can be adopted. Furthermore, it is not necessarily required to unify the flow rate adjustment mechanisms in the raw material supply means 4 and the raw material discharge means 5. For example, a shutter type may be adopted as the flow rate adjustment mechanism in the raw material supply means 4, and a screw feeder or a cut gate valve may be adopted as the flow rate adjustment mechanism in the raw material discharge means 5.

[0062] Furthermore, the loss-in-weight weighing device 1 according to this embodiment may be provided with an air injection device or the like that discharges the raw material 9 remaining inside the weighing tank 2 to the downstream side of the weighing tank 2 before closing the discharge gate 5A in step S19 of the termination operation 200 shown in FIG. In this case, when the area around lower opening 2b of metering vessel 2 is flat or the slope toward lower opening 2b is gentle, raw material 9 can be more reliably prevented from remaining inside metering vessel 2.

[0063] Furthermore, the weighing means 3 according to this embodiment may use a weight sensor other than a load cell, for example, a piezoelectric element type or a capacitance type sensor.

[0064] Furthermore, the first cylinder 4C and the second cylinder 5B according to this embodiment may be cylinders other than electric cylinders as long as they can adjust the opening degree of the outlet port 41 by the supply gate 4B and the opening degree of the lower opening 2b by the discharge gate 5A. For example, air cylinders or hydraulic cylinders may be used. Furthermore, the opening degrees of the supply gate 4B and the discharge gate 5A may be adjusted using driving means such as a stepping motor or a servo motor. [Industrial Applicability]

[0065] As described above, the present invention provides a loss-in-weight weighing device and a control method thereof that prevents any raw material from remaining in the measuring tank when a target amount of raw material is removed, and can be used in technical fields related to powder and granular material supply equipment, etc. [Explanation of symbols]

[0066] 1...Loss-in-weight type weighing device 2...Measuring tank 2a...Upper opening 2b...Lower opening 3...Measuring means (load cell) 4...Material supply means 4A...Hopper 41...Outlet 4B...Supply gate 4C...First cylinder 5...Material discharge means 5A...Discharge gate 5B...Second cylinder 6...Control unit 7...Memory unit 9...Material 100...Fixed amount discharge operation 200...End operation

Claims

1. a control unit that controls the raw material supply flow rate and raw material discharge flow rate of the raw material supply means and the raw material discharge means, wherein the control unit is configured to be able to calculate the raw material discharge flow rate based on a change in the weight value measured by the weighing means, The control unit calculates the cumulative weight W of the raw material sequentially discharged from the raw material discharge means. Ｓ１ reaches a predetermined threshold P, a first control that controls the raw material supply means so that the raw material supply flow rate and the raw material discharge flow rate become equal to or approximate each other; a second control for controlling the measuring means in a state in which the raw material supply flow rate and the raw material discharge flow rate are equal to or approximate to each other by the first control, thereby measuring a weight A of the raw material remaining in the measuring tank; The accumulated weight W Ｓ１ is the target amount of the raw material to be discharged and taken out from the measuring tank, Ｅ and a third control for stopping the supply of the raw material to the measuring tank by the raw material supply means when the difference in weight of the raw material remaining in the measuring tank reaches the difference in weight of the remaining raw material A from the first control.

2. The threshold value P is set when the upper limit of the weight of the raw material stored in the measuring tank is M １ If 0<P<(W Ｅ -M １ ) 2. The loss-in-weight weighing instrument according to claim 1, wherein the following is satisfied:

3. The threshold value P is set when the maximum weight of the raw material that can be stored in the measuring tank is W Ｍ If 0<P≦(W Ｅ -W Ｍ ) 3. The loss-in-weight type weighing instrument according to claim 2, wherein the following is satisfied:

4. the raw material supply means comprises: a hopper provided above the upper opening of the metering tank and having an outlet for supplying the raw material into the metering tank; and a supply gate for adjusting the flow rate of the raw material supplied into the metering tank by changing the opening of the outlet to change the amount of the raw material falling, 3. The loss-in-weight weighing instrument according to claim 1, wherein the raw material discharge means includes a discharge gate that adjusts the raw material discharge flow rate downstream of the measuring tank by changing the opening of the lower opening to change the amount of raw material that falls.

5. a control unit for controlling the raw material supply flow rate and raw material discharge flow rate of the raw material supply means and the raw material discharge means, the control unit being capable of calculating the raw material discharge flow rate based on a change in the measured value measured by the weighing means, and a loss-in-weight weighing device for measuring the weight of the raw material stored in the measuring tank; Ｅ A control method for a loss-in-weight type weighing device that controls so that the raw material does not remain inside the measuring tank when removing only the raw material, The cumulative weight W of the raw material sequentially discharged by the raw material discharge means Ｓ１ reaches a predetermined threshold P, the raw material supply means starts to supply the raw material until the raw material supply flow rate matches or approximates the raw material discharge flow rate; Next, when the raw material supply flow rate and the raw material discharge flow rate become equal to or approximate each other, the measuring means measures a weight A of the raw material remaining in the measuring tank, Thereafter, the cumulative weight W Ｓ１ The set take-out weight W Ｅ when the difference in the weight of the remaining raw material from the weight of the raw material A is reached, the raw material supply means stops supplying the raw material to the inside of the measuring tank, and thereafter the raw material discharge means discharges all of the raw material remaining in the measuring tank.

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