JP4694292B2 - Weighing conveyor - Google Patents

Description

  The present invention relates to a weighing conveyor, and more particularly to a weighing conveyor having a plurality of weighing means.

  When weighing an article being conveyed on a weighing conveyor, it is necessary to determine its weighing timing. An example of a technique for determining the measurement timing is disclosed in Patent Document 1. In this technique, a photosensor is provided on the carry-in side of the weighing conveyor, and the time when a predetermined time elapses from the time when an article to be weighed is detected by the photosensor is set as the weighing timing.

Specification of Japanese Patent No. 3253698

  However, in the technology using a photosensor, malfunction may occur due to dirt on the lens of the photosensor, etc., and the article touches the photosensor itself or the mounting bracket of the photosensor, and the detection position of the article by the photosensor is May be crazy. In this case, the measurement timing is different from that assumed in advance. Therefore, it is desired that the measurement timing can be determined without using a photosensor.

  As a technique for determining the weighing timing without using a photosensor, for example, when the weight received by the weighing conveyor increases, it is determined that the article has been placed on the weighing conveyor, and the time when a predetermined time has passed since then is defined as the weighing timing. It is also possible to do. However, with this technology, there is a possibility of erroneously determining that an article has been placed on the weighing conveyor when a person, an article, or an object unrelated to weighing comes into contact with the weighing conveyor.

  An object of the present invention is to provide a weighing conveyor that can accurately determine the weighing timing without using a photosensor or the like.

  The weighing conveyor of the present invention includes a conveyor. This conveyor supports and conveys articles on the upper surface, and for example, a belt conveyor or a chain conveyor can be used. Weighing means for supporting the conveyor from below is provided on each of the article loading side and the unloading side of the conveyor. For these weighing means, for example, a load cell can be used. The value of the analog weighing signal generated by these weighing means changes according to the state of conveyance of the article on the conveyor. For example, when the article is normally conveyed, the value of the analog weighing signal of the carry-in weighing means increases to the maximum value and then decreases as the article is conveyed. The analog weighing signal of the carry-out weighing means continues to increase and decreases after reaching the maximum value even when the analog weighing signal of the carry-in weighing means has already decreased. The A / D conversion means sequentially converts the carry-in and carry-out analog weighing signals from the carry-in and carry-out weighing means into carry-in and carry-out digital weighing signals. Two A / D conversion means can be provided corresponding to the carry-in side weighing means and the carry-out side weighing means, respectively, to obtain carry-in and carry-out side digital weighing signals, or carried into one A / D conversion means The side analog weighing signal and the carry-out side analog weighing signal can be supplied in a time-sharing manner to obtain the carry-in side and carry-out side digital weighing signals. The carry-in and carry-out analog weighing signals may be amplified by the amplification means and then supplied to the A / D conversion means. When the carry-in digital weighing signal has a value greater than or equal to a predetermined first value for a predetermined time or more, and the carry-out digital weighing signal does not fluctuate beyond a predetermined second value The timer starting means activates the measurement timing measuring timer. When the measurement timing measurement timer measures a predetermined measurement timing determination time, the addition means adds the carry-in side and carry-out side digital measurement signals.

  When an article is placed on the conveyor from the carry-in side and does not pass through the carry-in conveyor, the weight of the article is applied to the conveyor from its upper surface, so the load in the same direction as the weight of the article is applied to the carry-in weighing means. In addition, a load in the direction opposite to the weight of the article is applied to the delivery-side weighing means by the lever principle. As a result, if the article is normally conveyed on the conveyor toward the carry-in weighing means, the weighing signal of the carry-in weighing means continues to a value not less than the first value for a predetermined time or more. The weighing signal of the carry-out weighing means does not increase beyond the second value. As long as it is in this state, disturbance due to the contact of an object unrelated to people or weighing with the conveyor does not occur. Therefore, the weighing timing measuring timer is started, and after the timer times the weighing timing determination time, the weight of the article is measured by summing the carry-in and carry-out digital weighing signals.

  Abnormality detection means may be provided for outputting an abnormal signal when the carry-in digital weighing signal increases before the timer activation means completes the measurement of the predetermined time.

  When the article is normally on the conveyor, the digital weighing signal on the loading side is in the decreasing state and the increasing state after the weighing timing measurement timer is started and before the measurement timing determination time elapses. There shouldn't be. The increase state means that there is a high possibility that another article is getting on the conveyor while the article is being conveyed on the conveyor. Therefore, the abnormality detection means outputs an abnormality signal.

  Alternatively, after detecting the maximum value of the carry-in digital weighing signal, an abnormality detection means for outputting an abnormal signal when the maximum value of the carry-out digital weighing signal is not detected can be provided.

  When an article is normally conveyed on the conveyor, and then the next article is normally conveyed on the conveyor, the weighing signal of the input-side weighing means increases from 0 to the maximum value and then reaches 0. Decrease. On the other hand, when the weighing signal of the carry-in weighing means is in a decreasing state, the weighing signal of the carry-out weighing means still continues to increase toward the maximum value and then decreases toward zero. If the maximum value of the carry-in digital weighing signal is not detected after the maximum value of the carry-in digital weighing signal is detected, it is considered that some abnormality, for example, retention on the conveyor has occurred. Therefore, the abnormality detection means outputs an abnormality signal.

  As described above, according to the present invention, it is possible to detect the entry of an article into the conveyor without using a sensor such as a photosensor, and this detection is not affected by disturbances, Measurement timing can be determined with high accuracy.

  The weighing conveyor according to one embodiment of the present invention includes a conveyor, for example, a belt conveyor 2 as shown in FIG. The article 4 is conveyed from the carry-in side to the carry-out side on the upper surface of the belt conveyor 2. The article 4 applies a downward load to the belt conveyor 2. On the carry-in side of the belt conveyor 2, a feed conveyor 6 for feeding the articles 4 to the belt conveyor 2 is arranged. On the carry-out side of the belt conveyor 2, it is carried onto a carry-out conveyor for carrying out the articles 4 carried on the belt conveyor 2, for example, a sorting conveyor 8. Although not shown, the sorting conveyor 8 is provided with a sorting device, and distributes the articles 4 to predetermined positions according to the weighing results of the weighing conveyor including the conveyor 2.

  A carry-in weighing means, for example, a load cell 10 is attached to the carry-in side of the lower surface of the conveyor 2, and a carry-out weighing means, for example, the load cell 12 is attached to the carry-out side of the lower surface of the conveyor 2. The load cell 10 receives a load of the article 4 and generates a carry-in analog weighing signal, and the load cell 12 receives a load of the article 4 and generates a carry-out analog weighing signal. The values of the carry-in side and carry-out side analog weighing signals change according to which position on the conveyor 2 the article 4 is being conveyed.

  These carry-in and carry-out analog weighing signals are respectively amplified by amplifiers 14 and 16 and then supplied to A / D conversion means, for example, A / D converters 18 and 20, where carry-in and carry-out are converted into digital weighing signals. The data is sequentially converted at a predetermined sampling rate. The A / D converters 18 and 20 are unidirectional and perform digital conversion only on a positive value of the analog weighing signal. If the analog weighing signal is a negative value, the digital signal is 0. Is output.

  The carry-in side and carry-out side digital weighing signals are supplied to the control means, for example, the CPU 24 via the input / output circuit 22. The CPU 24 determines the weight of the article 4 from the carry-in side and carry-out side digital weighing signals while using the memory 26 as a work area in accordance with a storage means, for example, a program stored in the memory 26. Furthermore, the reference weight signal and the allowable range signal supplied from the operation setting display unit 28 via the input circuit 22 are compared with the determined weight of the article to determine how to distribute the articles 4. According to the determination, the sorting device on the sorting conveyor 8 is controlled. That is, the conveyor 2, the load cells 10, 12 and the CPU 24 constitute a weighing conveyor, and an operation setting display unit 26 is added to the weighing conveyor to constitute a weight sorter. The result of article distribution performed by the CPU 4 is displayed on the operation setting display unit 28.

  FIG. 2 schematically shows changes in the carry-in analog weighing signal and the carry-out analog weighing signal when only one article 4 is normally conveyed on the conveyor 2. As indicated by the symbol a, when the carry-in side analog weighing signal enters the conveyor 2, the value rapidly increases from zero to a maximum value. The maximum value occurs when the article 4 passes over the load-side load cell 4. From this maximum value, the carry-in side analog weighing signal decreases. As indicated by the symbol b, the value of the carry-out side analog weighing signal increases to the maximum value when the article 4 enters the conveyor 2, but the gradient thereof is gentler than the increase gradient of the carry-in side analog weighing signal. Even if the carry-in side analog weighing signal starts to decrease, the increase still continues, and when the article 4 passes through the center of the conveyor 2, the value becomes equal to the carry-in side analog weighing signal. Then, when the article 4 passes through the unloading side load cell 12, the unloading side analog weighing signal becomes a maximum value, and then rapidly decreases toward zero. The carry-out analog weighing signal produces a negative value for some time after the article 4 enters the conveyor 2. This is because, at the stage where the center of gravity of the article 4 does not pass through the load cell 10 on the carry-in side, a downward load, that is, a positive load is applied to the load cell 10 by the lever principle, but the load cell 12 on the carry-out side is directed upward. This is because a negative load is applied. For the same reason, a negative value is generated in the carry-in analog signal after the article 4 passes through the carry-out load cell 12. These negative values become zero when digitally converted by the A / D converters 18 and 20.

  Therefore, the carry-in digital weighing signal continues to be equal to or more than the first threshold value Wth1 set to a value somewhat larger than zero, for example, for a predetermined time, for example, Tth, and the carry-out digital weighing signal is In the meantime, when a predetermined value, for example, 0 is maintained, it is considered that the article 4 has successfully entered the conveyor 2. The value of both digital weighing signals is defined as a measurement time tw, which is a predetermined time from the time when Tth has elapsed, for example, the time Ts until the carry-out digital weighing signal increases to a value slightly before the maximum value. Should be added.

  Therefore, the CPU 24 performs processing as shown in FIGS. The process of FIG. 3 is executed each time the A / D converters 10 and 12 generate the carry-in and carry-out digital weighing signals. First, the carry-in digital weighing signal Din and the carry-out digital weighing signal Dout are read (step S2). ). Next, it is determined whether or not the carry-in side digital weighing signal Din is equal to or greater than a predetermined first threshold value Wth (step S4). If the answer to this determination is no, a flag indicating whether or not the carry-in digital weighing signal Din is equal to or greater than a predetermined first threshold value Wth and counting for determining the weighing timing is started. It is determined whether or not F is 1 (step S6). This flag F is set to 0 in the initial state. If the answer to the determination in step S6 is yes, the carry-in digital weighing signal Din is already greater than or equal to the first threshold value Wth and counting for determining the weighing timing is started, but the carry-in digital weighing signal Din is started. Has changed to a value smaller than the first threshold value Wth, there is an abnormality in the conveyance of the article 4, and accurate measurement timing cannot be determined. Therefore, a measurement timing abnormality process is performed. If the answer to the determination in step S6 is no, the carry-in side digital weighing signal Din has not yet reached the first threshold value, and the counting for determining the weighing timing has not started, so this process ends. .

  If the answer to the determination in step S4 is yes, it is determined whether or not the flag F1 is 1 (step S8). If the answer to this determination is no, it means that the carry-in digital weighing signal Din has become equal to or higher than the first threshold value Wth for the first time, and therefore the flag F1 is set to 1 (step S10). A counter t1 for determining the measurement timing is set to 0 (step S10).

  If the answer to the determination in step S8 is yes, counting for determining the measurement timing has already been started, so the value of the counter t1 is incremented by 1 (step S14).

  Next, it is determined whether or not the value of the carry-out side digital weighing signal Dout is equal to the previous value Doutp representing the carry-out side digital weighing signal Dout when this processing was performed last time (step S16). The previous value Doutp is set to zero in the initial setting. In the state where the article 4 has not yet reached the carry-in side load cell 10, as described above, the carry-out side analog weighing signal is a negative value, and the value of the carry-out side digital weighing signal is maintained at 0. Therefore, if the answer to the determination in step S16 is no, the value of the carry-out side digital weighing signal Dout has changed from the previous time. This is because there is a high possibility that an article other than a person or the article 4 has contacted the conveyor 2. Perform weighing error processing. For example, an abnormality is displayed on the operation setting display 28. At this time, if an article other than a person or the article 4 is in contact with the conveyor 2, the value of the carry-in digital weighing signal Din also changes, but this has already exceeded the first threshold value Wth. Therefore, it cannot be detected by the process of step S4.

  If the answer to the determination in step S16 is yes, it is determined whether the count value of the counter t1 is equal to or greater than a predetermined time Tth (step S18). If the answer to this determination is no, the carry-in side digital weighing signal Din is not less than the first threshold value Wth and the carry-out side digital weighing signal Dout has not changed, that is, has changed to a value larger than 0. If no state continues for more than the time Th, it can be determined that the article 4 is normally on the conveyor 4, so that it is set to 0 in order to start a measuring timing measuring timer, for example, the counter t2. S20). If the answer to the determination in step S18 is no, the carry-in digital weighing signal Din is not less than the first threshold value Wth and the carry-out digital weighing signal Dout has not changed, that is, it changes to a value larger than 0. This state is terminated because the state that has not been continued for more than the time Th.

  Thus, as shown in FIG. 3, the counter t2 counts the clock every time the clock signal is input to the CPU 22 (step S22). Then, as shown in FIG. 4, it is determined whether the value of the counter t2 coincides with a predetermined time Ts (step S24). If the result of this determination is yes, a weighing process is performed (step S25). In this weighing process, the carry-in and carry-out digital weighing signals Din and Dout are added together.

  For example, a new article may get on the conveyor 2 while the article 4 is being conveyed toward the carry-out load cell 12 and has not yet reached the measurement timing. In other words, double boarding of articles may occur. In such a case, as shown in FIG. 6, the carry-in analog weighing signal starts to increase before the weighing timing comes. Therefore, if an increase in the carry-in digital weighing signal is detected before the weighing timing is reached, it is determined that double boarding has occurred and processing is performed.

  Therefore, if the answer to the determination of whether the value of the counter t2 matches Ts in step S24 shown in FIG. 4 is NO, the carry-in digital weighing signal Din is the carry-in digital weighing signal obtained when this process was performed last time. It is determined whether it is larger than the previous value Dinp which is the value of (step S26). If the answer to this determination is yes, as is clear from FIG. 3, either the carry-in digital weighing signal Din is increasing toward the maximum value or a double boarding has occurred.

  Therefore, first the carry-in digital weighing signal is stored as the previous value Dinp (step S28), and then the maximum value flag Fp that is set to 1 when the carry-in digital weighing signal increases to the maximum value is already set to 1. It is determined whether it has been performed (step S30). If the answer to this determination is no, the answer to the determination in step S28 is yes because the maximum value has not yet been detected, and thus this process ends.

  If the answer to the determination in step S26 is yes, the maximum value has been detected, so the maximum value flag Fp is set to 1 (step S32), and the carry-in digital weighing signal is stored as the previous value Dinp (step S34), this process is terminated.

  If the answer to the determination in step S30 is yes, it is determined that the value of the counter t2 is greater than Ts since the carry-in digital weighing signal has increased again after the maximum value has elapsed. Step S36).

  If the answer to this determination is no, since another article has been boarded before the weighing timing as shown in FIG. 6, a weighing abnormality double boarding process is performed (step S38). In this double boarding process, since a new article is placed on the conveyor 2 before the measurement timing is reached, the weight of the article previously placed on the conveyor 2 is not accurately represented. Therefore, this article 4 is distributed on the sorting conveyor 8 to a double-riding re-weighed product, and subsequent articles are also distributed to the re-weighed product.

  If the answer to the determination in step S36 is yes, as shown in FIG. 7, since the article has been boarded after reaching the weighing timing, the weighing normal double boarding process is performed (step S40). In this case, since the weighing of the article 4 is normally performed, only the subsequent article is distributed to the re-weighed article. Steps S26 to S40 constitute an abnormality detection means.

  As is apparent from FIGS. 2, 6 and 7, as long as the article 4 is being conveyed, after the maximum value is generated in the carry-in digital weighing signal Din, the maximum value is also generated in the carry-out digital weighing signal Dout. ing. If a maximum value is generated in the carry-in digital weighing signal Din, a maximal value is generated in the carry-out digital weighing signal Dout even though a strange time has passed even if the next article enters the conveyor 2. Otherwise, the article is stopped on the conveyor 2 for some reason, or the carry-out load cell is broken. In order to detect the presence or absence of such a state, the CPU 22 performs a process as shown in FIG.

  The process of FIG. 8 is executed each time a carry-in digital weighing signal is generated. First, it is determined whether or not the carry-in local maximum finding flag Finmax that is set to 1 when the local maximum is generated in the carry-in digital weighing signal is already set to 1 (step S42). If the answer to this determination is no, it is determined whether the carry-in side digital weighing signal Din is larger than the carry-in temporary maximum value Maxin (step S44). The carry-in temporary maximum value Maxin is set to 0 in the initial state. If the answer to this determination is yes, since the maximum value has not yet been found, the carry-in side digital weighing signal Din is stored in the carry-in temporary provisional maximum value Maxin (step S46), and this process ends.

  If the answer to the determination in step S44 is yes, a local maximum value has been found, so the carry-in local maximum value discovery flag Finmax is set to 1 (step S48). Steps S44, 46 and 48 correspond to the carry-in local maximum value determining means.

  Subsequent to step S48, the value of the counter t3 is set to 0 (step S49). Next, it is determined whether the value of the carry-out side digital weighing signal Dout is larger than the carry-out side temporary maximum value Maxout (step S50). The carry-in temporary maximum value Maxout is set to 0 in the initial state. If the answer to this determination is yes, the maximum value has not been found, and the carry-out side digital weighing signal Dout is stored in the carry-out side temporary maximum value Maxout (step S52). Steps S50 and S52 correspond to the carry-out local maximum value detecting means. Next, it is determined that the time Td at which the next article is normally expected to enter the conveyor 2 has elapsed since the maximum value of the carry-in digital weighing signal was found (step S54). If the answer to this determination is no, this process ends. If the answer to the determination in step S54 is yes, since there is no maximum value found even though the maximum value may be detected in the carry-out side digital weighing signal, an abnormality for performing abnormality processing A flag is set (step S56), and this process is terminated.

  If the answer to the determination in step S42 is yes, the maximum value of the carry-in digital weighing signal has been found, so the value of the counter t3 is incremented by 1 (step S58), and step S50 and subsequent steps are executed to determine the value of the counter t3. If the maximum value is not found before elapses after Td, processing is performed in the same manner as described above.

  If the maximum value is found in step S50 and the answer to the determination in step S50 is yes, it is determined whether the value of the counter t3 is greater than Td (step S60). If the answer is yes, it is normal, so a normal flag is set (step S62), and this process ends. If the answer to the determination at step S60 is no, there is still some abnormality, and step S56 is executed.

  When the abnormality flag is set, an abnormality is displayed on the operation setting display 28. An operator performs an inspection based on this display.

  In the above embodiment, when determining the weighing timing, it is determined whether or not the carry-out side digital weighing signal is larger than 0, but it is determined whether or not it is larger than an appropriate value larger than 0. Alternatively, when an A / D converter that converts a negative value is used, it may be determined whether or not the value of the carry-out digital weighing signal is larger than an appropriate value set to a negative value. In the above embodiment, a belt conveyor is used, but a chain conveyor or the like can also be used. In the above embodiment, the load cell is provided as the weighing means only on the carry-in side and the carry-out side. However, a single or plural weighing means may be provided between them.

It is a schematic block diagram of the weighing conveyor of one Embodiment of this invention. It is a figure which shows the change of the measurement signal of the carrying-in side and carrying-out side load cell when an article is normally conveyed in the weighing conveyor of FIG. It is a flowchart of the process which determines the measurement start point of the measurement timing in the measurement conveyor of FIG. It is a flowchart of the measurement process of the measurement timing in the measurement conveyor of FIG. It is a flowchart of the process which determines whether the boarding of the articles | goods in the weighing conveyor of FIG. 1 is normal. It is a figure which shows the change of the measurement signal of the carrying-in side and carrying-out side load cell of an example of the goods board | substrate abnormality in the weighing conveyor of FIG. It is a figure which shows the change of the measurement signal of the carrying-in side and carrying-out side load cell of the other example of the goods boarding abnormality in the weighing conveyor of FIG. It is a flowchart of the process which determines whether there exists abnormality, such as an article retention in the weighing conveyor of FIG.

Explanation of symbols

2 Conveyor 10 Loading-side load cell (loading-side weighing means)
12 Unloading side load cell (unloading side weighing means)
18 20 A / D converter 24 CPU (timer starting means, summing means)

Claims (3)

A conveyor for supporting and transporting articles on the upper surface;
Weighing means provided at each of the lower part of the conveyor on the article carry-in side and the carry-out side, wherein the value of the analog weighing signal changes according to the state of conveyance of the article,
A / D conversion means for sequentially converting the carry-in and carry-out analog weighing signals from the carry-in and carry-out weighing means into carry-in and carry-out digital weighing signals;
When the carry-in digital weighing signal has a value that is equal to or greater than a predetermined first value over a predetermined time and the carry-out digital weighing signal is not more than a predetermined second value, Timer starting means for operating a timer for measuring the measurement timing;
Summing means for summing the carry-in and carry-out digital weighing signals when the weighing timing measurement timer times a predetermined weighing timing determination time;
Weighing conveyor provided.   2. The weighing conveyor according to claim 1, further comprising an abnormality detecting means for outputting an abnormal signal when the carry-in digital weighing signal is increased before the timer starting means completes the measurement of the predetermined time. . 2. The weighing conveyor according to claim 1, further comprising an abnormality detecting means for outputting an abnormality signal when the maximum value of the carry-in digital weighing signal is not detected after detecting the maximum value of the carry-in digital weighing signal. .

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