JP2003149037A - Combination weighing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate maintenance inspection by reducing the number of constituent apparatus of the fundamental units of a combination weighing apparatus. SOLUTION: In a plurality of load cells 10a, strain gauges 31 fitted to strain producing elements 30 generates analog load signals corresponding to loads applied to the elements 30. Weighing function computing units 34 having at least analog-to-digital converters 40 for converting these analog load signals into digital load signals, are arranged on the elements 30, or inside the elements 30. Loads independent of each other are applied to individual substances 30. Digital load signals from the computing units 34 of these load cells 10a, are supplied to a display/operation panel 16. One display/operation panel 16 has at least a combination computation means. The combination computation means combines individual digital load signals variously, and selects a combination whose total value is equal or near to a target value out of individual combinations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combination scale for weighing articles and selecting a combination equal to or close to a target weight from various combinations of the measured values, and more particularly to a weighing mechanism thereof.

[0002]

2. Description of the Related Art An example of a conventional combination scale is shown in FIGS. As shown in FIG. 4, this combination scale has a dispersion feeder 2. A plurality of linear feeders 4 are arranged around the dispersion feeder 2. Dispersion feeder 2
Are driven by the drive unit 2a. The articles distributed around the dispersion feeder 2 are supplied to the respective straight advance feeders 4 and are forwardly conveyed by the drive unit 4a of the straight advance feeders 4. Supply hoppers 6 are arranged below the front end portions of the linear feeders 4, respectively. Below the supply hoppers 6, a weighing hopper 8 is arranged. The articles in the supply hopper 6 are supplied to the weighing hopper 8 by opening its gate 6a. Each of these weighing hoppers 8 is provided with a load cell 10. The load cell 10 produces a load signal corresponding to the load it receives. These load signals are sent to each weighing hopper 8
Is supplied to the control device 12 provided corresponding to.
As shown in FIG. 5, the weighing function computing device 14 provided in the control device 12 processes the load signal to generate a weighing signal representing the weight of the article in each weighing hopper 8. These weighing signals are supplied to the display / operation panel 16, where a combination calculation is performed, and a combination whose total weight is equal to or close to the target weight value is selected. The gate control device 18 of the corresponding control device 12 opens the gate 8a of the weighing hopper 8 in which the articles constituting the selected combination are stored, and the selected article is packaged via the collecting chute 20 not shown. Supply to the device. The gate control device 18 also controls the supply hopper gate 6a for the supply hopper 6 located above the corresponding weighing hopper. In addition, the control device 1
2 is provided with a straight-travel feeder control device 24 corresponding to the straight-travel feeder 4 located above the corresponding supply hopper 6 and controls the straight-travel feeder 4.

[0003]

Generally, it is desirable for the scale to be compact in design. However, in order to obtain a combination suitable for high speed and high accuracy as a combination weigher, it is necessary to increase the number of units in a row composed of the linear feeder 4, the supply hopper 6 and the weighing hopper 8 around the dispersion feeder 2. is there. Therefore, the combination scale is provided with a large number of the above-mentioned units having the same shape and function, and from the viewpoint of improving the efficiency of assembly work and reducing the size of the combination scale,
It is desired to reduce the number of devices that make up one unit.

Further, when a failure occurs in the weight measuring system of the combination weigher, it is difficult for a general user to find out which one of the load cell 10 and the weigher function computing device 14 has a failure. When a failure occurs, it takes time and effort to recover it. In the end, both had to be prepared in advance as spare parts, both of them had to be replaced, and the span had to be adjusted using the reference weight, which made maintenance and inspection troublesome.

It is an object of the present invention to provide a combination scale and a load cell suitable for the combination scale, which reduce the number of constituent devices of a basic unit of the combination scale and facilitate maintenance.

[0006]

The combination scale according to the present invention has a plurality of load cells. In these load cells, the load detection means provided on the flexure element generates an analog load signal corresponding to the load loaded on the flexure body. A strain gauge or the like can be used as the load detecting means. The lower calculation means is provided on or inside the flexure element. The lower order calculation means has at least a digital conversion means. The digital conversion means
Converts an analog load signal into a digital load signal. Loads that are independent of each other are applied to the flexure elements of these load cells. For example, a flexure element can be provided in each of a plurality of article accommodating means to which articles are supplied, such as a weighing hopper and a mounting table. Furthermore, the upper-level calculation means is provided in the combination scale. The upper-order arithmetic means has at least a combination arithmetic means, and the combination arithmetic means variously combines the digital load signals from the lower-order arithmetic means of each load cell, and the total value of the combinations is equal to or close to the target value. Select. The higher-order computing means can also be configured to display each digital load signal independently. The higher-order arithmetic means can control the discharge of the article from the article storage means, and can also control the article supply means for supplying the article to the article storage means, for example, the supply hopper or the straight feeder. When the number of balances is large and the number of combinations is extremely large, a plurality of upper-order arithmetic means, for example, two, are provided, and the weight check by the combination including a certain scale is performed by one upper-order arithmetic means, and the combination not including the scales. The weight check by can also be performed by another higher-order arithmetic means. Each subordinate computing means can also be provided with scale function computing means. As the scale function calculation means, for example, a value corresponding to the weight of the article storage means is subtracted from the load signal,
There are an initial value processing means for obtaining the true weight of the article to be weighed, a zero point adjusting means for correcting the fluctuation of the initial value when the article is not loaded, and the like.

In recent years, various electronic parts have been drastically reduced in size, and an electronic circuit which performs highly functional operation can be designed in a compact size. In the load cell used for the combination scale,
Since a flexure element having sufficient strength to receive a load of several kg is required, and the flexure element has a volume of a certain value or more, the environment and conditions for integrated production are ready. When the lower strain calculation means is integrated with the flexure element equipped with the load detection means, and one in which the unit is morphologically formed is applied to the combination weigher, it contributes to the reduction of the space of the combination weigher main body and the load cell. Arrange it in the combination weigher as a unit with the lower-order calculation means,
Assembly work efficiency is higher than wiring between them. Further, since the combination weigher uses a large number of load cells and low-order arithmetic means, the failure probability increases. However, if only one type of unit that is integrated is prepared as a spare, in case of failure, it is sufficient to replace the failed unit, so that efficient repair can be performed. Further, if the span of the unit prepared for the spare is adjusted in advance with respect to the reference weight, it is not necessary to perform the span adjustment work when the unit is replaced.

An example of a scale using a unit in which an arithmetic circuit board is integrally arranged on a strain-generating body of a load cell and a digital load signal and a weight value signal are output is disclosed in Japanese Patent Laid-Open No.
There is one disclosed in Japanese Patent No. 250028. In this scale, the weighing platform is supported by a plurality of load cells. A circuit board provided with an A / D conversion circuit, a CPU, a serial communication circuit, and the like is arranged on the side of the strain generating element of these load cells. The digital load signal output from the circuit board of each load cell is collected by the main controller to generate a weighing value as one scale. Since this scale is configured to support one weighing platform by a plurality of load cells, each load cell has a structure in which it interferes mechanically through the weighing platform. Therefore, even if the load signals from the individual load cells are displayed on the main controller so that they can be read, and they are used for maintenance work, they are caused by mechanical structures such as distortion of the platform load receiver of the specific load cell. When a trouble occurs, the load signals of all the load cells are affected by this distortion, so that it is not possible to determine whether the specific load cell is normal or abnormal from each load signal.

On the other hand, in this combination weigher, loads independent from each other are applied to the load cell in which the subordinate calculation means are integrated, so that the respective load signals are not subjected to the mechanical interference of other flexure elements. . Therefore, if the higher-order arithmetic means provided on the upper side of each load cell collects the load signals of each load cell and can display them independently, the normal operation of each load cell,
Can monitor and inspect abnormal operation.

Japanese Unexamined Patent Publication No. 4-194710 discloses an electronic device having a structure in which a display, a keyboard and the like are connected to the circuit board of the load cell as described above, and signals are exchanged between them via a serial signal communication line. A scale is disclosed. This electronic scale is intended for weighing signal processing of only one static scale, and all scale calculations are completed in the load cell unit including the calculation function for the static scale.

On the other hand, in the combination weigher, it is necessary to process load signals from many load cells simultaneously in parallel. Further, it is necessary to control the discharge and supply of the articles based on the result of the combination calculation. For example, it is also necessary to control the discharge of articles from the article storage means provided with the load cell, for example, the gate control of the weighing hopper, and the control of the article supply means to the article storage means, such as the supply hopper and the straight feeder.
In order to improve the efficiency of data processing and control, a lower-order calculation means is provided for each load cell that receives a load independently, and by this, the fixed measurement value of the load is output. Is supplied to the higher-order arithmetic means to perform a combination operation. In this way, since the processing required as the combination scale is shared by each of the lower-order arithmetic means and the upper-order arithmetic means, it is necessary to exchange a large amount of data at high speed between the upper-order arithmetic means and each of the lower-order arithmetic means. Not efficient.

The weighing device according to the present invention comprises a plurality of load cells. Each load cell has a flexure element.
A load signal generating means is provided on the strain generating body. The load signal generating means generates a load signal when loading of the load is started. A load determining means for determining the value of the load based on a load signal generated by the loading of the load is provided. This load confirmation means is a means for confirming the load when the amplitude of the load signal is below a certain value, and a load signal obtained within a predetermined time from the time of loading the load signal. The value of the load may be determined based on the load, or the load may be determined within a predetermined time after the load is loaded. The load cells are configured to be loaded with loads independent of each other. For example, each load cell can be provided in the article housing means and the load of the article supplied to the article housing means can be detected. As the article storage means, a weighing hopper or a loading table on which articles are loaded can be used. The arithmetic means processes the output signals of the load determining means of these load cells. As the calculation means, there are various combinations of the load values from the load determination means of each load cell, and a combination calculation means having a combination calculation means for selecting a combination whose total value is equal to or close to a target value from among these combinations Means can be used. When the load determining means determines the value of the load on the basis of the load signal obtained within a predetermined time from the time of loading the load, the higher-order arithmetic means, with respect to the load determining means,
You may comprise so that the start timing of the preset time may be notified. It is also possible to provide an article supply means for supplying an article to the article storage means, for example, a supply hopper or a linear feeder. The host computing means can also control the discharge of the articles from the article storage means and the control of the supply of the articles from the article supply means to the article storage means. The load determining means may be provided on or inside the flexure element.

In the combination weigher, the weight value is not fixed until the load signal of each load cell is completely stabilized, but because of the high speed weighing, when the change of the amplitude of the load signal becomes less than a certain value. Confirm the load, confirm the load based on the load signal obtained within the predetermined time from the start of load loading, or determine the load value at the preset time from the start of load loading. It may happen. In the present invention, the load determining means is provided in each load cell. When the host computing means determines each measured value based on the load signal of each load cell, the load cell generates many load signals almost at the same time due to the characteristics of the combination weigher. Must be done and the burden is very heavy. In particular, when the higher-order arithmetic means also performs other real-time processing, for example, control of the article storage means and control of the article supply means, there is a high possibility that the timing for determining the load is prolonged or varies. As a result, the combination calculation is also started from the timing when the load is finalized, so that the processing capacity of the combination scale is reduced. On the other hand, if load determining means is provided in each load cell as in the present invention, the higher-order computing means may notify the load determining means of only the timing at which the article is supplied to the article storage means. The load on the means is reduced, and the throughput of the combination weigher is not reduced.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A combination scale according to one embodiment of the present invention is a combination scale as shown in FIG.
1, the load cell 10 and the balance function calculation device 14 provided corresponding thereto are separate units, but as shown in FIG. 1, a load cell incorporating the balance function calculation device is provided. The difference is that 10a is provided for each weighing hopper 8. In FIG. 1, reference numeral 29
Shown by 1 is one weighing unit including one straight feeder 4, one supply hopper 6, one weighing hopper 8, a load cell 10a, a gate controller 18, and a straight feeder controller 22. A plurality of units 29 are provided.

Each load cell 10a has a flexure element 30 as shown in FIG. 2 (a). The flexure element 30 is provided with load detection means, such as a plurality of strain gauges 31, for generating an analog load signal corresponding to the load applied thereto. A lower-order calculation means, for example, a balance function calculation device 34 is attached to one surface, for example, a side of the flexure element 30, via a mounting bracket 32. Scale function computing device 3
4 is formed on a rectangular substrate, for example. Alternatively,
As shown in FIG. 6B, a circular cavity having an opening on one side surface thereof is formed in the flexure element 30, and the weighing function computing device 34a is accommodated in the cavity and the opening is sealed. One can also be used. In this case, the balance function computing device 34
a is formed on a circular substrate.

As described above, in each load cell 10a, the strain function device 34 or 34a is integrally formed on the flexure element 30, so that the load cell and the scale function operation device are configured as one unit. The combined scale assembled by using can be downsized, and the wiring between the load cell and the scale function calculation device is not required, so that the wiring work is simplified. When the combination scale fails, the integrated unit itself can be replaced to completely repair the failure, and efficient repair can be performed. Further, if the load cell 10a prepared in advance for a failure is subjected to span adjustment described later with the reference weight, it is not necessary to perform span adjustment again at the time of replacement.

The balance function computing device 34 or 34a is constructed, for example, as shown in FIG. That is, the analog weight signal from the strain gauge 31 is supplied to the digital converting means, for example, the A / D converter 40 via the amplifier 36 and the analog filter 38, and is converted into the digital weight signal here. The digital load signal is input / output circuit 42
Is supplied to the control means, for example, the CPU 44 via the. C
The PU 44 is attached with a storage means, for example, a memory 46 including a ROM and a RAM. Further, the CPU 44 is provided with a serial communication controller 48, and is configured to be capable of serial data communication with a higher-order arithmetic means, for example, the display / operation panel 16. The function of the scale function computing device 34 or 34a will be described later.

The display / operation panel 16 includes display means, for example, a graphic liquid crystal display device 50 and its controller 52.
And a controller 54, for example, a keyboard 54, and a CPU 58, a memory 60, and a serial communication controller 62, like the balance function computing device 34 or 34a.

The display / operation panel 16 variously combines the digital load signals supplied from the load cells 10a in accordance with the program stored in the memory 60, and the total weight of the combinations is equal to a predetermined target weight. A combination calculation is performed to select a combination that is close to each other. Further, according to the result of the combination calculation, the weighing hopper 8 for discharging the articles is determined, and the weighing hopper 8 is opened so that the gate 8a thereof is opened.
Signal is transmitted to the gate control device 18 corresponding to. Further, the gate 6a of the supply hopper 6 located above the weighing hopper 8 with the gate 8a opened is opened, and a signal is transmitted to the gate control device 18 so as to feed articles to the empty weighing hopper 8. Further, in order to supply the articles to the empty supply hopper 6, a signal is transmitted to the straight advance feeder control device 22 to operate the straight advance feeder 4 corresponding to the supply hopper 6. Further, on the display / operation panel 16, a target weight value or the like is set by operating the keyboard 54, and the set value, the weighing hopper selected as a result of the combination calculation, the selected combination weight or the like is displayed on the display device. 50, and at the time of maintenance and inspection, the digital load signals from each weighing hopper 8 are displayed.

As one of the above settings, prior to the operation of the combination weigher, in each weighing hopper 8, the time from the opening of the gate 6a of the upper supply hopper 6 to the completion of the weighing is set as the weighing timer value. Set. This weighing timer value is set so that a predetermined weighing accuracy and the ability of the combined product to be obtained per predetermined time can be obtained. The set timer value is stored in the memory 46 of each load cell 10a via the serial communication line.

The total load applied to the load cell 10a, for example, the weight signal of the article to be weighed including the weighing hopper 8, is output from the strain gauge 31 as an analog load signal. The analog weight signal is amplified by the amplifier 36, and thereafter, unnecessary components are removed by the analog filter 38,
It is A / D converted by the A / D converter 40 and becomes a digital load signal Wa. At the time of adjusting the combination weigher, the digital load signal Wa in a state where no articles to be weighed exist in the weighing hopper 6 is stored in the memory 46 as the initial value Wi in advance. When the item to be weighed is put into the weighing hopper 8, the digital load signal Wa increases. The weight Wn of the article to be weighed is calculated by subtracting Wi from the digital load signal Wa and multiplying it by the span coefficient K (Wn = K (Wa−Wi)).

The span coefficient K is a coefficient that is adjusted and set so that the value of Wn becomes equal to the weight value of the reference weight when the reference weight is placed in the weighing hopper 8 during weighing adjustment. Load cell 10a prepared in advance for failure
Also, the span coefficient K is set by this reference weight.

Wn is originally zero when no articles to be weighed are present in the weighing hopper 8, but is displaced from zero when dust or the like is attached to the weighing hopper 8. Therefore, the zero point movement amount is set to Wz, and Wn = K (Wa-Wi) -Wz is an equation representing the weight of the article to be weighed in the weighing hopper 8, and Wn ≠ 0 in a state where no article is present in the weighing hopper 8. If so, the CPU 44 shifts the value of Wn to Wz. This calculation is called zero adjustment. Wn representing the weight of the item to be weighed thus generated is transmitted to the display / operation panel 16.
In this way, processing the digital load signal Wa so that the digital load signal Wn represents the weight of the article to be weighed is referred to as scale function calculation. The scale function calculation device 34 or 34a
Achieve this function.

On the display / operation panel 16, the gate 8a of the weighing hopper 8 in which the selected articles are stored as a result of the combination calculation is opened, and the gate 6a of the supply hopper 6 above it is opened.
A signal is transmitted to the gate controller 18 corresponding to the selective weighing hopper 8 so as to open. The signal for opening the gate 6a of the supply hopper 6 is transmitted to the scale function arithmetic unit 34 or 34a of the corresponding load cell 10a. Then, the weighing timer value is stored in the memory 46 of the balance function computing device 34 or 34a as described above. The CPU 44 starts counting the timer from the time when the signal is received, and outputs Wa when the time set as the measurement timer value has elapsed.

That is, the CPU 44 stores the digital weight signal in the memory 46 each time the A / D converter 40 generates, until the required number of filtering operations is reached. Iterate to update in order. Then, when the time set as the measurement timer value has elapsed, the digital load signal is smoothed by performing the filtering calculation using the number of digital load signals necessary for the filtering calculation, and Wa is calculated. In this way, the CPU 44 functions as load determining means. Then, as mentioned above,
Wn = K (Wa-Wi) -Wz is calculated and Wn is sent to the display / operation panel 16.

These filtering operations are individually performed by the balance function operating device 34 or 34a of each load cell 10a, and are not performed on the display / operation panel 16. Therefore, the processing load on the display / operation panel 16 is small,
The above-mentioned problem of delay in the start of combination calculation does not occur.

As described above, in the weighing function computing device 34 or 34a integrally provided in each flexure element, weight measurement, digital load signal conversion, timer management, and weighing function computation are performed for each corresponding weighing hopper 8. The display / operation panel 16 performs combination calculation, control of the straight-line feeder 4, gate control of the supply hopper 6 and the weighing hopper 8, and the like, and performs calculation of the entire combination scale and transmission of a control signal based on the calculation. That is, the functions are shared between the balance function calculation device 34 or 34a and the display / operation panel 16. Moreover, the processing by each of the balance function calculation devices 34 or 34a and the display / operation panel 16 are performed in parallel in time, and high-speed processing can be performed. For the communication between the scale function computing device 34 or 34a and the display / operation panel 16, it is not necessary to successively transmit the A / D-converted digital signal from each load cell in succession, but only by transmitting the determined Wn. Therefore, it does not require a special communication speed.

In the above-described embodiment, the weighing function computing device 34 or 34a performs the initial value processing and the zero adjustment computation, but the display / operation panel 16 has a high-performance CPU.
If you use the
Only the digital load conversion by the D converter 40, the timer management by the CPU 44, and the confirmation of the digital load signal by the filter calculation are performed, and the confirmed digital load signal is transmitted to the display / operation panel 16, and the display / operation panel 16 In, it is also possible to perform calculations such as initial value processing and zero adjustment.

Further, the balance function computing device 34 or 34a is converted into a digital load by the A / D converter 40, and the CPU 4
4 is configured to perform only timer management and confirmation of a digital load signal by filter calculation, and a plurality of scale function calculation devices 34 are provided between the scale function calculation device 34 or 34a and the display / operation panel 16. Alternatively, the digital load signals from 34a are collected, initial value processing and zero adjustment processing are performed on these digital load signals, and the digital load signals representing the weight of the articles to be weighed in each weighing hopper 8 are displayed / operation panel 16 It is also possible to provide an intermediate calculation means for outputting to.

In the above embodiment, the combination calculation is performed with the digital load signal representing the weight of the article to be weighed in each weighing hopper 8 as an object.
A memory hopper is provided below the weighing hopper 8 and after weighing is performed by the weighing hopper 8, the article is transferred to the memory hopper, the weighing value is stored in the display / operation panel 16, and the weighing hopper 8 becomes empty.
It is also possible to newly supply and weigh the articles to be weighed, and perform a combination calculation on the weighing values of the articles in each weighing hopper 8 and the weighing values of the articles in each memory hopper. In the above embodiment, all the weighing hoppers 8 are
The combination calculation was performed for the weight of the articles to be weighed in the items. For example, while discharging the articles, supplying new articles, and weighing to the weighing hopper 8 in which the articles selected by the combination calculation are stored. The combination calculation may be performed on the weights of the articles to be weighed in the remaining weighing hoppers 8.

[0031]

As described above, in the combination weigher according to the present invention, many load cells used in the combination weigher have the lower-order arithmetic means integrally formed, and therefore, the combination weigher can be downsized. In addition, the assembly and maintenance of the combination scale can be efficiently performed. Further, when the lower-order calculation means is configured to execute the scale calculation function, the load on the higher-order calculation means is reduced, and the time until the result of the combination calculation is obtained does not become long. Further, in the weighing device according to the present invention, since the weight determination means is provided in each load cell, the load on the calculation means is small and high-speed calculation processing can be performed. In particular, if the calculation means is a higher-order calculation means capable of executing combination calculation, the processing of combination calculation can be performed at high speed.

[Brief description of drawings]

FIG. 1 is a block diagram of a combination scale according to an embodiment of the present invention.

2 is a side view of two load cells used in the combination weigher of FIG. 1. FIG.

FIG. 3 is a detailed block diagram of a part of the block diagram of FIG. 1.

FIG. 4 is a front view and a side view of a conventional combination scale.

5 is a block diagram of the combination weigher of FIG. 4. FIG.

[Explanation of symbols]

10a Load cell 16 Display / operation panel (upper-level calculation means) 34 34a Scale function calculation device (lower-level means, weight determination means)

Claims (4)

[Claims] 1. A digital conversion means for causing a load detecting means provided on the flexure element to generate an analog load signal corresponding to a load applied to the flexure element and for converting the analog load signal into a digital load signal. And a plurality of load cells to which loads independent from each other are applied to each of the flexure elements, and each subordinate calculation means of the load cells. Various combinations of digital load signals from the above, and a host scale having at least a combination calculator for selecting a combination having a total value equal to or close to a target value from each combination. 2. The combination weigher according to claim 1, wherein each of the lower-order calculation means includes a balance function calculation means. 3. A load signal generating means for generating a load signal when a load is applied is provided on the flexure element, and a load determining means for determining a value of the load based on the load signal generated by the load is provided. A weighing apparatus comprising: a plurality of load cells on which the loads are loaded independently of each other; and an arithmetic means for processing output signals from the load determining means of these load cells. 4. The weighing device according to claim 3, wherein the computing means variously combines the values of the load from the load determining means of each of the load cells, and a total value is set as a target value from each of the combinations. A weighing device which is a higher-order arithmetic means having a combination arithmetic means for selecting an equal or close combination.