JP2739347B2 - Automatic zero correction device for combination weigher - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic zero-point correcting device that automatically corrects a zero point when no articles are supplied in a combination weigher.

[Related Art] In general, a combination weigher is configured such that an operator or the like manually supplies an article to each weighing hopper, which is a component of the combination weigher, so that a combination whose total weight is equal to or close to a target weight is configured. There is a semi-automatic combination weigher that automatically discharges from a weighing hopper containing articles.

By the way, the weighing hopper is provided with load detecting means for generating an output signal indicating the weight of the supplied article, for example, a load cell. In this load cell, the zero point of the output may fluctuate due to the influence of a change in temperature or a change with time, or the influence of an article attached to the weighing hopper. In order to correct this, the weighing signal of the load cell when the article is not supplied is stored in the zero point storage section, and the storage section of the zero point storage section needs to be subtracted from the output signal of the load cell when the article is supplied. Therefore, it is necessary to store the output signal of the load cell in the zero point storage unit when the weighing hopper is empty.

In the above-described semi-automatic combination weigher, when a weighing hobber that requires zero adjustment appears, an indicator light that prohibits the supply of articles to the weighing hopper is turned on, and the operator is notified of the weighing hopper by the weighing hopper. The output signal of the load cell is stored in the zero point storage unit after a lapse of a stabilization time required for the weighing signal to be in a stable state after turning on the indicator lamp and notifying the supply of the load signal.

[Problems to be Solved by the Invention] However, in the automatic zero-point correction device as described above, the operator must constantly monitor which weighing hopper is turned on by the indicator light indicating the prohibition of loading. Therefore, there is a problem that it is not possible to concentrate on the supply of articles.

The present invention has been made in view of the above problems, and in a combination weigher in which articles are manually supplied,
It is an object of the present invention to provide an automatic zero-point correcting device that automatically searches for a weighing hopper to which no articles are supplied and performs zero correction.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, each of the weighing means, which is a component of the combination weigher, includes a load detection means, a zero point storage means, and an output of the load detection means. Calculating means for calculating the algebraic sum of the signal and the stored value of the zero point storage means to generate the weighed signal. A storage means for sequentially storing an output signal of the load detection means each time a predetermined time elapses is attached to each of the load detection means. When the zero point correction command signal is supplied, the output signal of the load detection means is output. Is provided near the zero point to select a value equal to or less than a preset threshold value, and a predetermined number of recent values among the stored values of the storage means attached to the selected load detecting means are continuously equal to or less than the threshold value. At this time, a zero point changing means for storing the output signal of the load detecting means at that time in the zero point storing means is provided.

[Operation] According to the present invention, when a zero point correction command signal is generated,
The output of the load detecting means is selected below the threshold.
The selected one is the load detecting means to which no articles are currently supplied. Then, among the stored values of the storage means that sequentially store the output signals of the selected load detection means, if the latest predetermined number of consecutive values are equal to or less than the threshold, the selected load detection means It is determined that no article has been supplied, that is, empty, up to a certain point in time after the time when the zero point correction command signal is generated. Therefore, the zero point is automatically corrected by storing the output signal of the load detecting means at the time when the zero point correction command signal is generated in the zero point storage means.

Embodiment FIG. 2 is a schematic view showing a mechanical configuration of a semi-automatic combination weigher equipped with an automatic zero-point correcting device embodying the present invention. In FIG. 2, reference numeral 2 denotes a weighing hopper, Total n in column
A table is arranged. The weighing hopper 2 includes a main body 4
Are supplied manually through input ports 6, 6,... Provided on the upper wall corresponding to the respective weighing hoppers 2. Each of these weighing hoppers 2 is opened on both sides by a gate drive mechanism 7 as indicated by arrows in FIG. 2, and the articles stored therein are discharged. These ejected items are:
It is carried out by the conveyor 8. Each weighing hopper 2 is provided with a load detecting means, for example, a load cell 10. These load cells generate an output signal indicating the weight of the article supplied to the associated weighing hopper 2,
The output signal fluctuates due to a change in temperature or a change with time, or the output signal changes due to the influence of a small amount of articles attached to the weighing hopper. In addition,
Thereafter, when it is necessary to identify each of the n weighing hoppers 2 and the n load cells 10,
2 ₁ represented as 2 _n or load cell 10 ₁ to 10 _n.

Further, a control unit 12 is provided on the side of the upper part of the main body 4. The control unit 12, as shown in FIG. 3, and has a multiplexer 14 the output signal from the load cell 10 ₁ to 10 _n are supplied. Each time the weighing timing signal is supplied from the timer 21 to the CPU 18, the multiplexer 14 controls the load cell 10 ₁ based on a control signal generated by the CPU 18.
The 10n output signals are sequentially supplied to the A / D converter 16. A /
The D converter 16 is configured to sequentially load the load cells 10 _{1 to} 10 _n
Each output signal is converted to a digital signal, and
Supply 8

The CPU 18, Yes comes with RAM 20, this is the load cell 10 ₁ to 10 zeros storage area in correspondence with _n z ₁ to z _n are provided as shown in FIG. 4, each load cell 10 ₁ Each time a signal obtained by converting the output signals of _n to 10 _n into a digital signal is supplied, the stored values of the corresponding zero-point storage areas z _{1 to} z _n are subtracted by the CPU 18 from these, and each weighing hopper 2
It is a digital weighing signal representing the weight of the article supplied to _{1 to 2n} . Thus, the load cell 10, the CPU 18 and the R
Each weighing means is constituted by AM20. CPU 18
These digital weighing signals are combined in various manners, and a combination operation is performed to select a combination having a total value equal to or closest to the target weight value set by the setting display unit 22 from the combinations, thereby forming the selected combination. A signal is supplied to each gate drive circuit 7 via a drive circuit 24 so as to open the weighing hopper 2 containing the articles to be discharged and to discharge the articles onto the conveyor 8. Further, CPU 18, when the timer 21 generates a zero point correction timing signal, searching the weighing hoppers was empty back some time from the time, for example, when the weighing hoppers of the air is assumed to be weighing hoppers 2 _1, As to store the output signal of the load cell 10 ₁ to those digitized zero memory area z ₁ when. In order to use the weighing hopper to search whether it is empty as described above, the CPU 18 generates
Those digitized output signal of each load cell 10 ₁ to 10 _n are stored in the RAM 20. To remember this, R
As shown in FIG. 4, each load cell 10 _{1 to} 10 _n
In each case, a total of n areas D are provided, and these areas are partitioned so that a total of m digitized output signals of the load cell 10 can be stored. That is, these divided areas are n × m pieces of D ₁₁ to D _nm. The number m is related to the time interval t at which the output signal of the load cell 10 is digitized.
If the output signals of the load cells are all below a certain threshold A as shown in FIG.
For example, mxt is set to be the time required for the weighing signal of the load cell 10 to stabilize. Then, digitized output signals of the load cell 10 are sequentially stored in these m partitioned areas from the beginning. When the output signals of the load cell 10 are stored up to the final partitioned area m, the output signals of the load cells 10 are again read from the leading partitioned area. The digitized data is stored sequentially. Therefore, digitized output signals of the latest m load cells are always stored in these m areas.

Note that such processing is performed based on a program stored in the ROM 26. Hereinafter, this program will be described with reference to the flowchart shown in FIG. First, each of the weighing hoppers 2 _{1 to} 2 _n , the load cells 10 _{1 to} 10 _n , RA
M20 n-number of regions D and to zero the storage area z ₁ of a 1 the value of the pointer P for specifying z _n (step S2). Next, it is determined whether a weighing timing signal is supplied from the timer 21 (step S4). If the answer is YES, the value of the pointer C for designating the partitioned area in the area D of the RAM 20 is incremented by one. (Step S6). Note that this pointer C is initially reset to 0. Then, at that time the output signal of the load cell 10 _p of the pointer P is specified by supplying the A / D converter 16 via the multiplexer 14, reads the digitized W _P to CPU 18, the pointer P from the W _P There by subtracting the stored value of zero memory area z _P that specifies the pointer P is calculated on the weight of the articles supplied to the weighing hoppers 2 _P specifying (step S8). Next, the pointer P
There is stored the W _P in divided area D _PC the pointer C in the area D _P is specified is designated (step S10). Then, the value of the pointer P by one increment (step S12), the value of the pointer P which is the stepping is, the load cell 10 ₁ to 10 _n
(Step S14), the answer is NO
, The process returns to step S8, and steps S8 to S14 are repeated until the answer to step S14 is YES. Therefore, when the answer to step S14 becomes to YES, for example, when the value of the pointer C is assumed to be 1, D ₁₁ to D _n1 shown in FIG. 4
Stores the digitized output signal of each of the load cells 10 _{1 to} 10 _n at this weighing timing. If the answer to step S14 is YES, then the pointer C
Is determined to be greater than or equal to m (step S16). If the answer is NO, it is determined whether the combination timing signal is supplied from the timer 21 (step S18). And repeats steps S2 to S18 until step S18 becomes YES. Here, as shown in FIGS. 5 (b) and (c), the weighing timing signal occurs much more frequently than the combination timing signal.
Each time the metering timing signal is generated, D ₁₂ to D _n2, D
₁₃ to which digitized output signals of the load cells 10 ₁ to 10 _n to the D _n3 · · · are stored, and, finally
When D _{1m to} D _{nm are} stored, the answer to step S16 becomes YES, the pointer C is reset to 0 (step S16).
S20), execute step S18, and if this determination is NO,
It returns to step S2. Thus, next time the metering timing signal is supplied, that digitizes the output signal of the load cell 10 at that time is stored in the D ₁₁ to D _n1,
Hereinafter, similarly, until the combination timing signal is supplied,
Repeated. Thus, when a combination timing signal is supplied, the latest one is stored into m RAM which always Dishitaru the output signal of the load cell 10 ₁ to 10 _n.

When the combination timing signal is supplied and the answer to step S18 is YES, the latest W _{1t to} W _{nt at} that time is obtained.
, A combination calculation is performed, a combination whose total value is equal to or closest to the target weight value is selected, the weighing hopper 2 containing the articles constituting the combination is opened, and The article is discharged (step S22). It is to be noted that the combination calculation is well-known, and thus a detailed description is omitted. Further, since the supplying articles to each weighing hopper 2 by manual, when it is combined calculation timing, not necessarily the article is supplied to all the n-number of weighing hoppers 2 ₁ 2 _n, the combination The total number of weighing hoppers 2 to be calculated may be smaller than n.

Next, it is determined whether the zero point correction timing signal is supplied from the timer 21 (step S24). If the answer is NO, the process returns to step S2, and as described above, each load cell 10
_The storage of digitized _{1 to} 10 _n signals is repeated.

If the answer to step S24 is YES, the pointer P,
The value of C is set to 1 (step S26). And
Load the W _P obtained by digitizing the output signal of the load cell 10 that the pointer P is indicated (step S28), the W _P
As shown in FIG. 5 (a), as shown in FIG. 5 (a), an article is not supplied to the weighing hopper 2 if the output of the load cell 10 is less than or equal to the preset threshold A near the zero point. (Step S30). If the answer is YES, the weighing hopper 2 designated by the pointer P at this time is regarded as being empty, so that the weighing hopper 2 is fixed at this point in time. until the time of going back time, the load cell 10 to the output signal of _P is determined whether or not stabilized below the threshold value a, defined areas D _PC value pointer C is designated in the area D _P of the RAM20 the pointer P designates Is read (step S32), and it is determined whether or not this is equal to or less than the above threshold value A (step S34). If the answer is YES, the value of the pointer C is incremented by one (step S36), and it is determined whether or not the incremented value of C is larger than the total number m of the divided areas (step S38). In this case, since it is not determined whether or not the values of all the partitioned areas in the area specified by the pointer P are equal to or smaller than the threshold A, the process returns to step S32.

While the value of the area specified by the pointer P is sequentially determined to be equal to or smaller than the threshold value A, if a value not equal to or smaller than the threshold value A appears (NO in step S34), the value of the load cell 10 specified by the pointer P is determined. It turns out that the output signal is not stable below the threshold value A. Therefore, the load cell 10 cannot be zero-corrected, so that the value of the pointer P is incremented by one to specify the next load cell 10 (step S40), and the value of the pointer P has finished specifying all the load cells. In order to determine whether or not the value of the pointer P is greater than n (step S42), if the answer is NO, the first partitioned area of the next area specified by the pointer P is designated. The value of the pointer C is set to 1 (step S44), and the process returns to step S28.

Further, when the determination in step S38 is YES, the output signal of the load cell 10 designated by the pointer P continuously falls below the threshold value A for m × t time (= T) as shown in FIG. Since the weighing hopper 2 currently designated by the pointer P is empty and the output signal of the load cell 10 attached to the weighing hopper 2 can be considered to be stable, the pointer P at that time is those digitized output signal of the load cell 10 that the pointer P is to be stored in the specified to have zero memory area z _P as a new zero point (step S4
6). As a result, the weighing timing comes next, and when the pointer P designates the weighing hopper 2, the output signal of the load cell 10 attached to the weighing hopper 2
New zero point stored in the zero point storage area z _P is subtracted, the digital weighing signal corrected zero point is obtained.

Then, in order to inspect the next load cell 10 in the same manner as described above, steps S40, 42, and 44 are executed, and step S28 is executed. Then, when the above inspection is completed for all the load cells 10, the answer to step S42 is YES, so the process returns to step S2, and every time the weighing timing comes again, the digitized output signal of each load cell 10 is output. When the combination timing is reached, the combination calculation is performed, and when the zero point correction timing is reached, the zero correction is performed.

In the above embodiment, the present invention is applied to a semi-automatic combination weigher that performs the supply of articles manually and discharges the articles automatically, but the present invention is also applied to a manual combination weigher that manually supplies and discharges both articles. The present invention can be implemented. Also,
In the above embodiment, the combination calculation was performed only for the weight of the articles supplied to the weighing hoppers.However, auxiliary hoppers were provided below each of the weighing hoppers, and the articles were weighed by the respective weighing hoppers. Is moved to the lower auxiliary hopper, a new article is supplied to the empty weighing hopper and weighed, and the combination calculation is performed on the weight of the articles supplied to the auxiliary hopper and the weighing hopper. Good.

[Effects of the Invention] As described above, according to the present invention, when the zero point adjustment timing comes, the output of the load detecting means such as the load cell attached to each weighing hopper is compared with a predetermined threshold value. If the output of the load detecting means attached to the searched weighing hopper is equal to or less than the threshold value for a predetermined time, the output of the load detecting means is close to the zero point. Therefore, the output of the load detecting means at that time is stored as a new zero point. Therefore, when the zero point adjustment timing comes, the zero point is automatically corrected. Therefore, even in a combination weigher in which the articles are manually supplied to the respective weighing hoppers, the zero point correction is performed one by one, unlike the conventional one. It is not necessary for the worker to check whether the loading ban indicator light on the weighing hopper is lit while loading the articles, so the worker can be immersed in the loading work of the articles, and the work efficiency can be reduced. Can be enhanced.

[Brief description of the drawings]

FIG. 1 is a flowchart of one embodiment of a semi-automatic combination weigher implementing an automatic zero correction apparatus according to the present invention, FIG. 2 is a diagram showing a schematic mechanical configuration of the embodiment, and FIG. FIG. 4 is a block diagram, and FIG. 4 is a RAM used in the embodiment.
FIG. 5 is a timing chart of the embodiment. 2 _{1 to} 2 _n ... weighing hopper, 10 _{1 to} 10 _n ... load cell (load detecting means), 18 ... CPU (calculating means, selecting means,
Zero change means), 20 RAM (zero point storage means, storage means).

Claims (1)

(57) [Claims] A plurality of weighing means for generating a weighing signal each time an article is manually supplied is provided, and various ones of the weighing signals to be combined are variously combined. , The combination of which the total value is equal to or close to the predetermined target weight is selected and discharged, and each of the weighing means includes a load detection means, a zero point storage means, and the load detection means. A combination means for calculating the algebraic sum of the output signal of the means and the stored value of the zero point storage means to generate the weighed signal, wherein the output signal is predetermined for each of the load detection means. Attach storage means for sequentially storing each time, and when the zero point correction command signal is supplied, select one of the load detection means whose output signal is equal to or less than a preset threshold value near the zero point. When the latest predetermined number of the stored values of the storage means attached to the selected load detection means are continuously below the threshold value, the load detection means of the load detection means at that time is provided. An automatic zero-point correcting device for a combination weigher, comprising a zero-point changing means for storing an output signal in the zero-point storing means.