JPH0687026B2 - Weighing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weighing device for loading a belt conveyor on a load cell, receiving an object to be weighed from a feed-in belt conveyor, and measuring the weight of the object while transferring it to an unloading belt conveyor. .

[0002]

2. Description of the Related Art When inspecting the weight of an object to be weighed, for example, a packed product which has been weighed and packed in advance, a weight measuring device in which a load conveyor serving as a load detecting means is loaded with a belt conveyor is used and is fed to one end side. In addition, the carry-out belt conveyor is arranged on the other end side, the packed products are sent in, sent to the weighing device by the belt conveyor, and the finished products are discharged by the carry-out belt conveyor, and the sorting means is operated as necessary. It is configured.

By the way, in such weighing, since the belt conveyor is mounted on the load detecting means as described above, the load detecting means receives the vibration of the belt conveyor and the weight of the object to be weighed on the belt conveyor. The vibration load will be superimposed.

Therefore, the output signal from the load detecting means is configured to remove a vibration component having a relatively high frequency due to the vibration of the belt conveyor through a low pass filter.

Since such a low-pass filter has an extremely large time constant, a steady-state output cannot be obtained until a certain time elapses from the time when the object to be weighed is mounted on the belt conveyor of the weighing device, and the constant value output is not obtained. An error occurs when weighing an object that is very long.

Therefore, from the stage when the articles arrive at the weighing conveyor until the stable weighing data is output from the low-pass filter, the object to be weighed detecting means on the carry-in side of the weighing conveyor is forbidden to take in the weighing data. Is provided, and data is taken in based on a signal from this point. This object to be weighed detection means is usually arranged with a light emitting element and a light receiving element on the side of the weighing conveyor so as to detect reflected light from the object to be weighed and to detect light interception by the object to be weighed. Due to this, if there is unevenness on the top surface of the object to be weighed, the same signal to be weighed is output, but the same signal as if two objects to be weighed in was output due to intermittent light. Therefore, there is a problem in that the reference time for data processing becomes incorrect and a measurement error occurs.

In order to solve this problem, a fixed time from when the signal is output from the object-to-be-measured detection means is a time for prohibiting reception of the signal from the object-to-be-measured means,
The so-called re-detection prohibited time is set by a data input means such as a keyboard.

[0008]

However, when the length of the object to be weighed or the speed of the conveyor changes, the length of the object to be weighed is measured each time, and this is divided by the belt speed to obtain the re-detection prohibition time. There was the trouble of having to input the time again from the keyboard. The present invention has been made in view of such a problem, and an object thereof is to automatically re-detect the prohibition time by inputting the length of the object to be weighed or by carrying the object to be weighed once. It is to provide a new weighing device to be set.

[0009]

In order to solve such a problem, according to the present invention, a conveyor for conveying an object to be weighed is loaded on the weight detecting means, and a feeding side of the weighing conveyor. Based on the provided object detecting means, data input means for inputting the length of the object in the conveying direction, and the input object length and the set conveyor speed, the object length is measured. Recalculation prohibition for ignoring the detection signal from the object to be weighed until the transfer time elapses from the time when the tip of the object to be weighed is detected by the object to be weighed detection unit. And means.

[0010]

When the length of the object to be weighed in the carrying direction is set by the data input means, the carrying time for the object to be weighed is calculated from the preset carrying speed of the weighing conveyor and the length of the object to be weighed. This is automatically set as the re-detection prohibition time. Alternatively, when the object to be weighed is sent to the weighing conveyor in the registration mode, the object to be weighed detection unit outputs a detection signal upon detection of the object to be weighed. At that time, by measuring the output time of the detection signal, the transport time corresponding to the length of the object to be weighed is detected, and this is automatically set as the re-detection prohibition time. Then, in the weighing mode, when the detection signal is output from the object-to-be-measured detection means, the object-to-be-measured detection signal is ignored until the conveyance time elapses from that time. This makes it possible to reliably detect the tip of the object to be weighed and thereafter perform signal processing with high reliability.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a weighing conveyor, which is a belt in which a conveyor belt is stretched around rollers 2 and idle rollers 3 connected to a motor (not shown). The conveyor mechanism 4 is configured to be supported by a load cell 5, and an object to be weighed detector 7 that optically detects an object to be weighed carried in from a feed belt conveyor 6 is arranged at the carry-in end side.

On the other hand, the analog signal output from the load cell 5 is input to the analog-digital converter 9 via the preamplifier 8, and the digital signal output from the analog-digital converter 9 is further input to the digital filter 10. It is configured to be input and extract a DC component as a weight signal. The object to be weighed detector 7 is configured as a transmissive or reflective optical sensor including a light emitting element and a light receiving element, and when the detection light emitted from the light emitting element is blocked by the object to be weighed M, a detection signal is output. Is configured to output.

The digital filter 10 is composed of a digital signal processor, is programmed to function as an FIR type low-pass filter, and its filter characteristic can be arbitrarily set by the control device 20 described later. There is.

The control device 20 includes a CPU 21 and a ROM 2
2. The microcomputer comprises the RAM 23 and the interface 24, and the signal from the object to be weighed 7, the data from the keyboard 26 for inputting various data, and the weight signal from the digital filter 10 are input, which will be described later. It is programmed so as to execute various kinds of processing to be performed and output control parameters to the digital filter and display data to a display device (not shown).

In such a structure, the object M to be weighed which has been conveyed from the infeed conveyor 6 to the weighing conveyor 1
Is weighed at the timing described later, and the measured weight with respect to the target weight is determined to be a correct amount, defective, etc., and if the determination result is defective, a distribution signal is output to a distribution device (not shown) on the downstream side. It is configured. Further, the objects to be weighed, which have been determined to be positive, pass through the sorting device and are transferred to the downstream side by the discharge conveyor 11.

FIG. 2 shows the functions to be performed by the microcomputer constituting the above-mentioned control device.
In the AM 23, the lengths L and l of the weighing conveyor 1 and the object to be weighed M in the transport direction, and the sampling time T
3, the belt speed V of the weighing conveyor 1 is stored.

From the set belt speed V and the length 1 of the object M in the carrying direction, the carrying time (T0
= 1 / V) as the re-detection prohibition time, and the measurement start timer 31 is started at the time when the detection signal is input from the object to be measured detector 7,
From that time until the re-detection prohibition time T0 elapses, even if the signal from the object-to-be-measured detector 7 is repeatedly turned on and off, the re-detection prohibition means 30 and the set weighing conveyor 1 are ignored. From the length L and the belt speed V of the object M to be weighed on the measuring conveyor 1 (T1 = L /
V), the object conveying time calculating means 33, the calculated conveying time T1, the settable sampling time T3, and the re-detection prohibition time T0.
Filter response time calculation means 34 for calculating the response time (Tn = T1−T0−T3), and a filter constant is calculated based on this response time Tn and output to the digital filter 10 to set the filter characteristic. From the filter constant calculation means 35, the response time Tn and the re-detection prohibition time T0, or the transport time T1 and the sampling possible time T3, from when the object M to be weighed begins to ride on the weighing conveyor 1 until the start of weight signal acquisition. Of the instability time (T2 = Tn + T0) or (T2 = T1−T3), and the instability time T2 are set, so that the object to be weighed detector 7 is set to the object to be weighed M. Counting is started from the time when the tip of the is detected, stopped when the unstable time T2 has elapsed, and then the weight signal output from the digital filter 10 in a constant cycle is RA. Measurement starting timer 3 for sequentially stored in the memory 37 formed in a predetermined area of the 23
1 and the transport time T1 of the object to be weighed M on the weighing conveyor 1 and the unstable time T2, the zero adjustment prohibition time (T4 = T1 + T
2) is calculated and is set in the zero point input prohibition timer 38. The automatic zero point adjustment prohibition time calculation means 39 and the automatic zero point adjustment prohibition time T4 are set so that the object to be weighed detector 7 detects the tip of the object to be weighed M. Counting starts from the time of detection,
Stop when the automatic zero adjustment prohibition time T4 has elapsed,
After that, by subtracting the zero point of the zero point storage means 40 from the weight data stored in the memory 37 and the zero point input prohibition timer 38 for storing the weight signal output from the digital filter 10 in a constant cycle in the zero point storage means 40, The weight calculation means 41 for calculating the net weight of the object to be weighed M, and the belt speed control means 42 for adjusting the conveying speed of the weighing conveyor 1 and the feeding conveyor 6 to the set speed based on the set belt speed V. A program is stored in the ROM 22 so as to be provided.

The belt speed V, the conveyor length L, the length of the object to be weighed 1, the sampleable time T3, etc. stored in the RAM 23 are input by the keyboard 26 as a data input means. Since it is necessary to set the size every time the dimensions change, a scale is attached to a cover or the like provided along the conveying direction of the weighing conveyor 1,
When the object M to be weighed is applied to this scale, the approximate dimensions can be measured on the spot.

Regarding the length l of the object to be weighed M, these are registered in advance in a memory for each kind of the object to be weighed.
When the length of the object to be weighed is changed, the calling number may be input from the keyboard 26 to call from the memory. Further, the belt speed V may be fixed to a predetermined value, or may be detected by a speed detector and registered.

In the embodiment shown in FIG. 3, the re-detection prohibition time T0 is automatically set by transporting the object to be weighed M in the registration mode. Measures the output time of the detection signal of the object-to-be-measured 7 and stores the transport time corresponding to the length l of the object-to-be-measured as the re-detection prohibition time T0. During the period when the output time of No. is measured, even if the OFF state occurs for a short time, by ignoring it, the re-detection prohibition time can be set accurately regardless of the shape of the object to be weighed M. ing.

Also in this embodiment, the re-detection prohibition time corresponding to the object to be weighed is measured and registered in advance for each object to be weighed having a different size. May be called by the calling number.

Next, the operation of the apparatus thus constructed will be described with reference to FIG.
It will be described based on. The registration mode is set by the keyboard 26, and the length L of the weighing conveyor 1, the length l of the object to be weighed, the sampling time T3, and the belt speed V as necessary are input. These data are stored in the control device 2
It is registered in a predetermined area of the RAM 23 by 0, and the control device 20 performs a predetermined calculation based on these data.

That is, the re-detection prohibition time calculation means 30
Calculates T0 = 1 / V from the belt speed V and the length l of the object to be measured, and calculates the re-detection prohibition time T0. The weighed object transport time calculation means 33 calculates T1 = L / V from the length L of the weighing conveyor and the belt speed V to calculate the transport time T1 of the object M to be weighed on the weighing conveyor 1. The filter response time calculation means 34 executes the calculation of Tn = T1−T0−T3 from the transport time T1, the sampling time T3 and the re-detection prohibition time T0 to obtain the response time Tn of the digital filter 10.
To calculate. However, if the filter time has a margin, it can be set shorter than the obtained response time Tn.

The filter constant calculating means 35 calculates a filter constant based on the response time Tn and outputs it to the digital filter 10 to set the filter characteristic.
As a result, when the length l of the object to be weighed M is short, the response time Tn can be set to be long to make the filter 10 more effective, and when the length l of the object to be weighed is long, a response is obtained. By shortening the time Tn, it is possible to avoid the deterioration of the weighing capacity. In this case, the influence of disturbance may remain by shortening the response time Tn, but it is possible to obtain weighing data of sufficient accuracy in practice by performing processing such as moving average on the weighing value. it can.

The measurement timing calculation means 36 executes the calculation of T2 = Tn + T0 from the response time Tn and the re-detection prohibition time T0, and the weight measurement is started after the object M to be weighed starts to get on the weighing conveyor 1. The unstable time T2 up to is calculated. Of course, the unstable time T2 can be calculated from the re-detection prohibition time T1 and the sampling available time T3.

Instability time T2 calculated in this way
Is set in the measurement start timer 31, and the belt speed control means 42 adjusts the convey speed of each of the conveyors 1, 6 and 11 to the set speed V based on the set belt speed V. It is obvious that the control means 42 is unnecessary when the belt speed V does not need to be changed.

When the re-detection prohibition time T0 is automatically set by transporting the object to be weighed, the object M to be weighed is fed to the weighing conveyor 1 by the feeding belt 6 under the registration mode. The object to be weighed detector 7 outputs a detection signal while detecting the object to be weighed M. By measuring the output time of this detection signal by the object conveying time measuring means 50, the length l of the object M can be known.
Is set in the re-detection prohibition means 32 as the re-detection prohibition time.

When the registration work is completed, the keyboard 26 is switched to the weighing mode. When the object to be weighed is mounted on the feeding conveyor 6, the object to be weighed M becomes
When the object to be weighed 7 is reached, the detector 7 outputs a signal. When this signal is input to the control device 20, the re-detection prohibiting means 32 activates the measurement start timer 31, and thereafter the re-detection prohibition time T0 elapses, that is, the measured object M as a whole detects the measured object detector 7 at the detection position. Until it passes, the signal change from the object to be measured detector 7 is ignored. As a result, the object to be weighed M
Only the timing based on the signal output when the tip of the object reaches the object-to-be-measured detector 7 is established as the reference time for the subsequent data processing.

On the other hand, the digital filter 10 sequentially takes in numerical data from the converter 9 at a constant cycle while synchronizing with the analog-digital converter 9, and determines a predetermined value from the inputted new numerical data and past numerical data string. Then, the result is output to the control device 20. The measurement start timer 31 starts counting from the time when the object M to be weighed is detected, and the unstable time T2 shown in FIG.
When the time elapses, the counting is terminated and the weight data output from the digital filter 10 is stored in the memory 36. The weight calculation means 41 subtracts the zero point stored in the zero point storage means 40 from the weight data stored in the memory 37 to calculate the net weight of the object to be weighed M, and outputs it to a display device (not shown). At the time when this display is made, the objects to be weighed are already being discharged from the weighing conveyor 1.

By the way, when the object M to be weighed is completely discharged from the weighing conveyor 1, the metering conveyor 1 is in an unloaded state, but the above-mentioned unstable time T2 elapses from the time when the discharge of the object M to be weighed is completed. During the period up to, the load of the load cell 5 during this period cannot be said to be a state where the load is zero due to the vibration and the like of the weighing conveyor 1 caused by the rapid load change due to the discharge of the object to be weighed. Does not represent zero load. The automatic zero point prohibition time calculation means 39 calculates T4 = T1 + T2 from the transport time T1 of the object M to be weighed on the weighing conveyor 1 and the unstable time T2 to calculate the zero point adjustment prohibition time T4, and inputs this to the zero point. The prohibit timer 38 is set. The timer 38 starts counting at the timing of detecting the tip of the object to be weighed M in synchronization with the measurement start timer 31, stops counting when the zero-point adjustment prohibition time T4 has elapsed, and thereafter outputs from the digital filter 10. The weight signal is stored in the zero point storage means. This makes it possible to store a weight signal of zero load, which can be regarded as a stable state because the vibration of the weighing conveyor 1 is stopped, in the zero point storage means 40, and an accurate weighing value can be obtained.

When the next object to be weighed M is detected before the zero point adjustment prohibition time T4 elapses, the zero point input prohibition timer 38 is reset at that time point and the counting is started again. As a result, the zero point data is updated only when the object to be weighed is conveyed at a time interval longer than the zero point adjustment prohibition time T4, and when it is shorter than that, the previous zero point is saved and the operating rate is lowered. Without this, it is possible to correct the zero point variation due to the change over time of the weighing device.

[0032]

As described above, in the present invention,
A weighing conveyor formed by loading a conveyor for conveying an object to be weighed on the weight detecting means, an object to be weighed provided on the feeding side of the weighing conveyor, and data for inputting the length of the object to be weighed in the conveying direction. Input means, means for calculating a transport time for the length of the object to be weighed based on the inputted length of the object to be weighed and the set conveyor speed, and for detecting the tip of the object to be weighed by the object to be weighed detection means. From the time point until the conveyance time elapses, re-detection prohibition means for ignoring the detection signal from the object to be weighed is provided, so that the pseudo signal accompanying ON / OFF of the object to be weighed is ignored. You can automatically set the re-detection prohibition time. This eliminates the need to calculate the re-detection prohibition time required each time the length of the object to be weighed is changed, which simplifies the weighing operation and minimizes mistakes in setting the re-detection prohibition time, resulting in reliability. It is possible to improve the sex. Further, in the present invention, since the length of the object to be weighed is automatically measured by setting the re-detection prohibition time by conveying the object to be weighed, it becomes unnecessary to input data from the keyboard. Therefore, it is possible to efficiently and efficiently weigh an object to be weighed whose size changes frequently.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus showing an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of the control device in FIG. 1 with the functions to be performed by a microcomputer constituting the control device.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing constants set in the control device of the above device,
Explanatory diagram showing the relationship of the parameters calculated by this constant

[Explanation of symbols]

 1 Measuring Conveyor 4 Belt Conveyor Mechanism 5 Load Cell 5a Strain Gauge 7 Object to be Measured 9 Analog-Digital Converter 10 Digital Filter 20 Controller 26 Keyboard

Claims (2)

[Claims] 1. A weighing conveyor, in which a conveyor for carrying an object to be weighed is loaded on the weight detecting means, an object to be weighed provided on the feeding side of the weighing conveyor, and a length in the carrying direction of the object to be weighed. Data input means for inputting the length, means for calculating the transport time for the length of the object to be weighed based on the inputted length of the object to be weighed and the set conveyor speed, and the object to be weighed by the object to be weighed detection means. A weighing device comprising re-detection prohibiting means for ignoring a detection signal from the object-to-be-measured detection means from the time of detecting the tip of the object to be measured until the conveyance time elapses. 2. A weighing conveyor, in which a conveyor for conveying an object to be weighed is loaded on the weight detecting means, an object to be weighed detecting means provided on the feeding side of the weighing conveyor, and an object to be weighed on the weighing conveyor. A means for measuring the output time of the detection signal from the object to be weighed when it is sent and storing the output time as a transport time corresponding to the length of the object to be weighed; A weighing device comprising re-detection prohibiting means for ignoring a detection signal from the object-to-be-measured detection means from the time when the tip of the object is detected until the conveyance time elapses.