JPH0743233A - Device for discriminating internal pressure of can - Google Patents

Abstract

PURPOSE:To discriminate the propriety of the internal pressure of cans containing goods to be measured without receiving any influence from temperature regardless of the magnitude of the pressure by calculating a correcting value for a can to be measured based on the internal pressure and temperature, and correcting the internal pressure at a prescribed temperature by using the correcting value. CONSTITUTION:Cans 12 are put on a belt conveyor 10 and an electromagnetic 14 and microphone 16 are provided above the cans 12 as internal pressure measuring means to give impacts to the lid parts 12a of the cans 12 passing under the magnet 14 by applying magnetic forces and detect echoes from the parts 12a with the microphone 16. An infrared temperature sensor 22 which measures the surface temperature of the cans 12 is positioned on the right side of the cans 12 as a can temperature measuring means and the output of the sensor 22 is inputted to a correcting value calculating circuit 20. A correcting value calculated by the circuit 20 is inputted to a frequency correcting circuit 24 provided as an internal pressure correcting means and a frequency outputted from a frequency detecting circuit 18 based on the correcting value is corrected to the frequency value at a reference temperature. The corrected frequency value is inputted to a discrimination circuit 26 which discriminates the propriety of the internal pressure of the cans 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for determining can internal pressure (or vacuum within a can), and in particular, can accurately measure can internal pressure (or vacuum within a can) of cans having variations in temperature to determine the quality. Related to the device.

In the case of a negative pressure canned product whose internal pressure is lower than atmospheric pressure, measuring the internal pressure of the can is nothing but measuring the vacuum level in the can (vacuum level in the can = high level). Atmospheric pressure-internal pressure), therefore, in the present specification, when only the degree of vacuum is meant, it is expressed as a degree of vacuum, but when it means both the internal pressure of the can and the internal vacuum of the can, the internal pressure of the can (internal pressure of the can). Will be expressed.

[0003]

2. Description of the Related Art Canned goods, bottled goods, and the like must have a predetermined internal pressure in order to prevent deterioration of the contents to be filled or to maintain the shape of the can properly.
A can internal pressure inspection device is arranged in the canned product manufacturing process or the like to determine whether or not the can internal pressure is appropriate.

As such a can internal pressure inspection device, a device described in, for example, Japanese Patent Application Laid-Open No. 55-18939 has been widely used.

In these can internal pressure inspection devices, the can internal pressure is measured by magnetically impacting the can lid and measuring the frequency of the reverberant sound. However, since the internal pressure of the can depends on the internal gas pressure, it is unavoidable that the internal pressure of the can fluctuates due to variations in the temperature of the can during the internal pressure measurement.

Therefore, the applicant of the present invention has previously disclosed the Japanese Patent Laid-Open No. 2-28.
A method for discriminating the internal pressure of a can, which is disclosed in JP 4033, is proposed. This measures the canning temperature in order to eliminate the effect of variations in the canning temperature when measuring the canning pressure, corrects the measured canning internal pressure to the canning pressure at a predetermined temperature with a correction coefficient according to the canning temperature, and then corrects the corrected canning pressure value. The suitability of the internal pressure of the can is determined by comparison with a reference value.

[0007]

In the method of discriminating the internal pressure of a can equipped with the temperature correction means, the measured internal pressure of the can is corrected to a corrected internal pressure value at a predetermined temperature by a correction coefficient corresponding to each canning temperature. Although the can internal pressure can be determined more appropriately, as a result of further study, it was found that the influence of the temperature of the can on the can internal pressure value is slightly different depending on the can internal pressure value at that time.

That is, in the conventional can internal pressure determination method, the correlation between the echo frequency and the can temperature is previously obtained by an experiment using one can having a reference internal pressure, and the can pressure at each can temperature is obtained from the correlation line. One correction line was calculated to correct each value to the corrected can internal pressure value at a predetermined temperature. Then, the one correction line is uniformly applied regardless of the can internal pressure value obtained by the measurement, and the can internal pressure value is corrected only by the measured canning temperature.

However, the can internal pressure value and the can temperature do not always have a constant correlation.

FIG. 2 is a graph showing an example of the relationship between the canning temperature and the degree of vacuum in the can or the pressure inside the can. (Kg
/ Cm ² ), and the lower part indicates the degree of vacuum (cmHg) in the can). Thus, when the canning temperature is the same, the can inside pressure value is different from the can inside pressure value. The rate of change in temperature also changes.

That is, as is apparent from the figure, for example, when the canning temperature is 20 ° C., the value of the degree of vacuum in the can is 50.
The cmHg canned product (shown by the correlation line (a)) is about 42 cmHg at 40 ° C, and +8 cmHg may be added as a correction value for the degree of vacuum in the can from 40 ° C to 20 ° C. The degree of vacuum is 20 cm
Canned Hg (correlation line (b)) is 6 cmH at 40 ° C
It becomes about g, and +14 cmHg must be added as the correction value. Thus, even if the canning temperature at the time of measurement is the same, the correction value must be increased for a canned product having a lower degree of vacuum in the can, that is, a canned product having a higher can internal pressure. For this reason, the correction lines calculated from the respective correlation lines shown in the figure also differ slightly.

Therefore, like the conventional method for discriminating the internal pressure of a can,
Correcting a can inner pressure value that is different from the can inner pressure value used in the experiment at the same temperature on the basis of one correction line obtained by the experiment makes it impossible to obtain a correct can inner pressure value.

The present invention has been made in view of the above problems newly found in the above-mentioned prior art, and its object is to change the can internal pressure value at the canning temperature to the can internal pressure value at a predetermined temperature,
An object of the present invention is to provide a device for discriminating the internal pressure of a can that can perform more accurate correction.

[0014]

Means for Solving the Problems In order to achieve the above object, a can internal pressure discriminating apparatus according to the present invention comprises a can internal pressure measuring means for measuring the internal pressure of a measured canned product and a canned product for measuring the temperature of the measured canned product. Based on the correction value calculated from both the temperature measuring means, the can internal pressure value output from the can internal pressure measuring means, and the can temperature output from the can temperature measuring means, the can internal pressure value at the can temperature is set to a predetermined can temperature. And a can internal pressure determining means for comparing the corrected can internal pressure value with a reference value to determine whether the internal pressure of the can is appropriate.

[0015]

The apparatus of the present invention applies the correction value corresponding to the canning temperature and the can internal pressure value when the can internal pressure value at the canning temperature measured as described above is corrected to the corrected can internal pressure value at the predetermined canning temperature. .

That is, even if the canned temperatures measured as described above are the same, if the canned cans have different internal pressures, the correction values for correcting the measured canned internal pressures to the corrected canned internal pressures at a predetermined temperature are obtained. Will be different.

Therefore, with respect to each standard canned product showing different can internal pressure values at a predetermined temperature, a correction value for each canned temperature for correcting to the corrected internal pressure value is obtained in advance,
The correction is performed by the correction value corresponding to the combination of the can internal pressure value and the canning temperature obtained by the measurement.

Therefore, compared to the case where a uniform correction value is applied only by the canning temperature, the correction can internal pressure value can be corrected more accurately at the predetermined temperature, and the accuracy of the can internal pressure adequacy determination can be improved. Is possible.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic structure of a can internal pressure discriminating apparatus according to this embodiment.

In FIG. 1, a canned product 12 to be measured is placed on the belt conveyor 10. An electromagnet 14 and a microphone 16 as a means for measuring the internal pressure of the can 12 are arranged above the can 12, and the lid 12a of the can 12 passing under the electromagnet 14 is impacted by a magnetic force to generate a reverberant sound (canning sound). ) Is detected by the microphone 16.

The output of the microphone 16 is frequency-detected by the frequency detection circuit 18, and the frequency is input to the correction value calculation circuit 20. Here, since the tapping sound frequency and the degree of vacuum in the can (pressure inside the can) have a constant correlation as shown in FIG. 3, the pressure inside the can is detected as a frequency, and the can is detected from the frequency. It is possible to determine the suitability of the internal pressure.

On the other hand, on the right side of the canned food 12 in the drawing, an infrared temperature sensor 22 as a canned temperature measuring means is arranged. The temperature sensor 22 measures the surface temperature of the canned food 12, and its output is a correction value calculation circuit. It is input to 20.

Then, a correction value for correcting the frequency at the canning temperature input in the correction value calculation circuit 20 to the frequency at the reference temperature is calculated. Further, the correction value is input to the frequency correction circuit 24 as a can internal pressure correction means, and the frequency output from the frequency detection circuit 18 is corrected to the frequency value at the reference temperature (for example, 35 ° C.) based on the correction value.

Then, the correction frequency value is input to the discriminating circuit 26 as the can internal pressure determining means, and the discriminating circuit 26 determines the corrected frequency value (= can internal pressure at the reference temperature) as
By comparing with a reference frequency (= reference can internal pressure), it is discriminated whether it is within an allowable range or not, and the cans are separated.

Here, it is characteristic that the correction value calculation circuit 20 calculates the correction value based on both the frequency detected by the frequency detection circuit 18 and the canning temperature measured by the temperature sensor 22. is there.

That is, conventionally, when the can internal pressure at the canning temperature is corrected to the can internal pressure at the reference temperature as described above, the correction value is calculated only by the measured canning temperature. However, as shown in FIG. 2, the degree of influence of the temperature on the internal pressure of the can differs depending on the internal pressure of the can at that time even if the temperature is the same.

Therefore, when correcting the can internal pressure at the can temperature based on the difference between the measured can temperature and the reference temperature, if the can pressure is the same, but the can pressure is different, the can pressure at the reference temperature is used. The correction value for correction is different.

Therefore, the inventor uses a plurality of cans having different can internal pressures at a reference temperature by an experiment and corrects each can internal pressure obtained by changing the temperature of each can to each can internal pressure at the reference temperature. It was decided to calculate the correction value of.

That is, each correction value corresponding to each combination of the measured canning temperature and the detected frequency is set in the correction value calculation circuit 20, and the correction value calculation circuit 20 is set.
The correction value corresponding to the combination is obtained from both the canning temperature and the frequency input to.

Therefore, the correction frequency value corrected by the frequency correction circuit 24 on the basis of the correction value calculated by the correction value calculation circuit 20 accurately indicates the can internal pressure when the measured canned product is at the reference temperature. Therefore, it becomes possible to make an extremely accurate determination of suitability of the internal pressure of the can.

At this time, for example, a correlation diagram of the canning temperature and the can internal pressure as shown in FIG. 2 is obtained in advance, and for example, when the corrected can internal pressure of a predetermined temperature of 20 ° C. is obtained, when the canning temperature is 40 ° C. If the degree of vacuum in the can is measured to be 42 cmHg, the correction value +8 cmHg is added, and it is determined that the corrected degree of vacuum in the can of the can is 50 cmHg. On the other hand, if the degree of vacuum inside the can at the canning temperature of 40 ° C. is measured to be 6 cmHg, the above-mentioned +8 cm
The correction value of +14 cmHg is applied instead of the correction value of Hg, and it is determined that the correction can internal vacuum degree is 20 cmHg.

[0033]

As described above, according to the apparatus of the present invention, the can internal pressure correcting means calculates the correction value based on both the can internal pressure and the can temperature of the can of the can to be measured, and the can at the predetermined temperature is calculated from the correction value. Since the internal pressure is corrected, it is possible to measure the internal pressure of the can and determine whether the internal pressure is proper or not, regardless of the internal pressure of the can of the measured can, when the influence of the can temperature is completely removed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a schematic configuration of a can internal pressure determination device according to an embodiment of the present invention.

FIG. 2 is a graph illustrating the relationship between the temperature of canned food and the degree of vacuum in the can or pressure inside the can.

FIG. 3 is a graph illustrating the relationship between the degree of vacuum in the can and the tapping sound frequency.

[Explanation of symbols]

 12 canned goods 14 electromagnet 16 microphone 18 frequency detection circuit 20 correction value calculation circuit 22 infrared temperature sensor 24 frequency correction circuit 26 discrimination circuit

Claims (1)

[Claims] 1. A can internal pressure measuring means for measuring an internal pressure of a measured canned product, a canned temperature measuring means for measuring a temperature of the measured canned product, a can internal pressure value output from the canned internal pressure measuring device, and a canned temperature. Based on a correction value calculated from both the canning temperature output from the measuring means, a can internal pressure correcting means for correcting the can internal pressure value at the canning temperature to a corrected can internal pressure value at a predetermined canning temperature, and the corrected can internal pressure value as a reference. A can internal pressure determination device comprising: a can internal pressure determination means for determining whether or not the internal pressure of the can of food is appropriate by comparing the value with a value.