JPS6342732B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for testing the internal pressure of a sealed container, and more particularly to a method and apparatus for testing the internal pressure of a sealed container that has an internal pressure higher than atmospheric pressure at room temperature (herein referred to as positive internal pressure). Regarding equipment.

As a method or device for testing the internal pressure of sealed containers filled with food and beverages, etc., conventional methods or devices are of the type that measure the frequency of the hammering sound generated by hitting the almost flat lid or bottom, or A type that measures the decay time, and a type that measures the deformation of the lid or bottom due to internal pressure as the light gathering power using an optical concave mirror effect have been proposed. However, these conventional types are mainly suitable for negative internal pressure metal containers with substantially flat lids or bottoms that are filled and sealed by hot pack methods, vacuum filling methods, steam displacement methods, etc. Generally hemispherical and relatively thick,
It is difficult to apply this method to leakage inspections of sealed metal containers with positive internal pressure, which have a bottom that hardly deforms in response to internal pressure, and a lid that is easy to open with a pull tab. be. Recently, biaxially oriented and blow-molded polyester (e.g. polyethylene terephthalate) bottles have been used as containers for beer and carbonated beverages, but this type of positive pressure plastic has poor acoustic properties and poor light reflectivity. Conventional types are also difficult to apply to sealed containers.

Recently filled (leaving head space)
A positive pressure sealed container has been proposed that has a thin body wall portion that is filled with nitrogen gas and is sealed after dropping liquid nitrogen onto the contents. In this case, if the amount of liquid nitrogen dropped is too small, sufficient positive internal pressure cannot be obtained and the thin barrel wall is likely to dent, while if it is too large, the internal pressure becomes too high, resulting in retort heat sterilization, etc. There is a risk of permanent deformation or rupture of the container. Therefore, it is necessary to measure the internal pressure after sealing and feed it back to the dripping device to control the internal pressure within a certain range, but conventional internal pressure testing methods or devices cannot meet this type of requirement. It is difficult to

The present invention aims to solve the problems of the prior art described above.

In order to achieve the above object, the present invention is a method for inspecting the internal pressure of a sealed container such as a canned food, which has a positive internal pressure property and is provided with an elastically displaceable body wall section, the containers being arranged facing each other, The sealed container is moved so that the body wall passes through the gap between the pressing tool and the receiving member, the width of which is smaller than the outer diameter of the body wall, and the body wall is locally moved during movement. The present invention provides a method for inspecting the internal pressure of a sealed container, characterized in that the container is elastically displaced by pressing with a predetermined pushing amount, and the internal pressure is determined based on the measured value of the reaction force against the displacement.

Furthermore, the present invention is an internal pressure testing device for a sealed container such as a canned food, which has a positive internal pressure property and has an elastically displaceable body wall portion, the device comprising: A pressing tool for elastically displacing by pressing with a pushing amount, a receiving member disposed opposite to the pressing tool and having a width of a gap with the pressing tool smaller than the outer diameter of the body wall, and a receiving member for displacing the body wall portion elastically; a load sensor that senses the reaction force against the load sensor, a circuit that holds the maximum value of the electrical output signal of the load sensor, a circuit that generates a pulse signal when the output signal reaches the maximum value, and a circuit that generates a pulse signal when the output signal reaches the maximum value. The present invention provides an internal pressure testing device for a sealed container characterized by comprising an A/D converter that converts the maximum value of the output signal into a digitized signal.

The present invention will be described below with reference to the drawings which are examples.

The body wall of a relatively small positive internal pressure sealed container (usually with an internal volume of about 100 to 3000 ml) filled with food and drink, etc. is generally cylindrical and easily deformed elastically (sealed). (in the previous state) is thinner than thin material. For example, the thickness of the body wall of a metal can formed by drawing and ironing a tinned steel plate or an aluminum alloy plate is about 0.10 to 0.15 mm. The thickness of the body wall of the biaxially stretched and blow-molded polyethylene terephthalate bottle is about 0.3 mm.
However, when it is sealed and the internal pressure is normal, tension is generated in the barrel wall, making it difficult to deform due to external force. Resistance to this external force has a correlation with internal pressure.

This will be explained below using an experimental example.

101 in Fig. 1 is formed from a tin-plated steel plate with an outer diameter of 53 mm, a height of 130 mm, a body wall portion 101a with a thickness of 0.11 mm, a hemispherical concave bottom portion 101b with a thickness of 0.32 mm, and a capacity of 250 ml. It is a squeezed can. After filling this with the contents 102 leaving a head space 103, the thickness of the container with a pull tab (not shown) is
A 0.35 mm lid portion 102 was double-sealed to produce a sealed container 104 with various internal pressures, and the container was placed horizontally on an anvil 105 as shown.

A tip portion 106 is located directly above the center of the body wall portion 101a.
A pressing tool 10 having a hemispherical shape with a radius of 10 mm
FIG. 2 shows the results of measuring the relationship between the pushing amount (D) and the reaction force (F) when 6 is pressed by a pressing device (not shown) at different positive internal pressures (P).
Within the scope of this experiment, the relatively thick bottom 101b
And the lid part 102 is not substantially deformed, and the body wall part 1
Although only the vicinity of the upper part of the body wall 101a was deformed, after the pushing was released, the body wall part 101a elastically returned to its original shape.

Figure 3 shows the relationship between internal pressure (P) and reaction force (F) when the pushing amount (D) in Figure 2 is 1 mm. ) increases monotonically. Therefore, it is possible to determine the internal pressure by measuring the reaction force (F) at a predetermined pushing amount (D) at a fixed position on the body wall of the sealed container.
In addition, by setting the shape, dimensions, and pushing amount (D) of the tip 106a of the pressing tool 106 within a predetermined range, the deformation (i.e., displacement) of the body wall 101a is kept within the elastic range, and the measurement Rear, trunk wall part 10
It is possible to prevent defects such as permanent dents from occurring in 1a.

201 in Fig. 4 is biaxially stretched and blow-molded polyethylene with an outer diameter of 75 mm, a height of 250 mm, a thickness of the trunk wall portion 201a of 0.30 mm, an average thickness of the hemispherical bottom portion 201b of 0.6 mm, and a capacity of 1000 ml. It's a terephthalate bottle. After filling this with the contents, the screw cap 202
Regarding the sealed container 204 sealed by
Similar to the case of FIG. 1, the relationship between the pushing amount (D) and the reaction force (F) was measured for each internal pressure, and FIG. 5 shows the results. Figure 6 shows the relationship between internal pressure (P) and reaction force (F) when the pushing amount (D) is 1 mm. From this figure, it can be seen that the predetermined pushing amount (D) It can be seen that the internal pressure can be determined by measuring the reaction force (F) at .

Next, examples of the present invention will be described.

In FIG. 7, 301 is a guide plate, on which the sealed container 302 is placed horizontally and is conveyed in the direction of arrow A by a feeding device (not shown). Hole 301 of guide plate 301
a, and is fixed to the fixed plate 316 via the load cell 306 so that the rod-shaped pressing tool 303 protrudes from the upper surface 301b of the guide plate 301 by a predetermined height D. The protrusion height D corresponds to the above-mentioned pushing amount. The protrusion height D is adjusted by a screw mechanism 317 provided on the fixed plate 316. The above adjustment includes the outer diameter of the sealed container 302,
This is done depending on the thickness and material of the trunk wall portion 302a, or the type of painting or printing on the inner and outer surfaces. This is because if the protrusion height D is too low, the accuracy of determining the internal pressure will decrease, while if it is too high, there is a risk that permanent deformation may remain in the body wall portion 302a or scratches may occur on the painted or printed surface. .

Reference numeral 305 is a back-up roll that is constantly rotating in the direction of arrow B, and is rotated so that its axis intersects with the axis of the pressing tool 303 and its lower end 305a.
is higher than the upper surface 301b of the guide plate 301,
The distance between the lower end 305a and the upper end of the tip 303a of the pressing tool 303 is such that the height is substantially equal to or slightly smaller than the outer diameter of the body wall 302a of the sealed container 302. The spacing, that is, the width of the gap between the back-up roll 305 and the pressing tool 303 is arranged so that it is smaller than the outer diameter of the trunk wall portion 302a. Backup Prowl 3
05 is preferably made of a relatively soft rubber roll with a rubber hardness of about JIS (A) 50 to 60. This is to prevent the surface of the sealed container 302 in contact with the roll 305 from being deformed and affecting the measured internal pressure value. Also, the guide plate 301 and the roll 30
5, these are the body wall portion 30 of the sealed container 302.
2a so as to be able to contact the entire length thereof. This is because if non-contact portions exist at the upper and lower ends of the trunk wall portion 302a, the diameter of the portions will protrude, causing fluctuations in the measured internal pressure value.

306 is a load cell that senses the force applied to the pressing tool 303, and is fixed on the fixed plate 316. The output signal 306a of the load cell 306 is
A preamplifier 307 amplifies the voltage to a voltage suitable for the processing described below (typically about 1 to 10 volts). As shown in FIG. 8a, the signal 306a starts to rise at the same time as the sealed container 302 starts to contact the hemispherical tip 303a of the pressing tool 303, and the signal 306a starts to rise as the sealed container 302 starts to roll (in the direction of arrow C). )
As the axis of the sealed container 302 passes over the axis of the pressing tool 303, the height of the body wall 3 increases.
The pushing amount of 02a reaches the maximum value, and at the same time the signal 30
6a also shows the maximum value, and thereafter decreases as the sealed container 302 rolls, resulting in a peak-to-peak pulse waveform. Find the reaction force (F) by reading the maximum value of the above signal waveform.

Next, a processing circuit for reading the above maximum value will be described. 309 is a peak hold circuit to which the output signal 308 of the preamplifier 307 is input. The peak hold circuit 309 has the characteristic of responding to an increasing input as it is and outputting the same value as the input, and not responding to a decreasing input, and therefore retaining the past maximum value. . Therefore, the output signal 312 of the peak hold circuit 309 is
It has the waveform shown in Figure b.

Reference numeral 310 is a voltage comparator, which receives the input branched output signal 308 of the preamplifier 307;
The output signal 312 of the peak hold circuit 309 is compared. When signal 312>signal 308, that is, when signal 308 begins to fall,
The voltage comparator 310 emits the pulse shown in FIG. 8c as an output signal 311.

313 is an A/D converter, into which the output signal 312 of the peak hold circuit 309 and the pulse signal 311 are input. Then, using the pulse signal 311 as a trigger, the signal 312 is digitized and a digitized signal 314 is output. The digitized signal 314 is a numeric display for reading;
Recording or determining whether the internal pressure is good or bad is done using a conventional digital display, printer, or numerical comparison. At the same time pulse signal 311
is used as a signal to control the above-mentioned processing such as display, recording, and discrimination.

315 is a delay circuit, which outputs the pulse signal 311.
Based on the input, a delay pulse 318 shown in FIG. 8d is output after a time delay sufficient for the operation of the A/D converter 313 to be completed.
The peak hold circuit 309 is reset by the delay pulse 318, and the series of processing is completed.

Before performing an internal pressure test using the above device, the protrusion height D is adjusted and set in advance according to the type of sealed container 302 using the screw mechanism 317. but
10 mm, and when pressing approximately the center of the body wall in the height direction, for a drawn and drawn aluminum can with an outer diameter of 53 mm and a body wall thickness of 0.11 mm, a value of D of approximately 0.5 to 1.5 mm is appropriate; Size reduction - For ironed steel cans, a value of D of about 0.5 to 2.0 mm is appropriate. Also outer diameter 75
In a biaxially stretched and blow-molded polyethylene terephthalate bottle with a body wall thickness of 0.3 mm, the range of D is preferably wider, and no problem occurred between 0.5 and 3.0 mm. The internal pressure is approximately 0.5-7.0Kg/cm ² and the outer diameter is approximately
For commonly used sealed beverage containers of 50 to 100 mm,
It has been found that by setting the protrusion height D to 2.0 mm, it can be used in almost all cases.

After the above adjustment, the sealed container 302 to be inspected
The roll 30 is moved by a feeding device (not shown).
5 and the guide plate 301 so that the fixed position in the height direction passes over the pressing tool 303.
When the sealed container 302 is fed in the direction of the roll 30
5 and rotates in the direction of arrow C, and rolls while being lightly pressed against the guide plate 301. At this time, the sealed container 302 is deformed by being pushed by the tip 303a of the pressing tool 303, and the load cell 306 senses the reaction force at this time. The maximum value of the sensed reaction force is output as a digitized signal 314, as previously described. Therefore, the type, push position, and protrusion height D of each sealed container
By calibrating the relationship between the internal pressure and the digitized signal 314 in advance, it is possible to measure the internal pressure and determine whether the internal pressure is good or not (whether the internal pressure is within an appropriate range or not) by comparing it with a reference value. The following tests can be carried out.

In the method of testing the internal pressure of a sealed container such as a can, which has a positive internal pressure property and has an elastically displaceable body wall, the containers are disposed facing each other, and the width of the gap is set to the outside of the body wall. Move the sealed container so that the body wall passes through the gap between the pressing tool smaller than the diameter and the receiving member (for example, a back-up roll), and locally press the body wall by a predetermined amount while moving. Since the internal pressure of the sealed container is determined based on the measured value of the reaction force against the displacement, it is not affected by the acoustic characteristics or light reflectivity of the wall, and the container is made of metal or plastic. The internal pressure of a positive internal pressure sealed container with a wall can be inspected to determine whether there is any leakage or whether the internal pressure is within a predetermined range, at high speed (because it is measured while moving) and with high precision (by measuring the reaction force against changes). This has the advantage that the internal pressure has a substantially linear correlation) and that it can be carried out without leaving defects such as permanent dents in the body wall (because it is an elastic displacement).

According to the apparatus of the present invention, the above method of the present invention can be easily implemented.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a first example showing the principle of the method of the present invention, FIG. 3 is a diagram showing the relationship between the reaction force and internal pressure determined based on FIG. 2, FIG. 4 is a front view of the second example showing the principle of the method of the present invention, and FIG. Diagram showing the relationship between the pushing amount and the reaction force measured by the means shown in the figure, No. 6
The figure is a diagram showing the relationship between the reaction force and internal pressure determined based on Fig. 5, Fig. 7 is a front view of a device that is an embodiment of the present invention, and a block diagram of its electric circuit. Figures a, b, c, and d are signal waveform diagrams of the electric circuit of Figure 7. 104,204,302... Sealed container, 101
a, 201a, 302a... body wall part, 106, 3
03... Pressing tool, 305... Backup roll (receiving member), 306... Load cell (load sensor), 309... Peak hold circuit, 310...
...Voltage comparator (circuit that generates a pulse signal), 313...A/D converter.

Claims (1)

[Scope of Claims] 1. A method for inspecting the internal pressure of sealed containers such as canned goods, which have positive internal pressure properties and have elastically displaceable body wall parts, which are arranged facing each other and have a width of a gap. The sealed container is moved so that the body wall passes through the gap between the pressing tool and the receiving member, which is smaller than the outer diameter of the body wall, and the body wall is locally pushed into a predetermined position during the movement. A method for inspecting the internal pressure of a sealed container, characterized in that the container is pressed by a pushing amount to elastically displace the container, and the internal pressure is determined based on a measured value of a reaction force against the displacement. 2. An internal pressure testing device for sealed containers such as cans, which has positive internal pressure properties and has an elastically displaceable body wall portion, which device locally presses the body wall portion by a predetermined pushing amount. a pressing tool for elastically displacing the body wall; a receiving member disposed opposite to the pressing tool and having a width of a gap with the pressing tool smaller than the outer diameter of the body wall; A sensing load sensor, a circuit that holds the maximum value of the electrical output signal of the load sensor,
It is characterized by comprising a circuit that generates a pulse signal when the output signal reaches a maximum value, and an A/D converter that converts the maximum value of the output signal held based on the pulse signal into a digitized signal. Internal pressure testing device for sealed containers.