JPH11351999A - Method and apparatus for inspecting leakage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and apparatus for inspecting leakage of a PET bottle exhibiting significant elastic deformation accurately in a short time. SOLUTION: A variable tank 2 is coupled with a container 1 to be inspected and initial pressure P0 is measured sealing the container hermetically. Inner pressure of the container is then increased temporarily by driving the variable tank 2 in the direction for decreasing the volume. Subsequently, the volume of the variable tank 2 is recovered and the inner pressure P2 of the container 1 is measured. A decision is made that a PET bottle is not leaky if P2 =P0 , and otherwise it is leaky.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leakage inspection method for inspecting the presence or absence of leakage of a plastic container called, for example, a PET bottle, and a leakage inspection apparatus using the inspection method.

[0002]

2. Description of the Related Art Conventionally, a method of inspecting a container made of a plastic resin such as a plastic bottle for leakage is to apply a certain gas pressure to a container to be inspected, close a valve after pressurizing to create a sealed state, A method of detecting whether or not the container to be inspected has leaked by detecting a change in pressure has been adopted.

[0003]

This conventional leak inspection method requires time to pressurize the gas pressure and time to close the valve and monitor for the occurrence of a pressure change due to the leak. Because it is a resin product, it deforms when pressure is applied, and it is difficult to determine whether it is a pressure change due to leakage or a pressure change due to deformation, even if a pressure change (reduction in pressure) is detected. There was a disadvantage that it could not be detected.

An object of the present invention is to detect a small leak without being affected by deformation of a container to be inspected, and to inspect the leak in a short time, and a leak using the inspection method. It is intended to provide an inspection device.

[0005]

According to the present invention, the container to be inspected is sealed, the initial pressure P ₀ in the sealed state is measured, and the sealed volume including the container to be inspected is changed back to the original state.
Gas pressure in a state where the back sealed volume based on the proposes a testing method leakage is determined that there is leakage by detecting that deviates from the original initial pressure P _0.

According to the leak inspection method of the present invention, the presence or absence of leakage of a container to be inspected is detected by utilizing a change in gas pressure. In the present invention, however, the change in pressure is measured near the atmospheric pressure. And the presence or absence of leakage can be detected with high sensitivity. Further, there is an advantage that the inspection can be performed in a short time.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a principle configuration diagram for explaining a leakage inspection method according to the present invention. In the figure, reference numeral 1 denotes an inspected container such as a PET bottle, 2 denotes a variable tank, and 3 denotes a pressure sensor. The variable tank 2 is a cylinder 2A in this example.
And a piston 2B. The variable tank 2 and the container 1 to be inspected are connected by a pipe 4, and the container 1 to be inspected is sealed by the connection of the variable tank 2.

The initial pressure P ₀ is measured by the pressure sensor 3 with the container 1 to be inspected connected to the variable tank 2 (sealed state). This initial pressure P ₀ is generally atmospheric pressure. Next, the piston 2B is moved, for example, by D to control the variable tank 2 in a direction to reduce the volume. Due to the movement of the piston 2B, the sealed volume (the sum of the volumes of the variable tank 2, the container 1 to be inspected, and the pipe 4) including the inner volume of the container 1 to be inspected changes in a direction to decrease.

[0009] inner pressure of the test container 1 by the volume change since this case is increased, if no leakage is to be inspected vessel 1 is maintained at a constant pressure P _1, as shown in FIG. 2A, based on the piston 2B , The pressure P ₂ becomes the initial pressure P
Return to ₀ . On the other hand if if leakage is present in the test container 1 moves the piston 2B variable tank 2 by D, the pressure in the sealed volume once rises to a pressure P _1, the presence of leakage, pressure Figure 2B Gradually declines as shown in
Negative pressure P ₂ to the back of the piston 2B to its original position corresponding to the amount leaked during pressing occurs.

Accordingly it is possible to detect values of the pressure sensor 3 is determined that there is leakage unless original initial value P ₀ when returning the piston 2B to its original position. FIG. 3 shows an embodiment of a leakage inspection apparatus according to the present invention. In the leak inspection apparatus according to the present invention, a connection jig 5 is provided at an end of a pipe 4 connected to a variable tank 2, and the connection jig 5 is detachably clamped to a container 1 to be inspected such as a plastic bottle.

A driving device 6 such as an air cylinder is mounted on the piston 2B of the variable tank 2, and the driving device 6 drives the piston 2B at a stroke D. An inspection device 7 is electrically connected to the pressure sensor 3. The inspection device 7 can be constituted by a microcomputer, for example. As is well known, the microcomputer is a central processing unit 7A, a read-only memory 7B called a ROM or the like, a writable / readable memory 7C called a RAM, an input port 7D, and an output port 7E.
It is constituted by and.

In the example shown in FIG. 3, the read only memory 7B
Shows a configuration in which a program constituting the comparison / determination means is stored, and the comparison / determination operation is executed by this program. The comparing and judging means calculates the initial pressure P _{0 of the} inspected container 1.
And the drive device 6 is extended to move the piston 2
B is moved by the stroke D, and executes an operation to perform control again returns to the original position, the operation of reading the pressure P ₂ from the pressure sensor 3 when the piston 2B returns to the original position.

The RAM 7C stores the initial pressure P ₀ and the pressure P ₂ at the time when the pressure returns to the original pressure, and determines whether P ₀ and P ₂ match according to the storage. If P ₀ = P ₂ , it is determined that there is no leakage, and if P ₀ ≠ P ₂ , it is determined that there is leakage. The determination result is displayed on, for example, the display 8 connected to the output port 7E. [Modified Embodiment] In the above description, the piston 2 of the variable tank 2 is used.
B is moved in the direction of pushing the cylinder 2A, the sealed volume is moved in the direction of decreasing the sealed volume, and the case where a positive pressure is applied to the container 1 to be inspected has been described. Even if a method of applying a negative pressure to the inspection container 1 is employed, the same operation and effect as described above can be obtained.

In the above description, the initial pressure P₀And reverted
State pressure P_TwoIs measured and the pressure P_TwoIs P₀= P_TwoIs
It was determined whether or not there was a leak depending on whether
If there is a large leak, the initial pressure P₀To pressurized pressure
P₁(FIG. 2) and the final pressure P _TwoIs all P₀= P₁= P_Two
Could be Therefore, the pressure P at the time of pressurization₁Is prescribed
Add a sequence to measure whether it rises to the value
It may be configured as follows.

[0015]

As described above, according to the present invention, since only the pressure near the atmospheric pressure is applied to the container 1 to be inspected, the container 1 to be inspected is not greatly deformed. Therefore, it is possible to eliminate the inconvenience of determining that the pressure change caused by the deformation of the container to be inspected 1 is leaked. Further, the inspection can be completed in a short time.

Further, according to the leak inspection method of the present invention, even if pressure is once applied to the container to be inspected, the sealed volume is returned to the initial state, so that it is less affected by the deformation of the container to be inspected. Further, even if the gas is pressurized by the variable tank, the variable tank is returned to the original state, so that there is an advantage that the influence of the adiabatic change due to the compression is small.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram for explaining a leak inspection method according to the present invention.

FIG. 2 is a waveform chart for explaining the operation of FIG.

FIG. 3 is a block diagram for explaining one embodiment of a leakage inspection device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 container to be inspected 2 variable tank 3 pressure sensor 4 pipe 5 connection jig 6 driving device 7 inspection device 8 display

Claims (5)

[Claims] 1. A leakage inspection method for inspecting leakage of a container having remarkable elastic deformation, comprising: measuring an initial pressure in a sealed container to be inspected; A leak inspection method characterized by returning the volume change, measuring the internal pressure of the container under inspection in that state, detecting that the measured pressure has changed from the initial pressure, and determining that there is a leak. . 2. The leak inspection method according to claim 1, wherein
The sealed volume is changed to a smaller direction, and a positive pressure is applied to the container to be inspected to return to the original volume. When the original volume is restored, it is determined that there is a leak in a state where a difference from the initial pressure occurs. A leak inspection method, characterized in that: 3. The leak inspection method according to claim 1, wherein
Apply a negative pressure to the container to be inspected from the initial state and return to the original state,
A leak inspection method, comprising: measuring the pressure of the container to be inspected at this time; detecting that the measured pressure deviates from an initial pressure; and determining that there is a leak. 4. A leak inspection apparatus, wherein a variable tank and a pressure gauge are connected to a container to be inspected, and the volume of the variable tank is changed to execute the leak inspection method according to claim 1. 5. The leak inspection apparatus according to claim 4, wherein
A leak inspection apparatus, wherein the variable tank is constituted by a cylinder and a piston, and a volume of the container to be inspected is changed by movement of the piston.