JP2000111443A - Method and device for inspecting leakage of container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the reaching time to inspection vacuum degree and also prevent the permanent distortion of a container at the same time by suppressing the expanding deformation of the container by covering the container with a chamber and deaerating the inside of the chamber under the condition wherein the inside of the container is opened to atmosphere. SOLUTION: A container A to be inspected, which is mounted on a stationary stage 2, is covered with a chamber 9. At the same time, the surrounding part of an opening B of the container A and the part between the lower edge of the chamber 9 and the surface of the stationary stage 2 is airtightly held by a sealing packing 4. Then, under the condition where the inside of the container 4 is communicated to the atmosphere and opened, the air in the chamber 9 is deaerated. The vacuum degree after the deaeration and the change of the deaeration after the passage of the specified time are detected, and the leakage of the container A is judged. By forming the inner surface of the chamber 9 so as to approach the outer surface of the container, the volume of the space in the chamber at the time of measurement is made small, and the detection is performed in the short time. Since the detecting environment is made to be negative pressure, the pressure stabilizing time becomes short by the positive-pressure environment. Since the expansion of the container A is constrained at the inner wall of the chamber 9, deformation does not remain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting leakage of a container having an opening at the top.

[0002]

2. Description of the Related Art Conventionally, for leak inspection of metal cans, plastic containers, etc., the periphery of the container opening is sealed and compressed air is filled into the container. When a set pressure is reached, a valve is closed, and after a predetermined time elapses. If the difference is greater than a certain value, it is determined that there is a leak and the test is rejected. And a method in which the container is placed in a chamber that covers the outer periphery of the container, air at a constant pressure is continuously supplied into the container, and a leak is detected by detecting a pressure increase in the chamber. In the conventional method described above, after the compressed air is filled and the compressed air is shut off, the pressure in the container continues to drop for a while due to adiabatic expansion even if there is no leakage, especially in the case of large capacity such as an 18 liter can. Has a disadvantage that it takes a long time to fill the compressed air and a very long stabilization time, so that it is not possible to determine in a short time whether a pressure drop due to leakage or a natural pressure drop occurs. The method of vacuuming the inside of the container cannot be applied to any container because of the relationship with the container strength. In the method of covering with the chamber, it takes a considerable time until the container expands due to the compressed air put in the container and the pressure in the chamber is stabilized. As described above, when the container is large to some extent, or when the container strength is weak against external pressure, it is extremely difficult or inefficient to detect leakage by a conventionally known method.

[0003]

SUMMARY OF THE INVENTION The present invention eliminates the method of sealing compressed air in a container in leak inspection of a can container, keeping the inside of the container in communication with the atmosphere, and removing a small amount of air in a sealed chamber covering the container. It is an object of the present invention to provide an inspection method and apparatus which reduce the time required to reach the inspection vacuum degree by suppressing the expansion of a weak portion of the container and leave no permanent distortion in the container by evacuating the space.

[0004]

The inspection method of the present invention is directed to a container having an opening at an upper part and capable of being self-supporting, and covers a container to be inspected placed on a stationary table with a chamber. The air in the chamber is degassed in a state where the peripheral surface of the opening and the lower end edge of the chamber and the bottom surface of the chamber and the stationary table surface are kept airtight and the inside of the container is communicated with the atmosphere, and the degree of vacuum after degassing is determined. This is to detect and determine the change in the degree of vacuum after a lapse of time, and to make the chamber inner surface close to the outer peripheral surface of the test container to reduce the volume of the chamber space at the time of measurement and to perform a short inspection. Is performed. In the device of the present invention, a seal packing is fixedly mounted on the outer periphery of the test container mounting table provided at a constant angular interval around the rotary table,
A chamber having a lower end opened above each of the mounting tables and covering the container to be tested is suspended by being connected to an elevating cylinder, and a lower end edge of the chamber is in close contact with the seal packing and an opening of the container to be tested is provided above the chamber. A ring packing that is in close contact with the peripheral surface, and a movable cylindrical body provided with an atmosphere communication part at the center thereof are provided so as to be able to move up and down, and each of the chambers is connected to a vacuum source via a vacuum gauge and an electromagnetic on-off valve. The leakage inspection is performed by measuring a decrease in the degree of vacuum in each of the chambers within a time period during which one cycle is performed. An air cylinder is used for raising and lowering the chamber and the movable cylinder, and a support and a guide rod are used for supporting the chamber to ensure vertical operation. Known means such as a lamp provided for each chamber or a digital transmitter of measured values can be applied as a means for discriminating signals from the vacuum gauge.
In order to prevent the container wall of the container from bulging and deforming under vacuum or reduced pressure during the measurement, it is preferable to protrude the pressing portion on the inner surface of the upper portion of the chamber.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a top view of a rotary table of an inspection apparatus in which 24 18-liter square cans are placed as test containers A on a rotary table having a diameter of about 3 m. Reference numeral 1 denotes a turntable, which is rotated at a constant speed by a driving device (not shown). Reference numeral 2 denotes a container mounting table, 3 denotes a position regulating piece, and 4 denotes a seal packing embedded in a base plate so as to surround the mounting table. Numeral 5 is a column vertically provided corresponding to each mounting table 2, numeral 6 is a guide bar juxtaposed, and numeral 7 is an upper plate.
Reference numeral 8 denotes an elevating cylinder fixed downward to the upper plate, 8a denotes a rod penetrating the upper plate, and the tip is connected to the upper surface of the chamber 9. The inner peripheral surface 9a of the chamber 9 is formed such that a slight gap, for example, a gap of 2 to 3 mm can be secured between the inner peripheral surface 9a and the outer periphery of the container. Therefore, the shape of the chamber is substantially equal to the outer shape of the container, with the lower end having an opening 9d. Reference numeral 10 denotes a lower edge of the chamber, which is in close contact with the seal packing 4. Reference numeral 11 denotes a lifting / lowering guide bearing unit protruding from the side surface of the chamber, which is fitted to the guide rod 6. Reference numeral 12 denotes a suction port connected to the vacuum hose 13, reference numeral 14 denotes an electromagnetic on-off valve provided between the vacuum source and a vacuum source, and reference numeral 15 denotes a vacuum gauge. 1
Reference numeral 6 denotes a holding portion projecting from the upper inner surface 9b of the chamber 9, and suppresses the upper surface of the container from swelling due to reduced pressure. 9c is a receptacle for the container opening. Reference numeral 17 denotes a ring packing that is in close contact with the peripheral surface of the can opening, and is fixed in a ring shape to the lower end of a movable cylinder 18 having an air communication portion 19 at the center. It is driven by a pressing cylinder 21 if possible. The movable cylindrical body 18 with ring packing is provided at a position corresponding to the container opening, and has a function of keeping the opening peripheral surface airtight with a constant pressing force for each container and releasing the inside of the vacuum chamber to the atmosphere. ing.

[0006] The container A is transported by the feeding conveyor 30 and is fixed on the mounting table 2 by the mounting protruding cylinder 31 and the position regulating piece 3. The turntable is rotating at a speed of 2 to 4 revolutions per minute. After the container A is fixed on the mounting table 2, the elevating cylinder 8 operates to lower the chamber 9 to the state shown in FIG. In this state, the lower end edge 10 of the chamber is in close contact with the seal packing 4 and the ring packing 17 is in close contact with the peripheral surface of the can opening B, and the holding portion 16 on the inner surface of the upper portion of the chamber is in contact with the upper surface of the container. The pressing force of the ring packing is controlled to be constant for each container by the pressure of the pressing cylinder 21. Subsequently, the electromagnetic on-off valve 14 is opened and the space in the chamber is depressurized and reaches a certain degree of vacuum. Then, the electromagnetic on-off valve is closed and the measurement is started. A decrease in the degree of vacuum after a predetermined time, for example, 10 to 15 seconds, is measured based on the output of the vacuum gauge 15, and leakage of the container is determined. After the measurement is completed, the pressure cylinder 21 is operated to release the ring packing 17 from the can opening, thereby introducing air into the chamber. Subsequently, the elevating cylinder 8 is operated to return the chamber 9 to the standby state of FIG. The defective product of the container is discharged to the discharge chute 33, and the normal product is transferred to the chute 32. 34 is a take-out device. FIG. 4 shows that the degree of vacuum in the chamber was 24
0 mmHg, normal container A1 and container A2 with 50 μm pinhole
4 is a graph in which the degree of vacuum reduction was measured. In the case of this experimental example, the pressure in the chamber of the container A2 becomes 235 mmHg about 10 seconds after the start of the measurement, and the difference from the chamber pressure of the good product A1 is about 3 m.
mHg, about 6 mmHg after 15 seconds.

[0007]

According to the method of the present invention, since the test environment is set to a negative pressure, the pressure stabilization time is extremely short compared to the positive pressure environment, so that the measurement can be performed in a short time. In addition, expansion of the thin-walled container due to an external negative pressure is restrained by the inner wall of the chamber, so that no deformation is left after the inspection. In addition, the expansion of the container does not gradually expand as in the compressed air filling type, but the expansion is instantaneously completed by degassing the outer periphery of the can, so the time from degassing to the start of inspection is greatly reduced. You. A part of the vessel wall adheres to the chamber inner wall due to the expansion of the container.
In the case of liter cans, the leaked parts are concentrated on the top plate, the bottom plate, and the welded portions at the corners of the body plate, and these portions are relatively strong and do not deform at a vacuum of about 240 mmHg. Further, since the volume of the chamber space is reduced by the expansion of the can body, the vacuum sensor or the vacuum gauge is sensitively sensitive, and there is an advantage that the expansion of the can body leads to an improvement in inspection accuracy. Also, since a small space between the outer periphery of the container and the inner periphery of the chamber is evacuated, a small-capacity vacuum pump can be used in time, so that it is extremely economical and a remarkable effect can be expected as compared with the conventional method.

[Brief description of the drawings]

FIG. 1 is an overall top view of an apparatus of the present invention from which a chamber is removed.

FIG. 2 is a sectional view of a chamber in an inspection standby state.

FIG. 3 is a sectional view of a chamber at the time of inspection.

FIG. 4 is a graph showing a pressure change in a chamber.

[Explanation of symbols]

 1 Rotary table 2 Container mounting table 3 Position regulating piece 4 Seal packing 5 Support column 6 Guide rod 7 Upper plate 8 Elevating cylinder 9 Chamber 10 Lower edge 11 Bearing unit 12 Suction port 13 Vacuum hose 14 Solenoid on-off valve 15 Vacuum gauge 16 Swelling presser Part 17 Ring packing 18 Movable cylinder 19 Atmospheric communication part 20 Holder 21 Pressing cylinder A Can body to be tested B Can body opening

Claims (3)

[Claims] 1. A self-supporting container having an opening at the top is placed on a stationary table and covered with a chamber, and the periphery of the opening of the container and the lower edge of the chamber and the surface of the stationary table are hermetically sealed. Leakage of the container characterized by degassing the air in the chamber while holding and releasing the container to the atmosphere, and detecting and determining the degree of vacuum after deaeration and the degree of vacuum after a predetermined time has elapsed. Inspection methods. 2. A leak inspection apparatus for an autonomous container having an opening at an upper portion, wherein a seal packing is provided on an outer periphery of a test container mounting table provided at a fixed angle interval around a turntable. A chamber, which is fixed and has a lower end opened above each of the mounting tables and covers the container to be tested, is connected to an elevating cylinder, and a lower end edge of the chamber is in close contact with the seal packing, and an opening of the container to be tested is provided above the chamber. A ring packing that is in close contact with the peripheral surface, and a movable cylindrical body provided with an atmosphere communication part at the center thereof are provided so as to be able to move up and down, and each of the chambers is connected to a vacuum source via a vacuum gauge and an electromagnetic on-off valve. Is 1
An apparatus for performing a leak test by measuring a decrease in the degree of vacuum in each of the chambers within a circulating time. 3. The apparatus according to claim 2, wherein a swelling suppression pressing portion is provided on an inner surface of an upper portion of the chamber.