JP3302824B2 - Can lid leak inspection method and 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 method and an apparatus for detecting the presence or absence of a pinhole in, for example, a can lid having an easy-open structure. The present invention relates to a method and an apparatus for inspecting can lid leakage, which detects the presence or absence of a pinhole by detecting sound waves.

[0002]

2. Description of the Related Art As a device for detecting a pinhole in a can lid, there is a device disclosed in Japanese Utility Model Publication No. 58-5239. This device supplies compressed air from one side of the can lid, and if there is a pinhole in the can lid, picks up the sound of the compressed air ejected from the pinhole with a microphone and inspects the can lid for leakage. is there. In addition, compressed air that explodes explosively from the pinhole and pressure waves that are generated when the can lid suddenly expands when compressed air is supplied breaks the microphone and interferes with microphone sound measurement. A labyrinth baffle is provided to attenuate the compressed air and pressure waves that have been blown out, and the air that has passed through the labyrinth baffle is discharged to the atmosphere from an exhaust port. The inspection speed of this apparatus is 400 sheets per minute, and the minimum detectable pinhole diameter has a measurement accuracy of 1/1000 inch.

[0003]

However, in the above-described conventional apparatus, ultrasonic waves generated by mechanical vibrations and the like at a lid manufacturing plant are
There is a risk that the lid will pass through the labyrinth baffle and reach the microphone from the exhaust port, and the can lid without pinholes will be rejected. In addition, the co-seismic vibration of the can lid leak inspection apparatus itself caused by vibrations in the factory such as mechanical vibration may cause the microphone to be perceived, and the can lid having no pinhole may be defective.

[0004] It is an object of the present invention to provide a can lid leak inspection apparatus which can perform high-accuracy and high-speed processing without causing such malfunctions.

[0005]

As a result of frequency analysis of the noise in the can lid manufacturing factory, the factory noise contains a lot of ultrasonic waves of about 20 to 40 kHz, while the leaked ultrasonic waves of the can lid are converted to frequency. As a result of the analysis, the leakage ultrasonic wave of the can lid was 40 to 9
It turned out that the ultrasonic wave near 0 kHz changed remarkably.

The present invention has been made based on this finding, and the first invention is to supply compressed air from one side of a sealed can lid separated from the front and back, and to supply the compressed air to the can lid on the other side. In a method of detecting leakage of air from a pinhole by detecting a sound of air blown out from a pinhole with a microphone, a leakage of 50 to 70 kHz is required.
This is a can lid leakage inspection method for detecting ultrasonic waves in the frequency band of z and determining whether or not leakage has occurred.

In the second invention, compressed air is supplied from one side of a sealed can lid whose front and back are isolated, and the sound of air blowing from a pinhole of the can lid is detected by a microphone on the other side. In the device that inspects the can lid for leakage,
An air chamber having a gap is provided behind the sound sensing part of the microphone, and the air relief valve that seals the air chamber and is opened when the air chamber becomes high pressure is separated from the sound sensing part of the microphone. It is a can lid leak inspection device provided.

Further, in the third invention, compressed air is supplied from one sealed side of a can lid whose front and back are isolated, and the sound of air blowing from a pinhole of the can lid is detected by a microphone on the other side. In a device for inspecting leakage of a can lid, an air chamber having a gap is provided behind a sound sensing portion of a microphone, and the air chamber is sealed and released when the air chamber becomes high pressure. This is a can lid leak inspection device which is provided with a valve separated from a sound sensing part of a microphone, detects ultrasonic waves in a frequency band of 50 to 70 kHz, and determines the presence or absence of leakage.

[0009]

First, the first aspect of the present invention is to detect the presence or absence of leakage by detecting an ultrasonic wave in a frequency band of 50 to 70 kHz which is relatively not included in the noise of a lid manufacturing plant.
Even if the can lid leak inspection device itself is co-seismic with the factory noise, if there is no pinhole, almost no change is detected in the ultrasonic wave in the frequency band of 50 to 70 kHz. A malfunction such as a defective product does not occur, and a high-speed and high-precision inspection can be performed.

According to the second aspect of the present invention, since an air chamber having an air gap is provided behind the sound sensing portion of the microphone, a sudden change in pressure can be suppressed, and the air chamber is sealed. The air relief valve, which is released when the air chamber becomes high pressure, is set apart from the sound-sensitive part of the microphone.Therefore, there is no danger of the microphone picking up factory noise, enabling high-precision inspection and high-speed inspection. It becomes possible.

Further, a third aspect of the present invention is to provide an air relief provided with an air gap behind a sound sensing portion of a microphone, wherein the air chamber is sealed and released when the air chamber becomes high pressure. In order to detect the ultrasonic wave in the frequency band of 50 to 70 kHz and determine the presence or absence of leakage, the microphone is provided with a valve provided separately from the sound-sensing part of the microphone.
High-precision and high-speed inspection is possible because it can detect only the ultrasonic waves in the frequency band of 50 to 70 kHz generated from the pinhole and determine the presence or absence of the leak, regardless of the factory noise or the co-seismic vibration of the can lid leak inspection device itself. Becomes possible.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a can lid leakage inspection apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an inspection head 1 of the apparatus of the present invention. In the figure, reference numeral 6 denotes a lower pocket having a substantially cylindrical shape. The lower pocket 6 has an unevenness on the upper end surface on which the can lid H is placed. An annular elastic ring 62 that supports the lower edge of the peripheral edge of the can lid H is provided at the place where the can lid is placed. The lower pocket 6
Is provided with a compressed air supply pipe 61 divided into two parts, and can supply compressed air between the unevenness of the lower pocket 6 and the lower surface of the can lid H. Further, the lower pocket 6 can be moved downward by a cam mechanism (not shown) when supplying the can lid H to the upper end surface of the lower pocket 6 and when discharging the can lid H.

Above the lower pocket 6, a housing 7 is provided coaxially with the lower pocket 6. At the lower end of the housing 7, the housing 7 is engaged with the outer periphery of the upper surface of the lower pocket 6 to supply compressed air. An annular packing 71 is provided to prevent the compressed air from the pipe 61 from leaking outside. Inside the annular packing 71, an annular seal ring 72 is provided which is locked to the upper end of the peripheral edge of the can lid H and separates the upper and lower surfaces of the can lid H.

Further, inside the annular seal ring 72, a holding plate 5 having a lower surface shape that is engaged with the countersink wall of the can lid H and the upper surface of the outer end of the pull ring is provided.
Eight sheets are provided radially below the horizontal partition 73 of the housing 7 except for a hole provided in the axis. The holding plate 5 serves to press the can lid H from the front side of the can lid H so that when the pressure of the compressed air is applied to the back side of the can lid H, the can lid H is not excessively deformed.

The microphone 4 is installed through the hole in the axial center of the horizontal partition 73 and at the sound-sensing portion at the tip of the holding plate 5 at substantially the center thereof. The microphone 4 is fixed to the upper housing 8 via two elastic rings 41 and 42 provided for vibration isolation, sound insulation and electrical insulation. The microphone 4 is a condenser type microphone. In order to remove a low-frequency vibration component which is not directly related to the inspection, a fine hole is provided in a vibrating film which is a sound-sensitive portion, and an ultrasonic wave of approximately 5 kHz or more is provided. The sensitivity is limited only to the band.

In a can lid manufacturing plant, a large amount of ultrasonic waves including mechanical noise and air discharge noise are generated. As a result of frequency analysis, the plant noise includes many ultrasonic waves of about 20 to 40 kHz. On the other hand, when the frequency analysis of the leaking ultrasonic wave from the can lid was performed, it was found that the ultrasonic wave around 40 to 90 kHz significantly changed. In addition, 70k
In a frequency band of not less than Hz, there is a concern about the influence of electric noise due to electromagnetic waves. Therefore, in the present invention, the frequency band used for determination is set to a band of 50 to 70 kHz.

The ultrasonic signal picked up by the microphone 4 is
Only an ultrasonic signal in a frequency band of 50 to 70 kHz is amplified by an electric amplifier and a frequency filter directly connected to the microphone 4 and converted into a DC voltage. The signal in the frequency band of 50 to 70 kHz converted into the DC voltage is
The signal is taken out to a fixed portion outside the device via a rotary connector (not shown), and a pass / fail judgment on whether or not the signal is a leakage signal is made by a judgment processing device (not shown).

Above the horizontal partition 73, an air chamber 2 having a wide gap is provided. The gap of the air chamber 2 prevents a sudden pressure change on the upper surface side of the can lid H from an unexpected explosive leak or a pressure wave generated when the can lid suddenly expands when compressed air is supplied. This prevents the vibrating membrane of the microphone 4 from being protected and does not hinder the measurement of the microphone 4. Further, at the upper end of the air chamber 2, an air relief valve 3, which is normally closed, but is opened when the pressure in the air chamber 2 becomes 0.01 MPa or more, is provided. Since the air relief valve 3 is normally closed, no external sound is introduced, and the air chamber 2 is provided, and the microphone 4 and the air relief valve 3 are provided.
, The influence of external sound on the microphone 4 is almost eliminated even when the air relief valve 3 is open.

The inspection head 1 having the above-described structure is fixed to the machine frame 9, forms a set of inspection devices with the six inspection heads 1, and is incorporated in a can lid production line.

FIG. 2 is a schematic plan view showing a case where the inspection apparatus 12 of the present invention is incorporated in a lid production line. Figure 1,
Along with the description of 2, the operation of the device of the present invention will be described.

The manufactured can lids are stacked vertically, separated one by one from the lower lid by a lid separating device 10, sent in the direction of arrow A, and fed into the infeed turret 11.
Is sent in the direction of arrow B and sent to the inspection device 12.

In the inspection head 1 of the inspection device 12, the lower pocket 6 is lowered downward by a cam mechanism (not shown) and stands by. When the can lid is received, the lower pocket 6 rotates in the direction of arrow C when receiving the can lid. 6 is closed again, and the can lid is separated from the front and back by an annular packing 71 and an annular seal ring 72.

Next, 0.5 megapascal compressed air is sent from the compressed air supply pipe 61 to the back side of the can lid, and the can lid expands rapidly to generate a pressure wave. Actuates to attenuate this pressure wave. Ten milliseconds later, the microphone 4 is set to 50 for the next 20 milliseconds.
The ultrasonic signal having a frequency of about 70 kHz is converted into a DC voltage and sent to a determination processing device (not shown). The determination processing device determines the presence or absence of leakage based on the magnitude of the transmitted DC voltage, and when it is determined that the lid is a leakage lid, orders a reject device (not shown) to operate. As described above, the device of the present invention is provided with the air chamber 2 and the air relief valve 3, the distance between the diaphragm of the microphone 4 and the air relief valve 3 is sufficiently long, the air chamber is sealed, and the determination frequency is further reduced. Since the frequency is set to 50 to 70 kHz, which is not included in the factory noise, it is unlikely that a malfunction such as a conventional device that determines a good product as a leakage lid is likely to occur, and a highly accurate inspection result can be obtained. This enables high-speed processing.

When the pinhole of the can lid is broken by the pressure of the compressed air, or when a considerably large pinhole is previously formed in the can lid, a considerable loud sound including a frequency of 50 to 70 kHz is generated. Therefore, the determination processing device transmits a reject signal, and the compressed air flowing into the surface side of the can lid is released from the air chamber 2 to the outside air through the air relief valve 3 to damage the diaphragm of the microphone 4. Also, the measurement of the microphone 4 is not disturbed.

On the other hand, the can lid in the inspection head 1 to which the supply of the compressed air has been stopped after the inspection is finished is transferred to the reject turret 13 with the lower pocket 6 opened, and the arrow D
If it is a leaky lid, it is sent out by the reject device in the direction of arrow E, and if it is a good product, it is sent out in the direction of arrow F.

The above operation is performed sequentially and sequentially by each of the inspection heads 1.

[0028]

According to the present invention having the above-described structure, there is no possibility that a malfunction will occur as in the conventional device.
5 / 10,000 at 0.5 MPa of compressed air pressure
It is possible to detect pinholes as small as inches. Thus, when the apparatus of the present invention is incorporated in a lid production line, it is possible to inspect a can lid at a very high speed of 800 sheets / minute with a small six-unit apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an inspection head of an apparatus of the present invention.

FIG. 2 is a schematic plan view showing a case where the apparatus of the present invention is incorporated into a lid production line.

[Explanation of symbols]

 Reference Signs List 1 inspection head 2 air chamber 3 air relief valve 4 microphone 41 elastic ring 42 elastic ring 5 holding plate 6 lower pocket 61 compressed air supply pipe 62 annular elastic ring 7 housing 71 annular packing 72 annular seal ring 73 horizontal partition 8 upper housing 9 Machine frame 10 Lid separating device 11 Infeed turret 12 Inspection device 13 Reject turret H Can lid

Continuation of front page (56) References JP-A-63-249033 (JP, A) JP-A-2-143134 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01M 3 / twenty four

Claims (3)

(57) [Claims] 1. Compressed air is supplied from one side of a sealed can lid whose front and back are isolated, and air blowing sound from a pinhole of the can lid is detected by a microphone on the other side to detect leakage of the can lid. In the inspection method, a can lid leakage inspection method for detecting ultrasonic waves in a frequency band of 50 to 70 kHz and determining whether or not leakage has occurred. 2. Compressed air is supplied from one side of a sealed can lid whose front and back are isolated, and air blowing sound from a pinhole of the can lid is detected by a microphone on the other side to detect leakage of the can lid. In the inspection apparatus, an air chamber having a gap is provided behind the sound sensing part of the microphone, and the air relief valve which seals the air chamber and is released when the air chamber becomes high pressure is used as the sound sensing sound of the microphone. A can lid leak inspection device provided separately from the part. 3. The can lid leakage inspection device according to claim 2, wherein an ultrasonic wave in a frequency band of 50 to 70 kHz is detected to determine the presence or absence of leakage.