JPH07280693A - Method and equipment for inspecting leakage from can cover - Google Patents

Abstract

PURPOSE:To provide a method and an equipment for inspecting leakage from a can cover detecting an air blow-off sound from the pinhole of the can cover by a microphone and inspecting leakage from the can cover at a high speed with high accuracy without misoperation. CONSTITUTION:Compressed air is supplied from the rear side of a can cover H, and an air blow-off sound from a pinhole is detected by a microphone 4 when there is the pinhole. An air chamber 2 with an air gap is mounted in the rear of the sound sensing section of the microphone 4. An air relief valve 3 hermetically sealing the air chamber 2 and being released when the air chamber 2 reaches a high pressure is installed while being separated from the sound sensing section of the microphone 4. Ultrasonic waves in a frequency band of 50-70kHz are detected, and the presence or absence of leakage is decided. Accordingly, there is no possibility that noises in a factory are picked up by the microphone, thus allowing inspection having high accuracy, then also allowing the increase of the speed of inspection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting the presence or absence of pinholes in a can lid having an easy-open structure, that is, the compressed air is ejected from the pinholes and the ultra-high The present invention relates to a can lid leakage inspection method and device for detecting the presence or absence of pinholes 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, it picks up the sound of compressed air ejected from the pinhole with a microphone and inspects the can lid for leaks. is there. In addition, the device is further affected by the compressed air explosively ejected from the pinholes and the pressure waves generated by the can lid suddenly expanding when compressed air is supplied, which destroys the microphone or interferes with the sound measurement of the microphone. In order to prevent this from happening, a labyrinth baffle that attenuates the jetted compressed air and pressure waves is provided, and the air that has passed through the labyrinth baffle is discharged into the atmosphere from the exhaust port. It is described that the inspection speed of this device is 400 sheets per minute, and the minimum detectable pinhole diameter is 1/1000 inch.

[0003]

However, in the above-mentioned conventional apparatus, the ultrasonic waves generated by mechanical vibration of the lid factory are
It may pass through the labyrinth baffle from the exhaust port and reach the microphone, causing the can lid without pinholes to be defective. Further, the co-seismic vibration of the can lid leakage inspection device itself caused by the vibration in the factory such as mechanical vibration may cause the microphone to sense a sound, and the can lid having no pinhole may be defective.

An object of the present invention is to obtain a can lid leakage inspection device which is highly accurate and capable of high-speed processing without the risk of such malfunctions.

[0005]

As a result of frequency analysis of noise in a can lid manufacturing factory, the factory noise contains a lot of ultrasonic waves of about 20 to 40 kHz, while the leak ultrasonic waves of the can lid are frequency-determined. As a result of analysis, the leakage ultrasonic wave of the can lid is 40 to 9
It was found that the ultrasonic waves around 0 kHz changed significantly.

The present invention was made based on this finding. The first invention supplies compressed air from one sealed side of a can lid whose front and back are separated from each other, and the other side of the can lid. In the method of inspecting the leakage of the can lid by detecting the air blowing sound from the pinhole with a microphone, 50 to 70 kHz
This is a can lid leakage inspection method that detects ultrasonic waves in the z frequency band and determines the presence or absence of leakage.

In the second invention, compressed air is supplied from one closed side of the can lid whose front and back are separated from each other, and the other side detects air blowing sound from a pin hole of the can lid by a microphone. In the device that inspects the can lid for leakage,
An air chamber having a gap is provided behind the sound-sensing portion of the microphone, and the air relief valve that is sealed when the air chamber is at a high pressure is separated from the sound-sensing portion of the microphone. It is a can lid leakage inspection device provided.

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

[0009]

In the first aspect of the invention, the presence or absence of leakage is determined by detecting the ultrasonic waves in the frequency band of 50 to 70 kHz, which is relatively not included in the noise of the lid factory.
Even if the can lid leakage inspection device itself is in sympathetic vibration with factory noise, if there is no pinhole, almost no change is detected in the ultrasonic waves in the frequency band of 50 to 70 kHz. There is no malfunction such as a defective product, and high-speed and highly accurate inspection is possible.

Further, in the second aspect of the invention, since the air chamber having the air gap is provided behind the sound-sensing portion of the microphone, it is possible to suppress a sudden pressure change, and further the air chamber is sealed. Since the air relief valve, which is released when the air chamber becomes high pressure, is installed separately from the sound-sensing part of the microphone, there is no risk of factory noise being picked up by the microphone, making it possible to perform highly accurate inspections and high speed. It becomes possible.

Furthermore, a third aspect of the present invention is to provide an air chamber having a space behind a sound-sensing portion of a microphone, which seals the air chamber and is released when the air chamber has a high pressure. The microphone is provided so as to be separated from the sound-sensing portion of the microphone, detect ultrasonic waves in the frequency band of 50 to 70 kHz, and determine the presence or absence of leakage.
Despite the factory noise and the co-seismic vibration of the can lid leakage inspection device itself, it is possible to 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 leakage, so a highly accurate and high speed inspection Is possible.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a can lid leakage inspection device of 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 drawing, 6 is a lower pocket having a substantially cylindrical shape, and the lower pocket 6 has an unevenness for mounting the can lid H on its upper end surface. An annular elastic ring 62 that supports the lower end of the peripheral edge of the can lid H is provided at the place of placement. The lower pocket 6
A compressed air supply pipe 61, which is divided into two branches, is provided in the inside of the container, and compressed air can be supplied 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 when the can lid H is supplied to the upper end surface of the lower pocket 6 and when the can lid H is discharged by a cam mechanism (not shown).

A housing 7 is provided above the lower pocket 6 coaxially with the lower pocket 6. The lower end surface of the housing 7 is engaged with the outer periphery of the upper surface of the lower pocket 6 to feed compressed air. An annular packing 71 is provided to prevent compressed air from the pipe 61 from leaking to the outside. Inside the annular packing 71, an annular seal ring 72 that is engaged with the upper end of the peripheral edge of the can lid H and divides the upper surface and the lower surface of the can lid H is provided.

Further, inside the annular seal ring 72, a holding plate 5 having a lower surface shape for engaging with the counter sink wall of the can lid H and the upper surface of the outer end of the pull ring is provided.
Eight radial pieces are provided below the horizontal partition wall 73 of the housing 7 except for the hole provided at the axial center portion. The holding plate 5 plays a role of pressing the can lid H from the front surface side of the can lid H so that the can lid H is not excessively deformed when compressed air pressure is applied to the back surface side of the can lid H.

The microphone 4 is installed by passing through the hole at the axial center of the horizontal partition wall 73, with the sound-sensitive portion at the tip of the holding plate 5 positioned substantially in the center. The microphone 4 is fixed to the upper housing 8 via elastic rings 41 and 42 provided at two places for vibration isolation, sound insulation and electrical insulation. Further, the microphone 4 is a condenser type microphone, and in order to remove low-frequency vibration components that are not directly related to the inspection, a fine hole is provided in the vibration film that is a sound-sensing portion, and an ultrasonic wave of about 5 kHz or more is generally used. The structure limits sensitivity to only the band.

At the can lid manufacturing plant, a very large amount of ultrasonic waves such as mechanical noise and air discharge noise are generated, and as a result of frequency analysis, the factory noise includes a large amount of ultrasonic waves around 20 to 40 kHz. On the other hand, when frequency analysis of leaked ultrasonic waves from the can lid was performed, it was found that ultrasonic waves in the vicinity of 40 to 90 kHz significantly changed. Furthermore, 70k
In the frequency band of Hz or higher, the influence of electrical noise due to electromagnetic waves is a concern, so 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 the ultrasonic signal in the frequency band of 50 to 70 kHz is amplified by the electric amplifier and the 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 to DC voltage is
It is taken out to a fixed part outside the device through a rotary connector (not shown), and a judgment processing device (not shown) judges whether the signal is a leak signal or not.

Above the horizontal partition wall 73, the air chamber 2 having a wide gap is provided. The void in the air chamber 2 causes a sudden pressure change on the upper surface side of the can lid H due to a pressure wave generated when the can lid suddenly swells when an explosive leak occurs or when compressed air is supplied. It prevents, protects the diaphragm of the microphone 4, and does not interfere with 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, it does not introduce an external sound, and the air chamber 2 is provided so that the microphone 4 and the air relief valve 3 are provided.
By increasing the physical distance between the air relief valve 3 and the air relief valve 3, 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-mentioned structure is fixed to the machine frame 9, and the six inspection heads 1 form a set of inspection devices, which are incorporated in the can lid manufacturing line.

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

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

In the inspection head 1 of the inspection device 12, the lower pocket 6 is lowered by a cam mechanism (not shown) and is on standby. When the can lid is received, the lower pocket 6 is rotated in the direction of the arrow C and is rotated. 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 of compressed air is sent from the compressed air supply pipe 61 to the back side of the can lid, and the can lid abruptly expands to generate a pressure wave. Acts on to dampen this pressure wave. After this 10 milliseconds, the microphone 4 turns 50 for the next 20 milliseconds.
An ultrasonic signal with a frequency of up to 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 if it determines that the lid is a leakage lid, commands 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, and the distance between the vibrating membrane of the microphone 4 and the air relief valve 3 is made sufficiently long to seal the air chamber, and the determination frequency is Since it is set to 50 to 70 kHz, which is not so much included in factory noise, it is unlikely that a malfunction such as a conventional device that determines a non-defective product as a leak lid occurs, and a highly accurate inspection result can be obtained. Enables high-speed processing.

When the pinhole of the can lid is broken by the pressure of the compressed air, or when the can lid has a considerably large pinhole in advance, a considerable loud sound including a frequency of 50 to 70 kHz is generated. Therefore, the determination processing device emits 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 vibrating membrane of the microphone 4. However, it does not interfere with the measurement of the microphone 4.

On the other hand, the can lid in the inspection head 1 in which the supply of the compressed air is stopped after the inspection is completed, the lower pocket 6 is opened and is transferred to the reject turret 13, and the arrow D
If it is a leaking lid, it is sent by the reject device in the direction of arrow E, and if it is a non-defective product, it is sent in the direction of arrow F.

The above-mentioned operation is successively performed in each inspection head 1.

[0028]

Since the present invention has the above-mentioned structure, it eliminates the possibility of malfunctioning as in the conventional device, and
5/10000 with 0.5 MPa pressure of compressed air
It becomes possible to detect pinholes as small as one inch. As a result, when the device of the present invention is incorporated in a lid making line, it becomes possible to inspect can lids at a very high speed of 800 sheets per minute with a small device having six consecutive units.

[Brief description of drawings]

FIG. 1 is a 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 device of the present invention is incorporated in a lid making line.

[Explanation of symbols]

 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 separation device 11 Infeed turret 12 Inspection device 13 Reject turret H Can lid

Claims (3)

[Claims] 1. A compressed air is supplied from one closed side of a can lid whose front and back are separated, and the other side detects a sound of air blowing from a pin hole of the can lid by a microphone to prevent leakage of the can lid. In the inspection method, a can lid leakage inspection method that detects ultrasonic waves in the frequency band of 50 to 70 kHz and determines the presence or absence of leakage. 2. Compressed air is supplied from one closed side of the can lid whose front and back are separated, and the other side detects the air blowing sound from the pin hole of the can lid by a microphone to prevent leakage of the can lid. In the device to be inspected, an air chamber with a gap is provided behind the sound-sensing part of the microphone, and the air-relief valve that is sealed when the air chamber becomes high pressure is released by the microphone. A can lid leakage inspection device provided separately from the part. 3. The can lid leakage inspection device according to claim 2, wherein the presence / absence of leakage is determined by detecting ultrasonic waves in the frequency band of 50 to 70 kHz.