Method for nondestructively detecting packaging tightness of pre-packaged product by adopting dynamic pressure difference

Abstract

The invention discloses a method for nondestructively detecting the packaging tightness of a pre-packaged product by adopting dynamic pressure difference. A device comprises a sealed cabin (1), a negative pressure suction unit (2), a pressure difference sensor (4), a data recorder (5) and a shaped box body model (6), the suction capacity and speed of the negative pressure suction unit (2) are adjustable; and a connecting pipeline (3) is arranged between the sealed cabin (1) and the negative pressure suction unit (2). The test sealed cabin (1) is of a piston-like structure with the process and the suction speed capable of being adjusted and controlled, the flexibility and accuracy of the packaging tightness test of the pre-packaged product are greatly improved, and in addition, due to the piston-like structure design, negative pressure response is faster and more accurate. The device for non-destructively detecting the packaging tightness of the pre-packaged product by adopting the dynamic differential pressure not only reduces the requirements on the opening and closing mode and space of the system, but also improves the stability and efficiency of the test.

Description

Technical Field

[0001] The invention relates to the technical field of soft and hard pre-packaged product packaging sealing degree detection, and in particular to a method for non-destructively detecting the packaging sealing degree of pre-packaged products by using dynamic pressure difference. Background Art

[0002] At present, there are many testing methods for packaging sealing of food, medicine and other pre-packaged products represented by cigarettes at home and abroad, mainly covering vacuum decay method, bubble test method, tracer labeling method, high-voltage discharge method, microbial immersion method, etc. The existing detection methods are mostly for evaluating the differences in macroscopic state parameters of products under enhanced leakage conditions. The vacuum decay method uses the pressure difference value under limited test conditions to feedback the packaging sealing. As a common testing method for packaging sealing, it is widely used in food, medicine and other packaging fields.

[0003] For example, the American Society for Testing and Materials ASTM F2338-09 (2020) and the food packaging airtightness test method T / CNFIA 177-2023 jointly developed by many companies in my country's food and packaging industry are based on this, using the vacuum decay method for non-destructive leak detection, but the recorded results are all pressure difference values ​​representing the leakage state parameters. In the tobacco industry, YQ-JY / T 2-2018 uses the "negative pressure extraction-water immersion method" to place the punched cigarette box in a closed measuring chamber to conduct a test using the pressure difference to characterize the airtightness of the cigarette box.

[0004] The bubble method is an intuitive means of testing the sealing of packaging. During the operation, the sample needs to be immersed in the test solution, resulting in the complete loss of the test sample. For example, the standard method for testing the sealing of food packaging GB / T 15171-1994 uses the water bubble method. The location of the bubble can accurately indicate the location of the leak, but the sensitivity of this method is not high; similarly, when measuring the leakage point of YQ-JY / T2-2018, an appropriate amount of water is injected into the measurement chamber to immerse the cigarette box in water. The location where the bubble is generated during the test is the leak point.

[0005] The tracer marking method is mainly used to determine the sealing degree of the package. It uses colored water as the test liquid, immerses the package directly in the colored water or injects the color into the package, and determines the sealing degree of the package by comparing the coloring inside and outside the package. ASTM D4991-07 (2023), JIS Z0382-1981, ZBC 08003-1987 and GB / T 15171-1994 all propose test methods for characterizing the sealing degree of the package using leakable traces and markable test liquids. In addition to the tracer liquid, it is usually possible to fill the package with a tracer gas to monitor its leakage and characterize its sealing degree.

[0006] The high-voltage discharge method uses a high-frequency and high-voltage dielectric barrier discharge method to collect the packaging discharge signal. After denoising, the characteristic parameters are extracted under the conditions where the packaging film is intact and pinholes exist.

[0007] Without destroying the original packaging products, it is of great significance to explore the numerical simulation of packaging sealing from the perspective of the microscopic physical process of gas movement. At present, there is an instantaneous vacuum formation in the non-destructive method, which generally has a rapid flow process of gas to form a negative pressure. This process has high requirements on the space and the opening and closing method of the system. Inventions such as CN201910788793.0, ZL202010318808.X, and ZL202010319660.1 involve the use of a negative pressure generator to form a vacuum environment in the test chamber, and weaken the system error through simulation parts and interpolation methods, but there are disadvantages such as complex operation, poor repeatability, and difficulty in automation, which cannot meet the needs of "digital" factories for data element collection and delivery from the production line.

[0008] Therefore, in order to solve the above-mentioned problems, the present invention is proposed. Summary of the invention

[0009] The purpose of the present invention is to address the deficiencies of the prior art and to provide a device for nondestructively testing the sealing degree of pre-packaged products by dynamic pressure difference, and a method for testing the sealing performance of a pre-packaged box body. The test sealing cabin 1 of the present invention is directly connected to the negative pressure suction unit 2 through a connecting pipe 3, and the suction capacity and speed of the negative pressure suction unit 2 are adjustable. The test sealing cabin 1 of the present invention is a piston-like structure with adjustable process and suction speed, which greatly improves the flexibility and accuracy of the test of the sealing degree of pre-packaged products. In addition, the piston-like structural design makes the negative pressure response faster and more accurate.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] The first aspect of the present invention provides a device for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference, which comprises a sealed cabin 1, a negative pressure suction unit 2, a pressure difference sensor 4, a data recorder 5 and a shaped box model 6;

[0012] The sealed cabin 1 is used to accommodate the shaped box model 6 and the pre-packaged product to be tested;

[0013] The negative pressure suction unit 2 has at least one airflow channel for completing the suction action, and the suction capacity and speed of the negative pressure suction unit 2 are adjustable;

[0014] A connecting pipe 3 is provided between the sealed cabin 1 and the negative pressure suction unit 2, which is used to connect the sealed cabin 1 and the speed-adjustable negative pressure suction unit 2, so that the sealed cabin 1 and the negative pressure suction unit 2 form an airflow connection;

[0015] The three-dimensional structural dimensions of the shaped box model 6 are consistent with the three-dimensional structural dimensions of the pre-packaged product to be tested, and the shaped box model 6 can assume the real sealing performance of the pre-packaged product to be tested.

[0016] Preferably, the sealed cabin 1 has at least one opening for storing the cavity of the shaped box body to be tested. The opening can be sealed manually or automatically during testing, and the sealing degree meets the test requirements.

[0017] Preferably, the suction capacity and speed of the negative pressure suction unit 2 can be adjusted by an external automation device or control equipment.

[0018] Preferably, the detection end of the pressure difference sensor 4 may be connected to the inside of the sealed cabin 1 or to the inside of the connecting pipe 3 . Preferably, the detection end of the pressure difference sensor 4 is connected to the inside of the sealed cabin 1 .

[0019] Preferably, the data acquisition end of the data recorder 5 is connected to the data output end of the pressure difference sensor 4, and the data recorder 5 is used to collect and record the pressure difference data during the test, and the data acquisition frequency is not less than 1 Hz, preferably 10 Hz to 1000 Hz.

[0020] Preferably, the presumable true sealing performance is characterized by the prepackaged product packaging leakage area S. The leakage area is analyzed by the pressure difference curve obtained by the sample test, and is obtained by combining the test results of the shaped box body with the presumable true sealing performance and the physical process of gas leakage using a mathematical model.

[0021] Preferably, the shaped box model 6 includes multiple groups according to different pre-packaged products to be tested.

[0022] Preferably, for the same prepackaged product to be tested, at least two shaped box models 6 are prepared, one of which has an assumed true sealing performance of no leakage (extremely high sealing degree, leakage area on the box is 0), and the other has an assumed true sealing performance slightly lower than all tested box packages (extremely low sealing degree, leakage area on the box is X). Preferably, a plurality of shaped box models 6 with the same specifications and sizes of the tested samples and assumed true sealing performance can be set according to the distribution of leakage areas of the shaped box.

[0023] The second aspect of the present invention provides a method for non-destructively testing the sealing degree of pre-packaged products by dynamic pressure difference. The method for non-destructively testing the sealing degree of pre-packaged products by dynamic pressure difference of the present invention is to measure the three-dimensional structure of the box body to be tested, prepare a number of shaped box body models 6 that are consistent with the specifications and dimensions of the sample to be tested and can assume true sealing performance, and the assumed true value can be measured by physical methods The leakage area is recorded as: S1, S2, S3,..., Sn; the total suction volume and suction time or the suction speed or the suction time of the negative pressure suction unit 2 with adjustable speed is set; the shaped box body models 6 are placed in turn in the sealed cabin 1 containing the shaped box body, and before testing, the sealed cabin 1 is ensured to be completely sealed, the negative pressure suction unit 2 with adjustable speed is started for suction, the pressure difference change of the sealed cabin 1 during the suction process is recorded, and the pressure difference change rate is calculated.

[0024] Repeat the above operation using different shaped box models 6 to calculate the pressure difference change rate; establish a related mathematical model between the pressure difference change rate obtained by testing and calculation and the assumed true value of the above shaped box model 6, and this mathematical model is the operating equation for detecting the sealing performance (leakage area).

[0025] Place the shaped box body to be tested into the sealed cabin 1 accommodating the shaped box body, repeat the above-mentioned detection operation process, or the pressure difference change during the suction process, calculate the pressure difference change rate, substitute the pressure difference change rate into the above-mentioned operation equation for detecting the sealing performance, calculate and obtain the sealing performance (leakage area) of the shaped box body to be tested, and complete one detection.

[0026] The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference uses the device for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference as described in the first aspect of the present invention, and comprises the following steps:

[0027] Step 1: Measure the three-dimensional structural dimensions of the pre-packaged product to be tested, prepare a number of shaped box models 6 that are consistent with the three-dimensional structural dimensions of the pre-packaged product to be tested and can assume real sealing performance, and measure the leakage area by physical methods assuming real sealing performance, and record it;

[0028] Step 2: setting the total suction volume and suction time of the negative pressure suction unit 2; placing one of the shaped box models 6 into the sealed cabin 1 containing the shaped box in turn, and sealing it before testing, starting the negative pressure suction unit 2 to suction, and recording the pressure difference change (Pi~t) during the suction process;

[0029] Step 3: Repeat step 2 using different shaped box models 6 to obtain pressure difference variation curves of several shaped box models 6;

[0030] Step 4: Obtain the pressure difference change rate of each shaped box model 6 from the pressure difference change curves of the shaped box models 6 in step 3, and further draw a relationship curve between the pressure difference change rate of the shaped box model 6 and its leakage area S;

[0031] Step 5: Based on the relationship curve between the pressure difference change rate of the box model 6 and its leakage area S in step 4, a related mathematical model S=F(f(Pi~t)) is established. The mathematical model is the operating equation for detecting the leakage area of ​​the pre-packaged product packaging;

[0032] Step 6: Place the pre-packaged product to be tested into the sealed cabin 1, repeat the detection operation process of step 2 above, record the pressure difference change (Pi~t) during the suction process, calculate the pressure difference change rate f(Pi~t), substitute the pressure difference change rate into the operating equation for detecting the sealing performance obtained in step 5 above, calculate and obtain the leakage area S of the pre-packaged product to be tested, and thus complete one detection. The leakage area S represents the sealing degree of the pre-packaged product to be tested.

[0033] Preferably, the total suction volume and suction time of the negative pressure suction unit 2 in step 2 are adjusted according to the different sealing properties of the pre-packaged products to be tested.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The prior art devices for non-destructive testing of the sealing degree of pre-packaged products all first use a negative pressure generator to form a vacuum environment in the test cabin, and then perform the test. This method requires the existence of an instantaneous vacuum formation, and this process has high requirements on the space and the opening and closing method of the system. The test sealed cabin 1 of the present invention is directly connected to the negative pressure suction unit 2 through a connecting pipe 3, and the suction capacity and speed of the negative pressure suction unit 2 are adjustable. The test sealed cabin 1 of the present invention is a piston-like structure with adjustable process and suction speed, which greatly improves the flexibility and accuracy of the pre-packaged product packaging sealing test. In addition, the piston-like structural design makes the negative pressure response faster and more accurate. In general, the device for non-destructive testing of the sealing degree of pre-packaged products using dynamic pressure difference in the present invention not only reduces the requirements for the system opening and closing method and space, but also improves the stability and efficiency of the test.

[0036] 2. The present invention innovatively proposes to use a group of shaped box models 6 for measuring the sealing degree of pre-packaged products. The pressure difference change rate of the shaped box model 6 is first obtained through test calculation, and then an operating equation is established using the pressure difference change rate and the assumed true leakage area of ​​the shaped box model 6. Finally, the leakage area of ​​the pre-packaged product to be tested is obtained by measuring the pressure difference change rate of the pre-packaged product to be tested. The measuring method is simple, accurate and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of a device for non-destructively testing the sealing performance of a shaped box packaging in an embodiment of the patent of the present invention.

[0038] Figure 2 It is the pressure difference change data of testing a shaped box model in the embodiment of the patent of the present invention, which has the same appearance as the tested sample and can assume real sealing performance.

[0039] Figure 3 It is the operating equation in the embodiment of the patent of the present invention.

[0040] Figure 4 It is the pressure difference change data of the test sample in the embodiment of the patent of this invention.

[0041] The names of the figure numbers in the figure description: 1-sealed cabin, 2-negative pressure suction unit, 3-connecting pipe, 4-differential pressure sensor, 5-data recorder, 6-shaped box model. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with embodiments.

[0043] Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

[0044] Those skilled in the art will appreciate that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" to another element, it may be directly connected to the other element, or there may be intermediate elements. In addition, the "connection" used herein may include wireless connections.

[0045] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two. The terms "inside", "upper", "lower", etc., indicating positions or state relationships, are based on the positions or state relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operate in a specific position, and therefore cannot be understood as limiting the present invention.

[0046] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "provided with" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention will be understood according to specific circumstances.

[0047] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0048] Example

[0049] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0050] like Figure 1 As shown, a device for nondestructively testing the sealing degree of pre-packaged products using dynamic pressure difference comprises a sealed cabin 1, a negative pressure suction unit 2, a pressure difference sensor 4, a data recorder 5 and a shaped box model 6;

[0051] The sealed cabin 1 is used to accommodate the shaped box model 6 and the pre-packaged product to be tested;

[0052] The negative pressure suction unit 2 has at least one airflow channel for completing the suction action, and the suction capacity and speed of the negative pressure suction unit 2 are adjustable;

[0053] A connecting pipe 3 is provided between the sealed cabin 1 and the negative pressure suction unit 2, which is used to connect the sealed cabin 1 and the speed-adjustable negative pressure suction unit 2, so that the sealed cabin 1 and the negative pressure suction unit 2 form an airflow connection;

[0054] The three-dimensional structural dimensions of the shaped box model 6 are consistent with the three-dimensional structural dimensions of the pre-packaged product to be tested, and the shaped box model 6 can assume the real sealing performance of the pre-packaged product to be tested.

[0055] The sealed cabin 1 has at least one opening for storing the cavity of the shaped box body to be tested. The opening can be sealed manually or automatically during testing, and the sealing degree meets the test requirements.

[0056] The suction capacity and speed of the negative pressure suction unit 2 can be adjusted by an external automation device or control equipment.

[0057] The detection end of the differential pressure sensor 4 is connected to the interior of the sealed cabin 1 .

[0058] The data acquisition end of the data recorder 5 is connected to the data output end of the pressure difference sensor 4. The data recorder 5 is used to collect and record the pressure difference data during the test. The data acquisition frequency is not less than 1 Hz, preferably 10 Hz to 1000 Hz.

[0059] The assumed true sealing performance is characterized by the pre-packaged product packaging leakage area S. The leakage area is analyzed by the pressure difference curve obtained by the sample test, and is obtained by combining the test results of the shaped box body with the assumed true sealing performance and the physical process of gas leakage and using a mathematical model.

[0060] According to the leakage area distribution of the shaped box, 9 shaped box models 6 with the same specifications and dimensions of the tested samples and the assumed real sealing performance are set.

[0061] Combination Figure 1 , Figure 2 , Figure 3 and Figure 4 , the implementation process can be described in the following specific steps:

[0062] Step 1: Measure the three-dimensional structure of the tested box body, prepare the above-mentioned 9 shaped box body models 6 with the same appearance as the tested sample and the assumed true sealing performance. The assumed true value can be measured by physical method and its leakage area is recorded as: 0, 3.1μm 2 , 7.1μm 2 , 12.6μm 2 , 23.5μm 2 , 245.8μm 2 , 375.8μm 2 , 610μm 2 , 947.7μm 2 .

[0063] Step 2: Set the total suction volume of the adjustable speed negative pressure suction unit 2 to 2 ml and the suction time to 20 s; place several shaped box models 6 in turn into the sealed cabin 1 containing the shaped box, and seal it before testing, start the adjustable speed negative pressure suction unit 2 to suction, and record the pressure difference change (Pi~t) during the suction process.

[0064] Step 3: Repeat step 2 using different shaped box models 6 to obtain pressure difference variation curves of several shaped box models 6, such as Figure 2 .

[0065] Step 4: From step 3 Figure 2The pressure difference change rate of each shaped box model 6 is obtained, and a relationship curve between the pressure difference change rate of the shaped box model 6 with an assumed true value and its leakage area S is further obtained, such as Figure 3 shown.

[0066] Step 5: Figure 3 Relationship curve, establish the relevant mathematical model S = 1.24E28 × exp (dP i / dt)-13.87, the mathematical model is the operating equation for detecting the leakage area of ​​pre-packaged product packaging.

[0067] Step 6: Place the sample to be tested into the sealed chamber 1, repeat the above detection operation process, record the pressure difference change (Pi~t) during the suction process, calculate the pressure difference change rate (or other mathematical methods) f(Pi~t), and bring the pressure difference change rate (or other mathematical methods) into the above-obtained operating equation for detecting the sealing performance, and calculate the sealing performance (leakage area) of the tested shaped box body to be 4.15μm 2 , that is, one detection is completed.

Claims

1. A method for non-destructively testing the sealing degree of pre-packaged products by using dynamic pressure difference, characterized in that: A device for non-destructively testing the sealing degree of pre-packaged products using a dynamic pressure difference is used, wherein the device for non-destructively testing the sealing degree of pre-packaged products using a dynamic pressure difference comprises a sealed cabin (1), a negative pressure suction unit (2), a pressure difference sensor (4), a data recorder (5) and a shaped box model (6); The sealed cabin (1) is used to accommodate the shaped box model (6) and the pre-packaged product to be tested; The negative pressure suction unit (2) has at least one air flow channel for completing the suction action, and the suction capacity and speed of the negative pressure suction unit (2) are adjustable; A connecting pipe (3) is provided between the sealed cabin (1) and the negative pressure suction unit (2), which is used to connect the sealed cabin (1) and the speed-adjustable negative pressure suction unit (2), so that the sealed cabin (1) and the negative pressure suction unit (2) are in airflow communication; The three-dimensional structural dimensions of the shaped box model (6) are consistent with the three-dimensional structural dimensions of the pre-packaged product to be tested, and the shaped box model (6) can assume the real sealing performance of the pre-packaged product to be tested; The method for non-destructively testing the sealing degree of pre-packaged products by using dynamic pressure difference comprises the following steps: Step 1: Measure the three-dimensional structural dimensions of the pre-packaged product to be tested, prepare a number of shaped box models (6) that are consistent with the three-dimensional structural dimensions of the pre-packaged product to be tested and can assume real sealing performance, and measure the leakage area by physical methods assuming real sealing performance, and record it; Step 2: setting the total suction volume and suction time of the negative pressure suction unit (2); placing one of the shaped box models (6) into the sealed cabin (1) containing the shaped box in sequence, and sealing it before testing, starting the negative pressure suction unit (2) to suction, and recording the pressure difference change (Pi~t) during the suction process; Step 3: Repeat the operation of step 2 using different shaped box models (6) to obtain pressure difference variation curves of several shaped box models (6); Step 4: Obtain the pressure difference change rate of each shaped box model (6) from the pressure difference change curves of the plurality of shaped box models (6) in step 3, and further draw a relationship curve between the pressure difference change rate of the shaped box model (6) and its leakage area S; Step 5: Based on the relationship curve between the pressure difference change rate and the leakage area S of the box model (6) in step 4, a related mathematical model S=F(f(Pi~t)) is established. The mathematical model is the operating equation for detecting the leakage area of ​​the pre-packaged product packaging; Step 6: Place the pre-packaged product to be tested into the sealed cabin (1), repeat the detection operation process of step 2, record the pressure difference change (Pi~t) during the suction process, calculate the pressure difference change rate f(Pi~t), substitute the pressure difference change rate into the operating equation for detecting the sealing performance obtained in step 5, calculate and obtain the leakage area S of the pre-packaged product to be tested, and thus complete one detection. The leakage area S represents the sealing degree of the pre-packaged product to be tested.

2. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 1, characterized in that: The sealed cabin (1) has at least one opening for storing the cavity of the shaped box body to be tested. The opening can be sealed manually or automatically during testing, and the sealing degree meets the test requirements.

3. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 1, characterized in that: The suction capacity and speed of the negative pressure suction unit (2) can be adjusted by an external automation device or control equipment.

4. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 1, characterized in that: The detection end of the differential pressure sensor (4) may be connected to the interior of the sealed cabin (1) or to the interior of the connecting pipe (3).

5. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 1, characterized in that: The data acquisition end of the data recorder (5) is connected to the data output end of the pressure difference sensor (4), and the data recorder (5) is used to collect and record the pressure difference data during the test process, and the data acquisition frequency is not less than 1 Hz.

6. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 1, characterized in that: The assumed true sealing performance is characterized by the pre-packaged product packaging leakage area S. The leakage area is analyzed by the pressure difference curve obtained by the sample test, and is obtained by combining the test results of the shaped box body with the assumed true sealing performance and the physical process of gas leakage and using a mathematical model.

7. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 1, characterized in that: The shaped box model (6) includes multiple groups according to different pre-packaged products to be tested.

8. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 1, characterized in that: For the same pre-packaged product to be tested, at least two shaped box models (6) are prepared, one of which has an assumed true sealing performance of no leakage, and the other has an assumed true sealing performance of slightly lower than all the tested box packages.

9. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 8, characterized in that: According to the leakage area distribution of the shaped box, a plurality of shaped box models (6) with the same specifications and dimensions of the tested samples and the assumed real sealing performance are set.

10. The method for nondestructively testing the sealing degree of pre-packaged products by using dynamic pressure difference according to claim 1, characterized in that: The total suction volume and suction time of the negative pressure suction unit (2) in step 2 are adjusted according to the different sealing properties of the pre-packaged products to be tested.

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