A device for nondestructive testing of cigarette box sealing performance using gas volume transfer method

Abstract

This utility model relates to the field of cigarette packaging quality inspection technology, and discloses a device for non-destructive testing of the sealing performance of cigarette packs using a gas volume transfer method. The device includes a sealing measurement chamber, a sample restraint frame, a suction piston, a differential pressure sensor, a cigarette pack sample, a balance valve, a signal acquisition and processing control system, and a precision lead screw. The operating steps are as follows: calibrate the volume of the sealing measurement chamber as V1; measure the volume of the cigarette pack sample as V2; record the initial air volume in the sealing measurement chamber as V3; drive the suction piston through the precision lead screw to draw air from the sealing measurement chamber, record the air pressure as Pe, and the suction volume as Vp; calculate the sealing performance based on Boyle's law. The testing process does not require drilling, thus enabling non-destructive testing. The sample restraint frame, through its six-sided semi-circular elastic contact positioning structure, evenly distributes local negative pressure, thereby reducing stress concentration on the membrane surface to avoid pressure rupture, resulting in high reliability.

Description

Technical Field

[0001] This invention relates to the field of cigarette packaging quality testing technology, specifically to a device and method for non-destructive testing of the sealing performance of cigarette packs using a gas volume transfer method. Background Technology

[0002] Cigarette packaging is the final production stage of finished cigarettes. With the development of production technology, cigarette packaging mainly uses machines to seal the folded ends of the cigarette box. Cigarettes with poor sealing will mold in humid environments and become cracked and brittle in dry climates during long-term storage. At the same time, a large amount of aroma will leak out, which directly affects the interests of consumers and the reputation of cigarette manufacturers. In recent years, some consumers have reported that some cigarettes have become moldy and cracked. Therefore, measuring the sealing degree of cigarette packaging is crucial for improving cigarette packaging technology and enhancing the sealing degree of cigarette packaging.

[0003] Patent CN 112432745 A, "A Non-destructive Testing Method for the Sealing Degree of Cigarette Packaging", states that if the instantaneous change in applied negative pressure is not properly controlled, the sealing film of the cigarette pack may burst under the action of negative pressure.

[0004] Based on the above-mentioned problems, this testing method was developed. It can prevent the packaging film of cigarette boxes from bursting under negative pressure and test the sealing of cigarette boxes without damage. This can help companies improve product quality and reduce production losses. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a device and method for non-destructive testing of the sealing performance of cigarette packs using a gas volume transfer method. This method combines the advantages of being non-destructive and highly reliable, and solves the problems of destructive testing and easy breakage of the thin film.

[0007] (II) Technical Solution

[0008] To achieve the aforementioned objectives of non-destructive and highly reliable testing, the present invention provides the following technical solution:

[0009] A device for non-destructive testing of the sealing performance of cigarette packs using a gas volume transfer method includes a sealing measurement chamber, a sample restraint frame, a suction piston, a differential pressure sensor, a cigarette pack sample, a balance valve, a signal acquisition and processing control system, and a precision lead screw. The volume of the sealing measurement chamber is larger than the volume of the cigarette pack sample, and the precision lead screw is connected to the suction piston and is in a straight line.

[0010] A method for nondestructive testing of the airtightness of cigarette packs using gas volume transfer includes the following steps:

[0011] 1) Record the initial pressure value of the sealed measuring chamber as P0 (normal pressure), and calibrate the internal volume of the sealed measuring chamber (including the limiting frame and dead zone) as V1;

[0012] 2) Measure the volume V2 of the cigarette box sample (V1 > V2);

[0013] 3) Fix the cigarette box sample into the sealed measurement chamber using the sample limiting frame, and record the initial air volume in the sealed measurement chamber as V3, where V3 = V1 - V2;

[0014] 4) The suction piston is driven by a precision lead screw to draw air from the sealed measuring chamber. During the suction process, the pressure value of the differential pressure sensor and the volume of the suction piston are collected in real time. When the suction pressure reaches the set pressure value, the suction stops. When the pressure value stabilizes, the reading of the differential pressure sensor is recorded as Pe and the suction capacity is recorded as Vp.

[0015] 5) Based on Boyle's law, under constant temperature, the pressure (P) of a certain amount of ideal gas is inversely proportional to its volume (V). Convert Vp to the capacity V4 under P0 conditions, V4 = Vp * (P0 - Pe) / P0. V4 - V3 is the air overflowing from the small box. Define the sealing rate Q under specified test conditions as 100% * (V3 - V4) / V3. The closer the value of Q is to 100%, the better the sealing effect.

[0016] Preferably, the sealed measuring chamber is made of 304 stainless steel, with an inner wall roughness Ra≤0.8μm, an adjustable volume range of 500-1500mL, and is equipped with a vacuum sealing door and a silicone sealing ring (Shore hardness 70A).

[0017] Preferably, the cigarette box sample is placed into the sealed measurement chamber by the support of the sample limiting frame. The sample limiting frame contacts the six sides of the cigarette box sample. The contact head is semi-circular (R=3mm) and covered with a polyurethane elastic layer (2mm thick). An adjustable contact pressure of 0.1-0.5MPa is achieved by a gas spring (50mm stroke, elastic coefficient 20N / mm). The semi-circular shape ensures that there is no damage to the cigarette box packaging and prevents the sealing film of the cigarette box sample from bursting during the inhalation process. The sample limiting frame positions and pressurizes the cigarette box sample, ensuring that the negative pressure in the chamber during the inhalation process does not cause the sealing film of the cigarette box sample to burst.

[0018] Preferably, the precision lead screw is driven by a servo motor with a pitch of 0.5 mm and equipped with a linear guide rail with an accuracy of ±0.01 mm. The precision lead screw controls the reciprocating suction piston.

[0019] Preferably, the differential pressure sensor has a range of -10000~0 Pa, an accuracy of ±0.1% FS, and a response time of <50ms;

[0020] Preferably, the sealed measurement cavity V1 is calibrated using a standard volume block (accuracy ±0.1%) for multi-point calibration, and the cigarette box sample V2 is measured based on laser scanning three-dimensional reconstruction technology with an accuracy of ±0.5%.

[0021] Preferably, the suction flow rate of the suction piston is controlled within the range of 50-500 mL / min, evacuating air to -5000 Pa, with a time control accuracy of ±0.1 s, maintaining stable pressure (fluctuation ≤ ±50 Pa), and a duration of 60 ± 2 s. The signal acquisition and calculation control system acquires the internal pressure of the sealed measurement chamber in real time, records the displacement data of the suction piston in real time, calculates the air suction capacity, records the pressure change curve (resolution 0.1 Pa), and judges the sealing degree of the cigarette box based on the pressure change.

[0022] Compared with the prior art, the present invention provides an apparatus and method for non-destructive testing of the sealing performance of cigarette packs using a gas volume transfer method, which has the following beneficial effects:

[0023] 1. The apparatus and method for non-destructive testing of the airtightness of cigarette boxes using the gas volume transfer method involves quantitatively extracting and transferring air from the sealed measurement chamber using a suction piston to reduce the air pressure around the cigarette box sample. After maintaining the pressure for a period of time, the relationship between air pressure and volume is calculated based on Boyle's law. The greater the deviation of the result, the more air leakage the cigarette box sample has. During this process, the cigarette box sample does not need to be perforated, thus enabling non-destructive testing.

[0024] 2. The device and method for non-destructive testing of the sealing performance of cigarette packs using the gas volume transfer method utilizes the positioning structure of the six semi-circular elastic contacts on the sample limiting frame to evenly distribute local negative pressure, thereby reducing stress concentration on the membrane surface and preventing pressure-induced rupture, resulting in high reliability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0026] In the diagram: 1. Sealed measuring chamber; 2. Sample restraint frame; 3. Suction piston; 4. Differential pressure sensor; 5. Cigarette box sample; 6. Balance valve; 7. Signal acquisition and processing control system; 8. Precision lead screw. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1: Standard Cigarette Pack Testing

[0029] Parameter settings:

[0030] Pumping pressure: -5000Pa

[0031] Pressure holding time: 60s

[0032] Ambient temperature: 23±1℃

[0033] Relative humidity: 50±5% RH

[0034] Test results:

[0035] Calibration data: V1 = 800.0 mL, V2 = 120.5 mL → V3 = 679.5 mL

[0036] Measured data: Vp = 250.0 mL, Pe = -4980 Pa

[0037] Calculation result: V4 = 250 × (101325 - 4980) / 101325 = 238.5 mL

[0038] The sealing rate Q = (679.5 - 238.5) / 679.5 × 100% = 64.9%

[0039] Example 2: Leakage Simulation Test

[0040] Micropores with a diameter of 0.1 mm were created on a standard cigarette box. The test results showed that the Q value decreased to 42.3%, which verified the effectiveness of the method.

[0041] Example 3: Testing of Cigarette Boxes of Different Sizes

[0042] Test objective: To verify the device's compatibility with cigarette boxes of different sizes.

[0043] Test subject:

[0044] Standard cigarette pack (84mm×54mm×22mm, volume 120.5mL)

[0045] Slim cigarette case (97mm×48mm×18mm, volume 85.2mL)

[0046] Medium-sized cigarette pack (89mm×52mm×20mm, volume 93.8mL)

[0047] Parameter settings:

[0048] Pumping pressure: -5000Pa

[0049] Pressure holding time: 60s

[0050] Contact pressure: 0.3 MPa

[0051] Test results:

[0052]

[0053] Analysis: The Q value of cigarette boxes of different sizes is stable in the range of 64%-66%, indicating that the device is not sensitive to size differences and the positioning structure is highly adaptable.

[0054] Example 4: Extreme Environment Testing

[0055] Test objective: To verify the detection stability under high temperature and high humidity conditions.

[0056] Test conditions:

[0057] Temperature: 40±1℃

[0058] Relative humidity: 85±5% RH

[0059] Cigarette pack type: Standard hard pack (well-sealed)

[0060] Parameter settings:

[0061] Pumping pressure: -5000Pa

[0062] Pressure holding time: 60s

[0063] Dynamic compensation parameters: Temperature correction coefficient k = 1 + 0.003 × (40 - 23) = 1.051

[0064] Test results:

[0065]

[0066] Analysis: High temperature causes gas expansion, and the Q value was underestimated by about 3.2% before correction. Through temperature compensation algorithm, the Q value returned to the normal range, which verifies the necessity of dynamic compensation.

[0067] Example 5: Detection of Different Leak Types

[0068] Test objective: To verify the response capability to different leakage modes.

[0069] Simulated leak types:

[0070] 1. Micropore leakage (0.1mm in diameter)

[0071] 2. Crack leakage (3mm in length, 0.05mm in width)

[0072] 3. Adhesive layer defects (localized lack of adhesion)

[0073] Parameter settings:

[0074] Pumping pressure: -5000Pa

[0075] Pressure holding time: 60s

[0076] Ambient temperature: 23℃

[0077] Test results:

[0078]

[0079] Analysis: The characteristic curves corresponding to different leakage types provide data support for leakage point location algorithms.

[0080] Example 6: Bursting Limit Test of Membrane

[0081] Test objective: To verify the tolerance of the positioning structure to high negative pressure.

[0082] Test conditions:

[0083] Cigarette pack type: Standard hard pack (leak-proof)

[0084] Pumping pressure: -8000Pa (60% above standard pressure)

[0085] Contact pressure: 0.5 MPa

[0086] Test results:

[0087] No film rupture was observed after 1000 consecutive tests.

[0088] Average Q value: 64.5% ± 0.7%

[0089] Stress distribution on the thin film surface: maximum stress 1.2 MPa (safety threshold 3.5 MPa)

[0090] Analysis: The six-sided elastic positioning structure distributes negative pressure evenly, avoiding stress concentration and breaking through the pressure limitations of traditional methods.

[0091] Example 7: Comparison Experiment with Water Immersion Method

[0092] Test objective: To verify the equivalence of the detection method.

[0093] Test subjects: 200 randomly selected regular cigarette packs

[0094] Detection method:

[0095] The method of this invention (Q value)

[0096] Water immersion method (YQ-JYT 2-2018 standard)

[0097] Result comparison:

[0098] The two methods showed 98.5% consistency in leak detection.

[0099] Linear correlation: R 2 =0.987 (p<0.001)

[0100] Typical Difference Cases:

[0101] This invention detected Q=58% (microbubbles as observed by water immersion method).

[0102] Of the 15 boxes detected by water immersion testing, all showed obvious leakage; the Q value of this invention was <55%.

[0103] Conclusion: The method of this invention is highly equivalent to the water immersion method and can detect even more subtle leaks.

[0104] Example 8: Testing of Multiple Brand Cigarette Packs

[0105] Test objective: To verify the adaptability to different brand packaging materials.

[0106] Test subject:

[0107] Brand A (Aluminum Foil Composite Film)

[0108] Brand B (metallized paper)

[0109] Brand C (plain cardstock)

[0110] Parameter settings:

[0111] Contact pressure: 0.3 MPa (adjustable according to material hardness)

[0112] Pumping pressure: -5000Pa

[0113] Test results:

[0114]

[0115] Analysis: The difference in Q value between different materials stems from differences in sealing processes, and the test results are consistent with actual production feedback.

[0116] Example 9: Sealing Test After Long-Term Storage

[0117] Test objective: To verify the applicability of the testing method to cigarette boxes after long-term storage.

[0118] Test conditions:

[0119] Cigarette pack type: Regular hard pack

[0120] Storage conditions: Temperature 30℃, Humidity 75% RH, for 6 months.

[0121] Test parameters: Standard conditions

[0122] Pumping pressure: -5000Pa

[0123] Pressure holding time: 60s

[0124] Ambient temperature: 23±1℃

[0125] Relative humidity: 50±5% RH

[0126] Test results:

[0127] Q value before storage: 65.0% ± 1.0%

[0128] Q value after storage: 58.2% ± 1.5%

[0129] Pressure change curve characteristics: During the pressure holding phase, the pressure drop rate increases by 0.3 Pa / s.

[0130] Verification: Slight mold growth appeared on the cigarette box after storage, which is consistent with the decreasing trend of the Q value, proving that the test method can effectively reflect long-term changes in airtightness.

[0131] Example 10: Comparison of different pumping rates

[0132] Test objective: To optimize the pumping rate parameters

[0133] Test conditions:

[0134] Cigarette pack type: Standard hard pack (leak-proof)

[0135] Pumping rates: 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min

[0136] Test results:

[0137]

[0138] Conclusion: The detection efficiency and stability are optimal at a pumping rate of 200 mL / min, consistent with the patented technology.

[0139] In summary, the device and method for non-destructive testing of cigarette box sealing using the gas volume transfer method quantitatively extracts and transfers air from the sealed measurement chamber using a suction piston, thereby reducing the air pressure around the cigarette box sample. After maintaining the pressure for a period of time, the relationship between air pressure and volume is calculated based on Boyle's law. The greater the deviation in the result, the more air leakage the cigarette box sample exhibits. During this process, no holes need to be drilled in the cigarette box sample, thus enabling non-destructive testing. The positioning structure of the six semi-circular elastic contacts on the sample limiting frame evenly distributes the local negative pressure, thereby reducing stress concentration on the membrane surface and preventing pressure-induced rupture, resulting in high reliability.

[0140] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for non-destructive testing of the sealing performance of cigarette packs using a gas volume transfer method, characterized in that: The system includes a sealed measuring chamber (1), a sample limiting frame (2), a suction piston (3), a differential pressure sensor (4), a cigarette box sample (5), a balance valve (6), a signal acquisition and calculation control system (7), and a precision lead screw (8). The volume of the sealed measuring chamber (1) is larger than the volume of the cigarette box sample (5), and the precision lead screw (8) is connected to the suction piston (3) and is on a straight line.

2. The apparatus for non-destructive testing of the sealing performance of cigarette packs using the gas volume transfer method according to claim 1, characterized in that: The sealed measuring chamber (1) is made of 304 stainless steel with an inner wall roughness Ra≤0.8μm and an adjustable volume range of 500-1500mL. It is equipped with a vacuum sealing door and a silicone sealing ring.

3. The apparatus for non-destructive testing of the sealing performance of cigarette packs using the gas volume transfer method according to claim 1, characterized in that: The cigarette box sample (5) is placed into the sealed measurement chamber (1) by the support of the sample limiting frame (2). The sample limiting frame (2) contacts the six sides of the cigarette box sample (5) respectively. The contact head is divided into semicircles and the surface is covered with a polyurethane elastic layer. The contact pressure is adjustable from 0.1 to 0.5 MPa by the air pressure spring. The semicircular shape can ensure that there is no damage to the packaging of the cigarette box and prevent the sealing film of the cigarette box sample (5) from bursting during the smoking process. The cigarette box sample (5) is positioned and pressurized by the sample limiting frame (2) to ensure that the negative pressure in the chamber will not cause the sealing film of the cigarette box sample (5) to burst during the smoking process.

4. The apparatus for non-destructive testing of the sealing performance of cigarette packs using the gas volume transfer method according to claim 1, characterized in that: The precision lead screw (8) is driven by a servo motor with a pitch of 0.5 mm and is equipped with a linear guide rail with an accuracy of ±0.01 mm. The precision lead screw (8) controls the suction piston (3) to reciprocate for suction.

5. The apparatus for non-destructive testing of the sealing performance of cigarette packs using the gas volume transfer method according to claim 1, characterized in that: The differential pressure sensor (4) has a range of -10000~0Pa, an accuracy of ±0.1%FS, and a response time of <50ms.

6. The method for non-destructive testing of the sealing performance of cigarette packs using the gas volume transfer method according to claim 2, characterized in that: The sealing measurement chamber (1) V1 is calibrated using a standard volume block with an accuracy of ±0.1% and multi-point calibration is performed. The cigarette box sample (5) V2 is measured based on laser scanning three-dimensional reconstruction technology with an accuracy of ±0.5%.

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