A cigarette filter rod punching and air permeability online detection system and method based on pneumatic noise spectrum analysis

Abstract

This invention belongs to the field of tobacco processing and quality testing technology, specifically relating to an online detection system for the permeability of cigarette filter rods based on aerodynamic noise spectrum analysis. The system includes a negative pressure excitation unit, an acoustic pickup unit, a sound-focusing resonance cavity, and a signal processing unit. The negative pressure excitation unit is intermittently connected to a negative pressure gas source via a gas distribution valve to simulate a standard inhalation action. The front end of the acoustic pickup unit corresponds to the negative pressure excitation unit, and the rear end of the acoustic pickup unit is connected to the input port of the signal processing unit via a signal. The sound-focusing resonance cavity is located at the front end of the acoustic pickup unit. This technical solution achieves accurate identification of permeability, pore size consistency, and blockage / blind hole defects by extracting the frequency domain characteristics of the aerodynamic noise of the micropore airflow.

Description

Technical Field

[0001] This invention belongs to the field of tobacco processing and quality inspection technology, specifically relating to an online non-destructive testing system and method that uses the aerodynamic noise characteristics generated by airflow passing through micropores to determine the quality of laser perforation of cigarettes or filter rods (permeability, pore size consistency, blockage / blind hole defects). Background Technology

[0002] Cigarette perforation is a crucial process that creates tiny air-permeable holes in the tipping paper or the cigarette itself. Its core functions are: to dilute the smoke by introducing external air, reducing the intake of harmful substances such as tar and nicotine, and optimizing the smoking experience and physiological sensation; in heated cigarettes, perforation can lower the aerosol temperature and improve aerosol carry-out efficiency through the Venturi effect. Current mainstream perforation methods include online laser perforation, plasma perforation, electrostatic perforation, and laser pre-perforation, among which online laser perforation is the most widely used.

[0003] The quality of perforation directly determines the ventilation rate of cigarettes: the more perforations, the larger the hole diameter, and the better the penetration, the stronger the air dilution effect, the lower the tar release, and the lower the draw resistance, directly affecting product consistency and smoking experience. Ventilation rate is a quality indicator that must be strictly controlled during cigarette processing.

[0004] Production practice shows that pre-drilled cigarettes are prone to clogging of holes due to overlapping glue on the tipping paper and excess glue on the nozzle. Online laser drilling is easily affected by machine differences, voltage fluctuations, and dust pollution, all of which can cause significant fluctuations in ventilation rate. The current mainstream detection technology is machine vision inspection, which uses an industrial camera to capture images of the tipping paper surface and identifies holes based on grayscale differences. However, it has significant technical defects: when pre-drilled holes are blocked by glue, they cannot be identified visually; online drilling is prone to producing "false holes" (paper burned through, glue layer not penetrated), which cannot be detected by visual inspection; and it cannot quantitatively characterize the consistency of hole size and actual air permeability, making it difficult to support precise control of ventilation rate. Summary of the Invention

[0005] The purpose of this invention is to provide an online detection system and method for the permeability of cigarette filter rods based on aerodynamic noise spectrum analysis, so as to solve the problems existing in the background art.

[0006] To achieve the above objectives, this application employs the following technical solution:

[0007] An online detection system for the perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis includes a negative pressure excitation unit, an acoustic pickup unit, a sound-focusing resonance cavity, and a signal processing unit.

[0008] The negative pressure excitation unit is intermittently connected to the negative pressure gas source through the gas distribution valve to simulate a standard suction action.

[0009] The front end of the acoustic pickup unit corresponds to the negative pressure excitation unit, and the rear end of the acoustic pickup unit is connected to the input port of the signal processing unit through a signal.

[0010] The sound-focusing resonance cavity is located at the front end of the acoustic pickup unit.

[0011] Furthermore, the negative pressure excitation unit is a detection drum with a built-in vacuum flow channel, and the negative pressure gas source is a negative pressure source of -5kPa to -20kPa.

[0012] Furthermore, the acoustic pickup unit is a wideband MEMS microphone or an ultrasonic sensor, with an effective response frequency band covering 20kHz~100kHz.

[0013] Furthermore, the sound-focusing resonance cavity is a semi-enclosed sound-focusing cover configured at the front end of the acoustic sensor.

[0014] Furthermore, the signal processing unit performs fast Fourier transform and frequency domain feature extraction on the acquired acoustic wave signal.

[0015] An online detection method for the perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis, utilizing any of the above-mentioned detection systems, includes the following steps:

[0016] S1. The cigarettes rotate with the detection drum at height 2 and continuously enter the detection station;

[0017] S2. The photoelectric switch detects when the cigarette reaches the detection position, and simultaneously triggers acoustic acquisition and negative pressure control; the gas distribution valve opens instantaneously, and the set negative pressure is applied to the mouthpiece end;

[0018] S3. Collect an audio signal at a set distance from the perforated area of ​​the cigarette and send it to the signal processing unit for a set time.

[0019] S4. The signal processing unit calculates the total acoustic energy in the characteristic frequency band of 30kHz to 40kHz. If the energy is lower than the preset threshold, it is determined that the hole is not penetrated / blocked. The system outputs a rejection signal, and the rejection mechanism removes the unqualified cigarettes.

[0020] Furthermore, a signal processing unit is provided between steps S3 and S4 to perform high-pass filtering and filter out industrial low-step noise.

[0021] The beneficial effects of this invention are:

[0022] This technical solution achieves precise identification of permeability, aperture consistency, and blockage / blind hole defects by extracting the frequency domain characteristics of the aerodynamic noise of the micro-perforation airflow. The technical principle involves applying a controllable instantaneous negative pressure to the cigarette mouthpiece, causing external air to flow into the cigarette at high speed through the laser-drilled micro-perforations. The vortex-like shedding of airflow at the micro-perforation edges generates aerodynamic noise in a specific frequency band. The sound pressure level, center frequency, and frequency band energy of this noise directly correspond to the perforation status, aperture size, and consistency. By extracting the acoustic fingerprint through spectral analysis, the perforation quality can be quantitatively determined.

[0023] Non-destructive and non-contact: No physical contact, no consumable consumption, does not affect the quality of the cigarette body, and is suitable for high-speed online production;

[0024] Strong anti-interference capability: It adopts ultrasonic detection to avoid low-frequency noise in the industrial environment, resulting in a high signal-to-noise ratio and stable detection.

[0025] High detection accuracy: It can identify adhesive layer blockage and false through-hole defects that cannot be detected by vision, and quantitatively characterize pore size and permeability;

[0026] Good real-time performance: Signal acquisition and analysis are completed in milliseconds, and can be linked with the rejection mechanism to realize online rejection of defective products;

[0027] Wide compatibility: Compatible with traditional cigarettes and heated cigarettes, and adaptable to various processes such as pre-drilling and online laser drilling. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the online detection system of the present invention.

[0029] Figure 2 for Figure 1 Enlarged view of part A.

[0030] Figure 3 This is a frequency diagram.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Testing drum; 2. Cigarette; 3. Soundbox; 4. Microphone. Detailed Implementation

[0033] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solution of the present invention, and should not be construed as limiting the technical solution of the present invention.

[0034] like Figures 1 to 3As shown, this application provides a non-contact, consumable-free, environmentally resistant, and online real-time detection system and method for detecting the permeability of cigarette filter rods. By extracting the frequency domain characteristics of the aerodynamic noise of the micropore airflow, it achieves accurate identification of permeability, pore size consistency, and blockage / blind hole defects. The technical principle is to apply a controllable instantaneous negative pressure to the cigarette mouthpiece, allowing external air to flow into the cigarette at high speed through laser micropores; the vortex-like shedding of airflow at the micropore edges generates aerodynamic noise in a specific frequency band. The sound pressure level, center frequency, and frequency band energy of the noise directly correspond to the permeability state, pore size, and consistency; by extracting the acoustic fingerprint through spectral analysis, the permeation quality can be quantitatively determined.

[0035] It includes a negative pressure excitation unit, an acoustic pickup unit, a sound-focusing resonance cavity, and a signal processing unit; the negative pressure excitation unit is intermittently connected to a negative pressure air source through a gas distribution valve to simulate a standard suction action; the front end of the acoustic pickup unit corresponds to the negative pressure excitation unit, and the rear end of the acoustic pickup unit is connected to the input port of the signal processing unit through a signal; the sound-focusing resonance cavity is located at the front end of the acoustic pickup unit.

[0036] Negative pressure excitation unit. The detection drum 1 with built-in vacuum flow channel is used. When the cigarette 2 moves to the detection position with the drum, the negative pressure source of -5kPa to -20kPa is instantly connected through the mechanical gas distribution valve to simulate the standard strong suction action, so as to ensure that the airflow passes through the micropore stably and generate aerodynamic noise.

[0037] Acoustic pickup unit. Employs a wideband MEMS microphone or ultrasonic sensor, with an effective frequency response covering 20kHz~100kHz. Ultrasonic band acquisition is preferred, naturally avoiding low-frequency mechanical noise in industrial environments and significantly improving the signal-to-noise ratio (SNR).

[0038] Sound-focusing resonance cavity. A semi-enclosed sound-focusing cover 3 (acoustic shielding structure) is configured for the front end of the acoustic sensor to achieve dual functions: ① physically isolate environmental noise and reduce interference; ② directionally focus the weak sound waves in the perforated area to the sensor probe, improving the ability to pick up weak signals.

[0039] Signal processing unit. Performs Fast Fourier Transform (FFT) and frequency domain feature extraction on the acquired acoustic signals: qualified holes (consistent diameter, sharp edges, and full penetration) exhibit stable acoustic energy peaks in the 20kHz–80kHz ultrasonic band; blind / blocked holes have insufficient air intake and weak eddy current intensity, resulting in a significant decrease in sound pressure level (SPL) in the characteristic frequency band; abnormal hole diameter can cause noise center frequency drift (similar to the principle of pitch shifting in a flute); through spectral feature comparison, defects such as full penetration, blind / blocked holes, and discrete hole diameters can be accurately identified.

[0040] This application provides an online detection method for the perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis, utilizing any of the above-mentioned detection systems, including the following steps:

[0041] S1. The cigarettes rotate with the detection drum at height 2 and continuously enter the detection station.

[0042] S2. The photoelectric switch detects when the cigarette reaches the detection position, and simultaneously triggers acoustic acquisition and negative pressure control; the gas distribution valve opens instantaneously, and a negative pressure of 5kPa to -20kPa is applied to the mouthpiece end, and external air flows in at high speed through the micropores, generating high-frequency aerodynamic noise.

[0043] S3. An ultrasonic microphone located 2mm from the drilling area collects a 5ms audio signal. The signal is then subjected to a 20kHz high-pass filter to remove low-frequency industrial noise.

[0044] S4. The signal processing unit calculates the total acoustic energy in the characteristic frequency band of 30kHz to 40kHz. If the energy is lower than the preset threshold, it is determined that the hole is not penetrated / blocked. The system outputs a rejection signal, and the rejection mechanism removes the unqualified cigarettes.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An online detection system for the perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis, characterized in that, It includes a negative pressure excitation unit, an acoustic pickup unit, a sound-focusing resonance cavity, and a signal processing unit; The negative pressure excitation unit is intermittently connected to the negative pressure gas source through the gas distribution valve to simulate a standard suction action. The front end of the acoustic pickup unit corresponds to the negative pressure excitation unit, and the rear end of the acoustic pickup unit is connected to the input port of the signal processing unit through a signal. The sound-focusing resonance cavity is located at the front end of the acoustic pickup unit.

2. The online detection system for perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis according to claim 1, characterized in that, The negative pressure excitation unit is a detection drum with a built-in vacuum flow channel, and the negative pressure gas source is a negative pressure source of -5kPa to -20kPa.

3. The online detection system for perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis according to claim 1, characterized in that, The acoustic pickup unit is a wideband MEMS microphone or an ultrasonic sensor, with an effective response frequency band covering 20kHz~100kHz.

4. The online detection system for perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis according to claim 3, characterized in that, The sound-focusing resonance cavity is a semi-enclosed sound-focusing cover configured at the front end of the acoustic sensor.

5. The online detection system for perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis according to claim 1, characterized in that, The signal processing unit performs fast Fourier transform and frequency domain feature extraction on the acquired acoustic wave signal.

6. An online detection method for the perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis, utilizing the detection system of any one of claims 1 to 5, characterized in that, Includes the following steps: S1. The cigarettes rotate with the detection drum at height 2 and continuously enter the detection station; S2. The photoelectric switch detects when the cigarette reaches the detection position, and simultaneously triggers acoustic acquisition and negative pressure control; the gas distribution valve opens instantaneously, and the set negative pressure is applied to the mouthpiece end; S3. Collect an audio signal at a set distance from the perforated area of ​​the cigarette and send it to the signal processing unit for a set time. S4. The signal processing unit calculates the total acoustic energy in the characteristic frequency band of 30kHz to 40kHz. If the energy is lower than the preset threshold, it is determined that the hole is not penetrated / blocked. The system outputs a rejection signal, and the rejection mechanism removes the unqualified cigarettes.

7. The online detection method for perforation permeability of cigarette filter rods based on aerodynamic noise spectrum analysis according to claim 6, characterized in that, A signal processing unit is also provided between steps S3 and S4 to perform high-pass filtering and filter out industrial low-step noise.

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