On-line moisture measurement system for filling casings and system for on-line moisture measurement of group of filling casings

Abstract

An on-line moisture measurement system for filling casings and a system for on-line moisture measurement of a set of filling casings are provided. The online moisture measuring system for filling the casings is formed by a plurality of microwave moisture measuring heads, each microwave moisture measuring head is provided with a microwave generator and a sensor part (1), and the sensor part is a microwave annular resonator of which the central part is provided with a dielectric channel (2) for the casings to continuously pass through; a resonance signal detector and a microprocessor (3) for controlling the generation of microwaves and measuring and processing amplitude and resonance frequency variations in the presence and absence of casings in the resonator channel.

Description

Technical Field

[0001] The present invention relates to a moisture measurement system for various food packaging, and more specifically to an online moisture measurement system for filling sausage casings.

[0002] The model of this invention is used in the manufacture of artificial food packaging. These packages, based on natural polymers such as proteins and polysaccharides, are inherently hydrophilic, and therefore can gain or lose moisture depending on the processing itself and in a controlled manner.

[0003] More specifically, this invention relates to a system for measuring the water content of a package at a very specific time—just before the package is wound into a coil—and to a system connected to a humidifier. Background Technology

[0004] Measuring the water content of films used for food packaging, whether flat or tubular, at different points in the production process provides crucial information for proper operation of the process and for obtaining products with guaranteed integrity.

[0005] Moisture content varies significantly between different stages of the production process, and at each stage, the moisture value must be close to a very specific value for the film to achieve its adequate performance. Therefore, at each of these stages, it is necessary to select appropriate measurement points and equipment to obtain information about the film's moisture content with the highest possible accuracy. In this way, the supply and extraction of moisture from the material being processed can be calibrated online to adjust the moisture parameter to the desired value at each stage of the production process.

[0006] During the manufacturing process of casings (such as those made of collagen), the extruded casings are taken to a dryer to remove most of their water content, allowing the polymer matrix to solidify. The moisture content of the dried collagen casings can be in the range of <5%. However, the water present in the casing acts as a plasticizer, and at such a low content, the collagen membrane becomes too brittle, potentially causing the casing to break if subjected to any slight deformation. Therefore, after drying and solidification, the casings need to be rewetted until they regain the flexibility required for subsequent winding. For this rewetting after drying, the collagen casings pass through a “rewetting zone” before being wound into coils. Once rewetted, the casings acquire a moisture content between 12% and 15%, which is also crucial for successful winding, but must not exceed this moisture content to avoid compromising the biostability of the casings on the coils during storage, such as before conversion treatment.

[0007] Another very important aspect is selecting the most suitable measurement method for the operating conditions and materials used in performing continuous control.

[0008] There are various methods for indirectly estimating the moisture content of products in progress, such as artificial films. Some of these methods are based on the electrical conductivity of water, and require prior calibration of how the presence of water affects the conductivity in order to indirectly quantify its presence.

[0009] In some cases, touch electrodes are used to measure the electrical conductivity of materials and determine the moisture content of products. These methods are highly accurate, for example, when measuring residual water after a drying process. Differences in sample density and temperature can also affect the measurement results. However, these methods can be affected by contaminants in the water, such as dissolved salts. Their effectiveness in measuring moisture is also limited.

[0010] Microwave moisture meters are one of the possible techniques for measuring dielectric properties within the electromagnetic frequency range. This technique involves analyzing persistent waves that may exist in a microwave resonator or a metallic cavity at a specific resonant frequency, and how these waves are affected by the presence of water in an electromagnetic field.

[0011] Microwave sensors provide measurements of moisture present throughout the entire volume of a material, not just on its surface. Furthermore, microwave sensors do not require contact with the material, allowing measurements to be taken without interfering with the processing.

[0012] Generally speaking, compared with other methods, the following advantages can be observed:

[0013] • Compared to methods using low frequencies, the effect of ionic conductivity on material properties is negligible.

[0014] • Penetration depth is greater than that of infrared measurement methods.

[0015] • No contact is required between the measuring device and the material, allowing for continuous determination of moisture content.

[0016] • Unlike infrared radiation, it is relatively insensitive to environmental conditions, so dust and water vapor in industrial facilities will not affect the measurement.

[0017] • Unlike ionizing radiation, microwave methods are safer and faster.

[0018] • The high specificity of water at certain frequencies in the microwave region allows even small amounts of water to be detected because water molecules highly absorb electrical energy due to their dipole properties. Utility Model Content

[0019] This invention enables continuous control of the moisture content of sausage casings before winding, allowing for anticipation of adverse effects due to excessive or insufficient moisture content. Furthermore, the use of microwaves minimizes the impact of impurities, color, particle size, or temperature on the measurement process. This invention provides an online moisture measurement system for a set of food casings, with a set of measuring heads selected for that set of casings and connected to an external control / adjustment device.

[0020] In each of the selected heads, two parts can be distinguished: a "sensor" part consisting of a ring resonator or a microwave resonator sensor, and another "processor" part or microprocessor.

[0021] In the sensor section of the system, the ring resonator has a central dielectric tubular channel, which is where the electromagnetic wave establishes an interaction with the casing having a given moisture content. At this point, a sensor equipped with a microwave generator provides a microwave signal at the desired frequency, which is transmitted to the reference material as it passes through the central channel. Thus, a transition from the material's moisture content to its physical property, namely its permittivity (ε), is established, which will be used later for moisture determination.

[0022] The processing section integrates a signal processing unit that compares the voltage input with a standard voltage and provides an output signal (in analog or digital form). Due to the gradual integration of the results, this output signal can be used for processing control (instrument wetting).

[0023] Measurement Processing

[0024] A microwave generator, under the control of a microprocessor, generates electromagnetic radiation, which is fed to a sensor section, generating a harmonic electromagnetic resonant field. The casing passes through the resonator via a channel. Water incorporated into the product then interacts with this field, reflected in changes in the field, which are recorded by a detector. In the resonator, the microwave signal exiting the applicator channel is fed to a transducer element, which consists of a microwave oscillator, a transmission system, and a detector. Its function is to convert the microwave signal, proportional to the moisture content, into a low-frequency electrical signal, such as a voltage. A temperature sensor is also integrated into the channel. The electronic components mentioned and / or described are not intended for this invention.

[0025] The processing unit, a microprocessor, commands and adjusts the frequency generated by the generator. It also calculates moisture values ​​using a corresponding algorithm based on analyzed resonator parameter variations and a calibration curve corrected for temperature data. Through a corresponding output interface, the processing unit can connect and exchange data with other peripheral components for data display, control, and operation, thus establishing a system for continuous control and correction of sausage casing moisture. The algorithm used in the resonator processing is not the focus of this invention.

[0026] The resonance parameters vary depending on the content of water molecules in the material due to their fluidity, but this is not the only reason, as the temperature of the sample also causes changes in molecular fluidity. Therefore, calibration must be performed with the sample at the same temperature, because if the material changes temperature relative to the calibration temperature, recalibration must be performed within that range.

[0027] Using linear or nonlinear regression, a calibration surface in a space consisting of temperature, moisture, and microwave axis can be calculated.

[0028] By simultaneously measuring microwave values ​​and product temperature, moisture parameters can be determined without errors caused by temperature variations.

[0029] According to one aspect of the present invention, an online moisture measurement system for filling sausage casings is provided, comprising multiple microwave moisture measurement heads, each microwave moisture measurement head comprising: a microwave generator and a sensor portion, wherein the sensor portion is a microwave ring resonator with a dielectric channel for continuous passage of sausage casings disposed in its central portion; a resonant signal detector and a microprocessor, the microprocessor being used to control the generation of microwaves and to measure and process the amplitude and resonant frequency changes of the resonator with and without sausage casings to calculate moisture content.

[0030] A system for online moisture measurement of a set of filled sausage casings is also provided, comprising an online moisture measurement system for filling sausage casings according to the above aspects, the online moisture measurement system for filling sausage casings according to the above aspects being placed on a frame in a direction transverse to the filling line. Attached Figure Description

[0031] To aid in a better understanding of the features of this utility model and to supplement this specification, the following drawings are included as an integral part thereof, and are illustrative rather than restrictive in nature:

[0032] Figure 1 The shape and basic components of a microwave ring resonator measuring head, such as those used in this invention, are schematically shown.

[0033] Figure 2A model of the present invention with several parallel sausage casing production lines is shown. Detailed Implementation

[0034] Microwave moisture meters operate on the principle of the difference in dielectric constant (relative permittivity) between most dried products and water. To accurately measure moisture (the number of water molecules present), the material to be measured must pass through a microwave moisture sensor head that radiates an extremely low electromagnetic field. This head integrates a low-power generator operating at 300 MHz; it sends a signal to the material being tested in a so-called "resonator." In practice, the parameters of the resonator change as the electromagnetic wave interacts with materials having different moisture levels. Due to the dipole effect of water molecules, the resonant frequency of the microwave resonator varies with the moisture content.

[0035] In certain frequency ranges, the resonance curve of a microwave cavity changes due to the filling of wet material. Specifically, by inserting dielectric material, the resonant frequency decreases with increasing ε′ (dielectric constant), while the amplitude of the resonance curve increases with increasing ε″ (dielectric loss factor or a measure of energy absorbed by the material).

[0036] In practice, when a sample is placed in the electromagnetic field of a resonator, it can be observed how the resonant frequency of the resonator decreases compared to an empty resonator, and how the amplitude of the resonance curve increases compared to the empty state of the resonator. These two effects are primarily due to the presence of water molecules in the material. The decrease in resonant frequency is a direct result of the decrease in wavelength due to the water molecules in the sample; the broadening of the resonance curve is a direct result of the water component in the material converting electromagnetic energy into heat.

[0037] In each measurement, the changes in two resonant parameters are measured while the resonator is operating with the object being measured. The changes in both measured parameters also depend on the mass of the object; however, the dependence on the object's moisture content is different in each case. Therefore, the quotient of the two measurements is solely a function of the moisture content of the object. Thus, this quotient is a suitable value for measuring moisture content independently of density and mass.

[0038] The moisture content of the sample is determined using the following formula:

[0039]

[0040] Where f0 (resonant frequency of the resonator) and f1 (frequency of the empty resonator) represent the offset of the resonant frequency; Q1 and Q0 are the Q factor or quality factor of the cavity before and after the sample is inserted.

[0041] The quality factor depends on the energy losses in the cavity (walls and couplings, etc.) and is expressed as follows:

[0042]

[0043] Therefore, when the sample is introduced into the cavity, the resonant frequency decreases and the factor becomes lower, resulting in a wider and flatter resonant curve.

[0044] These parameters depend on the cavity volume, geometry, operating mode, sample permittivity, shape, size, and position within the cavity. For a given cavity and a homogeneous sample with a regular shape and well-defined dimensions, the material permittivity can be determined.

[0045] These changes are detected by the sensor's electronic sensing element. A microprocessor then measures them in "unscaled units," which are scaled through a calibration process to give an accurate reading of the present moisture. The resulting signal is sent back to the factory control system, for example via an analog (0 to 20 mA [0 to 10 V] or 4 mA to 20 mA) or digital RS485 communication link, allowing for automatic adjustments to the water addition process as needed.

[0046] This invention relates to a continuous moisture measurement system for multi-casion lines, wherein a ring resonator is positioned at the head, with a dielectric tube-shaped measurement channel at its center, suitable for the continuous passage of expanding casings. The microwave moisture sensor for casings operates based on the fundamental difference in the ultra-high dielectric capacitance between dry matter and water. Simultaneous measurement of two resonator parameters (resonant frequency and resonant amplitude) and a special density-independent processing algorithm for casing moisture achieve highly reliable and repeatable measurements.

[0047] This type of resonator is available, for example, from PCE Instruments' model PCE-A-315. Regardless of product density, the sensor can continuously and accurately detect the product's moisture percentage. Furthermore, once calibrated, it requires no further recalibration. It features a temperature sensor integrated into the measurement channel, which automatically corrects the casing's moisture value based on the material's temperature.

[0048] The technical specifications of the sensor are as follows: a) Continuous moisture measurement range is 5% to 45%; b) For the above range, the absolute error is between ±0.2% and 1%; c) Operating temperature is 5℃ to 55℃; d) 24 VDC power supply; e) Input power is up to 5 W.

[0049] The validation curve (for moisture correlation) integrated into the moisture measurement system allows for automated, continuous measurement and precise determination of the absolute moisture content of the casings. In addition to continuously obtaining the current moisture content integrated into industrial processes, the microwave moisture meter can also be connected via a 4 mA to 20 mA interface to, for example, a controller or processing system (PLC) that regulates the pre-wetting step.

[0050] Calibration must be performed with the sample at the same temperature because if the material changes its temperature relative to the calibration temperature, it must be recalibrated within that range.

[0051] Because the membrane that makes up the casing is relatively thin, the surface temperature obtained in channel measurements will be considered an effective parameter for representing the average temperature of the casing and for temperature compensation in microwave measurements.

[0052] Instrument calibration must be performed using direct methods. The Karl Fischer method is a technique used as a reference method for determining the moisture content of sausage casings.

[0053] Calibration measurements are performed in a very simple manner; the vacuum state of the resonator is automatically determined and automatically zeroed. After filling, the moisture value is displayed within a fraction of a second, and the resonator must finally be emptied.

[0054] Once the moisture content results determined by the reference method are obtained, these values ​​will be assigned to their corresponding microwave values. Subsequently, a regression line with correlation and tolerance will be determined, which will allow the moisture value of each casing sample to be obtained immediately in future measurements.

[0055] Figure 1 The diagram schematically illustrates the basic components constituting a resonator measurement head suitable for the model of this invention, having the aforementioned commercial type, namely the PCE-A-315 of a PCE instrument; and its connection to other power supplies and control units; namely: a resonator sensor section 1, a central tubular dielectric measurement channel 2 with the resonator, and a measurement section or microprocessor 3 and a connector 4. The head integrates electronic components for low-power microwave generation / transmission (operating at a frequency of 300 MHz; and transmitting signals to the material to be measured), frequency detection / transmission, and a temperature probe, none of which are shown in the figure.

[0056] Each measuring head uses a microwave ring resonator as a sensor. The microwave ring resonator has a dielectric tube-shaped measuring channel at its center, through which the casing passes continuously. Each sensor also includes corresponding electronic components for generating and receiving frequencies, as well as a temperature sensor integrated into the channel; however, this description is not intended to describe the capabilities of this model. The sensor section is connected to a microprocessor, which processes the received parameter values ​​and calculates the moisture content. The microprocessor sends the corresponding output signal to various online control systems (see [link to relevant documentation]). Figure 1 (e.g., reading units, data loggers, regulators, or controllers) that act on other devices in the production process, such as devices that act on the moisture level in the casing, in order to correct for deviations between the moisture value measured during the process and a predetermined threshold.

[0057] The microprocessor commands the generation of microwave frequencies toward the resonator, thereby generating a harmonic electromagnetic resonant field. This harmonic electromagnetic resonant field interacts with the water bonded to the product, causing a modification of the field. This modification is recorded by electronic sensing elements and evaluated in the microprocessor along with temperature parameters. The microprocessor then calculates the moisture content value and transmits the information to the control device.

[0058] calibration

[0059] Instrument calibration must be performed using direct methods. The Karl Fischer method is a technique used as a reference method for determining the moisture content of sausage casings.

[0060] Once the moisture content results determined by the reference method are obtained, these values ​​will be assigned to their corresponding microwave values. Subsequently, a regression line with correlation and tolerance will be determined, which will allow the moisture value of each casing sample to be obtained immediately in future measurements.

[0061] Temperature compensation

[0062] As mentioned above, temperature is a factor to be considered during the measurement process. Therefore, the moisture content must be compensated for based on the temperature on the casing surface before measuring microwave values ​​and using the temperature sensor located in the resonator channel. This is because if the temperature difference between the surface temperatures of the hottest and coldest casings exceeds the expected 5°C, this parameter has a significant impact on the measurement of moisture content. That is, if five casing samples are taken to average the moisture content, and the difference between the measurements of the first and last samples exceeds 5°C, the temperature factor must be taken into account.

[0063] Because the membrane that makes up the casing is relatively thin, the surface temperature obtained in channel measurements will be considered an effective parameter for representing the average temperature of the casing and for temperature compensation in microwave measurements.

[0064] In one practical implementation, the model includes a device consisting of several microwave moisture meters (sensors) connected by hooks or fasteners to a frame transverse to the line direction (device and frame not shown in the model), such that once the casing leaves the dryer, the moisture meters are placed in a battery at a specific point or station in the casing manufacturing process, particularly downstream of the rewetting point of the casing, and wherein the casing passes individually through each resonator ring. Figure 2 The assembly layout of the three-head moisture measurement system on three casing production lines downstream of the wetting station is shown. Information processed in the head is sent to a controller, which acts on the individual wetting system of each casing line to correct its moisture content.

[0065] To accurately measure moisture content, the material to be measured must pass through a microwave moisture sensor head that radiates an extremely low electromagnetic field. The head integrates a low-power transmitter operating at 300 MHz, which sends a signal to the material being tested.

[0066] The main advantage and key feature of moisture sensors is that, due to the simultaneous measurement of two parameters of the resonator (resonant frequency and amplitude) and the processing algorithm, they can determine the moisture content of materials with high reliability and reproducibility. Furthermore, it allows for the measurement of casing moisture without damaging the material or wearing down the sensor, as the online microwave moisture measurement method is non-destructive. The emitted microwave power is very low, so the material will not heat up or deform. Another advantage of continuous online / in-line measurement is that it can even determine the core moisture content of a product.

[0067] The measurement channel of the PCE-A-315 model also includes a temperature sensor (not shown in the figure). This sensor automatically corrects the measurement results of moisture in the casing based on the temperature of the film forming the casing, obtaining the correct ratio.

[0068] The moisture meter can be connected to a reading unit, data logger, controller, or processing system via a 4 mA to 20 mA interface. In a preferred embodiment, the moisture meter is connected to a control system (not shown in this model) to regulate the moisture supply to the rewetting station.

[0069] Based on the description and accompanying drawings, those skilled in the art will understand that the present invention has been described according to some preferred embodiments, but various modifications may be introduced in the preferred embodiments without departing from the claimed purpose of the present invention.

Claims

1. An on-line moisture measurement system for filling casings, characterized in that The online moisture measurement system comprises a plurality of microwave moisture measurement heads, each comprising: a microwave generator and a sensor portion (1), wherein the sensor portion is a microwave ring resonator whose central portion is provided with a dielectric passage (2) for the continuous passage of the casing; a resonant signal detector and a microprocessor (3) for controlling the generation of microwaves and for measuring and processing the amplitude and resonant frequency variations in the resonator with and without the casing to calculate the moisture.

2. The on-line moisture measurement system for filling casings according to claim 1, characterized in that, The tubular passage of the sensor portion (1) is also provided with a temperature sensor.

3. The in-line moisture measurement system for filling casings according to claim 1 or 2, characterized in that The online moisture measurement system is also provided with a control system for sending a signal to a re-moistening station in the event that the moisture measurement given by the microprocessor is below a certain threshold.

4. A system for on-line moisture measurement of a group of filled casings, characterized by The system comprises an online moisture measurement system for filled casings according to claim 1, placed on a frame transversely to the direction of the filling line.

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