Method and system for measuring diameter of continuous rod of tobacco industry product

Abstract

A method of measuring the diameter of a continuous rod of a tobacco industry product, characterized in that it comprises the steps of: calculating the diameter of the continuous rod on the basis of a signal of a first sensor using a characteristic of the diameter relating to the value of the signal generated by the first sensor; calculating a diameter of the continuous rod based on a signal generated by the second sensor, wherein the diameter is related to the signal of the second sensor; comparing the diameter measured by the first sensor with the diameter measured by the second sensor; if the diameter measured by the first sensor is different from the diameter at the same point on the continuous rod measured by the second sensor, the characteristic of the first sensor is changed such that the value of the signal generated by the first sensor correlates with the diameter measured by the second sensor.

Description

[0001] The object of the present invention is a method and a system for measuring the diameter of continuous rods of tobacco industry products.

[0002] In the prior art, there is a known method of measuring the diameter of a rod-shaped object using an optical system.

[0003] Patent application US2006109485A1 discloses a system for measuring the diameter of a rod-shaped object in the tobacco industry using a light beam. The disclosed method is based on the concept that all light sources illuminate the rod-shaped object at one point at the same time, so that light is scattered from the surface of the object at the illumination point, and the scattered light is detected by a sensor. Here, a sensor is assigned to each light source, so that the profile of a partial surface of the entire circumferential surface of the object illuminated by the light source is determined by one sensor. In order to be able to simultaneously determine the diameter at a predetermined point of the object and without a shadow area, several light sources are required to illuminate the object at this point. Therefore, it is ensured that the diameter of the object is determined quickly and reliably. In addition, several light sources are required to completely cover the object, i.e., without shadows or the like.

[0004] A problem that occurs when performing optical measurements in the tobacco industry is the distribution of dust on the active surface of the sensor, which affects the measurement over time.

[0005] It has been noted that sensors with higher accuracy are less prone to dust accumulation, but if the goal is to control the annular rod-shaped article with a high enough frequency to control the diameter of each rod-shaped article cut from the annular rod in the next step of the manufacturing process, the sensor is usually not fast enough to be placed in the control loop.

[0006] According to the invention, fast but less reliable and more susceptible to dust accumulation sensors are used in the control loop in order to obtain measurements with sufficiently high frequency and accuracy.

[0007] A method for measuring the diameter of a continuous rod of a tobacco industry product comprises the following steps: transmitting the continuous rod through a sensor unit comprising a first sensor and a second sensor, wherein the first sensor is an analog sensor and the second sensor is an analog sensor, and the operating frequency of the first sensor is higher than the operating frequency of the second sensor; and calculating the diameter of the transmitted continuous rod by means of a calculation unit that receives signals from the first sensor and the second sensor.

[0008] The method according to the invention comprises the further steps of calculating the diameter of the continuous rod based on the signal of the first sensor, using the characteristic that the diameter is correlated to the value of the signal generated by the first sensor; calculating the diameter of the continuous rod based on the signal generated by the second sensor, wherein the diameter is correlated to the signal of the second sensor; comparing the diameter measured by the first sensor with the diameter measured by the second sensor; and, if the diameter measured by the first sensor is different from the diameter measured by the second sensor at the same point on the continuous rod, changing the characteristic of the first sensor so that the value of the signal generated by the first sensor is correlated to the diameter measured by the second sensor.

[0009] According to the method of the present invention, the first frequency is in the range of 20 kHz to 200 kHz, preferably 100 kHz.

[0010] According to the method of the present invention, the second frequency is in the range of 0.5 kHz to 3 kHz, preferably 1 kHz.

[0011] According to the method of the present invention, wherein the annular rod of the tobacco industry product is an annular rod of a multi-segment rod-shaped tobacco industry product, the first frequency is selected to be related to the speed to obtain at least one first accuracy sample of each segment, and the second frequency is selected to obtain at least one second accuracy sample of each multi-segment tobacco industry product.

[0012] According to the method of the invention, the changing of the characteristic of the first sensor is performed with a correction frequency which is lower than the second frequency.

[0013] According to the method of the present invention, the correction frequency is in the range of 0.001 Hz to 10 Hz, preferably 0.1 Hz.

[0014] According to the method of the invention, the light is split into two by a beam splitter before reaching said type of sensor, and one beam reaches the first type of sensor and the other beam reaches the second type of sensor.

[0015] A measuring system for measuring the diameter of a continuous rod of the tobacco industry, comprising: a sensor unit, the sensor unit comprising a first sensor and a second sensor, the first sensor being an analog sensor, the second sensor being an analog sensor, the first sensor operating at a higher frequency than the second sensor, a calculation unit arranged to receive signals from the first sensor and the second sensor and to calculate the diameter of the continuous rod. The system according to the invention comprises a calculation unit arranged to calculate the diameter of the continuous rod based on the signal of the first sensor using a property that the calculated diameter is related to the value of the signal generated by the first sensor, and to calculate the diameter of the continuous rod based on the signal generated by the second sensor, wherein the diameter is related to the signal from the second sensor, and the calculation unit is arranged to change the property of the first sensor if the diameter measured by the first sensor is different from the diameter measured by the second sensor at the same point on the continuous rod, so that the value of the signal generated by the first sensor is related to the diameter measured by the second sensor.

[0016] The system according to the invention, wherein the sensor unit comprises a set of three individual first type sensors, each first type sensor covering 120° of a diameter arc.

[0017] The system according to the invention, wherein the sensor unit comprises a set of six individual first type sensors, each first type sensor covering 60° of a diameter arc.

[0018] The system according to the present invention, wherein the sensor unit comprises one, two or three second type sensors.

[0019] The newly proposed method and system for measuring the diameter of continuous rods of tobacco industry products is able to maintain the measurement accuracy at designed levels at high measurement frequencies in a dusty factory floor environment.

[0020] The present invention is described in detail below with reference to the accompanying drawings in preferred embodiments:

[0021] Figure 1 shows a measuring device used in the method according to the invention;

[0022] Figure 2 is a schematic representation of the measurement principle according to the invention;

[0023] Figure 3 is a schematic representation of the measurement principle according to the invention using three sensors;

[0024] Figure 4 is an isometric view of a measuring system according to the invention.

[0025] Figure 1 The measuring device used in the method according to the invention is shown. The measuring arrangement further explained with respect to FIG. 5 comprises a measuring unit 100, a cutting unit 200 and a computerized data recording unit 300. The measuring device comprises a sensor unit with two sensors 10, 11 and a light source S. The measuring unit 100 measures at a measuring point M at a distance L from a cutting point C, wherein the cutting unit 200 cuts a rod-shaped article 1 in the form of an annular rod of a tobacco industry product R. The annular rod or continuous rod CR of the tobacco industry product travels at a speed v in the direction from the measuring point M towards the cutting point C.

[0026] Figure 2 is a schematic representation of the measuring principle according to the invention. A light source S emits a collimated light beam 15 having a selected wavelength. The light source may be a laser light source emitting visible light or infrared light. The light beam is guided by an optical unit 16 in the measuring direction towards the rod-shaped object 1. The width of the light beam 15 is selected so that it is larger than the diameter of the object to be measured, so that the light beam 15 reaches the first sensor 10 above and below the object to be measured (i.e. the rod-shaped object 1). Before reaching the first sensor 10, the light beam is split by a semi-transparent mirror 12, so that the light beam also reaches the second sensor 11.

[0027] In a preferred embodiment, the method for measuring the diameter of a continuous rod of a tobacco industry product as a rod-shaped article 1 comprises the following steps: the continuous rod is transmitted through a sensor unit comprising a first sensor 10 and a second sensor 11. The first sensor and the second sensor are analog sensors, while digital sensors can be used in other embodiments. The first operating frequency of the first sensor 10 is higher than the second operating frequency of the second sensor 11. In a next step, the diameter of the transmitted continuous rod 1 is calculated by means of a calculation unit that receives signals from the first sensor 10 and the second sensor 11. In a preferred embodiment, the diameter of the continuous rod 1 is calculated based on the signal of the first sensor 10 using the characteristic that the diameter is related to the value of the signal generated by the first sensor 10.

[0028] The characteristic of a sensor is a function that describes how the measured physical property is converted into an analog electrical signal (i.e. the voltage at the output of the sensor) and how this electrical signal is converted into a measured value (i.e. the diameter of the rod-shaped article 1). There are at least two ways to change the characteristics of a sensor, either on the analog side by modifying the analog voltage or on the digital side where the diameter is already measured in a digitally corrected form.

[0029] The next step of the method is to calculate the diameter of the continuous rod based on the signal generated by the second sensor, wherein the diameter is correlated with the signal generated by the second sensor, and to compare the diameter measured by the first sensor with the diameter measured by the second sensor. In a preferred embodiment, the next step includes changing the characteristics of the first sensor 10 so that the value of the signal generated by the first sensor 10 is correlated with the diameter measured by the second sensor 11 if the diameter measured by the first sensor is different from the diameter at the same point on the continuous rod measured by the second sensor 11.

[0030] The first frequency is in the range of 20 kHz to 200 kHz, preferably 100 kHz, and the second frequency is in the range of 0.5 kHz to 3 kHz, preferably 1 kHz.

[0031] In another preferred embodiment, the annular rod of the tobacco industry product 1 is an annular rod of a multi-segment rod-shaped tobacco industry product, the first frequency is selected to be related to the speed (v) to obtain at least one first accuracy sample of each segment, and the second frequency is selected to obtain at least one second accuracy sample of each multi-segment tobacco industry product.

[0032] In yet another embodiment, the changing of the characteristic of the first sensor is performed with a calibration frequency which is less than the second frequency. The calibration frequency is in the range of 0.001 Hz to 10 Hz, preferably 0.1 Hz.

[0033] In a preferred embodiment, the light beam is split into two beams by a beam splitter 12 before reaching a sensor of said type, one beam reaching a first sensor 10 and the other beam reaching a second sensor 11 .

[0034] In a preferred embodiment, a measuring system for measuring the diameter of a continuous rod of the tobacco industry comprises a sensor unit comprising a first sensor 10 and a second sensor 11, the first sensor being an analog sensor and the second sensor being an analog sensor, the operating frequency of the first sensor 10 being higher than the operating frequency of the second sensor 11. The system further comprises a calculation unit arranged to receive signals from the first sensor and the second sensor and to calculate the diameter of the continuous rod. The calculation unit is arranged to calculate the diameter of the continuous rod based on the signal of the first sensor 10 using a property that the calculated diameter is related to the value of the signal generated by the first sensor. The calculation unit is arranged to calculate the diameter of the continuous rod based on the signal generated by the second sensor 11, wherein the diameter is related to the signal generated by the second sensor 11. The calculation unit is arranged to change the property of the first sensor 10 if the diameter measured by the first sensor 10 is different from the diameter measured by the second sensor 11 at the same point on the continuous rod, so that the value of the signal generated by the first sensor 10 is related to the diameter measured by the second sensor 11.

[0035] exist Figure 3 In yet another preferred embodiment presented, the sensor unit comprises a set of three pairs of first sensors 10 and second sensors 11, whereas each pair of sensors covers 120° of a diametric arc.

[0036] In an alternative embodiment, the sensor unit comprises a set of six individual first sensors, each first sensor covering 60° of the diametrical arc.

[0037] In yet another alternative embodiment, the sensor unit comprises one, two or three second sensors 11 .

[0038] Figure 4 An isometric view of a measurement system according to a preferred embodiment is shown, with the specific relationships being more clearly visible.

Claims

1. A method for measuring the diameter of a continuous rod (1) of a tobacco industry product, comprising the following steps: The continuous rod is conveyed through a sensor unit comprising a first sensor (10) and a second sensor (11), the first sensor (10) being an analog sensor and the second sensor (11) being an analog sensor, the operating frequency of the first sensor (10) being higher than the operating frequency of the second sensor (11), calculating the diameter of the conveyed continuous rod by means of a calculation unit receiving signals from said first sensor (10) and said second sensor (11), It is characterized in that it also includes the following steps: calculating the diameter of the continuous rod (1) based on the signal of the first sensor (10) using the property that the diameter is related to the value of the signal generated by the first sensor (10), calculating the diameter of the continuous rod based on the signal generated by the second sensor (11), wherein the diameter is related to the signal generated by the second sensor (11), comparing the diameter measured by the first sensor (10) and the diameter measured by the second sensor (11), and If the diameter measured by the first sensor (10) is different from the diameter measured by the second sensor (11) at the same point on the continuous rod, the characteristics of the first sensor (10) are changed so that the value of the signal generated by the first sensor (10) is related to the diameter measured by the second sensor (11).

2. The method according to claim 1, wherein the first frequency of the first sensor (10) is in the range of 20 kHz to 200 kHz, preferably 100 kHz.

3. The method according to claim 1 or 2, wherein the second frequency of the second sensor (11) is in the range of 0.5 kHz to 3 kHz, preferably 1 kHz.

4. A method according to any one of claims 1 to 3, wherein the annular rod of the tobacco industry product is a continuous rod of a multi-segment rod-shaped tobacco industry product, the first frequency is selected to be related to the speed (v) to obtain at least one first precision sample for each segment, and the second frequency is selected to obtain at least one second precision sample for each multi-segment tobacco industry product.

5. The method according to any one of claims 1 to 4, wherein the changing of the characteristic of the first sensor is performed with a correction frequency which is lower than the second frequency.

6. The method according to claim 5, wherein the correction frequency is in the range of 0.001 Hz to 10 Hz, preferably 0.1 Hz.

7. The method according to any one of claims 1 to 6, wherein the light is split into two beams by a beam splitter before reaching the type of sensor, and one beam reaches the first type of sensor and the other beam reaches the second type of sensor.

8. A measuring system for measuring the diameter of a continuous rod for the tobacco industry, comprising: A sensor unit, wherein the sensor unit comprises a first sensor and a second sensor, wherein the first sensor is an analog sensor, the second sensor is an analog sensor, and an operating frequency of the first sensor is higher than an operating frequency of the second sensor. a calculation unit arranged to receive signals from the first sensor and the second sensor and to calculate a diameter of the continuous rod, It is characterized in that The calculation unit is arranged to calculate the diameter of the continuous rod based on the signal of the first sensor using the property that the calculated diameter is related to the value of the signal generated by the first sensor, and calculating a diameter of the continuous rod based on a signal generated by the second sensor, wherein the diameter is related to the signal from the second sensor, and The calculation unit is arranged to, if the diameter measured by the first sensor differs from the diameter measured by the second sensor at the same point on the continuous rod, change a characteristic of the first sensor so that the value of the signal generated by the first sensor is related to the diameter measured by the second sensor.

9. System according to claim 8, wherein the sensor unit comprises a set of three separate pairs of first type sensors (10, 11), each pair of sensors covering 120° of a diametric arc.

10. System according to claim 8 or 9, wherein the sensor unit comprises a set of six individual first sensors (10), each first sensor covering 60° of a diametric arc.

11. System according to any one of claims 8 to 10, wherein the sensor unit comprises one, two or three second sensors (11).

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