Method for determining the temperature of rubber-like material entering the structure of a tire

Abstract

The present invention relates to a method for determining the temperature of at least one layer of a multi-layer polymeric product, the method comprising: - positioning the product to be measured on a transfer table; -advancing the product under a structure including at least one terahertz sensor; - emitting incident terahertz radiation in the direction of the product; - detecting signals corresponding to the spectra of a plurality of terahertz radiations reflected at interfaces encountered by the incident terahertz radiation; - analyzing the signal in order to determine different peaks corresponding to the different interfaces encountered; - determining the temperature of each material layer through which the incident radiation passes according to the amplitude of each peak; Includes:

Description

[Technical Field]

[0001] The present invention relates to the field of tire manufacturing, and more particularly to the management, monitoring and control of temperatures in the manufacturing process of rubber products forming tires. [Background technology]

[0002] The tire manufacturing method is - a preparatory stage for preparing semi-finished products to be used in the construction of tires; - assembly stage, in which these semi-finished products are assembled according to the configuration originally specified by the designer; - the vulcanization stage, which involves vulcanization, also known as vulcanization; The method includes several main steps:

[0003] To optimally control the preparation and assembly stages, it is useful to measure the temperature during each stage. This can be done for simple products consisting of a single layer or for complex products consisting of a combination of various layers. These measurements are currently performed by drilling holes in the uncured rubber. This method is easy to implement but does not guarantee sufficient measurement accuracy. In particular, because this method is performed manually, it is susceptible to many parameters that are difficult to control, including the drilling depth (in complex products, an incorrect depth can lead to measuring the wrong layer), the drilling time, which can vary from measurement to measurement, and the interpretation of values, which can vary from operator to operator.

[0004] To correct for these shortcomings, quality control personnel responsible for manufacturing processes introduce safety margins, which reduce production performance.

[0005] Furthermore, to ensure control over the entire manufacturing process, temperature measurements are also made at the end of the line, i.e., on the tire after curing. Such measurements are currently made by inserting thermocouples into the cured rubber, which leads to damage or destruction of the product on which the measurements are made. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention therefore aims to remedy these drawbacks by proposing an accurate and non-invasive method for measuring the temperature of at least one layer of a multilayer polymer material. [Means for solving the problem]

[0007] In one particular embodiment, the invention proposes a method that makes it possible to determine the temperatures of the various rubber material layers of a tire during any stage of manufacture.

[0008] Accordingly, the present invention relates to a method for determining the temperature of at least one layer of a multi-layer polymer product, the method comprising: - positioning the product to be measured on a transfer table; -advancing the product under a frame including at least one terahertz sensor; - emitting incident terahertz radiation (a scanning portion of the terahertz spectrum) in the direction of the product; - detecting signals corresponding to multiple spectra of terahertz light reflected by interfaces encountered by the incident terahertz light (frequency scanning according to the type of product); - analyzing the signal to determine different peaks corresponding to the different interfaces encountered; - determining the temperature of each material layer through which the incident light beam passes based on the amplitude of each peak; Includes:

[0009] Terahertz radiation is emitted at several frequencies by a scanning system for the desired spectrum, preferably at a normal or substantially normal angle of incidence to the product, and preferably in the focal plane.

[0010] The spectrum is selected depending on the absorptivity of the material being analyzed, the desired accuracy and the thickness of the sample.

[0011] The emitted terahertz waves are partially returned from each product interface they encounter, and each returned signal is analyzed to infer two pieces of information: the wave's propagation speed and its attenuation.

[0012] Specifically, the shape of the received wave can be modeled in complex form as n=n'+i*n'', where: -n is the amplitude of the THz wave returned at each interface, -n' is the real part of the THz wave (refractive index) and represents the propagation velocity, which allows the layer thickness to be determined by measuring the wave's propagation time; -n'' is the imaginary part of the wave (absorption coefficient) that represents the attenuation of the THz wave.

[0013] However, surprisingly, it has been found that changing the temperature of the sample changes the amplitude of the terahertz waves while keeping the propagation time stable.

[0014] As a result, by analyzing the various peaks of the signal it is possible to determine the temperatures of the various media encountered.

[0015] In this case, it is noted that the change in amplitude differs for each rubber series (shape, progression, etc.). Therefore, it is useful to create a chart for each series. The chart is created from a rubber sample equipped with a thermocouple probe. The sample is then heated and then allowed to cool naturally in air. Between these two stages, the terahertz data and the thermocouple data can be correlated to create a chart.

[0016] Therefore, based on these data, the temperature of a single or multi-layer sample can be determined from a predefined chart and the amplitude of the external interface.

[0017] In this case, it is specified that in order to be able to determine the temperature, it is necessary to know the refractive index of the support.

[0018] The method according to the invention therefore makes it possible to carry out an accurate and non-invasive temperature measurement, which can be carried out on any type of product and whatever its condition.

[0019] Thus, in one embodiment, the multilayer polymer product is a product composed of multiple layers of rubber material, either before or after curing. Furthermore, the product is advantageously a tire, a caterpillar track, or a conveyor belt. Nevertheless, it can be used for any product composed of one or more layers of polymeric material, more preferably elastomeric material. It is also applicable to products further comprising metal or fiber reinforcing elements.

[0020] Because this measurement is performed automatically, it is not subject to the variability of manual measurements. Therefore, such a method can obtain more reliable measurements and reduce the safety margin to ensure the quality of the final product. Therefore, by using this method, better production efficiency can be achieved by both increasing production speed and reducing non-conforming products.

[0021] In one advantageous embodiment, the method according to the invention comprises a step of processing the raw signals before the analysis step.

[0022] In one advantageous embodiment, the advancement speed of the product is between 0 and 70 m / min.

[0023] In one advantageous embodiment, the acquisition rate of the terahertz sensor is greater than 100 Hz.

[0024] The present invention also relates to a method for determining the properties of at least one layer of a multilayer polymer product, comprising all the steps of the temperature determination method according to one of the above embodiments, and further comprising the step of determining the thickness of each material layer passed by an incident light beam as a function of the difference between the two peaks of the signal.

[0025] Specifically, when an incident terahertz beam reaches a layer of polymer material, it has been found that the characteristics of the reflected beam depend on the thickness of the layer.

[0026] Finally, the invention relates to a system making it possible to implement such a method.

[0027] Accordingly, the present invention relates to a system for determining the properties of at least one layer of a multi-layer polymeric product, the system comprising: a support table for advancing the multilayer polymer product; - a terahertz sensor; means for acquiring and analyzing the signal reflected from the polymer product; means for determining the temperature of the multi-layer material layer based on analysis of the reflected signal; Equipped with.

[0028] In a preferred embodiment, the system further comprises means for determining the thickness of the material layer based on analysis of the reflected signal.

[0029] Further advantages and embodiments of the present invention will become apparent from the non-limiting description of various exemplary figures. [Brief explanation of the drawings]

[0030] [Figure 1] 1 shows a system for implementing the method according to the invention; [Figure 2] 1 illustrates a schematic representation of the effect of terahertz radiation on a multilayer product. [Figure 3] 1 shows raw and processed signals resulting from acquisition by a terahertz sensor implemented in accordance with the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] In one example of embodiment of the method according to the invention, shown in Figure 1, a multi-layer product 101 is placed on a support table 102. The support table comprises means for advancing the product in the X direction. The table carries a frame on which a terahertz sensor 103 is arranged. The speed of advancement of the product is set according to the acquisition speed of the terahertz sensor, preferably between 10 and 70 meters per minute.

[0032] 2 shows a schematic representation of an article 1 comprising two layers 11 and 12 forming media with different refractive indices n1 and n2, respectively, which are placed on a support 102 (corresponding to table 102 in FIG. 1) also with different refractive indices, with the upper surface of layer 11 in contact with ambient air 13.

[0033] When the terahertz sensor emits radiation, the incident terahertz ray reaches product 1. This product actually has three interfaces: the interface between air and layer 11, the interface between layer 11 and layer 12, and the interface between layer 12 and support 102.

[0034] When an incident THz pulse 14 passes through an interface, part of the pulse is reflected, and therefore when a THz pulse propagates within a multilayer product, a series of pulses 15 is reflected.

[0035] Figure 3 shows the shape of a signal representing a series of pulses obtained on a product containing two layers of rubber material.

[0036] The upper curve shows the raw signal, the lower curve shows the signal after pre-processing to aid in analysis.

[0037] It is known that the delay between two successive pulses is directly proportional to the thickness of the material through which it passes. Calculating the thickness of a layer based on the delay between two successive pulses is done using the real part of the refractive index. This number is a property of the material that makes up the layer and represents the propagation speed of the THz pulse through it. Thus, in the processed signal shown in Figure 3, the thickness of layer 11 is determined by measuring the time lag between Peak 1 and Peak 2, and the thickness of layer 12 is determined by measuring the time lag between Peak 2 and Peak 3. [Explanation of symbols]

[0038] 101 Multilayer products 102 Support Table 103 Terahertz Sensor

Claims

1. 1. A method for determining the temperature of at least one layer of a multi-layer polymeric article, comprising: - positioning the product to be measured on a transfer table; - advancing said product under a frame containing at least one terahertz sensor; - emitting incident terahertz radiation in the direction of said product; - detecting a signal corresponding to a series of pulses reflected by an interface encountered by the incident light beam; - analyzing said signal to determine different peaks corresponding to the different interfaces encountered; - determining the temperature of each of the material layers through which the incident light beam passes based on the amplitude of each of said peaks; A method of determining

2. The method of claim 1 , wherein the multilayer polymer product is a product comprised of multiple layers of rubber material, either before or after curing.

3. The method of claim 2 , wherein the product is a tire, a caterpillar track, or a conveyor belt.

4. The method of claim 1 , further comprising a step of processing the raw signals prior to the analyzing step.

5. 5. A method for determining a temperature according to any one of claims 1 to 4, wherein the advancement speed of the product is between 0 and 70 m / min.

6. The method according to claim 1 , wherein the acquisition rate of the terahertz sensor is greater than 100 Hz.

7. 1. A method for determining a property of at least one layer of a multilayer polymeric article, comprising: The method includes all the steps of the temperature determination method according to any one of claims 1 to 6, and further includes the step of determining the thickness of each of the material layers through which the incident light beam passes as a function of the difference between two peaks of the signal.

8. 1. A system for determining a property of at least one layer of a multi-layer polymeric product, comprising: a support table for advancing said multilayer polymer product; - a terahertz sensor; - means for acquiring and analyzing the signal reflected from said polymer product; - means for implementing the method for determining the temperature of a multi-material layer according to any one of claims 1 to 6; A system comprising:

9. 9. The system of claim 8, further comprising means for implementing a method for determining the thickness of a material layer according to claim 7.

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