Method and apparatus for tread measurement system

Abstract

A method and apparatus for measuring the thickness of each layer of a tire tread or tire component, where the tire tread or tire component has conductive and non-conductive layers. One or more sensors are used that emit a beam or pulse of radiation that travels through one or more of the layers. The beam or pulse of radiation reflects off the surface of the layers and the interfaces and is received by a receiving device of the one or more sensors. The reflected beam or pulse of radiation is used to determine the thickness of each tread layer.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for determining the thickness of material layers in the manufacture of tire components, and more particularly, to a method and apparatus for determining the thickness of tread layers. Background Technology

[0002] The manufacturing of vehicle tire treads is typically accomplished using an extruder. The tread is also conventionally formed from several layers of material, which can be made from different materials to provide the desired performance. Importantly, the thickness of each tread layer must be uniform and consistent to ensure tire uniformity and performance. Radar technology is known to be used to measure tread layer thickness during tread manufacturing. However, this technology has significant limitations when the tread layers contain one or more conductive compounds with low resistivity. Such materials absorb radiation from radar technology, making the measurement of conductive tread layers problematic or impossible. Therefore, methods and devices to overcome this limitation are desired. Summary of the Invention

[0003] The present invention provides a method for measuring the thickness of a tire tread in a first aspect, comprising the steps of: providing a tire tread having a first tread layer formed of a conductive compound and a second tread layer formed of a non-conductive compound; continuously conveying the tire tread, wherein a first sensor and a second sensor are respectively arranged above and below the tire tread, wherein the first sensor and the second sensor are configured to emit a first radiation beam and a second radiation beam into the tire tread, respectively, and receive a first reflected radiation beam from the surface of the first tread layer from the first radiation beam and determine a first distance d1, and receive a first reflected radiation beam from the first tread layer and the second reflected radiation beam from the surface of the first tread layer and the second reflected radiation beam from the second tread layer and the second reflected radiation beam from the first tread layer and the second reflected radiation beam. The second sensor and the second sensor are connected together at a fixed height D. The first sensor emits a first radiation beam and the second radiation beam, respectively, and the first sensor and the second sensor receive a third reflected radiation beam from the surface of the second tread layer and the third reflected radiation beam and the third reflected radiation beam, and the third reflected radiation beam is received. The thickness d4 of the first tread layer is then determined by subtracting distances d1, d2 and d3 from the fixed height D. The continuous material thickness measurement of the first tread layer and the second tread layer is performed by the first sensor and the second sensor respectively emitting the first radiation beam and the second radiation beam, receiving the first reflected radiation beam, the second reflected radiation beam and the third reflected radiation beam, and then determining the thickness d4 of the first tread layer from the fixed height D.

[0004] In a second aspect, the present invention provides an apparatus for measuring the depth of each tread layer of a tire having at least two tread layers, comprising: a bridge having an upper surface for conveying the tire tread thereon and a plurality of support legs for supporting the bridge; a first sensor and a second sensor, wherein the first sensor is connected to a stepper motor mounted to an upper track located above the upper surface of the bridge for translating the first sensor across the width of the upper surface of the bridge; wherein the first sensor is rigidly connected to the second sensor via a translation support frame; and wherein the translation support frame and the second sensor translate together with the first sensor.

[0005] This invention provides the following technical solutions:

[0006] 1. A method for measuring the thickness of a tire tread, comprising the following steps:

[0007] A tire tread is provided, wherein the tire tread has a first tread layer formed of a conductive compound and a second tread layer formed of a non-conductive compound;

[0008] The tire tread is continuously conveyed, and a first sensor and a second sensor are respectively arranged above and below the tire tread. The first and second sensors are configured to emit a first radiation beam and a second radiation beam towards the tire tread, respectively. They receive a first reflected radiation beam from the surface of the first tread layer from the first radiation beam and determine a first distance d1; receive a second reflected radiation beam from the interface between the first and second tread layers from the second radiation beam and determine a second distance d2; and receive a third reflected radiation beam from the surface of the second tread layer from the second radiation beam and determine a second distance d3. The first and second sensors are connected together at a fixed height D.

[0009] Continuous material thickness measurement of the first and second tread layers is performed by emitting the first radiation beam and the second radiation beam respectively by the first sensor and the second sensor, receiving the first reflected radiation beam, the second reflected radiation beam and the third reflected radiation beam, and then determining the thickness d4 of the first tread layer by subtracting distances d1, d2 and d3 from the fixed height D.

[0010] 2. The method according to Scheme 1, wherein the first sensor and the second sensor are either the same sensor or different sensors.

[0011] 3. The method according to Scheme 1, wherein the second sensor is one of a pulse terahertz sensor and a pulse frequency sensor.

[0012] 4. The method according to Scheme 1, wherein the tire tread further comprises a third tread layer formed of a non-conductive compound.

[0013] 5. The method according to Scheme 1, wherein the second sensor is a low-frequency terahertz sensor having a frequency range of 50 to 200 GHz.

[0014] 6. The method according to Scheme 3, wherein the second sensor is a pulse frequency sensor having a frequency range of one of 50 GHz to 2.2 THz and 50 GHz to 400 GHz.

[0015] 7. The method according to Scheme 1, wherein one or both of the first sensor and the second sensor are frequency-modulated continuous wave terahertz sensors.

[0016] 8. The method according to Scheme 1, wherein first spectral data from the first sensor is superimposed on second spectral data from the second sensor.

[0017] 9. The method according to Scheme 1, wherein the first sensor and the second sensor are collinear.

[0018] 10. An apparatus for measuring the depth of each tread layer of a tire having at least two tread layers, comprising:

[0019] The bridge abutment has an upper surface for conveying the tire tread thereon and a plurality of support legs for supporting the bridge abutment.

[0020] A first sensor and a second sensor, wherein the first sensor is connected to a stepper motor mounted on an upper track above the upper surface of the bridge abutment for translating the first sensor across the width of the upper surface of the bridge abutment, wherein the first sensor is rigidly connected to the second sensor via a translation support frame, and wherein the translation support frame and the second sensor translate together with the first sensor.

[0021] 11. The device according to claim 10, wherein the second sensor is located below the upper surface of the bridge abutment.

[0022] 12. The device according to claim 10, wherein the tire tread has a first tread layer formed of a conductive compound and a second tread layer formed of a non-conductive compound.

[0023] 13. The device according to claim 10, wherein the first sensor and the second sensor are separated by a fixed distance D by the translational support frame.

[0024] 14. The device according to claim 10, wherein one or both of the first sensor and the second sensor are frequency-modulated continuous wave terahertz sensors.

[0025] 15. The device according to claim 10, wherein the first sensor and the second sensor are one of the same sensor and different sensors.

[0026] 16. The device according to claim 10, wherein one of the first sensor and the second sensor is a pulse terahertz sensor.

[0027] 17. The device according to claim 10, wherein one of the first sensor and the second sensor is a low-frequency terahertz sensor having a frequency range of 50 to 200 Hz.

[0028] 18. The device according to claim 14, wherein the second sensor is a pulse frequency sensor having a frequency range of one of 50 GHz to 2.2 THz and 50 GHz to 400 GHz.

[0029] definition

[0030] "Cloth layer" refers to a continuous layer of parallel cords coated with rubber.

[0031] "Radial" and "radially" refer to directions that are radially toward or away from the axis of rotation of the tire. Attached Figure Description

[0032] The present invention will be described by way of example and with reference to the accompanying drawings, in which:

[0033] Figure 1A This is a schematic cross-sectional view of a tire tread having a non-conductive tread layer subjected to terahertz radiation according to the present invention.

[0034] Figure 1B This is a schematic cross-sectional view of a tire tread having a conductive outer tread layer subjected to terahertz radiation according to the present invention.

[0035] Figure 2 This is a schematic diagram illustrating a tire tread with a conductive outer tread layer undergoing bi-directional differential measurement according to the present invention.

[0036] Figure 3 The illustration shows a continuous tire tread or tire component being continuously conveyed on a conveyor belt system, as well as a continuous measurement system;

[0037] Figure 4 The diagram illustrates the bridge abutment and continuous measurement system; and

[0038] Figure 5The second embodiment of the present invention is illustrated. Detailed Implementation

[0039] Figure 1A The illustration shows a measurement system 10 used to measure the thickness of each layer of a tire tread or tire component, such as a sidewall or ply composite, where each layer may be made of a different compound. A typical tire tread is formed from layers of different compounds to provide desired rolling resistance and other performance characteristics. Figure 1A The illustration shows a typical tire tread having a base tread layer 20 formed of a base tread compound, an intermediate tread layer 30 formed of a first tread compound, and an outer tread layer 40 formed of a second tread compound. The base tread compound, the first tread compound, and the second tread compound are each non-conductive.

[0040] like Figure 1A As shown, a terahertz (THz) sensor 50 can be positioned above (or below) the tire tread to measure the thickness of each tread layer 20, 30, 40. The terahertz sensor 50 has a radiation source for emitting a continuous electromagnetic radiation beam or pulse in the THz frequency range. For simplicity, the term "beam" will include both beams and pulses in the remainder of this disclosure. The terahertz sensor 50 continuously emits a high-frequency incident radiation beam 52 that travels through the air and the tread layers 40, 30, 20. The incident radiation beam 52 is in the frequency range of 100 GHz to 10 THz, and more preferably in the frequency range of 100 to 400 GHz. Reflections of the incident radiation beam occur at the radially outer surface 41 of the outer tread layer 40, at the interface 31 between the outer tread layer 40 and the intermediate tread layer 30, at the interface 21 between the intermediate tread layer 30 and the base tread layer 20, and at the radially inner surface 11 of the base tread layer 20. Therefore, the incident radiation beam 52 is reflected from the radially outer surface 41 of the outer tread layer 40 and is shown as the reflected radiation beam 42. Similarly, the incident radiation beam 52 is reflected from the interface 31 between the outer tread layer 40 and the intermediate tread layer 30 and is shown as the reflected radiation beam 32. Moreover, the incident radiation beam 52 is reflected from the interface 21 between the intermediate tread layer 30 and the base tread layer 20 and is shown as the reflected radiation beam 22. Finally, the incident radiation beam 52 is reflected from the radially inner surface 11 of the base tread layer 20 and is shown as the reflected radiation beam 12.

[0041] The terahertz sensor 50 includes receiving devices for receiving reflected radiation beams 42, 32, 22, and 12, wherein distances from the radially outer surface 41 of the outer tread layer 40, the tread interfaces 31 and 21, and the radially inner surface 11 of the base tread layer 20 to the terahertz sensor 50 are measured, respectively. The thickness of each tread layer 20, 30, and 40 can then be calculated.

[0042] The receiving device of the terahertz sensor 50 receives each reflected radiation beam 42, 32, 22, 12 and records the data in either time-domain or frequency-domain format. The time between reflections is the time of flight, or TOF, and is used to calculate the tread layer thickness. The formula for calculating the tread layer thickness is:

[0043] Thickness = (flight time) / 2 * c / RI

[0044] Where c is the speed of light, and RI is the refractive index of each tread layer.

[0045] Figure 1B The diagram illustrates a measuring system 10 for measuring the thickness of each layer of a tire tread, which is in relation to... Figure 1A Similarly, but including tire treads where the outer tread layer 60 is formed of a conductive compound or has a volume resistivity of less than 10E 9 Ohm*cm, as measured using a Keithley resistivity test kit. Figure 1B As shown, the terahertz sensor 50 emits an incident radiation beam 52 that travels through air, the radially outer surface 61 of the outer tread layer 60, the outer tread layer 60, the intermediate tread layer 30, and the base tread layer 20. The incident radiation beam 52 is reflected from the radially outer surface 61 of the outer tread layer 60 and is shown as a reflected radiation beam 42. The reflected radiation beam 42 is then received by the receiving device of the terahertz sensor 50. However, because the tread has a conductive outer tread layer 60, the reflected radiation beams 32, 22, and 21 are absorbed by the outer tread layer 60. Therefore, the reflected radiation beams 32, 22, and 12 are not received by the receiving device of the terahertz sensor 50. As a result, the distances from the terahertz sensor 50 to the other surfaces and interfaces 31, 21, and 11 cannot be determined, and ultimately the thicknesses of the tread layers 60, 30, and 20 cannot be determined. To overcome this problem, the following methods and devices can be used.

[0046] Figure 2 The illustration shows a method for performing biplane differential measurements using a dual-sensor measurement system 100 to determine the thickness of each layer of a tire tread or tire component having a conductive outer layer.

[0047] Specifically, such as Figure 2As shown, the tire tread includes an outer tread layer 160 formed of a conductive compound, or a layer with low emissivity, an intermediate tread layer 130 formed of a non-conductive compound, and a base tread layer 120 formed of a non-conductive compound. An upper terahertz sensor 150 has a radiation source for emitting a continuous electromagnetic radiation beam in the THz frequency range. The upper terahertz sensor 150 emits an incident radiation beam or pulse 152 that travels through the air, the outer tread layer 160, the intermediate tread layer 130, and the base tread layer 120. The incident radiation beam 152 is reflected from the radially outer surface 161 of the outer tread layer 160 and is shown as a reflected radiation beam 162. The reflected radiation beam 162 is received by a receiving device of the upper terahertz sensor 150, and the distance d11 between the upper terahertz sensor 150 and the radially outer surface 161 is determined.

[0048] The incident radiation beam 152 is also reflected from the interface 141 between the outer tread layer 160 and the intermediate tread layer 130, the interface 131 between the intermediate tread layer 130 and the base tread layer 120, and the radially inner surface 121 of the base tread layer 120. However, each of these reflected radiation beams is absorbed by the conductive outer tread layer 160. As a result, the distance between the upper terahertz sensor 150 and each interface and surface 141, 131, 121 cannot be determined, and ultimately the thickness d12 of the outer tread layer 160 cannot be determined.

[0049] To determine the thickness d12 of the outer tread layer 160, a lower terahertz sensor 155 is used in conjunction with an upper terahertz sensor 150. The lower terahertz sensor 155 also has a radiation source for emitting a continuous electromagnetic radiation beam in the THz frequency range. The lower sensor 155 emits an incident radiation beam or pulse 166 that travels through the air, the radially inner surface 121 of the base tread layer 120, and each tread layer 120, 130, 160. The incident radiation beam 166 is reflected from the radially outer surface 161 of the outer tread layer 160; however, it is absorbed by the conductive outer tread layer 160. Because tread layers 120 and 130 are non-conductive, reflection of the incident radiation beam 166 with respect to tread layers 120 and 130 is possible. The incident radiation beam 166 is reflected from the radially inner surface 121 of the base tread layer 120 and is shown as a reflected radiation beam 163. The reflected radiation beam 163 is received by the receiving device of the lower terahertz sensor 155, and the distance d21 between the lower terahertz sensor 155 and the radial inner surface 121 is determined. Furthermore, the incident radiation beam 166 is reflected from the interface 131 between the intermediate tread layer 130 and the base tread layer 120, and is shown as the reflected radiation beam 164. The reflected radiation beam 164 is received by the receiving device of the lower terahertz sensor 155, and the distance d22 between the lower terahertz sensor 155 and the interface 131 between the intermediate tread layer 130 and the base tread layer 120 is determined. Additionally, the incident radiation beam 166 is reflected from the interface 141 between the intermediate tread layer 130 and the outer tread layer 160, and is shown as the reflected radiation beam 165. The reflected radiation beam 165 is received by the receiving device of the lower terahertz sensor 155, and the distance d23 between the lower terahertz sensor 155 and the interface 141 between the intermediate tread layer 130 and the outer tread layer 160 is determined.

[0050] Then, the thickness d12 of the outer tire tread layer 160 can be determined as follows:

[0051] d12 = D - (d11 + d23)

[0052] Where D is the fixed distance or height between the sensors.

[0053] Figure 3 The illustration depicts a typical scenario when the continuous measurement system 300 can be used. The tire tread or tire component 310 is continuously formed by the extrusion system 320 and then continuously conveyed to the continuous measurement system 300 on the conveyor belt system 330.

[0054] like Figure 4As shown, the continuous measurement system 400 includes a bridge 440 with an upper surface 442 for supporting a tire tread or tire component 410. The bridge 440 includes a plurality of support legs 443. The measurement system 400 further includes an upper terahertz sensor 450 and a lower terahertz sensor 455. The upper terahertz sensor 450 is mounted to a stepper motor 452. The stepper motor 452 is optionally mounted on a C-frame or upper rail 454 located above the upper surface 442 of the bridge 440. In the example including the optional upper rail 454, the upper rail 454 is mounted across the width of the bridge 440 and thus perpendicular to the longitudinal axis of the bridge 440. Therefore, the upper terahertz sensor 450 can be translated by the stepper motor 452 across the width of the bridge 440, and thus across the width of the tire tread or tire component 410, to perform continuous depth measurements on each surface and interface of each layer of the tire tread or tire component 410.

[0055] The lower terahertz sensor 455 is fixedly connected to the upper terahertz sensor 450 via a translational support frame 460, such that the upper and lower terahertz sensors 450 and 455 maintain a fixed height, a distance D apart from each other, and move synchronously together. The upper and lower terahertz sensors 450 are mounted to the translational support frame 460. The translational support frame 460 has an upper frame member 462 connected to the upper terahertz sensor 450, a lower frame member 464 connected to the lower terahertz sensor 455, and two opposing side members 466 and 468 rigidly connected to the upper frame member 462 and the lower frame member 464. The translational support frame 460 has an open interior or window 470 positioned around a portion of the bridge abutment 440 to allow the tire tread or tire component 410 to pass freely through the window 470 while the upper and lower sensors 450 and 455 are taking measurements. The translation support frame 460, along with the upper terahertz sensor 450 and the lower terahertz sensor 455, are translated in unison by a stepper motor 452. The lower terahertz sensor 455 may optionally be connected to the lower support rail 456 by a support member 461 to provide stability.

[0056] Each terahertz sensor 450, 455 has a radiation source for emitting electromagnetic radiation beams or pulses in the THz frequency range, and a receiving device for receiving radiation reflected by the tire tread or layers of the tire component 410. The electromagnetic radiation beams or pulses are in the terahertz frequency range of 100 GHz to 10 THz, and more preferably in the frequency range of 100 to 400 GHz.

[0057] Figure 5 The diagram illustrates a method for performing biplane differential measurements using a dual-sensor system 600, which is similar to... Figure 2 The method shown is similar. Figure 5 A tire tread is shown having a non-conductive outer tread crown 510, an optional non-conductive inner tread crown 520, a conductive base tread layer 530, and an optional conductive cushioning layer 540. Because the tread 500 includes the conductive base tread layer 530 and the optional conductive cushioning layer 540, a dual-sensor measurement system 600 with an upper sensor 605 and a lower sensor 610 is required to determine the thickness of the tread layers 510, 520, 530, and 540.

[0058] In some examples, the lower sensor 610 can be a low-frequency sensor. The lower sensor 610 measures the depth of the conductive base tread layer 530 and the depth of the optional conductive cushioning layer 540. If a lower frequency sensor is used, a preferred frequency range is 50 to 200 GHz. Pulsed terahertz radar can also be used for the lower sensor 610. The pulse sensor can have a frequency range of 50 GHz to 2.2 THz or 50 to 400 GHz.

[0059] In an example excluding the optional cushioning layer 540, the lower sensor 610 emits an incident radiation beam 511 that travels through air, the radially inner surface 531 of the base tread layer 530, and the base tread layer 530 itself. The incident radiation beam 511 is reflected from the radially inner surface 531 of the base tread layer 530 and is shown as a reflected radiation beam 513. The reflected radiation beam 513 is received by a receiving device of the lower sensor 610, and the distance between the lower sensor 610 and the radially inner surface 531 of the base tread layer 530 is determined.

[0060] In an example including an optional cushioning layer 540, the lower sensor 610 emits an incident radiation beam 511 that travels through air, the radially inner surface 541 of the cushioning layer 540, the cushioning layer 540, and the base tread layer 530. The incident radiation beam 511 is reflected from the radially inner surface 541 of the cushioning layer 540 and is shown as a reflected radiation beam 512. The reflected radiation beam 512 is received by a receiving device of the lower sensor 610, and the distance between the lower sensor 610 and the radially inner surface 541 of the cushioning layer 540 is determined.

[0061] In an example excluding the optional inner tread layer 520, the lower sensor emits an incident radiation beam 511 that travels through air, the radially inner surface 541 of an optional cushioning layer 540 (if included), the optional cushioning layer 540 (if included), and the base tread layer 530. The incident radiation beam 511 from the lower sensor 610 is reflected from the interface 522 between the base tread layer 530 and the outer tread layer 510 and is shown as a reflected radiation beam 514. The reflected radiation beam 514 is received by a receiving device of the lower sensor 610, and the distance between the lower sensor 610 and the interface 522 between the base tread layer 530 and the outer tread layer 510 is determined.

[0062] Additionally, in an example including an optional inner tread crown 520, the lower sensor emits an incident radiation beam 511 that travels through air, the radially inner surface 541 of an optional cushioning layer 540 (if included), the optional cushioning layer 540 (if included), and the base tread layer 530. The incident radiation beam 511 from the lower sensor 610 is reflected from the interface 522 between the base tread layer 530 and the inner tread crown 520 and is shown as a reflected radiation beam 514. These measurements can be used to determine the thickness of each conductive tread layer 530, 540.

[0063] In some examples, the upper sensor 605 may be the same as the lower sensor 610. In other examples, the upper sensor 605 uses a frequency-modulated continuous wave (FMCW) terahertz radar, which measures the non-conductive outer tread crown 510 and optionally the non-conductive inner tread crown 520. The FMCW frequency can be in the range of 100 to 300 GHz, with a bandwidth of 90 GHz. When using FMCW radar, the distance to each interface or layer is given by the following formula:

[0064]

[0065] in

[0066] c = speed of light

[0067] RI = Refractive Index

[0068] Df = the difference between the transmit frequency and the receive frequency

[0069] df / dt = Rate of change of frequency.

[0070] In an example excluding the optional inner tread layer 520, the upper sensor 605 emits an incident radiation beam 501 that travels through the air, the radially outer surface 509 of the outer tread layer 510, and the outer tread layer 510 itself. The incident radiation beam 501 is reflected from the radially outer surface 509 of the outer tread layer 510 and is shown as a reflected radiation beam 502. The incident radiation beam 501 is also reflected from the interface 521 between the outer tread layer 510 and the base tread layer 530 and is shown as a reflected radiation beam 504. The reflected radiation beams 502 and 504 are received by a receiving device of the upper sensor 605, and the distances between the upper sensor 605 and the radially outer surface 509 of the outer tread layer 510, and between the upper sensor 605 and the interface 521 between the outer tread layer 510 and the base tread layer 530, are determined.

[0071] In an example including an optional inner tread layer 520, the upper sensor 605 emits an incident radiation beam 501 that travels through air, the radially outer surface 509 of the outer tread layer 510, the outer tread layer 510, and the inner tread layer 520. The incident radiation beam 501 is reflected from the interface 521 between the outer tread layer 510 and the inner tread layer 520 and is shown as a reflected radiation beam 504. Furthermore, the incident radiation beam 501 is reflected from the interface 522 between the inner tread layer 520 and the base tread layer 530 and is shown as a reflected radiation beam 506. These measurements can be used to determine the thickness of each tread layer 510, 520.

[0072] In cases where the interface between tread layers is difficult to see due to minute differences in refractive index (RI) of less than 3%, the interface can be better "seen" by using an upper sensor 605 and a lower sensor 610, and then superimposing the spectral data collected from the upper sensor 605 and the lower sensor 610.

[0073] The measurement system 600 may further include an electronic control system communicatively coupled to the upper sensor 605 and the lower sensor 610, as well as a stepper motor connected to the upper sensor 605. The electronic control system may include a processor and memory that combine with multiple sensors and actuators to perform the various controls described herein. In one example, the evaluation device is included as a module in the control system. Furthermore, the control system may include a display for showing data about the tire generated by the evaluation device. For example, radiation pulses described below may be displayed on the display.

[0074] The measurements described above can be performed using either THz pulses or THz waves, such as sine waves, as excitation. In pulse systems, we are referring to time-domain spectrometers; in wave systems, we are referring to frequency-domain spectrometers. There are devices that detect both the amplitude and travel time of the signal, as well as devices that determine only the amplitude.

[0075] Through Fourier transform, the measured time signal can be converted to the frequency domain. The amplitude is recovered in the frequency domain as a frequency-dependent amplitude, i.e., in the form of an amplitude spectrum, and the travel time is recovered as a frequency-dependent phase, i.e., in the form of a phase spectrum. For spectral analysis, the so-called transfer function can be determined, that is, the quotient of the sample spectrum divided by the reference spectrum. Based on the transfer function, the frequency-dependent refractive index of the rubber sample can be determined. This parameter is a characteristic material variable of the rubber sample. Here, the refractive index is representative of the optical density or time delay caused by the rubber sample. If the refractive index is known, a measurement of a rubber sample is sufficient to determine the layer thickness.

[0076] Regarding any of the tire tread or tire component examples explained herein, the tire tread or tire component is not limited to the described layer configuration. For example, the tire tread may have a base tread layer and an outer tread layer, the outer tread layer comprising both a first outer tread compound and a second outer tread compound. The first and second outer tread compounds may be conductive or non-conductive. The first and second outer tread compounds may occupy a portion of the axial width of the outer tread layer, such that the first outer tread compound occupies a first portion of the axial width of the outer tread layer, and the second outer tread compound occupies a second portion of the axial width of the outer tread layer. The first and second outer tread compounds have an interface, wherein the first and second outer tread compounds are adjacent.

[0077] One of the first and second tire tread compounds may also occupy a third portion of the axial width of the tire tread layer, such that the first and second tire tread compounds alternate along the axial width of the tire tread layer. In one example, the first tire tread compound occupies a first portion of the axial width of the tire tread layer, the second tire tread compound occupies a second portion of the axial width of the tire tread layer, and the first tire tread compound occupies a third portion of the axial width of the tire tread layer. The first and second tire tread compounds have a first interface, wherein the first and second portions are adjacent, and the second and first tire tread compounds have a second interface, wherein the second and third portions are adjacent. The thickness of the base tread layer and the tire tread layer can be measured using a sensor or a dual-sensor measurement system, as explained herein.

[0078] Variations are possible based on the description of the invention provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention. Therefore, it should be understood that changes can be made to the particular embodiments described, which will be within the full scope of the invention as defined in the appended claims.

Claims

1. A method for measuring the thickness of a tire tread, comprising the following steps: A tire tread is provided, wherein the tire tread has a first tread layer formed of a conductive compound and a second tread layer formed of a non-conductive compound; The tire tread is continuously conveyed, and a first sensor and a second sensor are respectively arranged above and below the tire tread. The first sensor and the second sensor are configured to emit a first radiation beam and a second radiation beam to the tire tread, respectively. The first sensor receives a first reflected radiation beam from the surface of the first tread layer from the first radiation beam and determines a first distance d1. The second sensor receives a second reflected radiation beam from the interface between the first tread layer and the second tread layer from the second radiation beam and determines a second distance d2. The second sensor receives a third reflected radiation beam from the surface of the second tread layer from the second radiation beam and determines a second distance d3. The first sensor and the second sensor are connected together at a fixed height D. as well as By emitting the first radiation beam and the second radiation beam by the first sensor and the second sensor respectively, receiving the first reflected radiation beam, the second reflected radiation beam and the third reflected radiation beam, and then determining the thickness d4 of the first tread layer by subtracting distances d1 and d2 from the fixed height D, continuous material thickness measurement of the first tread layer and the second tread layer is performed. The first sensor and the second sensor are collinear.

2. The method according to claim 1, wherein the first sensor and the second sensor are one of the same sensor and different sensors.

3. The method according to claim 1, wherein the second sensor is one of a pulse terahertz sensor and a pulse frequency sensor.

4. The method of claim 1, wherein the tire tread further comprises a third tread layer formed of a non-conductive compound.

5. The method of claim 1, wherein the second sensor is a low-frequency terahertz sensor having a frequency range of 50 to 200 GHz.

6. The method of claim 3, wherein the second sensor is a pulse frequency sensor having a frequency range of one of 50 GHz to 2.2 THz and 50 GHz to 400 GHz.

7. The method according to claim 1, wherein one or both of the first sensor and the second sensor are frequency-modulated continuous wave terahertz sensors.

8. The method of claim 1, wherein the first spectral data from the first sensor is superimposed on the second spectral data from the second sensor.

9. An apparatus for measuring the depth of each tread layer of a tire tread having at least two tread layers using the method according to any one of claims 1-8, comprising: The bridge abutment has an upper surface for conveying the tire tread thereon and a plurality of support legs for supporting the bridge abutment. A first sensor and a second sensor, wherein the first sensor and the second sensor are collinear, the first sensor is connected to a stepper motor mounted on an upper track located above the upper surface of the bridge abutment for translating the first sensor across the width of the upper surface of the bridge abutment, wherein the first sensor is rigidly connected to the second sensor via a translation support frame, and wherein the translation support frame and the second sensor translate together with the first sensor.

10. The device of claim 9, wherein the second sensor is located below the upper surface of the bridge abutment.

11. The device of claim 9, wherein the tire tread has a first tread layer formed of a conductive compound and a second tread layer formed of a non-conductive compound.

12. The device according to claim 9, wherein the first sensor and the second sensor are separated by a fixed distance D by the translational support frame.

13. The device of claim 9, wherein one or both of the first sensor and the second sensor are frequency-modulated continuous wave terahertz sensors.

14. The device according to claim 9, wherein the first sensor and the second sensor are one of the same sensor and different sensors.

15. The device of claim 9, wherein one of the first sensor and the second sensor is a pulse terahertz sensor.

16. The device of claim 9, wherein one of the first sensor and the second sensor is a low-frequency terahertz sensor having a frequency range of 50 to 200 Hz.

17. The device of claim 13, wherein the second sensor is a pulse frequency sensor having a frequency range of one of 50 GHz to 2.2 THz and 50 GHz to 400 GHz.

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