MXPA06002804A - Tire inspection apparatus and method - Google Patents

Abstract

Described is an anomaly detector apparatus 10 for detecting an anomaly in a tire comprising;a source of coherent light 18 to shine the light 27 directly onto the tiresurface 24 and the light being reflected 32 from the tire;a stressing apparatus 12 which can stress the tire;a reflected light receiving apparatus 40 for receiving the light 32 reflected directly from the tire surface 24 when the tire is in a stressed and unstressed condition;a processor 44 which compares images of reflected light from the reflected light receiving apparatus 40 when the tire is stressed and unstressed thereby ascertaining an anomaly in the tire and generates an output from the comparison;and a display apparatus 46 electronically connected to the processor for displaying the output form the processor.

Description

APPARATUS AND METHOD FOR INSPECTION OF TIRES FIELD OF THE INVENTION The present invention pertains to the field of Non Destructive Testing (NDT). In particular the invention pertains to said tire tests using a computer for the automated output deployment of a tested tire image.

BACKGROUND OF THE INVENTION For many years the standard practice for tire testing machines by calibration for graphical / holographic slip resistance has been ASTM F1364-92. This test method describes the construction and use of a calibration device to demonstrate the anomaly detection capability of a non-destructive laser imaging inspection system for interferometric laser images. A typical graphical slip resistance edge pattern results from said test technique shown in Figure 1.

As described in US Patent No. 6,433,874, the technique of slip resistance interferometry or graphic slip resistance involves the interference of two laterally unfolded images of the same object to form an interference image. Conventional image slip resistance methods require that a first interference image (or baseline image) be taken while the object is in a first tensioned or unstressed condition and another interference image can be taken while the object is in a second condition stretched. The comparison of those two interference images (preferably by means of image subtraction methods) reveals information about the stress concentrations and the integrity of the object in a simple image called the control graph. Figure 1 shows an image that is the direct result of two laterally displaced images being obtained by an interference technique. The images obtained are not on the scale of the abnormality in the tire. In addition to very minute anomalies those in the order of 1.7 mm are not readily verifiable from a control chart such as that shown in Figure 1.

While some systems for control graphics have an output so that the deployment of the computerized systems of the '874 patent, many of the systems used are such that they have a highly sensitive film output that is extremely expensive and requires a special display In addition, film-based control graphic tire testing machines (and individual tire tests) are typically very expensive therefore a limited number in the industry is used within individual plants.

The electronic control charts of the '874 patent are based on the control charts described in US Patent No. 4,887,899 which describes an apparatus that produces an interference image by passing light, reflected from the test object through the material birefractario and a polarizador. The birefractive material divides the ray of light into two rays and polarizes it making it possible for the light rays of a couple of points to interfere with each other. In addition each point in the object generates two rays and the result is an interference image formed by the optical interference of two laterally deployed images of the same object.

There is a need for improved tire testing techniques and apparatus that facilitate direct measurements that allow a quantitative analysis or analysis by digitization of the anomaly in the tire.

There is a need to obtain an output of the tire test equipment that does not rely on an interferogram or proprietary optics, thus making the output of that exact test technique which describes and identifies the abnormality.

There is a need for a technique and apparatus for tire testing that allows the use of coherent light and the reflection of said light to be captured by inexpensive equipment and deployed using the commonly available computer systems.

Accordingly, it is an object of the invention to provide an approved tire testing technique and apparatus, which facilitate direct measurements and a quantitative analysis or scalability of the anomaly in the tire.

It is an object of the present invention to provide a technique and apparatus for tire testing that does not rely on an interferogram to accurately describe and identify the abnormality.

It is an object of the present invention to provide a tire testing technique and apparatus that allows the use of coherent light and reflection of said light to be captured by non-coded equipment and deployed using commonly available computer systems that do not use laterally displayed images but a simple image of the anomaly as output.

SUMMARY OF THE INVENTION An anomaly detector apparatus is disclosed for detecting an abnormality in a tire comprising: a coherent light source for shining light directly on the surface of the tire with the light being reflected from the tire; a tension apparatus, which can tension if pneumatic, an apparatus that receives the reflected light to receive light reflected directly from the tire when the tire is in an unstressed and tensioned condition; a processor that compares the images of the reflected light of the apparatus that receives the reflected light when the tire is tightened and does not tighten thereby checking the anomaly in the tire and which generates an output of the comparison and an electronically connected display device to the processor to display the processor output.

Also disclosed is a method for detecting an abnormality in a tire comprising: providing a coherent light source; the light shining directly on the surface, therefore generating a light reflected from the tire; tightening the tire, providing a reflected light that receives the apparatus to receive the reflected light directly from the tire when the tire is in a tensioned and unstressed condition, providing a processor that captures and compares the images of the light reflected from the reflected light that receives the device when the tire is stressed and not stressed and generates an output of the comparison therefore checking an anomaly in the tire and deploying that output from a device electronically connected to the processor from the output of the processor.

Also described is an image of an anomaly of a tire comprising: an output from a computer where the output is from a simple diffuse beam reflected from a coherent light source shown directly on the surface of the tire where on the surface of the tire has had the light shown on it when the tire is in an unstressed and tensioned condition; The output is the result of the comparison of the reflected light displayed on the tire in a tensioned and unstressed condition or in multiple tensioned conditions and the output is characterized as a simple image of the anomaly obtained from the simple diffuse beam of coherent light shown on the tire.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features and advantages of this invention will be apparent from the following detailed description, the appended claims and the accompanying drawings in which: Figure 1 is a prior art control chart .

Figure 2 is a schematic representation of the apparatus of the present invention.

Figure 3 is a schematic drawing of the tire test equipment wherein the tire is in an unstressed condition, wherein: A = Diffuser element B = Computer monitor C = .CCD camera.

Figure 3A is a schematic drawing of the tire test equipment wherein the tire is in a tensioned condition.

Figure 4 is a legend for Figure 4A. This legend serves to name the images captured with the tire subjected to several levels during the sequence of stages used in Figure 4A, where: D = Vacuum level at which the image is captured (Inches of Hg) E = Name of the picture.

Figure 4A is a block diagram of the sequences of a computer's computations to capture and process different images of the unstressed and stressed conditions as the typical voltage conditions that are applied, such as a vacuum application, where: F = Difference of A with CG = Capture 1_0, stored as "C" H = Capture 1_5, stored as "D" I = Difference of A with DJ = Stored as "AD" K = Stored as "A_D" L = Display A_D M = Capture 2_0, stored as "E" N = Difference of A with EO = Stored as "AE" P = Stored as "A_E" Q = Display A_E R = Difference of A with FS = Stored as "AF" T = Stored as "A_F".

Figure 5 is a typical output of the tire test apparatus showing a calibration block used as the test object and method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions Anomaly is defined as a defect in a tire that can be characterized generally as air trapped in a cured tire as a result of variations in the thickness of tire components, porosity and voids in the tire, a separation , a minor cure of the tire, air and trapped bubbles, low interply adhesion, low adhesion of the rope, bare wires, broken cords and construction errors of the machines.

The bitmap is a data file or structure that corresponds bit by bit with an image displayed on a screen, preferably in the same format as it should be stored in the video memory of the deployment or alternatively as a separate bitmap device. A bitmap is characterized by the width and height of the image in pixels and the number of bits per pixel that determines the number of shades of gray or colors it can represent.

Coherent light is a light that has a simple wavelength, frequency and phase. It is also radiant electromagnetic energy of the same or almost the same wavelength and with definitive phase relationships between the different points in the field.

Differentiated or also known as delta box means an animation box containing only the different pixels of the preceding key frame.

Diffuser is a device that transmits light through a translucent material that allows the distribution of incident light on the tire to be tested.

Interferometer is an instrument in which the light of a source is divided into two or more beams that are subsequently joined after traveling on different routes and displays interference.

Laser is a device that produces a monochromatic and coherent beam of light as a result of emission stimulated with photons. These beams have a simple wavelength and frequency. The materials capable of producing this effect are certain high period crystals such as ruby, yttrium garnet, metallic tungstates or molybdates doped with rare terrestrial ions, semiconductors such as gallium arsenide, glass doped with neodymium, various gases including carbon dioxide, helium, argon, neon and plasmas and the like.

Laterally displaced is a term that means that it appears to be a side-by-side or double image but is actually a negative or positive optical interference of a simple anomaly. Also laterally means side by side but depending on the orientation of the optical element in the device could be any angle.

In this form of Non Destructive Test (NDT), non-destructive means a test technique in which the object to be tested is subjected to a tension element and at the end of the test the object is substantially inverted to its original condition.

The processor is a device or program, usually a central processing unit, it can also be a program that transforms some of the input into something output such as a computer or a joint editor, it facilitates image comparisons, it can be a device Wired using embedded instructions to perform the comparisons.

The tension element means an element that is used to apply tension or subject an object to an effort to cause a change from its original condition. This tension can take the form of the application of a vacuum, the application of light, the application of a gas, the application of a mechanical force to allow bending, the application of acoustic sound to thereby vibrate the tire or some other vibration technique.

In general, the apparatus and method of the present invention can be described as follows: The inner surface of the tire is a diffuse reflecting surface, it is a mirror that is a specular reflecting surface. A design spec le. A speckle design is visible in the diffusion rather than in mirror reflective surfaces that are illuminated by laser light. These reflections of the irregular regions change during the tension cycle as the surface becomes deformed. With multiple images captured by the camera during this cycle, the computer can process the image information using a program algorithm as described in Figure 4 and Figure 4A. In the present invention light does not pass through a bi-reflective material or an optical slip material.

A typical test configuration for the present invention is described as follows: The tire to be inspected is placed horizontally on a plate inside a vacuum chamber. A commonly available industrial digital camera is located in the center of the tire so that a region of the inner surface of the tire is observed so that the camera model LU-205C available from Lumenra Corporation of Ottawa, Ontario, Canada (Lumenera.com ) which is a 2.0 megapixel color that has subsampling (800 x 600) SVGA which provides 40 frames / sec. The digital camera uses commonly available lenses to focus the image of the speckle design reflected from the region of the tire on the digital image sensor.

A cable connects the camera to a computer. The image information is sent through this cable to the computer's memory. The images of the memory can be observed in the screen of the computer in time near the real one, that is to say how the images are captured and processed by the equipment.

Generally, each image will be stored in the memory as a bitmap file in black and white, therefore 8 bits are used to store the grayscale levels of each image element of the image sensor or pixel, value. Likewise, the images observed on the computer screen will be in the form of 8 bits, gray scale bitmap display images corresponding to the bitmap images, as the images are stored in the memory. There are 28 = 256 (0 to 255 decimal) possible 8-bit greyscale values associated with each pixel of the displayed images. The decimal value "0" as it directly represents the gray scale level of the pixels of the individual display image corresponds to a black pixel, the pixel in grayscale darker. Similarly, the decimal value "255" represents the gray scale pixel that is "white". The remaining numerical values between 0 and 255 represent a progress of gray levels from dark to light.

Note that two digital images that are exactly equivalent will have the same numerical values from 0 to 255, for each image pixel. Conversely, two digital images that are not equivalent will not have the same numerical values for each pixel of the image. The arithmetic difference between each corresponding image pixel of two exactly equivalent digital images will be 0. This means that the difference image obtained from differentiating two equivalent digital images will be displayed as a totally black image. The image obtained from the differentiation of two bi-similar digital images will not be a totally black image. The difference image obtained from difference the two bi-similar digital images will not be a totally black image. The image differentiation function provides a tool to observe the slight changes between two digital images.

In one embodiment, the tension element is the use of vacuum. The speckle design associated with a given region of a tire will change with very small deformations of the tire surface. Such deformation of the surface occurs when the pressure drops in the vacuum test chamber and the interior air of a fold separation expands creating a deformation on the inner surface of the tire.

Practically speaking the two speckle images of a region of the tire surface where there is an underlying localized fold separation will be different if the two images are taken at different vacuum levels. Also the images will only be numerically different in the region of deformation associated with the fold separation. The difference image of the two images will be black anywhere except the area where the deformation occurs. In the region of deformation of the image there will be gray pixels of various tonalities. The deformation region is visible in the differentiated image.

In one embodiment of the test method, six digital images of a laser-illuminated interior surface region of a tire are taken with each image taken at one of six vacuum levels. The laser is a gallium arsenide laser having a wavelength of 808 nm (nanometer), model UH5-200 808 supplied by World Star Tech of Toronto, Ontario, Canada (worldstartech.com). The first image will be taken at 0.0"Hg (atmospheric pressure) The first image will be called the base image The five remaining images will be taken respectively to 0.5, 1.0, 1.5, 2.0 and finally 2.5" Hg. The six images will be stored in the computer's memory. The five differentiated images were obtained using the base image always as one of the two differentiated images. The other images used to make the five differentiated images will be the five non-base images. Each of the five differentiated images will be processed to filter the noise and increase the contrast / brightness. Other processing can also be used. Any combination of common or available image processing programs includes: auto anomaly detection, special effects, filtering, noise reduction, brightness, procrastination, coloration, positive or negative or the like. The five processed images will be added together in a cumulative design. After each addition of two images, the new image formed by the addition will be processed. The final image will be used for the evaluation of the region of the given tire. There will be a plurality of inspected inspection regions using the preferred test method to evaluate the entire tire.

It will be appreciated that a deployment means covering the varied electronic output of the images if they are visible to the single eye or not and includes a display screen, a backup or an electronic image. The electronic image can be used to determine if the test object passes or fails the test criteria without actually displaying the image for the eye.

Returning now to the drawings in the case. Figure 1 is a prior art control chart of the test characteristic identified in ASTM F 1364-92. For ease of reading, Figure 1 is a black-on-white image as opposed to a white-on-black image that is an output of the ASTM test. It should be noted that the anomalies in that output are laterally displaced images.

Figure 2 is a schematic diagram of the anomaly detecting apparatus of the present invention. In general, the anomaly detecting apparatus 10 is encased within a vacuum chamber 12 which is indicated as having a vacuum outlet 14. The tire 16 can be placed on a transport member (not shown) and can be placed on a motorized conveyor (not shown) outside the vacuum chamber and moved in the vacuum chamber. These techniques are well known in the technique. The anomaly detecting apparatus is comprised of the laser 18 mounted on a shaft 20 that can be rotated as it moves back and forth in the vacuum apparatus. The coherent light 22 emitted from the laser 18 is reflected on the inner surface 24 of the tire at points 26 as well as numerous other points. The coherent light 22 of the laser 18 is passed through the diffuser 30 which facilitates the scattering of the light through the portions of the substrate of the tire 24 to be observed. The diffused light 27 is reflected off the points 26 in a stained design that is reflected off the substrate 24 as shown by the beams 32. The light is stained and captured in a chamber 40. Preferably, the camera or cameras are a CCD variety well known in the industry as a loaded docked device. Other photosensitive detection equipment may be used. The camera can be called an image sensor, namely, sensitive to the stained image 32 of the application of direct laser light on the surface of the tire 24.

The diffuser is a holographic diffuser of 25 mm in diameter with greater efficiency of diffuser transmission. Alternatively, the diffuser may be an opal diffusion crystal having a diameter of 25 millimeters, both available from Edmund Industrial Optics of Barrington, New Jersey.

The camera and the computer are electrically connected through a cable 42. It will be appreciated while the electrical current may be necessary for the operation of the laser and the camera, the output of the camera is therefore supplied to the computer 44 by techniques of well-known wireless communications represented by parallel lines 43. The hard disk of the computer 44 is attached to a monitor 46 to display the stained output 32.

It will be appreciated that the coherent laser light that diffuses on the substrate 24 is reflected off the substrate and the capture is a direct capture of the reflections 32 by the CCD 40. This is despite the fact that it is used in the control graphics of the prior art or interferometry using an optical gliding device. The direct output of the device shown in Figures 2, 3 and 3A is shown in Figure 5. It will be appreciated that the output of Figure 5 can be black on white or white on black depending on how you want to observe the output desired. Because the image is captured by an image sensor, each pixel of the image can be identified or stored in digital form, such as, one can assign colors to the different portions of the image, in addition a bank or black color thereby improving the picture.

In a similar design, the operation of the equipment is shown in Figures 3 and 3A where there is a large number of diffuse rays 27 at different points 26. The light 27 of the diffusion element 30 is dispersed as shown in Figures 2, 3 and 3A.

After the tire is subjected to a tension element such as the application of a vacuum, the application of light, the application of gas, the application of a mechanical force to allow bending, the application of acoustic sound thereby vibrating the tire or some other vibration technique, the result is the movement of the substrate of the tire 24 which in turn causes a reflection of the laser light from the points 26. Figure 3A shows in an exaggerated design the variation of the smooth surface 24 of the tire for an expanded version or deformation 24 that is shown. The laser light therefore deviates at a different angle and is therefore shown as reflected spot light 32 which creates images that are captured by the CCD camera 40.

Electric power 42 is shown as having parallel markings 43 to indicate that it can not necessarily be a direct cable to pass the images from the camera to the computer monitor but can be done by a wireless technique. Capturing the images in a camera is well known in the art. It can take the form of animation of images, whose techniques are well known.

To graphically explain how the animation occurs, reference can be made to Figures 4 and 4A. Figure 4 shows a legend by means of which images that are captured at various vacuum levels provide names for reference purposes. The figure 4A shows the sequence of the steps used to evaluate a region of the inner surface of a tire. The test sequence begins in the box designated 50 and ends in step 68. At 51 the image of the base of the tire region is captured while the tire is not tensioned and is subjected to 0.0"Hg (atmospheric pressure). From the legend shown in Figure 4, this image is designated 0_0.This base image, referenced as 0_0, is stored as an image, - "A" during step 51. For consistency, in box 52, the base image was differentiated of itself to provide a black image that was displayed as the first image of the animation.This image was stored in 53 as "AA." It can be seen that a black image could have been produced in the program without actually forming the images of the Tire region, however, the base image "A" is displayed at 54 to the next image that is captured in step 55 while the tire is subjected to 0.5"Hg of vacuum.This image," 0_5, "is stored as" B " in step 55. In 56 the image B differs with the base image, A, producing the image "AB" which is stored in step 57. AB subsequently unfolds in 58 and AB serves as the second image in the sequence In stage 0, as well as the subsequent stages, 63, 64, 66, the previously displayed image was added to the image formed in the immediately preceding stages, for example, in step 60, the image previously displayed is AB and the image added to this image is the just image formed, "AC" stored in step 59. The newly formed image is stored as "A_C" in step 61. A_C is subsequently displayed in step 62. During the course of the test, the images are captured increments of 0.5"Hg with the final image, 2_5" being captured urated with the tire submitted to 2.5"Hg vacuum (stage 65). In 67, the final image is displayed in the animation sequence. The images obtained during the tire test can be the subject of a printed output as shown in Figure 5. A technique representative of said technique is shown in Figure 5 where the procedure, as follows in the ASTM test technique above described was used, except the apparatus of Figures 1 and 2 were used instead of an interferometer technique.

It is also understood that even though Fig. 4 and Fig. 4A show the vacuum cycle from 0.0 Hg to 2.5 Hg, any combination of the vacuum levels or the increase or decrease setting points can be used. As an example of 5.5 Hg at 1.0 Hg.

The program used to process the stained image and display it may be any commercially available image processing program such as PAINT SHOP PRO V # 8.0, provided by Jase Software Inc., of Eden Prairie, Minnesota. Another program that can be used is LabView available at National Instruments of Austin, Texas.

Figure 5 is a representative example of any of one of the AA up to A_F images when the ASTM method is used except the apparatus of Figures 1 and 2 was used in place of an interferometer technique. Figure 5 shows an image of an ASTM calibration device in which the image is a reflected image of the substrate of the calibration device that has been stretched and the laser light has diffused directly into the substrate and the reflection of a diffused light. -capture as a mage stained by the camera and stored in the computer's memory which in turn can be used to generate the output of Figure 5. It should be noted that the output is characterized as a scalable representation of the anomaly obtained from the diffused beam of coherent light diffused in the tire. It should be noted that the image of the reflected light source can be characterized as a level speckle reflection. It is appreciated that the tire may be in an unstressed or tensioned condition or multiple tensioned conditions. The computer can compare and display all conditions or a portion of them. The invention includes all such comparisons in the completed output form.

The use of the present technique facilitates the quantitative measurement of the anomaly. As an alternative to the quantitative determination one can check the extent of the anomaly by scaling the anomaly with the image that is displayed on the computer monitor or generated in the output tai as Figure 5. The art price techniques did not allow measurements or scale of the anomaly to check the extent of an anomaly in a tire.

The invention described in this document in a preferred embodiment does not use mirrors for the movement of light. However, it is appreciated that the mirrors can be used depending on the light source, the camera, the diffuser, the test substrate and the number of images taken from the substrate. The mirrors can be used under particular desired test conditions and techniques.

While the forms of the invention described herein constitute the currently preferred embodiments, many others are possible. It is not attempted in this document to mention all possible equivalent forms or ramifications of the invention. It will be understood that the terms used in this document are merely descriptive rather than limiting and that various changes may be made without departing from the spirit and scope of the invention. For example, the type of laser used may vary substantially, the program on the computer described in this document may vary depending on the changes in technology with respect to the computer, computer devices, and updates of the types of programs.

Claims (24)

1. An abnormality detecting apparatus for detecting an abnormality in a tire comprising: a coherent light source for shining the light directly on the surface of the tire with the light being reflected from the tire; a tension apparatus, which can tighten the tire; an apparatus that receives the reflected light to receive light reflected directly from the tire when the tire is in a tensioned and unstressed condition; a processor, which compares the images of the reflected light of the apparatus receiving the reflected light when the tire is tightened and not tensed thereby checking an abnormality in the tire and which generates a comparison output and a deployment apparatus Electronically connected to the processor to display the processor output.

2. The apparatus according to claim 1, wherein the light does not pass through a birefractive material or an optical sliding material.

3. The apparatus according to claim 1, wherein the light source is a laser.

4. The apparatus according to claim 1, further comprising a diffuser positioned between the light source and the tire to distribute the light on a portion of the surface of the tire.

5. The apparatus according to claim 1 further comprising a diffuser positioned between the light source and the tire to distribute the light on a portion of the tire with uniform distribution.

6. The apparatus according to claim 1, wherein the apparatus receiving the reflected light is a camera.

7. The apparatus according to claim 6, wherein the camera is electronically connected to a computer.

8. The apparatus according to claim 1, wherein the processor is a program that is operated on a computer, which displays the output.

9. A method for detecting an abnormality in a tire comprising: providing a coherent light source; shine light on the surface of the tire, therefore generating a light reflected from the tire; tighten the tire; providing an apparatus that receives the reflected light to receive light reflected directly from the tire when the tire is in a tensioned and unstressed condition; provide a processor that observes and compares the reflected light images of the apparatus receiving the reflected light when the tire is tightened and does not tighten therefore checking an abnormality in the tire and generating a comparison output and deploying the electronically connected device to the processor, the processor output.

10. The method according to claim 9, wherein the light does not pass through a birefractive material or an optical sliding material.

11. The method according to claim 9, wherein the light source is a laser.

12. The method according to claim 9, further comprises distributing light on a portion of the tire by a diffuser positioned between the light source and the tire.

13. The method according to claim 9, further comprising distributing light on a portion of the tire with even distribution of light by a diffuser positioned between the light source and the tire.

14. The method according to claim 9, wherein the apparatus that receives the light is a camera.

15. The method according to claim 14, further comprising passing the images from the camera to a computer.

16. The method according to claim 9, wherein the processor is a program operating on a computer, which displays the output.

17. The product of the method according to claim 9.

18. An image of an anomaly of a tire comprising the output of a computer where the output is from a diffused beam reflected from a coherent light source shown directly on a surface of the tire, said tire surface having had the light shown on it when the tire is in a tensioned and unstressed condition; an output is the result of comparing the reflected light shown in the tire in a tensioned and unstressed condition or in multiple tensioned conditions and the output is characterized as a simple image of the anomaly obtained from the diffused beam of coherent light shown in the tire.

19. The image according to claim 18, wherein the light does not pass through a birefractive material or an optical sliding material.

20. The image according to claim 18 scaled to the size of the anomaly in the tire.

21. The image according to claim 18, wherein it is characterized as a level speckle reflection.

22. The image according to claim 18, wherein the light source is passed through a diffuser before the light shines on the surface of the tire.

23. The image according to claim 18, wherein the output is black on white or white on black.

24. The image according to claim 18, wherein the output is in multiple colors to improve the visibility of the image.