Measuring and testing – Tire – tread or roadway
Reexamination Certificate
2000-03-17
2003-01-07
Oen, William (Department: 2855)
Measuring and testing
Tire, tread or roadway
Reexamination Certificate
active
06502453
ABSTRACT:
The invention relates to a method of testing tires, wherein before and after an alteration in the tire pressure a respective interferogram is produced of the tire surface using coherent radiation and, from the interferogram, the information concerning any defects present in the tire is obtained, and furthermore to an apparatus for the performance of the method.
BACKGROUND OF THE INVENTION
The German patent publication 42 31 578 A1 discloses a method for the determination of the structural strength of tires, in which the tire is illuminated with coherent light, the radiation diffusely reflected back from the tire is divided up in a twin beam interferometer into two beam parts, in the twin beam interferometer one of the two beam parts is tilted in relation to the other beam part as a shearing operation, in the twin beam interferometer one of the two beam parts is phase shifted in steps, the radiation diffusely reflected by the object being tested and split up into two beam parts and then united again is returned through components presenting an image of the surface of the tire with a large aperture to an electronic image sensor system and the signals produced by the image sensor system are digitalized and further processed to give a modulo 2&pgr; image and the modulo 2&pgr; image is confirmed as an output gray value image.
In accordance with the German patent publication 195 02 073 A1 the above mentioned method is further developed to the extent that the output gray value image is partially differentiated, a second gray value image identical to the output gray value image is produced and it is geometrically displaced in the shearing direction in relation to the output gray value image and is altered by a gray value which is constant over the entire image area and the second gray value image manipulated in this manner is subtracted from the output gray value image and so that a resulting gray value image is produced, from which any defects in the tire may be seen.
When it is considered that structural damage in tires and more particularly in the carcass including the belt, may in the case of car tires substantially impair the safety of the vehicle, it will be seen to be desirable for a device to be available able to perform tire testing.
The EP 0 884 574 discloses a method of testing tires wherein before and after an alteration in the tire pressure a respective interferogram is produced of the tire surface using coherent radiation and, from the interferogram, the information concerning any defects present in the tire is obtained. For testing a tire, the wheel having the tire to be tested is mounted on a balancing machine. A testing head located at the balancing machine, is moved towards the tire up to a preselected testing distance for deriving the interferogram. The testing on defects is carried out at a first testing segment of the tire. Thereafter, the wheel is rotated on by the balancing machine in the amount of a testing segment, and the last mentioned steps are repeated until the complete tire is tested. The tire testing apparatus comprises a balancing machine on which the wheel having the tire to be tested, is mounted, a positioning device for the testing head by means of which device the testing head is moved towards the tire up to a preselecting testing distance for deriving the interferograms, and a control device for the balancing machine in order to rotate the wheel by the amount of a testing segment forwards when the testing of the previous testing segment has been completed.
Since the costs for the test head are substantially dependent on the area which may be covered in a single measuring step, the above mentioned method is advantageous in that the costs for the test head may be reduced substantially in that a segmentwise testing of the tire is provided for, wherein a plurality of testing segments of the tire are subsequently brought into the field of view of the test head. On the other hand, the required investments are higher than necessary when the user only needs a tire testing device but no balancing machine.
SUMMARY OF THE INVENTION
It is the object of the invention is to create a tire testing method and apparatus rendering possible the testing of tires by as simple means as possible.
For this purpose, the method in accordance with the invention provides that, for testing a tire, the wheel which has the tire to be tested, is mounted on a rotatable shaft of a tire testing machine, that the distance of the tire from the test head is adjusted thereby that the wheel is shifted together with the shaft in the direction of the shaft, and that the shaft is locked thereafter, that the relative location of the test head with respect to the tire is adjusted thereby that the test head is, in order to bring it into position for differently sized tires, moved in a vertical direction, that the wheel is, thereafter, rotated further on by the amount of a testing segment by hand and locked mechanically when the next segment is in a test position in front of the test head, that the testing as to defects is carried on a first testing segment of the tire, and that the two last mentioned steps are repeated until the complete tire has been tested.
Some expenditure for hardware may be saved in that the wheel is rotated by hand. However, it has to be taken care that the wheel is rotated exactly by one segment since otherwise the position of the detected defects cannot be evaluated with a sufficient accuracy, and that the test head is positioned accurately in relation to the tire. This, however, is ensured by the way in which the machine is adjusted and by the mechanical locking of the shaft with the wheel. The test head may be arranged in a simple manner and without further means at an accurate testing position by such a simple scheme of movements.
In accordance with an advantageous development of the method, the relative position of the test head with respect to the tire adjusted thereby that the test head is moved in a vertical direction and perpendicular to the longitudinal direction of the shaft. Thereby, advantages are obtained with respect to the integration of the test head into the tire testing apparatus, and the adjustment of the test head can be carried out from above, which means from the console of the apparatus.
In accordance with an advantageous development of the method, the field of view of the test head is inspected by means of a camera which is arranged in the test head and is directed to the tire whereby the picture taken by the camera, is shown on a monitor. Thereby, it can be verified without further means when the test head is in the correct position with respect to the tire, and there are no further measurements necessary in order to verify this. It is also advantageous that the monitor which is already provided for, is also used for this purpose.
In accordance with a further advantageous embodiment of the method of the invention, the values necessary for the further rotation of the wheel, for example the tire size, are input into a computer, and the computer issues an information about the number of segments which are required in order to test the complete tire. If the sizes are stored in form of a table, this table can concurrently be updated by inputs made by hand such that the effort for the adjustment for a test run is becoming ever smaller.
A further advantageous embodiment of the method of the invention is characterized in that the number of the required segments is adjusted at the shaft. This adjustment is done by hand while using the information given from the computer. Therefore, the corresponding adjustment can be made with a minimum of hardware.
A further advantageous embodiment of the method of the invention is characterized in that, upon adjustment of the distance between the test head and the tire, this distance is watched and an indication is given when the test head has reached the desired distance, and that the test head is, thereafter, locked. Thereby, a secure, fast and accurate adjustment of the test head with respect to the tire is possib
Beissbarth GmbH
Crompton Seager & Tufte LLC
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