Apparatus for testing tire tread depth

• US 5,987,978 A
• Filed: 03/16/1998
• Issued: 11/23/1999
• Est. Priority Date: 04/02/1997
• Status: Expired due to Fees

• Current Assignee: Assembly Technology & Test Ltd. (DT Industries, Inc.)
• Original Assignee: Assembly Technology & Test Ltd. (DT Industries, Inc.)
• Inventors: Whitehead, Mark
• Primary Examiner(s): Felber, Joseph L.
• Application Number:
  US09/039,237
• Time in Patent Office: 617 Days
• Field of Search: 73/146
• US Class Current: 73/146
• CPC Class Codes: G01B 11/22 for measuring depth
• CPC Class Codes: G01B 2210/50 Using chromatic effects to achieve wavelength-dependent depth resolution

Abstract

An apparatus for determining the depth of a tire tread includes a radiation source for illuminating the tread of a tire, the direction of the illumination being non-normal with respect to the local surface of a portion of a tire under inspection, at least one detector responsive to radiation reflected from the tire, and a data processor responsive to the at least one detector for calculating the tread depth. In one embodiment, differences in displacement between radiation reflected from the top surface of a tread and radiation reflected from the bottom surface of a tread are measured to determine tread depth. In a second embodiment, the shadow cast by the top surface of the tread over the bottom surface of the tread is measured to determine tread depth. A third embodiment employs a sheet of radiation with varying wavelength to determine the tread depth.

Claims

1. An apparatus for measuring the depth of a tire tread having a top surface and a bottom surface, the apparatus comprising:

a radiation source for producing radiation for illuminating the surface of a tire, the radiation source being positioned such that an angle of incidence of radiation emanating therefrom with respect to a tire tread surface being measured is non-normal;

a radiation detector responsive to radiation reflected from the tire; and

a processor in communication with the detector for determining the tire tread depth by comparing differences in displacement between radiation reflected from the bottom surface of the tire tread and radiation reflected from the top surface of the tire tread.

2. The apparatus of claim 1, wherein the radiation source produces collimated radiation.

3. The apparatus of claim 1, wherein the radiation source produces light.

4. The apparatus of claim 1, wherein the radiation source is a laser.

5. The apparatus of claim 1, wherein the radiation source comprises an elongate light source and a collimator.

6. The apparatus of claim 1, wherein the radiation source produces a sheet of light.

7. The apparatus of claim 1, wherein the radiation source produces a light spot, and the light spot is displaced linearly across a tire tread surface being measured.

8. The apparatus of claim 7, wherein the light spot is displaced by a rotating mirror.

9. The apparatus of claim 7, wherein the light spot is displaced by displacement of the radiation source.

10. The apparatus of claim 1, wherein the detector is a photodetector.

11. The apparatus of claim 10, wherein the photodetector is a charged coupled device.

12. The apparatus of claim 1, wherein the apparatus further comprises a reflector sized and positioned between the radiation source and a tire tread surface.

13. The apparatus of claim 12, wherein the reflector is a faceted mirror.

14. The apparatus of claim 12, wherein the reflector is a transparent prism utilizing total internal reflection.

15. An apparatus for measuring the depth of a tire tread having a top surface and a bottom surface, the apparatus comprising:

a radiation source for producing radiation for illuminating the surface of a tire, the radiation source being positioned such that an angle of incidence of radiation emanating therefrom with respect to a tire tread surface being measured is non-normal;

a radiation detector responsive to radiation reflected from the tire; and

a processor in communication with the detector for determining the tire tread depth by comparing differences in displacement between radiation reflected from the bottom surface of the tire tread and radiation reflected from the top surface of the tire tread;

wherein the radiation source and the radiation detector remain in fixed positions during operation of the apparatus.

16. The apparatus of claim 15, wherein the radiation source produces collimated radiation.

17. The apparatus of claim 16, wherein the radiation source and the radiation detector are fixedly attached to a surface incorporating a rolling road.

18. An apparatus for measuring the depth of a tire tread having a top surface and a bottom surface, the apparatus comprising:

a radiation source for producing radiation for illuminating the surface of a tire, the radiation source being positioned such that an angle of incidence of radiation emanating therefrom with respect to a tire tread surface being measured is non-normal;

a radiation detector responsive to radiation reflected from the tire; and

a transceiver in communication with the detector and a processor for determining the tire tread depth by comparing differences in displacement between radiation reflected from the bottom surface of the tire tread and radiation reflected from the top surface of the tire tread;

wherein the radiation source, the radiation detector and the transceiver are enclosed in a hand-held housing.

19. The apparatus of claim 18, wherein the radiation source produces collimated radiation.

20. The apparatus of claim 19, further comprising a reflector positioned between the radiation source and the radiation detector.

21. The apparatus of claim 18, wherein the hand-held housing further comprises:

a first surface;

a second surface rotatably attached to the first surface;

a guide roller for following the contour of a tire, the guide roller being rotatably attached to the first surface;

an antenna electrically connected to the transceiver; and

a display electrically connected to the transceiver for displaying tire tread depth information.

22. A method for measuring the depth of a tire tread having a top surface and a bottom surface, the method comprising the steps of:

collimating radiation;

radiating the surface of a tire with collimated radiation such that an angle of incidence of the collimated radiation with respect to a tire tread surface being measured is non-normal; and

measuring differences in displacement between radiation reflected from the bottom surface of the tire tread and radiation reflected from the top surface of the tire tread.

23. The method of claim 22, wherein the radiating step is performed by scanning a light spot across the tire tread surface being measured.

24. The method of claim 23, wherein the scanning step is performed using a rotating mirror.

25. The method of claim 22, wherein the radiating step is performed by forming a sheet of light across the tire tread surface being measured.

26. The method of claim 25, wherein the sheet of light is reflected by a faceted mirror.

27. The method of claim 25, wherein the sheet of light is reflected by a prism.