Method and gauge for measuring the tread depth of a motor vehicle tire

• US 5,895,845 A
• Filed: 01/24/1997
• Issued: 04/20/1999
• Est. Priority Date: 05/26/1995
• Status: Expired due to Term

• Current Assignee: Joachim Burger
• Original Assignee: Joachim Burger
• Inventors: Burger, Joachim
• Primary Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US08/776,360
• Time in Patent Office: 816 Days
• Field of Search: 73/146, 356/3.08, 356/356
• US Class Current: 73/146
• CPC Class Codes: G01B 11/22 for measuring depth

Abstract

For measuring the tread depth of the tyre of a motor vehicle by means of a measuring head containing a laser (67), the laser measuring head is positioned relative to the tyre of the motor vehicle in such a way, that a reference surface or plane adopts a well-defined position with respect to the tyre. The laser beam (66) of the laser (67) is directed through the reference surface (68) at an angle (α) to the bottom (64) of the tyre tread, whereby a light spot (78) is generated on this bottom (64) of the tyre tread. The position (e) of the light spot (78) is observed by an image resolving sensor (82). Therefrom, a measure (t) of the depth of the tyre tread is gained.

Claims

1. A measuring device for measuring the tread depth of a motor vehicle tyre comprising:

(a) a laser for generating a laser beam, which is directed to the tread surface of the motor vehicle tyre to generate a light spot thereon;

(b) an image resolving sensor arranged to observe the position of the light spot;

(c) signal processing means designed to generate, from position data, a measured value indicative of the tread depth of one or more tread grooves of the tyre tread;

characterized in that;

(d) the laser and the image resolving sensor are accommodated within a common housing to provide a laser measuring head;

(e) the laser measuring head having an engagement surface permitting the laser measuring head to be brought into engagement with the motor vehicle tyre, whereby the laser and the image resolving sensor are positioned in a well-defined position relative to the motor vehicle tyre;

(f) the laser and the image resolving sensor are fixedly arranged relative to the engagement surface; and

(g) the measuring head including the laser, the image resolving sensor and the engagement surface defines a manually portable unit, the laser measuring head of which is capable of being swept manually over the tyre tread.

2. A measuring device as claimed in claim 1, further including a printer and a battery which are accommodated within a common housing.

3. A measuring device as claimed in claim 2, characterized in that all components of the signal processing means, the battery and the printer are accommodated within a common housing.

4. A measuring device as claimed in claim 2, characterized in that the laser measuring head is connected with the housing through a flexible cable.

5. A measuring device as claimed in claim 1, characterized in that the laser measuring head is attached to the end of a rod which permits convenient movement of the laser measuring head into contact with the tyre of a parked motor vehicle.

6. A measuring device as claimed in claim 5, characterized in that the rod is substantially z-shaped and has a bent-off handle end, a long median portion and a measuring head end bent-off substantially parallel to the handle end and carrying the laser measuring head.

7. A measuring device as claimed in claim 1, characterized in that the image resolving sensor comprises a linear array of light sensitive detectors which extends in a plane containing the laser beam, and imaging means, which image the light spot generated on the tread surface of the motor vehicle tyre on the array.

8. A measuring device as claimed in claim 7, characterized in that the imaging means are a slit light stop having a slit extending crosswise to the linear array.

9. A method of measuring the tread depth of a motor vehicle tyre by means of a laser measuring head containing a laser, an image resolving sensor and an engagement surface, the laser and image resolving sensor fixedly arranged relative to the engagement surface, wherein:

(a) the laser measuring head is brought manually into engagement with the motor vehicle tyre, whereby the engagement surface contacts the tyre tread;

(b) the laser beam of the laser is directed through the engagement surface at an angle onto the tread surface, whereby a light spot is generated thereon;

(c) the position of the light spot is observed by means of an image resolving sensor and a measure of the tread depth of one or more tread grooves of the tyre tread is derived therefrom; and

(d) the laser measuring head is swept manually over the tyre tread to generate measured values of a plurality of tread grooves, from which a measure of the tread depth is determined.

10. A method as claimed in claim 9, characterized in that the relation between the depth of the tyre tread and the position of the light spot as observed by the image resolving sensor is determined by calibration with treads of known tread depth.

11. A measuring device for measuring the tread depth of a motor vehicle tyre comprising:

(a) a laser for generating a laser beam, which is directed to the tread surface of the motor vehicle tyre to generate a light spot thereon;

(b) an image resolving sensor arranged to observe the position of the light spot;

(c) signal processing means designed to generate, from position data, a measured value indicative of the tread depth of one or more tread grooves of the tyre tread;

characterized in that;

(d) the laser and the image resolving sensor are accommodated within a common housing to provide a laser measuring head;

(e) the laser measuring head having an engagement surface permitting the laser measuring head to be brought into engagement with the motor vehicle tyre, whereby the laser and the image resolving sensor are positioned in a well-defined position relative to the motor vehicle tyre;

(f) the measuring device furthermore comprises;

(f1) a printer for printing output data indicative of tread depth; and

(f2) a battery for the power supply of the laser, of the sensor and of the printer;

(g) the measuring device being a mobile unit; and

(h) the laser measuring head is attached to the end of a substantially Z-shaped rod which has a bent-off handle end, a long median portion and a measuring head end bent-off substantially parallel to the handle end carrying the laser measuring head, which permits convenient movement of the laser measuring head into contact with the tyre of a parked motor vehicle.

12. A measuring device for measuring the tread depth of a motor vehicle tyre comprising:

(a) a laser for generating a laser beam, which is directed to the tread surface of the motor vehicle tyre to generate a light spot thereon;

(b) an image resolving sensor arranged to observe the position of the light spot;

(c) signal processing means designed to generate, from position data, a measured value indicative of the tread depth of one or more tread grooves of the tyre tread;

characterized in that;

(d) the laser and the image resolving sensor are accommodated within a common housing to provide a laser measuring head;

(e) the laser measuring head having an engagement surface permitting the laser measuring head to be brought into engagement with the motor vehicle tyre, whereby the laser and the image resolving sensor are positioned in a well-defined position relative to the motor vehicle tyre;

(f) the measuring device furthermore comprises;

(f1) a printer for printing output data indicative of tread depth; and

(f2) a battery for the power supply of the laser, of the sensor and of the printer;

(g) the measuring device being a mobile unit; and

(h) the image resolving sensor comprises a linear array of light sensitive detectors which extends in a plane containing the laser beam, and imaging means which are a slit light stop having a slit extending crosswise to the linear array which image the light spot generated on the tread surface of the motor vehicle tyre on the array.

13. A measuring device for measuring the tread depth of a motor vehicle tyre, comprising:

(a) a laser for generating a laser beam, which is directed to the tread surface of the motor vehicle tyre to generate a light spot thereon;

(b) an image resolving sensor arranged to observe the position of the light spot;

(c) signal processing means designed to generate, from position data, a measured value indicative of the tread depth of one or more tread grooves of the tyre tread;

characterized in that;

(d) the laser and the image resolving sensor are accommodated within a common housing to provide a laser measuring head;

(e) the laser measuring head having an engagement surface permitting the laser measuring head to be brought into engagement with the motor vehicle tyre, whereby the laser and the image resolving sensor are positioned in a well-defined position relative to the motor vehicle tyre;

(f) the image resolving sensor comprises a linear array of light sensitive detectors which extends in a plane containing the laser beam, and imaging means which are a slit light stop having a slit extending crosswise to the linear array which image the light spot generated on the tread surface of the motor vehicle tyre on the array; and

(g) the measuring device being a mobile unit.

14. A measuring device for measuring the tread depth of a motor vehicle tyre, comprising:

(a) a laser for generating a laser beam, which is directed to the tread surface of the motor vehicle tyre to generate a light spot thereon;

(b) an image resolving sensor arranged to observe the position of the light spot;

(c) signal processing means designed to generate, from position data, a measured value indicative of the tread depth of one or more tread grooves of the tyre tread;

characterized in that;

(d) the laser and the image resolving sensor are accommodated within a common housing to provide a laser measuring head;

(e) the laser measuring head having an engagement surface permitting the laser measuring head to be brought into engagement with the motor vehicle tyre, whereby the laser and the image resolving sensor are positioned in a well-defined position relative to the motor vehicle tyre;

(f) the measuring device being a mobile unit; and

(g) the laser measuring head is attached to the end of a substantially Z-shaped rod which has a bent-off handle end, a long median portion and a measuring head end bent-off substantially parallel to the handle end carrying the laser measuring head, which permits convenient movement of the laser measuring head into contact with the tyre of a parked motor vehicle.