Position-measuring method and device adapted for the positioning of a wheel

1. A position-measuring method for positioning a wheel in a mash seam resistance welding process for butt-joining steel strips on a continuous processing line, the method which comprises:

a) positioning a rotary roller which is fastened to a movable frame in a measuring position vertically below a reference wheel;

b) continuously lowering the reference wheel in a vertical direction so that a lower surface thereof comes into contact with the rotary roller and produces a bearing force on the roller;

c) continuously moving the roller in the vertical direction;

d) repeatedly measuring a distance between an index that is secured to a measuring arm of the movable frame and an articulated post fixed to the movable frame during the continuous movement;

e) comparing the distance with a distance threshold for each of the repeated measurements until the reference wheel reaches a first operating position in which the distance is equal to a predefined factor of the distance threshold; and

f) recording the first operating position as a reference point in a system for the vertical movement of the reference wheel.

2. The method according to claim 1 , which comprises adopting one of the following two methods for positioning the reference wheel:

stopping the vertical lowering and locking the reference wheel in the first operating position; or

stopping the vertical lowering in the first operating position and subsequently moving the reference wheel vertically in a second operating position, wherein the second operating position is adjustable remotely by an operator.

3. The method according to claim 2 , which comprises calculating a diameter of the reference wheel after having positioned the wheel in the first operating position or in the second operating position.

4. The method according to claim 1 , which comprises measuring the position after changing or remachining the reference wheel and a second wheel.

5. The method according to claim 1 , wherein the position measurement is adapted for positioning reference wheels of different diameters.

6. The method according to claim 1 , which comprises adopting at least one of the following three measurement methods:

carrying out a measurement at the end of each welding process;

carrying out at least two measurements during a series of welding processes; or

carrying out a measurement initiated by a production line operator.

7. A measuring device adapted for positioning the wheels of a mash seam resistance welding machine for butt-joining steel strips on a continuous processing line, comprising:

a tiltable frame and an hydraulic cylinder for actuating said tiltable frame from a position of repose to an active measuring position;

said tiltable frame including an articulated post and a measuring arm articulated on said post, and a resilient return member coupling said arm to said post;

a rotary roller carried by said measuring arm;

a position detection and measuring device fixed to said frame;

an index fixed to said measuring arm, said index having a length enabling a position thereof to be detected by said position detection and measuring device;

a device stop disposed to mechanically block a movement of said frame beyond the active measuring position; and

a stop affixed to said post and disposed to oppose said resilient return member to prevent a return of said measuring arm beyond the parking position.

8. The device according to claim 7 , wherein a ratio between a length of said measuring arm and a length of said articulated post determines a range of measurable values of the position of said index.

9. The device according to claim 7 , comprising two superposed rollers capable of coming into contact respectively with a lower welding wheel on the steel strip and a reference wheel and to subject an active external surface of said active welding wheel and an external surface of said reference wheel to a cold working treatment.

10. The device according to claim 7 , wherein said position detection and measuring device comprises optical distance measurement means.

11. The device according to claim 10 , wherein said position detection and measuring device comprises ultrasound distance measurement means.