GB1598013A

GB1598013A - Strip end alignment

Info

Publication number: GB1598013A
Application number: GB1031/78A
Authority: GB
Original assignee: British Federal Welder and Machine Co Ltd
Current assignee: British Federal Welder and Machine Co Ltd
Priority date: 1978-01-11
Filing date: 1978-01-11
Publication date: 1981-09-16

Description

(54) STRIP END ALIGNMENT (71) We, BRltlsH FEDERAL WELDER & MACHINE COMPANY IIMITED a British company, of Castle Mill Works, Birmingham New Road, Dudley, West Midlands DY1 4DA, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention is concerned with the alignment of the strip ends in a strip flash welding machine.

Strip flash welding machines are used to join together the ends of strips of steel, the strips passing from the welding machine to a continuous process. Such welding machines are therefore required to weld the leading end of a new strip to the trailing end of an old strip in a very short time but to a very high standard to avoid, as far as possible, interruptions in the continuous process caused by a weld break downstream of the welding machine.

One aspect of the problem of providing the necessary quality of weld is correct alignment of the strip ends for welding, and it is an object of the present invention to provide a method of and apparatus for aligning strip ends in a flash welding machine.

The present invention is a method of aligning strip ends in a flash welding machine comprising detecting the edges of the old strip end, deriving a displacement signal related to the displacement of the strip centre line from the machine centre line, detecting the edges of the new strip end and deriving a displacement signal related to the displacement of the new strip end from the machine centre line, and adjusting the transverse position of the new strip end, by using the displacement signals, to align the strip centre lines.

The present invention is also a strip flash welding machine including both main and auxiliary clamps on the entry and exit sides of the machine, first transversely movable edge detector means on the exit side of the machine for locating the edges of the old strip, means coupled to the first edge detector means for deriving a displacement signal related to the displacement of the centre line of the old strip, from the machine centre line, second transversely movable edge detector means on the entry side of the machine for locating the edges of the new strip, means coupled to the second edge detector means for deriving a second displacement signal related to the displacement of the centre line of the new strip from the centre line of the machine, means for comparing the displacement signals and producing an error signal, and servo means responsive to the error signal to drive the end of the new strip into alignment with the end of the old strip.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 diagrammatically illustrates a flash welding machine in plan with the leading and trailing strip ends in position; and Figure 2 is an elevation on the line Il-Il of Figure 1.

Referring now the drawings, the trailing end 11 of an old steel strip 12 is located in the die gap 13 of a strip flash welding machine, the die gap 13 being defined by pairs of main clamps, one pair 15 being on the exit side of the machine and the other pair 16 being on the entry side of the machine. It should be understood that in the drawing only the lower of each pair of clamps is illustrated, the strip ends being located between the upper and lower clamps of each pair.

Associated with each of the pairs of main clamps is a pair of auxiliary clamps 17 and 18, and the leading end 19 of a new strip 20 is located in the die gap 13.

Figure 1 illustrates the situation just prior to commencement of the alignment process, all the clamps being open.

The first step is to locate the edges of the old strip 12 and this is done by closing the exit main and auxiliary clamps 15 and 17 respectively and transversing inwardly from their datum positions a pair of edge detectors (not illustrated) to determine the values X and Y.

It should be noted that X and Y need not be and often are not the same as the centre line 22 of the strip 12 need not, at least within limits, coincide with the centre line 23 of the machine.

The values X and Y are passed to a differencing network which produces a difference signal (X-Y), i.e. a signal related to the displacement of the centre line 22 from the centre line 23. In fact (X-Y) is twice the displacement.

The auxiliary clamps 18 mounted on a carriage 30 are now closed by means of a clamp cylinder 31 and a difference signal is derived for the new strip centre line 25 in the same way as for the first difference signal using edge detectors 32 and 35 co-operating with fixed transducers 36 and 37 and driven by air cylinders 38 and 39 respectively. This second difference is then subtracted from the first difference signal to give an error signal related, again by a factor of two, to the mismatch of the centre lines of the strip. The error signal is fed to a servo mechanism 26 which drives the carriage 30 transversely on slides 40 to bring the centre lines of the strips into line. The subsequent welding process can then take place in the normal fashion.

The clamps 18 are released after the main clamps are closed on the strip and the servomechanism responds to retraction of the edge detectors 32 and 35 to recentre the clamps 18 on the centre line of the machine.

The embodiment described may be modified by making both the entry and the exit auxiliary clamps transversely movable thus allowing the strip ends to be positioned relative to the machine centreline as well as relative to each other. This involves, for the trailing end, reverse feeding of the strip by a downstream pinch roll after the auxiliary clamps are closed to form a loop in the strip.

WHAT WE CLAIM IS: 1. A method of aligning strip ends in a flash welding machine comprising detecting the edges of the old strip end, deriving a displacement signal related to the displacement of the strip centre line from the machine centre line, detecting the edges of the new strip end and deriving a displacement signal related to the displacement of the new strip end from the machine centre line, and adjusting the transverse position of the new strip end, by using the displacement signals, to align the strip centre lines.

2. A method as claimed in claim 1, in which the distances of the edges of each strip from datum points are measured and the displacement signal is derived by substracting the measured distances.

3. A method as claimed in claim 2, in which the difference signals are subtracted to provide a control signal for controlling the adjustment of the transverse position of the new strip end.

4. A strip flash welding machine including both main and auxiliary clamps on the entry and exit sides of the machine, first transversely movable edge detector means on the exit side of the machine for locating the edges of the old strip, means coupled to the first edge detector means for deriving a displacement signal related to the displacement of the centre line of the old strip, from the machine centre line, second transversely movable edge detector means on the entry side of the machine for locating the edges of the new strip, means coupled to the second edge detector means for deriving a second displacement signal related to the displacement of the centre line of the new strip from the centre line of the machine, means for comparing the displacement signals and producing an error signal, and servo means responsive to the error signal to drive the end of the new strip into alignment with the end of the old strip.

5. A method of aligning strip ends in a flash welding machine substantially as hereinbefore described with reference to the accompanying drawing.

6. A strip flash welding machine substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

the displacement of the centre line 22 from the centre line 23. In fact (X-Y) is twice the displacement.

The auxiliary clamps 18 mounted on a carriage 30 are now closed by means of a clamp cylinder 31 and a difference signal is derived for the new strip centre line 25 in the same way as for the first difference signal using edge detectors 32 and 35 co-operating with fixed transducers 36 and 37 and driven by air cylinders 38 and 39 respectively. This second difference is then subtracted from the first difference signal to give an error signal related, again by a factor of two, to the mismatch of the centre lines of the strip. The error signal is fed to a servo mechanism 26 which drives the carriage 30 transversely on slides 40 to bring the centre lines of the strips into line. The subsequent welding process can then take place in the normal fashion.

The clamps 18 are released after the main clamps are closed on the strip and the servomechanism responds to retraction of the edge detectors 32 and 35 to recentre the clamps 18 on the centre line of the machine.

The embodiment described may be modified by making both the entry and the exit auxiliary clamps transversely movable thus allowing the strip ends to be positioned relative to the machine centreline as well as relative to each other. This involves, for the trailing end, reverse feeding of the strip by a downstream pinch roll after the auxiliary clamps are closed to form a loop in the strip.

WHAT WE CLAIM IS: 1. A method of aligning strip ends in a flash welding machine comprising detecting the edges of the old strip end, deriving a displacement signal related to the displacement of the strip centre line from the machine centre line, detecting the edges of the new strip end and deriving a displacement signal related to the displacement of the new strip end from the machine centre line, and adjusting the transverse position of the new strip end, by using the displacement signals, to align the strip centre lines.
2. A method as claimed in claim 1, in which the distances of the edges of each strip from datum points are measured and the displacement signal is derived by substracting the measured distances.
3. A method as claimed in claim 2, in which the difference signals are subtracted to provide a control signal for controlling the adjustment of the transverse position of the new strip end.
4. A strip flash welding machine including both main and auxiliary clamps on the entry and exit sides of the machine, first transversely movable edge detector means on the exit side of the machine for locating the edges of the old strip, means coupled to the first edge detector means for deriving a displacement signal related to the displacement of the centre line of the old strip, from the machine centre line, second transversely movable edge detector means on the entry side of the machine for locating the edges of the new strip, means coupled to the second edge detector means for deriving a second displacement signal related to the displacement of the centre line of the new strip from the centre line of the machine, means for comparing the displacement signals and producing an error signal, and servo means responsive to the error signal to drive the end of the new strip into alignment with the end of the old strip.
5. A method of aligning strip ends in a flash welding machine substantially as hereinbefore described with reference to the accompanying drawing.
6. A strip flash welding machine substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.