Butt welding sheets

Fusible sheet edges are joined by first forming each of the edges with a laterally projecting burr and then butting the edges together at a join line with both the burrs directed in the same lateral direction adjacent each other and plastically deforming the laterally projecting burrs at the join line in the lateral direction opposite their projection direction. Finally the edges are fused together at the join line. The burrs are plastically deformed by pressing them with a barrel-shaped roller that is moved along the join line.

FIELD OF THE INVENTION 
The present invention relates to a method of joining sheet workpieces. More 
particularly this invention concerns welding together the edges of 
metallic sheets 
BACKGROUND OF THE INVENTION 
In butt welding metallic sheets such as described in German patent document 
3,713,527 it is necessary to avoid the formation of any gaps at the butted 
edges being welded, whether they are of two different workpieces or 
opposite edges of a single workpiece as in a tube-forming operation 
Accordingly the edges are formed as straight and square as possible, 
typically by shearing, and then are pressed together and held before 
welding heat is applied. If a gap is left that is as small as one-tenth 
the workpiece thickness the result can be a mechanically weak joint that 
in certain applications will create a leak. When the gap is larger a laser 
beam used to apply the heat might pass between the workpieces, preventing 
them from being fused together at all. 
Accordingly it is known from German patent document 3,901,319 to overlap 
the workpiece edges slightly by a distance equal to the maximum possible 
variation of straightness of these edges. The overlapped edges are then 
flattened together by a roller or the like before welding, producing in 
regions of some overlap a workpiece thickness equal to 1.3 to 1.5 times 
the material thickness. Trying to reduce the thickness further damages the 
workpieces. This procedure therefore produces a thick unsightly weld 
where, due to varying material thickness, actual fusion will normally vary 
along the weld, being less in the thick regions and more in the regions 
where there is little or no overlap. 
OBJECTS OF THE INVENTION 
It is therefore an object of the present invention to provide an improved 
method for joining workpiece edges by butt welding. 
Another object is the provision of such an improved method for joining 
workpiece edges by butt welding which overcomes the above-given 
disadvantages, that is which produces a smooth and perfectly continuous 
weld that is not thicker than the balance of the workpiece or workpieces. 
SUMMARY OF THE INVENTION 
A method of joining fusible sheet edges according to this invention 
comprises the steps of first forming each of the edges with a laterally 
projecting burr and then butting the edges together at a join line with 
both the burrs directed in the same lateral direction adjacent each other 
and plastically deforming the laterally projecting burrs at the join line 
in the lateral direction opposite their projection direction. Finally the 
edges are fused together at the join line. 
The burr itself can be the burr formed by many machining operations in 
cutting a straight edge on a workpiece, particularly shearing. In 
locations where the edges do not quite meet, the burrs will be pressed 
together to fill the gap, ensuring a continuous weld, and in places where 
they abut, these burrs will just be flattened somewhat. In particular it 
is standard for the face of the workpiece opposite that face that has a 
burr to be bent in or chamfered somewhat, so in locations where the edges 
meet flatly, pushing in the burr will merely serve to eliminate the void 
on the opposite side at the join line. 
According to another feature of this invention the burrs are plastically 
deformed by pressing them with a roller that is moved along the join line. 
The roller is barrel-shaped. Furthermore the edges are formed with burrs 
by shearing and the sheared edges are trimmed to form the burrs. This can 
be done by trimming two sheared edges to form burrs thereon 
simultaneously.

SPECIFIC DESCRIPTION 
As seen in FIG. 1 a pair of sheet workpieces 1 and 2 are both held flat on 
a flat support table 3 by respective clamps 9 and 10 so that edges of 
these workpieces 1 and 2 butt at a join line 8. These workpieces 1 and 2 
have at the join line burrs 5 and 6 which according to this invention both 
face laterally in the same direction, here upward away from the support 
table 3, and in fact they have opposite outer edges formed with identical 
such burrs 4 and 7 both also facing upward. 
According to this invention after the workpieces 1 and 2 are thus clamped, 
with inevitably there being some voids formed at the join line 8, a roller 
11 is pressed down and rolled along the burrs 5 and 6 at this join line 8. 
This causes the burrs to reenter, thereby squaring the respective 
workpiece edge where the workpieces 1 and 2 abut, and causes the burrs to 
fold inward and butt where there is a void. 
Subsequently a laser beam such as illustrated at 12 in FIG. 2 is used to 
fuse the two edges together. The result is a perfect weld 24 that is of 
the same thickness as the adjacent workpieces. 
FIG. 3 shows how a workpiece 13 can be formed by a standard pair of 
oppositely acting shear blades 15 and 16 with oppositely directed edge 
burrs 16 and 17. To join adjacent such edges of such workpieces 13 it is 
necessary to turn one of the workpieces 13 over to orient its edge burr so 
that is projects laterally in the same direction as that of the burr of 
the edge to which it is to be joined. 
Alternately FIG. 4 shows a pair of lower blades 18 and 19 working with a 
double-edge upper blade or die 20 that can cut workpieces 21 so that burrs 
23 at both edges point in the same direction. This trimming cuts out a 
waste piece 22, but leaves a workpiece 21 which can be rolled to form a 
tube that is subsequently welded into pipe, with a cylindrical mandrel 
replacing the table 3 of FIG. 1.