Device for positioning metal ends to be lap welded one to the other

Described herein is an invention that belongs to the technical field of machines for effecting lap welding operations and relates, in particular, to a device for positioning the metal ends of strips destined, once the said ends are joined one to the other, to constitute can bodies. Envisaged by the invention is a device in which the slots for housing the ends to be welded are defined by at least one pair of guide blocks that are substantially opposed and are shaped in the form of a step in such a way that each constitutes means of abutment for one of the said ends and supporting surfaces for both of the said ends. Advantageously, at least one block in the said at least one pair of blocks can be set with respect to the other.

BACKGROUND OF THE INVENTION 
The invention relates to a device for positioning metal ends to be lap 
welded one to the other. 
DESCRIPTION OF THE PRIOR ART 
As is known, the machines for effecting the lap welding of the ends of 
prior rounded metal strips that are destined to constitute the bodies of 
cans, drums, and similar containers, are provided with a device for 
positioning correctly the said ends. Seam welders have, for example, a 
device defined by a guide shaped in the form of a "Z", the slots of which 
receive the ends to be welded and, as the strips are carried along the 
said slots, gradually determine the overlap for the said ends. 
Provision is generally made for numerous "Z" shaped guides placed in 
alignment one with the other, in such a way as to extend up to the welding 
station. These guides operate in cooperation with other means: for example 
gage checking devices which, at the welding station, encircle the body to 
be formed. 
The position of the slots of the said guides determines both the extent of 
the overlap, one with respect to the other, of the ends to be welded and 
the precise centering of the welding with respect to the overlap. 
Qualitatively speaking, the guides in question are decisive in defining 
the satisfactory outome of the welding operation. 
In practice, it has been seen for some time now that with the use of the 
said guides, numerous problems exist that adversely affect the operating 
costs and the versatility of the welding machines on which they are 
utilized. The said "Z" shaped guides are, in fact, difficult to make 
because the bottom of the slots therein is of a minimum cross section (for 
example, the width can be in the region of one millimeter) yet has to be 
completely minus any unevenness. 
Furthermore, the said guides are fragile at the very point, namely between 
the two slots, where the gap between the two ends to be overlapped is 
extremely small. No modification can be made to the said gap since it is a 
welding exigency. 
Also, it has been seen that wear in the bottom of the said slots alters the 
overlap value for the two ends right along the guide, with the consequent 
formation of cans and the like which, on account of the welding operation, 
are substantially imperfect. 
Once set, the extent of the overlap between the two ends of a can to be 
formed cannot be modified. When the requirements undergo a variation, the 
only possible solution is to replace the "Z" shaped guide with another 
guide of a different cross section area. 
SUMMARY OF THE INVENTION 
The technical task forming the basis of the invention is, in view of what 
has been stated above, to devise a device for positioning metal ends to be 
lap welded one to the other with which it is possible to virtually 
overcome the aforementioned problems, so as to enable cans, drums, and 
similar containers to be formed in a precise, inexpensive and versatile 
way out of metal strips. 
The requirements outlined above are substantially satisfied with the device 
according to the invention for positioning metal ends to be lap welded one 
to the other, comprising two slots for housing two of the said ends to be 
welded and for defining the position for the welding of the said ends, 
wherein the said slots are defined by at least one pair of guide blocks 
that are substantially opposed and are shaped in the form of a step in 
such a way that each constitutes means of abutment for one of the said 
ends and lower, or alternatively upper, supporting surfaces for both of 
the said ends. 
Advantageously, at least one block in the said at least one pair of blocks 
can be set with respect to the other.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
With reference to the said figures, the device according to the invention 
is fitted to a seam welder 1, one arm 2 of which can be seen in FIG. 1. 
The said arm 2 ends in the region of a pair of rollers 3 and 4, in between 
which the current required for welding circulates. The device itself, 
shown globally at 5, is virtually placed in alignment with the tangent 
common to the two rollers 3 and 4. 
In particular, provision is made in the device 5 for three pairs of guide 
blocks 6, placed consecutively one with respect to the other. The first 
two pairs of guide blocks 6 are stationary, while the third pair, 
immediately adjacent to the rollers 3 and 4, are provided with blocks that 
can be set one with respect to the other. 
On account of the transverse shape thereof, the said third pair of guide 
blocks 6 can be seen in FIGS. 2 to 4. 
It is obvious from the above mentioned figures that each block 6 positioned 
in proximity of the rollers 3 and 4 is shaped in the form of a step, and 
that the two blocks in the pair are placed, one at the side of the other, 
in opposed positions, in such a way as to define slots 7 in which the ends 
of the strips to be welded are inserted. 
FIG. 2 shows specifically that each block 6 is rendered integral, through 
screws 8, with a corresponding support 9 belonging to the arm 2. 
Furthermore, on account of the step shape thereof, each block 6 forms a 
stop and abutment means 10 for one end to be welded, and lower, or 
alternatively, upper supporting surfaces 11 for both of the ends to be 
welded. The supporting surfaces 11 extend in opposite directions, from the 
upper and lower extremities of the abutment means 10, and are partially 
curved so as to define slots 7 with a bevel to encourage the insertion 
therein of the strips. 
The gap D.sub.1 in between the blocks 6, in a direction parallel to the 
abutment means or walls 10, determines the spacing between the ends of the 
strips to be welded, while the gap D.sub.2 in between the abutment means 
or walls 10, parallel one to the other, determines the extent of the 
overlap, one with respect to the other, of the said ends to be welded. 
An original feature is that the said blocks 6 can be positioned, one with 
respect to the other, in such a way as to vary at will, within 
predetermined limits, both the extent of the overlap of the ends, one with 
respect to the other, of the strips to be welded, and the spacing there in 
between. 
This technical characteristic is achieved with the means depicted in FIGS. 
3 and 4 which, in practice, are defined by adjustable spacer screws 12 
(FIG. 3) for setting the extent of the overlap of the said ends, and by 
eccentric connection elements 13 for regulating the spacing between the 
said ends. The adjustable spacer screws 12 act in opposition to the screws 
8, while the eccentric connection elements 13, that vary the position in 
height of the blocks 6 to suit the angular position of these, are intended 
to be in substitution of the screws 8. In the specific case illustrated, 
only the upper block 6 is provided with adjustable spacer screws 12, while 
both of the blocks 6 adjacent to the rollers 3 and 4 are provided with 
eccentric connection elements 13. 
The device according to the invention can, however, be so constructed as to 
have each pair of blocks 6 adjustable, and the relevant choice depends 
solely on the working requirements. 
Once mounted, the blocks 6 form, one with respect to the other, the slots 7 
inside which the ends of the strips to be welded are positioned with 
precision, eventually with the possibility of varying the extent of the 
overlap of the said ends, or the of the spacing there in between. 
The setting of the blocks 6 necessitates a simple rotation to tighten or 
loosen the locking screws 8, the adjustable spacer screws 12 and the 
eccentric connection elements 13. 
Thanks to this expedient, it is particularly easy to construct the device 
for positioning the said ends since the machining of narrow, precise, 
slots is no longer necessary. Furthermore, the blocks according to the 
invention are robust and thoroughly reliable, even when the slots 7 are 
very close to one another. 
Finally, wear on the blocks does not influence either the dimensions or the 
finish of the cans to be formed by welding, and this is because the extent 
of the overlap, one with respect to the other, of the ends to be welded 
can be returned, through a simple adjustment, to the initial value. In the 
event of a variation in the product to be formed, the extent of the 
overlap, one with respect to the other, of the said ends can be modified, 
even to a considerable extent, without it being necessary to replace the 
blocks. 
The invention, as envisaged in the foregoing text, is liable to undergo 
numerous modifications and variants, all of which falling within the 
conceptual framework thereof. For example, the means provided to effect 
the setting of the said blocks can be of any type. 
Also, all parts may be substituted with others that are technically 
equivalent, while the materials used and the shapes and sizes thereof, may 
be any depending on the requirements.