"Wire straightening device for a welding or brazing plant"

[0001] The present invention relates to the field of wire welding or brazing plants, and particularly relates to a wire straightening device adapted to straighten the welding wire wound in coils and stored in a drum.

[0002] As it is known, some welding or brazing plants use a welding wire stored in a drum. The wire is progressively extracted from the drum and fed to the welding apparatus, for example a welding torch moved by a robot.

[0003] A problem with these welding plants is that the welding wire contained in the drum is wound in coils and this geometric arrangement of the wire alters the structure of the wire itself and therefore remains "memorized" even when the wire is extracted from the drum and fed to the welding apparatus.

[0004] In practice, the wire end subjected to the welding operation does not take a perfectly constant welding position but varies in a sinusoidal manner. Therefore, the welding line also takes a sinusoidal pattern.

[0005] In order to try to obviate such a drawback, wire traction devices have been suggested which try to straighten the wire in addition to feeding the wire from the drum to the welding apparatus. [0006] In one embodiment, such known traction devices employ motorized opposing rollers. The rollers, driven by an electric motor so as to rotate in opposite direction, act in traction on the wire extracting it from the drum and, by compressing the wire therebetween, cause a sort of stretching or flattening thereof which reduces the tendency to remain in the coiled configuration.

[0007] Such devices, however, not only are unable to completely straighten the welding wire but, since they compress it between the rollers, cause a permanent deformation of the section, with negative consequences on the welding process.

[0008] Furthermore, due to dust, dirt or other external agents which may deposit on the conveying rollers, the welding wire surface is susceptible of alterations which may negatively reflect on the welding process.

[0009] In other embodiments, the drum is closed at the top by a lid (usually referred to as "pay off") equipped with a wire straightening tube in which a plurality of metal rollers is accommodated, through which the wire exiting the drum is passed.

[0010] Such a straightening tube, in addition to being complex and expensive, does not completely eliminate the wire memory.

[0011] It is the object of the present invention to suggest a wire straightening device capable of obviating the drawbacks and overcoming the limitations of the prior art devices mentioned above.

[0012] Said object is achieved by a wire straightening device according to claim 1.

[0013] The dependent claims describe preferred embodiments of the invention.

[0014] The features and advantages of the wire straightening device according to the invention will however become apparent from the following description of preferred embodiments, given by way of indicative and non-liniting example, with reference to the accompanying drawings, in which:

[0015] - Figure 1 schematically shows a drum in which a welding wire wound in coils is stored and a wire straightening device according to the invention;

[0016] - Figure 2 shows the wire straightening device according to the invention applied to a drum, in a practical embodiment; and

[0017] - Figures 3, 3a and 3b are a perspective view, a front view, and a side view of the wire straightening device according to the invention alone.

[0018] In said drawings, 100 indicates as a whole a wire straightening device according to the invention.

[0019] The wire straightening device 100 is particularly adapted to be employed in a welding or brazing plant using a welding wire 1 wound in coils 1' and stored in a drum 2.

[0020] The wire straightening device 100 is positioned downstream of drum 2 and is adapted to feed wire 1 to a welding apparatus (not shown) .

[0021] Figure 1 schematically shows a drum 2, generally cylindrical in shape, in which a welding wire 1 wound in coils 1' is placed. The coils 1' of wire 1 are kept in an orderly overlapping relationship allowing a correct exit of the wire from the drum by means of a wire guide device 3, usually also referred to as "pay off", for example of the type described in patent publication DE202011108769. Such a wire guide device 3 generally is conical in shape and comprises a base resting on the coils 1' of the wire and a rotating tubular element guiding the wire of the upper coil towards an outlet opening 2' of drum 2.

[0022] In one embodiment, such an outlet opening 2' is obtained in a lid 4 which closes off drum 2.

[0023] In a general embodiment, with reference to Figures 2 and 3, the wire straightening device 100 comprises a wire conveying assembly 10 and a straightening assembly 50.

[0024] The two assemblies are arranged in cascade, i.e. in series, in the wire feeding direction. The straightening assembly 50 may be positioned downstream or upstream of the wire conveying assembly 10.

[0025] In a preferred embodiment, the two assemblies are mutually integral, so as to form a single assembly placed between the drum 2 and the welding apparatus. For example, as described below in more detail, the two mutually integral assemblies are supported by a structure extending immediately above drum 2, for example by an upper crosspiece of a movable frame on which drum 2 is placed.

[0026] The wire conveying assembly 10 comprises two opposing conveying belts 12, 12' . The two conveying belts form two respective rectilinear belt portions 14 facing each other so as to receive and move wire 1 exiting drum 2.

[0027] In other words, each conveying belt 12; 12' is returned by respective tensioning belt rollers 13; 13' so as to form a closed loop. One of such tensioning belt rollers 13, 13' is a motor roller adapted to cause the rotation of the respective conveying belt 12; 12' .

[0028] In one embodiment, the motor roller is fitted on a shaft of an actuator 16, for example a pneumatic or electric actuator.

[0029] In one embodiment, each conveying belt 12; 12' is returned on three tensioning belt rollers 13; 13' .

[0030] In one embodiment, the extension of the rectilinear portion 14 is at least equal to the diameter of the tensioning belt rollers 13; 13', i.e. is of the order of tens or, preferably, hundreds of mm.

[0031] In fact, as compared to the conveying rollers of the prior art which, having a punctual contact with the welding wire, exert a high specific pressure on the wire itself, the conveying belts 12; 12', having a much wider contact surface with the wire than the rollers, exert a much lesser specific pressure.

[0032] The welding wire 1 is therefore not deformed by passing between the conveying belts 12; 12' , and even the possible sediment of dust or other external agents on the belts has no effect on the wire surface.

[0033] Furthermore, this wire handling without effects of deformation or alteration of the wire is facilitated by the fact that the conveying belts 12; 12' may be made of a material softer than that of which the conveying rollers are usually made.

[0034] In one embodiment, the tensioning belt rollers 13; 13' of the two opposing conveying belts 12; 12' are supported by respective conveying plates 120; 120' mutually separable, for example by means of micrometer screws 122, as a function of the diameter of the welding wire 1.

[0035] The straightening assembly 50, which, as mentioned above, may be positioned downstream or upstream of the wire conveying assembly 10, comprises at least two straightening roller units 52, 52a arranged in series along the wire feeding direction.

[0036] Each straightening unit 52; 52a comprises at least two opposing straightening rollers 54, 54'; 54a, 54a' between which the welding wire 1 is passed being moved by the wire conveying assembly 10.

[0037] The straightening rollers 54, 54' of a straightening unit 52 are oriented perpendicularly with respect to the straightening rollers 54a, 54a' of at least another straightening unit 52a. All straightening rollers 54, 54' ; 54a, 54a' have, however, the respective rotation axes perpendicular to the feeding direction of the welding wire 1, i.e. perpendicular to the rectilinear portions 14 of the conveying belts 12, 12' .

[0038] With such an arrangement of the straightening rollers, it has been experienced that the memory of the welding wire 1 exiting drum 2 is completely eliminated. The welding wire 1 exiting the straightening assembly 54 is therefore completely neutral.

[0039] In one embodiment, the straightening rollers 54, 54' ; 5a, 54a' are idly mounted to a respective roller support plate 56, 56a. Therefore, the straightening rollers actually carry out only the welding wire 1 straightening function. Since the wire does not exert any torque on the wire, it is straightened but the section thereof is not deformed nor the surface thereof is altered.

[0040] In accordance with one embodiment, each straightening unit 52, 52a is provided with at least five straightening rollers 54, 54'; 5a, 54a': at least two first rollers 54; 54a placed side-by-side along the wire feeding direction opposing and staggered with respect to at least three second rollers 54'; 54a' placed side-by- side along the wire feeding direction.

[0041] In one embodiment, the straightening rollers of each straightening unit are seven in number: three first rollers 54; 54a placed side-by-side along the wire feeding direction opposing and staggered with respect to four second rollers 54' ; 54a' placed side-by-side along the wire feeding direction.

[0042] In one embodiment, also the distance between the first and the second straightening rollers may be adjusted as a function of the diameter of the welding wire 1.

[0043] In one embodiment shown in Figures 2 and 2a, drum 2 is positioned on a movable trailer 60. The movable trailer 60 is provided with a frame 62 comprising a top crosspiece 64 extending above the opening 2' of drum 2. The wire straightening device 100 according to the invention is secured to a device support bracket 110, for example movable along and/or tilting with respect to the top crosspiece 64.

[0044] It should be noted that since the rotating tubular element guiding the wire out of drum 2 is not to carry out any wire straightening function, it may be made with a simple tube having only the guiding and wire protection function. Such a tube may extend up to the inlet of the wire straightening device 100.

[0045] Therefore, the present invention further relates to a storage and feeding assembly for a welding wire 1, comprising a drum 2 adapted to contain the welding wire 1 wound in coils 1' , welding wire guiding means associated with drum 2 and adapted to guide the welding wire 1 towards an outlet opening 2' of the wire from the drum, a support frame 62 comprising a top crosspiece 64 extending above the outlet opening 2', and a wire straightening device 100 supported by the top crosspiece 64.

[0046] Those skilled in the art may make changes and adaptations to the embodiments of the wire straightening device 100 according to the invention or may replace elements with others functionally equivalent in order to meet contingent needs without departing from the scope of the following claims. Each of the features described as belonging to a possible embodiment may be achieved irrespective of the other embodiments described.