Electric heating – Metal heating – Nonatmospheric environment at hot spot
Reexamination Certificate
2001-10-30
2003-08-26
Elve, M. Alexandra (Department: 1725)
Electric heating
Metal heating
Nonatmospheric environment at hot spot
C219S075000, C228S247000, C228S256000, C228S041000
Reexamination Certificate
active
06610958
ABSTRACT:
FIELD OF INVENTION
This invention pertains generally to welding systems, and more particularly to an apparatus and method for feeding weld wire to a welding tip of a welding torch in a welding system
BACKGROUND
Welding wire feed apparatuses, commonly known as wirefeeders, are widely used in a automated and semi-automated welding operations to feed filler wire to a molten pool on a workpiece being heated by a welding torch on a welding system to form a weld.
A conventional, prior art wirefeeder will now be described with reference to FIG.
1
.
FIG. 1
is a diagrammatic illustration showing a cross-sectional side view of a welding system
10
having a conventional wirefeeder
12
. Referring to
FIG. 1
, a conventional wirefeeder
12
includes a filler wire supply
14
, such as a spool, on which filler wire
16
is stored, a wirefeed mechanism
18
mounted to the welding system
10
, a wire liner or conduit
20
through which the filler wire is passed from the wirefeed mechanism to an adjustment mechanism
22
attached to a welding torch
24
on the welding system. The adjustment mechanism
22
positions a wire guide
26
through which the filler wire
16
is passed to location or point near to the welding torch
24
. Typically, the wirefeed mechanism
18
includes an electric motor
28
driving one or more gears or drive wheels (not shown) that engage the filler wire
16
forcing it through the conduit
20
to the adjustment mechanism
22
. The wirefeed mechanism
18
can be operated manually by an operator, or automatically by a controller (not shown) to synchronize feeding of the filler wire
16
to movement of a workpiece (not shown) being welded on the welding system
10
.
A disadvantage of conventional wirefeeders
12
is that complicated and cumbersome adjustment mechanisms
22
make it difficult to precisely position the wire guide
26
in relation to the welding torch
24
or workpiece. One commonly used adjustment mechanism
22
involves the use of a number of interconnected dovetail slides or sliding members repositioned by thumbscrews
28
. A first dovetail slide allows the wire guide
26
to be moved up and down vertically in relation to the welding torch
24
. A second dovetail slide depending from the first allows the wire guide
26
to be moved horizontally, and a third dovetail slide depending from the second allows the wire guide to be moved in and out relative to the welding torch
24
. Because the slides are interconnected, adjustment of any one of them can necessitate repositioning of the others, which in turn can lead to the need to reposition the first slide and so on. The adjustment procedure is often made even more difficult by the use of fasteners on the slides which require a wrench, screwdriver or other tool to tighten.
A related problem with the adjustment mechanism
22
of conventional wirefeeders
12
is that it is often difficult or impossible to efficiently or subtly adjust the angle at which the filler wire enters the molten pool on the workpiece, commonly known as the wire entry angle. The entry angle is important because if the filler wire is fed into the molten pool too low, i.e., at too shallow an angle relative to the surface of the workpiece, it can hit the workpiece before entering the molten pool, causing the workpiece to wobble, or the filler wire to stick to the surface of the workpiece. On the other hand, if the wire comes in too high, i.e., at too large an angle relative to the surface of the workpiece, the heat from the welding torch can cause the end of filler wire “ball up” or burn back without contacting the molten pool. For example, the entry angle for an automated Gas Tungsten Arc Welding (GTAW) welding operations is from about 14 to about 40 degrees relative to the horizontal plane. However, possible entry angles are often constrained by a number of circumstances including workpiece configuration, welding system or process setup, and interference with tooling used to position the workpeice. This is particularly a problem with conventional wirefeeders
12
, which are generally designed to provide a single, fixed entry angle determined by the mounting or attachment of the wire guide
26
to the adjustment mechanism
22
that can be changed little if at all, and then only with great difficulty.
Yet another problem with conventional wirefeeders
12
is that the weight of the adjustment mechanism
22
and the wireguide
26
, which is not in-line with a centerline of a main body or support structure of the welding system
10
, often results in wobbling during the welding operations leading to filler wire deposition irregularities. These irregularities are magnified in a multi-pass buildup processes in which as the filler wire is welded to that deposited on a previous pass to form a flange or knife edge of deposited metal. This situation is exacerbated by adjustment mechanisms, such as the dovetail slides (not shown), in which the brackets and interconnections of components of the adjustment mechanism project a significant distance from the centerline of the main body of the welding system
10
. Moreover, conventional prior art wirefeeders typically encompass a single contiguous adjustment mechanism
22
for both fine and course adjustments making fine adjustments difficult. The above is true of all welding operations, including only those in which the welding torch is moved over the workpiece and those in which the workpiece moved under the welding torch.
In addition to the difficulties with the adjustment mechanism and procedure, another significant problem with conventional wirefeeders is the complex and circuitous path the filler wire must take within the conduit from the wirefeed mechanism to the adjustment mechanism. This complex and circuitous path causes binding or constriction of filler wire within the conduit resulting in non-uniform feeding of the filler wire and leading to deposition inconsistencies in the weld. This is particularly a problem for wirefeeders in which the wirefeed mechanism uses gears to engage and drive the filler wire. The gears score the surface of the filler wire producing sharp or rough edges that catch on the inner surface of the conduit, resulting in sharp or rough edges on the inner surface of the conduit that further impede movement of the filler wire through the conduit. One approach to dealing with this shortcoming in conventional wirefeeders involves the regular replacement of the conduit. However, this is not a wholly satisfactory solution since, in addition to the expense and lost operating time of the welding system, it is generally sometime before need to replace the conduit is recognized, and in the meantime binding of the filler wire will lead to welds with deposition inconsistencies necessitating costly reworking or replacement of numerous workpieces.
A related problem involves the juncture between the conduit and the wire guide. The filler wire supply is generally not in-line with the wire guide and because the wire guide is moved during the adjustment procedure prior to the welding operation, if not during the welding operation itself, the conduit can form a sharp bend at this point leading to binding or constriction of filler wire within the conduit.
Accordingly, there is a need for a wirefeeder and method for feeding filler wire to a welding tip of a welding torch in a welding system that reduces or eliminates binding or constriction of the filler wire whereby deposition inconsistencies are reduced or eliminated. There is a need for a wirefeeder and method that reduce or eliminate wobbling by the wirefeeder whereby irregularities in welding are reduced or eliminated. There is yet a further need for a wirefeeder and method that provides a straightforward adjustment mechanism for easy positioning of the wire guide, including easy adjustment of wirefeed entry angles over a wide range of angles.
SUMMARY
The present invention provides an apparatus and method for feeding welding or filler wire to a welding tip of a welding torch in a welding system.
In one aspect, the invention is directe
Dorsey & Whitney LLP
McHenry Kevin
Precision Welding Technologies, Inc.
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