Patent Description:
When welding, it is often desirable to increase the width of the weld bead or increase the length of the weld puddle during welding. There can be many different reasons for this desire, which are well known in the welding industry. For example, it may be desirable to elongate the weld puddle to keep the weld and filler metals molten for a longer period of time so as to reduce porosity. That is, if the weld puddle is molten for a longer period of time there is more time for harmful gases to escape the weld bead before the bead solidifies. Further, it may desirable to increase the width of a weld bead so as to cover wider weld gap or to increase a wire deposition rate. In both cases, it is common to use an increased electrode diameter. The increased diameter will result in both an elongated and widened weld puddle, even though it may be only desired to increase the width or the length of the weld puddle, but not both. However, this is not without its disadvantages. Specifically, because a larger electrode is employed more energy is needed in the welding arc to facilitate proper welding. This increase in energy causes an increase in heat input into the weld and will result in the use of more energy in the welding operation, because of the larger diameter of the electrode used. Further, it may create a weld bead profile or cross-section that is not ideal for certain mechanical applications. Rather than increasing the diameter of the electrode, it may be desirable to use two smaller electrodes simultaneously.

The following summary presents a simplified summary in order to provide a basic understanding of some aspects of the devices, systems and/or methods discussed herein. This summary is not an extensive overview of the devices, systems and/or methods discussed herein. It is not intended to identify critical elements or to delineate the scope of such devices, systems and/or methods. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

In accordance with of the present invention, provided is a welding or additive manufacturing wire drive system as defined in claim <NUM>. The system includes a welding wire spool, a first drive roll, and a second drive roll. One or both of the first drive roll and the second drive roll has a circumferential groove. The system includes a first welding wire, drawn from the welding wire spool, and located between the first drive roll and the second drive roll in the circumferential groove, and a second welding wire, drawn from the welding wire spool, and located between the first drive roll and the second drive roll in the circumferential groove. The first welding wire contacts the second welding wire between the first drive roll and the second drive roll. The first welding wire further contacts a first sidewall portion of the circumferential groove, and the second welding wire further contacts a second sidewall portion of the circumferential groove. Both of the first welding wire and the second welding wire are radially offset from a central portion of the circumferential groove.

Further embodiments are given in the ensuing description, drawings and claims.

The foregoing and other aspects of the invention will become apparent to those skilled in the art to which the invention relates upon reading the following description with reference to the accompanying drawings, in which:.

Exemplary embodiments of the invention will now be described below by reference to the attached Figures. The described exemplary embodiments are intended to assist the understanding of the invention, and are not intended to limit the scope of the invention in any way.

Embodiments of the present invention are described herein in the context of a welding system. Example welding systems include gas metal arc welding (GMAW) systems, submerged arc welding (SAW) systems, flux-cored arc welding (FCAW) systems, metal-cored arc welding (MCAW) systems, and the like. Further, while the electrodes described herein can be solid electrodes, embodiments of the present invention are not limited to the use of solid electrodes. For example, flux-cored electrodes and metal-cored electrodes can also be used without departing from the spirit or scope of the present invention. Further, embodiments of the present invention can also be used in manual, semi-automatic and robotic welding operations. Because such systems are well known, they will not be described in detail herein.

Embodiments of the present invention will be discussed in the context of a welding system. However, in addition to welding operations, embodiments can be used in additive manufacturing processes and other welding-type processes involving driven wire electrodes (e.g., hardfacing).

Turning now to the Figures, <FIG> depicts an exemplary embodiment of a welding system <NUM>. The welding system <NUM> contains a welding power source or power supply <NUM> which is coupled to both a welding torch <NUM> and a wire feeder <NUM>. The power supply <NUM> can be any known type of welding power source capable of delivering welding current and welding waveforms, for example, pulse spray, STT and/or short arc type welding waveforms. Because the construction, design and operation of such power supplies are well known, they need not be described in detail herein. It is also noted that welding power can be supplied by more than one power supply at the same time - again the operation of such systems are known. The power supply <NUM> can include a controller <NUM> which is coupled to a user interface to allow a user to input control or welding parameters for the welding operation. The controller <NUM> can have a processor, CPU, memory etc. to be used to control the operation of the welding process and the generation of welding waveforms. The torch <NUM> can be constructed similar to known manual, semi-automatic or robotic welding torches and can be of a straight or gooseneck type. The wire feeder <NUM> draws wire electrodes E1 and E2 from electrode sources <NUM> and <NUM>, respectively, which can be of any known type, such as reels, spools, containers or the like. The wire feeder <NUM> employs drive rolls <NUM> to draw the electrodes or welding wires E1 and E2 and push or pull the electrodes to the torch <NUM>. Details of the drive rolls <NUM> are discussed further below. The drive rolls <NUM> and wire feeder <NUM> are configured for a dual electrode welding operation. That is, they supply both electrodes E1 and E2 simultaneously to the torch <NUM> for creating an arc and welding the workpiece W. As shown, the wire feeder <NUM> is operatively connected to the power source <NUM> consistent with known configurations of welding operations.

Once driven by the drive rolls <NUM>, the electrodes E1 and E2 can be passed through a liner <NUM> to deliver the electrodes E1 and E2 to the torch <NUM>. The liner <NUM> is appropriately sized to allow for the passage of the electrodes E1 and E2 to the torch <NUM>. For example, for two <NUM> inch diameter electrodes, a standard <NUM> inch diameter liner <NUM> (which is typically used for a single <NUM> inch diameter electrode) can be used with no modification.

In certain embodiments, the wire electrodes E1, E2 can have different diameters. That is, embodiments of the present invention can use an electrode of a first, larger, diameter and an electrode of a second, smaller, diameter. In such an embodiment, it may be possible to more conveniently weld two workpieces of different thicknesses. For example, the larger electrode can be oriented to the larger workpiece while the smaller electrode can be oriented to the smaller workpiece. Further, embodiments of the present invention can be used for many different types of welding operations including, but not limited to, GMAW, SAW, FCAW, and MCAW. Additionally, embodiments of the present invention can be utilized with different electrode types. For example, it is contemplated that a cored electrode (e.g., flux-cored or metal-cored) can be coupled with a non-cored or solid electrode. Further, electrodes of differing compositions can be used to achieve desired weld properties and composition of the final weld bead. Two different, but compatible, consumables can be combined to create a desired weld joint. For example, compatible consumables such as hardfacing wires, stainless wires, nickel alloys and steel wires of different composition can be combined. As one specific example a mild steel wire can be combined with an overalloyed wire to make a <NUM> stainless steel composition. This can be advantageous when a single consumable of the type desired does not have desirable weld properties. For example, some consumables for specialized welding provide the desired weld chemistry but are extremely difficult to use and have difficulty providing a satisfactory weld. However, embodiments of the present invention allow for the use of two consumables that are easier to weld with to be combined to create the desired weld chemistry. Embodiments of the present invention can be used to create an alloy/deposit chemistry that is not otherwise commercially available, or otherwise very expensive to manufacture. Thus, two different consumables can be used to obviate the need for an expensive or unavailable consumable. Further, embodiments can be used to create a diluted alloy. For example, a first welding wire could be a common, inexpensive alloy and a second welding wire could be a specialty wire. The resulting deposit would be the average of the two wires, mixed well in the formation of a molten droplet, at the lower average cost of the two wires, over an expensive specialty wire. Further, in some applications, the desired deposit could be unavailable due to the lack of appropriate consumable chemistry, but could be achieved by mixing two standard alloy wires, mixed within the molten droplet and deposited as a single droplet. Further, in some applications, such as the application of wear resistance metals, the desired deposit may be a combination of tungsten carbide particles from one wire and chrome carbide particles from another. Still in another application, a larger wire housing larger particles within is mixed with a smaller wire containing fewer particles or smaller particles, to deposit a mixture of the two wires. Here the expected contribution from each of the wires is proportional to the size of wire. Further, although exemplary embodiments are discussed herein utilizing two wire electrodes simultaneously, other embodiments of the present invention can utilize more than two electrodes. For example, it is contemplated that a three or more electrode configuration can be utilized consistent with the descriptions and discussions set forth herein.

<FIG> provides a perspective view of the welding system <NUM>. The wire feeder <NUM> comprises drive rolls for conveying wire electrodes E1, E2 from electrode sources <NUM>, <NUM>, for use in a particular application. The wire electrodes E1, E2, may be drawn continuously from a reel, spool, or container (e.g., a box or a drum), and delivered to the workpiece W, which in the current embodiment is a weldment. The wire feeder <NUM> may include a drive assembly that utilizes power from one or more locomotive devices, such as an electric motor, that drive the wire electrodes E1, E2 to the application work site or workpiece W.

The welding power supply <NUM> may receive electrical input power from an outside source (e.g., utility power), that is directed to an onboard transformer and processor-controlled inverter or chopper circuitry, not depicted in the figures. Output from the power supply <NUM> may be provided through welding output terminals <NUM> or studs of the welding power supply. A welding gun or torch <NUM> and wire conduit may be electrically connected to the welding power supply <NUM> through the welding wire feeder <NUM> for delivering welding current to the workpiece W in a manner known in the art. It follows that the welding wires E1, E2 are fed through the torch <NUM> and metered out, i.e. dispensed, at the discretion of the application and/or end user in any manner suitable for conducting the welding process. It is noted that the electrodes E1, E2 conduct electricity for establishing a welding arc, wherein the electrodes are conveyed to the workpiece W having a voltage potential equal to or approximately equal to the output voltage of the welding power supply <NUM>, which may be substantially greater than ground.

Different modes of conveying the wire electrodes E1, E2 are known in the art, an example of which includes pushing the electrodes to the torch <NUM> via power or torque provided by the locomotive device. Other modes of conveying the electrodes include push/pull modes that utilize multiple locomotive devices. The electrodes E1, E2 are delivered to the torch <NUM>, which may have a trigger or other activation mechanism for dispensing the electrodes at the user's discretion. At times, it may be necessary to deliver the electrodes E1, E2 at varying rates of feed. Therefore, the locomotive device has an output that is adjustable for varying the wire feed speed (WFS) of the electrodes E1, E2. In particular, a drive motor of the wire feeder <NUM> may be a variable speed motor to adjust the WFS.

A drive motor <NUM> is shown in <FIG>. The wire feeder <NUM> and/or drive motor(s) <NUM> may draw operating power from the welding power supply <NUM>, or an altogether separate power source. Still any manner of providing power to operate the welding wire feeder <NUM> and/or the drive motors <NUM> may be chosen with sound engineering judgment as is appropriate for use with the embodiments of the present invention.

Referring to <FIG> and <FIG>, the welding wire feeder <NUM> may include a drive assembly, or drive roll assembly. As mentioned above, the drive motor <NUM>, also called a wire feeder motor, delivers power, i.e. torque, to convey the first and second welding wires E1, E2 through the wire feeder and to the torch <NUM> and subsequently to the workpiece W. Drive rolls <NUM> are included that grip the welding wires E1, E2 for pushing or pulling the welding wires in the appropriate direction, i.e. toward the workpiece W. Sets of drive rolls <NUM> are vertically aligned and have corresponding aligned annular or circumferential grooves through which the wending wires E1, E2 pass simultaneously. It can be seen that the vertically-aligned sets of drive rolls <NUM> rotate in opposite directions to drive the welding wires E1, E2 through the wire feeder <NUM>. For example, in <FIG>, the upper drive rolls <NUM> rotate clockwise and the lower drive rolls rotate counterclockwise. The drive rolls <NUM> may be cylindrical in configuration, or more specifically disk-shaped, although the particular configuration should not be construed as limiting. The surface, i.e. the outer circumference, of the drive rolls <NUM> may be comprised of a sufficiently hardened material, like steel, that is durable and suitable for gripping the welding wires E1, E2. As shown, the drive rolls <NUM> may be disposed in pairs along the wire trajectory with each drive roll of the pair being supported on opposing sides of the welding wires E1, E2, such that respective outer circumferential portions of the rolls engage opposite sides of the wires (e.g., from above and below). It is noted that the central axes of respective drive rolls <NUM> extend substantially parallel with one another and generally transverse to the trajectory of the welding wires E1, E1.

The wire feeder <NUM> can include a biasing member that biases the vertically-aligned sets of drive rolls <NUM> toward one another. The biasing member sets the clamping force or compression that the drive rolls <NUM> apply to the welding wires E1, E2. For example, the wire feeder <NUM> can include biasing springs <NUM> that apply a bias force to one or more drive rolls <NUM> to set the compression that the drive rolls apply to the welding wires E1, E2. In the example embodiment of <FIG>, the biasing springs <NUM> are mounted to an adjusting rod <NUM> that can be moved inward and outward to adjust the compression of the biasing springs <NUM>. The force of the biasing springs <NUM> is transferred to the upper drive rolls <NUM> via pivoting levers <NUM>. As noted above, the vertically-aligned sets of drive rolls <NUM> have corresponding aligned annular or circumferential grooves through which the wending wires E1, E2 pass simultaneously. That is, the welding wires E1, E2 are located together in the grooves of an upper drive roll and a lower drive roll. The welding wires E1, E2 are squeezed or compressed within the grooves by the bias force applied by the biasing springs <NUM> to the drive rolls <NUM>. As will be explained further below, the welding wires E1, E2 are made to contact each other within the grooves when squeezed by the drive rolls <NUM>. In addition to an upward/downward compressive force applied to the welding wires E1, E2, a sideways compressive force is also applied to the welding wires E1, E2 to force them together inside of the grooves. The sideways compressive force is provided through the shape of the sidewalls of the grooves.

Further details regarding the structure of welding wire feeders can be found in <CIT> and <CIT>.

<FIG> provides a perspective view of the welding system <NUM> having a single electrode source <NUM> (e.g. a single welding wire spool, according to the present invention) that provides both wire electrodes E1, E2. In <FIG>, the wire electrodes E1, E2 are wound on the same spool <NUM> and are drawn simultaneously therefrom by the wire feeder <NUM>. An advantage of providing both wire electrodes E2, E2 on a single spool <NUM> is that existing welding systems can be configured to perform dual wire welding with minimal modifications. Existing welding systems would typically have a single spindle for one welding wire spool. The dual wire spool shown in <FIG> can be mounted on such a system. By replacing the drive rolls in the wire feeder <NUM> with drive rolls configured for dual wire feeding, and replacing the contact tip in the torch <NUM> with a contact tip configured for dual wire welding, a conventional single wire welding system can be readily converted to dual wire welding. As discussed above, the electrodes E1, E2 can have the same composition and diameter, or have different compositions and/or diameters.

<FIG> shows the spool <NUM> without the electrodes wound thereon, and <FIG> shows the spool with the electrodes E1, E2. The spool <NUM> has a central barrel <NUM> located between end flanges <NUM>, <NUM>, and the wire electrodes E1, E2 are both wound on the central barrel between the end flanges. <FIG> shows a further example spool <NUM> that has an annular divider <NUM> located along the central barrel. The annular divider is located between the windings of the electrodes E1, E2 to separate them.

<FIG> illustrate an example drive roll <NUM>. The drive roll has a central bore. The inner surface of the bore can include contoured recesses <NUM> for receiving projections on a driving mechanism, such as a drive gear, to transfer drive torque to the drive roll <NUM>. The drive roll <NUM> includes one or more annular or circumferential wire receiving grooves <NUM>, <NUM>. The wire receiving grooves <NUM>, <NUM> are spaced axially along the circumference of the drive roll <NUM>. The wire receiving grooves <NUM>, <NUM> are designed to receive two welding wires. Example standard welding wire diameters for use with the drive rolls <NUM> include <NUM> inches, <NUM> inches, <NUM> inches, <NUM> inches, etc. The wire receiving grooves <NUM>, <NUM> can have the same width and depth as each other, or have different widths and depths to accommodate different sizes or combinations of dual welding wires. If the wire receiving grooves <NUM>, <NUM> each have the same width and depth, then the drive roll <NUM> can be reused when one groove is worn out by simply flipping the drive roll over and reinstalling it on the wire feeder. The wire receiving grooves <NUM>, <NUM> can be configured to simultaneously drive two wires having the same diameter, or two wires having different diameters. In <FIG>, the wire receiving grooves <NUM>, <NUM> have a trapezoidal shape with straight, angled or inwardly-tapered sidewalls and a flat base extending between the sidewalls. However, the wire receiving grooves <NUM>, <NUM> could have other shapes besides a trapezoidal shape, such as having a curved, concave groove base for example. In certain embodiments, the grooves <NUM>, <NUM> can include knurling or other frictional surface treatments to help grip the welding wires.

<FIG> show partial cross sections of example drive rolls <NUM> as they would be mounted on a wire feeder for supplying dual welding wires. The drive rolls <NUM> are biased together to provide a clamping force on the first E1 and the second E2 welding wires. The welding wires E1, E2 are both located in the annular grooves of the upper and lower drive rolls <NUM>. The annular grooves are aligned and can have a trapezoidal shape. In <FIG>, the trapezoidal shape is an isosceles trapezoid formed by an inner sidewall <NUM>, an outer sidewall <NUM>, and a groove base <NUM> extending between the sidewalls. The isosceles trapezoidal shape is inverted as a cross-sectional recess from the outer circumferential surface of the drive rolls <NUM>.

Due to the bias force applied to the drive rolls <NUM>, the welding wires E1, E2 are clamped in the annular grooves between upper and lower sidewalls <NUM>, <NUM> forming the grooves and the neighboring welding wire. The welding wires E1, E2 are stably held via three points of contact within the annular grooves. This clamping system can allow both wires to be fed through the wire feeder in a consistent manner. The two welding wires E1, E2 support each other during feeding and pull each other along via friction. Because the inner <NUM> and outer <NUM> sidewalls of the annular grooves are angled, they apply both vertical and horizontal clamping forces on the welding wires E1, E2. The horizontal clamping force pushes the welding wires E1, E2 together, causing them to contact each other. In certain embodiments, the welding wires E1, E2 are clamped within the annular grooves so as to be radially offset from both of the groove bases <NUM>. That is, the welding wires E1, E2 are pinned between each other and the angled sidewalls <NUM>, <NUM> of the grooves such that gaps exist between the welding wires and the groove bases <NUM>. This can be seen clearly in <FIG>.

The clamping system discussed above allows for some variability (e.g., due to manufacturing tolerances) in the diameters of the welding wires E1, E2. If each welding wire E1, E2 had its own dedicated annular groove in the drive rolls <NUM>, and one of the welding wires was slightly larger than the other, then the smaller welding wire might not be adequately clamped between the drive rolls. In such a situation, the larger welding wire would limit the radial displacement of the drive rolls <NUM> toward each other, thereby preventing proper clamping of the smaller wire. This could lead to feeding problems and so-called birdnesting of the smaller welding wire during feeding. The clamping system discussed above can accommodate wires of different sizes because the clamping system is self-adjusting. As can be seen in <FIG>, when one welding wire E2 is larger than the other E1, the contact point between the wires is shifted axially from a central position within the annular grooves toward the smaller wire. Three points of contact are maintained on each welding wire E1, E2 by the sidewalls <NUM>, <NUM> of the groove and the neighboring welding wire.

<FIG> shows drive rolls <NUM> having annular grooves <NUM> with cross sections having an acute trapezoid shape instead of an isosceles trapezoid. The inner <NUM> and outer <NUM> sidewalls of the grooves have different lengths and form different angles with the outer circumferential surface of the drive rolls. In <FIG>, the drive rolls <NUM> have annular grooves <NUM> having a right trapezoid shape. Acute and right trapezoidal grooves can accommodate greater differences in welding wire diameters than isosceles trapezoids. Thus, acute and right trapezoidal grooves can be used when the groove is intended to drive welding wires having different diameters, such as a <NUM> inch welding wire with a <NUM> inch welding wire. In certain embodiments, the sidewalls and/or base of the grooves can be curved (e.g., concave or convex). Also, the inside corner transitions between the sidewalls and the base of the trapezoidal grooves can be curved or radiused. <FIG> shows example drive rolls having annular grooves with straight, angled sidewalls <NUM> joined by a concave curved or radiused groove base <NUM>. In an example embodiment, the angle between the sidewalls <NUM> and the outer circumference of the drive roll <NUM> is about <NUM>°, although other angles are possible and can be determined with sound engineering judgment.

<FIG> shows an example embodiment in which one drive roll <NUM> has a trapezoidal groove for the welding wires E1, E2, and the other drive roll 107a has a non-trapezoidal groove. In <FIG>, the non-trapezoidal groove is rectangular in shape, however other shapes are possible. For example, the non-trapezoidal groove could be curved, such as elliptical or rounded in shape. Further, the trapezoidal groove is shown as being located on the lower drive roll <NUM>. However, the trapezoidal groove could be located on the upper drive roll 107a and the non-trapezoidal groove located on the lower drive roll. The welding wires E1, E2 are clamped between respective sidewalls <NUM>, <NUM> of the trapezoidal groove and the base <NUM> of the non-trapezoidal groove <NUM>, and the welding wires are forced into contact with each other as discussed above. Thus, the welding wires E1, E2 are stably held via three points of contact within the annular grooves <NUM>, 107a.

<FIG> shows an example embodiment in which one drive roll <NUM> has a trapezoidal groove for the welding wires E1, E2, and the other drive roll 107b has no groove, but rather directly contacts the welding wires on its outer circumferential surface <NUM>. The trapezoidal groove is shown as being located on the lower drive roll <NUM>. However, the trapezoidal groove could be located on the upper drive roll. The welding wires E1, E2 are clamped between respective sidewalls <NUM>, <NUM> of the trapezoidal groove and the outer circumferential surface <NUM> of the upper drive roll 107b, and the welding wires are forced into contact with each other as discussed above. Thus, the welding wires E1, E2 are stably held via three points of contact.

It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the scope of the preent invention as defined in the appended claims.

Claim 1:
A welding or additive manufacturing wire drive system (<NUM>), comprising
a single welding wire spool (<NUM>, <NUM>) having a first welding wire (E1) and a second welding wire (E2), wherein the first and second welding wires (E1, E2) are wound on the single wire spool (<NUM>, <NUM>);
a first drive roll (<NUM>);
a second drive roll (<NUM>), wherein one or both of the first drive roll (<NUM>) and the second drive roll (<NUM>) has a circumferential groove (<NUM>);
the wire drive system (<NUM>) being characterised by:
the circumferential groove (<NUM>) comprises a first sidewall portion (<NUM>), a second sidewall portion (<NUM>) and a groove base (<NUM>, <NUM>, <NUM>) extending between the sidewalls portions (<NUM>, <NUM>) and is designed to receive the two welding wires (E1, E2), wherein the system (<NUM>) is configured that the first welding wire (E1) is drawn from the single welding wire spool (<NUM>, <NUM>), located between the first drive roll (<NUM>) and the second drive roll (<NUM>) in the circumferential groove (<NUM>); and
wherein the system (<NUM>) is configured that the second welding wire (E2) is drawn simultaneously with the first welding wire (E1) from the single welding wire spool (<NUM>, <NUM>), located between the first drive roll (<NUM>) and the second drive roll (<NUM>) in the circumferential groove (<NUM>),
wherein system (<NUM>) is configured that the first welding wire (E1) contacts the second welding wire (E2) between the first drive roll (<NUM>) and the second drive roll (<NUM>), and wherein the system (<NUM>) is configured that the first welding wire (E1) further contacts the first sidewall portion (<NUM>, <NUM>, <NUM>) of the circumferential groove (<NUM>), and wherein the system (<NUM>) is configured that the second welding wire (E2) further contacts the second sidewall portion (<NUM>, <NUM>, <NUM>) of the circumferential groove (<NUM>), and
wherein the system (<NUM>) is configured that both of the first welding wire (E1) and the second welding wire (E2) are radially offset from a central portion of the circumferential groove (<NUM>).