Patent Description:
Gas-shielded welding processes, such as gas metal arc welding (GMAW) metal-cored arc welding (MCAW), gas tungsten arc welding (GTAW) and sometimes flux-cored arc welding (FCAW), employ a shielding gas to protect the welding arc and weld puddle from the surrounding air. Specifically, the shielding gas prevents, or shields, the weld zone from atmospheric oxygen, which causes oxidation, and other atmospheric contaminants. A high flow rate of shielding gas will increase the amount of shielding gas discharged during welding. However, a high flow rate of shielding gas can also lead to porosity in the completed weld due to turbulence and the gas flow disrupting the weld pool. A high flow rate of shielding gas also increases the consumption rate of the shielding gas which raises the cost of the welding operation. A more laminar flow of shielding gas during the welding operation, rather than a turbulent flow, would be desirable as it is less disruptive to the weld pool and can allow for lower gas flow rates and less consumption of shielding gas. A more laminar flow of shielding gas also introduces less undesirable reactive gases from the atmosphere into the gas column shielding the weld zone. A more laminar shielding gas flow can also allow for the capability of operating with a longer electrical stickout.

Document <CIT> discloses embodiments of an insulated sleeve and a perforated screen that may be used in a nozzle assembly for a welding torch. In one embodiment, a welding system includes an electrically insulated sleeve and a perforated screen disposed adjacent to the electrically insulated sleeve. The perforated screen is configured to be captured removably between a nozzle and a contact tip of a torch head, and the perforated screen is configured to be installed and removed independent of the nozzle.

Document <CIT> discloses a gas lens assembly for use in a gas shielded welding torch to provide laminar gas flow to the weld puddle. The assembly includes a plurality of annular fine mesh inner filter screens mounted in fixed axially spaced disposition in a gas chamber formed between the lens body and lens sleeve. The filter screens are preferably spaced apart a predetermined distance by a plurality of wave-shaped open mesh spacer discs disposed in a sandwich configuration between the filter screens. A stack of adjacently disposed outer filter screens are mounted in the gas chamber outwardly of the fine mesh filter screens. Each of the outer screens in the stack is individually removable such that the outermost screen can be readily peeled from the stack when damaged by spatter or heat to maintain the laminar gas flow through the assembly and prolong the useful life of the assembly.

Document <CIT> discloses a welding or additive manufacturing contact tip including an electrically conductive body extending from a proximal end of the body to a distal end of the body. The body forms a first bore terminating at a first exit orifice at a distal end face of the body, and a second bore terminating at a second exit orifice at the distal end face of the body. The first and second exit orifices are separated from each other by a distance configured to facilitate formation of a bridge droplet between a first wire electrode delivered through the first bore and a second wire electrode delivered through the second bore during a deposition operation.

Document <CIT> discloses a gas-shielded arc torch comprising an elongated electrode, an electrical contact for said electrode, means supporting said contact, said means having an annular chamber and arc shielding gas passages for delivering are shielding gas to such chamber, and a gas lens surrounding said electrode and constituting a wall of such chamber, for fully expanding and directing such gas around said electrode in the direction of the arc end thereof.

The following summary presents a simplified summary in order to provide a basic understanding of the present invention.

According to the present invention a welding or metal additive manufacturing torch is defined in claim <NUM>.

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:.

The present invention relates to torches for gas-shielded arc welding and/or metal additive manufacturing operations. The present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It is to be appreciated that the various drawings are not necessarily drawn to scale from one figure to another nor inside a given figure, and in particular that the size of the components are arbitrarily drawn for facilitating the understanding of the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention.

As used herein, "at least one", "one or more", and "and/or" are open-ended expressions that are both conjunctive and disjunctive in operation. Any disjunctive word or phrase presenting two or more alternative terms, whether in the description of embodiments, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" should be understood to include the possibilities of "A" or "B" or "A and B.

While embodiments of the present invention described herein are discussed in the context of a gas metal arc welding (GMAW) system, other embodiments of the invention are not limited thereto. For example, embodiments can be utilized in flux-cored arc welding (FCAW), metal-cored arc welding (MCAW), submerged arc welding (SAW) and various GMAW processes such as GMAW-P (pulsed GMAW) and GMAW-S (short circuit GMAW). Further, embodiments of the present invention can be used in manual, semi-automatic and robotic welding operations. Embodiments of the present invention can also be used in metal deposition operations that are similar to welding, such as metal additive manufacturing (3D printing), hardfacing, and cladding. As used herein, the term "welding" is intended to encompass all of these technologies as they all involve material deposition to either join or build up a workpiece. Therefore, in the interests of efficiency, the term "welding" is used below in the description of exemplary embodiments, but is intended to include all of these material deposition operations, whether or not joining of multiple workpieces occurs.

Referring now to the drawings, <FIG> shows an example welding system <NUM>. The welding system <NUM> includes welding power supply <NUM>, a wire feeder <NUM>, and a shielding gas supply <NUM>. Welding power supply <NUM> includes power cables <NUM>, control cable <NUM>, and power supply cables (not shown). Power cables <NUM> include a ground wire and clamp <NUM> connected to a workpiece W, and a power cable <NUM> for supplying welding waveforms generated by the welding power supply <NUM> to the wire feeder <NUM>. Control cable <NUM> may be configured to connect to wire feeder <NUM> to provide communications between the power supply <NUM> and the wire feeder. Such communications could also be wireless. It is understood that welding power supply <NUM>, power cables <NUM>, and control cable <NUM> can have any configuration suitable for supplying power and welding controls within the welding system <NUM>. Although the wire feeder <NUM> and welding power supply <NUM> are shown as two separate devices interconnected by cabling, the welding power supply and wire feeder could be integrated into a single welding machine.

Further illustrated in <FIG>, gas conduit <NUM> and regulator <NUM> are configured to connect the shielding gas supply <NUM> to the wire feeder <NUM>. The shielding gas supply <NUM> may include inert gases, active gases, or a combination of both, including but not limited to argon, helium, carbon dioxide, argon and helium, argon and hydrogen, and other gas combinations. The gas supply may be any gas or combination of gases configured to shield a weld from the atmosphere.

As shown in <FIG>, wire feeder <NUM> may include a housing <NUM>, gear box <NUM>, wire spool assembly <NUM>, and user interface <NUM>. Extending from the gear box <NUM> is a hose <NUM> that is configured to connect to a welding torch <NUM>. The housing <NUM> may be connected to the user interface <NUM> and gear box <NUM>. Further, the control cable <NUM> and power cable <NUM> extending from welding power supply <NUM>, and the gas conduit <NUM> extending from gas supply <NUM>, are configured to connect to housing <NUM>, gear box <NUM>, and hose <NUM>. Gear box <NUM> includes at least a drive motor and a plurality of rollers that advance and retract a wire electrode drawn from a spool (not shown) mounted on the spool assembly <NUM> or drawn from a bulk package, such as a box or drum. Extending between the gear box <NUM> and the welding torch <NUM> is the hose <NUM>. The hose <NUM> provides a conduit for the welding electrode and shielding gas and conducts the welding waveforms to the torch <NUM>. The hose <NUM> can conduct a trigger signal from the torch <NUM> to the wire feeder <NUM> and to the welding power supply <NUM> to control feeding of the wire electrode and the provision of the welding waveforms and shielding gas to the torch. It is understood that the hose <NUM> and welding torch <NUM> may have any configuration suitable for supplying welding wire, shielding gas, and controls between the torch and wire feeder <NUM>. The torch <NUM> can include a contact tip for conducting the welding waveforms from the wire feeder <NUM> to the wire electrode, and a shielding gas diffuser and nozzle to direct the shielding gas around the arc and toward the molten puddle. The torch <NUM> can also include a shielding gas lens to create a more laminar flow of shielding gas around the weld zone and molten puddle. The shielding gas lens is discussed in detail below.

Referring now to <FIG>, a schematic view of a distal portion of a gas-shielded welding torch <NUM> is shown in position above workpiece W. The distal end of the torch handle <NUM> is shown in <FIG> along with a gooseneck <NUM> extending from the torch handle. Welding torch <NUM> is supplied with one or more wire electrodes <NUM> (e.g., steel, aluminum, alloys, composites, cored, etc., or other welding wire known to those in the art) from a wire supply spool, drum, etc. by a wire feeder. The wire feeder not only regulates the rate at which welding wire <NUM> is fed through the torch <NUM>, but it can also control the flow of shielding gas from a gas source to the torch.

The torch <NUM> includes a nozzle <NUM>. The nozzle <NUM> directs the flow of shielding gas toward the workpiece W and molten puddle. Within the nozzle <NUM> are a shielding gas diffuser <NUM> and a contact tip <NUM>. The contact tip <NUM> extends from the shielding gas diffuser <NUM> and is attached to the diffuser, such as via a threaded connection. The contact tip <NUM> has a through bore and entrance and exit orifices for the wire electrode <NUM>. In certain embodiments, the contact tip <NUM> can accommodate two or more wire electrodes fed simultaneously during a multi-wire deposition operation, and can have multiple through bores and entrance and exit orifices for the wire electrodes.

A typical example welding operation may utilize a shielding gas flow rate in the range of <NUM>-<NUM> cubic feet per hour (CFH). The shielding gas flow rate is set by the regulator on the shielding gas supply. An operator may increase the shielding gas flow rate for a high deposition welding operation, such as during multi-wire welding, when there is a large weld puddle and weld bead to protect. An operator may also increase the shielding gas flow rate when welding outdoors because wind can blow the shielding gas away from the weld zone. An example high shielding gas flow rate is <NUM> CFH.

The flow of shielding gas is often turbulent, in particular at high flow rates, which is undesirable. Turbulent shielding gas flows can draw contaminants from the ambient air into the weld zone and can disrupt the weld pool leading to porosity. Turbulent shielding gas flows also reduce the amount of electrical stickout that can be employed during welding. High shielding gas flow rates, which are often turbulent, increase the consumption rate of the shielding gas which raises the cost of the welding operation. A laminar flow of shielding gas from the torch <NUM> is preferable to a turbulent flow of gas as it allows for lower gas flow rates and reduced porosity while adequately protecting the weld zone. A laminar flow of shielding gas also allows for the use of a longer electrical stickout when the laminar flow is maintained for a longer distance from the nozzle <NUM> as compared to typical welding operations.

To improve the laminar flow profile of the shielding gas, the torch <NUM> includes a shielding gas lens <NUM>. The shielding gas lens <NUM> includes one or more annular screens having a mesh. The diffuser <NUM> has a plurality of shielding gas discharge holes <NUM> spaced annularly around the diffuser. The shielding gas lens <NUM> and its annular screen(s) are located within the nozzle <NUM> distal of the shielding gas discharge holes <NUM>. The shielding gas flows through the mesh screen(s) of the shielding gas lens <NUM> after being discharged from the shielding gas discharge holes <NUM>. The shielding gas <NUM> flowing through the lens <NUM> is generally laminar as shown schematically in <FIG>. The screen(s) on the shielding gas lens <NUM> reduce shielding gas turbulence and provide a long, generally undisturbed laminar flow to the weld puddle. <FIG> also shows a dual wire welding process in which two wire electrodes are simultaneously fed through the contact tip.

A filtered GMAW nozzle setup as shown can improve the gas coverage during welding by distributing laminar gas flow around the electrodes and onto the weld puddle. The laminar gas flow <NUM> can help to stabilize the welding arc when using high deposition welding processes such as multi-wire welding. Not only does the weld puddle need shielding, but the arc and droplets that travel through the arc need stable shielding gas coverage, which is provided by a laminar gas flow <NUM>. A laminar gas flow <NUM> also provides the capability to run lower shielding gas flow rates and conserve shielding gas versus running extremely high flow rates (which may not even be available when using a standard gas regulator rather than a high flow regulator). A more stable delivery of shielding gas flow will correspond with a weld that will yield less porosity and better visual aesthetics.

As shielding gases conforming to the American Welding Society (AWS) A5. <NUM> specification become more accurate at fill plants, welding waveform control technology based on shielding gases becomes more relevant. An example would be distributors that offer gas cylinders with <NUM>% accurate shielding blends. This in turn will correspond with the delivery of the shielding gas at the nozzle of the welding torch. A filtered, stable, generally laminar delivery of shielding gas will deliver a more precise droplet of metal through the arc, especially when using waveform control technology. Aluminum GMAW and critical alloy welding applications that use high shielding gas flow rates or are sensitive to changes or lack of shielding gas coverage could also benefit from the use of a shielding gas lens <NUM> in the torch.

<FIG> shows the shielding gas lens <NUM> in detail. The shielding gas lens <NUM> has one or more annular screens <NUM>, <NUM>. The annular screens <NUM>, <NUM> are located within the nozzle distal of the diffuser's shielding gas discharge holes. The annular screens <NUM>, <NUM> extend radially within the nozzle of the torch, between the diffuser and the nozzle, to filter the shielding gas flow from the diffuser's gas discharge holes. The annular screens <NUM>, <NUM> have a mesh size suitable to provide a generally laminar flow of shielding gas from the torch at a desired gas flow rate and distance from the end of the nozzle. Although the shielding gas lens <NUM> shown in <FIG> has two annular screens <NUM>, <NUM>, it is to be appreciated that the gas lens could have a single screen or more than two screens if desired.

In an example embodiment, the shielding gas lens <NUM> can include a central hub <NUM> that is attached to the annular screens <NUM>, <NUM>. The central hub <NUM> can be mounted on the diffuser distal of the shielding gas discharge holes, mounted on the contact tip which is located distal of the shielding gas discharge holes, or mounted between a portion of the contact tip and the diffuser. For example, attaching the contact tip to the diffuser can hold the gas lens <NUM> in place within the nozzle by clamping the gas lens between a portion of the contact tip and the end face of the diffuser. In an example embodiment, the screens <NUM>, <NUM> and hub <NUM> are made from suitable metallic materials. However, the hub <NUM> and screens <NUM>, <NUM> could be made from other appropriate materials suitable for exposure to the high temperatures at the distal end of the torch. For example, the hub could be made of an electrically-insulating material such as a ceramic.

<FIG> shows an exploded view of the distal end of an example torch that includes the shielding gas lens <NUM>. The nozzle <NUM> can be attached to the torch's gooseneck via an insulator <NUM>. As is known in the art, the metallic nozzle <NUM> (in particular the exposed outer surface of the nozzle) should be electrically insulated from the contact tip and the diffuser, which can be energized during welding. Located inside of the nozzle <NUM> are the diffuser <NUM>, contact tip <NUM>, and shielding gas lens <NUM>. As noted above, the shielding gas lens <NUM> can be located at various positions within the nozzle downstream of the shielding gas discharge holes. For example, the shielding gas lens <NUM> could be mounted on the diffuser <NUM>.

The shielding gas lens <NUM> is a consumable component of the torch that can be replaced from time to time, similar to the contact tip <NUM> and the diffuser <NUM>. The shielding gas lens <NUM> is shown in the figures as a separate component from the contact tip <NUM> and the diffuser <NUM>. However, the shielding gas lens <NUM> need not be a separate component from the diffuser <NUM> but could be directly attached to the diffuser so as to be replaceable therewith. For example, the diffuser <NUM> could have the gas lens <NUM> built into the diffuser to form a common consumable component of the torch.

<FIG> shows the distal portion of the welding torch <NUM> with the shielding gas lens <NUM> located between the diffuser <NUM> and a portion of the contact tip <NUM> that is distal of the diffuser. For example, the shielding gas lens <NUM> is clamped between the end face of the diffuser <NUM> and the portion of the contact tip <NUM> that is distal of the diffuser. The contact tip <NUM> can include a shank that is inserted (e.g., threaded) into the diffuser <NUM> and a shoulder that normally seats against the end face of the diffuser. The shoulder on the contact tip <NUM> can clamp the shielding gas lens <NUM> against the diffuser <NUM> as the contact tip is threaded into the diffuser. The central hub of the shielding gas lens <NUM> can be located between the shoulder of the contact tip <NUM> and the end face of the diffuser <NUM>.

The outer surface of the nozzle <NUM> should be electrically insulated from the contact tip <NUM> and the diffuser <NUM>, which can be energized during welding. The annular screen(s) of the shielding gas lens <NUM> extend radially outward from the diffuser <NUM> toward the nozzle <NUM> and across the air gap that normally exists between the diffuser/contact tip and the nozzle. The nozzle <NUM> is typically made of a metallic material. The annular screen(s) of the shielding gas lens <NUM> can also be made of a metallic material and be electrically conductive. To avoid energizing the nozzle <NUM> via the shielding gas lens <NUM>, the shielding gas lens <NUM> and its annular screen(s) can be electrically isolated or insulated from the nozzle <NUM> (in particular from the outer surface of the nozzle which can come into contact with the workpiece or the operator) and/or be electrically insulated from the diffuser <NUM>. For example, the central hub of the shielding gas lens <NUM> can electrically insulate the annular screen(s) of the lens from the diffuser <NUM>. The central hub of the shielding gas lens <NUM> can be made from a nonmetallic material such as a ceramic that is electrically insulating and resistant to high temperatures. The central hub of the shielding gas lens <NUM> could also include an insulating layer or barrier between the hub and the diffuser or between the hub and the annular screen(s). An electrical insulating layer <NUM> can also be located radially between the annular screen(s) of the shielding gas lens <NUM> and the nozzle <NUM> (<FIG>). In this case, the shielding gas lens <NUM> can have the same electrical potential as the diffuser <NUM> and contact tip <NUM>, but it will be electrically insulated from the nozzle <NUM> and the outer surface of the nozzle, to prevent the gas lens from energizing the nozzle.

<FIG> shows schematically a contact tip <NUM> for a dual wire welding operation. The use of a shielding gas lens in a dual wire welding operation can be beneficial because of the high deposition rate and molten puddle size and the need for adequate shielding gas coverage. The use of a shielding gas lens to provide a more laminar shielding gas flow in a dual wire welding operation can allow for lower shielding gas flow rates (CFH) during welding and provide reduced porosity, as compared to conventional dual wire welding operations. The contact tip <NUM> for a dual wire welding operation has a first bore and exit orifice <NUM> for a first wire electrode <NUM>, and a second bore and exit orifice <NUM> for a second wire electrode <NUM>. Welding current is simultaneously conducted to both wire electrodes <NUM>, <NUM> through the contact tip <NUM> during the welding operation.

Claim 1:
A welding or metal additive manufacturing torch (<NUM>), comprising:
- a nozzle (<NUM>);
- a shielding gas diffuser (<NUM>) located within the nozzle (<NUM>) and having a plurality of shielding gas discharge holes (<NUM>) spaced annularly around the shielding gas diffuser (<NUM>);
the torch (<NUM>) being characterised by:
- a contact tip (<NUM>) extending from the shielding gas diffuser (<NUM>) distal of the shielding gas discharge holes (<NUM>);
- an annular screen (<NUM>, <NUM>) located distal of the shielding gas discharge holes (<NUM>), wherein the annular screen (<NUM>, <NUM>) is electrically insulated from at least one of the shielding gas diffuser (<NUM>) and an outer surface of the nozzle (<NUM>), wherein the annular screen (<NUM>, <NUM>) extends radially between the nozzle (<NUM>) and the shielding gas diffuser (<NUM>).