Patent Application
20210219412
The present invention generally relates to nozzles for liquid-cooled plasma arc cutting torches, and more particularly, to nozzles with clocking-independent cooling features and passages.
Thermal processing torches, such as plasma arc torches, are widely used for high temperature processing (e.g., heating, cutting, gouging, and marking) of materials. A plasma arc torch generally includes a torch body, an electrode mounted within the torch body, an emissive insert disposed within a bore of the electrode, a nozzle with a central exit orifice mounted within the torch body, a shield, electrical connections, passages for cooling, passages for arc control fluids (e.g., plasma gas), and a power supply. A swirl ring can be used to control fluid flow patterns in the plasma chamber formed between the electrode and the nozzle. In some torches, a retaining cap is used to maintain the nozzle and/or swirl ring in the plasma arc torch. In operation, the torch produces a plasma arc, which is a constricted jet of an ionized gas with high temperature and sufficient momentum to assist with removal of molten metal. Gases used in the torch can be non-reactive (e.g., argon or nitrogen), or reactive (e.g., oxygen or air).
Design considerations for a plasma arc torch include features for cooling, since the arc generated can produce temperatures in excess of 10,000° C., which, if not controlled, can destroy the torch, particularly the nozzle itself. Thus, the erosion rate of the nozzle is affected by the cooling efficiency at the nozzle. Efficient cooling can help to maintain a relatively low temperature, which leads to a lower erosion rate. Additionally, because a nozzle deteriorates over time from use, it needs to be easily replaceable in the field. Hence, clocking-independent installation of the nozzle is preferable.
When a consumable component is on a coolant flow path inside of a plasma arc torch, it can be relatively straightforward to force the flow path through and/or around the consumable component to cool the component while not requiring the consumable component to clock (i.e., maintain a specific orientation) relative to the other torch components or for its own sub-components, but this favorable condition is only likely to occur when the inlet and outlet of the coolant flow are axially offset. For example, this clocking independent feature can be accomplished by forming on the consumable component two axially spaced, circumferential grooves (as an inlet and an outlet) with a relatively fluid-tight seal between them.
An alternative nozzle design involves having inlet and outlet areas defined as openings on the nozzle exterior (e.g., through the nozzle jacket) with flow channels inside of the nozzle (e.g., between the nozzle jacket and the nozzle body), thereby forcing the coolant to follow a preferred flow path to and from the nozzle tip. This configuration, however, requires clocking of the nozzle components during manufacturing and/or fixing the nozzle in a specific orientation/alignment with the torch body during assembly so that coolant from the torch body can be directed along the channel(s) extending over the length of the nozzle to cool the nozzle and return the coolant flow to the torch body.
In general, these clocking-dependent prior art designs require multistep machining, inspection, inventory, part numbers etc. that increases not only the complexity and cost of manufacturing the consumable components, but also the supply chain complexity and cost.
It is therefore an objective of the present invention to provide nozzle designs that optimize coolant flow through the nozzles, thereby improving service life of the nozzles and increasing cut quality. It is another objective of the present invention to provide clocking-independent nozzles to facilitate assembly within plasma arc torches.
In one aspect, a nozzle for a liquid cooled plasma arc cutting torch is provided. The nozzle defines a central longitudinal axis extending between a proximal region and a distal region of the nozzle with a plasma exit orifice disposed along the longitudinal axis at the distal region. The nozzle includes a hollow nozzle body, and a nozzle jacket disposed about an external surface of the nozzle body. The jacket defines (i) a length along the central longitudinal axis and (ii) a diameter of a distal tip of the jacket at the distal region of the nozzle, where the length is greater than about 1.5 inches and a ratio of the length to the diameter is greater than about 1.4. The nozzle also includes a coolant inlet and a coolant outlet defined between the nozzle body and nozzle jacket at the proximal region of the nozzle. The coolant inlet is configured to receive a liquid coolant flow from a torch body of the plasma arc cutting torch to cool the nozzle and the coolant outlet is configured to return the coolant flow to the torch body. The nozzle also includes a plurality of coolant channels cooperatively defined between the nozzle body and the nozzle jacket. The plurality of coolant channels extend axially between the proximal region and the distal region of the nozzle.
In another aspect, a nozzle for a liquid cooled plasma arc cutting torch is provided. The nozzle defines a central longitudinal axis extending between a proximal region and a distal region of the nozzle. The nozzle comprises a nozzle body including an internal surface shaped to form a portion of a plasma plenum and an external surface shaped to form a portion of a coolant flow path substantially about the nozzle body. The external surface defines a plurality of substantially axial channels extending from the proximal region to the distal region of the nozzle. The nozzle also includes a nozzle jacket disposed about the external surface of the nozzle body and shaped to cooperatively form the plurality of axial channels with the nozzle body. The plurality of axial channels define the coolant flow path about the nozzle body. The nozzle further includes a plurality of windows disposed into the nozzle body. Each window is circumferentially defined by a pair of adjacent dividers of the nozzle body to prevent the coolant flow path through one window from flowing circumferentially into an adjacent window.
In yet another aspect, a consumable set in a liquid cooled plasma arc cutting torch is provided, where the consumable set is configured to direct a plasma arc to process a workpiece. The consumable set comprises an electrode and a nozzle disposed about the electrode. The nozzle has a nozzle body, a nozzle jacket and a plurality of windows. An external surface of the nozzle body and an internal surface of the nozzle jacket cooperatively define a plurality of axial channels for circulating a coolant flow about the nozzle. Each axial channel is located within one of the windows that is defined by a pair of adjacent dividers configured to prevent the coolant flow in one window from circumferentially bypassing into an adjacent window. The consumable set further comprises a shield disposed about the nozzle jacket.
In yet another aspect, a nozzle for a liquid cooled plasma arc cutting torch is provided. The nozzle defines a central longitudinal axis extending between a proximal region and a distal region of the nozzle with a plasma exit orifice disposed along the longitudinal axis at the distal region. The nozzle includes a hollow nozzle body, a nozzle jacket disposed about an external surface of the nozzle body, and a coolant inlet and a coolant outlet defined between the nozzle body and nozzle jacket at the proximal region of the nozzle. The coolant inlet is configured to receive a liquid coolant flow from a torch body of the plasma arc cutting torch to cool the nozzle and the coolant outlet is configured to return the liquid coolant flow to the torch body. The nozzle also includes a plurality of windows cooperatively defined between the nozzle body and the nozzle jacket and located at the proximal region of the nozzle. The plurality of windows includes at least a first window in fluid communication with the coolant inlet for receiving the liquid coolant flow from the coolant inlet and flowing the liquid coolant to the nozzle, and at least a second window in fluid communication with the coolant outlet for returning the liquid coolant flow from the nozzle to the coolant outlet. The first and second windows are in fluid communication with each other within the nozzle. The nozzle further includes a plurality of axial channels cooperatively defined between the nozzle body and the nozzle jacket. Each of the plurality of axial channels extends between the proximal and distal regions of the nozzle. The plurality of axial channels include a single axial channel in fluid communication with one of the first or second window, and a pair of axial channels in fluid communication with another of the first or second window. The pair of axial channels are located substantially circumferentially opposite from the single axial channel. The single axial channel and the pair of axial channels are in fluid communication at the distal region of the nozzle for passing the liquid coolant flow between the first and second windows, such that a desired pressure drop for the liquid coolant flow is established between the single axial channel and the pair of axial channels independent of a circumferential orientation of the nozzle body relative to the nozzle jacket.
In other examples, any of the aspects above can include one or more of the following features. In some embodiments, the coolant inlet and the coolant outlet are (i) substantially axially aligned along the longitudinal axis and (ii) circumferentially offset relative to each other.
In some embodiments, a plurality of windows are disposed into the nozzle body, each window being circumferentially defined by a pair of adjacent dividers of the nozzle body. In some embodiments, each divider is configured to prevent the coolant flow in one window from flowing circumferentially into an adjacent window to restrict coolant flow bypass. In some embodiments, each coolant channel is disposed in the nozzle body within a corresponding window such that the coolant channel is located between a pair of the dividers associated with the corresponding window. In some embodiments, each axial coolant channel is circumferentially isolated from one another via the dividers of the windows.
In some embodiments, the coolant inlet is in fluid communication with at least one of the plurality of windows, such that the coolant flow received from the coolant inlet is adapted to flow through the at least one coolant channel associated with the corresponding window. In some embodiments, one of the plurality of coolant channels is in fluid communication with one of the coolant inlet or outlet, and two of the plurality of coolant channels are in fluid communication with other one of the coolant inlet or outlet, irrespective of a radial orientation between the nozzle jacket and the nozzle body. In some embodiments, at least one of the plurality of coolant channels is fluidly insulated from the coolant inlet and the coolant outlet, thereby prevented from conducting a fluid flow therethrough. In some embodiments, two windows of the plurality of windows are in fluid communication with a coolant inlet or a coolant outlet of the nozzle, and the two windows are fluidly connected to respective ones of the axial coolant channels, such that the corresponding coolant inlet or outlet is fluidly connected to two axial coolant channels irrespective of a circumferential orientation between the nozzle jacket and the nozzle body. In some embodiments, one window of the plurality of windows is in fluid communication with a coolant inlet or a coolant outlet of the nozzle, and the one window is fluidly connected to a corresponding axial channel, such that the corresponding coolant inlet or outlet is fluidly connected to one axial channel irrespective of a circumferential orientation between the nozzle jacket and the nozzle body.
In some embodiments, the jacket includes a distal conical section that axially extends about 50% of the length of the jacket. The distal conical section has (i) a proximal end axially located at about a midpoint of the jacket length and (ii) a distal end tapered radially inward at the distal tip of the jacket. In some embodiments, the distal conical section comprises two angled sections, a first angled section radially extending from the midpoint of the jacket length toward the distal end of the nozzle, and a second angled section extending from the first angled section to the distal tip of the jacket. The first angled section defines a first angle relative to the longitudinal axis and the second angled section defines a second angle relative to the longitudinal axis. The second angle is larger than the first angle such that the second angled section is more tapered than the first angled section. In some embodiments, the first angle is about 14 degrees and the second angle is about 23.5 degrees. In some embodiments, a shield is disposed about an external surface of the nozzle jacket. The shield comprises a distal conical section with two angled sections, each angled section having about the same angle as the corresponding section of the nozzle jacket. In some embodiments, a diameter of an end face at a distal tip of the shield is about 0.45 inches. The shield can comprise substantially same shape and one or more angled sections as the nozzle jacket.
In some embodiments, the plurality of liquid coolant channels axially extend at least about 75% of the length of the nozzle jacket. In some embodiments, each coolant channel has a substantially rectangular cross section. In some embodiments, an axial length of each coolant channel is greater than about 1.2 inches. In some embodiments, a width of each coolant channel is less than about 0.2 inches. In some embodiments, the diameter of the distal tip of the jacket is less than about 0.4 inches.
In some embodiments, the nozzle jacket defines (i) a length along the central longitudinal axis and (ii) a diameter of a distal tip of the jacket at the distal region of the nozzle. The length is greater than about 1.5 inches and a ratio of the length to the diameter is greater than about 1.4.
In some embodiments, the plurality of coolant channels fluidly merge into a circumferential channel at the distal region of the nozzle. The circumferential channel is configured to circumferentially circulate a coolant flow about the distal region of the nozzle. In some embodiments, the circumferential channel is defined at least in part by a sealing member disposed between the nozzle body and the nozzle jacket. The sealing member has a diameter of between about 0.15 inches and about 0.3 inches.
In some embodiments, the plasma arc torch is configured to operate at a current level of above about 120 amps. In some embodiments, both the nozzle body and the nozzle jacket are electrically conductive. In some embodiments, the nozzle jacket is constructed from brass.
In some embodiments, the plurality of windows comprise a plurality of holes formed through the nozzle jacket.
In some embodiments, an axial length of the electrode is greater than about 2.4 inches. In some embodiments, the electrodes includes a cooling bore having an axial length greater than about 1.8 inches. In yet another aspect, a method of conducting a liquid coolant through a nozzle of plasma arc cutting torch is provided. The nozzle defines a central longitudinal axis extending between a proximal region and a distal region of the nozzle. The method includes supplying the liquid coolant to a coolant inlet in the proximal region of the nozzle between a hollow nozzle body and a nozzle jacket disposed about the hollow nozzle body. An external surface of the nozzle body and an internal surface of the nozzle jacket cooperatively define a plurality of axial channels that extend from the proximal region to the distal region. The method also includes flowing the liquid coolant from the coolant inlet to at least a first window of a plurality of windows disposed into the nozzle body. Each window is circumferentially defined by a pair of adjacent dividers of the nozzle body, and each window includes at least one of the plurality of axial channels. The method includes conducting the liquid coolant to the distal region of the nozzle via at least a first axial channel associated with the first window while preventing the liquid coolant from flowing circumferentially into an adjacent window by the pair of dividers of the first window. The method includes returning the liquid coolant from the distal region to the proximal region of the nozzle via at least a second axial channel of the plurality of axial channels. The at least second axial channel is located in a second window of the plurality of windows and the second window being in fluid communication with a coolant outlet located between the nozzle body and the nozzle jacket in the proximal region. The method further includes expelling the liquid coolant from of the nozzle via the coolant outlet at the proximal region of the nozzle.
In some embodiments, the coolant inlet is fluid communication with at least the first axial channel and the coolant outlet is in fluid communication with at least the second axial channel irrespective of a circumferential orientation between the nozzle body and the nozzle jacket.
In some embodiments, the method further comprises achieving a desired pressure disparity between the liquid coolant flow to the distal region and the liquid coolant flow to the proximal region irrespective of a radial orientation of the nozzle body relative to the nozzle jacket.
In some embodiments, the method further comprises conducting the liquid coolant to the distal region of the nozzle via a pair of the plurality of axial channels corresponding to respective ones of a pair of the plurality of windows, where the pair of windows being in fluid communication with the coolant inlet, and returning the liquid coolant to the proximal region of the nozzle via a single one of the plurality of axial channels corresponding to a single one of the plurality of windows. The single window is in fluid communication with the coolant outlet. The single axial channel is (i) located substantially circumferentially opposite from the pair of axial channels and (ii) in fluid communication with the pair of axial channels at the distal region of the nozzle.
In some embodiments, the method further comprises conducting the liquid coolant to the distal region of the nozzle via a single one of the plurality of axial channels corresponding to a single one of the plurality of windows, where the single window is in fluid communication with the coolant inlet, and returning the liquid coolant to the proximal region of the nozzle via a pair of the plurality of axial channels corresponding to respective ones of a pair of the plurality of windows. The pair of windows are in fluid communication with the coolant outlet. The single axial channel is (i) located substantially circumferentially opposite from the pair of axial channels and (ii) in fluid communication with the pair of axial channels at the distal region of the nozzle.
The advantages of the invention described above, together with further advantages, may be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.
Within the torch tip 304, the clocking-independent nozzle 310 is spaced distally from the electrode 305 to cooperatively define a plasma plenum 321. As shown, the nozzle 310 includes (i) an elongated inner nozzle body 312 that is substantially hollow and (ii) an elongated outer nozzle jacket 314 disposed about and substantially surrounding an external surface of the inner nozzle body 312. The swirl ring 320 is mounted between the torch body 302 and the nozzle 310 and has a set of radially offset or canted gas distribution holes that impart a tangential velocity component to the plasma gas flow therethrough. A retaining cap 342 can be used to securely retain the nozzle 310 to the torch body 302 while radially and/or axially positioning the nozzle 310 with respect to the longitudinal axis A. The shield 340 can be disposed about an external surface of the nozzle jacket 314 and secured (e.g., threaded) to the torch body 302 via the retaining cap 342. The shield 340 includes a shield exit orifice 344 for introducing a plasma arc to a workpiece during processing.
In general, the nozzle 310 defines a proximal region 311 and a distal region 313 disposed along the central longitudinal axis A. At the distal region 313 of the nozzle 310, an internal surface of the nozzle body 312 is shaped to form at least a portion of the plasma plenum 321 as well as a nozzle exit orifice 322, which in combination with the shield exit orifice 344, define a plasma arc exit orifice through which a plasma arc is delivered to a workpiece during torch operation. At the proximal region 311 of the nozzle 310, a coolant inlet 324 and a coolant outlet 326 are defined between the nozzle body 312 and the nozzle jacket 314. The coolant inlet 324 is configured to receive a liquid coolant flow from the torch body 302 (e.g., via the coolant inlet channel 328 of the torch body 302) to cool the nozzle 310, and the coolant outlet 326 is configured to return the coolant flow from the nozzle 310 to the torch body 302 (e.g., by supplying the coolant flow to the coolant return channel 330 of the torch body 302).
In some embodiments, the nozzle 310 includes multiple coolant channels 332 cooperatively defined between an external surface of the nozzle body 312 and an internal surface of the nozzle jacket 314. For example, the multiple coolant channels 332 can be disposed in the nozzle body 312 and dispersed circumferentially about the nozzle body 312, where each coolant channel 332 is configured to extend axially between the proximal region 311 and the distal region 313 of the nozzle 310. At the distal region 313 of the nozzle 310, these coolant channels 332 fluidly communicate with one another, such as, in some embodiments, merge into a circumferential channel 336 located between the nozzle body 312 and the nozzle jacket 314 at the distal region 313. The circumferential channel 336 can comprise a cavity disposed into the nozzle body 312 from an external surface of the nozzle body 312. The circumferential channel 336 is configured to circumferentially circulate a coolant flow received from one or more of the axially-extending coolant channels 332 about the distal region 313 of the nozzle 310. As shown in
In some embodiments, at least one of the windows 402 (including the coolant channel(s) 332 located within that window 402), such as window 402a in
For example, one window 402 (including the coolant channel(s) 332 located within that window 402) can be in fluid communication with one of the coolant inlet 324 or outlet 326, and two of the remaining windows 402 (including the coolant channels 332 located in these two windows 402) can be in fluid communication with the other one of the coolant inlet 324 or outlet 326, independent of a radial orientation between the nozzle body 312 and the nozzle jacket 314. As shown in
In some embodiments, each window 402 maintains an angular span 406 of about 45 degrees. In some embodiments, an angular span 408 of each divider 404 is less than the angular span 406 of each window 401, but is sufficiently wide to avoid undercutting from an endmill operation (e.g., during the component manufacturing process) to form the windows 402, while being able to restrict flow bypass around a circumference of the nozzle 310. For example, each divider 404 can have an angular span 408 of between about 5 degrees and about 30 degrees, such as about 13 degrees.
In operation, when a liquid coolant enters the nozzle 310 via the coolant inlet 324 at the proximal region 311 of the nozzle 310, the coolant is only provided to one or two of the windows 402 that are in fluid communication with the inlet 324, irrespective of the radial orientation between the nozzle body 312 and the nozzle jacket 314. Thereafter, the coolant is adapted to flow axially toward the distal region 313 of the nozzle 310 only via the coolant channel(s) 332 associated with the one or two inlet windows 402 (hereinafter referred to as the supply channel(s)). During the distal axial flow, the coolant is prevented from circumferentially bypassing to the other coolant channels due to the dividers 404 located between the windows 402. Once the coolant reaches the distal region 313 of the nozzle 310 between the nozzle body 312 and the nozzle jacket 314, the coolant merges into the circumferential channel 336 that is in fluid communication with the axially-extending supply coolant channels 332. The circumferential channel 336 is adapted to circulate the coolant flow around to cool the distal region 313 of the nozzle 310. Further, the circulating coolant is adapted to return from the circumferential channel 336 to the outlet 326 at the proximal region 311 of the nozzle 310 via only one or two of the coolant channels 332 (hereinafter referred to as the return channel(s)) that are offset (e.g., substantially opposite) from the supply coolant channel(s). This is because the return coolant channel(s) 332 are associated with the one or two windows 402 that are in fluid communication with coolant outlet 326. The remaining channels 332 do not conduct the return coolant flow because their corresponding windows 402 are not in fluid communication with the coolant outlet 326. Additionally, during the proximal axial flow, the return coolant is prevented from circumferentially bypassing to the other coolant channels due to the dividers 404 located between the windows 402. Once the coolant reaches the proximal region 311 of the nozzle 310 between the nozzle body 312 and the nozzle jacket 314, the coolant is expelled from the nozzle 310 via the coolant outlet 326. As described above, in various embodiments, the nozzle 310 is clocking independent, such that it can have (i) one coolant supply channel and one coolant return channel, (ii) two coolant supply channels and one coolant return channel, (iii) one coolant supply channel and two coolant return channels, or (iv) two coolant supply channels and two coolant return channels, regardless of the radial orientation between the nozzle body 312 and the nozzle jacket 314. For the configuration of
In general, the nozzle design of
In some embodiments, because the number of supply and return channels of the nozzle 310 is predictable independent of the radial orientation of the nozzle body 312 relative to the nozzle jacket 312, the pressure disparity (i.e., pressure drop/loss) between the coolant supply flow and coolant return flow through the nozzle 310 can be managed (e.g., a desired pressure disparity achieved) irrespective of the parts orientation. This can be achieved even if the number of coolant and supply channels are not the same. The total pressure drop in the flow path from the proximal region 311 to the distal region 313 of the nozzle 310 and back from the distal region 313 to the proximal region 311 of the nozzle 310 is defined by the sum of the channels in both directions. The total pressure drop for the case of 2 supply channels and 1 return channel has a total pressure drop equal to 1 supply and 2 return channels. Thus, in this case the coolant supply and return channels are different in number but equal in total pressure drop through the nozzle 310. In some embodiments, the circumferential channel 336 is designed to have a sufficient wall thickness to enable effective component manufacturing while providing a sufficient flow area to limit the pressure disparity in the coolant flow path. Specifically, the wall thickness of the circumferential channel 336 can be sufficiently large such that (i) the circumferential channel 336 is structurally sound (e.g., won't break under operating conditions), (ii) enough thermal energy is conducted away from the distal region 313 of the nozzle 310, and/or (iii) enough spacing among the nozzle components is achieved to minimize pressure disparity in the coolant flow.
In another aspect, both the nozzle body 312 and the nozzle jacket 314 of the nozzle 310 are electrically conductive and constructed from the same or different electrically conductive materials. For example, the nozzle jacket 314 can be made from brass and the nozzle body 312 can be made from copper.
In yet another aspect, the consumable components of the plasma arc torch 300 are shaped and dimensioned to enhance bevel cutting. The narrow, lengthened cooling design of the clocking-independent nozzle 310 as described above drives the design of a generally longer and steeper torch 300 capable of delivering a plasma arc closer to parallel relative to the surface of a workpiece being processed, in comparison to prior art liquid-cooled plasma arc torches.
Referring to
In some embodiments, if the optional shield 340 is assembled into the torch 300 such that it substantially surrounds an external surface of the nozzle jacket 314, the shield 340 also comprises a proximal conical section and a distal conical section with two angled sections having about the same angular shapes/profiles as their corresponding sections of the nozzle jacket 314. In some embodiments, the diameter of the distal end face 360 of the shield 340 (shown in
In an exemplary operation, independent of a circumferential orientation between the nozzle body 312 and the nozzle jacket 314, the supply coolant flow is conducted over one window 402 and one corresponding axial channel 332 in fluid communication with the inlet 324, while the return coolant flow is conducted over two windows 404 and two corresponding axial channels 332 in fluid communication with the outlet 326. In alternative embodiments, the supply coolant flow is over two windows/two corresponding axial channels while the return coolant flow is over one window/one corresponding axial channel. Because a predicted number of supply and return axial channels 332 is used for conducting a coolant flow through the nozzle 310 independent of the circumferential orientation between the nozzle body 312 and the nozzle jacket 314, a desired (e.g., minimized) pressure disparity between the supply and coolant flows can be achieved.
As described above, advantages of the present invention include eliminating the need for end users to clock the nozzle for installation into the plasma arc torch and/or clock the nozzle body relative to the nozzle jacket for assembling the nozzle, thus facilitating error-proof installation and assembly. In addition, the nozzle coolant designs of the present invention frees more design space for added torch features. Further, the nozzle coolant designs of the present invention drive the design for a more elongated, narrowed torch that can cut sharp angles and/or into confined spaces with improved cooling.
It should also be understood that various aspects and embodiments of the invention can be combined in various ways. Based on the teachings of this specification, a person of ordinary skill in the art can readily determine how to combine these various embodiments. For example, in some embodiments, any of the aspects above can include one or more of the above features. One embodiment of the invention can provide all of the above features and advantages.
This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/959,035, filed Jan. 9, 2020, the entire content of which is owned by the assignee of the instant application and is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62959035 | Jan 2020 | US |
