Abstract
A torch tip is provided for a liquid-cooled plasma arc cutting torch. The torch tip includes an electrode with an elongated electrode body having a distal end and a proximal end extending along a longitudinal axis. The electrode body includes at least one interior threaded connection at the proximal end for engaging a liquid-cooled electrode holder. The electrode holder comprises a liquid coolant channel that does not extend into the electrode body. The electrode body has (i) a length extending along the longitudinal axis and (ii) a diameter associated with a widest portion of the electrode body along the longitudinal axis between the proximal and distal ends, where a ratio of the length to the diameter of the electrode body is greater than about 5.
Claims
1. A torch tip for a liquid-cooled plasma arc cutting torch, the torch tip comprising: an electrode with an elongated electrode body having a distal end and a proximal end extending along a longitudinal axis, the electrode body including a bore at the distal end for receiving a hafnium insert and at least one interior threaded connection at the proximal end for engaging a liquid-cooled electrode holder, wherein the electrode holder comprises a liquid coolant channel that does not extend into the electrode body, the electrode body having (i) a length extending along the longitudinal axis and (ii) a diameter associated with a widest portion of the electrode body along the longitudinal axis between the proximal and distal ends, wherein a ratio of the length to the diameter of the electrode body is greater than 5; a nozzle including a substantially hollow, elongated nozzle body for receiving the electrode, the nozzle body defining (i) a length extending along the longitudinal axis and (ii) a diameter associated with a widest portion of the nozzle body along the longitudinal axis, wherein a ratio of the length to the diameter of the nozzle body is greater than 1.75; and a shield coupled to the nozzle via an insulator, wherein the shield includes: a set of radially-oriented passages dispersed around a first circumference of the shield, the radially-oriented passages fluidly connecting an exterior surface to an interior surface of the shield and configured to impart a swirling motion on a first portion of a combined gas flow therethrough, and a set of axially-oriented passages dispersed around a second circumference of the shield, the axially-oriented passages configured to axially conduct a second portion of the combined gas flow over an external surface of the shield.
2. The torch tip of claim 1, wherein the diameter of the electrode is less than 0.25 inches.
3. The torch tip of claim 1, wherein the at least one threaded connection is configured to engage a complementary threaded connection on an external surface of the electrode holder, such that a distal portion of the electrode holder is disposed in a cavity of the electrode body upon engagement.
4. The torch tip of claim 3, wherein the cavity within the electrode body is shaped and sized to substantially surround a protruding boss portion at the distal portion of the electrode holder, thereby axially and radially aligning the electrode relative to the electrode holder.
5. The torch tip of claim 1, wherein the ratio of the length to the diameter of the electrode body is greater than 7.
6. The torch tip of claim 1, wherein the set of axially-oriented passages of the shield comprises at least one groove disposed on the exterior surface of the shield.
7. The torch tip of claim 1, wherein the combined gas flow comprises a combination of a plasma gas flow and a shield gas flow.
8. The torch tip of claim 7, wherein the nozzle comprises a set of radially-oriented passages each connecting an interior surface of the nozzle body to an exterior surface of the nozzle body, the set of radially-oriented passages of the nozzle configured to fluidly communicate with the radially-oriented and axially-oriented passages of the shield to supply a portion of the plasma gas flow to the shield.
9. The torch tip of claim 7, wherein the torch tip, including the electrode, the shield and the nozzle, is substantially cooled by at least one of the plasma gas flow, the shield gas flow or the combined gas flow without being cooled by a liquid coolant in the liquid coolant channel of the electrode holder.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) 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.
(2) FIGS. 1a and 1b show the positioning of a conventional plasma arc torch in relation to a vertical flange to be cut and the resulting cut made by the conventional plasma arc torch, respectively.
(3) FIG. 2 shows a known liquid cooling path in a conventional liquid-cool plasma arc torch.
(4) FIG. 3 shows a cross-sectional view of an exemplary liquid-cooled plasma arc torch that includes an extender operably connect to a set of one or more adjustable/extended-length consumables, according to some embodiments of the present invention.
(5) FIG. 4 shows a sectional-view of a portion of the torch tip of FIG. 3 that includes the nozzle and the shield, according to some embodiments of the present invention.
(6) FIGS. 5a and 5b show a perspective view and a profile view, respectively, of the shield of FIG. 4, according to some embodiments of the present invention.
(7) FIG. 6 shows a profile view of the plasma arc torch of FIG. 3, according to some embodiments of the present invention.
(8) FIG. 7 shows a visual comparison of the plasma arc torch of FIG. 3 with the prior art torch of FIG. 2 when processing a flanged workpiece, according to some embodiments of the present invention.
(9) FIGS. 8a-8c show various stages of assembly of the plasma arc torch of FIG. 3, according to some embodiments of the present invention.
DETAILED DESCRIPTION
(10) FIG. 3 shows a cross-sectional view of an exemplary liquid-cooled plasma arc torch 300 that includes an extender 302 operably connected to a set of one or more adjustable/extended-length consumables, according to some embodiments of the present invention. As shown, the extender 302 is generally located between a torch body 304 of the plasma arc torch 300 and the set of consumables at a torch tip 306 of the plasma arc torch 300. The extender 302 has an elongated body that includes at least one of an electrode holder 350, a swirl ring holder 352, a nozzle holder 354 and a shield holder 356. The elongated body of the extender 302 defines a longitudinal axis A between a proximal end 310 and a distal end 312, where the distal end 312 is the end that is closest to a workpiece during torch operation and the proximal end 310 is opposite of the distal end. The set of consumables at the torch tip 306 of the plasma arc torch 300 that can be coupled to the extender 302 includes one or more of an electrode 318, a nozzle 320 and a shield 322. In some embodiments, the extender 302 and torch tip 306 are configured to operate at a high amperage (e.g., greater than about 55 Amps, about 60 Amps, about 70 Amps, about 110 Amps, about 115 Amps, or about 170 Amps) and extend the cutting reach of liquid-cooled plasma arc torch 300 into hard to reach areas to cut materials with a thickness greater than about ¾ of an inch (e.g., about 1 inch, about 1.5 inches, or about 2 inches).
(11) In some embodiments, the proximal end 310 of the elongated body of the extender 302 is configured to matingly engage the torch body 304 via a proximal interface that includes, for example, a threaded connection between the torch body 304 and the extender 302. The distal end 312 of the elongated body of the extender 302 is configured to matingly engage the one or more consumables of the torch tip 306 via a distal interface. The extender 302 has an extended length along the longitudinal axis A such that it extends and relocates the engagement/mounting locations of the consumables in a spaced relationship relative to the proximal interface at which the torch body 304 is connected. In some embodiments, at the distal end 312 of the extender 302, the electrode holder 350, the swirl ring holder 352, the nozzle holder 354 and the shield holder 356 of the extender 302 are configured to physically engage the electrode 318, a swirl ring 358, the nozzle 320 and the shield 322, respectively. Thus, the extender 302 functions as a holder to physically retain various consumables of the torch tip 306 at its distal end 312 while extending their mounting locations relative to the torch body 304. As shown, the electrode holder 350, the swirl ring holder 352, the nozzle holder 354 and the shield holder 356 can be concentrically disposed relative to each other about the central longitudinal axis A. For example, the swirl ring holder 352 can substantially surround an exterior surface of the electrode holder 350, the nozzle holder 354 can substantially surround an exterior surface of the swirl ring holder 352, and the shield holder 356 can substantially surround an exterior surface of the nozzle holder 354.
(12) In some embodiments, the electrode holder 350 is configured to engage and hold the electrode 318, where the electrode 318 can also be elongated (i.e., has an elongated body) along the longitudinal axis A. The elongated body of the electrode 318 can be defined by (i) a length extending along the longitudinal axis A between the distal end 324 and the proximal end 326 of the electrode 318, and (ii) a diameter associated with the widest portion of the electrode body along the longitudinal axis A. The distal end 324 of the electrode body includes a bore for receiving a hafnium insert. In some embodiments, the length of the electrode body is variable, such as greater than about 1.75 inches (e.g., about 4.75 inches, about 7.75 inches or about 8.75 inches). In some embodiments, the diameter of the electrode body is less than about 0.25 inches (e.g., 0.245 inches). In some embodiments, the ratio of the length to the diameter of the electrode body is greater than about 5, such as greater than about 7.
(13) The proximal end 326 of the electrode 318 and the distal end of the electrode holder 350 of the extender 302 are configured to physically engage with each other, such that the proximal end 326 of the electrode body is mounted onto the distal end of the electrode holder 350. For example, the proximal end 326 of the electrode body can include at least one interior thread (not shown) disposed along the wall of a cavity 328 within the electrode body, where the opening of the cavity 328 is exposed at the proximal end 326 of the electrode 318. The cavity 328 is configured to receive a distal portion 330 of the electrode holder 350. Specifically, the thread on the wall of the cavity 328 is configured to engage a complementary thread (not shown) on an external surface of the distal portion 330 of the electrode holder 350 after the distal portion 330 is inserted into the cavity 328.
(14) In some embodiments, the cavity 328 of the electrode body comprises two portions, a wider portion 328a located proximal to a narrower portion 328b. Specifically, the width of the wider portion 328a along a radial axis (that is perpendicular to the longitudinal axis A) is larger than the width of the narrower portion 328b. Similarly, the distal portion 330 of the electrode holder 350 of the extender 302 can have a wider part 330a adjacent to a protruding boss part 330b that is narrower in width (along the radial axis) than that of the wider part 330a. The threaded connections can be disposed on the respective ones of the wider cavity portion 328a and the wider electrode holder part 330a to enable the threaded engagement of the two components as described above. The narrower cavity portion 328b of the electrode 318 can be shaped and sized to snuggly receive and substantially surround the protruding boss part 330b of the electrode holder 350 (e.g., via a tolerance fit), which further axially and radially aligns the electrode 318 relative to the extender 302 while providing extra rigidity to the connection. This additional alignment minimizes physical contact (e.g., ensures no physical contact) between the distal end 324 of the electrode 318 and the inner surface of the nozzle 320 while the electrode 318 is suspended within the hollow body of the nozzle 320. In alternative embodiments, the threads can be disposed on the narrower portion 328b of the electrode 318 and the narrower part 330b of the electrode holder 350 to facilitate thread engagement between the two components, while the wider portion 328a of the electrode 318 and the wider part 330a of the electrode holder 350 have the alignment surfaces for aligning the two components relative to each other.
(15) The proximal end of the electrode holder 350 is configured to matingly engage the torch body 304 so that the electrode holder 350 is able to retain the electrode 318 against the torch body 304. In some embodiments, a cavity 332 is formed in the elongated body of the electrode holder 350 with an opening to the cavity 332 exposed at the proximal end 310. The cavity 332 of the electrode holder 350 is configured to receive and house at least a portion of a liquid coolant tube 334 of the torch body 304. The liquid coolant tube 334 conducts a liquid coolant flow distally along the longitudinally axis A within the cavity 332 of the electrode holder 350, thus providing a liquid cooling path in the interior of the elongated body of the electrode holder 350. In some embodiments, the liquid coolant tube 334 only extends through a first portion 336a of the electrode holder body and is absent from the remaining portion 336b of the electrode holder body. In some embodiments, a diameter of the first portion 336a (along a radial axis perpendicular to the longitudinal axis A) within which the coolant tube extends is less than about 1 inch. Further, the cavity 332 within which the coolant tube 334 is inserted does not extend through the entire length of the remaining portion 336 of the electrode holder 350, but terminates proximate to a set of radial passages 364 in the remaining portion 336. Thus the remaining portion 336b of the body of the electrode holder 350 spaces the liquid coolant tube 334 and the cavity 332 from the electrode 318 upon assembly of the plasma arc torch, such that the liquid coolant tube 334 and the cavity 332 do not extend into the body of the electrode 318. In some embodiments, a spaced distance 362 along the longitudinal axis A between the distal end of the coolant tube 334 and the proximal end 326 of the electrode 318 within the torch 300 is about 1.25 inches. In some embodiments, a spaced distance along the longitudinal axis A between the radial passages 364 (i.e., the distal end of the cavity 332) and the proximal end 326 of the electrode 318 is about 0.2 inches to about 0.3 inches. In some embodiments, a spaced distance along the longitudinal axis A between the distal end of the coolant tube 334 and the radial passages 364 is about 0.3 inches (e.g., about 0.25 inches or about 0.15 inches).
(16) In some embodiments, the swirl ring holder 352 of the extender 302 is configured to engage the swirl ring 358 of the torch tip 306. As shown in FIG. 3, the swirl ring 358 substantially surrounds an exterior surface of the electrode 318 at the torch tip 306, where swirl ring 358 is configured to impart a swirling motion to a plasma gas flow therethrough. The swirl ring holder 352 is configured to (i) engage the swirl ring 358 at the distal end of the swirl ring holder 352 (ii) engage the torch body 304 at the proximal end of the swirl ring holder 352, and (iii) substantially surround the electrode holder 350 in a radially-spaced relationship within the extender 302. Therefore, the swirl ring holder 352 is able to axially and radially align the swirl ring 358 relative to the electrode 318 while retaining the swirl ring 358 against the torch body 304. In some embodiments, the swirl ring 358 is pre-assembled into the extender 302, such as coupled to the swirl ring holder 352, prior to attaching other consumables (e.g., the electrode 318, the nozzle 320 and/or the shield 322) to the distal end of the extender 302 to assemble the torch 300. In some embodiments, the swirl ring holder 352 and the nozzle holder 354 are permanently connected/assembled/joined as a single extender.
(17) In some embodiments, the nozzle holder 354 of the extender 302 is configured to engage the nozzle 320 of the torch tip 306, where the nozzle 320 can also be elongated (i.e., has an elongated body) along the longitudinal axis A. The elongated nozzle body can be defined by a length extending along the longitudinal axis A and a diameter associated with the widest portion of the nozzle body along the longitudinal axis A. In some embodiments, the ratio of the length to the diameter of the nozzle body is greater than about 1.75. For example, the length of the nozzle body can be variable, such as about 1.45 inches, about 4.45 inches, about 7.45 inches, or about 8.45 inches. The diameter of the nozzle body can be less than about 0.6 inches (e.g., 0.58 inches).
(18) The nozzle body is substantially hollow to receive at least a portion of the electrode 318, while maintaining a spaced relationship relative to the portion of the electrode 318 disposed therein. Such radial and axial alignment of the nozzle 320 relative to the electrode 318 can be at least partly provided by the nozzle holder 354, which is configured to engage the nozzle 320 at its distal end, engage the torch body 304 at its proximal end, and substantially surround the swirl ring holder 352 (which surrounds the electrode holder 350) within the extender 302.
(19) In some embodiments, the shield holder 356 of the extender 302 is configured to engage the shield 322 of the torch tip 306. As shown in FIG. 3, the shield 322 has a substantially hollow body configured to receive at least a portion of the nozzle 320. The shield holder 356 is configured to (i) engage the shield 322 at the distal end of the shield holder 356 (ii) engage the torch body 304 at the proximal end of the shield holder 356, and (iii) substantially surround the nozzle holder 356 in a radially-spaced relationship within the extender 302. Therefore, the shield holder 356 is able to axially and radially align the shield 322 relative to the nozzle 320 while retaining the shield 322 against the torch body 304.
(20) FIG. 4 shows a sectional-view of a portion of the torch tip 306 of FIG. 3 that includes the nozzle 320 and the shield 322, according to some embodiments of the present invention. As shown, the nozzle 320 can have a set of passages 402 disposed along a circumference of the nozzle 320, where the passages 402 can be located proximal to the shield 322 along the longitudinal axis A. The set of nozzle passages 402 can be radially-oriented to conduct a plasma gas from the interior surface of the nozzle 320 to the exterior surface of the nozzle 320. Details regarding this gas flow will be described below in detail. The shield 322 substantially surrounds a distal portion of the nozzle 320 and is coupled to the nozzle 320 via an insulator 360 disposed therebetween. The insulator 360 can be made from an electrically insulating material to provide electrical insulation between the shield 322 and the nozzle 320. Additionally, the insulator 360 can provide thermal insulation between the shield 322 and the nozzle 320 for balancing and isolating heat loads. Further, the insulator 360 physically spaces the shield 322 from the nozzle 320 to create a channel 416 therebetween for gas flows, which will be described in detail below. In some embodiments, the nozzle 320 and the shield 322 are coupled together via the insulator 360, where the resulting combination is installed onto the distal end of the extender 302, such as retained by the shield holder 356 of the extender 302 and aligned by the combination of the nozzle holder 354 and the shield holder 356.
(21) FIGS. 5a and 5b show a perspective view and a profile view, respectively, of the shield 322 of FIG. 4, according to some embodiments of the present invention. As shown, the shield 322 has a substantially hollow body extending between a distal end 502 and a proximal end 504. The proximal end 504 of the shield 322 can include a set of radially-oriented passages 506 dispersed around a first circumference of the shield 322. The radially-oriented passages 506 are configured to fluidly connect an exterior surface of the shield 322 to an interior surface of the shield 322 and impart a swirling motion on a gas flow therethrough. Additionally, the shield 322 can include a set of axially-oriented passages 508 dispersed around a second circumference of the shield 322. The axially-oriented passages 508 can be one or more grooves etched into the external surface of the shield 322. These axially-oriented passages 508 are configured to axially conduct, along the longitudinal axis A, a gas flow over the external surface of the shield 322 from the proximal end 504 to the distal end 502. In some embodiments, the axially-oriented passages 508 are interspersed with the radially-oriented passages 506 around a circumference of the proximal end 504 of the shield 322. Further, the shield 322 can include a set of vent passages 510 disposed at the distal end 502 of the shield 322 close to a shield exit orifice 512. Details regarding gas flows through these passages 504, 508 and 510 will be provided below.
(22) Referring back to the plasma arc torch 300 of FIG. 3, in some embodiments, the torch 300 includes one or more retaining components to further retain the consumables of the torch tip 306 to the extender 302 and/or the extender 302 to the torch body 304. For example, an inner retaining cap 380 can be disposed between the nozzle holder 354 and the shield holder 356, where the inner retaining cap 380 is configured to retain the nozzle holder 354 and the components that are either directly or indirectly attached to the nozzle holder 354 (e.g., the electrode holder 350, the swirl ring holder 352, the electrode 318, the swirl ring 358 and/or the nozzle 320), to the torch body 304. In some embodiments, an outer retaining cap 382 can be disposed over the inner retaining cap 380 and configured to retain the shield holder 356 (hence the shield 322 connected to the shield holder 356) to the torch body 304. The inner retaining cap 380 and/or the outer retaining cap 382 can be components of the extender 302 or stand-alone components separate from the extender 302.
(23) In another aspect, the plasma arc torch 300 of FIG. 3 is configured to minimize (e.g., prevent) liquid cooling of the torch tip 306. Instead, the torch tip 306, which includes the electrode 318, the nozzle 320 and the shield 322, can be gas cooled by one or more gases introduced to the torch tip 306. In some embodiments, the coolant tube 334 of the torch body 304 conveys a liquid coolant to the extender 302 upon insertion of the coolant tube 334 into the cavity 332 of the electrode holder 350 of the extender 302 at its proximal end. However, the extender 302 is configured to return the liquid coolant to the torch body 304 without the coolant being circulated to the torch tip 306.
(24) FIG. 3 illustrates an exemplary coolant flow path 680 within the torch 300. As shown, the liquid coolant conveyed by the coolant tube 334 is adapted to flow distally within the cavity 332, through the first portion 336a of the electrode holder 350 (within which the coolant tube 334 is inserted). Upon exiting the coolant tube 334, the coolant flow 680 is released into the cavity 332 and flows distally through only a section of the remaining portion 336b of the electrode holder 350. This is because the cavity 334 does not extend through the entire length of the remaining portion 336 and thus does not conduct the liquid coolant to the electrode 318. Instead, upon entering the remaining portion 336b of the electrode holder 350 within the cavity 332, the coolant flow 680 encounters the set of radial passages 364 that are located within the remaining portion 336b and spaced from the proximal end 326 of the electrode 318. The cavity 332 is configured to terminate at the set of radial passages 364 within the remaining portion 336b. Each radial passage 364 is in fluid communication with the cavity 332 and connects an interior surface of the electrode holder 350 to an exterior surface of the electrode holder 350. Each radial passage 364 can be radially oriented (i.e., along a radial axis perpendicular to the longitudinal axis A) to convey the liquid coolant flow 680 in the cavity 332 radially away from the electrode holder 350 and into the swirl ring holder 352. In some embodiments, liquid cooling within the electrode holder 350 is confined to a region of less than one inch in diameter (e.g., the cavity 332 has a diameter of less than one inch at its widest section).
(25) Upon exiting the electrode holder 350 and entering a region between the electrode holder 350 and the swirl ring holder 352, the coolant flow 680 is adapted to immediately exit the swirl ring holder 352 via one or more radial passages 365 disposed in the body of the swirl ring holder 352 and axially aligned with the radial passages 364 of the electrode holder 350. Each radial passage 365 of the swirl ring holder 352 is adapted to connect an interior surface to an exterior surface of the swirl ring holder 352. Upon exiting from the swirl ring holder 352, the coolant flow 680 is adapted to travel proximally toward the torch body 304 in an axially-oriented channel 366 defined by the external surface of the swirl ring holder 352 and the internal surface of the nozzle holder 354. In some embodiments, one or more radial passages 368 are disposed in the body of the nozzle holder 354, where each radial passage 368 connects an interior surface to an exterior surface of the nozzle holder 354. Further, one or more radial passages 370 can be disposed in the body of the inner retaining cap 380, where each radial passage 370 connects an interior surface to an exterior surface of the inner retaining cap 380. The passages 368 in the nozzle holder 354 and the passages 370 in the inner retaining cap 380 can be axially aligned with each other, but positioned proximal to the radial passages 364, 365 in the electrode holder 350 and the swirl ring holder 352. In operation, the radial passages 368, 370 are in fluid communication with the channel 366 between the swirl ring holder 352 and the nozzle holder 354 to conduct the liquid coolant flow 680 radially away from the nozzle holder 354 and into an axially-oriented channel 372 between an exterior surface of the inner retaining cap 380 and an interior surface of the outer retaining cap 382. The coolant flow 680 is adapted to travel proximally within this channel 372 to return to the torch body 304.
(26) Thus, the liquid coolant flow 680 does not make contact with the electrode 318 or other components in the torch tip 306, such as the swirl ring 358, the nozzle 320 and/or the shield 322, before being returned to the torch body 304. This U-shaped flow path 680 is different from the coolant flow path 250 in the prior art plasma arc torch 200 of FIG. 2, where the coolant flow 250 travels in a zig-zag, back-and-forth fashion to contact cool the electrode 205, the nozzle 210 and the shield 225 before being returned to the torch body along the outer retaining cap 218. In alternative embodiments, the liquid coolant flow 680 extends completely through electrode holder 350, passing through cavity sections 328a and 328b to contact and/or enter a portion of electrode 318.
(27) In some embodiments, the various consumable components in the torch tip 306 of the plasma arc torch 300 are cooled by one or more gases. With reference to FIG. 4, a plasma gas flow 410 can be provided to the nozzle 320 between an interior surface of the nozzle 320 and an exterior surface of the electrode 318 (not shown in FIG. 4). The plasma gas flow 410 travels distally within the nozzle 320 toward the set of passages 402 disposed along a circumference of the nozzle 320. The set of nozzle passages 402 can be radially-oriented to divert at least a portion 411 of the plasma gas flow 410 from an interior surface to an exterior surface of the nozzle 320. In addition, a shield gas flow 412 can be provided to travel distally toward the shield 322 over an exterior surface of the nozzle 320. The diverted plasma gas flow 411 and the shield gas flow 412 are adapted to combine at the exterior surface of the nozzle 320 to form a combined gas flow 414 that travels distally toward the shield exit orifice 512 over an exterior surface of the shield 322. In general, the diverted plasma gas flow 411, the shield gas flow 412 and the combined gas flow 414 can cooperatively cool various consumable components of the torch tip 306, including the electrode 318, the nozzle 320 and the shield 322.
(28) In some embodiments, the combined gas flow 414 cools the shield 322 and the nozzle 320 as it travels distally toward the shield exit orifice 512. As shown in FIG. 4, a portion 414a of the combined gas flow 414 is adapted to enter the set of radially-oriented passages 506 of the shield 322 from an exterior surface of the shield 322 to an interior surface of the shield 322. Thereafter, the combined gas flow portion 414a flows distally through a channel 416 formed between the exterior surface of the nozzle 320 and the interior surface of the shield 322. This distal flow 414a is adapted to cool both the nozzle 320 and the shield 322 as it travels through the channel 416 and exits via the shield exit orifice 512. In some embodiments, the set of radially-oriented passages 506 are configured (e.g., canted) to impart a swirling motion to the combined gas flow portion 414a therethrough. In some embodiments, a portion of the distal flow portion 414a in the channel 416 can be vented to atmosphere via the vent passages 510 to further facilitate shield cooling. In addition, another portion 414b of the combined gas flow 414 is configured to flow through the set of axially-oriented passages 508 (shown in FIGS. 5a and 5b), such as in the form of one or more grooves etched into the external surface of the shield 322. These passages 508 are configured to axially conduct, along the longitudinal axis A, the combined gas flow portion 414b over the external surface of the shield 322 from the proximal end 504 to the distal end 502 to cool the external surface of the shield 322.
(29) As explained above, the radially-oriented passages 402 of the nozzle 320 are in fluid communication with the radially-oriented passages 506 and axially-oriented passages 508 of the shield 322 to propagate the diverted plasma gas flow 411 and facilitate gas cooling at the torch tip 306. Further, the torch tip 306 can be substantially cooled by at least one of the plasma gas flow 411, the shield gas flow 412 or the combined gas flow 414 (including gas flows 414a and 414b) without being cooled by a liquid coolant in the coolant tube 334 of the electrode holder 350. Thus, the plasma arc torch 300 can have a hybrid cooling configuration that includes liquid cooling of the extender 302 and gas cooling of the torch tip 306.
(30) In some embodiments, the plasma arc torch 300 is adapted to generate a plasma arc using a contact start method. In alternative embodiments, the plasma arc torch 300 can initiate a plasma arc using a high-frequency, high-voltage (HFHV) method, as is known in the art. For example, the plasma arc torch 300 can generate a pilot arc using a pilot arc current supplied from a power supply (not shown) to the torch 300, where the pilot arc current is associated with a HFHV signal.
(31) FIG. 6 shows a profile view of the plasma arc torch 300 of FIG. 3, according to some embodiments of the present invention. As shown, the combination of the extender 302 and the consumables elongate the overall length of the torch 300 along the longitudinal axis A while reducing the width/thickness of the torch 300 at the tip portion 612. The length (L) 602 of a distal portion 610 of the torch 300, which includes the narrow tip portion 612 of the extender 302 and the shield 322 after assembly, can be about 3 inches. However, the lengths of the extender 302 and/or the consumable components, such as the electrode 318, the nozzle 322 and/or the shield 322, can be extended to any desirable dimension to adapt to any desirable application. For example, the length L 602 of the distal portion 610 can be greater than 3 inches, such as 6 inches, 9 inches or 10 inches, or any desired length. To achieve a length L 602 of 3 inches, the length of the electrode can be 1.75 inches and the length of the nozzle can be 1.45 inches. To achieve a length L 602 of 6 inches, the length of the electrode can be 4.75 inches and the length of the nozzle can be 4.45 inches. To achieve a length L 602 of 9 inches, the length of the electrode can be 7.75 inches and the length of the nozzle can be 7.45 inches. To achieve a length L 602 of 10 inches, the length of the electrode can be 8.75 inches and the length of the nozzle can be 8.45 inches. In some embodiments, the length of the extender 302 is variable and can be selected to achieve a desired overall length of the torch and/or accommodate certain features of the consumable component(s) attached to the extender 302. For example, if the electrode 318 and nozzle 320 are extended, then the shield holder 356 also needs to be extended to hold together these components and retain them to the torch body 304. In addition, one or more of the nozzle holder 354, the swirl ring holder 352, or the electrode holder 350 can be lengthened as well. Further, the extender 302 and/or the consumables at the torch tip 306 can be easily engaged and disengaged from the torch body 304 in order to achieve the combination with the desired overall length. For example, a shorter torch 300 with a shorter extender 302 can be used for a more beveled cut while a longer extender 302 can be used to cut larger flanges. Such interchangeability increases the versatility of plasma arc torch usage.
(32) In some embodiments, the diameter (D) 604 of the narrow tip portion of the extender 302 can be less than about 1 inch, such as about 0.8 inches. This means that the diameter of each the electrode holder 350, the swirl ring holder 352, the nozzle holder 354 and the shield holder 356 of the extender 302 along the entirety of the extended tip portion 602 (e.g., for greater than at least one inch in length) is less than about 1 inch. In some embodiments, the diameter 606 of the shield exit orifice 512 is about 0.2 inches. In addition, an angle 608 of the shield 322 can be about 60 degrees. This long and narrow distal portion 610 of the torch 300 allows the torch 300 to reach and operate in distant or hard-to-reach cutting zones and make cuts at steep angles that a conventional prior art torch cannot, such as the torch 100 of FIG. 1 or the torch 200 of FIG. 2.
(33) FIG. 7 shows a visual comparison of the plasma arc torch 300 of FIG. 3 with the prior art torch 200 of FIG. 2 when processing a flanged workpiece 700, according to some embodiments of the present invention. As shown, the distal portion 610 of the plasma arc torch 300 is able to be positioned much closer to the vertical flange 702 of the workpiece 700 along the horizontal flange 704 than that of the conventional torch 200. Thus, the plasma arc torch 300 is able to cut the flange 702 from the workpiece 700 with minimal damage in comparison to the cut that can be made by the conventional torch 300.
(34) In yet another aspect, a method is provided for assembling the plasma arc torch 300 of FIG. 3. FIGS. 8a-8c show various stages of assembly of the plasma arc torch 300 of FIG. 3, according to some embodiments of the present invention. In general, as shown in FIG. 8a, the plasma arc torch 300 can be assembled in four parts, a proximal sub-assembly 802, the electrode 318, a central sub-assembly 804, and a distal sub-assembly 806. As shown in FIG. 8b, the proximal sub-assembly 802 includes the torch body 304, the electrode holder 350, a combination 806 of the swirl ring holder 352, the swirl ring 358 and the nozzle holder 354, and the inner retaining cap 380. Details for assembling the holder combination 806 is provided below with reference to FIG. 8c. To assemble the proximal sub-assembly 802, the electrode holder 350 is inserted into the hollow body of the holder combination 806 from its proximal end, such that the holder combination 806 substantially surrounds the electrode holder 350. The resulting combination of the electrode holder 350 and the holder combination 806 is then disposed into the inner retaining cap 380 from its proximal end such that the inner retaining cap 380 substantially surrounds an exterior section of the distal end of the holder combination 806. Thereafter, the resulting combination of the electrode holder 350, the holder combination 806 and the inner retaining cap 380 is attached to the proximal end of the torch body 304 to form the proximal sub-assembly 802. To assemble the central sub-assembly 804, the nozzle 320 is disposed into the hollow body of the shield 322 from the proximal end of the shield 322 such that the shield 322 substantially surrounds the nozzle 320 and is attached to the shield 322 via the insulator 360. To assemble the distal sub-assembly 806, the shield holder 356 is disposed into the outer retaining cap 382 from the distal end of the outer retaining cap 382 such that the outer retaining cap 382 substantially surrounds an exterior section of the distal end of the shield holder 356.
(35) Referring back to FIG. 8a, to fully assembly the torch 300, the electrode 318 is coupled to the distal end of the proximal sub-assembly 802 such that a proximal portion of the electrode 318 is in threaded engagement with the electrode holder 352 in the sub-assembly 802. The central sub-assembly 804, which includes the nozzle 320 coupled to the shield 322 is then attached to proximal sub-assembly 802 by engaging the proximal end of the nozzle 320 of the central sub-assembly 804 with the distal end of the nozzle holder 354 of the proximal sub-assembly 802. This engagement allows the distal end of the electrode 318 to be suspended within the hollow body of the nozzle 320. Thereafter, to fully assembly the torch 300, the distal sub-assembly 806, which includes the outer retaining cap 382 and the shield holder 806, is attached to the torch body 304 of the proximal sub-assembly 802 such that the shield holder 354 substantially surrounds the nozzle holder 352 and the outer retaining cap 382 substantially surrounds the inner retaining cap 380. The outer retaining cap 382 retains the shield holder 806 to the proximal sub-assembly 802.
(36) With reference to FIG. 8c, to form the holder combination 806 of the proximal sub-assembly 802, the swirl ring 358 is coupled to an outer circumference of the swirl ring holder 352 from the distal end of the swirl ring holder 352, where the swirl ring 358 can be held in place by a groove 810 etched into an exterior surface of the swirl ring holder 352. A nozzle insulator 812 can be disposed into the hollow body of the nozzle holder 354 such that the nozzle insulator 812 is coupled to an inner circumference of the nozzle holder 354. The nozzle insulator 812 is configured to electrically insulate/distance the conductive surfaces of the nozzle holder 354 and the electrode holder 350 through radial passages 364 to prevent arcing during operation (e.g., via the liquid coolant). To form the holder combination 806, the combination 814 of the swirl ring 358 and the swirl-ring holder 352 is coupled to the combination 816 of the nozzle insulator 812 and the nozzle holder 354 such that the nozzle holder 354 substantially surrounds the swirl ring holder 352 (and the swirl ring 358), with the nozzle insulator 812 sandwiched between the two components.
(37) It should 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. Modifications may also occur to those skilled in the art upon reading the specification.
