Plasma arc cutting system including retention cap and related method of operation

Abstract

The invention relates to an inner cap for a liquid-cooled plasma arc welding gun. The inner cap includes a body having a longitudinal axis, a first end, and a second end. The first end includes an annular portion disposed proximate the welding gun tip. A liquid channel is formed within the body, shaped to transport a liquid therethrough, and has a first set of ports formed in the annular portion. A gas channel is formed within the body, shaped to transport gas therethrough, and includes a second set of ports formed in the annular portion. The annular portion is configured such that a subset of ports in the first set of ports directs the liquid in a radial direction relative to the longitudinal axis, and alternate in a rotational direction about the longitudinal axis with a subset of ports in the second set of ports.

Description

[0001] Related Applications This application claims the benefit of U.S. Provisional Patent Application Serial No. 62 / 320,935, filed on April 11, 2016, and entitled “Consumables for Plasma Arc Welding Guns,” the entire contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] The present invention relates generally to the field of plasma arc cutting systems and processes. More specifically, the present invention relates to improved consumable components (eg, inner caps, nozzle caps, or retaining caps) and operating methods for operating and cooling plasma arc welding guns. Background Art

[0003] Plasma arc welding guns are widely used for cutting and marking materials. Plasma arc welding guns generally include an electrode and a nozzle having a central outlet orifice mounted in the welding gun body, electrical connections, channels for cooling, and channels for arc control fluid (for example, plasma gas). The welding gun produces a plasma arc, i.e., a compressed, ionized jet of gas with high temperature and high momentum. The gas used in the welding gun can be non-reactive (for example, argon or nitrogen) or reactive (for example, oxygen or air). During operation, a pilot arc is first generated between the electrode (cathode) and the nozzle (anode). The generation of the pilot arc can rely on a high frequency, high voltage signal connected to a DC power supply and the welding gun or on any of a variety of starting methods.

[0004] In many prior art plasma arc welding guns, the coolant travels along a circuitous path within the welding gun (for example, forward to the nozzle, then back to the welding gun head, then forward to the shield, then back to the welding gun head), thereby requiring significant driving force to propel the coolant within the welding gun. One example of such a prior art welding gun is shown and described in U.S. Patent No. 8,389,887, entitled "Apparatus and Method for Liquid-Cooled Shield for Improved Penetration Performance". In this arrangement, the coolant flows from a source through the plasma arc welding gun to the surface of the shield and back through the plasma arc welding gun, thereby requiring the coolant to make multiple passes to contact both the shield and the nozzle. Some other prior art welding guns still have significant dead spots in the coolant flow and / or unidirectional coolant flow, which does not provide uniform cooling of the nozzle, shield and other consumables in the welding gun tip. What is needed is a configuration in which the coolant is sent directly to the consumables so that minimal driving force is required to move the coolant through the plasma arc welding gun in a substantially consistent and symmetrical manner. Summary of the invention

[0005] The present invention relates to improved consumables (for example, inner caps, including nozzle caps and retaining caps) for plasma arc welding guns and associated methods of directing fluid flow and cooling consumables in plasma arc welding guns. A staggered series of orifices or slots, some of which convey liquid coolant and some of which convey shroud gas, are disposed in the inner cap to produce a cross-flow of liquid and gas within and / or through the inner cap. An axially oriented group of holes permits shroud gas to be conveyed to the shroud, and a radially oriented group of holes permits liquid coolant to be conveyed from the nozzle to the shroud, all within an annular portion (or "neck") of the inner cap proximate the plenum.

[0006] The present invention enables coolant to move directly through the consumables via a direct coolant path, thereby minimizing the driving force needed to propel the coolant through the welding gun. Additionally, the present invention uses space more efficiently in the annular portion of the inner cap, enabling certain structures to be removed from the welding gun itself. In some embodiments, this reorganization allows the "pointiness" of the welding gun to be increased, which can be beneficial for robotic applications and can make it easier for the welding gun to fit into tight spaces.

[0007] In addition, the present invention reorganizes the inlet and outlet to be substantially radially symmetrical, where the consumables are fed from 360 degrees. This is in contrast to previous designs, which were fed from 180 degrees (i.e., there was an "in" flow side and an "out" flow side), where the inlet and outlet needed to be oriented relative to each other, and where dead spots and uneven cooling in the welding gun tip were common. The key feature is to push some of the more complex welding gun structures into the retaining cap, allowing complex machining processes to be completed less frequently. In addition, the shield cap is allowed to be manufactured as a single part (rather than as two parts), which leads to cost and weight savings. In particular, the shield cap now needs to guide the coolant in only one direction. In the previous technology, the shield cap included two parts because the coolant traveled back into the welding gun after cooling the nozzle. The coolant then had to be guided forward to the shield and back through the shield cap to the power supply. Because the coolant had to go to the shield and back from the shield, it required two parts. The direct path from the nozzle to the shield enables the present invention to use a single-part shield cap.

[0008] In one aspect, the present invention relates to an inner cap for a liquid-cooled plasma arc welding gun. The inner cap includes a substantially hollow body having a longitudinal axis, a first end, and a second end. The first end includes an annular portion configured to be arranged adjacent to a torch tip of the plasma arc welding gun. The inner cap also includes a liquid channel formed in the body and shaped to transport liquid therethrough. The liquid channel has a first set of ports formed in the annular portion. The inner cap also has a gas channel formed in the body and shaped to transport gas therethrough. The gas channel includes a second set of ports formed in the annular portion. The annular portion is constructed so that a subset of the ports in the first set of ports directs liquid in a radial direction relative to the longitudinal axis, and alternates in a rotational direction around the longitudinal axis with a subset of the ports in the second set of ports that direct gas in a direction substantially parallel to the longitudinal axis.

[0009] In some embodiments, the first set of ports is staggered with the second set of ports to produce a cross flow of liquid and gas in the annular portion during operation of the plasma torch. In some embodiments, each port in the first set of ports is perpendicular or substantially perpendicular to a corresponding port in the second set of ports. In some embodiments, the first set of ports is oriented perpendicular to the longitudinal axis and the second set of ports is oriented parallel to the longitudinal axis. In some embodiments, the plenum region is at least partially formed within the body. In some embodiments, a passage is formed in the body and is configured to transfer fluid between an inner surface of the plenum region and an outer surface of a nozzle of the plasma arc torch during operation of the plasma arc torch. In some embodiments, the passage extends circumferentially around the plenum region.

[0010] In some embodiments, the inner cap is electrically insulating. In some embodiments, at least one of the first and second sets of ports includes a notch in the body. In some embodiments, the gas passage is configured to convey shield gas and the liquid passage is configured to convey consumable coolant. In some embodiments, the inner cap includes a third set of ports aligned with the first set of ports to form a grouped liquid flow path through the inner cap. In some embodiments, the first end includes a tapered portion adjacent to the annular portion. In some embodiments, the first end includes a neck portion.

[0011] In some embodiments, the gas channel includes a first group of paths that are connected to the inner area of ​​the inner cap in a flow-through manner, and the liquid channel includes a second group of paths that are connected to the inner and outer areas of the inner cap in a flow-through manner. In some embodiments, the inner cap includes an outer portion and an inner portion, and the outer portion at least substantially surrounds the inner portion. In some embodiments, the inner cap includes a snap-on structure configured to fasten the outer portion to the inner portion. In some embodiments, the outer portion is formed of plastic, and the inner portion is formed of metal or a metal alloy, for example, brass. Notches can be milled into the brass piece, which is helpful during assembly because when the plastic is squeezed onto the brass piece, a stress riser (riser) that can break or cut the plastic is eliminated. In some embodiments, the first group of holes in the inner cap includes five to nine holes, and the second group of holes in the inner cap includes six to eighteen holes. In some embodiments, the ratio of the flow area between the second group of holes and the grouped measurement holes in the first end of the inner cap is at least 2: 1. In some embodiments, the inner cap is symmetrical in the direction of rotation.

[0012] In another aspect, the present invention relates to an inner cap for a liquid-cooled plasma arc welding gun. The inner cap includes an inner member having an inner surface and an outer surface, the inner member defining a longitudinal axis of the inner cap. The inner cap also includes an outer member arranged circumferentially around the inner member, the outer member having an inner surface, an outer surface, and an annular region. The annular region extends beyond the inner member toward the welding gun end of the inner cap along the longitudinal axis. The inner cap also includes a group of radial liquid flow channels formed in the annular region of the outer member and oriented perpendicular to the longitudinal direction. The group of liquid flow channels is configured to convey liquid coolant from the nozzle of the plasma arc welding gun to the shield of the plasma arc welding gun. The inner cap also includes a gas passage formed in the inner cap. The gas passage includes a first portion defined at least in part by a portion of the outer surface of the inner member and a portion of the inner surface of the outer member. The gas passage also includes a second portion defined in the annular region of the outer member. The second portion includes a group of axial gas flow channels configured to convey gas to the shield of the plasma arc welding gun. In the annular region, subsets of flow channels in the group of liquid flow channels and the group of gas flow channels alternate in a rotational direction about the longitudinal axis to generate cross-flows of liquid and gas during operation of the plasma arc torch. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The foregoing discussion will be more readily understood from the following detailed description of the invention taken in conjunction with the accompanying drawings.

[0014] Figure 1A is a perspective view of an inner cap for a liquid-cooled plasma arc welding torch according to an illustrative embodiment of the invention.

[0015] Figure 1B According to an illustrative embodiment of the present invention, Figure 1A A half-section perspective view of the inner cap shown in FIG.

[0016] Figure 2 is a cross-sectional view of an inner cap of a liquid-cooled plasma arc torch for installation in a plasma arc torch according to an illustrative embodiment of the invention. DETAILED DESCRIPTION

[0017] Figure 1A is a perspective view of an inner cap 100 for a liquid-cooled plasma arc welding torch according to an illustrative embodiment of the present invention, and Figure 1B is Figure 1A 1 is a half-section perspective view of the inner cap 100 shown in FIG. The inner cap 100 includes a substantially hollow body 102 having a longitudinal axis 104, a first end 106, and a second end 108. The first end 106 includes an annular portion 110 configured to be disposed proximate to a torch tip of a plasma arc torch. The inner cap 100 includes a liquid passage 114 (for example, having a first set of ports 114A-114F in the annular portion 110) formed in the body 102 and shaped to transport liquid therethrough. The inner cap 100 also includes a gas passage 118 (for example, having a second set of ports 118A-118C formed in the annular portion 110) formed in the body 102 and shaped to transport gas therethrough. The gas passage is configured to convey shield gas, and the liquid passage is configured to convey consumable coolant.

[0018] As in Figure 1A-1B As shown in the embodiment of FIG. 1 , a subset of ports in the first set of ports 114A-114F directs liquid in a radial direction relative to the longitudinal axis 104 and alternates with a subset of ports in the second set of ports 118A-118C directing gas in a direction substantially parallel to the longitudinal axis 104 in a rotational direction about the longitudinal axis 104. For example, in Figure 1A-1B , the subsets of ports alternate in radial directions about the longitudinal axis 104 as follows: 114A-114C; 118A; 114D-F; 118B; etc., such that the alternating pattern is three liquid ports followed by one gas port. In this manner, the first set of ports can be interleaved with the second set of ports to create alternating cross-flow regions of liquid and gas through the tip of the inner retaining cap during operation of the plasma torch. In such an arrangement, the inner cap 100 can create a full radial "shower head" effect, with liquid passing radially through the first set of ports in multiple streams, and gas passing vertically or substantially vertically through the second set of ports. This arrangement promotes, for example, more uniform cooling (for example, consistent cooling around the entire 360 ​​degrees) and gas flow.

[0019] In general, the subgroups of ports can each include one or more ports. In some embodiments, the subgroups of ports alternate in a regular pattern, for example, one gas port, followed by two liquid ports, followed by one gas port, followed by two liquid ports. In some embodiments, the subgroups of ports alternate in an irregular pattern, for example, one liquid port, two gas ports, three liquid ports, two gas ports. In some embodiments, only one liquid port and / or one gas port is used. In some embodiments, the grouped ports are oriented perpendicular or substantially perpendicular to each other, for example, each port in the first group of ports is perpendicular or substantially perpendicular to the corresponding port in the second group of ports. For example, the first group of ports can be oriented perpendicular to the longitudinal axis, and the second group of ports is oriented parallel to the longitudinal axis. In some embodiments, the first group of holes includes five to nine holes, and the second group of holes includes six to eighteen holes. In some embodiments, the axially oriented gas flow holes (for example, including but not limited to 118A-C) have a total cross-sectional area of ​​at least 0.0053 square inches. In some embodiments, the radially oriented coolant holes (including but not limited to 114A-F, for example) have a total cross-sectional area of ​​at least about 0.02 square inches, or alternatively about 0.041 square inches. In other embodiments, the total cross-sectional area of ​​the radially oriented coolant holes will permit as much as other constraints on the plasma arc torch. In some embodiments, the holes are uniformly distributed around the circumference to provide uniform cooling to the shroud.

[0020] In some embodiments, the inner cap 100 includes an outer portion (or outer member) 122 and an inner portion (or inner member) 123. The outer portion 122 has an outer surface 122A and an inner surface 122B, and the inner portion 123 has an outer surface 123A and an inner surface 123B. The outer portion 122 at least substantially surrounds the inner portion 123. The outer portion 122 can be formed of plastic, and the inner portion 123 can be formed of a metal or a metal alloy, such as brass. In some embodiments, the inner cap 100 includes a snap structure 124 configured to fasten the outer portion 122 to the inner portion 123. In some embodiments, the snap structure 124 includes a ridge or groove in the outer portion 122 and a corresponding protrusion in the inner portion 123, the protrusion fitting snugly into the ridge or groove to fasten the inner portion 123 to the outer portion 122. In some embodiments, the inner cap 100 is electrically insulating. In some embodiments, the first end 106 includes a tapered portion 126 adjacent to the annular portion 110. In some embodiments, the tapered portion 126 and the annular portion 110 form a neck portion.

[0021] As in Figure 1A-1BAs shown in FIG. 1 , a first portion 132 of the gas passageway is defined at least in part by a portion of the outer surface 123A of the inner member 123 and a portion of the inner surface 122B of the outer member 122. In some embodiments, a second portion 134 of the gas passageway is defined within the annular region 110 of the outer member 122. In some embodiments, at least one of the first and second sets of ports can include a slot in the body 102. Slots can be desirable because they are easier to manufacture than holes, which can be more expensive to drill. Slots can also be desirable because they allow for a larger coolant flow area than some alternative geometries, and in some embodiments, produce less pressure drop due to resistance from the walls of the slots. In some embodiments, the inner cap 100 includes a third set of ports 130 (e.g., 130A, 130B, 130C) aligned with the first set of ports 114 to form a set of liquid flow paths through the inner cap.

[0022] The second portion 134 can include a set of axial gas flow passages configured to deliver gas to a shield (hereinafter referred to as a shield) of the plasma arc torch. Figure 2 1 and 2). The second portion 134 can include a set of (e.g., six) holes drilled in the axial direction. The axial holes can simply "pass through", e.g., they do not have a swirl effect (contrary to past designs where they imparted some directionality to the fluid flow). In general, there should be a sufficient number and / or cross-sectional area of ​​the axial holes so that the holes are not a clogging point in the system. Additionally, the second set of holes and the set of measurement holes in the first end of the inner cap (e.g., in Figure 2 The ratio of the flow area between the vortex insulator 212 shown in FIG. 1 and described below can be at least 2: 1. In one exemplary configuration, the ratio is about 2.6: 1. In some embodiments, the inner cap 100 includes a plenum region 136 formed at least partially within the body 102.

[0023] Figure 2 FIG. 1 is a cross-sectional view of an inner cap 100 for a liquid-cooled plasma arc torch for installation in a plasma arc torch 200 according to an illustrative embodiment of the present invention. In this view, the features of the inner cap 100 described and shown above correspond to those in FIG. Figure 1A-1B. When installed in the plasma arc torch 200, the inner cap 100 surrounds (e.g., at least partially surrounds) the nozzle 204. The shield gas flows through the flow channel 132 along the flow path 233 within the inner cap 100 and impinges on the inner surface 204A of the shield 208. The shield gas then continues through the orifice 212A in the swirl insulator 212 of the plasma arc torch 200. The shield gas then continues along the flow channel 216 and exits the front orifice 220 of the plasma arc torch 200. Meanwhile, the liquid coolant flows from the nozzle 204 through the flow channel 224 of the inner cap 100 along the flow path 234. The liquid coolant is then transferred from the nozzle 204 side of the inner cap 100 to the shield 208 side of the inner cap 100 into the flow channel 228 (e.g., impinging on the contact point 133), back to the welding gun head. In this manner, the total distance traveled by the liquid coolant is reduced relative to past designs because the liquid coolant can be delivered directly from the nozzle to the shroud using the shortest path between the nozzle and the shroud.

[0024] During operation of the welding torch, both the liquid coolant and the shroud gas can flow simultaneously, thereby creating a cross-flow of liquid and gas within the inner cap. The nozzle 204 and the shroud 208 can be electrically isolated to minimize the risk of short circuiting, for example, via the coolant. In some embodiments, a passage (not shown) is formed in the body 102 and is configured to convey fluid between the inner surface of the plenum region 136 and the outer surface of the nozzle 204 of the plasma arc torch during operation of the plasma arc torch. In some embodiments, the passage extends circumferentially around the plenum region 136. In some embodiments, the shroud cap 260 is manufactured as a single part because the shroud cap 260 only directs coolant in one direction.

[0025] While the present invention has been particularly shown and described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes of details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An inner cap for a liquid-cooled plasma arc welding gun, the inner cap comprising: a substantially hollow body having a longitudinal axis, a first end, and a second end, the first end including an annular portion configured to be disposed proximate a torch tip of the plasma arc torch; a liquid passage formed in the body and shaped to transport liquid therethrough, the liquid passage including a first set of ports formed in the annular portion; as well as a gas passage formed in the body and shaped to transport shroud gas therethrough, the gas passage including a second set of ports formed in the annular portion, wherein the annular portion is configured such that a subset of ports in the first set of ports directs the liquid in a radial direction relative to the longitudinal axis and alternates rotationally about the longitudinal axis with a subset of ports in the second set of ports directing the shroud gas in a direction substantially parallel to the longitudinal axis, and wherein the first set of ports and the second set of ports are circumferentially spaced apart about the annular portion and positioned perpendicular or substantially perpendicular to each other to create a cross flow of liquid and shroud gas in the annular portion during operation of the welding gun.

2. The inner cap according to claim 1, characterized in that: The first set of ports is staggered with the second set of ports to create a cross flow of liquid and shroud gas in the annular portion during operation of the plasma torch.

3. The inner cap according to claim 1, characterized in that: Each port in the first set of ports is perpendicular or substantially perpendicular to a corresponding port in the second set of ports.

4. The inner cap according to claim 1, characterized in that: The first set of ports are oriented perpendicular to the longitudinal axis and the second set of ports are oriented parallel to the longitudinal axis.

5. The inner cap according to claim 1, characterized in that: Also included is a plenum region formed at least partially within the body.

6. The inner cap according to claim 5, characterized in that: Also included is a passage formed in the body and configured to communicate a fluid between an inner surface of the plenum region and an outer surface of a nozzle of the plasma arc torch during operation of the plasma arc torch.

7. The inner cap according to claim 6, characterized in that: The passage extends circumferentially around the plenum region.

8. The inner cap according to claim 1, characterized in that: The inner cap is electrically insulating.

9. The inner cap according to claim 1, characterized in that: At least one of the first set of ports and the second set of ports includes a notch in the body.

10. The inner cap according to claim 1, characterized in that: The liquid passage is configured to convey a consumable coolant.

11. The inner cap according to claim 1, characterized in that: Also included is a third set of ports aligned with the first set of ports to form a set of fluid flow paths through the inner cap.

12. The inner cap according to claim 1, characterized in that: The first end includes a tapered portion adjacent the annular portion.

13. The inner cap according to claim 1, characterized in that: The first end includes a neck portion.

14. The inner cap according to claim 1, characterized in that: The gas passage includes a first set of paths fluidly connected to an inner region of the inner cap, and the liquid passage includes a second set of paths fluidly connected to the inner region and the outer region of the inner cap.

15. The inner cap according to claim 1, characterized in that: The inner cap includes an outer portion and an inner portion, the outer portion at least substantially surrounding the inner portion.

16. The inner cap according to claim 15, characterized in that: Also included is a snap structure configured to secure the outer portion to the inner portion.

17. The inner cap according to claim 15, characterized in that: The outer portion is formed from plastic and the inner portion is formed from metal or a metal alloy.

18. The inner cap according to claim 1, characterized in that: The first set of ports includes five to nine holes, and the second set of ports includes six to eighteen holes.

19. The inner cap according to claim 1, characterized in that: The ratio of flow area between the second set of ports and the set of measurement holes in the first end of the inner cap is at least 2:

1.

20. The inner cap according to claim 1, characterized in that The inner cap is symmetrical in the rotation direction.

21. An inner cap for a liquid-cooled plasma arc welding gun, the inner cap comprising: an inner member having an inner surface and an outer surface, the inner member defining a longitudinal axis of the inner cap; an outer member disposed circumferentially around the inner member, the outer member having an inner surface, an outer surface, and an annular region extending beyond the inner member along the longitudinal axis toward a torch end of the inner cap; a set of radial liquid flow passages formed in an annular region of the outer member and oriented perpendicular to the longitudinal direction, the set of liquid flow passages configured to deliver liquid coolant from a nozzle of the plasma arc torch through a first set of ports to a shroud of the plasma arc torch; as well as A gas passage is formed in the inner cap, the gas passage comprising: a first portion of the gas passageway at least partially defined by a portion of the outer surface of the inner member and a portion of the inner surface of the outer member; and a second portion of the gas passageway defined within the annular region of the outer member, the second portion comprising a set of axial gas flow passages configured to deliver shield gas to a shield of the plasma arc torch through a second set of ports, wherein, in the annular region, subsets of the flow channels in the group of liquid flow channels and the group of gas flow channels alternate in a rotational direction about the longitudinal axis to produce alternating cross-flow regions of liquid and shield gas during operation of the plasma arc torch, and Wherein the first set of ports and the second set of ports are spaced circumferentially around the annular portion and are positioned perpendicular or substantially perpendicular to each other.

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