Field of Invention

[001] The present invention is in the technical field of plasma cutting torches and, more particularly, relates to consumables for use in a plasma cutting torch typically known as a nozzle.

Background of the Invention

[002] Prior art plasma cutting devices, which include plasma torches, have been well- known for many years and are used in cutting and piercing metal work pieces. Plasma cutting devices use an anode and cathode to generate an electrical arc that ionizes a working fluid, usually compressed air or oxygen. Plasma torches generate a significant amount of heat during operation and require active cooling to prolong the useful life of the components of the plasma torch. Active cooling can be provided by a continuous flow of a working fluid, before ionization, and or a shielding gas flow. Active cooling can be augmented by closed-circuit liquid cooling. [003] Plasma torches typically require an electrical ignition to generate an electrical arc between the cathode and the anode, generally known as a pilot arc. The electrical ignition can be generated by a high frequency alternating current that creates an initiation arc at an initiation point between the shortest gap between the anode and the cathode. In this type of plasma torch the electrode and nozzle are fixed in position after installation. In another type of plasma torch, generally known as a contact start plasma torch, the initiation arc is generated by current flow from the anode or nozzle to the cathode or electrode and is facilitated by physical contact between the nozzle and electrode. After the initiation arc, the electrode and nozzle are separated. This is generally accomplished using the working fluid flow to overcome a biasing means that urges the cathode and anode together during the absence of working fluid flow. The most common type of contact start configuration is a fixed nozzle and an electrode that is urged against the nozzle via a biasing means, typically a spring arrangement, prior to the flow of the working fluid. After the initiation of a plasma arc, a working fluid (typically compressed air) is circulated through the plasma torch and out of the exit orifice of the plasma torch. As the flow rate and pressure increases within the plasma torch, the electrode is moved away from the nozzle. The nozzle and electrode are generally concentric about a central axis. The electrode is moved toward a contact surface on the plasma torch along the central axis by the pneumatic pressure created by the working fluid flow. The pneumatic pressure of the working fluid presses the electrode against the contact surface and is typically the only force that urges the surfaces together. This arrangement has several disadvantages associated with a gap existing between the contact surfaces of the plasma torch and the electrode when the plasma torch is not operating. One disadvantage is the possibility of foreign contamination between the contact surfaces. This contamination may reduce the amount of current or result in micro-arcs that can prematurely damage the electrode or the plasma torch body itself. Another disadvantage of this type of plasma torch arrangement is the reduced of thermal conductivity between the electrode and plasma torch body because of the contact resistance between the electrode and contact surface of the plasma torch body. In this type of plasma torch, thermal conduction is dependent on the contact force pressing the parts together, i.e. the pneumatic pressure that presses the electrode into the contact surface of the plasma torch. Additionally, contaminants can reduce the surface area available for contact and thereby reduce the amount of thermal or electrical conduction between the electrode and plasma torch body.

[004] Prior art plasma torches such as disclosed in US Patent No. 5,897,795 have used fixed electrodes and moveable nozzles, including embodiments in which the electrodes are fixed in position by threading into the torch body. Threaded connections inherently wear out after repeated use. Moreover, electrodes tend to have a relatively small diameter which makes hand threading of an electrode, to the required torque for a reliable electrical conduction, difficult. For this reason, embodiments of threaded electrodes have a hex or parallel flat section on the tip or body of the electrode to facilitate the use of a tool to tighten and install the electrode. The nozzle is generally the highest wear rate consumable in a plasma torch assembly, with the electrode generally being the second highest wear rate consumable in a plasma torch assembly. The addition of a hex section and threaded section to the electrode increase the cost and manufacturing time of the part. Considerable cost savings can be had by eliminating these features from a high-volume part, such as an electrode. With the elimination of these features the end user is not required to use a tool to install and remove the electrode. A threaded connection increases the amount of thermal conduction between the electrode and the torch body due to the reduced thermal contact resistance that occurs from the relatively high contact force generated by a threaded connection, as opposed to an electrode that is pressed against a contact surface by pneumatic pressure alone. [005] The plasma torch in the ‘795 patent employs a spring to place the movable nozzle in the starting position or pre-energized state. The spring in the ‘795 patent has a spring rate of 48 Ib/in (8.57 kg/cm) and it is disclosed that a force of 3.12 pounds (1.42 kg) is needed to achieve full travel of the nozzle to place the nozzle in the operating position for cutting operations. The pneumatic force generated by the flow of the working fluid during operation is disclosed as 6.08 pounds (2.76 kg) in the ‘795 patent. This is just under double the force needed to compress the spring, only giving the torch assembly a factor of safety of - 2. For example, once the spring wears or is otherwise contaminated it may require a force greater than 6.08 pounds (2.76 kg) such that the torch will no longer be able to properly initiate a plasma arc. The ‘795 patent describes the need to routinely replace the spring in the torch assembly due to thermal stress, cyclic loading and contamination from the compressed air being used as the working fluid. In several of the embodiments of the ‘795 patent the spring is in the direct flow path of the shield gas flow.

BRIEF DESCRIPTION OF THE DRAWINGS

[006] The figures illustrate one or more embodiments of a plasma cutting torch and associated consumables where like reference numerals designate identical or corresponding parts throughout the several views. Embodiments of a plasma cutting torch are described with reference to the following drawings, where:

[007] FIG. 1 A is a cross-section view of a plasma torch in accordance with an embodiment of the invention that is in the starting position.

[008] FIG. IB is an exploded view in cross-section of a plasma torch in accordance with an embodiment of the invention.

[009] FIG. 2 is a view in cross-section of a torch body of a plasma torch in accordance with an embodiment of the invention.

[0010] FIG. 3 A is a view in cross-section of an electrode of a plasma torch in accordance with an embodiment of the invention.

[0011] FIG. 3B is a view in cross-section of an electrode, nozzle assembly and swirler in a plasma torch in accordance with an embodiment of the invention that are in the operating position. [0012] FIG. 3C is a partial view in cross-section of a plasma torch in accordance with an embodiment of the invention with the working fluid flow paths designated by arrows.

[0013] FIG. 4 is a view in cross-section view of a swirler of a plasma torch in accordance with an embodiment of the invention.

[0014] FIG. 5 is a view in cross-section of a retainer assembly for use in a plasma torch in accordance with an embodiment of the invention.

[0015] FIG. 6 is perspective view of an electrode in accordance with an embodiment of the invention.

[0016] FIG. 7 is an exploded view of a nozzle assembly in accordance with an embodiment of the invention.

[0017] FIG. 8A is a view in cross-section of a nozzle assembly in accordance with an embodiment of the invention in the starting position.

[0018] FIGS. 8B and 8C are views in cross-section of a nozzle assembly in accordance with an embodiment of the invention in a freestanding position.

[0019] FIG. 9A is a view in cross-section of a plasma torch in accordance with an embodiment of the invention in the operating position.

[0020] FIG. 9B is a partial view in cross-section of a plasma torch in accordance with an embodiment of the invention with the shield gas flow paths designated by arrows.

[0021] FIG. 10 is a view in cross-section of a plasma torch in accordance with an embodiment of the invention in an intermediate position.

[0022] FIG. 11 is a view in cross-section of a nozzle assembly in accordance with an embodiment of the present invention in the operating position.

[0023] FIG. 12 is a view in cross-section of a nozzle assembly in accordance with an embodiment of the present invention in a freestanding position.

[0024] FIG. 13 is a view in cross-section of a nozzle assembly in accordance with an embodiment of the invention in the operating position.

[0025] FIG. 14 is a view in cross-section of a nozzle assembly in accordance with an embodiment of the present invention in an intermediate position.

[0026] FIG. 15A is a view in cross-section of a nozzle assembly in accordance with an embodiment of the invention illustrating a possible tilt of the inner nozzle about the central axis when in a starting position. [0027] FIG. 15B is a view in cross-section of a nozzle assembly in accordance with an embodiment of the invention illustrating a possible tilt of the inner nozzle about the central axis when in an intermediate position.

[0028] FIG. 16 is a view in cross-section view of a nozzle assembly in accordance with an embodiment of the invention in the operating position.

[0029] To the extent features are illustrated schematically, details, connections and components of an apparent nature may not be shown or drawn to scale to emphasize certain features of the invention. Suggested dimensions of features are only exemplary.

[0030] The figures illustrate one or more embodiments of a plasma cutting torch and component features thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0031] Referring now to the drawings, the invention provides a plasma cutting torch incorporating a movable nozzle assembly that requires a low amount of pneumatic pressure to move the inner nozzle to an operating position during initiation of the plasma torch.

[0032] Referring to Figures 1A and IB, a plasma cutting torch 1 includes a series of consumables assembled on a torch body 24. The illustrated consumables are shown installed concentrically along a central axis 10. See Figure IB. The plasma cutting torch has a distal end located at the downstream end of the plasma torch 1 about an exit orifice 37 in the shield body 19; and has an upstream or proximal end along a handle or mount (not shown). The electrode 4 is mated with the contact post 5 and is fixed in place by swirler 16, which is concentrically installed over the electrode 4. The nozzle assembly 17 is concentrically mated with the swirler 16 and fits over the distal end of the electrode 4. The retainer assembly 22 is concentrically installed over the stack-up formed by the electrode 4, swirler 16, and nozzle assembly 17. In one embodiment the retainer assembly 22 is threaded onto the torch 24 and locks the stack-up in place. In one embodiment a shield 19 can be threaded onto retainer assembly 22. The completed or assembled plasma cutting torch 1 is in a pre-energized or starting position after assembly, as seen in Figure 1A.

[0033] In order to generate a pilot or initiation arc, the plasma cutting torch 1 has two current paths: one for the anode and one for the cathode. The torch body 24 accommodates the two current paths by isolating the anode and cathode current paths. In one embodiment, the anode current path begins in the torch body threads 25, continues through the inner retainer 14, and ends in the nozzle assembly 17. See Figure 1 A. The cathode current path begins at the contact post 5 of the torch body 24 and continues through the electrode 4. The pilot arc is generated at a point of physical contact between the distal end of the electrode 4 and the inner nozzle 12 of the nozzle assembly 17. See Figure 1 A.

[0034] In this embodiment the consumable generally known as a nozzle is separated into two concentric pieces that are urged apart by a biasing means, e.g., in this embodiment a spring 32, to form a nozzle assembly 17. See Figures 8A-8C. The nozzle assembly 17, as seen in Figures 1 and 8 A, is in the pre-energized or starting position. The nozzle assembly 17 has an outer nozzle

13 that is in mating contact along a recess 43 in the swirler 16 when installed in the plasma torch 1. See Figures 1A and 4. The outer nozzle 13 is also mated with the retainer assembly 22 via physical contact with the threaded retainer insulator 15 and inner retainer 14. See Figures 1A and 5. The flange 23 of inner retainer 14 is in physical contact with step 18 of outer nozzle 13. The retainer assembly 22 is formed by attaching the threaded retainer insulator 15 to the inner retainer

14 via any known method of mechanical attachment, including but not limited to any of press fitting, threaded attachment, adhesive, welding, and brazing. As discussed above, the retainer assembly 22 is threaded onto the torch body 24.

[0035] Figure 7 illustrates an exploded view of the nozzle assembly 17, having an annular slot 36 near the distal end, is mated with a retaining ring 34 installed in a slot 36 of the inner nozzle 12. When assembled, the spring 32 is in contact with the flange 21 of the inner nozzle 12 and the step 40 of the outer nozzle 13. See Figures 1A and 8 A. In certain aspects of the present teaching, the spring is not symmetrical but rather, has an open end and a closed end. The open end of the spring is assembled against the flange 21 of the inner nozzle 12 and the closed end of the spring is assembled against the step 40 of the outer nozzle 13. Installing the spring 32 in the reverse direction may cause the nozzle to get stuck, preventing it from freely springing back and forth. The spring 32 can be a helical spring or any suitable known arrangement of resilient member. In this embodiment, the inner nozzle 12 can be press fit or snapped into place by pushing the inner nozzle 12 into the outer nozzle 13 and overcoming the resistive force created by the interference between the retaining step 42 and retaining ring 34. In some embodiments the retaining ring 34 is a resilient section of wire that is semi-circular or crescent shaped, commonly known as a snap ring. A snap ring is designed to elastically deform to a smaller diameter than a predefined resting or free state when sufficient force is applied in the radial direction, e.g., compressing the retaining ring 32 so that it clears the retaining step 42. The retaining ring 34 elastically deforms in the radial direction, about the central axis 10, when sufficient force in the axial direction is applied during removal or installation. Once installed in the torch body 24, the nozzle assembly 17 is in a pre-energized state where the spring 32 is forcing the inner nozzle 12 into physical contact with the electrode 4, as seen in Figures 1 A and 8A. The location of physical contact between the inner nozzle 12 and the electrode 4 is designed to be the initiation point of the plasma arc or location of the pilot arc.

[0036] Prior to assembly in the plasma torch 1, the nozzle assembly 17 is in a free-standing condition. While in the free-standing condition, the spring 32 pushes the inner nozzle 12 in the upstream or proximal direction, about the central axis 10, until the retaining ring 34 comes into physical contact with the retaining step 43, see Figures 8B and 8C. The physical contact or interference between the retaining ring 34 and retaining step 42 prevents the separation of the inner nozzle 12 from the nozzle assembly 17. After the useful life of the inner nozzle 12 has been exceeded or during routine maintenance the nozzle assembly can be disassembled. The inner nozzle 12 of the nozzle assembly 17 can be separated or disassembled by an external force, in the axial direction, of greater magnitude than the spring 32 can generate. Separation is achieved by an external force or pressing of the inner nozzle 12 toward the upstream direction while the outer nozzle 13 is fixed in place by the operator. A sufficient external force can be reached by the operator pressing the inner nozzle 12, with their fingers or rigid surface, towards the upstream or proximal direction. Sufficient external force is reached when the interference between the retaining step 42 and retaining ring 34 is overcome, i.e. elastically deform the retaining ring 34 to a small diameter than the retaining step 42, thereby separates the inner nozzle 12 from the nozzle assembly 17. Separation or disassembly of the nozzle assembly 17 by the end user is advantageous as it allows for the replacement of the inner nozzle 12 and or the spring 32.

[0037] During operation the working fluid, in this embodiment compressed air, flows into the swirler cavity 29 via the swirler passages 28, See Figures 1 A and 3C. The working fluid then flows downstream toward the discharge orifice 37 of the shield body 19 in a primary flow and upstream toward the contact flange 3 of the electrode 4 in a secondary flow. The secondary flow vents a portion of the working fluid flow to the atmosphere. In one embodiment, the nozzle assembly 17 requires a minimal amount of working fluid flow to move the inner nozzle 12 about the central axis 10 and into the operating or cutting position. See Figures 9A and 13 which illustrate the nozzle assembly 17 in the operating or cutting position. As seen in Figures 9 A and 13, the stop flange 20 of the inner nozzle 12 is in physical contact with the upstream side of retaining step 42 from the pneumatic pressure created within the plasma cavity 33 by the continuous flow of the working fluid. The pneumatic pressure within the plasma cavity 33 causes the inner nozzle 12 to move downstream, along the central axis 10, until the stop flange 20 comes into contact with the retaining step 42. Neither the retaining step 42 nor the stop flange 20 of the inner nozzle 12 is susceptible to elastic deformation from the resultant axial force generated from the pneumatic force exerted inside the plasma cavity 33. In this embodiment the resultant force in the axial direction, that is generated from the pneumatic force within the plasma cavity 33, can be several orders of magnitude greater than the biasing force created by the spring 32.

[0038] In this embodiment, the spring 32 is manufactured from Stainless Steel or Inconel but the spring may be made of another material, e.g., even a non-conductive material. The spring 32 has an exemplary free length of 0.4 inches and a spring rate of 0.78 Ibf/in. When the nozzle assembly 17 is in the pre-energized or starting position, the spring 32 is deflected or compressed 0.189 inches which results in a biasing force or pre-load of 0.19656 Ibf separating the inner nozzle 12 from the outer nozzle 13. During operation, the inner nozzle 12 will reach the operating position with a working fluid pressure entering the plasma cavity 33 of 1.2 psi or greater. The spring 32 is deflected or compressed 0.252 inches when the plasma torch 1 is in the cutting position. See Figures 9A and 13. Generally, the working fluid pressure entering the swirler cavity is approximately 62.5 psi when performing cutting operations. This embodiment of the invention reaches an operating position with 1.2 psi or ~2% of the operating pressure. This can extend the usable life of the electrode 4 and inner nozzle 12 by minimizing the time needed to separate the inner nozzle 12 and electrode 14 after the plasma arc has been initiated. This design allows for the inner nozzle 12 to reach the operating position or cutting position before the working fluid has reached operating pressure. This, in turn, allows for the ionized working fluid or plasma to begin exiting the orifice 44 of the inner nozzle 12 with minimal damage to the interior of the inner nozzle 12, particularly at transition 35. See Figure 14. In prior art plasma torches, higher pressures and flow rates of plasma can damage the anode and cathode because significant plasma flow can be achieved before the anode and cathode are separated, i.e., reach operating position. In prior art plasma torches, damage or wear occurs when the plasma flow erodes the tip of the electrode and the interior wall(s) of the nozzle while the plasma flow is being pushed out the nozzle’s orifice. [0039] The ability to enter the operating position at low pressures is advantageous for several reasons. One advantage is extended consumable life, which is achieved because the amount of wear inflicted on the electrode 4 and inner nozzle 12 during a contact start is reduced by the inner nozzle 12 moving to operating position before the plasma flow has reached an operating flow rate having an operating pressure of about 62.5 psi, thereby reducing the amount of wear inflicted on the inner nozzle 12 and electrode 4 during pilot arc initiation. Another advantage of entering the operating state at low pressures is that the nozzle assembly 17 can be used with different consumable sets. Different consumables are used for different current ranges, for example one consumable set may be designed for use in the 40-80 amp range while another may be designed for the 80 to 100 amp range. The nozzle assembly 17 would potentially need to exchange the one inner nozzle 12 for anther inner nozzle 12 designated for a different current range for a cutting operation. Generally, higher current ranges require that the orifice 44 of the inner nozzle 12 be of a larger diameter to accommodate an increased amount of flow. As the primary and secondary flow are both supplied from the same source, an increase in the diameter of the orifice 44 decreases the amount of surface area within the inner nozzle 12 that is perpendicular to the central axis 10. With only 1.2 psi needed to retract inner nozzle 12 within the nozzle assembly 17, the spring 32 can be used with all of the available current ranges. This is advantageous in that the end user is not required to purchase or stock several variations of outer nozzle 13 and spring 32.

[0040] The anode’s current path reaches nozzle assembly 17 via physical contact between the outer nozzle 13 and the flange 23 of inner retainer 14. In one embodiment the inner retainer 14 and outer nozzle 13 are manufactured from Copper or Brass alloys. The nozzle assembly 17 may have multiple current paths between in the inner nozzle 12 and outer nozzle 13 to facilitate plasma arc initiation, commonly known as a pilot arc initiation. A first conduction path is achieved by radial movement of the inner nozzle 12 about the central axis 10 or tilting. When the nozzle assembly 17 is in the starting or pre-energized position, as seen in Figures 1 A and 8 A, the inner nozzle 12 and outer nozzle 13 are in continuous electrical communication. The continuous electrical communication is achieved by forced physical contact between the cylindrical section 48 of the outer nozzle 13 and the cylindrical section 49 of the inner nozzle 12., See Figures 8B and 8C. The inner diameter of cylindrical section 48 of the outer nozzle 13 is sized to allow the inner nozzle 12 to freely move within the outer nozzle 13 but sized to allow for the cylindrical sections of the inner nozzle 12 and outer nozzle 13 to come into physical contact by the tilting of the inner nozzle 12. See Figures 15A and 15B. The inner nozzle 12 is subjected to tilting or movement in the radial direction by the radial component(s) of the reaction force of the biased spring 32 against the step 40 of the outer nozzle 13 and flange 21 of the inner nozzle 12. In this embodiment, the spring 32 is an as-cut helical spring. The ends are not ground or flattened. Springs are normally ground or flattened on the ends to reduce or eliminate the tilting of the spring, i.e., to only have a biasing force in the axial direction. Using an as-cut spring reduces the cost of the spring 32 and uses the resultant forces caused by imperfect seating of the spring ends 56 to force physical contact between the inner nozzle 12 and outer nozzle 13, i.e., titling the inner nozzle 12 until it is forced against the outer nozzle 13. In this embodiment the radial clearance between the concentric cylindrical sections of the inner nozzle 12 and outer nozzle 13 is 0.05 mm (0.002 inches).

[0041] A second conduction path between the inner nozzle 12 and the outer nozzle 13 is through a conductive retaining ring 34. In some embodiments the retaining ring 34 is a resilient section of wire that is semi-circular or crescent shaped, e.g., a snap ring. A snap ring may be designed to elastically deform to a smaller diameter than a predefined resting or free state. In this embodiment the retaining ring 34 has a resting outer diameter that causes the retaining ring 34 to come into contact with the bottom 46 of the slot 36 of the inner nozzle 12 and the inner diameter of the outer nozzle 13 when the nozzle assembly 17 is in the starting or pre-energized position. See Figure 10. The retaining ring 34 may also be sized to ensure that it no longer contacts the outer nozzle 13 after the inner nozzle 12 has begun to move to the operating position, see Figures 5 and 8A-8C. The clearance between the inner nozzle 12 and outer nozzle 13 is sized to prevent physical contact between the retaining ring 34 and the outer nozzle 13 even when the inner nozzle 12 is at a maximum state of radial or tilt movement about the central axis 10. Advantageously, the current path is eliminated as soon as the inner nozzle has begun to move to the operating position, i.e., when the pneumatic pressure within the plasma cavity 33 is above 1.2 psi.

[0042] Embodiments of the invention can have a third current path through the spring 32. With the spring 32 manufactured out of Inconel or Stainless Steel, the spring 32 is in physical contact with the step 40 of the outer nozzle 13 and the biasing flange 21 of the inner nozzle 12. These points of contact create a conduction path between the inner nozzle 12 and outer nozzle 13. In this embodiment, the current path through the spring 32 is the least desirable path due to the higher resistance across the spring 32, while the inner nozzle 12 is manufactured from a Copper alloy and the outer nozzle 13 is manufactured from a Brass or Copper alloy, both of which are much better electrical conductors than the material(s) used to manufacture the spring 32. The most desirable current path, and path of least resistance by design, is by forced direct contact between the inner nozzle 12 and outer nozzle 13 via tilting as discussed above. By having multiple current paths, the pilot arc reliability of the nozzle assembly 17 and the plasma torch 1 are increased.

[0043] In one embodiment, working fluid and or shielding gas flow is prevented from flowing into the spring cavity 39, which cavity is between the inner nozzle 12 and the outer nozzle 13, during operation. See Figures 11 and 12. In this embodiment a seal 45, such as an o- ring or elastic washer, is attached to stop flange 20 of the inner nozzle 12 such that when the inner nozzle 12 is in operating position, the pneumatic force within the plasma cavity 33 compresses the seal 45 between the stop flange 20 and retaining step 42, thereby creating a pneumatic seal. It is advantageous to prevent the working fluid from entering the spring cavity 39 because compressed air, the typical working fluid, can have significant sources of contamination. Contaminants can include oil, rust particles and other debris that can enter the air compressor or supply lines. These contaminants can enter the spring cavity and interfere with normal operation of the nozzle assembly 17 by preventing or limiting the movement of the inner nozzle 12 or interfering with one or more of the current paths between the inner nozzle 12 and outer nozzle 13.

[0044] When the inner nozzle 12 of the nozzle assembly 17 is in the operating position, the inner nozzle 12 completes a continuous flow path or shield gas flow path 50, that is defined by the space between the nozzle assembly 17 and the shield 19. See Figures 9A and 9B. When the stop flange 20 of the inner nozzle 12 is in physical contact with the retaining step 42 of the outer nozzle 13, a continuous line segment 53 is created by the outer diameter features on the downstream or distal end of the inner nozzle 12 and outer nozzle 13. See Figure 13. The outer nozzle 13 has a cylindrical section 52 that is contoured to match the inner diameter of the shield 12, See Figures 9A and 13. During operation, the combination of the continuous line segment 53 and cylindrical section 52 of the outer nozzle 13 are contoured to match the entire length of the shield gas flow path 50 defined, in part, by the inner diameter of the shield 19. The shield gas flow exits the plasma torch 1 via a plurality of vents 51 or via the exit orifice 37. See Figure 9A. This design allows for the shield gas flow, inside of the shield gas flow path 50, to exit the plasma torch 1 without additional turbulence from a step or non-continuous section at the intersection 55 of the inner nozzle 12 and outer nozzle 13. See, again, Figure 9A. When in the operating position, nozzle assembly 17 has the equivalent geometry of a one-piece nozzle that is fixed, similar to the geometry of prior art plasma torches that use a fixed nozzle and a movable electrode. This embodiment incorporates the beneficial continuous flow paths seen in fixed nozzle plasma torch designs without the disadvantages of a movable electrode.

[0045] In this embodiment, the axial length of the outer nozzle 13, about the central axis 10, is longer than the axial length of the internal cavity 47 of the inner nozzle 12. See Figure 10. The internal cavity 47 is defined by the internal bore of the inner nozzle 12. In other embodiments the axial length of the internal cavity 47 can be equal in length to the axial length of the outer nozzle 13. It is advantageous to size the axial length of the outer nozzle 13 to be equal to or longer than the axial length of the inner nozzle 12 because, depending on the embodiment of the invention, the working fluid and shield gas flows can separate up to the downstream end of the orifice 44 of the inner nozzle 12. When the flows are separated, the nozzle assembly 17 is functioning as a single piece nozzle seen in fixed nozzle torch design without the disadvantages of a movable electrode design. Embodiments that do not incorporate a seal 45 can sufficiently limit the flow of working fluid between the inner and outer nozzles with physical contact between the flange 20 and retaining step 21 that is maintained by pneumatic pressure during operation of the plasma torch.

[0046] For another embodiment of the invention, an outer nozzle 113 of a nozzle assembly 117, illustrated in Figure 16, has a slot 136 near the distal end. A retaining ring 134, in this embodiment a snap-ring or O-ring, is installed in the slot 136. The inner nozzle 112 has a stop flange 120 that comes into contact with a retaining step 142 when the nozzle assembly 117 is in the operating position, as seen in Figure 16. This embodiment reduces cost by moving the slot 136 to the outer nozzle 113, thereby reducing complexity and manufacturing expense associated with the inner nozzle 112, which is commonly the most frequently replaced plasma torch consumable.

[0047] According to Clause 1, provided is a nozzle assembly for use in a plasma cutting torch including: a central axis, an inner nozzle, an outer nozzle, a spring, and a seal, wherein the inner nozzle comprises an internal cavity defined by an inner bore of the inner nozzle and the axial length of the internal cavity is equal to or greater in axial length than the outer nozzle. [0048] According to Clause 2, the nozzle assembly of Clause 1 is provided, wherein the inner nozzle is concentrically disposed within the outer nozzle, about the central axis and is movable between first and second positions, along the central axis, within the outer nozzle. [0049] According to Clause 3, the nozzle assembly of Clause 1 or Clause 2 is provided, wherein when the inner nozzle is in the first position, the inner nozzle and outer nozzle are spaced-apart about the central axis by the spring which is limited in axial movement by a retaining step.

[0050] According to Clause 4, the nozzle assembly of any of Clauses 1-3 is provided, wherein a pneumatic force of at least 1.2 psi is required to overcome a force of the spring and move the inner nozzle in a direction along the central axis until the inner nozzle moves from the first position to the second position, which the second position is an operating position.

[0051] According to Clause 5, the nozzle assembly of any of Clauses 1-4 is provided, wherein a continuous line segment is created by the inner nozzle and outer nozzle when the nozzle assembly is in the operating position and a shield gas flow path is defined by the inner nozzle and outer nozzle.

[0052] According to Clause 6, the nozzle assembly of any of Clauses 1-5 is provided, further comprising a plurality of electrical current paths between the inner nozzle and the outer nozzle.

[0053] According to Clause 7, the nozzle assembly of any of Clauses 1-6 is provided, wherein a first of the current paths is created by physical contact between the inner nozzle and the outer nozzle.

[0054] According to Clause 8, the nozzle assembly of any of Clauses 1-7 is provided, wherein a second of the current paths is created by physical contact between a retaining ring and the inner and outer nozzles.

[0055] According to Clause 9, the nozzle assembly of any of Clauses 1-8 is provided, wherein a third of the current paths is created by physical contact between the spring and the inner and outer nozzles.

[0056] According to Clause 10, the nozzle assembly of any of Clauses 1-9 is provided, wherein the first current path is created by tilting of the inner nozzle about the central axis. [0057] According to Clause 11, the nozzle assembly of any of Clauses 1-10 is provided, wherein a seal prevents the flow of a pneumatic working fluid into a spring cavity defined by a space between the inner nozzle and the outer nozzle.

[0058] According to Clause 12, provided is a nozzle assembly for use in a plasma cutting torch. The nozzle assembly includes: a central axis, an inner nozzle, an outer nozzle, a biasing means, and a retaining means, wherein the inner nozzle comprises an internal cavity defined by an inner bore of the inner nozzle and an axial length of the internal cavity equal to or greater than an axial length of the outer nozzle.

[0059] According to Clause 13, the nozzle assembly of Clause 12 is provided, wherein the inner nozzle is concentrically disposed within the outer nozzle, about the central axis and is movable, along the central axis, within the outer nozzle.

[0060] According to Clause 14, the nozzle assembly of Clause 12 or Clause 13 is provided, wherein the inner nozzle and outer nozzle are separated about the central axis by the biasing means which is limited in axial movement.

[0061] According to Clause 15, the nozzle assembly of any of Clauses 12-14 is provided, wherein a force of at least 1.2 psi is required to overcome the biasing means and move the inner nozzle in the downstream direction along the central axis until the inner nozzle reaches an operating position.

[0062] According to Clause 16, the nozzle assembly of any of Clauses 12-15 is provided, wherein a continuous line segment is created by the inner nozzle and outer nozzle when the nozzle assembly is in the operating position; and a shield gas flow path is defined by the inner nozzle and outer nozzle.

[0063] According to Clause 17, the nozzle assembly of any of Clauses 12-16 is provided, wherein the nozzle assembly further comprises a plurality of electrical current paths between the inner nozzle and outer nozzle.

[0064] According to Clause 18, the nozzle assembly of any of Clauses 12-17 is provided, wherein a first of the current paths is created by physical contact between the inner nozzle and outer nozzle.

[0065] According to Clause 19, the nozzle assembly of any of Clauses 12-18 is provided, wherein a second of the current paths is created by physical contact between the retaining means and the inner and outer nozzles.

[0066] According to Clause 20, the nozzle assembly of any of Clauses 12-19 is provided, wherein a third of the current paths is created by physical contact between the biasing means and the inner and outer nozzles.

[0067] According to Clause 21, the nozzle assembly of any of Clauses 12-20 is provided, wherein the first current path is created by tilting of the inner nozzle about the central axis. [0068] According to Clause 22, the nozzle assembly of any of Clauses 12-21 is provided, wherein the nozzle assembly further comprises a sealing means between the inner nozzle and the outer nozzle.

[0069] According to Clause 23, the nozzle assembly of any of Clauses 12-22 is provided, wherein the sealing means prevents the flow of a working fluid into a cavity about the biasing means defined by a space between the inner nozzle and the outer nozzle.

[0070] While the nozzle assembly and associated components, devices and processes have been described above in connection with various illustrative embodiments, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiments for performing the same function disclosed herein without deviating therefrom. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments may be combined or subtracted to provide the desired characteristics. Variations can be made by one having ordinary skill in the art without departing from the spirit and scope hereof. Therefore, the present disclosure should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitations of the appended claims.