Patent Publication Number: US-11665807-B2

Title: Cartridge for a liquid-cooled plasma arc torch

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/228,750, filed on Aug. 4, 2016, which claims the benefit of and priority to U.S. Provisional Patent Application No. 62/200,913, filed Aug. 4, 2015. The entire contents of these applications are owned by the assignee of the instant application and incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to cartridges for a liquid-cooled plasma arc torch, and more particularly, to one or more replaceable, low-cost cartridges having integrated components. 
     BACKGROUND 
     Thermal processing torches, such as plasma arc torches, are widely used for high temperature processing (e.g., heating, cutting, gouging and marking) of materials. A plasma arc torch generally includes a torch head, an electrode mounted within the torch head, an emissive insert disposed within a bore of the electrode, a nozzle with a central exit orifice mounted within the torch head, a shield, electrical connections, passages for cooling, passages for arc control fluids (e.g., plasma gas) and a power supply. A swirl ring can be used to control fluid flow patterns in the plasma chamber formed between the electrode and the nozzle. In some torches, a retaining cap is used to maintain the nozzle and/or swirl ring in the plasma arc torch. In operation, the torch produces a plasma arc, which is a constricted jet of an ionized gas with high temperature and sufficient momentum to assist with removal of molten metal. Gases used in the torch can be non-reactive (e.g., argon or nitrogen), or reactive (e.g., oxygen or air). 
     Existing plasma cutting systems include a large array of separate consumables available for use with different currents and/or operating modes that are repeatedly assembled and disassembled in the field by a user to perform thermal processing operations. The large number of consumable options requires large part counts and inventories for users, and can confuse users and increase the possibility of installing incorrect consumables. The large number of consumable options can also cause lengthy torch setup time(s) and make it difficult to transition among cutting processes that require different arrangements of consumables in the torch that is often performed in the field one component at a time. For example, before a cutting operation, selecting and installing the correct set of consumables for a particular cutting task can be burdensome and time-consuming. Furthermore, selection, assembly, and installation of these components in the field can cause alignment issues or compatibility issues when old components are used with new components. During torch operation, existing consumables can experience performance issues such as failing to maintain proper consumable alignment and spacing. Furthermore, current consumables include substantial amounts of expensive materials (e.g., Vespel™) and often require a relatively complex manufacturing process, which leads to significant manufacturing costs and inhibits their widespread commercialization, production and adoption. What is needed is a new and improved consumable platform for liquid-cooled plasma arc torches that decreases manufacturing costs and time, decreases part count, increases system performance (e.g., component alignment, cut quality, consumable life, variability/versatility, etc.), and eases installation and use of consumables by end users. 
     SUMMARY 
     The present invention provides one or more integrated, cost-effective cartridge designs for a liquid-cooled plasma arc torch. Generally, because a cartridge includes a suite of two or more consumable components, it provides ease of use and shortens the time for installation into a plasma arc torch in comparison to installing/replacing each consumable component individually. Using a consumable cartridge also reduces the possibility of an operator putting in the wrong consumable parts, contaminating the parts during installation and/or placing a weak or bad part back onto the torch by accident. These advantages eliminate the need for experienced operators to operate the resulting liquid-cooled plasma arc torches. In addition, the use of a cartridge in a liquid-cooled torch improves component alignment, cut consistency and cut quality experience. Further, using consumable cartridges enhance suppliers&#39; experience as fewer consumable parts need to be inventoried and stocked. In some cases, a supplier can buy back used cartridges and recycle components for other uses. However, manufacturing and material costs can prohibit the widespread commercialization and production of cartridges. The present invention solves this problem by providing one or more cost effective cartridge designs that facilitate cartridge commercialization and production and improve their installation. 
     In one aspect, the present invention features a consumable cartridge frame for a liquid-cooled plasma arc torch, the consumable cartridge frame includes an insulator body configured to be disposed between a torch head and a cartridge tip, a first cooling channel, disposed in the body, configured to conduct a first fluid flow received from the torch head to contact a component of the cartridge tip connected to the cartridge frame, and a first return channel, disposed in the body, configured to conduct at least a portion of the first fluid flow from the component to the torch head. The first cooling channel and the first return channel are non-concentric in relation to a central longitudinal axis of the body. 
     In some embodiments, the consumable cartridge frame further includes a torch engagement feature configured to radially secure the cartridge tip to the torch head in a predetermined orientation. The first cooling channel can be configured to substantially align with a corresponding first cooling channel of the torch head when the cartridge tip is radially secured to the torch head via the torch engagement feature. The first liquid cooling channel can be adapted to conduct a cooling liquid from the torch head into the cartridge tip. The first return channel can be configured to substantially align with a corresponding first return channel of the torch head when the cartridge tip is radially secured to the torch head via the torch engagement feature. The first return channel can be adapted to return the cooling liquid from the cartridge tip into the torch head. 
     In some embodiments, the consumable cartridge frame further includes a central channel disposed in the insulator body and concentric with respect to the central longitudinal axis of the insulator body, the central channel configured to perform at least one of (i) conduct the first fluid flow from the torch head to an electrode or (ii) pass an electrical current from the torch head to the electrode. The consumable cartridge frame can further include a second cooling channel, disposed in the insulator body, configured to conduct at least a portion of the first fluid flow received from the torch head to contact a second component of the cartridge tip different from the first component and a second return channel, disposed in the insulator body, configured to conduct at least a portion of the first fluid flow from the second component to the torch head. The second cooling channel and the second return channel can be non-concentric in relation to the central longitudinal axis of the insulator body. 
     In some embodiments, the consumable cartridge frame further includes at least one gas channel, disposed in the insulator body, configured to conduct a second fluid flow to a second component of the cartridge tip. The at least one gas channel is non-concentric with respect to the central longitudinal axis of the insulator body. The second fluid flow can comprise a plasma gas flow or a shield gas flow. The second component can comprise one of a nozzle or shield. 
     In some embodiments, the first fluid flow comprises a liquid coolant flow. In some embodiments, the component of the cartridge tip comprises one of a nozzle or shield. In some embodiments, the first cooling channel and the first return channel extend longitudinally from a proximal region to a distal region of the insulator body and are non-overlapping. 
     In another aspect, a cartridge frame for a liquid-cooled plasma arc torch cartridge consumable is provided. The cartridge frame includes a cartridge frame body having a central region, an internal surface, an external surface, a proximal portion and a distal portion, where the cartridge frame body is at least substantially made of a non-conductive material. The cartridge frame also includes a torch engagement interface surface located at the proximal portion of the cartridge frame body, the torch engagement interface surface configured to engage a torch head. The cartridge frame further includes a plurality of component alignment features formed in the central region and a plurality of channels between the proximal portion and the distal portion. The plurality of channels are located offset from a central axis of the central region. The plurality of channels are configured to direct liquid and gas through the cartridge frame. 
     In some embodiments, one or more of the component alignment features are configured to align a nozzle to the internal surface of the cartridge frame and matingly engage the nozzle to the internal surface. The one or more component alignment features can comprise one or more steps configured to axially align and matingly engage the nozzle to the cartridge frame. The one or more component alignment features can comprise a varying diameter along a section of the internal surface of the cartridge frame to radially align and matingly engage the nozzle to the cartridge frame. In some embodiments, one or more of the component alignment features are configured to align a shield to the external surface of the cartridge frame and matingly engage the shield to the external surface. 
     In some embodiments, the plurality of channels comprises a shield gas channel configured to provide a metered shield gas flow therethrough. The cartridge frame can further include a baffle and a shield swirl ring disposed at the distal portion of the cartridge frame body. The baffle and the shield swirl ring can be in fluid communication with the shield gas channel to adjust at least one parameter of the shield gas flow therethrough. 
     In some embodiments, the cartridge frame further includes an opening on the internal surface of the cartridge frame. The plurality of channels include a coolant channel configured to supply a liquid coolant to a nozzle, and the opening is in fluid communication with the coolant channel to conduct the liquid coolant away from the nozzle. In some embodiments, the cartridge frame further includes an opening on the external surface of the cartridge frame. The plurality of channels include a coolant channel configured to supply a liquid coolant to a shield, and the opening is in fluid communication with the coolant channel to conduct the liquid coolant away from the shield. 
     In some embodiments, the cartridge frame further includes a vent passage extending from the internal surface to the external surface of the cartridge frame. 
     In another aspect, a consumable cartridge for a liquid-cooled plasma arc torch is provided. The consumable cartridge includes a body portion having a distal region and a proximal region, a tip portion located at the distal region the tip portion including a plasma emitter and a plasma arc constrictor, and two or more non-concentric channels extending from the proximal region to the tip portion in the distal region of the body. 
     In some embodiments, the two or more non-concentric channels are disposed in a cartridge frame made of an insulator material. In some embodiments, the cartridge frame forms an interface between the tip portion and a torch head. 
     In some embodiments, the tip portion comprises at least one of a nozzle, a shield or an electrode. In some embodiments, the two or more non-concentric channels include (i) a first set of channels including a coolant channel and a return channel in fluid communication with the nozzle to supply a liquid coolant to and from the nozzle and (ii) a second set of channels including a coolant channel and a return channel in fluid communication with the shield to supply at least a portion of the liquid coolant to and from the shield. In some embodiments, the two or more non-concentric channels include a plasma gas channel to supply a plasma gas to a passage between a swirl ring and the nozzle. In some embodiments, the two or more non-concentric channels include a shield gas channel to supply a shield gas to a passage between the shield and the nozzle. In some embodiments, the consumable cartridge further includes a central channel in fluid communication with the electrode, where the central channel is configured to pass at least one of a liquid coolant or an electrical current to the electrode. 
     In another aspect, a consumable cartridge frame for a liquid-cooled plasma arc torch is provided. The consumable cartridge frame includes a first interface configured to connect to a torch head of the plasma arc torch, and a second interface spaced axially relative the first surface along a longitudinal axis of the consumable, where the second interface is configured to connect to a plurality of components including at least a nozzle, a shield, an electrode, and a swirl ring. The consumable cartridge frame further includes a body portion extending along the longitudinal axis to connect the first interface with the second interface. The body portion includes a plurality of channels configured to convey liquid and gas between the torch head and the plurality of components through the first interface and the second interface. 
     In some embodiments, the first interface includes an alignment feature configured to radially secure to the torch head in a predetermined orientation. The plurality of channels can be adapted to align with corresponding channels in the torch head in the predetermined orientation to convey liquid and gas between the torch head and the plurality of components. In some embodiments, two or more of the plurality of channels are non-concentric. 
     In some embodiments, the second interface comprises (i) at least one step on an internal surface of the consumable cartridge frame to matingly engage and axially align the nozzle to the cartridge frame and (ii) at least one section of the internal surface of the consumable cartridge frame with varying diameter to matingly engage and radially align the nozzle to the cartridge frame. The second interface can also include alignment features configured to axially and radially align the shield with the cartridge frame and matingly engage the shield to the cartridge frame. The alignment features can comprise at least one of a step or a mating section on an external surface of the consumable cartridge. 
     In some embodiments, the consumable cartridge frame can further include a cavity disposed in the body portion adjacent to the first interface. The cavity is configured to receive a radio-frequency identification (RFID) tag for communicating with a reader device of the torch head. 
     In yet another aspect, a cartridge frame for a liquid cooled plasma arc torch cartridge consumable is provided. The cartridge frame includes a cartridge frame body having a proximal portion, a distal portion, an exterior surface, and an internal opening to a central channel in the cartridge frame body. The cartridge frame also includes a shield gas channel extending from the proximal portion of the cartridge frame body to the distal portion of the cartridge frame body, a nozzle coolant supply channel extending from the proximal portion of the cartridge frame body to the internal opening, and a nozzle coolant return channel extending from the internal opening of the cartridge frame body to the proximal portion. The cartridge frame further includes a circumferential coolant flow channel in the exterior surface of the cartridge frame body, a shield coolant supply channel extending from the proximal portion to the circumferential coolant flow channel, and a shield coolant return channel extending from the circumferential coolant flow channel to the proximal portion. 
     In yet another aspect, a liquid-cooled consumable cartridge for a plasma arc torch is provided. The cartridge includes (i) an electrode, (ii) a swirl ring with a first outer retaining feature and a second outer retaining feature on an exterior surface, where the electrode is secured to the swirl ring, and (iii) a nozzle with an inner retaining feature on an interior surface, where the inner retaining feature of the nozzle is mated with the first outer retaining feature of the swirl ring. The cartridge also includes a cartridge frame with an inner retaining feature on an interior surface and an outer retaining feature on an exterior surface. The inner retaining feature of the cartridge frame is mated with the second outer retaining feature of the swirl ring. The cartridge further includes a shield with an inner retaining feature on an interior surface mated with the outer retaining feature of the cartridge frame. At least the nozzle, the swirl ring, the cartridge frame and the shield are axially secured in a predetermine position upon mating with each other to provide at least one liquid flow path from the cartridge frame to the shield or the nozzle. 
     In some embodiments, the electrode and the nozzle are axially and radially aligned relative to each other without physical contact between the electrode and the nozzle. In some embodiments, the nozzle and the shield are axially and radially aligned relative to each other without physical contact between the nozzle and the shield. 
     In some embodiments, at least one of the shield, the nozzle, or the swirl ring mates directly with the cartridge frame. The electrode can be indirectly mated with the cartridge frame via at least one of the swirl ring or an electrode insulator. 
     In some embodiments, mating between the inner retaining feature of the nozzle and the first outer retaining feature of the swirl ring radially aligns the nozzle with the swirl ring. In some embodiments, mating between the inner retaining feature of the cartridge frame and the second outer retaining feature of the swirl ring provides at least one of axial or radial alignment between the cartridge frame and the swirl ring. In some embodiments, mating between an inner retaining feature of the shield and the outer retaining feature of the cartridge frame provides at least one of axial or radial alignment between the cartridge frame and the shield. In some embodiments, the cartridge frame further comprises a second inner retaining feature on the interior surface configured to be mated with an outer retaining feature on an outer surface of the nozzle. The mating between the cartridge frame and the nozzle provides at least one of axial or radial alignment between the cartridge frame and the nozzle. 
     In some embodiments, the nozzle is a non-vented nozzle coupled to a nozzle jacket. In some embodiments, the nozzle is a vented nozzle coupled to a nozzle liner. 
     In yet another aspect, a liquid-cooled consumable cartridge for a plasma arc torch is provided. The cartridge includes (i) an electrode, (ii) a swirl ring with an outer retaining feature on an exterior surface and an inner retaining feature on an interior surface, where the electrode is secured to the inner retaining surface of the swirl ring, and (iii) a nozzle with an outer retaining feature on an outer surface. The cartridge also includes a cartridge frame with a first inner retaining feature and a second inner retaining feature on an interior surface and an outer retaining feature on an exterior surface. The first inner retaining feature of the cartridge frame is mated with the outer retaining feature of the swirl ring and the second inner retaining feature of the cartridge frame is mated with the outer retaining feature of the nozzle. The cartridge further includes a shield with an inner retaining feature on an interior surface mated with the outer retaining feature of the cartridge frame. At least the nozzle, the swirl ring, the cartridge frame and the shield are axially secured in a predetermined position upon mating. 
     In yet another aspect, a consumable cartridge for a liquid-cooled plasma arc torch is provided. The consumable cartridge includes a non-conductive cartridge frame, and a set of conductive consumable components defining, in part, a plasma plenum. The set of conductive components are affixed to the cartridge frame. The consumable cartridge is composed of at least 50% non-conductive material by volume. In some embodiments, the consumable cartridge is composed of about 60% to about 80% non-conductive material by volume. 
     In some embodiments, the consumable cartridge is a single use cartridge. The set of conductive consumable components may not be individually disposable or serviceable after being affixed to the cartridge frame. 
     In some embodiments, the cartridge frame comprises liquid and gas channels in fluid communication with the set of conductive components. The liquid and gas channels are non-concentric in relation to a central longitudinal axis of the cartridge frame. 
     In some embodiments, the set of conductive consumable components comprises a shield, a nozzle and an electrode. 
     In another aspect, a method of manufacturing a unitary consumable cartridge from a plurality of components is provided. The method includes axially and radially securing an electrode to a swirl ring, axially and radially securing a retaining feature on an outer surface of the swirl ring to at least one of a mated retaining feature on an inner surface of a cartridge frame or a nozzle, and axially and radially securing a retaining feature on an outer surface of the cartridge frame to a mated retaining feature on an inner surface of a shield. The axial and radial securing of the consumable components relative to each other positions at least one internal fluid channel of the cartridge frame with (i) a fluid passage of the nozzle or (ii) a fluid passage of the shield. 
     In some embodiments, axially and radially securing an electrode to a swirl ring comprises axially and radially securing the electrode to an electrode insulator and axially and radially securing the electrode insulator to the swirl ring. 
     In some embodiments, the method further comprises radially aligning a plasma gas channel within the cartridge frame with a gas passage between the swirl ring and the nozzle. In some embodiments, the method further comprises radially aligning a shield gas channel within the cartridge frame with a gas passage between the nozzle and the shield. In some embodiments, the method further comprises radially aligning a central channel within the cartridge frame with the electrode. In some embodiments, the method further comprises radially aligning a first coolant channel and a second coolant channel within the cartridge frame with the nozzle, and radially aligning a third coolant channel and a fourth coolant channel within the cartridge frame with the shield. 
     In some embodiments, the method further comprises forming the swirl ring through die cast using zinc. In some embodiments, the method further comprises forming the cartridge frame through molding using a non-conductive material. In some embodiments, the method further comprises forming the shield through stamping using a conductive material. In some embodiments, the axial and radial securing of the plurality of components is through one or more of snap fit, press fit or interference, crimping, gluing, cementing or welding. 
     In another aspect, a method of assembling a liquid cooled consumable cartridge for a plasma arc cutting torch is provided. The method includes providing an insulator cartridge frame having a central region, an outer surface, a distal end, and a proximal end. The method further includes coupling a swirling component to the cartridge frame in the central region, coupling an electrode to the cartridge frame in the central region, coupling a nozzle to the cartridge frame in the central region, and coupling a shield to the cartridge frame at the outer surface. 
     In some embodiments, coupling a swirling component to the cartridge frame comprises mating an exterior surface of the swirling component to an interior surface of the cartridge frame that provides at least one of axial or radial alignment of the swirling component to the cartridge frame. In some embodiments, coupling a nozzle to the cartridge frame comprises coupling an exterior surface of the nozzle to an interior surface of the cartridge frame that provides at least one of axial or radial alignment of the nozzle to the cartridge frame. In some embodiments, coupling a shield to the cartridge frame at the outer surface provides at least one of axial or radial alignment of the shield to the cartridge frame. In some embodiments, the method further comprises coupling the electrode to the cartridge frame via at least one of the swirling component and an electrode insulator. In some embodiments, the coupling aligns at least one internal fluid channel of the cartridge frame with (i) a fluid passage of the nozzle or (ii) a fluid passage of the shield. 
     In some embodiments, the method further comprises disposing a baffle and a second swirling component at a distal end of the cartridge frame in the central region. 
     A consumable cartridge for a liquid-cooled plasma arc torch is provided. The consumable cartridge comprises a cartridge frame including a proximal end having an end surface, a distal end and a body having a central longitudinal axis extending therethrough. The cartridge configured to form a radio-frequency identification (RFID) interface with a torch head. The consumable cartridge also comprises an arc emitter and an arc constrictor affixed to the cartridge frame at the distal end and an RFID mounting feature formed on or in the cartridge frame adjacent to the end face. The RFID mounting feature is non-concentric with the central longitudinal axis of the body. The consumable cartridge further comprises an RFID tag disposed in or on the RFID mounting feature for transmitting information about the cartridge to a reader device in the torch head when the cartridge is connected to the torch head, and a clocking feature configured to rotationally align the RFID tag to the reader device in the torch head upon connection of the cartridge to the torch head. 
     In some embodiments, the RFID mounting feature comprises a cavity disposed in the body of the cartridge frame. The RFID tag can be embedded in the cavity of the body of the cartridge frame and surrounded by an insulator material of the body. In some embodiments, the end surface is substantially planar to allow an RFID reader to interrogate the RFID tag from outside of the plasma arc torch. In some embodiments, the RFID tag is readable from inside or outside of the plasma arc torch. 
     In some embodiments, the body of the cartridge frame is constructed from an insulator material. In some embodiments, the body of the cartridge frame comprises at least one channel for conducting a liquid coolant therethrough. The at least one channel can be configured to substantially align with a corresponding channel of the torch head upon the rotational alignment by the clocking feature to conduct the liquid coolant between the torch head and the cartridge. 
     In some embodiments, upon the rotational alignment, the RFID tag in the cartridge frame and the reader device in the torch head are oriented such that a central axis extends through a centerline of the RFID tag and a centerline of the reader device. In some embodiments, upon the rotational alignment, a first distance between the RFID tag and the reader device is less than a second distance between the RFID tag and adjacent metallic material disposed in the torch head or the cartridge. 
     In some embodiments, the clocking feature comprises a cavity configured to receive a clocking pin extending from the torch head. 
     In yet another aspect, a consumable cartridge for a liquid-cooled plasma arc cutting torch is provided. The consumable cartridge includes a cartridge tip located at a first portion of the cartridge. The cartridge tip has an electrode, a nozzle, and a shield. The consumable cartridge includes a plasma gas inlet opening at a second portion of the consumable cartridge, a shield gas inlet opening at the second portion, an electrode coolant inlet opening at the second portion, a nozzle coolant inlet opening and a nozzle coolant outlet opening at the second portion, and a shield coolant inlet opening and a shield coolant outlet opening at the second portion. 
     In some embodiments, the second portion comprises an end face of a proximal portion of the cartridge. The end face can be substantially planar. 
     In some embodiments, the plasma gas inlet opening, the shield gas inlet opening, the nozzle coolant inlet opening, the nozzle coolant outlet opening, the shield coolant inlet opening and the shield coolant outlet opening are non-concentric relative to a central longitudinal axis of the cartridge. 
     In some embodiments, the plasma gas inlet opening is configured to align with a corresponding opening of a torch head to direct a plasma gas flow from the torch head to the nozzle. In some embodiments, the shield gas inlet opening is in fluid communication with the shield. The shield gas inlet opening is configured to align with a corresponding opening of a torch head to direct a shield gas flow to the shield. In some embodiments, the electrode coolant inlet opening maintains at least one of electrical or fluid communication with the electrode. The electrode coolant inlet opening is configured to align with a corresponding opening of a torch head to direct at least one of a liquid coolant or a current to the electrode. In some embodiments, the nozzle coolant inlet opening and the nozzle coolant outlet opening are in fluid communication with the nozzle. The nozzle coolant inlet opening and the nozzle coolant outlet opening are configured to align with respective ones of corresponding openings on the torch head to direct the liquid coolant between the torch head and the nozzle. In some embodiments, the shield coolant inlet opening and the shield coolant outlet opening are in fluid communication with the shield. The shield coolant inlet opening and the shield coolant outlet opening are configured to align with respective ones of corresponding openings on the torch head to direct the liquid coolant between the torch head and the shield. In some embodiments, the nozzle coolant outlet opening is fluidly connected to the shield coolant inlet opening. 
     In some embodiments, the consumable cartridge further comprises a clocking pin receptacle at the second portion. The clocking pin receptacle is configured to receive a clocking pin of a torch head to radially secure the cartridge to the torch head in a predetermined orientation. 
     In some embodiments, the consumable cartridge further comprises a cartridge frame having an insulator body. The cartridge frame is coupled to the cartridge tip. The plasma gas inlet opening, the shield gas inlet opening, the electrode coolant inlet opening, the nozzle coolant inlet opening, the nozzle coolant outlet opening, the shield coolant inlet opening and the shield coolant outlet opening are located at a proximal end of the insulator body. In some embodiments, the consumable cartridge further comprises a non-concentric cavity disposed in the insulator body of the cartridge frame and a radio-frequency identification (RFID) tag disposed in the cavity. 
     In yet another aspect, a consumable cartridge for a liquid-cooled plasma arc cutting torch is provided. The consumable cartridge includes a cartridge tip located at a first portion of the cartridge. The cartridge tip has an electrode, a nozzle, and a shield. The consumable cartridge also includes a cartridge frame at a second portion of the cartridge. The cartridge frame comprises a distal end connected to the cartridge tip and a proximal end. The cartridge frame includes a plasma gas inlet opening at the proximal end configured to maintain fluid communication with the nozzle to introduce a plasma gas flow to the nozzle, a shield gas inlet opening at the proximal end configured to maintain fluid communication with the shield to introduce a shield gas flow to the shield, and an electrode interface at the proximal end configured to maintain at least one of electrical or fluid communication with the electrode to introduce at least one of a coolant flow or electrical current to the electrode. The cartridge frame further includes a nozzle coolant inlet opening and a nozzle coolant outlet opening at the proximal end configured to circulate the coolant flow between the cartridge frame and the nozzle and a shield coolant inlet opening and a shield coolant outlet opening at the proximal end configured to circulate the coolant flow between the cartridge frame and the shield. 
     In another aspect, a torch head for a liquid-cooled plasma arc torch is provided. The torch head includes a torch body and a torch insulator having a substantially non-conductive insulator body. The torch insulator is coupled to the torch body. The torch insulator includes (i) a first liquid coolant channel, disposed within the insulator body, configured to conduct a fluid flow from the torch head into a consumable cartridge along a first preexisting flow path, (ii) a first liquid return channel, disposed within the insulator body, configured to return at least a portion of the fluid flow from the cartridge to the torch head along the first preexisting flow path, and (iii) a gas channel, disposed within the insulator body, configured to conduct a first gas flow from the torch head to the cartridge along a second preexisting flow path. The first and second preexisting flow paths are fluidly isolated from each other. 
     In some embodiments, the torch head further comprises an alignment feature configured to radially secure the torch head to the cartridge in a predetermined orientation to maintain the first and second preexisting flow paths extending through the torch insulator and the cartridge. The first liquid coolant channel can be configured to substantially align with a corresponding first liquid coolant channel of the cartridge when the torch head is radially secured to the cartridge via the alignment feature. The first liquid return channel can be configured to substantially align with a corresponding first liquid return channel of the cartridge when the torch head is radially secured to the cartridge via the alignment feature. The first preexisting flow path can comprise the first liquid coolant channel of the torch head, the corresponding first liquid coolant channel of the cartridge, the corresponding first liquid return channel of the cartridge and the first liquid return channel of the torch head. 
     In some embodiments, the torch insulator further comprises a gas valve embedded in the insulator body, the gas valve in fluid communication with the gas channel, the gas valve configured to select one of a plurality of gases for supply to the gas channel. In some embodiments, the torch insulator further comprises a second gas channel, disposed within the insulator body, configured to conduct a second gas flow from the torch head to the cartridge along a third preexisting flow path. The second and third preexisting flow paths are fluidly isolated from each other. In some embodiments, the torch insulator further comprises a central channel disposed in the insulator body, the central channel configured to provide at least one of (i) a current or (ii) at least a portion of the fluid flow from the torch head to the cartridge. In some embodiments, the torch insulator further comprises an electrical channel disposed in the insulator body, the electrical channel configured to receive an ohmic contact connection that establishes an ohmic contact between the torch head and the cartridge. 
     In some embodiments, the torch insulator further comprises (i) a current ring at a distal end of the insulator body, the current ring configured to receive a pilot arc current from the cartridge, and (ii) a pilot arc channel configured to receive a pilot arc connection that is in electrical communication with the current ring to pass the pilot arc current from the cartridge to the torch head. 
     In some embodiments, the torch insulator further comprises (i) a second liquid coolant channel, disposed within the insulator body, configured to conduct at least a portion of the fluid flow from the torch head into the cartridge along the first preexisting flow path, (ii) a second liquid return channel, disposed within the insulator body, configured to return at least a portion of the fluid flow from the cartridge to the torch head along the first preexisting flow path, and (iii) a distribution channel, disposed within the insulator body, connecting the first liquid return channel with the second liquid coolant channel. The first preexisting flow path can flow over a sequence of channels in the insulator body comprising the first liquid coolant channel, the first liquid return channel, the distribution channel the second liquid coolant channel, and the second liquid return channel. 
     In some embodiments, the first liquid coolant channel, the first liquid return channel and the gas channel are non-concentric with respect to a longitudinal axis extending through the insulator body. 
     In another aspect, a torch head for a liquid-cooled plasma arc torch is provided. The torch head includes (i) a torch insulator having an insulator body, (ii) a first cooling channel and a third cooling channel, disposed in the insulator body, each configured to conduct a first fluid flow from the torch head into a cartridge, (iii) a second cooling channel and a fourth cooling channel, disposed in the insulator body, each configured to return at least a portion of the first fluid flow from the cartridge to the torch head, and (iv) a first distribution channel, disposed in the insulator body, connecting the second cooling channel and the third cooling channel. The first distribution channel is configured to direct the first fluid flow from the second channel to the third channel. 
     In some embodiments, the first distribution channel is circumferentially oriented to connect the second cooling channel and the third cooling channel. In some embodiments, the first, the second, the third and the fourth cooling channels are non-concentric about a longitudinal axis extending through the insulator body. In some embodiments, each of the first, the second, the third and the fourth cooling channels are asymmetric with respect to a central longitudinal axis extending through the insulator body. 
     In yet another aspect, a torch head for a liquid-cooled plasma arc torch is provided. The torch head includes (i) a torch insulator having an insulator body including a proximal end and a distal end, (ii) a plurality of gas and liquid channels extending substantially from the proximal end to the distal end of the insulator body, (iii) a cavity in the insulator body, and (iv) a communication device comprising a circuit board and a radio-frequency identification (RFID) antenna coil. The RFID antenna coil is electrically connected to the circuit board and positioned adjacent a distal end of the communication device. The communication device is located in the cavity such that the RFID antenna coil is positioned at the distal end of the insulator body. 
     In some embodiments, the communication device further comprises a sealed housing for preventing liquid from entering therein. In some embodiments, the circuit board of the communication device is configured to power the antenna coil and read an RFID signal received by the antenna coil. The antenna coil can be positioned at an end face of the distal end of the communication device. In some embodiments, the communication device further comprises a connector at a proximal end of the communication device. 
     In some embodiments, the plurality of gas and liquid channels and the cavity are non-concentric in relation to a central longitudinal axis of the insulator body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
         FIGS.  1   a  and  1   b    are exploded and assembled views, respectively, of a liquid-cooled plasma arc torch  10  generally comprising a torch head and a cartridge, according to an illustrative embodiment of the invention. 
         FIG.  2    is a cross-sectional view of the assembled plasma arc torch of  FIG.  1   b   , according to an illustrative embodiment of the invention. 
         FIG.  3    is a view of the proximal end of the torch head of  FIG.  1   , according to an illustrative embodiment of the invention. 
         FIG.  4    is a view of the distal end of the torch head of  FIG.  1   , according to an illustrative embodiment of the invention. 
         FIG.  5    is an exemplary design of the cathode of the torch head of  FIG.  1   , according to an illustrative embodiment of the invention. 
         FIG.  6    is an exemplary design of the coolant tube of the torch head of  FIG.  1   , according to an illustrative embodiment of the invention. 
         FIG.  7    is a sectional view of the plasma arc torch of  FIG.  2    oriented to illustrate an exemplary pilot arc current flow path between the torch head and the cartridge of the plasma arc torch, according to an illustrative embodiment of the present invention. 
         FIG.  8    is a sectional view of the plasma arc torch of  FIG.  2    oriented to illustrate an exemplary ohmic contact path, according to an illustrative embodiment of the present invention. 
         FIG.  9    is an exemplary design of the current ring in the torch head of  FIG.  1   , according to an illustrative embodiment of the present invention. 
         FIG.  10    is an exemplary design of the communication device of the torch head  102 , according to an illustrative embodiment of the present invention. 
         FIGS.  11   a  and  b    are sectional views of the plasma arc torch of  FIG.  2    oriented to illustrate an exemplary shield gas flow path from the torch head to the cartridge of the plasma arc torch, according to an illustrative embodiment of the present invention. 
         FIGS.  12   a - c    are sectional views of the plasma arc torch of  FIG.  2    oriented to illustrate an exemplary plasma gas flow path from the torch head to the cartridge of the plasma arc torch, according to an illustrative embodiment of the present invention. 
         FIGS.  13   a  and  b    are sectional views of the plasma arc torch of  FIG.  2    oriented to illustrate an exemplary liquid coolant flow path that circulates between the torch head and the cartridge of the plasma arc torch, according to an illustrative embodiment of the present invention. 
         FIGS.  14   a  and  b    are exemplary profile and proximal views of the cathode block of the torch head, respectively, according to an illustrative embodiment of the present invention. 
         FIG.  15    is a view of the proximal end of the cartridge frame of the cartridge of  FIG.  1   , according to an illustrative embodiment of the present invention. 
         FIG.  16    is a sectional view of an exemplary design of the retaining cap  120  of  FIG.  1   , according to an illustrative embodiment of the present invention. 
         FIG.  17    is a sectional view of the cartridge of  FIG.  1   , according to an illustrative embodiment of the present invention. 
         FIG.  18    is an exemplary design of the cartridge frame of the cartridge of  FIG.  17   , according to an illustrative embodiment of the present invention. 
         FIG.  19    is an exemplary design of the electrode of the cartridge of  FIG.  17   , according to an illustrative embodiment of the present invention. 
         FIG.  20    is a cross-sectional view of the baffle and the shield swirl ring attached to the cartridge frame of the cartridge of  FIG.  17   , according to an illustrative embodiment of the present invention. 
         FIG.  21    is a cross-sectional view of the shield swirl ring of the cartridge of  FIG.  17   , according to an illustrative embodiment of the present invention. 
         FIG.  22    is a perspective view of the cartridge frame of the cartridge of  FIG.  17    illustrating various channel openings, according to an illustrative embodiment of the present invention. 
         FIG.  23    is an exemplary design of the swirl ring of the cartridge of  FIG.  17   , according to an illustrative embodiment of the present invention. 
         FIGS.  24   a  and  b    are exterior views of the non-vented nozzle and the nozzle jacket of the cartridge of  FIG.  17   , respectively, according to an illustrative embodiment of the present invention. 
         FIG.  25    is a cross sectional view of the shield of the cartridge of  FIG.  17   , according to an illustrative embodiment of the present invention. 
         FIG.  26    is an exemplary vented cartridge compatible with the torch head of the plasma arc torch of  FIG.  1   , according to an illustrative embodiment of the present invention. 
         FIGS.  27   a  and  b    are exterior views of the nozzle liner and the vented nozzle of the cartridge of  FIG.  26   , respectively, according to an illustrative embodiment of the present invention. 
         FIG.  28    is another exemplary cartridge frame that can be suitably configured to form a cartridge compatible with the torch head of  FIG.  1   , according to an illustrative embodiment of the present invention. 
         FIG.  29    is an exemplary vented cartridge that includes a non-planar proximal end, according to an illustrative embodiment of the present invention. 
         FIG.  30    is an exploded view of the cartridge of  FIG.  17   , according to an illustrative embodiment of the present invention. 
         FIG.  31    is a portion of the plasma arc torch of  FIG.  2    illustrating exemplary locations of the communication device and the signal device, according to an illustrative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention provides a liquid-cooled plasma arc torch that includes a torch head and a consumable cartridge. In some embodiments, the consumable cartridge is a unitary component where the components of the cartridge are not individually serviceable or disposable. Thus, if one component of the consumable cartridge needs to be replaced, the entire cartridge is replaced. In some embodiments, the consumable cartridge is a “single use” cartridge, where the cartridge is replaced by the operator after any of the components thereof reaches the end of its service life rather than repairing and replacing the individual consumables like in traditional torch designs. In some embodiments, the cartridge is replaced after a single session, which can involve multiple arcs. In some embodiments, the cartridge is replaced after a single arc event. 
       FIGS.  1   a  and  1   b    are exploded and assembled views, respectively, of a liquid-cooled plasma arc torch  10  generally comprising a torch head  102  and a cartridge  104 , according to an illustrative embodiment of the invention. The cartridge  104 , which comprises a plurality of consumable torch components, has a proximal end (region)  14  and a distal end (region)  16  along a central longitudinal axis A of the plasma arc torch  10 . The torch head  102  includes a torch body  18 , a proximal end (region)  20  and a distal end (region)  22  along the longitudinal axis A. The torch body  18  can be made of an electrically conductive material, such as brass. In some embodiments, the proximal end  14  of the cartridge  104  is aligned with and secured to the distal end  22  of the torch head  102  by a retaining cap  120 . In some embodiments, the proximal end  14  of the cartridge  104  matingly engages/connects to the distal end  22  of torch  102 . For example, the proximal end  14  and the distal end  22  can be connected via at least seven distinct mating joints/junctions/connection points. Other engagement means between the torch head  102  and cartridge  104  are possible, including threading, interference fit, snap fit, quick lock, etc. 
     Hereinafter, a proximal end of a component defines a region of the component along the longitudinal axis A that is away from a workpiece when the torch  10  is used to process the workpiece, and a distal end of the component defines a region of the component that is opposite of the proximal end and close to the workpiece when the torch  10  is used to process the workpiece. 
       FIG.  2    is a cross-sectional view of the assembled plasma arc torch  10  of  FIG.  1   b   , according to an illustrative embodiment of the invention. As shown, an interface  106  in  FIG.  1    defines the boundary between the cartridge  104  and the torch head  102  after they are engaged to each other. The cartridge  104 , which is a substantially unitary element, includes a cartridge tip comprising an electrode  108  (i.e., an arc emitter), a nozzle  110  (i.e., an arc constrictor) and a shield  114  disposed concentrically about the central longitudinal axis A. Components of the cartridge tip can be connected to a cartridge frame  112  of the cartridge  104 . In some embodiments, the cartridge  104  also includes a swirl ring  150  disposed about the longitudinal axis A. Details regarding the cartridge  104  are explained below with reference to  FIGS.  15  and  17 - 25   . The torch head  102  includes a torch insulator  118  disposed in the torch body  18  about the longitudinal axis A. Details regarding the torch head  102  are explained below with reference to  FIGS.  2 - 14     b.    
     Torch Head 
     As shown in  FIG.  2   , the torch insulator  118  of the torch head  102  is substantially disposed in and surrounded by the torch body  18  about the central longitudinal axis A. The torch body  18  can be made of an electrically conductive material, such as brass. The torch insulator  118 , which include a proximal end  21  and a distal end  23 , can be made of an electrically insulating material, such as plastic. The torch insulator  118 , at its proximal end  21 , can couple to one or more of a cathode  130 , a communication device  122 , a pilot arc connection  124  and an ohmic connection  131  while electrically insulating these components from each other and from the torch body  18 . In some embodiments, at least one of the cathode  130 , the communication device  122 , the pilot arc connection  124 , or the ohmic connection  131  is fixed to the torch insulator  118  (e.g., threaded to or embedded in the torch insulator  118 ) such that they cannot be easily or quickly disconnected from the torch insulator  118 . In addition, the torch insulator  118  can include at least one gas opening  126   a  for coupling to a source of gas (not shown) and introducing the gas to the torch  10 . The torch insulator  118  can further include at least one coolant opening  128   a  for coupling to a source of liquid coolant (not shown) and introducing the coolant to the torch  10 .  FIG.  3    is a view of the proximal end  20  of the torch head  102 , which shows various electrical, gas and liquid openings at the proximal end  21  of the torch insulator  118 , according to an illustrative embodiment of the invention.  FIG.  4    is a view of the distal end  22  of the torch head  102 , which shows various electrical, gas and liquid openings at the distal end  23  of the torch insulator  118 , according to an illustrative embodiment of the invention. 
     a. Pilot Arc and Transferred Arc Connection 
     In one aspect, the torch insulator  118  can interconnect a plurality of components that are used to maintain a pilot arc current and/or a transferred arc current between the torch head  102  to the cartridge  104 . For example, the torch insulator  118  is adapted to connect the cathode  130 , a coolant tube  116 , the pilot arc connection  124  and a current ring  800  in a configuration that supports both pilot arc current and transferred arc current conduction between the torch head  102  and the cartridge  104 . 
     In some embodiments, the torch insulator  118  includes a main channel  132  (shown in  FIG.  2   ) extending from an opening  132   a  at the proximal end  21  of the torch insulator  118  (shown in  FIG.  3   ) to an opening  132   b  at the distal end  23  of the torch insulator  118  (shown in  FIG.  4   ). The main channel  132  can be centrally located within the torch insulator  118  such that it is concentric with respect to the central longitudinal axis A. The main channel  132  can extend substantially straight within the insulator  118  to connect the openings  132   a  and  132   b . The main channel  132  can be configured to house at least a portion of the cathode  130 . As shown in  FIG.  2   , the cathode  130  can extend within the main channel  132  along the length of the torch insulator  118 . In some embodiments, a cathode block locking component  250  is used to secure the cathode  130  to the main channel  132  inside of the torch insulator  118 . 
       FIG.  5    is an exemplary design of the cathode  130  of the torch head  102 , according to an illustrative embodiment of the invention. The cathode  130  includes a cathode fitting  602  with a distal end coupled to a cathode tube  604 , which has a distal end coupled to a cathode block  606 . Each of the cathode fitting  602 , the cathode tube  604  and the cathode block  606  can be made from a conductive material, such as brass or copper. In one exemplary design, the cathode fitting  602  and the cathode block  606  are made of brass, while the cathode tube  604  is made of copper. 
     As shown in  FIG.  2   , the distal end of the cathode block  606  can electrically and/or physically couple to the coolant tube  116  within the main channel  132  of the torch insulator  118 . In some embodiments, the coolant tube  116  defines an o-ring groove that houses an o-ring  133  to form an interface between an outer surface of the coolant tube  116  and an inner surface of the cathode block  606 . Thus, at least a proximal portion of the coolant tube  116  is inserted within the distal end of the cathode block  606 . Generally, during operation the coolant tube  116  distributes a cooling fluid to the cartridge  104  once the torch head  102  is coupled to the cartridge  104 . In some embodiments, the coolant tube  116  is configured to additionally pass a current from the cathode  130  to the cartridge  104 , such as to the electrode  108  of the cartridge  104 . In some embodiments, a cathode block electrode tube  252  (shown in  FIG.  2   ), which can be made of a non-conductive material, can be configured to connect with (e.g., threaded into or sealed by interference fit) the cathode block  606  at its proximal end and with the electrode  108  at its distal end. The resulting housing, which comprises the cathode  130 , the cathode block electrode tube  252  and the electrode  108 , substantially encases the coolant tube  116  to contain the coolant flow therein. 
       FIG.  6    is an exemplary design of the coolant tube  116  of the torch head  102 , according to an illustrative embodiment of the invention. The coolant tube  116  can be made of a conductive material, such as brass. In some embodiments, the coolant tube  116  is affixed (e.g., by threading) to the distal end of the cathode block  606  such that it cannot be easily or quickly disconnected. In some other embodiments, the coolant tube  116  is affixed (e.g., by an interference fit) to the distal end of the cathode block  606  such that it can be easily or quickly disconnected. The coolant tube  116  can have an electrical connector, such as a Louvertac™ band  702  around an external surface at a proximal end  740 , which is the end that is configured to mate with the cathode block  606 . The Louvertac band  702  is configured to conduct the cutting current carried from the interior surface of the cathode block  606  to the exterior surface of the coolant tube  116  once the proximal end  740  of the coolant tube  116  is inserted into and affixed to the distal end of the cathode block  606 . Alternatively, the coolant tube  116  can be fixedly secured to the cathode  130  via threads or other current-carrying methods without the Louvertac band  702 . In some embodiments, the coolant tube  116  has an electrical connector, such as a Louvertac™ band  704 , around an exterior surface at a distal end  742  of the coolant tube  116 , which is the end that is configured to mate with an internal surface of the electrode  108  once the torch head  102  is secured to the cartridge  104 . In some embodiments, the coolant tube  116  includes one or more longitudinal channels  744  on its exterior surface below the Louvertac band  704  at the distal end  742  to limit a pressure drop in the coolant flow between the coolant tube  116  and the electrode  108 . In addition to conducting electrical current, the coolant tube  116  can be configured to conduct a coolant flow to the electrode  108 . For example, the coolant tube  116  has an opening  745  at its proximal end  740  and an opening  746  at its distal end  742  for allowing a coolant flow to enter and leave the coolant tube  116 , respectively. In some embodiments, the use of a Louvertac™ band  702  or  704  at one of the distal end  742  or the proximal end  740  or at both ends allows the coolant tube  116  to be slidably coupled to the torch head  102  and likewise allows a cartridge  104  to be slidably coupled to the coolant tube  116 . This feature is described below in detail. 
     In some embodiments, the torch insulator  118  includes a cavity  148  (shown in  FIG.  2   ) with an opening  148   a  at the proximal end  21  of the torch insulator  118  (shown in  FIG.  3   ). As shown in  FIG.  2   , the cavity  148  can be configured to house the pilot arc connection  124 . In some embodiments, the cavity  148  extends partially into the torch insulator  118  along the longitudinal axis A. 
     In some embodiments, a current ring  800 , made of an electrically conductive material (e.g., brass), is located in the distal end  23  of torch insulator  118 .  FIG.  9    is an exemplary design of the current ring  800  of the torch insulator  118  in the torch head  102 , according to an illustrative embodiment of the present invention. As shown, the current ring  800  has a ring portion  800   a  and a protrusion portion  800   b . The ring portion  800   a  has a thin distal rim  802  and the protrusion portion  800   b  has a distal surface  805 . The ring portion  800   a  of the current ring  800  can be concentrically situated with respect to the coolant tube  116  and the cathode  130  in the torch insulator  118 , while the protrusion portion  800   b  of the current ring  800  can be oriented such that it electrically and/or physically contacts the proximal end of the pilot arc connection  124  housed in the cavity  148 . In some embodiments, the current ring  800  is electrically insulated from the coolant tube  116  and the cathode  130  by a cathode insulator  804  (shown in  FIG.  2   ) such that substantially no current is passed between the current ring  800  and the cathode  130  or between the current ring  800  and the coolant tube  116 . In some embodiments, as shown in  FIG.  4   , at least a surface of the current ring  800  is exposed from the distal end  23  of the torch insulator  118  via the main electrical channel opening  132   b  such that a component of the cartridge  104  can physically contact the current ring  800  once the cartridge  104  is attached to the torch head  102 . For example, both the thin distal rim  802  of the ring portion  800   a  and the distal surface  805  of the protrusion portion  800   b  of the current ring  800  can be exposed from the opening  132   b.    
       FIG.  7    is a sectional view of the plasma arc torch  10  of  FIG.  2    oriented to illustrate an exemplary pilot arc current flow path  752  between the torch head  102  and the cartridge  104  of the plasma arc torch  10 , according to an illustrative embodiment of the present invention. To start a pilot arc, a pilot arc current  752  associated with a high-frequency, high-voltage (HFHV) signal is coupled to a power line from a power supply (not shown) to the plasma arc torch  10 . The pilot arc current flow  752  can be passed from the power supply to the cathode  130  via the cathode fitting  602 . The cathode tube  604  that is connected to the cathode fitting  602  then passes the pilot arc current  752  to the cathode block  606 , which transfers the current to the coolant tube  116  via the Louvertac band  702  at the proximal end  740  of the coolant tube  116 . The pilot arc current  752  flows distally through the coolant tube  116  and is transferred to the internal surface of the electrode  108  via the Louvertac band  704  at the distal end  742  of the coolant tube  116 , thereby energizing the internal surface of the electrode  108 . In alternative embodiments, the pilot arc current is passed from the cathode  130  to the electrode  108  without using the coolant tube  116 , such as through a physical connection between the cathode  130  and the electrode  108 . Once at the electrode  108 , the pilot arc current path  752  induces a spark discharge in a plasma gas flowing in the gap between the electrode  108  and the nozzle  110 , thereby generating a pilot arc in the gap. To complete the pilot arc circuit, the pilot arc current path  752  can return to the torch head  102  by flowing proximally from the nozzle  110 , to the swirl ring  150  (which can be made of a conductive material), and to the current ring  800  in the torch head  102 . As shown, the distal end of the swirl ring  150  physically contacts the nozzle  110  at an interface  758 . The proximal end of the swirl ring  150  physically contacts at least the distal rim  802  of the ring portion  800   a  of the current ring  800  via a Louvertac electrical connector  756 . The swirl ring  150  is thus configured to return the pilot arc current  752  from the nozzle  110  of the cartridge  104  to the torch head  102 . The ring portion  800   a  of the current ring  800  can transfer the pilot arc current  752  to the protrusion portion  800   b  of the current ring  800 , which passes the pilot arc current flow  752  to to the pilot arc current connection  124  within the cavity  148  to return the pilot arc current to the power supply. 
     The gas flow in the gap between the electrode  108  and the nozzle  110  is ionized by the pilot arc so that electrical resistance between the electrode  108  and a workpiece (not shown) becomes small. A voltage higher than the voltage used to initiate the pilot arc can be applied across the electrode  108  and the workpiece to induce the arc to transfer to the workpiece after the gap is ionized. This arc between the electrode  108  and the workpiece is a transferred arc. To maintain the transferred arc, a transferred arc current, which supplies the higher voltage from the power supply, is passed from the cathode  130  to the electrode  108  via the coolant tube  116  and the Louvertac bands  702 ,  704  in substantially similar fashion as the distal pilot arc current flow  752 . To complete the transferred arc circuit, the transferred arc current is returned from the workpiece to the power supply through separate wirings (not shown). 
     b. Communication Device (RFID Reader) 
     In another aspect, the torch insulator  118  can be configured to support wireless communication between the torch head  102  and the cartridge  104 . In some embodiments, the torch insulator  118  includes a cavity  144  (shown in  FIG.  2   ) with an opening  144   a  at the proximal end  21  of the torch insulator  118  (shown in  FIG.  3   ). The cavity  144  can be configured to retain the communication device  122  within the torch insulator  118 . The communication device  122  is removable from the cavity  144  via the opening  144   a . In some embodiments, the cavity  144  extends partially into the torch insulator  118  along the central longitudinal axis A such that there is no corresponding opening on the distal end  23  of the torch insulator  118 . 
       FIG.  10    is an exemplary design of the communication device  122  of the torch head  102 , according to an illustrative embodiment of the present invention. The communication device  122  can comprise a radio-frequency identification (RFID) reader adapted to receive RFID signals wirelessly transmitted from a nearby signal device  160  (e.g., an RFID tag) located in the cartridge  104  (shown in  FIG.  2   ). The communication device  122  is adapted to process these signals to extract pertinent data transmitted by the signal device  160  about the cartridge  104  (and/or other torch information) and forward the data to a processor (not shown) for analysis. In general, the communication device  122  can be placed at a location in the plasma arc torch  10 , such as in the torch insulator  118 , to minimize the possibility of plasma arc and arc ignition disrupting the wireless communication between the signal device  160  and the communication device  122 . The communication device  122  can include a connector  806  at its proximal end, an antenna assembly  808  at its distal end, and a processing assembly  810  between the connector  806  and the antenna assembly  808 . 
     The antenna assembly  808  can include an antenna coil  814  configured to wirelessly transmit RF signals to the signal device  160  to interrogate the signal device  160  and/or receive RF signals from the signal device  160  in response to the interrogation. This antenna coil  814  can be located at the distal end of the antenna assembly  808  (i.e., the distal end of the communication device  122 ) such that when the communication device  122  is inserted into the cavity  144 , the antenna coil  814  is embedded at the distal end  23  of the torch insulator  118 . Such a placement minimizes wireless communication distance between the antenna coil  814  and the signal device  160  in the cartridge  104  and reduces communication interference between them. In some embodiments, the antenna coil  814  is positioned at an end face of the distal end of the communication device. For example, the antenna coil  814  can be wound around the post  812  at the distal end of the antenna assembly  808 . The assembly  808  can also include a plastic cylindrical housing configured to feed one or more wires connected to the antenna coil  814  to the processing assembly  810 . The processing assembly  810  can include a plastic cylindrical housing having one or more hardware components (e.g., a printed circuit board (PCB)) disposed therein. The PCB, which is connected to the wires from the antenna coil  814  of the antenna assembly  808 , is configured to (i) power the communication device  122  including the antenna assembly  808 , (ii) power the signal device  160 , and/or (iii) wirelessly communicate with the signal device  160  via the antenna coil  814  using a communication protocol (e.g., an RFID protocol such as ISO/IEC 15693) to process data from the signal device  160 . In some embodiments, the PCB can power an entire torch communication circuit on board the torch  10  that includes the communication device  122 , the signal device  160  and related components. The connector  806 , which is in electrical communication with the PCB of the processing assembly  810 , is configured to transmit the data processed by the processing assembly  810  to a computing device (e.g., a central processing unit or the like) external to the torch  10 . For example, the connector  806 , in cooperation with the PCB of the processing assembly  810 , can convey information obtained from the signal device  160  to the external computing device using either a wireless or wired connection. 
     In some embodiments, the circuitry that enables wireless communication between the communication device  122  and the signal device  160  is analog while the circuitry that enables (wired or wireless) communication between the communication device  122  and the external computing device is digital. In this configuration, placing the communication device  122 , including the PCB, in the torch  10  reduces the distance of communication between the communication device  122  and the signal device  160  and therefore reduces noise pickup in the corresponding analog circuitry. However, placing the communication device  122  in the torch  10  can lengthen the communication distance between the communication device  122  and the remote computing device, and therefore can increase noise pickup in the corresponding digital circuitry, but the digital circuitry is more robust (i.e., more immune) to noise pickup than the analog circuitry. 
     In some embodiments, the communication device  122  is encased in one or more layers of protective material providing, for example, electrical insulation, liquid coolant leakage protection (plus protection from waste carried by the coolant flow), and protection against other environmental factors. In some embodiments, the housing of the processing assembly  810  and/or the housing of the antenna assembly  808  are made of durable plastic to protect the components therein from liquid and debris. The housings can be translucent such that LED signals of the PCB therein can be visible from outside of the housings. In some embodiments, one or more o-ring seals are used to protect the communication device  122  against liquid damage and create an electrically insulated barrier. 
     In some embodiments, the communication device  122  in the torch insulator  118  is electrically isolated from the plasma power and ignition circuitry, such as by about 30,000 V of electrical isolation. In some embodiments, the communication device  122  is configured to fit inside of the torch insulator  118  while accommodating all other components of the torch insulator  118  described above as well the protective layers around the communication device  122 , which adds to its bulk. For example, the communication device  122  can be designed to be long, thin and/or flexible to better fit within the torch insulator  118 . 
     During operation, the plasma arc torch  100  can cause up to 100 Celsius in ambient temperature, which leaves little margin for operating temperature rise. Therefore, in some embodiments, the communication device  122  is designed to generate minimal operating temperature. For example, the communication device  122  can have a low circuit power voltage, a low multi-point-control-unit (MCU) clock frequency, a low operational duty cycle and/or a sleep mode for while not performing to minimize heat generation. 
     In some embodiments, the torch communication circuit, which includes the communication device  122  and the signal device  160 , is off axis from the central longitudinal axis A of the plasma arc torch  10 . This offset allows the communication circuitry to be away from the region of the torch that defines plasma process performance. In general, the area where the communication circuit is placed is not vulnerable to variation in plasma process designs, which allows design freedom for the plasma process and stability for the communication circuitry performance. In some embodiments, to reduce unwanted coupling between the torch communication circuit and nearby metal components, the size of the antenna coil  814  is minimized (e.g., reduced coil diameter) and/or the RFID power is minimized to reduce the size of the resulting RFID field. In general, adjacent metal components that can potentially couple with the RFID field can be accounted for and held substantially consistent in size and proximity relative to the torch communication circuit. 
     In alternative embodiments, the plasma arc torch  10  does not include a communication system that comprises, for example, the communication device  122  in the torch head  102  or the signal device  106  in the cartridge  104 . For example, a communication system can be absent in a torch where the cartridge  104  is connected to the torch head  102  or a quick-disconnect torch head, which in turn is connected to a torch receptacle. 
     In some embodiments, as illustrated in  FIGS.  2  and  10   , the communication system of the plasma arc torch  10  further includes a second signal device  162  (e.g., an RFID tag) disposed in or on the communication device  122  in the torch insulator  118 , such as in the antenna assembly  808  of the communication device  122  close to the antenna coil  814 . Alternatively, the second signal device  162  can be located in the torch head  102  external to the communication device  122  and/or the torch insulator  118 . An optional base  164  can be used to hold the second signal device  162  in place. The second signal device  162  is configured to read and/or write information about the plasma arc torch  10  (e.g., number of arcs fired) and communicate the information to the plasma cutting system, which can then relay the information to first signal device  160  in the cartridge  104 . Generally, the first and second signal devices  160 ,  162  can transfer information back and forth between them. 
     c. Ohmic Contact 
     In another aspect, the torch insulator  118  can be configured to support ohmic contact for the purpose of controlling a relative height between the torch  10  and a workpiece to facilitate torch operation. In some embodiments, the torch insulator  118  includes an ohmic contact cavity  146  (shown in  FIG.  8   ) with an opening  146   a  at the proximal end  21  of the torch insulator  118  (shown in  FIG.  3   ).  FIG.  8    is a sectional view of the plasma arc torch  10  of  FIG.  2    oriented to illustrate an exemplary ohmic contact path  780 , according to an illustrative embodiment of the present invention. As shown, the ohmic contact cavity  146  of the torch insulator  118  in the torch head  102  can be configured to retain an ohmic contact connection  131 , which is removable from the cavity  146  via the opening  146   a  (shown in  FIG.  3   ). In some embodiments, the ohmic contact cavity  146  extends partially into the torch insulator  118  along the longitudinal axis A such that there is no corresponding opening on the distal end  23  of the torch insulator  118 . 
     The ohmic contact path  780  of  FIG.  8    allows a controller (not shown) of the torch  10  to detect and sense a workpiece/plate  782  for the purpose of controlling the relative height between the torch  10  and the workpiece/plate  782  prior to or during a torch operation. With respect to the ohmic contact path  780 , when the torch head  102  is mounted during torch operation, an incoming pin (not shown) makes electrical contact with the ohmic contact connection  131  to form the electrical contact path  780 . The path  780  then continues through the length of the ohmic contact connection  131  to electrically contact the torch body  18  via a set screw  784 . The path  780  travels distally over the torch body  18  and the retaining cap  120  to reach the shield  114  of the cartridge  104 . This path  780  allows the controller to sense the location of the workpiece/plate  782  and adjust the relative height accordingly. In some embodiments, the shield  114  of the cartridge  104  is electrically isolated from the nozzle  110  of the cartridge  104  to allow the ohmic contact path  780  to travel from the torch head  102  to the shield  114  on the outer surface of the torch  10 . 
     In some embodiments, the ohmic contact path  780  of  FIG.  8    is electrically isolated from the pilot arc current flow path  752  and/or the transferred arc current flow path by the use of the torch insulator  118 . For example, pilot arc current flow path  752  and the transferred arc current flow path can be through the torch insulator  118  while the ohmic contact path  780  is mostly through the torch body  18 . 
     d. Shield Gas 
     In another aspect, the torch insulator  118  can be configured to direct one or more gas flows from the torch head  102  to the cartridge  104 . In some embodiments, the torch insulator  118  is configured to direct at least one shield gas from the torch head  102  to the cartridge  104 . Exemplary shield gases include air, oxygen (i.e. O 2 ), and argon. In some embodiments, the shield gas flow path and channels described herein are also compatible with conducting a shield fluid, such as water, between the torch head  102  and the cartridge  104 . The torch insulator  118  can include a shield gas channel  850  extending from an opening  126   a  at the proximal end  21  of the torch insulator  118  (shown in  FIG.  3   ) to a shield gas opening  126   b  at the distal end  23  of the torch insulator  118  (shown in  FIG.  4   ). 
       FIGS.  11   a  and  b    are sectional views of the plasma arc torch  10  of  FIG.  2    oriented to illustrate an exemplary shield gas flow path  868  from the torch head  102  to the cartridge  104  over the shield gas channel  850  (including shield gas channel segments  850   a  and  850   c ), according to an illustrative embodiment of the present invention. As shown, the shield gas channel  850  can comprise several segments. A first channel segment  850   a  connects the opening  126   a  on the proximal end  21  of the torch insulator  118  to an internal opening  860  in or on the insulator  118 . The first channel segment  850   a  can extend substantially parallel to the longitudinal axis A. A second channel segment (not shown) can connect the opening  860  with another internal opening  862  in or on the insulator  118 , where the second internal opening  862  is radially offset from the first internal opening  860 . For example, the internal openings  860 ,  862  can be radially offset by about 30 degrees to about 90 degrees. The second channel segment can extend circumferentially around the torch insulator  118  (or in a different orientation) to connect the internal openings  860 ,  862 . A third channel segment  850   c  connects the internal opening  862  to the opening  126   b  on the distal end  23  of the torch insulator  118 . The third channel segment  850   c  can extend substantially parallel to the longitudinal axis A. 
     In some embodiments, upon attachment of the cartridge  104  onto the torch head  102 , a corresponding shield gas channel  864  within the cartridge frame  112  of the cartridge  104  fluidly aligns with the shield gas channel segment  850   c . The shield gas flow  868  can enter the cartridge  104  via a proximal opening  864   a  of the shield gas channel  864  in the cartridge frame  112 . The shield gas channel  864  also has an opening  864   b  at a distal end of the cartridge frame  112  that is fluidly connected to a gas passage  872  between the shield  114  and the nozzle  110 . Thus, the shield gas channel  864  can introduce a shield gas from the torch head  102  to the gas passage  872 . In some embodiments, the cartridge frame  112  includes one or more components in the path of the shield gas channel  864  to adjust one or more parameters (e.g., flow pattern and rate) of the shield gas flow  868  therein. Details regarding the shield gas channel  864 , the swirling components of the cartridge frame  112  and the shield gas flow  868  through the cartridge  104  are described below. 
     With respect to the shield gas flow path  868  shown in  FIGS.  11   a  and  b   , a shield gas is introduced to the torch head  102  via the shield gas opening  126   a  at the proximal end  21  of the torch insulator  118 . The gas  868  flows distally through the shield gas channel segment  850   a  to reach the internal opening  860 . The gas  868  can then flow circumferentially (or in a different orientation) around the torch insulator  118  via the second segment of the shield gas channel  850  to reach the internal opening  862  that is spaced relative to the internal opening  860 . The gas  868  flows longitudinally from the opening  862  to the opening  126   b  on the distal end  23  of the torch insulator  118  via the shield gas channel segment  850   c  to reach the cartridge  104 . Upon exiting the torch head  102  via the opening  126   b , the shield gas flow  868  enters the shield gas channel  864  of the cartridge frame  112  in the cartridge  104 . The gas  868  flows distally through the shield gas channel  864  of the cartridge frame  112  and exits from the opening  864   b  of the shield gas channel  864  to the gas passage  872  between the shield  114  and the nozzle  110  to cool the two components. The shield gas  868  is adapted to exit the cartridge  104  via the shield exit orifice  870 . 
     e. Plasma Gas 
     In some embodiments, the torch insulator  118  of the torch head  102  can direct one or more plasma gases from the torch head  102  to the cartridge  104 . For example, the torch insulator  118  can be configured to receive multiple sources of gas, select one of the gases or mix the gases, and introduce the selected gas or gas mixture to the cartridge  104 .  FIGS.  12   a - c    are sectional views of the plasma arc torch  10  of  FIG.  2    oriented to illustrate an exemplary plasma gas flow path  900  from the torch head  102  to the cartridge  104 , according to an illustrative embodiment of the present invention. 
     The torch insulator  118  includes two plasma gas openings  200   a  and  200   b  at the proximal end  21  of the torch insulator  118 , where each opening is configured to receive a plasma gas, such as oxygen (O 2 ), air, nitrogen (N 2 ), hydrogen-based gases (e.g., H35), F5 fuel gas, or a mixture of one or more of these chemicals. In addition, the torch insulator  118  can include a cavity  202  (shown in  FIGS.  12   a - c   ) configured to house a plasma gas valve  204 . The cavity  202  is connected to an opening  202   a  at the proximal end  21  of the torch insulator  118  (shown in  FIG.  3   ), through which the plasma gas valve  204  can be removably disposed in the cavity  202 . The plasma gas valve  204  is configured to select one of the gases or mix the gases received from the plasma gas openings  200   a  and  200   b  and introduce the resulting gas or gas mixture to the cartridge  104  over a plasma gas channel  206  (shown in  FIGS.  12   a - c   ) and via an opening  200   c  on the distal end  23  of the torch insulator  118  (also shown in  FIG.  4   ). 
     As shown in  FIG.  12   a   , the exemplary plasma gas flow path  900  comprises a first plasma gas flow  900   a  introduced from the plasma gas opening  200   a  to the plasma gas valve  204  located in the cavity  202  via a connection channel  902 . The connection channel  902  fluidly connects the opening  200   a  with an inlet  904  of the plasma gas valve  204  to introduce the first plasma gas flow  902  to the valve  204 . As shown in  FIG.  12   b   , the plasma gas flow path  900  comprises a second plasma gas flow  900   b  introduced from the plasma gas opening  200   b  to the plasma gas valve  204  via a connection channel  906 . The connection channel  906  fluidly connects the opening  200   b  with a second inlet  908  for introducing the second plasma gas flow  900   b  to the plasma gas valve  204 . As shown in  FIG.  12   c   , the plasma gas valve  204  selects one of the gases or mixes the gases and transmits the resulting plasma gas flow  900   c  over the plasma gas channel  206  to exit from the opening  200   c  at the distal end  23  of the torch insulator  118 . The plasma gas channel  206  is adapted to extend longitudinally along the length of the torch  10  and fluidly connect an outlet  910  of the plasma gas valve  204  to the opening  200   c  at the distal end  23  of the torch insulator  118 . 
     With respect to the plasma gas flow path  900   c  shown in  FIG.  12   c   , upon exiting the torch head  102  via the opening  200   c , the plasma gas flow  900   c  enters a corresponding plasma gas channel  912  of the cartridge frame  112  in the cartridge  104  via an opening  912   a  on a proximal end  15  of the cartridge frame  112 . The gas  900   c  flows longitudinally through the plasma gas channel  912  of the cartridge frame  112  and exits from an opening  912   b  at the distal end  17  of the cartridge frame  112 , which introduces the gas to the plasma gas passage  918  between the electrode  108  and the nozzle  110  of the cartridge  104 . The plasma gas  900   c  is adapted to flow distally through the passage  918  and exit the cartridge  104  via the central nozzle exit orifice  916  and the central shield exit orifice  870 . In some embodiments, the swirl ring  150  in the path of the plasma gas flow  900   c  can introduce a swirling motion to the plasma gas flow  900   c . Details regarding the plasma gas channel  912 , the swirl ring  150 , and the plasma gas flow  900   c  through the cartridge  104  are described below. 
     In some embodiments, the shield gas flow  868  and the plasma gas flow  900  are fluidly isolated from each other in both the torch head  102  and the cartridge  104  such that these gases do not cross paths or share the same channels. For example, the plasma gas channel  206  and the shield gas channel  850  are fluidly isolated from each other. In some embodiments, the torch insulator  118  of the torch head  102  is configured to control gas flows through the torch  10  by directing the shield gas flow  868  and the plasma gas flow  900  to the appropriate channels within the cartridge frame  112  for distribution to the appropriate gas passageways in the cartridge  104  (e.g., the passage  872  between the nozzle  110  and the shield  114  for the shield gas flow  868  and the passage  918  between the electrode  108  and the nozzle  110  for the plasma gas flow  900   c ). 
     f. Liquid Coolant Flow 
     In another aspect, the torch insulator  118  can be configured to direct a sequence of liquid coolant flow for circulation between the torch head  102  to the cartridge  104 . Exemplary liquid coolant includes water, propylene glycol, ethylene glycol, or any number of commercially available coolants specially designed for plasma cutting systems. As shown in  FIG.  3   , the torch insulator  118  can include a coolant opening  128   a  at the proximal end  21  of the torch insulator  118  for introducing a liquid coolant to the torch head  102 . 
       FIGS.  13   a  and  b    are sectional views of the plasma arc torch  10  of  FIG.  2    oriented to illustrate an exemplary liquid coolant flow path  950  that circulates between the torch head  102  and the cartridge  104  in a series of flow segments, according to an illustrative embodiment of the present invention. Along the liquid coolant flow path  950  of  FIG.  13   a   , a liquid coolant is first introduced to the torch head  102  via the opening  128   a  at the proximal end  21  of the torch insulator  118 . The coolant  950  flows from the opening  128   a  to the cathode block  606  within the torch insulator  118  over a connection channel  952  and enters the cathode bock  606  via at least one inlet of the cathode block  606 .  FIGS.  14   a  and  b    are exemplary profile and proximal views of the cathode block  606  of the torch head  102 , respectively, according to an illustrative embodiment of the present invention. As shown in  FIG.  14   b   , the cathode block  606  can include a first set of three liquid inlets  620   a - c  dispersed around an inner circumference of the cathode block  606 . In other embodiments, more or fewer inlets are defined. The connection channel  952  fluidly connects the torch insulator opening  128   a  to the first set of liquid inlets  620   a - c  to conduct the coolant into the cathode block  606 . The liquid inlets  620   a - c  of the cathode block  606  can further conduct the liquid coolant into the opening  745  at the proximal end  740  of the coolant tube  116  that can be physically attached to the cathode block  606  as described above. In some embodiments, the connections between the inlets  620   a - c  and the opening  745  at the proximal end of the coolant tube  116  are crisscrossed (e.g., for spacing saving purpose) to deliver the coolant from the cathode block  606  to the coolant tube  116 . 
     Once in the coolant tube  116 , the coolant flow path  950  continues on longitudinally toward the distal end  742  of the coolant tube  116 . The coolant flow  950  exits from the coolant tube  116  via the distal opening  746  of the coolant tube  116  and enters into a cavity  954  defined by the inner surface of the electrode  108  of the cartridge  104 , thereby substantially cooling the electrode  108 . Hence, the initial coolant flow path  950  is substantially confined within the main channel  132  of the torch insulator  118  (which receives at least a portion of the cathode  130  and the coolant tube  116 ) and a corresponding main channel  1020  of the cartridge frame  112  (which connects to the the cavity  954  of the electrode  108 ). As guided by the wall of the cavity  954 , the coolant flow  950  reverses direction and continues on proximally in the main channels  1020 ,  132 , along the outer surface of the coolant tube  116 . This reverse flow also substantially cools the Louvertac band  704  surrounding an exterior portion of the distal end  742  of the coolant tube  116 . 
     The coolant flow  950  continues toward the cathode block  606  of the torch head  102 . The coolant flow  950  can enter the cathode block  606  via the distal opening  622  of the cathode block  606  (shown in  FIG.  14   a   ). Once inside of the cathode block  606 , the coolant  950  flows radially outward over an exit channel  624  of the cathode  130 . The exist channel  624  fluidly connects the cathode  606  to a first coolant channel  958  of the torch insulator  118  that extends longitudinally along the length of the torch head  102  to again conduct the coolant flow  950  from the torch head  102  into the cartridge  104 . Specifically, the first coolant channel  958  fluidly connects the exit channel  624  to a first liquid coolant opening  960   a  on the distal end  23  of the torch insulator  118  (also shown in  FIG.  4   ). The first coolant channel  958  conducts the coolant flow  950  from the cathode  130  to the cartridge  104  via the opening  960   a  of the torch insulator  118  and introduces the coolant flow  950  into an opening  962   a  on the proximal end  15  of the cartridge frame  112 , where the proximal opening  962   a  is connected to a corresponding first coolant channel  962  of the cartridge frame  112  in the cartridge  104 . 
     The coolant  950  flows distally through the cartridge frame  112  over the first coolant channel  962  to reach an opening  962   b  at the distal end  17  of the cartridge frame  112 , which fluidly connects the first coolant channel  962  in the cartridge frame  112  to a nozzle opening  966  associated with the nozzle  110 . Specifically, the nozzle  110  can be coupled to an outer nozzle component  111  (such as a nozzle jacket for a non-vented nozzle or a nozzle liner for a vented nozzle) and the opening  966  can be on the outer nozzle component  111  such that it can introduce the coolant flow from the distal coolant channel opening  962   b  to a nozzle coolant flow chamber  965  between an exterior surface the nozzle  110  and an interior surface of the outer nozzle component  111 . As the coolant flow  950  is conducted distally through the nozzle coolant flow chamber  965  via the nozzle opening  966 , it substantially cools the nozzle  110  and the outer nozzle component  111 . Upon reaching a distal tip of the nozzle  110 , the coolant flow  950  can swirl around at least a portion of a circumference of the nozzle  110  via a circumferential channel (not shown) disposed on the external surface of the nozzle  110 . The coolant flow  950  can return proximally on a different side of the nozzle  110  within the flow chamber  965  and toward another opening  967  on the outer nozzle component  111 . The second nozzle opening  967  is in turn fluidly connected to a second coolant channel  968  in the cartridge frame  112 . Specifically, the second coolant channel  968  interfaces with the second opening  967  of the outer nozzle component  111  at an opening  968   b  at the distal end  17  of the cartridge frame  112 . The second coolant channel  968  of the cartridge frame  112  is adapted to conduct the liquid coolant flow  950  away from the nozzle coolant flow chamber  965  and into a corresponding second coolant channel  970  of the torch insulator  118  in the torch head  102  via a a second liquid coolant channel opening  968   a  on the proximal end  15  of the cartridge frame  112  and a second liquid coolant channel opening  960   b  at the distal end  23  of the torch insulator  118  (also shown in  FIG.  4   ). As the coolant flow  950  travels proximally through the torch insulator  118  within the second coolant channel  970  of the torch head  102 , the coolant flow encounters an internal opening  972  of the second coolant channel  970  in the torch insulator  118 . That is, the second coolant channel  970  connects the internal opening  972  with the opening  960   b  on the distal end  23  of the torch insulator  118 . 
     As illustrated in  FIG.  13   b   , the internal opening  972  of the second coolant channel  970  can be fluidly connected to an internal opening  974  of a third coolant channel  976  of the torch insulator  118  via a distribution channel (not shown) extending circumferentially around the torch insulator  118 . The second coolant channel  970  and the third coolant channel  976  can be radially offset from each other at about 30 degrees to about 90 degrees (e.g., 70 degrees). The distribution channel thus connects the internal openings  972 ,  974  to deliver the coolant flow  950  from the second coolant channel  970  to the third coolant channel  976 . Within the third coolant channel  976 , the coolant  950  flows distally toward a third coolant channel opening  960   c  on the distal end  23  of the torch insulator  118  (also shown in  FIG.  4   ) to again enter the cartridge  104 . Specifically, upon exiting the third coolant channel  976  of the torch insulator  118  of the torch head  102  via the opening  960   c , the coolant flow  950  is adapted to enter the cartridge  104  via a corresponding third coolant channel opening  978   a  on the proximal end  15  of the cartridge frame  112  that is connected to a third coolant channel  978  of the cartridge frame  112  to continue the distal flow toward the shield  114  in the cartridge  104 . The coolant flow  950  exits the third coolant channel  978  via an opening  978   b  at the distal end  17  of the cartridge frame  112  to enter a circumferential shield coolant flow region  1222  defined between an outer side surface of the cartridge frame  112  and a corresponding inner surface of the shield  114 . The coolant flow  950  can travel circumferentially around the shield coolant flow region  1222 , thereby cooling the shield  114 . Following the circumferential shield coolant flow region  1222 , the coolant flow  950  can return to the cartridge frame  112  on a different side of the flow region  1222  by entering an opening  982   b  at the distal end  17  of the cartridge frame  112 . The opening  982   b , which is in fluid communication with the shield coolant flow region  1222 , is connected to a fourth coolant channel  982  of the cartridge frame  112 . The coolant flow  950  then travels proximally in the fourth coolant channel  982 , exits the fourth coolant channel  982  via an opening  982   a  at the proximal end  15  of the cartridge frame  112 , and flows into the torch head  102 . The coolant flow  950  enters the torch head  102  via a fourth coolant channel opening  960   d  at the distal end  23  of the torch insulator  118  (also shown in  FIG.  4   ). The opening  960   d  at the distal end  23  of the torch insulator  118  is fluidly connected to a fourth coolant channel  984  of the torch insulator  118  configured to deliver the coolant flow  950  from the cartridge  104  to an internal opening  986  in the torch insulator  118 , which is fluidly connected to the cathode block  606 . 
     As shown in  FIGS.  14   a  and  b   , the cathode block  606  comprises a second set of one or more liquid inlets  626  extending from an exterior surface to an interior surface of the cathode block  606 . In some embodiments, the cathode block  606  includes a second set of three liquid inlets  626   a - c  dispersed around an outer circumference of the cathode block  606 . In other embodiments, more or fewer inlets are defined. Shown with respect to  FIG.  13   b   , a connection channel  988  fluidly connects the internal opening  986  of the fourth coolant channel  984  of the torch insulator  118  to the second set of liquid inlets  626   a - c  to conduct the coolant  950  from the fourth coolant channel  984  into the cathode block  606 . In some embodiments, the connections between the second set of inlets  626   a - c  and the internal opening  986  are crisscrossed (e.g., for space saving purpose) to deliver the coolant from the fourth coolant channel  984  to the cathode block  606  in a swirling fashion. Once inside of the cathode block  606 , the coolant flow  950  continues on proximally to exit the torch insulator  118  via the cathode tube  604  and the cathode fitting  602  in that order. 
     In some embodiments of the torch insulator  118 , the first coolant channel  958  and the second coolant channel  970  can be radially offset from each other at about 30 degrees to 90 degrees (e.g., about 90 degrees). The third coolant channel  976  and the fourth coolant channel  984  can be radially offset from each other at about 30 degrees to 90 degrees (e.g., about 90 degrees). In some embodiments of the cartridge frame  112 , the first coolant channel  962  and the second coolant channel  968  can be radially offset from each other by the same degree as the offset between the first coolant channel  958  and the second coolant channel  970  of the torch insulator  118  (e.g., about 90 degrees). The third coolant channel  978  and the fourth coolant channel  982  can be radially offset from each other by the same degree as the offset between the third coolant channel  976  and the fourth coolant channel  984  of the torch insulator  118  (e.g., about 90 degrees). In some embodiments of the plasma arc torch  10 , the second coolant channels  970 ,  968  are radially offset from the third coolant channels  976 ,  978  by about 30 degrees to about 90 degrees (e.g., 70 degrees). 
     In general, the torch insulator  118  of the torch head  102 , in collaboration with the cartridge frame  112  of the cartridge  104 , is configured to control distribution of a coolant flow  950  in and out of the the torch head  102  and the cartridge  104  to various components of the cartridge tip, as described above with respect to  FIGS.  13     a  and  b . For example, the torch insulator  118  and the cartridge frame  112  can direct the coolant flow  950  in the following sequence: (i) from the cathode  600  to the coolant tube  116  and reverse in the main channel  132  of the torch insulator  118  and the main channel  1020  of the cartridge frame  112  to cool the electrode  108 , where each of the main channels  132 ,  1020  acts as both a supply and return channel; (ii) from the first coolant channel  958  of the torch insulator  118  (i.e. a supply channel), to the first coolant channel  962  of the cartridge  104  (i.e., a supply channel), to the second coolant channel  968  of the cartridge  104  (i.e., a return channel) and to the second coolant channel  970  of the torch insulator  118  (i.e., a return channel) to cool the nozzle  110 ; (iii) from the third coolant channel  976  of the torch insulator  118  (i.e., a supply channel), to the third coolant channel  978  of the cartridge  104  (i.e., a supply channel), to the four coolant channel  982  of the cartridge  104  (i.e., a return channel) and to the fourth coolant channel  984  of the torch insulator  118  (i.e., a return channel) to cool the shield  114 . In alternative embodiments, the coolant flow  950  comprises only one of the three sets of the supply and return channels to cool one cartridge tip component. In alternative embodiments, the coolant flow  950  comprises two of the three sets of the supply and return channels to cool two cartridge tip components. 
     Even though the coolant flow path  950  of  FIGS.  13   a  and  b    is illustrated in a sequence that cools the electrode  108 , followed by the nozzle  110 , and then the shield  114  of the cartridge tip, other cooling sequences are equally applicable. For example, a different sequence can include cooling of the shield  114 , followed by the nozzle  110  and then the electrode  108 . Yet another sequence can include cooling of the nozzle  110 , followed by the shield  114  and then the electrode  108 . In some embodiments, any order for cooling these three components of the cartridge tip is contemplated by the present invention. 
     In some embodiments, the shield gas flow path  868 , the plasma gas flow path  900  and the coolant flow path  950  are fluidly isolated from each other in both the torch head  102  and the cartridge  104  such that these fluids do not cross paths nor share the same channels. In some embodiments, the shield gas flow path  868 , the plasma gas flow path  900  and the coolant flow path  950  are predefined based on locking of the torch head  102  with the cartridge  104  in a predetermined orientation. This locking feature will be described below in detail. In some embodiments of the torch insulator  118 , one or more of the coolant channels  968 ,  970 ,  976 ,  984 , the plasma gas channel  206  and the shield gas channel  850  are non-concentric with respect to the central longitudinal axis A. One or more of the pilot arc connection cavity  148 , the communication device cavity  144  and the plasma gas valve cavity  202  are non-concentric with respect to the central longitudinal axis A. In some embodiments of the torch insulator  118  (shown in  FIG.  3   ), one or more of the opening  202   a  for receiving the plasma gas valve  204 , the plasma gas openings  200   a ,  200   b , the cavity opening  148   a  for receiving the pilot arc connection  123 , the liquid coolant opening  128   a , the cavity opening  146   a  for receiving the ohmic connection  131 , the shield gas opening  126   a , the cavity opening  144   a  for receiving the communication device  122 , and the main channel opening  132   a  are disposed on an end face of the proximal end  21  of the torch insulator  118 , where the end face can be substantially planar. These openings, with the exception of the main channel opening  132   a , can be disposed non-concentrically on the proximal end face with respect to the central longitudinal axis A. In some embodiments of the torch insulator  118  (shown in  FIG.  4   ), one or more of the plasma gas opening  200   c , the liquid coolant openings  960   a - d  and the shield gas opening  126   b , the main channel opening  132   b  are disposed on an end face of the distal end  23  of the torch insulator  118 , where the end face can be substantially planar. These openings, with the exception of the main channel opening  132   a , can be disposed non-concentrically on the distal end face with respect to the central longitudinal axis A. In the context of the present invention, “non-concentric” means that the applicable channel, cavity or opening is offset relative to the longitudinal axis A. In some embodiments, each non-concentric channel, cavity or opening is oriented non-symmetrically with respect to the longitudinal axis A. 
     In some embodiments, the main channel opening  132   a  at the proximal end  21  of the torch insulator  118 , the main channel  132 , and the main channel opening  132   b  at the distal end  23  of the torch insulator  118  are centrally located and disposed concentrically with respect to the central longitudinal axis A. As described above, the main channel  132  is configured to provide at least one of (i) a pilot arc or transferred arc current or (ii) at least a portion of the liquid coolant flow  950  from the torch head to the cartridge. 
     Interface Between the Torch Head and the Cartridge 
     With reference to  FIG.  4   , the distal end  23  of the torch insulator  118  can further include a clocking feature  220  (e.g. a pin) configured to secure the torch insulator  118  with the cartridge frame  112  in a predetermined radial orientation upon engagement between the torch head  102  and cartridge  104 .  FIG.  15    is a view of the proximal end  15  of the cartridge frame  112 , according to an illustrative embodiment of the present invention. The proximal end  15  of the cartridge frame  112  can include a clocking feature (e.g., a pin cavity)  1002  that can interact with the corresponding clocking feature  220  on the distal end  23  of the torch insulator  118  to form at least a section of the interface  106  (shown in  FIG.  2   ) between the torch head  102  and the cartridge  104 . Such an interface  106  allows alignment of various electrical, liquid coolant, and gas channels between the torch head  102  and the cartridge  104 , thereby maintaining the predefined electrical, liquid coolant and gas flow paths described above with reference to  FIGS.  7 ,  8  and  11     a - 13   b . In some embodiments, the end face of the distal end  23  of the torch insulator  118  is substantially planar. The end face of the proximal end  15  of the cartridge frame  112  can also be substantially planar such that the interface  106  between them is substantially planar. 
     With respect to the continuity of coolant flow between the torch head  102  and the cartridge  104 , upon clocking of the torch insulator  118  with the cartridge frame  112  in the predetermined radial orientation, the first liquid coolant channel opening  960   a  on the distal end  23  of the torch insulator  118  (shown in  FIGS.  4  and  13     a ) is aligned with the first coolant channel opening  962   a  at the proximal end  15  of the cartridge frame  112  (shown in  FIGS.  13   a    and  15 ) to fluidly connect the first liquid coolant channel  958  of the torch insulator  118  with the first liquid coolant channel  962  of the cartridge frame  112  (shown in  FIG.  13   a   ). In the same predetermined radial orientation, the second liquid coolant channel opening  960   b  of the torch insulator  118  (shown in  FIGS.  4  and  13     a ) is aligned with the second coolant channel opening  968   a  at the proximal end  15  of the cartridge frame  112  (shown in  FIGS.  13   a    and  15 ) to fluidly connect the second coolant channel  970  of the torch insulator  118  with the second coolant channel  968  of the cartridge frame  112  (shown in  FIG.  13   a   ). In the same predetermined radial orientation, the third liquid coolant channel opening  960   c  of the torch insulator  118  (shown in  FIGS.  4  and  13     b ) is aligned with the third coolant channel opening  978   a  at the proximal end  15  of the cartridge frame  112  (shown in  FIGS.  13   b    and  15 ) to fluidly connect the third coolant channel  976  of the coolant insulator  118  with the third coolant channel  978  of the cartridge frame  112  (shown in  FIG.  13   b   ). In the same predetermined radial orientation, the fourth liquid coolant channel opening  960   d  of the torch insulator  118  (shown in  FIGS.  4  and  13     b ) is aligned with the fourth coolant channel opening  982   a  of the cartridge frame  112  (shown in  FIGS.  13   b    and  15 ) to fluidly connect the fourth coolant channel  984  of the coolant insulator  118  with the fourth coolant channel  982  of the cartridge frame  112  (shown in  FIG.  13   b   ). 
     With respect to the continuity of gas flows between the torch head  102  and the cartridge  104 , in the predetermined radial orientation, the shield gas opening  126   b  on the distal end  23  of the torch insulator  118  (shown in  FIGS.  4  and  11     b ) is aligned with the shield gas opening  864   a  at the proximal end  15  of the cartridge frame  112  (shown in  FIGS.  11   b    and  15 ) to fluidly connect the third shield gas channel segment  850   c  of the torch insulator  118  with the shield gas channel  864  of the cartridge frame  112  (shown in  FIG.  11   b   ). In the same predetermined radial orientation, the plasma gas opening  200   c  on the distal end  23  of the torch insulator  118  (shown in  FIGS.  4  and  12     c ) is aligned with the plasma gas proximal opening  912   a  at the proximal end  15  of the cartridge frame  112  (shown in  FIGS.  12   c    and  15 ) to fluidly connect the plasma gas channel  206  of the torch insulator  118  with the plasma gas channel  912  of the cartridge frame  118  (shown in  FIG.  12   c   ). 
     With respect to data communication between the torch head  102  and the cartridge  104 , in the predetermined radial orientation enabled by the clocking features  220 ,  1002 , the reader device  122  is rotationally aligned with the signal device  160 . For example, the antenna coil  814  embedded in the torch insulator  118  can map to an area  230  at the distal end  23  of the torch insulator  118  (shown in  FIG.  4   ) with a center  232  that substantially aligns with a center  1018  of an area  1016  at the proximal end  15  of the cartridge frame  112  (shown in  FIG.  15   ), which maps to the signal device  160  embedded in the cartridge  104 . Such rotational alignment between the centers  232 ,  1018  reduces communication interference between the reader device  122  and the signal device  160 . 
       FIG.  31    is a portion of the plasma arc torch  10  of  FIG.  2    illustrating exemplary locations of the communication device  122  and the signal device  160  once the torch head  102  and the cartridge  104  are in the predetermined radial orientation relative to each other, according to an illustrative embodiment of the present invention. In some embodiments, in the aligned position, a distance  816  between the longitudinal and radial center of the antenna coil  814  and the longitudinal and radial center of the signal device  160  is less than a distance between the longitudinal and radial center of the signal device  160  and any adjacent metallic material disposed in the torch head  102  or the cartridge  104 . In some embodiments, the RFID field generated by the antenna coil  814  is toroidal in shape around the perimeter of the disc-shaped RFID tag  160 . A cross section of the toroidal field at any point is a circle. To prevent interference, the distance between the RFID tag  160  and the reader device  122  along an x axis (measured at the center point of the circular cross-section of the field) is smaller or closer than the distance between the RFID tag  160  to any adjacent metal along the Y axis. Thus, as the RFID field moves in a circular path around the toroidal shape, the field is configured such that it does not encounter any metal before it encounters the RFID tag  160 . In some embodiments, in the aligned position, the signal device  160  and the reader device  122  are oriented such that a straight-line axis extends through a centerline of the signal device  160  and a centerline of the reader device  122 . In some embodiments, the antenna coil  814  of the reader device  122  is oriented substantially parallel to the signal device  160 . In some embodiments, the antenna coil  814  and the RFID tag  160  communicate at a frequency of about 13.5 MHz. 
     With respect to the continuity of electrical connections between the torch head  102  and the cartridge  104  as shown in  FIG.  2   , upon interfacing the torch insulator  118  with the cartridge frame  112 , the distal opening  132   b  of the main channel  132  of the torch insulator  118  is adapted to align with the opening  1020   a  at the proximal end  15  of the cartridge frame  112  to connect to the main channel  1020  of the cartridge frame  112 . Thus, the distal end  742  of the coolant tube  116  is adapted to be inserted into the main channel  1020  of the cartridge frame  112  via the opening  1020   a . An opening  1020   b  of the main channel  1020  at the distal end  17  of the cartridge frame  112  is connected to the cavity  954  of the electrode  108  such that the coolant tube  116  extends through the opening  1020   b  and into the cavity  954 . As explained above, pilot arc current and/or transferred arc current from the power supply can be routed from the cathode  130  of the torch head  102  to the coolant tube  116 , both of which are affixed to the torch insulator  118 , and to the electrode  108  of the cartridge  104  via the inner surface of the electrode cavity  954 . The current-carrying coolant tube  116  thus energizes the interior surface of the electrode  108 . In some embodiments, one or more Louvertac bands  702 ,  704  on either or both ends  740 ,  742  of the coolant tube  116  are used to facilitate conduction of electricity from the power supply to the inner surface of the electrode  108 . The use of at least the Louvertac band  704  at the distal end  742  of the coolant tube  116  radially aligns/centers the electrode  108  relative to the coolant tube  116 , but does not affix the electrode  108  to any particular radial orientation. For example, during assembly, an operator can apply an axial force to push the electrode  108  proximally against the coolant tube  116  until the Louvertac band  704  at the distal end  742  of the coolant tube  116  is fully seated within the cavity  954  of the electrode  108  and is covered by most of the cavity  954 . The Louvertac band  704  of the coolant tube  116  thus allows the electrode  108  to be axially pushed on or pulled off during engagement or disengagement, respectively, without the use of threading (or other clocking movement), thereby enabling the use of a tool-free and/or threadless electrode  108 . 
     The simple push-on/pull-off feature is also compatible with the engagement between the clocking feature  220  of the torch insulator  118  and the clocking feature  1002  of the cartridge frame  112  to form the interface  106 . That is, the coupling between the torch head  102  and the cartridge  104  can be governed by the locking features  220 ,  1002  without the need to account for any threading or other clocking requirement between the electrode  108  and the coolant tube  116 . In general, allowing the coolant tube  116  and the Louvertac band  704  to carry the pilot arc/transferred arc current to the cartridge  104  separates (i) the physical interface between the torch insulator  118  and the cartridge frame  112  from (ii) the electrical connection between the cathode  130 /coolant tube  116  and the electrode  108 . This separation is adapted to maximize design space and simplify torch assembly. In addition, the relatively straight axial installation and removal of the coolant tube  116  (and thus the torch head  102 ) from the electrode  108  (and thus the cartridge  104 ) promotes quicker consumable replacement and installation. Further, due to the placement of the Louvertac band  704  in relation to the coolant tube  116  (e.g., on an exterior surface of the coolant tube  116 ), the Louvertac band  704  can be easily inspected and readily serviced. In alternative embodiments, instead of using the Louvertac band  704 , other current-carrying and/or retaining features can be used, such as thread attachments, interference fits, etc. 
     In some embodiments, because the cutting current is carried from the power supply to the electrode  108  by the coolant tube  116 , the electrode  108  does not need to be in directly electrical or physical contact with the torch head  102  for current transfer purposes. In some embodiments, the electrode  108  is electrically isolated from the torch head  102  by the cathode block electrode tube  252 , which connects the electrode  108  to the cathode  130  and the coolant tube  116 . The cathode block electrode tube  252  can be made of a non-conductive material such as plastic. In another aspect, the electrode  108  is shorter than an electrode that is used to receive a current directly from the cathode. In this case, because the electrode  108  no longer physically or electrically contacts the cathode  130 , the electrode  108  can be shorter, such as more than 25% shorter, than a direct-contact electrode. 
     Upon axial insertion of the coolant tube  116  into the cavity  954  of the electrode  108  and radial clocking of the torch insulator  118  with the cartridge frame  112  (e.g., via insertion of the clocking pin  220  of the torch insulator  118  into the clocking pin cavity/receptacle  1002  of the cartridge frame  112 ), the cartridge  104  can be retained against the torch head  102  using the retaining cap  120  (shown in  FIG.  1   ). Other engagement methods between the torch head  102  and the cartridge  104  are possible, including threading, snap fit, interference fit, etc.  FIG.  16    is a sectional view of an exemplary design of the retaining cap  120  of  FIG.  1    used to secure the cartridge  104  and the torch head  102  to each other, according to an illustrative embodiment of the present invention. The retaining cap  120  includes a body  764 , a proximal end  760  and a distal end  762  extending along the longitudinal axis A. The proximal end  760  of the retaining cap body  764  includes an engagement feature  766  (e.g., groove, thread or step) circumferentially disposed on an internal surface to capture the torch head  102  against the retaining cap body  764 . Similarly, the distal end  762  of the retaining cap body  764  includes an engagement feature  768  (e.g., groove, thread or step) disposed on an internal surface to capture the cartridge  104  against the retaining cap body  764 . Thus, upon clocking of the cartridge  104  with the torch head  102 , the retaining cap  120  can securely and circumferentially surround an external surface of the torch head  102  at the distal end  22  of the torch head  102  and an external surface of the cartridge  104  at the proximal end  14  of the cartridge  104 . In some embodiments, the torch head  102  and/or the cartridge do not rotate with respect to the retaining cap  120 . In this case, an operator can slide the retaining cap  120  over the cartridge  104  and/or the torch head  102  to lock the parts without using any rotational movement. In some embodiments, the retaining cap  120  is provided as a part of the torch head  102 . In some embodiments, the retaining cap  120  is provided as a part of the cartridge  104 . In some embodiments, the retaining cap  120  is provided as a distinct component separate from the cartridge  104  or torch head  102 . 
     Cartridge 
       FIG.  17    is a sectional view of the cartridge  104  of  FIG.  1   , where the cartridge  104  is a non-vented cartridge, according to an illustrative embodiment of the present invention. As described above, the cartridge  104  can generally include the cartridge frame  112  coupled to the cartridge tip that includes the electrode  108 , the nozzle  110 , which is a non-vented nozzle attached to a nozzle jacket  111 , and the shield  114 . The cartridge frame  112  is adapted to form an interface between the cartridge tip and the torch head  102 , thereby connecting the cartridge tip to the torch head  102 . The various components of the cartridge  104 , including the cartridge frame  112 , the electrode  108 , the nozzle  110 , the nozzle jacket  111  and the shield  114 , can be concentrically disposed about the longitudinal axis A of the plasma arc torch  10 . In some embodiments, the cartridge  104  includes multiple retaining features that allow the components of the cartridge tip to align with and engage to one or more channels in the cartridge frame  112  such that these channels can conduct liquid and gas from the torch head  102 , through the cartridge frame  112 , and to the desired components in the cartridge tip. In some embodiments, the proximal end  14  of the cartridge  104 , including the proximal end  15  of the cartridge frame  112 , is substantially planar. 
     In general, the various components of the cartridge tip can be secured, either directly or indirectly, to the cartridge frame  112  while achieving axial alignment and radial alignment (i.e., centering) with respect to the cartridge frame  112 . The electrode  108  can be secured to the cartridge frame  112  with at least a portion of the electrode  108  disposed in the central channel  1020  of the cartridge frame  112 . In some embodiments, the electrode  108  is secured to the cartridge frame  112  via the swirl ring  150  that surrounds at least a portion of the main channel  1020 . Specifically, an outer diameter of the electrode  108  can be secured to an inner diameter of the swirl ring  150  such that at least a proximal portion of the electrode  108  is inserted into a distal portion of the swirl ring  150 . If the swirl ring  150  is electrically conductive, the swirl ring  150  can be secured to the electrode  108  via the electrode insulator  754 . As shown, the electrode  108  includes an outer retaining feature  1066  (e.g., one or more steps of varying diameter of the electrode  108 ) on an exterior surface configured to matingly engage an inner retaining feature  1068  (e.g., one or more complementary steps or protrusions) on an interior surface of the electrode insulator  754  to prevent axial movement of the electrode  108  and the electrode insulator  754  relative to each other. The mating between the retaining features  1066 ,  1068  can be one of snap fit, press fit or interference fit. The resulting interface  1067  between the electrode  108  and the electrode insulator  754  also radially aligns/centers the two components. In turn, the electrode insulator  754  includes an outer retaining feature  1056  (e.g., a step of varying diameter of the electrode insulator  754 ) on an exterior surface to matingly engage an inner retaining feature  1054  (e.g., a complementary step or protrusion) on an interior surface of the swirl ring  150  to prevent axial movement of the electrode insulator  754  and the swirl ring  150  relative to each other. The mating between the retaining feature  1054 ,  1056  can be one of snap fit, press fit or interference fit. The resulting interface  1055  between the electrode insulator  754  and the swirl ring  150  also radially aligns/centers the two components. If the swirl ring  150  is substantially non-conductive, the swirl ring  150  can be directly secured to the electrode  108  without the use of the electrode insulator  754 . In some embodiments, an outer diameter of the swirl ring  150  is matingly engaged to an inner diameter of the cartridge frame  112  to couple the electrode  108  to the cartridge frame  112 . For example, the swirl ring  150  can be secured to the cartridge frame  112  by matingly engaging an outer retaining feature  1052  (e.g., a step of varying diameter of the swirl ring  150 ) on an exterior surface with an inner retaining feature  1058  (e.g., a complementary step or protrusion) on an interior surface of the cartridge frame  112  to prevent axial movement of the swirl ring  150  and the cartridge frame  112  relative to each other. The mating between the retaining features  1052 ,  1058  can be one of snap fit, press fit or interference fit. The resulting interface  1053  between the the swirl ring  150  and the cartridge frame  112  also radially aligns/centers the two components. 
     The nozzle  110  and the nozzle jacket  111  can be engaged between the swirl ring  150  and the cartridge frame  112 . In some embodiments, an outer diameter of the swirl ring  150  is engaged to an inner diameter of the nozzle  110 . The swirl ring  150  can be secured to the nozzle  110  by matingly engaging an outer retaining feature  1050  (e.g., one or more steps of varying diameter of the swirl ring  150 ) on an exterior surface with an inner retaining feature  1060  (e.g., a complementary step or protrusion) on an interior surface of the nozzle  110  to prevent axial movement of the swirl ring  150  and the nozzle  110  relative to each other. The mating between the retaining features  1050 ,  1060  can be one of snap fit, press fit or interference fit. The resulting interface  1051  between the the swirl ring  150  and the nozzle  110  also radially aligns/centers the two components. In some embodiments, an outer diameter of the nozzle  110  is secured to an inner diameter of the cartridge frame  112 . The nozzle  110  can be secured to the cartridge frame  112  by matingly engaging at least one outer retaining feature  1070  (e.g., one or more steps of varying diameter of the nozzle  110 ) on an exterior surface to at least one inner retaining feature  1072  (one or more complementary steps or protrusions) on an interior surface of the cartridge frame  112  to prevent axial movement of the nozzle  110  and the cartridge frame  112  relative to each other. The mating between the retaining features  1070 ,  1072  can be one of snap fit, press fit or interference fit. The resulting interface  1071  between the nozzle  110  and the cartridge frame  112  also radially aligns/centers the two components. 
     The shield  114  can be coupled to an outer surface the cartridge frame  112 . For example, an outer diameter of the cartridge frame  112  is secured to an inner diameter of the shield  114  by matingly engaging an outer retaining feature  1062  (e.g., a step of varying diameter of the cartridge frame  112 ) on an exterior surface of the cartridge frame  112  with an inner retaining feature  1064  (e.g., a complementary step or protrusion) on an interior surface of the shield  114  to prevent axial movement of the cartridge frame  112  and the shield  114  relative to each other. The mating between the retaining features  1062 ,  1064  can be one of snap fit, press fit or interference fit. The resulting interface  1063  between the cartridge frame  112  and the shield  114  also radially aligns/centers the two components. In addition, the cartridge frame  112  can include an indentation  1065  on an exterior surface configured to receive a distal portion of the shield  114  via crimping, thereby further securing and aligning the shield  114  to the cartridge frame  112 . 
     In some embodiments, the retaining features  1050 - 1072  described above can mate with their corresponding retaining features through one of snap fit, press fit, interference fit, crimping, frictional fitting, gluing, cementing or welding. In some embodiments, the retaining features  1050 - 1072  include one or more sealing o-rings or gaskets, made of hardening epoxy or rubber for example. In some embodiments, the retaining features  1050 - 1072  allow the nozzle  110 , the jacket  111 , the shield  114  and/or the electrode  108  of the cartridge tip to align with and engage to one or more channels in the cartridge frame  112  such that these channels can conduct liquid and/or gas from the torch head  102 , through the cartridge frame  112 , and to the desired components in the cartridge tip. The liquid and gas connections between the cartridge frame  112  and the cartridge tip is described below in detail. 
       FIG.  18    is an exemplary design of the cartridge frame  112  of the cartridge  104  of  FIG.  17   , according to an illustrative embodiment of the present invention. The cartridge frame  112  includes a generally cylindrical insulator body  1100  disposed between the torch head  102  and the cartridge tip. More specifically, the insulator body  1100  includes an inner region  1106 , an outer side surface  1108 , an inner side surface  1110  surrounding and forming the main channel  1020 , the proximal end  15  having an end face  1102 , and the distal end  17  having an end face  1104 . The proximal end  15  of the cartridge frame  112 , which is described above with respect to  FIG.  15   , comprises the central opening  1020   a  for receiving an electrical current and/or the coolant flow  950  from a coolant tube  116  of the torch head  102 , a plasma gas opening  912   a  for receiving the plasma gas flow  900   c  from the torch insulator  118 , a shield gas opening  864   a  for receiving the shield gas flow  868  from the torch insulator  118  and four liquid coolant openings  968   a ,  978   a ,  962   a  and  982   a  for conducting the liquid coolant flow  950  in and out of the cartridge  104 . In some embodiments, these openings are disposed on the end face  1102  of the proximal end  15  of the insulator body  1100 . In some embodiments, the end face  1102  is substantially coplanar with the proximal end  14  of the cartridge  104 . In general, these openings are configured to be in electrical and/or fluid communication with their corresponding openings on the distal end  23  of the torch insulator  118  once the torch head  102  is aligned with and connected to the cartridge  104  in a predetermined orientation via the locking feature  1002  of the cartridge frame  112  and the corresponding locking feature  220  of the torch insulator  118 . 
     Electrical Connections in the Cartridge 
     In some embodiments, the electrode  108  is aligned with and connected to the main channel  1020  disposed in the insulator body  1100  of the cartridge frame  112 . The channel  1020  can be centrally disposed in the insulator body  110  with the central longitudinal axis A extending therethrough to connect the opening  1020   a  on the end face  1102  of the proximal end  15  of the cartridge frame  112  to the opening  1020   b  on the end face  1104  of the distal end  17  of the cartridge frame  112 . The distal opening  1020   b  is in turn connected to and aligned with the cavity  954  of the electrode  108  (shown in  FIG.  2   ). Such an electrode interface allows the coolant tube  116  to be inserted into the main channel  1020  to pass an electrical current (i.e., a pilot arc or transferred arc current) from the cathode  130  of the torch head  102  to the inner surface of the electrode  108 , as described above. In such a case, the electrode  108  can be electrically isolated from the cathode  130 , as described above. In alternative embodiments, the electrode  108  is electrically connected to the cathode  130  to receive a current directly from the cathode  130 . In some embodiments, the same electrode interface (i.e., between the electrode  108  and the torch head  102  via the main channel  1020  of the cartridge frame  112 ) can allow the torch head  102  to introduce a liquid coolant to the electrode  118  from inside of the coolant tube  116 . This liquid coolant conduction feature of the main channel  1020  of the cartridge frame  112  is explained in detail below. 
       FIG.  19    is an exemplary design of the electrode  108  of the cartridge  104  of  FIG.  17   , according to an illustrative embodiment of the present invention. An emissive insert  1200  can be disposed in the distal end  1202  of the electrode  108  so that an emission surface is exposed. The insert  1200  can be made of hafnium or other materials that possess suitable physical characteristics, including corrosion resistance and a high thermionic emissivity. Forging, impact extrusion, or cold forming can be used to initially form the electrode  108  prior to finish machining the component. The proximal end  1204  of the electrode  108  can be disposed in and aligned with the main channel  1020  of the cartridge frame  112  via the distal opening  1020   b  of the cartridge frame  112 . The electrode  108  can be connected to the cartridge frame  112  using at least the swirl ring  150  and the electrode insulator  754 . In some embodiments, the electrode  108  does not include any threads for connection to the electrode insulator  754  or the swirl ring  150 . As explained above, such a connection can be made through one of press fit, interference fit, crimping or snap fit. In some embodiments, the electrode  108  is shorter than an electrode that is used to receive an electrical current directly from the cathode  130  (i.e., without using the coolant tube  116 ). In these cases, because the electrode  108  does not need to physically or electrically contact the cathode  130 , the electrode  108  can be shorter, such as more than 25% shorter, than a direct-contact electrode. In some embodiments, the electrode  108  includes an o-ring groove  1205  at the proximal end  1204 , where the o-ring groove  1205  is configured to house an o-ring that can be used to seal a plasma chamber/plenum  109  cooperatively defined by the electrode  108  and the nozzle  110 . Such sealing prevents the plasma gas flow  900   c  from traveling between the electrode  108  and the electrode insulator  754  (shown in  FIG.  17   ). 
     Shield Gas Connections in the Cartridge 
     In some embodiments, the shield gas passage  872  formed between the shield  114  and the nozzle jacket  111  is aligned with the shield gas channel  864  disposed in the insulator body  1100  of the cartridge frame  112  (shown in  FIGS.  11   a  and  b   ). The shield gas channel  864  (shown in  FIGS.  11   a  and  b   ) can extend substantially parallel to the longitudinal axis A in the inner region  1106  of the insulator body  1100 , but offset from the central longitudinal axis A (i.e., non-concentric with respect to the longitudinal axis A). The shield gas channel  864  connects the opening  864   a  on the end face  1102  at the proximal end  15  of the cartridge frame  112  to the opening  864   b  at the distal end  17  of the cartridge frame  112 . In some embodiments, the opening  864   b  is disposed on the end face  1104  of the distal end  17  of the cartridge frame  112 . In alternative embodiments, the opening  864   b  of the shield gas channel  864 , which is distal to the opening  864   a  along the longitudinal axis A, is disposed on the outer side surface  1108  or the inner side surface  1110  of the cartridge frame body  1100  (i.e., the channel  864  does not extend through the entire length of the body  1100  in the longitudinal direction). The opening  864   b  is in turn fluidly connected to the shield gas passage  872 , which allows the shield gas flow  868  to pass from the torch head  102 , through the cartridge frame  112  of the cartridge  104 , and into the shield gas passage  872  (shown in  FIGS.  11   a  and  b   ). In some embodiments, the shield gas channel  864  can be configured to provide a metering function to the shield gas flow  868  therein. For example, the diameter of the shield gas channel  864  can vary over the length of the channel to provide the metering function. The diameter of the shield gas channel  864  at the distal end  17  of the cartridge frame  112  can be about half of the diameter of the shield gas channel  864  at the proximal end  15  of the cartridge frame  112  to reduce the flow rate of the shield gas flow  868 . 
     In some embodiments, the cartridge frame  112  includes one more components in the path of the shield gas channel  864  to adjust one or more properties of the shield gas flow  868  therein. For example, the cartridge frame  112  can include an adjustment component, such as a two-piece component comprising a baffle  1112  and a shield swirl ring  1114 . As shown in  FIG.  17   , the baffle  1112  and the shield swirl ring  1114  are circumferentially disposed within the insulator body  1100  of the cartridge frame  112  at its distal end  17  and the two components are in the path of the shield gas channel opening  864   b  such that they adjust certain flow parameters and introduce a swirling motion to the shield gas flow  868  as it exits the cartridge frame  112  and into the shield gas passage  872 . The use of these two separate components  1112 ,  1114  provide manufacturing and assembly advantages as an operator can use different combinations of baffles and shield swirl rings to develop different types of shield gas flows. 
       FIG.  20    is a cross-sectional view of the baffle  1112  and the shield swirl ring  1114  attached to the cartridge frame  112  of the cartridge  104  of  FIG.  17   , according to an illustrative embodiment of the present invention. In some embodiments, at least one of the baffle  1112  or the shield swirl ring  1114  is made of a non-conductive material, such as Torlon™. In some embodiments, at least one of the baffle  1112  or the shield swirl ring  1114  is made of a conductive material. The baffle  1112  and the shield swirl ring  1114  can be individually manufactured through molding, stamping or die casting. 
     As shown, the baffle  1112  is situated proximal to the shield swirl ring  1114  such that when the shield gas flow  868  travels distally, it is first regulated by the baffle  1112  and then by the shield swirl ring  1114 . In other embodiments, the position of the baffle  1112  and the shield swirl ring  1114  are reversed. The baffle  1112  can be circumferentially disposed within the insulator body  1100  of the cartridge frame  112 , such as within a cavity  1116  at the distal end  17  of the insulator body  1100 . The baffle  1112  can be secured to the cavity  1116  by one of interference fit or press fit. The baffle  1112  includes a longitudinal portion  1118  and and a radial portion  1120  that is connected to the longitudinal portion  1118  at an angle such that the radial portion  1120  covers a portion of the width  1122  of the cavity  1116 , but leaves a radial clearance  1124  between an outer diameter of the radial portion  1120  and an inner surface of the cavity  1116 . The shield gas flow  868  within the shield gas channel  864  is adapted to be dispersed by the baffle  1112  to flow evenly around its outer diameter through the radial clearance  1124  and into the swirl ring  1114 . The radial clearance  1124  is shaped and dimensioned to adjust at least one parameter of the shield gas flow  868 . For example, the radial clearance  1124  can adjust a flow rate and/or fluid pressure of the shield gas flow  868 . In some embodiments, increasing the size of the radial clearance  1124  increases the flow rate of the shield gas flow  868 , in which case the plasma arc torch system can adjust accordingly to maintain a constant pressure. In some embodiments, increasing the size of the radial clearance  1124  decreases the gas pressure, in which case the plasma arc torch system can adjust accordingly to maintain a constant flow rate. 
     The shield swirl ring  1114  can be inserted into at least a portion of the cavity  1116  by at least one of interference fit or press fit such that it is distal in relation to the baffle  1112 .  FIG.  21    is a cross-sectional view of the shield swirl ring  1114 , according to an illustrative embodiment of the present invention. The shield swirl ring  1114  can define a first set of ports  1126  around a first circumference of the swirl ring  1114  and a second set of ports  1128  around a second circumference of the swirl ring  1114 , where each port connects an interior surface of the cartridge frame  112  to an exterior surface of the cartridge frame  112 . The first set of ports  1126  are offset from their respective ones of the second set of ports  1128 . Such an offset imparts a swirling motion to the shield gas flow  868  therethrough. Therefore, the combination of the baffle  1112  and the shield swirl ring  1114  can adjust parameters of the shield gas flow  868  as it travels distally through the shield gas channel  864  to the shield gas passage  872 . Generally, the shield gas flow  868  in the plasma arc torch  10  is configurable by varying the size of the clearance  1124  of the baffle and/or the sizes of the first and second sets of ports  1126 ,  1128  in the shield swirl ring  1114 . 
     Plasma Gas Connections in the Cartridge 
     In some embodiments, the plasma gas passage  918  formed between the electrode  108  and the nozzle  110  is aligned with the plasma gas channel  912  disposed in the insulator body  1100  of the cartridge frame  112  (shown in  FIGS.  12   a - c   ). The plasma gas channel  912  (shown in  FIGS.  12   a - c   ) can extend substantially parallel to the longitudinal axis A in the inner region  1106  of the insulator body  1100 , but offset from the longitudinal axis A (i.e., non-concentric with respect to the longitudinal axis A). The plasma gas channel  912  connects the opening  912   a  on the proximal surface  1102  at the proximal end  15  of the cartridge frame  112  to the opening  912   b . In some embodiments, the opening  912   b  of the plasma gas channel  912 , which is distal to the opening  912   a  along the longitudinal axis A, is disposed on the inner side surface  1110  of the cartridge frame body  1100  and in fluid communication with the central channel  1020 . Thus, in this configuration, the plasma gas channel  912  does not extend over the entire length of the cartridge frame body  1100  in the longitudinal direction. 
       FIG.  22    is a perspective view of the cartridge frame  112  illustrating various channel openings, including the opening  912   b  of the plasma gas channel  912 , according to an illustrative embodiment of the present invention. As shown, the opening  912   b  is on the inner side surface  1110  in a central region of the cartridge frame  112 , and the opening  912   b  is fluidly connected to the central channel  1020 . In alternative embodiments, the plasma gas channel  912  extends over the entire length of the cartridge frame  112  with the opening  912   b  located on the distal end face  1104  of the cartridge frame insulator body  1100 . The opening  912   b  is fluidly connected to the plasma gas passage  918 . Such a connection allows the plasma gas flow  900   c  to pass from the torch head  102 , through the cartridge frame  112 , and into the plasma gas passage  918 , which merges into the central main channel  1020 , before the plasma gas flow  900   c  exits the torch  10  via the central nozzle exit orifice  916  and the central shield exit orifice  870  (shown in  FIGS.  12   a - c   ). 
     In some embodiments, the cartridge frame  112  includes one more components in the path of the plasma gas channel  912  configured to adjust one or more properties of the plasma gas flow  900   c  therein. For example, the cartridge frame  112  can include the swirl ring  150  circumferentially situated between the electrode insulator  754  and the nozzle  110  around the main channel  1020 . The swirl ring  150  can be aligned with the distal plasma gas channel opening  912   b  such that the swirl ring  150  can introduce a swirling motion to the plasma gas flow  900   c  as it exits the plasma gas channel  912  via the opening  912   b  on the inner side surface  1110  of the cartridge frame  112  and into the plasma gas passage  918 . 
       FIG.  23    is an exemplary design of the swirl ring  150  of the cartridge  104  of  FIG.  17   , according to an illustrative embodiment of the present invention. As shown, the swirl ring  150  can be defined by a substantially hollow, elongated body  1170  having a proximal end  1174  and a distal end  1172  along the central longitudinal axis A of the plasma arc torch  10 . In some embodiments, the hollow body  1170  of the swirl ring  102  at the distal end  1172  is dimensioned to receive a least a portion of the electrode  104  either directly or indirectly via the electrode insulator  754 . In some embodiments, the swirl ring  150  includes a set of radially spaced gas flow openings  1176  disposed about the distal end  1172  of the elongated body  1170 , such as around a circumference of its distal end  1172 . Each gas flow opening  1176  can extend from an interior surface to an exterior surface of the elongated body  1170  and is oriented to impart a tangential velocity component to the plasma gas flow  900   c  traveling in the gas passage  918  between the electrode  108  and the nozzle  110 , thereby causing the gas flow  900   c  to swirl. This swirl creates a vortex that constricts the plasma arc and stabilizes the position of the arc on the insert  1200  of the electrode  108 . 
     Coolant Connections in the Cartridge 
     In some embodiments, as described above, a component of the cartridge tip (e.g., the electrode  108 , the nozzle  110  or the shield  114 ) can be aligned with at least one cooling channel (e.g., channel  1002 ,  962  or  978 ) and at least one coolant return channel (channel  1002 ,  968  or  982 ) in the insulator body  1100  of the cartridge frame  112  to receive a liquid coolant flow from the torch head  102  and return at least a portion of the fluid flow to the torch head  102 , respectively. Each of the cooling channels and the return channels, with the exception of the main channel  1002 , can be non-concentric with respect to the central longitudinal axis A and asymmetric about the longitudinal axis A. In some embodiments, with the exception of the main channel  1002 , none of the cooling and returning channels are overlapping. That is, with the exception of the main channel  1002 , each of the cooling and returning channels is either a liquid inlet channel or a liquid outlet channel. 
     In some embodiments, the central channel  1020  extends through the insulator body  1100  of the cartridge frame  112  to connect its opening  1020   a  on the end face  1102  at the proximal end  15  of the cartridge frame  112  to its opening  1020   b  at the distal end  17  of the cartridge frame  112 . The proximal opening  1020   a  is aligned with and connected to the main channel opening  132   b  of the torch insulator  118 . The distal opening  1020   b  is aligned with and connected to the cavity  954  of the electrode  108 , which allows the coolant flow  950  to pass from the torch head  102 , through the cartridge frame  112  while inside of the coolant tube  116 , and into the cavity  954  of the electrode  108  (shown in  FIGS.  13   a  and  b   ). This connection also allows the coolant flow  950  to impinge on the inner surface of the distal end of the cavity  954  such that the coolant flow  950  can reverse direction and travel proximally through the main channel  1020  along an outer surface of the coolant tube  116  toward the torch head  102  (shown in  FIGS.  13   a  and  b   ). This reverse coolant flow over the exterior surface of the coolant tube  116  also substantially cools the Louvertac band  704  attached to the distal end  742  of the coolant tube  116 . In some embodiments, the reverse coolant flow can travel through the longitudinal channels  744  on the exterior surface of the coolant tube  116  beneath the Louvertac band  704 , thereby limiting a pressure drop between the coolant tube  116  and the electrode  108 . 
     In some embodiments, the nozzle opening  966 , which can be formed on the nozzle jacket  111 , is aligned with the first coolant channel  962  disposed in the insulator body  1100  of the cartridge frame  112  (shown in  FIGS.  13   a  and  b   ). The nozzle opening  966  allows the coolant flow  950  from the first coolant channel  962  to enter the nozzle coolant flow chamber  965  between an exterior surface of the nozzle  110  and an interior surface of the nozzle jacket  111 . The first coolant channel  962  (shown in  FIGS.  13   a  and  b   ) can extend substantially parallel to the longitudinal axis A in the inner region  1106  of the insulator body  1100 , but offset from the longitudinal axis A (i.e., non-concentric with respect to the longitudinal axis A). The first coolant channel  962  can connect the opening  962   a  on the end face  1102  at the proximal end  15  of the cartridge frame  112  to the opening  962   b  of the cartridge frame  112 , which is distal to the opening  962   a  along the longitudinal axis A. The opening  962   b  is in turn fluidly connected to the nozzle opening  966 , which allows the coolant flow  950  to travel distally from the torch head  102 , through the cartridge frame  112  of the cartridge  104 , and into the nozzle coolant flow chamber  965  (shown in  FIGS.  13   a  and  b   ). 
     In some embodiments, the opening  962   b  of the first coolant channel  962  is disposed on the inner side surface  1110  of the cartridge frame body  1100  and in fluid communication with the central channel  1020 . Thus, in this configuration, the first coolant channel  962  does not extend over the entire length of the cartridge frame body  1100  in the longitudinal direction. The opening  962   b  of the first coolant channel  962  is illustrated in  FIG.  22   . As shown, the opening  962   b  is on the inner side surface  1110  toward the distal end  17  of the cartridge frame  112 , and the opening  962   b  is fluidly connected to the central channel  1020 . In alternative embodiments, the first coolant channel  962  extends over the entire length of the cartridge frame  112  with the opening  962   b  located on the distal end face  1104  of the cartridge frame insulator body  1100 . The opening  962   b  is fluidly connected to the nozzle opening  966  in the nozzle jacket  111 . Such a connection allows the liquid coolant flow  950  to pass from the torch head  102 , through the cartridge frame  112 , and into the nozzle coolant flow chamber  965  between the nozzle  110  and the nozzle jacket  111  to cool the two nozzle components. 
     As explained above, the nozzle opening  966  is configured to be aligned with the first coolant channel  962  of the cartridge frame  112  such that the coolant flow  950  can be introduced into the nozzle coolant flow chamber  965  from the first coolant channel  962  via the nozzle opening  966 . The nozzle opening  966  can be in fluid communication with the second nozzle opening  967  on the nozzle jacket  111 , where the two coolant openings  966 ,  967  are radially offset from each other (i.e., on different sides of the nozzle  110 ). The coolant flow  950  can enter the nozzle coolant flow chamber  965  via the nozzle opening  966 , flow proximally through the flow chamber  965 , return distally on a different side of the chamber  965 , and exit the chamber  965  via the second opening  967 . In some embodiments, the second opening  967  is aligned with and connected to the second coolant channel  968  disposed in the cartridge frame  112  (shown in  FIGS.  13   a  and  b   ). The second coolant channel  968  can extend substantially parallel to the longitudinal axis A within the inner region  1106  of the insulator body  1100 , but offset from the longitudinal axis A (i.e., non-concentric with respect to the longitudinal axis A). The second coolant channel  968  connects the opening  968   a  on the end face  1102  at the proximal end  15  of the cartridge frame  112  to the opening  968   b  at the distal end  17  of the cartridge frame  112 , which is in turn connected to the second nozzle opening  967 . Such a connection allows the coolant flow  950  to travel proximally from the nozzle coolant chamber  965 , through the cartridge frame  112  of the cartridge  104 , and into the torch head  102  (shown in  FIGS.  13   a  and  b   ). In some embodiments, the opening  968   b  of the second coolant channel  968 , which is distal to the opening  968   a  along the longitudinal axis A, is disposed on the inner side surface  1110  of the cartridge frame body  1100 . Thus the first and second coolant channels  962 ,  968 , in cooperation with the nozzle openings  966 ,  967  allow the coolant flow  950  to cool the nozzle  110  and the nozzle jacket  111  via the nozzle coolant flow chamber  965 . 
       FIGS.  24   a  and  b    are exterior views of the non-vented nozzle  110  and the nozzle jacket  111  of  FIG.  17   , respectively, according to an illustrative embodiment of the present invention. The non-vented nozzle  110  includes a proximal end/portion  1206 , a middle portion  1208 , and a distal end/portion  1210  along the longitudinal axis A of the torch  10 . The distal end  1210  of the nozzle  108  includes the centrally-located nozzle exit orifice  916  for introducing a plasma arc, such as an ionized gas jet, to a workpiece (not shown) to be cut. The nozzle jacket  111  includes a substantially hollow body  1212  defining a proximal end  1214  and a distal end  1216  along the longitudinal axis A. The nozzle  110  is adapted to be inserted into the hollow body  1212  of the nozzle jacket  111  such that the distal end  1210  of the nozzle  108  extends through the opening of the distal end  1216  of the nozzle jacket  111 . 
     In some embodiments, the nozzle jacket  111  includes the nozzle openings  966 ,  967  at its proximal end  1214 , where each opening connects an exterior surface to an interior surface of the nozzle jacket body  1212 . The openings  966 ,  967  can be oriented on substantially opposite sides of nozzle jacket  111  (e.g., about 180 degrees from each other). In some embodiments, the exterior surface of the middle portion  1208  of the nozzle  111  and a corresponding interior surface of the nozzle jacket  111  cooperatively define the nozzle coolant flow chamber  965 . The flow chamber  965  can be located approximately in the middle of the nozzle  110  and the nozzle jacket  111  along the longitudinal axis A and/or at their widest radial sections. In some embodiments, the distal portion  1210  of the nozzle  110  includes a circumferential flow channel  1218  about the nozzle  110  (i.e., a flow channel extending about 360 degrees around the nozzle  110 ) that is located through the opening at the distal end  1216  of the nozzle jacket  111 . The circumferential channel  1218  permits a coolant to flow over the exterior surface of the tip of the nozzle  110 , thereby promoting convective cooling of the nozzle tip during torch operation and reducing stagnation of the flowing liquid. The circumferential flow channel  1218  can be defined at least in part by a curvilinear surface of the nozzle  110 . 
     In operation, the cooling liquid flow  950  can enter the flow chamber  965  via the opening  966  on one side of the nozzle jacket  111 . The cooling liquid flow  950  can travel distally toward the circumferential flow channel  1218  in a longitudinal direction over one side of the flow chamber  965 . Upon reaching the circumferential flow channel  1218 , the coolant flow  950  can swirl about the nozzle tip and return proximally on the other side of the nozzle  110  substantially opposite (e.g., about 180 degrees) of the distal flow. The return flow  950  can exit from the nozzle coolant flow chamber  965  to the cartridge frame  112  via the opening  967 . 
     In some embodiments, an internal surface of the shield  114  is in fluid communication with the third coolant channel  978  disposed in the insulator body  1100  of the cartridge frame  112  (shown in  FIGS.  13   a  and  b   ). The third coolant channel  978  can extend substantially parallel to the longitudinal axis A in the inner region  1106  of the insulator body  1100 , but offset from the longitudinal axis A (i.e., non-concentric with respect to the longitudinal axis A). The third coolant channel  978  can connect the opening  978   a  on the end face  1102  at the proximal end  15  of the cartridge frame  112  to the opening  978   b  in the cartridge frame  112 , which is distal to the opening  978   a  along the longitudinal axis A. In some embodiments, the opening  978   b  of the third coolant channel  978  is disposed on the outer side surface  1108  of the cartridge frame body  1100 . Thus, in this configuration, the third coolant channel  978  does not extend over the entire length of the cartridge frame body  1100  in the longitudinal direction. The opening  978   b  of the third coolant channel  978  is illustrated in  FIG.  22   . As shown, the opening  978   b  is on the outer side surface  1108  in the middle portion of the cartridge frame  112 . In alternative embodiments, the third coolant channel  978  extends over the entire length of the cartridge frame  112  with the opening  978   b  located on the distal end face  1104  of the cartridge frame insulator body  1100 . The opening  978   b  can be fluidly exposed to an inner surface of the shield  114 , which allows the coolant flow  950  to travel distally from the torch head  102 , through the cartridge frame  112  of the cartridge  104 , and into the shield  114  (shown in  FIGS.  13   a  and  b   ). 
     In some embodiments, as shown in  FIG.  22   , the outer side surface  1108  of the middle section of the cartridge frame  112  defines a circumferential flow channel  1220  about the cartridge frame  112  (i.e., a flow channel extending about 360 degrees around the cartridge frame  112 ). The circumferential channel  1220  is fluidly connected to the opening  978   b  of the third coolant channel  978 . The circumferential channel  1220 , in cooperation with an inner circumference of the shield  114 , forms a shield coolant flow region  1222  (shown in  FIG.  13   b   ) that permits the coolant flow  950  to flow therethrough, thereby cooling the inner circumference of the shield  114 . In some embodiments, the circumferential channel  1220  is in fluid communication with the opening  982   b  of the fourth coolant channel  982  of the cartridge frame  112  that can also be located on the outer side surface  1108  of the cartridge frame  112 . The opening  982   b  is distal to the opening  982   a  along the longitudinal axis A. The openings  978   b ,  982   b  can be radially offset relative to each other, such as by 180 degrees so they are on opposite sides of the cartridge frame  112 . The fourth coolant channel  982  can extend substantially parallel to the longitudinal axis A, but offset from the longitudinal axis A (i.e., non-concentric with respect to the longitudinal axis A). The fourth coolant channel  982  is adapted to connect the opening  982   a  on the end face  1102  at the proximal end  15  of the cartridge frame  112  to the opening  982   b.    
     In operation, the coolant flow  950  can travel distally to the shield  114  via the opening  978   b  of the third coolant channel  978 . Upon entering the shield coolant flow region  1222  (i.e., defined by the circumferential flow channel  1220  on the outer side surface  1108  of the cartridge frame  112  and the corresponding inner circumference of the shield  114 ), the coolant flow  950  can swirl about the shield coolant flow region  1222  and return proximally on the other side of the shield coolant flow region  1222  substantially opposite (e.g., about 180 degrees) of the distal flow. The return flow  950  can exit the shield coolant flow region  1222  to the cartridge frame  112  via the opening  982   b  of the fourth coolant channel  982 . 
       FIG.  25    is a cross sectional view of the shield  114  of the cartridge  104  of  FIG.  17   , according to an illustrative embodiment of the present invention. The shield  114  comprises a substantially hollow body including a centrally located shield exit orifice  870  and, optionally, one or more gas vent holes (not shown) extending from an interior surface to an exterior surface of the shield  114 . The shield  114  can be cold formed or stamped using copper. 
     In general, with reference to the proximal end  15  of the cartridge frame  112 , the first coolant channel opening  962   a  can function as a coolant inlet to the nozzle  110 , the second coolant channel opening  968   a  can function as a coolant outlet from the nozzle  110 , the third coolant channel opening  978   a  can function as a coolant inlet to the shield  114 , and the fourth coolant channel opening  982   a  can function as a coolant outlet from the shield  114 . In some embodiments, when the torch head  102  is coupled to the cartridge  104 , the second coolant channel opening  968   a , which functions as a coolant outlet from the nozzle  110  is fluidly connected to the third coolant channel opening  978   a , which functions as a coolant inlet to the shield  114 . Specifically, a distribution channel in the torch insulator  118 , which connects the internal openings  972 ,  974  of the torch insulator  118  as described above with reference to  FIGS.  13   a  and  b   , can direct the coolant flow  950  from the second coolant channel  968  to the third coolant channel  978  to cool both the nozzle and the shield. 
     In some embodiments, one or more of the liquid coolant channel openings  962   a ,  968   a ,  978   a ,  982   a , the plasma gas channel opening  912   a , the shield gas channel opening  864   a , and the main channel opening  1020   a  are disposed on the end face  1102  of the proximal end  21  of the torch insulator  118 , where the end face can be substantially planar. These openings, with the exception of the main channel opening  1020   a , can be disposed non-concentrically on the proximal end face  1102  with respect to the central longitudinal axis A. In some embodiments, one or more of the coolant channels  962 ,  968 ,  978 ,  982 , the plasma gas channel  912 , and the shield gas channel  864  of the cartridge frame  112  are non-concentric with respect to the central longitudinal axis A. 
     RFID Communication in the Cartridge 
     In some embodiments, the cartridge frame  112  forms a communication interface (e.g., an RFID communication interface) between the torch head  102  and the cartridge tip. With reference to  FIG.  17   , the insulator body  1100  of the cartridge frame includes an RFID mounting feature  1230  formed on or in cartridge frame  112  adjacent to the end face  1102  of the proximal end  15  of the cartridge frame  112 . For example, the mounting feature  1230  can be a cavity disposed in the cartridge frame body  1110  from the end face  1102 . The RFID mounting feature  1230  (e.g., a cavity) can be disposed in the inner region  1106  of the cartridge frame  112  and can be located/oriented in a non-concentric manner relative to the central longitudinal axis A. 
     The signal device  160  can be disposed in or on the mounting feature  1230  to transmit information about the cartridge  104  (e.g., about the electrode  108 , the nozzle  110 , the shield  114  and/or the cartridge frame  112  itself) to an adjacent reader device, such as to the communication device  122  in the torch insulator  118  when the torch head  102  is coupled to the cartridge  104 . For example, the signal device  160  can be embedded in the cavity  1230  and surrounded by the insulator material of the cartridge frame body  1100 . The signal device  160  can be an electrically writable and/or readable RFID tag. Exemplary information encoded on the signal device  160  can include generic or fixed information, such as a component&#39;s name, trademark, manufacturer, serial number, and/or type. In some embodiments, the encoded information is unique to the component, such as metal composition of the component, weight of the component, date, time and/or location of when the component was manufactured, etc. Information encoded to the signal device  160  can also specify operating parameters and/or data about the component that is independent of a detectable physical characteristic of the component. The signal device  160  can be an RFID tag or card, bar code label or tag, integrated circuit (IC) plate, or the like. 
     In some embodiments, the end face  1102  of the proximal end  15  of the cartridge frame  112  is substantially planar. In this configuration, if the cartridge  104  is not coupled to the torch head  102 , an operator can place a reader, such as an RFID reader installed on a handheld device, flat against the substantially planar end face  1102  to interrogate the signal device  160  and extract information stored on the signal device  160 . Hence, the cartridge frame  112  can be configured such that the signal device  160  mounted in or on the cartridge frame  112  is readable from inside of the plasma arc torch  10  (e.g., by the communication device  122  of the torch head  102 ) or outside of the plasma arc torch  10  (e.g., by an external reader). 
     In another aspect of the present invention, the torch head  102  can be coupled to a cartridge that includes a vented nozzle, in which case the torch head  102  still provides substantially the same functions as it provides for the non-vented cartridge  104 .  FIG.  26    is an exemplary vented cartridge  1300  compatible with the torch head  102  of the plasma arc torch  10  of  FIG.  1   , according to an illustrative embodiment of the present invention. The cartridge frame  1302  of the vented cartridge  1300  can be substantially the same in configuration and/or material composition as the cartridge frame  112  of the non-vented cartridge  104  such that the cartridge frame  1302  maintains the same interface between the torch head  102  and the components of the cartridge tip, including an electrode  1308 , a vented nozzle  1310  coupled to a nozzle liner  1311 , and a shield  1314 . For example, the electrode  1308  can be substantially the same as the electrode  108  of the non-vented cartridge  104 , and the electrode  1308  can be affixed to the cartridge frame  1302  in the same manner as the electrode  108  to the cartridge frame  112 . The shield  1314  can be substantially the same as the shield  114  of the non-vented cartridge  104 , and the shield  1314  can be be affixed to the cartridge frame  1302  in the same way as the shield  114  to the cartridge frame  112 . 
     The nozzle liner  1311  can be disposed in and affixed to an interior surface of the vented nozzle  1310 . Each of the nozzle liner  1311  and the nozzle  1310  can be directly affixed to the cartridge frame  1302  such that the nozzle liner  1311  and the nozzle  1310  are axially and radially aligned to the cartridge frame  1302 . In some embodiments, as illustrated in  FIG.  26   , a radial distance  1360  between an interior surface of a swirl ring  1316  of the vented cartridge  1300  and an exterior surface of the electrode  1308  is about 0.08 inches. In some embodiments, the closest breakdown gap distance  1362  between an exterior surface of the electrode  108  and an interior surface of the nozzle liner  1311  is about 0.05 inches. 
       FIGS.  27   a  and  b    are exterior views of the nozzle liner  1311  and the vented nozzle  1310  of the cartridge  1300  of  FIG.  26   , respectively, according to an illustrative embodiment of the present invention. As shown in  FIG.  27   b   , the vented nozzle  1310  includes a substantially hollow body having a proximal end/portion  1326  and a distal end/portion  1328  along the longitudinal axis A of the torch  10 . The distal end  1328  of the nozzle  1310  includes a centrally-located nozzle exit orifice  1332  for introducing a plasma arc, such as an ionized gas jet, to a workpiece (not shown) to be cut. In some embodiments, the nozzle  1310  includes a circumferential coolant channel  1339  about an exterior surface of the nozzle  1310  (i.e., a flow channel extending about 360 degrees around the nozzle  110 ) that is located at the proximal end  1326 . The circumferential channel  1339  permits a liquid coolant to flow over the exterior surface of the nozzle  1310  in a swirling pattern, thereby promoting convective cooling and reducing stagnation of the flowing liquid. 
     As shown in  FIG.  27   a   , the nozzle liner  1311  includes a substantially hollow body defining a proximal end  1334  and a distal end  1336  along the longitudinal axis A. The nozzle liner  1311  includes a central opening  1338  at the distal end  1336  and one or more plasma gas channels  1337  oriented longitudinally on an outer surface of the liner  1311  around the central opening  1338 . In some embodiments, the nozzle liner  1311  includes one or more vent holes  1346  at its proximal end  1334  for allowing a vented plasma gas flow to travel from an interior surface to an exterior surface of the nozzle liner  1311 . The vent holes  1346  can be suitably metered to control one or more flow parameters. The nozzle liner  1311  is adapted to be disposed in the hollow body of the nozzle  1310  from an opening at the distal portion  1326  of the nozzle  1310 . The nozzle liner  1311  can be radially aligned/centered with respect to the nozzle  1310 . The central opening  1338  can be in fluid communication with the nozzle exit orifice  1332  once the nozzle liner  1311  is disposed into the nozzle  1310 . The distal end  1334  of the nozzle liner  1311  can be exposed such that the vent holes  1346  are unobstructed by the nozzle  1310 . 
     In some embodiments, the shield gas flow through the vented cartridge  1300  is substantially the same as the shield gas flow  868  through the non-vented cartridge  104 . In some embodiments, the plasma gas flow through the cartridge frame  1302  is the same as the plasma gas flow  900   c  through the cartridge frame  112 . The plasma gas flow path after it exits from the cartridge frame  112  is illustrated in  FIG.  26   . Substantially the same as the plasma gas flow path  900   b  of the cartridge frame  112 , the swirl ring  1316  can be configured to introduce a swirling motion to the plasma gas flow  1340  as it flows distally to exit the cartridge frame  1302 . The plasma gas flow  1340  then travels distally between the electrode  1308  and the nozzle liner  1311  to reach a plenum  1342  cooperatively defined by the electrode  1308 , the nozzle liner  1311  and the nozzle  1310 . The plasma gas flow  1340  can exit the plasma arc torch  10  by travelling through the plenum  1342 , the central opening  1338  of the nozzle liner  1311 , the central nozzle exit orifice  1332  and a central shield exit orifice  1344 . A small portion  1341  of the plasma gas flow  1340  in the plenum  1342  can be vented distally via the one or more plasma gas channels  1337  between the exterior surface of the liner  1311  and the interior surface of the nozzle  1310 . 
     As the plasma gas flow  1341  travels distally between the liner  1311  and the nozzle  1310 , it reaches the proximal end  1324  of the nozzle liner  1311  and can exit the nozzle liner  1311  via the vent hole  1346  at the proximal end  1324 , which connects an interior surface of the nozzle liner body  1311  to an exterior surface of the nozzle liner body  1311 . The vent hole  1346  is adapted to be in fluid communication with a vent channel  1348  that is radially oriented in the body of the cartridge frame  1302  to connect an inner side surface of the cartridge frame  1302  and an outer side surface of the cartridge frame  1302 , which is in turn exposed to atmosphere. In some embodiments, a similar vent channel can be constructed in the insulator body  1100  of the cartridge frame  112  for the non-vented cartridge  112  such that the same cartridge frame is usable in both the vented and the non-vented cartridge design. Thus, the distal plasma gas flow  1341  can exit the nozzle  1310  via the vent hole  1346  to enter the vent channel  1348  disposed in the body of the cartridge frame  1302 . The distal plasma gas flow  1341  can be vented to atmosphere by following the vent channel  1348  from the inner side surface to the outer side surface of the cartridge frame  1302 . In some embodiments, if a retaining cap  120  is used to connect the cartridge frame  1302  to the torch head  102 , a vent hole disposed in the body of the retaining cap  120  can align with the vent channel  1348  of the cartridge frame to allow the distal plasma gas flow  1341  to escape from the torch  10 . In general, by allowing the plasma gas flow  1341  to be vented from the cartridge  1300  instead of the torch head  102 , the ozone in the plasma gas flow  1341  would not otherwise destroy the torch  10  since the torch head  102  is a more durable component that can be repeatedly used while the cartridge  1300  is a consumable component that can be regularly replaced (e.g., about every 2-20 hours of operation, such as about every 8 hours of operation) or replaced after each use. 
     In some embodiments, the coolant flow through the cartridge frame  1302  is substantially the same as the liquid coolant flow  950  through the cartridge frame  112 . In the vented cartridge  1300 , the coolant flow can cool the electrode  1308  and the shield  1314  in substantially the same manner as the coolant flow  950  for the non-vented cartridge  104  using same coolant channels and passages/flow regions. For example, cooling the electrode  1308  in the vented cartridge  1300  can be the same as cooling the electrode  108  of the non-vented cartridge  104  by using the main coolant channel  1002  connected to the cavity  954  of the electrode  108 . As another example, cooling the shield  1314  in the vented cartridge  1300  can be the same as cooling the shield  114  of the non-vented cartridge  104  by using the third and fourth coolant channels  978 ,  982  connected to the shield coolant flow region  1222  of the shield  114 . 
     For cooling the vented nozzle  1310  in the vented cartridge  1300 , the coolant flow through the cartridge frame  1302  is substantially the same as the liquid coolant flow  950  through the cartridge frame  112  over the first and second coolant channels  962 ,  968 . The coolant flow path towards the vented nozzle  1310  after it exits from the cartridge frame  112  is illustrated in  FIG.  26   . As shown, the opening  962   b  of the first coolant channel  962 , which is situated on the inner side surface of the cartridge frame  1302 , conducts a coolant flow  1350  from the inner region of the cartridge frame  1302  to a central main channel  1351  (e.g., same as the main channel  1020  of the cartridge frame  112 ). The coolant flow  1350  can travel distally out of the cartridge  1302  over the main channel  1351  and into a nozzle coolant flow region  1352  defined between the circumferential channel  1339  on the exterior surface of the nozzle  1310  and an interior surface of the shield  1314 . For example, the opening  962   b  of first coolant channel  962  can be in fluid communication with the circumferential channel  1339  (and the nozzle coolant flow region  1352 ) such that it centrally conducts the coolant flow  1350  from the cartridge frame  1302  to the nozzle coolant flow region  1352  from one side of the nozzle  1310 . The coolant flow  1350  can travel distally toward the circumferential flow channel  1339  in a longitudinal direction over one side of the nozzle coolant flow region  1352 . Upon reaching the circumferential flow channel  1339 , the coolant flow  1350  can swirl about the nozzle  1310  and return proximally on the other side of the nozzle  1310  substantially opposite (e.g., about 180 degrees) of the distal flow. The circumferential flow channel  1339  can also be in fluid communication with the opening  968   b  of the second coolant channel  968  such that the return flow  1350  can exit from the nozzle coolant flow region  1352  and enter the cartridge frame  1302  via the opening  968   b  of the second coolant channel  968 . 
     In some embodiments, unlike the coolant flow  950  with respect to the non-vented nozzle  110 , the coolant flow  1350  for the vented cartridge  1300  does not enter a region between the liner  1311  and the vented nozzle  1310 . Instead, the coolant flow  1350  flows around an exterior circumference of the nozzle  1310  that is spaced distally relative to the liner  1311 . 
     Generally, the cartridge frame  112  for the non-vented cartridge  104  and the cartridge frame  1302  for the vented cartridge  1300  can be the same. In some embodiments, the same cartridge frame can be used in different types of cartridges by aligning and attaching different types of components to the cartridge frame. For example, as described above, a cartridge frame of the present invention can be coupled to a vented or non-vented nozzle to customize plasma gas venting capabilities. As another example, different swirl rings (e.g., the swirl ring  150  or swirl ring  1316 ) can be attached to the cartridge frame to customize the swirling pattern of the plasma gas flow through the cartridge. As yet another example, different baffles (e.g., the baffle  1112 ) or shield swirl rings (e.g., the shield swirl ring  1114 ) can be attached to the cartridge frame to customize flow properties of the shield gas flow through the cartridge. Thus, the cartridge frame of the present invention allows the consumable cartridge to be configurable and customizable to realize different cutting objectives. 
       FIG.  28    is another exemplary cartridge frame  1400  that can be suitably configured to form a cartridge compatible with the torch head  102  of  FIG.  1   , according to an illustrative embodiment of the present invention. The cartridge frame  1400  is substantially the same as the cartridge frame  112  or the cartridge frame  1302 . The main difference is the shape of the proximal end  1402  of the cartridge frame  1400 , which has a “flower petal” configuration. All other features of the cartridge frame  1400 , including the inlet and outlet openings and channels, remain the same as those of the cartridge frame  112 . Same as the cartridge frame  112 , the cartridge frame  1400  can be made of an insulator material, such as Torlon™ or polyphenylene sulfide. The “flower petal” configuration of the proximal end  1402  of the cartridge frame  1400  allows the cartridge frame  1400  to be manufactured using an injection molding technique, which provides a faster and cheaper manufacturing approach in comparison to traditional processes, including using less mass, cools better and more evenly with no cavitation. In alternative embodiments, the cartridge frame  112  or  1400  can be machined. 
     In some embodiments, at least one of the nozzle jacket  111  or the electrode insulator  754  is made from a non-conductive material, such as Torlon™ or polyphenylene sulfide. At least one of the electrodes  108 ,  1308 , the insert  1200 , the non-vented nozzle  110 , the vented nozzle  1310 , the nozzle liner  1311 , or the shields  114 ,  1314  can be made from a conductive material, such as copper or brass. The swirl rings  150 ,  1316  can be made from a conductive material, such as zinc (e.g., Zamac 3). Each of the baffle  1112  or the shield swirl ring  1114  can be made from an insulator material or a conductive material. In some embodiments, each of the non-vented cartridge  104  or vented cartridge  1300  is composed of at least about 50% of plastic by volume. In some embodiments, an overall length of the cartridge  104  or  1300  along the longitudinal axis A is about 2 inches, and the largest diameter of the cartridge  104  or  1300  along a plane perpendicular to the longitudinal axis A is about 1.7 inches. 
     The electrodes  108 ,  1308  and the shields  114 ,  1314  can be manufactured using a cold forming, stamping or machining technique. The non-vented nozzle  110  or the vented nozzle  1310  can be manufactured using cold forming, stamping or machining with features (e.g., holes) drilled in. The swirl rings  150 ,  1316  can be manufactured using die casting with swirl holes drilled in, injection molding with swirl holes drilled in, or machining. The baffle  1112  can be formed using stamping, die casting, machining or molding. The shield swirl ring  1114  can be formed using die casting, molding or machining. In general, to reduce manufacturing cost and complexity, the cartridge  104  or  1300  includes little or no Vespel™, little or no lava, little or no aluminum, minimal copper usage, and/or very few o-ring grooves. Further, the components of the cartridges  104 ,  1300  are manufactured to minimize drilled holes. 
     In some embodiments, the cartridge  104  or the cartridge  1300  is designed to be non-planar in the proximal end such that the interface between the cartridge and the torch head  102  is also non planar.  FIG.  29    is an exemplary vented cartridge  1450  that includes a non-planar proximal end  1452 , according to an illustrative embodiment of the present invention. The vented cartridge  1450  can comprise an end face  1458  and a protruding distal portion  1460  disposed on a cartridge frame  1454 . Specifically, the protruding distal portion  1460  is a portion of the cartridge frame  1454  that forms the main central channel  1456 . The protruding distal portion  1460  can extend distally along the longitudinal axis A beyond the end face  1458  of the inner region  1462  of the cartridge frame  1454 . All other features/functions of the cartridge  1450  can remain substantially the same as the vented cartridge  1300  described above. 
       FIG.  30    is an exploded view of the cartridge  104  of  FIG.  18   , according to an illustrative embodiment of the present invention. To assemble the cartridge  104 , the emissive insert  1200  can be first inserted into the electrode  108  at the distal end  1202  of the electrode  108 . The electrode  108  can then be coupled to the electrode insulator  754  from the distal end of the electrode insulator  754 . For example, the outer retaining features  1066  of the electrode  108  can matingly engage the inner retaining features  1068  of the electrode  754  to axially align the components and radially align/center them along the interface  1067 . The resulting components can be coupled to the swirl ring  150  to form a first sub-assembly  1502 . For example, the outer retaining feature  1056  of the electrode insulator  754  can matingly engage the inner retaining feature  1054  of the swirl ring  150  to axially align the components and radially align/center them along the interface  1055 . In some embodiments, one or more o-rings are used to further secure the components (e.g., the swirl ring  150 , the electric insulator  75  and the electrode  108 ) relative to each other in the first sub-assembly  1502 . A second sub-assembly  1504  can be formed by affixing the nozzle  110  to the nozzle jacket  111 , where the nozzle  110  can be disposed in the hollow body of the nozzle jacket  111 . In some embodiments, one or more o-rings are used to further secure the nozzle  110  and the nozzle jacket  111  relative to each other in the second sub-assembly  1504 . 
     The first sub-assembly  1502 , the second sub-assembly  1504 , and the shield  114  can be directly attached to the cartridge frame  112  to form the cartridge  104 . For example, an outer retaining feature  1052  of the swirl ring  150  can matingly engage an inner retaining feature  1058  of the cartridge frame  112  to axially align the components and radially align/center them along the interface  1053 . An outer retaining feature  1070  of the nozzle  110  can matingly engage another inner retaining feature  1072  of the cartridge frame  112  to axially align the components and radially align/center them along the interface  1071 . An outer retaining feature  1062  of the cartridge frame  112  can matingly engage an inner retaining feature  1064  of the shield  114  to axially align the components and radially align/center them along the interface  1063 . In addition, a distal end of the shield  114  can be crimped into an indentation  1065  on the outer surface of the cartridge frame  112  to further secure the two components together. In some embodiments, one or more o-rings are used to assist in the engagement of the first sub-assembly  1502 , the second sub-assembly  1504 , and/or the shield  114  to the cartridge frame  112 . 
     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.