Abstract: An electrode for a contact start plasma arc torch includes an elongated electrode body formed of an electrically conductive material. The electrode body is movable relative to the torch. A resilient element, contacting a proximal end of the electrode body, is used for imparting a separation force to the electrode body. The electrode body is adapted to overcome the separation force and engage a contact element of the torch when the torch is operated in a transferred arc mode.

Abstract: An improved electrode for use in a plasma arc torch. The electrode includes an electrode body, a bore defined by and disposed in the electrode body, and an insert disposed in the bore. The insert and/or the bore of the electrode are configured to improve retention of the insert in the electrode, thereby extending electrode life. The invention also includes a method for forming the electrode. The method includes a step of positioning an insert into a bore of an electrode such that an exterior gap is established that is greater than a second gap.

Abstract: An electrode for use in a plasma arc torch has an insert designed to improve the service life of the electrode, particularly for high current processes. The electrode comprises an elongated electrode body formed of a high thermal conductivity material and having a bore disposed in a bottom end of the electrode body. The bore can be cylindrical or ring-shaped. An insert comprising a high thermionic emissivity material, and in some embodiments, a high thermal conductivity material, is disposed in the bore. The insert can be ringed-shaped or cylindrical.

Abstract: An electrode for a contact start plasma arc torch includes an elongated electrode body formed of an electrically conductive material that defines a longitudinal axis and a distal end for housing an emissive element. The electrode includes a second end positioned adjacent the electrode body. The second end defines an extensive portion having a first length along a first direction and a second length along a second direction. The second length is greater than the first length. A component for use with the electrode includes a hollow body element having an interior surface with one or more of a contour, step, or flange that defines a shaped opening capable of slideably receiving a complementary-shaped portion of an electrode body.

Abstract: An electrode for a contact start plasma arc torch includes an elongated electrode body formed of an electrically conductive material. The electrode body is movable relative to the torch. A resilient element is used for passing substantially all of a pilot arc current between a power supply, a power connection in electrical communication with the power supply, and the electrode body during pilot arc operation of the plasma arc torch. The electrode and torch can include a contact element having a first surface in electrical communication with the power contact and a second surface for physical contact and electrical communication with a corresponding contact surface of the electrode body for passing substantially all of a transferred arc current between the power supply and the electrode body during transferred arc mode.

Abstract: In a plasma arc torch, an electrode is movable axially into and out of electrical connection with an anode, typically a nozzle secured to one end of a torch body. A flow of pressurized plasma gas is directed to a plasma chamber between the electrode and the nozzle, preferably through a replaceable swirl ring that closely surrounds and guides the electrode at a larger diameter shoulder portion of the electrode. A gas flow passage, preferably a spiral passage machined on the outer side surface of the shoulder portion, diverts a portion of the gas flow from the plasma chamber to a region above the electrode where it is vented to atmosphere. The passage is sufficiently constricted that a substantial pressure drop appears along the path, while at the same time allowing a sufficient flow to produce the desired cooling. The revolutions of the spiral are preferably closely spaced to enhance the surface area of the electrode in a heat transfer relationship with the cooling gas flow.

Abstract: A plasma arc torch that includes a torch body having a nozzle mounted relative to a composite electrode in the body to define a plasma chamber. The torch body includes a plasma flow path for directing a plasma gas to the plasma chamber in which a plasma arc is formed. The nozzle includes a hollow, body portion and a substantially solid, head portion defining an exit orifice. The composite electrode can be made of a metallic material (e.g., silver) with high thermal conductivity in the forward portion electrode body adjacent the emitting surface, and the aft portion of the electrode body is made of a second low cost, metallic material with good thermal and electrical conductivity. This composite electrode configuration produces an electrode with reduced electrode wear or pitting comparable to a silver electrode, for a price comparable to that of a copper electrode.

Abstract: A coolant tube for a liquid-cooled electrode disposed a plasma arc torch does not become damaged during an electrode blow-out condition. The coolant tube includes a hollow member and a substantially solid member. The hollow member has a first end, a second end and a coolant passage extending between the first and second ends. The first end can be secured within the torch such that the coolant tube is disposed adjacent the interior surface of the electrode and such that the coolant passage is in fluid communication with a coolant supply. The substantially solid member extends from the second end of the hollow member and has at least one flow restriction orifice extending therethrough. Each flow restriction orifice is fluid communication with the coolant passage for providing at least one high velocity jet of coolant to the interior surface of the electrode.

Abstract: An improved electrode for use in a plasma arc torch. The electrode includes an electrode body, a cavity in a front face at a first end of the electrode body, and an insert disposed in the cavity. The first end of the electrode body is formed of high purity copper containing at least 99.81% copper. The insert has a first end and a second end and is formed of a high emissivity material. A diameter of the first end of the insert is less than a diameter of a second end of the insert. An electrode is compressed to retain the insert using radial compression. The invention also includes a method for forming the electrode, and a method of operation of an electrode in a plasma torch.

Abstract: Disclosed is a novel method and structure for contact starting a plasma arc torch. A translatable, electrically conductive component such as a nozzle or swirl ring is biased into contact with an electrode by a compliant spring element. A pilot arc is formed by first passing current through the electrode/component interface. Thereafter, the component is translated under the influence of gas pressure in a plasma chamber formed between the electrode and component, compressing the compliant element and initiating the pilot arc. The spring element may be a separate element or may be maintained integrally with the nozzle, swirl ring, or a retaining cap, facilitating removal and replacement of the spring element with consumable components of the torch.

Abstract: A flow of ionizable gas is provided to a shielded plasma arc torch which includes an electrode, a translatable nozzle, a nozzle retainer, and a shield. After passing through a heat exchanger to cool the electrode, the gas flow enters an annular chamber where the flow is divided into three subflows. A first subflow enters a plasma chamber formed by the electrode, the nozzle, and a swirl ring to pressurize the plasma chamber and support a plasma arc. The second subflow passes serially through apertures in the nozzle retainer and the shield to shield the plasma arc. The remaining flow is vented to ambient. Accordingly, a single gas flow may be employed to independently support multiple torch operating requirements.

Abstract: A plasma arc torch mounts an electrode and a nozzle, with a mutual spacing, symmetrically about a common longitudinal axis at one end of the torch adjacent a workpiece. The inner surface of the nozzle has an annular, inwardly-directed projection, located opposite the electrode and at a point of closest spacing between the electrode and the nozzle. The projection, or "angle kink", is characterized by a minimum radius of curvature as compared to the radii of curvature of adjacent portions of the nozzle opposite said electrode. The inner surface is adjacent a central exit passage of the nozzle and the angle kink is spaced from the intersection of the exit port and the inner nozzle. In the preferred form the interior nozzle surface is formed by two conical surfaces each having different slopes with respect to the longitudinal axis so as to form the circumferentially extending angle kink at their plane of intersection.

Abstract: A translatable nozzle is supported in a contact start plasma arc torch at an aft end by a swirl ring and at a longitudinally spaced forward end by an insulative bearing member of a nozzle retainer. The nozzle is biased into contact with an electrode by a compliant spring element. A pilot arc is formed by first passing current through the electrode and nozzle. Upon pressurization of a plasma chamber formed therebetween, the nozzle is translated forward, compressing the spring element and initiating the pilot arc. The spring element may be maintained integrally with the nozzle to facilitate removal and replacement of the spring element with the consumable nozzle.

Abstract: Disclosed is a novel method and structure for contact starting a plasma arc torch. A translatable, electrically conductive component such as a nozzle or swirl ring is biased into contact with an electrode by a compliant spring element. A pilot arc is formed by first passing current through the electrode/component interface. Thereafter, the component is translated under the influence of gas pressure in a plasma chamber formed between the electrode and component, compressing the compliant element and initiating the pilot arc. The spring element may be maintained integrally with the nozzle, swirl ring, or a retaining cap, facilitating removal and replacement of the spring element with consumable components of the torch. Exemplary spring elements include wave spring washers, finger spring washers, curved spring washers, helical compression springs, flat wire compression springs, and slotted conical discs.

Abstract: A method and apparatus for a gas-cooled plasma arc torch. Components of the torch can include an electrode, nozzle and a shield, each of which can be gas-cooled. The nozzle can be disposed relative to the electrode and can include a generally hollow conductive body and a cooling gas flow channel defined by at least one fin disposed about an exterior surface of the body, the body providing a thermal conductive path that transfers heat between the nozzle to the cooling gas flow channel during operation of the torch. The shield can be disposed relative to the nozzle and can include a generally hollow conductive body and a cooling gas flow channel defined by at least one fin disposed about an exterior surface of the body, the body providing a thermal conductive path that transfers heat between the shield to the cooling gas flow channel during operation of the torch.

Abstract: A plasma arc torch includes a torch body and a nozzle mounted relative to an electrode at a first end of the torch body to define a plasma chamber. The torch body includes a plasma gas flow path for directing a plasma gas from a plasma gas inlet to a plasma chamber in which a plasma arc is formed. The nozzle includes a hollow, body portion defining a cavity and a substantially solid, head portion formed integrally with the body portion defining an exit orifice extending from the chamber. The exit orifice has a converging inlet and an outlet, where the inlet has a radius of curvature, and the exit orifice has a length to diameter ratio of greater than 2.5.

Abstract: A nozzle for a plasma torch can include a body that has an inner surface, an outer surface, a proximal end, and an exit orifice at a distal end. The nozzle can also include a liner surrounded by the inner surface of the body. The liner can include a proximal end and an exit orifice at a distal end adjacent the exit orifice of the body. The nozzle can include at least one vent passage formed in the body. The vent passage can have an inlet formed in the inner surface of the body and an outlet formed in the outer surface of the body. The vent passage can be disposed between the proximal end of the body and the proximal end of the liner. The plasma arc torch can include a configuration that allows for increased electrode life and nozzle life for a vented high current plasma process.