Abstract: A thermochemical scarfing method is disclosed which allows a greater diagonal standoff distance from the metal workpiece during preheating. The method includes preheating the end of the metal workpiece, and then scarfing the workpiece by directing a scarfing oxygen stream onto the workpiece at an acute angle and while moving the workpiece past the oxygen outlet port. The preheating step includes generating a high speed stream of oxidizing gas and a concentric stream of fuel gas coaxially about the central stream, so that the momentum of the central stream is maintained. As a result, the effective flame heating distance may be extended, and the manifold and head assembly which supports the preheating gas nozzles may be moved back from the workpiece a significant standoff distance so as to avoid damage from dislodged molten metal slag.

Abstract: A cutting and welding system is disclosed which includes a metering system for controlling at a location remote from the plasma arc torch the amount of gas and water fed to the plasma arc torch. The system includes at least one torch having an electrode, a nozzle assembly positioned adjacent the discharge end of the electrode, and structure for generating a flow of gas between the electrode and the nozzle assembly to create plasma flow through the bore to a workpiece. A gas line communicates with a source of gas and the plasma arc torch for supplying gas to the torch. A plurality of metering orifices are positioned within the gas flow line in a parallel bank with each other so that the gas may flow through each of the metering orifices. Each metering orifice has a predetermined diameter opening. A gas control valve is mounted adjacent each of the metering orifices within the gas flow line on the upstream side toward the supply of gas.

Abstract: A scarfing apparatus which allows a greater diagonal stand-off distance from a slab during preheating and scarfing is disclosed. The apparatus includes a manifold and head assembly for receiving and distributing oxygen and fuel gas. Upper and lower preheat blocks extend from the manifold and head assembly. The blocks are spaced to define an oxygen scarfing slot and discharge orifice of predetermined size for receiving a flow of scarfing oxygen from the manifold and head assembly. A plurality of preheat nozzle inserts are mounted within the upper preheat block adjacent to each other in a row substantially across the width of the upper preheat block. Each nozzle insert includes a central bore through which a flow of oxygen is received from the manifold and head assembly and discharged through the insert.

Abstract: A plasma arc torch has an outer heat shield removably secured onto the torch body. The heat shield includes an electrically conductive member secured on the interior surface of the heat shield and in electrical contact with the nozzle assembly or a nozzle assembly retainer member when the nozzle assembly and heat shield are secured onto the torch body. A closed loop electrical circuit is completed through a portion of the nozzle assembly and the electrically conductive member of the heat shield when both the nozzle assembly and the heat shield are secured onto the torch body. When the heat shield or the nozzle assembly are removed, the electrical circuit is open and the electrical voltage flow to the electrode is disabled.

Abstract: A plasma torch assembly that provides a removable and replaceable barrier to prevent catastrophic failure of a plasma arc torch following failure of an electrode. The torch assembly comprises the combination of an electrode body for providing an electrical path in a plasma arc torch, an electrode, and an electrode adaptor positioned between the electrode body and the electrode and formed of an electrically conductive material. The adaptor comprises an adaptor body portion having structure for removably fitting the adaptor body to the electrode body and structure for removably fitting the adaptor body to the electrode so that the adaptor forms an electrically conductive path between the electrode body and the electrode and contains features and components essential to the gas distribution.

Abstract: An improved plasma torch nozzle which has a substantially barrel shaped body having a longitudinal opening therethrough for directing the flow of gas for a plasma arc from rearward portions of the body downstream to forward portions of the body and then out of a face at the forward portions to form a plasma arc in the presence of a sufficient electrical potential difference. The nozzle body particularly comprises a rear section for which the outer surface portions diverge with respect to the downstream direction, a center section for which the outer surface portions are cylindrical with respect to the downstream direction, and a forward section for which the outer surface portions converge with respect to the downstream direction so that the respective outer surface portions form a continuous outer surface for the nozzle body that encourages the flow of gases that is directed along the outer surface of the nozzle body to follow the outer surface and converge at the face of the nozzle body.

Abstract: A plasma arc torch used in underwater cutting is disclosed. The plasma arc torch includes a torch body having a front end of substantially cylindrical configuration, and an electrode supported by the torch body and defining a discharge end extending toward the front end. A nozzle is mounted on the front end of the torch body adjacent the front discharge end of the electrode, and has a bore through which plasma is ejected. A cylindrical support body is secured onto the outer surface of the torch body and extends in spaced relation from the torch body outer surface toward the front end and forms an annular opening. A cylindrical sleeve has a rear portion received within the annular opening of the cylindrical support body and extends in spaced relation along the front end of the torch body to define an annular air chamber extending along the front end and forming an annular outlet opening positioned adjacent the nozzle. A high velocity gas is injected into the annular air chamber.

Abstract: A plasma cutting and gouging torch has a torch body and a torch head that defines a longitudinal axis. A nozzle is aligned with the longitudinal axis and is secured to the torch head at the plasma discharge end for discharging plasma through the nozzle outlet and onto a workpiece. A handle is secured onto the head and extends outward from the torch head. A shield is secured to the torch head and extends substantially around the periphery of the torch head opposite the handle and extends along the surface of the handle confronting toward the nozzle. The shield extends in close, spaced relation to the torch head and handle to define a narrow, insulating air gap between the torch body and the shield. A flow of air may be introduced into the formed air gap to aid in cooling the torch body during cutting or gouging.

Abstract: An apparatus for mounting a cutting torch to a shape cutting machine is disclosed, and which incorporates a control system for signaling the machine in the event the torch contacts an obstruction during either vertical or lateral movement of the torch by the machine. The control system includes a pair of plates mounted to the torch so that the plates are displaced relative to each other when the torch contacts an obstruction, and a number of gas release valves are mounted to the plates and which are connected to a gas line so that a signal is generated upon a relative displacement of the plates. The signal is directed to the control logic of the shape cutting machine so that it may take corrective action.

Abstract: A plasma arc torch is disclosed and includes an electrode defining a discharge end and a longitudinal axis. A nozzle base, formed of metallic material, is positioned adjacent the discharge end of the electrode. The nozzle base has an outer, annular configured mounting surface and a frusto-conical surface positioned adjacent the mounting surface and tapering toward the longitudinal axis in a direction away from the electrode. A lower nozzle member, formed of metallic material, is secured onto the nozzle base mounting surface on the side opposite the electrode, and includes an interior surface spaced from the outer frusto-conical surface of the nozzle base to form a water passage. A ceramic insulator is secured onto the outer surface of the lower nozzle member and extends substantially along that surface for preventing double arcing and insulating the lower nozzle member from heat and plasma generated during torch operation. In a one embodiment the ceramic insulator is secured by means of glue.

Abstract: An electrode for a plasma arc torch and a method of fabricating the same are disclosed, and wherein the electrode includes a copper holder having a lower end which mounts an emissive insert which acts as the cathode terminal for the arc during operation. Where the torch is used in an oxidizing atmosphere, the copper holder tends to oxidize, and the arc tends to attach to the oxidized copper rather than the insert, which results in the rapid destruction of the holder. To prevent this destruction, the present invention incorporates a sleeve of silver or other metal having a relatively high work function, and which is positioned to surround the insert and form an annular ring on the lower end surface of the holder and thus to surround the exposed end face of the emissive insert. The annular ring serves to prevent arcing from the copper holder, and so that the arc is maintained on the insert.

Abstract: An electrode for a plasma arc torch and a method of fabricating the same are disclosed, and wherein the electrode includes a copper holder having a lower end which mounts an emissive insert which acts as the cathode terminal for the arc during operation. Where the torch is used in an oxidizing atmosphere, the copper holder tends to oxidize, and the arc tends to attach to the oxidized copper rather than the insert, which results in the rapid destruction of the holder. To prevent this destruction, the present invention incorporates a sleeve of silver or other metal having a relatively high work function, and which is positioned to surround the insert and form an annular ring on the lower end surface of the holder and thus to surround the exposed end face of the emissive insert. The annular ring serves to prevent arcing from the copper holder, and so that the arc is maintained on the insert.

Abstract: A process for starting a plasma arc torch is disclosed which minimizes the oxidation of the electrode to thereby extend the life of the electrode. A flow of non-oxidizing gas is first generated between the discharge end of the torch electrode and the nozzle assembly of the torch. A pilot arc then is created between the discharge end of the electrode and the nozzle assembly. The pilot arc is transferred and the flow of non-oxidizing gas is terminated. A flow of oxidizing gas then is generated for plasma formation.

Abstract: A nozzle for use with a plasma arc torch having a first gas flow within the nozzle for engaging an electrode and generating a plasma and a second gas flow in surrounding engagement to the outer surface of the nozzle is disclosed. The nozzle includes an outer surface of substantially hourglass configuration in longitudinal cross-section so that the second gas remains in close contact with the outer hourglass surface of the nozzle to provide efficient heat transfer from the nozzle to the surrounding second gas flow.

Abstract: A plasma arc cutting torch is disclosed which includes a nozzle assembly below the electrode for injection of water around the plasma flow so as to constrict the arc. The nozzle assembly includes upper and lower disc like nozzle members which are spaced apart to define a water gap therebetween, and the members include aligned bores for permitting the plasma to flow therethrough to the underlying workpiece. The lower nozzle member is of extended length, and its forward or lower end portion is beveled to define a frusto-conical exterior surface, so as to permit the torch to be positioned closely adjacent the workpiece when making beveled cuts and so as to achieve the predetermined standoff which maximizes the quality and speed of the cut.

Abstract: A high frequency arc stabilizing circuit includes a free running oscillator for generating a non-synchronized square wave. An output from the oscillator is buffered and inverted. The asserted and inverted outputs drive field effect transistors coupled to the primary of a high voltage step-up transformer. The circuit can also be gated so as to only operate during selected time intervals.

Abstract: A welding system with an electronic control includes four switching elements coupled together to form a bridge. An inductor with a center tap is located between two legs of the bridge. A load, including an output electrode and the metal parts being welded, is coupled between the center tap of the inductor and the other two branches of the bridge. Two of the switching elements are turned on and off at a relatively high rate to control the power to the load. The other two are turned on and off at a relatively low rate to control the duty cycle and polarity of the load voltage and current.

Abstract: A welding power system is described wherein a programmable controller and a conventional power supply are coupled by a circuit which simulates a control potentiometer. The coupling circuit provides an adjustable output signal intermediate between high and low potentials depending upon the level of an input control signal. The coupling circuit converts the input control signal into a pulse width modulated signal, multiplexes the high and low potentials in accordance with the pulse width modulated signal, and time-averages the multiplexed signal to provide an output control signal. An optical isolator is preferably included for direct current isolation of the input and output signals.