Abstract: Plasma arc or laser cutting uses a mix of reactive and reducing gas flows to cut sheets of stainless steel, aluminum and other non-ferrous metals. The reducing gas flow to the cut varies as a percentage of the total gas flow to maintain a reducing atmosphere down through the cut, but to leave a predominantly oxidizing atmosphere at the intersection of the cut and the bottom surface of the sheet being cut. In plasma arc cutting these flows can also be characterized as either a plasma gas flow, one that forms the arc, or a shield gas flow that surrounds the arc. The reactive gas is preferably a flow of air, oxygen, nitrogen, carbon dioxide or a combination of these gases. The reducing gas is preferably hydrogen, hydrogen 35, methane, or a mixture of these gases. For aluminum, the reactive gas is preferably air or nitrogen and the reducing gas is preferably methane or a mixture of methane and air. In laser cutting the reducing gases such as methane can be used by mixing them with reactive assist gases.

Abstract: A plasma arc torch uses a mix of reactive and reducing gas flows to cut sheets of stainless steel, aluminum and other non-ferrous metals. The reducing gas flow to the cut is varied as a percentage of the total gas flow to maintain a reducing atmosphere down through the cut, but to leave a predominantly oxidizing atmosphere at the intersection of the cut and the bottom surface of the sheet being out. These flows can also be characterized as either a plasma gas flow, one that forms the arc, or a shield gas flow that surrounds the arc. The reactive gas is preferably a flow of air, oxygen, nitrogen, carbon dioxide or a combination of these gases. The reactive gas is usually in the plasma gas flow, whether alone or mixed with other gases. The reducing gas is preferably hydrogen, hydrogen 35, methane, or a mixture of these gases. For aluminum, the reactive gas is preferably air or nitrogen and the reducing gas is preferably methane or a mixture of methane and air.

Abstract: A plasma arc torch has a secondary gas flow that is extremely large during piercing of a workpiece to keep splattered molten metal away from the torch and thereby prevent "double arcing". The secondary flow exits the torch immediately adjacent the transferred plasma arc and is an extremely uniform, swirling flow. A swirl ring is located in the secondary gas flow path at the exit point. A prechamber feeds gas to the swirl ring, which is in turn fed through a flow restricting orifice. For certain applications the secondary gas is a mixture of an oxidizing gas, preferably oxygen, and a non-oxidizing gas, preferably nitrogen, in a flow ratio of oxygen to nitrogen in the range of 2:3 to 9:1. Preferably the flow ratio is about 2:1. A network of conduits and solenoid valves operated under the control of a central microprocessor regulates the flows of plasma gas and secondary gas and mixes the secondary gas.

Abstract: Plasma arc or laser cutting uses a mix of reactive and reducing gas flows to cut sheets of stainless steel, aluminum and other non-ferrous metals. The reducing gas flow to the cut varies as a percentage of the total gas flow to maintain a reducing atmosphere down through the cut, but to leave a predominantly oxidizing atmosphere at the intersection of the cut and the bottom surface of the sheet being cut. In plasma arc cutting these flows can also be characterized as either a plasma gas flow, one that forms the arc, or a shield gas flow that surrounds the arc. The reactive gas is preferably a flow of air, oxygen, nitrogen, carbon dioxide or a combination of these gases. The reducing gas is preferably hydrogen, hydrogen 35, methane, or a mixture of these gases. For aluminum, the reactive gas is preferably air or nitrogen and the reducing gas is preferably methane or a mixture of methane and air. In laser cutting the reducing gases such as methane can be used by mixing them with reactive assist gases.

Abstract: In a plasma arc cutting torch a flow of plasma gas is bypassed out of a plasma chamber, preferably at an annular gap between a pre-orifice in an inner nozzle piece and an exit nozzle orifice in an outer nozzle piece. A bypass channel formed between the inner and outer nozzle pieces directs the bypass flow to atmosphere. A metering valve or restricting orifice remote from the gap controls the amount of the bypass flow and delays the response of changes in the flow parameters in the plasma chamber to changes in the bypass flow. The pre-orifice and nozzle orifice are positioned and dimensioned to optimize the mass flow velocity and the strength of a vortex-type flow at the pre-orifice, thereby creating a virtual nozzle immediately below the electrode. The gas flow in the plasma chamber is highly uniform and very steady.

Abstract: A process and apparatus for reducing wear of an electrode in a plasma arc torch involves providing a substantial pressure drop in a flow of plasma gas from the torch to a plasma arc chamber defined by the electrode and a nozzle. The pressure drop is immediately before the plasma arc chamber. There is also a small, localized supply of the plasma gas located between the pressure drop and the plasma chamber. The supply is sufficient to stabilize the arc when the gas flow is cut off upstream of the pressure drop and the arc current is cut off very shortly thereafter. The pressure drop is small enough to permit an adequate flow of plasma gas to the plasma arc chamber during normal operations, but large enough to isolate residual gas in the torch from the plasma arc chamber when the arc current is cut off. The apparatus is preferably a swirl ring with an annular pre-chamber fed by a set of choke holes to feed gas to the chamber and create the pressure drop.

Abstract: A process and apparatus for reducing wear of an electrode in a plasma arc torch involves altering the gas flow in a plasma chamber surrounding the electrode immediately before and continuing after cutting of the current that sustains the arc. The altering includes closing off the gas flow upstream of the chamber, switching from a swirling flow to a radial/axial flow through the plasma chamber, reducing the arc current level in conjunction with either of the above, the venting the plasma chamber to rapidly change the gas flow and pressure in the chamber. The interval is sufficient to reduce electrode wear, but short enough that the arc remains stabilized until cut-off. In the flow stop mode, a solenoid valve is placed on an inlet tube for the plasma gas. Flow altering also occurs on start up. A gas preflow is established prior to pilot arc ignition. On transfer, the flow increases to its full operating value in conjunction with an increase in the arc current. The preflow can be axial, or partially axial.

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 plasma arc cutting torch, particularly one operating in the 0-200 ampere range, has a shield mounted at its lower end adjacent a workpiece to block splattered molten metal from reaching a nozzle of the torch. The shield is electrically insulated, preferably by mounting it on an insulating ring that is itself secured on a cap screwed onto the torch body. A secondary gas flow through the torch passes through the space between the nozzle and the shield to provide cooling. Bleed ports in the shield allow an enhanced flow rate with the remaining flow being at a rate, in conjunction with the size of an exit orifice in the shield, to stabilize the plasma arc. The bleed ports are outwardly angled away from the arc. Canted ports in the secondary gas flow path, but before the bleed ports, produce a swirling of the gas flow which enhances the quality of the cut.

Abstract: A plasma arc cutting torch, particularly one operating in the 0-200 ampere range, has a shield mounted at its lower end adjacent a workpiece to block splattered molten metal from reaching a nozzle of the torch. The shield is electrically insulated, preferably by mounting it on an insulating ring that is itself secured on a cap screwed onto the torch body. A secondary gas flow through the torch passes through the space between the nozzle and the shield to provide cooling. Bleed ports in the shield allow an enhanced flow rate with the remaining flow being at a rate, in conjunction with the size of an exit orifice in the shield, to stabilize the plasma arc. The bleed ports are outwardly angled away from the arc. Canted ports in the secondary gas flow path, but before the bleed ports, produce a swirling of the gas flow which enhances the quality of the cut.

Abstract: A quick disconnect connector for both electrical power and gas flow to a plasma arc torch has a plug that includes at least one pin contact and a mating receptacle that includes at least one socket contact that receives the pin contact axially. Both contacts have a central axial passage that conducts the gas flow at a sufficient rate to cool the contacts when they are conducting a large heavy operating current, typically 20 to 1,000 amperes, D.C. For high voltage operation, each contact is closely surrounded by a barrier sleeve of a dielectric material which is supported in an insulating body filling the plug or receptacle. The sleeved contacts are mounted to pivot independently of one another about a central mounting boss for self-alignment on mating. O-rings seal the sleeves to the insulator bodies to restrict the gas to a connection zone of the connector.

Abstract: A process and apparatus for reducing wear of an electrode in a plasma arc torch involves altering the gas flow in a plasma chamber surrounding the electrode immediately before and continuing after cutting of the current that sustains the arc. The altering includes closing off the gas flow upstream of the chamber, switching from a swirling flow to a radial/axial flow through the plasma chamber, reducing the arc current level in conjunction with either of the above, and venting the plasma chamber to rapidly change the gas flow and pressure in the chamber. The interval is sufficient to reduce electrode wear, but short enough that the arc remains stabilized until cut-off. In the flow stop mode, a solenoid valve is placed on an inlet tube for the plasma gas. For venting, a vent tube and another solenoid valve are added to the torch.

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 cutting torch, particularly one operating in the 0-200 ampere range, has a shield mounted at its lower end adjacent a workpiece to block splattered molten metal from reaching a nozzle of the torch. The shield is electrically insulated, preferably by mounting it on an insulating ring that is itself secured on a cap screwed onto the torch body. A secondary gas flow through the torch passes through the space between the nozzle and the shield to provide cooling. Bleed ports in the shield allow an enhanced flow rate with the remaining flow being at a rate, in conjunction with the size of an exit orifice in the shield, to stabilize the plasma arc. Canted ports in the secondary gas flow path produce a swirling of the gas flow which enhances the quality of the cut.

Abstract: A plasma arc cutting torch and method for obtaining more efficient cuts underwater, and for muffling the noise and radiation of a plasma cutting torch when used above water, surrounds the plasma arc with high-pressure, high-velocity annular flows of air and water. In one embodiment, a radially inward air flow creates a high-pressure, water-free cutting zone around the plasma while a surrounding radially outward water flow cooperates with and stabilizes the air flow. The water-free cutting zone created during underwater cutting, or above-water cutting on a water-table, includes the cut itself and the underside of the workpiece in the vicinity of the plasma. The air flow prevents water from interfering with the progress of the cut and hydrogen gas from accumulating under the workpiece.

Abstract: An arc plasma torch includes a moveable cathode and a fixed anode which are automatically separated by the buildup of gas pressure within the torch after a current flow is established between the cathode and the anode. The gas pressure draws a nontransferred pilot arc to produce a plasma jet. The torch is thus contact started, not through contact with an external workpiece, but through internal contact of the cathode and anode. Once the pilot arc is drawn, the torch may be used in the nontransferred mode, or the arc may be easily transferred to a workpiece. In a preferred embodiment, the cathode has a piston part which slidingly moves within a cylinder when sufficient gas pressure is supplied. In another embodiment, the torch is a hand-held unit and permits control of current and gas flow with a single control.

Abstract: Stressing tendons used in prestressing concrete are generally anchored to the concrete by wedge plates which are embedded in the concrete. The anchorage is accomplished by the use of gripping wedges which are placed around the stressing tendons and into the wedge plates.A gripping tool is provided which inserts and seats, in a single operation, gripping wedges. The tool is generally comprised of a holding and guiding piece and a sliding mechanism.

Abstract: A thin sheet heat exchanger is provided which facilitates the transfer of heat between two flowing streams of gas. The heat exchanger is formed of a packing of rectangular heat exchange plates positioned by the method of the present invention separately and parallelly to one another. The packing realizes a crossflow channel pattern for the two gas streams. The heat exchange plates which compose the bulk of the heat exchanger are, by the method of the present invention, folded at two opposite sides. The plates are stacked as prescribed by the method of this invention, and seamweld (or equivalent) sealed along the folded sides of each pair of consecutive plates, thus forming individual gas channels. Also by the method of the present invention gasket sealing surfaces and flange mounting surfaces are realized by the said folds of the said heat exchange plates.

Abstract: A fuel tank is provided for the automotive transport of a cryogenic liquid fuel which in the course of transport is being consumed by an engine or the like. The fuel tank consists essentially of two containers, one for the cryogenic fuel and the other for a secondary cryogenic liquid which is used to cool the fuel during storage when no fuel is being consumed. By the method of the invention the build up of fuel vapor pressure during storage is avoided and the vapor pressure maintained at a predetermined level. The fuel tank described herein was two distinct modes of operation, namely, the fuel storage mode and the fuel supply mode. In the fuel storage mode the cryogenic fuel is being stored for later use while the secondary fluid is being used as a heat sink for the heat absorbed by the tank from the environment.

Abstract: An apparatus is provided which utilizes the heat of fusion of a storage material to store heat from a vehicle exhaust system for later use in warming the lubricant or cooling fluid of the engine. An elongated canister has a portion of the exhaust system running through it, and that portion is located near the bottom of the canister. Located in the top of the canister is a heat exchanger through which flows engine coolant or lubricant. The remainder of the canister is filled with a heat storage material which may consist of various eutectic salt mixtures or single salts having temperatures of fusion and heats of fusion such that the material is in a liquid state when warmed by the exhaust system and in a solid state at ambient temperatures.