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. The network includes valved parallel branches that provide a quick charge capability and a set of venting valves, also electrically actuated by the microprocessor, to provide a quick discharge. In a preferred high-definition embodiment, a nozzle with a cut back outer surface and a large, conical head allows a metal seal and enhanced cooling. A two-piece cap protects the nozzle during cutting.

Plasma arc cutting process and apparatus using an oxygen-rich gas shield

A device and a method for generating a truly pulsed plasma flow are disclosed. The device includes a cathode assembly comprising a cathode and a cathode holder, an anode, and two or more intermediate electrodes, the anode and the intermediate electrodes forming a plasma channel expanding toward the anode. The intermediate electrode closest to the cathode may form a plasma chamber around the cathode tip. An extension nozzle forming an extension channel having a tubular insulator along at least a portion of its interior surface is affixed to the anode end of the device. During operation, a voltage is applied between the cathode and the anode and a current is passed through the cathode, the plasma, and the anode. The voltage and current profiles are selected to cause the rapid development of a plasma flow with required characteristics. A substantially uniform temperature and power density distribution of the plasma pulse is achieved in the extension nozzle. Additionally, ozone may be generated in the extension nozzle during the generation of the plasma pulse.

Pulsed plasma device and method for generating pulsed plasma

A dust collection system for portable sanding or grinding equipment employs a cyclone separator mounted directly on the tool or machine, with a dust outlet duct at the narrow lower end of the cyclone, and a cartridge air filter mounted on the top of the cyclone. The filter returns the air flow from the machine to the ambient air in the vicinity of the tool. The dust is concentrated in the cyclone, and a small volume air flow then moves the dust through an elongated flexible hose or duct to a remote dust collection station. An air pump at the remote dust collection station provides sufficient air flow to draw the small volume of air plus entrained dust from the tool-mounted cyclonic separator. A cyclonic separator at the remote station separates this dust from the air flow and deposits it in a collection tank or drum.

Dust collection system

(2004). Development of hot wire TIG welding methods using pulsed current to heat filler wire – research on pulse heated hot wire TIG welding processes. Welding International: Vol. 18, No. 6, pp. 456-468.

Development of hot wire TIG welding methods using pulsed current to heat filler wire – research on pulse heated hot wire TIG welding processes

The present invention relates to a plasma-generating device, comprising an anode, a cathode and at least one intermediate electrode, said intermediate electrode being arranged at least partly between said anode and said cathode, and said intermediate electrode and said anode forming at least a part of a plasma channel which has an opening in said anode. Further, the plasma-generating device comprises at least one coolant channel which is arranged with at least one outlet opening which is positioned beyond, in the direction from the cathode to the anode, said at least one intermediate electrode, and the channel direction of said coolant channel at said outlet opening has a directional component which is the same as that of the channel direction of the plasma channel at the opening thereof. The invention also concerns a plasma surgical device and use of such a plasma surgical device.

Plasma-generating device, plasma surgical device and use of a plasma surgical device

The invention relates to a welding torch for welding underwater and to a method of underwater welding using the welding torch. A high speed stream of water is directed from a nozzle on the welding torch obliquely onto a member or members to be welded to form a flared-out curtain of water. Gas is injected into the volume enclosed by the curtain of water to create a gaseous atmosphere and welding is carried out in the gaseous atmosphere.

Welding torch for underwater welding

Method of underwater welding

A hydraulic blasting apparatus has an abrasive storage tank disposed operatively between an abrasive recovery tank and a hydraulic pressurized tank. The abrasive storage tank is provided with a first valve openable from the inside of the storage tank to the atmospheric pressure, and also with a second valve to open the connection between the storage tank and the recovery tank and with a third valve to open the connection between the storage tank and the pressurized tank. The pressure in the abrasive storage tank will become the same as the atmospheric pressure by opening the first valve. Next the first and second valve are closed, and after that the third valve is opened so as to drop the abrasive only into the pressurized abrasive tank for a recycle use.

Continuously-operable abrasive blasting apparatus

In horizontal position, welding bead has an inclination to become hanging bead by gravity, and this problem makes horizontal welding difficult for high-deposition rate welding. A new basic concept so called Electromagnetically Controlled Molten Pool (ECMP) welding process that used electromagnetic force was proposed to solve this problem, and it was proved the possibility by new TIG welding process (1 wire type) with ECMP in horizontal position. In this paper, TIG welding using 2 filler wires with ECMP is proposed for higher deposition rate welding in horizontal position. 2 filler wire feeders are connected in series to a. wire heating power source, and one wire is inserted at front position, and another is inserted at rear position of the arc. So, joule heating ability and heat exchanging ability to the arc is increased comparison to 1 wire process. Farther more, area of unidirectional current in molten pool is increased by this wire arrangement. So, more wide upward electromagnetic force compared to 1 wire type is generated, and controlling ability of bead shape is increased under magnetic field. In the test, wire melting characteristics were investigated, and it was found that stable welding was possible under high deposition rate such as 100•`150g/min. Bead shape was improved remarkably, and contact angle of bottom side in weld bead was decreased under the half of magnetic flux density that was required in lwire process. V groove joint weld was done for stainless clad steel, and good penetration, smooth bead shape, sound weld joint property was obtained under high deposition rate welding condition such as 100 g/min. After these basic tests, new 2 wires type TIG welding process with ECMP was applied to huge steel structure, and practicability of this process was proved by successful result.

Hirokazu Wada

Papers

Welding torch for underwater welding

Method of underwater welding

Continuously-operable abrasive blasting apparatus

Investigation on TIG Welding Using 2 Filler Wires with Electromagnetically Controlled Molten Pool Process in Horizontal Position.