Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K9/00—Arc welding or cutting
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21B—FUSION REACTORS
  • G21B1/00—Thermonuclear fusion reactors
  • G21B1/11—Details
  • G21B1/23—Optical systems, e.g. for irradiating targets, for heating plasma or for plasma diagnostics
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/346—Working by laser beam, e.g. welding, cutting or boring in combination with welding or cutting covered by groups B23K5/00 - B23K25/00, e.g. in combination with resistance welding
  • B23K26/348—Working by laser beam, e.g. welding, cutting or boring in combination with welding or cutting covered by groups B23K5/00 - B23K25/00, e.g. in combination with resistance welding in combination with arc heating, e.g. TIG [tungsten inert gas], MIG [metal inert gas] or plasma welding
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/26—Plasma torches
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/10—Nuclear fusion reactors

Definitions

• the present invention relates to the use of high power lasers in industrial operations and more particularly relates to a laser sustained plasma torch and a method for employing the torch.
• Lasers have attained a substantial commercial market for industrial material processing applications, particularly in the areas of cutting and drilling of metals and non etallic materials, welding of metals, heat treatment of metals, and for surface alloying of metals.
• the carbon dioxide laser is the laser of choice because of its high power, high efficiency, and good reliability in the industrial environment.
• This laser operates at a wavelength of 10.6 micrometers in the far- infrared portion of the portion of the spectrum.
• many materials of interest are highly reflective which results in poor energy coupling efficiency. This necessitates the use of lasers of larger size and power output, increasing considerably the cost of the laser systems and virtually precludes the use of these lasers for processing some commercially important materials such as copper and brass.
• the apparatus includes a laser for producing laser radiation and a source of pressurized gas.
• a plasma torch nozzle includes an outlet and structure is provided to direct a flow of the gas received from the source toward the outlet.
• a lens focuses the laser radiation into the nozzle in a focal region at least partially within the nozzle and a plasma is sustained and at least partially confined within the nozzle by the flow of gas toward the outlet.
• focused laser radiation is directed into a nozzle having an outlet with the focal region of the laser radiation being at least partially within the nozzle.
• Pressured gas is introduced into the nozzle to cause the gas to flow towards the outlet.
• Plasma is initiated within the nozzle and is sustained in the focal region of the laser radiation, and at least a portion of the plasma is confined with the nozzle by the flow of gas being caused to flow toward the outlet.
• the method further includes employing the plasma as a working medium in performing an operation.
• FIGURE 1 is a somewhat diagrammatical perspective view partially in cross section of apparatus providing a laser sustained plasma torch embodying one form of the present invention
• FIGURE 2 is a partial cross-sectional view of the torch of FIGURE 1 shown cutting a steel plate; and FIGURE 3 is a partial cross section of the torch taken through lines 3-3. Best Mode of Carrying Out the Invention
• Apparatus 10 for producing a laser sustained plasma torch includes a laser 12 for transmitting a beam 14 of laser radiation to a focusing lens 16 which is preferably a plano-convex lens as illustrated although other focusing systems can also be employed.
• the laser 12 is any one of a wide variety of continuous wave lasers providing sufficient power when focused to sustain a plasma by inverse bremsstrahlung absorption of the laser beam.
• a suitable laser 12, for example, is a 1.5 KW carbon dioxide laser operating at a wavelength of 10.6 micrometers.
• laser radiation is focused by the focusing lens 16 to a focal region 17, and the lens 16 is mounted in support housing 18 having a frustro-conical throat 20 which preferably tapers slightly from top to bottom as depicted.
• the lens 16 is sealingly secured by a recessed externally threaded ring 22 adjacent the upper end of the throat 20 and thus closes off the upper opening into the throat 20.
• the lower end of the throat 20 opens into a nozzle 24 which is preferably secured to the housing similarly to the focusing lens 16 by externally threaded ring 25.
• the nozzle 24 tapers from top to bottom in the orientation depicted and is provided with an outlet 26 at its lower end. It is necessary for the nozzle 24 to be resistant to the extremely high heat produced by a plasma.
• the nozzle is fabricated from ceramic materials such as those produced by chemical vapor deposition or refractory metals such as tungsten or rhenium, but it will be understood that numerous nozzles of different materials and shapes are suitable for use in the torch depending on the particular application.
• the focusing lens 16, housing 18, and nozzle 24 collectively define an enclosed area 28 into which the focused laser radiation .is directed.
• the focusing lens 16, housing 18 and nozzle 24 are appropriately dimensioned and configured so that the focal region 17 of the laser radiation is at least partially within the enclosed area and preferably entirely within the volume defined by the nozzle 24.
• pressurized gas is introduced to provide a flow field and pressure coordinated with the configuration of the interior area and the size of the outlet 26 to at least partially confine and sustain a plasma in focal region 17 of the laser radiation within the nozzle 24.
• pressurized gas is supplied from a source (not shown) to supply line and regulator 30 which supplies gas at a selected pressure to the housing 18.
• the housing 18 is provided with passageways for introducing the gas into the enclosed area 28.
• annular discharge opening 32 is employed to discharge the gas with the annular discharge opening 32 being located coaxially with the axis of the beam 14 of laser radiation.
• Annular restriction structure 34 is advantageously employed to create a uniform higher pressure in the annular opening 32 upstream from the restriction structure 34 to assure uniform flow of gas into the enclosed area 28.
• the flow of gas is sufficient to create a sonic flow at the outlet 26 from the nozzle 24 when the apparatus 10 is in operation to isolate the plasma within the nozzle 24 from pressure disturbances generated by the proximity of a workpiece to the apparatus 10.
• the gas introduced into the enclosed area 28 functions in cooperation with the laser beam 14 to sustain a plasma 37 in the focal region 17.
• a plasma 37 When the plasma 37 is created within the nozzle 24 it will migrate away from the focal point of the laser beam 14 toward the laser 12 if it is not controlled.
• the flow of gas in cooperation with the configuration of the nozzle 24 stops the migration of the plasma and forces some of the plasma through the outlet 26 to form a torch or jet.
• an inert gas such as argon or helium is employed which does not react chemically with the workpiece and from which a plasma is generated without extremely high laser energies.
• a second supply line 36 is provided to introduce additional gas to further tailor the flow field within the enclosed area 28 and for providing secondary materials to be introduced into the enclosed area 28 with the additional gas if desired.
• Secondary materials to be introduced into the apparatus 10 are particulate or gaseous materials to be processed within the laser sustained plasma to produce a chemical or physical change in the material and may be collected from the torch after processing or deposited on a workpiece.
• the supply line 36 connects to an annular opening 38 generally coaxial with the beam 14 of laser radiation and in a plane generally perpendicular to the beam 14.
• the annular opening 38 is provided with an annular restriction 40 which provides for even flow into the enclosed area 28.
• vanes 46 or similar structure may be employed in the annular restriction 40 to direct the gas in a helical flow path.
• vanes, such as vanes 46 may be employed in the annular opening 32 to achieve desired gas flow characteristics.
• a flow of gas is created through the enclosed area 28 to outlet 26 by supplying pressurized gas through supply line and regulator 30 and into the enclosed area 28 through discharge opening 32.
• a beam of laser radiation 14 is transmitted by laser 12 to the focusing lens 16 where it is focused into the focal region 17.
• a suitable material is a tungsten rod inserted through nozzle 26.
• a plasma is sustained by inverse bremsstrahlung absorption of the laser beam and the pressure and gas flow field within the enclosed area 28 are operable to confine the plasma in the nozzle 24 adjacent the outlet 26.
• gas flow is begun through the second supply line 36 and annular opening 38 to achieve the desired plasma characteristics or to introduce secondary materials to be processed into the enclosed area 28.
• the plasma produced by apparatus 10 is confined and sustained within the enclosed area 28 by the gas flow, the plasma is not dependent on the proximity to a work surface and can be moved to any position or orientation without affecting the operation of the apparatus 10 or the characteristics of the plasma.
• the confined plasma is essentially isolated from any pressure disturbances generated by the proximity of the outlet 26 of the nozzle 24 to a workpiece.
• a small jet of plasma is ejected from the nozzle 24 and is impinging upon a steel plate 42 and forming a cut 44.
• the plasma 37 which is the working medium in the cutting operation, is formed in the focusing region by laser radiation and directed out of the nozzle 24.
• the infrared laser radiation is converted to shorter wavelength thermal radiation in the plasma which couples much more effectively with most metals. Energy transfer is increased due to the ionized components at the plasma recombining on the surface of the workpiece.
• the apparatus 10 produces a high velocity, high temperature jet which can greatly aid in dross removal in laser cutting operations.
• the plasma within the enclosed area 28 is employed as the working medium and the nozzle 24 is appropriately configured to eject the materials as desired as the materials are processed within the apparatus or are applied to a workpiece.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Optics & Photonics (AREA)
• Mechanical Engineering (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Laser Beam Processing (AREA)
• Plasma Technology (AREA)

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• 1987
  • 1987-06-22 EP EP19870904598 patent/EP0325583A4/de not_active Withdrawn
  • 1987-06-22 JP JP62504165A patent/JPH01503612A/ja active Pending
  • 1987-06-22 KR KR1019880700162A patent/KR880701151A/ko not_active Application Discontinuation
  • 1987-06-22 WO PCT/US1987/001504 patent/WO1987007862A1/en not_active Application Discontinuation

Non-Patent Citations (2)

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