Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/305—Electron-beam or ion-beam tubes for localised treatment of objects for casting, melting, evaporating, or etching
  • H01J37/3053—Electron-beam or ion-beam tubes for localised treatment of objects for casting, melting, evaporating, or etching for evaporating or etching
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/02—Details
  • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
  • H01J37/09—Diaphragms; Shields associated with electron or ion-optical arrangements; Compensation of disturbing fields

Definitions

• the subject invention relates to electron beam furnaces for processing metallic materials and, more particularly, to apparatuses and methods for controlling and limiting the interaction of electron beams generated by adjacent electron beam guns mounted within an electron beam furnace.
• an electron beam furnace includes a vacuum chamber that has a hearth and crucible system therein.
• a number of electron beam guns are typically mounted in the vacuum chamber above the hearth to melt metals that are introduced into the chamber. As the metal is melted, it flows into the crucible to be re-solidified into an ingot.
• the electron beam from each gun can be deflected and scanned over the surfaces of the metal.
• the deflection of the electron beam is typically controlled by computers and electromagnetic coils in the base of each electron beam gun which serve to deflect the beam in accordance with changes in the magnetic fields.
• the use and construction of such electron beam guns are known in the art as exemplified by those electron beam guns disclosed in U.S. Patent No. 3,857,014 to Prudkovsky et al . and U.S. Patent No. RE 35,024 to Hanks .
• the generation of electron beams by multiple electron beam guns in close proximity to each other can result in undesirable electromagnetic interaction between the beams. Changes in deflection or beam power of one gun can cause a change of deflection in an adjacent gun, which also influences the gun adjacent to it and so on. That interaction can make it difficult to control the beams to obtain the desired result.
• the interaction of the electron beams is largely a function of the location of the electron beam guns relative to each other within the vacuum chamber, the further away from the metal that the electron guns are located, the greater the likelihood of electron beam interaction.
• the size of the vacuum chamber is often dictated by the number and location of electron beam guns. Small vacuum chambers require more frequent cleaning to remove the buildup of condensate material therein that could hamper and possibly lead to contamination of the material passing therein.
• an apparatus for limiting interaction between beams generated by at least two electron beam guns mounted within an electron beam furnace having a superstructure may include a planar barrier ' sized to extend between at least two electron beam guns and a superstructure hanger connected to the planar barrier.
• the subject invention may also comprise an electron beam furnace that includes a vacuum chamber that has an upper portion and a lower portion.
• the furnace also has a hearth assembly located within the lower portion of said vacuum chamber and at least two electron beam guns mounted within the vacuum chamber above the hearth assembly.
• the furnace includes at least one planar barrier suspended from the upper portion of the vacuum chamber such that it extends between at least two electron beam guns .
• the subject invention may also comprise a method for limiting interaction between electron beams generated by at least two electron beam guns within a vacuum chamber of an electron beam furnace.
• the method includes suspending a barrier from an upper portion of the vacuum chamber such that the barrier extends between the electron beams produced by the electron beam guns.
• Yet another feature of the present invention is to provide magnetic shield barriers that enable the electron beam guns to be positioned farther from their targets which enables larger vacuum chambers to be employed in electron beam furnaces .
• Larger chambers reduce the frequency of clean-outs required because the condensate collection can be placed further away from the melting process and can be provided with a larger surface area which results in a slower buildup of condensate.
• the present invention provides solutions to the shortcomings of prior furnaces that employ electron beam guns.
• FIG. 1 is a partial cross-sectional elevational view of a portion of an electron beam furnace employing shield assemblies of the present invention
• FIG. 2 is a partial cross-sectional end view of the furnace of Figure 1 ;
• FIG. 3 is a partial plan view of the furnace of Figures 1 and 2, illustrating the orientation of the shield assemblies relative to the electron beam guns;
• FIG. 4 is a partial plan view of another electron beam furnace employing another shield assembly embodiment of the present invention.
• FIG. 5 is a side elevational view of the shield assembly depicted in Figure 4 ;
• FIG. 6 is a top view of the shield assembly of Figure 5;
• FIG. 7 is an end view of the shield assembly of Figures 5 and 6;
• FIG. 8 is an enlarged partial view showing the struts of the shield assembly attached to the longitudinal barrier.
• FIG. 9 is an end elevational view of the furnace of Figure 4, showing a transverse endplate of the subject invention attached to the condensate assembly of the furnace.
• Figures 1-3 show an electron beam furnace 10 for melting metals that has a shield assembly 60 of the present invention installed therein.
• the shield assembly 60 may be successfully employed in connection with a variety of different electron beam furnace configurations.
• the present invention should not be limited to use only in connection with furnaces that are constructed the manner depicted in the present Figures and described herein.
• the furnace 10 includes a vacuum chamber 12 that has a hearth assembly 20 extending therethrough.
• the vacuum chamber 12 has an entry end 14 into which raw material is introduced, a melting zone 16, and a crucible mold 18.
• molten material flows along the hearth assembly 20 under the influence of gravity.
• Raw material is introduced into the entry end 14.
• the raw material is melted by bombarding it with beams of charged particles from a series of electron beam guns (40, 42, 44, 46, 48, 50, 52, 54) mounted within the vacuum chamber 12 above the hearth assembly 20.
• the molten material flows in one continuous path through the hearth assembly 20 into the crucible mold 18.
• the vacuum chamber 12 is typically provided with a series of condensate frame assemblies 30 that are supported from the upper superstructure 13 of the vacuum chamber 12. See Figures 1 and 2.
• Such condensate frame assemblies 30 may be fabricated from, for example, mild steel and have a series of screens, plates, etc. that provide surfaces upon which the molten metal may adhere. Removing the excess material from the condensate frame assembly 30 can be an arduous task. Often times the excess material must be chiseled or ground from the condensate screens.
• the condensate frame assemblies 30 are typically constructed so that they may be removed from the vacuum chamber 12 and replaced with clean frame assemblies 30 to permit the contaminated frame assemblies 30 to be cleaned off line.
• FIG. 1 a series of conventional electron beam guns are mounted above the hearth assembly 20 to direct electron particle beams onto the molten material thereon.
• the furnace 10 depicted in Figures 1-3 has a total of eight conventional electron beam guns (40, 42, 44, 46, 48, 50, 52, 54) mounted thereto.
• the shield assembly 60 of the present invention may be advantageously employed in furnaces that have at least two electron beam guns mounted in adjacent relationship to each other such that the beams from the guns may interact with each other. Therefore, the shield assembly 60 of the present invention should not be limited to use in connection with furnace arrangements that employ eight electron beam guns.
• Figures 2 and 3 illustrate the layout of the electron beam guns (40, 42, 44, 46, 48, 50, 52, 54) in this embodiment.
• Figure 3 is a plan view of the melting zone 16 of the vacuum chamber 12.
• a barrier wall 17 separates the melting zone 16 into a first zone 19 and a second zone 21 and the center of the melting zone 16 is defined by axis A-A.
• Conventional electron beam guns (40, 42, 44, 46) are equally spaced along an axis B-B within the chamber 12.
• Axis B-B is substantially parallel to axis A-A.
• conventional electron beam guns (48, 50, 52, 54) are equally spaced along an axis C-C that is substantially parallel to axes A-A and B-B.
• the centers of guns (40, 48) are aligned on an axis D-D that is substantially transverse to axis A-A.
• the centers of guns (52, 54) are aligned on an axis E-E that is also substantially transverse to axis A-A.
• the centers of guns (44, 46) are offset from the centers of guns (52, 54) .
• the shield assembly 60 of the present invention comprises a first assembly 62 that is adapted to be mounted within the first melting zone segment 19 and a second assembly 70 that is adapted to be mounted within the second melting zone segment 21.
• First assembly 62 comprises a first longitudinal planar barrier 64 that may be fabricated from mild steel.
• a first transverse barrier 66, fabricated from mild steel may be attached to the first longitudinal barrier 64 by, for example, welding.
• the first transverse barrier member 66 may be centrally disposed between guns (40, 42) (i.e., distance ⁇ G ⁇ equals distance ⁇ H ⁇ ) .
• First assembly 62 may further comprise a second transverse barrier member 68 fabricated from mild steel that may be attached to the first longitudinal barrier member 62 by, for example, welding such that it is centrally disposed between the guns (48, 50) when installed (i.e., distance ⁇ ⁇ I ⁇ equals distance ⁇ Kg ) .
• the first and second transverse barriers (66, 68) are configured to substantially conform to the contour of the corresponding ceiling portion 13 of the vacuum chamber 12 and the corresponding condensate frame assembly 30.
• the first shield segment 62 may be suspended from the corresponding condensate frame assembly with chain or wire.
• first shield assembly 62 may be attached to the corresponding condensate frame assembly 30 by bolted connections or other mechanical fasteners and connections.
• first transverse barrier 66 and the second transverse barrier 68 do not have to be attached to the longitudinal barrier 62. Instead, the first transverse barrier 66 and the second transverse barrier 68 may be separately suspended or otherwise attached to the condensate frame assembly 30.
• the second shield assembly 70 is adapted to be mounted within the second melting zone segment 21 and comprises a second longitudinal barrier 72 that may be fabricated from, for example, mild steel.
• a primary transverse barrier 74, fabricated from, for example, mild steel may be attached to the second longitudinal barrier 72 by, for example, welding.
• the primary transverse barrier 74 may be centrally disposed between guns (44,46) (i.e., distance ⁇ £ L ⁇ equals distance ⁇ M$ ⁇ ) .
• the second shield assembly 70 may further comprise a secondary transverse barrier member 76 fabricated from mild steel that may be attached to the second longitudinal barrier member 72 by, for example, welding such that it is centrally disposed between the guns (52, 54) when installed (i.e., distance ⁇ £ N ⁇ equals distance $ . ⁇ £ ) .
• the primary and secondary transverse barriers (74, 76) are configured to substantially conform to the contour of the corresponding ceiling portion 13 of the vacuum chamber 12 and the corresponding condensate frame assembly 30.
• the second shield assembly 70 may be suspended from the corresponding section of the condensate frame assembly 30 with chain, wire or other suitable material. Those of ordinary skill in the art will appreciate that the second shield assembly 70 may also be attached to the corresponding portions of condensate frame assembly 30 by bolted connections or other mechanical fasteners and connections. In addition, it will be further appreciated that the primary transverse barrier 74 and the secondary transverse barrier 76 do not have to be attached to the second longitudinal barrier 72. Instead, the primary transverse barrier 74 and the secondary transverse barrier 76 may be separately suspended or otherwise attached to the condensate frame assembly 30. It will be further appreciated, however, that, in those furnace applications lacking the transverse barrier 17, the first and second longitudinal barriers (62, 72) may comprise a unitary member.
• the electron beam guns (42, 44, 46, 48, 50, 52, 54) emit beams of electron particles generally designated as 80.
• the barriers 64, 66, 68, 72, 74, 76
• the distance that the shield assembly 60 protrudes downward is a function of the orientation of the electron beam guns.
• the shield assembly 60 it is desirable for the shield assembly 60 to extend downward from the condensate shield assembly 30 as far as possible to minimize the amount of interaction between the beams 80 of adjacent guns, but not so far such that the beams 80 begin to degrade and/or melt the barriers (64, 66, 68, 72, 74, 76) .
• Such distance may be determined by installing plates of various sizes between the adjacent guns to determine the maximum distance that the barriers can extend without being degraded or melted. In the embodiment depicted in Figures 1 and 2, the distance P ⁇ is approximately 18 inches (45.7cm). Angle g Rg is approximately 15° and angle g S$£ is approximately 15°. It is conceivable, however, that other distances and angles may be successfully employed.
• FIG. 4 is a plan view of a portion of a condensate frame assembly 130 of an electron beam furnace 110 that corresponds to a section of the furnace that has four electron beam guns.
• the condensate frame assembly 130 has four gun ports (132, 134, 136, 138) therein.
• this embodiment of the shield assembly 160 comprises a longitudinal barrier 162 that is fabricated from, for example, mild steel.
• first and second transverse plates (164, 166) may be attached together by, for example, welding to opposing sides of the longitudinal barrier 162.
• first and second transverse plates (164, 166) do not have to be attached to the longitudinal barrier, but may be separately suspended or otherwise attached to the condensate frame assembly 130.
• the longitudinal barrier 162 is centrally disposed between the gun ports (132, 134) and the gun ports (136, 138) .
• the first and second transverse plates (164, 166) are centrally disposed between ports (132, 136) and ports (134, 138), respectively. See Figure 4.
• the end of the first transverse plate 164 may be approximately six inches (15.24cm) from the centerlines of gun ports (132, 134) (distance g T ⁇ ) and the end of the second transverse barrier 166 may be approximately six inches (15.24cm) from the centerlines of the gun ports (136, 138) (distance g Ug ) .
• superstructure hangers in the form of transverse hanger struts 180 fabricated from, for example, mild steel, are attached to the longitudinal barrier 162 by pieces of steel angle 182 welded thereto.
• the hanger struts 180 may be attached to the longitudinal barrier 162 by a variety of different methods without departing from the spirit and scope of the present invention.
• the struts 180 are oriented to correspond with cross members of the condensate frame assembly 130 to enable the struts 180 to be removably affixed thereto by chain or wire 182.
• the struts 180 may be attached to the condensate frame assembly 130 or the vacuum chamber 112 by any suitable means including bolting, clamping, welding, etc.
• additional barrier plates 190 may be affixed to each end of the frame assembly 130.
• a series of holes 192 may be provided through the plate 190 to enable the plate 190 to be wired or chained to the frame assembly 130.
• the plate 190 may, however, be attached to the condensate frame assembly or vacuum chamber superstructure 13 by a variety of different fastening methods such as bolting or welding.
• the plates 190 may be provided with a relatively arcuate upper edge 196 to enable the plates to conform to the shape of the upper portion of the vacuum chamber 112 or the condensate frame assembly 130. In that embodiment, the bottom of the barrier plate 190 coincides with the bottom of the condensate frame assembly 130.
• the present invention may be used in connection with a variety of different electron beam furnaces.
• the subject invention may be advantageously adapted to limit interaction of electron beams emitted from adjacent electron beam guns mounted within a furnace.
• the shield assemblies are removably attached to the condensate screen assemblies, they can be easily removed therefrom for cleaning purposes.
• the shield assemblies of the present invention may be non-removably affixed to the condensate screen assembly or to the vacuum chamber itself, if so desired. Accordingly, the present invention represents an easy and inexpensive method of limiting interaction of electron beams in an electron beam furnace.

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• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Furnace Details (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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• 1999
  • 1999-07-15 US US09/354,286 patent/US6175585B1/en not_active Expired - Fee Related
• 2000
  • 2000-07-14 AU AU63500/00A patent/AU776095B2/en not_active Ceased
  • 2000-07-14 JP JP2001511709A patent/JP2003532856A/ja active Pending
  • 2000-07-14 CA CA002379913A patent/CA2379913A1/en not_active Abandoned
  • 2000-07-14 EP EP00950389A patent/EP1204984A4/en not_active Withdrawn
  • 2000-07-14 WO PCT/US2000/019410 patent/WO2001006537A1/en not_active Ceased

Patent Citations (4)

Non-Patent Citations (1)

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