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Title: Electrode construction for resistance heating furnace
Claims: The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 1. For use in a furnace for heating an electrically resistive crucible held between electrodes, improved electrode construction comprising: a pair of electrodes made of an electrically conductive material, at least one of said electrodes movable toward and away from the remaining electrode for alternately clamping and releasing an electrically resistive specimen-holding crucible between said electrodes; and a thin insert mounted to said at least one electrode to contact said crucible, said insert comprising an electrically conductive material with a melting point exceeding about 2500.degree. Centigrade. 2. The apparatus as defined in claim 1 and further including a fluid-actuated cylinder having a movable rod extending therefrom and coupled to said movable electrode for moving said electrode toward and away from said remaining electrode for clamping said crucible between said electrodes. 3. The apparatus as defined in claim 1 wherein said remaining electrode further includes a thin insert mounted to the surface of said electrode to contact said crucible, said insert made of an electrically conductive material with a melting point exceeding about 2500.degree. Centigrade. 4. The apparatus as defined in claim 1 wherein said electrodes are vertically oriented and said insert is mounted to the lower electrode and includes a substantially annular surface for supporting a crucible thereon. 5. For use in a furnace for heating an electrically resistive crucible held between electrodes, improved electrode construction comprising: a pair of electrodes made of an electrically conductive material, at least one of said electrodes movable toward and away from the remaining electrode for alternately clamping and releasing an electrically resistive specimen-holding crucible between said electrodes; and a thin insert mounted to said at least one electrode to contact said crucible, said insert comprising and electrically conductive high melting point material made of tungsten. 6. The apparatus as defined in claim 5 wherein said insert comprises a pressed mixture of particulate copper and tungsten. 7. The apparatus as defined in claim 1 wherein said electrodes are mounted in a vertical plane and the lower electrode is movable and includes a pedestal for supporting said crucible thereon and wherein said insert is mounted to the top of said pedestal and includes annular crucible supporting means. 8. The apparatus as defined in claim 7 wherein said insert comprises a generally disc-shaped member having a flattened annular surface and including a circular recess centrally formed therein for receiving a button-like projection extending downwardly from a bottom surface of said crucible. 9. The apparatus as defined in claim 8 wherein the upper electrode includes a passageway formed through said upper electrode and communicating with the interior of a crucible when clamped between said electrodes and defining a generally annular shoulder extending around a lower end of said passageway, and wherein said upper electrode includes an insert comprising an electrically conductive material with a melting point exceeding about 2500.degree. Centigrade, said insert being substantially washer-shaped and mounted to said annular shoulder of said electrode. 10. In a resistance heating furnace for fusing a specimen positioned in a crucible and directing an inert carrier gas into said crucible for sweeping gases therefrom as said specimen is fused during the heating of said crucible, an improved electrode construction comprising: an upper conductive electrode including a crucible-receiving chamber having an end defining an annular shoulder and including a washer-shaped insert including at least one notch formed therein and extending outwardly from an inner edge of said insert, said insert mounted to said annular shoulder for engaging the rim surrounding an open end of a crucible, said insert being made of an electrically conductive material with a melting point exceeding about 2500.degree. Centigrade, said upper electrode further including a passageway extending therethrough and opening at the center of said insert for supplying an inert gas to said crucible, said upper electrode also including an outlet port communicating with said crucible chamber for transporting gas passing through said notch in said insert outwardly from said electrode; a lower electrode including an annular chamber formed downwardly therein and an upwardly extending pedestal surrounded by said annular chamber and having an insert mounted thereto, said insert including means for supporting a crucible thereon, said insert made an electrically conductive material with a melting point exceeding about 2500.degree. Centigrade; means for moving one of said electrodes relative to the other for clamping said crucible between said inserts with said crucible positioned in said crucible-receiving chamber and said annular chamber of said lower chamber surrounding a lower portion of said upper electrode; and sealing means coupled to one of said electrodes to seal said crucible-receiving chamber at the junction of said electrodes when said electrodes are in a crucible-clamping position. 11. In a resistance heating furnace for fusing a specimen positioned in a crucible and directing an inert carrier gas into said crucible for sweeping gases therefrom as said specimen is fused during the heating of said crucible, an improved electrode construction comprising: an upper conductive electrode including a crucible-receiving chamber having an end defining an annular shoulder and including a washer-shaped insert including at least one notch formed therein and extending outwardly from an inner edge of said insert, said insert mounted to said annular shoulder for engaging the rim surrounding an open end of a crucible, said insert being made of a high melting point and high electrical conductivity material including tungsten, said upper electrode further including a passageway extending therethrough and opening at the center of said insert for supplying an inert gas to said crucible, said upper electrode also including an outlet port communicating with said crucible chamber for transporting gas passing through said notch in said insert outwardly from said electrode; a lower electrode including an annular chamber formed downwardly therein and an upwardly extending pedestal surrounded by said annular chamber and having an insert mounted thereto, said insert including means for supporting a crucible thereon, said insert made of a high melting point and high electrical conductivity material including tungsten; means for moving one of said electrodes relative to the other for clamping said crucible between said inserts with said crucible positioned in said crucible-receiving chamber and said annular chamber of said lower chamber surrounding a lower portion of said upper electrode; and sealing means coupled to one of said electrodes to seal said crucible-receiving chamber at the junction of said electrodes when said electrodes are in a crucible-clamping position. 12. The apparatus as defined in claim 11 wherein said inserts comprise a pressed mixture of particulate copper and tungsten. 13. The apparatus as defined in claim 12 wherein the crucible-engaging surface of the insert for said lower electrode defines a substantially annular contact with the bottom of said crucible. 14. The apparatus as defined in claim 10 wherein said upper electrode is fixed and said lower electrode is movable, and wherein said moving means comprises a fluid-actuated cylinder having a movable rod coupled to said lower electrode and fluid supply means coupled to said cylinder for clamping said crucible between said electrodes with a selectable pressure. 15. In copper electrode assemblies for use in a furnace for heating a specimen-holding resistive crucible clamped between said electrodes when a power supply is coupled to said electrode assemblies to pass electrical current throuogh said crucible, the improvement comprising: thin tipping inserts shaped to cover the surface of the electrodes which contact the crucible, said inserts comprising a electrically conductive material having a melting point greater than 2500.degree. Centigrade. 16. In copper electrode assemblies for use in a furnace for heating a specimen-holding resistive crucible clamped between said electrodes when a power supply is coupled to said electrode assemblies to pass electrical current through said crucible, the improvement comprising: tipping inserts shaped to cover the surface of the electrodes which contact the crucible, said inserts comprising a material including the metal tungsten having a melting point greater than about 2500.degree. Centigrade. 17. The structure as defined in claim 16 wherein said inserts comprise a pressed mixture of particulate copper and tungsten. 18. The structure as defined in claim 17 wherein said mixture is approximately 25 percent copper and 75 percent tungsten. 19. For use in a furnace for heating an electrically resistive crucible held between electrodes, improved electrode construction comprising: a pair of electrodes of electrically conductive material shaped for engaging a resistive crucible therebetween wherein at least one electrode includes an annular crucible-engaging surface providing substantially annular contact between said electrode and said crucible. Other info: Inventors: Sitek, George J. (Stevensville, MI, US) Revesz, Robert N. (St. Joseph, MI, US) Berk, Charles W. (St. Joseph, MI, US) Application Number: 484453 Filing Date: 1974-06-28 Publication_date: 1976-02-03 Assignee: Leco Corporation (St. Joseph, MI) Primary Class(es): 373/118 219/426 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Envall, Jr., R. N. Assistant Examiner: Attorney: Price, Heneveld, Huizenga & Cooper |
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