Vacuum furnace with an electric heater assembly

Claim 1

Apparatus for radiantly heating the interior of an enclosed vacuum vessel wherein the vessel has a port at the top thereof through which a heater may be entered, comprising: a. a housing positioned on the vessel over said port, b. a tubular extension on said housing projecting upwardly therefrom, c. a winch and cable at the top of the tubular extension, d. an elongated resistance heater adapted to be received in said housing and extension and moved up and down therein, said heater comprising: 1. inner and outer concentric spaced elongated resistance elements joined together at their lower ends, both of which have coaxially-extending concentric conducting terminal portions on their upper ends with the terminal portion of the inner element extending axially beyond the terminal portion of the outer one, 2. electrical connector means yieldably connecting the terminal portions of the inner and outer resistance elements arranged to yieldably resist relative thermal expansion between said elements but arranged to electrically insulate said terminal portions from each other, e. attachment means connecting said cable with the upper end of the resistance heater, f. vertically separate pairs of clamping electrodes in the housing, the upper electrodes being in position to clamp the terminal portion of the inner resistance element when the heater is lowered through said port into the vessel and the lower clamping electrodes being positioned to clamp the terminal portion of the outer resistance element when the heater is so lowered, g. resilient means for effecting radial movement of said pairs of clamping electrodes into gripping contact with the terminal portions which they engage or to release them from said engagement, and h. electrical lead means externally of the housing for connecting the clamping electrode with electrical conductors.