An electric resistance high temperature vacuum furnace having radiant
heating units evenly spaced around the sides and ends of the furnace hot
zone. Pairs of units are automatically regulated both radially and
longitudinally according to the temperature required by the workload in
the hot zone. The units each comprise parallel aligned elements
electrically connected in series at their one ends. Each element has
lengthwise surfaces angularly disposed from each other to form a beam
structure of high section modulus for stiffness and resistance to sagging.
Also, the angles of the element surfaces facing a heat-reflective assembly
substantially enable all of the energy radiated toward the assembly to be
reflected into the hot zone in addition to the direct radiation from the
surfaces facing the hot zone. The furnace includes a re-circulating
cooling system for rapid cooling of the furnace and workload. An inert
cooling fluid bypasses the hot zone, passing instead around the outside of
the heat assembly and through a heat exchanger until the circulated fluid
temperature drops below the maximum tolerated by all component parts in
the cooling system, after which the fluid passes directly through the hot
zone.