Solar Manufacturing, Inc, located in Sellersville, Pennsylvania, USA, has been granted a patent for an enhanced vacuum furnace control thermocouple design. This new design is said to be particularly beneficial for controlling operating temperatures ranging from ambient up to 649°C (1200°F), especially within smaller diameter hot zones of 91.44 cm (36”) or less.
Typically, the outer ceramic protection tube of the conventional control thermocouple design serves as a heat sink. This thermal conduction, or heat loss, is compounded by the shorter length of the thermocouple assembly. As a result, the control thermocouple operates at a lower temperature, thereby increasing the power output to the furnace heating elements to maintain the set-point temperature. Consequently, the workload temperature becomes hotter than the furnace temperature. This phenomenon is more noticeable at lower processing temperatures (<649°C / 1200°F).
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The new thermocouple design from Solar Manufacturing aims to reduce unwanted thermal conduction losses in the assembly. This configuration has also shown improved temperature uniformity survey results. For compliance with AMS 2750 standard temperature uniformity specifications, proper positioning of control thermocouples in the hot zone is crucial to ensure accurate survey thermocouple measurements without the need for correction factors.
The patent inventor is William R Jones, owner of Solar Manufacturing.