This furnace design produces a highly efficient gravity seal as light reducing atmospheres such as dissociated ammonia and hydrogen enter the elevated furnace muffle and aggressively displace heavy contaminant laden air molecules to produce a chemically pure protective atmosphere within the vessels. Thus, very low atmosphere dewpoints can be maintained within the muffle and horizontal cooling section component to effectively resist oxidation of the most vulnerable metallic surfaces at elevated temperatures. For this reason, heat treatment of stainless-steel materials can be achieved with bright results. The "A"-Type furnace can be designed to accommodate any conveyor belt width or vertical opening requirement enabling it to copper braze a wide variety of stainless-steel components with bright results.
 

Protective atmosphere consumption requirements in an "A"-Type Furnace are much lower than a horizontal furnace of comparable size. If the process permits a curtain chamber or nitrogen seal could also be provided adjacent to the front door in the purge chamber to further minimize atmosphere consumption.
 

The purge chamber in an "A"-Type Furnace is provided with a supplemental piggyback conveyor belt drive which is synchronized with the speed of the primary conveyor belt drive. The piggyback drive will carry the loaded conveyor belt up through the inclined purge chamber for the full length, discharging it at the muffle inlet where the primary drive assumes transfer function. The assistance provided by the piggyback drive will allow heavier load carrying capabilities for a specific conveyor belt mesh designation.
 

Thus, a lightweight belt will be capable of carrying a load heavier than that called for through conventional design, because of the supplemental drive and more available heat can be directed to the load rather than the conveyer belt thereby enabling the equipment to operate more efficiently.