Gas duct arrangement for a vacuum furnace

A gas duct arrangement for use with a hot zone chamber of a vacuum furnace, wherein said gas duct and said hot chamber when used are located within a vacuum furnace and subjected to repeated cycles of expansion and contraction due to heating and cooling within said vacuum furnace and wherein said hot zone chamber has an outer wall, comprising in combination:

• plenum means having an outside wall, two side walls and an inside wall, said outside wall and said inside wall being of substantially the width of said outer wall, said plenum means formed and disposed to fit substantially completely in width and length around said outer wall of said hot zone chamber with said inside wall of said plenum being formed integral with said outer wall of said hot zone chamber;
• a plurality of apertures, each formed to pass from the inside of said hot zone chamber, through said outer wall thereof, through said inside wall of said plenum means thereby opening into said plenum means;
• a plurality of pipe means formed independently of the plenum and with each disposed to respectively pass through an associated one of said plurality of apertures and each formed to be threaded and disposed to be in threaded engagement at its associated aperture so as to be independently removable from its associated aperture, said pipe means further formed and disposed to direct gas into said hot zone in a direction substantially axial to its associated aperture;
• and input aperture means formed in said outside walls of said plenum means whereby gas can pass into said plenum means and therefrom through said plurality of pipe means into said hot zone chamber.