Kiln with ventilation system

An electrically heated kiln having a ventilation system for oxidizing ceramic objects being fired in the interior of the kiln and for safely ventilating kiln gases produced during the firing process while providing greater uniformity in temperature inside the kiln, said kiln comprising:

• an upper wall, a lower wall and side walls forming a substantially fully enclosed firing chamber in which ceramic objects are placed;
• at least one upper ventilation aperture formed in the upper portion of said firing chamber through which incoming air may be drawn into the firing chamber;
• at least one lower ventilation aperture formed in the lower portion of said firing chamber;
• a duct coupled between said lower ventilation aperture and the outside environment;
• an exhaust fan coupled to said duct for placing the firing chamber under negative pressure so that kiln gases produced within the kiln are prevented from escaping from said firing chamber through said upper aperture into the room where the kiln is located, said fan drawing air into said firing chamber through said upper aperture and drawing air and kiln gases downwardly through said firing chamber and outwardly through said lower ventilation aperture into said duct, the downward movement of the air and kiln gases causing turbulence near the upper portion of said firing chamber to create a more uniform temperature within said firing chamber;
• said upper and lower apertures being sized and the draw rate of said exhaust fan being selected to limit the amount of air withdrawn at the bottom of the kiln so that less than 100% of the kiln volume is removed per minute when the kiln is operated at room temperature thereby permitting proper oxidation of the ceramic objects and preventing the escape of kiln gases into the room;
• and
• temperature reducing means coupled between said lower ventilation aperture and said duct to reduce the temperature of the kiln gases to within the temperature limits of the materials from which said duct is formed to protect the materials used in the duct and the exhaust fan.

In an electrically heated kiln having an upper wall, a lower wall and side walls forming a substantially fully enclosed firing chamber in which ceramic objects are placed, a ventilation system for oxidizing ceramic objects being fired in the firing chamber and for safely ventilating kiln gases produced during the firing process, while providing greater uniformity of temperature inside said firing chamber, said ventilation system comprising:

• at least one upper ventilation aperture formed in the upper portion of said firing chamber through which incoming air may be drawn into said firing chamber;
• at least one lower ventilation aperture formed in the lower portion of said firing chamber through which kiln gases may be expelled;
• a duct coupled between said lower ventilation aperture and the outside environment;
• an exhaust fan coupled to said duct for placing the firing chamber under negative pressure so that the kiln gases produced within the kiln are prevented from escaping from said firing chamber through said upper aperture into the room where the kiln is located, said fan drawing air into said firing chamber through said upper aperture and causing air and kiln gases to move downwardly through said firing chamber and outwardly through said lower ventilation aperture into said duct, the downward movement of the air and kiln gases causing a more uniform temperature within said firing chamber;
• said upper and lower apertures being sized and the draw rate of said exhaust fan being selected to limit the amount of air withdrawn at the bottom of the kiln so that less than 100% of the kiln volume is removed per minute when the kiln is operated at room temperature thereby permitting proper oxidation of the ceramic objects and preventing the escape of kiln gases into the room;
• a plenum connecting said lower ventilation aperture to said duct, said plenum having a room air inlet including a damper to permit room air to mix with the kiln gases in said plenum to cool the kiln gases and thus protect the materials used in said duct and said exhaust fan;
• heat sensing means positioned in the interior of said plenum for sensing the temperature of kiln gases in the plenum;
• and
• temperature control means connected to said heat sensing means and said damper to control the damper to permit room air to enter the plenum.