Particle feeding device and method for pyrolytic carbon coaters

A pyrolytic carbon coater which includes a system for feeding precise amounts of granular materials to a fluidized bed, which system comprises:

• hopper means for holding a supply of granular material which hopper means has a lower outlet;
• a connector unit attached to said hopper means in the region of said lower outlet which unit includes means providing a generally horizontal passageway communicating with said outlet;
• said connector unit also including delivery conduit means for receiving granular material from said horizontal passageway and for delivering granular material to said fluidized bed;
• said delivery conduit means leading to said fluidized bed for gravity delivery of said granular material to said fluidized bed that is maintained within the coater;
• a gas-tight enclosure which encloses said hopper means and said connector unit, and which is essentially gas-tight except for the exit therefrom of said delivery conduit means;
• means for delivering gas to said enclosure at a substantially constant rate so as to create a substantially constant purge flow of gas out of said gas-tight enclosure through said delivery conduit means and into the coater;
• gas jet means extending into said passageway to a location below said outlet and oriented to deliver a gas stream past said outlet and toward said delivery conduit means, said gas jet means being located beneath said outlet, so that it extends essentially diametrically therepast, and also located within a pile of said granular material, said pile being defined by said generally horizontal passageway, and a generally vertical passageway, which interconnects said outlet and said generally horizontal passageway, and an angle of repose for said granular material;
• a load cell for determining the weight of granular material remaining in said hopper means;
• means for discharging pulses of gas under pressure, from said gas delivered to said enclosure at a constant rate, through said gas jet means so as to periodically blow granular material from the region below said outlet, which blown material then falls via gravity to said fluidized bed through said delivery conduit means along with said substantially constant purge flow of gas;
• and
• control means for actuating said pulse-discharging means in response to said determined weight of granular material, said control means being programmable to activate or not activate said pulse-discharging means in response to said determined weight and in response to a programmed set point, said programmed set point changing as a function of time, so as to cause precise amounts of granular material, per unit time, to be fed to said fluidized bed over an extended period of time.