Patent ID: 6777029
Filing Date: 2004-08-17
Classification: C23C

Abstract:
A method of controlling a pyrolytic carbon coating process performed in a fluidized bed coating apparatus, said fluidized bed having an initial weight and being comprised of a plurality of particles, the method comprising:collecting a quantity of particles from said bed, said collected particles being coated with a pyrolytic carbon material; determining a weight of said collected particles; determining a deposition rate of said pyrolytic carbon material on said collected particles by analyzing historically obtained data and creating a model of the deposition rate as a function of trap weight at one or marc specified points in time within a given coating run, wherein determining a deposition rate of said pyrolytic carbon material on said collected particles comprises determining a deposition rate of said pyrolytic carbon material on said collected particles over a period of time using the following formula: DR=a0+a1TW1+a2TW2+a3TW3+a4TW4+a5TW5+a6TW6 where: DR=pyrolytic carbon deposition rate on bed particles in grams/min TW1=average trap weight for a first time period TW2=average trap weight for a second time period TW3=average trap weight for a third time period TW4=average trap weight for a fourth time period TW5=average trap weight for a fifth time period, and TW6=average trap weight for a sixth time period; determining a feed rate of additional bed particles added to said fluidized bed during said process; determining a new weight of said fluidized bed based upon said initial bed weight, said determined deposition rate of said pyrolytic carbon material, said determined weight of said collected particles, and said feed rate of said additional particles; calculating a coating rate for a product positioned in said fluidized bed based upon, in part, said determined new weight of said bed; and determining a desired duration of said coaxing process by dividing a desired coating thickness by said determined coating rate.