Carbon Implants, Inc.

Medical Carbon Research Institute, LLC

Medtronic Carbon Implants, Inc.

James A Accuntius

Michael R Emken

David S Wilde

Axel D Haubold

John L Ely

Billie F Hightower

Pyrolytic carbon of extremely uniform crystalline characteristics and essentially free of discontinuities is obtained in a fluidized bed coater by creating an asymmetric recirculation of the fluidized bed within the high temperature coating chamber. Through the use of any of a variety of gas injection schemes, fluidizing/coating gas mixtures are injected through the three-dimensionally curved concave bottom surface of the coater to create a pattern where the fluidized bed ascends within about one-half of the volume of the coater and then spills over to become a descending bed in the other half.

Deposition of pyrocarbon

Pure unalloyed pyrocarbons having wear resistance suitable for use in pyrocarbon-coated heart valve components and having mechanical properties, such as flexural strength and toughness, superior to commercial silicon-alloyed pyrocarbons are deposited in fluidized bed coaters. Coating conditions are carefully controlled so as to maintain a precise bed size within a defined coating enclosure which will assure a substantially constant surface deposition temperature that in turn assures deposition of homogenous unalloyed pyrocarbons having these improved mechanical properties.

Pyrocarbon and process for depositing pyrocarbon coatings

A particle feeding device and method for fluidized bed coaters that has no moving parts. It preferably provides for constant flow of purge gas into the fluidized bed coater and has a feedback control means for monitoring and precisely controlling the flow of particles into the coater. The particle feeding device includes a supply of granular material in communication with a generally horizontal passageway and a delivery conduit for feeding granular material into a desired location, such as a fluidized bed coater. The amount of granular material remaining in the supply is periodically determined and pulses of gas are periodically discharged through said generally horizontal passageway so as to blow granular material into said delivery conduit in a manner so as to feed the precise amount of granular material for predetermined periods of time.

Particle feeding device and method for pyrolytic carbon coaters

Precise control of pyrocarbon being coated upon an object in a fluidized particle bed is achieved by monitoring the weight change of the fluidized particle bed over a period of time. Measurement of such weight change is truly representative of bed size in such a coater, which is a most important factor in achieving the desired characteristics of the pyrocarbon being deposited. By monitoring the bed size by repeatedly determining such changes in the weight, compensating adjustments are made by either adding additional particles to the bed or by changing the rate at which particles are withdrawn so that precise coating characteristics are achieved, and coatings can be deposited within very close thickness tolerances.

Precise regulation of fluidized bed weight in pyrolytically coating

Precise control of pyrocarbon being coated upon an object in a fluidized particle bed is achieved by monitoring the pressure difference between a region above the bed and a region in the lower portion of or just below the bed. Measurement of such pressure differential has been found to be truly representative of bed size in such a coater, and bed size is recognized to be a most important factor in achieving the desired characteristics of the substance being deposited. By adjusting bed size in response to changes in the pressure difference being monitored, a substantially constant bed size is readily achieved; alternatively, the pressure difference can be caused to gradually change in accord with a predetermined program. In either instance, adjustments are effected by adding additional particles to the bed or by changing the rate at which particles are withdrawn, and precise coating characteristics, e.g. thicknesses within very close tolerances, are achievable.

Growing community of inventors

Georgetown, TX, United States of America

James A Accuntius