Patent ID: 7208091

Claim:
A method for withdrawing and filtering a partial volume of a particle-containing process fluid enclosed in a container, the method comprising the following steps: providing an aperture in a wall of the container, providing a filtering device having a filtering screen having a filter surface and adapted for rotation about an axis of rotation, wherein said surface is rotated around said axis at a speed sufficient to cause at least a substantial area of said surface to move at a tangential speed of at least approx. 0.3 meters/second, withdrawing means for withdrawing filtered process fluid and rotating means for rotating said surface around said axis, fixing said filtering device in said aperture such that the filtering screen is immersed in said process fluid, establishing a pressure differential through said filtering screen for causing said process fluid to flow therethrough to said withdrawing means, said flow of the process fluid having a linear velocity, and rotating said surface around said axis, while ensuring free access of said process fluid to at least a portion of said surface and wherein the method does not include a step of relying on a narrow gap between a stationary body and said rotating filter surface and wherein the linear velocity of said process fluid through the filtering screen is at least approx. 0.2 meters/second less than said tangential speed and wherein the method is used for essentially continuous, on-line filtration of biological process fluids.