Patent ID: 8231752

Claim:
A method of making a filter element comprising spinning fibers from a plurality of dies onto a collector in a coordinate system having X, Y, Z axes orthogonal to each other, said X and Y axes defining an X-Y plane transverse to said Z axis, wherein said collector comprises a rotating mandrel rotating about said Z axis, and comprising spacing at least a first of said dies from said mandrel along said X axis, namely said first die, and spacing at least a second of said dies from said first die along said X-Y plane, namely said second die, said first and second dies being coplanar in the same said X-Y plane and positioned about said Z axis, and varying fiber diameter along the length of the fiber during fiber production by varying distance between said mandrel and said first die by moving said mandrel and said first die relative to one another in said Y axis during or before said rotating, wherein the fibers spun from said first die are filtration fibers forming a first annular filtration zone, and the fibers spun from said second die are filtration fibers forming a second annular filtration zone, spinning said filtration fibers from each of said first and second dies spaced along said X-Y plane directly onto said rotating mandrel, the method further comprising spinning a first set of fibers of a first filter characteristic from said first die, and spinning a second set of fibers of a second different filter characteristic from said second die.