US Patent 7497257 Particle control screen with depth filtration

A particle control screen includes a support layer. A first filter layer is disposed around the support layer. A second filter layer is disposed around the first filter layer. A third filter layer is disposed around the second filter layer. Each of the filter layers has a pore size. The pore size of the third filter layer is greater than the pore size of the second filter layer. The pore size of the second filter layer is greater than the pore size of the first filter layer.