| 摘要 |
Disclosed are a plurality of cooperating filter discs defining a plurality of paired cooperating filter surfaces, including a first surface having a large surface area and a second surface contacting only a portion of the large surface area of the first and leaving portion of the large surface area or the upstream side of the stack not contacted thereby, at least one of said first and second surfaces being formed with grooves at the areas at which the first and second surfaces contact to allow for the accumulation of particles.
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