| 摘要 |
Improvements in filters used in heavy duty internal combustion engines which include: an exterior concentric tube with perforations, an interior concentric tube with perforations, a concentric spring that is found inside the interior concentric tube with perforations, a lower cap for the filter and an upper cap for the filter, characterized by two layers of filtering means between the exterior and interior concentric tubes without any stabilizing means existing between these layers such as a spring; the two layers of filtering means are of equal or different porosity and include a substantial portion of pulp of fibers that contain lignin, derived from the disc type refining of chips of wood that have a lignin content of at least 10 percent, with steam pressures in the range of 6.3 to 8.4 kg/cm2 at temperatures between 165 and 176.5.degree.C, and using energy levels in the range of approximately 8 to 35 brake horsepower days/air dry ton of raw material.
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