Abstract: A tank for storing oil includes a suction strainer with first and second filtration portions. The first filtration portion has a substantially cylindrical shape and formed by bending a thin plate into a pleated shape. The second filtration portion is provided on the outer side of the first filtration portion. The second filtration portion has a substantially cylindrical shape and is formed of a material having a plurality of spaces formed in a surface and interior of the material.

Abstract: When a lid covers an opening portion formed at an upper end of a filter case with a bottomed substantially cylindrical shape inside which a filter element is disposed, the internal space between the lid and the filter case is formed. A bypass flow path connecting the internal space and outside space is formed in the lid, and a relief valve disposed moveably between a position closing the bypass flow path and a position opening the bypass flow path includes an air bleeder formed from a porous material.

Abstract: A return filter is provided in a tank, for removing bubbles from hydraulic oil before returning the hydraulic oil to the tank. A vortex forming portion that includes a spiral-shaped blade member is provided in an outflow portion that has a substantially cylindrical shape and communicates with a hollow portion of a filter element. Thus, a vortex forms in the hydraulic oil flowing through the outflow portion and bubbles contained in the hydraulic oil are collected.

Abstract: A first discharge tube having a substantially cylindrical shape with openings at both ends is inserted through an outflow hole of a filter case and provided protruding toward the bottom surface of the tank. A second discharge tube having a substantially cylindrical shape is provided so as to cover the first discharge tube. The second discharge tube includes a first end that comes into contact with a bottom surface of the filter case, and is provided protruding from the bottom surface of the filter case toward the bottom surface of the tank. A tip end of the second discharge tube is covered by a bottom surface cover, and a plurality of discharge holes are formed in a region near an upper end of a side surface.

Abstract: When a lid covers an opening portion formed at an upper end of a filter case with a bottomed substantially cylindrical shape inside which a filter element is disposed, the internal space between the lid and the filter case is formed. A bypass flow path connecting the internal space and outside space is formed in the lid, and a relief valve disposed moveably between a position closing the bypass flow path and a position opening the bypass flow path includes an air bleeder formed from a porous material.

Abstract: In a filter element, plates are provided in a manner of covering ends of an outer cylinder and an inner cylinder. A packing having a substantially hollow annular plate shape is provided on the plate. A filtering material is provided between the outer cylinder and the inner cylinder. The packing is abutted against a surface of the case in parallel with the plate and a cylindrical outflow portion having a surface parallel to the inner cylinder.

Abstract: A return filter is provided in a tank, for removing bubbles from hydraulic oil before returning the hydraulic oil to the tank. A vortex forming portion that includes a spiral-shaped blade member is provided in an outflow portion that has a substantially cylindrical shape and communicates with a hollow portion of a filter element. Thus, a vortex forms in the hydraulic oil flowing through the outflow portion and bubbles contained in the hydraulic oil are collected.

Abstract: A tank for storing oil includes a suction strainer with first and second filtration portions. The first filtration portion has a substantially cylindrical shape and formed by bending a thin plate into a pleated shape. The second filtration portion is provided on the outer side of the first filtration portion. The second filtration portion has a substantially cylindrical shape and is formed of a material having a plurality of spaces formed in a surface and interior of the material.

Abstract: In a filter element, plates are provided in a manner of covering ends of an outer cylinder and an inner cylinder. A packing having a substantially hollow annular plate shape is provided on the plate. A filtering material is provided between the outer cylinder and the inner cylinder. The packing is abutted against a surface of the case in parallel with the plate and a cylindrical outflow portion having a surface parallel to the inner cylinder.