| 摘要 |
Sections of the outer surface of a horizontally-disposed rotary drum suction filter each consist of a portion of a cylinder (e.g. one twelfth, circumferentially), having on its convex surface a plurality of spaced parallel ridges defining grooves extending in the direction of the curve of the surface, and having openings through it providing communication between the grooves and its inner surface. Each section has a sheet filter medium covering its convex side and attached to the outside rim of the section along all four edges. Each element thus formed rests on three radially spaced axial ribs 24, 22, 26, Fig. 6 (not shown), secured to the drum surface proper, 12. The element is fastened to the drum by spaced screws 30, extending through that one of the axial rims which is leading in the direction of drum rotation, and p engaging threaded plates extending between rib 26 under that element and rib 24 under the adjacent element. The filtrate compartments formed by the axial ribs are interrupted at the centre of the length of the drum by a fixed annular valve element 16, Fig. 3 (not shown), which encircles the drum at this point. The drum interior is also interrupted by two transverse discs at the region within the valve element, these discs 34, 36, being connected by axially extending tie members, to form a passageway 38 for radially inward flow of filtrate. Disc 34 has a central opening connected by a pipe 18 with an opening in one end wall 31 of the drum. The pipe 18 extends through end wall 31 and through an opening in a fixed framework 13 in which it is rotatably mounted, and connects with a stationary pipe elbow 20 to which vacuum is applied. The inner surface of the valve element 16 is closed from the "1 o'clock" position to the "4 o'clock" position to cut off the filtrate compartments at that region from vacuum and allow air-venting through the filter medium during cake-removal; elsewhere the inner surface has an elongated opening to provide communication with passageway 38. The openings 47 in the grooves of each filter element are at the "trailing" end of the element, so that as the element progressively inverts after the "12 o'clock" position, any trapped filtrate is caught between drum surface 12 and the under-surface of the element and cannot re-wet the filter medium. |
