Patent GB-992139-A (GB)
Title: A capillary filter
IPC: B01D39/10
Filed: 1962-09-21
Abstract: 992,139. Fishing. HANS-JOACHIM DIETZSCH G.m.b.H. Sept. 21, 1962 [Sept. 25, 1961; Jan. 20, 1962], No. 36058/62. Heading A1A. [Also in Division B1] A filter 1 suitable for harvesting plankton from seawater comprises a large number of straight, parallel closely packed capillary tubes 2 of plastics materials which are open at both ends and have parallel walls, so arranged that the openings 3 at one end of the capillary tubes define a smooth continuous surface, the capillary walls at said end converging towards the surface, preferably at an angle of 30-60 degrees and forming, at least on one side, a sharp acute-angled cutting edge with the surface. As shown, the capillary walls are thickened at the end defining the filter surface, to constrict the capillary openings, and tightly connected or bonded to the surrounding capillary ends. The internal diameter of the capillaries may be from a few hundredths to a few tenths of a millimetre, and at least ten times the thickness of the capillary walls, the constriction of the capillary ends being at least 10% of the diameter of the unconstricted capillaries, and the thickness of the filter may be from a few tenths of a millimetre to a few millimetres. The filters may be made by combining a large number of tubes to form capillaries in a pack, the length of the capillaries corresponding to many times the thickness of a single filter, subjecting the surface at the top of the pack containing the capillary openings to a treatment for constricting said openings and cutting off a section from the top of the pack sufficiently thick for the length of the capillaries contained in the section to exceed the length of their constricted end, this treatment being repeated until the entire pack is cut into sections for forming filters. Preferably the said treatment simultaneously bonds together the structural elements of the pack. Thus if the filter elements are made of a material softened by heat, e.g. polyethylene, polyformaldehyde, polyvinylbutyral resin, or cellulose acetobutyrate, a hot body may be applied to the top of the pack to effect the above treatments. To obtain a very smooth surface, a thin foil, e.g. of metal, terephthalic acid ester or cellulose, may be interposed between the hot body and the pack and later peeled off. The filters 24 may be placed between the rib members 21a of a divided holder (Fig. 6) the spaces formed between the ribs of one part of the divided holder opening towards one side of the holder, while the spaces between the ribs on the other part open towards the other side of the holder. The ribs may be at intervals of about 1/10th to 1/100th of the length of the ribs. In Fig. 7 solid is removed from the frame, which is drawn through the liquid to be filtered in the direction of the arrow P, by drawing one edge of the scraper 26 across the smooth filter surface, while the opposite edge is guided along a surface formed by the holder opposite and parallel to the swept filter surface. Solid matter accumulating in front of the scraper is removed through the hollow tube 27. Fig. 8 shows a tiered stack of juxtaposed holders and filters in an assembly frame. The frame is dragged through the sea as shown at A in Fig. 9, water passing through the frame in the direction of the arrows. The ship B has a recessed hull C into which the frame A can be drawn after turning it about its vertical axis so that the longest side of the frame aligns with the axis of the wall, as at A<SP>1</SP>. Finally the frame is upended about its horizontal longitudinal axis as shown at A<SP>11</SP>, and pulled upwards until the entry openings are slightly below or above water level. Suction pipes, scrapers or brushes D are inserted into the openings from above to remove the plankton from the filter surfaces, while the frame A is slowly lifted from position A<SP>111</SP> until it is finally completely clear of the water.