Filtering liq esp. blood sample - using plunger with flexible piston head, filter plug and central cylindrical passage to receive filtrate

摘要

A filtering device operating by pressure difference for sepg. two constituents of a liq. esp. for sepg. blood cells from serum in blood samples, is intended for insertion into the open mouth of a vessel, e.g., a test tube, contg. the liq. The filtering device comprises a long tube, open at both ends and of smaller dia. than the sampling vessel, and having fitted to one end a piston of flexible material, also having central through pasage and fitted at its outer end with a peripheral rim or flange of larger dia. than the sampling vessel so that, when the piston and sampling tube are introduced into the sampling vessel, the piston forms a peripheral seal at its flexible flange to the vessel wall. A porous filter unit is inserted into the central passage through the piston and forms a tight seal, so that as the piston is pressed into the sampling vessel, liq. must pass through the filter to enter the long cylindrical sampling tube. Pref., the flexibility and dimensions of the piston are such that when it is pressed firmly to one side, a gap is formed between the flexible lip and the vessel wall on one side so that the piston can be moved without appreciable pressure difference across it. The piston may be of rubber, neoprene or other flexible material. The filter may be of a solid, porous plastics, or glass wool, asbestos, synthetic plastics fibres, porous ceramic material or other insert filtering material such as sintered glass and diatomaceous silica.