Positive displacement liquid drawing and dispensing apparatus

摘要

A positive displacement liquid drawing and dispensing apparatus (21) having a tubular member (22) with an axially extending lumen (24) and a plunger (31) mounted for axial displacement in the lumen (24). The plunger (31) has a first seal (33) positioned proximate an end (34) of the plunger and a second seal (37) axially spaced from the first seal (33). The first and second seal each slidably and sealingly engage an interior surface (23) defining the lumen (24) as the plunger (31) is displaced in the lumen. The plunger further includes a recess (38) intermediate the first and second seals for receipt of trapped gas (40,41) which can be drawn in through an intake end (27) of the lumen during drawing of the liquid (36) into the tubular member (22). The plunger is formed for positioning of the first seal (33) beyond the intake opening (27) so that air will automatically be isolated between the first and second seals (33,37) as the plunger is withdrawn into a lumen. A substantially gas-free draw of liquid will result between the first seal (33) and the intake opening (27). A method of drawing the liquid in the apparatus which includes automatically isolating an uppermost portion of the liquid (36) and gas (41) from a lower portion of the volume drawn into the apparatus (21).