Liquid metering and transfer valve assembly

Abstract

A rotary liquid metering and transfer valve assembly for a diluting system which includes a pair of stationary valve disc elements sandwiching a central, rotatable valve disc element, said disc elements being coaxially aligned and mounted on a spindle. One of the outer stationary elements has a first external loop secured thereto, said loop having a precise interior volume. An aspirator probe is secured to the other of said stationary elements. The central element has formed therein an axial segmenting passageway having a precise interior volume. A second external loop is secured to the center element. The second loop extends outwardly, preferably radially, of said element and has a precise interior volume. Appropriate interior passageways are provided in the outer elements for directing a liquid sample in a continuous path through the valve assembly, the path including the one segmenting passageway and the first and the second external loops. Additional interior passageways also are provided for coupling the valve assembly to sources of diluent and to exterior destinations. The central element is rotated to isolate the contents of the segmenting passageway and of the first and the second external loops and diluent is fed thereto to drive the isolated contents to said destinations. Only a single loading step is required to obtain three precise volumes of liquid sample. The valve assembly can be rinsed and continuous internals channels are provided for preventing any liquid from reaching the circumferential surface of the valve assembly.