Liquid metering and transfer valve assembly

Abstract

A liquid diluting valve assembly for delivering a pair of different sample volumes in the microliter range along with a predetermined volume of diluent to different locations. The valve assembly includes a pair of outer discs and an inner disc sandwiched therebetween, the facing surface portions being sealingly frictionally engaged. The discs have central axial passages aligned to accommodate a spindle the inner disc being independently movable relative to the other discs. The discs carry passageways with at least one segmenting passageway provided in the inner disc. One of the outer discs is stationary and carries an external hollow loop having a precise volume in the microliter range. The other outer disc carries a single outwardly extending aspirator probe for introduction of a liquid sample from an exterior sample source, the probe being coupled in series with the external hollow loop. After a continuous stream of sample is disposed through the serially connected segmenting passageway and loop, the inner member is rotated to place the content of the segmenting passageway in communication with an exterior source of diluent and a passage leading to the exterior of the valve assembly for delivery of the resulting dilution to a selected location. Backwash may be effected by reverse rotation of the inner disc.