Patent ID: 6872361

Claim:
A dual-pad liquid shear valve assembly for isolating a first, relatively small prescribed volume of sample liquid from a larger volume of sample liquid presented to said valve assembly from a source of sample liquid and for positioning said prescribed volume of sample liquid for subsequent dispensing together with a diluent adapted to dilute said sample liquid, said valve assembly comprising: a first valve pad having a first planar surface and containing a first plurality of liquid pathways therethrough which intersect said first planar surface; a second valve pad having a second planar surface and containing a second plurality of liquid pathways therethrough which intersect said second planar surface, said first and second planar surfaces of said first and second valve pads slidably engaging each other to enable selected ones of said first plurality of liquid pathways to be moved into and out of liquid flow alignment with selected ones of said second plurality of liquid pathways, said second planar surface having formed therein an open, liquid-retention channel having a volume equal to said prescribed volume, said open, liquid-retention channel being positioned on said second planar surface to be selectively aligned and coupled with (i) a first pair of liquid pathways of said first valve pad during relative sliding movement between said first and second planar surfaces to enable said open, liquid-retention channel to be filled with a sample liquid supplied by a sample liquid source, and (ii) a second pair of liquid pathways of said first valve pad during relative sliding movement between said first and second planar surfaces to enable said prescribed volume of sample liquid contained in said open, liquid-retention channel to be dispensed therefrom by the introduction of a diluent into one of said second pair of liquid pathways.