Ventana Medical Systems, Inc.

Thomas P Krawzak

Brian J McGraw

Michael J DeGroff

David W Nunnery

A dispenser which can deliver precise small amounts of a liquid is disclosed. The dispenser is particularly suited to applying reagents in a biological test such as an immunoassay. It includes a reservoir chamber linked to a dispense chamber via a check valve, the two chambers preferably being in the form of syringes. An outlet line leading from the dispense chamber to a nozzle includes a delay check valve (preferably a ball inside a cylindrical chamber) which allows continuous outward flow, but shuts off flow in the reverse direction after allowing a predetermined volume to pass. The process of refilling the dispense chamber from the reservoir chamber creates reverse flow in the nozzle and causes a hanging drop of liquid at the tip of the nozzle to be withdrawn.

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Leominster, MA, United States of America

Thomas P Krawzak