Patent ID: 6348354
Filing Date: 2002-02-19
Classification: G01N,Y10T

Abstract:
An apparatus for controlling a stream of liquid packages, each liquid package comprising a plurality of liquid and air segments, the apparatus comprising:a first and second fluid conduit each being internally coated with an isolation liquid; a probe for selectively aspirating liquid segments and air segments into the first fluid conduit in a plurality of cycles, each cycle ending with the aspiration of a final liquid segment and a final air segment in that order said liquid segments each occupying a length of said first and second fluid conduits wherein the length occupied by each liquid segment is dependent upon the surface tension of the liquid comprising the segment, a valve coupled to said first fluid conduit and said second fluid conduit, said valve being adapted to be actuated between a first position in which said second fluid conduit is coupled to said first fluid conduit and a second position in which said second fluid conduit is not coupled to said first fluid conduit; an air and liquid interface detector positioned along said second fluid conduit a fixed distance from said valve, said fixed distance corresponding to a predetermined fixed volume within said second fluid conduit; and a means for stopping the aspiration of the final air segment in a current cycle when said air and liquid interface detector detects an interface between an air segment and a liquid segment of a previous cycle which have moved into said second fluid conduit after the final liquid segment of said previous cycle has fully entered said second fluid conduit and for actuating said valve from said first position to said second position at a time subsequent to said detection; wherein stopping the aspiration of the final air segment in a current cycle controls the length of the liquid segments in the previous and current cycle ensuring that the liquid and air segments of the previous cycle are at a desired distance from the valve before the valve is actuated, and wherein each of said cycles begins with the aspiration of a first air segment and a first liquid segment in that order, the apparatus further comprising: a third fluid conduit being internally coated with an isolation liquid into which the liquid and air segments aspirated in each of said cycles are inserted and in which the stream of liquid packages is repeatedly bi-directionally flowed in a forward and a reverse direction, said third fluid conduit being coupled to said valve such that when said valve is in said second position said third fluid conduit is coupled to said second fluid conduit; a second air and liquid interface detector positioned along said third fluid conduit adjacent said valve; and means for stopping said flow of said stream of liquid packages in said reverse direction at a point in time when said second air and liquid interface detector detects an interface between the first air segment and the first liquid segment most recently inserted into said third fluid conduit adjusted by a delay, said delay being normalized around a predetermined nominal center point delay according to a feedback loop.