Liquid sample valve

Claim 1

Sample valve apparatus comprising an elongated hollow cylinder having a side wall, a closed end, an open end and an array of four ports extending through said side wall, two of said ports lying essentially in a common plane perpendicular to the longitudinal axis of said cylinder, first and second normally spaced apart plungers having forward and rear ends, each of said plungers fitting closely but slidably in said cylinder in end to end relationship, each of said plungers having a portion of reduced cross section intermediate its ends, said first plunger being closest to the closed end of said cylinder and having a rod coupled thereto and extending from the rear end thereof, said second plunger having an axially extending bore therethrough through which said rod fits closely but slidably, means for spring loading said rod with respect to said second plunger, means for driving said plungers in reciprocating motion, said two ports lying essentially in a plane perpendicular to the longitudinal axis of said cylinder being aligned with the space between said plungers and the other two ports being aligned with the reduced cross section portion when said plungers are in their withdrawn reciprocating motion position, said space between said plungers being aligned with one of said other two ports when said plungers are in their forward position, the other of said other two ports being disposed closer to said closed end of said cylinder and being isolated from said space between said plungers at all times during operation of said apparatus, said means for spring loading applying pressure to closed the space between said plungers on maximum forward movement of said reciprocating motion.