Chromatographic analyzer sample valve

Claim 1

In a sample valve which includes a housing enclosing a body having six longitudinal passages therethrough which terminate in a generally circular first path at a first face of the body, a cap having six longitudinal passages therethrough which terminate in a generally circular second path at a first face of the cap, said first and second paths having substantially the same diameter, a diaphragm positioned adjacent the first face of said body, means urging said cap against said diaphragm so that the first face of said cap is adjacent the first face of said body member and said first and second circular paths are adjacent one another with the longitudinal passages in said cap terminating between the longitudinal passages in said body member, a first annular piston positioned adjacent said body on the side thereof remote from said cap, a second piston positioned adjacent said first piston, said second piston having a central section which extends through said first piston, said first and second pistons being of such configuration that a chamber is formed therebetween, said housing having an opening therein which communicates with said chamber, spring means positioned to exert a force on said second piston urging said second piston toward said first piston, and plungers positioned in each of the passages in said body member, the lengths of said plungers and the configurations of said pistons being such that first alternate plungers engage said diaphragm in thE absence of external fluid pressure being applied to said chamber and second alternate plunger means engage said diaphragm when external fluid pressure is applied to said chamber; the improvement comprising a plate having a central protrusion thereon, said plate being positioned between said spring means and said second piston so that said protrusion engages said second piston and concentrates the force of said spring means at a central region of said second piston relative to said first circular path.