Pressure regulator with minimum dead volume

Claim 1

A pressure regulating valve for use in a high-pressure liquid chromatography fluid flow line, said valve comprising: a housing, a cylindrical slidable piston structure having an axial bore therein such that said piston structure has a partially hollow interior volume having a bore opening, cylindrical walls and a bore bottom, said cylindrical walls surrounding said hollow interior volume having a radial port therethrough immediately adjacent said bore bottom, said piston structure fitted in said housing and slidable in respect thereto, a valve seat structure disposed externally of said piston structure, said valve seat structure including a valve seat, means for urging said piston structure toward said valve seat structure at a selectable pressure, means for preventing contact of said piston structure with said valve seat, a cylindrical needle structure disposed within said piston structure, and spring biasing means disposed entirely within said bore of said piston structure for urging said needle structure toward said valve seat structure, said piston structure being configured so that the flow line fluid in the interior volume of said piston structure urges said piston structure away from said valve seat structure when the pressure of said flow line fluid is greater than the selected pressure at which said piston structure is urged toward said valve seat structure, thereby establishing an equilibrium between said flow line pressure and said selected pressure, said needle structure moving toward contact with said valve seat structure when the pressure in said flow line is slightly less than said selected pressure, thereby tending to close said valve, conduit means connectable to said flow line, said conduit means terminating in an annular space formed in said housing substantially surrounding said piston structure immediately adjacent said port, said annular space having a larger dimension than said port in the direction in which said housing is slidable, said bore containing said spring bias means and said needle structure and whereby the entire bore is directly in a non-branching flow path between said flow line and said valve seat so that there are minimum trapped fluid areas and rapid purging of said bore is attainable.