Abstract: The disclosed syringe pump and valve assembly utilizes a cylindrical housing having a piston axially moved therein for defining a pump chamber, where the housing is mounted to rotate about its longitudinal axis. A port seat is disposed concentrically of this axis spaced from one housing end, and a seal/valving member has one face seated slidably on the port seat and has its opposite face exposed to the pump chamber. Connectors serve to communicate separate liquid lines to separate respective ports on the port seat, which the seal/valving member first face overlies. The seal/valving member has through opening and/or radial or arcuate channels operable in different rotational member positions to selectively isolate or communicate the lines relative to one another and/or the pump chamber. The seal/valving member is designed to rotate in unison with the housing, and mechanism rotates the housing to locate the seal/valving member as required.

Abstract: The disclosed HPLC syringe or pump has valve components housed immediately adjacent a defined pump chamber, effectively minimizing dead flow passage spaces and the needed volume of flushing liquid between tests. The mated surfaces of the valve components are biased together with forces substantially proportional to the pumped liquid pressures, and the drive for moving the syringe chamber piston also and concurrently shifts the valving components before driving the piston in the pump chamber, effectively minimizing leakage while allowing valve shifting without excessive wear. The chamber piston drive is comprised of concentrically positioned lead screw and pump cylinder structure keyed to the valve components. Spaced seals isolate the defined pump chamber from the piston drive lead screw for minimizing damaging solvent contact with the screw, and passages allow for flushing the pump chamber walls between the seals of solvent left thereon to minimize solvent crust buildup thereon.