Pump having relief valve seat free of direct structural restraint

摘要

A pump includes a coaxially integrated pump bypass/relief valve element of high density polymer material seats against a hard metallic sleeve that is pressed into a first counterbore around the bypass flow channel with an interference fit. That axial end of the sleeve bearing the valve seat face projects, for a substantial proportion of the sleeve length, beyond the first counterbore shoulder into a second counterbore space to provide an annular space around the outside diameter surface of the sleeve to free the seat face end of the sleeve from direct structural restraint.