US Patent 7104281 Fluid flow regulation

Fluid flow regulation may be achieved by a system including a housing, a first flow throttling area, and a second flow throttling area. The housing includes a flow inlet port, a flow outlet port, and a passage between the ports. The first flow throttling area is in the passage, and the second flow throttling area is movably positionable proximate the first flow throttling area to facilitate fluid flow regulation, the second flow throttling area restricting flow more than the first flow throttling area. The second flow throttling area primarily regulates flow when flow is low, and the first flow throttling area primarily regulates flow when flow is high.