| 摘要 |
Improved low flow impedance flow control valves are disclosed in the present invention wherein spring valve means (12) captured between a valve spool (28) and a shoulder (30) are utilized for selectively metering a flow of fluid from an inlet port (18) to an outlet port (14) via a round edged helical orifice (82) formed between the open coils of the spring valve (12) as a function of the instant axial position of the valve spool (28) and the differential pressure therebetween. An improved method of controlling low impedance flow control valves is also disclosed in the present invention. The improved method provides better accuracy in controlling fluid flow through low flow impedance flow control valves through continually cycling a means for substantially interrupting fluid flow therethrough in a low frequency pulse width modulated fashion.
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