| 摘要 |
A two, three or four-way valve includes two stages each with working valve components linked by a feedback spring so that a first stage servo unit is auto-nulling and the stroke of the valve member in a second stage valve unit is proportional to the input current to the first stage. An inherently balanced clevis member in the first stage controls flow of pressurized control media, which in combination with direct pressure flow, controls the position of a spool member in the second stage. The spool in turn controls pressure flow to a either one or two metering or input/output flow ports. Transient movement of the clevis due to change in input current to a magnetic servo drive assembly is opposed by bending of the feedback spring arising from the associated movement of the spool, which returns the clevis to its centered null position and stops the spool.
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